Published ahead of print on May 28, 2003, doi:10.1164/rccm.200209-1027OC Am. J. Respir. Crit. Care Med., Volume 168, Number 3, August 2003, 287-296 A more recent version of this article appeared on August 1, 2003
Submitted on September 27, 2002 Effects of acute hypoxia and lipopolysaccharide on NOS2 expression in acute lung injuryJackeline Agorreta1,1 Histology and Pathology, Carcinogenesis Unit, Center for Applied Medical Research (CIMA), University of Navarra, Pamplona, Navarra, Spain, 2 Pulmonary Service, Clinica Universitaria, Pamplona, Navarra, Spain * To whom correspondence should be addressed. E-mail: jzulueta{at}unav.es.
The potential role of NOS2 in acute lung injury (ALI) has gained increasing attention. This study evaluates the effects of hypoxia, an important feature of ALI, on NOS2 expression in a rat model of ALI caused by exposure to hypoxia and LPS. Exposure to hypoxia alone had no effect on the expression of NOS2 in rat lungs. LPS treatment resulted in a significant increase of NOS2 in the lungs, which was further enhanced by concomitant exposure to hypoxia. Immunohistochemical analysis and in situ hybridization showed no changes in the expression of NOS2 in lung resident cells under any conditions. The increase in NOS2 levels is mainly due to the influx of NOS2-expressing inflammatory cells. By morphological analysis, these inflammatory cells were identified as neutrophils, lymphocytes and monocytes. In vitro experiments of lung epithelial and endothelial cell lines showed no detectable expression of NOS2 with any of the treatments. In a macrophage cell line, LPS-induced NOS2 expression was not affected by the concomitant exposure to hypoxia. In conclusion, LPS increases NOS2 expression in rat lungs due to the recruitment of NOS2-producing leukocytes. Simultaneous exposure to LPS and hypoxia results in a greater influx of inflammatory cells that further enhances NOS2 expression. Key words: acute respiratory distress syndrome, endotoxin, leukocytes, sepsis
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