Cytochrome P-450 Under Pressure

The association between CYP1A1 genetic polymorphisms and coronary artery disease in the Uygur and Han of China

Background

The cytochrome P450, family 1, subfamily A, polypeptide 1 (CYP1A1) gene is expressed in the vascular endothelium, which metabolizes arachidonic acid into 20-hydroxyeicosatetraenoic acid (20-HETE) and epoxyeicosatrienoic acids (EETs). 20-HETE mediates cardiovascular homeostasis and growth response in vascular smooth muscle cells (VSMCs) as well as the anti-platelet effect. EETs are potent endogenous vasodilators and inhibitors of vascular inflammation. This study assessed the association between human CYP1A1 gene polymorphisms and coronary artery disease (CAD) in the Uygur and Han in China.

Methods

Two independent case–control studies that recruited Han (389 patients with CAD and 411 controls) and Uygur participants (293 patients with CAD and 408 controls) analyzed the relationship between CYP1A1 single nucleotide polymorphisms (SNPs: rs4886605, rs12441817, rs4646422 and rs1048943) and CAD. All patients with CAD and controls were genotyped for the four SNPs of CYP1A1 using TaqMan SNP genotyping assays.

Results

In the Uygur group, the distribution of the dominant model(CC vs CT + TT) of rs4886605 for the total sample and the males was significantly different between CAD patients and control participants (P = 0.001 and P = 0.012, respectively), The difference remained significant after a multivariate adjustment (P = 0.018, P = 0.015, respectively). The rs12441817 was also associated with CAD in a dominant model for all participants (P = 0.003) and men (P = 0.012), and the difference remained significant after a multivariate adjustment (P = 0.016, P = 0.002, respectively). However, we did not observe differences in the Uygur females and Han group with regard to the allele frequency or genotypic distribution of rs4886605 and rs12441817 between patients with CAD and control participants. Patients with CAD did not significantly differ from the control participants with regard to the distributions of rs4646422 and rs1048943 genotypes, the dominant model, the recessive model, or allele frequency in the Han and Uygur groups.

Conclusion

Both rs4886605 and rs12441817 SNPs of the CYP1A1 gene are associated with CAD in the Uygur population of China.

Ancestral genetic complexity of arachidonic acid metabolism in Metazoa

Eicosanoids play an important role in inducing complex and crucial physiological processes in animals. Eicosanoid biosynthesis in animals is widely reported; however, eicosanoid production in invertebrate tissue is remarkably different to vertebrates and in certain respects remains elusive. We, for the first time, compared the orthologs involved in arachidonic acid (AA) metabolism in 14 species of invertebrates and 3 species of vertebrates. Based on parsimony, a complex AA-metabolic system may have existed in the common ancestor of the Metazoa, and then expanded and diversified through invertebrate lineages. A primary vertebrate-like AA-metabolic system via cyclooxygenase (COX), lipoxygenase (LOX), and cytochrome P450 (CYP) pathways was further identified in the basal chordate, amphioxus. The expression profiling of AA-metabolic enzymes and lipidomic analysis of eicosanoid production in the tissues of amphioxus supported our supposition. Thus, we proposed that the ancestral complexity of AA-metabolic network diversified with the different lineages of invertebrates, adapting with the diversity of body plans and ecological opportunity, and arriving at the vertebrate-like pattern in the basal chordate, amphioxus.

Targeted mutation of SLC4A5 induces arterial hypertension and renal metabolic acidosis

The human SLC4A5 gene has been identified as a hypertension susceptibility gene based on the association of single nucleotide polymorphisms with blood pressure (BP) levels and hypertension status. The biochemical basis of this association is unknown particularly since no single gene variant was linked to hypertension in humans. SLC4A5 (NBCe2, NBC4) is expressed in the collecting duct of the kidney and acts as an electrogenic ion-transporter that transports sodium and bicarbonate with a 1:2 or 1:3 stoichiometry allowing bicarbonate reabsorption with relatively minor concurrent sodium uptake. We have mutated the Slc4a5 gene in mice, which caused a persistent increase in systolic and diastolic BP. Slc4a5 mutant mice also displayed a compensated metabolic acidosis and hyporeninemic hypoaldosteronism. Analysis of kidney physiology revealed elevated fluid intake and urine excretion and increased glomerular filtration rate. Transcriptome analysis uncovers possible compensatory mechanisms induced by SLC4A5 mutation, including upregulation of SLC4A7 and pendrin as well as molecular mechanisms associated with hypertension. Induction of metabolic alkalosis eliminated the BP difference between wild-type and Slc4a5 mutant mice. We conclude that the impairment of the function of SLC4A5 favors development of a hypertensive state. We reason that the loss of sodium-sparing bicarbonate reabsorption by SLC4A5 initiates a regulatory cascade consisting of compensatory bicarbonate reabsorption via other sodium-bicarbonate transporters (e.g. SLC4A7) at the expense of an increased sodium uptake. This will ultimately raise BP and cause hypoaldosteronism, thus providing a mechanistic explanation for the linkage of the SLC4A5 locus to hypertension in humans.

Study on the association between environmental cadmium exposure, cytochrome P450-mediated 20-HETE, heme-oxygenase-1 polymorphism and hypertension in Thai population residing in a malaria endemic areas with cadmium pollution

The aims of the study were to investigate (i) the effects of environmental cadmium (Cd) on hypertension, biological markers of renal dysfunction and renal cytochrome P450-mediated arachidonate metabolism; and (ii) the association between genetic polymorphism of heme oxygenase-1 (HO-1) and hypertension and Cd-induced renal injury in the exposed Thai population. The study was conducted in adult subjects residing in Cd-contaminated malaria endemic areas of Mae Sot District, Thailand. All subjects were randomly selected and consistently distributed for sex, age and residential areas. Blood and urinary Cd levels were not significantly different between the case (hypertensive) and control (matched-pair normotensive) groups. While other renal dysfunction biomarkers were comparable between the two groups, urinary microalbumin, urinary 20-hydroxy-5,8,11,14-eicosatetraenoic acid (20-HETE) and serum creatinine were siginificantly higher in the hypertensive group. Only N-acetyl-β-glucosaminidase (NAG) showed positive correlation with Cd in hypertensive and normotensive group. With respect to heme oxygenase-1 (HO-1) polymorphism, the frequencies of (GT)(n) alleles were similar in both case and control groups. The frequency of SL genotype was significantly higher in the control group, whereas the frequency of ML genotype was significantly higher in the case group. Although no significant difference between 20-HETE and NAG levels in various HO-1 genotypes was found, a trend of increase in 20-HETE and NAG levels was observed in subjects carrying longer (GT)(n) repeats. Results from the present study provide no clear evidence on the direct effects of environmental Cd on high blood pressure development in the non-occupational exposed Thai population. Furthermore, the indirect effect of Cd through HO-1 (genetic polymorphism and prevalence of long GT(n) repeats) and 20-HETE was inconclusive. Based on the data obtained in the present investigation further studies should be performed which use a larger sample size and effectively control for confounding. This should provide more definitive evidence of the relationship between Cd exposure and high blood pressure.

Interaction of nitric oxide and the cytochrome P-450 system on blood pressure and renal function in the rat: dependence on sodium intake

AIM

Interaction was examined of nitric oxide (NO) and cytochrome P-450 (CYP-450)-dependent arachidonic acid derivatives, 20-HETE and EETs, in control of arterial pressure (MABP) and renal function. Modification of this interaction by changing sodium intake was also studied.

METHODS

On low, standard or high Na diet (LS, STD and HS rats respectively) effects of sequential blockade of NO synthases (NOS) and CYP-450 enzyme activity on MABP, renal blood flow (RBF, Transonic probe), renal medullary perfusion (MBF, laser-Doppler technique), medullary tissue NO (selective electrode) and renal excretion were examined in anaesthetized rats. All NOS were blocked with N(ϖ) -nitro-l-arginine methyl ester (l-NAME), the neuronal NOS with S-methyl-l-thiocitrulline (SMTC), and CYP-450 with 1-aminobenzotriazole (ABT).

RESULTS

In each diet group the baseline MABP was highest in rats pre-treated with l-NAME. CYP-450 inhibition significantly decreased MABP only in LS (-9%) and HS rats (-22%) pre-treated with l-NAME. This MABP decrease correlated directly with the dietary sodium content (r = 0.644, P < 0.001). CYP-450 inhibition decreased RBF in LS and HS rats (not in HS pre-treated with l-NAME). Acute exclusion of CYP-450 significantly increased MBF only in STD, SMTC pre-treated rats; in HS group it significantly increased medullary tissue NO by about 1.0 nA. The post-ABT changes in renal excretion occurred in LS and HS rats, irrespective of the status of NO synthesis.

CONCLUSIONS

Both NO- and CYP-450-dependent agents contribute to blood pressure and kidney function control, however, the role of 20-HETE and EETs becomes crucial only under conditions of high sodium intake or after NOS inhibition.

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.

Thematic Review Series: Proteomics. An integrated omics analysis of eicosanoid biology

Eicosanoids have been implicated in a vast number of devastating inflammatory conditions, including arthritis, atherosclerosis, pain, and cancer. Currently, over a hundred different eicosanoids have been identified, with many having potent bioactive signaling capacity. These lipid metabolites are synthesized de novo by at least 50 unique enzymes, many of which have been cloned and characterized. Due to the extensive characterization of eicosanoid biosynthetic pathways, this field provides a unique framework for integrating genomics, proteomics, and metabolomics toward the investigation of disease pathology. To facilitate a concerted systems biology approach, this review outlines the proteins implicated in eicosanoid biosynthesis and signaling in human, mouse, and rat. Applications of the extensive genomic and lipidomic research to date illustrate the questions in eicosanoid signaling that could be uniquely addressed by a thorough analysis of the entire eicosanoid proteome.

CYP1B1 expression promotes the proangiogenic phenotype of endothelium through decreased intracellular oxidative stress and thrombospondin-2 expression

Reactive species derived from cell oxygenation processes play an important role in vascular homeostasis and the pathogenesis of many diseases including retinopathy of prematurity. We show that CYP1B1-deficient (CYP1B1(-/-)) mice fail to elicit a neovascular response during oxygen-induced ischemic retinopathy. In addition, the retinal endothelial cells (ECs) prepared from CYP1B1(-/-) mice are less adherent, less migratory, and fail to undergo capillary morphogenesis. These aberrant cellular responses were completely reversed when oxygen levels were lowered or an antioxidant added. CYP1B1(-/-) ECs exhibited increased oxidative stress and expressed increased amounts of the antiangiogenic factor thrombospondin-2 (TSP2). Increased lipid peroxidation and TSP2 were both observed in retinas from CYP1B1(-/-) mice and were reversed by administration of an antioxidant. Reexpression of CYP1B1 in CYP1B1(-/-) ECs resulted in down-regulation of TSP2 expression and restoration of capillary morphogenesis. A TSP2 knockdown in CYP1B1(-/-) ECs also restored capillary morphogenesis. Thus, CYP1B1 metabolizes cell products that modulate intracellular oxidative stress, which enhances production of TSP2, an inhibitor of EC migration and capillary morphogenesis. Evidence is presented that similar changes occur in retinal endothelium in vivo to limit neovascularization.

The molecular sources of reactive oxygen species in hypertension

In both animal models and humans, increased blood pressure has been associated with oxidative stress in the vasculature, i.e. an excessive endothelial production of reactive oxygen species (ROS), which may be both a cause and an effect of hypertension. In addition to NADPH oxidase, the best characterized source of ROS, several other enzymes may contribute to ROS generation, including nitric oxide synthase, lipoxygenases, cyclo-oxygenases, xanthine oxidase and cytochrome P450 enzymes. It has been suggested that also mitochondria could be considered a major source of ROS: in situations of metabolic perturbation, increased mitochondrial ROS generation might trigger endothelial dysfunction, possibly contributing to the development of hypertension. However, the use of antioxidants in the clinical setting induced only limited effects on human hypertension or cardiovascular endpoints. More clinical studies are needed to fully elucidate this so called "oxidative paradox" of hypertension.

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.

Genetic polymorphisms and haplotype structures of the CYP4A22 gene in a Japanese population

The CYP4A fatty acid monooxygenases oxidize endogenous arachidonic acid to 20-hydroxyeicosatetraenoic acid that acts as a regulator of blood pressure. Among the isoforms of the CYP4A subfamily, the human CYP4A22 was recently identified. In this study, we report the comprehensive investigation of polymorphisms in the CYP4A22 gene. To investigate genetic variation in CYP4A22 in 191 Japanese subjects, we used denaturing HPLC (DHPLC) and direct sequencing. Our investigation has enabled the identification of 13 sequence variations in the CYP4A22 coding region, thereby demonstrating for the first time that this gene is subject to polymorphism. Two of these sequence variations correspond to silent mutations located in exons 8 (His323His) and 9 (Gly390Gly). Nine of these sequence variations correspond to missense mutations located in exons 1 (Arg11Cys), 3 (Arg126Trp), 4 (Gly130Ser and Asn152Tyr), 5 (Val185Phe), 6 (Cys231Arg), 7 (Lys276Thr), 10 (Leu428Pro), and 12 (Leu509Phe). One of these sequence variations corresponds to nonsense mutations located in exon 9 (Gln368stop). The 13th mutation corresponds to a nucleotide deletion (G7067del) that causes a frameshift and consequently results in a stop codon 80 nucleotides downstream. In addition to the wild-type CYP4A22*1 allele, 20 variants, namely CYP4A22*2-15, were characterized by haplotype analysis. Based on these data, we concluded that allelic variants of the human CYP4A22 gene exist and speculated that some of these variants may be functionally relevant.

CYP1A in TCDD toxicity and in physiology-with particular reference to CYP dependent arachidonic acid metabolism and other endogenous substrates

Toxicologic and physiologic roles of CYP1A enzyme induction, the major biochemical effect of aryl hydrocarbon receptor activation by TCDD and other receptor ligands, are unknown. Evidence is presented that CYP1A exerts biologic effects via metabolism of endogenous substrates (i.e., arachidonic acid, other eicosanoids, estrogens, bilirubin, and melatonin), production of reactive oxygen, and effects on K(+) and Ca(2+) channels. These interrelated pathways may connect CYP1A induction to TCDD toxicities, including cardiotoxicity, vascular dysfunction, and wasting. They may also underlie homeostatic roles for CYP1A, especially when transiently induced by common chemical exposures and environmental conditions (i.e., tryptophan photoproducts, dietary indoles, and changes in oxygen tension).