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Stone TW, Clanchy FIL, Huang YS, Chiang NY, Darlington LG, Williams RO. An integrated cytokine and kynurenine network as the basis of neuroimmune communication. Front Neurosci 2022; 16:1002004. [PMID: 36507331 PMCID: PMC9729788 DOI: 10.3389/fnins.2022.1002004] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2022] [Accepted: 10/31/2022] [Indexed: 11/25/2022] Open
Abstract
Two of the molecular families closely associated with mediating communication between the brain and immune system are cytokines and the kynurenine metabolites of tryptophan. Both groups regulate neuron and glial activity in the central nervous system (CNS) and leukocyte function in the immune system, although neither group alone completely explains neuroimmune function, disease occurrence or severity. This essay suggests that the two families perform complementary functions generating an integrated network. The kynurenine pathway determines overall neuronal excitability and plasticity by modulating glutamate receptors and GPR35 activity across the CNS, and regulates general features of immune cell status, surveillance and tolerance which often involves the Aryl Hydrocarbon Receptor (AHR). Equally, cytokines and chemokines define and regulate specific populations of neurons, glia or immune system leukocytes, generating more specific responses within restricted CNS regions or leukocyte populations. In addition, as there is a much larger variety of these compounds, their homing properties enable the superimposition of dynamic variations of cell activity upon local, spatially limited, cell populations. This would in principle allow the targeting of potential treatments to restricted regions of the CNS. The proposed synergistic interface of 'tonic' kynurenine pathway affecting baseline activity and the superimposed 'phasic' cytokine system would constitute an integrated network explaining some features of neuroimmune communication. The concept would broaden the scope for the development of new treatments for disorders involving both the CNS and immune systems, with safer and more effective agents targeted to specific CNS regions.
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Affiliation(s)
- Trevor W. Stone
- The Kennedy Institute of Rheumatology, NDORMS, University of Oxford, Oxford, United Kingdom,*Correspondence: Trevor W. Stone,
| | - Felix I. L. Clanchy
- The Kennedy Institute of Rheumatology, NDORMS, University of Oxford, Oxford, United Kingdom
| | - Yi-Shu Huang
- The Kennedy Institute of Rheumatology, NDORMS, University of Oxford, Oxford, United Kingdom
| | - Nien-Yi Chiang
- The Kennedy Institute of Rheumatology, NDORMS, University of Oxford, Oxford, United Kingdom
| | - L. Gail Darlington
- Department of Internal Medicine, Ashtead Hospital, Ashtead, United Kingdom
| | - Richard O. Williams
- The Kennedy Institute of Rheumatology, NDORMS, University of Oxford, Oxford, United Kingdom
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Martos D, Tuka B, Tanaka M, Vécsei L, Telegdy G. Memory Enhancement with Kynurenic Acid and Its Mechanisms in Neurotransmission. Biomedicines 2022; 10:biomedicines10040849. [PMID: 35453599 PMCID: PMC9027307 DOI: 10.3390/biomedicines10040849] [Citation(s) in RCA: 33] [Impact Index Per Article: 16.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2022] [Revised: 03/28/2022] [Accepted: 04/02/2022] [Indexed: 02/04/2023] Open
Abstract
Kynurenic acid (KYNA) is an endogenous tryptophan (Trp) metabolite known to possess neuroprotective property. KYNA plays critical roles in nociception, neurodegeneration, and neuroinflammation. A lower level of KYNA is observed in patients with neurodegenerative diseases such as Alzheimer’s and Parkinson’s diseases or psychiatric disorders such as depression and autism spectrum disorders, whereas a higher level of KYNA is associated with the pathogenesis of schizophrenia. Little is known about the optimal concentration for neuroprotection and the threshold for neurotoxicity. In this study the effects of KYNA on memory functions were investigated by passive avoidance test in mice. Six different doses of KYNA were administered intracerebroventricularly to previously trained CFLP mice and they were observed for 24 h. High doses of KYNA (i.e., 20–40 μg/2 μL) significantly decreased the avoidance latency, whereas a low dose of KYNA (0.5 μg/2 μL) significantly elevated it compared with controls, suggesting that the low dose of KYNA enhanced memory function. Furthermore, six different receptor blockers were applied to reveal the mechanisms underlying the memory enhancement induced by KYNA. The series of tests revealed the possible involvement of the serotonergic, dopaminergic, α and β adrenergic, and opiate systems in the nootropic effect. This study confirmed that a low dose of KYNA improved a memory component of cognitive domain, which was mediated by, at least in part, four systems of neurotransmission in an animal model of learning and memory.
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Affiliation(s)
- Diána Martos
- MTA-SZTE Neuroscience Research Group, Hungarian Academy of Sciences, University of Szeged (MTA-SZTE), Semmelweis u. 6, H-6725 Szeged, Hungary; (D.M.); (B.T.); (M.T.)
| | - Bernadett Tuka
- MTA-SZTE Neuroscience Research Group, Hungarian Academy of Sciences, University of Szeged (MTA-SZTE), Semmelweis u. 6, H-6725 Szeged, Hungary; (D.M.); (B.T.); (M.T.)
| | - Masaru Tanaka
- MTA-SZTE Neuroscience Research Group, Hungarian Academy of Sciences, University of Szeged (MTA-SZTE), Semmelweis u. 6, H-6725 Szeged, Hungary; (D.M.); (B.T.); (M.T.)
| | - László Vécsei
- MTA-SZTE Neuroscience Research Group, Hungarian Academy of Sciences, University of Szeged (MTA-SZTE), Semmelweis u. 6, H-6725 Szeged, Hungary; (D.M.); (B.T.); (M.T.)
- Department of Neurology, Albert Szent-Györgyi Medical School, University of Szeged, Semmelweis u. 6, H-6725 Szeged, Hungary
- Correspondence: ; Tel.: +36-62-342-361
| | - Gyula Telegdy
- Department of Pathophysiology, Albert Szent-Györgyi Medical School, University of Szeged, Semmelweis u. 5, H-6725 Szeged, Hungary;
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Ostapiuk A, Urbanska EM. Kynurenic acid in neurodegenerative disorders-unique neuroprotection or double-edged sword? CNS Neurosci Ther 2022; 28:19-35. [PMID: 34862742 PMCID: PMC8673711 DOI: 10.1111/cns.13768] [Citation(s) in RCA: 31] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2021] [Revised: 10/27/2021] [Accepted: 11/02/2021] [Indexed: 12/24/2022] Open
Abstract
AIMS The family of kynurenine pathway (KP) metabolites includes compounds produced along two arms of the path and acting in clearly opposite ways. The equilibrium between neurotoxic kynurenines, such as 3-hydroxykynurenine (3-HK) or quinolinic acid (QUIN), and neuroprotective kynurenic acid (KYNA) profoundly impacts the function and survival of neurons. This comprehensive review summarizes accumulated evidence on the role of KYNA in Alzheimer's, Parkinson's and Huntington's diseases, and discusses future directions of potential pharmacological manipulations aimed to modulate brain KYNA. DISCUSSION The synthesis of specific KP metabolites is tightly regulated and may considerably vary under physiological and pathological conditions. Experimental data consistently imply that shift of the KP to neurotoxic branch producing 3-HK and QUIN formation, with a relative or absolute deficiency of KYNA, is an important factor contributing to neurodegeneration. Targeting specific brain regions to maintain adequate KYNA levels seems vital; however, it requires the development of precise pharmacological tools, allowing to avoid the potential cognitive adverse effects. CONCLUSIONS Boosting KYNA levels, through interference with the KP enzymes or through application of prodrugs/analogs with high bioavailability and potency, is a promising clinical approach. The use of KYNA, alone or in combination with other compounds precisely influencing specific populations of neurons, is awaiting to become a significant therapy for neurodegenerative disorders.
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Affiliation(s)
- Aleksandra Ostapiuk
- Laboratory of Cellular and Molecular PharmacologyDepartment of Experimental and Clinical PharmacologyMedical University of LublinLublinPoland
- Present address:
Department of Clinical Digestive OncologyKU LeuvenLeuvenBelgium
| | - Ewa M. Urbanska
- Laboratory of Cellular and Molecular PharmacologyDepartment of Experimental and Clinical PharmacologyMedical University of LublinLublinPoland
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Butler MI, Long-Smith C, Moloney GM, Morkl S, O'Mahony SM, Cryan JF, Clarke G, Dinan TG. The immune-kynurenine pathway in social anxiety disorder. Brain Behav Immun 2022; 99:317-326. [PMID: 34758380 DOI: 10.1016/j.bbi.2021.10.020] [Citation(s) in RCA: 27] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/30/2021] [Revised: 10/18/2021] [Accepted: 10/31/2021] [Indexed: 12/28/2022] Open
Abstract
BACKGROUND The tryptophan-kynurenine pathway is of major interest in psychiatry and is altered in patients with depression, schizophrenia and panic disorder. Stress and immune alterations can impact this system, through cortisol- and cytokine-induced activation. In addition, there is emerging evidence that the kynurenine pathway is associated with suicidality. There have been no studies to date exploring the immune-kynurenine system in social anxiety disorder (SAD), and indeed very limited human studies on the kynurenine pathway in any clinical anxiety disorder. METHODS We investigated plasma levels of several kynurenine pathway markers, including kynurenine (KYN), tryptophan (TRYP) and kynurenic acid (KYNA), along with the KYN/TRYP and KYNA/KYN ratios, in a cohort of 32 patients with SAD and 36 healthy controls. We also investigated a broad array of both basal and lipopolysaccharide (LPS)-stimulated blood cytokine levels including IFN-γ, interleukin (IL)-10, IL-1β, IL-2, IL-4, IL-6, IL-8 and tumor necrosis factor (TNF)-α. RESULTS SAD patients had elevated plasma KYNA levels and an increased KYNA/KYN ratio compared to healthy controls. No differences in KYN, TRYP or the KYN/TRYP ratio were seen between the two groups. SAD patients with a history of past suicide attempt showed elevated plasma KYN levels and a higher KYN/TRYP ratio compared to patients without a history of suicide attempt. No differences were seen in basal or LPS-stimulated pro-inflammatory cytokine levels between the patients and controls. However, unstimulated IL-10, an anti-inflammatory cytokine, was significantly lower in the SAD group. A significant sex influence was evident with SAD males having lower levels of IL-10 compared to healthy males but no difference seen between SAD females and healthy females. CONCLUSIONS The peripheral kynurenine pathway is altered in SAD and preferentially directed towards KYNA synthesis. Additionally, kynurenine pathway activation, as evidenced by elevated KYN and KYN/TRYP ratio, is evident in SAD patients with a history of past suicide attempt. While no differences in pro-inflammatory cytokines is apparent in SAD patients, lower anti-inflammatory IL-10 levels are seen in SAD males. Further investigation of the role of the immune-kynurenine pathway in SAD and other clinical anxiety disorders is warranted.
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Affiliation(s)
- Mary I Butler
- Department of Psychiatry and Neurobehavioural Science, University College Cork, Ireland; APC Microbiome Ireland, University College Cork, Ireland.
| | | | - Gerard M Moloney
- APC Microbiome Ireland, University College Cork, Ireland; Department of Anatomy and Neuroscience, University College Cork, Ireland
| | - Sabrina Morkl
- APC Microbiome Ireland, University College Cork, Ireland; Department of Psychiatry and Psychotherapeutic Medicine, Medical University of Graz, Austria
| | - Siobhain M O'Mahony
- APC Microbiome Ireland, University College Cork, Ireland; Department of Anatomy and Neuroscience, University College Cork, Ireland
| | - John F Cryan
- APC Microbiome Ireland, University College Cork, Ireland; Department of Anatomy and Neuroscience, University College Cork, Ireland
| | - Gerard Clarke
- Department of Psychiatry and Neurobehavioural Science, University College Cork, Ireland; APC Microbiome Ireland, University College Cork, Ireland
| | - Timothy G Dinan
- Department of Psychiatry and Neurobehavioural Science, University College Cork, Ireland; APC Microbiome Ireland, University College Cork, Ireland
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Tomczyk T, Urbańska EM. Experimental hypothyroidism raises brain kynurenic acid - Novel aspect of thyroid dysfunction. Eur J Pharmacol 2020; 883:173363. [PMID: 32663543 DOI: 10.1016/j.ejphar.2020.173363] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2020] [Revised: 07/06/2020] [Accepted: 07/09/2020] [Indexed: 01/09/2023]
Abstract
Hypothyroidism frequently manifests with altered mood and disturbed cognition. Kynurenic acid may influence cognition through antagonism of N-methyl-d-aspartate receptors (NMDA) and α7 nicotinic receptors. In here, thyroid hormones effects on kynurenic acid synthesis in rat cortical slices and on kynurenine aminotransferases (KATs) activity in semi-purified cortical homogenates were studied. Furthermore, brain kynurenic acid levels and KATs activities were evaluated in experimental model of hypothyroidism, induced by chronic administration of 0.05% propylthiouracil in drinking water. In vitro, L-thyroxine (T4) and 3,3,5-triiodothyronine (T3), reduced kynurenic acid synthesis and KATs activities (IC50 ~ 50-150 μM). In vivo, propylthiouracil increased cortical, hippocampal and striatal, but not cerebellar kynurenic acid content (192%, 142% and 124% of control, respectively), despite uniformly decreased KAT II activity and lower cortical and striatal KAT I activity. T4 application to hypothyroid animals restored kynurenic acid levels to control values and reversed enzymatic changes. T4 alone did not change brain kynurenic acid levels, despite increased activities of brain KATs. Hence, thyroid hormones modulate kynurenic acid levels by two opposing mechanisms, stimulation of KATs activity, most probably transcriptional, and direct, post-translational inhibition of KATs. Lack of correlation between KATs activity and kynurenic acid level may reflect the influence of T4 on organic anion transporter and result from impaired removal of kynurenic acid from the brain during hypothyroidism. Our data reveal novel mechanism linked with thyroid hormones deficiency and imply the potential involvement of increased brain kynurenic acid in the hypothyroidism-related cognitive disturbance.
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Affiliation(s)
- Tomasz Tomczyk
- Department of Experimental and Clinical Pharmacology, Medical University in Lublin, Poland
| | - Ewa M Urbańska
- Laboratory of Cellular and Molecular Pharmacology, Department of Experimental and Clinical Pharmacology, Medical University in Lublin, Poland.
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Dietary hydrogenated vegetable fat exacerbates the activation of kynurenine pathway caused by peripheral lipopolysaccharide immune challenge in aged mice. Chem Biol Interact 2018; 293:28-37. [DOI: 10.1016/j.cbi.2018.07.023] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2018] [Revised: 07/13/2018] [Accepted: 07/23/2018] [Indexed: 11/22/2022]
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Kocki T, Urbańska EM, Kocki J, Kloc R, Kocka K, Olajossy M, Owe-Larsson B. Prolonged therapy with antidepressants increases hippocampal level of kynurenic acid and expression of Kat1 and Kat2 genes. Pharmacol Rep 2018; 70:737-745. [DOI: 10.1016/j.pharep.2018.01.004] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2017] [Revised: 01/11/2018] [Accepted: 01/11/2018] [Indexed: 12/19/2022]
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O'Farrell K, Harkin A. Stress-related regulation of the kynurenine pathway: Relevance to neuropsychiatric and degenerative disorders. Neuropharmacology 2015; 112:307-323. [PMID: 26690895 DOI: 10.1016/j.neuropharm.2015.12.004] [Citation(s) in RCA: 88] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2015] [Revised: 12/02/2015] [Accepted: 12/08/2015] [Indexed: 02/08/2023]
Abstract
The kynurenine pathway (KP), which is activated in times of stress and infection has been implicated in the pathophysiology of neurodegenerative and psychiatric disorders. Activation of this tryptophan metabolising pathway results in the production of neuroactive metabolites which have the potential to interfere with normal neuronal functioning which may contribute to altered neuronal transmission and the emergence of symptoms of these brain disorders. This review investigates the involvement of the KP in a range of neurological disorders, examining recent in vitro, in vivo and clinical discoveries highlights evidence to indicate that the KP is a potential therapeutic target in both neurodegenerative and stress-related neuropsychiatric disorders. Furthermore, this review identifies gaps in our knowledge with regard to this field which are yet to be examined to lead to a more comprehensive understanding of the role of KP activation in brain health and disease. This article is part of the Special Issue entitled 'The Kynurenine Pathway in Health and Disease'.
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Affiliation(s)
- Katherine O'Farrell
- Neuropsychopharmacology Research Group, School of Pharmacy and Pharmaceutical Sciences & Trinity College Institute of Neuroscience, Trinity College Dublin, Ireland
| | - Andrew Harkin
- Neuropsychopharmacology Research Group, School of Pharmacy and Pharmaceutical Sciences & Trinity College Institute of Neuroscience, Trinity College Dublin, Ireland; Neuroimmunology Research Group, Department of Physiology, School of Medicine & Trinity College Institute of Neuroscience, Trinity College Dublin, Ireland.
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9
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Anderson G, Rodriguez M. Multiple sclerosis: the role of melatonin and N-acetylserotonin. Mult Scler Relat Disord 2014; 4:112-23. [PMID: 25787187 DOI: 10.1016/j.msard.2014.12.001] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2013] [Revised: 11/06/2014] [Accepted: 12/09/2014] [Indexed: 12/31/2022]
Abstract
Multiple sclerosis (MS) is an immune mediated disorder that is under intensive investigation in an attempt to improve on available treatments. Many of the changes occurring in MS, including increased mitochondrial dysfunction, pain reporting and depression may be partly mediated by increased indoleamine 2,3-dioxygenase, which drives tryptophan to the production of neuroregulatory tryptophan catabolites and away from serotonin, N-acetylserotonin and melatonin production. The consequences of decreased melatonin have classically been attributed to circadian changes following its release from the pineal gland. However, recent data shows that melatonin may be produced by all mitochondria containing cells to some degree, including astrocytes and immune cells, thereby providing another important MS treatment target. As well as being a powerful antioxidant, anti-inflammatory and antinociceptive, melatonin improves mitochondrial functioning, partly via increased oxidative phosphorylation. Melatonin also inhibits demyelination and increases remyelination, suggesting that its local regulation in white matter astrocytes by serotonin availability and apolipoprotein E4, among other potential factors, will be important in the etiology, course and treatment of MS. Here we review the role of local melatonin and its precursors, N-acetylserotonin and serotonin, in MS.
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Anderson G, Kubera M, Duda W, Lasoń W, Berk M, Maes M. Increased IL-6 trans-signaling in depression: focus on the tryptophan catabolite pathway, melatonin and neuroprogression. Pharmacol Rep 2014; 65:1647-54. [PMID: 24553013 DOI: 10.1016/s1734-1140(13)71526-3] [Citation(s) in RCA: 63] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2013] [Revised: 10/15/2013] [Indexed: 12/13/2022]
Abstract
Depression has been conceptualized as a disorder driven by immuno-inflammatory pathways and oxidative and nitrosative stress. These factors couple to the induction of neuroregulatory tryptophan catabolites via the activation of indoleamine 2,3-dioxygenase (IDO) and tryptophan 2,3-dioxygenase (TDO). Oxidative damage to neoepitopes increases autoimmune responses, changing the nature of the neural substrate of recurrent depression, which leads to neuroprogression and drives treatment resistance. A number of pro-inflammatory cytokines are linked to these processes. Here, we focus on the role of interleukin (IL)-6 in depression and its associated disorders; we highlight the progress made since the first paper showing increased IL-6 levels was published 20 years ago by Maes and colleagues. When coupled with increased levels of the soluble IL-6 receptor in depression, higher levels of IL-6 may indicate increased IL-6 trans-signaling, whereby IL-6 receptor signaling occurs in cells not normally expressing the IL-6 receptor. It has been suggested that IL-6 is intimately associated with two crucial aspects of depression, as well as central inflammation more broadly. First, the regulation of the local inflammatory response via its interactions with macrophage and glia melatonin production is coupled to local epigenetic modulation via methyl CpG-binding protein 2 (MeCP2). Second, the more systemic regulation of tryptophan availability occurs via the IL-6 induction of IDO. Coupled to its role in the regulation of autoimmune associated T-helper 17 cells and IL-17 production, IL-6 has wide and differential impacts on processes driving depression and a wider range of psychiatric and neurodegenerative conditions.
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Affiliation(s)
- George Anderson
- CRC Clinical Research Centre/Communications, Rm 30, 57 Laurel Street, Glasgow, G11 7QT, Scotland.
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Dorris DM, Hauser CA, Minnehan CE, Meitzen J. An aerator for brain slice experiments in individual cell culture plate wells. J Neurosci Methods 2014; 238:1-10. [PMID: 25256645 DOI: 10.1016/j.jneumeth.2014.09.017] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2014] [Revised: 09/12/2014] [Accepted: 09/15/2014] [Indexed: 11/29/2022]
Abstract
BACKGROUND Ex vivo acute living brain slices are a broadly employed and powerful experimental preparation. Most new technology regarding this tissue has involved the chamber used when performing electrophysiological experiments. Alternatively we instead focus on the creation of a simple, versatile aerator designed to allow maintenance and manipulation of acute brain slices and potentially other tissue in a multi-well cell culture plate. NEW METHOD Here we present an easily manufactured aerator designed to fit into a 24-well cell culture plate. It features a nylon mesh and a single microhole to enable gas delivery without compromising tissue stability. The aerator is designed to be individually controlled, allowing both high throughput and single well experiments. RESULTS The aerator was validated by testing material leach, dissolved oxygen delivery, brain slice viability and neuronal electrophysiology. Example experiments are also presented, including a test of whether β1-adrenergic receptor activation regulates gene expression in ex vivo dorsal striatum using qPCR. COMPARISON WITH EXISTING METHODS Key differences include enhanced control over gas delivery to individual wells containing brain slices, decreased necessary volume, a sample restraint to reduce movement artifacts, the potential to be sterilized, the avoidance of materials that absorb water and small biological molecules, minimal production costs, and increased experimental throughput. CONCLUSION This new aerator is of high utility and will be useful for experiments involving brain slices and other potentially tissue samples in 24-well cell culture plates.
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Affiliation(s)
- David M Dorris
- Department of Biological Sciences, North Carolina State University, Raleigh, NC, USA
| | - Caitlin A Hauser
- Department of Biological Sciences, North Carolina State University, Raleigh, NC, USA
| | - Caitlin E Minnehan
- Department of Biological Sciences, North Carolina State University, Raleigh, NC, USA
| | - John Meitzen
- Department of Biological Sciences, North Carolina State University, Raleigh, NC, USA; W.M. Keck Center for Behavioral Biology, Center for Human Health and the Environment, and Center for Comparative Medicine and Translational Research, North Carolina State University, Raleigh, NC, USA.
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Anderson G, Berk M, Maes M. Biological phenotypes underpin the physio-somatic symptoms of somatization, depression, and chronic fatigue syndrome. Acta Psychiatr Scand 2014; 129:83-97. [PMID: 23952563 DOI: 10.1111/acps.12182] [Citation(s) in RCA: 74] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 06/19/2013] [Indexed: 12/26/2022]
Abstract
OBJECTIVE Somatization is a symptom cluster characterized by 'psychosomatic' symptoms, that is, medically unexplained symptoms, and is a common component of other conditions, including depression and myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS). This article reviews the data regarding the pathophysiological foundations of 'psychosomatic' symptoms and the implications that this has for conceptualization of what may more appropriately be termed physio-somatic symptoms. METHOD This narrative review used papers published in PubMed, Scopus, and Google Scholar electronic databases using the keywords: depression and chronic fatigue, depression and somatization, somatization and chronic fatigue syndrome, each combined with inflammation, inflammatory, tryptophan, and cell-mediated immune (CMI). RESULTS The physio-somatic symptoms of depression, ME/CFS, and somatization are associated with specific biomarkers of inflammation and CMI activation, which are correlated with, and causally linked to, changes in the tryptophan catabolite (TRYCAT) pathway. Oxidative and nitrosative stress induces damage that increases neoepitopes and autoimmunity that contribute to the immuno-inflammatory processes. These pathways are all known to cause physio-somatic symptoms, including fatigue, malaise, autonomic symptoms, hyperalgesia, intestinal hypermotility, peripheral neuropathy, etc. CONCLUSION Biological underpinnings, such as immune-inflammatory pathways, may explain, at least in part, the occurrence of physio-somatic symptoms in depression, somatization, or myalgic encephalomyelitis/chronic fatigue syndrome and thus the clinical overlap among these disorders.
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Anderson G, Maes M. Neurodegeneration in Parkinson's disease: interactions of oxidative stress, tryptophan catabolites and depression with mitochondria and sirtuins. Mol Neurobiol 2013; 49:771-83. [PMID: 24085563 DOI: 10.1007/s12035-013-8554-z] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2013] [Accepted: 09/19/2013] [Indexed: 11/29/2022]
Abstract
The biological underpinnings to the etiology and course of neurodegeneration in Parkinson's disease are an area of extensive research that has yet to produce an early biological marker or disease-slowing or preventative treatment. Recent conceptualizations of Parkinson's disease have integrated immuno-inflammation and oxidative and nitrosative stress occurring in depression, somatization and peripheral inflammation into the course of Parkinson's disease. We review the data showing the importance of immuno-inflammatory processes and oxidative and nitrosative stress in such classically conceived 'comorbidities', suggesting that lifetime, prodromal and concurrent depression and somatization may be intricately involved in the etiology and course of Parkinson's disease, rather than psychiatric comorbidities. This produces a longer term developmental perspective of Parkinson's disease, which incorporates tryptophan catabolites (TRYCATs), lipid peroxidation, sirtuins, cyclic adenosine monophosphate, aryl hydrocarbon receptor, and circadian genes. This integrates wider bodies of data pertaining to neuronal loss in Parkinson's disease, emphasizing how these interact with susceptibility genes to drive changes in mitochondria, blood-brain barrier permeability and intercellular signalling. We review this data here in the context of neurodegeneration in Parkinson's disease and to the future directions indicated for slowing disease progression.
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Anderson G, Maes M, Berk M. Schizophrenia is primed for an increased expression of depression through activation of immuno-inflammatory, oxidative and nitrosative stress, and tryptophan catabolite pathways. Prog Neuropsychopharmacol Biol Psychiatry 2013; 42:101-14. [PMID: 22930036 DOI: 10.1016/j.pnpbp.2012.07.016] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/27/2012] [Revised: 07/25/2012] [Accepted: 07/26/2012] [Indexed: 02/08/2023]
Abstract
Schizophrenia and depression are two common and debilitating psychiatric conditions. Up to 61% of schizophrenic patients have comorbid clinical depression, often undiagnosed. Both share significant overlaps in underlying biological processes, which are relevant to the course and treatment of both conditions. Shared processes include changes in cell-mediated immune and inflammatory pathways, e.g. increased levels of pro-inflammatory cytokines and a Th1 response; activation of oxidative and nitrosative stress (O&NS) pathways, e.g. increased lipid peroxidation, damage to proteins and DNA; decreased antioxidant levels, e.g. lowered coenzyme Q10, vitamin E, glutathione and melatonin levels; autoimmune responses; and activation of the tryptophan catabolite (TRYCAT) pathway through induction of indoleamine-2,3-dioxygenase. Both show cognitive and neurostructural evidence of a neuroprogressive process. Here we review the interlinked nature of these biological processes, suggesting that schizophrenia is immunologically primed for an increased expression of depression. Such a conceptualization explains, and incorporates, many of the current perspectives on the nature of schizophrenia and depression, and has implications for the nature of classification and treatment of both disorders. An early developmental etiology to schizophrenia, driven by maternal infection, with subsequent impact on offspring immuno-inflammatory responses, creates alterations in the immune pathways, which although priming for depression, also differentiates the two disorders.
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Anderson G, Maes M. Schizophrenia: linking prenatal infection to cytokines, the tryptophan catabolite (TRYCAT) pathway, NMDA receptor hypofunction, neurodevelopment and neuroprogression. Prog Neuropsychopharmacol Biol Psychiatry 2013; 42:5-19. [PMID: 22800757 DOI: 10.1016/j.pnpbp.2012.06.014] [Citation(s) in RCA: 100] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/22/2012] [Revised: 06/06/2012] [Accepted: 06/18/2012] [Indexed: 02/07/2023]
Abstract
In 1995, the macrophage-T lymphocyte theory of schizophrenia (Smith and Maes, 1995) considered that activated immuno-inflammatory pathways may account for the higher neurodevelopmental pathology linked with gestational infections through the detrimental effects of activated microglia, oxidative and nitrosative stress (O&NS), cytokine-induced activation of the tryptophan catabolite (TRYCAT) pathway and consequent modulation of the N-methyl d-aspartate receptor (NMDAr) and glutamate production. The aim of the present paper is to review the current state-of-the art regarding the role of the above pathways in schizophrenia. Accumulating data suggest a powerful role for prenatal infection, both viral and microbial, in driving an early developmental etiology to schizophrenia. Models of prenatal rodent infection show maintained activation of immuno-inflammatory pathways coupled to increased microglia activation. The ensuing activation of immuno-inflammatory pathways in schizophrenia may activate the TRYCAT pathway, including increased kynurenic acid (KA) and neurotoxic TRYCATs. Increased KA, via the inhibition of the α7 nicotinic acetylcholine receptor, lowers gamma-amino-butyric-acid (GABA)ergic post-synaptic current, contributing to dysregulated glutamatergic activity. Hypofunctioning of the NMDAr on GABAergic interneurons will contribute to glutamatergic dysregulation. Many susceptibility genes for schizophrenia are predominantly expressed in early development and will interact with these early developmental driven changes in the immuno-inflammatory and TRYCAT pathways. Maternal infection and subsequent immuno-inflammatory responses are additionally associated with O&NS, including lowered antioxidants such as glutathione. This will contribute to alterations in neurogenesis and myelination. In such a scenario a) a genetic or epigenetic potentiation of immuno-inflammatory pathways may constitute a double hit on their own, stimulating wider immuno-inflammatory responses and thus potentiating the TRYCAT pathway and subsequent NMDAr dysfunction and neuroprogression; and b) antipsychotic-induced changes in immuno-inflammatory, TRYCAT and O&NS pathways would modulate the CNS glia-neuronal interactions that determine synaptic plasticity as well as myelin generation and maintenance.
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Anderson G, Beischlag TV, Vinciguerra M, Mazzoccoli G. The circadian clock circuitry and the AHR signaling pathway in physiology and pathology. Biochem Pharmacol 2013; 85:1405-16. [PMID: 23438471 DOI: 10.1016/j.bcp.2013.02.022] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2013] [Revised: 02/14/2013] [Accepted: 02/14/2013] [Indexed: 12/14/2022]
Abstract
Life forms populating the Earth must face environmental challenges to assure individual and species survival. The strategies predisposed to maintain organismal homeostasis and grant selective advantage rely on anticipatory phenomena facing periodic modifications, and compensatory phenomena facing unpredictable changes. Biological processes bringing about these responses are respectively driven by the circadian timing system, a complex of biological oscillators entrained to the environmental light/dark cycle, and by regulatory and metabolic networks that precisely direct the body's adjustments to variations of external conditions and internal milieu. A critical role in organismal homeostatic functions is played by the aryl hydrocarbon receptor (AHR) complex, which senses environmental and endogenous compounds, influences metabolic responses controlling phase I/II gene expression, and modulates vital phenomena such as development, inflammation and adaptive immunity. A physiological cross-talk between circadian and AHR signaling pathways has been evidenced. The alteration of AHR signaling pathway deriving from genetic damage with polymorphisms or mutations, or produced by exogenous or endogenous AHR activation, and chronodisruption caused by mismatch between the body's internal clock and geophysical time/social schedules, are capable of triggering pathological mechanisms involved in metabolic, immune-related and neoplastic diseases. On the other hand, the molecular components of the circadian clock circuitry and AHR signaling pathway may represent useful tools for preventive interventions and valuable targets of therapeutic approaches.
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Affiliation(s)
- George Anderson
- Clinical Research Centre/Communications, Glasgow, United Kingdom
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Abstract
Postpartum depression (PPD) is common, occurring in 10%-15% of women. Due to concerns about teratogenicity of medications in the suckling infant, the treatment of PPD has often been restricted to psychotherapy. We review here the biological underpinnings to PPD, suggesting a powerful role for the tryptophan catabolites, indoleamine 2,3-dixoygenase, serotonin, and autoimmunity in mediating the consequences of immuno-inflammation and oxidative and nitrosative stress. It is suggested that the increased inflammatory potential, the decreases in endogenous anti-inflammatory compounds together with decreased omega-3 poly-unsaturated fatty acids, in the postnatal period cause an inflammatory environment. The latter may result in the utilization of peripheral inflammatory products, especially kynurenine, in driving the central processes producing postnatal depression. The pharmacological treatment of PPD is placed in this context, and recommendations for more refined and safer treatments are made, including the better utilization of the antidepressant, and the anti-inflammatory and antioxidant effects of melatonin.
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Affiliation(s)
- George Anderson
- CRC Clincial Research Centre/Communications, Glasgow, Scotland
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Anderson G, Maes M. Melatonin: an overlooked factor in schizophrenia and in the inhibition of anti-psychotic side effects. Metab Brain Dis 2012; 27:113-9. [PMID: 22527998 DOI: 10.1007/s11011-012-9307-9] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/27/2012] [Accepted: 04/11/2012] [Indexed: 12/11/2022]
Abstract
This paper reviews melatonin as an overlooked factor in the developmental etiology and maintenance of schizophrenia; the neuroimmune and oxidative pathophysiology of schizophrenia; specific symptoms in schizophrenia, including sleep disturbance; circadian rhythms; and side effects of antipsychotics, including tardive dyskinesia and metabolic syndrome. Electronic databases, i.e. PUBMED, Scopus and Google Scholar were used as sources for this review using keywords: schizophrenia, psychosis, tardive dyskinesia, antipsychotics, metabolic syndrome, drug side effects and melatonin. Articles were selected on the basis of relevance to the etiology, course and treatment of schizophrenia. Melatonin levels and melatonin circadian rhythm are significantly decreased in schizophrenic patients. The adjunctive use of melatonin in schizophrenia may augment the efficacy of antipsychotics through its anti-inflammatory and antioxidative effects. Further, melatonin would be expected to improve sleep disorders in schizophrenia and side effects of anti-psychotics, such as tardive dyskinesia, metaboilic syndrome and hypertension. It is proposed that melatonin also impacts on the tryptophan catabolic pathway via its effect on stress response and cortisol secretion, thereby impacting on cortex associated cognition, amygdala associated affect and striatal motivational processing. The secretion of melatonin is decreased in schizophrenia, contributing to its etiology, pathophysiology and management. Melatonin is likely to have impacts on the metabolic side effects of anti-psychotics that contribute to subsequent decreases in life-expectancy.
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Anderson G, Maes M, Berk M. Inflammation-Related Disorders in the Tryptophan Catabolite Pathway in Depression and Somatization. ADVANCES IN PROTEIN CHEMISTRY AND STRUCTURAL BIOLOGY VOLUME 88 2012; 88:27-48. [DOI: 10.1016/b978-0-12-398314-5.00002-7] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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New insight into the antidepressants action: modulation of kynurenine pathway by increasing the kynurenic acid/3-hydroxykynurenine ratio. J Neural Transm (Vienna) 2011; 119:235-43. [PMID: 21660485 DOI: 10.1007/s00702-011-0668-8] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2011] [Accepted: 05/22/2011] [Indexed: 12/21/2022]
Abstract
Altered function of kynurenine pathway has emerged recently as one of the factors contributing to the pathogenesis of depression. Neuroprotective kynurenic acid (KYNA) and neurotoxic 3-hydroxykynurenine (3-HK) are two immediate metabolites of L: -kynurenine. Here, we aimed to assess the hypothesis that antidepressant drugs that may change brain KYNA/3-HK ratio. In primary astroglial cultures, fluoxetine, citalopram, amitriptyline and imipramine (1-10 μM) increased de novo production of KYNA and diminished 3-HK synthesis (24 and 48, but not 2 h). RT-PCR studies revealed that Kat1, Kat2 and kynurenine-3-monooxygenase (Kmo) gene expressions were not altered after 2 h. At 24 h, the expression of Kat1 and Kat2 genes was enhanced by all studied drugs, whereas Kmo expression was diminished by citalopram, fluoxetine and amitriptyline, but not imipramine. After 48 h, the expression of Kat1 and Kat2 was further up-regulated, and Kmo expression was down-regulated by all antidepressants. The ratio KYNA/3-HK was increased by fluoxetine, citalopram, amitriptyline and imipramine in a time-dependent manner-the effect was not observed after 2 h, modest after 24 h and robust after 48 h incubation time. Our findings indicate that the action of antidepressants may involve re-establishing of the beneficial ratio between KYNA and 3-HK. Shift in the kynurenine pathway, observed after prolonged exposure to antidepressant drugs, may partly explain their delayed therapeutic effectiveness.
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Chmiel-Perzyńska I, Kloc R, Perzyński A, Rudzki S, Urbańska EM. Novel Aspect of Ketone Action: β-Hydroxybutyrate Increases Brain Synthesis of Kynurenic Acid In Vitro. Neurotox Res 2010; 20:40-50. [DOI: 10.1007/s12640-010-9220-0] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2010] [Revised: 08/12/2010] [Accepted: 08/28/2010] [Indexed: 02/07/2023]
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