Dysregulated Hypothalamic-pituitary-adrenal Axis During Biliary Hyperplasia

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DESCRIPTION (provided by applicant): Cholestatic liver diseases such as primary biliary cirrhosis and primary sclerosing cholangitis are often associated with increased serum bile acid concentrations. Previous reports have also indicated a decrease in circulating glucocorticoid levels in these diseases. Glucocorticoid production and secretion are under the direct control of the hypothalamus-pituitary-adrenal (HPA) axis. We have obtained novel preliminary data indicating that there is a dampening of the HPA axis activity in our rodent model of cholestatis liver disease and that this may contribute to the cholangiocyte outgrowth seen in the early stages of cholestasis. The overall objective of this proposal is to determine the consequences of cholestatic liver disease on the brain and more specifically on the HPA axis and in turn determine the subsequent effects of a dampened HPA axis activity have on cholangiocyte proliferation. Based upon strong preliminary data, we propose the novel central hypothesis that the bile acids that accumulate in the serum during cholestasis are responsible for the dampening of the HPA axis and that the subsequent decrease in circulating glucocorticoid levels have implications on cholangiocyte proliferation. Our proposed work will focus on three specific aims that have been designed to test the following working hypotheses: (1) Decreased HPA axis activity is a consequence of cholestasis and contributes to the resulting increased cholangiocyte proliferation, (2) Serum bile acids accumulate in the brain during cholestasis and subsequently suppresses the HPA axis via the specific uptake of bile acids by bile acid transporters into neurons of particular brain regions and subsequent activation of glucocorticoid receptors, and (3) Reactivation of the HPA axis by central administration of corticotropin releasing hormone effectively inhibits the cholangiocyte outgrowth seen during cholestasis via the glucocorticoid receptor- mediated inhibition of AP-1 and NFkB transcriptional activity. Dissecting the pathophysiological interactions between the brain and the liver during cholestatic liver diseases may lead to an enhanced understanding of the pathological processes and consequences of this particular type of live disease. This knowledge may play a paramount role in the development of therapeutic strategies for the treatment of cholangiopathies.