Metal toxicity and neuroinflammation

Characterization of lung function impairment and pathological changes induced by chronic lead and cadmium inhalation: Insights from a mouse model study

Exposure to environmental heavy metals such as lead (Pb) and cadmium (Cd) is a global concern due to their widespread presence. However, the specific pulmonary effects of inhaled exposure, especially related to long-term effects, remain poorly understood. In this study, we developed a novel mouse model of Pb and Cd inhalation to mimic real-world conditions and investigate pulmonary effects. Mice were exposed to Pb and Cd inhalation for 6 months using a whole-body exposure system, resulting in decreased lung compliance and progression from emphysematous changes to fibrosis. In addition, the blood Pb/Cd levels of mice exposed to Pb/Cd for 6 months are like those of humans occupationally exposed to heavy metals. Histology revealed inflammation and collagen deposition. Transcriptomic analysis highlighted immune responses and macrophage activity in developing fibrosis. These results confirm an association between Pb/Cd exposure and emphysema and fibrosis, reflecting clinical findings. The study highlights the importance of long-term exposure assessment and time-course analysis for understanding Pb/Cd-induced lung disease. The relevance of the mouse model in replicating human exposure scenarios underscores its value in studying fibrosis and emphysema simultaneously. These findings provide a basis for targeted therapeutic interventions against heavy metal-induced lung injury.

Dendrimers-Novel Therapeutic Approaches for Alzheimer's Disease

Dendrimers are covalently bonded globular nanostructures that may be used in the treatment of Alzheimer's disease (AD). Nowadays, AD therapies are focused on improving cognitive functioning and not causal treatment. However, this may change with the use of dendrimers, which are being investigated as a drug-delivery system or as a drug per se. With their ability to inhibit amyloid formation and their anti-tau properties, they are a promising therapeutic option for AD patients. Studies have shown that dendrimers may inhibit amyloid formation in at least two ways: by blocking fibril growth and by breaking already existing fibrils. Neurofibrillary tangles (NFTs) are abnormal filaments built by tau proteins that can be accumulated in the cell, which leads to the loss of cytoskeletal microtubules and tubulin-associated proteins. Cationic phosphorus dendrimers, with their anti-tau properties, can induce the aggregation of tau into amorphous structures. Drug delivery to mitochondria is difficult due to poor transport across biological barriers, such as the inner mitochondrial membrane, which is highly negatively polarized. Dendrimers may be potential nanocarriers and increase mitochondria targeting. Another considered use of dendrimers in AD treatment is as a drug-delivery system, for example, carbamazepine (CBZ) or tacrine. They can also be used to transport siRNA into neuronal tissue and to carry antioxidants and anti-inflammatory drugs to act protectively on the nervous system.

Metallomics analysis of metal exposure and cognitive function in older adults: A combined epidemiological and bioinformatics study

Dementia is a significant cause of elderly disability and Alzheimer's disease (AD) is the most prevalent form of dementia. As an early stage of AD, the mechanism related to mild cognitive impairment (MCI) and heavy metals is still unclear. This study utilized a cross-sectional design and enrolled 514 older adults in Bejing, China. Cognitive function was assessed by the Mini-Mental State Examination (MMSE) and fourteen blood metals were measured by inductively coupled plasma mass spectrometry (ICP-MS). In the adjusted single-metal models, we observed that copper [Cu, β (95% CI): 3.73 (-6.42, -1.03)] and lead [Pb, β (95% CI): 0.79 (-1.26, -0.32)] demonstrated negative associations with cognitive function, while selenium [Se, β (95% CI): 2.97 (1.23, 4.70)] was beneficial to cognition. Our findings were robust in secondary analysis using multi-metal models, which included generalized linear models (GLM), Bayesian kernel machine regression (BKMR), and quantile g-computation (qgcomp). Moreover, the toxic metal mixture (Cu and Pb) exhibited a significant negative association with MMSE scores and the inclusion of Se in the metal mixture attenuated the neurotoxicity of Cu-Pb mixture. The in silico analysis was used to examine the potential molecular mechanisms (genes, biological processes, pathways, and illnesses) of interaction among metal mixtures. We identified 20 cognition-related genes that are associated with both Cu-Pb and Se. Among these genes, eight (APOE, APP, BAX, BDNF, CASP3, HMOX1, TF, and TPP1) exhibited opposite effects on protein activity, mRNA expression, or protein expression in response to Se and Cu/Pb exposure, which could be the key genes accounting for the anti-neurotoxic effects of Se. Our findings support that Se can attenuate the neurotoxicity of exposure to single Cu or Pb, and Cu-Pb mixture. More research is needed to confirm our findings and gain knowledge about the molecular mechanisms of combined metal exposure on cognitive function.

Methylmercury effects on avian brains

Methylmercury (MeHg) is a concerning contaminant due to its ubiquity and harmful effects on organisms. Although birds are important models in the neurobiology of vocal learning and adult neuroplasticity, the neurotoxic effects of MeHg are less understood in birds than mammals. We surveyed the literature on MeHg effects on biochemical changes in the avian brain. Publication rates of papers related to neurology and/or birds and/or MeHg increased with time and can be linked with historical events, regulations, and increased understanding of MeHg cycling in the environment. However, publications on MeHg effects on the avian brain remain relatively low across time. The neural effects measured to evaluate MeHg neurotoxicity in birds changed with time and researcher interest. The measures most consistently affected by MeHg exposure in birds were markers of oxidative stress. NMDA, acetylcholinesterase, and Purkinje cells also seem sensitive to some extent. MeHg exposure has the potential to affect most neurotransmitter systems but more studies are needed for validation in birds. We also review the main mechanisms of MeHg-induced neurotoxicity in mammals and compare it to what is known in birds. The literature on MeHg effects on the avian brain is limited, preventing full construction of an adverse outcome pathway. We identify research gaps for taxonomic groups such as songbirds, and age- and life-stage groups such as immature fledgling stage and adult non-reproductive life stage. In addition, results are often inconsistent between experimental and field studies. We conclude that future neurotoxicological studies of MeHg impacts on birds need to better connect the numerous aspects of exposure from molecular physiological effects to behavioural outcomes that would be ecologically or biologically relevant for birds, especially under challenging conditions.

Glial Cell-Mediated Neuroinflammation in Alzheimer's Disease

Alzheimer's disease (AD) is a progressive neurodegenerative disorder; it is the most common cause of dementia and has no treatment. It is characterized by two pathological hallmarks, the extracellular deposits of amyloid beta (Aβ) and the intraneuronal deposits of Neurofibrillary tangles (NFTs). Yet, those two hallmarks do not explain the full pathology seen with AD, suggesting the involvement of other mechanisms. Neuroinflammation could offer another explanation for the progression of the disease. This review provides an overview of recent advances on the role of the immune cells' microglia and astrocytes in neuroinflammation. In AD, microglia and astrocytes become reactive by several mechanisms leading to the release of proinflammatory cytokines that cause further neuronal damage. We then provide updates on neuroinflammation diagnostic markers and investigational therapeutics currently in clinical trials to target neuroinflammation.