Epoxyeicosatrienoic Acids Attenuate LPS-Induced NIH/3T3 Cell Fibrosis through the A2AR and PI3K/Akt Signaling Pathways.

Inflammation plays a crucial role in progression of fibrosis. Epoxyeicosatrienoic acids (EET) have multiple protective effects in different diseases, but their ability to inhibit the development of LPS-induced fibrosis remains unknown. The potential therapeutic effects of 11,12-EET were studied in in vitro model of LPS-induced fibrosis. Mouse embryonic fibroblast cells NIH/3T3 were pre-incubated with 1 µM 11,12-EET and/or a structural analogue and selective EET antagonist 14,15-epoxyeicosa-5(Z)-enoic acid before exposing to LPS. The effect of EET was evaluated by the protein and mRNA expression of NF-κB, collagens I and III, and α-smooth muscle actin by Western blotting and quantitative reverse transcription PCR, respectively. LPS provoked inflammation and fibrosis-like changes accompanied by elevated expression of NF-κB and collagens in NIH/3T3 cells. We also studied the effects of 11,12-EET on the A2AR and PI3K/Akt signaling pathways in intact and LPS-treated NIH/3T3 cells. 11,12-EET prevented inflammation and fibrosis-like changes through up-regulation of A2AR and PI3K/Akt signaling pathways. Our findings demonstrate the potential antifibrotic effects of 11,12-EET, which can be natural antagonists of tissue fibrosis.

9-HODE and 9-HOTrE alter mitochondrial metabolism, increase triglycerides, and perturb fatty acid uptake and synthesis associated gene expression in HepG2 cells.

Non-Alcoholic Fatty Liver Disease (NAFLD) prevalence is rising and can lead to detrimental health outcomes such as Non-Alcoholic Steatohepatitis (NASH), cirrhosis, and cancer. Recent studies have indicated that Cytochrome P450 2B6 (CYP2B6) is an anti-obesity CYP in humans and mice. Cyp2b-null mice are diet-induced obese, and human CYP2B6-transgenic (hCYP2B6-Tg) mice reverse the obesity or diabetes progression, but with increased liver triglyceride accumulation in association with an increase of several oxylipins. Notably, 9-hydroxyoctadecadienoic acid (9-HODE) produced from linoleic acid (LA, 18:2, ω-6) is the most prominent of these and 9-hydroxyoctadecatrienoic acid (9-HOTrE) from alpha-linolenic acid (ALA, 18:3, ω-3) is the most preferentially produced when controlling for substrate concentrations in vitro. Transactivation assays indicate that 9-HODE and 9-HOTrE activate PPARα and PPARγ. In Seahorse assays performed in HepG2 cells, 9-HOTrE increased spare respiratory capacity, slightly decreased palmitate metabolism, and increased non-glycolytic acidification in a manner consistent with slightly increased glutamine utilization; however, 9-HODE exhibited no effect on metabolism. Both compounds increased triglyceride and pyruvate concentrations, most strongly by 9-HOTrE, consistent with increased spare respiratory capacity. qPCR analysis revealed several perturbations in fatty acid uptake and metabolism gene expression. 9-HODE increased expression of CD36, FASN, PPARγ, and FoxA2 that are involved in lipid uptake and production. 9-HOTrE decreased ANGPTL4 expression and increased FASN expression consistent with increased fatty acid uptake, fatty acid production, and AMPK activation. Our findings support the hypothesis that 9-HODE and 9-HOTrE promote steatosis, but through different mechanisms as 9-HODE is directly involved in fatty acid uptake and synthesis; 9-HOTrE weakly inhibits mitochondrial fatty acid metabolism while increasing glutamine use.

Platelet and epithelial cell interations can be modeled in cell culture, and are not affected by dihomo-gamma-linolenic acid.

Increasing evidence is implicating roles for platelets in the development and progression of ovarian cancer, a highly lethal disease that can arise from the fallopian tubes, and has no current method of early detection or prevention. Thrombosis is a major cause of mortality of ovarian cancer patients suggesting that the cancer alters platelet behavior. The objective of this study was to develop a cell culture model of the pathological interactions of human platelets and ovarian cancer cells, using normal FT epithelial cells as a healthy control, and to test effects of the anti-platelet dihomo-gamma-linolenic acid (DGLA) in the model. Both healthy and cancer cells caused platelet aggregation, however platelets only affected spheroid formation by cancer cells and had no effect on healthy cell spheroid formation. When naturally-formed spheroids of epithelial cells were exposed to platelets in transwell inserts that did not allow direct interactions of the two cell types, platelets caused increased size of the spheroids formed by cancer cells, but not healthy cells. When cancer cell spheroids formed using magnetic nanoshuttle technology were put in direct physical contact with platelets, the platelets caused spheroid condensation. In ovarian cancer cells, DGLA promoted epithelial-to-mesenchymal (EMT) transition at doses as low as 100 µM, and inhibited metabolic viability and induced apoptosis at doses ≥150 µM. DGLA doses ≤150 µM used to avoid direct DGLA effects on cancer cells, had no effect on the pathological interactions of platelets and ovarian cancer cells in our models. These results demonstrate that the pathological interactions of platelets with ovarian cancer cells can be modeled in cell culture, and that DGLA has no effect on these interactions, suggesting that targeting platelets is a rational approach for reducing cancer aggressiveness and thrombosis risk in ovarian cancer patients, however DGLA is not an appropriate candidate for this strategy.

Sorafenib reduces the production of epoxyeicosatrienoic acids and leads to cardiac injury by inhibiting CYP2J in rats.

Sorafenib, an important cancer drug in clinical practice, has caused heart problems such as hypertension, myocardial infarction, and thrombosis. Although some mechanisms of sorafenib-induced cardiotoxicity have been proposed, there is still more research needed to reach a well-established definition of the causes of cardiotoxicity of sorafenib. In this report, we demonstrate that sorafenib is a potent inhibitor of the CYP2J enzyme. Sorafenib significantly inhibited the production of epoxyeicosatrienoic acids (EETs) in rat cardiac microsomes. The in vivo experimental results also showed that after the administration of sorafenib, the levels of 11,12-EET and 14,15-EET in rat plasma were significantly reduced, which was similar to the results of CYP2J gene knockout. Sorafenib decreased the levels of EETs, leading to abnormal expression of mitochondrial fusion and fission factors in heart tissue. In addition, the expression of mitochondrial energy metabolism factors (Pgc-1α, Pgc-1ß, Ampk, and Sirt1) and cardiac mechanism factors (Scn5a and Prkag2) was significantly reduced, increasing the risk of arrhythmia and heart failure. Meanwhile, the increase in injury markers Anp, CK, and CK-MB further confirmed the cardiotoxicity of sorafenib. This study is of great significance for understanding the cardiotoxicity of sorafenib, and is also a model for studying the cardiotoxicity of other drugs that inhibit CYP2J activity.

Awakening neural survival mechanisms after stroke: Lipid metabolism in brain-autonomous repair.

In this issue of Neuron, Nakamura et al.1 report the discovery that neuronally secreted phospholipase PLA2G2E releases dihomo-γ-linolenic acid (DGLA) that generates 15-hydroxy-eicosatrienoic acid (15-HETrE), which in turn induces peptidyl arginine deiminase 4 (PAD4/PADI4) to elicit neuronal pro-survival and pro-reparative events following ischemic brain injury.

CYP2J deficiency leads to cardiac injury and presents dual regulatory effects on cardiac function in rats.

Cytochrome P450 2J2 (CYP2J2) enzyme is widely expressed in aortic endothelial cells and cardiac myocytes and affects cardiac function, but the underlying mechanism is still unclear. Based on CYP2J knockout (KO) rats, we have directly studied the metabolic regulation of CYP2J on cardiac function during aging. The results showed that CYP2J deficiency significantly reduced the content of epoxyeicosatrienoic acids (EETs) in plasma, aggravated myocarditis, myocardial hypertrophy, as well as fibrosis, and inhibited the mitochondrial energy metabolism signal network Pgc-1α/Ampk/Sirt1. With the increase of age, the levels of 11,12-EET and 14,15-EET in plasma of KO rats decreased significantly, and the heart injury was more serious. Interestingly, we found that after CYP2J deletion, the heart initiated a self-protection mechanism by upregulating cardiac mechanism factors Myh7, Dsp, Tnni3, Tnni2, and Scn5a, as well as mitochondrial fusion factors Mfn2 and Opa1. However, this protective effect disappeared with aging. In conclusion, CYP2J deficiency not only reduces the amount of EETs, but also plays a dual regulatory role in cardiac function.

Epoxyeicosatrienoic Acid and Prostanoid Crosstalk at the Receptor and Intracellular Signaling Levels to Maintain Vascular Tone.

Epoxyeicosatrienoic acids (EETs) are signaling lipids produced by the cytochrome P450-(CYP450)-mediated epoxygenation of arachidonic acid. EETs have numerous biological effects on the vascular system, but aspects including their species specificity make their effects on vascular tone controversial. CYP450 enzymes require the 450-reductase (POR) for their activity. We set out to determine the contribution of endothelial CYP450 to murine vascular function using isolated aortic ring preparations from tamoxifen-inducible endothelial cell-specific POR knockout mice (ecPOR-/-). Constrictor responses to phenylephrine were similar between control (CTR) and ecPOR-/- mice. Contrastingly, sensitivity to the thromboxane receptor agonist U46619 and prostaglandin E2 (PGE2) was increased following the deletion of POR. Ex vivo incubation with a non-hydrolyzable EET (14,15-EE-8(Z)-E, EEZE) reversed the increased sensitivity to U46619 to the levels of CTR. EETs had no effect on vascular tone in phenylephrine-preconstricted vessels, but dilated vessels contracted with U46619 or PGE2. As U46619 acts through RhoA-dependent kinase, this system was analyzed. The deletion of POR affected the expression of genes in this pathway and the inhibition of Rho-GTPase with SAR407899 decreased sensitivity to U46619. These data suggest that EET and prostanoid crosstalk at the receptor level and that lack of EET production sensitizes vessels to vasoconstriction via the induction of the Rho kinase system.

Antinociception role of 14,15-epoxyeicosatrienoic acid in a central post-stroke pain model in rats mediated by anti-inflammation and anti-apoptosis effect.

Central post stroke pain (CPSP) is an intractable neuropathic pain syndrome that occurs after the acute focal lesion of the central nervous system (CNS) due to a cerebrovascular cause. Epoxyeicosatrienoic acids (EETs) exert many pharmacological effects in vivo and in vitro, such as anti-apoptosis, anti-inflammatory, and anti-oxidative stress. Neuroinflammation and apoptosis are the potential pathophysiological mechanisms of neuropathic pain. This study aimed to investigate whether 14,15-EET has an antinociception effect on CPSP rats through its anti-inflammation and anti-apoptosis mechanisms. Rats were treated with type IV collagenase (CPSP group) or saline (Sham group) via injection with a Hamilton syringe into the ventral posterior lateral nucleus (VPL) according to the stereotaxic coordinates. We first tested the mechanical withdrawal threshold, as well as neuroinflammation- and apoptosis-related protein expressions in the per-lesion site of CPSP and Sham rats. Sprague-Dawley rats were randomly divided into five groups, as follows: vehicle; EET at 0.025, 0.05, and 0.1 µg; and EET (0.1 µg) + EEZE (3.25 ng). EET or and vehicle were administered into VPL nuclei three consecutive days after hemorrhagic stroke. Immunostaining, ELISA, and Western blot were performed to evaluate neuroinflammation and apoptosis. Hemorrhagic stroke induced mechanical allodynia, glial activation, neuroinflammation, and apoptosis-related protein upregulation. However, early treatment with 14,15-EET inhibited glial cell activation, decreased proinflammatory cytokines and apoptosis-related protein, and alleviated the pain behavior of CPSP rats. Our results provided strong evidence that antinociception produced by 14,15-EET is partly mediated by the inhibition of neuroinflammation and apoptosis.

New Alkoxy- Analogues of Epoxyeicosatrienoic Acids Attenuate Cisplatin Nephrotoxicity In Vitro via Reduction of Mitochondrial Dysfunction, Oxidative Stress, Mitogen-Activated Protein Kinase Signaling, and Caspase Activation.

The usage of cisplatin, a highly potent chemotherapeutic, is limited by its severe nephrotoxicity. Arachidonic acid (ARA)-derived epoxyeicosatrienoic acids (EETs) and soluble epoxide hydrolase (sEH) inhibitors were shown to ameliorate this dose-limiting side effect, but both approaches have some pharmacological limitations. Analogues of EETs are an alternative avenue with unique benefits, but the current series of analogues face concerns regarding their structure and mimetic functionality. Hence, in this study, regioisomeric mixtures of four new ARA alkyl ethers were synthesized, characterized, and assessed as EET analogues against the concentration- and time-dependent toxicities of cisplatin in porcine proximal tubular epithelial cells. All four ether groups displayed bioisostere activity, ranging from marginal for methoxy- (1), good for n-propoxy- (4), and excellent for ethoxy- (2) and i-propoxy- (3). Compounds 2 and 3 displayed cytoprotective effects comparable to that of an EET regioisomeric mixture (5) against high, acute cisplatin exposures but were more potent against low to moderate, chronic exposures. Compounds 2 and 3 (and 5) acted through stabilization of the mitochondrial transmembrane potential and attenuation of reactive oxygen species, leading to reduced phosphorylation of mitogen-activated protein kinases p38 and JNK and decreased activation of caspase-9 and caspase-3. This study demonstrates that alkoxy- groups are potent and more metabolically stable bioisostere alternatives to the epoxide within EETs that enable sEH-independent activity. It also illustrates the potential of ether-based mimics of EETs and other epoxy fatty acids as promising nephroprotective agents to tackle the clinically relevant side effect of cisplatin without compromising its antineoplastic function.

11,12 Epoxyeicosatrienoic Acid Rescues Deteriorated Wound Healing in Diabetes.

Epoxyeicosatrienoic acids (EET) facilitate regeneration in different tissues, and their benefit in dermal wound healing has been proven under normal conditions. In this study, we investigated the effect of 11,12 EET on dermal wound healing in diabetes. We induced diabetes by i.p. injection of streptozotocin 2 weeks prior to wound creation on the dorsal side of the mouse ear. 11,12 EET was applied every second day on the wound, whereas the control groups received only solvent. Epithelialization was monitored every second day intravitally up to wound closure. Wounds were stained for VEGF, CD31, TGF-ß, TNF-α, SDF-1α, NF-κB, and Ki-67, and fibroblasts were counted after hematoxylin-eosin stain on days 3, 6, 9, and 16 after wounding. After induction of diabetes, wounds closed on day 13.00 ± 2.20 standard deviation (SD). Local 11,12 ETT application improved wound closure significantly to day 8.40 ± 1.39 SD. EET treatment enhanced VEGF and CD31 expression in wounds on day 3. It also seemed to raise TNF-α level on all days investigated as well as TGF-ß level on days 3 and 6. A decrease in NF-κB could be observed on days 9 and 16 after EET application. The latter findings were not significant. SDF-1α expression was not influenced by EET application, and Ki-67 was significantly less in the EET group on day 9 after EET application. The number of fibroblasts was significantly increased on day 9 after the 11,12 EET application. 11,12 EET improve deteriorated wound healing in diabetes by enhancing neoangiogenesis, especially in the early phase of wound healing. Furthermore, they contribute to the dissolution of the initial inflammatory reaction, allowing the crucial transition from the inflammatory to proliferative phase in wound healing.

14,15-EET Reduced Brain Injury from Cerebral Ischemia and Reperfusion via Suppressing Neuronal Parthanatos.

To investigate the effect of 14,15-EET on the parthanatos in neurons induced by cerebral ischemia and reperfusion, middle cerebral artery occlusion and reperfusion (MCAO/R) and oxygen glucose deprivation/reoxygenation (OGD/R) were used to simulate cerebral ischemia reperfusion in vivo and in vitro, respectively. TTC staining and the Tunel method were used to detect cerebral infarct volume and neuronal apoptosis. Western blot and immunofluorescence were used to detect poly (ADP-ribose) polymerase-1 (PARP-1) activation and AIF nuclear translocation. The production of reactive oxygen species (ROS) and the expression of antioxidant genes were detected by Mito SOX, DCFH-DA and qPCR methods. MCAO/R increased cerebral infarct volume and neuronal apoptosis in mice, while 14,15-EET pretreatment increased cerebral infarct volume and neuronal apoptosis. OGD/R induced reactive oxygen species generation, PARP-1 cleavage, and AIF nuclear translocation in cortical neurons. 14,15-EET pretreatment could enhance the antioxidant gene expression of glutathione peroxidase (GSH-Px), heme oxygenase-1 (HO-1) and superoxide dismutase (SOD) in cortical neurons after ischemia and reperfusion. 14,15-EET inhibits the neuronal parthanatos induced by MCAO/R through upregulation of the expression of antioxidant genes and by reducing the generation of reactive oxygen species. This study advances the EET neuroprotection theory and provides a scientific basis for targeted clinical drugs that reduce neuronal parthanatos following cerebral ischemia and reperfusion.

[Endogenous protective effects of arachidonic acid epoxygenase metabolites, epoxyeicosatrienoic acids, in cardiovascular system].

The morbidity and mortality of cardiovascular diseases are increasing annually, which is one of the primary causes of human death. Recent studies have shown that epoxyeicosatrienoic acids (EETs), endogenous metabolites of arachidonic acid (AA) via CYP450 epoxygenase, possess a spectrum of protective properties in cardiovascular system. EETs not only alleviate cardiac remodeling and injury in different pathological models, but also improve subsequent hemodynamic disturbances and cardiac dysfunction. Meanwhile, various studies have demonstrated that EETs, as endothelial-derived hyperpolarizing factors, regulate vascular tone by activating various ion channels on endothelium and smooth muscle, which in turn can lower blood pressure, improve coronary blood flow and regulate pulmonary artery pressure. In addition, EETs are protective in endothelium, including inhibiting inflammation and adhesion of endothelial cells, attenuating platelet aggregation, promoting fibrinolysis and revascularization. EETs can also prevent aortic remodeling, including attenuating atherosclerosis, adventitial remodeling, and aortic calcification. Therefore, it is clinically important to study the physiological and pathophysiological effects of EETs in the cardiovascular system to further elucidate the mechanisms, as well as provide new strategy for the prevention and treatment of cardiovascular diseases. This review summarizes the endogenous cardioprotective effects and mechanisms of EETs in order to provide a new insight for research in this field.

Soluble epoxide hydrolase deletion attenuated nicotine-induced arterial stiffness via limiting the loss of SIRT1.

Arterial stiffness, a consequence of smoking, is an underlying risk factor of cardiovascular diseases. Epoxyeicosatrienoic acids (EETs), hydrolyzed by soluble epoxide hydrolase (sEH), have beneficial effects against vascular dysfunction. However, the role of sEH knockout in nicotine-induced arterial stiffness was not characterized. We hypothesized that sEH knockout could prevent nicotine-induced arterial stiffness. In the present study, Ephx2 (the gene encodes sEH enzyme) null (Ephx2-/-) mice and wild-type (WT) littermate mice were infused with or without nicotine and administered with or without nicotinamide [NAM, sirtuin-1 (SIRT1) inhibitor] simultaneously for 4 wk. Nicotine treatment increased sEH expression and activity in the aortas of WT mice. Nicotine infusion significantly induced vascular remodeling, arterial stiffness, and SIRT1 deactivation in WT mice, which was attenuated in Ephx2 knockout mice (Ephx2-/- mice) without NAM treatment. However, the arterial protective effects were gone in Ephx2-/- mice with NAM treatment. In vitro, 11,12-EET treatment attenuated nicotine-induced matrix metalloproteinase 2 (MMP2) upregulation via SIRT1-mediated yes-associated protein (YAP) deacetylation. In conclusion, sEH knockout attenuated nicotine-induced arterial stiffness and vascular remodeling via SIRT1-induced YAP deacetylation.NEW & NOTEWORTHY We presently show that sEH knockout repressed nicotine-induced arterial stiffness and extracellular matrix remodeling via SIRT1-induced YAP deacetylation, which highlights that sEH is a potential therapeutic target in smoking-induced arterial stiffness and vascular remodeling.

Kidney-Targeted Epoxyeicosatrienoic Acid Analog, EET-F01, Reduces Inflammation, Oxidative Stress, and Cisplatin-Induced Nephrotoxicity.

Although epoxyeicosatrienoic acid (EET) analogs have performed well in several acute and chronic kidney disease models, targeted delivery of EET analogs to the kidney can be reasonably expected to reduce the level of drug needed to achieve a therapeutic effect and obviate possible side effects. For EET analog kidney-targeted delivery, we conjugated a stable EET analog to folic acid via a PEG-diamine linker. Next, we compared the kidney targeted EET analog, EET-F01, to a well-studied EET analog, EET-A. EET-A or EET-F01 was infused i.v. and plasma and kidney tissue collected. EET-A was detected in the plasma but was undetectable in the kidney. On the other hand, EET-F01 was detected in the plasma and kidney. Experiments were conducted to compare the efficacy of EET-F01 and EET-A for decreasing cisplatin nephrotoxicity. Cisplatin was administered to WKY rats treated with vehicle, EET-A (10 mg/kg i.p.) or EET-F01 (20 mg/kg or 2 mg/kg i.p.). Cisplatin increased kidney injury markers, viz., blood urea nitrogen (BUN), N-acetyl-ß-(D)-glucosaminidase (NAG), kidney injury molecule-1 (KIM-1), and thiobarbituric acid reactive substances (TBARS). EET-F01 was as effective as EET-A in decreasing BUN, NAG, KIM-1, TBARS, and renal histological injury caused by cisplatin. Despite its almost 2×-greater molecular weight compared with EET-A, EET-F01 was comparably effective in decreasing renal injury at a 10-fold w/w lower dose. EET-F01 decreased cisplatin nephrotoxicity by reducing oxidative stress and inflammation. These data demonstrate that EET-F01 targets the kidney, allows for a lower effective dose, and combats cisplatin nephrotoxicity. In conclusion, we have developed a kidney targeted EET analog, EET-F01, that demonstrates excellent potential as a therapeutic for kidney diseases.

Role of endothelium-pericyte signaling in capillary blood flow response to neuronal activity.

Local blood flow in the brain is tightly coupled to metabolic demands, a phenomenon termed functional hyperemia. Both capillaries and arterioles contribute to the hyperemic response to neuronal activity via different mechanisms and timescales. The nature and specific signaling involved in the hyperemic response of capillaries versus arterioles, and their temporal relationship are not fully defined. We determined the time-dependent changes in capillary flux and diameter versus arteriolar velocity and flow following whisker stimulation using optical microangiography (OMAG) and two-photon microscopy. We further characterized depth-resolved responses of individual capillaries versus capillary networks. We hypothesized that capillaries respond first to neuronal activation, and that they exhibit a coordinated response mediated via endothelial-derived epoxyeicosatrienoates (EETs) acting on pericytes. To visualize peri-capillary pericytes, we used Tie2-GFP/NG2-DsRed mice, and to determine the role of endothelial-derived EETs, we compared cerebrovascular responses to whisker stimulation between wild-type mice and mice with lower endothelial EETs (Tie2-hsEH). We found that capillaries respond immediately to neuronal activation in an orchestrated network-level manner, a response attenuated in Tie2-hsEH and inhibited by blocking EETs action on pericytes. These results demonstrate that capillaries are first responders during functional hyperemia, and that they exhibit a network-level response mediated via endothelial-derived EETs' action on peri-capillary pericytes.

Epoxyeicosatrienoic acids improve glucose homeostasis by preventing NF-κB-mediated transcription of SGLT2 in renal tubular epithelial cells.

Studies have shown that epoxyeicosatrienoic acids (EETs) can regulate glucose homeostasis, but the specific mechanisms need further exploration. The sodium-glucose co-transporter 2 (SGLT2) is highly expressed in diabetic kidneys, which further promotes renal reabsorption of glucose to respond to the hyperglycemic state of diabetes. Herein, whether EETs can be a latent inhibitor of SGLT2 to regulate glucose homeostasis in diabetic state needs to be elucidated. Our study demonstrated that EETs attenuated the glucose reabsorption via renal tubular epithelial cells in diabetic mice, which partly accounted for the beneficial effects of EETs on glucose homeostasis. Moreover, 14,15-EET suppressed SGLT2 expression in both diabetic kidney and renal tubular epithelial cells. Further, inhibition of NF-κB with BAY 11-7082 decreased insulin-induced SGLT2 expression while NF-κB overexpression reversed the above effects. In addition, 14,15-EET attenuated SGLT2 expression via inactivating NF-κB. Mechanistically, 14,15-EET attenuated NF-κB mediated SGLT2 transcription at the -1821/-1812 P65-binding site. These results showed that EETs ameliorated glucose homeostasis via preventing NF-κB-mediated transcription of SGLT2 in renal tubular epithelial cells, providing a unique therapeutic strategy for insulin resistance and diabetes.

Dietary Lipids Induce Ferroptosis in Caenorhabditiselegans and Human Cancer Cells.

Dietary lipids impact development, homeostasis, and disease, but links between specific dietary fats and cell fates are poorly understood. Ferroptosis is an iron-dependent form of nonapoptotic cell death associated with oxidized polyunsaturated phospholipids. Here, we show that dietary ingestion of the polyunsaturated fatty acid (PUFA) dihomogamma-linolenic acid (DGLA; 20:3n-6) can trigger germ-cell ferroptosis and sterility in the nematode Caenorhabditis elegans. Exogenous DGLA is also sufficient to induce ferroptosis in human cells, pinpointing this omega-6 PUFA as a conserved metabolic instigator of this lethal process. In both C. elegans and human cancer cells, ether-lipid synthesis protects against ferroptosis. These results establish C. elegans as a powerful animal model to study the induction and modulation of ferroptosis by dietary fats and indicate that endogenous ether lipids act to prevent this nonapoptotic cell fate.

Epoxyeicosatrienoic acid metabolites inhibit Kir4.1/Kir5.1 in the distal convoluted tubule.

Cytochrome P-450 (Cyp) epoxygenase-dependent metabolites of arachidonic acid (AA) have been shown to inhibit renal Na+ transport, and inhibition of Cyp-epoxygenase is associated with salt-sensitive hypertension. We used the patch-clamp technique to examine whether Cyp-epoxygenase-dependent AA metabolites inhibited the basolateral 40-pS K+ channel (Kir4.1/Kir5.1) in the distal convoluted tubule (DCT). Application of AA inhibited the basolateral 40-pS K+ channel in the DCT. The inhibitory effect of AA on the 40-pS K+ channel was specific because neither linoleic nor oleic acid was able to mimic the effect of AA on the K+ channel. Inhibition of Cyp-monooxygenase with N-methylsulfonyl-12,12-dibromododec-11-enamide or inhibition of cyclooxygenase with indomethacin failed to abolish the inhibitory effect of AA on the 40-pS K+ channel. However, the inhibition of Cyp-epoxygenase with N-methylsulfonyl-6-(propargyloxyphenyl)hexanamide abolished the effect of AA on the 40-pS K+ channel in the DCT. Moreover, addition of either 11,12-epoxyeicosatrienoic acid (EET) or 14,15-EET also inhibited the 40-pS K+ channel in the DCT. Whole cell recording demonstrated that application of AA decreased, whereas N-methylsulfonyl-6-(propargyloxyphenyl)hexanamide treatment increased, Ba2+-sensitive K+ currents in the DCT. Finally, application of 14,15-EET but not AA was able to inhibit the basolateral 40-pS K+ channel in the DCT of Cyp2c44-/- mice. We conclude that Cyp-epoxygenase-dependent AA metabolites inhibit the basolateral Kir4.1/Kir5.1 in the DCT and that Cyp2c44-epoxygenase plays a role in the regulation of the basolateral K+ channel in the mouse DCT.

Cytochrome 450 metabolites of arachidonic acid (20-HETE, 11,12-EET and 14,15-EET) promote pheochromocytoma cell growth and tumor associated angiogenesis.

The importance of cytochrome P450 (CYP)-derived arachidonic acid (AA) metabolites, 20-hydroxyeicosatetraenoic acid (20-HETE) and epoxyeicosatrienoic acids (EETs) as tumor growth promotors has already been described in several cancer types. The aim of this study was to evaluate the role of these compounds in the biology of pheochromocytoma/paraganglioma. These tumors originate from chromaffin cells derived from adrenal medulla (pheochromocytomas) or extra-adrenal autonomic paraganglia (paragangliomas), and they represent the most common hereditary endocrine neoplasia. According to mutations in the driver genes, these tumors are divided in two clusters: pseudo-hypoxic and kinase-signaling EETs, but not 20-HETE, exhibited a potent ability to sustain growth in a murine pheochromocytoma cell line (MPC) in vitro, EETs promoted an increase in cell proliferation and a decrease in cell apoptosis. In a mouse model of pheochromocytoma, the inhibition of CYP-mediated AA metabolism using 1-aminobenzotriazol resulted in slower tumor growth, a decreased vascularization, and a lower final volume. Also, the expression of AA-metabolizing CYP monooxygenases was detected in tumor samples from human origin, being their apparent abundance and the production of both metabolites higher in tumors from the kinase-signaling cluster. This is the first evidence of the importance of CYP- derived AA metabolites in the biology and development of pheochromocytoma/paraganglioma tumors.