Inhibition of excessive neuronal apoptosis by the calcium antagonist amlodipine and antioxidants in cerebellar granule cells

Hypertension & dementia: Pathophysiology & potential utility of antihypertensives in reducing disease burden

Dementia is a common cause of disability and dependency among the elderly due to its progressive neurodegenerative nature. As there is currently no curative therapy, it is of major importance to identify new ways to reduce its prevalence. Hypertension is recognised as a modifiable risk factor for dementia, particularly for the two most common subtypes; vascular dementia (VaD) and Alzheimer's disease (AD). From the current literature, identified through a comprehensive literature search of PubMed and Cochrane Library, this review aims to establish the stage in adulthood when hypertension becomes a risk for cognitive decline and dementia, and whether antihypertensive treatment is effective as a preventative therapy. Observational studies generally found hypertension in mid-life (age 45-64) to be correlated with an increased risk of cognitive decline and dementia incidence, including both VaD and AD. Hypertension manifesting in late life (age ≥ 65) was demonstrated to be less of a risk, to the extent that incidences of high blood pressure (BP) in the very elderly (age ≥ 75) may even be related to reduced incidence of dementias. Despite the evidence linking hypertension to dementia, there were conflicting findings as to whether the use of antihypertensives was beneficial for its prevention and this conflicting evidence and inconsistent results could be due to the methodological differences between the reviewed observational and randomised controlled trials. Furthermore, dihydropyridine calcium channel blockers and potassium-sparing diuretics were proposed to have neuroprotective properties in addition to BP lowering. Overall, if antihypertensives are confirmed to be beneficial by larger-scale homogenous trials with longer follow-up durations, treatment of hypertension, particularly in mid-life, could be an effective strategy to considerably lower the prevalence of dementia. Furthermore, greater clarification of the neuroprotective properties that some antihypertensives possess will allow for better clinical practice guidance on the choice of antihypertensive class for both BP lowering and dementia prevention.

Possible Pharmacodynamic Interaction of Azelnidipine with Citicoline Against Ischemic Brain Injury: Behavioral, Biochemical and Histological Alterations

BACKGROUND

Currently, no drug has been approved for the management of postischemic neuronal damage. Existing studies show that calcium channel blockers have neuroprotective properties, while citicoline is involved in maintaining neuronal integrity.

PURPOSE

This study was envisaged to investigate the effect of azelnidipine (novel calcium channel blocker) alone and in combination with citicoline (phosphatidyl-choline analogue) against ischemic brain damage in Wistar rats.

METHODS

Previously standardized bilateral common carotid artery occlusion model was used to induce cerebral ischemic injury in Wistar rats. Pretreatment with azelnidipine (1.5 mg/Kg and 3 mg/Kg; p.o.) or citicoline (250 mg/Kg; i.p.) was done every 24 h starting 7 days before the bilateral common carotid artery occlusion surgery. Pharmacological assessments (behavioral, biochemical, mitochondrial, molecular, and histological) were done after 48 h of the reperfusion period.

RESULTS

Azelnidipine and citicoline were found to protect the brain from progressive neuronal damage as seen by improved sensorimotor behavior (locomotion, rota rod, and beam balance performance) and reduced oxidative stress (decreased malondialdehyde (MDA), nitrite, increased glutathione (GSH), superoxide dismutase (SOD)). Impairment of mitochondrial enzyme system and increase in the infarct area were found to be arrested by individual treatments with azelnidipine and citicoline. These effects were further potentiated synergistically as the combination of citicoline and azelnidipine was found to decrease glutamate levels, caspase-3 activity and histological alterations as compared to their individual effects.

CONCLUSION

Azelnidipine and citicoline synergistically decrease excitotoxic and oxidative damage against ischemic brain injury in Wistar rats and, therefore, propose a clinically relevant combination for the prevention of postischemic neuronal damage.

Investigation of Blood Characteristics in Nonsyndromic Retinitis Pigmentosa: A Retrospective Study

Purpose

To investigate the characteristics of blood in nonsyndromic retinitis pigmentosa (RP) and reveal the pathogenesis of blood cells involved in blood stasis in RP.

Design

This is a retrospective observational study.

Methods

We collected vein blood from 101 cases of patients with nonsyndromic RP and 120 cases of normal individuals according to a single-blind study and used routine clinical examination to detect the indicators of blood. All the subjects were mainly from the central south of China. Data were analyzed statistically between the RP group and normal control.

Results

The indicator of platelet distribution width (PDW) in patients with RP was higher than that in the normal group; the indicators of red blood cell (RBCs), hemoglobin (HGB), hematocrit (HCT), basophils (BASs), platelets (PLTs), and plateletcrit (PCT) in the RP group were lower than those in the normal control. The differences were statistically very significant between the RP group and normal group (p < 0.01). There were no statistical differences in the other indicators between the RP and normal group.

Conclusions

The changes in RBCs and PLTs in patients with RP implied that RP induces RBC aggregation and platelet activation, leading to blood stasis which in turn initiates more apoptosis.

Formulations of Amlodipine: A Review

Amlodipine (AD) is a calcium channel blocker that is mainly used in the treatment of hypertension and angina. However, latest findings have revealed that its efficacy is not only limited to the treatment of cardiovascular diseases as it has shown to possess antioxidant activity and plays an important role in apoptosis. Therefore, it is also employed in the treatment of cerebrovascular stroke, neurodegenerative diseases, leukemia, breast cancer, and so forth either alone or in combination with other drugs. AD is a photosensitive drug and requires protection from light. A number of workers have tried to formulate various conventional and nonconventional dosage forms of AD. This review highlights all the formulations that have been developed to achieve maximum stability with the desired therapeutic action for the delivery of AD such as fast dissolving tablets, floating tablets, layered tablets, single-pill combinations, capsules, oral and transdermal films, suspensions, emulsions, mucoadhesive microspheres, gels, transdermal patches, and liposomal formulations.

Central Nervous System-Toxic Lidocaine Concentrations Unmask L-Type Ca²⁺ Current-Mediated Action Potentials in Rat Thalamocortical Neurons: An In Vitro Mechanism of Action Study

BACKGROUND

High systemic lidocaine concentrations exert well-known toxic effects on the central nervous system (CNS), including seizures, coma, and death. The underlying mechanisms are still largely obscure, and the actions of lidocaine on supraspinal neurons have received comparatively little study. We recently found that lidocaine at clinically neurotoxic concentrations increases excitability mediated by Na-independent, high-threshold (HT) action potential spikes in rat thalamocortical neurons. Our goal in this study was to characterize these spikes and test the hypothesis that they are generated by HT Ca currents, previously implicated in neurotoxicity. We also sought to identify and isolate the specific underlying subtype of Ca current.

METHODS

We investigated the actions of lidocaine in the CNS-toxic concentration range (100 μM-1 mM) on ventrobasal thalamocortical neurons in rat brain slices in vitro, using whole-cell patch-clamp recordings aided by differential interference contrast infrared videomicroscopy. Drugs were bath applied; action potentials were generated using current clamp protocols, and underlying currents were identified and isolated with ion channel blockers and electrolyte substitution.

RESULTS

Lidocaine (100 μM-1 mM) abolished Na-dependent tonic firing in all neurons tested (n = 46). However, in 39 of 46 (85%) neurons, lidocaine unmasked evoked HT action potentials with lower amplitudes and rates of de-/repolarization compared with control. These HT action potentials remained during the application of tetrodotoxin (600 nM), were blocked by Cd (50 μM), and disappeared after superfusion with an extracellular solution deprived of Ca. These features implied that the unmasked potentials were generated by high-voltage-activated Ca channels and not by Na channels. Application of the L-type Ca channel blocker, nifedipine (5 μM), completely blocked the HT potentials, whereas the N-type Ca channel blocker, ω-conotoxin GVIA (1 μM), had little effect.

CONCLUSIONS

At clinically CNS-toxic concentrations, lidocaine unmasked in thalamocortical neurons evoked HT action potentials mediated by the L-type Ca current while substantially suppressing Na-dependent excitability. On the basis of the known role of an increase in intracellular Ca in the pathogenesis of local anesthetic neurotoxicity, this novel action represents a plausible contributing candidate mechanism for lidocaine's CNS toxicity in vivo.

Polyphenolic Antioxidants and Neuronal Regeneration

Many studies indicate that oxidative stress is involved in the pathophysiology of neurodegenerative diseases. Oxidative stress can induce neuronal damages, modulate intracellular signaling and ultimately leads to neuronal death by apoptosis or necrosis. To review antioxidants preventive effects on oxidative stress and neurodegenerative diseases we accumulated data from international medical journals and academic informations’ sites. According to many studies, antioxidants could reduce toxic neuronal damages and many studies confirmed the efficacy of polyphenol antioxidants in fruits and vegetables to reduce neuronal death and to diminish oxidative stress. This systematic review showed the antioxidant activities of phytochemicals which play as natural neuroprotectives with low adverse effects against some neurodegenerative diseases as Parkinson or Alzheimer diseases.

Antihypertensive drug use and risk of cognitive decline in the very old: an observational study - the Newcastle 85+ Study

OBJECTIVES

Older adults are a fast growing group in society and are at high risk of hypertension, cognitive decline and dementia. Antihypertensive drugs, particularly calcium channel blockers (CCB), have been associated with a decreased risk of cognitive decline and dementia. We used observational data to examine the association between antihypertensive drug class and change in cognitive function.

METHODS

The Newcastle 85+ Study is a population-based cohort study recruiting individuals aged 85 (born in 1921) via general/family practices in Newcastle/North Tyneside, United Kingdom. Data, including blood pressure, antihypertensive drug use and cognitive function [assessed using the Standardized Mini-Mental State Exam (SMMSE)], were collected at baseline and 3-year follow-up.

RESULTS

The study population comprised 238 participants with a diagnosis of hypertension, prescribed antihypertensive drug treatment and with baseline and follow-up SMMSE assessment. There was an association between CCB use and less cognitive decline over 3 years (rate of decline was lower by 1.29 SMMSE points (95% confidence interval 0.16-2.42; P = 0.03) compared with those taking other antihypertensive classes after adjustment for age, sex, years of education, baseline SMMSE score, smoking, BMI, baseline blood pressure, and incident cerebrovascular event. This finding was even stronger in the cognitively intact (SMMSE >24), wherein rate of cognitive decline was lower by 1.33 SMMSE points (95% confidence interval 0.30-2.37; P = 0.01), but was not seen for other antihypertensive classes.

CONCLUSION

Findings provide support for an association between CCB use and a lower rate of cognitive decline in very old adults with hypertension.

A systematic review of calcium channel blocker use and cognitive decline/dementia in the elderly

OBJECTIVE

Treating hypertension in those aged at least 80 years is now recommended; however, the best antihypertensive to choose remains unexplored. Calcium channel blocker (CCB) use has been associated with a decreased risk of incident dementia in a younger hypertensive group but with an increased risk of cognitive decline in the very elderly. Either result could have a large impact on a vulnerable population. The aim of this review was to assess the evidence relating CCB use to later cognitive decline or dementia in the very elderly.

METHODS

A systematic review of the literature was carried out. The databases Medline, PubMed, Embase and Psychinfo were searched from 1980 to 22 August 2013. Abstracts were reviewed by two independent reviewers and papers meeting the inclusion criteria were extracted.

RESULTS

One thousand, nine hundred and sixty-eight records were reviewed and 10 articles reporting on nine studies retained and extracted. Data were primarily from cohort studies. Only one reported a randomized controlled trial comparing CCBs with placebo. Populations, comparator groups, follow-up times, outcomes and exposure varied and overall results were mixed. It was not possible to combine all studies, but those reporting Alzheimer's disease outcomes were combined to produce an overall risk ratio of 0.79 (95% confidence interval 0.53-1.17).

CONCLUSION

At present, there is no clear evidence to suggest that CCB use increases or decreases risk of cognitive decline or dementia in the very elderly. A robust clinical trial is now required to resolve this.

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.

Use of calcium channel blockers and Parkinson's disease

Experimental evidence and case-control studies suggest that dihydropyridine calcium channel blockers (DiCCBs) may protect against Parkinson's disease. The authors conducted a historical cohort study in Denmark to investigate the association between DiCCB use and risk of Parkinson's disease (1998-2006). Individual-level data on filled drug prescriptions, diagnostic information, and covariates were linked between nationwide registries. Among DiCCB users, 173 incident cases of Parkinson's disease were detected during 461,984 person-years of follow-up, compared with 5,538 cases during 17,343,641 person-years of follow-up among nonusers. After adjustment for age, sex, year, propensity score, and use of other antihypertensive drugs and statins, DiCCB use was associated with a reduced risk of Parkinson's disease (rate ratio (RR) = 0.71, 95% confidence interval (CI): 0.60, 0.82). This association was not present in patients who had previously used DiCCBs (RR = 1.04, 95% CI: 0.87, 1.24). DiCCB users aged ≥65 years were at lower risk of Parkinson's disease than DiCCB users aged <65 years (RR = 0.59, 95% CI: 0.40, 0.85). Among patients with Parkinson's disease, DiCCB use was associated with reduced risk of death (adjusted RR = 0.66, 95% CI: 0.47, 0.91) but not dementia (adjusted RR = 0.97, 95% CI: 0.60, 1.56). In conclusion, DiCCB exposure was associated with a reduced risk of incident Parkinson's disease, particularly in older patients, and with reduced mortality among patients with Parkinson's disease.

Melatonin modulates wireless (2.45 GHz)-induced oxidative injury through TRPM2 and voltage gated Ca(2+) channels in brain and dorsal root ganglion in rat

We aimed to investigate the protective effects of melatonin and 2.45 GHz electromagnetic radiation (EMR) on brain and dorsal root ganglion (DRG) neuron antioxidant redox system, Ca(2+) influx, cell viability and electroencephalography (EEG) records in the rat. Thirty two rats were equally divided into four different groups namely group A1: Cage control, group A2: Sham control, group B: 2.45 GHz EMR, group C: 2.45 GHz EMR+melatonin. Groups B and C were exposed to 2.45 GHz EMR during 60 min/day for 30 days. End of the experiments, EEG records and the brain cortex and DRG samples were taken. Lipid peroxidation (LP), cell viability and cytosolic Ca(2+) values in DRG neurons were higher in group B than in groups A1 and A2 although their concentrations were increased by melatonin, 2-aminoethyldiphenyl borinate (2-APB), diltiazem and verapamil supplementation. Spike numbers of EEG records in group C were lower than in group B. Brain cortex vitamin E concentration was higher in group C than in group B. In conclusion, Melatonin supplementation in DRG neurons and brain seems to have protective effects on the 2.45 GHz-induced increase Ca(2+) influx, EEG records and cell viability of the hormone through TRPM2 and voltage gated Ca(2+) channels.

The role of mitochondria in brain aging and the effects of melatonin

Melatonin is an endogenous indoleamine present in different tissues, cellular compartments and organelles including mitochondria. When melatonin is administered orally, it is readily available to the brain where it counteracts different processes that occur during aging and age-related neurodegenerative disorders. These aging processes include oxidative stress and oxidative damage, chronic and acute inflammation, mitochondrial dysfunction and loss of neural regeneration. This review summarizes age related changes in the brain and the importance of oxidative/nitrosative stress and mitochondrial dysfunction in brain aging. The data and mechanisms of action of melatonin in relation to aging of the brain are reviewed as well.

Potential mechanisms involved in the prevention of neurodegenerative diseases by lithium

Lithium is a monovalent cation that was introduced in 1949 by John Cade for the treatment of bipolar disorder. Clinical reports and subsequent studies confirmed this application and the beneficial effects of this compound. However, over the last 15 years, various authors have also demonstrated the neuroprotective effects of lithium against several neurotoxic paradigms. Thus, experimental studies in neuronal cell cultures and animal models of Alzheimer disease and others pathologies have provided strong evidence for the potential benefits of lithium. The main mechanism underlying its neuroprotective effects is thought to be inhibition of glycogen synthase kinase-3 (GSK-3), although other biochemical pathways in the brain could also be affected. In this review, the main mechanisms of lithium action are summarized, including the modulation of glutamate receptors, effects on arachidonic acid metabolism, its role with respect to AKT, and other potential mechanisms. In addition, its effects on neuroprotective proteins such as Bcl-2 and p53 are also discussed. Although the cellular and molecular biological effects of lithium may constitute an effective therapeutic strategy for Alzheimer disease, further clinical and experimental studies with this drug and specific GSK-3 inhibitors are necessary to confirm the use of lithium in therapeutic approaches to neurodegenerative diseases.

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.

Isradipine antagonizes hypobaric hypoxia induced CA1 damage and memory impairment: Complementary roles of L-type calcium channel and NMDA receptors

Hypobaric hypoxia leads to cognitive dysfunctions due to increase in intracellular calcium through ion channels. The purpose of this study was to examine the temporal contribution of L-type calcium channels and N-methyl-D-aspartate receptors (NMDARs) in mediating neuronal death in male Sprague Dawley rats exposed to hypobaric hypoxia simulating an altitude of 25,000 ft for different durations. Decreasing exogenous calcium loads by blocking voltage-gated calcium influx with isradipine (2.5 mg kg(-1)), and its efficacy in providing neuroprotection and preventing memory impairment following hypoxic exposure was also investigated. Effect of isradipine on calcium-dependent enzymes mediating oxidative stress and apoptotic cell death was also studied. Blocking of L-type calcium channels with isradipine reduced hypoxia-induced activation of calcium dependent xanthine oxidases, monoamine oxidases, cytosolic phospholipase A(2) and cycloxygenases (COX-2) along with concomitant decrease in free radical generation and cytochrome c release. Increased expression of calpain and caspase 3 was also observed following exposure to hypobaric hypoxia along with augmented neurodegeneration and memory impairment which was adequately prevented by isradipine administration. Administration of isradipine during hypoxic exposure protected the hippocampal neurons following 3 and 7 days of exposure to hypobaric hypoxia along with improvement in spatial memory.

Current Concepts in Vascular Cognitive Impairment and Pharmacotherapeutic Implications

Objective:

To review evolution of the vascular cognitive impairment (VCI) construct, including diagnosis, pharmacotherapeutic implications, and address challenges that will shape future developments.

Data Sources:

Literature retrieval was accessed through PubMed, from 1966 to December 2008, using the terms vascular cognitive impairment, vascular dementia, post-stroke dementia, vascular cognitive disorder, mild cognitive impairment, criteria, disease progression, outcomes, treatment, prevention, biomarkers, and neuroimaging.

Study Selection and Data Extraction:

All articles in published English identified from the data sources were evaluated for inclusion. Regarding pharmacotherapy, prospective double-blind, placebo-controlled studies were included as well as extensions or relevant post hoc analyses.

Data Synthesis:

In the 1970s, “senile dementia due to hardening of the arteries” was used to describe dementia due to vascular causes. This was a narrow view of what is now known to be a common form of cognitive impairment in older people. Multiple infarct dementia (MID) was first proposed to describe dementia attributable to multiple cerebral infarcts, followed by the vascular dementia (VaD) construct, itself meant to be an improvement over MID. The VaD construct had limitations, not the least of which was that, by the time a patient was diagnosed with VaD, the opportunity for prevention was lost. Thus arose the concept of VCI, representing a group of heterogeneous disorders that share presumed vascular causes. The importance of VCI is centered on the fact that vascular risk factors are treatable, and thus should lead to a reduction in the incidence of cognitive impairment due to vascular causes. There is evidence that treatment of hypertension can lead to a reduction in the incidence of cognitive impairment and dementia, and that treatment of VaD with acetylcholinesterase inhibitors may be beneficial.

Conclusions:

Careful attention needs to be given to controlling vascular risk factors in at-risk patients. Pharmacists should play an active role in this important area of geriatric pharmacotherapy.

An evaluation of the neuroprotective effects of melatonin in an in vitro experimental model of age-induced neuronal apoptosis

The neuroprotective effects of melatonin in an experimental model of aging-induced apoptosis have been examined. Cerebellar granule neurons show characteristics of apoptosis after 17 days in culture (DV). The addition of melatonin to neuronal cell cultures (100-500 mum) resulted in neuroprotective and antiapoptotic effects, which were revealed by nuclear condensed cell counting. In a thorough analysis by Western-blot of the potential pathways responsible for melatonin's neuroprotective effects, we found an increase in the activation of prosurvival Akt. Subsequently GSK3beta inhibition and an increase in p-FOXO1 phosphorylation occurred. In this model of aging, apoptosis was associated with an elevated DNA damage, as demonstrated by an increase in the activation of ataxia telangiectasia muted (ATM). Subsequently, downstream targets such as p53 were activated. Furthermore, the process of DNA damage was coupled to an increase in the expression of certain proteins involved in cell cycle regulation; these were cyclin D and the proapoptotic transcription factor E2F-1. We conclude that the antiapoptotic effects of melatonin were mediated by two potential mechanisms: by increasing the activity of prosurvival pathways via Akt and by the prevention of DNA damage (via ATM inhibition) followed by the reduction of cell cycle re-entry.

Activation of Akt by lithium: pro-survival pathways in aging

The effects of lithium on senescence were investigated using the senescence-accelerated mouse prone 8 (SAMP8) mice and cultures of aging cerebellar granule cells. Our in vitro findings, using cerebellar granule neurons, demonstrate that lithium (1-10mM) exerts neuroprotective effects in young cultures (7-8 days) against LY294002-induced Akt inhibition. Furthermore, lithium (10mM) inhibits GSK-3beta activity by upregulating p-GSK-3beta (ser-9) and increases p-FOXO1 (Ser256) suggesting an effective anti-apoptotic effect. Our data also showed that lithium in aged cultures exerts anti-apoptotic effects via Akt activation and consequent inhibition of downstream targets regulated by this enzyme. Finally, the administration of lithium to senescence-accelerated mice (SAMP8) and senescence-accelerated resistant mice (SAMR1) at 3 months of age also caused increased Akt activity and p-FoxO-1. These results demonstrate the effectiveness of lithium in preventing age-related neural loss and the potential therapeutic applications of lithium in treatment/prevention of neurological disease.

Calcium channel blocker, azelnidipine, reduces lipid hydroperoxides in patients with type 2 diabetes independent of blood pressure

Anti-hypertensive agents with antioxidative effects are potentially useful for diabetic patients with hypertension to prevent the onset and progression of their complication. While dihydropyridine-type calcium antagonists are among the frequently used anti-hypertensive drugs, azelnidipine, a novel calcium antagonist, has been reported to have a unique anti-oxidative effect in vitro and in animals. In this study, we measured lipid hydroperoxides in human sample using diphenyl-1-pyrenylphosphine for the first time, and used the value of lipid hydroperoxides as an index of oxidative stress. Then, we compared the antioxidative properties of azelnidipine and amlodipine, a frequently used calcium antagonist in hypertensive diabetic patients. Administration of vitamin C and E for 8 weeks significantly reduced lipid hydroperoxides in erythrocyte membrane in normal subjects. In hypertensive diabetic patients, azelnidipine treatment for 12 weeks induced a more significant fall in erythrocyte lipid hydroperoxide level than amlodipine, though blood pressure during each treatment was comparable. Our data confirm the usefulness of lipid hydroperoxides in erythrocyte membrane as a marker of oxidative stress in vivo, and indicate that azelnidipine has a unique antioxidative property in human.

Melatonin prevents formaldehyde-induced neurotoxicity in prefrontal cortex of rats: an immunohistochemical and biochemical study

This study was undertaken to investigate the protective effects of melatonin against formaldehyde-induced neurotoxicity in prefrontal cortex of rats. For this purpose, 21 male Wistar rats were divided into three groups. The rats in Group I were used as a control, while the rats in Group II were injected every other day with formaldehyde. The rats in Group III received melatonin daily while exposed to formaldehyde. At the end of 14-day experimental period, all rats were killed by decapitation. The brains of the rats were removed and the prefrontal cortex tissues were obtained from all brain specimens. Some of the prefrontal cortex tissue specimens were used for determination of superoxide dismutase (SOD), glutathione peroxidase (GSH-Px) and malondialdehyde (MDA) levels. The remaining prefrontal cortex tissue specimens were used for immunohistochemical evaluation. The levels of SOD and GSH-Px were significantly decreased, and MDA levels, were significantly increased in rats treated with formaldehyde compared with those of the controls. In the immunohistochemical evaluation of this group, apoptotic cells were observed. However, increased SOD and GSH-Px enzyme activities, and decreased MDA levels, were detected in the rats administered melatonin while exposed to formaldehyde. Furthermore, apoptotic changes caused by formaldehyde were decreased in these rats. The results of our study suggest that melatonin treatment prevents formaldehyde-induced neuronal damage in prefrontal cortex.

Calcium channel antagonist (nifedipine) attenuates Plasmodium berghei-specific T cell immune responses in Balb/C mice

Nifedipine and verapamil (Martin et al. Science 1987;235:899-901) are a class of calcium channel blockers involved in the reversal of chloroquine (CQ) drug resistance in CQ-sensitive Plasmodium spp. Nifedipine alters calcium-dependent functions of macrophages and neutrophils during Plasmodium berghei malaria. However, knowledge of nifedipine-induced immunomodulation of T cell functions during P. berghei malaria is still limited. We investigated the effect of nifedipine on the immune status of splenic T cells during P. berghei malaria. The intracellular calcium levels were determined in the FURA-2A/M loaded T cells by spectrofluorometry. Splenic T cell proliferation, phosphatidylserine (PS) externalization, Fas expression and Bcl2/Bax expression were determined by flow cytometry. We report a significant increase in mean percent parasitemia in nifedipine-treated and P. berghei-infected mice. Although nifedipine treatment alone did not affect the resting state free calcium levels in splenic T cells, the rise in intracellular calcium levels of T cells following P. berghei infection was significantly less in nifedipine-treated mice compared to untreated groups at various parasitemia levels. Antigen-specific splenic T cell proliferation and apoptosis was ablated in nifedipine-treated and untreated groups at various parasitemia levels. The study unequivocally reflects the suppression of P. berghei-specific T cell immune responses by nifedipine.

Protective effect of cerebrocrast on rat brain ischaemia induced by occlusion of both common carotid arteries

Diabetes mellitus is accompanied by several cardiovascular complications including atherosclerosis, cerebral ischaemia and stroke. We examined the neuroprotective effect of a 1,4-dihydropyridine derivative cerebrocrast (C, a new antidiabetic agent, synthesized in the Latvian Institute of Organic Synthesis) on the level of ATP in the brain, and on changes of the EEG and ECG, as well as blood pressure parameters in anaesthetized Wistar male rats before and during 10-min occlusion of both common carotid arteries. Cerebrocrast was administered i.v. at doses of 1.0 and 10 microg/kg in the v. femoralis 20 min prior to ischaemia. After 10-min ischaemia animals were decapitated and the brain was immediately frozen in liquid nitrogen and subsequently used for analysis of changes of ATP contention. Cerebrocrast, administered at doses of 1.0 and 10 microg/kg 20 min prior to occlusion of both common carotid arteries, completely prevented a fall in the ATP content of brain compared with the control rats. In control rats the content of ATP in brain during ischaemia decreased from 2.77 +/- 0.22 (basal level) to 1.74 +/- 0.20 micromol/g as a result of ischaemia. By administration of cerebrocrast 20 min before occlusion of the arteries, the content of ATP in the brain remained at the level of preischaemia (1.0 microg/kg C + ischaemia 2.82 +/- 0.36; 10 microg/kg C + ischaemia 2.42 +/- 0.22 micromol/g). Analysis of EEG parameters both before and during 10 min of occlusion showed that at a C dose of 1.0 microg/kg before occlusion produced a regular alpha rhythm during ischaemia and prevented cerebral bioelectric activity from significant changes. The depression of basal rhythm was observed at a C dose of 10 microg/kg during ischaemia in two rats out of six as well as an increase in the ECG ST segment above the isoelectric line. Blood pressure was decreased by about 10-20 mm Hg. We propose that pretreatment of rats with cerebrocrast at doses of 1.0 or 10 microg/kg 20 min prior to ischaemia can prevent ischaemic damage of rat brain, maintain necessary energy consumption, promote ATP production in brain cells, and prevent significant changes in EEG and ECG parameters. These properties are important in diabetes mellitus and its evoked cardiovascular complications as stroke, ischaemia, etc.

The critical role of voltage-dependent calcium channel in axonal repair following mechanical trauma

Membrane disruption following mechanical injury likely plays a critical role in the pathology of spinal cord trauma. It is known that intracellular calcium is a key factor that is essential to membrane resealing. However, the differential role of calcium influx through the injury site and through voltage dependent calcium channels (VDCC) has not been examined in detail. Using a well-established ex vivo guinea-pig spinal cord white matter preparation, we have found that axonal membrane resealing was significantly inhibited following transection or compression in the presence of cadmium, a non-specific calcium channel blocker, or nimodipine, a specific L-type calcium channel blocker. Membrane resealing was assessed by the changes of membrane potential and compound action potential (CAP), and exclusion of horseradish peroxidase 60 min following trauma. Furthermore, 1 microM BayK 8644, a VDCC agonist, significantly enhanced membrane resealing. Interestingly, this effect was completely abolished when the concentration of BayK 8644 was increased to 30 microM. These data suggest that VDCC play a critical role in membrane resealing. Further, there is likely an appropriate range of calcium influx through VDCC which ensures effective axonal membrane resealing. Since elevated intracellular calcium has also been linked to axonal deterioration, blockage of VDCC is proposed to be a clinical treatment for various injuries. The knowledge gained in this study will likely help us better understand the role of calcium in various CNS trauma, which is critical for designing new approaches or perhaps optimizing the effectiveness of existing methods in the treatment of CNS trauma.

Favourable effects of nilvadipine on cognitive function and regional cerebral blood flow on SPECT in hypertensive patients with mild cognitive impairment

OBJECTIVE

We compared the effects of nilvadipine and amlodipine on the cognitive function and regional cerebral blood flow (rCBF) in patients with mild cognitive impairment (MCI) and hypertension.

METHODS

Twelve patients with MCI and hypertension were randomly assigned to receive nilvadipine or amlodipine for 12-16 weeks. Before and after treatment all patients underwent neuropsychological evaluation and single photon emission computed tomography (SPECT) studies with N-isopropyl-p-[123I]iodoamphetamine.

RESULTS

Both nilvadipine (n=6) and amlodipine (n=6) groups had similar significant reduction in systolic and diastolic blood pressure after treatment. The Logical Memory subscore of the Wechsler Memory Scale-Revised increased significantly in the nilvadipine group, but not in the amlodipine group after treatment. Although SPECT demonstrated no significant differences in rCBF deficits at baseline between the two groups, the nilvadipine group showed an improvement of rCBF in the left frontal lobe, while the amlodipine group showed a decrease of rCBF in the left temporal lobe.

CONCLUSION

Our results suggest that nilvadipine, a highly lipophilic agent that easily penetrates the central nervous system, may have additional benefits and be potentially useful for the treatment of patients with MCI and hypertension.

Azelnidipine inhibits H2O2-induced cell death in neonatal rat cardiomyocytes

PURPOSE

Oxidative stress plays an important role in the pathogenesis of cardiovascular diseases. Azelnidipine is a novel dihydropyridine calcium channel blocker. Several studies have demonstrated that some dihydropyridine calcium channel blockers have antioxidant effects. We evaluated the antioxidant effects of azelnidipine compared to another dihyropyridine calcium channel blocker, nifedipine, in neonatal rat cardiomyocytes.

MATERIALS AND METHODS

We examined effects of azelnidipine and nifedipine on the H(2)O(2)-induced mitogen-activated protein kinase (MAPK) activity and cell death in neonatal rat cardiomyocytes.

RESULTS

Extracellular signal-regulated protein kinases (ERK), p38 MAPK and c-Jun NH(2)-terminal kinases (JNK) were activated by H(2)O(2) stimulation. Azelnidipine and nifedipine did not affect the H(2)O(2)-induced activation of ERK and p38 MAPK. In contrast, azelnidipine, but not nifedipine, inhibited the H(2)O(2)-induced JNK activation. The numbers of viable cell were significantly decreased by H(2)O(2) treatments (65.8 +/- 4.11% of control, P < 0.0001). Azelnidipine, but not nifedipine, inhibited the H(2)O(2)-induced cell death (azelnidipine: 76.0 +/- 4.66% of control, P < 0.05; nifedipine: 70.7 +/- 4.01% of control, P = 0.32).

CONCLUSION

Azelnidipine inhibited the H(2)O(2)-induced JNK activation and cardiac cell death. Azelnidipine may have cardioprotective effects against oxidative stress.

Antihypertensive medication is associated with less cognitive impairment in the very old with apolipoprotein-E epsilon4 allele

BACKGROUND AND OBJECTIVES

High and low blood pressure and apolipoprotein (Apo)-E epsilon4 alleles have been shown to be associated with dementia of the Alzheimer's type. The aim of this study was to examine the relationship between Apo-E epsilon4 allele status and the effect of antihypertensive treatment on cognitive performance in persons > or =80 years of age.

METHODS

A sample of 258 individuals 80-102 years of age was studied. Associations between the Mini-Mental State Examination (MMSE) score and treatment with antihypertensive medication, blood pressure, Apo-E polymorphism, sex, age and education were assessed. Patients treated with antihypertensive drugs typically used two to ten different medications.

RESULTS

Individuals with no Apo-E epsilon4 alleles who were not treated with antihypertensive medications had a significantly higher diastolic blood pressure than other participants in the study but no cognitive deficits. Participants who had at least one Apo-E epsilon4 allele who were not treated with antihypertensive medications scored significantly lower on the MMSE compared with other participants in the study.

CONCLUSIONS

Individuals with an Apo-E epsilon4 allele who were not treated with antihypertensive medication showed the poorest cognitive performance. This could suggest that individuals with the Apo-E epsilon4 allele may benefit cognitively from treatment with antihypertensive drugs.

Nilvadipine Prevents the Impairment of Spatial Memory Induced by Cerebral Ischemia Combined with .BETA.-Amyloid in Rats

In the present study, we examined the effects of nilvadipine and amlodipine, both dihydropyridine-derivative calcium antagonists, on the impairment of spatial memory induced by a combination of ischemia and beta-amyloid (Abeta). Nilvadipine (3.2 mg/kg, i.p.) significantly prevented the impairment of spatial memory and neuronal apoptosis in this model. By contrast, amlodipine had no effect on this impairment of spatial memory. These findings suggest that nilvadipine may prevent impairment of spatial memory by inhibiting neuronal apoptosis; this drug might therefore be useful for the prevention of the progression to dementia in Alzheimer's disease (AD).

Potential Roles of Electrogenic Ion Transport and Plasma Membrane Depolarization in Apoptosis

Apoptosis is characterized by the programmed activation of specific biochemical pathways leading to the organized demise of cells. To date, aspects of the intracellular signaling machinery involved in this phenomenon have been extensively dissected and characterized. However, recent studies have elucidated a novel role for changes in the intracellular milieu of the cells as important modulators of the cell death program. Specially, intracellular ionic homeostasis has been reported to be a determinant in both the activation and progression of the apoptotic cascade. Several apoptotic insults trigger specific changes in ionic gradients across the plasma membrane leading to depolarization of the plasma membrane potential (PMP). These changes lead to ionic imbalance early during apoptosis. Several studies have also suggested the activation and/or modulation of specific ionic transport mechanisms including ion channels, transporters and ATPases, as mediators of altered intracellular ionic homeostasis leading to PMP depolarization during apoptosis. However, the role of PMP depolarization and of the changes in ionic homeostasis during the progression of apoptosis are still unclear. This review summarizes the current knowledge regarding the causes and consequences of PMP depolarization during apoptosis. We also review the potential electrogenic ion transport mechanisms associated with this event, including the net influx/efflux of cations and anions. An understanding of these mechamisms could lead to the generation of new therapeutic approaches for a variety of diseases involving apoptosis.

Proteomics analyses of specific protein oxidation and protein expression in aged rat brain and its modulation by L-acetylcarnitine: insights into the mechanisms of action of this proposed therapeutic agent for CNS disorders associated with oxidative stress

Impaired function of the central nervous system (CNS) in aged animals is associated with increased susceptibility to the development of many neurodegenerative diseases. Age-related functional deterioration in brain is consistent with the free radical theory of aging that predicts, among other things, that free radical reactions with and damage to biomolecules, such as proteins and membrane lipid bilayers, leads to loss of neurons and subsequently diminished cognition. These oxidatively modified biomolecules are believed to contribute to the decreased antioxidant content, mitochondrial dysfunction, and impaired plasticity in aged brains. Treatment of rodents with L-acetylcarnitine (LAC; gamma-trimethyl-beta-acetylbutyrobetaine) can improve these functional losses. Although it is well established that administration of LAC can decrease protein oxidation in aged brains, it is not clear which proteins are decreased in their level of oxidation in the brains of aged rats treated with LAC. The current study used a parallel redox proteomics approach to identify the proteins that are oxidized in aged rat cortex and hippocampus of aged rats. Moreover, those proteins that are reduced in oxidation status were identified in aged brains from rats treated in vivo with LAC. The findings are discussed in reference to brain aging and age-related cognitive impairment.

Effect of donepezil and lercanidipine on memory impairment induced by intracerebroventricular streptozotocin in rats

Intracerebroventricular (ICV) injection of streptozotocin (STZ) causes cognitive impairment in rats. ICV STZ is known to impair cholinergic neurotransmission by decreasing choline acetyltransferase (ChAT) levels, glucose and energy metabolism in brain and synthesis of acetyl CoA. However, no reports are available regarding the cholinesterase inhibitors in this model. In aging brain, reduced energy metabolism increases glutamate release, which is blocked by L-type calcium channel blockers. These calcium channel blockers have shown beneficial effects on learning and memory in various models of cognitive impairment. The present study was designed to investigate the influence of chronic administration of donepezil (cholinesterase inhibitor, 1 and 3 mg/kg) and lercanidipine (L-type calcium channel blocker, 0.3 and 1 mg/kg) on cognitive impairment in male Sprague-Dawley rats injected twice with ICV STZ (3 mg/kg) bilaterally on days 1 and 3. ICV STZ injected rats developed a severe deficit in learning and memory indicated by deficits in passive avoidance paradigm and elevated plus maze as compared to control rats. Cholinesterase activity in brain was significantly increased in ICV STZ injected rats. Donepezil dose-dependently inhibited cholinesterase activity and improved performance in memory tests at both the doses. Lercanidipine (0.3 mg/kg) showed significant improvement in memory. When administered together, the effect of combination of these two drugs on memory and cholinesterase activity was higher than that obtained with either of the drugs when used alone.

Calcium channel blockers and risk of AD: the Baltimore Longitudinal Study of Aging

OBJECTIVE

To investigate the association between use of calcium channel blockers (CCB), dihydropyridine (DHP) or nondihydropyridine (nonDHP) type CCB and risk of developing Alzheimer's Disease (AD) or mortality. There is evidence suggesting that calcium plays a key role in changes in the brain leading to AD. Previous reports suggest a possible role for CCB in the treatment of AD. However, there are some indications that CCB increase mortality in patients with cardiac disease.

METHODS

Subjects were 1092 participants in the Baltimore Longitudinal Study of Aging (BLSA) older than 60 years of age. Data on CCB use was collected prospectively for up to 19 years. Cox proportional hazards regression was used to estimate relative risks (RR) and confidence intervals (CI) of AD and mortality associated with use of CCB or use of only DHP or nonDHP-CCB. Analyses were adjusted for gender, education, smoking, blood pressure and history of heart problems.

RESULTS

Use of DHP-CCB was not associated with a significantly reduced risk of AD compared to non-users, although the estimate of the RR was low with DHP-CCB (RR = 0.30, 95% CI = 0.07-1.25, P = 0.10). Use of nonDHP-CCB was not associated with reduced risk of AD and the estimate of the RR risk was close to one (RR = 0.82, 95% CI = 0.37-1.83, P = 0.63). In addition, there was no increase in mortality among users of DHP-CCB (RR = 0.64, 95% CI = 0.32-1.29, P = 0.21) or nonDHP-CCB (RR = 1.10, 95% CI = 0.65-1.87, P = 0.72).

CONCLUSION

Users of DHP-CCB and nonDHP-CCB in this study did not have a significantly reduced risk of AD.

A link between hyperbilirubinemia, oxidative stress and injury to neocortical synaptosomes

Cytotoxicity by unconjugated bilirubin involves disturbances of membrane structure, excitotoxicity and cell death. These events were reported to trigger elevated free radicals production and impairment of calcium homeostasis, and to result in loss of cell membrane integrity. Therefore, this study was designed to investigate whether interaction of clinically relevant concentrations of free unconjugated bilirubin with synaptosomal membrane vesicles could be linked to oxidative stress, cytosolic calcium accumulation and perturbation of membrane function. Synaptosomal vesicles were prepared from gerbil cortical brain tissue and incubated with purified bilirubin (<or=1 microM), for 4 h at 37 degrees C. Intracellular concentrations of reactive oxygen species (ROS) and calcium were determined by dichlorofluorescin and BAPTA fluorescent probes, respectively. Membrane protein and lipid oxidation were evaluated by immunocytochemistry and phosphatidylserine exposure by annexin V binding. Levels of reduced and oxidized glutathione (GSH and GSSG, respectively), as well as activities of Mg(2+)-ATPase aminophospholipid translocase (flippase) and Na(+),K(+)-ATPase, were also measured. Our results showed that bilirubin induced oxidative stress, due to a rise in lipid (>or=10%, P<0.05) and protein oxidation (>or=20%, P<0.01), ROS content (approximately 17%, P<0.01), and a decrease in GSH/GSSG ratio (>30%, P<0.01). In addition, synaptosomes exposed to bilirubin exhibited increased externalization of phosphatidylserine (approximately 10%, P<0.05), together with decreased flippase and NA(+),K(+)-ATPase (>or=15%, P<0.05) activities, events that were accompanied by enhanced intracellular calcium levels ( approximately 20%, P<0.01). The data obtained point out that interaction of unconjugated bilirubin with synaptosomal membrane vesicles leads to oxidative injury, loss of membrane asymmetry and functionality, and calcium intrusion, thus potentially contributing to the pathogenesis of encephalopathy by hyperbilirubinemia.

Prevention of dementia: lessons from SYST-EUR and PROGRESS

Hypertension is one of the principal risk factors for cerebrovascular diseases, closely correlated also with cognitive decline and dementia. Data from recent therapeutic trials (SYST-EUR, PROGRESS) open the way toward the prevention of dementia (vascular or Alzheimer's type) by antihypertensive treatments. The results of these two studies suggest different mechanisms of action of antihypertensive drugs in the prevention of cognitive decline. The use of angiotensin converting enzyme (ACE) inhibitors, with or without diuretics, resulted in decrease incidence of stroke-related dementia, but dementia without stroke was not reduced. With the dihydropyridine calcium antagonists, a reduction in both Alzheimer's type and vascular dementia was demonstrated.

Cyclosporine A and adverse effects on organs: histochemical studies

The discovery that cyclosporine A (CsA) was a powerful immunosuppressant had a significant impact on transplant medicine. Its molecular mechanism of action has been well defined in T cells and involved inhibition of critical signalling pathways that regulated T-cell activation. In fact, CsA inhibited calcineurin phosphatase activity and thereby activation of the transcription factor nuclear factor of activated T cells. Over 10 years, its use is limited by side effects, determining nephro- and hepatotoxicity, gingival hypertrophy, tremor and increased blood pressure. These negative effects have been identified through morphological alterations and/or clinical parameters, i.e. variation in glomerular filtration rate for nephrotoxicity. Nevertheless, CsA remains a therapeutic valuable agent and it is normally utilized into clinical practice even if different dose adjustments or discontinuations in a significant percentage of patients must be used. This review focuses on the following topics: mechanisms of action and drug metabolism, interactions with other drugs, clinical and morphological evaluation of toxic effects on target organs. In particular, the morphological evaluation of negative effects has been considered reporting light and ultrastructural studies on target organs both in normal and immunosuppressive conditions. Moreover, the histochemical and immunohistochemical variations in cellular metabolism and antigenic properties of cells present in the parenchyma of these organs are discussed.

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

We previously reported that vitamin E prevents apoptosis in neurons during cerebral ischemia and reperfusion in stroke-prone spontaneously hypertensive rats (SHRSP). In this paper, we analyzed the effects of antihypertensives as well as vitamin E, which were added to neuron cultures after reoxygenation (20% O2) following hypoxia (1% O2). When added after hypoxia before reoxygenation, vitamin E conferred significant protection to neuronal cells. It was also shown that vitamin E conferred complete protection from neural cell death when added hypoxia and again before reoxygenation. At higher concentrations of vitamin E, strong neuroprotection was observed. Moreover, we verified that pretreatment with either amlodipine, carvedilol or dipyridamole consistently prevented cell death during hypoxia and reoxygenation (H/R). On the other hand, nilvadipine, a dihydropyridine-type calcium entry blocker, had no apparent effect on neuroprotection during H/R. The order of neuroprotective potency was vitamin E > dipyridamole > carvedilol > or = amlodipine > nilvadipine. In parallel experiments, we examined whether these antihypertensive agents were more effective when combined with vitamin E and dipyridamole. The results suggested that in our in vitro model system, antioxidants were the most important agents for the reduction of oxygen-free radical damage in cortical neurons. These findings suggest that amlodipine and carvedilol, with their antioxidant properties and antihypertensive activity, would be useful to inhibit neuronal cell death in the treatment of cerebrovascular stroke and neurodegenerative diseases in hypertensive patients.

Antiapoptotic mechanisms of benidipine in the ischemic/reperfused heart

1. Considerable evidence indicates that calcium plays a critical role in apoptosis. We have previously shown that benidipine, a vasodilatory calcium channel blocker, attenuates postischemia myocardial apoptosis. The present study was designed to determine the mechanisms by which benidipine exerts its antiapoptotic effect. 2. Adult male rats were subjected to 30 min of ischemia followed by 3 h of reperfusion. Rats were randomized to receive either vehicle or benidipine (10 microg x kg(-1), i.v.) 10 min before reperfusion. 3. Compared with rats receiving vehicle, those rats treated with benidipine had reduced postischemic myocardial apoptosis as evidenced by decreased TUNEL-positive staining (8.4+/-1.2 vs 15.3+/-1.3%, P<0.01) and caspase-3 activity (1.94+/-0.25 vs 3.43+/-0.29, P<0.01). 4. Benidipine treatment significantly reduced mitochondrial cytochrome c release and caspase-9 activation, but had no effect on caspase-8 activation, suggesting that benidipine exerts its antiapoptotic effect by inhibiting the mitochondrial-mediated, but not death receptor-mediated, apoptotic pathway. 4. 5. Benidipine treatment not only increased the maximal activity of ERK1/2 at 10 min after reperfusion, but also prolonged the duration of ERK1/2 activation. Benidipine treatment had no significant effect on other apoptotic regulating molecules, such as p38 MAPK. 6. Taken together, our present study demonstrated for the first time the differential regulation of a calcium channel blocker. Benidipine tilted the balance between ERK1/2 and p38 MAPK toward an antiapoptotic state, decreased mitochondrial cytochrome c release, reduced caspase-9 activation, and attenuated subsequent caspase-3 activation and postischemic myocardial apoptosis.

Antioxidant Effect of a New Calcium Antagonist, Azelnidipine, in Cultured Human Arterial Endothelial Cells

Azelnidipine is a novel dihydropyridine-type calcium antagonist with long-acting anti-hypertensive action and a low reported incidence of tachycardia. We aimed to evaluate its antioxidant activity in cultured human arterial endothelial cells under oxidative stress. Endothelial cells were exposed to 1 mM H2O2 and treated with 100 μM α-tocopherol, 1 nM, 10 nM or 100 nM azelnidipine, 100 nM nifedipine or 100 nM amlodipine. After 3 h, the cell number and level of lipid peroxidation were evaluated by measuring the total protein and 8-iso-PGF2α concentrations, respectively. The total protein concentration was similar with each treatment. Inhibition of 8-iso-PGF2α was greatest with 10 nM azelnidipine (compared with the other drugs); the difference between 10 nM and 100 nM azelnidipine was not significant. We conclude that azelnidipine has a potent antioxidative effect that could be of significant clinical benefit when combined with its long-lasting anti-hypertensive action and low incidence of tachycardia.

Caffeic acid phenethyl ester blocks apoptosis induced by low potassium in cerebellar granule cells

Primary cultures of cerebellar granule neurons (CGNs) were prepared from 8-day-old Wistar rats, and maintained in an appropriate medium containing a high (25 mM) concentration of KCl. To induce apoptosis, culture medium was replaced with serum-free medium (containing 5mM KCl) 8 days after plating. Apoptosis was measured by the terminal deoxynucleotidyl transferase-mediated dUTP-fluorescein nick end-labeling (TUNEL) method, and by flow cytometry. Since there is evidence that an increased formation of reactive oxygen species (ROS) is involved in the apoptosis induced by low K(+) (5mM) concentrations, the potential anti-apoptotic effect of caffeic acid phenethyl ester (CAPE), a potent flavonoid antioxidant, was tested in this experimental model. It was found that CAPE (10 microg/ml) promoted cell survival and was capable of blocking the apoptotic process as assayed by both TUNEL and flow cytometric methods. The same concentration of CAPE prevented the formation of ROS induced by low K(+). Since there is evidence that low K(+)-induced apoptosis in CGNs is associated with a drop in intracellular Ca(2+) concentration ([Ca(2+)](i)), activation of the cell death effector proteases caspase-3 and caspase-9, and of the transcription factor nuclear factor kappa B (NF-kappaB), the interference of CAPE with these purported mediators of apoptosis was also evaluated. It was found that CAPE did not interfere with the marked decrease in [Ca(2+)](i) induced by low K(+), whereas it completely blocked caspase-3, caspase-9, and NF-kappaB activation. It is concluded that CAPE could exert its anti-apoptotic effect in CGNs by blocking ROS formation and by inhibiting caspase activity.

Survivin-dependent angiogenesis in ischemic brain: molecular mechanisms of hypoxia-induced up-regulation

Approaches to regulating angiogenesis in the brain, which may diminish parenchymal damage after stroke, are lacking. Survivin, the inhibitor of apoptosis protein, is up-regulated in vitro in vascular endothelial cells by angiogenic factors, including vascular endothelial cell growth factor (VEGF). To evaluate the in vivo role of survivin in the brain in response to hypoxia/ischemia, we used a mouse model of stroke and show that 2 days after permanent middle cerebral artery occlusion, survivin is uniquely expressed by microvessels that form in the peri-infarct and infarct regions. The extent of vascularization of the infarct is dependent on expression of survivin, since vessel density is significantly reduced in mice with heterozygous deficiency of the survivin gene (survivin+/- mice), even though infarct sizes were not different. Hypoxia alone induces survivin expression in the brain, by cultured endothelial cells and by embryonic stem cells, but this response is at least partially independent of VEGF, hypoxia inducible factor 1alpha, or placental growth factor. Delineating the spatiotemporal pattern of expression of survivin after stroke, and the molecular mechanisms by which this is regulated, may provide novel approaches to therapeutically optimize angiogenesis in a variety of ischemic disorders.

Atheroprotective effects of long-acting dihydropyridine-type calcium channel blockers: evidence from clinical trials and basic scientific research

Atherosclerosis is a systemic disease that can ultimately lead to ischaemia and infarction in the heart, brain and peripheral vasculature. According to the "response to injury" hypothesis, endothelial dysfunction is the early event that allows penetration of lipids and inflammatory cells into the arterial wall, contributing to the development of the atherosclerotic lesion. Endothelial dysfunction is causally related to a variety of risk factors for atherosclerosis, including hyperlipidaemia and hypertension. Agents that restore endothelial function and NO bioavailability have beneficial anti-atherogenic activities and can improve cardiovascular outcomes; this has been observed with angiotensin-converting enzyme (ACE) inhibitors, statins and certain dihydropyridine-type calcium channel blockers (CCBs). In the Prospective Randomised Evaluation of the Vascular Effects of Norvasc Trial (PREVENT), the CCB amlodipine provided significant clinical benefits compared with placebo, including a marked reduction in cardiovascular morbidity and a reduction in the progression of carotid atherosclerosis. As these beneficial effects of amlodipine have not been observed with other dihydropyridine-type CCBs, it has been proposed that this agent has distinct anti-atherosclerotic properties related to its strong lipophilicity and membrane location. Experimental support for this hypothesis has been obtained from various in vitro and in vivo models of atherosclerosis. These findings support a broader therapeutic role for third-generation dihydropyridine-type CCBs in the treatment of atherosclerosis.

Melatonin nocturnal surge modulates nicotinic receptors and nicotine-induced [3H]glutamate release in rat cerebellum slices

In mammals, the most important synchronizer for endogenous rhythms is the environmental light/dark cycle. In this report we have explored the ability of light/dark cycle and melatonin, the pineal hormone released during the night, to modulate cerebellar cholinergic input by interfering with the nicotinic acetylcholine receptors' (nAChRs) availability. Through the analysis of the response to selective cholinergic agonists and antagonists, we observed that nAChRs containing the alpha7 gene product mediate the release of [(3)H]glutamate from rat cerebellum slices. The [(3)H]glutamate overflow induced by alpha7 nAChR activation was higher during the dark phase, although the number of alpha-[(125)I]bungarotoxin binding sites, but not the [(3)H]nicotine binding sites (B(max)), was reduced. On the other hand, glutamate-evoked [(3)H]glutamate release was not modified by the hour of the day. Finally, we show that the nocturnal increase in nicotine-evoked [(3)H]glutamate release is imposed by a nocturnal surge of melatonin, as it is abolished when pineal melatonin production is inhibited by either maintaining the animals in constant light for 48 h or by injecting propranolol just before lights off for 2 days. The difference between light and dark [(3)H]glutamate-evoked release is restored in propranolol-treated animals that received melatonin during the dark period. In conclusion, we show that nicotine-evoked [(3)H]glutamate release in rat cerebellum presents a diurnal variation, driven by nocturnal pineal melatonin surge.