Inhibition of Excessive Neuronal Apoptosis by the Calcium Antagonist Amlodipine and Antioxidants in Cerebellar Granule Cells

Abstract

Abstract:Neuronal cell death as a result of apoptosis is associated with cerebrovascular stroke and various neurodegenerative disorders. Pharmacological agents that maintain normal intracellular Ca 2ϩ levels and inhibit cellular oxidative stress may be effective in blocking abnormal neuronal apoptosis. In this study, a spontaneous (also referred to as age-induced) model of apoptosis consisting of rat cerebellar granule cells was used to evaluate the antiapoptotic activities of voltage-sensitive Ca 2ϩ channel blockers and various antioxidants. The results of these experiments demonstrated that the charged, dihydropyridine Ca 2ϩ channel blocker amlodipine had very potent neuroprotective activity in this system, compared with antioxidants and neutral Ca 2ϩ channel blockers (nifedipine and nimodipine). Within its effective pharmacological range (10 -100 nM), amlodipine attenuated intracellular neuronal Ca 2ϩ increases elicited by KCl depolarization but did not affect Ca 2ϩ changes triggered by N-methyl-D-aspartate receptor activation. Amlodipine also inhibited free radical-induced damage to lipid constituents of the membrane in a dose-dependent manner, independent of Ca 2ϩ channel modulation. In parallel experiments, spontaneous neuronal apoptosis was inhibited in dose-and time-dependent manners by antioxidants (U-78439G, ␣-tocopherol, and melatonin), nitric oxide synthase inhibitors (N-nitro-L-arginine and N-nitro-D-arginine), and a nitric oxide chelator (hemoglobin) in the micromolar range. These results suggest that spontaneous neuronal apoptosis is associated with excessive Ca 2ϩ influx, leading to further intracellular Ca 2ϩ increases and the generation of reactive oxygen species. Agents such as amlodipine that block voltage-sensitive Ca 2ϩ channels and inhibit cellular oxidative stress may be effective in the treatment of cerebrovascular stroke and neurodegenerative diseases associated with excessive apoptosis.

Amlodipine and Carvedilol Prevent Cytotoxicity in Cortical Neurons Isolated from Stroke-Prone Spontaneously Hypertensive Rats

“…We demonstrated that amlodipine clearly inhibited cell death in cultured SHRSP neuron during H/R. Our finding is confirmed by the data previously reported (23). The effective dose, however, was much higher than that reported by in this previous study.…”

“…2). These findings correspond to the results of a similar study that showed that amlodipine has a more potent neuroprotective effect than neutral Ca 2 channel blockers (nifedipine and nimodipine) in rat CGCs cells (23). Amlodipine exhibited very potent neuroprotective activity in this system, compared with antioxidants and neutral Ca 2 channel blockers (nifedipine and nimodipine).…”

The Prevention of Dementia With Antihypertensive Treatment<subtitle>New Evidence From the Systolic Hypertension in Europe (Syst-Eur) Study</subtitle>

“…38 The aging brain loses its ability to regulate intracellular calcium, leading to a cascade of cellular impairments and ultimately to cell death. 39,40 Alterations in calcium homeostasis are involved in the aging process of the brain and in the neuropathology of Alzheimer disease. [42][43][44] In patients with degenerative dementia, ␤-amyloid may raise the concentration of intraneuronal free calcium and through this mechanism may sensitize the brain to neurotoxins, such as proinflammatory substances or pro-oxidants.…”

Antiapoptotic mechanisms of benidipine in the ischemic/reperfused heart

“…Calcium overloading also increases free radical generation (Bagchi et al, 1997), a well-defined apoptosis-inducing factor (Das et al, 1999). Moreover, in cell culture systems, addition of dihydropyridine calcium channel blockers, amlodipine and nifedipine, reduces excessive apoptosis in aging cerebellar granule cells (Mason et al, 1999) and in hypoxic neonatal rat cardiac myocytes (Chen et al, 1998). In animals subjected to renal ischemia, administration of verapamil, an L-type calcium blocker, has been demonstrated to reduce tissue apoptosis (Raafat et al, 1997).…”