t0901317 and Arteriosclerosis

Topics: Animals; Anticholesteremic Agents; Arteriosclerosis; Biological Transport; Cholesterol; DNA-Binding Proteins; Humans; Hydrocarbons, Fluorinated; Ligands; Liver X Receptors; Mice; Models, Biological; Orphan Nuclear Receptors; Receptors, Cytoplasmic and Nuclear; Sulfonamides; Triglycerides

A series of substituted 2-benzyl-3-aryl-7-trifluoromethylindazoles were prepared as LXR modulators. These compounds were partial agonists in transactivation assays when compared to 1 (T0901317) and were slightly weaker with respect to potency and efficacy on LXRalpha than on LXRbeta. Lead compounds in this series 12 (WAY-252623) and 13 (WAY-214950) showed less lipid accumulation in HepG2 cells than potent full agonists 1 and 3 (WAY-254011) but were comparable in efficacy to 1 and 3 with respect to cholesterol efflux in THP-1 foam cells, albeit weaker in potency. Compound 13 reduced aortic lesion area in LDLR knockout mice equivalently to 3 or positive control 2 (GW3965). In a 7-day hamster model, compound 13 showed a lesser propensity for plasma TG elevation than 3, when the compounds were compared at doses in which they elevated ABCA1 and ABCG1 gene expression in duodenum and liver at equal levels. In contrast to results previously published for 2, the lack of TG effect of 13 correlated with its inability to increase liver fatty acid synthase (FAS) gene expression, which was up-regulated 4-fold by 3. These results suggest indazoles such as 13 may have an improved profile for potential use as a therapeutic agent.

Topics: Animals; Arteriosclerosis; Cell Differentiation; Cell Line; Cricetinae; Crystallography, X-Ray; DNA-Binding Proteins; Humans; Hydrogen Bonding; Indazoles; Ligands; Liver; Liver X Receptors; Male; Mice; Mice, Inbred C57BL; Mice, Knockout; Models, Animal; Models, Molecular; Molecular Structure; Orphan Nuclear Receptors; Receptors, Cytoplasmic and Nuclear; Recombinant Proteins; Structure-Activity Relationship; Triglycerides

Complications of atherosclerotic cardiovascular disease due to elevated blood cholesterol levels are the major cause of death in the Western world. The liver X receptors, LXRalpha and LXRbeta (LXRs), are ligand-dependent transcription factors that act as cholesterol sensors and coordinately control transcription of genes involved in cholesterol and lipid homeostasis as well as macrophage inflammatory gene expression. LXRs regulate cholesterol balance through activation of ATP-binding cassette transporters that promote cholesterol transport and excretion from the liver, intestine, and macrophage. Although LXR agonists are known to delay progression of atherosclerosis in mouse models, their ability to abrogate preexisting cardiovascular disease by inducing regression and stabilization of established atherosclerotic lesions has not been addressed.. We demonstrate that LXR agonist treatment increases ATP-binding cassette transporter expression within preexisting atherosclerotic lesions, resulting in regression of these lesions as well as remodeling from vulnerable to stable lesions and a reduction in macrophage content. Further, using macrophage-selective LXR-deficient mice created by bone marrow transplantation, we provide the first evidence that macrophage LXR expression is necessary for the atheroprotective actions of an LXR agonist.. These data substantiate that drugs targeting macrophage LXR activity may offer therapeutic benefit in the treatment of atherosclerotic cardiovascular disease.

Topics: Animals; Anticholesteremic Agents; Aorta, Abdominal; Aorta, Thoracic; Arteriosclerosis; DNA-Binding Proteins; Hydrocarbons, Fluorinated; Liver X Receptors; Macrophages; Male; Mice; Mice, Inbred C57BL; Mice, Mutant Strains; Orphan Nuclear Receptors; Receptors, Cytoplasmic and Nuclear; Remission Induction; Sulfonamides

The high-cholesterol/high-fat Western diet has abetted an epidemic of atherosclerotic cardiovascular disease, the leading cause of death in industrialized nations. Liver X receptors (LXRs) are oxysterol sensors that are required for normal cholesterol and triglyceride homeostasis, yet synthetic LXR agonists produce undesirable hypertriglyceridemia. Here we report a previously unrecognized role for hepatic LXRalpha in the links between diet, serum lipids, and atherosclerosis. A modest increase in hepatic LXRalpha worsened serum lipid profiles in LDL-receptor null mice fed normal chow but had the opposite effect on lipids and afforded strong protection against atherosclerosis on a Western diet. The beneficial effect of hepatic LXRalpha was abrogated by a synthetic LXR agonist, which activated SREBP-1c and its target genes. Thus, the interplay between diet and hepatic LXRalpha is a critical determinant of serum lipid profiles and cardiovascular risk, and selective modulation of LXR target genes in liver can ameliorate hyperlipidemia and cardiovascular disease.

Topics: Animals; Anticholesteremic Agents; Arteriosclerosis; Cardiovascular Diseases; CCAAT-Enhancer-Binding Proteins; Diet; DNA-Binding Proteins; Female; Gene Expression Regulation; Humans; Hydrocarbons, Fluorinated; Lipid Metabolism; Lipids; Liver; Liver X Receptors; Male; Mice; Mice, Inbred C57BL; Mice, Knockout; Mice, Transgenic; Orphan Nuclear Receptors; Receptors, Cytoplasmic and Nuclear; RNA, Messenger; Sterol Regulatory Element Binding Protein 1; Sulfonamides; Transcription Factors

Liver X receptors (LXRs) regulate target genes that are critical in lipoprotein metabolism and atherosclerosis. Apolipoprotein AIV (ApoAIV) is an apolipoprotein that is associated with chylomicrons and high-density lipoproteins. Plasma ApoAIV level in humans is inversely correlated with coronary artery events and overexpression of ApoAIV in mice results in significant reduction in atherosclerosis. We report here that LXRs directly regulate apoAIV at the transcriptional level. Treatment of C57B6 mice with a synthetic LXR agonist, T0901317, resulted in significant increases in plasma apoAIV that was associated with high-density lipoprotein. Examination of both intestinal and liver apoAIV mRNA revealed specific increases in liver mRNA only. In a human heptoma HepG2 cell model, apoAIV mRNA was up-regulated upon the treatment with either native or synthetic LXR agonists. Nuclear run-on study revealed a significant increase in the ApoAIV transcriptional rate upon LXR activation. Examination of the human apoAIV proximal promoter revealed a potential LXR response element that demonstrated binding with HepG2 nuclear extracts. Cotransfection studies in HepG2 cells indicated that this responsive element was functional in mediating the human ApoAIV gene response to LXR agonists. In addition, we identified a functional LXR-responsive element at 3' end enhancer region of mouse ApoAIV gene. We conclude that ApoAIV is a direct target gene of LXRs that may contribute to the antiatherogenic effect of LXR activation.

Topics: Animals; Anticholesteremic Agents; Apolipoproteins A; Arteriosclerosis; Base Sequence; Cell Line, Tumor; DNA-Binding Proteins; Gene Expression Regulation; Humans; Hydrocarbons, Fluorinated; Ligands; Liver; Liver X Receptors; Male; Mice; Mice, Inbred C57BL; Molecular Sequence Data; Orphan Nuclear Receptors; Promoter Regions, Genetic; Receptors, Cytoplasmic and Nuclear; Response Elements; Retinoid X Receptors; RNA, Messenger; Sequence Alignment; Sulfonamides; Transcription, Genetic

Liver X receptors (LXR alpha and LXR beta) are nuclear receptors, which are important regulators of cholesterol and lipid metabolism. LXRs control genes involved in cholesterol efflux in macrophages, bile acid synthesis in liver and intestinal cholesterol absorption. LXRs also regulate genes participating in lipogenesis. To determine whether the activation of LXR promotes or inhibits development of atherosclerosis, T-0901317, a synthetic LXR ligand, was administered to low density lipoprotein receptor (LDLR)(-/-) mice. T-0901317 significantly reduced the atherosclerotic lesions in LDLR(-/-) mice without affecting plasma total cholesterol levels. This anti-atherogenic effect correlated with the plasma concentration of T-0901317, but not with high density lipoprotein cholesterol, which was increased by T-0901317. In addition, we observed that T-0901317 increased expression of ATP binding cassette A1 in the lesions in LDLR(-/-) mice as well as in mouse peritoneal macrophages. T-0901317 also significantly induced cholesterol efflux activity in peritoneal macrophages. These results suggest that LXR ligands may be useful therapeutic agents for the treatment of atherosclerosis.

Topics: Animals; Anticholesteremic Agents; Arteriosclerosis; ATP Binding Cassette Transporter 1; ATP-Binding Cassette Transporters; Biological Transport; Cholesterol; DNA-Binding Proteins; Hydrocarbons, Fluorinated; Ligands; Lipids; Lipoproteins; Liver X Receptors; Male; Mice; Mice, Inbred C57BL; Mice, Knockout; Models, Biological; Orphan Nuclear Receptors; Receptors, Cytoplasmic and Nuclear; Receptors, LDL; RNA, Messenger; Sulfonamides

Apolipoprotein E (apoE) secreted by macrophages in the artery wall exerts an important protective effect against the development of atherosclerosis, presumably through its ability to promote lipid efflux. Previous studies have shown that increases in cellular free cholesterol levels stimulate apoE transcription in macrophages and adipocytes; however, the molecular basis for this regulation is unknown. Recently, Taylor and colleagues [Shih, S. J., Allan, C., Grehan, S., Tse, E., Moran, C. & Taylor, J. M. (2000) J. Biol. Chem. 275, 31567-31572] identified two enhancers from the human apoE gene, termed multienhancer 1 (ME.1) and multienhancer 2 (ME.2), that direct macrophage- and adipose-specific expression in transgenic mice. We demonstrate here that the nuclear receptors LXRalpha and LXRbeta and their oxysterol ligands are key regulators of apoE expression in both macrophages and adipose tissue. We show that LXR/RXR heterodimers regulate apoE transcription directly, through interaction with a conserved LXR response element present in both ME.1 and ME.2. Moreover, we demonstrate that the ability of oxysterols and synthetic ligands to regulate apoE expression in adipose tissue and peritoneal macrophages is reduced in Lxralpha-/- or Lxrbeta-/- mice and abolished in double knockouts. Basal expression of apoE is not compromised in Lxr null mice, however, indicating that LXRs mediate lipid-inducible rather than tissue-specific expression of this gene. Together with our previous work, these findings support a central role for LXR signaling pathways in the control of macrophage cholesterol efflux through the coordinate regulation of apoE, ABCA1, and ABCG1 expression.

Topics: 3T3 Cells; Adipocytes; Animals; Anticholesteremic Agents; Apolipoproteins E; Arteriosclerosis; ATP Binding Cassette Transporter 1; ATP Binding Cassette Transporter, Subfamily G, Member 1; ATP-Binding Cassette Transporters; Carcinoma, Hepatocellular; Cell Differentiation; Cells, Cultured; Cholesterol; Diet, Atherogenic; Dimerization; DNA-Binding Proteins; Enhancer Elements, Genetic; Gene Expression Regulation; Humans; Hydrocarbons, Fluorinated; Hydroxycholesterols; Ligands; Lipids; Liver Neoplasms; Liver X Receptors; Lovastatin; Macrophages, Peritoneal; Male; Mevalonic Acid; Mice; Mice, Knockout; Organic Chemicals; Orphan Nuclear Receptors; Receptors, Cytoplasmic and Nuclear; Receptors, Retinoic Acid; Recombinant Fusion Proteins; Retinoid X Receptors; RNA, Messenger; Sulfonamides; Tetradecanoylphorbol Acetate; Transcription Factors; Tumor Cells, Cultured