Activation of USP30 Disrupts Endothelial Cell Function and Aggravates Acute Lung Injury Through Regulating the S‐Adenosylmethionine Cycle

Abstract Microvascular dysfunction is a key contributor to the development of acute inflammatory diseases, characterized by heightened vascular hyperpermeability and leukocyte infiltration into interstitial tissues. Despite substantial research efforts, the precise mechanisms remain partially elucidated. Here, it is identified that USP30 is a critical regulator of lung microvascular inflammation and endothelial cell (EC) barrier integrity. Lipopolysaccharide (LPS) induces deubiquitinase activity of USP30. It is demonstrated that USP30 activation exacerbates EC dysfunction. Inhibiting USP30 leads to a 50% attenuation of inflammatory responses in ECs. In vivo, EC‐specific USP30‐deficient mice exhibit reduced microvascular dysfunction in models of endotoxin‐induced and ischemia‐reperfusion lung injury. Inhibition of USP30 preserves EC function via a mitophagy‐independent mechanism involving the S‐adenosylmethionine (SAM) cycle, DNA methylation, and miR‐30a‐5p expression. Mechanistically, USP30 depletion destabilizes and reduces methionine adenosyltransferase 2A (MAT2A) by deubiquitination, which in turn lowers SAM levels by ≈40%, and decreases global DNA methylation by roughly 35%, thereby resulting in a fourfold upregulation of miR‐30a‐5p. Elevated miR‐30a‐5p suppresses MDM2 and NFAT5 expression, contributing to the maintenance of EC function. These findings highlight that targeting USP30 may represent a potential therapeutic strategy warranting further preclinical and clinical exploration in acute lung injury.