Prenylcysteine Oxidase 1 Deficiency Protects the Cardiac Muscle Cell Line <scp>HL</scp> ‐1 Against Ischaemic/Hypoxic Stress

Loss of cardiomyocytes during hypoxia-reoxygenation injury contributes to adverse myocardial remodeling, resulting in hypertrophy of surviving cardiomyocytes, interstitial fibrosis, and ultimately, heart dysfunction. Despite extensive research in the field, there is currently no specific treatment available for myocardial hypoxia-reoxygenation injury to prevent cardiomyocyte death. Prenylcysteine oxidase 1 (PCYOX1) is a pro-oxidant, FAD-dependent thioether oxidase that generates hydrogen peroxide during prenylcysteine metabolism, but its role in cardiomyocytes is poorly defined. Here, using HL-1 cardiomyocytes stably silenced for Pcyox1, we show that PCYOX1 contributes to both basal and stress-induced oxidative burden and cell death. Pcyox1 silencing reduced reactive oxygen species (ROS) levels at baseline and blunted the ROS increase during ischaemic/hypoxic stress. Consistently, Pcyox1 silencing decreased apoptosis after prolonged ischaemic/hypoxic exposure. Quantitative proteomics of whole-cell lysates and isolated mitochondria revealed coordinated remodeling of pathways involved in energy buffering and contractile machinery, including increased abundance of mitochondrial creatine kinases (CKMT1/CKMT2), acetyl-CoA synthetase 2-like (ACSS1), and multiple myosin components, changes that persisted under ischaemic/hypoxic stress and after reoxygenation. Overall, these data identify PCYOX1 as a modulator of redox homeostasis and proteomic adaptation in cardiomyocytes and support PCYOX1 inhibition as a potential strategy to limit hypoxia-reoxygenation-associated injury.