Cholinergic hyperactivity in patients with myasthenia gravis with MuSK antibodies: A neurophysiological study

ObjectivePatients with myasthenia gravis associated with muscle-specific tyrosine kinase antibodies (MuSK-MG) often manifest signs of cholinergic hyperactivity with standard doses of acetylcholinesterase inhibitors (AChE-Is). Aim of the study was to investigate whether repetitive compound muscle action potential (R-CMAP), the neurophysiological correlate of cholinergic hyperactivity, was present in MuSK-MG irrespective of AChE-I treatment.MethodsPatients with confirmed diagnosis of MuSK-MG were consecutively enrolled during follow-up visits, from January 2019 to April 2020. All these subjects underwent the same neurophysiological protocol, including motor nerve conduction studies and repetitive nerve stimulation. In patients taking pyridostigmine, neurophysiological testing was performed at least 12 hours after the last dose. For comparison, the presence of R-CMAP was investigated in 20 consecutive acetylcholine receptor antibody positive myasthenia gravis (AChR-MG) patients.ResultsWe enrolled 25 MuSK-MG patients (20 females), aged 16–79 years at the study time, with disease duration ranging 0.6–48.8 years (median: 17.7 years). R-CMAP was detected in 12/25 (48%) MuSK-MG cases and in none of the AChR-MG controls (p = 0.0003). In the MuSK-MG population, a history of muscle cramps and fasciculations, during low-dose pyridostigmine therapy, was significantly more frequent in R-CMAP positive than in R-CMAP negative patients (100% vs 31%, p = 0.001). At the time of the study, the proportion of patients still symptomatic for MG was higher among R-CMAP positive cases (92% vs 23%, p = 0.0005).ConclusionsCholinergic hyperactivity is a relatively common finding in MuSK-MG patients, independent of AChE-I treatment, and may constitute an intrinsic feature of the disease.SignificanceR-CMAP detection can represent a useful diagnostic clue for MuSK-MG and predicts poor tolerance to AChE-Is.     

加兰他敏和石杉碱甲生物合成的研究进展

植物来源的加兰他敏、石杉碱甲等乙酰胆碱酯酶抑制剂(AChEIs)以其高效低毒的优势成为当前临床治疗阿尔茨海默病的主流药物。由于目前加兰他敏、石杉碱甲等AChEIs尚未实现工业规模化合成,故仍主要依赖植物提取。然而,药源植物培育周期长、难度大,药效物质含量低,随着社会需求的急剧攀升,供求矛盾日益突出。开发新替代资源以及利用现代基因工程技术合成加兰他敏、石杉碱甲等AChEIs是缓解当前矛盾的有效途径。对近年来加兰他敏和石杉碱甲生物合成的相关研究进展进行综述,总结了替代资源的开发研究现状,以期为挖掘加兰他敏、石杉碱甲等AChEIs优势新资源及利用代谢工程合成药效物质研究提供参考。     

Interacting with α7 nAChR is a new mechanism for AChE to enhance the inflammatory response in macrophages

Acetylcholine (ACh) regulates inflammation via α7 nicotinic acetylcholine receptor (α7 nAChR). Acetylcholinesterase (AChE), an enzyme hydrolyzing ACh, is expressed in immune cells suggesting non-classical function in inflammatory responses. Here, the expression of PRiMA-linked G4 AChE was identified on the surface of macrophages. In lipopolysaccharide-induced inflammatory processes, AChE was upregulated by the binding of NF-κB onto the ACHE promotor. Conversely, the overexpression of G4 AChE inhibited ACh-suppressed cytokine release and cell migration, which was in contrast to that of applied AChE inhibitors. AChEmt, a DNA construct without enzymatic activity, was adopted to identify the protein role of AChE in immune system. Overexpression of G4 AChEmt induced cell migration and inhibited ACh-suppressed cell migration. The co-localization of α7 nAChR and AChE was found in macrophages, suggesting the potential interaction of α7 nAChR and AChE. Besides, immunoprecipitation showed a close association of α7 nAChR and AChE protein in cell membrane. Hence, the novel function of AChE in macrophage by interacting with α7 nAChR was determined. Together with hydrolysis of ACh, AChE plays a direct role in the regulation of inflammatory response. As such, AChE could serve as a novel target to treat age-related diseases by anti-inflammatory responses.     

Promising therapies for the treatment of frontotemporal dementia clinical phenotypes: from symptomatic to disease-modifying drugs

Introduction: Frontotemporal dementia (FTD) is a heterogeneous clinical entity that includes several disorders characterized by different cellular mechanisms. Distinctive clinical features in FTD include behavioral, affective, and cognitive symptoms. Unfortunately, little progress has been made over the past 20 years in terms of the development of effective disease-modifying drugs with the currently available symptomatic treatments having limited clinical utility.

Areas covered: This article reviews the principal pharmacological intervention studies for FTD. These are predominantly randomized clinical trials and include symptomatic treatments and potential disease-modifying drugs.

Expert opinion: There is insufficient evidence on effective treatments for FTD and studies with better methodological backgrounds are needed. Most studies reporting therapeutic benefits were conducted with selective serotonin reuptake inhibitors, while anti-dementia drugs have been ineffective in FTD. Since the underlying pathology of FTD mostly consists of abnormal tau protein or TDP-43 aggregates, treatments are being developed to interfere with their aggregation process or with the clearance of these proteins. Furthermore, disease-modifying treatments remain years away as demonstrated by the recent negative Phase III findings of a tau aggregation inhibitor (LMTM) for treating the behavioral variant of FTD. The results from current ongoing Phase I/II trials will hopefully give light to future treatment options.     

Discovery of nitazoxanide-based derivatives as autophagy activators for the treatment of Alzheimer's disease

Drug repurposing is an efficient strategy for new drug discovery. Our latest study found that nitazoxanide (NTZ), an approved anti-parasite drug, was an autophagy activator and could alleviate the symptom of Alzheimer's disease (AD). In order to further improve the efficacy and discover new chemical entities, a series of NTZ-based derivatives were designed, synthesized, and evaluated as autophagy activator against AD. All compounds were screened by the inhibition of phosphorylation of p70S6K, which was the direct substrate of mammalian target of rapamycin (mTOR) and its phosphorylation level could reflect the mTOR-dependent autophagy level. Among these analogs, compound 22 exhibited excellent potency in promoting β-amyloid (Aβ) clearance, inhibiting tau phosphorylation, as well as stimulating autophagy both in vitro and in vivo. What's more, 22 could effectively improve the memory and cognitive impairments in APP/PS1 transgenic AD model mice. These results demonstrated that 22 was a potential candidate for the treatment of AD.     

Synthesis and biological evaluation of phloroglucinol derivatives possessing α‐glycosidase,acetylcholinesterase, butyrylcholinesterase,carbonic anhydrase inhibitory activity

A series of novel phloroglucinol derivatives were designed, synthesized, characterized spectroscopically and tested for their inhibitory activity against selected metabolic enzymes, including α‐glycosidase, acetylcholinesterase (AChE), butyrylcholinesterase (BChE), and human carbonic anhydrase I and II (hCA I and II). These compounds displayed nanomolar inhibition levels and showed K_i values of 1.14–3.92 nM against AChE, 0.24–1.64 nM against BChE, 6.73–51.10 nM against α‐glycosidase, 1.80–5.10 nM against hCA I, and 1.14–5.45 nM against hCA II.

     

Can we increase the speed and efficacy of antidepressant treatments? Part II. Glutamatergic and RNA interference strategies

In the second part we focus on two treatment strategies that may overcome the main limitations of current antidepressant drugs. First, we review the experimental and clinical evidence supporting the use of glutamatergic drugs as fast-acting antidepressants. Secondly, we review the involvement of microRNAs (miRNAs) in the pathophysiology of major depressive disorder (MDD) and the use of small RNAs (e.g.., small interfering RNAs or siRNAs) to knockdown genes in monoaminergic and non-monoaminergic neurons and induce antidepressant-like responses in experimental animals.The development of glutamatergic agents is a promising venue for antidepressant drug development, given the antidepressant properties of the non-competitive NMDA receptor antagonist ketamine. Its unique properties appear to result from the activation of AMPA receptors by a metabolite [(2 S,6 S;2 R,6 R)-hydroxynorketamine (HNK)] and mTOR signaling. These effects increase synaptogenesis in prefrontal cortical pyramidal neurons and enhance serotonergic neurotransmission via descending inputs to the raphe nuclei. This view is supported by the cancellation of ketamine's antidepressant-like effects by inhibition of serotonin synthesis.We also review existing evidence supporting the involvement of miRNAs in MDD and the preclinical use of RNA interference (RNAi) strategies to target genes involved in antidepressant response. Many miRNAs have been associated to MDD, some of which e.g., miR-135 targets genes involved in antidepressant actions. Likewise, SSRI-conjugated siRNA evokes faster and/or more effective antidepressant-like responses. Intranasal application of sertraline-conjugated siRNAs directed to 5-HT_1A receptors and SERT evoked much faster changes of pre- and postsynaptic antidepressant markers than those produced by fluoxetine.     

Cholinesterase Inhibitors for the Treatment of Alzheimer's Disease:: Getting On and Staying On

Background: Cholinesterase (ChE) inhibitors currently used in the treatment of Alzheimer's disease (AD) are the acetylcholinesterase (AChE)-selective inhibitors, donepezil and galantamine, and the dual AChE and butyrylcholinesterase (BuChE) inhibitor, rivastigmine. In addition to differences in selectivity for AChE and BuChE, ChE inhibitors also differ in pharmacokinetic and pharmacodynamic properties, and these differences could significantly impact on safety, tolerability, and efficacy.Objective: The aim of this article was to provide an overview of the ChE inhibitors widely used in AD, focusing on key pharmacologic differences among agents and how these may translate into important differences in safety, tolerability, and efficacy in clinical practice.Methods: Using published literature collected over time by the author, a review was conducted, focusing on the pharmacology and clinical data of donepezil, galantamine, and rivastigmine.Results: All ChE inhibitors have the potential to induce centrally mediated cholinergic adverse events (AEs), such as nausea and vomiting, if the dose is increased too rapidly or in increments that are too large. These AEs, which are most likely to occur during the “getting on,” or dose-escalation, phase of treatment, may result in patients discontinuing treatment early without achieving optimum therapeutic benefit. To reduce the incidence of these AEs, a slow dose-escalation schedule has been established in clinical practice, consisting of a “start low, go slow” procedure with a minimum of 4 weeks between dose increases. After “getting on” treatment, maintaining treatment in the long term, or “staying on,” may be achieved with good safety, tolerability, and sustained symptomatic efficacy across the key symptom domains (activities of daily living, behavior, and cognition).Conclusions: ChE inhibitors provide symptomatic benefit in AD across key symptom domains. Factors influencing the safety, tolerability, and efficacy of these agents in clinical practice include ChE enzymes inhibited, brain and brain-region ChE selectivity, and metabolism route. Class-specific cholinergic AEs can be minimized using slow, flexible dose escalation.     

Phytochemical Characterization,Antibacterial, Acetylcholinesterase Inhibitory and Cytotoxic Properties of Cryptostephanus vansonii,an Endemic Amaryllid

Cryptostephanus vansonii I. Verd., an endemic Amaryllidaceae species from Zimbabwe, was evaluated for its acetylcholinesterase (AChE) inhibitory and cytotoxicity properties using Ellman's colorimetric method and the tetrazolium‐based colorimetric assay against Vero monkey kidney cells, respectively. The plant extracts were also evaluated for their antibacterial activity against five bacteria. Furthermore, phytochemical profiles of the extracts were determined using ultra‐high performance liquid chromatography coupled with tandem mass spectrometry analysis. A plant part‐dependent AChE inhibitory activity was observed, in the order, root > rhizome > basal leaf > leaf. Overall, C. vansonii extracts exhibited better antibacterial activity against Gram‐negative compared with Gram‐positive bacteria. Cytotoxic effects were not detected in Vero monkey kidney cell lines suggesting the possible absence of toxophores in C. vansonii extracts. Similar to the trend in biological activity, a distinct plant part‐dependent variation in hydroxybenzoates, hydroxycinnamates and flavonoids was observed in the plant extracts. In addition, 5‐hydroxymetylfurfural and eucomic acid were detected in the different plant parts of C. vansonii. The results of the present study provide valuable AChE inhibition activity, toxicological and phytochemical profiles of C. vansonii. Further studies on isolation of bioactive compounds and their subsequent evaluation in other pharmacological and toxicological model systems are required. Copyright © 2017 John Wiley & Sons, Ltd.