Functional polymorphism in human CYP4F2 decreases 20-HETE production

Race-Specific Influence of CYP4F2 on Dose and Risk of Hemorrhage Among Warfarin Users

OBJECTIVE

The p.V433M in cytochrome P450 4F2 (rs2108622, CYP4F2*3) is associated with a higher warfarin dose and lower risk of hemorrhage among European Americans. We evaluate the influence of CYP4F2*3 on warfarin dose, time to target international normalized ratio (INR), and stable dose, proportion of time spent in target range (PTTR), as well as the risk of overanticoagulation and hemorrhage among European and African Americans.

DESIGN

CYP4F2*3 was genotyped in 1238 patients initiated on warfarin in a prospective inception cohort. Multivariable linear regression was used to assess warfarin dose and PTTR; proportional hazards analysis was performed to evaluate time to target INR and stable dose, overanticoagulation, and hemorrhage.

SETTING

Two outpatient anticoagulation clinics.

PARTICIPANTS

A total of 1238 anticoagulated patients.

OUTCOMES

Warfarin dose (mg/day), time to target INR and stable dose, PTTR, overanticoagulation (INR more than 4), and major hemorrhage.

RESULTS

Minor allele frequency for the CYP4F2*3 variant was 30.3% among European Americans and 8.4% among African Americans. CYP4F2*3 was associated with higher dose among European Americans but not African Americans. Compared to CYP4F2*1/*1, *1/*3 was associated with a statistically nonsignificant increase in dose (4.5%, p=0.22) and *3/*3 was associated with a statistically significant increase in dose (13.2%, p=0.02). CYP4F2 genotype did not influence time to target INR, time to stable dose, or PTTR in either race group. CYP4F2*3/*3 was associated with a 31% lower risk of over anticoagulation (p=0.06). Incidence of hemorrhage was lower among participants with CYP4F2 *3/*3 compared with *1/*3 or *1/*1 (incidence rate ratio = 0.45, 95% confidence interval 0.14-1.11, p=0.09). After controlling for covariates, CYP4F2 *3/*3 was associated with a 52% lower risk of hemorrhage, although this was not statistically significant (p=0.24).

CONCLUSION

Possession of CYP4F2*3 variant influences warfarin dose among European Americans but not African Americans. The CYP4F2-dose, CYP4F2-overanticoagulation, and CYP4F2-hemorrhage association follows a recessive pattern with possession of CYP4F2*3/*3 genotype likely demonstrating a protective effect. These findings need further confirmation.

Risk factors for post-transplant diabetes mellitus in renal transplant: Role of genetic variability in the CYP450-mediated arachidonic acid metabolism

Arachidonic acid (AA) is metabolized by cytochrome P450 (CYP) enzymes to epoxyeicosatrienoic acids (EETs) and 20-hidroxyeicosatetraenoic acid (20-HETE), which play an important role both in renal transplant and diabetes mellitus (DM). We searched for associations between polymorphisms in this metabolic pathway and the risk of post-transplant diabetes mellitus (PTDM) in kidney recipients. One-hundred-sixty-four patients were genotyped for common SNPs in this route, namely CYP2C8*3, CYP2C8*4, CYP2C9*2, CYP2C9*3, CYP2J2*7, CYP4A11 F434S and CYP4F2 V433M. Demographic and clinical parameters were retrospectively collected at four time-points in the first year after grafting. Thirty-four patients (20.73%) developed PTDM, which was more prevalent among older patients [OR for older age = 1.06 (1.03-1.10), p < 0.001] and in those with higher body mass index (BMI) [OR for higher average BMI in the first year = 1.13 (1.04-1.23); p < 0.01]. Creatinine clearance [OR = 0.97 (0.95-0.99); p < 0.01] and exposure to tacrolimus [OR = 3.25 (1.15-9.19); p < 0.05] were also relevant for PTDM risk. With regard to genetic variants, logistic regression analysis controlling for significant demographic and clinical variables showed that the V433M polymorphism in CYP4F2, responsible for 20-HETE synthesis, was an independent risk factor for PTDM [OR = 3.94 (1.08-14.33); p < 0.05]. We have shown that a genetic variant in the CYP4F2 gene, the main gene implicated in 20-HETE synthesis, is associated with the risk for PTDM. Our findings suggest that genes in the metabolic pathways of AA may become good candidates in genetic association studies for PTDM.

Polymorphisms in CYP-mediated arachidonic acid routes affect the outcome of renal transplantation

BACKGROUND

Arachidonic acid (AA) is metabolized by cytochrome P450 (CYP) enzymes to vasoactive metabolites (mainly epoxyeicosatrienoic acids) which are known to play a protective role against damaging processes that may occur after re-oxygenation of the graft. We aimed to investigate whether the presence of functional polymorphisms along these metabolic routes may play a role in the outcome of renal transplantation.

DESIGN

One-hundred and forty Caucasian renal transplant recipients and 137 donors were included. We determined the presence of seven common functional polymorphisms in the five genes governing the CYP-mediated AA metabolic pathway (CYP2C8, CYP2C9, CYP2J2, CYP4A11 and CYP4F2). Associations with parameters and events related to graft function and survival were retrospectively investigated throughout the first year after grafting.

RESULTS

The CYP2J2*7 allele of the donor was significantly associated with higher risk for delayed graft function [OR = 4·40 (1·45-13·37), P < 0·01] and lower death-censored graft survival [107·90 (84·19-131·62) vs. 176·89 (166·47-187·32) months for CYP2J2*1/*1 grafts; log-rank P = 0·015]. In addition, patients whose donors carried the CYP4A11 434S variant of the F434S polymorphism displayed impaired creatinine clearance, with statistically significant differences vs. 434FF subjects throughout the whole period of study (P < 0·05, P < 0·01, P < 0·001 and P < 0·05 for 1 week, 1 month, 5 months and 1 year after grafting, respectively).

CONCLUSIONS

Taken together, these results indicate that variability in the CYP450 genes involved in the synthesis of eicosanoids from AA may have a significant impact on graft function and survival in renal transplantation.

The role of clinical parameters and of CYP2C19 G681 and CYP4F2 G1347A polymorphisms on platelet reactivity during dual antiplatelet therapy

Dual antiplatelet therapy with aspirin and clopidogrel is used to lower the risk of arterial thrombosis. However, this strategy is not always successful owing to high interindividual variability in response to antiplatelet therapy. To evaluate an impact of CYP2C19 G681A and CYP4F2 G1347A polymorphisms and clinical factors on dual antiplatelet effect of clopidogrel and aspirin. Totally 89 patients who continued dual aspirin and clopidogrel antiplatelet therapy for at least of 14 days were included into the further study. Test for platelet aggregation was performed according to the classical Born method. Genotyping of CYP2C19*2 and CYP2C19*3 and CYP4F2*3 was done by using commercial probes from Applied Biosystems (UK). Patient age, weight and body weight index did not correlate significantly with platelet aggregation level both induced by ADP and epinephrine (P > 0.05). Serum concentration of creatinine, diabetes, angiotensin II receptor blockers, B-blockers, statin or omeprazole use had no significant effect on platelet aggregation. The users of angiotensin-converting enzyme inhibitors had lower platelet aggregation levels with epinephrine vs. nonusers: 28.80 ± 13.25 vs. 51.15 ± 23.50, P < 0.03, respectively. Platelet aggregation with ADP was higher in CYP2C19*1*2 genotype carriers than in CYP2C19*1*1 carriers (P = 0.01). Platelet aggregation with epinephrine was higher in CYP4F2 GA genotype carriers than in GG (P = 0.04) or AA (P = 0.01) carriers. Our study confirms that CYP2C19 G681A genotype has an impact on antiplatelet effect of clopidogrel. The novelty is that the platelet aggregation after induction with epinephrine is influenced by CYP4F2 G1347A genotype.

20-HETE is associated with unfavorable outcomes in subarachnoid hemorrhage patients

Emerging evidence has suggested that patients experiencing aneurysmal subarachnoid hemorrhage (aSAH) develop vascular dysregulation as a potential contributor to poor outcomes. Preclinical studies have implicated the novel microvascular constrictor, 20-hydroxyeicosatetraenoic acid (20-HETE) in aSAH pathogenesis, yet the translational relevance of 20-HETE in patients with aSAH is largely unknown. The goal of this research was to determine the relationship between 20-HETE cerebrospinal fluid (CSF) levels, gene variants in 20-HETE synthesis, and acute/long-term aSAH outcomes. In all, 363 adult patients (age 18 to 75) with aSAH were prospectively recruited from the University of Pittsburgh Medical Center neurovascular Intensive Care Unit. Patients were genotyped for polymorphic variants and cytochrome P450 (CYP)-eicosanoid CSF levels were measured over 14 days. Outcomes included delayed cerebral ischemia (DCI), clinical neurologic deterioration (CND), and modified Rankin Scores (MRS) at 3 and 12 months. Patients with CND and unfavorable 3-month MRS had 2.2- and 2.7-fold higher mean 20-HETE CSF levels, respectively. Patients in high/moderate 20-HETE trajectory groups (35.7%) were 2.5-, 2.1-, 3.1-, 3.3-, and 2.1-fold more likely to have unfavorable MRS at 3 months, unfavorable MRS at 12 months, mortality at 3 months, mortality at 12 months, and CND, respectively. These results showed that 20-HETE is associated with acute and long-term outcomes and suggest that 20-HETE may be a novel target in aSAH.

Vascular actions of 20-HETE

20-hydroxyeicosatetraenoic acid (20-HETE) is a metabolite of arachidonic acid that exhibits a myriad of biological effects in the vascular system. This review discusses the current knowledge related to the effects of 20-HETE on vascular reactivity, activation, and remodeling, as well as its role in vascular inflammation and angiogenesis. The information explaining how 20-HETE and the renin-angiotensin system interact to promote hypertension, vasoconstriction, and vascular dysfunction is summarized in this article. 20-HETE enhances vascular inflammation and injury in models of diabetes, ischemia/reperfusion, and cerebrovascular oxidative stress. Recent studies also established a role for 20-HETE in normal and pathological angiogenesis conditions. This review will also discuss the molecular mechanisms through which 20-HETE induces these vascular actions. Potential additional studies are suggested to address shortcomings in the current knowledge of 20-HETE in the vascular system.

Cytochrome 4A11 Genetic Polymorphisms Increase Susceptibility to Ischemic Stroke and Associate with Atherothrombotic Events After Stroke in Chinese

To evaluate the associations between four single-nucleotide polymorphisms (SNPs) in CYP4A11 and CYP4F2 and ischemic stroke (IS), and between these variants and atherothrombotic events after stroke. IS patients (n=396) and controls (n=378) were genotyped for two CYP4A11 SNPs (rs2269231 and rs9333025) and two CYP4F2 SNPs (rs2108622 and rs3093135). Patients were followed up for 12 months after the stroke for the atherothrombotic events. The frequency of the rs9333025 GG genotype was significantly higher in IS patients than in controls. Logistic regression analysis showed that the presence of rs9333025 GG in patients was associated with significantly higher risk of IS. Cox regression analysis revealed that the rs9333025 GG genotype was an independent risk factor for atherothrombotic events after stroke. The rs9333025 GG genotype increases patients' susceptibility to IS and is associated with high frequencies of atherothrombotic events in stroke patients.

Effect of clinical factors and gene polymorphism of CYP2C19*2, *17 and CYP4F2*3 on early stent thrombosis

Aim: To determine the main clinical and genetic factors having impact on early coronary stent thrombosis. Materials & methods: Genotyping of CYP2C19*2, *17 and CYP4F2*3 in patients with (n = 31) and without stent thrombosis (n = 456) was performed. Clinical and genetic data were analyzed by binary logistic regression. Results: Smoking (OR: 0.317; 95% CI: 0.131–0.767), high-density lipoprotein level in mmol/l (OR: 0.142; 95% CI: 0.040–0.506), CYP2C19*2*2 versus *1*1 and *1*2 genotype (OR: 11.625; 95% CI: 3.498–38.633), CYP4F2 AA versus GA and GG genotype (OR: 3.532; 95% CI: 1.153–10.822) were associated with early stent thrombosis. Conclusion: For the first time we have identified a clinically important polymorphism (CYP4F2 G1347A) that was independently associated with early stent thrombosis.

Original submitted 18 August 2014; Revision submitted 10 November 2014

Cytochrome P450 eicosanoids in hypertension and renal disease

PURPOSE OF REVIEW

Cytochrome (CYP) P450 metabolites of arachidonic acid, 20-hydroxyeicosatetraenoic acid (20-HETE) and epoxyeicosatrienoic acids (EETs) contribute to the regulation of renal tubular and vascular function. This review highlights the results of the recent genetic studies in humans and rodent models, indicating that these eicosanoids participate in the control of blood pressure (BP), chronic kidney disease (CKD), renal ischemia-reperfusion injury (IRI) and polycystic kidney disease (PKD).

RECENT FINDINGS

Endogenous 20-HETE has been reported to play an essential role in the myogenic and tubuloglomerular feedback responses in the afferent arteriole, and a deficiency of 20-HETE contributes to the development of hypertension and renal injury in Dahl S rats. Mutations in CYP4A11 and CYP4F2 have been linked to elevated BP in humans. EETs have been shown to regulate epithelial sodium channel in the collecting duct, lower BP and have renoprotective properties. 20-HETE also opposes the development of CKD and IRI, and may play a role in PKD.

SUMMARY

These studies indicate that CYP P450 metabolites of arachidonic acid play an important role in the control of BP, CKD, AKI and PKD. Drugs targeting these pathways could be useful in the treatment of IRI and CKD.

20-HETE and blood pressure regulation: clinical implications

20-Hydroxy-5, 8, 11, 14-eicosatetraenoic acid (20-HETE) is a cytochrome P450 (CYP)-derived omega-hydroxylation metabolite of arachidonic acid. 20-HETE has been shown to play a complex role in blood pressure regulation. In the kidney tubules, 20-HETE inhibits sodium reabsorption and promotes natriuresis, thus, contributing to antihypertensive mechanisms. In contrast, in the microvasculature, 20-HETE has been shown to play a pressor role by sensitizing smooth muscle cells to constrictor stimuli and increasing myogenic tone, and by acting on the endothelium to further promote endothelial dysfunction and endothelial activation. In addition, 20-HETE induces endothelial angiotensin-converting enzyme, thus, setting forth a potential feed forward prohypertensive mechanism by stimulating the renin-angiotensin-aldosterone system. With the advancement of gene sequencing technology, numerous polymorphisms in the regulatory coding and noncoding regions of 20-HETE-producing enzymes, CYP4A11 and CYP4F2, have been associated with hypertension. This in-depth review article discusses the biosynthesis and function of 20-HETE in the cardiovascular system, the pharmacological agents that affect 20-HETE action, and polymorphisms of CYP enzymes that produce 20-HETE and are associated with systemic hypertension in humans.

Urinary CYP eicosanoid excretion correlates with glomerular filtration in African-Americans with chronic kidney disease

Previous studies have indicated that cytochrome P450 (CYP) metabolites of arachidonic acid (AA), i.e., 20-hydroxyeicosatetraenoic acid (20-HETE) and epoxyeicosatrienoic acids (EETs), play an important role in the regulation of renal tubular and vascular function. The present study for the first time profiled HETEs and epoxygenase derived dihydroxyeicosatetraenoic acid diHETEs levels in spot urines and plasma in 262 African American patients from the University of Mississippi Chronic Kidney Disease Clinic and 31 African American controls. Significant correlations in eGFR and urinary 20-HETE/creatinine and 19-HETE/creatinine levels were observed. The eGFR increased by 17.47 [p=0.001] and 60.68 [(p=0.005]ml/min/for each ng/mg increase in 20-HETE and 19-HETE levels, respectively. Similar significant positive associations were found between the other urinary eicosanoids and eGFR and also with 19-HETE/urine creatinine concentration and proteinuria. We found that approximately 80% of plasma HETEs and 30% diHETEs were glucuronidated and the fractional excretion of 20-HETE was less than 1%. These results suggest that there is a significant hepatic source of urinary 20-HETE glucuronide and EETs with extensive renal biotransformation to metabolites which may play a role in the pathogenesis of CKD.

CYP4F2 genetic polymorphisms are associated with coronary heart disease in a Chinese population

BACKGROUND

To explore the relationship between CYP4F2 gene polymorphism and coronary heart disease (CHD) in a Chinese Han population.

METHODS

We selected 440 CHD patients and 440 control subjects to perform a case - control study. Four SNPs (rs2108622, rs3093100, rs3093105 and rs3093135) in CYP4F2 gene were genotyped using polymerase chain reaction - restriction fragment length polymorphism (PCR - RFLP) methods. The genotype and haplotype distributions were compared between the case and the control group.

RESULTS

We found both rs2108622 and rs3093105 in CYP4F2 gene were associated with the risk for CHD (P <0.01). Haplotype analysis indicated that GGGT haplotype consisted by rs2108622-rs3093100-rs3093105-rs3093135 was associated with CHD risk (OR = 4.367, 95% CI: 2.241 ~ 8.510; P < 0.001), but GGTA haplotype was associated with decreased risk for CHD (OR = 0.450, 95% CI: 0.111 ~ 0.777; P <0.001).

CONCLUSION

CYP4F2 gene polymorphisms were associated with the risk of CHD in Chinese population.

Genetic polymorphism of cytochrome P450 4F2, vitamin E level and histological response in adults and children with nonalcoholic fatty liver disease who participated in PIVENS and TONIC clinical trials

Vitamin E improved liver histology in children and adults with NAFLD who participated in TONIC and PIVENS clinical trials, but with significant inter-individual variability in its efficacy. Cytochrome P450 4F2 (CYP4F2) is the major enzyme metabolizing Vit E, with two common genetic variants (V433M, rs2108622 and W12G, rs3093105) found to alter its activity. We investigated the relationship between CYP4F2 genotypes, α-tocopherol levels and histological improvement in these two trials. V433M and W12G variants were genotyped in TONIC (n = 155) and PIVENS (n = 213) DNA samples. The relationships between CYP4F2 genotypes, plasma α-tocopherol levels at baseline and weeks 48 (w48) and 96 (w96) and histological end points (overall improvement in liver histology and resolution of NASH) were investigated. As a result, the V433M genotype was significantly associated with baseline plasma α-tocopherol in the TONIC trial (p = 0.004), but not in PIVENS. Among those receiving Vit E treatment, CYP4F2 V433M genotype was associated with significantly decreased plasma α-tocopherol levels at w48 (p = 0.003 for PIVENS and p = 0.026 for TONIC) but not at w96. The w96 α-tocopherol level was significantly associated with resolution of NASH (p = 0.006) and overall histology improvement (p = 0.021)in the PIVENS, but not in the TONIC trial. There was no significant association between CYP4F2 genotypes and histological end points in either trial. Our study suggested the a moderate role of CYP4F2 polymorphisms in affecting the pharmacokinetics of Vit E as a therapeutic agent. In addition, there may be age-dependent relationship between CYP4F2 genetic variability and Vit E pharmacokinetics in NAFLD.

Cytochrome P450-dependent catabolism of vitamin K: ω-hydroxylation catalyzed by human CYP4F2 and CYP4F11

Vitamin K plays an essential role in many biological processes including blood clotting, maintenance of bone health, and inhibition of arterial calcification. A menaquinone form of vitamin K, MK4, is increasingly recognized for its key roles in mitochondrial electron transport, as a ligand for the nuclear receptor SXR, which controls the expression of genes involved in transport and metabolism of endo- and xenobiotics, and as a pharmacotherapeutic in the treatment of osteoporosis. Although cytochrome P450 (CYP) 4F2 activity is recognized as an important determinant of phylloquinone (K1) metabolism, the enzymes involved in menaquinone catabolism have not been studied previously. CYP4F2 and CYP4F11 were expressed and purified and found to be equally efficient as in vitro catalysts of MK4 ω-hydroxylation. CYP4F2, but not CYP4F11, catalyzed sequential metabolism of MK4 to the ω-acid without apparent release of the intermediate aldehyde. The ω-alcohol could also be metabolized to the acid by microsomal NAD(+)-dependent alcohol and aldehyde dehydrogenases. LC-MS/MS analysis of trypsinized human liver microsomes (using a surrogate peptide approach) revealed the mean concentrations of CYP4F2 and CYP4F11 to be 14.3 and 8.4 pmol/mg protein, respectively. Microsomal MK4 ω-hydroxylation activities correlated with the CYP4F2 V433M genotype but not the CYP4F11 D446N genotype. Collectively, these data expand the lexicon of vitamin K ω-hydroxylases to include the 'orphan' P450 CYP4F11 and identify a common variant, CYP4F2 (rs2108622), as a major pharmacogenetic variable influencing MK4 catabolism.

GENETIC FACTORS INFLUENCING THE EFFECTIVENESS AND SAFETY OF LONG-TERM ANTICOAGULANT THERAPY

Late postoperative thrombotic and haemorrhagic complications in anticoagulant-treated patients remain one of the key problems of the modern clinical medicine. At present, the most widely used anticoagulant is warfarin, a vitamin K antagonist. One of the reasons for a pathological reaction to the therapeutic concentration of warfarin could be individual features of warfarin metabolism, determined by relevant genes. The literature data suggest that protein-coding CYP2C9 and VKORC1 genes play an important role in the development of postoperative complications. However, the individual warfarin dosage can be influenced by a wide range of other genetic polymorphisms. 

Effect of NQO1 and CYP4F2 genotypes on warfarin dose requirements in Hispanic-Americans and African-Americans

AIM

The objective of this study was to determine the additional contribution of NQO1 and CYP4F2 genotypes to warfarin dose requirements across two racial groups after accounting for known clinical and genetic predictors.

PATIENTS & METHODS

The following were assessed in a cohort of 260 African-Americans and 53 Hispanic-Americans: clinical data; NQO1 p.P187S (*1/*2); CYP2C9*2, *3, *5, *6, *8 and *11; CYP4F2 p.V433M; and VKORC1 c.-1639G>A genotypes.

RESULTS

Both the CYP4F2 433M (0.23 vs 0.06; p < 0.05) and NQO1*2 (0.27 vs 0.18; p < 0.05) allele frequencies were higher in Hispanic-Americans compared with African-Americans. Multiple regression analysis in the Hispanic-American cohort revealed that each CYP4F2 433M allele was associated with a 22% increase in warfarin maintenance dose (p = 0.019). Possession of the NQO1*2 allele was associated with a 34% increase in warfarin maintenance dose (p = 0.004), while adjusting for associated genetic (CYP2C9, CYP4F2 and VKORC1) and clinical factors. In this population, the inclusion of CYP4F2 and NQO1*2 genotypes improved the dose variability explained by the model from 0.58 to 0.68 (p = 0.001), a 17% relative improvement. By contrast, there was no association between CYP4F2 or NQO1*2 genotype and therapeutic warfarin dose in African-Americans after adjusting for known genetic and clinical predictors.

CONCLUSION

In our cohort of inner-city Hispanic-Americans, the CYP4F2 and NQO1*2 genotypes significantly contributed to warfarin dose requirements. If our findings are confirmed, they would suggest that inclusion of the CYP4F2 and NQO1*2 genotypes in warfarin dose prediction algorithms may improve the predictive ability of such algorithms in Hispanic-Americans.

Androgen-sensitive hypertension associates with upregulated vascular CYP4A12-20-HETE synthase

Although the mechanism underlying the effect of androgen on BP and cardiovascular disease is not well understood, recent studies suggest that 20-hydroxy-5,8,11,14-eicosatetraenoic acid (20-HETE), a primary cytochrome P450 4 (Cyp4)-derived eicosanoid, may mediate androgen-induced hypertension. Here, treatment of normotensive mice with 5α-dihydrotestosterone increased BP and induced both Cyp4a12 expression and 20-HETE levels in preglomerular microvessels. Administration of a 20-HETE antagonist prevented and reversed the effects of dihydrotestosterone on BP. Cyp4a14(-/-) mice, which exhibit androgen-sensitive hypertension in the male mice, produced increased levels of vascular 20-HETE; furthermore, administration of a 20-HETE antagonist normalized BP. To examine whether androgen-independent increases in 20-HETE are sufficient to cause hypertension, we studied Cyp4a12-transgenic mice, which express the CYP4A12-20-HETE synthase under the control of a doxycycline-sensitive promoter. Administration of doxycycline increased BP by 40%, and administration of a 20-HETE antagonist prevented this increase. Levels of CYP4A12 and 20-HETE in preglomerular microvessels of doxycycline-treated transgenic mice approximately doubled, correlating with increased 20-HETE-dependent sensitivity to phenylephrine-mediated vasoconstriction and with decreased acetylcholine-mediated vasodilation in the renal microvasculature. We observed a similar contribution of 20-HETE to myogenic tone in the mesenteric microvasculature. Taken together, these results suggest that 20-HETE both mediates androgen-induced hypertension and can cause hypertension independent of androgen.

Optimal dosing of warfarin and other coumarin anticoagulants: the role of genetic polymorphisms

Coumarin anticoagulants, which include warfarin, acenocoumarol and phenprocoumon, are among the most widely prescribed drugs worldwide. There is now a large body of published data showing that genotype for certain common polymorphisms in the genes encoding the target vitamin K epoxide reductase (G-1639A/C1173T) and the main metabolizing enzyme CYP2C9 (CYP2C9*2 and *3 alleles) are important determinants of the individual coumarin anticoagulant dose requirement. Additional less common polymorphisms in these genes together with polymorphisms in other genes relevant to blood coagulation such as the cytochrome P450 CYP4F2, gamma-glutamyl carboxylase, calumenin and cytochrome P450 oxidoreductase may also be significant predictors of dose, especially in ethnic groups such as Africans where there have been fewer genetic studies compared with European populations. Using relevant genotypes to calculate starting dose may improve safety during the initiation period. Various algorithms for dose calculation, which also take patient age and other characteristics into consideration, have been developed for all three widely used coumarin anticoagulants and are now being tested in ongoing large randomised clinical trials. One recently completed study has provided encouraging results suggesting that calculation of warfarin dose on the basis of individual patient genotype leads to few adverse events and a higher proportion of time within the therapeutic coagulation rate window, but these findings still need confirmation.

Eicosanoids in metabolic syndrome

Chronic persistent inflammation plays a significant role in disease pathology of cancer, cardiovascular disease, and metabolic syndrome (MetS). MetS is a constellation of diseases that include obesity, diabetes, hypertension, dyslipidemia, hypertriglyceridemia, and hypercholesterolemia. Nonalcoholic fatty liver disease (NAFLD) is associated with many of the MetS diseases. These metabolic derangements trigger a persistent inflammatory cascade, which includes production of lipid autacoids (eicosanoids) that recruit immune cells to the site of injury and subsequent expression of cytokines and chemokines that amplify the inflammatory response. In acute inflammation, the transcellular synthesis of antiinflammatory eicosanoids resolve inflammation, while persistent activation of the autacoid-cytokine-chemokine cascade in metabolic disease leads to chronic inflammation and accompanying tissue pathology. Many drugs targeting the eicosanoid pathways have been shown to be effective in the treatment of MetS, suggesting a common linkage between inflammation, MetS and drug metabolism. The cross-talk between inflammation and MetS seems apparent because of the growing evidence linking immune cell activation and metabolic disorders such as insulin resistance, dyslipidemia, and hypertriglyceridemia. Thus modulation of lipid metabolism through either dietary adjustment or selective drugs may become a new paradigm in the treatment of metabolic disorders. This review focuses on the mechanisms linking eicosanoid metabolism to persistent inflammation and altered lipid and carbohydrate metabolism in MetS.

CYP4 enzymes as potential drug targets: focus on enzyme multiplicity, inducers and inhibitors, and therapeutic modulation of 20-hydroxyeicosatetraenoic acid (20-HETE) synthase and fatty acid ω-hydroxylase activities

The Cytochrome P450 4 (CYP4) family of enzymes in humans is comprised of thirteen isozymes that typically catalyze the ω-oxidation of endogenous fatty acids and eicosanoids. Several CYP4 enzymes can biosynthesize 20- hydroxyeicosatetraenoic acid, or 20-HETE, an important signaling eicosanoid involved in regulation of vascular tone and kidney reabsorption. Additionally, accumulation of certain fatty acids is a hallmark of the rare genetic disorders, Refsum disease and X-ALD. Therefore, modulation of CYP4 enzyme activity, either by inhibition or induction, is a potential strategy for drug discovery. Here we review the substrate specificities, sites of expression, genetic regulation, and inhibition by exogenous chemicals of the human CYP4 enzymes, and discuss the targeting of CYP4 enzymes in the development of new treatments for hypertension, stroke, certain cancers and the fatty acid-linked orphan diseases.

Positive selection in the chromosome 16 VKORC1 genomic region has contributed to the variability of anticoagulant response in humans

VKORC1 (vitamin K epoxide reductase complex subunit 1, 16p11.2) is the main genetic determinant of human response to oral anticoagulants of antivitamin K type (AVK). This gene was recently suggested to be a putative target of positive selection in East Asian populations. In this study, we genotyped the HGDP-CEPH Panel for six VKORC1 SNPs and downloaded chromosome 16 genotypes from the HGDP-CEPH database in order to characterize the geographic distribution of footprints of positive selection within and around this locus. A unique VKORC1 haplotype carrying the promoter mutation associated with AVK sensitivity showed especially high frequencies in all the 17 HGDP-CEPH East Asian population samples. VKORC1 and 24 neighboring genes were found to lie in a 505 kb region of strong linkage disequilibrium in these populations. Patterns of allele frequency differentiation and haplotype structure suggest that this genomic region has been submitted to a near complete selective sweep in all East Asian populations and only in this geographic area. The most extreme scores of the different selection tests are found within a smaller 45 kb region that contains VKORC1 and three other genes (BCKDK, MYST1 (KAT8), and PRSS8) with different functions. Because of the strong linkage disequilibrium, it is not possible to determine if VKORC1 or one of the three other genes is the target of this strong positive selection that could explain present-day differences among human populations in AVK dose requirement. Our results show that the extended region surrounding a presumable single target of positive selection should be analyzed for genetic variation in a wide range of genetically diverse populations in order to account for other neighboring and confounding selective events and the hitchhiking effect.

Impact of the CYP4F2 p.V433M polymorphism on coumarin dose requirement: systematic review and meta-analysis

A systematic review and a meta-analysis were performed to quantify the accumulated information from genetic association studies investigating the impact of the CYP4F2 rs2108622 (p.V433M) polymorphism on coumarin dose requirement. An additional aim was to explore the contribution of the CYP4F2 variant in comparison with, as well as after stratification for, the VKORC1 and CYP2C9 variants. Thirty studies involving 9,470 participants met prespecified inclusion criteria. As compared with CC-homozygotes, T-allele carriers required an 8.3% (95% confidence interval (CI): 5.6-11.1%; P < 0.0001) higher mean daily coumarin dose than CC homozygotes to reach a stable international normalized ratio (INR). There was no evidence of publication bias. Heterogeneity among studies was present (I(2) = 43%). Our results show that the CYP4F2 p.V433M polymorphism is associated with interindividual variability in response to coumarin drugs, but with a low effect size that is confirmed to be lower than those contributed by VKORC1 and CYP2C9 polymorphisms.

Synergistical effect of 20-HETE and high salt on NKCC2 protein and blood pressure via ubiquitin-proteasome pathway

We previously generated a cytochrome P450 4F2 (CYP4F2) transgenic mouse model and demonstrated that overexpressed CYP4F2 and overproduced 20-HETE in the kidneys contribute to the increase of blood pressure in the CYP4F2 transgenic mice with normal salt intake. We currently expect to elucidate a potential mechanism of salt-related hypertension whereby diverse levels of 20-HETE interact with dietary salt on Na(+)-K(+)-2Cl(-) cotransporter, isoform 2 (NKCC2) in the kidneys of the transgenic and wild-type mice with high salt intake. High salt intake reduced about 85 % abundance of renal NKCC2 protein in the transgenic mice and about 24 % in the wild-type mice by Western blot. Furthermore, we first found that NKCC2 was ubiquitinated and interacted with Nedd4-2 by immunoprecipitation in the transgenic mice with high salt intake. In addition, inhibition of 20-HETE synthesis or proteasome activity reversed the reduction of NKCC2 expression induced by 20-HETE and high salt intake. These results suggest that 20-HETE and high salt intake synergistically decrease the expression of NKCC2 protein via Nedd4-2-mediated ubiquitin-proteasome pathway, and thereby modulate natriuresis and blood pressure. We propose that diverse levels of 20-HETE have diverse effects on blood pressure in different salt concentrations.

Urinary α-carboxyethyl hydroxychroman can be used as a predictor of α-tocopherol adequacy, as demonstrated in the Energetics Study

BACKGROUND

Other than the in vitro erythrocyte hemolysis test, no valid biomarkers of vitamin E status currently exist.

OBJECTIVE

We hypothesized that the urinary vitamin E metabolite α-carboxyethyl hydroxychroman (α-CEHC) could serve as a biomarker.

DESIGN

The relations between urinary α-CEHC, plasma α-tocopherol, and vitamin E intakes were assessed by using a previously validated multipass, Web-based, 24-h self-administered dietary recall, and we concurrently collected plasma and 24-h urine samples from 233 participants of both sexes.

RESULTS

Median vitamin E intakes were 9.7 mg α-tocopherol/d. Intakes were correlated with plasma α-tocopherol (R = 0.40, P < 0.001) and urinary α-CEHC (R = 0.42, P < 0.001); these correlations were essentially unchanged after multivariate adjustments. On the basis of multiple regression analysis, urinary α-CEHC excretion increased by ~0.086 μmol/g creatinine (95% CI: 0.047, 0.125) for every 1-mg (2.3-μmol) increase in dietary α-tocopherol. Urinary α-CEHC excretion remained at a plateau (median: 1.39 μmol/g creatinine) until dietary intakes of α-tocopherol exceeded 9 mg α-tocopherol/d. The inflection point at which vitamin E metabolism increased was estimated to be at an intake of 12.8 mg α-tocopherol/d. Daily excretion of >1.39 μmol α-CEHC/g creatinine is associated with a greater than adequate α-tocopherol status, as evidenced by increased vitamin E metabolism and excretion.

CONCLUSION

Thus, urinary α-CEHC is a valid biomarker of α-tocopherol status that can be used to set a value for the Estimated Adequate Requirement of vitamin E.

The functional variant V433M of the CYP4F2 and the metabolic syndrome in Swedes

BACKGROUND AND AIM

The genetic basis of Metabolic syndrome (MetS) is largely unknown but a link with salt sensitivity is recognized. The cytochrome P450 isoform 4F2 (CYP4F2) is involved in renal production of 20-hydroxyeicosatethraenoic acid (20-HETE), a natriuretic substance associated with salt sensitivity. The same enzyme is implicated in ω-hydroxylation of very long and medium chain fatty acids in the liver suggesting its possible influence on gluco-metabolic components of MetS. The aim of the present study was to evaluate the effect of CYP4F2 V433M, a functional polymorphism previously associated with hypertension via renal salt reabsorption, on the individual components of MetS and MetS itself.

METHODS

The polymorphism was genotyped in the cardiovascular cohort of the Malmö Diet and Cancer (MDC-CVA) study and successively in the Malmö Preventive Project (MPP) cohort. Different definitions of the MetS were applied.

RESULTS

In the MDC-CVA, male, but not female, CYP4F2 M433 carriers had significantly higher levels of waist, triglycerides, BP and a composite sum of MetS phenotypes (MetS score) beside lower HDL-cholesterol respect to V-homozygotes. MetS, as defined in the ATPIII and the AHA/NHLBI definitions, was more prevalent in M-carriers with respect to V-homozygotes. In the MPP cohort, significant association was detectable only for triglycerides at baseline and for Diastolic BP at reinvestigation in male M-carriers.

CONCLUSION

The initial positive association of the CYP4F2 V433M polymorphism with components of MetS and MetS itself, found in MDC-CVA, was partially denied in another large cohort. The first association either could be due to a false positive result or alternatively, different genetic background or population stratification could have hidden the effect of the polymorphism in the replication cohort.

Genetic polymorphisms affecting drug metabolism: recent advances and clinical aspects

Though current knowledge of pharmacogenetic factors relevant to drug metabolism is fairly comprehensive and this should facilitate translation to the clinic, there are a number of gaps in knowledge. Recent studies using both conventional and novel approaches have added to our knowledge of pharmacogenetics of drug metabolism. Genome-wide association studies have provided new insights into the major contribution of cytochromes P450 to response to therapeutic agents such as coumarin anticoagulants and clopidogrel as well as to caffeine and nicotine. Recent advances in understanding of factors affecting gene expression, both regulation by transcription factors and by microRNA and epigenetic factors, have added to understanding of variation in expression of genes such as CYP3A4 and CYP2E1. The implementation of testing for pharmacogenetic polymorphisms in prescription of selected anticancer drugs and cardiovascular agents is considered in detail, with current controversies and barriers to implementation of pharmacogenetic testing assessed. Though genotyping for thiopurine methyltransferase is now common prior to prescription of thiopurines, genotyping for other pharmacogenetic polymorphisms prior to drug prescription remains uncommon. However, it seems likely that it will become more widespread as both increased evidence that certain pharmacogenetic tests are valuable and cost-effective and more accessible genotyping methods become available.

The role of 20-HETE in androgen-mediated hypertension

Androgen plays an important role in blood pressure regulation. Epidemiological studies have shown that men have a higher prevalence for developing hypertension than aged-matched, premenopausal women. Interestingly, postmenopausal women and women with polycystic ovary syndrome, both of which have increased endogenous androgen production, have elevated risks for hypertension suggesting that androgen may contribute to its development. Studies from our laboratory and others have provided substantial evidence that 20-hydroxyeicosatetraenoic acid (20-HETE) mediates the hypertension seen in rodents treated with androgen. 20-HETE is the cytochrome P450 (CYP)-derived ω-hydroxylated metabolite of arachidonic acid. 20-HETE plays a complex role in blood pressure regulation. In the kidney tubules, 20-HETE decreases blood pressure by promoting natriuresis, while in the microvasculature it has a pressor effect. In the microcirculation, 20-HETE participates in the regulation of vascular tone by sensitizing the smooth muscle cells to constrictor stimuli and contributes to myogenic, mitogenic and angiogenic responses. In addition, 20-HETE acts on the endothelium to promote endothelial dysfunction and endothelial activation. Recently, we have demonstrated that 20-HETE induces endothelial ACE thus setting forth a potential feed forward mechanism through activation of the renin-angiotensin-aldosterone system. In this review, we will discuss the pro-hypertensive effects of 20-HETE and its role in androgen-induced vascular dysfunction and hypertension.

Peripheral and central augmentation indexes in relation to the CYP4F2 polymorphisms in Chinese

OBJECTIVE

Cytochrome (CYP) 4F2 isoform is a key metabolizing enzyme for the renal 20-hydroxyeicosatetraenoic acid (20-HETE), which, as an endogenous vasoconstrictor, may influence properties of the peripheral muscular arteries and arterioles. We, therefore, investigated the CYP4F2 polymorphisms in relation to arterial wave reflections, as measured by augmentation indexes (AIx) in Chinese.

METHODS

We performed arterial measurements by SphygmoCor and genotyped three CYP4F2 polymorphisms (V433M, rs3093089, and rs3093098) by PCR-restriction fragment length polymorphism in 1421 participants enrolled in the JingNing Population study. A replication study for the V433M polymorphism was performed in 924 Chinese recruited from a workplace setting. Urinary 20-HETE concentration was determined by ELISA in a randomly selected subsample of 318 JingNing individuals.

RESULTS

In spite of the fact that genetic associations were not significant (P ≥ 0.12) in all JingNing participants, there was significant (Pint ≤ 0.02) interaction of the V433M polymorphism with sex and pulse rate in relation to peripheral and central AIx. M433 allele carriers, compared with V433V homozygotes, had significantly greater peripheral (+5.0%, P = 0.0002) and central AIx (+3.2%, P = 0.001) in 693 men. The corresponding values were +2.7% (P = 0.04) and +1.9% (P = 0.04) in 490 individuals of the top tertile of pulse rate (≥ 76 beats/min), and were +4.0% (P = 0.02) and +3.3% (P = 0.02) in 315 replication participants with a pulse rate at least 76 beats/min. Urinary 20-HETE concentration was significantly higher (P = 0.002) in M433M (2.06 ng/ml) and V433M (1.13 ng/ml) individuals than in V433V homozygotes (0.98 ng/ml).

CONCLUSION

The CYP4F2 V433M polymorphism is associated with the size of arterial wave reflections in male Chinese, or individuals with a faster pulse rate.

Association of 1347 G/A cytochrome P450 4F2 (CYP4F2) gene variant with hypertension and stroke

Genetic variants of cytochrome P450 4F2 (CYP4F2) gene have been suggested to be risk factors for hypertension, cardiovascular diseases and stroke. In the present case-control study we investigated the association of 1347 G/A polymorphism (rs2108622) in the 11th exon region of CYP4F2 gene with hypertension, ischemic stroke and stroke subtypes classified according to TOAST (Trial of Org 10172 in Acute Stroke Treatment) classification. Five hundred and seven stroke patients (hypertensives: normotensives = 279:228) and four hundred and eighty seven, age and sex matched controls (males: females = 356:131) (hypertensives: normotensives = 148:339) were involved in the study. The genotypes were determined by PCR-RFLP technique. Genotypes were confirmed by subjecting the PCR products to sequencing. Significant difference was observed in the genotypic distribution and allelic frequency between the stroke patients and healthy controls. AA genotype and A allele associated significantly with stroke and hypertension [P = 0.009; OR = 1.59 (95% CI = 1.119-2.283) and P = 0.010; OR = 1.26 (95% CI = 1.056-1.502); P = 0.01; OR = 1.58 (95% CI = 1.11-2.272) and P = 0.010; OR = 1.25(95% CI = 1.054-1.504) respectively]. A stepwise logistic regression analysis confirmed these findings. To establish that this polymorphism is associated with stroke independent of hypertension; we compared stroke patients without hypertension with normotensive controls. Significant difference was observed in genotypic distribution and allelic frequency between the two groups (P = 0.001 and 0.002 respectively). Evaluating the association of this polymorphism with stroke subtypes we found significant associations with cardioembolic stroke (P < 0.001). In conclusion our study suggests that 1347A allele of CYP4F2 gene is an important risk factor for hypertension and ischemic stroke.

20-hydroxyeicosatetraeonic acid: a new target for the treatment of hypertension

Arachidonic acid is metabolized by enzymes of the CYP4A and 4F families to 20-hydroxyeicosatetraeonic acid (20-HETE), which plays an important role in the regulation of renal function, vascular tone, and the long-term control of arterial pressure. In the vasculature, 20-HETE is a potent vasoconstrictor, and upregulation of the production of this compound contributes to the elevation in oxidative stress and endothelial dysfunction and the increase in peripheral vascular resistance associated with some forms of hypertension. In kidney, 20-HETE inhibits Na transport in the proximal tubule and thick ascending loop of Henle, and deficiencies in the renal formation of 20-HETE contributes to sodium retention and development of some salt-sensitive forms of hypertension. 20-HETE also has renoprotective actions and opposes the effects of transforming growth factor β to promote proteinuria and renal end organ damage in hypertension. Several new inhibitors of the synthesis of 20-HETE and 20-HETE agonists and antagonists have recently been developed. These compounds along with peroxisome proliferator-activated receptor-α agonists that induce the renal formation of 20-HETE seem to have promise as antihypertensive agents. This review summarizes the rationale for the development of drugs that target the 20-HETE pathway for the treatment of hypertension and associated cardiovascular complications.

Increased vitamin E intake is associated with higher alpha-tocopherol concentration in the maternal circulation but higher alpha-carboxyethyl hydroxychroman concentration in the fetal circulation

BACKGROUND

The transfer of vitamin E across the placenta is limited, but no data exist on the concentrations of vitamin E metabolites carboxyethyl hydroxychromans (α- and γ-CEHCs) in the fetal circulation.

OBJECTIVE

We measured α- and γ-CEHC concentrations in maternal and umbilical cord blood pairs and examined their relations to circulating vitamin E (α- and γ-tocopherol) and maternal dietary vitamin E intake.

DESIGN

Healthy, pregnant women were enrolled from Oregon Health and Science University's obstetric clinic (<22 wk gestation), and at least one fasting blood sample and a previous day's 24-h diet recall were collected during their pregnancy (n = 19). Umbilical cord blood samples were obtained at the time of delivery and were analyzed for α- and γ-tocopherol, α- and γ-CEHC, and total lipid concentrations.

RESULTS

Mean (±SD) concentrations of umbilical cord blood α-CEHC (30.2 ± 28.9 nmol/L) and γ-CEHC (104.5 ± 61.3 nmol/L) were not significantly different from maternal concentrations (P = 0.07 and 0.08, respectively), but metabolite:tocopherol ratios were significantly higher in cord blood (P < 0.01 and 0.001, respectively). Maternal α-tocopherol:total lipids ratios were correlated with cord blood α-CEHCs (r = 0.67, P = 0.004), and higher vitamin E intakes were associated with higher cord blood α-CEHC concentrations (r = 0.75, P < 0.003).

CONCLUSION

Higher maternal intake of vitamin E during pregnancy may result in increased metabolite concentrations in the fetal circulation, suggesting increased maternal or fetal liver metabolism of vitamin E. This trial was registered at clinicaltrials.gov as NCT00632476.

Genistein, resveratrol, and 5-aminoimidazole-4-carboxamide-1-β-D-ribofuranoside induce cytochrome P450 4F2 expression through an AMP-activated protein kinase-dependent pathway

Activators of AMP-activated protein kinase (AMPK) increase the expression of the human microsomal fatty acid ω-hydroxylase CYP4F2. A 24-h treatment of either primary human hepatocytes or the human hepatoma cell line HepG2 with 5-aminoimidazole-4-carboxamide-1-β-D-ribofuranoside (AICAR), which is converted to 5-aminoimidazole-4-carboxamide-1-β-D-ribofuranosyl 5'-monophosphate, an activator of AMPK, caused an average 2.5- or 7-fold increase, respectively, of CYP4F2 mRNA expression but not of CYP4A11 or CYP4F3, CYP4F11, and CYP4F12 mRNA. Activation of CYP4F2 expression by AICAR was significantly reduced in HepG2 cells by an AMPK inhibitor, 6-[4-(2-piperidin-1-yl-ethoxy)-phenyl)]-3-pyridin-4-yl-pyrrazolo[1,5-a]-pyrimidine (compound C) or by transfection with small interfering RNAs for AMPKα isoforms α1 and α2. A 2.5-fold increase in CYP4F2 mRNA expression was observed upon treatment of HepG2 cells with 6,7-dihydro-4-hydroxy-3-(2'-hydroxy[1,1'-biphenyl]-4-yl)-6-oxo-thieno[2,3-b]pyridine-5-carbonitrile (A-769662), a direct activator for AMPK. In addition, the indirect activators of AMPK, genistein and resveratrol increased CYP4F2 mRNA expression in HepG2 cells. Pretreatment with compound C or 1,2-dihydro-3H-naphtho[2,1-b]pyran-3-one (splitomicin), an inhibitor of the NAD(+) activated deacetylase SIRT1, only partially blocked activation of CYP4F2 expression by resveratrol, suggesting that a SIRT1/AMPK-independent pathway also contributes to increased CYP4F2 expression. Compound C greatly diminished genistein activation of CYP4F2 expression. 7H-benz[de]benzimidazo[2,1-a]isoquinoline-7-one-3-carboxylic acid acetate (STO-609), a calmodulin kinase kinase (CaMKK) inhibitor, reduced the level of expression of CYP4F2 elicited by genistein, suggesting that CaMKK activation contributed to AMPK activation by genistein. Transient transfection studies in HepG2 cells with reporter constructs containing the CYP4F2 proximal promoter demonstrated that AICAR, genistein, and resveratrol stimulated transcription of the reporter gene. These results suggest that activation of AMPK by cellular stress and endocrine or pharmacologic stimulation is likely to activate CYP4F2 gene expression.

Influence of CYP4F2 rs2108622 (V433M) on warfarin dose requirement in Asian patients

Warfarin exhibits wide interpatient variability in dosing requirements. Recent studies have shown a novel polymorphism (rs2108622, V433M) in the CYP4F2 gene to be associated with variability in warfarin requirements in Caucasians. The purpose of this study was to evaluate the impact of rs2108622 on warfarin dose requirements in the Asian population. The mean warfarin dose was found to be significantly lower in patients carrying homozygous wild-type allele CC when compared with patients carrying variant alleles CT and TT (CC vs CT+TT: 3.0 mg/day vs 3.75 mg/day, p = 0.033). In patients harboring VKORC1 diplotypes associated with low warfarin requirements, a linear regression model which included age, weight, CYP2C9 and CYP4F2 variants accounted for 38% of the variability in warfarin dose. Approximately 11% of the dose variation was explained by CYP4F2 rs2108622 (p = 0.004). The influence of rs2108622 in patients harboring VKORC1 diplotypes associated with high warfarin requirements was not significant. This study suggests that CYP4F2 rs2108622 may significantly affect warfarin dose requirements in carriers of VKORC1 low-dose-associated diplotypes.

CYP4F enzymes are responsible for the elimination of fingolimod (FTY720), a novel treatment of relapsing multiple sclerosis

Fingolimod (FTY720, Gilenya, 2-amino-2-[2-(4-octylphenyl)ethyl]-1,3-propanediol) is a novel drug recently approved in the United States for the oral treatment of relapsing multiple sclerosis. The compound is eliminated predominantly by ω-hydroxylation, followed by further oxidation. The ω-hydroxylation was the major metabolic pathway in human liver microsomes (HLM). The enzyme kinetics in HLM were characterized by a Michaelis-Menten affinity constant (K(m)) of 183 μM and a maximum velocity (V(max)) of 1847 pmol/(min · mg). Rates of fingolimod metabolism by a panel of HLM from individual donors showed no correlation with marker activities of any of the major drug-metabolizing cytochrome P450 (P450) enzymes or of flavin-containing monooxygenase (FMO). Among 21 recombinant human P450 enzymes and FMO3, only CYP4F2 (and to some extent CYP4F3B) produced metabolite profiles similar to those in HLM. Ketoconazole, known to inhibit not only CYP3A but also CYP4F2, was an inhibitor of fingolimod metabolism in HLM with an inhibition constant (K(i)) of 0.74 μM (and by recombinant CYP4F2 with an IC(50) of 1.6 μM), whereas there was only a slight inhibition found with azamulin and none with troleandomycin. An antibody against CYP4F2 was able to inhibit the metabolism of fingolimod almost completely in HLM, whereas antibodies specific to CYP2D6, CYP2E1, and CYP3A4 did not show significant inhibition. Combining the results of these four enzyme phenotyping approaches, we demonstrated that CYP4F2 and possibly other enzymes of the CYP4F subfamily (e.g., CYP4F3B) are the major enzymes responsible for the ω-hydroxylation of fingolimod, the main elimination pathway of the drug in vivo.

Common variants of cytochrome P450 4F2 exhibit altered vitamin E-{omega}-hydroxylase specific activity

Human cytochrome P450 4F2 (CYP4F2) catalyzes the ω-hydroxylation of the side chain of tocopherols (TOH) and tocotrienols (T3), the first step in their catabolism to polar metabolites excreted in urine. CYP4F2, in conjunction with α-TOH transfer protein, results in the conserved phenotype of selective retention of α-TOH. The purpose of this work was to determine the functional consequences of 2 common genetic variants in the human CYP4F2 gene on vitamin E-ω-hydroxylase specific activity using the 6 major dietary TOH and T3 as substrate. CYP4F2-mediated ω-hydroxylase specific activity was measured in microsomal preparations from insect cells that express wild-type or polymorphic variants of the human CYP4F2 protein. The W12G variant exhibited a greater enzyme specific activity (pmol product · min(-1) · pmol CYP4F2(-1)) compared with wild-type enzyme for both TOH and T3, 230-275% of wild-type toward α, γ, and δ-TOH and 350% of wild-type toward α, γ, and δ-T3. In contrast, the V433M variant had lower enzyme specific activity toward TOH (42-66% of wild type) but was without a significant effect on the metabolism of T3. Because CYP4F2 is the only enzyme currently shown to metabolize vitamin E in humans, the observed substrate-dependent alterations in enzyme activity associated with these genetic variants may result in alterations in vitamin E status in individuals carrying these mutations and constitute a source of variability in vitamin E status.

CYP4F2 gene V433M polymorphism is associated with ischemic stroke in the male Northern Chinese Han population

BACKGROUND

CYP4F2 is a member of the cytochrome P450 enzymes and is responsible for metabolizing arachidonic acid to 20-hydroxyeicosatetraenoic acid (20-HETE); 20-HETE plays a role in the regulation of vascular tone in the cerebral, coronary, and renal circulation. The present study aimed to evaluate whether or not the CYP4F2 gene polymorphism V433M (rs2108622) is involved in ischemic stroke in the Northern Chinese Han population.

METHODS

In a case-control study, the participants included 302 (193 males and 109 females) patients with ischemic stroke and 350 (212 males and 138 females) healthy subjects. The V433M polymorphism of the CYP4F2 gene was analyzed by polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP) with the restriction enzyme PvuII.

RESULTS

The frequencies of the GG genotype and the G allele were higher in participants with ischemic stroke than in the control group (P=0.018). Multiple logistic regression analysis revealed the significance of the rs2108622 in males after adjustment for confounding factors. No difference was found in all participants and females.

CONCLUSION

The GG genotype and G allele were associated with ischemic stroke in the male Northern Chinese Han population.

Association of common variants of CYP4A11 and CYP4F2 with stroke in the Han Chinese population

OBJECTIVE

20-Hydroxyeicosatetraenoic acid has been shown to play an important role in cerebral vascular function. We hypothesized that polymorphisms in genes encoding 20-Hydroxyeicosatetraenoic acid synthesizing enzymes might confer susceptibility to stroke.

METHODS AND RESULTS

To test the hypothesis, haplotype tagging single nucleotide polymorphisms and potential functional polymorphisms of CYP4A11 and CYP4F2 genes were genotyped in 558 ischemic stroke patients, 221 hemorrhagic stroke patients and 557 controls. The association analyses were performed at both single nucleotide polymorphism and haplotype levels. We further verified our findings in an independent cohort of 551 ischemic stroke cases and 48 hemorrhagic stroke cases and 694 unaffected controls. We identified CYP4A11 C-296T and CYP4F2 V433M were associated with significantly increased risk of ischemic stroke (CT+TT vs. CC, adjusted odds ratio: 1.50, 95% confidence interval: 1.17-1.93, Pcombined=0.001, Pcorr=0.008; V/M+M/M vs. V/V, odds ratio: 1.38, 95% confidence interval: 1.15-1.65, Pcombined=5.6x10, Pcorr=0.005, respectively). Interestingly, the effects of CYP4F2 V433M on ischemic stroke in our study was only evident in male individuals.

CONCLUSION

Our results suggest that genetic variation in CYP4A11 and CYP4F2 alters susceptibility to stroke in the Han Chinese population.

Effect of cytochrome P450 polymorphism on arachidonic acid metabolism and their impact on cardiovascular diseases

Cardiovascular diseases (CVDs) remain the leading cause of death in the developed countries. Taking into account the mounting evidence about the role of cytochrome P450 (CYP) enzymes in cardiovascular physiology, CYP polymorphisms can be considered one of the major determinants of individual susceptibility to CVDs. One of the important physiological roles of CYP enzymes is the metabolism of arachidonic acid. CYP epoxygenases such as CYP1A2, CYP2C, and CYP2J2 metabolize arachidonic acid to epoxyeicosatrienoic acids (EETs) which generally possess vasodilating, anti-inflammatory, anti-apoptotic, anti-thrombotic, natriuretic, and cardioprotective effects. Therefore, genetic polymorphisms causing lower activity of these enzymes are generally associated with an increased risk of several CVDs such as hypertension and coronary artery disease. EETs are further metabolized by soluble epoxide hydrolase (sEH) to the less biologically active dihydroxyeicosatrienoic acids (DHETs). Therefore, sEH polymorphism has also been shown to affect arachidonic acid metabolism and to be associated with CVDs. On the other hand, CYP omega-hydroxylases such as CYP4A11 and CYP4F2 metabolize arachidonic acid to 20-hydroxyeicosatetraenoic acid (20-HETE) which has both vasoconstricting and natriuretic effects. Genetic polymorphisms causing lower activity of these enzymes are generally associated with higher risk of hypertension. Nevertheless, some studies have denied the association between polymorphisms in the arachidonic acid pathway and CVDs. Therefore, more research is needed to confirm this association and to better understand the pathophysiologic mechanisms behind it.

Effects of CYP4F2 genetic polymorphisms and haplotypes on clinical outcomes in patients initiated on warfarin therapy

BACKGROUND

A variant in the CYP4F2 gene, rs2108622, has been recently shown to determine stable warfarin dose requirements. CYP4F2 has also been shown recently to metabolize vitamin K.

METHODS

Three hundred and eleven patients were recruited prospectively from two UK hospitals and followed-up for 6 months. Fine mapping of the whole CYP4F2 region was performed to try and define the haplotype structure of CYP4F2. Genotyping was performed on the Sequenom platform. Univariate and multiple regression analyses were undertaken to assess the effect of CYP4F2 on predefined clinical outcomes of warfarin response.

RESULTS

Fifty-nine single nucleotide polymorphisms in the CYP4F2 gene were analyzed. There was a high degree of linkage disequilibrium in the gene with two haplotype blocks. No association was found with warfarin stable dose and rs2108622 in our prospective cohort of patients even after adjustments to reduce patient heterogeneity. Interestingly, a single nucleotide polymorphism (rs2189784), which is in strong linkage disequilibrium with rs2108622, showed an association with time-to-therapeutic international normalized ratio which remained significant after the correction for multiple testing (Pc = 0.03). No association was shown with the haplotypes after false discovery rate correction.

CONCLUSION

Although we were unable to demonstrate an association between rs2108622 and stable warfarin dose, our finding of an association between rs2189784 and time-to-therapeutic international normalized ratio is consistent with the recent finding that CYP4F2 plays a role in vitamin K metabolism. However, the effect of CYP4F2 is relatively small in all studies undertaken so far, and thus seems unlikely to be of clinical relevance.

CYP4F2 is a vitamin K1 oxidase: An explanation for altered warfarin dose in carriers of the V433M variant

Genetic polymorphisms in VKORC1 and CYP2C9, genes controlling vitamin K(1) (VK1) epoxide reduction and (S)-warfarin metabolism, respectively, are major contributors to interindividual variability in warfarin dose. The V433M polymorphism (rs2108622) in CYP4F2 has also been associated with warfarin dose and speculatively linked to altered VK1 metabolism. Therefore, the purpose of the present study was to determine the role of CYP4F2 and the V433M polymorphism in the metabolism of VK1 by human liver. In vitro metabolic experiments with accompanying liquid chromatography-tandem mass spectrometry analysis demonstrated that recombinant CYP4F2 (Supersomes) and human liver microsomes supplemented with NADPH converted VK1 to a single product. A screen of all commercially available P450 Supersomes showed that only CYP4F2 was capable of metabolizing VK1 to this product. Steady-state kinetic analysis with recombinant CYP4F2 and with human liver microsomes revealed a substrate K(m) of 8 to 10 microM. Moreover, anti-CYP4F2 IgG, as well as several CYP4F2-selective chemical inhibitors, substantially attenuated the microsomal reaction. Finally, human liver microsomes genotyped for rs2108622 demonstrated reduced vitamin K(1) oxidation and lower CYP4F2 protein concentrations in carriers of the 433M minor allele. These data demonstrate that CYP4F2 is a vitamin K(1) oxidase and that carriers of the CYP4F2 V433M allele have a reduced capacity to metabolize VK1, secondary to an rs2108622-dependent decrease in steady-state hepatic concentrations of the enzyme. Therefore, patients with the rs2108622 polymorphism are likely to have elevated hepatic levels of VK1, necessitating a higher warfarin dose to elicit the same anticoagulant response.

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

This study assessed associations between the CYP4F2 gene and myocardial infarction (MI), using a haplotype-based case-control study of 234 MI patients and 248 controls genotyped for 5 single-nucleotide polymorphisms (rs3093105, rs3093135, rs1558139, rs2108622, rs3093200). For men, G allele frequency of rs2108622 and frequency of the T-C-G haplotype were significantly higher, and frequency of the T-C-A haplotype was significantly lower for MI patients than for controls (P=0.006, P=0.001 and P=0.002, respectively).

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.