To investigate the regulatory role and molecular mechanism of Rab26 in airway epithelial cell senescence induced by cigarette smoke exposure in chronic obstructive pulmonary disease (COPD). Impaired autophagy is a key feature of cellular senescence, characterized by the dysregulation of vesicle transport processes dependent on the Rab GTPase family.

An in vitro senescence model was established by treating human bronchial epithelial cells BEAS-2B with cigarette smoke extract (CSE), COPD mouse models were generated by chronic cigarette smoke exposure. Ten male C57BL/6 mice aged 6~8 weeks were selected and divided into an exposure group (n=5) and a room air control group (n=5). Techniques such as Western blotting, quantitative polymerase chain reaction, and immunohistochemistry were employed to detect the expression of Rab26, ubiquitin-specific protease 13 (USP13), and the senescence marker p21. Gain-of-function (overexpression) and loss-of-function (gene knockdown) experiments were conducted to evaluate the role of Rab26, and transcriptome sequencing was used to screen its downstream targets.

Cigarette smoke exposure successfully induced airway epithelial cell senescence. In mouse lung tissues and BEAS-2B cells, the protein expression of the senescence marker p21 was significantly increased. Specifically, treatment of BEAS-2B cells with 2% CSE for 9 days increased p21 protein levels (1.06 vs. 1.56 )(P<0.01), accompanied by an increase in the proportion of SA-β-gal-positive cells. Compared with control groups, Rab26 expression was decreased at both the mRNA and protein levels in lung tissues from smoke-exposed mice and in BEAS-2B cells treated with 2% CSE for 9 days, with Rab26 protein levels reduced (0.79 vs. 0.33)(P<0.05). In gain-of-function experiments, overexpression of Rab26 under CSE exposure significantly attenuated the upregulation of p21 protein expression (2.27 vs. 1.36) (P<0.01) and reduced the proportion of SA-β-gal-positive cells (P<0.01). Further mechanistic analyses demonstrated that USP13 is an important downstream-associated molecule involved in Rab26-mediated regulation of airway epithelial cell senescence. USP13 protein expression was decreased(0.94 vs. 0.57) in lung tissues of smoke-exposed mice (P<0.01) and (0.90 vs. 0.64)in Rab26-/- mouse lung tissues (P<0.01). Moreover, in vitro overexpression of USP13 significantly suppressed CSE-induced p21 upregulation (P<0.01), thereby alleviating the senescent phenotype.

Rab26 regulates cigarette smoke-induced airway epithelial cell senescence through the USP13 signaling pathway.