Anti-hypertensive Effect Of Synthetic ACE Polypeptides From Chinese Wolfberry In Spontaneously Hypertensive Rats And Mechanism Involved

Objective Synthetic angiotensin-converting enzyme(ACE)polypeptides from Chinese wolfberry was used as a test substance and long-term administration experiment in spontaneously hypertensive rats(SHR).The purpose of our research was to explore the anti-hypertensive effect and mechanism of synthetic ACE polypeptides from Chinese wolfberry and observe the effects on the Renin-angiotensin system(RAS)and possible anti-hypertensive mechanism in SHR.Our results would be provide a theoretical basis for the prevention and treatment of hypertension in the future.Methods Methods: A total of 30 SHR were randomly divided into 5 groups: model control group,positive control group(10 mg/kg of captopril),low-dose group of synthetic ACE polypeptides from Chinese wolfberry(5 mg/kg),middle-dose group(10 mg/kg)and high-dose group(20 mg/kg);and 6 Wistar-Kyoto(WKY)rats as normal control group.The normal control group and model control group were treated with equal volume of normal saline respectively.After one week of adaptive feeding,the rats were given one-time administration and long-term administration experiment(orally fed for 8 consecutive weeks).During the experimental period,the rats were fed and drank freely,and SBP(systolic blood pressure)and DBP(diastolic blood pressure)was measured at a fixed time per week(two hours after feeding).At the end of the experiment,blood was collected from the arteriae coeliaea and taken its heart,kidney,hypothalamus,pituitary tissue.The contents of Angiotensin-(1-7)(Ang-(1-7))?Angiotensin?(AngII)?ACE and angiotensin-converting enzyme 2(ACE2)in plasma and kidney were detected by enzyme-linked immunosorbent assay respectively.The mRNA expression levels of ACE,Ang?,type 1 receptor(AT1-R),ACE2 and mas receptor(Mas-R)in four tissues(heart,kidney,hypothalamus and pituitary)were respectively analyzed by RT-qPCR(real-time fluorescent quantitative polymerase chain reaction)method.Western blotting was used to detect the expression levels of ACE,ACE2,AT1-R and Mas-R proteins in heart and kidney tissues.Results 1.Rats weight and blood pressure: Compared with the WKY,the body weight of SHR rats was significantly decreased(p<0.05);Compared with model control group,the weight gain of SHR in the middle and high dose groups was decreased significantly which were treated with synthetic ACE polypeptides from Chinese wolfberry(p<0.05).Compared with WKY,the SBP and DBP in SHR were significantly increased(p<0.05);compared with model control group,the DBP in SHR of positive control group,low-,middle-,and high dose group SHR were significantly decreased at 6 week and 8 week(p<0.05);During the experimental period,the SBP of SHR had a certain downward trend with the extension of orally fed time.2.Changes of RAS system related enzymes in rats plasma and kidney tissues: Compared with WKY,the concentration of Ang? and ACE were significantly increased and Ang-(1-7)was significantly decreased in plasma and kidney tissues of SHR(p<0.05).Compared with model control group,the synthetic ACE polypeptides from Chinese wolfberry can significantly decrease ACE concentration(p<0.05)and increase ACE2 concentration.3.Changes in expression of RAS system related factors: Compared with WKY,the expression of ACE and AT1-R mRNA were significantly up-regulated,while ACE2 and Mas-R mRNA were down-regulated in heart and kidney tissues of SHR(p<0.05).Compared with the model control group,the groups of synthetic ACE polypeptides from Chinese wolfberry could significantly down-regulate the expression of ACE mRNA in the SHR kidney tissues,and down-regulate the expression of AT1-R mRNA in the heart and kidney tissues(p<0.05).The expression of ACE2 mRNA in heart and kidney tissues were up-regulated(p<0.05),the expression of Mas-R mRNA varying degrees of increase.The expression of the related proteins were consistent with mRNA.Compared with WKY,the expression of ACE and AT1-R protein were significantly increased,while ACE2 was significantly decreased in heart and kidney tissues of SHR(p<0.05).Compared with the model control group,the groups of synthetic ACE polypeptides from Chinese wolfberry could significantly decrease the expression of ACE and AT1-R protein in heart and kidney tissues(p<0.05).ACE2 in the mid-and high-dose groups were significantly increased(p<0.05).There was no significant difference in the expression of Mas-R protein(p>0.05).4.Changes in expression of RAS system related factors in rats hypothalamus and pituitary tissues: Compared with WKY,the expression of ACE and AT1-R mRNA in hypothalamus and pituitary tissues were significantly up-regulated,while ACE2 and Mas-R mRNA were down-regulated in model control group(p<0.05).Compared with the model control group,the expression of ACE and AT1-R mRNA could significantly down-regulate in the SHR hypothalamus tissue in the synthetic ACE polypeptides groups(p<0.05).The expression of ACE2 mRNA of middle-dose group were up-regulated in the hypothalamus and pituitary tissues(p<0.05).The up-regulation of Mas-R mRNA was in varying degrees(p>0.05).Conclusion The synthetic ACE polypeptides from Chinese wolfberry can effectively reduce the blood pressure of SHR,it may be through regulating the balance of ACE-AngII-AT1-R pathway and ACE2-Ang-(1-7)-Mas-R pathway to achieve anti-hypertensive effect.