Hoda, Md Nasrul

Abstract The AMP-activated protein kinase, AMPK, is an energy-sensing, metabolic switch implicated in various metabolic disorders; however, its role in inflammation is not well defined. We have previously shown that loss of AMPK exacerbates experimental autoimmune encephalomyelitis (EAE) disease severity. In this study, we investigated the mechanism through which AMPK modulates inflammatory disease like EAE. AMPKα1 knockout (α1KO) mice with EAE showed severe demyelination and inflammation in the brain and spinal cord compared with wild-type due to higher expression of proinflammatory Th17 cytokines, including IL-17, IL-23, and IL-1β, impaired blood–brain barrier integrity, and increased infiltration of inflammatory cells in the CNS. Infiltrated CD4 cells in the brains and spinal cords of α1KO with EAE were significantly higher compared with wild-type EAE and were characterized as IL-17 (IL-17 and GM-CSF double-positive) CD4 cells. Increased inflammatory response in α1KO mice was due to polarization of macrophages (Mϕ) to proinflammatory M1 type phenotype (IL-10lowIL-23/IL-1β/IL-6high), and these M1 Mϕ showed stronger capacity to induce allogenic as well as Ag-specific (myelin oligodendrocyte glycoprotein [MOG]35–55) T cell response. Mϕ from α1KO mice also enhanced the encephalitogenic property of MOG35–55–primed CD4 T cells in B6 mice. The increased encephalitogenic MOG-restricted CD4+ T cells were due to an autocrine effect of IL-1β/IL-23–mediated induction of IL-6 production in α1KO Mϕ, which in turn induce IL-17 and GM-CSF production in CD4 cells. Collectively, our data indicate that AMPK controls the inflammatory disease by regulating the M1 phenotype–Th17 axis in an animal model of multiple sclerosis.

Abstract 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.