Adrenergic Receptor‐Stimulated Cardiac Myocyte Apoptosis: Role of Cytochrome P450 ω‐Hydroxylase Cytochrome P450 ω‐Hydroxylase

Abstract

Prolonged or excessive β‐adrenergic activation leads to cardiomyocyte loss and heart dysfunction. However, the underlying cellular mechanisms are still unclear. Therefore, we first confirmed the effect of isoproterenol (ISO), a β‐adrenergic receptor agonist, on cardiac toxicity using TUNEL and Caspase activity assays in cultured rat cardiomyocytes. ISO treatment significantly increased cardiomyocyte apoptosis. Persistent ISO stimulation of cardiomyocytes also increased the expression of CYP4A3, a major CYP450 ω‐hydroxylase that produces 20‐Hydroxyeicosatetraenoic acid (20‐HETE), in a time‐dependent manner. Next, we examined the effect of ISO and 20‐HETE on cardiomyocyte apoptosis using annexin V and propidium iodide staining. Treatment with either 20‐HETE or ISO significantly increased cardiomyocyte apoptosis, and inhibition of 20‐HETE production using 17‐ODYA, a CYP450 ω‐hydroxylase inhibitor, dramatically attenuated ISO‐induced cardiomyocyte apoptosis. To determine the apoptotic pathway involved, the mitochondrial membrane potential (ΔΨm) was measured by detecting the ratio of JC‐1 green/red emission intensity. The results demonstrated that 17‐ODYA significantly abolished ISO‐induced disruption in ΔΨm and that 20‐HETE alone induced a marked disruptive effect on ΔΨm in cardiomyocytes. 20‐HETE‐induced ΔΨm disruption and apoptosis were attenuated by KN93, a CaMKII blocker, suggesting that this action of 20‐HETE is mediated by a CaMKII‐dependent mechanism. Taken together, these results demonstrate that 20‐HETE treatment induces significant apoptosis via mitochondrial‐dependent pathways, and that inhibition of 20‐HETE production using 17‐ODYA attenuates ISO‐induced cardiomyocyte apoptosis. Thus, CYP450 ω‐hydroxylase could be a novel target to protect against cardiac damage induced by excessive β‐adrenergic activation or hypersympathoexcitability.Support or Funding InformationThis work was supported by Grants from the National Institute of Neurological Disorders and Stroke, National Institutes of Health (NIH, NS55008), American Heart Association (10GRNT3170012), Norman Bethune Program of Jilin University (2015221), and Education Department of Jilin Province (2015498).