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Microcystin Variants Induce Cytotoxicity in Primary Human Hepatocytes and Colon Epithelial Cells
Citation:
Richardson, V., C. Korson, AND E. Hilborn. Microcystin Variants Induce Cytotoxicity in Primary Human Hepatocytes and Colon Epithelial Cells. Society of Toxicology, Baltimore, Maryland, March 12 - 16, 2017.
Impact/Purpose:
Multiple data gaps exist in the understanding of the specific effects of cyanotoxins on human cells. Microcystins are a diverse group of hepatotoxic cyclopeptides, but toxicological data focuses primarily on the effects of one congener, microcystin-LR, and on one tissue, liver. Epidemiologic and in vitro studies suggest that microcystins may be associated with multiple adverse health effects including : respiratory damage, renal impairment, reproductive dysfunction and carcinogenesis in liver and colon. This study attempts to narrow the data gaps through the investigation of the cytotoxic effects of microcystin-LR and the more lipophilic congener, microcystin-LF on primary human colonocytes and hepatocytes.
Description:
Microcystins (MCs) are hepatotoxic algal toxins produced by cyanobacterial species that pose a risk to humans and animals due to their presence in drinking and recreational waters. Over 100 microcystin congeners have been identified with variable amino acid compositions that determine the lipophilicity of each congener. Microcystin-LR (MCLR) is a highly active congener and induced hepatic apoptosis and reactive oxygen species (ROS) when administered to laboratory animals. Overall, there is limited non-hepatic toxicity data for MCs and any toxicity data on congeners other than MCLR are even scarcer. In this study, primary human hepatocytes (HH) and primary human colon epithelial cells (HCC) were used to examine the effects of MCLR and the more lipophilic congener, microcystin-LF (MCLF), on cell viability and ROS formation. HH and HCC were plated in 96-well microtiter plates at a density of 20,000 cells/well and 10,000 cells/well, respectively. 24 hours after plating, the cells were exposed to MCLR or MCLF (0 or 10µM) for 24 hours. After 24 hours, the cells were assayed for viability (CellTiter Glo 2.0; Promega Corp.) and ROS formation (ROS Glo H2O2; Promega Corp.). HH exposed to MCLR or MCLF resulted in a decrease in cell viability by 95% and 98%, respectively. Because most of the HH were not viable after exposure to MCLR and MCLF, ROS formation could not be accurately measured. HCC viability was unchanged with MCLR exposure, but MCLF decreased viability by 79%. ROS formation was unchanged in HCC treated with MCLR; however, MCLF increased ROS levels almost 3-fold. These results indicate that the more lipophilic MCLF exhibited greater cytotoxic activity than MCLR in HCC; however, cytotoxic activity between the two congeners was nearly equal in HH. This study also suggests that the human colon can be a target tissue for MCs. [This abstract of a proposed presentation does not necessarily reflect the policies of the US EPA.]