Are microcystin-LR and cylindrospermopsin neurotoxic for human cells? An in vitro study on induced pluripotent stem cells-derived models.

Microcystin LR (MC LR) and cylindrospermopsin (CYN) are cyanobacterial toxins commonly detected during harmful algal blooms in freshwater systems. Their increasing occurrence raises concerns about water quality and potential risks to human health. Although the liver is their target organ, these cyanotoxins can also affect the nervous system. The potential neurotoxicity of MC-LR and CYN is still scarcely investigated, particularly for CYN. In this study, the effects of both cyanotoxins on neural progenitor cells were evaluated. MC-LR did not significantly affect cell viability at concentrations up to 60 µM, whereas CYN induced evident cytotoxicity starting at 1 µM after 24-48 h. Additionally, CYN was also tested in BrainSpheres (also called brain microphysiological system, bMPS) for the first time. Statistically significant cytotoxicity was observed from 1 µM onward after 1 week exposure. Downstream analysis revealed that subcytotoxic concentrations of CYN altered the gene expression of different nervous (TUBB3, NEFH, SYP, OLIG1, and GFAP), inflammatory (IL-1β, TNF-α and Nf-κβ) and oxidative stress (SOD1, HMOX and GSTT) markers analysed by RT-qPCR. Overall, the results obtained showed that BrainSpheres is an effective new approach methodology for evaluating the neurotoxic potential of cyanotoxins and points out the importance of including neurotoxicity in the risk assessment of cyanotoxins to human health.