scholarly journals The metabolism of amiodarone by various CYP isoenzymes of human and rat, and the inhibitory influence of ketoconazole

2008 ◽  
Vol 11 (1) ◽  
pp. 147 ◽  
Author(s):  
Marwa E. Elsherbiny ◽  
Ayman O.S. El-Kadi ◽  
Dion R. Brocks
Keyword(s):  
Cytochrome P450 ◽  
Inhibitory Effect ◽  
Intrinsic Clearance ◽  
Significant Inhibition ◽  
Inhibitory Influence ◽  
Relative Kinetic ◽  
Cyp Isoforms ◽  
High Concentrations ◽  
In Vivo Administration

PURPOSE. To evaluate the metabolism of amiodarone (AM) to desethylamiodarone (DEA) by selected human and rat cytochrome P450, and the inhibitory effect of ketoconazole (KTZ). METHODS. Some important CYP isoenzymes (rat CYP1A1, 1A2, 2C6, 2C11, 2D1, 2D2, and 3A1 and human CYP1A1, 1A2, 2D6 and 3A4) were spiked with various concentrations of AM to determine the relative kinetic parameters for formation of DEA in the presence and absence of various concentrations of KTZ. RESULTS. The formation of DEA was observed when AM was exposed to each of the CYP tested, although the rates were varied. Human CYP1A1 followed by 3A4 had the highest intrinsic clearance (CLint) for DEA formation whereas in rat, CYP2D1 followed by CYP2C11 had the highest CLint. Human and rat CYP1A2 seemed to have the lowest CLint. At high concentrations of AM and KTZ, near those expected in vivo, significant inhibition of all isoforms except for rat CYP1A2 was observed. At lower concentration ranges of both drugs, the inhibitory constant was determined. At these levels, KTZ was found to potently inhibit human CYP1A1 and 3A4 and rat 2D2 and 1A1. CONCLUSION. Human CYP1A1 and 3A4 and rat CYP2D1 and 2C11 were most efficient in converting AM to DEA. For DEA formation, the in vivo administration of KTZ could inhibit other CYP isoforms besides CYP3A in human and rat.

scholarly journals In vitro inhibition of porcine cytochrome P450 by 17β-estradiol and 17α-estradiol

2011 ◽  
Vol 4 (2) ◽  
pp. 78-84 ◽  
Author(s):  
Galia Zamaratskaia ◽  
Martin Rasmussen ◽  
Isabelle Herbin ◽  
Bo Ekstrand ◽  
Vladimir Zlabek
Keyword(s):  
Cytochrome P450 ◽  
Inhibitory Effect ◽  
17Β Estradiol ◽  
Cyp2e1 Activity ◽  
High Concentrations ◽  
Testicular Steroids ◽  
Sexually Mature

In vitro inhibition of porcine cytochrome P450 by 17β-estradiol and 17α-estradiol Sexually mature pigs are known to possess high concentrations of testicular steroids, which have been shown to change the activities of cytochrome P450 in vitro. The aim of the present study was to evaluate the regulation of CYP1A and CYP2E1 activity by the steroids dihydrotestosterone (DHT), 3β-androstenol, 17β-estradiol and 17α-estradiol. Catalytic activities of 7-ethoxyresorufin O-deethylase (EROD) and 7-methoxyresorufin O-demethylase (MROD) were used as markers of CYP1A activities, while p-nitrophenol hydroxylase (PNPH) was used as a marker of CYP2E1 activities. Of the steroids tested, only 17β-estradiol and 17α-estradiol inhibited EROD and MROD activities. This inhibition was observed when a steroid concentration of 100 μM was used, while lower concentrations showed no inhibitory effect. PNPH activities were inhibited only by 100 μM of 17β-estradiol. The significance of these results in vivo is unknown because inhibition was only found when concentrations of estrogens higher than physiological levels were used. Nevertheless, the results provided further evidence on the important role of estrogens in regulation of porcine cytochrome P450 activities.

Neopterin-induced Suppression of Erythropoietin Production In Vitro

Pteridines ◽  
1995 ◽  
Vol 6 (1) ◽  
pp. 12-16 ◽  
Author(s):  
W. Schobersberger ◽  
W. Jelkmann ◽  
J. Fandrey ◽  
S. Frede ◽  
H. Wachter ◽  
...  
Keyword(s):  
Inhibitory Effect ◽  
Inhibitory Influence ◽  
Mrna Levels ◽  
Dependent Manner ◽  
Anemia Of Chronic Disease ◽  
Erythropoietin Production ◽  
High Concentrations ◽  
Dose Dependent

Summary The production of neopterin increases in several diseases with activation of the ceIlular immune response. As previously shown serum concentrations of neopterin are inversely correlated with blood hemoglobin concentrations in the anemia of hematological and malignant disorders. Besides the role of chronic immune activation on the disturbed iron metabolism, an inhibitory influence of pteridines on cellular erythropoietin production could not be excluded. To test the possibility that pteridines are able to suppress the hypoxia-induced production of erythropoietin, the effects of neopterin and 7,8-dihydroneopterin on the human ceIl line HepG2 (hepatoceIlular carcinoma) were investigated. 24 h incubation with neopterin induced a dose-dependent reduction of erythropoietin production. The erythropoietin concentration significantly decreased by - 57.6% with 300 11M and by - 34.9% with 100 11M neopterin, respectively. 7,8 dihydroneopterin did not influence erythropoietin production. The inhibitory effect of neopterin on erythropoietin production was a consequence of reduced erythropoietin-mRNA levels. The results of this study show a neopterin-induced suppression of hypoxia-induced erythropoietin formation in HepG2 cultures in a dose dependent manner. We speculate that under in vivo conditions high concentrations of neopterin can aggravate the anemia of chronic disease.

scholarly journals Inhibition of Cytochrome P450 (CYP450) Isoforms by Isoniazid: Potent Inhibition of CYP2C19 and CYP3A

2001 ◽  
Vol 45 (2) ◽  
pp. 382-392 ◽  
Author(s):  
Zeruesenay Desta ◽  
Nadia V. Soukhova ◽  
David A. Flockhart
Keyword(s):  
Cytochrome P450 ◽  
Liver Microsomes ◽  
Cost Effective ◽  
Competitive Inhibitor ◽  
Inhibitory Effect ◽  
Significant Inhibition ◽  
Specific Substrate ◽  
Dependent Manner ◽  
Concentration Dependent Manner ◽  
The Mean

ABSTRACT Isoniazid (INH) remains the most safe and cost-effective drug for the treatment and prophylaxis of tuberculosis. The use of INH has increased over the past years, largely as a result of the coepidemic of human immunodeficiency virus infection. It is frequently given chronically to critically ill patients who are coprescribed multiple medications. The ability of INH to elevate the concentrations in plasma and/or toxicity of coadministered drugs, including those of narrow therapeutic range (e.g., phenytoin), has been documented in humans, but the mechanisms involved are not well understood. Using human liver microsomes (HLMs), we tested the inhibitory effect of INH on the activity of common drug-metabolizing human cytochrome P450 (CYP450) isoforms using isoform-specific substrate probe reactions. Incubation experiments were performed at a single concentration of each substrate probe at its Km value with a range of INH concentrations. CYP2C19 and CYP3A were inhibited potently by INH in a concentration-dependent manner. At 50 μM INH (∼6.86 μg/ml), the activities of these isoforms decreased by ∼40%. INH did not show significant inhibition (<10% at 50 μM) of other isoforms (CYP2C9, CYP1A2, and CYP2D6). To accurately estimate the inhibition constants (Ki values) for each isoform, four concentrations of INH were incubated across a range of five concentrations of specific substrate probes. The meanKi values (± standard deviation) for the inhibition of CYP2C19 by INH in HLMs and recombinant human CYP2C19 were 25.4 ± 6.2 and 13 ± 2.4 μM, respectively. INH showed potent noncompetitive inhibition of CYP3A (Ki = 51.8 ± 2.5 to 75.9 ± 7.8 μM, depending on the substrate used). INH was a weak noncompetitive inhibitor of CYP2E1 (Ki = 110 ± 33 μM) and a competitive inhibitor of CYP2D6 (Ki = 126 ± 23 μM), but the mean Ki values for the inhibition of CYP2C9 and CYP1A2 were above 500 μM. Inhibition of one or both CYP2C19 and CYP3A isoforms is the likely mechanism by which INH slows the elimination of coadministered drugs, including phenytoin, carbamazepine, diazepam, triazolam, and primidone. Slow acetylators of INH may be at greater risk for adverse drug interactions, as the degree of inhibition was concentration dependent. These data provide a rational basis for understanding drug interaction with INH and predict that other drugs metabolized by these two enzymes may also interact.

Granulocyte Adherence is Inhibited by Radiographic Contrast Media in Vitro

1992 ◽  
Vol 33 (4) ◽  
pp. 379-383 ◽  
Author(s):  
F. Rasmussen ◽  
S. Antonsen ◽  
J. Georgsen
Keyword(s):  
Contrast Media ◽  
Whole Blood ◽  
Inhibitory Effect ◽  
Significant Inhibition ◽  
Autologous Plasma ◽  
Radiographic Contrast ◽  
Radiographic Contrast Media ◽  
Meglumine Diatrizoate ◽  
High Concentrations

Different amounts of diatrizoate, ioxaglate, iohexol, iodixanol, NaCl 1000 mOsm/kg, mannitol 1098 mOsm/kg, and meglumine (meglumine concentrations corresponding to the content in the diatrizoate solutions) were added to either whole blood or a suspension of granulocytes in autologous plasma, and the adherence to nylon fibers was determined. At high concentrations all the investigated contrast media (CM) inhibited granulocyte adherence. The degree of inhibition was significantly greater when the ionic CM diatrizoate and ioxaglate were used, as compared with the nonionic media. Meglumine solutions at high concentrations also inhibited adherence but significantly less than diatrizoate solutions containing the same amount of meglumine. Diatrizoate showed the greatest inhibitory effect on granulocyte adherence, and significant inhibition could be detected even with a 1.25% solution.

In vitro inhibitory effects of glucosamine, chondroitin and diacerein on human hepatic CYP2D6

2021 ◽  
Vol 36 (4) ◽  
pp. 259-270
Author(s):  
Boon Hooi Tan ◽  
Nafees Ahemad ◽  
Yan Pan ◽  
Uma Devi Palanisamy ◽  
Iekhsan Othman ◽  
...  
Keyword(s):  
Cytochrome P450 ◽  
High Performance ◽  
Inhibitory Effect ◽  
Inhibitory Effects ◽  
Time Curve ◽  
Clinical Drugs ◽  
Inhibition Potencies ◽  
P450 2D6

Abstract Objectives Glucosamine, chondroitin and diacerein are natural compounds commonly used in treating osteoarthritis. Their concomitant intake may trigger drug–natural product interactions. Cytochrome P450 (CYP) has been implicated in such interactions. Cytochrome P450 2D6 (CYP2D6) is a major hepatic CYP involved in metabolism of 25% of the clinical drugs. This study aimed to investigate the inhibitory effect of these antiarthritic compounds on CYP2D6. Methods CYP2D6 was heterologously expressed in Escherichia coli. CYP2D6–antiarthritic compound interactions were studied using in vitro enzyme kinetics assay and molecular docking. Results The high-performance liquid chromatography (HPLC)-based dextromethorphan O-demethylase assay was established as CYP2D6 marker. All glucosamines and chondroitins weakly inhibited CYP2D6 (IC50 values >300 µM). Diacerein exhibited moderate inhibition with IC50 and K i values of 34.99 and 38.27 µM, respectively. Its major metabolite, rhein displayed stronger inhibition potencies (IC50=26.22 μM and K i =32.27 μM). Both compounds exhibited mixed-mode of inhibition. In silico molecular dockings further supported data from the in vitro study. From in vitro–in vivo extrapolation, rhein presented an area under the plasma concentration-time curve (AUC) ratio of 1.5, indicating low potential to cause in vivo inhibition. Conclusions Glucosamine, chondroitin and diacerein unlikely cause clinical interaction with the drug substrates of CYP2D6. Rhein, exhibits only low potential to cause in vivo inhibition.

scholarly journals Inhibitory Effect of Lygodium Root on the Cytochrome P450 3A Enzyme in vitro and in vivo

2020 ◽  
Vol Volume 14 ◽  
pp. 1909-1919
Author(s):  
Yunfang Zhou ◽  
Ailian Hua ◽  
Quan Zhou ◽  
Peiwu Geng ◽  
Feifei Chen ◽  
...  
Keyword(s):  
Cytochrome P450 ◽  
Inhibitory Effect ◽  
Cytochrome P450 3A

scholarly journals Inhibition of α-Glucosidase, Intestinal Glucose Absorption, and Antidiabetic Properties by Caralluma europaea

2018 ◽  
Vol 2018 ◽  
pp. 1-8 ◽  
Author(s):  
Hayat Ouassou ◽  
Touda Zahidi ◽  
Saliha Bouknana ◽  
Mohamed Bouhrim ◽  
Hassane Mekhfi ◽  
...  
Keyword(s):  
Ethyl Acetate Fraction ◽  
Inhibitory Effect ◽  
Tolerance Test ◽  
Glucose Absorption ◽  
Significant Inhibition ◽  
Oral Glucose ◽  
Glucosidase Activity ◽  
Intestinal Glucose Absorption

Many medicinal plants around the world are used for therapeutic purposes against several diseases, including diabetes mellitus. Due to their composition of natural substances that are effective and do not represent side effects for users, unlike synthetic drugs, in this study, we investigated the inhibitory effect of Caralluma europaea (CE) on α-glucosidase activity in vitro; then the kinetics of the enzyme were studied with increasing concentrations of sucrose in order to determine the inhibition type of the enzyme. In addition, this effect of Caralluma europaea (CE) was confirmed in vivo using rats as an experimental animal model. Among the five fractions of CE, only the ethyl acetate fraction of C. europaea (EACe) induced a significant inhibition of α-glucosidase and its inhibition mode was competitive. The in vivo studies were conducted on mice and rats using glucose and sucrose as a substrate, respectively, to determine the oral glucose tolerance test (OGTT). The results obtained showed that the EACe and the aqueous extract of C. europaea (AECe) have significantly reduced the postprandial hyperglycemia after sucrose and glucose loading in normal and diabetic rats. AECe, also, significantly decreased intestinal glucose absorption, in situ. The results obtained showed that Caralluma europaea has a significant antihyperglycemic activity, which could be due to the inhibition of α-glucosidase activity and enteric absorption of glucose.

scholarly journals Anti-Nociceptive and Anti-Inflammation Effect Mechanisms of Mutants of Syb-prII, a Recombinant Neurotoxic Polypeptide

Toxins ◽  
2019 ◽  
Vol 11 (12) ◽  
pp. 699
Author(s):  
Chunli Li ◽  
Mengqi Ban ◽  
Fei Bai ◽  
Jianzhao Chen ◽  
Xiaoquan Jin ◽  
...  
Keyword(s):  
Sodium Channel ◽  
Inhibitory Effect ◽  
Significant Inhibition ◽  
Dependent Manner ◽  
Patch Clamp Technique ◽  
Analgesic Effects ◽  
Medicinal Value ◽  
Inflammatory Nociception ◽  
Channel Currents

Syb-prII, a recombinant neurotoxic polypeptide, has analgesic effects with medicinal value. Previous experiments indicated that Syb-prII displayed strong analgesic activities. Therefore, a series of in vivo and vitro experiments were designed to investigate the analgesic and anti-inflammatory properties and possible mechanisms of Syb-prII. The results showed that administered Syb-prII-1 and Syb-prII-2 (0.5, 1, 2.0 mg/kg, i.v.) to mice significantly reduced the time of licking, biting, or flicking of paws in two phases in formalin-induced inflammatory nociception. Syb-prII-1 inhibited xylene-induced auricular swelling in a dose-dependent manner. The inhibitory effect of 2.0 mg/kg Syb-prII-1 on the ear swelling model was comparable to that of 200 mg/kg aspirin. In addition, the ELISA and Western blot analysis suggested that Syb-prII-1 and Syb-prII-2 may exert an analgesic effect by inhibiting the expression of Nav1.8 and the phosphorylation of ERK, JNK, and P38. Syb-prII-1 markedly suppressed the expression of IL-1β, IL-6, and TNF-α of mice in formalin-induced inflammatory nociception. We used the patch-clamp technique and investigated the effect of Syb-prII-1 on TTX-resistant sodium channel currents in acutely isolated rat DRG neurons. The results showed that Syb-prII-1 can significantly down regulate TTX-resistant sodium channel currents. In conclusion, Syb-prII mutants may alleviate inflammatory pain by significantly inhibiting the expression of Nav1.8, mediated by the phosphorylation of MAPKs and significant inhibition of TTX-resistant sodium channel currents.

scholarly journals Development of SGC-GAK-1 as an orally active in vivo probe for cyclin G associated kinase through cytochrome P450 inhibition

2019 ◽  
Author(s):  
Christopher R. M. Asquith ◽  
James M. Bennett ◽  
Lianyong Su ◽  
Tuomo Laitinen ◽  
Jonathan M. Elkins ◽  
...  
Keyword(s):  
Cytochrome P450 ◽  
Liver Microsomes ◽  
Intrinsic Clearance ◽  
In Vivo Studies ◽  
Chemical Probe ◽  
Active Chemical ◽  
Rapid Clearance ◽  
Cyclin G ◽  
Orally Active

AbstractSGC-GAK-1 (1), a potent, selective, cell-active chemical probe for cyclin G associated kinase (GAK), was rapidly metabolized in mouse liver microsomes by P450 mediated oxidation. 1 displayed rapid clearance in mice, limiting its utility for in vivo studies. All chemical modifications of 1 that improved metabolic stability led to a loss in GAK activity. However, pretreatment of liver microsomes with the irreversible cytochrome P450 inhibitor 1-aminobenzotriazole (ABT) decreased intrinsic clearance of 1. Coadministration of ABT also greatly improved plasma exposure of 1 in mice, supporting its use as a chemical probe to study the in vivo biology of GAK inhibition.

Effects of triiodothyronine, triiodothyroacetic acid, iopanoic acid and iodide on the thyrotropin-releasing hormone-induced thyrotropin release from superfused rat pituitary fragments

1991 ◽  
Vol 125 (4) ◽  
pp. 427-434 ◽  
Author(s):  
I. Szaboles ◽  
H. Schultheiss ◽  
H. Astier ◽  
F. A. Horster
Keyword(s):  
Potassium Iodide ◽  
Inhibitory Effect ◽  
Thyrotropin Releasing Hormone ◽  
Detectable Effect ◽  
Releasing Hormone ◽  
Iopanoic Acid ◽  
Rat Pituitary ◽  
High Concentrations

Abstract. The effects of triiodothyronine, triiodothyroacetic acid, iopanoic acid and potassium iodide were investigated on basal and stimulated thyrotropin release in an in vitro experimental model. Rat pituitary fragments were superfused by Medium-199 with or without T3 (10−7 mol/l), triiodothyroacetic acid (10−8-10−6 mol/l), iopanoic acid (10−7-10−5 mol/l) or potassium iodide (10−7-10−4 mol/l). This was followed by a 6-min pulse of thyrotropin-releasing hormone (10−8 mol/l). TSH was measured in 3-min fractions. The TRH-induced TSH release from the pituitary fragments was inhibited by T3 (10−7 mol/l), by triiodothyroacetic acid (10−7-10−6 mol/l), and by high concentrations of iodide (10−4 or 10−5 mol/l). Iopanoic acid had no significant effect at the concentrations tested. It is assumed that in vitro, and at similar concentrations, the inhibitory effect of triiodothyroacetic acid on the TRH-induced TSH secretion is comparable to that of T3, whereas iopanoic acid may have no direct detectable effect. In contrast, a direct inhibitory effect of inorganic iodide, at least in pharmacological concentrations in vivo, cannot be excluded.

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