The TLR4–NOS1–AP1 signaling axis regulates macrophage polarization

Objective Macrophages polarize to proinflammatory M1 or anti-inflammatory M2 states with distinct physiological functions. This transition within the M1–M2 phenotypes decides the nature, duration and severity of an inflammatory response. Although there is a substantial understanding of the fate of these phenotypes, the underlying molecular mechanism of transition within the M1–M2 phenotypes is not well understood. We have investigated the role of neuronal nitric oxide synthase (NOS1)-mediated regulation of activator protein 1 (AP-1) transcription factor in macrophages as a critical effector of macrophage phenotypic change.