TRIM13 Reduces Damage to Alveolar Epithelial Cells in COPD by Inhibiting Endoplasmic Reticulum Stress-Induced ER-Phagy.

Purpose: Tripartite motif-containing protein 13 (TRIM13) directly or indirectly participates in autophagy and apoptosis. However, it remains unclear whether TRIM13 participates in chronic obstructive pulmonary disease (COPD) progression. This study aimed to reveal the molecular mechanisms through which TRIM13 regulates alveolar epithelial cell injury in COPD to provide new molecular targets for COPD treatment.

Methods: The TRIM13 expression levels were determined in clinical COPD patients and a rat emphysema model. A cigarette smoke-induced model of endoplasmic reticulum stress (ERS) and endoplasmic reticulum autophagy (ER-phagy) was developed using A549 cells, and the effects of TRIM13 gene overexpression/knockdown on ERS, ER-phagy, and cell apoptosis were assessed in these cells.

Results: TRIM13 expression was significantly decreased in the lung tissues of COPD patients and rats with emphysema. Moreover, the apoptosis level was significantly increased in the lung tissues of rats with emphysema. TRIM13 gene overexpression reduced the expression levels of ERS-related molecules (GRP78, GRP94, XBP-1, and eIF2a) in the COPD model; it also lowered the ER-phagy level, as evidenced by decreased number of autolysosomes observed by transmission electron microscopy, improved endoplasmic reticulum structure, reduced LC3-II/LC3-I and Beclin1 expression levels, and increased expression level of the autophagy inhibitory molecule Bcl-2. TRIM13 gene knockdown, however, led to opposite results.

Conclusion: TRIM13 expression attenuated alveolar epithelial cell injury in COPD by inhibiting ERS-induced ER-phagy.