Genetics and Epigenetics of Manganese Toxicity

Signal Transduction Associated with Mn-induced Neurological Dysfunction

Manganese (Mn) is a heavy metal that occurs widely in nature and has a vital physiological role in growth and development. However, excessive exposure to Mn can cause neurological damage, especially cognitive dysfunction, such as learning disability and memory loss. Numerous studies on the mechanisms of Mn-induced nervous system damage found that this metal targets a variety of metabolic pathways, for example, endoplasmic reticulum stress, apoptosis, neuroinflammation, cellular signaling pathway changes, and neurotransmitter metabolism interference. This article reviews the latest research progress on multiple signaling pathways related to Mn-induced neurological dysfunction.

Biomarkers of methylmercury neurotoxicity and neurodevelopmental features: A systematic review

The issue of MeHg contamination is a significant concern due to its detrimental impact on the environment. This study aimed to thoroughly investigate the effects of MeHg on neurodevelopmental biomarkers, as there is a lack of systematic reviews in this area. We conducted a comprehensive search of three databases (PubMed, Scopus, and Web of Science) and found 522 records, which were then meticulously reviewed by two independent reviewers. A total of 66 studies were included, with biomarkers related to oxidative stress, neurotransmission, inflammation, epigenetics, and apoptosis being the most prominent. The results of both in vitro and in vivo models indicate that antioxidant enzymes and other oxidative stress-related markers are indeed, altered following MeHg exposure. Moreover, MeHg exposure causes significant disruptions to neurotransmitter levels, activities of neurotransmitter synthesis enzymes, receptor densities, and proteins involved in synaptic function. Proinflammatory biomarkers are consistently overexpressed in both MeHg-treated cells and the brains of exposed rats. Furthermore, studies on DNA methylation and biomarker activity suggest that MeHg exposure may lead to neurotoxicity and neurodevelopmental issues via perturbations to epigenetic markers and the apoptosis pathway.

Melatonin promotes cell cycle progression of neural stem cells subjected to manganese via Nurr1

Excessive exposure to manganese (Mn) through drinking water and food during pregnancy significantly heightens the likelihood of neurodevelopmental damage in offspring. Multiple studies have indicated that melatonin (Mel) may help to relieve neurodevelopmental disorders caused by Mn, but potential mechanisms underlying this effect require further exploration. Here, we utilized primary neural stem cells (NSCs) as a model to elucidate the molecular mechanism underlying the protective function of Mel on Mn-induced cell proliferation dysfunction and cycle arrest. Our results showed that Mn disrupted the cell cycle in NSCs by suppressing positive regulatory proteins (CDK2, Cyclin A, Cyclin D1, and E2F1) and enhancing negative ones (p27KIP1 and p57KIP2), leading to cell proliferation dysfunction. Mel inhibited the Mn-dependent changes to these proteins and the cell cycle through nuclear receptor-related protein 1 (Nurr1), thus alleviating the proliferation dysfunction. Knockdown of Nurr1 using lentivirus-expressed shRNA in NSCs resulted in a diminished protective effect of Mel. We concluded that Mel mitigated Mn-induced proliferation dysfunction and cycle arrest in NSCs through Nurr1.

Supplementation of Micro- and Macronutrients-A Role of Nutritional Status in Non-Alcoholic Fatty Liver Disease

Non-alcoholic fatty liver disease (NAFLD) is a condition in which the pathological cumulation of fat with coexisting inflammation and damage of hepatic cells leads to progressive dysfunctions of the liver. Except for the commonly well-known major causes of NAFLD such as obesity, dyslipidemia, insulin resistance, or diabetes, an unbalanced diet and imbalanced nutritional status should also be taken into consideration. In this narrative review, we summarized the current knowledge regarding the micro- and macronutrient status of patients suffering from NAFLD considering various diets and supplementation of chosen supplements. We aimed to summarize the knowledge indicating which nutritional impairments may be associated with the onset and progression of NAFLD at the same time evaluating the potential therapy targets that could facilitate the healing process. Except for the above-mentioned objectives, one of the most important aspects of this review was to highlight the possible strategies for taking care of NAFLD patients taking into account the challenges and opportunities associated with the micronutrient status of the patients. The current research indicates that a supplementation of chosen vitamins (e.g., vitamin A, B complex, C, or D) as well as chosen elements such as zinc may alleviate the symptoms of NAFLD. However, there is still a lack of sufficient data regarding healthy ranges of dosages; thus, further research is of high importance in this matter.

Upregulation of Intracellular Zinc Ion Level after Differentiation of the Neural Stem/Progenitor Cells In Vitro with the Changes in Gene Expression of Zinc Transporters

We measured the intracellular zinc ion concentration of murine fetal neural stem/progenitor cells (NSPCs) and that in the differentiated cells. The NSPCs cultured with 1.5 μM Zn2+ proliferated slightly faster than that in the zinc-deficient medium and the intracellular zinc concentration of the NSPCs and that of their differentiated cells (DCs) cultured with 1.5 μM Zn2+ was 1.34-fold and 2.00-fold higher than those in the zinc-deficient medium, respectively. The zinc transporter genes upregulated over the 3.5-fold change were Zip1, Zip4, Zip12, Zip13, ZnT1, ZnT8, and ZnT10 whereas the only downregulated one was Zip8 during the differentiation of NSPCs to DCs. The cell morphologies of both NSPCs and DCs in the low oxygen culture condition consisting of 2%O2 and 5%CO2, the high carbon dioxide condition consisting of 21%O2 and 10%CO2, and the normal condition consisting of 21%O2 and 5%CO2 were essentially the same each other. The expression of Zip4, Zip8, Zip12, and Zip14 was not drastically changed depending on the O2 and CO2 concentrations.

Effect of Melissa officinalis L. leaf extract on manganese-induced cyto-genotoxicity on Allium cepa L

Although the antioxidant properties of Melissa officinalis extract (Mox) are widely known, little work has focused on its protective capacity against heavy metal stress. The primary objective of this study was to determine the potential of Mox to mitigate manganese (II) chloride (MnCI2)-induced cyto-genotoxicity using the Allium and comet assays. Physiological, genotoxic, biochemical and anatomical parameters as well as the phenolic composition of Mox were examined in Allium cepa (L.). Application of 1000 µM MnCl2 reduced the rooting percentage, root elongation, weight gain, mitotic index and levels of chlorophyll a and chlorophyll b pigments compared to the control group. However, it increased micronuclei formation, chromosomal abnormality frequencies, tail DNA percentage, proline amount, lipid peroxidation level and meristematic damage severity. The activities of superoxide dismutase and catalase also increased. Chromosomal aberrations induced by MnCl2 were fragment, sticky chromosome, vagrant chromosome, unequal distribution of chromatin and bridge. Application of 250 mg/L Mox and 500 mg/L Mox along with MnCl2 significantly alleviated adverse effects dose dependently. The antioxidant activity bestowed by the phenolic compounds in Mox assisted the organism to combat MnCl2 toxicity. Consequently, Mox exerted remarkable protection against MnCl2 toxicity and it needs to be investigated further as a potential therapeutic option.

Iron Oxide Nanoparticles with and without Cobalt Functionalization Provoke Changes in the Transcription Profile via Epigenetic Modulation of Enhancer Activity

Despite the progress in the field of nanotoxicology, much about the cellular mechanisms that mediate the adverse effects of nanoparticles (NPs) and, in particular, the possible role of epigenetics in nanotoxicity, remains to be clarified. Therefore, we studied the changes occurring in the genome-wide distribution of H3K27ac, H3K4me1, H3K9me2, and H3K27me3 histone modifications and compared them with the transcriptome after exposing NIH3T3 cells to iron-based magnetic NPs (i.e., Fe2O3 and Fe2O3@Co NPs). We found that the transcription response is mainly due to changes in the genomic distribution of H3K27ac that can modulate the activity of enhancers. We propose that alteration of the epigenetic landscape is a key mechanism in defining the gene expression program changes resulting in nanotoxicity. With this approach, it is possible to construct a data set of genomic regions that could be useful for defining toxicity in a manner that is more comprehensive than what is possible with the present toxicology assays.

Evolution of Status of Trace Elements and Metallothioneins in Patients with COVID-19: Relationship with Clinical, Biochemical, and Inflammatory Parameters

The inflammatory reaction and pathogenesis of COVID-19 may be modulated by circulating trace elements (Iron (Fe), Zinc (Zn), Copper (Cu), Manganese (Mn)) and Metallothioneins (MTs). Thus, the present study aimed to investigate their relationship with clinical, biochemical, and inflammatory parameters in patients with COVID-19 at the early Intensive Care Unit (ICU) phase. Critically ill patients (n = 86) were monitored from the first day of ICU admission until the third day of stay. Serum samples were used to assess mineral levels via Inductively Coupled Plasma Mass Spectrometry (ICP-MS) and MT levels via differential pulse voltammetry. Levels of Cu and MTs were significantly decreased after 3 days (p < 0.05), increasing the prevalence of Cu-deficient values from 50% to 65.3% (p = 0.015). Fe and Zn were shown to have a predictive value for mortality and severity. The present study suggests trace element deficiency may be a risk factor during early ICU treatment of COVID-19, as it is related to different biochemical and clinical parameters, indicating a possible beneficial effect of restoring proper levels of these micronutrients.

Manganese-induced apoptosis through the ROS-activated JNK/FOXO3a signaling pathway in CTX cells, a model of rat astrocytes

Manganese (Mn) is an essential trace element that maintains many normal physiological functions. However, multi-system disorders would occur once overexposure to Mn, especially neurotoxicity. Despite evidence demonstrating the critical role of ROS-activated JNK/FOXO3a signaling pathway in neuronal survival, the specific mechanisms by which it contributes to Mn-induced neurotoxicity are still unclear. The objectives of this study was to examine the modulation of the JNK/FOXO3a signaling pathway, which is activated by ROS, in Mn-induced apoptosis, using a rat brain astrocyte cell line (CTX cells). This study found that a dose-dependent decrease in cell viability of CTX cells was observed with 150, 200, 250, 300 μmol/L Mn. The results of apoptosis-related protein assay showed that Mn decreased the expression of anti-apoptotic protein Bcl-2 and enhanced the expression of apoptosis-related proteins like Bax and Cleaved-Caspase3. In addition, treatment with Mn resulted in elevated ROS levels and increased phosphorylation levels of JNK. Conversely, phosphorylation of nuclear transcription factors FOXO3a, which regulates expression of transcription factors including Bim and PUMA, was decreased. Depletion of ROS by N-acetyl-L-cysteine (NAC) and inhibition of the JNK pathway by SP600125 prevented Mn-induced JNK/FOXO3a pathway activation and, more importantly, the level of apoptosis was also significantly reduced. Confirmation of Mn-induced apoptosis in CTX cells through ROS generation and activation of the JNK/FOXO3a signaling pathway was the outcome of this study. These findings offer fresh insights into the neurotoxic mechanisms of Mn and therapeutic targets following Mn exposure.

Association of the DNA Methylation of Obesity-Related Genes with the Dietary Nutrient Intake in Children

The occurrence of obesity stems from both genetic and external influences. Despite thorough research and attempts to address it through various means such as dietary changes, physical activity, education, and medications, a lasting solution to this widespread problem remains elusive. Nutrients play a crucial role in various cellular processes, including the regulation of gene expression. One of the mechanisms by which nutrients can affect gene expression is through DNA methylation. This modification can alter the accessibility of DNA to transcription factors and other regulatory proteins, thereby influencing gene expression. Nutrients such as folate and vitamin B12 are involved in the one-carbon metabolism pathway, which provides the methyl groups necessary for DNA methylation. Studies have shown that the inadequate intake of these nutrients can lead to alterations in DNA methylation patterns. For this study, we aim to understand the differences in the association of the dietary intake between normal weight and overweight/obese children and between European American and African American children with the DNA methylation of the three genes NRF1, FTO, and LEPR. The research discovered a significant association between the nutritional intake of 6-10-years-old children, particularly the methyl donors present in their diet, and the methylation of the NRF1, FTO, and LEPR genes. Additionally, the study emphasizes the significance of considering health inequalities, particularly family income and maternal education, when investigating the epigenetic impact of methyl donors in diet and gene methylation.