Anti-hypertensive effects of rosiglitazone on renovascular hypertensive rats: role of oxidative stress and lipid metabolism

LI Yan(李岩), GUO Nan(郭楠), FU Zhen-ping(付振平), DONG Ji-rui(董继锐),ZHAO Jian-pu(赵剑璞), FENG Hui-hong(冯会红), LIU Pin-duo(刘品多), XIA Yu(夏雨)

(School of Life Science, Beijing Institute of Technology, Beijing 100081, China)



Anti-hypertensive effects of rosiglitazone on renovascular hypertensive rats: role of oxidative stress and lipid metabolism

LI Yan(李岩), GUO Nan(郭楠), FU Zhen-ping(付振平), DONG Ji-rui(董继锐),ZHAO Jian-pu(赵剑璞), FENG Hui-hong(冯会红), LIU Pin-duo(刘品多), XIA Yu(夏雨)

(School of Life Science, Beijing Institute of Technology, Beijing 100081, China)

This study investigated the anti-hypertensive mechanism of rosiglitazone in renovascular hypertensive rats, and examined its relationship to oxidative stress and lipid metabolism. The renovascular hypertension was induced by stenosis of the left renal artery. Four groups of rats were selected: control, induced untreated, rosiglitazone (20 mg/kg) and captopril (10 mg/kg). After 14 d of administration, compared with induced untreated group, rosiglitazone group reduced the renovascular hypertensive rats’ systolic blood pressure and diastolic blood pressure, and decreased total cholesterol (TCH), triglyceride (TG), angiotensin II (Ang II) and angiotensin receptor (AT1) levels(P<0.05). Meanwhile, rosiglitazone remarkably decreased the levels of malondialdehyde (MDA) and hydrogen peroxide (H2O2) while improved the levels of supperoxide dismutase (SOD) and reduced glutathione (GSH). These results suggested that rosiglitazone could effectively decreased the blood pressure in renovascular hypertensive rats, and this might be performed by regulating the activity of angiotensin and the lipid metabolism and improving the oxidative stress.

rosiglitazone; renovascular hypertensive rat; lipid metabolism; oxidative stress

Human hypertension is a slowly-developed disorder, and involves the complex structural and functional alterations of its target organs. Hypertension is manifested by an increased arterial pressure[1]. Epidemiological data revealed that elevation of blood pressure alone in hypertension patients is less than 20%, most hypertension patients is always accompany with other metabolic disorder, such as obesity and lipid abnormality[2]. Chronic kidney artery diseases such as renal artery stenosis generally result in hypertension. Two-kidney, one-clip (2K1C) model in which one of the renal arteries is subjected to artery stenosis by clip placement, is one of the kidney related animal models of hypertension. Kidney ischemia leads to increase in plasma renin and angiotensin activity which successively results in persistent rise in blood pressure[3].

Thiazolidinediones (TZDs), a class of synthetic insulin-sensitizing agent (e.g., pioglitazone, rosiglitazone) used in the treatment of diabetes mellitus type 2, act by enhancing sensitivity to insulin to lower blood sugar. Overseas study found that in diabetic animals and patients, TZDs can not only lower blood glucose by enhancing insulin sensitivity, but also reduce blood pressure, suggesting that lower blood pressure is associated with enhanced insulin sensitivity[4-5]. As TZDs represented drug, rosiglitazone can improve insulin resistance and have a hypoglycemic effect which may be related to competitive peroxisome proliferator-activated receptor γandregulationofinsulingenetranscriptionreactivity[6-7].Althoughrosiglitazonereducesbloodpressurebyreducingtheroleofinsulinresistancehasbeenconfirmedbyclinicalandanimalstudies[8],itsmechanismremainsunclear.Toinvestigateanti-hypertensivemechanismofrosiglitazone,therenovascularhypertensiveratmodelwasinducedbystenosisoftheleftrenalartery,andangiotensinanditsreceptorlevel,lipidmetabolism,andoxidativestressweredetected.

1 Materials and methods

1.1Experimentaldrugs

RosiglitazonewasfromHenryPharmaceuticalCo.,Ltd.Chengdu(batchnumber: 110901).CaptoprilwasorderedfromNorthChinaPharmaceuticalCo.,Ltd. (batchnumber: 1109002).

1.2Preparationofhypertensionmodel

FortymaleSDrats(180-220g)werepurchasedfromthePekingUniversityHealthScienceLaboratoryAnimalScienceMinistry,CertificateofConformitySCXK-(Beijing) 2011-0012.Animalsweremaintainedunder12hlight/darkcyclesatatemperatureofapproximately24±1 ℃withfoodandwateradlibitum.After3days,animalswererandomlydividedintotwogroups,thecontrolgroupandthehypertensionmodelgroup.Leftrenalarterystenosiswasinducedusingthe2K1Cmethodtoestablishhypertensionmodel.Heartrateandbloodpressureinratsafteroperationweredeterminedbythedetector(CODAMonitorTypenoninvasivebloodpressuremeter,USAKentScientificCorporation).Bloodpressurewasmonitoredwiththetailcuffmethodfor4weeks.Ratswithhigherthan160mmHgsystolicbloodpressureswereselectedandrandomlydividedintothreegroups(n=8foreachgroup).Groupinganddosingregimenisasfollows:rosiglitazonegroup: 20mg/kg;captoprilgroup: 10mg/kg;blankgroupandmodelgroupweregivenanequalvolumeofsaline.Ratswereadministratedbyintragastricadministrationonceadayforconsecutive14days.

1.3 Blood pressure monitoring and sample collection

Rats’ blood pressures were measured at 0 d, 4 d, 7 d, 10 d, and 14 d respectively after administration. After the last administration, rats were anesthetized with 10% chloral hydrates (300 mg/kg, ip). Abdominal aortic blood samples were used to determine AngII (Beijing Biotechnology Co., Keno spring, lot: 20120501A), serum total cholesterol (kit, TCH, batch number: 2011110012), triglycerides (kit,TG, batch number: 2011110011), superoxide dismutase (kit,SOD, batch number: 20120306), malondialdehyde (kit, MDA, batch number: 20111101), reduced glutathione (kit, GSH, batch number: 20120515) and hydrogen peroxide (kit, H2O2, batch number: 20120511, purchased from Nanjing Jiancheng Bioengineering Institute). Rats were sacrificed to take kidneys for detecting angiotensin II receptor 1 (Angiotensin II type 1 receptor, AT1) (kit, Beijing Keno spring Biotech Co., Ltd., batch number: 20120501A).

1.4 Statistical analysis

2 Results and discussion

2.1 Effect of rosiglitazone on renal vascular hypertension in rats

Experimental results show that systolic blood pressure and diastolic blood pressureof model group were significantly higher compared with control group, rosiglitazone group and captopril group (P<0.01) on 0 d, suggesting the hypertension model was established successfully; after 14 d administration compared with model group, systolic blood pressure in captopril group and rosiglitazone group were significantly lower, with the average reduction of 20.2% and 30.0%, respectively (P<0.01). And the diastolic blood pressure were also significantly lower with the average reduction of 21.8%， 28.0% respectively (P<0.01). The results shown in Tab.1 and Tab.2 suggest that rosiglitazone has a significant anti-hypertensive effect on renal hypertensive rats.

Tab.1 Effect of rosiglitazone on systolic blood pressure in renovascular hypertensive rats ±s, n=8, mmHg)

Compared with control,*P<0.05, **P<0.01; compared with Induced untreated group,#P<0.05,##P<0.01

Tab.2 Effect of rosiglitazone on diastolic blood pressure in renovascular hypertensive rats ±s, n=8, mmHg)

Compared with control,*P<0.05, **P<0.01; compared with Induced untreated group,#P<0.05,##P<0.01

2.2 Effects of rosiglitazone on AngII and AT1in renal hypertensive rats

Experimental results(Fig.1) showed that: compared with the control group, the contents of Ang II, AT1in model group were significantly increased (P<0.01); compared with induced untreated group, the contents of Ang II, AT1in rosiglitazone group and captopril group were significantly reduced (P<0.01). Thus, the results suggested that rosiglitazone plays an important role of regulating the activity of the renin-angiotensin in vivo.

2.3 Effect of rosiglitazone on the levels of oxidative stress in renal hypertensive rats

Tab.3 showed that, the activity of SOD and GSH in induced untreated group was significantly lower than the control group (P<0.05), and MDA and H2O2content was significantly higher than the control group (P<0.05); SOD and GSH levels in rosiglitazone and captopril group were significantly increased compared with the induced untreated group. The level of MDA and H2O2were significantly reduced (P<0.05). Conclusion can be made that rosiglitazone can regulate SOD, GSH, MDA; H2O2levels, and enhance body’s ability of anti-oxidative stress to mediate the hypertension.

Fig.1 Effects of rosiglitazone on AngII and AT1 in renal hypertensive rats (compared with control, *P<0.05, **P<0.01; compared with Induced untreated group，#P<0.05,##P<0.01)

2.4 Effect of rosiglitazone on TCH and TG in renal hypertensive rats

As shown in Fig.2, TCH and TG serum contents in induced untreated group was significantly increased compared with the control group (P<0.05); Compared with induced untreated group, TCH, TG contents of the rosiglitazone group and captopril group decreased significantly (P<0.01). These results indicated that rosiglitazone had effect on the TCH and TG contents in renal hypertensive rats.

Tab.3 Effect of rosiglitazone on serum oxidative stress level in renovascular hypertensive rats ±s, n=8)

compared with control, *P<0.05, **P<0.01; compared with Induced untreated group,#P<0.05,##P<0.01

Fig.2 Effect of rosiglitazone on TCH and TG in renal hypertensive rats ±s, n=8)(compared with control, *P<0.05, **P<0.01; compared with Induced untreated group,#P<0.05,##P<0.01)

3 Discussion and conclusions

In the 2K1C model, renovascular hypertension is featured by elevated AngII expression resulted from ischemia in the clipped kidney and shear stress in the non-clipped kidney, activating rennin-angiotensial-aldosterone system (RAAS), and sustained increase of blood pressure. AngII is the primary effector molecule of the renin-angiotensin system. It is primarily recognized for its role in the regulation of arterial pressure and blood volume[9]. The effects of Ang II on cardiovascular and reproductive functions are mainly mediated through Ang II type 1 (AT1) receptor. Therefore, specific AT1antagonists are potentially useful for treating hypertension and for improving sexual dysfunction in hypertensive patients[10]. Our data suggest that rosiglitazone could decline the AngII content, and decrease the ability of the vasoconstriction. Meanwhile, the expression value of AT1in vivo was also reduced. Thus, rosiglitazone can inhabit RAS in rats, and improved hypertension system.

In previous studies, Raji et al. have showed a positive correlation between BP values and insulin sensitivity in patients treated with rosiglitazone[11]. Whether oxidative stress and lipid metabolism play roles in mediating the blood pressure in hypertension rat has not been determined. Lipid metabolism disorder can influence the membrane Ca2+transporters involved in the pathogenesis of hypertension through affect lipid structure[12]. Previous studies have found that cholesterol-lowering is beneficial to the reduction of blood pressure. The present study reveals that rosiglitazone can attenuate hypertension by the reduction of TCH and TG in renal vascular hypertension rats.

Oxidative stress has been implicated in pathophysiological conditions (e.g., cigarette smoking, hypercholesterolemia, diabetes, and hypertension[13-15]) that affect the cardiovascular system[16-18]. Oxidative stress is a major factor in mediating hypertension[10]. In spontaneously hypertensive rats, there is a found of increased level of oxyradical production from xanthine oxidase activity and the formation of lipid peroxide[19]. Level of MDA is an estimate of lipid per oxidation[20]. The results indicate that rosiglitazone could improve the levels of SOD and GSH, decrease the contents of MDA and H2O2, and improve the oxidative stress which maybe the mechanism of contributing to the reduction of blood pressure.

In conclusion, the present study reveals the potential protective effect of rosiglitazone against the renovascular hypertensive, which seems to be related to down-regulated activity of angiotensin, improved oxidative stress, and attenuation of serum lipid.

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(Edited by Wang Yuxia)

10.15918/j.jbit1004-0579.201524.0321

R 977 Document code: A Article ID: 1004- 0579(2015)03- 0422- 05

Received 2014- 01- 07

E-mail: leeyan@bit.edu.cn