MicroRNA 379 Regulates Klotho Deficiency-Induced Cardiomyocyte Apoptosis Via Repression of Smurf1

Klotho is an aging-suppressor gene. Klotho gene deficiency impairs heart function leading to heart failure, but the underlying mechanism remains poorly understood. MicroRNAs are increasingly recognized to play important roles in the pathogenesis of cardiomyopathy. The objective of this study is to investigate whether microRNA 379 (Mir379) regulates Klotho deficiency-associated cardiomyocyte apoptosis. Using inducible Cre-Loxp recombination technology, we first found that kidney-specific deletion of the Klotho gene caused heart failure. Using microRNA sequencing analysis, we found that Mir379 may be a target of Klotho. In cultured H9c2 heart cells, we found that treatment with Klotho-free medium increased Mir379 levels and induced apoptosis. To test whether Mir379 mediates Klotho deficiency-induced apoptosis, H9c2 cells were transfected with Mir379 inhibitor. Interestingly, Mir379 inhibitor (anti-Mir379) prevented Klotho deficiency-induced H9c2 cell apoptosis. On the contrary, Mir379 mimic itself caused apoptosis in H9c2 cells. These findings suggest that Mir379 may mediate Klotho deficiency-induced apoptosis in H9C2 cells. Using the mRNA-miRNA target interaction assay, we found that Smurf1(SMAD specific E3 ubiquitin protein ligase 1) mRNA contained the 3-UTR binding site for Mir379. Importantly, Mir379 mimic suppressed Smurf1 expression, and the Mir379 mimic-induced apoptosis can be rescued by treatment with exogenous Smurf1 protein. Therefore, Smurf1 repression may be involved in Mir379-induced H9c2 cells apoptosis. In conclusion, Mir379 may mediate Klotho deficiency-associated cardiomyocyte apoptosis through repression of Smurf1 which is required for Mir379-induced apoptotic cell death. Mir379 may be a potential therapeutic target for cardiomyocyte apoptosis-associated heart failure due to Klotho deficiency.