Inhibition Of CYP2B6 Research Articles

The Expression of Genes CYP1A1, CYP1B1, and CYP2J3 in Distinct Regions of the Heart and Its Possible Contribution to the Development of Hypertension.

It is believed that alterations in the functioning of the cytochrome P450 (CYP), which participates in metabolic transformations of endogenous polyunsaturated fatty acids (PUFAs) (with the formation of cardioprotective or cardiotoxic products), affects the development of age-related cardiovascular diseases and reduces the effectiveness of some cardioselective drugs. For example, CYP2J2 activation or CYP1B1 inhibition protects against the cardiovascular toxicity of anticancer drugs. It is currently unclear whether CYPs capable of metabolizing arachidonic acid and ω-3 PUFAs to vasodilatory and vasoconstrictive derivatives are expressed in all heart regions. The work was performed on senescence-accelerated OXYS rats featuring elevated blood pressure, OXYSb rats (an OXYS substrain with normal blood pressure), and Wistar rats as a "healthy" control. The mRNA level was determined in the right and left ventricles, the right and left atria, and the aorta of 1-, 3-, and 12-month-old rats. We showed that all heart regions express CYPs capable of metabolizing arachidonic acid and ω-3 PUFAs and revealed significant differences between heart regions both in the mRNA level of genes CYP1B1, CYP2J3, and CYP1A1 and in the time course of expression changes with age. We noticed that expression levels of these CYPs in the heart regions and aorta differ between hypertensive OXYS rats, normotensive OXYSb rats, and healthy Wistar rats but could not detect any clear-cut patterns associated with the hypertensive status of OXYS rats.

Synthesis and evaluation of novel tetrahydroisoquinoline-benzo[h]chromen-4-one conjugates as dual ABCB1/CYP1B1 inhibitors for overcoming MDR in cancer

The emergence of multidrug resistance (MDR) in malignant tumors is one of the major threats encountered currently by many chemotherapeutic agents. Among the various mechanisms involved in drug resistance, P-glycoprotein (P-gp, ABCB1), a member of the ABC transporter family that significantly increases the efflux of various anticancer drugs from tumor cells, and the metabolic enzyme CYP1B1 are widely considered to be two critical targets for overcoming MDR. Unfortunately, no MDR modulator has been approved by the FDA to date. In this study, based on pharmacophore hybridization, bioisosteric and fragment-growing strategies, we designed and synthesized 11 novel tetrahydroisoquinoline-benzo[h]chromen-4-one conjugates as dual ABCB1/CYP1B1 inhibitors. Among them, the preferred compound A10 exhibited the best MDR reversal activity (IC50 = 0.25 μM, RF = 44.4) in SW620/AD300 cells, being comparable to one of the most potent third-generation P-gp inhibitors WK-X-34. In parallel, this dual ABCB1/CYP1B1 inhibitory effect drives compound A10 exhibiting prominent drug resistance reversal activity to doxorubicin (IC50 = 4.7 μM, RF = 13.7) in ABCB1/CYP1B1-overexpressing DOX-SW620/AD300-1B1 resistant cells, which is more potent than that of the CYP1B1 inhibitor ANF. Furthermore, although compound A2 possessed moderate ABCB1/CYP1B1 inhibitory activity, it showed considerable antiproliferative activity towards drug-resistant SW620/AD300 and MKN45-DDP-R cells, which may be partly related to the increase of PUMA expression to promote the apoptosis of the drug-resistant MKN45-DDP-R cells as confirmed by proteomics and western blot assay. These results indicated that the tetrahydroisoquinoline-benzo[h]chromen-4-one conjugates may provide a fundamental scaffold reference for further discovery of MDR reversal agents.

Abstract P440: Discovery of clinical candidate GSC002219, a highly selective oral CYP11B2 inhibitor for hypertension

Background: Aldosterone is an important mediator of hypertension and its aberration could contribute to heart and kidney diseases. Aldosterone synthase inhibitors (ASI) attenuate the production of aldosterone directly and have been proposed as an alternative to mineralocorticoid receptor antagonists (MRA) for treatment of resistant hypertension and chronic renal disease. GSC002219 is a potent inhibitor of aldosterone synthase (CYP11B2) with high selectivity over the closely related enzyme CYP11B1. The aim of the study was to evaluate the effect of GSC002219 on aldosterone and blood pressure. Methods: The inhibitory effect of GSC002219 against CYP11B2 and CYP11B1 proteins was assessed in human renal leiomyoblastoma cells expressing recombinant human / cynomolgus CYP11B1or CYP11B2 enzymes, respectively. GSC002219 was further evaluated in Synacthen (ACTH) challenged cynomolgus monkey model for its effects against various related key biomarkers including cortisol, aldosterone and precursors. The effects of GSC002219 on systolic blood pressure (SBP) and diastolic blood pressure (DBP) were evaluated in stroke-prone spontaneously hypertensive rat (SHRSP) model. Results: GSC002219 potently inhibits CYP11B2 with an IC 50 of 27nM, while maintains a >150-fold selectivity over CYP11B1. In ACTH challenged cynomolgus monkey model, single oral doses of GSC002219 at 0.03 mg/kg and 0.1 mg/kg could suppress aldosterone production to 80% and 93%, respectively, comparing to vehicle-treated animals without any effect towards cortisol levels. In the rat SHRSP hypertension model, GSC002219 could effectively lower both SBP and DBP. GSC002219 has an excellent in vitro ADME and toxicology profile as well as a balanced physicochemical property. In 14-day rat and monkey toxicology studies, GSC002219 displayed good tolerance, excellent PK profile and a great safety window (>100 fold). Conclusions: Taken together, GSC002219 is a safe and potent inhibitor of CYP11B2 and efficacious in various disease models of hypertension. GSC002219 is under IND-enabling study and may enter the clinical development early 2025.

Evaluating the role of aldosterone synthesis on adrenal cell fate.

Hypertension affects one-third of the adult population worldwide, with primary aldosteronism (PA) accounting for at least 5-10% of these cases. The aldosterone synthase enzyme (CYP11B2) plays a pivotal role in PA manifestation, as increased expression of CYP11B2 leads to excess aldosterone synthesis. Physiological expression of CYP11B2 in humans is normally limited to cells of the adrenal zona glomerulosa under tight homeostatic regulation. In PA, however, there are CYP11B2-positive lesions in the adrenal cortex that autonomously secrete aldosterone, highlighting the dysregulation of adrenal cortex zonation and function as a key aspect of PA pathogenesis. Thus, this review aims to summarize the development of the adrenal glands, the key regulators of adrenal cortex homeostasis, and the dysregulation of this homeostasis. It also discusses the development of CYP11B2 inhibitors for therapeutic use in patients with hypertension, as well as the current knowledge of the effects of CYP11B2 inhibition on adrenal cortex homeostasis and cell fate. Understanding the control of adrenal cell fate may offer valuable insights into both the pathogenesis of PA and the development of alternative treatment approaches for PA.

Design and synthesis of new alfa-naphthoflavanones as potent and selective CYP1B1 inhibitors

Natural Flavanones are abundant in human diet and a few of them exhibited chemopreventive effects against xenobiotic procarcinogens through the inhibition of tumour specific CYP1B1 enzyme. Herein, a series of new alfa-naphthoflavanones were synthesised and evaluated for their enzymatic inhibitory potency and selectivity of CYP1B1 over its isoenzyme CYP1A1. The most active compound 8c displayed highest inhibitory potency against CYP1B1 with the IC50 value of 0.1 nM. The structure activity relationship studies implied that the methoxy groups on the core scaffold of naphthalene ring significantly influenced CYP1B1 inhibition efficacy, while B-ring substitutions played important roles in activity. Molecular docking studies were conducted to provide a better understanding on the key structural features involved in CYP1B1 inhibitory activity. The results of the study implied that these naphthoflavanones could be considered as new leads and further investigation be conducted to explore the flavanone scaffold as skeleton for inhibiting CYP1B1.

Identification of the human Cytochrome P450 enzymes (P450s) responsible for metabolizing infigratinib to its pharmacologically active Metabolites, BHS697, and CQM157, and assessment of their in vitro inhibition of P450s and UDP-glucuronosyltransferases (UGTs)

Infigratinib, an oral FGFR inhibitor for advanced cholangiocarcinoma, yielded two active metabolites, BHS697 and CQM157, with similar receptor affinity. Our study characterized P450s that are responsible for the metabolism of infigratinib to its two major active metabolites, BHS697 and CQM157. In vitro inhibition of P450s and UGTs by infigratinib, BHS697 or CQM157 was further investigated. The unbound apparent Km values for metabolism of infigratinib to BHS697 by HLM, human recombinant CYP2C8, CYP2C19, CYP2D6 and CYP3A4 enzymes are 4.47, 0.65, 2.50, 30.6 and 2.08 μM, while Vmax values are 90.0 pmol/min/mg protein, 0.13, 0.027, 0.81, and 0.56 pmol/min/pmol protein, respectively. The unbound apparent Km value for metabolism of infigratinib to CQM157 by HLM is 0.049 μM, while the Vmax value is 0.32 pmol/min/mg protein respectively. In HLM, infigratinib displayed moderate inhibition of CYP3A4 and CYP2C19 and weak or negligible inhibition of other P450 isoforms. BHS697 exhibited weak inhibition of CYP2B6, CYP2C9, CYP2C19 and CYP3A4, and no inhibition of CYP2C8 and CYP2D6. CQM157 moderately inhibited CYP2C9 and CYP3A4, and weakly or negligibly inhibited other P450 isoforms. Regarding UGTs, infigratinib moderately inhibited UGT1A4 and weakly inhibited UGT1A1, respectively. BHS697 weakly inhibited UGT1A1. In contrast, CQM157 moderately inhibited both UGT1A1 and UGT1A4. Our findings provide novel insights into the metabolism of and potential DDIs implicating infigratinib.

Modulation of Angiotensin II-Induced Cellular Hypertrophy by Cannflavin-C: Unveiling the Impact on Cytochrome P450 1B1 and Arachidonic Acid Metabolites.

This research aimed to clarify the impacts of cannflavin-C on angiotensin II (Ang II)-induced cardiac hypertrophy and their potential role in modulating cytochrome P450 1B1 (CYP1B1) and arachidonic acid (AA) metabolites. Currently there is no evidence to suggest that cannflavin-C, a prenylated flavonoid, has any significant effects on the heart or cardiac hypertrophy. The metabolism of arachidonic acid (AA) into midchain hydroxyeicosatetraenoic acids (HETEs), facilitated by CYP1B1 enzyme, plays a role in the development of cardiac hypertrophy, which is marked by enlarged cardiac cells. Adult human ventricular cardiomyocyte (AC16) cell line was cultured and exposed to cannflavin-C in the presence and absence of Ang II. The assessment of mRNA expression pertaining to cardiac hypertrophic markers and cytochromes P450 (P450s) was conducted via real-time polymerase chain reaction (PCR), whereas the quantification of P450 protein levels was carried out through western blot analysis. Ang II induced hypertrophic markers myosin heavy chain (β/α-MHC), atrial natriuretic peptide (ANP), and brain natriuretic peptide (BNP) and increased cell surface area, whereas cannflavin-C mitigated these effects. Gene and protein expression analysis revealed that cannflavin-C downregulated CYP1B1 gene expression, protein level, and enzyme activity assessed by 7-methoxyresorufin O-deethylase (MROD). Arachidonic acid metabolites analysis, using liquid chromatography-tandem mass spectrometry (LC-MS/MS), demonstrated that Ang II increased midchain (R/S)-HETE concentrations, which were attenuated by cannflavin-C. This study provides novel insights into the potential of cannflavin-C in modulating arachidonic acid metabolites and attenuating Ang II-induced cardiac hypertrophy, highlighting the importance of this compound as potential therapeutic agents for cardiac hypertrophy. SIGNIFICANCE STATEMENT: This study demonstrates that cannflavin-C offers protection against cellular hypertrophy induced by angiotensin II. The significance of this research lies in its novel discovery, which elucidates a mechanistic pathway involving the inhibition of CYP1B1 by cannflavin-C. This discovery opens up new avenues for leveraging this compound in the treatment of heart failure.

Attenuation of Polycyclic Aromatic Hydrocarbon (PAH)-Induced Carcinogenesis and Tumorigenesis by Omega-3 Fatty Acids in Mice In Vivo.

Lung cancer is the leading cause of cancer death worldwide. Polycyclic aromatic hydrocarbons (PAHs) are metabolized by the cytochrome P450 (CYP)1A and 1B1 to DNA-reactive metabolites, which could lead to mutations in critical genes, eventually resulting in cancer. Omega-3 fatty acids, such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), are beneficial against cancers. In this investigation, we elucidated the mechanisms by which omega-3 fatty acids EPA and DHA will attenuate PAH-DNA adducts and lung carcinogenesis and tumorigenesis mediated by the PAHs BP and MC. Adult wild-type (WT) (A/J) mice, Cyp1a1-null, Cyp1a2-null, or Cyp1b1-null mice were exposed to PAHs benzo[a]pyrene (BP) or 3-methylcholanthrene (MC), and the effects of omega-3 fatty acid on PAH-mediated lung carcinogenesis and tumorigenesis were studied. The major findings were as follows: (i) omega-3 fatty acids significantly decreased PAH-DNA adducts in the lungs of each of the genotypes studied; (ii) decreases in PAH-DNA adduct levels by EPA/DHA was in part due to inhibition of CYP1B1; (iii) inhibition of soluble epoxide hydrolase (sEH) enhanced the EPA/DHA-mediated prevention of pulmonary carcinogenesis; and (iv) EPA/DHA attenuated PAH-mediated carcinogenesis in part by epigenetic mechanisms. Taken together, our results suggest that omega-3 fatty acids have the potential to be developed as cancer chemo-preventive agents in people.

Utility of human cytochrome P450 inhibition data in the assessment of drug-induced liver injury

Drug-induced liver injury (DILI) is a major cause of drug development discontinuation and drug withdrawal from the market, but there are no golden standard methods for DILI risk evaluation. Since we had found the association between DILI and CYP1A1 or CYP1B1 inhibition, we further evaluated the utility of cytochrome P450 (P450) inhibition assay data for DILI risk evaluation using decision tree analysis. The inhibitory activity of drugs with DILI concern (DILI drugs) and no DILI concern (no-DILI drugs) against 10 human P450s was assessed using recombinant enzymes and luminescent substrates. The drugs were also subjected to cytotoxicity assays and high-content analysis using HepG2 cells. Molecular descriptors were calculated by alvaDesc. Decision tree analysis was performed with the data obtained as variables with or without P450-inhibitory activity to discriminate between DILI drugs and no-DILI drugs. The accuracy was significantly higher when P450-inhibitory activity was included. After the decision tree discrimination, the drugs were further discriminated with the P450-inhibitory activity. The results demonstrated that many false-positive and false-negative drugs were correctly discriminated by using the P450 inhibition data. These results suggest that P450 inhibition assay data are useful for DILI risk evaluation.

Scaffold hopping for designing of potent and selective CYP1B1 inhibitors to overcome docetaxel resistance: synthesis and evaluation

Cytochrome P450 1B1, a tumor-specific overexpressed enzyme, significantly impairs the pharmacokinetics of several commonly used anticancer drugs including docetaxel, paclitaxel and cisplatin, leading to the problem of resistance to these drugs. Currently, there is no CYP1B1 inhibition-based adjuvant therapy available to treat this resistance problem. Hence, in the current study, exhaustive in-silico studies including scaffold hopping followed by molecular docking, three-dimensional quantitative structure-activity relationships (3D-QSAR), molecular dynamics and free energy perturbation studies were carried out to identify potent and selective CYP1B1 inhibitors. Initially, scaffold hopping analysis was performed against a well-reported potent and selective CYP1B1 inhibitor (i.e. compound 3n). A total of 200 scaffolds were identified along with their shape and field similarity scores. The top three scaffolds were further selected on the basis of these scores and their synthesis feasibility to design some potent and selective CYP1B1 inhibitors using the aforementioned in-silico techniques. Designed molecules were further synthesized to evaluate their CYP1B1 inhibitory activity and docetaxel resistance reversal potential against CYP1B1 overexpressed drug resistance MCF-7 cell line. In-vitro results indicated that compounds 2a, 2c and 2d manifested IC50 values for CYP1B1 ranging from 0.075, 0.092 to 0.088 μM with at least 10-fold selectivity. At low micromolar concentrations, compounds 1e, 1f, 2a and 2d exhibited promising cytotoxic effects in the docetaxel-resistant CYP1B1 overexpressed MCF-7 cell line. In particular, compound 2a is most effective in reversing the resistance with IC50 of 29.0 ± 3.6 μM. All of these discoveries could pave the way for the development of adjuvant therapy capable of overcoming CYP1B1-mediated resistance. Communicated by Ramaswamy H. Sarma

Dihydrotanshinone I-Induced CYP1 Enzyme Inhibition and Alteration of Estradiol Metabolism.

Dihydrotanshinone I (DHTI) is a pharmacologically active component occurring in the roots of the herbal medicine Salvia miltiorrhiza Bunge. This study investigated DHTI-induced inhibition of CYP1A1, CYP1A2, and CYP1B1 with the aim to determine the potential effects of DHTI on the bioactivation of estradiol (E2), possibly related to preventive/therapeutic strategy for E2-associated breast cancer. Ethoxyresorufin as a specific substrate for CYP1s was incubated with human recombinant CYP1A1, CYP1A2, or CYP1B1 in the presence of DHTI at various concentrations. Enzymatic inhibition and kinetic behaviors were examined by monitoring the formation of the corresponding product. Molecular docking was further conducted to define the interactions between DHTI and the three CYP1s. The same method and procedure were employed to examine the DHTI-induced alteration of E2 metabolism. DHTI showed significant inhibition of ethoxyresorufin O-deethylation activity catalyzed by CYP1A1, CYP1A2 and CYP1B1 in a concentration-dependent manner (IC50 = 0.56, 0.44, and 0.11 μM, respectively). Kinetic analysis showed that DHTI acted as a competitive type of inhibitor of CYP1A1 and CYP1B1, whereas it noncompetitively inhibited CYP1A2. The observed enzyme inhibition was independent of NADPH and time. Molecular docking analysis revealed hydrogen bonding interactions between DHTI and Asp-326 of CYP1B1. Moreover, DHTI displayed preferential activity to inhibit 4-hydroxylation of E2 (a genotoxic pathway) mediated by CYP1B1. Exposure to DHTI could reduce the risk of genotoxicity induced by E2. SIGNIFICANCE STATEMENT: CYP1A1, CYP1A2, and CYP1B1 enzymes are involved in the conversion of estradiol (E2) into 2-hydroxyestradiol (2-OHE2) and 4-hydroxyestradiol (4-OHE2) through oxidation. 2-OHE2 is negatively correlated with breast cancer risk, and 4-OHE2 may be a significant initiator and promoter of breast cancer. The present study revealed that dihydrotanshinone I (DHTI) competitively inhibits CYP1A1/CYP1B1 and noncompetitively inhibits CYP1A2. DHTI exhibits a preference for inhibiting the genotoxicity associated with E2 4-hydroxylation pathway mediated by CYP1B1, potentially reducing the risk of 4-OHE2-induced genotoxicity.

Estrogen genotoxicity causes preferential development of Fuchs endothelial corneal dystrophy in females

Fuchs endothelial corneal dystrophy (FECD) is a genetically complex, age-related, female-predominant disorder characterized by loss of post-mitotic corneal endothelial cells (CEnCs). Ultraviolet-A (UVA) light has been shown to recapitulate the morphological and molecular changes seen in FECD to a greater extent in females than males, by triggering CYP1B1 upregulation in females. Herein, we investigated the mechanism of greater CEnC susceptibility to UVA in females by studying estrogen metabolism in response to UVA in the cornea. Loss of NAD(P)H quinone oxidoreductase 1 (NQO1) resulted in increased production of estrogen metabolites and mitochondrial-DNA adducts, with a higher CEnC loss in Nqo1−/− female compared to wild-type male and female mice. The CYP1B1 inhibitors, trans-2,3′,4,5′-tetramethoxystilbene (TMS) and berberine, rescued CEnC loss. Injection of wild-type male mice with estrogen (E2; 17β-estradiol) increased CEnC loss, followed by increased production of estrogen metabolites and mitochondrial DNA (mtDNA) damage, not seen in E2-treated Cyp1b1−/−male mice. This study demonstrates that the endo-degenerative phenotype is driven by estrogen metabolite-dependent CEnC loss that is exacerbated in the absence of NQO1; thus, explaining the mechanism accounting for the higher incidence of FECD in females. The mitigation of estrogen-adduct production by CYP1B1 inhibitors could serve as a novel therapeutic strategy for FECD.

Design, Synthesis, and Evaluation of 18F-Labeling CYP1B1 PET Tracer Based on 2-Phenylquinazolin

Cytochrome P450 (CYP)1B1 has been identified to be specifically overexpressed in several solid tumors, thus it’s a potential target for the detection of tumors. Based on the 2-Phenylquinazolin CYP1B1 inhibitors, we designed and synthesized several positron emission computed tomography (PET) imaging probes targeting CYP1B1. Through IC50 determinations, most of these probes exhibited good affinity and selectivity to CYP1B1. Considering their affinity, solubility, and their 18F labeling methods, we chose compound 5c as the best candidate. The 18F radiolabeling of [18F] 5c was easy to handle with good radiolabeling yield and radiochemical purity. In vitro and in vivo stability study indicated that probe [18F]5c has good stability. In cell binding assay, [18F]5c could be specifically taken up by tumor cells, especially HCT-116 cells. Although the tumor-blood (T/B) and tumor-muscle (T/M) values and PET imaging results were unsatisfied, it is still possible to develop PET probes targeting CYP1B1 by structural modification on the basis of 5c in the future.

SAT014 Involvement Of Cytochrome P450 1B1 In Synthesis Of Neurosteroid Pregnenolone In Human Brain Cells

Abstract Disclosure: Y. Lin: None. G. Cheung: None. Z. Zhang: None. V. Papadopoulos: None. Neurosteroids, steroids synthesized in the nervous system, have important functions in modulating brain function, neuroprotection, and reducing neuroinflammation. The neurosteroid pregnenolone, the precursor to all other neurosteroids, is one of the most abundant neurosteroids in the brain. Still, the enzyme known to make it, CYP11A1, has been difficult to detect in the human brain. We recently reported that unlike in peripheral steroidogenic organs, pregnenolone is not synthesized by CYP11A1 in human brain cells but rather by another mitochondrial cytochrome P450 enzyme (J Biol Chem. 2022 Jul;298(7):102110). Therefore, we aimed to identify the enzyme responsible for producing pregnenolone in the current study. Upon bioinformatic analyses of publicly available datasets for mitochondrial CYP450s expressed in the human brain, we identified three potential candidates: CYP27A1, CYP1A1, and CYP1B1. Given that CYP27A1 is highly expressed in the brain and is involved in cholesterol metabolism, we first tested the effects of CYP27A1 inhibition via drug treatment and siRNA knockdown on pregnenolone synthesis in steroidogenic MGM-1 human glioma cells. Neither treatment with CYP27A1 inhibitors anastrozole or dexmedetomidine nor CYP27A1 siRNA knockdown resulted in a significant reduction in pregnenolone formation by MGM-1 cells, suggesting that CYP27A1 likely is not involved in pregnenolone synthesis in human brain cells. On the other hand, MGM-1 cells treated with the CYP1A1/CYP1B1 inhibitors α-napthoflavone and 2,4,3’,5’-tetramethoxystilbene showed a significant reduction in pregnenolone production in the presence of the pregnenolone precursor 22R-hydroxycholesterol. To investigate whether this effect was due to the inhibition of CYP1A1 or CYP1B1, we knocked down CYP1A1 or CYP1B1 in MGM-1 cells using siRNA. While CYP1A1 knockdown did not result in any significant changes to pregnenolone synthesis, CYP1B1 knockdown significantly decreased secreted pregnenolone formation by MGM-1 cells. Together, these results suggest that CYP1B1 is likely involved in the alternative pathway for pregnenolone synthesis in human brain cells. Presentation: Saturday, June 17, 2023

Virtual screening and biological evaluation to identify pharmaceuticals potentially causing hypertension and hypokalemia by inhibiting steroid 11β-hydroxylase

Several drugs were found after their market approval to unexpectedly inhibit adrenal 11β-hydroxylase (CYP11B1)-dependent cortisol synthesis. Known side-effects of CYP11B1 inhibition include hypertension and hypokalemia, due to a feedback activation of adrenal steroidogenesis, leading to supraphysiological concentrations of 11-deoxycortisol and 11-deoxycorticosterone that can activate the mineralocorticoid receptor. This results in potassium excretion and sodium and water retention, ultimately causing hypertension. With the risk known but usually not addressed in preclinical evaluation, this study aimed to identify drugs and drug candidates inhibiting CYP11B1. Two conceptually different virtual screening methods were combined, a pharmacophore based and an induced fit docking approach. Cell-free and cell-based CYP11B1 activity measurements revealed several inhibitors with IC50 values in the nanomolar range. Inhibitors include retinoic acid metabolism blocking agents (RAMBAs), azole antifungals, α2-adrenoceptor ligands, and a farnesyltransferase inhibitor. The active compounds share a nitrogen atom embedded in an aromatic ring system. Structure activity analysis identified the free electron pair of the nitrogen atom as a prerequisite for the drug-enzyme interaction, with its pKa value as an indicator of inhibitory potency. Another important parameter is drug lipophilicity, exemplified by etomidate. Changing its ethyl ester moiety to a more hydrophilic carboxylic acid group dramatically decreased the inhibitory potential, most likely due to less efficient cellular uptake. The presented work successfully combined different in silico and in vitro methods to identify several previously unknown CYP11B1 inhibitors. This workflow facilitates the identification of compounds that inhibit CYP11B1 and therefore pose a risk for inducing hypertension and hypokalemia.

In vitro Assessment of the Effects of Silybin on CYP2B6-mediated Metabolism.

Silybin is a flavonol compound with a variety of physiological properties, such as hepatoprotective, anti-fibrogenic, and hypocholesterolemic effects. Although the in vivo and in vitro effects of silybin are frequently reported, studies on herb-drug interactions have yet to be performed. With the discovery of multiple important substrates of CYP2B6 recently, there is a growing body of evidence indicating that CYP2B6 plays a much larger role in human drug metabolism than previously thought.The purpose of this study is to determine how silybin affects the CYP2B6 enzyme's activity, as well as to clarify the molecular mechanisms for inhibition by silybin. The results showed that silybin inhibited CYP2B6 activity in liver microsomes in a non-competitive manner, with IC50 and Ki values of 13.9 µM and 38.4 µM, respectively. Further investigations revealed that silybin could down-regulate the expression of CYP2B6 protein in HepaRG cells. The hydrogen bond conformation of silybin in the active site of the CYP2B6 isoform was revealed by a molecular docking study. Collectively, our findings verify that silybin is an inhibitor of CYP2B6 and explain the molecular mechanism of inhibition. This can lead to a better understanding of the herb-drug interaction between silybin and the substrates of the CYP2B6 enzyme, as well as a more rational clinical use of silybin.

Mitochondrial cytochrome P450 1B1 is involved in pregnenolone synthesis in human brain cells

Neurosteroids, which are steroids synthesized by the nervous system, can exert neuromodulatory and neuroprotective effects via genomic and nongenomic pathways. The neurosteroid and major steroid precursor pregnenolone has therapeutical potential in various diseases, such as psychiatric and pain disorders, and may play important roles in myelination, neuroinflammation, neurotransmission, and neuroplasticity. Although pregnenolone is synthesized by CYP11A1 in peripheral steroidogenic organs, our recent study showed that pregnenolone must be synthesized by another mitochondrial cytochrome P450 (CYP450) enzyme other than CYP11A1 in human glial cells. Therefore, we sought to identify the CYP450 responsible for pregnenolone production in the human brain. Upon screening for CYP450s expressed in the human brain that have mitochondrial localization, we identified three enzyme candidates: CYP27A1, CYP1A1, and CYP1B1. We found that inhibition of CYP27A1 through inhibitors and siRNA knockdown did not negatively affect pregnenolone synthesis in human glial cells. Meanwhile, treatment of human glial cells with CYP1A1/CYP1B1 inhibitors significantly reduced pregnenolone production in the presence of 22(R)-hydroxycholesterol. We performed siRNA knockdown of CYP1A1 or CYP1B1 in human glial cells and found that only CYP1B1 knockdown significantly decreased pregnenolone production. Furthermore, overexpression of mitochondria-targeted CYP1B1 significantly increased pregnenolone production under basal conditions and in the presence of hydroxycholesterols and low-density lipoprotein. Inhibition of CYP1A1 and/or CYP1B1 via inhibitors or siRNA knockdown did not significantly reduce pregnenolone synthesis in human adrenal cortical cells, implying that CYP1B1 is not a major pregnenolone-producing enzyme in the periphery. These data suggest that mitochondrial CYP1B1 is involved in pregnenolone synthesis in human glial cells.

Predictions of the Biological Effects of Several Acyclic Monoterpenes as Chemical Constituents of Essential Oils Extracted from Plants.

Acyclic terpenes are biologically active natural products having applicability in medicine, pharmacy, cosmetics and other practices. Consequently, humans are exposed to these chemicals, and it is necessary to assess their pharmacokinetics profiles and possible toxicity. The present study considers a computational approach to predict both the biological and toxicological effects of nine acyclic monoterpenes: beta-myrcene, beta-ocimene, citronellal, citrolellol, citronellyl acetate, geranial, geraniol, linalool and linalyl acetate. The outcomes of the study emphasize that the investigated compounds are usually safe for humans, they do not lead to hepatotoxicity, cardiotoxicity, mutagenicity, carcinogenicity and endocrine disruption, and usually do not have an inhibitory potential against the cytochromes involved in the metabolism of xenobiotics, excepting CYP2B6. The inhibition of CYP2B6 should be further analyzed as this enzyme is involved in both the metabolism of several common drugs and in the activation of some procarcinogens. Skin and eye irritation, toxicity through respiration and skin-sensitization potential are the possible harmful effects revealed by the investigated compounds. These outcomes underline the necessity of in vivo studies regarding the pharmacokinetics and toxicological properties of acyclic monoterpenes so as to better establish the clinical relevance of their use.

CYP1B1: A Promising Target in Cancer Drug Discovery.

CYP1B1 plays an essential role in cancer's pathogenesis since it activates procarcinogens. Significantly, this enzyme catalyzes the hydroxylation of 17β-estradiol, leading to carcinogenic metabolites involved in carcinogenesis and cancer progression. Therefore, the inhibition of CYP1B1 activity is considered a therapeutic target for chemotherapy. In addition, CYP1B1 is overexpressed in hormone-dependent cancer cells and could be related to resistance to anticancer drugs. However, the activity of CYP1B1 in the tumor microenvironment can metabolize and activate prodrugs in cancer cells, providing more selectivity and being useful for chemoprevention or chemotherapy strategies. Furthermore, due to its importance in anticancer drug design, recent studies have reported using computational methods to understand the intermolecular interactions between possible ligands and CYP1B1. Therefore, in this perspective, we highlight recent findings in developing CYP1B1 inhibitors (flavonoids, trans-stilbenes, estradiol derivatives, and carbazoles) and CYP1B1-activated prodrugs (a chalcone DMU-135 and an oxime DMAKO-20). Finally, we have analyzed their possible molecular interactions with this enzymatic target by molecular docking, which can help to design new active substances.

Selectivity of osilodrostat as an inhibitor of human steroidogenic cytochromes P450

Osilodrostat (LCI699) is a potent inhibitor of the human steroidogenic cytochromes P450 11β-hydroxylase (CYP11B1) and aldosterone synthase (CYP11B2). LCI699 is FDA-approved for the treatment of Cushing disease, which is characterized by chronic overproduction of cortisol. While phase II and III clinical studies have proven the clinical efficacy and tolerability of LCI699 for treating Cushing disease, few studies have attempted to fully assess the effects of LCI699 on adrenal steroidogenesis. To this end, we first comprehensively analyzed LCI699-mediated inhibition of steroid synthesis in the NCI-H295R human adrenocortical cancer cell line. We then studied LCI699 inhibition using HEK-293 or V79 cells stably expressing individual human steroidogenic P450 enzymes. Our studies using intact cells confirm the potent inhibition of CYP11B1 and CYP11B2 with negligible inhibition of 17-hydroxylase/17,20-lyase (CYP17A1) and 21-hydroxylase (CYP21A2). Furthermore, partial inhibition of the cholesterol side-chain cleavage enzyme (CYP11A1) was observed. To calculate the dissociation constant (Kd) of LCI699 with the adrenal mitochondrial P450 enzymes, we successfully incorporated P450s into lipid nanodiscs and carried out spectrophotometric equilibrium and competition binding assays. Our binding experiments confirm the high affinity of LCI699 to CYP11B1 and CYP11B2 (Kd ≈ 1 nM or less) and much weaker binding for CYP11A1 (Kd = 18.8 μM). Our results confirm the selectivity of LCI699 for CYP11B1 and CYP11B2 and demonstrate partial inhibition of CYP11A1 but not CYP17A1 and CYP21A2.