The proinflammatory cytokines TNF-alpha and IL-1 beta impair economy of contraction in human myocardium.

Considerable experimental evidence has accumulated over the past years that proinflammatory cytokines, especially TNF-alpha and IL-1beta, impair myocardial function in different animal species. On the other hand, several prospective clinical trials studying TNF-alpha antagonist in patients with chronic heart failure were not able to demonstrate a benefit. As there might be a relevant species-related discrepancy, we intended to prove our previous results demonstrating impaired myocardial economy after exogenous administration of recombinant TNF-alpha in rat myocardium. In the present study, both TNF-alpha and IL-1beta not only revealed an immediate negative inotropic effect but also increased specific oxygen demand in human right-atrial myocardium. Enhanced oxygen consumption was not caused by an elevated basal metabolism but an impaired economy of contraction. Our results suggest that proinflammatory cytokines have a considerable effect on myocardial mechano-energetic parameters in human myocardium as well.

Influence of aldosterone vs. endothelin receptor antagonism on renovascular function in liquorice-induced hypertension.

BACKGROUND: The enzyme 11beta-hydroxysteroid dehydrogenase type 2 (11beta-HSD2) provides mineralocorticoid receptor specificity for aldosterone by metabolizing glucocorticoids to their receptor inactive 11-dehydro derivatives. Inhibition of 11beta-HSD2 by liquorice-derived glycyrrhizic acid (GA) therefore results in sodium retention and hypertension. The present study investigated the effect of the aldosterone receptor antagonist spironolactone in comparison with the endothelin ET(A) receptor antagonist darusentan on renovascular endothelial function in liquorice-induced hypertension. METHODS: GA, a recognized inhibitor of 11beta-HSD2 was supplemented to the drinking water (3 g/l) of Wistar Kyoto rats over a period of 21 days. From day 8 to 21, spironolactone (5.8+/-0.6 mg/kg/day), darusentan (45.2+/-6.5 mg/kg/day), or placebo was added to chow (n=7 per group). After the animals were killed, vascular function of isolated renal artery segments was assessed by isometric tension recording. RESULTS: Relaxation of pre-constricted renal artery segments in response to acetylcholine (10(-10) to 10(-5) mol/l) was impaired by GA as compared with controls (12+/-4% vs 98+/-5% of norepinephrine 3x10(-7) mol/l), whereas endothelium independent relaxations were unaffected. Endothelin receptor antagonism improved renovascular endothelium-dependent relaxation (32+/-4%, P<0.05 vs placebo) whereas endothelium-dependent relaxation was completely normalized by aldosterone receptor antagonism (85+/-4%, P<0.01 vs placebo). CONCLUSIONS: In GA-induced hypertension, both aldosterone receptor antagonism and endothelin receptor antagonism normalize blood pressure and improve renovascular function and, thus, may represent a new therapeutic approach in cardiovascular disease associated with impaired 11beta-HSD2 activity.

Abnormalities in uremic lipoprotein metabolism and its impact on cardiovascular disease.

Patients with end-stage renal disease (ESRD) suffer from a secondary form of complex dyslipidemia consisting of both quantitative and qualitative abnormalities in serum lipoproteins resulting from alterations in lipoprotein metabolism and composition. The prominant features of uremic dyslipidemia are an increase in serum triglyceride levels (due to elevated very low density lipoprotein [VLDL]-remnants and intermediate-density lipoprotein [IDL]) and low high-density lipoprotein (HDL) cholesterol. Low-density lipoprotein (LDL) cholesterol often is normal, but the cholesterol may originate from the atherogenic small and dense LDL subclass (sdLDL). The apolipoprotein B (apoB)-containing part of the lipoprotein may undergo modifications (enzymatic- and advanced glycation end-product [AGE]-peptide modification, oxidation, or glycosilation). Modifications contribute to impaired LDL receptor-mediated clearance from plasma and promote prolonged circulation. While LDL particles undergo a vicious cycle of accumulation and modification, reverse cholesterol transport is also impaired due to low lecithin:cholesterol acyltransferase (LCAT) and paraoxonase activity. Therefore, discoid HDL particles are structurally altered and hepatic cholesterol clearance is limited. The composition of HDL may also be altered during states of inflammation. The contribution of this complex and atherogenic form of dyslipidemia to cardiovascular disease in patients with renal disease is unclear at present. Most studies are negative in demonstrating the predictive power of serum lipids for the development of cardiovascular disease. This is most likely due to interference with deteriorating aspects of the activated acute-phase response. Nevertheless, patients with renal disease belong to a very high cardiovascular risk group and dyslipidemia should most likely be subjected to sufficient lipid-lowering therapy in most patients. Because it is also still unclear whether we have available therapies with sufficient impact on LDL size, remnant lipoprotein-lowering, and restoration of HDL function, we urgently need the results from large scale intervention trials such as the 4D-trial and the CHORUS study.

Endothelin 1 type a receptor antagonism prevents vascular dysfunction and hypertension induced by 11beta-hydroxysteroid dehydrogenase inhibition: role of nitric oxide.

BACKGROUND: The enzyme 11beta-hydroxysteroid dehydrogenase (11beta-HSD) prevents inappropriate activation of the nonselective mineralocorticoid receptors by glucocorticoids. Renal activity of 11beta-HSD is decreased in patients with apparent mineralocorticoid excess (SAME), licorice-induced hypertension, and essential hypertension. Although expressed in vascular cells, the role of 11beta-HSD in the regulation of vascular tone remains to be determined. METHODS AND RESULTS: lycyrrhizic acid (GA; 50 mg/kg IP, twice daily for 7 days) caused a significant inhibition of 11beta-HSD activity and induced hypertension in Wistar-Kyoto rats (157 versus 127 mm Hg in controls; P<0.01). After 11beta-HSD inhibition, aortic endothelial nitric oxide (NO) synthase (eNOS) protein content, nitrate tissue levels, and acetylcholine-induced release of NO were blunted (all P<0.05 versus controls). In contrast, vascular prepro-endothelin (ET)-1 gene expression, ET-1 protein levels, and vascular reactivity to ET-1 were enhanced by GA treatment (P<0.05 versus controls). Chronic ET(A) receptor blockade with LU135252 (50 mg. kg(-1). d(-1)) normalized blood pressure, ET-1 tissue content, vascular reactivity to ET-1, vascular eNOS protein content, and nitrate tissue levels and improved NO-mediated endothelial function in GA-treated rats (P<0.05 to 0.01 versus untreated and verapamil-treated controls). In human endothelial cells, GA increased production of ET-1 in the presence of corticosterone, which indicates that activation of the vascular ET-1 system by 11beta-HSD inhibition can occur independently of changes in blood pressure but is dependent on the presence of glucocorticoids. CONCLUSIONS: Chronic ET(A) receptor blockade normalizes blood pressure, prevents upregulation of vascular ET-1, and improves endothelial dysfunction in 11beta-HSD inhibitor-induced hypertension and may emerge as a novel therapeutic approach in cardiovascular disease associated with reduced 11beta-HSD activity.

Chronic vasopeptidase inhibition restores endothelin-converting enzyme activity and normalizes endothelin levels in salt-induced hypertension.

BACKGROUND: Vasopeptidase inhibition (VPI) represents a new therapeutic principle including both inhibition of angiotensin-converting enzyme (ACE) and neutral endopeptidase (NEP). The present study investigated the effect of the vasopeptidase inhibitor omapatrilat on endothelin-1 (ET-1)-mediated vascular function in salt-induced hypertension. METHODS: Dahl salt-sensitive rats (n=6/group) on standard or salt-enriched (4% NaCl) chow were treated for 8 weeks with either omapatrilat (36+/-4 mg/kg/day), captopril (94+/-2 mg/kg/day) or placebo. Aortic and renal artery segments were isolated and suspended in organ chambers for isometric tension recording. Functional endothelin-converting enzyme (ECE) activity was assessed in native segments and after preincubation with omapatrilat. Furthermore, vascular ECE protein levels as well as plasma and tissue ET-1 levels were determined. RESULTS: The increase in systolic blood pressure of salt-fed rats was prevented by omapatrilat and captopril to a comparable degree. In salt-induced hypertension, functional ECE activity (calculated as the ratio of the contraction to big ET-1 divided by the contraction to ET-1) in renal arteries (0.46+/-0.05) and in aorta (0.68+/-0.05) was reduced as compared with control animals (0.9+/-0.05 and 0.99+/-0.04, respectively; P<0.05). While omapatrilat in vitro blunted the response to big endothelin-1 (big ET-1) and diminished ECE activity further (P<0.01 vs native segments), chronic treatment with omapatrilat in vivo restored contractions to ET-1 (120+/-6%) and big ET-1 (98+/-9%) in renal arteries, and therefore normalized renovascular ECE activity. In addition, omapatrilat normalized plasma ET-1 concentrations (12.9+/-1.2 vs 16.6+/-1.4 pg/ml on high salt diet; P<0.05) and renovascular ECE protein levels. CONCLUSIONS: In salt-induced hypertension, vasopeptidase inhibition restores alterations in the endothelin system, such as renovascular ECE activity and responsiveness to ET-1 and big ET-1 with chronic but not acute in vitro application. Thus, the beneficial effects of vasopeptidase inhibition may reflect a resetting of cardiovascular control systems and therefore may be particularly suited to treat hypertension and heart failure.

Vasopeptidase inhibition exhibits endothelial protection in salt-induced hypertension.

Omapatrilat represents a new class of drugs capable of inhibiting both ACE and neutral endopeptidase 24.11, the so-called vasopeptidase inhibitors. It therefore contributes to neurohumoral modulation, which might improve endothelial function in cardiovascular diseases. This study investigated the effect of omapatrilat in comparison to the ACE inhibitor captopril on systolic blood pressure and endothelial function in salt-induced hypertension. Dahl salt-sensitive rats (n=6/group) on standard or salt-enriched (4% NaCl) chow were treated for 8 weeks with either omapatrilat (36+/-4 mg/kg per day), captopril (94+/-2 mg/kg per day), or placebo. Aortic rings were then isolated and suspended in organ chambers for isometric tension recording. Systolic blood pressure of salt-fed, placebo-treated animals increased to 196+/-6 mm Hg, which was prevented by omapatrilat (162+/-5 mm Hg, P<0.05) and captopril (164+/-7 mm Hg, P<0.05) to a comparable degree. In control rats, acetylcholine (10(-10) to 10(-5) mol/L) induced endothelium-dependent relaxation (97+/-4%), which was reduced by high-salt diet to 30+/-5% (P<0.005; n=6). Omapatrilat improved relaxation to a greater extent (86+/-5%) than did captopril (57+/-6%; P<0.05). eNOS protein expression and aortic nitrite/nitrate content were reduced in hypertensive rats and improved by both omapatrilat and captopril. Aortic endothelin-1 levels were increased in salt-fed animals and unaffected by omapatrilat or captopril. These data suggest that despite comparable blood pressure, omapatrilat is superior to captopril in improving endothelium-dependent relaxation in salt-sensitive hypertension.

Aldosterone receptor antagonism normalizes vascular function in liquorice-induced hypertension.

The enzyme 11beta-hydroxysteroid dehydrogenase (11beta-HSD2) provides mineralocorticoid receptor specificity for aldosterone by metabolizing glucocorticoids to their receptor-inactive 11-dehydro derivatives. The present study investigated the effects of the aldosterone receptor antagonists spironolactone and eplerenone on endothelial function in liquorice-induced hypertension. Glycyrrhizic acid (GA), a recognized inhibitor of 11beta-HSD2, was supplemented to the drinking water (3 g/L) of Wistar-Kyoto rats over a period of 21 days. From days 8 to 21, spironolactone (5.8+/-0.6 mg. kg(-1). d(-1)), eplerenone (182+/-13 mg. kg(-1). d(-1)), or placebo was added to the chow (n=7 animals per group). Endothelium-dependent or -independent vascular function was assessed as the relaxation of preconstricted aortic rings to acetylcholine or sodium nitroprusside, respectively. In addition, aortic endothelial nitric oxide synthase (eNOS) protein content, nitrate tissue levels, and endothelin-1 (ET-1) protein levels were determined. GA increased systolic blood pressure from 142+/-8 to 185+/-9 mm Hg (P<0.01). In the GA group, endothelium-dependent relaxation was impaired compared with that in controls (73+/-6% versus 99+/-5%), whereas endothelium-independent relaxation remained unchanged. In the aortas of 11beta-HSD2-deficient rats, eNOS protein content and nitrate tissue levels decreased (1114+/-128 versus 518+/-77 microgram/g protein, P<0.05). In contrast, aortic ET-1 protein levels were enhanced by GA (308+/-38 versus 497+/-47 pg/mg tissue, P<0.05). Both spironolactone and eplerenone normalized blood pressure in animals on GA (142+/-9 and 143+/-9 mm Hg, respectively, versus 189+/-8 mm Hg in the placebo group; P<0.01), restored endothelium-dependent relaxation (96+/-3% and 97+/-3%, respectively, P<0.01 versus placebo), blunted the decrease in vascular eNOS protein content and nitrate tissue levels, and normalized vascular ET-1 levels. This is the first study to demonstrate that aldosterone receptor antagonism normalizes blood pressure, prevents upregulation of vascular ET-1, restores NO-mediated endothelial dysfunction, and thus, may advance as a novel and specific therapeutic approach in 11beta-HSD2-deficient hypertension.

Dyslipidemia and renal disease: pathogenesis and clinical consequences.

Patients with chronic renal disease suffer from a secondary form of complex dyslipidemia. The most important abnormalities are an increase in serum triglyceride levels (elevated VLDL-remnants/IDL), small LDL particles and a low HDL cholesterol level. The highly atherogenic LDL subclass, namely LDL-6 or small dense LDL, accumulates preferentially in hypertriglyceridemic diabetic patients with nephropathy or on hemodialysis treatment. All these lipoprotein particles contain apolipoprotein B, thus the complex disorder can be summarized as an elevation of triglyceride-rich apolipoprotein B-containing complex lipoprotein particles. Growing evidence suggests that all of the components of this type of dyslipidemia are independently atherogenic. These particles, specifically the apolipoprotein B moiety, are predominantly prone to modification such as oxidation and glycosilation, which contributes to impaired clearance by the LDL receptor. These complex alterations in lipoprotein composition not only passively accompany chronic renal disease but on the contrary also promote its progression and the development of atherosclerosis. Therefore, renal patients with dyslipidemia should be subjected to lipid-lowering therapy. The effectiveness of lipid lowering on the reduction of cardiovascular endpoints or the progression of renal disease is under investigation or remains to be studied.

Lipid changes and statins in chronic renal insufficiency and dialysis.

Chronic renal failure patients suffer from a secondary form of complex dyslipidemia, similar to the so-called atherogenic dyslipidemia in insulin resistant patients or to diabetic dyslipidemia. The most important abnormalities are an increase in the serum level of triglyceride (elevated VLDL-remnants/IDL), small LDL particles and a low HDL cholesterol. The highly atherogenic LDL subclass, namely LDL-6 or small dense LDL, accumulates in hypertriglyceridemic diabetic hemodialysis patients. All these lipoprotein particles contain apoB, thus much of this complex disorder can be summarized as an elevation of triglyceride-rich apoB containing complex lipoprotein particles. Growing evidence suggests that all of the components of this type of dyslipidemia are independently atherogenic. Further disturbances exist in the dynamics of cholesterol exchange between the various lipoprotein particles and in transport from cells to catabolic sites. The European Joint Task Force and the US National Cholesterol Education Program expert panel have issued guidelines for the general population to lower the cardiovascular risk in hyper- and dyslipidemias. There is preliminary consensus that these guidelines should be applied to dialysis patients. However, the genesis of atherosclerosis in the dialysis population may be different and real benefit from lipid-lowering has not yet been demonstrated in this population. Large-scale, prospective randomized trials (4D-trial, HARP) are underway to determine whether statins reduce cardiovascular complications in diabetic and non-diabetic patients with end-stage renal disease (ESRD) and on hemodialysis treatment.

Abnormal lipid metabolism after renal transplantation.

The evidence that lipid disorders in patients following renal transplantation play a major role in the pathogenesis of atherosclerosis and chronic renal allograft rejection is circumstantial. The high rate of clinical vascular disease and cardiovascular complications in renal transplant recipients, the high prevalence of an atherogenic dyslipidemia and the evidence from the statin regression trials in the general population suggest that lipid lowering treatment is beneficial in patients after renal transplantation. In addition, animal models and observational studies in patients have demonstrated correlations between plasma lipid levels and both acute and chronic rejection. Animal transplant models and clinical trials in heart transplant patients also suggest that statin treatment decreases the incidence of chronic rejection. However, the mechanisms behind this protective effect remain unsolved and no conclusive data exist proving that statins directly inhibit the development of chronic rejection. However, sufficient evidence exists to consider the use of these agents in the posttransplant setting for their possible effects on cardiovascular complications.

Enhanced peroxynitrite formation is associated with vascular aging.

Vascular aging is mainly characterized by endothelial dysfunction. We found decreased free nitric oxide (NO) levels in aged rat aortas, in conjunction with a sevenfold higher expression and activity of endothelial NO synthase (eNOS). This is shown to be a consequence of age-associated enhanced superoxide (.O(2)(-)) production with concomitant quenching of NO by the formation of peroxynitrite leading to nitrotyrosilation of mitochondrial manganese superoxide dismutase (MnSOD), a molecular footprint of increased peroxynitrite levels, which also increased with age. Thus, vascular aging appears to be initiated by augmented.O(2)(-) release, trapping of vasorelaxant NO, and subsequent peroxynitrite formation, followed by the nitration and inhibition of MnSOD. Increased eNOS expression and activity is a compensatory, but eventually futile, mechanism to counter regulate the loss of NO. The ultrastructural distribution of 3-nitrotyrosyl suggests that mitochondrial dysfunction plays a major role in the vascular aging process.

Nitric oxide prevents cardiovascular disease and determines survival in polyglobulic mice overexpressing erythropoietin.

Nitric oxide (NO) induces vasodilatatory, antiaggregatory, and antiproliferative effects in vitro. To delineate potential beneficial effects of NO in preventing vascular disease in vivo, we generated transgenic mice overexpressing human erythropoietin. These animals induce polyglobulia known to be associated with a high incidence of vascular disease. Despite hematocrit levels of 80%, adult transgenic mice did not develop hypertension or thromboembolism. Endothelial NO synthase levels, NO-mediated endothelium-dependent relaxation and circulating and vascular tissue NO levels were markedly increased. Administration of the NO synthase inhibitor N(G)-nitro-L-arginine methyl ester (L-NAME) led to vasoconstriction of peripheral resistance vessels, hypertension, and death of transgenic mice, whereas wild-type siblings developed hypertension but did not show increased mortality. L-NAME-treated polyglobulic mice revealed acute left ventricular dilatation and vascular engorgement associated with pulmonary congestion and hemorrhage. In conclusion, we here unequivocally demonstrate that endothelial NO maintains normotension, prevents cardiovascular dysfunction, and critically determines survival in vivo under conditions of increased hematocrit.

Tissue endothelin-converting enzyme activity correlates with cardiovascular risk factors in coronary artery disease.

BACKGROUND: Endothelin-converting enzymes (ECEs) are the key enzymes in endothelin-1 (ET-1) generation. However, their pathophysiological role in patients with cardiovascular disease remains elusive. METHODS AND RESULTS: Vascular reactivity to big endothelin-1 (bigET-1; 10(-9) to 10(-7) mol/L) and ET-1 (10(-9) to 10(-7) mol/L) were examined in the internal mammary artery (IMA, n=33) and saphenous vein (SV, n=27) of patients with coronary artery disease with identified cardiovascular risk factors. Vascular ECE activity was determined by conversion of exogenously added bigET-1 to ET-1. Tissue contents of bigET-1 and ET-1 were measured by radioimmunoassay. In addition, the effects of LDL and oxidized LDL on ECE-1 protein levels were determined by Western blot analysis in human IMA endothelial cells. In the IMA, vascular ECE activity showed an inverse correlation with serum LDL levels (r=-0.76; P<0.01) and systolic and diastolic blood pressure and a positive correlation with fibrinogen (r=0.58; P<0.05). In the SV, fibrinogen was the only parameter to be correlated with vascular ECE activity. Vascular tissue content of bigET-1 was attenuated in the IMA of patients with hyperfibrinogenemia but increased in patients with elevated systolic blood pressure and increased serum LDL levels (P<0.05). Most interestingly, LDL and oxidized LDL downregulated ECE-1 protein levels in human IMA endothelial cells (P<0.05). CONCLUSIONS: These data demonstrate, for the first time, that vascular ECE activity is (1) inversely correlated with serum LDL levels and blood pressure and (2) positively associated with fibrinogen in human vascular tissue. Hence, ECE-1 activity may modulate cardiovascular risk in patients with coronary artery disease.

Impact of dyslipidaemia in renal transplant recipients.

The evidence that lipid disorders in patients following renal transplantation play a major role in the pathogenesis of atherosclerosis and chronic renal allograft rejection is circumstantial. The absolute rate of clinical vascular disease and cardiovascular complications in transplant patients, the high prevalence of an atherogenic lipid profile and the evidence from the large HMG-CoA reductase inhibitor (statin) regression trials in the general population suggest that lipid lowering treatment is necessary in most patients after renal transplantation. Furthermore, animal models and observational studies in patients have found correlations between plasma lipid levels and both acute and chronic rejection. Animal transplant models and clinical trials in heart transplant patients also suggest that statin treatment decrease the incidence of chronic rejection in a manner that may also be independent of lipid lowering. Although the mechanisms behind this protective effect remains unclear, statins may be the first agents to be effective in preventing chronic rejection and in reducing the rate of cardiovascular complication in renal transplant recipients.

Immunosuppression enhances atherogenicity of lipid profile after transplantation.

BACKGROUND: Patients after renal transplantation exhibit high cardiovascular morbidity and mortality because of the accumulation of cardiovascular risk factors such as hypertension or dyslipidemia. To elucidate the influence of immunosuppressive therapy on hyperlipidemia, we studied serum lipids and lipoproteins in renal transplant patients who received prednisone and either azathioprine or cyclosporine or triple immunosuppressive therapy. METHODS: Serum lipids and lipoprotein levels were measured in 216 renal transplant patients (81 female and 135 male) with stable graft function of 4.8 +/- 2.3 years (range six months to eight years) after transplantation. Patients were divided into three groups according to one of the following immunosuppressive regimens: (a) prednisone and azathioprine, (b) prednisone and cyclosporine, or (c) prednisone, azathioprine, and cyclosporine. Healthy, age- and sex-matched subjects served as controls. In addition to measurement of total serum lipids, lipoproteins were isolated by preparative ultracentrifugation, and lipids were determined in very low-density lipoprotein (VLDL), low-density lipoprotein (LDL), and high-density lipoprotein (HDL) density classes. RESULTS: Total serum triglycerides, VLDL, and LDL triglycerides, as well as VLDL cholesterol were elevated in all renal transplant patients, but elevation was pronounced in female patients. In contrast to total serum cholesterol, which was significantly increased in only female patients, elevation of LDL-triglyceride/apo B ratio was more marked in male patients. Patients in group A exhibited only mild hypertriglyceridemia, whereas triglyceride enrichment in VLDL and LDL was more distinct in group B and was most pronounced in patients of group C. Furthermore, hypertriglyceridemia increased with the dose of administered prednisone. CONCLUSIONS: Immunosuppressive therapy in renal transplant patients leads to accumulation of triglyceride-enriched VLDL and LDL. Triglyceride enrichment in LDL indicates the accumulation of small, dense LDLs, which are known to bear enhanced atherosclerotic risk. This study provides data that underline the use of individually adjusted immunosuppressive therapy and steroid-sparing protocols in renal transplant patients to improve their atherogenic lipoprotein profile.