Relationship between premature arthrosclerosis with bilirubin and heme oxigenase 2 gene polymorphism in Iranian patients

Heme oxygenase 2 (HMOX2) is a critical anti oxidative stress enzyme found in the endothelial cells and adventitial nerves. This enzyme in conjunction with other heme oxygenase 1 and 3 enzymes metabolizes heme molecules into ferrous iron, carbon monoxide (CO) and biliverdin which is further converting to bilirubin. Both biliverdin and bilirubin are potent antioxidants, reducing the chance of atherosclerosis. HMOX2 also induces endothelial relaxation by synthesizing CO. This is the first study to evaluate association of heme oxygenase 2 gene mutation in 137 patients affected with atherosclerosis and 100 normal controls with premature atheroesclerosis. Pairs of primers were designed to amplify exons 2 to 4 from HMOX2 gene. These products were analyzed by PCR-SSCP analysis and sequencing. The level of Iron and Bilirubines (Total, Direct and Indirect) were determined in both patients and control groups.). Two nucleotide substitutions were observed among 13 patients consisted of, one newly reported transversion mutation, C to A substitution in codone A70D (GCC to GAC) (Ala to Asp) and one already reported transition mutation, A to G substitution in codone K89E (AAG to GAG) (Leu to Glu). Significant associations were obtained between A437G substitution in codon K89E of hemoxygenase 2 gene (P< 0.006 and χ2 >6.82), total bilirubin (P< 0.016 and χ2 >6.01) and indirect bilirubin (P< 0.016 and χ2 >5.99) and risk of atherosclerosis but with no significant associations to the level of serum Iron P> 0.10 and direct bilirubin P> 0.24. No significant associations were observed among C381A substitution in codon A70D, P< 0.11 and χ2 >2.97, level of serums Iron P> 0.57 and bilirubins (Total P> 0.50, Direct P> 0.34 and Indirect P> 0.45) and risk of atherosclerosis. This finding presents the importance of A437G substitution in the development of atherosclerosis. Further studies are required to study the association of hemoxygenase 2 gene mutations with atherosclerosis in other populations.