The use of anthracyclines such as doxorubicin (DOX) has improved outcome in cancer patients, yet associated risks of
cardiomyopathy have limited their clinical application. DOX-associated cardiotoxicity is frequently irreversible and typically
progresses to heart failure (HF) but our understanding of molecular mechanisms underlying this and essential for development of
cardioprotective strategies remains largely obscure. As microRNAs (miRNAs) have been shown to play potent regulatory roles in
both cardiovascular disease and cancer, we investigated miRNA changes in DOX-induced HF and the alteration of cellular
processes downstream. Myocardial miRNA profiling was performed after DOX-induced injury, either via acute application to
isolated cardiomyocytes or via chronic exposure in vivo, and compared with miRNA profiles from remodeled hearts following
myocardial infarction. The miR-30 family was downregulated in all three models. We describe here that miR-30 act regulating the
β-adrenergic pathway, where preferential β1- and β2-adrenoceptor (β1AR and β2AR) direct inhibition is combined with Giα-2
targeting for fine-tuning. Importantly, we show that miR-30 also target the pro-apoptotic gene BNIP3L/NIX. In aggregate, we
demonstrate that high miR-30 levels are protective against DOX toxicity and correlate this in turn with lower reactive oxygen
species generation. In addition, we identify GATA-6 as a mediator of DOX-associated reductions in miR-30 expression. In
conclusion, we describe that DOX causes acute and sustained miR-30 downregulation in cardiomyocytes via GATA-6. miR-30
overexpression protects cardiac cells from DOX-induced apoptosis, and its maintenance represents a potential cardioprotective
and anti-tumorigenic strategy for anthracyclines.