Functional impact of genetic polymorphisms in NAD(P)H oxidase p22phox subunit on vascular superoxide production in atherosclerosis

Background: Increased superoxide (SO) production is an important aspect of vascular disease states. The principal source of vascular SO is NAD(P)H oxidase. Some case control studies suggest an association between coronary artery disease and polymorphisms in the p22phox gene encoding the p22 subunit of NAD(P)H oxidase. The C242T (His to Tyr amino acid change) and A640G (3′ UTR) have received most attention, although continued controversy exists due to lack of functional data. Accordingly, we have investigated the relationship between p22phox genotype and NAD(P)H oxidase activity in human saphenous veins from 88 patients undergoing CABG. Methods: We studied NADH-stimulated SO production using lucigenin-enhanced chemiluminescence from vessel segments; DNA was extracted from peripheral blood leukocytes and amplified by PCR. C242T and A640G genotypes were characterised using RFLP. Results: The frequencies of C242T and A640G polymorphisms and NAD(P)H oxidase activity (RLU/sec/mg, mean ± SEM) in 88 patients are shown below: C242T A640G CC n=42(48%) 331±24 AA n=20 (23%) 265±17 CT+TT n=46(52%) 262+16 AG+GG n=68 (77%) 292±16 p=0.021 p=0.45 The T allele of the C242T polymorphism remained independently associated with increased NAD(P)H oxidase activity in relation to other major clincial risk factors (hypertension, smoking, diabetes hypercholesterolaemia). Conclusions: Precence of the p22phox 242T allele is associated with reduced vascular NAD(P)H oxidase activity. These findings suggest a possible role for genetic variation in modulating vascular SO production in atherosclerosis.