Constitutive expression and inducibility of CYP1A1 in the H9c2 rat cardiomyoblast cells

Gene-gene interaction between PPARG and CYP1A1 gene on coronary artery disease in the Chinese Han Population

AIMS

To observe the influence of the peroxisome proliferator-activator receptor-G (PPAR-G) gene and cytochrome P4501A1 (CYP1A1) single-nucleotide polymorphisms (SNPs), and interactions among several SNPs on coronary artery disease (CAD) risk.

METHODS

A total of 1106 participants (including 583 males and 523 females) including 550 CAD patients and 556 control subjects were recruited in this study, and the mean age for these participants was 55.5 ± 11.8 years old. Logistic regression was used to observe association of SNP within PPARG and CYP1A1 with CAD risk and GMDR model was used to screen the best interaction combinations.

RESULTS

CAD susceptibility was higher in those with homozygous mutant of rs10865710, rs1805192 and rs4646903 than those with wild-type homozygotes, OR (95%CI) were 1.47 (1.15-1.92), 1.69 (1.27-2.09) and 1.72 (1.35-2.32), respectively. We also found a significant two-locus model involving rs1805192 and rs4646903 (p = 0.0107), and the cross-validation consistency of this locus model was 10 of 10, the testing accuracy of this model is 62.17%. Logistic regression shown that CAD risk was the highest in those with rs1805192- Pro/Ala or Ala/Ala and rs4646903- AG+GG genotype, and was lowest in those with rs1805192- Pro/ Pro and rs4646903- AA genotype, OR(95%CI) = 3.56 (1.91-5.42).

CONCLUSIONS

Polymorphism in rs10865710, rs1805192 and rs4646903 and interaction between rs1805192 and rs4646903 were related with increased CAD susceptibility.

Mechanisms of 2,3,7,8-tetrachlorodibenzo-p-dioxin- induced cardiovascular toxicity: An overview

2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) is an environmental contaminant and its toxicity is mediated by the aryl hydrocarbon receptor (AHR). Mechanisms of TCDD cardiovascular toxicity consist of oxidative stress, growth factor modulation, and ionic current alteration. It is indicated that the rodent cardiovascular system is a target for TCDD cardiomyopathy. Here, our understanding of TCDD cardiovascular toxicity is reviewed.

Mitochondrial activity and oxidative stress functions are influenced by the activation of AhR-induced CYP1A1 overexpression in cardiomyocytes

There is an endemic cardiomyopathy currently occurring in China, termed, Keshan disease (KD). The authors previously compared mitochondrial-associated gene expression profiles of peripheral blood mononuclear cells (PBMCs) derived from KD patients and normal controls, using mitochondria-focused cDNA microarray technology. The results detected an upregulation of the enzyme-associated CYP1A1 gene, (ratios ≥2.0). The aryl hydrocarbon receptor (AhR) regulates the expression of numerous cytochrome P450 (CYP) genes including members of the CYP1 family; CYP1A1 and CYP1A2. Several previous studies have suggested roles for the aryl hydrocarbon receptor (AhR) and the genes that it regulates. An example involves cytochrome P4501A1 (CYP1A1), in the pathogenesis of heart failure, cardiac hypertrophy and other cardiomyopathies. Mitochondria comprise ~30% of the intracellular volume in mammalian cardiomyocytes, and subtle alterations in mitochondria can markedly influence cardiomyopathies. The present study investigated alterations in the activity and functions of mitochondria following AhR-induced overexpression of CYP1A1. AC16 cells were treated with the CYP1A1 inducer 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), and cytotoxicity was then evaluated in MTT assays. Reverse transcription-quantitative polymerase chain reactions, western blot analysis and 7-ethoxyresorufin O-deacylase assays were performed to analyze the mRNA and protein levels, and the enzymatic activity of CYP1A1. Mitochondrial activity and mass were analyzed using an inverted fluorescence microscope and a fluorescence microplate reader. Reactive oxygen species (ROS) activity was analyzed using flow cytometry. The results of the current study demonstrated that TCDD gradually increased mRNA and protein levels of AhR and CYP1A1, in addition to the enzymatic activity. Mitochondrial activity and the quality of mitochondrial membranes were also significantly attenuated, and mitochondrial ROS levels were elevated in the TCDD-induced cardiomyocytes. The results indicate the involvement of the AhR/CYP1A1 signaling pathway in the mechanism of action of TCDD in human cardiomyocytes. The present findings may provide an explanation for myocardial injuries caused by polycyclic aromatic hydrocarbons. The authors conclude that exposure to TCDD results in regulatory alteration to the expression of detoxification genes that ultimately affect the metabolic activation and function of cardiomyocytes.

β-Naphthoflavone induces oxidative stress in the intertidal copepod, Tigriopus japonicus

β-Naphtoflavone (β-NF) is a flavonoid and enhances oxidative stress in vertebrates with little information from aquatic invertebrates as yet. In this study, we investigated the effects of β-NF on the antioxidant defense systems of the intertidal copepod Tigriopus japonicus. To measure the β-NF-triggered changes in oxidative stress markers, such as intracellular reactive oxygen species (ROS), glutathione (GSH) concentration, residual glutathione S-transferase (GST), glutathione peroxidase (GPx), glutathione reductase (GR), and superoxide dismutase (SOD) activity, T. japonicus were exposed to β-NF (0.5 and 1 mg/L) for 72 h. Significant (P < 0.05) induction of the intracellular ROS content (%) was observed in 1 mg/L of β-NF exposed T. japonicus, compared to the negative control and H2O2-exposed group. The GSH levels were significantly increased in the 0.5 mg/L of β-NF-exposed group for 12 h and 1 mg/L of β-NF-exposed groups for 12-24 h. GPx, GST, and GR activities showed a significant increase in the 1 mg/L β-NF-exposed group, indicating that β-NF induces oxidative stress in T. japonicus. To understand the effects of β-NF at the level of transcript expression, a 6K microarray analysis was employed. Transcript profiles of selected antioxidant-related genes were modulated after 72 h exposure to 1 mg/L of β-NF. From microarray data, 10 GST isoforms, GR, GPx, PH-GPx, and Se-GPx were chosen for a time-course test by real-time RT-PCR. T. japonicus GST-S, GST-O, GST-M, and GST-D1 were significantly increased in a 1 mg/L β-NF-exposed group. T. japonicus GPx, GR, and Se-GPx mRNA levels were also significantly increased at both concentrations. Our results revealed that oxidative stress was induced by β-NF exposure in T. japonicus.

Human fetal ventricular cardiomyocyte, RL-14 cell line, is a promising model to study drug metabolizing enzymes and their associated arachidonic acid metabolites

INTRODUCTION

RL-14 cells, human fetal ventricular cardiomyocytes, are a commercially available cell line that has been established from non-proliferating primary cultures derived from human fetal heart tissue. However, the expression of different drug metabolizing enzymes (DMEs) in RL-14 cells has not been elucidated yet. Therefore, the main objectives of the current work were to investigate the capacity of RL-14 cells to express different cytochrome P450 (CYP) isoenzymes and correlate this expression to primary cardiomyocytes.

METHODS

The expression of CYP isoenzymes was determined at mRNA, protein and catalytic activity levels using real time-PCR, Western blot analysis and liquid chromatography-electron spray ionization-mass spectrometry (LC-ESI-MS), respectively.

RESULTS

Our results showed that RL-14 cells constitutively express CYP ω-hydroxylases, CYP1A, 1B, 4A and 4F; CYP epoxygenases, CYP2B, 2C and 2J; in addition to soluble epoxide hydrolayse (EPHX2) at mRNA and protein levels. The basal expression of CYP ω-hydroxylases, epoxygenases and EPHX2 was supported by the ability of RL-14 cells to convert arachidonic acid to its biologically active metabolites, 20-hydroxyeicosatetraenoic acids (20-HETEs), 14,15-epoxyeicosatrienoic acids (14,15-EET), 11,12-EET, 8,9-EET, 5,6-EET, 14,15-dihydroxyeicosatrienoic acid (14,15-DHET), 11,12-DHET, 8,9-DHET and 5,6-DHET. Furthermore, RL-14 cells express CYP epoxygenases and ω-hydroxylase at comparable levels to those expressed in adult and fetal human primary cardiomyocytes cells implying the importance of RL-14 cells as a model for studying DMEs in vitro. Lastly, different CYP families were induced in RL-14 cells using 2,3,7,8-tetrachlorodibenzo-p-dioxin and fenofibrate at mRNA and protein levels.

DISCUSSION

The current study provides the first evidence that RL-14 cells express CYP isoenzymes at comparable levels to those expressed in the primary cells and thus offers a unique in vitro model to study DMEs in the heart.

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.

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.

2,3,7,8-Tetrachlorodibenzo-p-dioxin and beta-naphthoflavone induce cellular hypertrophy in H9c2 cells by an aryl hydrocarbon receptor-dependant mechanism

Cigarette smoke is a major risk factor for cardiovascular diseases. It contains thousands of compounds that activate the aryl hydrocarbon receptor (AhR). In addition, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), the most potent AhR ligand, has been shown to cause cardiotoxic effects in several in vivo models. Although induction of CYP1 family is the most important effect of AhR activation, the role of CYP1 induction in mediating the cardiotoxic effect of TCDD is usually overlooked. Therefore, we investigated whether AhR activation causes a hypertrophic effect in H9c2 cells and we related this effect to changes in CYP gene expression. In the current study, the cardiac derived H9c2 cells were treated with two AhR ligands, TCDD and beta-naphthoflavone (BNF), for 24 and 48h. The expression of the hypertrophic markers, atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP), and several CYP genes were measured by real-time PCR. Treatment of H9c2 cells with TCDD or BNF for 24h caused a significant induction of CYP1A1, CYP1B1, and CYP4A1; however, there was no change in the expression of other genes. On the other hand, treatment of the cells with TCDD or BNF for 48h caused a significant induction of the hypertrophic markers, ANP and BNP, and several CYP genes such as CYP1A1, CYP1B1, CYP2E1, CYP2J3, and CYP4F4 parallel to a significant increase in the cell surface area. Neither TCDD nor BNF increased the oxidative stress in H9c2 cells at all concentrations tested. Interestingly, resveratrol, an AhR antagonist, protected the cells from TCDD-induced hypertrophy. In conclusion, AhR ligands caused a hypertrophic effect in H9c2 cells which was associated with induction of several CYP genes which can be prevented by resveratrol.