Influência do uso de estatinas sobre a estabilidade de membrana de eritrócitos em portadores de esclerose múltipla

Abstract

Multiple sclerosis (MS), degenerative disease characterized by defects in the myelin membrane of neural cells, takes place probably by oxidative, inflammatory and autoimmune mechanisms in genetically vulnerable individuals, under the influence of environmental factors associated with feeding. [Hypothesis] As the structural composition of biological membranes is largely affected by diet, physical activity and use of medicines, the interference of environmental factors in the homeostasis of structural membranes of neural cells in carriers of MS must also be shared by other post-mitotic cells of the body, such as erythrocytes. [Objective] This study aimed to investigate the influence of statin use on the stability of erythrocytes membranes against hypotonic shock and chaotropic action of ethanol in patients with MS. [Methods] The population was composed of 16 women suffering from MS (26-58 years) who were being monitored at the Clinical Hospital of the Federal University of Uberlândia. They were divided into two groups, one group treated with 20 mg/day of simvastatin for 2.66 ± 1.03 years (n = 6) and another group without the use of statin (n = 10). A control group consisted of 6 healthy women with BMI and age (28-56 years) similar to problem group, all without the use of medications and without chronic consumption of alcohol. We evaluated the scores of patients in the Expanded Disability Status Scale (EDSS), hematological and biochemical variables, in addition to the stability of erythrocytes against hypotonic shock and ethanol. The stability of erythrocytes was evaluated by the half-transition points, H50 and D50, obtained from the curves of hemolysis induced by hypotonic shock and chaotropic action of ethanol, respectively. Statistical comparisons of results between groups were made by ANOVA and Tukey post-hoc test. [Results] There were no statistically significant differences in EDSS scores or the hematological variables between groups, but the MS patients under use of statin showed levels of total cholesterol and LDL-cholesterol significantly lower than those without use of that drug. The values of H50 of the MS patients without use of statins (0.472 ± 0.013 g.dL-1 NaCl) were significantly higher than those of volunteers in the control group (0.427 ± 0.015 g.dL-1 NaCl). The H50 values of the carriers of MS with use of statins (0.457 ± 0.013 g.dL-1 NaCl) declined (although not in a statistically significant basis) compared to carriers of MS without the use of statins, but they were not equal to the values of H50 of volunteers in the control group. Moreover, the values of D50 of MS patients without use of statin (13.87 ± 0.74% v/v ethanol) were significantly lower than those of volunteers in the control group (15.38 ± 0.24 g.dL-1 NaCl), but the values of D50 in the MS patients under statin therapy (15.20 ± 0.15 g.dL-1 NaCl) were not significantly different from those of volunteers in the control group, although they had been significantly higher than those of MS patients without use of statins. [Conclusions] The carriers of MS without use of statin showed erythrocytes less stable against hypotonic chock and action of ethanol than the control group. The use of statins increased the stability of erythrocytes against ethanol in the MS patients, making it similar to the RBC stability of the volunteers without the disease. But the use of statins did not increase osmotic stability of the erythrocyte membrane against hypotonicity in such a way to make it similar to the membrane stability of the volunteers without the disease. These findings are important and reflect the homeostatic conditions in the erythrocytes membranes by the moment of their evaluation. This could be merely a consequence of changes in lifestyle associated with the development of the disease, but could also be associated with a lifestyle that may have implications in the development of MS. The reasons for believing in the validity of the last hypothesis are discussed.