Cytisine eye drops for benzalkonium chloride-induced dry eye: safety and efficacy evaluation

This experiment aimed to investigate the feasibility of cytisine (CYT) in treating eye diseases with ocular topical application. An in vitro cytotoxicity test, a hen's egg test-chorioallantoic membrane (HET-CAM), and a mouse eye tolerance test were used to fully reveal the ocular safety profiles of CYT. For the efficacy evaluations, CYT's effects on cell wound healing, against H2O2-induced oxidative stress damages on cells, and on benzalkonium chloride (BAC)-induced dry eye disease (DED) in mice were evaluated. Results showed that CYT did not show any cytotoxicities at concentrations no higher than 250 μg/ml, while lipoic acid (α-LA) at 250 μg/ml and BAC at 1.25 μg/ml showed significant cytotoxicities within 48 h incubation. The HET-CAM and mouse eye tolerance test confirmed that 0.5% CYT eye drops demonstrated good safety characteristics. Efficacy evaluations showed that CTY significantly promoted cell migration and wound healing. CYT significantly improved cell survival against H2O2-induced oxidative stress damage by reversing the imbalance between the reactive oxygen species (ROS) and antioxidant defense mechanisms. The animal evaluation of the BAC-induced dry eye model revealed that CYT demonstrated a strong treatment effect, including reversing ocular surface damages, recovering corneal sensitivity, and inhibiting neovascularization; HMGB1/NF-κB signaling was involved in this DED treatment by CTY. In conclusion, CYT had strong experimental treatment efficacy against DED with good ocular safety profiles, and it might be a novel and promising drug for DED.

Evaluation of the effectiveness of cytisine for the treatment of smoking cessation: A systematic review and meta-analysis

BACKGROUND AND AIMS

Smoking is considered the main cause of preventable death world-wide. This study aimed to review the efficacy and safety of cytisine for smoking cessation.

METHODS

This review included an exhaustive search of databases to identify randomized controlled trials (RCTs) in health centers of any level with smokers of any age or gender investigating the effects of cytisine at standard dosage versus placebo, varenicline or nicotine replacement therapy (NRT).

RESULTS

We identified 12 RCTs. Eight RCTs compared cytisine with placebo at the standard dose covering 5922 patients, 2996 of whom took cytisine, delivering a risk ratio (RR) of 2.25 [95% confidence interval (CI) = 1.42-3.56; I2  = 88%; moderate-quality evidence]. The greater intensity of behavioral therapy was associated directly with the efficacy findings (moderate-quality evidence). The confirmed efficacy of cytisine was not evidenced in trials conducted in low- and middle-income countries. We estimate a number needed to treat (NNT) of 11. Two trials compared the efficacy of cytisine versus NRT, and the combination of both studies yields modest results in favor of cytisine. Three trials compared cytisine with varenicline, without a clear benefit for cytisine. Meta-analyses of all non-serious adverse events in the cytisine group versus placebo groups yielded a RR of 1.24 (95% CI = 1.11-1.39; participants = 5895; studies = 8; I2  = 0%; high-quality evidence).

CONCLUSIONS

Cytisine increases the chances of successful smoking cessation by more than twofold compared with placebo and has a benign safety profile, with no evidence of serious safety concerns. Limited evidence suggests that cytisine may be more effective than nicotine replacement therapy, with modest cessation rates.

Cytisine: State of the art in pharmacological activities and pharmacokinetics

Cytisine is a naturally occurring bioactive compound, an alkaloid mainly isolated from legume plants. In recent years, various biological activities of cytisine have been explored, showing certain effects in smoking cessation, reducing drinking behavior, anti-tumor, cardiovascular protection, blood sugar regulation, neuroprotection, osteoporosis prevention and treatment, etc. At the same time, cytisine has the advantages of high efficiency, safety, and low cost, has broad development prospects, and is a drug of great application value. However, a summary of cytisine's biological activities is currently lacking. Therefore, this paper summarizes the pharmacological action, mechanism, and pharmacokinetics of cytisine by referring to numerous databases, and analyzes the new and core targets of cytisine with the help of computer simulation technology, to provide reference for doctors.

Anti-smoking drugs cytisine and varenicline reduce cardiac reperfusion injury in rat model of myocardial ischemia

Evidence to date indicates that activation of nicotinic acetylcholine receptors (nAChRs) can reduce cardiac injury from ischemia and subsequent reperfusion. The use of nAChR agonists in various animal models leads to a reduction in reperfusion injury. Earlier this effect was shown for the agonists of α7 nAChR subtype. In this work, we demonstrated the expression of mRNA encoding α4, α6 and β2 nAChR subunits in the left ventricle of rat heart. In a rat model of myocardial ischemia, we studied the effect of α4β2 nAChR agonists cytisine and varenicline, medicines used for the treatment of nicotine addiction, and found them to significantly reduce myocardium ischemia-reperfusion injury, varenicline manifesting a higher protection. Dihydro-β-erythroidine, antagonist of α4β2 nAChR, as well as methyllycaconitine, antagonist of α7 and α6β2-containing nAChR, prevented protective effect of varenicline. This together with the presence of α4, α6 and β2 subunit mRNA in the left ventricule of rat heart raises the possibility that the varenicline effect is mediated by α4β2 as well as by α7 and/or α6β2-containing receptors. Our results point to a new way for the use of cytisine and varenicline as cardioprotective agents.

Assessment of cytisine as an insecticide candidate for Hyphantria cunea management: Toxicological, biochemical, and control potential insights

In the present study, the toxicological effects of cytisine on the H. cunea larvae were investigated, and the potential of cytisine as a botanical insecticide through field simulation experiments was evaluated. The results showed that cytisine treatment (0.25-2.5%) exerted significant biotoxic effects on the H. cunea larvae, including diminished weight, disruption of both positive (HcCKS1, HcPLK, HcCCNA) and negative (HcGADD and HcCDKN) regulatory genes associated with larval growth, increased mortality, and heightened oxidative damage (H2O2 and MDA). Cytisine treatment significantly reduced glucose content and inhibited the expression of key rate-limiting enzyme genes (HcPFK, HcPK, HcHK1, HcCS, and HcIDH2) within glycolysis and the tricarboxylic acid cycle pathways. Under cytisine treatment, detoxification enzyme activities (CarE and GST) and expression of detoxification genes (HcCarE1, HcCarE2, HcCarE3, HcGST1, and HcGST3) were inhibited in H. cunea larvae. An increased contents of SOD, CAT, ASA and T-AOC, as well as expression of antioxidant enzyme genes HcSOD1 and HcCAT2, was found in cytisine-treated H. cunea larvae. Simultaneously, this is accompanied by a significant reduction in the expression of four antioxidant enzyme genes (e.g., HcPOD1 and HcPOD2). In the field experiment, a cytisine aqueous solution (25 g/L) with pre-sprayed and directly sprayed ways demonstrated potent insecticidal activity against H. cunea larvae, achieving a mortality rate of 53.75% and 100% at 24 h, respectively. Taken together, cytisine has significantly weight inhibition and lethal toxicity on the H. cunea larvae, and can be developed as a botanical insecticide for H. cunea control.

Cytisine for smoking cessation: A systematic review and meta-analysis

BACKGROUND

Cytisine is a smoking cessation medication. This systematic review incorporates recently published randomized controlled trials (RCTs) to provide an updated evidence-based assessment of cytisine's efficacy and safety.

METHODS

We searched Cochrane Library, MEDLINE, and EMBASE, for RCTs comparing cytisine to other smoking cessation treatments in adults who smoke.

PRIMARY OUTCOME

6-month biochemically verified continuous abstinence. Other outcomes: abstinence at longest follow-up, adverse events, mortality, and health-related quality of life (HRQOL). We used Grading of Recommendations Assessment, Development and Evaluation (GRADE) to assess evidence certainty.

RESULTS

We included 14 RCTs involving 9953 adults. Cytisine was superior to placebo (risk ratio [RR] 2.25, 95% confidence interval [CI] 1.13-4.47; 5 RCTs, 4325 participants), but not varenicline (RR 1.13, 95% CI 0.65-1.95; 2 RCTs, 2131 participants) for the primary outcome. Cytisine was superior to placebo (RR 2.78, 95% CI 1.64-4.70; 8 RCTs, 5762 participants) and nicotine replacement therapy [NRT] (RR 1.39, 95% CI 1.12-1.73; 2 RCTs, 1511 participants), but not varenicline (RR 1.02, 95% CI 0.72-1.44; 4 RCTs, 2708 participants) for abstinence at longest follow-up. Cytisine increased mostly gastrointestinal adverse events compared to placebo (RR 1.15; 95% CI 1.06-1.25; 8 RCTs, 5520 participants) and NRT (RR 1.52, 95% CI 1.26-1.84; 1 RCT, 1310 participants) but less adverse events compared to varenicline (RR 0.67; 95% CI 0.48-0.95; 3 RCTs, 2484 participants).

CONCLUSION

Cytisine shows greater efficacy than placebo and NRT, but more adverse events. It is comparable to varenicline, with fewer adverse events. This can inform clinicians and guidelines on cytisine for smoking cessation.

Effectiveness of nicotine salt vapes, cytisine, and a combination of these products, for smoking cessation in New Zealand: protocol for a three-arm, pragmatic, community-based randomised controlled trial

BACKGROUND

Combining short-acting nicotine replacement therapy with varenicline increases smoking cessation rates compared with varenicline alone, but not all people tolerate these medications or find them helpful. We aim to investigate the therapeutic potential of an analogous combination, by evaluating the effectiveness, safety, and acceptability of combining nicotine salt e-cigarettes with cytisine, compared to nicotine salt e-cigarettes or cytisine only, on smoking abstinence at six months.

METHODS

A pragmatic, community-based, investigator-blinded, randomised superiority trial design will be utilised. Eligible participants will be people who smoke daily (N = 800, 90% power) from throughout New Zealand, who are: aged ≥ 18 years, motivated to quit in the next two weeks, able to provide online consent, willing to use e-cigarettes and/or cytisine, and have daily access to a mobile phone. Recruitment will utilise multi-media advertising. Participants will be randomised (3:3:2 ratio) to 12 weeks of: 1) e-cigarettes (closed pod system, 3% nicotine salt, tobacco flavour) plus cytisine; 2) e-cigarettes alone, or 3) cytisine alone. All groups will receive a six-month, text-message-based behavioural support programme. The primary outcome is self-reported, biochemically verified, continuous abstinence at six months post-quit date. Secondary outcomes, measured at quit date, then one, three, six, and 12 months post-quit date, include self-reported continuous abstinence, 7-day point prevalence abstinence, cigarettes smoked per day, withdrawal and urge to smoke, time to (re)lapse, treatment use and compliance, treatment crossover, dual-use, use of other cessation products, change in e-cigarette products, continuation of product use, acceptability, change in health state, health-related quality of life, change in body mass index, adverse events, and cost per quitter.

DISCUSSION

Pragmatic trials are of particular value as they reflect the 'real world' impact of interventions. The trial will provide some of the first evidence on the effectiveness of combining nicotine salt e-cigarettes with cytisine for smoking cessation, in a country with strong tobacco control policy. Findings will be incorporated into relevant systematic reviews, informing practice and policy.

TRIAL REGISTRATION

NCT05311085 ClinicalTrials.gov. Registered 5th April, 2022.

Reduction of nicotine and ethanol intake in alcohol-preferring (UChB) female rats by the α4β2 nicotinic acetylcholine receptor partial agonists 5-bromocytisine and cytisine

RATIONALE

Neuronal nicotinic acetylcholine receptors (nAChRs) are implicated in the reinforcing effects of nicotine and ethanol. Previous studies have shown that cytisine and its 5-bromo derivative are partial agonists at the α4β2 nAChRs and that the parent molecule cytisine is effective in reducing both nicotine- and ethanol-self-administration in rats. However, whether 5-bromocytisine affects nicotine or ethanol self-administration was unknown.

OBJECTIVES

The present study compared the effects of 5-bromocytisine and cytisine on nicotine self-administration and further assessed the effect of daily drug injection on voluntary ethanol consumption in alcohol-preferring female rats. Animals were administered a 1.5mg/kg i.p. dose of 5-bromocytisine or cytisine every day for 15-16 days.

RESULTS

The initial efficacy of 5-bromocytisine and cytisine in reducing nicotine intake was similar (-80%) while for voluntary ethanol intake 5-bromocytisine was a superior inhibitor over cytisine (-78% and -40% respectively). The efficacy of cytisine began to diminish after 10 days of daily administration, which was attributed to tolerance development to its inhibitory effects both on nicotine and ethanol self-administration. Tolerance did not develop for 5-bromocytisine.

CONCLUSION

5-Bromocytisine, a weaker α4β2 nAChR partial agonist than cytisine, also produces a sustained inhibition of both nicotine and ethanol self-administration, and unlike cytisine, it does not develop tolerance.

Comparison between cytisine and Nicotine Replacement Therapy in smoking cessation among inpatient psychiatric patients

Introduction: Smoking is more common among people with mental disorders and is associated with adverse effects. Some compounds, including nicotine and cytisine, have been used in many individuals to increase success in smoking cessation. In this study, the effect of cytisine on the smoking status of patients hospitalized in the psychiatry department was investigated.Method: Forty-seven patients, hospitalized in the psychiatry ward, motivated to quit smoking, participated in this open-label randomized trial. Thirty patients used nicotine gums 2 mg (Nicolife®) for eight weeks, and the remaining took cytisine pills (Tabex®) according to the manufacturer's instructions for 25 days. All patients were followed up for six months. The primary outcome was smoking cessation, measured by the mood and physical symptoms scale (MPSS), the AUDIT alcohol consumption questions (AUDIT-C), confirmatory factor analyses, and reliability of the modified cigarette evaluation questionnaire at the end of the 1st week and at 1st, 2nd and 6th months after quit day.Findings: Only two out of 30 patients (6.66%) in the group taking Nicotine Replacement Therapy (NRT) could quit smoking entirely (no cigarettes after six months). In contrast, three out of 17 patients (17.64%) managed to do so in the cytisine group. The number of cigarettes smoked by the patients in both groups decreased, but the reduction was significant in the cytisine group.Conclusion: Cytisine is an effective and suitable agent for smoking cessation in patients with psychological problems, with fewer adverse effects and more success rate compared to NRT.

The cytisine-enriched poly(3-hydroxybutyrate) fibers for sustained-release dosage form

The polymeric cytisine-enriched fibers based on poly(3-hydroxybutyrate) were obtained using electrospinning method. The biocompatibility study, advanced thermal analysis and release of cytisine from the poly(3-hydroxybutyrate) fibers were carried out. The nanofibers' morphology was evaluated by scanning electron microscopy. The formation and description of phases during the thermal processes of fibers by the advanced thermal analysis were examined. The new quantitative thermal analysis of polymeric fibers with cytisine phases based on vibrational, solid and liquid heat capacities was presented. The apparent heat capacity of fibers was measured using the standard differential scanning calorimetry. The quantitative analysis allowed for the study of the glass transition and melting/crystallization process. The mobile amorphous fraction, degree of crystallinity and rigid amorphous fraction were determined depending on the thermal history of semicrystalline polymeric fibers. Furthermore, the cytisine dissolution behaviour was studied. It was observed that the kinetic of the release from polymeric nanofiber is delayed than for the marketed product. The immunosafety of the tested polymeric nanofibers with cytisine was confirmed by the Food and Drug Agency Guidance as well as the European Medicines Agency. The polymeric matrix with cytisine seems to be a promising candidate for the prolonged release formulation.

Heat capacity of cytisine - the drug for smoking cessation

The characterization of cytisine (CYT) and its blends with poly(lactic acid) was performed using thermal analysis, elemental analysis, infrared spectroscopy, and powder X-ray diffractometry. The heat capacities, total enthalpy, and phase transitions of CYT were established from 1.8 to 448.15 K (-271.35 - 175 °C) by advanced thermal analysis. Data were obtained using a Quantum Design Physical Property Measurement System (PPMS) and a differential scanning calorimetry (DSC). The low-temperature heat capacity of the crystalline CYT in the range of 1.8 to 300 K (-271.35 - 26.86 °C) was measured by PPMS and fitted to a theoretical model in the low temperature region below 11 K (-262.15 °C), to orthogonal polynomials in the middle range 5 K < T < 60 K (-268.15 °C < t < -213.15 °C) and to the Debye and Einstein functions in the high range of temperature above 60 K (-213.15 °C). The liquid heat capacity was calculated based on the approximated linear regression data above the molten state of the experimental heat capacity of CYT obtained by the standard DSC measurements, and it was expressed as C_p^liquid = 0.0838T + 346.78 J·K^-1·mol^-1. The calculated heat capacity in the solid state was extended to a higher temperature and was used, together with liquid heat capacity, as the reference baselines for the advanced thermal analysis of CYT. The PPMS and DSC/TMDSC methods are complementary methods for thermal analysis of cytisine. The PPMS method allowed determination of the equilibrium heat capacity in the solid state, which together with the equilibrium heat capacity in the liquid state allowed to analyze of the experimental apparent heat capacity of cytisine obtained based on DSC. The melting temperature and the total heat of fusion of crystalline material were established as 431.8 K (158.65 °C) and 26.5 kJ·mol^-1, respectively. The solid and liquid heat capacities and transition parameters of CYT were applied to calculate total enthalpies for fully amorphous and crystalline states. Analyses of DSC and X-ray confirmed the presence of the solid-solid transition linking with not so far described a polymorphism phenomenon of CYT. Based on the thermogravimetric analysis the temperature of degradation of CYT was determined as 460.5 K (187.35 °C). Also, a preliminary thermal analysis of the blends of cytisine and poly(lactic acid) as a new candidate for drug delivery system was presented.

Cytisine Therapy Improved Smoking Cessation in the Randomized Screening and Multiple Intervention on Lung Epidemics Lung Cancer Screening Trial

INTRODUCTION

Cytisine, a partial agonist-binding nicotine acetylcholine receptor, is a promising cessation intervention. We conducted a single-center, randomized, controlled trial (RCT) in Italy to assess the efficacy and tolerability of cytisine as a smoking cessation therapy among lung cancer screening participants.

METHODS

From July 2019 to March 2020, the Screening and Multiple Intervention on Lung Epidemics RCT enrolled 869 current heavy tobacco users in a low-dose computed tomography screening program, with a randomized comparison of pharmacologic intervention with cytisine plus counseling (N = 470) versus counseling alone (N = 399). The primary outcome was continuous smoking abstinence at 12 months, biochemically verified through carbon monoxide measurement.

RESULTS

At the 12-month follow-up, the quit rate was 32.1% (151 participants) in the intervention arm and 7.3% (29 participants) in the control arm. The adjusted OR of continuous abstinence was 7.2 (95% confidence interval: 4.6-11.2). Self-reported adverse events occurred more frequently in the intervention arm (399 events among 196 participants) than in the control arm (230 events among 133 participants, p < 0.01). The most common adverse events were gastrointestinal symptoms, comprising abdominal swelling, gastritis, and constipation.

CONCLUSIONS

The efficacy and safety observed in the Screening and Multiple Intervention on Lung Epidemics RCT indicate that cytisine, a very low-cost medication, is a useful treatment option for smoking cessation and a feasible strategy to improve low-dose computed tomography screening outcomes with a potential benefit for all-cause mortality.

Cytisine versus varenicline for smoking cessation in New Zealand indigenous Māori: a randomized controlled trial

AIM

To determine whether cytisine was at least as effective as varenicline in supporting smoking abstinence for ≥ 6 months in New Zealand indigenous Māori or whānau (extended-family) of Māori, given the high smoking prevalence in this population.

DESIGN

Pragmatic, open-label, randomized, community-based non-inferiority trial.

SETTING

Bay of Plenty, Tokoroa and Lakes District Health Board regions of New Zealand.

PARTICIPANTS

Adult daily smokers who identified as Māori or whānau of Māori, were motivated to quit in the next 2 weeks, were aged ≥ 18 years and were eligible for subsidized varenicline. Recruitment used multi-media advertising.

INTERVENTIONS

A total of 679 people were randomly assigned (1 : 1) to receive a prescription for 12 weeks of cytisine or varenicline, plus low-intensity cessation behavioural support from the prescribing doctor and community stop-smoking services or a research assistant. Day 5 of treatment was the designated quit date.

MEASUREMENTS

The primary outcome was carbon monoxide-verified continuous abstinence at 6 months, analysed as intention-to-treat (with multiple imputation for missing data). Secondary outcomes measured at 1, 3, 6 and 12 months post-quit date included: self-reported continuous abstinence, 7-day point prevalence abstinence, cigarettes per day, time to (re)lapse, adverse events, treatment adherence/compliance and acceptability, nicotine withdrawal/urge to smoke and health-care utilization/health-related quality of life.

FINDINGS

Verified continuous abstinence rates at 6 months post-quit date were 12.1% (41 of 337) for cytisine versus 7.9% (27 of 342) for varenicline [risk difference 4.29%, 95% confidence interval (CI) = -0.22 to 8.79; relative risk 1.55; 95% CI = 0.97-2.46]. Sensitivity analyses confirmed that the findings were robust. Self-reported adverse events over 6 months occurred significantly more frequently in the varenicline group (cytisine: 313 events in 111 participants; varenicline: 509 events in 138 participants, incidence rate ratio 0.56, 95% CI = 0.49-0.65, P < 0.001) compared with the cytisine group. Common adverse events were headache, nausea and difficulty sleeping.

CONCLUSION

A randomized controlled trial found that cytisine was at least as effective as varenicline at supporting smoking abstinence in New Zealand indigenous Māori or whānau (extended-family) of Māori, with significantly fewer adverse events.

More than smoking cessation aids

Cytisine, a natural bioactive compound that is mainly isolated from plants of the Leguminosae family (especially the seeds of Laburnum anagyroides), has been marketed in central and eastern Europe as an aid in the clinical management of smoking cessation for more than 50 years. Its main targets are neuronal nicotinic acetylcholine receptors (nAChRs), and pre-clinical studies have shown that its interactions with various nAChR subtypes located in different areas of the central and peripheral nervous systems are neuroprotective, have a wide range of biological effects on nicotine and alcohol addiction, regulate mood, food intake and motor activity, and influence the autonomic and cardiovascular systems. Its relatively rigid conformation makes it an attractive template for research of new derivatives. Recent studies of structurally modified cytisine have led to the development of new compounds and for some of them the biological activities are mediated by still unidentified targets other than nAChRs, whose mechanisms of action are still being investigated. The aim of this review is to describe and discuss: 1) the most recent pre-clinical results obtained with cytisine in the fields of neurological and non-neurological diseases; 2) the effects and possible mechanisms of action of the most recent cytisine derivatives; and 3) the main areas warranting further research.

Design of a randomized controlled trial of smoking cessation medications for alcohol reduction among HIV-positive heavy drinkers and daily smokers in St. Petersburg, Russia

BACKGROUND

HIV, heavy drinking, and smoking are all pro-inflammatory and increase risk for coronary heart disease (CHD). Interventions that reduce alcohol use, smoking, or both in HIV-positive people could lower inflammation, CHD and death risk. Varenicline and cytisine are proven therapies for smoking cessation and may also reduce alcohol consumption. The comparative efficacy of varenicline and cytisine to reduce alcohol consumption has not been tested, nor has their comparative effectiveness been reported for smoking.

OBJECTIVE

This paper describes the protocol of the Studying Partial agonists for Ethanol and Tobacco Elimination in Russians with HIV (St PETER HIV), a four-arm parallel-group randomized controlled trial comparing effects of varenicline, cytisine, and nicotine replacement therapy (NRT).

METHODS

The study is recruiting four hundred HIV-positive heavy drinking smokers interested in cutting down on alcohol and/or tobacco in St. Petersburg, Russia. Participants are randomly assigned to receive either active varenicline + NRT placebo, varenicline placebo + active NRT, active cytisine + NRT placebo, cytisine placebo + active NRT. All participants receive evidence-based counseling for alcohol and tobacco use, one active medication, and one placebo. Outcomes are: 1) % heavy drinking days in the past month (primary study outcome at three months) and alcohol craving; 2) cigarettes per day (primary smoking outcome at 3 months) and 7-day point prevalence abstinence and; 3) inflammation, CHD risk, and mortality risk.

CONCLUSION

St PETER HIV addresses the paucity of randomized controlled trial data to guide treatment of alcohol consumption and smoking in HIV-positive heavy drinking smokers.

Cytisine exerts anti-tumour effects on lung cancer cells by modulating reactive oxygen species-mediated signalling pathways

Cytisine is a natural product isolated from plants and is a member of the quinolizidine alkaloid family. This study aims to investigate the effect of cytisine in human lung cancer. Cell viability was determined using the CCK-8 assay, and the results showed that cytisine inhibited the growth of lung cancer cell lines. The apoptotic effects were evaluated using flow cytometry, and the results showed that cytisine induced mitochondrial-dependent apoptosis through loss of the mitochondrial membrane potential; increased expression of BAD, cleaved caspase-3, and cleaved-PARP; and decreased expression levels of Bcl-2, pro-caspase-3, and pro-PARP. In addition, cytisine caused G2/M phase cell cycle arrest that was associated with inhibiting the AKT signalling pathway. During apoptosis, cytisine increased the phosphorylation levels of JNK, p38, and I-κB, and decreased the phosphorylation levels of ERK, STAT3, and NF-κB. Furthermore, cytisine treatment led to the generation of ROS, and the NAC attenuated cytisine-induced apoptosis. In vivo, cytisine administration significantly inhibited the lung cancer cell xenograft tumorigenesis. In conclusion, cytisine plays a critical role in suppressing the carcinogenesis of lung cancer cells through cell cycle arrest and induction of mitochondria-mediated apoptosis, suggesting that it may be a promising candidate for the treatment of human lung cancer.

Spartium junceum L. poisoning in small ruminants

An outbreak of neurological disorders in a flock of 20 sheep coming from a rural farm in Civitella Roveto, Italy, occurred in winter 2015. All the animals showed tonic-clonic convulsions followed by muscle paralysis associated with dilated pupils, tremor, tachycardia, tachypnea and diarrhea. The presence of bundles of dry broom of Spartium junceum L. in the feed, eaten by the animals supported the hypothesis of plant intoxication. Two animals died after worsening of clinical signs. The anatomopathological findings and the laboratory results ruled out viral or bacterial infections or accidental exposure to other toxics. Phytochemical study showed the presence of large amount of cytisine, a nicotinic acetylcholine receptor agonist, in all parts of the plant eaten by the animals. Clinical and pathological findings, the complete remission of clinical signs after the exclusion of dry broom from the diet, together with the results of phytochemical analyses results corroborated the hypothesis of S. junceum L. intoxication.

Cytisine - From the Past to the Future

INTRODUCTION

Neuronal nicotinic acetylcholine receptors are ligand-gated ion channel receptors, distributed throughout central nervous system, as well as in peripheral ganglia and some non-neuronal cells. Cytisine, a qulinolizidine alkaloid, could be considered a high affinity ligand of those receptors. It is a partial agonist of β2*-containing receptors and a full agonist of α7 and β4*-containing receptors.

Current indication

At present, pharmacodynamic properties of cytisine are leveraged only in a few European countries where it is available as medicinal product (Desmoxan and Tabex) indicated in the pharmacotherapy of nicotine addiction. Cytisine mimics the influence of nicotine on α4β2* receptors, but with higher affinity and lower activity. It lowers rewarding and reinforcing effects of nicotine in smoking persons and reduces withdrawal symptoms and craving in quitting ones.

Potential indications

The results of non-clinical studies suggest that cytisine could affect ethanol consumption, has an antidepressant and neuroprotective effect and could be useful in reducing body mass and preventing weight gain. Although there is a lack of research on cytisine in the treatment of areca nuts usage, the preliminary data suggest its usefulness. The combination of cytisine and Trolox C was selected as a possible effective treatment for type 2 diabetes. Though these drugs alone are not effective, their theoretical usefulness was confirmed in animal models.

SUMMARY

Treatment with cytisine is an effective, cost-efficient, affordable and well tolerated nicotine addiction therapy. Potential new indications for cytisine include the treatment of alcoholism, areca nuts usage, Parkinson's disease, an autonomic-system failure. Further studies are necessary.

Cytisine versus varenicline for smoking cessation for Māori (the indigenous people of New Zealand) and their extended family: protocol for a randomized non-inferiority trial

BACKGROUND AND AIMS

Cytisine, a nicotinic acetylcholine receptor partial agonist (like varenicline) found in some plants, is a low-cost, effective smoking cessation medication that may appeal to Māori [the indigenous people of New Zealand (NZ)]. The RAUORA trial aims to determine the effectiveness, safety and cost-effectiveness of cytisine (Tabex^® ) versus varenicline (Champix^® ) for smoking cessation in Māori and the whānau (extended family) of Māori.

DESIGN

Pragmatic, community-based, open-label randomized non-inferiority trial.

SETTING

Lakes District Health Board region, NZ.

PARTICIPANTS

Daily smokers (n = 2140) who self-identify as Māori or whānau of Māori, and are: aged ≥ 18 years, motivated to quit smoking in the next 2 weeks, eligible for subsidized varenicline, able to provide verbal consent and have daily access to a mobile phone/internet. Recruitment uses multi-media advertising.

INTERVENTION AND COMPARATOR

Participants are randomized (1 : 1 ratio) to receive a prescription for 12 weeks of cytisine tablets [following the manufacturer's dosing regimen for 25 days, then one 1.5-mg tablet every 6 hours (two per day) until 12 weeks] or varenicline tablets (following the manufacturer's dosing regimen). Both groups receive brief stop-smoking advice from the prescribing doctor and withdrawal-orientated behavioural support via community-based stop-smoking counselling services (frequency, duration and mode of delivery tailored for participants) or a research assistant (six weekly 10-15-minute calls). Participants are advised to reduce their smoking over the first 4 days of treatment, with day 5 as their designated quit-date.

MEASUREMENTS

The primary outcome is carbon monoxide-verified continuous abstinence at 6 months post-quit date. Secondary outcomes at 1, 3, 6 and 12 months post-quit date include: self-reported continuous abstinence, 7-day point prevalence abstinence, cigarettes per day, time to (re)lapse, adverse events, treatment adherence/compliance, treatment acceptability, nicotine withdrawal/urge to smoke and health-care utilization/health-related quality of life.

COMMENTS

This trial compares cytisine and varenicline when used by the indigenous people of NZ and their extended family for smoking cessation.

Spectral and photophysical properties of cytisine in acetonitrile - Theory and experiment

Spectral and photophysical properties of (-)-cytisine that is used as a smoking cessation aid, and which derivatives are promising tools in a treatment of neurological diseases, were investigated in acetonitrile, non-specifically interacting solvent with a polarity similar to water. The two chair conformers of cytisine were found the most stable in the ground state S₀ and the lowest excited singlet state S₁(π,π*), wherein axial one was characterized by a significantly larger abundance, fluorescence lifetime 0.15 ns and fluorescence quantum yield 0.008. The S₁(π,π*) excited state of both cytisine conformers deactivated almost exclusively via internal conversion.

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).

Plasma concentrations of cytisine, a commercially available plant-based alkaloid, in healthy adult smokers taking recommended doses for smoking cessation

1. Cytisine is a plant alkaloid that is a partial agonist for the α₄β₂ -nAChRs and is used as an aid to smoking cessation. To date, there are no published data on cytisine concentrations in humans following multiple dosing. The aim of this study was to determine cytisine plasma concentrations after taking recommended doses for smoking cessation and to report on adverse effects. 2. Subjects (n=10) were instructed to follow the 25-day standard dosing regimen of cytisine. Blood was collected at 0, 2, 4, 8 and 10 hours on day 1 then on subsequent visits (days 2, 3, 4, 6, 13, 14, 17, 18, 21, 22, 25 and 26) to measure plasma cytisine concentrations. Plasma concentrations were determined using a validated LC-MS method. 3. Accumulation of cytisine was observed with repeated dosing of cytisine on day 1. Mean ± SEM plasma cytisine concentration measured at 10 hours was 50.8 ± 4.7 ng/mL. Due to dose tapering, there was an overall decrease in plasma cytisine concentration over the whole treatment period. 4. Overall, cytisine was well-tolerated and adverse effects reported were minor, indicating that cytisine is safe at concentrations measured in this study. This study is registered in the Australia and New Zealand Clinical Trials Registry (ACTRN12613000002785).

Cytisine inhibits the protective activity of various classical and novel antiepileptic drugs against 6 Hz-induced psychomotor seizures in mice

BACKGROUND

Cytisine (CYT) is a partial agonist of brain α4β2 nicotinic acetylcholine receptors widely used in Central/Eastern Europe for smoking cessation.

OBJECTIVES

This study evaluated the effect of CYT on the ability of classical and novel antiepileptic drugs to prevent seizures evoked by the 6-Hz test, a model of psychomotor seizures in mice thought as a model of drug-resistant seizures.

RESULTS

CYT administered intraperitoneally (i.p.) in a dose of 2 mg kg^-1 significantly inhibited the anticonvulsant activity of lacosamide, levetiracetam, and pregabalin, increasing their median effective doses 50 (ED₅₀) values from 6.88 to 10.52 mg kg^-1 (P < 0.05) for lacosamide, from 22.08 to 38.26 mg kg^-1 (P < 0.05) for levetiracetam, and from 40.48 to 64.61 mg kg^-1 (P < 0.01) for pregabalin, respectively. There were no significant changes in total brain concentrations of lacosamide, levetiracetam, and pregabalin following CYT i.p. administration. CYT administered in a dose of 2 mg kg^-1 failed to change the protective action of clobazam, clonazepam, phenobarbital, tiagabine, and valproate in the 6-Hz test. Neither CYT (2 mg kg^-1) alone nor its combination with the anticonvulsant drugs (at their ED₅₀ values from the 6-Hz test) affected motor coordination; skeletal muscular strength and long-term memory, as determined in the chimney; and grip strength and passive avoidance tests, respectively.

CONCLUSION

CYT-evoked alterations in the protection provided by some antiepileptic drugs against seizures can be of serious concern for epileptic smokers, who might demonstrate therapeutic failure to lacosamide, levetiracetam, and pregabalin, resulting in possible breakthrough seizure attacks.

Nicotinic Acetylcholine Receptors as Targets for Tobacco Cessation Therapeutics: Cutting-Edge Methodologies to Understand Receptor Assembly and Trafficking

Tobacco dependence is a chronic relapsing disorder and nicotine, the primary alkaloid in tobacco, acts at nicotinic receptors to stimulate dopamine release in brain, which is responsible for the reinforcing properties of nicotine, leading to addiction. Although the majority of tobacco users express the desire to quit, only a small percentage of those attempting to quit are successful using the currently available pharmacotherapies. Nicotine upregulates the number of specific nicotinic receptors on the neuronal cell surface. An increase in receptor trafficking or preferential stoichiometric assembly of receptor subunits involves changes in assembly, endoplasmic reticulum export, vesicle transport, decreased degradation, desensitization, enhanced maturation of functional pentamers, and pharmacological chaperoning. Understanding these changes on a mechanistic level is important to the development of nicotinic receptors as drug targets. For this reason, cutting-edge methodologies are being developed and employed to pinpoint distinct changes in localization, assembly, export, vesicle trafficking, and stoichiometry in order to further understand the physiology of these receptors and to evaluate the action of novel therapeutics for smoking cessation.

Cytisine, a Partial Agonist of α4β2 Nicotinic Acetylcholine Receptors, Reduced Unpredictable Chronic Mild Stress-Induced Depression-Like Behaviors

Cytisine (CYT), a partial agonist of α4β2-nicotinic receptors, has been used for antidepressant efficacy in several tests. Nicotinic receptors have been shown to be closely associated with depression. However, little is known about the effects of CYT on the depression. In the present study, a mouse model of depression, the unpredictable chronic mild stress (UCMS), was used to evaluate the activities of CYT. UCMS caused significant depression-like behaviors, as shown by the decrease of total distances in open field test, and the prolonged duration of immobility in tail suspension test and forced swimming test. Treatment with CYT for two weeks notably relieved the depression-like behaviors in the UCMS mice. Next, proteins related to depressive disorder in the brain region of hippocampus and amygdala were analyzed to elucidate the underlying mechanisms of CYT. CYT significantly reversed the decreases of 5-HT1A, BDNF, and mTOR levels in the hippocampus and amygdala. These results imply that CYT may act as a potential anti-depressant in the animals under chronic stress.

Differential expression of the beta4 neuronal nicotinic receptor subunit affects tolerance development and nicotinic binding sites following chronic nicotine treatment

The role of neuronal nicotinic acetylcholine receptors (nAChR) containing the β4 subunit in tolerance development and nicotinic binding site levels following chronic nicotine treatment was investigated. Mice differing in expression of the β4-nAChR subunit [wild-type (β4(++)), heterozygote (β4(+-)) and null mutant (β4(--))] were chronically treated for 10 days with nicotine (0, 0.5, 1.0, 2.0 or 4.0mg/kg/h) by constant intravenous infusion. Chronic nicotine treatment elicited dose-dependent tolerance development. β4(--) mice developed significantly more tolerance than either β4(++) or β4(+-) mice which was most evident following treatment with 4.0mg/kg/h nicotine. Subsets of [(125)I]-epibatidine binding were measured in several brain regions. Deletion of the β4 subunit had little effect on initial levels of cytisine-sensitive [(125)I]-epibatidine binding (primarily α4β2-nAChR sites) or their response (generally increased binding) to chronic nicotine treatment. In contrast, β4 gene-dose-dependent decreases in expression 5IA-85380 resistant [(125)I]-epibatidine binding sites (primarily β4*-nAChR) were observed. While these β4*-nAChR sites were generally resistant to regulation by chronic nicotine treatment, significant increases in binding were noted for habenula and hindbrain. Comparison of previously published tolerance development in β2(--) mice (less tolerance) to that of β4(--) mice (more tolerance) supports a differential role for these receptor subtypes in regulating tolerance following chronic nicotine treatment.

Wilson

Four alkaloids named hosieines A-D were isolated from the root and stem of Ormosia hosiei. Their flat structures were established by mass spectrometry and by a combination of NMR experiments. These molecules probably share a common biosynthetic origin with the lupin alkaloids but they differ in the formation of the last ring, being here part of a rare 2-azabicyclo[3.2.1]octane system. Their absolute configuration was determined by X-ray crystallography using CuKα radiation. As has been described for cytisine, they display a remarkable affinity towards neuronal nicotinic acetylcholine α4β2 receptor.

The 3,7-diazabicyclo[3.3.1]nonane scaffold for subtype selective nicotinic acetylcholine receptor ligands. Part 2: carboxamide derivatives with different spacer motifs

3,7-Diazabicyclo[3.3.1]nonane (bispidine) based nicotinic acetylcholine receptor (nAChR) ligands have been synthesized and evaluated for nAChRs interaction. Diverse spacer motifs were incorporated between the hydrogen bond acceptor (HBA) part and a variety of substituted (hetero)aryl moieties. Bispidine carboxamides bearing spacer motifs often showed high affinity in the low nanomolar range and selectivity for the α4β2(∗) nAChR. Compounds 15, 25, and 47 with Ki values of about 1 nM displayed the highest affinities for α4β2(∗) nAChR. All evaluated compounds are partial agonists or antagonists at α4β2(∗), with reduced or no effects on α3β4(∗) with the exception of compound 15 (agonist), and reduced or no effect at α7 and muscle subtypes.

The effects of noncontingent and self-administered cytisine on body weight and meal patterns in male Sprague-Dawley rats

RATIONALE

Increased appetite and weight gain after cessation are deterrents for quitting smoking. Pharmacotherapies that can reduce this weight gain in ex-smokers would be invaluable, and yet are not well studied in this context.

OBJECTIVE

To examine the effects of extended daily exposure to intravenous cytisine, an alpha4beta2 nAChR partial agonist used for smoking cessation in some European countries, on body weight and patterns of food intake in rats.

METHODS

In the first experiment, programmed infusions of cytisine were administered over 15 h per day. Food intake, meal patterns, and weight change were examined relative to a vehicle-infused group during treatment, and in a post-cytisine phase. The second experiment examined the effects of cytisine on food intake, meal patterns, and weight change when substituted for nicotine in a self-administration protocol. Rats self-administered nicotine and cytisine during alternating four day periods, and changes in body weight, drug infusions, and meal patterns were compared between drugs and during an extinction phase.

RESULTS

In the first experiment, cytisine-treated rats ate less and gained less weight than those that received the vehicle. This occurred primarily by a reduced frequency of meals. In the 12 day post-cytisine phase, animals maintained a lower body weight relative to controls throughout. In the second experiment, total pellet intake increased during cytisine substitution relative to nicotine and animals self-administered cytisine significantly less than nicotine. However, cytisine substitution maintained decreases in food intake and weight gain compared to baseline via decreases in total pellet intake and meal size.

CONCLUSION

Cytisine administration results in decreased weight gain and changes in meal patterns dependent upon mode and pattern of administration and a previous history of nicotine administration.

Partial nicotinic acetylcholine (alpha4beta2) agonists as promising new medications for smoking cessation

OBJECTIVE

To review the pharmacology, clinical efficacy and safety of partial agonists of alpha4beta2 nicotinic acetylcholine receptor.

DATA SOURCES

Primary literature and review articles were obtained via a PUBMED search (1988-August 2006) using the key terms smoking cessation, partial agonist alpha4beta2 nicotinic acetylcholine receptor, varenicline, cytisine and SSR591813. Additional studies and abstracts were identified from the bibliographies of reviewed literature.

STUDY SELECTION AND DATA EXTRACTION

Studies and review articles related to varenicline, cytisine and the partial agonist alpha4beta2 nicotinic acetylcholine receptor were reviewed.

DATA SYNTHESIS

Smoking is widely recognized as a serious health problem. Smoking cessation has major health benefits. According to the US Public Health Services, all patients attempting to quit smoking should be encouraged to use one or more effective pharmacotherapy. Currently, along with nicotine replacement therapy, bupropion, nortriptyline and clonidine, are the mainstay of pharmacotherapy. More than (3/4) of patients receiving treatment for smoking cessation return to smoking within the first year. Nicotine, through stimulating alpha4beta2 nAChR, releases dopamine in the reward pathway. Partial agonist of alpha4beta2 nAChR elicits moderate and sustained release of dopamine, which is countered during the cessation attempts; it simultaneously blocks the effects of nicotine by binding with alpha4beta2 receptors during smoking. Recently, varenicline, a partial agonist at alpha4beta2 nAChR, has been approved by the FDA (Food and Drug Administration) for smoking cessation.

CONCLUSION

Partial agonist alpha4beta2 nAChR appears to be a promising target in smoking cessation. Varenicline of this group is approved for treatment of smoking cessation by the FDA in May 2006.