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.

Histone 3 Trimethylation Patterns are Associated with Resilience or Stress Susceptibility in a Rat Model of Major Depression Disorder.

Major Depressive Disorder (MDD) is a severe and multifactorial psychiatric condition. Evidence has shown that environmental factors, such as stress, significantly explain MDD pathophysiology. Studies have hypothesized that changes in histone methylation patterns are involved in impaired glutamatergic signaling. Based on this scenario, this study aims to investigate histone 3 involvement in depression susceptibility or resilience in MDD pathophysiology by investigating cellular and molecular parameters related to i) glutamatergic neurotransmission, ii) astrocytic functioning, and iii) neurogenesis. For this, we subjected male Wistar rats to the Chronic Unpredictable Mild Stress (CUMS) model of depression. We propose that by evaluating the sucrose consumption, open field, and object recognition test performance from animals submitted to CUMS, it is possible to predict with high specificity rats with susceptibility to depressive-like phenotype and resilient to the depressive-like phenotype. We also demonstrated, for the first time, that patterns of H3K4me3, H3K9me3, H3K27me3, and H3K36me3 trimethylation are strictly associated with the resilient or susceptible to depressive-like phenotype in a brain-region-specific manner. Additionally, susceptible animals have reduced DCx and GFAP and resilient animals present increase of AQP-4 immunoreactivity. Together, these results provide evidence that H3 trimethylations are related to the development of the resilient or susceptible to depressive-like phenotype, contributing to further advances in the pathophysiology of MDD and the discovery of mechanisms behind resilience.

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/GSK3ß/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/GSK3ß/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.

Oral administration of carvacrol/ß-cyclodextrin complex protects against 6-hydroxydopamine-induced dopaminergic denervation.

Carvacrol (CARV) presents valuable biological properties such as anti-inflammatory and antioxidant activities. However, pharmacological uses of CARV are largely limited due to disadvantages related to solubility, bioavailability, preparation and storage processes. The complexation of monoterpenes with ß-cyclodextrin (ß-CD) increases their stability, solubility and oral bioavailability. Here, the protective effect of oral treatment with CARV/ß-CD complex (25 µg/kg/day) against dopaminergic (DA) denervation induced by unilateral intranigral injection of 6-hydroxydopamine (6-OHDA - 10 µg per rat) was analyzed, in order to evaluate a putative application in the development of neuroprotective therapies for Parkinson's disease (PD). Pretreatment with CARV/ß-CD for 15 days prevented the loss of DA neurons induced by 6-OHDA in adult Wistar rats. This effect may occur through CARV anti-inflammatory and antioxidant properties, as the pretreatment with CARV/ß-CD inhibited the release of IL-1ß and TNF-α; besides, CARV prevented the increase of mitochondrial superoxide production induced by 6-OHDA in cultured SH-SY5Y cells. Importantly, hepatotoxicity or alterations in blood cell profile were not observed with oral administration of CARV/ß-CD. Therefore, this study showed a potential pharmacological application of CARV/ß-CD in PD using a non-invasive route of drug delivery, i.e., oral administration.

The effects of retinol oral supplementation in 6-hydroxydopamine dopaminergic denervation model in Wistar rats.

Vitamin A (retinol) is involved in signaling pathways regulating gene expression and was postulated to be a major antioxidant and anti-inflammatory compound of the diet. Parkinson's disease (PD) is a progressive neurodegenerative disorder, characterized by loss of nigral dopaminergic neurons, involving oxidative stress and pro-inflammatory activation. The aim of the present study was to evaluate the neuroprotective effects of retinol oral supplementation against 6-hydroxydopamine (6-OHDA, 12 µg per rat) nigrostriatal dopaminergic denervation in Wistar rats. Animals supplemented with retinol (retinyl palmitate, 3000 IU/kg/day) during 28 days exhibited increased retinol content in liver, although circulating retinol levels (serum) were unaltered. Retinol supplementation did not protect against the loss of dopaminergic neurons (assessed through tyrosine hydroxylase immunofluorescence and Western blot). Retinol supplementation prevented the effect of 6-OHDA on Iba-1 levels but had no effect on 6-OHDA-induced GFAP increase. Moreover, GFAP levels were increased by retinol supplementation alone. Rats pre-treated with retinol did not present oxidative damage or thiol redox modifications in liver, and the circulating levels of TNF-α, IL-1ß, IL-6 and IL-10 were unaltered by retinol supplementation, demonstrating that the protocol used here did not cause systemic toxicity to animals. Our results indicate that oral retinol supplementation is not able to protect against 6-OHDA-induced dopaminergic denervation, and it may actually stimulate astrocyte reactivity without altering parameters of systemic toxicity.

Systemic Inflammation Changes the Site of RAGE Expression from Endothelial Cells to Neurons in Different Brain Areas.

The receptor for advanced glycation endproducts (RAGE) is a transmembrane, immunoglobulin-like receptor that interacts with a broad repertoire of extracellular ligands. RAGE belongs to a family of cell adhesion molecules and is considered a key receptor in the inflammation axis and a potential contributor to the neurodegeneration. The present study aimed to investigate the content and cell localization of RAGE in the brain of Wistar rats subjected to systemic inflammation induced by a single dose of lipopolysaccharide (LPS, 5 mg/kg, i.p.). Fifteen days after LPS administration, the content of RAGE was analyzed in the prefrontal cortex (PFC), hippocampus (HIPP), cerebellum (CB), and substantia nigra (SN) were investigated. RAGE levels increased in all structures, except HIPP; however, immunohistochemistry analysis demonstrated that the cell site of RAGE expression changed from blood vessel-like structures to neuronal cells in all brain areas. Besides, the highest level of RAGE expression was found in SN. Immunofluorescence analysis in SN confirmed that RAGE expression was mainly co-localized in endothelial cells (RAGE/PECAM-1 co-staining) in untreated animals, while LPS-treated animals had RAGE expression predominantly in dopaminergic neurons (RAGE/TH co-staining). Decreased TH levels, as well as increased pro-inflammatory markers (TNF-α, IL-1ß, Iba-1, GFAP, and phosphorylated ERK1/2) in SN, occurred concomitantly to RAGE stimulation in the same site. These results suggest a role for RAGE in the establishment of a neuroinflammation-neurodegeneration axis that develops as a long-term response to systemic inflammation by LPS.