We analyzed the CYP2J2 gene for genetic variants in patients with and without angiographically documented CAD. The frequency of coding SNPs was <1%. Functional importance of these relatively rare variants is not known. In contrast to the coding SNPs, the relatively frequent promoter polymorphism G-50T is much more likely to influence the cardiovascular risk of a population.
The G-50T variant has previously been described by King et al11
with variable frequency in different racial groups. They also described 5 relatively rare (frequency <2%) coding region variants that previously were observed primarily in individuals of African descent. Thus, as a result of 2 independent sequencing studies of the entire CYP2J2
gene-coding region, there does not appear to be any frequent polymorphisms with amino acid substitutions in the CYP2J2
There are 4 putative Sp1 binding sites in the proximal CYP2J2 promoter, with their 5-ends in positions −84, −72, −50, and −45. The loss of an SP1 binding site in G-50T variants significantly reduces binding of Sp1. This finding is in accordance with our transfection studies demonstrating strong basal transcriptional activity from the WT but not G-50T CYP2J2 promoter, although no inducibility by cytokines and other substances able to induce CYP2C8/9 was observed. Constitutive expression of CYP2J2 mRNA and protein has been found in human heart tissue.1
These findings are consistent with the CYP2J2 promoter being TATA-less and that its basal activity is regulated predominantly by Sp1.11
To the best of our knowledge, inducibility of CYP2J2 has not been reported so far.
The relevance of our experimental findings with reduced gene activity of the G-50T mutant is confirmed by reduced concentrations of the stable CYP2J2-dependent arachidonic acid metabolite 14,15-DHET in individuals with the polymorphism. Endothelial cells do contain an active soluble epoxide hydrolase; therefore, most of the EET that is formed will be rapidly hydrated to the corresponding diol (DHET), which is the stable metabolite.13
After transfection of endothelial cells with CYP2J2, most epoxygenase metabolites observed are DHET, indicating that even high amounts of epoxygenase metabolites are predominantly hydrated to DHET.2
Therefore, we believe that 14,15-DHET levels are more reflective of CYP2J2 activity than soluble epoxide hydrolase activity. Also 11,12-EET is 1 of the primary products of CYP2J2 epoxidation; the major CYP2J2 product is 14,15-EET.1,11
For the reasons mentioned above, 14,15-DHET can be considered a relevant marker of CYP2J2 activity.
We demonstrated a higher frequency of the G-50T polymorphism in subjects with angiographically documented CAD. Individuals with angiographic exclusion of CAD instead of a random population sample were chosen as a matched control group, because the morphological diagnosis of CAD cannot be excluded in some “healthy individuals.” Our findings indicate a close association between variation in the CYP2J2 gene and human disease. Although our data do not prove a causal relationship, they are certainly consistent with a vascular protective role of products of this gene in humans. Strong constitutive expression of CYP2J2 would contribute to the biosynthesis of EETs, leading to protective vascular effects. Individuals with the G-50T polymorphism would have considerably less basal transcriptional activity of CYP2J2, which might result in reduced vascular protection. Given the multifactorial nature of atherosclerosis, it is unlikely that a polymorphism in a single gene will have a profound effect on the risk of atherosclerotic diseases. On the other hand, given a polymorphism frequency of 8% to 11% in whites, the G-50T SNP might contribute significantly to the risk of cardiovascular disease by allowing other proinflammatory and proatherogenic risk factors to go unchecked. The level of CYP2J2 protein expression in WT and variant individuals would be interesting to know. However, given the organ-specific expression of CYP2J2, protein expression cannot be simply measured in blood samples but requires organ biopsies (ie, endomyocardial biopsy).
Interestingly, lower CYP2J2
gene transcription might contribute to hypertension via reduced levels of the vasodilator eicosanoid 11,12-EET. Indeed, gene deletion of soluble epoxide hydrolase, which degrades EETs, in mice results in systemic hypotension.14
However, many other known and unknown factors contribute to systemic hypertension. In our study population, systemic hypertension as a single factor was not significantly associated with the G-50T polymorphism, and after adjustment for systemic hypertension, the association between G-50T SNP and CAD remains significant.
The incidence of adverse cardiovascular events is based on a retrospective analysis. Therefore, only nonfatal events were recorded. Additionally, a retrospective analysis is limited to what has been clinically documented. The incidence of acute coronary syndromes and cerebral ischemia needs further prospective evaluation, because a higher incidence of cardiovascular fatalities within 1 group could bias our findings. Nevertheless, our findings provide the first evidence for disease relevance of a polymorphism of a novel gene, CYP2J2. The association between the G-50T promoter polymorphism in younger patients and the prevalence of CAD further supports the role of P450-derived eicosanoids in limiting vascular inflammatory diseases such as atherosclerosis.