In vitro effects of Ala16Val manganese superoxide dismutase gene polymorphism on human white blood cells exposed to methylmercury

Environmental contamination by methylmercury (MeHg) is an enormous public health problem in world regions such as Amazonia. MeHg toxic effects seem to be influenced by environmental and genetic factors. However, few studies have evaluated the genetic influences of MeHg toxicity in humans. Therefore, the aim of this study was to evaluate the genetic influence of Ala16Val manganese superoxide dismutase gene polymorphism (Ala16Val-MnSOD) on the cytotoxic effects of in vitro human leukocytes exposed to MeHg. Subjects were selected from 100 individuals aged 26.4 ± 7.3 years genotyped to Ala16Val-MnSOD polymorphism (AA = 6, VV = 6, and AV = 12) to perform in vitro testing using white blood cells (WBCs). Reactive oxygen species production was measured using 2',7'-dichlorofluorescein diacetate fluorimetric assay, and cell viability was measured using MTT assay on WBC samples from the same subjects that were both exposed and not exposed to MeHg (2.5 µM for 6 h). The results showed that AA- and VV-WBCs exposed to MeHg did not display increased reactive oxygen species levels compared to those in cells that were not exposed. However, AV-leukocytes exposed to MeHg displayed increased ROS levels. Cellular viability comparison among genotypes exposed to MeHg showed that the viability of AA-WBCs was lower than that of VV-WBC, with mean values of 3.46 ± 0.13 and 3.08 ± 0.77 (standard error), respectively (P = 0.033), whereas heterozygous cells (AV) displayed intermediate values. This difference was likely due to the higher basal H2O2 production of AA-WBCs compared to that of other genotypes. These results suggest that the Ala16Val-MnSOD polymorphism has toxicogenetic effects in human cells exposed to MeHg.

Association between interleukin-1 beta polymorphism (+3953) and obesity

It now appears that obesity is associated with a low-grade inflammation of white adipose tissue resulting from chronic activation of the innate immune system as interleukin-1 beta (IL-1). Previous investigations have described a positive association between IL-1 beta +3953 (C>T) gene polymorphism (rs 1143634) and obesity, suggesting functional effects on fat mass, fat metabolism and body mass. However, it is necessary to determine if these results occur in other populations and if they are influenced by sex and age. Therefore, we performed a case-control study using 880 Caucasian subjects (59.7+/-11.9 years old) from the Brazilian Aging Research Program (non-overweight=283, overweight=334, obese=263) previously investigated in genetic studies, in whom we analyzed the IL-1 beta +3953C/T polymorphism. We observed higher T allele (CT/TT) frequency in non-overweight than overweight and obese groups. The odds ratio showed 1.340 (95% CI: 1.119-1.605) times more chance of the obese group being CC carriers compared to non-overweight group independent of sex and age. This study corroborates the idea that the IL-1 system is linked to the development of obesity.