This Article Full Text Full Text (PDF) Online Supplement All Versions of this Article: 200907-1061OCv1 181/4/374    most recent Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Moon, C. Articles by Kang, J. L. PubMed PubMed Citation Articles by Moon, C. Articles by Kang, J. L.

N-Acetylcysteine Inhibits RhoA and Promotes Apoptotic Cell Clearance during Intense Lung Inflammation

¹ Department of Physiology, and ² Department of Microbiology, Division of Cell Biology, Ewha Medical Research Center, School of Medicine, Ewha Womans University, Seoul, South Korea

Correspondence and requests for reprints should be addressed to Jihee Lee Kang, M.D., Ph.D., Department of Physiology, School of Medicine, Ewha Womans University 911-1 Mok-6-dong, Yangcheon-gu, Seoul 158-056, Korea. E-mail: jihee{at}ewha.ac.kr

Rationale: The resolution of pulmonary inflammation seen in various inflammatory lung conditions depends on the clearance of apoptotic cells to prevent permanent tissue damage or progressive disease. Uptake of apoptotic cells by alveolar macrophages is suppressed by oxidants through the activation of Rho signaling.

Objectives: We hypothesized that antioxidant exposure would increase the ability of alveolar macrophages to clear pulmonary apoptotic cells through the inhibition of RhoA.

Methods: The effects of the antioxidant N-acetylcysteine (NAC) on the pulmonary immune response were seen in mice treated intratracheally with LPS, LPS + NAC, or saline. Apoptotic cell clearance, RhoA activity, and changes in the lung inflammatory responses were analyzed in vivo or ex vivo.

Measurements and Main Results: Neutrophil accumulation, apoptosis, necrosis, and oxidant production peaked at 3 days post LPS treatment. NAC enhanced the clearance of apoptotic cells and inhibited RhoA activity in alveolar macrophages at 3 days post LPS treatment. NAC suppressed LPS-induced proinflammatory mediators, enhanced the production of transforming growth factor-β1, reduced the accumulation of inflammatory cells, and reduced levels of protein and lactate dehydrogenase in bronchoalveolar lavage fluid. In the presence of ex vivo apoptotic cells, alveolar macrophages exposed to LPS or LPS + NAC had reduced tumor necrosis factor- levels and increased transforming growth factor-β1 levels. A Rho kinase inhibitor mimicked the effects of NAC on the clearance of apoptotic cells and the inflammatory responses.

Conclusions: These results indicate that NAC can expedite the resolution of LPS-induced pulmonary inflammation through the inhibition of RhoA activity and the enhancement of apoptotic cell clearance.

Key Words: reactive oxygen species • apoptotic cell clearance • alveolar macrophages • lung inflammation • RhoA activity

AT A GLANCE COMMENTARY Scientific Knowledge on the Subject Uptake of apoptotic cells by alveolar macrophages is suppressed by oxidants through the activation of Rho signaling. However, this finding has not been examined in an in vivo model of lung inflammation associated with oxidant stress. What This Study Adds to the Field There is a relative suppression of apoptotic cell clearance under oxidant stress in acute lung injury. N-acetylcysteine promotes apoptotic cell clearance through down-regulation of the RhoA/Rho kinase pathway, resulting in resolution of lung inflammation.