GENETIC REGULATION OF THE HEPATIC ACUTE PHASE RESPONSE

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DESCRIPTION: Tissue damage and infection initiate a local inflammatory reaction that is designed to mobilize the immediate defense mechanisms of the organism, constituting the acute phase (AP) response and innate immune responses. Induction of hepatic acute phase plasma protein production is one of the systemic effects elicited by all inflammatory processes. Haptoglobin (Hp), the pronciple hemoglobin-binding protein in the plasma is one of the major APPs in mammals. Hp moderates the functions of inflammatory cells, and contributes to a bacteriostatic milieu. The project's goal is to define, in the mouse model, the roles of AP induced Hp controlling inflammatory responses. The specific aims are: 1) To identify the mechanism of Hp gene induction in cell culture. Three types of experiments are proposed all of which follow standard procedures employing transient transfection into HepG2 cells. In the first, sequence elements and factors which bind to a 115 bp region of the Hp promoter will be further dissected. In the second, exon shuffling between Stat1 and Stat3 is proposed to define functional domains of the latter in this system. In the third, sequence element identification is proposed outside the proximal promoter region. 2) To establish Hp-deficient mice. Inbred and congenic Hp null mice will be established. The response of Hp +/- and Hp -/- animals to representative inflammatory challenges, including tissue damage, endotoxin and infections will be defined by the pattern of acute phase protein genes induced in the liver and changes in composition of acute phase proteins and leukocytes in the blood. 3) To verify the specific action of Hp in these null animals and cell culture systems. Differences in response pattern may suggest potential functions of Hp which will be verified in Hp null animals by Hp administration or adenovirally re-introduced hepatic Hp production. The cellular action of Hp on differentiated functions associated with inflammatory cells will be determined in tissue culture systems. 4) To determine the consequence of a deleted acute phase induction of Hp expression. Mice null of the IL-6 response element in the Hp promoter will be generated by homologous recombination and targeted mutatgenesis and subjected to acute phase stimulants to assess the contribution of these sequence to Hp gene regulation.