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-gamma, TNF-alpha, 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-gamma 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.
Subject(s)
Central Nervous System/drug effects , Encephalomyelitis, Autoimmune, Experimental/drug therapy , Metformin/therapeutic use , Multiple Sclerosis/drug therapy , AMP-Activated Protein Kinases/metabolism , Animals , Cells, Cultured , Central Nervous System/immunology , Central Nervous System/metabolism , Chronic Disease , Cytokines/immunology , Cytokines/metabolism , Disease Models, Animal , Encephalomyelitis, Autoimmune, Experimental/immunology , Encephalomyelitis, Autoimmune, Experimental/metabolism , Female , Lipid Metabolism/drug effects , Mice , Mice, Inbred C57BL , Multiple Sclerosis/immunology , Multiple Sclerosis/metabolism , Th1 Cells/drug effects , Th1 Cells/immunologyABSTRACT
AMP-activated protein kinase (AMPK) is an energy sensing metabolic switch in mammalian cells. Here, we report our novel finding that AMPK is lost in all immune cells of experimental autoimmune encephalomyelitis (EAE), an inflammatory disease of Central Nervous System (CNS). AMPKalpha1 is predominantly expressed in T cells and antigen presenting cells (APCs), which are primarily involved in EAE disease progression. AMPK is lost at protein level in spleen macrophages, total T cells and their subsets (CD4, CD8 and regulatory T cells) isolated from EAE afflicted animals compared to control, without affecting its mRNA levels suggesting that the loss of AMPK protein is the result of posttranscriptional modification. To examine its pathological relevance in inflammatory disease, EAE was induced in wild type (+/+) and AMPKalpha1 null mice (-/-) using MOG(35-55) peptide. AMPKalpha1(-/-) mice exhibited severe EAE disease with profound infiltration of mononuclear cells compared to wild type mice however, AMPKalpha2 is not involved in enhancing the severity of the disease. Spleen cells isolated from AMPKalpha1(-/-) immunized mice exhibited a significant induction in the production of IFNgamma. Our study identifies AMPK as a down regulated target during disease in all immune cells and possibly restoring AMPK may serve as a novel therapeutic target in autoimmune diseases like multiple sclerosis (MS).
