Sirtuin 3 deficiency exacerbates emphysema and lung inflammation in a murine model of chronic obstructive pulmonary disease.

Chronic obstructive pulmonary disease (COPD) is a progressive lung disease caused mainly by cigarette smoke-mediated induction of oxidative stress. Sirtuin 3 (SIRT3) regulates reactive oxygen species levels, but there are no definitive reports on its role in COPD pathogenesis. We hypothesized that SIRT3 plays a protective role in COPD. First, we observed significantly reduced SIRT3 expression in COPD lungs and identified smoking as a suppressive factor for SIRT3 expression in the airway epithelium. Next, we analyzed the lung phenotypes of SIRT3 knockout (KO) mice and SIRT3-overexpressing transgenic (OE) mice, and induced a COPD model in these mice using elastase and lipopolysaccharide. We subsequently investigated the effects of SIRT3 on cytokine production, oxidative stress, and apoptosis in airway epithelial cells in vitro. SIRT3 knockout mice exhibited increased expression of apoptosis markers, and aged SIRT3 KO mice and SIRT3 KO COPD model mice exhibited a worsened emphysematous phenotype. By contrast, this effect was mitigated in SIRT3 OE COPD model mice. In vitro studies revealed that SIRT3 deficiency exacerbated inflammation, oxidative stress, and apoptosis in airway epithelial cells. We concluded that SIRT3 plays a vital role in COPD pathogenesis and could be a novel therapeutic target. Our study is the first to elucidate the protective role of SIRT3 in the pathogenesis of COPD by modulating inflammatory responses and apoptosis. We have demonstrated that SIRT3 knockout mice spontaneously develop emphysema, and SIRT3 overexpression reduced elastase and LPS-induced emphysematous changes. In vitro studies have shown that SIRT3 deficiency leads to increased inflammation, oxidative stress, and apoptosis in airway and alveolar epithelium, contributing to the formation and exacerbation of emphysema.