Effects of methylmercury and retinol palmitate co-administration in rats during pregnancy and breastfeeding: Metabolic and redox parameters in dams and their offspring

Transgenerational inheritance of methylmercury and vitamin A-induced toxicological effects in a Wistar rats environmental-based model

Mercury (Hg) and vitamin A (VitA) are two environmental factors with potential health impacts, especially during pregnancy and early childhood. Fish and seafood may present elevated levels of methylmercury (MeHg), the major Hg derivative, and VitA. This study aimed to evaluate the transgenerational effects of exposure to MeHg and/or VitA on epigenetic and toxicological parameters in a Wistar rat model. Our findings revealed persistent toxicological effects in generations F1 and F2 following low/mild doses of MeHg and/or VitA exposure during dams' (F0) gestation and breastfeeding. Toxicological effects observed in F2 included chronic DNA damage, bone marrow toxicity, altered microglial content, reduced neuronal signal, and diminished male longevity. Sex-specific patterns were also observed. Co-exposure to MeHg and VitA showed both synergistic and antagonistic effects. Additionally, the study demonstrated that MeHg and VitA affected histone methylation and caused consistent effects in F2. While MeHg exposure has been associated with transgenerational inheritance effects in other organisms, this study provides the first evidence of transgenerational inheritance of MeHg and VitA-induced toxicological effects in rodents. Although the exact mechanism is not yet fully understood, these findings suggest that MeHg and VitA may perpetuate their impacts across generations. The study highlights the need for remedial policies and interventions to mitigate the potential health problems faced by future generations exposed to MeHg or VitA. Further research is warranted to investigate the transgenerational effects beyond F2 and determine the matrilineal or patrilineal inheritance patterns.

Dietary exposure to mercury and its relation to cytogenetic instability in populations from "La Mojana" region, northern Colombia

Fish consumption and chronic exposure to low doses of mercury (Hg) seems to activate several molecular mechanisms leading to carcinogenic and/or teratogenic processes. However, Hg genotoxic effects on humans are not completely described. In the present study, we assessed cytogenetic damage in isolated human peripheral lymphocytes using the cytokinesis-block micronucleus cytome assay (CBMN-Cyt), micronucleus formation with anti-kinetochore antibody (CREST staining), levels of total Hg in hair (T-Hg), fish consumption, and estimated Hg dose. The study comprised 39 non-exposed, and 73 residents from La Mojana region, an area with a well-documented Hg contamination. Data showed a significant increase in micronuclei (MNBN), nucleoplasmic bridges (NPB), and necrotic and apoptotic cell frequencies in residents of "La Mojana." The overall mean T-Hg level in hair for exposed residents was 1.12 ± 0.94 mg kg^-1 and 0.15 ± 0.05 in individuals from the reference area. Approximately 40% of analyzed individuals showed T-Hg levels that exceeded US Environmental Protection Agency (USEPA) reference dose. Increased T-Hg levels in hair were related to increased MNBN frequencies and high fish consumption. Other cellular markers, such as necrotic and apoptotic cell frequencies, were also correlated with high fish intake and T-Hg contents. Results of the CREST staining demonstrated that in vivo exposure to Hg induces genetic instability by chromosome fragment loss (clastogenic). Additionally, a high average intake of some fish species, particularly with carnivorous habits like Caquetaia kraussii, Hoplias malabaricus, and Sorubin cuspicaudus, seems to increase MNBN frequencies significantly.

Effects of foetal and breastfeeding exposure to methylmercury (MeHg) and retinol palmitate (Vitamin A) in rats: Redox parameters and susceptibility to DNA damage in liver

Methylmercury (MeHg) is known to be a chemical that poses a risk to public health. Exposure to MeHg and vitamin A (VitA) occurs through the ingestion of fish, present in the diet of most pregnant women. The absorption of these elements generates oxidative stress and can generate adaptations for future stressful events. Here, we assessed how exposure to VitA and/or MeHg during the fetal and breastfeeding period modulates the toxicity of MeHg reexposure in adulthood. We focus on redox systems and repairing DNA damage. Male rats (n = 50), were divided into 5 groups. Control received mineral oil; The VitA group received VitA during pregnancy, during breastfeeding and was exposed to MeHg in adulthood; VitA + MeHg received VitA and MeHg during pregnancy and breastfeeding and was exposed to MeHg in adulthood. The single exposure group (SE) was exposed to MeHg only in adulthood; and the MeHg group was pre-exposed to MeHg during pregnancy and breastfeeding and re-exposed to MeHg in adulthood. After treating the animals, we evaluated the redox status and the level of DNA damage in all rats. The results revealed that MeHg significantly decreased the activity of glutathione peroxidase (GPx) and sulfhydryl levels and increased the activity of superoxide dismutase (SOD), glutathione transferase, glutathione and carbonyl in all exposed groups. These results suggest that the second exposure to MeHg directly altered the effects of oxidation and that there were no specific effects associated with exposure during the fetal and breastfeeding periods. In addition, our findings indicate that MDA levels increased in MeHg and SE levels and no differences in MDA levels were observed between the VitA and MeHg + VitA groups. We also observed that animals pretreated exclusively with VitA showed residual damage similar to the control's DNA, while the other groups showed statistically higher levels of damage. In conclusion, low doses of MeHg and VitA during fetal and breastfeeding periods were unable to condition an adaptive response to subsequent exposure to MeHg in adulthood in relation to the observed levels of oxidative damage assessed after exposure.

Hepatic and neurobiological effects of foetal and breastfeeding and adulthood exposure to methylmercury in Wistar rats

Methylmercury (MeHg) is an organic bioaccumulated mercury derivative that strongly affects the environment and represents a public health problem primarily to riparian communities in South America. Our objective was to investigate the hepatic and neurological effects of MeHg exposure during the phases foetal and breast-feeding and adult in Wistar rats. Wistar rats (n = 10) were divided into 3 groups. Control group received mineral oil; The simple exposure (SE) group was exposed only in adulthood (0.5 mg/kg/day); and double exposure (DE) was pre-exposed to MeHg 0.5 mg/kg/day during pregnancy and breastfeeding (±40 days) and re-exposed to MeHg for 45 days from day 100. After, we evaluated possible abnormalities. Behavioral and biochemical parameters in liver and occipital cortex (CO), markers of liver injury, redox and AKT/GSK3β/mTOR signaling pathway. Our results showed that both groups treated with MeHg presented significant alterations, such as decreased locomotion and exploration and impaired visuospatial perception. The rats exposed to MeHg showed severe liver damage and increased hepatic glycogen concentration. The MeHg groups showed significant impairment in redox balance and oxidative damage to liver macromolecules and CO. MeHg upregulated the AKT/GSK3β/mTOR pathway and the phosphorylated form of the Tau protein. In addition, we found a reduction in NeuN and GFAP immunocontent. These results represent the first approach to the hepatotoxic and neural effects of foetal and adult MeHg exposure.

Dietary co-exposure to methylmercury and monosodium glutamate disrupts cellular and behavioral responses in the lobster cockroach, Nauphoeta cinerea model

The present study aims to investigate the effect of monosodium glutamate (MSG) both separately and combined with a low dose of methylmercury (MeHg) on behavioral and biochemical parameters in Nauphoeta cinerea (lobster cockroach). Cockroaches were fed with the basal diet alone, basal diet + 2% NaCl, basal diet + 2% MSG; basal diet + 0.125 mg/g MeHg, basal diet + 0.125 mg/g MeHg + 2% NaCl; and basal diet + 0.125 mg/g MeHg + 2% MSG for 21 days. Behavioral parameters such as distance traveled, immobility and turn angle were automatically measured using ANY-maze video tracking software (Stoelting, CO, USA). Biochemical end-points such as acetylcholinesterase (AChE), glutathione-S-transferase (GST), total thiol and TBARS were also evaluated. Results show that MeHg + NaCl, increased distance traveled while MeHg + MSG increased time immobile. AChE activity was significantly reduced in cockroaches across all the groups when compared to the control. There was no significant alteration in GST activity and total thiol levels. It could be that both NaCl and MSG potentiates the neurotoxic effect of MeHg in cockroaches.