Role of toll-like receptor 4 in acute neutrophilic lung inflammation induced by intratracheal bacterial products in mice

• Main Authors: Wakako Yamada, Sadatomo Tasaka, Hidefumi Koh, Mie Shimizu, Yuko Ogawa, et al
• Format: Article
• Language: English
• Published: Dove Medical Press 2008-09-01
• Series: Journal of Inflammation Research
• Online Access: http://www.dovepress.com/role-of-toll-like-receptor-4-in-acute-neutrophilic-lung-inflammation-i-a2156

Wakako Yamada1, Sadatomo Tasaka1, Hidefumi Koh1, Mie Shimizu1, Yuko Ogawa1, Naoki Hasegawa1, Taku Miyasho2, Kazuhiro Yamaguchi1, Akitoshi Ishizaka11Division of Pulmonary Medicine, Keio University School of Medicine, Shinjuku-ku, Tokyo, Japan; 2Laboratory of Veterinary Biochemistry, School of Veterinary Medicine, Rakuno Gakuen University, Ebetsu, JapanBackground: Toll-like receptors (TLRs) represent a conserved family of innate immune recognition receptors. Among TLRs, TLR4 is important for the recognition of Gram-negative bacteria, whereas TLR2 recognizes cell wall constituents of Gram-positive microorganisms, such as peptidoglycan (PGN).Methods: To evaluate the role of TLR4 in the pathogenesis of acute lung injury induced by Escherichia coli endotoxin (lipopolysaccharide; LPS) or PGN, we compared inflammatory cell accumulation in bronchoalveolar lavage (BAL) fluid and lung pathology between C3H/HeJ (TLR4 mutant) and wild-type C3H/HeN mice. The levels of proinflammatory cytokines and chemokines in plasma and BAL fluid and nuclear factor-κB (NF-κB) translocation in the lung were also evaluated.Results: In C3H/HeJ mice, LPS-induced neutrophil emigration was significantly decreased compared with C3H/HeN mice, whereas PGN-induced neutrophil emigration did not differ. Differential cell count in BAL fluid revealed comparable neutrophil recruitment in the alveolar space. In TLR4 mutant mice, LPS-induced upregulation of tumor necrosis factor-alpha (TNF-α), KC, and CXCL10 in plasma and BAL fluid was attenuate, which was not different after PGN. NF-κB translocation in the lung was significantly decreased in C3H/HeJ compared with C3H/HeN mice, whereas PGN-induced NF-κB translocation was not different.Conclusion: These results suggest that TLR4 mediates inflammatory cascade induced by Gram-negative bacteria that is locally administered.Keywords: rodent, TLR4, endotoxin, neutrophils, NF-κB