Amlodipine and carvedilol prevent cytotoxicity in cortical neurons isolated from stroke-prone spontaneously hypertensive rats

R-carvedilol, a potential new therapy for Alzheimer's disease

For decades, the amyloid cascade hypothesis has been the leading hypothesis in studying Alzheimer's disease (AD) pathology and drug development. However, a growing body of evidence indicates that simply removing amyloid plaques may not significantly affect AD progression. Alternatively, it has been proposed that AD progression is driven by increased neuronal excitability. Consistent with this alternative hypothesis, recent studies showed that pharmacologically limiting ryanodine receptor 2 (RyR2) open time with the R-carvedilol enantiomer prevented and reversed neuronal hyperactivity, memory impairment, and neuron loss in AD mouse models without affecting the accumulation of ß-amyloid (Aβ). These data indicate that R-carvedilol could be a potential new therapy for AD.

Beta-blockers in hypertension: overview and meta-analysis of randomized outcome trials

BACKGROUND

Meta-analyses from randomized outcome-based trials have challenged the role of beta-blockers for the treatment of hypertension. However, because they often include trials on diseases other than hypertension, the role of these drugs in the choice of the blood pressure (BP)-lowering treatment strategies remains unclear.

METHODS

Electronic databases were searched for randomized trials that compared beta-blockers vs. placebo/no-treatment/less-intense treatment (BP-lowering trials) or beta-blockers vs. other antihypertensive agents in patients with or without hypertension (comparison trials). Among BP-lowering trials and according to baseline comorbidity, we separately considered trials in hypertension, trials without chronic heart failure or acute myocardial infarction, and trials with either chronic heart failure or acute myocardial infarction. Seven fatal and nonfatal outcomes were calculated (random-effects model) for BP-lowering or comparison trials.

RESULTS

A total of 84 BP-lowering or comparison trials (165 850 patients) were eligible. In 67 BP-lowering trials (68 478 patients; mean follow-up 2.5 years; baseline SBP/DBP, 136/82 mmHg), beta blockers were associated with a lower incidence of major cardiovascular events [risk ratio 0.85 and 95% confidence interval (95% CI) 0.78-0.92] and all-cause death (risk ratio 0.81 and 95% CI 0.75-0.86). Restriction of the analysis to five trials recruiting exclusively hypertensive patients (18 724 patients; mean follow-up 5.1 years; baseline SBP/DBP 163/94 mmHg), a -10.5/-7.0 mmHg BP decrease was accompanied by reduction of major cardiovascular events by 22% (95% CI, 6-34). In 24 comparison trials (103 764 patients, 3.92 years of mean follow-up), beta-blockers compared with other agents were less protective for stroke and all-cause death in all trials and in trials conducted exclusively in hypertensive patients (averaged risk ratio increase 20 and 6%, respectively, for both cases).

CONCLUSION

Compared with other antihypertensive agents, beta-blockers appear to be substantially less protective against stroke and overall mortality. However, they exhibit a substantial risk-reducing ability for all events when prescribed to lower BP in patients with modest or more clear BP elevations, and therefore can be used as additional agents in hypertensive patients.

The Neuroprotective Effect of Carvedilol on Diabetic Neuropathy: An In Vitro Study

Diabetic neuropathy serves as a major complication for diabetic patients across the world. The use of effective treatment is integral for reducing the health complications for diabetic patients. This study has evaluated the carvedilol potential neuroprotective effect on diabetic neuropathy. An in vitro model of diabetic neuropathy was used, including dorsal root ganglia (DRG) that were cultured from male adult mice C57BL. These were incubated for about twenty-four hours in high glucose (HG) media (45 mM). Some cells were incubated with carvedilol (10 μM). Neuronal viability, neuronal morphology, and activating transcription factor 3 (AFT3) were measured. The cell viability was decreased, along with neuronal length, soma area, and soma perimeter with HG media. Also, there was an overexpression of ATF3, which is a neuronal stress response marker. The pretreatment with carvedilol increased the viability of DRG as compared to HG-treated cells. Also, it significantly protected the DRG from HG-induced morphology changes. Though it shows a decrease in AFT3 expression, the statistical results were insignificant. The current study demonstrates the neuroprotective effect of carvedilol against HG-induced DN using an in vitro model. This could be through carvedilol antioxidant effects.

Astrocytic nutritional dysfunction associated with hypoxia-induced neuronal vulnerability in stroke-prone spontaneously hypertensive rats

Stroke-prone spontaneously hypertensive rats (SHRSP) is a valuable animal model to investigate human strokes. SHRSP Izumo strain (Izm) neurons are highly sensitive to blood supply changes. Furthermore, SHRSP/Izm astrocytes show various abnormalities upon hypoxic stimulation compared to control Wistar Kyoto (WKY/Izm) rats. This study aimed to describe stroke-related characteristics of SHRSP/Izm-derived neurons and astrocytes. In addition, we discuss the role of astrocytes in the development of stroke in SHRSP/Izm model. In SHRSP/Izm, neuronal death is induced upon reoxygenation after hypoxia. Furthermore, it was shown that SHRSP/Izm astrocytes show significantly reduced lactate production and supply ability to nerve cells when subjected to hypoxic stimulation. In particular, decreased lactate production and monocarboxylic acid transporter (MCT) expression in SHRSP/Izm astrocytes are factors that induce neuronal cell death. Remarkable differences in glial cell line-derived neurotrophic factor (GDNF) expression and L-serine production were also observed in SHRSP/Izm-derived astrocytes compared to WKY/Izm. Reduced production of both GDNF and L-serine contributes to diminished neuronal survival. The differences between SHRSP/Izm and WKY/Izm astrocyte cellular properties may contribute to compromised neuronal nutrition and induction of neuronal death. These properties are likely to be the factors that enhance stroke in SHRSP/Izm.

Mitochondria damaged by Oxygen Glucose Deprivation can be Restored through Activation of the PI3K/Akt Pathway and Inhibition of Calcium Influx by Amlodipine Camsylate

Amlodipine, a L-type calcium channel blocker, has been reported to have a neuroprotective effect in brain ischemia. Mitochondrial calcium overload leads to apoptosis of cells in neurologic diseases. We evaluated the neuroprotective effects of amlodipine camsylate (AC) on neural stem cells (NSCs) injured by oxygen glucose deprivation (OGD) with a focus on mitochondrial structure and function. NSCs were isolated from rodent embryonic brains. Effects of AC on cell viability, proliferation, level of free radicals, and expression of intracellular signaling proteins were assessed in OGD-injured NSCs. We also investigated the effect of AC on mitochondrial structure in NSCs under OGD by transmission electron microscopy. AC increased the viability and proliferation of NSCs. This beneficial effect of AC was achieved by strong protection of mitochondria. AC markedly enhanced the expression of mitochondrial biogenesis-related proteins and mitochondrial anti-apoptosis proteins. Together, our results indicate that AC protects OGD-injured NSCs by protecting mitochondrial structure and function. The results of the present study provide insight into the mechanisms underlying the protective effects of AC on NSCs.

Carvedilol protection against endogenous Aβ-induced neurotoxicity in N2a cells

Mutations in amyloid precursor protein (APP) and presenilin1 result in overproduction and accumulation of β-amyloid (Aβ) peptide, which has been shown to play an important role in Alzheimer's disease (AD) pathogenesis. Carvedilol, a nonselective β-adrenergic receptor blocker used for treatment for heart failure and hypertension, has displayed its neuroprotective capacity due to its antioxidant property. In this study, we investigated whether Carvedilol has a neuronal protective effect against endogenous Aβ neurotoxicity in mouse Neuro2a (N2a) cells transfected with Swedish amyloid precursor protein (Swe-APP) mutant and Presenilin exon9 deletion mutant (N2a/Swe.D9). Elevated levels of reactive oxygen species (ROS), protein carbonyls, and 4-HNE were found in N2a/Swe.D9 cells, which were ameliorated by administration of Carvedilol in a dose-dependent manner. In addition, the levels of ATP and mitochondrial membrane potential were reduced in N2a/Swe.D9 cells, which were restored by treatment with Carvedilol. N2a/Swe.D9 cells displayed increased vulnerability to H2O2-induced cell death and apoptosis, which could be attenuated by Carvedilol. Mechanistically, we found that Carvedilol prevented apoptosis signals through reducing cytochrome C release and the level of cleaved caspase-3. Taken together, our findings suggest a possible use of Carvedilol in AD treatment.

Effect of β-Adrenergic Antagonists on In-Hospital Mortality after Ischemic Stroke

BACKGROUND

Ischemic stroke accounts for 85%-90% of all strokes and currently has very limited therapeutic options. Recent studies of β-adrenergic antagonists suggest they may have neuroprotective effects that lead to improved functional outcomes in rodent models of ischemic stroke; however, there are limited data in patients. We aimed to determine whether there was an improvement in mortality rates among patients who were taking β-blockers during the acute phase of their ischemic stroke.

METHODS

A retrospective analysis of a prospectively collected database of ischemic stroke patients was performed. Patients who were on β-adrenergic antagonists both at home and during the first 3 days of hospitalization were compared with patients who were not on β-adrenergic antagonists to determine the association with patient mortality rates.

RESULTS

The study included a patient population of 2804 patients. In univariate analysis, use of β-adrenergic antagonists was associated with older age, atrial fibrillation, hypertension, and more-severe initial stroke presentation. Despite this, multivariable analysis revealed a reduction in in-hospital mortality among patients who were treated with β-adrenergic antagonists (odds ratio, .657; 95% confidence interval, .655-.658).

CONCLUSIONS

The continuation of home β-adrenergic antagonist medication during the first 3 days of hospitalization after an ischemic stroke is associated with a decrease in patient mortality. This supports the work done in rodent models suggesting neuroprotective effects of β-blockers after ischemic stroke.

Preclinical Evidences for an Antimanic Effect of Carvedilol

Oxidative imbalance, alterations in brain-derived neurotrophic factor (BDNF), and mitochondrial dysfunction are implicated in bipolar disorder (BD) pathophysiology and comorbidities, for example, cardiovascular conditions. Carvedilol (CVD), a nonselective beta-blocker widely used for the treatment of hypertension, presents antioxidant and mitochondrial stabilizing properties. Thus, we hypothesized that CVD would prevent and/or reverse mania-like behavioral and neurochemical alterations induced by lisdexamfetamine dimesylate (LDX). To do this, male Wistar rats were submitted to two different protocols, namely, prevention and reversal. In the prevention treatment the rats received daily oral administration (mg/kg) of CVD (2.5, 5 or 7.5), saline, valproate (VAL200), or the combination of CVD5 + VAL100 for 7 days. From the 8th to 14th day LDX was added. In the reversal protocol LDX was administered for 7 days with the drugs being added from the 8th to 14th day of treatment. Two hours after the last administration the behavioral (open field and social interaction) and neurochemical (reduced glutathione, lipid peroxidation, and BDNF) determinations were performed. The results showed that CVD prevented and reversed the behavioral and neurochemical alterations induced by LDX. The administration of CVD5 + VAL100 potentiated the effect of VAL200 alone. Taken together these results demonstrate a possible antimanic effect of CVD in this preclinical model.

Amlodipine prevents apoptotic cell death by correction of elevated intracellular calcium in a primary neuronal model of Batten disease (CLN3 disease)

CLN3 disease (Spielmeyer-Vogt-Sjogren-Batten disease) is a severe pediatric neurodegenerative disorder for which there is currently no effective treatment. The disease is characterized by progressive neuronal death, which may be triggered by abnormal intracellular calcium levels leading to neuronal apoptosis. Previously, we demonstrated reversal of the calcium effect in a neuroblastoma cell line using amlodipine and other calcium channel antagonists. In the present studies, we developed a CLN3 siRNA-inhibited primary rat neuron model to further study etoposide-induced calcium changes and apoptosis in CLN3 disease followed by recovery experiments with amlodipine. Our results show that intracellular calcium is significantly elevated in siRNA-inhibited cortical neurons after potassium chloride-induced depolarization. We were also able to show that amlodipine, a predominantly L-type dihydropyrimidine calcium channel antagonist can reverse the aberrant calcium elevations in this model of the disease. We performed an in situ TUNEL assay following etoposide-exposure to siRNA inhibited primary neurons, and apoptotic nuclei were detected providing additional evidence that increased neuronal apoptosis is associated with increased calcium levels. Amlodipine also reduced the absolute number of apoptotic cells in this experimental model.

Ginsenoside-Rd potentiates apoptosis induced by hydrogen peroxide in basilar artery smooth muscle cells through the mitochondrial pathway

Our previous studies showed that ginsenoside-Rd, a purified component from Panax notoginseng, inhibited cell proliferation and reversed basilar artery remodeling. The aim of this study was to investigate whether ginsenoside- Rd influences H(2)O(2)-induced apoptosis in basilar artery smooth muscle cells (BASMCs). The results showed that ginsenoside-Rd significantly potentiated H(2)O(2)-induced cell death and cell apoptosis. This resulted in a concentration-dependent reduction of the cell viability. Ginsenoside-Rd further increased cytochrome C release and caspase-9/caspase-3 activations, and reduced the stability of mitochondrial membrane potential (MMP) and the ratio of Bcl-2/Bax. Cyclosporine A, an inhibitor of mitochondrial-permeability transition, inhibited alteration of mitochondrial permeability induced by H(2)O(2) and reversed the effect of ginsenoside-Rd on MMP. Our data strongly suggest that ginsenoside-Rd potentiated H(2)O(2)-induced apoptosis of BASMCs through the mitochondria-dependent pathway.

Effects of carvedilol on delayed rectifier and transient inactivating potassium currents in rat hippocampal CA1 neurons

1. The aims of the present study were to investigate the mechanism(s) underlying the protective effect of carvedilol against neural damage. 2. The transient inactivating potassium current (I(A) ) and the delayed rectifier potassium current (I(K) ) in rat hippocampal CA1 pyramidal neurons were recorded using whole-cell patch-clamp techniques. 3. Carvedilol (0.1-3 μmol/L) significantly inhibited I(K) with an IC(50) of 1.3 μmol/L and the inhibition was voltage independent. Over the same concentration range, carvedilol had no effect on the amplitude of I(A). At 1 μmol/L, carvedilol did not significantly change the steady state activation curves of I(A) and I(K), but did negatively shift their steady state inactivation curves. Recovery from inactivation was slowed for both I(A) and I(K). The inhibitory effect of carvedilol on I(K) was not affected by the adrenoceptor agonists phenylephrine and prazosin or the adrenoceptor antagonist isoproterenol, but propranolol was able to shift the dose-response curve of carvedilol for I(K) to the right. 4. Because I(K) is the main pathway for loss of intracellular potassium from depolarized neurons, selective obstruction of I(K) by carvedilol could be useful for neuroprotection.

Investigation of carvedilol-evoked Ca²+ movement and death in human oral cancer cells

The effect of carvedilol on cytosolic free Ca²⁺ concentrations ([Ca²⁺](i)) in OC2 human oral cancer cells is unknown. This study examined if carvedilol altered basal [Ca²⁺](i) levels in suspended OC2 cells by using fura-2 as a Ca²⁺-sensitive fluorescent probe. Carvedilol at concentrations between 10 and 40 µM increased [Ca²⁺](i) in a concentration-dependent fashion. The Ca²⁺ signal was decreased by 50% by removing extracellular Ca²⁺. Carvedilol-induced Ca²⁺ entry was not affected by the store-operated Ca²⁺ channel blockers nifedipine, econazole, and SK&F96365, but was enhanced by activation or inhibition of protein kinase C. In Ca²⁺-free medium, incubation with the endoplasmic reticulum Ca²⁺ pump inhibitor thapsigargin did not change carvedilol-induced [Ca²⁺](i) rise; conversely, incubation with carvedilol did not reduce thapsigargin-induced Ca²⁺ release. Pretreatment with the mitochondrial uncoupler carbonylcyanide m-chlorophenylhydrazone (CCCP) inhibited carvedilol-induced [Ca²⁺](i) release. Inhibition of phospholipase C with U73122 did not alter carvedilol-induced [Ca²⁺](i) rise. Carvedilol at 5-50 µM induced cell death in a concentration-dependent manner. The death was not reversed when cytosolic Ca²⁺ was chelated with 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid acetoxymethyl ester (BAPTA/AM). Annexin V/propidium iodide staining assay suggests that apoptosis played a role in the death. Collectively, in OC2 cells, carvedilol induced [Ca²⁺](i) rise by causing phospholipase C-independent Ca²⁺ release from mitochondria and non-endoplasmic reticulum stores, and Ca²⁺ influx via protein kinase C-regulated channels. Carvedilol (up to 50 μM) induced cell death in a Ca²⁺-independent manner that involved apoptosis.

Neuronal vulnerability of stroke-prone spontaneously hypertensive rats to ischemia and its prevention with antioxidants such as vitamin E

Stroke-prone spontaneously hypertensive rats (SHRSP/Izm) develop severe hypertension, and more than 95% of them die of cerebral stroke. Hypoxic stimulation followed by oxygen reperfusion induces neuronal damage in both normotensive Wistar Kyoto/Izm (WKY/Izm) and SHRSP/Izm rats, and the percentage of neurons that undergo apoptosis during hypoxia-reperfusion is markedly higher in SHRSP/Izm rats than in WKY/Izm rats. The biochemical characteristics of the SHRSP/Izm rats, unlike those of WKY/Izm rats, might act as a factor in the stroke proneness of SHRSP/Izm rats. In the hippocampus, the formation of hydroxyl radicals and the cerebral blood flow-independent formation of nitric oxide (NO) were strongly increased after reperfusion in SHRSP/Izm rats, and the neuronal expression of the thioredoxin and Bcl-2 genes was significantly decreased in the SHRSP/Izm rats compared with the WKY/Izm rats. On the other hand, the effects of antioxidants against neuronal death associated with cerebral ischemia-reperfusion were stronger in the SHRSP/Izm rats, in which the addition of vitamin E or ebselen almost completely inhibited neuronal death. Namely, the addition of 100 microg/ml of vitamin E under hypoxia/reoxygenation (H/R) conditions completely inhibited WKY and SHRSP/Izm neuronal death. Vitamin E exerts a marked inhibitory effect against neuronal damage via its incorporation into mitochondrial membranes, where it captures reactive oxygen and free radicals. The susceptibility of neurons to apoptosis in SHRSP/Izm rats is partly due to an insufficiency of mitochondrial redox regulation and apoptosis-inhibitory proteins. In this review, we describe the neuronal vulnerability of SHRSP/Izm rats induced by cerebral ischemia and the effects of antioxidants such as vitamin E.

Carvedilol-induced elevation in cytosolic free Ca(2+) level and apoptosis in SIRC corneal epithelial cells

The effect of the cardiovascular drug carvedilol on cytosolic free Ca(2+) concentrations ([Ca( 2+)](i)) and viability was examined in Statens Seruminstitut rabbit cornea (SIRC) corneal epithelial cells. [Ca(2+)](i) and cell viability were measured using the fluorescent dyes fura-2 and 4-[3-[4-lodophenyl]-2-4(4-nitrophenyl)-2H-5-tetrazolio-1,3-benzene disulfonate] (WST-1), respectively. Carvedilol at concentrations between 1 and 30 microM increased [Ca( 2+)](i) in a concentration-dependent manner. The Ca(2+) signal was reduced partly by removing extracellular Ca(2+). Carvedilol induced Mn(2+) quench of fura-2 fluorescence implicating Ca(2+) influx. The Ca(2+) influx was inhibited by suppression of protein kinase C activity. In Ca(2+)-free medium, after pretreatment with 1 microM thapsigargin (an endoplasmic reticulum Ca( 2+) pump inhibitor), carvedilol-induced [Ca(2+)](i) rise was reduced; and conversely, carvedilol pretreatment inhibited a major part of thapsigargin-induced [Ca( 2+)](i) rise. Addition of the phospholipase C inhibitor 1-[6-[[17 beta-3-methoxyestra-1,3,5(10)-trien-17-yl]amino] hexyl]-1H-pyrrole-2,5-dione (U73122; 2 microM) did not change carvedilol-induced [Ca(2+)](i) rise. At concentrations between 5 and 70 microM, carvedilol killed cells in a concentration-dependent manner. The cytotoxic effect of 20 microM carvedilol was not reversed by prechelating cytosolic Ca(2+) with BAPTA/AM. Apoptosis was induced by 5-70 microM carvedilol. Collectively, in SIRC corneal epithelial cells, carvedilol-induced [Ca(2+)](i) rises by causing Ca(2+) release from the endoplasmic reticulum in a phospholipase C-independent manner, and Ca( 2+) influx via protein kinase C-regulated Ca(2+) channels. Carvedilol-caused cytotoxicity was mediated by Ca(2+)-independent apoptosis in a concentration-dependent manner.

Cholinergic receptor pathways involved in apoptosis, cell proliferation and neuronal differentiation

Acetylcholine (ACh) has been shown to modulate neuronal differentiation during early development. Both muscarinic and nicotinic acetylcholine receptors (AChRs) regulate a wide variety of physiological responses, including apoptosis, cellular proliferation and neuronal differentiation. However, the intracellular mechanisms underlying these effects of AChR signaling are not fully understood. It is known that activation of AChRs increase cellular proliferation and neurogenesis and that regulation of intracellular calcium through AChRs may underlie the many functions of ACh. Intriguingly, activation of diverse signaling molecules such as Ras-mitogen-activated protein kinase, phosphatidylinositol 3-kinase-Akt, protein kinase C and c-Src is modulated by AChRs. Here we discuss the roles of ACh in neuronal differentiation, cell proliferation and apoptosis. We also discuss the pathways involved in these processes, as well as the effects of novel endogenous AChRs agonists and strategies to enhance neuronal-differentiation of stem and neural progenitor cells. Further understanding of the intracellular mechanisms underlying AChR signaling may provide insights for novel therapeutic strategies, as abnormal AChR activity is present in many diseases.

Protective effects of amlodipine on ischemia-reperfusion injury of rat ovary: biochemical and histopathologic evaluation

OBJECTIVE

To evaluate the effects of amlodipine as an antioxidant and analyze the histopathologic changes in experimental ischemic and ischemic-reperfusion (I/R) injury in rat ovaries.

DESIGN

Experimental study.

SETTING

Experimental surgery laboratory.

ANIMAL(S)

Forty-two rats with experimentally induced ovarian torsion.

INTERVENTION(S)

Group 1: sham operation; group 2: bilateral ovarian ischemia; group 3: 3-hour period of ischemia plus 3 hours of reperfusion; groups 4 and 5: amlodipine administration at 3 and 5 mg/kg respectively before one half hour of ischemia, and then bilateral ovarian ischemia. The ovaries were removed at the third hour of ischemia. Groups 6 and 7: 3-hour period of bilateral ovarian ischemia. Two and a half hours after the induction of ischemia, the rats received amlodipine. At the end of a 3-hour period of ischemia, 3 hours of reperfusion was continued; then the ovaries were removed.

MAIN OUTCOME MEASURE(S)

Ovarian tissue superoxide dismutase and nitric oxide activity; histopathologic examination of all ovarian rat tissue.

RESULT(S)

Ischemia and I/R increased the inducible nitric oxide synthase activity while decreasing the superoxide dismutase activity significantly in comparison with the sham group. Both doses of amlodipine before ischemia and I/R reversed the trend in nitric oxide synthase activities and reversed the trend in the rat's ovary.

CONCLUSION(S)

Conservative treatment with amlodipine is effective in reducing tissue damage induced by ischemia, I/R, or both in ovaries.

Mechanisms of carvedilol-induced [Ca2+] i rises and death in human hepatoma cells

The effect of the cardiovascular drug carvedilol on cytosolic free Ca2+ concentrations ([Ca2+]i) and viability has not been explored in human hepatoma cells. This study examined whether carvedilol altered [Ca2+]i and caused cell death in HA59T cells. [Ca2+]i and cell viability were measured using the fluorescent dyes fura-2 and WST-1, respectively. Carvedilol at concentrations >or=1 microM increased [Ca2+]i in a concentration-dependent manner with an EC50 value of 20 microM. The Ca2+ signal was reduced partly by removing extracellular Ca2+. Carvedilol induced Mn2+ quench of fura-2 fluorescence, implicating Ca2+ influx. The Ca2+ influx was sensitive to La3+, econazole, nifedipine, and SKF96365. In Ca2+-free medium, after pretreatment with 1 muM thapsigargin (an endoplasmic reticulum Ca2+ pump inhibitor), carvedilol-induced [Ca2+]i rises were abolished; and conversely, carvedilol pretreatment inhibited a major part of thapsigargin-induced [Ca2+]i rises. Inhibition of phospholipase C with 2 microM U73122 did not change carvedilol-induced [Ca2+]i rises. At concentrations between 1 and 50 microM, carvedilol killed cells in a concentration-dependent manner. The cytotoxic effect of 1 microM (but not 30 microM) carvedilol was fully reversed by prechelating cytosolic Ca2+ with 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid-acetoxymethyl ester (BAPTA/AM). Apoptosis was induced by 30 (but not 1) microM carvedilol. Collectively, in HA59T hepatoma cells, carvedilol induced [Ca2+]i rises by causing Ca2+ release from the endoplasmic reticulum in a phospholipase-C-independent manner and Ca2+ influx via store-operated Ca2+ channels. Carvedilol-caused cytotoxicity was mediated by Ca2+ and apoptosis in a concentration-dependent manner.

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.

Beta-blockers reduce the risk of early death in ischemic stroke

OBJECTIVES

Beta-blockers reduce mortality in patients after myocardial infarction. Experimental studies suggest that beta-blockers have also neuroprotective properties. The aim of this study was to assess if use of beta-blockers is associated with reduced risk of early death in ischemic stroke patients.

MATERIALS AND METHODS

Retrospective data analysis of 841 consecutive patients with acute ischemic stroke admitted to the stroke unit within 24 h after stroke onset.

RESULTS

10.6% of patients received beta-blockers during hospitalization. Thirty-day case fatality was significantly lower in patients treated with beta-blockers than in those not treated with beta-blockers (6.8% versus 19.0%, P < 0.01). After adjustment for other prognostic factors, the use of beta-blockers was associated with reduced risk of early death (relative hazard 0.37, 95% confidence interval 0.16-0.84) independently of age, stroke severity, fasting glucose, total cholesterol level and pneumonia. When patients who died of cardiovascular causes were excluded from the analysis, the use of beta-blocker was no longer significantly associated with risk of death (P = 0.12).

CONCLUSION

In a retrospective series the use of beta-blockers was associated with reduced risk of early death in patients with ischemic stroke.

The calcium-channel blocker, azelnidipine, enhances the inhibitory action of AT1 receptor blockade on ischemic brain damage

OBJECTIVE

The combined effects of a calcium-channel blocker (CCB) with an angiotensin (Ang) II type 1 (AT1) receptor blocker were investigated in focal brain ischemia induced by middle cerebral artery (MCA) occlusion.

METHODS AND RESULTS

In male C57BL/6J mice, permanent occlusion of the MCA-induced focal cerebral ischemia and neurological deficit after 24 h, accompanied by a reduction of cerebral blood flow and an increase in superoxide production in the ischemic area. Administration of azelnidipine, a CCB, at 1.0 mg/kg per day for 10 days significantly suppressed these changes after MCA without affecting systolic blood pressure. Such inhibitory effects of azelnidipine on brain ischemia could be observed in AT1a receptor-deficient mice. In addition, olmesartan, an AT1 receptor blocker, at 3.0 mg/kg per day also diminished the ischemic brain area and neurological score, as well as superoxide production and the reduction of cerebral surface blood flow in C57BL/6 mice. The combination of lower doses of azelnidipine (0.1 mg/kg per day) and olmesartan (0.5 mg/kg per day) significantly attenuated the ischemic brain area, neurological score, superoxide production and the reduction of cerebral surface blood flow after MCA occlusion in C57BL/6 mice, whereas either of these agents alone at these doses did not affect brain ischemia.

CONCLUSION

These results indicate that azelnidipine inhibited ischemic brain damage induced by MCA occlusion, at least in part, through suppression of blood flow change and oxidative stress via a signaling mechanism independent of AT1 receptor stimulation. Moreover, azelnidipine synergistically enhanced the inhibitory action of olmesartan on brain ischemia, suggesting beneficial combined effects of a CCB with an AT1 receptor blocker on ischemic brain damage.

Amlodipine-induced reduction of oxidative stress in the brain is associated with sympatho-inhibitory effects in stroke-prone spontaneously hypertensive rats

Amlodipine is a dihydropyridine calcium channel blocker that is widely used for the treatment of hypertensive patients and has an antioxidant effect on vessels in vitro. The aim of the present study was to examine whether treatment with amlodipine reduced oxidative stress in the brains of stroke-prone spontaneously hypertensive rats (SHRSP). The animals received amlodipine, nicardipine or hydralazine for 30 days in their drinking water. Levels of thiobarbituric acid-reactive substances (TBARS) in the brain (cortex, cerebellum, hypothalamus, and brainstem) were measured before and after each treatment. Systolic blood pressure decreased to similar levels in the amlodipine-, nicardipine-, and hydralazine-treated groups. Urinary norepinephrine excretion was significantly reduced in SHRSP after treatment with amlodipine, but not with nicardipine or hydralazine. Levels of TBARS in the cortex, cerebellum, hypothalamus, and brainstem were significantly higher in SHRSP than in Wistar-Kyoto rats (WKY), and were reduced in amlodipine-treated, but not in nicardipine- or hydralazine-treated, SHRSP. Electron spin resonance spectroscopy revealed increased levels of reactive oxygen species in the brains of SHRSP, which were reduced by treatment with amlodipine. Intracisternal infusion of amlodipine also reduced systolic blood pressure, urinary norepinephrine excretion, and the levels of TBARS in the brain. These results suggested that oxidative stress in the brain was enhanced in SHRSP compared with WKY rats. In addition, antihypertensive treatment with amlodipine reduced oxidative stress in all areas of the brain examined and decreased blood pressure without a reflex increase in sympathetic nerve activity in SHRSP.

Comparison of the effects of cilnidipine and amlodipine on ambulatory blood pressure

Cilnidipine is a novel and unique 1,4-dydropyridine derivative calcium antagonist that exerts potent inhibitory actions not only on L-type but also on N-type voltage-dependent calcium channels. Blockade of the neural N-type calcium channel inhibits the secretion of norepinephrine from peripheral neural terminals and depresses sympathetic nervous system activity. The purpose of this study was to assess the effect of cilnidipine and amlodipine on ambulatory blood pressure (BP) levels. We performed 24-h ambulatory BP monitoring before and after once-daily use of cilnidipine (n=55) and amlodipine (n=55) in 110 hypertensive patients. Both drugs significantly reduced clinic and 24-h systolic BP (SBP) and diastolic BP (DBP) (p < 0.005). However, the reductions of 24-h (-1.19+/-6.78 vs. 1.55+/-6.13 bpm, p=0.03), daytime (-1.58+/-6.72 vs. 1.68+/-7.34 bpm, p=0.02) and nighttime (-1.19+/-5.72 vs. 1.89+/-6.56 bpm, p=0.01) pulse rate (PR) were significantly greater in the cilnidipine group than the amlodipine group. There was no correlation between the degree of daytime SBP change and that of daytime PR change after amlodipine treatment (r=-0.08, n.s.), but there was a significant negative correlation between the degree of daytime SBP change and that of day-time PR change after cilnidipine treatment (r=-0.27, p<0.05). N-type calcium channel blockade by cilnidipine may not cause reflex tachycardia, and may be useful for hypertensive treatment.

Different Effects of Amlodipine and Enalapril on the Mitogen-Activated Protein Kinase/Extracellular Signal-Regulated Kinase Kinase-Extracellular Signal-Regulated Kinase Pathway for Induction of Vascular Smooth Muscle Cell Differentiation In Vivo

Although recent clinical trials have shown that amlodipine exerts antiatherogenic effects, the mechanism of these effects remains unknown. This study was designed to examine which signal transduction pathway might be important for the antiatherogenic property of amlodipine, as assessed by aortic smooth muscle cell (SMC) phenotypes in hypertension in vivo. Stroke-prone spontaneously hypertensive rats (SHRSP) were randomly treated with a vehicle, amlodipine, or enalapril while Wistar-Kyoto rats (WKY) used as controls were treated with only the vehicle. Both drugs were equally effective at reducing systolic blood pressure, and inhibiting the progression of aortic remodeling and fibrosis in comparison to those of vehicle-treated SHRSP. In the aortas of vehicle-treated SHRSP, the level of contractile-type smooth muscle (SM) myosin heavy chain (MHC) SM2 was significantly lower, whereas the level of synthetic-type MHC NMHC-B/SMemb was significantly higher compared with those in the WKY aortas. Compared to the vehicle-treated SHRSP group, both drugs significantly and equally shifted the aortic SMC phenotype in SHRSP toward the differentiated state by reducing NMHC-B/SMemb and increasing SM2. The levels of MKK6, p38 MAPK, MEK1 and p-42/44 ERK were significantly higher in the vehicle-treated SHRSP than in the WKY. Both drugs significantly reduced these values in the SHRSP aorta. Furthermore, the levels of MEK1 and p-42/44 ERK were significantly lower in the amlodipine- than in the enalapril-treated SHRSP group, whereas enalapril was more effective than amlodipine at increasing p-Akt and endothelial NO synthase in SHRSP aortas, which were significantly lower in the vehicle SHRSP group than in the WKY group. Thus, the MEK-ERK pathway might be one of the crucial determinants of the aortic SMC phenotype activated by amlodipine treatment of hypertension in vivo.

Pharmacological treatment of ischemic stroke

Current pharmacological strategies for acute ischemic stroke largely mirror those employed in acute coronary syndromes. However, important differences in the effectiveness and versatility of the principal agents have emerged between these 2 clinical settings. In general, the level of success achieved with drugs in acute coronary syndromes has not carried over to the same extent when the same drug types are used in stroke. The principal reason is that reperfusion or anticoagulant therapies in the setting of brain infarction run a significant risk of hemorrhagic transformation that has no direct equivalent in myocardial infarction. Consequently, a significant challenge in acute stroke therapeutics is the ability to select patients for drugs where only a narrow therapeutic margin exists and to identify methods that can minimize hemorrhage risk. Other brain-specific vascular factors also pertain in explaining differences in outcome of drugs generally regarded as having a broad cardiovascular remit. The relatively limited efficacy of antiplatelets in stroke might relate to the composition and heterogeneity of the cerebrovascular lesion, while the poor outcome associated with acute anti-hypertensive use is partly due to loss of cerebrovascular autoregulation. Finally, downstream consequences of arterial occlusion within the brain such as excitotoxicity and plasticity are organ specific and, as such, deserve their own pharmacological approaches. In this review, we describe the general mechanism of each drug class used in ischemic stroke and then report on the clinical experience and application for each.

Can thromboembolism be the result, rather than the inciting cause, of acute vascular events such as stroke, pulmonary embolism, mesenteric ischemia, and venous thrombosis?: a maladaptation of the prehistoric trauma response

Thromboembolism is considered the inciting cause of many vascular disorders including acute coronary syndrome (ACS), ischemic stroke, pulmonary embolism (PE), deep vein thrombosis (DVT), and mesenteric ischemia. Adrenergia and inflammation are known to accompany these conditions, particularly among arterial thromboembolic disorders, but the teleologic basis of these associations remains poorly understood. We argue that thromboembolism may sometimes be the result, rather than the cause, of acute vascular events, and may be precipitated by underlying adrenergia. Thromboembolic events are most prone to occur during parts of the circadian, seasonal, lifespan, and reproductive cycles with sympathetic dominance, as well as during behavioral, exertional, physiologic, and iatrogenic activation of sympathetic stress. Molecular evidence suggests that adrenergia and inflammation can promote coagulation and lead to co-activation of the pathways. Acute vascular events that occur without angiographic evidence of occlusion suggest that some infarcts may be attributable to adrenergia alone. "Embolic" disorders may represent asynchronous systemic phenomena rather than clot migration. During acute thromboembolism, downstream tissue hypoxia can activate maladaptive self-propelling cycles of sympathetic bias, inflammation, and coagulation. The counterproductive co-activation of these pathways may reflect a maladaptive interlink forged during the primordial evolution of trauma physiology. Their rapid co-mobilization enables rapid control of hemorrhage, microbial defense, and perfusion maintenance during trauma, but the pathways may behave maladaptively in the setting of modern diseases where endothelial injury may be more often precipitated by smoking, diabetes, dyslipidemia, or hypertension. Sympathetic blockade is already employed in ACS, and beta-blockers are used as antihypertensives to prevent stroke. Our hypothesis suggests that the benefits of beta-blockers in stroke may be independent of antihypertensive effects, and that adrenergia may represent a target for managing all thromboembolic disorders, independent of anti-coagulative and thrombolytic therapies. Perhaps reducing adrenergia, rather than maintaining high cerebral perfusion pressure, may represent a counterintuitive strategy for treating stroke and for reducing reperfusion injury. Plausible mechanisms by which autonomic dysfunction may induce venous thrombosis are discussed, especially in those with baroreceptor dysfunction, immobilization, or dehydration. Unexplained hypercoagulability of cancer may also operate through tumor-induced adrenergia and inflammation.

Protective effect of antioxidant ebselen (PZ51) on the cerebral cortex of stroke-prone spontaneously hypertensive rats

An increase in reactive oxygen species has been shown to play a role in perpetuating hypertension and cerebral injury in stroke-prone spontaneously hypertensive rats (SHRsp). Lipid peroxidation in the cerebral cortex is much more intense in SHRsp after establishment of severe hypertension as compared to that in normotensive Wistar-Kyoto rats (WKY). Cortical neurons from SHRsp are more vulnerable to hypoxia and hyponutritional conditions. We sought to investigate whether long-term administration of seleno-glutathione peroxidase mimic ebselen (PZ51) would have a protective effect on cortical neurons in SHRsp, and, if so, the possible mechanisms of this effect. Twenty-two 8-week-old SHRsp were randomized into a PZ51 group and control group. Age-matched WKY were used as normal controls. We examined the levels of malonaldehyde (MDA) and nitric oxide (NO) in the cerebral cortex (CC) homogenate, detected the three isoforms of nitric oxide synthase (NOS) by Western blotting, and examined cortical neurons by transmission electron microscopy. The results showed that PZ51 treatment significantly decreased both MDA and NO in the CC, inhibited inducible nitric oxide synthase (iNOS) protein expression, and alleviated the damage to cortical neurons compared to the findings for the control group. In conclusion, the present study showed that PZ51 administration suppressed lipid peroxidation and inhibited iNOS protein expression in CC homogenate, and it was suggested that these mechanisms may play a role in the protective effects of PZ51 on cortical neurons of SHRsp.

Oxidative stress during the chronic phase after stroke

Stroke is a complex disease originating and developing on the background of genetic predisposition and interaction between different risk factors that chronically damage blood vessels. The search for an effective treatment of stroke patients is the main priority of basic and clinical sciences. The chronic phase of stroke provides possibilities for therapy directed toward stimulation of recovery processes as well as prophylaxis, which reduces the probability of subsequent cerebrovascular events. Oxidative stress is a potential contributor to the pathophysiological consequences of stroke. The aim of the present review is to summarize the current knowledge of the role of oxidative stress during the chronic phase after stroke and its contribution to the initiation of subsequent stroke. The relationship among inflammation, hemostatic abnormalities, and platelet activation in chronic stroke patients is discussed in the context of ongoing free radical processes and oxidative damage. Free radical-mediated effects of increased plasma level of homocysteine and its possible contribution to the processes leading to recurrent stroke are discussed as well. The status of the antioxidant defense system and the degree of oxidative damage in the circulation of stroke survivors are examined. The results are interpreted in view of the effects of the vascular risk factors for stroke that include additional activation of inflammatory and free radical mechanisms. Also, the possibilities for combined therapy including antioxidants in the acute and convalescent stages of stroke are considered. Future investigations are expected to elucidate the role of free radical processes in the chronic phase after stroke and to evaluate the prophylactic and therapeutic potential of anti-radical agents.