Donepezil potentiates nerve growth factor-induced neurite outgrowth in PC12 cells

Is Target-Based Drug Discovery Efficient? Discovery and "Off-Target" Mechanisms of All Drugs

Target-based drug discovery is the dominant paradigm of drug discovery; however, a comprehensive evaluation of its real-world efficiency is lacking. Here, a manual systematic review of about 32000 articles and patents dating back to 150 years ago demonstrates its apparent inefficiency. Analyzing the origins of all approved drugs reveals that, despite several decades of dominance, only 9.4% of small-molecule drugs have been discovered through "target-based" assays. Moreover, the therapeutic effects of even this minimal share cannot be solely attributed and reduced to their purported targets, as they depend on numerous off-target mechanisms unconsciously incorporated by phenotypic observations. The data suggest that reductionist target-based drug discovery may be a cause of the productivity crisis in drug discovery. An evidence-based approach to enhance efficiency seems to be prioritizing, in selecting and optimizing molecules, higher-level phenotypic observations that are closer to the sought-after therapeutic effects using tools like artificial intelligence and machine learning.

Donepezil, an anti-Alzheimer's disease drug, promotes differentiation and regeneration in injured skeletal muscle through the elevation of the expression of myogenic regulatory factors

We previously demonstrated that donepezil, an anti-Alzheimer's disease drug, improved skeletal muscle atrophy by enhancing the angiogenesis of endothelial cells and activating the proliferation of satellite cells in a mouse model of peripheral arterial disease. However, the effect of donepezil on muscle differentiation during regeneration remains unclear. Therefore, we measured the expressions of myogenic regulatory factors and late muscle differentiation markers in donepezil-treated C2C12 myoblast cells before and after the induction of cell differentiation. The results indicate that the expressions of myogenin, troponin T (TnT) and myosin heavy chain (MyHC) were significantly increased and myotube formation was accelerated in donepezil-treated cells under the differentiation condition. However, the promotive effect of donepezil on muscle differentiation could not be reproduced by the addition of acetylcholine (ACh) and was not disrupted after treatment with ACh receptor blockers. Moreover, other kinds of acetylcholinesterase inhibitors failed to promote muscle differentiation in C2C12 cells. These results indicate that the specific characteristics of donepezil in the promotion of muscle differentiation are independent of its acetylcholinesterase-inhibitory action. We further found that donepezil induced an incremental shift of the cross-sectional area of myofibers and elevated the expressions of myogenin, TnT and MyHC in a mouse model of cardiotoxin injury. These results suggest that donepezil promotes the differentiation of muscle regeneration upon injury via the elevation of the expressions of myogenic regulatory factors and late muscle differentiation markers. Our findings suggest that donepezil can be a useful therapeutic agent for injured skeletal muscle treatment.

Influence of Acetylcholine Esterase Inhibitors and Memantine, Clinically Approved for Alzheimer's Dementia Treatment, on Intestinal Properties of the Mouse

Four drugs are currently approved for the treatment of Alzheimer’s disease (AD) by the FDA. Three of these drugs—donepezil, rivastigmine, and galantamine—belong to the class of acetylcholine esterase inhibitors. Memantine, a NMDA receptor antagonist, represents the fourth and a combination of donepezil and memantine the fifth treatment option. Recently, the gut and its habitants, its microbiome, came into focus of AD research and added another important factor to therapeutic considerations. While the first data provide evidence that AD patients might carry an altered microbiome, the influence of administered drugs on gut properties and commensals have been largely ignored so far. However, the occurrence of digestive side effects with these drugs and the knowledge that cholinergic transmission is crucial for several gut functions enforces the question if, and how, this medication influences the gastrointestinal system and its microbial stocking. Here, we investigated aspects such as microbial viability, colonic propulsion, and properties of enteric neurons, affected by assumed intestinal concentration of the four drugs using the mouse as a model organism. All ex vivo administered drugs revealed no direct effect on fecal bacteria viability and only a high dosage of memantine resulted in reduced biofilm formation of E. coli. Memantine was additionally the only compound that elevated calcium influx in enteric neurons, while all acetylcholine esterase inhibitors significantly reduced esterase activity in colonic tissue specimen and prolonged propulsion time. Both, acetylcholine esterase inhibitors and memantine, had no effect on general viability and neurite outgrowth of enteric neurons. In sum, our findings indicate that all AD symptomatic drugs have the potential to affect distinct intestinal functions and with this—directly or indirectly—microbial commensals.

Using sigma-ligands as part of a multi-receptor approach to target diseases of the brain

INTRODUCTION

The sigma receptors are found abundantly in the central nervous system and are targets for the treatment of various diseases, including Alzheimer's (AD), Parkinson's (PD), Huntington's disease (HD), depression, amyotrophic lateral sclerosis (ALS), and multiple sclerosis (MS). However, for many of these diseases, other receptors and targets have been the focus of the most, such as acetylcholine esterase inhibitors in Alzheimer's and dopamine replacement in Parkinson's. The currently available drugs for these diseases have limited success resulting in the requirement of an alternative approach to their treatment.

AREAS COVERED

In this review, we discuss the potential role of the sigma receptors and their ligands as part of a multi receptor approach in the treatment of the diseases mentioned above. The literature reviewed was obtained through searches in databases, including PubMed, Web of Science, Google Scholar, and Scopus.

EXPERT OPINION

Given sigma receptor agonists provide neuroprotection along with other benefits such as potentiating the effects of other receptors, further development of multi-receptor targeting ligands, and or the development of multi-drug combinations to target multiple receptors may prove beneficial in the future treatment of degenerative diseases of the CNS, especially when coupled with better diagnostic techniques.

Cholinesterase inhibitor rivastigmine enhances nerve growth factor-induced neurite outgrowth in PC12 cells via sigma-1 and sigma-2 receptors

Rivastigmine (Riv) is a potent and selective cholinesterase (acetylcholinesterase, AChE and butyrylcholinesterase, BuChE) inhibitor developed for the treatment of Alzheimer's disease (AD). To elucidate whether Riv causes neuronal differentiation, we examined its effect on nerve growth factor (NGF)-induced neurite outgrowth in PC12 cells. At concentrations of 0-100 μM, Riv was non-toxic in PC12 cells. Riv caused dose-dependent (10-100 μM) enhancement of NGF-induced neurite outgrowth, which was completely inhibited by the TrkA antagonist GW-441756. By contrast, Riv-mediated enhancement of neurite outgrowth was not blocked by the acetylcholine receptor antagonists, scopolamine and hexamethonium. However, the sigma-1 receptor (Sig-1R) antagonist NE-100 and sigma-2 receptor (Sig-2R) antagonist SM-21 each blocked about half of the Riv-mediated enhancement of NGF-induced neurite outgrowth. Interestingly, the simultaneous application of NE-100 and SM-21 completely blocked the enhancement of NGF-induced neurite outgrowth by Riv. These findings suggest that both Sig-1R and Sig-2R play important roles in NGF-induced neurite outgrowth through TrkA and that Riv may contribute to neuronal repair via Sig-1R and Sig-2R in AD therapy.

Reduced basal forebrain atrophy progression in a randomized Donepezil trial in prodromal Alzheimer's disease

Acetylcholinesterase inhibitors are approved drugs currently used for the treatment of Alzheimer's disease (AD) dementia. Basal forebrain cholinergic system (BFCS) atrophy is reported to precede both entorhinal cortex atrophy and memory impairment in AD, challenging the traditional model of the temporal sequence of topographical pathology associated with AD. We studied the effect of one-year Donepezil treatment on the rate of BFCS atrophy in prodromal AD patients using a double-blind, randomized, placebo-controlled trial of Donepezil (10 mg/day). Reduced annual BFCS rates of atrophy were found in the Donepezil group compared to the Placebo treated arm. Secondary analyses on BFCS subregions demonstrated the largest treatment effects in the Nucleus Basalis of Meynert (NbM) and the medial septum/diagonal band (Ch1/2). Donepezil administered at a prodromal stage of AD seems to substantially reduce the rate of atrophy of the BFCS nuclei with highest concentration of cholinergic neurons projecting to the cortex (NbM), hippocampus and entorhinal cortex (Ch1/2).

Prostaglandin E2 facilitates neurite outgrowth in a motor neuron-like cell line, NSC-34

Prostaglandin E2 (PGE2) exerts various biological effects by binding to E-prostanoid receptors (EP1-4). Although recent studies have shown that PGE2 induces cell differentiation in some neuronal cells such as mouse DRG neurons and sensory neuron-like ND7/23 cells, it is unclear whether PGE2 plays a role in differentiation of motor neurons. In the present study, we investigated the mechanism of PGE2-induced differentiation of motor neurons using NSC-34, a mouse motor neuron-like cell line. Exposure of undifferentiated NSC-34 cells to PGE2 and butaprost, an EP2-selective agonist, resulted in a reduction of MTT reduction activity without increase the number of propidium iodide-positive cells and in an increase in the number of neurite-bearing cells. Sulprostone, an EP1/3 agonist, also significantly lowered MTT reduction activity by 20%; however, no increase in the number of neurite-bearing cells was observed within the concentration range tested. PGE2-induced neurite outgrowth was attenuated significantly in the presence of PF-0441848, an EP2-selective antagonist. Treatment of these cells with dibutyryl-cAMP increased the number of neurite-bearing cells with no effect on cell proliferation. These results suggest that PGE2 promotes neurite outgrowth and suppresses cell proliferation by activating the EP2 subtype, and that the cAMP-signaling pathway is involved in PGE2-induced differentiation of NSC-34 cells.

Kai-Xin-San, a traditional Chinese medicine formula, induces neuronal differentiation of cultured PC12 cells: Modulating neurotransmitter regulation enzymes and potentiating NGF inducing neurite outgrowth

ETHNOPHARMACOLOGICAL RELEVANCE

Kai-Xin-San, an ancient formula composed of Ginseng Radix et Rhizoma, Polygalae Radix, Acori Tatarinowii Rhizoma and Poria, was frequently applied for major depression disorders for thousands of years. However, its molecular mechanism has not clearly been investigated.

AIM OF THE STUDY

We aimed to reveal the action mechanism of KXS on anti-depression on inducing neuronal differentiation on PC12 cells.

MATERIALS AND METHODS

A chemically standardized water extract of KXS was applied onto cultured PC12 cells in determining its effect on neurotransmitter regulation enzymes and neurite outgrowth.

RESULTS

Single KXS treatment showed obvious changes in the expression of neurofilament and neurotransmitter regulation enzymes, which in parallel to treatment of nerve growth factor (NGF). Although KXS by itself did not show significant inductive effect on neurite outgrowth of PC12 cells, KXS could potentiate the NGF induced neurite outgrowth. Among the three ratios, K-652 showed the most powerful effect and cAMP-dependent pathway might play the major role.

CONCLUSIONS

KXS might exert the anti-depressant-like action of be inducing neuronal differentiation, which supported the clinically usage of this decoction.

miR-210 mediates vagus nerve stimulation-induced antioxidant stress and anti-apoptosis reactions following cerebral ischemia/reperfusion injury in rats

Vagus nerve stimulation (VNS) exerts neuroprotective effects against cerebral ischemia/reperfusion (I/R) injury and modulates redox status, potentially through the activity of miR-210, an important microRNA that is regulated by hypoxia-inducible factor and Akt-dependent pathways. The aim of this study was to determine the mechanisms of VNS- and miR-210-mediated hypoxic tolerance. Male Sprague-Dawley rats were preconditioned with a miR-210 antagomir (A) or with an antagomir control (AC), followed by middle cerebral artery occlusion and VNS treatment. The animals were divided into eight groups: sham I/R, I/R, I/R+AC, I/R+A, sham I/R+VNS, I/R+VNS, I/R+VNS+AC, and I/R+VNS+A. Activation of the endogenous cholinergic a7 nicotinic acetylcholine receptor (a7nAchR) pathway was identified using double immunofluorescence staining. miR-210 expression was measured by PCR. Behavioral outcomes, infarct volume, and neuronal apoptosis were observed at 24 h following reperfusion. Markers of oxidative stress were detected using ELISA. Rats treated with VNS showed increased miR-210 expression as well as decreased apoptosis and antioxidant stress responses compared with the I/R group; these rats also showed increased p-Akt protein expression and significantly decreased levels of cleaved caspase 3 in the ischemic penumbra, as measured by western blot and immunofluorescence analyses, respectively. Strikingly, the beneficial effects of VNS were attenuated following miR-210 knockdown. In conclusion, our results indicate that miR-210 is a potential mediator of VNS-induced neuroprotection against I/R injury. Our study highlights the neuroprotective potential of VNS, which, to date, has been largely unexplored. Since approved by the FDA in 1997, vagus nerve stimulation (VNS) has proven to be a safe and effective treatment for refractory epilepsy and resistant depression. Recent studies have found that VNS also provided neuroprotective effects against ischemic injury in a rat stroke model. We showed that miR-210 played an important role in the antioxidant stress and anti-apoptosis responses induced by VNS. This is the first report showing the effects of VNS at the mRNA level. Therefore, VNS represents a promising candidate treatment for ischemic stroke patients. Schematic view of the role of miR210 mediated in the protective effects of the VNS on the acute cerebral ischemia. VNS acts to activate neuronal and astrocytes a7nAchR , inhibits the apoptosis and oxidant stress responses possibly associated with increased Akt phosphorylation and miR210 expression.

Increased brain bio-distribution and chemical stability and decreased immunogenicity of an engineered variant of GDNF

Several lines of evidence indicate that Glial cell line-derived neurotrophic factor (GDNF) is a trophic factor for dopaminergic neurons. Direct parenchymal administration of GDNF is robustly neuroprotective and neurorestorative in multiple neurotoxin-based animal models (rat and non-human primate (NHP)) of Parkinson's Disease (PD), suggesting its potential as a therapeutic agent. Although small, open-label clinical trials of intra-putamenal administration of bacteria-derived, full length, wild type GDNF (GDNFwt) were efficacious in improving standardized behavioral scores, a double-blinded, randomized controlled trial failed to do so. We hypothesize that the lack of clinical efficacy of GDNFwt in the larger randomized trial was due to poor bio-distribution in the putamen and/or poor chemical stability while in the delivery device for prolonged time periods at 37°C. The development of neutralizing antibodies in some patients may also have been a contributing factor. GDNFv is an engineered form of GDNFwt, expressed and purified from mammalian cells, designed to overcome these limitations, including removal of the N-terminal heparin-binding domain to improve its diffusivity in brain parenchyma by reducing its binding to extracellular matrix (ECM), and key amino acid substitutions to improve chemical stability. Intra-striatal administration of a single injection of GDNFv in the rat produced significantly greater brain distribution than GDNFwt, consistent with reduced binding to ECM. Using liquid chromatography/mass spectrometry (LS/MS) methods GDNFv was shown to have improved chemical stability compared to GDNFwt when stored at 37°C for 4weeks. In addition, GDNFv resulted in lower predicted clinical immunogenicity compared to GDNFwt, as demonstrated by reduced CD4+ T cell proliferation and reduced IL-2-induced secretion in peripheral blood mononucleated cells collected from volunteers representing the world's major histocompatibility complex (MHC) haplotypes. GDNFv was demonstrated to be pharmacologically equivalent to GDNFwt in the key parameters in vitro of GFRα1 receptor binding, c-Ret phosphorylation, neurite outgrowth, and in vivo in its ability to increase dopamine turnover (DA). GDNFv protected dopamine nerve terminals and neurons in a 6-hydroxy-dopamine (6-OHDA) rat model. In summary, we empirically demonstrate the superior properties of GDNFv compared to GDNFwt through enhanced bio-distribution and chemical stability concurrently with decreased predicted clinical immunogenicity while maintaining pharmacological and neurotrophic activity. These data indicate that GDNFv is an improved version of GDNF suitable for clinical assessment as a targeted regenerative therapy for PD.

Therapeutic potential of human adipose-derived stem cells in neurological disorders

Stem cell therapy has been noted as a novel strategy to various diseases including neurological disorders such as Alzheimer's disease, Parkinson's disease, stroke, amyotrophic lateral sclerosis, and Huntington's disease that have no effective treatment available to date. The adipose-derived stem cells (ASCs), mesenchymal stem cells (MSCs) isolated from adipose tissue, are well known for their pluripotency with the ability to differentiate into various types of cells and immuno-modulatory property. These biological features make ASCs a promising source for regenerative cell therapy in neurological disorders. Here we discuss the recent progress of regenerative therapies in various neurological disorders utilizing ASCs.

Roles of σ1 receptors in the mechanisms of action of CNS drugs

Accumulating evidence suggests that σ1 receptors play a role in the mechanisms of action of some therapeutic drugs, such as the selective serotonin reuptake inhibitors (SSRIs), donepezil, and ifenprodil. Among the SSRIs, fluvoxamine, a potent σ1 receptor agonist, has the highest affinity for σ1 receptors, while donepezil and ifenprodil also show high affinity for σ1 receptors. These drugs affect neuronal plasticity indicated by potentiation of nerve-growth factor (NGF)-induced neurite outgrowth in PC12 cells. Furthermore, phencyclidine (PCP)-induced cognitive impairment, associated with animal models of schizophrenia, is significantly improved by sub-chronic administration of fluvoxamine and donepezil. These pharmacological actions are antagonised by treatment with the selective σ1 receptor antagonist NE-100. Positron emission tomography (PET) with the σ1 specific ligand carbon-11-labelled 1-[2-(3,4-dimethoxyphenyl)ethyl]-4-(3-phenylpropyl)piperazine ([11C]SA4503) indicated that fluvoxamine and donepezil can bind to σ1 receptors in the healthy human brain in a dose-dependent manner. These findings suggest that σ1 receptors may be involved in the mechanisms of action of some therapeutic drugs.

The cholinergic system, sigma-1 receptors and cognition

This article provides an overview of present knowledge regarding the relationship between the cholinergic system and sigma-1 receptors, and discusses potential applications of sigma-1 receptor agonists in the treatment of memory deficits and cognitive disorders. Sigma-1 receptors, initially considered as a subtype of the opioid family, are unique ligand-regulated molecular chaperones in the endoplasmatic reticulum playing a modulatory role in intracellular calcium signaling and in the activity of several neurotransmitter systems, particularly the cholinergic and glutamatergic pathways. Several central nervous system (CNS) drugs show high to moderate affinities for sigma-1 receptors, including acetylcholinesterase inhibitors (donepezil), antipsychotics (haloperidol, rimcazole), selective serotonin reuptake inhibitors (fluvoxamine, sertraline) and monoamine oxidase inhibitors (clorgyline). These compounds can influence cognitive functions both via their primary targets and by activating sigma-1 receptors in the CNS. Sigma-1 agonists show powerful anti-amnesic and neuroprotective effects in a large variety of animal models of cognitive dysfunction involving, among others (i) pharmacologic target blockade (with muscarinic or NMDA receptor antagonists or p-chloroamphetamine); (ii) selective lesioning of cholinergic neurons; (iii) CNS administration of β-amyloid peptides; (iv) aging-induced memory loss, both in normal and senescent-accelerated rodents; (v) neurodegeneration induced by toxic compounds (CO, trimethyltin, cocaine), and (vi) prenatal restraint stress.

Microwave-assisted synthesis of 4-chloro-N-(naphthalen-1-ylmethyl)-5-(3-(piperazin-1-yl)phenoxy)thiophene-2-sulfonamide (B-355252): a new potentiator of Nerve Growth Factor (NGF)-induced neurite outgrowth

The synthesis of 4-chloro-N-(naphthalen-1-ylmethyl)-5-(3-(piperazin-1-yl)phenoxy)thiophene-2-sulfonamide (B-355252) using a MW-assisted nucleophilic aromatic substitution (S(N)Ar) reaction will be discussed. Utilization of this method allowed for the rapid generation of B-355252 heteroaryl ether core structure in the presence of cesium carbonate in dimethylformamide or tripotassium phosphate in N-methyl-2-pyrrolidone in 94% yield. Evaluation of B-355252 enhancement of nerve growth factor's ability to stimulate neurite outgrowths was determined using NS-1 cells.

Enhanced dendritic spine number of neurons of the prefrontal cortex, hippocampus, and nucleus accumbens in old rats after chronic donepezil administration

In Alzheimer's disease brains, morphological changes in the dendrites of pyramidal neurons of the prefrontal cortex (PFC) and hippocampus have been observed. These changes are particularly reflected in the decrement of both the dendritic tree and spine number. Donepezil is a potent and selective acetylcholinesterase inhibitor used in the treatment of Alzheimer's disease. We have studied the effect of oral administration of this drug on the morphology of neuronal cells from the brain of aged rats. We examined dendrites of pyramidal neurons of the PFC, dorsal or ventral hippocampus (VH), and medium spiny neurons of the nucleus accumbens (NAcc). Donepezil (1 mg/kg, vo) was administrated every day for 60 days to rats aged 10 and 18 months. Dendritic morphology was studied by the Golgi-Cox stain procedure followed by Sholl analysis at 12 and 20 months ages, respectively. In all Donepezil-treated rats, a significant increment of the dendritic spines number in pyramidal neurons of the PFC and dorsal hippocampus was observed. However, pyramidal neurons of the VH and medium spiny cells of the NAcc only showed an increase in the number of their spines in 12-month-old rats. Our results suggest that Donepezil prevents the alterations of the neuronal dendrite morphology caused by aging.

Sigma receptors: potential targets for a new class of antidepressant drug

Despite the widespread and devastating impact of depression on society, our current understanding of its pathogenesis is limited. Likewise, existing treatments are inadequate, providing relief to only a subset of people suffering from depression. The search for more effective antidepressant drugs includes the investigation of new molecular targets. Among them, current data suggests that sigma receptors are involved in multiple processes effecting antidepressant-like actions in vivo and in vitro. This review summarizes accumulated evidence supporting a role for sigma receptors in antidepressant effects and provides a conceptual framework for delineating their potential roles over the course of antidepressant treatment.

Potentiation of nerve growth factor-induced neurite outgrowth in PC12 cells by donepezil: role of sigma-1 receptors and IP3 receptors

In addition to acetylcholinesterase (AChE) inhibition, donepezil binds to sigma-1 receptors. In this study, we examined the effects of donepezil on nerve growth factor (NGF)-induced neurite outgrowth in PC12 cells. Donepezil significantly potentiated the NGF-induced neurite outgrowth in a concentration-dependent manner whereas the AChE inhibitor physostigmine did not alter NGF-induced neurite outgrowth. Potentiation of NGF-induced neurite outgrowth by donepezil was significantly blocked by co-administration of the selective sigma-1 receptor antagonist NE-100 or the inositol 1,4,5-triphosphate (IP3) receptor antagonist xestospongin C. These findings suggest that sigma-1 receptors and interaction with IP3 receptors may be involved in the pharmacological action of donepezil.

Effect of synthetic cell-penetrating peptides on TrkA activity in PC12 cells

As TrkA, a high-affinity receptor of nerve growth factor (NGF), is a potential target for relieving uncontrolled inflammatory pain, an effective inhibitor of TrkA has been required for pain management. To identify a specific inhibitor of TrkA activity, we designed cell-penetrating peptides combined with amino-acid sequences in the activation loop of TrkA to antagonize tyrosine kinase activity. To select a peptide inhibiting TrkA activity, we examined the effect of cell-penetrating peptides on tyrosine kinase activity of recombinant TrkA in vitro and studied their effects on NGF-stimulated neurite outgrowth and protein phosphorylation in PC12 cells. Thereafter we investigated the effect of the selected peptide on NGF-stimulated TrkA activity and the expression of transient receptor potential channel 1 in PC12 cells. The selected peptide inhibited TrkA activity, but did not inhibit tyrosine kinase activities of other receptor-type tyrosine kinases in vitro. It also suppressed NGF-stimulated responses in PC12 cells. The selected synthetic cell-penetrating peptide antagonizing TrkA function would be a candidate for inflammatory pain therapy.