Effects of lipid-lowering agents in the Dahl salt-sensitive rat

Long-term modifications of blood pressure in normotensive and spontaneously hypertensive rats by gene delivery of rAAV-mediated cytochrome P450 arachidonic acid hydroxylase

Arachidonic acid cytochrome P-450 (CYP) hydroxylase 4A isoforms, including 4A1, 4A2, 4A3 and 4A8 in the rat kidney, catalyze arachidonic acid to produce 19/20-Hydroxyeicosatetraenoic acids (20-HETE), a biologically active metabolite, which plays an important role in the regulation of blood pressure. However, controversial results have been reported regarding the exact role of 20-HETE on blood pressure. In the present study, we used recombinant adeno-associated viral vector (rAAV) to deliver CYP 4A1 cDNA and antisense 4A1 cDNA into Sprague-Dawley (SD) rats and spontaneously hypertensive rats (SHR), respectively, to investigate the effects of long-term modifications of blood pressure and the potential for gene therapy of hypertension. The mean systolic pressure increased by 14.2+/-2.5 mm Hg in rAAV.4A1-treated SD rats and decreased by 13.7+/-2.2 mm Hg in rAAV.anti4A1-treated SHR rats 5 weeks after the injection compared with controls and these changes in blood pressure were maintained until the experiments ended at 24 weeks. In 4A1 treated animals CYP4A was overexpressed in various tissues, but preferentially in the kidney at both mRNA and protein levels. In anti-4A1-treated SHR, CYP4A mRNA in various tissues was probed, especially in kidneys, but 4A1 protein expression was almost completely inhibited. These results suggest that arachidonic acid CYP hydroxylases contribute not only to the maintenance of normal blood pressure but also to the development of hypertension. rAAV-mediated anti4A administration strategy has the potential to be used as targeted gene therapy in human hypertension by blocking expression of CYP 4A in kidneys.

Statin Monotherapy Attenuates Renal Injury in a Salt-Sensitive Hypertension Model of Renal Disease

BACKGROUND

Several salutary biological effects of statins have been described. We sought to investigate more closely the anti-inflammatory and antiproliferative effects of simvastatin (SIMV) in a model of hypertension and progressive renal disease, as well as its effects on the cyclin-cdk inhibitors p21 and p27.

METHODS

Munich-Wistar rats received the nitric oxide (NO) synthase inhibitor L-NAME (25 mg/kg/day p.o.) for 20 days accompanied by a high-salt diet (HS, 3% Na) and then were kept on HS for 60 days. Animals were then divided into two groups: vehicle (VH) or SIMV 2 mg/kg/day p.o. Albuminuria and tail-cuff pressure were determined at 30 and 60 days. RT-PCR was done to assess renal expression of TGF-beta1, collagen I and III, fibronectin, p27, p21 and monocyte chemoattractant protein-1 (MCP-1). Renal protein expression was assessed by Western blot (proliferating cell nuclear antigen (PCNA)) and immunostaining (macrophage, lymphocyte, PCNA).

RESULTS

SIMV did not prevent the development of severe hypertension or albuminuria. SIMV-treated animals had less severe renal interstitial inflammation and cell proliferation. MCP-1 expression was significantly diminished in the SIMV-treated animals (55.4 +/- 7.3 vs. 84.4 +/- 8.2 OD, p = 0.02). mRNA renal expression for p27 and TGF-beta did not change between groups, but p21 mRNA renal expression, highly induced in this model, significantly decreased with SIMV treatment (31.6 +/- 6.6 vs. 50.2 +/- 5.8 OD, p < 0.05). The interstitial fibrosis score significantly decreased with SIMV (2.46 +/- 0.40 vs. 4.07 +/- 0.38%, p < 0.01), which was confirmed by a decrease in renal collagen I and fibronectin expression. Serum cholesterol level did not change with SIMV.

CONCLUSION

SIMV attenuated interstitial fibrosis associated with this model of hypertensive renal disease. The mechanism involved MCP-1 downregulation. SIMV treatment was also associated with a p21 downregulation in the kidney, which might be involved in the protection of renal scarring.

Simvastatin attenuates renal inflammation, tubular transdifferentiation and interstitial fibrosis in rats with unilateral ureteral obstruction

BACKGROUND

The pleiotropic actions of statins have been largely explored. These drugs have been tested in several models of progressive renal disease, most of them accompanied by hypertension. We sought to investigate more closely the effects of simvastatin on renal interstitial fibrosis due to unilateral ureteral obstruction (UUO).

METHODS

Munich-Wistar rats were submitted to UUO and studied after 14 days. Animals were divided into two groups: vehicle (VH) or simvastatin (SIMV) 2 mg/kg b.i.d. by gavage. At sacrifice kidneys were harvested for morphology, mRNA and protein analysis. RT-PCR was done to assess expression of collagen I and III, fibronectin, MCP-1, TGF-beta1 and bFGF. Protein expression was assessed by western blot (TGF-beta) and immunostaining (macrophage, lymphocyte, PCNA, vimentin and alpha-smooth muscle actin). Contralateral kidneys (CL) were used as controls.

RESULTS

SIMV-treated animals had less severe renal inflammation. MCP-1 was markedly expressed in obstructed kidneys and diminished with SIMV (48.9+/- 2.5 vs 64.3+/-3.1 OD in VH, P<0.01). Interstitial fibrosis (IF) was significantly attenuated with SIMV (8.2+/-1.3 vs 13.2+/-0.6%, P<0.01 SIMV vs VH), which was confirmed by a decrease in collagen I and fibronectin renal expression. Vimentin, a marker of dedifferentiation, was expressed in tubular cells of VH and decreased with SIMV treatment. alpha-SMA, a marker of myofibroblast-type cells, was increased in renal interstitium of VH rats and SIMV significantly reduced its expression. PCNA was increased in the UUO kidneys, but SIMV did not decrease tubular or interstitial proliferating cells. TGF-beta1, which was highly induced in the obstructed kidneys, decreased at the post-transcriptional level with SIMV treatment (5.35+/-0.75 vs 13.10+/-2.9 OD in VH, P<0.05). bFGF mRNA was also overexpressed in the obstructed kidneys, although SIMV treatment did not significantly decrease its expression.

CONCLUSIONS

SIMV had an evident protective effect on renal interstitial inflammation and fibrosis. It is conceivable that by attenuating inflammation, SIMV prevented tubular activation and transdifferentiation, two processes largely involved in the renal fibrosis of the UUO model.

Nitric oxide, angiotensin II, and hypertension

Although initially adaptive, the changes that accompany hypertension, namely, cell growth, endothelial dysfunction, and extracellular matrix deposition, eventually can become maladaptive and lead to end-organ disease such as heart failure, coronary artery disease, and renal failure. A functional imbalance between angiotensin II (Ang II) and nitric oxide (NO) plays an important pathogenetic role in hypertensive end-organ injury. NO, an endogenous vasodilator, inhibitor of vascular smooth muscle and mesangial cell growth, and natriuretic agent, is synthesized in the endothelium by a constitutive NO synthase. NO antagonizes the effects of Ang II on vascular tone, cell growth, and renal sodium excretion, and also down-regulates the synthesis of angiotensin-converting enzyme (ACE) and Ang II type 1 receptors. On the other hand, Ang II decreases NO bioavailability by promoting oxidative stress. A better understanding of the pathophysiologic mechanisms involved in hypertensive end-organ damage may aid in identifying markers of cardiovascular susceptibility to injury and in developing therapeutic interventions. We propose that those antihypertensive agents that lower blood pressure and concomitantly restore the homeostatic balance of vasoactive agents such as Ang II and NO within the vessel wall would be more effective in preventing or arresting end-organ disease.

Inhibition of the formation of EETs and 20-HETE with 1-aminobenzotriazole attenuates pressure natriuresis

This study examined the effects of chronic blockade of the renal formation of epoxyeicosatrienoic acids and 20-hydroxyeicosatetraenoic acid with 1-aminobenzotriazole (ABT; 50 mg·kg−1· day−1ip for 5 days) on pressure natriuresis and the inhibitory effects of elevations in renal perfusion pressure (RPP) on Na+-K+-ATPase activity and the distribution of the sodium/hydrogen exchanger (NHE)-3 in the proximal tubule of rats. In control rats ( n = 15), sodium excretion rose from 2.3 ± 0.4 to 19.4 ± 1.8 μeq·min−1·g kidney weight−1when RPP was increased from 114 ± 1 to 156 ± 2 mmHg. Fractional excretion of lithium rose from 28 ± 3 to 43 ± 3% of the filtered load. Chronic treatment of the rats with ABT for 5 days ( n = 8) blunted the natriuretic response to elevations in RPP by 75% and attenuated the increase in fractional excretion of lithium by 45%. In vehicle-treated rats, renal Na+-K+-ATPase activity fell from 31 ± 5 to 19 ± 2 μmol Pi·mg protein−1·h−1and NHE-3 protein was internalized from the brush border of the proximal tubule after an elevation in RPP. In contrast, Na+-K+-ATPase activity and the distribution of NHE-3 protein remained unaltered in rats treated with ABT. These results suggest that cytochrome P-450 metabolites of arachidonic acid contribute to pressure natriuresis by inhibiting Na+-K+-ATPase activity and promoting internalization of NHE-3 protein from the brush border of the proximal tubule.

Role of 20-hydroxyeicosatetraenoic acid and epoxyeicosatrienoic acids in hypertension

PURPOSE OF REVIEW

Cytochrome P-450 metabolites of arachidonic acid have been reported to play an important role in the control of renal function and vascular tone, and in the long-term control of arterial pressure. In this regard, 20-hydroxyeicosatetraenoic acid is a potent vasoconstrictor that inhibits sodium reabsorption in the kidney. Epoxyeicosatrienoic acids are endothelium-derived relaxing factors that hyperpolarize vascular smooth muscle cells and also promote sodium excretion in the kidney.

RECENT FINDINGS

Studies have demonstrated that the expression of cytochrome P-450 enzymes and the synthesis of 20-hydroxyeicosatetraenoic acid and epoxyeicosatrienoic acids in the kidney and peripheral vasculature are altered in many genetic and experimental models of hypertension. The production of these compounds is altered following exposure to high-salt or high-fat diets, in hepatorenal syndrome, in diabetes and in patients with toxemia of pregnancy. However, the functional significance of changes in the formation of 20-hydroxyeicosatetraenoic acid and epoxyeicosatrienoic acids in the pathogenesis of hypertension are just being uncovered.

SUMMARY

This review summarizes recent findings that address the issue of whether cytochrome P-450 metabolites of arachidonic acid play an important role in the regulation of renal tubular and peripheral vascular function and contribute to the pathogenesis of hypertension.

Lipid-lowering-independent effects of simvastatin on the kidney in experimental hypercholesterolaemia

BACKGROUND

Hypercholesterolaemia (HC), an independent risk factor for renal injury, is associated with formation of oxidized low-density-lipoprotein (ox-LDL), increased oxidative-stress and renal inflammation. HMG-CoA-reductase inhibitors are commonly used in HC, but their effects on renal haemodynamics and function in HC are poorly understood.

METHODS

Pigs were studied after a 12-week normal diet, a 2% high-cholesterol diet (HC) or an HC diet supplemented with simvastatin (HC+simvastatin, 80 mg/day) (n=6-8 each group). Renal haemodynamics and function were quantified in vivo with electron-beam computed tomography (EBCT). Shock-frozen renal tissue was subsequently studied using immunohistochemistry.

RESULTS

LDL cholesterol was similarly increased in HC and HC+simvastatin. Simvastatin-treated animals showed increased expression of endothelial nitric-oxide-synthase (eNOS), and decreased expression of the ox-LDL receptor LOX-1 in renal endothelial cells. Simvastatin also decreased tubular immunoreactivity of inducible-NOS, nitrotyrosine, nuclear-factor-kappaB, and tubuloglomerular trichrome staining. These were associated with a significant increase in cortical (6.1+/-0.1 vs 5.0+/-0.3 and 5.0+/-0.1 ml/min/cc, respectively, P<0.001) and medullary perfusion in HC+simvastatin compared to normal and HC.

CONCLUSIONS

Simvastatin attenuated the inflammatory and pro-oxidative environment as well as fibrosis in kidneys in pigs with diet-induced HC, in association with enhanced renal perfusion. These cholesterol-lowering-independent changes imply novel renoprotective effects of statins in the setting of HC and atherosclerosis.

Randomized, double-blind, placebo-controlled comparison of the action of orlistat, fluvastatin, or both an anthropometric measurements, blood pressure, and lipid profile in obese patients with hypercholesterolemia prescribed a standardized diet

OBJECTIVE

The aim of this study was to assess obese patients with hypercholesterolemia whom were prescribed a standardized diet, comparing the action of orlistat, fluvastatin, orlistat with fluvastatin, and placebo on anthropometric measurements, blood pressure (BP), and lipid profile.

METHODS

This was a 1-year, randomized, double-blind, placebo-controlled trial. The patients were prescribed a controlled-energy diet and were randomly allocated to receive placebo, orlistat 120 mg TID (O group), fluvastatin 80 mg/d (F group), or olistat 120 mg TID with fluvastatin 80 mg/d (OF group). Clinical measurements (body weight, body mass index [BMI], waist circumference, and BP) and lipid profile assessment (total cholesterol [TC], low-density lipoprotein cholesterol [LDL-C], high-density lipoprotein cholesterol [HDL-C], and triglycerides [TGs]) were performed at baseline and after 6 months and 1 year of treatment.

RESULTS

The study included 99 obese patients with hypercholesterolemia (48 men and 51 women; mean [SD] age, 51 [9] years). There were no significant differences between groups in baseline demographic, BP, or plasma lipid values. Three patients dropped out (2 women in the O group and 1 man in the OF group) due to adverse events related to orlistat treatment, including gastrointestinal events (oily spotting and fecal urgency). Ninety-six patients completed the study. There were significant differences from baseline (mean [SD]) in BMI, waist circumference reduction (WCR), and body weight loss (BWL) at 6 months in the OF group (29.9 [1.1] kg/m(2), 2.7 [0.8] cm, and 7.4 [0.9] kg, respectively; all P < 0.05), and BMI, WCR, and BWL at 1 year in the O group (29.0 [1.0] kg/m(2), 3.0 [1.0] cm, and 8.6 [1.0] kg, respectively; all P < 0.02), the F group (29.3 [1.6] kg/m(2), 2.4 [1.0] cm, and 8/0 [1.0] kg, respectively; all P < 0.05), and the OF group (28.4 [0.6] kg/m(2), 4.0 [0.6] cm, and 11.4 [1.0] kg, respectively; all P < 0.01). Significant reductions from baseline in systolic and diastolic BP were observed at 1 year in the O and F groups (all P < 0.05) and the OF group (both P < 0.01). At 6 months, there were significant reductions from baseline in TC and LDL-C in the F group (both P < 0.05) and in TC, LDL-C, and TGs in the OF group (P < 0.02, P < 0.02, and P < 0.05, respectively), as well as a significant increase in HDL-C in the OF group (P < 0.02). At 1 year, there were significant reduction from baseline in TC in the O, F, and OF groups (P < 0.05 and P < 0.01, respectively), LDL-C (P < 0.05, P < 0.02, and P < 0.01, respectively), and TGs (P < 0.02, P < 0.05, and P < 0.02, respectively). Also at 1 year, HDL-C was significantly higher than baseline in the F and OF groups (P < 0.02 and P < 0.01, respectively).

CONCLUSION

Improvements in clinical and lipid-profile parameters were found at 1 year with all 3 treatments.

Atorvastatin causes depressor and sympatho-inhibitory effects with upregulation of nitric oxide synthases in stroke-prone spontaneously hypertensive rats

OBJECTIVE

Recent studies have suggested that statins decrease blood pressure in hypertensive animals and upregulate endothelial nitric oxide synthase (eNOS) expression. However, the effects of statins on the expression of nitric oxide synthase (NOS) in the brain and the sympathetic nervous system remain to be elucidated. The aim of this study was thus to examine the effects of atorvastatin on blood pressure, sympathetic nerve activity, and the expression of NOS in stroke-prone spontaneously hypertensive rats (SHRSP) as well as in Wistar-Kyoto (WKY) rats.

METHODS

The animals received atorvastatin (50 mg/kg per day) for 30 days. Systolic blood pressure and heart rate were evaluated using the tail-cuff method. Urinary norepinephrine excretion was measured for 24 h. The expression of eNOS, neuronal NOS (nNOS), and inducible NOS (iNOS) in the brain (cortex, cerebellum, hypothalamus and brainstem), aorta and heart were determined by Western blot analysis.

RESULTS

Systolic blood pressure and 24-h urinary norepinephrine excretion were significantly decreased in SHRSP, but not in WKY, after the treatment with atorvastatin. The eNOS and iNOS expression in the brain and aorta was significantly increased in atorvastatin-treated SHRSP and WKY. However, the nNOS expression in the brain was not altered in the atorvastatin-treated group.

CONCLUSIONS

These results suggest that atorvastatin decreases blood pressure, at least in part via the reduction of sympathetic nervous system activity in SHRSP. They also suggest that this sympatho-inhibitory effect may be mediated by an increase in NO production, with the upregulation of eNOS expression in the brain.

Use of lipid-lowering drugs and blood pressure control in patients with arterial hypertension

A large proportion of patients have both hypertension and hypercholesterolemia, two of the most important risk factors for cardiovascular diseases. Statins are the most widely used drugs for the treatment of plasma lipid abnormalities and have been reported to interact with elevated blood pressure. A reduction in blood pressure associated with the use of these agents has been reported in patients with untreated hypertension and in patients treated with antihypertensive drugs, particularly angiotensin-converting enzyme inhibitors and calcium channel blockers. This effect on blood pressure control has also been observed in diabetic patients. The mechanism responsible for the hypotensive effect seems to be largely independent of the effect of statins on plasma cholesterol, and probably is related to the interaction of the medications with endothelial function or angiotensin II receptors. The capacity of statins to improve blood pressure control may represent a useful tool for improvement in the prevention of cardiovascular diseases.

Simvastatin improves endothelial function in spontaneously hypertensive rats through a superoxide dismutase mediated antioxidant effect

BACKGROUND

Hydroxymethylglutaryl coenzyme A (HMGCoA) reductase inhibitors have beneficial effects beyond their cholesterol-lowering properties. The antioxidant mechanism of HMGCoA reductase inhibitors is not completely understood.

OBJECTIVES

To elucidate the antioxidant effect of simvastatin.

METHODS

We studied the influence of simvastatin treatment on the development of hypertension, modification of antioxidant systems, and reactivity of aortic rings in Wistar-Kyoto (WKY) and spontaneously hypertensive (SHR) rats.

RESULTS

Simvastatin had no effect on blood pressure (BP). Simvastatin treatment (either 1 or 2 mg/kg body weight for 12 or 20 weeks) increased superoxide dismutase (SOD) and glutathione peroxidase (GPx) activities in SHR rats compared with untreated control SHR rats. Carbachol-induced relaxation of aortic rings was impaired in control SHR rats and was restored by simvastatin treatment. Addition of SOD improved the response in control SHR rats and did not have any effect in treated SHR rats. Addition of diethyldithiocarbamic acid, a selective inhibitor of SOD, produced a mild non-significant impairment in carbachol-induced relaxation in control SHR rats, suggesting a deficient antioxidant system in these animals. However, in treated SHR and in WKY rats, impairment of the relaxation was marked, implying that SOD activity in these animals was important to maintain endothelial function. In aortic rings without endothelium from SHR rats, contraction induced by free radicals was substantially higher than in WKY rats. This effect was attenuated in 1-mg-treated rats and abolished in 2-mg-treated rats.

CONCLUSIONS

Simvastatin promotes intracellular antioxidant systems, fundamentally SOD, restoring endothelial function but not having any effect on blood pressure.

P-450 metabolites of arachidonic acid in the control of cardiovascular function

Recent studies have indicated that arachidonic acid is primarily metabolized by cytochrome P-450 (CYP) enzymes in the brain, lung, kidney, and peripheral vasculature to 20-hydroxyeicosatetraenoic acid (20-HETE) and epoxyeicosatrienoic acids (EETs) and that these compounds play critical roles in the regulation of renal, pulmonary, and cardiac function and vascular tone. EETs are endothelium-derived vasodilators that hyperpolarize vascular smooth muscle (VSM) cells by activating K(+) channels. 20-HETE is a vasoconstrictor produced in VSM cells that reduces the open-state probability of Ca(2+)-activated K(+) channels. Inhibitors of the formation of 20-HETE block the myogenic response of renal, cerebral, and skeletal muscle arterioles in vitro and autoregulation of renal and cerebral blood flow in vivo. They also block tubuloglomerular feedback responses in vivo and the vasoconstrictor response to elevations in tissue PO(2) both in vivo and in vitro. The formation of 20-HETE in VSM is stimulated by angiotensin II and endothelin and is inhibited by nitric oxide (NO) and carbon monoxide (CO). Blockade of the formation of 20-HETE attenuates the vascular responses to angiotensin II, endothelin, norepinephrine, NO, and CO. In the kidney, EETs and 20-HETE are produced in the proximal tubule and the thick ascending loop of Henle. They regulate Na(+) transport in these nephron segments. 20-HETE also contributes to the mitogenic effects of a variety of growth factors in VSM, renal epithelial, and mesangial cells. The production of EETs and 20-HETE is altered in experimental and genetic models of hypertension, diabetes, uremia, toxemia of pregnancy, and hepatorenal syndrome. Given the importance of this pathway in the control of cardiovascular function, it is likely that CYP metabolites of arachidonic acid contribute to the changes in renal function and vascular tone associated with some of these conditions and that drugs that modify the formation and/or actions of EETs and 20-HETE may have therapeutic benefits.

Statins and blood pressure regulation

Hypertension and high serum cholesterol levels are two of the most relevant risk factors for cardiovascular diseases. A combined increase in both risk factors has been reported in a significant proportion of patients with coronary artery disease. Statins are the most widely used drugs to treat hypercholesterolemia, and they interact with blood pressure control in different populations of hypertensive patients. A significant reduction in blood pressure associated with the use of statins has been described in patients with untreated hypertension and in patients treated with antihypertensive drugs, particularly angiotensin converting enzyme inhibitors and calcium channel blockers. The effect of statins on blood pressure control has also been reported in diabetic patients. The mechanisms responsible for the hypotensive effect seem to be largely independent of the effect of statins on lipid profile, and are probably related to their interaction with endothelial function or angiotensin II receptors. The capacity of statins to improve blood pressure control could be a useful consideration for an integrated approach to better prevention of cardiovascular diseases.

Cytochrome P450 metabolites of arachidonic acid in the control of renal function

Recent studies indicate that arachidonic acid is primarily metabolized by cytochrome P450 enzymes of the 4A and 2C families in the kidney to 20-hydroxyeicosatetraenoic acid (HETE), epoxyeicosatrienoic acids (EETs) and dihydroxyeicosatrienoic acids. These compounds play central roles in the regulation of renal tubular and vascular function. 20-HETE is produced by renal vascular smooth muscle (VSM) cells and is a potent constrictor that depolarizes VSM cells by blocking the calcium-activated potassium channel. Inhibition of the formation of 20-HETE blocks the myogenic response of isolated renal arterioles in vitro, and autoregulation of renal blood flow and tubuloglomerular feedback responses in vivo. EETs are products formed in the endothelium and are potent dilators that activate the calcium-activated potassium channel in renal VSM. Endothelial-dependent vasodilators stimulate the release of EETs, and these compounds appear to serve as an endothelial-derived hyperpolarizing factor. EETs and 20-HETE are produced in the proximal tubule. There, they regulate sodium/potassium-ATPase activity and serve as second messengers for the natriuretic effects of dopamine, parathyroid hormone and angiotensin II. 20-HETE is also produced in the thick ascending loop of Henle. It regulates sodium-potassium-chloride transport in this nephron segment. The renal production of cytochrome P450 metabolites of arachidonic acid is altered in hypertension, diabetes, toxemia of pregnancy, and hepatorenal syndrome. Given the importance of cytochrome P450 metabolites of arachidonic acid in the control of renal function, it is likely that changes in this system contribute to the abnormalities in renal function that are associated with many of these conditions.

Cerivastatin prevents angiotensin II-induced renal injury independent of blood pressure- and cholesterol-lowering effects

BACKGROUND

Statins are effective in prevention of end-organ damage; however, the benefits cannot be fully explained on the basis of cholesterol reduction. We used an angiotensin II (Ang II)-dependent model to test the hypothesis that cerivastatin prevents leukocyte adhesion and infiltration, induction of inducible nitric oxide synthase (iNOS), and ameliorates end-organ damage.

METHODS

We analyzed intracellular targets, such as mitogen-activated protein kinase and transcription factor (nuclear factor-kappaB and activator protein-1) activation. We used immunohistochemistry, immunocytochemistry, electrophoretic mobility shift assays, and enzyme-linked immunosorbent assay techniques. We treated rats transgenic for human renin and angiotensinogen (dTGR) chronically from week 4 to 7 with cerivastatin (0.5 mg/kg by gavage).

RESULTS

Untreated dTGR developed hypertension, cardiac hypertrophy, and renal damage, with a 100-fold increased albuminuria and focal cortical necrosis. dTGR mortality at the age of seven weeks was 45%. Immunohistochemistry showed increased iNOS expression in the endothelium and media of small vessels, infiltrating cells, afferent arterioles, and glomeruli of dTGR, which was greater in cortex than medulla. Phosphorylated extracellular signal regulated kinase (p-ERK) was increased in dTGR; nuclear factor-kappaB and activator protein-1 were both activated. Cerivastatin decreased systolic blood pressure compared with untreated dTGR (147 +/- 14 vs. 201 +/- 6 mm Hg, P < 0.001). Albuminuria was reduced by 60% (P = 0.001), and creatinine was lowered (0.45 +/- 0.01 vs. 0.68 +/- 0.05 mg/dL, P = 0. 003); however, cholesterol was not reduced. Intercellular adhesion molecule-1 and vascular cell adhesion molecule-1 expression was diminished, while neutrophil and monocyte infiltration in the kidney was markedly reduced. ERK phosphorylation and transcription factor activation were reduced. In addition, in vitro incubation of vascular smooth muscle cells with cerivastatin (0.5 micromol/L) almost completely prevented the Ang II-induced ERK phosphorylation.

CONCLUSION

Cerivastatin reduced inflammation, cell proliferation, and iNOS induction, which led to a reduction in cellular damage. Our findings suggest that 3-hydroxy-3-methylglutaryl coenzyme (HMG-CoA) reductase inhibition ameliorates Ang II-induced end-organ damage. We suggest that these effects were independent of cholesterol.

Fenofibrate lowers blood pressure in two genetic models of hypertension

Fenofibrate, a commonly used lipid lowering drug, induces the expression of the gene coding for cytochrome P450-4A, whose major product is 20-hydroxyeicosatetraenoic acid (20-HETE). 20-HETE, a potassium channel antagonist, could increase or decrease blood pressure (BP). We studied the effects of four weeks of oral fenofibrate on BP, urine output (UVol), plasma renin activity (PRA), and urine protein excretion in young (4-5 weeks) stroke prone spontaneously hypertensive rats (SHRSP), older (25 weeks) SHRSP, Dahl salt sensitive rats (Dahl S) on a high salt diet, Dahl S rats on a normal salt diet, and normotensive Sprague-Dawley (SD) rats. Fenofibrate prevented the increase in BP in 4-5 week old SHRSP, reduced BP in 25 week old SHRSP, but had no effect on BP in normotensive SD rats. Similarly, fenofibrate prevented the increase in BP in Dahl S rats on a high salt diet, but had no effect in Dahl S rats on a low salt diet. Fenofibrate increased UVol (and reduced weight gain) in young SHRSP and tended to increase it in other groups. It also increased PRA 2 to 5-fold in all groups except older SHRSP. Young SHRSP receiving fenofibrate excreted significantly less urine protein than control rats. The drug reduced proteinuria in Dahl S rats on high salt diet, but had no significant effect on proteinuria in other groups. In summary, fenofibrate reduced blood pressure and weight gain, increased UVol and PRA, and reduced urine protein excretion in young SHRSP. Other groups of animals showed these changes to a variable, but directionally similar extent. These findings are consistent with a natriuretic effect of fenofibrate.

Key words: hypertension, animal models, natriuresis, fenfibrate, lipid lowering agents.

Use of statins and blood pressure control in treated hypertensive patients with hypercholesterolemia

High serum cholesterol has been frequently reported in patients with arterial hypertension in whom it might influence the blood pressure control. The aim of this study was to compare the extent of blood pressure changes in 41 patients with hypertension and hypercholesterolemia, taking antihypertensive drugs and treated for 3 months with statins (HC-S; pravastatin or simvastatin) and compared with matched controls with high (HC-D; 44) or normal serum cholesterol (NC-D; 45) undergoing antihypertensive treatment combined with dietary treatment alone. After 3 months of follow-up, a greater reduction of systolic (SBP) and diastolic (DBP) blood pressure values was observed in HC-S patients (ASBP/DBP, -11.3 +/-3/-10.6 +/- 2%) when compared with both HC-D (deltaSBP/DBP, -6.6 +/- 2/-6.1 +/- 2%; p < 0.05) and NC-D (deltaSBP/DBP, -6.9 +/- 2/-6.8 +/- 1.5%; p < 0.05). In statin-treated patients, a slight linear relation has been found between the percentage changes in DBP and those in plasma total cholesterol (R = 0.37, p = 0.043), whereas no relation was found with SBP changes (R =0.11; p = 0.35). In conclusion, the results of this study demonstrate that the use of statins in combination with antihypertensive drugs can improve blood pressure control in patients with uncontrolled hypertension and high serum cholesterol levels. The additional blood pressure reduction observed in patients treated with statins is clinically relevant and only partially related to the lipid-lowering effect.

Cholesterol enhances contractile responses in isolated small mesenteric arteries of normotensive and spontaneously hypertensive rats

OBJECTIVE

In order to examine possible mechanisms by which hypercholesterolemia may contribute to the development of cardiovascular disease, we investigated the effect of cholesterol enrichment on contractility in isolated small rat mesenteric arteries.

DESIGN

Contractile responses of cholesterol-enriched isolated small mesenteric arteries of normotensive Wistar-Kyoto (WKY) rats and spontaneously hypertensive rats (SHR) were compared with control groups.

METHODS

First- to second-order mesenteric arteries (327-349 microm internal lumen diameter) were dissected from the mesenteric bed of 10-20-week-old male WKY rats and SHR, and incubated in cholesterol-free and cholesterol-rich (150 microg/ml) medium. Isolated arteries were mounted on a Mulvany-Halpern myograph for measurement of isometric tension.

RESULTS

Cholesterol significantly increased active wall tension and active wall pressure in WKY rat arteries and active wall tension in SHR arteries in response to potassium chloride, norepinephrine and serotonin (P < 0.05). In addition, contractile responses to all agonists were significantly higher in cholesterol-enriched SHR arteries compared with cholesterol-enriched WKY rat vessels (P < 0.05).

CONCLUSIONS

These findings suggest that elevated cholesterol content enhances agonist-stimulated contractility in small mesenteric resistance arteries, providing a possible mechanism by which hypercholesterolemia may contribute to the development of hypertension.

Pravastatin sodium activates endothelial nitric oxide synthase independent of its cholesterol-lowering actions

OBJECTIVES

We tested the hypothesis that pravastatin (PRA) activates endothelial nitric oxide synthase (eNOS).

BACKGROUND

Pravastatin has been found to have clinical benefits beyond those predicted by its actions in reducing plasma low density lipoprotein cholesterol (LDL). Both PRA and simvastatin (SIM) are equally effective in reducing LDL, but only PRA reduces platelet aggregation and is an effective vasodilator. Nitric oxide (NO) also inhibits platelet aggregation and vasodilates.

METHODS

We determined PRA and SIM effects on vasorelaxation in aortic rings and NO production by cultured bovine aortic endothelial cells. Nitric oxide was measured by using a NO electrode and by an assay for conversion of hemoglobin to methemoglobin. Specificity of NOS activation was tested by using the NOS inhibitor nitro-L-arginine methyl ester (L-NAME, 1 mmol/liter) in the presence or absence of excess L-arginine (L-ARG, 1 mmol/liter).

RESULTS

Endothelium-dependent vasorelaxation was maximal with acetylocholine (ACH, 100%), followed by PRA (62.8%) and then SIM (37.1%). Direct measurement of NO confirmed that vasorelaxation is due to NO release and showed that PRA and ACH had similar dose-dependent effects on NO production, while SIM was only 25% to 30% as effective. Methemoglobin assay confirmed these results and demonstrated their specificity for NOS activity. The L-NAME blunted the responses to 45% of initial values. Excess L-ARG reversed this effect and potentiated NO production to 133% of initial levels.

CONCLUSIONS

Both PRA and SIM activate eNOS, but SIM is much less effective. Clinical benefits with PRA not explained by LDL reductions may be the result of an independent action of PRA on eNOS activation.