Epoxygenase Cyp2c44 regulates hepatic lipid metabolism and insulin signaling by controlling FATP2 localization and activation of the DAG/PKCδ axis

Cytochrome P450 epoxygenase Cyp2c44, a murine epoxyeicosatrienoic acid (EET) producing enzyme, promotes insulin sensitivity and Cyp2c44(-/-) mice show hepatic insulin resistance. Because insulin resistance leads to hepatic lipid accumulation and hyperlipidemia, we hypothesized that Cyp2c44 regulates hepatic lipid metabolism. Standard chow diet (SD) fed male Cyp2c44(-/-) mice had significantly decreased EET levels and increased hepatic and plasma lipid levels compared to wild-type mice. We showed increased hepatic plasma membrane localization of the FA transporter 2 (FATP2) and total unsaturated fatty acids and diacylglycerol levels. Cyp2c44(-/-) mice had impaired glucose tolerance and increased hepatic plasma membraneassociated PKCδ and phosphorylated IRS-1, two negative regulators of insulin signaling. Surprisingly, SD and high fat diet fed (HFD) Cyp2c44(-/-) mice had similar glucose tolerance and hepatic plasma membrane PKCδ levels, suggesting that SD-fed Cyp2c44(-/-) mice have reached their maximal glucose intolerance. Inhibition of PKCδ resulted in decreased IRS-1 serine phosphorylation and improved insulin-mediated signaling in Cyp2c44(-/-) hepatocytes. Finally, Cyp2c44(-/-) HFD-fed mice treated with the analog EET-A showed decreased hepatic plasma membrane FATP2 and PCKDδ levels with improved glucose tolerance and insulin signaling. In conclusion, loss of Cyp2c44 with concomitant decreased EET levels leads to increased hepatic FATP2 plasma membrane localization, diacylglycerol accumulation, and PKCδ-mediated attenuation of insulin signaling. Thus, Cyp2c44 acts as a regulator of lipid metabolism by linking it to insulin signaling.

Cardioprotective Action of a Novel Synthetic 19,20-EDP Analog Is Sirt Dependent

ABSTRACT

Mounting evidence suggests that cytochrome P450 epoxygenase-derived metabolites of docosahexaenoic acid, called epoxydocosapentaenoic acids (EDPs), limit mitochondrial damage after cardiac injury. In particular, the 19,20-EDP regioisomer has demonstrated potent cardioprotective action. Thus, we investigated our novel synthetic 19,20-EDP analog SA-22 for protection against cardiac ischemia-reperfusion (IR) injury. Isolated C57BL/6J mouse hearts were perfused through Langendorff apparatus for 20 minutes to obtain baseline function, followed by 30 minutes of global ischemia. Hearts were then treated with vehicle, 19,20-EDP, SA-22, or SA-22 with the pan-sirtuin inhibitor nicotinamide or the SIRT3-selective inhibitor 3-(1H-1,2,3-triazol-4-yl) pyridine (3-TYP) at the start of 40 minutes reperfusion (N = 5-8). We assessed IR injury-induced changes in recovery of myocardial function, using left ventricular developed pressure and systolic and diastolic pressure change. Tissues were assessed for electron transport chain function, SIRT1 and SIRT3, optic atrophy type 1, and caspase-1. We also used H9c2 cells in an in vitro model of hypoxia/reoxygenation injury (N = 3-6). Hearts perfused with SA-22 had significantly improved postischemic left ventricular developed pressure, systolic and diastolic recovery (64% of baseline), compared with vehicle control (15% of baseline). In addition, treatment with SA-22 led to better catalytic function observed in electron transport chain and SIRT enzymes. The protective action of SA-22 resulted in reduced activation of pyroptosis in both hearts and cells after injury. Interestingly, although nicotinamide cotreatment worsened functional outcomes, cell survival, and attenuated sirtuin activity, it failed to completely attenuate SA-22-induced protection against pyroptosis, possibly indicating EDPs exert cytoprotection through pleiotropic mechanisms. In short, these data demonstrate the potential of our novel synthetic 19,20-EDP analog, SA-22, against IR/hypoxia-reoxygenation injury and justify further development of therapeutic agents based on 19,20-EDP.

Effect of Chronically Suppressed Plasma Angiotensin II on Regulation of the CYP4A/20-HETE Pathway in the Dahl Salt-Sensitive Rat

In Dahl salt-sensitive (SS) rats, impaired vascular relaxation can be restored by: (1) minipump infusion of a low (sub-pressor) dose of angiotensin II (ANG II) to restore physiological levels of plasma ANG II, (2) inhibition of 20-HETE production, and (3) introgression of a normally functioning renin allele from the Brown Norway rat (SS-13^BN consomic rat). Unlike SS rats, SS-13^BN rats have normal levels of ANG II on a normal-salt diet and suppressed ANG II on a high-salt (HS) diet. This study tested whether chronically low ANG II levels in SS rats upregulate cytochrome P450-4A (CYP4A) increasing the production of the vasoconstrictor 20-HETE. Although salt-induced suppression of ANG II levels increased reactive oxygen species (ROS) in basilar arteries from SS-13^BN rats in previous studies, this study showed no change in vascular 20-HETE levels in response to ANGII suppression. CYP4A inhibition significantly reduced vascular ROS levels and restored endothelium-dependent relaxation in response to acetylcholine in the middle cerebral artery (MCA) of SS rats and HS-fed SS-13^BN rats. These data demonstrate that both the renin-angiotensin system and the CYP4A/20-HETE pathway play a direct role in the vascular dysfunction of the Dahl SS rat but are independent of each other, even though they may both contribute to vascular dysfunction through ROS production.

20-Hydroxyeicosatetraenoic acid (20-HETE): Bioactions, receptors, vascular function, cardiometabolic disease and beyond

Vascular function is dynamically regulated and dependent on a bevy of cell types and factors that work in concert across the vasculature. The vasoactive eicosanoid, 20-Hydroxyeicosatetraenoic acid (20-HETE) is a key player in this system influencing the sensitivity of the vasculature to constrictor stimuli, regulating endothelial function, and influencing the renin angiotensin system (RAS), as well as being a driver of vascular remodeling independent of blood pressure elevations. Several of these bioactions are accomplished through the ligand-receptor pairing between 20-HETE and its high-affinity receptor, GPR75. This 20-HETE axis is at the root of various vascular pathologies and processes including ischemia induced angiogenesis, arteriogenesis, septic shock, hypertension, atherosclerosis, myocardial infarction and cardiometabolic diseases including diabetes and insulin resistance. Pharmacologically, several preclinical tools have been developed to disrupt the 20-HETE axis including 20-HETE synthesis inhibitors (DDMS and HET0016), synthetic 20-HETE agonist analogues (20-5,14-HEDE and 20-5,14-HEDGE) and 20-HETE receptor blockers (AAA and 20-SOLA). Systemic or cell-specific therapeutic targeting of the 20-HETE-GPR75 axis continues to be an invaluable approach as studies examine the molecular underpinnings activated by 20-HETE under various physiological settings. In particular, the development and characterization of 20-HETE receptor blockers look to be a promising new class of compounds that can provide a considerable benefit to patients suffering from these cardiovascular pathologies.

20-HETE/GPR75 pairing modulates the expression and transcriptional activity of the androgen receptor in androgen-sensitive prostate cancer cells

The androgen receptor (AR) and AR-driven genes are crucial in normal and neoplastic prostate tissue. Previous results showed a link between 20-hydroxyeicosatetraenoic acid (20-HETE) production and AR-driven prostate cancer (PCa) progression. This study aims to describe the contribution of GPR75, 20-HETE membrane receptor, in 20-HETE-mediated expression and transcriptional activity of AR in PCa. In LNCaP cells, 20-HETE increased AR expression, nuclear localization, and its transcriptional activity. Also, 20-HETE enhanced dihydrotestosterone (DHT) induced effects. All was abrogated by chemical antagonism of GPR75 (19-HEDE) or its transient knockdown. In human PCa, the expression of AR-driven genes correlated with GPR75. In LNCaP xenografts, tumors from castrated animals expressed higher levels of AR, this was impaired by inhibition of 20-HETE synthesis. These data suggest that 20-HETE, through the GPR75 receptor, regulates transcriptionally active AR in PCa cells, thus making 20-HETE/GRP75 potential targets to limit the expression of AR-driven phenotype in PCa cells.

Directed, Remote Dirhodium C(sp3)-H Functionalization, Desaturative Annulation, and Desaturation

Iminodirhodium reactive intermediates generated in situ from O-tosyloximes using Rh₂(esp)₂ in CH₂Cl₂ at rt were exploited for an agile trichotomy of challenging transformations: (1) remote C-H functionalizations using an exceptionally broad diversity of inorganic and organic nucleophiles including several unconventional examples, for example, ethers and acyl silanes; (2) desaturative annulation, a biomimetic 1,3-methylene C-C ring-closure with an overall loss of two hydrogens; and (3) directed desaturation for the acceptor-less, regioselective creation of γ,δ- or γ,δ,ε,ζ-olefins. Compared with typical iminyl transition-metal-mediated and 1,5-hydrogen atom-transfer (1,5-HAT) processes, iminodirhodium intermediates are largely underexplored, especially with respect to C(sp³)-H centers and, yet, have the potential to be transformative by virtue of their substrate breadth, regiocontrol, and elusive reaction modality. A substrate scope includes benzylic, allylic, propargylic, tertiary, and α-alkyloxy centers.

Abstract LB564: (±) 14,15-epoxyeicosatrienoic acid induces hallmark ER and MYC gene expression and associated ER and c-Myc nuclear translocation in ER+/HER2- breast cancer cells

While epoxyeicosatrienoic acids (EETs) have been implicated in breast cancer growth and progression, less is known about their effects on oncogene transcription. We have previously found that the oncogenic regioisomer (±)14,15-EET drives mitochondrial respiration, ATP synthesis, and proliferation of ER+/HER2- breast cancer cells [Cell Chem Biol. 2017 Oct 19;24(10):1259-1275]. RNAseq analysis was performed (5 replicates per condition) on serum starved (16 hours) MCF-7 cells which were then treated with (±)14,15-EET or vehicle (2 hours; serum and phenol red free medium without estradiol). Using gene set enrichment analysis (GSEA), we found that (±)14,15-EET activated an estrogen receptor alpha (ER) hallmark early response gene set and synchronously activated a MYC hallmark gene set. With activation of the MYC hallmark gene set, c-Myc gene expression was also induced at 2 hours (3.99-fold; P=2.3 x 10-17; FDR=2.8 x 10-14). These data suggest an alternative pathway for activation of estrogen and MYC regulated genes in the absence of estradiol. The 15 genes most transcriptionally activated by (±)14,15-EET at 2 hours were: VMP1, ZFP36, JUNB, FOS, IER3, EGR1, IER5L, ELF3, JUN, NR4A1, HES1, DUSP1, MYC, TOB1, and CITED2 [fold change range: 3.25 (CITED2) to 90.5 (FOS); all P< 2.86 x 10-17; all FDR < 3.03 x 10-14]. The ER regulated genes most transcriptionally activated (>1.5 fold) were: IER3, TOB1, AREG, CISH, KCNMB3, and PDK4 (fold change range: 1.77 to 4.35; P= 1.74 x 10-18 to 1.35 x 10-5; FDR=5.54 x 10-15 to 6.4 x 10-4). The MYC regulated genes most transcriptionally activated (> 1.5-fold change) were EIF4A1 (fold change= 2.37; P=1.0 x 10-7; FDR=1.33 x 10-5), IRF9 (fold change=1.58; P=0.0044; FDR= 0.026), and FOSL1 (fold change=1.51; P=0.008; FDR=0.04). Supporting the hypothesis of (±)14,15-EET activation of ER-regulated transcription, (±)14,15-EET promoted nuclear translocation of ER at 1 hour measured by DAPI normalized immunofluorescence [MCF-7 nuclear ER increase of 1.66-fold (P=0.031); ZR75-1 nuclear ER increase of 1.77-fold (P=0.015)]. Supporting the hypothesis of (±)14,15-EET activation of MYC-regulated transcription, (±)14,15-EET treatment promoted nuclear translocation of c-Myc with MCF-7 cells exhibiting a 1.22-fold increase at 2 hours (P=0.002). (±)14,15-EET also promoted nuclear translocation of FITC-70 kDa dextran with MCF-7 cells exhibiting an increase of 1.35-fold at 1 hour (P=0.029). These data suggest that (±)14,15-EET can induce an estradiol-like immediate early gene response in ER+/HER2- breast cancer cells correlating with c-Myc activation. In summary, while the effect of (±)14,15-EET on nuclear translocation may be partially cargo agnostic, (±)14,15-EET promotes ER and c-Myc nuclear translocation and associated transcription, mimicking a tandem hormonal and growth factor response.

Citation Format: Jianxun Lei, Zhijun Guo, Julissa Molina-Vega, Paloma Cervantes, Swaathi Jayaraman, John R. Hawse, Carlos Perez, Juan Abrahante, Xiaojia Tang, Krishna Kalari, Jinhua Wang, John R. Falck, Carol Lange, Matthew P. Goetz, David Potter. (±) 14,15-epoxyeicosatrienoic acid induces hallmark ER and MYC gene expression and associated ER and c-Myc nuclear translocation in ER+/HER2- breast cancer cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr LB564.

Site-selective amination and/or nitrilation via metal-free C(sp2)-C(sp3) cleavage of benzylic and allylic alcohols

Benzylic/allylic alcohols are converted via site-selective C(sp²)-C(sp³) cleavage to value-added nitrogenous motifs, viz., anilines and/or nitriles as well as N-heterocycles, utilizing commercial hydroxylamine-O-sulfonic acid (HOSA) and Et₃N in an operationally simple, one-pot process. Notably, cyclic benzylic/allylic alcohols undergo bis-functionalization with attendant increases in architectural complexity and step-economy.

Blockade of 20-hydroxyeicosatetraenoic acid receptor lowers blood pressure and alters vascular function in mice with smooth muscle-specific overexpression of CYP4A12-20-HETE synthase

OBJECTIVE

20-Hydroxyeicosatetraenoic acid (20-HETE) is a vasoactive eicosanoid exhibiting effects on vascular smooth muscle cell (VSMC) via G-protein coupled receptor 75 (GPR75) and include stimulation of contractility, migration, and growth. We examined whether VSMC-targeted overexpression of CYP4A12, the primary 20-HETE-producing enzyme in mice, is sufficient to promote hypertension.

METHODS

Mice with VSM-specific Cyp4a12 overexpression (Myh11-4a12) and their littermate controls (WT) were generated by crossbreeding Cyp4a12-floxed with Myh11-Cre mice. The 20-HETE receptor blocker, N-disodium succinate-20-hydroxyeicosa-6(Z),15(Z)-diencarboxamide (AAA), was administered in the drinking water. Experiments were carried out for 12 days. SBP was measured by tail cuff. Renal interlobar and mesenteric arteries were harvested for assessment of gene expression, 20-HETE levels, vascular contractility, vasodilation, and remodeling.

RESULTS

Vascular and circulatory levels of 20-HETE were several folds higher in Myh11-4a12 mice compared with WT. The Myh11-4a12 mice compared with WT were hypertensive (145 ± 2 vs. 127 ± 2 mmHg; P < 0.05) and their vasculature displayed a contractile phenotype exemplified by increased contractility, reduced vasodilatory capacity, and increased media to lumen ratio. All these features were reversed by the administration of AAA. The mechanism of increased contractility includes, at least in part, Rho-kinase activation followed by increased myosin light chain phosphorylation and activation of the contractile apparatus.

CONCLUSION

VSM-specific Cyp4a12 overexpression is sufficient to alter VSM cell phenotype through changes in contractile markers and enhancement in contractility that promote hypertension and vascular dysfunction in a 20-HETE-dependent manner. The 20-HETE receptor GPR75 may represent a novel target for the treatment of hypertension and associated vascular conditions.

Epoxyeicosatrienoic Acid Analog and 20-HETE Antagonist Combination Prevent Hypertension Development in Spontaneously Hypertensive Rats

Numerous studies indicate a significant role for cytochrome P-450-dependent arachidonic acid metabolites in blood pressure regulation, vascular tone, and control of renal function. Epoxyeicosatrienoic acids (EETs) exhibit a spectrum of beneficial effects, such as vasodilatory activity and anti-inflammatory, anti-fibrotic, and anti-apoptotic properties. 20-Hydroxyeicosatetraenoic acid (20-HETE) is a potent vasoconstrictor that inhibits sodium reabsorption in the kidney. In the present study, the efficiency of EET-A (a stable analog of 14,15-EET) alone and combined with AAA, a novel receptor antagonist of 20-HETE, was tested in spontaneously hypertensive rats (SHR). Adult SHR (16 weeks old) were treated with two doses of EET-A (10 or 40 mg/kg/day). In the following experiments, we also tested selected substances in the prevention of hypertension development in young SHR (6 weeks old). Young rats were treated with EET-A or the combination of EET-A and AAA (both at 10 mg/kg/day). The substances were administered in drinking water for 4 weeks. Blood pressure was measured by telemetry. Once-a-week observation in metabolic cages was performed; urine, blood, and tissue samples were collected for further analysis. The combined treatment with AAA + EET-A exhibited antihypertensive efficiency in young SHR, which remained normotensive until the end of the observation in comparison to a control group (systolic blood pressure, 134 ± 2 versus 156 ± 5 mmHg, respectively; p < 0.05). Moreover the combined treatment also increased the nitric oxide metabolite excretion. Considering the beneficial impact of the combined treatment with EET-A and AAA in young rats and our previous positive results in adult SHR, we suggest that it is a promising therapeutic strategy not only for the treatment but also for the prevention of hypertension.

Macrophage 12(S)-HETE Enhances Angiotensin II-Induced Contraction by a BLT2 (Leukotriene B4 Type-2 Receptor) and TP (Thromboxane Receptor)-Mediated Mechanism in Murine Arteries

12/15-LO (12/15-lipoxygenase), encoded by Alox15 gene, metabolizes arachidonic acid to 12(S)-HETE (12-hydroxyeicosatetraenoic acid). Macrophages are the major source of 12/15-LO among immune cells, and 12/15-LO plays a crucial role in development of hypertension. Global Alox15- or macrophage-deficient mice are resistant to Ang II (angiotensin II)-induced hypertension. This study tests the hypothesis that macrophage 12(S)-HETE contributes to Ang II-mediated arterial constriction and thus to development of Ang II-induced hypertension. Ang II constricted isolated abdominal aortic and mesenteric arterial rings. 12(S)-HETE (100 nmol/L) alone was without effect; however, it significantly enhanced Ang II-induced constriction. The presence of wild-type macrophages also enhanced the Ang II-induced constriction, while Alox15^-/- macrophages did not. Using this model, pretreatment of aortic rings with inhibitors, receptor agonists/antagonists, or removal of the endothelium, systematically uncovered an endothelium-mediated, Ang II receptor-2-mediated and superoxide-mediated enhancing effect of 12(S)-HETE on Ang II constrictions. The role of superoxide was confirmed using aortas from p47^phox-/- mice where 12(S)-HETE failed to enhance constriction to Ang II. In cultured arterial endothelial cells, 12(S)-HETE increased the production of superoxide, and 12(S)-HETE or Ang II increased the production of an isothromboxane-like metabolite. A TP (thromboxane receptor) antagonist inhibited 12(S)-HETE enhancement of Ang II constriction. Both Ang II-induced hypertension and the enhancing effect of 12(S)-HETE on Ang II contractions were eliminated by a BLT2 (leukotriene B₄ receptor-2) antagonist. These results outline a mechanism where the macrophage 12/15-LO pathway enhances the action of Ang II. 12(S)-HETE, acting on the BLT2, contributes to the hypertensive action of Ang II in part by promoting endothelial synthesis of a superoxide-derived TP agonist.

20-HETE Participates in Intracerebral Hemorrhage-Induced Acute Injury by Promoting Cell Ferroptosis

Intracerebral hemorrhage (ICH) is a highly fatal type of stroke that leads to various types of neuronal death. Recently, ferroptosis, a form of cell death resulting from iron-dependent lipid peroxide accumulation, was observed in a mouse ICH model. N-hydroxy-N'-(4-n-butyl-2-methylphenyl)-formamidine (HET0016), which inhibits synthesis of the arachidonic acid metabolite 20-hydroxyeicosatetraenoic acid (20-HETE), has shown a protective effect after ICH. However, the underlying mechanisms of the neuroprotective effect need further investigation. We explored whether 20-HETE participates in ICH-induced ferroptosis ex vivo by using hemoglobin-treated organotypic hippocampal slice cultures (OHSCs) and in vivo by using a collagenase-induced ICH mouse model. Ex vivo, we found that the 20-HETE synthesis inhibitor HET0016 and antagonist 20-6,15-HEDGE reduced hemoglobin-induced cell death, iron deposition, and lipid reactive oxygen species levels in OHSCs. Furthermore, 20-HETE inhibition in OHSCs increased the expression of glutathione peroxidase (GPX) 4, an antioxidant enzyme that serves as a main regulator of ferroptosis. In contrast, exposure of OHSCs to the 20-HETE stable mimetic 20-5,14-HEDGE induced cell death that was significantly inhibited by the ferroptosis inhibitor ferrostatin-1. In vivo, HET0016 treatment ameliorated focal deficits, reduced lesion volume, and decreased iron accumulation around the lesion at day 3 and 7 after ICH. In addition, lipid peroxidation was decreased and expression of GPX4 was increased in the HET0016-treated ICH group. The mitogen-activated protein kinase pathway also was inhibited by HET0016 in vivo. These results indicate that 20-HETE contributes to ICH-induced acute brain injury in part by activating ferroptosis pathways, thereby providing an upstream target for inhibiting ferroptosis.

EET Analog Treatment Improves Insulin Signaling in a Genetic Mouse Model of Insulin Resistance

We previously showed that global deletion of the cytochrome P450 epoxygenase Cyp2c44, a major epoxyeicosatrienoic acid (EET) producing enzyme in mice, leads to impaired hepatic insulin signaling resulting in insulin resistance. This finding led us to investigate whether administration of a water soluble EET analog restores insulin signaling in vivo in Cyp2c44(-/-) mice and investigated the underlying mechanisms by which this effect is exerted. Cyp2c44(-/-) mice treated with the analog EET-A for 4 weeks improved fasting glucose and glucose tolerance compared to Cyp2c44(-/-) mice treated with vehicle alone. This beneficial effect was accompanied by enhanced hepatic insulin signaling, decreased expression of gluconeogenic genes and increased expression of glycogenic genes. Mechanistically, we show that insulin-stimulated phosphorylation of insulin receptor β (IRβ) is impaired in primary Cyp2c44(-/-) hepatocytes and this can be restored by cotreatment with EET-A and insulin. Plasma membrane fractionations of livers indicated that EET-A enhances the retention of IRβ in membrane rich fractions, thus potentiating its activation. Altogether, EET analogs ameliorate insulin signaling in a genetic model of hepatic insulin resistance by stabilizing membrane-associated IRβ and potentiating insulin signaling.

Uncovering the signalling, structure and function of the 20-HETE-GPR75 pairing: Identifying the chemokine CCL5 as a negative regulator of GPR75

BACKGROUND AND PURPOSE

The G-protein-coupled receptor GPR75 (Gq) and its ligand, the cytochrome P450-derived vasoactive eicosanoid 20-hydroxyeicosatetraenoic acid (20-HETE), are involved in the activation of pro-inflammatory and hypertensive signalling cascades contributing to diabetes, obesity, vascular dysfunction/remodelling, hypertension and cardiovascular disease. Little is known as to how, where and with what affinity 20-HETE interacts with GPR75.

EXPERIMENTAL APPROACH

To better understand the pairing of 20-HETE and its receptor (GPR75), we used surface plasmon resonance (SPR) to determine binding affinity/kinetics. The PRESTO-Tango receptor-ome methodology for GPR75 overexpression was coupled with FLIPR Calcium 6 assays, homogeneous time-resolved fluorescence (HTRF) IP-1 and β-arrestin recruitment assays to determine receptor activation and downstream signalling events.

KEY RESULTS

SPR confirmed 20-HETE binding to GPR75 with an estimated K_D of 1.56 × 10^-10  M. In GPR75-transfected HTLA cells, 20-HETE stimulated intracellular Ca²⁺ levels, IP-1 accumulation and β-arrestin recruitment, all of which were negated by known 20-HETE functional antagonists. Computational modelling of the putative ligand-binding pocket and mutation of Thr212 within the putative 20-HETE binding site abolished 20-HETE's ability to stimulate GPR75 activation. Knockdown of GPR75 in human endothelial cells nullified 20-HETE-stimulated intracellular Ca²⁺ . The chemokine CCL5, a suggested GPR75 ligand, binds to GPR75 (K_D of 5.85 × 10^-10  M) yet fails to activate GPR75; however, it inhibited 20-HETE's ability to activate GPR75 signalling.

CONCLUSIONS AND IMPLICATIONS

We have identified 20-HETE as a high-affinity ligand for GPR75 and CCL5 as a low-affinity negative regulator of GPR75, providing additional evidence for the deorphanization of GPR75 as a 20-HETE receptor.

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-β-(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.

Early Renal Vasodilator and Hypotensive Action of Epoxyeicosatrienoic Acid Analog (EET-A) and 20-HETE Receptor Blocker (AAA) in Spontaneously Hypertensive Rats

Cytochrome P450 (CYP-450) metabolites of arachidonic acid: epoxyeicosatrienoic acids (EETs) and 20-hydroxyeicosatetraenoic acid (20-HETE) have established role in regulation of blood pressure (BP) and kidney function. EETs deficiency and increased renal formation of 20-HETE contribute to hypertension in spontaneously hypertensive rats (SHR). We explored the effects of 14,15-EET analog (EET-A) and of 20-HETE receptor blocker (AAA) on BP and kidney function in this model. In anesthetized SHR the responses were determined of mean arterial blood pressure (MABP), total renal (RBF), and cortical (CBF) and inner-medullary blood flows, glomerular filtration rate and renal excretion, to EET-A, 5 mg/kg, infused i.v. for 1 h to rats untreated or after blockade of endogenous EETs degradation with an inhibitor (c-AUCB) of soluble epoxide hydrolase. Also examined were the responses to AAA (10 mg/kg/h), given alone or together with EET-A. EET-A significantly increased RBF and CBF (+30% and 26%, respectively), seen already within first 30 min of infusion. The greatest increases in RBF and CBF (by about 40%) were seen after AAA, similar when given alone or combined with EET-A. MABP decreased after EET-A or AAA but not significantly after the combination thereof. In all groups, RBF, and CBF increases preceded the decrease in MABP. We found that in SHR both EET-A and AAA induced renal vasodilation but, unexpectedly, no additive effect was seen. We suggest that both agents have a definite therapeutic potential and deserve further experimental and clinical testing aimed at introduction of novel antihypertensive therapy.

Intramolecular N-Me and N-H aminoetherification for the synthesis of N-unprotected 3-amino-O-heterocycles

A mild Rh-catalyzed method for synthesis of cyclic unprotected N-Me and N-H 2,3-aminoethers using an olefin aziridination-aziridine ring-opening domino reaction has been developed. The method is readily applicable to the stereocontrolled synthesis of a variety of 2,3-disubstituted aminoether O-heterocyclic scaffolds, including tetrahydrofurans, tetrahydropyrans and chromanes.

Abstract 4372: Metformin inhibits nuclear localization of estrogen receptor alpha in breast cancer cells, in part, by inhibition of CYP-mediated epoxyeicosatrienoic acid (EET) biosynthesis

Introduction: Cancer cell-intrinsic CYP monooxygenases promote tumor progression. In ER+HER2-, breast cancer cells, CYP3A4 promotes tumor growth, in part, through epoxyeicosatrienoic acid (EET) biosynthesis (1). The biguanide diabetes drug metformin is currently being studied in breast cancer clinical trials. We have discovered that metformin binds to the active site heme of CYP3A4, thereby inhibiting EET biosynthesis (1). Structure-based design led to the discovery of the 100-fold more potent metformin analog N1-hexyl-N5-benzyl-biguanide (HBB). HBB specifically inhibits CYP3A4 arachidonic acid (AA) epoxygenase activity in breast cancer cells, suppresses the growth of breast cancer cell lines (IC50=3-30 uM), and inhibits growth of the MCF-7 ER+ mammary tumor model, similar to CYP3A4 gene silencing. Although CYP3A4 synthesizes EETs, how EETs may promote tumor growth is unknown. Recently, we found that HBB inhibits nuclear transit of estrogen receptor alpha (ERα) and 70kD FITC-dextran, but the mechanism was unknown (2). Metformin was discovered to inhibit nuclear pore complex (NPC) function, but the mechanism was also unknown (3). We therefore hypothesized that CYP-derived EETs function as second messengers that regulate nuclear translocation of ERα in breast cancer by promoting permeability of the NPC. This hypothesis implies that biguanide drugs suppress nuclear translocation of the ERα through inhibition of CYP-derived EETs that serve as second messengers to open the NPC.

Methods: Breast cancer cells were serum-starved for 16 hours and then treated with metformin, HBB, the (±)-14,15-EET regioisomer, or EET agonists, for varying times (30 min to 6 hours). Cells were fixed, permeabilized, and incubated with antibodies specific for ERα. After incubation with fluorescent secondary antibodies and Hoechst 33342 dye, cell images were acquired with a confocal microscope and the nuclear ERα fluorescence signal was quantified relative to the Hoechst signal. Quantitative PCR was used to measure the expression of ERα regulated genes.

Results: (±) 14,15-EET (5 uM) treatment for 1 hour increased nuclear ERα by 66 ± 26% (n=9, p=0.031) in MCF-7 cells and 77 ± 24% (n=7, p=0.015) in ZR-75 cells. Treatment with EET agonists C22 (5 uM) and EET-A (5 uM) for 1 hour increased nuclear ERα by 32 ± 13% (n=7, p=0.047) and 39 ± 14% (n=7, p=0.02) in MCF-7 cells. Metformin (5 mM) treatment for 6 hours reduced nuclear ERα in MCF-7 by 35 ± 4.9 % (mean ± SEM, n=8, p=0.003). HBB (20 uM) treatment for 2 hours reduced the expression of three ERα regulated genes in MCF-7 cells: estrogen receptor alpha (ESR1) was reduced by 15 ± 1.7% (n=3, p=0.001), progesterone receptor (PGR) by 21 ± 0.6% (n=3, p=0.02) and L-type amino acid transporter 1 (SLC7A5) by 14 ± 0.2% (n=3, p=0.002).

Conclusion: CYP epoxygenase activity in ER+HER2- breast cancer cells produces EETs, which function as second messengers that promote nuclear transit of ERα. Metformin and HBB inhibit nuclear ERα translocation, in part, through inhibition of CYP3A4 AA epoxygenase activity and this inhibition reduces ERα mediated gene expression, providing a novel mechanism for ERα regulation.

1. Cell Chem Biol. 2017 Oct 19; 24(10) 1259 - 1275.

2. Abstract of 109th AACR meeting (#LB-023), April 2019

3. Cell. 2016 Dec 15;167(7):1705-1718

Citation Format: Zhijun Guo, Jianxun Lei, Shaoping Wu, Julissa Molina-Vega, Paloma Cervantes, Aline R. Rom'Mand, Dylan C. Castillejo Mijangos, John R. Falck, Carol Lange, Jinhua Wang, David A. Potter. Metformin inhibits nuclear localization of estrogen receptor alpha in breast cancer cells, in part, by inhibition of CYP-mediated epoxyeicosatrienoic acid (EET) biosynthesis [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 4372.

A Synthetic Epoxydocosapentaenoic Acid Analogue Ameliorates Cardiac Ischemia/Reperfusion Injury: The Involvement of the Sirtuin 3-NLRP3 Pathway

While survival rates have markedly improved following cardiac ischemia-reperfusion (IR) injury, the resulting heart damage remains an important issue. Preserving mitochondrial quality and limiting NLRP3 inflammasome activation is an approach to limit IR injury, in which the mitochondrial deacetylase sirtuin 3 (SIRT3) has a role. Recent data demonstrate cytochrome P450 (CYP450)-derived epoxy metabolites, epoxydocosapentaenoic acids (EDPs), of docosahexaenoic acid (DHA), attenuate cardiac IR injury. EDPs undergo rapid removal and inactivation by enzymatic and non-enzymatic processes. The current study hypothesizes that the cardioprotective effects of the synthetic EDP surrogates AS-27, SA-26 and AA-4 against IR injury involve activation of SIRT3. Isolated hearts from wild type (WT) mice were perfused in the Langendorff mode with vehicle, AS-27, SA-26 or AA-4. Improved postischemic functional recovery, maintained cardiac ATP levels, reduced oxidative stress and attenuation of NLRP3 activation were observed in hearts perfused with the analogue SA-26. Assessment of cardiac mitochondria demonstrated SA-26 preserved SIRT3 activity and reduced acetylation of manganese superoxide dismutase (MnSOD) suggesting enhanced antioxidant capacity. Together, these data demonstrate that the cardioprotective effects of the EDP analogue SA-26 against IR injury involve preservation of mitochondrial SIRT3 activity, which attenuates a detrimental innate NLRP3 inflammasome response.

GPR75 receptor mediates 20-HETE-signaling and metastatic features of androgen-insensitive prostate cancer cells

PURPOSE

Recent studies have shown that 20-hydroxyeicosatetraenoic acid (20-HETE) is a key molecule in sustaining androgen-mediated prostate cancer cell survival. Thus, the aim of this study was to determine whether 20-HETE can affect the metastatic potential of androgen-insensitive prostate cancer cells, and the implication of the newly described 20-HETE receptor, GPR75, in mediating these effects.

METHODS

The expression of GPR75, protein phosphorylation, actin polymerization and protein distribution were assessed by western blot and/or fluorescence microscopy. Additionally, in vitro assays including epithelial-mesenchymal transition (EMT), metalloproteinase-2 (MMP-2) activity, scratch wound healing, transwell invasion and soft agar colony formation were used to evaluate the effects of 20-HETE agonists/antagonists or GPR75 gene silencing on the aggressive features of PC-3 cells.

RESULTS

20-HETE (0.1 nM) promoted the acquisition of a mesenchymal phenotype by increasing EMT, the release of MMP-2, cell migration and invasion, actin stress fiber formation and anchorage-independent growth. Also, 20-HETE augmented the expression of HIC-5, the phosphorylation of EGFR, NF-κB, AKT and p-38 and the intracellular redistribution of p-AKT and PKCα. These effects were impaired by GPR75 antagonism and/or silencing. Accordingly, the inhibition of 20-HETE formation with N-hydroxy-N'-(4-n-butyl-2-methylphenyl) formamidine (HET0016) elicited the opposite effects.

CONCLUSIONS

The present results show for the first time the involvement of the 20-HETE-GPR75 receptor in the activation of intracellular signaling known to be stimulated in cell malignant transformations leading to the differentiation of PC-3 cells towards a more aggressive phenotype. Targeting the 20-HETE/GPR75 pathway is a promising and novel approach to interfere with prostate tumor cell malignant progression.

Development of Robust 17(R),18(S)-Epoxyeicosatetraenoic Acid (17,18-EEQ) Analogues as Potential Clinical Antiarrhythmic Agents

17(R),18(S)-Epoxyeicosatetraenoic acid (EEQ) is a cytochrome P450 metabolite of eicosapentaenoic acid (EPA) and a powerful negative chronotrope with low nanomolar activity in a neonatal rat cardiomyocyte (NRCM) arrhythmia model. Prior studies identified oxamide 2b as a soluble epoxide hydrolase (sEH) stable replacement but unsuitable for in vivo applications due to limited oral bioavailability and metabolic stability. These ADME limitations have been addressed in an improved generation of negative chronotropes, e.g., 4 and 16, which were evaluated as potential clinical candidates.

Eicosanoids derived from cytochrome P450 pathway of arachidonic acid and inflammatory shock

Sepsis is a life-threatening organ dysfunction caused by a dysregulated host response to infection. Septic shock, the most common form of vasodilatory shock, is a subset of sepsis in which circulatory and cellular/metabolic abnormalities are severe enough to increase mortality. Inflammatory shock constitutes the hallmark of sepsis, but also a final common pathway of any form of severe long-term tissue hypoperfusion. The pathogenesis of inflammatory shock seems to be due to circulating substances released by pathogens (e.g., bacterial endotoxins) and host immuno-inflammatory responses (e.g., changes in the production of histamine, bradykinin, serotonin, nitric oxide [NO], reactive nitrogen and oxygen species, and arachidonic acid [AA]-derived eicosanoids mainly through NO synthase, cyclooxygenase, and cytochrome P450 [CYP] pathways, and proinflammatory cytokine formation). Therefore, refractory hypotension to vasoconstrictors with end-organ hypoperfusion is a life threatening feature of inflammatory shock. This review summarizes the current knowledge regarding the role of eicosanoids derived from CYP pathway of AA in animal models of inflammatory shock syndromes with an emphasis on septic shock in addition to potential therapeutic strategies targeting specific CYP isoforms responsible for proinflammatory/anti-inflammatory mediator production.

A synthetic epoxyeicosatrienoic acid analogue prevents the initiation of ischemic acute kidney injury

AIM

Imbalances in cytochrome P450 (CYP)-dependent eicosanoid formation may play a central role in ischemic acute kidney injury (AKI). We reported previously that inhibition of 20-hydroxyeicosatetraenoic acid (20-HETE) action ameliorated ischemia/reperfusion (I/R)-induced AKI in rats. Now we tested the hypothesis that enhancement of epoxyeicosatrienoic acid (EET) actions may counteract the detrimental effects of 20-HETE and prevent the initiation of AKI.

METHODS

Male Lewis rats underwent right nephrectomy and ischemia was induced by 45 min clamping of the left renal pedicle followed by up to 48 h of reperfusion. Circulating CYP-eicosanoid profiles were compared in patients who underwent cardiac surgery with (n = 21) and without (n = 38) developing postoperative AKI.

RESULTS

Ischemia induced an about eightfold increase of renal 20-HETE levels, whereas free EETs were not accumulated. To compensate for this imbalance, a synthetic 14,15-EET analogue was administered by intrarenal infusion before ischemia. The EET analogue improved renal reoxygenation as monitored by in vivo parametric MRI during the initial 2 h reperfusion phase. The EET analogue improved PI3K- as well as mTORC2-dependent rephosphorylation of Akt, induced inactivation of GSK-3β, reduced the development of tubular apoptosis and attenuated inflammatory cell infiltration. The EET analogue also significantly alleviated the I/R-induced drop in creatinine clearance. Patients developing postoperative AKI featured increased preoperative 20-HETE and 8,9-EET levels.

CONCLUSIONS

Pharmacological interventions targeting the CYP-eicosanoid pathway could offer promising new options for AKI prevention. Individual differences in CYP-eicosanoid formation may contribute to the risk of developing AKI in clinical settings.

Cu(OTf)2-catalyzed Beckmann Rearrangement of Ketones Using Hydroxylamine-O-sulfonic Acid (HOSA)

The Beckmann Rearrangement (BKR) of ketones to secondary amides often requires harsh reaction conditions that limit its practicality and scope. Herein, we describe the Cu(OTf)2-catalyzed BKR of ketones under mild reaction conditions using hydroxylamine-O-sulfonic acid (HOSA), a commercial water soluble aminating agent. This method is compatible with most functional groups and directly provides the desired amides in good to excellent yields.

19-Hydroxyeicosatetraenoic acid analogs: Antagonism of 20-hydroxyeicosatetraenoic acid-induced vascular sensitization and hypertension

19-Hydroxyeicosatetraenoic acid (19-HETE, 1), a metabolically and chemically labile cytochrome P450 eicosanoid, has diverse biological activities including antagonism of the vasoconstrictor 20-hydroxyeicosatetraenoic acid (20-HETE, 2). A SAR study was conducted to develop robust analogs of 1 with improved in vitro and in vivo efficacy. Analogs were screened in vitro for inhibition of 20-HETE-induced sensitization of rat renal preglomerular microvessels toward phenylephrine and demonstrated to normalize the blood pressure of male Cyp4a14(-/-) mice that display androgen-driven, 20-HETE-dependent hypertension.

20-HETE synthesis inhibition promotes cerebral protection after intracerebral hemorrhage without inhibiting angiogenesis

20-HETE, an arachidonic acid metabolite synthesized by cytochrome P450 4A, plays an important role in acute brain damage from ischemic stroke or subarachnoid hemorrhage. We tested the hypothesis that 20-HETE inhibition has a protective effect after intracerebral hemorrhage (ICH) and then investigated its effect on angiogenesis. We exposed hippocampal slice cultures to hemoglobin and induced ICH in mouse brains by intrastriatal collagenase injection to investigate the protective effect of 20-HETE synthesis inhibitor N-hydroxy-N'-(4-n-butyl-2-methylphenyl)-formamidine (HET0016). Hemoglobin-induced neuronal death was assessed by propidium iodide after 18 h in vitro. Lesion volume, neurologic deficits, cell death, reactive oxygen species (ROS), neuroinflammation, and angiogenesis were evaluated at different time points after ICH. In cultured mouse hippocampal slices, HET0016 attenuated hemoglobin-induced neuronal death and decreased levels of proinflammatory cytokines and ROS. In vivo, HET0016 reduced brain lesion volume and neurologic deficits, and decreased neuronal death, ROS production, gelatinolytic activity, and the inflammatory response at three days after ICH. However, HET0016 did not inhibit angiogenesis, as levels of CD31, VEGF, and VEGFR2 were unchanged on day 28. We conclude that 20-HETE is involved in ICH-induced brain damage. Inhibition of 20-HETE synthesis may provide a viable means to mitigate ICH injury without inhibition of angiogenesis.

CYP4A/20-HETE regulates ischemia-induced neovascularization via its actions on endothelial progenitor and preexisting endothelial cells

20-Hydroxyeicosatetraenoic acid (20-HETE) was recently identified as a novel contributor of ischemia-induced neovascularization based on the key observation that pharmacological interferences of CYP4A/20-HETE decrease ischemic neovascularization. The objective of the present study is to examine whether the underlying cellular mechanisms involve endothelial progenitor cells (EPCs) and preexisting endothelial cells (ECs). We found that ischemia leads to a time-dependent increase of cyp4a12 expression and 20-HETE production, which are endothelial in origin, using immunofluorescent microscopy, Western blot analysis, and LC-MS/MS. This is accompanied by increases in the tissue stromal cell-derived factor-1α (SDF-1α) expressions as well as SDF-1α plasma levels, EPC mobilization from bone marrow, and subsequent homing to ischemic tissues. Pharmacological interferences of CYP4A/20-HETE with a 20-HETE synthesis inhibitor, dibromo-dodecenyl-methylsulfimide (DDMS), or a 20-HETE antagonist, N-(20-hydroxyeicosa-6(Z), 15(Z)-dienoyl) glycine (6, 15-20-HEDGE), significantly attenuated these increases. Importantly, we also determined that 20-HETE plays a novel role in maintaining EPC functions and increasing the expression of Oct4, Sox2, and Nanog, which are indicative of increased progenitor cell stemness. Flow cytometric analysis revealed that pharmacological interferences of CYP4A/20-HETE decrease the EPC population in culture, whereas 20-HETE increases the cultured EPC population. Furthermore, ischemia also markedly increased the proliferation, oxidative stress, and ICAM-1 expression in the preexisting EC in the hindlimb gracilis muscles. We found that these increases were markedly negated by DDMS and 6, 15-20-HEDGE. Taken together, CYP4A/20-HETE regulates ischemia-induced compensatory neovascularization via its combined actions on promoting EPC and local preexisting EC responses that are associated with increased neovascularization. NEW & NOTEWORTHY CYP4A/20-hydroxyeicosatetraenoic acid (20-HETE) was recently discovered as a novel contributor of ischemia-induced neovascularization. However, the underlying molecular and cellular mechanisms are completely unknown. Here, we show that CYP4A/20-HETE regulates the ischemic neovascularization process via its combined actions on both endothelial progenitor cells (EPCs) and preexisting endothelial cells. Moreover, this is the first study, to the best of our knowledge, that associates CYP4A/20-HETE with EPC differentiation and stemness.

Epoxyeicosatrienoic Acid Analog EET-A Blunts Development of Lupus Nephritis in Mice

Systemic lupus erythematosus (SLE) is a chronic autoimmune inflammatory disorder that causes life threatening renal disease and current therapies are limited with serious side-effects. CYP epoxygenase metabolites of arachidonic acid epoxyeicosatrienoic acids (EETs) demonstrate strong anti-inflammatory and kidney protective actions. We investigated the ability of an orally active EET analog, EET-A to prevent kidney injury in a mouse SLE model. Twenty-weeks old female NZBWF1 (SLE) and age-matched NZW/LacJ (Non SLE) were treated with vehicle or EET-A (10 mg/kg/d, p.o.) for 14 weeks and urine and kidney tissues were collected at the end of the protocol. SLE mice demonstrated marked renal chemotaxis with 30-60% higher renal mRNA expression of CXC chemokine receptors (CXCR) and CXC chemokines (CXCL) compared to Non SLE mice. In SLE mice, the elevated chemotaxis is associated with 5-15-fold increase in cytokine mRNA expression and elevated inflammatory cell infiltration in the kidney. SLE mice also had elevated BUN, serum creatinine, proteinuria, and renal fibrosis. Interestingly, EET-A treatment markedly diminished renal CXCR and CXCL renal mRNA expression in SLE mice. EET-A treatment also reduced renal TNF-α, IL-6, IL-1β, and IFN-γ mRNA expression by 70-80% in SLE mice. Along with reductions in renal chemokine and cytokine mRNA expression, EET-A reduced renal immune cell infiltration, BUN, serum creatinine, proteinuria and renal fibrosis in SLE mice. Overall, we demonstrate that an orally active EET analog, EET-A prevents renal injury in a mouse model of SLE by reducing inflammation.

Cu(II)-Mediated N-H and N-Alkyl Aryl Amination and Olefin Aziridination

Cu(II)-mediated direct NH₂ and NH alkyl aryl aminations and olefin aziridinations are described. These room-temperature, one-pot, environmentally friendly procedures replace costly Rh₂ catalysts and, in some instances, display important differences with comparable Rh₂- and Fe-supported reactions.

Epoxyeicosatrienoic Acid-Based Therapy Attenuates the Progression of Postischemic Heart Failure in Normotensive Sprague-Dawley but Not in Hypertensive Ren-2 Transgenic Rats

Epoxyeicosatrienoic acids (EETs) and their analogs have been identified as potent antihypertensive compounds with cardio- and renoprotective actions. Here, we examined the effect of EET-A, an orally active EET analog, and c-AUCB, an inhibitor of the EETs degrading enzyme soluble epoxide hydrolase, on the progression of post-myocardial infarction (MI) heart failure (HF) in normotensive Hannover Sprague-Dawley (HanSD) and in heterozygous Ren-2 transgenic rats (TGR) with angiotensin II-dependent hypertension. Adult male rats (12 weeks old) were subjected to 60-min left anterior descending (LAD) coronary artery occlusion or sham (non-MI) operation. Animals were treated with EET-A and c-AUCB (10 and 1 mg/kg/day, respectively) in drinking water, given alone or combined for 5 weeks starting 24 h after MI induction. Left ventricle (LV) function and geometry were assessed by echocardiography before MI and during the progression of HF. At the end of the study, LV function was determined by catheterization and tissue samples were collected. Ischemic mortality due to the incidence of sustained ventricular fibrillation was significantly higher in TGR than in HanSD rats (35.4 and 17.7%, respectively). MI-induced HF markedly increased LV end-diastolic pressure (P_ed) and reduced fractional shortening (FS) and the peak rate of pressure development [+(dP/dt)_max] in untreated HanSD compared to sham (non-MI) group [P_ed: 30.5 ± 3.3 vs. 9.7 ± 1.3 mmHg; FS: 11.1 ± 1.0 vs. 40.8 ± 0.5%; +(dP/dt)_max: 3890 ± 291 vs. 5947 ± 309 mmHg/s]. EET-A and c-AUCB, given alone, tended to improve LV function parameters in HanSD rats. Their combination amplified the cardioprotective effect of single therapy and reached significant differences compared to untreated HanSD controls [P_ed: 19.4 ± 2.2 mmHg; FS: 14.9 ± 1.0%; +(dP/dt)_max: 5278 ± 255 mmHg/s]. In TGR, MI resulted in the impairment of LV function like HanSD rats. All treatments reduced the increased level of albuminuria in TGR compared to untreated MI group, but neither single nor combined EET-based therapy improved LV function. Our results indicate that EET-based therapy attenuates the progression of post-MI HF in HanSD, but not in TGR, even though they exhibited renoprotective action in TGR hypertensive rats.

High-fat diet-induced obesity and insulin resistance in CYP4a14-/- mice is mediated by 20-HETE

20-Hydroxyeicosatetraenoic acid (20-HETE) has been shown to positively correlate with body mass index, hyperglycemia, and plasma insulin levels. This study seeks to identify a causal relationship between 20-HETE and obesity-driven insulin resistance. Cyp4a14-/- male mice, a model of 20-HETE overproduction, were fed a regular or high-fat diet (HFD) for 15 wk. 20-SOLA [2,5,8,11,14,17-hexaoxanonadecan-19-yl 20-hydroxyeicosa-6( Z),15( Z)-dienoate], a 20-HETE antagonist, was administered from week 0 or week 7 of HFD. HFD-fed mice gained significant weight (16.7 ± 3.2 vs. 3.8 ± 0.35 g, P < 0.05) and developed hyperglycemia (157 ± 3 vs. 121 ± 7 mg/dl, P < 0.05) and hyperinsulinemia (2.3 ± 0.4 vs. 0.5 ± 0.1 ng/ml, P < 0.05) compared with regular diet-fed mice. 20-SOLA attenuated HFD-induced weight gain (9.4 ± 1 vs. 16.7 ± 3 g, P < 0.05) and normalized the hyperglycemia (157 ± 7 vs. 102 ± 5 mg/dl, P < 0.05) and hyperinsulinemia (1.1 ± 0.1 vs. 2.3 ± 0.4 ng/ml, P < 0.05). The impaired glucose homeostasis and insulin resistance in HFD-fed mice evidenced by reduced insulin and glucose tolerance were also ameliorated by 20-SOLA. Circulatory and adipose tissue 20-HETE levels significantly increased in HFD-fed mice correlating with impaired insulin signaling, including reduction in insulin receptor tyrosine (Y972) phosphorylation and increased serine (S307) phosphorylation of the insulin receptor substrate-1 (IRS-1). 20-SOLA treatments prevented changes in insulin signaling. These findings indicate that 20-HETE contributes to HFD-induced obesity, insulin resistance, and impaired insulin signaling.

Infarct size-limiting effect of epoxyeicosatrienoic acid analog EET-B is mediated by hypoxia-inducible factor-1α via downregulation of prolyl hydroxylase 3

Epoxyeicosatrienoic acids (EETs) decrease cardiac ischemia-reperfusion injury; however, the mechanism of their protective effect remains elusive. Here, we investigated the cardioprotective action of a novel EET analog, EET-B, in reperfusion and the role of hypoxia-inducible factor (HIF)-1α in such action of EET-B. Adult male rats were subjected to 30 min of left coronary artery occlusion followed by 2 h of reperfusion. Administration of 14,15-EET (2.5 mg/kg) or EET-B (2.5 mg/kg) 5 min before reperfusion reduced infarct size expressed as a percentage of the area at risk from 64.3 ± 1.3% in control to 42.6 ± 1.9% and 46.0 ± 1.6%, respectively, and their coadministration did not provide any stronger effect. The 14,15-EET antagonist 14,15-epoxyeicosa-5( Z)-enoic acid (2.5 mg/kg) inhibited the infarct size-limiting effect of EET-B (62.5 ± 1.1%). Similarly, the HIF-1α inhibitors 2-methoxyestradiol (2.5 mg/kg) and acriflavine (2 mg/kg) completely abolished the cardioprotective effect of EET-B. In a separate set of experiments, the immunoreactivity of HIF-1α and its degrading enzyme prolyl hydroxylase domain protein 3 (PHD3) were analyzed in the ischemic areas and nonischemic septa. At the end of ischemia, the HIF-1α immunogenic signal markedly increased in the ischemic area compared with the septum (10.31 ± 0.78% vs. 0.34 ± 0.08%). After 20 min and 2 h of reperfusion, HIF-1α immunoreactivity decreased to 2.40 ± 0.48% and 1.85 ± 0.43%, respectively, in the controls. EET-B blunted the decrease of HIF-1α immunoreactivity (7.80 ± 0.69% and 6.44 ± 1.37%, respectively) and significantly reduced PHD3 immunogenic signal in ischemic tissue after reperfusion. In conclusion, EET-B provides an infarct size-limiting effect at reperfusion that is mediated by HIF-1α and downregulation of its degrading enzyme PHD3. NEW & NOTEWORTHY The present study shows that EET-B is an effective agonistic 14,15-epoxyeicosatrienoic acid analog, and its administration before reperfusion markedly reduced myocardial infarction in rats. Most importantly, we demonstrate that increased hypoxia-inducible factor-1α levels play a role in cardioprotection mediated by EET-B in reperfusion likely by mechanisms including downregulation of the hypoxia-inducible factor -1α-degrading enzyme prolyl hydroxylase domain protein 3.

The arachidonic acid monooxygenase: from biochemical curiosity to physiological/pathophysiological significance

The initial studies of the metabolism of arachidonic acid (AA) by the cytochrome P450 (P450) hemeproteins sought to: a) elucidate the roles for these enzymes in the metabolism of endogenous pools of the FA, b) identify the P450 isoforms involved in AA epoxidation and ω/ω-1 hydroxylation, and c) explore the biological activities of their metabolites. These early investigations provided a foundation for subsequent efforts to establish the physiological relevance of the AA monooxygenase and its contributions to the pathophysiology of, for example, cancer, diabetes, hypertension, inflammation, nociception, and vascular disease. This retrospective analyzes the history of some of these efforts, with emphasis on genetic studies that identified roles for the murine Cyp4a and Cyp2c genes in renal and vascular physiology and the pathophysiology of hypertension and cancer. Wide-ranging investigations by laboratories worldwide, including the authors, have established a better appreciation of the enzymology, genetics, and physiologic roles for what is now known as the third branch of the AA cascade. Combined with the development of analytical and pharmacological tools, including robust synthetic agonists and antagonists of the major metabolites, we stand at the threshold of novel therapeutic approaches for the treatment of renal injury, pain, hypertension, and heart disease.

The Cytochrome P450 Slow Metabolizers CYP2C9*2 and CYP2C9*3 Directly Regulate Tumorigenesis via Reduced Epoxyeicosatrienoic Acid Production

Increased expression of cytochrome P450 CYP2C9, together with elevated levels of its products epoxyeicosatrienoic acids (EET), is associated with aggressiveness in cancer. Cytochrome P450 variants CYP2C9*2 and CYP2C9*3 encode proteins with reduced enzymatic activity, and individuals carrying these variants metabolize drugs more slowly than individuals with wild-type CYP2C9*1, potentially affecting their response to drugs and altering their risk of disease. Although genetic differences in CYP2C9-dependent oxidation of arachidonic acid (AA) have been reported, the roles of CYP2C9*2 and CYP2C9*3 in EET biosynthesis and their relevance to disease are unknown. Here, we report that CYP2C9*2 and CYP2C9*3 metabolize AA less efficiently than CYP2C9*1 and that they play a role in the progression of non-small cell lung cancer (NSCLC) via impaired EET biosynthesis. When injected into mice, NSCLC cells expressing CYP2C9*2 and CYP2C9*3 produced lower levels of EETs and developed fewer, smaller, and less vascularized tumors than cells expressing CYP2C9*1. Moreover, endothelial cells expressing these two variants proliferated and migrated less than cells expressing CYP2C*1. Purified CYP2C9*2 and CYP2C9*3 exhibited attenuated catalytic efficiency in producing EETs, primarily due to impaired reduction of these two variants by NADPH-P450 reductase. Loss-of-function SNPs within CYP2C9*2 and CYP2C9*3 were associated with improved survival in female cases of NSCLC. Thus, decreased EET biosynthesis represents a novel mechanism whereby CYPC29*2 and CYP2C9*3 exert a direct protective role in NSCLC development.Significance: These findings report single nucleotide polymorphisms in the human CYP2C9 genes, CYP2C9*2 and CYP2C9*3, exert a direct protective role in tumorigenesis by impairing EET biosynthesis. Cancer Res; 78(17); 4865-77. ©2018 AACR.

The contribution of TRPV1 channel to 20-HETE-Aggravated ischemic neuronal injury

20-Hydroxyeicosatetraenoic acid (20-HETE), a cytochrome P450 (CYP) 4A/4F-derived metabolite of arachidonic acid, directly contributes to ischemic neuronal injury. However, little is known about mediators of 20-HETE neurotoxicity after ischemia. Here, we focus on the role of transient receptor potential cation channel subfamily V member 1 (TRPV1) in 20-HETE-induced neurotoxicity. Our results showed that TRPV1 and CYP4A immunoreactivity were colocalized in neurons. TRPV1 inhibition attenuated 20-HETE mimetic 20-5,14-HEDGE-induced reactive oxygen species (ROS) production and neuronal injury in cultured neurons and protected ischemic neurons in vitro and in vivo. TRPV1 inhibition in combination with 20-HETE synthesis inhibitor HET0016 did not produce additional protective effects. Furthermore, TRPV1 genetic inhibition and NADPH oxidase inhibitor gp91ds-dat each attenuated ROS production to a similar extent. However, combined treatment did not achieve additional reduction. Therefore, we conclude that TRPV1 channels are involved in 20-HETE's ROS generation and neurotoxicity after ischemia.

GPR40 is a low-affinity epoxyeicosatrienoic acid receptor in vascular cells

Endothelium-derived epoxyeicosatrienoic acids (EETs) have numerous vascular activities mediated by G protein-coupled receptors. Long-chain free fatty acids and EETs activate GPR40, prompting us to investigate the role of GPR40 in some vascular EET activities. 14,15-EET, 11,12-EET, arachidonic acid, and the GPR40 agonist GW9508 increase intracellular calcium concentrations in human GPR40-overexpressing HEK293 cells (EC₅₀ = 0.58 ± 0.08 μm, 0.91 ± 0.08 μm, 3.9 ± 0.06 μm, and 19 ± 0.37 nm, respectively). EETs with cis- and trans-epoxides had similar activities, whereas substitution of a thiirane sulfur for the epoxide oxygen decreased the activities. 8,9-EET, 5,6-EET, and the epoxide hydrolysis products 11,12- and 14,15-dihydroxyeicosatrienoic acids were less active than 11,12-EET. The GPR40 antagonist GW1100 and siRNA-mediated GPR40 silencing blocked the EET- and GW9508-induced calcium increases. EETs are weak GPR120 agonists. GPR40 expression was detected in human and bovine endothelial cells (ECs), smooth muscle cells, and arteries. 11,12-EET concentration-dependently relaxed preconstricted coronary arteries; however, these relaxations were not altered by GW1100. In human ECs, 11,12-EET increased MAP kinase (MAPK)-mediated ERK phosphorylation, phosphorylation and levels of connexin-43 (Cx43), and expression of cyclooxygenase-2 (COX-2), all of which were inhibited by GW1100 and the MAPK inhibitor U0126. Moreover, siRNA-mediated GPR40 silencing decreased 11,12-EET-induced ERK phosphorylation. These results indicated that GPR40 is a low-affinity EET receptor in vascular cells and arteries. We conclude that epoxidation of arachidonic acid to EETs enhances GPR40 agonist activity and that 11,12-EET stimulation of GPR40 increases Cx43 and COX-2 expression in ECs via ERK phosphorylation.

Deactivation of 12(S)-HETE through (ω-1)-hydroxylation and β-oxidation in alternatively activated macrophages

Polarization of macrophages to proinflammatory M1 and to antiinflammatory alternatively activated M2 states has physiological implications in the development of experimental hypertension and other pathological conditions. 12/15-Lipoxygenase (12/15-LO) and its enzymatic products 12(S)- and 15(S)-hydroxyeicosatetraenoic acid (HETE) are essential in the process since disruption of the gene encoding 12/15-LO renders the mice unsusceptible to hypertension. The objective was to test the hypothesis that M2 macrophages catabolize 12(S)-HETE into products that are incapable of promoting vasoconstriction. Cultured M2 macrophages metabolized externally added [¹⁴C]12(S)-HETE into more polar metabolites, while M1 macrophages had little effect on the catabolism. The major metabolites were identified by mass spectrometry as (ω-1)-hydroxylation and β-oxidation products. The conversion was inhibited by both peroxisomal β-oxidation inhibitor, thioridazine, and cytochrome P450 inhibitors. Quantitative PCR analysis confirmed that several cytochrome P450 enzymes (CYP2E1 and CYP1B1) and peroxisomal β-oxidation markers were upregulated upon M2 polarization. The identified 12,19-dihydroxy-5,8,10,14-eicosatetraenoic acid and 8-hydroxy-6,10-hexadecadienoic acid metabolites were tested on abdominal aortic rings for biological activity. While 12(S)-HETE enhanced vasoconstrictions to angiotensin II from 15% to 25%, the metabolites did not. These results indicate that M2, but not M1, macrophages degrade 12(S)-HETE into products that no longer enhance the angiotensin II-induced vascular constriction, supporting a possible antihypertensive role of M2 macrophages.

Elevated 20-HETE in metabolic syndrome regulates arterial stiffness and systolic hypertension via MMP12 activation

Arterial stiffness plays a causal role in development of systolic hypertension. 20-hydroxyeicosatetraeonic acid (20-HETE), a cytochrome P450 (CYP450)-derived arachidonic acid metabolite, is known to be elevated in resistance arteries in hypertensive animal models and loosely associated with obesity in humans. However, the role of 20-HETE in the regulation of large artery remodeling in metabolic syndrome has not been investigated. We hypothesized that elevated 20-HETE in metabolic syndrome increases matrix metalloproteinase 12 (MMP12) activation leading to increased degradation of elastin, increased large artery stiffness and increased systolic blood pressure. 20-HETE production was increased ~7 fold in large, conduit arteries of metabolic syndrome (JCR:LA-cp, JCR) vs. normal Sprague-Dawley (SD) rats. This correlated with increased elastin degradation (~7 fold) and decreased arterial compliance (~75% JCR vs. SD). 20-HETE antagonists blocked elastin degradation in JCR rats concomitant with blocking MMP12 activation. 20-HETE antagonists normalized, and MMP12 inhibition (pharmacological and MMP12-shRNA-Lnv) significantly improved (~50% vs. untreated JCR) large artery compliance in JCR rats. 20-HETE antagonists also decreased systolic (182 ± 3 mmHg JCR, 145 ± 3 mmHg JCR + 20-HETE antagonists) but not diastolic blood pressure in JCR rats. Whereas diastolic pressure was fully angiotensin II (Ang II)-dependent, systolic pressure was only partially Ang II-dependent, and large artery stiffness was Ang II-independent. Thus, 20-HETE-dependent regulation of systolic blood pressure may be a unique feature of metabolic syndrome related to high 20-HETE production in large, conduit arteries, which results in increased large artery stiffness and systolic blood pressure. These findings may have implications for management of systolic hypertension in patients with metabolic syndrome.