LUNG SOURCES AND CYTOKINE REQUIREMENTS FOR IN-VIVO EXPRESSION OF INDUCIBLE NITRIC-OXIDE SYNTHASE

Products of inducible nitric oxide synthase (iNOS) are known to be inv olved in lung injury following intrapulmonary deposition of immunoglob ulin G immune complexes (IgG-ICx). In the current studies rat alveolar macrophages stimulated in vitro with murine interferon gamma (IFN-gam ma), tumor necrosis factor alpha, interleukin 1 alpha, (IL-1 alpha), l ipopolysaccharide (LPS), or IgG-ICx immunostained for iNOS and produce d nitrite/nitrate- (NO2-/NO3-) in a dose- and time-dependent manner re quiring availability of L-arginine. Under the same conditions, IL-4 an d IL-10 reduced NO2-/NO3- generation. Type II alveolar epithelial cell s, which were obtained from normal rat lungs and stimulated in vitro w ith IgG-ICx, LPS, or IFN-gamma, also immunostained for iNOS and genera ted NO2-/NO3-. Special techniques of bronchoalveolar lavage (BAL) were used to retrieve alveolar macrophages and type II alveolar epithelial cells. Under these conditions, intrapulmonary deposition of LPS yield ed BAL fluids containing increased amounts of NO2-/NO3- and macrophage s that spontaneously released NO2-/NO3- and stained for iNOS. After in trapulmonary deposition of IgG both macrophages as well as type II cel ls (retrieved by BAL) spontaneously produced NO2-/NO3- and both cell t ypes immunostained for iNOS (approximately 20% of all type II cells an d 35% of all alveolar macrophages). Using dual fluorescence staining f or cell identification, frozen sections of lung tissue after IgG immun e complex deposition revealed iNOS in both alveolar macrophages and ty pe II cells. Finally, in the immune complex model of alveolitis, the a ppearance of iNOS in macrophages as well as macrophage production in v itro of NO2-/NO3- was dependent on the in vivo availability of tumor n ecrosis factor alpha, IL-1, and IFN-gamma. These studies suggest a dua l cell source for nitric oxide in inflamed lungs and the requirements for iNOS of several cytokines.