Effects of a hydroxylated metabolite of the beta-andrenoreceptor antagonist, carvedilol, on post-ischaemic splachnic tissue injury

Carvedilol abrogates hypoxia-induced oxidative stress and neuroinflammation in microglial BV2 cells

Microglia initially undergo rapid activation in response to injury and stressful stimuli, such as hypoxia. Oxidative stress and the inflammatory response play critical roles in hypoxic-ischemic brain injury. Carvedilol is a β-blocker used to treat high blood pressure and heart failure. In this study, we investigated whether carvedilol had a protective effect against hypoxia-induced oxidative stress and inflammation in microglial BV2 cells. Our results indicate that hypoxic exposure significantly reduced mean cell viability of BV2 microglia, which was significantly restored by carvedilol (10 and 50μM). In addition, carvedilol treatment significantly inhibited the hypoxia-induced increase in reactive oxygen species (ROS) and 4-hydroxy-2-nonenal (4-HNE). Administration of carvedilol significantly inhibited expression of IL-1β, TNF-α, and IL-6 at both the mRNA and protein levels. Mechanistically, we found that hypoxia significantly increased phosphorylation of IKK, IκBα, and NF-κB p65. However, treatment with carvedilol inhibited phosphorylation of these molecules. Notably, hypoxia resulted in a significant nuclear translocation of NF-κB p65, which was inhibited by administration of carvedilol. Luciferase reporter assay results demonstrate that treatment with carvedilol inhibited the hypoxia-induced increase in NF-κB binding activity. These data suggest that carvedilol may be of potential use as a novel therapy against hypoxia or ischemia.

Comparison of free-radical inhibiting antioxidant properties of carvedilol and its phenolic metabolites

Carvedilol is a widely prescribed drug for the treatment of heart failure and the prevention of associated ventricular arrhythmias. It has also been reported to function as a biological antioxidant via hydrogen atom transfer from its carbazole N-H moiety to chain-propagating radicals. Metabolites of the drug include phenolic derivatives, such as 3-hydroxy-, 4'-hydroxy- and 5'-hydroxycarvedilol, which are also potential antioxidants. A comparison of the radical-inhibiting activities of the parent drug and the three metabolites was carried out in two separate assays. In the first, hydrogen atom transfer from these four compounds to the stable radical DPPH was measured by the decrease in the UV-visible absorption at 515 nm of the latter. The known radical inhibitors BHT, 4-hydroxycarbazole and α-tocopherol were employed as benchmarks in parallel experiments. In the second assay, inhibition of the photoinduced free-radical 1,2-addition of Se-phenyl p-tolueneselenosulfonate to cyclopropylacetylene, along with competing ring-opening of the cyclopropane ring, was monitored by ¹H NMR spectroscopy in the presence of the carvedilol-based and benchmark antioxidants. In both assays, carvedilol displayed negligible antioxidant activity, while the three metabolites all proved superior radical inhibitors to BHT, with radical-quenching abilities in the order 3-hydroxy- > 5'-hydroxy > 4'-hydroxycarvedilol. Among the metabolites, 3-hydroxycarvedilol displayed even stronger activity in both assays than α-tocopherol, the best of the benchmark antioxidants. These results suggest that the radical-inhibiting antioxidant properties that have been attributed to carvedilol are largely or exclusively due to its metabolites and not to the parent drug itself.

Cardioprotection by Carvedilol: Antiapoptosis is Independent of β-Adrenoceptor Blockage in the Rat Heart

Background: Carvedilol, a β-blocking agent with α-blocking properties is now widely used for the treatment of congestive heart failure. In addition to its β-adrenergic receptor blockage, antiapoptotic effects have been demonstrated in experimental animals.

Objective: The cardioprotective effects of carvedilol and its hydroxylated analogue BM-91.0228 were tested with regard to their infarct-limiting and antiapoptotic properties in an experimental infarct model in the rat heart.

Methods: Anesthetized rats were subjected to either 30 (groups I to 3) or 60 minutes (groups. 4 to 6) of coronary artery occlusion followed by 30 minutes of reperfusion. Groups 1 and 4 served as the control; groups 2 and 5 received intravenous Carvedilol (1 mg/kg) and groups 3 and 6 received intravenous administration of BM-91.0228 (1 mg/kg), respectively, 5 minutes prior to coronary occlusion. Infarct sizes were measured by triphenyltetrazolium chloride staining. In situ visualization of apoptosis was measured by nick end labeling.

Results: Carvedilol reduced infarct size after 30 minutes of coronary occlusion compared to controls (8.7% ± 2.7% versus 27.3% ± 3.4%, P < .001), while BM-91.0228 showed no significant infarct size reduction (23.7% ± 5.9%, NS). Neither Carvedilol (36.9% ± 3.9%) nor BM-91.0228 (42.4% ± 3.6%) reduced infarct size after 60 minutes of coronary occlusion compared to controls (47.7% ± 3.9%, NS). Carvedilol reduced apoptosis after 30 minutes (4.9% ± 1.3% versus 16.7% ± 3.2%, P < .01) and after 60 minutes (11.7% ± 1.8% versus 25.5% ± 0.5%, P < .001) of coronary occlusion compared to controls. BM-91.0228 reduced apoptosis after 30 minutes (7.3% ± 1.4% versus 16.7% ± 3.2%, P < .01) and after 60 minutes (13.4% ± 1.8% versus 25.5% ± 0.5%, P < .001) of coronary occlusion compared to controls.

Conclusion: Carvedilol is cardioprotective by preventing ischemia-perfusion-induced necrosis and apoptosis of cardiomyocytes. The antiapoptotic effects of Carvedilol are independent of its β-adrenoceptor blocking effects, but its effects might be caused by antioxidant properties and by modulation of the signalling pathway.

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.

β-Blocker carvedilol protects cardiomyocytes against oxidative stress-induced apoptosis by up-regulating miR-133 expression

Oxidative stress is a causal factor and key promoter of a variety of cardiovascular diseases associated with apoptotic cell death by causing deregulation of related genes. Though carvedilol, a β-adrenergic blocker, has been shown to produce cytoprotective effects against cardiomyocyte apoptosis, the mechanisms are not fully understood. The present study was designed to investigate whether the beneficial effects of carvedilol are related to microRNAs which have emerged as critical players in cardiovascular pathophysiology via post-transcriptional regulation of protein-coding genes. In vivo, we demonstrated that carvedilol ameliorated impaired cardiac function of infarct rats and restored miR-133 expression. In vitro, carvedilol protected cardiomyocytes from H2O2 induced apoptosis detected by TUNEL staining and MTT assays, and increased miR-133 expression in cardiomyocytes. Overexpression of miR-133, a recognized anti-apoptotic miRNA, produced similar effects to carvedilol: reduction of reactive oxygen species (ROS) and malondialdehyde (MDA) content and increment of superoxide dismutase (SOD) activity and glutathione peroxidase (GPx) level, so as to protect cardiomyocytes from apoptosis by downregulating caspase-9 and caspase-3 expression in the presence of H2O2. Transfection with AMO-133 (antisense inhibitor oligodeoxyribonucleotides) alone abolished the beneficial effects of carvedilol. Caspase-9-specific inhibitor z-LEHD-fmk, caspase-3-specific inhibitor z-DEVD-fmk, caspase-9 siRNA and caspase-3 siRNA were used to establish caspase-3 as a downstream target of miR-133. In conclusion, our data indicated that carvedilol protected cardiomyocytes by increasing miR-133 expression and suppressing caspase-9 and subsequent apoptotic pathways.

Cardiovascular disease in dialysis patients: do some antihypertensive drugs have specific antioxidant effects or is it just blood pressure reduction? Does antioxidant treatment reduce the risk for cardiovascular disease?

PURPOSE OF REVIEW

Patients with end-stage renal disease have an extremely high cardiovascular disease mortality. Oxidative stress is one of the 'nontraditional' risk factors for cardiovascular disease mortality in dialysis patients. This review discusses antioxidant activity of the commonly prescribed antihypertensive agents and the effects of antioxidant interventions on cardiovascular disease mortality in patients with end-stage renal disease.

RECENT FINDINGS

Several lines of evidence confirm antioxidant activity of the renin-angiotensin-aldosterone antagonists, some of the calcium channel blockers, carvedilol, and hydralazine. This appears to be independent of their antihypertensive activity. Clinical evidence of their superiority in improving cardiovascular disease endpoints in end-stage renal disease, however, is lacking. There are no randomized trials that have examined the effect of correcting oxidative stress on clinical endpoints. One randomized study in patients on hemodialysis reported a reduction in oxidative stress and the plasma methylarginines with valsartan and amlodipine but no clinical endpoints were examined.

SUMMARY

The effects of the antihypertensive agents with antioxidant activity on cardiovascular disease mortality in end-stage renal disease have not been examined in randomized clinical trials. These agents may offer specific clinical advantage in addition to lowering the blood pressure, but this remains to be proven. Two studies show a reduction in cardiovascular disease events with vitamin E and N-acetylcysteine in patients on hemodialysis without an effect on overall mortality.

Prevention of cold-preservation injury of cultured endothelial cells by catecholamines and related compounds

The present study was conducted to dissect the underlying mechanisms by which catecholamines protect cells against preservation injury. To this end, we firstly defined the cellular and molecular differences between protected and nonprotected cells and secondly defined the mediators that were involved in cold-induced damage. Cold storage of untreated human umbilical vein endothelial cells (HUVECs) resulted in profound cellular damage as assessed by lactate dehydrogenase (LDH) release and by morphological changes, e.g. cell size alterations and loss of cytoskeletal organization. Treatment of HUVECs with catecholamines before cold storage prevented cellular damage in a dose- and time-dependent fashion. Similar results were obtained with carvedilol or its hydroxylated derivative BM91.0228. Protection was not receptor-mediated and did not require de novo protein synthesis. The onset of protection occurred relatively quickly and the duration was long lasting. Addition of superoxide dismutase (SOD) to untreated HUVECs during cold preservation also was protective. Oxidation of catecholamines completely abrogated the protective effect of these compounds on cold-induced damage. Both at 4 degrees and 37 degrees C, catecholamines reduced the amount of reactive oxygen species (ROS) produced by HUVECs. In conclusion we have demonstrated that catecholamines protect cells against preservation injury either by scavenging of ROS or by inhibition of ROS production.

Oxidative stress and vascular damage in hypertension

Oxidative stress, a state of excessive reactive oxidative species activity, is associated with vascular disease states such as hypertension. In this review, we discuss the recent advances in the field of reactive oxidative species-mediated vascular damage in hypertension. These include the identification of redox-sensitive tyrosine kinases, the characterization of enzymatic sources of superoxide production in human blood vessels, and their relationship with vascular damage in atherosclerosis and hypertension. Finally, recent developments in the search for strategies to attenuate vascular oxidative stress are reviewed.

Endothelial protective and antishock effects of a selective estrogen receptor modulator in rats

This study investigated whether idoxifene, a selective estrogen receptor modulator (SERM), exerted protective effects against ischemia-reperfusion-induced shock. Ovariectomized rats were treated with vehicle, idoxifene, or 17beta-estradiol for 4 days. Rats were subjected to splanchnic artery occlusion (SAO) followed by reperfusion (SOA/R). In vehicle-treated rats, SAO/R resulted in hypotension, hemoconcentration, increased plasma tumor necrosis factor (TNF)-alpha levels, intestinal neutrophil accumulation, and endothelial dysfunction. 17beta-Estradiol treatment increased plasma estradiol concentration and reduced SAO/R-induced tissue injury. Idoxifene treatment had no effect on plasma estradiol concentration but reduced SAO/R-induced hemoconcentration (+8.8 +/- 1.3 vs. +14 +/- 1.3% in the vehicle group, P < 0.01), TNF-alpha production (98 +/- 3.2 vs. 214 +/- 13 pg/ml, P < 0.01), and neutrophil accumulation (0.025 +/- 0.005 vs. 0.047 +/- 0.005 U/g protein, P < 0.01). It also improved endothelial function, prolonged survival time (172 +/- 3.5 vs. 147 +/- 8 min, P < 0.01), and increased survival rate (69 vs. 23%, P < 0.01). Moreover, treatment with 17beta-estradiol or idoxifene in vivo reduced TNF-alpha-induced endothelial dysfunction in vitro. Taken together, these results demonstrated that idoxifene exerted estrogen-like, endothelial-protective, and antishock effects in ovariectomized rats, suggesting that SERMs have therapeutic potential in tissue injury resulting from ischemia-reperfusion.

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.

N-acetylcysteine enhances endothelium-dependent vasorelaxation in the isolated rat mesenteric artery

STUDY HYPOTHESIS

Previous studies have suggested that N-acetylcysteine (NAC) may confer additional protection in acetaminophen (APAP) overdose by improving hepatic microcirculation. We hypothesize that NAC enhances release of nitric oxide (NO) from the vasculature.

METHODS

Sprague-Dawley rat superior mesenteric artery rings were suspended in oxygenated Krebs-Henseleit tissue baths and contracted with U-46619 (a thromboxane A2-mimetic). In part 1, the effect of NAC on endothelial cell (EC) release of NO was assessed by measurement of vasorelaxation induced by acetylcholine (ACh, an EC-dependent vasorelaxor) in the presence and absence of NAC. In part 2, the effect of glutathione (a major component of NAC hepatoprotection) was examined by measuring ACh-induced vasorelaxation in rings from rats treated with L-buthionine sulfoxamine (BSO, a glutathione synthesis inhibitor). Data were analyzed by repeated-measures ANOVA.

RESULTS

Addition of 15 to 30 mmol/L NAC after ring contraction had no direct vasodilatory effect. By contrast, pretreatment of rings with NAC (15 mmol/L) enhanced vasorelaxation induced by ACh (95.0% +/- 7.9% versus 62.3% +/- 7.6% for control; ACh dose, 1 mumol/L; P < .001) or by A23187, a receptor-independent, NO-mediated vasodilator (91.6% +/- 9.6% versus 68.3% +/- 12.1% for control; A23187 dose, 1 mumol/L; P < .001). In rings from BSO-treated rats, NAC also enhanced vasorelaxation (76.5% +/- 7.1%; P < .001 versus control), but to a lesser degree than in nontreated rats.

CONCLUSION

NAC enhances endothelium-dependent vasodilation in an isolated rat mesenteric artery ring preparation. In addition to its antioxidant effects, NAC may decrease APAP hepatotoxicity by stimulating NO production and improving microvascular circulation.

Novel mechanisms in the treatment of heart failure: inhibition of oxygen radicals and apoptosis by carvedilol

Carvedilol is a novel cardiovascular drug of proven efficacy in the treatment of hypertension, angina, and heart failure. Several mechanisms may account for the beneficial effects of carvedilol in patients with heart failure. As with other beta-blockers, blockade of cardiac beta-adrenergic receptors (both beta1 and beta2), and hence reduction of cardiac work load and oxygen consumption, plays an important role in the actions of this agent. Additional benefit is provided by vasodilation (alphal-adrenergic blockage) at peripheral resistance vessels, which decreases preload and after-load, thereby further reducing cardiac work and wall tensions. In addition, potential advantages of carvedilol resulting from alpha1-adrenergic blockade are likely because alpha1-adrenergic receptors mediate cardiac remodeling by inducing hypertrophy. Finally, carvedilol is a potent antioxidant and is unique among beta-blockers in this respect. In recent years, evidence has accumulated in support of the role played by reactive oxygen radicals in chronic pathological states of the myocardium. In this article, the role of oxygen radicals in heart failure is discussed with special reference to apoptosis, a phenomenon believed to be involved in progressive cardiac myocyte loss in ischemic or myopathic heart diseases. The potential role of the antioxidant actions of carvedilol, especially in prevention of apoptotic cell death, is highlighted as a novel mechanism of action in heart failure.