The Omega-3 Polyunsaturated Fatty Acid Docosahexaenoic Acid (DHA) Reverses Corticosterone-Induced Changes in Cortical Neurons.

BACKGROUND: Chronic exposure to the glucocorticoid hormone corticosterone exerts cellular stress-induced toxic effects that have been associated with neurodegenerative and psychiatric disorders. Docosahexaenoic acid is a polyunsaturated fatty acid that has been shown to be of benefit in stress-related disorders, putatively through protective action in neurons. METHODS: We investigated the protective effect of docosahexaenoic acid against glucocorticoid hormone corticosterone-induced cellular changes in cortical cell cultures containing both astrocytes and neurons. RESULTS: We found that glucocorticoid hormone corticosterone (100, 150, 200 µM) at different time points (48 and 72 hours) induced a dose- and time-dependent reduction in cellular viability as assessed by methyl thiazolyl tetrazolium. Moreover, glucocorticoid hormone corticosterone (200 µM, 72 hours) decreased the percentage composition of neurons while increasing the percentage of astrocytes as assessed by ßIII-tubulin and glial fibrillary acidic protein immunostaining, respectively. In contrast, docosahexaenoic acid treatment (6 µM) increased docosahexaenoic acid content and attenuated glucocorticoid hormone corticosterone (200 µM)-induced cell death (72 hours) in cortical cultures. This translates into a capacity for docosahexaenoic acid to prevent neuronal death as well as astrocyte overgrowth following chronic exposure to glucocorticoid hormone corticosterone. Furthermore, docosahexaenoic acid (6 µM) reversed glucocorticoid hormone corticosterone-induced neuronal apoptosis as assessed by terminal deoxynucleotidyl transferase-mediated nick-end labeling and attenuated glucocorticoid hormone corticosterone-induced reductions in brain derived neurotrophic factor mRNA expression in these cultures. Finally, docosahexaenoic acid inhibited glucocorticoid hormone corticosterone-induced downregulation of glucocorticoid receptor expression on ßIII- tubulin-positive neurons. CONCLUSIONS: This work supports the view that docosahexaenoic acid may be beneficial in ameliorating stress-related cellular changes in the brain and may be of value in psychiatric disorders.

A role for interleukin-1ß in determining the lineage fate of embryonic rat hippocampal neural precursor cells.

Neurogenesis occurs in the hippocampus of the developing and adult brain due to the presence of multipotent stem cells and restricted precursor cells at different stages of differentiation. It has been proposed that they may be of potential benefit for use in cell transplantation approaches for neurodegenerative disorders and trauma. Prolonged release of interleukin-1ß (IL-1ß) from activated microglia has a deleterious effect on hippocampal neurons and is implicated in the impaired neurogenesis and cognitive dysfunction associated with aging, Alzheimer's disease and depression. This study assessed the effect of IL-1ß on the proliferation and differentiation of embryonic rat hippocampal NPCs in vitro. We show that IL-1R1 is expressed on proliferating NPCs and that IL-1ß treatment decreases cell proliferation and neurosphere growth. When NPCs were differentiated in the presence of IL-1ß, a significant reduction in the percentages of newly-born neurons and post-mitotic neurons and a significant increase in the percentage of astrocytes was observed in these cultures. These effects were attenuated by IL-1 receptor antagonist. These data reveal that IL-1ß exerts an anti-proliferative, anti-neurogenic and pro-gliogenic effect on embryonic hippocampal NPCs, which is mediated by IL-1R1. The present results emphasise the consequences of an inflammatory environment during NPC development, and indicate that strategies to inhibit IL-1ß signalling may be necessary to facilitate effective cell transplantation approaches or in conditions where endogenous hippocampal neurogenesis is impaired.

Plasma IL-6 and IL-17A Correlate with Severity of Motor and Non-Motor Symptoms in Parkinson's Disease.

The nature of the inflammatory response in Parkinson's disease (PD) remains to be better understood. Here, we used highly sensitive Single Molecule Array (SIMOA) technology to measure the levels of the inflammatory mediators Interleukin 6 (IL-6), Interleukin 17A (IL-17A), Tumour Necrosis Factor α (TNFα) and Transforming Growth Factor ß (TGFß) in plasma from PD patients and age- and gender-matched healthy controls. We report that IL-17A correlates with non-motor symptoms (NMS) scores, while IL-6 positively correlates with motor scores. We found no correlations between cytokines and disease duration suggesting that IL-6 and IL-17A are associated with disease severity rather than disease duration in this cohort, furthermore IL-17A may be involved in the underlying pathophysiology of NMS in PD.

Inflammation and the developing brain: consequences for hippocampal neurogenesis and behavior.

While the detrimental impact of inflammation on adult hippocampal neurogenesis and associated behaviors has recently gained credence, the effects of inflammation on the developing brain is an area of research which is quickly gaining momentum, and a growing number of research articles on this topic have been published in recent years. Indeed, we now know that pro-inflammatory mediators negatively influence both hippocampal neurogenesis and neuronal cytoarchitecture during brain development. Here we present a comprehensive review of the current literature on inflammation-induced changes in hippocampal neurogenesis during early life and the consequent behavioral deficits which may ensue in later life. We also offer insights into the cellular and molecular mechanisms underlying the hippocampal-dependant behavioral changes observed in neurodevelopmental disorders, particularly in those where cognitive dysfunction plays a major role. We further consider whether early-life inflammation-induced changes in hippocampal neurogenesis may contribute to the onset of mood and cognitive deficits in later life.

GSK-3 mediates the release of IL-1ß, TNF-α and IL-10 from cortical glia.

Neuroinflammation has been shown to contribute to neurodegenerative and psychiatric disorders such as Alzheimer's disease and major depression due to the inappropriate release of pro-inflammatory cytokines from activated microglia. The precise molecular events that mediate cytokine release from glia remain unknown but we suggest that the serine/threonine kinase glycogen synthase kinase-3 (GSK-3) may be involved. The aim of this study therefore was to investigate the effect of lipopolysaccharide (LPS) on expression and activity of the GSK-3ß isoform in glia, and to assess if GSK-3 mediates the LPS-induced change in inflammatory cytokine levels in culture medium from rat glial-enriched cortical cultures. GSK-3ß was expressed in microglia and astrocytes, and stimulation of these cultures with LPS induced an increase in GSK-3ß expression and activity, and in pro-inflammatory cytokine levels in culture media. We show that GSK-3 inhibition using a small molecule inhibitor SB216763 or the mood stabiliser lithium chloride reduced the LPS-induced elevated levels of pro-inflammatory cytokines present in culture media from rat glial-enriched cortical cultures. These results demonstrate a role for GSK-3 as a modulator of inflammatory cytokine levels in the brain, and contribute to a mechanistic insight into neurological disorders in which neuroinflammation is a characteristic feature.