Dihydropyridine L-type Calcium Channel Blockers Research Articles

Amlodipine inhibits the proliferation and migration of esophageal carcinoma cells through the induction of endoplasmic reticulum stress.

L-type calcium channels are the only protein channels sensitive to calcium channel blockers, and are expressed in various cancer types. The Cancer Genome Atlas database shows that the mRNA levels of multiple L-type calcium channel subunits in esophageal squamous cell carcinoma tumor tissue are significantly higher than those in normal esophageal epithelial tissue. Therefore, we hypothesized that amlodipine, a long-acting dihydropyridine L-type calcium channel blocker, may inhibit the occurrence and development of esophageal cancer (EC). To investigate the inhibitory effects of amlodipine on EC through endoplasmic reticulum (ER) stress. Cav1.3 protein expression levels in 50 pairs of EC tissues and corresponding paracancerous tissues were examined. Subsequently, the inhibitory effects of amlodipine on proliferation and migration of EC cells in vitro were detected using 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide and Transwell assays. In vivo experiments were performed using murine xenograft model. To elucidate the underlying mechanisms, in vitro cell studies were performed to confirm that ER stress plays a role in inhibition proliferation and migration of EC cells treated with amlodipine. The expression level of Cav1.3 in esophageal carcinoma was 1.6 times higher than that in paracancerous tissues. Amlodipine treatment decreased the viability of esophageal carcinoma cells in a dose- and time-dependent manner. In vivo animal experiments also clearly indicated that amlodipine inhibited the growth of EC tumors in mice. Additionally, amlodipine reduces the migration of tumor cells by inhibiting epithelial-mesenchymal transition (EMT). Mechanistic studies have demonstrated that amlodipine induces ER stress-mediated apoptosis and suppresses EMT. Moreover, amlodipine-induced autophagy was characterized by an increase in autophagy lysosomes and the accumulation of light chain 3B protein. The combination of amlodipine with the ER stress inhibitor 4-phenylbutyric acid further confirmed the role of the ER stress response in amlodipine-induced apoptosis, EMT, and autophagy. Furthermore, blocking autophagy increases the ratio of apoptosis and migration. Collectively, we demonstrate for the first time that amlodipine promotes apoptosis, induces autophagy, and inhibits migration through ER stress, thereby exerting anti-tumor effects in EC.

Azelnidipine Inhibits the Differentiation and Activation of THP-1 Macrophages through the L-Type Calcium Channel

Aim: Recently, calcium channel blockers (CCBs) have been reported to reduce atherosclerosis with anti-inflammatory or antiatherosclerotic effects in vivo. It is well established that monocytes and macrophages play important roles in promoting atherosclerosis. However, the effects of CCBs on macrophage activation remain unclear. The aim of this study was to evaluate the effects of azelnidipine, a dihydropyridine L-type CCB, on the activation of macrophages and to clarify the mechanisms of the effects of CCBs on atherosclerosis.Methods: THP-1 monocytes, a human leukemic cell line, were stimulated with 50 ng/mL of phorbol-12-myristate-13-acetate (PMA) 1 h after pretreatment with 10 µM azelnidipine or dimethyl sulfoxide (DMSO), and harvested.Results: Azelnidipine blocked the expression of intercellular adhesion molecule-1 quantified by FACS analysis. The expression levels of Apo E and MMP9, which are markers of macrophage differentiation, were inhibited by azelnidipine as evaluated by quantitative RT-PCR. The level of LOX-1 mRNA, a scavenger receptor, was also reduced significantly by pretreatment with 10 µM azelnidipine. Azelnidipine also lowered the uptake of acetylated LDL. The expression of the L-type calcium channel Cav1.2 was 10-fold higher after 24 h of PMA stimulation. A knockdown of the CACNA1C gene, which encodes Cav1.2 protein in humans, with siRNA blocked the effect of reducing adhesion by azelnidipine, indicating that the effects of azelnidipine on macrophage differentiation were expressed through the CACNA1C gene.Conclusion: Our results suggest that azelnidipine has potent antiatherosclerotic properties by inhibition of macrophage activation through Cav1.2.

The ECLIPSE Trials: Comparative Studies of Clevidipine to Nitroglycerin, Sodium Nitroprusside, and Nicardipine for Acute Hypertension Treatment in Cardiac Surgery Patients

Acute hypertension during cardiac surgery can be difficult to manage and may adversely affect patient outcomes. Clevidipine is a novel, rapidly acting dihydropyridine L-type calcium channel blocker with an ultrashort half-life that decreases arterial blood pressure (BP). The Evaluation of CLevidipine In the Perioperative Treatment of Hypertension Assessing Safety Events trial (ECLIPSE) was performed to compare the safety and efficacy of clevidipine (CLV) with nitroglycerin (NTG), sodium nitroprusside (SNP), and nicardipine (NIC) in the treatment of perioperative acute hypertension in patients undergoing cardiac surgery. We analyzed data from three prospective, randomized, open-label, parallel comparison studies of CLV to NTG or SNP perioperatively, or NIC postoperatively in patients undergoing cardiac surgery at 61 medical centers. Of the 1964 patients enrolled, 1512 met postrandomization inclusion criteria of requiring acute treatment of hypertension based on clinical criteria. The patients were randomized 1:1 for each of the three parallel comparator treatment groups. The primary outcome was the incidence of death, myocardial infarction, stroke or renal dysfunction at 30 days. Adequacy and precision of BP control was evaluated and is reported as a secondary outcome. There was no difference in the incidence of myocardial infarction, stroke or renal dysfunction for CLV-treated patients compared with the other treatment groups. There was no difference in mortality rates between the CLV, NTG or NIC groups. Mortality was significantly higher, though, for SNP-treated patients compared with CLV-treated patients (P=0.04). CLV was more effective compared with NTG (P=0.0006) or SNP (P=0.003) in maintaining BP within the prespecified BP range. CLV was equivalent to NIC in keeping patients within a prespecified BP range; however, when BP range was narrowed, CLV was associated with fewer BP excursions beyond these BP limits compared with NIC. CLV is a safe and effective treatment for acute hypertension in patients undergoing cardiac surgery.

Very low frequency blood pressure fluctuations: not only myogenic responsiveness

Very low frequency blood pressure fluctuations: not only myogenic responsiveness

Nitrendipine Blocks the Nociceptive Effects of Chronically Administered Ethanol

Background Calcium channel blockers prevent the development of tolerance to ethanol and prevent seizures and other signs of ethanol withdrawal. Calcium channels may also mediate the development of tolerance to the antinociceptive effects of ethanol. Methods A radiant-heat tail-flick assay was used to assess the effects of nitrendipine, a dihydropyridine L-type calcium channel blocker, on ethanol-induced changes in nociception in rats. Chronic effects of ethanol were tested in four groups of rats, which received 10 days of exposure to a liquid diet. The groups received twice-daily injections of saline or nitrendipine (1, 5, or 10 mg/kg). Tail-flick latencies were measured on days 0 (baseline), 2, 4, 6, 8, and 10 and at 12 hr after removal of the liquid diet. Results Chronic exposure to ethanol produced maximal levels of antinociception by day 4 of exposure. The observed level of antinociception gradually decreased to baseline levels by day 8. Marked decreases in tail-flick latencies below baseline (hyperalgesia) were observed during ethanol withdrawal. Repeated administration of nitrendipine blocked the antinociceptive effects of chronic ethanol and prevented the hyperalgesia produced by ethanol withdrawal. The highest dose of nitrendipine (10 mg/kg, twice daily) reduced consumption of the ethanol diet. Conclusions L-type calcium channel blockers block hyperalgesia during ethanol withdrawal and may mediate, at least in part, the antinociceptive effects of chronic ethanol.

Nitrendipine Blocks the Nociceptive Effects of Chronically Administered Ethanol

Background Calcium channel blockers prevent the development of tolerance to ethanol and prevent seizures and other signs of ethanol withdrawal. Calcium channels may also mediate the development of tolerance to the antinociceptive effects of ethanol.Methods A radiant‐heat tail‐flick assay was used to assess the effects of nitrendipine, a dihydropyridine L‐type calcium channel blocker, on ethanol‐induced changes in nociception in rats. Chronic effects of ethanol were tested in four groups of rats, which received 10 days of exposure to a liquid diet. The groups received twice‐daily injections of saline or nitrendipine (1, 5, or 10 mg/kg). Tail‐flick latencies were measured on days 0 (baseline), 2, 4, 6, 8, and 10 and at 12 hr after removal of the liquid diet.Results Chronic exposure to ethanol produced maximal levels of antinociception by day 4 of exposure. The observed level of antinociception gradually decreased to baseline levels by day 8. Marked decreases in tail‐flick latencies below baseline (hyperalgesia) were observed during ethanol withdrawal. Repeated administration of nitrendipine blocked the antinociceptive effects of chronic ethanol and prevented the hyperalgesia produced by ethanol withdrawal. The highest dose of nitrendipine (10 mg/kg, twice daily) reduced consumption of the ethanol diet.Conclusions L‐type calcium channel blockers block hyperalgesia during ethanol withdrawal and may mediate, at least in part, the antinociceptive effects of chronic ethanol.

Effects of calcium channel blockers on pentylenetetrazol drug discrimination in rats

The effects of the dihydropyridine L-type calcium channel blockers nitrendipine and nimodipine on the pentylenetetrazol (PTZ) drug discrimination, an operant model of anxiety, were investigated. Male Long–Evans rats were trained to discriminate PTZ (16 mg/kg, i.p.) from saline. Both nitrendipine (5.0–25 mg/kg, i.p.) and nimodipine (5.0–25 mg/kg, i.p.) partially substituted for the PTZ discriminative stimulus. However, pretreatment with nitrendipine (25 mg/kg, i.p.) or nimodipine (25 mg/kg, i.p.) produced no change in the PTZ dose-effect function. Rats were given a nutritionally balanced liquid diet containing 6.5% ethanol for 10 days. Rats selected the PTZ drug lever during withdrawal. Subchronic coadministration of nitrendipine (1.25–5.0 mg/kg, i.p., b.i.d.) with ethanol failed to dose-dependently reduce PTZ-lever responding, but it did reverse withdrawal signs. Acute administration of nitrendipine (5, 10, and 20 mg/kg, i.p.) produced marked suppression of lever responding, but it failed to significantly reduce levels of PTZ-lever responding. Although calcium channel blockers reduce signs of ethanol withdrawal, they also markedly reduce rates of behavior and produce no clear effects on anxiety-like behaviors induced by ethanol withdrawal.

Beyond Lithium in the Treatment of Bipolar Illness

Dramatic changes have recently occurred in the availability of treatment options for bipolar illness. Second generation mood stabilizing anticonvulsants carbamazepine and valproate are now widely used as alternatives or adjuncts to lithium. High potency benzodiazepines are also used as alternatives to typical neuroleptics, and now atypical neuroleptics are demonstrating efficacy and better side-effects profiles than the typicals. Thyroid augmentation strategies and dihydropyridine L-type calcium channel blockers require further clinical trials to define their role. Putative third generation mood stabilizing anticonvulsants lamotrigine, gabapentin, and topiramate have unique mechanisms of action and deserve further systematic study, as does the potential role for nonconvulsive brain stimulation with repeated transcranial magnetic stimulation (rTMS). These and a host of other potential treatment options now require a new generation of clinical trials to help identify clinical and biological markers of response and optimal use alone and in complex combination therapeutic regimens.

Degeneration of pre-labelled nigral neurons induced by intrastriatal 6-hydroxydopamine in the rat: behavioural and biochemical changes and pretreatment with the calcium-entry blocker nimodipine.

Intrastriatal application of 6-hydroxydopamine (6-OHDA) initiates a delayed and progressive loss of nigral dopaminergic neurons and therefore may better resemble the slowly developing neuropathology of Parkinson's disease. We investigated the anatomical, behavioural and biochemical consequences of intrastriatal 6-OHDA after prior labelling of nigral dopaminergic neurons in rats and whether the dihydropyridine L-type calcium channel blocker nimodipine protected from the induced deficits. Adult rats received bilateral intrastriatal injections of the retrograde fluorescence tracer fluorogold and nimodipine (n=12) or placebo (n=9) pellets implanted subcutaneously. One week later all rats were injected unilaterally with 6-OHDA (20 microg) at the same intrastriatal site. Placebo-treated rats displayed relatively few d-amphetamine-induced ipsilateral net rotations (R) (1.3+/-1.4 R/min; mean+/-SEM) 1 week after the lesion with a slight but non-significant decline thereafter (after 2, 3 and 4 weeks). In nimodipine-treated rats the rotation behaviour after 1 week was more prominent (3.5+/-0.8 R/min; mean+/-SEM) with a similar slight decline until week 4. Fluorescent and immunocytochemical analysis of the midbrain after 4 weeks revealed a 35% and 39% loss of tyrosine hydroxylase positive cells and a 62% and 56% (placebo and nimodipine, respectively) loss of fluorogold-labelled cells in the ipsilateral substantia nigra pars compacta. Striatal dopamine levels were reduced to 47% (placebo) and 43% (nimodipine) of the control side and the dopamine metabolites dihydroxyphenylacetic acid and homovanillic acid to about 50%. Pretreatment with nimodipine failed to antagonize or to ameliorate any of the lesion-induced deficits. We conclude that pretreatment with 80 mg nimodipine pellets does not prevent nigrostriatal damage induced by intrastriatal 6-OHDA.

Failure of isradipine to reduce infarct size in mouse, gerbil, and rat models of cerebral ischemia.

The dihydropyridine L-type calcium channel blocker isradipine has been reported to exhibit neuroprotective properties in some, but not all, studies performed in the rat middle cerebral artery occlusion (MCAO) model. In the present study, we examined isradipine in several other models of focal and global ischemia: rat rose bengal, mouse MCAO, and gerbil bilateral carotid artery occlusion (BCAO). For comparison, a novel calcium channel blocker, SB201823A, that we have previously shown to be neuroprotective in rat and gerbil models was also examined in the mouse. In the gerbil BCAO model, isradipine was administered at 2.5 mg/kg i.p. as a single dose 60 minutes after ischemia (n = 10). Corresponding controls received vehicle (n = 10), and sham-operated animals received no treatment (n = 6). Locomotor activity and histological assessments were made at 4 days after ischemia. In the rat photothrombotic occlusion model, isradipine was administered at 2.5 mg/kg i.p. as a single dose 60 minutes after ischemia (n = 10), and corresponding controls (n = 10) received vehicle. Histological assessment was made at 7 days after ischemia. In the mouse MCAO model, isradipine was also administered at 2.5 mg/kg i.p. as a single dose 60 minutes after ischemia. Histological assessments were made at 1 (n = 13), 2 (n = 9), and 4 (n = 9) days after ischemia. Vehicle numbers were n = 10, n = 6, and n = 8, respectively. Isradipine and SB201823A were also examined using a combined preischemia and postischemia regimen. Isradipine was administered at 2.5 mg/kg i.p. before occlusion, 1.25 mg/kg i.p. 1 hour after occlusion, 1.25 mg/kg i.p. 2 hours after occlusion, and 2.5 mg/kg twice a day for 3 days after occlusion (n = 16). Corresponding controls received vehicle at the same time points (n = 14). SB201823A was administered 30 minutes before occlusion, 30 minutes after occlusion, and twice daily for 3 days (n = 12). Corresponding controls received vehicle (n = 9). Histological assessment was performed at 4 days after ischemia. When given after ischemia, isradipine failed to affect lesion volume in both the rat and mouse models. In the gerbil, locomotor hyperactivity and hippocampal cell loss were unaffected. Given before and after ischemia in the mouse, isradipine was also ineffective, whereas SB201823A produced a significant reduction in lesion volume. The L-type calcium channel blocker isradipine was devoid of neuroprotective activity in focal and global models of cerebral ischemia in three species of normotensive animals. These results were compared with data for the novel calcium channel blocker SB201823A, which exhibited a significant effect after pre- and postocclusion administration in the mouse model of permanent focal ischemia.