2008, Feurstein, Daniel, Fischer, Andreas, Dietrich, Daniel R.

Contamination of natural waters by cyanobacterial blooms is a worldwide problem, resulting in serious water pollution and health hazards for humans and livestock. The cyanobacterial micro- cystins (MCs) represent a group of >80 cyclic heptapeptide toxin congeners, known to induce hepato-, nephro-, and potentially neu- rotoxic effects via protein phosphatase (PP)-inhibition. Present evidence suggests that organic anion transporting polypeptides (rodent Oatps/human OATPs) are required for active uptake of MCs into hepatocytes and kidney epithelial cells. Based on the presence of Oatps/OATPs at the blood–brain-barrier (BBB) and blood–cerebrospinal fluid-barrier (BCFB) it was hypothesized that MCs can be transported across the BBB/BCFB and into neurons in an Oatp/OATP-dependent manner and will induce neurotoxic effects. To test this hypothesis, primary murine neurons (Cere- bellar Granule Cells, mCGC) were analyzed for the presence of mCGC Oatps (mRNA level). Subsequently, the uptake, localization and neurotoxic effects of MC-LR, -LW, and -LF were investigated using MC-immunoblotting, confocal microscopy of immunostained neurons, PP-inhibition assay, TNF- ELISA and caspase 3/7 activ- ity assay. RT-PCR demonstrated the presence of six murine Oatps (Oatp1c1, 1a5, 3a1, 1a1, 1b2 and 6d1) in mCGC. MC-LR-specific immunodetection demonstrated a concentration-dependent accu- mulation of this congener and covalent binding to PP-1 and -2A. mCGC PP activity was reduced by 20% following 48 h exposure to ≥300 nM MC-LR, -LW and -LF concurrent with a congener and concentration-dependent up regulation of TNF- expression and caspase 3/7 activity. In conclusion, the data suggest an MC congener-dependent uptake and neurotoxicity in primary mouse CGC.