ETB/endothelin receptor type B

In human Girardi cardiac cells, BQ-788 potently and competitively blocks the binding of 125I-labeled ET-1 to the ETB receptor with an IC50 of 1.2 nM; however, binding to the human neuroblastoma cell line SK-N-MC is very weakly inhibited. The ETA receptor's (IC50, 1300 nM) cell binding. According to pA2, 8.4, BQ-788 reduces ETB-selective agonist-induced vasoconstriction competitively and shows no agonistic activity at doses up to 10 μM. Moreover, bronchoconstriction, cell proliferation, and the clearance of infused ET-1 are among the biological functions of ET-1 that BQ-788 suppresses [1].

In awake rats, boosting response is not inhibited by BQ-788 (3 mg/kg/h, iv), but it is totally inhibited by ETB receptor-mediated antihypertensive medications caused by pharmacological dosages of ET-1- or sarafotoxin6c (0.5 nmol/kg, iv). Moreover, BQ-788 markedly raised ET-1 plasma concentrations, which is thought to be a marker of possible in vivo ETB receptor blockage. BQ-788 (3 mg/kg/h, intravenously) raised blood pressure in Dahl salt-sensitive hypertensive (DS) rats by about 20 mm Hg. According to reports, BQ-788 can also prevent tumor growth, bronchoconstriction caused by ET-1, and organ failure caused by lipopolysaccharide [1]. The ET-1 dose-response curve shifted eight times to the left when BQ 788 (3 mg/kg) was administered, suggesting a major role for the ETB dilator receptor [2]. Mice's mechanical hyperalgesia (47% and 42%), thermal hyperalgesia (68% and 76%), edema (50% and 30%), myeloperoxidase activity (64% and 32%), and notable pain-like behavior were all decreased when 30 nmol BQ-788 was injected into the foot. Furthermore, intraplantar therapy with clazosentan or BQ-788 reduced superoxide anion generation in the spinal cord (45% and 41%) and peripheral (47% and 47%), as well as in the spinal cord (47% and 47%) and peripheral (47% and 47%). 33% and 54%) generation of superoxide anions. ) are correspondingly lipid peroxidation [3].

---

The overall effects of endothelin-1 (ET-1) on blood pressure are caused by a composite activation of constrictor ETA and ETB receptors and dilator ETB receptors. Therefore, it is difficult to accurately compare the ETA activity of selective ETA receptor antagonists (BQ 123 and BMS 182874) with mixed ETA/ETB antagonists (SB 209670 and bosentan) on the cumulative dose-response curve to ET-1. The development of a selective ETB antagonist (BQ 788), which inhibits both the dilator and constrictor ETB receptors, offered the opportunity to investigate the role of ETB receptors in the response to exogenous ET-1 in the pithed rat. BQ 788 (3 mg/kg) resulted in an eightfold leftward shift in the ET-1 dose-response curve, suggesting a significant involvement of ETB dilator receptors. In the absence or presence of BQ 788, each ET antagonist evoked a rightward shift from vehicle. With the exception of BMS 182874, BQ 788 increased the magnitude of the shifts. Furthermore, the profile of the shifts changed from nonparallel to parallel in the presence of BQ 788. The inclusion of BQ 788 also altered the rank order of the ET antagonists tested. The results presented describe an in vivo system that accurately characterizes the ETA activity of ET antagonists. [2]

Researchers describe characteristics of a selective endothelin (ET) ET(B) receptor antagonist, BQ-788 [N-cis-2,6-dimethylpiperidinocarbonyl-L-gamma-methylleucyl-D-1-methoxycarbonyltryptophanyl-D-norleucine], which is widely used to demonstrate the role of endogenous or exogenous ETs in vitro and in vivo. In vitro, BQ-788 potently and competitively inhibited (125)I-labeled ET-1 binding to ET(B) receptors in human Girrardi heart cells (hGH) with an IC(50) of 1.2 nM, but only poorly inhibited the binding to ET A receptors in human neuroblastoma cell line SK-N-MC cells (IC(50), 1300 nM). In isolated rabbit pulmonary arteries, BQ-788 showed no agonistic activity up to 10 microM and competitively inhibited the vasoconstriction induced by an ET(B)-selective agonist (pA(2), 8.4). BQ-788 also inhibited several bioactivities of ET-1, such as bronchoconstriction, cell proliferation, and clearance of perfused ET-1. Thus, it is confirmed that BQ-788 is a potent, selective ET(B) receptor antagonist. In vivo, in conscious rats, BQ-788, 3 mg/kg/h, i.v., completely inhibited a pharmacological dose of ET-1- or sarafotoxin6c (S6c) (0.5 nmol/kg, i.v.)-induced ET(B) receptor-mediated depressor, but not pressor responses. Furthermore, BQ-788 markedly increased the plasma concentration of ET-1, which is considered an index of potential ET(B) receptor blockade in vivo. In Dahl salt-sensitive hypertensive (DS) rats, BQ-788, 3 mg/kg/h, i.v., increased blood pressure by about 20 mm Hg. It is reported that BQ-788 also inhibited ET-1-induced bronchoconstriction, tumor growth and lipopolysaccharide-induced organ failure. These data suggest that BQ-788 is a good tool for demonstrating the role of ET-1 and ET(B) receptor subtypes in physiological and/or pathophysiological conditions.[1]

Myeloperoxidase (MPO) assay[3]
Neutrophil migration to the hind paw skin tissue of mice was evaluated using a MPO kinetic-colourimetric assay, as described previously. Samples of paw skin tissue were collected 7 h after the stimulus in ice-cold 50 mM K2HPO4 buffer (pH 6.0) containing 0.5% hexadecyltrimethylammonium bromide (HTAB) and kept at −80 °C until use. Samples were homogenised, centrifuged (16 100×g × 4 min), with the resulting supernatant being assayed for MPO activity spectrophotometrically at 450 nm, with three readings in 1 min. The MPO activity of samples was compared to a standard curve of neutrophils. Briefly, 10 µL of sample was mixed with 200 µL of 50 mM phosphate buffer, pH 6.0, containing 0.167 mg/mL o-dianisidine dihydrochloride and 0.015% hydrogen peroxide. The results are presented as MPO activity (number of neutrophils ×104/mg of skin paw).

---

Leukocyte recruitment in the peritoneal cavity[3]
Leukocyte recruitment in the peritoneal cavity was evaluated 6 h after i.p. KO2 injection (30 µg/cavity). Total leukocyte counts were performed in a Neubauer chamber after dilution in Turk’s solution (2% acetic acid). Differential cell counts were performed using the Fast Panotic Kit for histological analysis, and the values are expressed as the number of cells (×106) per cavity. Total and differential cell counts were performed under a light microscope.

All measures were taken following the injection of KO2 in the paw, with the exception of the writhing response and leukocyte recruitment, which were performed following the injection of KO2 into the peritoneal cavity. The following groups were used: saline (no stimulus); KO2+saline (stimulus + treatment vehicle); KO2+clazosentan (stimulus + ETA antagonist); and KO2 +BQ-788 (stimulus + ETB antagonist). Therefore, in all tests mice received intraplantar (i.pl.) pre-treatment with vehicle (saline), or clazosentan (ETA antagonist; 3, 10 or 30 nmol) or BQ-788 (ETB antagonist; 3, 10 or 30 nmol); except in the tests that evaluated writhing response and leukocyte recruitment in which mice were pre-treated by intraperitoneal (i.p.) route with vehicle (saline), or clazosentan (ETA antagonist; 30 nmol), or BQ-788 (ETB antagonist, 30 nmol), 30 min before stimulus. Based on the mechanical hyperalgesia, thermal hyperalgesia and oedema results (Figure 2), the dose of 30 nmol of the ETA or ETB antagonists was chosen and used for the subsequent experiments. At the indicated time points, the following parameters were determined: mechanical and thermal hyperalgesia; as well as oedema (Figure 2), overt pain-like behaviours (Figure 3), myeloperoxidase (MPO) activity and leukocyte recruitment (Figure 4). Furthermore, paw skin and spinal cord superoxide anion production, as well as lipid peroxidation (Figure 5) and cytokine production (Figure 6), were also evaluated. The doses of KO2 and time points for sample analysis were determined as described previously. KO2 was diluted in sterile saline immediately before application. [3]

[1]. BQ-788, a selective endothelin ET(B) receptor antagonist. Cardiovasc Drug Rev. 2002 Winter;20(1):53-66.

[2]. Effect of endothelin antagonists with or without BQ 788 on ET-1 responses in pithed rats. J Cardiovasc Pharmacol. 1995;26 Suppl 3:S216-8.

[3]. Differential regulation of oxidative stress and cytokine production by endothelin ETA and ETB receptors in superoxide anion-induced inflammation and pain in mice. J Drug Target. 2016 Oct 5:1-27.

The present study investigated whether endothelin-1 acts via ETA or ETB receptors to mediate superoxide anion-induced pain and inflammation. Mice were treated with clazosentan (ETA receptor antagonist) or BQ-788 (ETB receptor antagonist) prior to stimulation with the superoxide anion donor, KO2. Intraplantar treatment with 30 nmol of clazosentan or BQ-788 reduced mechanical hyperalgesia (47% and 42%), thermal hyperalgesia (68% and 76%), oedema (50% and 30%); myeloperoxidase activity (64% and 32%), and overt-pain like behaviours, such as paw flinching (42% and 42%) and paw licking (38% and 62%), respectively. Similarly, intraperitoneal treatment with 30 nmol of clazosentan or BQ-788 reduced leukocyte recruitment to the peritoneal cavity (58% and 32%) and abdominal writhing (81% and 77%), respectively. Additionally, intraplantar treatment with clazosentan or BQ-788 decreased spinal (45% and 41%) and peripheral (47% and 47%) superoxide anion production as well as spinal (47% and 47%) and peripheral (33% and 54%) lipid peroxidation, respectively. Intraplantar treatment with clazosentan, but not BQ-788, reduced spinal (71%) and peripheral (51%) interleukin-1 beta as well as spinal (59%) and peripheral (50%) tumor necrosis factor-alpha production. Therefore, the present study unveils the differential mechanisms by which ET-1, acting on ETA or ETB receptors, regulates superoxide anion-induced inflammation and pain.[3]

C34H50N5NAO7

663.7918

663.361

C, 61.52; H, 7.59; N, 10.55; Na, 3.46; O, 16.87

156161-89-6

BQ-788;173326-37-9

16759603

White to off-white solid powder

4.595

3

7

14

47

1080

5

CCCC[C@H](C(=O)[O-])NC(=O)[C@@H](CC1=CN(C2=CC=CC=C21)C(=O)OC)NC(=O)[C@H](CC(C)(C)C)NC(=O)N3[C@@H](CCC[C@@H]3C)C.[Na+]

QCVIFBRTTLMEOV-FUKQNADPSA-M

InChI=1S/C34H51N5O7.Na/c1-8-9-16-25(31(42)43)35-29(40)26(18-23-20-38(33(45)46-7)28-17-11-10-15-24(23)28)36-30(41)27(19-34(4,5)6)37-32(44)39-21(2)13-12-14-22(39)3/h10-11,15,17,20-22,25-27H,8-9,12-14,16,18-19H2,1-7H3,(H,35,40)(H,36,41)(H,37,44)(H,42,43)/q+1/p-1/t21-,22+,25-,26-,27+/m1./s1

sodium (R)-2-((R)-2-((S)-2-((2R,6S)-2,6-dimethylpiperidine-1-carboxamido)-4,4-dimethylpentanamido)-3-(1-(methoxycarbonyl)-1H-indol-3-yl)propanamido)hexanoate

BQ788; 156161-89-6; BQ-788 sodium salt; BQ788 sodium salt; BQ-788 (sodium salt); BQ 788; UNII-44OLL8XEJ4; BQ-788; BQ 788.

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Note: (1). This product requires protection from light (avoid light exposure) during transportation and storage.  (2). Please store this product in a sealed and protected environment (e.g. under nitrogen), avoid exposure to moisture.

Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

DMSO : ≥ 43 mg/mL (~64.78 mM)
H2O : ~20 mg/mL (~30.13 mM)

Solubility in Formulation 1: ≥ 3 mg/mL (4.52 mM) (saturation unknown) in 10% DMSO + 40% PEG300 + 5% Tween80 + 45% Saline (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 30.0 mg/mL clear DMSO stock solution to 400 μL PEG300 and mix evenly; then add 50 μL Tween-80 to the above solution and mix evenly; then add 450 μL normal saline to adjust the volume to 1 mL.
Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH₂ O to obtain a clear solution.

---

Solubility in Formulation 2: ≥ 3 mg/mL (4.52 mM) (saturation unknown) in 10% DMSO + 90% (20% SBE-β-CD in Saline) (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 30.0 mg/mL clear DMSO stock solution to 900 μL of 20% SBE-β-CD physiological saline solution and mix evenly.
Preparation of 20% SBE-β-CD in Saline (4°C，1 week): Dissolve 2 g SBE-β-CD in 10 mL saline to obtain a clear solution.

---

View More

Solubility in Formulation 3: ≥ 3 mg/mL (4.52 mM) (saturation unknown) in 10% DMSO + 90% Corn Oil (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 30.0 mg/mL clear DMSO stock solution to 900 μL of corn oil and mix evenly.

---

Solubility in Formulation 4: 50 mg/mL (75.33 mM) in PBS (add these co-solvents sequentially from left to right, and one by one), clear solution; with ultrasonication.

---

 (Please use freshly prepared in vivo formulations for optimal results.)