Verapamil: metabolism in cultures of primary human coronary arterial endothelial cells

Pharmacogenomic study-A pilot study of the effect of pharmacogenomic phenotypes on the adequate dosing of verapamil for migraine prevention

OBJECTIVE

To investigate factors affecting the efficacy and tolerability of verapamil for migraine prevention using individual pharmacogenomic phenotypes.

BACKGROUND

Verapamil has a wide range of dosing in headache disorders without reliable tools to predict the optimal doses for an individual.

METHODS

This is a retrospective chart review examining adults with existing pharmacogenomic reports at Mayo Clinic who had used verapamil for migraine. Effects of six cytochrome P450 phenotypes on the doses of verapamil for migraine prevention were assessed.

RESULTS

Our final analysis included 33 migraine patients (82% with aura). The mean minimum effective and maximum tolerable doses of verapamil were 178.2(20-320) mg and 227.9(20-480) mg. A variety of CYP2C9, CYP2D6, and CYP3A5 phenotypes were found, without significant association with the verapamil doses after adjusting for age, sex, body mass index, and smoking status.

CONCLUSIONS

We demonstrated a wide range of effective and tolerable verapamil doses used for migraine in a cohort with various pharmacogenomic phenotypes.

Genetic and Enzymatic Characteristics of CYP2A13 in Relation to Lung Damage

Cytochrome P450 2A13 is an omitted brother of CYP2A6 that has an important role in the drug metabolism of liver. Due to extrahepatic expression, it has gained less attention than CYP2A6, despite the fact that it plays a significant role in toxicant-induced pulmonary lesions and, therefore, lung cancer. The purpose of this mini-review is to summarize the basic knowledge about this enzyme in relation to the substrates, inhibitors, genetic polymorphisms, and transcriptional regulation that are known so far (September 2021).

Pharmacogenomics in Papua New Guineans: unique profiles and implications for enhancing drug efficacy while improving drug safety

Papua New Guinea (PNG) can be roughly divided into highland, coastal and island peoples with significant mitochondrial DNA differentiation reflecting early and recent distinct migrations from Africa and East Asia, respectively. Infectious diseases such as tuberculosis, malaria and HIV severely impact on the health of its peoples for which drug therapy is the major treatment and pharmacogenetics has clinical relevance for many of these drugs. Although there is generally little information about known single nucleotide polymorphisms in the population, in some instances, their frequencies have been shown to be higher than anywhere worldwide. For example, CYP2B6*6 is over 50%, and CYP2C19*2 and *3 are over 40 and 25%, respectively. Conversely, CYP2A6*9, 2B6*2, *3, *4 and *18, and 2C8*3 appear to be much lower than in Whites. CYP2D6 known variants are unclear, and for phase II enzymes, only UGT2B7 and UGT1A9 data are available, with variant frequencies either slightly lower than or similar to Whites. Although almost all PNG people tested are rapid acetylators, but which variant(s) define this phenotype is not known. For HLA-B*13:01, HLA-B*35:05 and HLA-C*04:01, the frequencies show some regioselectivity, but the clinical implications with respect to adverse drug reactions are not known. There are minimal phenotype data for the CYPs and nothing is known about drug transporter or receptor genetics. Determination of genetic variants that are rare in Whites or Asians but common in PNG people is a topic of both scientific and clinical importance, and further research needs to be carried out. Optimizing the safety and efficacy of infectious disease drug therapy through pharmacogenetic studies that have translation potential is a priority.

Altered Protein Expression of Cardiac CYP2J and Hepatic CYP2C, CYP4A, and CYP4F in a Mouse Model of Type II Diabetes-A Link in the Onset and Development of Cardiovascular Disease?

Arachidonic acid can be metabolized by cytochrome P450 (CYP450) enzymes in a tissue- and cell-specific manner to generate vasoactive products such as epoxyeicosatrienoic acids (EETs-cardioprotective) and hydroxyeicosatetraenoic acids (HETEs-cardiotoxic). Type II diabetes is a well-recognized risk factor for developing cardiovascular disease. A mouse model of Type II diabetes (C57BLKS/J-db/db) was used. After sacrifice, livers and hearts were collected, washed, and snap frozen. Total proteins were extracted. Western blots were performed to assess cardiac CYP2J and hepatic CYP2C, CYP4A, and CYP4F protein expression, respectively. Significant decreases in relative protein expression of cardiac CYP2J and hepatic CYP2C were observed in Type II diabetes animals compared to controls (CYP2J: 0.80 ± 0.03 vs. 1.05 ± 0.06, n = 20, p < 0.001); (CYP2C: 1.56 ± 0.17 vs. 2.21 ± 0.19, n = 19, p < 0.01). In contrast, significant increases in relative protein expression of both hepatic CYP4A and CYP4F were noted in Type II diabetes mice compared to controls (CYP4A: 1.06 ± 0.09 vs. 0.18 ± 0.01, n = 19, p < 0.001); (CYP4F: 2.53 ± 0.22 vs. 1.10 ± 0.07, n = 19, p < 0.001). These alterations induced by Type II diabetes in the endogenous pathway (CYP450) of arachidonic acid metabolism may increase the risk for cardiovascular disease by disrupting the fine equilibrium between cardioprotective (CYP2J/CYP2C-generated) and cardiotoxic (CYP4A/CYP4F-generated) metabolites of arachidonic acid.

Antihypertensive drugs metabolism: an update to pharmacokinetic profiles and computational approaches

Drug discovery and development is a high-risk enterprise that requires significant investments in capital, time and scientific expertise. The studies of xenobiotic metabolism remain as one of the main topics in the research and development of drugs, cosmetics and nutritional supplements.

Antihypertensive drugs are used for the treatment of high blood pressure, which is one the most frequent symptoms of the patients that undergo cardiovascular diseases such as myocardial infraction and strokes. In current cardiovascular disease pharmacology, four drug clusters - Angiotensin Converting Enzyme Inhibitors, Beta-Blockers, Calcium Channel Blockers and Diuretics - cover the major therapeutic characteristics of the most antihypertensive drugs. The pharmacokinetic and specifically the metabolic profile of the antihypertensive agents are intensively studied because of the broad inter-individual variability on plasma concentrations and the diversity on the efficacy response especially due to the P450 dependent metabolic status they present.

Several computational methods have been developed with the aim to: (i) model and better understand the human drug metabolism; and (ii) enhance the experimental investigation of the metabolism of small xenobiotic molecules. The main predictive tools these methods employ are rule-based approaches, quantitative structure metabolism/activity relationships and docking approaches.

This review paper provides detailed metabolic profiles of the major clusters of antihypertensive agents, including their metabolites and their metabolizing enzymes, and it also provides specific information concerning the computational approaches that have been used to predict the metabolic profile of several antihypertensive drugs.

N-demethylation and N-oxidation of imipramine in rat thoracic aortic endothelial cells

The aim of this study was to examine whether cultured rat thoracic aortic endothelial cells (TAECs) have the ability to metabolize the tertiary amine, imipramine. In rat TAECs, imipramine was biotransformed into N-demethylate and N-oxide by cytochrome P450 (CYP) and flavin-containing monooxygenase (FMO), respectively. The intrinsic clearance (V max/K m) for the N-oxide formation was approximately five times as high as that for the N-demethylate formation, indicating that oxidation by CYP was much higher than that by FMO. Moreover, we suggest that CYP2C11 and CYP3A2 are key players in the metabolism to N-demethylate in rat TAECs using the respective anti-rat CYP antibodies (anti-CYP2C11 and anti-CYP3A2). The presence of CYP2C11 and CYP3A2 proteins was also confirmed in cultured rat TAECs using a polyclonal anti-CYP antibody and immunofluorescence microscopy. In contrast, the formation rate of N-oxide at pH 8.4 was higher than that at pH 7.4. Inhibition of N-oxide formation by methimazole was found to be the best model of competitive inhibition yielding an apparent K i value of 0.80 μmol/L, demonstrating that N-oxidation was catalyzed by FMO in rat TAECs. These results suggest that rat TAEC enzymes can convert substrates of exogenous origin such as imipramine, indicating that TAECs have an important function for metabolic products, besides hepatic cells.

Roles of the epoxygenase CYP2J2 in the endothelium

Cytochrome p450 (CYP)2J2 is an epoxygenase enzyme that metabolises arachidonic acid to epoxyeicosatrienoic acids (EETs). EETs are inactivated by soluble epoxide hydrolase (sEH), which converts them in to their corresponding dihydroxyeicosatrienoic acids (DHETs). CYP2J2 is highly expressed in cardiovascular tissue including the heart and vascular endothelial cells. CYP2J2 and the EETs it produces have been shown to have a diverse range of effects on the vasculature, including the regulation of inflammation, vascular tone, cellular proliferation, angiogenesis, and metabolism. This review will examine these established and emerging roles of CYP2J2 in the biology of vascular endothelial cells.

Expression and inducibility of CYP1A1, 1A2, 1B1 by β-naphthoflavone and CYP2B22, CYP3As by rifampicin in heart regions and coronary arteries of pig

In this study, the constitutive and inducible expression of the CYP genes (1A1, 1A2, 1B1, 2B22, 3A22, 3A29 and 3A46), related transcriptional factors (AhR, CAR, PXR, and Nrf2) and the antioxidant enzymes SOD, catalase, GSSH-reductase and GSH-peroxidase were investigated in the liver, heart regions and coronary arteries of control pigs and pigs treated with β-naphthoflavone (βNF) or with rifampicin (RIF). Real-time PCR experiments and enzymatic or immunoblot assays showed that CYP1A1 was predominantly enhanced by βNF in a similar manner in all the heart regions, whereas antioxidant enzyme activity was not affected. The rifampicin treatment resulted in an induction of CYP2B22 and CYP3As, at the transcriptional, activity and protein level in liver but not in heart nor in the coronary arteries, despite the expression of CAR and PXR in the cardiac tissues. These results obtained in vivo suggest that pig cardiac tissues may represent a useful model for humans.

Deletion of the NADPH-cytochrome P450 reductase gene in cardiomyocytes does not protect mice against doxorubicin-mediated acute cardiac toxicity

A genetic mouse model (designated cardiomyocyte-Cpr-null) with cardiomyocyte-specific deletion of the cytochrome P450 (P450) reductase (Cpr) gene was generated in this study. CPR protein levels, as well the enzyme activity of P450s, were greatly reduced in heart microsomes from the null mice compared with wild-type mice, whereas CPR expression in other organs remained unchanged. Nonetheless, homozygous null mice were normal in appearance, gross anatomy, tissue morphology, and general cardiac functional parameters, and there was no indication of embryonic lethality or premature mortality in contrast to the recognized role of CPR in embryonic development. Thus, this new mouse model should be useful for determination of the in vivo roles of cardiomyocyte CPR and CPR-dependent enzymes, including microsomal P450s, not only in the metabolism and toxicity of numerous xenobiotic compounds but also in cardiac pathophysiology. As a first application, we studied the role of cardiomyocyte CPR and CPR-dependent enzymes in doxorubicin (Dox)-mediated acute cardiotoxicity. Wild-type and null mice were treated with a single i.p. dose of Dox at 5, 10, or 20 mg/kg. The Dox treatment caused apoptosis and vacuolization in cardiomyocytes at the dose of 20 mg/kg and a significant increase in the levels of serum creatine kinase at 10 and 20 mg/kg in both wild-type and null mice. However, there was no significant difference in the extent of Dox-induced cardiac injury between the two strains; this lack of difference suggests that cardiomyocyte CPR and CPR-dependent enzymes do not play critical roles in the acute cardiotoxicity induced by Dox.

Selective, competitive and mechanism-based inhibitors of human cytochrome P450 2J2

Twenty five derivatives of the drugs terfenadine and ebastine have been designed, synthesized and evaluated as inhibitors of recombinant human CYP2J2. Compound 14, which has an imidazole substituent, is a good non-competitive inhibitor of CYP2J2 (IC(50)=400nM). It is not selective towards CYP2J2 as it also efficiently inhibits the other main vascular CYPs, such as CYP2B6, 2C8, 2C9 and 3A4; however, it could be an interesting tool to inhibit all these vascular CYPs. Compounds 4, 5 and 13, which have a propyl, allyl and benzo-1,3-dioxole terminal group, respectively, are selective CYP2J2 inhibitors. Compound 4 is a high-affinity, competitive inhibitor and alternative substrate of CYP2J2 (K(i)=160+/-50nM). Compounds 5 and 13 are efficient mechanism-based inhibitors of CYP2J2 (k(inact)/K(i) values approximately 3000Lmol(-1)s(-1)). Inactivation of CYP2J2 by 13 is due to the formation of a stable iron-carbene bond which occurs upon CYP2J2-catalyzed oxidation of 13 with a partition ratio of 18+/-3. These new selective inhibitors should be interesting tools to study the biological roles of CYP2J2.

The role of aryl hydrocarbon receptor in the pathogenesis of cardiovascular diseases

Numerous experimental and epidemiological studies have demonstrated that polycyclic aromatic hydrocarbons (PAHs), which are major constituents of cigarette tobacco tar, are strongly involved in the pathogenesis of the cardiovascular diseases (CVDs). Knowing that PAH-induced toxicities are mediated by the activation of a cytosolic receptor, aryl hydrocarbon receptor (AhR), which regulates the expression of a group of xenobiotic metabolizing enzymes (XMEs) such as CYP1A1, CYP1A2, CYP1B1, NQO1, and GSTA1, suggests a direct link between AhR-regulated XMEs and CVDs. Therefore, identifying the localization and expression of the AhR and its regulated XMEs in the cardiovascular system (CVS) is of major importance in understanding their physiological and pathological roles. Generally, it was believed that the levels of AhR-regulated XMEs are lower in the CVS than in the liver; however, it has been shown that similar or even higher levels of expression are demonstrated in the CVS in a tissue- and species-specific manner. Moreover, most, if not all, AhR-regulated XMEs are differentially expressed in most of the CVS, particularly in the endothelium cells, aorta, coronary arteries, and ventricles. Although the exact mechanisms of PAH-mediated cardiotoxicity are not fully understood, several mechanisms are proposed. Generally, induction of CYP1A1, CYP1A2, and CYP1B1 is considered cardiotoxic through generating reactive oxygen species (ROS), DNA adducts, and endogenous arachidonic acid metabolites. However the cardioprotective properties of NQO1 and GSTA1 are mainly attributed to the antioxidant effect by decreasing ROS and increasing the levels of endogenous antioxidants. This review provides a clear understanding of the role of AhR and its regulated XMEs in the pathogenesis of CVDs, in which imbalance in the expression of cardioprotective and cardiotoxic XMEs is the main determinant of PAH-mediated cardiotoxicity.

Modeling Cardiac Uptake and Negative Inotropic Response of Verapamil in Rat Heart: Effect of Amiodarone

PURPOSE

To determine the effect of the P-glycoprotein (Pgp) modulator amiodarone on the pharmacokinetics and pharmacodynamics (PK/PD) of Pgp substrate verapamil in the perfused rat heart.

METHODS

In Langendorff-perfused rat hearts, the outflow concentration-time curve and inotropic response data were measured after a 1.5 nmol dose of [3H]-verapamil (infused within 1 min) in the absence and presence of the amiodarone (1 microM) in perfusate, as well as using a double dosing regimen (0.75 nmol in a 10 min interval). These data were analyzed by a PK/PD model.

RESULTS

Amiodarone failed to influence the rapid uptake and equilibrium partitioning of verapamil into the heart. The time course of the negative inotropic effect of verapamil, including the 'rebound' above the original baseline after the infusion of verapamil was stopped, could be described by a PK/PD tolerance model. Tolerance development (mean delay time, 12 min) led to a reduction in predicted steady-state effect (16%). The EC50 and Emax values as estimated in single dose experiments were 16.4+/-4.1 nM and 50.5+/-18.9 mmHg, respectively.

CONCLUSIONS

The result does not support the hypothesis that Pgp inhibition by amiodarone increases cardiac uptake of the Pgp substrate verapamil.

Design and synthesis of selective, high-affinity inhibitors of human cytochrome P450 2J2

The active site topology, substrate specificity, and biological roles of the human cytochrome P450 CYP2J2, which is mainly expressed in the cardiovascular system, are poorly known even though recent data suggest that it could be a novel biomarker and potential target for therapy of human cancer. This paper reports a first series of high-affinity, selective CYP2J2 inhibitors that are related to terfenadine, with K(i) values as low as 160nM, that should be useful tools to determine the biological roles of CYP2J2.

CYP2C8 polymorphism among the Portuguese

Cytochrome P450 2C8 (CYP2C8) is a polymorphic phase I drug-metabolising enzyme involved in the metabolism of a wide variety of xenobiotics, as well as a proposed player in the regulation of vascular tone. Polymorphisms in this gene may have an impact on the metabolism of therapeutic drugs such as paclitaxel and verapamil. In this report we have determined the frequencies of the main non-synonymous

Ethanol-Induced Activation of Myosin Light Chain Kinase Leads to Dysfunction of Tight Junctions and Blood-Brain Barrier Compromise

BACKGROUND

Brain endothelial cells form the blood-brain barrier (BBB) that regulates solute and macromolecule flux in and out of the brain, leukocyte migration, and maintains the homeostasis of the central nervous system. BBB dysfunction is associated with disruption of tight junctions (TJ) in the brain endothelium. We propose that alcohol abuse may impair BBB permeability through TJ modification.

METHODS

Primary cultured bovine brain microvascular endothelial cells (BBMEC) were treated with 50 mM ethanol (EtOH), and monolayer tightness was assessed by measurement of transendothelial electrical resistance (TEER). Changes in TEER were correlated with alterations in TJ protein distribution [occludin, zonula occludens-1 (ZO-1), claudin-5] using immunofluorescence (IF). Expression of myosin light chain (MLC) kinase (MLCK), ZO-1, claudin-5, and phosphorylated MLC, occludin and claudin-5 were determined by immunoprecipitation and Western blot. EtOH-induced changes in monocyte migration across in vitro BBB constructs were also examined.

RESULTS

EtOH induced a decrease in TEER of BBMEC monolayers that was reversed by EtOH withdrawal. Treatment of BBMEC with EtOH or its metabolite, acetaldehyde, prior to monocyte application resulted in a 2-fold increase in monocyte migration across the BBB. IF demonstrated decrease in claudin-5 staining, occludin translocation from cell borders to cytoplasm and gap formation in EtOH-treated BBMEC monolayer. These changes paralleled significant increase in phosphorylation of MLC, occludin and claudin-5. EtOH-treated BBMEC showed reduction of total occludin and claudin-5 without changes in ZO-1 or MLC. TEER decrease, changes in occludin/claudin staining, increase in MLC, occludin and claudin-5 phosphorylation and enhanced monocyte migration across the BBB were all reversed by inhibition of MLCK. Inhibition of EtOH metabolism in BBMEC also reversed these events.

CONCLUSION

These results suggest that EtOH activates MLCK leading to phosphorylation of MLC, occludin and claudin-5. Cytoskeletal alterations (MLC) and TJ changes (occludin and claudin-5 phosphorylation) result in BBB impairment (decrease in TEER). TJ compromise is associated with increased monocyte migration across the BBB.

Androgen metabolism in thymus of fetal and adult rats

Cytochrome P450 (P450) monooxygenases play a role in target tissue metabolic activation of xenobiotics and/or endogenous compounds, such as vasoactive molecules or hormones. Indeed, tissue-specific metabolism of steroids is important in a variety of organs, including thymus, and may alter tissue-specific functions. Steroids have been shown to regulate thymus growth and function, but surprisingly little is known about expression of the responsible enzyme systems in thymus tissue, nor is the thymus-specific biotransformation of testosterone known. We therefore investigated gene and protein expression, total protein content, and enzyme activity of major P450 isoforms and other key steroid-metabolizing enzymes in thymus tissue of adult and fetal rats. We detected 6 beta-hydroxytestosterone (HT), 7 alpha-HT, 16 alpha-HT, 2 alpha-HT, and androstenedione to be major testosterone metabolites in the adult thymus. The high production of 7 alpha-HT and 16 alpha-HT correlated well with the gene and protein expression of CYP2A1/2 and CYP2B1/2 in thymus of adult animals. When compared with fetal thymic tissue, CYP2A1/2, 17beta-hydroxysteroid dehydrogenase isoform 1 (17 beta-HSDH1) and the androgen receptor were 8-, 3-, and 3-fold more highly expressed in adult rats, whereas 17 beta-HSDH2, 17 beta-HSDH3, and 5 alpha-reductase were reduced to 12%, 0%, and 32% of those in fetal thymus. In conclusion, we demonstrated that rat thymus expresses a variety of cytochrome P450 monooxygenases and other steroid-metabolizing enzymes, and it successfully metabolizes testosterone. Changes of the underlying steroid-metabolizing enzyme systems may aid in understanding the role of androgens in altering biological functions of the thymus.

Metabolism and Disposition Kinetics of Nicotine

Nicotine is of importance as the addictive chemical in tobacco, pharmacotherapy for smoking cessation, a potential medication for several diseases, and a useful probe drug for phenotyping cytochrome P450 2A6 (CYP2A6). We review current knowledge about the metabolism and disposition kinetics of nicotine, some other naturally occurring tobacco alkaloids, and nicotine analogs that are under development as potential therapeutic agents. The focus is on studies in humans, but animal data are mentioned when relevant to the interpretation of human data. The pathways of nicotine metabolism are described in detail. Absorption, distribution, metabolism, and excretion of nicotine and related compounds are reviewed. Enzymes involved in nicotine metabolism including cytochrome P450 enzymes, aldehyde oxidase, flavin-containing monooxygenase 3, amine N-methyltransferase, and UDP-glucuronosyltransferases are represented, as well as factors affecting metabolism, such as genetic variations in metabolic enzymes, effects of diet, age, gender, pregnancy, liver and kidney diseases, and racial and ethnic differences. Also effects of smoking and various inhibitors and inducers, including oral contraceptives, on nicotine metabolism are discussed. Due to the significance of the CYP2A6 enzyme in nicotine clearance, special emphasis is given to the effects and population distributions of CYP2A6 alleles and the regulation of CYP2A6 enzyme.

CYTOCHROME P4501A INDUCED DIFFERENTIALLY IN ENDOTHELIAL CELLS CULTURED FROM DIFFERENT ORGANS OF ANGUILLA ROSTRATA

Endothelial cells are a structural barrier and an active regulator of many bodily processes. Cytochrome P4501A (CYP1A) activity is induced in the endothelium of teleosts and mammals exposed to lipophilic xenobiotics, such as polycyclic aromatic hydrocarbons, and can have significant consequences for endothelial functions. We exposed cultures of characterized endothelial cells from the heart, kidney, and rete mirabile of the eel, Anguilla rostrata, to aryl hydrocarbon receptor (AhR) agonists. In heart endothelial cells, the maximum response (based on O-deethylation of 7-ethoxyresorufin to resorufin [EROD] activity) to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), 113 pmol/mg/min, was at 1 nM TCDD and the peak response to beta-napthoflavone (betaNF), 135 pmol/mg/min, was at 3 microM betaNF. The maximum response to TCDD in the kidney endothelial cells is 12 pmol/mg/min at 0.3 nM TCDD. The rete mirabile capillary endothelial cells responded minimally or not at all to exposure to TCDD and betaNF. Both the heart and kidney endothelial cells (but not the rete mirabile capillary cells) have a low level of EROD activity (12.7 and 5.2 pmol/mg/min, respectively) in untreated or dimethylsulfoxide-treated cells. The robust response of the heart endothelial cells to induction and the lack of response in the rete mirabile capillary endothelial cells indicate that these cells are a good resource to use to investigate the physiological consequences of AhR agonist exposure and CYP1A induction in different areas of the vasculature.

Growth hormone induces eNOS expression and nitric oxide release in a cultured human endothelial cell line

Growth hormone deficiency is linked to cardiovascular disease and particularly increased peripheral vascular resistance. Surprisingly, its role in endothelial nitric oxide (NO) synthetase (eNOS) regulation and NO release is basically unknown. We therefore studied the effects of different doses of somatotropin in cultures of a human endothelial cell line (EAhy926). We investigated expression and activity of eNOS, as well as other target genes known to be deregulated in cardiovascular disease including E-selectin and the lectin-like oxidized low density lipoprotein receptor. Treatment of cultured human endothelial cells with somatotropin resulted in significant (P<0.05) increases of eNOS gene and protein expression, as well as NO release, whereas production of intracellular reactive oxygen species was significantly reduced, at the highest somatotropin dose level. The enhanced eNOS gene/protein expression and enzyme activity correlate well. Our findings are suggestive for a novel role of growth hormone in endothelial biology, and particularly NO production.