Functional polymorphism in human CYP4F2 decreases 20-HETE production

Pharmacogenomics of anticoagulants: steps toward personal dosage

Warfarin and other coumarin anticoagulants are widely used clinically, but currently dosing is determined individually on the basis of patient response. There is increasing evidence that genetic factors, together with several non-genetic patient-specific factors, are important determinants of stable dose requirement for these compounds. Genotype for CYP2C9, which encodes the main cytochrome P450 enzyme that metabolizes warfarin, and VKORC1, the gene encoding the warfarin target vitamin K epoxide reductase, together account for approximately 30% of the variability in dose requirement. The past two years have seen several advances in the area of genetic factors affecting coumarin anticoagulant response. In particular, prospective studies have taken place to analyze whether earlier small retrospective studies can be confirmed, and the question of whether genes other than CYP2C9 and VKORC1 are important in determining dose requirement has been examined. So far, no strong evidence that other genes contribute to dose requirement has been found, apart from a minor but novel role for another cytochrome P450 gene, CYP4F2. A recently published whole genome association study confirms that the main genes important in warfarin response are CYP2C9 and VKORC1. Clinical trials comparing genotype-guided and conventional warfarin initiation have suggested that genotyping may be of value, but larger studies are still needed to show clear clinical benefit. Current knowledge of genetic factors affecting other coumarin anticoagulants is more limited and this area requires further study, as does the impact of ethnic variation in genes relevant to coumarin responses. Here we review recent advances in the area of coumarin anticoagulant genetics and its potential clinical application.

Haplotype-based case-control study of the human CYP4F2 gene and essential hypertension in Japanese subjects

CYP4F2 acts primarily as an enzyme that converts arachidonic acid to 20-hydroxyeicosatetraenoic acid (20-HETE), a metabolite involved in the regulation of blood pressure in humans. The aim of the present study was to assess the association between the human CYP4F2 gene and essential hypertension (EH) using a haplotype-based case-control study that included separate analysis of the two gender groups. The 249 EH patients and 238 age-matched controls were genotyped for 5 single-nucleotide polymorphisms (SNPs) of the human CYP4F2 gene (rs3093105, rs3093135, rs1558139, rs2108622, rs3093200). Data were analyzed for 3 separate groups: all subjects, and men and women separately. For the total population and for male subjects, the distribution of the dominant model of rs1558139 (CC vs. CT+TT) differed significantly between the EH patients and control subjects (p=0.037 and p=0.005, respectively), with a higher percentage of EH patients showing the CC genotype. Logistic regression showed that, for men, the CC genotype of rs1558139 was more prevalent in the EH patients than in the control subjects (p=0.026), while, for the total population, the difference disappeared (p=0.247). For men, the overall distribution of the haplotypes was significantly different between the EH patients and the control subjects (p=0.042), and the frequency of the T-T-G haplotype was also significantly lower for EH patients than for control subjects (p=0.009). In conclusion, the present results indicate that rs1558139 might be a genetic marker for EH and the T-T-G haplotype might be a protective genetic marker for EH in Japanese men.

A haplotype of the CYP4F2 gene is associated with cerebral infarction in Japanese men

BACKGROUND

CYP4F2, a member of the cytochrome P450 family, acts mainly as an enzyme and is involved not only in the metabolism of leukotriene B4, but also in that of arachidonic acid. It converts arachidonic acid to 20-hydroxyeicosatetraenoic acid (20-HETE), a metabolite involved in the regulation of the vascular tone in the brain. The aim of this study was to assess the association between the human CYP4F2 gene and cerebral infarction (CI), using a haplotype-based case-control study with separate analyses of data from the gender groups.

METHODS

A total of 175 CI patients and 246 control subjects were genotyped for five single-nucleotide polymorphisms (SNPs) of the human CYP4F2 gene (rs3093105, rs3093135, rs1558139, rs2108622, rs3093200). For data analysis, three separate groups were assessed: all subjects, men, and women.

RESULTS

In the male subjects, the G allele frequency for rs2108622 was significantly higher in CI patients as compared to control subjects (P = 0.025). The overall distribution of the haplotypes in the men was significantly different between the CI patients and the control subjects (P = 0.027). Additionally, the frequency of the T-C-G haplotype for men was significantly higher in the CI patients than in the control subjects (P = 0.008). Multiple logistic regression analysis also revealed the significance of the T-C-G haplotype in men, even after adjustment for confounding factors.

CONCLUSIONS

The results of this study indicate that, in Japanese men, CI is associated with the G allele of rs2108622 and, in addition, that the T-C-G haplotype appears to be a useful genetic marker for CI.

Expression of CYP4F2 in human liver and kidney: assessment using targeted peptide antibodies

P450 enzymes comprising the human CYP4F gene subfamily are catalysts of eicosanoid (e.g., 20-HETE and leukotriene B4) formation and degradation, although the role that individual CYP4F proteins play in these metabolic processes is not well defined. Thus, we developed antibodies to assess the tissue-specific expression and function of CYP4F2, one of four CYP4F P450s found in human liver and kidney. Peptide antibodies elicited in rabbits to CYP4F2 amino acid residues 61-74 (WGHQGMVNPTEEG) and 65-77 (GMVNPTEEGMRVL) recognized on immunoblots only CYP4F2 and not CYP4F3b, CYP4F11 or CYP4F12. Immunoquantitation with anti-CYP4F2 peptide IgG showed highly variable CYP4F2 expression in liver (16.4+/-18.6pmol/mg microsomal protein; n=29) and kidney cortex (3.9+/-3.8 pmol/mg; n=10), with two subjects lacking the hepatic or renal enzyme entirely. CYP4F2 content in liver microsomes was significantly correlated (r> or =0.63; p<0.05) with leukotriene B4 and arachidonate omega-hydroxylase activities, which are both CYP4F2-catalyzed. Our study provides the first example of a peptide antibody that recognizes a single CYP4F P450 expressed in human liver and kidney, namely CYP4F2. Immunoquantitation and correlation analyses performed with this antibody suggest that CYP4F2 functions as a predominant LTB4 and arachidonate omega-hydroxylase in human liver.

Inhibition of oxidative metabolism of tocopherols with omega-N-heterocyclic derivatives of vitamin E

The oxidative metabolism of tocopherols and tocotrienols by monooxygenases is a key factor in the plasma and tissue clearance of forms of vitamin E other than alpha-tocopherol. It is well known that a commonly ingested form of vitamin E, gamma-tocopherol, has greatly reduced plasma half-life (faster clearance) than alpha-tocopherol. The tocotrienols are metabolized even faster than gamma-tocopherol. Both gamma-tocopherol and alpha- and delta-tocotrienol possess intriguing biological activities that are different from alpha-tocopherol, making them potentially of interest for therapeutic use. Unfortunately, the fast clearance of non-alpha-tocopherols from animal tissues is a significant hurdle to maximizing their effect(s) as dietary supplements. We report here the design and synthesis of N-heterocycle-containing analogues of alpha-tocopherol that act as inhibitors of Cyp4F2, the key monooxygenase responsible for omega-hydroxylation of the side chain of tocols. In particular, an omega-imidazole containing compound, 1, [(R)-2-(9-(1H-imidazol-1-yl)nonyl)-2,5,7,8-tetramethylchroman-6-ol] had an ED(50) for inhibition of gamma-CEHC production from gamma-tocopherol of approximately 1 nM when tested in HepG2 cells in culture. Furthermore, feeding of 1 to mice along with rapidly metabolized delta-tocopherol, resulted in a doubling of the delta-tocopherol/alpha-tocopherol ratio in liver (P<0.05). Thus, 1 may be a useful adjuvant to the therapeutic use of non-alpha-tocopherols.

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

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

A single nucleotide polymorphism in the CYP4F2 but not CYP4A11 gene is associated with increased 20-HETE excretion and blood pressure

Arachidonic acid is a major fatty acid that can be metabolized by the cytochrome P450 enzyme to a number of bioactive eicosanoids. A major metabolite of this oxidation is 20-hydroxyeicosatetraenoic acid, which acts as a potent vasoconstrictor. However, in the kidney, its vasoconstrictor actions can be offset by its natriuretic properties. A guanine-to-adenine polymorphism in the CYP4F2 gene was associated with a reduction in 20-hydroxyeicosatetraenoic acid production in vitro. A thymidine-to-cytosine polymorphism in the CYP4A11 gene reduced catalytic activity by >50% in vitro and was associated with hypertension. The aim was to determine whether these 2 mutations are associated with urinary 20-hydroxyeicosatetraenoic acid excretion and blood pressure in humans. For the CYP4F2, 51% were homozygous for the G allele, 40% were carriers, and 9% were homozygous for the A allele. For CYP4A11, 72% were homozygous for the T allele, 25% were carriers, and 3% were homozygous for the C allele. The CYP4F2 GA/AA genotype was significantly associated with an increase in both 20-hydroxyeicosatetraenoic acid excretion and systolic blood pressure. The CYP4A11 CC/TC genotype was significantly associated with a reduction in 20-hydroxyeicosatetraenoic acid excretion but was not associated with blood pressure. We have demonstrated for the first time in humans that polymorphisms of the CYP4F2 and CYP4A11 genes have opposite effects on 20-hydroxyeicosatetraenoic acid excretion. The positive association between the CYP4F2 GA/AA genotype and both systolic blood pressure and 20-hydroxyeicosatetraenoic acid excretion strengthens a role for 20-hydroxyeicosatetraenoic acid in the modulation of blood pressure.

Cytochrome P450 omega hydroxylase (CYP4) function in fatty acid metabolism and metabolic diseases

The cytochrome P450 gene 4 family (CYP4) consists of a group of over 63 members that omega-hydroxylate the terminal carbon of fatty acids. In mammals, six subfamilies have been identified and three of these subfamily members show a preference in the metabolism of short (C7-C10)-CYP4B, medium (C10-C16)-CYP4A, and long (C16-C26)-CYP4F, saturated, unsaturated and branched chain fatty acids. These omega-hydroxylated fatty acids are converted to dicarboxylic acids, which are preferentially metabolized by the peroxisome beta-oxidation system to shorter chain fatty acids that are transported to the mitochondria for complete oxidation or used either to supply energy for peripheral tissues during starvation or in lipid synthesis. The differential regulation of the CYP4A and CYP4F genes during fasting, by peroxisome proliferators and in non-alcoholic fatty liver disease (NAFLD) suggests different roles in lipid metabolism. The omega-hydroxylation and inactivation of pro-inflammatory eicosanoids by members of the CYP4F subfamily and the association of the CYP4F2 and CYP4F3 genes with inflammatory celiac disease indicate an important role in the resolution of inflammation. Several human diseases have been genetically linked to the expression CYP4 gene polymorphic variants, which may link human susceptibility to diseases of lipid metabolism and the activation and resolution phases of inflammation. Understanding how the CYP4 genes are regulated during the fasting and feeding cycles and by endogenous lipids will provide therapeutic avenues in the treatment of metabolic disorders of lipid metabolism and inflammation.

CYP4F2 genetic variant alters required warfarin dose

Warfarin is an effective, commonly prescribed anticoagulant used to treat and prevent thrombotic events. Because of historically high rates of drug-associated adverse events, warfarin remains underprescribed. Further, interindividual variability in therapeutic dose mandates frequent monitoring until target anticoagulation is achieved. Genetic polymorphisms involved in warfarin metabolism and sensitivity have been implicated in variability of dose. Here, we describe a novel variant that influences warfarin requirements. To identify additional genetic variants that contribute to warfarin requirements, screening of DNA variants in additional genes that code for drug-metabolizing enzymes and drug transport proteins was undertaken using the Affymetrix drug-metabolizing enzymes and transporters panel. A DNA variant (rs2108622; V433M) in cytochrome P450 4F2 (CYP4F2) was associated with warfarin dose in 3 independent white cohorts of patients stabilized on warfarin representing diverse geographic regions in the United States and accounted for a difference in warfarin dose of approximately 1 mg/day between CC and TT subjects. Genetic variation of CYP4F2 was associated with a clinically relevant effect on warfarin requirement.

Vitamin E revisited: do new data validate benefits for chronic disease prevention?

PURPOSE OF REVIEW

Vitamin E benefits in human health and chronic disease prevention are evaluated with respect to established alpha-tocopherol functions during vitamin E deficiency, adequacy, and excess.

RECENT FINDINGS

Baseline vitamin E status of the 29 092 Finnish men participating in the Alpha-Tocopherol, Beta-Carotene Cancer Prevention study showed that the men in the highest compared with the lowest quintile of serum alpha-tocopherol had significantly lower incidences of total and cause-specific mortality. New findings from the Women's Health Study support a role for vitamin E supplements in decreasing the risk for sudden death from cardiovascular disease and from thromboembolism. We speculate that a potential mechanism may involve vitamin E interference in vitamin K activation.

SUMMARY

alpha-Tocopherol acts as a peroxyl and alkoxyl radical scavenger in lipid environments, and thus it prevents lipid peroxidation in lipoproteins and membranes, especially nervous tissues. Decreased chronic disease incidence is associated with lifelong generous dietary vitamin E intakes, but more than 90% of Americans do not consume the recommended dietary amounts (15 mg/day). Vitamin E supplements can have beneficial effects on health beyond those from dietary amounts, perhaps because pharmacologic levels also upregulate hepatic xenobiotic pathways.

Association of a functional cytochrome P450 4F2 haplotype with urinary 20-HETE and hypertension

Cytochrome P450 4F2 (CYP4F2) catalyzes the omega-hydroxylation of arachidonic acid to 20-hydroxyeicosatetraenoic acid (20-HETE), a natriuretic and vasoactive eicosanoid that participates in the development of hypertension. The relationship among CYP4F2 genetic variants in the regulatory region, formation of renal 20-HETE, and hypertension is unknown. Here are reported seven genetic variants around the CYP4F2 intronic regulatory region. Four of these variants made up two common haplotypes, Hap I (c.-91T/c.-48G/c.-13T/c.+34T) and Hap II (c.-91C/c.-48C/c.-13C/c.+34G). Hap I included a major functional variant, c.-91T-->C, which was identified by reporter assay and electrophoretic mobility shift assay. Transfected into HEK293 cells, the Hap I construct showed a trend toward higher basal transcriptional activity and exhibited significantly greater LPS-stimulated activity than Hap II; these findings were the result of different NF-kappaB binding affinity between the two constructs. In vivo, a case-control study demonstrated that homozygosity for Hap I doubled the risk for hypertension in a Chinese population, even after adjustment for risk factors including age, gender, and body mass index. This association was confirmed in a family-based association study. In addition, Hap I was associated with elevated urinary 20-HETE. These results indicate that a functional variant of the CYP4F2 regulatory region, which increases the binding affinity of NF-kappaB, increases the risk for hypertension, likely by modulating the production of 20-HETE.

The T8590C polymorphism of CYP4A11 and 20-hydroxyeicosatetraenoic acid in essential hypertension

A role for a deficit in transport actions of 20-hydroxyeicosatetraenoic acid (20-HETE) in hypertension is supported by the following: (1) diminished renal 20-HETE in Dahl-S rats; (2) altered salt- and furosemide-induced 20-HETE responses in salt-sensitive hypertensive subjects; and (3) increased population risk for hypertension in C allele carriers of the T8590C polymorphism of CYP4A11, which encodes an enzyme with reduced catalytic activity. We determined T8590C genotypes in 32 hypertensive subjects, 25 of whom were phenotyped for salt sensitivity of blood pressure and insulin sensitivity. Urine 20-HETE was lowest in insulin-resistant, salt-sensitive subjects (F=5.56; P<0.02). Genotypes were 13 TT, 2 CC, and 17 CT. C allele frequency was 32.8% (blacks: 38.9%; whites: 25.0%). C carriers (CC+CT) and TT subjects were similarly distributed among salt- and insulin-sensitivity phenotypes. C carriers had higher diastolic blood pressures and aldosterone:renin and waist:hip ratios but lower furosemide-induced fractional excretions of Na and K than TT. The T8590C genotype did not relate to sodium balance or pressure natriuresis. However, C carriers, compared with TT, had diminished 20-HETE responses to salt loading after adjustment for serum insulin concentration and resetting of the negative relationship between serum insulin and urine 20-HETE to a 1-microg/h lower level of 20-HETE. The effect of C was insulin independent and equipotent to 18 microU/mL of insulin (Delta20-HETE= 2.84-0.054xinsulin-0.98xC; r(2)=0.53; F=11.1; P<0.001). Hence, genetic (T8590C) and environmental (insulin) factors impair 20-HETE responses to salt in human hypertension. We propose that genotype analyses with sufficient homozygous CC will establish definitive relationships among 20-HETE, salt sensitivity of blood pressure, and insulin resistance.