Knockdown of long non-coding RNA TTTY15 protects cardiomyocytes from hypoxia-induced injury by regulating let-7b/MAPK6 axis.

Acute myocardial infarction (AMI) is a serious threat to human health. Long non-coding RNAs (lncRNAs) are known to be involved in the progression of AMI. The objective of this paper was to explore the functional effect of lncRNA testis-specific transcript Y-linked 15 (TTTY15) on hypoxia-induced cardiomyocyte injury. Human cardiomyocytes AC16 were cultured under hypoxic conditions to induce cardiomyocyte injury. Quantitative real-time polymerase chain reaction (qRT-PCR) was employed to check the expression of TTTY15, microRNA let-7b, and Mitogen-activated protein kinase 6 (MAPK6). Western blot was implemented for protein detection. Cell viability and apoptosis were examined by Cell counting kit-8 (CCK-8) assay and flow cytometry, respectively. The target association among TTTY15, let-7b, and MAPK6 was validated by dual-luciferase reporter assay, pull-down assay and RNA immunoprecipitation (RIP) assay. We found that the abundances of TTTY15 and MAPK6 were elevated, while let-7b level declined in hypoxia-induced AC16 cells. Knockdown of TTTY15 increased cell viability, and inhibited apoptosis of hypoxia-induced AC16 cells. TTTY15 bound to and inversely regulated let-7b. Likewise, MAPK6 was a target of let-7b and was negatively regulated by let-7b. Silencing of TTTY15 ameliorated the impact of let-7b downregulation or MAPK6 upregulation on hypoxia-induced cardiomyocyte injury. TTTY15 modulated MAPK6 enrichment by sponging let-7b. In conclusion, knockdown of TTTY15 suppressed hypoxia-induced cardiomyocyte injury through the let-7b/MAPK6 axis.