Verapamil prevents, in a dose-dependent way, the loss of ChAT-immunoreactive neurons in the cerebral cortex following lesions of the rat nucleus basalis magnocellularis

Verapamil and Alzheimer's Disease: Past, Present, and Future

Verapamil is a phenylalkylamine class calcium channel blocker that for half a century has been used for the treatment of cardiovascular diseases. Nowadays, verapamil is also considered as a drug option for the treatment of several neurological and psychiatric disorders, such as cluster headache, bipolar disorders, epilepsy, and neurodegenerative diseases. Here, we review insights into the potential preventive and therapeutic role of verapamil on Alzheimer’s disease (AD) based on limited experimental and clinical data. Pharmacological studies have shown that verapamil has a wide therapeutic spectrum, including antihypertensive, anti-inflammatory, and antioxidative effects, regulation of the blood-brain barrier function, due to its effect on P-glycoprotein, as well as adjustment of cellular calcium homeostasis, which may result in the delay of AD onset or ameliorate the symptoms of patients. However, the majority of the AD individuals are on polypharmacotherapy, and the interactions between verapamil and other drugs need to be considered. Therefore, for an appropriate and successful AD treatment, a personalized approach is more than necessary. A well-known narrow pharmacological window of verapamil efficacy may hinder this approach. It is therefore important to note that the verapamil efficacy may be conditioned by different factors. The onset, grade, and brain distribution of AD pathological hallmarks, the time-sequential appearances of AD-related cognitive and behavioral dysfunction, the chronobiologic and gender impact on calcium homeostasis and AD pathogenesis may somehow be influencing that success. In the future, such insights will be crucial for testing the validity of verapamil treatment on animal models of AD and clinical approaches.

Verapamil attenuates scopolamine induced cognitive deficits by averting oxidative stress and mitochondrial injury - A potential therapeutic agent for Alzheimer's Disease

Alzheimer's disease (AD) is a multifactorial disorder where amyloid beta (Aβ) plaques, Ca2+ dysregulation, excessive oxidative stress, mitochondrial dysfunction and synaptic loss operate synergistically to bring about cholinergic deficits and dementia. New therapeutic interventions are gaining prominence as the morbidity and mortality of AD increases exponentially every year. Treating AD with antihypertensive drugs is thought to be a promising intervention; however, its mechanism of action of ameliorating AD needs further investigation. In this context, the present study explores the protective effect of verapamil, an antihypertensive agent of Ca2+ channel blocker (CCB) class against scopolamine-induced in vitro neurotoxicity and in vivo cognitive impairment. Supplementation of verapamil was found to attenuate oxidative stress by preventing mitochondrial injury, and augment the expression of genes involved in the cholinergic function (mACR1), synaptic plasticity (GAP43, SYP) and Ca2+-dependent memory-related genes (CREB1, CREBBP, BDNF). Further, verapamil treatment in mice attenuated the cognitive and behavioural deficits induced by scopolamine as measured by the elevated plus maze and passive avoidance test (P < 0.05). Thus, the present study demonstrates the neuroprotective effect of verapamil against the pathogenesis of AD such as oxidative stress, mitochondrial dysfunction and cognitive decline. These observations emphasize the importance of ‛Ca2+ dysregulation' and ‛mitochondrial dysfunction' theories in AD and recommends the supplementation of compounds that regulate Ca2+ homeostasis and mitochondrial function in susceptible AD individuals.

Verapamil Blocks Scopolamine Enhancement Effect on Memory Consolidation in Passive Avoidance Task in Rats

Our recent data have indicated that scopolamine, a non-selective muscarinic receptor antagonist, improves memory consolidation, in a passive avoidance task, tested in rats. It has been found that verapamil, a phenylalkylamine class of the L-type voltage-dependent calcium channel antagonist, inhibits [3H] N-methyl scopolamine binding to M1 muscarinic receptors. However, there are no data about the effect of verapamil on memory consolidation in the passive avoidance task, in rats. The purpose of the present study was to examine the effects of verapamil (0.5, 1.0, 2.5, 5.0, 10, or 20 mg/kg i.p.) as well as the interaction between scopolamine and verapamil on memory consolidation in the step-through passive avoidance task, in Wistar rats. Our results showed that verapamil (1.0 and 2.5 mg/kg) administered immediately after the acquisition task significantly increased the latency of the passive avoidance response, on the 48 h retested trial, improving memory consolidation. On the other hand, verapamil in a dose of 5 mg/kg, that per se does not affect memory consolidation, significantly reversed the memory consolidation improvement induced by scopolamine (1 mg/kg, i.p., administered immediately after verapamil treatment) but did not change the passive avoidance response in rats treated by an ineffective dose of scopolamine (30 mg/kg). In conclusion, the present data suggest that (1) the post-training administration of verapamil, dose-dependently, improves the passive avoidance response; (2) verapamil, in ineffective dose, abolished the improvement of memory consolidation effect of scopolamine; and (3) exists interaction between cholinergic muscarinic receptors and calcium homeostasis-related mechanisms in the consolidation of emotional memory.

Possible role of P-glycoprotein in the neuroprotective mechanism of berberine in intracerebroventricular streptozotocin-induced cognitive dysfunction

RATIONALE

The therapeutic potential of berberine has been well documented in various neurological problems. However, the neurological mechanism of berberine remains untapped in the light of its P-glycoprotein (P-gp)-mediated gut efflux properties responsible for reduced bioavailability. Verapamil, a well known L-type calcium channel blocker, has additional inhibitory activity against P-gp efflux pump. Thus, there is a strong scientific rationale to explore the interaction of berberine with verapamil as a possible neuroprotective strategy.

OBJECTIVE

The present study was designed to evaluate the effect of berberine, verapamil, and their combination on behavioral alterations, oxidative stress, mitochondrial dysfunction, neuroinflammation, and histopathological modifications in intracerebroventricular streptozocin (ICV-STZ)-induced sporadic dementia of Alzheimer's type in rats.

METHODS

Single bilateral ICV-STZ (3 mg/kg) administration was used as an experimental model of sporadic dementia of Alzheimer's type.

RESULTS

Berberine (25, 50, and 100 mg/kg, oral gavage) or verapamil (2.5 and 5 mg/kg, intraperitoneally) were used as treatment drugs, and memantine (5 mg/kg, intraperitoneally) was used as a standard. Berberine and verapamil significantly attenuated behavioral, biochemical, cellular, and histological alterations, suggesting their neuroprotective potential. Further, treatment of berberine (25 and 50 mg/kg) with verapamil (2.5 and 5.0 mg/kg) combinations respectively significantly potentiated their neuroprotective effect which was significant as compared to their effect per se in ICV-STZ-treated animals.

CONCLUSION

The augmentative outcome of verapamil on the neuroprotective effect of berberine can be speculated due to the inhibition of P-gp efflux mechanism and the prevention of calcium homeostasis alteration. Additionally, anti-inflammatory and antioxidant effects of both berberine and verapamil could also contribute in their protective effect.

Inhibition of human astrocyte and microglia neurotoxicity by calcium channel blockers

We examined the effects of L-type calcium channel blockers (CCBs) on toxicity exerted by activated human astrocytes and microglia towards SH-SY5Y human neuronal cells. The CCBs nimodipine (NDP) and verapamil (VPM) both significantly suppressed toxic secretions from human astrocytes and astrocytoma U-373 MG cells that were induced by interferon (IFN)-γ. NDP also inhibited neurotoxic secretions of human microglia and monocytic THP-1 cells that were induced by the combination of lipopolysaccharide and IFN-γ. In human astrocytes, both NDP and VPM reduced IFN-γ-induced phosphorylation of signal transducer and activator of transcription (STAT) 3. They also inhibited the astrocytic production of IFN-γ-inducible T cell α chemoattractant (I-TAC). These results suggest that CCBs attenuate IFN-γ-induced neurotoxicity of human astrocytes through inhibition of the STAT3 signaling pathway. L-type CCBs, especially NDP, might be a useful treatment option for a broad spectrum of neurodegenerative diseases, including Alzheimer disease, where the pathology is believed to be exacerbated by neurotoxic glial activation.

Verapamil protects dopaminergic neuron damage through a novel anti-inflammatory mechanism by inhibition of microglial activation

Verapamil has been shown to be neuroprotective in several acute neurotoxicity models due to blockade of calcium entry into neurons. However, the potential use of verapamil to treat chronic neurodegenerative diseases has not been reported. Using rat primary mesencephalic neuron/glia cultures, we report that verapamil significantly inhibited LPS-induced dopaminergic neurotoxicity in both pre- and post-treatment experiments. Reconstituted culture studies revealed that the presence of microglia was essential in verapamil-elicited neuroprotection. Mechanistic studies showed that decreased production of inflammatory mediators from LPS-stimulated microglia underlay neuroprotective property of verapamil. Further studies demonstrated that microglial NADPH oxidase (PHOX), the key superoxide-producing enzyme, but not calcium channel in neurons, is the site of action for the neuroprotective effect of verapamil. This conclusion was supported by the following two observations: 1) Verapamil failed to show protective effect on LPS-induced dopaminergic neurotoxicity in PHOX-deficient (deficient in the catalytic subunit of gp91(phox)) neuron/glia cultures; 2) Ligand binding studies showed that the binding of [(3)H]Verapamil onto gp91(phox) transfected COS7 cell membranes was higher than the non-transfected control. The calcium channel-independent neuroprotective property of verapamil was further supported by the finding that R(+)-verapamil, a less active form in blocking calcium channel, showed the same potency in neuroprotection, inhibition of pro-inflammatory factors production and binding capacity to gp91(phox) membranes as R(-)-verapamil, the active isomer of calcium channel blocker. In conclusion, our results demonstrate a new indication of verapamil-mediated neuroprotection through a calcium channel-independent pathway and provide a valuable avenue for the development of therapy for inflammation-related neurodegenerative diseases.