PIFA-mediated ethoxyiodination of enamides with potassium iodide.

The regioselective ethoxyiodination of enamides was developed using PIFA in combination with potassium iodide in ethanol. The reaction proceeds regioselectively with excellent yields and diastereoselectivities, providing valuable synthons for further functionalisations. Control experiments were conducted, indicating that the transformation occurs through an ionic manifold involving an in situ generated hypoiodite species.

The expression and function of Ca(2+)-sensing receptors in rat mesenteric artery; comparative studies using a model of type II diabetes.

BACKGROUND AND PURPOSE: The extracellular calcium-sensing receptor (CaR) in vascular endothelial cells activates endothelial intermediate-conductance, calcium-sensitive K(+) channels (IK(Ca)) indirectly leading to myocyte hyperpolarization. We determined whether CaR expression and function was modified in a rat model of type II diabetes. EXPERIMENTAL APPROACH: Pressure myography, western blotting, sharp microelectrode and K(+)-selective electrode recordings were used to investigate the functional expression of the CaR and IK(Ca) in rat mesenteric arteries. KEY RESULTS: Myocyte hyperpolarization to the CaR activator calindol was inhibited by Calhex 231. U46619-induced vessel contraction elevated the extracellular [K(+)] around the myocytes, and inhibition of this 'K(+) cloud' by iberiotoxin was needed to reveal calindol-induced vasodilatations. These were antagonized by Calhex 231 and significantly smaller in Zucker diabetic fatty rat (ZDF) vessels than in Zucker lean (ZL) controls. Myocyte hyperpolarizations to calindol were also smaller in ZDF than in ZL arteries. In ZDF vessels, endothelial cell CaR protein expression was reduced; IK(Ca) expression was also diminished, but IK(Ca)-generated hyperpolarizations mediated by 1-EBIO were unaffected. CONCLUSIONS AND IMPLICATIONS: The reduced CaR-mediated hyperpolarizing and vasodilator responses in ZDF arteries result from a decrease in CaR expression, rather than from a modification of IK(Ca) channels. Detection of CaR-mediated vasodilatation required the presence of iberiotoxin, suggesting a CaR contribution to vascular diameter, that is, inversely related to the degree of vasoconstriction. Compromise of the CaR pathway would favour the long-term development of a higher basal vascular tone and could contribute to the vascular complications associated with type II diabetes.

Human Papillomavirus and Head and Neck Cancer: Psychosocial Impact in Patients and Knowledge of the Link - A Systematic Review.

Head and neck cancer (HNC) currently affects approximately 11 200 people in the UK, with an increasing proportion known to be caused by the human papillomavirus (HPV). We undertook a systematic review of studies measuring the psychosocial impact of HPV-related HNC and also studies measuring knowledge about the link between HPV and HNC among different populations. Searches were conducted on MEDLINE, Embase, PsycINFO, CINAHL Plus and Web of Science, with reference and forward citation searches also carried out on included studies. Studies were selected if they (i) were original peer-reviewed research (qualitative or quantitative), (ii) mentioned HPV and HNC, (iii) measured an aspect of the psychosocial impact of the diagnosis of HPV-related HNC as the dependent variable and/or (iv) measured knowledge of the association between HPV and HNC. In total, 51 papers met the inclusion criteria; 10 measuring psychosocial aspects and 41 measuring knowledge of the link between HPV and HNC. Quality of life in those with HPV-positive HNC was found to be higher, lower or equivalent to those with HPV-negative HNC. Longitudinal studies found quality of life in patients was at its lowest 2-3 months after diagnosis and some studies found quality of life almost returned to baseline levels after 12 months. Knowledge of the link between HPV and HNC was measured among different populations, with the lowest knowledge in the general population and highest in medical and dental professionals. Due to the limited studies carried out with patients measuring the psychosocial impact of a diagnosis of HPV-positive HNC, future work is needed with the partners of HPV-positive HNC patients and health professionals caring for these patients. The limited knowledge of the association between HPV and HNC among the general population also indicates the need for research to explore the information that these populations are receiving.

Anticonvulsant activity of the diaryltriazine, LY81067: studies using electroencephalographic recording and positron emission tomography.

It is reported that LY81067, a new diaryltriazine, possesses anticonvulsant properties against grand mal status epilepticus induced by intravenous administration of picrotoxin binding site ligands (Ro 5-4864 and pentylenetetrazole) in the baboon. Intravenous administration of LY81067 during the seizures blocked grand mal type electroencephalographic (EEG) paroxysmal discharges and led to a long electrical silence, progressively replaced by spike-and-wave discharges of low frequency (2 c/sec). A transient blocking effect was also observed when LY81067 was injected during grand mal status epilepticus induced by the benzodiazepine inverse agonist methyl beta-carboline-3-carboxylate; however, the long electrical silence observed after administration of LY81067 was rapidly followed by grand mal type paroxysmal discharges in the EEG, which could be stopped by a subsequent injection of Ro 15-1788. However, LY81067 also displayed intrinsic epileptogenic properties. Administration of this drug alone led to the appearance of rhythmic EEG (2-3 c/sec) associated with myoclonia. Concomitantly with the EEG studies, interactions of all these drugs with benzodiazepine receptors were observed in vivo using [11C]Ro 15-1788 as radioligand and positron emission tomography (PET) as a non-invasive technique to measure the binding of the [11C]benzodiazepine antagonist in brain, in vivo. The [11C]Ro 15-1788 bound in the brain could not be displaced by the administration of LY81067 but rather, the [11C]antagonist binding in the brain was somewhat enhanced. Administration of pentylenetetrazole or Ro 5-4864 decreased the rate of wash-out of the radioligand. This fast effect of these two convulsant drugs was partially inhibited by the subsequent administration of LY81067. The concomitant blocking of the grand mal status epilepticus was also observed.(ABSTRACT TRUNCATED AT 250 WORDS)

Hybrid molecules: growth inhibition of Leishmania donovani promastigotes by thiosemicarbazones of 3-carboxy-beta-carbolines.

The thiosemicarbazones of beta-carboline-3-carboxaldehyde (compound 2) and 3-acetyl-beta-carboline (compound 3) were found to effectively inhibit the in vitro growth of the promastigote form of Leishmania donovani, 50% inhibition being obtained at concentrations of 5.0 and 2.5 microM, respectively, while irreversible growth inhibition was achieved at 40 (compound 2) and 17.5 microM (compound 3). The thiosemicarbazone of pyridine-2-carboxyaldehyde (compound 4) was considerably less active while both methyl beta-carboline-3-carboxylate (compound 1) and the thiosemicarbazone of ethyl 5-formyl-6-azaindole-2-carboxylate (compound 5) were inactive at the highest concentrations tested. At concentrations provoking approximately 50% growth inhibition of promastigotes, compound 2 was observed to preferentially block DNA rather than RNA synthesis, but for compound 3, the reverse was true. Compound 3, the most active analogue studied, may thus act, at least partially, via a novel, though as yet unelucidated, mechanism.

Synthesis of beta-carboline-benzodiazepine hybrid molecules: use of the known structural requirements for benzodiazepine and beta-carboline binding in designing a novel, high-affinity ligand for the benzodiazepine receptor.

Hybrid molecules incorporating pharmacologically important structural features of both 3-carboxy-beta-carbolines and 1,4-benzodiazepines were synthesized, and their affinities for the benzodiazepine receptor were determined in vitro. One of these hybrids, 8,14-dioxo-13,14-dihydro-8H-indolo[3',2':4,5]pyrido[2,1-c] [1,4]benzodiazepine (13), demonstrated high affinity for the receptor, displacing both benzodiazepines (IC50 = 23 nM) and beta-carbolines (IC50 = 47 nM) from their binding sites. Of the compounds synthesized, 13 also most closely satisfied the structural requirements that generally ensure a high affinity of both beta-carbolines and benzodiazepines for the receptor (e.g., aromaticity of the beta-carboline, presence of a carbonyl at C-3 of the beta-carboline and of a pi 2-region on the benzodiazepine). The hybrids not fulfilling these requirements had no affinity for the receptor. In vivo pharmacological properties of 13 could not be demonstrated because of its metabolic instability and/or its poor transport into the brain. The results are discussed in terms of a possible overlapping of beta-carboline binding sites with those of benzodiazepines on the receptor.

Synthetic routes to 4-amino-3-carboxy-beta-carboline derivatives: incidental formation of novel furo[3,4-c]-beta-carbolin-2-ones displaying high affinities for the benzodiazepine receptor.

The synthesis of the first 4-amino-3-carboxy-beta-carboline derivative (35) is described. This synthesis is based on ozonolysis of the 4-vinyl-beta-carboline-3-carboxamide 17 to give the 4-aldehyde 20 and potassium permanganate oxidation of the latter to the 4-carboxylic acid 34 followed by a DPPA-promoted Curtius rearrangement. During the course of these transformations, a number of furo[3,4-c]-beta-carbolin-2-ones, differing in substituents at the C-10 position, were formed. While these beta-carboline lactones (15,25,26,33) generally displayed good affinities for the central type benzodiazepine receptor in vitro (IC50's in the 10-50 nM range), one compound, 29, demonstrated an exceptionally high binding affinity (IC50 = 0.2 nM). Compound 29 was shown in electrophysiological and behavioral studies to act as a benzodiazepine receptor antagonist. The unusually high binding affinity of compound 29 corroborates the hypothesis that the benzodiazepine receptor preferentially recognizes the C-3 carbonyl function of 3-carboxy-beta-carbolines in an s-cis conformation (i.e., the carbonyl oxygen on the same side as the pyridinyl nitrogen).

Synthesis and benzodiazepine receptor affinities of rigid analogues of 3-carboxy-beta-carbolines: demonstration that the benzodiazepine receptor recognizes preferentially the s-cis conformation of the 3-carboxy group.

1H-Indolo[3',2':4,5]pyrido[3,2-b]-2-penten-5-olide (6) and 1H,5H-indolo[3',2'-c]-6,7-dihydro-2-pyridone (7), rigid analogues of methyl 4-ethyl-beta-carboline-3-carboxylate (8) and N-methyl-4-ethyl-beta-carboline-3-carboxamide (9), respectively, were synthesized and their in vitro binding affinities to the central type benzodiazepine receptors were compared. The IC50 values of 6 and 8 were approximately equivalent (42 and 27 nM, respectively). The amide derivative 9, for which theoretical energy calculations indicate that the s-trans carbonyl conformation is the preferred one, displayed very low affinity (IC50 greater than 10(4) nM). However, when the carbonyl group of 9 was forced to adopt the s-cis conformation as in lactam 7, binding to the benzodiazepine receptor was largely restored (IC50 = 150 nM), indicating that the s-cis carboxy conformation at C-3 of beta-carbolines is preferentially recognized by this receptor. In vivo, compound 6 showed neither convulsant, proconvulsant, nor anticonvulsant activity in mice. Moreover, 6 did not antagonize methyl beta-carboline-3-carboxylate induced convulsions in mice. This lack of activity of 6 was attributed to its inability to cross the blood-brain barrier since no significant displacement of [3H]Ro 15-1788 from mouse brain benzodiazepine receptors by 6 could be observed in vivo.

3-Amino-beta-carboline derivatives and the benzodiazepine receptor. Synthesis of a selective antagonist of the sedative action of diazepam.

Seven 3-N-substituted derivatives of 3-amino-beta-carboline were synthesized and their affinities for the benzodiazepine receptor were assessed in vitro. Two compounds, 3-(ethylamino)-beta-carboline and 3-[(methoxycarbonyl)amino]-beta-carboline (beta-CMC), showing IC50 values of 460 and 71 nM, respectively, were selected for in vivo studies. The former compound showed long-lasting proconvulsant activity in Papio papio baboons while beta-CMC was shown in mice to selectively antagonize the sedative effects of diazepam without exhibiting convulsant, proconvulsant, or anxiogenic activity by itself.

A novel positive allosteric modulator of the GABA(A) receptor: the action of (+)-ROD188.

(+)-ROD188 was synthesized in the search for novel ligands of the GABA binding site. It shares some structural similarity with bicuculline. (+)-ROD188 failed to displace [(3)H]-muscimol in binding studies and failed to induce channel opening in recombinant rat alpha1beta2gamma2 GABA(A) receptors functionally expressed in Xenopus oocytes. (+)-ROD188 allosterically stimulated GABA induced currents. Displacement of [(3)H]-Ro15-1788 indicated a low affinity action at the benzodiazepine binding site. In functional studies, stimulation by (+)-ROD188 was little sensitive to the presence of 1 microM of the benzodiazepine antagonist Ro 15-1788, and (+)-ROD188 also stimulated currents mediated by alpha1beta2, indicating a major mechanism of action different from that of benzodiazepines. Allosteric stimulation by (+)-ROD188 was similar in alpha1beta2N265S as in unmutated alpha1beta2, while that by loreclezole was strongly reduced. (+)-ROD188 also strongly stimulated currents elicited by either pentobarbital or 5alpha-pregnan-3alpha-ol-20-one (3alpha-OH-DHP), in line with a mode of action different from that of barbiturates or neurosteroids as channel agonists. Stimulation by (+)-ROD188 was largest in alpha6beta2gamma2 (alpha6beta2gamma2>>alpha1beta2gamma2=alpha5beta2gamma2++ +>alpha2beta2ga mma2= alpha3beta2gamma2), indicating a unique subunit isoform specificity. Miniature inhibitory postsynaptic currents (mIPSC) in cultures of rat hippocampal neurons, caused by spontaneous release of GABA showed a prolonged decay time in the presence of 30 microM (+)-ROD188, indicating an enhanced synaptic inhibitory transmission.

Synthesis of cyclic sulfonamides via intramolecular copper-catalyzed reaction of unsaturated iminoiodinanes.

Olefinic primary sulfonamides were treated with iodobenzene diacetate and potassium hydroxide in methanol to give intermediate iminoiodinanes. Catalytic copper(I) or (II) triflate then provided intramolecular nitrene delivery leading to aziridine formation except in one case where a rare copper-catalyzed C-H insertion was observed. The aziridines could be opened by various nucleophiles (methanol, thiophenol, allylmagnesium bromide, benzylamine) to give the corresponding substituted cyclic sulfonamides.

Olfactory memory in rats, cholinergic agents and benzodiazepine receptor ligands.

Drugs and their effects on olfactory learning processes in rats were tested using a modified version of the runway apparatus developed by Ades. Rats were first exposed to a conspecific urine sample and 24 h later were exposed to the same stimulus in the runway. Observations recorded the time spent investigating the urine and the number of sniffs at the site, these being considered to be indices of memory. Diazepam-treated rats (4 or 6 mg/kg) and scopolamine-treated rats (0.5 or 1 mg/kg) showed increases for both parameters. When both drugs were administered simultaneously, the impairing effect was potentiated. However, no changes in learning responses were observed in rats treated with physostigmine (0.125, 0.25, 0.5 mg/kg) or methyl beta-carboline-3-carboxylate (0.3, 0.5, 1 mg/kg), although the administration of physostigmine or methyl beta-carboline-3-carboxylate was shown to antagonize the impairing effect of diazepam or scopolamine respectively. These observations support the hypothesis of interactions existing between cholinergic agents and benzodiazepine receptor ligands and of such interactions affecting olfactory acquisition processes. The runway apparatus appears to be a valid candidate model to be used for the assessment of pharmacological influences on olfactory learning in rats.

Cognitive enhancing properties of beta-CCM infused into the nucleus basalis magnocellularis of the rat.

Peripheral administration of various benzodiazepine derivatives or beta-carbolines (inverse agonists at benzodiazepine receptors), has been shown to affect memory. In this study, the effect of local infusion of a beta-carboline-methyl beta carboline-3-carboxylate (beta-CCM) into the nucleus basalis magnocellularis (NBM) of rats was examined in a two-trial recognition task. The results show that beta-CMM (3 micrograms/0.5 microliter) enhances recognition performance when injected both before or immediately after the acquisition trial. These effects appear to be mediated by a benzodiazepine (BZD) receptor since they were blocked by pretreatment with Ro 15-1788, a BZD receptor antagonist. This study supports the involvement of the NBM in cognitive processes, and demonstrates that these processes can be influenced by alteration of GABAergic neurotransmission.

In vivo bidirectional modulatory effect of benzodiazepine receptor ligands on GABAergic transmission evaluated by positron emission tomography in non-human primates.

The central type benzodiazepine receptor (BDZr), an allosteric modulatory site of the GABAA receptor-anion channel, has been shown in vitro to respond to drugs with positive efficacy (agonists), zero efficacy (competitive antagonists) and drugs with negative efficacy (inverse agonists). However, this general concept of the function of BDZr drugs has rarely been assessed in intact living brain. We report here in on a non-invasive in vivo assessment of the intrinsic efficacies of BDZr drugs in the brain of non-human primates. We have performed an in vivo simultaneous determination of fractional BDZr occupancy and the resulting pharmacological efficacies of the full agonist diazepam, the partial agonist bretazenil, the antagonist flumazenil (Ro15-1788), the partial inverse agonist Ro15-4513 and the full inverse agonist methyl beta-carboline-3-carboxylate (beta-CCM). Positron emission tomography (PET) was used to estimate fractional BDZr occupancy measured as the in vivo displacement in the brain of the positron emitter radioligand, [11C]flumazenil. Simultaneously, the proconvulsant or anticonvulsant efficacies of the BDZr drugs were measured as their abilities to facilitate or counteract the central effects of an infusion of pentylenetetrazol, a non-competitive GABA antagonist acting on the picrotoxin site of the receptor complex. This was measured using electroencephalographic recording (EEG). Our results show that, in vivo, the fractional receptor occupancy by a given drug is perfectly correlated with its resulting graded pharmacological effects, as predicted from the competitive drug receptor interaction theory. Furthermore, the slope of the relationship between fractional receptor occupancies and the resulting pharmacological effects (an index of intrinsic efficacy) strictly depends on the BDZr ligand considered. Diazepam displayed a strong positive intrinsic efficacy, and, in contrast, beta-CCM a marked negative one. Between these two extremes, the partially active drugs bretazenil and Ro15-4513, which required a large fractional receptor occupancy to produce significant anti- or proconvulsant effects, respectively, displayed only a weak intrinsic efficacy. Flumazenil did not produce any significant pharmacological effect. We observed that the in vivo intrinsic efficacies of diazepam, flumazenil and beta-CCM correlate with their intrinsic efficacies as measured by their modulatory effects on the GABA-dependent membrane chloride conductance in vitro. Thus, the intrinsic efficacies measured using PET and EEG are likely to reflect the different in vivo abilities of BDZr drugs to induce or stabilize the GABAA-benzodiazepine chloride channel in a given conformation.(ABSTRACT TRUNCATED AT 400 WORDS)

First use of a beta-carboline as photoaffinity label for the benzodiazepine receptor.

Photolabelling of benzodiazepine receptors isolated from rat cortex with a new beta-carboline-type photoaffinity label, ethyl 6-azido-beta-carboline-3-carboxylase, at 254 nm produced a 42% decrease in the maximal number of propyl beta-carboline-3-carboxylate binding sites but practically no decrease in the number of flunitrazepam binding sites. Moreover, the binding affinity of ethyl beta-carboline-3-carboxylase was diminished 11-fold by photolabelling while that of diazepam was diminished less than 2-fold. These results provide additional evidence that beta-carbolines and benzodiazepines bind to discrete sites on the benzodiazepine receptor.

[3H]propyl-6-azido-beta-carboline-3-carboxylate: a new photoaffinity label for the GABAA-benzodiazepine receptor.

[3H]Propyl-6-azido-beta-carboline-3-carboxylate ([3H]ACCP) exhibited a high affinity for GABAA receptors affinity purified from the brains of adult rats, and binding of this compound could be inhibited by several ligands of the benzodiazepine binding site of GABAA receptors. On irradiation with UV light, [3H]ACCP, similarly to [3H]flunitrazepam, irreversibly labeled a protein with an apparent molecular weight of 51 kDa in affinity-purified GABAA receptors, and this labeling could be inhibited in the presence of diazepam. These data indicate that [3H]ACCP can be used as a photoaffinity label for GABAA receptors.

Loreclezole as a simple functional marker for homomeric rho type GABA(C) receptors.

GABA(C) receptors are expressed in the whole brain, but predominantly in the retina. They can be identified by their unique pharmacology. The establishment of the entire pharmacology is, however, quite tedious. We show here that loreclezole dose dependently inhibits ionic currents elicited by GABA (gamma-aminobutyric acid) with an IC(50) of about 0.5 microM in homomeric rho1 GABA(C) receptors expressed in Xenopus oocytes. Thus, loreclezole may constitute a functional marker for these receptors.

Characterization of convulsions induced by methyl beta-carboline-3-carboxylate in mice.

The convulsive properties of methyl beta-carboline-3-carboxylate (beta-CCM) were evaluated in mice. When injected subcutaneously at a dose of 10 mg/kg beta-CCM induced convulsions in 75% of the mice with a median latency of 2.12 +/- 0.25 min. The CD50 was determined to be about 5 mg/kg. Electroencephalographic recordings showed that convulsions were brief (10 s), of cortical origin and propagating rapidly to the hippocampus. EEG alterations induced by low doses of beta-CCM lasted up to 1 h. The convulsive effect of beta-CCM was compared to that of PTZ. PTZ-induced convulsions occurred with a longer latency (9.26 +/- 1.33 min). beta-CCM and PTZ could act synergistically when injected in non-convulsive doses. When beta-CCM was injected 2-30 min before pentylenetetrazol (PTZ) there was a clear potentiation of the convulsive effect of PTZ. The convulsions induced by beta-CCM were blocked by diazepam (DZ) and by Ro 15-1788. In addition, beta-CCM reversed the sedative effect of a high dose of DZ for more than 30 min. Our results confirm that beta-CCM acts through the BZ receptor and indicate that the effects induced by a single dose of beta-CCM last more than 30 min.

Methyl-beta-carboline-induced convulsions are antagonized by Ro 15-1788 and by propyl-beta-carboline.

Injected i.v. into baboons, Ro 15-1788 (a benzodiazepine antagonist) and propyl-beta-carboline-3-carboxylate did not modify either the behavior or the electroencephalogram at doses up to 2 mg/kg. Methyl-beta-carboline-3-carboxylate is a potent convulsant at doses of 20 micrograms/kg in photosensitive baboons and 100 micrograms/kg in non-photosensitive baboons. These convulsive doses of methyl-beta-carboline-3-carboxylate are effectively antagonized by 0.5 mg/kg of Ro 15-1788 and also by 2 mg/kg of propyl-beta-carboline-3-carboxylate.

Benzodiazepine receptors studied in living primates by positron emission tomography: inverse agonist interactions.

The convulsant actions of methyl 6,7-dimethoxy-4-ethyl-beta-carboline-3-carboxylate (DMCM) and of methyl beta-carboline-3-carboxylate (beta-CCM) were evaluated in the baboon (Papio papio). DMCM, 0.6-4 mg/kg, induced epileptic seizures with short latency. DMCM convulsive seizures could be blocked by i.v. administration of the benzodiazepine agonist diazepam (10 mg). Similarly, beta-CCM, 0.3-3 mg/kg i.v., provoked generalized seizures in the baboons. These seizures were also reversed by the administration of propyl beta-carboline-3-carboxylate (3 mg/kg) or of diazepam (5 mg/kg). Combining the results from Positron Emission Tomography and the EEG assessments, benzodiazepine receptor occupancy by beta-CCM and DMCM was directly correlated with their convulsant actions in the living baboon. beta-CCM exerted its convulsant action in the living baboon at 76 and 74% benzodiazepine receptor occupancy in, respectively, occipital and temporal cortices whereas DMCM displayed a similar convulsive activity when only 58 and 65% of these receptors in the above regions were occupied.