Hepatic biliary excretion is an essential process that exists to aid the in the elimination of foreign chemicals, and protects the body from accumulating chemicals and toxicants. Understanding the underlying processes by which specific transporters that aid in biliary excretion are regulated is integral for improving human health, predicting chemical exposure, and preventing disease associated with chemical exposure. Nutrition (i.e. dietary intake, fasting, and caloric restriction [CR]) is an important factor in the susceptibility/progression of a variety of diseases associated, especially those associated with aging and environmental exposure. Trans- resveratrol (RES) is an antioxidant in red wine with anti-aging effects that mimic CR, and is an agonist for the deacetylase Sirt1. Understanding how RES, fasting, and CR regulate the expression and function of liver transporters involved in hepatic excretion (i.e. Multidrug Resistance-Associated Proteins [MRPs]) is important for understanding mechanisms by which nutrition is beneficial against chemical exposure and disease. Preliminary data demonstrates that RES increases the mRNA and protein expression of Mrp1-4, 6 in human hepatocytes and mouse liver along with induction of genes regulated by the transcription factor Nuclear Factor- E2-Related Factor 2 (NRF2), suggesting that RES activates human and mouse NRF2. Additionally, liver Mrp1, 2, and 3 expression, along with Ho-1 expression, is increased during fasting in which liver cAMP is increased and Protein Kinase A (PKA) is activated. Furthermore, constitutive activation of NRF2 in livers of KEAP1-null mice results in increased Mrp1-5 expression. The hypothesis of this proposal is that RES, fasting, and CR induce expression of MRPs through Sirt1- and PKA- upstream regulation of NRF2-mediated transcription.
Specific aims will determine whether 1) RES treatment induces MRP expression in human hepatocytes and mouse liver through NRF2, 2) fasting and CR induce MRP expression via upstream activation of PKA and downstream activation of Nrf2, 3) RES, fasting, and CR induce MRP via Sirt1, and 4) RES, fasting, and CR affect bisphenol A and polybrominated diphenyl ethers (PBDE) disposition in mice. Together, these studies will define mechanisms by which nutritional status alters expression of human and mouse MRPS, as well as demonstrate whether nutritional status enhances biliary excretion of environmental chemicals. Moreover, they will also provide novel insights into mechanisms that regulate NRF2-induction of human MRP genes. Project Narrative Nutritional status is an important factor for the development of many age-related diseases. Some environmental chemicals are thought to exacerbate or contribute to the development/progression of age- related diseases. The purpose of this project is to determine whether nutrition affects mechanisms involved in the liver's ability to uptake and clear environmental chemicals from the body.
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