Arachidonic acid (AA) is metabolized to epoxyeicosatrienoic acids (EETs) via cytochrome enzymes such as CYP 2C9, 2C8 and 2J2. EETs play a role in cardioprotection and regulation of blood pressure. Recently, adverse reactions such as sudden heart attack and fatal myocardial infarction were reported among patients taking angiotensin II receptor blockers (ARBs). As some ARBs have affinity for these CYP enzymes, metabolic inhibition of AA by ARBs is a possible cause for the increase in cardiovascular events. In this study, we quantitatively investigated the inhibitory effects of ARBs on the formation of EETs and further metabolites, dihydroxyeicosatrienoic acids (DHETs), from AA via CYP2C8. In incubations with recombinant CYP2C8 in vitro, the inhibitory effects were compared by measuring EETs and DHETs by HPLC-MS/MS. Inhibition of AA metabolism by ARBs was detected in a concentration-dependent manner with IC 50 values of losartan (42.7 µM), telmisartan (49.5 µM), irbesartan (55.6 µM), olmesartan (66.2 µM), candesartan (108 µM), and valsartan (279 µM). Losartan, telmisartan and irbesartan, which reportedly accumulate in the liver and kidneys, have stronger inhibitory effects than other ARBs. The lower concentration of EETs leads to less protective action on the cardiovascular system and a higher incidence of adverse effects such as sudden heart attack and myocardial infarction in patients taking ARBs.Key words epoxyeicosatrienoic acid; arachidonic acid; drug-endogenous interaction; angiotensin II receptor blocker; dihydroxyeicosatrienoic acid Arachidonic acid (AA), a component of the cell membrane, is known to be metabolized to prostaglandins, thromboxaneA 2 , leukotrienes and other bioactive substances 1) (Fig. 1). AA is also metabolized to epoxyeicosatrienoic acids (EETs) via cytochrome P450 isoforms such as CYP 2C9, 2C8 and 2J2, and is further converted to the corresponding dihydroxyeicosatrienoic acids (DHETs) by soluble epoxide hydrolase (sEH).2-7) There are four structural isomers, 14,15-, 11,12-, 8,9-and 5,6-EET, that are reported to have vasodilatory and anti-inflammatory effects, while endothelium-derived hyperpolarizing factor (EDHF) action has been reported for 14,15-, 11,12-EET, [8][9][10][11][12] preconditioning effects have been reported for 14,15-EET, 13) and blood pressure regulating effects have been reported for 11,12-EET. 14)Totah and Rettie reported that CYP2C8, which constitutes about 7% of total microsomal CYP content in the human liver, appears to be important for metabolizing AA.15) CYP2C8 mainly generates 14,15-, 11,12-EET from AA, and the ratio of 14,15-EET : 11,12-EET is reported to be 1.25 : 1. 11) These results suggest that cardiovascular events such as hypertension and myocardial infarction are caused by decreased concentrations of these EETs.Angiotensin II receptor blockers (ARBs) are used for hypertensive patients with diabetes because of their cardio-and renoprotective effects. However, effects of ARBs other than the lowering of hypertension have recently been reported. 16)In a meta-a...
Cytochrome P450 (CYP) 2C9, CYP2C8 and CYP2J2 enzymes, which metabolize arachidonic acid (AA) to epoxyeicosatrienoic acids, have cardioprotective effects including anti-inflammation and vasodilation. We have recently shown that some angiotensin II receptor blockers (ARBs) may inhibit AA metabolism via CYP2C8. Using recombinant CYP2C9, CYP2J2 and human liver microsomes (HLMs), the aim was now to compare the ability of six different clinically used ARBs to inhibit AA metabolism in vitro. The rank order of the ARBs for the 50% inhibitory concentration (IC ) of AA metabolism was losartan
Epoxyeicosatrienoic acids (EETs) are produced primarily by CYPs from arachidonic acid (AA) and then further metabolized to the corresponding dihydroxyeicosatrienoic acids (DHETs). EETs play important roles in physiological processes such as regulating vasodilation and inflammation. Thus, the drug inhibition of CYP-mediated AA metabolism could reduce production of EETs, potentially resulting in adverse cardiovascular events. The aim of this study was to develop a simple method to simultaneously determine the concentrations of both EETs and DHETs using a conventional LC-MS/MS system to evaluate drug-endogenous substance interactions, including eicosanoids. Eight eicosanoids (5,6-EET, 8,9-EET, 11,12-EET, 14,15-EET, 5,6-DHET, 8,9-DHET, 11,12-DHET, and 14,15-DHET) were detected with their corresponding deuteriumlabeled eicosanoids as internal standards. The samples were purified by solid-phase extraction columns. Liquid chromatographic separation was achieved on a C18 column. DHETs and EETs were eluted at 4-7 and 18-26 min, respectively. The weighted (1/y 2 ) calibration curves were linear over a range of 5-2000 nmol/L for EETs and 2-2000 nmol/L for DHETs. In quality control (QC) samples, the recoveries of eicosanoids were 95.2-118%. The intra-day precisions were within 6% in all three QC samples, and the inter-day precisions were <16.7% at 50 nmol/L, <8.6% at 200 nmol/L, and <9.8% at 1000 nmol/L. We have applied this method for the determination of the eicosanoid levels in samples from incubation studies of AA by using human recombinant CYP enzyme (rCYP), and confirmed that the method has sensitivity sufficient for assessment of rCYP incubation study.Key words epoxyeicosatrienoic acid; dihydroxyeicosatrienoic acid; arachidonic acid; LC-MS/MS Arachidonic acid (AA) is metabolized to various eicosanoids via several pathways.1) These eicosanoids play important roles in physiological processes, including the regulation of inflammation.2-5) Three major metabolic pathways for conversion of AA to eicosanoids are recognized, including routes that incorporate cyclooxygenase (COX), lipoxygenase (LOX), and CYP.6) The CYP pathway, which is mediated primarily by CYP2C9, CYP2C8, and CYP2J2, produces epoxyeicosatrienoic acids (EETs) and hydroxyeicosatetraenoic acids (HETEs). 7,8) EETs exist as one of 4 regioisomers (5,6-EET, 8,9-EET, 11,12-EET, and 14,15-EET), depending on the location of the epoxidized residue. Each EET is substantially metabolized to its corresponding diol, a dihydroxyeicosatrienoic acid (DHET), by soluble epoxide hydrolase (sEH).1,9-12) The EETs have been shown to play important roles on cardiovascular homeostasis. [13][14][15] Thus, the drug inhibition of CYP-mediated AA metabolism via could reduce production of EETs, potentially resulting adverse cardiovascular events.Traditional analytical methods such as HPLC or capillary electrophoresis with UV or fluorescence detection, 16,17) and GC-MS 18) lack sufficient sensitivity to detect the low levels of AA metabolites typically found in physiological matrices. Sev...
The cytochrome P450 (CYP) 2C8*3 allele is associated with reduced metabolic activity of paclitaxel. This study was aimed to investigate the inhibitory effect of losartan on paclitaxel metabolism in human liver microsomes (HLMs) and to determine the impact of the CYP2C8*3 polymorphism. HLMs that contained the CYP2C8*1 homozygote (HL60) or CYP2C8*3 heterozygote (HL54) genotype were used for the inhibition study. Losartan, at a concentration of 50 lmol/L, significantly inhibited paclitaxel metabolism by 29% and 57% in the HL60 (p < 0.001) and HL54 (p < 0.01), respectively. When using HL60, losartan and the CYP3A4-selective inhibitors, erythromycin and ketoconazole, caused a greater inhibition of the paclitaxel metabolism than quercetin, a CYP2C8-selective inhibitor. This demonstrated that the paclitaxel metabolism was mainly catalysed by CYP3A4 in HL60. There were no significant differences found for the inhibitory effects caused by the four inhibitors of the paclitaxel metabolism in HL54, indicating that both CYP2C8 and CYP3A4 play important roles in paclitaxel metabolism in HL54. These findings suggest that 50 lmol/L of losartan inhibits both CYP2C8 and CYP3A4 in HLMs. In summary, losartan inhibited paclitaxel metabolism, with concentrations over 50 lmol/L in HLMs. The CYP2C8*3 allele carriers are likely susceptible to the interactions of losartan and CYP3A4 inhibitors to paclitaxel metabolism.Paclitaxel, a frequently used anticancer drug, is primarily metabolized to 6a-hydroxypaclitaxel by cytochrome P450 (CYP) 2C8 [1][2][3][4]. Studies have reported that both plasma concentration and the area under the concentration-time curve (AUC) of paclitaxel are correlated with its toxicity [5,6]. Therefore, interindividual variability of paclitaxel clearance should be taken into consideration to avoid paclitaxel adverse events. Previous studies have shown that genetic variants of CYP2C8, especially CYP2C8*3, can cause reduced metabolism to 6a-hydroxypaclitaxel in vitro [7][8][9]. In the ovarian cancer patients with the CYP2C8*3 allele, it has been shown that the clearance of paclitaxel is lower than that found for individuals with the CYP2C8*1 homozygote [5,10]. Therefore, AUC of paclitaxel is considered to be higher than those with CYP2C8*1 homozygote. Leskel€ a [11] et al. have reported that CYP2C8*3 was associated with paclitaxel neurotoxicity in Spanish cancer patients.The inhibition of paclitaxel metabolism by drug-drug interactions in relation to the CYP2C8 genotypes needs to be clarified, as concomitant drug administration could possibly cause further increases in the AUC for paclitaxel in individuals with the CYP2C8*3 allele. However, little is currently known about the drugÀdrug interactions for paclitaxel in relation to the CYP2C8 genotypes.Losartan, an angiotensin II receptor blocker, is primarily metabolized to its active metabolite, EXP-3174, by CYP2C9 in addition to being partially metabolized by CYP3A4 [12]. The maximum plasma concentration of losartan after a 7-day oral administration of 100 mg h...
The aim of the present study was to further investigate a previously identified metabolic interaction between losartan and paclitaxel, which is one of the marker substrates of CYP2C8, by using human liver microsomes (HLMs) from donors with different CYP2C8 and CYP2C9 genotypes. Although CYP2C8 and CYP2C9 exhibit genetic linkage, previous studies have yet to determine whether losartan or its active metabolite, EXP-3174 which is specifically generated by CYP2C9, is responsible for CYP2C8 inhibition. Concentrations of 6a-hydroxypaclitaxel and EXP-3174 were measured by high-performance liquid chromatography after incubations with paclitaxel, losartan or EXP-3174 in HLMs from seven donors with different CYP2C8 and CYP2C9 genotypes. The half maximal inhibitory concentration (IC 50 ) values were not fully dependent on CYP2C8 genotypes. Although the degree of inhibition was small, losartan significantly inhibited the production of 6a-hydroxypaclitaxel at a concentration of 1 lmol/L in only HL20 with the CYP2C8*3/*3 genotype. HLMs with either CYP2C9*2/*2 or CYP2C9*1/*3 exhibited a lower losartan intrinsic clearance (V max /K m ) than other HLMs including those with CYP2C9*1/*1 and CYP2C9*1/*2. Significant inhibition of 6a-hydroxypaclitaxel formation by EXP-3174 could only be found at levels that were 50 times higher (100 lmol/L) than the maximum concentration generated in the inhibition study using losartan. These results suggest that the metabolic interaction between losartan and paclitaxel is dependent on losartan itself rather than its metabolite and that the CYP2C8 inhibition by losartan is not affected by the CYP2C9 genotype. Further study is needed to define the effect of CYP2C8 genotypes on losartan-paclitaxel interaction.Cytochrome P450 (CYP) 2C8 is one of the major hepatic CYPs with polymorphic variants that can catalyse at least 5% of the oxidative metabolism drugs such as paclitaxel and pioglitazone [1]. CYP2C8*2 and CYP2C8*3 are relatively common allelic variants that cause amino acid substitutions [1]. Gao et al. [2] have reported that the inhibition of CYP2C8 by various drugs appeared to be influenced by CYP2C8 genetic polymorphisms, even though the effects for the half maximal inhibitory concentration (IC 50 ) of several CYP2C8 inhibitors in the recombinant expression system were quite small. Aquilante et al. [3] have recently reported that gemfibrozil, which is one of the strong inhibitors of CYP2C8, caused a 5.2 times mean increase in the area under the concentration-time curve (AUC) of pioglitazone in individuals with CYP2C8*3, whereas only a 3.3 times mean increase was observed for the CYP2C8*1 homozygotes. In 10 individuals exhibiting the largest relative increases in the pioglitazone AUC, 8 were found to be CYP2C8*3 carriers [3]. Although these findings suggest that the CYP2C8 genotypes affect the drug-drug interaction, there has been little information reported on the effects of the CYP2C8 variants on drug-drug interactions.We have recently reported that losartan, a substrate of CYP2C9, co...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.