Comparison of bisoprolol and carvedilol cardioprotection in a rabbit ischemia and reperfusion model

Influence of Alveolar Fluid on Aquaporins and Na+/K+-ATPase and Its Possible Theoretical or Clinical Significance

OBJECTIVE

Pulmonary edema is the most common pathophysiological change in pulmonary disease. Aquaporins (AQPs) and Na⁺/K⁺-ATPase play pivotal roles in alveolar fluid clearance. This study aimed to explore the influence of increased alveolar fluid on the absorption of lung fluid.

STUDY DESIGN

Eighty New Zealand rabbits were randomly divided into eight groups (n = 10 in each group), and models of different alveolar fluid contents were established by the infusion of different volumes of normal saline (NS) via the endotracheal tube. Five animals in each group were sacrificed immediately after infusion to determine the wet/dry ratio, while the remaining animals in each group were killed 4 hours later to determine the wet/dry ratio at 4 hours. Additionally, lung specimens were collected from each group, and quantitative real-time PCR (qRT-PCR), western blot, and immunohistochemical (IHC) analyses of AQPs and Na⁺/K⁺-ATPase were performed.

RESULTS

The qRT-PCR analysis and western blot studies showed markedly decreased mRNA and protein levels of AQP1 and Na⁺/K⁺-ATPase when the alveolar fluid volume was ≥6 mL/kg, and the mRNA level of AQP5 was significantly reduced when the alveolar fluid volume was ≥4 mL/kg. In addition, IHC analysis showed the same results. At 4 hours, the lung wet/dry ratio was significantly increased when the alveolar fluid volume was ≥6 mL/kg; however, compared with 0 hours after NS infusion, there was still a significant absorption of alveolar fluid for a period of 4 hours.

CONCLUSION

The results of this study suggest that increased alveolar fluid may induce the downregulation of the mRNA and protein expression of AQPs and Na⁺/K⁺-ATPase, which appear to affect alveolar fluid clearance in rabbit lungs. Early intervention is required to avoid excessive alveolar fluid accumulation.

KEY POINTS

· The expression levels of AQPs and Na+/K+--ATPase were significantly decreased as alveolar fluid increased.. · At 4 hours, wet/dry ratio was significantly increased when infusion volume was ≥ 6 mL/kg.. · Early intervention is required to avoid excessive alveolar fluid accumulation..

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.

Matrix Metalloproteinase-2 Inhibition in Acute Ischemia-Reperfusion Heart Injury-Cardioprotective Properties of Carvedilol

Matrix metalloproteinase 2 (MMP-2) is activated in hearts upon ischemia-reperfusion (IR) injury and cleaves sarcomeric proteins. It was shown that carvedilol and nebivolol reduced the activity of different MMPs. Hence, we hypothesized that they could reduce MMPs activation in myocytes, and therefore, protect against cardiac contractile dysfunction related with IR injury. Isolated rat hearts were subjected to either control aerobic perfusion or IR injury: 25 min of aerobic perfusion, followed by 20 min global, no-flow ischemia, and reperfusion for 30 min. The effects of carvedilol, nebivolol, or metoprolol were evaluated in hearts subjected to IR injury. Cardiac mechanical function and MMP-2 activity in the heart homogenates and coronary effluent were assessed along with troponin I content in the former. Only carvedilol improved the recovery of mechanical function at the end of reperfusion compared to IR injury hearts. IR injury induced the activation and release of MMP-2 into the coronary effluent during reperfusion. MMP-2 activity in the coronary effluent increased in the IR injury group and this was prevented by carvedilol. Troponin I levels decreased by 73% in IR hearts and this was abolished by carvedilol. Conclusions: These data suggest that the cardioprotective effect of carvedilol in myocardial IR injury may be mediated by inhibiting MMP-2 activation.

Wet lung leading to RDS: the lung ultrasound findings and possible mechanisms - a pilot study from an animal mode

BACKGROUND

Clinically, the lung ultrasound (LUS) showed wet lung could cause respiratory distress syndrome (RDS) in newborns. This work aimed to investigate LUS changes over time and its potential mechanism as alveolar fluid increase in a rabbit model.

METHODS

A total of 35 New Zealand Rabbits were randomly assigned to seven groups. Models of various alveolar fluid levels were induced by infusion of different volumes of normal saline (NS) via the endotracheal tube. LUS was performed before NS infusion, immediately after NS infusion and 4 h after NS infusion. To appraise LUS changes and its potential mechanism as alveolar fluid increase, histopathological examination, the mRNA and protein expression of surfactant protein (SP), and immunohistochemistry (IHC) were performed. The expression levels of SP-B and SP-C proteins were detected using western blotting, and the relative expression levels of SP-B and SP-C mRNA were detected using qRT-PCR.

RESULTS

The results showed that LUS changed from B-line to lung consolidations accompanied by air-bronchograms in some locations of lungs at 4 h when the injection volume ≥ 6 ml/kg. Histopathological examination showed alveoli collapse, inflammatory cell infiltration and alveolar wall thickened. SP-B and SP-C mRNA and protein expression were statistically significantly reduced when the injection volume ≥6 ml/kg (p < .05). IHC staining displayed the same findings.

CONCLUSIONS

As alveolar fluid increase, LUS changed from wet lung to RDS after 4 h. The possible mechanism was that the SP protein expression was significantly reduced. LUS can be used to guide the administration of exogenous surfactant in this situation.

Using lung ultrasound to quantitatively evaluate pulmonary water content

BACKGROUND

Increases in extravascular lung water (EVLW) can lead to respiratory failure. This study aimed to investigate whether the B-line score (BLS) was correlated with the EVLW content determined by the lung wet/dry ratio in a rabbit model.

METHODS

A total of 45 New Zealand rabbits were randomly assigned to nine groups. Among the animals, models of various lung water content levels were induced by the infusion of different volumes of warm sterile normal saline (NS) via the endotracheal tube. The arterial blood gas, spontaneous respiratory rate, and PaO₂ /FiO₂ ratio were detected before and after infusion. In addition, the B-lines were determined before and immediately after infusion in each group. Finally, both lungs were resected to determine the wet/dry ratio. In addition, all lung specimens were analyzed histologically, and EVLW was quantified using the BLS based on the number and confluence of B-lines in the intercostal space.

RESULTS

The BLS increased with increasing infusion volume. The BLS was statistically correlated with the wet/dry ratio (r² = .946) and with the PaO₂ /FiO₂ ratio (r² = .916). Furthermore, a repeatability study was performed for the lung ultrasound (LUS) technology (Bland-Altman plots), and the results suggest that LUS had favorable intraobserver and interobserver reproducibility.

CONCLUSIONS

This study is the first to suggest that the BLS can serve as a sensitive, quantitative, noninvasive, and real-time indicator of EVLW in a rabbit model of lung water accumulation. Notably, the BLS displayed an obvious correlation with the experimental gravimetry results and could also be used to predict the pulmonary oxygenation status.

Myeloperoxidase - A bridge linking inflammation and oxidative stress with cardiovascular disease

Myeloperoxidase (MPO) is a member of the superfamily of heme peroxidases that is mainly expressed in neutrophils and monocytes. MPO-derived reactive species play a key role in neutrophil antimicrobial activity and human defense against various pathogens primarily by participating in phagocytosis. Elevated MPO levels in circulation are associated with inflammation and increased oxidative stress. Multiple lines of evidence suggest an association between MPO and cardiovascular disease (CVD) including coronary artery disease, congestive heart failure, arterial hypertension, pulmonary arterial hypertension, peripheral arterial disease, myocardial ischemia/reperfusion-related injury, stroke, cardiac arrhythmia and venous thrombosis. Elevated MPO levels are associated with a poor prognosis including increased risk for overall and CVD-related mortality. Elevated MPO may signify an increased risk for CVD for at least 2 reasons. First, low-grade inflammation and increased oxidative stress coexist with many metabolic abnormalities and comorbidities and consequently an elevated MPO level may represent an increased cardiometabolic risk in general. Second, MPO produces a large number of highly reactive species which can attack, destroy or modify the function of every known cellular component. The most common MPO actions relevant to CVD are generation of dysfunctional lipoproteins with an increased atherogenicity potential, reduced NO availability, endothelial dysfunction, impaired vasoreactivity and atherosclerotic plaque instability. These actions strongly suggest that MPO is directly involved in the pathophysiology of CVD. In this regard MPO may be seen as a mediator or an instrument through which inflammation promotes CVD at molecular and cellular level. Clinical value of MPO therapeutic inhibition remains to be tested.

Sevoflurane, Propofol and Carvedilol Block Myocardial Protection by Limb Remote Ischemic Preconditioning

The effects of remote ischemic preconditioning (RIPC) in cardiac surgery have been inconsistent. We investigated whether anesthesia or beta-blockers interfere with RIPC cardioprotection. Fifty patients undergoing cardiac surgery were randomized to receive limb RIPC (four cycles of 5-min of upper arm cuff inflation/deflation) in the awake state (no-anesthesia; n = 17), or under sevoflurane (n = 17) or propofol (n = 16) anesthesia. In a separate crossover study, 11 healthy volunteers received either carvedilol or no medication prior to RIPC. Plasma dialysates were obtained and perfused through an isolated male Sprague⁻Dawley rat heart subjected to 30-min ischemia/60-min reperfusion, following which myocardial infarct (MI) size was determined. In the cardiac surgery study, pre-RIPC MI sizes were similar among the groups (39.7 ± 4.5% no-anesthesia, 38.9 ± 5.3% sevoflurane, and 38.6 ± 3.6% propofol). However, post-RIPC MI size was reduced in the no-anesthesia group (27.5 ± 8.0%; p < 0.001), but not in the anesthesia groups (35.7 ± 6.9% sevoflurane and 35.8 ± 5.8% propofol). In the healthy volunteer study, there was a reduction in MI size with RIPC in the no-carvedilol group (41.7 ± 4.3% to 30.6 ± 8.5%; p < 0.0001), but not in the carvedilol group (41.0 ± 4.0% to 39.6 ± 5.6%; p = 0.452). We found that the cardioprotective effects of limb RIPC were abolished under propofol or sevoflurane anesthesia and in the presence of carvedilol therapy.

Antiarrhythmic activity in occlusion-reperfusion model of 1-(1H-indol-4-yloxy)-3-{[2-(2-methoxyphenoxy)ethyl]amino} propan-2-ol and its enantiomers

Acute myocardial infarction (AMI) is a leading cause of mortality and morbidity worldwide, especially in developed countries. The most serious problem after myocardial infarction is reperfusion injury that manifests as functional impairment, arrhythmia, and accelerated progression of cell death in certain critically injured myocytes. Subsequently the infarcted myocardium develops features of necrosis and reactive inflammation. To reduce lethal reperfusion injury in patient with AMI antioxidants, anti-inflammatory agents, adenosine, opioids, metabolic modulators (glucose, insulin, and potassium, nicorandil and agents which reduce intracellular Ca(2+) overload and inhibit Na(+)-H(+) exchange) are used. In this study a novel compound (compound 9) 1-(1 h-indol-4-yloxy)-3-{[2-(2-methoxyphenoxy) ethyl]amino}propan-2-ol and its enantiomers are examined in arrhythmia associated with coronary artery occlusion and reperfusion in a rat model. Antioxidant properties are also determined for test compounds using the malondialdehyde (MDA) lipid peroxidation and ferric reducing antioxidant power (FRAP) tests. In summary, the tested compounds, especially the S enantiomer has a strong antiarrhythmic activity in a model of occlusion and reperfusion of the left coronary artery which is probably related to their adrenolytic action. In contrast to carvedilol, none of the test compound reduced the lipid peroxidation but increased ferric reducing antioxidant power. In the antioxidant effect, there was no difference between the optical forms of compound 9.

Additive effects of β-blockers on renin-angiotensin system inhibitors for patients after acute myocardial infarction treated with primary coronary revascularization

BACKGROUND

Although some β-blockers are effective for patients after acute myocardial infarction (AMI), few studies have compared their additive effects on renin-angiotensin system inhibitors (RAS-Is).

METHODS AND RESULTS

The 251 consecutive AMI patients administered angiotensin-converting-enzyme inhibitors (ACE-Is) or angiotensin-II receptor blockers (ARBs) were retrospectively investigated and divided into 2 groups: treated without β-blockers (no-β-blocker group, n=80) or treated with β-blockers before discharge (β-blocker group, n=171; carvedilol [n=91] or bisoprolol [n=80]). The doses of RAS-Is used for patients in the no-β-blocker group were at least double those used in the β-blocker group. No significant differences between the 2 groups were observed with regard to baseline characteristics. After a 12-month follow-up, the survival and cardiac event-free rates in the β-blocker group were significantly higher than those in the no-β-blocker group. The percent change in blood pressure did not significantly differ between the 2 groups, but the levels of brain natriuretic peptide, metalloproteinase-2, and metalloproteinase-9 and the left ventricular ejection fraction improved significantly in the β-blocker group compared with the no-β-blocker group. Regarding the 2 β-blockers, carvedilol treatment produced more favorable outcomes than bisoprolol.

CONCLUSIONS

The data suggest that treatment with RAS-I in combination with β-blocker is more effective for patients after AMI than treatment with RAS-I alone.

Catestatin improves post-ischemic left ventricular function and decreases ischemia/reperfusion injury in heart

The Chromogranin A (CgA)-derived anti-hypertensive peptide catestatin (CST) antagonizes catecholamine secretion, and is a negative myocardial inotrope acting via a nitric oxide-dependent mechanism. It is not known whether CST contributes to ischemia/reperfusion injury or is a component of a cardioprotective response to limit injury. Here, we tested whether CST by virtue of its negative inotropic activity improves post-ischemic cardiac function and cardiomyocyte survival. Three groups of isolated perfused hearts from adult Wistar rats underwent 30-min ischemia and 120-min reperfusion (I/R, Group 1), or were post-conditioned by brief ischemic episodes (PostC, 5-cycles of 10-s I/R at the beginning of 120-min reperfusion, Group 2), or with exogenous CST (75 nM for 20 min, CST-Post, Group-3) at the onset of reperfusion. Perfusion pressure and left ventricular pressure (LVP) were monitored. Infarct size was evaluated with nitroblue-tetrazolium staining. The CST (5 nM) effects were also tested in simulated ischemia/reperfusion experiments on cardiomyocytes isolated from young-adult rats, evaluating cell survival with propidium iodide labeling. Infarct size was 61 ± 6% of risk area in hearts subjected to I/R only. PostC reduced infarct size to 34 ± 5%. Infarct size in CST-Post was 36 ± 3% of risk area (P < 0.05 respect to I/R). CST-Post reduced post-ischemic rise of diastolic LVP, an index of contracture, and significantly improved post-ischemic recovery of developed LVP. In isolated cardiomyocytes, CST increased the cell viability rate by about 65% after simulated ischemia/reperfusion. These results suggest a novel cardioprotective role for CST, which appears mainly due to a direct reduction of post-ischemic myocardial damages and dysfunction, rather than to an involvement of adrenergic terminals and/or endothelium.

Impact of therapy with statins, beta-blockers and angiotensin-converting enzyme inhibitors on plasma myeloperoxidase in patients with coronary artery disease

PURPOSE

The present study investigated whether therapy with statins, beta-blockers and angiotensin-converting enzyme (ACE) inhibitors on admission affects the plasma level of myeloperoxidase (MPO) in patients with coronary artery disease (CAD).

METHODS

This study included a consecutive series of 680 patients with angiographically confirmed CAD: 382 patients with stable CAD, 107 patients with unstable angina and 191 patients with ST-segment elevation acute myocardial infarction. Blood samples for MPO measurement were taken before angiography prior to heparin administration.

RESULTS

On admission, 316 patients were receiving statins, 432 patients were receiving beta-blockers and 354 patients were receiving ACE inhibitors. MPO level was: 65.5 [48.8-101.6] μg/L among patients on statin therapy versus 86.7 [56.0-159.9] μg/L among patients without statin therapy (P < 0.001); 68.1 [50.1-105.1] μg/L among patients on beta-blocker therapy versus 97.3 [56.0-181.9] μg/L among patients without beta-blocker therapy (P < 0.001) and 65.5 [49.2-102.0] μg/L among patients receiving ACE inhibitors versus 92.0 [56.1-171.1] μg/L among patients not receiving ACE inhibitors on admission (P < 0.001). The MPO-lowering effect of these drugs was observed only in patients with acute coronary syndrome but not in patients with stable CAD. The multivariable analysis, adjusting for cardiovascular risk factors, clinical variables and concomitant therapy identified beta-blockers on admission as an independent correlate of lower MPO levels (P = 0.016).

CONCLUSIONS

In patients with symptomatic CAD, beta-blocker therapy on admission was independently associated with lower levels of plasma MPO. Pre-admission therapy with statins, beta-blockers or ACE inhibitors reduced MPO levels in patients with acute coronary syndromes, but not in patients with stable CAD.

Opioid-induced preconditioning is dependent on caveolin-3 expression

We tested the hypothesis that caveolin-3 (Cav-3) is essential for opioid-induced preconditioning in vivo. Cav-3 overexpressing mice, Cav-3 knockout mice, and controls were exposed to myocardial ischemia/reperfusion (I/R) in the presence of SNC-121 (SNC), a δ-selective opioid agonist, or naloxone, a nonselective opioid antagonist. Controls were protected from I/R injury by SNC. No protection was produced by SNC in Cav-3 knockout mice. Cav-3 overexpressing mice showed innate protection from I/R compared with controls that was abolished by naloxone. Our results show that opioid-induced preconditioning is dependent on Cav-3 expression and that endogenous protection in Cav-3 overexpressing mice is opioid dependent.

Antioxidant activity of carvedilol in cardiovascular disease

Oxidative and inflammatory stresses are cardinal in the pathogenesis of hypertension and atherosclerosis. Oxidative stress also leads to the induction of inflammation through the activation of proinflammatory transcription factors. Understanding the mechanisms leading to oxidative stress and the means of suppressing it are important in controlling complications related to atherogenesis, since oxidative and inflammatory stress are important in the pathogenesis of atherosclerosis. The failure of chemical antioxidants [which scavenge reactive oxygen species (ROS)], such as vitamins E and C, has led to further exploration of the ROS-suppressive effects of drugs used in the treatment of cardiovascular disease. Carvedilol has been shown to possess both ROS-scavenging and ROS-suppressive effects, and its use is associated with a reduction in oxidative stress. Furthermore, anti-inflammatory effects of carvedilol have now been described. Although further clinical investigations are required, these properties may contribute to the improvement in clinical outcomes observed with carvedilol.

Vasopressors for cardiopulmonary resuscitation. Does pharmacological evidence support clinical practice?

Adrenaline (epinephrine) has been used for cardiopulmonary resuscitation (CPR) since 1896. The rationale behind its use is thought to be its alpha-adrenoceptor-mediated peripheral vasoconstriction, causing residual blood flow to be diverted to coronary and cerebral circulations. This protects these tissues from ischaemic damage and increases the likelihood of restoration of spontaneous circulation. Clinical trials have not demonstrated any benefit of adrenaline over placebo as an agent for resuscitation. Adrenaline has deleterious effects in the setting of resuscitation, predictable from its promiscuous pharmacological profile. This article discusses the relevant pharmacology of adrenaline in the context of CPR. Experimental and clinical evidences for the use of adrenaline and alternative vasopressor agents in resuscitation are given, and the properties of an ideal vasopressor are discussed.

Metoprolol treatment decreases tissue myeloperoxidase activity after spinal cord injury in rats

Neutrophil infiltration has been reported to play an important role in spinal cord injury (SCI). In addition to their cardioprotective effects, beta-blockers have been found to have neuroprotective effects on the central nervous system, but their effect on SCI has not yet been studied. In the current study, we investigated the effect of metoprolol on myeloperoxidase (MPO) activity, a marker of neutrophil activation, in the spinal cord after experimental SCI in rats. Rats were divided into six groups: controls received only laminectomy and spinal cord samples were taken immediately; the sham operated group received laminectomy, and spinal cord samples were taken 4h after laminectomy; the trauma only group underwent a 50g/cm contusion injury but received no medication; and three other groups underwent trauma as for the trauma group, and received 30mg/kg methylprednisolone, 1mg/kg metoprolol, or 1mL saline, respectively. All the medications were given intraperitoneally as single doses, immediately after trauma. Spinal cord samples were taken 4h after trauma and studied for MPO activity. The results showed that tissue MPO activity increased after injury. Both metoprolol and methylprednisolone treatments decreased MPO activity, indicating a reduction in neutrophil infiltration in damaged tissue. The effect of metoprolol on MPO activity was found to be similar to methylprednisolone. In view of these data, we conclude that metoprolol may be effective in protecting rat spinal cord from secondary injury.

Carvedilol Protects Better Against Vascular Events Than Metoprolol in Heart Failure

OBJECTIVES

We explored whether vascular protection by carvedilol could contribute to its superior effects in the treatment of heart failure (HF) compared with metoprolol tartrate in the COMET (Carvedilol Or Metoprolol European Trial) study.

BACKGROUND

Full adrenergic blockade by carvedilol and additional (e.g., antioxidative) properties may lead to vascular protection relative to beta-1 blockade alone, and contribute to its efficacy in HF treatment.

METHODS

Three thousand twenty-nine patients with HF due to ischemic (51%) or idiopathic cardiomyopathy (44%) were randomized double-blind to carvedilol (n = 1,511) or metoprolol (n = 1,518) and followed for 58 months. Vascular end points were cardiovascular death, stroke, stroke death, myocardial infarction (MI), and unstable angina.

RESULTS

The effect of carvedilol on cardiovascular death improved consistently in subgroups with prespecified baseline variables. Myocardial infarctions were reported in 69 carvedilol and 94 metoprolol patients (hazard ratio [HR] 0.71, 95% confidence interval [CI] 0.52 to 0.97, p = 0.03). Cardiovascular death or nonfatal MI combined were reduced by 19% in carvedilol (HR 0.81, 95% CI 0.72 to 0.92, p = 0.0009 vs. metoprolol). Unstable angina was reported as an adverse event in 56 carvedilol and in 77 metoprolol patients (HR 0.71, 95% CI 0.501 to 0.998, p = 0.049). A stroke occurred in 65 carvedilol and 80 metoprolol patients (HR 0.79, 95% CI 0.57 to 1.10). Stroke or MI combined occurred in 130 carvedilol and 168 metoprolol patients (HR 0.75, 95% CI 0.60 to 0.95, p = 0.015), and fatal MI or fatal stroke occurred in 34 carvedilol and in 72 metoprolol patients (HR 0.46, 95% CI 0.31 to 0.69, p = 0.0002). Death after a nonfatal MI or stroke occurred in 61 of 124 carvedilol and in 106 of 160 metoprolol patients (HR 0.66, 95% CI 0.48 to 0.90, p = 0.0086).

CONCLUSIONS

Carvedilol improves vascular outcomes better than metoprolol. These results suggest a ubiquitous protective effect of carvedilol against major vascular events.

Comparison of carvedilol and metoprolol in patients with acute myocardial infarction undergoing primary coronary intervention

BACKGROUND

The value of early therapy with beta-blocking agents in acute myocardial infarction (AMI) undergoing reperfusion is not yet well established. Newer beta-blocking agents such as carvedilol offer potential advantages in the setting of ischemia and reperfusion injury.

METHODS

We randomized 100 patients with acute ST-elevation myocardial infarction (STEMI) to receive either 12.5 mg carvedilol or 50 mg metoprolol tartrate orally already before percutaneous coronary intervention (PCI) of the infarct-related artery, uptitrating to a daily target dose of 50 mg carvedilol or 150 mg metoprolol during the first week. Pts. were subjected to left ventricular (LV) angiography just before reperfusion and after 14 days to compare ejection fraction (EF) and regional wall motion abnormalities by quantitative LV analysis. Furthermore, kinetics of cardiac troponin T (cTnT), NT-proANP, NT-proBNP, endothelin, argenine vasopressin, epinephrine and norepinephrine were assessed during the first 12 hours and again at 2 weeks. In addition, reperfusion-induced rhythm abnormalities like VT, triplets, couplets, and bradycardic events were assessed continuously during the first 12 hours starting at reperfusion by Holter analysis.

RESULTS

Both groups did not differ with respect to onset of pain, target vessel, extent of coronary heart disease, age, gender, rate of stenting or use of a GP IIb/IIIa inhibitor, pre- and postinterventional TIMI flow grade, time course of heart rate or blood pressure. There were neither significant differences in the cardiac and neurohumoral markers nor in the occurrence of arrhythmias between both treatment groups. Within 14 days, EF improved by 5.8+/-2.0% (mean+/-SEM) in the metoprolol group and by 5.2+/-2.1% in the carvedilol group (n.s.). Area of infarction was reduced by 6.1+/-2.9% in the metoprolol group and by 12.8+/-3.6% of total LV outline in the carvedilol group (n.s.). Maximum hypokinesia in the central infarcted region was diminished by 0.40+/-0.11 standard deviation (SD) in the metoprolol group and by 0.34+/-0.13 SD in the carvedilol group (n.s.).

CONCLUSION

In the setting of direct PCI in acute STEMI, administration of carvedilol before reperfusion appears not to be superior to metoprolol with respect to myocardial injury and improvement of global and regional LV function. The study documents equivalent improvement of LV function and similar kinetics of cardiac and neurohumoral markers in pts. with acute STEMI undergoing direct PCI if the pts. were immediately treated with either carvedilol or metoprolol. Thus, superiority of carvedilol in experimental studies did not translate into a clinical benefit.

Neutrophils superoxide anion generation during carvedilol therapy in patients with stable angina

Neutrophil superoxide anion (O(2)(*-)) generation was measured during carvedilol therapy in patients with stable angina. The carvedilol group comprised 27 patients (18 men and 9 women), aged 38-51 years (mean 47.6 years) with stable angina. Carvedilol was administered in increased every 4-week doses: 12.5, 25 and 50 mg/24 h, respectively. The control group included 12 healthy subjects, aged 39-49 years (mean 45.7 years) with no drug administered. Blood samples were collected from cubital vein before and 4, 8 and 12 weeks after the therapy and once in the control group. Neutrophil O(2)(*-) generation was determined in whole blood without and with opsonized zymosan (OZ) stimulation according to Bellavite et al. method using superoxide dismutase from bovine erythrocytes. O(2)(*-) generation by nonstimulated and OZ-stimulated neutrophils was significantly higher (p<0.05) in patients with stable angina than in the control group. In carvedilol group, statistically significant (p<0.05) decrease in superoxide anion generation by nonstimulated and OZ-stimulated neutrophils was observed 8 and 12 weeks after the therapy and it did not differ from that in healthy subjects. Carvedilol has been shown to inhibit neutrophil O(2)(*-) generation in patients with stable angina.

The roles of alpha- and beta-adrenoceptor stimulation in myocardial ischaemia

beta-Adrenoceptor (AR) ligands have been the mainstay of cardiovascular therapy for decades, with beta-AR antagonist being used for hypertension, angina and myocardial infarction and adrenaline in use for cardiopulmonary resuscitation for nearly 100 years. Ischaemia of the heart through coronary artery occlusion causes cell injury and death through necrosis and apoptosis. Reperfusion of the ischaemic myocardium results in cardiac dysfunction and infarction. Stimulation of alpha- and beta-ARs in the ischaemic heart have variable and inconsistent effects depending on when the agonist is applied. This review describes the different effects of stimulation of the three established beta-AR subtypes (beta(1)-, beta(2)- and beta(3)-ARs) either before ischaemia (preconditioning) or during ischaemia and reperfusion of the heart (postconditioning). Brief periods of ischaemia preceding a major ischaemic episode can have a protective effect against post-ischaemia-reperfusion damage, known as ischaemic preconditioning. This review considers the role of endogenous catecholamines released during preconditioning and the nature of the adrenoceptor subtypes that mediate these effects. The clinical significance of this to the use of beta-AR antagonists is considered. The transduction pathways and effects on apoptosis of the cardioprotective and deleterious effects of AR activation are considered. This commentary reviews the literature and attempts to bring together a unified synopsis of the effects of adrenoceptor stimulation in myocardial ischaemia and the potential clinical relevance.

Intravenous atenolol and esmolol maintain the protective effect of ischemic preconditioning in vivo

Catecholamines bind to alpha- and beta-adrenoreceptors and are capable of preconditioning ischemic myocardium. Our purpose was to investigate the effect of acute either short or prolonged i.v. administration of beta-adrenoreceptor antagonists on ischemic preconditioning in vivo. Fifty-five anesthetized rabbits were divided into 10 groups (n=5-7 per group) and were subjected to 30-min regional ischemia of the heart after ligation of a prominent left coronary artery and 3-h reperfusion after releasing the snare. Ischemic preconditioning was obtained by three cycles of 5-min ischemia separated by 10-min reperfusion. beta-Adrenoreceptor blockade was obtained by the long acting beta-adrenoreceptor antagonist atenolol or by the short acting esmolol, which were given as a short 5-min infusion or as a prolonged 45-min infusion, starting respectively 20 min before and ending 15 min before the beginning of sustained ischemia, or starting 45 min before and ending immediately before the beginning of sustained ischemia. Atenolol was given at a rate of 0.2 mg min(-1) during 5 min or at a rate of 0.088 mg min(-1) as a 45-min infusion. Esmolol was given as an initial dose of 500 microg kg(-1) within 1 min, followed by a 4-min infusion at a rate of 50 microg kg(-1) min(-1) or as an initial dose of 3.4 mg within 1 min, followed by a 44-min infusion at a rate of 0.15 mg min(-1). Blood pressure and heart rate were continuously monitored. The infarcted and risk areas were delineated with the aid of tetrazolium chloride staining and fluorescent Zn-Cd particles. Infarct size was expressed in percent of the area at risk. All the animals without preconditioning developed an infarct size ranging between 36.3+/-2.4% and 49.6+/-7.6% (P=NS) and all the preconditioning groups developed an infarct size ranging between 14.9+/-1.2% and 21.0+/-2.2% (P=NS). All the preconditioning groups, independently of the use of beta-adrenoreceptor antagonists, had a smaller infarct size than the control group, which developed an infarct size of 47.3+/-2.5% (P<0.01). Intravenous atenolol and esmolol, independent of timing and mode of administration, does not seem to interfere with protection afforded by ischemic preconditioning in vivo.

Carvedilol: a new candidate for reversal of MDR1/P-glycoprotein-mediated multidrug resistance

In 1983, carvedilol [1-[carbazolyl-(4)-oxy]-3-[(2-methoxyphenoxyethyl)amino]-2-propanol] was designed and developed as a beta-adrenoceptor antagonist with vasodilating activity for efficacious and safe treatment of hypertension and coronary artery disease. Carvedilol belongs to the 'third generation' of beta-adrenoceptor antagonists and shows selectivity for the beta1- rather than beta2-adrenoceptor. Carvedilol is also an alpha1-blocking agents, with around 2- to 3-fold more selectivity for beta1- than alpha1-adrenoceptors. This degree of alpha1-blockade is responsible for the moderate vasodilator properties of carvedilol, being different from other beta-adrenoceptor antagonists. In addition, carvedilol is a potent antioxidant, with a 10-fold greater activity than vitamin E. Some carvedilol metabolites found in human plasma also exhibit antioxidative activity approximately 50- to 100-fold greater than carvedilol and other antioxidants. These unique properties of carvedilol, i.e. adrenergic (beta1, beta2 and alpha1) blockade and antioxidative activity, may be important in preventing progressive deterioration of left ventricular dysfunction and chronic heart failure. Recently, carvedilol has been demonstrated to reverse multidrug resistance (MDR) to anticancer drugs in tumor cells in vitro and its reversal effects were comparable with verapamil, which has been used in the first clinical trial for the reversal of MDR. This review introduces the reversal activity and usefulness against MDR, as well as an overview of the pharmacological and pharmacokinetic properties, of carvedilol.

Effects of carvedilol on oxidative stress in polymorphonuclear and mononuclear cells in patients with essential hypertension

PURPOSE

To compare the effects of carvedilol and propranolol on oxidative stress in leukocytes and C-reactive protein levels in patients with hypertension.

METHODS

Sixty hypertensive patients were randomly assigned to carvedilol (20 mg; n = 30) or propranolol (60 mg; n = 30) for 6 months. Thirty normotensive subjects who were given placebo served as controls. Oxidative stress in polymorphonuclear cells and mononuclear cells were measured by gated flow cytometry. C-reactive protein levels were measured by immunonephelometric assay.

RESULTS

Oxidative stress in polymorphonuclear cells and mononuclear cells was increased significantly in hypertensive patients compared with in normotensive controls. After 6 months of treatment, carvedilol decreased oxidative stress significantly in polymorphonuclear cells by a mean of 45 arbitrary units (95% confidence interval [CI]: 32 to 59 arbitrary units; P <0.001) and propranolol decreased oxidative stress significantly by 20 arbitrary units (95% CI: 7 to 33 arbitrary units; P <0.003; P = 0.001 for difference between treatments). Carvedilol also decreased oxidative stress significantly in mononuclear cells by 23 arbitrary units (95% CI: 15 to 31 arbitrary units; P <0.001), whereas propranolol decreased oxidative stress by 2 arbitrary units (95% CI: 7 to 12 arbitrary units; P = 0.62; P = 0.002 for difference between treatments). Carvedilol decreased C-reactive protein levels significantly by a median of 0.073 mg/dL (interquartile range, 0.034 to 0.112 mg/dL; P <0.001), whereas propranolol decreased levels by 0.012 mg/dL (interquartile range, 0.009 to 0.032 mg/dL; P = 0.26; P = 0.003 for difference between treatments).

CONCLUSION

These findings suggest that carvedilol inhibits oxidative stress in polymorphonuclear and mononuclear cells, as well as lowers C-reactive protein levels, to a greater extent than does propranolol in hypertensive patients.

Effect of isoproterenol on lipid peroxidation and antioxidant enzymes of myocardial tissue of mice and protection by quinidine

Administration of isoproterenol to mice at a dose of 30 mg/100 g body weight for 3 consecutive days at an interval of 24 h induced lipid peroxidation in cardiac tissue and exhibited a significantly elevated serum glutamate oxaloacetate transaminase (SGOT) level. Increased superoxide dismutase (SOD) activity with a concomitant decrease in catalase activity has also been observed in cardiac tissue with isoproterenol treatment. Quinidine, a class I antiarrhythmic agent has been found to exhibit a protective role in isoproterenol induced myocardial ischaemia. Cardiac tissue of quinidine treated mice showed reduction of lipid peroxidation reaction. In addition, quinidine treatment is found to influence the cardiac antioxidant enzymes - catalase and SOD. The decrease of SOD activity and increase of catalase activity suggests that quinidine also exerts an 'indirect antioxidant' effect in protecting the myocardial tissue from reactive oxygen species. Furthermore, our current in vitro studies with quinidine have clearly shown in this work that it possesses a very convincing hydroxyl radical scavenging potential with almost no ability to scavenge superoxide anion and hydrogen peroxide (H2O2) in vitro. Thus, our present investigation suggests that quinidine, when administered to mice, strengthens the antioxidant defense system to resist the free radical induced damage brought about by isoproterenol induced ischaemic condition.

Effects of carvedilol on cardiomyocyte apoptosis and gene expression in vivo after ischemia-reperfusion in rats

The effects of carvedilol on cardiomyocyte apoptosis and expression of bcl-2, bax genes following ischemia (0.5 h) and reperfusion (48 h) in vivo and the possible biological mechanism of carvedilol inhibiting cardiomyocyte apoptosis were studied. The left anterior descending artery in Wistar rats were ligated to establish ischemia-reperfusion (I/R) models. The model animals were divided into two groups: I/R group, the model rats not subject to other treatments except ischemia-reperfusion (n = 8); carvedilol-treated group (n = 8), I/R model rats treated with carvedilol. Eight rats in the sham-operated group were subjected to only experimental open operation. The number of apoptotic cardiomyocyte was determined by TUNEL staining. Immunohistochemistry and in situ hybridization histochemistry (ISHH) were used to detect the expression of bcl-2 and bax genes. Image processing system was used to quantitatively dispose the positive metric substances of both immunohistochemistry and ISHH through the average optical density (OD) value. The results showed that the number of the apoptotic cells were 36.18 +/- 9 (I/R group), 0-1 (sham-operated group) and 9.5 +/- 3 (carvedilol-treated group) in each visual field respectively with the difference being very significant among the groups (P < 0.001). The OD values of bcl-2 protein in sham-operated group, I/R group and carvedilol-treated group were 0.14 +/- 0.01, 0.08 +/- 0.02 and 0.15 +/- 0.03, respectively. The OD values of bcl-2 mRNA in sham-operated group, I/R group and carvedilol-treated group were 0.08 +/- 0.01, 0.06 +/- 0.01 and 0.09 +/- 0.01, respectively. There was no significant difference between carvedilol-treated group and I/R group (P > 0.05). The OD values of bax protein in I/R group, sham-operated and carvedilol-treated-treated group were 0.13 +/- 0.02, 0.07 +/- 0.01, 0.06 +/- 0.01, respectively. There was very significant difference between carvedilol-treated group and I/R group (P < 0.01). Bcl-2/bax ratio was 1.07 +/- 0.14 (I/R group), 1.28 +/- 0.16 (sham-operated group), 2.5 +/- 0.26 (carvedilol-treated group) respectively with the difference being very significant between carvedilol-treated group and I/R group (P < 0.05). It was indicated that carvedilol could inhibit cardiomyocyte apoptosis following ischemia and reperfusion, which was related to the increased bcl-2/bax ratio due to inhibition of bax gene expression.

Significance of beta-blockers in the perioperative period

Beta-blockers have emerged as one of the key therapeutic agents that can decrease cardiac morbidity and mortality. Advances in cardiac beta-adrenergic receptor physiology and pharmacology have provided new insights into the beneficial effects of beta-blockers in cardiovascular medicine. Although significant advances have been made, many specific questions still remain to be answered. We will review some of these developments and the current role of beta-blockers in peri-operative medicine.