Inhibiting toll-like receptor 4 signaling ameliorates pulmonary fibrosis during acute lung injury induced by lipopolysaccharide: an experimental study.
BACKGROUND
Toll-like receptor 4 (TLR4) is essential in lipopolysaccharide (LPS)-induced fibroblast activation and collagen secretion in vitro. However, its effects on the process of lung fibroblast activation and fibrosis initiation during LPS induced acute lung injury (ALI) remain unknown. The goal of the present study was to determine the effect of inhibiting TLR4 on LPS-induced ALI and fibrosis in vivo.


METHODS
The ALI model was established by intraperitoneal injection of LPS in mice. TLR4-small hairpin RNA (shRNA) lentivirus was injected intravenously into the mice to inhibit TLR4 expression. mRNA and protein levels were detected by real-time PCR and Western-blot analysis, respectively. The contents of the C-terminal propeptide of type I procollagen (PICP) in bronchoalveolar lavage fluid (BALF) were detected by ELISA, and the degree of fibrosis was detected by van Gieson collagen staining, the hydroxyproline assay, and alpha smooth muscle actin (alpha-SMA) immunohistochemical staining.


RESULTS
Overexpression of TLR4, type I procollagen, alpha-SMA, and p-AKT in murine pulmonary tissue after intraperitoneal injection of LPS at 72 hours and 28 days were detected. Moreover, the degree of fibrosis was shown to increase by ELISA analysis of PICP in BALF, van Gieson collagen staining, the hydroxyproline assay, and alpha-SMA immunohistochemical staining. All of these changes were alleviated by intravenous infection with TLR4-shRNA lentivirus.


CONCLUSIONS
Inhibiting TLR4 signaling could ameliorate fibrosis at the early stage of ALI induced by LPS.
He
ZhengYu
Z
Department of Anesthesiology, Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 200011, China. hzyyy@163.com
Zhu
YeSen
Y
Jiang
Hong
H
D000818:Animals; D008070:Lipopolysaccharides; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D011658:Pulmonary Fibrosis / Q000139:chemically induced* / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects*; D051197:Toll-Like Receptor 4 / Q000037:antagonists & inhibitors* / Q000378:metabolism*
D008070:Lipopolysaccharides; C493487:Tlr4 protein, mouse; D051197:Toll-Like Receptor 4