Experimental autoimmune encephalomyelitis (EAE) is a T cell-mediated autoimmune disease of the CNS. Metformin is the most widely used drug for diabetes and mediates its action via activating AMP-activated protein kinase (AMPK). We provide evidence that metformin attenuates the induction of EAE by restricting the infiltration of mononuclear cells into the CNS, down-regulating the expression of proinflammatory cytokines (IFN-γ, TNF-α, IL-6, IL-17, and inducible NO synthase (iNOS)), cell adhesion molecules, matrix metalloproteinase 9, and chemokine (RANTES). Furthermore, the AMPK activity and lipids alterations (total phospholipids and in free fatty acids) were restored by metformin treatment in the CNS of treated EAE animals, suggesting the possible involvement of AMPK. Metformin activated AMPK in macrophages and thereby inhibited biosynthesis of phospholipids as well as neutral lipids and also down-regulated the expression of endotoxin (LPS)-induced proinflammatory cytokines and their mediators (iNOS and cyclooxygenase 2). It also attenuated IFN-γ and IL-17-induced iNOS and cyclooxygenase 2 expression in RAW267.4 cells, further supporting its anti-inflammatory property. Metformin inhibited T cell-mediated immune responses including Ag-specific recall responses and production of Th1 or Th17 cytokines, while it induced the generation of IL-10 in spleen cells of treated EAE animals. Altogether these findings reveal that metformin may have a possible therapeutic value for the treatment of multiple sclerosis and other inflammatory diseases.

The 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors or statins are newly identified immunomodulators. In vivo treatment of SJL/J mice with lovastatin reduced the duration and clinical severity of active and passive experimental autoimmune encephalomyelitis (EAE), an animal model for multiple sclerosis. Lovastatin induced the expression of GATA3 and the phosphorylation of STAT6, whereas it inhibited tyrosine phosphorylation of Janus kinase 2, tyrosine kinase 2, and STAT4. Inhibition of the Janus kinase-STAT4 pathway by lovastatin modulated T0 to Th1 differentiation and reduced cytokine (IFN-γ and TNF-α) production, thus inducing Th2 cytokines (IL-4, IL-5, and IL-10). It inhibited T-bet (T box transcription factor) and NF-κB in activated T cells and significantly reduced infiltration of CD4- and MHC class II-positive cells to CNS. Further, it stabilized IL-4 production and GATA-3 expression in differentiated Th2 cells, whereas in differentiated Th1 cells it inhibited the expression of T-bet and reduced the production of IFN-γ. Moreover, lovastatin-exposed macrophage and BV2 (microglia) in allogeneic MLRs induced the production of the anti-inflammatory cytokine IL-10. These observations indicate that the anti-inflammatory effects of lovastatin are mediated via T cells as well as APCs, because it modulates the polarization patterns of naive T cell activation in an APC-independent system. Together, these findings reveal that lovastatin may have possible therapeutic value involving new targets (in both APCs and T cells) for the treatment of multiple sclerosis and other inflammatory diseases.

Experimental autoimmune encephalomyelitis (EAE), an animal model of multiple sclerosis, is a Th1-mediated inflammatory demyelinating disease of the CNS. AMP-activated protein kinase was reported recently to have anti-inflammatory activities by negatively regulating NF-κB signaling. In this study, we investigated the prophylactic and therapeutic efficacy of an AMP-activated protein kinase activator, 5-aminoimidazole-4-carboxamide ribonucleoside (AICAR), in active and passive EAE induced by active immunization with PLP139–151 or MOG35–55 and in adoptive transfer of PLP139–151-sensitized T cells, respectively. In vivo treatment with AICAR exerted both prophylactic and therapeutic effects on EAE, attenuating the severity of clinical disease. The anti-inflammatory effects of AICAR were associated with the inhibition of the Ag-specific recall responses and inhibition of the Th1-type cytokines IFN-γ and TNF-α, whereas it induced the production of Th2 cytokines IL-4 and IL-10. Treatment of PLP139–151-specific T cells in vitro with AICAR decreased their expression of T-bet in response to IL-12, a Th1 transcription factor, whereas in response to IL-4, it induced the expression and phosphorylation of Th2 transcription factors GATA3 and STAT6, respectively. Moreover, treatment of APCs in vitro with AICAR inhibited their capability to present the proteolipid protein peptide to PLP139–151-specific T cells. In an irrelevant Th1-mediated, OT-2 TCR transgenic mouse model, AICAR impaired in vivo Ag-specific expansion of CD4+ T cells. Together, these findings show for the first time that AICAR is a novel immunomodulator with promising beneficial effects for the treatment of multiple sclerosis and other Th1-mediated inflammatory diseases.

S-Nitrosoglutathione (GSNO) is an endogenous nitric oxide carrier and recently, has been documented for its anti-inflammatory effects in rat model of cerebral ischemia (Khan et al. (2005) J Cereb Blood Flow Metab 25:177-192). Here, we explored the neuroprotective effects mediated by GSNO in Lewis rat model of EAE and its mechanism of action using in vitro model of monocyte-endothelial cell interaction. Oral administration of GSNO attenuated the clinical disease course in EAE animals by inhibiting the infiltration of vascular immune cells in the CNS that subsequently led to the reduction in the expression of proinflammatory cytokines and consequently limited demyelination. Based on the inhibition in infiltration of immune cells, we hypothesized that GSNO modulated endothelial cell activation that led to reduce cellular infiltration in the CNS. Using an in vitro model, we established that GSNO inhibited monocyte adhesion to the activated endothelial cell, which was mediated by down regulation of endothelial cell adhesion molecules (CAMs). The mechanism by which GSNO modulated CAMs expression appeared to be via S-nitrosylation of p65, which consequently inhibited nuclear factor kappa B (NF-kappaB) activation in endothelial cells. These observations suggest that GSNO exerts its protective effects in EAE by inhibition of cellular infiltration into the CNS by S-nitrosylation of p65, thereby modulating NF-kappaB-CAMs pathway in endothelial cells.