Study of the toxic effects produced by cylindrospermopsin and microcystin-LR co-exposure on the rat brain

Cylindrospermopsin (CYN) and microcystins (MCs), primarily classified as cytotoxin and hepatotoxins, are among the most prevalent cyanotoxins produced by cyanobacteria. Studies assessing the toxic effects of co-exposure to CYN and MC-LR are very scarce, especially in mammals. Furthermore, to our knowledge, there are no studies that evaluate the potential effects of their mixture on the nervous system in rats. This study evaluated on the brain of rats the potential effect of an oral exposure to CYN + MC-LR mixture (7.5 + 75, 23.7 + 237 and 75 + 750 μg kg b.w.) and sacrificed at 48h. Results showed sex-dependent responses, with the intermediate dose showing the highest response. This dose caused important alteration in the lipid peroxidation (LPO) levels, superoxide dismutase (SOD) and catalase (CAT) and acetylcholinesterase (AChE) activities compared to controls in males. In females, all doses increased LPO levels, without changes in SOD or CAT and decreased AChE activity. Alterations in expression of genes related to oxidative stress, inflammation and apoptosis were detected. CYN and MC-LR metabolites were identified by UHPLC-MS/MS. These findings suggest that oral exposure to CYN + MC-LR mixtures may cause neurotoxic effects in rats and that oxidative stress and inflammation could be associated toxic mechanisms. Moreover, they highlight the importance of considering sex as a biological variable in cyanotoxins risk assessment.