Mixed Metal Components in PM2.5 Contribute to Chemokine Receptor CCR5-Mediated Neuroinflammation and Neuropathological Changes in the Mouse Olfactory Bulb

Particulate matter, especially PM2.5, can invade the central nervous system (CNS) via the olfactory pathway to induce neurotoxicity. The olfactory bulb (OB) is the key component integrating immunoprotection and olfaction processing and is necessarily involved in the relevant CNS health outcomes. Here we show that a microglial chemokine receptor, CCR5, is the target of environmentally relevant PM2.5 in the OB to trigger neuroinflammation and then neuropathological injuries. Mechanistically, PM2.5-induced CCR5 upregulation results in the pro-inflammatory paradigm of microglial activation, which subsequently activates TLR4-NF-κB neuroinflammation signaling and induces neuropathological changes that are closely related to neurodegenerative disorders (e.g., Aβ deposition and disruption of the blood-brain barrier). We specifically highlight that manganese and lead in PM2.5 are the main contributors to CCR5-mediated microglial activation and neuroinflammation in synergy with aluminum. Our results uncover a possible pathway of PM2.5-induced neuroinflammation and identify the principal neurotoxic components, which can provide new insight into efficiently diminishing the adverse health effects of PM2.5.

Agmatine prevents the memory impairment and the dysfunction of hippocampal GSK-3β and ERK signaling induced by aluminum nanoparticle in mice

The growing usage of aluminum nanoparticles (Al-NP) and their exposure may influence body function. Considering the proposed relationship between Al and the pathogenesis of Alzheimer's disease and the concern about the effect of this nanoparticle on brain health and cognitive function, the use of neuroprotective agents might be helpful. According to the reported neuroprotective effects of agmatine, in the present study, the possible protective effect of agmatine was assessed in mice model of Al-NP-induced memory impairment. In addition, due to the roles of hippocampal Glycogen synthase kinase-3 beta (GSK-3β) and ERK signaling in memory and its disorders, these pathways were also investigated. Al-NP (10 mg/kg/p.o.) with/without agmatine (5 or 10 mg/kg/i.p.) was administered to adult male NMRI mice for 5 days. Novel object recognition (NOR) test session was used to assess cognitive function. Following the behavioral assessments, the hippocampi were used to determine the phosphorylated and total levels of GSK-3β and ERK as well as GAPDH using western blot analysis. The results showed that Al-NP impaired NOR memory in mice while agmatine 10 mg/kg prevented the memory deficit induced by Al-NP. Furthermore, Al-NP activated GSK-3β as well as ERK signals within the hippocampus while agmatine prevented the effects of Al-NP on GSK-3β and ERK signals within the hippocampus. Besides supporting the neuroprotective effects of agmatine, these findings suggest the possibility of the connection of hippocampal GSK-3β and ERK signaling in the neuroprotective effect of this polyamine against Al-NP.

Role of aluminum exposure on Alzheimer's disease and related glycogen synthase kinase pathway

Aluminum (Al) is an environmentally abundant metal that is not essential for life. There is considerable evidence that Al as a neurotoxic xenobiotic may play a role in the pathogenesis of neurodegenerative diseases like Alzheimer's disease (AD). Exposure to aluminum has been shown to cause neuronal damage that resembles the symptoms of AD. In this review, we will summarize recent data about Al as the possible risk of incidence of AD. Then glycogen synthase kinase-3 beta (GSK3β) contributes to the hyperphosphorylation of Tau protein, the main component of neurofibrillary tangles, one of the hallmarks of AD as one of the mechanisms behind Al neurotoxicity will be covered. Overall, there is still a need for epidemiological studies and more in vivo and in vitro studies to determine the exact mechanisms of its neurotoxicity and the role of GSK3β in both Al toxic effect and AD.

Neurotoxic effects of aluminium exposure as a potential risk factor for Alzheimer's disease

Aluminium is one of the most widely distributed elements of the Earth's crust. Its routine use has resulted in excessive human exposure and due to the potential neurotoxic effects has attained a huge interest in recent years. Despite its ubiquitous abundance, aluminium has no crucial biological functions in the human body. Oxidative stress and neuroinflammatory effects are attributed to its neurotoxic manifestations implicated in Alzheimer's disease. In this review, we have discussed the neuroinflammatory and neurodegenerative events in the brain induced by aluminium exposure. We have highlighted the neurotoxic events caused by aluminium, such as oxidative stress, apoptosis, inflammatory events, calcium dyshomeostasis, Aβ deposition, and neurofibrillary tangle formation in the brain. In addition, the protective measures needed for prevention of aluminium-induced neuronal dysregulations have also been discussed.

A dose response effect of oral aluminum nanoparticle on novel object recognition memory, hippocampal caspase-3 and MAPKs signaling in mice

The increasing use of aluminum nanoparticles (nano-Al) leads to increased human exposure and might affect human health. Considering the suggested connection between aluminum exposure and Alzheimer's disease (AD) pathogenesis, there is a concern about the effect of nano-Al on cognitive function and brain health. This study was aimed to assess the effect of a 5-day oral gavage of aluminum oxide nanoparticle (nano-Al) on memory and the phosphorylation levels of hippocampal p38, JNK (c-Jun N-terminal kinase), ERK (extracellular signal-regulated kinase) as well as cleaved caspase-3 in mice. Adult male NMRI mice were treated with nano-Al in doses 5 and 10 mg/kg/oral gavage for 5 days. The test session of novel object recognition (NOR) task was performed on day 5. Following the NOR test, the hippocampi were isolated for western blot analysis to determine the total and phosphorylated levels of p38, JNK, ERK as well as cleaved caspase-3 proteins. The results showed that nano-Al oral gavage in doses of 5 and 10 mg/kg impairs NOR memory in mice. Moreover, the memory impairing effect of nano-Al coincided with a dose dependent increase in phosphorylated p38 and cleaved caspase-3 in the hippocampus. It also increased the ratio of phosphorylated to total content of ERK in the hippocampus while JNK signaling was not affected by nano-Al. This study showed that nano-Al in doses as low as 5 and 10 mg/ kg ingested for 5 days impairs NOR memory and activates p38, ERK and cleaved caspase-3 in the hippocampus.

Acrolein-conjugated proteomics in brains of adult C57BL/6 mice chronically exposed to acrolein and aged APP/PS1 transgenic AD mice

Acrolein is a universal contaminant with high nucleophilicity in environment and also an endogenous product from lipid peroxidation or polyamine metabolism. Acrolein can react with nucleophilic amino acids, such as cysteines, lysines and histidines via Michael addition. Also, Schiff base products can be formed between acrolein and free amine of lysines. Accumulating evidences demonstrated that acrolein is involved in many diseases, including Alzheimer's disease (AD). Previously we found that oral exposure of acrolein induced AD-like pathology in rats. Here we investigated the acrolein-conjugated proteins in the hippocampus of acrolein-treated mice (3.0 mg/kg/d by gavage for 4 weeks) and aged APP/PS1 mice (the age of 22 months). Acrolein-conjugated proteins were enriched by an aniline-based aldehyde-directed probe, meta-aminophenylacetylene (m-APA). Combined with a quantitative chemoproteomic strategy, 912 proteins were finally identified. Gene ontology analysis revealed several acrolein affected pathways including glycolysis, tricarboxylic acid (TCA) cycle and carbon metabolism. Acrolein are mainly conjugated with 14-3-3 protein and members of small GTPase family in hippocampus. Taken together, our results provide new evidences for the roles of acrolein in AD.