Changes of the actin and transforming growth factor-beta1 expression in the small airways of the rat with chronic obstructive lung disease

OBJECTIVE: To study the roles of actin and transforming growth factor (TGF)-beta(1) in the injury repair and the development of emphysema. METHODS: Wistar rats were randomly divided into two groups: the smoking and infection group (group SI) and the control group (group C). The rats of group SI received smoking irritation accompanying with repeated intranasal infection. Subgroups of the experimental animals were killed in the 2nd, 4th, 8th and 16th weeks respectively. The morphological changes of lungs were compared and PaO(2), PaCO(2) as well as the right ventricular systolic pressure (RVSP) were analysed. The lung sections were stained with immunohistochemistry for actin and TGF-beta(1). RESULTS: In comparison with animals of group C, thickening of the bronchiolar walls, narrowing of bronchiolar lumens, and area of emphysema were much severe in animals of group SI (P < 0.05). The muscularization of intra-alveolar arteries in group SI in the 16th week was apparent in comparing with that in group C (P < 0.05). PaO(2) values in group SI were significantly decreased, and RVSP values in group SI were significantly increased in the 8th and 16th week (P < 0.05). Actin expression was increased in animals of group SI in the 4th and 8th week (0.24 +/- 0.06 and 0.25 +/- 0.05) in comparing with that of group C (0.09 +/- 0.03) (P < 0.05). Animals of group SI showed a significant increase of TGF-beta(1) in lung tissue in different periods as mentioned in above (33.33 +/- 12.11, 45.71 +/- 15.12, 71.43 +/- 16.76 and 86.25 +/- 20.66 respectively). CONCLUSIONS: The increased expression of actin and TGF-beta(1) protein in small airways induced by smoking irritation and Klebsiella Pneumoniae may interfere with the repair response, and contributes to the development of emphysema.