Human Epidemiologic and Toxicity Assessment of Microcystin Mixture Effects on Hepatic Disease and Cancer

ABSTRACT – RESEARCH PROJECT 2 The primary objective for Project 2 of the North Carolina Center for Coastal Algae, People, and Environment (NC C-CAPE), is to define the toxicity of human and environmentally relevant microcystin (MC) mixtures found in recent harmful algal blooms (HABs) and seafood biomonitoring efforts in Project 1, and predicted in future

HABs through modeling data of Project 3. Aim 1 will address the biomedical research component of NC C- CAPE by leveraging the specimens and questionnaire data repository of the ongoing Southern Liver Health Study. This secondary analysis will determine the extent to which MCs, including MC-LR and -RR, increase the

risk of non-alcoholic fatty liver diseases and liver cancer in Eastern North Carolina populations. The geographic focus for this nested case-control study is the Pamlico Albemarle Sound System (PASS) of Eastern North Carolina, one of the most impacted waterways in the region, but the results and lessons learned will be

generalizable across coastal communities and the Great Lakes where HABs and MC toxin exposures occur. Recent regulatory assessment of evidence for MC carcinogenicity concluded that there was essentially no human data useful for risk assessment of MC carcinogenicity; therefore, Aim 1 will fill a crucial data gap.

Furthermore, Aims 2 and 3 will comprehensively evaluate adverse impacts of MC-LR/-RR mixtures found in PASS HABs (Project 1) and define how the ubiquitous PFAS pollutant PFOS impacts MC toxicity. The dose responsiveness of liver toxicity, biomarkers of NAFLD, and hepatocellular carcinoma will be assessed in male

and female CD1(ICR) mice chronically exposed to MC-LR alone or in combination with MC-RR, and/or perfluorooctane sulfonic acid (PFOS) in drinking water. Mechanistic studies using a 3D model of differentiated HepG2 spheroids and chemical combination analysis, will evaluate the impacts of MC-RR on MC-LR active

transporter uptake mechanism and will define mechanisms of MC-mixture toxicity. Together the proposed research of Project 2 is especially relevant to public health and the goals outlined by NIEHS for the Centers for Oceans and Human Health because it will elucidate how exposures to microcystin congeners alone, or in

combination with other environmental contaminates including toxic metals and perfluoroalkyl substances (PFAS), interact to induce liver toxicity (short-term outcome), non-alcoholic fatty liver disease, and progression to liver cancer (long-term outcomes). The experiments and analysis proposed in Project 2 of the NC C-CAPE

are highly significant and will address critical data gaps in the understanding of MC toxicity and impacts on human health, and will yield critical data needed to implement regulatory policy change, interventions, and public and clinical health measures to limit adverse impacts of MC toxins on liver disease and its progression to

hepatocellular carcinoma.