SIRT2 Alleviates Chronic Cold Stress-Induced Lung Injury by Regulating Lung Macrophage M1 Polarization

SIRT2 (Sirtuin 2) is an NAD+-dependent deacetylase that exerts crucial regulatory effects on immune homeostasis and macrophage activation. While chronic cold exposure is a known predisposing factor for pulmonary dysfunction, the precise mechanisms by which SIRT2 potentially modulates lung macrophage polarization under cold stress remains poorly understood. In this study, we evaluated the protective capacity of SIRT2 using both wild-type (WT) and Sirt2-knockout (Sirt2-/-) murine models subjected to chronic cold exposure (4 °C for 3 h daily over 21 days). Our results demonstrated that Sirt2 deficiency significantly exacerbated cold-induced pulmonary histopathological damage and increased the secretion of pro-inflammatory cytokines (TNF-α, IL-1β, and IL-6) (p < 0.05). Furthermore, chronic cold stress triggered a macrophage-centered inflammatory response, a process wherein SIRT2 was found to curtail M1 pro-inflammatory polarization. To further investigate these mechanisms, in vitro experiments were conducted using the mouse alveolar macrophage cell line MH-S. While LPS was utilized as a canonical inflammatory stimulus to mimic the injury environment, SIRT2 overexpression was found to reverse the LPS-induced increase in M1 markers and attenuate inflammatory cytokine secretion. These findings suggest that SIRT2 maintains intracellular homeostasis by modulating macrophage plasticity and plays a protective role in the development of chronic cold stimulus-induced lung injury. Consequently, SIRT2 activation may represent a potential therapeutic pathway for the treatment of environment-related respiratory diseases.