ACID-INDUCED ACUTE LUNG INJURY IN MICE IS ASSOCIATED WITH P44/42 AND C-JUN N-TERMINAL KINASE ACTIVATION AND REQUIRES THE FUNCTION OF TUMOR NECROSIS FACTOR α RECEPTOR I

Aspiration of hydrochloric acid (HCl)-containing gastric juice leads to acute lung injury (ALI) and hypoxemic respiratory failure due to an exuberant inflammatory response associated with pulmonary edema from increased vascular and epithelial permeability. The aim of this study was to determine the role and signaling mechanisms of tumor necrosis factor alpha (TNF-alpha) in experimental ALI from HCl aspiration using a combination of genetic animal models and pharmacologic inhibition strategies. To this end, HCl was instilled intratracheally to mice, followed by respiratory system elastance measurement, bronchoalveolar lavage, and lung tissue harvesting 24 h after injection. Hydrochloric acid instillation induced an inflammatory response in the lungs of wild-type mice, evidenced as increased bronchoalveolar lavage total cells, neutrophils, and total protein; histologic lung injury score; and respiratory system elastance, whereas TNF-alpha receptor I mRNA levels were maintained. These alterations could be prevented by pretreatment with etanercept or genetic deletion of the 55-kd TNF-alpha receptor I, but not by deletion of the TNF-alpha gene. Hydrochloric acid induced a 6-fold increase in apoptotic, caspase 3-positive cells in lung sections from wild-type mice, which was abrogated in mice lacking TNF-alpha receptor I. In immunoblotting and immunohistochemistry studies, HCl stimulated signaling via p44/42 and c-Jun N-terminal kinase, which was blocked in TNF-alpha receptor I knockout mice. In conclusion, ALI induced by HCl requires TNF-alpha receptor I function and associates with activation of downstream proinflammatory signaling pathways p44/42 and c-Jun N-terminal kinase.