Oxidation of prostaglandin H(2) and prostaglandin H(2) analogues by human cytochromes P450: analysis of omega-side chain hydroxy metabolites and four steroisomers of 5-hydroxyprostaglandin I(1) by mass spectrometry

A Comparative Genomic and Phylogenetic Investigation of the Xenobiotic Metabolism Enzymes of Cytochrome P450 in Elephants Shows Loss in CYP2E and CYP4A

Cytochrome P450 is an important enzyme that metabolizes a variety of chemicals, including exogenous substances, such as drugs and environmental chemicals, and endogenous substances, such as steroids, fatty acids, and cholesterol. Some CYPs show interspecific differences in terms of genetic variation. As little is known about the mechanisms of elephant metabolism, we carried out a comparative genomic and phylogenetic analysis of CYP in elephants. Our results suggest that elephant CYP genes have undergone independent duplication, particularly in the CYP2A, CYP2C, and CYP3A genes, a unique cluster specific to elephant species. However, while CYP2E and CYP4A were conserved in other Afrotheria taxa, their decay in elephants resulted in genetic dysfunction (pseudogene). These findings outline several remarkable characteristics of elephant CYP1-4 genes and provide new insights into elephant xenobiotic metabolism. Further functional investigations are necessary to characterize elephant CYP, including expression patterns and interactions with drugs and sensitivities to other chemicals.

Exploring human CYP4 enzymes: physiological roles, function in diseases and focus on inhibitors

The cytochrome P450 (CYP)4 family of enzymes are monooxygenases responsible for the ω-oxidation of endogenous fatty acids and eicosanoids and play a crucial part in regulating numerous eicosanoid signaling pathways. Recently, CYP4 gained attention as a potential therapeutic target for several human diseases, including cancer, cardiovascular diseases and inflammation. Small-molecule inhibitors of CYP4 could provide promising treatments for these diseases. The aim of the present review is to highlight the advances in the field of CYP4, discussing the physiology and pathology of the CYP4 family and compiling CYP4 inhibitors into groups based on their chemical classes to provide clues for the future discovery of drug candidates targeting CYP4. Teaser: This review provides an updated view of the physiology and pathology of CYP4 enzymes. CYP4 inhibitors are compiled based on their skeletons to provide clues for the future discovery of drug candidates targeting CYP4.

Diverse reactions catalyzed by cytochrome P450 and biosynthesis of steroid hormone

Steroid hormones modulate numerous physiological processes in various higher organisms. Research on the physiology, biosynthesis, and metabolic degradation of steroid hormones is crucial for developing drugs, agrochemicals, and anthelmintics. Most steroid hormone biosynthetic pathways, excluding those in insects, have been elucidated, and the roles of several cytochrome P450s (CYPs, P450s), heme (iron protoporphyrin IX)-containing monooxygenases, have been identified. Specifically, P450s of the animal steroid hormone biosynthetic pathways and their three dimensional structures and reaction mechanisms have been extensively studied; however, the mechanisms of several uncommon P450 reactions involved in animal steroid hormone biosynthesis and structures and reaction mechanisms of various P450s involved in plant and insect steroid hormone biosynthesis remain unclear. Recently, we determined the crystal structure of P450 responsible for the first and rate-determining step in brassinosteroids biosynthesis and clarified the regio- and stereo-selectivity in the hydroxylation reaction mechanism. In this review, we have outlined the general catalytic cycle, reaction mechanism, and structure of P450s. Additionally, we have described the recent advances in research on the reaction mechanisms of steroid hormone biosynthesis-related P450s, some of which catalyze unusual P450 reactions including C–C bond cleavage reactions by utilizing either a heme–peroxo anion species or compound I as an active oxidizing species. This review article is an extended version of the Japanese article, Structure and mechanism of cytochrome P450s involved in steroid hormone biosynthesis, published in SEIBUTSU BUTSURI Vol. 61, p. 189–191 (2021).

The Functions of Cytochrome P450 ω-hydroxylases and the Associated Eicosanoids in Inflammation-Related Diseases

The cytochrome P450 (CYP) ω-hydroxylases are a subfamily of CYP enzymes. While CYPs are the main metabolic enzymes that mediate the oxidation reactions of many endogenous and exogenous compounds in the human body, CYP ω-hydroxylases mediate the metabolism of multiple fatty acids and their metabolites via the addition of a hydroxyl group to the ω- or (ω-1)-C atom of the substrates. The substrates of CYP ω-hydroxylases include but not limited to arachidonic acid, docosahexaenoic acid, eicosapentaenoic acid, epoxyeicosatrienoic acids, leukotrienes, and prostaglandins. The CYP ω-hydroxylases-mediated metabolites, such as 20-hyroxyleicosatrienoic acid (20-HETE), 19-HETE, 20-hydroxyl leukotriene B4 (20-OH-LTB₄), and many ω-hydroxylated prostaglandins, have pleiotropic effects in inflammation and many inflammation-associated diseases. Here we reviewed the classification, tissue distribution of CYP ω-hydroxylases and the role of their hydroxylated metabolites in inflammation-associated diseases. We described up-regulation of CYP ω-hydroxylases may be a pathogenic mechanism of many inflammation-associated diseases and thus CYP ω-hydroxylases may be a therapeutic target for these diseases. CYP ω-hydroxylases-mediated eicosanods play important roles in inflammation as pro-inflammatory or anti-inflammatory mediators, participating in the process stimulated by cytokines and/or the process stimulating the production of multiple cytokines. However, most previous studies focused on 20-HETE,and further studies are needed for the function and mechanisms of other CYP ω-hydroxylases-mediated eicosanoids. We believe that our studies of CYP ω-hydroxylases and their associated eicosanoids will advance the translational and clinal use of CYP ω-hydroxylases inhibitors and activators in many diseases.

l-Arginine supplementation in severe asthma

BACKGROUNDDysregulation of l-arginine metabolism has been proposed to occur in patients with severe asthma. The effects of l-arginine supplementation on l-arginine metabolite profiles in these patients are unknown. We hypothesized that individuals with severe asthma with low fractional exhaled nitric oxide (FeNO) would have fewer exacerbations with the addition of l-arginine to their standard asthma medications compared with placebo and would demonstrate the greatest changes in metabolite profiles.METHODSParticipants were enrolled in a single-center, crossover, double-blind l-arginine intervention trial at UCD. Subjects received placebo or l-arginine, dosed orally at 0.05 mg/kg (ideal body weight) twice daily. The primary end point was moderate asthma exacerbations. Longitudinal plasma metabolite levels were measured using mass spectrometry. A linear mixed-effect model with subject-specific intercepts was used for testing treatment effects.RESULTSA cohort of 50 subjects was included in the final analysis. l-Arginine did not significantly decrease asthma exacerbations in the overall cohort. Higher citrulline levels and a lower arginine availability index (AAI) were associated with higher FeNO (P = 0.005 and P = 2.51 × 10-9, respectively). Higher AAI was associated with lower exacerbation events. The eicosanoid prostaglandin H2 (PGH2) and Nα-acetyl-l-arginine were found to be good predictors for differentiating clinical responders and nonresponders.CONCLUSIONSThere was no statistically significant decrease in asthma exacerbations in the overall cohort with l-arginine intervention. PGH2, Nα-acetyl-l-arginine, and the AAI could serve as predictive biomarkers in future clinical trials that intervene in the arginine metabolome.TRIAL REGISTRATIONClinicalTrials.gov NCT01841281.FUNDINGThis study was supported by NIH grants R01HL105573, DK097154, UL1 TR001861, and K08HL114882. Metabolomics analysis was supported in part by a grant from the University of California Tobacco-Related Disease Research Program program (TRDRP).

Cytochrome P450 ω-Hydroxylases in Inflammation and Cancer

Cytochrome P450-dependent ω-hydroxylation is a prototypic metabolic reaction of CYP4 family members that is important for the elimination and bioactivation of not only therapeutic drugs, but also endogenous compounds, principally fatty acids. Eicosanoids, derived from arachidonic acid, are key substrates in the latter category. Human CYP4 enzymes, mainly CYP4A11, CYP4F2, and CYP4F3B, hydroxylate arachidonic acid at the omega position to form 20-HETE, which has important effects in tumor progression and on angiogenesis and blood pressure regulation in the vasculature and kidney. CYP4F3A in myeloid tissue catalyzes the ω-hydroxylation of leukotriene B4 to 20-hydroxy leukotriene B4, an inactivation process that is critical for the regulation of the inflammatory response. Here, we review the enzymology, tissue distribution, and substrate selectivity of human CYP4 ω-hydroxylases and their roles as catalysts for the formation and termination of the biological effects of key eicosanoid metabolites in inflammation and cancer progression.

Effects of PCB126 and 17β-oestradiol on endothelium-derived vasoactive factors in human endothelial cells

Epidemiological and experimental studies suggest an association between elevated serum levels of co-planar PCBs and hypertension, and one study indicate that this effect is dependent on the level of oestrogen. This study investigated the effects of 3,3',4,4',5-pentachlorobiphenyl (PCB126) and 17β-oestradiol (E₂) on vasoactive factors in human umbilical vein endothelial cells (HUVEC). The results reveal that PCB126 stimulated the vasoconstriction factors COX-2 and PGF(2α) in HUVEC. An up-regulation of COX-2 expression was demonstrated using qRT-PCR, western blot and immunofluorescence and increased production of PGF(2α) was demonstrated using LC/MS² and enzyme immunoassay. Also, PCB126 slightly increased ROS production and decreased NO production in HUVEC. The addition of E₂ enhanced PCB126-induced transcription of CYP1A1, CYP1B1 and COX-2 in HUVEC whereas an increased transcription of eNOS only occurred following combined treatment with E₂ and PCB126. Immunofluorescence demonstrated that HUVEC expressed AHR and ERβ but lacked ERα and the involvement of AHR and ERβ on the effects of PCB126 was examined by the addition of AHR and ER antagonists. The binding of PCB126 to AHR was critical for the effects of PCB126 whereas the role of ERβ was equivocal. In conclusion, these studies suggest that PCB126 induced changes in human endothelial cells that are characteristic for endothelial dysfunction in human hypertension and that PCB126-induced transcription of genes important for vascular function in human endothelial cells can be elevated by increased oestrogen levels. These findings may help understanding the mechanism for the association between PCB126 exposure and hypertension reported in human subjects and experimental animals.

Biochemical characterization of the oxygenation of unsaturated fatty acids by the dioxygenase and hydroperoxide isomerase of Pseudomonas aeruginosa 42A2

We have studied oxygenation of fatty acids by cell extract of Pseudomonas aeruginosa 42A2. Oleic acid ((9Z)-18:1) was transformed to (10S)-hydroperoxy-(8E)-octadecenoic acid ((10S)-HPOME) and to (7S,10S)-dihydroxy-(8E)-octadecenoic acid (7,10-DiHOME). Experiments under oxygen-18 showed that 7,10-DiHOME contained oxygen from air and was formed sequentially from (10S)-HPOME by isomerization. (10R)-HPOME was not isomerized. The (10S)-dioxygenase and hydroperoxide isomerase activities co-eluted on ion exchange chromatography and on gel filtration with an apparent molecular size of approximately 50 kDa. 16:1n-7, 18:2n-6, and 20:1n-11 were also oxygenated to 7,10-dihydroxy fatty acids, and (8Z)-18:1 was oxygenated to 6,9-dihydroxy-(7E)-octadecenoic acid. A series of fatty acids with the double bond positioned closer to ((6Z)-18:1, (5Z,9Z)-18:2) or more distant from the carboxyl group ((11Z)-, (13Z)-, and (15Z)-18:1) were poor substrates. The oxygenation mechanism was studied with [7S-(2)H]18:1n-9, [7R-(2)H]18:2n-6, and [8R-(2)H]18:2n-6 as substrates. The pro-R hydrogen at C-8 was lost in the biosynthesis of (10S)-HPODE, whereas the pro-S hydrogen was lost and the pro-R hydrogen was retained at C-7 during biosynthesis of the 7,10-dihydroxy metabolites. Analysis of the fatty acid composition of P. aeruginosa revealed relatively large amounts of (9E/Z)-16:1 and (11E/Z)-18:1 and only traces of 18:1n-9. We found that (11Z)-18:1 (vaccenic acid) was transformed to (11S,14S)-dihydroxy-(12E)-octadecenoic acid and to a mixture of 11- and 12-HPOME, possibly due to reverse orientation of (11Z)-18:1 at the active site compared with oleic acid. The reaction mechanism of the hydroperoxide isomerase suggests catalytic similarities to cytochrome P450.

Liquid chromatography/tandem mass spectrometric analysis of 7,10-dihydroxyoctadecenoic acid, its isotopomers, and other 7,10-dihydroxy fatty acids formed by Pseudomonas aeruginosa 42A2

Pseudomonas aeruginosa is an opportunistic pathogen, which oxidizes oleic acid to 7(S),10(S)-dihydroxy-8(E)-octadecenoic acid (7,10-(OH)(2)-18:1) of biological and industrial interest. Electrospray tandem mass spectrometric (MS/MS) analysis of hydroxylated fatty acids usually generates characteristic fragments containing the carboxylate anion and formed by alpha-cleavage at the oxidized carbon. These fragments indicate the positions of the hydroxyl group. In contrast, liquid chromatography (LC)/MS/MS analysis of 7,10-(OH)(2)-18:1 yielded a series of other ions with structural information. To study the fragmentation mechanism, we prepared (2)H- and (18)O-labeled isotopomers. We also performed MS(3) analysis of the major ions, and for comparison we generated the corresponding 7,10-dihydroxy metabolites of 16:1n-7, 18:2n-6, and 20:1n-11 with a protein extract of P. aeruginosa. The MS/MS spectra of 7,10-(OH)(2)-18:1 and its isotopomers, 7,10-(OH)(2)-16:1, and 7,10-(OH)(2)-20:1, contained a series of prominent fragments that all hold the omega end. The 8,9-double bond was not essential for this fragmentation, as 7,10-(OH)(2)-18:0, and its isotopomers, formed essentially the same fragments in the lower mass range. In contrast, 7,10-dihydroxy-8(E),12(Z)-octadecadienoic acid (7,10-(OH)(2)-18:2) fragmented by alpha-cleavage at the oxidized carbons with formation of carboxylate anions. Our results demonstrate that C(16)-C(20) fatty acids with a 7,10-dihydroxy-8(E) functionality undergo charge-driven fragmentation after charge migration to the omega-end, whereas the main ions of 7,10-(HO)(2)-18:2 retain charge at the carboxyl group.

Gene deletion of 7,8-linoleate diol synthase of the rice blast fungus: studies on pathogenicity, stereochemistry, and oxygenation mechanisms

Linoleate diol synthases (LDS) are heme enzymes, which oxygenate 18:2n-6 sequentially to (8R)-hydroperoxylinoleic acid ((8R)-HPODE) and to (5S,8R)-dihydroxy-, (7S,8S)-dihydroxy-, or (8R,11S)-dihydroxylinoleic acids (DiHODE). The genome of the rice blast fungus, Magnaporthe oryzae, contains two genes with homology to LDS. M. oryzae oxidized 18:2n-6 to (8R)-HPODE and to (7S,8S)-DiHODE, (6S,8R)-DiHODE, and (8R,11S)-HODE. Small amounts of 10-hydroxy-(8E,12Z)-octadecadienoic acid and traces of 5,8-DiHODE were also detected by liquid chromatography-mass spectrometry. The contribution of the 7,8-LDS gene to M. oryzae pathogenicity was evaluated by replacement of the catalytic domain with hygromycin and green fluorescent protein variant (SGFP) cassettes. This genetically modified strain Delta7,8-LDS infected rice leaves and roots and formed appressoria and conidia as the native fungus. The Delta7,8-LDS mutant had lost the capacity to biosynthesize all the metabolites except small amounts of 8-hydroxylinoleic acid. Studies with stereospecifically deuterated linoleic acids showed that (8R)-HPODE was formed by abstraction of the pro-S hydrogen at C-8 and antarafacial oxygenation, whereas (7S,8S)-DiHODE and (8R,11S)-DiHODE were formed from (8R)-HPODE by suprafacial hydrogen abstraction and oxygenation at C-7 and C-11, respectively. A mac1 suppressor mutant (Delta mac1 sum1-99) of M. oryzae, which shows cAMP-independent protein kinase A activity, oxygenated 18:2n-6 to increased amounts of (10R)-HPODE and (5S,8R)-DiHODE. Expression of the 7,8-LDS gene but not of the second homologue was detected in the suppressor mutant. This suggests that PKA-mediated signaling pathway regulates the dioxygenase and hydroperoxide isomerase activities of M. oryzae.

CYP7B1-mediated metabolism of 5alpha-androstane-3alpha,17beta-diol (3alpha-Adiol): a novel pathway for potential regulation of the cellular levels of androgens and neurosteroids

The current study presents data indicating that 5alpha-androstane-3alpha,17beta-diol (3alpha-Adiol) undergoes a previously unknown metabolism into hydroxymetabolites, catalyzed by CYP7B1. 3alpha-Adiol is an androgenic steroid which serves as a source for the potent androgen dihydrotestosterone and also can modulate gamma-amino butyric acid A (GABA(A)) receptor function in the brain. The steroid hydroxylase CYP7B1 is known to metabolize cholesterol derivatives, sex hormone precursors and certain estrogens, but has previously not been thought to act on androgens or 3alpha-hydroxylated steroids. 3alpha-Adiol was found to undergo NADPH-dependent metabolism into 6- and 7-hydroxymetabolites in incubations with porcine microsomes and human kidney-derived HEK293 cells, which are high in CYP7B1 content. This metabolism was suppressed by addition of steroids known to be metabolized by CYP7B1. In addition, 3alpha-Adiol significantly suppressed CYP7B1-mediated catalytic reactions, in a way as would be expected for substrates that compete for the same enzyme. Recombinant expression of human CYP7B1 in HEK293 cells significantly increased the rate of 3alpha-Adiol hydroxylation. Furthermore, the observed hydroxylase activity towards 3alpha-Adiol was very low or undetectable in livers of Cyp7b1(-/-) knockout mice. The present results indicate that CYP7B1-mediated catalysis may play a role for control of the cellular levels of androgens, not only of estrogens. These findings suggest a previously unknown mechanism for metabolic elimination of 3alpha-Adiol which may impact intracellular levels of dihydrotestosterone and GABA(A)-modulating steroids.

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.

CYP1A in TCDD toxicity and in physiology-with particular reference to CYP dependent arachidonic acid metabolism and other endogenous substrates

Toxicologic and physiologic roles of CYP1A enzyme induction, the major biochemical effect of aryl hydrocarbon receptor activation by TCDD and other receptor ligands, are unknown. Evidence is presented that CYP1A exerts biologic effects via metabolism of endogenous substrates (i.e., arachidonic acid, other eicosanoids, estrogens, bilirubin, and melatonin), production of reactive oxygen, and effects on K(+) and Ca(2+) channels. These interrelated pathways may connect CYP1A induction to TCDD toxicities, including cardiotoxicity, vascular dysfunction, and wasting. They may also underlie homeostatic roles for CYP1A, especially when transiently induced by common chemical exposures and environmental conditions (i.e., tryptophan photoproducts, dietary indoles, and changes in oxygen tension).

On the mechanism of biosynthesis of 19-hydroxyprostaglandins of human seminal fluid and expression of cyclooxygenase-2, PGH 19-hydroxylase (CYP4F8) and microsomal PGE synthase-1 in seminal vesicles and vas deferens

The predominating prostaglandins of human seminal fluid are 19R-hydroxyprostaglandins E1 and E2, conceivably formed sequentially by prostaglandin H (PGH) synthase-2, PGH 19-hydroxylase (CYP4F8), and microsomal PGE synthase-1 of seminal vesicles. Our aim was to study this enzyme system. Quantification by real-time PCR suggested that the transcripts of PGH synthase-2, CYP4F8, and microsomal PGE synthase-1 were abundant and correlated in seminal vesicles of seven patients (p < 0.05). The three enzymes were detected in seminal vesicles by Western blot analysis, and immunohistological analysis confirmed the localization to the epithelia of seminal vesicles and distal vas deferens. Immunofluorescence analysis showed co-localization of the three enzymes in epithelial cells of seminal vesicles and vas deferens. 19-Hydroxy-PGE compounds were detected by mass spectrometry in the mucosa of distal vas deferens. Recombinant CYP4F8 catalyzes n-2 hydroxylation of PGH1 and PGH2 and n-3 hydroxylation of arachidonic acid. Arachidonic acid was oxidized to 18-hydroxyarachidonic acid and to PGE2 and by microsomes of seminal vesicles in the presence of NADPH and GSH, and to relatively small amounts of 19-hydroxy-PGE2. We conclude that PGH synthase-2, CYP4F8, and PGE synthase-1 likely forms 19-hydroxy-PGE compounds in seminal vesicles and vas deferens, but the catalytic properties of CYP4F8 suggest additional biological functions. Recombinant CYP4F8 was also found to catalyze n-2 hydroxylation of PGI2 and carbaprostacyclin (Km to approximately 40 microM), and n-2 and n-3 hydroxylation of carbocyclic TXA2.

Oxygenation of polyunsaturated long chain fatty acids by recombinant CYP4F8 and CYP4F12 and catalytic importance of Tyr-125 and Gly-328 of CYP4F8

Recombinant CYP4F8 and CYP4F12 metabolize prostaglandin H2 (PGH2) analogs by omega2- and omega3-hydroxylation and arachidonic acid (20:4n-6) by omega3-hydroxylation. CYP4F8 was found to catalyze epoxidation of docosahexaenoic acid (22:6n-3) and docosapentaenoic acid (22:5n-3) and omega3-hydroxylation of 22:5n-6. CYP4F12 oxidized 22:6n-3 and 22:5n-3 in the same way, but 22:5n-6 was a poor substrate. The products were identified by liquid chromatography-mass spectrometry. The missense mutation 374A>T of CYP4F8 (Tyr125Phe in substrate recognition site-1 (SRS-1)) occurs in low frequency. This variant oxidized two PGH2 analogs, U-51605 and U-44069, in analogy with CYP4F8, but 20:4n-6 and 22:5n-6 were not oxidized. CYP4F enzymes with omega-hydroxylase activity contain a heme-binding Glu residue, whereas CYP4F8 (and CYP4F12) with omega2- and omega 3-hydroxylase activities has a Gly residue in this position of SRS-4. The mutant CYP4F8 Gly328Glu oxidized U-51605 and U-44069 as recombinant CYP4F8, but the hydroxylation of arachidonic acid was shifted from C-18 to C-19. Single amino acid substitutions in SRS-1 and SRS-4 of CYP4F8 may thus influence oxygenation of certain substrates. We conclude that CYP4F8 and CYP4F12 catalyze epoxidation of 22:6n-3 and 22:5n-3, and CYP4F8 omega3-hydroxylation of 22:5n-6.

Expression of CYP4F8 (prostaglandin H 19-hydroxylase) in human epithelia and prominent induction in epidermis of psoriatic lesions

Our aim was to determine the tissue distribution of CYP4F8, which occurs in human seminal vesicles and catalyzes 19-hydroxylation of prostaglandin H(1) and H(2) in vitro (J. Bylund, M. Hidestrard, M. Ingelman-Sundberg, E.H. Oliw, J. Biol. Chem. 275 (2000) 21844-21849). Polyclonal antibodies were raised in rabbits against RVEPLG, the C-terminal end of CYP4F8, and purified by affinity chromatography. Screening of 50 human tissues for CYP4F8 immunoreactivity revealed protein expression, inter alia, in seminal vesicles, epidermis, hair follicles, sweat glands, corneal epithelium, proximal renal tubules, and epithelial linings of the gut and urinary tract. The CYP4F8 transcripts were detected by reverse transcription polymerase chain reaction and by Northern blot analysis. There was a prominent induction of CYP4F8 immunoreactivity and mRNA in psoriasis in comparison with unaffected epidermis of the same patients. The cDNA of CYP4F8 from plucked scalp hair roots was identical with the genital cDNA sequence. We conclude that CYP4F8 is present in epithelial linings and up regulated in epidermis of psoriatic lesions.

Distribution of cytochrome P-450 4A and 4F isoforms along the nephron in mice

The production of 20-hydroxyeicosatetraenoic acid (20-HETE) in the kidney is thought to be involved in the control of renal vascular tone and tubular sodium and chloride reabsorption. 20-HETE production in the kidney has been extensively studied in rats and humans and occurs primarily via the actions of P-450 enzymes of the CYP4A and -4F families. Recent advancements in molecular genetics of the mouse have made it possible to disrupt genes in a cell-type-specific fashion. These advances could help in the creation of models that could distinguish between the vascular and tubular actions of 20-HETE. However, isoforms of the CYP4A and -4F families that may be responsible for the production of 20-HETE in the vascular and tubular segments in the kidney of the mouse are presently unknown. The goal of this study was to identify the isoforms of the CYP4A and -4F families along the nephron by RT-PCR of RNA isolated from microdissected renal blood vessels and nephron segments from 16- to 24-wk-old male and female C57BL/6J mice. CYP4A and -4F isoforms were detected in every segment analyzed, with sex differences only observed in the proximal tubule and glomeruli. In the proximal tubular segments from male mice, the 4A10 and -12 isoforms were present, whereas the 4A10 and -14 isoforms were detected in segments from female mice. In glomeruli, sex differences in the expression pattern of CYP4F isoforms were also observed, with male mice expressing the 4F13, -14, and -15 isoforms, whereas female mice expressed the 4F13, -16, and -18 isoforms. These results demonstrate that isolated nephron and renal vessel segments express multiple isoforms of the CYP4A and -4F families; therefore, elimination of a single CYP4A or -4F isoform may not decrease 20-HETE production in all nephron segments or the renal vasculature of male and female mice. However, the importance of CYP4A vs. -4F isoforms to the production of 20-HETE in each of these renal tubular and vascular segments of the mouse remains to be determined.

Cyclooxygenase-2, prostaglandin synthases, and prostaglandin H2 metabolism in traumatic brain injury in the rat

Inflammatory mediators are important in traumatic brain injury (TBI). The objective of the present study was to investigate the expression of cyclooxygenase-2 (COX-2), prostaglandin E (PGE) and PGD synthases, and PGH2 metabolism in two rat models of TBI. Fluid percussion injury (FPI) resulted in bilateral induction of COX-2 mRNA in the dentate gyri and the cortex, whereas controlled cortical contusion injury (CCC) induced COX-2 mRNA in the ipsilateral dentate gyrus and intensely in the cortex as judged by in situ hybridization. The induction subsided within 24 h. COX-2 immunoreactivity was detectable in these areas and persisted in the ipsilateral cortex for at least 72 h after CCC. Regions with COX-2 induction co-localized with TUNEL staining, suggesting a link between COX-2 expression and cell damage. COX-2 forms PGH2, which can be isomerized to PGD2, PGE2, and PGF2alpha by enzymatic and non-enzymatic mechanisms. In situ hybridization showed that mRNA of PGD synthase and microsomal PGE synthase were present in the choroid plexus. The microsomal PGE synthase was induced bilaterally after FPI and unilaterally after CCC. Liquid chromatography-mass spectrometry showed that low speed supernatant of normal and traumatized cortex and hippocampus transformed PGH2 to PGD2 as main product. PGD2 was dehydrated in brain homogenates to biological active compounds, for example, 15-deoxy-delta12,14-PGJ2. Thus COX-2 increases in certain neurons following TBI without neuronal induction of PGD and microsomal PGE synthases, suggesting that PGH2 may decompose to PGD2 and its dehydration products by nonenzymatic mechanisms or to PGD2 by low constitutive levels of PGD synthase.

Prostaglandin and leukotriene omega-hydroxylases

Omega and subterminal hydroxylations of prostaglandins (PGs), leukotriene B4 (LTB4) and some related eicosanoids are catalyzed by the cytochrome P450 (CYP) enzymes belonging to the CYP4A and CYP4F subfamilies. CYP4A4, which is induced in pregnant rabbits, is the only elucidated PGE omega-hydroxylase within the CYP4A subfamily. CYP4F3 is the most tissue specific and most efficient LTB4 omega-hydroxylase, judging from its restricted localization in human polymorphonuclear leukocytes (PMN) and its very low Km value for LTB4. CYP4F2 is widely distributed in human liver and other tissues, and catalyzes omega-hydroxylation of various lipoxygenase-derived eicosanoids as well as LTB4, with relatively comparable and high Km values. CYP4F3B is very similar to CYP4F2 in its tissue localization and its Km value for LTB4. Human seminal vesicle CYP4F8 is the first elucidated hydroxylase with substrate specificity for PG endoperoxides, whereas ram seminal vesicle CYP4F21 is the only elucidated PGE omega-hydroxylase within the CYP4F subfamily [corrected]. Rat CYP4F1, CYP4F4 and CYP4F5, and mouse Cyp4f14 have LTB4 omega-hydroxylase activity. Three additional human, four mouse, and one fish members of the CYP4F subfamily have been identified.