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Obesity represents a low‐grade chronic inflammation status, which is associated with compromised adaptive thermogenesis. However, the mechanisms underlying the defective activation of thermogenesis in chronic inflammation remain unclear. Here, a chronic inflammatory model is first estabolished by injecting mice with low‐dose lipopolysaccharide (LPS) before cold exposure, and then it is verified that LPS treatment can decrease the core body temperature of mice and alter the microbial distribution in epididymal white adipose tissue (eWAT). An adipose tissue‐resident bacterium Sphingomonas paucimobilis is identified as a potential inhibitor on the activation of brown fat and browning of inguinal WAT, resulting in defective adaptive thermogenesis. Mechanically, LPS and S. paucimobilis inhibit the production and release of 15‐HETE by suppressing its main metabolic enzyme 12 lipoxygenase (12‐LOX) and 15‐ Hydroxyeicosatetraenoic acid (15‐HETE) rescues the impaired thermogenesis. Interestingly, 15‐HETE directly binds to AMP‐activated protein kinase α (AMPKα) and elevates the phosphorylation of AMPK, leading to the activation of uncoupling protein 1 (UCP1) and mitochondrial oxidative phosphorylation (OXPHOS) complexes. Further analysis with human obesity subjects reveals that individuals with high body mass index displayed lower 15‐HETE levels. Taken together, this work improves the understanding of how chronic inflammation impairs adaptive thermogenesis and provides novel targets for alleviating obesity. [ABSTRACT FROM AUTHOR]

Hydroperoxyeicosatetraenoic acids (HETEs) are metabolites of arachidonic acid that are oxidized by a family of enzymes including cyclooxygenase, lipoxygenase, and cytochrome P450 enzymes. These enzymes are widely present in various organs and tissues, and the HETEs they synthesize perform an important function in the regulation of immune reactions and haemostasis processes under physiological and pathophysiological conditions. More researchers confirm the role of these oxidized metabolites in modulating inflammation in asthma. The high production of HETEs in allergic and severe asthma indicates their involvement in the processes of an acute inflammatory response. On the other hand, disturbance of the metabolic transformation of arachidonic acid contributes to the development of chronic inflammation due to insufficient synthesis of mediators that resolve inflammatory processes. Several HETEs have both pro-inflammatory and anti-inflammatory effects, which underscores the ongoing interest in their involvement in the pathogenesis of asthma. At the same time, research results are scarce. Based on an analysis of the literature, the pathways of metabolic transformation of 5-HETE, 12-HETE, and 15-HETE with the participation of cyclooxygenases, lipoxygenases, and cytochrome P-450, as well as their role in asthma pathogenesis, were discussed. The PubMed database was searched for information covering the last five years using selected inclusion criteria. Information queries included the following set of keywords: "bronchial asthma, hydroxyeicosatetraenoic acids, 5-HETE, 12-HETE, 15-HETE." Literature data indicate that the role of HETEs in human physiology and pathology, including the modulation of inflammation in asthma, requires comprehensive study to selectively modulate the enzymatic pathways of arachidonic acid metabolism leading to the production of these mediators. [ABSTRACT FROM AUTHOR]

BACKGROUND: Aspirin-exacerbated respiratory disease (AERD) is associated with high levels of cysteinyl leukotrienes, prostaglandin D2, and low levels of prostaglandin E2. Further, 15-hydroxyeicosatetraenoic acid (15-HETE) levels may have predictive value in therapeutic outcomes of aspirin desensitization. Accumulation of nasal group 2 innate lymphoid cells (ILC2s) has been demonstrated during COX-1 inhibition in AERD, although the relationships between tissue ILC2 accumulation, reaction symptom severity, and novel lipid biomarkers are unknown. OBJECTIVE: We sought to determine whether novel lipid mediators are predictive of nasal ILC2 accumulation and symptom scores during COX-1 inhibitor challenge in patients with AERD. METHODS: Blood and nasal scraping samples from patients with AERD were collected at baseline and COX-1 inhibitor reaction and then processed for flow cytometry for nasal ILC2s and serum for lipidomic analysis. RESULTS: Eight patients with AERD who were undergoing aspirin desensitization were recruited. Of the 161 eicosanoids tested, 42 serum mediators were detected. Baseline levels of 15-HETE were negatively correlated with the change in numbers of airway ILC2s (r = -0.6667; P = .0428). Docosahexaenoic acid epoxygenase metabolite 19,20-dihydroxy-4Z,7Z,10Z,13Z,16Z-docosapentaenoic acid (19,20-diHDPA) was positively correlated with both changes in airway ILC2s (r = 0.7143; P = .0305) and clinical symptom scores (r = 0.5000; P = .0081). CONCLUSION: Low levels of baseline 15-HETE predicted a greater accumulation of airway ILC2s in patients with AERD who were receiving COX-1 inhibition. Further, increases in the cytochrome P pathway metabolite 19,20-dihydroxy-4Z,7Z,10Z,13Z,16Z-docosapentaenoic acid (19,20-diHDPA) were associated with increased symptoms and nasal ILC2 accumulation. Future studies to assess how these mediators might control ILC2s may improve the understanding of AERD pathogenesis.

Glutathione (GSH) and cysteine are important antioxidants in maintaining the oxidation-reduction balance. 14,15-epoxyeicosatrienoic acid (14,15-EET) and 15-hydroxyeicosatetraenoic acid (15-HETE) are biological active compounds metabolized from arachidonic acid. To dynamically monitor GSH, cysteine, 14,15-EET, and 15-HETE, an ultra-high-performance liquid chromatography-mass spectrometry (UPLC-MS/MS) method was developed. The derivative GSH, cysteine, and underivatized 14,15-EET, 15-HETE were determined by electrospray ionization source with multiple reaction monitoring. The developed method was well validated and applied to monitor the extracellular concentration of GSH, cysteine, 14,15-EET, and 15-HETE in paraquat (PQ) poisoning LO2 cells. It was shown that the derivation of GSH and cysteine is complete and specific. There was a good linear relationship among GSH, cysteine, 14,15-EET, and 15-HETE. The relative standard deviations of precision and accuracy were all within 15%. After PQ poisoning, the extracellular concentrations of GSH and cysteine were increased at 72 h. 14,15-EET and 15-HETE started to increase at 24 h, earlier than GSH and cysteine. Irreversible pathological alterations appeared at 48 h. In conclusion, a fast and specific UPLC-MS/MS method for the determination of GSH, cysteine, 14,15-EET, and 15-HETE has been developed and validated. PQ induced the increase of 14,15-EET and 15-HETE earlier than that of GSH and cysteine in LO2 cells culture medium. [ABSTRACT FROM AUTHOR]

Background: This project aimed to investigate the role of two arachidonic acid metabolites (14,15-epoxyeicosatrienoic acid (14,15-EET) and 15-hydroxyeicosateraenoic acid (15-HETE)) as a precursor of hypertensive disorders in pregnancy by comparing their serum levels between third-trimester hypertensive and normal pregnant women. The relationship between their differential levels and pregnancy outcomes was investigated to clarify the role of arachidonic acid metabolites in the occurrence and development of hypertensive disorders during pregnancy. Methods: This is a prospective cohort study and a total of 88 patients were included in the study. 17 of them were recognized as the gestational hypertension and 25 of them were considered to be the preeclampsia. 24 women were diagnosed with severe preeclampsia. The control group consisted of 22 healthy patients pregnancy course, with no disease at the present and in the history. For this purpose, the serum levels of 14,15-EET and 15-HETE of gestational hypertension, preeclampsia (PE) and normal pregnant women group were detected by enzyme-linked immunosorbent assay (ELISA) during the third trimester of pregnancy. It was followed by detecting placental cytochrome P450 2J2 (CYP2J2) and 15-lipoxygenase-2 (15-LOX-2) expression and localization using immunohistochemistry, their corresponding proteins employing western blotting. All outcomes of maternal pregnancy were then statistically analyzed. Results: The analysis indicated that the levels of 14,15-EET, and 15-HETE were significantly higher (p < 0.05) in gestational hypertension compared to control, where the same differences were observed when severe preeclampsia and preeclampsia groups were compared, which were altogether higher than gestational hypertension group patients. Similarly, the 14,15-EET and 15-HETE levels were significantly (p < 0.05) higher in the adverse pregnancy outcome than in the normal pregnancy outcome group in severe preeclampsia. The immunohistochemical analysis results revealed that the positive staining for CYP2J2 and 15-LOX-2 expression in the placenta of the preeclampsia group was significant (p < 0.05) compared to the normal pregnant control and gestational hypertension groups, with significantly higher (p < 0.05) relative CYP2J2 and 15-LOX-2 protein levels in preeclampsia compared to normal control pregnancy group. Conclusions: The study concluded that the 14,15-EET and 15-HETE might be involved in gestational hypertension pathophysiology and preeclampsia, associated with disease severity and adverse pregnancy outcomes. Moreover, CYP2J2 and 15-LOX-2 signaling expression in the placenta may be related to arachidonic acid metabolites generated in preeclampsia.

Ischemic strokes are caused by one or more blood clots that typically obstruct one of the major arteries in the brain, but frequently also result in leakage of the blood-brain barrier and subsequent hemorrhage. While it has long been known that the enzyme 12/15-lipoxygenase (12/15-LOX) is up-regulated following ischemic strokes and contributes to neuronal cell death, recent research has shown an additional major role for 12/15-LOX in causing this hemorrhagic transformation. These findings have important implications for the use of 12/15-LOX inhibitors in the treatment of stroke.

As a lipoxygenase (LOX), arachidonate 15-lipoxygenase type B (ALOX15B) peroxidizes polyenoic fatty acids (PUFAs) including arachidonic acid (AA), eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), and linoleic acid (LA) to their corresponding fatty acid hydroperoxides. Distinctive to ALOX15B, fatty acid oxygenation occurs with positional specificity, catalyzed by the nonheme iron containing active site, and in addition to free PUFAs, membraneesterified fatty acids serve as substrates for ALOX15B. Like other LOX enzymes, ALOX15B is linked to the formation of specialized pro-resolving lipid mediators (SPMs), and altered expression is apparent in various inflammatory diseases such as asthma, psoriasis, and atherosclerosis. In primary human macrophages, ALOX15B expression is associated with cellular cholesterol homeostasis and is induced by hypoxia. Like in inflammation, the role of ALOX15B in cancer is inconclusive. In prostate and breast carcinomas, ALOX15B is attributed a tumorsuppressive role, whereas in colorectal cancer, ALOX15B expression is associated with a poorer prognosis. As the biological function of ALOX15B remains an open question, this review aims to provide a comprehensive overview of the current state of research related to ALOX15B. [ABSTRACT FROM AUTHOR]

As a lipoxygenase (LOX), arachidonate 15-lipoxygenase type B (ALOX15B) peroxidizes polyenoic fatty acids (PUFAs) including arachidonic acid (AA), eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), and linoleic acid (LA) to their corresponding fatty acid hydroperoxides. Distinctive to ALOX15B, fatty acid oxygenation occurs with positional specificity, catalyzed by the non-heme iron containing active site, and in addition to free PUFAs, membrane-esterified fatty acids serve as substrates for ALOX15B. Like other LOX enzymes, ALOX15B is linked to the formation of specialized pro-resolving lipid mediators (SPMs), and altered expression is apparent in various inflammatory diseases such as asthma, psoriasis, and atherosclerosis. In primary human macrophages, ALOX15B expression is associated with cellular cholesterol homeostasis and is induced by hypoxia. Like in inflammation, the role of ALOX15B in cancer is inconclusive. In prostate and breast carcinomas, ALOX15B is attributed a tumor-suppressive role, whereas in colorectal cancer, ALOX15B expression is associated with a poorer prognosis. As the biological function of ALOX15B remains an open question, this review aims to provide a comprehensive overview of the current state of research related to ALOX15B.

Recently, an increase in the incidence of inflammatory bowel disease (IBD) has been observed, especially among children and adolescents. Currently, few studies focus on the differentiation of inflammation in IBD subunits, i.e., Crohn's Disease (CD) and Ulcerative Colitis (UC). The aim of this study was to compare the concentrations of proinflammatory mediators of arachidonic acid (ARA) and linoleic acid (LA) in patients with CD (n = 34) and UC (n = 30), in order to identify differences in inflammation in both diseases and within the same entity, according to disease activity. Sixty-four adolescents with a mean age of 13.76 ± 2.69 and 14.15 ± 3.31, for CD and UC, respectively, were enrolled in the study. Biochemical analysis of ARA and LA derivatives was performed using a liquid chromatography. A trend was observed in the concentration of 15S-HETE (hydroxyeicosatetraenoic acids) in CD relative to UC. The active phase of both diseases showed a higher 15S-HETE concentration in active CD relative to active UC. Comparing patients with CD with active and inactive disease showed a trend of increased levels of thromboxane B2, leukotriene B4 and 9S-HODE (hydroxyoctadecadienoic acid) in the active versus the inactive disease. We also observed statistically significantly higher levels of 12S-HETE in inactive CD relative to active CD. In the UC group, on the other hand, statistically significantly higher levels of prostaglandin E2 and 16RS-HETE were observed in active UC relative to inactive UC. Moreover, significantly higher concentrations of LTX A4 5S, 6R were observed in inactive UC relative to the active phase. In conclusion, the present study indicated the activity of the 15-LOX pathway in CD. Further studies involving lipid mediators in patients with IBD may contribute to the development of new therapies for the treatment of IBD. The identification of differences in the course of inflammation may help to target therapy in CD and UC, and perhaps allow the introduction of an additional diagnostic marker between the two main IBD subtypes. [ABSTRACT FROM AUTHOR]

Abstract Background Platelet activation is an important side effect of dialysis, resulted in a subsequent release of arachidonic acid (AA) from activated platelets. AA is involved in many pathologic conditions, such as inflammation, asthma, cancer, diabetes, hypertension, and the pathogenesis of kidney disease. The aim of this study was to define whether the dialysis type affects the concentration of AA derivatives in patients with chronic kidney disease. Methods 117 patients were qualified to the study group. Based on the type of renal replacement therapy, patients were divided into the following groups: hemodialysis (HD A – before/HD B - after hemodialysis), peritoneal dialysis (PD), kidney transplant patients (TE - before/TE A – after transplantation) and conservative treatment (CT) (30; 30; 27; 30 patients, respectively). The control group consisted of 30 healthy volunteers (NK). The ELISA methods were used to measure the concentrations of TXB2, 5-HETE, 12-HETE, and 15-HETE in the blood serum. Results Renal replacement therapy significantly influences the concentration of TXB2 (mean ± SD [ng/mL]: HD A- 34.6 ± 9; HD B- 28.3 ± 15.2; PD- 28.3 ± 15.2; CT- 34.2 ± 8.0; TE- 36.7 ± 42.9; TE A- 27.9 ± 8.8; NK– 19.6 ± 15; p = 0.010), 5-HETE (mean ± SD [ng/mL]: HD A- 284.2 ± 428.4; HD B- 304.8 ± 516.2; PD – 530.0 ± 553.3; CT- 318.7 ± 366.0; TE- 525.6 ± 358.0; TE A – 409.8 ± 377.1; NK 838.1 ± 497.8; p

Background: Dysregulation of eicosanoids is associated with asthma and a composite of oxylipins, including exhaled leukotriene B4 (LTB4), characterizes childhood asthma. While fractional exhaled nitric oxide (FeNO) has been used as the standard for monitoring steroid responsiveness, the potential utility of eicosanoids in monitoring the therapeutic outcomes remains unclear. We aimed to examine the levels of major eicosanoids representing different metabolic pathways in exhaled breath condensates (EBCs) of children with asthma during exacerbation and after treatment. Methods: Levels of 6 exhaled eicosanoid species in asthmatic children and healthy subjects were evaluated using ELISA. Results: In addition to those previously reported, including LTB4, the levels of exhaled 15‐hydroxyeicosatetraenoic acid (15‐HETE), but not thromboxane B2 (TXB2), showed significant difference between asthmatics (N = 318) and healthy controls (N = 97), particularly the severe group showed the lowest levels of exhaled 15‐HETE. Receiver operating characteristic (ROC) curve analyses revealed similar distinguishing power for the levels of 15‐HETE, FEV1 (forced expiratory volume in the first second), and FeNO, while the 15‐HETE/LTB4 ratio was significantly lower in subjects with asthma as compared to that of healthy controls (p < 0.0001). Analysis of asthmatics (N = 75) during exacerbation and convalescence showed significant improvement in lung function (FEV1, p <.001), but not FeNO, concomitant with significantly increased levels of 15‐HETE (p <.001) and reduced levels of TXB2 (p <.05) at convalescence, particularly for those who at the top 30% level during exacerbation. Further, decreased LTB4 and lipoxin A4 (LXA4) at convalescence were noted only in those at the top 30 percentile during exacerbation. Conclusion: The exhaled 15‐HETE was found to discriminate childhood asthma while decreased levels of exhaled TXB2 and increased levels of 15‐HETE were prominent at convalescence. [ABSTRACT FROM AUTHOR]

Prostanoids and PGE2 in particular have been long viewed as one of the major mediators of inflammation in arthritis. However, experimental data indicate that PGE2 can serve both pro- and anti-inflammatory functions. We have previously shown (Kojima et al., J. Immunol. 180 (2008) 8361-8368) that microsomal prostaglandin E synthase-1 (mPGES-1) deletion, which regulates PGE2 production, resulted in the suppression of collagen-induced arthritis (CIA) in mice. This suppression was attributable, at least in part, to the impaired generation of type II collagen autoantibodies. In order to examine the function of mPGES-1 and PGE2 in a non-autoimmune form of arthritis, we used the collagen antibody-induced arthritis (CAIA) model in mice deficient in mPGES-1, thereby bypassing the engagement of the adaptive immune response in arthritis development. Here we report that mPGES-1 deletion significantly increased CAIA disease severity. The latter was associated with a significant (~3.6) upregulation of neutrophil, but not macrophage, recruitment to the inflamed joints. The lipidomic analysis of the arthritic mouse paws by quantitative liquid chromatography/tandem mass-spectrometry (LC/MS/MS) revealed a dramatic (~59-fold) reduction of PGE2 at the peak of arthritis. Altogether, this study highlights mPGES-1 and its product PGE2 as important negative regulators of neutrophil-mediated inflammation and suggests that specific mPGES-1 inhibitors may have differential effects on different types of inflammation. Furthermore, neutrophil-mediated diseases could be exacerbated by inhibition of mPGES-1.

The goal of this study was to elucidate the mechanisms of protection of Sodium (±)-5-bromo-2-(α-hydroxypentyl) benzoate (trade name: Brozopine, BZP) against cerebral ischemia in vivo and in vitro. To explore the protective effect of BZP on focal cerebral ischemia-reperfusion injury, we evaluated the effects of various doses of BZP on neurobehavioral score, cerebral infarction volume, cerebral swelling in MCAO rats (ischemia for 2 h, reperfusion for 24 h). In addition, the effects of various doses of BZP on OGD/R-induced-PC12 cells injury (hypoglycemic medium containing 30 mmol Na2S2O4 for 2 h, reoxygenation for 24 h) were evaluated. Four in vivo and in vitro groups were evaluated to characterize targets of BZP: Control group, Model group, BZP group (10 mg/kg)/BZP group (30 μmol/L), C8E4 group (10 mg/kg)/C8E4 group (30 μmol/L). An ELISA kit was used to determine the levels of 15-HETE (a 15-LOX-2 metabolite) in vivo and in vitro. Rat nuclear factor κB subunit p65 (NF-κB p65), tumor necrosis factor (TNF-α), interleukin-6 (IL-6), and intercellular adhesion molecule-1 (ICAM-1) were also quantified in vivo and in vitro. The results showed that BZP improved focal cerebral ischemia-reperfusion injury in rats and PC12 cells treated with Na2S2O4 in dose/concentration-dependent manners through inhibition of production of 15-HETE and expression of NF-κB, IL-6, TNF-α, and ICAM-1. In conclusion, BZP exerted protective effects against cerebral ischemia via inhibition of 15-LOX-2 activity.

The goal of this study was to elucidate the mechanisms of protection of Sodium (±)-5-bromo-2-(α-hydroxypentyl) benzoate (trade name: Brozopine, BZP) against cerebral ischemia in vivo and in vitro. To explore the protective effect of BZP on focal cerebral ischemia-reperfusion injury, we evaluated the effects of various doses of BZP on neurobehavioral score, cerebral infarction volume, cerebral swelling in MCAO rats (ischemia for 2 h, reperfusion for 24 h). In addition, the effects of various doses of BZP on OGD/R-induced-PC12 cells injury (hypoglycemic medium containing 30 mmol Na2S2O4 for 2 h, reoxygenation for 24 h) were evaluated. Four in vivo and in vitro groups were evaluated to characterize targets of BZP: Control group, Model group, BZP group (10 mg/kg)/BZP group (30 μmol/L), C8E4 group (10 mg/kg)/C8E4 group (30 μmol/L). An ELISA kit was used to determine the levels of 15-HETE (a 15-LOX-2 metabolite) in vivo and in vitro. Rat nuclear factor κB subunit p65 (NF-κB p65), tumor necrosis factor (TNF-α), interleukin-6 (IL-6), and intercellular adhesion molecule-1 (ICAM-1) were also quantified in vivo and in vitro. The results showed that BZP improved focal cerebral ischemia-reperfusion injury in rats and PC12 cells treated with Na2S2O4 in dose/concentration-dependent manners through inhibition of production of 15-HETE and expression of NF-κB, IL-6, TNF-α, and ICAM-1. In conclusion, BZP exerted protective effects against cerebral ischemia via inhibition of 15-LOX-2 activity. [ABSTRACT FROM AUTHOR]

[Display omitted] • GPR39 is an orphan GPCR of class A (rhodopsin family) that engages with G q , G s , G 12/13 , Gi, and β-arrestin. • GPR39 has constitutive activity. • Zn2+ ions and/or eicosanoids (15-HETE and 14,15-EET) are candidate endogenous ligands. • TC-G 1008 is the most widely used small-molecule agonist, which has off-site targets. • Inverse agonists need to be examined in addition to agonists in future drug development. Progress in the understanding of the receptor GPR39 is held up by inconsistent pharmacological data. First, the endogenous ligand(s) remain(s) contentious. Data pointing to zinc ions (Zn2+) and/or eicosanoids as endogenous ligands are a matter of debate. Second, there are uncertainties in the specificity of the widely used synthetic ligand (agonist) TC-G 1008. Third, activation of GPR39 has been often proposed as a novel treatment strategy, but new data also support that inhibition might be beneficial in certain disease contexts. Constitutive activity/promiscuous signaling suggests the need for antagonists/inverse agonists in addition to (biased) agonists. Here, we scrutinize data on the signaling and functions of GPR39 and critically assess factors that might have contributed to divergent outcomes and interpretations of investigations on this important receptor. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Hypoxia upregulates SIRT1 expression levels in PASM cells. • 15-HETE promotes SIRT1 expression levels in PASM cells. • SIRT1 mediates 15-HETE-induced PASM cells proliferation. • Exogenous 15-HETE induces SIRT1-dependent apoptosis in PASM cells. Abstract 15-Hydroxyeicosatetraenoic acid (15-HETE) is produced by the catalytic metabolism of arachidonic acid by the enzyme 15-lipoxygenase. It is produced during hypoxia, and participates in the remodeling of pulmonary artery smooth muscle (PASM). Previous research has revealed that sirtuin 1 (SIRT1) involved in apoptosis in various cells and tissues. Herein, we attempted to determine whether 15-HETE counteracts SIRT1-promoted cell death in murine PASM cells (PASMCs). To verify this theory, we investigated changes in SIRT1 concentration in response to the counteraction of cell death by 15-HETE. We used western blotting and a terminal deoxynucleotidyl transferase (TdT) dUTP nick-end labeling (TUNEL) assay, and investigated the survival, nuclear morphology, and mitochondrial potential of the cells. Our results revealed that 15-HETE promotes the transcription and translation of SIRT1. Moreover, 15-HETE increases viability and impaired mitochondrial depolarization, and promotes the expression of Bcl-2 and Bcl-xL in PASMCs without serum. The reactions mentioned above were eliminated by SIRT1 inhibitors (EX 527 and SIRT1 inhibitor IV). Our findings suggest that 15-HETE is crucial for the protection of PASMCs against cell death, and the SIRT1 pathway may provide a new strategy for pulmonary artery hypertension therapy. [ABSTRACT FROM AUTHOR]

Matrix metalloproteinase-2 (MMP-2) and matrix metalloproteinase-9 (MMP-9) are the predominant gelatinases in the developing lung. Studies have shown that the expression of MMP-2 and MMP-9 is upregulated in hypoxic fibroblasts, 15-hydroxyeicosatetraenoic acid (15-HETE) regulated fibroblasts migration via modulating MMP-2 or MMP-9, and that hypoxia/15-HETE is a predominant contributor to the development of pulmonary arterial hypertension (PAH) through increased angiogenesis. However, the roles of MMP-2 and MMP-9 in pulmonary arterial endothelial cells (PAECs) angiogenesis as well as the molecular mechanism of hypoxia-regulated MMP-2 and MMP-9 expression have not been identified. The aim of this study was to investigate the role of MMP-2 and MMP-9 in PAEC proliferation and vascular angiogenesis and to determine the effects of hypoxia-induced 15-HETE on the expression of MMP-2 and MMP-9. Western blot, immunofluorescence, and real-time PCR were used to measure the expression of MMP-2 and MMP-9 in hypoxic PAECs. Immunohistochemical staining, flow cytometry, and tube formation as well as cell proliferation, viability, scratch-wound, and Boyden chamber migration assays were used to identify the roles and relationships between MMP-2, MMP-9, and 15-HETE in hypoxic PAECs. We found that hypoxia increased MMP-2 and MMP-9 expression in pulmonary artery endothelium both in vivo and in vitro in a time-dependent pattern. Moreover, administration of the MMP-2 and MMP-9 inhibitor MMI-166 significantly reversed hypoxia-induced increases in right ventricular systemic pressure (RVSP), right ventricular function, and thickening of the tunica media. Furthermore, up-regulation of MMP-2 and MMP-9 expression was induced by 15-HETE, which regulates PAEC proliferation, migration, and cell cycle transition that eventually leads to angiogenesis. Our study demonstrated that hypoxia increases the expression of MMP-2 and MMP-9 through the 15-lipoxygenase/15-HETE pathway, and that MMP-2 and MMP-9 promote PAEC angiogenesis. These findings suggest that MMP-2 and MMP-9 may serve as new potential therapeutic targets for the treatment of PAH. [ABSTRACT FROM AUTHOR]

Aims/hypothesis: Our earlier studies have established the role of 12/15-lipoxygenase (LO) in mediating the inflammatory reaction in diabetic retinopathy. However, the exact mechanism is still unclear. The goal of the current study was to identify the potential role of endoplasmic reticulum (ER) stress as a major cellular stress response in the 12/15-LO-induced retinal changes in diabetic retinopathy.Methods: We used in vivo and in vitro approaches. For in vivo studies, experimental diabetes was induced in wild-type (WT) mice and 12/15-Lo (also known as Alox15) knockout mice (12/15-Lo−/−); ER stress was then evaluated after 12-14 weeks of diabetes. We also tested the effect of intravitreal injection of 12-hydroxyeicosatetraenoic acid (HETE) on retinal ER stress in WT mice and in mice lacking the catalytic subunit of NADPH oxidase, encoded by Nox2 (also known as Cybb) (Nox2−/− mice). In vitro studies were performed using human retinal endothelial cells (HRECs) treated with 15-HETE (0.1 μmol/l) or vehicle, with or without ER stress or NADPH oxidase inhibitors. This was followed by evaluation of ER stress response, NADPH oxidase expression/activity and the levels of phosphorylated vascular endothelial growth factor receptor-2 (p-VEGFR2) by western blotting and immunoprecipitation assays. Moreover, real-time imaging of intracellular calcium (Ca2+) release in HRECs treated with or without 15-HETE was performed using confocal microscopy.Results: Deletion of 12/15-Lo significantly attenuated diabetes-induced ER stress in mouse retina. In vitro, 15-HETE upregulated ER stress markers such as phosphorylated RNA-dependent protein kinase-like ER-regulated kinase (p-PERK), activating transcription factor 6 (ATF6) and protein disulfide isomerase (PDI) in HRECs. Inhibition of ER stress reduced 15-HETE-induced-leucocyte adhesion, VEGFR2 phosphorylation and NADPH oxidase expression/activity. However, inhibition of NADPH oxidase or deletion of Nox2 had no effect on ER stress induced by the 12/15-LO-derived metabolites both in vitro and in vivo. We also found that 15-HETE increases the intracellular calcium in HRECs.Conclusions/interpretation: ER stress contributes to 12/15-LO-induced retinal inflammation in diabetic retinopathy via activation of NADPH oxidase and VEGFR2. Perturbation of calcium homeostasis in the retina might also play a role in linking 12/15-LO to retinal ER stress and subsequent microvascular dysfunction in diabetic retinopathy. [ABSTRACT FROM AUTHOR]

Aims Our previous studies have established a role for 12/15-lipoxygenase (LO) in mediating the inflammatory response in diabetic retinopathy (DR). However, the extent at which the local or systemic induction of 12/15-LO activity involved is unclear. Thus, the current study aimed to characterize the relative contribution of retinal endothelial versus monocytic/macrophagic 12/15-LO to inflammatory responses in DR. Materials & methods We first generated a clustered heat map for circulating bioactive lipid metabolites in the plasma of streptozotocin (STZ)-induced diabetic mice using liquid chromatography coupled with mass-spectrometry (LC–MS) to evaluate changes in circulating 12/15-LO activity. This was followed by comparing the in vitro mouse endothelium-leukocytes interaction between leukocytes isolated from 12/15-LO knockout (KO) versus those isolated from wild type (WT) mice using the myeloperoxidase (MPO) assay. Finally, we examined the effects of knocking down or inhibiting endothelial 12/15-LO on diabetes-induced endothelial cell activation and ICAM-1 expression. Results Analysis of plasma bioactive lipids' heat map revealed that the activity of circulating 12/15-LO was not altered by diabetes as evident by no significant changes in the plasma levels of major metabolites derived from 12/15-lipoxygenation of different PUFAs, including linoleic acid (13-HODE), arachidonic acid (12- and 15- HETEs), eicosapentaenoic acid (12- and 15- HEPEs), or docosahexaenoic acid (17-HDoHE). Moreover, leukocytes from 12/15-LO KO mice displayed a similar increase in adhesion to high glucose (HG)-activated endothelial cells as do leukocytes from WT mice. Furthermore, abundant proteins of 12-LO and 15-LO were detected in human retinal endothelial cells (HRECs), while it was undetected (15-LO) or hardly detectable (12-LO) in human monocyte-like U937 cells. Inhibition or knock down of endothelial 12/15-LO in HRECs blocked HG-induced expression of ICAM-1, a well-known identified important molecule for leukocyte adhesion in DR. Conclusion Our data support that endothelial, rather than monocytic/macrophagic, 12/15-LO has a critical role in hyperglycemia-induced ICAM-1 expression, leukocyte adhesion, and subsequent local retinal barrier dysfunction. This may facilitate the development of more precisely targeted treatment strategies for DR. [ABSTRACT FROM AUTHOR]

Angiogenesis plays a critical role in the progression of cardiovascular disease, retinal ischemia, or tumorigenesis. The imbalance of endothelial cell proliferation and apoptosis disturbs the establishment of the vasculogenesis, which is affected by several arachidonic acid metabolites. 15-Hydroxyeicosatetraenoic acid (15-HETE) is one of the metabolites. However, the underlying mechanisms of angiogenesis induced by 15-HETE in human umbilical vascular endothelial cells (HUVECs) are still poorly understood. Since extracellular signal-regulated kinase (ERK) is a critical regulator of cell proliferation, there may be a crosstalk between 15-HETE-regulating angiogenic process and ERK-proliferative effect in HUVECs. To test this hypothesis, we study the effect of 15-HETE on cell proliferation, angiogenesis, and apoptosis using cell viability measurement, cell cycle analysis, western blot, scratch–wound, tube formation assay, and nuclear morphology determination. We found that 15-HETE promoted HUVEC angiogenesis, which were mediated by ERK. Moreover, 15-HETE-induced proliferation and cell cycle transition from the G0/G1 phase to the G2/M + S phase. All these effects were reversed after blocking ERK with PD98059 (an ERK inhibitor). In addition, HUVEC apoptosis was relieved by 15-HETE through the ERK pathway. Thus, ERK is necessary for the effects of 15-HETE in the regulation of HUVEC angiogenesis, which may be a novel potential target for the treatment of angiogenesis-related diseases. [ABSTRACT FROM AUTHOR]

15( S )-Hydroxyeicosa-(5 Z ,8 Z ,11 Z ,13 E )-tetraenoic acid (15( S )-HETE) is a metabolite of arachidonic acid that elicits a number of biological effects including vasoconstriction and angiogenesis. (5 Z ,11 Z ,15 R )-15-Hydroxyeicosa-5,11-dien-13-ynoic acid (HETE analog 1 ) is a synthetic isomer of 15( S )-HETE that is much more stable to autoxidation. Using isometric recording of isolated pulmonary arteries from male and female rabbits, HETE analog 1 and 15( S )-HETE were found to elicit concentration-dependent contractions that were slightly greater in females compared to males. The maximal response in females was greater with 15( S )-HETE. HETE analog 1 and 15( S )-HETE increased [ 3 H]-thymidine incorporation in vascular smooth muscle cells cultured from male rabbit pulmonary arteries; both the maximal response and potency were greater with 15( S )-HETE. In contrast, HETE analog 1 produced a concentration-dependent inhibition in proliferation and migration of human hormone-independent prostate carcinoma PC-3 cells. The protocol for synthesis of HETE analog 1 is reported. The stability of this substance and its similar biological profile to 15( S )-HETE support future studies in eicosanoid research. [ABSTRACT FROM AUTHOR]

Hydroxyeicosatetraenoic acids (HETEs) are metabolites of arachidonate acid (AA) oxidized by lipoxygenases or cytochrome P450 enzymes (CYP450). Since lipoxygenases and CYP450 enzymes widely exist in different organs and tissues, HETEs play significant roles in normal physiological and pathophysiological conditions. Mounting evidence has shown that HETEs play roles in modulation of inflammation during diabetes development. And accumulating evidence suggests that in prediabetic conditions, HETEs have already impacted on adipose tissue, kidney, heart, and islet. In the current review, we focused on the role of specific HETEs, namely 5-HETE, 12-HETE, 15-HETE and 20-HETE in diabetes, and highlighted their effects in the development of diabetes and diabetes-related complications. In conclusion, elucidation of HETEs' impacts on different organs that contribute to the development of diabetes leads to identification of novel therapeutic modalities. [Display omitted] • Provide information of hydroxyeicosatetraenoic acids in diabetes. • Summarize the different role of 5-HETE, 12-HETE, 15-HETE and 20-HETE in diabetes and obesity. • Discuss the potential impacts of HETEs in the prevention and treatment of diabetes. [ABSTRACT FROM AUTHOR]

Background: Pulmonary adventitial fibroblasts (PAFs) are activated under stress stimuli leading to their differentiation into myofibroblasts, which is involved in vessel remodeling. 15-HETE is known as an important factor in vessel remodeling under hypoxia; however, the role of 15-HETE in PAF phenotypic alteration is not clear. Results: The effect of 15-HETE on PAF phenotypic alterations was investigated in the present study. PAFs were treated with 15-HETE (0.5 μM) for 24 h, and the myofibroblast marker α-smooth muscle actin (α-SMA) was analyzed. The 15-HETE induced α-SMA expression and cell morphology. 15-HETE upregulated FGF-2 levels in PAFs, and knockdown FGF-2 by siRNAs blocked the enhanced α-SMA expression induced by 15-HETE. p38 kinase was activated, and blocked depressed 15-HETE-induced FGF-2 expression. The downstream of p38 pathway, Egr-1 activation, was also raised by 15-HETE treatment, and silenced Egr-1 suppressed the 15-HETE-induced upregulation of FGF-2. TGF-β1 was upregulated with FGF-2 treatment, and α-SMA expression induced by FGF-2 was inhibited after the cell was transferred with TGF-β1 siRNA. Meanwhile, FGF-2 increased α-SMA expression and improved proliferation, which was associated with p27kip1 and cyclin E variation. Conclusions: The above results suggest that p38/Egr-1 pathway-mediated FGF-2 is involved in 15-HETE-induced differentiation of PAFs into myofibroblasts and cell proliferation. [ABSTRACT FROM AUTHOR]

Several lines of evidence indicate that 15-lipoxygenase type 1 (15-LO-1) plays a pathophysiological role in asthma. The aim for this study was to investigate the 15-LO-1 expression and activity in primary human airway epithelial cells cultivated on micro-porous filters at air–liquid interface. Incubation of human airway epithelial cells with arachidonic acid led to the formation of 15(S)-hydroxy-eicosatetraenoic acid (15-HETE) and exposing the cells to bacteria or physical injury markedly increased their production of 15-HETE. The cells were also found to convert arachidonic acid to eoxin C 4 (EXC 4 ). Subcellular fractionation revealed that the conversion of EXA 4 to EXC 4 was catalyzed by a soluble glutathione transferase (GST). The GST P1-1 enzyme was found to possess the highest activity of the investigated soluble GSTs. Following IL-4 treatment of airway epithelial cells, microarray analysis confirmed high expression of 15-LO-1 and GST P1-1, and immunohistochemical staining of bronchial biopsies revealed co-localization of 15-LO-1 and GST P1-1 in airway epithelial cells. These results indicate that respiratory infection and cell injury may activate the 15-LO pathway in airway epithelial cells. Furthermore, we also demonstrate that airway epithelial cells have the capacity to produce EXC 4 . [ABSTRACT FROM AUTHOR]

Objective Vascular adventitial fibroblasts (VAFs) migration was involved in neointima formation, and increased 15-HETE levels contributed to vascular remodeling. However, how 15-HETE-induced VAF migration was not clear. Methods and results 15-HETE-stimulated VAF phenotypic changes and migration as measured by the wound healing assay required STAT3 phosphorylation. JNK1 and CREB inhibition blocked 15-HETE-induced STAT3 activation and VAF changes. 15-HETE-induced MMP-2 expression and secretion were analyzed by Western blot and ELISA, respectively. MMP-2 knockdown blocked VAF migration and phenotypic alterations. JNK1, STAT3 and CREB blockade suppressed 15-HETE-induced MMP-2 expression in VAFs. MMP-2 promoter activity was assessed by chromatin immunoprecipitation using anti-STAT3 antibodies, which demonstrated that STAT3 was essential for 15-HETE-induced MMP-2 expression. Rats that suffered from hypoxia injury with or without treatment were examined. Pulmonary artery remodeling was obviously observed, and even the media was broken. MMP-2-positive staining was observed in the adventitia and intima. MMP-2 Serum secretion was enhanced as detected by ELISA, and MMP-2 and α-SMA protein expressions were increased after inducing hypoxia in the rats, which was restored in rats that had been administrated with NDGA. Conclusion These results reveal that STAT3-mediated MMP-2 expression is required for 15-HETE induced-VAF migration. [ABSTRACT FROM AUTHOR]

Peroxisome proliferator activated receptor gamma coactivator 1 α (PGC-1 α ) has been confirmed as a key regulatory factor in pulmonary artery smooth muscle cells to mediate mitochondrial biogenesis and proliferation during hypoxia. However, the functional role of PGC-1 α in hypoxic pulmonary artery endothelial cells (PAECs) still needs to be determined. In the present study, we found a marked elevation in the expression of PGC-1 α under hypoxia, which was predominate in the nucleus of PAECs. This alteration of PGC-1 α showed a significant association with 15-Hydroxyeicosatetraenoic acid (15-HETE), a regulator known to be protective against apoptosis at the concentration of 1 μM. By silencing PGC-1 α , the action against cell viability suppression induced by 15-HETE was blocked, not only in normoxic condition but also in hypoxia-stimulated condition. Likewise, the tendency to reduce TUNEL-positive cells, abnormal nuclei and apoptotic cells in response to 15-HETE was depending on PGC-1 α . Furthermore, 15-HETE and PGC-1 α siRNA caused significant alterations in related mechanisms including caspase activity, mitochondrial membrane potential, and Bcl-2 expression. Taken together, these results provide the first evidence to confirm the importance of PGC-1 α in mediating the protective effect of 15-HETE against apoptosis. Therefore, a clear role of PGC-1 α in hypoxic PAECs is demonstrated, which may be attributed to pulmonary vascular remodeling. [ABSTRACT FROM AUTHOR]

Hypoxia activates nuclear factor of activated T cells isoforms c3 (NFATc3), a Ca2+-dependent transcription factor in murine pulmonary arteries (PAs), and NFATc3 has been proved to be implicated in hypoxia-induced pulmonary arterial smooth muscle cells (PASMCs) proliferation, but it remains unclear whether NFATc3 acts on the apoptosis of PASMCs, an important step in PAs remodeling. Our laboratory has demonstrated that 15-hydroxyeicosatetraenoic acid (15-HETE) is a key factor in hypoxia-induced PA remodeling and can increase PASMC intracellular Ca2+ ([Ca2+]i) in rats. It is possible that NFATc3 is related with the function of 15-HETE anti-apoptosis during hypoxia. Our results identified that NFATc3 was mainly localized in rat PASMCs and was upregulated in PAs during hypoxia-induced rat pulmonary hypertension (PH), while this effect was inhibited by administration of nordihydroguaiaretic acid (NDGA), a 15-lipoxygenase (15-LO) inhibitor. Moreover, hypoxia and exogenous 15-HETE promoted the expression and nuclear translocation of NFATc3 in PASMCs, which was inhibited by NDGA or small interfering RNA targeted to rat 15-LO1 or 15-LO2. Furthermore, endogenous 15-HETE induced by hypoxia and exogenous 15-HETE suppressed serum deprivation-induced loss of rat PASMCs survival and prevented annexin V binding, mitochondrial membrane potential depolarization, DNA nick end labeling and chromatin condensation. Although all these effects were suppressed after the cells were treated with cyclosporin A (a calcineurin/NFAT inhibitor), it aggravated the apoptosis induced by serum deprivation. Thus, all these results indicate that 15-HETE-mediated PASMCs anti-apoptosis in hypoxic PH via the Ca2+-NFATc3 pathway. [ABSTRACT FROM AUTHOR]

Inhibition of cyclooxygenase (COX)-2 increases cardiovascular deaths. Identifying a biomarker of COX-2 is desirable but difficult, since COX-1 and COX-2 ordinarily catalyze formation of an identical product, prostaglandin H2. When acetylated by aspirin, however, COX-2 (but not COX-1) can form 15(R)-HETE, which is metabolized to aspirin-triggered lipoxin (ATL), 15-epi-lipoxin A4. Here we have used COX-1- and COX-2-knockout mice to establish whether plasma ATL could be used as a biomarker of vascular COX-2 in vivo. Vascular COX-2 was low but increased by LPS (10 mg/kg; i.p). Aspirin (10 mg/kg; i.v.) inhibited COX-1, measured as blood thromboxane and COX-2, measured as lung PGE2. Aspirin also increased the levels of ATL in the lungs of LPS-treated wild-type C57Bl6 mice (vehicle: 25.5±9.3 ng/ml; 100 mg/kg: 112.0±7.4 ng/ml; P<0.05). Despite this, ATL was unchanged in plasma after LPS and aspirin. This was true in wild-type as well as COX-1-/- and COX-2-/- mice. Thus, in mice in which COX-2 has been induced by LPS treatment, aspirin triggers detectable 15-epi-lipoxin A4 in lung tissue, but not in plasma. This important study is the first to demonstrate that while ATL can be measured in tissue, plasma ATL is not a biomarker of vascular COX-2 expression. [ABSTRACT FROM AUTHOR]

Background: The fatty acid mixture of human milk is ideal for the newborn but little is known about its composition in the first few weeks of lactation. Of special interest are the levels of long-chain PUFAs (LCPUFAs), since these are essential for the newborn's development. Additionally, the LCPUFAs arachidonic acid (AA), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are precursors for lipid mediators which regulate inflammation. Methods: We determined the composition of 94 human milk samples from 30 mothers over the first month of lactation for fatty acids using GC-MS and quantified lipid mediators using HPLC-MS/MS. Results: Over the four weeks period, DHA levels decreased, while levels of γC18:3 and αC18:3 steadily increased. Intriguingly, we found high concentrations of lipid mediators and their hydroxy fatty acid precursors in human milk, including pro-inflammatory leukotriene B4 (LTB4) and anti-inflammatory and pro-resolving lipoxin A4 (LXA4), resolvin D1 (RvD1) and resolvin E1 (RvE1). Lipid mediator levels were stable with the exception of two direct precursors. Conclusions: Elevated levels of DHA right after birth might represent higher requirements of the newborn and the high content of anti-inflammatory and pro-resolving lipid mediators and their precursors may indicate their role in neonatal immunity and may be one of the reasons for the advantage of human milk over infant formula. [ABSTRACT FROM AUTHOR]

Acute transplant rejection is the leading cause of graft loss in the first months after kidney transplantation. Lipoxygenase products mediate pro- and anti-inflammatory actions and thus we aimed to correlate the histological reports of renal transplant biopsies with urinary lipoxygenase products concentrations to evaluate their role as a diagnostic marker. This study included a total of 34 kidney transplant recipients: 17 with an acute transplant rejection and 17 controls. LTE4, LTB4, 12-HETE and 15-HETE concentrations were measured by enzyme immunoassay. Urinary lipoxygenase product concentrations were not significantly changed during an acute allograft rejection. Nevertheless, LTB4 concentrations correlated significantly with the body temperature ( P ≤ 0.05) 3 months after transplantation, and 12- and 15-HETE concentrations correlated significantly with renal function ( P ≤ 0.05) 2 weeks after transplantation. In conclusion, our data show a correlation for LTB4 with the body temperature 3 months after transplantation and urinary 12- and 15-HETE concentrations correlate positively with elevated serum creatinine concentrations but do not predict acute allograft rejection. [ABSTRACT FROM AUTHOR]

Abstract: 15-Hydroxyeicosatetraenoic acid, a predominant metabolic product of arachidonic acid (AA) catalyzed by 15-lipoxygenase (15-LO), plays an important role in hypoxic pulmonary arterial hypertension (PAH). Hypoxia-inducible factor-1α (HIF-1α) as a critical oxygen-sensitive transcriptional factor participates in many physiological and pathological processes including PAH. Therefore, it is possible that there may be some connections between HIF-1α and 15-LO/15-HETE in hypoxic pulmonary artery smooth muscle cells. Our results showed that HIF-1α inhibitor or siRNA reduced hypoxia-induced upregulation of 15-LO and endogenous 15-HETE, meanwhile HIF-1α expression and transcriptional activity were induced by 15-HETE under both normoxic and hypoxic conditions. It suggests there exists a potential positive feedback regulatory loop between HIF-1α and 15-LO/15-HETE. Furthermore, cell viability assay and several cell apoptosis assays, including TUNEL assay, Western blot, nuclear morphology determination, mitochondrial potential analysis, indicated that blocking HIF-1α induced apoptosis, decreased cell viability and suppressed the anti-apoptosis effects of 15-HETE. Taken together, our data indicate that upregulation of 15-LO/15-HETE in response to hypoxia may be partially mediated by HIF-1α which is also regulated by 15-HETE in a positive feedback manner, and HIF-1α can effectively inhibit pulmonary artery smooth muscle cells apoptosis which leads to vascular remodeling. The feedback loop between HIF-1α and 15-LO/15-HETE would obviously reinforce hypoxia-induced anti-apoptosis effect and may become a novel target of therapy in PAH. [Copyright &y& Elsevier]

Abstract: 15-Hydroxyeicosatetraenoic acid (15-HETE), one of many important metabolic products of arachidonic acid (AA) catalyzed by 15-lipoxygenase, plays an important role in pulmonary vascular smooth muscle remodeling. We have previously shown its unsubstituted effects on the apoptotic responses of pulmonary artery smooth muscle cells (PASMCs), but the underlying mechanisms are still poorly manifested. Previous studies have shown that inducible nitric oxide synthase (iNOS) plays an important protective role against sepsis-induced pulmonary apoptosis. Therefore, the purpose of this study is to determine whether 15-HETE anti-apoptotic process is mediated through the iNOS pathway in rat PASMCs. To test this hypothesis, we studied the contribution of iNOS to the 15-HETE induced anti-apoptotic responses using cell viability measurement, Western blot, mitochondrial potential analysis, nuclear morphology determination and TUNEL assay. Our results showed that both exogenous and endogenous 15-HETE up-regulated iNOS protein and mRNA expression and 15-HETE enhanced the cell survival, attenuated mitochondrial depolarization, up-regulated the expression of Bcl-2 and procaspase-3 in PASMCs under serum-deprived condition. These effects were reversed by iNOS inhibitor SMT or l-canavanine. Taken together, our data indicates that iNOS is a novel signaling transduction pathway, which is necessary for the effects of 15-HETE in protection PASMCs from apoptosis and may be an important mechanism underlying the treatment of pulmonary artery hypertension and also provides a novel therapeutic insight in future. [Copyright &y& Elsevier]

Both mast cells and eosinophils were implicated in the pathophysiology of allergic conjunctivitis; however, the potential role of eosinophils in an early phase of allergic reaction has not been elucidated. The aim of this study was to assess the relation between clinical symptoms and sequence of mast cells and eosinophils specific mediators release into tear fluid during conjunctival allergen provocation. Patients with grass pollen rhinoconjunctivitis (n = 38) and healthy volunteers (n = 10) were challenged with increasing doses of allergen applied on the conjunctiva. The clinical symptoms were assessed by clinical score. Tear fluid was collected from 12 patients before provocation, at 20 and 40 minutes after positive response. Tryptase and eosinophil cationic protein (ECP) were measured using UniCap and 15-hydroxyeicosanoid acid (15-HETE) with a specific immunoassay. All allergic patients (but no control subjects) had a positive clinical response to the challenge. In 1 patient symptoms appeared after 50 BU/mL of grass allergen administration, in 3 patients symptoms appeared after 500 BU/mL (7.9% of patients), in 14 patients symptoms appeared after 1600 BU/mL (36.8%), and in 20 patients symptoms appeared after 5000 BU/mL (52.6%). The allergen dose was not correlated with the skin-prick test diameter. The mean tryptase concentration increased at 20 minutes from 'nondetectable' to 5.89 ± 1.97 micrograms/L and then decreased to 1.77 ± 1.07 micrograms/L (n = 12; p < 0.05) at 40 minutes. ECP concentration was not changed at 20 minutes but increased at 40 minutes from 1.38 ± 0.98 micrograms/L before provocation to 10.61 ± 7.78 micrograms/L (n = 7; p < 0.05). There was no change in 15-HETE release. Both mast cells and eosinophils are activated during allergic reaction in conjunctiva and activation of eosinophils is preceded by activation of mast cells. [ABSTRACT FROM AUTHOR]

Abstract: This mini-review is focused on the enzyme 15-lipoxygenase-1 (15-LO-1) and eoxins in airway inflammatory diseases and Hodgkin lymphoma. Several studies have demonstrated increased expression and activity of 15-LO-1 in the respiratory tissue from asthma patients , indicating a pathophysiological role of this enzyme in airway inflammation. Eoxins were recently identified as pro-inflammatory metabolites of arachidonic acid, formed through the 15-LO-1 pathway, in human eosinophils, mast cells, airway epithelial cells and Hodgkin lymphoma. Mice deficient of 12/15-LO, the ortholog to human 15-LO-1, had an attenuated allergic airway inflammation compared to wild type controls, also indicating a pathophysiological role of this enzyme in respiratory inflammation. The putative therapeutic implications of 15-LO-1 inhibitors in the treatment of asthma, chronic obstructive pulmonary disorder and Hodgkin lymphoma are discussed. [Copyright &y& Elsevier]

Abstract: Several reports have demonstrated an important role of leukotriene B4 (LTB4) in the immune system. We investigated whether leukemic blasts from acute myeloid leukemic (AML) and acute lymphoid leukemic (ALL) patients produced LTB4, 12- and 15-hydroxyeicosatetraenoic acids (12-HETE and 15-HETE) and whether these compounds affected blast proliferation and apoptosis. Leukemic blasts from AML M0-2 and ALL patients expressed 5-LOX, 12-LOX and 15-LOX transcripts. Quantitative polymerase chain reaction indicated that 5-LOX transcripts were far more abundant than 12-LOX and 15-LOX ones. Leukemic blasts expressed 5-LOX activating protein (FLAP) transcripts and produced LTB4 in response to calcium ionophore. In contrast no 15-HETE production was found. Calcium ionophore-stimulated leukemic blasts produced 12-HETE but also released thromboxane A2 suggesting that contaminating platelets accounted for the release of these compounds. No significant effect of LTB4, 12-HETE or 15-HETE could be documented on leukemic blast growth and on their apoptose rate. Results of the present study indicate that immature form of leukemic blasts produce LTB4. However, the three major lipoxygenase metabolites of arachidonic acid; i.e., LTB4, 12-HETE or 15-HETE, had no evident effect on their growth and apoptosis. We may speculate that LTB4-derived blast cells might initiate, augment or prolong tissue inflammation and damages by affecting the marrow and blood cytokine network. [Copyright &y& Elsevier]

Background The mechanism of aspirin (acetylsalicylic acid: ASA) hypersensitivity in asthmatic patients is related to arachidonic acid metabolism abnormalities, and specific triggering by ASA of 15-hydroxyeicosatetraenoic acid (15-HETE) generation was observed in leucocytes from aspirin-sensitive (AS) but not from aspirin-tolerant (AT) asthmatics. Objective The aim of this study was to identify the enzymatic pathway involved in ASA-induced 15-HETE generation in AS asthmatics and to assess the regulatory role of prostaglandin EP receptors. Methods Peripheral blood leucocytes (PBLs) were isolated from AS ( n=18) and AT ( n=20) asthmatics and challenged with ASA, with and without pre-incubation with caffeic acid (CA) [15-lipoxygenase (15-LO) inhibitor] or prostaglandin receptor non-specific (misoprostol, sulprostone) and specific EP1–4 receptors agonists. Eicosanoids were measured in supernatants using specific immunoassays. Results Aspirin triggered 15-HETE generation in PBLs of AS asthmatics (mean increase 292%) but not in AT asthmatics and inhibited prostaglandin2 (PGE2) generation in both groups of patients to the same degree. Leucocytes from AS patients produced less PGE2, both before and after ASA incubation. Pre-incubation of PBLs with CA decreased basal 15-HETE production in all patients and completely inhibited ASA-induced 15-HETE generation in AS asthmatics. CA did not change basal PGE2 production but enhanced induced by ASA inhibition of PGE2. Non-specific agonists of EP receptors (misoprostol and sulprostone) did not affect basal 15-HETE production but inhibited in a dose-dependent manner the ASA-induced increase of 15-HETE generation in AS asthmatics. On the contrary, in AT asthmatics, pre-incubation of PBLs with misoprostol or sulprostone resulted in a significant increase in 15-HETE generation after addition of ASA (200 μm). EP1–3 receptor agonists inhibited (range 72–94%) the ASA-induced 15-HETE production significantly. Conclusion Our study demonstrated that ASA-triggered 15-HETE generation involves the activation of 15-LO and is modulated by prostaglandin EP1–3 receptors. The relevance of these observations to the mechanism of in vivo ASA-induced asthmatic attack remains to be established. [ABSTRACT FROM AUTHOR]

Abstract: A festschrift for Dr. John Martyn Bailey, Professor of Biochemistry and Molecular Biology was organized by the Biochemistry department of the George Washington University School of Medicine and Health Sciences on December 4–5, 2006 to honor his 48 years of contributions. He made important contributions in the areas of essential fatty acids, prostaglandins, thromboxanes and lipoxygenase metabolites. [Copyright &y& Elsevier]

We have previously demonstrated that aspirin triggers specific generation of 15-hydroxyeicosateraenoic acid (15-HETE) from nasal polyp epithelial cells and peripheral blood leukocytes (PBL) from aspirin-sensitive (AS) but not aspirin-tolerant (AT) patients with asthma/rhinosinusitis. The goal of this study was to assess the diagnostic value of ASA-induced 15-HETE generation measurement to identify AS patients. PBL were obtained from 43 AS patients with asthma and rhinosinusitis, 35 AT asthmatics and 17 healthy control (HC) subjects. PBL were incubated with 2–200 μM aspirin (ASA) and 15-HETE release was measured in cell supernatants with competitive ELISA. Unstimulated PBL from all three groups of patients generated similar amount of 15-HETE. Incubation with 200 μM ASA resulted in an increase in an 15-HETE generation (mean increase +421%) in AS-asthmatics but small and nonsignificant response in AT-asthmatics or control subjects. Receiver operating curve (ROC) analysis revealed that the sensitivity of the test for confirmation of ASA-sensitivity was 83% and the specificity 82%. Positive predictive value was 0.79 and negative predictive value was 0.86. Naproxen induced a significant increase in 15-HETE only in some AS-asthmatics, but not in AT-asthmatics. Our data demonstrate that ASA-induced 15-HETE generation by PBL is a specific and sensitive aspirin-sensitive patients identification test (ASPITest). [ABSTRACT FROM AUTHOR]

The diagnosis of allergic reactions in clinical practice is based on both clinical history and the determination of specific immunoglobulin E (IgE), either in the serum or on skin mast cells. However, for various reasons, identification of the causative factors is not possible in all the cases. Moreover, not all allergies are IgE-dependent. In an attempt to find sensitive, specific and cost-effective methods to investigate hypersensitivity reactions, in vitro tests were developed at a very early stage. Allergen-induced mediator release assays analyze the mediator released from effector cells, mainly peripheral blood cells, when stimulated in vitro with serial dilutions of the putative allergens. Described initially as research tools, they could well become diagnostic tests. However, relatively few high quality reports have been published so far. In this review, we will detail allergen-dependent histamine, tryptase, arachidonic acid metabolite, e.g. cysteinyl leukotrienes and 15-hydroxyeicosatetraenoic mediator release tests. [ABSTRACT FROM AUTHOR]

Monohydroxy derivatives of polyunsaturated fatty acids such as arachidonic acid (AA) and linoleic acid (LA) can modulate inflammation and epidermal proliferation. The purpose of this study was to determine the in vivo distribution of the AA derivatives; 12- and 15-hydroxy-eicosatetraenoic acid (12-HETE and 15-HETE) and the LA derivatives; 9- and 13- hydroxyotadecadienoic acid (9-HODE and 13-HODE) in specific phospholipids of normal human skin. Lipids were extracted from 6 normal keratome skin biopsies and phospholipids were separated into the major classes by two-dimensional thin layer chromatography. Monohydroxy fatty acids (MHFAs) released from specific phospholipids after treatment with phospholipase A[SUB2], were identified by reversed phase and straight phase high-performance liquid chromatography and UV-absorption spectra. Unesterified MHFAs were determined in a similar way. 9-HODE, 13-HODE and 15-HETE were detectable in phosphatidyicholine (PC), phosphatidylinositol (PI) and phosphatidylethanolamine (PE). Interestingly, 12-HETE was not detectable in these phospholipids, although the unesterified 12-HETE was detectable in amounts similar to unesterified 15-HETE. Esterified 15-HETE was equally distributed between PI and PC, in which 15-HETE was predominant, accounting for 60% and 69% of the total MHFAs, respectively (p<0.05). These results demonstrate that the LA derivatives 9-HODE and 13-HODE, as well as the AA derivative 15-HETE, are esterified to PC, PI and PE of normal human epidermis in vivo. The possibility remains that 9-HODE, 13-HODE and 15-HETE, may mediate their biological effects by being incorporated into specific phospholipids. [ABSTRACT FROM AUTHOR]

15-Hydroxyeicosatetraenoic acid (15-HETE), a 15-lipoxygenase product of arachidonic acid, inhibits leukotriene B (LTB)-induced chemotaxis of polymorphonuclear leukocytes (PMNs) in vitro. In this study the effects of intradermal injections of LTB were determined in the absence or presence of 15-HETE. For comparison intradermal injections of purified human complement split product C5a were performed in the absence or presence of 15-HETE. The skin response was evaluated by measuring the diameter of the wheal, the area of the flare and by intensity of the erythema (erythema index). LTB and C5a were injected at the concentration of 200 ng/ml. At this concentration the maximal skin response of LTB and C5a were equivalent. In contrast to C5a reaction, which resolved within 1 h, LTB-induced skin response lasted up to 18 h. In all subjects the skin response was significantly decreased when LTB was injected together with 300 ng of 15-HETE. The decrease of wheal, flare, and erythema index averaged 81.9%, 56.6%, 53.6%, respectively, when all parameters were obtained at the maximal skin response. In contrast, the C5a-induced skin response was not affected by addition of 15-HETE, even when the final dose of 15-HETE was increased 10 times to 3 μg. The LTB-induced reaction could last up to 18 h after injection. After the addition of 300 ng of 15-HETE the skin response resolved after 1 h. The present results demonstrate that 15-HETE is a specific inhibitor of the LTB-induced skin response and brings additional evidence in support of the ability of 15-HETE to regulate the proinflammatory effects of LTB in vivo. [ABSTRACT FROM AUTHOR]

Incubation of rocker-cultured neonatal rat heart cells with 3 mM L(+)-lactate led to a sharp increase in the sensitivity of cardiomyocytes to the beta-adrenergic agonist isoprenaline, as measured by their chronotropic response. This effect was accompanied by a reduction in the arachidonic acid content of the total phospholipids. The phospholipase A-activator melittin as well as free arachidonic acid induced this supersensitivity to the same degree. On the other hand, the L(+)-lactate-evoked supersensitivity could be blocked by the phospholipase A inhibitors mepacrine and n-bromophenacyl-bromide, suggesting an involvement of phospholipase A in the process of beta-adrenergic sensitization. The sensitizing action of arachidonic acid was blocked by the lipoxygenase inhibitors esculetin and nordihydroguaiaretic acid, but not by the cyclooxygenase inhibitor indomethacin. Supersensitivity was likewise evoked by 15-S-hydroxyeicosatetraenoic acid (15-S-HETE), but not by 5-S-HPETE or 5-S-HETE. These findings suggest that the phospholipase A-15-lipoxygenase pathway plays a role in the induction of beta-adrenergic supersensitivity in the cultured cardiomyocytes and point to a new physiological role of the lipoxygenase product 15-S-HETE. [ABSTRACT FROM AUTHOR]

Investigate the involvement of 15-hydroxyeicosatetraenoic acid (15-HETE), an anti-inflammatory molecule, on the beneficial effects of exercise therapy for osteoarthritis (OA). 15-HETE (10 μM, twice a week) and monosodium iodoacetate (MIA) (1 mg) were injected into rat knee joints. Treadmill exercise was applied on OA rat. Primary rat chondrocytes were treated with 15-HETE, LY294002 and interleukin (IL)-1β. Rats undergo a 1 hour single session treadmill exercise once. 15-HETE levels in the knee joint were evaluated using ELISA after a single session of treadmill exercise on healthy and OA rats. Matrix metalloproteinase (MMP)3, MMP-13, a disintegrin and metalloproteinase with thrombospondin motif (ADAMTS)-5, p-Akt, Akt, and collagen type 2 (COL2) expression were evaluated using RT-PCR and western blotting. OA degree was evaluated using X-ray, scored by Osteoarthritis Research Society International (OARSI) and Mankin scores. COL2 and MMP-13 expression in articular was evaluated using immunohistochemistry. Medium intensity exercise alleviated OA. 15-HETE levels after exercise was increased. 15-HETE inhibited IL-1β-induced inflammation in primary chondrocytes and increased p-Akt levels. LY294002 blocked the effect of 15-HETE in vitro. Finally, 15-HETE alleviated cartilage damage, inhibited MMP-13 expression, and increased COL2 expression in joint cartilage tissue. Treadmill exercise alleviates OA and increases 15-HETE levels in the knee joint, which suppresses inflammation in chondrocytes via PI3k-Akt signalling in vitro and in vivo. [ABSTRACT FROM AUTHOR]

Background: Platelet activation is an important side effect of dialysis, resulted in a subsequent release of arachidonic acid (AA) from activated platelets. AA is involved in many pathologic conditions, such as inflammation, asthma, cancer, diabetes, hypertension, and the pathogenesis of kidney disease. The aim of this study was to define whether the dialysis type affects the concentration of AA derivatives in patients with chronic kidney disease.Methods: 117 patients were qualified to the study group. Based on the type of renal replacement therapy, patients were divided into the following groups: hemodialysis (HD A - before/HD B - after hemodialysis), peritoneal dialysis (PD), kidney transplant patients (TE - before/TE A - after transplantation) and conservative treatment (CT) (30; 30; 27; 30 patients, respectively). The control group consisted of 30 healthy volunteers (NK). The ELISA methods were used to measure the concentrations of TXB2, 5-HETE, 12-HETE, and 15-HETE in the blood serum.Results: Renal replacement therapy significantly influences the concentration of TXB2 (mean ± SD [ng/mL]: HD A- 34.6 ± 9; HD B- 28.3 ± 15.2; PD- 28.3 ± 15.2; CT- 34.2 ± 8.0; TE- 36.7 ± 42.9; TE A- 27.9 ± 8.8; NK- 19.6 ± 15; p = 0.010), 5-HETE (mean ± SD [ng/mL]: HD A- 284.2 ± 428.4; HD B- 304.8 ± 516.2; PD - 530.0 ± 553.3; CT- 318.7 ± 366.0; TE- 525.6 ± 358.0; TE A - 409.8 ± 377.1; NK 838.1 ± 497.8; p < 0.001) and 15-HETE (HD A-18.1 ± 8.7; HD B- 42.2 ± 14; PD - 36.3 ± 13.8; CT- 33.7 ± 14.0; TE- 19.5 ± 10.2; TE A - 34.4 ± 16.3; NK 22.2 ± 17.8; p < 0,001). There was a significant relationship between the type of renal replacement therapy and the duration of dialysis, and the concentration of TXB2, 12-HETE acid, and 15-HETE.Conclusions: The type of renal replacement therapy significantly affects the concentration of AA derivatives. Peritoneal dialysis is the best method of dialysis, taking into account the concentration of arachidonic acid derivatives. [ABSTRACT FROM AUTHOR]

As arachidonic acid metabolites are implicated in hypersensitivity reactions, we measured arachidonic acid metabolites of dialysed patient's granulocytes, preincubated with different dialysis membranes. Results indicate that cuprophan and cellulose acetate membranes partially inhibit in vitro production of 15-HETE and 5-HETE, whereas polyacrylonitrile membrane does not. This suggests that polyacrylonitrile is a more biocompatible membrane. [ABSTRACT FROM PUBLISHER]