gw-3965 and 22-hydroxycholesterol

Topics: Angiogenic Proteins; ATP Binding Cassette Transporter 1; Benzoates; Benzylamines; Blood Platelets; Cell-Derived Microparticles; Dendritic Cells; Endothelial Cells; Gene Expression Regulation; Humans; Hydrocarbons, Fluorinated; Hydroxycholesterols; Imidazoles; Immunity, Innate; Liver X Receptors; NF-kappa B; Oligodeoxyribonucleotides; Phenylenediamines; Primary Cell Culture; Receptors, G-Protein-Coupled; Signal Transduction; Sterol Regulatory Element Binding Protein 1; Sulfonamides; Toll-Like Receptor 7; Tumor Necrosis Factor-alpha

Liver X receptors (LXRs) play an important role in the regulation of cholesterol by regulating several transporters. In this study, we investigated the role of LXRs in the regulation of human organic anion transporter 1 (hOAT1), a major transporter localized in the basolateral membrane of the renal proximal tubule. Exposure of renal S2 cells expressing hOAT1 to LXR agonists (TO901317 and GW3965) and their endogenous ligand [22(R)-hydroxycholesterol] led to the inhibition of hOAT1-mediated [(14)C]PAH uptake. This inhibition was abolished by coincubation of the above agonists with 22(S)-hydroxycholesterol, an LXR antagonist. Moreover, it was found that the effect of LXR agonists was not mediated by changes in intracellular cholesterol levels. Interestingly, the inhibitory effect of LXRs was enhanced in the presence of 9-cis retinoic acid, a retinoic X receptor agonist. Kinetic analysis revealed that LXR activation decreased the maximum rate of PAH transport (J(max)) but had no effect on the affinity of the transporter (K(t)). This result correlated well with data from Western blot analysis, which showed the decrease in hOAT1 expression following LXR activation. Similarly, TO901317 inhibited [(14)C]PAH uptake by the renal cortical slices as well as decreasing mOAT1 protein expression in mouse kidney. Our findings indicated for the first time that hOAT1 was downregulated by LXR activation in the renal proximal tubule.

Topics: Animals; Benzoates; Benzylamines; Cell Line; Cells, Cultured; Down-Regulation; Humans; Hydrocarbons, Fluorinated; Hydroxycholesterols; Kidney Tubules, Proximal; Liver X Receptors; Mice; Organic Anion Transport Protein 1; Orphan Nuclear Receptors; Sulfonamides

Liver X receptors (LXRs) are nuclear receptors that regulate cholesterol, fatty acid, and glucose metabolism in various tissues. However, the renal action of LXRs is not well understood. Here we investigated the effects of LXR-activating ligands on modulation of epithelial sodium channel (ENaC)-mediated sodium transport in collecting duct cells. Exposure of the M1 cells to the synthetic LXR agonists T0901317 and GW3965 or the natural ligand 22R-hydroxycholesterol for 24 h decreased amiloride-sensitive sodium transport, corresponding with an increase of transepithelial resistance. The inhibition of amiloride-sensitive sodium transport after incubation with T0901317 or GW3965 was not mediated by a reduction of Na(+)/K(+)-ATPase-mediated basolateral sodium transport. On the other hand, T0901317 and GW3965 decreased mRNA abundance and membrane expression of ENaC. Preincubation the monolayer with GW3965 attenuated aldosterone-induced stimulation sodium transport. In primary cultures of collecting duct cells, T0901317 and GW3965 similarly inhibited ENaC transport function as in M1 cells. This is the first evidence showing LXR-activating ligands modulate ENaC-mediated sodium transport in collecting duct cells. These results suggest that LXRs may represent a novel therapeutic target for treatment of conditions with dysregulation of ENaC such as hypertension.

Topics: Animals; Anticholesteremic Agents; Benzoates; Benzylamines; Biological Transport; Cells, Cultured; Epithelial Sodium Channels; Hydrocarbons, Fluorinated; Hydroxycholesterols; Kidney Tubules, Collecting; Ligands; Liver X Receptors; Mice; Orphan Nuclear Receptors; Sodium; Sodium-Potassium-Exchanging ATPase; Sulfonamides

Liver X receptors alpha and beta (LXRalpha, LXRbeta) are key regulators of cholesterol homeostasis. The effects of LXR ligands on endothelial cells are largely unknown. While oxysterol LXR agonists can increase the endothelial-leukocyte interaction, synthetic LXR agonists are anti-atherogenic and anti-inflammatory. Mechanistic differences may underlie such findings.. LXRalpha and LXRbeta were found to be expressed in human endothelial cells. While synthetic LXR agonists could blunt the LPS-induced up-regulation of adhesion molecules (ICAM-1, VCAM-1, E-Selectin), 22-hydroxycholesterol and 24,25-epoxycholesterol enhanced such response. Microarray profiling further showed that the endothelial gene expression fingerprints of 22-hydroxycholesterol and T0901317 largely differed and unexpectedly shared only a restricted number of genes. Indeed, 22-hydroxycholesterol down-regulated eNOS and up-regulated a vast cohort of inflammatory mediators such as adhesion molecules, cytokines, enzymes and transcription factors. Other LXR-activating oxysterols such as 24,25-epoxycholesterol, 25-hydroxycholesterol and 27-hydroxycholesterol could also stimulate the endothelial expression of inflammatory markers, although significant differences were observed. These effects persisted in LXR-silenced cells, confirming the mechanistic dissociation of oxysterol and LXR pathways. Furthermore, the oxysterol-induced expression of inflammatory markers was not secondary to cell apoptosis and may relate to oxidative stress.. LXR-activating oxysterols comprehensively activate the expression of endothelial inflammation markers independently from LXRs. At proper dosage, synthetic LXR agonists are safe on endothelial cells and may even transrepress inflammatory reactions.

Topics: Anticholesteremic Agents; Benzoates; Benzylamines; Cells, Cultured; Chemokines; Cholesterol; E-Selectin; Endothelial Cells; Gene Expression Profiling; Gene Expression Regulation; Humans; Hydrocarbons, Fluorinated; Hydroxycholesterols; Inflammation Mediators; Intercellular Adhesion Molecule-1; Lipopolysaccharides; Liver X Receptors; Orphan Nuclear Receptors; RNA Interference; RNA, Messenger; Signal Transduction; Sulfonamides; Transcription Factors; Transfection; Tumor Necrosis Factor-alpha; Vascular Cell Adhesion Molecule-1

Prostate cancer is the most commonly diagnosed and the second leading cause of cancer death in men. The androgens-androgen receptor signaling plays an important role in normal prostate development, as well as in prostatic diseases, such as benign hyperplasia and prostate cancer. Accordingly, androgen ablation has been the most effective endocrine therapy for hormone-dependent prostate cancer. Here, we report a novel nuclear receptor-mediated mechanism of androgen deprivation. Genetic or pharmacological activation of the liver X receptor (LXR) in vivo lowered androgenic activity by inducing the hydroxysteroid sulfotransferase 2A1, an enzyme essential for the metabolic deactivation of androgens. Activation of LXR also inhibited the expression of steroid sulfatase in the prostate, which may have helped to prevent the local conversion of sulfonated androgens back to active metabolites. Interestingly, LXR also induced the expression of selected testicular androgen synthesizing enzymes. At the physiological level, activation of LXR in mice inhibited androgen-dependent prostate regeneration in castrated mice. Treatment with LXR agonists inhibited androgen-dependent proliferation of prostate cancer cells in a LXR- and sulfotransferase 2A1-dependent manner. In summary, we have revealed a novel function of LXR in androgen homeostasis, an endocrine role distinct to the previously known sterol sensor function of this receptor. LXR may represent a novel therapeutic target for androgen deprivation, and may aid in the treatment and prevention of hormone-dependent prostate cancer.

Topics: Androgens; Animals; Benzoates; Benzylamines; Cells, Cultured; DNA-Binding Proteins; Drug Resistance, Neoplasm; Gene Expression Regulation, Enzymologic; Humans; Hydroxycholesterols; Liver X Receptors; Male; Mice; Mice, Inbred C57BL; Mice, Transgenic; Neoplasms, Hormone-Dependent; Orphan Nuclear Receptors; Prostate; Prostatic Neoplasms; Receptors, Cytoplasmic and Nuclear; Regeneration; Sulfotransferases; Testosterone