Regulation of a Novel CircTRRAP/miR-761/MAP3K2 CeRNA Cascade in Inflammation, Apoptosis, and Oxidative Stress in Human AC16 Cardiomyocytes under Hypoxia Conditions.

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.