Agostino Marrazzo

Neuroprotective effects of sigma-1 receptor agonists against beta-amyloid-induced toxicity.

Prolonged exposure of cultured cortical neurons to the residue 25–35 fragment of &bgr;-amyloid protein, in the presence of dizocilpine, an antagonist of the N-methyl-D-aspartate receptor, and of 6,7-dinitroquinoxaline-2,3-dione, an antagonist of &agr;-amino-3-hydroxy-5-methylisoxazole-4-propionate receptors, resulted in the expression of the proapoptotic protein Bax and neuronal death. Beta-amyloid protein(25–35)-induced neuronal death was substantially attenuated by the σ1 receptor agonist 2-(4-morpholinethyl)1-phenylcyclohexanecarboxylate. The neuroprotective action of 2-(4-morpholinethyl)1-phenylcyclohexanecarboxylate was mimicked by the σ1 ligand methyl (1S,2R)-2-[1-adamantyl(methyl)amino]methyl-1-phenylcyclopropanecarboxylate and was antagonized by the σ1 receptor antagonist N,N-dipropyl-2-[4-methoxy-3-(2-phenylethoxy)-phenyl]-ethylamine monohydrochloride. These results suggest that σ1 receptor agonists might function as neuroprotectant agents in Alzheimers disease.

Anti‐amnesic properties of (±)‐PPCC, a novel sigma receptor ligand, on cognitive dysfunction induced by selective cholinergic lesion in rats

J. Neurochem. (2009) 109, 744–754.

Opioid and sigma receptor studies. New developments in the design of selective sigma ligands

New racemic and chiral methyl 2-{[4-(4-chlorophenyl)-4-hydroxypiperi-din-1-yl]methyl}-1-phenylcyclopropanecarboxylate derivatives were synthesized in order to obtain sigma ligands with increased affinity and selectivity compared to (+)-MPCB and haloperidol. The cis-(±)-7 racemic mixture showed a better binding affinity and selectivity than the (±)-8 trans isomers. Between the two cis enantiomers, (+)-7, with configuration (1R,2S), showed a very high affinity and the best selectivity for s1. All compounds synthesized (79) showed a reduced or negligible affinity for opioid and dopaminergic D1 and D2 receptors. Nociceptive in vivo test confirms that (+)-7 (namely MR200), such as non-selective antagonist haloperidol, increased the analgesic effect induced by the k opioid selective ligand U50,488H and reversed the inhibiting effect of (+)-pentazocine on analgesia.

Intrastriatal administration of sigma ligands inhibits basal dopamine release in vivo.

In this study, using the new sigma(1/2) (sigma(1/2)) compound MR200, its parent drug haloperidol and the sigma ligand 1,3-di-o-tolylguanidine (DTG), we have investigated the role of striatal sigma receptors in the control of basal dopamine (DA) outflow, by coupling in vitro binding experiments and in vivo microdialysis in the striatum of halothane-anesthetized rats. MR200 with respect to haloperidol, exhibits high affinity for sigma(1) (1.5 nM) and sigma(2) (21.9 nM) receptors, but only negligible affinity for DA receptors. Compared to DTG, MR200 has similar selectivity across neurotransmitter systems, and 46 times higher affinity for sigma(1) receptors. Intrastriatal application of MR200 at 10, but not 0.1 or 1 microM, elicited a pronounced decrease in striatal DA release (-45% of control values). This inhibitory effect was preceded by a transient increase in DA release (+50% over baseline) after 100 microM MR200 administration. DTG at 100, but not 10 microM, significantly reduced DA release (-40%). Haloperidol, whilst increasing DA release at 1 microM, induced a delayed decrease in DA release after 10 microM application. Finally, haloperidol (10 microM) did not modify the inhibitory effect of 10 microM MR200. These results show that striatal sigma receptors control striatal DA release in resting conditions.

A new sigma ligand, (±)-PPCC, antagonizes kappa opioid receptor-mediated antinociceptive effect

The compound (1R,2S/1S,2R)-2-[4-hydroxy-4-phenylpiperidin-1-yl)methyl]-1-(4-methylphenyl) cyclopropanecarboxylate [(+/-)-PPCC] is a ligand with high affinity for sigma (sigma) sites of which the selectivity towards several other receptor systems has been demonstrated. Given the existence of a relationship between the sigma system and the kappa opioid (KOP)-mediated analgesia, to characterize the pharmacological properties of (+/-)-PPCC we analyzed its influence on the analgesic effect of the systemic injected kappa agonist (-)-U-50,488H comparing the effects with those shown by (+)-pentazocine and BD1047. The results demonstrate that the systemic administration of (+/-)-PPCC (1 mg/kg s.c.) does not modify basal tail-flick latency. Pre-treatment with (+/-)-PPCC, at the same dose, significantly decreased the antinociceptive effect of (-)-U-50,488H, analogously to the sigma compounds used. This study confirms that (+/-)-PPCC plays the role of sigma agonist in this model and strengthens the hypothesis of the sigma receptor modulatory role on KOP-mediated analgesia.

Simultaneous determination of amphetamine and one of its metabolites by HPLC with electrochemical detection

A high-performance liquid chromatographic method coupled with electrochemical detector was developed for the separation and quantitation of amphetamine and one of its metabolites, the 4-hydroxynorephedrine. The pre-column derivatisation of these compounds was carried out with 2,5-dihydroxybenzaldehyde as electroactive labelling reagent, in presence of Borohydride Exchange Resin. The new synthetic method developed was fast, clean and high yielding. The analysis was performed in isocratic mode on a reversed phase column 5 microm Hypersil ODS RP-18, 15 cm, using as a mobile phase methanol-NaH(2)PO(4) buffer (50 mM, pH 5.5)(30:70 v/v) containing trietylamine (0.5% v/v) and the products were detected by a porous graphite electrode set at an oxidation potential of +0.6 V. The linearity of response was examined for each derivatised compound and was analysed using solutions in the range 10-40 nmol/ml. The correlation coefficients of the linear regression of the standard curves were greater than 0.99. The method developed in this study was sensitive and very selective. Because of the specificity for primary phenylethylamines, it could be applicable for the assay of other related substances in toxicology and drugs abuse.

Novel Potent and Selective σ Ligands: Evaluation of Their Agonist and Antagonist Properties

Novel enantiomers and diastereoisomers structurally related to σ ligand (+)-MR200 were synthesized to improve σ(1)/σ(2) subtype selectivity. The selective σ(1) ligand (-)-8 showed an antagonist profile determined by phenytoin differential modulation of binding affinity in vitro, confirmed in vivo by an increase of κ opioid analgesia. The σ(2) ligand (-)-9 displayed agonist properties in an in vitro isolated organ bath assay and antiproliferative effects on LNCaP and PC3 prostate cancer cell lines.

Anti-Amnesic and Neuroprotective Actions of the Sigma-1 Receptor Agonist (-)-MR22 in Rats with Selective Cholinergic Lesion and Amyloid Infusion

Sigma-1 receptor agonists have recently attracted much attention as potential therapeutic drugs for cognitive and affective disorders, however, it is still unclear whether they act via modulation of transmitter release or activation of sigma-1 receptors in memory-related brain regions. In the present study,we have investigated the anti-amnesic and neuroprotective actions of the compound (-)-methyl (1S,2R)-2-{[1-adamantyl(methyl)amino]methyl}-1-phenylcyclopropane-carboxylate) [(-)-MR22],a selective sigma-1 receptor agonist able to protect cultured cortical neurons from amyloid toxicity. To this aim, cognitive deficits, cholinergic loss, and amyloid peptide accumulation were obtained in the rat by simultaneous injections of a selective immunotoxin and pre-aggregated amyloid peptide into the basal forebrain and the hippocampus, respectively. At about five–six weeks post-lesion, the double-lesioned animals exhibited dramatic deficits in spatial learning and memory, whereas animals with single injections of either compound were not or only marginally affected, in spite of equally severe cholinergic loss oramyloid deposition. Administration of (-)-MR22 appeared to reverse cognitive impairments in double lesioned animals, whereas pre-treatment with the selective sigma-1 antagonist BD1047 abolished this effect. Moreover, (-)-MR22 normalized the levels of cell-associated amyloid-β protein precursor (AβPP) in the neocortex and hippocampus, thus sustaining a non-amyloidogenic AβPP processing. By contrast, treatment with (-)-MR22 produced no effects whatsoever in intact animals. Thus, sigma-1 receptor agonists such as (-)-MR22 may ameliorate perturbed cognitive abilities and exert a protective action onto target neurons, holding promises as viable tools for memory enhancement and neuroprotection.

Novel imidazole derivatives as heme oxygenase-1 (HO-1) and heme oxygenase-2 (HO-2) inhibitors and their cytotoxic activity in human-derived cancer cell lines

Heme oxygenase (HO) is a cytoprotective enzyme that can be overexpressed in some pathological conditions, including certain cancers. In this work, novel imidazole derivatives were designed and synthesized as inhibitors of heme oxygenase-1 (HO-1) and heme oxygenase-2 (HO-2). In these compounds the imidazole ring, crucial for the activity, is connected to a hydrophobic group, represented by aryloxy, benzothiazole, or benzoxazole moieties, by means of alkyl or thioalkyl chains of different length. Many of the tested compounds were potent and/or selective against one of the two isoforms of HO. Furthermore, most of the pentyl derivatives showed to be better inhibitors of HO-2 with respect to HO-1, revealing a critical role of the alkyl chain in discriminating between the two isoenzymes. Compounds which showed the better profile of HO inhibition were selected and tested to evaluate their cytotoxic properties in prostate and breast cancer cell lines (DU-145, PC3, LnCap, MDA-MB-231, and MCF-7). In these assays, aryloxyalkyl derivatives resulted more cytotoxic than benzothiazolethioalkyl ones; in particular compound 31 was active against all the cell lines tested, confirming the anti-proliferative properties of HO inhibitors and their potential use in the treatment of specific cancers.

Antinociceptive profile of LP1, a non-peptide multitarget opioid ligand

AIMS Opioid drugs are the principal treatment option for moderate to severe pain and exert their biological effects through interactions with opioid receptors that are widely distributed throughout the CNS and peripheral tissues. Ligands capable of simultaneously targeting different receptors could be successful candidates for the treatment of chronic pain. Enhanced antinociception coupled with a low incidence of side effects has been demonstrated for ligands possessing mixed mu-opioid receptor (MOR) and delta-opioid receptor (DOR) activity. We previously reported that 3-[(2R,6R,11R)-8-hydroxy-6,11-dimethyl-1,4,5,6-tetrahydro-2,6-methano-3-benzazocin-3(2H)-yl]-N-phenylpropanamide (LP1) acted as a MOR-DOR ligand in in vitro functional assays and moreover this drug produced a valid antinociception that was longer lasting than that of morphine. The aim of this work was to determine whether the antinociceptive effect produced by LP1 was central or peripheral and to assess which opioid receptor subtypes are involved in its effects. MAIN METHODS We explored the effects of naloxone methiodide (NX-M), a quaternary opioid antagonist, administered either intracerebroventricularly (i.c.v.) or subcutaneously (s.c.), on LP1-mediated antinociception in male Sprague-Dawley rats. In addition, we administered s.c. selective antagonists for MOR, DOR and kappa-opioid receptor (KOR) to investigate the effects of LP1. To characterise this drugs DOR profile better, we also investigated the effects of LP1 on DPDPE, a selective DOR agonist. KEY FINDINGS Data obtained by tail flick test showed that LP1 induced predominantly MOR-mediated supraspinal antinociception and was able to counteract DPDPE analgesia. SIGNIFICANCE LP1, a multitarget opioid ligand, is a supraspinal acting antinociceptive agent that is useful for the treatment of chronic pain.