Fig. 4.

Differential metabolism in macrophage polarization.

This figure represents the metabolic differences in macrophage polarization. There is increased glycolytic activity induced by M1 macrophages which leads to higher production of lactate. Increase in NADPH is observed due to PPP (Pentose Phosphate Pathway) which contributes to the generation of ROS (reactive oxygen species) responsible for killing activity exerted by M1 cells. The cytotoxic activity of M1 cells is due to the production of NO (Nitric oxide) which is produced by catabolism of L-Arginine via i-NOS (Inducible Nitric oxide synthase) dependent pathway. M2 cells are involved in the catabolism of L-ornithine and polyamines mediated by Arg-1 expression. They also induce β oxidation, Krebs cycle and oxidative phosphorylation. Polyamines and L-Ornithine generated are involved in tissue repair and regeneration activity of M2 macrophages.