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Selective agonism of the estrogen receptor (ER) subtypes, ERα and ERβ, has historically been difficult to achieve due to the high degree of ligand-binding domain structural similarity. Multiple efforts have focused on the use of classical organic scaffolds to model 17β-estradiol geometry in the design of ERβ selective agonists, with several proceeding to various stages of clinical development. Carborane scaffolds offer many unique advantages including the potential for novel ligand/receptor interactions but remain relatively unexplored. We synthesized a series of para-carborane estrogen receptor agonists revealing an ERβ selective structure-activity relationship. We report ERβ agonists with low nanomolar potency, greater than 200-fold selectivity for ERβ over ERα, limited off-target activity against other nuclear receptors, and only sparse CYP450 inhibition at very high micromolar concentrations. The pharmacological properties of our para-carborane ERβ selective agonists measure favorably against clinically developed ERβ agonists and support further evaluation of carborane-based selective estrogen receptor modulators.

Selective agonism of the estrogen receptor (ER) subtypes, ERα and ERβ, has historically been difficult to achieve due to the high degree of ligand-binding domain structural similarity. Multiple efforts have focused on the use of classical organic scaffolds to model 17β-estradiol geometry in the design of ERβ selective agonists, with several proceeding to various stages of clinical development. Carborane scaffolds offer many unique advantages including the potential for novel ligand/receptor interactions but remain relatively unexplored. We synthesized a series of

Hepatocellular carcinoma (HCC) remains a highly prevalent and deadly disease, being among the top causes of cancer-related deaths worldwide. Despite the fact that the liver is the major site of biotransformation, studies on drug metabolizing enzymes in HCC are scarce. It is known that malignant transformation of hepatocytes leads to a significant alteration of their metabolic functions and overall deregulation of gene expression. Advanced stages of the disease are thus frequently associated with liver failure, and severe alteration of drug metabolism. However, the impact of dysregulation of metabolic enzymes on therapeutic efficacy and toxicity in HCC patients is largely unknown. Here we demonstrate a significant down-regulation in European Caucasian patients of cytochromes P450 (CYPs), the major xenobiotic-metabolizing enzymes, in HCC tumour samples as compared to their surrounding non-cancerous (reference) tissue. Moreover, we report for the first time the association of the unique CYP profiles with specific transcriptome changes, and interesting correlations with expression levels of nuclear receptors and with the histological grade of the tumours. Integrated analysis has suggested certain co-expression profiles of CYPs with lncRNAs that need to be further characterized. Patients with large tumours with down-regulated CYPs could be more vulnerable to drug toxicity; on the other hand, such tumours would eliminate drugs more slowly and should be more sensitive to pharmacotherapy (except in the case of pro-drugs where activation is necessary).

Rocuronium is a neuromuscular blocking agent acting as a competitive antagonist of acetylcholine. Results of an inhibition of eight individual liver microsomal cytochromes P450 (CYP) are presented. As the patients are routinely premedicated with diazepam, possible interaction of diazepam with rocuronium has been also studied. Results indicated that rocuronium interacts with human liver microsomal CYPs by binding to the substrate site. Next, concentration dependent inhibition of liver microsomal CYP3A4 down to 42% (at rocuronium concentration 189 μM) was found. This effect has been confirmed with two CYP3A4 substrates, testosterone (formation of 6β-hydroxytestosterone) and diazepam (temazepam formation). CYP2C9 and CYP2C19 activities were inhibited down to 75–80% (at the same rocuronium concentration). Activities of other microsomal CYPs have not been inhibited by rocuronium. To prove the possibility of rocuronium interaction with other drugs (diazepam), the effect of rocuronium on formation of main diazepam metabolites, temazepam (by CYP3A4) and desmethyldiazepam, (also known as nordiazepam; formed by CYP2C19) in primary culture of human hepatocytes has been examined. Rocuronium has caused inhibition of both reactions by 20 and 15%, respectively. The results open a possibility that interactions of rocuronium with drugs metabolized by CYP3A4 (and possibly also CYP2C19) may be observed.

Sesquiterpenes, the main components of plant essential oils, are often taken in the form of folk medicines and dietary supplements. Several sesquiterpenes possess interesting biological activities but they could interact with concurrently administered drugs via inhibition of drug-metabolizing enzymes. Therefore, the present study was designed to test the potential inhibitory effect of tree structurally relative sesquiterpenes β-caryophyllene (CAR), β-caryophyllene oxide (CAO) and α-humulene (HUM) on the activities of the main drug-metabolizing enzymes. For this purpose, rat and human hepatic subcellular fractions were incubated with CAR, CAO or HUM together with specific substrates for oxidation, reduction and conjugation enzymes and their coenzymes. HPLC, spectrophotometric and spectrofluorimetric analyses of product formations were used. All tested sesquiterpenes significantly inhibited cytochromes P4503A (CYP3A) activities in rats as well as in human hepatic microsomes, with CAO being the strongest inhibitor. A non-competitive type of inhibition was found. On the other hand, none of the tested sesquiterpenes significantly affected the activities of carbonyl-reducing enzymes (CBR1, AKRs, NQO1) or conjugation enzymes (UGTs, GSTs, SULTs, COMT). As CYP3A enzymes metabolize many drugs, their inhibition by CAO, CAR and HUM might affect the pharmacokinetics of concurrently administered drugs. Similar results obtained in rat and human hepatic microsomes indicate that rats could be used for further testing of possible drug-sesquiterpenes interactions in vivo.

Sesquiterpenes, 15-carbon compounds formed from three isoprenoid units, are the main components of plant essential oils. Sesquiterpenes occur in human food, but they are principally taken as components of many folk medicines and dietary supplements. The aim of our study was to test and compare the potential inhibitory effect of acyclic sesquiterpenes, trans-nerolidol, cis-nerolidol and farnesol, on the activities of the main xenobiotic-metabolizing enzymes in rat and human liver in vitro. Rat and human subcellular fractions, relatively specific substrates, corresponding coenzymes and HPLC, spectrophotometric or spectrofluorometric analysis of product formation were used. The results showed significant inhibition of cytochromes P450 (namely CYP1A, CYP2B and CYP3A subfamilies) activities by all tested sesquiterpenes in rat as well as in human hepatic microsomes. On the other hand, all tested sesquiterpenes did not significantly affect the activities of carbonyl-reducing enzymes and conjugation enzymes. The results indicate that acyclic sesquiterpenes might affect CYP1A, CYP2B and CYP3A mediated metabolism of concurrently administered drugs and other xenobiotics. The possible drug–sesquiterpene interactions should be verified in in vivo experiments.

Sesquiterpenes, 15-carbon compounds formed from three isoprenoid units, are the main components of plant essential oils. Sesquiterpenes occur in human food, but they are principally taken as components of many folk medicines and dietary supplements. The aim of our study was to test and compare the potential inhibitory effect of acyclic sesquiterpenes, trans-nerolidol, cis-nerolidol and farnesol, on the activities of the main xenobiotic-metabolizing enzymes in rat and human liver in vitro. Rat and human subcellular fractions, relatively specific substrates, corresponding coenzymes and HPLC, spectrophotometric or spectrofluorometric analysis of product formation were used. The results showed significant inhibition of cytochromes P450 (namely CYP1A, CYP2B and CYP3A subfamilies) activities by all tested sesquiterpenes in rat as well as in human hepatic microsomes. On the other hand, all tested sesquiterpenes did not significantly affect the activities of carbonyl-reducing enzymes and conjugation enzymes. The results indicate that acyclic sesquiterpenes might affect CYP1A, CYP2B and CYP3A mediated metabolism of concurrently administered drugs and other xenobiotics. The possible drug–sesquiterpene interactions should be verified in in vivo experiments.

Two non-symmetric bispyridine oxime - based reactivators of acetylcholinesterase enzyme (AChE), labeled as K027 (1-(4-carbamoylpyridinium)-3-(4-hydroxyiminomethylpyridinium)-propane dibromide) and K203 ((E)-1-(4- carbamoylpyridinium)-4-(4-hydroxyiminomethylpyridinium)-but-2-ene dibromide) were tested for their potential to inhibit activities of human liver microsomal cytochromes P450 (CYP). Both oximes are very potent reactivators of organophosphate-inhibited AChE. An interaction of both compounds with CYP in human liver microsomal preparation was detected using difference spectroscopy. The compounds were shown to bind to CYP enzymes with spectral binding constants of 5.04 ± 1.79 nM (K027) and 5.2 ± 2.6 nM (K203). Enzymology studies were subsequently performed aimed at determining which of the nine most important CYP involved in drug is affected by this interaction. The results have shown no prominent inhibition of individual CYP activities with either compounds except in the case of CYP2E1 and K203. Diagnostic Dixon plot revealed that K203 acted as an uncompetitive inhibitor of CYP2E1. Inhibition of this activity however is not as prominent as to make a potent drug interaction likely. Hence, the interaction of K027 and K203 oxime-type AChE reactivators with human liver microsomal CYP enzymes does not seem to be of prominent clinical importance and both compounds could be safely used in this respect as antidotes with low risk of drug interactions.

The aim was to investigate whether rosuvastatin affect rat cytochrome P450 (CYP) 2C11 and CYP2C6. CYP2C11 and CYP2C6 are considered as counterparts of human CYP2C9, which metabolizes many drugs including S-warfarin, diclofenac or ibuprofen. The male Wistar rats were fed standard laboratory diet (STD) or high cholesterol diet (HCD, 1% of cholesterol, 10% of lard fat) for 21 days. Rosuvastatin administration in STD (0.03% w/w) resulted in decreased mRNA expression of CYP2C11 as well as of CYP2C6 (here significant) and in a significant decrease of the respective protein expression as well as of the enzyme activity of both CYP2C forms. When rosuvastatin was administered in the HCD, the mRNA expression of both CYP2C forms was significantly lowered; the protein and activity parameters did not show significant changes. These results suggest that CYP2C11 as well as CYP2C6 expression and activity are negatively affected by rosuvastatin and may be modulated by high cholesterol high fat diet. Therefore, it should be taken into consideration that drugs metabolized by CYP2C9 in human could interact with rosuvastatin, as it has been already suggested for warfarin (rosuvastatin has increased its anticoagulant effect in human), and for telmisartan, sildenafil and glimepiride.