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Biomedical subjects

Jorge D Brioni

Publications and source records attributed to Jorge D Brioni.

At least 19 recordsLinked to original sources
PubMed2007

Fatty acid amide hydrolase inhibitors display broad selectivity and inhibit multiple carboxylesterases as off-targets.

Fatty acid amide hydrolase (FAAH) is the primary regulator of several bioactive lipid amides including anandamide. Inhibitors of FAAH are potentially useful for the treatment of pain, anxiety, depression, and other nervous system disorders. However, FAAH inhibitors must display selectivity for this enzyme relative to the numerous other serine hydrolases present in the human proteome in order to be therapeutically acceptable. Here we employed activity-based protein profiling (ABPP) to assess the selectivity of FAAH inhibitors in multiple rat and human tissues. We discovered that some inhibitors, including carbamate compounds SA-47 and SA-72, and AM404 are exceptionally selective while others, like URB597, BMS-1, OL-135, and LY2077855 are less selective, displaying multiple off-targets. Since proteins around 60kDa constitute the major off-targets for URB597 and several other FAAH inhibitors with different chemical structures, we employed the multi-dimensional protein identification technology (MudPIT) approach to analyze their identities. We identified multiple carboxylesterase isozymes as bona fide off-targets of FAAH inhibitors. Consistently, enzymatic assay confirmed inhibition of carboxylesterase activities in rat liver by FAAH inhibitors. Since carboxylesterases hydrolyze a variety of ester-containing drugs and prodrugs, we speculate that certain FAAH inhibitors, by inhibiting carboxylesterases, might have drug-drug interactions with other medicines if developed as therapeutic agents.

Amidohydrolases↗
PubMed2006

Discovery of 3-methyl-N-(1-oxy-3',4',5',6'-tetrahydro-2'H-[2,4'-bipyridine]-1'-ylmethyl)benzamide (ABT-670), an orally bioavailable dopamine D4 agonist for the treatment of erectile dysfunction.

The goal of this study was to identify a structurally distinct D(4)-selective agonist with superior oral bioavailability to our first-generation clinical candidate 1a (ABT-724) for the potential treatment of erectile dysfunction. Arylpiperazines such as (heteroarylmethyl)piperazine 1a, benzamide 2, and acetamides such as 3a,b exhibit poor oral bioavailability. Structure-activity relationship (SAR) studies with the arylpiperidine template provided potent partial agonists such as 4d and 5k that demonstrated no improvement in oral bioavailability. Further optimization with the (N-oxy-2-pyridinyl)piperidine template led to the discovery of compound 6b (ABT-670), which exhibited excellent oral bioavailability in rat, dog, and monkey (68%, 85%, and 91%, respectively) with comparable efficacy, safety, and tolerability to 1a. The N-oxy-2-pyridinyl moiety not only provided the structural motif required for agonist function but also reduced metabolism rates. The SAR study leading to the discovery of 6b is described herein.

Action Potentials↗
PubMed2006

1-aryl-3-(4-pyridine-2-ylpiperazin-1-yl)propan-1-one oximes as potent dopamine D4 receptor agonists for the treatment of erectile dysfunction.

A new series of dopamine D4 receptor agonists, 1-aryl-3-(4-pyridinepiperazin-1-yl)propanone oximes, was designed through the modification of known dopamine D4 receptor agonist PD 168077. Replacement of the amide group with a methylene-oxime moiety produced compounds with improved stability and efficacy. Structure-activity relationsips (SAR) of the aromatic ring linked to the N-4-piperazine ring confirmed the superiority of 2-pyridine as a core for D4 agonist activity. A two-methylene linker between the oxime group and the N-1-piperazine ring displayed the best profile. New dopamine D4 receptor agonists, exemplified by (E)-1-(4-chlorophenyl)-3-(4-pyridin-2-ylpiperazin-1-yl)propan-1-one O-methyloxime (59a) and (E)-1-(3-chloro-4-fluorophenyl)-3-(4-pyridin-2-ylpiperazin-1-yl)propan-1-one O-methyloxime (64a), exhibited favorable pharmacokinetic profiles and showed oral bioavailability in rat and dog. Subsequent evaluation of 59a in the rat penile erection model revealed in vivo activity, comparable in efficacy to apomorphine. Our results suggest that the oximes provide a novel structural linker for 4-arylpiperazine-based D4 agonists, possessing leadlike quality and with potential to develop a new class of potent and selective dopamine D4 receptor agonists.

Animals↗
PubMed2006

Correlation between brain/plasma ratios and efficacy in neuropathic pain models of selective metabotropic glutamate receptor 1 antagonists.

We have discovered a novel, potent, and selective triazafluorenone series of metabotropic glutamate receptor 1 (mGluR1) antagonists with efficacy in various rat pain models. Pharmacokinetic and pharmacodynamic profiles of these triazafluorenone analogs revealed that brain/plasma ratios of these mGluR1 antagonists were important to achieve efficacy in neuropathic pain models. This correlation could be used to guide our in vivo SAR (structure-activity relationship) modification. For example, compound 4a has a brain/plasma ratio of 0.34, demonstrating only moderate efficacy in neuropathic pain models. On the other hand, antagonist 4b with a brain/plasma ratio of 2.70 was fully efficacious in neuropathic pain models.

Animals↗
PubMed2006

Association of Catsper1 or -2 with Ca(v)3.3 leads to suppression of T-type calcium channel activity.

Sperm-specific CatSper1 and CatSper2 proteins are critical to sperm-hyperactivated motility and male fertility. Although architecturally resembling voltage-gated ion channels, neither CatSper1 nor CatSper2 alone forms functional ion channels in heterologous expression systems, which may be related to the absence of yet unidentified accessory subunits. Here we isolated CatSper1- and CatSper2-associated protein(s) from human sperm and analyzed their identities by a multidimensional protein identification technology approach. We identified the T-type voltage-gated calcium channel Ca(v)3.3 as binding to both CatSper1 and CatSper2. The specificity of their interactions was verified by co-immunoprecipitation in transfected mammalian cells. Electrophysiological studies revealed that the co-expression of CatSper1 or CatSper2 specifically inhibited the amplitude of Ca(v)3.3-evoked T-type calcium current without altering other biophysical properties of Ca(v)3.3. Immunostaining studies revealed co-localization of CatSper1 and Ca(v)3.3 on the principal piece of human sperm tail. Furthermore, fluorescence resonance energy transfer analysis revealed close proximity and physical association of these two proteins on the sperm tail. These studies demonstrate that CatSper1 and CatSper2 can associate with and modulate the function of the Ca(v)3.3 channel, which might be important in the regulation of sperm function.

Calcium Channels↗
PubMed2006

Acrylamide analog as a novel nitric oxide-independent soluble guanylyl cyclase activator.

Soluble guanylyl cyclase (sGC) is a target enzyme for endogenous nitric oxide (NO), and it converts GTP to cyclic GMP (guanosine 3',5'-cyclic monophosphate) as part of a cascade that results in physiological processes such as smooth muscle relaxation, neurotransmission, and inhibition of platelet aggregation. Here we examine a representative of the novel class sCG activators, A-778935 ((+/-)-cis-3-[2-(2,2-dimethyl-propylsulfanyl)-pyridin-3-yl]-N-(3-hydroxy-cyclohexyl)-acrylamide). A-778935 activated sGC synergistically with sodium nitroprusside (SNP) over a wide range of concentration, inducing up to 420-fold activation. A specific inhibitor of sGC, ODQ (1H-[1,2,4]-oxadiazolo[4,3-alpha]quinoxalin-1-one), did not block basal sGC activity, but competitively inhibited the activation by A-778935. A-778935, with or without SNP, did not activate heme-deficient sGC, indicating that the activation of sGC by A-778935 is fully heme-dependent. A-778935 increased intracellular cGMP level dose-dependently in smooth muscle cells. In the presence of 1 microM SNP, a lower concentration of A-778935 increased cGMP than A-778935 alone, and the cGMP concentration reached the same level at 100 microM of A-778935. A-778935 relaxed cavernosum tissue strips in a dose-dependent manner; and in the presence of 1 microM SNP, A-778935 relaxed the strips more potently, shifting the dose-response curve to the left. This novel activator of sGC may have potential efficacy for the treatment of a variety of disorders associated with reduced NO signaling.

Acrylamides↗
PubMed2005

Dopamine D4 receptor signaling in the rat paraventricular hypothalamic nucleus: Evidence of natural coupling involving immediate early gene induction and mitogen activated protein kinase phosphorylation.

The dopamine D4 receptor has been investigated for its potential role in several CNS disorders, notably schizophrenia and more recently, erectile dysfunction. Whereas studies have investigated dopamine D4 receptor-mediated signaling in vitro, there have been few, if any, attempts to identify dopamine D4 receptor signal transduction pathways in vivo. In the present studies, the selective dopamine D4 agonist PD168077 induces c-Fos expression and extracellular signal regulated kinase (ERK) phosphorylation in the hypothalamic paraventricular nucleus (PVN), a site known to regulate proerectile activity. The selective dopamine D4 receptor antagonist A-381393 blocked both c-Fos expression and ERK1/2 phosphorylation produced by PD168077. In addition, PD168077-induced ERK1/2 phosphorylation was prevented by SL327, an inhibitor of ERK1/2 phosphorylation. Interestingly, treatment with A-381393 alone significantly reduced the amount of Fos immunoreactivity as compared to basal expression observed in vehicle-treated controls. Dopamine D4 receptor and c-Fos coexpression in the PVN was observed using double immunohistochemical labeling, suggesting that PD168077-induced signaling may result from direct dopamine D4 receptor activation. Our results demonstrate functional dopamine D4 receptor expression and natural coupling in the PVN linked to signal transduction pathways that include immediate early gene and MAP kinase activation. Further, the ability of the selective dopamine D4 antagonist A-381393 alone to reduce c-Fos expression below control levels may imply the presence of a tonic dopamine D4 receptor activation under basal conditions in vivo. These findings provide additional evidence that the PVN may be a site of dopamine D4 receptor-mediated proerectile activity.

Aminoacetonitrile↗
PubMed2005

Structure-activity relationship of triazafluorenone derivatives as potent and selective mGluR1 antagonists.

SAR (structure-activity relationship) studies of triazafluorenone derivatives as potent mGluR1 antagonists are described. The triazafluorenone derivatives are non-amino acid derivatives and noncompetitive mGluR1 antagonists that bind at a putative allosteric recognition site located within the seven-transmembrane domain of the receptor. These triazafluorenone derivatives are potent, selective, and systemically active mGluR1 antagonists. Compound 1n, for example, was a very potent mGluR1 antagonist (IC50 = 3 nM) and demonstrated full efficacy in various in vivo animal pain models.

Analgesics↗
PubMed2005

A-412997 is a selective dopamine D4 receptor agonist in rats.

A-412997 (2-(3',4',5',6'-tetrahydro-2'H-[2,4'] bipyridinyl-1'-yl)-N-m-tolyl-acetamide) is a highly selective dopamine D4 receptor agonist that binds with high affinity to rat dopamine D4 and human dopamine D4.4 receptors (Ki=12.1 and 7.9 nM, respectively). In contrast to the dopamine D4 receptor agonists PD168077 and CP226269, A-412997 showed a better selectivity profile and no affinity <1000 nM for other dopamine receptors or any other proteins in a panel of seventy different receptors and channels. In functional assays using calcium flux, A-412997 was a potent full agonist at rat dopamine D4 receptors (28.4 nM, intrinsic activity=0.83) and did not activate rat dopamine D2L receptors, unlike CP226269. Dopamine D4 receptor selective agonists have been shown to induce penile erection in rats by central mechanisms. A-412997 induces penile erection in a conscious rat model (effective dose=0.1 micromol/kg, s.c.) with comparable efficacy as the nonselective D2-like agonist, apomorphine. When dosed systemically, A-412997 crossed the blood brain barrier rapidly and achieved significantly higher levels than PD168077. A-412997 is a highly selective dopamine D4 receptor agonist and a useful tool to understand the role of dopamine D4 receptors in rat models of central nervous system processes and disease.

Acetamides↗
PubMed2005

A-412997, a selective dopamine D4 agonist, improves cognitive performance in rats.

The recent development of a highly selective dopamine D4 receptor agonist, A-412997 (2-(3',4',5',6'-tetrahydro-2'H-[2,4'] bipyridinyl-1'-yl)-N-m-tolyl-acetamide), has provided a pharmacological tool with which to conduct systematic investigations into the putative role for dopamine D4 receptors in the central nervous system. These present studies evaluated the potential cognitive enhancing properties of A-412997 in rat models of ADHD (5-trial repeated acquisition inhibitory avoidance in Spontaneous Hypertensive Rat pups) and short-term memory (Social Recognition), in comparison with the less selective dopamine D4 receptor agonists PD168077 and CP226269. A-412997 showed significant dose-dependent efficacy in both models. PD168077 repeatedly improved acquisition in the 5-trial inhibitory avoidance model but failed to reach significance at any dose tested, although significantly improved social recognition was observed (albeit less potent than A-412997). CP226269 showed a significant enhancement in the 5-trial inhibitory avoidance model. These results support a role for the dopamine D4 receptor subtype in cognition.

Acetamides↗
PubMed2005

2-[4-(3,4-Dimethylphenyl)piperazin-1-ylmethyl]-1H benzoimidazole (A-381393), a selective dopamine D4 receptor antagonist.

2-[4-(3,4-Dimethylphenlyl)piperazin-1-ylmethyl]-1H benzoimidazole (A-381393) was identified as a potent dopamine D4 receptor antagonist with excellent receptor selectivity. [3H]-spiperone competition binding assays showed that A-381393 potently bound to membrane from cells expressing recombinant human dopamine D4.4 receptor (Ki=1.5 nM), which was 20-fold higher than that of clozapine (Ki=30.4 nM). A-381393 exhibited highly selective binding for the dopamine D4.4 receptor (>2700-fold) when compared to D1, D2, D3 and D5 dopamine receptors. Furthermore, in comparison to clozapine and L-745870, A-381393 exhibits better receptor selectivity, showing no affinity up to 10 microM for a panel of more than 70 receptors and channels, with the exception of moderate affinity for 5-HT2A (Ki=370 nM). A-381393 potently inhibited the functional activity of agonist-induced GTP-gamma-S binding assay and 1 microM dopamine induced-Ca2+ flux in human dopamine D4.4 receptor expressing cells, but not in human dopamine D2L or D3 receptor cells. In contrast to L-745870, A-381393 did not exhibit any significant intrinsic activity in a D4.4 receptor. In vivo, A-381393 has good brain penetration after subcutaneous administration. A-381393 inhibited penile erection induced by the selective D4 agonist PD168077 in conscious rats. Thus, A-381393 is a novel selective D4 antagonist that will enhance the ability to study dopamine D4 receptors both in vitro and in vivo.

Animals↗
PubMed2005

Electrophysiological and in vivo characterization of A-317567, a novel blocker of acid sensing ion channels.

Acid Sensing Ion Channels (ASICs) are a group of sodium-selective ion channels that are activated by low extracellular pH. The role of ASIC in disease states remains unclear partly due to the lack of selective pharmacological agents. In this report, we describe the effects of A-317567, a novel non-amiloride blocker, on three distinct types of native ASIC currents evoked in acutely dissociated adult rat dorsal root ganglion (DRG) neurons. A-317567 produced concentration-dependent inhibition of all pH 4.5-evoked ASIC currents with an IC50 ranging between 2 and 30muM, depending upon the type of ASIC current activated. Unlike amiloride, A-317567 equipotently blocked the sustained phase of ASIC3-like current, a biphasic current akin to cloned ASIC3, which is predominant in DRG. When evaluated in the rat Complete Freud's Adjuvant (CFA)-induced inflammatory thermal hyperalgesia model, A-317567 was fully efficacious at a dose 10-fold lower than amiloride. A-317567 was also potent and fully efficacious when tested in the skin incision model of post-operative pain. A-317567 was entirely devoid of any diuresis or natriuresis activity and showed minimal brain penetration. In summary, A-317567 is the first reported small molecule non-amiloride blocker of ASIC that is peripherally active and is more potent than amiloride in vitro and in vivo pain models. The discovery of A-317567 will greatly help to enhance our understanding of the physiological and pathophysiological role of ASICs.

Acid Sensing Ion Channels↗
PubMed2005

Dopamine D2, but not D4, receptor agonists are emetogenic in ferrets.

Agents that activate the dopamine D2-like family of receptors elicit emesis in humans and other species with a vomiting/emetic reflex; however, the lack of dopamine receptor subtype selective agonists has hampered an understanding of which dopamine D2-like receptor subtype(s) contributes to the emetic response. In this study, stable cell lines expressing the ferret dopamine D2-long (D2L) and D4 receptors were used to characterize known dopamine agonists via radioligand binding and calcium ion flux assays, while emetic activity of these dopamine receptor agonists was determined in male ferrets. Latencies to first emetic event, average number of emetic episodes, and stereotypical behaviors which may be indicative of nausea were also determined. Agonists at dopamine D1-like and D4 receptors had no emetic effect in ferrets. Conversely, stimulation of dopamine D2 and/or D3 receptors resulted in a robust emetic response characterized by a relatively short latency (<15 min) and multiple emetic events. Competitive antagonists of dopamine D2-like receptors (domperidone, haloperidol) dose-dependently blocked the emetic response to PNU95666E, a dopamine D2 receptor selective agonist. Thus, dopamine D2 and/or D3 receptor agonists elicit emesis, while dopamine D1/D5 or D4 receptor-selective agonists are devoid of emetic properties.

Animals↗
PubMed2005

Antidepressant-like effect of D(2/3) receptor-, but not D(4) receptor-activation in the rat forced swim test.

Dopamine plays a role in the pathophysiology of depression and therapeutic effects of antidepressants but the contribution of individual D(2)-like receptor subtypes (D(2), D(3), D(4)) to depression is not known. We present evidence that activation of D(2)/D(3), but not D(4) receptors, can affect the outcome in the rat forced swim test (FST). Nomifensine, a dopamine uptake inhibitor (7, 14, and 28 micromol/kg); quinpirole, a D(2)-like receptor and agonist (0.4, 1.0, and 2.0 micromol/kg); PD 12,8907, a preferential D(3) receptor agonist (0.17, 0.35, and 0.7 micromol/kg); PD 168077 (0.1, 0.3, and 1.0 micromol/kg) and CP 226269 (0.3, 1.0, and 3.0 micromol/kg), both selective D(4) receptor agonists, were administered s.c. 24, 5, and 0.5/1 h before testing. Nomifensine, quinpirole at all doses and PD 128907 at the highest dose decreased immobility time in FST. PD 168077 and CP 226269 had no effect on the model. To further clarify what type of dopamine receptors were involved in the anti-immobility effect of quinpirole, we tested different antagonists. Haloperidol, a D(2)-like receptor antagonist (0.27 micromol/kg), completely blocked the effect of quinpirole; A-437203 (LU-201640), a selective D(3) receptor antagonist (17.46 micromol/kg), showed a nonsignificant trend to attenuate the effect of the low dose of quinpirole, and L-745,870, a selective D(4) receptor antagonist (1.15 micromol/kg), had no effect. The pharmacological selectivity of the compounds tested suggests that the antidepressant-like effects of quinpirole are most likely mediated mainly by D(2) and to a lesser extent by D(3) but not D(4) receptors.

Analysis of Variance↗
PubMed2004

Synthesis and activity of 2-[4-(4-[3H]-2-cyanophenyl)piperazinyl]-N-(2,4,6-[3H]3-3-methylphenyl)acetamide: a selective dopamine D4 receptor agonist and radioligand.

The first selective dopamine D4 agonist radioligand is described. The synthesis of these piperazine radioligands relied on the transformation of brominated precursors 4a and 4b with tritium gas in the presence of a sensitive cyano functional group. The specific activity of these two radioligands was measured and [3H]6b found to be suitable for use in D4 saturation and competition binding studies. The synthesis, biological, and radioactivity of this new agonist radioligand as well as preliminary SAR will be discussed.

Acetamides↗
PubMed2004

[3H] A-369508 ([2-[4-(2-cyanophenyl)-1-piperazinyl]-N-(3-methylphenyl) acetamide): an agonist radioligand selective for the dopamine D4 receptor.

Tritiation of the dopamine D(4) receptor selective agonist A-369508 ([2-[4-(2-cyanophenyl)-1-piperazinyl]-N-(3-methylphenyl) acetamide) has provided a radioligand for the characterization of dopamine D(4) receptors. [(3)H] A-369508 binds with high affinity to the major human dopamine D(4) receptor variants D(4.2), D(4.4) and D(4.7) (K(d)=1.7, 4, and 1.2 nM, respectively). It also binds to the rat dopamine D(4) receptor, (K(d)=4.4 nM), implying similar binding affinity across human and rat receptors. A-369508 shows >400-fold selectivity over D(2L), >350-fold selectivity over 5-HT(1A) and >700-1,000-fold selectivity over all other receptors tested. Agonist activity determined by inhibition of forskolin-induced cAMP in Chinese hamster ovary cells transfected with the human dopamine D(4.4) receptor (EC(50)=7.5 nM, intrinsic activity=0.71) indicates that A-369508 is a potent agonist at the human dopamine D(4) receptor. Similar data was observed in other functional assays. [(3)H] A-369508 binds to a single, high affinity site on membranes containing the human dopamine D(4.4) receptor. When compared to the D(2)-like antagonist [(3)H] spiperone, competition binding for agonists like dopamine and apomorphine were 2-10-fold more potent with [(3)H] A-369508, while the antagonists clozapine, haloperidol and L-745870 bind with similar affinity to both ligands. Binding to rat brain regions demonstrated that the most abundant area was cerebral cortex (51.2 fmol/mg protein) followed by hypothalamus, hippocampus, striatum and cerebellum. [(3)H] A-369508 is a useful tool to define the localization and physiological role of dopamine D(4) receptors in central nervous system and can facilitate measuring accurate affinities (K(i)) for structure/activity relationship studies designed to identify dopamine D(4) receptor selective agonists.

Acetamides↗
PubMed2004

Comparative pharmacology of human dopamine D(2)-like receptor stable cell lines coupled to calcium flux through Galpha(qo5).

The goal of this study was to develop a new approach to study the pharmacology of the dopamine D(4) receptor that could be used in comparative studies with dopamine D(2) and D(3) receptors. Stable HEK-293 cell lines co-expressing recombinant human D(2L), D(3) or D(4) receptors along with Galpha(qo5) cDNA were prepared. Dopamine induced a robust, transient calcium signal in these cell lines with EC(50)s for D(2L), D(3) and D(4) of 18.0, 11.9 and 2.2 nM, respectively. Reported D(4)-selective agonists CP226269 and PD168077 were potent, partial D(4) agonists exhibiting 31-1700-fold selectivity for D(4) over D(3) or D(2). Non-selective D(2)-like agonists apomorphine and quinpirole showed full efficacy but did not discriminate across the three receptors. D(3)-selective agonists 7-hydroxy-DPAT and PD128907 were potent but non-selective D(2)-like agonists. The reported D(3) partial agonist BP-897 exhibited minimal agonist activity at D(3) but was a potent D(3) antagonist and a partial D(4) agonist. Other D(2)-like antagonists, haloperidol, clozapine, and domperidone showed concentration-dependent inhibition of dopamine responses at all three receptors with K(i) ranging from 0.05 to 48.3 nM. The D(3) selective antagonist S33084 and D(4)-selective antagonist L-745870 were highly selective for D(3) and D(4) receptors with K(b) of 0.7 and 0.1 nM, respectively. Stable co-expression of D(2)-like receptors with chimeric Galpha(qo5) proteins in HEK-293 cells is an efficient method to study receptor activation in a common cellular background and an efficient method for direct comparison of ligand affinity and efficacy across human D(2L), D(3) and D(4) receptors.

Animals↗