Marcadores bioquímicos e moleculares das modificações oxidativas em pacientes com malária vivax

Abstract

CHAPTER II: This study evaluated the influence of infection by Plasmodium vivax on the relations between hematological and biochemical variables and the osmotic stability of the erythrocyte membrane in a Brazilian Amazon population. A total of 72 patients with P. vivax malaria were included in the study and invited to return after 14 days, post treatment with chloroquine and primaquine, for clinical and laboratorial re-evaluations. The osmotic stability of the erythrocyte membrane was analyzed by non-linear regression of the dependency of the absorbance of hemoglobin, released with hemolysis, as a function of the salt concentration, and it was represented by the inverse of the salt concentration at the midpoint of the curve (1/H50) and by the variation of salt concentration, which promotes lysis (dX). Bivariate and multivariate methods were used in the analysis of the results. Prior to treatment of the disease, the erythrocytes showed greater stability, probably due to the natural selection of young and also more stable erythrocytes. The bivariate analysis showed that 1/H50 was positively correlated with red cell distribution width (RDW), urea, triglycerides, and very low-density lipoprotein (VLDL)-cholesterol, but negatively associated with albumin, HDL-cholesterol and indirect bilirubin, while dX was negatively associated with mean corpuscular hemoglobin concentration. These associations were confirmed by canonical correlation analysis. Stepwise multiple linear regression showed that albumin, urea, triglycerides and VLDLcholesterol are the variables with highest abilities of predicting the erythrocyte stability. The bivariate analysis also showed that the hematological index RDW was related to elevated levels of bilirubin and decreased levels of albumin and urea, associated with liver damage resulting from malaria. CHAPTER III: Studies in the Brazilian Amazon region, an endemic area for Plasmodium vivax, has been featured in the characterization of the mechanisms involved in the pathogenesis of infection by this species of Plasmodium. Intense inflammatory response and oxidative stress have been involved in the clinical complications of the disease. However, the exact role of oxidative stress responses in malaria disease is unclear, but certainly the combination of environmental, host and parasite factors are involved in susceptibility and severity of this disease. The present study aimed to evaluate the influence of genetic polymorphisms of the antioxidant enzymes superoxide dismutase (SOD1 A35C and SOD2 Ala16Val), glutathione peroxidase (GPx1 Pro197Leu), N5,N10- metilenetetrahydrofolate reductase (MTHFR C677T) and NADPH-quinone oxidoreductase (NQO1 C609T) on the oxidative stress responses in patients infected with P. vivax. An evaluation of redox markers profile was performed in 73 P. vivax infected patients at day 1 and day 14 after antimalarial therapy and 30 non-infected individuals. The genotyping of the polymorphic sites for enzymes were performed by PCR/RFLP methods. Associations between genotype and oxidative markers were analyzed by chi-square statistic with determination of relative risk and confidence intervals, adjusted for baseline factors that include gender. The distribution patterns of MTHFR C677T, GPx1 Pro197Leu and SOD2 Ala16Val genotypes is certainly due to the selective pressure that malaria has on human populations from endemic areas. P. vivax patients showed decrease in catalase (Cat) and GPx activities and total antioxidant capacity (TAC), as well as elevated levels of malondialdehyde (MDA) and allantoin. Regarding the polymorphisms, T allele carriers for MTHFR C677T SNP presented lower levels of AST, ALT and GGT, resulting from a possible protective effect against severe liver injury. Wild-type patients for GPx1 Pro197Leu SNP showed lower risk to develop thrombocytopenia. The SOD2 Ala16Val SNP was associated with decreased levels of MDA (reduced lipoperoxidation) and lower Cat and GPx activities. The GPx activity presented an inverse correlation with RDW, a hematological index that is a potential marker of erythropoietic and oxidative stress conditions.