Sexual dimorphism and tissue specificity in the expression of CYP4F forms in Sprague Dawley rats

Scientific opinion on the tolerable upper intake level for vitamin E

Following a request from the European Commission, the EFSA Panel on Nutrition, Novel Foods and Food Allergens (NDA) was asked to deliver a scientific opinion on the revision of the tolerable upper intake level (UL) for vitamin E. As α-tocopherol is recognised as the only essential form of vitamin E, the Panel restricted its evaluation to α-tocopherol. Systematic reviews of the literature were conducted to assess evidence on priority adverse health effects of excess intake of vitamin E, namely risk of impaired coagulation and bleeding, cardiovascular disease and prostate cancer. The effect on blood clotting and associated increased risk of bleeding is considered as the critical effect to establish an UL for vitamin E. No new evidence has been published that could improve the characterisation of a dose-response. The ULs for vitamin E from all dietary sources, which were previously established by the Scientific Committee on Food, are retained for all population groups, i.e. 300 mg/day for adults, including pregnant and lactating women, 100 mg/day for children aged 1-3 years, 120 mg/day for 4-6 years, 160 mg/day for 7-10 years, 220 mg/day for 11-14 years and 260 mg/day for 15-17 years. A UL of 50 mg/day is established for infants aged 4-6 months and a UL of 60 mg/day for infants aged 7-11 months. ULs apply to all stereoisomeric forms of α-tocopherol. ULs do not apply to individuals receiving anticoagulant or antiplatelet medications (e.g. aspirin), to patients on secondary prevention for CVD or to patients with vitamin K malabsorption syndromes. It is unlikely that the ULs for vitamin E are exceeded in European populations, except for regular users of food supplements containing high doses of vitamin E.

Changes in cardiovascular arachidonic acid metabolism in experimental models of menopause and implications on postmenopausal cardiac hypertrophy

Menopause is a normal stage in the human female aging process characterized by the cessation of menstruation and the ovarian production of estrogen and progesterone hormones. Menopause is associated with an increased risk of several different diseases. Cardiovascular diseases are generally less common in females than in age-matched males. However, this female advantage is lost after menopause. Cardiac hypertrophy is a disease characterized by increased cardiac size that develops as a response to chronic overload or stress. Similar to other cardiovascular diseases, the risk of cardiac hypertrophy significantly increases after menopause. However, the exact underlying mechanisms are not yet fully elucidated. Several studies have shown that surgical or chemical induction of menopause in experimental animals is associated with cardiac hypertrophy, or aggravates cardiac hypertrophy induced by other stressors. Arachidonic acid (AA) released from the myocardial phospholipids is metabolized by cardiac cytochrome P450 (CYP), cyclooxygenase (COX), and lipoxygenase (LOX) enzymes to produce several eicosanoids. AA-metabolizing enzymes and their respective metabolites play an important role in the pathogenesis of cardiac hypertrophy. Menopause is associated with changes in the cardiovascular levels of CYP, COX, and LOX enzymes and the levels of their metabolites. It is possible that these changes might play a role in the increased risk of cardiac hypertrophy after menopause.

Sexual Dimorphism in the Expression of Cytochrome P450 Enzymes in Rat Heart, Liver, Kidney, Lung, Brain, and Small Intestine

Cytochrome P450 (P450) enzymes are monooxygenases that are expressed hepatically and extrahepatically and play an essential role in xenobiotic metabolism. Substantial scientific evidence indicates sex-specific differences between males and females in disease patterns and drug responses, which could be attributed, even partly, to differences in the expression and/or activity levels of P450 enzymes in different organs. In this study, we compared the mRNA and protein expression of P450 enzymes in different organs of male and female Sprague-Dawley rats by real-time polymerase chain reaction and western blot techniques. We found significant sex- and organ-specific differences in several enzymes. Hepatic Cyp2c11, Cyp2c13, and Cyp4a2 showed male-specific expression, whereas Cyp2c12 showed female-specific expression. Cyp2e1 and Cyp4f enzymes demonstrated higher expression in the female heart and kidneys compared with males; however, they showed no significant sexual dimorphism in the liver. Male rats showed higher hepatic and renal Cyp1b1 levels. All assessed enzymes were found in the liver, but some were not expressed in other organs. At the protein expression level, CYP1A2, CYP3A, and CYP4A1 demonstrated higher expression levels in the females in several organs, including the liver. Elucidating sex-specific differences in P450 enzyme levels could help better understand differences in disease pathogeneses and drug responses between males and females and thus improve treatment strategies. SIGNIFICANCE STATEMENT: This study characterized the differences in the mRNA and protein expression levels of different cytochrome P450 (P450) enzymes between male and female rats in the heart, liver, lung, kidney, brain, and small intestine. It demonstrated unique sex-specific differences in the different organs. This study is considered a big step towards elucidating sex-specific differences in P450 enzyme levels, which is largely important for achieving a better understanding of the differences between males and females in the disease's processes and treatment outcomes.

The Sex-Gender Effects in the Road to Tailored Botanicals

Phenols are a wide family of phytochemicals that are characterized by large chemical diversity and are considered to bioactive molecules of foods, beverages, and botanicals. Although they have a multitude of biological actions, their beneficial effects are rarely evidenced in clinical research with high scientific rigor. This may occur due to the presence of numerous confounders, such as the modulation of phenol bioavailability, which can be regulated by microbiota, age, sex-gender. Sex-gender is an important determinant of health and well-being, and has an impact on environmental and occupational risks, access to health care, disease prevalence, and treatment outcomes. In addition, xenobiotic responses may be strongly influenced by sex-gender. This review describes how sex–gender differentially influences the activities of phenols also in some critical periods of women life such as pregnancy and lactation, considering also the sex of fetuses and infants. Thus, sex–gender is a variable that must be carefully considered and should be used to propose directions for future research on the road to tailored medicine and nutrition.

Bexarotene, a Selective RXRα Agonist, Reverses Hypotension Associated with Inflammation and Tissue Injury in a Rat Model of Septic Shock

Peroxisome proliferator-activated receptors (PPARs) are nuclear receptors that can activate or inhibit the expression of many target genes by forming a heterodimer complex with the retinoid X receptor (RXR). The aim of this study was to investigate effects of bexarotene, a selective RXRα agonist, on the changes in renal, cardiac, hepatic, and pulmonary expression/activity of inducible nitric oxide synthase (iNOS) and cytochrome P450 (CYP) 4F6 in relation to PPARα/β/γ-RXRα heterodimer formation in a rat model of septic shock. Rats were injected with dimethyl sulfoxide or bexarotene 1 h after administration of saline or lipopolysaccharide (LPS). Mean arterial pressure (MAP) and heart rate (HR) were recorded from rats, which had received either saline or LPS before and after 1, 2, 3, and 4 h. Serum iNOS, LTB₄, myeloperoxidase (MPO), and lactate dehydrogenase (LDH) levels as well as tissue iNOS and CYP4F6 mRNA expression in addition to PPARα/β/γ and RXRα proteins were measured. LPS-induced decrease in MAP and increase in HR were associated with a decrease in PPARα/β/γ-RXRα heterodimer formation and CYP4F6 mRNA expression. LPS also caused an increase in systemic iNOS, LTB₄, MPO, and LDH levels as well as iNOS mRNA expression. Bexarotene at 0.1 mg/kg (i.p.) prevented the LPS-induced changes, except tachycardia. The results suggest that increased formation of PPARα/β/γ-RXRα heterodimers and CYP4F6 expression/activity in addition to decreased iNOS expression contributes to the beneficial effect of bexarotene to prevent the hypotension associated with inflammation and tissue injury during rat endotoxemia.

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.

Detrimental Effects of Testosterone Addition to Estrogen Therapy Involve Cytochrome P-450-Induced 20-HETE Synthesis in Aorta of Ovariectomized Spontaneously Hypertensive Rat (SHR), a Model of Postmenopausal Hypertension

Postmenopausal period has been associated to different symptoms such as hot flashes, vulvovaginal atrophy, hypoactive sexual desire disorder (HSDD) and others. Clinical studies have described postmenopausal women presenting HSDD can benefit from the association of testosterone to conventional hormonal therapy. Testosterone has been linked to development of cardiovascular diseases including hypertension and it also increases cytochrome P-450-induced 20-HETE synthesis which in turn results in vascular dysfunction. However, the effect of testosterone plus estrogen in the cardiovascular system is still very poorly studied. The aim of the present study is to evaluate the role of cytochrome P-450 pathway in a postmenopausal hypertensive female treated with testosterone plus estrogen. For that, hypertensive ovariectomized rats (OVX-SHR) were used as a model of postmenopausal hypertension and four groups were created: SHAM-operated (SHAM), ovariectomized SHR (OVX), OVX treated for 15 days with conjugated equine estrogens [(CEE) 9.6 μg/Kg/day/po] or CEE associated to testosterone [(CEE+T) 2.85 mg/kg/weekly/im]. Phenylephrine-induced contraction and generation of reactive oxygen species (ROS) were markedly increased in aortic rings from OVX-SHR compared to SHAM rats which were restored by CEE treatment. On the other hand, CEE+T abolished vascular effects by CEE and augmented both systolic and diastolic blood pressure of SHR. Treatment of aortic rings with the CYP/20-HETE synthesis inhibitor HET0016 (1 μM) reduced phenylephrine hyperreactivity and the augmented ROS generation in the CEE+T group. These results are paralleled by the increased CYP4F3 protein expression and activity in aortas of CEE+T. In conclusion, we showed that association of testosterone to estrogen therapy produces detrimental effects in cardiovascular system of ovariectomized hypertensive females via CYP4F3/20-HETE pathway. Therefore, our findings support the standpoint that the CYP/20-HETE pathway is an important therapeutic target for the prevention of cardiovascular disease in menopausal women in the presence of high levels of testosterone.

Gender differences in safety issues during Fingolimod therapy: Evidence from a real-life Relapsing Multiple Sclerosis cohort

OBJECTIVE

Benefits and risks of new therapies in Multiple Sclerosis (MS) must be balanced carefully and tailored to patients. We aimed to describe our experience with Fingolimod (FTY), correlating demographics, clinical and hematological features of the Relapsing MS (RMS) cohort with the occurring Adverse Events (AEs).

MATERIAL AND METHODS

Pretreatment screening tests, cardiological observation, and safety follow-up data were analyzed in 225 RMS patients. Changes in continuous data were analyzed post hoc with Wilcoxon ranks test; categorical variables were examined using McNemar test. Two-way repeated-measures analysis of variance (ANOVA) was used to analyze differences between baseline characteristic of the cohorts and Liver Function Tests (LFT) alterations. Binary logistic regression models were used to identify which of the baseline factors influenced LFT alterations and the occurrence of infections.

RESULTS

During 2 years of follow-up 24 patients (10%) interrupted FTY. Discontinuation most often was due to AEs (n = 14) or breakthrough disease (n = 5). The most frequently AEs were infections (10.6%). After the first year patients showing an infectious episode were mostly female (p = .04). The infections did not correlate with the decrease in white blood cells or to lymphocyte count. AST and ALT alterations ​​were observed mostly in males (p = .002 and p = .01, respectively), and increase in GGT ​​was reported in subjects older at FTY beginning (p < .05).

CONCLUSIONS

For a patient-centered safety monitoring of FTY, we may apply gender-specific warnings, for the detection of transaminases abnormalities and infectious episodes.

Sex and the Lab: An Alcohol-Focused Commentary on the NIH Initiative to Balance Sex in Cell and Animal Studies

In May 2014, Dr. Francis Collins, the director of U.S. National Institutes of Health (NIH), and Dr. Janine Clayton, the director of the U.S. National Institutes of Health Office of Research on Women's Health, published a commentary in the journal Nature announcing new policies to ensure that preclinical research funded by the NIH considers both males and females. While these policies are still developing, they have already generated great interest by the scientific community and triggered both criticism and applause. This review provides a description and interpretation of the NIH guidelines, and it traces the history that led to their implementation. As expected, this NIH initiative generated some anxiety in the scientific community. The use of female animals in the investigation of basic mechanisms is perceived to increase variability in the results, and the use of both sexes has been claimed to slow the pace of scientific discoveries and to increase the cost at a time characterized by declining research support. This review discusses issues related to the study of sex as a biological variable (SABV) in alcohol studies and provides examples of how researchers have successfully addressed some of them. A practical strategy is provided to include both sexes in biomedical research while maintaining control of the research direction. The inclusion of sex as an important biological variable in experimental design, analysis, and reporting of preclinical alcohol research is likely to lead to a better understanding of alcohol pharmacology and the development of alcohol use disorder, may promote drug discovery for new pharmacotherapies by increasing scientific rigor, and may provide clinical benefit to women's health. This review aims to promote the understanding of the NIH's SABV guidelines and to provide alcohol researchers with a theoretical and practical framework for working with both sexes in preclinical research.

Complexity of vitamin E metabolism

Bioavailability of vitamin E is influenced by several factors, most are highlighted in this review. While gender, age and genetic constitution influence vitamin E bioavailability but cannot be modified, life-style and intake of vitamin E can be. Numerous factors must be taken into account however, i.e., when vitamin E is orally administrated, the food matrix may contain competing nutrients. The complex metabolic processes comprise intestinal absorption, vascular transport, hepatic sorting by intracellular binding proteins, such as the significant α-tocopherol-transfer protein, and hepatic metabolism. The coordinated changes involved in the hepatic metabolism of vitamin E provide an effective physiological pathway to protect tissues against the excessive accumulation of, in particular, non-α-tocopherol forms. Metabolism of vitamin E begins with one cycle of CYP4F2/CYP3A4-dependent ω-hydroxylation followed by five cycles of subsequent β-oxidation, and forms the water-soluble end-product carboxyethylhydroxychroman. All known hepatic metabolites can be conjugated and are excreted, depending on the length of their side-chain, either via urine or feces. The physiological handling of vitamin E underlies kinetics which vary between the different vitamin E forms. Here, saturation of the side-chain and also substitution of the chromanol ring system are important. Most of the metabolic reactions and processes that are involved with vitamin E are also shared by other fat soluble vitamins. Influencing interactions with other nutrients such as vitamin K or pharmaceuticals are also covered by this review. All these processes modulate the formation of vitamin E metabolites and their concentrations in tissues and body fluids. Differences in metabolism might be responsible for the discrepancies that have been observed in studies performed in vivo and in vitro using vitamin E as a supplement or nutrient. To evaluate individual vitamin E status, the analytical procedures used for detecting and quantifying vitamin E and its metabolites are crucial. The latest methods in analytics are presented.

Soluble epoxide hydrolase inhibitor, TUPS, protects against isoprenaline-induced cardiac hypertrophy

BACKGROUND AND PURPOSE

We have previously shown that isoprenaline-induced cardiac hypertrophy causes significant changes in the expression of cytochromes P450 (CYP) and soluble epoxide hydrolase (sEH) genes. Therefore, it is important to examine whether the inhibition of sEH by 1-(1-methanesulfonyl-piperidin-4-yl)-3-(4-trifluoromethoxy-phenyl)-urea (TUPS) will protect against isoprenaline-induced cardiac hypertrophy.

EXPERIMENTAL APPROACH

Male Sprague-Dawley rats were treated with TUPS (0.65 mg kg(-1) day(-1), p.o.), isoprenaline (5 mg kg(-1) day(-1), i.p.) or the combination of both. In vitro H9c2 cells were treated with isoprenaline (100 μM) in the presence and absence of either TUPS (1 μM) or 11,12 EET (1 μM). The expression of hypertrophic, fibrotic markers and different CYP genes were determined by real-time PCR.

KEY RESULTS

Isoprenaline significantly induced the hypertrophic, fibrotic markers as well as the heart to body weight ratio, which was significantly reversed by TUPS. Isoprenaline also caused an induction of CYP1A1, CYP1B1, CYP2B1, CYP2B2, CYP4A3 and CYP4F4 gene expression and TUPS significantly inhibited this isoprenaline-mediated effect. Moreover, isoprenaline significantly reduced 5,6-, 8,9-, 11,12- and 14,15-EET and increased their corresponding 8,9-, 11,12- and 14,15-dihydroxyeicosatrienoic acid (DHET) and the 20-HETE metabolites. TUPS abolished these isoprenaline-mediated changes in arachidonic acid (AA) metabolites. In H9c2 cells, isoprenaline caused a significant induction of ANP, BNP and EPHX2 mRNA levels. Both TUPS and 11,12-EET significantly decreased this isoprenaline-mediated induction of ANP, BNP and EPHX2.

CONCLUSIONS AND IMPLICATIONS

TUPS partially protects against isoprenaline-induced cardiac hypertrophy, which confirms the role of sEH and CYP enzymes in the development of cardiac hypertrophy.

Catabolism of (2E)-4-hydroxy-2-nonenal via ω- and ω-1-oxidation stimulated by ketogenic diet

Oxidative stress triggers the peroxidation of ω-6-polyunsaturated fatty acids to reactive lipid fragments, including (2E)-4-hydroxy-2-nonenal (HNE). We previously reported two parallel catabolic pathways of HNE. In this study, we report a novel metabolite that accumulates in rat liver perfused with HNE or 4-hydroxynonanoic acid (HNA), identified as 3-(5-oxotetrahydro-2-furanyl)propanoyl-CoA. In experiments using a combination of isotopic analysis and metabolomics studies, three catabolic pathways of HNE were delineated following HNE conversion to HNA. (i) HNA is ω-hydroxylated to 4,9-dihydroxynonanoic acid, which is subsequently oxidized to 4-hydroxynonanedioic acid. This is followed by the degradation of 4-hydroxynonanedioic acid via β-oxidation originating from C-9 of HNA breaking down to 4-hydroxynonanedioyl-CoA, 4-hydroxyheptanedioyl-CoA, or its lactone, 2-hydroxyglutaryl-CoA, and 2-ketoglutaric acid entering the citric acid cycle. (ii) ω-1-hydroxylation of HNA leads to 4,8-dihydroxynonanoic acid (4,8-DHNA), which is subsequently catabolized via two parallel pathways we previously reported. In catabolic pathway A, 4,8-DHNA is catabolized to 4-phospho-8-hydroxynonanoyl-CoA, 3,8-dihydroxynonanoyl-CoA, 6-hydroxyheptanoyl-CoA, 4-hydroxypentanoyl-CoA, propionyl-CoA, and acetyl-CoA. (iii) The catabolic pathway B of 4,8-DHNA leads to 2,6-dihydroxyheptanoyl-CoA, 5-hydroxyhexanoyl-CoA, 3-hydroxybutyryl-CoA, and acetyl-CoA. Both in vivo and in vitro experiments showed that HNE can be catabolically disposed via ω- and ω-1-oxidation in rat liver and kidney, with little activity in brain and heart. Dietary experiments showed that ω- and ω-1-hydroxylation of HNA in rat liver were dramatically up-regulated by a ketogenic diet, which lowered HNE basal level. HET0016 inhibition and mRNA expression level suggested that the cytochrome P450 4A are main enzymes responsible for the NADPH-dependent ω- and ω-1-hydroxylation of HNA/HNE.

Differential expression of cytochrome P450 omega-hydroxylase isoforms and their association with clinicopathological features in pancreatic ductal adenocarcinoma

BACKGROUND

The cytochrome P450 (CYP) superfamily consists of enzymes that catalyze the oxidation of lipids, steroids, and drugs. In particular, the CYP4 family plays an essential role in lipid metabolism by the ω-hydroxylation of terminal ends of fatty acids. Disturbance of this system has been associated with increased angiogenesis, proliferation, and metastasis of several cancers. This study aimed to detect the expression of CYP4 isoforms (CYP4A11, CYP4F2, CYP4F3) in pancreatic ductal adenocarcinoma (PDA) and their association with clinicopathological features.

METHODS

Pancreatic specimens were collected from 73 patients who underwent surgical resection at the Thomas Jefferson University Hospital. Quantitative polymerase chain reaction was used to examine the cytochrome P450 isoforms in PDA (n = 62), adjacent-normal (n = 30), and benign tissues (n = 11). Logistic regression models were used to analyze gene expression among tissue types. Spearman rank correlations were calculated for isoform expression and for age. Differences in expression by gender were assessed via t test. Other clinicopathological variables (diabetes, smoking, obesity, T stage, perineural invasion, nodal status) were analyzed by Wilcoxon rank sum.

RESULTS

CYP4 expression for isoforms was significantly higher in PDA tissues versus matched-adjacent tissues (p < 0.01). PDA tumors expressed significantly higher levels of CYP4F2 and CYP4F3 when compared to benign lesions (p < 0.01). Significant associations were found between low levels of CYP4F2 and CYP4F3 and increased age of PDA patients. Interestingly, all isoforms were expressed at higher levels in male patients.

CONCLUSIONS

Transcriptional upregulation of cytochrome P450 ω-hydroxylase suggests that these enzymes have the potential to be used as distinguishing markers in pancreatic pathology.

Cytochrome P450 epoxygenase metabolite, 14,15-EET, protects against isoproterenol-induced cellular hypertrophy in H9c2 rat cell line

We have previously shown that isoproterenol-induced cardiac hypertrophy causes significant changes to cytochromes P450 (CYPs) and soluble epoxide hydrolase (sEH) gene expression. Therefore, in this study, we examined the effect of isoproterenol in H9c2 cells, and the protective effects of 14,15-EET against isoproterenol-induced cellular hypertrophy. Isoproterenol was incubated with H9c2 cells for 24 and 48 h. To determine the protective effects of 14,15-EET, H9c2 cells were incubated with isoproterenol in the absence and presence of 14,15-EET. Thereafter, the expression of hypertrophic markers and different CYP genes were determined by real time-PCR. Our results demonstrated that isoproterenol significantly increased the expression of hypertrophic marker, atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP), parallel to a significant increase in cell surface area. Also, isoproterenol increased the mRNA expression of CYP1A1, CYP1B1, CYP2J3, CYP4F4 and CYP4F5, as well as the gene encoding sEH, EPHX2. On other hand, 14,15-EET significantly attenuated the isoproterenol-mediated induction of ANP, BNP, CYP1A1, CYP2J3, CYP4F4, CYP4F5 and EPHX2. Moreover 14,15-EET prevented the isoproterenol-mediated increase in cell surface area. Interestingly, 20-hydroxyeicosatetraenoic acid (20-HETE) treatment caused similar effects to that of isoproterenol treatment and induced cellular hypertrophy in H9c2 cells. In conclusion, isoproterenol induces cellular hypertrophy and modulates the expression of CYPs and EPHX2 in H9c2 cells. Furthermore, 14,15-EET exerts a protective effect against isoproterenol-induced cellular hypertrophy whereas, 20-HETE induced cellular hypertrophy in H9c2 cells.

Cytochrome P450-mediated metabolism in brain: functional roles and their implications

INTRODUCTION

Cytochromes P450 (P450) and associated monooxygenases are a family of heme proteins involved in metabolism of endogenous compounds (arachidonic acid, eicosanoids and prostaglandins) as also xenobiotics including drugs and environmental chemicals. Liver is the major organ involved in P450-mediated metabolism and hepatic enzymes have been characterized. Extrahepatic organs, such as lung, kidney and brain have the capability for biotransformation through P450 enzymes. Brain, including human brain, expresses P450 enzymes that metabolize xenobiotics and endogenous compounds.

AREAS COVERED

An overview of P450-mediated metabolism in brain is presented focusing on distinct differences seen in expression of P450 enzymes, generation of unique P450 enzymes in brain through alternate splicing and their consequences in terms of metabolism of psychoactive drugs and inflammatory prompts, such as leukotrienes, thus modulating inflammatory response.

EXPERT OPINION

The brain possesses unique P450s that metabolize drugs and endogenous compounds through pathways that are markedly different from that seen in liver indicating that extrapolation directly from liver to brain is not appropriate. It is therefore necessary to characterize the unique brain P450s and their ability to metabolize xenobiotics and endogenous compounds to better understand the functions of this important class of enzymes in brain, especially human brain.

Sex-related differences in renal toxicodynamics in rodents

INTRODUCTION

An issue yet to be addressed, in the investigation of the xenobiotic toxicity, is a detailed characterization of the sex differences in toxicological responses. The 'sex issue' is particularly significant in nephrotoxicology as the kidney is a relevant target organ for xenobiotics and few studies have approached this subject in the past. There is a strong need to improve our understanding regarding the influence of sex in toxicology, given their increased requirement to establish the limits of exposure to chemicals in the environment and at work.

AREAS COVERED

In this review, the authors provide the reader with the current knowledge of sex differences in kidney toxicity for rats and mice. To make the review easier to consult, these studies have been organized according to the class of xenobiotic.

EXPERT OPINION

From the analysis of the present knowledge emerges a dramatic need for information on sex differences in xenobiotics toxicity. Although animals are reasonably good predictors of adverse renal effects in patients, there is need to identify alternative methods (e.g. in vitro/ex vivo) to better study sex differences in organ toxicity.

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.

Nutrition and human health from a sex-gender perspective

Nutrition exerts a life-long impact on human health, and the interaction between nutrition and health has been known for centuries. The recent literature has suggested that nutrition could differently influence the health of male and female individuals. Until the last decade of the 20th century, research on women has been neglected, and the results obtained in men have been directly translated to women in both the medicine and nutrition fields. Consequently, most modern guidelines are based on studies predominantly conducted on men. However, there are many sex-gender differences that are the result of multifactorial inputs, including gene repertoires, sex steroid hormones, and environmental factors (e.g., food components). The effects of these different inputs in male and female physiology will be different in different periods of ontogenetic development as well as during pregnancy and the ovarian cycle in females, which are also age dependent. As a result, different strategies have evolved to maintain male and female body homeostasis, which, in turn, implies that there are important differences in the bioavailability, metabolism, distribution, and elimination of foods and beverages in males and females. This article will review some of these differences underlying the impact of food components on the risk of developing diseases from a sex-gender perspective.

3-methylcholanthrene and benzo(a)pyrene modulate cardiac cytochrome P450 gene expression and arachidonic acid metabolism in male Sprague Dawley rats

BACKGROUND AND PURPOSE

There is a strong correlation between cytochrome P450 (P450)-dependent arachidonic acid metabolism and the pathogenesis of cardiac hypertrophy. Several aryl hydrocarbon receptor (AhR) ligands were found to alter P450-dependent arachidonic acid metabolism. Here, we have investigated the effect of 3-methylcholanthrene (3-MC) and benzo(a)pyrene (BaP), two AhR ligands, on the development of cardiac hypertrophy.

EXPERIMENTAL APPROACH

Male Sprague Dawley rats were injected (i.p.) daily with either 3-MC (10 mg kg(-1)) or BaP (20 mg kg(-1)) for 7 days. Then hearts were removed, and the heart to body weight ratio and the gene expression of the hypertrophic markers and P450 genes were determined. Levels of arachidonic acid metabolites were determined by liquid chromatography-electron spray ionization-mass spectrometry.

KEY RESULTS

Both 3-MC and BaP increased the heart to body weight ratio as well as the hypertrophic markers, atrial natriuretic peptide and brain natriuretic peptide. 3-MC and BaP treatment increased the gene expression of CYP1A1, CYP1B1, CYP2E1, CYP4F4, CYP4F5 and soluble epoxide hydrolase. Both 3-MC and BaP treatments increased the dihydroxyeicosatrienoic acids (DHETs) : epoxyeicosatrienoic acids (EETs) ratio and the 20-hydroxyeicosatetraenoic acid (20-HETE) : total EETs ratio. Treatment with benzo(e)pyrene, an isomer of BaP that is a poor ligand for the AhR, did not induce cardiac hypertrophy in rats, confirming the role of AhR in the development of cardiac hypertrophy. Treatment with the omega-hydroxylase inhibitor, HET0016, significantly reversed BaP-induced cardiac hypertrophy.

CONCLUSIONS AND IMPLICATIONS

3-MC and BaP induce cardiac hypertrophy by increasing the ratio of DHETs : EETs and/or the ratio of 20-HETE : total EETs, through increasing soluble epoxide hydrolase activity.

Vitamin E status and metabolism in adult and aged aryl hydrocarbon receptor null mice

The aryl hydrocarbon receptor (AhR) is involved in regulation of mechanisms for detoxification of xenobiotics, as well as vitamin A metabolism. Vitamin E is a fat-soluble nutrient whose metabolism is initialized via the cytochrome P450 system. Thus, AhR absence could alter hepatic regulation of α-tocopherol metabolism. To test this hypothesis, we assessed vitamin E status in adult (2-5 m) and old (21-22 m), wild-type and AhR-null mice. Plasma α-tocopherol concentrations in AhR-null mice (2.3±1.2 μmol/L, n=19) were lower than those of wild-type mice (3.2±1.2, n=17, P=.0131); those in old mice (3.2±1.2, n=20) were higher than those of adults (2.2±1.0, n=16, P=.0075). Hepatic α-tocopherol concentrations were not different between genotypes, but were nearly double in old (32±8 nmol/g, n=20) as compared with adult mice (17±2, n=16, P<.0001). Hepatic Cyp3a concentrations in AhR-null mice were greater than those in wild-type mice (P=.0011). Genotype (P=.0047), sex (P<.0001) and age (P<.0001) were significant modifiers of liver α-tocopherol metabolite (α-CEHC) concentrations. In general, Cyp3a concentrations correlated with hepatic α-tocopherol (r=0.3957, P<.05) and α-CEHC (r=0.4260, P<.05) concentrations. Since there were no significant genotype differences in the hepatic α- or γ-tocopherol concentrations, AhR-null mice did not have dramatically altered vitamin E metabolism. Since they did have higher hepatic α-CEHC concentrations, these data suggest metabolism was up-regulated in the AhR-null mice in order to maintain the hepatic tocopherol concentrations similar to those of wild-type mice.

2,3,7,8-Tetrachlorodibenzo-p-dioxin and beta-naphthoflavone induce cellular hypertrophy in H9c2 cells by an aryl hydrocarbon receptor-dependant mechanism

Cigarette smoke is a major risk factor for cardiovascular diseases. It contains thousands of compounds that activate the aryl hydrocarbon receptor (AhR). In addition, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), the most potent AhR ligand, has been shown to cause cardiotoxic effects in several in vivo models. Although induction of CYP1 family is the most important effect of AhR activation, the role of CYP1 induction in mediating the cardiotoxic effect of TCDD is usually overlooked. Therefore, we investigated whether AhR activation causes a hypertrophic effect in H9c2 cells and we related this effect to changes in CYP gene expression. In the current study, the cardiac derived H9c2 cells were treated with two AhR ligands, TCDD and beta-naphthoflavone (BNF), for 24 and 48h. The expression of the hypertrophic markers, atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP), and several CYP genes were measured by real-time PCR. Treatment of H9c2 cells with TCDD or BNF for 24h caused a significant induction of CYP1A1, CYP1B1, and CYP4A1; however, there was no change in the expression of other genes. On the other hand, treatment of the cells with TCDD or BNF for 48h caused a significant induction of the hypertrophic markers, ANP and BNP, and several CYP genes such as CYP1A1, CYP1B1, CYP2E1, CYP2J3, and CYP4F4 parallel to a significant increase in the cell surface area. Neither TCDD nor BNF increased the oxidative stress in H9c2 cells at all concentrations tested. Interestingly, resveratrol, an AhR antagonist, protected the cells from TCDD-induced hypertrophy. In conclusion, AhR ligands caused a hypertrophic effect in H9c2 cells which was associated with induction of several CYP genes which can be prevented by resveratrol.

Predominant modifier of extreme liver cancer susceptibility in C57BR/cdJ female mice localized to 6 Mb on chromosome 17

Sex hormones influence the susceptibility of inbred mice to liver cancer. C57BR/cdJ (BR) females are extremely susceptible to spontaneous and chemically induced liver tumors, in part due to a lack of protection against hepatocarcinogenesis normally offered by ovarian hormones. BR males are also moderately susceptible, and the susceptibility of both sexes of BR mice to liver tumors induced with N,N-diethylnitrosamine relative to the resistant C57BL/6J (B6) strain is caused by two loci designated Hcf1 and Hcf2 (hepatocarcinogenesis in females) located on chromosomes 17 and 1, respectively. The Hcf1 locus on chromosome 17 is the predominant modifier of liver cancer in BR mice. To validate the existence of this locus and investigate its potential interaction with Hcf2, congenic mice for each region were generated. Homozygosity for the B6.BR(D17Mit164-D17Mit2) region resulted in a 4-fold increase in liver tumor multiplicity in females and a 4.5-fold increase in males compared with B6 controls. A series of 16 recombinants covering the entire congenic region was developed to further narrow the area containing Hcf1. Susceptible heterozygous recombinants demonstrated a 3- to 7-fold effect in females and a 1.5- to 2-fold effect in males compared with B6 siblings. The effect in susceptible lines completely recapitulated the susceptibility of heterozygous full-length chromosome 17 congenics and furthermore narrowed the location of the Hcf1 locus to a single region of the chromosome from 30.05 to 35.83 Mb.

CYP4Fs expression in rat brain correlates with changes in LTB4 levels after traumatic brain injury

Cytochrome P450 (CYP) 4Fs constitute a subgroup of the cytochrome P450 superfamily and are involved in cellular protection and metabolism of numerous molecules, including drugs, toxins, and eicosanoids. CYP4Fs are widely distributed in rat brain with each isoform having a unique distribution pattern throughout different brain regions. The present study shows that traumatic brain injury (TBI) triggers inflammation and elicits changes in mRNA expression of CYP4Fs in the frontal and occipital lobes and the hippocampus. At 24 h post-injury, almost all CYP4F mRNA expression is suppressed compared with sham control throughout these three regions, while at 2 weeks post-injury, all CYP4F mRNAs increase, reaching levels higher than those at 24 h post-injury or uninjured controls. These changes in CYP4F levels inversely correlate with levels of leukotriene B4 (LTB4) levels in the brain following injury at the same time points. TBI also causes changes in CYP4F protein expression and localization around the injury site. CYP4F1 and CYP4F6 immunoreactivity increases in surrounding astrocytes, while CYP4F4 immunoreactivity shifts from endothelia of cerebral vessels to astrocytes.

Genomic structure and regulation of the rat hepatic CYP4F1 gene by peroxisome proliferators

The rat hepatic gene CYP4F1 encodes a fatty acid omega hydroxylase P450 that metabolizes proinflammatory eicosanoids and long-chain fatty acids. We have completely sequenced the CYP4F1 gene (Accession Nos. AF200361 and AF181083), identified multiple transcription start sites, and characterized a strong core promoter region, -760/116, induced by retinoic acids and peroxisome proliferators in rat hepatoma McA-RH7777 cells. Three peroxisome proliferator responsive elements (PPRE) bind both PPARalpha/RXRalpha and HNF4alpha. Co-transfection of McA-RH7777 cells with the -760/116 reporter construct and PPARalpha/RXRalpha or HNF4alpha showed that HNF4alpha activated while PPARalpha/RXRalpha inhibited CYP4F1 promoter activity. Treating cells with Wy14,643 reversed all initial effects, indicating co-regulation of CYP4F1 gene transcription by PPARalpha/RXRalpha and HNF4alpha. Chromatin immunoprecipitation analysis of cells treated with Wy14,643 showed association of PPARalpha/RXRalpha with the active transcription of the CYP4F1 gene while in clofibrate treated rats HNF4alpha binds during gene repression, suggesting differential regulation of the CYP4F1 gene in vivo and in cell lines.

Human cytochrome p450 family 4 enzymes: function, genetic variation and regulation

The microsomal cytochrome P450 (CYP) family 4 monooxygenases are the major fatty acid omega-hydroxylases. These enzymes remove excess free fatty acids to prevent lipotoxicity, catabolize leukotrienes and prostanoids, and also produce bioactive metabolites from arachidonic acid omega-hydroxylation. In addition to endogenous substrates, recent evidence indicates that CYP4 monooxygenases can also metabolize xenobiotics, including therapeutic drugs. This review focuses on human CYP4 enzymes and updates current knowledge concerning catalytic activity profiles, genetic variation and regulation of expression. Comparative differences between the human and rodent CYP4 enzymes regarding catalytic function and conditional expression are also discussed.

Regulatory mechanisms to control tissue alpha-tocopherol

To test the hypothesis that hepatic regulation of alpha-tocopherol metabolism would be sufficient to prevent overaccumulation of alpha-tocopherol in extrahepatic tissues and that administration of high doses of alpha-tocopherol would up-regulate extrahepatic xenobiotic pathways, rats received daily subcutaneous injections of either vehicle or 0.5, 1, 2, or 10 mg alpha-tocopherol/100 g body wt for 9 days. Liver alpha-tocopherol increased 15-fold in rats given 10 mg alpha-tocopherol/100 g body wt (mg/100 g) compared with controls. Hepatic alpha-tocopherol metabolites increased with increasing alpha-tocopherol doses, reaching 40-fold in rats given the highest dose. In rats injected with 10 mg/100 g, lung and duodenum alpha-tocopherol concentrations increased 3-fold, whereas alpha-tocopherol concentrations of other extrahepatic tissues increased 2-fold or less. With the exception of muscle, daily administration of less than 2 mg/100 g failed to increase alpha-tocopherol concentrations in extrahepatic tissues. Lung cytochrome P450 3A and 1A levels were unchanged by administration of alpha-tocopherol at any dose. In contrast, lung P-glycoprotein (MDR1) levels increased dose dependently and expression of this xenobiotic transport protein was correlated with lung alpha-tocopherol concentrations (R(2)=0.88, p<0.05). Increased lung MDR1 may provide protection from exposure to environmental toxins by increasing alveolar space alpha-tocopherol.

Gender differences in kidney function

Sex hormones influence the development of female (F) and male (M) specific traits and primarily affect the structure and function of gender-specific organs. Recent studies also indicated their important roles in regulating structure and/or function of nearly every tissue and organ in the mammalian body, including the kidneys, causing gender differences in a variety of characteristics. Clinical observations in humans and studies in experimental animals in vivo and in models in vitro have shown that renal structure and functions under various physiological, pharmacological, and toxicological conditions are different in M and F, and that these differences may be related to the sex-hormone-regulated expression and action of transporters in the apical and basolateral membrane of nephron epithelial cells. In this review we have collected published data on gender differences in renal functions, transporters and other related parameters, and present our own microarray data on messenger RNA expression for various transporters in the kidney cortex of M and F rats. With these data we would like to emphasize the importance of sex hormones in regulation of a variety of renal transport functions and to initiate further studies of gender-related differences in kidney structure and functions, which would enable us to better understand occurrence and development of various renal diseases, pharmacotherapy, and drug-induced nephrotoxicity in humans and animals.

Catalytic characterization and cytokine mediated regulation of cytochrome P450 4Fs in rat hepatocytes

Cytochrome P450 (CYP) 4F mediated leukotriene B(4) (LTB(4)) metabolism modulates inflammation during injury and infection. Here we show that in addition to LTB(4), the recombinant rat CYP4Fs catalyze omega-hydroxylations of lipoxin A(4), and hydroxyeicosatetraeonic acids. CYP4F gene regulation studies in primary hepatocytes reveal that pro-inflammatory cytokines interleukin (IL) -1beta, IL-6 and tumor necrosis factor (TNF) -alpha produce a general inductive response whereas IL-10, an anti-inflammatory cytokine, suppresses CYP4F expression. The molecular mechanism behind IL-6 related induction of CYP4F4 and 4F5 is partially signal transducer and activator of transcription 3 (STAT3) dependent. When hepatocytes are subjected to high concentrations of LTB(4) or prostaglandin E(2), lipid mediators of inflammation, only an increase in CYP4F5 mRNA expression is observed. Collectively, the results from isozyme activity and substrate driven CYP4F induction do not support the notion that an autoregulatory pathway could control the excessive concentrations of LTB(4) during an inflammatory challenge to hepatocytes.

Distribution of tocotrienols in rats fed a rice bran tocotrienol concentrate

To examine the distribution of rice bran tocotrienol (T3), we gave rice bran T3 to rats after considering an acceptable daily intake of vitamin E for humans. Male SD rats (5 weeks of age) were fed for 3 weeks on a commercial diet containing 6.4 mg of vitamin E per 100 g wt and additively received vitamin E or the vehicle (vitamin E-free corn oil) by oral intubation. The animals were randomly divided into 4 groups depending on the type of test diet: control (vehicle), non-T3 (no T3 + 4.3 mg of tocopherol (TOC)/kg body weight (b.w.)/day), low-T3 (0.8 mg T3 + 3.5 mg TOC/kg b.w./day), and high-T3 (3.2 mg T3 + 1.1 mg TOC/kg b.w./day). The control rats and rats in the non-T3, low-T3, and high-T3 groups took 4.3 and 8.6 mg of vitamin E/kg b.w./day, respectively. Rice bran gamma-T3 was significantly distributed to the adipose tissue and increased from 1.1 to 10.2 nmol/g of adipose tissue according to the rice bran T3 intake.

Alpha-tocopherol regulation of hepatic cytochrome P450s and ABC transporters in rats

To test the hypothesis that supra-elevated hepatic alpha-tocopherol concentrations would up-regulate mechanisms that result in increased hepatic alpha-tocopherol metabolism and excretion, rats received daily subcutaneous alpha-tocopherol injections (10 mg/100 g body wt) and then were sacrificed on Day 0 or 12 h following their previous injection on Days 3, 6, 9, 12, 15, and 18. Liver alpha-tocopherol concentrations increased from 12 +/- 1 nmol/g (mean +/- SE) to 819 +/- 74 (Day 3), decreased at Day 9 (486 +/- 67), and continued to decrease through Day 18 (338 +/- 37). alpha-Tocopherol metabolites and their intermediates increased and decreased similarly to alpha-tocopherol albeit at lower concentrations. There were no changes in known vitamin E regulatory proteins, i.e., hepatic alpha-tocopherol transfer protein or cytochrome P450 (CYP) 4F. In contrast, both CYP3A and CYP2B, key xenobiotic metabolizing enzymes, doubled by Day 6 and remained elevated, while P450 reductase increased more slowly. Consistent with the decrease in liver alpha-tocopherol concentrations, a protein involved in biliary xenobiotic excretion, p-glycoprotein, increased at Day 9, doubling by Day 15. Thus hepatic alpha-tocopherol concentrations altered hepatic proteins involved in metabolism and disposition of xenobiotic agents.

Cytochrome P450 4F subfamily: at the crossroads of eicosanoid and drug metabolism

The cytochrome P450 4F (CYP4F) subfamily has over the last few years come to be recognized for its dual role in modulating the concentrations of eicosanoids during inflammation as well as in the metabolism of clinically significant drugs. The first CYP4F was identified because it catalyzed the hydroxylation of leukotriene B(4) (LTB(4)) and since then many additional members of this subfamily have been documented for their distinct catalytic roles and functional significance. Recent evidence emerging in relation to the temporal change of CYP4F expression in response to injury and infection supports an important function for these isozymes in curtailing inflammation. Their tissue-dependent expression, isoform-based catalytic competence and unique response to the external stimuli imply a critical role for them to regulate organ-specific functions. From this standpoint variations in relative CYP4F levels in humans may have direct influence on the metabolic outcome through their ability to generate and/or degrade bioactive eicosanoids or therapeutic agents. This review covers the enzymatic characteristics and regulatory properties of human and rodent CYP4F isoforms and their physiological relevance to major pathways in eicosanoid and drug metabolism.

Regulation of neuronal type genes in congestive heart failure rats

AIM

After myocardial infarction (MI), complex changes in the heart occur during progression into congestive heart failure (CHF). This study sought to identify regulated genes that could have a functional role in some of the changes seen in CHF.

METHODS

Myocardial infarction was induced by ligation of the left anterior descending coronary artery (LAD) in Wistar rats. Gene expression changes in 1- and 7-day MI left ventricular myocardium was analysed using complementary DNA (cDNA) filter arrays. Regulated genes were identified by repeated measurements and a ranked ratio analysis method.

RESULTS

A total of 135 genes were identified as differentially expressed. A few genes were robustly regulated at 1-day MI. In 7-day CHF hearts, changes in the expression of neuronal type genes was prominent (32%, n = 28). Eleven of these genes with no described association with CHF were selected for validation. One gene failed the validation. In CHF hearts, the expression of the muscarinic m4 (Chrm4) and nicotinic alpha4 (Chrna4) acetylcholin receptors, the ATP receptor P2rx4, nerve growth factor receptor (Ngfr), discoidin domain receptor 1 (Ddr1), neuronal pentraxin receptor (Nptxr), peripheral myelin protein Pmp-22, leukocyte type 12-lipoxygenase (Alox15), cytochrome P450 4F5 (Cyp4F5) and cardiac Kcne1 were all increased (range 1.6-6.0-fold, P < 0.01 for all genes). The lack of significant regulation of these genes at 1-day post-MI, suggests that the induction of these genes at 7-day post-MI is not a short-term response induced by the infarct itself.

CONCLUSION

These neuronal type genes may participate in underlying processes that affect contractility, intracardiac nerve function and development of arrhythmias in CHF hearts.

Renal localization, expression, and developmental regulation of P450 4F cytochromes in three substrains of spontaneously hypertensive rats

Cytochrome P450 4F isoforms have been shown to metabolize arachidonic acid to generate 20-hydroxyeicosatetraenoic acid (20-HETE), a potent eicosanoid that modulates vascular tone and renal tubular function. 20-HETE production in the kidney is implicated in the development of essential hypertension in the spontaneously hypertensive rat (SHR). In this study, we determined CYP4F mRNA localization and distribution in rat liver and kidney by in situ hybridization and real time quantitative PCR. CYP4Fs are regionally distributed in the kidney with CYP4F1, 4F4, and 4F5 being expressed more in the renal cortex than medulla while CYP4F6 shows higher medullary expression. We investigated developmental CYP4F gene expression in three different substrains of SHR. Distinct age-dependent patterns of expression were seen for individual CYP4F isoforms in Wistar-Kyoto (WKY) and three SHR substrains (B2, C, and A3). A steady increase in CYP4F1 expression with age was seen in each of the three substrains which correlate well with increased 20-HETE levels and elevated blood pressure seen in these animals. CYP4F4 expression increased significantly at 8 weeks followed by a precipitous fall in WKY and A3 strains at 12 weeks of age. In strains B2 and C, CYP4F4 levels started declining as early as 8 weeks of age. CYP4F5 and 4F6 levels fluctuated with age in a biphasic manner with a different profile for each sub-strain. Based on the expression profile and catalytic activity, CYP4F1 seems to be the most critical 4F isoform involved in the production of 20-HETE in the SHR kidney.

Evaluation of cytochrome P450 4 family as mediator of phospholipase D activation in aortic vascular smooth muscle cells

Norepinephrine (NE) stimulates phospholipase D (PLD) activity via phospholipase A2-dependent arachidonic acid release in rabbit aortic vascular smooth muscle cells (VSMC). We have previously shown that exogenous 20-hydroxyeicosatetraenoic acid (20-HETE), an eicosanoid generated through the cytochrome P450 (CYP) 4A pathway in vivo, stimulates PLD activity. Whether endogenous CYP4-derived arachidonic acid metabolites act as intracellular mediators of NE-induced PLD activation in VSMC is not known. In rabbit aortic VSMC, prototypical hepatic/renal CYP4A inducers such as fenofibrate and Wy 14643 inhibited both basal and NE-induced PLD activity after 48 h of exposure. The level of CYP4F, and to a lesser extent CYP4A, was also decreased by these agents. The expression levels of rabbit aortic VSMC CYP4A and CYP4F isoforms were reduced by antisense oligonucleotides treatment for 48 hours as measured by RTQ-PCR or Western blotting. This reduction in CYP4A or CYP4F levels did not change NE-induced PLD activation. The corresponding CYP4A scrambled and CYP4F sense oligonucleotides did not alter CYP levels. PLD activity was increased by ~70% after 15 min of stimulation with NE, whereas lauric acid omega-hydroxylase activity, a measure of fatty acid omega-hydroxylation, was unchanged. Inhibition of omega-hydroxylation with DDMS and HET0016, selective omega-hydroxylase inhibitors, and 20-HEDE, an antagonist of 20-HETE, increased PLD activity in a concentration-dependent manner and did not alter NE-induced PLD activation. These data suggest that PLD activation by NE is independent of the CYP4A/4F enzymes in rabbit aortic VSMC.

Regulation and inhibition of arachidonic acid omega-hydroxylases and 20-HETE formation

Cytochrome P450-catalyzed metabolism of arachidonic acid is an important pathway for the formation of paracrine and autocrine mediators of numerous biological effects. The omega-hydroxylation of arachidonic acid generates significant levels of 20-hydroxyeicosatetraenoic acid (20-HETE) in numerous tissues, particularly the vasculature and kidney tubules. Members of the cytochrome P450 4A and 4F families are the major omega-hydroxylases, and the substrate selectivity and regulation of these enzymes has been the subject of numerous studies. Altered expression and function of arachidonic acid omega-hydroxylases in models of hypertension, diabetes, inflammation, and pregnancy suggest that 20-HETE may be involved in the pathogenesis of these diseases. Our understanding of the biological significance of 20-HETE has been greatly aided by the development and characterization of selective and potent inhibitors of the arachidonic acid omega-hydroxylases. This review discusses the substrate selectivity and expression of arachidonic acid omega-hydroxylases, regulation of these enzymes during disease, and the application of enzyme inhibitors to study 20-HETE function.

Protective effect of 20-hydroxyeicosatetraenoic acid (20-HETE) on glomerular protein permeability barrier

BACKGROUND

Proteinuria is a significant problem in medicine today, although glomerular events underlying it are unknown. Products of cytochrome P450 (CYP450) pathway of arachidonic acid metabolism are increasingly recognized as playing major roles in renal function. We used in vitro albumin permeability (P(alb)) as a measure of injury and puromycin aminonucleoside (PAN) as an injurious agent to test the hypothesis that 20-hydroxyeicosatetraenoic acid (20-HETE) protects the glomerular filtration barrier from increased P(alb).

METHODS

We determined P(alb) in the following experimental groups: (1) isolated rat glomeruli incubated with PAN (5 microg/mL) for 5, 15, 30 or 60 minutes; (2) isolated glomeruli preincubated with 20-HETE (1.0 nmol/L to 100 nmol/L) for 15 minutes followed by additional incubation with PAN (5 microg/mL) for 15 minutes; (3) isolated glomeruli from rats treated with the CYP450 4A inducer clofibrate, and incubated with PAN (5 microg/mL) for 15 minutes; and (4) appropriate controls for each group. CYP450 4A levels were measured in glomeruli isolated from rats treated with clofibrate or vehicle.

RESULTS

PAN increased P(alb) of isolated glomeruli as early as 5 minutes (P(alb) 0.33 +/- 0.21, P < 0.05 vs. control). Maximal effect occurred at 30 minutes (P(alb) 0.75 +/- 0.16, P < 0.001 vs. control). Inclusion of 20-HETE (100 nmol/L) blocked the increased P(alb) caused by PAN (P(alb) 0.05 +/- 0.13). Likewise, glomeruli isolated from rats treated with clofibrate were protected from PAN-induced increase in P(alb) (P(alb) 0.19 +/- 0.03). Treatment with clofibrate significantly increased glomerular CYP450 4A expression.

CONCLUSION

PAN directly and immediately affects the glomerular permeability barrier. Furthermore, exogenous 20-HETE or clofibrate treatment protects glomeruli from increased P(alb) caused by PAN. Relative lack of 20-HETE may be a general characteristic of proteinuric states. Conversely, measures used to treat and/or prevent proteinuria may act to restore or increase glomerular 20-HETE levels.

Estrogen regulation of the cytochrome P450 3A subfamily in humans

This study examines the possible role of estrogen in regulating the expression of the human CYP3A subfamily: CYP3A4, CYP3A5, CYP3A7, and CYP3A43. To accomplish this goal, mRNA was quantified from human livers and endometrial samples, and total CYP3A protein levels were evaluated by Western immunoblot analysis of the liver samples. The human endometrial samples were from premenopausal and postmenopausal women. The premenopausal endometrium was either in the proliferative or secretory phase, whereas for the postmenopausal endometrium samples, the women had been treated with either a placebo or estropipate, an estrogen substitute. After analyses, CYP3A4 mRNA was shown to have lower hepatic expression in females than in males. In the endometrium, CYP3A4 and CYP3A43 are down-regulated by estrogen, whereas CYP3A5 is expressed at higher levels during the secretory phase. CYP3A7 was not detected in the endometrium. In addition, the CYP3A subfamily showed increased mRNA expression in the liver as age increased. The expression levels of total CYP3A protein and total CYP3A mRNA showed good correlation. Despite apparent regulation of CYP3A4 mRNA expression by estrogen, the effects of estrogen may be overshadowed by additional regulators of gene expression.

Functional characterization of genetic polymorphisms identified in the human cytochrome P450 4F12 (CYP4F12) promoter region

The human cytochrome CYP4F12 has been shown to be active toward inflammatory mediators and exogenous compounds such as antihistaminic drugs. In the present study, we report the first investigation of polymorphisms in the human CYP4F12 gene. A screening for sequence variations in the 5'-flanking region was performed by a Polymerase Chain Reaction-Single Strand Conformational Polymorphism (PCR-SSCP) strategy, using DNA samples from 53 unrelated French individuals of Caucasian origin. Several polymorphisms were identified, comprising a large deletion located in intron 1 (CYP4F12*v1), two isolated substitutions -402G>A (CYP4F12*v3) and -188 T>C (CYP4F12*v4) and nine combined mutations, -474T>C, -279A>C, -224A>G, -173G>A, -145C>G, -140T>C, -126T>C, -56T>C, and -21T>G (CYP4F12*v2). Considering the nature and location of the polymorphisms characterizing the CYP4F12*v1 and *v2, the functional relevance of those two allelic variants was further examined by transfecting different cell lines with constructs of the related region of the CYP4F12/luciferase reporter gene. Both alleles lead to a significant decrease of CYP4F12 gene expression in HepG2 cell line and, therefore, are likely to determine interindividual differences in CYP4F12 gene expression.

Sex differences in pharmacokinetics and pharmacodynamics

The importance of reviewing and studying sex-based differences in pharmacologic parameters is demonstrated by the increasing data on gender variation in drug efficacy and toxicity profiles. Sex-based differences in the four major factors that contribute to interindividual pharmacokinetic variability--bioavailability, distribution, metabolism, and elimination--are theorized to stem from variations between men and women in factors such as body weight, plasma volume, gastric emptying time, plasma protein levels, cytochrome P450 activity, drug transporter function, and excretion activity. Sex-determined variations in pharmacodynamics have traditionally been more difficult to study, but a number of recent studies have explored these differences. This review examines the biologic basis of differences in pharmacokinetics and pharmacodynamics between the sexes and summarizes studies that have addressed these differences. As an example, sex-based variation in the efficacy and toxicity of antiretroviral therapy in human immunodeficiency virus (HIV)-infected patients is explored more thoroughly to illustrate some of the factors underlying sex-based differences in drug therapy.

Differential effects of traumatic brain injury on the cytochrome p450 system: a perspective into hepatic and renal drug metabolism

Traumatic brain injury is known to cause several secondary effects, one of which is altered drug clearance. Given the fact that patients who sustain TBI are subsequently treated with a variety of pharmacological agents for the purpose of either neuroprotection or physiological support, it is imperative to clarify changes in expression and/or activities of enzymes involved in clearing drugs. The mixed function oxidase system, which consists of cytochrome P450 and cytochrome P450 reductase, plays a vital role in phase I drug metabolism. This paper addresses the issue as to what extent TBI affects the levels and activity of various rat CYP450 subfamilies. Our results show that TBI induces tissue-specific and time-dependent alterations. Total hepatic CYP450 content showed a biphasic response with a decrease seen at 24 h followed by an increase at 2 weeks. CYP450 reductase, in contrast, showed an opposite temporal profile. Immunoblot analyses and marker substrate metabolism demonstrated a clear decrease in hepatic CYP1A levels while a significant increase in kidney was seen at both 24 h and 2 weeks. A dramatic induction of CYP3A was evident at 2 weeks in liver, while no changes were noticed in CYP2B or CYP2D subfamilies. CYP4F subfamily showed induction in kidney only. Collectively, the data reveal the differential effects of TBI on hepatic and renal drug metabolism.

Expression of CYP4F12 in Gastrointestinal and Urogenital Epithelia*

Cytochrome P450 4F12 (CYP4F12) was originally cloned from human liver and small intestine. CYP4F12 can oxidize arachidonic acid, two stable prostaglandin H2 analogues, and an antihistamine, ebastine, but the tissue distribution and catalytic properties of CYP4F12 have not been fully investigated. An antipeptide polyclonal antibody was raised against the C-terminal of CYP4F12 (PLNVGLQ), evaluated by Western blot analysis and used for immunohistological analysis of 50 human tissues. Western blot analysis of recombinant CYP4F12, expressed in yeast, and microsomal proteins from adult and foetal liver, kidney, placenta at term, seminal vesicles, the prostate gland and purified prostasomes showed that the polyclonal antibody detected a protein of the expected size, approximately 60 kDa. CYP4F12 mRNA could be detected in seminal vesicles and prostate gland by reverse transcription-PCR. Prominent CYP4F12 immunoreactivity occurred, inter alia, in the epithelial cells of the gastrointestinal tract (stomach, small intestine, and colon), collecting tubules, transitional epithelium, ovarian follicles, the endothelium of microvessels of placental villi (first trimester), and epidermis. We screened recombinant CYP4F12 for catalytic activity. Arachidonic acid (20:4n-6) was hydroxylated at C18 and laurate at C11, but significant amounts of metabolites of 18:2n-6, 20:3n-9, 20:5n-3, 22:5n-6, and some prostaglandins could not be detected. We conclude that CYP4F12 is widely distributed in gastrointestinal and urogenital epithelia and exhibits a narrow substrate specificity.

A PROTEOMIC APPROACH TO THE IDENTIFICATION OF CYTOCHROME P450 ISOFORMS IN MALE AND FEMALE RAT LIVER BY NANOSCALE LIQUID CHROMATOGRAPHY-ELECTROSPRAY IONIZATION-TANDEM MASS SPECTROMETRY

Nanoscale reversed-phase liquid chromatography (LC) combined with electrospray ionization-tandem mass spectrometry (ESI-MS/MS) has been used as a method for the direct identification of multiple cytochrome P450 (P450) isoforms found in male and female rat liver. In this targeted proteomic approach, rat liver microsomes were subjected to sodium dodecyl sulfate-polyacrylamide gel electrophoresis followed by in-gel tryptic digestion of the proteins present in the 48- to 62-kDa bands. The resultant peptides were extracted and analyzed by LC-ESI-MS/MS. P450 identifications were made by searching the MS/MS data against a rat protein database containing 21,576 entries including 47 P450s using Sequest software (Thermo Electron, Hemel Hempstead, UK). Twenty-four P450 isoforms from the subfamilies 1A, 2A, 2B, 2C, 2D, 2E, 3A, 4A, 4F, CYP17, and CYP19 were positively identified in rat liver.