Polarization and Repolarization of Macrophages

Macrophages can acquire distinct phenotypes and biological functions depending on the microenvironment and\udthe metabolic state. Macrophages classically activated by IFN-γ and/or microbial products display an M1 phenotype\udcharacterized by high expression of interleukin (IL)-12, inducible nitric oxide synthase (iNOS) and TNF-α. They\udtrigger a Th1 immune response and are generally considered potent effector cells which kill microorganisms and\udtumor cells. Alternatively activated or M2 macrophages are stimulated by IL-4, IL-10, IL-13, immune complexes, or\udglucocorticoids. M2 phenotype is characterized by low iNOS and IL-12 production and triggers Th2 response. M2\udmacrophages are involved in tissue repair and angiogenesis. M1 and M2 macrophages display differences in\udmetabolism and reduced glutathione (GSH) concentration. This review describes the main macrophage phenotypes\udwith a major focus on the differences in protein, glucose and lipid metabolism. Moreover, repolarization of\udmacrophages as potential therapeutic approach and the critical role of GSH in regulating repolarization are\uddiscussed