Cytochrome P450 2C9-derived epoxyeicosatrienoic acids induce angiogenesis via cross-talk with the epidermal growth factor receptor (EGFR)

Multi-tissue profiling of oxylipins reveal a conserved up-regulation of epoxide:diol ratio that associates with white adipose tissue inflammation and liver steatosis in obesity

BACKGROUND

Obesity drives maladaptive changes in the white adipose tissue (WAT) which can progressively cause insulin resistance, type 2 diabetes mellitus (T2DM) and metabolic dysfunction-associated liver disease (MASLD). Obesity-mediated loss of WAT homeostasis can trigger liver steatosis through dysregulated lipid pathways such as those related to polyunsaturated fatty acid (PUFA)-derived oxylipins. However, the exact relationship between oxylipins and metabolic syndrome remains elusive and cross-tissue dynamics of oxylipins are ill-defined.

METHODS

We quantified PUFA-related oxylipin species in the omental WAT, liver biopsies and plasma of 88 patients undergoing bariatric surgery (female N = 79) and 9 patients (female N = 4) undergoing upper gastrointestinal surgery, using UPLC-MS/MS. We integrated oxylipin abundance with WAT phenotypes (adipogenesis, adipocyte hypertrophy, macrophage infiltration, type I and VI collagen remodelling) and the severity of MASLD (steatosis, inflammation, fibrosis) quantified in each biopsy. The integrative analysis was subjected to (i) adjustment for known risk factors and, (ii) control for potential drug-effects through UPLC-MS/MS analysis of metformin-treated fat explants ex vivo.

FINDINGS

We reveal a generalized down-regulation of cytochrome P450 (CYP)-derived diols during obesity conserved between the WAT and plasma. Notably, epoxide:diol ratio, indicative of soluble epoxide hydrolyse (sEH) activity, increases with WAT inflammation/fibrosis, hepatic steatosis and T2DM. Increased 12,13-EpOME:DiHOME in WAT and liver is a marker of worsening metabolic syndrome in patients with obesity.

INTERPRETATION

These findings suggest a dampened sEH activity and a possible role of fatty acid diols during metabolic syndrome in major metabolic organs such as WAT and liver. They also have implications in view of the clinical trials based on sEH inhibition for metabolic syndrome.

FUNDING

Wellcome Trust (PS3431_WMIH); Duke-NUS (Intramural Goh Cardiovascular Research Award (Duke-NUS-GCR/2022/0020); National Medical Research Council (OFLCG22may-0011); National Institute of Environmental Health Sciences (Z01 ES025034); NIHR Imperial Biomedical Research Centre.

Pathological and pharmacological functions of the metabolites of polyunsaturated fatty acids mediated by cyclooxygenases, lipoxygenases, and cytochrome P450s in cancers

Oxylipins have garnered increasing attention because they were consistently shown to play pathological and/or pharmacological roles in the development of multiple cancers. Oxylipins are the metabolites of polyunsaturated fatty acids via both enzymatic and nonenzymatic pathways. The enzymes mediating the metabolism of PUFAs include but not limited to lipoxygenases (LOXs), cyclooxygenases (COXs), and cytochrome P450s (CYPs) pathways, as well as the down-stream enzymes. Here, we systematically summarized the pleiotropic effects of oxylipins in different cancers through pathological and pharmacological aspects, with specific reference to the enzyme-mediated oxylipins. We discussed the specific roles of oxylipins on cancer onset, growth, invasion, and metastasis, as well as the expression changes in the associated metabolic enzymes and the associated underlying mechanisms. In addition, we also discussed the clinical application and potential of oxylipins and related metabolic enzymes as the targets for cancer prevention and treatment. We found the specific function of most oxylipins in cancers, especially the underlying mechanisms and clinic applications, deserves and needs further investigation. We believe that research on oxylipins will provide not only more therapeutic targets for various cancers but also dietary guidance for both cancer patients and healthy humans.

1,3-Dichloroadamantyl-Containing Ureas as Potential Triple Inhibitors of Soluble Epoxide Hydrolase, p38 MAPK and c-Raf

Soluble epoxide hydrolase (sEH) is an enzyme involved in the metabolism of bioactive lipid signaling molecules. sEH converts epoxyeicosatrienoic acids (EET) to virtually inactive dihydroxyeicosatrienoic acids (DHET). The first acids are "medicinal" molecules, the second increase the inflammatory infiltration of cells. Mitogen-activated protein kinases (p38 MAPKs) are key protein kinases involved in the production of inflammatory mediators, including tumor necrosis factor-α (TNF-α) and cyclooxygenase-2 (COX-2). p38 MAPK signaling plays an important role in the regulation of cellular processes, especially inflammation. The proto-oncogenic serine/threonine protein kinase Raf (c-Raf) is a major component of the mitogen-activated protein kinase (MAPK) pathway: ERK1/2 signaling. Normal cellular Raf genes can also mutate and become oncogenes, overloading the activity of MEK1/2 and ERK1/2. The development of multitarget inhibitors is a promising strategy for the treatment of socially dangerous diseases. We synthesized 1,3-disubstituted ureas and diureas containing a dichloroadamantyl moiety. The results of computational methods show that soluble epoxide hydrolase inhibitors can act on two more targets in different signaling pathways of mitogen-activated protein kinases p38 MAPK and c-Raf. The two chlorine atoms in the adamantyl moiety may provide additional Cl-π interactions in the active site of human sEH. Molecular dynamics studies have shown that the stability of ligand-protein complexes largely depends on the "spacer effect." The compound containing a bridge between the chloroadamantyl fragment and the ureide group forms more stable ligand-protein complexes with sEH and p38 MAPK, which indicates a better conformational ability of the molecule in the active sites of these targets. In turn, a compound containing two chlorine atoms forms a more stable complex with c-Raf, probably due to the presence of additional halogen bonds of chlorine atoms with amino acid residues.

SGLT2 Inhibitor—Dapagliflozin Attenuates Diabetes-Induced Renal Injury by Regulating Inflammation through a CYP4A/20-HETE Signaling Mechanism

Diabetic kidney disease (DKD) is a serious complication of diabetes, affecting millions of people worldwide. Inflammation and oxidative stress are key contributors to the development and progression of DKD, making them potential targets for therapeutic interventions. Sodium-glucose cotransporter 2 inhibitors (SGLT2i) have emerged as a promising class of drugs, with evidence demonstrating that they can improve renal outcomes in people with diabetes. However, the exact mechanism by which SGLT2i exert their renoprotective effects is not yet fully understood. This study demonstrates that dapagliflozin treatment attenuates renal injury observed in type 2 diabetic mice. This is evidenced by the reduction in renal hypertrophy and proteinuria. Furthermore, dapagliflozin decreases tubulointerstitial fibrosis and glomerulosclerosis by mitigating the generation of reactive oxygen species and inflammation, which are activated through the production of CYP4A-induced 20-HETE. Our findings provide insights onto a novel mechanistic pathway by which SGLT2i exerts their renoprotective effects. Overall, and to our knowledge, the study provides critical insights into the pathophysiology of DKD and represents an important step towards improving outcomes for people with this devastating condition.

Targeting soluble epoxide hydrolase promotes osteogenic-angiogenic coupling via activating SLIT3/HIF-1α signalling pathway

Type H vessels have recently been identified to modulate osteogenesis. Epoxyeicostrioleic acids (EETs) have an essential contribution to vascular homeostasis. However, whether increased EETs with soluble epoxide hydrolase (sEH) inhibitor TPPU enhance the coupling of angiogenesis and osteogenesis remains largely unknown. The effects of TPPU on cross-talk between co-cultured human umbilical vein endothelial cells (HUVECs) and human dental pulp stem cells (hDPSCs), and on long bone growth and calvarial defect repair in mice were investigated in vitro and in vivo. TPPU enhanced osteogenic differentiation of co-cultured HUVECs and hDPSCs in vitro and increased type H vessels, and long bone growth and bone repair of calvarial defect. Mechanistically, TPPU promoted cell proliferation and angiogenesis, reclined cell apoptosis, and significantly increased CD31^hi EMCN^hi endothelial cells (ECs) and SLIT3 and HIF-1α expression levels in co-cultured HUVECs and hDPSCs. Knockdown of Slit3 in hDPSCs or Hif-1α in HUVECs impaired the formation of CD31^hi EMCN^hi ECs and reversed TPPU-induced osteogenesis. We defined a previously unidentified effect of TPPU coupling angiogenesis and osteogenesis. TPPU induced type H vessels by upregulating the expression of hDPSCs-derived SLIT3, which resulted in the activation of ROBO1/YAP1/HIF-1α signalling pathway in ECs. Targeting metabolic pathways of EETs represents a new strategy to couple osteogenesis and angiogenesis, sEH is a promising therapeutic target for bone regeneration and repair.

Cytochromes P450: Role in Carcinogenesis and Relevance to Cancers

Abstracts:

Cancer is a leading factor of mortality globally. Cytochrome P450 (CYP) enzymes play a pivotal role in the biotransformation of both endogenous and exogenous compounds. Evidence from numerous epidemiological, animal, and clinical studies points to instrumental role of CYPs in cancer initiation, metastasis, and prevention. Substantial research has found that CYPs are involved in activating different carcinogenic chemicals in the environment, such as polycyclic aromatic hydrocarbons and tobacco-related nitrosamines. Electrophilic intermediates produced from these chemicals can covalently bind to DNA, inducing mutation and cellular transformation that collectively result in cancer development. While bioactivation of procarcinogens and promutagens by CYPs has long been established, the role of CYP-derived endobiotics in carcinogenesis has emerged in recent years. Eicosanoids derived from arachidonic acid via CYP oxidative pathways have been implicated in tumorigenesis, cancer progression and metastasis. The purpose of this review is to update on the current state of knowledge about the cancer molecular mechanism involving CYPs with focus on the biochemical and biotransformation mechanisms in the various CYP-mediated carcinogenesis, and the role of CYP-derived reactive metabolites, from both external and endogenous sources, on cancer growth and tumour formation.

Cytochrome P450-derived fatty acid epoxides and diols in angiogenesis and stem cell biology

Cytochrome P450 (CYP) enzymes are frequently referred to as the third pathway for the metabolism of arachidonic acid. While it is true that these enzymes generate arachidonic acid epoxides i.e. the epoxyeicosatrienoic acids (EETs), they are able to accept a wealth of ω-3 and ω-6 polyunsaturated fatty acids (PUFAs) to generate a large range of regio- and stereo-isomers with distinct biochemical properties and physiological actions. Probably the best studied are the EETs which have well documented effects on vascular reactivity and angiogenesis. CYP enzymes can also participate in crosstalk with other PUFA pathways and metabolize prostaglandin G₂ and H₂, which are the precursors of effector prostaglandins, to affect macrophage function and lymphangiogenesis. The activity of the PUFA epoxides is thought to be kept in check by the activity of epoxide hydrolases. However, rather than being inactive, the diols generated have been shown to regulate neutrophil activation, stem and progenitor cell proliferation and Notch signaling in addition to acting as exercise-induced lipokines. Excessive production of PUFA diols has also been implicated in pathologies such as severe respiratory distress syndromes, including COVID-19, and diabetic retinopathy. This review highlights some of the recent findings related to this pathway that affect angiogenesis and stem cell biology.

Atypical kinetics of cytochrome P450 2J2: Epoxidation of arachidonic acid and reversible inhibition by xenobiotic inhibitors

Extrahepatic CYP2J2 metabolism of arachidonic acid (AA) to bioactive regioisomeric epoxyeicosatrienoic acids (EETs) is implicated in both physiological and pathological conditions. Here, we aimed to characterize atypical substrate inhibition kinetics of this endogenous metabolic pathway and its reversible inhibition by xenobiotic inhibitors when AA is used as the physiologically-relevant substrate vis-à-vis conventional probe substrate astemizole (AST). As compared to typical Michaelis-Menten kinetics observed for AST, complete substrate inhibition was observed for CYP2J2 metabolism of AA to 14,15-EET whereby velocity of the reaction declined significantly at concentrations of AA above 20-30 µM with an estimated substrate inhibition constant (K_s) of 31 µM. In silico sequential docking of two AA substrates to orthosteric (OBS) and adjacent secondary binding sites (SBS) within a 3-dimensional homology model of CYP2J2 revealed favorable and comparable binding poses of glide-scores -3.1 and -3.8 respectively. Molecular dynamics (MD) simulations ascertained CYP2J2 conformational stability with dual AA substrate binding as time-dependent root mean squared deviation (RMSD) of protein Cα atoms and ligand heavy atoms stabilized to a plateau in all but one trajectory (n=6). The distance between heme-iron and ω6 (C14, C15) double bond of AA in OBS also increased from 7.5 ± 1.4 Å to 8.5 ± 1.8 Å when CYP2J2 was simulated with only AA in OBS versus the presence of AA in both OBS and SBS (p<0.001), supporting the observed in vitro substrate inhibition phenomenon. Poor correlation was observed between inhibitory constants (K_i) determined for a panel of nine competitive and mixed mode xenobiotic inhibitors against CYP2J2 metabolism of AA as compared to AST, whereby 4 out of 9 drugs had a greater than 5-fold difference between K_i values. Nonlinear Eadie-Hofstee plots illustrated that complete substrate inhibition of CYP2J2 by AA was not attenuated even at high concentrations of xenobiotic inhibitors which further corroborates that CYP2J2 may accommodate three or more ligands simultaneously. In light of the atypical kinetics, our results highlight the importance of using physiologically-relevant substrates in in vitro enzymatic inhibition assays for the characterization of xenobiotic-endobiotic interactions which is applicable to other complex endogenous metabolic pathways beyond CYP2J2 metabolism of AA to EETs. The accurate determination of K_i would further facilitate the association of xenobiotic-endobiotic interactions to observed therapeutic or toxic outcomes.

Metabolism pathways of arachidonic acids: mechanisms and potential therapeutic targets

The arachidonic acid (AA) pathway plays a key role in cardiovascular biology, carcinogenesis, and many inflammatory diseases, such as asthma, arthritis, etc. Esterified AA on the inner surface of the cell membrane is hydrolyzed to its free form by phospholipase A2 (PLA2), which is in turn further metabolized by cyclooxygenases (COXs) and lipoxygenases (LOXs) and cytochrome P450 (CYP) enzymes to a spectrum of bioactive mediators that includes prostanoids, leukotrienes (LTs), epoxyeicosatrienoic acids (EETs), dihydroxyeicosatetraenoic acid (diHETEs), eicosatetraenoic acids (ETEs), and lipoxins (LXs). Many of the latter mediators are considered to be novel preventive and therapeutic targets for cardiovascular diseases (CVD), cancers, and inflammatory diseases. This review sets out to summarize the physiological and pathophysiological importance of the AA metabolizing pathways and outline the molecular mechanisms underlying the actions of AA related to its three main metabolic pathways in CVD and cancer progression will provide valuable insight for developing new therapeutic drugs for CVD and anti-cancer agents such as inhibitors of EETs or 2J2. Thus, we herein present a synopsis of AA metabolism in human health, cardiovascular and cancer biology, and the signaling pathways involved in these processes. To explore the role of the AA metabolism and potential therapies, we also introduce the current newly clinical studies targeting AA metabolisms in the different disease conditions.

Expression and Function of Eicosanoid-Producing Cytochrome P450 Enzymes in Solid Tumors

Oxylipins derived from the oxidation of polyunsaturated fatty acids (PUFAs) act as important paracrine and autocrine signaling molecules. A subclass of oxylipins, the eicosanoids, have a broad range of physiological outcomes in inflammation, the immune response, cardiovascular homeostasis, and cell growth regulation. Consequently, eicosanoids are implicated in the pathophysiology of various diseases, most notably cancer, where eicosanoid mediated signaling is involved in tumor development, progression, and angiogenesis. Cytochrome P450s (CYPs) are a superfamily of heme monooxygenases generally involved in the clearance of xenobiotics while a subset of isozymes oxidize PUFAs to eicosanoids. Several eicosanoid forming CYPs are overexpressed in tumors, elevating eicosanoid levels and suggesting a key function in tumorigenesis and progression of tumors in the lung, breast, prostate, and kidney. This review summarizes the current understanding of CYPs' involvement in solid tumor etiology and progression providing supporting public data for gene expression from The Cancer Genome Atlas.

Cyp2c44 regulates prostaglandin synthesis, lymphangiogenesis, and metastasis in a mouse model of breast cancer

Arachidonic acid epoxides generated by cytochrome P450 (CYP) enzymes have been linked to increased tumor growth and metastasis, largely on the basis of overexpression studies and the application of exogenous epoxides. Here we studied tumor growth and metastasis in Cyp2c44^-/- mice crossed onto the polyoma middle T oncogene (PyMT) background. The resulting PyMT^2c44 mice developed more primary tumors earlier than PyMT mice, with increased lymph and lung metastasis. Primary tumors from Cyp2c44-deficient mice contained higher numbers of tumor-associated macrophages, as well as more lymphatic endothelial cells than tumors from PyMT mice. While epoxide and diol levels were comparable in tumors from both genotypes, prostaglandin (PG) levels were higher in the PyMT^Δ2c44 tumors. This could be accounted for by the finding that Cyp2c44 metabolized the PG precursor, PGH₂ to 12(S)-hydroxyheptadeca-5Z,8E,10E-trienoic acid (12-HHT), thus effectively reducing levels of effector PGs (including PGE₂). Next, proteomic analyses revealed an up-regulation of WD repeating domain FYVE1 (WDFY1) in tumors from PyMT^Δ2c44 mice, a phenomenon that was reproduced in Cyp2c44-deficient macrophages as well as by PGE₂ Mechanistically, WDFY1 was involved in Toll-like receptor signaling, and its down-regulation in human monocytes attenuated the LPS-induced phosphorylation of IFN regulatory factor 3 and nuclear factor-κB. Taken together, our results indicate that Cyp2c44 protects against tumor growth and metastasis by preventing the synthesis of PGE₂ The latter eicosanoid influenced macrophages at least in part by enhancing Toll-like receptor signaling via the up-regulation of WDFY1.

Time-resolved phosphoproteomic analysis elucidates hepatic 11,12-Epoxyeicosatrienoic acid signaling pathways

Epoxyeicosatrienoic acids (EETs) are potent lipid mediators with well-established effects in vascular tissues. Recent studies indicated an emerging role of these eicosanoids in metabolic diseases and the EET signaling pathway was shown to be involved in hepatic insulin sensitivity. However, compared to vascular tissues, there is only limited knowledge about the underlying signaling pathways in the liver. Therefore, we employed an LC-MS/MS-based time-resolved phosphoproteomics approach to characterize 11,12-EET-mediated signaling events in the liver cell line Hepa 1-6. 11,12-EET treatment resulted in the time-dependent regulation of phosphopeptides involved in processes as yet unknown to be affected by EETs, including RNA processing, splicing and translation regulation. Pathway analysis combined with western blot-based validation revealed enhanced AKT/mTOR/p70S6K signaling as demonstrated by increased acute phosphorylation of AKT (Ser473) and p70S6K (Thr389). In addition, 11,12-EET treatment led to differential regulation of phosphopeptides including important mediators of the DNA damage response and we observed a prolonged induction of the etoposide-induced DNA damage marker γH2AX in response to 11,12-EET. In summary, our findings extend current knowledge of 11,12-EET signaling events and emphasize the importance of the AKT/mTOR/p70S6K pathway in hepatic 11,12-EET signaling. Based on the results presented in this study, we furthermore propose a novel role of EET signaling in the regulation of the DNA damage response.

Epoxyeicosatrienoic acid (EET)-stimulated angiogenesis is mediated by epoxy hydroxyeicosatrienoic acids (EHETs) formed from COX-2

Epoxyeicosatrienoic acids (EETs) are formed from the metabolism of arachidonic acid by cytochrome P450s. EETs promote angiogenesis linked to tumor growth in various cancer models that is attenuated in vivo by cyclooxygenase 2 (COX-2) inhibitors. This study further defines a role for COX-2 in mediating endothelial EET metabolism promoting angiogenesis. Using human aortic endothelial cells (HAECs), we quantified 8,9-EET-induced tube formation and cell migration as indicators of angiogenic potential in the presence and absence of a COX-2 inducer [phorbol 12,13-dibutyrate (PDBu)]. The angiogenic response to 8,9-EET in the presence of PDBu was 3-fold that elicited by 8,9-EET stabilized with a soluble epoxide hydrolase inhibitor (t-TUCB). Contributing to this response was the COX-2 metabolite of 8,9-EET, the 11-hydroxy-8,9-EET (8,9,11-EHET), which exogenously enhanced angiogenic responses in HAECs at levels comparable to those elicited by vascular endothelial growth factor (VEGF). In contrast, the 15-hydroxy-8,9-EET isomer was also formed but inactive. The 8,9,11-EHET also promoted expression of the VEGF family of tyrosine kinase receptors. These results indicate that 8,9-EET-stimulated angiogenesis is enhanced by COX-2 metabolism in the endothelium through the formation of 8,9,11-EHET. This alternative pathway for the metabolism of 8,9-EET may be particularly important in regulating angiogenesis under circumstances in which COX-2 is induced, such as in cancer tumor growth and inflammation.

Polymorphisms of CYP2C8 Alter First-Electron Transfer Kinetics and Increase Catalytic Uncoupling

Cytochrome P450 2C8 (CYP2C8) epoxygenase is responsible for the metabolism of over 60 clinically relevant drugs, notably the anticancer drug Taxol (paclitaxel, PAC). Specifically, there are naturally occurring polymorphisms, CYP2C8*2 and CYP2C8*3, that display altered PAC hydroxylation rates despite these mutations not being located in the active site. Herein, we demonstrate that these polymorphisms result in a greater uncoupling of PAC metabolism by increasing the amount of hydrogen peroxide formed per PAC turnover. Anaerobic stopped-flow measurements determined that these polymorphisms have altered first electron transfer kinetics, compared to CYP2C8*1 (wildtype), that suggest electron transfer from cytochrome P450 reductase (CPR) is disfavored. Therefore, these data demonstrate that these polymorphisms affect the catalytic cycle of CYP2C8 and suggest that redox interactions with CPR are disrupted.

New Lipid Mediators in Retinal Angiogenesis and Retinopathy

Retinal diseases associated with vascular destabilization and the inappropriate proliferation of retinal endothelial cells have major consequences on the retinal vascular network. In extreme cases, the development of hypoxia, the upregulation of growth factors, and the hyper-proliferation of unstable capillaries can result in bleeding and vision loss. While anti-vascular endothelial growth factor therapy and laser retinal photocoagulation can be used to treat the symptoms of late stage disease, there is currently no treatment available that can prevent disease progression. Cytochrome P450 enzymes metabolize endogenous substrates (polyunsaturated fatty acids) to bioactive fatty acid epoxides that demonstrate biological activity with generally protective/anti-inflammatory and insulin-sensitizing effects. These epoxides are further metabolized by the soluble epoxide hydrolase (sEH) to fatty acid diols, high concentrations of which have vascular destabilizing effects. Recent studies have identified increased sEH expression and activity and the subsequent generation of the docosahexaenoic acid-derived diol; 19,20-dihydroxydocosapentaenoic acid, as playing a major role in the development of diabetic retinopathy. This review summarizes current understanding of the roles of cytochrome P450 enzyme and sEH–derived PUFA mediators in retinal disease.

Catalytic Mechanisms of Nanozymes and Their Applications in Biomedicine

The research on nanozymes has increased dramatically in recent years and a new interdiscipline, nanozymology, has emerged. A variety of nanomaterials have been designed to mimic the characteristics of natural enzymes, which connects an important bridge between nanotechnology and biological science. Unlike natural enzymes, the nanoscale properties of nanozymes endow them with the potential to regulate their enzymatic-like activity from different perspectives. The mechanisms behind those methods are intriguing. In this Review, we introduce these mechanisms from the aspects of surface chemistry, surface modification, molecular imprinting, and hybridization and then focus attention on some specific catalytic mechanisms of several representative nanozymes. The applications of nanozymes ranging from bioassay, imaging, to disease therapy are also discussed in detail to prove the fact that the inherent physicochemical properties of nanomaterials not only make nanozymes the analogues of biological enzymes, but also endow them with incomparable advantages and broad prospects in biomedical fields. Finally, four characteristics and some challenges of nanozymes are summarized.

Angiogenesis and vascular stability in eicosanoids and cancer

Angiogenesis and inflammation are hallmarks of cancer. Arachidonic acid and other polyunsaturated fatty acids (PUFAs) are primarily metabolized by three distinct enzymatic systems initiated by cyclooxygenases, lipoxygenases, and cytochrome P450 enzymes (CYP) to generate bioactive eicosanoids, including prostanoids, leukotrienes, hydroxyeicosatetraenoic acids, and epoxyeicosatrienoic acids. As some of the PUFA metabolites playing essential roles in inflammatory processes, these pathways have been widely studied as therapeutic targets of inflammation. Because of their anti-inflammatory effects, these pathways were also proposed as anti-cancer targets. However, although the eicosanoids were linked to endothelial cell proliferation and angiogenesis almost two decades ago, it is only recently PUFA metabolites, especially those generated by CYP enzymes and the soluble epoxide hydrolase (sEH), have been recognized as important signaling mediators in physiological and pathological angiogenesis. Despite the fact that tumor growth and invasion are heavily dependent on inner-tumor angiogenesis and influenced by vascular stability, the role played by PUFA metabolites in tumor angiogenesis and vessel integrity has been largely overlooked. This review highlights current knowledge on the function of PUFA metabolites generated by the CYP/sEH pathway in angiogenesis and vascular stability as well as their potential involvement in cancer development.

Prospective for cytochrome P450 epoxygenase cardiovascular and renal therapeutics

Therapeutics for arachidonic acid pathways began with the development of non-steroidal anti-inflammatory drugs that inhibit cyclooxygenase (COX). The enzymatic pathways and arachidonic acid metabolites and respective receptors have been successfully targeted and therapeutics developed for pain, inflammation, pulmonary and cardiovascular diseases. These drugs target the COX and lipoxygenase pathways but not the third branch for arachidonic acid metabolism, the cytochrome P450 (CYP) pathway. Small molecule compounds targeting enzymes and CYP epoxy-fatty acid metabolites have evolved rapidly over the last two decades. These therapeutics have primarily focused on inhibiting soluble epoxide hydrolase (sEH) or agonist mimetics for epoxyeicosatrienoic acids (EET). Based on preclinical animal model studies and human studies, major therapeutic indications for these sEH inhibitors and EET mimics/analogs are renal and cardiovascular diseases. Novel small molecules that inhibit sEH have advanced to human clinical trials and demonstrate promise for cardiovascular diseases. Challenges remain for sEH inhibitor and EET analog drug development; however, there is a high likelihood that a drug that acts on this third branch of arachidonic acid metabolism will be utilized to treat a cardiovascular or kidney disease in the next decade.

Extract of Penicillium sclerotiorum an endophytic fungus isolated from Cassia fistula L. induces cell cycle arrest leading to apoptosis through mitochondrial membrane depolarization in human cervical cancer cells

Seventeen endophytic fungi were isolated from various tissues of Cassia fistula and the ethyl acetate extracts obtained from 21-day cultures of all the endophytic fungal isolates were initially screened for their cytotoxicity against HeLa (human cervical carcinoma) cells using MTT assay. Of these, Penicillium sclerotiorum extract (PSE), significantly affected the viability of HeLa cells in a dose-dependent manner. The extract of P. Sclerotiorum was further analyzed by GC-MS, which showed three compounds, hexadecanoic acid, oleic acid and benzoic acid to be the major active principles in the extracts.The extract was further tested for invitro cytotoxicity against five cancer cell lines. Of the cell lines tested, HeLa cells showed maximum sensitivity followed by A549, while A431 and U251 were moderately sensitive and MCF-7 was insensitive to the treatment. In addition, normal human embryonic kidney cells, HEK293 remained insensitive to the treatment. Furthermore, the mechanism of cytotoxic activity exhibited by PSE was investigated by evaluating cell cycle progression and apoptotic induction in HeLa cells. Cell cycle analysis revealed that the PSE arrested cells at S and G2/M phase of the cell cycle in a dose-dependent manner. Annexin V- Propidium iodide double staining showed that, the extract potentiates apoptosis rather than necrosis in cells. This was supported by the down regulation in the proapoptotic protein BCL2 and up regulation of BAX (BCL2 Associated X), tumor suppressor protein, p53 and Apaf-1 [Apoptotic Peptidase Activating Factor 1]. Loss of mitochondrial membrane potential and a distinct DNA fragmentation pattern observed following the treatment, suggest that the PSE treatment leads to activation of mitochondrial pathway of apoptosis. Further, the extract also exhibited both antioxidant and anti-angiogenic properties. These results indicate that endophytic fungi isolated from medicinal plants may serve as potential sources of the anti-cancerous compounds.

Lysosomal acid lipase promotes cholesterol ester metabolism and drives clear cell renal cell carcinoma progression

OBJECTIVES

Clear cell renal cell carcinoma (ccRCC) is characterized histologically by accumulation of cholesterol esters, cholesterol and other neutral lipids. Lysosomal acid lipase (LAL) is a critical enzyme involved in the cholesterol ester metabolism. Here, we sought to determine whether LAL could orchestrate metabolism of cholesterol esters in order to promote ccRCC progression.

MATERIALS AND METHODS

Quantitative reverse-transcription PCR and western blots were conducted to assess the expression of LAL in human ccRCC tissues. We analysed the relationship between LAL levels and patient survival using tissue microarrays. We used cell proliferation assays, colony formation assays, cell death assays, metabolic assays and xenograft tumour models to evaluate the biological function and underlying mechanisms.

RESULTS

LAL was up-regulated in ccRCC tissue. Tissue microarray analysis revealed higher levels of LAL in advanced grades of ccRCC, and high LAL expression indicated lower patient survival. Suppressing LAL expression not only blocked the utilization of cholesterol esters but also impaired proliferation and cellular survival. Furthermore, immunohistochemistry staining showed that LAL expression was correlated with Akt phosphorylation. Suppressing LAL expression decreased the phosphorylation level of Akt and Src and reduced the level of 14,15-epoxyeicosatrienoic acids in ccRCC cells. Supplement of 14,15-epoxyeicosatrienoic acids rescued proliferation in vitro and in vivo.

CONCLUSIONS

LAL promoted cell proliferation and survival via metabolism of epoxyeicosatrienoic acids and activation of the Src/Akt pathway.

Orally Active Epoxyeicosatrienoic Acid Analogs

Biologically active epoxyeicosatrienoic acid (EET) regioisomers are synthesized from arachidonic acid by cytochrome P450 epoxygenases of endothelial, myocardial, and renal tubular cells. EETs relax vascular smooth muscle and decrease inflammatory cell adhesion and cytokine release. Renal EETs promote sodium excretion and vasodilation to decrease hypertension. Cardiac EETs reduce infarct size after ischemia-reperfusion injury and decrease fibrosis and inflammation in heart failure. In diabetes, EETs improve insulin sensitivity, increase glucose tolerance, and reduce the renal injury. These actions of EETs emphasize their therapeutic potential. To minimize metabolic inactivation, 14,15-EET agonist analogs with stable epoxide bioisosteres and carboxyl surrogates were developed. In preclinical rat models, a subset of agonist analogs, termed EET-A, EET-B, and EET-C22, are orally active with good pharmacokinetic properties. These orally active EET agonists lower blood pressure and reduce cardiac and renal injury in spontaneous and angiotensin hypertension. Other beneficial cardiovascular actions include improved endothelial function and cardiac antiremodeling actions. In rats, EET analogs effectively combat acute and chronic kidney disease including drug- and radiation-induced kidney damage, hypertension and cardiorenal syndrome kidney damage, and metabolic syndrome and diabetes nephropathy. The compelling preclinical efficacy supports the prospect of advancing EET analogs to human clinical trials for kidney and cardiovascular diseases.

Role of Müller cell cytochrome P450 2c44 in murine retinal angiogenesis

Polyunsaturated fatty acids (PUFA) and their cytochrome P450 (CYP450) metabolites have been linked to angiogenesis and vessel homeostasis. However, the role of individual CYP isoforms and their endogenous metabolites in those processes are not clear. Here, we focused on the role of Cyp2c44 in postnatal retinal angiogenesis and report that Cyp2c44 is highly expressed in Müller glial cells in the retina. The constitutive as well as inducible postnatal genetic deletion of Cyp2c44 resulted in an increased vessel network density without affecting vessel radial expansion during the first postnatal week. This phenotype was associated with an increased endothelial cell proliferation and attenuated Notch signaling. LC-MS/MS analyses revealed that levels of hydroxydocosahexaenoic acids (HDHA), i.e., 10-, 17- and 20-HDHA were significantly elevated in retinas from 5day old Cyp2c44^-/- mice compared to their wild-type littermates. Enzymatic activity assays revealed that HDHAs were potential substrates for Cyp2c44 which could account for the increased levels of HDHAs in retinas from Cyp2c44^-/- mice. These data indicate that Cyp2c44 is expressed in the murine retina and, like the soluble epoxide hydrolase, is expressed in Müller glia cells. The enhanced endothelial cell proliferation and Notch inhibition seen in retinas from Cyp2c44-deficient mice indicate a role for Cyp2c44-derived lipid mediators in physiological angiogenesis.

Association of serum levels of AngII, KLK1, and ACE/KLK1 polymorphisms with acute myocardial infarction induced by coronary artery stenosis

Introduction:

The study aims to confirm the association of acute myocardial infarction (AMI) with serum angiotensin II (AngII), kallikrein1 (KLK1), and ACE/KLK1 polymorphisms.

Materials and methods:

Serum AngII/KLK1 levels and ACE and KLK1 genotypes were determined in 208 patients with AMI and 216 normal controls. Binary logistic regression was used for data analysis.

Results:

The differences in serum AngII levels were statistically significant between the groups. After adjusting for potential confounding factors, high serum levels of AngII and KLK1 significantly increased the risk of AMI. The individuals with ACE DD and KLK1 GG genotypes significantly increased the risk of AMI compared with those harboring the ACE II and KLK1 AA genotypes (OR = 8.77, 95% CI = 1.74–44.16).

Conclusions:

(1) Increasing the serum levels of AngII increased the risk of AMI. (2) The risk of AMI increased significantly when the serum levels of AngII and KLK1 simultaneously increased. (3) Individuals with the combined genotypes of ACE DD and KLK1 GG showed significantly increased risk of AMI compared with those with the combined genotypes of ACE II and KLK1 AA.

Soluble Epoxide Hydrolase as a Potential Key Factor for Human Prenatal Development

Soluble epoxide hydrolase (sEH) converts highly active epoxyeicosatrienoic acids (EETs) generated by cytochrome P450 (CYP) epoxygenases from arachidonic acid to less active dihydroxyeicosatrienoic acids. Because of the role of EETs in processes potentially relevant to the development of organisms, EETs could be suggested as potential morphogens. Unfortunately, only little is known about sEH expression during human intrauterine development (IUD). We investigated the spatio-temporal expression pattern of sEH in human embryonic/foetal intestines, liver and kidney from the 6th to the 20th week of IUD by two-step immunohistochemistry. sEH was expressed during the whole tested period of prenatal development and its level of expression remained more or less the same during the estimated period of IUD. Distribution of CYP epoxygenases and sEH in the intestinal epithelium and the nephrogenic zone of the kidney suggests an influence of EETs on cell proliferation and differentiation and, consequently, on the development of intestines and kidney. Thus, alterations in the strict spatio-temporal pattern of expression of CYP epoxygenases and/or sEH during human prenatal development by xenobiotics could have a harmful impact for developing organisms.

Epoxyeicosatrienoic Acids and 20-Hydroxyeicosatetraenoic Acid on Endothelial and Vascular Function

Endothelial and vascular smooth cells generate cytochrome P450 (CYP) arachidonic acid metabolites that can impact endothelial cell function and vascular homeostasis. The objective of this review is to focus on the physiology and pharmacology of endothelial CYP metabolites. The CYP pathway produces two types of eicosanoid products: epoxyeicosatrienoic acids (EETs), formed by CYP epoxygenases, and hydroxyeicosatetraenoic acids (HETEs), formed by CYP hydroxylases. Advances in CYP enzymes, EETs, and 20-HETE by pharmacological and genetic means have led to a more complete understanding of how these eicosanoids impact on endothelial cell function. Endothelial-derived EETs were initially described as endothelial-derived hyperpolarizing factors. It is now well recognized that EETs importantly contribute to numerous endothelial cell functions. On the other hand, 20-HETE is the predominant CYP hydroxylase synthesized by vascular smooth muscle cells. Like EETs, 20-HETE acts on endothelial cells and impacts importantly on endothelial and vascular function. An important aspect for EETs and 20-HETE endothelial actions is their interactions with hormonal and paracrine factors. These include interactions with the renin-angiotensin system, adrenergic system, puringeric system, and endothelin. Alterations in CYP enzymes, 20-HETE, or EETs contribute to endothelial dysfunction and cardiovascular diseases such as ischemic injury, hypertension, and atherosclerosis. Recent advances have led to the development of potential therapeutics that target CYP enzymes, 20-HETE, or EETs. Thus, future investigation is required to obtain a more complete understanding of how CYP enzymes, 20-HETE, and EETs regulate endothelial cell function.

20-HETE Activates the Transcription of Angiotensin-Converting Enzyme via Nuclear Factor-κB Translocation and Promoter Binding

Increased vascular 20-hydroxyeicosatetraenoic acid (20-HETE), a cytochrome P450 arachidonic acid metabolite, promotes vascular dysfunction, injury, and hypertension that is dependent, in part, on the renin angiotensin system (RAS). We have shown that, in human microvascular endothelial cells, 20-HETE increases angiotensin-converting enzyme (ACE) mRNA, protein, and ACE activity via an epidermal growth factor receptor (EGFR)/tyrosine kinase/mitogen-activated protein kinase (MAPK)/inhibitor of κB kinase (IKK)β-mediated signaling pathway. In this work, we show that, similar to epidermal growth factor (EGF), 20-HETE (10 nM) activates EGFR by stimulating tyrosine phosphorylation; however, unlike 20-HETE, EGF does not induce ACE expression, and pretreatment with a neutralizing antibody against EGF does not prevent the 20-HETE-mediated ACE induction. Inhibition of nuclear factor κB (NF-κB) activation prevented the 4.58-fold (±0.78; P < 0.05) 20-HETE-mediated induction of ACE. The 20-HETE increased NF-κB-binding activity in nuclear extracts and the activity of both the somatic and germinal ACE promoters by 4.37-fold (±0.18; P < 0.05) and 2.53-fold (± 0.24; P < 0.05), respectively. The 20-HETE-stimulated ACE promoter activity was abrogated by the 20-HETE antagonist 20-hydroxy-6,15-eicosadienoic acid and by inhibitors of EGFR, MAPK, IKKβ, and NF-κB activation. Sequence analysis demonstrated the presence of two and one putative NF-κB binding sites on the human somatic and germinal ACE promoters, respectively. Chromatin immunoprecipitation assay indicated that 20-HETE stimulates the translocation and subsequent binding of NF-κB to each of the putative binding sites (S1, 3.43 ± 0.3-fold enrichment versus vehicle; S2, 3.72 ± 0.68-fold enrichment versus vehicle; S3, 3.20 ± 0.18-fold enrichment versus vehicle; P < 0.05). This is the first study to identify NF-κB as a transcriptional factor for ACE and to implicate a distinct EGFR/MAPK/IKK/NF-κB signaling cascade underlying 20-HETE-mediated transcriptional activation of ACE mRNA and stimulation of ACE activity.

Pulmonary hypertension after prolonged hypoxic exposure in mice with a congenital deficiency of Cyp2j

Cytochrome P450 epoxygenase-derived epoxyeicosatrienoic acids contribute to the regulation of pulmonary vascular tone and hypoxic pulmonary vasoconstriction. We investigated whether the attenuated acute vasoconstrictor response to hypoxic exposure of Cyp2j(-/-) mice would protect these mice against the pulmonary vascular remodeling and hypertension associated with prolonged exposure to hypoxia. Cyp2j(-/-) and Cyp2j(+/+) male and female mice continuously breathed an inspired oxygen fraction of 0.21 (normoxia) or 0.10 (hypoxia) in a normobaric chamber for 6 weeks. We assessed hemoglobin (Hb) concentrations, right ventricular (RV) systolic pressure (RVSP), and transthoracic echocardiographic parameters (pulmonary acceleration time [PAT] and RV wall thickness). Pulmonary Cyp2c29, Cyp2c38, and sEH mRNA levels were measured in Cyp2j(-/-) and Cyp2j(+/+) male mice. At baseline, Cyp2j(-/-) and Cyp2j(+/+) mice had similar Hb levels and RVSP while breathing air. After 6 weeks of hypoxia, circulating Hb concentrations increased but did not differ between Cyp2j(-/-) and Cyp2j(+/+) mice. Chronic hypoxia increased RVSP in Cyp2j(-/-) and Cyp2j(+/+) mice of either gender. Exposure to chronic hypoxia decreased PAT and increased RV wall thickness in both genotypes and genders to a similar extent. Prolonged exposure to hypoxia produced similar levels of RV hypertrophy in both genotypes of either gender. Pulmonary Cyp2c29, Cyp2c38, and sEH mRNA levels did not differ between Cyp2j(-/-) and Cyp2j(+/+) male mice after breathing at normoxia or hypoxia for 6 weeks. These results suggest that murine Cyp2j deficiency does not attenuate the development of murine pulmonary vascular remodeling and hypertension associated with prolonged exposure to hypoxia in mice of both genders.

Whatever happened to the epoxyeicosatrienoic Acid-like endothelium-derived hyperpolarizing factor? The identification of novel classes of lipid mediators and their role in vascular homeostasis

SIGNIFICANCE

Cytochrome P450 (CYP) epoxygenases metabolize arachidonic acid (AA) to generate epoxyeicosatrienoic acids (EETs). The latter are biologically active and reported to act as an endothelium-derived hyperpolarizing factor as well as to affect angiogenic and inflammatory signaling pathways.

RECENT ADVANCES

In addition to AA, the CYP enzymes also metabolize the ω-3 polyunsaturated fatty acids (PUFAs) eicosapentaenoic acid and docosahexaenoic acid to generate bioactive lipid epoxide mediators. The latter can be more potent than the EETs, but their actions are under investigated. The ω3-epoxides, like the EETs, are metabolized by the soluble epoxide hydrolase (sEH) to corresponding diols, and epoxide hydrolase inhibition increases epoxide levels and demonstrates anti-hypertensive as well as anti-inflammatory effects.

CRITICAL ISSUES

It seems that the overall consequences of CYP activation largely depend on enzyme substrate preference and the endogenous ω-3/ω-6 PUFA ratio.

FUTURE DIRECTIONS

More studies combining PUFA profiling with cell signaling and disease studies are required to determine the spectrum of molecular pathways affected by the different ω-6 and ω-3 PUFA epoxides and diols. Such information may help improve dietary studies aimed at promoting health via ω-3 PUFA supplementation and/or sEH inhibition.

Opioid receptors and cardioprotection - 'opioidergic conditioning' of the heart

Ischaemic heart disease (IHD) remains a major cause of morbidity/mortality globally, firmly established in Westernized or 'developed' countries and rising in prevalence in developing nations. Thus, cardioprotective therapies to limit myocardial damage with associated ischaemia-reperfusion (I-R), during infarction or surgical ischaemia, is a very important, although still elusive, clinical goal. The opioid receptor system, encompassing the δ (vas deferens), κ (ketocyclazocine) and μ (morphine) opioid receptors and their endogenous opioid ligands (endorphins, dynorphins, enkephalins), appears as a logical candidate for such exploitation. This regulatory system may orchestrate organism and organ responses to stress, induces mammalian hibernation and associated metabolic protection, triggers powerful adaptive stress resistance in response to ischaemia/hypoxia (preconditioning), and mediates cardiac benefit stemming from physical activity. In addition to direct myocardial actions, central opioid receptor signalling may also enhance the ability of the heart to withstand I-R injury. The δ- and κ-opioid receptors are strongly implicated in cardioprotection across models and species (including anti-infarct and anti-arrhythmic actions), with mixed evidence for μ opioid receptor-dependent protection in animal and human tissues. A small number of clinical trials have provided evidence of cardiac benefit from morphine or remifentanil in cardiopulmonary bypass or coronary angioplasty patients, although further trials of subtype-specific opioid receptor agonists are needed. The precise roles and utility of this GPCR family in healthy and diseased human myocardium, and in mediating central and peripheral survival responses, warrant further investigation, as do the putative negative influences of ageing, IHD co-morbidities, and relevant drugs on opioid receptor signalling and protective responses.

Anti-tumor activities of lipids and lipid analogues and their development as potential anticancer drugs

Lipids have the potential for development as anticancer agents. Endogenous membrane lipids, such as ceramides and certain saturated fatty acids, have been found to modulate the viability of tumor cells. In addition, many tumors over-express cyclooxygenase, lipoxygenase or cytochrome P450 enzymes that mediate the biotransformation of ω-6 polyunsaturated fatty acids (PUFAs) to potent eicosanoid regulators of tumor cell proliferation and cell death. In contrast, several analogous products from the biotransformation of ω-3 PUFAs impair particular tumorigenic pathways. For example, the ω-3 17,18-epoxide of eicosapentaenoic acid activates anti-proliferative and proapoptotic signaling cascades in tumor cells and the lipoxygenase-derived resolvins are effective inhibitors of inflammatory pathways that may drive tumor expansion. However, the development of potential anti-cancer drugs based on these molecules is complex, with in vivo stability a major issue. Nevertheless, recent successes with the antitumor alkyl phospholipids, which are synthetic analogues of naturally-occurring membrane phospholipid esters, have provided the impetus for development of further molecules. The alkyl phospholipids have been tested against a range of cancers and show considerable activity against skin cancers and certain leukemias. Very recently, it has been shown that combination strategies, in which alkyl phospholipids are used in conjunction with established anticancer agents, are promising new therapeutic approaches. In future, the evaluation of new lipid-based molecules in single-agent and combination treatments may also be assessed. This could provide a range of important treatment options in the management of advanced and metastatic cancer.

Role of epidermal growth factor receptor in vascular structure and function

PURPOSE OF THE REVIEW

The epidermal growth factor receptor (EGFR) is a receptor tyrosine kinase with a wide implication in tumor biology, wound healing and development. Besides acting as a growth factor receptor activated by ligands such as EGF, the EGFR can also be transactivated and thereby mediate cross-talk with different signaling pathways. The aim of this review is to illustrate the Janus-faced function of the EGFR in the vasculature with its relevance for vascular biology and disease.

RECENT FINDINGS

Over recent years, the number of identified signaling partners of the EGFR has steadily increased, as have the biological processes in which the EGFR is thought to be involved. Recently, new models have allowed investigation of EGFR effects in vivo, shedding some light on the overall function of the EGFR in the vasculature. At the same time, EGFR inhibitors and antibodies have become increasingly established in cancer therapy, providing potential therapeutic tools for decreasing EGFR signaling.

SUMMARY

The EGFR is a versatile signaling pathway integrator associated with vascular homeostasis and disease. In addition to modulating basal vascular tone and tissue homeostasis, the EGFR also seems to be involved in proinflammatory, proliferative, migratory and remodeling processes, with enhanced deposition of extracellular matrix components, thereby promoting vascular diseases such as hypertension or atherosclerosis.

A potential therapeutic effect of CYP2C8 overexpression on anti-TNF-α activity

Epoxyeicosatrienoic acids (EETs) are generated from arachidonic acid catalysed by cytochrome P450 (CYP) epoxygenases. In addition to regulating vascular tone EETs may alleviate inflammation and ROS. The present study was conducted to determine whether CYP2C8 gene overexpression was able to increase the level of EETs, and subsequently prevent TNF-α induced inflammation and reactive oxygen species (ROS) in human umbilical vein endothelial cells (HUVECs) and macrophages. Peroxisome proliferator-activated receptor γ (PPARγ) activation, nuclear factor-κB (NF-κB) activation, endothelial nitric oxide synthase (eNOS) activation, gp-91 activation, and inflammatory cytokine expression were detected by western blot analysis or enzyme-linked immunosorbent assay. Intracellular reactive oxygen species (ROS) was measured by flow cytometry, while the migration of vascular smooth muscle cells (VSMCs) was detected by Transwell assay. pCMV-mediated CYP2C8 overexpression and its metabolites, EETs, markedly suppressed TNF-α induced inflammatory cytokines IL-6 and MCP-1 expression via the activation of NF-κB and degradation of IκBα. Moreover, pretreatment with 11,12-EET significantly blocked TNF-α-induced ROS production. CYP2C8-derived EETs also effectively alleviated the migration of VSMCs and improved the function of endothelial cells through the upregulation of eNOS, which was significantly decreased under the stimulation of TNF-α. Furthermore, these protective effects observed were mediated by PPARγ activation. To the best of our knowledge, the results of the present study demonstrated for the first time that CYP2C8-derived EETs exerted antivascular inflammatory and anti-oxidative effects, at least in part, through the activation of PPARγ. Thus, the CYP2C8 gene may be useful in the prevention and treatment of vascular inflammatory diseases.

The role of cytochrome P450 epoxygenases in retinal angiogenesis

PURPOSE

The purpose of this study was to investigate the role(s) of cytochrome P450 epoxygenases (CYPs) and their products, the epoxyeicosatrienoic acids (EETs), in hypoxia-induced VEGF production and pathologic retinal angiogenesis.

METHODS

Human retinal astrocytes, Müller cells, and retinal microvascular endothelial cells (HRMEC) were exposed to hypoxia, and relative CYP2C expression was measured by RT-PCR. Astrocyte and Müller cell VEGF production was measured by ELISA after exposure to hypoxia and treatment with the general CYP inhibitor, SKF-525a. Human retinal microvascular endothelial cells were treated with the CYP product, 11,12-epoxyeicosatrienoic acid [EET], or SKF-525a in the presence or absence of VEGF. Proliferation of HRMEC and tube formation were assayed. Oxygen-induced retinopathy (OIR) was induced in newborn rats. Retinal CYP2C11 and CYP2C23 expression were measured by RT-PCR. The OIR rats received SKF-525a by intravitreal injection and preretinal neovascularization (NV) was quantified. Retinal VEGF protein levels were measured by ELISA.

RESULTS

Human retinal astrocytes were the only cells to exhibit significant induction of CYP2C8 and CYP2C9 mRNA expression by hypoxia. Astrocytes, but not Müller cells, exhibited reduced hypoxia-induced VEGF production when treated with SKF-525a. 11,12-EET induced HRMEC proliferation and tube formation, and SKF-525a inhibited VEGF-induced proliferation. Oxygen-induced retinopathy induced expression of CYP2C23, but had no effect on CYP2C11. SKF-525a inhibited retinal NV and reduced retinal VEGF levels in OIR rats.

CONCLUSIONS

The CYP-derived 11,12-EET may exhibit a proangiogenic biological function in the retina following stimulation by hypoxia in astrocytes. Inhibition of CYP may provide a rational therapy against retinal NV, because it can reduce VEGF production and VEGF-induced angiogenic responses in endothelial cells.

Lipid-metabolizing CYPs in the regulation and dysregulation of metabolism

The cytochrome P450s (CYPs) represent a highly divergent class of enzymes involved in the oxidation of organic compounds. A subgroup of CYPs metabolize ω3-arachidonic and linoleic acids and ω6-docosahexaenoic and eicosapentaenoic polyunsaturated fatty acids (PUFAs) into a series of related biologically active mediators. Over the past 20 years, increasing evidence has emerged for a role of these PUFA-derived mediators in physiological and pathophysiological processes in the vasculature, during inflammation, and in the regulation of metabolism. With recent technological advances and increased availability of lipid mass spectroscopy, we are now starting to discern the patterns of these CYP-PUFA products in health and disease. These analyses not only are revealing the diverse spectrum of lipid nutrients regulated by CYPs, but also clearly indicate that the balance of these mediators changes with dietary intake of different PUFA classes. These findings suggest that we are only just beginning to understand all of the relevant lipid species produced by CYP pathways. Moreover, we are still a long way from understanding the nature and presence of their receptors, their tissue expression, and the pathophysiological processes they regulate. This review highlights these future issues in the context of lipid-metabolizing CYP enzymes, focusing particularly on the CYP450 family of epoxygenases and the lipid mediators they produce.

The biological actions of 11,12-epoxyeicosatrienoic acid in endothelial cells are specific to the R/S-enantiomer and require the G(s) protein

Cytochrome P450-derived epoxides of arachidonic acid [i.e., the epoxyeicosatrienoic acids (EETs)] are important lipid signaling molecules involved in the regulation of vascular tone and angiogenesis. Because many actions of 11,12-cis-epoxyeicosatrienoic acid (EET) are dependent on the activation of protein kinase A (PKA), the existence of a cell-surface G(s)-coupled receptor has been postulated. To assess whether the responses of endothelial cells to 11,12-EET are enantiomer specific and linked to a potential G protein-coupled receptor, we assessed 11,12-EET-induced, PKA-dependent translocation of transient receptor potential (TRP) C6 channels, as well as angiogenesis. In primary cultures of human endothelial cells, (±)-11,12-EET led to the rapid (30 seconds) translocation a TRPC6-V5 fusion protein, an effect reproduced by 11(R),12(S)-EET, but not by 11(S),12(R)-EET or (±)-14,15-EET. Similarly, endothelial cell migration and tube formation were stimulated by (±)-11,12-EET and 11(R),12(S)-EET, whereas 11(S),12(R)-EET and 11,12-dihydroxyeicosatrienoic acid were without effect. The effects of (±)-11,12-EET on TRP channel translocation and angiogenesis were sensitive to EET antagonists, and TRP channel trafficking was also prevented by a PKA inhibitor. The small interfering RNA-mediated downregulation of G(s) in endothelial cells had no significant effect on responses stimulated by vascular endothelial growth or a PKA activator but abolished responses to (±)-11,12-EET. The downregulation of G(q)/11 failed to prevent 11,12-EET-induced TRPC6 channel translocation or the formation of capillary-like structures. Taken together, our results suggest that a G(s)-coupled receptor in the endothelial cell membrane responds to 11(R),12(S)-EET and mediates the PKA-dependent translocation and activation of TRPC6 channels, as well as angiogenesis.

Cytochrome P450 2J2: distribution, function, regulation, genetic polymorphisms and clinical significance

Cytochrome P450 2J2 (CYP2J2) is an enzyme mainly found in human extrahepatic tissues, with predominant expression in the cardiovascular systems and lower levels in the intestine, kidney, lung, pancreas, brain, liver, etc. During the past 15 years, CYP2J2 has attracted much attention for its epoxygenase activity in arachidonic acid (AA) metabolism. It converts AA to four epoxyeicosatrienoic acids (EETs) that have various biological effects, especially in the cardiovascular systems. In recent publications, CYP2J2 is shown highly expressed in various human tumor cells, and its EET metabolites are demonstrated to implicate in the pathologic development of human cancers. CYP2J2 is also a human CYP that involved in phase I xenobiotics metabolism. Antihistamine drugs and many other compounds were identified as the substrates of CYP2J2, and studies have demonstrated that these substrates have a broad structural diversity. CYP2J2 is found not readily induced by known P450 inducers; however, its expression could be regulated in some pathological conditions, might through the activator protein-1(AP-1), the AP-1-like element and microRNA let-7b. Several genetic mutations in the CYP2J2 gene have been identified in humans, and some of them have been shown to have potential associations with some diseases. With the increasing awareness of its roles in cancer disease and drug metabolism, studies about CYP2J2 are still going on, and various inhibitors of CYP2J2 have been determined. Further studies are needed to delineate the roles of CYP2J2 in disease pathology, drug development and clinical practice.

Müller glia cells regulate Notch signaling and retinal angiogenesis via the generation of 19,20-dihydroxydocosapentaenoic acid

Cytochrome P450 (CYP) epoxygenases generate bioactive lipid epoxides which can be further metabolized to supposedly less active diols by the soluble epoxide hydrolase (sEH). As the role of epoxides and diols in angiogenesis is unclear, we compared retinal vasculature development in wild-type and sEH(-/-) mice. Deletion of the sEH significantly delayed angiogenesis, tip cell, and filopodia formation, a phenomenon associated with activation of the Notch signaling pathway. In the retina, sEH was localized in Müller glia cells, and Müller cell-specific sEH deletion reproduced the sEH(-/-) retinal phenotype. Lipid profiling revealed that sEH deletion decreased retinal and Müller cell levels of 19,20-dihydroxydocosapentaenoic acid (DHDP), a diol of docosahexenoic acid (DHA). 19,20-DHDP suppressed endothelial Notch signaling in vitro via inhibition of the γ-secretase and the redistribution of presenilin 1 from lipid rafts. Moreover, 19,20-DHDP, but not the parent epoxide, was able to rescue the defective angiogenesis in sEH(-/-) mice as well as in animals lacking the Fbxw7 ubiquitin ligase, which demonstrate strong basal activity of the Notch signaling cascade. These studies demonstrate that retinal angiogenesis is regulated by a novel form of neuroretina-vascular interaction involving the sEH-dependent generation of a diol of DHA in Müller cells.

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.

PPARα activation can help prevent and treat non-small cell lung cancer

Non-small cell lung cancer (NSCLC) not amenable to surgical resection has a high mortality rate, due to the ineffectiveness and toxicity of chemotherapy. Thus, there remains an urgent need of efficacious drugs that can combat this disease. In this study, we show that targeting the formation of proangiogenic epoxyeicosatrienoic acids (EET) by the cytochrome P450 arachidonic acid epoxygenases (Cyp2c) represents a new and safe mechanism to treat NSCLC growth and progression. In the transgenic murine K-Ras model and human orthotopic models of NSCLC, we found that Cyp2c44 could be downregulated by activating the transcription factor PPARα with the ligands bezafibrate and Wyeth-14,643. Notably, both treatments reduced primary and metastatic NSCLC growth, tumor angiogenesis, endothelial Cyp2c44 expression, and circulating EET levels. These beneficial effects were independent of the time of administration, whether before or after the onset of primary NSCLC, and they persisted after drug withdrawal, suggesting the benefits were durable. Our findings suggest that strategies to downregulate Cyp2c expression and/or its enzymatic activity may provide a safer and effective strategy to treat NSCLC. Moreover, as bezafibrate is a well-tolerated clinically approved drug used for managing lipidemia, our findings provide an immediate cue for clinical studies to evaluate the utility of PPARα ligands as safe agents for the treatment of lung cancer in humans.