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.

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.

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 ±â€Š2 vs. 127 ±â€Š2 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.

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 ß-arrestin recruitment assays to determine receptor activation and downstream signalling events. KEY RESULTS: SPR confirmed 20-HETE binding to GPR75 with an estimated KD of 1.56 × 10-10  M. In GPR75-transfected HTLA cells, 20-HETE stimulated intracellular Ca2+ levels, IP-1 accumulation and ß-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 (KD 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-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.

20-HETE interferes with insulin signaling and contributes to obesity-driven insulin resistance.

20-HETE, a metabolite of arachidonic acid produced by Cytochrome P450 (CYP) 4A/4 F, has been implicated in the development of obesity-associated complications such as diabetes and insulin resistance. In this study, we examined whether the acute elevation of 20-HETE levels contributes to the development of diet-driven hyperglycemia and insulin resistance. We employed a conditional transgenic mouse model to overexpress Cyp4a12 (Cyp4a12tg), a murine 20-HETE synthase, together with high fat diet (HFD) feeding. Mice in which Cyp4a12 was induced by doxycycline (DOX) at the onset of HFD feeding gained weight at a greater rate and extent than corresponding DOX-untreated Cyp4a12 mice. Cyp4a12tg mice fed HFD + DOX displayed hyperglycemia and impaired glucose metabolism while corresponding HFD-fed Cyp4a12tg mice (no DOX) did not. Importantly, administration of a 20-HETE antagonist, 20-SOLA, to Cyp4a12tg mice fed HFD + DOX significantly attenuated weight gain and prevented the development of hyperglycemia and impaired glucose metabolism. Levels of insulin receptor (IR) phosphorylation at Tyrosine 972 and insulin receptor substrate-1 (IRS1) phosphorylation at serine 307 were markedly decreased and increased, respectively, in liver, skeletal muscle and adipose tissues from Cyp4a12tg mice fed HFD + DOX; 20-SOLA prevented the IR and IRS1 inactivation, suggesting that 20-HETE interferes with insulin signaling. Additional studies in 3T3-1 differentiated adipocytes confirmed that 20-HETE impairs insulin signaling and that its effect may require activation of its receptor GPR75. Taken together, these results provide strong evidence that 20-HETE interferes with insulin function and contributed to diet-driven insulin resistance.

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.

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.

Catalyst-Controlled Diastereoselective Synthesis of Cyclic Amines via C-H Functionalization.

Reliable regio- and stereochemical techniques applicable to nonactivated aliphatic systems remain largely elusive due to the challenges of discriminating between multiple, relatively strong sp3 C-H bonds whose chemical behavior often differ only subtly. Nevertheless, approaches that employ directing groups and/or auxiliaries have emerged, but impose practical restrictions, especially in complex molecule synthesis. This report describes a catalyst-controlled regio- and diastereoselective synthesis of N-unprotected pyrrolidines via dirhodium catalyzed intramolecular nitrene insertion into sp3 C-H bonds. The reaction proceeds at rt without external oxidants, nitrene stabilizing groups, or directing functionality. The insights that emerged from the conformational/stereoselectivity relationships (CSR) between catalysts and substrates provide a framework for rational catalyst design that can accommodate a broader range of aliphatic C-H chemistry.

Dirhodium-catalyzed C-H arene amination using hydroxylamines.

Primary and N-alkyl arylamine motifs are key functional groups in pharmaceuticals, agrochemicals, and functional materials, as well as in bioactive natural products. However, there is a dearth of generally applicable methods for the direct replacement of aryl hydrogens with NH2/NH(alkyl) moieties. Here, we present a mild dirhodium-catalyzed C-H amination for conversion of structurally diverse monocyclic and fused aromatics to the corresponding primary and N-alkyl arylamines using NH2/NH(alkyl)-O-(sulfonyl)hydroxylamines as aminating agents; the relatively weak RSO2O-N bond functions as an internal oxidant. The methodology is operationally simple, scalable, and fast at or below ambient temperature, furnishing arylamines in moderate-to-good yields and with good regioselectivity. It can be readily extended to the synthesis of fused N-heterocycles.

Regio- and enantioselective catalytic monoepoxidation of conjugated dienes: synthesis of chiral allylic cis-epoxides.

Ti(IV)-salan 4 catalyzes the diastereo- and enantioselective monoepoxidation of conjugated dienes using 30% H2O2 at rt or below even in the presence of other olefins and adjacent stereocenters. Its enantiomer, ent-4, provides access to the opposite diastereomer or enantiomer. The resultant chiral allylic epoxides, and the triols derived from them, are versatile synthetic intermediates as well as substructures present in many bioactive natural products. The epoxidation is highly specific for Z-olefins. For 1-acyl(silyl)oxypenta-2,4-dienes, epoxidation of the distal olefin is generally favored in contrast to the adjacent regioselectivity characteristic of Sharpless, peracid, and other directed epoxidations of hydroxylated dienes.

Regio- and stereoselective monoepoxidation of dienes using methyltrioxorhenium: synthesis of allylic epoxides.

Methyltrioxorhenium (MTO) complexed with pyridine was shown to be a highly effective catalyst for the regioselective monoepoxidation of conjugated di- and trienes using 30% H2O2 at or below room temperature. The resultant allylic epoxides, and the triols derived from them, are versatile synthetic intermediates as well as substructures present in many bioactive natural products. The site of epoxidation was dependent upon olefin substitution, olefin geometry (Z vs E), and the presence of electron-withdrawing substituents on adjacent carbons. For 1-acyl(silyl)oxypenta-2,4-dienes, epoxidation of the distal olefin was generally favored in contrast to the adjacent regioselectivity characteristic of Sharpless, peracid, and other directed epoxidations of hydroxylated dienes.