Rosario Herranz

Pharmacological evaluation of IQM-95,333, a highly selective CCKA receptor antagonist with anxiolytic-like activity in animal models

The pyridopyrimidine derivative IQM‐95,333 ((4aS,5R)‐2‐benzyl‐5‐[Nα‐tert‐butoxicarbonyl)L‐tryptophyl]amino‐1,3dioxoperhydropyrido[1,2‐c]pyrimidine), a new non‐peptide antagonist of cholecystokinin type A (CCKA) receptors, has been evaluated in vitro and in vivo in comparison with typical CCKA and CCKB receptor antagonists, such as devazepide, lorglumide, L‐365,260 and PD‐135,158. IQM‐95,333 displaced [3H]‐CCK‐8S binding to CCKA receptors from rat pancreas with a high potency in the nanomolar range. Conversely, the affinity of this new compound at brain CCKB receptors was negligible (IC50>10 μM). IQM‐95,333 was a more selective CCKA receptor ligand than devazepide and other CCKA receptor antagonists. Like devazepide, IQM‐95,333 was a more potent antagonist of CCK‐8S‐ than of CCK‐4‐induced contraction of the longitudinal muscle from guinea‐pig ileum, suggesting selective antagonism at CCKA receptors. IQM‐95,333 and devazepide were also potent inhibitors of CCK‐8S‐stimulated amylase release from isolated pancreatic acini, a CCKA receptor‐mediated effect. The drug concentrations required (IC50s around 20 nM) were higher than in binding studies to pancreas homogenates. Low doses (50–100 μg kg−1, i.p.) of IQM‐95,333 and devazepide, without any intrinsic effect on food intake or locomotion, blocked the hypophagia and the hypolocomotion induced by systemic administration of CCK‐8S, two effects associated with stimulation of peripheral CCKA receptors. IQM‐95,333 showed an anxiolytic‐like profile in the light/dark exploration test in mice over a wide dose range (10–5,000 μg kg−1). Typical CCKA and CCKB antagonists, devazepide and L‐365,260 respectively, were only effective within a more limited dose range. In a classical conflict paradigm for the study of anxiolytic drugs, the punished‐drinking test, IQM‐95,333, devazepide and L‐365,260 were effective within a narrow dose range. The dose‐response curve for the three drugs was biphasic, suggesting that other mechanisms are operative at higher doses. In conclusion, IQM‐95,333 is a potent and selective CCKA receptor antagonist both in vitro and in vivo with an anxiolytic‐like activity in two different animal models, which can only be attributed to blockade of this CCK receptor subtype.

The N-terminal tripeptide of insulin-like growth factor-I protects against β-amyloid-induced somatostatin depletion by calcium and glycogen synthase kinase 3β modulation

The protective effects of insulin‐like growth factor I on the somatostatin (SRIF) system in the temporal cortex after β‐amyloid (Aβ) injury may be mediated through its N‐terminal tripeptide glycine‐proline‐glutamate (GPE). GPE is cleaved to cyclo[Pro‐Gly] (cPG), a metabolite suggested to mediate in neuroprotective actions. We evaluated the effects of GPE and cPG in the temporal cortex of Aβ25–35‐treated rats on SRIF and SRIF receptor protein and mRNA levels, adenylyl cyclase activity, cell death, Aβ25–35 accumulation, cytosolic calcium levels ([Ca2+]c) and the intracellular signaling mechanisms involved. GPE and cPG did not change Aβ25–35 levels, but GPE partially restored SRIF and SRIF receptor 2 protein content and mRNA levels and protected against cell death after Aβ25–35 insult, which was coincident with Akt activation and glycogen synthase kinase 3β inhibition. In addition, GPE displaced glutamate from NMDA receptors and blocked the glutamate induced rise in cytosolic calcium in isolated rat neurons and moderately increased Ca2+ influx per se. Our findings suggest that GPE, but not its metabolite, mimics insulin‐like growth factor I effects on the SRIF system through a mechanism independent of Aβ clearance that involves modulation of calcium and glycogen synthase kinase 3β signaling.

Strategies for Design of Non Peptide CCK1R Agonist/Antagonist Ligands

This review mainly covers last five year literature on CCK1R agonists and antagonists. These CCK1R ligands have been found following the two usual and complementary strategies for drug discovery: rational design based on structure activity relationships on the CCK-7 and CCK-4 peptide sequences of the endogenous ligands and random screening of diverse compounds, followed by hit optimization. The first group includes: chimeric bifunctional opioid/CCK peptides, designed as opioid agonists with balanced CCK1R/CCK2R antagonist activity for the treatment of neuropathic pain, antagonist and agonist dipeptoids, and 1,3-dioxoperhydropyrido[1,2-c]pyrimidine- and anthranilic acid-based antagonists. Among the ligands derived from random screening, a few new 1,4-benzodiazepine-, 1,5-benzodiazepine-, and five member ring heterocycle-based CCK1R ligands have been reported. Finally, taking into account the importance of receptor mapping studies for ligand optimization and future precise de novo receptor structure-based design of new selective and more effective ligands, the most significant conclusions of these studies have also been reviewed.

Ketomethylene and Methyleneamino Pseudopeptide Analogues of Insect Allatostatins Inhibit Juvenile Hormone and Vitellogenin Production in the Cockroach Blattella germanica

Metabolic studies on insect allatostatins have suggested that the dipeptide Leu-Tyr may be a target for endopeptidases. In order to increase resistance to degradation, methyleneamino psi [CH2NH] and ketomethylene psi [COCH2] peptide bond surrogates have been introduced at the position Leu3-Tyr4 of the allatostatin Asp-Arg-Leu-Tyr-Ser-Phe-Gly-Leu-amide (BLAST-2), and Leu3-Phe4 of [Phe4]BLAST-2, respectively. Assays of inhibition of juvenile hormone (JH) synthesis in vitro by corpora allata from the cockroach Blattella germanica showed that both analogues were similarly active to the respective model peptides. The methyleneamino analogue was further tested in vivo as an inhibitor of JH synthesis, and in vivo and in vitro as an inhibitor of vitellogenin production by the fat body of B. germanica. The analogue was less active than BLAST-2 when tested in vitro, but more active than it when tested in vivo.

Synthesis of Ψ[CH(CN)NH] pseudopeptides. A new peptide bond surrogate

Abstract An easy and versatile general method for the preparation of the new peptide bond surrogate Ψ[CH(CN)NH], by the Lewis acid catalyzed reaction of N-protected α-amino aldehydes with a C-protected amino acid or peptide in the presence of TMSCN, is described.

Antinociceptive effects in rodents of the dipeptide Lys-Trp (Nps) and related compounds

Intracerebroventricular administration of the synthetic dipeptide derivative Lys-Trp (Nps) (LTN) elicits a potent and naloxone-sensitive antinociceptive effect in mice and in rats using heat and electrical current respectively as the noxious stimuli. LTN does not induce analgesia by directly acting on opioid receptors but the peptidase inhibiting activity of the new compound may account in part for the behavioral effect. LTN produces also a marked decrease in the met-enkephalin content of the periaqueductal gray suggesting a possible enkephalin releasing property. Structure-activity studies with different analogs of LTN indicate that replacement of Lys by other basic amino acids results also in compounds with a potent antinociceptive effect whereas replacement by neutral or acidic amino acids leads to a complete loss of activity.

Design, synthesis and biological evaluation of new peptide-based ureas and thioureas as potential antagonists of the thrombin receptor PAR1.

By applying a diversity oriented synthesis strategy for the search of new antagonists of the thrombin receptor PAR1, a series of peptide-based ureas and thioureas, including analogues of the PAR1 reference antagonist RWJ-58259, has been designed and synthesized. The general synthetic scheme involves reduction of basic amino acid-derived amino nitriles by hydrogen transfer from hydrazine monohydrate in the presence of Raney Ni, followed by reaction with diverse isocyanates and isothiocyanates, and protecting group removal. All new compounds have been evaluated as inhibitors of human platelet aggregation induced by the PAR1 agonist SFLLRN. Some protected peptide-based ureas displayed significant antagonist activity.

Pseudopeptide CCK-4 analogues incorporating the Ψ[CH(CN)NH] peptide bond surrogate

Abstract The synthesis, binding to CCK receptors, and in vitro functional activity of pseudopeptide CCK-4 analogues incorporating the ( R ) or ( S ) Ψ[CH(CN)NH] peptide bond surrogate at the NIe 31 -Asp 32 or or Trp 30 -NIe 13 bonds are described. Z-TrpΨ[( S )CH(CN)NH]NIe-Asp-Phe-NH 2 retained the high CCK-B receptor binding affinity of Boc-[NIe 31 ]-CCK-4, and was a potent and selective CCK-B antagonist in the isolated guinea pig ileum.

Branched peptides and conformationally constrained analogues from cyanomethyleneamino pseudopeptides

Abstract Catalytic hydrogenation of cyanomethyleneamino pseudopeptides, followed by peptide coupling and cyclization of the resulting aminomethyleneamino intermediates, gives access to branched and conformationally constrained peptide analogues.

Aminodeoxybestatin and epi-aminodeoxybestatin: stereospecific synthesis and aminopeptidase inhibition

The synthesis of aminodeoxybestatin and epi-aminodeoxybestatin [(2S,3R)- and (2R,3R)-2,3-di-amino-4-phenylbutanoyl-L-leucine; (2S,3R)- and (2R,3R)-DAPBA-L-Leu)], bestatin and epi-bestatin analogues, respectively, in which the hydroxy group has been replaced with an amino group, is described by two different methods. The first one involves the synthesis of bis-(N-Z)-DAPBA, by homologation of N-Z-phenylalanine, via a modified Strecker synthesis followed by subsequent coupling with the methyl ester of L-leucine and removal of the protecting groups. Following this procedure, 25% racemization at the C-3 centre of the DAPBA derivatives took place during the homologation reaction. The second method involves the stereospecific SN2 nucleophilic substitution of the 2-hydroxy group of (2R,3R)- and (2S,3R)-3-(benzyloxycarbonyl)amino-2-hydroxy-4-phenylbutanoyl-L-leucine methyl esters [(2R,3R)- and (2S,3R)-N-Z-AHPBA-L-Leu-OMe], and subsequent saponification, azido reduction and removal of the N-Z-protecting group. Replacement of the hydroxy group of bestatin and epi-bestatin with an amino group results in a decrease in their aminopeptidase (AP-B, AP-M and Leu-AP)-inhibitory potencies.