Prepubertal exposure to Pb alters autophagy in the brain of aging mice: A time-series based model

Chronic low-level exposure to Pb, Hg, and Cd mixture triggers brain premature aging in rat

Lead (Pb), mercury (Hg), and cadmium (Cd), prevalent neurotoxic heavy metals in the environment, are commonly detected at low concentrations in the blood of the general population. Our previous studies demonstrated that Pb, Hg, and Cd mixture induced neurodevelopmental toxicity even at very low levels. However, the long-term effects of low-level Pb, Hg, Cd exposure on brain aging remain unclear. In this study, female rats were exposed to a mixture of 10 mg/L Pb(CH3COO)2, 0.05 mg/L HgCl2, and 3.5 mg/L CdCl2 via drinking water from mating until offspring weaning. Offspring continued to exposed to heavy metal mixture (3.5 mg/L Pb(CH3COO)2, 0.015 mg/L HgCl2, and 0.5 mg/L CdCl2) for 32 weeks. At 52 weeks of age, brain aging was comprehensively evaluated through behavioral testing, histopathological examination, and telomere assessment. The results revealed that prolonged low-level exposure to the Pb, Hg, and Cd mixture compromised telomeric function by shortening telomere length, inhibiting telomerase activity, and induced neuronal loss in the hippocampal CA1 and CA3 regions. Additionally, Golgi staining revealed disrupted dendritic spines in the hippocampus and altered spine-related signaling pathways (Snk-SPAR pathway). Furthermore, behavioral testing showed that exposure to this mixture impaired spatial memory and social cognition. In conclusion, prolonged exposure to low levels of Pb, Hg, and Cd accelerated brain aging by causing hippocampal telomere dysfunction, neuronal loss, dendritic degeneration, and cognitive decline in rats. These findings offer novel insights into the potential neurotoxic effects of chronic exposure to low-level of Pb, Hg, and Cd mixtures on neurological health.

Heavy metal-induced disruption of the autophagy-lysosomal pathway: implications for aging and neurodegenerative disorders

Heavy metals such as lead, mercury, cadmium, magnesium, manganese, arsenic, copper pose considerable threats to neuronal health and are increasingly recognized as factors contributing to aging-related neurodegeneration. Exposure to these environmental toxins disrupts cellular homeostasis, resulting in oxidative stress and compromising critical cellular processes, particularly the autophagy-lysosomal pathway. This pathway is vital for preserving cellular integrity by breaking down damaged proteins and organelles; however, toxicity from heavy metals can hinder this function, leading to the buildup of harmful substances, inflammation, and increased neuronal injury. As individuals age, the consequences of neurodegeneration become more significant, raising the likelihood of developing disorders like Alzheimer's and Parkinson's disease. This review explores the intricate relationship between heavy metal exposure, dysfunction of the autophagy-lysosomal pathway, and aging-related neurodegeneration, emphasizing the urgent need for a comprehensive understanding of these mechanisms. The insights gained from this analysis are crucial for creating targeted therapeutic approaches aimed at alleviating the harmful effects of heavy metals on neuronal health and improving cellular resilience in aging populations.

The effect of resveratrol on lead-induced oxidative damage and apoptosis in HT-22 cells

OBJECTIVE

The purpose of this work was to investigate whether resveratrol affects lead-induced oxidative damage in HT-22 cells, characterizing mechanisms and strategies for preventing and treating lead-induced neurotoxicity.

METHODS

Various lead and resveratrol concentrations were applied to HT-22 cells over different time periods. First, we established the lead treatment (12.5, 50 and 200 μmol/L) and resveratrol (40 μmol/L) intervention model for the study. MTT was used to analyze HT-22 cell survival rate. The rates of cell death, mitochondrial membrane potential, lipid peroxidation, and reactive oxygen species (ROS) generation were all measured by flow cytometry. Cellular oxidant (MDA) and antioxidant (SOD, GSH-Px) levels were measured with test kits. Western blotting was used to assess the expression of proteins related to autophagy and apoptosis.

RESULTS

Lead reduced HT-22 cell viability in a concentration/time-dependent manner. In addition, lead (200 μmol/L) decreased the protein expression of BCL2, while increasing PARP and BAX expression and apoptotic rate. Moreover, the lead-exposed group had significantly higher levels of ROS, lipid-ROS, and MDA than the control group. This was accompanied by increased MDA levels and decreased SOD, GSH-Px, and MMP levels in the lead-exposed cells. Furthermore, lead lowered SIRT1 protein expression, while increasing the levels of autophagy-related proteins, including P62, ATG5, Beclin-1 and LC3 Ⅱ/Ⅰ. Resveratrol (40 μmol/L), an agonist of SIRT1, restored the effects of lead (200 μmol/L) to levelsindistinguishable from controls.

CONCLUSION

Resveratrol inhibited mitochondrial damage and restored the lead-induced block of autophagic flux and oxidative stress by activating SIRT1, thereby alleviating lead-induced damage in HT-22 cells.

From Fundamentals to Innovation in Alzheimer's Disease: Molecular Findings and Revolutionary Therapies

Alzheimer's disease (AD) is a global health concern and the leading cause of dementia in the elderly. The prevalence of this neurodegenerative condition is projected to increase concomitantly with increased life expectancy, resulting in a significant economic burden. With very few FDA-approved disease-modifying drugs available for AD, there is an urgent need to develop new compounds capable of impeding the progression of the disease. Given the unclear etiopathogenesis of AD, this review emphasizes the underlying mechanisms of this condition. It explores not only well-studied aspects, such as the accumulation of Aβ plaques and neurofibrillary tangles, but also novel areas, including glymphatic and lymphatic pathways, microbiota and the gut-brain axis, serotoninergic and autophagy alterations, vascular dysfunction, the metal hypothesis, the olfactory pathway, and oral health. Furthermore, the potential molecular targets arising from all these mechanisms have been reviewed, along with novel promising approaches such as nanoparticle-based therapy, neural stem cell transplantation, vaccines, and CRISPR-Cas9-mediated genome editing techniques. Taking into account the overlap of these various mechanisms, individual and combination therapies emerge as the future direction in the AD strategy.

Heavy Metal Mediated Progressive Degeneration and Its Noxious Effects on Brain Microenvironment

Heavy metals, including lead (Pb), cadmium (Cd), arsenic (As), cobalt (Co), copper (Cu), manganese (Mn), zinc (Zn), and others, have a significant impact on the development and progression of neurodegenerative diseases in the human brain. This comprehensive review aims to consolidate the recent research on the harmful effects of different metals on specific brain cells such as neurons, microglia, astrocytes, and oligodendrocytes. Understanding the potential influence of these metals in neurodegeneration is crucial for effectively combating the ongoing advancement of these diseases. Metal-induced neurodegeneration involves molecular mechanisms such as apoptosis induction, dysregulation of metabolic and signaling pathways, metal imbalance, oxidative stress, loss of synaptic transmission, pathogenic peptide aggregation, and neuroinflammation. This review provides valuable insights by compiling the supportive evidence from recent research findings. Additionally, we briefly discuss the modes of action of natural neuroprotective compounds. While this comprehensive review aims to consolidate the recent research on the harmful effects of various metals on specific brain cells, it may not cover all studies and findings related to metal-induced neurodegeneration. Studies that are done using bioinformatics tools, microRNAs, long non-coding RNAs, emerging disease models, and studies based on the modes of exposure to toxic metals are a future prospect to be explored.

Kaempferol improves Pb-induced cognitive impairments via inhibiting autophagy

Kaempferol (Kam) is a flavonoid antioxidant found in fruits and vegetables, which was discovered as neuroprotective antioxidants. Lead (Pb), an environmental pollution, could induce learning and memory deficits. Nevertheless, little is known about the mechanisms underlying Kam actions in Pb-induced learning and memory deficits. In this study, we investigated the effects of Kam on Pb-induced cognitive deficits. Pb-exposed rats were treated with 50 mg/kg Kam from postnatal day (PND) 30 to PND 60. Then, Y-maze and Morris water maze have been used to detect the spatial memory in all groups of rats. Hematoxylin and eosin (HE) staining and Nissl staining were used to analyze the neuronal structure damages. The results found Kam treatment improved the learning and memory ability and alleviated hippocampal neuronal pathological damages. Besides, Kam could significantly reverse the synaptic transmission related protein expression including PSD95 and NMDAR2B. Further research found that Kam downregulated autophagy markers, P62, ATG5, Beclin1, and LC3-II. Furthermore, 3-MA, autophagy inhibitor, increased the levels of NMDAR2B and PSD95 in Pb-induced PC12 cells, indicating Kam alleviated Pb-induced neurotoxicity through inhibiting autophagy activation. Our results showed that Kam could ameliorate Pb-induced cognitive impairments and neuronal damages by decreasing Pb-induced excess autophagy accumulation.

Association between heavy metal exposures and the prevalence of pelvic inflammatory disease: a cross-sectional study from the National Health and Nutrition Examination Survey 2013-2018

Pelvic inflammatory disease (PID) is a common medical condition in women. However, the correlation between exposure to heavy metals, including cadmium (Cd), lead (Pb), manganese (Mn), mercury (Hg), and selenium (Se), and PID, is unclear. Using a large sample size from the National Health and Nutrition Examination Survey, these relationships were studied and verified. PID diagnosis was acquired through a self-reported questionnaire (2013-2018). Heavy metal exposure (Cd, Pb, Mn, Hg, and Se) was measured using mass spectrometry of blood samples. Covariate data were obtained through questionnaires and physical tests. Individuals with complete covariate data were included in the study. The relationship between heavy metal exposure (Cd, Pb, Mn, Hg, and Se) and PID was demonstrated using logistic regression analysis, weighted quantile sum (WQS) regression analysis, and restricted cubic splines (RCS). Overall, 2743 participants were included. Of these, 183 were diagnosed with PID. Through weighted univariate and multivariate regression analyses, the heavy metals of Cd and Pb were positively correlated with the prevalence of PID. However, no significant relationship was observed in the heavy metals of Mn, Hg, and Se. The joint effect of heavy metals further confirmed the important role of Cd and Pb in WQS analysis. After visualizing the RCS, significant curved and linear relationships were observed for Cd and Pb, respectively. Most subgroup analyses confirmed these results. In conclusion, exposure to Cd was nonlinearly correlated with the risk of PID, whereas exposure to Pb showed a linear relationship. Our findings increase the awareness of the environmental effects of exposure to heavy metals in PID. However, further studies are needed to elucidate the causality and underlying mechanisms between heavy metal exposure and the prevalence of PID.