The microsyringe was loaded with a solution of the protein sample (534 or 483 M protein for BRD3[2] and BRD4[1] respectively, in ITC buffer) and was carefully inserted into the calorimetric cell, which was filled with an amount of the ligand (0.2 mL, 2025 M in ITC buffer). BET inhibitor, strongly stimulated apoA-I production in Hep-G2 cells, but that its enantiomer ()-JQ1, which has no BET inhibitor activity, also showed considerable effect on apoA-I production. MDCO-3770 and MDCO-3783 also inhibited BRD3 and BRD4 in vitro, with potency somewhat below that of (+)-JQ1. We conclude that the effect of thieno-TZDs on apoA-I expression is not due to inhibition of the BZD or PAF receptors and is not completely explained by transcriptional repression by BET proteins. Keywords:apolipotein A-I, thienotriazolodiazepines, bromodomain inhibition == Introduction == Several impartial lines of research have shown that direct administration of High Density Lipoprotein (HDL) or hepatic transgenic overexpression of its main protein apolipoprotein A-I (apoA-I) can rapidly produce plaque regression in animal K252a models of atherosclerosis.15Tus, upregulation of apoA-I production might be beneficial for treatment of this disease. Previously, using cell-based assay systems, triazolodiazepines (TZDs) were discovered, which are able to enhance apoA-I gene expression and protein synthesis/secretion in cultured liver cells or Hep-G2 cells. These comprise members of thieno-TZDs such as Ro 11-1464,6the benzo-TZDs U-34599, and U-51477,7as well as GW841819X,8all reported to stimulate apoA-I production 4- to 6-fold at micromolar concentrations (structures of these compound shown inFig. 1). Recently, we showed that Ro 11-1464 increased plasma levels of apoA-I in mice transgenic for human apoA-I.9 == K252a Determine 1. == Structures of compounds tested in this study. TZDs were developed in the past as sedatives acting as agonist around the benzodiazepine (BZD) receptor in the central nervous system (eg, triazolam, brotizolam) or Rabbit Polyclonal to Smad1 as antiplatelet brokers acting as antagonists of the platelet-activating factor (PAF) receptor.10,11However, whether the stimulating effect of TZDs on apoA-I expression is mediated by binding of these TZDs to the central BZD receptor and/or K252a to the PAF receptor has not been demonstrated. The first aim of this paper, therefore, is to describe synthesis and characterisation of 2 novel thieno-TZDs derived from Ro 11-1464, which are completely free of binding to these receptors but nevertheless remain good apoA-I upregulators. Researchers at Resverlogix Inc have described novel quinazolines as upregulators of apoA-I. Their most advanced compound, RVX-208, stimulates apoA-I protein production by HepG2 cells K252a 2-fold at 40 M.12The second aim of our work was to compare our thieno-TZDs with RVX-208 with respect to apoA-I production and potential cytotoxicity. Recent work by GlaxoSmithKline investigators ascribed the activity of certain benzo-TZDs on apoA-I expression to displacement of bromodomain and extraterminal (BET) proteins from acetylated histones.8Likewise, other TZDs were recently established as potent and selective BET inhibitors, that is, the thieno-TZD (+)-JQ1,13the benzo-TZD GSK525762A (also called I-BET),14and the benzotriazolotriazepine BzT-7.15The third purpose of this work, therefore, was to establish a comparison of our thieno-TZDs with these recently described thieno-TZDs with respect to apoA-I upregulation and establish if the effect on apoA-I production correlated with BET binding and inhibition. Our findings show that our new thieno-TZDs are effective upregulators of apoA-I production in liver cells without cytotoxic effects and act independently of binding to central BZD or PAF receptors. These thieno-TZDs are able to bind and inhibit BET, but additional mechanisms may be involved in their effect on apoA-I expression. == Materials and Methods == == Compounds == The structures of the compounds studied in this paper are depicted inFigure 1. Synthesis of the thieno-TZDs MDCO-3760 (Ro 11-1464), MDCO-3783, and MDCO-3770 were described in detail previously.16RVX-208 was synthesized as described by Hansen et al.17In addition, (+)-JQ1 and ()-JQ1 were synthesized as described.12 == Testing of compounds in cultured hepatocytes and Hep-G2 cells == == Source of hepatocytes, culture conditions == Primary human hepatocytes (Ready Heps Fresh Human Hepatocytes) as well as the appropriate cell culture medium (HCM BulletKit) were obtained from Lonza Cologne GmbH, Cologne, Germany. The cells were delivered in 96-well platescoated with human collagen at a density of ~5 105/well. Upon arrival, cells were handled according to the manufacturers instructions: briefly, plates were immediately unpacked, the transport film was removed, and cells were allowed to recover for 2 hours at 37C in 5%.