Cigarette Smoke-Induced Alveolar Macrophage Senescence via GEM/SIRT3-Mediated Mitochondrial Dysfunction

Smoking injury extends beyond the epithelium and endothelium; we show that alveolar macrophage senescence is a central driver. Using single‑cell RNA sequencing of human bronchoalveolar lavage fluid integrated with macrophage models exposed to cigarette smoke extract (CSE), we profiled senescence at the cell‑type level. The results of functional assays (mitochondrial reactive oxygen species (mitoROS), DNA damage, Senescence-associated β-galactosidase, p16/p21, apoptosis, phagocytosis, senescence-associated secretory phenotype) confirmed the biology of these effects. Smokers' macrophages were enriched for senescence and the SASP. In vitro, CSE increased mitoROS and DNA damage signaling, impaired phagocytosis, and induced apoptosis. Multiple cohort analyses revealed the GTP Binding Protein Overexpressed In Skeletal Muscle (GEM) as a causal driver: GEM was elevated in smokers and correlated with CDKN1A, and its perturbation altered the phenotype. GEM increased mitoROS, suppressed SIRT3/SOD2, lowered adenosine triphosphate (ATP), and amplified p16/p21 and SASP. Pharmacologic SIRT3 activation reversed these defects. In addition, the results from the mouse smoking model strongly support the role of the GEM/SIRT3 pathway in mediating the effects of cigarette smoke on macrophage senescence. Upstream, CSE induced ATF3 to transactivate GEM, while IGF2BP2 stabilized GEM mRNA via m⁶A. These data suggest that GEM-SIRT3 is an actionable biomarker and target for precision intervention in smoking‑related lung aging.