Cytisine--a tobacco treatment hiding in plain sight

Separation and purification of quinolyridine alkaloids from seeds of Thermopsis lanceolata R. Br. by conventional and pH-zone-refining counter-current chromatography

In this work, the preparative separation of quinolyridine alkaloids from seeds of T. lanceolata by conventional and pH-zone-refining counter-current chromatography. Traditional counter-current chromatography separation was performed by a flow-rate changing strategy with a solvent system of ethyl acetate-n-butanol-water (1:9:10, v/v) and 200 mg sample loading. Meanwhile, the pH-zone-refining mode was adopted for separating 2.0 g crude alkaloid extracts with the chloroform-methanol-water (4:3:3, v/v) solvent system using the stationary and mobile phases of 40 mM hydrochloric acid and 10 mM triethylamine. Finally, six compounds, including N-formylcytisine (two conformers) (1), N-acetycytisine (two conformers) (2), (-)-cytisine (3), 13-β-hydroxylthermopsine (4), N-methylcytisine (5), and thermopsine (6) were successfully obtained in the two counter-current chromatography modes with the purities over 96.5%. Moreover, we adopted nuclear magnetic resonance and mass spectrometry for structural characterization. Based on the obtained findings, the pH-zone-refining mode was the efficient method to separate quinolyridine alkaloids relative to the traditional mode.

Mechanism of Neural Regeneration Induced by Natural Product LY01 in the 5×FAD Mouse Model of Alzheimer’s Disease

Background: A sharp decline in neural regeneration in patients with Alzheimer’s disease (AD) exacerbates the decline of cognition and memory. It is of great significance to screen for innovative drugs that promote endogenous neural regeneration. Cytisine N-methylene-(5,7,4′-trihydroxy)-isoflavone (LY01) is a new compound isolated from the Chinese herbal medicine Sophora alopecuroides with both isoflavone and alkaloid characteristic structures. Its pharmacological effects are worth studying.

Objective: This study was designed to determine whether LY01 delays the cognitive and memory decline in the early stage of AD and whether this effect of LY01 is related to promoting neural regeneration.

Methods: Eight-week-old 5×Familial Alzheimer’s Disease (5×FAD) mice were used as disease models of early AD. Three doses of LY01 administered in two courses (2 and 5 weeks) of treatment were tested. Cognition, memory, and anxiety-like behaviors in mice were evaluated by the Morris water maze, fear conditioning, and open field experiments. Regeneration of neurons in the mouse hippocampus was observed using immunofluorescence staining. The effect of LY01 on cell regeneration was also demonstrated using a series of tests on primary cultured neurons, astrocytes, and neural stem cells (NSCs). In addition, flow cytometry and transcriptome sequencing were carried out to preliminarily explored the mechanisms.

Results: We found that LY01 reduced the decline of cognition and memory in the early stage of 5×FAD mice. This effect was related to the proliferation of astrocytes, the proliferation and migration of NSCs, and increases in the number of new cells and neural precursor cells in the dentate gyrus area of 5×FAD mice. This phenomenon could be observed both in 2-week-old female and 5-week-old male LY01-treated 5×FAD mice. The neuronal regeneration induced by LY01 was related to the regulation of the extracellular matrix and associated receptors, and effects on the S phase of the cell cycle.

Conclusion: LY01 increases the proliferation of NSCs and astrocytes and the number of neural precursor cells in the hippocampus, resulting in neural regeneration in 5×FAD mice by acting on the extracellular matrix and associated receptors and regulating the S phase of the cell cycle. This provides a new idea for the early intervention and treatment of AD.

Cytisine for nicotine addiction treatment: a review of pharmacology, therapeutics and an update of clinical trial evidence for smoking cessation

AIMS

To review cytisine's history of use, pre-clinical evidence, clinical pharmacokinetics, efficacy, adverse reactions (ARs) and safety for smoking cessation.

METHODS

A synoptic review of the use of cytisine as a smoking cessation medication, mechanism of action, pharmacokinetics and safety. Relevant literature on data included in these sections were identified through a search of 11 databases with additional literature obtained from reports and monographs. Three databases (PubMed, EMBASE and www.elibrary.ru) were systematically searched for studies published from 2012 to August 2018 in any language to provide an updated meta-analysis of cytisine's efficacy and ARs for smoking cessation compared with placebo. We pooled the relative risks (RR) of abstinence in the efficacy analysis and RR of ARs, either reported by the authors or calculated from the reports.

RESULTS

Cytisine has been in use since 1964 and is currently marketed in 18 countries. Systemic bioavailability from oral ingestion is high and clearance is primarily renal, with minimal or no metabolism. Brain uptake in animal models is moderate. The plasma half-life averages 4.8 hours. Eight studies were included for meta-analysis of efficacy. With heterogeneous results, the overall RR versus placebo of successful continuous abstinence at the longest follow-up was 1.74 [95% confidence interval (CI) = 1.38-2.19]. Nausea, vomiting, dyspepsia, upper abdominal pain and dry mouth that were mild or moderate were the most common ARs, with RR versus placebo 1.10 (95% CI = 0.95-1.28). The cost of cytisine in eastern and central Europe is several-fold less than that of other smoking cessation medications.

CONCLUSIONS

Cytisine is a low-cost medication found to increase the likelihood of smoking cessation. The most frequently reported ARs of cytisine involve gastrointestinal symptoms that are mostly reported as either mild or moderate in severity.

The effectiveness, safety and cost-effectiveness of cytisine versus varenicline for smoking cessation in an Australian population: a study protocol for a randomized controlled non-inferiority trial

BACKGROUND AND AIMS

Smoking cessation medications are effective, but often underutilized because of costs and side effects. Cytisine is a plant-based smoking cessation medication with more than 50 years of use in central and eastern Europe. While cytisine has been found to be well-tolerated and more effective than nicotine replacement therapy, direct comparisons with varenicline have not been conducted. This study evaluates the effectiveness, safety and cost-effectiveness of cytisine compared with varenicline.

DESIGN

Two-arm, parallel group, randomized, non-inferiority trial, with allocation concealment and blinded outcome assessment.

SETTING

Australian population-based study.

PARTICIPANTS

Adult daily smokers (n = 1266) interested in quitting will be recruited through advertisements and Quitline telephone-based cessation support services.

INTERVENTION AND COMPARATOR

Eligible participants will be randomized (1 : 1 ratio) to receive either cytisine capsules (25-day supply) or varenicline tablets (12-week supply), prescribed in accordance with the manufacturer's recommended dosing regimen. The medication will be mailed to each participant's nominated residential address. All participants will also be offered standard Quitline behavioural support (up to six 10-12-minute sessions).

MEASUREMENTS

Assessments will be undertaken by telephone at baseline, 4 and 7 months post-randomization. Participants will also be contacted twice (2 and 4 weeks post-randomization) to ascertain adverse events, treatment adherence and smoking status. The primary outcome will be self-reported 6-month continuous abstinence from smoking, verified by carbon monoxide at 7-month follow-up. We will also evaluate the relative safety and cost-effectiveness of cytisine compared with varenicline. Secondary outcomes will include self-reported continuous and 7-day point prevalence abstinence and cigarette consumption at each follow-up interview.

COMMENTS

If cytisine is as effective as varenicline, its lower cost and natural plant-based composition may make it an acceptable and affordable smoking cessation medication that could save millions of lives world-wide.

The contribution of agonist and antagonist activities of α4β2* nAChR ligands to smoking cessation efficacy: a quantitative analysis of literature data

RATIONALE AND OBJECTIVE

Two mechanisms underlie smoking cessation efficacies of α4β2* nicotinic acetylcholine receptor (nAChR) agonists: a "nicotine-like" agonist activity reduces craving by substituting for nicotine during a quit attempt, and a "nicotine-blocking" antagonist activity attenuates reinforcement by competing with inhaled nicotine during a relapse. To evaluate the contribution of each mechanism to clinical efficacy, we estimated the degree of agonist and antagonist activities of nicotine replacement therapy (NRT), varenicline, cytisine, and the discontinued nAChR agonists dianicline, ABT-418, ABT-089, CP-601927, and CP-601932, relative to the functional effects of nicotine from smoking.

METHODS

Functional activities that occur in vivo with clinical doses were predicted from literature data on binding and functional potencies at the target α4β2 nAChR, as well as at α6β2* nAChRs, and from estimates of free drug exposures in human brain. Agonist activity is comprised of nAChR activation and desensitization, which were expressed as percentages of desensitization and activation by nicotine from smoking. Antagonist activity was expressed as the reduction in nAChR occupancy by nicotine during smoking in the presence of an agonist.

RESULTS

Comparisons with odds ratios at end of treatment suggest that extensive α4β2 and α6β2* nAChR desensitization combined with α6β2* nAChR activation at similar levels as nicotine from smoking is associated with clinical efficacy (NRT, varenicline, cytisine, ABT-418). Effective competition with inhaled nicotine for α4β2 and α6β2* nAChRs further improves clinical efficacy (varenicline). Other discontinued nAChR agonists have lower agonist and antagonist activities at α4β2 nAChRs and are inactive or less efficacious than NRT (dianicline, ABT-089, CP-601927, CP-601932).

CONCLUSION

Three pharmacological effects appear to be key factors underlying smoking cessation efficacy: the degree of activation of α6β2* nAChRs, desensitization of α4β2 and α6β2* nAChRs (agonist activity), and the reduction of nicotine occupancy at α4β2 and α6β2* nAChRs (antagonist activity). No single activity is dominant, and the level of smoking cessation efficacy depends on the profile of these activities achieved at clinical doses. While adequate agonist activity alone seems sufficient for a clinical effect (e.g., NRT, cytisine), clinical efficacy is improved with substantial competitive antagonism of α4β2 nAChRs, i.e., if the drug has a dual agonist-antagonist mechanism of action (e.g., varenicline).

Understanding the implications of the biobehavioral basis of nicotine addiction and its impact on the efficacy of treatment

INTRODUCTION

Tobacco use remains the leading cause of preventable death in the United States. There are efficacious behavioral and pharmacological options for smoking cessation including three FDA approved therapies - nicotine replacement therapy, varenicline and bupropion. Nevertheless, uptake of smoking cessation treatments continues to be poor and there is a need for novel smoking cessation treatments. Areas covered: This article reviews the biobehavioral basis of nicotine addiction, its implications for smoking cessation treatments, the various neurotransmitter systems involved in nicotine addictive effects, and their potential therapeutic value. Included are discussions around the role of genetic factors in predicting response to pharmacotherapy and what we know about appropriate application of pharmacotherapy and behavioral interventions for tobacco use disorder. The evidence for harm reduction measures in individuals who are not willing or able to quit smoking is also reviewed. Expert commentary: Many neurotransmitter system targets have been investigated as a result of our understanding of the underlying neurobiology of tobacco use disorder, and there remain important targets that have yet to be fully explored. rTMS or combination therapies are proposed as possible novel strategies to improve smoking cessation.

Cytisine basicity, solvation, logP, and logD theoretical determination as tool for bioavailability prediction

Cytisine, an α4β2 nicotinic receptor partial agonist, is a plant alkaloid widely used as a smoking cessation agent. Despite long history of use, knowledge on pharmacokinetics of cytisine still demands an extension. This work is aimed at theoretical determination of physicochemical parameters that affect the bioavailability of cytisine. The acidic dissociation constant, Gibbs free energy of solvation in water and n-octanol as well as n-octanol/water partition coefficient and n-octanol/water distribution coefficient of cytisine were calculated as quantities corresponding to its solubility and permeability. Cytisine structure was optimized with several quantum chemical methods-ab initio: HF and MP2, and DFT functionals (B3LYP, B3LYP-D3, CAM-B3LYP, M06-2X, TPSS, VSXC) with 6-311++G(d,p) basis set. Solvation of cytisine in water and n-octanol was determined with the SMD continuum model. It was shown that lipophilicity of cytisine depends on the pH of an environment. Protonated cytisine, the most populated state under acidic conditions, is characterized by enhanced hydrophilicity. Then neutral cytisine, dominating in a basic environment, demonstrates more lipophilic character. It appears that cytisine is very well soluble in the gastrointestinal (GI) tract fluids. Then the distribution of cytisine ought to occur very rapidly. However, permeability of cytisine through the mucous membrane of the GI tract may be limited, leading to the diminished bioavailability.