Effect Of Angiotensin â…¡ And Angiotensin â…¡ Receptors On Airway Remodeling In Asthmatic Model

Partâ… Expression of angiotensinâ…¡and angiotensinâ…¡receptors in the lung of asthmatic rats and its correlation with airway inflammation and airway remodelingObjective:To investigate the expression of angiotensinâ…¡(Angâ…¡)and angiotensinâ…¡receptors(AGTR)in the lung of asthmatic rats and its correlation with airway inflammation and remodeling in asthma.Methods:twenty Wistar rats were randomly divided into two groups: control group and asthma group.Chronic asthmatic model was established by OVA-sensitization of intraperitoneal injection and repeated inhalation of OVA.Asthma symptoms were observed.Acetylcholine(Ach)-induced bronchoconstriction(represented by expiratory airway resistance,Re) was measured after the final antigen challenge.Cells in bronchoalvoelar lavage fluid(BALF)were counted and classified and the morphological changes in airways were assessed.The levels of TGF-β1,PDGF,VEGF and Angâ…¡in BALF were detected by enzyme linked immunosorbent assay(ELISA)and radioimmunoassay(RIA).The levels of AGTR (AGTR1 and AGTR2)mRNA and protein in lung tissues were measured by reverse transcriptase-polymerase chain reaction assay (RT-PCR)and Western blot.Signal transducer and activator of transcription factor3(STAT3)were also measured by Western blot. Results:Ach-evoked bronchoconstriction(Re)was increased in asthma group compared with that of control group(p＜0.05～0.01).Total BALF cells,eosinophils and neutrophils from asthma group were significantly higher than those in control group(p＜0.05,respectively).TGF-β1,PDGF and VEGF levels in BALF from asthma group increased greatly compared with control group(p＜0.05～＜0.01).Chronic OVA-challenged rats had an increase in total bronchial wall area(WAt/Pi)and smooth muscle area(WAm/Pi),including a region ofα-SMA-positive cells in the airway wall.The Angâ…¡level in BALF from asthma group was higher than that of control group,simultaneously.The AGTR1,AGTR2 mRNA and protein levels were significantly increased in asthma group compared with control group(p＜0.01).STAT3 level in asthma group was also increased(p＜0.01).There was a positive correlation between total BALF cells and level of Angâ…¡or AGTR1mRNA(r=0.523,0.724 respectively, p＜0.05～0.01),and between Wat/Pi and AGTR1 mRNA(r=0.671,p＜0.05).Conclusion- There may be a local angiotensin system in the lung of rat.Angâ…¡and AGTR may be involved in airway inflammation and airway remodeling of asthma. Partâ…¡Effect of angiotensinâ…¡receptor antagonist on airway inflammation and airway remodeling in asthmatic ratsObjective:To study the effect of valsartan,a type 1 angiotensinâ…¡receptor antagonist on airway inflammation and airway remodeling induced by repeated antigen inhalation in experimental rats.Methods: Fifty Wistar rats were randomly divided into five groups:control group,asthma group and three valsartan-treatment groups(C1,15 mg·kg ^-1·d^-1;C2,30 mg·kg ^-1·d^-1·C3,50 mg·kg ^-1·d^-1).Asthma group and three valsartan-treatment groups were sensitized and repeatedly challenged with OVA.Sixty minutes before the inhalation challenge,rats were pretreated either with valsartan or saline intragastrically.Ach-induced bronchoconstriction(represented by Re)was measured after the final antigen challenge.Cells in BALF were counted and classified and the morphological changes in airways were assessed.The levels of TGF-β1,PDGF,VEGF and Angâ…¡in BALF were detected by ELISA and RIA, respectively.Results:Valsartan significantly decreased the total BALF cell,eosinophils,and neutrophils and attenuated Ach-evoked bronchoconstriction in valsartan-treatment groups compared with that of asthma group(p＜0.05～0.01).Valsartan also decreased allergen-induced structural airway changes(including total bronchial wall area (WAt/Pi),smooth muscle area(WAm/Pi)andα-SMA-positive cells region)and the levels of TGF-β₁,PDGF and VEGF in BALF in valsartan-treatment groups compared with that of asthma group(p＜0.05～0.01).However,The level of Angâ…¡in BALF in high dose valsartan-treatment group(C3)was higher than that in the other groups.Conclusion:Valsartan,a type 1 angiotensinâ…¡receptor antagonist, has the inhibition effect on airway inflammation and airway remodeling in asthmatic rats.Partâ…¢Effect of valsartan on expression of angiotensinâ…¡and angiotensinâ…¡receptors in the lung of asthmatic ratsObjective:To observe the effect of a type 1 angiotensinâ…¡receptor antagonist,valsartan,on expression of angiotensinâ…¡and angiotensinâ…¡receptors in the lung of asthmatic rats.Methods:Fifty Wistar rats were randomly divided into five groups:control group,asthma group, valsartan-treatment groupC1(15 mg·kg ^-1·d^-1),C2(30 mg·kg ^-1·d^-1)and C3(50 mg·kg ^-1·d^-1).Asthma group and three valsartan-treatment groups were sensitized and repeatedly challenged with OVA.Sixty minutes before the inhalation challenge,rats were pretreated either with valsartan or saline intragastrically.The levels of Angâ…¡in BALF and blood were detected by RIA.The levels of TGF-β1 mRNA,VEGF mRNA and AGTR(AGTR1 and AGTR2)mRNA in lung tissues were measured by RT-PCR.The protein levels of AGTR(AGTR1 and AGTR2)and STAT3 in lung tissues were measured by Western blot.Distribution and expression of AGTR1 and AGTR2mRNA in rat lung were analyzed by in situ hybridization.Results:The Angâ…¡level in BALF was higher in valsartan-treatment groupC2 and C3 than that in the other groups, especially in valsartan-treatment groupC3(p＜0.01).The asthma group had higher expression of AGTR1 mRNA than control group(p＜0.01).The valsartan-treatment groups(C1,C2 and C3)had significantly lower expression of AGTR1 mRNA than asthma groups(p＜0.01).The expression level of AGTR2 mRNA in control group and valsartan-treatment groupC1 was significantly lower than that in asthma group(p＜0.01).The expression of AGTR2 mRNA in valsartan-treatment groupC2 and C3 was higher than that in the control group and valsartan-treatment groupC1,but significantly lower than that in asthma group(p＜0.05～＜0.01).The protein expression level of AGTR1 by Western blot analysis was parallel with its mRNA levels,but the AGTR2 were not detected in control group and valsartan-treatment groups C1. The protein level of AGTR2 in valsartan-treatment group C2 and C3 was lower than that in asthma group(p＜0.05).In situ hybridization analysis for AGTR1 and ATGR2 mRNA showed similar results.That the expression of AGTR1 mRNA in asthma group was significantly greater than that in the control group and valsartan-treatment groups(C1,C2 and C3).However,the expression of AGTR2 mRNA in the asthma group and valsartan-treatment groups C3 was significantly greater than that in the control group and valsartan-treatment groupsC1 and C2.The expression of TGF-β1 mRNA and VEGF mRNA in asthma group were higher than that in control group(p＜0.01)and valsartan-treatment groups(C1,C2 and C3)(p＜0.01).Similarly,STAT3 protein level in asthma group was higher than that in control group(p＜0.01)and valsartan-treatment groups(C1,C2 and C3)(p＜0.01).A negative correlation was observed between the expression of AGTR1 mRNA and the dose of valsartan(r= -0.775,p＜0.01).Conclusion:Angâ…¡may participate in airway inflammation and airway remodeling of asthma through AGTR1.The part mechanism of valsartan reducing airway changes in asthma may be that valsartan reduced the biological effects of Angâ…¡by down-regulating AGTR1 expression,and so leads to a reactive rise in Angâ…¡levels, increased Angâ…¡may act on AGTR2 and enhance AGTR2 expression. AGTR2 play a potential role in airway protection,Partâ…£Effect of angiotensinâ…¡on human airway smooth muscle cell proliferation and the intervention of valsartanObjective:To investigate the effect of angiotensinâ…¡on human airway smooth muscle cell proliferation and the intervention of valsartan on cell proliferation induced by angiotensinâ…¡.Methods:Primary cultures of human airway smooth muscle cells(HASMC)were established.After passage,HASMC were incubated with Angâ…¡and/or valsartan.The proliferation of cells was detected by MTT assay.The expression of caspase-3 and Cell cycle were analyzed by flow cytometry(FCM).Results:(1)Angâ…¡increasd the absorbance at 570nm(A₅₇₀)and proliferation rate of HASMC in a concentration dependent manner.In comparison with A₅₇₀of control group,the A₅₇₀value in 10^-5mol/L Angâ…¡and in 10^-6mol/L Angâ…¡group were markedly increased at 24h (p＜0.01 and p＜0.05,respectively).Combination of Angâ…¡and valsartan showed significant decrease of A₅₇₀and proliferation rate of HASMC, compared to Angâ…¡alone(p＜0.01).(2)Compare with control group, HASMC at S phase were increased in 10^-5mol/L Angâ…¡group.The analysis of the cell growth cycle showed that the combination of Angâ…¡and valsartan significantly decreased S phase in a dose dependent manner, compared with Angâ…¡alone(P＜0105).(3)Caspase-3 expression in Angâ…¡+ valsartan group was higher than that in Angâ…¡group,but no statistical difference was found.The effect of valsartan on the proliferation of HASMC induced by histamine analogous to those of valsartan on the proliferation of HASMC induced by Angâ…¡(p＜0.05～＜0.01).Conclusion:Angâ…¡can promote the proliferation of HASMC.Valsartan can antagonize the HASMC proliferation induced by Angâ…¡.The high expression of the caspase-3 in Angâ…¡+valsartan group indicate that valsartan might promote apoptosis of HASMC.