Polychlorinated biphenyls act through EGFR to worsen NAFLD

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Non-alcoholic fatty liver disease (NAFLD) is associated with obesity and diabetes. The development of the NAFLD has previously been assumed to be due to excess calorie intake and genetic predisposition, but our recent studies show that steatosis and steatohepatitis can be exacerbated upon exposure to polychlorinated biphenyls (PCBs). The Anniston, AL cohort, who have higher exposure to PCBs have significant increases in steatohepatitis biomarkers and a prevalence of diabetes relative to healthy populations. Currently there is no well-established mechanism for exacerbated metabolic diseases due to PCB exposure. The literature and our preliminary data characterize PCBs as epidermal growth factor receptor (EGFR) antagonists that diminish activity of downstream effector kinases and transcription factors implicated in NAFLD/Diabetes. The literature and our preliminary data urges us to evaluate PCB-mediated EGFR inhibition as a key feature in the progression of NAFLD/diabetes. As we hypothesize that genetic loss of EGFR function will make mice more susceptible to PCB-mediated NAFLD/diabetes and epidermal growth factor (EGF) supplementation will ablate PCB-driven NAFLD/diabetes. Current risk assessment for PCB- mediated NAFLD/diabetes is limited. We recently characterized PCBs as EGFR antagonists which urges us to evaluate the binding affinities of PCB congeners for the EGFR extracellular domain to develop a EGFR toxic equivalency quotient (TEQ). Our preliminary data suggests that PCBs may outcompete epidermal growth factor (EGF) for EGFR binding at environmental exposure concentrations. We hypothesize that PCB congeners found in human serum directly antagonize the EGFR promoting NAFLD/diabetes. Preliminary data demonstrates that many PCB congeners prevent EGF-mediated phosphorylation of EGFR but only the non-dioxin like (NDL) PCBs are found in human serum at high concentrations. Preliminary proteomic data indicate that while the EGFR pathway is highly affected so are other EGFR independent pathways. To elucidate other hepatic aberrations due to PCB exposure we propose conducting a kinetic phosphoproteomic study in vitro. This will characterize what other pathways are altered due to PCB exposure. The proposed research aims to elucidate signaling pathways altered due to PCB exposure and if those alterations contribute to the development of liver disease and diabetes observed in animals and human populations. I plan to address these questions through genetic loss of function EGFR animal models, therapeutic EGF animal studies, binding assays, and kinetic phosphoproteomic analysis. The proposed research will provide valuable information on altered cell signaling pathways due to PCB mediated NAFLD and elucidate potential therapeutic targets for treatment of organopollutant-induced liver disease.