BF2.649 [1-{3-[3-(4-Chlorophenyl)propoxy]propyl}piperidine, hydrochloride], a nonimidazole inverse agonist/antagonist at the human histamine H3 receptor: Preclinical pharmacology

Histamine H3 receptor inverse agonists are known to enhance the activity of histaminergic neurons in brain and thereby promote vigilance and cognition. 1-{3-[3-(4-Chlorophenyl)propoxy]propyl}piperidine, hydrochloride (BF2.649) is a novel, potent, and selective nonimidazole inverse agonist at the recombinant human H3 receptor. On the stimulation of guanosine 5'-O-(3-[35S]thio)triphosphate binding to this receptor, BF2.649 behaved as a competitive antagonist with a Ki value of 0.16 nM and as an inverse agonist with an EC50 value of 1.5 nM and an intrinsic activity approximately 50% higher than that of ciproxifan. Its in vitro potency was approximately 6 times lower at the rodent receptor. In mice, the oral bioavailability coefficient, i.e., the ratio of plasma areas under the curve after oral and i.v. administrations, respectively, was 84%. BF2.649 dose dependently enhanced tele-methylhistamine levels in mouse brain, an index of histaminergic neuron activity, with an ED50 value of 1.6 mg/kg p.o., a response that persisted after repeated administrations for 17 days. In rats, the drug enhanced dopamine and acetylcholine levels in microdialysates of the prefrontal cortex. In cats, it markedly enhanced wakefulness at the expense of sleep states and also enhanced fast cortical rhythms of the electroencephalogram, known to be associated with improved vigilance. On the two-trial object recognition test in mice, a promnesiant effect was shown regarding either scopolamine-induced or natural forgetting. These preclinical data suggest that BF2.649 is a valuable drug candidate to be developed in wakefulness or memory deficits and other cognitive disorders.

Ventilatory predictors of pulmonary hypoplasia in congenital diaphragmatic hernia, confirmed by morphologic assessment

We carried out a prospective study in 66 infants with congenital diaphragmatic hernia within the first 6 hours of life to determine whether outcome is related to the degree of underlying pulmonary hypoplasia, as predicted by preoperative PaCO2, when correlated with an index of ventilation (VI = mean airway pressure X respiratory rate) and confirmed by postmortem analysis of the lung. Those infants with PaCO2 greater than 40 mm Hg before surgery had a 77% mortality; when PaCO2 reduction could be achieved only with VI greater than 1000, the mortality was still greater than 50%. After repair, however, the ability to hyperventilate to PaCO2 less than 40 mm Hg proved to be an important determinant of survival; only one of 31 infants in this group died, whereas only two of 27 infants with PaCO2 greater than 40 mm Hg survived. In 16 infants with PaCO2 greater than 40 mm Hg despite hyperventilation, high-frequency oscillatory ventilation was started. This resulted in a rapid fall in PaCO2, but 14 of the 16 infants had only temporary improvement in oxygenation, and died. In five of the infants who died, alveolar number was assessed by postmortem morphometric analysis; there was a severe reduction to less than 10% of published normal neonatal values. Pulmonary vascular changes of increased muscularization were less remarkable than those observed in infants with persistent pulmonary hypertension. Our findings suggest that the degree of pulmonary hypoplasia (which would not be influenced by surgical repair), rather than the pulmonary vascular abnormality, mainly determines survival. Consideration could therefore be given to an initial nonsurgical approach to congenital diaphragmatic hernia, with the expectation that pulmonary function might improve and pulmonary vascular resistance decrease.

Anti-alpha-fodrin inhibits secretion from permeabilized chromaffin cells

Chromaffin cells release catecholamine- and peptide-containing granules by exocytosis, by a mechanism involving movement of secretory granules towards the cell membrane, their apposition to it and the fusion of the granule membrane with the plasma membrane. One of the two subunits of membrane-associated brain spectrin, alpha-fodrin is an actin-binding protein which is found at the periphery of chromaffin cells and may be involved in secretion. Because cultured chromaffin cells can be permeabilized with detergents, giving pores large enough to permit the entry of immunoglobulin molecules, we used permeabilized cells to test the effect of specific antibodies on secretory mechanisms. Incubation of permeabilized cells with polyclonal immunoaffinity-purified monospecific anti-alpha-fodrin antibody or its Fab fragments did not modify basal release but did specifically inhibit Ca2+-induced catecholamine release by exocytosis. Our observations indicate that fodrin and the cytoskeleton participate in the release mechanism.

Reorganization of alpha-fodrin induced by stimulation in secretory cells

Spectrin is an ubiquitous protein composed of heterodimers with alpha and beta subunits. It was first described in erythrocyte cell membranes (see ref. 1 for review) and subsequently in brain, intestinal brush borders, kidney, liver and adrenals. Brain spectrin (fodrin) alpha-subunit, responsible for actin binding, has a relative molecular mass (Mr) of 240,000, whereas the beta-subunit, involved in membrane attachment, has an Mr of 235,000 (refs 1, 3, 9-13). The membrane of secretory granules from adrenal chromaffin cells membrane of secretory granules from adrenal chromaffin cells increases the viscosity of F-actin solution, and spectrin-like protein is associated with storage granule and plasma membranes. Here, we report the localization of fodrin in secretory cells using monospecific antibodies against the alpha-subunit of fodrin using indirect immunofluorescence. We find that the alpha-subunit forms an intensely stained continuous ring in the subplasmalemmal region of resting chromaffin cells. On stimulation of the cell with nicotine, high potassium or ionophores in the presence of calcium, fodrin forms patches. This aggregation is inhibited by trifluoperazine, hence the entrance of calcium into cells following cell depolarization seems to be the calmodulin-dependent stimulus initiating patch formation.

Isosorbide mononitrate and propranolol compared with propranolol alone for the prevention of variceal rebleeding

The aim of this study was to test the effectiveness of isosorbide-5-mononitrate (IM) as an adjunct to propranolol (PR) in the prevention of variceal rebleeding. Ninety-five cirrhotic patients with variceal bleeding were randomly assigned to treatment with PR + IM (46 patients) or PR alone (49 patients). Eighteen patients in the PR + IM group and 28 in the PR group had rebleeding during the 2 years after randomization. The actuarial probability of rebleeding 2 years after randomization was lower in the PR + IM group (40.4% vs. 57.4%) but the difference was not significant (P =. 09). However, the decrease in the risk of rebleeding reached statistical significance after stratification according to age, i.e. less than 50 versus >/=50 years old, (P =.03) or by adding an additional year of follow-up (P =.05). No significant difference was found in rebleeding index and survival. The multivariate Cox analysis indicated first, that both treatment (P =.03) and age (P =. 001) were factors predictive of rebleeding and second, that PR + MI reduced the risk of rebleeding by half (relative risk: 0.51, 95% confidence interval: 0.28-0.95). Seven patients in the PR + MI group and 1 patient in the PR group had to discontinue one of the drugs because of adverse events (P =.03). These results suggest that the addition of IM improves the efficacy of PR alone in the prevention of variceal rebleeding in cirrhotic patients. However no beneficial effects were observed on other parameters reflecting the efficacy of treatment.

Biological properties of acid etched titanium implants: effect of sandblasting on bone anchorage

The SLA (sandblasted with large grit and acid etched) surface is a textured surface that has been documented to lead to a rapid and strong implant fixation. The purpose of the present study was to determine the contribution of sandblasting in addition to etching to implant anchorage. It was also aimed to determine if the pits carved during etching alone have a bone-interlocking capacity that leads to microanchorage between the implant and bone. SLA implants and machined-and-acid-etched (MA) implants were placed in the maxilla of Land Race pigs. After 10 weeks of healing, they were reverse torqued. The reverse torque of the SLA and MA implants was 157.29 +/- 38.04 N cm and 105.33 +/- 25.12 N cm, respectively. Sandblasting increased bone anchorage by 49.3%; the difference was statistically significant (p =.028). Bone was found attached to both surfaces; bone ingrowth was found in the pits of both surfaces. It is suggested that the two surfaces are able to generate bone interlocking and mechanical coupling at the interface. When finite-element modeling is performed with these surfaces, it is suggested that the bound mode be used instead of the slip mode.

cAMP and Ca(2+)-mediated secretion in parotid acinar cells is associated with reversible changes in the organization of the cytoskeleton

The potential involvement of actin and fodrin (brain spectrin) in secretory events has been assessed in primary cultured guinea pig parotid acinar cells, using as a tool affinity purified anti-alpha-fodrin antibody, phalloidin, and immunofluorescence techniques. In resting parotid acinar cells fodrin and actin appeared as a continuous ring under the plasma membrane of most of the cells. Upon stimulation with secretagogues fodrin and actin labeling at the level of the plasma membrane disappeared almost completely. To establish a correlation between secretion and cytoskeletal changes at the individual cell level, anti-alpha-amylase-antibodies were used to label secreted amylase exposed at the surface of secreting cells. The number of cells expressing alpha-amylase on their surface followed bulk secretion of alpha-amylase. A strict correlation between secretion and alteration of the actin-fodrin labeling was observed at the individual cell level. The cytoskeletal changes occurred in parallel with secretion independently of the secretagogue used (carbamoylcholine in the presence of Ca2+, isoproterenol in presence or absence of Ca2+, forskolin, or dibutyryl-cyclic-AMP). The changes were reversible upon removal of the secretagogue. Since Ca2+, as well as cAMP-mediated secretion, was associated with the same kind of cytoskeletal changes, a reorganization of the cytoskeleton may play an essential part in regulated secretion.

Palindromic units are part of a new bacterial interspersed mosaic element (BIME)

Palindromic Units (PU or REP) were defined as DNA sequences of 40 nucleotides highly repeated on the genome of Escherichia coli and other Enterobacteriaceae. PU are found in clusters of up to six occurrences always localized in extragenic regions. By sorting the DNA sequences of the known PU containing regions into different classes, we show here for the first time that, besides the PU themselves, each PU clusters contains a number of other conserved sequence motifs. Seven such motifs were identified with the present list of PU regions. Remarkably, each PU cluster is exclusively composed of a mosaic combination of PU and of these other sequence motifs. We demonstrate directly by hybridization experiments that one of these motifs (called L) is indeed present at a large number of copies on the Escherichia coli chromosome and that its distribution follows the same species specificity as PU sequences themselves. We propose that the mosaic pattern of motif combination in PU clusters reveals a new type of bacterial genetic element which we propose to call BIME for Bacterial Interspersed Mosaic Element. The Escherichia coli genome contains about 500 BIME.

DNA polymerase I and a protein complex bind specifically to E. coli palindromic unit highly repetitive DNA: implications for bacterial chromosome organization

Starting from a crude E. coli extract, two activities which specifically protect highly repetitive bacterial DNA sequences (called PU for Palindromic Unit or REP for Repetitive Extragenic Palindromic sequence) against a digestion with Exonuclease III have been purified. We show that one of these activities is due to the DNA polymerase I (Pol I). This constitutes the first indication for a specific interaction between Pol I and a duplex DNA. This interaction requires the presence of PU. It was confirmed and analyzed by native gel electrophoresis and DNase I footprinting experiments. The other activity contained at least five polypeptides. Its binding to PU DNA sequences was confirmed by native gel electrophoresis. Implications for the possible origin and functions of PU are discussed.

F 11782, a novel epipodophylloid non-intercalating dual catalytic inhibitor of topoisomerases I and II with an original mechanism of action

F 11782, a novel epipodophylloid, proved a potent inhibitor of the catalytic activities of both topoisomerases I and II. Unlike classical inhibitors such as camptothecin or etoposide, F 11782 did not stabilise cleavable complexes induced by either topoisomerases I or II nor did it preferentially inhibit the religation step of the catalytic cycle of either enzyme. F 11782 neither intercalated DNA nor bound in its minor groove, and showed only weak inhibition of the ATPase activity associated with topoisomerase II. F 11782 appeared to act by inhibiting the binding of topoisomerases I and II to DNA in a manner dependent both on drug and enzyme concentrations, via a mechanism not previously described or shared by other known topoisomerase 'poisons' or inhibitors. In contrast, F 11782 had only a weak effect or none at all on various other DNA-interacting enzymes. In conclusion, F 11782, as a non-intercalating, specific catalytic inhibitor of both topoisomerases I and II with an original mechanism of action, may be considered to represent the first of a new class of topoisomerase-interacting agents.

Vinflunine (20',20'-difluoro-3',4'-dihydrovinorelbine), a novel Vinca alkaloid, which participates in P-glycoprotein (Pgp)-mediated multidrug resistance in vivo and in vitro

Vinflunine (VFL) is a novel derivative of vinorelbine (NVB, Navelbine), which has shown markedly superior antitumor activity to NVB, in various experimental animal models. To establish whether this new Vinca alkaloid participates in P-glycoprotein (Pgp)-mediated multidrug resistance (MDR), VFL-resistant murine P388 cells (P388/VFL) were established in vivo and used in conjunction with the well established MDR P388/ADR subline, to define the in vivo resistance profile for VFL. P388/VFL cells proved cross-resistant to drugs implicated in MDR (other Vinca alkaloids, doxorubicin, etoposide), but not to campothecin or cisplatin and showed an increased expression of Pgp, without any detectable alterations in topoisomerase II or in glutathione metabolism. The P388/ADR cells proved cross-resistant to VFL both in vivo and in vitro, and this VFL resistance was efficiently modulated by verapamil in vitro. Cellular transport experiments with tritiated-VFL revealed differential uptake by P388 sensitive and P388/ADR resistant cells, comparable with data obtained using tritiated-NVB. In various in vitro models of human MDR tumor cells, whilst full sensitivity was retained in cells expressing alternative non-Pgp-mediated MDR mechanisms, cross resistance was identified in Pgp-overexpressing cells. Differences were, however, noted in terms of the drug resistance profiles relative to the other Vinca, with tumor cell lines proving generally least cross-resistant to VFL. Overall, these results suggest that VFL, like other Vinca alkaloids, participates in Pgp-mediated MDR, with tumor cells selected for resistance to VFL overexpressing Pgp, yet MDR tumor cell lines proved generally less cross resistant to VFL relative to the other Vinca alkaloids.

Effect of enkephalins and morphine on insulin secretion from isolated rat islets

The direct effects of an enkephalin analogue, (D-Ala2/MePhe4/Met/(O)-o1) enkephalin (DAMME), on insulin release from isolated islets of Langerhans of the rat have been investigated. DAMME had a dose-dependent effect on insulin secretion: low concentrations (10(-10) to 10(-8) mol/l) were stimulatory while high concentrations (10(-5) mol/l) were inhibitory in the presence of 8 mmol/l glucose. Similar effects were found with met-enkephalin, and with the longer acting alanine substituted met-enkephalin. Morphine sulphate (5 X 10(-7) mol/l) also stimulated insulin release. The effects of enkephalin and morphine were blocked by the specific opiate antagonist naloxone hydrochloride (1.2 X 10(-6) mol/l). The insulin secretory response of perifused islets to enkephalins and morphine was rapid, corresponding to the first phase of glucose induced insulin release. These observations suggest that there may be opiate receptors in islets, and that opioid peptides could modulate insulin release.

Chromaffin granule membrane-F-actin interactions and spectrin-like protein of subcellular organelles: a possible relationship

The membrane of chromaffin granule, the secretory vesicle of adrenal medullary cells storing catecholamines, enkephalins, and many other components, interacts with F-actin. Using low shear falling ball viscometry to estimate actin binding to membranes, we demonstrated that mitochondrial and plasma membranes from chromaffin cells also provoked large increases in viscosity of F-actin solutions. Mitochondrial membranes also had the capacity to cause complete gelation of F-actin. In addition, vasopressin-containing granules from neurohypophysial tissue were shown to bind F-actin and to increase the viscosity of F-actin solutions. Using an antibody directed against human erythrocyte spectrin, it was found that a spectrin-like protein was associated with secretory granule membrane, mitochondrial membrane, and plasma membrane. The chromaffin granule membrane-associated spectrin-like protein faces the cytoplasmic side, is composed of two subunits (240 kD and 235kD ), the alpha-subunit (240 kD, pHi5 .5) being recognized by the antibody. Nonionic detergents such as Triton X-100 or Nonidet P40 failed to release fully active spectrin-like protein. In contrast, Kyro EOB , a different nonionic detergent, was found to release spectrin-like protein while keeping intact F-actin binding capacity, at least below 0.5% Kyro EOB concentration. Chromaffin cells in culture were stained with antispectrin antibody, showing the presence of spectrin-like protein in the cell periphery close to the cell membrane but also in the cytoplasm. We conclude that in living cells the interaction of F-actin with chromaffin granule membrane spectrin observed in vitro is important in controlling the potential function of secretory vesicles.

Preclinical evaluation of the abuse potential of Pitolisant, a histamine H₃ receptor inverse agonist/antagonist compared with Modafinil

BACKGROUND AND PURPOSE

Pitolisant, a histamine H₃ receptor inverse agonist/antagonist is currently under Phase III clinical trials for treatment of excessive daytime sleepiness namely in narcoleptic patients. Its drug abuse potential was investigated using in vivo models in rodents and monkeys and compared with those of Modafinil, a psychostimulant currently used in the same indications.

EXPERIMENTAL APPROACH

Effects of Pitolisant on dopamine release in the nucleus accumbens, on spontaneous and cocaine-induced locomotion, locomotor sensitization were monitored. It was also tested in three standard drug abuse tests i.e. conditioned place preference in rats, self-administration in monkeys and cocaine discrimination in mice as well as in a physical dependence model.

KEY RESULTS

Pitolisant did not elicit any significant changes in dopaminergic indices in rat nucleus accumbens whereas Modafinil increased dopamine release. In rodents, Pitolisant was without any effect on locomotion and reduced the cocaine-induced hyperlocomotion. In addition, no locomotor sensitization and no conditioned hyperlocomotion were evidenced with this compound in rats whereas significant effects were elicited by Modafinil. Finally, Pitolisant was devoid of any significant effects in the three standard drug abuse tests (including self-administration in monkeys) and in the physical dependence model.

CONCLUSIONS AND IMPLICATIONS

No potential drug abuse liability for Pitolisant was evidenced in various in vivo rodent and primate models, whereas the same does not seem so clear in the case of Modafinil.

DNA sequence encoding the NH2-terminal peptide involved in transport of lambda receptor, an Escherichia coli secretory protein

lamB encodes the lambda receptor of Escherichia coli, an outer membrane protein. We have identified the beginning of the lamB gene by correlating DNA nucleotide sequence with a partial sequence of the primary translation product of lamB. We show that lambda receptor is synthesized as a precursor containing an extra 25 amino acids at its NH2 terminus. These amino acids are predominately hydrophobic and probably comprise a structure required for initiation of transport of lambda receptor from the cytoplasm to the outer membrane.

Viral genome organizer: a system for analyzing complete viral genomes

The viral genome organizer (VGO) is designed to simplify the characterization and annotation of complete viral genomes (particularly those of large poxviruses) and to help researchers discover new genes and detect gene fragmentation. VGO is based on Genotator [Harris, N.L., 1997. Genome Res. 7, 754-762], an annotation workbench designed for the analysis of eukaryotic genomic sequences. VGO automates a number of database search routines (FASTA, BLASTP, PSI-BLAST and TBLASTN), processes the results through a multiple-alignment viewer (MView; [Brown, N.P., Leroy, C., Sander, C. , 1998. Bioinformatics 14, 380-381]) and serves to manage the hundreds of DNA, protein and database search results files that must be organized when dealing with large complete poxviral genomes. It also directs the generation a self-dotplot of the genome by Dotter [Sonnhammer, E.L.L., Durbin, R., 1995. A dot-matrix program with dynamic threshold control suited for genomic DNA and protein sequence analysis. Gene 167: GC1-10. http://www.sanger.ac. uk/Software/Dotter/] to uncover repeated genes and sequences and provides Internet links to programs for generation of restriction maps and analysis of potential PCR primers. The user-friendly graphical interface displays DNA and protein sequences, links to search results, ORFs, stop-start codons, restriction sites and flags of database searches. Currently, VGO and associated programs run in an X-windows environment on commonly available UNIX machines.

The quantitative oxidation of methionine to methionine sulfoxide by peroxynitrite

Both peroxynitrous acid and peroxynitrite react with methionine, k(acid) = (1.7 +/- 0.1) x 10(3) M(-1) s(-1) and k(anion) = 8.6 +/- 0.2 M(-1) s(-1), respectively, and with N-acetylmethionine k(acid) = (2.8 +/- 0.1) x 10(3) M(-1) s(-1) and k(anion) = 10.0 +/- 0.1 M(-1) s(-1), respectively, to form sulfoxides. In contrast to the results of Pryor et al. (1994, Proc. Natl. Acad. Sci. USA 91, 11173-11177), a linear correlation between k(obs) and [met] was obtained. Surprisingly, for every two sulfoxides and nitrites formed, one peroxynitrite is converted to nitrate. Thus, methionine also catalyzes the isomerization of peroxynitrite to nitrate. Neither the pH nor the concentration of methionine affected the distribution of the yields of nitrite, nitrate, and methionine sulfoxide, which were the only products detected. No products other than nitrite, nitrate, and methioninesulfoxide could be detected. The reactions of methionine and N-acetylmethionine with peroxynitrous acid and peroxynitrite are simple bimolecular reactions that do not involve an activated form of peroxynitrous acid or of peroxynitrite. Nitrite, produced together with methionine sulfoxide, or present as a contamination in the peroxynitrite preparation, is not innocuous, but oxidizes methionine by one electron, which leads to the formation of methional and ethylene.

Structural and functional diversity among bacterial interspersed mosaic elements (BIMEs)

Palindromic units (PU or REP) were defined as 40-nucleotide DNA sequences which are highly repeated in the genome of several members of the Enterobacteriaceae. They were shown to be a constituent of the bacterial interspersed mosaic element (BIME), in which they are associated with other repetitive sequences. We report here that Escherichia coli PU sequences contain three motifs (Y, Z1 and Z2), leading to the definition of two BIME families. The BIME-1 family, highly conserved over 145 nucleotides, contains two PUs (motifs Y and Z1). The BIME-2 family contains a variable number of PUs (motifs Y and Z2). We present evidence, using band shift experiments, that each PU motif binds DNA gyrase with a different affinity. This suggests that the two families are functionally distinct.

Inhibition of RAS-targeted prenylation: protein farnesyl transferase inhibitors revisited

The ras oncogene and its 21 kD protein product, Ras, has emerged during the last decade as a potentially exploitable target for anticancer drug development. The knowledge that Ras was readily prenylated by protein farnesyl transferase (PFTase) and that inhibition of this prenylation had functional consequences for the transformed phenotype that expressed oncogenic Ras provided the rational for the development of PFTase inhibitors. The initial enthusiasm for this approach seemed justified by the early identification of PFTase inhibitors that were able potently and specifically to block Ras processing, signalling and transformation in transformed and tumour cell lines in vitro and in certain selected animal models. More recently the recognition that geranylgeranyl transferase (GGTase) I might also be a therapeutic target is being actively researched. The last couple of years though have proved remarkable with the disclosure of a series of structurally-diverse molecules, whose major in vivo preclinical activites have been well documented against experimental animal tumours, and culminating this year in preliminary reporting of their Phase I clinical evaluations. Nevertheless, during the research and development phases of PFTase inhibitors as pharmaceutical agents for clinical use, there have been several unexpected findings which have raised intriguing and potentially crucial questions about their activities. This review aims to highlight and offer new insights into many of these issues and to bring into perspective concerns arising from basic research, as well as from clinical studies. There seems little doubt that these inhibitors of RAS-targeted prenylation represent a new generation of anticancer drugs for the preclinical researcher, whether they can be successfully exploited in clinical practice should be resolved early in the next millenium.