nuclear receptor farnesoid X receptor

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Intestinal farnesoid X receptor signaling promotes nonalcoholic fatty liver disease

Intestinal farnesoid X receptor signaling promotes nonalcoholic fatty liver disease

indicating that decreased fatty acid catabolism was not involved in intestinal FXR–dependent hepatic lipid accumulation (Supple- mental Figure 9, F and G). Western blot analysis further revealed that the protein levels of the mature nuclear form of SREBP1 (SREBP1-N) and CIDEA were significantly downregulated in the livers of antibiotic-treated mice on a HFD for 7 weeks (Figure 6, F and G). The rate-limiting enzyme cholesterol 7α-hydroxylase (CYP7A1) initiates the classical pathway for bile acid synthesis and plays an important role in regulating lipid metabolism (20). How- ever, Cyp7a1 mRNA levels were induced in antibiotic-treated mice, but were similar in tempol-treated mice (Supplemental Figure 9H). In addition, inflammation-related genes, such as toll-like recep- tor 2 (Tlr2), toll-like receptor 4 (Tlr4), toll-like receptor 9 (Tlr9), and TNF-α (Tnfa), were at comparable levels in tempol- or antibi- otic-treated mice (Supplemental Figure 9I). To investigate whether the decrease in ceramide is a major contributing factor in improv- ing HFD-induced NAFLD development in antibiotic-treated mice, daily i.p. injections of purified C16:0 ceramide were administered to HFD-fed and antibiotic-treated mice. Liver histology indicated that ceramide treatment reversed the decrease in hepatic lipid droplets in antibiotic-treated mice fed a HFD for 7 weeks (Figure 7A). The liver weights, liver/body mass ratios, and hepatic triglyc- eride content were also significantly increased after ceramide treat- ment in the antibiotic-treated mice (Figure 7, B and C). Ceramide treatment also increased serum ceramide levels above those found to be reduced in the antibiotic-treated mice, and this was accom- panied by an upregulation of SREBP1C/CIDEA signaling and gene expression in the livers of antibiotic-treated mice (Figure 7, D and E). Interestingly and unexpectedly, other ceramides were also increased in C16:0 ceramide–treated mice.
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Farnesoid X receptor agonists attenuate colonic epithelial secretory function and prevent experimental diarrhoea in vivo

Farnesoid X receptor agonists attenuate colonic epithelial secretory function and prevent experimental diarrhoea in vivo

There is currently a great deal of research interest in the thera- peutic potential of the FXR. Agonists of this nuclear receptor are already in advanced clinical trials for treatment of liver dis- eases, 27 and they have also been proposed as potential targets for therapy of several other conditions, including obesity, type II diabetes, atherosclerosis and IBD. 12 28 The current studies suggest that, due to their potent antisecretory actions on intes- tinal epithelial cells, FXR agonists may also be bene fi cial in Figure 2 FXR activation inhibits colonic epithelial Cl − secretion in vitro. (A) Monolayers of T 84 cells were treated with GW4064 (5 μ mol/L) for 24 h
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TO901317 regulating apolipoprotein M expression mediates via the farnesoid X receptor pathway in Caco-2 cells

TO901317 regulating apolipoprotein M expression mediates via the farnesoid X receptor pathway in Caco-2 cells

Previous studies have demonstrated that hepatic apoM expression could be regulated by certain cytokines and nuclear factors. In our previous study [15], we demon- strated that LXR agonist, TO901317, could significantly downregulate apoM expression in the hepatic cell line, HepG2 cells. Moreover, Calayir., et al. [16] confirmed our findings that TO901317 did inhibit apoM expression in HepG2 cells, however, they found that TO901317 could significantly upregulate apoM expression in intestinal cell, which suggest that TO901317 regulating apoM expression is cellular dependent. Moreover, Mosialou., et al. [12] reported that the natural LXR ligand oxysterols could sig- nificantly upregulate apoM mRNA level and protein level in HepG2 cells, and LXR could bind to the HRE in the proximal apoM promoter examined by the Chromatin Immunoprecipitation Assays (CHIP). They found that
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Hepatoprotection by the farnesoid X receptor agonist GW4064 in rat models of intra  and extrahepatic cholestasis

Hepatoprotection by the farnesoid X receptor agonist GW4064 in rat models of intra and extrahepatic cholestasis

Farnesoid X receptor (FXR) is a bile acid–activated transcription factor that is a member of the nuclear hormone receptor superfamily. Fxr-null mice exhibit a phenotype similar to Byler disease, an inherited cholestatic liver disorder. In the liver, activation of FXR induces transcription of trans- porter genes involved in promoting bile acid clearance and represses genes involved in bile acid biosynthesis. We investigated whether the synthetic FXR agonist GW4064 could protect against cholestatic liver damage in rat models of extrahepatic and intrahepatic cholestasis. In the bile duct–ligation and α-naphthylisothiocyanate models of cholestasis, GW4064 treatment resulted in significant reductions in serum alanine aminotransferase, aspartate aminotransferase, and lactate dehydrogenase, as well as other markers of liver damage. Rats that received GW4064 treatment also had decreased incidence and extent of necrosis, decreased inflammatory cell infiltration, and decreased bile duct proliferation. Analysis of gene expression in livers from GW4064-treated cholestatic rats revealed decreased expression of bile acid biosynthetic genes and increased expres- sion of genes involved in bile acid transport, including the phospholipid flippase MDR2. The hepatoprotection seen in these animal models by the synthetic FXR agonist suggests FXR agonists may be useful in the treatment of cholestatic liver disease.
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Inhibitory Effects of Bile Acids and Synthetic Farnesoid X Receptor Agonists on Rotavirus Replication

Inhibitory Effects of Bile Acids and Synthetic Farnesoid X Receptor Agonists on Rotavirus Replication

Earlier studies during the 1970s and 1980s showed that bile acids (CDCA) lowered triglyceride levels in blood through a mechanism not fully understood. Recent studies suggested that triglyceride-lowering effects of bile acids and some synthetic FXR agonists were mediated by FXR/SHP (13, 43). The ex- pression of SHP by activation of FXR led to the repression of sterol regulatory element-binding protein 1c, a transcription factor that controls genes involved in fatty acid and triglyceride synthesis (43). It is also reported that FXR regulates several genes in fatty acid and triglyceride synthesis, as well as lipo- protein metabolism (2, 14, 39). It was previously reported that bile acids differ markedly in binding affinity to FXR (27, 34). The activation of FXR is specific and limited to CDCA, the most potent activator, and DCA to a much lesser degree (27, 34). The ED 50 s of CDCA for activating FXR were reported to be 50 ␮ M and 10 ␮ M on murine and human FXR, respectively (27), which are within the physiological intracellular range (1). GW4064 is known as one of the most potent synthetic FXR agonists and has no activity on other nuclear receptors, includ- ing retinoic A receptor, at concentrations up to 1 mM (28, 45). In our study, GW4064 significantly inhibited virus replication at concentrations as low as 1 ␮ M, and the ED 50 of CDCA (45
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Farnesoid X receptor agonist INT-767 attenuates liver steatosis and inflammation in rat model of nonalcoholic steatohepatitis

Farnesoid X receptor agonist INT-767 attenuates liver steatosis and inflammation in rat model of nonalcoholic steatohepatitis

collectively leading to less BA toxicity. FXR-mediated gene suppression occurs through the novel pathway of SHP induction, a member of the nuclear receptor superfamily that binds to and interferes with the positive regulation of gene expression by other nuclear receptors including liver receptor homolog-1 on the target gene such as CYP7A1. INT-767 directly activates the expression of BSEP that transports BAs from the liver to the gall bladder. FXR coordinates the biliary secretion of BAs, cholesterol and phospholipids to form micelles in the canaliculus. This process increases cholesterol solubility and prevents BAs toxicity to the bile duct epithelial cells. 22 Furthermore, this process decreases intracellular
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Current therapies in alleviating liver disorders and cancers with a special focus on the potential of vitamin D

Current therapies in alleviating liver disorders and cancers with a special focus on the potential of vitamin D

The farnesoid X receptor belongs to the nuclear recep- tor family and is expressed in organs like the kidney, liver, adipose tissue and intestine. It influences the synthesis of bile acids, cholic and chenodeoxycholic acids which is through two known pathways. The classical or neu- tral pathway instigated by 7α- hydroxylation produces both bile acids, whereas the acidic pathway commen- cing with the side chain hydroxylation (C27) produces only chenodeoxycholic acid. A major difference is that the key enzyme cytochrome P450 oxidase and the sterol 27-hydroxylase CYP27A1 of the acidic pathway are neither regulated by the bile acids nor its levels altered in FXR-deficient mice. But FXR is involved in the down-regulation of expression of the microsomal rate-limiting enzyme CYP7A1 of the neutral pathway promoting it as a potential therapeutic agent [46]. Hypovitaminosis D is associated with increased body fat mass, and greater severity of NAFLD [47]. Hypo vitaminosis in NAFLD patients ’ needs to be demon- strated in future long term follow up studies to attri- bute a causal role to the vitamin, so that a therapeutic solution could be adopted.
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Characterization of EDP-305, a Highly Potent and Selective Farnesoid X Receptor Agonist, for the Treatment of Non-alcoholic Steatohepatitis

Characterization of EDP-305, a Highly Potent and Selective Farnesoid X Receptor Agonist, for the Treatment of Non-alcoholic Steatohepatitis

In vitro selectivity was conducted by INDIGO Biosciences (State College, PA). Briefly, reporter cells used in the various nuclear receptor agonist assays express either the native receptor or a receptor hybrid in which the native N-terminal DNA binding domain (DBD) is replaced by a yeast Gal4 DBD. A firefly luciferase reporter gene is functionally linked to an upstream receptor-specific genetic response elements (GRE) or a Gal4 upstream activation sequence (UAS). Agonist activity was tested against the following nuclear receptors: AhR, AR, CAR2, CAR3, ERα, ERβ, FXR, GR, LXRα, LXRβ, MR, PGR, PPARα, PPARδ, PPARγ, PXR, RARα, RARβ, RARγ, RXRα, RXRβ, RXRγ, TRα, TRβ, and VDR. Reference compounds were used to confirm assay performance for each nuclear receptor and results are reported as relative activation where the respective reference agonist at EC100 is 100% activity and 0.1% DMSO is 0% activity.
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Regulation of lipid metabolism-related gene expression in whole blood cells of normo- and dyslipidemic men after fish oil supplementation

Regulation of lipid metabolism-related gene expression in whole blood cells of normo- and dyslipidemic men after fish oil supplementation

The molecular mechanisms by which n-3 PUFAs mod- ify the lipid metabolism are not completely clarified. The regulation of gene expression is believed to be a key mechanism of how n-3 PUFAs mediate their functions. Specifically, n-3 PUFAs can modulate the activity of sev- eral transcription factors, such as sterol regulatory element-binding protein (SREBP) 1 [14], hepatic nuclear factor (HNF) 4α [15], liver X receptors [16], retinoid X receptor (RXR) [17], farnesoid X receptor [18], and per- oxisome proliferator-activated receptors (PPARs) [19], resulting in an altered expression of corresponding tar- get genes [20-24]. Although it is known that these genes, or rather their products, play eminent roles in the regu- lation of the lipid metabolism, the influence of n-3 PUFAs on a number of additional lipid metabolism- related genes and involved pathways remain to be dis- covered. Unravelling these connections may contribute to the understanding of the molecular mechanisms explaining the physiological functions of n-3 PUFAs.
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Farnesoid X receptor represses hepatic human APOA gene expression

Farnesoid X receptor represses hepatic human APOA gene expression

repressor, it has no DNA binding motif (56) but interacts with sev- eral nuclear receptors, such as LRH-1 or HNF4α, thereby interfering with gene transcription. Recently, the SHP/LRH-1/CYP7A1 signal- ing pathway was disproved, and LRH-1 was identified as a master regulator of Cyp8b1 (57, 58). Since SHP is able to interact in vitro with multiple partners, the identification of the actual SHP targets is still an open quest. Our transgenic APOA mice fed with CA or pri- mary hepatocytes incubated with FXR activators were found to have more Shp and less APOA gene expression. We therefore wondered whether Shp induction could repress APOA. However, dose response transfection experiments with SHP expression plasmid showed that SHP did not repress and instead increased the APOA promoter activity in HepG2 as well as in COS-7 cells (Supplemental Figure 6). Conversely, FXR directly repressed APOA promoter activity by binding to a DR-1 also recognized by HNF4α. This was verified by ChIP assay, which impressively confirmed that the DR-1 element at the –826- to –814-bp region of the APOA promoter is occupied by HNF4α, whereas CA activation leads to a switch of occupancy of the site by FXR (Figure 7E). Taken together, our data suggest that SHP does not regulate the APOA promoter in contrast to FXR.
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Emerging evidences for the opposite role of apolipoprotein C3 and apolipoprotein A5 in lipid metabolism and coronary artery disease

Emerging evidences for the opposite role of apolipoprotein C3 and apolipoprotein A5 in lipid metabolism and coronary artery disease

Initiation of gene expression is executed by specific bind- ing of transcription factors to gene regulatory elements, and molecules affecting this process can regulate corre- sponding gene expression. The concrete structure and regulation mechanisms of APOC3 and APOA5 gene ex- pression have been reviewed elsewhere [9], and we will focus here on regulators that are shared by APOC3 and APOA5. Indeed, several molecules have been implicated in the same direction regulation of APOC3 and APOA5 ex- pression, including upregulation with hepatocyte nuclear factor 4-α (HNF4-α) [15, 16] and glucose [17, 18], and downregulation with AMP-activated protein kinase [15, 19], insulin [20–22] and tumor necrosis factor-α (TNF-α) [23, 24]. Noticeably, these substances, except for TNF-α, are all important components directly involved in glucose metabolism, suggesting APOC3 and APOA5 dysregula- tion may contribute to diabetic dyslipidemia. Opposite direction regulation was also found in that peroxi- some proliferator-activated receptor-α (PPAR-α) and farnesoid X-activated receptor (FXR) promoted APOA5 [13, 14] while inhibited APOC3 expression [25, 26]. In contrast to APOA5, the human APOC3 gene promoter doesn’t contain PPAR-α and FXR posi- tive response elements. Actually, these two nuclear receptors acted indirectly by interfering the binding of other transcriptional factors, like HNF4-α, to specific elements of APOC3, thereby further inhibiting APOC3 gene transcription [26, 27]. Thus, the plasma TG low- ering effect of fibrates, one type of PPAR-α agonists, may be partly mediated by increasing the circulating concentration of apoA5 and/or decreasing apoC3 levels. Indeed, recent studies showed that both fenofi- brates and omega-3 polyunsaturated fatty acids ther- apy significantly decreased plasma apoC3 levels in humans [28, 29].
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Farnesoid X Receptor Signaling Shapes the Gut Microbiota and Controls Hepatic Lipid Metabolism

Farnesoid X Receptor Signaling Shapes the Gut Microbiota and Controls Hepatic Lipid Metabolism

Recent evidence suggests that modulation of farnesoid X receptor (FXR) signaling has beneficial effects on the development of obesity (8–11). FXR is a bile acid-activated nuclear receptor that regulates the homeostasis of bile acids, lipids, and glucose (12–14). Endogenous ligands of FXR include bile acids such as cholic acid (CA), chenodeoxycholic acid (CDCA), deoxycholic acid (DCA), lithocholic acid (LCA), and ursodeoxycholic acid (UDCA) (14, 15). UDCA is used to treat human liver diseases, such as nonalcoholic fatty liver disease (NAFLD) and nonalcoholic steatohepatitis (NASH) (16). Further, UDCA was found to improve NASH, insulin resistance, and high-fat diet (HFD)-induced obesity through suppression of FXR signaling, which is manifested by a significant reduction of FXR and fibroblast growth factor 19 (FGF19) levels coupled with elevation of cholesterol 7 ␣ -hydroxylase (CYP7A1) expression in the intestine (17). Interestingly, tauro- ␤ -muricholic acid (T- ␤ -MCA) was also identified as a naturally occurring FXR antagonist that inhibits FXR signaling in vivo in mouse intestine (9, 18). Previous studies showed that tempol, an antioxidant, and antibiotic treatments resulted in reduction of the genus Lactobacillus, thus improving obesity, NAFLD, and insulin resistance via inhibition of intestinal FXR signaling (9, 11). However, T- ␤ -MCA is rapidly metabolized in the ileum by bacterial bile salt hydrolase (BSH) through deconjugation, yielding ␤ -MCA and taurine (19–21). Therefore, a new high-affinity intestinal FXR antagonist, glycine- ␤ -muricholic acid (Gly-MCA), was designed that is structurally and functionally similar to T- ␤ -MCA and that demonstrated stability in the gut by its resistance to hydrolysis by BSH. Gly-MCA improved HFD-induced obesity and insulin resistance (11); however, the underlying mechanisms by which Gly-MCA alters the gut microbiota population and its impact on host metabolism remain largely undeter- mined.
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Farnesoid X receptor is essential for normal glucose homeostasis

Farnesoid X receptor is essential for normal glucose homeostasis

of PEPCK, PGC-1α, or G-6-Pase expression in response to CA feeding (Figure 6E). On a chow diet, they exhibited modestly elevated serum glucose in both fasted and fed conditions (Fig- ure 6F) without significant changes in insulin. However, they did not decrease serum glucose in response to dietary CA, suggesting that this effect of CA is mediated through the induction of SHP by FXR. Taken together, these results allow us to conclude that the previously identified pathways of bile acid feedback regula- tion by the FXR-SHP nuclear receptor cascade (4–6, 24) also tar- get glucose metabolism.
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Activation of the Farnesoid X-receptor in breast cancer cell lines results in cytotoxicity but not increased migration potential

Activation of the Farnesoid X-receptor in breast cancer cell lines results in cytotoxicity but not increased migration potential

The nuclear receptor FXR is classically associated with bile acid homeostasis in the body and its target genes impact on the metabolic and transporter-mediated clearance of both bile acids and their precursors [15]. However, FXR activation has also been reported to elicit a number of other phenotypes, including cell death. To confirm this phenotype in breast cancer cell lines, we examined the effect of the endogenous ligand CDCA and the more potent and selective artificial ligand GW4064 [31]. Four cell lines were chosen to represent different breast cancer phenotypes: normal (i.e. MCF-10A), receptor positive tumour (i.e. MCF-7) and triple negative tumours (i.e. MDA-MB-231 and MDA-MB-468). We confirmed that FXR is expressed in these cell lines, and for MCF-7 and MDA-MB-231 cells that the FXR- dependent signalling cascade is intact, with activation of SHP expression in response to FXR activation (supplemental figure S1).
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Farnesoid X receptor associates with β-catenin and inhibits its activity in hepatocellular carcinoma

Farnesoid X receptor associates with β-catenin and inhibits its activity in hepatocellular carcinoma

example, activated β-Catenin has been shown to co- activate Retinoic Acid Receptor (RAR) associated with RAR response elements in MCF7 breast cancer cells [24]. And activation of Vitamin D receptor (VDR) could repress Wnt/β-Catenin signaling and decrease 1α, 25(OH) 2 vitamin D3 induced tumorigenesis [25]. In the case of FXR interaction with β-Catenin, FXR appears to regulate β-Catenin activity but not affecting β-Catenin localization and protein stability since the knockdown of FXR does not affect the translocation of β-Catenin (Figure S2), and the total protein level of β-Catenin expression was not altered by either FXR activation by GW4064 or FXR depletion by FXR-siRNA in Huh7 cells. Activated β-Catenin forms a complex together with TCF4, and is recruited to the corresponding promoter region of Wnt target genes to elicit transcriptional activity [26]. We identified that FXR, a member of nuclear receptor (NR) family, directly interacted with β-Catenin in vitro and in vivo, to disrupt the formation of β-Catenin/TCF4 complex and subsequently the binding ability with corresponding promoter. Interestingly, FXR can bind with and inhibit the corresponding transcriptional activity of both wild type β-Catenin and two oncogenic β-Catenin hot spot mutants (S33A/S37A/T41A/S45A and ΔN90) (Figure S3). These findings suggested that β-Catenin is a pathway through which FXR affects tumorigenesis.
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Case Report Mammary carcinoma with osteoclast-like giant cells: a case report

Case Report Mammary carcinoma with osteoclast-like giant cells: a case report

eight cases; five ductal and three lobular phe- notypes. Three patients had nodal metastasis. In their cohort patients seemed to have a less favorable prognosis acknowledging the limited clinical follow up period [2]. Subsequently, addi- tional case reports followed [13-33]. The cases occurred over a wide age range 28-88 years [18]. Reported cases on non-metaplastic carci- noma associated osteoclast-like giant cells, showed that 34% of cases had lymph node involvement, and 86% of patients were free of disease on a mean follow up period of 2.4 years [9]. Bone -one case- and lung metastases -two cases- have been reported [9, 18]. The majority of the patients underwent modified radical ma- stectomy as the mainstay management option. Radiologically most tumors are solitary and well defined but rarely multiple [1]. Many of these tumors are readily diagnosed by fine needle aspiration. A task greatly facilitated by the pres- ence of large osteoclast-like giant cells in addi- tion to the neoplastic epithelial component. On cytological smears the osteoclast-like giant cells display branching cytoplasmic processes, voluminous cytoplasm, monomorphic oval nu- clei and small nucleoli. Haemosiderin-laden macrophages are seen in a considerable num- ber of the cases [25, 31, 32]. On gross exami- nation, the previously reported tumors as well as the current case reveal circumscribed mass that is dark brown or red-brown in color. The tumor size varied from 0.5 to 10 cm [2, 18]. The gross differential diagnoses are listed in Table 1. On microscopic examination, the osteoclast- like giant cells are often seen admixed with other histological subtypes of invasive breast carcinomas most commonly ductal, but also lobular, mucinous, cribriform, papillary, and metaplastic [20, 26]. The majority of the tumors are ER, PR positive, and Her2 negative. Tumors studied with proliferation labeling index Ki-67, confirms luminal phenotype especially luminal A subtype [9]. Receptor activator of nuclear- (RANK), RANK ligand (RANKL), and matrix me- talloproteinase 1 (MMP1) are absent or not overexpressed in the current case. This finding is in concordance with the reported favorable prognosis of this subtype. However, this finding is based on a single case, and would be pru- dent to validate it on a greater number of cases. The osteoclast-like giant cells are of mesenchy- mal origin and are histiocytically derived as evi- denced from immunohistochemical and ultra- structural data [9, 12-25]. It is postulated that
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Independent Activation of Hepatitis B Virus Biosynthesis by Retinoids, Peroxisome Proliferators, and Bile Acids

Independent Activation of Hepatitis B Virus Biosynthesis by Retinoids, Peroxisome Proliferators, and Bile Acids

sion of FXR ␣ , PPAR ␣ , LXR ␣ , and CAR did not greatly modulate RXR␣-mediated HBV biosynthesis (Fig. 3A and B, lanes 7, 8, 10, and 11), suggesting that in the absence of their ligands these nu- clear receptors did not affect viral transcription and replication (Fig. 3C). Interesting, overexpression of RAR ␣ inhibited RXR ␣ - mediated HBV biosynthesis (Fig. 3A and B, lane 6). This observa- tion strongly suggests that the RXR ␣ /RAR ␣ heterodimer does not activate HBV biosynthesis, and therefore it appears likely that RXR ␣ can directly activate HBV transcription and replication in the absence of any additional ligand-activated nuclear receptors. The mechanism(s) of inhibition of HBV biosynthesis by RAR ␣ and PXR is unclear (Fig. 3A and B, lanes 6 and 9). It is possible that these nuclear receptors might shift the cellular equilibrium from RXR␣ homodimers capable of activating HBV transcription to RXR ␣ /RAR ␣ or RXR ␣ /PXR heterodimers that are incapable of binding to the nucleocapsid promoter to activate HBV transcrip- tion. This equilibrium shift would reduce HBV biosynthesis, but then it is difficult to rationalize why LXR␣ and CAR would not affect viral RNA and DNA synthesis similarly. In the case of the RXR␣/RAR␣ heterodimer, it is likely that binding to the direct repeat 1 (DR1) sequence comprising two copies of the AGGTCA- related sequence separated by a single nucleotide within the HBV nucleocapsid promoter mediates corepressor recruitment and hence transcriptional repression (24, 30, 31). In contrast, RXR/ PXR does not bind to DR1 sequences (18, 33) but might sequester coactivators, such as peroxisome proliferator-activated receptor ␥ FIG 2 Effect of all-trans-retinoic acid and 9-cis-retinoic acid concentrations on HBV biosynthesis in the human embryonic kidney cell line 293T expressing RXR ␣ . Cells were transfected with the HBV DNA (4.1-kbp) construct alone (lane 1) or the HBV DNA (4.1-kbp) construct plus the RXR ␣ expression vector (lanes 2 to 14) as indicated. Cells were treated with various concentrations of all-trans-retinoic acid (0.05 to 10 ␮ M RA; lanes 3 to 8) and 9-cis-retinoic acid (0.05 to 10 ␮ M 9-cis-RA; lanes 9 to 14). (A) RNA (Northern) filter hybridization analysis of HBV transcripts. The glyceraldehyde-3-phosphate dehydrogenase (GAPDH) transcript was used as an internal control for RNA loading per lane. (B) Quantitative analysis of the HBV 3.5-kb RNA from two independent experiments. Trend lines were calculated using GraphPad Prism 5 software to determine the sigmoidal dose response (variable slope) curve plus 50% effective concentrations (EC 50 s).
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Microcantilever based Nanomechanical Studies of the Orphan Nuclear Receptor Pregnane X Receptor Ligand Interactions

Microcantilever based Nanomechanical Studies of the Orphan Nuclear Receptor Pregnane X Receptor Ligand Interactions

Human pregnane X receptor (PXR) is of vital importance in pharmaceutical and exogenous compound metabolism within the body. This provides strong motivation for investigating this orphan receptor’s activation by various pharma- ceuticals, xenobiotics, and endocrine disrupting chemicals (EDCs). A nanomechanical transducer is developed to study xenobiotic and EDC interactions with the bioreceptor PXR’s ligand binding domain (LBD). The combination of immo- bilized LBD PXR with a nanostructured microcantilever (MC) platform allows for the sensitive, label-free study of li- gand interaction with the receptor. PXR shows real-time, reversible responses when exposed to a specific pharmaceu- tical, EDCs, and xenobiotic ligands. Three EDCs binding interactions are tested, which include phthalic acid, nonyl- phenol, and bisphenol A, with PXR. PXR LBD was exposed to rifampicin, a potent PXR activator, with various injection and recovery times to study their interaction. A two protein array of PXR and estrogen receptor  (ER-) directly compares the nanomechanical responses of these receptors with rifampicin on a single platform.
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Cholesterol Metabolism and Its Regulation by Functional Foods

Cholesterol Metabolism and Its Regulation by Functional Foods

amembrane protein of the erythrocyte, which is an insulin inductor (INSIG). The INSIG protein produces a crossroad between the transcriptional and post transcriptional regulatory mechanisms that ensure cholesterol metabolism 10 . In presence of this molecule, the SREBP are retained in the erythrocyte; in its absence they are released by proteolysis that allows the activation of target genes that control lipid metabolism Molecularly it occurs as follows: after the translation of the mRNA, SREBP precursors are retained in the erythrocyte membrane through an association with the SCAP. Under low cholesterol conditions, the SCAP accompanies the SREBP precursors from the erythrocyte to the Golgi apparatus where two functionally differ proteases, site 1 of protease (S1P) and site 2 of protease (S2P), hydrolyzed sequentially the precursor protein releasing nuclear SREBP (nSREBP) in the cytoplasm In contrast, when cells have abundant cholesterol SCAP binds to INSING, stabilizing the protein and allowing the accumulation of a stable complex INSIG/SCAP/SREBP. In consequence, the content of SREBP and INSING decrease, serving as a reservoir for SREBP. When cells are lacking cholesterol, SCAP/SREBP of INSING dissociates and then it is degraded in proteasomes. The free SCAP/SREBP complex binds proteins from the rough endoplasmic reticulum and migrates to the Golgi apparatus where SREBP is processed into nSREBP. This activates the transactivation genes of the cholesterol biosynthetic enzymes and LDLR. At the same time, nSREBP activates genes for INSING, for this reason it relates to the carbohydrates metabolism 15,10
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Retinoid X Receptor Antagonists

Retinoid X Receptor Antagonists

Retinoid X receptor (RXR) antagonists are not only useful as chemical tools for biological research, but also are candidate drugs for treatment of various diseases, including diabetes and allergy, although no RXR antagonist has yet been approved for clinical use. In this review, we describe currently available RXR antagonists, their structural classification, and their evaluation, focusing on the latest research.

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