USP43‐mediated deubiquitination of SLC7A11 protects against LPS‐induced acute lung injury by inhibiting ferroptosis

BACKGROUND: Acute lung injury (ALI) is a common inflammatory pulmonary disorder, with increasing evidence implicating ferroptosis as a critical type of cell death in its pathogenesis. Ubiquitin-specific protease 43 (USP43) is an important deubiquitinating enzyme that plays a significant role in both inflammation and ferroptosis regulation. In this study, we mainly analysed whether USP43 could participate in the process of ALI by regulating the ferroptosis process, and clarified its molecular mechanism. METHODS: To investigate the functional role of USP43 in ALI, Usp43 knockout mice, USP43 knockdown and overexpressed human bronchial epithelial BEAS-2B cells and mouse alveolar type II epithelial MLE12 cells were treated with lipopolysaccharide (LPS) in vivo and in vitro. Subsequently, ferroptosis inhibitor and activator, Ferrostatin-1 and Erastin, were taken to explore the effect of ferroptosis on the regulation function of USP43 in ALI. Finally, co-immunoprecipitation (Co-IP), ubiquitination and rescue assays were conducted to determine the regulation mechanism of USP43. RESULTS: The expression of USP43 was up-regulated during ALI. Usp43-KO mice exhibited aggravated lung injury, inflammation and ferroptosis. Consistently, USP43 knockdown exacerbated LPS-stimulated cellular damage, inflammation and ferroptosis, while its overexpression exerted the opposite effect in vitro. Furthermore, the regulation effects of USP43 on ALI mainly depended on ferroptosis by administering a ferroptosis inducer and inhibitor, respectively. Mechanistically, USP43 was found to inhibit K48-linked polyubiquitination of solute carrier family 7 member 11 (SLC7A11), thereby stabilising SLC7A11. Overexpression of SLC7A11 rescued the ferroptosis, cellular and lung tissue injury and inflammation aggravated by USP43 knockdown or deficiency. CONCLUSION: USP43 prevents the progression of ALI by mediating K48-linked deubiquitination of SLC7A11, thereby inhibiting ferroptosis. Targeting USP43 may represent a potential therapeutic strategy for ALI treatment by enhancing SLC7A11 stability and inhibiting ferroptosis. KEY POINTS: USP43 has been proven to be upregulated during LPS-induced ALI. This study is the first to demonstrate that USP43 can inhibit the progression of LPS-induced ALI by suppressing ferroptosis. This study proved that USP43 can interects with SLC7A11 and removes the K48-linked ubiquitinaiton of SLC7A11, thereby enhances the stability of it and subsequently inhibiting ferroptosis during the LPS-induced ALI process. The regulation of USP43 on LPS-induced ALI mainly depends on SLC7A11, and USP43 is expected to become a new target for the treatment of ALI/ADRS.