Research progress of the regulation of orphan nuclear receptors on chronic liver diseases / 生理学报

The development of chronic liver disease can be promoted by excessive fat accumulation, dysbiosis, viral infections and persistent inflammatory responses, which can lead to liver inflammation, fibrosis and carcinogenesis. An in-depth understanding of the etiology leading to chronic liver disease and the underlying mechanisms influencing its development can help identify potential therapeutic targets for targeted treatment. Orphan nuclear receptors (ONRs) are receptors that have no corresponding endogenous ligands to bind to them. The study of these ONRs and their biological properties has facilitated the development of synthetic ligands, which are important for investigating the effective targets for the treatment of a wide range of diseases. In recent years, it has been found that ONRs are essential for maintaining normal liver function and their dysfunction can affect a variety of liver diseases. ONRs can influence pathophysiological activities such as liver lipid metabolism, inflammatory response and cancer cell proliferation by regulating hormones/transcription factors and affecting the biological clock, oxidative stress, etc. This review focuses on the regulation of ONRs, mainly including retinoid related orphan nuclear receptors (RORs), pregnane X receptor (PXR), leukocyte cell derived chemotaxin 2 (LECT2), Nur77, and hepatocyte nuclear factor 4α (HNF4α), on the development of different types of chronic liver diseases in different ways, in order to provide useful references for the therapeutic strategies of chronic liver diseases based on the regulation of ONRs.

Expression of LXR-β in human gastric cancer tissue and the effect of GW3965 on the proliferation of gastric cancer cell line SGC-7901 / 中南大学学报(医学版)

OBJECTIVE@#To examine the expression of liver X receptor-β (LXR-β) in human gastric cancer tissue, and to explore the effect of GW3965, an agonist of LXRs, on proliferation of gastric cancer cell line SGC-7901.
@*METHODS@#The immunohistochemical assay was used to detect the expression of LXR-β, activating transcription factor 4 (ATF4) in gastric cancer tissues and the corresponding pericarcinoma tissues in 114 patients. Real-time quantitative PCR and Western blot were used to determine mRNA and protein levels of ATF4 and ATP-binding cassette 1 (ABCA1), one of the downstream target genes of LXRs, in SGC-7901 cells with or without GW3965 treatment. Cell counting kit-8 (CCK-8) assay was performed to detect cell proliferation. The expression of ATF4 was silenced by short hairpin RNA (shRNA).
@*RESULTS@#The expressions of LXR-β and ATF-4 were obviously down-regulated in the gastric cancer tissues than that in the corresponding pericarcinoma tissues (both P<0.05). Compared with the control cells, GW3965 treatment inhibited proliferation of SGC-7901 cells and up-regulated ATF4 and ABCA1 expressions (both P<0.05). Knockdown of ATF4 can reverse the antiproliferative effect of GW3965 on SGC-7901 cells.
@*CONCLUSION@#The expression of LXR-β is decreased in human gastric cancer tissues, and activation of LXRs by GW3965 could inhibit the proliferation of SGC-7901 cells via ATF4.

Small Heterodimer Partner and Innate Immune Regulation

The nuclear receptor superfamily consists of the steroid and non-steroid hormone receptors and the orphan nuclear receptors. Small heterodimer partner (SHP) is an orphan family nuclear receptor that plays an essential role in the regulation of glucose and cholesterol metabolism. Recent studies reported a previously unidentified role for SHP in the regulation of innate immunity and inflammation. The innate immune system has a critical function in the initial response against a variety of microbial and danger signals. Activation of the innate immune response results in the induction of inflammatory cytokines and chemokines to promote anti-microbial effects. An excessive or uncontrolled inflammatory response is potentially harmful to the host, and can cause tissue damage or pathological threat. Therefore, the innate immune response should be tightly regulated to enhance host defense while preventing unwanted immune pathologic responses. In this review, we discuss recent studies showing that SHP is involved in the negative regulation of toll-like receptor-induced and NLRP3 (NACHT, LRR and PYD domains-containing protein 3)-mediated inflammatory responses in innate immune cells. Understanding the function of SHP in innate immune cells will allow us to prevent or modulate acute and chronic inflammation processes in cases where dysregulated innate immune activation results in damage to normal tissues.

Natural modulators of liver X receptors / 中西医结合学报

Nuclear receptor transcription factors are ligand-activated proteins that control various biological events from cell growth and development to lipid metabolism, and energy and glucose homeostasis. Nuclear receptors are important drug targets for metabolic diseases. Liver X receptors (LXRs) are nuclear receptor transcription factors that play essential roles in regulation of cholesterol, triglyceride, fatty acid, and glucose homeostasis. LXR-deficient mice have shown the association of LXR-signaling pathway dysfunction with several human pathologies including atherosclerosis, hyperlipidemia, Alzheimer's disease and cancer. Thus, LXRs are promising pharmacological targets for these diseases. Synthetic LXR agonists may lower cholesterol, but increase triglyceride and induce fatty liver. The naturally occurring LXR ligands, with moderate activity, may serve as nutraceuticals for prevention or treatment of the disorders, while minimizing potential side effects. In this review, recent advances in natural LXR modulators are summarized including agonist, antagonist and the modulator of LXR pathway.

Effect of Shugan Jianpi Recipe on LXRα/FAS signaling pathway mediated hepatocyte fatty deposits in NAFLD rats / 中国中西医结合杂志

<p><b>OBJECTIVE</b>To explore the effect of Shugan Jianpi Recipe (SJR) on LXRα/FAS signaling pathway mediated hepatocyte fatty deposits in nonalcoholic fatty liver disease (NAFLD) rats.</p><p><b>METHODS</b>Totally 75 SPF grade male SD rats were randomly divided into 5 groups, i.e., the normal control group, the model group, the Shugan Recipe (SR) treatment groups, the Jianpi Recipe (JR) treatment group, and the SJR group. Except rats in the normal control group, the NAFLD rat model was duplicated using high fat diet (HFD). SR (Chaihu Shugan Powder) was administered to rats in the SR group. JR (Shenlin Baizhu Powder) was administered to rats in the JR group. SJR (Chaihu Shugan Powder plus Shenlin Baizhu Powder) was administered to rats in the SJR group. Changes of liver fat were analyzed using automatic biochemical analyzer. Liver cells were separated by low-speed centrifugation. Their activities and purities were identify using Typan blue and flow cytometry (FCM). Expression levels of LXRα and FAS mRNA in hepatocytes detected by Real-time quantitative PCR. Expression levels of LXRα and FAS protein were detected by Western blot.</p><p><b>RESULTS</b>(1) Pathological results showed in the model group, hepatocytes were swollen with nucleus locating at the cell edge after oil red O staining; unequal sized small vacuoles could be seen inside cytoplasm. Some small vacuoles merged big vacuoles. All these indi- cated a NAFLD rat model was successfully established by high fat diet. Pathological structural changes could be impaired to some degree in all medicated groups, especially in the SR group. (2) Compared with the normal control group, expression levels of LXRα and FAS genes and proteins obviously increased in the model group (P < 0.01). Compared with the model group, their expression levels were obviously down-regulated in the JR group and the SR group (P < 0.01, P < 0.05).</p><p><b>CONCLUSIONS</b>LXRα/FAS signaling pathway was an important signaling pathway for mediating lipid metabolism disorders of NAFLD rats. SJR could make hepatocyte fatty deposits tend to repair by adjusting the LXRα/FAS signaling pathway in NAFLD rats, which might be one of important mechanisms for SJR to prevent and cure NAFLD.</p>

Lentiviral-mediated RNA interference of LXRα gene in donor rats with fatty liver enhances liver graft function after transplantation / 南方医科大学学报

<p><b>OBJECTIVE</b>To investigate whether RNA interference (RNAi) of LXRα gene in donor rats with fatty liver improves liver graft function after transplantation.</p><p><b>METHODS</b>Fifty donor SD rats were fed a high-fat diet and 56% alcohol to induce macrovesicular steatosis exceeding 60% in the liver. The donor rats were injected via the portal veins with 7 × 10⁷ TU LXRα-RNAi-LV mixture (n=25) or negative control-LV (NC-LV) vector (n=25) 72 h before orthotopic liver transplantation. At 2, 24, and 72 h after the transplantation, the recipient rats were sacrificed to examine liver transaminases, liver graft histology, immunostaining (TUNEL), and protein and mRNA levels of LXRα.</p><p><b>RESULTS</b>Lentivirus-LXRα RNAi inhibited LXRα gene expression at both the mRNA and protein levels in the liver graft and reduced the expressions of SREBP-1c and CD36 as compared with the controls, resulting also in reduced fatty acid accumulation in the hepatocytes. The recipient rats receiving RNAi-treated grafts showed more obvious reduction in serum ALT, AST, IL-1β and TNF-α levels, and exhibited milder hepatic pathologies than the control rats after the transplantation. TUNEL assay demonstrated a significant reduction in cell apoptosis in LXRα-RNAi-LV-treated liver grafts, and the rats receiving treated liver grafts had a prolonged mean overall survival time.</p><p><b>CONCLUSION</b>LXRα-RNAi-LV treatment of the donor rats with fatty liver can significantly down-regulate LXRα gene expression in the liver graft and improve the graft function and recipient rat survival after liver transplantation.</p>

Effect of simvastatin on the expression of farnesoid X receptor in diabetic animal models of altered glucose homeostasis / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>Statin therapy has affected glucose homoeostasis of type 2 diabetes patients, which could be related with bile acids metabolism. Whether bile acid metabolism and the expression of farnesoid X receptor (FXR), liver X receptor-α (LXR-α) and sterol regulatory element-binding protein (Srebp)-1c is regulated by hyperglycemia, or whether simvastatin therapy led to higher glucose is related with down-regulated expression of FXR in diabetic rats remained unclear.</p><p><b>METHODS</b>Forty male Wistar rats were randomly divided into four groups: normal control rats, insulin resistance rats, diabetic model rats, and the late simvastatin induced diabetic rats. Normal control rats were fed with standard diet, others were fed with high-fat diet. Diabetic model rats were induced by a single intraperitoneal injection of streptozotocin (STZ). The late simvastatin induced diabetic rats started simvastatin administration after STZ induced diabetic model rats. Characteristics of fasting blood glucose (FPG), lipid files and total bile acids (TBAs) were measured and the oral glucose tolerance test (OGTT) was performed after overnight fasting at the eighth weekend. RNA and protein levels of FXR, LXR-α and Srebp-1c were tested by Western blotting and reverse transcription polymerase chain reaction (RT-PCR).</p><p><b>RESULTS</b>The insulin resistance rats showed higher glucose, lipid files and lower expression of FXR compared with normal control rats (P > 0.05). The diabetic model rats showed significantly higher glucose, lipid files, TBA and lower expression of FXR compared with insulin resistance rats (P < 0.05). The late simvastatin induced diabetic rats displayed higher glucose and TBA and lower expression of FXR compared with diabetic model rats (P < 0.05).</p><p><b>CONCLUSIONS</b>Changes in bile acid homeostasis, including the alterations of bile acid levels and bile acid receptors, are either a cause or a consequence of the metabolic disturbances observed during diabetic models. Statin therapy induced hyperglycemia may be related with FXR, SHP, LXR-α and Srebp-1 pathways.</p>

Effect of Bilirubin on Triglyceride Synthesis in Streptozotocin-Induced Diabetic Nephropathy

We aimed to elucidate the effect of bilirubin on dyslipidemia and nephropathy in a diabetes mellitus (DM) type I animal model. Sprague-Dawley rats were separated into control, DM, and bilirubin-treated DM (Bil) groups. The Bil group was injected intraperitoneally with 60 mg/kg bilirubin 3 times per week and hepatoma cells were cultured with bilirubin at a concentration of 0.3 mg/dL. The Bil group showed lower serum creatinine levels 5 weeks after diabetes onset. Bilirubin treatment also decreased the amount of mesangial matrix, lowered the expression of renal collagen IV and transforming growth factor (TGF)-beta1, and reduced the level of apoptosis in the kidney, compared to the DM group. These changes were accompanied by decreased tissue levels of hydrogen superoxide and NADPH oxidase subunit proteins. Bilirubin decreased serum total cholesterol, high-density lipoprotein cholesterol (HDL-C), free fatty acids, and triglycerides (TGs), as well as the TG content in the liver tissues. Bilirubin suppressed protein expression of LXRalpha, SREBP-1, SCD-1, and FAS, factors involved in TG synthesis that were elevated in the livers of DM rats and hepatoma cells under high-glucose conditions. In conclusion, bilirubin attenuates renal dysfunction and dyslipidemia in diabetes by suppressing LXRalpha and SREBP-1 expression and oxidative stress.

Effect of cell-penetrating peptide-conjugated estrogen-related receptor beta on the development of mouse embryos cultured in vitro / 대한생식의학회지

OBJECTIVE: Estrogen related receptor beta (Esrrb) is a member of the orphan nuclear receptors and may regulate the expression of pluripotency-related genes, such as Oct4 and Nanog. Therefore, in the present study, we have developed a method for delivering exogenous ESRRB recombinant protein into embryos by using cell-penetrating peptide (CPP) conjugation and have analyzed their effect on embryonic development. METHODS: Mouse oocytes and embryos were obtained from superovulated mice. The expression of Oct4 mRNA and the cell number of inner cell mass (ICM) in the in vitro-derived and in vivo-derived blastocysts were first analyzed by real time-reverse transcription-polymerase chain reaction and differential staining. Then 8-cell embryos were cultured in KSOM media with or without 2 microg/mL CPP-ESRRB protein for 24 to 48 hours, followed by checking their integration into embryos during in vitro culture by Western blot and immunocytochemistry. RESULTS: Expression of Oct4 and the cell number of ICM were lower in the in vitro-derived blastocysts than in the in vivo-derived ones (p<0.05). In the blastocysts derived from the CPP-ESRRB-treated group, expression of Oct4 was greater than in the non-treated groups (p<0.05). Although no difference in embryonic development was observed between the treated and non-treated groups, the cell number of ICM was greater in the CPP-ESRRB-treated group. CONCLUSION: Treatment of CPP-ESRRB during cultivation could increase embryos' expression of Oct4 and the formation rate of the ICM in the blastocyst. Additionally, an exogenous delivery system of CPP-conjugated protein would be a useful tool for improving embryo culture systems.

Cilostazol inhibits insulin-stimulated expression of sterol regulatory binding protein-1c via inhibition of LXR and Sp1

Hepatic steatosis is common in obese individuals with hyperinsulinemia and is an important hepatic manifestation of metabolic syndrome. Sterol regulatory binding protein-1c (SREBP-1c) is a master regulator of lipogenic gene expression in the liver. Hyperinsulinemia induces transcription of SREBP-1c via activation of liver X receptor (LXR) and specificity protein 1 (Sp1). Cilostazol is an antiplatelet agent that prevents atherosclerosis and decreases serum triglyceride levels. However, little is known about the effects of cilostazol on hepatic lipogenesis. Here, we examined the role of cilostazol in the regulation of SREBP-1c transcription in the liver. The effects of cilostazol on the expression of SREBP-1c and its target genes in response to insulin or an LXR agonist (T0901317) were examined using real-time RT-PCR and western blot analysis on cultured hepatocytes. To investigate the effect of cilostazol on SREBP-1c at the transcriptional level, transient transfection reporter assays and electrophoretic mobility shift assays (EMSAs) were performed. Cilostazol inhibited insulin-induced and LXR-agonist-induced expression of SREBP-1c and its downstream targets, acetyl-CoA carboxylase and fatty acid synthase, in cultured hepatocytes. Cilostazol also inhibited activation of the SREBP-1c promoter by insulin, T0901317 and Sp1 in a luciferase reporter assay. EMSA analysis showed that cilostazol inhibits SREBP-1c expression by repressing the binding of LXR and Sp1 to the promoter region. These results indicate that cilostazol inhibits insulin-induced hepatic SREBP-1c expression via the inhibition of LXR and Sp1 activity and that cilostazol is a negative regulator of hepatic lipogenesis.

An evaluation of the mechanism of ABCA7 on cellular lipid release in ABCA7-HEC293 cell / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>ABCA7 is a member of the ABCA subfamily that shows a high degree of homology to ABCA1 and, like ABCA1, mediates cellular cholesterol and phospholipid release by apolipoproteins when transfected in vitro. However, expression of ABCA7 has been shown to be downregulated by increased cellular cholesterol while ABCA1 was upregulated.</p><p><b>METHODS</b>The underlying mechanism for this effect was examined in ABCA1 or ABCA7-transfected HEC293. Lipid content in the medium and cells was determined by enzymatic assays. Gene expression was quantitated by real time PCR, and protein content was determined by Western blotting.</p><p><b>RESULTS</b>While ABCA7 mRNA was decreased by 25-hydroxycholesterol treatment, ABCA1 was apparently increased. Treatment with the synthetic LXR agonist T0901317 (T09) upregulated ABCA1 expression and apoAI-mediated cellular lipid release in ABCA1-transfected HEC293 cells, but ABCA7 expression and cellular lipid release in ABCA7-transfected HEC293 cells showed no obvious changes.</p><p><b>CONCLUSION</b>The ABCA7 gene is regulated by sterol in a direction opposite to that of ABCA1.</p>

Effect of an Ilex asprella root decoction on the related genes of lipid metabolism from chronic stress and hyperlipidemic fatty liver in rats / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>The gradually increasing changes in a human hyperlipidemic diet along with chronic stress might play an important role in the increased numbers of fatty liver. This study investigated the effects of Ilex asprella root decoction on related genes of lipid metabolism in chronic stress in hyperlipidemic fatty liver in rats.</p><p><b>METHODS</b>Forty-eight male Wistar rats were randomly divided into four groups: normal control group, model control group, simvastatin group, and Ilex asprella root group. To establish chronic stress and hyperlipidemic fatty liver models in rats, the levels of serum lipids, glucose, liver index, insulin (INS), insulin resistant (IR) index, adiponectin, superoxide dismutase (SOD), glutathione peroxidase (GSH-pX), glutathione (GSH), liver X receptor (LXR), and sterol responsive element binding protein (SREBP)-1c in rats were measured.</p><p><b>RESULTS</b>When compared to the normal control group, the levels of serum lipids, glucose, liver index, INS, IR index, and GSH in the model control group significantly increased (P < 0.01). The protein levels of LXRα and SREBP-1c increased (P < 0.05), and the serum adiponectin and the SOD and GSH-pX decreased significantly (P < 0.01). When compared to the model control group, the levels of serum lipids, glucose, liver index, INS, IR index, SOD, and GSH-pX in the simvastatin group and Ilex asprella root group increased in varying degrees (P < 0.01 or 0.05); the serum adiponectin and GSH decreased (P < 0.05), while the protein levels of LXRα and SREBP-1c decreased in varying degrees (P < 0.01 or 0.05). When compared to the simvastatin group, the IR index and protein levels of LXRα in the Ilex asprella root group decreased (P < 0.05), and the serum adiponectin and SOD increased (P < 0.05).</p><p><b>CONCLUSION</b>The Ilex asprella root decoction has some protective effects on regulating the related genes of lipid metabolism caused by chronic stress and hyperlipidemic fatty liver in rats.</p>

Beneficial effects of liver X receptor agonist on adipose-derived mesenchymal stem cells transplantation in mice with myocardial infarction / 中华心血管病杂志

<p><b>OBJECTIVE</b>To investigate the effects of liver X receptor (LXR) agonist on adipose-derived mesenchymal stem cells (AD-MSCs) implantation into infarcted hearts of mice.</p><p><b>METHOD</b>AD-MSC(Fluc+) which stably expressed firefly luciferase (Fluc) were isolated from β-actin-Fluc transgenic mice and characterized by flow cytometry. Male FVB mice were randomly allocated into the following four groups (n = 10 each): (1) sham group; (2) MI + PBS group; (3) MI + AD-MSC(Fluc+) group; (4) MI + AD-MSC(Fluc+) + LXR agonist (T0901317) group. AD-MSC(Fluc+) or PBS were injected intramyocardial into peri-infarcted region of mice heart after permanent left anterior descending (LAD) artery ligation. Bioluminescence imaging (BLI) was performed for quantification of injected cells retention and survival. Cardiac function was evaluated by echocardiography.</p><p><b>RESULTS</b>The AD-MSC(Fluc+) were positive for CD44 and CD90 by flow cytometry. BLI evidenced the firefly luciferase expression of AD-MSC(Fluc+) which was positively correlated with cell numbers (r(2) = 0.98). The results of BLI in vivo revealed that LXR agonist could improve the survival of AD-MSC(Fluc+) at day 7, 14 and 21 after transplantation compared with AD-MSC(Fluc+) alone group. Cardiac function was further improved in combination therapy group compared with AD-MSC(Fluc+) alone group (P < 0.05).</p><p><b>CONCLUSIONS</b>LXR agonist T0901317 can improve the retention and survival of intramyocardial injected AD-MSC(Fluc+) post-MI, and the combination therapy of T0901317 and AD-MSC(Fluc+) has a synergetic effect on improving cardiac function in this model.</p>

Effect of liver X receptor agonist T0901317 on endothelin-1 induced murine HL-1 cardiomyocytes hypertrophy / 中华心血管病杂志

<p><b>OBJECTIVE</b>To investigate the role of liver X receptors (LXRs) on endothelin-1 (ET-1) induced murine HL-1 cardiomyocytes hypertrophy.</p><p><b>METHODS</b>Cultured murine HL-1 cardiomyocytes were divided into four experiment groups: (1) CONTROL GROUP:treated with DMSO; (2) T0901317 group:treated with LXRs agonist T0901317 (1 µmol/L); (3) ET-1 group:treated with ET-1 (1 nmol/L); (4) T0901317 + ET-1 group:treated with T0901317 (1 µmol/L) for 8 hours, then treated with ET-1 (1 nmol/L). Twenty-four hours later, immunofluorescent staining was performed on HL-1 cells, the surface area of HL-1 cells was analyzed with NIH Image J software, and the synthetic rate of protein in HL-1 cells was detected by (3)H-leucine incorporation. The mRNA level of atrial natriuretic peptide (ANP) and β-myosin heavy chain (β-MyHC) was measured by quantitative realtime PCR. The effect of T0901317 on mRNA expression of ANP was also detected after LXRs gene silencing.</p><p><b>RESULTS</b>The surface area of HL-1 cells, mRNA expression of ANP and β-MyHC, and (3)H-leucine incorporation in ET-1 group were 2.00 ± 0.29, 1.98 ± 0.47, 2.13 ± 0.39 and 1.79 ± 0.17, respectively, which were significantly higher than those of control group (1.00 ± 0.26, 1.00 ± 0.21, 1.00 ± 0.31 and 1.00 ± 0.03, respectively, all P < 0.05). Compared with ET-1 group, the surface area of HL-1 cells, mRNA expression of ANP and β-MyHC, and (3)H-leucine incorporation were significantly decreased in T0901317 + ET-1 group (1.24 ± 0.25, 1.19 ± 0.21, 1.48 ± 0.27 and 1.15 ± 0.11, respectively, all P < 0.05). After inhibition of LXRα/β expression in HL-1 cardiomyocytes using the specific siRNAs, the mRNA expression of ANP in T0901317 + ET-1 group was 1.78 ± 0.05, which was similar as that in ET-1 group (1.94 ± 0.17, P > 0.05).</p><p><b>CONCLUSION</b>T0901317, an agonist of LXRs, could inhibit ET-1 induced cardiac hypertrophy in vitro, and LXR ligand-mediated inhibition on ANP mRNA expression by T0901317 is receptor dependent.</p>

Research progress of liver X receptor agonists / 药学学报

Liver X receptor (LXR), a member of the superfamily of nuclear receptors, plays an important role in the activation of transcription factors involved in cholesterol metabolism, glucose homeostasis inflammation and lipogenesis. It is shown that LXR agnoists have the potentiality to be used as drugs for the prevention and treatment of atherosclerosis, which is its best investigated therapeutic indication. There are many compounds being studied in preclinical evaluation and biological assay. This paper will review briefly the LXR agonists in recent years.

Rapamycin pre-treatment abrogates Tumour Necrosis Factor-alpha down-regulatory effects on LXR-alpha and PXR mRNA expression via inhibition of c-Jun N-terminal kinase 1 activation in HepG2 cells

The Liver X Receptor (LXR) and Pregnane X Receptor (PXR) are members of the nuclear receptor superfamily. Previously, they have been classified as important regulators of lipid homeostasis. However, recent studies have shown that they may be implicated in anti-inflammatory responses as well. This study shows that Tumour Necrosis Factor-alpha (TNF-alpha) treatment reduces both LXR-alpha and PXR mRNA expression. However, pre-treatment with rapamycin, an mTOR inhibitor, followed by TNF-alpha stimulation, significantly induces LXR-alpha and PXR mRNA expression to ~17- and ~2-fold, respectively. This suggests that mTORC1, a multi-molecular complex of which mTOR is a member, may act as a negative regulator that inhibits the induction of LXR-alpha and PXR as anti-inflammatory genes. It is also shown here that inhibition of JNK1 via the mTOR/Akt pathway coincides with the up-regulation of LXR-alpha and PXR mRNA, after TNF-alpha treatment. Together, these observations suggest that JNK1 possibly act downstream of mTORC1 as an LXR-alpha and PXR inhibitor. From the results gleaned in this study, rapamycin (and its analogues) may be used to reduce acute inflammation by promoting the induction of LXR-alpha and PXR as anti-inflammatory genes.

Relationship of NOR-1 with the regulation of inflammation via liver X receptor alpha in Kupffer cells / 中华肝脏病杂志

<p><b>OBJECTIVE</b>To investigate the relationship of NOR-1 with the inhibition of inflammatory reaction in mice Kupffer cells (KCs) induced by lipopolysaccharide (LPS) via liver X receptor alpha (LXR alpha).</p><p><b>METHODS</b>KCs from male KM mice were isolated by density gradient centrifugation, incubated and then randomly assigned to three groups: control group, LPS treated group and LPS+T0901317 treated group.</p><p><b>RESULTS</b>The mRNA and protein expressions of LXR alpha and NOR-1 in each group were determined by RT-PCR, immunofluorescent assay and western blot, respectively. The densities of TNF alpha and IL-10 in supernatants were evaluated by enzyme linked immunosorbent assay (ELISA). The mRNA and protein expression levels of LXR alpha in LPS + T0901317 group were the highest as compared to the other two groups (0.748+/-0.072 and 1.217+/-0.133 respectively), The mRNA and protein expression levels of NOR-1 in LPS+ T0901317 group were the highest as compared to the other two groups (2.726+/-0.065 and 0.842+/-0.058 respectively). The densities of supernatant TNF alpha in LPS group and IL-10 in LPS+T0901317 group were the highest [(450.89+/-78.52) ng/L and (537.41+/-36.41) ng/L respectively].</p><p><b>CONCLUSIONS</b>Promoting the expression of LXR alpha in KCs can elevate the NOR-1 expression and then inhibit inflammatory reaction.</p>

Liver X receptor agonist T0901317 inhibits TGF-β1-induced α-SMA expression in normal human lung fibroblasts / 南方医科大学学报

<p><b>OBJECTIVE</b>To investigate the effect of liver X receptor agonist T0901317 on transforming growth factor-β1 (TGF-β1)-induced expression of α-smooth muscle actin (α-SMA) in normal human lung fibroblasts.</p><p><b>METHODS</b>Primary normal human lung fibroblast isolated from the lung specimens of lung cancer patients by explant culture technique were identified with immunostaining for vimentin and keratin. The cells in passages 4 to 10 were treated with T0901317 and/or TGF-β1, and RT-PCR, Western blotting and immunofluorescence assay were used to detect α-SMA expression in the fibroblasts.</p><p><b>RESULTS</b>Lung fibroblast expressed vimentin but not keratin. The results of RT-PCR, Western blotting and immunofluorescence assay all showed that normal human lung fibroblasts constitutively expressed α-SMA under baseline condition, and TGF-β1 at 5 ng/ml induced a significant upregulation of α-SMA both at the mRNA and protein levels. Liver X receptor agonist T0901317 (5 µg/ml) significantly inhibited TGF-β1-induced upregulation of α-SMA expression.</p><p><b>CONCLUSION</b>Liver X receptor agonist T0901317 can inhibit the upregulation of α-SMA in normal human lung fibroblasts induced by TGF-β1, suggesting the potential value of liver X receptor agonist in the treatment of lung fibrosis.</p>

Effect of Thyroid Hormone to the Expression of ATP-binding Cassette Transporter ABCG5 / 대한갑상선학회지

BACKGROUND AND OBJECTIVES: Excretion of bile acid and free cholesterol of bile was important to maintain cholesterol homeostasis. ATP-binding cassette transporter G5 (ABCG5) and G8 (ABCG8) promoted biliary cholesterol excretion. In previous study, hepatic secretion of cholesterol and ABCG5/G8 expression are strongly stimulated in hypophysectomized rats during treatment with thyroid hormone. In this study, we aimed to evaluate the effect of thyroid hormone to expression of ABCG5 and G8 in mouse liver. MATERIALS AND METHODS: We administered thyroid hormone (T3) to C57BL/6 mice and then RNA and protein was isolated from liver. We isolated primary hepatocyte and administered T3 to evaluate in vitro effect. HepG2 cells were cotransfected with either a control plasmid or expression plasmids for human thyroid hormone receptor (hTR)beta/human retinoid X receptor (hRXR)alpha or human liver X receptor (hLXR)alpha in combination with reporter plasmids TK-LXRE3-LUC with or without T3. RESULTS: Serum total cholesterol was decreased after 5 days of T3 treatment. Expression of ABCG5/8 mRNA and ABCG5 protein was increased after T3 treatment. In primary hepatocytes, T3 also increased ABCG5/8 mRNA expression. LXRalpha mRNA was not increased by T3. However, when we cotransfected liver X receptor response element (LXRE) construct and TRbeta/RXRalpha with T3, the activity of LXRE containing construct was markedly increased. CONCLUSION: We confirmed that thyroid hormone increased expression of ABCG5/8. This result suggested that thyroid hormone played an important role in decreasing serum cholesterol through bile excretion.

Effect of hepatitis B virus X protein on expression of lipid metabolism-related genes in HepG2 cells / 中华肝脏病杂志

<p><b>OBJECTIVE</b>To investigate the effect of Hepatitis B Virus X Protein (HBx) on the expression of lipid metabolism-related genes and its role in pathogenesis of hepatocyte fatty degeneration.</p><p><b>METHODS</b>Hepatitis B Virus X gene eukaryon expression vector pIRES2-eGFP-HBx was transfected into HepG2 cells to establish HepG2/HBx cell model for HBx expression. HepG2 cells transfected with pIRES2-eGFP (HepG2/pIRES2 cell) and non-transfected were used as controls. At 24, 48 and 72 hours after transfection, the expression of green fluorescent protein (GFP) was observed by fluorescence microscope and the triglyceride(TG) content was detected. RT-PCR and Western blot were applied to detect the levels of sterol regulatory element binding protein-1 (SREBP-1), liver x receptor alpha (LXRalpha) mRNA and the levels of HBx, LXRalpha and fatty acid synthase (FAS) protein. At 24, 48 and 72 hours after transfection, the expression of GFP was found in HepG2/HBx and HepG2/pIRES2 cells, and increased gradually. The expression of HBx was detected only in HepG2/HBx cells, and was increased with time after transfection (F = 32.21, P less than 0.01). These suggested successful obtaining of HepG2-HBx cell model for HBx expression.</p><p><b>RESULTS</b>At 24h, 48h and 72h after transfection, the expression levels of LXRalpha mRNA (0.386+/-0.055, 0.505+/-0.071, 0.649+/-0.058 ) and SREBP-1 mRNA (0.395+/-0.055, 0.548+/-0.047, 0.795+/-0.058), as well as the levels of LXRalpha protein(0.178+/-0.036, 0.263+/-0.047, 0.347+/-0.058) and FAS protein(0.436+/-0.055, 0.608+/-0.053, 0.827+/-0.046) in HepG2-HBx group were dramatically higher than those in the controls at the same time points (all P less than 0.05/0.01), and were gradually increased with time (all P less than 0.05/0.01). A positive correlationship was observed between HBX protein level and the LXRalpha, SREbP-1 mRNA and LXRalpha, FAS protein levels. The difference of TG content between HepG2/HBx group and control groups was not statistically significant (P more than 0.05).</p><p><b>CONCLUSIONS</b>HBx-LXRalpha-SREBP-1/FAS pathway suggested regulating transcription and expression of lipid metabolism-related genes, which might be one of the important molecular mechanism causing hepatocyte fatty degeneration.</p>