Nicotine and Cytisine Embryotoxicity in the Experimental Zebrafish Model.

Tobacco smoking is one of the most serious health problems. Potentially lethal effects of nicotine for adults can occur with as little as 30 to 60 mg, although severe symptoms can arise with lower doses. Furthermore, the route of administration also influences the toxicity. Cytisine is one of the most popular medications in nicotinism treatment. Like nicotine, cytisine is a plant alkaloid, signaling through nicotinic acetylcholine receptors. Our study evaluated the effects of cytisine in nicotine-induced embryotoxic effects using zebrafish larvae. We examined the teratogenicity of nicotine and cytisine alone or in combination. Nicotine increased mortality and delayed hatching of zebrafish larvae in a dose-dependent manner. Cytisine did not affect mortality in a wide range of concentrations, and hatching delay was observed only at the highest concentrations, above 2 mM. Administering compounds together partially reduced the adverse teratogenic effect induced by nicotine alone. The protective effect of cytisine against the nicotine effect, observed in zebrafish, will contribute to future studies or treatments related to nicotine addiction or prenatal nicotine exposure in humans.

Cytisine and cytisine derivatives. 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.

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 α4ß2 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.

Polyamine modification by acrolein exclusively produces 1,5-diazacyclooctanes: a previously unrecognized mechanism for acrolein-mediated oxidative stress.

Acrolein, a toxic unsaturated aldehyde generated as a result of oxidative stress, readily reacts with a variety of nucleophilic biomolecules. Polyamines, which produced acrolein in the presence of amine oxidase, were then found to react with acrolein to produce 1,5-diazacyclooctane, a previously unrecognized but significant downstream product of oxidative stress. Although diazacyclooctane formation effectively neutralized acrolein toxicity, the diazacyclooctane hydrogel produced through a sequential diazacyclooctane polymerization reaction was highly cytotoxic. This study suggests that diazacyclooctane formation is involved in the mechanism underlying acrolein-mediated oxidative stress.

Primary constituents of blue cohosh: quantification in dietary supplements and potential for toxicity.

Dietary supplements containing dried roots or extracts of the roots and/or rhizomes of blue cohosh (Caulophyllum thalictroides) are widely available. This botanical has a long history of use by Native Americans and its use continues to the present day. The primary constituents of blue cohosh are its alkaloids and saponins. The structures of the alkaloids magnoflorine, baptifoline, anagyrine, and N-methylcytisine have been known for many years. The last 10 years have seen a great increase in isolation and identification of the large number of saponins present in blue cohosh. Important developments in nuclear magnetic resonance techniques have contributed substantially to the increase in elucidation of the structures of the complex saponins. Several authors have described quantitative methods for both the alkaloids and saponins in blue cohosh. Such methods have made it possible to quantify these constituents in dietary supplements containing this botanical ingredient. Concentrations of both alkaloids and saponins vary substantially in dietary supplements of blue cohosh. The nicotinic alkaloid, N-methylcytisine, a potent toxicant, has been found in all dietary supplements of blue cohosh analyzed. The teratogenic alkaloid anagyrine has been found in some but not all dietary supplements.

Cytotoxicity of new pyrazino[1,2-b]isoquinoline and 6,15-iminoisoquino[3,2-b]3-benzazocine compounds.

Looking for optimised analogues of compound 2 that might be useful in colon cancer therapy, we here explore the in vitro cytotoxicity against MDA-MB 231 human breast carcinoma, A-549 human lung carcinoma and HT-29 human colon carcinoma cell lines of several analogues and derivatives. The effect of the R2-substituent and/or the introduction of an arylmethyl side-chain at C-3, as well as the presence of a double bond in the skeleton or a methoxy group at C-1 have been investigated. New 6,15-iminoisoquino[3,2-b]3-benzazocine compounds, related to the saframycin family, in which the C(7)-N(8)-C(9)-substructure contains a lactam function, a fused oxazolidine or an aminonitrile function were also studied, and many of them showed low micromolar GI50 values.

Cytisine for smoking cessation: a research agenda.

Cytisine has a molecular structure somewhat similar to that of nicotine and varenicline. The concept for the new smoking cessation drug varenicline was based partly on cytisine. Like varenicline, cytisine is a partial agonist of nicotinic acetylcholine receptors, with high affinity for alpha4beta2 receptors. Cytisine has been used since the 1960s as a smoking cessation drug in Eastern and Central Europe, but has remained largely unnoticed elsewhere. Three placebo-controlled trials, conducted in East and West Germany in the 1960s and 1970s, suggest that cytisine, even with minimal behavioural support, may be effective in aiding smoking cessation. Cytisine tablets are very inexpensive to produce and could be a more affordable treatment than nicotine replacement, bupropion and varenicline. There is however a dearth of scientific research on the properties of cytisine, including safety, abuse liability and efficacy. This paper seeks to identify research priorities for molecular, animal and clinical studies. In particular, new studies are necessary to define the nicotinic receptor interaction profile of cytisine, to establish its pharmacokinetics and pharmacodynamics in humans, to determine whether animals self-administer cytisine, and to ascertain whether cytisine is safe and effective as a smoking cessation drug. Potentially, this research effort, contributing to wider use of an inexpensive drug, could save many lives.

Reduction of octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine by zerovalent iron: product distribution.

RDX (hexahydro-1,3,5-trinitro-1,3,5-triazine) and HMX (octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine) are cyclic nitramines ((CH2NNO2)n; n = 3 or 4, respectively) widely used as energetic chemicals. Their extensive use led to wide environmental contamination. In contrast to RDX, HMX tends to accumulate in soils due to its unique recalcitrance. In the present study, we investigated the potential of zerovalent iron (ZVI) to transform HMX under anoxic conditions. HMX underwent a rapid transformation when added in well-mixed anoxic ZVI-H2O batch systems to ultimately produce formaldehyde (HCHO), ammonium (NH4+), hydrazine (NH2NH2), and nitrous oxide (N2O). Time course experiments showed that the mechanism of HMX transformation occurred through at least two initial reactions. One reaction involved the sequential reduction of N-NO2 groups to the five nitroso products (1NO-HMX, cis-2NO-HMX, trans-2NO-HMX, 3NO-HMX, and 4NO-HMX). Another implied ring cleavage from either HMX or 1NO-HMX as demonstrated by the observation of methylenedinitramine (NH(NO2)CH2NH(NO2)) and another intermediate that was tentatively identified as (NH(NO2)CH2N(NO)CH2NH-(NO2)) or its isomer (NH(NO)CH2N(NO2)CH2NH(NO2)). This is the first study that demonstrates transformation of HMX by ZVI to significant amounts of NH2NH2 and HCHO. Both toxic products seemed to persist under reductive conditions, thereby suggesting that the ultimate fate of these chemicals, particularly hydrazine, should be understood prior to using zerovalent iron to remediate cyclic nitramines.

In vivo autoradiography and nitrosoheptamethyleneimine carcinogenesis in hamsters.

Quantitative autoradiograms were made, in vivo, in European hamsters with the use of [14C]nitrosoheptamethyleneimine (260 muCi/animal; time between administration of nitrosamine and killing of animals, 6 hr). In this species, the lung is the principal target, and radioactivity was found in the Clara cells of the bronchial epithelium and in the nitrosoheptamethyleneimine-induced tumors which derive from these cells. Tumors are not induced in the liver, which can metabolize this compound, and labeling is found principally in the cytoplasm, whereas in the target cells there is a high degree of labeling in both the cytoplasm and the nuclei.

Carcinogenicity of subcutaneously injected N-nitrosoheptamethyleneimine in European hamsters.

Male and female European hamsters (45 of each sex) recieved sc injections once weekly for life of N-nitrosoheptamethyleneimine (NHMI) at one-fifth the median lethal dose (LD50) (females: 44 mg/kg body wt; males: 66 mg/kg body wt), one-tenth the LD50 (females: 22 mg/kg body wt; males: 33 mg/kg body wt), or one-twentieth the LD50 (females: 11 mg/kg body wt; males: 16.5 mg/kg body wt). Survival times for both males and females were dependent on the dose of NHMI. Pulmonary neoplasms were induced in almost all the treated animals. They were histologically diagnosed as adenocarcinomas, squamous cell carcinomas, and mixed cell carcinomas. In addition, nasal cavity tumors developed in all hamsters of all treatment groups; these were papillomas, squamous cell carcinomas, and a few adenocarcinomas. Only 1 tumor of the larynx and 1 tumor of the trachea were observed. Several papillomas and a few carcinomas were also detected in the forestomach. The results were discussed with reference to previous findings in rats and Syrian golden hamsters.

Some studies on cytisine and its methylated derivatives.

1. In mice cytisine hydrochloride is less toxic intravenously than nicotine hydrogen tartrate, but more toxic by intraperitoneal or oral administration. Compared with cytisine, caulophylline hydrogen iodide is one-fifth to one-tenth as toxic and caulophylline methiodide is less than one-thirtieth as toxic.2. The surprising low oral toxicity of cytisine and nicotine may be ascribed to the method of administration; if the drug is placed directly in the stomach there is no possibility of absorption through buccal mucous membranes.3. The peripheral effects of nicotine, cytisine and caulophylline are similar, though on some preparations those of nicotine last longer. In most tests cytisine is active in doses from a quarter to three-quarters of those of nicotine, caulophylline in doses from 10 to 20 times those of cytisine. Caulophylline methiodide is virtually inactive.4. Cytisine and caulophylline may differ from nicotine in their central effects.5. Cytisine and caulophylline are active as the cations. The pKa of cytisine is 7.92 and that of caulophylline is 7.04; the difference accounts, in part, for the weaker activity of caulophylline. The caulophylline ion is generally one-sixth to one-third as active as the cytisine ion.6. The introduction of the second methyl group to form the quaternary salt does not appear to cause a dramatic change in the conformation of the molecule. Caulophylline methiodide appears to be feebly active because it has feeble affinity.