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

Dietary sodium intake and sodium load is associated with arterial stiffness in children and young adults

OBJECTIVE

The aim of this study was to examine the association of sodium intake (g/day) and sodium load (Na-L; mg/kcal/day) on arterial stiffness in youth.

METHODS

A cross-sectional analysis of 723 youth enrolled in a study evaluating the cardiovascular effects of obesity and type 2 diabetes mellitus (T2DM). Three measures of arterial stiffness were evaluated: brachial distensibility (BrachD), carotid-femoral pulse wave velocity (PWVcf) and augmentation index (AIx). Three-day diet histories yielded mean daily sodium and calorie intake. Youth were divided into Na-L tertiles: Low (≤1.67 mg/kcal per day); Medium (1.68--1.98 mg/kcal per day) and High (>1.98 mg/kcal per day). General linear models adjusting for demographics, % body fat, T2DM and SBP z-score evaluated the independent association of Na-L with arterial stiffness.

RESULTS

Mean age was 17.9 years (10-24 years), 35% male, 59% nonwhite and 31% T2DM. Mean (±standard deviation) dietary intake was calories = 2074 (±797) kcal/day; Na = 3.793 (±1567) g/day; Na- = 1.86 (±0.753) mg/kcal per day. With higher levels of dietary Na intake and Na-L, measures of arterial stiffness worsened: BrachD decreased (Na intake: beta = -0.09, P = 0.003; Na-L: beta = -0.28, P < 0.0001), PWVcf increased (Na intake: beta = 0.07, P = 0.007; Na-L: beta = 0.21, P < 0.0001) but AIx did not change (Na intake: beta = -0.4, P = 0.2; Na-L: beta = 0.89, P = 0.11). In multivariable analysis, High Na-L was independently associated with BrachD, PWVcf and AIx (P < 0.05 for all), with age modifying the association of High Na-L with PWVcf and AIx.

CONCLUSION

Sodium intake and load are associated with arterial stiffness, a preclinical measure of CVD, among a paediatric population. Paediatricians should stress healthy dietary choices to reduce accelerated vascular ageing.

The CYP/20-HETE/GPR75 axis in hypertension

20-Hydroxyeicosatetraenoic acid (20-HETE) is a bioactive lipid generated from the ω-hydroxylation of arachidonic acid (AA) by enzymes of the cytochrome P450 (CYP) family, primarily the CYP4A and CYP4F subfamilies. 20-HETE is most notably identified as a modulator of vascular tone, regulator of renal function, and a contributor to the onset and development of hypertension and cardiovascular disease. 20-HETE-mediated signaling promotes hypertension by sensitizing the vasculature to constrictor stimuli, inducing endothelial dysfunction, and potentiating vascular inflammation. These bioactions are driven by the activation of the G-protein coupled receptor 75 (GPR75), a 20-HETE receptor (20HR). Given the capacity of 20-HETE signaling to drive pro-hypertensive mechanisms, the CYP/20-HETE/GPR75 axis has the potential to be a significant therapeutic target for the treatment of hypertension and cardiovascular diseases associated with increases in blood pressure. In this chapter, we review 20-HETE-mediated cellular mechanisms that promote hypertension, highlight important data in humans such as genetic variants in the CYP genes that potentiate 20-HETE production and describe recent findings in humans with 20HR/GPR75 mutations. Special emphasis is given to the 20HR and respective receptor blockers that have the potential to pave a path to translational and clinical studies for the treatment of 20-HETE-driven hypertension, and obesity/metabolic syndrome.

Vascular contributions to cognitive impairment and dementia: the emerging role of 20-HETE

The accumulation of extracellular amyloid-β (Aβ) and intracellular hyperphosphorylated τ proteins in the brain are the hallmarks of Alzheimer's disease (AD). Much of the research into the pathogenesis of AD has focused on the amyloid or τ hypothesis. These hypotheses propose that Aβ or τ aggregation is the inciting event in AD that leads to downstream neurodegeneration, inflammation, brain atrophy and cognitive impairment. Multiple drugs have been developed and are effective in preventing the accumulation and/or clearing of Aβ or τ proteins. However, clinical trials examining these therapeutic agents have failed to show efficacy in preventing or slowing the progression of the disease. Thus, there is a need for fresh perspectives and the evaluation of alternative therapeutic targets in this field. Epidemiology studies have revealed significant overlap between cardiovascular and cerebrovascular risk factors such as hypertension, diabetes, atherosclerosis and stroke to the development of cognitive impairment. This strong correlation has given birth to a renewed focus on vascular contributions to AD and related dementias. However, few genes and mechanisms have been identified. 20-Hydroxyeicosatetraenoic acid (20-HETE) is a potent vasoconstrictor that plays a complex role in hypertension, autoregulation of cerebral blood flow and blood-brain barrier (BBB) integrity. Multiple human genome-wide association studies have linked mutations in the cytochrome P450 (CYP) 4A (CYP4A) genes that produce 20-HETE to hypertension and stroke. Most recently, genetic variants in the enzymes that produce 20-HETE have also been linked to AD in human population studies. This review examines the emerging role of 20-HETE in AD and related dementias.

20-HETE Enzymes and Receptors in the Neurovascular Unit: Implications in Cerebrovascular Disease

20-HETE is a potent vasoconstrictor that is implicated in the regulation of blood pressure, cerebral blood flow and neuronal death following ischemia. Numerous human genetic studies have shown that inactivating variants in the cytochrome P450 enzymes that produce 20-HETE are associated with hypertension, stroke and cerebrovascular disease. However, little is known about the expression and cellular distribution of the cytochrome P450A enzymes (CYP4A) that produce 20-HETE or the newly discovered 20-HETE receptor (GPR75) in the brain. The present study examined the cell types and regions in the rat forebrain that express CYP4A and GPR75. Brain tissue slices from Sprague Dawley (SD), Dahl Salt-Sensitive (SS) and CYP4A1 transgenic rat strains, as well as cultured human cerebral pericytes and cerebral vascular smooth muscle cells, were analyzed by fluorescent immunostaining. Tissue homogenates from these strains and cultured cells were examined by Western blot. In the cerebral vasculature, CYP4A and GPR75 were expressed in endothelial cells, vascular smooth muscle cells and the glial limiting membrane of pial arteries and penetrating arterioles but not in the endothelium of capillaries. CYP4A, but not GPR75, was expressed in astrocytes. CYP4A and GPR75 were both expressed in a subpopulation of pericytes on capillaries. The diameters of capillaries were significantly decreased at the sites of first and second-order pericytes that expressed CYP4A. Capillary diameters were unaffected at the sites of other pericytes that did not express CYP4A. These findings implicate 20-HETE as a paracrine mediator in various components of the neurovascular unit and are consistent with 20-HETE's emerging role in the regulation of cerebral blood flow, blood-brain barrier integrity, the pathogenesis of stroke and the vascular contributions to cognitive impairment and dementia. Moreover, this study highlights GPR75 as a potential therapeutic target for the treatment of these devastating conditions.

Proximal tubular-targeted overexpression of the Cyp4a12-20-HETE synthase promotes salt-sensitive hypertension in male mice

20-Hydroxyeicosatetraenoic acid (20-HETE) has been linked to blood pressure (BP) regulation via actions on the renal microvasculature and tubules. We assessed tubular 20-HETE contribution to hypertension by generating transgenic mice overexpressing the CYP4A12-20-HETE synthase (PT-4a12 mice) under the control of the proximal tubule (PT)-specific promoter, phosphoenolpyruvate carboxykinase (PEPCK). 20-HETE levels in the kidney cortex of male (967±210 vs. 249±69 pg/mg protein), but not female (121±15 vs. 92±11 pg/mg protein) PT-4a12 mice, showed a 2.5-fold increase compared to WT. Renal cortical Cyp4a12 mRNA and CYP4A12 protein in male, but not female PT-4a12 mice increased by 2-3-fold compared to WT. Male PT-4a12 mice displayed elevated BP (142±1 vs. 111±4 mmHg, p<0.0001), whereas BP in females PT-4a12 mice was not significantly different from WT (118±2 vs. 117±2 mmHg; p=0.98). In male PT-4a12 mice, BP decreased when transitioned from a control salt (0.4%) to a low-salt diet (0.075%) from 135±4 to 120±6 mmHg (p<0.01) and increased to 153±5 mmHg (p<0.05) when placed on a high-salt diet (4%). Female PT-4a12 mice did not show changes in BP on either low- or high-salt diet. In conclusion, the expression of Cyp4a12 driven by the PEPCK promoter is sex-specific probably due to its X-linkage. The salt-sensitive hypertension seen in PT-4a12 male mice suggests a potential anti-natriuretic activity of 20-HETE that needs to be further explored.

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.

Maternal vitamin B12 deficiency in rats alters DNA methylation in metabolically important genes in their offspring

Vitamin B₁₂ deficiency is a critical problem worldwide and peri-conceptional deficiency of this vitamin is associated with the risk of complex cardio-metabolic diseases. Nutritional perturbations during these stages of development may lead to changes in the fetal epigenome. Using Wistar rat model system, we have earlier shown that low maternal B₁₂ levels are associated with low birth weight, adiposity, insulin resistance, and increased triglyceride levels in the offspring, which might predispose them to the risk of cardio-metabolic diseases in adulthood. In this study, we have investigated the effects of maternal B₁₂ deficiency on genome-wide DNA methylation profile of the offspring and the effect of rehabilitation of mothers with B₁₂ at conception. We have performed methylated DNA immunoprecipitation sequencing of liver from pups in four groups of Wistar rats: Control (C), B₁₂-restricted (B₁₂R), B₁₂-rehabilitated at conception (B₁₂RC), and B₁₂-rehabilitated at parturition (B₁₂RP). We have analyzed differentially methylated signatures between the three groups as compared to controls. We have identified a total of 214 hypermethylated and 142 hypomethylated regions in the 10 kb upstream region of transcription start site in pups of B₁₂-deficient mothers, which are enriched in genes involved in fatty acid metabolism and mitochondrial transport/metabolism. B₁₂ rehabilitation at conception and parturition is responsible for reversal of methylation status of many of these regions to control levels suggesting a causal association with metabolic phenotypes. Thus, maternal B₁₂ restriction alters DNA methylation of genes involved in important metabolic processes and influences the offspring phenotype, which is reversed by B₁₂ rehabilitation of mothers at conception.

Conflicting Roles of 20-HETE in Hypertension and Stroke

Hypertension is the most common modifiable risk factor for stroke, and understanding the underlying mechanisms of hypertension and hypertension-related stroke is crucial. 20-hydroxy-5, 8, 11, 14-eicosatetraenoic acid (20-HETE), which plays an important role in vasoconstriction, autoregulation, endothelial dysfunction, angiogenesis, inflammation, and blood-brain barrier integrity, has been linked to hypertension and stroke. 20-HETE can promote hypertension by potentiating the vascular response to vasoconstrictors; it also can reduce blood pressure by inhibition of sodium transport in the kidney. The production of 20-HETE is elevated after the onset of both ischemic and hemorrhagic strokes; on the other hand, subjects with genetic variants in CYP4F2 and CYP4A11 that reduce 20-HETE production are more susceptible to stroke. This review summarizes recent genetic variants in CYP4F2, and CYP4A11 influencing 20-HETE production and discusses the role of 20-HETE in hypertension and the susceptibility to the onset, progression, and prognosis of ischemic and hemorrhagic strokes.

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.

KLHL3 single-nucleotide polymorphism is associated with essential hypertension in Chinese Han population

Hypertension, including secondary and essential hypertension (EH) variants, is a multifactorial disease, affecting more than one billion people worldwide. Secondary hypertension results from mutations in the putative gene KLHL3 (Kelch-like protein 3); however, it has not been reported whether the KLHL3 gene polymorphisms are associated with EH. Here, we investigated the association between KLHL3 (rs2301708 and rs7444370) polymorphisms and EH in the Chinese Han population.This case-control study included 522 subjects-260 patients with EH and 262 normotensive controls matched for age, gender, body mass index (BMI), hemoglobin A1c (HbA1c), total cholesterol (TC), triglyceride (TG), and levels of Na, K, and Cl. The distribution of functional rs2301708 and rs7444370 polymorphisms within the KLHL3 gene was assessed through polymerase chain reaction (PCR) and restriction-fragment length polymorphism (RFLP).There was no significant difference in allelic and genotypic frequencies of KLHL3 rs2301708 between the EH and normotensive groups; however, the rs7444370 T allele and CT genotype in females was significantly associated with a protective effect against EH (P = .001, P = .002; P = .019, P = .052), and the haplotype CT of rs2301708 and rs7444370 among females in the EH group was less than in the normotensive group (P = .000; P = .007).The KLHL3 rs7444370 variant could be a protective factor in the pathogenesis of females' EH.

The arachidonic acid monooxygenase: from biochemical curiosity to physiological/pathophysiological significance

The initial studies of the metabolism of arachidonic acid (AA) by the cytochrome P450 (P450) hemeproteins sought to: a) elucidate the roles for these enzymes in the metabolism of endogenous pools of the FA, b) identify the P450 isoforms involved in AA epoxidation and ω/ω-1 hydroxylation, and c) explore the biological activities of their metabolites. These early investigations provided a foundation for subsequent efforts to establish the physiological relevance of the AA monooxygenase and its contributions to the pathophysiology of, for example, cancer, diabetes, hypertension, inflammation, nociception, and vascular disease. This retrospective analyzes the history of some of these efforts, with emphasis on genetic studies that identified roles for the murine Cyp4a and Cyp2c genes in renal and vascular physiology and the pathophysiology of hypertension and cancer. Wide-ranging investigations by laboratories worldwide, including the authors, have established a better appreciation of the enzymology, genetics, and physiologic roles for what is now known as the third branch of the AA cascade. Combined with the development of analytical and pharmacological tools, including robust synthetic agonists and antagonists of the major metabolites, we stand at the threshold of novel therapeutic approaches for the treatment of renal injury, pain, hypertension, and heart disease.

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.

Conflicting roles of 20-HETE in hypertension and renal end organ damage

20-HETE is a cytochrome P450-derived metabolite of arachidonic acid that has both pro- and anti-hypertensive actions that result from modulation of vascular and kidney function. In the vasculature, 20-HETE sensitizes vascular smooth muscle cells to constrictor stimuli and increases myogenic tone. By promoting smooth muscle cell migration and proliferation, as well as by acting on the vascular endothelium to cause endothelial dysfunction, angiotensin converting enzyme (ACE) expression, and inflammation, 20-HETE contributes to adverse vascular remodeling and increased blood pressure. A G protein-coupled receptor was recently identified as the effector for the vascular actions of 20-HETE. In addition, evidence suggests that 20-HETE contributes to hypertension via positive regulation of the renin-angiotensin-aldosterone system, as well as by causing renal fibrosis. On the other hand, 20-HETE exerts anti-hypertensive actions by inhibiting sodium reabsorption by the kidney in both the proximal tubule and thick ascending limb of Henle. This review discusses the pro- and anti-hypertensive roles of 20-HETE in the pathogenesis of hypertension-associated renal disease, the association of gene polymorphisms of cytochrome P450 enzymes with the development of hypertension and renal end organ damage in humans, and 20-HETE related pharmaceutical agents.

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.

Association between Cullin-3 Single-Nucleotide Polymorphism rs17479770 and Essential Hypertension in the Male Chinese Han Population

Background

Hypertension, including essential and secondary hypertension, is a multifactorial disease, affecting more than one billion people worldwide. Secondary hypertension can result from mutations of cullin-3 (CUL3); however, whether polymorphisms of CUL3 are associated with essential hypertension (EH) has not been reported. Here, we investigated the association between CUL3 SNPs rs17479770 and rs3738952 and EH in the Chinese Han population.

Methods

This case-control study investigated 520 representatives, including 259 patients with EH and 261 normotensive controls matched for age, gender, BMI, TG, TC, and HbA1c for the distribution of functional rs17479770 and rs3738952 within the CUL3 gene by using PCR and RFLP.

Results

Our results showed that there was no significant difference in allele and genotype distribution of rs3738952 and haplotype distribution of rs17479770 and rs3738952 between the EH group and normotensive group, whereas the rs17479770 TT genotype in male and the full data set were significantly associated with the decreased risk of EH (P = 0.050, P = 0.042), and rs17479770 allele T in male was shown to have the correlation tendency of the decreased risk of EH (P = 0.064).

Conclusion

Our data suggest that the CUL3 rs17479770 variant could be a protective factor in the pathogenesis of EH.

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.

Heme-thiolate sulfenylation of human cytochrome P450 4A11 functions as a redox switch for catalytic inhibition

Cytochrome P450 (P450, CYP) 4A11 is a human fatty acid ω-hydroxylase that catalyzes the oxidation of arachidonic acid to the eicosanoid 20-hydroxyeicosatetraenoic acid (20-HETE), which plays important roles in regulating blood pressure regulation. Variants of P450 4A11 have been associated with high blood pressure and resistance to anti-hypertensive drugs, and 20-HETE has both pro- and antihypertensive properties relating to increased vasoconstriction and natriuresis, respectively. These physiological activities are likely influenced by the redox environment, but the mechanisms are unclear. Here, we found that reducing agents (e.g. dithiothreitol and tris(2-carboxyethyl)phosphine) strongly enhanced the catalytic activity of P450 4A11, but not of 10 other human P450s tested. Conversely, added H₂O₂ attenuated P450 4A11 catalytic activity. Catalytic roles of five of the potentially eight implicated Cys residues of P450 4A11 were eliminated by site-directed mutagenesis. Using an isotope-coded dimedone/iododimedone-labeling strategy and mass spectrometry of peptides, we demonstrated that the heme-thiolate cysteine (Cys-457) is selectively sulfenylated in an H₂O₂ concentration-dependent manner. This sulfenylation could be reversed by reducing agents, including dithiothreitol and dithionite. Of note, we observed heme ligand cysteine sulfenylation of P450 4A11 ex vivo in kidneys and livers derived from CYP4A11 transgenic mice. We also detected sulfenylation of murine P450 4a12 and 4b1 heme peptides in kidneys. To our knowledge, reversible oxidation of the heme thiolate has not previously been observed in P450s and may have relevance for 20-HETE-mediated functions.

The Crystal Structure of Cytochrome P450 4B1 (CYP4B1) Monooxygenase Complexed with Octane Discloses Several Structural Adaptations for ω-Hydroxylation

P450 family 4 fatty acid ω-hydroxylases preferentially oxygenate primary C-H bonds over adjacent, energetically favored secondary C-H bonds, but the mechanism explaining this intriguing preference is unclear. To this end, the structure of rabbit P450 4B1 complexed with its substrate octane was determined by X-ray crystallography to define features of the active site that contribute to a preference for ω-hydroxylation. The structure indicated that octane is bound in a narrow active-site cavity that limits access of the secondary C-H bond to the reactive intermediate. A highly conserved sequence motif on helix I contributes to positioning the terminal carbon of octane for ω-hydroxylation. Glu-310 of this motif auto-catalytically forms an ester bond with the heme 5-methyl, and the immobilized Glu-310 contributes to substrate positioning. The preference for ω-hydroxylation was decreased in an E310A mutant having a shorter side chain, but the overall rates of metabolism were retained. E310D and E310Q substitutions having longer side chains exhibit lower overall rates, likely due to higher conformational entropy for these residues, but they retained high preferences for octane ω-hydroxylation. Sequence comparisons indicated that active-site residues constraining octane for ω-hydroxylation are conserved in family 4 P450s. Moreover, the heme 7-propionate is positioned in the active site and provides additional restraints on substrate binding. In conclusion, P450 4B1 exhibits structural adaptations for ω-hydroxylation that include changes in the conformation of the heme and changes in a highly conserved helix I motif that is associated with selective oxygenation of unactivated primary C-H bonds.

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.

Molecular mechanisms and cell signaling of 20-hydroxyeicosatetraenoic acid in vascular pathophysiology

Cytochrome P450s enzymes catalyze the metabolism of arachidonic acid to epoxyeicosatrienoic acids (EETs), dihydroxyeicosatetraenoic acid and hydroxyeicosatetraeonic acid (HETEs). 20-HETE is a vasoconstrictor that depolarizes vascular smooth muscle cells by blocking K+ channels. EETs serve as endothelial derived hyperpolarizing factors. Inhibition of the formation of 20-HETE impairs the myogenic response and autoregulation of renal and cerebral blood flow. Changes in the formation of EETs and 20-HETE have been reported in hypertension and drugs that target these pathways alter blood pressure in animal models. Sequence variants in CYP4A11 and CYP4F2 that produce 20-HETE, UDP-glucuronosyl transferase involved in the biotransformation of 20-HETE and soluble epoxide hydrolase that inactivates EETs are associated with hypertension in human studies. 20-HETE contributes to the regulation of vascular hypertrophy, restenosis, angiogenesis and inflammation. It also promotes endothelial dysfunction and contributes to cerebral vasospasm and ischemia-reperfusion injury in the brain, kidney and heart. This review will focus on the role of 20-HETE in vascular dysfunction, inflammation, ischemic and hemorrhagic stroke and cardiac and renal ischemia reperfusion injury.

The stress response of human proximal tubule cells to cadmium involves up-regulation of haemoxygenase 1 and metallothionein but not cytochrome P450 enzymes

Enzymes of the cytochrome P450 (CYP) super-family are implicated in cadmium (Cd) -induced nephrotoxicity, however, direct evidence is lacking. This study investigated the endogenous expression of various CYP proteins together with the stress-response proteins, heme oxygenase-1 (HO-1) and metallothionein (MT) in human kidney sections and in cadmium-exposed primary cultures of human proximal tubular epithelial cells (PTC). By immunohistochemistry, the CYP members 2B6, 4A11 and 4F2 were prominently expressed in the cortical proximal tubular cells and to a lesser extent in distal tubular cells. Low levels of CYPs 2E1 and 3A4 were also detected. In PTC, in the absence of Cd, CYP2E1, CYP3A4, CYP4F2 and MT were expressed, but HO-1, CYP2B6 and CYP4A11 were not detected. A range of cadmium concentrations (0-100μM) were utilized to induce stress conditions. MT protein was further induced by as little as 0.5μM cadmium, reaching a 6-fold induction at 20μM, whereas for HO-1, a 5μM cadmium concentration was required for initial induction and at 20μM cadmium reached a 15-fold induction. The expression of CYP2E1, CYP3A4, and CYP4F2 were not altered by any cadmium concentrations tested at 48h. Cadmium caused a reduction in cell viability at concentrations above 10μM. In conclusion although cultured PTC, do express CYP proteins, (CYP2E1, CYP3A4, and CYP4F2), Cd-induced cell stress as indicted by induction of HO-1 and MT does not alter expression of these CYP proteins at 48h.

Arachidonic acid monooxygenase: Genetic and biochemical approaches to physiological/pathophysiological relevance

Studies with rat genetic models of hypertension pointed to roles for the CYP2C and CYP4A arachidonic acid epoxygenases and ω-hydroxylases in tubular transport, hemodynamics, and blood pressure control. Further progress in defining their physiological functions and significance to human hypertension requires conclusive identifications of the relevant genes and proteins. Here we discuss unequivocal evidence of roles for the murine Cyp4a14, Cyp4a10, and Cyp2c44 genes in the pathophysiology of hypertension by showing that: (a) Cyp4a14(-/-) mice develop sexually dimorphic hypertension associated with renal vasoconstriction, and up-regulated expression of Cyp4a12a and pro-hypertensive 20-hydroxyeicosatetraenoic acid (20-HETE) levels, and b) Cyp4a10(-/-) and Cyp2c44(-/-) mice develop salt sensitive hypertension linked to downregulation or lack of the Cyp2c44 epoxygenase, reductions in anti-hypertensive epoxyeicosatrienoic acids (EETs), and increases in distal sodium reabsorption. Based on these studies, the human CYP4A11 and CYPs 2C8 and 2C9 genes and their products are identified as potential candidates for studies of the molecular basis of human hypertension.

Deficiency in the Formation of 20-Hydroxyeicosatetraenoic Acid Enhances Renal Ischemia-Reperfusion Injury

Ischemia-reperfusion (IR) injury is the most common cause of AKI. The susceptibility to develop AKI varies widely among patients. However, little is known about the genes involved. 20-Hydroxyeicosatetraenoic acid (20-HETE) has an important role in the regulation of renal tubular and vascular function and has been implicated in IR injury. In this study, we examined whether a deficiency in the renal formation of 20-HETE enhances the susceptibility of Dahl salt-sensitive (SS) rats to ischemic AKI. Transfer of chromosome 5 containing the CYP4A genes responsible for the formation of 20-HETE from the Brown Norway (BN) rat onto the SS genetic background increased renal 20-HETE levels after ischemia and reduced plasma creatinine levels (±SEM) 24 hours after IR from 3.7±0.1 to 2.0±0.2 mg/dl in an SS.5(BN)-consomic strain. Transfer of this chromosome also prevented the secondary decline in medullary blood flow and ischemia that develops 2 hours after IR in the susceptible SS strain. Blockade of the synthesis of 20-HETE with HET0016 reversed the renoprotective effects in SS.5(BN) rats. Similar results were observed in an SS.5(Lew)-congenic strain, in which a smaller region of chromosome 5 containing the CYP4A genes from a Lewis rat was introgressed onto the SS genetic background. These results indicate that 20-HETE has a protective role in renal IR injury by maintaining medullary blood flow and that a genetic deficiency in the formation of 20-HETE increases the susceptibility of SS rats to ischemic AKI.

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.

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.

Activation of neuronal transient receptor potential vanilloid 1 channel underlies 20-hydroxyeicosatetraenoic acid-induced vasoactivity: role for protein kinase A

A rise in intraluminal pressure triggers vasoconstriction in resistance arteries, which is associated with local generation of the vasoconstrictor 20-hydroxyeicosatetraenoic acid (20-HETE). Importantly, dysregulation of 20-HETE synthesis and activity has been implicated in several cardiovascular disease states, including ischemic disease, hypertension, and stroke; however, the exact molecular pathways involved in mediating 20-HETE bioactivity are uncertain. We investigated whether 20-HETE activates the transient receptor potential vanilloid 1 (TRPV1) and thereby regulates vascular function and blood pressure. We demonstrate that 20-HETE causes dose-dependent increases in blood pressure, coronary perfusion pressure (isolated Langendorff), and pressure-induced constriction of resistance arteries (perfusion myography) that is substantially attenuated in TRPV1 knockout mice and by treatment with the neurokinin 1 receptor antagonist RP67580. Furthermore, we show that both channel activation (via patch-clamping of dorsal root ganglion neurons) and vessel constriction are enhanced under inflammatory conditions, and our findings indicate a predominant role for protein kinase A-mediated sensitization of TRPV1 in these phenomena. Finally, we identify a prominence of these pathway in males compared with females, an effect we relate to reduced protein kinase A-induced phosphorylation of TRPV1. 20-HETE-induced activation of TRPV1, in part, mediates pressure-induced myogenic constriction and underlies 20-HETE-induced elevations in blood pressure and coronary resistance. Our findings identify a novel vasoconstrictor 20-HETE/TRPV1 pathway that may offer potential for therapeutic targeting in cardiovascular diseases associated with elevated 20-HETE implicated in dysregulated organ blood flow, such as stroke or hypertension.

Introgression of Brown Norway CYP4A genes on to the Dahl salt-sensitive background restores vascular function in SS-5(BN) consomic rats

The present study tested the hypothesis that the Dahl SS (salt-sensitive) rat has vascular dysfunction due, in part, to the up-regulation of the CYP4A/20-HETE (cytochrome P450 ω-hydroxylase 4A)/20-hydroxyeicosatetraenoic acid) system. To assess the role of vascular 20-HETE, SS rats were compared with SS-5(BN) consomic rats, carrying CYP4A alleles on chromosome 5 from the normotensive BN (Brown Norway) introgressed on to the SS genetic background. Cerebral arteries from SS-5(BN) rats had less CYP4A protein than arteries from SS rats fed either NS (normal-salt, 0.4% NaCl) or HS (high-salt, 4.0% NaCl) diet. ACh (acetylcholine)-induced dilation of MCAs (middle cerebral arteries) from SS and SS-5(BN) rats was present in SS-5(BN) rats fed on either an NS or HS diet, but absent in SS rats. In SS rats fed on either diet, ACh-induced dilation was restored by acute treatment with the CYP4A inhibitor DDMS (N-methyl-sulfonyl-12,12-dibromododec-11-enamide) or the 20-HETE antagonist 20-HEDE [20-hydroxyeicosa-6(Z),15(Z)-dienoic acid]. The restored response to ACh in DDMS-treated SS rats was inhibited by L-NAME (N(G)nitro-L-arginine methyl ester) and unaffected by indomethacin or MS-PPOH [N-methylsulfonyl-6-(2-propargyloxyphenyl)hexanamide]. Vascular relaxation responses to the NO donor C(5)FeN(6)Na(2)O were intact in both SS and SS-5(BN) rats and unaffected by the acute addition of DDMS, indicating that the vascular dysfunction of the SS rat is due to a reduced bioavailability of NO instead of failure of the VSMCs (vascular smooth muscle cells) to respond to the vasodilator. Superoxide levels in cerebral arteries of SS-5(BN) rats [evaluated semi-quantitatively by DHE (dihydroethidium) fluorescence] were lower than those in the arteries of SS rats. These findings indicate that SS rats have an up-regulation of the CYP4A/20-HETE pathway resulting in elevated ROS (reactive oxygen species) and reduced NO bioavailability causing vascular dysfunction.

Haplotype-based case-control study of CYP4A11 gene and myocardial infarction

CYP4A11, which is a member of the cytochrome P450 family, acts mainly as an enzyme that converts arachidonic acid to 20-hydroxyeicosatetraenoic acid (20-HETE), a metabolite involved in the maintenance of cardiovascular health. Recently, it was reported that many subfamilies of CYP genes have an association with myocardial infarction (MI). The aim of the present study was to assess the association between the human CYP4A11 gene and MI, using a haplotype-based case-control study with a separate analysis of the gender groups. A total of 239 MI patients and 285 controls were genotyped for 3 single-nucleotide polymorphisms (SNPs) of the human CYP4A11 gene (rs2269231, rs1126742, rs9333025). The data obtained via haplotype-based case-control studies were assessed for 3 separate groups: total subjects, men, and women. For the total, men and women groups, the distribution of the genotypes and alleles of the 3 SNPs did not show any significant difference between the MI patients and the control subjects. For the total and the men groups, the overall distribution of the haplotypes constructed with the 3 SNPs significantly differed between the MI patients and control subjects (P < 0.001). Also, for the total and for the men, the frequency of the T-T-A haplotype constructed with the 3 SNPs was significantly lower for the MI patients than for the control subjects (both P < 0.001). The T-T-A haplotype constructed with the 3 SNPs appears to be a protective genetic marker for MI in Japanese men.

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.

CYP4A11 T8590C polymorphism, salt-sensitive hypertension, and renal blood flow

OBJECTIVE AND METHODS

A loss-of-function cytosine (C) for thymidine (T) transition at nucleotide 8590 of CYP4A11 has been associated with increased blood pressure in humans. We tested the hypothesis that CYP4A11 T8590C genotype is associated with salt sensitivity in the International Hypertensive Pathotype cohort.

RESULTS

CYP4A11 T8590C genotype was associated with hypertension in whites. Among normotensive individuals, CYP4A11 T8590C genotype was associated with mean arterial pressure (MAP) during both high and low salt diets, such that there was no relationship between genotype and salt sensitivity of blood pressure. Among hypertensive individuals, CYP4A11 T8590C genotype did not associate with MAP during high salt intake, whereas MAP decreased with increasing number of C alleles during salt restriction. Consequently, among hypertensive individuals, change in MAP with salt restriction was greatest in individuals homozygous for the C allele (-10.9 ± 9.9, -11.1 ± 12.3, and -18.8 ± 12.0 mmHg in TT, CT, and CC groups, respectively, P = 0.02). In both normotensive and hypertensive individuals, individuals homozygous for the C allele exhibited an attenuated increase in renal blood flow during high salt. CYP4A11 genotype did not affect pressor responses to Angiotensin II in normotensive or hypertensive individuals.

CONCLUSION

The loss-of-function CYP4A11 8590C allele is associated with a diagnosis of hypertension and, in normotensive individuals, with higher blood pressure regardless of salt intake. Among hypertensive individuals, the C allele is associated with salt-sensitive blood pressure. Impaired renal vasodilation during high salt intake may contribute to salt sensitivity. Studies are needed to determine whether CYP4A11 T8590C genotype predicts responses to medications that affect sodium homeostasis in hypertensive individuals.

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.

Sodium sensitivity of blood pressure in Chinese populations

Clinical trials have demonstrated that a reduced intake of dietary sodium lowers blood pressure. However, blood pressure reduction in response to a decrease in dietary sodium intake varies considerably among different individuals-a phenomenon described as sodium sensitivity. The Genetic Epidemiology Network of Salt Sensitivity (GenSalt) study was a large family-based dietary-feeding study conducted in rural north China. This study indicated that approximately 39% of Chinese adults were sodium-sensitive. Sodium sensitivity was more common in women and in persons who were older and had higher usual blood pressure. Sodium sensitivity was also more common in individuals with higher responses to a cold pressor test and in individuals with the metabolic syndrome. Genetic factors may play an important role in determining sodium sensitivity in the Chinese population. A better understanding of the genetic and environmental determinants of sodium sensitivity has important public health and clinical implications.

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.

Cerebrospinal fluid 20-HETE is associated with delayed cerebral ischemia and poor outcomes after aneurysmal subarachnoid hemorrhage

BACKGROUND AND PURPOSE

Delayed cerebral ischemia (DCI) is a major complication after aneurysmal subarachnoid hemorrhage (aSAH); it is manifested by changes in cerebral blood flow accompanied by neurological decline, and it results in long-term functional and neuropsychological impairment. Preclinical evidence has demonstrated that the arachidonic acid metabolite, 20-hydroxyeicosatetraenoic acid (20-HETE), affects cerebral microvascular tone and cerebral blood flow after aSAH. The purpose of this study was to determine whether cerebrospinal fluid 20-HETE levels were associated with DCI and long-term neuropsychological outcomes in aSAH patients.

METHODS

Cerebrospinal fluid samples were collected twice daily through 14 days after hemorrhage on 108 acute, adult, aSAH patients. Samples were analyzed for 20-HETE via HPLC MSQ single quadrupole mass spectrometry. DCI was defined as the presence of impaired cerebral blood flow (angiographic vasospasm, elevated transcranial Dopplers, abnormal computed tomography or magnetic resonance perfusion scans) accompanied by neurological deterioration. Outcomes, including death and neuropsychological testing, were completed at 3 months after hemorrhage.

RESULTS

Detectable 20-HETE levels were observed in 31% of patient samples and were associated with severity of hemorrhage (Hunt & Hess [HH], P=0.04; Fisher, P=0.05). Detection of 20-HETE was not associated with angiographic vasospasm (P=0.34); however, detectable 20-HETE was significantly associated with DCI (P=0.016). Our data also suggest that detectable 20-HETE was associated with decreased performance in 5 neuropsychological domains.

CONCLUSIONS

These results provide the first clinical evidence that cerebrospinal fluid 20-HETE concentrations are associated with DCI and poor outcomes, and this provides impetus for future studies to elucidate the clinical utility of inhibiting 20-HETE formation as a novel therapeutic intervention in patients with aSAH.

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.

A critical appraisal of the clinical effectiveness of a fixed combination of valsartan, amlodipine, and hydrochlorothiazide in achieving blood pressure goals

Recent guidelines for the treatment of hypertension have focused on the need for multiple medications to get most patients to goal blood pressure (BP). Two to three different classes of antihypertensive agents are frequently required, increasing the risk of poor compliance with therapy. Hence, the guidelines have recommended starting with combination therapy in patients with BP that is over 20 mm Hg systolic or 10 mm Hg diastolic above goal. The latest advance in treatment regimen has been the development of triple-therapy combinations of an angiotensin receptor blocker, amlodipine, and hydrochlorothiazide. We review the pathophysiologic rationale for such a combination and the efficacy, safety, and tolerability of the first triple therapy that has become available: valsartan + amlodipine + hydrochlorothiazide. Finally, we suggest that use of triple therapy could improve the accuracy of diagnosing resistant hypertension, an increasingly prevalent and severe condition, by enhancing adherence to treatment and weeding out patients with pseudoresistance. This would allow for implementation of expensive and invasive workup only in those truly resistant patients in whom it is justified.

CYP4A2-induced hypertension is 20-hydroxyeicosatetraenoic acid- and angiotensin II-dependent

We have shown previously that increased vascular endothelial expression of CYP4A2 leads to 20-hydroxyeicosatetraenoic (20-HETE)-dependent hypertension. The renin-angiotensin system is a key regulator of blood pressure. In this study, we examined possible interactions between 20-HETE and the renin-angiotensin system. In normotensive (110±3 mm Hg) Sprague-Dawley rats transduced with a lentivirus expressing the CYP4A2 cDNA under the control of an endothelial-specific promoter (VECAD-4A2), systolic blood pressure increased rapidly, reaching 139±1, 145±3, and 150±2 mm Hg at 3, 5, and 10 days after transduction; blood pressure remained elevated, thereafter, with maximum levels of 163±3 mm Hg. Treatment with lisinopril, losartan, or the 20-HETE antagonist 20-hydroxyeicosa-6(Z), 15(Z)-dienoic acid decreased blood pressure to control values, but blood pressure returned to its high levels after cessation of treatment. Endothelial-specific overexpression of CYP4A2 resulted in increased expression of vascular angiotensin-converting enzyme (ACE) and angiotensin II type 1 receptor and increased levels of plasma and tissue angiotensin II; all were attenuated by treatment with HET0016, an inhibitor of 20-HETE synthesis, or with 20-hydroxyeicosa-6(Z), 15(Z)-dienoic acid. In cultured endothelial cells, 20-HETE specifically and potently induced ACE expression without altering the expression of ACE2, angiotensinogen, or angiotensin II receptors. This is the first study to demonstrate that 20-HETE, a key constrictor eicosanoid in the microcirculation, induces ACE and angiotensin II type 1 receptor expression and increases angiotensin II levels, suggesting that the mechanisms by which 20-HETE promotes hypertension include activation of the renin-angiotensin system that is likely initiated at the level of ACE induction.

Role of valsartan, amlodipine and hydrochlorothiazide fixed combination in blood pressure control: an update

The treatment of moderate or severe hypertension in most cases requires the contemporaneous use of multiple antihypertensive agents. The most available two-drug combinations have an agent that addresses renin secretion and another one that is statistically more effective in renin-independent hypertension. The practice of combining agents that counteract different mechanisms is the most likely explanation for the fact that most available two-drug combinations have an agent that addresses renin secretion (beta-blocker, angiotensin converting enzyme inhibitor, angiotensin II receptor blocker or direct renin inhibitor) and another one that is more effective in renin-independent hypertension (diuretic, dihydropyridine or non-dihydropyridine calcium channel blocker). Based on these considerations, addition of hydrochlorothiazide to the combination of an antagonist of the renin-angiotensin system with a calcium channel blocker would constitute a logical approach. Inclusion of a diuretic in the triple combination is based on the evidence that these agents are effective and cheap, enhance the effect of other antihypertensive agents, and add a specific effect to individuals with salt-sensitivity of blood pressure. The benefit of triple combination therapy with amlodipine, valsartan and hydrochlorothiazide over its dual component therapies has been demonstrated, and the use of a single pill will simplify therapy resulting in better blood pressure control.

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.