The Role of Agmatine in Modulating Autophagy Under Neuroinflammatory Conditions Induced by Metabolic Alteration in Mouse Brain

Abstract

Changes in microglia, a specialized population of glial cells found in the central nervous system (CNS), is often associated with hyperglycemic conditions. It has been reported that exogenous administration of agmatine (agm) has neuroprotective effects in CNS injuries, including neurodegenerative diseases, while also being involved with modulating macrophage subdivision. In this study, the effects of agmatine on microglial polarization has been investigated and whether this effect can be related to the modulation of autophagy in neuroinflammatory conditions induced by high glucose (HG) concentrations. Neuroinflammatory conditions were mimicked through treatment to BV2 microglial cells. BV2 cells were mainly induced into proinflammatory M1 phenotype when treated with HG (100 mM), shown by the increase in M1 marker, CD86, and shifted to M2 phenotype in HG condition with agm (100 μM), indicated by the upregulation of mannose receptor CD206. When agm was treated with HG, the level of LC3-II was increased while p62/SQSTM1 level was downregulated, and the expression of LAMP1 was increased. In transmission electron microscopy, autophagosomes has shown that HG conditions led to severe mitochondrial damage while elongating phagophore membranes and autolysosomes were seen in cells treated with HG and agm, showing stimulated mitophagy. In a high-fat diet-induced T2DM metabolic dementia animal model, agmatine administration upregulated autophagy and shifted microglial polarization from proinflammatory to anti-inflammatory phenotype, improving cognitive function and alleviating neuroinflammation. In this study, it has been demonstrated that agm treatment can ameliorate neuroinflammation by upregulating autophagy on a cellular level and shifting microglia polarization from M1 to M2 phenotype, showing a therapeutic potential in metabolic AD.