Characterisation of paraoxonase-1 gene polymorphism as a biomarker of oxidative stress in sickle cell disease patients in Uganda

Abstract

Oxidative stress, chronic inflammation, vasoocclusion, and free iron are all features present in sickle cell disease. Paraoxonases are a family of antioxidant enzymes with anti-inflammatory and anti-oxidative action. However there is limited information about oxidative stress and prevalence of Paraoxonase-1 gene in sickle cell disease patients in Uganda. Here, for the first time Paraoxonase-1 polymorphisms in patients with sickle cell disease were characterized as biomarkers of oxidative stress. OBJECTIVES To characterize Glutamine/Arginine 192 Paraoxonase-1 gene polymorphism in sickle cell disease patients in Uganda. METHODS A total of 50 blood samples were analysed consisting of 25 sickle cell disease blood samples and 25 blood control samples obtained from Mulago sickle cell clinic and Nakasero blood bank respectively. Prevalence of sickle cell disease in all samples was determined using Bidirectional PCR. Paraoxonase-1 gene polymorphisms in all samples were determined by Polymerase Chain Reaction Fragment Restriction Length Polymorphism. (PCR-RFLP) RESULTS The study revealed that all sickle cell blood samples analysed (100%) were homozygous of the disease while 76% of blood control samples were homozygous for the normal hemoglobin gene and 24% were heterozygous for sickle cell disease. (Carriers) All Sickle cell disease patients and 92% of controls had Glutamine/Glutamine Paraoxonase-1 genotype. 8% of the blood control samples analysed showed absence of the gene. Statistical evaluation by Chi square test showed that there was no relationship between disease status and Paraoxonase-1 polymorphisms. (χ2 = 2.084, df = 1, and p> 0.05) CONCLUSION The presence of all sickle cell disease blood samples with the wild type Glutamine/Glutamine Paraoxonase-1 gene polymorphism indicated the presence of increased risk of endothelial dysfunction and oxidative stress reaction among these patients in Uganda. However, results were not conclusive about the status of oxidative stress among patients as a smaller sample size was used instead of the minimum approximated size of 138.