Mechanisms of Lung Inflammation Following Discrete Hepatic Injury

Vanderbilt University, Nashville TN

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Abstract

There is increasing evidence that injury to the liver can precipitate or exaggerate lung injury. For example, when hepatic dysfunction accompanies acute lung injury in patients with the Systemic Inflammatory Response Syndrom (SIRS), mortality and morbidity are high. Cytokines which are produced in both the liver and the lungs, including tumor necrosis factor alpha (TNF-alpha) and interleukin (IL- 1), are implicated in the pathogenesis of SIRS and animal experiments have demonstrated them capable of precipitating acute lung injury. Increased expression of the genes encoding these cytokines involves activation of the transcription factor nuclear factor kappa B (NF-kappaB) and such activation is well-documented in several inflammatory states. Hepatic cryoablation, a recently introduced non-resectional surgical technique for eliminating primary and metastatic liver tumors, is associated with acute lung injury when more than 30-35% of the liver is ablated but mechanisms of this response remain undefined. We have shown that the direct and selective liver injury produced by cryoablation in experimental animals causes an early activation of NF-kappaB in the liver, followed by TNF-alpha release from the liver and then NF-kappaB activation in the lungs with histologic findings similar to those seen in other conditions of neutrophilic lung injury; none of these events follows hepatic resection. The specific aims of this project are: 1) To determine whether altering NF-kappaB activation in the liver affects the response to cryoablation induced lung injury. NF-kappaB activation will be specifically modulated by expressing transgenes in the liver which induce or inhibit NF-kappaB activity. We will also utilize the cell permeable cSN50 peptide, which contains the nuclear localization signal sequence (NLS) derived from the p50-NF-kappaB1 subunit to inhibit NF-kappaB prior to and following direct liver injury. 2) To determine the role of the proximal cytokines, TNF-alpha and IL-1, in the response to hepatic cryoablation by comparing responses in mice deficient in TNF-alpha and IL-1, in the response to hepatic cryoablation by comparing responses in mice deficient in TNF-alpha, TNF-alpha receptor 1 and/or IL-1 receptor 1. Outcome variables will include neutrophilic lung inflammation, histologically defined lung injury, NF- kappaB activation, and serum and lung lavage cytokine and eicosanoid concentrations. 3) To determine the role of eicosanoids in the response to hepatic cryoablation by altering cyclooxygenase (COX) expression and/or activity in liver or lungs. In these studies we will define COX-2 expression in response to cryoablation in lung and liver and measure prostanoid products, determine the role of COX-2 in the cryoablation response by using COX-2 inhibitors and COX-2 knockout mice, and establish whether liver COX-2 expression is critical for modulating the cryoablation response by transplantation of wild type hepatocytes into COX-2 knockout mice and by delivering transgenes to express COX-2 in these animals. Results of these studies should enhance our understanding of the role of the liver in propagation in response to direct liver injury.