Prophylactic angiotensin type 1 receptor antagonism confers neuroprotection in an aged rat model of postoperative cognitive dysfunction

A53T α-synuclein mutation increases susceptibility to postoperative delayed neurocognitive recovery via hippocampal Ang-(1-7)/MasR axis

Delayed neurocognitive recovery (dNCR) is a common complication in geriatric surgical patients. The impact of anesthesia and surgery on patients with neurodegenerative diseases, such as Parkinson's disease (PD) or prion disease, has not yet been reported. In this study, we aimed to determine the association between a pre-existing A53T genetic background, which involves a PD-related point mutation, and the development of postoperative dNCR. We observed that partial hepatectomy induced hippocampus-dependent cognitive deficits in 5-month-old A53T transgenic mice, a model of early-stage PD without cognitive deficits, unlike in age-matched wild-type (WT) mice. We respectively examined molecular changes at 6 h, 1 day, and 2 days after partial hepatectomy and observed that cognitive changes were accompanied by weakened angiotensin-(1-7)/Mas receptor [Ang-(1-7)/MasR] axis, increased alpha-synuclein (α-syn) expression and phosphorylation, decreased methylated protein phosphatase-2A (Me-PP2A), and prompted microglia M1 polarization and neuronal apoptosis in the hippocampus at 1 day after surgery. Nevertheless, no changes in blood-brain barrier (BBB) integrity or plasma α-syn levels in either A53T or WT mice. Furthermore, intranasal administration of selective MasR agonist AVE 0991, reversed the mentioned cognitive deficits in A53T mice, enhanced MasR expression, reduced α-syn accumulation and phosphorylation, and attenuated microglia activation and apoptotic response. Our findings suggest that individuals with the A53T genetic background may be more susceptible to developing postoperative dNCR. This susceptibility could be linked to central α-syn accumulation mediated by the weakened Ang-(1-7)/MasR/methyl-PP2A signaling pathway in the hippocampus following surgery, independent of plasma α-syn level and BBB.

AT 1 inhibition mediated neuroprotection after experimental traumatic brain injury is dependent on neutrophils in male mice

After traumatic brain injury (TBI) cerebral inflammation with invasion of neutrophils and lymphocytes is a crucial factor in the process of secondary brain damage. In TBI the intrinsic renin-angiotensin system is an important mediator of cerebral inflammation, as inhibition of the angiotensin II receptor type 1 (AT1) reduces secondary brain damage and the invasion of neutrophil granulocytes into injured cerebral tissue. The current study explored the involvement of immune cells in neuroprotection mediated by AT1 inhibition following experimental TBI. Four different cohorts of male mice were examined, investigating the effects of neutropenia (anti-Ly6G antibody mediated neutrophil depletion; C57BL/6), lymphopenia (RAG1 deficiency, RAG1^-/-), and their combination with candesartan-mediated AT1 inhibition. The present results showed that reduction of neutrophils and lymphocytes, as well as AT1 inhibition in wild type and RAG1^-/- mice, reduced brain damage and neuroinflammation after TBI. However, in neutropenic mice, candesartan did not have an effect. Interestingly, AT1 inhibition was found to be neuroprotective in RAG1^-/- mice but not in neutropenic mice. The findings suggest that AT1 inhibition may exert neuroprotection by reducing the inflammation caused by neutrophils, ultimately leading to a decrease in their invasion into cerebral tissue.

Preclinical and translational models for delirium: Recommendations for future research from the NIDUS delirium network

Delirium is a common, morbid, and costly syndrome that is closely linked to Alzheimer's disease (AD) and AD-related dementias (ADRD) as a risk factor and outcome. Human studies of delirium have advanced our knowledge of delirium incidence and prevalence, risk factors, biomarkers, outcomes, prevention, and management. However, understanding of delirium neurobiology remains limited. Preclinical and translational models for delirium, while challenging to develop, could advance our knowledge of delirium neurobiology and inform the development of new prevention and treatment approaches. We discuss the use of preclinical and translational animal models in delirium, focusing on (1) a review of current animal models, (2) challenges and strategies for replicating elements of human delirium in animals, and (3) the utility of biofluid, neurophysiology, and neuroimaging translational markers in animals. We conclude with recommendations for the development and validation of preclinical and translational models for delirium, with the goal of advancing awareness in this important field.

Effects of different types of non-cardiac surgical trauma on hippocampus-dependent memory and neuroinflammation

Background

Older individuals have been reported to suffer from cognitive disorders after surgery. Various types of surgical trauma have been used to establish postoperative cognitive dysfunction (POCD) animal models in preclinical studies. However, few comparative analyses of these animal models were conducted.

Methods

Tibial surgery, abdominal surgery, and extended abdominal surgery were performed on aged ICR mice to establish POCD models. Behavioral tests included open field, novel object recognition, fear conditioning, and Morris water maze tests. The Z-score methodology was adopted to obtain a comprehensive and integrated memory performance profile. The changes in hippocampal neuroinflammation were analyzed by ELISA, PCR, and immunofluorescence.

Results

In this study, we found that each type of non-cardiac surgical trauma has a different effects on locomotor activity. Tibial and extended abdominal surgeries led to more significant cognitive impairment than abdominal surgery. Inflammatory cytokines peaked on postoperative day 1 and decreased to control levels on days 3 and 7. Hippocampal neuroinflammation indicators between the three surgery types on postoperative day 1 had no statistical differences.

Conclusion

Overall, the type and intensity of non-cardiac surgical trauma can affect cognitive behavioral outcomes and central inflammation. The shortcomings and emerging issues of POCD animal research methods need to be further studied and solved.

Network Biology Approaches to Uncover Therapeutic Targets Associated with Molecular Signaling Pathways from circRNA in Postoperative Cognitive Dysfunction Pathogenesis

Postoperative cognitive dysfunction (POCD) is a cognitive deterioration and dementia that arise after a surgical procedure, affecting up to 40% of surgery patients over the age of 60. The precise etiology and molecular mechanisms underlying POCD remain uncovered. These reasons led us to employ integrative bioinformatics and machine learning methodologies to identify several biological signaling pathways involved and molecular signatures to better understand the pathophysiology of POCD. A total of 223 differentially expressed genes (DEGs) comprising 156 upregulated and 67 downregulated genes were identified from the circRNA microarray dataset by comparing POCD and non-POCD samples. Gene ontology (GO) analyses of DEGs were significantly involved in neurogenesis, autophagy regulation, translation in the postsynapse, modulating synaptic transmission, regulation of the cellular catabolic process, macromolecule modification, and chromatin remodeling. Pathway enrichment analysis indicated some key molecular pathways, including mTOR signaling pathway, AKT phosphorylation of cytosolic targets, MAPK and NF-κB signaling pathway, PI3K/AKT signaling pathway, nitric oxide signaling pathway, chaperones that modulate interferon signaling pathway, apoptosis signaling pathway, VEGF signaling pathway, cellular senescence, RANKL/RARK signaling pathway, and AGE/RAGE pathway. Furthermore, seven hub genes were identified from the PPI network and also determined transcription factors and protein kinases. Finally, we identified a new predictive drug for the treatment of SCZ using the LINCS L1000, GCP, and P100 databases. Together, our results bring a new era of the pathogenesis of a deeper understanding of POCD, identified novel therapeutic targets, and predicted drug inhibitors in POCD.

Multiple Aspects of Inappropriate Action of Renin-Angiotensin, Vasopressin, and Oxytocin Systems in Neuropsychiatric and Neurodegenerative Diseases

The cardiovascular system and the central nervous system (CNS) closely cooperate in the regulation of primary vital functions. The autonomic nervous system and several compounds known as cardiovascular factors, especially those targeting the renin-angiotensin system (RAS), the vasopressin system (VPS), and the oxytocin system (OTS), are also efficient modulators of several other processes in the CNS. The components of the RAS, VPS, and OTS, regulating pain, emotions, learning, memory, and other cognitive processes, are present in the neurons, glial cells, and blood vessels of the CNS. Increasing evidence shows that the combined function of the RAS, VPS, and OTS is altered in neuropsychiatric/neurodegenerative diseases, and in particular in patients with depression, Alzheimer's disease, Parkinson's disease, autism, and schizophrenia. The altered function of the RAS may also contribute to CNS disorders in COVID-19. In this review, we present evidence that there are multiple causes for altered combined function of the RAS, VPS, and OTS in psychiatric and neurodegenerative disorders, such as genetic predispositions and the engagement of the RAS, VAS, and OTS in the processes underlying emotions, memory, and cognition. The neuroactive pharmaceuticals interfering with the synthesis or the action of angiotensins, vasopressin, and oxytocin can improve or worsen the effectiveness of treatment for neuropsychiatric/neurodegenerative diseases. Better knowledge of the multiple actions of the RAS, VPS, and OTS may facilitate programming the most efficient treatment for patients suffering from the comorbidity of neuropsychiatric/neurodegenerative and cardiovascular diseases.

Intervention of NF-Κb Signaling Pathway and Preventing Post-Operative Cognitive Dysfunction as Well as Neuronal Apoptosis

Background:

The Postoperative cognitive dysfunction (POCD) model was constructed by resection of the left hepatic lobe in aged mice to determine the behavioral effects of the POCD model in aged mice and the relationship between NF-κB and POCD in apoptosis and autophagy. Provide a theoretical basis for POCD prevention and treatment.

Methods:

This study was carried out in Ningbo No. 6 Hospital, Zhejiang, China, from Jun 2019 to Dec 2020. The POCD model was constructed after resection of the left extrahepatic lobe in aged mice and randomly divided into 6 groups: sham operation group, operation group (normal saline control group, solvent group, YC-1 group, PDTC group and 3-MA group). Related indicators of behavioral changes, neuronal inflammatory responses, apoptosis, and autophagy were examined.

Results:

The escape latency of the aged mice in the surgical group was significantly prolonged at three time points compared with the control group, and the number of insertions decreased significantly. Microglia are activated and the inflammatory response is increased, whereas PDTC has an inhibitory effect. It was demonstrated that apoptosis and necrosis of neurons can be induced by the NF-κb pathway, and autophagy can be promoted, whereas autophagy occurs before apoptosis.

Conclusion:

Activation of NF-κb pathway in neurons after POCD causes neuronal apoptosis and autophagy, and cognitive impairment occurs. PDTC, a NF-κb pathway inhibitor, can effectively reduce neuronal apoptosis induced by secondary brain injury after POCD. Necrosis, to protect the brain tissue.

Identification of the Potential Gene Regulatory Networks and Therapeutics in Aged Mice With Postoperative Neurocognitive Disorder

Postoperative neurocognitive disorder (PND) is one of the most common postoperative neurological complications in aged patients, characterized by mental disorder, anxiety, personality changes, and impaired memory. At present, the molecular mechanism of PND remains largely unclear, and the ideal biomarker for clinical diagnosis and prognosis are lacking. Circular RNA (circRNA) and microRNA (miRNA), as unique non-coding RNAs, affecting the regulation of miRNAs on genes and further intervening in the progression of diseases through the sponge action between the two. Besides, it could be served as novel biomarkers in various diseases. In order to detect the differential expression profiles of genes caused by PND, a total of 26 18-month-old male C57BL/6 mice were randomly assigned to control group and PND group. Behavioral tests showed that mice in the PND group had impaired cognitive function compared with the control group. Three mice in each group were randomly selected to harvest the brain for analysis the expressions of circRNAs, miRNAs, and mRNAs in the prefrontal cortex by next-generation sequencing (NGS) technology. Differentially expressed genes, including 1192 circRNAs, 27 miRNAs, and 266 mRNAs were identified, and its accuracy was further confirmed by qRT-PCR. Bioinformatics analysis results suggested that neuroinflammation was the main pathological mechanism of PND. The construction of competitive endogenous RNA (ceRNA) networks and the identification of hub genes provided possible therapeutic targets for PND. Cinnarizine and Clemastine were predicted to have the potential therapeutic effects on PND. This is the first study to explore the differential expression profiles of genes and their regulation mechanisms in PND, our results provided new clues and targets for the treatment of this refractory disease.

Conventional cardiovascular risk factors in Transient Global Amnesia: Systematic review and proposition of a novel hypothesis

Transient Global Amnesia (TGA) is an enigmatic amnestic syndrome. We conducted a systematic review to investigate the relationship between the conventional cardiovascular risk factors and TGA. MEDLINE, CENTRAL, EMBASE and PsycINFO were comprehensively searched and 23 controlled observational studies were retrieved. The prevalence of hypertension, diabetes mellitus, dyslipidemia and smoking was lower among patients with TGA compared to Transient Ischemic Attack. Regarding the comparison of TGA with healthy individuals, there was strong evidence suggesting a protective effect of diabetes mellitus on TGA and weaker evidence for a protective effect of smoking. Hypertension was associated with TGA only in more severe stages, while dyslipidemia was not related. In view of these findings, a novel pathophysiological hypothesis is proposed, in which the functional interactions of Angiotensin-II type-1 and N-methyl-D-aspartate receptors are of pivotal importance. The whole body of clinical evidence (nature of precipitating events, associations with migraine, gender-based association patterns) was integrated.

The Non-peptide Angiotensin-(1-7) Mimic AVE 0991 Attenuates Delayed Neurocognitive Recovery After Laparotomy by Reducing Neuroinflammation and Restoring Blood-Brain Barrier Integrity in Aged Rats

Delayed neurocognitive recovery (dNCR) after surgery is a common postoperative complication in older adult patients. Our previous studies have demonstrated that cognitive impairment after surgery involves an increase in the brain renin-angiotensin system (RAS) activity, including overactivation of the angiotensin 2/angiotensin receptor-1 (Ang II/AT1) axis, which provokes the disruption of the hippocampal blood-brain barrier (BBB). Nevertheless, the potential role of the counter-regulatory RAS axis, the Ang-(1–7)/Mas pathway, in dNCR remains unknown. Using an aged rat model of dNCR, we dynamically investigated the activity of both axes of the RAS following laparotomy. AVE 0991, a nonpeptide analog of Ang-(1–7), was administered intranasally immediately after laparotomy. We found that the elevation of Ang II, induced by surgery was accompanied by a decrease of Ang-(1–7) in the hippocampus, but not in the circulation. Surgery also significantly downregulated hippocampal Mas receptor expression at 24 h postsurgery. Mas activation with intranasal AVE 0991 treatment significantly improved hippocampus-dependent learning and memory deficits induced by surgery. Furthermore, it attenuated hippocampal neuroinflammation, as shown by the decreased level of the microglial activation marker cluster of differentiation 11b (CD11b) and the decreased production of several inflammatory molecules. Along with these beneficial effects, the AVE 0991 treatment also alleviated the imbalance between matrix metalloproteinase-9 (MMP-9) and tissue inhibitor of matrix metalloproteinase-3 (TIMP-3), modulated the expression of occludin, and alleviated the IgG extravasation, thereby restoring the integrity of the BBB. In conclusion, these data indicate that activation of Mas by AVE 0991 attenuates dNCR after surgery by reducing neuroinflammation and restoring BBB integrity. Our findings suggest that the Ang-(1–7)/Mas pathway may be a novel therapeutic target for treating dNCR after surgery in older adult patients.

Inhibition of PLCβ1 signaling pathway regulates methamphetamine self-administration and neurotoxicity in rats

Studies have shown that the central renin-angiotensin system is involved in neurological disorders. Our previous studies have demonstrated that angiotensin II receptor type 1 (AT1R) in the brain could be a potential target against methamphetamine (METH) use disorder. The present study was designed to investigate the underlying mechanisms of the inhibitory effect of AT1R on various behavioural effects of METH. We first examined the effect of AT1R antagonist, candesartan cilexetil (CAN), on behavioural and neurotoxic effects of METH. Furthermore, we studied the role of phospholipase C beta 1 (PLCβ1) blockade behavioural and neurotoxic effects of METH. The results showed that CAN significantly attenuated METH-induced behavioral disorders and neurotoxicity associated with increased oxidative stress. AT1R and PLCβ1 were significantly upregulated in vivo and in vitro. Inhibition of PLCβ1 effectively alleviated METH-induced neurotoxicity and METH self-administration (SA) by central blockade of the PLCβ1 involved signalling pathway. PLCβ1 blockade significantly decreased the reinforcing and motivation effects of METH. PLCβ1 involved signalling pathway, as well as a more specific role of PLCβ1, involved the inhibitory effects of CAN on METH-induced behavioural dysfunction and neurotoxicity. Collectively, our findings reveal a novel role of PLCβ1 in METH-induced neurotoxicity and METH use disorder.

Neurofilament degradation is involved in laparotomy-induced cognitive dysfunction in aged rats

Excessive neuroinflammatory responses play important roles in the development of postoperative cognitive dysfunction (POCD). Neurofilaments (NFs) were essential to the structure of axon and nerve conduction; and the abnormal degradation of NFs were always accompanied with degenerative diseases, which were also characterized by excessive neuroinflammatory responses in brain. However, it is still unclear whether the NFs were involved in the POCD. In this study, the LC-MS/MS method was used to explore the neuroinflammatory response and NFs of POCD in aged rats. Moreover, trichostatin A (TSA), an inflammation-related drug, was selected to test whether it could improve the surgery-induced cognitive dysfunction, inflammatory responses and NFs. Evident cognitive dysfunction, excessive microglia activation, neuroinflammatory responses and upregulated NFs in hippocampus were observed in the POCD group. TSA pretreatment could significantly mitigate these changes. The KEGG analysis revealed that nine pathways were enriched in the TSA + surgery group (versus the surgery group). Among them, two signaling pathways were closely related with the changes of NFs proteins. In conclusion, surgery could impair the cognitive function and aggravate neuroinflammation and NFs. The TSA could significantly improve these changes which might be related to the activation of the “focal adhesion” and “ECM-receptor interaction” pathways.

The Brain AT2R-a Potential Target for Therapy in Alzheimer's Disease and Vascular Cognitive Impairment: a Comprehensive Review of Clinical and Experimental Therapeutics

Dementia is a potentially avertable tragedy, currently considered among the top 10 greatest global health challenges of the twenty-first century. Dementia not only robs individuals of their dignity and independence, it also has a ripple effect that starts with the inflicted individual's family and projects to the society as a whole. The constantly growing number of cases, along with the lack of effective treatments and socioeconomic impact, poses a serious threat to the sustainability of our health care system. Hence, there is a worldwide effort to identify new targets for the treatment of Alzheimer's disease (AD), the leading cause of dementia. Due to its multifactorial etiology and the recent clinical failure of several novel amyloid-β (Aβ) targeting therapies, a comprehensive "multitarget" approach may be most appropriate for managing this condition. Interestingly, renin angiotensin system (RAS) modulators were shown to positively impact all the factors involved in the pathophysiology of dementia including vascular dysfunction, Aβ accumulation, and associated cholinergic deficiency, in addition to tau hyperphosphorylation and insulin derangements. Furthermore, for many of these drugs, the preclinical evidence is also supported by epidemiological data and/or preliminary clinical trials. The purpose of this review is to provide a comprehensive update on the major causes of dementia including the risk factors, current diagnostic criteria, pathophysiology, and contemporary treatment strategies. Moreover, we highlight the angiotensin II receptor type 2 (AT2R) as an effective drug target and present ample evidence supporting its potential role and clinical applications in cognitive impairment to encourage further investigation in the clinical setting.

Identification of the Potential Key Circular RNAs in Elderly Patients With Postoperative Cognitive Dysfunction

Background

Postoperative cognitive dysfunction (POCD) is one of the severe complications after surgery, inducing low life quality and high mortality, especially in elderly patients. However, the underlying molecular mechanism of POCD remains largely unknown, and the ideal biomarker for clinical diagnosis and prognosis is lacking. Circular RNAs (circRNAs), as a unique class of non-coding RNAs, were characterized by its stability and conservativeness, serving as novel biomarkers in various diseases. Nevertheless, the role of circRNAs in the occurrence of POCD remains elusive.

Methods

To investigate the differentially expressed circRNAs in the serum of POCD patients and its potential role in the development of POCD, we performed a circRNA microarray to screen the differentially expressed circRNAs in the serum samples from three patients of the POCD group and three paired patients of the non-POCD group. Subsequently, quantitative real-time polymerase chain reaction analysis (qRT-PCR) was utilized to verify the microarray data with the serum samples from 10 paired patients. Cytoscape software was used to construct the circRNA–miRNA–mRNA network for circRNAs with different expression levels as well as the target genes. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses showed the biological functions of the differentially expressed circRNAs target genes.

Results

In total, we have analyzed 10,198 circRNAs through the microarray. Compared with the non-POCD patient group, there were 210 differentially expressed circRNAs with 133 upregulated and 77 downregulated in the POCD group (≥2-fold differential expression, P ≤ 0.05). The qRT-PCR confirmed 10 circRNAs with different expressed levels, and the results were consistent with the microarray findings. Among them, hsa_circRNA_001145, hsa_circRNA_101138, and hsa_circRNA_061570 had the highest magnitude of change. The GO analysis showed that the differentially expressed circRNAs were associated with the regulation of the developmental process, cell-to-cell adhesion, and nervous system development. The KEGG analysis showed that the target genes of circRNAs were enriched in the MAPK signaling pathway and RAS signaling pathway. According to the targetscan7.1 and mirdbV5 databases, the circRNA–miRNA–mRNA network was constructed, and these results provided a vital landscape of circRNA expression profile in POCD.

Conclusions

Our study provides an essential perspective for the differential expression of circRNAs in POCD patients. Further studies need to be performed to explore their potential therapeutic roles in the development of POCD.

Autophagy prevents hippocampal α-synuclein oligomerization and early cognitive dysfunction after anesthesia/surgery in aged rats

Stress-induced α-synuclein aggregation, especially the most toxic species (oligomers), may precede synaptic and cognitive dysfunction. Under pathological conditions, α-synuclein is degraded primarily through the autophagic/lysosomal pathway. We assessed the involvement of autophagy in α-synuclein aggregation and cognitive impairment following general anesthesia and surgical stress. Autophagy was found to be suppressed in the aged rat hippocampus after either 4-h propofol anesthesia alone or 2-h propofol anesthesia during a laparotomy surgery. This inhibition of autophagy was accompanied by profound α-synuclein oligomer aggregation and neurotransmitter imbalances in the hippocampus, along with hippocampus-dependent cognitive deficits. These events were not observed 18 weeks after propofol exposure with or without surgical stress. The pharmacological induction of autophagy using rapamycin markedly suppressed α-synuclein oligomerization, restored neurotransmitter equilibrium, and improved cognitive behavior after prolonged anesthesia or anesthesia combined with surgery. Thus, both prolonged propofol anesthesia alone and propofol anesthesia during surgery impaired autophagy, which may have induced abnormal hippocampal α-synuclein aggregation and neurobehavioral deficits in aged rats. These findings suggest that the activation of autophagy and the clearance of pathological α-synuclein oligomers may be novel strategies to ameliorate the common occurrence of postoperative cognitive dysfunction.

Constitutive accessibility of circulating proteins to hippocampal neurons in physiologically normal rats

INTRODUCTION

Although the hippocampus (HIP) is thought impermeable to blood-borne proteins because of the integrity of the blood-brain barrier (BBB), it was recently suggested to be susceptible to hydrophilic hormones. The present study determined the accessibility of blood-borne signal molecules such as hormones to hippocampal neurons in physiologically normal rats.

METHODS

As a probe for accessibility, Evans blue dye (EB) that rapidly binds to albumin (Alb), which is impermeable to the BBB, was injected intravenously. To increase the vascular permeability of the BBB, a daily single administration of angiotensin II (Ang II) was applied intravenously for seven consecutive days.

RESULTS

Fifteen minutes after the injection of EB, histological observation revealed that a number of neurons had entrapped and accumulated EB into their cell bodies in the hippocampal dentate gyrus in all rats. Of these, relatively large oval neurons (>15 µm) in the hilus and molecular layer showed parvalbumin immunopositivity, indicating they are GABAergic interneurons. The population of EB-accumulating neurons (approximately 10 µm) were localized in the inner margin of the granule cell layer, suggesting they were granule cells. However, the number of EB-positive neurons did not change in rats treated with Ang II compared with vehicle injection.

CONCLUSIONS

These findings suggest an intriguing possibility that blood-derived proteins such as hormones have access to hippocampal neurons constitutively in the absence of stimuli that increase the vascular permeability of the BBB in a physiologically normal state.

The Angiotensin Type 1 Receptor Antagonist Losartan Prevents Ovariectomy-Induced Cognitive Dysfunction and Anxiety-Like Behavior in Long Evans Rats

Women who have bilateral oophorectomies prior to the age of natural menopause are at increased risk of developing mild cognitive decline, dementia, anxiety, and depressive type disorders. Clinical and animal studies indicate angiotensin type 1 receptor (AT₁R) blockers (ARBs) have blood pressure (BP)-independent neuroprotective effects. To investigate the potential use of ARBs in normotensive women at increased risk of developing neurocognitive problems, we studied a rat model of bilateral oophorectomy. Long Evans rats were sham-operated (Sham) or ovariectomized (Ovx) at 3 months of age and immediately treated continuously with vehicle (Veh) or the ARB losartan (Los) for the duration of the experiment. In contrast to many hypertensive rat models, ovariectomy did not increase mean arterial pressure (MAP) in these normotensive rats. Ovariectomized rats spent less time in the open arms of the elevated plus maze (EPM) [(% total time): Veh, 34.1 ± 5.1 vs. Ovx, 18.7 ± 4.4; p < 0.05] and in the center of the open field (OF) [(s): Veh, 11.1 ± 1.7 vs. Ovx, 6.64 ± 1.1; p < 0.05]. They also had worse performance in the novel object recognition (NOR) test as evidenced by a reduction in the recognition index [Veh, 0.62 ± 0.04 vs. Ovx, 0.45 ± 0.03; p < 0.05]. These adverse effects of ovariectomy were prevented by Los. Losartan also reduced plasma corticosterone in Ovx rats compared to Veh treatment [(ng/mL): Ovx–Veh, 238 ± 20 vs. Ovx–Los, 119 ± 42; p < 0.05]. Ovariectomy increased AT₁R mRNA expression in the CA3 region of the hippocampus (Hc) [(copies x 10⁶/µg RNA): Sham–Veh, 7.15 ± 0.87 vs. Ovx–Veh, 9.86 ± 1.7; p < 0.05]. These findings suggest the neuroprotective effects of this ARB in normotensive Ovx rats involve reduction of plasma corticosterone and blockade of increased AT₁R activity in the hippocampus. These data suggest ARBs have therapeutic potential for normotensive women at increased risk of developing cognitive and behavioral dysfunction due to bilateral oophorectomy prior to the natural age of menopause.

Isoflurane-Induced Postoperative Neurovascular and Cognitive Dysfunction Is Associated with VEGF Overexpression in Aged Rats

Postoperative cognitive dysfunction (POCD) is a common complication in older adults; however, its aetiology remains unclear. Although vascular endothelial growth factor (VEGF) is associated with blood-brain barrier (BBB) disorders and neurological disease, its role in POCD is unknown. Here, we investigated the effect of brain VEGF inhibition on isoflurane-induced cognitive impairment in an aged rat model of POCD. VEGF protein expression was increased in the hippocampus after isoflurane exposure, suggesting that inhalation anaesthesia induces hippocampal VEGF protein overexpression in aged rats. Pretreatment with 2 mg/kg RB-222, an anti-VEGF neutralizing antibody, may partially abolish the degradation of occludin protein in cerebral capillaries, thereby maintaining the ultrastructural and functional integrity of the hippocampal BBB. Inhibition of VEGF also significantly attenuated the isoflurane-induced cognitive deficits in the Morris water maze task. Together, our findings show, for the first time, that elevated expression of brain VEGF after isoflurane exposure contributes to POCD in aged rats. Therefore, therapeutic strategies involving VEGF should take into consideration its role in the pathogenesis of POCD.

Application of sevoflurane inhalation combined with epidural anesthesia in patients with colorectal cancer and its effect on postoperative perceptual function

Effect of sevoflurane inhalation combined with epidural anesthesia on postoperative perceptual function in patients with colorectal cancer (CRC) was investigated. The clinical data of 78 patients undergoing laparoscopic CRC radical surgery in The Second Cancer Hospital of Heilongjiang Province from June 2016 to June 2017 were retrospectively analyzed and divided into 2 groups: Sevoflurane inhalation combined with epidural anesthesia (observation group, n=40); propofol intravenous general anesthesia (control group, n=38). The mean arterial pressure and heart rate before anesthesia (T0), immediate intubation (T1), 30 min after surgery started (T2), end of surgery (T3), 10 min after extubation (T4) were compared between the two groups. The recovery conditions were also compared between the two groups. The cognitive functions were evaluated by mini-mental state scale (MMSE). The mean arterial pressure and heart rate in the observation group were significantly lower than those in the control group at T2, T3 and T4 (P<0.05). The recovery time, extubation time, anal exhaust time, eating time, urinary catheter removal time and hospital stay in the observation group were significantly lower than those in the control group (P<0.05). There was a significant difference in cognitive function between the two groups at different time points (P<0.001). Postoperative cognitive function showed a trend of decreasing first and then increasing; the scores of cognitive function in both groups 1 day after surgery were at trough level, and recovered gradually from 3 days after surgery. The mean arterial pressure and heart rate during the perioperative period are more stable in the elderly patients with sevoflurane inhalation combined with epidural anesthesia; the recovery time is shorter and more rapid, and the recovery time of postoperative cognitive function is also faster. Therefore, it provides a reference for patients undergoing CRC radical surgery to select high-quality and appropriate anesthetic protocols.

Sevoflurane-induced memory impairment in the postnatal developing mouse brain

The aim of the present study was to confirm that sevoflurane induces memory impairment in the postnatal developing mouse brain and determine its mechanism of action. C57BL/6 mice 7 days old were randomly assigned into a 2.6% sevoflurane (n=68), a 1.3% sevoflurane (n=68) and a control (n=38) group. Blood gas analysis was performed to evaluate hypoxia and respiratory depression during anesthesia in 78 mice. Measurements for expression of caspase-3 by immunohistochemistry, cleavage of poly adenosine diphosphate-ribose polymerase (PARP) by western blotting, as well as levels of brain-derived neurotrophic factor (BDNF), tyrosine kinase receptor type 2 (Ntrk2), pro-BDNF, p75 neurotrophin receptor (p75NTR) and protein kinase B (PKB/Akt) by enzyme-linked immunosorbent assay were performed in the hippocampus of 12 mice from each group. A total of 60 mice underwent the Morris water maze (MWM) test. Results from the MWM test indicated that the time spent in the northwest quadrant and platform site crossovers by mice in the 2.6 and 1.3% sevoflurane groups was significantly lower than that of the control group. Meanwhile, levels of caspase-3 and cleaved PARP in the 2.6 and 1.3% sevoflurane groups were significantly higher than that in the control group. Levels of pro-BDNF and p75NTR were significantly increased and the level of PKB/Akt was significantly decreased following exposure to 2.6% sevoflurane. Finally, the memory of postnatal mice was impaired by sevoflurane, this was determined using a MWM test. Therefore, the results of the current study suggest that caspase-3 induced cleavage of PARP, as well as pro-BDNF, p75NTR and PKB/Akt may be important in sevoflurane-induced memory impairment in the postnatal developing mouse brain.

Isoflurane‑induced postoperative cognitive dysfunction is mediated by hypoxia‑inducible factor‑1α‑dependent neuroinflammation in aged rats

Elderly patients are at high risk of developing postoperative cognitive dysfunction (POCD) after prolonged exposure to inhaled anesthetics. However, the pathogenesis of POCD remains unknown. Hypoxia-inducible factor-1α (HIF-1α) is activated by inhaled anesthetics. The aim of the present study was to determine the role of HIF-1α in isoflurane-induced neuroinflammation and the resulting cognitive impairment. Following a 4-h exposure to 1.5% isoflurane in 20-month-old rats, increased expression of HIF-1α protein, activation of nuclear factor (NF)-κB signaling and increased expression of TNF-1α were observed in the hippocampus of isoflurane-exposed rats compared with the control group. Pharmacological inhibition of HIF-1α activation by 5-[1-(phenylmethyl)-1H-indazol-3-yl]-2-furanmethanol (YC-1) markedly suppressed the enhanced expression of HIF-1α, disrupted NF-κB signaling pathway activity and inhibited the isoflurane-induced increase of TNF-1α expression. YC-1 pretreatment also significantly attenuated isoflurane-induced cognitive deficits according to the results of the Morris water maze task. These results suggest that hippocampal HIF-1α appears to be involved in an upstream mechanism of isoflurane-induced cognitive impairment. Further research is warranted to fully clarify the pathogenesis and investigate HIF-1α as a potential therapeutic target for POCD.

Hypoxia-inducible factor-1α is involved in isoflurane-induced blood-brain barrier disruption in aged rats model of POCD

Prolonged exposure to inhaled anesthetics may lead to postoperative cognitive dysfunction (POCD). Nevertheless, the underlying mechanisms are not known. Hypoxia-inducible factor-1α (HIF-1α) and its target gene vascular endothelial growth factor (VEGF) were shown to be activated by inhaled anesthetics. The aim of the present study was to determine the role of HIF-1α in isoflurane-induced blood-brain barrier (BBB) disruption and resultant cognitive impairment. After a 4-h exposure to 1.5% isoflurane in 20-month-old rats, increases in vascular permeability, and disrupted BBB ultrastructure were accompanied by the degradation of tight junction proteins occludin and collagen type IV in brain blood vessels. Increases in HIF-1α and VEGF proteins and activation of MMP-2 in the hippocampus were also observed in the hippocamp of isoflurane-exposed rats compared with control rats. Pharmacological inhibition of HIF-1α activation by 3-(5'-hydroxymethyl-2'-furyl)-1-benzylindazole (YC-1) markedly suppressed the expression of HIF-1α, VEGF and MMP-2, and mitigated the severity of BBB disruption.YC-1 pretreatment also significantly attenuated isoflurane-induced cognitive deficits in the Morris water maze task. Overall, our results demonstrate that hippocampal HIF-1α/VEGF signaling seems to be the upstream mechanism of isoflurane-induced cognitive impairment, and provides apotential preventive and therapeutic target for POCD.

Pathophysiological and behavioral effects of systemic inflammation in aged and diseased rodents with relevance to delirium: A systematic review

Delirium is a frequent outcome for aged and demented patients that suffer a systemic inflammatory insult. Animal models that reconstruct these etiological processes have potential to provide a better understanding of the pathophysiology of delirium. Therefore, we systematically reviewed animal studies in which systemic inflammation was superimposed on aged or diseased animal models. In total, 77 studies were identified. Aged animals were challenged with a bacterial endotoxin in 29 studies, 25 studies superimposed surgery on aged animals, and in 6 studies a bacterial infection, Escherichia coli (E. coli), was used. Diseased animals were challenged with a bacterial endotoxin in 15 studies, two studies examined effects of the cytokine IL-1β, and one study used polyinosinic:polycytidilic acid (poly I:C). This systematic review analyzed the impact of systemic inflammation on the production of inflammatory and neurotoxic mediators in peripheral blood, cerebrospinal fluid (CSF), and on the central nervous system (CNS). Moreover, concomitant behavioral and cognitive symptoms were also evaluated. Finally, outcomes of behavioral and cognitive tests from animal studies were compared to features and symptoms present in delirious patients.

Neuroinflammatory challenges compromise neuronal function in the aging brain: Postoperative cognitive delirium and Alzheimer's disease

Alzheimer's disease (AD) is a progressive neurodegenerative disease that targets memory and cognition, and is the most common form of dementia among the elderly. Although AD itself has been extensively studied, very little is known about early-stage preclinical events and/or mechanisms that may underlie AD pathogenesis. Since the majority of AD cases are sporadic in nature, advancing age remains the greatest known risk factor for AD. However, additional environmental and epigenetic factors are thought to accompany increasing age to play a significant role in the pathogenesis of AD. Postoperative cognitive delirium (POD) is a behavioral syndrome that primarily occurs in elderly patients following a surgical procedure or injury and is characterized by disruptions in cognition. Individuals that experience POD are at an increased risk for developing dementia and AD compared to normal aging individuals. One way in which cognitive function is affected in cases of POD is through activation of the inflammatory cascade following surgery or injury. There is compelling evidence that immune challenges (surgery and/or injury) associated with POD trigger the release of pro-inflammatory cytokines into both the periphery and central nervous system. Thus, it is possible that cognitive impairments following an inflammatory episode may lead to more severe forms of dementia and AD pathogenesis. Here we will discuss the inflammation associated with POD, and highlight the advantages of using POD as a model to study inflammation-evoked cognitive impairment. We will explore the possibility that advancing age and immune challenges may provide mechanistic evidence correlating early life POD with AD. We will review and propose neural mechanisms by which cognitive impairments occur in cases of POD, and discuss how POD may augment the onset of AD.

Surgery-Induced Hippocampal Angiotensin II Elevation Causes Blood-Brain Barrier Disruption via MMP/TIMP in Aged Rats

Reversible blood-brain barrier (BBB) disruption has been uniformly reported in several animal models of postoperative cognitive dysfunction (POCD). Nevertheless, the precise mechanism underlying this occurrence remains unclear. Using an aged rat model of POCD, we investigated the dynamic changes in expression of molecules involved in BBB disintegration, matrix metalloproteinase-2 (MMP-2) and -9 (MMP-9), as well as three of their endogenous tissue inhibitors of MMP (TIMP-1, -2, -3), and tried to establish the correlation between MMP/TIMP balance and surgery-induced hippocampal BBB disruption. We validated the increased hippocampal expression of angiotensin II (Ang II) and Ang II receptor type 1 (AT1) after surgery. We also found MMP/TIMP imbalance as early as 6 h after surgery, together with increased BBB permeability and decreased expression of Occludin and zonula occludens-1 (ZO-1), as well as increased basal lamina protein laminin at 24 h postsurgery. The AT1 antagonist candesartan restored MMP/TIMP equilibrium and modulated expression of Occludin and laminin, but not ZO-1, thereby improving BBB permeability. These events were accompanied by suppression of the surgery-induced canonical nuclear factor-κB (NF-κB) activation cascade. Nevertheless, AT1 antagonism did not affect nuclear receptor peroxisome proliferator-activated receptor-γ (PPARγ) expression. Collectively, these findings suggest that surgery-induced Ang II release impairs BBB integrity by activating NF-κB signaling and disrupting downstream MMP/TIMP balance via AT1 receptor.

Impact of Angiotensin-II receptor blockers on vasogenic edema in glioblastoma patients

Glioblastoma patients often require chronic administration of steroids due to peri-tumoral edema. Preliminary studies showed that treatment with Angiotensin-II Receptor Blockers (ARBs) for high blood pressure might be associated with reduced peri-tumoral edema. In this study, we aim to radiologically assess the effect of ARBs on peri-tumoral edema. We conducted a cross-sectional survey on patients with newly diagnosed GBM. Patients treated with ARBs for high blood pressure were paired to non ARB-treated patients based on similar age, tumor location and tumor size. Patients taking steroids at the time of pre-operative Magnetic Resonance Imaging were excluded from the study. In each pair of patients, we compared the volumes of peri-tumoral hyper T2-Fluid Attenuated Inversion Recovery (FLAIR) signal and the Apparent Diffusion Coefficient (ADC) in the same area. Eleven (11) ARB-treated patients were selected and paired to 11 non ARB-treated controls. Volumes of peri-tumoral hyper T2-FLAIR signal were significantly lower in the ARB-treated group than in the non ARB-treated group (p = 0.02). Additionally, peri-tumoral ADCs were also significantly lower in the treated group (p = 0.02), suggesting that the peri-tumoral area in this group had less edematous features. These results suggest that ARBs may reduce the volume of peri-tumoral hyper T2-FLAIR signal by decreasing edema.

Opposing tissue-specific roles of angiotensin in the pathogenesis of obesity, and implications for obesity-related hypertension

Metabolic disease, specifically obesity, has now become the greatest challenge to improving cardiovascular health. The renin-angiotensin system (RAS) exists as both a circulating hormone system and as a local paracrine signaling mechanism within various tissues including the brain, kidney, and adipose, and this system is strongly implicated in cardiovascular health and disease. Growing evidence also implicates the RAS in the control of energy balance, supporting the concept that the RAS may be mechanistically involved in the pathogenesis of obesity and obesity hypertension. Here, we review the involvement of the RAS in the entire spectrum of whole organism energy balance mechanisms, including behaviors (food ingestion and spontaneous physical activity) and biological processes (digestive efficiency and both aerobic and nonaerobic resting metabolic rates). We hypothesize that opposing, tissue-specific effects of the RAS to modulate these various components of energy balance can explain the apparently paradoxical results reported by energy-balance studies that involve stimulating, versus disrupting, the RAS. We propose a model in which such opposing and tissue-specific effects of the RAS can explain the failure of simple, global RAS blockade to result in weight loss in humans, and hypothesize that obesity-mediated uncoupling of endogenous metabolic rate control mechanisms can explain the phenomenon of obesity-related hypertension.

Phloroglucinol protects the urinary bladder via inhibition of oxidative stress and inflammation in a rat model of cyclophosphamide-induced interstitial cystitis

Background:

Phloroglucinol plays an important role in oxidative stress and inflammatory responses. The effects of phloroglucinol have been proven in various disease models. The aim of the present study was to investigate the efficacy and possible mechanisms of phloroglucinol in the treatment of interstitial cystitis (IC).

Methods:

Thirty-two female Sprague-Dawley (SD) rats were used in this study. IC was induced by intraperitoneal injection of cyclophosphamide (CYP). Rats were randomly allocated to one of four groups (n = 8 per group): A control group, which was injected with saline (75 mg/kg; i.p.) instead of CYP on days 1, 4, and 7; a chronic IC group, which was injected with CYP (75 mg/kg; i.p.) on days 1, 4, and 7; a high-dose (30 mg/kg) phloroglucinol-treated group; and a low-dose (15 mg/kg) phloroglucinol-treated group. On day 8, the rats in each group underwent cystometrography (CMG), and the bladders were examined for evidence of oxidative stress and inflammation. Statistical analysis was performed by analysis of variance (ANOVA) followed by least square difference multiple comparison post-hoc test.

Results:

Histological evaluation showed that bladder inflammation in CYP-treated rats was suppressed by phloroglucinol. CMG revealed that the CYP treatment induced overactive bladder in rats that was reversed by phloroglucinol. Up-regulated tumor necrosis factor-α and interleukin-6 expression in the CYP-treated rats were also suppressed in the phloroglucinol treated rats. CYP treatment significantly increased myeloperoxidase activity as well as the decreased activities of catalase of the bladder, which was reversed by treatment with phloroglucinol.

Conclusions:

The application of phloroglucinol suppressed oxidative stress, inflammation, and overactivity in the bladder. This may provide a new treatment strategy for IC.

Duration-dependent regulation of autophagy by isoflurane exposure in aged rats

Current evidence suggests a central role for autophagy in many inflammatory brain disorders, including Alzheimer's disease (AD). Furthermore, it is also well accepted that some inhalation anesthetics, such as isoflurane, may cause AD-like neuropathogenesis and resultant postoperative cognitive dysfunction, especially in the elderly population. However, the impact of inhalation anesthetics on autophagic components in the brain remains to be documented. Hence, our objective was to investigate the effects of different durations of isoflurane exposure on hippocampus-dependent learning and hippocampal autophagy in aged rats. Aged Sprague-Dawley rats (20 months old) were randomly exposed to 1.5% isoflurane or 100% oxygen for 1 or 4 h. Animals were then trained in the Morris water maze (4 trials/day for 5 consecutive days). Hippocampal phagophore formation markers, beclin 1 and protein microtubule-associated protein 1 light chain-3B (LC3B), as well as p62, an indicator of autophagic flux, were quantified by western blotting. There was no significant difference in the escape latencies and time spent in the target quadrant, as well as hippocampal expression of beclin 1, LC3B-II, and p62 at 24 h post-anesthesia between the 1-h isoflurane-exposed rats and their controls (P >0.05). Four-hour exposure to isoflurane resulted in spatial learning and memory deficits, as evidenced by prolonged escape latencies on days 4 and 5 post-anesthesia and less time spent in the target quadrant than sham-exposed animals (P <0.05). These events were accompanied by a decline in hippocampal expression of LC3B-I, LC3B-II, and beclin 1 24 h after isoflurane (P <0.01 and P <0.05). Nevertheless, no significant change in p62 expression was found. Further kinetics study of autophagic changes induced by 4 h of isoflurane showed a transient upregulation of LC3B-I, LC3B-II, and beclin 1 at the end of exposure and a subsequent striking decrease within 12-24 h post-anesthesia (P <0.05). Hippocampal p62 peaked at 6 h but subsequently resolved. These results from our pilot in vivo study support a duration-dependent relationship between 1.5% isoflurane exposure, and spatial cognitive function as well as hippocampal phagophore formation.

Neuroprotective mechanism of losartan and its interaction with nimesulide against chronic fatigue stress

Potential role of angiotensin-II and cyclooxygenase have been suggested in the pathophysiology of chronic fatigue stress. The present study has been designed to evaluate the neuroprotective effect of losartan and its interaction with nimesulide against chronic fatigue stress and related complications in mice. In the present study, male Laca mice (20-30 g) were subjected to running wheel activity test session (RWATS) for 6 min daily for 21 days. Losartan, nimesulide and their combinations were administered daily for 21 days, 45 min before being subjected to RWATS. Various behavioral and biochemical and neuroinflammatory mediators were assessed subsequently. 21 days RWATS treatment significantly decreased number of wheel rotations/6 min indicating fatigue stress like behaviors as compared to naive group. 21 days treatment with losartan (10 and 20 mg/kg, ip), nimesulide (5 and 10 mg/kg, po) and their combinations significantly improved behavior [increased number of wheel rotations, reversal of post-exercise fatigue, locomotor activity, antianxiety-like behavior (number of entries, latency to enter and time spent in mirror chamber), and memory performance (transfer latency in plus-maze performance task)], biochemical parameters (reduced serum corticosterone, brain lipid peroxidation, nitrite concentration, acetylcholinesterase activity, restored reduced glutathione levels and catalase activity) as compared to RWATS control. Besides, TNF-α, CRP levels were significantly attenuated by these drugs and their combinations as compared to control. The present study highlights the role of cyclooxygenase modulation in the neuroprotective effect of losartan against chronic fatigue stress-induced behavioral, biochemical and cellular alterations in mice.

Neuroinflammation in the normal aging hippocampus

A consequence of normal aging is a greater susceptibility to memory impairments following an immune challenge such as infection, surgery, or traumatic brain injury. The neuroinflammatory response, produced by these challenges results in increased and prolonged production of pro-inflammatory cytokines in the otherwise healthy aged brain. Here we discuss the mechanisms by which long-lasting elevations in pro-inflammatory cytokines in the hippocampus produce memory impairments. Sensitized microglia are a primary source of this exaggerated neuroinflammatory response and appear to be a hallmark of the normal aging brain. We review the current understanding of the causes and effects of normal aging-induced microglial sensitization, including dysregulations of the neuroendocrine system, potentiation of neuroinflammatory responses following an immune challenge, and the impairment of memories. We end with a discussion of therapeutic approaches to prevent these deleterious effects.

Surgical stress induces brain-derived neurotrophic factor reduction and postoperative cognitive dysfunction via glucocorticoid receptor phosphorylation in aged mice

AIMS

This study explored whether surgical stress-induced glucocorticoid receptor (GR) phosphorylation is related to postoperative cognitive dysfunction (POCD) in aged individuals. Inhibition of GR activation could be an effective treatment for POCD.

METHODS

A laparotomy was given to C57/BL6 mice in POCD group both 20 and 6 months old. Animals in control group were treated in identical manners except for laparotomy. Cognitive function was evaluated by Morris water maze and elevated plus maze. Western blot and Elisa assay were used to detect related molecules. Mifepristone and roscovitine were treated as inhibitions of GR phosphorylation.

RESULTS

The cognitive function was impaired, and brain-derived neurotrophic factor (BDNF) was found reduced in aged POCD group. GR translocation into nucleus and elevated GR phosphorylation were found in prefrontal cortex of aged POCD mice. Cyclin-dependent Kinase 5 (CDK5), kinase for GR phosphorylation also elevated in aged POCD mice. With GR antagonist and CDK5 inhibitor, reduction of BDNF and cognitive dysfunction in aged mice were both rescued.

CONCLUSION

These results presented a mechanism that surgical stress-induced GR phosphorylation contributes to POCD in aged individuals. Inhibition of GR activation and phosphorylation might be a potential treatment target of POCD.