Relationship Between Heme Oxygenase-1 And Coronary Artery Disease

Background Heme oxygenase-1(HO-1), a sort of stress protein, degrades heme into carbon monoxide, bilirubin and iron, exerting effects of anti-oxidative stress, dilating blood vessels, inhibiting vascular smooth muscle cells proliferation and endothelial cells apoptosis, therefore it is taken as an endo-genetic vessel protective factor. In the promoter of HO-1 gene, there are (GT)n short tandem repeat (STR) polymorphism and - 413A/T single nucleotide polymorphism (SNP), which regulate the transcription of HO-1. Under condition of hypoxia, the promoter connects with hypoxia inducible factor-1α(HIF-1α) and regulates transcription of HO-1 afterwards. The increased expression of heme oxygenase-1 and hypoxia inducible factor-1αunder oxidative stress and hypoxia only exist for a short time, they are removed by ubiquitin–proteasome system. Coronary artery disease (CAD) is a serious disease which threatens our health. Oxidative stress participates during plaque formation, growth and disruption in coronary atherosclerosis, but the roles of HO-1 and ubiquitin/HIF-1α/HO-1 pathway in pathogenesis and development of CAD are unknown yet.Objectives On base of our previous findings that level of HO-1 expression was associated with severity of CAD, this study is designed to understand the roles of HIF-1αand ubiquitin on regulating HO-1 expression in patients with CAD, to investigate the relationship between STR polymorphism and -413A/T SNP in HO-1 gene promoter and susceptibility or clinical presentation of CAD, in order to provide new strategy for prevention and treatment of CAD by using HO-1.Methods A total of 200 patients who were diagnosed as having CAD by coronary angiography were selected in this study. 60 of 200 cases were diagnosed as stable angina pectoris (AP), 60 of 200 cases as unstable angina pectoris (UAP), and 80 of 200 cases as acute myocardial infarction (AMI). In addition, 100 subjects without evidence of CAD under coronary angiography with their sex and age similar to CAD patients whom were selected as controls. The mRNA and protein expression of heme oxygenase-1, hypoxia inducible factor-1α, and ubiquitin in monocytes and lymphocytes isolated from the subjects were examined by semi-quantitative reverse transcriptase polymerase chain reaction and Western blotting, respectively. Genotyping was performed using polymerase chain reaction followed by capillary electrophoresis automated DNA sequencer. Each size of the (GT)n repeat was calculated using the GeneMapper Analysis software. Sequencing was carried out on the ABI 3730 DNA analyser platforms to determine the genotypes of -413A/T.Results The protein expression of heme oxygenase-1, hypoxia inducible factor-1α, and ubiquitin was significantly stronger in patients with coronary heart disease than in controls. The expression levels increased with the severity of the disease (all p<0.05). There was a positive association between heme oxygenase-1 and hypoxia inducible factor-1α(r1=0.73) or ubiquitin (r2=0.86). Antioxidative therapy up-regulated the expression of heme oxygenase-1 and hypoxia inducible factor-1α(P1<0.01, P2<0.05) in patients with CAD. The mRNA transcription of heme oxygenase-1 and ubiquitin was associated with the severity of coronary heart disease (p<0.05), but no significant difference was found in hypoxia inducible factor-1αmRNA transcription between the cases and the controls (P>0.05). A (GT)n polymorphism was found in the HO-1 gene promoter with n=16～39. Subjects with n≤29 expressed much more HO-1 protein than those with n>29(P<0.01). The alleles were then classified into two subgroups: 'S' allele ( n≤29 ) and 'L' allele (n>29), the subjects were then classified as having an S/S, S/L, or L/L genotype. Subjects with the L allele (L/L+L/S genotypes) had more chance to get CAD than those with S/S genotype (adjusted OR=1.83, 95%CI=1.04-3.24). Stratified analysis further showed that L allele (L/L+L/S genotypes) is susceptive to CAD in patients who smoke (adjusted OR=2.59, 95% CI=1.16-5.80). A single nucleotide polymorphism A(-413)T was also found in the HO-1 gene promoter. Genotype T/T was protective against CAD in patients with hypercholesterolemia or lower HDL (adjusted OR=0.179, 95%CI=0.05-0.642), and was protective against AMI (adjusted OR=0.384, 95% CI=0.162-0.938 ).Conclution Ubiquitin/ HIF-1α/HO-1 pathway play an important role in the pathogenesis and development of CAD. Anti-oxidative therapy can up-regulate the expression of heme oxygenase-1 and hypoxia inducible factor-1αin patients with CAD. The (GT)n polymorphism in HO-1 gene promoter is related to susceptibility to CAD, especially in those smoke. A(-413)T SNP may be an important marker to evaluate AMI and susceptibility to CAD in patients with hypercholesterolemia.