Astragalus Polysaccharides Downregulate The Expression Of α-SMA Of Airway Smooth Muscle

Objective:Bronchial asthma is a chronic respiratory disease characterized by airway inflammation dominated by many kinds of cells and inflammatory factors,and the dysfunction of airway smooth muscle plays a important role in asthma.a-Smooth muscle actin (a-SMA) is a important contractile and structural protein,which can induce airway hyperreactivity and aggravate airway remodeling of chronic asthma. Astragalus polysaccharides are the major component of the Astragalus mongholicus, which can modulate immunity through TLR4 as the analogs of LPS.It has been proved that Astragalus mongholicus can downregulate the a-SMA of mouse modle of asthma,and APS have an effect on anti-tumor,possess immunopotentiative functions,can cause improvement of diabetic nephropathy,however its effect on hunan ASM is still unclear. This study is to determine whether APS could suppress a-SMA expression of airway smooth muscle stimulated by transforming growth factor-β(TGF-β) in vitro,and investigate the possible mechanism of the effect, in order to provide a new treatment of asthma on clinical.Method:APS was isolated from Astragalus membranaceus, cultivated human airway smooth muscle cell were divided into APS 20μg/mL,100μg/mL,500μg/mL groups, control group, lipopolysaccharide (LPS) group,Toll-like receptor 4(TLR4)antagonist grope, and stimulated by TGF-βsubsequently.The levels of the expression of a-SMA and mRNA were measured by immunocytochemistry,Western blot and RT-PCR. All data are expressed as mean±SD. Statistical significance between groups was determined by one-way analysis of variance (ANOVA), multiple comparisons among groups was used. Data analysis was performed using the SPSS 13.0 statistical package programme. P<0.05 was considered as statistically significant.Result:1. APS inhibited a-SMA expression dose-dependly Compared with negative control group, the expression of a-SMA can be inhibited in lOOμg/mL,500μg/mL groups(P<0.01),but there's no difference in 20μg/mL group.2. the downregulation of a-SMA by APS occus at transcriptional levelCompared with negative control group, the expression of a-SMA mRNA can be inhibited in 100μg/mL,500μg/mL groups(P<0.01),but there's no difference in 20μg/mL group.3. The effect of APS were not due to endotoxin contamination As PMB is an known antibiotic to block various biological activities of LPS,pretreatment of PMB did not affect the inhibitory effects of APS,while it abolished the inhibitory effects of LPS.So the endotoxin contamination of APS can be eliminated.4. the inhibitory effect of APS depended on TLR4 activity partlyCompared with 500μg/mL group, the expression levels of a-SMA or mRNA could be upregulated in TLR4 antogonist group(P<0.01),but were still lower than negative control group (P<0.01).Conclusion:1. APS dose-dependly depress the expression of a-SMA at transcriptional level.2. The inhibitory effect of APS depended on TLR4 activity partly.3. APS is a potential agent in prevention and treatment of asthma.