miR-361-3p overexpression promotes apoptosis and inflammation by regulating the USP49/IκBα/NF-κB pathway to aggravate sepsis-induced myocardial injury.

Background: Sepsis is a major cause of in-hospital death, particularly in the intensive care unit. A huge amount of effort has been put into identifying reliable biomarkers to improve the prognosis of patients with sepsis. Among the numerous candidates, microRNAs have attracted attention because of their promising prognostic value. Multiple miRNAs have been suggested to play vital roles in manipulating the nuclear factor-kappa B (NF-κB) pathway, a key factor involved in sepsis. In this study, we attempted to elucidate the potential functions of miR-361-3p in sepsis-induced myocardial injury in vivo and in vitro.

Methods: A sepsis model was established by cecal ligation and puncture (CLP) in rats and by lipopolysaccharide (LPS) in H9c2 cells. The functions of miR-361-3p were revealed by assessing the level of biomarkers of myocardial injury and inflammation by Enzyme-linked immunosorbent assay, as well as the apoptosis by terminal deoxynucleotidyl transferase dUTP nick-end labeling staining and flow cytometry. Binding of miR-361-3p and the 3' untranslated region of ubiquitin-specific peptidase 49 (Usp49) was revealed by Dual luciferase reporter gene assay. The interaction of USP49 and its downstream target NF-κB inhibitor alpha (IκBα) was revealed by Co-immunoprecipitation and western blot analysis.

Results: miR-361-3p antagomir inhibited myocardial injury and inflammation in CLP-induced rats, as evidenced by a decrease in the serum levels of cardiac troponin I, creatine kinase-MB, interleukin-1 beta (IL-1β), IL-6, and tumor necrosis factor-alpha and cell apoptosis. However, miR-361-3p agomir aggravated sepsis-induced myocardial injury. Moreover, miR-361-3p inhibition induced the inhibition of LPS-induced apoptosis and inflammation in H9c2 cells. miR-361-3p could inhibit the expression of Usp49 by binding to its 3' untranslated region. Furthermore, we demonstrated that Usp49 binds to IκBα and mediates its deubiquitination, leading to the stabilization of IκBα, which results in the cytoplasmic accumulation of NF-κB and eventually the suppression of NF-κB activity.

Conclusion: Taken together, our data demonstrate that miR-361-3p overexpression promotes apoptosis and inflammation by regulating the USP49/IκBα/NF-κB pathway to aggravate sepsis-induced myocardial injury.