Alterations in the regulation of androgen-sensitive Cyp 4a monooxygenases cause hypertension

Increased renal proximal convoluted tubule transport contributes to hypertension in Cyp4a14 knockout mice

BACKGROUND/AIMS

Disrupting the enzyme Cyp4a14 in mice leads to hypertension, which is more severe in the male mice and appears to be due to androgen excess. Because the Cyp4a14 enzyme is located in the proximal tubule of the kidney, we hypothesized that there could be dysregulation of transport in this segment that could contribute to the hypertension.

METHODS

Wild-type (SV/129) mice and mice that had targeted disruption of the Cyp4a14 gene were studied. Proximal convoluted tubules (PCT) from knockout and wild-type mice were dissected and perfused in vitrofor measurement of volume absorption (J(V)). Expression of the sodium-hydrogen exchanger 3 (NHE3), the predominant transporter responsible for sodium transport in this segment, was measured by immunoblot. Renal vascular (afferent arteriole) responses to angiotensin and endothelin were also measured.

RESULTS

PCT volume absorption was elevated in tubules from the Cyp4a14 knockout mice as compared to the wild-type mice. Brush border membrane NHE3 expression was almost 2-fold higher in Cyp4a14 knockout mice than in wild-type mice. No difference was found in the afferent arteriolar response.

CONCLUSION

Thus, hypertension in the Cyp4a14 knockout mice appears to be driven by excessive fluid reabsorption in the proximal tubule, which is secondary to overexpression of NHE3.

Endothelial-specific CYP4A2 overexpression leads to renal injury and hypertension via increased production of 20-HETE

We have previously reported that adenoviral-mediated delivery of cytochrome P-450 (CYP) 4A2, which catalyzes the synthesis of 20-hydroxyeicosatetraenoic acid (20-HETE), results in endothelial dysfunction and hypertension in Sprague-Dawley (SD) rats (Wang JS, Singh H, Zhang F, Ishizuka T, Deng H, Kemp R, Wolin MS, Hintze TH, Abraham NG, Nasjletti A, Laniado-Schwartzman M. Circ Res 98: 962-969, 2006). In this study, we targeted the vascular endothelium by using a lentivirus construct expressing CYP4A2 under the control of the endothelium-specific promoter VE-cadherin (VECAD-4A2) and examined the effect of long-term CYP4A2 overexpression on blood pressure and kidney function in SD rats. A bolus injection of VECAD-4A2 increased blood pressure (P < 0.001) by 26, 36, and 30 mmHg 10, 20, and 30 days postinjection, respectively. Arteries from VECAD-4A2-transduced rats produced increased levels of 20-HETE (P < 0.01), expressed lower levels of endothelial nitric oxide synthase (eNOS) and phosphorylated eNOS (p-eNOS) (P < 0.05), generated higher levels of superoxide anion, and displayed decreased relaxing responsiveness to acetylcholine (P < 0.05). Proteinuria increased by twofold in VECAD-4A2-transduced rats compared with controls. Treatment of VECAD-4A2-transduced rats with HET0016, an inhibitor of 20-HETE biosynthesis, not only attenuated the increase in blood pressure (P < 0.05) but also improved vascular function (acetylcholine-induced relaxations) and reduced plasma creatinine and proteinuria. HET0016 treatment decreased oxidative stress and increased the phosphorylated state of key proteins that regulate endothelial function, including eNOS, AKT, and AMPK. Collectively, these findings demonstrate that augmentation of vascular endothelial 20-HETE levels results in hypertension, endothelial dysfunction, and renal injury, which is offset by HET0016 through a reduction in vascular 20-HETE coupled with a lessening of oxidative stress and the amplification of pAKT, pAMPK, and p-eNOS levels leading to normalization of endothelial responses.

Opposing roles of peroxisome proliferator-activated receptor alpha and growth hormone in the regulation of CYP4A11 expression in a transgenic mouse model

CYP4A11 transgenic mice (CYP4A11 Tg) were generated to examine in vivo regulation of the human CYP4A11 gene. Expression of CYP4A11 in mice yields liver and kidney P450 4A11 levels similar to those found in the corresponding human tissues and leads to an increased microsomal capacity for omega-hydroxylation of lauric acid. Fasted CYP4A11 Tg mice exhibit 2-3-fold increases in hepatic CYP4A11 mRNA and protein, and this response is absent in peroxisome proliferator-activated receptor alpha (PPARalpha) null mice. Dietary administration of either of the PPARalpha agonists, fenofibrate or clofibric acid, increases hepatic and renal CYP4A11 levels by 2-3-fold, and these responses were also abrogated in PPARalpha null mice. Basal liver CYP4A11 levels are reduced differentially in PPARalpha-/- females (>95%) and males (<50%) compared with PPARalpha-/+ mice. Quantitative and temporal differences in growth hormone secretion are known to alter hepatic lipid metabolism and to underlie sexually dimorphic gene expression, respectively. Continuous infusion of low levels of growth hormone reduced CYP4A11 expression by 50% in PPARalpha-proficient male and female transgenic mice. A larger decrease was observed for the expression of CYP4A11 in PPARalpha-/- CYP4A11 Tg male mice to levels similar to that of female PPARalpha-deficient mice. These results suggest that PPARalpha contributes to the maintenance of basal CYP4A11 expression and mediates CYP4A11 induction in response to fibrates or fasting. In contrast, increased exposure to growth hormone down-regulates CYP4A11 expression in liver.

Overexpression of cytochrome P450 4F2 in mice increases 20-hydroxyeicosatetraenoic acid production and arterial blood pressure

Cytochrome P450 4F2 (CYP4F2) activity is thought to be a factor in the pathogenesis of hypertension through its bioactive metabolite 20-hydroxyeicosatetraenoic acid (20-HETE). We previously found that a gain-in-function CYP4F2 variant in a Chinese cohort was associated with elevated urinary 20-HETE and hypertension. To further explore this association we generated a transgenic mouse model expressing CYP4F2 driven by a modified mouse kidney androgen-regulated protein promoter. This heterologous promoter regulated the expression of luciferase and his-tagged CYP4F2 in transfected HEK 293 cells. In the kidney of transgenic mice, CYP4F2 was localized to renal proximal tubule epithelia and was expressed at a higher level than in control mice, leading to increased urinary 20-HETE excretion. Assessment of CYP4F2 activity by an arachidonic acid hydroxylation assay showed that 20-HETE production was significantly higher in kidney microsomes of transgenic mice compared to control mice, as was their systolic blood pressure. There was a positive correlation of blood pressure with urinary 20-HETE levels. Our results show that increased expression of CYP4F2 in mice enhanced 20-HETE production and elevated blood pressure.

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

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

A 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.

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.

Androgens stimulate proximal tubule transport

BACKGROUND

Disrupting the enzyme cytochrome P4a14 in mice leads to hypertension, which is more severe in male than in female mice and appears to be due to androgen excess. Androgens are known to increase expression of angiotensinogen,but the effect of androgens on proximal tubule transport is unknown.

OBJECTIVE

These studies aimed to determine the effect of androgens on proximal tubule transport.

METHODS

Proximal tubules from knockout (KKO) and wild-ttype (WWT) (SSV/1129) mice were perfused in vitro. Volume resorption (JJ v ) was measured using 3 H-methoxy inulin as a volume marker. In separate experiments, male Sprague-Dawley rats were given dihydrotestosterone (DDHT) injections IP for 10 days. Proximal tubule transport was measured in this model using in vivo microperfusion. The renal expression of angiotensinogen was measured by Northern analysis, and brush border membrane protein abundance of the sodium-hhydrogen exchanger isoform 3 (NNHE3) was measured by Western blotting in the control and DHT-ttreated rats.

RESULTS

Mean (SSE) Jv was significantly elevated in proximal tubules from KO mice compared with WT mice (11.11 [0.006] vs 0.77 [0.112] nL/mm . mm, respectively; P<0.05). The mean proximal tubule Jv rate was significantly higher in DHT-ttreated rats than in control rats given vehicle injections (44.57 [0.331] vs 3.31 [0.223] nL/mm . min, respectively; P<0.01). Luminal perfusion with either enalaprilat or losartan decreased the proximal tubule J v rate in DHT-ttreated rats to a greater degree than in control rats. The DHT-treated rats had higher blood pressures and lower serum angiotensin II concentrations than did the control rats.

CONCLUSION

Results suggest that androgens may directly upregulate the proximal tubule reninangiotensin system, increase the expression of NHE3, and increase the Jv rate, thereby increasing extracel-lular volume and blood pressure and secondarily decreasing serum angiotensin II concentrations.

Increased blood pressure in mice lacking cytochrome P450 2J5

The cytochrome P450 (CYP) enzymes participate in a wide range of biochemical functions, including metabolism of arachidonic acid and steroid hormones. Mouse CYP2J5 is abundant in the kidney where its products, the cis-epoxyeicosatrienoic acids (EETs), modulate sodium transport and vascular tone. To define the physiological role of CYP2J5 in the kidney, knockout mice were generated using a conventional gene targeting approach. Cyp2j5 (-/-) mice develop normally and exhibit no overt renal pathology. While renal EET biosynthesis was apparently unaffected by the absence of CYP2J5, deficiency of this CYP in female mice was associated with increased blood pressure, enhanced proximal tubular transport rates, and exaggerated afferent arteriolar responses to angiotensin II and endothelin I. Interestingly, plasma 17beta-estradiol levels were reduced in female Cyp2j5 (-/-) mice and estrogen replacement restored blood pressure and vascular responsiveness to normal levels. There was no evidence of enhanced estrogen metabolism, or altered expression or activities of steroidogenic enzymes in female Cyp2j5 (-/-) mice, but their plasma levels of luteinizing hormone and follicle stimulating hormone were inappropriately low. Together, our findings illustrate a sex-specific role for CYP2J5 in regulation of blood pressure, proximal tubular transport, and afferent arteriolar responsiveness via an estrogen-dependent mechanism.

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.

Ovariectomy, but not estrogen deficiency, increases CYP4A modulation of alpha(1)-adrenergic vasoconstriction in aging female rats

BACKGROUND

Postmenopausal women are more likely to develop cardiovascular disease (CVD) than premenopausal women. Increased vasoconstriction in the peripheral vasculature may underlie this risk. In vascular smooth muscle, cytochrome P450 4A (CYP4A) enzymes form the vasoconstrictor 20-hydroxyeicosatetraenoic acid (20-HETE). CYP4A modulation of alpha(1)-adrenergic vasoconstriction is increased in aging male rats; however, this pathway has not been investigated in aging females. To generate an appropriate model of menopause, we ovariectomized aged Sprague-Dawley rats to create an aged, ovarian-depleted phenotype. Because estrogen has profound effects on the peripheral vasculature, we also determined the effect of estrogen replacement on CYP4A modulation of vasoconstriction.

METHODS

Aged (15-16 months) rats were assigned to be intact or ovariectomized. Ovariectomized rats received either placebo (OVX) or 17beta-estradiol (OVX-E) subcutaneously for 4 weeks. Mesenteric arteries were isolated and constricted with the alpha(1)-adrenergic agonist phenylephrine or intraluminal pressure in the absence or presence of the CYP4A inhibitor, DDMS.

RESULTS

Ovariectomy increased CYP4A modulation of alpha(1)-adrenergic vasoconstriction. This was unaffected by estrogen replacement. Arteries from OVX-E animals exhibited increased phenylephrine sensitivity and forced dilation relative to arteries from intact and OVX animals. Myogenic tone was increased in both OVX and OVX-E animals relative to intact rats; however, CYP4A inhibition had no effect on myogenic tone in any group.

CONCLUSIONS

In aged female rats, ovariectomy caused an increase in CYP4A modulation of alpha(1)-adrenergic vasoconstriction that was not prevented by estrogen replacement. Future study of these pathways may provide important targets for the prevention of CVD in aging women.

Vascular actions of estrogens: functional implications

The impact of estrogen exposure in preventing or treating cardiovascular disease is controversial. But it is clear that estrogen has important effects on vascular physiology and pathophysiology, with potential therapeutic implications. Therefore, the goal of this review is to summarize, using an integrated approach, current knowledge of the vascular effects of estrogen, both in humans and in experimental animals. Aspects of estrogen synthesis and receptors, as well as general mechanisms of estrogenic action are reviewed with an emphasis on issues particularly relevant to the vascular system. Recent understanding of the impact of estrogen on mitochondrial function suggests that the longer lifespan of women compared with men may depend in part on the ability of estrogen to decrease production of reactive oxygen species in mitochondria. Mechanisms by which estrogen increases endothelial vasodilator function, promotes angiogenesis, and modulates autonomic function are summarized. Key aspects of the relevant pathophysiology of inflammation, atherosclerosis, stroke, migraine, and thrombosis are reviewed concerning current knowledge of estrogenic effects. A number of emerging concepts are addressed throughout. These include the importance of estrogenic formulation and route of administration and the impact of genetic polymorphisms, either in estrogen receptors or in enzymes responsible for estrogen metabolism, on responsiveness to hormone treatment. The importance of local metabolism of estrogenic precursors and the impact of timing for initiation of treatment and its duration are also considered. Although consensus opinions are emphasized, controversial views are presented to stimulate future research.

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.

Association of a CYP4A11 variant and blood pressure in black men

CYP4A11 arachidonic acid monooxygenase oxidizes endogenous arachidonic acid to 20-hydroxyeicosatetraenoic acid, a renal vasoconstrictor and natriuretic. Cyp4a deficiency causes hypertension in male mice, and a loss-of-function variant (T8590C) of CYP4A11 is associated with hypertension in white individuals. Hypertension and hypertensive renal disease are more common among black than white individuals, but the relationship between genetic variation at CYP4A11 and hypertension in black individuals is not known. This study tested the hypothesis that the CYP4A11 T8590C polymorphism is associated with higher BP or clinical outcomes in 732 black Americans with hypertensive renal disease participating in the African American Study of Kidney Disease (AASK). Men with the 8590CC genotype had significantly higher systolic BP (CC 156.5 +/- 22.6 versus 148.4 +/- 24.3 mmHg in CT and TT combined; P = 0.04) and pulse pressure (P = 0.04) at baseline; this association was not observed among women. In addition, this genotype was associated with higher systolic and diastolic BP at 36-mo follow-up among those randomly assigned to the lower BP arm of the AASK. Among all participants (or men but not women) with proteinuria, the 8590CC genotype was associated with an increased cumulative incidence of ESRD or death, controlling for randomization and clinical characteristics. In summary, the CYP4A11 8590CC genotype is associated with increased BP in black men with hypertensive nephrosclerosis and is associated with adverse clinical outcomes in those with baseline proteinuria. These data support a role for renal monooxygenases and 20-hydroxyeicosatetraenoic acid in the regulation of BP and renal function in men.

Haplotype-based case study of human CYP4A11 gene and cerebral infarction in Japanese subject

OBJECTIVE

CYP4A11 is an enzyme that converts arachidonic acid to 20-hydroxyeicosatetraenoic acid, which is involved in regulation of vascular tone in the brain. Recent evidence indicates that the polymorphism of the CYP genes is associated with cerebral infarction (CI). The aim of the present study was to assess the association between the human CYP4A11 gene and CI using a haplotype-based case-control study divided by gender.

METHODS

Three SNPs of the human CYP4A11 gene (rs2269231, rs1126742, and rs9333025) were selected and genotyped for 174 CI patients and 293 controls. The data were assessed for three separate groups: total subjects, men and women.

RESULTS

In men, the genotype distribution of rs9333025 significantly differed between the CI patients and control subjects (P = 0.047). The distribution of the dominant model of rs9333025 (GG vs. GA + AA) significantly differed between both the total and the men groups (P = 0.033, P = 0.028, respectively). Logistic regression analysis adjusted for the history of hypertension and diabetes mellitus also showed that the GG genotype was significantly more frequent in the CI patients than in the controls, both for the total and men groups (P < 0.001, P = 0.008, respectively). The overall distribution of the haplotypes constructed with the 3 SNPs showed significant differences between the CI and the control in total group (P = 0.049). The T-C-G haplotype was significantly more frequent in control subjects than in the CI patients in the total group (P = 0.020).

CONCLUSIONS

The GG genotype of rs9333025 could be a genetic marker for CI in Japanese men. In addition, the T-C-G haplotype might also be a protective marker for CI in Japanese.

PPARs and the kidney in metabolic syndrome

The metabolic syndrome (MetS) is defined by a set of metabolic risk factors, including insulin resistance, central obesity, dyslipidemia, hyperglycemia, and hypertension for type 2 diabetes and cardiovascular disease. Although both retrospective and prospective clinical studies have revealed that MetS is associated with chronic renal disease, even with a nondiabetic cause, the cellular and molecular mechanisms in this association remain largely uncharacterized. Recently, increasing evidence suggests that peroxisome proliferator-activated receptors (PPARs), a subgroup of the nuclear hormone receptor superfamily of ligand-activated transcription factors, may play an important role in the pathogenesis of MetS. All three members of the PPAR nuclear receptor subfamily, PPARalpha, -beta/delta, and -gamma, are critical in regulating insulin sensitivity, adipogenesis, lipid metabolism, inflammation, and blood pressure. PPARs have also been implicated in many renal pathophysiological conditions, including diabetic nephropathy and glomerulosclerosis. Ligands for PPARs such as hypolipidemic PPARalpha activators, and antidiabetic thiazolidinedione PPARgamma agonists affect not only diverse aspects of MetS but also renal disease progression. Emerging data suggest that PPARs may be potential therapeutic targets for MetS and its related renal complications. This review focuses on current knowledge of the role of PPARs in MetS and discusses the potential therapeutic utility of PPAR modulators in the treatment of kidney diseases associated with MetS.

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

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

Regulation of ion transport and blood pressure by cytochrome p450 monooxygenases

PURPOSE OF REVIEW

Past and recent studies of the cytochrome P450 monooxygenase branch of the arachidonate cascade establish a role for this metabolic pathway in the regulation of vascular tone and tubular ion transport. Functional and electrophysiology studies indicate that the P450 eicosanoids participate in the regulation of vascular potassium and renal sodium channels, and of systemic blood pressures.

RECENT FINDINGS

Associations between genetically controlled alterations in blood pressure and the activity or transcriptional regulation of renal Cyp2c arachidonic acid epoxygenases and Cyp4a omega-hydroxylases document a role for these enzymes in the pathophysiology of hypertension--a leading cause of cardiovascular, cerebral, and renal morbidity and mortality. Associations between a functional variant of the human CYP4A11 gene and hypertension suggest a potential role for this gene as a determinant of polygenic blood pressure control in humans.

SUMMARY

These results provide new understandings of the role of P450s in renal physiology, as well as conceptually novel approaches for studies of the molecular basis of human hypertension that could lead to new strategies for the early diagnosis and clinical management of this devastating disease.

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.

Roles of the cytochrome P450 arachidonic acid monooxygenases in the control of systemic blood pressure and experimental hypertension

Studies of the cytochrome P450 arachidonic acid (AA) monooxygenase, now established as a major pathway for the bioactivation of this physiological important fatty acid, have uncovered new and important roles for this enzyme system in the regulation of kidney function, including renal hemodynamics and tubular ion transport. Associations between genetically controlled alterations in blood pressure and the activity and/or transcriptional regulation of the kidney Cyp2c AA epoxygenases and Cyp4a omega-hydroxylases revealed a role for these enzymes in the pathophysiology of hypertension, a leading cause of cardiovascular, cerebral, and renal morbidity and mortality. Furthermore, analysis of associations between genetic variants of human CYP4A11 and hypertension suggest a potential role for this gene as a determinant of polygenic blood pressure control in humans. These results are providing conceptually novel approaches for studies of the molecular basis of human hypertension that could lead to new strategies for the early diagnosis and clinical management of this devastating disease.

Vascular cytochrome P450 4A expression and 20-hydroxyeicosatetraenoic acid synthesis contribute to endothelial dysfunction in androgen-induced hypertension

Epidemiological evidence suggests a role for sex-dependent mechanisms in the pathophysiology of hypertension. It has been shown that 5alpha-dihydrotestosterone (DHT) administration (56 mg/kg of body weight per day IP for 14 days) increases blood pressure, cytochrome P450 4A expression, and 20-hydroxyeicosatetraenoic acid synthesis in rats. We examined whether increased vascular 20-hydroxyeicosatetraenoic acid synthesis underlies endothelial dysfunction and hypertension in DHT-treated male Sprague-Dawley rats by using HET0016, a selective cytochrome P450 4A inhibitor. Coadministration of HET0016 (10 mg/kg per day IP for 14 days) to DHT-treated rats markedly reduced DHT-induced interlobar arterial production of 20-hydroxyeicosatetraenoic acid (14.3+/-1.5 versus 1.5+/-0.5 ng/mg of protein per hour; P<0.05), superoxide anion (246+/-47 versus 31+/-8 cpm/microg of protein), and the levels of gp91-phox, p47-phox, and 3-nitrosylated proteins. Moreover, the maximal relaxing response to acetylcholine in phenylephrine-preconstricted renal interlobar arteries from DHT-treated rats (42.8+/-4.8%) significantly (P<0.05) increased in the presence of HET0016 (81.5+/-10.8%). Importantly, the administration of HET0016 negated DHT-induced hypertension; systolic blood pressure was reduced from 146+/-2 mm Hg in DHT-treated rats to 130+/-1 mm Hg (P<0.05). The results strongly implicate vascular cytochrome P450 4A-derived 20-hydroxyeicosatetraenoic acid in the development of androgen-induced endothelial dysfunction and hypertension.

Physiologic and pathophysiologic roles of lipid mediators in the kidney

Small lipids such as eicosanoids exert diverse and complex functions. In addition to their role in regulating normal kidney function, these lipids also play important roles in the pathogenesis of kidney diseases. Cyclooxygenase (COX)-derived prostanoids play important role in maintaining renal function, body fluid homeostasis, and blood pressure. Renal cortical COX2-derived prostanoids, particularly (PGI2) and PGE2 play critical roles in maintaining blood pressure and renal function in volume contracted states. Renal medullary COX2-derived prostanoids appear to have antihypertensive effect in individuals challenged with a high salt diet. 5-Lipoxygenase (LO)-derived leukotrienes are involved in inflammatory glomerular injury. LO product 12-hydroxyeicosatetraenoic acid (12-HETE) is associated with pathogenesis of hypertension, and may mediate angiotensin II and TGFbeta induced mesengial cell abnormality in diabetic nephropathy. P450 hydroxylase-derived 20-HETE is a potent vasoconstrictor and is involved in the pathogenesis of hypertension. P450 epoxygenase derived epoxyeicosatrienoic acids (EETs) have vasodilator and natriuretic effect. Blockade of EET formation is associated with salt-sensitive hypertension. Ceramide has also been demonstrated to be an important signaling molecule, which is involved in pathogenesis of acute kidney injury caused by ischemia/reperfusion, and toxic insults. Those pathways should provide fruitful targets for intervention in the pharmacologic treatment of renal disease.

Mouse Cyp4a isoforms: enzymatic properties, gender- and strain-specific expression, and role in renal 20-hydroxyeicosatetraenoic acid formation

AA (arachidonic acid) hydroxylation to 20-HETE (20-hydroxyeicosatetraenoic acid) influences renal vascular and tubular function. To identify the CYP (cytochrome P450) isoforms catalysing this reaction in the mouse kidney, we analysed the substrate specificity of Cyp4a10, 4a12a, 4a12b and 4a14 and determined sex- and strain-specific expressions. All recombinant enzymes showed high lauric acid hydroxylase activities. Cyp4a12a and Cyp4a12b efficiently hydroxylated AA to 20-HETE with V(max) values of approx. 10 nmol x nmol(-1) x min(-1) and K(m) values of 20-40 microM. 20-Carboxyeicosatetraenoic acid occurred as a secondary metabolite. AA hydroxylase activities were approx. 25-75-fold lower with Cyp4a10 and not detectable with Cyp4a14. Cyp4a12a and Cyp4a12b also efficiently converted EPA (eicosapentaenoic acid) into 19/20-OH- and 17,18-epoxy-EPA. In male mice, renal microsomal AA hydroxylase activities ranged between approx. 100 (NMRI), 45-55 (FVB/N, 129 Sv/J and Balb/c) and 25 pmol x min(-1) x mg(-1) (C57BL/6). The activities correlated with differences in Cyp4a12a protein and mRNA levels. Treatment with 5alpha-dihydrotestosterone induced both 20-HETE production and Cyp4a12a expression more than 4-fold in male C57BL/6 mice. All female mice showed low AA hydroxylase activities (15-25 pmol x min(-1) x mg(-1)) and very low Cyp4a12a mRNA and protein levels, but high Cyp4a10 and Cyp4a14 expression. Renal Cyp4a12b mRNA expression was almost undetectable in both sexes of all strains. Thus Cyp4a12a is the predominant 20-HETE synthase in the mouse kidney. Cyp4a12a expression determines the sex- and strain-specific differences in 20-HETE generation and may explain sex and strain differences in the susceptibility to hypertension and target organ damage.

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.

Nuclear receptors link gender dimorphism of renal disease progression

Profound gender differences in the progression of chronic kidney disease (CKD) remain poorly understood. Differential expression of the genes for male- and female-specific proteins in the kidney has been proposed to account for this clinical phenomenon. Lu and colleagues provide evidence that the signaling pathways of the nuclear receptors ERalpha, AR and PPARalpha are associated with gender differences in CKD progression.

Regulation of human cytochrome P450 4F2 expression by sterol regulatory element-binding protein and lovastatin

This report provides the first evidence that human P450 4F2 (CYP4F2) is induced by statins, which are widely used to treat hypercholesterolemia. Real time PCR and immunoblots indicate that lovastatin treatment increases expression of the endogenous CYP4F2 gene in human primary hepatocytes and HepG2 cells. The effects of lovastatin on gene expression are often mediated through sterol regulatory element-binding proteins (SREBPs). Immunoblots indicate that lovastatin-treated human hepatocytes display increased proteolytic processing of SREBP-2. In HepG2 cells, co-administration of a potent suppressor of SREBP-2 activation, 25-hydroxycholesterol, inhibits CYP4F2 mRNA induction by lovastatin. HepG2 cells transfected with an expression vector for the active nuclear form of SREBP-1a (nSREBP-1a) also display elevated endogenous CYP4F2 expression. Luciferase reporters containing the CYP4F2 proximal promoter are transactivated by nSREBPs (-1a, -1c, and -2) or a dominant positive form of the SREBP cleavage-activating protein (SCAP), which facilitates activation of endogenous SREBPs. Lovastatin-induced reporter expression is inhibited by overexpressed Insig-1, which prevents proteolytic activation of endogenous SREBPs. Electrophoretic mobility shift assays with in vitro translated nSREBP-1a identified two SREBP binding sites at -169/-152 and -109/-92, relative to the CYP4F2 transcription start site. Mutations in each site abolish SREBP binding. Chromatin immunoprecipitation experiments indicate that more SREBP-1 is associated with the CYP4F2 promoter after overexpression of nSREBP-1a. Transfection studies and mutagenesis indicate that the -109/-92 region is the primary site responsible for the effects of statins. Collectively, these results demonstrate that SREBPs transactivate CYP4F2 transcription and that CYP4F2 induction by statins is mediated by SREBP-2.

Compensatory mechanism for homeostatic blood pressure regulation in Ephx2 gene-disrupted mice

Arachidonic acid-derived epoxides, epoxyeicosatrienoic acids, are important regulators of vascular homeostasis and inflammation, and therefore manipulation of their levels is a potentially useful pharmacological strategy. Soluble epoxide hydrolase converts epoxyeicosatrienoic acids to their corresponding diols, dihydroxyeicosatrienoic acids, modifying or eliminating the function of these oxylipins. To better understand the phenotypic impact of Ephx2 disruption, two independently derived colonies of soluble epoxide hydrolase-null mice were compared. We examined this genotype evaluating protein expression, biofluid oxylipin profile, tissue oxylipin production capacity, and blood pressure. Ephx2 gene disruption eliminated soluble epoxide hydrolase protein expression and activity in liver, kidney, and heart from each colony. Plasma levels of epoxy fatty acids were increased, and fatty acid diols levels were decreased, while measured levels of lipoxygenase- and cyclooxygenase-dependent oxylipins were unchanged. Liver and kidney homogenates also show elevated epoxide fatty acids. However, in whole kidney homogenate a 4-fold increase in the formation of 20-hydroxyeicosatetraenoic acid was measured along with a 3-fold increase in lipoxygenase-derived hydroxylation and prostanoid production. Unlike previous reports, however, neither Ephx2-null colony showed alterations in basal blood pressure. Finally, the soluble epoxide hydrolase-null mice show a survival advantage following acute systemic inflammation. The data suggest that blood pressure homeostasis may be achieved by increasing production of the vasoconstrictor, 20-hydroxyeicosatetraenoic acid in the kidney of the Ephx2-null mice. This shift in renal metabolism is likely a metabolic compensation for the loss of the soluble epoxide hydrolase gene.

Cytochrome P450 enzymes: Central players in cardiovascular health and disease

Cardiovascular disease (CVD) is a human health crisis that remains the leading cause of death worldwide. The cytochrome P450 (CYP) class of enzymes are key metabolizers of both xenobiotics and endobiotics. Many CYP enzyme families have been identified in the heart, endothelium and smooth muscle of blood vessels. Furthermore, mounting evidence points to the role of endogenous CYP metabolites, such as epoxyeicosatrienoic acids (EETs), hydroxyeicosatetraenoic acids (HETEs), prostacyclin (PGI(2)), aldosterone, and sex hormones, in the maintenance of cardiovascular health. Emerging science and the development of genetic screening have provided us with information on the differences in CYP expression among populations and groups of individuals. With this information, a link between CYP expression and activity and CVD, such as hypertension, coronary artery disease (CAD), myocardial infarction, heart failure, stroke, and cardiomyopathy and arrhythmias, has been established. In fact many currently used therapeutic modalities in CVD owe their therapeutic efficacy to their effect on CYP metabolites. Thus, the evidence for the involvement of CYP in CVD is numerous. Concentrating on treatment modalities that target the CYP pathway makes ethical sense for the affected individuals and decreases the socioeconomic burden of this disease. However, more research is needed to allow the integration of this information into a clinical setting.

Gender differences in renal nuclear receptors and aryl hydrocarbon receptor in 5/6 nephrectomized rats

This study was aimed at delineating molecular pathways essential in gender-different pathogenesis of chronic kidney diseases (CKD). Renal transcripts of nuclear receptors and metabolic enzymes in male and female kidneys from 5/6 nephrectomized (Nx) rats 7 weeks post-Nx were examined using branched DNA signal amplification assay. Nx-males had marked kidney injury coupled with anemia and malnutrition. Nx-females had moderate renal injury, and were free of albuminuria, anemia, and malnutrition. Nx-males had systemic and renal inflammation, which were largely absent in Nx-females. Blood 17beta-estradiol, testosterone, and corticosterone did not change, whereas urinary testosterone decreased in both genders. Compared to males, female kidneys had higher androgen receptor (AR) and aryl hydrocarbon receptor (AhR) but lower estrogen receptor alpha (ERalpha). Compared to Nx-males, female remnant kidneys had less decreases in ERalpha and peroxisome proliferator-activated receptor alpha (PPARalpha), had no induction of AR and decrease of acyl-CoA oxidase, whereas had induction of cytochrome P450 4a1 (Cyp4a1) but decrease of AhR. Renal protein expression of a 52-kDa isoform of Wilm's tumor 1 (WT1), transcription factor critical in nephrogenesis, decreased dramatically in Nx-males but largely preserved in Nx-females. In conclusion, gender divergences in basal expression and alteration of ERalpha, AR, AhR, WT1, and PPARalpha/Cyp4a1 during CKD may explain gender differences in CKD progression and outcome of renal transplantation.

Cytochrome P450 4F subfamily: at the crossroads of eicosanoid and drug metabolism

The cytochrome P450 4F (CYP4F) subfamily has over the last few years come to be recognized for its dual role in modulating the concentrations of eicosanoids during inflammation as well as in the metabolism of clinically significant drugs. The first CYP4F was identified because it catalyzed the hydroxylation of leukotriene B(4) (LTB(4)) and since then many additional members of this subfamily have been documented for their distinct catalytic roles and functional significance. Recent evidence emerging in relation to the temporal change of CYP4F expression in response to injury and infection supports an important function for these isozymes in curtailing inflammation. Their tissue-dependent expression, isoform-based catalytic competence and unique response to the external stimuli imply a critical role for them to regulate organ-specific functions. From this standpoint variations in relative CYP4F levels in humans may have direct influence on the metabolic outcome through their ability to generate and/or degrade bioactive eicosanoids or therapeutic agents. This review covers the enzymatic characteristics and regulatory properties of human and rodent CYP4F isoforms and their physiological relevance to major pathways in eicosanoid and drug metabolism.

Background gene expression in rat kidney: influence of strain, gender, and diet

In order to gain better insight into factors (strain, gender, and diet) influencing background variability in kidney gene expression, we examined the transcriptomes of male and female Crl:CD(SD)IGSBR (Sprague-Dawley [SD]) and CDF(Fischer 344)/CrlBR rats maintained for 19 days on three different diets (ad libitum [AL], diet restriction-75% of AL, and casein-based phytoestrogen-free diet). Kidney RNA was analyzed using Agilent Rat oligo microarrays (approximately 20,000 genes). Principal component analysis demonstrated that strain and gender have the most impact on the variability in gene expression, while diet had a lesser effect. The majority of the affected genes differed by a magnitude of four-fold or less between strains/gender, with some previously known to be sex-hormone regulated (SLC22A7 and SLC21A1). One gene of particular interest was ornithine decarboxylase, a significant marker of cell proliferation and tumor promotion, which was expressed at an 18-fold greater level in SD rats. Further analysis revealed that the difference in expression was due to the use of an alternate polyadenylation signal resulting in the production of two different sizes of transcripts. These results demonstrate that gender and strain have significant influence on gene expression which could be a confounder when comparing results, especially when it involves predictive fingerprint/patterns.

Gonadectomy prevents endothelial dysfunction in fructose-fed male rats, a factor contributing to the development of hypertension

Insulin resistance has been shown to be associated with increased blood pressure (BP). The sex hormones estrogen and testosterone have opposing effects in the development of increased BP. Since testosterone has been implicated in increased BP following insulin resistance, we have tried to dissect out the effects of insulin resistance on endothelium-dependent vasorelaxation in the presence and absence of testosterone. Both gonadectomized and sham-operated male Wistar rats fed with a high-fructose diet developed insulin resistance, but BP increased only in the sham-operated rats. Reintroduction of testosterone in vivo restored the increase in BP, thereby abolishing the protective effects of gonadectomy. Fructose feeding did not affect plasma testosterone levels. Insulin resistance induced endothelial dysfunction in the mesenteric arteries of sham-operated rats, which was prevented by gonadectomy, thus suggesting a key role for testosterone in the pathogenesis of secondary vascular complications. Subsequent to blocking the actions of endothelium-dependent hyperpolarizing factor (EDHF), relaxation to acetylcholine (ACh) was lower in sham-operated fructose-fed rats compared with other groups, suggesting the involvement of nitric oxide (NO) in vasorelaxation. Inhibition of NO synthesis nearly abolished the ACh-evoked relaxation in both fructose-fed groups, thus suggesting a testosterone-independent impairment of EDHF-mediated relaxation. The improvement in endothelial function following gonadectomy could be ascribed to a NO component, although plasma nitrite and nitrate levels were unchanged. In summary, testosterone is essential in vivo for the development of endothelial dysfunction and hypertension secondary to insulin resistance, suggesting a facilitatory role for testosterone in increasing BP in fructose-fed male rats.

Eicosanoids and renal vascular function in diseases

Arachidonic acid metabolites are vital for the proper control of renal haemodynamics and, when not properly controlled, can contribute to renal vascular injury and end-stage renal disease. Three major enzymatic pathways, COX (cyclo-oxygenase), CYP450 (cytochrome P450) and LOX (lipoxygenase), are responsible for the metabolism of arachidonic acid metabolites to bioactive eicosanoids. These eicosanoids can dilate or constrict the renal vasculature and maintain vascular resistance in the face of changing vasoactive hormones. Renal vascular generation of eicosanoids is altered in pathophysiological conditions such as hypertension, diabetes, metabolic syndrome and acute renal failure. Experimental evidence supports the concept that altered eicosanoid metabolism contributes to renal haemodynamic alterations and the development and progression of nephropathy. The possible beneficial renal vascular actions of enzymatic inhibitors, eicosanoid analogues and receptor antagonists have been examined in hypertension, diabetes and metabolic syndrome. This review highlights the roles of renal vascular eicosanoids in the pathogenesis of nephropathy and therapeutic targets for renal disease related to hypertension, diabetes, metabolic syndrome and acute renal failure.

CYP4A11 is repressed by retinoic acid in human liver cells

CYP4A11, the major fatty acid omega-hydroxylase in human liver is involved in the balance of lipids, but its role and regulation are both poorly understood. We studied the effects of retinoids on the regulation of CYP4A11 in the human hepatoma cell line HepaRG. Treatment of HepaRG cells with all-trans-retinoic acid resulted in a strong decrease in CYP4A11 gene expression and apoprotein content and, furthermore, was associated with a 50% decrease in the microsomal lauric acid hydroxylation activity. Such a strong suppression of CYP4A11 expression by retinoids could have a major impact on fatty acid metabolism in the liver.

Salt-sensitive hypertension is associated with dysfunctional Cyp4a10 gene and kidney epithelial sodium channel

Functional and biochemical data have suggested a role for the cytochrome P450 arachidonate monooxygenases in the pathophysiology of hypertension, a leading cause of cardiovascular, cerebral, and renal morbidity and mortality. We show here that disruption of the murine cytochrome P450, family 4, subfamily a, polypeptide 10 (Cyp4a10) gene causes a type of hypertension that is, like most human hypertension, dietary salt sensitive. Cyp4a10-/- mice fed low-salt diets were normotensive but became hypertensive when fed normal or high-salt diets. Hypertensive Cyp4a10-/- mice had a dysfunctional kidney epithelial sodium channel and became normotensive when administered amiloride, a selective inhibitor of this sodium channel. These studies (a) establish a physiological role for the arachidonate monooxygenases in renal sodium reabsorption and blood pressure regulation, (b) demonstrate that a dysfunctional Cyp4a10 gene causes alterations in the gating activity of the kidney epithelial sodium channel, and (c) identify a conceptually novel approach for studies of the molecular basis of human hypertension. It is expected that these results could lead to new strategies for the early diagnosis and clinical management of this devastating disease.

Endothelial Dysfunction and Hypertension in Rats Transduced With CYP4A2 Adenovirus

Vascular cytochrome P450 (CYP) 4A enzymes catalyze the synthesis of 20-hydroxyeicosatetraenoic acid (20-HETE), an eicosanoid which participates in the regulation of vascular tone by sensitizing the smooth muscle cells to constrictor and myogenic stimuli. This study was undertaken to investigate the consequences of CYP4A overexpression on blood pressure and endothelial function in rats treated with adenoviral vectors carrying the CYP4A2 construct. Intravenous injection of Adv-CYP4A2 increased blood pressure (from 114+/-1 to 133+/-1 mm Hg, P<0.001), and interlobar renal arteries from these rats displayed decreased relaxing responsiveness to acetylcholine, which was offset by treatment with an inhibitor of CYP4A. Relative to data in control rats, arteries from Adv-CYP4A2-transduced rats produced more 20-HETE (129+/-10 versus 97+/-7 pmol/mg protein, P<0.01) and less nitric oxide (NO; 4.2+/-1.6 versus 8.4+/-1 nmol nitrite+nitrate/mg; P<0.05). They also displayed higher levels of oxidative stress as measured by increased generation of superoxide anion and increased expression of nitrotyrosine and gp91phox. Collectively, these findings demonstrate that augmentation in vascular 20-HETE promotes the development of hypertension and causes endothelial dysfunction, a condition characterized by decreased NO synthesis and/or bioavailability, imbalance in the relative contribution of endothelium-derived relaxing and contracting factors, and enhanced endothelial activation.

Cytochrome P450 Cyp4x1 is a major P450 protein in mouse brain

A novel cytochrome P450, CYP4x1, was identified in EST databases on the basis of similarity to a conserved region in the C-helix of the CYP4A family. The human and mouse CYP4x1 cDNAs were cloned and found to encode putative cytochrome P450 proteins. Molecular modelling of CYP4x1 predicted an unusual substrate binding channel for the CYP4 family. Expression of human CYP4x1 was detected in brain by EST analysis, and in aorta by northern blotting. The mouse cDNA was used to demonstrate that the Cyp4x RNA was expressed principally in brain, and at much lower levels in liver; hepatic levels of the Cyp4x1 RNA were not affected by treatment with the inducing agents phenobarbital, dioxin, dexamethasone or ciprofibrate, nor were the levels affected in PPARalpha-/- mice. A specific antibody for Cyp4x1 was developed, and shown to detect Cyp4x1 in brain; quantitation of the Cyp4x1 protein in brain demonstrated approximately 10 ng of Cyp4x1 protein.mg(-1) microsomal protein, showing that Cyp4x1 is a major brain P450. Immunohistochemical localization of the Cyp4x1 protein in brain showed specific staining of neurons, choroids epithelial cells and vascular endothelial cells. These data suggest an important role for Cyp4x1 in the brain.

Kidney Dysfunction and Hypertension: Role for Cadmium, P450 and Heme Oxygenases?

Cadmium (Cd) is a metal toxin of continuing worldwide concern. Daily intake of Cd, albeit in small quantities, is associated with a number of adverse health effects which are attributable to distinct pathological changes in a variety of tissues and organs. In the present review, we focus on its renal tubular effects in people who have been exposed environmentally to Cd at levels below the provisional tolerable intake level set for the toxin. We highlight the data linking such low-level Cd intake with tubular injury, altered abundance of cytochromes P450 (CYPs) in the kidney and an expression of a hypertensive phenotype. We provide updated knowledge on renal and vascular effects of the eicosanoids 20-hydroxyeicosatetraenoic acid (20-HETE) and eicosatrienoic acids (EETs), which are biologically active metabolites from arachidonate metabolism mediated by certain CYPs in the kidney. We note the ability of Cd to elicit "oxidative stress" and to alter metal homeostasis notably of zinc which may lead to augmentation of the defense mechanisms involving induction of the antioxidant enzyme heme oxygenase-1 (HO-1) and the metal binding protein metallothionein (MT) in the kidney. We hypothesize that renal Cd accumulation triggers the host responses mediated by HO-1 and MT in an attempt to protect the kidney against injurious oxidative stress and to resist a rise in blood pressure levels. This hypothesis predicts that individuals with less active HO-1 (caused by the HO-1 genetic polymorphisms) are more likely to have renal injury and express a hypertensive phenotype following chronic ingestion of low-level Cd, compared with those having more active HO-1. Future analytical and molecular epidemiologic research should pave the way to the utility of induction of heme oxygenases together with dietary antioxidants in reducing the risk of kidney injury and hypertension in susceptible people.

Role of 20-hydroxyeicosatetraenoic acid (20-HETE) in vascular system

Cytochrome P450s (P450) metabolize arachidonic acid (AA) to hydroxyeicosatetraenoic acids (HETEs) and epoxyeicosatrienoic acids (EETs). Among these eicosanoids, 20-HETE is formed in a tissue and cell-specific fashion and plays an important role in the regulation of vascular tone in the brain, kidney, heart and splanchnic beds. 20-HETE is a potent vasoconstrictor produced in vascular smooth muscle (VSM) cells. It depolarizes VSM by blocking the open-state probability of Ca2+-activated K+-channels. Inhibitors of the formation of 20-HETE block the myogenic response of renal and cerebral arterioles in vitro and autoregulation of renal and cerebral blood flow in vivo. The formation of 20-HETE in vascular smooth muscle is stimulated by angiotensin II, endothelin and norepinephrine and is inhibited by nitric oxide (NO). 20-HETE also stimulates mitogenic and angiogenic responses in vitro and in vivo. Changes in the production of 20-HETE have been observed in ischemic cerebrovascular diseases, cardiac ischemia-reperfusion injury, kidney diseases, hypertension, diabetes, uremia, toxemia of pregnancy. The physiological and pathophysiological role of 20-HETE in the regulation of vascular tone are being revealed by the use of newly developed inhibitors of the synthesis of 20-HETE and 20-HETE analogs. The present review summarizes recent findings implicating a critical role for 20-HETE in altering cardiovascular function in a variety of pathological conditions.

Renal and hepatic accumulation of cadmium and lead in the expression of CYP4F2 and CYP2E1

The present study examined accumulation of the metal toxins cadmium (Cd) and lead (Pb) in relation to the abundance of cytochrome P450 4F2 (CYP4F2), CYP2E1 and concentrations of zinc and copper in liver and kidney samples using immunoblotting coupled with metal analysis. The post mortem liver and kidney cortex samples were from 23 males and 8 females aged 3-89 years. All were Caucasians who had not been exposed to metals in the workplace. Average kidney cortex Cd load of 17.4 microg/g w.w. was 17 times greater than average liver Cd load (1.1 microg/g w.w.). In contrast, average kidney cortex Pb load of 0.09 microg/g w.w. was two times lower than liver Pb load of 0.19 microg/g w.w. Average Zn and Cu concentrations in the kidney cortex samples were 67% and 33% lower than those in the liver. Liver and kidney Cd loads, but not liver or kidney Pb loads, correlated positively with donors' age. After controlling for liver Cd load, an inverse correlation was seen between Zn and age (partial r=-0.39, P=0.02), suggesting reduction in liver Zn levels in old age. Liver CYP2E1 protein abundance correlated with age-adjusted Cd load (partial r=0.37, P=0.02) whereas kidney CYP4F2 protein abundance showed a positive correlation with age-adjusted Cd loads (partial r=0.40, P=0.02). These findings suggest that Cd may be an inducer of renal CYP4F2 and hepatic CYP2E1 and that increased renal CYP4F2 expression may implicate in Cd-linked renal tubular dysfunction and high blood pressure, involving CYP4F2-dependent arachidonic acid metabolism.

Association of the T8590C polymorphism of CYP4A11 with hypertension in the MONICA Augsburg echocardiographic substudy

Genetic variants of the arachidonic acid monooxygenase CYP4A11 result in decreased synthesis of 20-hydroxyeicostatetraenoic acid and experimental hypertension. Moreover, in humans, the T8590C polymorphism of CYP4A11 displayed association with arterial hypertension. The aim of the present study was to further investigate this association in a large population-based sample. Therefore, the participants of the echocardiographic substudy of the third MONICA (MONitoring trends and determinants In CArdiovascular disease) survey (n=1397) were studied by standardized anthropometric, echocardiographic, and biochemical measurements as well as genotyping for CYP4A11 T8590C allele status. Individuals with the CC genotype have higher systolic (CC 141.4+/-3.17 mm Hg versus CT 134.2+/-0.97 mm Hg and TT 134.3+/-0.53 mm Hg; P=0.03) and diastolic blood pressure levels (CC 85.4+/-2.06 mm Hg versus CT 80.3+/-0.63 mm Hg and TT 80.7+/-0.34 mm Hg; P=0.02). Accordingly, the odds ratio (adjusted for age, body mass index, and gender) of the CC genotype versus the CT and TT genotypes for hypertension was 3.31 (95% confidence interval [CI]), 1.38 to 7.96; P=0.016) in the entire study population, with similar trends in men (4.30 [95% CI, 1.08 to 17.15]) and women (2.93 [95% CI, 0.88 to 9.84]). Consistent with the renal effects of the gene, no blood pressure-independent association between the T8590C polymorphism and echocardiographic parameters of left ventricular function and geometry was found. In conclusion, our data strengthen the association between the T8590C polymorphism of CYP4A11 and hypertension and suggest a recessive mode of inheritance. In contrast, we found no blood pressure-independent modulatory effect of CYP4A11 T8590C on cardiac size, structure, and function.

Renal localization, expression, and developmental regulation of P450 4F cytochromes in three substrains of spontaneously hypertensive rats

Cytochrome P450 4F isoforms have been shown to metabolize arachidonic acid to generate 20-hydroxyeicosatetraenoic acid (20-HETE), a potent eicosanoid that modulates vascular tone and renal tubular function. 20-HETE production in the kidney is implicated in the development of essential hypertension in the spontaneously hypertensive rat (SHR). In this study, we determined CYP4F mRNA localization and distribution in rat liver and kidney by in situ hybridization and real time quantitative PCR. CYP4Fs are regionally distributed in the kidney with CYP4F1, 4F4, and 4F5 being expressed more in the renal cortex than medulla while CYP4F6 shows higher medullary expression. We investigated developmental CYP4F gene expression in three different substrains of SHR. Distinct age-dependent patterns of expression were seen for individual CYP4F isoforms in Wistar-Kyoto (WKY) and three SHR substrains (B2, C, and A3). A steady increase in CYP4F1 expression with age was seen in each of the three substrains which correlate well with increased 20-HETE levels and elevated blood pressure seen in these animals. CYP4F4 expression increased significantly at 8 weeks followed by a precipitous fall in WKY and A3 strains at 12 weeks of age. In strains B2 and C, CYP4F4 levels started declining as early as 8 weeks of age. CYP4F5 and 4F6 levels fluctuated with age in a biphasic manner with a different profile for each sub-strain. Based on the expression profile and catalytic activity, CYP4F1 seems to be the most critical 4F isoform involved in the production of 20-HETE in the SHR kidney.

Cytochrome p450 enzymes and cardiovascular disease

The cytochrome p450 (CYP) superfamily is responsible for the oxidation, peroxidation, and (or) reduction of vitamins, steroids, xenobiotics, and the majority of cardiovascular drugs in an oxygen- and NADPH-dependent manner. Although hepatic CYP have been studied extensively, the role of CYP in cardiovascular physiology and disease is poorly understood. Increasing evidence suggests that these enzymes play an important role in the pathogenesis of a number of cardiovascular diseases. The current review summarizes the understanding as to the role that dysregulated CYP expression and (or) activity may play in the onset and progression of cardiovascular disease.