Journal of Leukocyte Biology 45:283-292 (1989) © 1989 Alan R. Liss, Inc. Virus-Induced Enhancement of Arachidonate Metabolism by Bovine Alveolar Macrophages In Vitro W.W. Laegreid, S.M. Taylor, R.W. Leid, R.M. Silfiow, J.R. Evermann, R.G. Breeze, and H.D. Liggitt Departments of Veterinary Microbiology and Pathology (W.W.L., S.M.T., R.W.L., R.M.S.) and Veterinary Clinical Medicine and Surgery (J.R.E.), Washington State University, Pullman; Plum Island Animal Disease Center, NA.sA.JARS/USDA, Greenport, New York (R.G.B.), and Genentech, Inc., S. San Francisco, California (H.D.L.) Virus infection of alveolar macrophages both in vivo and in vitro has been associated with a variety of changes In cellular function. Some of these changes are identical to the effects that arachidonate-derived mediators, prostaglandins, leukotrienes, and hy- droxyeicosatetraenolc acids, have on macrophage function. Virus infection of macro- phages has been previously shown to Increase the output of some arachidonate metabolites, most notably PGE2. However, the effect of virus infection on arachidonate metabolism In general has not been well described. In our experiments, primary cultures of alveolar macrophages obtained from normal cattle by bronchoalveolar lavage, were Infected in vitro with parainfluenza type 3 virus. At days 0 to 4 post-infection (p.i.) these cells were labelled with 3H-arachidonic acId and stimulated with either serum-coated zymosan, the calcium lonophore A23187, or phorboi myristate acetate. The complete spectrum of arachidonete-derived metaboiltes was determined by reverse-phase high performance liquid chromatography with UV and on-line radiometric monitoring of column eluant. The total output of metabolites of arachidonic acid by virus-infected alveolar macrophages was Increased over that of noninfected controls (with all stimuli tested) by day 4 p.1. (P 0.05). The production of metaboiltes by the cyclooxygenase, 12- and 5-lipoxygenase enzyme systems was significantly increased, as was the release of 3H-arachidonate. The lack of stimulus specificity and the Increases in arachidonate release suggest that greater substrate availability, due either to increased phospholipase activity or direct virus-membrane interaction, may be responsible for the virus-induced enhancement of metabollte output. Key words: arachidonic acid, prostagiandin, leukotriene INTRODUCTION Virus infection of alveolar macrophages (AM) both in vivo and in vitro results in profound metabolic and functional changes in these cells [7,15,19]. Phagocy- tosis, respiratory burst, antigen-presenting ability, and bactericidal activity are some of the AM functions affected by virus infection [1,3,13,16,17,20,32]. Since AM are the cells primarily responsible for maintaining the sterility of the lower respiratory tract, impairment of their normal functions by a primary viral infection may result in the development of secondary bacterial pneu- monia [10,15]. These secondary pneumonias may be more severe than the primary viral infection, resulting in severe functional impairment and mortality [7,15]. In addition, the immunosuppressive effects of soluble fac- tors from virus-infected AM may predispose to second- ary viral infections such as occur with parainfluenza type 3 (P13) virus and bovine respiratory syncytial virus [5,41]. Thus, determination of the cause(s) of virus- induced AM dysfunction and methods to reverse this dysfunction are of considerable importance in preventing these pneumonic sequelae to primary pulmonary virus infection. Bacterial killing by AM is a complex process involv- ing phagocytosis, generation of reactive oxygen species such as superoxide anion and hydrogen peroxide, and fusion of phagosomes with lysosomes that contain a variety of substances toxic to bacteria [23]. All of these cell functions have been shown to be impaired to some degree by virus infection [7,15,17,20]. Interestingly, these same cellular functions have been shown to be inhibited by some of the metabolites of arachidonic acid, most notably PGE2 [4,21,22,24,28]. Further evidence Received June 24, 1988; accepted October 26. 1988. Reprint requests: William W. Laegreid. Department of Veterinary Microbiology and Pathology. Washington State University, Pullman. WA 99164-7040.