| Objective To investigate the protective action of bilirubin on airway in order to explore a new method of prevention and cure of chronic bronchitis. Methods 24 male Sprague-Dawley rats were divided into three groups at random, i.e. control group (8), chronic bronchitis model group (8), bilirubin treated group (8). Rat chronic bronchitis model was estabilished by intratracheal instillation of small dose of Lipopolysaccharide (LPS, lg/L) in chronic bronchitis group. Rats were treated by intratracheal instillation of the equal amount of normal saline in control group. Rats were treated by bilirubin (20mg/kg/d) through feeding 2 hours before the chronic bronchitis model had been estabilished in bilirubin treated group, once a day, 21 days in all. All of the rats in three groups were sacrificed to be tested on the twenty-second day. The levels of total bilirubin of serum, total white blood cell (WBC) counts, tumor necrosis factor (TNF)- aand MDA of broncho-alveolar lavage fluid (BALF) were determined. The expressions of intercellular adhesion molecule (ICAM)-l in bronchial epithelial cell and histology were examined. Results (1) The levels of total bilirubin of serum in rat chronic bronchitis group were not significantly decreased than those of control group (P>0.05), and those in rat bilirubin treated group were more significantly increased than those of chronic bronchitis group (P<0.05). (2) More significant increase in WBC, TNF- a and MDA in BALF was found in rat chronic bronchitis group than in control group (P<0.05, P<0.05 and P<0.05), and more significant decrease of those was found in rat bilirubin treated group as compared with those of chronic bronchitis group (P<0.05, P<0.05 and P<0.05). (3) The expression of ICAM-1 in bronchial epithelial cell was significantly increased in chronic bronchitis group than in control group (P<0.05), and those in bilirubin treated group was significantly decreased than in chronic bronchitis group (P<0.05). (4) Significant negative correlation was observed between the level of WBC of BALF and total bilirubin of serum ( r = - 0.815, P<0.05), and significant positivecorrelation was observed between the level of WBC and TNF- a of BALF, the level of WBC of BALF and the expression of ICAM-1 in bronchial epithelial cell (respectively, r = 0.114, P<0.05 and r = 0.743, P<0.05 ), in chronic bronchitis group. (5) From histological observation, the pathological change in chronic bronchitis group was accorded with those of chronic bronchitis, and the inflammatory reaction of airway in rat bilirubin treated group was decreased obviously. Conclusion (1) The decreased levels of total bilirubin of serum may be involved in the pathogenesis of chronic bronchitis. (2) Antioxidation can be provided by bilirubin and is very important in maintaining an oxidant/antioxidant balance. (3) The level of total bilirubin of serum can be increased by oral medication of exogenous bilirubin. (4) The proper level of bilirubin of serum is favourable to the protection for airway, and can prevent chronic bronchitis from developing. |
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