Association of a functional polymorphism in the CYP4A11 gene with systolic blood pressure in survivors of myocardial infarction

The role of cytochrome P450 gene rs1126742 polymorphism and risk of hypertension: a systematic review and meta-analysis

BACKGROUND

CYP4A11 gene T8590C (rs1126742) is proved to be an important locus that is relevant to hypertension. Various research on the relationship between rs1126742 polymorphism and hypertension have been published, but due to small sample sizes and limitations of the research objects, the combined results remain controversial.

METHODS

We searched PubMed, Embase, OVID, Web of Science, Wan Fang, and CNKI databases for related articles. Three authors individually extracted data and the quality of studies was evaluated by using the 9-point Newcastle-Ottawa Scale (NOS) independently. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated in different genetic models by using a random-effect model or fixed-effect model according to inter-study heterogeneity. Besides, subgroup analysis and sensitivity analysis were performed and the publication bias was assessed.

RESULTS

There were totally 12 independent case-control studies of 8673 cases and 6611 controls included. Significant associations were found between CYP4A11 gene T8590C polymorphism and hypertension under all genetic models (allele, homozygote, heterozygote, recessive, and dominant model). We also found that there was no obvious relationship between the rs1126742 polymorphism and hypertension in Asian. But positive association has been found in Caucasian in allele, homozygote, and recessive model.

CONCLUSIONS

CYP4A11 gene T8590C (rs1126742) polymorphism increases the occurrence of hypertension, particularly in Caucasian.

Molecular Functionality of Cytochrome P450 4 (CYP4) Genetic Polymorphisms and Their Clinical Implications

Enzymes in the cytochrome P450 4 (CYP4) family are involved in the metabolism of fatty acids, xenobiotics, therapeutic drugs, and signaling molecules, including eicosanoids, leukotrienes, and prostanoids. As CYP4 enzymes play a role in the maintenance of fatty acids and fatty-acid-derived bioactive molecules within a normal range, they have been implicated in various biological functions, including inflammation, skin barrier, eye function, cardiovascular health, and cancer. Numerous studies have indicated that genetic variants of CYP4 genes cause inter-individual variations in metabolism and disease susceptibility. Genetic variants of CYP4A11, 4F2 genes are associated with cardiovascular diseases. Mutations of CYP4B1, CYP4Z1, and other CYP4 genes that generate 20-HETE are a potential risk for cancer. CYP4V2 gene variants are associated with ocular disease, while those of CYP4F22 are linked to skin disease and CYP4F3B is associated with the inflammatory response. The present study comprehensively collected research to provide an updated view of the molecular functionality of CYP4 genes and their associations with human diseases. Functional analysis of CYP4 genes with clinical implications is necessary to understand inter-individual variations in disease susceptibility and for the development of alternative treatment strategies.

Subterminal hydroxyeicosatetraenoic acids: Crucial lipid mediators in normal physiology and disease states

Cytochrome P450 (P450) enzymes are superfamily of monooxygenases that hold the utmost diversity of substrate structures and catalytic reaction forms amongst all other enzymes. P450 enzymes metabolize arachidonic acid (AA) to a wide array of biologically active lipid mediators. P450-mediated AA metabolites have a significant role in normal physiological and pathophysiological conditions, hence they could be promising therapeutic targets in different disease states. P450 monooxygenases mediate the (ω-n)-hydroxylation reactions, which involve the introduction of a hydroxyl group to the carbon skeleton of AA, forming subterminal hydroxyeicosatetraenoic acids (HETEs). In the current review, we specified different P450 isozymes implicated in the formation of subterminal HETEs in varied tissues. In addition, we focused on the role of subterminal HETEs namely 19-HETE, 16-HETE, 17-HETE and 18-HETE in different organs, importantly the kidneys, heart, liver and brain. Furthermore, we highlighted their role in hypertension, acute coronary syndrome, diabetic retinopathy, non-alcoholic fatty liver disease, ischemic stroke as well as inflammatory diseases. Since each member of subterminal HETEs exist as R and S enantiomer, we addressed the issue of stereoselectivity related to the formation and differential effects of these enantiomers. In conclusion, elucidation of different roles of subterminal HETEs in normal and disease states leads to identification of novel therapeutic targets and development of new therapeutic modalities in different disease states.

Genetic role of CYP4A11 polymorphisms in the risk of developing cardiovascular and cerebrovascular diseases

BACKGROUND

We are interested in comprehensively evaluating the potential genetic influence of rs9332978 A/G, rs1126742 T/C, and rs9333025 G/A polymorphisms of CYP4A11 (cytochrome P450 family 4, subfamily A, member 11) in the risk of developing cardiovascular and cerebrovascular diseases.

METHODS

A meta-analysis was carried out using articles obtained from online databases and Stata/SE 12.0 software. We primarily used a P value of association test (P_association ) and odds ratios (OR) to assess the genetic relationships.

RESULTS

We included 22 eligible case-control articles for our meta-analysis. For the overall meta-analysis of the rs9332978 A/G polymorphism, there was an increased risk of cardiovascular and cerebrovascular diseases in cases under the models of allele G vs. A (P_association  = 0.001, OR = 1.16), AG vs. AA (P_association  < 0.001, OR = 1.22), and AG+GG vs. AA (P_association  < 0.001, OR = 1.22) compared with the controls. There were similar results in the subgroup analysis of "hypertension" (P_association  = 0.024 for the allele model; P_association  = 0.003 for the heterozygote model; and P_association  = 0.005 for the dominant model). For rs1126742, there was a significant difference between cases and controls in the overall meta-analysis and subgroup of "Caucasian," "hypertension," and "population-based (PB)" under all of the genetic models (all P_association  < 0.05, OR > 1). Furthermore, a decreased risk was detected in the overall and "PB" subgroup meta-analysis of rs9333025 under the models of A vs. G, AA vs. GG, and AA vs. GG+GA (all P_association  < 0.05, OR < 1).

CONCLUSION

The rs1126742 T/C polymorphism of CYP4A11 is more likely to be a genetic risk factor for the hypertension cases in the Caucasian population. Moreover, whereas the AG genotype of CYP4A11 rs9332978 may be associated with an increased risk of hypertension, the AA genotype of rs9333025 may be linked to a decreased risk of cardiovascular and cerebrovascular diseases.

20-HETE in the regulation of vascular and cardiac function

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

A Novel Polymorphism in the Promoter of the CYP4A11 Gene Is Associated with Susceptibility to Coronary Artery Disease

Enzymes CYP4A11 and CYP4F2 are involved in biosynthesis of vasoactive 20-hydroxyeicosatetraenoic acid and may contribute to pathogenesis of coronary artery disease (CAD). We investigated whether polymorphisms of the CYP4A11 and CYP4F2 genes are associated with the risk of CAD in Russian population. DNA samples from 1323 unrelated subjects (637 angiographically confirmed CAD patients and 686 age- and sex-matched healthy individuals) were genotyped for polymorphisms rs3890011, rs9332978, and rs9333029 of CYP4A11 and rs3093098 and rs1558139 of CYP4F2 by using the Mass-ARRAY 4 system. SNPs rs3890011 and rs9332978 of CYP4A11 were associated with increased risk of CAD in women: OR = 1.26, 95% CI: 1.02-1.57, P = 0.004, and Q = 0.01 and OR = 1.45, 95% CI: 1.13-1.87, P = 0.004, and Q = 0.01, respectively. Haplotype G-C-A of CYP4A11 was associated with increased risk of CAD (adjusted OR = 1.41, 95% CI: 1.12-1.78, and P = 0.0036). Epistatic interactions were found between rs9332978 of CYP4A11 and rs1558139 of CYP4F2 (P_interaction = 0.025). In silico analysis allowed identifying that SNP rs9332978 is located at a binding site for multiple transcription factors; many of them are known to regulate the pathways involved in the pathogenesis of CAD. This is the first study in Europeans that reported association between polymorphism rs9332978 of CYP4A11 and susceptibility to coronary artery disease.

Effect of Cytochrome P450 Metabolites of Arachidonic Acid in Nephrology

Thirty-five years ago, a third pathway for the metabolism of arachidonic acid by cytochrome P450 enzymes emerged. Subsequent work revealed that 20-hydroxyeicosatetraenoic and epoxyeicosatrienoic acids formed by these pathways have essential roles in the regulation of renal tubular and vascular function. Sequence variants in the genes that produce 20-hydroxyeicosatetraenoic acid are associated with hypertension in humans, whereas the evidence supporting a role for variants in the genes that alter levels of epoxyeicosatrienoic acids is less convincing. Studies in animal models suggest that changes in the production of cytochrome P450 eicosanoids alter BP. However, the mechanisms involved remain controversial, especially for 20-hydroxyeicosatetraenoic acid, which has both vasoconstrictive and natriuretic actions. Epoxyeicosatrienoic acids are vasodilators with anti-inflammatory properties that oppose the development of hypertension and CKD; 20-hydroxyeicosatetraenoic acid levels are elevated after renal ischemia and may protect against injury. Levels of this eicosanoid are also elevated in polycystic kidney disease and may contribute to cyst formation. Our review summarizes the emerging evidence that cytochrome P450 eicosanoids have a role in the pathogenesis of hypertension, polycystic kidney disease, AKI, and CKD.

Associations of CYP4A11 gene-gene and gene-smoking interactions with essential hypertension in the male eastern Chinese Han population

OBJECTIVES

The aim of this study was to investigate the impact of CYP4A11 single-nucleotide polymorphisms (SNP), additional gene-gene and gene-environment interactions on essential hypertension (EH) risk.

METHODS

A total of 1648 participants (788 males, 860 females), with a mean age of 56.1 ± 14.1 years old, were selected, including 820 EH patients and 828 normotension subjects. Logistic regression was performed to investigate association of SNPs within CYP4A11 gene with high DBP, high SBP and EH risk, and generalized multifactor dimensionality reduction (GMDR) was used to analyze the gene-gene interaction and gene-smoking interaction.

RESULTS

Logistic regression analysis showed that EH risk was significantly higher in carriers of C allele of the rs1126742 polymorphism than those with TT genotype (TC+CC versus TT, adjusted OR (95%CI) = 1.56 (1.24-1.91). In addition, we also found that EH risk was also significantly higher in carriers of G allele of the rs3890011polymorphism than those with CC genotype (CG+ GG versus CC, adjusted OR (95%CI) = 1.31 (1.15-2.03). GMDR analysis indicated a potential gene-gene interaction between rs1126742 and rs3890011 and a gene-environment interaction between rs1126742 and smoking. We found that subjects with TC or CC of rs1126742 and CG or GG of rs3890011genotype have the highest EH risk, OR (95%CI) was 2.52 (1.28-3.57). Smokers with TC or CC of rs1126742 genotype have the highest EH risk, OR (95%CI) was 2.20 (1.28-3.40).

CONCLUSIONS

Gene-gene interaction between rs1126742 and rs3890011 and gene-environment interaction between rs1126742 and smoking were associated with increased EH risk.

20-Hydroxyeicosatetraenoic Acid (HETE)-dependent Hypertension in Human Cytochrome P450 (CYP) 4A11 Transgenic Mice: NORMALIZATION OF BLOOD PRESSURE BY SODIUM RESTRICTION, HYDROCHLOROTHIAZIDE, OR BLOCKADE OF THE TYPE 1 ANGIOTENSIN II RECEPTOR

Male and female homozygous 129/Sv mice carrying four copies of the human cytochrome P450 4A11 gene (CYP4A11) under control of its native promoter (B-129/Sv-4A11(+/+)) develop hypertension (142 ± 8 versus 113 ± 7 mm Hg systolic blood pressure (BP)), and exhibit increased 20-hydroxyeicosatetraenoic acid (20-HETE) in kidney and urine. The hypertension is reversible by a low-sodium diet and by the CYP4A inhibitor HET0016. B-129/Sv-4A11(+/+) mice display an 18% increase of plasma potassium (p < 0.02), but plasma aldosterone, angiotensin II (ANGII), and renin activities are unchanged. This phenotype resembles human genetic disorders with elevated activity of the sodium chloride co-transporter (NCC) and, accordingly, NCC abundance is increased by 50% in transgenic mice, and NCC levels are normalized by HET0016. ANGII is known to increase NCC abundance, and renal mRNA levels of its precursor angiotensinogen are increased 2-fold in B-129/Sv-4A11(+/+), and blockade of the ANGII receptor type 1 with losartan normalizes BP. A pro-hypertensive role for 20-HETE was implicated by normalization of BP and reversal of renal angiotensin mRNA increases by administration of the 20-HETE antagonists 2-((6Z,15Z)-20-hydroxyicosa-6,15-dienamido)acetate or (S)-2-((6Z,15Z)-20-hydroxyicosa-6,15-dienamido)succinate. SGK1 expression is also increased in B-129/Sv-4A11(+/+) mice and paralleled increases seen for NCC. Losartan, HET0016, and 20-HETE antagonists each normalized SGK1 mRNA expression. These results point to a potential 20-HETE dependence of intrarenal angiotensinogen production and ANGII receptor type 1 activation that are associated with increases in NCC and SGK1 and identify elevated P450 4A11 activity and 20-HETE as potential risk factors for salt-sensitive human hypertension by perturbation of the renal renin-angiotensin axis.

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.

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.

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.

Cytochrome P450 and ischemic heart disease: current concepts and future directions

INTRODUCTION

The P450 enzymes (P450s) mediate the biotransformation of several drugs, steroid hormones, eicosanoids, cholesterol, vitamins, fatty acids and bile acids, many of which affect cardiovascular homeostasis. Experimental studies have demonstrated that several P450s modulate important steps in the pathogenesis of ischemic heart disease (IHD).

AREAS COVERED

This article discusses the current knowledge on i) the expression of P450s in cardiovascular and renal tissues; ii) the role of P450s in the pathophysiology of IHD, in particular the modulation of blood pressure and cardiac hypertrophy, coronary arterial tone, ischemia-reperfusion injury and the metabolism of cardiovascular drugs; iii) the available evidence from observational studies on the association between P450 gene polymorphisms and risk of myocardial infarction (MI); and iv) suggestions for further research in this area.

EXPERT OPINION

P450s exert important modulatory effects in experimental models of IHD and MI. However, observational studies have provided conflicting results on the association between P450 genetic polymorphisms and MI. Further, adequately powered studies are required to ascertain the biological and clinical impact of P450s on clinical IHD end-points, that is, fatal and nonfatal MI, revascularization and long-term outcomes post MI. Pharmacogenetic substudies of recently completed cardiovascular clinical trials might represent an alternative strategy in this context.

Association between the CYP4A11 T8590C variant and essential hypertension: new data from Han Chinese and a meta-analysis

Objective

CYP4A11 oxidizes endogenous arachidonic acid to 20-hydroxyeicosatetraenoic acid, a renal vasoconstrictor and natriuretic in humans. Previous studies demonstrated an association between a functional variant (T8590C) of CYP4A11 and essential hypertension, though with conflicting results. To elucidate this relationship, a case-control study and meta-analysis were performed to assess the possible association of essential hypertension with CYP4A11 genetic variations.

Methods

Associations between the T8590C polymorphism and essential hypertension were examined in 328 unrelated cases and 297 age-matched controls in Han Chinese individuals. High-resolution melting was used to identify the CYP4A11 variant. To further investigate the association, we conducted a meta-analysis including eight studies published previously in July 2012.

Results

The frequency of the CYP4A11 T8590C polymorphism showed no significant difference between cases and controls (all P>0.05). However, the meta-analysis showed that the CYP4A11 T8590C polymorphism may increase the risk of essential hypertension in an additive model (OR: 1.15, 95% CI: 1.02–1.29, P = 0.02), a dominant model (OR: 1.06, 95% CI: 1.01–1.32, P = 0.03), a recessive model (OR: 1.52, 95% CI: 1.15–2.02, P = 0.003) and a homozygote contrast (OR: 1.38, 95% CI: 1.07–1.78, P = 0.01). Also, a significant relationship was observed among Caucasians in the additive model, the homozygote contrast, the recessive model and the dominant model (all P<0.05). However, no association was observed in an Asian population (all P>0.05).

Conclusions

This meta-analysis suggests there is a significant association between the CYP4A11 T8590C variant and essential hypertension, especially in Caucasians. The case-control study did not find a significant association among the Han Chinese population, but the controls were poorly matched and meaningful conclusions cannot therefore be made. Further large-scale studies are needed to clarify whether the CYP4A11 T8590C polymorphism is associated with hypertension risk in Asians or has a gender-specific effect.

Genetic associations with hypertension: meta-analyses of six candidate genetic variants

AIMS

The aim of this study was to perform combined analyses of six genetic variants for the risk of hypertension.

METHODS

After a comprehensive literature search for genetic variants involved with the association study of hypertension, we harvested a total of five genes (six variants) for the current meta-analyses. These genes consisted of CYP4A11 (T8590C), RGS2 (1891-1892del TC and G638A), HTR2A (T102C), GNAS (T393C), and HSD3B1 (T→C Leu338).

RESULTS

A total of 20 studies among 13,816 cases and 19,248 controls were retrieved for the meta-analyses of six genetic variants. It was shown that the RGS2 1891-1892del TC (OR=1.10, 95% CI=1.02-1.19, p=0.02) polymorphism and the CYP4A11 T8590C (OR=1.19, 95% CI=1.00-1.41, p=0.05) polymorphism were significantly associated with increased risk of hypertension. No association was found between the other four variants and the risk of hypertension.

CONCLUSION

This meta-analysis revealed that the RGS2 1891-1892del TC polymorphism and CYP4A11 T8590C polymorphism were associated with hypertension risk. However, HSD3B1 T→C Leu338, HTR2A T102C, GNAS T393C, and RGS2 G638A polymorphisms were not associated with hypertension risk.

Role of 20-HETE in the antihypertensive effect of transfer of chromosome 5 from Brown Norway to Dahl salt-sensitive rats

This study examined whether substitution of chromosome 5 containing the CYP4A genes from Brown Norway rat onto the Dahl S salt-sensitive (SS) genetic background upregulates the renal production of 20-HETE and attenuates the development of hypertension. The expression of CYP4A protein and the production of 20-HETE were significantly higher in the renal cortex and outer medulla of SS.5(BN) (chromosome 5-substituted Brown Norway rat) consomic rats fed either a low-salt (LS) or high-salt (HS) diet than that seen in SS rats. The increase in the renal production of 20-HETE in SS.5(BN) rats was associated with elevated expression of CYP4A2 mRNA. MAP measured by telemetry rose from 117 ± 1 to 183 ± 5 mmHg in SS rats fed a HS diet for 21 days, but only increased to 151 ± 5 mmHg in SS.5(BN) rats. The pressure-natriuretic and diuretic responses were twofold higher in SS.5(BN) rats compared with SS rats. Protein excretion rose to 354 ± 17 mg/day in SS rats fed a HS diet for 21 days compared with 205 ± 13 mg/day in the SS.5(BN) rats, and the degree of glomerular injury was reduced. Baseline glomerular capillary pressure (Pgc) was similar in SS.5(BN) rats (43 ± 1 mmHg) and Dahl S (44 ± 2 mmHg) rats. However, Pgc increased to 59 ± 3 mmHg in SS rats fed a HS diet for 7 days, while it remained unaltered in SS.5(BN) rats (43 ± 2 mmHg). Chronic administration of an inhibitor of the synthesis of 20-HETE (HET0016, 10 mg·kg(-1)·day(-1) iv) reversed the antihypertensive phenotype seen in the SS.5(BN) rats. These findings indicate that the transfer of chromosome 5 from the BN rat onto the SS genetic background increases the renal expression of CYP4A protein and the production of 20-HETE and that 20-HETE contributes to the antihypertensive and renoprotective effects seen in the SS.5(BN) consomic strain.

A novel polymorphism of the CYP4A11 gene is associated with coronary artery disease

BACKGROUND

CYP4A11 (cytochrome P450, family 4, subfamily A, polypeptide 11) converts arachidonic acid to 20-hydroxyeicosatetraenoic acid (20-HETE), which plays a crucial role in the modulation of cardiovascular homeostasis. The aim of the present study was to assess the association between the human CYP4A11 gene and coronary artery disease (CAD).

METHODS

A total of 361 patients with CAD and 315 controls were genotyped for 4 single-nucleotide polymorphisms (SNPs) of the human CYP4A11 gene (rs9332978, rs4660980, rs3890011, and rs1126742). The data were assessed for 3 groups: total participants, men, and women via case-control studies.

RESULTS

For total participants and men, the distribution of SNP3 (rs3890011) genotypes showed a significant difference between CAD and control participants (P = .030 and P = .013, respectively), the distribution of the recessive model of SNP3 (GG vs CC + GC) was significantly higher in CAD patients than in control participants (P = .011 and P = .014, respectively), the significant difference was retained after adjustment for covariates (for total participants, 95% confidence interval [CI]: 1.137-2.423, P = .009; and for males, 95% CI: 1.173-3.013, P = .009).

CONCLUSIONS

rs3890011 maybe a novel polymorphism of the CYP4A11 gene associated with CAD in a Han Chinese population.

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.

Arachidonic acid ω-hydroxylase CYP4A11: inter-ethnic variations in the 8590T>C loss-of-function variant

The human Cytochrome P450 4A11 (CYP4A11) is a major ω-hydroxylase involved in the regulation of blood pressure in the kidney through the conversion of arachidonic acid into 20-hydroxyeicosatetraenoic acid (20-HETE). Previous studies have reported a significant association between the 8590T>C genetic variant of CYP4A11 and hypertension. Interestingly, several population-based studies have reported ethnic differences in the prevalence of hypertension, with the highest prevalence in African populations. The aim of this work was to determine the frequency and inter-ethnic comparison of the CYP4A11 (8590T>C) functional polymorphism, in five new ethnic groups: European (99 French Caucasians), African (36 Gabonese and 50 Senegalese), South American (60 Peruvians) and North African (53 Tunisians) populations, using polymerase chain reaction-single strand conformational polymorphism and sequencing strategies. We confirmed that the CYP4A11 (8590T>C) functional polymorphism exhibits inter-ethnic frequency differences. Noteworthy, the highest 8590C allele frequency was observed in the Tunisian (30.2%), followed by Senegalese (20%) populations. In addition, the CC genotype was only found in the Gabonese and Tunisian populations (5.6% and 8.4%, respectively). These populations may be of major interest to help to clarify the linkage between hypertension and CYP4A11 (8590T>C) genotype in African populations. These findings provide data for further studies that investigate the potential association of CYP4A11 (8590T>C) variant with an incidence of hypertension genesis in respect of ethnicity.

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.

Oxidation of the endogenous cannabinoid arachidonoyl ethanolamide by the cytochrome P450 monooxygenases: physiological and pharmacological implications

Arachidonoyl ethanolamide (anandamide) is an endogenous amide of arachidonic acid and an important signaling mediator of the endocannabinoid system. Given its numerous roles in maintaining normal physiological function and modulating pathophysiological responses throughout the body, the endocannabinoid system is an important pharmacological target amenable to manipulation directly by cannabinoid receptor ligands or indirectly by drugs that alter endocannabinoid synthesis and inactivation. The latter approach has the possible advantage of more selectivity, thus there is the potential for fewer untoward effects like those that are traditionally associated with cannabinoid receptor ligands. In that regard, inhibitors of the principal inactivating enzyme for anandamide, fatty acid amide hydrolase (FAAH), are currently in development for the treatment of pain and inflammation. However, several pathways involved in anandamide synthesis, metabolism, and inactivation all need to be taken into account when evaluating the effects of FAAH inhibitors and similar agents in preclinical models and assessing their clinical potential. Anandamide undergoes oxidation by several human cytochrome P450 (P450) enzymes, including CYP3A4, CYP4F2, CYP4X1, and the highly polymorphic CYP2D6, forming numerous structurally diverse lipids, which are likely to have important physiological roles, as evidenced by the demonstration that a P450-derived epoxide of anandamide is a potent agonist for the cannabinoid receptor 2. The focus of this review is to emphasize the need for a better understanding of the P450-mediated pathways of the metabolism of anandamide, because these are likely to be important in mediating endocannabinoid signaling as well as the pharmacological responses to endocannabinoid-targeting drugs.

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.

A Polymorphism Regulates CYP4A11 Transcriptional Activity and Is Associated With Hypertension in a Japanese Population

CYP4A11 oxidizes arachidonic acid to 20-hydroxyeicosatetraenoic acid, a metabolite with renovascular and tubular function in humans. A previous study demonstrated a significant association between the CYP4A11 gene polymorphism and hypertension; however, the precise mechanism of the association has not been clarified. To assess the involvement of CYP4A11 in the pathogenesis of hypertension, we sought to identify a functional polymorphism of CYP4A11 and examined its impact on predisposition to hypertension in the Tanno-Sobetsu Study. The −845A/G polymorphism was identified in the promoter region of CYP4A11 by direct sequencing. Luciferase expression driven by the promoter of CYP4A11 containing the wild-type −845GG genotype was 30% lower than expression with the variant −845AA genotype. Gel mobility shift assays with nuclear protein extracts showed specific binding to probes containing the variant −845GG. To assess the effect of CYP4A11 polymorphisms on hypertension, we also carried out a case-control study using 4 single nucleotide polymorphisms (−845A/G, −366C/T, 7119C/T, and 8590T/C) in the Tanno-Sobetsu Study. The odds ratio for hypertension in participants with the AG+GG genotype of −845A/G was 1.42 ( P =0.008), and the odds ratio for hypertension of the TT genotype of 7119C/T was 1.37 ( P =0.037) after adjusting for confounding factors. The haplotype-based case-control analysis using 4 single nucleotide polymorphisms revealed a significant haplotype (G-C-T-T) that was significantly associated with hypertension, with an odds ratio of 1.44 ( P =0.006) after adjusting for confounding factors. We have identified a functional variant (−845A/G) of CYP4A11 that is significantly associated with hypertension and that appears to be a novel candidate for a predisposing factor for hypertension.

Intravenous formulation of N-hydroxy-N'-(4-n-butyl-2-methylphenyl)formamidine (HET0016) for inhibition of rat brain 20-hydroxyeicosatetraenoic acid formation

N-hydroxy-N'-(4-n-butyl-2-methylphenyl)formamidine (HET0016) is a potent inhibitor of 20-hydroxyeicosatetraenoic acid (20-HETE) formation by specific cytochrome P450 isoforms. Previous studies have demonstrated that administration of HET0016 inhibits brain formation of 20-HETE and reduces brain damage in a rat model of thromboembolic stroke. Delineation of the dose, concentration, and neuroprotective effect relationship of HET0016 has been hampered by the relative insolubility of HET0016 in aqueous solutions and the lack of information concerning the mechanism and duration of HET0016 inhibition of brain 20-HETE formation. Therefore, it was the purpose of this study to develop a water-soluble formulation of HET0016 suitable for intravenous (i.v.) administration and to determine the time course and mechanism of brain 20-HETE inhibition after in vivo dosing. In this study we report that HET0016 is a noncompetitive inhibitor of rat brain 20-HETE formation, which demonstrates a tissue concentration range for brain inhibition. In addition, we demonstrate that complexation of HET0016 with hydroxypropyl-beta-cyclodextrin results in increased aqueous solubility of HET0016 from 34.2 +/- 31.2 to 452.7 +/- 63.3 microg/ml. Administration of the complex as a single HET0016 i.v. dose (1 mg/kg) rapidly reduced rat brain 20-HETE concentrations from 289 to 91 pmol/g. Collectively, these data demonstrate that the i.v. formulation of HET0016 rapidly penetrates the rat brain and significantly inhibits 20-HETE tissue concentrations. These results will enable future studies to determine biopharmaceutics of HET0016 for inhibition of 20-HETE after cerebral ischemia.

Transfer of the CYP4A region of chromosome 5 from Lewis to Dahl S rats attenuates renal injury

This study examined the effect of transfer of overlapping regions of chromosome 5 that includes (4A(+)) or excludes (4A(-)) the cytochrome P-450 4A (CYP4A) genes from the Lewis rat on the renal production of 20-hydroxyeicosatetraenoic acid (20-HETE) and the development of hypertension-induced renal disease in congenic strains of Dahl salt-sensitive (Dahl S) rats. The production of 20-HETE was higher in the outer medulla of 4A(+) than in Dahl S or 4A(-) rats. Mean arterial pressure (MAP) rose to 190 +/- 7 and 185 +/- 3 mmHg in Dahl S and 4A(-) rats fed a high-salt (HS) diet for 21 days but only to 150 +/- 5 mmHg in the 4A(+) strain. Protein excretion increased to 423 +/- 40 and 481 +/- 37 mg/day in Dahl S and 4A(-) rats vs. 125 +/- 15 mg/day in the 4A(+) strain. Baseline glomerular capillary pressure (Pgc) was lower in 4A(+) rats (38 +/- 1 mmHg) than in Dahl S rats (42 +/- 1 mmHg). Pgc increased to 50 +/- 1 mmHg in Dahl S rats fed a HS diet, whereas it remained unaltered in 4A(+) rats (39 +/- 1 mmHg). Baseline glomerular permeability to albumin (P(alb)) was lower in 4A(+) rats (0.19 +/- 0.05) than in Dahl S or 4A(-) rats (0.39 +/- 0.02). P(alb) rose to approximately 0.61 +/- 0.03 in 4A(-) and Dahl S rats fed a HS diet for 7 days, but it remained unaltered in the 4A(+) rats. The expression of transforming growth factor-beta2 was higher in glomeruli of Dahl S rats than in 4A(+) rats fed either a low-salt (LS) or HS diet. Chronic administration of a 20-HETE synthesis inhibitor (HET0016; 10 mg.kg(-1).day(-1) sc) reversed the fall in MAP and renoprotection seen in 4A(+) rats. These results indicate that the introgression of the CYP4A genes from Lewis rats into the Dahl S rats increases the renal formation of 20-HETE and attenuates the development of hypertension and renal disease.

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.

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 haplotype of the CYP4A11 gene associated with essential hypertension in Japanese men

OBJECTIVE

CYP4A11, a member of the cytochrome P450 family, acts mainly as an enzyme that converts arachidonic acid to 20-hydroxyeicosatetraenoic acid, a metabolite involved in blood pressure regulation in humans. Disruption of the murine cyp4a14 and cyp4a10 genes, homologues of human CYP4A11, was reported recently to cause hypertension. The gene-disrupted male mice had higher blood pressure than the gene-disrupted female mice. The present study aimed to assess the association between the human CYP4A11 gene and essential hypertension, using a haplotype-based case-control study including separate analysis of the gender groups.

METHODS

The 304 essential hypertension patients and 207 age-matched control individuals were genotyped for three single-nucleotide polymorphisms of the human CYP4A11 gene (rs2269231, rs1126742, rs9333025). Data were assessed for three separate groups: total participants, men and women.

RESULTS

For total participants, the genotypic distribution of rs1126742 differed significantly between the two groups (P = 0.005). For total participants, men and women, the recessive model (CC versus TC + TT) of rs1126742 differed significantly between the two groups (P = 0.007, P = 0.043, and P = 0.045, respectively). Logistic regression analysis showed the TC + TT genotype was significantly higher in essential hypertension patients than in control individuals for total participants and men (P = 0.022 and P = 0.043, respectively). The A-T-G haplotype frequency (established by rs2269231, rs1126742, rs9333025) was significantly higher in essential hypertension men than in control men (P = 0.043).

CONCLUSIONS

Essential hypertension is associated with the TC + TT genotype of rs1126742 in the human CYP4A11 gene. The A-T-G haplotype appears a useful genetic marker of essential hypertension in Japanese men.

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.

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

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

Association between arterial pressure and coronary artery calcification

OBJECTIVES

Coronary artery calcification (CAC) determined by electron beam computed tomography is a predictor of future cardiovascular events. This study investigates conditions affecting CAC severity in patients with coronary artery disease (CAD) undergoing coronary angiography.

METHODS

Presence and degree of CAC were assessed angiographically in 877 CAD patients grouped into no visible CAC (n = 333), mild to moderate CAC (n = 321), and severe CAC (n = 223). Regression analyses investigated relationships between CAC and demographic data, cardiovascular risk factors, and coronary anatomy.

RESULTS

Prevalences of hypertension and systolic blood pressure (SBP) values were higher in individuals with CAC (moderate CAC: 49.5%, 137.5 +/- 18.6 mmHg; severe CAC: 58.3%, 142.1 +/- 20.4 mmHg) compared to individuals with CAD but no CAC (42.0%, 134.0 +/- 18.4 mmHg; both P < 0.001). Likewise, pulse pressure was significantly elevated with increasing degree of CAC (no CAC, 52.3 +/- 13.6 mmHg vs moderate CAC, 55.7 +/- 14.4 mmHg vs severe CAC, 59.1 +/- 15.4 mmHg; P < 0.001). Further determinants of CAC were age, positive family history for CAC and severity of CAD. No differences in CAC severity were found in relation to body mass index, low-density lipoprotein-cholesterol, diabetes, and smoking habits. In multivariate analysis, CAC was independently related to age, SBP or pulse pressure, respectively, positive family history for CAC, and the severity of CAD.

CONCLUSIONS

Of the cardiovascular risk factors, SBP and pulse pressure display the strongest relationship with angiographic detection of CAC. Mechanistic studies need to clarify whether hypertension causes CAC, or whether coronary calcium deposition serves as a marker for a higher degree of vascular calcification and, thus, impaired vascular compliance and higher blood pressure levels.

Functional polymorphism in human CYP4F2 decreases 20-HETE production

20-Hydroxyeicosatetraenoic acid (20-HETE) plays an important role in the regulation of renal tubular and vascular function and a deficiency in the renal formation of 20-HETE has been linked to the development of hypertension. The cytochrome P450 4F2 ( CYP4F2) gene encodes for the major CYP enzyme responsible for the synthesis of 20-HETE in the human kidney. We screened two human sampling panels (African and European Americans: n = 24 and 23 individuals, respectively) using PCR and DNA resequencing to identify informative SNPs in the coding region of the CYP4F2 gene. Two nonsynonymous SNPs that lead to amino acid changes at position 12 (W12G) and 433 (V433M), were identified. Both of these variants were found to be frequent in both African and European American sampling panels (9–21% minor allele frequency), and the W12G polymorphism exhibited extensive linkage disequilibrium with surrounding SNPs. To determine the functional significance of these mutations on the ability of the CYP4F2 enzyme to metabolize arachidonic acid and leukotriene B4(LTB4), recombinant baculoviruses containing four different human CYP4F2 variants (i.e., W12/V433, W12/M433, G12/V433, G12/M433) were generated and the proteins were expressed in Sf9 insect cells. The presence of the M433 allele, W12/M433, or G12/M433 decreased 20-HETE production to 56–66% of control. In contrast these variants had no effect on the ω-hydroxylation of LTB4. These findings are the first to identify a functional variant in the human CYP4F2 gene that alters the production of 20-HETE.

Elevations in Renal Interstitial Hydrostatic Pressure and 20-Hydroxyeicosatetraenoic Acid Contribute to Pressure Natriuresis

This study examined the role of changes in renal interstitial pressure on the renal levels of cytochrome P450 metabolites of arachidonic acid and compared the effects of inhibition of the formation of 20-hydroxyeicosatetraenoic acid (20-HETE) and epoxyeicosatrienoic acids with 1-aminobenzotriazole on the pressure-natriuretic response versus that seen after administration of HET0016, a more selective inhibitor of the formation of 20-HETE. Renal interstitial pressure rose by 3.4±0.3 mm Hg, and the levels of 20-HETE in renal cortical tissue doubled when renal perfusion pressure was increased from 100 to 160 mm Hg. Removal of the renal capsule prevented the increase in renal interstitial pressure and 20-HETE levels after an elevation in renal perfusion pressure. Urine flow and sodium excretion increased 5-fold when renal perfusion pressure was increased from 106 to 160 mm Hg. The administration of 1-aminobenzotriazole (50 mg/kg, IP) or HET0016 (10 mg/kg IV bolus plus 1 mg/kg per hour of infusion) decreased the pressure-natriuretic response by 50% and inhibited the renal formation of 20-HETE and epoxyeicosatrienoic acids by 90% and 50%, respectively. Administration of a lower dose of HET0016 (1 mg/kg per hour, IV) selectively reduced the formation of 20-HETE by 80% without inhibiting renal epoxygenase activity and blunted the pressure-natriuretic response by 42%. These results indicate that elevations in renal perfusion pressure increase 20-HETE levels in the kidney secondary to a rise in renal interstitial pressure. They also suggest that 20-HETE, rather than epoxyeicosatrienoic acids, modulates the pressure-natriuretic response, because selective blockade of the formation of 20-HETE with HET0016 blunts the response to the same extent as that seen after inhibition of the formation of 20-HETE and epoxyeicosatrienoic acids with 1-aminobenzotriazole.

Effects of 20-HETE on Na+ transport and Na+ -K+ -ATPase activity in the thick ascending loop of Henle

Previous studies have indicated that 20-hydroxyeicosatetraenoic acid (20-HETE) inhibits Na+ transport in the medullary thick ascending loop of Henle (mTALH), but the mechanisms involved remain uncertain. The present study compared the effects of 20-HETE with those of ouabain and furosemide on intracellular Na+ concentration ([Na+]i), Na+ -K+ -ATPase activity, and 86Rb+ uptake, an index of Na+ transport, in mTALH isolated from rats. Ouabain (2 mM) increased, whereas furosemide (100 microM) decreased, [Na+]i in the mTALH of rats. Ouabain and furosemide inhibited 86Rb+ uptake by 91 and 30%, respectively. 20-HETE (1 microM) had a similar effect as ouabain and increased [Na+]i from 19 +/- 1 to 30 +/- 1 mM. 20-HETE reduced Na+ -K+ -ATPase activity by 30% and 86Rb+ uptake by 37%, but it had no effect on 86Rb+ uptake or [Na+]i in the mTALH of rats pretreated with ouabain. 20-HETE inhibited 86Rb+ uptake by 12% and increased [Na+]i by 19 mM in mTALH pretreated with furosemide. These findings indicate that 20-HETE secondarily inhibits Na+ transport in the mTALH of the rat, at least, in part by inhibiting the Na+ -K+ -ATPase activity and raising [Na+]i.