Efeitos da intoxicação mercurial no estresse oxidativo e em marcadores inflamatórios no duodeno de camundongos c57bl/6j submetidos à dieta ocidental

Abstract

Mercury (Hg) is a global pollutant with toxic action on several organs, both in animals and in humans. Recently, the increase in exposure to Hg may have occurred in environmental disasters in Brazil involving the collapse of dams, containing tailings with high concentrations of metals. The objective of this work was to evaluate the effect of MeHg intoxication in the duodenum of C57BL/6J mice subjected to the standard or western diet, on oxidative stress and inflammatory parameters. No study has been conducted evaluating the effects of MeHg on the duodenum after a high-fat diet. Male C57BL/6J mice, after weaning, with 21 days of age and weighing between 8-11 g were used. The animals were randomly divided into four experimental groups according to the type of diet and exposure to MeHg. For the induction of hyperlipidemia, the animals received a western diet (42% of lipids), during 21 to 61 days of age. The intoxicated groups received a MeHg chloride solution in their drinking water (20 mg/L) in the last 21 days after starting the diets. The experimental groups were: normonourished control group (CT), receiving a standard diet; hyperlipidic group (HF), receiving a western diet; normonourished group intoxicated with MeHg (Hg) and a hyperlipidic group intoxicated with MeHg (HFHg). The animals were weighed twice a week, after starting the diets. Mice were euthanized after completing 40 days of diet. Samples of duodenum, blood and hair were collected. The hair was harvested on the dorsal region of the animal by trichotomy to analyze the Hg concentration. The serum was obtained to analyze the levels of total cholesterol and triglycerides (mg/dL). For morphometric evaluation in the duodenum, the villus length, crypt depth and villus:crypt ratio in hematoxylin and eosin (H&E)-stained slides and PAS goblet cell count in Schiff periodic acid-stained slides were analyzed. To assess oxidative stress, the levels of malondialdehyde (MDA), glutathione peroxidase (GPx), glutathione (GSH) and NO2/NO3 ratio were analyzed. In addition, Nrf2 gene expression by qRT-PCR was evaluated. For the evaluation of inflammatory parameters, the levels of myeloperoxidase (MPO) were analyzed by ELISA and the transcription of IL-6, IL-10 and TNF-α by qRT-PCR. The expression of the pro-apoptotic and anti-apoptotic proteins Bax and Bcl2 was also analyzed by qRT-PCR. The western diet induced an obesogenic effect in the animals. Mercurial intoxication reduced weight gain in animals when compared to controls, regardless of diet. The intoxicated groups showed higher concentrations of MeHg in the hair 11 compared to the controls. The high-fat diet significantly increased serum levels of cholesterol and triglycerides. The HFHg group showed significant reductions in villus height, crypt depth and villus/crypt ratio and fewer PAS positive cells. The hyperlipidic diet significantly increased the levels of NO2/NO3 and MDA in the duodenum, regardless of intoxication. Exposure to MeHg was able to decrease GPx levels and increase NO2/NO3, MDA and GSH. The HFHg group showed a reduction in Nrf2 transcription. The levels of IL-10 and IL-6 and Bcl-2 mRNA were lower in the HF group when compared to controls. MeHg intoxication did not alter the transcriptional levels of IL-10, IL-6 and TNF-α. The HFHg group had lower levels of MPO compared to the other experimental groups. The results of this study suggest that MeHg intoxication caused oxidative stress in the duodenum without altering inflammatory markers. The hyperlipidic diet had an anti-inflammatory effect with increased oxidative stress, in addition to reducing the transcription of Bcl-2. The hyperlipidic (western) diet was able to influence the toxicity of MeHg in the duodenum by reducing the levels of NO2/NO3 and GSH. However, more studies need to be carried out to better understand the mechanisms involved in MeHg toxicity and modulation of the western diet in the small intestine.