PubMed Health⌕ Search

Biomedical subjects

Remo Guerrini

Publications and source records attributed to Remo Guerrini.

64 records · Page 4Linked to original sources
PubMed2002

Solution structure of nociceptin peptides.

Peptides embedded in the sequence of pre-pro-nociceptin, i.e. nociceptin, nocistatin and orphanin FQ2, have shed light on the complexity of the mechanisms involving the peptide hormones related to pain and have opened up new perspectives for the clinical treatment of pain. The design of new ligands with high selectivity and bioavailability, in particular for ORL1, is important both for the elucidation and control of the physiological role of the receptor and for their therapeutic importance. The failure to obtain agonists and antagonists when using, for nociceptin, the same substitutions that are successful for opioids, and the conformational flexibility of them all, justify systematic efforts to study the solution conformation under conditions as close as possible to their natural environment. Structural studies of linear peptides in solution are hampered by their high flexibility. A direct structural study of the complex between a peptide and its receptor would overcome this difficulty, but such a study is not easy since opioid receptors are membrane proteins. Thus, conformational studies of lead peptides in solution are still important for drug design. This review deals with conformational studies of natural pre-nociceptin peptides in several solvents that mimic in part the different environments in which the peptides exert their action. None of the structural investigations yielded a completely reliable bioactive conformation, but the global conformation of the peptides in biomimetic environments can shed light on their interaction with receptors.

Animals↗
PubMed2002

[Nphe(1)]N/OFQ-(1-13)-NH(2) is a competitive and selective antagonist at nociceptin/orphanin FQ receptors mediating K(+) channel activation in rat periaqueductal gray slices.

A novel member of the opioid related receptor family, the nociceptin/orphanin FQ (N/OFQ) peptide (NOP) receptor was identified and demonstrated to be involved in many physiological functions including pain regulation. [Nphe(1)]N/OFQ-(1-13)-NH(2) (Nphe) is a novel peptide antagonist of NOP receptors, developed using peripheral preparations. We have quantitatively investigated the interaction of Nphe with N/OFQ, the endogenous ligand of NOP receptors, in the midbrain ventrolateral periaqueductal gray (PAG), a crucial brain region for N/OFQ-induced reversal of opioid analgesia, using the patch-clamp recording technique in brain slices. N/OFQ concentration-dependently activated an inwardly rectifying K(+) current in response to hyperpolarization ramps from -60 to -140 mV. Nphe concentration-dependently attenuated the K(+) current activated by N/OFQ without changing its reversal potential. The presence of Nphe right-shifted the concentration-response curve to N/OFQ in a parallel manner. The Schild plot analysis yielded a slope of 1.16 and a pA(2) value of 6.64 that is similar to those obtained in peripheral preparations. At concentrations up to 3 microM, Nphe affected neither the membrane current per se, nor the inwardly rectifying K(+) current activated by [D-Ala(2), N-Me-Phe(4),Gly-ol(5)]-enkephalin or baclofen, a mu-opioid and GABA(B) receptor agonist, respectively. It is concluded that Nphe acts as a pure, selective and competitive antagonist at native NOP receptors of ventrolateral PAG neurons.

Animals↗
PubMed2002

Pharmacological characterization of the nociceptin receptor which mediates reduction of alcohol drinking in rats.

Chronic intracerebroventricular (ICV) treatment with nociceptin/orphanin FQ (NC), the endogenous ligand for the opioid receptor-like 1 (ORL1) receptor, reduces ethanol intake in alcohol-preferring rats and abolishes the rewarding properties of ethanol in the place conditioning paradigm. To pharmacologically characterize the receptor involved, the present study evaluated the effect on ethanol drinking in genetically selected Marchigian Sardinian alcohol-preferring (msP) rats of ICV injections for 8 days of NC or of the NC analogs NC(1-17)NH(2), NC(1-13)NH(2), NC(1-12)NH(2) and [Nphe(1)]NC(1-13)NH(2). In vitro studies indicate that NC, NC(1-17)NH(2), NC(1-13)NH(2) and NC(1-12)NH(2) are agonists, while [Nphe(1)]NC(1-13)NH(2) is a selective antagonist at the ORL1 receptor. Freely feeding and drinking rats were offered 10% ethanol 30 min/day at the beginning of the dark phase of the light cycle. NC significantly attenuated ethanol intake at 500 or 1000 ng/rat (210 or 420 pmol/rat). NC(1-17)NH(2), markedly reduced ethanol intake, but its effect was statistically significant at 1000 (420 pmol/rat), not at 500 ng/rat (210 pmol/rat). After the end of treatment ethanol drinking promptly came back to baseline level. Ethanol consumption was also reduced by NC(1-13)NH(2); however, its effect was less potent and pronounced. NC(1-12)NH(2) did not modify ethanol intake at doses up to 4000 ng/rat (2339 pmol/rat). Water and food consumption were not modified. Treatment with [Nphe(1)]NC(1-13)NH(2), 66 or 99 microg/rat, did not modify ethanol intake; however, [Nphe(1)]NC(1-13)NH(2), 66 microg/rat, given just before 1000 ng/rat of NC(1-17)NH(2), abolished the effect of the agonist. The present results show that the 13 amino acid N-terminal sequence of NC is essential for the effect on ethanol intake and indicate that [Nphe(1)]NC(1-13)NH(2) acts as an antagonist to block the effect of NC. These findings provide further evidence that selective agonists at the ORL-1 receptor attenuate ethanol intake in alcohol-preferring rats and suggest that the NC/ORL1 system may represent an interesting target for treatment of alcohol abuse.

Alcohol Drinking↗
PubMed2002

[Nphe1,Arg14,Lys15]nociceptin-NH2, a novel potent and selective antagonist of the nociceptin/orphanin FQ receptor.

1. Nociceptin/orphanin FQ (N/OFQ) modulates several biological functions by activating a specific G-protein coupled receptor (NOP). Few molecules are available that selectively activate or block the NOP receptor. Here we describe the in vitro and in vivo pharmacological profile of a novel NOP receptor ligand, [Nphe(1),Arg(14),Lys(15)]N/OFQ-NH(2) (UFP-101). 2. UFP-101 binds to the human recombinant NOP receptor expressed in Chinese hamster ovary (CHO) cells with high affinity (pK(i) 10.2) and shows more than 3000 fold selectivity over classical opioid receptors. UFP-101 competitively antagonizes the effects of N/OFQ on GTPgamma(35)S binding in CHO(hNOP) cell membranes (pA(2) 9.1) and on cyclic AMP accumulation in CHO(hNOP) cells (pA(2) 7.1), being per se inactive at concentrations up to 10 microM. 3. In isolated peripheral tissues of mice, rats and guinea-pigs, and in rat cerebral cortex synaptosomes preloaded with [(3)H]-5-HT, UFP-101 competitively antagonized the effects of N/OFQ with pA(2) values in the range of 7.3 - 7.7. In the same preparations, the peptide was inactive alone and did not modify the effects of classical opioid receptor agonists. 4. UFP-101 is also active in vivo where it prevented the depressant action on locomotor activity and the pronociceptive effect induced by 1 nmol N/OFQ i.c.v. in the mouse. In the tail withdrawal assay, UFP-101 at 10 nmol produces per se a robust and long lasting antinociceptive effect. 5. UFP-101 is a novel, potent and selective NOP receptor antagonist which appears to be a useful tool for future investigations of the N/OFQ-NOP receptor system.

Animals↗
PubMed2002

Central injections of nocistatin or its C-terminal hexapeptide exert anxiogenic-like effect on behaviour of mice in the plus-maze test.

. Nocistatin (NST) antagonizes several actions of nociceptin/orphanin FQ (N/OFQ), but acts on distinct receptors. As N/OFQ exerts anxiolytic-like actions in various tests, its behavioural actions in the elevated plus-maze (EPM) test were compared with those of bovine NST. 2. Five minutes after i.c.v. treatment, mice were placed on the EPM for 5 min and entries into and time spent on open and closed arms were recorded alongside other parameters. 3. NST (0.1 - 3 pmol) reduced percentages of entries into (control 39.6+/-3.1%, peak effect at 1 pmol NST 8.5+/-2.9%) and time spent on open arms (control 30.8+/-2.3%, NST 2.7+/-1.5%). The C-terminal hexapeptide of NST (NST-C6; 0.01 - 10 pmol) closely mimicked these actions of NST, with peak effects at 0.1 pmol. 4. N/OFQ (1 - 100 pmol) increased percentages of entries into (control 38.5+/-3.4%; peak effect at 10 pmol N/OFQ 67.9+/-4.9%) and time spent on open arms (control 32.0+/-3.8%; N/OFQ 74.9+/-5.8%). Closed arm entries, an index of locomotor activity, were unchanged by all peptides. 5. Effects of NST or NST-C6, but not N/OFQ, were still detectable 15 min after injection. Behaviour of animals co-injected with NST (1 pmol) or NST-C6 (0.1 pmol) plus N/OFQ (10 pmol) was indistinguishable from that of controls. 6. These results reveal potent anxiogenic-like actions of NST and NST-C6, and confirm the anxiolytic-like properties of N/OFQ. As NST and N/OFQ both derive from preproN/OF, anxiety may be modulated in opposing directions depending on how this precursor is processed.

Animals↗
PubMed2002

A new ligand for the urotensin II receptor.

The cyclic peptide human urotensin II (U-II) has been recently recognized as the endogenous ligand of an orphan GPCR, subsequently named the UT receptor. No synthetic ligands are available for investigating this novel peptide-receptor system. A novel UT receptor ligand, [Orn(8)]U-II, was synthesized and evaluated in calcium functional assays performed on HEK293 cells expressing the recombinant rat and human UT receptor and in the rat aorta bioassay. [Orn(8)]U-II behaves as a full agonist (pEC(50) approximately equal 8) at both human and rat UT receptors in the FlipR calcium assay eliciting similar maximal effects as the natural ligand U-II. On the contrary, in the rat aorta bioassay, [Orn(8)]U-II behaves as a competitive and selective antagonist (pA(2)=6.56) showing however a small but consistent residual agonist activity. It is therefore proposed that [Orn(8)]U-II is a partial agonist at UT receptors.

Analysis of Variance↗
PubMed2002

Solution structure of the Alzheimer amyloid beta-peptide (1-42) in an apolar microenvironment. Similarity with a virus fusion domain.

The major components of neuritic plaques found in Alzheimer disease (AD) are peptides known as amyloid beta-peptides (Abeta), which derive from the proteolitic cleavage of the amyloid precursor proteins. In vitro Abeta may undergo a conformational transition from a soluble form to aggregated, fibrillary beta-sheet structures, which seem to be neurotoxic. Alternatively, it has been suggested that an alpha-helical form can be involved in a process of membrane poration, which would then trigger cellular death. Conformational studies on these peptides in aqueous solution are complicated by their tendency to aggregate, and only recently NMR structures of Abeta-(1-40) and Abeta-(1-42) have been determined in aqueous trifluoroethanol or in SDS micelles. All these studies hint to the presence of two helical regions, connected through a flexible kink, but it proved difficult to determine the length and position of the helical stretches with accuracy and, most of all, to ascertain whether the kink region has a preferred conformation. In the search for a medium which could allow a more accurate structure determination, we performed an exhaustive solvent scan that showed a high propensity of Abeta-(1-42) to adopt helical conformations in aqueous solutions of fluorinated alcohols. The 3D NMR structure of Abeta-(1-42) shows two helical regions encompassing residues 8-25 and 28-38, connected by a regular type I beta-turn. The surprising similarity of this structure, as well as the sequence of the C-terminal moiety, with those of the fusion domain of influenza hemagglutinin suggests a direct mechanism of neurotoxicity.

Alzheimer Disease↗
PubMed2002

Pharmacological profile of nociceptin/orphanin FQ receptors.

1. Nociceptin/orphanin FQ (NC) and its receptor (OP4) represent a novel peptide/receptor system pharmacologically distinct from classical opioid systems. 2. Via OP4 receptor activation, NC regulates several biological functions, both at peripheral and central levels; therefore, the OP4 receptor may be viewed as a novel target for drug development. However, the pharmacology of this receptor is still in its infancy, with few molecules interacting selectively with this receptor. 3. In the present article, we review the findings of studies that have investigated the pharmacological profile of ligands selective for the OP4 receptor, these being two antagonists, the peptide [Nphe1]NC(1-13)NH2 and the non-peptide J-113397, and two agonists, the peptide [Arg14,Lys15]NC, and the non- peptide Ro 64-6198. 4. The results of these studies indicate that agents that selectively activate or block the OP4 receptor may represent new potential drugs for the treatment of human diseases.

Animals↗
PubMed2002

[Arg(14),Lys(15)]nociceptin, a highly potent agonist of the nociceptin/orphanin FQ receptor: in vitro and in vivo studies.

The nociceptin (NC)/orphanin FQ analog, [Arg(14),Lys(15)]NC, has been recently demonstrated to behave as a potent agonist at the human recombinant NC receptors (OP(4)). In this study, we evaluated the pharmacological profile of [Arg(14),Lys(15)]NC in vitro on the native OP(4) receptors expressed in isolated tissues and in vivo in the locomotor activity and the tail-withdrawal assays in mice. On isolated tissues, [Arg(14),Lys(15)]NC mimicked the effects of NC, showing similar maximal effects but higher potencies (17-fold in the mouse vas deferens, 10-fold in the rat vas deferens, and about 5-fold in the guinea pig ileum and mouse colon). In these preparations, the effects of [Arg(14),Lys(15)]NC were not modified by 1 microM naloxone, although antagonized by the OP(4) receptor antagonists [Nphe(1)]NC(1-13)NH(2) (pA(2) congruent with 6) and (+/-)trans-1-[1-cyclooctylmethyl-3hydroxymethyl-4-piperidyl]-3-ethyl-1,3-dihydro-2H-benzimidazol-2-one (J-113397) (pA(2) congruent with 8). In the rat vas deferens, a cocktail of peptidase inhibitors increased the maximal effects of NC, its analog, and the pEC(50) of NC (by 4-fold); the potency of [Arg(14),Lys(15)]NC was not significantly modified by peptidase inhibitors. In in vivo experiments, [Arg(14),Lys(15)]NC mimicked the effects of NC, producing, after intracerebroventricular administration, pronociceptive effects in the tail-withdrawal assay and inhibiting the locomotor activity of the mice. In both assays, [Arg(14),Lys(15)]NC was about 30-fold more potent than NC and produced longer lasting effects. Taken together, the present data demonstrate that [Arg(14),Lys(15)]NC behaves as a highly potent agonist of the OP(4) receptor and is able to produce long-lasting effects in vivo, compared with the natural ligand NC.

Animals↗