Heme Oxigenase 2 Gene Polymorphisms as Genetic Risk Factor in Atherosclerosis in Iranian Patients

Background: Heme oxygenase 2 (HMOX2) is an important antioxidative stress enzyme found in the endothelial cells of blood vessels and adventitial nerves. This enzyme in collaboration with heme oxygenase 1 metabolizes heme molecules into ferrous iron, carbon monoxide (CO) and biliverdin while the later is further converted to bilirubin. Both biliverdin and bilirubin are potent antioxidants, reducing the chance of atherosclerosis. HMOX2 also induces endothelial relaxation by synthesizing CO. Methods: Heme oxygenase 2 gene mutations were studied in 137 patients with atherosclerosis and in 100 normal controls. Pairs of primers were designed to amplify 2nd, 3rd and 5th exons of HMOX2 gene. These products were analyzed by single strand conformation polymorphism (SSCP) analysis and the shifted fragments were separated from SSCP polyacrylamide gel for further sequencing. Results: Two sequence variations were observed among 13 patients with atherosclerosis, consisting of C to A substitution in codone A70D (GCC to GAC) which was reported for the first time and A to G substitution in codone K89E (AAG to GAG). A significant association was noticed between A to G mutation in codon K89E of hemoxygenase 2 gene and the risk of atherosclerosis was supported with p=0.01 and χ2>6.82. However, no significant associations were observed among C to A substitution in codon A70D, p=0.11 and χ2>2.97 and the risk of atherosclerosis. Conclusion: Our findings denoted to the importance of K89E mutation in the development of atherosclerosis in Iranian cases. Further studies are required to show the importance of hemoxygenase 2 gene mutation in other populations.