TRPM2 deficiency contributes to M2b macrophage polarization via the PI3K/AKT/CREB pathway in murine sepsis

BackgroundPrevious studies suggest that transient receptor potential melastatin 2 (TRPM2) plays a protective role in sepsis by enhancing bacterial clearance. This effect is mediated through the modulation of macrophage phenotypic changes, which strengthen the immune response against infection. However, the specific role and underlying mechanism of TRPM2 in macrophage polarization during sepsis remain unclear.MethodCecal ligation and puncture (CLP) was used to establish a mouse sepsis model, and bone marrow-derived macrophages (BMDMs) and peritoneal macrophages were prepared from C57BL/6 wild-type and TRPM2 knockout (trpm2^-/-) mice. IPI549 was utilized as a specific inhibitor of PI3K. Macrophage polarization, bactericidal ability, and the PI3K/protein kinase B (AKT)/cyclic adenosine monophosphate response element-binding protein signaling pathway were assessed. In addition, survival rate, bacterial burden, lung wet/dry weight ratio, lung and liver injury scores, and cytokine levels were measured in CLP-induced septic mice.ResultsIn lipopolysaccharide (LPS)-stimulated BMDMs, trpm2 deficiency increased the expression of characteristic markers associated with the M2b phenotype, reduced the bactericidal ability, and activated the PI3K/AKT/CREB signaling pathway. Consequently, both trpm2^-/- BMDMs and trpm2^-/- mice exhibited impaired bactericidal clearance during CLP-induced sepsis. Furthermore, IPI549 attenuated TRPM2 deletion-induced M2b polarization and restored the bactericidal function of BMDMs. Notably, IPI549 preconditioning reversed the increased susceptibility of the trpm2^-/- mice to sepsis. The 7-day mortality rate was 92% in trpm2^-/- mice, compared to 42% in IPI549-pretreated trpm2^-/- mice. Moreover, IPI549-treated mice exhibited improved lung wet/dry ratios, reduced lung and liver injury scores, reversed M2b polarization and decreased bacterial load.ConclusionThe PI3K/AKT/CREB pathway mediates the effect of TRPM2 by inhibiting M2b macrophage polarization and promoting bacterial clearance during sepsis.