Curcumin Acts as Post-protective Effects on Rat Hippocampal Synaptosomes in a Neuronal Model of Aluminum-Induced Toxicity.

The neurotoxic effects of aluminum are generally associated with reduced antioxidant capacity, increased oxidative stress and apoptosis, which lead to the induction of neurodegenerative processes. Curcumin has a lipophilic polyphenol character and effects of antioxidant and anti-apoptotic. The present study was undertaken to examine possible aluminum exposure in rats brain synaptosomes and to investigate whether protective and therapeutic effects of curcumin on biochemical and morphological changes in both pre- and post-treated groups. Aluminum chloride (AlCl) at 50 µM concentration and curcumin at 5 and 10 µg/mL doses were applied to hippocampal synaptosomes of rats according to experimental design. Biochemical effects were evaluated by MTT cytotoxicity, malondialdehyde (MDA) levels, nitric oxide (NO) levels, glutathione (GSH) levels, caspase 3 activities, cytochrome c levels, DNA fragmentation values and protein levels. Morphological examinations were done by TEM analysis. AlCI exposure in the synaptosomes enhanced oxidative stress, triggered apoptosis and caused ultrastructural alterations which were well reflected in the TEM images. Curcumin pre-treatment slightly ameliorated the MDA levels, NO levels, cytochrome c levels and caspase 3 activities in AlCI-exposed synaptosomes, but these results were not statistically significant. Furthermore, curcumin post-treatment significantly improved oxidative damage and morphological alterations, and suppressed cytochrome c and caspase 3 activities. Taken together, our data showed that curcumin had more therapeutic effects than protective effects in AlCI-induced neurotoxicity. Nevertheless, the therapeutic (post-protective) effects of curcumin should be further investigated in in vivo neurodegenerative models involving behavioral tests.