Homocysteine upregulates soluble epoxide hydrolase in vascular endothelium in vitro and in vivo

Down-regulation of EPHX2 gene transcription by Sp1 under high-glucose conditions

sEH (soluble epoxide hydrolase), which is encoded by the EPHX2 gene, regulates the actions of bioactive lipids, EETs (epoxyeicosatrienoic acids). Previously, we found that high-glucose-induced oxidative stress suppressed sEH levels in a hepatocarcinoma cell line (Hep3B) and sEH was decreased in streptozotocin-induced diabetic mice in vivo. In the present study, we investigated the regulatory mechanisms underlying EPHX2 transcriptional suppression under high-glucose conditions. The decrease in sEH was prevented by an Sp1 (specificity protein 1) inhibitor, mithramycin A, and overexpression or knockdown of Sp1 revealed that Sp1 suppressively regulated sEH expression, in contrast with the general role of Sp1 on transcriptional activation. In addition, we found that AP2α (activating protein 2α) promoted EPHX2 transcription. The nuclear transport of Sp1, but not that of AP2α, was increased under high glucose concomitantly with the decrease in sEH. Within the EPHX2 promoter -56/+32, five Sp1-binding sites were identified, and the mutation of each of these sites showed that the first one (SP1_1) was important in both suppression by Sp1 and activation by AP2α. Furthermore, overexpression of Sp1 diminished the binding of AP2α by DNA-affinity precipitation assay and ChIP, suggesting competition between Sp1 and AP2α on the EPHX2 promoter. These findings provide novel insights into the role of Sp1 in transcriptional suppression, which may be applicable to the transcriptional regulation of other genes.

ERα inhibits epithelial-mesenchymal transition by suppressing Bmi1 in breast cancer

In human breast cancer, estrogen receptor-α (ERα) suppresses epithelial-mesenchymal transition (EMT) and stemness, two crucial parameters for tumor metastasis; however, the underlying mechanism by which ERα regulates these two processes remains largely unknown. Bmi1, the polycomb group protein B lymphoma Mo-MLV insertion region 1 homolog, regulates EMT transition, maintains the self-renewal capacity of stem cells, and is frequently overexpressed in human cancers. In the present study, ERα upregulated the expression of the epithelial marker, E-cadherin, in breast cancer cells through the transcriptional down-regulation of Bmi1. Furthermore, ERα overexpression suppressed the migration, invasion, and EMT of breast cancer cells. Notably, overexpression of ERα significantly decreased the CD44high/CD24low cell population and inhibited the capacity for mammosphere formation in ERα-negative breast cancer cells. In addition, overexpression of Bmi1 attenuated the ERα-mediated suppression of EMT and cell stemness. Immunohistochemistry revealed an inverse association of ERα and Bmi1 expression in human breast cancer tissue. Taken together, our findings suggest that ERα inhibits EMT and stemness through the downregulation of Bmi1.

Homocysteine accelerates senescence of endothelial cells via DNA hypomethylation of human telomerase reverse transcriptase

OBJECTIVE

Homocysteine can accelerate the senescence of endothelial progenitor cells or endothelial cells (ECs) via telomerase inactivation and length shortening. However, the underlying mechanism is unclear. Here, we investigated whether homocysteine promotes endothelial senescence by reducing the expression and activity of human telomerase reverse transcriptase (hTERT) by DNA methylation to reduce ECs telomerase activity.

APPROACH AND RESULTS

When compared with primary human umbilical vein endothelial cells grown under standard conditions, ECs with chronic homocysteine treatment showed accelerated upregulation of p16, p21, and p53, markers of cellular senescence, during 6 to 10 passages. Interestingly, homocysteine-stimulated but not angiotensin II-stimulated ECs senescence could be reversed by hypermethylation induced by folic acid or s-adenosylmethionine supplementation. Meanwhile, homocysteine promoted the shortening of telomere length specifically related to restoration of hTERT transcriptional expression and CCCTC-binding factor binding sites with hTERT promoter hypomethylation, as detected by quantitative real-time polymerase chain reaction, Western blot, methylation-specific polymerase chain reaction, and bisulfite sequencing assay. Electrophoretic mobility shift assay and chromatin immunoprecipitation results showed that homocysteine-reduced telomere activity and homocysteine-induced EC senescence might contribute to hTERT promoter demethylation by increasing CCCTC-binding factor repression and interfering in the SP1 binding to the demethylated hTERT promoter, which might relate with reduced of DNA methyltransferase 1. Furthermore, the CCCTC-binding factor-dependent mechanism of homocysteine-reduced hTERT expression via DNA demethylation was confirmed in aortic endothelia of mice with hyperhomocysteine levels.

CONCLUSIONS

CCCTC-binding factor and SP1 cross talk may contribute to homocysteine-reduced hTERT DNA methylation and expression in endothelial senescence.

Lipoxin generation is related to soluble epoxide hydrolase activity in severe asthma

RATIONALE

Severe asthma is characterized by airway inflammatory responses associated with aberrant metabolism of arachidonic acid. Lipoxins (LX) are arachidonate-derived pro-resolving mediators that are decreased in severe asthma, yet mechanisms for defective LX biosynthesis and a means to increase LXs in severe asthma remain to be established.

OBJECTIVES

To determine if oxidative stress and soluble epoxide hydrolase (sEH) activity are linked to decreased LX biosynthesis in severe asthma.

METHODS

Aliquots of blood, sputum, and bronchoalveolar lavage fluid were obtained from asthma subjects for mediator determination. Select samples were exposed to t-butyl-hydroperoxide or sEH inhibitor (sEHI) before activation. Peripheral blood leukocyte-platelet aggregates were monitored by flow cytometry, and bronchial contraction was determined with cytokine-treated human lung sections.

MEASUREMENTS AND MAIN RESULTS

8-Isoprostane levels in sputum supernatants were inversely related to LXA4 in severe asthma (r = -0.55; P = 0.03) and t-butyl-hydroperoxide decreased LXA4 and 15-epi-LXA4 biosynthesis by peripheral blood leukocytes. LXA4 and 15-epi-LXA4 levels were inversely related to sEH activity in sputum supernatants and sEHIs significantly increased 14,15-epoxy-eicosatrienoic acid and 15-epi-LXA4 generation by severe asthma whole blood and bronchoalveolar lavage fluid cells. The abundance of peripheral blood leukocyte-platelet aggregates was related to asthma severity. In a concentration-dependent manner, LXs significantly inhibited platelet-activating factor-induced increases in leukocyte-platelet aggregates (70.8% inhibition [LXA4 100 nM], 78.3% inhibition [15-epi-LXA4 100 nM]) and 15-epi-LXA4 markedly inhibited tumor necrosis factor-α-induced increases in bronchial contraction.

CONCLUSIONS

LX levels were decreased by oxidative stress and sEH activity. Inhibitors of sEH increased LXs that mediated antiphlogistic actions, suggesting a new therapeutic approach for severe asthma. Clinical trial registered with www.clinicaltrials.gov (NCT 00595114).

Elevated 14,15- epoxyeicosatrienoic acid by increasing of cytochrome P450 2C8, 2C9 and 2J2 and decreasing of soluble epoxide hydrolase associated with aggressiveness of human breast cancer

Background

Epoxyeicosatrienoic acids (EETs) are derived from arachidonic acid by cytochrome P450 (CYP) and metabolized by soluble epoxide hydrolase (sEH). EETs have been associated with cardiovascular disease, diabetes and several cancer diseases. However, the distribution in tissue and role of CYP2C8, 2C9, 2J2 and sEH in human breast carcinogenesis remains uncertain.

Methods

Breast cancer (BC) and adjacent noncancerous tissue was obtained from 40 breast cancer patients in the Chaoshan region in China from 2010 to 2012. The level of 14,15-EET/14,15-DHET in BC patients was detected by ELISA; the expression and distribution of CYP2C8, 2C9, 2J2 and sEH was determined by quantitative RT-PCR and immunohistochemical staining; and cell proliferation and migration was analyzed by MTT and transwell assays, respectively.

Results

The median 14,15-EET and 14,15-EET/DHET level was 2.5-fold higher in BC than noncancerous tissue. The mRNA and protein levels of CYP2C8, 2C9 and 2J2 were higher, and sEH was lower in BC than noncancerous tissue. Furthermore, CYP2C8 and 2C9 protein levels positively correlated with Ki67 status, and CYP2J2 levels positively correlated with histological grade and tumor size. The sEH protein level negatively correlated with tumor size, estrogen receptors and Ki67. In MDA-MB-231 cells, siRNA knockdown of CYP2C8, 2C9 or 2J2 reduced cell proliferation, by 24.5%, 29.13%, or 22.7% and decreased cell migration by 49.1%, 44.9%, and 50.9%, respectively. Similarly, with adenovirus overexpression of sEH, both cell proliferation and migration rates were reduced by 31.4% and 45.8%, respectively.

Conclusions

The present study shows that elevated EET levels in BC tissues are associated with upregulation of CYP2C8, 2C9, and 2J2, and downregulation of sEH, and are also associated with aggressive cell behavior in BC patients.

A MDM2-dependent positive-feedback loop is involved in inhibition of miR-375 and miR-106b induced by Helicobacter pylori lipopolysaccharide

Dysregulation of microRNAs (miRNAs) has been linked to virulence factors of Helicobacter pylori and shown to contribute to the progression of gastric cancer. However, the mechanisms of these processes remain poorly understood. The aim of this study was to investigate the mechanisms by which lipopolysaccharide (LPS), a virulence factor of H. pylori, regulates miR-375 and miR-106b expression in gastric epithelial cells. The results show that LPS from H. pylori 26695 downregulated the expression of miR-375 and miR-106b in gastric epithelial cells, and low levels of Dicer were also observed. Downregulation of miR-375 was found to increase expression of MDM2 with SP1 activation. Overexpression of MDM2 inhibited Dicer by repressing p63 to create a positive-feedback loop involving SP1/MDM2/p63/Dicer that leads to inhibition of miR-375 and miR-106b expression. In addition, we demonstrated that JAK1 and STAT3 were downstream target genes of miR-106b. H. pylori LPS also enhanced the tyrosine phosphorylation of JAK1, JAK2 and STAT3. Together, these results provide insight into the regulatory mechanisms of MDM2 on H. pylori LPS-induced specific miRNAs, and furthermore, suggest that gastric epithelial cells treated with H. pylori LPS may be susceptible to JAK/STAT3 signal pathway activation via inhibition of miR-375 and miR-106b.

The role of epoxide hydrolases in health and disease

Epoxide hydrolases (EH) are ubiquitously expressed in all living organisms and in almost all organs and tissues. They are mainly subdivided into microsomal and soluble EH and catalyze the hydration of epoxides, three-membered-cyclic ethers, to their corresponding dihydrodiols. Owning to the high chemical reactivity of xenobiotic epoxides, microsomal EH is considered protective enzyme against mutagenic and carcinogenic initiation. Nevertheless, several endogenously produced epoxides of fatty acids function as important regulatory mediators. By mediating the formation of cytotoxic dihydrodiol fatty acids on the expense of cytoprotective epoxides of fatty acids, soluble EH is considered to have cytotoxic activity. Indeed, the attenuation of microsomal EH, achieved by chemical inhibitors or preexists due to specific genetic polymorphisms, is linked to the aggravation of the toxicity of xenobiotics, as well as the risk of cancer and inflammatory diseases, whereas soluble EH inhibition has been emerged as a promising intervention against several diseases, most importantly cardiovascular, lung and metabolic diseases. However, there is reportedly a significant overlap in substrate selectivity between microsomal and soluble EH. In addition, microsomal and soluble EH were found to have the same catalytic triad and identical molecular mechanism. Consequently, the physiological functions of microsomal and soluble EH are also overlapped. Thus, studying the biological effects of microsomal or soluble EH alterations needs to include the effects on both the metabolism of reactive metabolites, as well as epoxides of fatty acids. This review focuses on the multifaceted role of EH in the metabolism of xenobiotic and endogenous epoxides and the impact of EH modulations.

Cardiovascular research is thriving in China

Cardiovascular disease has become the leading cause of death and constitutes a serious public health issue in China. Faced with the burgeoning epidemic of cardiovascular disease and the huge burden and economic losses it causes, the Chinese government has attached the utmost importance to cardiovascular research, increasing funding to support basic and clinical studies, integrating resources and recruiting outstanding talent from overseas. The continued and growing support from the government has yielded substantial changes in terms of new discoveries, scientific publications and drug research and development within the last decade. In spite of the advances in cardiovascular research, China still faces significant challenges ahead in encouraging innovation, developing the prevention-oriented health policies and strengthening international collaboration.

Endothelial dysfunction in conduit arteries and in microcirculation. Novel therapeutic approaches

The vascular endothelium not only is a single monolayer of cells between the vessel lumen and the intimal wall, but also plays an important role by controlling vascular function and structure mainly via the production of nitric oxide (NO). The so called "cardiovascular risk factors" are associated with endothelial dysfunction, that reduces NO bioavailability, increases oxidative stress, and promotes inflammation contributing therefore to the development of atherosclerosis. The significant role of endothelial dysfunction in the development of atherosclerosis emphasizes the need for efficient therapeutic interventions. During the last years statins, angiotensin-converting enzyme inhibitors, angiotensin-receptor antagonists, antioxidants, beta-blockers and insulin sensitizers have been evaluated for their ability to restore endothelial function (Briasoulis et al., 2012). As there is not a straightforward relationship between therapeutic interventions and improvement of endothelial function but rather a complicated interrelationship between multiple cellular and sub-cellular targets, research has been focused on the understanding of the underlying mechanisms. Moreover, the development of novel diagnostic invasive and non-invasive methods has allowed the early detection of endothelial dysfunction expanding the role of therapeutic interventions and our knowledge. In the current review we present the available data concerning the contribution of endothelial dysfunction to atherogenesis and review the methods that assess endothelial function with a view to understand the multiple targets of therapeutic interventions. Finally we focus on the classic and novel therapeutic approaches aiming to improve endothelial dysfunction and the underlying mechanisms.

β-amyloid deposition is shifted to the vasculature and memory impairment is exacerbated when hyperhomocysteinemia is induced in APP/PS1 transgenic mice

Introduction

Vascular dementia is the second most common cause of dementia after Alzheimer’s disease (AD). In addition, it is estimated that almost half of all AD patients have significant cerebrovascular disease comorbid with their AD pathology. We hypothesized that cerebrovascular disease significantly impacts AD pathological progression.

Methods

We used a dietary model of cerebrovascular disease that relies on the induction of hyperhomocysteinemia (HHcy). HHcy is a significant clinical risk factor for stroke, cardiovascular disease and type 2 diabetes. In the present study, we induced HHcy in APP/PS1 transgenic mice.

Results

While total β-amyloid (Aβ) load is unchanged across groups, Congophilic amyloid deposition was decreased in the parenchyma and significantly increased in the vasculature as cerebral amyloid angiopathy (CAA; vascular amyloid deposition) in HHcy APP/PS1 mice. We also found that HHcy induced more microhemorrhages in the APP/PS1 mice than in the wild-type mice and that it switched the neuroinflammatory phenotype from an M2a biased state to an M1 biased state. Associated with these changes was an induction of the matrix metalloproteinase protein 2 (MMP2) and MMP9 systems. Interestingly, after 6 months of HHcy, the APP/PS1 mice were cognitively worse than wild-type HHcy mice or APP/PS1 mice, indicative of an additive effect of the cerebrovascular pathology and amyloid deposition.

Conclusions

These data show that cerebrovascular disease can significantly impact Aβ distribution in the brain, favoring vascular deposition. We predict that the presence of cerebrovascular disease with AD will have a significant impact on AD progression and the efficacy of therapeutics.

High-risk human papillomavirus infection associated with telomere elongation in patients with esophageal squamous cell carcinoma with poor prognosis

BACKGROUND

Telomere maintenance is crucial in carcinogenesis and tumor progression. The results of a previous study from the authors indicated that infection with high-risk human papillomavirus (HR-HPV) types 16, 18, and 58 was a risk factor for esophageal squamous cell carcinoma (ESCC) in the Shantou region of China. In the current study, the authors explored the association between HR-HPV infection, telomere length (TL), and DNA methylation and their significance in the prognosis of patients with ESCC.

METHODS

TL and DNA methylation were analyzed by real-time polymerase chain reaction and methylation-specific polymerase chain reaction in 70 cases of ESCC tumor (T) and paired nontumor (NT) tissues and 50 cases of normal esophagus (NE). The prognostic value of TL and DNA methylation in ESCC was analyzed.

RESULTS

TL gradually decreased from NE to NT to T tissue. TL in tumor tissue (T-TL) was found to be longer in tissue that was positive for HR-HPV compared with negative tissue and was found to be positively associated with viral load (Spearman correlation, 0.410; P = .037) and integration (represented by the ratio of HR-HPV E2 to E6/E7 genes; P = .01). The DNA methylation ratio of human telomerase reverse transcriptase was more prevalent with long (≥ 0.7) compared with short (< 0.7) T-TL and was positively correlated with T-TL (Spearman correlation, 0.318; P = .007) and HR-HPV integration (P = .036). Furthermore, Cox proportional hazards modeling revealed a high ratio of T-TL to NT-TL (≥ 0.80) as a factor of poor prognosis, independent of other clinicopathologic variables.

CONCLUSIONS

HR-HPV infection and integration related to telomere elongation and DNA methylation of human telomerase reverse transcriptase may be a potential biomarker of prognosis in patients with ESCC.

Stabilized epoxygenated fatty acids regulate inflammation, pain, angiogenesis and cancer

Epoxygenated fatty acids (EpFAs), which are lipid mediators produced by cytochrome P450 epoxygenases from polyunsaturated fatty acids, are important signaling molecules known to regulate various biological processes including inflammation, pain and angiogenesis. The EpFAs are further metabolized by soluble epoxide hydrolase (sEH) to form fatty acid diols which are usually less-active. Pharmacological inhibitors of sEH that stabilize endogenous EpFAs are being considered for human clinical uses. Here we review the biology of ω-3 and ω-6 EpFAs on inflammation, pain, angiogenesis and tumorigenesis.

Activation of transsulfuration pathway by salvianolic acid a treatment: a homocysteine-lowering approach with beneficial effects on redox homeostasis in high-fat diet-induced hyperlipidemic rats

Background

Elevated homocysteine is a cardiovascular risk factor in hyperlipidemia. Transsulfuration pathway provides an endogenous pathway for homocysteine conversion to antioxidant glutathione (GSH). Salvianolic acid A (Sal A) contains two molecules of caffeic acid and one molecule of danshensu that is capable of enhancing homocysteine transsulfuration, which led to the hypothesis that Sal A has activatory effect on transsulfuration pathway and this effect may have beneficial effects on both homocysteine and redox status in hyperlipidemia.

Methods and results

To test this hypothesis, we developed a rat model of hyperlipidemia induced by high-fat diet for 16 weeks, during which rats were treated with 1 mg/kg salvianolic acid A (Sal A) for the final 4 weeks. Activities of key enzymes and metabolite profiling in the transsulfuration pathway revealed that hyperlipidemia led to elevated plasma homocysteine levels after 16-week dietary treatment, which was associated with reduced activities of homocysteine transsulfuration enzymes, cystathionine β-synthase (CBS) and cystathionine γ-lyase (CSE). The impaired transsulfuration pathway prevented homocysteine transsulfuration to cysteine, resulting in cysteine deficiency and subsequent reduction in GSH pool size. The redox status was altered in the setting of hyperlipidemia as indicated by GSH/GSSG ratio. Sal A treatment increased hepatic CBS and CSE activities, which was associated with reduced accumulation in circulating homocysteine levels and attenuated decline in hepatic cysteine content in hyperlipidemic rats. Sal A also led to an increase in GSH pool size, which subsequently caused a restored GSH/GSSG ratio. The activatory effect of Sal A on CBS was also observed in normal rats and in in vitro experiment.

Conclusion

Our results suggest that activation of transsulfuration pathway by Sal A is a promising homocysteine-lowering approach that has beneficial effects on redox homeostasis in hyperlipidemic settings.

Epigenetic regulation in vascular cells

PURPOSE OF REVIEW

This review summarizes recent findings in the epigenetics of vascular cells and discusses the new challenges for therapeutic strategies of cardiovascular diseases.

RECENT FINDINGS

There is emerging optimism that epigenetic mechanisms can provide the missing link to connect (epi)genomes with the cause of complex diseases. Environmental factors like intrauterine conditions during fetal development appear to preprogram humans for complex diseases. The purpose of this review is to summarize the newest results about the inheritable epigenetic features of cardiovascular diseases. Also, the recently discovered role of small RNAs in epigenetic gene regulation is discussed.

SUMMARY

Epigenetic mechanisms of gene regulation will likely become major determinants in the pathogenesis of complex diseases and may offer new opportunities for the treatment of these diseases.

Homocysteine-related hTERT DNA demethylation contributes to shortened leukocyte telomere length in atherosclerosis

AIMS

Leukocyte telomere length (LTL) is shortened in patients with clinical atherosclerosis (AS). Here we aimed to explore the contribution of elevated homocysteine (Hcy) level to LTL shortening in AS patients and the underlying mechanism.

METHODS

Circulating leukocytes were collected from 197 patients with AS and 165 sex- and age-matched healthy subjects for LTL determination. mRNA expression or DNA methylation of human telomerase reverse transcriptase (hTERT) was determined by real-time PCR and methylation-specific PCR assay, respectively. We established a hyperhomocysteinemia (HHcy) mice model to confirm human results.

RESULTS

Hcy was negatively correlated with LTL shortening in AS patients (r = -0.179, p = 0.015) and controls (r = -0.146, p = 0.031). Serum folate and high-sensitivity C-reactive protein levels significantly interacted with Hcy in LTL shortening. Hcy was related to hTERT mRNA downregulation and promoter demethylation, which combined was associated with LTL shortening in AS patients. Hcy-induced LTL shortening did not differ by sites of AS lesions or infarction. Similar to clinical observations, our HHcy mice model suggested that Hcy induced DNA demethylation and downregulation of mouse TERT and further contributed to LTL shortening.

CONCLUSIONS

Elevated Hcy level induced DNA demethylation of hTERT and was closely related with hTERT downregulation, which led to LTL shortening in AS. These findings provide novel insights into an epigenetic mechanism for Hcy-related AS.

Soluble epoxide hydrolase: gene structure, expression and deletion

Mammalian soluble epoxide hydrolase (sEH) converts epoxides to their corresponding diols through the addition of a water molecule. sEH readily hydrolyzes lipid signaling molecules, including the epoxyeicosatrienoic acids (EETs), epoxidized lipids produced from arachidonic acid by the action of cytochrome p450s. Through its metabolism of the EETs and other lipid mediators, sEH contributes to the regulation of vascular tone, nociception, angiogenesis and the inflammatory response. Because of its central physiological role in disease states such as cardiac hypertrophy, diabetes, hypertension, and pain sEH is being investigated as a therapeutic target. This review begins with a brief introduction to sEH protein structure and function. sEH evolution and gene structure are then discussed before human small nucleotide polymorphisms and mammalian gene expression are described in the context of several disease models. The review ends with an overview of studies that have employed the sEH knockout mouse model.

Roles of the epoxygenase CYP2J2 in the endothelium

Cytochrome p450 (CYP)2J2 is an epoxygenase enzyme that metabolises arachidonic acid to epoxyeicosatrienoic acids (EETs). EETs are inactivated by soluble epoxide hydrolase (sEH), which converts them in to their corresponding dihydroxyeicosatrienoic acids (DHETs). CYP2J2 is highly expressed in cardiovascular tissue including the heart and vascular endothelial cells. CYP2J2 and the EETs it produces have been shown to have a diverse range of effects on the vasculature, including the regulation of inflammation, vascular tone, cellular proliferation, angiogenesis, and metabolism. This review will examine these established and emerging roles of CYP2J2 in the biology of vascular endothelial cells.

Upregulation of soluble epoxide hydrolase in proximal tubular cells mediated proteinuria-induced renal damage

Epoxyeicosatrienoic acids, hydrolyzed by soluble epoxide hydrolase (sEH), have multiple biological functions, including the regulation of vascular tone, renal tubular transport, and being anti-inflammatory. Inhibitors of sEH have been demonstrated to be antihypertensive and renal protective. To elucidate the role of sEH in glomerulonephritis, we first determined the expression of sEH in human kidney by examining biopsies from 153 patients with a variety of glomerulonephritis, including minimal-change, membranous, and IgA nephropathy. Immunohistochemical staining of frozen kidney biopsy samples revealed sEH preferentially expressed in the renal proximal tubular cells, and its expression increased in all patients with glomerulonephritis. The level of sEH in the cortex was positively correlated with proteinuria and negatively with serum albumin level. To investigate the role of sEH in proteinuria-induced renal damage, we incubated purified urine protein from patients with rat renal proximal tubular epithelial cells in vitro. The level of sEH was elevated, as were monocyte chemoattractant protein 1 and the process of tubular epithelial-to-mesenchymal transition, characterized with increased α-smooth muscle actin (α-SMA) and decreased E-cadherin. These effects were attenuated by administration of a potent sEH inhibitor and mimicked with adenovirus-mediated sEH overexpression. In adriamycin-induced nephropathic mice, sEH inhibitor did not ameliorate proteinuria or level of serum albumin but reduced the long-term elevated serum creatinine level, interstitial inflammation, fibrosis, and α-SMA expression. Thus upregulation of sEH in proximal tubular cells in chronic proteinuric kidney diseases may mediate proteinuria-induced renal damage; sEH inhibition by increasing renal eicosanoid levels could prevent the progression of chronic proteinuric kidney diseases.

Mechanisms of epoxyeicosatrienoic acids to improve cardiac remodeling in chronic renal failure disease

Both clinical and basic science studies have demonstrated that cardiac remodeling in patients with chronic renal failure (CRF) is very common. It is a key feature during the course of heart failure and an important risk factor for subsequent cardiac mortality. Traditional drugs or therapies rarely have effects on cardiac regression of CRF and cardiovascular events are still the first cause of death. Epoxyeicosatrienoic acids (EETs) are the products of arachidonic acids metabolized by cytochrome P450 epoxygenases. It has been found that EETs have important biological effects including anti-hypertension and anti-inflammation. Recent data suggest that EETs are involved in regulating cardiomyocyte injury, renal dysfunction, chronic kidney disease (CKD)-related risk factors and signaling pathways, all of which play key roles in cardiac remodeling induced by CRF. This review analyzes the literature to identify the possible mechanisms for EETs to improve cardiac remodeling induced by CRF and indicates the therapeutic potential of EETs in it.

Homocysteine activates vascular smooth muscle cells by DNA demethylation of platelet-derived growth factor in endothelial cells

Hyperhomocysteinemia (HHcy), as an independent risk factor of atherosclerosis, facilitates endothelial dysfunction and activation of vascular smooth muscle cells (VSMCs). However, little is known about the crosstalk between endothelial cells (ECs) and VSMCs under HHcy. We investigated whether homocysteine (Hcy) activates VSMCs by aberrant secretion of mitogen platelet-derived growth factors (PDGFs) from ECs in human and in mice. In this study, we found that increased Hcy level did not affect VSMC activity in 24 hrs until the concentration reached 500 μM. In contrast, Hcy at 100 μM significantly promoted proliferation and migration of VSMCs co-cultured with human ECs. This effect was partially reversed by pretreatment with a PDGF receptor inhibitor. Hcy concentration-dependently upregulated the mRNA level of PDGF-A, -C and -D but not PDGF-B in ECs. Hcy reduced the expression and activity of DNA methyltransferase 1, demethylation of PDGF-A, -C and -D promoters and enhanced the binding activity of transcriptional factor SP-1 to the promoter. Hcy upregulation of PDGF was confirmed in the aortic intima of mice with HHcy. Multivariate regression analysis revealed HHcy was a predictor of increased serum PDGF level in patients. Thus, Hcy upregulates PDGF level via DNA demethylation in ECs, affects cross-talk between ECs and VSMCs and leads to VSMC activation.

Impact of soluble epoxide hydrolase and epoxyeicosanoids on human health

The presence of epoxyeicosatrienoic acids (EETs) in tissues and their metabolism by soluble epoxide hydrolase (sEH) to 1,2-diols were first reported 30 years ago. However, appreciation of their importance in cell biology and physiology has greatly accelerated over the past decade with the discovery of metabolically stable inhibitors of sEH, the commercial availability of EETs, and the development of analytical methods for the quantification of EETs and their diols. Numerous roles of EETs in regulatory biology now are clear, and the value of sEH inhibition in various animal models of disease has been demonstrated. Here, we review these results and discuss how the pharmacological stabilization of EETs and other natural epoxy-fatty acids could lead to possible disease therapies.

Anti-inflammatory effects of epoxyeicosatrienoic acids

Epoxyeicosatrienoic acids (EETs) are generated by the activity of both selective and also more general cytochrome p450 (CYP) enzymes on arachidonic acid and inactivated largely by soluble epoxide hydrolase (sEH), which converts them to their corresponding dihydroxyeicosatrienoic acids (DHETs). EETs have been shown to have a diverse range of effects on the vasculature including relaxation of vascular tone, cellular proliferation, and angiogenesis as well as the migration of smooth muscle cells. This paper will highlight the growing evidence that EETs also mediate a number of anti-inflammatory effects in the cardiovascular system. In particular, numerous studies have demonstrated that potentiation of EET activity using different methods can inhibit inflammatory gene expression and signalling pathways in endothelial cells and monocytes and in models of cardiovascular diseases. The mechanisms by which EETs mediate their effects are largely unknown but may include direct binding to peroxisome proliferator-activated receptors (PPARs), G-protein coupled receptors (GPCRs), or transient receptor potential (TRP) channels, which initiate anti-inflammatory signalling cascades.