The pharmacology of chlormethiazole: a potential neuroprotective agent?

Mechanistic aspects of reactive metabolite formation in clomethiazole catalyzed biotransformation by cytochrome P450 enzymes

Clomethiazole (CLM), a sedative and anticonvulsant drug, is commonly employed for the treatment of alcohol withdrawal syndrome because it suppresses cytochrome P450 (P450) activity associated with the generation of free radicals and liver damage. The catalyzed biotransformation of thiazole-containing drugs by P450 is known to afford reactive metabolites. These metabolites can alter the biological functions of macromolecules and result in toxicity and adverse drug interactions. Multitargeted molecular modeling and quantum chemical DFT calculations were performed to explore the binding modes and molecular mechanisms underlying the mechanism-based inactivation (MBI) of P450 by CLM. The mechanistic details associated with reactive metabolite formation from further metabolic processes were extensively assessed. Seven possible routes were proposed for CLM-P450 biotransformation including CLM hydroxylation, sulfoxidation, N-oxidation, CN epoxidation (oxaziridine formation), and CC epoxidation. The results revealed a degree of preference for the C-N epoxidation pathway because of the low energy requirements of its rate-determining step (8.74 and 10.07 kcal mol-1 for LS and HS states, respectively). A kinetic competition for the CLM-methyl hydroxylation pathway was detected because the H-abstraction energy barrier was relatively comparable to the thermodynamically prevailing oxaziridine formation rate-determining step (12.58 and 14.52 kcal mol-1 for quartet and doublet states, respectively). Our studies assessed the mechanisms of covalent nucleophilic epoxide adduct formation through nucleophilic addition, hydrolysis of epoxidation products, and nonenzymatic degradation. CLM was shown to display P450-inhibitory activity by forming covalent adducts rather than further metabolization to reactive metabolites. The outcomes of molecular docking allowed assessing the binding profile of CLM with three human P450 isozymes, namely, CYP2E1, CYP3A4, and CYP2D6.

The Role of Supplementation with Natural Compounds in Post-Stroke Patients

Malnutrition is a serious problem in post-stroke patients. Importantly, it intensifies with hospitalization, and is related to both somatic and psychological reasons, as well as is associated with the insufficient knowledge of people who accompany the patient. Malnutrition is a negative prognostic factor, leading to a reduction in the quality of life. Moreover, this condition significantly extends hospitalization time, increases the frequency of treatment in intensive care units, and negatively affects the effectiveness of rehabilitation. Obtaining growing data on the therapeutic effectiveness of new compounds of natural origin is possible through the use of pharmacodynamic and analytical methods to assess their therapeutic properties. The proper supply of nutrients, as well as compounds of natural origin, is an important element of post-stroke therapy, due to their strong antioxidant, anti-inflammatory, neuroprotective and neuroplasticity enhancing properties. Taking the above into account, in this review we present the current state of knowledge on the benefits of using selected substances of natural origin in patients after cerebral stroke.

Redox Post-translational Modifications of Protein Thiols in Brain Aging and Neurodegenerative Conditions-Focus on S-Nitrosation

Reactive oxygen species and reactive nitrogen species (RONS) are by-products of aerobic metabolism. RONS trigger a signaling cascade that can be transduced through oxidation-reduction (redox)-based post-translational modifications (redox PTMs) of protein thiols. This redox signaling is essential for normal cellular physiology and coordinately regulates the function of redox-sensitive proteins. It plays a particularly important role in the brain, which is a major producer of RONS. Aberrant redox PTMs of protein thiols can impair protein function and are associated with several diseases. This mini review article aims to evaluate the role of redox PTMs of protein thiols, in particular S-nitrosation, in brain aging, and in neurodegenerative diseases. It also discusses the potential of using redox-based therapeutic approaches for neurodegenerative conditions.

γ-Aminobutyric acid transporters as relevant biological target: Their function, structure, inhibitors and role in the therapy of different diseases

γ-Aminobutyric acid (GABA) is a major inhibitory neurotransmitter in the nervous system. It plays a crucial role in many physiological processes. Upon release from the presynaptic element, it is removed from the synaptic cleft by reuptake due to the action of GABA transporters (GATs). GATs belong to a large SLC6 protein family whose characteristic feature is sodium-dependent relocation of neurotransmitters through the cell membrane. GABA transporters are characterized in many contexts, but their spatial structure is not fully known. They are divided into four types, which differ in occurrence and role. Herein, the special attention was paid to these transporting proteins. This comprehensive review presents the current knowledge about GABA transporters. Their distribution in the body, physiological functions and possible utilization in the therapy of different diseases were fully discussed. The important structural features were described based on published data, including sequence analysis, mutagenesis studies, and comparison with known SLC6 transporters for leucine (LeuT), dopamine (DAT) and serotonin (SERT). Moreover, the most important inhibitors of GABA transporters of various basic scaffolds, diverse selectivity and potency were presented.

Interaction of oxidative stress and neurotrauma in ALDH2-/- mice causes significant and persistent behavioral and pro-inflammatory effects in a tractable model of mild traumatic brain injury

Oxidative stress induced by lipid peroxidation products (LPP) accompanies aging and has been hypothesized to exacerbate the secondary cascade in traumatic brain injury (TBI). Increased oxidative stress is a contributor to loss of neural reserve that defines the ability to maintain healthy cognitive function despite the accumulation of neuropathology. ALDH2^−/− mice are unable to clear aldehyde LPP by mitochondrial aldehyde dehydrogenase-2 (Aldh2) detoxification and provide a model to study mild TBI (mTBI), therapeutic interventions, and underlying mechanisms. The ALDH2^−/− mouse model presents with elevated LPP-mediated protein modification, lowered levels of PSD-95, PGC1-α, and SOD-1, and mild cognitive deficits from 4 months of age. LPP scavengers are neuroprotective in vitro and in ALDH2^−/− mice restore cognitive performance. A single-hit, closed skull mTBI failed to elicit significant effects in WT mice; however, ALDH2^−/− mice showed a significant inflammatory cytokine surge in the ipsilateral hemisphere 24 h post-mTBI, and increased GFAP cleavage, a biomarker for TBI. Known neuroprotective agents, were able to reverse the effects of mTBI. This new preclinical model of mTBI, incorporating significant perturbations in behavior, inflammation, and clinically relevant biomarkers, allows mechanistic study of the interaction of LPP and neurotrauma in loss of neural reserve.

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ALDH2^−/− mice have elevated brain LPP adducts and mild cognitive impairment.

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The effects of a “2nd hit” via LPS are exacerbated by LPP in vitro and in vivo.

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ALDH2^−/− mice + mTBI show amplified/prolonged cognitive deficits and neuroinflammation.

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This new preclinical model for mTBI supports a role for LPP in reduced neural reserve.

A comprehensive review of cytochrome P450 2E1 for xenobiotic metabolism

Cytochrome P450 2E1 (CYP2E1) plays a vital role in drug-induced hepatotoxicity and cancers (e.g. lung and bladder cancer), since it is responsible for metabolizing a number of medications and environmental toxins to reactive intermediate metabolites. CYP2E1 was recently found to be the highest expressed CYP enzyme in human livers using a proteomics approach, and CYP2E1-related toxicity is strongly associated with its protein level that shows significant inter-individual variability related to ethnicity, age, and sex. Furthermore, the expression of CYP2E1 demonstrates regulation by extensive genetic polymorphism, endogenous hormones, cytokines, xenobiotics, and varying pathological states. Over the past decade, the knowledge of pharmacology, toxicology, and biology about CYP2E1 has grown remarkably, but the research progress has yet to be summarized. This study presents a timely systematic review on CYP2E1's xenobiotic metabolism, genetic polymorphism, and inhibitors, with the focus on their clinical relevance for the efficacy and toxicity of various CYP2E1 substrates. Moreover, several knowledge gaps have been identified towards fully understanding the potential interactions among different CYP2E1 substrates in clinical settings. Through in-depth analyses of these knowns and unknowns, we expect this review will aid in future drug development and improve management of CYP2E1 related clinical toxicity.

Pharmacological manipulation of cGMP and NO/cGMP in CNS drug discovery

The development of small molecule modulators of NO/cGMP signaling for use in the CNS has lagged far behind the use of such clinical agents in the periphery, despite the central role played by NO/cGMP in learning and memory, and the substantial evidence that this signaling pathway is perturbed in neurodegenerative disorders, including Alzheimer's disease. The NO-chimeras, NMZ and Nitrosynapsin, have yielded beneficial and disease-modifying responses in multiple preclinical animal models, acting on GABAA and NMDA receptors, respectively, providing additional mechanisms of action relevant to synaptic and neuronal dysfunction. Several inhibitors of cGMP-specific phosphodiesterases (PDE) have replicated some of the actions of these NO-chimeras in the CNS. There is no evidence that nitrate tolerance is a phenomenon relevant to the CNS actions of NO-chimeras, and studies on nitroglycerin in the periphery continue to challenge the dogma of nitrate tolerance mechanisms. Hybrid nitrates have shown much promise in the periphery and CNS, but to date only one treatment has received FDA approval, for glaucoma. The potential for allosteric modulation of soluble guanylate cyclase (sGC) in brain disorders has not yet been fully explored nor exploited; whereas multiple applications of PDE inhibitors have been explored and many have stalled in clinical trials.

Gamma aminobutyric acid (GABA) receptor agonists for acute stroke

BACKGROUND

Gamma aminobutyric acid (GABA) receptor agonists have been shown to have a neuroprotectant effect in reducing infarct size and improving functional outcome in animal models of cerebrovascular disease. However, the sedative effects of GABA receptor agonists have limited their wider application in people with acute stroke, due to the potential risk of stupor. This is an update of a Cochrane Review first published in 2013, and previously updated in 2014 and 2016.

OBJECTIVES

To determine the efficacy and safety of GABA receptor agonists in the treatment of acute stroke.

SEARCH METHODS

We searched the Cochrane Stroke Group Trials Register (accessed May 2018), the Cochrane Central Register of Controlled Trials (CENTRAL) 2018, Issue 4 (accessed May 2018), MEDLINE (from 1949 to May 2018), Embase (from 1980 to May 2018), CINAHL (from 1982 to May 2018), AMED (from 1985 to May 2018), and 11 Chinese databases (accessed May 2018). In an effort to identify further published, unpublished, and ongoing trials we searched ongoing trial registers, reference lists, and relevant conference proceedings, and contacted authors and pharmaceutical companies.

SELECTION CRITERIA

We included randomized controlled trials (RCTs) investigating GABA receptor agonists versus placebo for people with acute stroke (within 12 hours after stroke onset), with the primary outcomes of efficacy and safety.

DATA COLLECTION AND ANALYSIS

Two review authors independently screened the titles and abstracts of identified records, selected studies for inclusion, extracted eligible data, cross-checked the data for accuracy, and assessed the risk of bias. We used the GRADE approach to assess the quality of the evidence.

MAIN RESULTS

We included five trials with 3838 participants (acute ischemic or hemorrhagic stroke patients, 3758 analyzed). Most of the participants recruited had acute ischaemic stroke, with limited data available from participants with other stroke subtypes, including total anterior circulation syndrome (TACS). The methodological quality of the included trials was generally good, with an unclear risk for selection bias only. For death and dependency at three months, pooled results did not find a significant difference for chlormethiazole versus placebo (risk ratio (RR) 1.03, 95% confidence interval (CI) 0.96 to 1.11; four trials; 2909 participants; moderate-quality evidence) and for diazepam versus placebo (RR 0.94, 95% CI 0.82 to 1.07; one trial; 849 participants; moderate-quality evidence). The most frequent adverse events related to chlormethiazole were somnolence (RR 4.56, 95% CI 3.50 to 5.95; two trials; 2527 participants; moderate-quality evidence) and rhinitis (RR 4.75, 95% CI 2.67 to 8.46; two trials; 2527 participants; moderate-quality evidence).

AUTHORS' CONCLUSIONS

This review provides moderate-quality evidence that fails to support the use of GABA receptor agonists (chlormethiazole or diazepam) for the treatment of people with acute stroke. More well-designed RCTs with large samples of participants with total anterior circulation syndrome are required to determine if there are benefits for this subgroup. Somnolence and rhinitis are frequent adverse events related to chlormethiazole.

An unusual synthesis of 3-(2-(arylamino)thiazol-4-yl)-2H-chromen-2-ones from ethyl 2-(chloromethyl)-2-hydroxy-2H-chromene-3-carboxylate via benzopyran ring opening

An unusual and unexpected synthesis of 3-(2-(arylamino)thiazol-4-yl)-2H-chromen-2-ones has been observed by the reaction of ethyl 2-(chloromethyl)-2-hydroxy-2H-chromene-3-carboxylate with various arylthioureas in ethanol under mild reaction conditions with excellent yields. The ambiguity in the structure of the obtained products has been solved by recording its single-crystal X-ray analysis. This protocol has been found to be a novel approach for the preparation of title compounds via benzopyran ring opening. A systematic plausible mechanism has been proposed for the formation of the product. Also, an efficient one-pot three-component method has been demonstrated for the formation of title compounds starting from salicylaldehyde.

2-(4-methyl-thiazol-5-yl) ethyl nitrate maleate-potentiated GABAA receptor response in hippocampal neurons

AIMS

2-(4-methyl-thiazol-5-yl) ethyl nitrate maleate (NMZM), a derivative of clomethiazole (CMZ), had been investigated for the treatment of Alzheimer's disease (AD). The beneficial effects of NMZM in AD included reversing cognitive deficit, improving learning and memory as well as neuroprotection. The pharmacological effects of NMZM on GABA_A receptors were reported previously; however, the mechanisms were unclear and were explored therefore.

RESULTS

In this study, we demonstrated that NMZM improved learning and memory by alleviating scopolamine-induced long-term potentiation (LTP) suppression in the dentate gyrus of rats, indicating that NMZM had protective effects against scopolamine-induced depression of LTP. Next, we investigated the action of NMZM on GABA_A receptors in hippocampal neurons and the binding site of NMZM on GABA_A receptors. NMZM directly activated GABA_A receptors in hippocampal neurons in a weak manner. However, NMZM could potentiate the response of GABA_A receptors to GABA and NMZM positively modulated GABA_A receptors with an EC₅₀ value of 465 μmol/L at 3 μmol/L GABA while this potentiation at low concentration of GABA (1, 3 μmol/L) was more significant than that at high concentration (10, 30 μmol/L). In addition, NMZM could enhance GABA currents after using diazepam and pentobarbital, the positive modulators of GABA_A receptors. NMZM could not affect the etomidate-potentiated GABA_A current. It suggested that the binding site of NMZM on GABA_A receptors is the same as etomidate.

CONCLUSIONS

These results provided support for the neuroprotective effect of NMZM, which was partly dependent on the potentiation of GABA_A receptors. The etomidate binding site might be a new target for neuronal protection and for drug development.

Range of therapeutic prothipendyl and prothipendyl sulfoxide concentrations in clinical blood samples

Due to a lack of reference blood concentrations in the literature, the forensic evaluation of prothipendyl findings in blood samples is difficult. Interpretations with regard to the assessment of blood concentrations as well as an estimation of the ingested prothipendyl amounts were often vague. To describe a concentration range in clinical samples, prothipendyl and prothipendyl sulfoxide concentrations were determined in serum samples of 50 psychiatric patients receiving 40 mg, 80 mg, or 160 mg doses of prothipendyl. The analyses of prothipendyl and prothipendyl sulfoxide were carried out using validated methods of high performance liquid chromatography coupled to triple quadrupole mass spectrometry (LC-QQQ-MS), respectively. 40 mg doses caused average prothipendyl serum concentrations of 18.0 ng/mL (1 hour after intake) and 7.9 ng/mL (10.5 hours after intake), while 80 mg doses caused averages of 42.6 ng/mL and 15.2 ng/mL at the mentioned times of sampling. Irrespective of the given dose, prothipendyl concentrations below 30 ng/mL were observed in 80% of the patient samples taken 1 hour after ingestion as well as in 90% of the samples collected 10.5 hours after administration. Serum concentrations of the Phase I metabolite prothipendyl sulfoxide averaged 4.3 ng/mL (1 hour after intake) and 3.6 ng/mL (10.5 hours after intake). Possible drug-drug interactions regarding absorption and metabolism of prothipendyl are discussed. Results of the herein presented study are useful for the interpretation of analytical prothipendyl findings in forensic toxicology. The utility of the described concentration range is demonstrated by discussing two death cases involving prothipendyl findings.

Gamma aminobutyric acid (GABA) receptor agonists for acute stroke

BACKGROUND

Gamma aminobutyric acid (GABA) receptor agonists have been shown to have a neuroprotectant effect in reducing infarct size and improving functional outcome in animal models of cerebrovascular disease. However, the sedative effects of GABA receptor agonists have limited their wider application in people with acute stroke, due to the potential risk of stupor. This is an update of a Cochrane review first published in 2013, and previously updated in 2014.

OBJECTIVES

To determine the efficacy and safety of GABA receptor agonists in the treatment of acute stroke.

SEARCH METHODS

We searched the Cochrane Stroke Group Trials Register (accessed March 2016), the Cochrane Central Register of Controlled Trials (CENTRAL) 2016, Issue 3, part of the Cochrane Library (accessed March 2016), MEDLINE (from 1949 to March 2016), Embase (from 1980 to March 2016), CINAHL (from 1982 to March 2016), AMED (from 1985 to March 2016), and 11 Chinese databases (accessed March 2016). In an effort to identify further published, unpublished, and ongoing trials we searched ongoing trials registers, reference lists, and relevant conference proceedings, and contacted authors and pharmaceutical companies.

SELECTION CRITERIA

We included randomized controlled trials (RCTs) investigating GABA receptor agonists versus placebo for people with acute stroke (within 12 hours after stroke onset), with the primary outcomes of efficacy and safety.

DATA COLLECTION AND ANALYSIS

Two review authors independently screened the titles and abstracts of identified records, selected studies for inclusion, extracted eligible data, cross-checked the data for accuracy, and assessed the risk of bias.

MAIN RESULTS

We included five trials with 3838 participants (3758 analyzed). The methodological quality of the included trials was generally good, with an unclear risk for selection bias only. Four trials (N = 2909) measured death and dependency at three months for chlormethiazole versus placebo; pooled results did not find a significant difference (risk ratio (RR) 1.03, 95% confidence interval (CI) 0.96 to 1.11). One trial (N = 849) measured this outcome for diazepam versus placebo (RR 0.94, 95% CI 0.82 to 1.07). The most frequent adverse events related to chlormethiazole were somnolence (RR 4.56, 95% CI 3.50 to 5.95; two trials; N = 2527) and rhinitis (RR 4.75, 95% CI 2.67 to 8.46; two trials; N = 2527).

AUTHORS' CONCLUSIONS

This review provides moderate-quality evidence that fails to support the use of GABA receptor agonists (chlormethiazole or diazepam) for the treatment of people with acute stroke. More well-designed RCTs with large samples of participants with total anterior circulation syndrome are required to determine if there are benefits for this subgroup. Somnolence and rhinitis are frequent adverse events related to chlormethiazole.

Selective Time- and NADPH-Dependent Inhibition of Human CYP2E1 by Clomethiazole

The sedative clomethiazole (CMZ) has been used in Europe since the mid-1960s to treat insomnia and alcoholism. It has been previously demonstrated in clinical studies to reversibly inhibit human CYP2E1 in vitro and decrease CYP2E1-mediated elimination of chlorzoxazone. We have investigated the selectivity of CMZ inhibition of CYP2E1 in pooled human liver microsomes (HLMs). In a reversible inhibition assay of the major drug-metabolizing cytochrome P450 (P450) isoforms, CYP2A6 and CYP2E1 exhibited IC50 values of 24 µM and 42 µM, respectively with all other isoforms exhibiting values >300 µM. When CMZ was preincubated with NADPH and liver microsomal protein for 30 minutes before being combined with probe substrates, however, more potent inhibition was observed for CYP2E1 and CYP2B6 but not CYP2A6 or other P450 isoforms. The substantial increase in potency of CYP2E1 inhibition upon preincubation enables the use of CMZ to investigate the role of human CYP2E1 in xenobiotic metabolism and provides advantages over other chemical inhibitors of CYP2E1. The KI and kinact values obtained with HLM-catalyzed 6-hydroxylation of chlorzoxazone were 40 µM and 0.35 minute(-1), respectively, and similar to values obtained with recombinant CYP2E1 (41 µM, 0.32 minute(-1)). The KI and kinact values, along with other parameters, were used in a mechanistic static model to explain earlier observations of a profound decrease in the rate of chlorzoxazone elimination in volunteers despite the absence of detectable CMZ in blood.

A multifunctional therapeutic approach to disease modification in multiple familial mouse models and a novel sporadic model of Alzheimer's disease

Background

Clinical failures singularly targeting amyloid-β pathology indicate a critical need for alternative Alzheimer’s disease (AD) therapeutic strategies. The mixed pathology reported in a large population of AD patients demands a multifunctional drug approach. Since activation of cAMP response element binding protein (CREB) plays a crucial role in synaptic strengthening and memory formation, we retooled a clinical drug with known neuroprotective and anti-inflammatory activity to activate CREB, and validated this novel multifunctional drug, NMZ, in 4 different mouse models of AD.

Results

NMZ was tested in three mouse models of familial AD and one model of sporadic AD. In 3 × Tg hippocampal slices, NMZ restored LTP. In vivo, memory was improved with NMZ in all animal models with robust cognitive deficits. NMZ treatment lowered neurotoxic forms of Aβ in both APP/PS1 and 3 × Tg transgenic mice while also restoring neuronal plasticity biomarkers in the 3 × Tg mice. In EFAD mice, incorporation of the major genetic AD risk factor, hAPOE4, did not mute the beneficial drug effects. In a novel sporadic mouse model that manifests AD-like pathology caused by accelerated oxidative stress in the absence of any familial AD mutation, oral administration of NMZ attenuated hallmark AD pathology and restored biomarkers of synaptic and neuronal function.

Conclusions

The multifunctional approach, embodied by NMZ, was successful in mouse models of AD incorporating Aβ pathology (APP/PS1), tau pathology (3xTg), and APOE4, the major human genetic risk factor for AD (EFAD). The efficacy observed in a novel model of sporadic AD (Aldh2^−/−) demonstrates that the therapeutic approach is not limited to rare, familial AD genetic mutations. The multifunctional drug, NMZ, was not designed directly to target Aβ and tau pathology; however, the attenuation of this hallmark pathology suggests the approach to be a highly promising, disease-modifying strategy for AD and mixed pathology dementia.

Current Research on Antiepileptic Compounds

Epilepsy affects about 1% of the world’s population. Due to the fact all antiepileptic drugs (AEDs) have some undesirable side effects and about 30% of epileptic patients are not seizure-free with the existing AEDs, there is still an urgent need for the development of more effective and safer AEDs. Based on our research work on antiepileptic compounds and other references in recent years, this review covers the reported work on antiepileptic compounds which are classified according to their structures. This review summarized 244 significant anticonvulsant compounds which are classified by functional groups according to the animal model data, although there are some limitations in the data. This review highlights the properties of new compounds endowed with promising antiepileptic properties, which may be proven to be more effective and selective, and possibly free of unwanted side effects. The reviewed compounds represent an interesting possibility to overcome refractory seizures and to reduce the percentage of patients with a poor response to drug therapy.

Re-engineering a neuroprotective, clinical drug as a procognitive agent with high in vivo potency and with GABAA potentiating activity for use in dementia

Background

Synaptic dysfunction is a key event in pathogenesis of neurodegenerative diseases such as Alzheimer’s disease (AD) where synapse loss pathologically correlates with cognitive decline and dementia. Although evidence suggests that aberrant protein production and aggregation are the causative factors in familial subsets of such diseases, drugs singularly targeting these hallmark proteins, such as amyloid-β, have failed in late stage clinical trials. Therefore, to provide a successful disease-modifying compound and address synaptic dysfunction and memory loss in AD and mixed pathology dementia, we repurposed a clinically proven drug, CMZ, with neuroprotective and anti-inflammatory properties via addition of nitric oxide (NO) and cGMP signaling property.

Results

The novel compound, NMZ, was shown to retain the GABA_A potentiating actions of CMZ in vitro and sedative activity in vivo. Importantly, NMZ restored LTP in hippocampal slices from AD transgenic mice, whereas CMZ was without effect. NMZ reversed amnestic blockade of acetylcholine receptors by scopolamine as well as NMDA receptor blockade by a benzodiazepine and a NO synthase inhibitor in the step-through passive avoidance (STPA) test of learning and working memory. A PK/PD relationship was developed based on STPA analysis coupled with pharmacokinetic measures of drug levels in the brain: at 1 nM concentration in brain and plasma, NMZ was able to restore memory consolidation in mice.

Conclusion

Our findings show that NMZ embodies a promising pharmacological approach targeting synaptic dysfunction and opens new avenues for neuroprotective intervention strategies in mixed pathology AD, neurodegeneration, and dementia.

Electronic supplementary material

The online version of this article (doi:10.1186/s12868-015-0208-9) contains supplementary material, which is available to authorized users.

Novel analogues of chlormethiazole are neuroprotective in four cellular models of neurodegeneration by a mechanism with variable dependence on GABA(A) receptor potentiation

BACKGROUND AND PURPOSE

Chlormethiazole (CMZ), a clinical sedative/anxiolytic agent, did not reach clinical efficacy in stroke trials despite neuroprotection demonstrated in numerous animal models. Using CMZ as a lead compound, neuroprotective methiazole (MZ) analogues were developed, and neuroprotection and GABA(A) receptor dependence were studied.

EXPERIMENTAL APPROACH

Eight MZs were selected from a novel library, of which two were studied in detail. Neuroprotection, glutamate release, intracellular calcium and response to GABA blockade by picrotoxin were measured in rat primary cortical cultures using four cellular models of neurodegeneration. GABA potentiation was assayed in oocytes expressing the α1β2γ2 GABA(A) receptor.

KEY RESULTS

Neuroprotection against a range of insults was retained even with substantial chemical modification. Dependence on GABAA receptor activity was variable: at the extremes, neuroprotection by GN-28 was universally sensitive to picrotoxin, while GN-38 was largely insensitive. In parallel, effects on extracellular glutamate and intracellular calcium were associated with GABA(A) dependence. Consistent with these findings, GN-28 potentiated α1β2γ2 GABA(A) function, whereas GN-38 had a weak inhibitory effect. Neuroprotection against moderate dose oligomeric Aβ₁₋₄₂ was also tolerant to structural changes.

CONCLUSIONS AND IMPLICATIONS

The results support the concept that CMZ does not contain a single pharmacophore, rather that broad-spectrum neuroprotection results from a GABA(A)-dependent mechanism represented by GN-28, combined with a mechanism represented in GN-38 that shows the least dependence on GABA(A) receptors. These findings allow further refinement of the neuroprotective pharmacophore and investigation into secondary mechanisms that will assist in identifying MZ-based compounds of use in treating neurodegeneration.

Gamma aminobutyric acid (GABA) receptor agonists for acute stroke

BACKGROUND

Gamma aminobutyric acid (GABA) receptor agonists have been shown to have a neuroprotectant effect in reducing infarct size and improving functional outcome in animal models of cerebral ischemia. However, the sedation effects of GABA receptor agonists have limited their wider application in acute stroke patients due to the potential risk of stupor.

OBJECTIVES

To determine the efficacy and safety of GABA receptor agonists in the treatment of acute stroke.

SEARCH METHODS

We searched the Cochrane Stroke Group Trials Register (February 2014), the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2014, Issue 5), MEDLINE (1949 to June 2014), EMBASE (1980 to June 2014), CINAHL (1982 to June 2014), AMED (1985 to June 2014) and 11 Chinese databases (June 2014). In an effort to identify further published, unpublished and ongoing trials we searched ongoing trials registers, reference lists and relevant conference proceedings, and contacted authors and pharmaceutical companies.

SELECTION CRITERIA

We included randomized controlled trials (RCTs) investigating GABA receptor agonists versus placebo for acute stroke patients (within 12 hours after stroke onset), with the outcomes of death or dependency, functional independence and adverse events.

DATA COLLECTION AND ANALYSIS

Two review authors independently screened the titles and abstracts of identified records, selected studies for inclusion, extracted eligible data, cross-checked the data for accuracy and assessed the methodological quality.

MAIN RESULTS

We included five trials with 3838 patients. The methodological quality of the included trials was generally good, with low risk of bias. Four trials measured death and dependency at three months in chlormethiazole versus placebo without significant difference (risk ratio (RR) 1.03, 95% confidence interval (CI) 0.95 to 1.11). One trial measured this outcome between diazepam and placebo (RR 0.94, 95% CI 0.82 to 1.07). In the subgroup analysis of total anterior circulation syndrome (TACS), a higher percentage of functional independence was found in the chlormethiazole group (RR 1.33, 95% CI 1.09 to 1.64). The frequent adverse events related to chlormethiazole were somnolence (RR 4.56, 95% CI 3.50 to 5.95) and rhinitis (RR 4.75, 95% CI 2.67 to 8.46).

AUTHORS' CONCLUSIONS

This review does not provide the evidence to support the use of GABA receptor agonists (chlormethiazole or diazepam) for the treatment of patients with acute ischemic or hemorrhagic stroke. Chlormethiazole appeared to be beneficial in improving functional independence in patients with TACS according to the subgroup analysis, but this result must be interpreted with great caution. More well-designed RCTs with large samples of TACS would be required for further confirmation. However, somnolence and rhinitis are frequent adverse events related to chlormethiazole.

Benzodiazepine use and risk of stroke: a retrospective population-based cohort study

AIM

The aim of this study was to investigate the possible association between benzodiazepine (BZD) use and risk of incident stroke by utilizing data from 2000 to 2003 from the National Health Insurance system of Taiwan.

METHODS

Study subjects consisted of 38,671 patients with new BZD use and 38,663 people without BZD use who were frequency-matched for age, sex and baseline comorbidity with BZD users. All subjects had no history of stroke. Each study patient's case was followed until a new diagnosis of stroke was made or until the patient was censored by loss to follow up, death, or termination of insurance. The study lasted until the end of 2009. A Cox proportional hazards regression model was used to estimate the incidences and hazard ratios (HR) of stroke.

RESULTS

The HR of hemorrhagic stroke was significantly lower in the BZD group when compared with the non-BZD group. For patients aged 20-39 years, the HR of ischemic stroke was significantly higher in the BZD group when compared with the non-BZD group. Compared to the non-BZD group, patients with a lower annual dosage (<1 g) or duration (<30 days) of BZD use had a lower risk of stroke in the elder group (P < 0.0001) and patients with a higher annual dosage (≥ 4 g) or duration (≥ 95 days) of BZD use had a higher risk of stroke in all age groups (P < 0.0001).

CONCLUSIONS

Our findings may suggest neuroprotection under lower-dosage BZD use and neurotoxicity under higher-dosage BZD use.

Modulating nitric oxide signaling in the CNS for Alzheimer's disease therapy

Nitric oxide (NO)/solube GC (sGC)/cGMP signaling is important for modulating synaptic transmission and plasticity in the hippocampus and cerebral cortex, which are critical for learning and memory. Physiological concentrations of NO also elicit anti-apoptotic/prosurvival effects against various neurotoxic challenges and brain insults through multiple mechanisms. Depression of the NO/sGC pathway is a feature of Alzheimer's disease (AD), attributed to amyloid-β neuropathology, and altered expression and activity of NOS, sGC and PDE enzymes. Different classes of NO-releasing hybrid drugs, including nomethiazoles, NO-NSAIDs and NO-acetylcholinesterase inhibitors were designed to deliver low concentrations of exogenous NO to the CNS while targeting other underlying disease mechanisms, such as excitotoxicity, neuro-inflammation and acetylcholine deficiency, respectively. Incorporating a NO-donating moiety may also reduce gastrointestinal and liver toxicity of the parent drugs. Progress has also been made in targeting downstream sGC and PDE enzymes. The PDE9 inhibitor PF-04447943 has completed Phase II clinical trials for AD. The search for effective NO-donating hybrid drugs, CNS-targeting sGC stimulators/activators and selective PDE inhibitors is an important goal for pharmacotherapy that manipulates NO biochemical pathways involved in cognitive function and neuroprotection. Rigorous preclinical validation of target engagement, and optimization of pharmacokinetic and toxicity profiles are likely to advance more drug candidates into clinical trials for mild cognitive impairment and early stage AD.

Synthesis and antimicrobial evaluation of some novel thiazole, pyridone, pyrazole, chromene, hydrazone derivatives bearing a biologically active sulfonamide moiety

This study aimed for the synthesis of new heterocyclic compounds incorporating sulfamoyl moiety suitable for use as antimicrobial agents via a versatile, readily accessible N-[4-(aminosulfonyl)phenyl]-2-cyanoacetamide (3). The 2-pyridone derivatives were obtained via reaction of cyanoacetamide with acetylacetone or arylidenes malononitrile. Cycloaddition reaction of cyanoacetamide with salicyaldehyde furnished chromene derivatives. Diazotization of 3 with the desired diazonium chloride gave the hydrazone derivatives 13a–e. Also, the reactivity of the hydrazone towards hydrazine hydrate to give Pyrazole derivatives was studied. In addition, treatment of 3 with elemental sulfur and phenyl isothiocyanate or malononitrile furnished thiazole and thiophene derivatives respectively. Reaction of 3 with phenyl isothiocyanate and KOH in DMF afforded the intermediate salt 17 which reacted in situ with 3-(2-bromoacetyl)-2H-chromen-2-one and methyl iodide afforded the thiazole and ketene N,S-acetal derivatives respectively. Finally, reaction of 3 with carbon disulfide and 1,3-dibromopropane afforded the N-[4-(aminosulfonyl) phenyl]-2-cyano-2-(1,3-dithian-2-ylidene)acetamide product 22. All newly synthesized compounds were elucidated by considering the data of both elemental and spectral analysis. The compounds were evaluated for both their in vitro antibacterial and antifungal activities and showed promising results.

Social interaction plays a critical role in neurogenesis and recovery after stroke

Stroke survivors often experience social isolation. Social interaction improves quality of life and decreases mortality after stroke. Male mice (20-25 g; C57BL/6N), all initially pair housed, were subjected to middle cerebral artery occlusion (MCAO). Mice were subsequently assigned into one of three housing conditions: (1) Isolated (SI); (2) Paired with their original cage mate who was also subjected to stroke (stroke partner (PH-SP)); or (3) Paired with their original cage mate who underwent sham surgery (healthy partner (PH-HP)). Infarct analysis was performed 72 h after stroke and chronic survival was assessed at day 30. Immediate post-stroke isolation led to a significant increase in infarct size and mortality. Interestingly, mice paired with a healthy partner had significantly lower mortality than mice paired with a stroke partner, despite equivalent infarct damage. To control for changes in infarct size induced by immediate post-stroke isolation, additional cohorts were assessed that remained pair housed for three days after stroke prior to randomization. Levels of brain-derived neurotrophic factor (BDNF) were assessed at 90 days and cell proliferation (in cohorts injected with 5-bromo-2'-deoxyuridine, BrdU) was evaluated at 8 and 90 days after stroke. All mice in the delayed housing protocol had equivalent infarct volumes (SI, PH-HP and PH-SP). Mice paired with a healthy partner showed enhanced behavioral recovery compared with either isolated mice or mice paired with a stroke partner. Behavioral improvements paralleled changes in BDNF levels and neurogenesis. These findings suggest that the social environment has an important role in recovery after ischemic brain injury.

Gamma aminobutyric acid (GABA) receptor agonists for acute stroke

BACKGROUND

Gamma aminobutyric acid (GABA) receptor agonists have been shown to have a neuroprotectant effect in reducing infarct size and improving functional outcome in animal models of cerebral ischemia. However, the sedation effects of GABA receptor agonists have limited their wider application in acute stroke patients due to the potential risk of stupor.

OBJECTIVES

To determine the efficacy and safety of GABA receptor agonists in the treatment of acute stroke.

SEARCH METHODS

We searched the Cochrane Stroke Group Trials Register (January 2012), the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2012, Issue 1), MEDLINE (1949 to March 2012), EMBASE (1980 to March 2012), CINAHL (1982 to March 2012), AMED (1985 to March 2012) and 11 Chinese databases (March 2012). In an effort to identify further published, unpublished and ongoing trials we searched ongoing trials registers, reference lists and relevant conference proceedings, and contacted authors and pharmaceutical companies.

SELECTION CRITERIA

We included randomized controlled trials (RCTs) investigating GABA receptor agonists versus placebo for acute stroke patients (within 12 hours after stroke onset), with the outcomes of death or dependency, functional independence and adverse events.

DATA COLLECTION AND ANALYSIS

Two review authors independently screened the titles and abstracts of identified records, selected studies for inclusion, extracted eligible data, cross-checked the data for accuracy and assessed the methodological quality.

MAIN RESULTS

We included five trials with 3838 patients. The methodological quality of the included trials was generally good, with low risk of bias. Four trials measured death and dependency at three months in chlormethiazole versus placebo without significant difference (risk ratio (RR) 1.03, 95% confidence interval (CI) 0.95 to 1.11). One trial measured this outcome between diazepam and placebo (RR 0.94, 95% CI 0.82 to 1.07). In the subgroup analysis of total anterior circulation syndrome (TACS), a higher percentage of functional independence was found in the chlormethiazole group (RR 1.33, 95% CI 1.09 to 1.64). The frequent adverse events related to chlormethiazole were somnolence (RR 4.56, 95% CI 3.50 to 5.95) and rhinitis (RR 4.75, 95% CI 2.67 to 8.46).

AUTHORS' CONCLUSIONS

This review does not provide the evidence to support the use of GABA receptor agonists (chlormethiazole or diazepam) for the treatment of patients with acute ischemic or hemorrhagic stroke. Chlormethiazole appeared to be beneficial in improving functional independence in patients with TACS according to the subgroup analysis, but this result must be interpreted with great caution. More well-designed RCTs with large samples of TACS would be required for further confirmation. However, somnolence and rhinitis are frequent adverse events related to chlormethiazole.

Design and synthesis of neuroprotective methylthiazoles and modification as NO-chimeras for neurodegenerative therapy

Learning and memory deficits in Alzheimer's disease (AD) result from synaptic failure and neuronal loss, the latter caused in part by excitotoxicity and oxidative stress. A therapeutic approach is described that uses NO-chimeras directed at restoration of both synaptic function and neuroprotection. 4-Methylthiazole (MZ) derivatives were synthesized, based upon a lead neuroprotective pharmacophore acting in part by GABA(A) receptor potentiation. MZ derivatives were assayed for protection of primary neurons against oxygen-glucose deprivation and excitotoxicity. Selected neuroprotective derivatives were incorporated into NO-chimera prodrugs, coined nomethiazoles. To provide proof of concept for the nomethiazole drug class, selected examples were assayed for restoration of synaptic function in hippocampal slices from AD-transgenic mice, reversal of cognitive deficits, and brain bioavailability of the prodrug and its neuroprotective MZ metabolite. Taken together, the assay data suggest that these chimeric nomethiazoles may be of use in treatment of multiple components of neurodegenerative disorders, such as AD.

Role of α2-agonists in the treatment of acute alcohol withdrawal

OBJECTIVE

To evaluate literature reporting on the role of norepinephrine in alcohol withdrawal and to determine the safety and efficacy of α(2)-agonists in reducing symptoms of this severe condition.

DATA SOURCES

Articles evaluating the efficacy and safety of the α(2)-agonists clonidine and dexmedetomidine were identified from an English-language MEDLINE search (1966-December 2010). Key words included alcohol withdrawal, delirium tremens, clonidine, dexmedetomidine, α(2)-agonist, norepinephrine, and sympathetic overdrive.

STUDY SELECTION AND DATA EXTRACTION

Studies that focused on the safety and efficacy of clonidine and dexmedetomidine in both animals and humans were selected.

DATA SYNTHESIS

The noradrenergic system, specifically sympathetic overdrive during alcohol withdrawal, may play an important role in withdrawal symptom development. Symptoms of sympathetic overdrive include anxiety, agitation, elevated blood pressure, tachycardia, and tremor. Therefore, α(2)-agonists, which decrease norepinephine release, may have a role in reducing alcohol withdrawal symptoms. The majority of controlled animal and human studies evaluated clonidine, but the most recent literature is from case reports on dexmedetomidine. The literature reviewed here demonstrate that these 2 α(2)-agonists safely and effectively reduce symptoms of sympathetic overdrive and concomitant medication use. Dexmedetomidine may offer an advantage over current sedative medications used in the intensive care unit, such as not requiring intubation with its use, and therefore further study is needed to fully elicit its benefit in alcohol withdrawal.

CONCLUSION

Clonidine and dexmedetomidine may provide additional benefit in managing alcohol withdrawal by offering a different mechanism of action for targeting withdrawal symptoms. Based on literature reviewed here, the primary role for clonidine and dexmedetomidine is as adjunctive treatment to benzodiazepines, the standard of care in alcohol withdrawal.

Neuroprotection for ischemic stroke: past, present and future

Neuroprotection for ischemic stroke refers to strategies, applied singly or in combination, that antagonize the injurious biochemical and molecular events that eventuate in irreversible ischemic injury. There has been a recent explosion of interest in this field, with over 1000 experimental papers and over 400 clinical articles appearing within the past 6 years. These studies, in turn, are the outgrowth of three decades of investigative work to define the multiple mechanisms and mediators of ischemic brain injury, which constitute potential targets of neuroprotection. Rigorously conducted experimental studies in animal models of brain ischemia provide incontrovertible proof-of-principle that high-grade protection of the ischemic brain is an achievable goal. Nonetheless, many agents have been brought to clinical trial without a sufficiently compelling evidence-based pre-clinical foundation. At this writing, around 160 clinical trials of neuroprotection for ischemic stroke have been initiated. Of the approximately 120 completed trials, two-thirds were smaller early-phase safety-feasibility studies. The remaining one-third were typically larger (>200 subjects) phase II or III trials, but, disappointingly, only fewer than one-half of these administered neuroprotective therapy within the 4-6h therapeutic window within which efficacious neuroprotection is considered to be achievable. This fact alone helps to account for the abundance of "failed" trials. This review presents a close survey of the most extensively evaluated neuroprotective agents and classes and considers both the strengths and weakness of the pre-clinical evidence as well as the results and shortcomings of the clinical trials themselves. Among the agent-classes considered are calcium channel blockers; glutamate antagonists; GABA agonists; antioxidants/radical scavengers; phospholipid precursor; nitric oxide signal-transduction down-regulator; leukocyte inhibitors; hemodilution; and a miscellany of other agents. Among promising ongoing efforts, therapeutic hypothermia, high-dose human albumin therapy, and hyperacute magnesium therapy are considered in detail. The potential of combination therapies is highlighted. Issues of clinical-trial funding, the need for improved translational strategies and clinical-trial design, and "thinking outside the box" are emphasized.

Neuroprotective Activity of Proproten in Rats with Experimental Local Photothrombosis of the Prefrontal Cortex

Proproten (ultralow doses of antibodies to S100 protein) exhibited neuroprotective activity in rats with experimental photochemical thrombosis of the prefrontal cortex. Proproten was more potent than standard neuroprotectors piracetam and vinpocetine in alleviating the signs of memory disorders produced by ischemic injury. Pathomorphological study of the damaged area confirmed the neuroprotective effect of Proproten.