Enhanced acetylcholine-induced dilation in afferent arterioles in simvastatin-fed rats

Pitavastatin Upregulates Nitric Oxide Synthases in the Kidney of Spontaneously Hypertensive Rats and Wistar-Kyoto Rats

BACKGROUND

Clinical trials show potent renoprotective effects of pitavastatin (PTV), although the precise mechanism for these renoprotective effects is not fully clarified. The aim of this study was to examine the antihypertensive and renoprotective effects of PTV, focusing on the nitric oxide (NO) system.

METHODS

Male, 6-week-old, spontaneously hypertensive rats (SHR) and Wistar-Kyoto rats (WKY) were randomized to receive vehicle or PTV (2 mg/kg bodyweight) for 8 weeks. Blood pressure and urinary albumin excretion were measured every 2 weeks. After 8 weeks, plasma biochemical parameters and renal histology were examined. NO synthase isoform (neuronal, nNOS; inducible, iNOS; and endothelial, eNOS) expression and eNOS phosphorylation were examined by western blotting.

RESULTS

PTV attenuated hypertension and albuminuria development in SHR. PTV decreased glomerular desmin expression and medullary interstitial fibrosis in SHR. PTV tended to increase plasma NO in both strains but significantly increased urinary NO excretion only in WKY. PTV significantly increased nNOS and eNOS expression, enhanced eNOS phosphorylation at serine1177, and inhibited eNOS phosphorylation at threonine495 in the kidney of both strains.

CONCLUSIONS

PTV treatment led to increased renal NOS expression and upregulated eNOS activity in both SHR and WKY. The antihypertensive and renoprotective effects of PTV may be related to upregulation of the NO system.

Simvastatin and GGTI-2133, a geranylgeranyl transferase inhibitor, increase erythrocyte deformability but reduce low O(2) tension-induced ATP release

Statin drugs inhibit 3-hydroxy-3-methylglutaryl CoA reductase, which reduces the synthesis of both cholesterol and isoprenoids (geranylgeranyl pyrophosphate and farnesyl pyrophosphate), with the latter being lipid molecules responsible for the posttranslational modification of small GTP-binding proteins such as Rho. Effects of statins, independent of lowering blood cholesterol levels, are thought to occur by inhibition of Rho/Rho kinase. The Rho kinase inhibitor Y-27632 has been reported to increase both erythrocyte deformability and low O2 tension-induced ATP release. Here, we tested the hypothesis that by inhibiting Rho/Rho kinase, simvastatin would increase both erythrocyte deformability and low O2 tension-induced ATP release. Male Sprague-Dawley rats were divided into two groups, control or simvastatin treated [simvastatin-supplemented chow (0.02%)], for 4 wk. Simvastatin treatment increased rat erythrocyte deformability compared with controls (n = 6, P < 0.05). However, erythrocytes of simvastatin-treated rats (n = 9, P < 0.05) exhibited impaired low O2 tension-induced ATP release. Similarly, the geranylgeranyl transferase inhibitor GGTI-2133 (10 μM) also increased deformability and impaired low O2 tension-induced ATP release in healthy human erythrocytes (P < 0.05). Interestingly, ATP release in response to mastoparan 7 (n = 7, P < 0.05), which directly activates Gi, and isoproterenol (n = 5, P < 0.05), which signals through Gs, was not altered by incubation with GGTI-2133. These results suggest that although statins increase erythrocyte deformability, likely by inhibiting geranylgeranylation, the finding that both statins and a geranylgeranyl transferase inhibitor attenuated low O2 tension-induced ATP release demonstrates that factors in addition to erythrocyte deformability are critical for ATP release in response to this physiological stimulus.

Simvastatin attenuates contrast-induced nephropathy through modulation of oxidative stress, proinflammatory myeloperoxidase, and nitric oxide

Contrast media- (CM-) induced nephropathy is a serious complication of radiodiagnostic procedures. Available data suggests that the development of prophylaxis strategies is limited by poor understanding of pathophysiology of CM-induced nephropathy. Present study was designed to determine the role of oxidative stress, myeloperoxidase, and nitric oxide in the pathogenesis of iohexol model of nephropathy and its modification with simvastatin (SSTN). Adult Sprague Dawley rats were divided into seven groups. After 24 h of water deprivation, all the rats except in control and SSTN-only groups were injected (10 ml/kg) with 25% glycerol. After 30 min, SSTN (15, 30, and 60 mg/kg) was administered orally, daily for 4 days. Twenty-four hours after the glycerol injection, iohexol was infused (8 ml/kg) through femoral vein over a period of 2 min. All the animals were sacrificed on day 5 and blood and kidneys were collected for biochemical and histological studies. The results showed that SSTN dose dependently attenuated CM-induced rise of creatinine, urea, and structural abnormalities suggesting its nephroprotective effect. A significant increase in oxidative stress (increased lipid hydroperoxides and reduced glutathione levels) and myeloperoxidase (MPO) and decreased nitric oxide in CM group were reversed by SSTN. These findings support the use of SSTN to combat CM-induced nephrotoxicity.

Glomerular filtration rate and blood pressure are unchanged by increased sodium intake in atorvastatin-treated healthy men

OBJECTIVE

Improved cardiovascular survival during statin treatment might be due to effects in addition to cholesterol lowering. We hypothesize that sodium intake affects renal function and vasoactive hormones in atorvastatin-treated healthy subjects.

METHODS

In a randomized, placebo-controlled, double-blind, crossover study we measured the effect of a moderate change in sodium intake on glomerular filtration rate (GFR), blood pressure (BP), renal tubular function, plasma concentrations of vasoactive hormones and urinary excretion of aquaporin-2 (u-AQP2) in 22 healthy subjects. The subjects were randomized to standardized fluid intake and diet corresponding to the need for calories in the 4 days before each of the 2 examination days. In one of the periods they were randomized to receive sodium chloride tablets (2 g) thrice daily for 4 days. Two doses of atorvastatin (80 mg) were given; one at 2200 h the evening before the study day, the other at 0830 h in the morning.

RESULTS

24-h urinary sodium excretion increased by 23%. GFR and BP were unchanged. Sodium clearance, fractional excretion of sodium and u-AQP2 increased, whereas free water clearance decreased during high sodium intake. PRC and aldosterone were suppressed during the high sodium diet.

CONCLUSIONS

A change in dietary sodium intake of approximately 100 mmol daily does not change GFR and BP in atorvastatin-treated healthy men. The lack of change in BP might reflect that the subjects studied were not sodium sensitive, or that atorvastatin treatment modified sodium sensitivity.