M1 and M2 macrophage polarization and potentially therapeutic naturally occurring compounds.

Macrophages, as crucial cellular components of innate immunity, are characterized by possessing high plasticity and an abnormal ability to differentiate in response to numerous stimuli. Given this, macrophages show extreme heterogeneity under both physiological and pathological conditions. Typically, macrophages can be polarized into classically activated macrophages (M1) and alternatively activated macrophages (M2) depending on their environment. The relative functions of these two subtypes are almost exactly opposed to one another. Recent studies have suggested that some naturally occurring compounds can exert regulatory effects on the progression of macrophage polarization, which implies that they could be promising therapeutic tools to treat relevant diseases. Therefore, in our current review, we summarize recent studies on several naturally occurring compounds that may possess the ability to regulate macrophage polarization and explore the associated molecular mechanisms.