Effect Of Aliskiren On The Renal Injury In AGT-REN Double Transgenic Hypertensive Mice

Objectives Dysfunction of the renin-angiotensin system (RAS) has an important role inthe development of hypertension and target organs damage. Renin, the rate-limitingenzyme acting on the first step of RAS reaction, plays a key role in the activation of RAS.In present study, we aim at approaching the effect of Aliskiren administration on RASimbalance, kidney injury and its mechanism in double transgenic hypertensive mice bymonitoring the blood pressure, renal damage index, and detecting the changes of AngⅡ/Ang(1-7) and ACE/ACE2expression in circulation and intrarenal.Methods1Animal grouping and drug delivery method: twelve10-month-old malehuman angiotensinogen-renin (AGT-REN) double transgenic hypertensive mice wererandomly divided into two groups (n=6, per group): HT group and HT+Aliskiren group;Six C57B6mice with the same background were used as wild type control group (WT).Adiministration of single dose was taken by irrigation stomach, with aliskiren in differentdoses of5mg/kg,10mg/kg and20mg/kg, respectively. Continuous medication wasadministered to animals by subcutaneous mini osmotic pump, with a dosage of20mg/kg/d given to the HT+Aliskiren group for28days, and the animals were killedmercily at the end of delivery.2Blood pressure (BP) monitoring: MAP was surveyedunder the conscious state by the non-invasive blood pressure meter for the singleadministration of different dosage within24h and continuous medication within28d.3Renal injury index testing:①Content of24h urinary protein was measured byCoomassie brilliant blue(CBB);②Concentrations of serum creatinine and urea weremeasured by automatic biochemical analyzer;③Light microscope (HE and Massonstains) and electron microscope were used for observing the renal pathological changes.4Detection of oxidative stress index: chemiluminescence method was taken for renalsuperoxide dismutase (SOD) and malondialdehyde (MDA) and Western blot was usedfor p47phoxexpression in local tissue.5Detection of expression of RAS components: thecontent of AngⅡ and Ang(1-7) in serum and kidney were measured by ELISA.Expression of kidney ACE and ACE2protein was determined by WB.Results1The antihypertensive effect of aliskiren: compared with that in WT mice,MAP in HT mice was siginifincantly increased. Both of single and continuous dosingexperiment show that MAP in HT+Aliskiren group mice were significantly lower thanthat of HT group mice.2Compared with that in WT mice, cortical thickness in HT micewas siginifincantly decreased, score of glomerulosclerosis and renal interstitial fibrosis were increased significantly; by contrast, compared with HT mice, cortical thickness wasincreased, score of glomerulosclerosis and renal interstitial fibrosis were decreasedsignificantly in HT+aliskiren group. The pathological changes including basementmembrane thickening, fusion of foot process, glomerulus extracellular matrixaccumulating and vacuolar degeneration of mitochondria were found under electronmicroscope. However, Aliskiren administration ameliorated the above-mentioned renalpathological damages.3Contents of24h urinary protein, serum creatinine and urea in HTgroup mice were significantly increased than that in WT group. The aboved index inHT+Aliskiren group were greatly decresed than that in HT group.4Compared with thatin WT mice, content of SOD in HT mice was siginifincantly decreased, and MDAincreased. Expression of p47phox, as an impaotant subunit of NADPH oxidase, wasgreatly increased in HT mice than that in WT mice. However, content of SOD increasedsignificantly, and content of MDA reduced in HT+aliskiren group, compared with that inHT mice. Expression of p47phoxwas also obviously decreased in HT+Aliskiren group.5Compared with that in WT mice, expression of ACE was increased, and ACE2decreasedin HT group mice. The ratio of AngⅡto Ang(1-7) in HT mice was also higher than thatin WT mice. After adiminstration of Aliskiren, the expression of ACE was reduced, andACE2expression was apparently raised in the kidney of mice. There was an apparentdown regulation of the ratio of AngⅡto Ang(1-7) in the serum and kidney ofHT+Aliskiren group.Conclusions1Aliskiren was effective for blood pressure control and renoprotection inhypertensive mice.2Aliskiren maintained the balance of intrarenal RAS by inhibiting thegeneration of AngⅡ and reducing the ratio of AngⅡ to Ang(1-7).3Aliskiren blockedthe RAS by inhibiting the rate-limiting step in the RAS cascade, but it did not significantlyreduce the production of Ang (1-7) and increased protein expression of ACE2.4Aliskiren may play a renoprotective effect by inhibiting the expression of NADPHoxidase.