MicroRNA‐181c‐5p enhances NFκB‐mediated inflammation via targeting PTPN4 in H9C2 cardiomyocytes during hypoxia/ reoxygenation

Abstract

BackgroundActivation of nuclear factor kappa B (NFκB) and subsequent inflammation occurs in various models of myocardial ischemia/reperfusion injury (I/RI). Thus, inhibition of NFκB‐mediated inflammation is of clinical significance for improving post‐ischemic recovery. miR‐181c‐5p was significantly up‐regulated in the early phase of myocardial infarction in patients. However, whether miR‐181c‐5p mediates cardiac I/RI through NFκB‐mediated inflammation is unknown. We aimed to explore the role and mechanism of miR‐181c‐5p in inflammation during I/RI in H9C2 cardiomyocytes under hypoxia/reoxygenation (H/R) injury.Methods and ResultsIn response to H/R (6 hours hypoxia followed by 6 hours reoxygenation), the expression of miR‐181c‐5p was significantly up‐regulated, suggestive of a potential role of miR‐181c‐5p in the pathology of myocardial I/RI. In addition, H/R significantly induced H9C2 cardiomyocytes injury, evidenced by increased release of lactic acid dehydrogenase (LDH, cell injury marker) and reduced cell viability, concomitantly with enhanced phosphorylation and degradation of IκBα, p65 nuclear translocation and increased production of NFκB‐mediated pro‐inflammatory cytokines tumor necrosis factor α (TNFα), interleukin (IL)6 and IL1β. To demonstrate the potential role of miR‐181c‐5p in H/R‐induced cell inflammation and injury, H9C2 cardiomyocytes were transfected with the miR‐181c‐5p agomir or its negative control. Overexpression of miR‐181c‐5p significantly aggravated H/R‐induced cell injury (increased LDH level and reduced cell viability) and exacerbated NFκB‐mediated inflammation [greater phosphorylation and degradation of IκBα, p65 nuclear translocation and increased levels of pro‐inflammatory cytokines (TNFα, IL6, IL1 β)]. By using computational prediction algorithms (TargetScan and miRDB), protein tyrosine phosphatase non‐receptor type 4 (PTPN4) was predicted as a potential target gene of miR‐181c‐5p, as also verified by the luciferase reporter assay. Indeed, overexpression of miR‐181c‐5p significantly attenuated the mRNA and protein expression of PTPN4 in H9C2 cardiomyocytes, while knockdown of PTPN4 significantly aggravated H/R‐induced enhancement of LDH level, phosphorylation and degradation of IκBα and pro‐inflammatory cytokines level, which mimicked the pro‐inflammatory effects of miR‐181c‐5p.ConclusionsmiR‐181c‐5p exacerbates H/R‐induced cardiomyocyte injury and NFκB‐mediated inflammation via targeting PTPN4, and the miR‐181c‐5p/PTPN4 signaling may be a novel target to combat myocardial I/RI.Support or Funding InformationThe work was supported by GRF (17117217M, Research Grants Council of Hong Kong).This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.