Carvedilol and its metabolites suppress endothelin-1 production in human endothelial cell culture

Beta-blocker efficacy for intra- and interdialytic hypertension patients: a systematic review and meta-analysis

PURPOSE

Intradialytic hypertension affects 5-15% of hemodialysis patients, yet relevant studies are relatively scarce. It is also associated with higher interdialytic blood pressure. Beta-blockers can be preferred as antihypertensive drugs due to their superior blood pressure control, decreased risk of cardiovascular events, improved endothelial cell function, and decreased noradrenaline levels. Through this study, beta-blocker antihypertensive effects in intra- and interdialytic hypertension were analyzed.

METHODS

Systematic review and meta-analysis were performed following PRISMA guidelines. We registered our PROSPERO protocol (Registration ID: CRD42023446184) and included relevant full-text clinical trials or RCTs from 2008 to 2023 with predetermined keywords and criteria from multiple databases including PUBMED, COCHRANE, SCOPUS, and citation searching. Seven eligible articles were included in this review study.

RESULTS

Four studies with 82 participants for intradialytic hypertension evaluation were included. Meta-analysis showed a decrease in SBP in intradialytic hypertensive patients after beta-blocker intervention, with a significant estimated mean difference of - 15.19 mmHg (P < 0.00001; 95% CI - 19.47 to - 10.91). Supporting previous data, SBP remains constant between pre- and post-dialysis with beta-blocker therapy, with an insignificant estimated mean difference of - 2.72 mmHg (P = 0.29; 95% CI - 7.80 to 2.36). Whereas five studies with 142 participants were included for interdialytic hypertension evaluation. Meta-analysis shows a significant decrease in SBP before to after therapy, with an estimated mean difference of - 10.92 (P < 0.0001; 95% CI - 16.33 to - 5.51).

CONCLUSION

Beta-blocker treatment resulted in significant reductions in post-hemodialysis systolic blood pressure among intra- and interdialytic hypertensive patients.

Management of intradialytic hypertension: current evidence and future perspectives

Intradialytic hypertension (IDH), that is, a paradoxical rise in blood pressure (BP) during or immediately after a hemodialysis session, affects approximately 10-15% of the hemodialysis population. It is currently recognized as a phenomenon of major clinical significance as recent studies have shown that BP elevation extends to the whole interdialytic interval and associates with increased cardiovascular and all-cause mortality. The pathophysiology of IDH is complex involving volume and sodium overload, endothelial dysfunction, excess renin-angiotensin-aldosterone system and sympathetic nervous system activation, and other mechanisms. For several years, there was a scarcity of studies regarding IDH treatment; recently, however, several attempts to examine the effect of nonpharmacological and pharmacological measures on BP levels in IDH are made. This review attempts to summarize this latest evidence in the field of management of IDH and discuss areas for future research.

A Potential Route to Reduce Ischemia/Reperfusion Injury in Organ Preservation

The pathophysiological process of ischemia and reperfusion injury (IRI), an inevitable step in organ transplantation, causes important biochemical and structural changes that can result in serious organ damage. IRI is relevant for early graft dysfunction and graft survival. Today, in a global context of organ shortages, most organs come from extended criteria donors (ECDs), which are more sensitive to IRI. The main objective of organ preservation solutions is to protect against IRI through the application of specific, nonphysiological components, under conditions of no blood or oxygen, and then under conditions of metabolic reduction by hypothermia. The composition of hypothermic solutions includes osmotic and oncotic buffering components, and they are intracellular (rich in potassium) or extracellular (rich in sodium). However, above all, they all contain the same type of components intended to protect against IRI, such as glutathione, adenosine and allopurinol. These components have not changed for more than 30 years, even though our knowledge of IRI, and much of the relevant literature, questions their stability or efficacy. In addition, several pharmacological molecules have been the subjects of preclinical studies to optimize this protection. Among them, trimetazidine, tacrolimus and carvedilol have shown the most benefits. In fact, these drugs are already in clinical use, and it is a question of repositioning them for this novel use, without additional risk. This new strategy of including them would allow us to shift from cold storage solutions to cold preservation solutions including multitarget pharmacological components, offering protection against IRI and thus protecting today's more vulnerable organs.

Potential Protective Role of Blood Pressure-Lowering Drugs on the Balance between Hemostasis and Fibrinolysis in Hypertensive Patients at Rest and During Exercise

In patients with hypertension, the triad represented by endothelial dysfunction, platelet hyperactivity, and altered fibrinolytic function disturbs the equilibrium between hemostasis and fibrinolysis and translates into a hypercoagulable state, which underlies the risk of thrombotic complications. This article reviews the scientific evidence regarding some biological effects of antihypertensive drugs, which can protect patients from the adverse consequences of hypertensive disease, improving endothelial function, enhancing antioxidant activity, and restoring equilibrium between hemostatic and fibrinolytic factors. These protective effects appear not to be mediated through blood pressure reduction and are not shared by all molecules of the same pharmacological class.

Protective Antioxidant Effects of Carvedilol in a Rat Model of Ischaemia-reperfusion Injury

This study investigated the protective effects of carvedilol, a potent antioxidant, in a rat model of tourniquet-induced ischaemia-reperfusion injury of the hind limb. Thirty rats were divided equally into three groups: the control group (group 1) was only anaesthetized, without creating an ischaemia-reperfusion injury; group 2 was submitted to ischaemia (4 h), followed by a 2-h reperfusion period; and group 3 was pre-treated with carvedilol (2 mg/kg per day) for 10 days prior to ischaemia-reperfusion. Ischaemia-reperfusion produced a significant decrease in superoxide dismutase and glutathione peroxidase activities in the liver, lungs, muscle and serum compared with control treatment, and pre-treatment with carvedilol prevented these changes. Ischaemia-reperfusion caused a significant increase in malondialdehyde and nitric oxide (NO) levels in liver, lungs, muscle (except NO) and serum compared with control treatment, and carvedilol prevented these changes. In conclusion, it might be inferred that carvedilol could be used safely to prevent oxidative injury during reperfusion following ischaemia in humans.

Mechanisms and Treatment of Intradialytic Hypertension

BACKGROUND

Intradialytic hypertension is a condition where there is an increase in blood pressure (BP) from pre- to post-hemodialysis; this condition has been recently identified as an independent mortality risk factor in hypertensive hemodialysis patients. The mechanisms and management of intradialytic hypertension have been explored in numerous research studies over the past few years.

SUMMARY

Patients with intradialytic hypertension have been found to be more chronically volume overloaded compared to other hemodialysis patients, although no causal role has been established. Patients with intradialytic hypertension have intradialytic vascular resistance surges that likely explain the BP increase during dialysis. Acute intradialytic changes in endothelial cell function have been proposed as etiologies for the increase in vascular resistance, although it is unclear if endothelin-1 or some other vasoconstrictive peptide is responsible. There is an association between dialysate to serum sodium gradients and BP increase during dialysis in patients with intradialytic hypertension, although it is unclear if this is related to endothelial cell activity or acute osmolar changes. In addition to probing the dry weight of patients with intradialytic hypertension, other management strategies include lowering dialysate sodium and changing antihypertensives to include carvedilol or other poorly dialyzed antihypertensives.

KEY MESSAGES

Hemodialysis patients with intradialytic hypertension have an increased mortality risk compared to patients with modest decreases in BP during dialysis. Intradialytic hypertension is associated with extracellular volume overload in addition to acute increases in vascular resistance during dialysis. Management strategies should include reevaluation of dry weight and modification of both the dialysate prescription and medication prescription.

Anti-neuroinflammatory effects of the calcium channel blocker nicardipine on microglial cells: implications for neuroprotection

BACKGROUND/OBJECTIVE

Nicardipine is a calcium channel blocker that has been widely used to control blood pressure in severe hypertension following events such as ischemic stroke, traumatic brain injury, and intracerebral hemorrhage. However, accumulating evidence suggests that inflammatory processes in the central nervous system that are mediated by microglial activation play important roles in neurodegeneration, and the effect of nicardipine on microglial activation remains unresolved.

METHODOLOGY/PRINCIPAL FINDINGS

In the present study, using murine BV-2 microglia, we demonstrated that nicardipine significantly inhibits microglia-related neuroinflammatory responses. Treatment with nicardipine inhibited microglial cell migration. Nicardipine also significantly inhibited LPS plus IFN-γ-induced release of nitric oxide (NO), and the expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2). Furthermore, nicardipine also inhibited microglial activation by peptidoglycan, the major component of the Gram-positive bacterium cell wall. Notably, nicardipine also showed significant anti-neuroinflammatory effects on microglial activation in mice in vivo.

CONCLUSION/SIGNIFICANCE

The present study is the first to report a novel inhibitory role of nicardipine on neuroinflammation and provides a new candidate agent for the development of therapies for inflammation-related neurodegenerative diseases.

The pathogenesis and management of hypertension in diabetic kidney disease

Hypertension commonly coexists with diabetes, and its prevalence is even higher in the presence of diabetic kidney disease. The pathogenesis of hypertension in this population stems from increased extracellular volume and increased vasoconstriction that results from mechanisms that may be attributed to both diabetes and the eventual impairment of renal function. Antihypertensive therapy aimed at reducing blood pressure remains a primary goal in preventing the incidence of diabetic kidney and slowing its progression. Initial therapy should consist of an ACE inhibitor or ARB titrated to the maximally tolerated dose. Using combination RAAS therapy further reduces proteinuria, but the benefits of this strategy compared with the potential risks of hyperkalemia and acute deterioration of renal function are still unknown. Endothelin receptor antagonists also lower proteinuria, but these can be associated with volume overload and edema with no clear long-term benefit on renal function yet identified. Further large clinical trials are needed to better understand how progression to ESRD can be slowed or halted in patients with diabetic kidney disease.

Probing the mechanisms of intradialytic hypertension: a pilot study targeting endothelial cell dysfunction

BACKGROUND AND OBJECTIVES

Intradialytic hypertension may be caused by an impaired endothelial cell response to hemodialysis. Carvedilol has been shown to improve endothelial cell function in vivo and to block endothelin-1 release in vitro. This study hypothesized that carvedilol would improve endothelial cell function and reduce the occurrence of intradialytic hypertension.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

A prospective 12-week pilot study of carvedilol titrated to 50 mg twice daily was performed among 25 hemodialysis participants with intradialytic hypertension. Each patient served as his or her own control. Paired tests were used to analyze changes in BP and endothelial cell function--assessed by flow-mediated vasodilation, endothelial progenitor cells (aldehyde dehydrogenase bright activity and CD34(+)CD133(+)), asymmetric dimethylarginine, and endothelin-1--from baseline to study end.

RESULTS

Flow-mediated vasodilation was significantly improved with carvedilol (from 1.03% to 1.40%, P=0.02). There was no significant change in endothelial progenitor cells, endothelin-1, or asymmetric dimethylarginine. Although prehemodialysis systolic BP was unchanged (144-146 mmHg, P=0.5), posthemodialysis systolic BP, 44-hour ambulatory systolic BP, and the frequency of intradialytic hypertension decreased with carvedilol (159-142 mmHg, P<0.001; 155-148 mmHg, P=0.05; and 77% [4.6 of 6] to 28% [1.7 of 6], P<0.001, respectively).

CONCLUSIONS

Among hemodialysis participants with intradialytic hypertension, targeting endothelial cell dysfunction with carvedilol was associated with modest improvements in endothelial function, improved intradialytic and interdialytic BP, and reduced frequency of intradialytic hypertension. Randomized controlled trials are required to confirm these findings.

Intradialytic hypertension: a less-recognized cardiovascular complication of hemodialysis

Intradialytic hypertension, defined as an increase in blood pressure during or immediately after hemodialysis that results in postdialysis hypertension, has long been recognized to complicate the hemodialysis procedure, yet often is largely ignored. In light of recent investigations suggesting that intradialytic hypertension is associated with adverse outcomes, this review broadly covers the epidemiologic characteristics, prognostic significance, potential pathogenic mechanisms, prevention, and possible treatment of intradialytic hypertension. Intradialytic hypertension affects up to 15% of hemodialysis patients and occurs more frequently in patients who are older, have lower dry weights, are prescribed more antihypertensive medications, and have lower serum creatinine levels. Recent studies associated intradialytic hypertension independently with higher hospitalization rates and decreased survival. Although the pathophysiologic mechanisms of intradialytic hypertension are uncertain, it likely is multifactorial and includes subclinical volume overload, sympathetic overactivity, activation of the renin-angiotensin system, endothelial cell dysfunction, and specific dialytic techniques. Prevention and treatment of intradialytic hypertension may include careful attention to dry weight, avoidance of dialyzable antihypertensive medications, limiting the use of high-calcium dialysate, achieving adequate sodium solute removal during hemodialysis, and using medications that inhibit the renin-angiotensin-aldosterone system or decrease endothelin 1 levels. In summary, although intradialytic hypertension often is underappreciated, recent studies suggest that it should not be ignored. However, further work is necessary to elucidate the pathophysiologic mechanisms of intradialytic hypertension and its appropriate management and determine whether treatment of intradialytic hypertension can improve clinical outcomes.

Effects of antihypertensive drugs on alcohol-induced functional responses of cultured human endothelial cells

Alcohol-induced endothelial changes might contribute to an increase in blood pressure in regular alcohol consumers. Some antihypertensive drugs affect oxidative stress and endothelial function and might counteract the effects of alcohol at the cellular level. The aim of this study was to investigate in vitro the effects of three different types of antihypertensive agents on alcohol-induced endothelial responses and oxidative stress. Cultured human endothelial cells were exposed to increasing concentrations (1, 10, 60 micromol/L) of zofenoprilat, carvedilol, and lacidipine in the absence and in the presence of ethanol (140 mmol/L). Concentrations of endothelin (ET) and nitric oxide (NO) were measured in the culture media as markers of endothelial function, and malondialdehyde (MDA) and intracellular glutathione (GSHi) were measured as markers of oxidative stress. Exposure to alcohol increased the levels of ET, NO, and MDA, and decreased GSHi. Carvedilol and zofenoprilat were more effective than lacidipine in counteracting the effects of alcohol on ET production. Alcohol-induced NO production was enhanced by carvedilol, whereas zofenoprilat and lacidipine did not have a significant effect. The alcohol-induced increase in MDA concentrations was blunted by all three drugs, but only carvedilol restored a normal response. All three drugs increased GSHi levels, with the effect being greater for carvedilol and lacidipine than zofenoprilat. Carvedilol is more effective than zofenoprilat and lacidipine in counteracting alcohol-induced endothelial responses in vitro and in decreasing oxidative stress. These effects might be particularly beneficial in patients with alcohol-related hypertension.

The vasodilatory beta-blockers

Although well established in treating hypertension and cardiovascular (CV) disease, clinical trial data suggest that beta-blockers (eg, atenolol) may be less effective than other antihypertensive classes in reducing stroke and CV mortality despite similar blood pressure (BP) reductions. One possible explanation is that atenolol is less effective in reducing central aortic pressure. Newer vasodilating beta-blockers may prove more effective in reducing central pressure and cardiovascular events. Carvedilol and labetalol appear to cause vasodilation through alpha(1)-receptor blockade; nebivolol induces endothelium-dependent vasodilation by stimulating nitric oxide bioactivity. Their favorable hemodynamic profile includes reduction of peripheral vascular resistance (PVR) while maintaining or improving cardiac output (CO), stroke volume, and left ventricular function, whereas nonvasodilating beta-blockers tend to raise PVR and reduce CO and left ventricular function. Compared with conventional beta-blockers, vasodilating beta-blockers have beneficial hemodynamic effects including decreased pressure wave reflection from the periphery, leading to decreases in central aortic blood pressure. Larger trials are needed to determine whether reduced central pressure will translate into improved CV outcomes compared with nonvasodilating beta-blockers.

Inflammation in hypertension

PURPOSE OF REVIEW

In this review we summarize the recent evidence that highlights the involvement of low-grade inflammation in the development and pathophysiology of hypertension.

RECENT FINDINGS

Essential hypertension is characterized by increased peripheral vascular resistance to blood flow, due in large part to vascular remodeling. Vascular changes in hypertension are associated with mechanical and humoral factors that modulate signaling events, resulting in abnormal function, media growth, extracellular matrix deposition and inflammation. Recent evidence suggests that inflammation is present in the vasculature in animal models of hypertension. Inflammatory markers, such as C-reactive protein, are associated with vascular lesions in humans, and are predictive of cardiovascular outcome. In animal and human studies, pro-inflammatory components of the renin-angiotensin-aldosterone system have been demonstrated in large conduit and small arteries in the kidney and heart. Peroxisome proliferator-activated receptor activators are drugs with metabolic properties that have been demonstrated to exert anti-inflammatory effects on the vasculature, and there is now evidence that these actions may be protective for blood vessels.

SUMMARY

Inflammatory processes are important participants in the pathophysiology of hypertension and cardiovascular disease. The identification of the mechanisms leading to the activation of inflammation should contribute to the development of specific therapeutic approaches to apply in hypertension and its complications.

Carvedilol inhibits basal and stimulated ACE production in human endothelial cells

Angiotensin-converting enzyme (ACE) plays an important role in the pathophysiology of cardiovascular disease. We examined the effect of carvedilol, a cardiovascular drug, on basal and stimulated ACE production in human endothelial cells. Carvedilol (0.625-5 microM), in a concentration-dependent manner, inhibited basal and vascular endothelial growth factor (VEGF, 0.5 nM) or phorbol 12-myristate 13-acetate (PMA, 10 nM) induced ACE up-regulation. Carvedilol has non-selective beta-adrenoceptor and selective alpha1-adrenoceptor blocking activity, calcium channel blocking, and anti-oxidant activity. To study whether these activities were related to ACE down-regulation, endothelial cells were treated with metoprolol (1-10 microM), propranolol (1-10 microM), prazosin (1-5 microM), nicardipine (1-10 microM), probucol (1-100 microM), or ascorbic acid (1-100 microM). None of these compounds modified ACE. VEGF (0.5 nM) and PMA (10 nM) induced PKC phosphorylation, which was inhibited by co-treatment of cell cultures with carvedilol (5 microM). In conclusion, carvedilol inhibited basal and VEGF or PMA induced ACE up-regulation. Inhibition of PKC phosphorylation was probably involved in carvedilol action.

Switching between beta blockers in heart failure patients: rationale and practical considerations

The clinical benefit of beta blockade has been proven in a variety of pathologic settings, including hypertension, angina pectoris, acute- and post-myocardial infarction, and congestive heart failure. However, beta blockers do not all share the same clinical outcomes with respect to efficacy or safety in many of these conditions. This is especially true in HF, where differences in reverse remodeling and effects on the periphery may be important differentiating factors leading to improved efficacy. In fact, beta blockers are a heterogeneous group of agents with respect to pharmacology, receptor biology, hemodynamic effects, and tolerability. As cardiovascular disease progresses, the issue of switching from one b blocker to another is an important consideration as to how to optimize the effectiveness of adrenergic blockade. Because of the differences among beta blockers, switching should be conducted in a manner that takes into account pharmacologic differences. For example, the similarities and differences of receptor subtype blockade of the two agents and the potential effects of ancillary properties. Two protocols for switching between carvedilol, a third-generation nonselective agent with vasodilation through alpha1 blockade, and a beta1-selective agent (e.g., metoprolol, atenolol) are described to simplify the process and maximize the safety and tolerability of this procedure. The optimal selection and use of adrenergic-blocking agents in the cardiovascular continuum will assist in providing improved management while minimizing safety and tolerability concerns.

Carvedilol: molecular and cellular basis for its multifaceted therapeutic potential

Carvedilol is a unique cardiovascular drug of multifaceted therapeutic potential. Its major molecular targets recognized to date are membrane adrenoceptors (beta 1, beta 2, and alpha 1), reactive oxygen species, and ion channels (K+ and Ca2+). Carvedilol provides prominent hemodynamic benefits mainly through a balanced adrenoceptor blockade, which causes a reduction in cardiac work in association with peripheral vasodilation. This drug assures remarkable cardiovascular protection through its antiproliferative/atherogenic, antiischemic, antihypertrophic, and antiarrhythmic actions. These actions are a consequence of its potent antioxidant effects, amelioration of glucose/lipid metabolism, modulation of neurohumoral factors, and modulation of cardiac electrophysiologic properties. The usefulness of carvedilol in the treatment of hypertension, ischemic heart disease, and congestive heart failure is based on a combination of hemodynamic benefits and cardiovascular protection.

Circulating endothelial nitric oxide synthase inhibitory factor in some patients with chronic renal disease

BACKGROUND

Chronic renal disease (CRD) is associated with hypertension and reduced synthesis of nitric oxide (NO). Here, we investigated whether there is a circulating endothelial NO synthase (eNOS) inhibitory factor(s) in some patients with CRD that might directly influence endothelial NOS.

METHODS

Human dermal microvascular endothelial cells (HDMECs) were incubated for six hours with 20% plasma from subjects with normal renal function (PCr = 0.8 +/- 0.2 mg%), and patients with moderate renal insufficiency of various causes (PCr = 4.0 +/- 1.5 mg%) and impact on NOS activity, transport of L-arginine, and abundance of eNOS protein were measured. Plasma concentrations of asymmetric and symmetric dimethyl L-arginine (ADMA and SDMA) were also measured.

RESULTS

There was no effect of any human plasma on L-arginine transport. The NOS activity was variable in CRD patients and fell into two subgroups: CRD I, individual values similar to control, and CRD II, individual values lower than control mean. The effect of CRD plasma on NOS activity in cultured cells was not related to the primary disease, but was predicted by plasma ADMA levels since plasma ADMA was elevated in CRD II versus both control and CRD I. Blood urea nitrogen and creatinine levels were uniformly elevated in CRD plasma. The abundance of eNOS protein was unaffected by plasma.

CONCLUSION

High plasma levels of ADMA in CRD patients are independent of reduced renal clearance, suggesting an alteration in ADMA synthesis and/or degradation. High ADMA is a marker and is partly responsible for the inhibition of eNOS activity in cultured cells and may also result in reduced eNOS activity in vivo, with consequent hypertension.

Antioxidant action of the antihypertensive drug, carvedilol, against lipid peroxidation

The action of carvedilol, a vasodilating, beta-adrenoceptor blocking agent, against lipid peroxidation has been the subject of many studies, but the results reported thus far are contradictory. In an attempt to define the antioxidant mechanism of carvedilol against lipid peroxidation, the dynamics of the action of carvedilol were studied in several oxidation systems. We investigated the reactivity of carvedilol toward radicals and its inhibitory effect on lipid peroxidation induced by several kinds of initiating species such as azo compounds and metal ions in solution, micelles, membranes, and low-density lipoprotein. Carvedilol exerted poor reactivity toward phenoxyl, alkoxyl, and peroxyl radicals in acetonitrile solution nor did it show an appreciable antioxidant effect against either the peroxyl radical-induced oxidation of methyl linoleate in acetonitrile or against phosphatidylcholine liposomal membranes in aqueous suspension. Carvedilol completely inhibited the ferric ion-induced oxidation of methyl linoleate micelles by sequestering ferric ions, but not by reducing hydroperoxide. It was shown that carvedilol enhanced the oxidation of micelles induced by either methemoglobin or peroxyl radical. Carvedilol, which was added exogenously, did not suppress the oxidation of isolated low-density lipoprotein induced by peroxyl radical or cupric ion. These results show that carvedilol does not act as a radical-scavenging antioxidant, but that it does act most efficiently as an antioxidant against ferric ion-induced oxidation by sequestering ferric ion.

Disparate effects of carvedilol versus metoprolol treatment of stroke-prone spontaneously hypertensive rats on endothelial function of resistance arteries

In human hypertension, blockade of beta-adrenoceptors does not improve resistance artery structure or endothelial dysfunction. We tested in hypertensive rats the hypothesis that carvedilol, a beta-blocker with antioxidant properties, would improve endothelial dysfunction, whereas the beta1-selective blocker, metoprolol, would not. Twenty-week-old SHRSP were treated orally for 10 weeks with carvedilol (50 mg/kg/day) or metoprolol (100 mg/kg/day), with or without hydralazine (25 mg/kg/day), the latter because neither beta-blocker was a very effective blood pressure-lowering agent in this model. Mesenteric arteries (lumen, <300 microm) were studied on a pressurized myograph. After 10 weeks, untreated SHRSP had a systolic blood pressure (mm Hg) of 239+/-3 that was unaffected by carvedilol or metoprolol treatment but decreased (p < 0.05) by hydralazine (187+/-4), carvedilol + hydralazine (221+/-3), and metoprolol + hydralazine (197+/-3). Carvedilol alone improved endothelium-dependent relaxation of resistance arteries, as elicited by the lowest concentration of acetylcholine studied (10(-7) M), whereas metoprolol had no effect. Hydralazine improved endothelial function as elicited by acetylcholine at a dose of 10(-6) M, also found under cotreatment with carvedilol but attenuated by cotreatment with metoprolol. Carvedilol or metoprolol alone had no significant effect on endothelium-independent relaxation produced by a nitric oxide donor (sodium nitroprusside). However, vessels from rats treated with carvedilol + hydralazine exhibited significantly greater relaxation than those from rats treated with metoprolol + hydralazine. These data suggest that carvedilol may have favorable effects on hypertension-related endothelial dysfunction not observed with metoprolol. Neither drug corrected small artery structure in SHRSP.

Plasma from ESRD patients inhibits nitric oxide synthase activity in cultured human and bovine endothelial cells

Our recent observations of reduced total nitric oxide synthesis in renal failure patients on peritoneal dialysis and haemodialysis suggest that hypertension in end-stage renal disease involves lack of vasodilatory endothelial NO. To directly test this, uraemic plasma was obtained from dialysis patients and incubated with cultured vascular endothelial cells, to determine the effect on nitric oxide synthase (NOS) activity in comparison with plasma from subjects with normal renal function. After incubation for 6 h with 20% uraemic plasma from peritoneal dialysis and immediately prehaemodialysis patients, NOS activity was reduced in human dermal microvascular endothelial cells. Haemodialysis did not remove the NOS-inhibitory activity of uraemic plasma nor did it activate inducible NOS, as NOS activity was always similar in control and dexamethasone pretreated cells. Nitric oxide production (accumulation of nitrite and nitrate) was lower in cells incubated with uraemic vs. normal plasma and excess arginine increased nitric oxide production by cells previously exposed to uraemic medium. This inhibitory effect was not associated with co-factor deficiency but did correlate with plasma concentrations of endogenous NOS inhibitors. These in vitro findings suggest that low endothelial NOS activity may contribute to hypertension in end stage renal disease patients.

Carvedilol and lacidipine prevent cardiac hypertrophy and endothelin-1 gene overexpression after aortic banding

Carvedilol and lacidipine have been shown to exert cardioprotective effects in rat models of chronic hypertension. We investigated their effects in an acute model of pressure overload produced by suprarenal aortic constriction, in which enhanced myocardial production of endothelin-1 could play a crucial role. In the absence of drug treatment, after 1 week, aortic banding provoked an increase in carotid pressure associated with left ventricular hypertrophy (29%; P<0.01). These changes were accompanied by increased myocardial expression of preproendothelin-1 (2.5 times; P<0.05) and skeletal alpha-actin (3.6 times; P<0.05), but the expression of cardiac alpha-actin was not modified. Oral administration of carvedilol at a dose of 30 mg. kg(-1). d(-1) to rats with aortic banding normalized carotid pressure and left ventricular weight as well as preproendothelin-1 and skeletal alpha-actin gene expression. Carvedilol at a lower dose (7.5 mg x kg(-1) x d(-1)) and lacidipine 1 mg x kg(-1) x d(-1) had only moderate and nonsignificant effects on carotid pressure but largely prevented left ventricular hypertrophy (P<0.01) and preproendothelin-1 overexpression (P<0.05). Labetalol (60 mg x kg(-1) x d(-1)) tended to exert similar effects but insignificantly. These results show that the antihypertrophic properties of carvedilol and lacidipine are partly independent of their antihypertensive effects and may be related to their ability to blunt myocardial preproendothelin-1 overexpression. Moreover, carvedilol at a dose of 7.5 mg x kg(-1) x d(-1) did not prevent myocardial overexpression of skeletal alpha-actin, which suggests that, in this model, reexpression of a fetal gene can be activated by pressure overload independently of cardiac hypertrophy.

Carvedilol reduces ischaemic skeletal muscle necrosis

Carvedilol is an alpha1 and nonselective beta-adrenergic receptor antagonist with antioxidative properties known to protect against reperfusion injury in the heart, brain, and kidneys. The aim of this study was to test the hypothesis that carvedilol improves postischaemic reperfusion and tissue survival in skeletal muscle. Sixteen Wistar rats underwent tourniquet ischaemia of the left hindlimb for 3 hours and 15 minutes at 27 degrees C. Single-fiber laser Doppler probes were inserted in the left and right anterior tibial muscles, and microvascular perfusion was measured until 2 hours after removal of the tourniquet. Perfusion indices for each 15-minute interval were calculated for the left hindlimb (tourniquet ischaemia) by dividing the postischaemic by the pre-ischaemic laser Doppler flowmetry values, and the geometrical areas under the curves representing a plot of perfusion index relative to time, measured in arbitrary units, were compared. Laser Doppler flowmetry values for the right anterior tibial muscle were compared. Tissue damage was measured by histomorphometry of necrotic areas and no-reflow zones in cross sections from the anterior tibial muscle 72 hours after ischaemia. Neutrophils were counted in the same sections. The treatment group received 1 mg carvedilol/kg body weight before ischaemia and 1 mg/kg immediately before removal of the tourniquets. The areas under the curves representing the plot of perfusion index relative to time were larger for the rats treated with carvedilol: 9.5 compared with 3.0 arbitrary units (p = 0.0003). Treatment did not change the laser Doppler flowmetry values for the right hindlimbs. The histomorphometric areas of necrosis in cross sections from the muscles were reduced from 88% (38-96%) in the control animals to 41% (7-85%) in those treated with carvedilol (p = 0.01), and the area of no-reflow was reduced from 20% (2-52%) to 0% (0-7%) (p = 0.006). The number of neutrophils did not differ between groups. The study supports the hypothesis that carvedilol improves early reperfusion and protects skeletal muscle subjected to 3 hours and 15 minutes of ischaemia.

Beta-blockers reduce the release and synthesis of endothelin-1 in human endothelial cells

BACKGROUND

Endothelins play an important role in cardiovascular diseases, and clinical trials have shown a reduction in endothelin levels after long-term treatment of chronic heart failure with beta-adrenergic antagonists. It is not known, however, whether this effect is caused by haemodynamic changes associated with the use of beta-adrenergic antagonists or by direct interaction of beta-blockers with human endothelial cells. The aim of this study was to determine whether beta-adrenergic antagonists have an influence on endothelin-1 (ET-1) synthesis and release in human endothelial cells.

METHODS

Pretreatment of cultured endothelial cells from human umbilical veins (HUVECs) with different concentrations of the non-selective beta-blocker propranolol, the beta 1-blocker metoprolol and the beta 1-blocker and beta 2-agonist celiprolol (all 10(-7)-10(-4) mol L-1) was found to reduce ET-1 production. This ET-1-reducing effect was even more pronounced in thrombin-stimulated cells (10(-5) mol L-1 of propranolol, metoprolol and celiprolol: 19% +/- 5.8%, 25% +/- 4% and 37% +/- 5.2% respectively).

RESULTS

Quantitative reverse transcriptase polymerase chain reaction and Northern blotting confirmed an inhibitory effect of the beta-blocker on biosynthesis. Furthermore, the ET-1-reducing effect of propranolol, metoprolol and celiprolol was not due to a compensatory increase in prostacyclin and was not reversible by N-nitro-L-arginine.

CONCLUSION

The effect of beta-adrenergic antagonists on ET-1 production of the endothelium may at least partially explain the efficacy of beta-blockers in the treatment of diseases such as advanced heart failure, essential hypertension as well as acute coronary syndromes.

Comparative effects of carvedilol and metoprolol on cardiac ischemia-reperfusion injury

The effects of carvedilol, a multiple-action neurohormonal antagonist, and metoprolol, a highly selective beta1 antagonist, were compared on postischemic contractile recovery and contracture. Isolated rabbit hearts were aerobically perfused for 45 min and subjected to zero-flow normothermic ischemia for 30 or 60 min followed by reperfusion for 30 min. Carvedilol and metoprolol were added to the perfusion solution 10 min before inducing ischemia and were maintained in the perfusate throughout reperfusion. Left ventricular developed pressure (LVDP) and left ventricular end-diastolic pressure (LVEDP) were assessed with an intraventricular balloon. Because the volume of the balloon was held constant, an increase in LVEDP reflected an increase in diastolic chamber stiffness or "contracture." After 30 min of ischemia, the carvedilol-treated hearts exhibited a significantly better cardiac function than did control or metoprolol-treated hearts. At the end of reperfusion, the control group LVDP recovered to 21.4+/-9.9% of the preischemic value. With 0.03, 0.1, and 0.3 microM metoprolol, LVDP recovered to 33.2+/-13.6%, 41.7+/-13.0%, and 48.8+/-13.3% of initial developed pressure, respectively. In the carvedilol group, a greater recovery of LVDP was obtained at 0.03, 0.1, and 0.3 microM: 64.0+/-2.5%, 60.4+/-6.3%, and 68.0+/-2.0% of preischemic values, respectively (p < 0.05 vs. controls). Within the first 5 min of reperfusion, LVEDP increased to 70.3+/-2.7 mm Hg in control hearts, indicating a pronounced contracture, whereas metoprolol reduced LVEDP when given at high concentration, 0.3 microM (41.9+/-10.7 mm Hg). Carvedilol, even at the lowest concentration, 0.03 microM, almost completely inhibited the postischemic contracture (16.5+/-4.0 mm Hg; p < 0.05 vs. control and metoprolol). The cardioprotection provided by carvedilol also is observed in hearts subjected to more severe ischemic periods. After 60 min of ischemia, control hearts failed to restore LVDP function; in the metoprolol group, ventricular function recovered to only 4.6+/-3.1%, whereas carvedilol-treated hearts exhibited 23.6+/-1.9% of preischemic values at the end of reperfusion. In addition, carvedilol induced a reduction in ischemic contracture: control, 36.7+/-3 mm Hg; metoprolol, 38.7+/-3.7 mm Hg; and carvedilol, 15.7+/-8.4 mm Hg at 50 min of ischemia. Similarly, carvedilol reduced contracture during the reperfusion compared with metoprolol and control groups (83.2+/-3.4 mm Hg, 106.9+/-3.3 mm Hg, and 107.6+/-4.1 mm Hg, respectively). These data clearly demonstrate that carvedilol was markedly more effective than metoprolol to protect systolic function after ischemia and to reduce postischemic contracture.

Mechanism of action of probucol on cholesteryl ester transfer protein (CETP) mRNA in a Chinese hamster ovary cell line that had been stably transfected with a human CETP gene

Probucol, a widely used lipid-lowering agent, is associated with a significant reduction of plasma high density lipoprotein (HDL)-cholesterol levels. To examine the mechanism of probucol HDL-lowering and probucol's effects on cholesteryl ester transfer protein (CETP) and cholesterol metabolism in cells, we used a Chinese hamster ovary (CHO) cell line that had been stably transfected with a human CETP gene (hCETP-CHO). After this cell line was incubated with various concentrations of probucol (5, 10 and 50 microM) for 24 h, mean intracellular probucol concentrations reached 0.47, 0.67, and 1.52 microg/mg cell protein, respectively. Northern blot analysis showed that cellular CETP mRNA was increased by probucol in a dose-dependent manner (137%, 162%, and 221% of the control, respectively). The specific CET activity in the culture medium, measured as the percentage of [3H]cholesterol oleate transferred from discoidal bilayer particles (which mimic HDL) to LDL, also increased in a dose-dependent manner. Intracellular total cholesterol levels were decreased to 87.5%, 74.9%, and 52.5% of the control, respectively. Probucol had no effects on HMG-CoA reductase activity or cholesterol synthesis from [14C]acetate in hCETP-CHO. However, 14C-incorporated cholesterol secretion into the culture medium from hCETP-CHO was increased to 181%, 256% and 354% of the control by 5, 10 and 50 microM probucol, respectively. We concluded that (1) treatment with probucol increased the CETP mRNA level and specific CET activity in the hCETP-CHO cell line, and (2) probucol promoted cholesterol efflux from hCETP-CHO, which resulted in a decrease in intracellular cholesterol levels.