Aluminum-induced "mixed" cell death in mice cerebral tissue and potential intervention

Neurotoxic effects of aluminum and manganese: From molecular to clinical effects

The existing data demonstrate that aluminum (Al) and manganese (Mn) possess neurotoxic effects upon overexposure due to induction of neuronal oxidative stress and apoptosis, synaptic dysfunction and neurotransmitter metabolism, neuroinflammation, and cytoskeletal pathology. However, systematic evidence regarding contribution of these metals to development of neurological diseases are lacking. Therefore, in this review we provide a summary of the existing data on contribution of Al and Mn exposure to brain diseases and its symptoms. Causal relations were demonstrated for development of parkinsonism upon exposure to high doses of Mn, whereas Al overload is considered the key contributor to dialysis encephalopathy. Certain studies demonstrate that Al and Mn overexposure is associated with neurodegenerative diseases including Alzheimer's and Parkinson's diseases, as well as neurodevelopmental disorders like autism spectrum disorder (ASD) and attention-deficit/hyperactivity disorder (ADHD). Although laboratory studies demonstrate the potential contribution of Al and Mn to molecular pathogenesis of these diseases, clinical findings supporting the causal role of metals is these pathologies are yet insufficient. Therefore, estimation of the contribution of these metals to neurological disorders is essential for development of more effective early diagnostics and prevention of diseases under exposure to adverse neurological effects of Al and Mn compounds.

miR-128-3p is involved in aluminum-induced cognitive impairment by regulating the Sirt1-Keap1/Nrf2 pathway

Aluminum (Al) is a common neurotoxicant in the environment, but the molecular mechanism of its toxic effects is still unclear. Studies have shown that aluminum exposure causes an increase in neuronal apoptosis. The aim of this study was to investigate the mechanism and signaling pathway of neuronal apoptosis induced by aluminum exposure. The rat model was established by intraperitoneal injection of maltol aluminum for 90 days. The results showed that the escape latency of the three groups exposed to maltol aluminum was higher than that of the control group on the 3rd, 4th and 5th days of the positioning cruise experiment (P < 0.05). On the 6th day of the space exploration experiment, compared with the control group(6.00 ± 0.71,15.33 ± 1.08) and the low-dose group(5.08 ± 1.69,13.67 ± 1.09), the number of times that the high-dose group crossed the platform(2.25 ± 0.76) and the platform quadrant(7.58 ± 1.43) was significantly reduced (P < 0.01). The relative expression levels of Sirt1 and Nrf2 in hippocampal tissues of all groups decreased gradually with increasing maltol aluminum exposure dose the relative expression levels of Sirt1 and Nrf2 in high-dose group (0.261 ± 0.094,0.325 ± 0.108) were significantly lower than those in control group (1.018 ± 0.222,1.009 ± 0.156)(P < 0.05). The relative expression level of Keap1 increased gradually with increasing maltol aluminum exposure dose (P < 0.05). The relative expression level of miR-128-3p in the high-dose group(1.520 ± 0.280) was significantly higher than that in the control group(1.000 ± 0.420) (P < 0.05). The content of GSH-Px in the hippocampus of rats decreased with increasing dose. ROS levels gradually increased. We speculated that subchronic aluminum exposure may lead to the activation of miR-128-3p in rat hippocampus of rats, thereby inhibiting the Sirt1-Keap1/Nrf2 pathway so that the Sirt1-Keap1/Nrf2 pathway could not be activated to exert antioxidant capacity, resulting in an imbalance in the antioxidant system of rats and the apoptosis of neurons, which caused reduced cognitive impairment in rats.

Role of the RIP3-PGAM5-Drp1 pathway in aluminum-induced PC12 cells necroptosis

Epidemiological studies from diverse global regions suggest a correlation between the accumulation of aluminum in the brain and the onset of various neurodegenerative diseases, including Alzheimer's disease, of which, neuronal cells death happen. Our previous research has found the potential of aluminum to induce neuronal cell death. A comprehensive exploration of the regulatory pathways influenced by aluminum in neuronal cell death could contribute to the development of strategies aimed at preventing the detrimental impact of aluminum on neuronal cells. This study is dedicated to exploring the impact of aluminum on mitochondrial homeostasis through the RIP3-PGAM5-Drp1 pathway, with a specific focus on its potential role in necroptosis. We observed that the inhibition of RIP3 function and the reduction in PGAM5 protein expression both mitigate aluminum-induced necroptosis in PC12 cells and enhance mitochondrial function. However, the inhibition of PGAM5 protein expression does not exert an impact on the expression of RIP3 and MLKL proteins. In summary, our study posits that aluminum can induce necroptosis in PC12 cells through the RIP3-PGAM5-Drp1 pathway.

Neurobehavioral and Immunohistochemical Studies of the Cerebral Cortex Following Treatment with Ethyl Acetate Leaf Fraction of Tamarindus indica During Prenatal Aluminum Chloride Exposure in Wistar Rats

Purpose

The recent increase in aluminum exposure and its effect on the development of the brain call for serious attention. The study investigated the behavioral and immunohistochemical changes in the cerebral cortex of Wistar rats following prenatal co-administration of ethyl acetate leaf fraction of Tamarindus indica (EATI) and aluminum chloride (AlCl3).

Methods

Pregnant Wistar rats were divided into 5 groups (n=4). Group I (negative control), Group II-V were experimental groups treated with 200 mg/kg of AlCl3 s/c. Group III and IV received an additional 400 mg/kg and 800 mg/kg of EATI respectively, while Group V received an additional 300 mg/kg of Vitamin E for 14 days (prenatal days 7-21) via the oral route. The pups were then exposed to cliff avoidance, negative geotaxis, and elevated plus maze (EPM) test on the post-natal day (PoND) 4-6, 7-10, and 18 respectively. On PoND 21 pups were sacrificed, and the skull dissected to remove the brain. The harvested brain tissues were processed for Cresyl fast (CF) and glial fibrillary acid protein (GFAP).

Results

The study showed that EATI administration during AlCl3 exposure was associated with significant improvement in sensory-motor development. The EPM, CF, and GFAP results revealed significant improvement in anxiety-like behavior, motor activities, GFAP expression, pyramidal cell count, and Nissl staining following prenatal EATI administration during AlCl3 exposure.

Conclusion

The present study concludes that EATI was associated with some protective potential during prenatal AlCl3 exposure in Wistar rats.

Aluminum Induced Necroptosis of PC12 Cells via TNFR1-RIP1/RIP3 Signalling Pathway

In addition to apoptosis, it has also been reported that aluminum (Al) causes necroptosis, a new form of programmed necrosis, which has recently been discovered, in nerve cells, but its molecular mechanism is not elucidated. In order to explore the answer, in this study, we apply for this method that after PC12 cells were exposed to maltol aluminum [200 μM Al(mal)₃], siRNA were used as interference technique to explore the role of Tumour necrosis factor receptor 1 (TNFR1), receptor interaction proteins 1 (RIP1) and receptor interaction proteins 3 (RIP3) in necroptosis caused by Al(mal)₃. After the end of this research, we demonstrated that, initially, Al(mal)₃ could trigger apoptosis and necroptosis in PC12 cells and up-regulate both mRNA and protein expressions of TNFR1, RIP1 and RIP3, also, up-regulate the phosphorylated mixed lineage kinase domain-like protein (MLKL) protein expression. Additionally, in PC12 cells treated with Al(mal)₃, suppression of TNFR1 was found to enhance apoptosis and attenuate the expression of RIP1/RIP3 and phosphorylated MLKL. At last, deficiency of RIP1/RIP3 reduced the extent of necroptosis. Briefly, our results verify that the TNFR1-RIP1/RIP3 pathway could be involved in Al(mal)₃ induced necroptosis.

Necrostatin-1 Relieves Learning and Memory Deficits in a Zebrafish Model of Alzheimer's Disease Induced by Aluminum

Aluminum (Al) is considered one of the environmental risk factors for Alzheimer's disease (AD). The present study aims to establish a zebrafish AD model induced by Al and explore if necrostation-1 (Nec-1), a specific inhibitor of necroptosis, is effective in relieving learning and memory deficits in the zebrafish AD models. We treated adult zebrafish with aluminum trichloride at various doses for 1 month, followed by a T-maze test to evaluate learning and memory performance. Al concentration, levels of acetylcholine (Ach), and AD-related protein and gene expression in the brain tissue were evaluated in the zebrafish AD models. Our results demonstrated that in the brain tissue of Al-treated zebrafish, Al accumulated, Ach levels decreased, and AD-related genes and proteins increased. As a result, the learning and memory performance of Al-treated zebrafish was impaired. This suggested that a zebrafish AD model was established. To test the effect of Nec-1 on the zebrafish AD model, we added Nec-1 into the culture medium of the Al-treated adult zebrafish. The results demonstrated that Nec-1 could relive the learning and memory deficits, enhance Ach levels and the numbers of neural cells, and impact necroptosis-related gene expression. We concluded that Nec-1 could reverse Al-induced learning and memory impairment and had potential theoretical value in the zebrafish AD model.

Relationship between the expression of TNFR1-RIP1/RIP3 in peripheral blood and cognitive function in occupational Al-exposed workers: A mediation effect study

Aluminium (Al), not essential for biological activities, accumulates in the tissues. It exerts toxic effects on the nervous system, inducing in humans' irreversible cognitive impairment. In this study, a cluster sampling method was used to observe the cognitive function of long-term occupational Al-exposed workers in a large Al factory, and determine the expression of peripheral blood tumour necrosis factor receptor 1 (TNFR1), receptor-interacting protein 1 (RIP1), and RIP3. TNF-alpha, expressed in blood macrophages and microglia, with its receptors TNFR1, TR1 and TR3, enhances the necroptosis of neurons. Additionally, the relationship between the expression of TNFR1, RIP1, and RIP3 in the peripheral blood of long-term occupational Al-exposed workers and changes in their cognitive function was explored. The differences in the distributions of clock drawing test (CDT) scores among the three groups were statistically significant (P < 0.05). The results of correlation analysis showed that RIP1 and RIP3 protein contents were negatively correlated with mini-mental state examination (MMSE) and CDT scores (P < 0.05). Plasma Al content was positively correlated with other biological indicators (P < 0.05), and negatively correlated with MMSE and CDT scores (P < 0.05). Results showed that RIP3 protein had an incomplete mediation effect between plasma Al content and cognitive function. This suggests that Al may affect cognitive function by influencing the expression of TNFR1, RIP1, and RIP3 in the nervous system.

miR-29a and the PTEN-GSK3β axis are involved in aluminum-induced damage to primary hippocampal neuronal networks

We previously reported that aluminum (Al) can cause a range of neurotoxic injuries including progressive irreversible synaptic structural damage and synaptic dysfunction, and eventually neuronal deaths. Mechanism of Al-induced electrophysiological and neuronal connectivity changes in neurons may indicate damage to the neuronal network. Here, mouse primary hippocampal neurons were cultured on micro-electrode array (MEA)- and high-content analysis (HCA)-related plates, showing that Al exposure significantly inhibited hippocampal neuronal electrical spike activity and neurite outgrowth characterized by a reduction in neurite branching and a decrease in the average total neurite length in relation to both Al dose and time of incubation. In recent years, miR-29a/ phosphatase and tensin homolog (PTEN) have been found to play pivotal roles in the morphogenesis of neurons, it has been confirmed in vitro and in vivo that the PTEN-Glycogen synthase kinase-3β (GSK-3β) axis regulates neurite outgrowth. The present study demonstrated that increases in Al exposure and dose gradually reduce miR-29a expression. Up-regulation of miR-29a in the hippocampal neurons by lentivirus transfection reversed the decrease in electrical spike activity and the reduction in both neurite branching and length induced by Al. Moreover, miR-29a suppressed the expression of PTEN and increased the level of phosphorylated Protein Kinase B (p-AKT) and p-GSK-3β which were inhibited by the Al treatment. This suggests that miR-29a is critically involved in the functional and structural neuronal damage induced by Al and is a potential target for Al neurotoxicity. Moreover, the reduction of neurite length and branching induced by Al exposure was regulated by miR-29a and its target neuronal PTEN-GSK3β signaling pathway, which also represents a possible mechanism of Al-induced the inhibition of the electrical activity. Collectively, Al-induced damage to the neuronal network occurred through miR-29a-mediated alterations of the PTEN-GSK3β signaling pathway.