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Departments of 1Pharmacology, 2Pharmaceutical Sciences, and 3Medicine, University of Colorado Health Sciences Center, Denver; 4Division of Pulmonary Sciences and Critical Care Medicine, Department of Medicine, Denver Veterans Affairs Medical Center, Denver, Colorado; and 5Division of Nephrology, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School and Harvard-Massachusetts Institute of Technology Division of Health Sciences and Technology, Charlestown, Massachusetts
Submitted 22 April 2005 ; accepted in final form 20 January 2006
Administration of butylated hydroxytoluene (BHT) to mice causes lung damage characterized by the death of alveolar type I pneumocytes and the proliferation and subsequent differentiation of type II cells to replace them. Herein, we demonstrate this injury elicits an inflammatory response marked by chemokine secretion, alveolar macrophage recruitment, and elevated expression of enzymes in the eicosanoid pathway. Cytosolic phospholipase A2 (cPLA2) catalyzes release of arachidonic acid from membrane phospholipids to initiate the synthesis of prostaglandins and other inflammatory mediators. A role for cPLA2 in this response was examined by determining cPLA2 expression and enzymatic activity in distal respiratory epithelia and macrophages and by assessing the consequences of cPLA2 genetic ablation. BHT-induced lung inflammation, particularly monocyte infiltration, was depressed in cPLA2 null mice. Monocyte chemotactic protein-1 (MCP-1) content in bronchoalveolar lavage fluid increases after BHT treatment but before monocyte influx, suggesting a causative role. Bronchiolar Clara cells isolated from cPLA2 null mice secrete less MCP-1 than Clara cells from wild-type mice, consistent with the hypothesis that cPLA2 is required to secrete sufficient MCP-1 to induce an inflammatory monocytic response.
eicosanoids; Clara cells; macrophages
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