Capsazepine, a vanilloid receptor antagonist, inhibits allergen-induced tracheal contraction

To investigate the possible role of the vanilloid receptor-1 (TRPV1) in allergic airway responses, the effect of the specific TRPV1 receptor antagonist capsazepine was examined. Capsazepine significantly decreased the ovalbumin-induced contraction of isolated tracheal rings from ovalbumin-sensitized guinea pigs. This is the first report directly showing the involvement of the TRPV1 in experimental allergic airway responses.     

Identification and characterisation of SB-366791, a potent and selective vanilloid receptor (VR1/TRPV1) antagonist

Vanilloid receptor-1 (TRPV1) is a non-selective cation channel, predominantly expressed by peripheral sensory neurones, which is known to play a key role in the detection of noxious painful stimuli, such as capsaicin, acid and heat. To date, a number of antagonists have been used to study the physiological role of TRPV1; however, antagonists such as capsazepine are somewhat compromised by non-selective actions at other receptors and apparent modality-specific properties. SB-366791 is a novel, potent, and selective, cinnamide TRPV1 antagonist isolated via high-throughput screening of a large chemical library. In a FLIPR-based Ca(2+)-assay, SB-366791 produced a concentration-dependent inhibition of the response to capsaicin with an apparent pK(b) of 7.74 +/- 0.08. Schild analysis indicated a competitive mechanism of action with a pA2 of 7.71. In electrophysiological experiments, SB-366791 was demonstrated to be an effective antagonist of hTRPV1 when activated by different modalities, such as capsaicin, acid or noxious heat (50 degrees C). Unlike capsazepine, SB-366791 was also an effective antagonist vs. the acid-mediated activation of rTRPV1. With the aim of defining a useful tool compound, we also profiled SB-366791 in a wide range of selectivity assays. SB-366791 had a good selectivity profile exhibiting little or no effect in a panel of 47 binding assays (containing a wide range of G-protein-coupled receptors and ion channels) and a number of electrophysiological assays including hippocampal synaptic transmission and action potential firing of locus coeruleus or dorsal raphe neurones. Furthermore, unlike capsazepine, SB-366791 had no effect on either the hyperpolarisation-activated current (I(h)) or Voltage-gated Ca(2+)-channels (VGCC) in cultured rodent sensory neurones. In summary, SB-366791 is a new TRPV1 antagonist with high potency and an improved selectivity profile with respect to other commonly used TRPV1 antagonists. SB-366791 may therefore prove to be a useful tool to further study the biology of TRPV1.     

Metabolism-based identification of a potent thrombin receptor antagonist

The metabolism of our prototypical thrombin receptor antagonist 1, Ki = 2.7 nM, was studied and three major metabolites (2, 4, and 5) were found. The structures of the metabolites were verified independently by synthesis. Compound 4 was shown to be a potent antagonist of the thrombin receptor with a Ki = 11 nM. Additionally, compound 4 showed a 3-fold improvement in potency with respect to 1 in an agonist-induced ex-vivo platelet aggregation assay in cynomolgus monkeys after oral administration; this activity was sustained with 60% inhibition observed at 24 h post-dose. Compound 4 was highly active in functional assays and showed excellent oral bioavailability in rats and monkeys. Compound 4 showed a superior rat enzyme induction profile relative to compound 1, allowing it to replace compound 1 as a development candidate.     

5'-Guanidinonaltrindole, a highly selective and potent kappa-opioid receptor antagonist

5'-Guanidinonaltrindole (GNTI) possesses 5-fold greater opioid antagonist potency (K(e)=0.04 nM) and an order of magnitude greater selectivity (selectivity ratios >500) than the prototypical kappa-opioid receptor antagonist, norbinaltorphimine, in smooth muscle preparations. Binding and functional studies conducted on cloned human opioid receptors expressed in Chinese hamster ovarian (CHO) cells afforded pA(2) values that were comparable to the smooth muscle data. In view of the high selectivity and potency of GNTI, it is a potentially valuable pharmacological tool for opioid research.     

Novel potent antagonists of transient receptor potential channel, vanilloid subfamily member 1: structure-activity relationship of 1,3-diarylalkyl thioureas possessing new vanilloid equivalents

Recently, 1,3-diarylalkyl thioureas have merged as one of the promising nonvanilloid TRPV1 antagonists possessing excellent therapeutic potential in pain regulation. In this paper, the full structure-activity relationship for TRPV1 antagonism of a novel series of 1,3-diarylalky thioureas is reported. Exploration of the structure-activity relationship, by systemically modulating three essential pharmacophoric regions, led to six examples of 1,3-dibenzyl thioureas, which exhibit Ca(2+) uptake inhibition in rat DRG neuron with IC(50) between 10 and 100 nM.     

Pharmacological profile of LF 16-0687, a new potent non-peptide bradykinin B2 receptor antagonist

LF 16-0687 (1-[[2,4-dichloro-3-[[(2,4-dimethylquinolin-8-yl)oxy] methyl]phenyl]sulfonyl]-N-[3-[[4-(aminoimethyl) phenyl] carbonylamino]propyl]-2(S)-pyrrolidinecarboxamide) has been selected from a large-scale medicinal chemistry program for further development. In competition binding studies using [3H]bradykinin (BK), LF 16-0687 bound to the human, rat and guinea-pig recombinant B2 receptor expressed in CHO cells giving K(i) values of 0.67 nM, 1.74 nM and 1.37 nM, respectively. It also bound to the native BK B2 receptor from human umbilical vein (HUV), rat uterus (RU) and guinea-pig ileum (GPI) giving K(i) values of 0.89 nM, 0.28 nM and 0.98 nM, respectively. It inhibited BK-induced IP1, IP2 and IP3 formation in INT407 cells yielding pK(B) values of 8.5, 8.6 and 8.7, respectively. In isolated organs experiments, LF 16-0687 behaved as a competitive antagonist of BK-mediated contractions giving pA2 values of 9.1 in HUV, 7.7 in RU and 9.1 in GPI. Binding and functional studies performed over 40 different receptors revealed that LF 16-0687 was selective for the BK B2 receptor. A continuous intravenous infusion of LF 16-0687 antagonized in a dose-dependent manner and with a rapid onset of action BK-induced hypotensive response. Subcutaneous administration of LF 16-0687 at 1.1 micromol/kg to rats markedly reduced BK-induced edema of the stomach (- 69%), duodenum (-65%) and pancreas (-56%).     

新型血管紧张肽受体拮抗药依普罗沙坦

依普罗沙坦是一个新型、高选择性血管紧张肽Ⅱ受体1拮抗药,尚具有改善血管内皮功能、延迟动脉粥样硬化、抗炎症等作用。依普罗沙坦不经CYP450系统代谢,故很少发生药物-药物相互作用。在降压治疗同时,依普罗沙坦尚有减少心脑血管事件发生率的作用。     

BMS-189453, a novel retinoid receptor antagonist, is a potent testicular toxin.

BMS-189453 is a synthetic retinoid that acts as an antagonist at retinoic acid receptors alpha, beta, and gamma. In Sprague Dawley rats at daily oral doses of 15, 60, or 240 mg/kg for 1 month, BMS-189453 produced increases in leukocyte counts, alkaline phosphatase and alanine aminotransferase levels, and marked testicular degeneration and atrophy at all doses. Significant overt signs of toxicity and deaths occurred at 240 mg/kg, whereas body-weight and food-consumption decreases occurred at 60 and 240 mg/kg. When BMS-189453 was administered to male rats at daily doses ranging from 12.5 to 100 mg/kg for 1 week, only minimal testicular changes occurred at all doses, shortly after the dosing period. However, after a 1-month drug-free observation period, marked testicular atrophy was evident at all doses. BMS-189453 was then administered at doses of 2, 10, or 50 mg/kg to male rats for 1, 3, or 7 consecutive days. Dose- and duration-dependent testicular toxicity that occurred after a 1-month observation period did not recover, and, in some cases, was more severe 4 months after the last dose. In rabbits administered BMS-189453 at oral doses of 2, 10, or 50 mg/kg for 1 week, testicular degeneration and atrophy were evident in the high-dose group at 1 month following treatment. These studies indicate that retinoid antagonists can selectively produce progressive and prolonged testicular toxicity after single or repeated oral doses that are otherwise well tolerated.     

Structural investigation of Cetrorelix,a new potent and long-acting LH-RH antagonist

The new decapeptide SB-75 (INN: Cetrorelix) has been characterized as a potent antagonist of luteinizinghormone releasing hormone (LH-RH). Such derivatives are of great medicinal interest owing to their potential application in areas such as hormone-dependent tumors, uterine fibroids, and in diseases and conditions which result from inappropriate hormone levels or which can be treated by suppression of estrogens. SB-75 is the subject of intensive ongoing clinical evaluation and is an accepted standard for the design of new LH-RH antagonists. We characterized SB-75 by means of modern MS and NMR techniques to demonstrate the significance of both sequencing methods on a complicated unnatural decapeptide. Our structural elucidations with nuclear Overhauser (NOE) experiments revealed clear evidence for a highly flexible molecule with no single predominant conformation even in sodium dodecyl sulfate (SDS) mimicking a cellular membrane.     

Synthesis and biological activity of a novel, highly potent progesterone receptor antagonist

Herein we describe the chemical synthesis and pharmacological characterization of a novel, highly potent progesterone receptor (PR) antagonist, ZK 230211. The introduction of a 17alpha-pentafluorethyl side chain in the D-ring of the steroid skeleton allowed the combination of high antiprogestagenic activity with little or no other endocrinological effects. In contrast to many other antiprogestins, ZK 230211 did not convert to an agonist in the presence of protein kinase A (PKA) activators and showed high antiprogestagenic activity on both PR isoforms PR-A and PR-B. This high antiprogestagenic activity could also be demonstrated in several in vivo models. Furthermore, this compound displayed only marginal antiglucocorticoid effects. In tumor models ZK 230211 exhibited strong antiproliferative action. The pharmacological properties of ZK 230211 may prove useful in the treatment of endometriosis, leiomyomas, breast cancer, and in hormone replacement therapy.     

The neuromedin B receptor antagonist,BIM-23127, is a potent antagonist at human and rat urotensin-II receptors

The functional activity of the peptidic neuromedin B receptor antagonist BIM-23127 was investigated at recombinant and native urotensin-II receptors (UT receptors). Human urotensin-II (hU-II) promoted intracellular calcium mobilization in HEK293 cells expressing the human UT (hUT) or rat UT (rUT) receptors with pEC(50) values of 9.80+/-0.34 (n=6) and 9.06+/-0.32 (n=4), respectively. While BIM-23127 alone had no effect on calcium responses in either cell line, it was a potent and competitive antagonist at both hUT (pA(2)=7.54+/-0.14; n=3) and rUT (pA(2)=7.70+/-0.05; n=3) receptors. Furthermore, BIM-23127 reversed hU-II-induced contractile tone in the rat-isolated aorta with a pIC(50) of 6.66+/-0.04 (n=4). In conclusion, BIM- 23127 is the first hUT receptor antagonist identified to date and should not be considered as a selective neuromedin B receptor antagonist.     

Design of a high-affinity competitive antagonist of the vanilloid receptor selective for the calcium entry-linked receptor population

We describe the synthesis and characterization of N-(4-chlorobenzyl) -N'-(4-hydroxy-3-iodo-5-methoxybenzyl)thiourea (IBTU), a novel antagonist of the vanilloid receptor 1 (TRPV1 or VR1). IBTU competitively inhibited 45Ca2+ uptake into CHO cells heterologously expressing rat TRPV1, whether induced by capsaicin or resiniferatoxin (Ki = 99 +/- 23 and 93 +/- 34 nM, respectively). IBTU was thus somewhat more potent (5-fold) than capsazepine. In contrast to its antagonism of vanilloid-induced calcium uptake, IBTU (30 microM) inhibited [3H]resiniferatoxin binding to TRPV1 by less than 10%. We hypothesize that these dramatically distinct potencies reflect different fractions of TRPV1 in this system: namely, a minor plasma membrane fraction controlling 45Ca2+ uptake, and the predominant intracellular fraction that dominates the [3H]resiniferatoxin binding measurements. Intracellular Ca2+ imaging supports this explanation. IBTU antagonized the elevation in intracellular Ca2+ in response to 50 nM capsaicin with an IC50 of 106 +/- 35 nM. Likewise, 600 nM IBTU was able to antagonize the elevation in intracellular Ca2+ in response to 100 pM resiniferatoxin in the presence of normal (1.8 mM) extracellular Ca2+, where the increase in intracellular calcium reflects calcium influx. In contrast, in the absence of extracellular Ca2+, where in this system resiniferatoxin induces a modest increase in calcium from intracellular stores, IBTU was unable to block the response to resiniferatoxin, although the TRPV1 antagonist 5-iodoresiniferatoxin was able to do so. In summary, IBTU is a novel, potent TRPV1 antagonist with marked selectivity between subpopulations of TRPV1 and may permit the function of these distinct pools to be explored and potentially exploited.     

JNJ16259685, a highly potent, selective and systemically active mGlu1 receptor antagonist

We examined the pharmacological profile of (3,4-dihydro-2H-pyrano[2,3]b quinolin-7-yl) (cis-4-methoxycyclohexyl) methanone (JNJ16259685). At recombinant rat and human metabotropic glutamate (mGlu) 1a receptors, JNJ16259685 non-competitively inhibited glutamate-induced Ca2+ mobilization with IC50 values of 3.24+/-1.00 and 1.21+/-0.53 nM, respectively, while showing a much lower potency at the rat and human mGlu5a receptor. JNJ16259685 inhibited [3H]1-(3,4-dihydro-2H-pyrano[2,3-b]quinolin-7-yl)-2-phenyl-1-ethanone ([3H]R214127) binding to membranes prepared from cells expressing rat mGlu1a receptors with a Ki of 0.34+/-0.20 nM. JNJ16259685 showed no agonist, antagonist or positive allosteric activity toward rat mGlu2, -3, -4 or -6 receptors at concentrations up to 10 microM and did not bind to AMPA or NMDA receptors, or to a battery of other neurotransmitter receptors, ion channels and transporters. In primary cerebellar cultures, JNJ16259685 inhibited glutamate-mediated inositol phosphate production with an IC50 of 1.73+/-0.40 nM. Subcutaneously administered JNJ16259685 exhibited high potencies in occupying central mGlu1 receptors in the rat cerebellum and thalamus ( ED50=0.040 and 0.014 mg/kg, respectively). These data show that JNJ16259685 is a selective mGlu1 receptor antagonist with excellent potencies in inhibiting mGlu1 receptor function and binding and in occupying the mGlu1 receptor after systemic administration.     

Characterisation of UBP296: a novel, potent and selective kainate receptor antagonist

Willardiine derivatives with an N3-benzyl substituent bearing an acidic group have been synthesized with the aim of producing selective antagonists for GLUK5-containing kainate receptors. UBP296 was found to be a potent and selective antagonist of native GLUK5-containing kainate receptors in the spinal cord, with activity residing in the S enantiomer (UBP302). In cells expressing human kainate receptor subunits, UBP296 selectively depressed glutamate-induced calcium influx in cells containing GLUK5 in homomeric or heteromeric forms. In radioligand displacement binding studies, the willardiine analogues displaced [3H]kainate binding with IC50 values >100 microM at rat GLUK6, GLUK2 or GLUK6/GLUK2. An explanation of the GLUK5 selectivity of UBP296 was obtained using homology models of the antagonist bound forms of GLUK5 and GLUK6. In rat hippocampal slices, UBP296 reversibly blocked ATPA-induced depressions of synaptic transmission at concentrations subthreshold for affecting AMPA receptor-mediated synaptic transmission directly. UBP296 also completely blocked the induction of mossy fibre LTP, in medium containing 2 mM (but not 4 mM) Ca2+. These data provide further evidence for a role for GLUK5-containing kainate receptors in mossy fibre LTP. In conclusion, UBP296 is the most potent and selective antagonist of GLUK5-containing kainate receptors so far described.     

Diosmetin,a novel transient receptor potential vanilloid 1 antagonist,alleviates the UVB radiation-induced skin inflammation in mice

Inflammopharmacology - UVB radiation-mediated inflammation and the oxidative process involve the transient receptor potential vanilloid 1 (TRPV1) channel activation in neuronal and non-neuronal...     

Study of SR 142801, a new potent non-peptide NK3 receptor antagonist on cardiovascular responses in conscious guinea-pig.

1. The cardiovascular responses to intravenous (i.v.) injection of natural tachykinins, substance P (SP), neurokinin A (NKA), neurokinin B (NKB) and selective tachykinin (NK) receptor agonists, [Sar9, Met(O2)11]SP, [beta Ala8]NKA(4-10), [MePhe7]NKB and senktide were assessed in conscious, freely moving, guinea-pigs. 2. SP and [Sar9, Met(O2)11]SP (1-1000 pmol kg-1) induced dose-dependent decreases in mean arterial blood pressure (MAP) accompanied by increases in heart rate (HR). NKA evoked only weak hypotensive effects at high doses (3000 pmol kg-1) whereas [beta Ala8]NKA(4-10) (1-3000 pmol kg-1) had no effects. By contrast, NKB [MePhe7]NKB (1-10,000 pmol kg-1) and senktide (1-1000 pmol kg-1), produced dose-related hypertensive effects with the following rank order of potency: senktide > [MePhe7]NKB > NKB. Bradycardia occurred simultaneously with the increases in arterial pressure. 3. The pressor response to intravenous injection of senktide (300 pmol kg-1) was partially reduced by pretreatment with prazosin (0.71 mumol kg-1), or clonidine (0.38 mumol kg-1) and was completely inhibited by the combination of the two compounds. Atropine (1.5 mumol kg-1) suppressed the decrease in HR induced by senktide without altering the blood pressure response. These findings suggest that the blood pressure response to senktide is an indirect effect mediated by noradrenaline released from sympathetic nerve endings, whereas the bradycardia is of vagal reflex origin. 4. SR 142801, ((S)-(N)-(1-(3-(1-benzoyl-3-(3,4-dichlorophenyl) piperidin-3-yl) propyl)-4-phenyl-piperidin-4-yl)-N-methylacetamide), a potent and specific non-peptide NK3 receptor antagonist dose-dependently (0.46-4.6 mumol kg-1, i.v.; 4.6-46 mumol kg-1, p.o.) inhibited the cardiovascular effects of senktide and displayed a long-lasting inhibitory effect after oral administration. By contrast, SR 142806 (4.6 mumol kg-1, i.v.), the (R)-enantiomer of SR 142801 had no effect on the responses to senktide. SR 142801 at a high dose (15 mumol kg-1, i.v.) was inactive toward the [Sar9, Met(O2)11]SP-induced hypotension. 5. SR 142801 did not modify MAP in conscious guinea-pigs both after i.v. (4.6 and 15 mumol kg-1) and oral (46 and 150 mumol kg-1) administration, showing a lack of agonistic properties. However, a slight reduction in HR was observed only after i.v. injection. 6. In conclusion, these results show evident differences in the functional role of tachykinin receptors in the peripheral control of the cardiovascular system. Furthermore, a clear pressor effect of senktide, which was selectively blocked by SR 142801, was observed in conscious guinea-pigs. Hence, this antagonist appears suitable for investigating the functional role of NK3 receptors.     

Buprenorphine has potent kappa opioid receptor antagonist activity

Buprenorphine was studied for its effects on urinary output to determine if it was an agonist, partial agonist, or antagonist at the kappa receptor. Buprenorphine was a potent antagonist of bremazocine-induced urination and had no kappa agonist activity. Thus, the high affinity that buprenorphine has for the kappa receptor results in potent kappa receptor antagonist activity in vivo.     

In vitro phamacology of MK-996, a new potent and selective angiotensin II (AT1) receptor antagonist

MK-996 (N-((4′-((5,7-Dimethyl-2-ethyl-3H-imidazo[4,5-b]pyridin-3-yl)methyl) (1,1′-biphenyl)-2-yl) sulfonylbenzamide) interacted in a competitive manner with rabbit aortic angiotensin II (All) receptors as determined by Scatchard analysis of specific binding of [¹²⁵l]-Sar¹lle⁸-All. MK-996 also exhibited high affinity at All receptors in several tissues from different animal species (K_i = 0.1–0.4 nM). In vitro functional assays utilizing All-induced aldosterone release in rat adrenal cortical cells demonstrated further that MK-996 acts as a competitive, high affinity antagonist of All (pA₂ = 10.3) and lacks agonist activity. MK-996 also potently inhibited All-induced contractile response in isolated rabbit aorta and pulmonary artery with a reduction in maximal response. The specificity of MK-996 for All receptors was demonstrated by its lack of activity (IC₅₀> 1 μM) in several other receptor binding assays and its inability to affect in vitro functional responses produced by other agonists. MK-996 demonstrated a very high selectivity for the AT₁ compared to AT₂ receptor subtype (AT₂ IC₅₀ ≥ 2 μM). Direct binding studies using [³H]-MK-996 in rat adrenal indicated specific binding of [³H]-MK-996 is saturable and of high affinity (K_d = 0.47 nM). The specific [³H]-MK-996 binding in rat adrenal represents binding to pharmacologically relevant AT₁ receptors as demonstrated by the similar K_i values for various All agonists and antagonists in inhibiting specific ³H-MK-996 and [¹²⁵l]-All binding to AT₁ receptors. Dissociation rate studies of specific [³H]-MK-996 binding indicated a t1/2 of 103 min. This slow dissociation may account for the reduction in maximal responses to All in MK-996 treated isolated blood vessels.