Transient Receptor Potential Melastatin 2 Protects Mice against Polymicrobial Sepsis by Enhancing Bacterial Clearance

Background: Recent studies suggest that the transient receptor potential melastatin 2 (TRPM2) channel plays an important role in inflammation and immune response. However, the role and mechanism of TRPM2 in polymicrobial sepsis remain unclear. Methods: The authors explored the effects of genetic disruption of TRPM2 on mortality (n = 15), bacterial clearance (n = 6), organ injury, and systemic inflammation during cecal ligation and puncture-induced sepsis. Electrophysiology, immunoblot, bacterial clearance experiment, and quantitative real-time polymerase chain reaction were used to explore the role and mechanism of TRPM2 in sepsis. Results: After cecal ligation and puncture, Trpm2-knockout mice had increased mortality compared with wild-type mice (73.3 vs. 40%, P = 0.0289). The increased mortality was associated with increased bacterial burden, organ injury, and systemic inflammation. TRPM2-mediated Ca2+ influx plays an important role in lipopolysaccharide or cecal ligation and puncture-induced heme oxygenase-1 (HO-1) expression in macrophage. HO-1 up-regulation decreased bacterial burden both in wildtype bone marrow-derived macrophages and in cecal ligation and puncture-induced septic wild-type mice. Disruption of TRPM2 decreased HO-1 expression and increased bacterial burden in bone marrow-derived macrophages. Pretreatment of Trpm2-knockout bone marrow-derived macrophages with HO-1 inducer markedly increased HO-1 expression and decreased bacterial burden. Pretreatment of Trpm2-knockout mice with HO-1 inducer reversed the susceptibility of Trpm2-knockout mice to sepsis by enhancing the bacterial clearance. In addition, septic patients with lower monocytic TRPM2 and HO-1 messenger RNA levels had a worse outcome compared with septic patients with normal monocytic TRPM2 and HO-1 messenger RNA levels. TRPM2 levels correlated with HO-1 levels in septic patients (r = 0.675, P = 0.001). Conclusion: The study data demonstrate a protective role of TRPM2 in controlling bacterial clearance during polymicrobial sepsis possibly by regulating HO-1 expression.