USP33 promotes pulmonary microvascular endothelial cell pyroptosis by stabilizing TRAF2 through deubiquitination.

Objective: Inhibiting the pyroptosis of human pulmonary microvascular endothelial cells (HPMECs) is a promising therapeutic modality for acute lung injury (ALI). Given the undefined effect of ubiquitin-specific protease 33 (USP33) and tumor necrosis factor receptor-associated factor 2 (TRAF2) on pyroptosis in lung injury, this study investigates their roles in the pyroptosis of HPMECs during ALI.

Methods: The hypoxia/reoxygenation (H/R)-induced model was constructed in HPMECs. Cell viability, cytotoxicity, and cell death were determined by the cell counting kit-8 (CCK-8), Lactate dehydrogenase (LDH), and Hoechst-PI staining, respectively. Western blot and qRT-PCR were used to detect protein and gene expression levels of pyroptosis-related markers, respectively. The TRAF2 ubiquitination level was measured via immunoprecipitation.

Results: USP33 and TRAF2 expressions were elevated in H/R-induced HPMECs. Knockdown of USP33 increased cell viability and inhibited cellular pyroptosis, accompanied by decreases in IL-1β, IL-18, and Caspase-1. USP33 stabilized TRAF2 by deubiquitination. TRAF2 overexpression reversed the effect of USP33 silencing on suppressing HPMEC pyroptosis.

Conclusion: USP33 stabilizes TRAF2 by deubiquitination to promote HPMEC pyroptosis during ALI.