Differential cardiotoxicity in response to chronic doxorubicin treatment in male spontaneous hypertension-heart failure (SHHF), spontaneously hypertensive (SHR), and Wistar Kyoto (WKY) rats

Life threatening complications from chemotherapy occur frequently in cancer survivors, however little is known about genetic risk factors. We treated male normotensive rats (WKY) and strains with hypertension (SHR) and hypertension with cardiomyopathy (SHHF) with 8 weekly doses of doxorubicin (DOX) followed by 12 weeks of observation to test the hypothesis that genetic cardiovascular disease would worsen delayed cardiotoxicity. Compared with WKY, SHR demonstrated weight loss, decreased systolic blood pressure, increased kidney weights, greater cardiac and renal histopathologic lesions and greater mortality. SHHF showed growth restriction, increased kidney weights and renal histopathology but no effect on systolic blood pressure or mortality. SHHF had less severe cardiac lesions than SHR. We evaluated cardiac soluble epoxide hydrolase (sEH) content and arachidonic acid metabolites after acute DOX exposure as potential mediators of genetic risk. Before DOX, SHHF and SHR had significantly greater cardiac sEH and decreased epoxyeicosatrienoic acid (EET) (4 of 4 isomers in SHHF and 2 of 4 isomers in SHR) than WKY. After DOX, sEH was unchanged in all strains, but SHHF and SHR rats increased EETs to a level similar to WKY. Leukotriene D4 increased after treatment in SHR. Genetic predisposition to heart failure superimposed on genetic hypertension failed to generate greater toxicity compared with hypertension alone. The relative resistance of DOX-treated SHHF males to the cardiotoxic effects of DOX in the delayed phase despite progression of genetic disease was unexpected and a key finding. Strain differences in arachidonic acid metabolism may contribute to variation in response to DOX toxicity.     

Acute mercury toxicity modulates cytochrome P450, soluble epoxide hydrolase and their associated arachidonic acid metabolites in C57Bl/6 mouse heart

Mercury exposure is associated with increased risk of cardiovascular disease and profound cardiotoxicity. However, the correlation between Hg²⁺-mediated toxicity and alteration in cardiac cytochrome P450s (Cyp) and their dependent arachidonic acid metabolites has never been investigated. Therefore, we investigated the effect of acute mercury toxicity on the expression of Cyp-epoxygenases and Cyp-ω-hydroxylases and their associated arachidonic acid metabolites in mice hearts. In addition, we examined the expression and activity of soluble epoxide hydrolase (sEH) as a key player in arachidonic acid metabolism pathway. Mercury toxicity was induced by a single intraperitoneal injection (IP) of 2.5 mg/kg of mercuric chloride (HgCl₂). Our results showed that mercury treatment caused a significant induction of the cardiac hypertrophy markers, atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP); in addition to Cyp1a1, Cyp1b1, Cyp2b9, Cyp2b10, Cyp2b19, Cyp2c29, Cyp2c38, Cyp4a10, Cyp4a12, Cyp4a14, Cyp4f13, Cyp4f15, Cyp4f16 and Cyp4f18 gene expression. Moreover, Hg²⁺ significantly increased sEH protein expression and activity levels in hearts of mercury-treated mice, with a consequent decrease in 14,15-, and 11,12-epoxyeicosatrienoic acids (EETs) levels. Whereas the formation of 14,15-, 11,12-, 8,9-dihydroxyeicosatrienoic acids (DHETs) was significantly increased. In conclusion, acute Hg²⁺ toxicity modulates the expression of several Cyp and sEH enzymes with a consequent decrease in the cardioprotective EETs which could represent a novel mechanism by which mercury causes progressive cardiotoxicity. Furthermore, inhibiting sEH might represent a novel therapeutic approach to prevent Hg²⁺-induced hypertrophy.     

Acute arsenic toxicity alters cytochrome P450 and soluble epoxide hydrolase and their associated arachidonic acid metabolism in C57Bl/6 mouse heart

Acute arsenic (As(III)) exposure has been reported to cause cardiac toxicity, however this toxicity was never linked to the disturbance in cytochrome P450 (P450)-mediated arachidonic acid metabolism. Therefore, we investigated the effect of acute As(III) toxicity on the expression of P450 and soluble epoxide hydrolase (sEH) and their associated arachidonic acid metabolism in mice hearts. As(III) toxicity was induced by a single intraperitoneal injection of 12.5 mg/kg of As(III). Our results showed that As(III) treatment caused a significant induction of the cardiac hypertrophic markers in addition to Cyp1b1, Cyp2b, Cyp2c, Cyp4f, and sEH gene expression in mice hearts. Furthermore, As(III) increased sEH protein expression and activity in hearts with a consequent decrease in 11,12-, and 14,15-epoxyeicosatrienoic acids (EETs) formation. Whereas the formation of 8,9-, 11,12-, 14,15-dihydroxyeicosatrienoic acids (DHETs) was significantly increased. As(III) also increased sEH mRNA and protein expression levels in addition to the hypertrophic markers which was reversed by knockdown of sEH in H9c2 cells. In conclusion, acute As(III) toxicity alters the expression of several P450s and sEH enzymes with a consequent decrease in the cardioprotective EETs which may represent a novel mechanism by which As(III) causes progressive cardiotoxicity. Furthermore, inhibiting sEH might represent a novel therapeutic approach to prevent As(III)-induced hypertrophy.     

The roles of CYP450 epoxygenases and metabolites, epoxyeicosatrienoic acids, in cardiovascular and malignant diseases

Cytochrome P450 (CYP) epoxygenases metabolize arachidonic acid to biologically active eicosanoids. The primary epoxidation products are four regioisomers of cis-epoxyeicosatrienoic acid (EET): 5,6-, 8,9-, 11,12-, and 14,15-EET. CYP2J2, CYP2C8, and CYP2C9 are the predominant epoxygenase isoforms involved in EET formation. CYP2J and CYP2C gene families in humans are abundantly expressed in the endothelium, myocardium, and kidney. The cardiovascular effects of CYP epoxygenases and EETs range from vasodilation, anti-hypertension, pro-angiogenesis, anti-atherosclerosis, and anti-inflammation to anti-injury caused by ischemia-reperfusion. Using transgenic animals for in vivo analyses of CYP epoxygenases revealed comprehensive and marked cardiovascular protective effects. In contrast, CYP epoxygenases and their metabolites, EETs, are upregulated in human tumors and promote tumor progression and metastasis. These biological effects result from the anti-apoptosis, pro-mitogenesis, and anti-migration roles of CYP epoxygenases and EETs at the cellular level. Importantly, soluble epoxide hydrolase (sEH) inhibitors are anti-hypertensive and anti-inflammatory and, therefore, protect the heart from damage, whereas the terfenadine-related, specific inhibitors of CYP2J2 exhibit strong anti-tumor activity in vitro and in vivo. Thus, CYP2J2 and arachidonic acid-derived metabolites likely play important roles in regulating cardiovascular functions and malignancy under physiological and/or pathological conditions. Moreover, although challenges remain to improving the drug-like properties of sEH inhibitors and identifying efficient ways to deliver sEH inhibitors, sEH will likely become an important therapeutic target for cardiovascular diseases. In addition, CYP2J2 may be a therapeutic target for treating human cancers and leukemia.     

Inhibition of soluble epoxide hydrolase confers cardioprotection and prevents cardiac cytochrome P450 induction by benzo(a)pyrene

We recently demonstrated that benzo(a)pyrene (BaP) causes cardiac hypertrophy by altering arachidonic acid metabolism through the induction of the expression of CYP ω-hydroxylases and soluble epoxide hydrolase (sEH) enzymes. The inhibition of CYP ω-hydroxylase enzymes partially reversed the BaP-induced cardiac hypertrophy. Therefore, it is important to examine whether the inhibition of sEH also confers cardioprotection. For this purpose, male Sprague-Dawley rats were injected intraperitoneally daily with either the sEH inhibitor 1-(1-methanesulfonyl-piperidin-4-yl)-3-(4-trifluoromethoxy-phenyl)-urea (TUPS; 0.65 mg/kg), BaP (20 mg/kg), or the combination of BaP (20 mg/kg) and TUPS (0.65 mg/kg) for 7 days. Thereafter, the heart, liver, and kidney were harvested, and the heart to body weight ratio was measured. The expression of the hypertrophic markers, sEH, heme oxygenase-1, and CYP450 enzymes was determined. Our results demonstrate that BaP alone significantly induced the expression of sEH and CYP ω-hydroxylases in the heart, liver, and kidney tissues. Treatment with TUPS significantly reversed the BaP-mediated induction of the hypertrophic markers, completely prevented the increase in the heart to body weight ratio, and reduced the BaP-induced CYP1A1, CYP1B1, CYP4F4, and CYP4F5 genes in the heart. The current study demonstrates the cardioprotective effect of sEH inhibitor, TUPS, against BaP-induced cardiac hypertrophy and further confirms the role of sEH and CYP450 enzymes in the development of cardiac hypertrophy.     

3-Methylcholanthrene and benzo(a)pyrene modulate cardiac cytochrome P450 gene expression and arachidonic acid metabolism in male Sprague Dawley rats

Background and purpose:

There is a strong correlation between cytochrome P450 (P450)-dependent arachidonic acid metabolism and the pathogenesis of cardiac hypertrophy. Several aryl hydrocarbon receptor (AhR) ligands were found to alter P450-dependent arachidonic acid metabolism. Here, we have investigated the effect of 3-methylcholanthrene (3-MC) and benzo(a)pyrene (BaP), two AhR ligands, on the development of cardiac hypertrophy.

Experimental approach:

Male Sprague Dawley rats were injected (i.p.) daily with either 3-MC (10 mg·kg⁻¹) or BaP (20 mg·kg⁻¹) for 7 days. Then hearts were removed, and the heart to body weight ratio and the gene expression of the hypertrophic markers and P450 genes were determined. Levels of arachidonic acid metabolites were determined by liquid chromatography-electron spray ionization-mass spectrometry.

Key results:

Both 3-MC and BaP increased the heart to body weight ratio as well as the hypertrophic markers, atrial natriuretic peptide and brain natriuretic peptide. 3-MC and BaP treatment increased the gene expression of CYP1A1, CYP1B1, CYP2E1, CYP4F4, CYP4F5 and soluble epoxide hydrolase. Both 3-MC and BaP treatments increased the dihydroxyeicosatrienoic acids (DHETs) : epoxyeicosatrienoic acids (EETs) ratio and the 20-hydroxyeicosatetraenoic acid (20-HETE) : total EETs ratio. Treatment with benzo(e)pyrene, an isomer of BaP that is a poor ligand for the AhR, did not induce cardiac hypertrophy in rats, confirming the role of AhR in the development of cardiac hypertrophy. Treatment with the ω-hydroxylase inhibitor, HET0016, significantly reversed BaP-induced cardiac hypertrophy.

Conclusions and implications:

3-MC and BaP induce cardiac hypertrophy by increasing the ratio of DHETs : EETs and/or the ratio of 20-HETE : total EETs, through increasing soluble epoxide hydrolase activity.     

Inhibition of soluble epoxide hydrolase enhances the anti-inflammatory effects of aspirin and 5-lipoxygenase activation protein inhibitor in a murine model

Inflammation is a multi-staged process whose expansive phase is thought to be driven by acutely released arachidonic acid (AA) and its metabolites. Inhibition of cyclooxygenase (COX), lipoxygenase (LOX), or soluble epoxide hydrolase (sEH) is known to be anti-inflammatory. Inhibition of sEH stabilizes the cytochrome P450 (CYP450) products epoxyeicosatrienoic acids (EETs). Here we used a non-selective COX inhibitor aspirin, a 5-lipoxygenase activation protein (FLAP) inhibitor MK886, and a sEH inhibitor t-AUCB to selectively modulate the branches of AA metabolism in a lipopolysaccharide (LPS)-challenged murine model. We used metabolomic profiling to simultaneously monitor representative AA metabolites of each branch. In addition to the significant crosstalk among branches of the AA cascade during selective modulation of COX, LOX, or sEH, we demonstrated that co-administration of t-AUCB enhanced the anti-inflammatory effects of aspirin or MK886, which was evidenced by the observations that co-administration resulted in favorable eicosanoid profiles and better control of LPS-mediated hypotension as well as hepatic protein expression of COX-2 and 5-LOX. Targeted disruption of the sEH gene displayed a parallel profile to that produced by t-AUCB. These observations demonstrate a significant level of crosstalk among the three major branches of the AA cascade and that they are not simply parallel pathways. These data illustrate that inhibition of sEH by both pharmacological intervention and gene knockout enhances the anti-inflammatory effects of aspirin and MK886, suggesting the possibility of modulating multiple branches to achieve better therapeutic effects.     

Cytochrome P450 epoxygenase metabolite, 14,15-EET,protects against isoproterenol-induced cellular hypertrophy in H9c2 rat cell line

We have previously shown that isoproterenol-induced cardiac hypertrophy causes significant changes to cytochromes P450 (CYPs) and soluble epoxide hydrolase (sEH) gene expression. Therefore, in this study, we examined the effect of isoproterenol in H9c2 cells, and the protective effects of 14,15-EET against isoproterenol-induced cellular hypertrophy. Isoproterenol was incubated with H9c2 cells for 24 and 48 h. To determine the protective effects of 14,15-EET, H9c2 cells were incubated with isoproterenol in the absence and presence of 14,15-EET. Thereafter, the expression of hypertrophic markers and different CYP genes were determined by real time-PCR. Our results demonstrated that isoproterenol significantly increased the expression of hypertrophic marker, atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP), parallel to a significant increase in cell surface area. Also, isoproterenol increased the mRNA expression of CYP1A1, CYP1B1, CYP2J3, CYP4F4 and CYP4F5, as well as the gene encoding sEH, EPHX2. On other hand, 14,15-EET significantly attenuated the isoproterenol-mediated induction of ANP, BNP, CYP1A1, CYP2J3, CYP4F4, CYP4F5 and EPHX2. Moreover 14,15-EET prevented the isoproterenol-mediated increase in cell surface area. Interestingly, 20-hydroxyeicosatetraenoic acid (20-HETE) treatment caused similar effects to that of isoproterenol treatment and induced cellular hypertrophy in H9c2 cells. In conclusion, isoproterenol induces cellular hypertrophy and modulates the expression of CYPs and EPHX2 in H9c2 cells. Furthermore, 14,15-EET exerts a protective effect against isoproterenol-induced cellular hypertrophy whereas, 20-HETE induced cellular hypertrophy in H9c2 cells.     

Induction of several cytochrome P450 genes by doxorubicin in H9c2 cells

Doxorubicin is a potent anti-neoplastic antibiotic used to treat a wide variety of malignancies; however, its use is limited by dose dependent cardiotoxicity. There is indirect evidence suggesting that doxorubicin cardiotoxicity is CYP-mediated. In the current study, we investigated the effect of doxorubicin on hypertrophic markers, and different CYP gene expression in cardiac derived H9c2 cells. H9c2 cells were incubated with increasing concentrations of doxorubicin and the expressions of different genes were determined by real-time PCR. Our results demonstrate that multiple CYP genes are expressed in H9c2 cells and the level of expression from the highest to the lowest were; CYP1B1, CYP2B1, CYP2J3, CYP1A1, CYP2C11, CYP2C23, CYP2E1, CYP1A2, and CYP2B2. Doxorubicin treatment caused an induction of the hypertrophic markers, ANP and BNP. In addition, doxorubicin caused a significant induction of CYP1A1, CYP1A2, CYP1B1, CYP2B2, CYP2E1, and CYP2J3 gene expression in a concentration-dependent manner. However, only the highest concentration tested, 10 μM, caused an induction of CYP2C11; whereas, CYP2B1 and CYP2C23 were not altered. Our findings demonstrate that doxorubicin induces the hypertrophic markers, ANP and BNP as well as several CYP genes in H9c2 cells. Doxorubicin-mediated CYP induction may represent a novel mechanism by which this drug induces cardiotoxicity.     

Red blood cells (RBCs), epoxyeicosatrienoic acids (EETs) and adenosine triphosphate (ATP)

In addition to serving as carriers of O₂, red blood cells (RBCs) regulate vascular resistance and the distribution of microvascular perfusion by liberating adenosine triphosphate (ATP) and epoxyeicosatrienoic acids (EETs) upon exposure to a low O₂ environment. Therefore, RBCs act as sensors that respond to low pO₂ by releasing millimolar amounts of ATP, a signaling molecule, and lipid mediators (EETs). The release of EETs occurs by a mechanism that is activated by ATP stimulation of P2X₇ receptors coupled to ATP transporters, which should greatly amplify the circulatory response to ATP. RBCs are reservoirs of EETs and the primary sources of plasma EETs, which are esterified to the phospholipids of lipoproteins. Levels of free EETs in plasma are low, about 3% of circulating EETs. RBC EETs are produced by direct oxidation of arachidonic acid (AA) esterified to glycerophospholipids and the monooxygenase-like activity of hemoglobin. On release, EETs affect vascular tone, produce profibrinolysis and dampen inflammation. A soluble epoxide hydrolase (sEH) regulates the concentrations of RBC and vascular EETs by metabolizing both cis- and trans-EETs to form dihydroxyeicosatrienoic acids (DHETs). The function and pathophysiological roles of trans-EETs and erythro-DHETs has yet to be integrated into a physiological and pathophysiological context.     

Localization of rat cytochrome P450 in various tissues and comparison of arachidonic acid metabolism by rat P450 with that by human P450 orthologs

Metabolites of arachidonic acid produced by P450 are interesting substances with prominent physiological functions. To elucidate the physiological function of P450, it is necessary to identify a specific P450 in a particular tissue or organ and to characterize its catalytic activities. In this study, the expression of CYP2A1, 2B1, 2C23, 2J3, and 4F1 was investigated in liver, lung, kidney, spleen, heart, brain, and testis of rats by RT-PCR. Furthermore, arachidonic acid metabolism was investigated using the rat P450s described above and human CYP2A6, 2B6, 2C9, 2C18, 2C19, 2J2, and 4F2. Among the rat P450s, CYP2B1 and 2C23 efficiently produced EETs and CYP4F1 produced 19/20-HETE in abundace. CYP2B1 was specifically expressed in the lung. CYP2C23 was detected in all tissues used in this study. CYP4F1 was expressed in the kidney as well as in the liver. Among the human P450s, CYP2C9 and 2C19 efficiently produced EETs. CYP4F2 produced 19/20-HETE. The catalytic properties of rat CYP2C23 were similar to those of human CYP2C9 and 2C19. The catalytic properties of CYP4F isoforms were also similar between humans and rats. A systematic analysis of P450 expression in various tissues and of its catalytic property may provide valuable information on the physiological roles of P450s in each tissue.     

Taiwanese and Japanese yam (Dioscorea spp.) extracts attenuate doxorubicin-induced cardiotoxicity in mice

The present study was designed to explore whether yam could protect the heart from doxorubicin (DOX)-induced oxidative stress leading to cardiotoxicity in vivo. In this study, the protective effects of water and ethanol extracts of three varieties of yam, including water extracts of Dioscorea japonica Thunb., ethanol extracts of D. japonica Thunb., water extracts of Dioscorea alata, ethanol extracts of D. alata, water extracts of Dioscorea purpurea, and ethanol extracts of D. purpurea, against DOX-induced cardiotoxicity in experimental mice were evaluated. DOX treatment led to significant decreases in the ratio of heart weight to body weight and heart rate, and increases in blood pressure and the serum level of lactate dehydrogenase, a marker of cardiotoxicity, were recovered by yam extracts, especially in water extracts of D. alata. Yam extracts also decreased the cardiac levels of thiobarbituric acid relative substances, reactive oxygen species, and inflammatory factors, as well as the expression of nuclear factor kappa B, while ethanol extracts of D. japonica Thunb. and D. purpurea were shown to be more potent. Moreover, yam extracts had a role in increasing the activities of glutathione peroxidase and superoxide dismutase, thus improving the DOX-induced alterations in oxidative status in the heart tissue of DOX-treated mice. All ethanol extracts of yam exhibited their antiapoptotic abilities on caspase-3 activation and mitochondrial dysfunction, and ethanol extracts of D. alata still exerted a superior effect. Based on these findings, it can be concluded that yam has significant cardioprotective properties against DOX-induced damage via its multiple effects on antioxidant, anti-inflammatory, or antiapoptotic activities.     

Liguzinediol improved the heart function and inhibited myocardial cell apoptosis in rats with heart failure

Aim:

Liguzinediol is a novel derivative of ligustrazine isolated from the traditional Chinese medicine Chuanxiong (Ligusticum wallichii Franch), and produces significant positive inotropic effect in isolated rat hearts. In this study we investigated the effects of liguzinediol on a rat model of heart failure.

Methods:

To induce heart failure, male SD rats were injected with doxorubicin (DOX, 2 mg/kg, ip) once a week for 4 weeks. Then the rats were administered with liguzinediol (5, 10, 20 mg·kg⁻¹·d⁻¹, po) for 2 weeks. Hemodynamic examination was conducted to evaluate heart function. Myocardial cell apoptosis was examined morphologically. The expression of related genes and proteins were analyzed using immunohistochemical staining and Western blot assays, respectively.

Results:

Oral administration of liguzinediol dose-dependently improved the heart function in DOX-treated rats. Electron microscopy revealed that liguzinediol (10 mg·kg⁻¹·d⁻¹) markedly attenuated DOX-induced injury of cardiomyocytes, and decreased the number of apoptotic bodies in cardiomyocytes. Furthermore, liguzinediol significantly decreased Bax protein level, and increased Bcl-2 protein level in cardiomyocytes of DOX-treated rats, led to an increase in the ratio of Bcl-2/Bax. Moreover, liguzinediol significantly decreased the expression of both cleaved caspase-3 and NF-κB in cardiomyocytes of DOX-treated rats. Administration of digitalis (0.0225 mg·kg⁻¹·d⁻¹) also markedly improved the heart function and the morphology of cardiomyocytes in DOX-treated rats.

Conclusion:

Liguzinediol improves the heart function and inhibits myocardial cell apoptosis in the rat model of heart failure, which is associated with regulating Bcl-2, Bax, caspase-3 and NF-κB expression.     

Induction of several cytochrome P450 genes by doxorubicin in H9c2 cells

Doxorubicin is a potent anti-neoplastic antibiotic used to treat a wide variety of malignancies; however, its use is limited by dose dependent cardiotoxicity. There is indirect evidence suggesting that doxorubicin cardiotoxicity is CYP-mediated. In the current study, we investigated the effect of doxorubicin on hypertrophic markers, and different CYP gene expression in cardiac derived H9c2 cells. H9c2 cells were incubated with increasing concentrations of doxorubicin and the expressions of different genes were determined by real-time PCR. Our results demonstrate that multiple CYP genes are expressed in H9c2 cells and the level of expression from the highest to the lowest were; CYP1B1, CYP2B1, CYP2J3, CYP1A1, CYP2C11, CYP2C23, CYP2E1, CYP1A2, and CYP2B2. Doxorubicin treatment caused an induction of the hypertrophic markers, ANP and BNP. In addition, doxorubicin caused a significant induction of CYP1A1, CYP1A2, CYP1B1, CYP2B2, CYP2E1, and CYP2J3 gene expression in a concentration-dependent manner. However, only the highest concentration tested, 10 μM, caused an induction of CYP2C11; whereas, CYP2B1 and CYP2C23 were not altered. Our findings demonstrate that doxorubicin induces the hypertrophic markers, ANP and BNP as well as several CYP genes in H9c2 cells. Doxorubicin-mediated CYP induction may represent a novel mechanism by which this drug induces cardiotoxicity.     

AHR2 knockdown prevents PAH-mediated cardiac toxicity and XRE- and ARE-associated gene induction in zebrafish (Danio rerio)

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous environmental contaminants often present in aquatic systems as complex mixtures. Embryonic fish are sensitive to the developmental toxicity of some PAHs, but the exact mechanisms involved in this toxicity are still unknown. This study explored the role of the aryl hydrocarbon receptor (AHR) in the oxidative stress response of zebrafish to the embryotoxicity of select PAHs. Embryos were exposed to two PAHs, benzo[k]fluoranthene (BkF; a strong AHR agonist) and fluoranthene (FL; a cytochrome P4501A (CYP1A) inhibitor), alone and in combination. CYP1A, CYP1B1, CYP1C1, and redox-responsive genes glutathione s-transferase pi 2 (GSTp2), glutathione peroxidase 1 (GPx1), the glutamate-cysteine ligase catalytic subunit (GCLc), MnSOD and CuZnSOD mRNA expression was examined. CYP1 activity was measured via an in vivo ethoxyresorufin-O-deethlyase (EROD) activity assay, and the area of the pericardium was measured as an index of cardiotoxicity. BkF or FL alone caused no deformities whereas BkF + FL resulted in extreme pericardial effusion. BkF induced CYP activity above controls and co-exposure with FL inhibited this activity. BkF induced expression of all three CYPs, GSTp2, and GCLc. BkF + FL caused greater than additive induction of the three CYPs, GSTp2, GPx1, and GCLc but had no effect on MnSOD or CuZnSOD. AHR2 knockdown protected against the cardiac deformities caused by BkF + FL and significantly inhibited the induction of the CYPs, GSTp2, GPx1, and GCLc after BkF + FL compared to non-injected controls. These results further show the protective role of AHR2 knockdown against cardiotoxic PAHs and the role of AHR2 as a mediator of redox-responsive gene induction.     

Alterations in cytochrome P450-derived arachidonic acid metabolism during pressure overload-induced cardiac hypertrophy

Cardiac hypertrophy is a major risk factor for many serious heart diseases. Recent data demonstrated the role of cytochrome P450 (CYP)-derived arachidonic acid (AA) metabolites in cardiovascular pathophysiology. In the current study our aim was to determine the aberrations in CYP-mediated AA metabolism in the heart during cardiac hypertrophy. Pressure overload cardiac hypertrophy was induced in Sprague Dawley rats using the descending aortic constriction procedure. Five weeks post-surgery, the cardiac levels of AA metabolites were determined in hypertrophied and normal hearts. In addition, the formation rate of AA metabolites, as well as, CYP expression in cardiac microsomal fraction was also determined. AA metabolites were measured by liquid chromatography–electrospray ionization-mass spectroscopy, whereas, the expression of CYPs was determined by Western blot analysis. Non-parametric analysis was performed to examine the association between metabolites formation and CYP expressions. Our results showed that 5,6-, 8,9-, 11,12-, and 14,15-epoxyeicosatrienoic acids (EETs), and 5-, 12-, 15-, and 20-hydroxyeicosatetraenoic acids (HETEs) levels were increased, whereas, 19-HETE formation was decreased in hypertrophied hearts. The increase in EETs was linked to CYP2B2. On the other hand, CYP1B1 and CYP2J3 were involved in mid-chain HETE metabolism, whereas, CYP4A2/3 inhibition was involved in the decrease in 19-HETE formation in hypertrophied hearts. In conclusion, CYP1B1 played cardiotoxic role, whereas, CYP2B2, CYP2J3 and CYP4A2/3 played cardioprotective roles during pressure overload-induced cardiac hypertrophy. These CYP can be valid targets for the development of drugs to treat and prevent cardiac hypertrophy and heart failure.     

Effects of water-soluble antioxidant from spinach, NAO, on doxorubicin-induced heart injury.

Doxorubicin (DOX) produces clinically restorative responses in numerous human cancers, but its cardiotoxicity has limited its usefulness. Because reactive oxygen species may affect DOX-induced antitumor activity and cardiotoxicity, we evaluated the prophylactic effect of spinach natural antioxidant (NAO) on DOX-induced cardiotoxicity and oxidative stress in female Balb/c mice using histological, electron microscopical and biochemical parameters. Mice were treated with NAO for 7 days prior to and/or for 6 days after DOX administration. Pretreatment with NAO (cumulative dose: 130 mg/kg) did not hinder the effectiveness of DOX. Light and electron microscopy of DOX-treated heart revealed myocardial degeneration. When administered combined before and after DOX, NAO conferred the most significant cardiac protection. The effects of NAO on the lipid peroxidation product, malondialdehyde, and on H2O2/ hydroperoxides were examined on day 6 following DOX administration; levels of both were elevated in DOX-treated mice, compared to control. Pretreatment with NAO prevented these changes. Pretreatment with NAO before DOX administration decreased catalase and increased superoxide dismutase activities compared to the DOX group. Our results suggest usage of NAO in combination with DOX as a prophylactic strategy to protect heart muscle from DOX-induced cellular damage.     

Overexpression of cytochrome P450 CYP2J2 protects against hypoxia-reoxygenation injury in cultured bovine aortic endothelial cells.

CYP2J2 is abundant in human heart and its arachidonic acid metabolites, the epoxyeicosatrienoic acids (EETs), have potent vasodilatory, antiinflammatory and cardioprotective properties. This study was designed to examine the role of CYP2J2 in hypoxia-reoxygenation-induced injury in cultured bovine aortic endothelial cells (BAECs). Early passage BAECs were exposed to 24-h hypoxia followed by 4-h reoxygenation (HR). HR resulted in cell injury, as indicated by significant increases in lactate dehydrogenase (LDH) release and trypan blue stained cells (p < 0.01) and was associated with a decrease in CYP2J2 protein expression. Transfection of BAECs with the CYP2J2 cDNA resulted in increased CYP2J2 expression and arachidonic acid epoxygenase activity, compared with cells transfected with an irrelevant green fluorescent protein (GFP) cDNA. HR induced significant injury in GFP-transfected BAECs, as indicated by increases in LDH release and trypan blue-stained cells (p < 0.01); however, the HR-induced injury was markedly attenuated in CYP2J2-transfected cells (p < 0.01). HR increased cellular 8-iso-prostaglandin F(2alpha) (p < 0.05), and decreased eNOS expression, L-arginine uptake and conversion, and nitrite production (p < 0.01) in GFP-transfected BAECs. CYP2J2 transfection attenuated the HR-induced increase in 8-iso-prostaglandin F(2alpha) (p < 0.05) and decreased the amount of extracellular superoxide detected by cytochrome c reduction under normoxic conditions (p < 0.05) but did not significantly affect HR-induced decreases in eNOS expression, L-arginine uptake and conversion, and nitrite production. Treatment of BAECs with synthetic EETs and/or epoxide hydrolase inhibitors also showed protective effects against HR injury (p < 0.05). These observations suggest: (1) HR results in endothelial injury and decreased CYP2J2 expression; (2) transfection with the CYP2J2 cDNA protects against HR injury; and (3) the cytoprotective effects of CYP2J2 may be mediated, at least in part, by antioxidant effects.     

Time course of cardiomyopathy induced by doxorubicin in rats

Background: Doxorubicin (DOX)-related cardiotoxicity may expose cancer survivors to increased risk of cardiovascular morbidity and mortality. Here, we characterized the time course of DOX-induced cardiomyopathy in rats.Methods: Sprague-Dawley male rats (12 wk old) received doxorubicin hydrochloride (1 mg/kg/d, ip) during 10 consecutive days and they were euthanized one (DOX1), two (DOX2) or four (DOX4) weeks after the last drug injection. Control group received NaCl 0.9% (ip). Hearts were mounted on a Langendorff perfusion system, left ventricle fragments were processed for microscopy and oxidative stress-related assays, and blood was collected for cardiac troponin I assay.Results: All DOX-treated groups showed swollen and vacuolated cardiomyocytes with myofilaments disarray and mitochondrial damage. These changes were already evident after one week and became more pronounced after four weeks. Cardiac troponin I plasma levels were significantly increased in DOX1 and further increased in DOX4 compared to control group. Increased oxidative damage to lipids was observed in DOX1, and to proteins in DOX4. Glutathione peroxidase activity increased in DOX4. The morphological changes resulted in cardiac remodeling, including interstitial fibrosis, apoptosis and significant impairment of both contractile and relaxation function in DOX 4 compared to control group. Hearts from all animals displayed an early reduction in the responsiveness to norepinephrine.Conclusions: These findings support the view that DOX cardiotoxicity occurs in a “continuum”, and as the hypothesis of an irreversible cardiac injury is being challenged, understanding the progression of morphological and functional changes caused by DOX may allow proper timing of initiation of prophylactic treatment.     

Protection of salvianolic acid A on rat brain from ischemic damage via soluble epoxide hydrolase inhibition

Epoxyeicosatrienoic acids (EETs) and their regulating enzyme soluble epoxide hydrolase (sEH) have been associated with ischemic stroke. Salvianolic acid A (SAA) is proved to display potent cerebroprotection. However, little information is available about the link between them. This study aimed to investigate whether SAA exhibits its protective effects in rats subjected to middle cerebral artery occlusion (MCAO) through sEH and EETs. The results showed that SAA treatment ameliorated neurological deficits and reduced infarct volume. Notably, the beneficial effects of SAA were attenuated by co-administration of (14,15-epoxyeicosa-5(Z)-enoic acid (14,15-EEZE)), a putative selective EETs antagonist. Furthermore, SAA increased the 14,15-EET levels in the blood and brain of sham and MCAO rats. Assay for hydrolase activity showed that 1 and 3 mg/kg of SAA significantly diminished brain sEH activity of MCAO rats. A fluorescent assay in vitro indicated that SAA could inhibit recombinant human sEH activity in a concentration-dependent manner (IC₅₀ = 1.62 μmol/l). Immunohistochemical analysis showed that SAA at the doses of 1 and 3 mg/kg significantly decreased sEH protein expression in hippocampus CA1 region of MCAO rats. In conclusion, cerebral protection of SAA is mediated, at least in part, via inhibiting sEH to increase EETs levels.