Targeting organophosphorus compounds poisoning by novel quinuclidine-3 oximes: development of butyrylcholinesterase-based bioscavengers.

A library of 14 mono-oxime quinuclidinium-based compounds with alkyl or benzyl substituent were synthesized and characterized in vitro as potential antidotes for organophosphorus compounds (OP) poisoning treatment. We evaluated their potency for reversible inhibition and reactivation of OP inhibited human acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) and evaluated interactions by molecular docking studies. The reactivation was notable for both AChE and BChE inhibited by VX, cyclosarin, sarin and paraoxon, if quinuclidinium compounds contained the benzyl group attached to the quinuclidinium moiety. Out of all 14, oxime Q8 [4-bromobenzyl-3-(hydroxyimino)quinuclidinium bromide] was singled out as having the highest determined overall reactivation rate of approximately 20,000 M-1 min-1 for cyclosarin-inhibited BChE. Furthermore, this oxime in combination with BChE exhibited a capability to act as a bioscavenger of cyclosarin, degrading within 2 h up to 100-fold excess of cyclosarin concentration over the enzyme. Molecular modeling revealed that the position of the cyclohexyl moiety conjugated with the active site serine of BChE directs the favorable positioning of the quinuclidinium ring and the bromophenyl moiety of Q8, which makes phosphonylated-serine easily accessible for the nucleophilic displacement by the oxime group of Q8. This result presents a novel scaffold for the development of new BChE-based bioscavengers. Furthermore, a cytotoxic effect was not observed for Q8, which also makes it promising for further in vivo reactivation studies.

A ruthenium polypyridyl intercalator stalls DNA replication forks, radiosensitizes human cancer cells and is enhanced by Chk1 inhibition.

Ruthenium(II) polypyridyl complexes can intercalate DNA with high affinity and prevent cell proliferation; however, the direct impact of ruthenium-based intercalation on cellular DNA replication remains unknown. Here we show the multi-intercalator [Ru(dppz)2(PIP)](2+) (dppz = dipyridophenazine, PIP = 2-(phenyl)imidazo[4,5-f][1,10]phenanthroline) immediately stalls replication fork progression in HeLa human cervical cancer cells. In response to this replication blockade, the DNA damage response (DDR) cell signalling network is activated, with checkpoint kinase 1 (Chk1) activation indicating prolonged replication-associated DNA damage, and cell proliferation is inhibited by G1-S cell-cycle arrest. Co-incubation with a Chk1 inhibitor achieves synergistic apoptosis in cancer cells, with a significant increase in phospho(Ser139) histone H2AX (γ-H2AX) levels and foci indicating increased conversion of stalled replication forks to double-strand breaks (DSBs). Normal human epithelial cells remain unaffected by this concurrent treatment. Furthermore, pre-treatment of HeLa cells with [Ru(dppz)2(PIP)](2+) before external beam ionising radiation results in a supra-additive decrease in cell survival accompanied by increased γ-H2AX expression, indicating the compound functions as a radiosensitizer. Together, these results indicate ruthenium-based intercalation can block replication fork progression and demonstrate how these DNA-binding agents may be combined with DDR inhibitors or ionising radiation to achieve more efficient cancer cell killing.

Ranking the Binding Energies of p53 Mutant Activators and Their ADMET Properties.

The guardian of the genome, p53, is the most mutated protein found in all cancer cells. Restoration of wild-type activity to mutant p53 offers promise to eradicate cancer cells using novel pharmacological agents. Several molecules have already been found to activate mutant p53. While the exact mechanism of action of these compounds has not been fully understood, a transiently open pocket has been identified in some mutants. In our study, we docked twelve known activators to p53 into the open pocket to further understand their mechanism of action and rank the best binders. In addition, we predicted the absorption, distribution, metabolism, excretion and toxicity properties of these compounds to assess their pharmaceutical usefulness. Our studies showed that alkylating ligands do not all bind at the same position, probably due to their varying sizes. In addition, we found that non-alkylating ligands are capable of binding at the same pocket and directly interacting with Cys124. The comparison of the different ligands demonstrates that stictic acid has a great potential as a p53 activator in terms of less adverse effects although it has poorer pharmacokinetic properties.

Gastrointestinal toxicity after vincristine or cyclophosphamide administered with or without maropitant in dogs: a prospective randomised controlled study.

OBJECTIVES: To assess the prevalence of gastrointestinal toxicity in dogs receiving chemotherapy with vincristine and cyclophosphamide and the efficacy of maropitant citrate (Cerenia™, Zoetis) in reducing these events. METHODS: Dogs receiving chemotherapy with cyclophosphamide or vincristine were randomised to either receive maropitant or not in the period immediately after treatment and for 4 days afterwards. Owners completed a diary of adverse events following treatment. RESULTS: Adverse events occurred in 40/58 (69%) dogs in the vincristine group. Most of these adverse events were mild and included: lethargy (62%), appetite loss (43%), diarrhoea (34%) and vomiting (24%). Adverse events occurred in 34/42 (81%) dogs treated with cyclophosphamide. Most of these adverse events were mild and included: lethargy (62%), diarrhoea (36%), appetite loss (36%) and vomiting (21%). There was no difference in total clinical score, vomiting, diarrhoea, appetite loss or lethargy score between dogs treated with maropitant and non-treated dogs in either the vincristine or cyclophosphamide groups. CLINICAL SIGNIFICANCE: Chemotherapy-related side effects are frequent but usually mild in dogs receiving vincristine or cyclophosphamide. Prophylactic administration of maropitant does not reduce the frequency of adverse events and maropitant should be administered only as required for individual cases.

Fertility and early embryonic development toxicity of penequine hydrochloride in mice.

Penequine hydrochloride, a novel anticholinergic agent, was developed as an effective treatment for organophosphorus intoxication. The potential for penequine hydrochloride to induce fertility and early embryonic developmental toxicity was evaluated in AMMS-1 mice. Totally 320 healthy, sexual mature and nulliparous AMMS-1 mice were orally treated with the chemical in drinking water at dose levels of 0, 2.5, 12.5 and 62.5 mg/L from 60 days before cohabitation to successful copulation in 160 males and from two weeks before cohabitation to GD 6 in 160 females, respectively. All the parental mice were observed for body weights, water consumption and any abnormal change during treatment period. Caesarean sections were carried out on day 14 of pregnancy in half assumed-pregnant females, and all the intrauterine data were recorded. Pups naturally delivered by the other half females were weighed, and examined for viability, sex ratio and gross malformations. About 7 days after cohabitation period, all the paternal males were examined for epididymal and testicular weights, sperm number and sperm motility. The decreases in fertility/fecundity indices and maternal weight gain were found at high-dose level in both caesarean sections and natural delivery observations. The primary developmental toxicity of the chemical included decreases in relative organ (epididymis, liver and lung) weights at mid- and high-dose levels in pups on postnatal day (PND) 35. The cause of both the decreased fertility/fecundity indices in F0 males and the decreased relative organ weights in F1 pups are not well known but are presently under investigation. Under the experimental conditions, penequine hydrochloride did not produce any adverse effects (expect the decreases in certain relative organ weights) up to and including 12.5 mg/L (2.53 mg/kg/day in males and 2.19 mg/kg/day in females) corresponding to approximately 72 times above anticipated dosage in human.

Embryo-fetal development toxicity of prenatal exposure to penequine hydrochloride intramuscularly in rats.

The potential for penequine hydrochloride to induce maternal and embryo-fetal developmental toxicity was evaluated in Wistar rats. The drug was administered intramuscularly (i.m.) at dose levels of 0, 10, 30 or 50mg/kg/day to groups of pregnant rats from day 6 to 15 of gestation. All dams were observed for maternal body weights, food consumption and any abnormal change, and subjected to caesarean-section on gestation day (GD) 20; all fetuses obtained from caesarean-section were assessed by external inspection, visceral and skeletal examinations. In the 50mg/kg/day group, maternal toxicity included an increase in the incidence of abnormal clinical signs, and decrease in the body weight and body weight gain. Developmental toxicity included an increase in the postimplantation loss, a decrease in the litter size, and a reduction in the gravid uterus weight. In addition, a statistically non-significant increase in the incidence of fetal external, visceral, and skeletal alterations including malformations and variations were seen in high-dose group. There were no treatment-related findings in maternal clinical and intrauterine observations, and fetal morphological examinations in mid-, low-dose and control groups. Thus, under the conditions of this study, the no-observed-adverse-effect-level (NOAEL) and lowest-observed-adverse-effect-level (LOAEL) of penequine hydrochloride for both maternal and embryo-fetal toxicity in the Wistar rats were considered to be 30mg/kg/day and 50mg/kg/day, which are approximately 900 and 1500 above the therapeutic dosage, respectively.

The pre- and post-natal toxicity of penequine hydrochloride in mice.

Penequine hydrochloride, a novel anticholinergic agent, was developed as an effective treatment for organophosphorus intoxication (e.g., soman poisoning). The current study was performed to assess the potential pre- and post-natal toxicity of penequine hydrochloride in mice. Approximately 120 timed-pregnant mice were assigned to four dose groups (n=30 per group). Dams were exposed orally to 0, 2.5, 12.5, 62.5 mg/L penequine hydrochloride in drinking water from gestation day 6 to lactation day 21. The F1 generation mice, which were not exposed directly to penequine hydrochloride as pups or as adults, were bred to produce F2 generation fetuses for the fertility test of the F1 population. Various pre- and post-natal measurements, including neurobehavioral tests, were performed with the F0 and F1 mice. Among the significant findings were decreases in water consumption, viability, organ weights and delay of physical landmarks in 62.5 mg/L groups. With the exception of treatment-unrelated abnormality in surface righting reflex in the F1 generation, penequine hydrochloride did not produce any adverse effects at doses up to and including 12.5 mg/L (equal to 2.5 mg/kg/day in mice) that were at least 75 times of human therapeutic dosage.

Combinations of neurokinin receptor antagonists reduce visceral hyperalgesia.

The effect of selective neurokinin receptor (NKR) antagonists for the NK1R (SR140,333), NK2R (SR48,968), and NK3R (SR142,801) on the visceromotor response to noxious colorectal distension (CRD) was examined. NKR antagonists or vehicle were given intrathecally (i.th.) to rats made hyperalgesic by intracolonic instillation of zymosan or after intracolonic instillation of saline (control). Given alone, the NK1R (up to 3 microg of SR140,333) and NK2R (up to 60 microg of SR48,968) antagonists tested failed to significantly affect responses to the noxious visceral stimulus. However, coadministration of 3 microg of SR140,333 and 60 microg of SR48,968 (both i.th.) significantly reduced responses to noxious CRD (p < 0.05 versus vehicle). The NK3R antagonist (60 microg of SR142,801) significantly reduced responses to noxious CRD when given alone to either hyperalgesic (zymosan-treated) or normal (saline-treated) rats (p < 0.05 versus vehicle for both groups). Responses of rats receiving the NK3R antagonist in combination with either the NK1R or the NK2R antagonist were not different from rats receiving the NK3R antagonist alone. These results suggest that activation of spinal NK1R and NK2R, presumably by their endogenous ligands (substance P and neurokinin A), maintain visceral hyperalgesia and support the notion that activation of NK3R (presumably by neurokinin B) is pronociceptive.

The comparative genotoxicological study of new local anesthetics, 3-(2-alkoxyphenylcarbamoyloxy)quinuclidium chlorides, on Salmonella typhimurium, Saccharromyces cerevisiae, Vicia faba, Hordeum vulgare and Drosophila melanogaster.

Potential gentoxicity of five new local anesthetics, derivatives of phenylcarbamic acid differing in the length of the alkyl chain of the alkoxy substituent, was studied on five test systems. There was a direct relationship with increased toxic effect in bacteria and yeast as a function of the elongation of the alkyl chain of the alkoxy substituents of the phenylcarbamic acid esters. On the other hand, no structure-toxicity relationship was found after application of 3-(2-alkoxyphenylcarbamoyloxy)-quinuclidium chlorides on plants and Drosophila. All anesthetics were nonmutagenic to Salmonella typhimurium strains TA97, TA98, TA100, and TA102 in the absence and in the presence of S9 mix. Pentyloxy and heptyloxy derivatives increased rates of genetic changes in Saccharomyces cerevisiae, mainly revertants at the isoleucine locus. Pentyloxy and hexyloxy derivatives increased the frequency of chromosome aberrations in Vicia faba root-tip meristems. No chlorophyll mutations were detected after treatment of Hordeum vulgare with pentyloxy, hexyloxy and heptyloxy derivatives. No sex-linked recessive lethals were scored in Drosphila melanogaster males. The rates of aneuploids induced in their germ cells were significantly increased after treatment with butoxy and octyloxy derivatives. However, the local toxic and genotoxic effects of test anesthetics on the microorganisms of the anesthetized tissues may be of some importance. In particular, the genotoxic effect exhibited in fungi by the heptyloxy derivative, a potent local anesthetic, was remarkable.

Salivary secretion and histopathological effects after single administration of the muscarinic agonist SNI-2011 in MRL/lpr mice.

The salivary secretion and the histopathological effects after administration of a single dose of cis-2-methylspiro (1,3-oxathiolane-5,3') quinuclidine hydrochloride hemihydrate (SNI-2011) were monitored in adult, male and female MRL/lpr mice, C57BL/6J mice and ICR mice. SNI-2011 (1-10 mg/kg, i.p.), dose-dependently increased the secretion of saliva in MRL/lpr mice. The flow rate decreased gradually over the course of 60 min. The total volume of saliva, secreted in response to SNI-2011, was significantly higher in male than in female MRL/lpr mice, but there was no significant difference in this parameter between male and female C57BL/6J and ICR mice. Degeneration, apparent as atrophy and necrosis of serous cells in MRL/lpr mice, was reversed by treatment with SNI-2011 (3 and 6 mg/kg). These results suggest that SNI-2011 could be useful in the treatment of xerostomia in patients with Sjögren's syndrome.

Cholinolytic activity of 3-hydroxyquinuclidyl-1-phenyl-1-cyclohexyl-1-carboxylate hydrochloride (ANC-821).

Compound ANC-821 antagonized the action of acetylcholine on the rat ileum, counteracted oxotremorine-induced salivation and convulsions and pilocarpine-induced salivation in mice and abolished acetylcholine-induced bronchospasm in rats. This shows that ANC-821 possesses cholinolytic properties, but it is much less potent in this respect than atropine.

[Subacute toxicity and recovery tests of mequitazine in beagle dogs (author's transl)].

Subacute toxicity and recovery tests of Mequitazine, a new phenothiazine ;type anti-histamine agent, were carried out using each 20 male and female dogs. The drugs was administered orally in doses of 0, 1, 5 and 25 mg/kg day for 14 weeks. Recovery test was carried out for following 4 weeks. As a result, transient decrease of the body weights and somnolences were observed in both male and female dogs given 25 mg/kg. In a female dog given 25 mg/kg, extrapyramidal reaction accompanied with tremors and muscle stiffenings was observed. But no dead animals were observed throughout experimental period. Vomitings, mydriasis and loss of appetite were observed with the dose-responsiveness, but these symptoms were reduced after 1-2 weeks administration. No abnormal changes were observed in hematological, serum biochemical, and other examinations. In histopathological examinations, slights changes were observed in liver, kidneys, mesenteric lymph nodes, palpebra and conjunctival membrane. But these changes were reversible in recovery period. From these results, it was suggested that the maximum non-effective and maximum safety doses were 1 mg/kg/day and 5 mg/kg/day, respectively.

[Mutagenicity tests on mequitazine (author's transl)].

Microbial backward mutation test, Ames Salmonella/microsome plate assay, on six bacterial strains (Salmonella typhimurium TA 98, 100, 1535, 1537, 1538 and E. coli WP 2uvrA) and micronucleus test in mice were carried out to detect mutagenic activity of mequitazine. Mequitazine caused no increases of revertants at doses from 1 to 1000 microgram/plate in every bacterial strains irrespective of metabolic activation. Similarly, mequitazine induced no significant increases of micronucleated polychromatic erythrocytes in mice over the control level at doses from 0.12 (clinical dose) to 48 mg/kg (approx. LD 50). From above results, we concluded that mequitazine has no mutagenic activity per se.

A preclinical study of EO-122, a new lidocaine-like antiarrhythmic drug.

The 2,6-dimethylanilide of quinuclidine-3-carboxylic acid hydrochloride (EO-122), a new structural analog of lidocaine, has been shown to possess potent antiarrhythmic activity in experimentally induced arrhythmias in animals. Restoration of normal sinus rhythm and suppression of ouabain-induced arrhythmia in cats and dogs, and of coronary occlusion-induced arrhythmia in dogs, followed a single IV injection of 1--3 mg/kg, with an onset of 2 minutes and a duration of 20--240 minutes. Occlusion-induced arrhythmia was likewise suppressed after an oral dose of 10--20 mg/kg, with an onset of 11--65 minutes and a duration of 25--120 minutes. Under similar conditions, lidocaine was either totally ineffective or of ultra-short duration. The bioavailability of EO0122 by the oral route exceeded 80% of the oral dose. Therapeutic blood concentrations were in the range 0.5--7 microgram/ml. At about 5 microgram/ml there was a slight depression of cardiac function in the anesthetized cat, but not in the conscious dog. In cats, complete A-V block occurred at concentrations of 60--70 microgram/ml. The IV LD50 in mice was 22 mg/kg, and in rabbits 8.5 mg/kg. No overt signs of neurotoxicity could be observed at any dose of EO-122. The pharmacokinetic profile of the drug fits a two-compartment open model, with t1/2 congruent to 150 min and Vd (SS) congruent to 1.5 l/kg.