Avaliação da contratilidade e do estresse oxidativo em íleo e cólon e análise proteômica do plasma de camundongos C57BL6J expostos ao metilmercúrio

Abstract

Methylmercury (MeHg) is an organic mercury (Hg) compound with high toxicity due to its easy absorption after exposure. MeHg rapidly distributes throughout all tissues, crossing the blood-brain barrier and the epithelial barrier in the central nervous system and gastrointestinal tract, respectively, and can lead to a wide range of debilitating symptoms and death. The aim of this study was to elucidate the effects of oral methylmercury chloride exposure on body weight gain, intestinal motility, oxidative stress, and the proteomic profile in the plasma of intoxicated animals compared with the control group. For this purpose, 46 adult male C57BL6 mice from the animal facility of the Drug Development Center (NPDM) under pathogen-free conditions were used. Mice aged 60 to 90 days with body weights between 15 and 20 g, were divided into two groups: the control group receiving a saline solution by gavage and the intoxicated group receiving a methylmercury chloride solution (2 mg/kg diluted in saline) by gavage for 14 consecutive days. All animals were weighed every 3 days. Seven days after the end of intoxication, the animals were euthanized, and samples of hair, blood, duodenum, ileum, and colon were collected. Quantification of Hg in the hair, evaluation of ileum and colon contractility ex vivo, in a bath chamber for isolated tissues after exposure to potassium chloride (20-160 mM) and carbachol (0.1-100μM), evaluation of oxidative stress in the ileum and colon (tissue concentrations of glutathione-GSH, malondialdehyde-MDA and catalase-CAT) and proteomic analysis of plasma were performed. A significant reduction in the curve of percentage weight gain (% of initial weight) (p<0.05) when compared to the control group. Furthermore, elevated Hg levels in the hair were observed in the intoxicated group compared to the control group (Difference between means ± SEM: 6067 ± 2180). There was no significant difference in intestinal contractility in the ileum or colon between the groups. A significant increase in GSH was detected in the colon and a significant increase of CAT in the ileum of intoxicated animals (p=0.05). Significant alterations were observed in the proteomics analyses between groups, notably an increase in the expression of apolipoproteins E and H and a reduction in phosphatidylcholinesterol acetyltransferase, suggesting metabolic alterations; an increase in the expression of complement factor I, the Mu constant of the heavy chain and the C region of the Ig alpha chain, and a reduction in the C9 and C4b components of the complement system, suggesting a systemic response. We also observed an increase in the expression of the fibrinogen alpha chain and coagulation factor X and a reduction in the expression of the fibrinogen beta chain, suggesting altered liver function and prothrombotic conditions; a reduction in selenoprotein P, expected in models of mercury intoxication without selenium supplementation, indicating deficiencies in this element caused by mercury intoxication; and a reduction in peroxiredoxin 2 levels, that may affect the net antioxidant capacity. In summary, these results corroborate the known deleterious effects of mercury toxicity on the intestinal tract and contribute to the identification of potential proteomic biomarkers. Further studies are needed to confirm these findings, especially in clinical trials.