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Ntuli Y, Shawcross DL. Infection, inflammation and hepatic encephalopathy from a clinical perspective. Metab Brain Dis 2024:10.1007/s11011-024-01402-y. [PMID: 39212845 DOI: 10.1007/s11011-024-01402-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/11/2024] [Accepted: 07/23/2024] [Indexed: 09/04/2024]
Abstract
Hepatic encephalopathy (HE) is a syndrome that is associated with both acute and chronic liver injury. It manifests as a wide spectrum of neuropsychological abnormalities, ranging from subtle impairments in executive higher functions observed in cirrhosis, through to coma in acute liver failure. In acute liver failure, the central role of ammonia in the development of brain oedema has remained undisputed for 130 years. It latterly became apparent that infection and inflammation were profound determinants for the development of severe hepatic encephalopathy, associated with the development of cerebral oedema and intracranial hypertension. The relationship of the development of hepatic encephalopathy with blood ammonia levels in cirrhosis is less clear cut and the synergistic interplay of inflammation and infection with ammonia has been identified as being fundamental in the development and progression of hepatic encephalopathy. A perturbed gut microbiome and the presence of an impaired gut epithelial barrier that facilitates translocation of bacteria and bacterial degradation products into the systemic circulation, inducing systemic inflammation and innate and adaptive immune dysfunction, has now become the focus of therapies that treat hepatic encephalopathy in cirrhosis, and may explain why the prebiotic lactulose and rifaximin are efficacious. This review summarises the current clinical perspective on the roles of inflammation and infection in hepatic encephalopathy and presents the evidence base for existing therapies and those in development in the setting of acute and chronic liver failure.
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Affiliation(s)
- Yevedzo Ntuli
- School of Immunology and Microbial Sciences, Faculty of Life Sciences and Medicine, King's College London, King's College Hospital, 125 Coldharbour Lane, London, SE5 9NU, UK
- Institute of Liver Studies, King's College Hospital, Denmark Hill, London, SE5 9RS, UK
| | - Debbie L Shawcross
- School of Immunology and Microbial Sciences, Faculty of Life Sciences and Medicine, King's College London, King's College Hospital, 125 Coldharbour Lane, London, SE5 9NU, UK.
- Institute of Liver Studies, King's College Hospital, Denmark Hill, London, SE5 9RS, UK.
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2
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Zhao L, Zhang Z, Wang P, Zhang N, Shen H, Wu H, Wei Z, Yang F, Wang Y, Yu Z, Li H, Hu Z, Zhai H, Wang Z, Su F, Xie K, Li Y. NHH promotes Sepsis-associated Encephalopathy with the expression of AQP4 in astrocytes through the gut-brain Axis. J Neuroinflammation 2024; 21:138. [PMID: 38802927 PMCID: PMC11131257 DOI: 10.1186/s12974-024-03135-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2024] [Accepted: 05/20/2024] [Indexed: 05/29/2024] Open
Abstract
Sepsis-associated encephalopathy (SAE) is a significant cause of mortality in patients with sepsis. Despite extensive research, its exact cause remains unclear. Our previous research indicated a relationship between non-hepatic hyperammonemia (NHH) and SAE. This study aimed to investigate the relationship between NHH and SAE and the potential mechanisms causing cognitive impairment. In the in vivo experimental results, there were no significant abnormalities in the livers of mice with moderate cecal ligation and perforation (CLP); however, ammonia levels were elevated in the hippocampal tissue and serum. The ELISA study suggest that fecal microbiota transplantation in CLP mice can reduce ammonia levels. Reduction in ammonia levels improved cognitive dysfunction and neurological impairment in CLP mice through behavioral, neuroimaging, and molecular biology studies. Further studies have shown that ammonia enters the brain to regulate the expression of aquaporins-4 (AQP4) in astrocytes, which may be the mechanism underlying brain dysfunction in CLP mice. The results of the in vitro experiments showed that ammonia up-regulated AQP4 expression in astrocytes, resulting in astrocyte damage. The results of this study suggest that ammonia up-regulates astrocyte AQP4 expression through the gut-brain axis, which may be a potential mechanism for the occurrence of SAE.
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Affiliation(s)
- Lina Zhao
- Department of Critical Care Medicine, Tianjin Medical University General Hospital, Tianjin, 300052, China
| | - Zhen Zhang
- Department of Critical Care Medicine, Tianjin Medical University General Hospital, Tianjin, 300052, China
| | - Pei Wang
- Department of Critical Care Medicine, Tianjin Medical University General Hospital, Tianjin, 300052, China
| | - Nannan Zhang
- Department of Critical Care Medicine, Tianjin Medical University General Hospital, Tianjin, 300052, China
| | - Hao Shen
- Department of Critical Care Medicine, Tianjin Medical University General Hospital, Tianjin, 300052, China
| | - Hening Wu
- Department of Critical Care Medicine, Tianjin Medical University General Hospital, Tianjin, 300052, China
| | - Zhiyong Wei
- Department of Critical Care Medicine, Tianjin Medical University General Hospital, Tianjin, 300052, China
| | - Fei Yang
- Department of Critical Care Medicine, Chifeng Municipal Hospital, Chifeng Clinical Medical College of Inner Mongolia Medical University, Chifeng, 024000, China
| | - Yunying Wang
- Department of Critical Care Medicine, Chifeng Municipal Hospital, Chifeng Clinical Medical College of Inner Mongolia Medical University, Chifeng, 024000, China
| | - Zhijie Yu
- Department of Critical Care Medicine, Chifeng Municipal Hospital, Chifeng Clinical Medical College of Inner Mongolia Medical University, Chifeng, 024000, China
| | - Haibo Li
- Department of Anesthesiology, Chifeng Municipal Hospital, Chifeng Clinical Medical College of Inner Mongolia Medical University, Chifeng, 024000, China
| | - Zhanfei Hu
- Department of Anesthesiology, Chifeng Municipal Hospital, Chifeng Clinical Medical College of Inner Mongolia Medical University, Chifeng, 024000, China
| | - Hongyan Zhai
- Department of Ultrasound, Tianjin Medical University General Hospital, Tianjin, 300052, China
| | - Zhiwei Wang
- Department of Critical Care Medicine, Tianjin Medical University General Hospital, Tianjin, 300052, China
| | - Fuhong Su
- Experimental Laboratory of the Department of Intensive Care, Erasme Hospital, Université Libre de Bruxelles, Brussels, 1070, Belgium
| | - Keliang Xie
- Department of Critical Care Medicine, Tianjin Medical University General Hospital, Tianjin, 300052, China.
- Department of Anesthesiology, Tianjin Institute of Anesthesiology, Tianjin Medical University General Hospital, Tianjin, 300052, China.
| | - Yun Li
- Department of Anesthesiology, Tianjin Institute of Anesthesiology, Tianjin Medical University General Hospital, Tianjin, 300052, China.
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Orzeł-Gajowik K, Milewski K, Zielińska M. miRNA-ome plasma analysis unveils changes in blood-brain barrier integrity associated with acute liver failure in rats. Fluids Barriers CNS 2023; 20:92. [PMID: 38066639 PMCID: PMC10709860 DOI: 10.1186/s12987-023-00484-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2023] [Accepted: 10/30/2023] [Indexed: 12/18/2023] Open
Abstract
BACKGROUND Hepatic encephalopathy (HE) symptoms associated with liver insufficiency are linked to the neurotoxic effects of ammonia and other toxic metabolites reaching the brain via the blood-brain barrier (BBB), further aggravated by the inflammatory response. Cumulative evidence documents that the non-coding single-stranded RNAs, micro RNAs (miRs) control the BBB functioning. However, miRs' involvement in BBB breakdown in HE is still underexplored. Here, we hypothesized that in rats with acute liver failure (ALF) or rats subjected to hyperammonemia, altered circulating miRs affect BBB composing proteins. METHODS Transmission electron microscopy was employed to delineate structural alterations of the BBB in rats with ALF (thioacetamide (TAA) intraperitoneal (ip.) administration) or hyperammonemia (ammonium acetate (OA) ip. administration). The BBB permeability was determined with Evans blue dye and sodium fluorescein assay. Plasma MiRs were profiled by Next Generation Sequencing (NGS), followed by in silico analysis. Selected miRs, verified by qRT-PCR, were examined in cultured rat brain endothelial cells. Targeted protein alterations were elucidated with immunofluorescence, western blotting, and, after selected miR mimics transfection, through an in vitro resistance measurement. RESULTS Changes in BBB structure and increased permeability were observed in the prefrontal cortex of TAA rats but not in the brains of OA rats. The NGS results revealed divergently changed miRNA-ome in the plasma of both rat models. The in silico analysis led to the selection of miR-122-5p and miR-183-5p with their target genes occludin and integrin β1, respectively, as potential contributors to BBB alterations. Both proteins were reduced in isolated brain vessels and cortical homogenates in TAA rats. We documented in cultured primary brain endothelial cells that ammonia alone and, in combination with TNFα increases the relative expression of NGS-selected miRs with a less pronounced effect of TNFα when added alone. The in vitro study also confirmed miR-122-5p-dependent decrease in occludin and miR-183-5p-related reduction in integrin β1 expression. CONCLUSION This work identified, to our knowledge for the first time, potential functional links between alterations in miRs residing in brain endothelium and BBB dysfunction in ALF.
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Affiliation(s)
- Karolina Orzeł-Gajowik
- Department of Neurotoxicology, Mossakowski Medical Research Institute, Polish Academy of Sciences, Pawińskiego St. 5, 02-106, Warsaw, Poland
| | - Krzysztof Milewski
- Department of Neurotoxicology, Mossakowski Medical Research Institute, Polish Academy of Sciences, Pawińskiego St. 5, 02-106, Warsaw, Poland
- Laboratory of Cellular Metabolism, Nencki Institute of Experimental Biology, Polish Academy of Sciences, Pasteura St. 3, 02-093, Warsaw, Poland
| | - Magdalena Zielińska
- Department of Neurotoxicology, Mossakowski Medical Research Institute, Polish Academy of Sciences, Pawińskiego St. 5, 02-106, Warsaw, Poland.
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Tamnanloo F, Ochoa-Sanchez R, Oliveira MM, Lima C, Lépine M, Dubois K, Bosoi C, Tremblay M, Sleno L, Rose CF. Multiple ammonia-induced episodes of hepatic encephalopathy provoke neuronal cell loss in bile-duct ligated rats. JHEP Rep 2023; 5:100904. [PMID: 37942225 PMCID: PMC10628859 DOI: 10.1016/j.jhepr.2023.100904] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/05/2023] [Revised: 07/25/2023] [Accepted: 08/31/2023] [Indexed: 11/10/2023] Open
Abstract
Background & Aims Hepatic encephalopathy (HE) is defined as a reversible syndrome and therefore should resolve following liver transplantation (LT). However, neurological complications have been reported in up to 47% of LT recipients, which have been documented to be associated with a history of overt HE pre-LT. We hypothesise that multiple episodes of HE lead to permanent cell injury and exacerbate neurological dysfunction. Our goal was to evaluate the impact of cumulative HE episodes on neurological status and brain integrity in rats with chronic liver disease. Methods Episodes of overt HE (loss of righting reflex) were induced following injection of ammonium acetate in bile duct ligation (BDL) rats (BDL-Ammonia) every 4 days starting at week 3 post-BDL. Neurobehaviour was evaluated after the last episode. Upon sacrifice, plasma ammonia, systemic oxidative stress, and inflammation markers were assessed. Neuronal markers including neuron-specific nuclear antigen and SMI311 (anti-neurofilament marker) and apoptotic markers (cleaved caspase-3, Bax, and Bcl2) were measured. Total antioxidant capacity, oxidative stress marker (4-hydroxynonenal), and proinflammatory cytokines (tumour necrosis factor-alpha and interleukin-1β) were measured in brain (hippocampus, frontal cortex, and cerebellum). Proteomic analysis was conducted in the hippocampus. Results In hippocampus of BDL-Ammonia rats, cleaved caspase-3 and Bax/Bcl2 ratio were significantly increased, whereas NeuN and SMI311 were significantly decreased compared with BDL-Vehicle rats. Higher levels of oxidative stress-induced post-translational modified proteins were found in hippocampus of BDL-Ammonia group which were associated with a lower total antioxidant capacity. Conclusions Ammonia-induced episodes of overt HE caused neuronal cell injury/death in BDL rats. These results suggest that multiple bouts of HE can be detrimental on the integrity of the brain, translating to irreversibility and hence neurological complications post-LT. Impact and implications Hepatic encephalopathy (HE) is defined as a reversible neuropsychiatric syndrome resolving following liver transplantation (LT); however, ∼47% of patients demonstrate neurological impairments after LT, which are associated with a previous history of overt HE pre-LT. Our study indicates that multiple episodes of overt HE can cause permanent neuronal damage which may lead to neurological complications after LT. Nevertheless, preventing the occurrence of overt HE episodes is critical for reducing the risk of irreversible neuronal injury in patients with cirrhosis.
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Affiliation(s)
- Farzaneh Tamnanloo
- Hepato-Neuro Lab, CRCHUM, Montréal, Canada
- Medicine Department, Université de Montréal, Montréal, Canada
| | | | | | - Carina Lima
- Chemistry Department/CERMO-FC, Université du Québec à Montréal, Montréal, Canada
| | - Maggy Lépine
- Chemistry Department/CERMO-FC, Université du Québec à Montréal, Montréal, Canada
| | | | | | | | - Lekha Sleno
- Chemistry Department/CERMO-FC, Université du Québec à Montréal, Montréal, Canada
| | - Christopher F. Rose
- Hepato-Neuro Lab, CRCHUM, Montréal, Canada
- Medicine Department, Université de Montréal, Montréal, Canada
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Sepehrinezhad A, Shahbazi A, Sahab Negah S, Stolze Larsen F. New Insight Into Mechanisms of Hepatic Encephalopathy: An Integrative Analysis Approach to Identify Molecular Markers and Therapeutic Targets. Bioinform Biol Insights 2023; 17:11779322231155068. [PMID: 36814683 PMCID: PMC9940182 DOI: 10.1177/11779322231155068] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2022] [Accepted: 01/17/2023] [Indexed: 02/19/2023] Open
Abstract
Hepatic encephalopathy (HE) is a set of complex neurological complications that arise from advanced liver disease. The precise molecular and cellular mechanism of HE is not fully understood. Differentially expressed genes (DEGs) from microarray technologies are powerful approaches to obtain new insight into the pathophysiology of HE. We analyzed microarray data sets of cirrhotic patients with HE from Gene Expression Omnibus to identify DEGs in postmortem cerebral tissues. Consequently, we uploaded significant DEGs into the STRING to specify protein-protein interactions. Cytoscape was used to reconstruct the genetic network and identify hub genes. Target genes were uploaded to different databases to perform comprehensive enrichment analysis and repurpose new therapeutic options for HE. A total of 457 DEGs were identified in 2 data sets totally from 12 cirrhotic patients with HE compared with 12 healthy subjects. We found that 274 genes were upregulated and 183 genes were downregulated. Network analyses on significant DEGs indicated 12 hub genes associated with HE. Enrichment analysis identified fatty acid beta-oxidation, cerebral organic acidurias, and regulation of actin cytoskeleton as main involved pathways associated with upregulated genes; serotonin receptor 2 and ELK-SRF/GATA4 signaling, GPCRs, class A rhodopsin-like, and p38 MAPK signaling pathway were related to downregulated genes. Finally, we predicted 39 probable effective drugs/agents for HE. This study not only confirms main important involved mechanisms of HE but also reveals some yet unknown activated molecular and cellular pathways in human HE. In addition, new targets were identified that could be of value in the future study of HE.
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Affiliation(s)
- Ali Sepehrinezhad
- Department of Neuroscience, Faculty of Advanced Technologies in Medicine, Iran University of Medical Sciences, Tehran, Iran
- Neuroscience Research Center, Mashhad University of Medical Sciences, Mashhad, Iran
| | - Ali Shahbazi
- Department of Neuroscience, Faculty of Advanced Technologies in Medicine, Iran University of Medical Sciences, Tehran, Iran
- Cellular and Molecular Research Center, Iran University of Medical Sciences, Tehran, Iran
| | - Sajad Sahab Negah
- Neuroscience Research Center, Mashhad University of Medical Sciences, Mashhad, Iran
- Department of Neuroscience, Faculty of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran
| | - Fin Stolze Larsen
- Department of Hepatology CA-3163, Rigshospitalet, Copenhagen University Hospital, Copenhagen, Denmark
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Nor Nazli NA, Muthuraju S, Ahmad F, Mohamed Yusoff AA, Jaafar H, Shamsuddin S, Abdullah JM. Characterisation of Primary Human Hippocampal Astrocyte Cell Culture Following Exposure to Hypoxia. Malays J Med Sci 2023; 30:92-106. [PMID: 36875187 PMCID: PMC9984107 DOI: 10.21315/mjms2023.30.1.8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2022] [Accepted: 07/01/2022] [Indexed: 03/05/2023] Open
Abstract
Background The present study aimed to understand the characterisation of human hippocampal astrocyte following hypoxia exposure. Based on the preliminary screening, 15 min was chosen as the time point and the cells were exposed to different oxygen percentages. Methods The Trypan blue viability assay used to examine cell death. Immunofluorescence assay, glial fibrillary acidic protein (GFAP) was used to portray the morphology of astrocytes. The hypoxia-inducible factor 1 (HIF-1) staining was performed to confirm hypoxia induced cell death and there was a dramatic expression of HIF-1α displayed in exposed astrocyte cells compared to the control. In molecular level, genes were chosen, such as glyceraldehyde 3-phosphate dehydrogenase (GAPDH), GFAP, HIF-1α and B-cell lymphoma 2 (Bcl-2) and ran the reverse transcription-polymerase chain reaction (RT-PCR). Results Microscope revealed a filamentous and clear nucleus appearance in a control whereas the rupture nuclei with no rigid structure of the cell were found in the 3% oxygen. The control and hypoxia cells were also stained with the annexin V-fluorescein isothiocyanate (annexin V-FITC). Fluorescence microscope reveals astrocyte cells after hypoxia showed higher expression of nuclei but not in control. Merging PI and FITC showed the differences of nuclei expression between the control and hypoxia. In the molecular analysis, there were significant changes of GFAP, HIF-1α and Bcl-2 in hypoxia exposed cells when compared to the control group. Conclusion Cells that were exposed to hypoxia (3% oxygen for 15 min) clearly showed damage. General view of human hippocampal astrocyte genomic response to hypoxia was obtained.
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Affiliation(s)
- Nurul Atikah Nor Nazli
- Department of Neurosciences, School of Medical Sciences, Universiti Sains Malaysia, Kelantan, Malaysia.,Brain and Behaviour Cluster, School of Medical Sciences, Universiti Sains Malaysia, Kelantan, Malaysia
| | - Sangu Muthuraju
- Department of Neurosciences, School of Medical Sciences, Universiti Sains Malaysia, Kelantan, Malaysia.,Brain and Behaviour Cluster, School of Medical Sciences, Universiti Sains Malaysia, Kelantan, Malaysia
| | - Farizan Ahmad
- Department of Neurosciences, School of Medical Sciences, Universiti Sains Malaysia, Kelantan, Malaysia.,Brain and Behaviour Cluster, School of Medical Sciences, Universiti Sains Malaysia, Kelantan, Malaysia
| | - Abdul Aziz Mohamed Yusoff
- Department of Neurosciences, School of Medical Sciences, Universiti Sains Malaysia, Kelantan, Malaysia.,Brain and Behaviour Cluster, School of Medical Sciences, Universiti Sains Malaysia, Kelantan, Malaysia
| | - Hasnan Jaafar
- Department of Pathology, School of Medical Sciences, Universiti Sains Malaysia, Kelantan, Malaysia
| | - Shaharum Shamsuddin
- Department of Biomedicine, School of Health Sciences, Universiti Sains Malaysia, Kelantan, Malaysia
| | - Jafri Malin Abdullah
- Department of Neurosciences, School of Medical Sciences, Universiti Sains Malaysia, Kelantan, Malaysia.,Brain and Behaviour Cluster, School of Medical Sciences, Universiti Sains Malaysia, Kelantan, Malaysia
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7
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Mikkelsen ACD, Thomsen KL, Mookerjee RP, Hadjihambi A. The role of brain inflammation and abnormal brain oxygen homeostasis in the development of hepatic encephalopathy. Metab Brain Dis 2022; 38:1707-1716. [PMID: 36326976 DOI: 10.1007/s11011-022-01105-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/30/2022] [Accepted: 10/10/2022] [Indexed: 11/06/2022]
Abstract
Hepatic encephalopathy (HE) is a frequent complication of chronic liver disease (CLD) and has a complex pathogenesis. Several preclinical and clinical studies have reported the presence of both peripheral and brain inflammation in CLD and their potential impact in the development of HE. Altered brain vascular density and tone, as well as compromised cerebral and systemic blood flow contributing to the development of brain hypoxia, have also been reported in animal models of HE, while a decrease in cerebral metabolic rate of oxygen and cerebral blood flow has consistently been observed in patients with HE. Whilst significant strides in our understanding have been made over the years, evaluating all these mechanistic elements in vivo and showing causal association with development of HE, have been limited through the practical constraints of experimentation. Nonetheless, improvements in non-invasive assessments of different neurophysiological parameters, coupled with techniques to assess changes in inflammatory and metabolic pathways, will help provide more granular insights on these mechanisms. In this special issue we discuss some of the emerging evidence supporting the hypothesis that brain inflammation and abnormal oxygen homeostasis occur interdependently during CLD and comprise important contributors to the development of HE. This review aims at furnishing evidence for further research in brain inflammation and oxygen homeostasis as additional therapeutic targets and potentially diagnostic markers for HE.
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Affiliation(s)
| | - Karen Louise Thomsen
- Department of Hepatology and Gastroenterology, Aarhus University Hospital, Aarhus, Denmark
- UCL Institute of Liver and Digestive Health, University College London, London, UK
| | - Rajeshwar Prosad Mookerjee
- Department of Hepatology and Gastroenterology, Aarhus University Hospital, Aarhus, Denmark
- UCL Institute of Liver and Digestive Health, University College London, London, UK
| | - Anna Hadjihambi
- The Roger Williams Institute of Hepatology London, Foundation for Liver Research, London, SE5 9NT, UK.
- Faculty of Life Sciences and Medicine, King's College London, London, UK.
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8
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Shafey GM, Rashed ER, Zaki HF, Attia AS, El-Ghazaly MA. Molecular mechanisms involved in the effects of morin in experimental hepatic encephalopathy. Biofactors 2022; 48:1166-1178. [PMID: 35332953 DOI: 10.1002/biof.1838] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/08/2021] [Accepted: 03/09/2022] [Indexed: 11/09/2022]
Abstract
This study aimed to investigate the possible usefulness of morin flavonoid in comparison to silymarin as a hepatic/neuronal-supportive agent with similar effects and higher bioavailability in a rat model of hepatic encephalopathy (HE). Morin effects on rat liver and brain were evaluated post-induction of HE by thioacetamide (TAA; 200 mg/kg/day for 3 successive days). Then, the serum activities of aspartate transaminase (AST) and alanine transaminase (ALT) together with ammonia concentration were estimated to assess the liver function. Also, the degree of brain effects was evaluated via the assessment of brain contents of reduced glutathione (GSH), malondialdehyde (MDA), tumor necrosis factor-alpha (TNF-α), and interleukin (IL-1β) together with glutathione peroxidase (GPx) activity. In addition, the apoptotic and inflammatory changes in brain and liver tissues were also assessed via immunohistochemical examination. Our findings revealed a promising effect of morin against HE complications; as it corrected the liver functions, attenuated the brain/liver tissue injuries, and reduced the apoptotic and inflammatory insults of HE on both organs. These effects are comparable to those of silymarin. Morin could be introduced as a promising hepato- and neuro-therapeutic adjuvant in HE-associated neuronal complications especially in cases like silymarin intolerance.
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Affiliation(s)
- Ghada M Shafey
- Drug Radiation Research Department, National Centre for Radiation Research and Technology, Egyptian Atomic Energy Authority, Cairo, Egypt
| | - Engy R Rashed
- Drug Radiation Research Department, National Centre for Radiation Research and Technology, Egyptian Atomic Energy Authority, Cairo, Egypt
| | - Hala F Zaki
- Pharmacology and Toxicology Department, Faculty of Pharmacy, Cairo University, Cairo, Egypt
| | - Amina S Attia
- Pharmacology and Toxicology Department, Faculty of Pharmacy, Cairo University, Cairo, Egypt
| | - Mona A El-Ghazaly
- Drug Radiation Research Department, National Centre for Radiation Research and Technology, Egyptian Atomic Energy Authority, Cairo, Egypt
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9
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Häussinger D, Dhiman RK, Felipo V, Görg B, Jalan R, Kircheis G, Merli M, Montagnese S, Romero-Gomez M, Schnitzler A, Taylor-Robinson SD, Vilstrup H. Hepatic encephalopathy. Nat Rev Dis Primers 2022; 8:43. [PMID: 35739133 DOI: 10.1038/s41572-022-00366-6] [Citation(s) in RCA: 55] [Impact Index Per Article: 27.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 05/12/2022] [Indexed: 01/18/2023]
Abstract
Hepatic encephalopathy (HE) is a prognostically relevant neuropsychiatric syndrome that occurs in the course of acute or chronic liver disease. Besides ascites and variceal bleeding, it is the most serious complication of decompensated liver cirrhosis. Ammonia and inflammation are major triggers for the appearance of HE, which in patients with liver cirrhosis involves pathophysiologically low-grade cerebral oedema with oxidative/nitrosative stress, inflammation and disturbances of oscillatory networks in the brain. Severity classification and diagnostic approaches regarding mild forms of HE are still a matter of debate. Current medical treatment predominantly involves lactulose and rifaximin following rigorous treatment of so-called known HE precipitating factors. New treatments based on an improved pathophysiological understanding are emerging.
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Affiliation(s)
- Dieter Häussinger
- Department of Gastroenterology, Hepatology and Infectious Diseases, Medical Faculty and University Hospital Düsseldorf, Heinrich Heine University Düsseldorf, Düsseldorf, Germany.
| | - Radha K Dhiman
- Department of Hepatology, Sanjay Gandhi Postgraduate Institute of Medical Sciences, Lucknow, (Uttar Pradesh), India
| | - Vicente Felipo
- Laboratory of Neurobiology, Centro de Investigación Principe Felipe, Valencia, Spain
| | - Boris Görg
- Department of Gastroenterology, Hepatology and Infectious Diseases, Medical Faculty and University Hospital Düsseldorf, Heinrich Heine University Düsseldorf, Düsseldorf, Germany
| | - Rajiv Jalan
- Liver Failure Group ILDH, Division of Medicine, UCL Medical School, Royal Free Campus, London, UK.,European Foundation for the Study of Chronic Liver Failure, Barcelona, Spain
| | - Gerald Kircheis
- Department of Gastroenterology, Diabetology and Hepatology, University Hospital Brandenburg an der Havel, Brandenburg Medical School, Brandenburg an der Havel, Germany
| | - Manuela Merli
- Department of Translational and Precision Medicine, Universita' degli Studi di Roma - Sapienza, Roma, Italy
| | | | - Manuel Romero-Gomez
- UCM Digestive Diseases, Virgen del Rocío University Hospital, Institute of Biomedicine of Seville (HUVR/CSIC/US), University of Seville, Seville, Spain
| | - Alfons Schnitzler
- Institute of Clinical Neuroscience and Medical Psychology, Heinrich Heine University Düsseldorf, Düsseldorf, Germany
| | - Simon D Taylor-Robinson
- Department of Surgery and Cancer, St. Mary's Hospital Campus, Imperial College London, London, UK
| | - Hendrik Vilstrup
- Department of Hepatology and Gastroenterology, Aarhus University Hospital, Aarhus, Denmark
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10
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Häussinger D, Butz M, Schnitzler A, Görg B. Pathomechanisms in hepatic encephalopathy. Biol Chem 2021; 402:1087-1102. [PMID: 34049427 DOI: 10.1515/hsz-2021-0168] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2021] [Accepted: 05/12/2021] [Indexed: 02/06/2023]
Abstract
Hepatic encephalopathy (HE) is a frequent neuropsychiatric complication in patients with acute or chronic liver failure. Symptoms of HE in particular include disturbances of sensory and motor functions and cognition. HE is triggered by heterogeneous factors such as ammonia being a main toxin, benzodiazepines, proinflammatory cytokines and hyponatremia. HE in patients with liver cirrhosis is triggered by a low-grade cerebral edema and cerebral oxidative/nitrosative stress which bring about a number of functionally relevant alterations including posttranslational protein modifications, oxidation of RNA, gene expression changes and senescence. These alterations are suggested to impair astrocyte/neuronal functions and communication. On the system level, a global slowing of oscillatory brain activity and networks can be observed paralleling behavioral perceptual and motor impairments. Moreover, these changes are related to increased cerebral ammonia, alterations in neurometabolite and neurotransmitter concentrations and cortical excitability in HE patients.
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Affiliation(s)
- Dieter Häussinger
- Clinic for Gastroenterology, Hepatology, and Infectious Diseases, Heinrich Heine University, Moorenstr. 5, D-40225 Düsseldorf, Germany
| | - Markus Butz
- Department of Neurology/Institute of Clinical Neuroscience and Medical Psychology, Medical Faculty, Heinrich Heine University, Moorenstr. 5, D-40225 Düsseldorf, Germany
| | - Alfons Schnitzler
- Department of Neurology/Institute of Clinical Neuroscience and Medical Psychology, Medical Faculty, Heinrich Heine University, Moorenstr. 5, D-40225 Düsseldorf, Germany
| | - Boris Görg
- Clinic for Gastroenterology, Hepatology, and Infectious Diseases, Heinrich Heine University, Moorenstr. 5, D-40225 Düsseldorf, Germany
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11
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DeMorrow S, Cudalbu C, Davies N, Jayakumar AR, Rose CF. 2021 ISHEN guidelines on animal models of hepatic encephalopathy. Liver Int 2021; 41:1474-1488. [PMID: 33900013 PMCID: PMC9812338 DOI: 10.1111/liv.14911] [Citation(s) in RCA: 27] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/15/2020] [Revised: 03/05/2021] [Accepted: 04/01/2021] [Indexed: 02/07/2023]
Abstract
This working group of the International Society of Hepatic Encephalopathy and Nitrogen Metabolism (ISHEN) was commissioned to summarize and update current efforts in the development and characterization of animal models of hepatic encephalopathy (HE). As defined in humans, HE in animal models is based on the underlying degree and severity of liver pathology. Although hyperammonemia remains the key focus in the pathogenesis of HE, other factors associated with HE have been identified, together with recommended animal models, to help explore the pathogenesis and pathophysiological mechanisms of HE. While numerous methods to induce liver failure and disease exist, less have been characterized with neurological and neurobehavioural impairments. Moreover, there still remains a paucity of adequate animal models of Type C HE induced by alcohol, viruses and non-alcoholic fatty liver disease; the most common etiologies of chronic liver disease.
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Affiliation(s)
- S DeMorrow
- Division of Pharmacology and Toxicology, College of Pharmacy, The University of Texas at Austin, Texas, USA; Department of Internal Medicine, Dell Medical School, The University of Texas at Austin, Texas, USA; Research division, Central Texas Veterans Healthcare System, Temple Texas USA.,Correspondance: Sharon DeMorrow, PhD, ; tel: +1-512-495-5779
| | - C Cudalbu
- Center for Biomedical Imaging, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
| | - N Davies
- Institute for Liver and Digestive Health, University College London, Royal Free Campus, London, United Kingdom
| | - AR Jayakumar
- General Medical Research, Neuropathology Section, R&D Service and South Florida VA Foundation for Research and Education Inc; Obstetrics, Gynecology and Reproductive Sciences, University of Miami School of Medicine, Miami FL, USA
| | - CF Rose
- Hepato-Neuro Laboratory, CRCHUM, Université de Montréal, Montreal, Canada
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12
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Ochoa-Sanchez R, Tamnanloo F, Rose CF. Hepatic Encephalopathy: From Metabolic to Neurodegenerative. Neurochem Res 2021; 46:2612-2625. [PMID: 34129161 DOI: 10.1007/s11064-021-03372-4] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2021] [Revised: 05/31/2021] [Accepted: 06/03/2021] [Indexed: 12/15/2022]
Abstract
Hepatic encephalopathy (HE) is a neuropsychiatric syndrome of both acute and chronic liver disease. As a metabolic disorder, HE is considered to be reversible and therefore is expected to resolve following the replacement of the diseased liver with a healthy liver. However, persisting neurological complications are observed in up to 47% of transplanted patients. Several retrospective studies have shown that patients with a history of HE, particularly overt-HE, had persistent neurological complications even after liver transplantation (LT). These enduring neurological conditions significantly affect patient's quality of life and continue to add to the economic burden of chronic liver disease on health care systems. This review discusses the journey of the brain through the progression of liver disease, entering the invasive surgical procedure of LT and the conditions associated with the post-transplant period. In particular, it will discuss the vulnerability of the HE brain to peri-operative factors and post-LT conditions which may explain non-resolved neurological impairment following LT. In addition, the review will provide evidence; (i) supporting overt-HE impacts on neurological complications post-LT; (ii) that overt-HE leads to permanent neuronal injury and (iii) the pathophysiological role of ammonia toxicity on astrocyte and neuronal injury/damage. Together, these findings will provide new insights on the underlying mechanisms leading to neurological complications post-LT.
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Affiliation(s)
- Rafael Ochoa-Sanchez
- Hepato-Neuro Laboratory, CRCHUM, Université de Montréal, 900, rue Saint-Denis Pavillon R, R08.422, Montreal, QC, H2X-0A9, Canada
| | - Farzaneh Tamnanloo
- Hepato-Neuro Laboratory, CRCHUM, Université de Montréal, 900, rue Saint-Denis Pavillon R, R08.422, Montreal, QC, H2X-0A9, Canada
| | - Christopher F Rose
- Hepato-Neuro Laboratory, CRCHUM, Université de Montréal, 900, rue Saint-Denis Pavillon R, R08.422, Montreal, QC, H2X-0A9, Canada.
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13
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Sun Q, Wang J, Wang X, Dai J, Wang X, Fan H, Wang Z, Li H, Huang X, Huang W. Treatment-dependent surface chemistry and gas sensing behavior of the thinnest member of titanium carbide MXenes. NANOSCALE 2020; 12:16987-16994. [PMID: 32780062 DOI: 10.1039/c9nr08350b] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
MXenes, a rapidly developing family of two-dimensional materials possessing tunable electronic properties and abundant surface functional groups, are promising gas-sensing materials. Ti2CTx, with a thinner unit cell thickness compared to its compositional analogue Ti3C2Tx and thus more profound surface-dependent properties, has been less explored over the past years. Herein, by etching the precursor Ti2AlC with a concentrated HF or LiF/HCl mixture, semiconducting Ti2CTx (HF) nanosheets and metallic Ti2CTx (LiF/HCl) nanosheets were obtained, respectively, arising from their treatment-dependent surface functionalization. In addition, the resulting metallic nanosheets were partially oxidized into TiO2/Ti2CTx (LiF/HCl) hybrid, which exhibited superior sensitivity toward NH3 gas as compared with Ti2CTx (HF) and Ti2CTx (LiF/HCl). Detailed analysis suggests that a high concentration of surface oxygen containing species, such as -Ox, -(OH)x and Ti-O-Ti, is generally beneficial for NH3 sensing, and a relatively higher -Ox concentration allows rapid gas desorption and sensor recovery.
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Affiliation(s)
- Qian Sun
- Key Laboratory of Flexible Electronics (KLOFE) & Institute of Advanced Materials (IAM), Jiangsu National Synergistic Innovation Center for Advanced Materials (SICAM), Nanjing Tech University (NanjingTech), 30 South Puzhu Road, Nanjing 211816, China.
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14
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Liotta EM, Kimberly WT. Cerebral edema and liver disease: Classic perspectives and contemporary hypotheses on mechanism. Neurosci Lett 2020; 721:134818. [PMID: 32035166 DOI: 10.1016/j.neulet.2020.134818] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2019] [Revised: 02/01/2020] [Accepted: 02/03/2020] [Indexed: 02/07/2023]
Abstract
Liver disease is a growing public health concern. Hepatic encephalopathy, the syndrome of brain dysfunction secondary to liver disease, is a frequent complication of both acute and chronic liver disease and cerebral edema (CE) is a key feature. While altered ammonia metabolism is a key contributor to hepatic encephalopathy and CE in liver disease, there is a growing appreciation that additional mechanisms contribute to CE. In this review we will begin by presenting three classic perspectives that form a foundation for a discussion of CE in liver disease: 1) CE is unique to acute liver failure, 2) CE in liver disease is only cytotoxic, and 3) CE in liver disease is primarily an osmotically mediated consequence of ammonia and glutamine metabolism. We will present each classic perspective along with more recent observations that call in to question that classic perspective. After highlighting these areas of debate, we will explore the leading contemporary mechanisms hypothesized to contribute to CE during liver disease.
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Affiliation(s)
- Eric M Liotta
- Northwestern University-Feinberg School of Medicine, Department of Neurology, United States; Northwestern University-Feinberg School of Medicine, Department of Surgery, Division of Organ Transplantation, United States; Northwestern University Transplant Outcomes Research Collaboration, United States.
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15
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El-Latif El-Ghazaly MA, Rashed ER, Shafey GM, Zaki HF, Attia AS. Amelioration of thioacetamide-induced hepatic encephalopathy in rats by low-dose gamma irradiation. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2020; 27:334-343. [PMID: 31786756 DOI: 10.1007/s11356-019-06934-w] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/14/2019] [Accepted: 10/31/2019] [Indexed: 06/10/2023]
Abstract
Brain affection is a common symptom of liver insufficiency. This study aimed to evaluate the role of low-dose γ irradiation (LDR) as a potential therapeutic agent in thioacetamide (TAA)-induced hepatic encephalopathy (HE) in rats. Effects of local and whole-body irradiation (0.5 Gy) on rat brain/liver were evaluated following the induction of HE by TAA (200 mg/kg/day/for 3 successive days). Serum activities of aspartate transaminase (AST) and alanine transaminase (ALT) and ammonia level were assessed. The effect of HE on brain was evaluated through the determination of brain contents of malondialdehyde (MDA), reduced glutathione (GSH), tumor necrosis factor-alpha (TNF-α), and interleukin-1beta (IL-1β) and glutathione peroxidase (GPx) activity. Moreover, apoptotic and inflammatory changes in brain and liver tissues were assessed together with alpha-smooth muscle actin (α-SMA); fibrosis marker. Results showed correction of the biochemical parameters which was supported by the results of the immunohistochemical examinations. LDR is a promising hepato- and neurotherapy against HE.
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Affiliation(s)
- Mona Abd El-Latif El-Ghazaly
- Drug Radiation Research Department, National Centre for Radiation Research and Technology, Atomic Energy Authority, PO box 29, Nasr City, Cairo, 11787, Egypt
| | - Engy Refaat Rashed
- Drug Radiation Research Department, National Centre for Radiation Research and Technology, Atomic Energy Authority, PO box 29, Nasr City, Cairo, 11787, Egypt
| | - Ghada Mahmoud Shafey
- Drug Radiation Research Department, National Centre for Radiation Research and Technology, Atomic Energy Authority, PO box 29, Nasr City, Cairo, 11787, Egypt.
| | - Hala Fahmy Zaki
- Pharmacology and Toxicology Department, Faculty of Pharmacy, Cairo University, Cairo, Egypt
| | - Amina Salem Attia
- Pharmacology and Toxicology Department, Faculty of Pharmacy, Cairo University, Cairo, Egypt
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16
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Jaeger V, DeMorrow S, McMillin M. The Direct Contribution of Astrocytes and Microglia to the Pathogenesis of Hepatic Encephalopathy. J Clin Transl Hepatol 2019; 7:352-361. [PMID: 31915605 PMCID: PMC6943208 DOI: 10.14218/jcth.2019.00025] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/05/2019] [Revised: 10/07/2019] [Accepted: 10/24/2019] [Indexed: 02/06/2023] Open
Abstract
Hepatic encephalopathy is a neurological complication resulting from loss of hepatic function and is associated with poor clinical outcomes. During acute liver failure over 20% of mortality can be associated with the development of hepatic encephalopathy. In patients with liver cirrhosis, 1-year survival for those that develop overt hepatic encephalopathy is under 50%. The pathogenesis of hepatic encephalopathy is complicated due to the multiple disruptions in homeostasis that occur following a reduction in liver function. Of these, elevations of ammonia and neuroinflammation have been shown to play a significant contributing role to the development of hepatic encephalopathy. Disruption of the urea cycle following liver dysfunction leads to elevations of circulating ammonia, which enter the brain and disrupt the functioning of astrocytes. This results in dysregulation of metabolic pathways in astrocytes, oxidative stress and cerebral edema. Besides ammonia, circulating chemokines and cytokines are increased following liver injury, leading to activation of microglia and a subsequent neuroinflammatory response. The combination of astrocyte dysfunction and microglia activation are significant contributing factors to the pathogenesis of hepatic encephalopathy.
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Affiliation(s)
- Victoria Jaeger
- Baylor Scott & White Health, Department of Internal Medicine, Temple, TX, USA
| | - Sharon DeMorrow
- Texas A&M University Health Science Center, Department of Medical Physiology, Temple, TX, USA
- Central Texas Veterans Health Care System, Temple, TX, USA
- University of Texas at Austin, Dell Medical School, Department of Internal Medicine, Austin, TX, USA
- University of Texas at Austin, College of Pharmacy, Austin, TX, USA
| | - Matthew McMillin
- Texas A&M University Health Science Center, Department of Medical Physiology, Temple, TX, USA
- Central Texas Veterans Health Care System, Temple, TX, USA
- University of Texas at Austin, Dell Medical School, Department of Internal Medicine, Austin, TX, USA
- Correspondence to: Matthew McMillin, University of Texas at Austin Dell Medical School, 1601 Trinity Street, Building B, Austin, TX 78701, USA. Tel: +1-512-495-5037, Fax: +1-512-495-5839, E-mail:
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17
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Vong LB, Ibayashi Y, Lee Y, Ngo DN, Nishikawa Y, Nagasaki Y. Poly(ornithine)-based self-assembling drug for recovery of hyperammonemia and damage in acute liver injury. J Control Release 2019; 310:74-81. [DOI: 10.1016/j.jconrel.2019.08.011] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2019] [Revised: 08/09/2019] [Accepted: 08/11/2019] [Indexed: 01/25/2023]
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González-Regueiro J, la Tijera MHD, Moreno-Alcántar R, Torre A. Pathophysiology of hepatic encephalopathy and future treatment options. REVISTA DE GASTROENTEROLOGÍA DE MÉXICO (ENGLISH EDITION) 2019. [DOI: 10.1016/j.rgmxen.2019.05.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/26/2022] Open
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19
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González-Regueiro JA, Higuera-de la Tijera MF, Moreno-Alcántar R, Torre A. Pathophysiology of hepatic encephalopathy and future treatment options. REVISTA DE GASTROENTEROLOGIA DE MEXICO (ENGLISH) 2019; 84:195-203. [PMID: 31014748 DOI: 10.1016/j.rgmx.2019.02.004] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/30/2018] [Revised: 01/28/2019] [Accepted: 02/18/2019] [Indexed: 06/09/2023]
Abstract
Understanding of the pathophysiology of hepatic encephalopathy has conditioned new treatment options. Ammonia detoxification in hepatic encephalopathy is regulated by two enzymes: glutaminase or glutamine synthetase. The first produces ammonia and the second detoxifies the ammonia, which is why treatments are aimed at glutaminase inhibition or glutamine synthetase activation. At present, we know that both enzymes are found not only in the liver, but also in the muscle, intestine, kidney, and brain. Therefore, current treatments can be directed at each enzyme at different sites. Awareness of those potential treatment sites makes different options of approach possible in the patient with hepatic encephalopathy, and each approach should be personalized.
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Affiliation(s)
- J A González-Regueiro
- Departamento de Gastroenterología, Instituto Nacional de Ciencias Médicas y Nutrición «Salvador Zubirán», Ciudad de México, México
| | | | - R Moreno-Alcántar
- Departamento de Gastroenterología, Centro Médico Nacional Siglo XXI, Ciudad de México, México
| | - A Torre
- Departamento de Gastroenterología, Instituto Nacional de Ciencias Médicas y Nutrición «Salvador Zubirán», Ciudad de México, México; Unidad de Hepatología y Trasplante Hepático, Departamento de Gastroenterología, Instituto Nacional de Ciencias Médicas y Nutrición «Salvador Zubirán», Ciudad de México, México.
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20
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Görg B, Karababa A, Häussinger D. Hepatic Encephalopathy and Astrocyte Senescence. J Clin Exp Hepatol 2018; 8:294-300. [PMID: 30302047 PMCID: PMC6175776 DOI: 10.1016/j.jceh.2018.05.003] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/08/2018] [Accepted: 05/08/2018] [Indexed: 02/07/2023] Open
Abstract
Hepatic Encephalopathy (HE) is a severe complication of acute or chronic liver diseases with a broad spectrum of neurological symptoms including motor disturbances and cognitive impairment of different severity. Contrary to former beliefs, a growing number of studies suggest that cognitive impairment may not fully reverse after an acute episode of overt HE in patients with liver cirrhosis. The reasons for persistent cognitive impairment in HE are currently unknown but recent observations raise the possibility that astrocyte senescence may play a role here. Astrocyte senescence is closely related to oxidative stress and correlate with irreversible cognitive decline in aging and neurodegenerative diseases. In line with this, surrogate marker for oxidative stress and senescence were upregulated in ammonia-exposed cultured astrocytes and in post mortem brain tissue from patients with liver cirrhosis with but not without HE. Ammonia-induced senescence in astrocytes involves glutamine synthesis-dependent formation of reactive oxygen species (ROS), p53 activation and upregulation of cell cycle inhibitory factors p21 and GADD45α. More recent studies also suggest a role of ROS-induced downregulation of Heme Oxygenase (HO)1-targeting micro RNAs and upregulation of HO1 for ammonia-induced proliferation inhibition in cultured astrocytes. Further studies are required to identify the precise sequence of events that lead to astrocyte senescence and to elucidate functional implications of senescence for cognitive performance in patients with liver cirrhosis and HE.
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Key Words
- ARE, Antioxidant Response Elements
- BDNF, Brain-Derived Neurotrophic Factor
- Eph, Ephrine
- EphR, Ephrine Receptor
- GADD45α, Growth Arrest and DNA Damage Inducible 45α
- GS, Glutamine Synthetase
- HE, Hepatic Encephalopathy
- HO1, Heme Oxygenase 1
- LOLA, l-Ornithine-l-Aspartate
- MAP, Mitogen Activated Protein Kinases
- NAPDH, Reduced Form of Nicotinamide Adenine Dinucleotide Phosphate
- Nox, NADPH Oxidase
- Nrf2, Nuclear Factor-Like 2
- PBR, Peripheral-Type Benzodiazepine Receptor
- PTN, Protein Tyrosine Nitration
- RNOS, Reactive Nitrogen and Oxygen Species
- ROS, Reactive Oxygen Species
- SA-β-Gal, Senescence-Associated β-d-Galactosidase
- TSP, Trombospondin
- TrkBT, Truncated Tyrosine Receptor Kinase B
- ZnPP, Zinc Protoporphyrin
- ammonia
- astrocytes
- heme oxygenase 1
- hepatic encephalopathy
- mPT, Mitochondrial Permeability Transition
- miRNAs
- nNOS, Neuronal-Type Nitric-Oxide Synthase
- oxidative stress
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Affiliation(s)
| | | | - Dieter Häussinger
- Address for correspondence: Dieter Häussinger, Universitätsklinikum Düsseldorf, Klinik für Gastroenterologie, Hepatologie und Infektiologie, Moorenstrasse 5, 40225 Düsseldorf, Germany. Tel.: +49 211 811 7569; fax: +49 211 811 8838.
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21
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Ochoa-Sanchez R, Rose CF. Pathogenesis of Hepatic Encephalopathy in Chronic Liver Disease. J Clin Exp Hepatol 2018; 8:262-271. [PMID: 30302043 PMCID: PMC6175755 DOI: 10.1016/j.jceh.2018.08.001] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/23/2018] [Accepted: 08/09/2018] [Indexed: 12/12/2022] Open
Abstract
Hepatic encephalopathy (HE) is a complex neuropsychiatric syndrome that occurs during chronic liver disease (CLD). While ammonia and other precipitating factors in liver disease including inflammation, bile acids, oxidative stress, and lactate play a role in the pathogenesis of HE, the exact mechanism that leads to HE is not fully understood. Notably, accumulating evidence points toward a synergic effect rather than independent actions among precipitating factors that contributes to the development and severity of HE in CLD. Hence, this review is aimed to briefly discuss the single and synergic interplay of pathological factors in the progression and severity of HE.
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Key Words
- AQP4, Aquaporin 4
- BAs, Bile Acids
- BBB, Blood-Brain Barrier
- BDL, Bile Duct Ligation
- CLD, Chronic Liver Disease
- CSF, Cerebrospinal Fluid
- GABA, Gamma-Aminobutyric Acid
- GAMSAs, GABAA Receptor Modulating Steroid Antagonists
- GFAP, Glial Fibrillary Acid Protein
- GLAST, Glial Glutamate-Aspartate Transporter
- GPR81, G-Protein-Coupled Receptor 81
- GS, Glutamine Synthetase
- HE, Hepatic Encephalopathy
- ICP, Intracranial Pressure
- ILs, Interleukins
- MRI, Magnetic Resonance Imaging
- NF-?B, Nuclear Factor Kappa B
- NMDA, N-Methyl-d-Aspartate Glutamate Receptor
- NO, Nitric Oxide
- PCA, Portacaval Anastomosis
- ROS, Reactive Oxygen Species
- TJ, Tight Junction
- TNF-a, Tumor Necrosis Alpha
- ammonia
- astrocyte swelling
- bile acids
- brain edema
- cGMP, Cyclic Guanosine Monophosphate
- cirrhosis
- hepatic encephalopathy
- inflammation
- lactate
- mGluR, Metabotropic Glutamate Receptor
- neurotransmission
- oxidative stress
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Affiliation(s)
| | - Christopher F. Rose
- Address for correspondence. Christopher F. Rose Professor, Dept. Medicine, Université de Montréal, CRCHUM, 900 Saint-Denis Street, Montréal, Québec, H2X 0A9, Canada.
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Jayakumar AR, Norenberg MD. Hyperammonemia in Hepatic Encephalopathy. J Clin Exp Hepatol 2018; 8:272-280. [PMID: 30302044 PMCID: PMC6175739 DOI: 10.1016/j.jceh.2018.06.007] [Citation(s) in RCA: 54] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/16/2018] [Accepted: 06/10/2018] [Indexed: 12/12/2022] Open
Abstract
The precise mechanism underlying the neurotoxicity of Hepatic Encephalopathy (HE) is remains unclear. The dominant view has been that gut-derived nitrogenous toxins are not extracted by the diseased liver and thereby enter the brain. Among the various toxins proposed, the case for ammonia is most compelling. Events that lead to increased levels of blood or brain ammonia have been shown to worsen HE, whereas reducing blood ammonia levels alleviates HE. Clinical, pathological, and biochemical changes observed in HE can be reproduced by increasing blood or brain ammonia levels in experimental animals, while exposure of cultured astrocytes to ammonium salts reproduces the morphological and biochemical findings observed in HE. However, factors other than ammonia have recently been proposed to be involved in the development of HE, including cytokines and other blood and brain immune factors. Moreover, recent studies have questioned the critical role of ammonia in the pathogenesis of HE since blood ammonia levels do not always correlate with the level/severity of encephalopathy. This review summarizes the vital role of ammonia in the pathogenesis of HE in humans, as well as in experimental models of acute and chronic liver failure. It further emphasizes recent advances in the molecular mechanisms involved in the progression of neurological complications that occur in acute and chronic liver failure.
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Key Words
- AHE, Acute Hepatic Encephalopathy
- ALF, Acute Liver Failure
- CHE, Chronic Hepatic Encephalopathy
- CNS, Central Nervous System
- CSF, Cerebrospinal Fluid
- ECs, Endothelial Cells
- HE, Hepatic Encephalopathy
- IL, Interleukin
- LPS, Lipopolysaccharide
- MAPKs, Mitogen-Activated Protein Kinases
- NCX, Sodium-Calcium Exchanger
- NF-κB, Nuclear Factor-kappaB
- NHE, Sodium/Hydrogen Exchanger-1 or SLC9A1 (SoLute Carrier Family 9A1)
- SUR1, The Sulfonylurea Receptor 1
- TDP-43 and tau proteinopathies
- TDP-43, TAR DNA-Binding Protein, 43 kDa
- TLR, Toll-like Receptor
- TNF-α, Tumor Necrosis Factor-Alpha
- TSP-1, Thrombospondin-1
- ammonia
- hepatic encephalopathy
- inflammation
- matricellular proteins
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Affiliation(s)
- A R Jayakumar
- General Medical Research, Neuropathology Section, R&D Service, Veterans Affairs Medical Center, Miami, FL 33125, United States
- South Florida VA Foundation for Research and Education Inc., Veterans Affairs Medical Center, Miami, FL 33125, United States
| | - Michael D Norenberg
- Department of Pathology, University of Miami School of Medicine, Miami, FL 33125, United States
- Department of Biochemistry & Molecular Biology, University of Miami School of Medicine, Miami, FL 33125, United States
- Department of Neurology and Neurological Surgery, University of Miami School of Medicine, Miami, FL 33125, United States
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23
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Dhanda S, Gupta S, Halder A, Sunkaria A, Sandhir R. Systemic inflammation without gliosis mediates cognitive deficits through impaired BDNF expression in bile duct ligation model of hepatic encephalopathy. Brain Behav Immun 2018. [PMID: 29518527 DOI: 10.1016/j.bbi.2018.03.002] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Chronic liver disease per se induces neuroinflammation that contributes to cognitive deficits in hepatic encephalopathy (HE). However, the processes by which pro-inflammatory molecules result in cognitive impairment still remains unclear. In the present study, a significant increase in the activity of liver function enzymes viz. alanine transaminase (ALT), aspartate transaminase (AST) and alkaline phosphatase (ALP) was observed along with increase in plasma ammonia levels after four weeks of bile duct ligation (BDL) in rats suggesting hepatocellular damage. A significant increase was observed in mRNA expression of interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-α) and monocyte chemoattractant protein-1 (MCP-1) in brain regions and liver of BDL rats. Concomitantly, IL-6, TNF-α and MCP-1 protein levels were also increased in brain regions, liver and serum of BDL rats suggesting the involvement of blood-brain-axis in inflammatory response. However, a significant decrease was observed in glial fibrillary acidic protein (GFAP) and ionized calcium-binding adaptor molecule-1 (Iba-1) expression at transcriptional and translation level in brain of BDL rats. Immunohistochemical and flowcytometric analysis revealed reduced number of GFAP-immunopositive astrocytes and Iba1-immunopositive microglia in the brain regions of BDL rats. Further, a significant decline was observed in cognitive functions in BDL rats assessed using Morris water maze and novel object recognition tests. Expression of pro and mature form of brain derived neurotrophic factor (BDNF) and its upstream transcription element showed significant reduction in brain of BDL rats. Taken together, the results of the present study suggest that systemic inflammation and reduced expression of BDNF and its upstream transcription factor plays a key role in cognitive decline in HE.
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Affiliation(s)
- Saurabh Dhanda
- Department of Biochemistry, Basic Medical Sciences Block-II, Sector-25, Panjab University, Chandigarh 160014, India
| | - Smriti Gupta
- Department of Biochemistry, Basic Medical Sciences Block-II, Sector-25, Panjab University, Chandigarh 160014, India
| | - Avishek Halder
- Department of Biochemistry, Basic Medical Sciences Block-II, Sector-25, Panjab University, Chandigarh 160014, India
| | - Aditya Sunkaria
- Department of Biochemistry, Basic Medical Sciences Block-II, Sector-25, Panjab University, Chandigarh 160014, India
| | - Rajat Sandhir
- Department of Biochemistry, Basic Medical Sciences Block-II, Sector-25, Panjab University, Chandigarh 160014, India.
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McMillin M, Grant S, Frampton G, Petrescu AD, Kain J, Williams E, Haines R, Canady L, DeMorrow S. FXR-Mediated Cortical Cholesterol Accumulation Contributes to the Pathogenesis of Type A Hepatic Encephalopathy. Cell Mol Gastroenterol Hepatol 2018; 6:47-63. [PMID: 29928671 PMCID: PMC6008252 DOI: 10.1016/j.jcmgh.2018.02.008] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/01/2018] [Accepted: 02/26/2018] [Indexed: 12/13/2022]
Abstract
BACKGROUND & AIMS Hepatic encephalopathy is a serious neurologic complication of acute and chronic liver diseases. We previously showed that aberrant bile acid signaling contributes to the development of hepatic encephalopathy via farnesoid X receptor (FXR)-mediated mechanisms in neurons. In the brain, a novel alternative bile acid synthesis pathway, catalyzed by cytochrome p450 46A1 (Cyp46A1), is the primary mechanism by which the brain regulates cholesterol homeostasis. The aim of this study was to determine if FXR activation in the brain altered cholesterol homeostasis during hepatic encephalopathy. METHODS Cyp7A1-/- mice or C57Bl/6 mice pretreated with central infusion of FXR vivo morpholino, 2-hydroxypropyl-β-cyclodextrin, or fed a cholestyramine-supplemented diet were injected with azoxymethane (AOM). Cognitive and neuromuscular impairment as well as liver damage and expression of Cyp46A1 were assessed using standard techniques. The subsequent cholesterol content in the frontal cortex was measured using commercially available kits and by Filipin III and Nile Red staining. RESULTS There was an increase in membrane-bound and intracellular cholesterol in the cortex of mice treated with AOM that was associated with decreased Cyp46A1 expression. Strategies to inhibit FXR signaling prevented the down-regulation of Cyp46A1 and the accumulation of cholesterol. Treatment of mice with 2-hydroxypropyl-β-cyclodextrin attenuated the AOM-induced cholesterol accumulation in the brain and the cognitive and neuromuscular deficits without altering the underlying liver pathology. CONCLUSIONS During hepatic encephalopathy, FXR signaling increases brain cholesterol and contributes to neurologic decline. Targeting cholesterol accumulation in the brain may be a possible therapeutic target for the management of hepatic encephalopathy.
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Key Words
- 2-HβC, 2-hypdroxypropyl-β-cyclodextrin
- AOM, azoxymethane
- Acute Liver Failure
- Azoxymethane
- CYP46A1, cytochrome p450 46A1
- CYP7A1, cytochrome p450 7A1
- Cytochrome p450 46A1
- FXR, farnesoid X receptor
- Farnesoid X Receptor
- GAPDH, glyceraldehyde-3-phosphate dehydrogenase
- PBS, phosphate-buffered saline
- PFA, paraformaldehyde
- RT-PCR, reverse-transcription polymerase chain reaction
- WT, wild-type
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Affiliation(s)
- Matthew McMillin
- Central Texas Veterans Healthcare System, Temple, Texas,Department of Medical Physiology, Texas A&M College of Medicine, Temple, Texas
| | - Stephanie Grant
- Central Texas Veterans Healthcare System, Temple, Texas,Department of Medical Physiology, Texas A&M College of Medicine, Temple, Texas
| | - Gabriel Frampton
- Central Texas Veterans Healthcare System, Temple, Texas,Department of Medical Physiology, Texas A&M College of Medicine, Temple, Texas
| | - Anca D. Petrescu
- Central Texas Veterans Healthcare System, Temple, Texas,Department of Medical Physiology, Texas A&M College of Medicine, Temple, Texas
| | - Jessica Kain
- Central Texas Veterans Healthcare System, Temple, Texas,Department of Medical Physiology, Texas A&M College of Medicine, Temple, Texas
| | - Elaina Williams
- Central Texas Veterans Healthcare System, Temple, Texas,Department of Medical Physiology, Texas A&M College of Medicine, Temple, Texas
| | - Rebecca Haines
- Department of Medical Physiology, Texas A&M College of Medicine, Temple, Texas
| | - Lauren Canady
- Department of Medical Physiology, Texas A&M College of Medicine, Temple, Texas
| | - Sharon DeMorrow
- Central Texas Veterans Healthcare System, Temple, Texas,Department of Medical Physiology, Texas A&M College of Medicine, Temple, Texas,Correspondence Address correspondence to: Sharon DeMorrow, PhD, Department of Medical Physiology, Texas A&M Health Science Center, Central Texas Veterans Health Care System, Building 205, 1901 South 1st Street, Temple, Texas 76504. fax: (254) 743-0378.
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25
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Onoda A, Takeda K, Umezawa M. Pretreatment with N-acetyl cysteine suppresses chronic reactive astrogliosis following maternal nanoparticle exposure during gestational period. Nanotoxicology 2017; 11:1012-1025. [PMID: 29046125 DOI: 10.1080/17435390.2017.1388864] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Early pregnant employees are potentially and unintendedly exposed to industrial chemicals including nanoparticles. Developmental toxicity of nanoparticle exposure has been concerned because exposure to fine particle including carbon black nanoparticle (CB-NP) during the brain developmental stage enhances the risk of brain disorders. Maternal CB-NP exposure dose-dependently induces astrogliosis, which is an abnormal increase in the reactive astrocytes with glial fibrillary acidic protein (GFAP) and aquaporin-4 overexpression due to the destruction of nearby neurons and blood vessels. The present study aimed to investigate protective effects of antioxidants on the histopathological denaturation with astrogliosis following maternal CB-NP exposure in offspring mice, thereby to evaluate the role of oxidative stress on the developmental toxicity. Pregnant ICR mice were treated with CB-NP by intranasal instillation on gestational days 5 and 9. N-acetyl cysteine (NAC) or ascorbic acid was intraperitoneally administered to the pregnant mice 1 h prior to CB-NP instillation. The brains were collected from 6- to 12-week-old offspring mice and analyzed using western blotting and immunohistochemistry. NAC suppressed GFAP overexpression in 6- and 12-week-old offspring mice following maternal CB-NP exposure. However, NAC did not suppress aquaporin-4 overexpression following maternal CB-NP exposure. Ascorbic acid did not suppress, but rather slightly and significantly enhanced the expression of GFAP and aquaporin-4. These results indicate that astrogliosis by maternal CB-NP exposure is partially prevented by NAC pretreatment. Oxidative stress is a possible key factor of developmental neurotoxicity of maternal NP exposure. This study will contribute to elucidating the mechanisms underlying the effects of developmental neurotoxicity of NPs.
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Affiliation(s)
- Atsuto Onoda
- a Department of Hygienic Chemistry, Graduate School of Pharmaceutical Sciences , Tokyo University of Science , Noda , Chiba , Japan.,b The Center for Environmental Health Science for the Next Generation, Research Institute for Science and Technology , Organization for Research Advancement, Tokyo University of Science , Noda , Chiba , Japan.,c Research Fellow of Japan Society for the Promotion of Science , Chiyoda-ku , Tokyo , Japan
| | - Ken Takeda
- b The Center for Environmental Health Science for the Next Generation, Research Institute for Science and Technology , Organization for Research Advancement, Tokyo University of Science , Noda , Chiba , Japan
| | - Masakazu Umezawa
- b The Center for Environmental Health Science for the Next Generation, Research Institute for Science and Technology , Organization for Research Advancement, Tokyo University of Science , Noda , Chiba , Japan.,d Department of Materials Science and Technology, Faculty of Industrial Science and Technology , Tokyo University of Science , Katsushika , Tokyo , Japan
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Cerebral Hemodynamics and Cognitive Function in Cirrhotic Patients with Hepatic Encephalopathy. Gastroenterol Res Pract 2016; 2016:8485032. [PMID: 28096811 PMCID: PMC5209626 DOI: 10.1155/2016/8485032] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/31/2016] [Revised: 10/23/2016] [Accepted: 11/17/2016] [Indexed: 02/08/2023] Open
Abstract
Aims. To investigate cerebral hemodynamics in cirrhotic patients with HE and to observe effects of treatment in cerebral hemodynamics and correlations among ammonia, cerebral hemodynamics, and cognitive function. Methods. There were four groups: healthy controls (group 1), cirrhosis without HE (group 2), cirrhosis with MHE (group 3), and cirrhosis with OHE (group 4). Ammonia and cerebral hemodynamics (by TCD) were assessed. Patients in group 3 were subsequently randomized to two subgroups: the control (group A) and the treated (group B, treated with lactulose for two months), and they were retested for ammonia and TCD after treatment. Results. Ammonia, Vm, Vd, PI, and RI were statistically different before treatment, and ammonia, PI, and RI levels paralleled the severity of HE (P < 0.05). In group B, Vd increased and ammonia, PI, and RI declined following treatment (P < 0.05), while there were no differences in group A (P > 0.05). Correlations were found between ammonia and Vd, PI, RI, NCT-A, and DST and also found between Vd, PI, RI, and NCT-A and DST (P < 0.05). Conclusions. This study revealed that cerebral hemodynamics were related to the severity of HE and cerebral autoregulation was impaired. There were tight correlations among ammonia, cerebral hemodynamics, and cognitive function, and, following treatment, cerebral hemodynamics improved.
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Patel VC, White H, Støy S, Bajaj JS, Shawcross DL. Clinical science workshop: targeting the gut-liver-brain axis. Metab Brain Dis 2016; 31:1327-1337. [PMID: 26446022 DOI: 10.1007/s11011-015-9743-4] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/04/2015] [Accepted: 10/02/2015] [Indexed: 02/08/2023]
Abstract
A clinical science workshop was held at the ISHEN meeting in London on Friday 11th September 2014 with the aim of thrashing out how we might translate what we know about the central role of the gut-liver-brain axis into targets which we can use in the treatment of hepatic encephalopathy (HE). This review summarises the integral role that inter-organ ammonia metabolism plays in the pathogenesis of HE with specific discussion of the roles that the small and large intestine, liver, brain, kidney and muscle assume in ammonia and glutamine metabolism. Most recently, the salivary and gut microbiome have been shown to underpin the pathophysiological changes which culminate in HE and patients with advanced cirrhosis present with enteric dysbiosis with small bowel bacterial overgrowth and translocation of bacteria and their products across a leaky gut epithelial barrier. Resident macrophages within the liver are able to sense bacterial degradation products initiating a pro-inflammatory response within the hepatic parenchyma and release of cytokines such as tumour necrosis factor alpha (TNF-α) and interleukin-8 into the systemic circulation. The endotoxemia and systemic inflammatory response that are generated predispose both to the development of infection as well as the manifestation of covert and overt HE. Co-morbidities such as diabetes and insulin resistance, which commonly accompany cirrhosis, may promote slow gut transit, promote bacterial overgrowth and increase glutaminase activity and may need to be acknowledged in HE risk stratification assessments and therapeutic regimens. Therapies are discussed which target ammonia production, utilisation or excretion at an individual organ level, or which reduce systemic inflammation and endotoxemia which are known to exacerbate the cerebral effects of ammonia in HE. The ideal therapeutic strategy would be to use an agent that can reduce hyperammonemia and reduce systemic inflammation or perhaps to adopt a combination of therapies that can address both.
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Affiliation(s)
- Vishal C Patel
- Institute of Liver Studies, King's College London School of Medicine, King's College Hospital, King's College Hospital, Denmark Hill, London, SE5 9RS, UK
| | - Helen White
- Institute of Liver Studies, King's College London School of Medicine, King's College Hospital, King's College Hospital, Denmark Hill, London, SE5 9RS, UK
| | - Sidsel Støy
- Institute of Liver Studies, King's College London School of Medicine, King's College Hospital, King's College Hospital, Denmark Hill, London, SE5 9RS, UK
| | - Jasmohan S Bajaj
- McGuire VA Medical Center, Virginia Commonwealth University, Richmond, VA, USA
| | - Debbie L Shawcross
- Institute of Liver Studies, King's College London School of Medicine, King's College Hospital, King's College Hospital, Denmark Hill, London, SE5 9RS, UK.
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28
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Butterworth RF. The concept of "the inflamed brain" in acute liver failure: mechanisms and new therapeutic opportunities. Metab Brain Dis 2016; 31:1283-1287. [PMID: 26481639 DOI: 10.1007/s11011-015-9747-0] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/07/2015] [Accepted: 10/05/2015] [Indexed: 12/29/2022]
Abstract
The presence and severity of a systemic inflammatory response is a major predictor of brain edema and encephalopathy in acute liver failure (ALF) and polymorphisms of the gene coding for the proinflammatory cytokine TNF-alpha are known to influence the clinical outcome in ALF. Recent reports provide robust evidence for a role of neuroinflammation(inflammation of the brain per se) in ALF with the cardinal features of neuroinflammation including activation of microglial cells and increased production in situ of pro-inflammatory cytokines such as TNF-alpha and interleukins IL-1beta and IL-6. Multiple liver-brain signalling pathways have been proposed to explain the phenomenon of neuroinflammation in liver failure and these include direct effects of systemically-derived cytokines, recruitment of monocytes relating to microglial activation as well as effects of liver failure-derived toxins and altered permeability of the blood-brain barrier. Synergistic mechanisms involving ammonia and cytokines have been proposed. Currently-available strategies aimed at lowering of blood ammonia such as lactulose, probiotics and rifaximin have the potential to dampen systemic inflammation as does the anti-oxidant N-acetyl cysteine, mild hypothermia and albumin dialysis. Experimental studies demonstrate that deletion of genes coding for TNF-alpha or IL-1 leads to attenuation of the CNS consequences of ALF and administration of the TNF-alpha receptor antagonist etanercept has comparable beneficial effects in experimental ALF. Together, these findings confirm a major role for central neuroinflammatory mechanisms in general and mechanisms involving TNF-alpha in particular in the pathogenesis of the cerebral consequences of ALF and open the door to novel therapeutic interventions in this often fatal disorder.
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29
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Butterworth RF. Pathogenesis of hepatic encephalopathy in cirrhosis: the concept of synergism revisited. Metab Brain Dis 2016; 31:1211-1215. [PMID: 26521983 DOI: 10.1007/s11011-015-9746-1] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/07/2015] [Accepted: 10/05/2015] [Indexed: 01/31/2023]
Abstract
The concept of synergistic mechanisms as the pathophysiologic basis of hepatic encephalopathy started with the pioneering work of Les Zieve in Minneapolis some 60 years ago where synergistic actions of the liver-derived toxins ammonia, methanethiol, and octanoic acid were described. More recently, synergistic actions of ammonia and manganese, a toxic metal that is normally eliminated via the hepatobiliary route and shown to accumulate in brain in liver failure, on the glutamatergic neurotransmitter system were described. The current upsurge of interest in brain inflammation (neuroinflammation) in relation to the CNS complications of liver failure has added a third dimension to the synergy debate. The combined actions of ammonia, manganese and pro-inflammatory cytokines in brain in liver failure result in oxidative/nitrosative stress resulting from activation of glutamate (NMDA) receptors and consequent nitration of key brain proteins. One such protein, glutamine synthetase, the sole enzyme responsible for brain ammonia removal is nitrated and inactivated in brain in liver failure. Consequently, brain ammonia levels increase disproportionately resulting in alterations of brain excitability, impaired brain energy metabolism, encephalopathy and brain swelling. Experimental therapeutic approaches for which proof-of-principle has been established include the NMDA receptor antagonist memantine, N-acetyl cysteine (recently shown to have antioxidant properties at both hepatic and cerebral levels) and probiotics.
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Affiliation(s)
- Roger F Butterworth
- Department of Medicine, University of Montreal, 45143 Cabot Trail, Englishtown, NS, B0C 1H0, Canada.
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30
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Karababa A, Groos-Sahr K, Albrecht U, Keitel V, Shafigullina A, Görg B, Häussinger D. Ammonia Attenuates LPS-Induced Upregulation of Pro-Inflammatory Cytokine mRNA in Co-Cultured Astrocytes and Microglia. Neurochem Res 2016; 42:737-749. [PMID: 27655254 DOI: 10.1007/s11064-016-2060-4] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2016] [Revised: 09/03/2016] [Accepted: 09/08/2016] [Indexed: 12/19/2022]
Abstract
Hepatic encephalopathy (HE) is associated with cerebral microglia activation. Ammonia, a major toxin of HE, activates microglia in vitro but does not trigger pro-inflammatory cytokine synthesis. In the present study we analysed effects of ammonia on lipopolysaccharide (LPS)-induced upregulation of microglia activation and cytokine mRNA as well as on cytokine secretion in mono-cultured microglia and co-cultured astrocytes and microglia. In mono-cultured microglia LPS (100 ng/ml, 18 h) strongly elevated mRNA levels of the microglia activation marker CD14 and the pro-inflammatory cytokines IL-1α/β, IL-6 and TNF-α. NH4Cl (5 mmol/l) had no effect on LPS-induced upregulation of CD14, IL-1α/β and IL-6 mRNA but enhanced LPS-induced upregulation of TNF-α mRNA in mono-cultured microglia. In co-cultured astrocytes and microglia, however, LPS-induced upregulation of IL-1α/β, TNF-α, IL-6, CD14 but not of IL-10, IL-12A/B or TGFβ1-3 mRNA was attenuated by NH4Cl. LPS-induced upregulation of IL-1α/β, IL-6 and TNF-α was also diminished by the TGR5-ligands allopregnanolone and taurolithocholic acid in mono-cultured microglia. NH4Cl also attenuated LPS-induced release of MCP-1, IL-6 and IL-10 in mono-cultured microglia. mRNA level of surrogate marker for microglia activation (CD14) and for the anti-inflammatory M2-type microglia (CD163, CXCL1, CXCL2) were also elevated in post mortem brain tissue taken from the fusiforme gyrus of patients with liver cirrhosis and HE. The findings suggest that ammonia attenuates LPS-induced microglia reactivity in an astrocyte-dependent way. One may speculate that these anti-inflammatory effects of ammonia may be triggered by neurosteroids derived from astrocytes and may account for absence of microglia reactivity in cerebral cortex of cirrhotic patients with HE.
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Affiliation(s)
- Ayse Karababa
- Clinic for Gastroenterology, Hepatology and Infectious Diseases, Heinrich-Heine-University, Moorenstrasse 5, D-40225, Düsseldorf, Germany
| | - Katerina Groos-Sahr
- Clinic for Gastroenterology, Hepatology and Infectious Diseases, Heinrich-Heine-University, Moorenstrasse 5, D-40225, Düsseldorf, Germany
| | - Ute Albrecht
- Clinic for Gastroenterology, Hepatology and Infectious Diseases, Heinrich-Heine-University, Moorenstrasse 5, D-40225, Düsseldorf, Germany
| | - Verena Keitel
- Clinic for Gastroenterology, Hepatology and Infectious Diseases, Heinrich-Heine-University, Moorenstrasse 5, D-40225, Düsseldorf, Germany
| | - Aygul Shafigullina
- Clinic for Gastroenterology, Hepatology and Infectious Diseases, Heinrich-Heine-University, Moorenstrasse 5, D-40225, Düsseldorf, Germany
| | - Boris Görg
- Clinic for Gastroenterology, Hepatology and Infectious Diseases, Heinrich-Heine-University, Moorenstrasse 5, D-40225, Düsseldorf, Germany
| | - Dieter Häussinger
- Clinic for Gastroenterology, Hepatology and Infectious Diseases, Heinrich-Heine-University, Moorenstrasse 5, D-40225, Düsseldorf, Germany.
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Yang N, Liu H, Jiang Y, Zheng J, Li DM, Ji C, Liu YY, Zuo PP. Lactulose enhances neuroplasticity to improve cognitive function in early hepatic encephalopathy. Neural Regen Res 2015; 10:1457-62. [PMID: 26604907 PMCID: PMC4625512 DOI: 10.4103/1673-5374.165516] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Lactulose is known to improve cognitive function in patients with early hepatic encephalopathy; however, the underlying mechanism remains poorly understood. In the present study, we investigated the behavioral and neurochemical effects of lactulose in a rat model of early hepatic encephalopathy induced by carbon tetrachloride. Immunohistochemistry showed that lactulose treatment promoted neurogenesis and increased the number of neurons and astrocytes in the hippocampus. Moreover, lactulose-treated rats showed shorter escape latencies than model rats in the Morris water maze, indicating that lactulose improved the cognitive impairments caused by hepatic encephalopathy. The present findings suggest that lactulose effectively improves cognitive function by enhancing neuroplasticity in a rat model of early hepatic encephalopathy.
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Affiliation(s)
- Nan Yang
- Department of Pharmacology, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences & School of Basic Medicine, Peking Union Medical College, Beijing, China
| | - He Liu
- Department of Pharmacology, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences & School of Basic Medicine, Peking Union Medical College, Beijing, China
| | - Yao Jiang
- Department of Pharmacology, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences & School of Basic Medicine, Peking Union Medical College, Beijing, China
| | - Ji Zheng
- Department of Pharmacology, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences & School of Basic Medicine, Peking Union Medical College, Beijing, China
| | - Dong-Mei Li
- Department of Pharmacology, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences & School of Basic Medicine, Peking Union Medical College, Beijing, China
| | - Chao Ji
- Department of Pharmacology, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences & School of Basic Medicine, Peking Union Medical College, Beijing, China
| | - Yan-Yong Liu
- Department of Pharmacology, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences & School of Basic Medicine, Peking Union Medical College, Beijing, China
| | - Ping-Ping Zuo
- Department of Pharmacology, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences & School of Basic Medicine, Peking Union Medical College, Beijing, China
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Main target of minimal hepatic encephalopathy: Morphophysiological, inflammatory and metabolic view. Physiol Behav 2015; 149:247-54. [PMID: 26079568 DOI: 10.1016/j.physbeh.2015.06.019] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2014] [Revised: 03/25/2015] [Accepted: 06/10/2015] [Indexed: 12/12/2022]
Abstract
Although often not considered clinically relevant and, therefore, not diagnosed or treated, minimal hepatic encephalopathy (MHE) has been shown to affect daily functioning, quality of life, driving and overall mortality. To discover early impairments involved in MHE, we studied one of its precipitating factors, portal hypertension. Rats were trained on a stimulus-response task using the Morris water maze. Two groups of animals were used: a SHAM (sham-operated) group (n= 13) and a portal hypertension (PH) group (n= 13). The triple portal vein ligation method was used to create an animal model of an early developmental phase of HE. Brain metabolic activity was studied with cytochrome c-oxidase histochemistry (C.O.). Neuronal nuclear volume was assessed by nucleator probe; the number of glial fibrillary acidic protein-immunoreactive astrocytes (GFAP-IR) and proinflammatory mediators was measured. The results revealed that the PH group was not able to reach the behavioural criterion, in contrast to the SHAM group. The metabolic brain consumption revealed decreased C.O. activity in the ventral striatum. The PH group showed lower density of GFAP-IR and an increase in the tumour necrotic factor-α (TNF-α). The PH group showed decreased neuronal nuclear volume in the dorsal striatum. On the contrary, increased neuronal nuclear volume was found in the ventral striatum. For the first time, a relationship has been established between inflammation, astrocytic and neural damage, and brain metabolic impairment in a model of MHE. Disruption of the striatum and related structures was highlighted as the main target in early stages of HE. Finally, a simple task was presented to assess the subtle impairments found in the clinic, which could provide fresh insights into the development of new tools for the assessment of MHE.
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Jayakumar AR, Rama Rao KV, Norenberg MD. Neuroinflammation in hepatic encephalopathy: mechanistic aspects. J Clin Exp Hepatol 2015; 5:S21-8. [PMID: 26041953 PMCID: PMC4442850 DOI: 10.1016/j.jceh.2014.07.006] [Citation(s) in RCA: 67] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/12/2014] [Accepted: 07/08/2014] [Indexed: 12/12/2022] Open
Abstract
Hepatic encephalopathy (HE) is a major neurological complication of severe liver disease that presents in acute and chronic forms. While elevated brain ammonia level is known to be a major etiological factor in this disorder, recent studies have shown a significant role of neuroinflammation in the pathogenesis of both acute and chronic HE. This review summarizes the involvement of ammonia in the activation of microglia, as well as the means by which ammonia triggers inflammatory responses in these cells. Additionally, the role of ammonia in stimulating inflammatory events in brain endothelial cells (ECs), likely through the activation of the toll-like receptor-4 and the associated production of cytokines, as well as the stimulation of various inflammatory factors in ECs and in astrocytes, are discussed. This review also summarizes the inflammatory mechanisms by which activation of ECs and microglia impact on astrocytes leading to their dysfunction, ultimately contributing to astrocyte swelling/brain edema in acute HE. The role of microglial activation and its contribution to the progression of neurobehavioral abnormalities in chronic HE are also briefly presented. We posit that a better understanding of the inflammatory events associated with acute and chronic HE will uncover novel therapeutic targets useful in the treatment of patients afflicted with HE.
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Key Words
- AHE, acute hepatic encephalopathy
- ALF, acute liver failure
- BBB, blood–brain barrier
- BDL, bile duct ligation
- COX2, cyclooxygenase-2
- ECs, endothelial cells
- FHF, fulminant hepatic failure
- HE, hepatic encephalopathy
- HO, hemoxygenase
- IL, interleukin
- LPS, lipopolysaccharide
- MAPK, mitogen-activated protein kinases
- NF-κB, nuclear factor-kappaB
- NOX, NADPH oxidase
- ONS, oxidative/nitrative stress
- PLA2, phospholipase-A2
- RONS, reactive oxygen and nitrogen species
- TLR, Toll-like receptor
- TNF-α, tumor necrosis factor-alpha
- Tg, transgenic
- WT, wild type
- ammonia
- cNOS, constitutive nitric oxide synthase
- hepatic encephalopathy
- iNOS, inducible nitric oxide synthase
- neuroinflammation
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Affiliation(s)
| | | | - Michael D. Norenberg
- Laboratory of Neuropathology, Veterans Affairs Medical Center, Miami, FL, USA,Department of Pathology, University of Miami School of Medicine, Miami, FL, USA,Biochemistry & Molecular Biology, University of Miami School of Medicine, Miami, FL, USA,Address for correspondence: Michael D. Norenberg, Department of Pathology (D-33), PO Box 016960, University of Miami School of Medicine, Miami, FL 33101. Tel.: +1 305 575 7000x4018.
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Karababa A, Görg B, Schliess F, Häussinger D. O-GlcNAcylation as a novel ammonia-induced posttranslational protein modification in cultured rat astrocytes. Metab Brain Dis 2014; 29:975-82. [PMID: 24292976 DOI: 10.1007/s11011-013-9454-7] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/30/2013] [Accepted: 11/12/2013] [Indexed: 12/12/2022]
Abstract
Hepatic encephalopathy (HE) is a clinical manifestation of a low grade cerebral edema with a mutual interrelationship between osmotic- and oxidative stress. This leads to RNA oxidation and posttranslational protein modifications such as protein tyrosine nitration with pathophysiological relevance. Here, we report on O-GlcNAcylation as another ammonia-induced posttranslational protein modification in cultured rat astrocytes. NH4Cl induced O-GlcNAcylation of distinct proteins (25-250 kDa) in astrocytes in a dose- and time-dependent manner. Exposure of astrocytes to NH4Cl (5 mmol/l) for 48 h and 72 h significantly increased protein O-GlcNAcylation by about 2-fold and 4-fold, respectively. NH4Cl at a concentration of 1 mmol/l was sufficient to double protein O-GlcNAcylation in astrocytes after 72 h as compared to untreated controls. Ammonia-induced protein O-GlcNAcylation was sensitive towards glutamine-synthetase inhibition by methionine sulfoximine (MSO), but was not induced by hypoosmolarity (205 mosmol/l) or CH3NH3Cl (5 mmol/l). Increased protein O-GlcNAcylation in NH4Cl (5 mmol/l, 48 h)-treated astrocytes was fully reversible within 24 h after withdrawal of NH4Cl from culture medium. Amongst the proteins which are O-GlcNAcylated in response to ammonia, GAPDH was identified. It is concluded that ammonia induces reversible protein O-GlcNAcylation in astrocytes that depends on glutamine synthesis but not on astrocyte swelling per se or ammonia-induced pH-changes. In view of the complex involvement of O-GlcNAcylation in cell regulation, such as energy metabolism, apoptosis and circadian rhythmicity and in pathologies, such as neurodegenerative diseases, O-GlcNAcylation might contribute to the pathophysiology of hepatic encephalopathy.
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Affiliation(s)
- Ayşe Karababa
- Clinic for Gastroenterology, Hepatology and Infectiology, Heinrich-Heine University, 40225, Düsseldorf, Germany
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35
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Li J, Yu Z, Wang Q, Li D, Jia B, Zhou Y, Ye Y, Shen S, Wang Y, Li S, Bai L, Kan Q. Hyperammonia induces specific liver injury through an intrinsic Ca2+-independent apoptosis pathway. BMC Gastroenterol 2014; 14:151. [PMID: 25145683 PMCID: PMC4236522 DOI: 10.1186/1471-230x-14-151] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/20/2014] [Accepted: 08/15/2014] [Indexed: 02/06/2023] Open
Abstract
Background Numerous pathological processes that affect liver function in patients with liver failure have been identified. Among them, hyperammonia is one of the most common phenomena.The purpose of this study was to determine whether hyperammonia could induced specific liver injury. Methods Hyperammonemic cells were established using NH4Cl. The cells were assessed by MTT, ELISA, and flow cytometric analyses. The expression levels of selected genes and proteins were confirmed by quantitative RT-PCR and western blot analyses. Results The effects of 20 mM NH4Cl pretreatment on the cell proliferation and apoptosis of primary hepatocytes and other cells were performed by MTT assays and flow cytometric analyses. Significant increasing in cytotoxicity and apoptosis were only observed in hepatocytes. The cell damage was reduced after adding BAPTA-AM but unchanged after adding EGTA. The expression levels of caspase-3, cytochrome C, calmodulin, and inducible nitric oxide synthase were increased and that of bcl-2 was reduced. The Na+-K+-ATPase activities in hyperammonia liver cells was no signiaficant difference compaired with the control group, but was decreased in astrocytes. NH4Cl pretreatment of primary hepatocytes promoted the activation of mitochondrial permeability transition pores and the mitochondria swelled irregularly. Conclusions Hyperammonia induces specific liver injury through an intrinsic Ca2+-independent apoptosis pathway.
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Affiliation(s)
| | | | | | | | | | | | | | | | | | | | | | - Quancheng Kan
- Department of Gastroenterology, The First Affiliated Hospital of Zhengzhou University, Zhengzhou, China.
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Thumburu KK, Dhiman RK, Vasishta RK, Chakraborti A, Butterworth RF, Beauchesne E, Desjardins P, Goyal S, Sharma N, Duseja A, Chawla Y. Expression of astrocytic genes coding for proteins implicated in neural excitation and brain edema is altered after acute liver failure. J Neurochem 2013; 128:617-27. [PMID: 24164438 DOI: 10.1111/jnc.12511] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2013] [Revised: 09/14/2013] [Accepted: 10/11/2013] [Indexed: 01/01/2023]
Abstract
In vitro and in vivo studies have suggested that reduced astrocytic uptake of neuronally released glutamate, alterations in expression of glial fibrillary acidic protein (GFAP) and aquaporin-4 (AQP-4) contribute to brain edema in acute liver failure (ALF). However, there is no evidence to date to suggest that these alterations occur in patients with ALF. We analyzed the mRNA expression of excitatory amino acid transporters (EAAT-1, EAAT-2), GFAP, and AQP-4 in the cerebral cortex obtained at autopsy from eight patients with ALF and from seven patients with no evidence of hepatic or neurological disorders by real-time PCR, and protein expression was assessed using immunoblotting and immunohistochemistry. We demonstrated a significant decrease in GFAP mRNA and protein levels in ALF patients compared to controls. While the loss of EAAT-2 protein in ALF samples was post-translational in nature, EAAT-1 protein remained within normal limits. Immunohistochemistry confirmed that, in all cases, the losses of EAAT-2 and GFAP were uniquely astrocytic in their localization. AQP-4 mRNA expression was significantly increased and its immunohistochemistry demonstrated increased AQP-4 immunoreactivity in the glial end-feet process surrounding the microvessels. These findings provide evidence of selective alterations in the expression of genes coding for key astrocytic proteins implicated in central nervous system (CNS) excitability and brain edema in human ALF. We investigated the gene expression of astrocytic proteins involved in astrocyte swelling causing brain edema in autopsied brain tissues of patients with acute liver failure. This study demonstrated loss of GFAP expression and up-regulation of AQP-4 protein expression leading to cerebral edema, and loss of EAAT-2 expression implicated in excitatory neurotransmission. These findings may provide new drug targets against CNS complications of acute liver failure.
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Affiliation(s)
- Kiran K Thumburu
- Department of Hepatology, Postgraduate Institute of Medical Education & Research, Chandigarh, India
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Jarius S, Wildemann B. Aquaporin-4 antibodies, CNS acidosis and neuromyelitis optica: a potential link. Med Hypotheses 2013; 81:1090-5. [PMID: 24182872 DOI: 10.1016/j.mehy.2013.10.011] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2013] [Revised: 09/17/2013] [Accepted: 10/09/2013] [Indexed: 12/12/2022]
Abstract
BACKGROUND Neuromyelitis optica (NMO, Devic's syndrome) is a severely disabling disorder of the central nervous system characterized by optic neuritis and longitudinally extensive myelitis. In around 80% of cases, NMO is caused by autoantibodies to astrocytic aquaporin-4 (AQP4), the most abundant water channel in the CNS. Acute NMO attacks are frequently accompanied by elevated levels of lactate in the cerebrospinal fluid (CSF). As a strongly dissociated anion (pK'=3.7) directly changing the strong ion difference, lactate causes a reduction in the dependent anion [HCO3-] and a rise in [H+], resulting in "metabolic" acidosis in the CSF. CSF acidosis also develops during respiratory failure due to brainstem or high cervical spinal cord lesions, the most common cause of death in NMO. However, lactic acid and more generally, a decrease in pH, has been shown to increase the membrane expression of AQP4 in astrocytes. An increase in AQP4 membrane expression during acute NMO attacks could potentially enhance the complement-mediated humoral immune reaction against AQP4-expressing astrocytes characteristic for NMO and, thus, result in more severe astrocytic damage. Moreover, lactate and acidosis have been shown to cause astrocytic swelling and to affect astrocytic viability, potentially rendering astrocytes more susceptible to AQP4-Ab-mediated damage. Finally, increased AQP4 expression could be an independent risk factor in NMO and other forms of CNS inflammation, as indicated by the finding of grossly attenuated experimental autoimmune encephalomyelitis in AQP4-null mice. Therefore, we hypothesize that CSF acidosis might play a role in the pathophysiology of AQP4-Ab-positive NMO and that alterations in CSF pH might possibly influence the outcome of acute attacks in this condition. In addition, we discuss potential clinical implications and make proposals on how to test the hypothesis. Finally, other factors that influence astrocytic AQP4 membrane expression and might play a role in NMO are discussed.
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Affiliation(s)
- S Jarius
- Division of Molecular Neuroimmunology, Department of Neurology, University of Heidelberg, Germany.
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Abstract
Systemic inflammation is common in liver failure and its acquisition is a predictor of hepatic encephalopathy severity. New studies provide convincing evidence for a role of neuroinflammation (inflammation of the brain per se) in liver failure; this evidence includes activation of microglia, together with increased synthesis in situ of the proinflammatory cytokines TNF, IL-1β and IL-6. Liver-brain signalling mechanisms in liver failure include: direct effects of systemic proinflammatory molecules, recruitment of monocytes after microglial activation, brain accumulation of ammonia, lactate and manganese, and altered permeability of the blood-brain barrier. Ammonia and cytokines might act synergistically. Existing strategies to reduce ammonia levels (including lactulose, rifaximin and probiotics) have the potential to dampen systemic inflammation, as does albumin dialysis, mild hypothermia and N-acetylcysteine, the latter two agents acting at both peripheral and central sites. Minocycline, an agent with potent central anti-inflammatory properties, reduces neuroinflammation, brain oedema and encephalopathy in liver failure, as does the anti-TNF agent etanercept.
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Jayakumar M, Subramanian P. Chronotherapeutic influence of fisetin on ammonium chloride-induced hyperammonemic rats. BIOL RHYTHM RES 2013. [DOI: 10.1080/09291016.2012.730890] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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Bémeur C, Butterworth RF. Liver-brain proinflammatory signalling in acute liver failure: role in the pathogenesis of hepatic encephalopathy and brain edema. Metab Brain Dis 2013; 28:145-50. [PMID: 23212479 DOI: 10.1007/s11011-012-9361-3] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/30/2012] [Accepted: 11/05/2012] [Indexed: 12/12/2022]
Abstract
A robust neuroinflammatory response characterized by microglial activation and increased brain production of pro-inflammatory cytokines is common in acute liver failure (ALF). Mechanisms proposed to explain the neuroinflammatory response in ALF include direct effects of systemically-derived proinflammatory cytokines and the effects of brain lactate accumulation on pro-inflammatory cytokine release from activated microglia. Cell culture studies reveal a positive synergistic effect of ammonia and pro-inflammatory cytokines on the expression of proteins involved in glutamate homeostasis and in oxidative/nitrosative stress. Proinflammatory cytokines have the capacity to alter blood-brain barrier (BBB) integrity and preliminary studies suggest that the presence of infection in ALF results in rupture of the BBB and vasogenic brain edema. Treatments currently under investigation that are effective in prevention of encephalopathy and brain edema in ALF which are aimed at reduction of neuroinflammation in ALF include mild hypothermia, albumin dialysis systems, N-acetyl cysteine and the antibiotic minocycline with potent anti-inflammatory actions that are distinct from its anti-microbial properties.
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Affiliation(s)
- Chantal Bémeur
- Département de nutrition, Faculté de médecine, Université de Montréal, Montréal, QC, Canada
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41
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Wang QM, Yin XY, Duan ZJ, Guo SB, Sun XY. Role of the heme oxygenase/carbon monoxide pathway in the pathogenesis and prevention of hepatic encephalopathy. Mol Med Rep 2013; 8:67-74. [PMID: 23670786 DOI: 10.3892/mmr.2013.1472] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2013] [Accepted: 04/29/2013] [Indexed: 11/05/2022] Open
Abstract
Hepatic encephalopathy (HE) is a severe complication of liver cirrhosis and its pathogenesis has yet to be fully elucidated. Previous studies have demonstrated that heme oxygenase-1 (HO-1) is important in the induction of liver cirrhosis. The present study aimed to investigate the role of HO-1 in the pathogenesis of HE. Rats were divided into 5 treatment groups; sham, bile duct ligation (BDL), HE, zinc protoporphyrin (ZnPP) and cobalt protoporphyrin (CoPP). The levels of HO-1 were examined by western blotting and quantitative real-time PCR (qRT-PCR). Serum levels of carboxyhemoglobin (COHb), ammonia levels in the plasma and brain, brain water content and portal vein pressure (PVP) were also quantified. Aquaporin-4 expression levels were measured by immunohistochemistry and qRT-PCR. The results demonstrated that the levels of HO-1 in the brain and the serum levels of COHb were significantly increased in the HE group compared with the BDL group. Brain water content, PVP and ammonia levels in the plasma and brain were increased in the HE and CoPP groups; however, these were reduced following the treatment with ZnPP. The levels of AQP-4 expression and oxidative stress in the brain were reduced following treatment with ZnPP and increased following treatment with CoPP. In conclusion, following the inhibition of HO-1 expression, treatment with ZnPP improved HE due to reducing the expression levels of AQP-4 and oxidative stress. Therefore, ZnPP treatment may represent a novel therapeutic approach for HE.
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Affiliation(s)
- Qiu-Ming Wang
- Department of Gastroenterology, The First Affiliated Hospital of Dalian Medical University, Dalian, Liaoning 116011, PR China
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Bosoi CR, Rose CF. Brain edema in acute liver failure and chronic liver disease: similarities and differences. Neurochem Int 2013; 62:446-57. [PMID: 23376027 DOI: 10.1016/j.neuint.2013.01.015] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2012] [Revised: 01/11/2013] [Accepted: 01/16/2013] [Indexed: 12/12/2022]
Abstract
Hepatic encephalopathy (HE) is a complex neuropsychiatric syndrome that typically develops as a result of acute liver failure or chronic liver disease. Brain edema is a common feature associated with HE. In acute liver failure, brain edema contributes to an increase in intracranial pressure, which can fatally lead to brain stem herniation. In chronic liver disease, intracranial hypertension is rarely observed, even though brain edema may be present. This discrepancy in the development of intracranial hypertension in acute liver failure versus chronic liver disease suggests that brain edema plays a different role in relation to the onset of HE. Furthermore, the pathophysiological mechanisms involved in the development of brain edema in acute liver failure and chronic liver disease are dissimilar. This review explores the types of brain edema, the cells, and pathogenic factors involved in its development, while emphasizing the differences in acute liver failure versus chronic liver disease. The implications of brain edema developing as a neuropathological consequence of HE, or as a cause of HE, are also discussed.
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Affiliation(s)
- Cristina R Bosoi
- Neuroscience Research Unit, Hôpital Saint-Luc (CRCHUM), Université de Montréal, Québec, Canada
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Chastre A, Bélanger M, Beauchesne E, Nguyen BN, Desjardins P, Butterworth RF. Inflammatory cascades driven by tumor necrosis factor-alpha play a major role in the progression of acute liver failure and its neurological complications. PLoS One 2012; 7:e49670. [PMID: 23166746 PMCID: PMC3499491 DOI: 10.1371/journal.pone.0049670] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2012] [Accepted: 10/12/2012] [Indexed: 12/31/2022] Open
Abstract
BACKGROUND/AIMS Acute liver failure (ALF) due to ischemic or toxic liver injury is a clinical condition that results from massive loss of hepatocytes and may lead to hepatic encephalopathy (HE), a serious neuropsychiatric complication. Although increased expression of tumor necrosis factor-alpha (TNF-α) in liver, plasma and brain has been observed, conflicting results exist concerning its roles in drug-induced liver injury and on the progression of HE. The present study aimed to investigate the therapeutic value of etanercept, a TNF-α neutralizing molecule, on the progression of liver injury and HE in mice with ALF resulting from azoxymethane (AOM) hepatotoxicity. METHODS/PRINCIPAL FINDINGS Mice were administered saline or etanercept (10 mg/kg; i.p.) 30 minutes prior to, or up to 6 h after AOM. Etanercept-treated ALF mice were sacrificed in parallel with vehicle-treated comatose ALF mice and controls. AOM induced severe hepatic necrosis, leading to HE, and etanercept administered prior or up to 3 h after AOM significantly delayed the onset of coma stages of HE. Etanercept pretreatment attenuated AOM-induced liver injury, as assessed by histological examination, plasma ammonia and transaminase levels, and by hepatic glutathione content. Peripheral inflammation was significantly reduced by etanercept as shown by decreased plasma IL-6 (4.1-fold; p<0.001) and CD40L levels (3.7-fold; p<0.001) compared to saline-treated ALF mice. Etanercept also decreased IL-6 levels in brain (1.2-fold; p<0.05), attenuated microglial activation (assessed by OX-42 immunoreactivity), and increased brain glutathione concentrations. CONCLUSIONS These results indicate that systemic sequestration of TNF-α attenuates both peripheral and cerebral inflammation leading to delayed progression of liver disease and HE in mice with ALF due to toxic liver injury. These results suggest that etanercept may provide a novel therapeutic approach for the management of ALF patients awaiting liver transplantation.
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Affiliation(s)
- Anne Chastre
- Neuroscience Research Unit, Hôpital Saint-Luc, CRCHUM, Montreal, Canada
| | - Mireille Bélanger
- Neuroscience Research Unit, Hôpital Saint-Luc, CRCHUM, Montreal, Canada
| | | | - Bich N. Nguyen
- Département de pathologie, Hôpital Saint-Luc, CHUM, Montreal, Canada
| | - Paul Desjardins
- Neuroscience Research Unit, Hôpital Saint-Luc, CRCHUM, Montreal, Canada
| | - Roger F. Butterworth
- Neuroscience Research Unit, Hôpital Saint-Luc, CRCHUM, Montreal, Canada
- * E-mail:
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Bodega G, Suárez I, López-Fernández LA, García MI, Köber M, Penedo M, Luna M, Juárez S, Ciordia S, Oria M, Córdoba J, Fernández B. Ammonia induces aquaporin-4 rearrangement in the plasma membrane of cultured astrocytes. Neurochem Int 2012; 61:1314-24. [PMID: 23022607 DOI: 10.1016/j.neuint.2012.09.008] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2012] [Revised: 09/06/2012] [Accepted: 09/13/2012] [Indexed: 11/30/2022]
Abstract
Aquaporin-4 (AQP4) is a water channel protein mainly located in the astroglial plasma membrane, the precise function of which in the brain edema that accompanies hepatic encephalopathy (HE) is unclear. Since ammonia is the main pathogenic agent in HE, its effect on AQP4 expression and distribution in confluent primary astroglial cultures was examined via their exposure to ammonium chloride (1, 3 and 5 mM) for 5 and 10 days. Ammonia induced the general inhibition of AQP4 mRNA synthesis except in the 1 mM/5 day treatment. However, the AQP4 protein content measured was dependent on the method of analysis; an apparent increase was recorded in treated cells in in-cell Western assays, while an apparent reduction was seen with the classic Western blot method, perhaps due to differences in AQP4 aggregation. Ammonia might therefore induce the formation of insoluble AQP4 aggregates in the astroglial plasma membrane. The finding of AQP4 in the pellet of classic Western blot samples, plus data obtained via confocal microscopy, atomic force microscopy (using immunolabeled cells with gold nanoparticles) and scanning electron microscopy, all corroborate this hypothesis. The effect of ammonia on AQP4 seems not to be due to any osmotic effect; identical osmotic stress induced by glutamine and salt had no significant effect on the AQP4 content. AQP4 functional analysis (subjecting astrocytes to a hypo-osmotic medium and using flow cytometry to measure cell size) demonstrated a smaller water influx in ammonia-treated astrocytes suggesting that AQP4 aggregates are representative of an inactive status; however, more confirmatory studies are required to fully understand the functional status of AQP4 aggregates. The present results suggest that ammonia affects AQP4 expression and distribution, and that astrocytes change their expression of AQP4 mRNA as well as the aggregation status of the ensuing protein depending on the ammonia concentration and duration of exposure.
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Affiliation(s)
- Guillermo Bodega
- Departamento de Biología Celular y Genética, Facultad de Biología, Universidad de Alcalá, 28871 Alcalá de Henares, Madrid, Spain.
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Pasantes-Morales H, Vázquez-Juárez E. Transporters and channels in cytotoxic astrocyte swelling. Neurochem Res 2012; 37:2379-87. [PMID: 22544664 DOI: 10.1007/s11064-012-0777-2] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2012] [Revised: 03/30/2012] [Accepted: 04/03/2012] [Indexed: 12/29/2022]
Abstract
Brain edema is a severe clinical complication in a number of pathologies and is a major cause of increased morbidity and death. The swelling of astrocytes caused by a disruption of water and ion homeostasis, is the primary event contributing to the cytotoxic form of brain edema. Astrocyte cytotoxic swelling ultimately leads to transcapillary fluxes of ions and water into the brain parenchyma. This review focuses on the implication of transporters and channels in cytotoxic astrocyte swelling in hyponatremia, ischemia, trauma and hepatic encephalopathy. Emphasis is put on some salient features of the astrocyte physiology, all related to cell swelling, i.e. predominance of aquaporins, control of K(+) homeostasis and ammonia accumulation during the brain ammonia-detoxifying process.
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Affiliation(s)
- Herminia Pasantes-Morales
- División de Neurociencias, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Mexico City, Mexico.
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Butterworth RF. Reprint of: Neuroinflammation in acute liver failure: mechanisms and novel therapeutic targets. Neurochem Int 2012; 60:715-22. [PMID: 22504574 DOI: 10.1016/j.neuint.2012.03.014] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2011] [Revised: 07/20/2011] [Accepted: 07/28/2011] [Indexed: 01/31/2023]
Abstract
It is increasingly evident that neuroinflammatory mechanisms are implicated in the pathogenesis of the central nervous system (CNS) complications (intracranial hypertension, brain herniation) of acute liver failure (ALF). Neuroinflammation in ALF is characterized by microglial activation and arterio-venous difference studies as well as studies of gene expression confirm local brain production and release of proinflammatory cytokines including TNF-α and the interleukins IL-1β and IL-6. Although the precise nature of the glial cell responsible for brain cytokine synthesis is not yet established, evidence to date supports a role for both astrocytes and microglia. The neuroinflammatory response in ALF progresses in parallel with the progression of hepatic encephalopathy (HE) and with the severity of brain edema (astrocyte swelling). Mechanisms responsible for the relaying of signals from the failing liver to the brain include transduction of systemic proinflammatory signals as well as the effects of increased brain lactate leading to increased release of cytokines from both astrocytes and microglia. There is evidence in support of a synergistic effect of proinflammatory cytokines and ammonia in the pathogenesis of HE and brain edema in ALF. Therapeutic implications of the findings of a neuroinflammatory response in ALF are multiple. Removal of both ammonia and proinflammatory cytokines is possible using antibiotics or albumen dialysis. Mild hypothermia reduces brain ammonia transfer, brain lactate production, microglial activation and proinflammatory cytokine production resulting in reduced brain edema and intracranial pressure in ALF. N-Acetylcysteine acts as both an antioxidant and anti-inflammatory agent at both peripheral and central sites of action independently resulting in slowing of HE progression and prevention of brain edema. Novel treatments that directly target the neuroinflammatory response in ALF include the use of etanercept, a TNF-α neutralizing molecule and minocycline, an agent with potent inhibitory actions on microglial activation that are independent of its antimicrobial properties; both agents have been shown to be effective in reducing neuroinflammation and in preventing the CNS complications of ALF. Translation of these findings to the clinic has the potential to provide rational targeted approaches to the prevention and treatment of these complications in the near future.
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Affiliation(s)
- Roger F Butterworth
- Neuroscience Research Unit, Saint-Luc Hospital, CHUM, University of Montreal, Montreal, Quebec, Canada.
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47
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Scheuermann K, Thiel C, Thiel K, Klingert W, Hawerkamp E, Scheppach J, Königsrainer A, Morgalla MH, Leckie P, Proven A, Jalan R, Davies N, Schuhmann MU, Schenk M. Correlation of the intracranial pressure to the central venous pressure in the late phase of acute liver failure in a porcine model. ACTA NEUROCHIRURGICA. SUPPLEMENT 2012; 114:387-391. [PMID: 22327729 DOI: 10.1007/978-3-7091-0956-4_75] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Volume loading is a common method used to ensure adequate circulation. However, in the late phase of acute liver failure complications that often lead to death are cerebral swelling and brainstem edema, which are considered to result from increasing intracranial pressure (ICP). In former studies cerebral venous pressure (CVP) and ICP were reported to be independent entities. Acute liver failure was induced in 25 German land race pigs by acetaminophen intoxication. CVP and ICP were measured continuously. Hydroxyethyl starch solution and noradrenalin were administered to stabilize the circulation at a mean arterial pressure above 60mmHg. There is an increasing correlation in quantity and quality between the CVP and ICP in the last 24 h before exitus. Beginning with a slope of 0.24 (ICP against CVP) and a low correlation coefficient of 0.08. 24h before exitus, this situation remained stable until 16 h to exitus (m = 0.22, r = 0.1). The correlation increased from 16 to 8 h prior to exitus to a slope of m = 0.5 and a correlation of r = 0.3 and remained until exitus. In late acute liver failure it seems therefore clinically reasonable to keep circulation within an adequate range by the use of noradrenalin and to avoid fluid overload.
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Affiliation(s)
- Kathrin Scheuermann
- Department of General, Visceral Transplant Surgery, Tuebingen University Hospital, Tuebingen, Germany
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Abstract
Adult hyperammonaemia is associated with severe liver disease in 90% of cases. In the remainder, noncirrhotic causes should be considered. Measurements of serum ammonia level must be part of the basic work-up in all patients presenting with encephalopathy of unknown origin, even when liver function is normal. Clinician awareness of noncirrhotic hyperammonaemic encephalopathy can contribute to early diagnosis and the initiation of sometimes life-saving treatment. This review focuses on the physiology, aetiology and underlying mechanisms of noncirrhotic hyperammonaemic encephalopathy and discusses the available treatment modalities.
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Affiliation(s)
- Ido Laish
- Department of Internal Medicine A and Rabin Medical Center, Beilinson Hospital, Petah Tiqwa, Israel
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49
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Butterworth RF. Neuroinflammation in acute liver failure: mechanisms and novel therapeutic targets. Neurochem Int 2011; 59:830-6. [PMID: 21864609 DOI: 10.1016/j.neuint.2011.07.014] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2011] [Revised: 07/20/2011] [Accepted: 07/28/2011] [Indexed: 12/21/2022]
Abstract
It is increasingly evident that neuroinflammatory mechanisms are implicated in the pathogenesis of the central nervous system (CNS) complications (intracranial hypertension, brain herniation) of acute liver failure (ALF). Neuroinflammation in ALF is characterized by microglial activation and arterio-venous difference studies as well as studies of gene expression confirm local brain production and release of proinflammatory cytokines including TNF-α and the interleukins IL-1β and IL-6. Although the precise nature of the glial cell responsible for brain cytokine synthesis is not yet established, evidence to date supports a role for both astrocytes and microglia. The neuroinflammatory response in ALF progresses in parallel with the progression of hepatic encephalopathy (HE) and with the severity of brain edema (astrocyte swelling). Mechanisms responsible for the relaying of signals from the failing liver to the brain include transduction of systemic proinflammatory signals as well as the effects of increased brain lactate leading to increased release of cytokines from both astrocytes and microglia. There is evidence in support of a synergistic effect of proinflammatory cytokines and ammonia in the pathogenesis of HE and brain edema in ALF. Therapeutic implications of the findings of a neuroinflammatory response in ALF are multiple. Removal of both ammonia and proinflammatory cytokines is possible using antibiotics or albumen dialysis. Mild hypothermia reduces brain ammonia transfer, brain lactate production, microglial activation and proinflammatory cytokine production resulting in reduced brain edema and intracranial pressure in ALF. N-Acetylcysteine acts as both an antioxidant and anti-inflammatory agent at both peripheral and central sites of action independently resulting in slowing of HE progression and prevention of brain edema. Novel treatments that directly target the neuroinflammatory response in ALF include the use of etanercept, a TNF-α neutralizing molecule and minocycline, an agent with potent inhibitory actions on microglial activation that are independent of its antimicrobial properties; both agents have been shown to be effective in reducing neuroinflammation and in preventing the CNS complications of ALF. Translation of these findings to the clinic has the potential to provide rational targeted approaches to the prevention and treatment of these complications in the near future.
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Affiliation(s)
- Roger F Butterworth
- Neuroscience Research Unit, Saint-Luc Hospital (CHUM), University of Montreal, Montreal, Quebec, Canada.
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50
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Zemtsova I, Görg B, Keitel V, Bidmon HJ, Schrör K, Häussinger D. Microglia activation in hepatic encephalopathy in rats and humans. Hepatology 2011; 54:204-15. [PMID: 21452284 DOI: 10.1002/hep.24326] [Citation(s) in RCA: 120] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
UNLABELLED Astrocytes play an important role in the pathogenesis of hepatic encephalopathy (HE) and ammonia toxicity, whereas little is known about microglia and neuroinflammation under these conditions. We therefore studied the effects of ammonia on rat microglia in vitro and in vivo and analyzed markers of neuroinflammation in post mortem brain tissue from patients with cirrhosis with and without HE and non-cirrhotic controls. In cultured rat microglia, ammonia stimulated cell migration and induced oxidative stress and an up-regulation of the microglial activation marker ionized calcium-binding adaptor molecule-1 (Iba-1). Up-regulation of Iba-1 was also found in the cerebral cortex from acutely ammonia-intoxicated rats and in the cerebral cortex from patients with cirrhosis who have HE, but not from patients with cirrhosis who do not have HE. However, ammonia had no effect on microglial glutamate release, prostaglandin synthesis, and messenger RNA (mRNA) levels of inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2), and the proinflammatory cytokines interleukin (IL)-1α/β, tumor necrosis factor α, or IL-6, whereas in cultured astrocytes ammonia induced the release of glutamate, prostaglandins, and increased IL-1β mRNA. mRNA and protein expression of iNOS and COX-2 or mRNA expression of proinflammatory cytokines and chemokine monocyte chemoattractive protein-1 in cerebral cortex from patients with liver cirrhosis and HE were not different from those found in patients with cirrhosis who did not have HE or control patients without cirrhosis. CONCLUSION These data suggest that microglia become activated in experimental hyperammonemia and HE in humans and may contribute to the generation of oxidative stress. However, HE in patients with liver cirrhosis is not associated with an up-regulation of inflammatory cytokines in cerebral cortex, despite microglia activation.
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Affiliation(s)
- Irina Zemtsova
- Clinic for Gastroenterology, Hepatology, and Infectiology, Heinrich-Heine University, Düsseldorf, Germany
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