Tight blood pressure control decreases apoptosis during renal damage

An excess rate of apoptosis could lead to the gradual loss of renal mass. In this study, we investigated the role of apoptosis in the renal damage secondary to hypertension.

Spontaneously hypertensive rats with 5/6 renal mass reduction (subtotal nephrectomy) were distributed to receive no-treatment, 200 mg/L quinapril, 360 mg/L losartan, or triple therapy (200 mg/L hydralazine, 4 mg/L reserpine, and 100 mg/L hydrochlorothiazide) for 5 weeks. Sham-operated spontaneously hypertensive rats served as controls. Age-matched Wistar-Kyoto (WKY) rats, with or without subtotal nephrectomy, were also studied.

Nontreated spontaneously hypertensive rats + subtotal nephrectomy developed proteinuria, glomerular sclerosis, and tubulointerstitial lesions. In comparison to spontaneously hypertensive rats, an increment in the number of [proliferating cell nuclear antigen (PCNA)]-positive and apoptotic [terminal deoxynucleotidyl transferase (Tdt)-mediated deoxyuridine triphosphate biotin nick end labeling (TUNEL)]-positive tubular and glomerular cells was observed. By contrast, WKY + subtotal nephrectomy rats showed less severe morphologic lesions, and only the number of proliferating cells increased. By Western blot, an up-regulation of renal Bax (apoptosis inducer) was noted both in spontaneously hypertensive rats + subtotal nephrectomy and WKY + subtotal nephrectomy rats. By contrast, Bcl-xL (apoptosis protector) was up-regulated in WKY + subtotal nephrectomy rats but not in spontaneously hypertensive rats + subtotal nephrectomy. The administration of appropriate doses of quinapril, losartan, or triple therapy to spontaneously hypertensive rats + subtotal nephrectomy normalized systolic blood pressure, partially prevented proteinuria, renal lesions and apoptosis, and decreased Bax, but no changes were noted in Bcl-xL. The Bax/Bcl-xL index was significantly increased in spontaneously hypertensive rats + subtotal nephrectomy compared to sham-operated spontaneously hypertensive rats and decreased in treated groups.

The combination of renal mass reduction and hypertension caused severe renal lesions associated to an increment of apoptosis rate, mainly in tubular epithelial cells. Tight blood pressure control decreased the apoptosis rate and morphologic lesions. These studies suggest that changes in the expression of apoptosis-regulatory genes contribute to the progressive damage in hypertensive rats with renal mass reduction.