Study On The Effect Of Cydonia Oblonga Mill.extracts On Hypertensive Rats And Mechanisms

Objective:Cydonia oblonga Mill.(COM)is used for the treatment of hypertension in traditional Uyghur medicine according to documentary records.In this study,the effective anti-hypertension part of COM was screened by 2K1C renal hypertensive rats and the chemical components were analysed preliminarily,flavonoids were possibly the main constituents in COM;Then flavonoids of COM(COMF)were separated and purified and the effects of anti-hypertension and protection of effect taget organs were investigated by spontaneously hypertensive rats,especially the effect on the structure and function of heart,the possible mechanism of action was further investigated from different aspects,which can provide theoretical data and basic information for the development and use of Cydonia oblonga Mill..Methods:?2K1C renal hypertensive rats were operated and divided into 7 groups randomly as:model group,captopril group(25mg/kg),low(80mg/kg)and high dose(160mg/kg)of the aqueous or 65%ethanol extracts of the fruit and leaf groups,and the sham group.All the rats were given intragastric administration for 8 weeks and SBP and DBP were tested every two weeks.The hemorheology indices were tested after the last administration.?2K1C renal hypertensive rats were operated and divided into 6 groups randomly as:sham group,model group,captopril group(25mg/kg),low,middle and high dose of COM leaf extract groups(40,80,160mg/kg).After intragastric administration for 8 weeks and SBP and DBP were tested every two weeks,the levels of Ang?,RA,apelin-12,ET-1 and NO were tested.?4 parts from 65%COM leaf extract were seperated by different solvent as petroleum ether part,ethyl acetate part,n-butyl alcohol part and aqueous part,which were administered for 8 weeks in 2K1C hypertensive rats and the changes of SBP and DBP were observed and recorded to determine the active part,the antioxidant effect of COM was evaluated preliminarily by determination of the levels of T-AOC,GSH-ST and SOD.?Total flavonoids of COM(COMF)were separated and purified by the optimal process,SHR were divided into 6 groups as SHR control group(SHR),captopril group(CAP,25mg·kg-1·d-1),Eucommia ulmoides Oliver group(EUO,30mg kg-1—d-1),low(COMF-L,40mg*kg-1·d-1),middle(COMF-M,80mg*kg-1·d-1)and high dose(COMF-H,160mg·kg-1·d-1)of COMF groups.8 Wistar-Kyoto(WKY)rats were given distilled water instead as control.The drugs were given by intragastric administration for 16 weeks.Systolic blood pressure(SBP)and diastolic pressure(DBP)was measured by tail cuff approach every two weeks.After 16 weeks,the echocardiography,hemodynamics,histological and pathological examination of the heart were performed and organic damage were valued.?The levels of Ang? and ALD in blood and heart were tested,the mRNA and protein expression of ACE,ACE2 and AT1 was determined by RT-PCR and Western blot to evaluate the impact of COMF on RAAS.?The levels of IL-1?,IL-6,IL-10,TNF-? and CRP in serum were tested to evaluate the impact of COMF on inflammatory factors.?The levels of ET-1,NO,NOS,SOD,MDA and CGRP in serum were tested to evaluate the impact of COMF on vascular endothelial function.Results:?After administration for 8 weeks,SBP and DBP of the rats in both of the fruit and leaf extracts of COM groups was lowered,the ethanol extract of COM leaves showed the strongest effect of the all,SBP and DBP lowered 9.0%and 11.8%respectively.Compared with the model group,whole blood viscosity,plasma viscosity,hematokrit(HCT),erythrocyte assembling and rigidity index was lowered and deformation index was elevated.?After administration for 8 weeks,compared with the model group,SBP and DBP of the rats in the leaf extracts of COM groups was lowered,the levels of Ang ?,RA and apelin-12 in blood and kidney and ET-1 in blood were all lowered and NO was elevated(P<0.05).?Compared with the model group,SBP and DBP in ethyl acetate part of COM group was lowered 4.3%and 9.1%respectively and the activity of T-AOC,GSH-ST,SOD and NOS was increased and MDA was decreased in COM groups(P<0.05).?After administration for 16 weeks,compared with SHR control group,SBP and DBP of the rats in COMF-H group was lowered 18.9%and 21.1%respectively;The echocardiography results showed that,compared with SHR control group,LVIDdI,LVIDsI and IVSTI were decreased in COMF groups(P<0.01 or P<0.05),LVW,LVWI and LVW/BW were decreased in COMF groups(P<0.01 or P<0.05),FS and LVEF were increased in COMF-M and COMF-H groups,COMF-H showed the strongest effect;The hemodynamics results showed that,compared with SHR control group,in COMF groups,SBP,DBP,LVSP and LVEDP were lowered(P<0.01 or P<0.05),LV+dp/dtmax and LV-dp/dtmax were decreased,SD showed no changes,DD was prolonged(P<0.05),HR was decreased but without significant difference(P<0.05);Compared with SHR control group,HW,HW/BW,LVM and LVM/BW were decreased in COMF-M and COMF-H groups(P<0.01 or P<0.05);The histopathological examination results showed that cadiomyocyte hypertrophy and expansion of intercellular substance was inhibited in COMF groups,CD and CAS was decreased 4,6%and 13.6%in COMF-H group respectively(P<0.05).Incrassation of tunica media of thoracic aorta and injury of endothelial cells was inhibited in COMF groups.Compared with SHR control group,in COMF-M and COMF-H groups,AW/lenth were decreased 8.1%(P<0.05)and 13.1%(P<0.01)respectively,IMT was shortened and IMT/ID was decreased(P<0.01 or P<0.05).Incrassation of the vessel wall and stenosis of afferent glomerular arteriole was inhibited in COMF-H group;?Compared with SHR control group,the concentration of Ang? and ALD in heart and blood was decreased 5.2%and 13.2%,15.4%and 19.2%respectively;ACE and AT1 mRNA and protein expression in heart tissue were decreased while ACE2 mRNA expression was increased(P<0.01 or P<0.05),data in COMF-H group changed the most.?Compared with SHR control group,the levels of IL-1?,IL-6,TNF-? and CRP were lowered in COMF groups(P<0.01 or P<0.05),while IL-10 was increased a little but without significant difference(P<0.05).?Compared with SHR control group,in COMF groups,the levels of ET-1 and MDA were lowered,while the levels of IL-1?,IL-6,TNF-? and CRP were elevated significantly(P<0.01 or P<0.05)Conclusions:Both of the fruit and leaf extracts showed anti-hypertensive effect in RHR or SHR,the active part was the ethyl acetate part of the ethanol crude extract and flavonoids was possible to be the main active components.The anti-hypertensive mechanism of COMF was related with:(1)Inhibition of activity of RAAS,the levels of Ang II and ALD were lowered,therefore vasoconstriction,retention of sodium and water,antidiuresis and proliferation of vascular smooth muscle were inhibited;(2)Inhibition of synthesis and release of inflammatory factors such as IL-1?,IL-6,TNF-? and CRP to prevent development and progression of hypertension;(3)Keeping ET-1/NO in balance,elevation the levels of CGRP and SOD,inhibition of synthesis of MDA,so that alleviate peroxidation damage and protect the vessel endothelium.The mechanism of inhibition of myocardial hypertrophy in SHR was related with:(1)Decreasing mRNA and protein expression of ACE and AT1 and increasing that of ACE2,so that the ratio of ACE/ACE2 was lowered,the synthesis of Ang? was inhibited,metabolic pathway of ACE2-Ang(1-7)-MAS was activated to protect the heart;(2)Inhibition of the synthesis and release of inflammatory to prevent development and progression of left ventricular hypertrophy.