CYP2D6 as an Emerging Endogenous Oxidative Stress Modulator in Cardiovascular Disease: Genetic, Pharmacological, and Redox Perspectives

Oxidative stress is a central and well-established driver of cardiovascular disease, contributing to mitochondrial dysfunction, endothelial injury, inflammatory activation, and progressive myocardial and vascular remodeling. Although the major endogenous sources of cardiovascular reactive oxygen species (ROS), including NADPH oxidases, mitochondrial electron transport chain leakage, and uncoupled nitric oxide synthase, are well characterized, an additional and underappreciated contributor has recently emerged: cytochrome P450 2D6 (CYP2D6), an enzyme classically regarded as a hepatic drug-metabolizing protein. Accumulating evidence indicates that CYP2D6 is expressed extrahepatically in cardiac, vascular, and neural tissue, where uncoupled catalytic cycling is proposed to generate ROS independently of its canonical xenobiotic-metabolizing role, although direct experimental evidence for this pathway in human cardiac and vascular tissue remains limited. CYP2D6-derived oxidative processes may interact with mitochondrial respiratory function, endothelial nitric oxide bioavailability, and redox-sensitive inflammatory pathways, potentially contributing to cardiovascular vulnerability under specific genetic or pathological conditions. Critically, the magnitude of this oxidative contribution is not fixed: it is dynamically shaped by inherited CYP2D6 genetic variation, with poor and ultra-rapid metabolizer phenotypes exhibiting divergent oxidative burden and pharmacokinetic vulnerability, and is further amplified by polypharmacy, multimorbidity, and inflammation-driven phenoconversion, whereby clinically expressed CYP2D6 activity diverges from inherited genotype in ways that intensify redox imbalance. These dynamics are particularly relevant in East Asian populations, where the decreased-function CYP2D6*10 allele is highly prevalent. In this narrative, hypothesis-generating review, we integrate evidence from pharmacogenomics, redox biology, and cardiovascular pharmacology to propose a conceptual framework that reframes CYP2D6 as a genetically and pharmacologically tunable node within cardiovascular redox biology. We further examine emerging redox biomarkers, multi-omics platforms, and AI-assisted modeling as translational strategies for capturing this dynamic oxidative risk in real time. This framework supports a shift from static genotype-guided prescribing toward oxidative-risk-informed, adaptive cardiovascular precision medicine. Importantly, our focus on CYP2D6 should not be interpreted as evidence that it is a major cardiovascular CYP isozyme or an established driver of cardiovascular pathology. Rather, CYP2D6 is examined here as a deliberately hypothesis-generating candidate whose unusually strong pharmacogenetic variability, clinically important cardiovascular drug substrates, dynamic susceptibility to phenoconversion, extrahepatic expression, and mechanistically plausible links to endogenous substrate metabolism and CYP-associated ROS generation provide a convergent rationale for focused investigation. The mechanistic framework proposed in this review has not yet been experimentally and prospectively validated and should not be applied directly to clinical decision-making without supporting clinical data.