UPF1 Alleviates Myocardial Ischemia-Reperfusion Injury by Regulating SMURF2-Mediated Ubiquitination Degradation of FOXA2.

BACKGROUND AND OBJECTIVES: Myocardial ischemia/reperfusion injury (MIRI) is an important factor affecting therapeutic effect and prognosis of acute myocardial infarction. Here, the effects of up-frameshift 1 (UPF1) on cardiomyocyte apoptosis in MIRI were evaluated. METHODS: H9C2 cells were cultured under hypoxia/reoxygenation (H/R) condition. The expression of UPF1, SMAD-specific E3 ubiquitin ligase 2 (SMURF2), forkhead box A2 (FOXA2), protease-activated receptor 4 (PAR4), Bax, and Cleaved caspase-3 was assessed utilizing reverse transcription quantitative polymerase chain reaction and western blot. Cell viability and apoptosis were measured by Cell Counting Kit-8 and flow cytometry. Infarct area was examined by tetrazolium chloride staining in myocardial ischemia/reperfusion (I/R) rat model. HE and immunohistochemistry staining evaluated myocardial injury and UPF1 expression, respectively. Terminal deoxynucleotidyl transferase mediated dUTP nick end-labeling staining tested apoptosis. RNA immunoprecipitation, chromatin immunoprecipitation and dual luciferase assay verified molecular interactions. FOXA2 ubiquitination was detected by immunoprecipitation assay. SMURF2 mRNA stability was tested by actinomycin D treatment. RESULTS: FOXA2 effectively suppressed cardiomyocyte apoptosis induced by H/R by inhibiting PAR4 at transcriptional level. Degradation of FOXA2 was facilitated through SMURF2-mediated ubiquitination. Increased expression of UPF1 resulted in a reduction of H/R-induced cardiomyocyte apoptosis, and improved myocardial dysfunction caused by I/R in vivo. UPF1 influenced the decay of SMURF2 mRNA, leading to a decrease in its expression. Through SMURF2/FOXA2/PAR4 axis, UPF1 effectively suppressed cardiomyocyte apoptosis triggered by H/R. CONCLUSIONS: By suppressing SMURF2 mRNA stability, UPF1 upregulated FOXA2 expression to inhibit PAR4, leading to inhibition of apoptosis during MIRI, which provides new therapeutic targets for MIRI treatment.