The phenotype of peritoneal mouse macrophages depends on the mitochondria and ATP/ADP homeostasis.

Different macrophage subtypes have different morphologies/shapes and functions. Naïve M0 macrophages are elongated. Pro-inflammatory M1 that produce the bactericidal molecule iNos are round. Anti-inflammatory M2 macrophages that produce the pro-healing enzyme Arg-1 are highly elongated. We showed previously that the morphologies of M0 and M2 but not M1 macrophages are RhoA-dependent. Macrophage-specific deletion of RhoA causes the extreme elongation (hummingbird phenotype) of M0 and M2 but not M1 macrophages. The M1 and M2 macrophages also differ in their metabolic status. Here, we studied the effect of the oxidative phosphorylation inhibitors, antimycin A and oligomycin A, at a suboptimal dose, which depolarizes mitochondria but does not eliminate mitochondrial functions, on the mitochondria/energy production and phenotype of wild-type and RhoA-deleted M0, M1 and M2 peritoneal mouse macrophages. We found that, while untreated M1 macrophages had the lowest and the M2 had the highest level of ATP the ATP/ADP ratio was nearly identical between M0, M1 and M2 macrophages. Inhibitor treatment resulted in approximately 60% increase in ATP level and ATP/ADP ratio in M0 and M2 macrophages, and decrease in the level of filamentous (F) actin, and these changes correlated with a drastic shortening/tail retraction of M0 and M2 macrophages, and decreased expression of Arg-1 in M2 macrophages. The treatment of M1 macrophages caused only a 30% increase in the ATP level and ATP/ADP ratio, and while it did not affect the shape of M1 macrophages, it increased the production of iNos. This indicates that the maintenance of mouse macrophage phenotypes depends on mitochondrial function and ATP/ADP homeostasis.