No abstract

IL-17–producing CD4+Th17 cells, CD8+Tc17 cells, and γδ T cells play critical roles in the pathogenesis of autoimmune psoriasis. RORγt is required for the differentiation of Th17 cells and expression of IL-17. In this article, we describe a novel, potent, and selective RORγt inverse agonist (TMP778), and its inactive diastereomer (TMP776). This chemistry, for the first time to our knowledge, provides a unique and powerful set of tools to probe RORγt-dependent functions. TMP778, but not TMP776, blocked human Th17 and Tc17 cell differentiation and also acutely modulated IL-17A production and inflammatory Th17-signature gene expression (Il17a, Il17f, Il22, Il26, Ccr6, and Il23) in mature human Th17 effector/memory T cells. In addition, TMP778, but not TMP776, inhibited IL-17A production in both human and mouse γδ T cells. IL-23–induced IL-17A production was also blocked by TMP778 treatment. In vivo targeting of RORγt in mice via TMP778 administration reduced imiquimod-induced psoriasis-like cutaneous inflammation. Further, TMP778 selectively regulated Th17-signature gene expression in mononuclear cells isolated from both the blood and affected skin of psoriasis patients. In summary, to our knowledge, we are the first to demonstrate that RORγt inverse agonists: 1) inhibit Tc17 cell differentiation, as well as IL-17 production by γδ T cells and CD8+ Tc17 cells; 2) block imiquimod-induced cutaneous inflammation; 3) inhibit Th17 signature gene expression by cells isolated from psoriatic patient samples; and 4) block IL-23–induced IL-17A expression. Thus, RORγt is a tractable drug target for the treatment of cutaneous inflammatory disorders, which may afford additional therapeutic benefit over existing modalities that target only IL-17A.

Pregnancy alters bile acid homeostasis and can unmask cholestatic disease in genetically predisposed but otherwise asymptomatic individuals. In this report, we show that normal pregnant mice have raised hepatic bile acid levels in the presence of procholestatic gene expression. The nuclear receptor farnesoid X receptor (FXR) regulates the transcription of the majority of these genes, and we show that both ablation and activation of Fxr prevent the accumulation of hepatic bile acids during pregnancy. These observations suggest that the function of Fxr may be perturbed during gestation. In subsequent in vitro experiments, serum from pregnant mice and humans was found to repress expression of the Fxr target gene, small heterodimer partner (Shp), in liver-derived Fao cells. Estradiol or estradiol metabolites may contribute to this effect because coincubation with the estrogen receptor (ER) antagonist fulvestrant (ICI 182780) abolished the repressive effects on Shp expression. Finally, we report that ERa interacts with FXR in an estradiol-dependent manner and represses its function in vitro. Conclusion: Ligand-activated ERa may inhibit FXR function during pregnancy and result in procholestatic gene expression and raised hepatic bile acid levels. We propose that this could cause intrahepatic cholestasis of pregnancy in genetically predisposed individuals. (HEPATOLOGY 2010;52:1341-1349 T he synthesis, metabolism, and enterohepatic circulation of bile acids is tightly regulated by nuclear hormone receptors.1 Farnesoid X receptor (FXR) is required for the basal maintenance of the enterohepatic circulation and its response to bile acid challenge. (CYP8B1) 8 ] through the induction of a transcriptional repressor, small heterodimer partner (SHP), in the liver 8 and aAbbreviations: BSEP, bile salt export pump; CA, cholic acid; CDCA, chenodeoxycholic acid; cDNA, complementary DNA; CYP7A1, cytochrome P450 7A1; CYP8B1, cytochrome P450 8B1; E2, 17b-estradiol; ER, estrogen receptor; EtOH, ethanol; FGF, fibroblast growth factor; FXR, farnesoid X receptor; GAPDH, glyceraldehyde 3-phosphate dehydrogenase; GST, glutathione S-transferase; GW4064, 3-(2,6-dichlorophenyl)-4-(3 0 -carboxy-2-chlorostilben-4-yl)oxymethyl-5-isopropylisoxazole; ICP, intrahepatic cholestasis of pregnancy; MDR, multidrug resistance protein; mRNA, messenger RNA; MRP, multidrug resistance-associated protein; NTCP, Na þ -taurocholate cotransporting polypeptide; OATP, organic anion-transporting polypeptide; qRT-PCR, quantitative reverse-transcription polymerase chain reaction; SHP, small heterodimer partner.From the

Circadian rhythms govern a wide variety of physiological and metabolic functions in many organisms, from prokaryotes to humans. We previously reported that silent information regulator 1 (SIRT1), a NAD + -dependent deacetylase, contributes to circadian control. In addition, SIRT1 activity is regulated in a cyclic manner in virtue of the circadian oscillation of the coenzyme NAD + . Here we used specific SIRT1 activator compounds both in vitro and in vivo. We tested a variety of compounds to show that the activation of SIRT1 alters CLOCK:BMAL1-driven transcription in different systems. Activation of SIRT1 induces repression of circadian gene expression and decreases H3 K9/K14 acetylation at corresponding promoters in a time-specific manner. Specific activation of SIRT1 was demonstrated in vivo using liver-specific SIRT1-deficient mice, where the effect of SIRT1 activator compounds was shown to be dependent on SIRT1. Our findings demonstrate that SIRT1 can fine-tune circadian rhythm and pave the way to the development of pharmacological strategies to address a broad range of therapeutic indications.

REV-ERBα has emerged as an important target for regulation of circadian rhythm and its associated physiology. Herein, we report on the optimization of a series of REV-ERBα agonists based on GSK4112 (1) for potency, selectivity, and bioavailability. Potent REV-ERBα agonists 4, 10, 16, and 23 are detailed for their ability to suppress BMAL and IL-6 expression from human cells while also demonstrating excellent selectivity over LXRα. Amine 4 demonstrated in vivo bioavailability after either IV or oral dosing.