Aluminum and benzo[a]pyrene co-operate to induce neuronal apoptosis in vitro.

Toxic and harmful factors co-exist in the environment; these factors often interact to induce combined toxicity, which is the main focus of toxicological research. Furthermore, a large number of studies have shown that aluminum (Al) and benzo[a]pyrene (BaP) are neurotoxic and target the central nervous system to cause neuronal apoptosis. Because we are exposed to both Al and BaP in the air, water, food, and even medicine, the combined effects of these agents in humans must be examined. The present study examines the ability of Al and BaP co-exposure to intensify neuronal apoptosis. The primary neurons of newborn rats were cultured for 5 days, and cells from the same batch that were growing well were selected and assigned to the blank control group, the solvent control group (DMSO+S9+maltol), BaP groups (10, 40 µmol/L), Al (mal)3 groups (50, 100, 400 µmol/L) and co-exposure groups with different combinations of BaP and Al (mal)3. The cell viabilities indicated that 10 µM BaP or 50 µM Al (mal)3 was mildly toxic, and we selected 10 µM BaP+50 µM Al (mal)3 for subsequent co-exposure experiments. The morphological characteristics of cell apoptosis were much more obvious in the co-exposure group than in the Al-exposed cells or the BaP-exposed cells, as observed with a transmission electron microscope and a fluorescence inverted microscope. The apoptotic rates and caspase-3 activity quantitatively significantly differed between the co-exposure and Al-exposure groups, while the BaP-exposure group did not significantly differ from the control group. These results indicate that Al and BaP co-exposure exert synergistic effects on neuronal cell apoptosis.

Necrostatin-1 inhibits the degeneration of neural cells induced by aluminum exposure.

PURPOSE: There are many in vivo and in vitro studies suggested the involvement of apoptosis in neurodegenerative processes. There is considerable evidence that various complex events may contribute to neural cell death. The present study focuses on the underlined neurodegenerative mechanism and the preventive effect of necrostatin-1 (Nec-1) on neural cell death induced by aluminum (Al). METHODS: Al-exposed primary cultures of newborn mice cortical cells were separately treated with 3-methylamphetamine (3-MA), benzyloxycarbonylvalyl-alanyl-aspartic acid (O-methyl)-fluoro-methylketone (zVAD-fmk), and Nec-1, the cell viability analysis was used to evaluate cell damage from apoptosis, necroptosis and autophagy. Morphology of neural cells treated with 2 mM Al, and 2 mM Al plus 60 µM Nec-1 were examined by fluorescent microscope, and the cell death rates were quantified by cytometry. For the in vivo experiments, male ICR mice were microinjected with normal saline, 2 mM Al, and 2 mM Al plus Nec-1 at the concentrations of 2 mM, 4 mM and 8 mM into the lateral cerebral ventricles. The Morris water maze task was performed in 20 days after intracerebroventricular injection, Nissl staining was used to demonstrate the loss of Nissl substance and the number of neural cells, and western blot was used to analyze the expressing of cell death and Alzheimer's disease related proteins. RESULTS: The cell viabilities inhibited by Al could be enhanced by 3-MA, zVAD-fmk and Nec-1, of which Nec-1 improved the cell viability most significantly. Furthermore, the cell viability of neural cells treated with Nec-1 increased concentration-dependently, and the expressions of cell death-related proteins were decreased also in a concentration-dependent manner. The in vivo experiments indicated that administration of Nec-1 on Al-treated mice significantly improved learning and memory retention in the Morris water maze task, decreased the neural cells death and inhibited the expression of Alzheimer's disease related proteins in the mice brain. CONCLUSIONS: The present study provides the first direct evidence of a connection between necroptosis and neurodegeneration, which indicates that necroptosis is involved in neurodegenerative cell death. Furthermore, Nec-1 may be useful for the prevention and treatment of neurodegenerative disorders.