Resolving macrophage polarization through distinct Ca²⁺ entry channel that maintains intracellular signaling and mitochondrial bioenergetics

Transformation of naive macrophages into classically (M1) or alternatively (M2) activated macrophages regulates the inflammatory response. Here, we identified that distinct Ca²⁺ entry channels determine the IFNγ-induced M1 or IL-4-induced M2 transition. Naive or M2 macrophages exhibit a robust Ca²⁺ entry that was dependent on Orai1 channels, whereas the M1 phenotype showed a non-selective TRPC1 current. Blockade of Ca²⁺ entry suppresses pNF-κB/pJNK/STAT1 or STAT6 signaling events and consequently lowers cytokine production that is essential for M1 or M2 functions. Of importance, LPS stimulation shifted M2 cells from Orai1 toward TRPC1-mediated Ca²⁺ entry and TRPC1^−/− mice exhibited transcriptional changes that suppress pro-inflammatory cytokines. In contrast, Orai1^−/− macrophages showed a decrease in anti-inflammatory cytokines and exhibited a suppression of mitochondrial oxygen consumption rate and inhibited mitochondrial shape transition specifically in the M2 cells. Finally, alterations in TRPC1 or Orai1 expression determine macrophage polarization suggesting a distinct role of Ca²⁺ channels in modulating macrophage transformation.