Intratracheal instillation of lipopolysaccharide in mice induces apoptosis in bronchial epithelial cells: no role for tumor necrosis factor-alpha and infiltrating neutrophils

J.H.J. Vernooy, M.A. Dentener, R.J. van Suylen, W.A. Buurman, E.F.M. Wouters

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Abstract

Intratracheal instillation of lipopolysaccharide in mice induces apoptosis in bronchial epithelial cells: no role for tumor necrosis factor-alpha and infiltrating neutrophils.

Vernooy JH, Dentener MA, van Suylen RJ, Buurman WA, Wouters EF.

Department of Pulmonology, Nutrition and Toxicology Research Institute Maastricht, Maastricht University, Maastricht, The Netherlands.

This study investigated apoptosis in lungs after local exposure to lipopolysaccharide (LPS). Mice were instilled intratracheally with 5 microg LPS, which corresponds to the amount acquired by smoking approximately 25 cigarettes, and killed at different time points after exposure. Our data demonstrate that local LPS exposure resulted in apoptosis in lungs from 2 h and peaked at 24 h, as detected by ligation-mediated polymerase chain reaction. Morphologic examination and terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end label staining demonstrated apoptosis in bronchial epithelial cells early after intratracheal (IT) LPS challenge, whereas infiltrating neutrophils displayed positive staining at 24 and 72 h after exposure. Apoptosis in lungs clearly preceded pulmonary neutrophil infiltration, confirming that neutrophils did not contribute to pulmonary apoptosis at early time points. Further, using three experimental approaches--namely, anti-tumor necrosis factor (TNF)-alpha treatment, IT TNF-alpha instillation, and TNF/lymphotoxin-alpha knockout mice--we demonstrate that TNF-alpha, which was elevated in lungs at both messenger RNA and protein levels after IT LPS challenge, was no primary mediator in LPS-induced apoptosis at early time points. Thus, local LPS exposure in mice resulted in early apoptosis of bronchial epithelial cells independent of infiltrating neutrophils and TNF-alpha, which suggests that apoptosis of bronchial epithelium may be involved in airway injury during exposure to LPS
Original languageEnglish
Pages (from-to)569-576
Number of pages9
JournalAmerican Journal of Respiratory Cell and Molecular Biology
Volume24
Issue number5
DOIs
Publication statusPublished - 1 Jan 2001

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