Animals ; Cardiovascular Diseases ; Humans ; Liver X Receptors ; Orphan Nuclear Receptors

PURPOSE: All-trans retinoic acid (ATRA) modulates immune responses by affecting T cells. Several studies have revealed that allergic inflammation of the lower airways is negatively associated with the vitamin A concentration. However, the role of ATRA in allergic inflammation of the upper airways is unclear. We investigated the effects of ATRA in an allergic rhinitis mouse model. METHODS: BALB/c mice except control groups (CON group) were sensitized with and challenged intra-nasally with Dermatophagoides farina (AR group). The ATRA groups were administered ATRA intraperitoneally. The steroid groups were administered steroid intranasally (ST group). Allergic symptoms and the average eosinophil number were counted. Cytokines and transcription factors were measured by Real-Time PCR and Western blotting. Der f-specific immunoglobulin E (IgE) was measured. Flow cytometry results of CD4+CD25+Foxp3+ T cells were analyzed. RESULTS: The symptom scores were lower in the ATRA group than in the AR group and higher than in the CON group. The levels of IgE were lower in the ATRA group than in the AR group and higher than in the CON and ST groups. The levels of Foxp3, TGF-beta, and IL-10 mRNA, as well as the percentage of CD4+CD25+Foxp3+ T cells, were higher in the ATRA group than in theAR group. In the ATRA group the levels of IFN-gamma mRNA were higher, and the levels of GATA-3 and IL-4 mRNA, and ROR-gammat were lower. In Western blotting analyses, the expression patterns of all factors, except Foxp3, showed similar to those of mRNA expression. CONCLUSIONS: ATRA has anti-allergic effects in an allergic rhinitis model, and its underlying mechanisms mainly include the induction of regulatory T cells and the inhibition of Th2 responses.
Animals ; Blotting, Western ; Cytokines ; Eosinophils ; Flow Cytometry ; Immunoglobulin E ; Immunoglobulins ; Inflammation ; Interleukin-10 ; Interleukin-4 ; Mice* ; Nuclear Receptor Subfamily 1, Group F, Member 3 ; Pyroglyphidae ; Real-Time Polymerase Chain Reaction ; Rhinitis* ; RNA, Messenger ; T-Lymphocytes ; T-Lymphocytes, Regulatory ; Th17 Cells ; Th2 Cells ; Transcription Factors ; Transforming Growth Factor beta ; Tretinoin* ; Vitamin A

Liver X receptors (LXRs) are members of the nuclear receptor superfamily and are activated by oxysterols and intermediates in the cholesterol synthetic pathway. The pivotal role of LXRs in the metabolic conversion of cholesterol to bile acids has been well established. Furthermore, insulin induces LXRa in hepatocytes, resulting in the suppression of key enzymes in gluconeogenesis, including phosphoenolpyruvate carboxykinase, glucose-6-phosphatase, and fructose-1, 6-bisphosphatase (FBPase). LXRs also play an important role in fatty acid metabolism by activating the sterol regulatory element-bing protein 1c gene (SREBP1c). This articles reviews the molecular mechanisms by which LXRs act to influence the lipid and carbohydrate metabolism.
Animals ; Carbohydrate Metabolism ; Humans ; Lipid Metabolism ; Liver X Receptors ; Orphan Nuclear Receptors ; physiology

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.
Humans ; Orphan Nuclear Receptors/metabolism* ; Receptors, Steroid/physiology* ; Ligands ; Liver ; Liver Diseases ; Intercellular Signaling Peptides and Proteins

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.
Animals ; Biological Products ; pharmacology ; Humans ; Liver ; metabolism ; physiopathology ; Liver X Receptors ; Orphan Nuclear Receptors ; drug effects ; physiology

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.
Chemokines ; Child ; Child, Orphaned ; Cholesterol ; Cytokines ; Glucose ; Humans ; Immune System ; Immunity, Innate ; Inflammasomes ; Inflammation ; Metabolism ; Orphan Nuclear Receptors ; Social Control, Formal ; Toll-Like Receptors

OBJECTIVETo explore liver X receptor alpha (LXR alpha) gene changes and their significance in nonalcoholic fatty liver disease (NAFLD) in rats.

METHODSA rat model of nonalcoholic fatty liver disease was produced with a fatty diet regime (feeding group, FG). Rats fed with normal diet served as controls (CG). The mRNA and protein expressions of LXR alpha in liver tissues were detected by reverse transcription and polymerase chain reaction (RT-PCR) and Western blot.

RESULTSThe concentration of free fatty acid (FFA) in the sera of GF rats started to increase to 0.33 mmol/L after 4 weeks of fat diet feeding, while the FFA of the CG was just 0.24+/-0.03 mmol/L, and the difference was significant (P<0.05). The concentration of ALT and AST in sera of the FG rats started to increase to 75.8 U/L and 138.9 U/L at the 8th week, much higher than those of the CG (P<0.01), and at the 12th week they increased further (P<0.01). Meanwhile, the mRNA and protein expressions of LXR alpha at the 2nd week was significantly increased to 0.62 (P>0.01) and its peak was reached at the 12th week (P<0.01). There was a significant positive correlation between the expression of LXR alpha and the degree of NAFLD.

CONCLUSIONThe changes of LXR alpha gene are closely related to the development of nonalcoholic fatty liver disease.

Animals ; Fatty Liver ; etiology ; metabolism ; pathology ; Gene Expression ; Liver ; metabolism ; pathology ; Liver X Receptors ; Male ; Orphan Nuclear Receptors ; genetics ; metabolism ; Rats ; Rats, Wistar

OBJECTIVETo explore the effects of the simultaneous activation of liver X receptor (LXR) and peroxisome proliferator-activated receptor alpha (PPARalpha) on bile acid biosynthesis in rats.

METHODSTotally 36 male SD rats were divided into three groups with 12 rats in each group: control group, high cholesterol (HC) group, and high cholesterol + fenofibrate (HC + FENO) group. Total bile acids (serum bile acids plus fecal bile acids) level was assayed. The levels of mRNA for peroxisomal palmitoyl-CoA oxidase (Acox1), LXR, cholesterol 7alpha-hydroxylase (CYP7A1), D-bifunctional protein (DBP), trihydroxycoprostanoyl-CoA oxidase (Acox2), sterol 12alpha-hydroxylase (CYP8B1), and sterol 27-hydroxylase (CYP27A1) in liver were detected by RT-PCR.

RESULTSTotal bile acid level was significantly higher in HC + FENO group than in HC group (P < 0.01), and both were significantly higher than that in control group (P < 0.01). Compared with HC group, the mRNA expression of Acox1 and DBP was significantly higher in HC + FENO group (P < 0.01), but no statistical differences was found between HC group and control group. The mRNA levels of LXR and CYP7A1 in HC + FENO group and HC group were not significantly different but were both significantly higher than that in control group (P < 0.01, P < 0.05). No changes were observed in Acox2, CYPSB1, and CYP27A1 mRNA levels among these three groups.

CONCLUSIONSimultaneous activation of LXR and PPARalpha can increase of CYP7A1 and DBP mRNA exDression and thus accelerates the biosynthesis of bile acid.

Animals ; Bile Acids and Salts ; biosynthesis ; Cholesterol ; pharmacology ; Fenofibrate ; pharmacology ; Hypolipidemic Agents ; pharmacology ; Liver ; drug effects ; enzymology ; Liver X Receptors ; Male ; Orphan Nuclear Receptors ; agonists ; PPAR alpha ; agonists ; Rats

AIMTo investigate the roles of liver X receptors (LXR) in the lipid composition and gene expression regulation in the murine caput epididymidis. LXR are nuclear receptors for oxysterols, molecules derived from cholesterol metabolism that are present in mammals as two isoforms: LXRalpha, which is more specifically expressed in lipid-metabolising tissues, such as liver, adipose and steroidogenic tissues, and macrophages, whereas LXRbeta is ubiquitous. Their importance in reproductive physiology has been sustained by the fact that male mice in which the function of both LXR has been disrupted have fertility disturbances starting at the age of 5 months, leading to complete sterility by the age of 9 months. These defects are associated with epididymal epithelial degeneration in caput segments one and two, and with a sperm midpiece fragility, leading to the presence of isolated sperm heads and flagella when luminal contents are recovered from the cauda epididymidis.

METHODSThe lipid composition of the caput epididymidis of wild-type and LXR-deficient mice was assessed using oil red O staining on tissue cryosections and lipid extraction followed by high performance liquid chromatography or gas chromatography. Gene expression was checked by quantitative real time polymerase chain reaction.

RESULTSUsing LXR-deficient mice, we showed an alteration of the lipid composition of the caput epididymidis as well as a significantly decreased expression of the genes encoding SREBP1c, SCD1 and SCD2, involved in fatty acid metabolism.

CONCLUSIONAltogether, these results show that LXR are important regulators of epididymal function, and play a critical role in the lipid maturation processes occurring during sperm epididymal maturation.

Animals ; DNA Primers ; DNA-Binding Proteins ; deficiency ; genetics ; physiology ; Epididymis ; cytology ; physiology ; Epithelial Cells ; physiology ; Fatty Acids ; metabolism ; Homeostasis ; Lipids ; physiology ; Liver X Receptors ; Male ; Mice ; Mice, Knockout ; Orphan Nuclear Receptors ; Polymerase Chain Reaction ; Receptors, Cytoplasmic and Nuclear ; deficiency ; genetics ; physiology

OBJECTIVETo clone and identify the proteins involved in regulating the transcription of hTERT and study the role of genes in both hTERT transcription and telomerase activity.

METHODSThe full cDNA of COUP-TFII was cloned from HeLa cDNA library by hTERT promoter-based yeast one-hybrid assay and then in-frame inserted into His-tag fusion expression vector pEK318. The His-tag COUP-TFII fusion proteins were purified by Ni-NTA chromatography. The interaction of COUP-TFII with hTERT promoter in vitro was identified by electrophoretic mobility shift assay and Footprint. The role of COUP-TFII in both hTERT transcription and telomerase activity were probed through Luciferase reporter assay, Northern blot, and TRAP-PCR ELISA.

RESULTSCOUP-TFII could firmly bind to the downstream E-box and the other two binding sites in hTERT promoter. Luciferase reporter assay indicated COUP-TFII could suppress hTERT promoter activity and stable introduction of COUP-TFII into HeLa cells also decreased both endogenous hTERT transcription and telomerase activity.

CONCLUSIONThe human COUP-TFII can firmly bind to hTERT promoter, and inhibit telomerase activity through decreasing hTERT transcription. It will greatly facilitate understanding of telomerase regulation in normal and cancer cells.

COUP Transcription Factor II ; COUP Transcription Factors ; Cloning, Molecular ; DNA, Complementary ; genetics ; DNA-Binding Proteins ; genetics ; pharmacology ; E-Box Elements ; genetics ; HeLa Cells ; Humans ; Promoter Regions, Genetic ; RNA, Messenger ; biosynthesis ; genetics ; Receptors, Steroid ; genetics ; Telomerase ; biosynthesis ; genetics ; metabolism ; Transcription Factors ; genetics ; pharmacology ; Transcription, Genetic ; Yeasts ; genetics