ABSTRACT: Background: Pathological upregulation of G protein-coupled receptor kinase 2 (GRK2) is a hallmark of heart failure and contributes to maladaptive signaling, hypertrophic remodeling, and cardiomyocyte death. MicroRNAs (miRNAs) are key post-transcriptional regulators of cardiac stress responses, however whether GRK2 is subject to miRNA targeting has not yet been fully established. Objective: We investigated potential miR-181a-mediated regulation of GRK2 in cardiomyocytes to better understand its effects on cardiac stress responses. Methods: miRNA microarray profiling was performed on mouse hearts two weeks after myocardial infarction. Bioinformatic target prediction analysis identified candidate miRNAs that are predicted to bind GRK2 in the 3’ untranslated region (UTR). Direct binding was assessed using luciferase reporter assays, and miR-181a was selected as the miRNA of interest to further pursue mechanistic and functional validation. miR-181a was overexpressed or inhibited in neonatal rat ventricular myocytes (NRVMs) and exposed to several modes of cellular stress to induce hypertrophy, hypoxia, and accumulation of reactive oxygen species. GRK2 expression, hypertrophic remodeling, oxidative stress, cell viability, and cyclic AMP (cAMP) signaling were assessed using quantitative PCR, immunoblotting, fluorescence imaging, and biochemical assays. Results: miR-181a directly targeted the GRK2 3′UTR and suppressed GRK2 expression at both mRNA and protein levels. miR-181a overexpression attenuated stress-induced hypertrophic gene expression, reduced cardiomyocyte cell size, decreased oxidative stress, improved survival under hypoxia, and enhanced cAMP production under β-AR stimulation. Conversely, inhibition of miR-181a resulted in sustained GRK2 expression, exacerbated hypertrophic signaling, and decreased cAMP production. Conclusion: These findings identify miR-181a as a functional post-transcriptional regulator of GRK2 that limits maladaptive signaling, hypertrophic remodeling, and cardiomyocyte injury. miR-181a-mediated GRK2 inhibition represents a potential therapeutic strategy for mitigating pathological signaling in heart failure.
