Effect Of Rg1 Ginsenosides On Pulmonary Arteriole Damages Generated In A Mouse Model Of Chronic Intermittent Hypoxia

Objective : Chronic intermittent hypoxia is closely related to the occurrence of pulmonary hypertension,however there is no effective treatment.Using a C57BL/6 mouse model of chronic intermittent hypoxia(CIH)to explore the effect of Rg1 ginsenosides on pulmonary arteriole damages induced in CIH.Methods: It was randomly divided into groups by using a random number table.8 of mice were randomly selected from 88 of SPF C57BL/6 male mice and were assigned to the normoxia group;After the additional 80 mice was successfully established to be the CIH model,8 of the mice were also randomly selected and were assigned to hypoxia group.72 of SPF C57BL/6 male mice were randomly divided into the experimental group and the control group.The experimental group was given either a low dose of Rg1 ginsenosides(10m/kg,T1 group)or a high dose(20mg/kg,T2 group)by daily intraperitoneal injection.The control group was given saline by daily intraperitoneal injection.After 7,10 and 14 days of intraperitoneal injection,8 mice from each group were sacrificed to collect the samples.SABC/DAB assay was used to compare the difference between the experimental and the control groups in terms of HIF-1ɑ,VEGF and ET-1 in the lung tissue.Enzyme linked immunosorbent assay(ELISA)was used to measure the serum level of HIF-1 ɑ,VEGF and ET-1.Real-time,fluorescence-based quantitative PCR was used to compare the m RNA level of HIF-1ɑ,VEGF and ET-1 in the lung tissues between the experimental and the control groups.Results:(1)The thickening of pulmonary arteriolar intima could be induced by CIH: the difference between the hypoxia group(2.72±0.31μm)and normoxia group(1.16±0.03μm)was significant(P<0.05).In addition,CIH could also induce the thickening of pulmonary arteriolar media: the difference between the hypoxia group(44.76±1.42μm)and normoxia group(28.23±1.00μm)was significant(P<0.05).(2)In terms of plasma HIF-1ɑ(16.87±1.53pg/mlvs13.15±1.72pg/ml),plasma VEGF(13.88±3.64pg/ml vs 6.07 ± 0.99pg/ml)and plasma ET-1(45.97 ± 1.44pg/ml vs 36.95 ±0.69pg/ml),the differences between the hypoxia and normoxia groups were all significant(all P<0.05).(3)The thickness of pulmonary arteriolar intima in the hypoxia group was positively correlated with the serum level of HIF-1ɑ(r=0.740,P<0.001),VEGF(r=0.876,P<0.05)and ET-1(r=0.952,P<0.05),respectively.The thickness of pulmonary arteriolar media in the hypoxia group was positively correlated with the serum level of HIF-1ɑ(r=0.738,P<0.001),VEGF(r=0.901,P<0.05)and ET-1(r=0.971,P<0.05),respectively.(5)Compare to the C group,the concentrations of serum HIF-1ɑ,VEGF and ET-1 in both experiment groups were significantly different(all P < 0.001).The differences between the T1 and T2 groups were also statistically significant(all P < 0.001).(6)The immunohistochemical IOD values of HIF-1ɑ,VEGF and ET-1 in the lung tissues of the two experiment groups all decreased.The differences were all significant as compared with the values of the control group(all P<0.001).The values in the T2 group and those in the C and T1 groups were all significantly different(all P < 0.001).(7)On day 14,the m RNA expression level of HIF-1ɑ,VEGF and ET-1 in the T1 group all decreased and was significantly different from that in the C group(all P<0.001).Similarly,the m RNA expression level of HIF-1ɑ,VEGF and ET-1 in the T2 group(except HIF-1ɑ m RNA on day 7 and ET-1 m RNA on day 10)also decreased and was significantly different from that in the C group(P<0.05 or P<0.001).The difference between the T1 and T2 groups was also significant(P<0.05 or P < 0.001).Conclusions: 1.CIH can cause damages to mouse pulmonary arterioles,increase the expression of HIF-1α,and regulates the expression of target genes downstream of HIF-1 α.The increased expression of vascular endothelial growth factor(VEGF)and endothelin-1(ET-1)is one of the important mechanisms underlying the damages to mouse pulmonary arterioles.2.The treatment of CIH mice by Rg1 ginsenoside could reduce the expression of HIF-1α,VEGF and ET-1.Significant differences were observed between two different dose groups.More protective effect against chronic intermittent hypoxia in mice was noted in high-dose group than the low/dose one.The results showed that Rg1 ginsenoside may provide certain protection against the damages to lung arterioles.