Effects of angiotensin II receptor antagonist on expression of collagen III, collagen V, and transforming growth factor beta1 in the airway walls of sensitized rats.
BACKGROUND
Repeated attacks of bronchial asthma lead to different degrees of airway remodeling, the mechanism of which is not yet clear. Some evidences indicate that it is related to the excessive expression of some growth promotion factors. Angiotensin II is a polypeptide that may be involved in airway remodeling. To evaluate its role in airway remodeling in asthma, we observed the effects of an angiotensin II type 1 receptor antagonist (valsartan) on the expression of collagen III, collagen V, and transforming growth factor beta1 (TGF-beta1) mRNA and protein in the airway walls of sensitized rats.


METHODS
Forty Wistar rats were randomly divided into 5 groups: control group, sensitized group, and valsartan groups 1, 2, and 3. The rats in the sensitized group and in valsartan groups 1, 2, and 3 were sensitized and challenged with ovalbumin. Rats in control group were sensitized and challenged with 0.9% NaCl. Rats from valsartan groups 1, 2, and 3 were drenched with valsartan (10 microg, 20 microg, or 30 microg, respectively) at the time of the ovalbumin challenges. The expression of collagen III, collagen V, and TGF-beta1 protein were detected using immunohistochemical method in combination with image analysis methods. The expression of TGF-beta1 mRNA was detected by in situ hybridization.


RESULTS
The expression in the airways of collagen III and collagen V was significantly higher in rats from the sensitized group (7.73 +/- 0.81, 1.34 +/- 0.28) and from valsartan groups 1, 2, and 3 (5.73 +/- 0.64, 1.13 +/- 0.15; 4.96 +/- 0.51, 0.98 +/- 0.08; 4.43 +/- 0.35, 0.93 +/- 0.06, respectively) than those in the control group (2.65 +/- 0.38, 0.67 +/- 0.08, P < 0.05). In addition, collagen levels were significantly lower in valsartan groups 1, 2, and 3 than those from the sensitized group (P < 0.05). The expression of TGF-beta1 mRNA and protein in the airways was significantly higher in rats from the sensitized group (20.49% +/- 3.46%, 29.73% +/- 3.25%) and from valsartan groups 1, 2, and 3 (16.47% +/- 1.94%, 19.41% +/- 1.87%; 14.38% +/- 1.58%, 18.29% +/- 1.43%; 12.96% +/- 1.73%, 18.63% +/- 1.11%, respectively) than that from the control group (7.84% +/- 1.61%, 5.63% +/- 1.07%, P < 0.05). TGF-beta1 mRNA and protein levels were significantly lower in valsartan groups 1, 2, and 3 than that in the sensitized group (P < 0.05).


CONCLUSIONS
Angiotensin II receptor antagonist valsartan can suppress synthesis of collagen III and collagen V by downregulating TGF-beta1 mRNA and protein expression. Valsartan can decrease airway remodeling and could play a role in asthma therapy.
Du
Yong-cheng
YC
Department of Respiratory Medicine, First Hospital, Shanxi Medical University, Taiyuan 030001, China.
Xu
Jian-ying
JY
Zhang
Shao-jun
SJ
D057911:Angiotensin Receptor Antagonists; D000818:Animals; D001249:Asthma / Q000503:physiopathology; D001980:Bronchi / Q000378:metabolism*; D024061:Collagen Type III / Q000032:analysis*; D024062:Collagen Type V / Q000032:analysis*; D007114:Immunization; D008297:Male; D010047:Ovalbumin; D012333:RNA, Messenger / Q000032:analysis; D011897:Random Allocation; D051381:Rats; D017208:Rats, Wistar; D013777:Tetrazoles / Q000494:pharmacology*; D016212:Transforming Growth Factor beta / Q000032:analysis*; D014633:Valine / Q000031:analogs & derivatives / Q000494:pharmacology*; D000068756:Valsartan
D057911:Angiotensin Receptor Antagonists; D024061:Collagen Type III; D024062:Collagen Type V; D012333:RNA, Messenger; D013777:Tetrazoles; D016212:Transforming Growth Factor beta; D000068756:Valsartan; D010047:Ovalbumin; D014633:Valine