20-HETE activates the Raf/MEK/ERK pathway in renal epithelial cells through an EGFR- and c-Src-dependent mechanism

20-Hydroxyeicosatetraenoic Acid Regulates the Src/EGFR/NF-κB Signaling Pathway Via GPR75 to Activate Microglia and Promote TBI in the Immature Brain

20-Hydroxyeicosatetraenoic acid (20-HETE) is associated with secondary damage in traumatic brain injury (TBI) of the immature brain. Microglial activation is pivotal in this process. However, the underlying mechanism of action remains unknown. While 20-HETE interacts with G protein-coupled receptor 75 (GPR75) in some pathological processes, their interaction in brain tissue remains uncertain. This study aimed to investigate whether 20-HETE can activate microglia by binding to GPR75 in TBI of the immature brain. Drug affinity responsive molecular target stability (DARTS) assays, cycloheximide (CHX) chase assays, and auto-dock assays were employed to analyze the interaction between 20-HETE and GPR75. The expression levels of cytochrome P450 4A (CYP4A) and GPR75 in activated microglia in an immature brain TBI model were observed by western blot and multiple immunofluorescence staining. The effects of different levels of 20-HETE expression and lentivirus-mediated GPR75 gene silencing on 20-HETE-induced inflammatory factor release from BV-2 cells were observed by enzyme-linked immunoassay (ELISA). The phosphorylation levels of the downstream Src kinase, epidermal growth factor receptor (EGFR), and nuclear factor (NF)-κB were assessed using western blot. Cell viability and apoptosis were detected by CCK-8 and terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) assays. 20-HETE bound to the GPR75 protein and inhibited its degradation. GPR75 gene silencing reversed the 20-HETE-induced inflammatory activation of BV-2 cells, effectively inhibiting the activation of the Src/EGFR/NF-κB pathway and the effects of 20-HETE on cell viability and the apoptosis rate. In contrast, overexpression of GPR75 had the opposite effect. In addition, after immature brain TBI, the 20-HETE and GPR75 expression levels were upregulated in microglia, with significant activation of the Src/EGFR/NF-κB pathway. Inhibition of 20-HETE synthesis with N-hydroxy-N'-(4-n-butyl-2-methylphenyl) formamidine (HET0016) produced the opposite effect. 20-HETE regulates the Src/EGFR/NF-κB signaling pathway via GPR75 to activate microglia, promoting immature brain TBI. These findings offer a novel target for promoting the brain injury effect of 20-HETE.

Key regulator PNPLA8 drives phospholipid reprogramming induced proliferation and migration in triple-negative breast cancer

BACKGROUND

Triple-negative breast cancer (TNBC) is the most aggressive breast cancer subtype and leads to the poorest patient outcomes despite surgery and chemotherapy treatment. Exploring new molecular mechanisms of TNBC that could lead to the development of novel molecular targets are critically important for improving therapeutic options for treating TNBC.

METHODS

We sought to identify novel therapeutic targets in TNBC by combining genomic and functional studies with lipidomic analysis, which included mechanistic studies to elucidate the pathways that tie lipid profile to critical cancer cell properties. Our studies were performed in a large panel of human breast cancer cell lines and patient samples.

RESULTS

Comprehensive lipid profiling revealed that phospholipid metabolism is reprogrammed in TNBC cells. We discovered that patatin-like phospholipase domain-containing lipase 8 (PNPLA8) is overexpressed in TNBC cell lines and tissues from breast cancer patients. Silencing of PNPLA8 disrupted phospholipid metabolic reprogramming in TNBC, particularly affecting the levels of phosphatidylglycerol (PG), phosphatidylcholine (PC), lysophosphatidylcholine (LPC) and glycerophosphocholine (GPC). We showed that PNPLA8 is essential in regulating cell viability, migration and antioxidation in TNBC cells and promoted arachidonic acid and eicosanoid production, which in turn activated PI3K/Akt/Gsk3β and MAPK signaling.

CONCLUSIONS

Our study highlights PNPLA8 as key regulator of phospholipid metabolic reprogramming and malignant phenotypes in TNBC, which could be further developed as a novel molecular treatment target.

Renoprotective Effect of TP0472993, a Novel and Selective 20-Hydroxyeicosatetraenoic Acid Synthesis Inhibitor, in Mouse Models of Renal Fibrosis

Kidney fibrosis is considered the essential pathophysiological process for the progression of chronic kidney disease (CKD) toward renal failure. 20-Hydroxyeicosatetraenoic acid (20-HETE) has crucial roles in modulating the vascular response in the kidney and the progression of albuminuria. However, the roles of 20-HETE in kidney fibrosis are largely unexplored. In the current research, we hypothesized that if 20-HETE has important roles in the progression of kidney fibrosis, 20-HETE synthesis inhibitors might be effective against kidney fibrosis. To verify our hypothesis, this study investigated the effect of a novel and selective 20-HETE synthesis inhibitor, TP0472993, on the development of kidney fibrosis after folic acid- and obstructive-induced nephropathy in mice. Chronic treatment with TP0472993 at doses of 0.3 and 3 mg/kg twice a day attenuated the degree of kidney fibrosis in the folic acid nephropathy and the unilateral ureteral obstruction (UUO) mice, as demonstrated by reductions in Masson's trichrome staining and the renal collagen content. In addition, TP0472993 reduced renal inflammation, as demonstrated by markedly reducing interleukin-1β (IL-1β) and tumor necrosis factor alpha (TNF-α) levels in the renal tissue. Chronic treatment with TP0472993 also reduced the activity of extracellular signal-regulated kinase 1/2 (ERK1/2) and signal transducer and activator of transcription 3 (STAT3) in the kidney of UUO mice. Our observations indicate that inhibition of 20-HETE production with TP0472993 suppresses the kidney fibrosis progression via a reduction in the ERK1/2 and STAT3 signaling pathway, suggesting that 20-HETE synthesis inhibitors might be a novel treatment option against CKD. SIGNIFICANCE STATEMENT: In this study, we demonstrate that the pharmacological blockade of 20-hydroxyeicosatetraenoic acid (20-HETE) synthesis using TP0472993 suppresses the progression of kidney fibrosis after folic acid- and obstructive-induced nephropathy in mice, indicating that 20-HETE might have key roles in the pathogenesis of kidney fibrosis. TP0472993 has the potential to be a novel therapeutic approach against chronic kidney disease.

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.

Translational insights into mechanisms and preventive strategies after renal injury in neonates

Adverse perinatal circumstances can cause acute kidney injury (AKI) and contribute to chronic kidney disease (CKD). Accumulating evidence indicate that a wide spectrum of perinatal conditions interferes with normal kidney development and ultimately leads to aberrant kidney structure and function later in life. The present review addresses the lack of mechanistic knowledge with regard to perinatal origins of CKD and provides a comprehensive overview of pre- and peri-natal insults, including genetic predisposition, suboptimal nutritional supply, obesity and maternal metabolic disorders as well as placental insufficiency leading to intrauterine growth restriction (IUGR), prematurity, infections, inflammatory processes, and the need for life-saving treatments (e.g. oxygen supplementation, mechanical ventilation, medications) in neonates. Finally, we discuss future preventive, therapeutic, and regenerative directions. In summary, this review highlights the perinatal vulnerability of the kidney and the early origins of increased susceptibility toward AKI and CKD during postnatal life. Promotion of kidney health and prevention of disease require the understanding of perinatal injury in order to optimize perinatal micro- and macro-environments and enable normal kidney development.

The CYP/20-HETE/GPR75 axis in hypertension

20-Hydroxyeicosatetraenoic acid (20-HETE) is a bioactive lipid generated from the ω-hydroxylation of arachidonic acid (AA) by enzymes of the cytochrome P450 (CYP) family, primarily the CYP4A and CYP4F subfamilies. 20-HETE is most notably identified as a modulator of vascular tone, regulator of renal function, and a contributor to the onset and development of hypertension and cardiovascular disease. 20-HETE-mediated signaling promotes hypertension by sensitizing the vasculature to constrictor stimuli, inducing endothelial dysfunction, and potentiating vascular inflammation. These bioactions are driven by the activation of the G-protein coupled receptor 75 (GPR75), a 20-HETE receptor (20HR). Given the capacity of 20-HETE signaling to drive pro-hypertensive mechanisms, the CYP/20-HETE/GPR75 axis has the potential to be a significant therapeutic target for the treatment of hypertension and cardiovascular diseases associated with increases in blood pressure. In this chapter, we review 20-HETE-mediated cellular mechanisms that promote hypertension, highlight important data in humans such as genetic variants in the CYP genes that potentiate 20-HETE production and describe recent findings in humans with 20HR/GPR75 mutations. Special emphasis is given to the 20HR and respective receptor blockers that have the potential to pave a path to translational and clinical studies for the treatment of 20-HETE-driven hypertension, and obesity/metabolic syndrome.

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.

Role of 20-hydroxyeicosatetraenoic acid in pulmonary hypertension and proliferation of pulmonary arterial smooth muscle cells

OBJECTIVE

To investigate the level of 20-Hydroxyeicosatetraenoic acid (20-HETE) in model of pulmonary hypertension (PH) and its effect on the proliferation of pulmonary arterial smooth muscle cells (PASMCs).

METHODS

Twenty male Sprague-Dawley rats were randomly divided into two groups, including control group and PH group. PH was induced by intra-peritoneal injection of 20 mg/kg monocrotaline (MCT) twice in a week in 10 rats, and control rats were given equal amount of saline. Mean pulmonary arterial pressure (mPAP), right ventricular hypertrophy index (RVHI) and pulmonary vascular remodeling index (WA%, WT%) were assessed at the week 4. The levels of 20-HETE were analysed by liquid chromatography tandem-mass spectrometry (LC-MS/MS). EdU test was used to determine the proliferation of PASMCs. Intracellular levels of reactive oxygen species (ROS) were detected using DCFH-DA dye.

RESULTS

(1) Prominent right ventricular hypertrophy and pulmonary vascular remodeling were verified in PH rats; (2) 20-HETE levels in lung tissue and serum were significantly lifted in PH rats; (3) Increased 20-HETE levels in cell culture supernatants were significantly noted in hypoxia condition; (4) Proliferation of PASMCs was induced by 20-HETE and hypoxia, and was inhibited by HET0016; (5) Production of ROS was elevated by 20-HETE and hypoxia, and was reduced by HET0016; CONCLUSION: Vascular remodeling was demonstrated in PH rats. 20-HETE levels were significantly increased in PH rats and under hypoxia condition. PASMCs proliferation and ROS production were elevated by 20-HETE and could be inhibited by HET0016, a specific inhibitor of 20-HETE. Taken together, changes in the level of 20-HETE may be related to the excessive proliferation of PASMCs in PH rats.

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.

Conflicting roles of 20-HETE in hypertension and renal end organ damage

20-HETE is a cytochrome P450-derived metabolite of arachidonic acid that has both pro- and anti-hypertensive actions that result from modulation of vascular and kidney function. In the vasculature, 20-HETE sensitizes vascular smooth muscle cells to constrictor stimuli and increases myogenic tone. By promoting smooth muscle cell migration and proliferation, as well as by acting on the vascular endothelium to cause endothelial dysfunction, angiotensin converting enzyme (ACE) expression, and inflammation, 20-HETE contributes to adverse vascular remodeling and increased blood pressure. A G protein-coupled receptor was recently identified as the effector for the vascular actions of 20-HETE. In addition, evidence suggests that 20-HETE contributes to hypertension via positive regulation of the renin-angiotensin-aldosterone system, as well as by causing renal fibrosis. On the other hand, 20-HETE exerts anti-hypertensive actions by inhibiting sodium reabsorption by the kidney in both the proximal tubule and thick ascending limb of Henle. This review discusses the pro- and anti-hypertensive roles of 20-HETE in the pathogenesis of hypertension-associated renal disease, the association of gene polymorphisms of cytochrome P450 enzymes with the development of hypertension and renal end organ damage in humans, and 20-HETE related pharmaceutical agents.

20-HETE in the regulation of vascular and cardiac function

20-HETE, the ω-hydroxylation product of arachidonic acid catalyzed by enzymes of the cytochrome P450 (CYP) 4A and 4F gene families, is a bioactive lipid mediator with potent effects on the vasculature including stimulation of smooth muscle cell contractility, migration and proliferation as well as activation of endothelial cell dysfunction and inflammation. Clinical studies have shown elevated levels of plasma and urinary 20-HETE in human diseases and conditions such as hypertension, obesity and metabolic syndrome, myocardial infarction, stroke, and chronic kidney diseases. Studies of polymorphic associations also suggest an important role for 20-HETE in hypertension, stroke and myocardial infarction. Animal models of increased 20-HETE production are hypertensive and are more susceptible to cardiovascular injury. The current review summarizes recent findings that focus on the role of 20-HETE in the regulation of vascular and cardiac function and its contribution to the pathology of vascular and cardiac diseases.

Sclt1 deficiency causes cystic kidney by activating ERK and STAT3 signaling

Ciliopathies form a group of inherited disorders sharing several clinical manifestations because of abnormal cilia formation or function, and few treatments have been successful against these disorders. Here, we report a mouse model with mutated Sclt1 gene, which encodes a centriole distal appendage protein important for ciliogenesis. Sodium channel and clathrin linker 1 (SCLT1) mutations were associated with the oral-facial-digital syndrome (OFD), an autosomal recessive ciliopathy. The Sclt1-/- mice exhibit typical ciliopathy phenotypes, including cystic kidney, cleft palate and polydactyly. Sclt1-loss decreases the number of cilia in kidney; increases proliferation and apoptosis of renal tubule epithelial cells; elevates protein kinase A, extracellular signal-regulated kinases, SMAD and signal transducer and activator of transcription 3 (STAT3) pathways; and enhances pro-inflammation and pro-fibrosis pathways with disease progression. Embryonic kidney cyst formation of Sclt1-/- mice was effectively reduced by an anti-STAT3 treatment using pyrimethamine. Overall, we reported a new mouse model for the OFD; and our data suggest that STAT3 inhibition may be a promising treatment for SCLT1-associated cystic kidney.

Induction of cytochrome P450 4A14 contributes to angiotensin II-induced renal fibrosis in mice

Angiotensin II (AngII) plays an important role in the pathogenesis of hypertension and associated renal injuries. To elucidate the molecular mechanism by which AngII induces renal damage, we found that AngII infusion significantly induced CYP4A14 expression in renal proximal tubule cells (RPTCs) with marked increases in blood pressure and proteinuria. Renal production of the major CYP4A metabolite, 20-HETE, was also significantly increased in the AngII-treated mice. Compared to wild-type (WT) mice, CYP4A14 knockout (CYP4A14^-/-) mice exhibited significantly lower levels of blood pressure, renal 20-HETE production, proteinuria and renal fibrosis following AngII infusion. Furthermore, AngII-induced renal expression of profibrotic genes and proinflammatory genes was significantly attenuated in CYP4A14^-/- mice. In vitro studies using cultured RPTCs demonstrated that AngII significantly induced CYP4A14 expression and 20-HETE production via the MAPK signaling pathway. AngII treatment increased TGF-β and collagen expression, which was attenuated by the CYP4A inhibitor, TS-011. Moreover, 20-HETE treatment potently induced CYP4A14 expression and TGF-β and collagen levels. Collectively, these findings suggest that attenuated renal fibrosis in AngII-treated CYP4A14^-/- mice may result from both reduced systemic blood pressure and renal 20-HETE production. Therefore, CYP4A14 may represent a useful target for the treatment of AngII-associated renal damage.

Role of 20-Hydroxyeicosatetraenoic Acid (20-HETE) in Androgen-Mediated Cell Viability in Prostate Cancer Cells

20-Hydroxyeicosatetraenoic acid (20-HETE) is generated intracellularly through the ω-hydroxylation of arachidonic acid by the cytochrome P450 (in humans, CYP4A11 and CYP4F2). 20-HETE induces mitogenic responses in different cancer cells. The aim of this study was to analyze how 20-HETE impacts cell survival, proliferation, and apoptosis in prostate cancer cells. Incubation of the human androgen-sensitive cells (LNCaP) with 1-10 μM HET0016 (a selective inhibitor of 20-HETE synthesis) reduced cell viability by 49*-64%* (*p < 0.05 vs. control). This was explained by a reduction in cell proliferation (vehicle, 46 ± 3%; 1 μM, 23 ± 3%*; 10 μM, 28 ± 3%*) and by an increase in apoptosis (vehicle, 2.1 ± 0%; 1 μM, 16 ± 4%*; 10 μM, 31 ± 3%*). Furthermore, the increase in LNCaP cell viability induced by dihydrotestosterone (DHT, 0.1 nM) was abrogated by 30*-42%* by 1-10 μM HET0016. Incubation with 20-HETE (5-1000 nM) increased LNCaP cell viability up to 50%*, together with a 70%* reduction in apoptosis. PC-3 (androgen-insensitive) cell viability was not affected by either HET0016 or 20-HETE. In LNCaP cells, HET0016 (10 μM) diminished the expression of androgen receptors (AR): messenger RNA (mRNA) (40%*) and protein (50%*). DHT (10 nM) augmented CYP4F2 protein expression (1.9-fold*) and 20-HETE levels (50%*). Oppositely, enzalutamide (AR antagonist) reduced CYP4F2 mRNA and protein expressions by 30 and 25%, respectively. Thus, intracellular availability of 20-HETE is necessary to sustain LNCaP cell viability. 20-HETE may act as a signaling molecule in the pathways involved in LNCaP cell viability upon stimulation of the AR. This effect may be partially attributed to its role on securing normal AR expression levels that in turn contribute to maintain intracellular levels of 20-HETE.

Effect of Cytochrome P450 Metabolites of Arachidonic Acid in Nephrology

Thirty-five years ago, a third pathway for the metabolism of arachidonic acid by cytochrome P450 enzymes emerged. Subsequent work revealed that 20-hydroxyeicosatetraenoic and epoxyeicosatrienoic acids formed by these pathways have essential roles in the regulation of renal tubular and vascular function. Sequence variants in the genes that produce 20-hydroxyeicosatetraenoic acid are associated with hypertension in humans, whereas the evidence supporting a role for variants in the genes that alter levels of epoxyeicosatrienoic acids is less convincing. Studies in animal models suggest that changes in the production of cytochrome P450 eicosanoids alter BP. However, the mechanisms involved remain controversial, especially for 20-hydroxyeicosatetraenoic acid, which has both vasoconstrictive and natriuretic actions. Epoxyeicosatrienoic acids are vasodilators with anti-inflammatory properties that oppose the development of hypertension and CKD; 20-hydroxyeicosatetraenoic acid levels are elevated after renal ischemia and may protect against injury. Levels of this eicosanoid are also elevated in polycystic kidney disease and may contribute to cyst formation. Our review summarizes the emerging evidence that cytochrome P450 eicosanoids have a role in the pathogenesis of hypertension, polycystic kidney disease, AKI, and CKD.

20-HETE Signals Through G-Protein-Coupled Receptor GPR75 (Gq) to Affect Vascular Function and Trigger Hypertension

RATIONALE

20-Hydroxyeicosatetraenoic acid (20-HETE), one of the principle cytochrome P450 eicosanoids, is a potent vasoactive lipid whose vascular effects include stimulation of smooth muscle contractility, migration, and proliferation, as well as endothelial cell dysfunction and inflammation. Increased levels of 20-HETE in experimental animals and in humans are associated with hypertension, stroke, myocardial infarction, and vascular diseases.

OBJECTIVE

To date, a receptor/binding site for 20-HETE has been implicated based on the use of specific agonists and antagonists. The present study was undertaken to identify a receptor to which 20-HETE binds and through which it activates a signaling cascade that culminates in many of the functional outcomes attributed to 20-HETE in vitro and in vivo.

METHODS AND RESULTS

Using crosslinking analogs, click chemistry, binding assays, and functional assays, we identified G-protein receptor 75 (GPR75), currently an orphan G-protein-coupled receptor (GPCR), as a specific target of 20-HETE. In cultured human endothelial cells, 20-HETE binding to GPR75 stimulated Gα_q/11 protein dissociation and increased inositol phosphate accumulation and GPCR-kinase interacting protein-1-GPR75 binding, which further facilitated the c-Src-mediated transactivation of epidermal growth factor receptor. This results in downstream signaling pathways that induce angiotensin-converting enzyme expression and endothelial dysfunction. Knockdown of GPR75 or GPCR-kinase interacting protein-1 prevented 20-HETE-mediated endothelial growth factor receptor phosphorylation and angiotensin-converting enzyme induction. In vascular smooth muscle cells, GPR75-20-HETE pairing is associated with Gα_q/11- and GPCR-kinase interacting protein-1-mediated protein kinase C-stimulated phosphorylation of MaxiKβ, linking GPR75 activation to 20-HETE-mediated vasoconstriction. GPR75 knockdown in a mouse model of 20-HETE-dependent hypertension prevented blood pressure elevation and 20-HETE-mediated increases in angiotensin-converting enzyme expression, endothelial dysfunction, smooth muscle contractility, and vascular remodeling.

CONCLUSIONS

This is the first report to identify a GPCR target for an eicosanoid of this class. The discovery of 20-HETE-GPR75 pairing presented here provides the molecular basis for the signaling and pathophysiological functions mediated by 20-HETE in hypertension and cardiovascular diseases.

Clinical Implications of 20-Hydroxyeicosatetraenoic Acid in the Kidney, Liver, Lung and Brain: An Emerging Therapeutic Target

Cytochrome P450-mediated metabolism of arachidonic acid (AA) is an important pathway for the formation of eicosanoids. The ω-hydroxylation of AA generates significant levels of 20-hydroxyeicosatetraenoic acid (20-HETE) in various tissues. In the current review, we discussed the role of 20-HETE in the kidney, liver, lung, and brain during physiological and pathophysiological states. Moreover, we discussed the role of 20-HETE in tumor formation, metabolic syndrome and diabetes. In the kidney, 20-HETE is involved in modulation of preglomerular vascular tone and tubular ion transport. Furthermore, 20-HETE is involved in renal ischemia/reperfusion (I/R) injury and polycystic kidney diseases. The role of 20-HETE in the liver is not clearly understood although it represents 50%-75% of liver CYP-dependent AA metabolism, and it is associated with liver cirrhotic ascites. In the respiratory system, 20-HETE plays a role in pulmonary cell survival, pulmonary vascular tone and tone of the airways. As for the brain, 20-HETE is involved in cerebral I/R injury. Moreover, 20-HETE has angiogenic and mitogenic properties and thus helps in tumor promotion. Several inhibitors and inducers of the synthesis of 20-HETE as well as 20-HETE analogues and antagonists are recently available and could be promising therapeutic options for the treatment of many disease states in the future.

Elevated 20-HETE impairs coronary collateral growth in metabolic syndrome via endothelial dysfunction

Coronary collateral growth (CCG) is impaired in metabolic syndrome (MetS). microRNA-145 (miR-145-Adv) delivery to our rat model of MetS (JCR) completely restored and neutrophil depletion significantly improved CCG. We determined whether low endogenous levels of miR-145 in MetS allowed for elevated production of 20-hydroxyeicosatetraenoic acid (20-HETE), which, in turn, resulted in excessive neutrophil accumulation and endothelial dysfunction leading to impaired CCG. Rats underwent 0-9 days of repetitive ischemia (RI). RI-induced cardiac CYP4F (neutrophil-specific 20-HETE synthase) expression and 20-HETE levels were increased (4-fold) in JCR vs. normal rats. miR-145-Adv and 20-HETE antagonists abolished and neutrophil depletion (blocking antibodies) reduced (~60%) RI-induced increases in CYP4F expression and 20-HETE production in JCR rats. Impaired CCG in JCR rats (collateral-dependent blood flow using microspheres) was completely restored by 20-HETE antagonists [collateral-dependent zone (CZ)/normal zone (NZ) flow ratio was 0.76 ± 0.07 in JCR + 20-SOLA, 0.84 ± 0.05 in JCR + 20-HEDGE vs. 0.11 ± 0.02 in JCR vs. 0.84 ± 0.03 in normal rats]. In JCR rats, elevated 20-HETE was associated with excessive expression of endothelial adhesion molecules and neutrophil infiltration, which were reversed by miR-145-Adv. Endothelium-dependent vasodilation of coronary arteries, endothelial nitric oxide synthase (eNOS) Ser1179 phosphorylation, eNOS-dependent NO^·- production and endothelial cell survival were compromised in JCR rats. These parameters of endothelial dysfunction were completely reversed by 20-HETE antagonism or miR-145-Adv delivery, whereas neutrophil depletion resulted in partial reversal (~70%). We conclude that low miR-145 in MetS allows for increased 20-HETE, mainly from neutrophils, which compromises endothelial cell survival and function leading to impaired CCG. 20-HETE antagonists could provide viable therapy for restoration of CCG in MetS.NEW & NOTEWORTHY Elevated 20-hydroxyeicosatetraenoic acid (20-HETE) impairs coronary collateral growth (CCG) in metabolic syndrome by eliciting endothelial dysfunction and apoptosis via excessive neutrophil infiltration. 20-HETE antagonists completely restore coronary collateral growth in metabolic syndrome. microRNA-145 (miR-145) is an upstream regulator of 20-HETE production in metabolic syndrome; low expression of miR-145 in metabolic syndrome promotes elevated production of 20-HETE.

Molecular mechanisms and cell signaling of 20-hydroxyeicosatetraenoic acid in vascular pathophysiology

Cytochrome P450s enzymes catalyze the metabolism of arachidonic acid to epoxyeicosatrienoic acids (EETs), dihydroxyeicosatetraenoic acid and hydroxyeicosatetraeonic acid (HETEs). 20-HETE is a vasoconstrictor that depolarizes vascular smooth muscle cells by blocking K+ channels. EETs serve as endothelial derived hyperpolarizing factors. Inhibition of the formation of 20-HETE impairs the myogenic response and autoregulation of renal and cerebral blood flow. Changes in the formation of EETs and 20-HETE have been reported in hypertension and drugs that target these pathways alter blood pressure in animal models. Sequence variants in CYP4A11 and CYP4F2 that produce 20-HETE, UDP-glucuronosyl transferase involved in the biotransformation of 20-HETE and soluble epoxide hydrolase that inactivates EETs are associated with hypertension in human studies. 20-HETE contributes to the regulation of vascular hypertrophy, restenosis, angiogenesis and inflammation. It also promotes endothelial dysfunction and contributes to cerebral vasospasm and ischemia-reperfusion injury in the brain, kidney and heart. This review will focus on the role of 20-HETE in vascular dysfunction, inflammation, ischemic and hemorrhagic stroke and cardiac and renal ischemia reperfusion injury.

20-HETE contributes to ischemia-induced angiogenesis

Angiogenesis is an important adaptation for recovery from peripheral ischemia. Here, we determined whether 20-hydroxyeicosatetraenoic acid (20-HETE) contributes to ischemia-induced angiogenesis and assessed its underlying molecular and cellular mechanisms using a mouse hindlimb-ischemia angiogenesis model. Hindlimb blood flow was measured by Laser Doppler Perfusion Imaging and microvessel density was determined by CD31 and tomato lectin staining. We found that systemic and local administration of a 20-HETE synthesis inhibitor, DDMS, or a 20-HETE antagonist, 6,15-20-HEDGE significantly reduced blood flow recovery and microvessel formation in response to ischemia. 20-HETE production, measured by LC/MS/MS, was markedly increased in ischemic muscles (91±11 vs. 8±2pg/mg in controls), which was associated with prominent upregulation of the 20-HETE synthase, CYP4A12. Immunofluorescence co-localized increased CYP4A12 expression in response to ischemia to CD31-positive EC in the ischemic hindlimb microvessels. We further showed that ischemia increased HIF-1α, VEGF, and VEGFR2 expression in gracilis muscles and that these increases were negated by DDMS and 6,15-20-HEDGE. Lastly, we showed that ERK1/2 of MAPK is a component of 20-HETE regulated ischemic angiogenesis. Taken together, these data indicate that 20-HETE is a critical contributor of ischemia-induced angiogenesis in vivo.

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

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

Cytochrome P450 and Lipoxygenase Metabolites on Renal Function

Arachidonic acid metabolites have a myriad of biological actions including effects on the kidney to alter renal hemodynamics and tubular transport processes. Cyclooxygenase metabolites are products of an arachidonic acid enzymatic pathway that has been extensively studied in regards to renal function. Two lesser-known enzymatic pathways of arachidonic acid metabolism are the lipoxygenase (LO) and cytochrome P450 (CYP) pathways. The importance of LO and CYP metabolites to renal hemodynamics and tubular transport processes is now being recognized. LO and CYP metabolites have actions to alter renal blood flow and glomerular filtration rate. Proximal and distal tubular sodium transport and fluid and electrolyte homeostasis are also significantly influenced by renal CYP and LO levels. Metabolites of the LO and CYP pathways also have renal actions that influence renal inflammation, proliferation, and apoptotic processes at vascular and epithelial cells. These renal LO and CYP pathway actions occur through generation of specific metabolites and cell-signaling mechanisms. Even though the renal physiological importance and actions for LO and CYP metabolites are readily apparent, major gaps remain in our understanding of these lipid mediators to renal function. Future studies will be needed to fill these major gaps regarding LO and CYP metabolites on renal function.

Activator of G-protein Signaling 3 Controls Renal Epithelial Cell Survival and ERK5 Activation

Activator of G-protein signaling 3 (AGS3) is an accessory protein that functions to regulate the activation status of heterotrimeric G-protein subunits. To date, however, the downstream signaling pathways regulated by AGS3 remain to be fully elucidated, particularly in renal epithelial cells. In the present study, normal rat kidney (NRK-52E) proximal tubular epithelial cells were genetically modified to regulate the expression of AGS3 to investigate its role on MAPK and mTOR signaling to control epithelial cell number. Knockdown of endogenous AGS3 protein was associated with a reduced phosphorylated form of ERK5 and increased apoptosis as determined by elevated cleaved caspase-3. In the presence of the ERK5 inhibitor, BIX02189, a significant 2-fold change (P < 0.05) in G2/M transition state was detected compared to control conditions. Neither of the other MAPK, ERK1/2 or p38 MAPK, nor another pro-survival pathway, mTOR, was significantly altered by the changes in AGS3 protein levels in the renal epithelial cells. The selective ERK5 inhibitor, BIX02189, was found to dose-dependently reduce NRK cell number by up to 41% (P < 0.05) compared to control cells. In summary, these findings demonstrated that cell viability was regulated by AGS3 and was associated with ERK5 activation in renal epithelial cells.

Epoxides Derived from Dietary Dihomo-Gamma-Linolenic Acid Induce Germ Cell Death in C. elegans

Dietary fats are not created equally, slight differences in structure lead to crucial differences in function. Muticellular organisms use polyunsaturated fatty acid as substrates to produce potent signaling molecules crucial for many physiological processes, including reproduction. Here we explored the mechanism responsible for germ cell loss induced by dietary supplementation of dihomo-gamma-linolenic acid (DGLA, 20:3n-6) in the roundworm Caenorhabditis elegans. In this study we found that C. elegans CYP-33E2 activity produces a range of epoxy and hydroxy metabolites from dietary DGLA. Knockdown of cyp-33E2 suppressed the DGLA-induced sterility phenotype. Additionally, direct exposure of two specific DGLA-derived epoxy products, 8,9- and 14,15-epoxyeicosadienoic acids, produced germ cell abnormalities in the C. elegans gonad. We propose that sterility is mediated by the production of toxic DGLA-derived epoxides that trigger germ cell destruction. These studies are the first to establish a biological activity for a CYP-produced metabolite of DGLA.

20-Hydroxyeicosatetraenoic acid involved in endothelial activation and thrombosis

Endothelial cells play an important role in the process of coagulation and the function of platelets. We have previously reported that 20-hydroxyeicosatetraenoic acid (20-HETE), a metabolite of arachidonic acid, increased platelet aggregation and induced hemostasis. The purpose of the present study is to investigate whether 20-HETE-mediated endothelial activation has effect on the coagulation and platelet aggregation. C57Bl/6 mice were treated with PBS or 20-HETE (20 μg/kg) for 2 h, and then we performed a carotid artery or femoral artery thrombosis model by FeCl3. Detection of blood flow indicated that 20-HETE pretreatment accelerated formation of thrombus in both common carotid artery and femoral artery. In vitro, the secretion and expression of von Willebrand factor (vWF) in cultured human umbilical vein endothelial cells (HUVECs) with 20-HETE stimulation were increased, subsequently. The protein level of vWF in HUVECs was decreased at 1 h but increased with prolonged treatment with 20-HETE (>4 h). In contrast, vWF in the culture medium was increased under administration of 20-HETE at 1 h. As a result, adhesion of platelets on HUVECs was significantly increased by 20-HETE. In HUVECs, the extracellular signal-regulated kinase (ERK) pathway was activated by 20-HETE in a dose-dependent manner, and the inhibitors of ERK and L-type Ca2+channel blocked the release of vWF mediated by 20-HETE. In conclusion, 20-HETE instigates endothelial activation and induces the expression and secretion of vWF via the activation of ERK and calcium channel and therefore triggers thrombosis.

Cytochrome P450 eicosanoids in hypertension and renal disease

PURPOSE OF REVIEW

Cytochrome (CYP) P450 metabolites of arachidonic acid, 20-hydroxyeicosatetraenoic acid (20-HETE) and epoxyeicosatrienoic acids (EETs) contribute to the regulation of renal tubular and vascular function. This review highlights the results of the recent genetic studies in humans and rodent models, indicating that these eicosanoids participate in the control of blood pressure (BP), chronic kidney disease (CKD), renal ischemia-reperfusion injury (IRI) and polycystic kidney disease (PKD).

RECENT FINDINGS

Endogenous 20-HETE has been reported to play an essential role in the myogenic and tubuloglomerular feedback responses in the afferent arteriole, and a deficiency of 20-HETE contributes to the development of hypertension and renal injury in Dahl S rats. Mutations in CYP4A11 and CYP4F2 have been linked to elevated BP in humans. EETs have been shown to regulate epithelial sodium channel in the collecting duct, lower BP and have renoprotective properties. 20-HETE also opposes the development of CKD and IRI, and may play a role in PKD.

SUMMARY

These studies indicate that CYP P450 metabolites of arachidonic acid play an important role in the control of BP, CKD, AKI and PKD. Drugs targeting these pathways could be useful in the treatment of IRI and CKD.

Localization and expression profile of Group I and II Activators of G-protein Signaling in the kidney

Activators of G-protein Signaling (AGS) are a family of accessory proteins that were discovered as modulators of heterotrimeric G-protein subunits. The primary aim of the present study was to localize Group I and II AGS proteins and determine the renal expression profile using immunohistochemistry and quantitative RT-PCR, respectively, during normal and injured states of the kidney. Group I AGS1 was found to be predominantly localized to the proximal tubule, Group II AGS3 and AGS5 were exclusively localized to the distal tubular segments, and Group II AGS6 was ubiquitously expressed in every nephron segment of the rodent kidney. In rat kidneys following ischemia-reperfusion injury (IRI), Group I AGS1 mRNA was dramatically increased after 24 h by fivefold (P < 0.05), whereas Group II AGS3 and AGS4 mRNA was significantly decreased at the same time point (P < 0.05). No significant change in the transcript levels were detected at other time points for any of the AGS genes between control and IRI groups. In polycystic diseased kidneys, mRNA levels for AGS3, AGS4 and AGS6 was significantly increased (P < 0.05) by 75-80 % in PCK rat kidneys. The identification of Group I and II AGS mRNA and protein in the kidney may provide insight into the potential mechanism of action during normal and varying states of renal disease or injury.

The molecular mechanisms of a novel multi-kinase inhibitor ZLJ33 in suppressing pancreatic cancer growth

ZLJ33, an oral active multi-kinase inhibitor, was evaluated both in vitro and in vivo against human pancreatic cancer. It could effectively inhibit cell proliferation, induce apoptosis, and cause inhibition of invasion in pancreatic cancer cells. At a dose of 15.0 mg/kg, ZLJ33 induced tumor shrink in Mia-PaCa2, Capan2, and AsPC-1 xenografts models by 60.59%, 74.19%, and 71.54% according to the tumor weight, respectively. The effect of ZLJ33 on pancreatic cancer was mainly mediated by inactivation of p-PDGFRβ, p-c-Raf, and p-RET. Treatment with ZLJ33 did not cause side effect of hematology indexes in the pancreatic cancer xenograft model. ZLJ33 could be a potential therapeutic agent against pancreatic cancer.

G-protein βγ subunit dimers modulate kidney repair after ischemia-reperfusion injury in rats

Heterotrimeric G-proteins play a crucial role in the control of renal epithelial cell function during homeostasis and in response to injury. In this report, G-protein βγ subunit (Gβγ) dimer activity was evaluated during the process of tubular repair after renal ischemia-reperfusion injury (IRI) in male Sprague Dawley rats. Rats were treated with a small molecule inhibitor of Gβγ activity, gallein (30 or 100 mg/kg), 1 hour after reperfusion and every 24 hours for 3 additional days. After IRI, renal dysfunction was prolonged after the high-dose gallein treatment in comparison with vehicle treatment during the 7-day recovery period. Renal tubular repair in the outer medulla 7 days after IRI was significantly (P < 0.001) attenuated after treatment with high-dose gallein (100 mg/kg) in comparison with low-dose gallein (30 mg/kg), or the vehicle and fluorescein control groups. Gallein treatment significantly reduced (P < 0.05) the number of proliferating cell nuclear antigen-positive tubular epithelial cells at 24 hours after the ischemia-reperfusion phase in vivo. In vitro application of gallein on normal rat kidney (NRK-52E) proximal tubule cells significantly reduced (P < 0.05) S-phase cell cycle entry compared with vehicle-treated cells as determined by 5'-bromo-2'-deoxyuridine incorporation. Taken together, these data suggest that Gβγ signaling contributes to the maintenance and repair of renal tubular epithelium and may be a novel therapeutic target for the development of drugs to treat acute kidney injury.

Effects of 5,14-HEDGE, a 20-HETE mimetic, on lipopolysaccharide-induced changes in MyD88/TAK1/IKKβ/IκB-α/NF-κB pathway and circulating miR-150, miR-223, and miR-297 levels in a rat model of septic shock

OBJECTIVES

We have previously demonstrated that a stable synthetic analog of 20-hydroxyeicosatetraenoic acid (20-HETE), N-(20-hydroxyeicosa-5[Z],14[Z]-dienoyl)glycine (5,14-HEDGE), which mimics the effects of endogenously produced 20-HETE, prevents vascular hyporeactivity, hypotension, tachycardia, inflammation, and mortality in a rodent model of septic shock. The present study was performed to determine whether decreased renal and cardiovascular expression and activity of myeloid differentiation factor 88 (MyD88)/transforming growth factor-activated kinase 1 (TAK1)/inhibitor of κB (IκB) kinase β (IKKβ)/IκB-α/nuclear factor-κB (NF-κB) pathway and reduced circulating microRNA (miR)-150, miR-223, and miR-297 expression levels participate in the protective effect of 5,14-HEDGE against hypotension, tachycardia, and inflammation in response to systemic administration of lipopolysaccharide (LPS).

METHODS

Conscious male Wistar rats received saline (4 ml/kg) or LPS (10 mg/kg) at time 0. Blood pressure and heart rate were measured using a tail-cuff device. Separate groups of LPS-treated rats were given 5,14-HEDGE (30 mg/kg) 1 h after injection of saline or LPS. The rats were killed 4 h after LPS challenge and blood, kidney, heart, thoracic aorta, and superior mesenteric artery were collected for measurement of the protein expression.

RESULTS

LPS-induced fall in blood pressure and rise in heart rate were associated with increased MyD88 expression and phosphorylation of TAK1 and IκB-α in cytosolic fractions of the tissues. LPS also caused an increase in both unphosphorylated and phosphorylated NF-κB p65 proteins in the cytosolic and nuclear fractions as well as nuclear translocation of NF-κB p65. In addition, serum miR-150, miR-223, and miR-297 expression levels were increased in LPS-treated rats. These effects of LPS were prevented by 5,14-HEDGE.

CONCLUSIONS

These results suggest that downregulation of MyD88/TAK1/IKKβ/IκB-α/NF-κB pathway as well as decreased circulating miR-150, miR-223, and miR-297 expression levels participate in the protective effect of 5,14-HEDGE against hypotension, tachycardia, and inflammation in the rat model of septic shock.

Role of cytochrome P450-mediated arachidonic acid metabolites in the pathogenesis of cardiac hypertrophy

A plethora of studies have demonstrated the expression of cytochrome P450 (CYP) and soluble epoxide hydrolase (sEH) enzymes in the heart and other cardiovascular tissues. In addition, the expression of these enzymes is altered during several cardiovascular diseases (CVDs), including cardiac hypertrophy (CH). The alteration in CYP and sEH expression results in derailed CYP-mediated arachidonic acid (AA) metabolism. In animal models of CH, it has been reported that there is an increase in 20-hydroxyeicosatetraenoic acid (20-HETE) and a decrease in epoxyeicosatrienoic acids (EETs). Further, inhibiting 20-HETE production by CYP ω-hydroxylase inhibitors and increasing EET stability by sEH inhibitors have been proven to protect against CH as well as other CVDs. Therefore, CYP-mediated AA metabolites 20-HETE and EETs are potential key players in the pathogenesis of CH. Some studies have investigated the molecular mechanisms by which these metabolites mediate their effects on cardiomyocytes and vasculature leading to pathological CH. Activation of several intracellular signaling cascades, such as nuclear factor of activated T cells, nuclear factor kappa B, mitogen-activated protein kinases, Rho-kinases, Gp130/signal transducer and activator of transcription, extracellular matrix degradation, apoptotic cascades, inflammatory cytokines, and oxidative stress, has been linked to the pathogenesis of CH. In this review, we discuss how 20-HETE and EETs can affect these signaling pathways to result in, or protect from, CH, respectively. However, further understanding of these metabolites and their effects on intracellular cascades will be required to assess their potential translation to therapeutic approaches for the prevention and/or treatment of CH and heart failure.

Contribution of iNOS/sGC/PKG pathway, COX-2, CYP4A1, and gp91(phox) to the protective effect of 5,14-HEDGE, a 20-HETE mimetic, against vasodilation, hypotension, tachycardia, and inflammation in a rat model of septic shock

We have previously demonstrated that a stable synthetic analog of 20-hydroxyeicosatetraenoic acid (20-HETE), N-[20-hydroxyeicosa-5(Z),14(Z)-dienoyl]glycine (5,14-HEDGE), prevents vascular hyporeactivity, hypotension, tachycardia, and inflammation in rats treated with lipopolysaccharide (LPS) and mortality in endotoxemic mice. These changes were attributed to decreased production of inducible nitric oxide (NO) synthase (iNOS)-derived NO, cyclooxygenase (COX)-2-derived vasodilator prostanoids, and proinflammatory mediators associated with increased cyctochrome P450 (CYP) 4A1-derived 20-HETE and CYP2C23-dependent antiinflammatory mediator formation. The aim of this study was to determine whether decreased expression and activity of iNOS, soluble guanylyl cyclase (sGC), protein kinase G (PKG), COX-2, gp91(phox) (NOX2; a superoxide generating NOX enzyme), and peroxynitrite production associated with increased expression of COX-1 and CYP4A1 and 20-HETE formation in renal and cardiovascular tissues of rats contributes to the effect of 5,14-HEDGE to prevent vasodilation, hypotension, tachycardia, and inflammation in response to systemic administration of LPS. Mean arterial pressure fell by 28mmHg and heart rate rose by 47beats/min in LPS (10mg/kg, i.p.)-treated rats. Administration of LPS also increased mRNA and protein expression of iNOS and COX-2 associated with a decrease in COX-1 and CYP4A1 mRNA and protein expression. Increased NOS activity, iNOS-heat shock protein 90 complex formation (an index for iNOS activity), protein expression of phosphorylated vasodilator stimulated phosphoprotein (an index for PKG activity), gp91(phox), p47(phox) (NOXO2; organizer subunit of gp91(phox)), and nitrotyrosine (an index for peroxynitrite production) as well as cGMP (an index for sGC activity), 6-keto-PGF1α (a stable metabolite PGI2) and PGE2 levels (indexes for COX activity), and nitrotyrosine levels by LPS were also associated with decreased CYP hydroxylase activity as measured by 20-HETE formation from arachidonic acid in renal microsomes of LPS-treated rats. These effects of LPS, except iNOS mRNA and COX-1 protein expression, were prevented by 5,14-HEDGE (30mg/kg, s.c.; 1h after LPS). A competitive antagonist of vasoconstrictor effects of 20-HETE, 20-hydroxyeicosa-6(Z),15(Z)-dienoic acid (30mg/kg, s.c.; 1h after LPS) reversed the effects of 5,14-HEDGE, except iNOS and COX-1 mRNA and protein expression as well as expression of CYP4A1 mRNA. These results suggest that increased CYP4A1 expression and 20-HETE formation associated with suppression of iNOS/sGC/PKG pathway, COX-2, and gp91(phox) participate in the protective effect of 5,14-HEDGE against vasodilation, hypotension, tachycardia, and inflammation in the rat model of septic shock.

Targeting 20-HETE producing enzymes in cancer - rationale, pharmacology, and clinical potential

Studies demonstrate that lipid mediator 20-Hydroxyeicosatetraenoic acid (20-HETE) synthesis and signaling are associated with the growth of cancer cells in vitro and in vivo. Stable 20-HETE agonists promote the proliferation of cancer cells, whereas selective inhibitors of the 20-HETE-producing enzymes of the Cytochrome (CYP450)4A and CYP4F families can block the proliferation of glioblastoma, prostate, renal cell carcinoma, and breast cancer cell lines. A recent observation that the expression of CYP4A/4F genes was markedly elevated in thyroid, breast, colon, and ovarian cancer further highlights the significance of 20-HETE-producing enzymes in the progression of different types of human cancer. These findings provide the rationale for targeting 20-HETE-producing enzymes in human cancers and set the basis for the development of novel therapeutic strategies for anticancer treatment.

5,14-HEDGE, a 20-HETE mimetic, reverses hypotension and improves survival in a rodent model of septic shock: contribution of soluble epoxide hydrolase, CYP2C23, MEK1/ERK1/2/IKKβ/IκB-α/NF-κB pathway, and proinflammatory cytokine formation

We have previously demonstrated that a stable synthetic analog of 20-HETE, N-[20-hydroxyeicosa-5(Z),14(Z)-dienoyl]glycine (5,14-HEDGE), restores vascular reactivity, blood pressure, and heart rate in endotoxemic rats. The aim of this study was to determine whether decreased renal expression and activity of soluble epoxide hydrolase (sEH), MEK1, ERK1/2, IKKβ, IκB-α, and NF-κB as well as systemic and renal proinflammatory cytokine production associated with increased expression and activity of CYP2C23 contributes to the effect of 5,14-HEDGE to prevent hypotension, tachycardia, inflammation, and mortality in response to systemic administration of lipopolysaccharide (LPS). Blood pressure fell by 33 mmHg and heart rate rose by 57 beats/min in LPS (10 mg/kg, i.p.)-treated rats. Administration of LPS also increased mRNA and protein expression of sEH associated with a decrease in CYP2C23 mRNA and protein expression. Increased activity of sEH and p-MEK1, p-ERK1/2, p-IκB-α, NF-κB, and p-NF-κB protein levels as well as TNF-α and IL-8 production by LPS were also associated with a decreased activity of AA epoxygenases. These effects of LPS were prevented by 5,14-HEDGE (30 mg/kg, s.c.; 1 h after LPS). Treatment of endotoxemic mice with 5,14-HEDGE also raised the survival rate of animals from 84% to 98%. A competitive antagonist of vasoconstrictor effects of 20-HETE, 20-hydroxyeicosa-6(Z),15(Z)-dienoic acid, 20-HEDE (30 mg/kg, s.c.; 1 h after LPS) prevented the effects of 5,14-HEDGE on blood pressure, heart rate, expression and/or activity of sEH, CYP2C23, and ERK1/2 as well as TNF-α and IL-8 levels in rats treated with LPS. These results suggest that decreased expression and/or activity of sEH and MEK1/ERK1/2/IKKβ/IκB-α/NF-κB pathway as well as proinflammatory cytokine production associated with increased CYP2C23 expression and antiinflammatory mediator formation participate in the protective effect of 5,14-HEDGE against hypotension, tachycardia, inflammation, and mortality in the rodent model of septic shock.

Thrombin-induced NF-κB activation and IL-8/CXCL8 release is mediated by c-Src-dependent Shc, Raf-1, and ERK pathways in lung epithelial cells

In addition to its functions in thrombosis and hemostasis, thrombin also plays an important role in lung inflammation. Our previous report showed that thrombin activates the protein kinase C (PKC)α/c-Src and Gβγ/Rac1/PI3K/Akt signaling pathways to induce IκB kinase α/β (IKKα/β) activation, NF-κB transactivation, and IL-8/CXCL8 expressions in human lung epithelial cells (ECs). In this study, we further investigated the mechanism of c-Src-dependent Shc, Raf-1, and extracellular signal-regulated kinase (ERK) signaling pathways involved in thrombin-induced NF-κB activation and IL-8/CXCL8 release. Thrombin-induced increases in IL-8/CXCL8 release and κB-luciferase activity were inhibited by the Shc small interfering RNA (siRNA), p66Shc siRNA, GW 5074 (a Raf-1 inhibitor), and PD98059 (a mitogen-activated protein kinase (MAPK) kinase (MEK) inhibitor). Treatment of A549 cells with thrombin increased p66Shc and p46/p52Shc phosphorylation at Tyr239/240 and Tyr317, which was inhibited by cell transfection with the dominant negative mutant of c-Src (c-Src DN). Thrombin caused time-dependent phosphorylation of Raf-1 and ERK, which was attenuated by the c-Src DN. Thrombin-induced IKKα/β phosphorylation was inhibited by GW 5074 and PD98059. Treatment of cells with thrombin induced Gβγ, c-Src, and p66Shc complex formation in a time-dependent manner. Taken together, these results show for the first time that thrombin activates Shc, Raf-1, and ERK through Gβγ, c-Src, and Shc complex formation to induce IKKα/β phosphorylation, NF-κB activation, and IL-8/CXCL8 release in human lung ECs.

A molecular case report: functional assay of tyrosine kinase inhibitors in cells from a patient's primary renal cell carcinoma

Current therapies for Renal Cell Carcinoma favor vascular endothelial growth factor receptor (VEGF-R) tyrosine kinase (TK) inhibitors (TKIs). In theory, these are most applicable in tumors that have lost VHL-with subsequent stabilization of HIF and upregulation of VEGF. A subset of patients harbor primary-refractory disease, as in this case, where there was no evidence for loss of VHL or chromosome 3p. We evaluated molecular targeted agents in viable tumor cells cultured from a patient's clear cell renal cell carcinoma (RCC). Of 66 agents, only dasatinib, an inhibitor of Src tyrosine kinase, strongly reduced viability of the patient's cultured kidney tumor cells. Immunostaining of the original primary tumor revealed strong positivity for VHL and Src protein expression. Functional evaluation of a patient's tumor cells appears feasible in the setting of RCC.

NS-398 reverses hypotension in endotoxemic rats: contribution of eicosanoids, NO, and peroxynitrite

We have previously demonstrated that inhibition of vasodilator prostanoids, PGI2 and PGE2, and nitric oxide (NO) synthesis by a selective cyclooxygenase-2 (COX-2) inhibitor, NS-398, restores blood pressure as a result of increased systemic and renal levels of 20-hydroxyeicosatetraenoic acid (20-HETE) in endotoxemic rats. The aim of this study was to further investigate the effects of NS-398 on the changes in expression and/or activity of COX-2, cytochrome P450 4A1 (CYP4A1), inducible NO synthase (iNOS), and peroxynitrite formation in serum, renal, cardiac, and/or vascular tissues of lipopolysaccharide (LPS)-treated rats. LPS (10mg/kg, i.p.)-induced decrease in blood pressure was associated with increased protein levels of COX-2, iNOS, and nitrotyrosine in kidney, heart, thoracic aorta, and superior mesenteric artery. The activities of COX-2 and iNOS as well as levels of PGI2, PGE2, and nitrotyrosine were also increased in the systemic circulation and renal, cardiac, and vascular tissues of LPS-treated rats. In contrast, renal, cardiac, and vascular CYP4A1 protein expression as well as systemic and tissue levels of 20-HETE were decreased in endotoxemic rats. These effects of LPS, except COX-2 protein expression, were prevented by NS-398 (10 mg/kg, i.p.), given 1h after injection of LPS. These data suggest that COX-2-derived vasodilator prostanoids, PGI2 and PGE2, produced during endotoxemia increase iNOS protein expression and activity as well as peroxynitrite formation resulting in decreased CYP4A1 protein expression and 20-HETE synthesis. Taken together, we concluded that an increase in 20-HETE levels associated with a decrease in the production of vasodilator prostanoids and NO participates in the effect of NS-398 to prevent hypotension in the rat model of septic shock.

20-HETE-producing enzymes are up-regulated in human cancers

BACKGROUND

20-Hydroxyeicosatetraenoic acid (20-HETE), a metabolite of arachidonic acid (AA) produced by the CYP4A and CYP4F enzyme families has been reported to induce mitogenic and angiogenic responses both in vitro and in vivo, and inhibitors of this pathway reduced growth of brain and kidney tumors.

MATERIALS AND METHODS

Real-Time PCR, western blot and immunohistochemistry were used to compare the expression of CYP4A/F mRNA and protein levels in human cancer tissue samples versus normal controls. Liquid chromatography/mass spectrometry analysis (LC-MS/MS) was performed to measure 20-HETE formation in tumor homogenates. Activation of Ras in human proximal tubule epithelial cells (HRPTEC) treated with stable agonist of 20-HETE was measured using a Ras pull-down detection kit.

RESULTS

The expression of CYP4A/4F genes was markedly elevated in thyroid, breast, colon, and ovarian cancer samples in comparison to matched normal tissues. Furthermore, the levels of the CYP4F2 protein and of 20-HETE were higher in ovarian cancer samples compared to normal control tissues. A stable 20-HETE agonist induced activation of the small-GTPase Ras in HRPTEC cells.

CONCLUSION

The present finding of elevated expression of CYP4A/F enzymes in human cancer tissue suggests that 20-HETE inhibitors and antagonists may be useful in the treatment of cancer.

Attenuation of neonatal ischemic brain damage using a 20-HETE synthesis inhibitor

20-Hydroxyeicosatetraenoic acid (20-HETE) is a cytochrome P450 metabolite of arachidonic acid that that contributes to infarct size following focal cerebral ischemia. However, little is known about the role of 20-HETE in global cerebral ischemia or neonatal hypoxia-ischemia (H-I). The present study examined the effects of blockade of the synthesis of 20-HETE with N-hydroxy-N'-(4-n-butyl-2-methylphenyl) formamidine (HET0016) in neonatal piglets after H-I to determine if it protects highly vulnerable striatal neurons. Administration of HET0016 after H-I improved early neurological recovery and protected neurons in putamen after 4 days of recovery. HET0016 had no significant effect on cerebral blood flow. cytochrome P450 4A immunoreactivity was detected in putamen neurons, and direct infusion of 20-HETE in the putamen increased phosphorylation of Na(+), K(+) -ATPase and NMDA receptor NR1 subunit selectively at protein kinase C-sensitive sites but not at protein kinase A-sensitive sites. HET0016 selectively inhibited the H-I induced phosphorylation at these same sites at 3 h of recovery and improved Na(+), K(+) -ATPase activity. At 3 h, HET0016 also suppressed H-I induced extracellular signal-regulated kinase 1/2 activation and protein markers of nitrosative and oxidative stress. Thus, 20-HETE can exert direct effects on key proteins involved in neuronal excitotoxicity in vivo and contributes to neurodegeneration after global cerebral ischemia in immature brain.

20-HETE in neovascularization

Cytochrome P450 4A/F (CYP4A/F) converts arachidonic acid (AA) to 20-HETE by ω-hydroxylation. The contribution of 20-HETE to the regulation of myogenic response, blood pressure, and mitogenic actions has been well summarized. This review focuses on the emerging role of 20-HETE in physiological and pathological vascularization. 20-HETE has been shown to regulate vascular smooth muscle cells (VSMC) and endothelial cells (EC) by affecting their proliferation, migration, survival, and tube formation. Furthermore, the proliferation, migration, secretion of proangiogenic molecules (such as HIF-1α, VEGF, SDF-1α), and tube formation of endothelial progenitor cells (EPC) are stimulated by 20-HETE. These effects are mediated through c-Src- and EGFR-mediated downstream signaling pathways, including MAPK and PI3K/Akt pathways, eNOS uncoupling, and NOX/ROS system activation. Therefore, the CYP4A/F-20-HETE system may be a therapeutic target for the treatment of abnormal angiogenic diseases.

Cytochrome P450 1B1 contributes to renal dysfunction and damage caused by angiotensin II in mice

Cytochrome P450 1B1 contributes to the development of angiotensin II-induced hypertension and associated cardiovascular pathophysiology. In view of the critical role of angiotensin II in the kidney, as well as in salt and water homeostasis, and blood pressure regulation, we determined the contribution of cytochrome P450 1B1 to renal dysfunction and injury associated with angiotensin II-induced hypertension in male Cyp1b1(+/+) and Cyp1b1(-/-) mice. Angiotensin II infusion (700 ng/kg per minute) given by miniosmotic pumps for 13 and 28 days increased systolic blood pressure in Cyp1b1(+/+) mice; this increase was significantly reduced in Cyp1b1(-/-) mice. Angiotensin II increased renal Cyp1b1 activity, vascular resistance, and reactivity to vasoconstrictor agents and caused endothelial dysfunction in Cyp1b1(+/+) but not Cyp1b1(-/-) mice. Angiotensin II increased water consumption and urine output, decreased urine osmolality, increased urinary Na(+) and K(+) excretion, and caused proteinuria and albuminuria in Cyp1b1(+/+) mice that was diminished in Cyp1b1(-/-) mice. Infusion of angiotensin II for 28 but not 13 days caused renal fibrosis, tubular damage, and inflammation in Cyp1b1(+/+) mice, which was minimized in Cyp1b1(-/-) mice. Angiotensin II increased levels of 12- and 20-hydroxyeicosatetraenoic acids; reactive oxygen species; and activity of NADPH oxidase, extracellular signal-regulated kinase 1/2, p38 mitogen-activated protein kinase, and c-Src in the kidneys of Cyp1b1(+/+) but not Cyp1b1(-/-) mice. These data suggest that increased thirst, renal dysfunction, and injury and inflammation associated with angiotensin II-induced hypertension in mice depend on cytochrome P450 1B1 activity, thus indicating that cytochrome P450 1B1 could serve as a novel target for treating renal disease and hypertension.

20-HETE in acute kidney injury

Ischemia/reperfusion injury (IRI) is a common cause of acute kidney injury (AKI) that is associated with a patient mortality of up to 50%. Currently there are not effective pharmacologic therapies for AKI. This Commentary highlights recent evidence indicating that 20-HETE plays an important role in IRI and that drugs that target this pathway have potential as therapeutic agents for AKI.