Éclosion de petites entreprises et bouquets d'alliances avec les géants de la pharmacie, le séquençage du génome est déjà devenu un business aux États-Unis. Quelles sont les stratégies déployées par les industriels ? Un aperçu sur ces chercheurs de gènes qui espèrent toucher le jackpot avec l'information génétique en ouvrant une nouvelle ère au diagnostic et au médicament.

Novel 3-thio-1,2,4-triazoles have been obtained via a solution-phase parallel synthesis strategy, affording potent non-peptidic human somatostatin receptor subtypes 2 and 5 agonists.

A new preparation of trisubstituted imidazopyrazines and dihydroimidazopyrazines via parallel synthesis using aminoacids and bromoketones resulted in the discovery of non-peptidic sst5 selective agonists.

Using a solution-phase parallel synthesis strategy, a series of non-peptide somatostatin analogues were prepared, and their binding affinities to the five human somatostatin receptor subtypes (sst(1-5)) were determined. Imidazolyl derivatives 2 were found to bind with moderate affinity but with high selectivity to the sst(3) receptor subtype. Further modifications of these structures led to a more potent class of ligands, the tetrahydro-beta-carboline derivatives 4. Among these, compounds 4k (BN81644) and 4n (BN81674) bind selectively and with high affinity to the sst(3) receptor subtype (K(i) = 0.64 and 0.92 nM, respectively). Furthermore, 4k and 4n reverse the inhibition of cyclic AMP accumulation induced by 1 nM somatostatin via sst(3) receptors, with IC(50) = 2.7 and 0.84 nM, respectively. The most potent compound 4n was shown to be a competitive antagonist of human sst(3) receptors by increasing the EC(50) of SRIF-14-mediated inhibition of cAMP accumulation with a K(B) of 2.8 nM (where K(B) is the concentration of antagonist that shifts the agonist dose-response 2-fold). These new derivatives are, to our knowledge, the first potent and highly selective non-peptide human sst(3) antagonists known and, as such, are useful tools for investigating the physiological role of sst(3) receptors.

A series of imidazole derivatives has been prepared using high throughput parallel synthesis. Several compounds showed high affinity (Ki in 10−6–10−8M range) and selectivity at recombinant human somatostatin receptor subtype 3 (hsst3).

Endothelin receptors were characterized in rat prostate and potential modification of these receptors was investigated in prostatic hypertrophy induced by testosterone. Both ETA and ETB endothelin receptor mRNA were detected in rat prostate, whereas binding experiments show the presence of only ETA receptors. Testosterone administration produced a 75% increase in prostate weight. Although the density of prostatic endothelin receptors was decreased from 348 +/- 75.0 fmol/mg protein in control rats to 252 +/- 39.9 fmol/mg protein in testosterone-treated animals, the total amount of receptors per prostate was unchanged. The steady-state level of ETA- and ETB-receptormRNA was not altered by testosterone treatment. These results suggest that endothelin receptors are not affected in prostatic hypertrophy induced by testosterone.

Modifications of rat prostatic α1-adrenoceptors were investigated in testosterone-induced prostatic hypertrophy. [3H]prazosin bound to a single class of binding sites with a dissociation constant of 57.9±5.02 pM. The greater part of the binding capacity (24.6±1.02 fmol/mg protein) was made up of chloroethylclonidine-resistant binding sites that showed high-affinity for oxymetazoline and 5-methyl-urapidil, and was identified as α1A-adrenoceptors. The remaining chloroethylclonidine-sensitive binding sites that showed low-affinity for oxymetazoline and 5-methyl-urapidil were preferentially identified as α1B-adrenoceptors. mRNA for the three α1-adrenoceptors (α1a, α1b and α1d) was detected. Testosterone administration produced a 23% decrease of α1-adrenoceptor density, likely by an increase of prostatic glandular epithelium and a decrease in the relative proportion of smooth muscle, thus of α1-adrenoceptor density. The steady state level of mRNAs for α1-adrenoceptors was not modified by testosterone treatment. These results indicate that prostate α1-adrenoceptors are not affected in the prostatic hypertrophy induced by testosterone.

Neuroblastoma is a pediatric cancer for which a cure is elusive for most children with disseminated disease. Neuroblastomas possess receptors for somatostatin (SS). Some SS analogues can inhibit their proliferation. In addition, when SS analogues were used as agents for scintigraphy, neuroblastoma tumor sites can be localized with high efficiency. In this study, to better characterize the SS receptor subtype(s) (sst1-5) present in primary tumors and metastases of neuroblastoma, we show that: (1) The ligand 125I-Tyr11-SS-14 binding on membrane proteins from primary tumors and metastases of neuroblastoma cell line IGR-N-91 developed in nude mice shows similar values of Kd (in order of 0.1 nM) and Bmax (in order of fmol/mg) by filter-retention assay. These data are close to those measured on two other neuroblastoma cell lines: SK-N-SH and IGR-N-835 or to that measured on the rat cerebral cortex. (2) The IGR-N-91 sublines derived from primary tumor and metastases show one major complex of 57 kD by the chemical cross-linking assay using the ligands: 125I-SS-14 and 125I-BIM23014. One similar major complex of 57 kD was also detected in SK-N-SH and IGR-N-835 or in the cerebral cortex. (3) Addition of excess nonlabeled peptides selective for sst2 (BIM23014, BIM23060, BIM23068) suppressed the formation of the complex 57 kD whereas addition of BIM23052 or BIM23056 (sst5 and sst3 selective respectively) does not. This pharmacological profile corresponds to sst2. (4) Only RNA message of sst2 gene is detected in IGR-N-91 cells and its metastases derived sublines by reverse-transcription-polymerase chain reaction and Northern hybridization in keeping with the presence of sst2. (5) In human biopsies, the complex of 57 kD corresponding to sst2 is consistently detected in three samples of the histological subset of the disease: benign ganglioneuroma, ganglioneuroblastoma and immature neuroblastoma. Therefore, the sst2 should be considered as the primary target to develop more potent SS analogues for neuroblastoma therapy or/and scintigraphy.

The two endothelin (ET) receptor subtypes (ETA and ETB) have been characterized in rat kidney from normal rats and rats with acute renal failure induced by hypertonic glycerol administration. In control rats, the total number of ET receptors in kidney cortex and medulla was 155 and 386 fmol/mg of protein, respectively. The ratio of ETA to ETB receptors was 54:46 in renal cortex and 35:65 in renal medulla. Treatment of rats with 10 ml/kg glycerol (50%, w/v) intramuscularly resulted in severe renal dysfunction; the serum urea concentration increased from 0.46 to 2.65 g/liter and the creatinine clearance decreased from 1.06 to 0.30 ml/min. Ligand binding studies showed that glycerol-induced acute renal failure was associated with a marked up-regulation of ETA and ETB receptor subtypes in both cortex and medulla. In glycerol-treated rats, the total ET receptor density in kidney cortex and medulla was increased to 294 and 1172 fmol/mg of protein, with ETA/ETB ratios of 52:48 and 31:69, respectively. The upregulatory effect of glycerol treatment was significantly more pronounced in renal medulla than renal cortex and affected ETB receptors preferentially, compared with ETA receptors. Subsequently, ETA and ETB receptor mRNA levels were markedly increased by glycerol administration in both kidney cortex and medulla, as assessed by polymerase chain reaction coupled to reverse transcription. These results suggest that up-regulation of renal ET receptors, particularly ETB receptors in kidney medulla, may account for or contribute to renal function impairment induced by glycerol, and they support a pathophysiological role for ET in acute renal failure.

Acute renal failure was induced in rat with a hypertonic glycerol solution and endothelin-1 (ET-1) binding was measured in kidney membrane preparations. In control animals, [125I]-ET-1 bound to specific recognition sites in kidney cortex (Bmax = 134 +/- 11 fmol/mg protein) and medulla (Bmax = 300 +/- 9 fmol/mg protein) with an apparent dissociation constant (Kd) of 0.16 +/- 0.06 nM and 0.39 +/- 0.07 nM for cortex and medulla, respectively. A single i.m. dose of 10 ml/kg glycerol (50% w/v) resulted in alterations of renal function that were maximal 48 h after glycerol administration. After this 48-h period, serum urea was increased from 0.20 +/- 0.01 g/L to 1.16 +/- 0.20 g/L (p < 0.001) and creatinine clearance was reduced from 1.04 +/- 0.15 ml/min to 0.23 +/- 0.06 ml/min (p < 0.001). Renal ET-1 receptor density was significantly increased in glycerol-treated rats to 255 +/- 14 fmol/mg protein in renal cortex (p < 0.01), and 576 +/- 55 fmol/mg protein in renal medulla (p < 0.01), with no significant modification of the Kd values. These results suggest that upregulation of ET-1 receptors is involved in renal hemodynamic impairment induced by glycerol.

One of the major biological effects of the endothelium-derived peptide endothelin-1 (ET-1) is its receptor-mediated constrictive action on vascular smooth muscle. In this study, we have examined the effects on the ET-1 pathway of 18 h exposure at 37 degrees C of cultured rat aortic smooth muscle cells to dexamethasone (DEX) and phosphoramidon. ET-1 synthesis was evaluated by radioimmunoassay, ET-1 binding characteristics were determined with [125I]iodo-ET-1, and ET-1-induced intracellular calcium mobilization was measured using fura-2-loaded cells. DEX (100 nM) led to a 2- to 3-fold-increase of ET-1 production, it down-regulated ET-1 receptors and reduced ET-1-stimulated calcium mobilization by 70%. In contrast, phosphoramidon (100 microM) inhibited ET-1 production by 60%, up-regulated ET-1 receptors and potentiated ET-1-induced calcium mobilization by 75%. These results indicate that the regulatory effects of DEX and phosphoramidon on ET-1 receptors are mediated via ET-1 production by the cells. This suggests an autocrine control of ET-1 receptors by endogenous ET-1 synthesis in vascular smooth muscle cells.

It has been shown that in vitro angiotensin II (Ang II) potently downregulates endothelin-1 (ET-1) binding sites. In this study, we investigated in vivo the interactions between the renin-angiotensin system and ET-1. Sprague-Dawley rats were pithed, ventilated, and diastolic blood pressure (DBP) was recorded. ET-1 (1 nmol/kg) induced a biphasic response: a transient hypotension followed by a sustained increase of DBP. Captopril (5 mg/kg, i.v.) or Sar1-Ile8-Ang II (10 ng/kg/min) did not affect ET-1 responses. In other experiments, DBP was increased by infusion of methoxamine (MTX: 10, 20, 25, 32.5 micrograms/kg/min) or Ang II (50, 100, 150, 200 ng/kg/min). ET-1-induced hypotension correlated with the level of DBP (r = 0.94) for both agonists. The elevation of DBP in response to ET-1 was also related to the vascular tone but was dose-dependently attenuated by Ang II infusion when compared with MTX. Conversely, infusion of ET-1 (0.1 nmol/kg/min) blunted the pressor response to Ang II (0.1 micrograms/kg) but not to MTX (50 micrograms/kg). These doses induced the same increase of DBP in pithed control rats. Similarly, increased plasma renin activity induced by chronic salt depletion (0% NaCl) in pithed rats provoked a shift to the right of the dose-response curves to Ang II and ET-1 but not to MTX. These results suggest an in vivo cross-desensitization between ET-1 and Ang II.

We investigated in human lung preparations the characteristics of endothelin-1 (ET-1) binding and the amount of ET-1-like immunoreactivity. Saturation experiments revealed the presence of a large number of high affinity specific ET-1 binding sites with a dissociation constant (Kd) of 1.35 nM and a binding capacity (Bmax) of 9.74 pmol/mg of protein. The binding was time- and temperature-dependent and dissociated by only 10% by the addition of 1 microM unlabeled ET-1. In competition experiments, [125I]ET-1 binding was totally inhibited by unlabeled ET-1 and ET-2 with inhibition constant (Ki) values of 0.20 and 0.21 nM respectively, and 80% inhibited by ET-3 with Ki value of 0.50 nM. The binding was not affected by 1 microM structurally unrelated compounds. Moreover a high level of ET-1-like immunoreactivity (2.3 pg/mg wet weight) was found in human lung by using a specific radioimmunoassay of ET-1 after extraction. HPLC analysis revealed the presence of both ET-1 and Big-ET. These results suggest that the lung may be an important target organ for ET-1 action and/or metabolism in human.

Among the different endothelin (ET) isoforms, ET-3 has been reported to exhibit a less potent constrictor activity than ET-1 and ET-2. Furthermore, distinct endothelin receptor subtypes have been identified in several tissues or cell types. In this study, we investigated the binding characteristics of the three endothelin isoforms in cultured rat aortic smooth muscle cells.[I-125]ET-3 exhibited an apparent affinity and a number of binding sites 10 and 6 times smaller, respectively, than [I-125]ET-1 and [I-125]ET-2. In contrast to ET-1 and ET-2, ET-3 appeared to elicit a reversible binding and did not modify ET-1 binding characteristics in receptor-regulation experiments. In competition experiments ET-1 and ET-2 equally inhibited the binding of the three endothelin isoforms, whereas ET-3 was less potent in competing with [I-125]ET-1 and [I-125]ET-2 than [I-125]ET-3. These results suggest that rat aortic smooth muscle cells possess 2 subtypes of endothelin receptors (A and B) differing by their affinity for ET-3, their proportion, the reversibility of the binding and their sensitivity to down-regulation.

The existence of distinct endothelin (ET) receptor subtypes has been reported in several tissues. In the present study, we investigated the binding characteristics of the three endothelin isoforms to cultured rat aortic smooth muscle cells. [125I]ET-1, [125I]ET-2, and [125I]ET-3 bound to an apparent single class of binding sites with apparent dissociation constants (Kd) of 111, 123, and 1410 pM and binding capacities (Bmax) of 54.1, 46.0, and 7.9 fmol/10(6) cells, respectively. The binding of the three radiolabeled endothelin isoforms was equally inhibited by ET-1 and ET-2. ET-3 was more effective in competing with [125I]ET-3 than with [125I]ET-1 or [125I]ET-2. In contrast to ET-1 and ET-2, the binding of ET-3 was reversible. Furthermore, 18 h of pre-exposure of the cells to 1 nM ET-1 or ET-2 decreased the ET-1 binding capacity, whereas ET-3 (10 nM) was ineffective. ET-3 binding characteristics were not affected by pretreatment of the cells with any of the endothelin isoforms. These results suggest the presence of two distinct endothelin receptor subtypes in rat aortic smooth muscle cells. The ET-1 and ET-2 preferring receptor (80-85%), sensitive to downregulation or internalization, elicits an irreversible binding. The second subtype (15-20%) binds the three endothelin isoforms with the same affinity in a reversible manner, and is insensitive to downregulation or internalization.

In anesthetized and ventilated guinea pigs intravenous injection of ET-1, ET-2, or ET-3 (1 or 2 nmol/kg) induced similar dose-dependent increases in pulmonary inflation pressure (PIP) associated with increases in mean arterial blood pressure (MBP). Pretreatment of the guinea pigs with 1 mg/kg intravenous indomethacin significantly inhibited the increase in PIP evoked by 2 nmol/kg of ET-1, ET-2, or ET-3. In contrast, the increase in MBP following injection of the various ET isotypes was not significantly affected by indomethacin. Injection of ET-1, ET-2, or ET-3 (40, 120, and 400 pmol) via the pulmonary artery of isolated and perfused guinea pig lungs induced dose-dependent increases in PIP and pulmonary perfusion pressure (PPP), thromboxane B2 (TXB2) release, and formation of lung edema. In keeping with the in vivo results, no marked differences were observed between the activities of ET-1, ET-2, and ET-3 on isolated and perfused guinea pig lungs. Indomethacin (5 microM) added to the perfusion medium significantly inhibited the alterations of PIP and PPP, TXB2 release, and edema formation evoked by 400 pmol ET-1, ET-2, or ET-3. High-affinity binding sites for ET-1, ET-2, and ET-3 exhibiting similar characteristics were identified on guinea pig lung membrane. Therefore ET-1, ET-2, and ET-3 exert comparable bronchopulmonary and pressor activities in the guinea pig and probably act via interaction with the same binding site. In addition, the ET-induced increase in PIP and pulmonary vasoconstriction are primarily mediated via the production of cyclooxygenase metabolites.