ABSTRACT
Objective To examine the effects of benazepril and losartan on glomerular podocyte autophagy in aged spontaneously hypertensive rats (SHRs) and investigate the underlying mechanisms of renal-protective effects of angiotensin-converting enzyme inhibitors (ACEI)/angiotensin receptor blockers (ARB).Methods Wistar-Kyoto rats (WKYs) were used as the normal control (NORM) group (2 ml physiological saline per day).SHRs were randomly divided into 4 groups:the CTRL group (2 ml physiological saline per day),the ACEI group (10 mg · kg-1 · d-1),the ARB group (30 mg· kg-1 ·d-1) and the combined group (10 mg· kg-1 · d-1 benazepril and 30 mg· kg-1 · d-1),with six 18-month-old make rats in each group.The experiments were conducted during a 4-month period.Blood pressure was monitored regularly.At the end of the experiments,we measured the levels of urine protein,urine creatinine,serum creatinine (SCR),blood urea nitrogen (BUN),and serum and renal cortex angiotensin Ⅱ (AngⅡ).Ultrastructural changes in the kidney were examined under light and transmission electron microscopy.The expressions of nephrin,LC3BⅡ,Atg5 and p62 in the glomerulus were analyzed by Western blot analysis.Results After treatment,the blood pressure and the urine albumin/creatinine ratio of the four SHR groups were still significantly higher than those of the NORM group,but the blood pressure and the urine albumin/creatinine ratio of the ARB group and the combined group were significantly lower than those of the CTRL group (all P＜ 0.05);There were no significant differences in SCR and BUN levels among these five groups (P＞ 0.05);The level of serum AngⅡ of the combined group was significantly higher than that of the CTRL group [CTRL (0.08±0.00) μg/L,Combined (0.12±0.01) μg/L,P＜0.05];The levels of cortex AngⅡ of the four SHR groups were significantly lower than those of the NORM group,while the level of cortex AngⅡ of the ARB group was significantly higher than that of the CTRL group (all P＜0.05);Renal ultrastructural examination revealed shrunken glomeruli,fused or effaced epithelial cell foot processes,and focal atrophy of renal tubules in the four SHR groups.These pathological changes were more serious in the CTRL group but less so in the combined group.There were significantly more autophagosomes in the NORM group and the combined group than in the CTRL group (P＜0.05).Compared with the NORM group,the expressions of nephrin,LC3BⅡ,Atg5 and p62 in the CTRL group were suppressed significantly (P ＜ 0.05).The expressions of nephrin,LC3BⅡ and Atg5 in the ACEI group and the expressions of nephrin,LC3BⅡ,Atg5 and p62 in the ARB group and the combined group were higher than in the CTRL group (P＜0.05).Conclusions ACEI/ARB can decrease the autophagic activity of glomerular podocytes.The renal-protective effects of ACEI/ARB may be mediated by glomerular podocyte autophagy,which is induced by AngⅡ.
ABSTRACT
Objective To study the changes of renal cortex angiotensin Ⅱ (AngⅡ) expression and podocyte autophagy in aging rats with normotension versus hypertension,to further investigate the possible mechanism of renal injury in hypertension during aging.Methods Normotensive Wistar-Kyoto-rats (WKYs) were allocated to three groups by age of 3-month-old group,13-month-old group,22-month-old group.Gender,age and number-matched spontaneously hypertensive rats (SHRs) served as controls.Blood pressure was monitored.Levels of urinary albumin,urinary creatinine,serum creatinine (SCR),blood urea nitrogen (BUN),Ang Ⅱ in serum and in renal cortex were detected.The kidney ultrastructural changes and podocyte autophagosomes were observed under light and transmission electron microscopy.Expressions of nephrin,LC3B Ⅱ,Atg5 and p62 in glomeruli were analyzed by Western blotting.Results Blood pressure was significantly higher in SHRs than in WKYs (P＜0.05).During aging from 3-month-old to 13-month-old and to 22 monthold group,the urinary albumin/creatinine ratio was increased significantly in SHRs with hypertension and in WKYs with normotension [WKY:(0.12±0.01) g/mmol,(0.14±0.04) g/mmol vs.(0.34± 0.05) g/mmol;in SHR:(0.29±0.04) g/mmol,(0.31±0.05) g/mmol vs.(0.72±0.16) g/mmol,P＜0.05],but SCR and BUN levels had no significant difference in SHRs and WKYs during aging (both P＞0.05).And Ang Ⅱ levels in both serum and renal cortex had no significant change in normotension group during aging three time points (both P＞0.05).An age-dependent decrease of Ang Ⅱ level in renal cortex appeared during aging three time points in hypertensive rats [SHR:(0.02 ±0.00) μg/L,(0.02±0.00) μg/L vs.(0.01±0.00) μg/L,P＜0.05],but serum level of Ang Ⅱ had no significant difference during aging three time points (P＞ 0.05) in hypertension group.The structural changes,including glomerulosclerosis,tubular atrophy and interstitial fibrosis were observed during aging three time points both in normotensive and hypertensive rats,but these pathological changes were more serious in hypertensive rats.Autophagosomes relatively accumulated in aging normotensive rats.The protein expressions of LC3B Ⅱ,Atg5 and p62 were increased in normotensive rats during aging (all P＜0.05).While the protein expressions of nephrin,LC3B Ⅱ,Atg5 and p62 were decreased in aging hypertensive rats (all P ＜ 0.05).Conclusions Ang Ⅱ expression level in renal cortex is decreased during aging in hypertensive rats.Podocyte autophagic activity is relatively decreased during aging in normotensive rats,but is relatively increased during aging in hypertensive rats.Ang Ⅱ-induced podocyte autophagy may be involved in the pathogenesis of renal injury in hypertension during aging.