Ursolic Acid, a Novel Liver X Receptor α (LXRα) Antagonist Inhibiting Ligand-Induced Nonalcoholic Fatty Liver and Drug-Induced Lipogenesis.

Nonalcoholic fatty liver disease (NAFLD) is a very common liver disease, and its incidence has significantly increased worldwide. The liver X receptor α (LXRα) is a multifunctional nuclear receptor that controls lipid homeostasis. Inhibition of LXRα transactivation may be beneficial for NAFLD and hyperlipidemia treatment. Ursolic acid (UA) is a plant triterpenoid with many beneficial effects; however, the mechanism of its action on LXRα remains elusive. We evaluated the effects of UA on T0901317 (T090)-induced LXRα activation and steatosis. UA significantly decreased the LXR response element and sterol regulatory element-binding protein-1c ( SREBP-1c) gene promoter activities, mRNA, protein expression of LXRα target genes, and hepatic cellular lipid content in a T090-induced mouse model. A molecular docking study indicated that UA bound competitively with T090 at the LXRα ligand binding domain. UA stimulated AMP-activated protein kinase (AMPK) phosphorylation in hepatic cells and increased corepressor, small heterodimer partner-interacting leucine zipper protein (SMILE) but decreased coactivator, steroid receptor coactivator-1 (SRC-1) recruitment to the SREBP-1c promoter region. In contrast, UA induced SRC-1 binding but decreased SMILE binding to reverse cholesterol transport-related gene promoters in intestinal cells, increasing lipid excretion from intestinal cells. Additionally, UA reduced valproate-induced LXRα mediated and rifampin-induced pregnane X receptor mediated lipogenesis, offering potential treatments for drug-induced hepatic steatosis. Thus, UA displays liver specificity and can be selectively repressed while RCT stimulation by LXRα is preserved and enhanced. This is a novel therapeutic option to treat NAFLD and may be helpful in developing LXR agonists to prevent atherosclerosis.

Modulation of pregnane X receptor (PXR) and constitutive androstane receptor (CAR) activation by ursolic acid (UA) attenuates rifampin-isoniazid cytotoxicity.

BACKGROUND: Interactions between transcriptional inducers of cytochrome P450 (CYP450) enzymes and therapeutic drugs may be prevented by antagonizing the activation of a nuclear receptor (NR), pregnane X receptor (PXR, NR1I2), thus improving therapeutic efficacy. PURPOSE: In the present study, we aim to identify that ursolic acid (UA), a widely distributed pentacyclic triterpene, may act as an effective antagonist of PXR and its sister NR receptor, constitutive androstane receptor (CAR, NR1I3). METHODS: The hepatocellular carcinoma cell line, HepG2, was used to evaluate the promoter activity of PXR and CAR target genes, CYP3A4 and CYP2B6, respectively. Catalytic activities, mRNA, and protein expression of CYP3A4 and CYP2B6 were evaluated in a differentiated HepaRG cell line. Coregulation of PXR with coregulators on CYP3A4 promoter response elements was also been characterized. RESULTS: Transient transfection assays showed that UA effectively attenuated CYP3A4 and CYP2B6 promoter activities mediated by rifampin (RIF, human PXR agonist) and CITCO (human CAR agonist). These inhibitory effects were well correlated with the expression and catalytic activities of CYP3A4 and CYP2B6. Furthermore, the interaction of co-regulators with PXR and the transcriptional complexes in the CYP3A4 promoter activity and CYP3A4 promoter xenobiotic response element (everted repeat 6, ER6), respectively, were disrupted in the presence of UA. UA showed an antagonistic effect against PXR, and reversed the cytotoxic effects of isoniazid (INH) induced by RIF. Taken together, these results show that UA inhibits the transactivation effects of PXR and CAR, and reduces the expression and function of CYP3A4 and CYP2B6. CONCLUSION: The present study suggests that UA could be a powerful agent for reducing potentially dangerous interactions between transcriptional inducers of CYP enzymes and therapeutic drugs.

Tamoxifen Treatment and the Reduced Risk of Hyperlipidemia in Asian Patients With Breast Cancer: A Population-Based Cohort Study.

PURPOSE: The association between tamoxifen (TMX) treatment and the risk of developing hyperlipidemia remains unclear. METHODS: The records of 41,726 patients with breast cancer (28,266 received TMX and 13,460 did not) were obtained from the Taiwan National Health Insurance Research Database for the period from January 2000 to December 2008. Three-fold women without breast cancer were the control group (N = 125, 178). The main end point was developing hyperlipidemia during the follow-up. RESULTS: During a mean follow-up of 9 years, the patients with breast cancer demonstrated a rate of developing hyperlipidemia that was 6% less (adjusted hazard ratio [HR], 0.94; 95% confidence interval [CI], 0.90-0.97) than that of the control participants without breast cancer. Stratification by age group indicated that only women aged ≥ 55 years who were diagnosed with breast cancer exhibited a significantly reduced risk of hyperlipidemia compared with the control group. With the use of 2 types of adjusted models, we observed that the TMX users (aged ≥ 55 years) consistently exhibited a significantly lower risk of hyperlipidemia than the non-TMX users and control participants (adjusted HRs, 0.79 and 0.82 from models 1 and 2, respectively). Within the 8-year follow-up period, patients with breast cancer and 366 to 1500 days of TMX therapy and > 1500 days of TMX therapy had significantly lower risks of hyperlipidemia compared with patients with ≤ 365 days of TMX therapy (adjusted HR, 0.54; 95% CI, 0.50-0.59; adjusted HR, 0.21; 95% CI, 0.18-0.24, respectively). CONCLUSIONS: In Asian patients with breast cancer, TMX use was associated with reduced risks of hyperlipidemia.

Increased risk of deep vein thrombosis and pulmonary thromboembolism in patients with organophosphate intoxication: a nationwide prospective cohort study.

Organophosphate (OP) poisoning is a critical cause of morbidity and mortality worldwide. We conducted a nationwide longitudinal cohort study to investigate the development of deep vein thrombosis (DVT) and pulmonary thromboembolism (PTE) among patients admitted with OP intoxication.We identified patients with OP intoxication by using the Taiwan National Health Insurance Research Database and enrolled 9223 patients who were hospitalized for OP intoxication between 2000 and 2011. OP intoxication was diagnosed based on a clinical assessment and serum acetylcholinesterase levels at the time of hospital admission. Each patient in the OP intoxication cohort was randomly frequency matched with 4 patients without OP intoxication based on their age, sex, and index year (36,892 patients as control cohort), and all patients were observed from the index date until the appearance of a DVT or a PTE event, or until December 31, 2011. We analyzed the risks of DVT and PTE by using Cox proportional hazards regression models that included the demographic variables of sex, age, and comorbidities (eg, hypertension, diabetes, cerebral vascular disease, heart failure, all cancer types, and lower leg fracture or surgery).The results revealed a significantly increased risk of developing DVT among patients with OP poisoning (adjusted hazard ratio [HR] = 1.55; 95% confidence interval [CI] = 1.03-2.34) but not PTE (adjusted HR = 1.44; 95% CI = 0.83-2.52). Among the patients without comorbidities, the OP poisoning patients compared with controls had a higher adjusted HR of 2.12 (95% CI = 1.21-3.71) for DVT.The results of this nationwide cohort study indicate that the risk of developing DVT is markedly higher in patients with OP intoxication compared with that of the general population.

Antiarrhythmic agents and the risk of malignant neoplasm of liver and intrahepatic bile ducts.

BACKGROUND: The objective of this study was to determine the association between the use of antiarrhythmic agents and the risk of malignant neoplasm of liver and intrahepatic bile ducts (MNLIHD). METHODS: We used the research database of the Taiwan National Health Insurance Program to conduct a population-based, case-control study. We identified 9944 patients with antiarrhythmic history who were first diagnosed as having MNLIHD between 2005 and 2010. We identified an additional 19,497 patients with antiarrhythmic history in the same period who did not develop MNLIHD and were frequency-matched using age, sex, and index year to form a control group. Five commercially available antiarrhythmic agents, amiodarone, mexiletine, propafenone, quinidine, and procainamide, were analyzed. RESULTS: The adjusted odds ratio (OR) of MNLIHD was 1.60 (95% confidence interval [CI], 1.45-1.77) for amiodarone users versus nonamiodarone users. In subgroup analysis, amiodarone use was significantly associated with an increased risk of MNLIHD with an adjusted OR of 18.0 (95% CI, 15.7-20.5) for patients with comorbidities compared to an OR of 2.43 (95% CI, 1.92-3.06) for those without comorbidities. After adjustment for age, sex, statins, anti-diabetes medications, non-steroidal antiinflammatory drugs, propafenone use, quinidine use, and comorbidities, the ORs were 1.49, 1.66, and 1.79 for MNLIHD associated with annual mean defined daily doses of ≤ 30, 31-145, and >145, respectively. CONCLUSIONS: The results of the present study indicated that amiodarone might be associated with the development of MNLIHD in a dose-dependent manner, particularly among patients with comorbidities.

Allyl isothiocyanate (AITC) inhibits pregnane X receptor (PXR) and constitutive androstane receptor (CAR) activation and protects against acetaminophen- and amiodarone-induced cytotoxicity.

Antagonizing the action of the pregnane X receptor (PXR) may have important clinical implications for preventing inducer-drug interactions and improving therapeutic efficacy. We identified a widely distributed isothiocyanate, allyl isothiocyanate (AITC), which acts as an effective antagonist of the nuclear receptor pregnane X receptor (PXR, NR1I2) and constitutive androstane receptor (CAR, NR1I3). HepG2 cells were used to assay reporter function, mRNA levels, and protein expression. Catalytic activities of the PXR and CAR target genes, CYP3A4 and CYP2B6, respectively, were also assessed in differentiated HepaRG cells. Protective effects of AITC on rifampin-induced cytotoxicity were observed, and transient transfection assays showed that AITC was able to effectively attenuate the agonist effects of rifampin and CITCO on human PXR and CAR activity, respectively. AITC-mediated reduction in the transcriptional activity of PXR and CAR correlated well with the suppression of CYP3A4 and CYP2B6 expression in HepG2 cells, which reflected the reduced catalytic activities of both of these genes following AITC treatment in differentiated HepaRG cells. Furthermore, AITC disrupts the co-regulations of PXR with several important co-regulators. Furthermore, the antagonist effect of AITC against PXR was found in HepaRG cells upon addition of acetaminophen (APAP) and amiodarone, indicating that AITC protects cells from drug-induced cytotoxicity. Taken together, our results show that AITC inhibits the transactivation effects of PXR and CAR and reduces the expression and function of CYP3A4 and CYP2B6. Additionally, AITC reversed the cytotoxic effects of APAP and amiodarone induced by PXR ligand. Results from this study suggest that AITC could be a powerful agent for reducing potentially dangerous interactions between transcriptional inducers of CYP enzymes and therapeutic drugs.

Inhibition of cytochrome P450 2C9 expression and activity in vitro by allyl isothiocyanate.

The growing interest in the use of natural herbal products and dietary supplements to treat and prevent diseases raises the question of medicinal drug safety. Allyl isothiocyanate, a hydrolysis product of a glucosinolate, sinigrin, has multiple beneficial properties, and based on this fact, allyl isothiocyanate-containing dietary supplements have been developed. To date, no studies of the effects of this compound on the cytochrome P450 2C9 have been reported. In this study, we found that allyl isothiocyanate reduced catalytic activity, messenger ribonucleic acid, and protein expression of cytochrome P450 2C9 in HepaRG cells. An investigation of the transcriptional activity of the pregnane X receptor and the constitutive androstane receptor revealed that allyl isothiocyanate disrupted the transcriptional coregulation effects of the pregnane X receptor/constitutive androstane receptor with several important coregulators and interfered with the assembly of transcriptional complexes of the cytochrome P450 2C9 pregnane X receptor/constitutive androstane receptor-response element. The decrease of cytochrome P450 2C9 expression and activity mediated by allyl isothiocyanate suggested that this agent could alter the metabolism of drugs metabolized by cytochrome P450 2C9. This may cause food/dietary supplement-drug interactions or alter the therapeutic effects, and even the toxicity of drugs coadministered with allyl isothiocyanate. Since the consumption of allyl isothiocyanate-containing food/dietary supplements continues to increase, it is important to predict and ultimately avoid interactions with concomitant drugs. It is required that these possible pharmacokinetic interactions be characterized and the recommendations available to patients and healthcare professionals be improved.