Differential Effects of a Novel Non-Peptide Endothelin Receptor Antagonist (Bosentan) in Rat Liver and Vasculature

1995 ◽  
Vol 89 (6) ◽  
pp. 575-579 ◽  
Author(s):  
Paddy A. Phillips ◽  
John Risvanis ◽  
Kathryn Aldred ◽  
Louise M. Burrell ◽  
Briony Bartholomeusz
Keyword(s):  
Receptor Antagonist ◽  
Time Course ◽  
Competitive Inhibition ◽  
Ex Vivo ◽  
Female Rat ◽  
Endothelin Receptor ◽  
Binding Characteristics ◽  
Orally Active

1. We studied the effects of the non-selective, non-peptide, orally active endothelin (ET) receptor antagonist bosentan (Ro 47–0203) on rat hepatic and mesenteric vascular membrane 125I-ET-1 binding characteristics in vitro and ex vivo (after bosentan by gavage in vivo). 2. Bosentan caused a concentration-dependent competitive inhibition of 125I-ET-1 binding to female rat mesenteric vascular (predominantly ETA receptors) and hepatic (predominantly ETB receptors) membranes in vitro and ex viva 3. The time course of the inhibition of binding ex vivo after administration of bosentan in vivo was 1–4 h for mesenteric vascular (predominantly ETA receptors) binding and 1–16 h for hepatic (predominantly ETB receptors) binding. 4. The time course of displacement of 125I-ET-1 binding from mesenteric vascular and hepatic membranes by bosentan in vitro was similar. 5. Since bosentan is significantly excreted by the liver, the prolonged hepatic 125I-ET-1 binding by bosentan presumably represents hepatic accumulation of bosentan, which may have implications for bosentan antagonizing the actions of ET in the liver.

The pharmacology of L-670,596, a potent and selective thromboxane/prostaglandin endoperoxide receptor antagonist

1989 ◽  
Vol 67 (9) ◽  
pp. 989-993 ◽  
Author(s):  
A. W. Ford-Hutchinson ◽  
Y. Girard ◽  
A. Lord ◽  
T. R. Jones ◽  
M. Cirino ◽  
...  
Keyword(s):  
Platelet Aggregation ◽  
Guinea Pig ◽  
Receptor Antagonist ◽  
Competitive Inhibition ◽  
Ex Vivo ◽  
Platelet Rich Plasma ◽  
Prostaglandin Endoperoxide ◽  
Induced Aggregation

L-670,596 ((−)6,8-difluoro-9-p-methylsulfonyl benzyl-1,2,3,4-tetrahydrocarbazol-1-yl-acetic acid) has been shown to be a potent receptor antagonist as evidenced by the inhibition of the binding of 125I-labeled PTA-OH to human platelets (IC50, 5.5 × 10−9 M), inhibition of U-44069 induced aggregation of human platelet rich plasma (IC50, 1.1 × 10−7 M), and competitive inhibition of contractions of the guinea pig tracheal chain induced by U-44069 (pA2,9.0). The compound was also active in vivo as shown by inhibition of arachidonic acid and U-44069 induced bronchoconstriction in the guinea pig (ED50 values, 0.04 and 0.03 mg/kg i.v., respectively), U-44069 induced renal vasoconstriction in the pig (ED50, 0.02 mg/kg i.v.), and inhibition of ex vivo aggregation of rhesus monkey platelets to U-44069 (active 1–5 mg/kg p.o.). The selectivity of the compound was indicated by the failure to inhibit, first, ADP-induced human or primate platelet aggregation and, second, bronchoconstriction in the guinea pig in vivo and contraction of the guinea pig tracheal chain in vitro to a variety of agonists. It is concluded that L-670,596 is a potent, selective, orally active thromboxane A2/prostaglandin endoperoxide receptor antagonist.Key words: thromboxane A2, thromboxane antagonist, prostaglandin endoperoxides, platelet aggregation.

scholarly journals Uptake and Distribution of Administered Bone Marrow Mesenchymal Stem Cell Extracellular Vesicles in Retina

Cells ◽  
2021 ◽  
Vol 10 (4) ◽  
pp. 730
Author(s):  
Biji Mathew ◽  
Leianne A. Torres ◽  
Lorea Gamboa Gamboa Acha ◽  
Sophie Tran ◽  
Alice Liu ◽  
...  
Keyword(s):  
Stem Cell ◽  
Mesenchymal Stem Cell ◽  
Extracellular Vesicles ◽  
Time Course ◽  
Ganglion Cells ◽  
Ex Vivo ◽  
Dependent Manner ◽  
Paracrine Effects

Cell replacement therapy using mesenchymal (MSC) and other stem cells has been evaluated for diabetic retinopathy and glaucoma. This approach has significant limitations, including few cells integrated, aberrant growth, and surgical complications. Mesenchymal Stem Cell Exosomes/Extracellular Vesicles (MSC EVs), which include exosomes and microvesicles, are an emerging alternative, promoting immunomodulation, repair, and regeneration by mediating MSC’s paracrine effects. For the clinical translation of EV therapy, it is important to determine the cellular destination and time course of EV uptake in the retina following administration. Here, we tested the cellular fate of EVs using in vivo rat retinas, ex vivo retinal explant, and primary retinal cells. Intravitreally administered fluorescent EVs were rapidly cleared from the vitreous. Retinal ganglion cells (RGCs) had maximal EV fluorescence at 14 days post administration, and microglia at 7 days. Both in vivo and in the explant model, most EVs were no deeper than the inner nuclear layer. Retinal astrocytes, microglia, and mixed neurons in vitro endocytosed EVs in a dose-dependent manner. Thus, our results indicate that intravitreal EVs are suited for the treatment of retinal diseases affecting the inner retina. Modification of the EV surface should be considered for maintaining EVs in the vitreous for prolonged delivery.

Pharmacology of MK-0591 (3-[1-(4-chlorobenzyl)-3-(t-butylthio)-5-(quinolin-2-yl-methoxy)-indol-2-yl]-2,2-dimethyl propanoic acid), a potent, orally active leukotriene biosynthesis inhibitor

1992 ◽  
Vol 70 (6) ◽  
pp. 799-807 ◽  
Author(s):  
C. Brideau ◽  
C. Chan ◽  
S. Charleson ◽  
D. Denis ◽  
J. F. Evans ◽  
...  
Keyword(s):  
Polymorphonuclear Leukocytes ◽  
Potent Inhibitor ◽  
Ex Vivo ◽  
Late Phase ◽  
Squirrel Monkeys ◽  
Propanoic Acid ◽  
Orally Active

MK-0591 (3-[1-(4-chlorobenzyl)-3-(t-butylthio)-5-(quinolin-2-yl-methoxy)-indol-2-yl]-2,2-dimethyl propanoic acid, previously L-686,708) is a potent inhibitor of leukotriene (LT) biosynthesis in intact human and elicited rat polymorphonuclear leukocytes (PMNLs) (IC50 values 3.1 and 6.1 nM, respectively) and in human, squirrel monkey, and rat whole blood (IC50 values 510, 69, and 9 nM, respectively). MK-0591 had no effect on rat 5-lipoxygenase. MK-0591 has a high affinity for 5-lipoxygenase activating protein (FLAP) as evidenced by an IC50 value of 1.6 nM in a FLAP binding assay and inhibition of the photoaffinity labelling of FLAP by two different photoaffinity ligands. Inhibition of activation of 5-lipoxygenase was shown through inhibition of the translocation of the enzyme from the cytosol to the membrane in human PMNLs. MK-0591 was a potent inhibitor of LT biosynthesis in vivo, first, following ex vivo challenge of blood obtained from treated rats and squirrel monkeys, second, in a rat pleurisy model, and, third, as monitored by inhibition of the urinary excretion of LTE4 in antigen-challenged allergic sheep. Inhibition of antigen-induced bronchoconstriction by MK-0591 was observed in inbred rats pretreated with methysergide, Ascaris-challenged squirrel monkeys, and Ascaris-challenged sheep (early and late phase response). These results indicate that MK-0591 is a potent inhibitor of LT biosynthesis both in vitro and in vivo indicating that the compound will be suitable for assessing the role of leukotrienes in pathological situations.Key words: leukotriene, 5-lipoxygenase, leukotriene inhibitor, bronchoconstriction, inflammation, 5-lipoxygenase activating protein.

scholarly journals Extrapolating In Vitro Screening Assay Data for Thyroperoxidase Inhibition to Predict Serum Thyroid Hormones in the Rat

2019 ◽  
Vol 173 (2) ◽  
pp. 280-292 ◽  
Author(s):  
Iman Hassan ◽  
Hisham El-Masri ◽  
Jermaine Ford ◽  
Amanda Brennan ◽  
Sakshi Handa ◽  
...  
Keyword(s):  
Thyroid Gland ◽  
Time Course ◽  
Ex Vivo ◽  
Response Analysis ◽  
In Vitro Screening ◽  
Screening Assay ◽  
High Throughput Screening Assay ◽  
Serum T4

Abstract Thyroperoxidase (TPO) is an enzyme essential for thyroid hormone (TH) synthesis and a target site for a number of xenobiotics that disrupt TH homeostasis. An in vitro high-throughput screening assay for TPO inhibition, the Amplex UltraRed-TPO (AUR-TPO), has been used to screen the ToxCast chemical libraries for this action. Output from this assay would be most useful if it could be readily translated into an in vivo response, namely a reduction of TH in serum. To this end, the relationship between TPO inhibition in vitro and serum TH decreases was examined in rats exposed to 2 classic TPO inhibitors, propylthiouracil (PTU) and methimazole (MMI). Serum and gland PTU, MMI, and TH levels were quantified using tandem liquid chromatography mass spectrometry. Thyroperoxidase activity was determined in thyroid gland microsomes treated with PTU or MMI in vitro and ex vivo from thyroid gland microsomes prepared from exposed animals. A quantitative model was constructed by contrasting in vitro and ex vivo AUR-TPO results and the in vivo time-course and dose-response analysis. In vitro:ex vivo correlations of AUR-TPO outputs indicated that less than 30% inhibition of TPO in vitro was sufficient to reduce serum T4 by 20%, a degree of regulatory significance. Although further testing of model estimates using other TPO inhibitors is essential for verification of these initial findings, the results of this study provide a means to translate in vitro screening assay results into predictions of in vivo serum T4 changes to inform risk assessment.

scholarly journals Pharmacological characterization of mutant huntingtin aggregate-directed PET imaging tracer candidates

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Frank Herrmann ◽  
Manuela Hessmann ◽  
Sabine Schaertl ◽  
Karola Berg-Rosseburg ◽  
Christopher J Brown ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Trinucleotide Repeat ◽  
Radioligand Binding ◽  
Ex Vivo ◽  
Binding Assays ◽  
Pharmacological Characterization ◽  
Binding Characteristics

AbstractHuntington’s disease (HD) is caused by a CAG trinucleotide repeat expansion in the first exon of the huntingtin (HTT) gene coding for the huntingtin (HTT) protein. The misfolding and consequential aggregation of CAG-expanded mutant HTT (mHTT) underpin HD pathology. Our interest in the life cycle of HTT led us to consider the development of high-affinity small-molecule binders of HTT oligomerized/amyloid-containing species that could serve as either cellular and in vivo imaging tools or potential therapeutic agents. We recently reported the development of PET tracers CHDI-180 and CHDI-626 as suitable for imaging mHTT aggregates, and here we present an in-depth pharmacological investigation of their binding characteristics. We have implemented an array of in vitro and ex vivo radiometric binding assays using recombinant HTT, brain homogenate-derived HTT aggregates, and brain sections from mouse HD models and humans post-mortem to investigate binding affinities and selectivity against other pathological proteins from indications such as Alzheimer’s disease and spinocerebellar ataxia 1. Radioligand binding assays and autoradiography studies using brain homogenates and tissue sections from HD mouse models showed that CHDI-180 and CHDI-626 specifically bind mHTT aggregates that accumulate with age and disease progression. Finally, we characterized CHDI-180 and CHDI-626 regarding their off-target selectivity and binding affinity to beta amyloid plaques in brain sections and homogenates from Alzheimer’s disease patients.

In-vitro profile and ex-vivo anticoagulant activity of the direct thrombin inhibitor dabigatran and its orally active prodrug, dabigatran etexilate

2007 ◽  
Vol 98 (07) ◽  
pp. 155-162 ◽  
Author(s):  
Jean-Marie Stassen ◽  
Henning Priepke ◽  
Uwe Joerg Ries ◽  
Norbert Hauel ◽  
Wolfgang Wienen
Keyword(s):  
Platelet Aggregation ◽  
Rhesus Monkeys ◽  
Ex Vivo ◽  
Anticoagulant Activity ◽  
Dabigatran Etexilate ◽  
Direct Thrombin Inhibitor ◽  
Thrombin Inhibitor ◽  
Orally Active

SummaryDabigatran is a reversible and selective, direct thrombin inhibitor (DTI) undergoing advanced clinical development as its orally active prodrug, dabigatran etexilate.This study set out to determine the molecular potency and anticoagulant efficacy of dabigatran and its prodrug dabigatran etexilate.This was achieved through enzyme inhibition and selectivity analyses, surface plasmon resonance studies, platelet aggregation, thrombin generation and clotting assays in vitro and ex vivo.These studies demonstrated that dabigatran selectively and reversibly inhibited human thrombin (Ki: 4.5 nM) as well as thrombin-induced platelet aggregation (IC50: 10 nM), while showing no inhibitory effect on other platelet-stimulating agents.Thrombin generation in platelet-poor plasma (PPP), measured as the endogenous thrombin potential (ETP) was inhibited concentration-dependently (IC50: 0.56 μM). Dabigatran demonstrated concentration-dependent anticoagulant effects in various species in vitro, doubling the activated partial thromboplastin time (aPTT), prothrombin time (PT) and ecarin clotting time (ECT) in human PPP at concentrations of 0.23, 0.83 and 0.18 μM, respectively. In vivo, dabigatran prolonged the aPTT dose-dependently after intravenous administration in rats (0.3, 1 and 3 mg/kg) and rhesus monkeys (0.15, 0.3 and 0.6 mg/kg). Dose- and time-dependent anticoagulant effects were observed with dabigatran etexilate administered orally to conscious rats (10, 20 and 50 mg/kg) or rhesus monkeys (1, 2.5 or 5 mg/kg), with maximum effects observed between 30 and 120 min after administration, respectively. These data suggest that dabigatran is a potent, selective thrombin inhibitor and an orally active anticoagulant as the prodrug, dabigatran etexilate.Footnote: Parts of this study were presented at the XVIII Congress of the International Society on Thrombosis and Haemostasis, Paris, July 2001. Thromb Haemost 2001; 86 (Suppl): Abstracts P755, P763.Institution where work was carried out: Boehringer Ingelheim Pharma GmbH &Co KG, 88397 Biberach, Germany.

scholarly journals The endothelin system in Morris hepatoma-7777: an endothelin receptor antagonist inhibits growth in vitro and in vivo

2004 ◽  
Vol 141 (2) ◽  
pp. 215-222 ◽  
Author(s):  
Thiemo Pfab ◽  
Gisela Stoltenburg-Didinger ◽  
Christoph Trautner ◽  
Michael Godes ◽  
Christian Bauer ◽  
...  
Keyword(s):  
Receptor Antagonist ◽  
Endothelin Receptor Antagonist ◽  
Endothelin Receptor ◽  
Endothelin System ◽  
Morris Hepatoma
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