Oxidative signaling in experimental autoimmune encephalomyelitis

SIRT1 inactivation switches reactive astrocytes to an antiinflammatory phenotype in CNS autoimmunity

Astrocytes are highly heterogeneous in their phenotype and function, which contributes to CNS disease, repair, and aging; however, the molecular mechanism of their functional states remains largely unknown. Here, we show that activation of sirtuin 1 (SIRT1), a protein deacetylase, played an important role in the detrimental actions of reactive astrocytes, whereas its inactivation conferred these cells with antiinflammatory functions that inhibited the production of proinflammatory mediators by myeloid cells and microglia and promoted the differentiation of oligodendrocyte progenitor cells. Mice with astrocyte-specific Sirt1 knockout (Sirt1-/-) had suppressed progression of experimental autoimmune encephalomyelitis (EAE), an animal model of CNS inflammatory demyelinating disease. Ongoing EAE was also suppressed when Sirt1 expression in astrocytes was diminished by a CRISPR/Cas vector, resulting in reduced demyelination, decreased numbers of T cells, and an increased rate of IL-10-producing macrophages and microglia in the CNS, whereas the peripheral immune response remained unaffected. Mechanistically, Sirt1-/- astrocytes expressed a range of nuclear factor erythroid-derived 2-like 2 (Nfe2l2) target genes, and Nfe2l2 deficiency shifted the beneficial action of Sirt1-/- astrocytes to a detrimental one. These findings identify an approach for switching the functional state of reactive astrocytes that will facilitate the development of astrocyte-targeting therapies for inflammatory neurodegenerative diseases such as multiple sclerosis.

Mechanism of oxidative stress p38MAPK-SGK1 signaling axis in experimental autoimmune encephalomyelitis (EAE)

Background

Multiple sclerosis (MS), a complex disease associated with multifocal demyelination of the central nervous system and poorly understood etiology. It has been previously indicated that many factors, including oxidative stress and p38MAPK-SGK1 pathway, contribute to the pathogenesis of MS.

Methods

This study, using an experimental autoimmune encephalomyelitis (EAE) model system, was aimed at investigating the molecular mechanisms determining interaction p38MAPK-SGK1 pathway and oxidative stress in MS pathogenesis. C57BL/6 mice was immunized with MOG35-55 peptide for EAE induction, which was followed by determination of the effect of treatment with classic p38 inhibitor SB203580 and antioxidant tempol on the development and progression of EAE.

Results

Our experiments showed a dynamic change of immune inflammation, oxidative stress and p38MAPK-SGK1 pathway involvement in EAE demonstrating that p38MAPK-SGK1 pathway and oxidative stress contribute to the demyelination in central nerve system caused by Th17 inflammatory responses in a synergistic way. The administration of SB203580 and Tempol both markedly suppressed the progression of EAE. Furthermore, tempol showed a strong inhibiting effect to the p38MAPK-SGK1 pathway similar to SB203580 suggesting that oxidative stress exacerbates EAE via the activation of p38MAPK-SGK1 pathway.

Conclusion

Cumulatively, our results show that oxidative stress p38MAPK-SGK1 signaling pathway may be a central player in EAE and even in MS.

Inflammation and oxidative stress induced by cigarette smoke in Lewis rat brains

Exposure to cigarette smoke has been associated with an increased risk of neurological diseases such as stroke, Alzheimer's disease and multiple sclerosis. In these studies, serum and brain sections from Lewis rats or those exposed to cigarette smoke and control rats were examined for evidence of increased inflammation and oxidative stress. Immunocytochemical staining of brain sections from CS-exposed rats showed increased expression of class II MHC and, in ELISA, levels of IFN-gamma and TNF-α were higher than for non-exposed rats. In polymerase chain reaction assays there was increased interferon-gamma, TNF-α, IL-1α, IL-1β, IL-23, IL-6, IL-23, IL-17, IL-10, TGF-β, T-bet and FoxP3 gene expression with CS exposure. There was also markedly elevated MIP-1α/CCL3, less prominent MCP-1/CCL2 and no elevation of SDF-1α gene expression. Analysis of samples from CS-exposed and control rats for anti-oxidant expression showed no significant difference in serum levels of glutathione and, in brain, similar levels of superoxide dismutase and decreased thioredoxin gene expression. In contrast, there was increased brain gene expression for the pro-oxidants iNOS and the NADPH components NOX4, dual oxidase 1 and p22(phox). Nrf2 expression, which is typically triggered as a secondary response to oxidative stress, was also increased in brains from CS-exposed rats with nuclear translocation of this protein from cytoplasm demonstrated in astrocytes in association with increased expression of the aryl hydrocarbon receptor gene, an Nrf2 target. These studies, therefore, demonstrate that CS exposure in these animals can trigger multiple immune and oxidative responses that may have important roles in the pathogenesis of CNS inflammatory neurological diseases.