USP18 exacerbates myocardial I/R injury by inhibiting Parkin mitophagy through the deubiquitinase PTEN-L

Background: Mitochondrial quality control is essential for limiting myocardial injury induced by ischemia/reperfusion (I/R), a major contributor to adverse outcomes after reperfusion therapy. This study aimed to determine whether the deubiquitinase ubiquitin-specific protease 18 (USP18) regulates mitophagy during cardiac I/R injury and thereby represents a potential therapeutic target to attenuate myocardial I/R injury. Methods: Cardiac-specific USP18 knockout mice were subjected to cardiac I/R injury. To elucidate the role of USP18 in mitophagy regulation and cardiac I/R injury, we performed RNA sequencing, proteomic mass spectrometry, transmission electron microscopy, and mitophagy assays. In parallel, adeno-associated virus serotype 9 (AAV9)-mediated overexpression of USP18, knockdown of Parkin and phosphatase and tensin homolog-long (PTEN-L), and administration of an anti-PTEN-L neutralizing antibody were used to elucidate the underlying mechanisms. Additionally, serum samples from patients with ST-segment elevation myocardial infarction (STEMI) were collected to assess clinical relevance. Results: USP18 expression was upregulated in mouse hearts following I/R injury and in ischemic human heart tissue. Cardiac-specific USP18 deficiency mitigated I/R-induced acute myocardial injury, mitochondrial dysfunction, and adverse cardiac remodeling, whereas USP18 overexpression exacerbated these pathological changes. Mechanistically, USP18 interacted with PTEN-L, which in turn bound to and inhibited the phosphorylation and translocation of Parkin to mitochondria, thereby suppressing mitophagy. Parkin knockdown abolished the cardioprotective effects conferred by USP18 deficiency, whereas PTEN-L knockdown reversed the detrimental effect of USP18 overexpression. Moreover, PTEN-L also exerted pathogenic effects via a paracrine mechanism, as neutralizing PTEN-L with an antibody attenuated cardiac I/R injury. Serum PTEN-L levels were elevated in STEMI patients, particularly postintervention. Conclusions: USP18 impairs mitophagy and exacerbates cardiac I/R injury through a PTEN-L-Parkin axis, involving both intracellular and paracrine mechanisms. Targeting the USP18-PTEN-L pathway may represent a novel therapeutic strategy to alleviate myocardial I/R injury.