Mechanisms of agonist synergism in human isolated platelets

The synergism between various platelet agonists which results in an aggregation response has been described frequently in vitro, however there are no satisfactory explanations for the mechanisms controlling this response. In vivo, platelets are exposed to many aggregating stimuli at low concentrations at an injury site and synergism between such stimuli would enable an intensive aggregation and release response to occur. This study has investigated the intracellular mechanisms associated with agonist synergism in human isolated platelets using the following agonist combinations; adrenaline and thrombin, adrenaline and LDL. The action of LDL alone in activating platelets was also studied. Subthreshold concentrations of adrenaline (5-20 μM), thrombin (0.006-0.02 U/ml) and LDL (0.1-0.2 mg protein/ml), which individually did not cause an aggregation response were combined in pairs to produce a synergistic aggregation response, which was not inhibited by the presence of aspirin. There was no hydrolysis of phosphatidylinositol 4,5, bisphosphate or production of inositol trisphosphate associated with the synergism. Using quin 2, no increases in intracellular calcium concentration ([Ca2+]i ) were detected during the synergistic aggregation responses, however small [([Ca2+]i increases were detected using aequorin. No release or metabolism of arachidonic acid from membrane phospholipids was observed. In agreement with the calcium results, there was no phosphorylation of the 20 kDa protein. However, despite no significant diacylglycerol production, the 47 kDa protein was clearly phosphorylated following synergism between both the agonist combinations. Whether the phosphorylation of the 47 kDa protein is important in the initiation of a synergistic response remains to be determined and the presence of other pathways must be considered. Activation of platelets with 2.75 mg protein/ml LDL was accompanied by a slow increase in inositol trisphosphate production and intracellular calcium levels. Low LDL concentrations (<0.25 mg protein/ml) did not stimulate either aggregation or any intracellular mechanism

Inhibition of the inositol kinase Itpkb augments calcium signaling in lymphocytes and reveals a novel strategy to treat autoimmune disease

Emerging approaches to treat immune disorders target positive regulatory kinases downstream of antigen receptors with small molecule inhibitors. Here we provide evidence for an alternative approach in which inhibition of the negative regulatory inositol kinase Itpkb in mature T lymphocytes results in enhanced intracellular calcium levels following antigen receptor activation leading to T cell death. Using Itpkb conditional knockout mice and LMW Itpkb inhibitors these studies reveal that Itpkb through its product IP4 inhibits the Orai1/Stim1 calcium channel on lymphocytes. Pharmacological inhibition or genetic deletion of Itpkb results in elevated intracellular Ca2+ and induction of FasL and Bim resulting in T cell apoptosis. Deletion of Itpkb or treatment with Itpkb inhibitors blocks T-cell dependent antibody responses in vivo and prevents T cell driven arthritis in rats. These data identify Itpkb as an essential mediator of T cell activation and suggest Itpkb inhibition as a novel approach to treat autoimmune disease

The development of automated patch clamp assays for canonical transient receptor potential channels TRPC3, 6, and 7

The canonical transient receptor potential channel subfamily (TRPC3, TRPC6, and TRPC7) contains Ca2+ permeable non-selective cation channels that are widely expressed in a variety of tissues. There is increasing evidence implicating TRPC channels, particularly TRPC3 and 6, in physiological and pathophysiological processes, eliciting interest in these channels as novel drug targets. Electrophysiology remains a benchmark technique for measuring ion channel function and accurately determining the pharmacological effects of compounds. In this report we describe the development of TRPC inhibitor assays on 2 automated planar patch clamp platforms - the IonWorks® Quattro™ and QPatch® systems. To enable activation of TRPC channels by carbachol, Chinese Hamster Ovary-K1 cells stably expressing the muscarinic M3 receptor were transduced with human TRPC3, TRPC6, or TRPC7 using BacMam viruses. TRPC3, 6, and 7 currents could be recorded on both platforms. However, the design of each platform limits which assay parameters can be recorded. Due to its continuous recording capabilities, the QPatch can capture both the activation and decay of the response. However, the transient nature of TRPC channels, the inability to reactivate and the large variation in peak currents limits the ability to develop assays for compound screening. The IonWorks Quattro, due to its discontinuous sampling, did not fully capture the peak of TRPC currents. However, due to the ability of the IonWorks Quattro to record from 64 cells per well, the variation from well to well was sufficiently reduced allowing for the development of medium-throughput screening assays. © Copyright 2014, Mary Ann Liebert, Inc. 2014

A new orally bioavailable dual adenosine A2B/A3 receptor antagonist with therapeutic potential.

The synthesis and SAR of 5-heterocycle-substituted aminothiazole adenosine receptor antagonists is described. Several compounds show high affinity and selectivity for the A2B and A3 receptors. One compound (5f) shows good ADME properties in the rat and as such may be an important new compound in testing the current hypotheses proposing a therapeutic role for a dual A2B/A3 antagonist in allergic diseases

The development of automated patch clamp assays for canonical transient receptor potential channels TRPC3, 6, and 7

The canonical transient receptor potential channel subfamily (TRPC3, TRPC6, and TRPC7) contains Ca2+ permeable non-selective cation channels that are widely expressed in a variety of tissues. There is increasing evidence implicating TRPC channels, particularly TRPC3 and 6, in physiological and pathophysiological processes, eliciting interest in these channels as novel drug targets. Electrophysiology remains a benchmark technique for measuring ion channel function and accurately determining the pharmacological effects of compounds. In this report we describe the development of TRPC inhibitor assays on 2 automated planar patch clamp platforms - the IonWorks® Quattro™ and QPatch® systems. To enable activation of TRPC channels by carbachol, Chinese Hamster Ovary-K1 cells stably expressing the muscarinic M3 receptor were transduced with human TRPC3, TRPC6, or TRPC7 using BacMam viruses. TRPC3, 6, and 7 currents could be recorded on both platforms. However, the design of each platform limits which assay parameters can be recorded. Due to its continuous recording capabilities, the QPatch can capture both the activation and decay of the response. However, the transient nature of TRPC channels, the inability to reactivate and the large variation in peak currents limits the ability to develop assays for compound screening. The IonWorks Quattro, due to its discontinuous sampling, did not fully capture the peak of TRPC currents. However, due to the ability of the IonWorks Quattro to record from 64 cells per well, the variation from well to well was sufficiently reduced allowing for the development of medium-throughput screening assays. © Copyright 2014, Mary Ann Liebert, Inc. 2014

The Discovery And Optimisation of 4-(8-(3-Fluorophenyl)-1,7-naphthyridin-6-yl)cyclohexanecarboxylic acid, An Improved PDE4 Inhibitor For The Treatment of COPD.

Herein we describe the optimisation of a series of PDE4 inhibitors, with special focus on solubility and pharamcokinetics, to clinical compound 2, 4-(8-(3-fluorophenyl)-1,7-naphthyridin-6-yl)cyclohexanecarboxylic acid. Compound 2 was found to have exemplary pharmacokinetics in humans, which enabled a novel dosing regime and the achievement of high plasma drug levels without associated nausea or emesis

Solubility-Driven Optimisation of Phosphodiesterase-4 Inhibitors Leading to a Clinical Candidate

The solubility-driven optimisation of a series of 1,7-napthyridine phosphodiesterase 4 inhibitors is described. Directed structural changes resulted in increased aqueous solubility, enabling superior pharmacokinetic properties, with retention of PDE4 inhibition. A range of potent and orally bioavailable compounds with good in vivo efficacy in animal models of inflammation and reduced emetic potential compared to previously described drugs were synthesised. Compound 2d was taken forward as a clinical candidate for the treatment of COPD