The influence of dexamethasone on the proliferation and apoptosis of pulmonary inflammatory cells in bleomycin-induced pulmonary fibrosis in rats.
OBJECTIVE
The aim of this study was to investigate the inhibitory effect of dexamethasone on the state of proliferation/apoptosis of the pulmonary inflammatory cells in a rat pulmonary fibrosis model induced by bleomycin.


METHODS
Seventy-five pathogen-free Sprague-Dawley (SD) rats were randomly divided into three groups: control, bleomycin (BLM) and dexamethasone (DXM) groups with 25 rats in each group. Each group was then divided into five subgroups based on time of study (1-, 3-, 7-, 14- and 28-days). BAL fluid was obtained, the cells were counted and a differential was performed. A lower DNA content in apoptotic cells was detected and quantitated by flow cytometry. Haematoxylin and eosin staining was performed to observe the extent of alveolitis and fibrosis of lung tissue; the morphological changes in apoptotic cells were discerned by transmission electron-microscopy and a semi-quantitative assessment of apoptotic cells in lung tissue was performed using in situ TUNEL (terminal deoxynucleotidyl transferase-mediated dUTP nick endlabelling).


RESULTS
The total number of inflammatory cells and the percentage of neutrophils in BAL fluid in almost every subgroup of the DXM group were significantly lower than those in corresponding subgroups of the BLM group (P < 0.01). The percentages of apoptotic cells in BAL fluid in the 14-day and 28-day subgroups of the DXM group were higher than those in corresponding subgroups of the BLM group (P < 0.05). The peak of alveolitis in the DXM group shifted backward and the extent of fibrosis was less than that in the BLM group. The apoptosis index (AI) of inflammatory cells in each of the DXM subgroups was higher than that in corresponding BLM subgroups except for day 14.


CONCLUSIONS
Dexamethasone can induce apoptosis of pulmonary inflammatory cells and reduce the extent of alveolitis and fibrosis in bleomycin-induced pulmonary fibrosis of rats.
Li
Hui-ping
HP
Department of Respiratory Diseases, Shanghai Pulmonary Hospital, Shanghai, China. wlwq@sh163.net
Li
Xia
X
He
Guo-jun
GJ
Yi
Xiang-hua
XH
Kaplan
Allen P
AP
D000818:Animals; D000893:Anti-Inflammatory Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D001761:Bleomycin; D001992:Bronchoalveolar Lavage Fluid / Q000166:cytology; D002455:Cell Division / Q000187:drug effects; D003907:Dexamethasone / Q000494:pharmacology*; D020287:In Situ Nick-End Labeling; D007958:Leukocyte Count; D008297:Male; D009504:Neutrophils; D011650:Pulmonary Alveoli / Q000187:drug effects / Q000473:pathology; D011658:Pulmonary Fibrosis / Q000139:chemically induced / Q000276:immunology* / Q000473:pathology / Q000503:physiopathology; D051381:Rats; D017207:Rats, Sprague-Dawley
D000893:Anti-Inflammatory Agents; D001761:Bleomycin; D003907:Dexamethasone