Abstract
Emerging evidence uncovers the important involvement of circular RNAs (circRNAs) in the dysfunction of cardiomyocytes under hypoxia conditions. However, no studies proved whether circTRRAP (hsa_circ_0081241) can participate in cardiomyocyte injury evoked by hypoxia.A qRT-PCR or immunoblotting method was used to evaluate the expression of circTRRAP, miR-761, and mitogen-activated protein kinase kinase kinase 2 (MAP3K2). The direct relationships of circTRRAP/miR-761 and miR-761/MAP3K2 were confirmed by RNA immunoprecipitation (RIP) assay, dual-luciferase reporter assay, and RNA pull-down assay. The effects of the circTRRAP/miR-761/MAP3K2 axis on cell functional behaviors were examined by 5-ethynyl-2'-deoxyuridine (EdU) assay, CCK-8 assay, and flow cytometry. The production levels of proinflammatory cytokines (IL-1β, TNF-α, and IL-6) were evaluated by enzyme-linked immunosorbent assay.CircTRRAP and MAP3K2 were overexpressed but miR-761 was downregulated in AC16 cardiomyocytes under hypoxia and in the serum of patients with acute myocardial infarction. Silencing circTRRAP attenuated hypoxia-evoked inflammation, apoptosis, and oxidative stress in human AC16 cardiomyocytes. CircTRRAP targeted miR-761, and miR-761 directly targeted and suppressed MAP3K2. CircTRRAP involved the post-transcriptional regulation of MAP3K2 through miR-761, indicating its competing endogenous RNA (ceRNA) activity. Moreover, miR-761 inhibition abolished the effects of circTRRAP depletion in hypoxia-induced cell injury. MAP3K2 silencing phenocopied miR-761 increase in attenuating hypoxia-evoked cardiomyocyte inflammation, apoptosis, and oxidative stress.Our study demonstrates that circTRRAP can protect AC16 cardiomyocytes from hypoxia-evoked injury through the miR-761/MAP3K2 axis.