Nilvadipine prevents cognitive decline of patients with mild cognitive impairment

Targeting calciumopathy for neuroprotection: focus on calcium channels Cav1, Orai1 and P2X7

As the uncontrolled entry of calcium ions (Ca2+) through plasmalemmal calcium channels is a cell death trigger, the conjecture is here raised that mitigating such an excess of Ca2+ entry should rescue from death the vulnerable neurons in neurodegenerative diseases (NDDs). However, this supposition has failed in some clinical trials (CTs). Thus, a recent CT tested whether isradipine, a blocker of the Cav1 subtype of voltage-operated calcium channels (VOCCs), exerted a benefit in patients with Parkinson's disease (PD); however, outcomes were negative. This is one more of the hundreds of CTs done under the principle of one-drug-one-target, that have failed in Alzheimer's disease (AD) and other NDDs during the last three decades. As there are myriad calcium channels to let Ca2+ ions gain the cell cytosol, it seems reasonable to predict that blockade of Ca2+ entry through a single channel may not be capable of preventing the Ca2+ flood of cells by the uncontrolled Ca2+ entry. Furthermore, as Ca2+ signaling is involved in the regulation of myriad functions in different cell types, it seems also reasonable to guess that a therapy should be more efficient by targeting different cells with various drugs. Here, we propose to mitigate Ca2+ entry by the simultaneous partial blockade of three quite different subtypes of plasmalemmal calcium channels that is, the Cav1 subtype of VOCCs, the Orai1 store-operated calcium channel (SOCC), and the purinergic P2X7 calcium channel. All three channels are expressed in both microglia and neurons. Thus, by targeting the three channels with a combination of three drug blockers we expect favorable changes in some of the pathogenic features of NDDs, namely (i) to mitigate Ca2+ entry into microglia; (ii) to decrease the Ca2+-dependent microglia activation; (iii) to decrease the sustained neuroinflammation; (iv) to decrease the uncontrolled Ca2+ entry into neurons; (v) to rescue vulnerable neurons from death; and (vi) to delay disease progression. In this review we discuss the arguments underlying our triad hypothesis in the sense that the combination of three repositioned medicines targeting Cav1, Orai1, and P2X7 calcium channels could boost neuroprotection and delay the progression of AD and other NDDs.

Network Proximity-based computational pipeline identifies drug candidates for different pathological stages of Alzheimer's disease

Despite the massive investment in Alzheimer's disease (AD), there are still no disease-modifying treatments (DMTs) for AD. One major reason is attributed to the limitation of clinical "one-size-fits-all" approach, since the same AD treatment solely based on clinical diagnosis was unlikely to achieve good clinical efficacy. In recent years, computational approaches based on multiomics data have provided an unprecedented opportunity for drug discovery since they can substantially lower the costs and boost the efficiency. In this study, we intended to identify potential drug candidates for different pathological stages of AD by computationally repurposing Food and Drug Administration (FDA) approved drugs. First, we assembled gene expression data from three different AD pathological stages, which include mild cognitive impairment (MCI) and early and late stages of AD (EAD, LAD). We next quantified the network distances between drug target networks and AD modules by utilizing a network proximity approach, and identified 193 candidates that possessed significant associations with AD. After searching for previous literature evidence, 63 out of 193 (32.6%) predicted drugs were demonstrated to exert therapeutic effects on AD. We further explored the novel mechanism of action (MOA) for these drug candidates by determining the specific brain cells they might function on based on AD patient single cell transcriptomic data. Additionally, we selected several promising candidates that could cross the blood brain barrier together with confirmed neuroprotective effects, and subsequently determined the antioxidative activity of these compounds. Experimental results showed that azathioprine decreased the reactive oxygen species (ROS) and malondialdehyde (MDA) levels and improved the superoxide dismutase (SOD) activity in APP-SH-SY5Y cells. Finally, we deciphered the potential MOA of azathioprine against AD via network analysis and validated several apoptosis-related proteins (Caspase 3, Cleaved Caspase 3, Bax, Bcl2) through western blotting. In summary, this study presented an effective computational strategy utilizing omics data for AD drug repurposing, which provides a new perspective for drug discovery and development.

Role of Oxysterols in the Activation of the NLRP3 Inflammasome as a Potential Pharmacological Approach in Alzheimer's Disease

Alzheimer's disease (AD), the most prevalent form of dementia, is a complex clinical condition with multifactorial origin posing a major burden to health care systems across the world. Even though the pathophysiological mechanisms underlying the disease are still unclear, both central and peripheral inflammation has been implicated in the process. Piling evidence shows that the nucleotide-binding domain, leucine-rich repeat and pyrin domain-containing protein 3 (NLRP3) inflammasome is activated in AD. As dyslipidemia is a risk factor for dementia, and cholesterol can also activate the inflammasome, a possible link between lipid levels and the NLRP3 inflammasome has been proposed in Alzheimer's. It is also speculated that not only cholesterol but also its metabolites, the oxysterols, may be involved in AD pathology. In this context, mounting data suggest that NLRP3 inflammasome activity can be modulated by different peripheral nuclear receptors, including liver-X receptors, which present oxysterols as endogenous ligands. In light of this, the current review explores whether the activation of NLRP3 by nuclear receptors, mediated by oxysterols, may also be involved in AD and could serve as a potential pharmacological avenue in dementia.

Post-Translational Modification of Cav1.2 and its Role in Neurodegenerative Diseases

Cav1.2 plays an essential role in learning and memory, drug addiction, and neuronal development. Intracellular calcium homeostasis is disrupted in neurodegenerative diseases because of abnormal Cav1.2 channel activity and modification of downstream Ca²⁺ signaling pathways. Multiple post-translational modifications of Cav1.2 have been observed and seem to be closely related to the pathogenesis of neurodegenerative diseases. The specific molecular mechanisms by which Cav1.2 channel activity is regulated remain incompletely understood. Dihydropyridines (DHPs), which are commonly used for hypertension and myocardial ischemia, have been repurposed to treat PD and AD and show protective effects. However, further studies are needed to improve delivery strategies and drug selectivity. Better knowledge of channel modulation and more specific methods for altering Cav1.2 channel function may lead to better therapeutic strategies for neurodegenerative diseases.

Oral nimodipine treatment has no effect on amyloid pathology or neuritic dystrophy in the 5XFAD mouse model of amyloidosis

Dysregulation of calcium homeostasis has been hypothesized to play a role in Alzheimer's disease (AD) pathogenesis. Increased calcium levels can impair axonal transport, disrupt synaptic transmission, and ultimately lead to cell death. Given the potential role of calcium dyshomeostasis in AD, there is interest in testing the ability of already approved drugs targeting various calcium channels to affect amyloid pathology and other aspects of disease. The objective of this study was to test the effects of FDA-approved L-type calcium channel antagonist nimodipine on amyloid accumulation and dystrophic neurite formation in 5XFAD mice, a mouse model of amyloid pathology. 5XFAD transgenic mice and non-transgenic littermates were treated with vehicle or nimodipine-containing chow from two to eight months of age, then brains were harvested and amyloid pathology assessed by immunoblot and immunofluorescence microscopy analyses. Nimodipine was well tolerated and crossed the blood brain barrier, as expected, but there was no effect on Aβ accumulation or on the relative amount of neuritic dystrophy, as assessed by either immunoblot, dot blot or immunofluorescence imaging of Aβ42 and dystrophic neurite marker LAMP1. While we conclude that nimodipine treatment is not likely to improve amyloid pathology or decrease neuritic dystrophy in AD, it is worth noting that nimodipine did not worsen the phenotype suggesting its use is safe in AD patients.

Nilvadipine suppresses inflammation via inhibition of P-SYK and restores spatial memory deficits in a mouse model of repetitive mild TBI

Repeated exposure to mild TBI (mTBI) has been linked to an increased risk of Alzheimer's disease (AD), chronic traumatic encephalopathy (CTE) and other neurodegenerative diseases. Some pathological features typically observed in AD have been found in postmortem brains of TBI and CTE, hence treatments tested for AD have a potential to be effective against r-mTBI outcomes. Neuroinflammation may present a possible answer due to its central role both in acute brain injury and in chronic degenerative-like disorders. Our previous studies have shown that drug nilvadipine, acting as an inhibitor of spleen tyrosine kinase (SYK), is effective at reducing inflammation, tau hyperphosphorylation and amyloid production in AD mouse models. To demonstrate the effect of nilvadipine in the absence of age-related variables, we introduced the same treatment to young r-mTBI mice. We further investigate therapeutic mechanisms of nilvadipine using its racemic properties. Both enantiomers, (+)-nilvadipine and (-)-nilvadipine, can lower SYK activity, whereas (+)-nilvadipine is also a potent L-type calcium channel blocker (CCB) and shown to be anti-hypertensive. All r-mTBI mice exhibited increased neuroinflammation and impaired cognitive performance and motor functions. Treatment with racemic nilvadipine mitigated the TBI-induced inflammatory response and significantly improved spatial memory, whereas (-)-enantiomer decreased microgliosis and improved spatial memory but failed to reduce the astroglial response to as much as the racemate. These results suggest the therapeutic potential of SYK inhibition that is enhanced when combined with the CCB effect, which indicate a therapeutic advantage of multi-action drugs for r-mTBI.

Blood-brain barrier dysfunction: the undervalued frontier of hypertension

The blood-brain barrier (BBB) constitutes the complex anatomic and physiologic interface between the intravascular compartment and the central nervous system, and its integrity is paramount for the maintenance of the very sensitive homeostasis of the central nervous system. Arterial hypertension is a leading cause of morbidity and mortality. The BBB has been shown to be disrupted in essential hypertension. BBB integrity is important for central autonomic control and this may be implicated in the pathophysiology of hypertension. On the other hand, evidence from experimental studies indicates that BBB disruption can be present in both hypertensive disease and dementia syndromes, suggesting a possibly key position of loss of BBB integrity in the pathophysiological pathways linking arterial hypertension with cognitive decline. Although much still remains to be elucidated with respect to the exact underlying mechanisms, the discovery of novel pathological pathways has changed our understanding of adult dementia and central nervous system disease overall, pointing out-in parallel-new potential therapeutic targets. The aim of this review is to summarize current scientific knowledge relevant to the pathophysiologic pathways that are involved in the disruption of the BBB function and potentially mediate hypertension-induced cognitive impairment. In parallel, we underline the differential cognition-preserving effect of several antihypertensive agents of similar blood pressure-lowering capacity, highlighting the presence of previously under-recognized BBB-protective actions of these drugs.

The Influence of Baseline Alzheimer's Disease Severity on Cognitive Decline and CSF Biomarkers in the NILVAD Trial

We examined the effects of a dihydropyridine calcium channel blocker nilvadipine with anti-inflammatory properties on cognition and cerebrospinal fluid (CSF) biomarkers by baseline Alzheimer's disease (AD) severity. Exploratory analyses were performed on the dataset (n = 497) of a phase III randomized placebo-controlled trial to examine the response to nilvadipine in AD subjects stratified by baseline AD severity into very mild (MMSE ≥ 25), mild (MMSE 20-24) and moderate AD (MMSE < 20). The outcome measures included total and subscale scores of the Alzheimer's Disease Assessment Scale Cognitive 12 (ADAS-Cog 12), the Clinical Dementia Rating Scale sum of boxes (CDR-sb) and the AD composite score (ADCOMS). Cerebrospinal fluid biomarkers Aβ38, Aβ40, Aβ42, neurofilament light chain (NFL), neurogranin, YKL-40, total tau and P181 tau (ptau) were measured in a subset of samples (n = 55). Regression analyses were adjusted for confounders to specifically examine the influence of nilvadipine and baseline AD severity on cognitive outcomes over 78-weeks. Compared to their respective placebo-controls, nilvadipine-treated, very mild AD subjects showed less decline, whereas moderate AD subjects showed a greater cognitive decline on the ADAS-Cog 12 test and the ADCOMS. A lower decline was observed after nilvadipine treatment for a composite memory trait in very mild AD subjects and a composite language trait in mild AD subjects. Cerebrospinal fluid Aβ42/Aβ40 ratios were increased in mild AD and decreased in moderate AD patients treated with nilvadipine, compared to their respective controls. Among moderate AD subjects, levels of ptau, total tau, neurogranin and YKL-40 increased in subjects treated with nilvadipine compared to placebo. These studies suggest that baseline AD severity influenced the treatment outcome in the NILVAD trial and that future clinical trials of nilvadipine should be restricted to mild and very mild AD patients.

Trial Registration: NCT02017340 Registered 20 December 2013, https://clinicaltrials.gov/ct2/show/NCT02017340

EUDRACT Reference Number 2012-002764-27 Registered 04 February 2013, https://www.clinicaltrialsregister.eu/ctr-search/search?query=2012-002764-27

Role of GPCR signaling and calcium dysregulation in Alzheimer's disease

Alzheimer's disease (AD), a late onset neurodegenerative disorder is characterized by the loss of memory, disordered cognitive function, caused by accumulation of amyloid-β (Aβ) peptide and neurofibrillary tangles (NFTs) in the neocortex and hippocampal brain area. Extensive research has been done on the findings of the disease etiology or pathological causes of aggregation of Aβ and hyperphosphorylation of tau protein without much promising results. Recently, calcium dysregulation has been reported to play an important role in the pathophysiology of AD. Calcium ion acts as one of the major secondary messengers, regulates many signaling pathways involved in cell survival, proliferation, differentiation, transcription and apoptosis. Calcium signaling is one of the major signaling pathways involved in the formation of memory, generation of energy and other physiological functions. It also can modulate function of many proteins upon binding. Dysregulation in calcium homeostasis leads to many physiological changes leading to neurodegenerative diseases including AD. In AD, GPCRs generate secondary messengers which regulate calcium homeostasis inside the cell and is reported to be disturbed in the pathological condition. Calcium channels and receptors present on the plasma membrane and intracellular organelle maintain calcium homeostasis through different signaling mechanisms. In this review, we have summarized the different calcium channels and receptors involved in calcium dysregulation which in turn play a critical role in the pathogenesis of AD. Understanding the role of calcium channels and GPCRs to maintain calcium homeostasis is an attempt to develop effective AD treatments.

1,4-Dihydropyridine: A Dependable Heterocyclic Ring with the Promising and the Most Anticipable Therapeutic Effects

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Nowadays, heterocyclic compounds act as a scaffold and are the backbone of medicinal chemistry. Among all of the heterocyclic scaffolds, 1,4-Dihydropyridine (1,4-DHP) is one of the most important heterocyclic rings that possess prominent therapeutic effects in a very versatile manner and plays an important role in synthetic, medicinal, and bioorganic chemistry. The main aim of the study is to review and encompass relevant studies related to 1,4-DHP and excellent therapeutic benefits of its derivatives. An extensive review of Pubmed-Medline, Embase and Lancet’s published articles was done to find all relevant studies on the activity of 1,4-DHP and its derivatives. 1,4-DHP is a potent Voltage-Gated Calcium Channel (VGCC) antagonist derivative which acts as an anti-hypertensive, anti- anginal, anti-tumor, anti-inflammatory, anti-tubercular, anti-cancer, anti-hyperplasia, anti-mutagenic, anti-dyslipidemic, and anti-ulcer agent. From the inferences of the study, it can be concluded that the basic nucleus, 1,4-DHP which is a voltage-gated calcium ion channel blocker, acts as a base for its derivatives that possess different important therapeutic effects. There is a need of further research of this basic nucleus as it is a multifunctional moiety, on which addition of different groups can yield a better drug for its other activities such as anti-convulsant, anti-oxidant, anti-mutagenic, and anti-microbial. This review would be significant for further researches in the development of several kinds of drugs by representing successful matrix for the medicinal agents.

Nilvadipine in mild to moderate Alzheimer disease: A randomised controlled trial

BACKGROUND

This study reports the findings of the first large-scale Phase III investigator-driven clinical trial to slow the rate of cognitive decline in Alzheimer disease with a dihydropyridine (DHP) calcium channel blocker, nilvadipine. Nilvadipine, licensed to treat hypertension, reduces amyloid production, increases regional cerebral blood flow, and has demonstrated anti-inflammatory and anti-tau activity in preclinical studies, properties that could have disease-modifying effects for Alzheimer disease. We aimed to determine if nilvadipine was effective in slowing cognitive decline in subjects with mild to moderate Alzheimer disease.

METHODS AND FINDINGS

NILVAD was an 18-month, randomised, placebo-controlled, double-blind trial that randomised participants between 15 May 2013 and 13 April 2015. The study was conducted at 23 academic centres in nine European countries. Of 577 participants screened, 511 were eligible and were randomised (258 to placebo, 253 to nilvadipine). Participants took a trial treatment capsule once a day after breakfast for 78 weeks. Participants were aged >50 years, meeting National Institute of Neurological and Communicative Disorders and Stroke/Alzheimer's disease Criteria (NINCDS-ADRDA) for diagnosis of probable Alzheimer disease, with a Standardised Mini-Mental State Examination (SMMSE) score of ≥12 and <27. Participants were randomly assigned to 8 mg sustained-release nilvadipine or matched placebo. The a priori defined primary outcome was progression on the Alzheimer's Disease Assessment Scale Cognitive Subscale-12 (ADAS-Cog 12) in the modified intention-to-treat (mITT) population (n = 498), with the Clinical Dementia Rating Scale sum of boxes (CDR-sb) as a gated co-primary outcome, eligible to be promoted to primary end point conditional on a significant effect on the ADAS-Cog 12. The analysis set had a mean age of 73 years and was 62% female. Baseline demographic and Alzheimer disease-specific characteristics were similar between treatment groups, with reported mean of 1.7 years since diagnosis and mean SMMSE of 20.4. The prespecified primary analyses failed to show any treatment benefit for nilvadipine on the co-primary outcome (p = 0.465). Decline from baseline in ADAS-Cog 12 on placebo was 0.79 (95% CI, -0.07-1.64) at 13 weeks, 6.41 (5.33-7.49) at 52 weeks, and 9.63 (8.33-10.93) at 78 weeks and on nilvadipine was 0.88 (0.02-1.74) at 13 weeks, 5.75 (4.66-6.85) at 52 weeks, and 9.41 (8.09-10.73) at 78 weeks. Exploratory analyses of the planned secondary outcomes showed no substantial effects, including on the CDR-sb or the Disability Assessment for Dementia. Nilvadipine appeared to be safe and well tolerated. Mortality was similar between groups (3 on nilvadipine, 4 on placebo); higher counts of adverse events (AEs) on nilvadipine (1,129 versus 1,030), and serious adverse events (SAEs; 146 versus 101), were observed. There were 14 withdrawals because of AEs. Major limitations of this study were that subjects had established dementia and the likelihood that non-Alzheimer subjects were included because of the lack of biomarker confirmation of the presence of brain amyloid.

CONCLUSIONS

The results do not suggest benefit of nilvadipine as a treatment in a population spanning mild to moderate Alzheimer disease.

TRIAL REGISTRATION

Clinicaltrials.gov NCT02017340, EudraCT number 2012-002764-27.

Calcium signaling in Alzheimer's disease & therapies

Alzheimer's disease (AD) is the most common type of dementia and is characterized by the accumulation of amyloid (Aβ) plaques and neurofibrillary tangles in the brain. Much attention has been given to develop AD treatments based on the amyloid cascade hypothesis; however, none of these drugs had good efficacy at improving cognitive functions in AD patients suggesting that Aβ might not be the disease origin. Thus, there are urgent needs for the development of new therapies that target on the proximal cause of AD. Cellular calcium (Ca²⁺) signals regulate important facets of neuronal physiology. An increasing body of evidence suggests that age-related dysregulation of neuronal Ca²⁺ homeostasis may play a proximal role in the pathogenesis of AD as disrupted Ca²⁺ could induce synaptic deficits and promote the accumulation of Aβ plaques and neurofibrillary tangles. Given that Ca²⁺ disruption is ubiquitously involved in all AD pathologies, it is likely that using chemical agents or small molecules specific to Ca²⁺ channels or handling proteins on the plasma membrane and membranes of intracellular organelles to correct neuronal Ca²⁺ dysregulation could open up a new approach to AD prevention and treatment. This review summarizes current knowledge on the molecular mechanisms linking Ca²⁺ dysregulation with AD pathologies and discusses the possibility of correcting neuronal Ca²⁺ disruption as a therapeutic approach for AD.

Drugs and Scaffold That Inhibit Cytochrome P450 27A1 In Vitro and In Vivo

Cytochrome P450 27A1 (CYP27A1) is a ubiquitous enzyme that hydroxylates cholesterol and other sterols. Complete CYP27A1 deficiency owing to genetic mutations is detrimental to human health, whereas 50% of activity retention is not and does not affect the whole body cholesterol levels. CYP27A1 is considered a potential therapeutic target in breast cancer and age-related neurodegenerative diseases; however, CYP27A1 inhibition should be ≤50%. Herein, 131 pharmaceuticals were tested for their effect on CYP27A1-mediated cholesterol 27-hydroxylation by in vitro enzyme assay. Of them, 14 drugs inhibited CYP27A1 by ≥75% and were evaluated for in vitro binding to the enzyme active site and for inhibition constants. All drugs except one (dasatinib) elicited a spectral response in CYP27A1 and had K_i values for cholesterol 27-hydroxylation either in the submicromolar (clevidipine, delavirdine, etravirine, felodipine, nicardipine, nilotinib, and sorafenib) or low micromolar range (abiratone, candesartan, celecoxib, dasatinib, nilvadipine, nimodipine, and regorafenib). Clevidipine, felodipine, nicardipine, nilvadipine, and nimodipine have the same 1,4-dihydropyridine scaffold and are indicated for hypertension. We used two of these antihypertensives (felodipine and nilvadipine) for administration to mice at a 1-mg/kg of body weight dose, daily, for 7 days. Mouse 27-hydroxycholesterol levels in the plasma, brain, and liver were reduced, whereas tissue levels of total cholesterol were unchanged. Structure-activity relationships within the 1,4-dihydropyridine scaffold were investigated, and features important for CY27A1 inhibition were identified. We confirmed our previous finding that CYP27A1 is a druggable enzyme and found additional drugs as well as the scaffold with potential for partial CYP27A1 inhibition in humans.

Pharmacotherapy for Vascular Cognitive Impairment

Vascular cognitive impairment (VCI) is the second most common type of dementia after Alzheimer's disease (AD). Stroke and cardiovascular risk factors have been linked to both AD and VCI and potentially can affect cognitive function in mid and later life. Various pharmacological agents, including donepezil, galantamine, and memantine, approved for the treatment of AD have shown modest cognitive benefits in patients with vascular dementia (VaD). However, their functional and global benefits have been inconsistent. Donepezil has shown some cognitive benefit in patients with VaD only, and galantamine has shown some benefit in mixed dementia (AD/VaD). The benefits of other drugs such as rivastigmine, memantine, nimodipine, and piracetam are not clear. Some other supplements and herbal therapies, such as citicoline, actovegin, huperzine A, and vinpocetine, have also been studied in patients with VaD, but their beneficial effects are not well established. Non-drug therapies and lifestyle modifications such as diet, exercise, and vascular risk factor control are important in the management of VCI and should not be ignored. However, there is a need for more robust clinical trials focusing on executive function and other cognitive measures and incorporation of newer imaging modalities to provide additional evidence about the utility of these strategies in patients with VCI.

Amlodipine, an L-type calcium channel blocker, protects against chlorpromazine-induced neurobehavioural deficits in mice

This study investigated the modulatory and chemopreventive benefit of amlodipine (AML), a dihydropyridine calcium channel antagonist, against neurobehavioural abnormalities (NAs) associated with chlorpromazine (CPZ) toxicity in mice. Adult mice were divided into five groups of six animals/group. Group 1 (control) was administered saline (10 mL/kg i.p.). Group 2 received CPZ (2 mg/kg i.p.). Groups 3 and 4 received bromocriptine (BMC, 2.5 mg/kg s.c.) and AML (1 mg/kg s.c.), respectively, while group 5 received their combination. Groups 3-5 later received CPZ 30 min after initial treatments. Animals were subjected to neurobehavioural tests and euthanized 18 h later. CPZ-induced NAs were characterized by significant increase (P < 0.001) in cataleptic behaviour and lowered (P < 0.05) spontaneous activity reaction time in mice. There were also significant (P < 0.001) increases in malondialdehyde levels and decreased locomotion plus learning and memory parameters (P < 0.05-0.001). AML pretreatment alone did not alleviate CPZ-induced motor deficits in the mice. While pretreatment with BMC alone attenuated CPZ-associated catalepsy, its combination with AML further protected mice against NAs. Furthermore, BMC pretreatment did not affect CPZ-induced increase in malondialdehyde level, but AML or BMC+AML significantly (P < 0.05) decreased malondialdehyde in the CPZ-treated rats. Reduced glutathione levels and activities of superoxide dismutase and catalase remained elevated in all treatment groups. In conclusion, data from this study suggest possible chemopreventive benefit of AML alone or in combination with BMC against CPZ-associated neurobehavioural deficits. The ameliorative effect of AML may be related to its antioxidant and/or calcium channel blocking property.

Amlodipine treatment of hypertension associates with a decreased dementia risk

Hypertension has been shown to be a risk factor for development of dementia. However, medical treatment of hypertension failed to reduce consistently the risk of dementia. Experimental study pointed to the possibility of difference between different calcium channel blockers (CCB) in their neuro-protective effect. The aim of our study was to evaluate the risk of dementia during treatment of hypertension with different CCBs. This is a retrospective cohort study based on electronic database of a large public health care organization. Study period was 11 years and it included patients aged 40-75 years old, having diagnosis of hypertension without diagnosis of dementia at the starting point, treated with either single specific CCB (study group) or with other than CCBs antihypertensive medications (control group) for at least 30 months during the study period. A total of 15,664 patients that satisfied these criteria were identified: 3,884 were treated with amlodipine, 2,062 were treated with nifedipine, 609 were treated with lercanidipine, and 9,109 never received CCBs. Dementia developed in 765 (4.9%) patients. Adjusted hazard ratio (HR) for dementia in patients treated with amlodipine, nifedipine, and lercanidipine was 0.60 (p < 0.001), 0.89 (NS), and 0.90 (NS). Decreased adjusted HR of dementia with amlodipine was demonstrated in the patients aged 60 or more (HR 0.61 [0.49-0.77], p < 0.001), but not in the patients aged less than 60 years old. This study shows that amlodipine therapy may be associated with a decreased dementia risk in hypertensive individuals older than 60 years, compared to those treated without CCBs.

Interaction between therapeutic interventions for Alzheimer's disease and physiological Aβ clearance mechanisms

Most therapeutic agents are designed to target a molecule or pathway without consideration of the mechanisms involved in the physiological turnover or removal of that target. In light of this and in particular for Alzheimer’s disease, a number of therapeutic interventions are presently being developed/investigated which target the amyloid-β peptide (Aβ). However, the literature has not adequately considered which Aβ physiological clearance pathways are necessary and sufficient for the effective action of these therapeutics. In this review, we evaluate the therapeutic strategies targeting Aβ presently in clinical development, discuss the possible interaction of these treatments with pathways that under normal physiological conditions are responsible for the turnover of Aβ and highlight possible caveats. We consider immunization strategies primarily reliant on a peripheral sink mechanism of action, small molecules that are reliant on entry into the CNS and thus degradation pathways within the brain, as well as lifestyle interventions that affect vascular, parenchymal and peripheral degradation pathways. We propose that effective development of Alzheimer’s disease therapeutic strategies targeting Aβ peptide will require consideration of the age- and disease-specific changes to endogenous Aβ clearance mechanisms in order to elicit maximal efficacy.

Drug repositioning approaches for the discovery of new therapeutics for Alzheimer's disease

Alzheimer's disease (AD) is the most common cause of dementia and represents one of the highest unmet needs in medicine today. Drug development efforts for AD have been encumbered by largely unsuccessful clinical trials in the last decade. Drug repositioning, a process of discovering a new therapeutic use for existing drugs or drug candidates, is an attractive and timely drug development strategy especially for AD. Compared with traditional de novo drug development, time and cost are reduced as the safety and pharmacokinetic properties of most repositioning candidates have already been determined. A majority of drug repositioning efforts for AD have been based on positive clinical or epidemiological observations or in vivo efficacy found in mouse models of AD. More systematic, multidisciplinary approaches will further facilitate drug repositioning for AD. Some experimental approaches include unbiased phenotypic screening using the library of available drug collections in physiologically relevant model systems (e.g. stem cell-derived neurons or glial cells), computational prediction and selection approaches that leverage the accumulating data resulting from RNA expression profiles, and genome-wide association studies. This review will summarize several notable strategies and representative examples of drug repositioning for AD.

NILVAD protocol: a European multicentre double-blind placebo-controlled trial of nilvadipine in mild-to-moderate Alzheimer's disease

INTRODUCTION

This study is a European multicentre, randomised, double-blind, placebo-controlled trial investigating the efficacy and safety of nilvadipine as a disease course modifying treatment for mild-to-moderate Alzheimer's disease (AD) in a phase III study that will run for a period of 82 weeks with a treatment period of 78 weeks.

METHODS AND ANALYSIS

Adult patients, males and females over 50 years with mild-to-moderate AD as defined by the National Institute of Neurological and Communicative Disorders and Stroke/Alzheimer's disease and Related Disorders Association (NINCDS-ADRDA) criteria, will be included in the study. It aims to recruit a total of 500 patients with AD; 250 in the nilvadipine group and 250 in the placebo group. Participants will be randomised to receive nilvadipine, an 8 mg overencapsulated, sustained release capsule, or a matching overencapsulated placebo (sugar pill) for a period of 78 weeks of treatment. The primary efficacy outcome measure in this study is the change in cognitive function as assessed by the Alzheimer's disease Assessment Scale (ADAS-Cog 12) from baseline to the end of treatment duration (78 weeks). There are two key secondary outcome measures, the Clinical Dementia Rating Scale Sum of Boxes (CDR-sb) and the Disability Assessment for Dementia (DAD). If a statistically significant effect is seen in the primary outcome, CDR-sb will be considered to be a coprimary end point and only the DAD will contribute to the secondary outcome analysis.

ETHICS AND DISSEMINATION

The study and all subsequent amendments have received ethical approval within each participating country according to national regulations. Each participant will provide written consent to participate in the study. All participants will remain anonymised throughout and the results of the study will be published in an international peer-reviewed journal.

TRIAL REGISTRATION NUMBER

EUDRACT Reference Number: 2012-002764-27.

Calcium channel blockers and dementia

Degenerative dementia is mainly caused by Alzheimer's disease and/or cerebrovascular abnormalities. Disturbance of the intracellular calcium homeostasis is central to the pathophysiology of neurodegeneration. In Alzheimer's disease, enhanced calcium load may be brought about by extracellular accumulation of amyloid-β. Recent studies suggest that soluble forms facilitate influx through calcium-conducting ion channels in the plasma membrane, leading to excitotoxic neurodegeneration. Calcium channel blockade attenuates amyloid-β-induced neuronal decline in vitro and is neuroprotective in animal models. Vascular dementia, on the other hand, is caused by cerebral hypoperfusion and may benefit from calcium channel blockade due to relaxation of the cerebral vasculature. Several calcium channel blockers have been tested in clinical trials of dementia and the outcome is heterogeneous. Nimodipine as well as nilvadipine prevent cognitive decline in some trials, whereas other calcium channel blockers failed. In trials with a positive outcome, BP reduction did not seem to play a role in preventing dementia, indicating a direct protecting effect on neurons. An optimization of calcium channel blockers for the treatment of dementia may involve an increase of selectivity for presynaptic calcium channels and an improvement of the affinity to the inactivated state. Novel low molecular weight compounds suitable for proof-of-concept studies are now available.

Psychostimulants, antidepressants and neurokinin-1 receptor antagonists ('motor disinhibitors') have overlapping, but distinct, effects on monoamine transmission: the involvement of L-type Ca2+ channels and implications for the treatment of ADHD

Both psychostimulants and antidepressants target monoamine transporters and, as a consequence, augment monoamine transmission. These two groups of drugs also increase motor activity in preclinical behavioural screens for antidepressants. Substance P-preferring receptor (NK1R) antagonists similarly increase both motor activity in these tests and monoamine transmission in the brain. In this article, the neurochemical and behavioural responses to these three groups of drugs are compared. It becomes evident that NK1R antagonists represent a distinct class of compounds ('motor disinhibitors') that differ substantially from both psychostimulants and antidepressants, especially during states of heightened arousal or stress. Also, all three groups of drugs influence the activation of voltage-gated Ca(v)1.2 and Ca(v)1.3 L-type channels (LTCCs) in the brain, albeit in different ways. This article discusses evidence that points to disruption of these functional interactions between NK1R and LTCCs as a contributing factor in the cognitive and behavioural abnormalities that are prominent features of Attention Deficit Hyperactivity Disorder (ADHD). Arising from this is the interesting possibility that the hyperactivity and impulsivity (as in ADHD) and psychomotor retardation (as in depression) reflect opposite poles of a behavioural continuum. A better understanding of this pharmacological network could help explain why psychostimulants augment motor behaviour during stress (e.g., in preclinical screens for antidepressants) and yet reduce locomotor activity and impulsivity in ADHD. This article is part of the Special Issue entitled 'CNS Stimulants'.

The changing landscape of voltage-gated calcium channels in neurovascular disorders and in neurodegenerative diseases

It is a common belief that voltage-gated calcium channels (VGCC) cannot carry toxic amounts of Ca²⁺ in neurons. Also, some of them as L-type channels are essential for Ca²⁺-dependent regulation of prosurvival gene-programs. However, a wealth of data show a beneficial effect of drugs acting on VGCCs in several neurodegenerative and neurovascular diseases. In the present review, we explore several mechanisms by which the “harmless” VGCCs may become “toxic” for neurons. These mechanisms could explain how, though usually required for neuronal survival, VGCCs may take part in neurodegeneration. We will present evidence showing that VGCCs can carry toxic Ca²⁺ when: a) their density or activity increases because of aging, chronic hypoxia or exposure to β-amyloid peptides or b) Ca²⁺-dependent action potentials carry high Ca²⁺ loads in pacemaker neurons. Besides, we will examine conditions in which VGCCs promote neuronal cell death without carrying excess Ca²⁺. This can happen, for instance, when they carry metal ions into the neuronal cytoplasm or when a pathological decrease in their activity weakens Ca²⁺-dependent prosurvival gene programs. Finally, we will explore the role of VGCCs in the control of nonneuronal cells that take part to neurodegeneration like those of the neurovascular unit or of microglia.

A review: treatment of Alzheimer's disease discovered in repurposed agents

BACKGROUND/AIMS

Many compounds that have already been approved for alternate diagnoses have been studied in relation to Alzheimer's disease (AD). The purpose of this review is to summarize these studies and discuss the rationale and benefits of repurposing drugs for AD treatment.

METHODS

Studies of drugs related to AD treatment that were relevant to a disease-modifying mechanism of action (MOA) and are already approved by the Food and Drug Administration for non-AD diagnoses were collected from PubMed.

RESULTS

Many drugs already approved for the treatment of other diseases have been studied in relation to AD treatment. Numerous drugs with known toxicity profiles have the potential to be repurposed as a treatment for AD.

CONCLUSION

Known MOA, toxicology, and pharmacodynamic profiles would accelerate the process and increase the odds of finding a more timely disease-modifying treatment for AD.

Antagonism of L-type Ca(v) channels with nifedipine differentially affects performance of wildtype and NK1R-/- mice in the 5-Choice Serial Reaction-Time Task

Mice with functional ablation of the substance P-preferring receptor gene ('Nk1r' in mice ('NK1R-/-'), 'TACR1' in humans) display deficits in cognitive performance that resemble those seen in patients with Attention Deficit Hyperactivity Disorder (ADHD): namely, inattentiveness, impulsivity and perseveration. A recent report suggested that the L-type Ca(v) channel blocker, nifedipine, can ameliorate behavioral abnormalities of this type in humans. In light of evidence that NK1R antagonists modulate the opening of these L-type channels, we investigated whether nifedipine modifies %premature responses (impulsivity), perseveration or %omissions (inattentiveness) in the 5-Choice Serial Reaction-Time Task (5-CSRTT) and whether the response differs in NK1R-/- and wildtype mice. %Premature responses and perseveration were reduced in both genotypes, although wildtype mice were more sensitive to the effects of nifedipine than NK1R-/- mice. By contrast, nifedipine greatly increased %omissions but, again, was more potent in wildtypes. %Accuracy and locomotor activity were unaffected in either genotype. We infer that behavior of mice in the 5-CSRTT depends on the regulation of striato-cortical networks by L-type Ca(v) channels and NK1R. We further suggest that disruption of NK1R signaling in patients with ADHD, especially those with polymorphisms of the TACR1 gene, could lead to compensatory changes in the activity of L-type channels that underlie or exacerbate their problems. This article is part of a Special Issue entitled 'Cognitive Enhancers'.

New pharmacological strategies for treatment of Alzheimer's disease: focus on disease modifying drugs

Current approved drug treatments for Alzheimer disease (AD) include cholinesterase inhibitors (donepezil, rivastigmine, galantamine) and the NMDA receptor antagonist memantine. These drugs provide symptomatic relief but poorly affect the progression of the disease. Drug discovery has been directed, in the last 10 years, to develop 'disease modifying drugs' hopefully able to counteract the progression of AD. Because in a chronic, slow progressing pathological process, such as AD, an early start of treatment enhances the chance of success, it is crucial to have biomarkers for early detection of AD-related brain dysfunction, usable before clinical onset. Reliable early biomarkers need therefore to be prospectively tested for predictive accuracy, with specific cut off values validated in clinical practice. Disease modifying drugs developed so far include drugs to reduce β amyloid (Aβ) production, drugs to prevent Aβ aggregation, drugs to promote Aβ clearance, drugs targeting tau phosphorylation and assembly and other approaches. Unfortunately none of these drugs has demonstrated efficacy in phase 3 studies. The failure of clinical trials with disease modifying drugs raises a number of questions, spanning from methodological flaws to fundamental understanding of AD pathophysiology and biology. Recently, new diagnostic criteria applicable to presymptomatic stages of AD have been published. These new criteria may impact on drug development, such that future trials on disease modifying drugs will include populations susceptible to AD, before clinical onset. Specific problems with completed trials and hopes with ongoing trials are discussed in this review.

Apolipoprotein E genotype-specific short-term cognitive benefits of treatment with the antihypertensive nilvadipine in Alzheimer's patients--an open-label trial

BACKGROUND

Evidence suggests that dihydropyridine calcium channel blockers may be useful in preventing and treating Alzheimer's disease (AD).

OBJECTIVE

In an open-label trial of safety and tolerability of nilvadipine in patients with AD, we examined cognition and executive function over a short time period to determine an influence of nilvadipine on these outcomes.

METHOD

We investigated change in cognition using the Mini mental state examination and in executive function using the EXIT25 in 55 patients with AD who received nilvadipine 8 mg daily for 6 weeks compared with 30 non-treated subjects with AD. Apolipoprotein E genotyping was performed, and the study team and caregivers were kept blinded to APOE ε4 status during the trial.

RESULTS

Aside from differences in gender and education, both the treatment and the control groups were similar in general demographics and on baseline cognition status. After correction for potential confounders, APOE ε4 status, and use of other antihypertensive medications, a significant impact of study intervention was observed on MMSE (F = 8.67, p < 0.01) and EXIT (F = 8.77, p < 0.03) scores. An interaction between APOE ε4 carrier status and treatment (p ≤ 0.05) was observed for both outcome measures.

CONCLUSION

In this open-label trial, among APOE ε4 non-carriers, we observed stabilization of cognition and improvement in executive function among treated individuals compared with non-treated individuals. Among APOE ε4 carriers, cognitive stabilization was evident for treated individuals whereas a cognitive decline was observed in non-treated individuals. These findings provide additional evidence for potential therapeutic efficacy of nilvadipine in treating AD and warrant further investigation.

Demonstration of safety in Alzheimer's patients for intervention with an anti-hypertensive drug Nilvadipine: results from a 6-week open label study

BACKGROUND

Nilvadipine may lower rates of conversion from mild-cognitive impairment to Alzheimer's disease (AD), in hypertensive patients. However, it remains to be determined whether treatment with nilvadipine is safe in AD patients, given the higher incidence of orthostatic hypotension (OH) in this population, who may be more likely to suffer from symptoms associated with the further exaggeration of a drop in BP.

OBJECTIVE

The aim of this study was to investigate the safety and tolerability of nilvadipine in AD patients.

METHODS

AD patients in the intervention group (n = 56) received nilvadipine 8  mg daily over 6-weeks, compared to the control group (n = 30) who received no intervention. Differences in systolic (SBP) and diastolic (DBP) blood pressure, before and after intervention, was assessed using automated sphygmomanometer readings and ambulatory BP monitors (ABP), and change in OH using a finometer. Reporting of adverse events was monitored throughout the study.

RESULTS

There was a significant reduction in the SBP of treated patients compared to non-treated patients but no significant change in DBP. Individuals with higher initial blood pressure (BP) had greater reduction in BP but individuals with normal BP did not experience much change in their BP. While OH was present in 84% of the patients, there was no further drop in BP recorded on active stand studies. There were no significant differences in adverse event reporting between groups.

CONCLUSION

Nilvadipine was well tolerated by patients with AD. This study supports further investigation of its efficacy as a potential treatment for AD.

Calcium channel blocking as a therapeutic strategy for Alzheimer's disease: the case for isradipine

Alzheimer's disease is the most devastating neurodegenerative disorder in the elderly, yet treatment options are severely limited. The drug development effort to modify Alzheimer's disease pathology by intervention at beta amyloid production sites has been largely ineffective or inconclusive. The greatest challenge has been to identify and define downstream mechanisms reliably predictive of clinical symptoms. Beta amyloid accumulation leads to dysregulation of intracellular calcium by plasma membrane L-type calcium channels located on neuronal somatodendrites and axons in the hippocampus and cortex. Paradoxically, L-type calcium channel subtype Ca(v)1.2 also promotes synaptic plasticity and spatial memory. Increased intracellular calcium modulates amyloid precursor protein processing and affects multiple downstream pathways including increased hyperphosphorylated tau and suppression of autophagy. Isradipine is a Federal Drug Administration-approved dihydropyridine calcium channel blocker that binds selectively to Ca(v)1.2 in the hippocampus. Our studies have shown that isradipine in vitro attenuates beta amyloid oligomer toxicity by suppressing calcium influx into cytoplasm and by suppressing Ca(v)1.2 expression. We have previously shown that administration of isradipine to triple transgenic animal model for Alzheimer's disease was well-tolerated. Our results further suggest that isradipine became bioavailable, lowered tau burden, and improved autophagy function in the brain. A better understanding of brain pharmacokinetics of calcium channel blockers will be critical for designing new experiments with appropriate drug doses in any future clinical trials for Alzheimer's disease. This review highlights the importance of Ca(v)1.2 channel overexpression, the accumulation of hyperphosphorylated tau and suppression of autophagy in Alzheimer's disease and modulation of this pathway by isradipine.

Selective dihydropyiridine compounds facilitate the clearance of β-amyloid across the blood-brain barrier

Increasing evidence suggests that the soluble form of the β-amyloid peptide (Aβ) plays a critical role in the pathogenesis of Alzheimer's disease. Previously, we reported that treatment with certain antihypertensive dihydropyridine (DHP) compounds can mitigate Aβ production in whole cells and reduce brain Aβ burden in a mouse model of Alzheimer's disease. As Aβ clearance across the blood-brain barrier (BBB) is a key regulatory step in the deposition of Aβ in the brain, we examined the effect of DHP treatment on Aβ brain clearance. Treatment with certain DHP compounds significantly increased Aβ(1-42) transcytosis across the BBB in an in vitro model. The rank order of these compounds was nitrendipine>nicardipine=cilnidipine=lercanidipine>nimodipine>azelnidipine=nilvadipine. Conversely, amlodipine, felodipine, isradipine, and nifedipine had no effect on Aβ(1-42) BBB transcytosis. In an in vivo paradigm of Aβ clearance across the BBB, peripheral administration of nitrendipine, cilnidipine, and nilvadipine to wild-type animals facilitated the brain clearance of centrally administered exogenous Aβ(1-42), whereas with amlodipine, there was no effect. We also observed improved cognitive function in mice treated with nilvadipine following central Aβ(1-42) insult. Thus, in addition to the effect of certain DHP compounds on Aβ production, we demonstrate that certain DHP compounds also facilitate the clearance of Aβ across the BBB. This dual mechanism of action may be particularly effective in attenuating Aβ brain burden in Alzheimer's disease and could open the door to a new class of therapies for the treatment of this disease.

Selective antihypertensive dihydropyridines lower Aβ accumulation by targeting both the production and the clearance of Aβ across the blood-brain barrier

Several large population-based or clinical trial studies have suggested that certain dihydropyridine (DHP) L-type calcium channel blockers (CCBs) used for the treatment of hypertension may confer protection against the development of Alzheimer disease (AD). However, other studies with drugs of the same class have shown no beneficial clinical effects. To determine whether certain DHPs are able to impact underlying disease processes in AD (specifically the accumulation of the Alzheimer Aβ peptide), we investigated the effect of several antihypertensive DHPs and non-DHP CCBs on Aβ production. Among the antihypertensive DHPs tested, a few, including nilvadipine, nitrendipine and amlodipine inhibited Aβ production in vitro, whereas others had no effect or raised Aβ levels. In vivo, nilvadipine and nitrendipine acutely reduced brain Aβ levels in a transgenic mouse model of AD (Tg PS1/APPsw) and improved Aβ clearance across the blood-brain barrier (BBB), whereas amlodipine and nifedipine were ineffective showing that the Aβ-lowering activity of the DHPs is independent of their antihypertensive activity. Chronic oral treatment with nilvadipine decreased Aβ burden in the brains of Tg APPsw (Tg2576) and Tg PS1/APPsw mice, and also improved learning abilities and spatial memory. Our data suggest that the clinical benefit conferred by certain antihypertensive DHPs against AD is unrelated to their antihypertensive activity, but rely on their ability to lower brain Aβ accumulation by affecting both Aβ production and Aβ clearance across the BBB.

Blood pressure and dementia - a comprehensive review

Alzheimer's disease (AD) and vascular dementia (VaD) are important causes of cognitive decline in the elderly. As a result of an ageing population worldwide, the incidence of dementia is expected to rise exponentially over the coming decades. Vascular risk factors are implicated in the pathogenesis of both AD and VaD. Hypertension in midlife is particularly associated with an increased risk of developing dementia. One might hope the treatment of high blood pressure in midlife would reduce the risk of developing dementia, as it does the risk of stroke. Divergent results have been reported in studies examining this effect, with the evidence suggesting that certain antihypertensives confer benefits beyond others. This implies that certain drugs may have neuroprotective properties separate to their blood pressure lowering capabilities. Recent trials have added to our understanding of these relationships.

[A patient with early Alzheimer's disease who showed improvement of cognitive function and cerebral perfusion by combined therapy of nilvadipine and PPAR gamma agonists]

A 76-year-old man was referred to our hospital because of memory impairment. He was diagnosed as having early Alzheimer's disease, in addition to hypertension and type II diabetes mellitus. Nilvadipine (a Ca-channel blocker), telmisartan (an angiotension II receptor blocker), and pioglitazone (an insulin sensitizer) were administered for the control of the hypertension and diabetes. After 6 months of treatment, the scores on verbal fluency (animals and vegetables/60 seconds) and frontal assessment battery of the patient improved despite no significant changes on the Mini-Mental State Examination and Alzheimer's Disease Assessment Scale. Moreover, follow-up examination of SPECT demonstrated an improvement of cerebral perfusion in the frontal and temporoparietal regions. In addition to nilvadipine, a highly lipophilic Ca channel antagonist agent that easily penetrates the central nervous system, PPARgamma agonists, such as pioglitazone and termisartan, may have had favourable effects on cognitive function and cerebral perfusion in this patient.