! PROJECT SUMMARY/ABSTRACT Non-alcoholic fatty liver disease (NAFLD) affects 30-40% of the U.S. population and has an estimated U.S. economic burden of $103 billion per year. NAFLD is also prevalent in children and adolescents, affecting 34.2% of obese individuals and 7.6% of this population overall. Higher-chlorinated polychlorinated biphenyls (PCBs) are implicated in the etiology of NAFLD, however, little is known about the hepatic toxicity potential of lower-chlorinated PCBs, including 3,3’-dichlorobiphenyl (PCB-11), widely detected in environmental and human samples, including in pregnant women. Preliminary research shows that acute developmental exposures to PCB-11 alone do not result in overt toxicological outcomes in zebrafish (Danio rerio), however, it misregulates hepatic-associated genes, stunts liver development, and increases vacuolization in liver tissue. Further, in combination with Aryl hydrocarbon receptor (Ahr) agonists, PCB-11 can either inhibit Cytochrome p4501a (Cyp1a) enzyme activity induced by a model PAH, exacerbating toxicity, or prevent toxicity induced by PCB-126, highlighting the importance of using a mixtures approach. The objective of this proposed study is to investigate the hepatic toxicity of PCB-11 metabolites, which have longer half-lives in vivo for rodents, and in preliminary data of low-dose exposures show increased hepatic lipid deposition in 15-day fish. The central hypothesis of this proposed study is that PCB-11 induced hepatic toxicity is attributed to its metabolites and is associated with a NAFLD liver phenotype during juvenile development. Aim 1 will determine the toxicity contribution of phenolic and sulfate PCB-11 metabolites in 4-day old fish. Aim 2 will assess PCB-11 and PCB-11-Sulfate toxicity in 30-day juvenile stage fish after low-dose chronic single and mixture exposures. The proposed training plan to execute these aims includes learning and/or performing methods such as EROD assays to measure Cyp1a activity, fluorescence microscopy to assess liver development, histopathology, Oil- Red-O staining to assess lipid deposition, and Fluorescence-Activated Cell Sorting (FACS) for fatty acid composition analysis of hepatocytes. In addition, chronic exposures will be carried out using the OECD Fish, Early-Life Stage (FELS) toxicity test (OECD TG 210) to gain practical experience in regulatory toxicity approaches and to increase preparation for the career goal of working as a government scientist to assess the public health impacts of contaminant exposures. This project will yield in vivo mechanistic toxicity data on PCB-11 and its metabolites at several developmental stages to be of use for public health regulators. The sponsor, Dr. Alicia Timme-Laragy, has a record of NIH funding, is a recent mentor of an NIH F32 Postdoctoral Fellow (now a faculty member at San Diego State University), has numerous equipment for fluorescence microscopy, molecular biology and biochemistry work, and is capable of provid...