Localization of rat Cytochrome P450 in Various Tissues and Comparison of Arachidonic Acid Metabolism by Rat P450 with that by Human P450 Orthologs

The potential impact of CYP and UGT drug-metabolizing enzymes on brain target site drug exposure

Drug metabolism is one of the critical determinants of drug disposition throughout the body. While traditionally associated with the liver, recent research has unveiled the presence and functional significance of drug-metabolizing enzymes (DMEs) within the brain. Specifically, cytochrome P-450 enzymes (CYPs) and UDP-glucuronosyltransferases (UGTs) enzymes have emerged as key players in drug biotransformation within the central nervous system (CNS). This comprehensive review explores the cellular and subcellular distribution of CYPs and UGTs within the CNS, emphasizing regional expression and contrasting profiles between the liver and brain, humans and rats. Moreover, we discuss the impact of species and sex differences on CYPs and UGTs within the CNS. This review also provides an overview of methodologies for identifying and quantifying enzyme activities in the brain. Additionally, we present factors influencing CYPs and UGTs activities in the brain, including genetic polymorphisms, physiological variables, pathophysiological conditions, and environmental factors. Examples of CYP- and UGT-mediated drug metabolism within the brain are presented at the end, illustrating the pivotal role of these enzymes in drug therapy and potential toxicity. In conclusion, this review enhances our understanding of drug metabolism's significance in the brain, with a specific focus on CYPs and UGTs. Insights into the expression, activity, and influential factors of these enzymes within the CNS have crucial implications for drug development, the design of safe drug treatment strategies, and the comprehension of drug actions within the CNS. To that end, CNS pharmacokinetic (PK) models can be improved to further advance drug development and personalized therapy.

Ameliorative Role of Fluconazole Against Abdominal Aortic Constriction-Induced Cardiac Hypertrophy in Rats

ABSTRACT

Cytochrome P450 1B1 (CYP1B1) is known to be involved in the pathogenesis of several cardiovascular diseases, including cardiac hypertrophy and heart failure, through the formation of cardiotoxic metabolites named as mid-chain hydroxyeicosatetraenoic acids (HETEs). Recently, we have demonstrated that fluconazole decreases the level of mid-chain HETEs in human liver microsomes, inhibits human recombinant CYP1B1 activity, and protects against angiotensin II-induced cellular hypertrophy in H9c2 cells. Therefore, the overall purpose of this study was to elucidate the potential cardioprotective effect of fluconazole against cardiac hypertrophy induced by abdominal aortic constriction (AAC) in rats. Male Sprague-Dawley rats were randomly assigned into 4 groups such as sham control rats, fluconazole-treated (20 mg/kg daily for 4 weeks, intraperitoneal) sham rats, AAC rats, and fluconazole-treated (20 mg/kg) AAC rats. Baseline and 5 weeks post-AAC echocardiography were performed. Gene and protein expressions were measured using real-time PCR and Western blot analysis, respectively. The level of mid-chain HETEs was determined using liquid chromatography-mass spectrometry. Echocardiography results showed that fluconazole significantly prevented AAC-induced left ventricular hypertrophy because it ameliorated the AAC-mediated increase in left ventricular mass and wall measurements. In addition, fluconazole significantly prevented the AAC-mediated increase of hypertrophic markers. The antihypertrophic effect of fluconazole was associated with a significant inhibition of CYP1B1, CYP2C23, and 12-LOX and a reduction in the formation rate of mid-chain HETEs. This study demonstrates that fluconazole protects against left ventricular hypertrophy, and it highlights the potential repurposing of fluconazole as a mid-chain HETEs forming enzymes' inhibitor for the protection against cardiac hypertrophy.

Contribution of DHA diols (19,20-DHDP) produced by cytochrome P450s and soluble epoxide hydrolase to the beneficial effects of DHA supplementation in the brains of rotenone-induced rat models of Parkinson's disease

Docosahexaenoic acid (DHA) has been shown to have neuroprotective effects in Parkinson's disease, but the underlying mechanism has not been fully elucidated. DHA is metabolized to DHA epoxides (EDPs) and hydroxides by cytochrome P450s (P450s), and EDPs are further hydroxylated to the corresponding diols, dihydroxydocosapentaenoic acids (DHDPs) by soluble epoxide hydrolase (sEH). In the present study, we investigated the roles of these DHA metabolites in the beneficial effects of DHA supplementation on a rotenone-induced rat model of Parkinson's disease. Metabolite analysis by LC-MS revealed that CYP2A1, 2C11, 2C13, 2C23, and 2E1 contributed to the formation of EDPs, and these P450s and sEH were expressed in the rat brain. We found that DHA supplementation in rats improved the motor dysfunction induced by rotenone. In addition, DHA reversed the decrease in tyrosine hydroxylase and the increase in lipid peroxidation generated by rotenone in the striatum. DHA supplementation also induced mRNA expression of antioxidant genes, such as sod1 and catalase, and Nrf2 protein expression in the striatum. However, these effects of DHA supplementation were eliminated by cosupplementation with the sEH inhibitor TPPU. Supplementation with DHA increased the amount of 19,20-DHDP in the rat brain, while the amount of EDPs was not significantly increased. In addition, TPPU suppressed the increase in DHDPs and increased EDPs in the brain. In PC12 cells, 19,20-DHDP increased the mRNA levels of sod1 and catalase along with Nrf2 induction. This study suggests that DHA metabolites-DHDPs generated by P450s and sEH-have an important role in improving rotenone-induced Parkinson's disease.

Expression and Function of Eicosanoid-Producing Cytochrome P450 Enzymes in Solid Tumors

Oxylipins derived from the oxidation of polyunsaturated fatty acids (PUFAs) act as important paracrine and autocrine signaling molecules. A subclass of oxylipins, the eicosanoids, have a broad range of physiological outcomes in inflammation, the immune response, cardiovascular homeostasis, and cell growth regulation. Consequently, eicosanoids are implicated in the pathophysiology of various diseases, most notably cancer, where eicosanoid mediated signaling is involved in tumor development, progression, and angiogenesis. Cytochrome P450s (CYPs) are a superfamily of heme monooxygenases generally involved in the clearance of xenobiotics while a subset of isozymes oxidize PUFAs to eicosanoids. Several eicosanoid forming CYPs are overexpressed in tumors, elevating eicosanoid levels and suggesting a key function in tumorigenesis and progression of tumors in the lung, breast, prostate, and kidney. This review summarizes the current understanding of CYPs' involvement in solid tumor etiology and progression providing supporting public data for gene expression from The Cancer Genome Atlas.

Fluconazole Represses Cytochrome P450 1B1 and Its Associated Arachidonic Acid Metabolites in the Heart and Protects Against Angiotensin II-Induced Cardiac Hypertrophy

Cytochrome P450 1B1 (CYP1B1) has been reported to have a major role in metabolizing arachidonic acid (AA) into cardiotoxic metabolites, mid-chain hydroxyeicosatetraenoic acids (HETEs). Recently, we have shown that fluconazole decreases the level of mid-chain HETEs in human liver microsomes. Therefore, the objectives of this study were to investigate the effect of fluconazole on CYP1B1 mediated mid-chain HETEs and to explore its potential protective effect against angiotensin II- (Ang II)-induced cellular hypertrophy. To do this, Sprague Dawley rats were injected intraperitoneally with a single dose of fluconazole (20 mg/kg) for 24 h. Also, H9c2 and RL-14 cells were treated with 10 μM Ang II in the presence and absence of 50 μM fluconazole for 24 h. Our results demonstrated that treatment of rats with fluconazole significantly decreased the expression of CYP1B1 enzyme and the level of mid-chain HETEs in the heart. Furthermore, fluconazole was able to attenuate Ang-II-induced cellular hypertrophy as evidenced by a significant down-regulation of hypertrophic markers; β-myosin heavy chain (MHC)/α-MHC and brain natriuretic peptide (BNP) as well as cell surface area. In conclusion, our findings indicate that fluconazole protects against Ang II-induced cellular hypertrophy by repressing CYP1B1 and its associated mid-chain HETEs.

The effects of endothelium-specific CYP2J2 overexpression on the attenuation of retinal ganglion cell apoptosis in a glaucoma rat model

Glaucoma is a leading cause of irreversible blindness worldwide. Vascular factors play a substantial role in the pathogenesis of glaucoma. Expressed in the vascular endothelium, cytochrome P450 (CYP) 2J2 is one of the CYP epoxygenases that metabolize arachidonic acid to produce epoxyeicosatrienoic acids and exert pleiotropic protective effects on the vasculature. In the present study, we investigated whether endothelium-specific overexpression of CYP2J2 (tie2-CYP2J2-Tr) protects against retinal ganglion cell (RGC) loss induced by glaucoma and in what way retinal vessels are involved in this process. We used a glaucoma model of retinal ischemia-reperfusion (I/R) injury in rats and found that endothelium-specific overexpression of CYP2J2 attenuated RGC loss induced by retinal I/R. Moreover, retinal I/R triggered retinal vascular senescence, indicated by up-regulated senescence-related proteins p53, p16, and β-galactosidase activity. The senescent endothelial cells resulted in pericyte loss and increased endothelial secretion of matrix metallopeptidase 9, which further contributed to RGC loss. CYP2J2 overexpression alleviated vascular senescence, pericyte loss, and matrix metallopeptidase 9 secretion. CYP2J2 suppressed endothelial senescence by down-regulating senescence-associated proteins p53 and p16. These 2 proteins were positively regulated by microRNA-128-3p, which was inhibited by CYP2J2. These results suggest that CYP2J2 protects against endothelial senescence and RGC loss in glaucoma, a discovery that may lead to the development of a potential treatment strategy for glaucoma.-Huang, J., Zhao, Q., Li, M., Duan, Q., Zhao, Y., Zhang, H. The effects of endothelium-specific CYP2J2 overexpression on the attenuation of retinal ganglion cell apoptosis in a glaucoma rat model.

14,15-epoxyeicosatrienoic acid produced by cytochrome P450s enhances neurite outgrowth of PC12 and rat hippocampal neuronal cells

Polyunsaturated fatty acids, such as arachidonic acid, are accumulated in brain and induce neuronal differentiation. Arachidonic acid is metabolized to epoxyeicosatrienoic acids (EETs) and hydroxyeicosatetraenoic acids (HETEs) by cytochrome P450s. In this study, we found that 14,15-EET and 20-HETE-enhanced NGF-induced rat pheochromocytoma PC12 cell neurite outgrowth even at the concentration of 100 nmol L-1. LC-MS analysis revealed that 14,15-EET was effectively produced from arachidonic acid by rat CYP2C11, 2C13, and 2C23, and these P450s were expressed in PC12 cells. An inhibitor of these P450s, ketoconazole, inhibited neurite outgrowth, whereas inhibition of soluble epoxide hydrolase, which hydrolyzes EETs to their corresponding diols enhanced neurite outgrowth. To determine the mechanism of neurite formation enhancement by arachidonic acid metabolites, we focused on transient receptor potential (TRP) channels expressed in PC12 cells. The TRPV4 inhibitor HC067047, but not the TRPV1 inhibitor capsazepine, inhibited the effects of 14,15-EET on neurite outgrowth of PC12. Furthermore, 14,15-EET increased the cytosolic calcium ion concentration and this increase was inhibited by HC067047. 14,15-EET also enhanced neurite outgrowth of primary cultured neuron from rat hippocampus. This study suggests that arachidonic acid metabolites produced by P450 contribute to neurite outgrowth through calcium influx.

20-HETE in the regulation of vascular and cardiac function

20-HETE, the ω-hydroxylation product of arachidonic acid catalyzed by enzymes of the cytochrome P450 (CYP) 4A and 4F gene families, is a bioactive lipid mediator with potent effects on the vasculature including stimulation of smooth muscle cell contractility, migration and proliferation as well as activation of endothelial cell dysfunction and inflammation. Clinical studies have shown elevated levels of plasma and urinary 20-HETE in human diseases and conditions such as hypertension, obesity and metabolic syndrome, myocardial infarction, stroke, and chronic kidney diseases. Studies of polymorphic associations also suggest an important role for 20-HETE in hypertension, stroke and myocardial infarction. Animal models of increased 20-HETE production are hypertensive and are more susceptible to cardiovascular injury. The current review summarizes recent findings that focus on the role of 20-HETE in the regulation of vascular and cardiac function and its contribution to the pathology of vascular and cardiac diseases.

Role of the CYP3A4-mediated 11,12-epoxyeicosatrienoic acid pathway in the development of tamoxifen-resistant breast cancer

Epoxyeicosatrienoic acid (EET) production via cytochrome P450 (CYP) epoxygenases closely correlates with the progression of breast cancer. However, its role in the development of chemoresistant breast cancers has yet to be elucidated. Here, we found that CYP3A4 expression and its epoxy-product, 11,12-epoxyeicosatrienoic acid (11,12-EET) was enhanced in tamoxifen (TAM)-resistant MCF-7 (TAMR-MCF-7) breast cancer cells compared to control MCF-7 cells. Treatment of TAMR-MCF-7 cells with ketoconazole and azamulin (selective CYP3A4 inhibitors) or 14,15-epoxyeicosa-5(Z)-enoic acid (14,15-EEZE, an EET antagonist) inhibited cellular proliferation and recovered the sensitivity to 4-hydroxytamoxifen. Chick chorioallantoic membrane and trans-well migration analyses revealed that the enhanced angiogenic, tumorigenic, and migration intensities of TAMR-MCF-7 cells were also significantly suppressed by ketoconazole and 14,15-EEZE. We previously reported that Pin1, a peptidyl prolyl isomerase, is a crucial regulator for higher angiogenesis and epithelial-mesenchymal transition characteristics of TAMR-MCF-7 cells. EET inhibition suppressed E2F1-dependent Pin1 gene transcription, and Pin1 silencing also blocked cell proliferation, angiogenesis, and migration of TAMR-MCF-7 cells. Our findings suggest that the CYP3A4-mediated EET pathway represents a potential therapeutic target for the treatment of tamoxifen-resistant breast cancer.

The role of dyslipidemia in diabetic retinopathy

Diabetic retinopathy (DR) affects over 93million people worldwide and is the number one cause of blindness among working age adults. These indicators coupled with the projected rise of patients diagnosed with diabetes, makes DR a serious and prevalent vision threating disease. Data from recent clinical trials demonstrate that in addition to the well accepted role of hyperglycemia, dyslipidemia is an important, but often overlooked factor in the development of DR. The central aim of this review article is to showcase the critical role of dyslipidemia in DR progression as well as highlight novel therapeutic solutions that take advantage of the vital roles lipid metabolism plays in DR progression.

Age-dependent features of CYP3A, CYP2C, and CYP2E1 functioning at metabolic syndrome

BACKGROUND

Complex investigations of cytochrome P450 (CYP) isoforms with metabolic syndrome (MS) development are limited, and specific features of adolescent's metabolisms are generally disregarded. The aim of present study was a comparative estimation of MS-mediated changes in CYP3A, CYP2C, and CYP2E1 mRNA expression and enzymatic activities, as well as antioxidant system parameters of adult and pubertal rats.

METHODS

Wistar albino male rats of two age categories [young animals of 21 days age (50-70 g) and adults (160-180 g)] were divided into four groups (eight animals in each group): (1) control 1 (intact young rats), (2) control 2 (intact adult rats), (3) MS3 (young rats with MS), and (4) MS4 (adult rats with MS). The MS was induced by full replacement of drinking water by 20% fructose solution (200 g/L). After 60 days of MS modeling, the investigation of rat liver CYP3A, CYP2C, and CYP2E1 mRNA expressions, their enzyme-marker activities, as well as the antioxidant system parameters was conducted.

RESULTS

Levels of liver CYP2E1 mRNA expression increased with MS: 40% (adults) and 80% (pubertal rats). Pubertal rats had also increased CYP3A2 mRNA expression (30%) and decreased CYP2C mRNA expression (30%). Changes in CYP2E1 and CYP2C enzymatic activities were consistent with the changes of corresponding gene expressions at both age-groups with MS. Simultaneously, liver reduced glutathione contents, and glutathione transferase and reductase activities were decreased in pubertal animals.

CONCLUSIONS

CYP isoform expression rates and glutathione system were greatly violated with MS. The greater changes were observed in pubertal rats with MS.

Repurposing Resveratrol and Fluconazole To Modulate Human Cytochrome P450-Mediated Arachidonic Acid Metabolism

Cytochrome P450 (P450) enzymes metabolize arachidonic acid (AA) to several biologically active epoxyeicosatrienoic acids (EETs) and hydroxyeicosatetraenoic acids (HETEs). Repurposing clinically-approved drugs could provide safe and readily available means to control EETs and HETEs levels in humans. Our aim was to determine how to significantly and selectively modulate P450-AA metabolism in humans by clinically-approved drugs. Liquid chromatography-mass spectrometry was used to determine the formation of 15 AA metabolites by human recombinant P450 enzymes, as well as human liver and kidney microsomes. CYP2C19 showed the highest EET-forming activity, while CYP1B1 and CYP2C8 showed the highest midchain HETE-forming activities. CYP1A1 and CYP4 showed the highest subterminal- and 20-HETE-forming activity, respectively. Resveratrol and fluconazole produced the most selective and significant modulation of hepatic P450-AA metabolism, comparable to investigational agents. Monte Carlo simulations showed that 90% of human population would experience a decrease by 6-22%, 16-39%, and 16-35% in 16-, 18-, and 20-HETE formation, respectively, after 2.5 g daily of resveratrol, and by 22-31% and 14-23% in 8,9- and 14,15-EET formation after 50 mg of fluconazole. In conclusion, clinically-approved drugs can provide selective and effective means to modulate P450-AA metabolism, comparable to investigational drugs. Resveratrol and fluconazole are good candidates to be repurposed as new P450-based treatments.

Changes in the concentrations of vitamin E analogs and their metabolites in rat liver and kidney after oral administration

Vitamin E analog, such as α- and γ-tocopherol, can undergo ω-oxidation without cleavage of the chroman ring, and this pathway is responsible for generation of the major urinary vitamin E metabolite, carboxyethyl hydroxychroman. However, it is still unclear how carboxyethyl hydroxychroman is changed in various tissues after vitamin E intake. We therefore investigated changes in the concentrations of α- and γ-tocopherol and their metabolites in rat liver and kidney. The concentration of α-tocopherol in rat liver increased until 6 h after oral administration, and then decreased. The change in the concentration of α-carboxyethyl hydroxychroman in rat liver in the α-Toc group slowly increased until 12 h after oral administration. Cytochrome P450 3A1 mRNA expression significantly increased from 12 h after the start of α-tocopherol administration. The change in the concentration of γ-carboxyethyl hydroxychroman in rat liver in the γ-Toc group markedly increased until 12 h after oral administration. On the other hand, γ-carboxyethyl hydroxychroman in rat kidney showed greater accumulation than α-carboxyethyl hydroxychroman from 3 h to 24 h after oral administration. From these results, we considered that γ-carboxyethyl hydroxychroman formed in the liver continues to be released into the bloodstream and is transported to the kidney rapidly.

Human fetal ventricular cardiomyocyte, RL-14 cell line, is a promising model to study drug metabolizing enzymes and their associated arachidonic acid metabolites

INTRODUCTION

RL-14 cells, human fetal ventricular cardiomyocytes, are a commercially available cell line that has been established from non-proliferating primary cultures derived from human fetal heart tissue. However, the expression of different drug metabolizing enzymes (DMEs) in RL-14 cells has not been elucidated yet. Therefore, the main objectives of the current work were to investigate the capacity of RL-14 cells to express different cytochrome P450 (CYP) isoenzymes and correlate this expression to primary cardiomyocytes.

METHODS

The expression of CYP isoenzymes was determined at mRNA, protein and catalytic activity levels using real time-PCR, Western blot analysis and liquid chromatography-electron spray ionization-mass spectrometry (LC-ESI-MS), respectively.

RESULTS

Our results showed that RL-14 cells constitutively express CYP ω-hydroxylases, CYP1A, 1B, 4A and 4F; CYP epoxygenases, CYP2B, 2C and 2J; in addition to soluble epoxide hydrolayse (EPHX2) at mRNA and protein levels. The basal expression of CYP ω-hydroxylases, epoxygenases and EPHX2 was supported by the ability of RL-14 cells to convert arachidonic acid to its biologically active metabolites, 20-hydroxyeicosatetraenoic acids (20-HETEs), 14,15-epoxyeicosatrienoic acids (14,15-EET), 11,12-EET, 8,9-EET, 5,6-EET, 14,15-dihydroxyeicosatrienoic acid (14,15-DHET), 11,12-DHET, 8,9-DHET and 5,6-DHET. Furthermore, RL-14 cells express CYP epoxygenases and ω-hydroxylase at comparable levels to those expressed in adult and fetal human primary cardiomyocytes cells implying the importance of RL-14 cells as a model for studying DMEs in vitro. Lastly, different CYP families were induced in RL-14 cells using 2,3,7,8-tetrachlorodibenzo-p-dioxin and fenofibrate at mRNA and protein levels.

DISCUSSION

The current study provides the first evidence that RL-14 cells express CYP isoenzymes at comparable levels to those expressed in the primary cells and thus offers a unique in vitro model to study DMEs in the heart.

Characterization of arachidonic acid metabolism by rat cytochrome P450 enzymes: the involvement of CYP1As

Cytochrome P450 (P450) enzymes mediate arachidonic acid (AA) oxidation to several biologically active metabolites. Our aims in this study were to characterize AA metabolism by different recombinant rat P450 enzymes and to identify new targets for modulating P450-AA metabolism in vivo. A liquid chromatography-mass spectrometry method was developed and validated for the simultaneous measurements of AA and 15 of its P450 metabolites. CYP1A1, CYP1A2, CYP2B1, CYP2C6, and CYP2C11 were found to metabolize AA with high catalytic activity, and CYP2A1, CYP2C13, CYP2D1, CYP2E1, and CYP3A1 had lower activity. CYP1A1 and CYP1A2 produced ω-1→4 hydroxyeicosatetraenoic acids (HETEs) as 88.7 and 62.7%, respectively, of the total metabolites formed. CYP2C11 produced epoxyeicosatrienoic acids (EETs) as 61.3%, and CYP2C6 produced midchain HETEs and EETs as 48.3 and 29.4%, respectively, of the total metabolites formed. The formation of CYP1A1, CYP1A2, CYP2C6, and CYP2C11 major metabolites followed an atypical kinetic profile of substrate inhibition. CYP1As inhibition by α-naphthoflavone or anti-CYP1As antibodies significantly reduced ω-1→4 HETE formation in the lungs and liver, whereas CYP1As induction by 3-methylcholanthrene resulted in a significant increase in ω-1→4 HETEs formation in the heart, lungs, kidney, and livers by 370, 646, 532, and 848%, respectively. In conclusion, our results suggest that CYP1As and CYP2Cs are major players in the metabolism of AA. The significant contribution of CYP1As to AA metabolism and their strong inducibility suggest their possible use as targets for the prevention and treatment of several diseases.

The role of cytochrome P450 epoxygenases in retinal angiogenesis

PURPOSE

The purpose of this study was to investigate the role(s) of cytochrome P450 epoxygenases (CYPs) and their products, the epoxyeicosatrienoic acids (EETs), in hypoxia-induced VEGF production and pathologic retinal angiogenesis.

METHODS

Human retinal astrocytes, Müller cells, and retinal microvascular endothelial cells (HRMEC) were exposed to hypoxia, and relative CYP2C expression was measured by RT-PCR. Astrocyte and Müller cell VEGF production was measured by ELISA after exposure to hypoxia and treatment with the general CYP inhibitor, SKF-525a. Human retinal microvascular endothelial cells were treated with the CYP product, 11,12-epoxyeicosatrienoic acid [EET], or SKF-525a in the presence or absence of VEGF. Proliferation of HRMEC and tube formation were assayed. Oxygen-induced retinopathy (OIR) was induced in newborn rats. Retinal CYP2C11 and CYP2C23 expression were measured by RT-PCR. The OIR rats received SKF-525a by intravitreal injection and preretinal neovascularization (NV) was quantified. Retinal VEGF protein levels were measured by ELISA.

RESULTS

Human retinal astrocytes were the only cells to exhibit significant induction of CYP2C8 and CYP2C9 mRNA expression by hypoxia. Astrocytes, but not Müller cells, exhibited reduced hypoxia-induced VEGF production when treated with SKF-525a. 11,12-EET induced HRMEC proliferation and tube formation, and SKF-525a inhibited VEGF-induced proliferation. Oxygen-induced retinopathy induced expression of CYP2C23, but had no effect on CYP2C11. SKF-525a inhibited retinal NV and reduced retinal VEGF levels in OIR rats.

CONCLUSIONS

The CYP-derived 11,12-EET may exhibit a proangiogenic biological function in the retina following stimulation by hypoxia in astrocytes. Inhibition of CYP may provide a rational therapy against retinal NV, because it can reduce VEGF production and VEGF-induced angiogenic responses in endothelial cells.

Role of cytochrome P450-mediated arachidonic acid metabolites in the pathogenesis of cardiac hypertrophy

A plethora of studies have demonstrated the expression of cytochrome P450 (CYP) and soluble epoxide hydrolase (sEH) enzymes in the heart and other cardiovascular tissues. In addition, the expression of these enzymes is altered during several cardiovascular diseases (CVDs), including cardiac hypertrophy (CH). The alteration in CYP and sEH expression results in derailed CYP-mediated arachidonic acid (AA) metabolism. In animal models of CH, it has been reported that there is an increase in 20-hydroxyeicosatetraenoic acid (20-HETE) and a decrease in epoxyeicosatrienoic acids (EETs). Further, inhibiting 20-HETE production by CYP ω-hydroxylase inhibitors and increasing EET stability by sEH inhibitors have been proven to protect against CH as well as other CVDs. Therefore, CYP-mediated AA metabolites 20-HETE and EETs are potential key players in the pathogenesis of CH. Some studies have investigated the molecular mechanisms by which these metabolites mediate their effects on cardiomyocytes and vasculature leading to pathological CH. Activation of several intracellular signaling cascades, such as nuclear factor of activated T cells, nuclear factor kappa B, mitogen-activated protein kinases, Rho-kinases, Gp130/signal transducer and activator of transcription, extracellular matrix degradation, apoptotic cascades, inflammatory cytokines, and oxidative stress, has been linked to the pathogenesis of CH. In this review, we discuss how 20-HETE and EETs can affect these signaling pathways to result in, or protect from, CH, respectively. However, further understanding of these metabolites and their effects on intracellular cascades will be required to assess their potential translation to therapeutic approaches for the prevention and/or treatment of CH and heart failure.

Aging, estrogen loss and epoxyeicosatrienoic acids (EETs)

Inflammation is a key element in many cardiovascular diseases. Both estrogen loss, caused by menopause, and aging have inflammatory consequences. Epoxyeicosatrienoic acids (EETs) are anti-inflammatory molecules synthesized by various cytochrome P450 (Cyp) enzymes from arachidonic acid. EETs are in the third (Cytochrome P450) pathway of arachindonic acid metabolism, others being cyclooxygenases and lipoxygenases. We hypothesized that aging and estrogen loss would reduce levels of anti-inflammatory EETs. Adult (6 mo) and aged (22 mo) ovariectomized rats with (OP) and without (Ovx) 17-∃-estradiol replacement were used in this study. Mass spectrometry was used to measure levels of EETs and their metabolites, dihydroxyeicosatrienoic acids (DHETs). Levels of Cyp2C2, Cyp2C6, and Cyp2J2, the principal Cyps responsible for EETs synthesis, as well as soluble epoxide hydrolase (sEH), which metabolizes EETS to DHETs, were determined via western blot. Overall Cyp levels decreased with age, though Cyp2C6 increased in the liver. sEH was increased in the kidney with estrogen replacement. Despite protein changes, no differences were measured in plasma or aortic tissue levels of EETs. However, plasma 14,15 DHET was increased in aged Ovx, and 5,6 DHET in adult OP. In conclusion neither aging nor estrogen loss decreased the anti-inflammatory EETs in the cardiovascular system.

20-HETE and EETs in diabetic nephropathy: a novel mechanistic pathway

Diabetic nephropathy (DN), a major complication of diabetes, is characterized by hypertrophy, extracellular matrix accumulation, fibrosis and proteinuria leading to loss of renal function. Hypertrophy is a major factor inducing proximal tubular epithelial cells injury. However, the mechanisms leading to tubular injury is not well defined. In our study, we show that exposure of rats proximal tubular epithelial cells to high glucose (HG) resulted in increased extracellular matrix accumulation and hypertrophy. HG treatment increased ROS production and was associated with alteration in CYPs 4A and 2C11 expression concomitant with alteration in 20-HETE and EETs formation. HG-induced tubular injury were blocked by HET0016, an inhibitor of CYPs 4A. In contrast, inhibition of EETs promoted the effects of HG on cultured proximal tubular cells. Our results also show that alteration in CYPs 4A and 2C expression and 20HETE and EETs formation regulates the activation of the mTOR/p70S6Kinase pathway, known to play a major role in the development of DN. In conclusion, we show that hyperglycemia in diabetes has a significant effect on the expression of Arachidonic Acid (AA)-metabolizing CYPs, manifested by increased AA metabolism, and might thus alter kidney function through alteration of type and amount of AA metabolites.

Temporal changes of cytochrome P450 (Cyp) and eicosanoid-related gene expression in the rat brain after traumatic brain injury

BACKGROUND

Traumatic brain injury (TBI) induces arachidonic acid (ArA) release from cell membranes. ArA metabolites form a class of over 50 bioactive eicosanoids that can induce both adaptive and/or maladaptive brain responses. The dynamic metabolism of ArA to eicosanoids, and how they affect the injured brain, is poorly understood due to their diverse activities, trace levels, and short half-lives. The eicosanoids produced in the brain postinjury depend upon the enzymes present locally at any given time. Eicosanoids are synthesized by heme-containing enzymes, including cyclooxygenases, lipoxygenases, and arachidonate monoxygenases. The latter comprise a subset of the cytochrome P450 "Cyp" gene family that metabolize fatty acids, steroids, as well as endogenous and exogenous toxicants. However, for many of these genes neither baseline neuroanatomical nor injury-related temporal expression have been studied in the brain.In a rat model of parietal cortex TBI, Cyp and eicosanoid-related mRNA levels were determined at 6 h, 24 h, 3d, and 7d postinjury in parietal cortex and hippocampus, where dynamic changes in eicosanoids have been observed. Quantitative real-time polymerase chain reaction with low density arrays were used to assay 62 rat Cyps, 37 of which metabolize ArA or other unsaturated fatty acids; 16 eicosanoid-related enzymes that metabolize ArA or its metabolites; 8 eicosanoid receptors; 5 other inflammatory- and recovery-related genes, plus 2 mouse Cyps as negative controls and 3 highly expressed "housekeeping" genes.

RESULTS

Sixteen arachidonate monoxygenases, 17 eicosanoid-related genes, and 12 other Cyps were regulated in the brain postinjury (p < 0.05, Tukey HSD). Discrete tissue levels and distinct postinjury temporal patterns of gene expression were observed in hippocampus and parietal cortex.

CONCLUSIONS

The results suggest complex regulation of ArA and other lipid metabolism after TBI. Due to the temporal nature of brain injury-induced Cyp gene induction, manipulation of each gene (or its products) at a given time after TBI will be required to assess their contributions to secondary injury and/or recovery. Moreover, a better understanding of brain region localization and cell type-specific expression may be necessary to deduce the role of these eicosanoid-related genes in the healthy and injured brain.

Murine atrial HL-1 cell line is a reliable model to study drug metabolizing enzymes in the heart

HL-1 cells are currently the only cells that spontaneously contract while maintaining a differentiated cardiac phenotype. Thus, our objective was to examine murine HL-1 cells as a new in vitro model to study drug metabolizing enzymes. We examined the expression of cytochrome P450s (Cyps), phase II enzymes, and nuclear receptors and compared their levels to mice hearts. Our results demonstrated that except for Cyp4a12 and Cyp4a14 all Cyps, phase II enzymes: glutathione-S-transferases (Gsts), heme oxygenase-1 (HO-1), and NAD(P)H: quinone oxidoreductase (Nqo1), nuclear receptors: aryl hydrocarbon receptor (AhR), constitutive androstane receptor (CAR), pregnane X receptor (PXR), and peroxisome proliferator activated receptor (PPAR-alpha) were all constitutively expressed in HL-1 cells. Cyp2b19, Cyp2c29, Cyp2c38, Cyp2c40, and Cyp4f16 mRNA levels were higher in HL-1 cells compared to mice hearts. Cyp2b9, Cyp2c44, Cyp2j9, Cyp2j11, Cyp2j13, Cyp4f13, Cyp4f15 mRNA levels were expressed to the same extent to that of mice hearts. Cyp1a1, Cyp1a2, Cyp1b1, Cyp2b10, Cyp2d10, Cyp2d22, Cyp2e1, Cyp2j5, Cyp2j6, Cyp3a11, Cyp4a10, and Cyp4f18 mRNA levels were lower in HL-1 cells compared to mice hearts. Moreover, 3-methylcholanthrene induced Cyp1a1 while fenofibrate induced Cyp2j9 and Cyp4f13 mRNA levels in HL-1 cells. Examining the metabolism of arachidonic acid (AA) by HL-1 cells, our results demonstrated that HL-1 cells metabolize AA to epoxyeicosatrienoic acids, dihydroxyeicosatrienoic acids, and 20-hydroxyeicosatetraenoic acids. In conclusion, HL-1 cells provide a valuable in vitro model to study the role of Cyps and their associated AA metabolites in addition to phase II enzymes in cardiovascular disease states.

Determination of the dominant arachidonic acid cytochrome p450 monooxygenases in rat heart, lung, kidney, and liver: protein expression and metabolite kinetics

Cytochrome P450 (P450)-derived arachidonic acid (AA) metabolites serve pivotal physiological roles. Therefore, it is important to determine the dominant P450 AA monooxygenases in different organs. We investigated the P450 AA monooxygenases protein expression as well as regioselectivity, immunoinhibition, and kinetic profile of AA epoxygenation and hydroxylation in rat heart, lung, kidney, and liver. Thereafter, the predominant P450 epoxygenases and P450 hydroxylases in these organs were characterized. Microsomes from heart, lung, kidney, and liver were incubated with AA. The protein expression of CYP2B1/2, CYP2C11, CYP2C23, CYP2J3, CYP4A1/2/3, and CYP4Fs in the heart, lung, kidney, and liver were determined by Western blot analysis. The levels of AA metabolites were determined by liquid chromatography-electrospray ionization mass spectroscopy. This was followed by determination of regioselectivity, immunoinhibition effect, and the kinetic profile of AA metabolism. AA was metabolized to epoxyeicosatrienoic acids and 19- and 20-hydroxyeicosatetraenoic acid in the heart, lung, kidney, and liver but with varying metabolic activities and regioselectivity. Anti-P450 antibodies were found to differentially inhibit AA epoxygenation and hydroxylation in these organs. Our data suggest that the predominant epoxygenases are CYP2C11, CYP2B1, CYP2C23, and CYP2C11/CYP2C23 for the heart, lung, kidney, and liver, respectively. On the other hand, CYP4A1 is the major ω-hydroxylase in the heart and kidney; whereas CYP4A2 and/or CYP4F1/4 are probably the major hydroxlases in the lung and liver. These results provide important insights into the activities of P450 epoxygenases and P450 hydroxylases-mediated AA metabolism in different organs and their associated P450 protein levels.

Tissue distribution of vitamin E metabolites in rats after oral administration of tocopherol or tocotrienol

We previously found that 2,7,8-trimethyl-2(2'-carboxyethyl)-6-hydroxychroman (γCEHC), a metabolite of the vitamin E isoforms γ-tocopherol or γ-tocotrienol, accumulated in the rat small intestine. The aim of this study was to evaluate tissue distribution of vitamin E metabolites. A single dose of α-tocopherol, γ-tocopherol or a tocotrienol mixture containing α- and γ-tocotrienol was orally administered to rats. Total amounts of conjugated and unconjugated metabolites in the tissues were measured by HPLC with an electrochemical detector, and 6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid (trolox) was used as an internal standard. Twenty-four hours later, the vitamin E isoforms were detected in most tissues and in the serum. However, 2,5,7,8-tetramethyl-2(2'-carboxyethyl)-6-hydroxychroman (αCEHC), a metabolite of α-tocopherol or α-tocotrienol, and γCEHC accumulated in the serum and in some tissues including the liver, small intestine and kidney. Administration of α-tocopherol increased the γCEHC concentration in the small intestine, suggesting that α-tocopherol enhances γ-tocopherol catabolism. In contrast, ketoconazole, an inhibitor of cytochrome P450 (CYP)-dependent vitamin E catabolism, markedly decreased the γCEHC concentration. These data indicate that vitamin E metabolite accumulates not only in the liver but also in the small intestine and kidney. We conclude that some dietary vitamin E is catabolized to carboxyethyl-hydroxychroman in the small intestine and is secreted into the circulatory system.

Pregnane X receptor regulates drug metabolism and transport in the vasculature and protects from oxidative stress

AIMS

Circulating endogenous, dietary, and foreign chemicals can contribute to vascular dysfunction. The mechanism by which the vasculature protects itself from these chemicals is unknown. This study investigates whether the pregnane X receptor (PXR), the major transcriptional regulator of hepatic drug metabolism and transport that responds to such xenobiotics, mediates vascular protection by co-ordinating a defence gene programme in the vasculature.

METHODS AND RESULTS

PXR was detected in primary human and rat aortic endothelial and smooth muscle cells (SMC) and blood vessels including the human and rat aorta. Metabolic PXR target genes cytochrome P450 3A, 2B, 2C, and glutathione S-transferase mRNA and activity were induced by PXR ligands in rodent and human vascular cells and absent in the aortas from PXR-null mice stimulated in vivo or in rat aortic SMC expressing dominant-negative PXR. Activation of aortic PXR by classical agonists had several protective effects: increased xenobiotic metabolism demonstrated by bioactivation of the pro-drug clopidogrel, which reduced adenosine diphosphate-induced platelet aggregation; increased expression of multidrug resistance protein 1, mediating chemical efflux from the vasculature; and protection from reactive oxygen species-mediated cell death.

CONCLUSION

PXR co-ordinately up-regulates drug metabolism, transport, and antioxidant genes to protect the vasculature from endogenous and exogenous insults, thus representing a novel gatekeeper for vascular defence.

Effects of acetylenic epoxygenase inhibitors on recombinant cytochrome p450s

Arachidonate epoxidation, which mediates important biological functions in several tissues, is catalyzed by specific cytochrome P450 (P450) enzymes. Two fatty acid derivatives [2-(2-propynyloxy)-benzenehexanoic acid (PPOH) and N-(methylsulfonyl)-2-(2-propynyloxy)-benzenehexanamide (MS-PPOH)] are used as general, mechanism-based P450 epoxygenase inactivators, but the effects of these drugs on nearly all P450 isoforms are unknown. Here, the activity of these compounds on nine human and three rat recombinant P450s was studied. As expected, PPOH inhibited five known epoxygenases [CYP2B1, 2B6, 2C6, 2C9, and 2C11 (IC(50) = 23-161 μM)] but had little or no activity on P450s typically not considered to be epoxygenases (CYP1A1, 1A2, 1B1, 2A6, 2D6, and 2E1). PPOH was only a very weak inhibitor (IC(50) = ∼300 μM) of CYP2C19, an important human expoxygenase. An unexpected finding was that MS-PPOH (a metabolically stable congener of PPOH) potently inhibited only two P450 epoxygenases (2C9 and 2C11, IC(50) = 11-16 μM) and showed considerably lower activity (IC(50) = >90 μM) on all other P450s tested, including three epoxygenases (CYP2B1, 2B6, and 2C19). In addition, PPOH and MS-PPOH displayed time- and NADPH-dependent inhibition of CYP2C9 and other epoxygenases. These results support the putative mechanism of action of PPOH and MS-PPOH on recombinant P450s and (with one exception) confirm a general epoxygenase inhibitory profile for PPOH. However, the heterogeneity of inhibitory potencies for MS-PPOH on these enzymes suggests caution in the use of this drug as a general epoxygenase inhibitor. These results will facilitate the judicious use of PPOH and MS-PPOH for epoxygenase research.

Inhibition of carcinoma cell motility by epoxyeicosatrienoic acid (EET) antagonists

Cytochrome P450 (CYP) epoxygenases, CYP2C8, 2C9 and 2J2 mRNA and proteins, were expressed in prostate carcinoma (PC-3, DU-145 and LNCaP) cells. 11,12-Epoxyeicosatrienoic acid (11,12-EET) was the major arachidonic acid metabolite in these cells. Blocking EET synthesis by a selective CYP epoxygenase inhibitor (N-methylsulfonyl-6-(2-propargyloxyphenyl)hexanamide [MS-PPOH]) inhibited tonic (basal) invasion and migration (motility) while exogenously added EET induced cell motility in a concentration-dependent manner. An epidermal growth factor receptor (EGFR) kinase inhibitor (AG494) or a PI3 kinase inhibitor (LY294002) inhibited cell migration and reduced 11,12-EET-induced cell migration. Importantly, synthetic EET antagonists (14,15-epoxyeicosa-5(Z)-enoic acid [14,15-EEZE], 14,15-epoxyeicosa-5(Z)-enoic acid 2-[2-(3-hydroxy-propoxy)-ethoxy]-ethyl ester [14,15-EEZE-PEG] and 14,15-epoxyeicosa-5(Z)-enoic-methylsulfonylimide [14,15-EEZE-mSI]) inhibited EET-induced cell invasion and migration. 11,12-EET induced cell stretching and myosin-actin microfilament formation as well as increased phosphorylation of EGFR and Akt (Ser473), while 14,15-EEZE inhibited these effects. These results suggest that EET induce and EET antagonists inhibit cell motility, possibly by putative EET receptor-mediated EGFR and PI3K/Akt pathways, and suggest that EET antagonists are potential therapeutic agents for prostate cancer.

Epoxyeicosatrienoic acids: formation, metabolism and potential role in tissue physiology and pathophysiology

BACKGROUND

CYP enzymes from the CYP2C and CYP2J subfamilies metabolize arachidonic acid in a regiospecific and stereoselective manner to eight epoxyeicosatrienoic acids (EETs). Various EETs have been detected in the liver, as well as in many extrahepatic tissues, and have been implicated in numerous physiological functions from cell signaling to vasodilation and angiogenesis.

OBJECTIVE

This report reviews the sites of expression and activity of arachidonic acid epoxygenase CYP isoforms, as well as the physiological role and metabolism of EETs in various extrahepatic tissues. Possible functions of EETs in tissue pathophysiology and implications as potential drug targets are also discussed.

METHODS

The most recent primary research literature on EET forming enzymes and the new physiological functions of EETs in various tissues were reviewed.

RESULTS/CONCLUSIONS

Epoxyeicosatrienoic acids are important in maintaining the homeostasis and in responding to stress in various extra hepatic tissues. It is not clear whether these effects are owing to EETs acting on a universal receptor or through a mechanism involving a second messenger. A better understanding of the regulation of EET levels and their mechanism of action on various receptors will accelerate research aiming at developing therapeutic agents that target EET formation or metabolism pathways.

7alpha-hydroxytestosterone affects 1 beta-hydroxysteroid dehydrogenase 1 direction in rat Leydig cells

The cytochrome P450 2A1 (CYP2A1) is a P450 enzyme that catalyzes the metabolism of testosterone. CYP2A1 has been reported to be present in rat testis. However, its developmental changes and function have not been well characterized. The purpose of this study was to measure the abundance of CYP2A1 (Cyp2a1) mRNA in the developing rat testis and Leydig cells and examine the effects of its product, 7 alpha-hydroxytestosterone (7HT), on an important enzyme, 11 beta-hydroxysteroid dehydrogenase type 1 (11 beta-HSD1) that interconverts active corticosterone and inactive 11-dehydrocorticosterone. As detected by real-time PCR, Cyp2a1 was found to be present exclusively in the Leydig cell. CYP2A1 activity in adult Leydig cells was 5-fold higher than those in progenitor or immature Leydig cells. 7HT competitively suppressed 11 beta-HSD1 oxidase and reductase activities in rat testis microsome with inhibitory constant of 1.2 and 2.9 mum, respectively. In intact Leydig cells, 7HT did not inhibit 11 beta-HSD1 reductase activity, but it stimulated its reductase activity. Thus, at 100 nm and higher concentrations, 7HT significantly switched 11 beta-HSD1 oxidoreductase activities toward reductase. The present data shows that 7HT, the product formed by CYP2A1 from testosterone, regulates the direction of 11 beta-HSD1 activity in rat Leydig cells.

Characterization and expression of extrahepatic CYP2S1

BACKGROUND

About one-third of the CYP enzymes identified so far, including several novel CYP enzymes such as CYP2S1, CYP2U1 and CYP2W1, belong to the CYP2 family. As with other recently discovered CYP enzymes, detailed information about the catalytic activity and function of CYP2S1 is lacking.

OBJECTIVE

To review and compare the expression of CYP2S1 mRNA and protein in humans, mice and rats, and to critically examine evidence pertaining to CYP2S1 regulation and its catalytic activity.

METHODS

Information about mouse and human CYP2S1 was summarized from published reports. Data about rat CYP2S1 expression was taken from recent work by the authors.

RESULTS/CONCLUSIONS

CYP2S1 shares molecular characteristics of both CYP1 and CYP2 family enzymes but shows a unique tissue profile of expression. Further studies are needed to identify selective substrates and to measure CYP2S1 protein levels before the role of CYP2S1 in xenobiotic metabolism and its relevance to physiological pathways and disease states can be determined.

Epoxyeicosanoid signaling in CNS function and disease

Epoxyeicosatrienoic acids (EETs) are arachidonic acid metabolites of cytochrome P450 epoxygenase enzymes recognized as key players in vascular function and disease, primarily attributed to their potent vasodilator, anti-inflammatory and pro-angiogenic effects. Although EETs' actions in the central nervous system (CNS) appear to parallel those in peripheral tissue, accumulating evidence suggests that epoxyeicosanoid signaling plays different roles in neural tissue compared to peripheral tissue; roles that reflect distinct CNS functions, cellular makeup and intercellular relationships. This is exhibited at many levels including the expression of EETs-synthetic and -metabolic enzymes in central neurons and glial cells, EETs' role in neuro-glio-vascular coupling during cortical functional activation, the capacity for interaction between epoxyeicosanoid and neuroactive endocannabinoid signaling pathways, and the regulation of neurohormone and neuropeptide release by endogenous EETs. The ability of several CNS cell types to produce and respond to EETs suggests that epoxyeicosanoid signaling is a key integrator of cell-cell communication in the CNS, coordinating cellular responses across different cell types. Under pathophysiological conditions, such as cerebral ischemia, EETs protect neurons, astroglia and vascular endothelium, thus preserving the integrity of cellular networks unique to and essential for proper CNS function. Recognition of EETs' intimate involvement in CNS function in addition to their multi-cellular protective profile has inspired the development of therapeutic strategies against CNS diseases such as cerebral ischemia, tumors, and neural pain and inflammation that are based on targeting the cellular actions of EETs or their biosynthetic and metabolizing enzymes. Based upon the emerging importance of epoxyeicosanoids in cellular function and disease unique to neural systems, we propose that the actions of "neuroactive EETs" are best considered separately, and not in aggregate with all other peripheral EETs functions.

Drug-virus interaction: effect of administration of recombinant adenoviruses on the pharmacokinetics of docetaxel in a rat model

Modern cancer therapy combines recombinant viruses with traditional chemotherapeutic agents that are metabolized by hepatic cytochrome P450 3A4 (CYP3A4). A single dose of recombinant adenovirus (Ad) expressing beta-galactosidase (AdlacZ) significantly alters CYP3A2, the correlate of CYP3A4, in rats for 14 days. Recombinant adenovirus expressing human p53 (Adp53) also suppresses CYP3A2. Plasma clearance of docetaxel (DTX) in animals given AdlacZ (3.38 ± 0.22 L/h/kg) was significantly lower than that of those given DTX alone (6.41 ± 1.10 L/h/kg, p≤0.05). Area under the plasma concentration-time curve of DTX in rats given AdlacZ (2,987.37 ± 197.97 ng/ml/h) was significantly greater than those given drug alone (1,666.59 ± 317.04 ng/ml/h, p≤0.05). Both viruses prolonged DTX half-life (t_1/2). Ad infection may cause significant variability in the pharmacokinetics and pharmacodynamics of anti-cancer agents and should be considered when designing therapeutic regimens for patients with viral infection and those enrolled in clinical trials employing recombinant viruses.

Epoxyeicosatrienoic acids and/or their metabolites promote hypoxic response of cells

Epoxyeicosatrienoic acids (EETs), including 5,6-EET, 8,9-EET, 11,12-EET, and 14,15-EET, are produced by cytochrome P450 (P450) such as CYP2C8 and 2C9; and they are hydrolyzed to dihydroxyeicosatrienoic acids (DHETs) by epoxide hydrolase. Particular interest in the epoxygenase reaction has developed because of the potent biological activities (modulation of vascular tone and anti-inflammatory activity, etc.) attributed to EETs. We focused on a new biological function of EETs and DHETs, which induce vascular endothelial growth factor (VEGF) and erythropoietin (EPO) under hypoxia. Human hepatoma cells, Hep3B, and human umbilical artery endothelial cells (HUAEC) were used in this study. An inhibitor of phospholipase A(2), methyl arachidonyl fluorophosphonate (MAFP), and inhibitors of P450s inhibited the VEGF and EPO induction of HUAEC and Hep3B, respectively, under hypoxia. Overexpression of CYP2C8 in Hep3B induced EPO and VEGF under hypoxia. Sulfaphenazole, an inhibitor of CYP2C8/2C9 suppressed luciferase promoter activity with the hypoxia response element (HRE) of VEGF in HUAEC. Exogenous 11,12-EET and 14,15-DHET induced reporter activity in HUAEC and Hep3B cells concomitant with increased levels of hypoxia-inducible factor-1alpha (HIF-1alpha), which is a key factor in the hypoxia response, but 11,12-DHET and 14,15-EET did not. These results suggested that EETs and DHETs play an important role in the hypoxia response of cells.

Expression and induction by rifampicin of CAR- and PXR-regulated CYP2B and CYP3A in liver, kidney and airways of pig

The transcript levels of CYP2B22, 3A22, 3A29, 3A46, CAR, PXR and HNF4alpha were investigated in liver, kidney and airways from control and rifampicin-treated male pigs. The presence and induction of CYP genes transcription were studied by RT-PCR, real-time PCR, Western blotting and enzymatic activity whereas the expression of receptors was studied by RT-PCR or real-time PCR. Pretreatment with rifampicin resulted in a transcriptional activation, although to different extents, of all the CYP3A genes in liver but not in kidney, lung, bronchi or trachea. In the hepatic microsomes, the induction of CYP3A genes was accompanied by an increase of CYP3As marker activities and of two protein bands immunoreactive with anti-human CYP3A4. The CYP2B22 transcript was found to be markedly induced only in liver and kidney. In parallel, a protein band immunoreactive with anti-rat CYP2B1 was elevated while enhanced CYP2B marker activities were observed in hepatic and renal microsomes. As expected, based on human data, the basal expression of CAR, PXR and HNF4alpha was found to be high in liver and low in airways and not susceptible to induction by rifampicin. A significant expression of these transcriptional factors was also demonstrated in kidney. Thus, it is likely that rifampicin induced CYP2B22 both in liver and kidney of pig, not via activation of CAR, but via PXR, through a cross-talk mechanism, as previously observed in human liver. Taken together, our results demonstrated a differential expression and regulation of three individual CYP3As, CYP2B22, CAR, PXR and HNF4alpha genes in liver, kidney and airways of pig.

The V433M variant of the CYP4F2 is associated with ischemic stroke in male Swedes beyond its effect on blood pressure

Cytochrome (CYP) 4A11 and CYP4F2 are responsible for renal production of 20-hydroxyeicosatetraenoic acid, a vasoconstrictor and natriuretic substance. The CYP4A11 F434S and CYP4F2 V433M polymorphisms reduce 20-hydroxyeicosatetraenoic acid production in vitro. The aim of the present study was to evaluate the effect of these polymorphisms on blood pressure (BP) levels, hypertension prevalence, and risk of incident cardiovascular events in middle-aged Swedes. The polymorphisms were genotyped in the cardiovascular cohort of the Malmö Diet and Cancer Study. The incidence of cardiovascular events (coronary events, n=276; ischemic stroke, n=199) was monitored over 10 years of follow-up. The analysis of BP levels was performed twice: either excluding or including subjects under antihypertensive treatment. In the whole population, CYP4A11 S434S homozygotes had higher systolic BP, both crude and adjusted for the number of antihypertensive drugs, and higher prevalence of hypertension with respect to F434 carriers. Male, but not female, CYP4F2 M433 carriers had significantly higher crude and adjusted systolic and diastolic BPs and a trend toward higher hypertension prevalence (P=0.06) with respect to V433V homozygotes. After adjustment for major cardiovascular risk factors, the hazard ratio for incident ischemic stroke in male CYP4F2 M433 carriers was significantly higher with respect to V433V homozygotes (hazard ratio: 1.69; 95% CI: 1.10 to 2.60) even when baseline BP levels and hypertension prevalence were included in the Cox proportional hazard model. A common CYP4F2 V433M polymorphism might increase the risk of incident ischemic stroke in male subjects only partially through its elevating effect on BP. Additional studies are needed to confirm these data.

Constitutive expression and inducibility of CYP1A1 in the H9c2 rat cardiomyoblast cells

Cardiomyocytes are a valuable tool for studying the drug metabolizing enzymes in the heart. However, isolated cardiomyocytes are rather fragile and difficult to isolate. Therefore, there is an urgent need for an in vitro cell line model. The H9c2 cells are commonly used as an in vitro model for studying the cellular mechanisms and signaling pathways involved in drug-induced cardiotoxicity. These cells maintain many molecular markers of cardiomyocytes and show morphological characteristics of immature embryonic cardiomyocytes. Therefore, in the present study we examined the expression and inducibility of CYP1A1 in the H9c2 rat cardiomyoblast cells. Our results showed that treatment of H9c2 cells with the CYP1A1 inducer, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) significantly induced CYP1A1 at mRNA, protein, and activity levels in a concentration-dependent manner. The RNA synthesis inhibitor, actinomycin D, completely blocked the CYP1A1 mRNA induction by TCDD, indicating the requirement of de novo RNA synthesis through transcriptional activation. In conclusion, we demonstrated for the first time the constitutive expression and inducibility of CYP1A1 in H9c2 cells. Therefore, this cell line offers a unique in vitro model to study the role of CYP1A1 in the pathogenesis of various cardiovascular diseases.

Reverse transcriptase-PCR quantification of mRNA levels from cytochrome (CYP)1, CYP2 and CYP3 families in 22 different human tissues

OBJECTIVE

The aim of this work was to study simultaneously the expression profile of the 23 CYP mRNAs of CYP1, CTP2 and CYP3 families in 22 different human tissues namely adrenal gland, bladder, bone marrow, colon, fetal liver, heart, kidney, liver, lung, mammary gland, ovary, placenta, prostate, salivary gland, skeletal muscle, small intestine, spleen, testis, thymus, thyroid, trachea and uterus.

METHODS

Analysis of the mRNA levels of each of these CYP isoforms was performed on total RNA from pooled specimens of human organs using reverse transcriptase-PCR-based CYP mRNA assays previously validated for their sensitivity and their specificity.

RESULTS

Our results confirmed previously reported data in the literature concerning isoforms expression in the most currently studied tissues. Moreover, they provided a great deal of new information, mainly about the expression of mRNA of little-known CYP isoforms. Among the 23 CYP isoforms studied, 12 were mainly hepatic (CYP1A2, 2A6, 2A7, 2A13, 2C8, 2C9, 2C18, 2C19, 2D6, 2E1, 3A4 and 3A43). Two CYP mRNAs were predominantly expressed in several extrahepatic tissues: CYP1B1 mRNA was the predominant CYP in seven extrahepatic tissues (bone marrow, kidney, mammary gland, prostate, spleen, thyroid and uterus) and CYP2J2 in four extrahepatic tissues (heart, placenta, salivary gland and skeletal muscle). Finally, some CYPs were nearly exclusively expressed in only one extrahepatic tissue. CYP2R1 was found in testis, CYP2U1 in the thymus and CYP2F1 in the respiratory tract (lung and trachea).

CONCLUSION

This description will broaden the understanding of the physiological functions of these CYPs.