8,9-Epoxyeicosatrienoic acid analog protects pulmonary artery smooth muscle cells from apoptosis via ROCK pathway

Soluble epoxide hydrolase (Ephx2) silencing attenuates the hydrogen peroxide-induced oxidative damage in IEC-6 cells

INTRODUCTION

Oxidative stress can cause intestinal disease. Soluble epoxide hydrolase (sEH, Ephx2) is related to cell apoptosis. The effect of Ephx2 on the H2O2-induced oxidative damage remains unclear. Thus, we aimed to explore the effect of Ephx2 on oxidative damage and the underlying potential mechanism.

MATERIAL AND METHODS

The cell viability was determined using cell counting kit-8 (CCK-8) assay. The reactive oxygen species (ROS), apoptosis, and mitochondrial membrane potential (MMP) were examined using flow cytometry analysis. Commercial kits were applied to respectively determine the lactate dehydrogenase (LDH) leakage, malondialdehyde (MDA) content, and superoxide dismutase (SOD) activity. The expressions of target factors were measured by conducting quantitative reverse transcription-polymerase chain reaction (qRT-PCR) and western blot.

RESULTS

We found that knockdown of Ephx2 enhanced the viability of H2O2-treated IEC-6 cells, and that si-Ephx2 reduced the ROS level, MMP loss, and apoptosis in comparison to the H2O2 model group. Knockdown of Ephx2 was found to decrease LDH activity and MDA content, and to improve the SOD activity in comparison to those in the H2O2 model group. Knockdown of Ephx2 reduced the expressions of Fas, Fasl, Bax, and cleavedcaspase-3 and elevated the expression of Bcl-2 in H2O2-treated IEC-6 cells. Furthermore, we observed that knockdown of Ephx2 enhanced the phosphorylation of PI3K, Akt, and GSK3β, which were reduced by the treatment of H2O2. In addition, the anti-apoptotic effect of si-Ephx2 was enhanced in the presence of AUDA-pharmacological Ephx2 inhibitor.

CONCLUSIONS

Ephx2 silencing inhibited H2O2-induced oxidative damage. The PI3K/Akt/GSK3β pathway was related to the effect of si-Ephx2. Our study provided a potential target for the prevention of intestinal injury.

14,15-EET Suppresses Neuronal Apoptosis in Ischemia-Reperfusion Through the Mitochondrial Pathway

Neuronal apoptosis mediated by the mitochondrial apoptosis pathway is an important pathological process in cerebral ischemia-reperfusion injury. 14,15-EET, an intermediate metabolite of arachidonic acid, can promote cell survival during ischemia/reperfusion. However, whether the mitochondrial apoptotic pathway is involved this survival mechanism is not fully understood. In this study, we observed that infarct size in ischemia-reperfusion injury was reduced in sEH gene knockout mice. In addition, Caspase 3 activation, cytochrome C release and AIF nuclear translocation were also inhibited. In this study, 14,15-EET pretreatment reduced neuronal apoptosis in the oxygen-glucose deprivation and re-oxygenation group in vitro. The mitochondrial apoptosis pathway was also inhibited, as evidenced by AIF translocation from the mitochondria to nucleus and the reduction in the expressions of cleaved-caspase 3 and cytochrome C in the cytoplasm. 14,15-EET could reduce neuronal apoptosis through upregulation of the ratio of Bcl-2 (anti-apoptotic protein) to Bax (apoptosis protein) and inhibition of Bax aggregation onto mitochondria. PI3K/AKT pathway is also probably involved in the reduction of neuronal apoptosis by EET. Our study suggests that 14,15-EET could suppress neuronal apoptosis and reduce infarct volume through the mitochondrial apoptotic pathway. Furthermore, the PI3K/AKT pathway also appears to be involved in the neuroprotection against ischemia-reperfusion by 14,15-EET.

Inhibition and inactivation of human CYP2J2: Implications in cardiac pathophysiology and opportunities in cancer therapy

Extrahepatic cytochrome P450 enzymes (CYP450) are pivotal in the metabolism of endogenous substrates and xenobiotics. CYP2J2 is a major cardiac CYP450 and primarily metabolizes polyunsaturated fatty acids such as arachidonic acid to cardioactive epoxyeicosatrienoic acids. Due to its role in endobiotic metabolism, CYP2J2 has been actively studied in recent years with the focus on its biological functions in cardiac pathophysiology. Additionally, CYP2J2 metabolizes a number of xenobiotics such as astemizole and terfenadine and is potently inhibited by danazol and telmisartan. Notably, CYP2J2 is found to be upregulated in multiple cancers. Hence a number of specific CYP2J2 inhibitors have been developed and their efficacy in inhibiting tumor progression has been actively studied. CYP2J2 inhibitor such as C26 (1-[4-(vinyl)phenyl]-4-[4-(diphenyl-hydroxymethyl)-piperidinyl]-butanone hydrochloride) caused marked reduction in tumor proliferation and migration as well as promoted apoptosis in cancer cells. In this review, we discuss the role of CYP2J2 in cardiac pathophysiology and cancer therapeutics. Additionally, we provide an update on the substrates, reversible inhibitors and irreversible inhibitors of CYP2J2. Finally, we discuss the current gaps and future directions in CYP2J2 research.

ROCK2 mediates the proliferation of pulmonary arterial endothelial cells induced by hypoxia in the development of pulmonary arterial hypertension

It has been reported that RhoA activation and Rho-kinase (ROCK) expression are increased in chronic hypoxic lungs, and the long-term inhibition of ROCK markedly improves the survival of patients with pulmonary arterial hypertension (PAH). However, whether Rho-kinase α (ROCK2) participates in regulation of the growth of pulmonary arterial endothelial cells (PAECs) remains unknown. The aim of the present study was to investigate the effect of hypoxia on the proliferation of PAECs and the role of ROCK2 in the underlying mechanism. The results of western blotting and reverse transcription-quantitative polymerase chain reaction analysis showed that hypoxia increased the activity and expression of ROCK2 in PAECs, and the stimulating effects of hypoxia on the proliferation of PAECs were attenuated by either the ROCK inhibitor Y27632 or transfection with ROCK2 small interfering RNA. Moreover, analysis of cyclin A and cyclin D1 mRNA expression indicated that ROCK2 mediates the cell cycle progression promoted by hypoxia. These results indicate that hypoxia promotes the proliferation of pulmonary arterial endothelial cells via activation of the ROCK2 signaling pathway.

Proinflammatory high-density lipoprotein results from oxidized lipid mediators in the pathogenesis of both idiopathic and associated types of pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is characterized by abnormal elaboration of vasoactive peptides, endothelial cell dysfunction, vascular remodeling, and inflammation, which collectively contribute to its pathogenesis. We investigated the potential for high-density lipoprotein (HDL) dysfunction (i.e., proinflammatory effects) and abnormal plasma eicosanoid levels to contribute to the pathobiology of PAH and assessed ex vivo the effect of treatment with apolipoprotein A-I mimetic peptide 4F on the observed HDL dysfunction. We determined the "inflammatory indices" HII and LII for HDL and low-density lipoprotein (LDL), respectively, in subjects with idiopathic PAH (IPAH) and associated PAH (APAH) by an in vitro monocyte chemotaxis assay. The 4F was added ex vivo, and repeat LII and HII values were obtained versus a sham treatment. We further determined eicosanoid levels in plasma and HDL fractions from patients with IPAH and APAH relative to controls. The LIIs were significantly higher for IPAH and APAH patients than for controls. Incubation of plasma with 4F before isolation of LDL and HDL significantly reduced the LII values, compared with sham-treated LDL, for IPAH and APAH. The increased LII values reflected increased states of LDL oxidation and thereby increased proinflammatory effects in both cohorts. The HIIs for both PAH cohorts reflected a "dysfunctional HDL phenotype," that is, proinflammatory HDL effects. In contrast to "normal HDL function," the determined HIIs were significantly increased for the IPAH and APAH cohorts. Ex vivo 4F treatment significantly improved the HDL function versus the sham treatment. Although there was a significant "salutary effect" of 4F treatment, this did not entirely normalize the HII. Significantly increased levels for both IPAH and APAH versus controls were evident for the eicosanoids 9-HODE, 13-HODE, 5-HETE, 12-HETE, and 15-HETE, while no statistical differences were evident for comparisons of IPAH and APAH for the determined plasma eicosanoid levels in the HDL fractions. Our study has further implicated the putative role of "oxidant stress" and inflammation in the pathobiology of PAH. Our data suggest the influences on the "dysfunctional HDL phenotype" of increased oxidized fatty acids, which are paradoxically proinflammatory. We speculate that therapies that target either the "inflammatory milieu" or the "dysfunctional HDL phenotype," such as apoA-I mimetic peptides, may be valuable avenues of further research in pulmonary vascular diseases.

ROS generated during early reperfusion contribute to intermittent hypobaric hypoxia-afforded cardioprotection against postischemia-induced Ca(2+) overload and contractile dysfunction via the JAK2/STAT3 pathway

Moderate enhanced reactive oxygen species (ROS) during early reperfusion trigger the cardioprotection against ischemia/reperfusion (I/R) injury, while the mechanism is largely unknown. Janus kinase 2 (JAK2)/signal transducer and activator of transcription 3 (STAT3) contributes to the cardioprotection but whether it is activated by ROS and how it regulates Ca(2+) homeostasis remain unclear. Here we investigated whether the ROS generated during early reperfusion protect the heart/cardiomyocyte against I/R-induced Ca(2+) overload and contractile dysfunction via the activation of JAK2/STAT3 signaling pathway by using a cardioprotective model of intermittent hypobaric hypoxia (IHH) preconditioning. IHH improved the postischemic recovery of myocardial contractile performance in isolated rat I/R hearts as well as Ca(2+) homeostasis and cell contraction in simulated I/R cardiomyocytes. Meanwhile, IHH enhanced I/R-increased STAT3 phosphorylation at tyrosine 705 in the nucleus and reversed I/R-suppressed STAT3 phosphorylation at serine 727 in the nucleus and mitochondria during reperfusion. Moreover, IHH improved I/R-suppressed sarcoplasmic reticulum (SR) Ca(2+)-ATPase 2 (SERCA2) activity, enhanced I/R-increased Bcl-2 expression, and promoted the co-localization and interaction of Bcl-2 with SERCA2 during reperfusion. These effects were abolished by scavenging ROS with N-(2-mercaptopropionyl)-glycine (2-MPG) and/or by inhibiting JAK2 with AG490 during the early reperfusion. Furthermore, IHH-improved postischemic SERCA2 activity and Ca(2+) homeostasis as well as cell contraction were reversed after Bcl-2 knockdown by short hairpin RNA. In addition, the reversal of the I/R-suppressed mitochondrial membrane potential by IHH was abolished by 2-MPG and AG490. These results indicate that during early reperfusion the ROS/JAK2/STAT3 pathways play a crucial role in (i) the IHH-maintained intracellular Ca(2+) homeostasis via the improvement of postischemic SERCA2 activity through the increase of SR Bcl-2 and its interaction with SERCA2; and (ii) the IHH-improved mitochondrial function.

Intermittent hypothermia is neuroprotective in an in vitro model of ischemic stroke

OBJECTIVE

To investigate whether the intermittent hypothermia (IH) protects neurons against ischemic insult and the potential molecular targets using an in vitro ischemic model of oxygen glucose deprivation (OGD).

METHODS

Fetal rat cortical neurons isolated from Day E18 rat embryos were subjected to 90-min OGD and hypothermia treatments during reoxygenation before examining the changes in microscopic morphology, cell viability, microtubule- associated protein 2 (MAP-2) release, intracellular pH value and calcium, reactive oxygen species (ROS) generation, mitochondrial membrane potential (△Ψm) and neuronal death using cell counting kit (CCK-8), enzyme-linked immunosorbent assay (ELISA), BCECF AM, Fluo-3 AM, DCFH-DA and dihydroethidium (DHE), JC-1 staining and terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL), respectively.

RESULTS

90-min OGD induced morphologic abnormalities, cell viability decline, MAP-2 release, intracellular acidosis, calcium overload, increased ROS generation, △Ψm decrease and cell death in primary neurons, which was partially inhibited by continuous hypothermia (CH) and intermittent hypothermia (IH). Interestingly, 6-h CH was insufficient to reduce intracellular calcium overload and stabilize mitochondrial membrane potential (△Ψm), while 12-h CH was effective in reversing the above changes. All IH treatments (6×1 h, 4×1.5 h or 3×2 h) effectively attenuated intracellular free calcium overload, inhibited ROS production, stabilized mitochondrial membrane potential (△Ψm) and reduced delayed cell death in OGD-treated cells. However, only IH intervals longer than 1.5 h appeared to be effective in preventing cell viability loss and intracellular pH decline.

CONCLUSION

Both CH and IH were neuroprotective in an in vitro model of ischemic stroke, and in spite of shorter hypothermia duration, IH could provide a comparable neuroprotection to CH.

Role of cytochrome P450-mediated arachidonic acid metabolites in the pathogenesis of cardiac hypertrophy

A plethora of studies have demonstrated the expression of cytochrome P450 (CYP) and soluble epoxide hydrolase (sEH) enzymes in the heart and other cardiovascular tissues. In addition, the expression of these enzymes is altered during several cardiovascular diseases (CVDs), including cardiac hypertrophy (CH). The alteration in CYP and sEH expression results in derailed CYP-mediated arachidonic acid (AA) metabolism. In animal models of CH, it has been reported that there is an increase in 20-hydroxyeicosatetraenoic acid (20-HETE) and a decrease in epoxyeicosatrienoic acids (EETs). Further, inhibiting 20-HETE production by CYP ω-hydroxylase inhibitors and increasing EET stability by sEH inhibitors have been proven to protect against CH as well as other CVDs. Therefore, CYP-mediated AA metabolites 20-HETE and EETs are potential key players in the pathogenesis of CH. Some studies have investigated the molecular mechanisms by which these metabolites mediate their effects on cardiomyocytes and vasculature leading to pathological CH. Activation of several intracellular signaling cascades, such as nuclear factor of activated T cells, nuclear factor kappa B, mitogen-activated protein kinases, Rho-kinases, Gp130/signal transducer and activator of transcription, extracellular matrix degradation, apoptotic cascades, inflammatory cytokines, and oxidative stress, has been linked to the pathogenesis of CH. In this review, we discuss how 20-HETE and EETs can affect these signaling pathways to result in, or protect from, CH, respectively. However, further understanding of these metabolites and their effects on intracellular cascades will be required to assess their potential translation to therapeutic approaches for the prevention and/or treatment of CH and heart failure.

Epoxyeicosatrienoic acids prevent cisplatin-induced renal apoptosis through a p38 mitogen-activated protein kinase-regulated mitochondrial pathway

Soluble epoxide hydrolase (sEH) catalyzes the conversion of epoxyeicosatrienoic acids into less active eicosanoids, and inhibitors of sEH have anti-inflammatory and antiapoptotic properties. Based on previous observations that sEH inhibition attenuates cisplatin-induced nephrotoxicity by modulating nuclear factor-κB signaling, we hypothesized that this strategy would also attenuate cisplatin-induced renal apoptosis. Inhibition of sEH with AR9273 [1-adamantan-1-yl-3-(1-methylsulfonyl-piperidin-4-yl-urea)] reduced cisplatin-induced apoptosis through mechanisms involving mitochondrial apoptotic pathways and by reducing reactive oxygen species. Renal mitochondrial Bax induction following cisplatin treatment was significantly decreased by treatment of mice with AR9273 and these antiapoptotic effects involved p38 mitogen-activated protein kinase signaling. Similar mechanisms contributed to reduced apoptosis in Ephx2(-/-) mice treated with cisplatin. Moreover, in pig kidney proximal tubule cells, cisplatin-induced mitochondrial trafficking of Bax and cytochrome c, caspase-3 activation, and oxidative stress are significantly attenuated in the presence of epoxyeicosatrienoic acids (EETs). Collectively, these in vivo and in vitro studies demonstrate a role for EETs in limiting cisplatin-induced renal apoptosis. Inhibition of sEH represents a novel therapeutic strategy for protection against cisplatin-induced renal damage.

Epoxides and soluble epoxide hydrolase in cardiovascular physiology

Epoxyeicosatrienoic acids (EETs) are arachidonic acid metabolites that importantly contribute to vascular and cardiac physiology. The contribution of EETs to vascular and cardiac function is further influenced by soluble epoxide hydrolase (sEH) that degrades EETs to diols. Vascular actions of EETs include dilation and angiogenesis. EETs also decrease inflammation and platelet aggregation and in general act to maintain vascular homeostasis. Myocyte contraction and increased coronary blood flow are the two primary EET actions in the heart. EET cell signaling mechanisms are tissue and organ specific and provide significant evidence for the existence of EET receptors. Additionally, pharmacological and genetic manipulations of EETs and sEH have demonstrated a contribution for this metabolic pathway to cardiovascular diseases. Given the impact of EETs to cardiovascular physiology, there is emerging evidence that development of EET-based therapeutics will be beneficial for cardiovascular diseases.

Silencing of the integrin-linked kinase gene induces the apoptosis in ovarian carcinoma

CONTEXT

Integrin-linked kinase (ILK), a multidomain focal adhesion protein serine/threonine kinase, plays an essential role in ovarian carcinoma. There are reports that the expression and activity of ILK are increased in ovarian cancer.

OBJECTIVE

To test the hypothesis that ILK pathway mediates the apoptosis of ovarian carcinoma SKOV3 cell influencing the cell survival, we performed these studies.

MATERIALS AND METHODS

We applied lentivirus transfection, 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyl-tetrazolium bromide (MTT), apoptotic proteins expressions assay, and Hoechst to study our hypothesis.

RESULTS

We found that silencing of the ILK increases the cell cytotoxic, growth inhibition, and apoptosis. Moreover, after blocking the activation of ILK with ILK shRNA, up-regulation of pro-apoptotic bax expression and down-regulation of the anti-apoptotic bcl-2 expression were found in ovarian cancer SKOV3 cell line. These were associated with an increasing cleaved caspase-3 activity and chromatin condensation of cell nuclear. Furthermore, the expressions of fas and fas ligand (fasL), belonging to the tumor necrosis factor family and controlling the cell apoptosis, were also enhanced.

CONCLUSIONS

Thus, these findings indicate that both the intrinsic pathway and the extrinsic death receptor pathway are involved in the process that silencing of the ILK gene induces the apoptosis in ovarian carcinoma SKOV3 cell.

Rho kinase proteins--pleiotropic modulators of cell survival and apoptosis

Rho kinase (ROCK) proteins are Rho-GTPase activated serine/threonine kinases that function as modulators of actin-myosin cytoskeletal dynamics via regulation of Lin11, Isl-1 & Mec-3 domain (LIM) kinase, myosin light chain (MLC), and MLC phosphatase. A strong correlation between cytoskeletal rearrangements and tumor cell invasion, metastasis, and deregulated microenvironment interaction has been reported in the literature, and the utilization of pharmacological inhibitors of ROCK signaling for the treatment of cancer is actively being pursued by a number of pharmaceutical companies. Indeed, in many preclinical models ROCK inhibitors have shown remarkable efficacy in reducing tumor growth and metastasis. Interestingly, ROCK signaling has been shown to be either pro-apoptotic or pro-survival in a cell type and context dependent manner, though the molecular mechanisms controlling ROCK-mediated cell fate decisions are unknown. This review summarizes the many pleiotropic roles of ROCK signaling in survival and apoptosis, and suggests that controlled modulation of ROCK activity in tumor cells has the potential to significantly affect tumor survival and patient outcome.

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.