Remodeling of neutrophil phospholipids with 15(S)-hydroxyeicosatetraenoic acid inhibits leukotriene B4-induced neutrophil migration across endothelium

15-Lipoxygenase promotes resolution of inflammation in lymphedema by controlling Treg cell function through IFN-β

Lymphedema (LD) is characterized by the accumulation of interstitial fluid, lipids and inflammatory cell infiltrate in the limb. Here, we find that LD tissues from women who developed LD after breast cancer exhibit an inflamed gene expression profile. Lipidomic analysis reveals decrease in specialized pro-resolving mediators (SPM) generated by the 15-lipoxygenase (15-LO) in LD. In mice, the loss of SPM is associated with an increase in apoptotic regulatory T (Treg) cell number. In addition, the selective depletion of 15-LO in the lymphatic endothelium induces an aggravation of LD that can be rescued by Treg cell adoptive transfer or ALOX15-expressing lentivector injections. Mechanistically, exogenous injections of the pro-resolving cytokine IFN-β restores both 15-LO expression and Treg cell number in a mouse model of LD. These results provide evidence that lymphatic 15-LO may represent a therapeutic target for LD by serving as a mediator of Treg cell populations to resolve inflammation.

Oxylipin status, before and after LC n-3 PUFA supplementation, has little relationship with skeletal muscle biology in older adults at risk of sarcopenia

INTRODUCTION

Oxylipins form endogenously via the oxygenation of long-chain polyunsaturated fatty acids (LC PUFA). Several oxylipins are highly bioactive molecules and are believed to be key mediators of LC PUFA metabolism in the body. However, little is known in relation to whether oxylipins mediate alterations in skeletal muscle mass and function. The objective of this study was to determine if a relationship exists between the oxylipin profile and skeletal muscle biology in healthy older adults at risk of sarcopenia and determine if this changes in response to LC n-3 PUFA supplementation.

MATERIALS AND METHODS

This exploratory study investigated the baseline correlations between LC n-3, n-6 and n-9 PUFA-derived oxylipins and markers of muscle biology. For this, the concentration of 79 free (i.e., non-esterified) oxylipins was quantified in human plasma by liquid chromatography-mass spectrometry (LC-MS) and retrospectively correlated to phenotypic outcomes obtained pre-intervention from the NUTRIMAL study (n = 49). After examining the baseline relationship, the potential effect of supplementation (LC n-3 PUFA or an isoenergetic control made of high-oleic sunflower and corn oil) was evaluated by correlating the change in oxylipins concentration and the change in markers of skeletal muscle biology. The relationship between oxylipins pre- and post-intervention and their parent PUFA were also examined.

RESULTS

At baseline, the hydroxy product of mead acid (n-9 PUFA), 5-HETrE, was negatively correlated to the phenotypic parameters appendicular lean mass index (ALMI) (p = 0.003, r=-0.41), skeletal muscle mass index (SMMI) (p = 0.001, r=-0.46), handgrip strength (HGS) (p<0.001, r = 0.48) and isometric knee extension (p<0.001, r=-0.48). Likewise, LC n-6 PUFA hydroxy‑PUFA were negatively correlated to HGS (i.e., 12-HETrE, p = 0.002, r=-0.42, and 5- and 11-HETE, p = 0.006, r=-0.47 and p<0.001, r=-0.50 respectively), single leg stand time (i.e., 12-HETrE, p = 0.006, r=-0.39 and 16-HETE, p = 0.002, r=-0.43), and five-time-sit-to-stand test (FTST) performance (16-HETE, p = 0.006, r = 0.39), and positively correlated to gait speed (i.e., 12-HETrE, p = 0.007, r = 0.38 and 16-HETE, p = 0.006, r = 0.39). LC n-3 PUFA supplementation increased eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) derived oxylipins and reduced n-6 PUFA derived oxylipins. Parameters of skeletal muscle mass and strength were not significantly altered in either LC n-3 PUFA or placebo groups. Changes in plasma oxylipins concentrations were closely related to changes in their parent PUFA, assessed in the erythrocyte membrane, but were not associated with any changes in skeletal muscle parameters.

DISCUSSION AND CONCLUSION

At baseline, the status n-9 (5-HETrE) and n-6 PUFA derivates [12-HETrE, and 5-, 11- and 16-HETE], but not n-3 PUFA derived oxylipins, were associated with poor skeletal muscle health parameters (i.e., mass and strength). However, these correlations were no longer present when correlating relative changes from pre to post timepoints. An independent cohort validation is needed to explore baseline correlations further. Further research is warranted to assess other biological mechanisms by which LC n-3 PUFA might affect muscle biology.

Development of Adaptive Immunity and Its Role in Lung Remodeling

Asthma is characterized by airflow limitations resulting from bronchial closure, which can be either reversible or fixed due to changes in airway tissue composition and structure, also known as remodeling. Airway remodeling is defined as increased presence of mucins-producing epithelial cells, increased thickness of airway smooth muscle cells, angiogenesis, increased number and activation state of fibroblasts, and extracellular matrix (ECM) deposition. Airway inflammation is believed to be the main cause of the development of airway remodeling in asthma. In this chapter, we will review the development of the adaptive immune response and the impact of its mediators and cells on the elements defining airway remodeling in asthma.

Eicosanoids in inflammation in the blood and the vessel

Polyunsaturated fatty acids (PUFAs) are structural components of membrane phospholipids in cells. PUFAs regulate cellular function through the formation of derived lipid mediators termed eicosanoids. The oxygenation of 20-carbon PUFAs via the oxygenases cyclooxygenases, lipoxygenases, or cytochrome P450, generates a class of classical eicosanoids including prostaglandins, thromboxanes and leukotrienes, and also the more recently identified hydroxy-, hydroperoxy-, epoxy- and oxo-eicosanoids, and the specialized pro-resolving (lipid) mediators. These eicosanoids play a critical role in the regulation of inflammation in the blood and the vessel. While arachidonic acid-derived eicosanoids are extensively studied due to their pro-inflammatory effects and therefore involvement in the pathogenesis of inflammatory diseases such as atherosclerosis, diabetes mellitus, hypertension, and the coronavirus disease 2019; in recent years, several eicosanoids have been reported to attenuate exacerbated inflammatory responses and participate in the resolution of inflammation. This review focused on elucidating the biosynthesis and the mechanistic signaling of eicosanoids in inflammation, as well as the pro-inflammatory and anti-inflammatory effects of these eicosanoids in the blood and the vascular wall.

Levels of 15-HETE and TXB2 in exhaled breath condensates as markers for diagnosis of childhood asthma and its therapeutic outcome

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.

Muscle Loss Associated Changes of Oxylipin Signatures During Biological Aging: An Exploratory Study From the PROOF Cohort

Characterizations of the multiple mechanisms determining biological aging are required to better understand the etiology and identify early biomarkers of sarcopenia. Oxylipins refer to a large family of signaling lipids involved in the regulation of various biological processes that become dysregulated during aging. To investigate whether comprehensive oxylipin profiling could provide an integrated and fine characterization of the early phases of sarcopenia, we performed a quantitative targeted metabolomics of oxylipins in plasma of 81-year-old subjects from the PROOF cohort with decreased (n = 12), stable (n = 16), or increased appendicular muscle mass (n = 14). Multivariate and univariate analyses identified significant and concordant changes of oxylipin profiles according to the muscle status. Of note, 90% of the most discriminant oxylipins were derived from EPA and DHA and were increased in the sarcopenic subjects. The oxylipins signatures of sarcopenic subjects revealed subtle activation of inflammatory resolution pathways, coagulation processes, and oxidative stress as well as the inhibition of angiogenesis. Heat maps highlighted relationships between oxylipins and the cardiometabolic health parameters which were mainly lost in sarcopenic subjects. This exploratory study supports that targeted metabolomics of oxylipins could provide relevant and subtle characterization of early disturbances associated with muscle loss during aging.

A composite of exhaled LTB4 , LXA4 , FeNO, and FEV1 as an "asthma classification ratio" characterizes childhood asthma

BACKGROUND

Aberrant generation of eicosanoids is associated with asthma, but the evidence remains incomplete and its potential utility as biomarkers is unclear. Major eicosanoids in exhaled breath condensates (EBCs) were assessed as candidate markers for childhood asthma.

METHODS

Ten exhaled eicosanoid species was evaluated using ELISA in the discovery phase, followed by prediction model-building and validation phases.

RESULTS

Exhaled LTB₄ , LTE₄ , PGE_2, and LXA₄ showed significant difference between asthmatics (N = 60) and controls (N = 20). For validation, an expanded study population consisting of 626 subjects with asthma and 161 healthy controls was partitioned into a training subset to establish a prediction model and a test sample subset for validation. Receiver operating characteristic (ROC) analyses of the training subset revealed the level of exhaled LTB₄ to be the most discriminative among all parameters, including FeNO, and a composite of exhaled LTB₄ , LXA₄ , together with FeNO and FEV₁ , distinguishing asthma with high sensitivity and specificity. Further, the Youden index (J) indicated the cut point value of 0.598 for this composite of markers as having the strongest discriminatory ability (sensitivity = 85.2% and specificity = 83.6%). The predictive algorithm as "asthma classification ratio" was further validated in an independent test sample with sensitivity and specificity being 84.4% and 84.8%, respectively.

CONCLUSIONS

In a pediatric study population in Taiwan, the levels of exhaled LTB₄ , LTE₄ , LXA_4, and PGE₂ in asthmatic children were significantly different from those of healthy controls, and the combination of exhaled LTB₄ and LXA₄ , together with FeNO and FEV₁ , best characterized childhood asthma.

Anti-allergic Hydroxy Fatty Acids from Typhonium blumei Explored through ChemGPS-NP

Increasing prevalence of allergic diseases with an inadequate variety of treatment drives forward search for new alternative drugs. Fatty acids, abundant in nature, are regarded as important bioactive compounds and powerful nutrients playing an important role in lipid homeostasis and inflammation. Phytochemical study on Typhonium blumei Nicolson and Sivadasan (Araceae), a folk anti-cancer and anti-inflammatory medicine, yielded four oxygenated fatty acids, 12R-hydroxyoctadec-9Z,13E-dienoic acid methyl ester (1) and 10R-hydroxyoctadec-8E,12Z-dienoic acid methyl ester (2), 9R-hydroxy-10E-octadecenoic acid methyl ester (3), and 12R^*-hydroxy-10E-octadecenoic acid methyl ester (4). Isolated compounds were identified by spectroscopic methods along with GC-MS analysis. Isolated fatty acids together with a series of saturated, unsaturated and oxygenated fatty acids were evaluated for their anti-inflammatory and anti-allergic activities in vitro. Unsaturated (including docosahexaenoic and eicosapentaenoic acids) as well as hydroxylated unsaturated fatty acids exerted strong anti-inflammatory activity in superoxide anion generation (IC₅₀ 2.14-3.73 μM) and elastase release (IC₅₀ 1.26-4.57 μM) assays. On the other hand, in the anti-allergic assays, the unsaturated fatty acids were inactive, while hydroxylated fatty acids showed promising inhibitory activity in A23187- and antigen-induced degranulation assays (e.g., 9S-hydroxy-10E,12Z-octadecadienoic acid, IC₅₀ 92.4 and 49.7 μM, respectively). According to our results, the presence of a hydroxy group in the long chain did not influence the potent anti-inflammatory activity of free unsaturated acids. Nevertheless, hydroxylation of fatty acids (or their methyl esters) seems to be a key factor for the anti-allergic activity observed in the current study. Moreover, ChemGPS-NP was explored to predict the structure-activity relationship of fatty acids. The anti-allergic fatty acids formed different cluster distant from clinically used drugs. The bioactivity of T. blumei, which is historically utilized in folk medicine, might be related to the content of fatty acids and their metabolites.

15-Lipoxygenases regulate the production of chemokines in human lung macrophages

BACKGROUND AND PURPOSE

15-Lipoxygenase (15-LOX) activity is associated with inflammation and immune regulation. The objectives of the present study were to investigate the expression of 15-LOX-1 and 15-LOX-2 and evaluate the enzymes' roles in the polarization of human lung macrophages (LMs) in response to LPS and Th2 cytokines (IL-4/-13).

EXPERIMENTAL APPROACH

LMs were isolated from patients undergoing surgery for carcinoma. The cells were cultured with a 15-LOX inhibitor (PD146176 or ML351), a COX inhibitor (indomethacin), a 5-LOX inhibitor (MK886) or vehicle and then stimulated with LPS (10 ng · mL(-1)), IL-4 (10 ng · mL(-1)) or IL-13 (50 ng · mL(-1)) for 24 h. Levels of ALOX15 (15-LOX-1) and ALOX15B (15-LOX-2) transcripts were determined by real-time quantitative PCR. Immunoassays were used to measure levels of LPS-induced cytokines (TNF-α, CCL2, CCL3, CCL4, CXCL1, CXCL8 and CXCL10) and Th2 cytokine-induced chemokines (CCL13, CCL18 and CCL22) in the culture supernatant.

KEY RESULTS

Stimulation of LMs with LPS was associated with increased expression of ALOX15B, whereas stimulation with IL-4/IL-13 induced the expression of ALOX15. PD146176 and ML351 (10 μM) reduced the release of the chemokines induced by LPS and Th2 cytokines. The effects of these 15-LOX inhibitors were maintained in the presence of indomethacin and MK886. Furthermore, indomethacin revealed the inhibitory effect of PD146176 on TNF-α release.

CONCLUSIONS AND IMPLICATIONS

Inhibition of the 15-LOX pathways is involved in the down-regulation of the in vitro production of chemokines in LMs. Our results suggest that the 15-LOX pathways have a role in the pathogenesis of inflammatory lung disorders and may thus constitute a potential drug target.

12/15-Lipoxygenase metabolites of arachidonic acid activate PPARγ: a possible neuroprotective effect in ischemic brain

The enzyme 12/15-lipoxygenase (LOX) oxidizes various free fatty acids, including arachidonic acid (AA). In the brain, the principal 12/15-LOX metabolites of AA are 12(S)-HETE and 15(S)-HETE. PPARγ is a nuclear receptor whose activation is neuroprotective through its anti-inflammatory properties. In this study, we investigate the involvement of 12(S)- and 15(S)-HETE in the regulation of PPARγ following cerebral ischemia and their effects on ischemia-induced inflammatory response. We show here the increased expression of 12/15-LOX, predominantly in neurons, and elevated production of 12(S)-HETE and 15(S)-HETE in ischemic brain. The exogenous 12(S)- and 15(S)-HETE increase PPARγ protein level, nuclear translocation, and DNA-binding activity in ischemic rats, suggesting the activation of PPARγ. This effect was further confirmed by showing the increased PPARγ transcriptional activity in primary cortical neurons when incubated with 12(S)- or 15(S)-HETE. Moreover, both 12(S)- and 15(S)-HETE potently inhibited the induction of nuclear factor-κB, inducible NO synthase, and cyclooxygenase-2 in ischemic rats, and elicited neuroprotection. The reversal of the effects of 12(S)- and 15(S)-HETE on pro-inflammatory factors by PPARγ antagonist GW9662 indicated their actions were mediated via PPARγ. Thus, the induction of 12(S)- and 15(S)-HETE during brain ischemia suggests that endogenous signals of neuroprotection may be generated.

Apolipoprotein A1 potentiates lipoxin A4 synthesis and recovery of allergen-induced disrupted tight junctions in the airway epithelium

BACKGROUND

Asthma is characterized by chronic airway inflammation triggered by various allergens in the environment. Defects in the bronchial epithelial interface with the external environment are the hallmark of asthma. Apolipoprotein A-1 (ApoA1) or ApoA1 mimetics have demonstrated anti-inflammatory activity and preventive effects in mouse models.

OBJECTIVE

We investigated airway levels of ApoA1 in asthmatics and the possible role of ApoA1 in protection of the bronchial epithelium and in resolution of inflammation in cellular and animal models of asthma.

METHODS

ApoA1 levels were measured in bronchoalveolar lavage fluid (BALF) from asthmatics and healthy controls. With treatment of ApoA1, mouse model of house dust mite (HDM)-driven asthma and cultured primary bronchial epithelial cells obtained from asthmatics were examined. Tight junction (TJ) expression in the bronchial epithelial cells was assessed by using confocal microscopy and immunoblot.

RESULTS

Asthmatics showed significantly lower ApoA1 levels in bronchoalveolar lavage fluid than did healthy controls. Local ApoA1 treatment significantly decreased lung IL-25, IL-33, and thymic stromal lymphopoietin levels in HDM-challenged mice and inhibited allergen-induced production of these cytokines in cultured primary bronchial epithelial cells. ApoA1 promoted recovery of disrupted TJ proteins zonula occludens-1 and occludin in cultured primary bronchial epithelium obtained from asthmatics. ApoA1-induced increases in the TJ proteins were dependent on increased production of lipoxin A4 (LX A4).

CONCLUSIONS AND CLINICAL RELEVANCE

ApoA1 enhances resolution of allergen-induced airway inflammation through promoting recovery of damaged TJs in the bronchial epithelium. ApoA1 could be a therapeutic strategy in chronic airway inflammatory diseases that are associated with a defective epithelial barrier, including asthma.

Gamma linolenic acid exerts anti-inflammatory and anti-fibrotic effects in diabetic nephropathy

PURPOSE

This study was undertaken to investigate the effects of gamma linolenic acid (GLA) on inflammation and extracellular matrix (ECM) synthesis in mesangial and tubular epithelial cells under diabetic conditions.

MATERIALS AND METHODS

Sprague-Dawley rats were intraperitoneally injected with either a diluent [n=16, control (C)] or streptozotocin [n=16, diabetes (DM)], and eight rats each from the control and diabetic groups were treated with evening primrose oil by gavage for three months. Rat mesangial cells and NRK-52E cells were exposed to medium containing 5.6 mM glucose and 30 mM glucose (HG), with or without GLA (10 or 100 μM). Intercellular adhesion molecule-1 (ICAM-1), monocyte chemoattractant protein-1 (MCP-1), and fibronectin (FN) mRNA and protein expression levels were evaluated.

RESULTS

Twenty-four-hour urinary albumin excretion was significantly increased in DM compared to C rats, and GLA treatment significantly reduced albuminuria in DM rats. ICAM-1, MCP-1, FN mRNA and protein expression levels were significantly higher in DM than in C kidneys, and these increases were significantly abrogated by GLA treatment. In vitro, GLA significantly inhibited increases in MCP-1 mRNA expression and protein levels under high glucose conditions in HG-stimulated mesangial and tubular epithelial cells (p<0.05, respectively). ICAM-1 and FN expression showed a similar pattern to the expression of MCP-1.

CONCLUSION

GLA attenuates not only inflammation by inhibiting enhanced MCP-1 and ICAM-1 expression, but also ECM accumulation in diabetic nephropathy.

Eliminating or blocking 12/15-lipoxygenase reduces neutrophil recruitment in mouse models of acute lung injury

INTRODUCTION

Acute lung injury (ALI) is a common disease in critically ill patients with a high morbidity and mortality. 12/15-lipoxygenase (12/15-LO) is an enzyme generating 12-hydroxy-eicosatetraenoic acid (12-HETE) and 15-HETE from arachidonic acid. It has been shown that 12/15-LO is involved in the regulation of vascular permeability during ALI.

METHODS

To test whether 12/15-LO participates in leukocyte recruitment into the lung, we investigated the role of 12/15-LO in mouse models of lipopolysaccharide (LPS)-induced pulmonary inflammation and acid-induced ALI, a clinically relevant model of acute lung injury.

RESULTS

The increase in neutrophil recruitment following LPS inhalation was reduced in 12/15-LO-deficient (Alox15(-/-)) mice and in wild-type (WT) mice after the blocking of 12/15-LO with a pharmacological inhibitor. Bone marrow chimeras revealed that 12/15-LO in hematopoietic cells regulates neutrophil accumulation in the interstitial and alveolar compartments, whereas the accumulation of neutrophils in the intravascular compartment is regulated by 12/15-LO in non-hematopoietic and hematopoietic cells. Mechanistically, the increased plasma levels of the chemokine CXCL1 in Alox15(-/-) mice led to a reduced response of the neutrophil chemokine receptor CXCR2 to stimulation with CXCL1, which in turn abrogated neutrophil recruitment. Alox15(-/-) mice also showed decreased edema formation, reduced neutrophil recruitment and improved gas exchange in an acid-induced ALI model.

CONCLUSIONS

Our findings suggest that 12/15-LO modulates neutrophil recruitment into the lung by regulating chemokine/chemokine receptor homeostasis.

Leukotriene b4 and its metabolites prime the neutrophil oxidase and induce proinflammatory activation of human pulmonary microvascular endothelial cells

Leukotrienes are proinflammatory lipid mediators, derived from arachidonic acid via 5-lipoxygenase (5-LO). Leukotriene B4 (LTB4) is an effective polymorphonuclear neutrophil (PMN) chemoattractant, as well as being a major product of PMN priming. Leukotriene B4 is rapidly metabolized into products that are thought to be inactive, and little is known about the effects of LTB4 on the pulmonary endothelium. We hypothesize that LTB4 and its metabolites are effective PMN priming agents and cause proinflammatory activation of pulmonary endothelial cells. Isolated PMNs were primed (5 min, 37°C) with serial concentrations 10 to 10 M of LTB4 and its metabolites: 6-trans-LTB4, 20-OH-LTB4, and 20-COOH-LTB4, and then activated with fMLP. Primary human pulmonary microvascular endothelial cells (HMVECs) were incubated with these lipids (6 h, 37°C, 5% CO2), and intercellular adhesion molecule 1 was measured by flow cytometry. Polymorphonuclear neutrophil adhesion was measured by myeloperoxidase assays, and to ensure that these reactions were specific to the LTB4 receptors, BLT1 and BLT2 were antagonized with CP105,696 (BLT1) or silenced with siRNA (BLT1 and BLT2). Leukotriene B4 and its metabolites primed PMNs over a wide range of concentrations, depending on the specific metabolite. In addition, at high concentrations these lipids also caused increases in the surface expression of intercellular adhesion molecule 1 on HMVECs and induced HMVEC-mediated adhesion of PMNs. Silencing of BLT2 abrogated HMVEC activation, and blockade of BLT1 inhibited the observed PMN priming activity. We conclude that LTB4 and its ω-oxidation and nonenzymatic metabolites prime PMNs over a range of concentrations and activate HMVECs. These data have expanded the repertoire of causative agents in acute lung injury and postinjury multiple organ failure.

12- and 15-lipoxygenases in human carotid atherosclerotic lesions: associations with cerebrovascular symptoms

Lipoxygenase (ALOX) enzymes are implicated in both pro- and anti-atherogenic processes. The aim of this study was to investigate mRNA expression of 12- and 15-lipoxygenases (ALOX12, ALOX12B, ALOX15, ALOX15B) and the atypical ALOXE3 in human carotid atherosclerotic lesions, in relation to cerebrovascular symptoms and risk factors. The Biobank of Karolinska Endarterectomies (BiKE) collection of human carotid plaque tissue and associated clinical data was utilized (n=132). Lesion mRNA levels were analyzed by TaqMan qPCR (n=132) and microarray hybridization (n=77). Of the investigated mRNAs, only ALOX15B (15-LOX-2; epidermis-type 15-LOX) was readily detected in all plaque samples by qPCR, and thus suitable for quantitative statistical evaluation. ALOX12, ALOX12B, ALOX15 and ALOXE3 were detected with lower frequency and at lower levels, or virtually undetected. Microarray analysis confirmed ALOX15B as the most abundant 12- or 15-lipoxygenase mRNA in carotid lesions. Comparing plaques with or without attributable cerebrovascular symptoms (amaurosis fugax, transient ischemic attack, or stroke), ALOX15B mRNA levels were higher in symptomatic than asymptomatic plaques (1.31 [1.11-1.56], n=102; and 0.79 [0.55-1.15], n=30, respectively; p=0.008; mean [95% CI], arbitrary units). Multiple regression analysis confirmed symptomatic/asymptomatic status as a significant determinant of ALOX15B mRNA levels, independently of potentially confounding factors. Immunohistochemical analyses showed abundant ALOX15B expression in macrophage-rich areas of carotid lesions, and lipidomic analyses demonstrated the presence of typical ALOX15B products in plaque tissue. In summary, we observed associations between high ALOX15B expression in carotid lesions and a history of cerebrovascular symptoms. These findings suggest a link between ALOX15B and atherothrombotic events that merits further investigation.

Functional and pathological roles of the 12- and 15-lipoxygenases

The 12/15-lipoxygenase enzymes react with fatty acids producing active lipid metabolites that are involved in a number of significant disease states. The latter include type 1 and type 2 diabetes (and associated complications), cardiovascular disease, hypertension, renal disease, and the neurological conditions Alzheimer's disease and Parkinson's disease. A number of elegant studies over the last thirty years have contributed to unraveling the role that lipoxygenases play in chronic inflammation. The development of animal models with targeted gene deletions has led to a better understanding of the role that lipoxygenases play in various conditions. Selective inhibitors of the different lipoxygenase isoforms are an active area of investigation, and will be both an important research tool and a promising therapeutic target for treating a wide spectrum of human diseases.

Hematopoietic stem cell function requires 12/15-lipoxygenase-dependent fatty acid metabolism

Fatty acid metabolism governs multiple intracellular signaling pathways in many cell types, but its role in hematopoietic stem cells (HSCs) is largely unknown. Herein, we establish a critical role for 12/15-lipoxygenase (12/15-LOX)-mediated unsaturated fatty acid metabolism in HSC function. HSCs from 12/15-LOX-deficient mice are severely compromised in their capacity to reconstitute the hematopoietic compartment in competitive and serial reconstitution assays. Furthermore, we demonstrate that 12/15-LOX is required for the maintenance of long-term HSC quiescence and number. The defect in HSCs is cell-autonomous and associated with a selective reduction in 12/15-LOX-mediated generation of bioactive lipid mediators and reactive oxygen species and with a decrease in canonical Wnt signaling as measured by nuclear beta-catenin staining. These results have implications for development, aging, and transformation of the hematopoietic compartment.

Signal transduction pathways linking the activation of alveolar macrophages with the recruitment of neutrophils to lungs in chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is a major and increasing global health problem. It is predicted by the World Health Organization to become the third most common cause of death and the fifth most common cause of disability in the world by 2020. COPD is a complex inflammatory disease involving several types of inflammatory cells and multiple inflammatory mediators. Although abnormal numbers of inflammatory cells such as macrophages, dendritic cells, neutrophils, and T lymphocytes have been documented in COPD, the relationship between these cell types and the sequence of their appearance and persistence is largely unknown. Alveolar macrophages have been identified as one of the major cell types that plays a key role in orchestrating the inflammatory events associated with the pathophysiology of COPD. One of the major functions of macrophages is the secretion of chemotactic factors and this function is markedly increased on exposure to cigarette smoke (CS). This enhanced release of chemoattractants results in increased lung neutrophil infiltration, which is thought to be a key event in the development of COPD. The molecular basis for this amplified inflammatory response is not very clear, but it could be due to an alteration in signal transduction pathways within the macrophage. Based on existing literature, an attempt has been made to create a comprehensive review of the signal transduction pathways that link the activation of macrophages with the increased recruitment of neutrophils into the airways. Some of the major stimuli that activate macrophages and cause them to secrete chemotactic factors have been identified as CS, wood smoke, ozone, bacterial endotoxin, and proinflammatory cytokines such as interleukin (IL)-1beta and tumor necrosis factor (TNF)-alpha. These stimuli seem to activate mainly redox-sensitive transcription factors such as nuclear factor (NF)-kappa B and activator protein (AP)-1, both of which play a major role in the synthesis and secretion of chemotactic factors such as IL-8 and leukotriene B(4) (LTB(4)). The pathways involved in the synthesis and secretion of other factors such as macrophage chemotactic protein-1 (MCP-1) and growth-related oncogene-alpha (Gro-alpha) have also been reviewed.

Improved survival and reduced vascular permeability by eliminating or blocking 12/15-lipoxygenase in mouse models of acute lung injury (ALI)

Acute lung injury (ALI) is a prevalent disease associated with high mortality. 12/15-lipoxygenase (12/15-LO) is an enzyme producing 12-hydroxyeicosatetraenoic acid (HETE) and 15-HETE from arachidonic acid. To test whether 12/15-LO is involved in increasing vascular permeability in the lung, we investigated the role of 12/15-LO in murine models of LPS-induced pulmonary inflammation and clinically relevant acid-induced ALI. The vascular permeability increase upon LPS inhalation was abolished in Alox15(-/-) mice lacking 12/15-LO and in wild-type mice after pharmacological blockade of 12/15-LO. Alox15(-/-) mice also showed improved gas exchange, reduced permeability increase, and prolonged survival in the acid-induced ALI model. Bone marrow chimeras and reconstitution experiments revealed that 12-HETE produced by hematopoietic cells regulates vascular permeability through a CXCR2-dependent mechanism. Our findings suggest that 12/15-LO-derived 12-HETE is a key mediator of vascular permeability in acute lung injury.

Inverse temporal changes of lipoxin A4 and leukotrienes in children with Henoch-Schönlein purpura

The pathogenesis of Henoch-Schönlein purpura (HSP) is not clearly understood. It remains unclear how changes of lipoxin A(4) (LXA(4)) that acts as a "braking signal" in inflammatory process occur in patients with HSP. In this study, we determined the temporal changes of blood and urinary LXA(4), Leukotriene (LT)B(4) and urinary LTE(4) in 49 children with HSP. Inverse temporal changes between gradually increased blood and urinary LXA(4) and gradually decreased blood and urinary LTB(4) and urinary LTE(4) were found in patients with HSP. Furthermore, both 15-S-hydroxyeicosatetraenoic acid and LXA(4) inhibited the LTB(4)-induced chemotaxis of leukocytes and release of LTB(4) from leukocytes obtained from the patients in the active phase of HSP. In 22 children with HSP nephritis, concordant with the gradually increased severity of mesangial proliferation and proteinuria, the glomerular expressions of 15-lipoxygenase and the levels of urinary LXA(4) gradually decreased and the glomerular expressions of LTC(4) synthase and the urinary LTE(4) and LTB(4) gradually increased. The levels of blood and urinary LXA(4) in patients with HSP nephritis were lower than those in patients with purpura alone in early resolution of HSP. The levels of blood and urinary LTB(4) and urinary LTE(4) in the patients with HSP nephritis were higher than those in patients with purpura alone in early resolution of HSP. There was positive correlation between blood LTB(4) and serum C-reactive protein in 49 children with HSP. These data suggest that LTs may play a proinflammatory and profibrotic role in the pathogenesis of HSP, and insufficiency of LXA(4) may be responsible for the patients with HSP whose illness become more serious.

15-LOX-1 transcription suppression through the NuRD complex in colon cancer cells

15-Lipoxygenase-1 (15-LOX-1) is transcriptionally silenced in cancer cells, and its transcription reactivation (for example, through histone deacetylase inhibitors (HDACIs)) restores apoptosis to cancer cells. However, the exact mechanism underlying 15-LOX-1 transcription reactivation in cancer cells is still undefined. Therefore, we evaluated the critical mechanisms required for 15-LOX-1 transcription reactivation in colon cancer cells. Specific HDAC1 and HDAC2 inhibition activated 15-LOX-1 transcription. 15-LOX-1 transcription was repressed through transcription repressor complex recruitment in the region of -120 to -391 of the 15-LOX-1 promoter. The nucleosome remodeling and histone deacetylase (NuRD) repression complex was recruited to this region. Depsipeptide significantly reduced the recruitment of NuRD key components (for example, metastasis-associated protein 1 (MTA1) and HDAC1) to the 15-LOX-1 promoter before 15-LOX-1 transcriptional activation. Knock down of NuRD key components (for example, MTA1 and HDAC1) by small interfering RNA (siRNA) activated 15-LOX-1 transcription, as measured by luciferase reporter assays in stably transfected SW480 cells with the 15-LOX-1 promoter construct of the -391, but not the -120 region. Relative to expression in normal tissue, MTA1 expression in colorectal cancer mucosa from colorectal cancer patients was negatively related to 15-LOX-1 expression. Thus, our results show that NuRD contributes to 15-LOX-1 transcription suppression in colon cancer cells and that HDACIs can inhibit NuRD recruitment to a promoter to activate gene transcription, as in the case of 15-LOX-1.

Apoptotic human cells inhibit migration of granulocytes via release of lactoferrin

Apoptosis is a noninflammatory, programmed form of cell death. One mechanism underlying the non-phlogistic nature of the apoptosis program is the swift phagocytosis of the dying cells. How apoptotic cells attract mononuclear phagocytes and not granulocytes, the professional phagocytes that accumulate at sites of inflammation, has not been determined. Here, we show that apoptotic human cell lines of diverse lineages synthesize and secrete lactoferrin, a pleiotropic glycoprotein with known antiinflammatory properties. We further demonstrated that lactoferrin selectively inhibited migration of granulocytes but not mononuclear phagocytes, both in vitro and in vivo. Finally, we were able to attribute this antiinflammatory function of lactoferrin to its effects on granulocyte signaling pathways that regulate cell adhesion and motility. Together, our results identify lactoferrin as an antiinflammatory component of the apoptosis milieu and define what we believe to be a novel antiinflammatory property of lactoferrin: the ability to function as a negative regulator of granulocyte migration.

Genetic variation in immune signaling genes differentially expressed in asthmatic lung tissues

BACKGROUND

Eight genes in the immune signaling pathway shown to be differentially expressed in asthmatic lung biopsy specimens in a previous microarray experiment were selected as candidate genes for asthma susceptibility.

OBJECTIVE

We sought to perform an association study with these genes and asthma-related phenotypes in 3 independent Canadian familial asthma collections and 1 Australian asthma case-control study.

METHODS

Tagging single nucleotide polymorphisms were selected by using the HapMap public database (r(2) > 0.8; minor allele frequency >0.10) and genotyped with the Illumina platform. Family-based association and trend tests for asthma, atopy, airway hyperresponsiveness, and allergic asthma phenotypes were done in each sample, correcting for multiple testing.

RESULTS

Uncorrected associations with polymorphisms within 7 genes were detected with 1 or more of the phenotypes in 1 or more of the 4 populations (.001 <P < .05). After correction, the 15-lipoxygenase (15-LO) associations with airway hyperresponsiveness and allergic asthma remained significant in 2 Canadian samples (corrected P = .022 and .049, respectively), and the association of the CD14 antigen with asthma remained significant in 1 Canadian sample (corrected P = .042). In both cases a protective effect of the minor alleles was observed.

CONCLUSION

Expression profiling studies are a useful way to identify candidate genes for asthma because this approach has led to the first report of an association with 15-LO in 2 independent populations. Because 15-LO is involved in anti-inflammatory processes, further functional and clinical investigation of the role of this biologic pathway in asthma is warranted.

The two faces of the 15-lipoxygenase in atherosclerosis

Chronic inflammation plays a major role in atherogenesis and understanding the role of inflammation and its resolution will offer novel approaches to interfere with atherogenesis. The 15(S)-lipoxygenase (15-LOX) plays a janus-role in inflammation with pro-inflammatory and anti-inflammatory effects in cell cultures and primary cells and even opposite effects on atherosclerosis in two different animal species. There is evidence for a pro-atherosclerotic effect of 15-LOX including the direct contribution to LDL oxidation and to the recruitment of monocytes to the vessel wall, its role in angiotensin II mediated mechanisms and in vascular smooth muscle cell proliferation. In contrast to the pro-atherosclerotic effects of 15-LOX, there is also a broad line of evidence that 15-LOX metabolites of arachidonic and linoleic acid have anti-inflammatory effects. The 15-LOX arachidonic acid metabolite 15-HETE inhibits superoxide production and polymorphonuclear neutrophil (PMN) migration across cytokine-activated endothelium and can be further metabolized to the anti-inflammatory lipoxins. These promote vasorelaxation in the aorta and counteract the action of most other pro-inflammatory factors like leukotrienes and prostanoids. Anti-atherogenic properties are also reported for the linoleic acid oxidation product 13-HODE through inhibition of adhesion of several blood cells to the endothelium. Furthermore, there is evidence that 15-LOX is involved in the metabolism of the long-chain omega-3 fatty acid docosahexaenoic acid (DHA) leading to a family of anti-inflammatory resolvins and protectins. From these cell culture and animal studies the role of the 15-LOX in human atherosclerosis cannot be predicted. However, recent genetic studies characterized the 15-LOX haplotypes in Caucasians and discovered a functional polymorphism in the human 15-LOX promoter. This will now allow large studies to investigate an association of 15-LOX with coronary artery disease and to answer the question whether 15-LOX is pro- or anti-atherogenic in humans.

Arachidonic acid cascade in endothelial pathobiology

Arachidonic acid (AA) and its metabolites (eicosanoids) represent powerful mediators, used by organisms to induce and suppress inflammation as a part of the innate response to disturbances. Several cell types participate in the synthesis and release of AA metabolites, while many cell types represent the targets for eicosanoid action. Endothelial cells (EC), forming a semi-permeable barrier between the interior space of blood vessels and underlying tissues, are of particular importance for the development of inflammation, since endothelium controls such diverse processes as vascular tone, homeostasis, adhesion of platelets and leukocytes to the vascular wall, and permeability of the vascular wall for cells and fluids. Proliferation and migration of endothelial cells contribute significantly to new vessel development (angiogenesis). This review discusses endothelial-specific synthesis and action of arachidonic acid derivatives with a particular focus on the mechanisms of signal transduction and associated intracellular protein targets.

Lipoxins: endogenous regulators of inflammation

Over the past decade, compelling in vivo and in vitro studies have highlighted lipoxins (LXs) and aspirin-triggered LXs (ATLs) as endogenously produced anti-inflammatory eicosanoids. LXs and ATLs elicit distinct anti-inflammatory and proresolution bioactions that include inhibition of leukocyte-mediated injury, stimulation of macrophage clearance of apoptotic neutrophils, repression of proinflammatory cytokine production, modulation of cytokine-stimulated metalloproteinase activity, and inhibition of cell proliferation and migration. An overview of recent advances in LX physiology is provided, with particular emphasis on the cellular and molecular processes involved. These data coupled with in vivo models of inflammatory diseases suggest that LX bioactions may be amenable to pharmacological mimicry for therapeutic gain.

Molecular dynamics study of a gelsolin-derived peptide binding to a lipid bilayer containing phosphatidylinositol 4,5-bisphosphate

Gelsolin is an actin-severing protein whose action is initiated by Ca(2+) and inhibited by binding to phosphorylated inositol lipid or phosphoinositides. The regions of gelsolin responsible for phosphoinositide binding are comprised of residues 150-169 (G150-169) and 135-142 (G135-142). The corresponding peptides possess similar binding potency as native gelsolin. Their common feature is the presence of arginine and lysine residues that can bind to negatively charged phosphate groups of phosphoinositides. In this work the binding of the G150-169 peptide to a phosphatidylinositol 4,5-bisphosphate (PIP2) cluster in a lipid membrane model was investigated by molecular dynamics calculations (MD) with the AMBER 4.1 force field, taking into account explicit solvent molecules. Initially the structure of G150-169 was simulated by using the electrostatically driven Monte Carlo (EDMC) and MD methods, and the resulting structure agreed within 3.7 A backbone-atom root mean square deviation with the corresponding experimentally derived structure (PDB code: 1SOL). Using this model for the peptide, a subsequent MD simulation of G150-169 in a periodic box containing a model of dimyristoyl-phosphatidylcholine (DMPC) lipids with a cluster of four PIP2 molecules was carried out. During the simulation G150-169 interacted strongly with PIP2 molecules, initially by formation of salt bridges between its N-terminal basic groups and the phosphate groups of PIP2, followed by formation of hydrophobic bonds between the hydrophobic side chains of the peptide and the fatty acid tail of the lipid. As a result of the formation of hydrophobic bonds, the PIP2 molecules were pulled out from the lipid bilayer. This mode of binding differs from those of other PIP2-binding protein motifs such as PH domains that interact solely with the hydrophilic head group of PIP2. These results suggest that dissociation of gelsolin from actin by PIP2 lipids may involve entering of the PIP2 molecules to the gelsolin-actin interface, thereby weakening the interactions between these proteins.

Mammalian arachidonate 15-lipoxygenases structure, function, and biological implications

Lipoxygenases (LOXs) constitute a heterogeneous family of lipid peroxidizing enzymes capable of oxygenating polyunsaturated fatty acids to their corresponding hydroperoxy derivatives. In mammals, LOXs are classified with respect to their positional specificity of arachidonic acid oxygenation into 5-, 8-, 12-, and 15-LOXs. Arachidonate 15-LOXs may be sub-classified into a reticulocyte-type (type-1) and an epidermis-type (type-2) enzyme. Since the leukocyte-type 12-LOXs are very similar to the reticulocyte-type 15-LOXs, these enzymes are designated 12/15-LOXs. Several LOX isoforms, in particular the reticulocyte-type 15-LOX and the human 5-LOX, are well characterized with respect to their structural and functional properties On the other hand, the biological role of most LOX-isozymes including the reticulocyte-type 15-LOC is far from clear. This review is intended to summarize the recent developments in 15-LOX research with particular emphasis to molecular enzymology and regulation of gene expression. In addition, the major hypotheses on the physiological and patho-physiological roles of 15-LOXs will be discussed briefly.

Induction of biologically active antineutrophil cytoplasmic antibodies by immunization with human apoptotic polymorphonuclear leukocytes

Translocation of intracellular components to the cell surface during the priming or apoptosis of polymorphonuclear leukocytes (PMN) is an important mechanism for interaction of antineutrophil cytoplasmic antibodies (ANCA) with these antigens. To test the capacity of apoptotic PMN to trigger production of ANCA, six groups of mice were immunized with either live or apoptotic lymphocytes, or with live, apoptotic, formalin-fixed, or lysed PMN. Mice immunized with both live and apoptotic neutrophils developed high titers of antibodies which gave a granular cytoplasmic immunofluorescent pattern. These antibodies were specific for lactoferrin and myeloperoxidase. Following a second intravenous infusion of apoptotic PMNs, mice developed anti-PR3 antibodies. Vasculitis lesions were not found in mice which developed ANCA. The ANCA-containing IgG fraction induced superoxide production by human PMNs. These results support the hypothesis that neutrophil-specific antigens presented on the cell membranes of apoptotic PMN may induce ANCA in the proper conditions.

Monohydroxylated fatty acid content in peripheral blood mononuclear cells and immune status of people at long times after the Chernobyl accident

The monohydroxylated fatty acid content of peripheral blood mononuclear cells from 23 cleanup workers and 16 unexposed individuals was studied in relation to their immune status after the Chernobyl accident. Men with absorbed doses below 0.32 Gy showed higher levels of free and esterified 12-hydroxyeicosatetraenoic acid (12-HETE) than unexposed men, whereas 15-HETE and the 17-hydroxy derivative of C22 fatty acid (17-OH 22), either free or esterified in phospholipids, were increased in a dose-dependent manner. The percentage of CD4-positive cells was also increased significantly in heavily irradiated men, whereas the percentage of CD8-positive cells tended to decrease with dose. Furthermore, the absolute count of CD4-positive cells was correlated positively with the amount of esterified 15-HETE in the phospholipid fraction of the mononuclear cells and with the total 15-HETE. These results show for the first time that the accumulation of autoxidized/lipoxygenase products of polyunsaturated fatty acids in the mononuclear cells of irradiated individuals was associated with immune imbalance. This may be the basis for certain late effects of radiation such as autoimmune disorders, somatic and neoplastic diseases, and early aging.

Persistent wheezing in very young children is associated with lower respiratory inflammation

Despite advances in understanding the pathophysiology of asthma, morbidity and mortality in pediatrics continue to rise. Little is known about the initiation and chronicity of inflammation resulting in asthma in this young population. We evaluated 20 "wheezing" children (WC) (median age 14.9 mo) with a minimum of two episodes of wheezing or prolonged wheezing > or = 2 mo in a 6-mo period with bronchoscopy and bronchoalveolar lavage (BAL). Comparisons were made with six normal controls (NC) (median age 23.3 mo) undergoing general anesthesia for elective surgery. BAL fluid cell counts and differentials were determined. The eicosanoids, leukotriene (LT) B(4), LTE(4), prostaglandin (PG)E(2), and 15-hydroxyeicosatetraenoic acid (HETE) and the mast cell mediators, beta-tryptase and PGD(2), were evaluated by enzyme immunoassay (EIA). WC had significant elevations in total BAL cells/ml (p = 0.01), as well as, lymphocytes (LYMPH, p = 0.007), macrophages/monocytes (M&M, p = 0.02), polymorphonuclear cells (PMN, p = 0.02), epithelial cells (EPI, p = 0.03), and eosinophils (EOS, p = 0.04) compared with NC. Levels of PGE(2) (p = 0.0005), 15-HETE (p = 0.002), LTE(4) (p = 0.04), and LTB(4) (p = 0.05) were also increased in WC compared with NC, whereas PGD(2) and beta-tryptase were not. This study confirms that inflammation is present in the airways of very young WC and may differ from patterns seen in adults with asthma.

16(R)-hydroxy-5,8,11,14-eicosatetraenoic acid, a new arachidonate metabolite in human polymorphonuclear leukocytes

Intact human polymorphonuclear leukocytes (PMNL) incubated with substimulatory amounts of arachidonic acid in the absence of a calcium ionophore formed four metabolites that were isolated by reverse-phase HPLC and characterized structurally by GC/MS. A major metabolite eluting as the most abundant peak of radioactivity lacked UV chromophores above 215 nm, and its formation was sensitive to 2-diethylaminoethyl-2,2-diphenylvalerate hydrochloride (SKF525A) but not 3-amino-1-[m(trifluoromethyl)phenyl]-2-pyrazoline (BW755C), suggesting that it was likely to be a product of cytochrome P450. The GC/MS analysis revealed the presence of two components: 20-hydroxy-5,8,11,14-eicosatetraenoic acid (20-HETE) and 16-hydroxy-5,8,11,14-eicosatetraenoic acid (16-HETE) in an approximate ratio of 4:1. The minor metabolites were identified as 15-HETE and 5-HETE. Although 20-HETE has been observed previously as a product of arachidonic acid metabolism in PMNL, the occurrence of 16-HETE was a novel finding. The stereochemistry of the hydroxyl group in PMNL-derived 16-HETE was established by analysis of 1-pentafluorobenzyl-16-naphthoyl derivatives on a chiral-phase chromatographic column and comparison with authentic synthetic stereoisomers. The PMNL-derived radioactive metabolite co-eluted with the synthetic 16(R)-HETE stereoisomer. Analysis of the total lipid extracts from intact PMNL followed by mild alkaline hydrolysis resulted in detectable amounts of 16-HETE (108+/-26 pg/10(8) cells) and 20-HETE (341+/-69 pg/10(8) cells), which suggested that these HETEs were formed from endogenous arachidonic acid and esterified within PMNL lipids. Thus, in contrast to calcium ionophore-stimulated neutrophils that generate large amounts of 5-lipoxygenase products, the intact PMNL generate 20-HETE and 16(R)-HETE via a cytochrome P450 omega- and omega-4 oxygenase(s).

Transfection of rat kidney with human 15-lipoxygenase suppresses inflammation and preserves function in experimental glomerulonephritis

The human 15-lipoxygenase (15-LO) gene was transfected into rat kidneys in vivo via intra-renal arterial injection. Three days later, acute (passive) or accelerated forms of antiglomerular basement membrane antibody-mediated glomerulonephritis were induced in transfected and nontransfected or sham-transfected controls. Studies of glomerular functions (filtration and protein excretion) and ex vivo glomerular leukotriene B(4) biosynthesis at 3 hr, and up to 4 days, after induction of nephritis revealed preservation or normalization of these parameters in transfected kidneys that expressed human 15-LO mRNA and mature protein, but not in contralateral control kidneys or sham-transfected animals. The results provide in vivo-derived data supporting a direct anti-inflammatory role for 15-LO during immune-mediated tissue injury.

15-HETE-substituted diglycerides selectively regulate PKC isotypes in human tracheal epithelial cells

Human tracheal epithelial (TE) cells selectively incorporate their major lipoxygenase product, 15-hydroxyeicosatetraenoic acid (15-HETE), into the sn-2 position of phosphatidylinositol (PI) (S. E. Alpert and R. W. Walenga. Am. J. Respir. Cell Mol. Biol. 8: 273-281, 1993). Here we investigated whether 15-HETE-PI is a substrate for receptor-mediated generation of 15-HETE-substituted diglycerides (DGs) and whether these 15-HETE-DGs directly activate and/or alter conventional diacylglycerol-induced activation of protein kinase C (PKC) isotypes in these cells. Primary human TE monolayers incubated with 0.5 microM 15-[3H]-HETE or 15-[14C]HETE for 1-2 h were stimulated with 1 nM to 1 microM platelet-activating factor (PAF) for 30 s to 6 min, and the radiolabel in the medium, cellular phospholipids, and neutral lipids was assessed by high-performance liquid and thin-layer chromatography. PAF mobilized radiolabel from PI in a dose-dependent manner (22 +/- 5% decrease after 1 microM PAF) without a concomitant release of free intra- or extracellular 15-HETE. 14C-labeled DGs were present in unstimulated TE monolayers incubated with 15-[14C]HETE, and the major 14C band, identified as sn-1,2-15-[14C]HETE-DG, increased transiently in response to PAF. Western blots of freshly isolated and cultured human TE cells revealed PKC isotypes alpha, betaI, betaII, delta, epsilon, and zeta. In vitro, cell-generated sn-1, 2-15-[14C]HETE-DG selectively activated immunoprecipitated PKC-alpha and inhibited diacylglycerol-induced activation of PKC-alpha, -delta, -betaI, and -betaII. Our observations indicate that 15-HETE-DGs can modulate the activity of PKC isotypes in human TE cells and suggest an intracellular autocrine role for 15-HETE in human airway epithelia.

Novel membrane target proteins for lipoxygenase-derived mono(S)hydroxy fatty acids

Hydroxyeicosatetraenoic acids (HETEs) and hydroxyoctadecadienoic acids (HODEs) are major bioactive lipids formed via the lipoxygenase oxygenation of arachidonic and linoleic acid, respectively. These metabolites appear to be involved in various cellular actions including cell proliferation, migration and regulation of enzyme activities such as phospholipases and kinases. In view of the diversity of biological effects of these hydroxy fatty acids, it seems likely that multiple mechanisms are involved. Previous reports showed that 15(S)-HETE inhibited the 5-lipoxygenase in rat basophilic leukemia (RBL-1) cell homogenates and established the presence of specific cellular HETE binding sites in these and other cells. The present study used 15(S)-HETE biotin hydrazide and 15(S)-HETE biotin pentyl amide as probes to identify membrane target proteins present in RBL-1 cells that specifically interact with HETEs and HODEs. Two membrane-associated proteins, with apparent molecular weights of 43 and 58 kDa, were identified that specifically interact with these probes and competition experiments indicated that 13(S)-HODE and 15(S)-HETE were the most effective competitors for the hydrazide probe, followed in decreasing effectiveness by 5(S)-HETE, arachidonic acid, 15(R)-HETE, stearic acid and 12(S)-HHT, a cyclooxygenase product. The two proteins were isolated and microsequencing analysis established their identities as actin and the alpha-subunit of mitochondrial ATP synthase, respectively. In vitro binding studies confirmed that purified actin is a potential 15-HETE binding protein. Subcellular cytosolic fractions exhibited fewer protein-probe complexes than membrane fractions. The association of HETEs and HODEs with these cytoskeletal and mitochondrial proteins, respectively, represents a new development in the potential actions of these hydroxy fatty acids.

Novel insights into structure and function of MRP8 (S100A8) and MRP14 (S100A9)

The two migration inhibitory factor- (MIF)-related protein-8 (MRP8; S100A8) and MRP14 (S100A9) are two calcium-binding proteins of the S100 family. These proteins are expressed during myeloid differentiation, are abundant in granulocytes and monocytes, and form a heterodimeric complex in a Ca2+-dependent manner. Phagocytes expressing MRP8 and MRP14 belong to the early infiltrating cells and dominate acute inflammatory lesions. In addition, elevated serum levels of MRP8 and MRP14 have been found in patients suffering from a number of inflammatory disorders including cystic fibrosis, rheumatoid arthritis, and chronic bronchitis, suggesting conceivable extracellular roles for these proteins. Although a number of possible functions for MRP8/14 have been proposed, the biological function still remains unclear. This review addresses recent developments regarding the MRP14-mediated promotion of leukocyte-endothelial cell-interactions and the characterization of MRP8/14 heterodimers as a fatty acid binding protein complex. In view of the current knowledge, the authors will hypothesize that MRP8 and MRP14 play an important role in leukocyte trafficking, but do not affect neutrophil effector functions.

Interleukin-4 and -13 Induce Upregulation of the Murine Macrophage 12/15-Lipoxygenase Activity: Evidence for the Involvement of Transcription Factor STAT6

When human monocytes or alveolar macrophages are cultured in the presence of interleukin (IL)-4 or IL-13, the expression of the reticulocyte-type 15-lipoxygenase is induced. In mice a 15-lipoxygenase is not expressed, but a leukocyte-type 12-lipoxygenase is present in peritoneal macrophages. To investigate whether both lipoxygenase isoforms exhibit a similar regulatory response toward cytokine stimulation, we studied the regulation of the leukocyte-type 12-lipoxygenase of murine peritoneal macrophages by interleukins and found that the activity of this enzyme is upregulated in a dose-dependent manner when the cells were cultured in the presence of the IL-4 or IL-13 but not by IL-10. When peripheral murine monocytes that do not express the lipoxygenase were treated with IL-4 expression of 12/15-lipoxygenase mRNA was induced, suggesting pretranslational control mechanisms. In contrast, no upregulation of the lipoxygenase activity was observed when the macrophages were prepared from homozygous STAT6-deficient mice. Peritoneal macrophages of transgenic mice that systemically overexpress IL-4 exhibited a threefold to fourfold higher 12-lipoxygenase activity than cells prepared from control animals. A similar upregulation of 12-lipoxygenase activity was detected in heart, spleen, and lung of the transgenic animals. Moreover, a strong induction of the enzyme was observed in red cells during experimental anemia in mice. The data presented here indicate that (1) the 12-lipoxygenase activity of murine macrophages is upregulated in vitro and in vivo by IL-4 and/or IL-13, (2) this upregulation requires expression of the transcription factor STAT6, and (3) the constitutive expression of the enzyme appears to be STAT6 independent. The cytokine-dependent upregulation of the murine macrophage 12-lipoxygenase and its induction during experimental anemia suggests its close relatedness with the human reticulocyte-type 15-lipoxygenase despite their differences in the positional specificity of arachidonic acid oxygenation.

Interleukin-4 and -13 Induce Upregulation of the Murine Macrophage 12/15-Lipoxygenase Activity: Evidence for the Involvement of Transcription Factor STAT6

When human monocytes or alveolar macrophages are cultured in the presence of interleukin (IL)-4 or IL-13, the expression of the reticulocyte-type 15-lipoxygenase is induced. In mice a 15-lipoxygenase is not expressed, but a leukocyte-type 12-lipoxygenase is present in peritoneal macrophages. To investigate whether both lipoxygenase isoforms exhibit a similar regulatory response toward cytokine stimulation, we studied the regulation of the leukocyte-type 12-lipoxygenase of murine peritoneal macrophages by interleukins and found that the activity of this enzyme is upregulated in a dose-dependent manner when the cells were cultured in the presence of the IL-4 or IL-13 but not by IL-10. When peripheral murine monocytes that do not express the lipoxygenase were treated with IL-4 expression of 12/15-lipoxygenase mRNA was induced, suggesting pretranslational control mechanisms. In contrast, no upregulation of the lipoxygenase activity was observed when the macrophages were prepared from homozygous STAT6-deficient mice. Peritoneal macrophages of transgenic mice that systemically overexpress IL-4 exhibited a threefold to fourfold higher 12-lipoxygenase activity than cells prepared from control animals. A similar upregulation of 12-lipoxygenase activity was detected in heart, spleen, and lung of the transgenic animals. Moreover, a strong induction of the enzyme was observed in red cells during experimental anemia in mice. The data presented here indicate that (1) the 12-lipoxygenase activity of murine macrophages is upregulated in vitro and in vivo by IL-4 and/or IL-13, (2) this upregulation requires expression of the transcription factor STAT6, and (3) the constitutive expression of the enzyme appears to be STAT6 independent. The cytokine-dependent upregulation of the murine macrophage 12-lipoxygenase and its induction during experimental anemia suggests its close relatedness with the human reticulocyte-type 15-lipoxygenase despite their differences in the positional specificity of arachidonic acid oxygenation.

Apoptosis of endothelial cells is associated with paracrine induction of adhesion molecules: evidence for an interleukin-1beta-dependent paracrine loop

Monocytic infiltration of the vessel wall is a hallmark of injury in a variety of vascular diseases. In the present study, we explored the relationship between endothelial apoptosis and hyperadhesiveness for monocytic cells. Apoptosis of human umbilical vein endothelial cells (HUVECs) was induced by either growth factor deprivation (GFD) for 24 hours or by incubation with mitomycin C (MMC) at 0.01 mg/ml for 24 hours and confirmed by light microscopy and DNA laddering. In parallel assessments of cell-cell adhesion, GFD and MMC induced hyperadhesiveness of HUVECs for the THP-1 monocytic cell line. Hyperadhesiveness developed in association with induction of intercellular adhesion molecule (ICAM)-1 and vascular cell adhesion molecule (VCAM)-1 on HUVECs and was attenuated by monoclonal antibodies directed against these ligands. Culture medium conditioned by apoptotic HUVECs up-regulated the expression of adhesion molecules on normal HUVECs, suggesting that paracrine factors in the apoptotic milieu led to induction of adhesion molecules. Interleukin (IL)-1beta was implicated as a putative mediator in this setting because 1) exogenous IL-1beta up-regulates ICAM-1 and VCAM-1 with kinetics similar to those noted during endothelial cell apoptosis, 2) endothelial apoptosis was associated with increased expression of IL-1beta converting enzyme, and 3) the adhesion-promoting actions of GFD and MMC were attenuated by an anti-IL-1beta antibody.

Altered responses of human macrophages to lipopolysaccharide by hydroperoxy eicosatetraenoic acid, hydroxy eicosatetraenoic acid, and arachidonic acid. Inhibition of tumor necrosis factor production

The regulation of allergic and autoimmune inflammatory reactions by polyunsaturated fatty acids and their metabolic products (eicosanoids) continues to be of major interest. Our data demonstrate that arachidonic acid 5,8,11,14-eicosatetraenoic acid (20:4n-6) and its hydroxylated derivatives 15(s)-hydroxy-5,8,11,13-eicosatetraenoic acid (15-HETE) and 15(s)-hydroperoxy-5,8,11,13-eicosatetraenoic acid (15-HPETE) regulate agonist-induced tumor necrosis factor alpha (TNF) production, a cytokine that plays a role in inflammatory diseases. Although 20:4n-6 and 15-HETE caused a reduction in production of TNF in mononuclear leukocytes stimulated with phytohaemagglutinin, pokeweed mitogen, concanavalin A, and Staphylococcus aureus, 15-HPETE was far more active. 15-HPETE was also found to dramatically depress the ability of bacterial lipopolysaccharide to induce TNF production in monocytes and the monocytic cell line Mono Mac 6. These fatty acids depressed the expression of TNF mRNA in Mono Mac 6 cells stimulated with LPS; 15-HPETE was fivefold more active than 20:4n-6 and 15-HETE. While 15-HPETE treatment neither affected LPS binding to Mono Mac 6 cells nor caused a decrease in CD14 expression, the fatty acid significantly reduced the LPS-induced translocation of PKC (translocation of alpha, betaI, betaII, and epsilon isozymes), suggesting that 15-HPETE acts by abrogating the early signal transduction events. The findings identify another molecule that could form the basis for development of antiinflammatory pharmaceuticals.

Inhibition of stimulus-induced endothelial cell intercellular adhesion molecule-1, E-selectin, and vascular cellular adhesion molecule-1 expression by arachidonic acid and its hydroxy and hydroperoxy derivatives

Localized adhesion of peripheral blood leukocytes to the endothelial lining is essential for their exit from the blood under both physiological and pathological conditions. The establishment, development, and resolution of the inflammatory response is regulated by an array of mediators, many of which remain to be categorized. These include arachidonic acid (20:4n-6) and its hydroperoxy (HPETE) and hydroxy (HETE) derivatives, which are released during inflammation. The data show that human umbilical vein endothelial cells, pretreated with these fatty acids, have a reduced ability to be stimulated by tumor necrosis factor-alpha (TNF-alpha) for enhanced neutrophil and monocyte adhesion; the order of inhibitory activity being 15-HPETE > 15-HETE > 20:4 (n-6). This fatty acid-induced inhibitory activity was reflected in the ability of the mediators to decrease the TNF-alpha-induced expression of the following endothelial adhesion molecules: intercellular adhesion molecule-1 (ICAM-1), E-selectin, and vascular cell adhesion molecule-1 (VCAM-1), measured by both enzyme-linked immunosorbent assay and flow cytometric analysis. TNF-alpha-induced increased expression of ICAM-1, E-selectin, and VCAM-1 mRNA was significantly depressed by 15-HPETE. Constitutively expressed ICAM-1 and ICAM-1 mRNAs were unchanged by the fatty acids. The saturated fatty acid 20:0 and the methyl ester of 20:4(n-6) had no inhibitory activity. The binding of TNF-alpha to its receptors was not altered by these fatty acids. The fatty acids also inhibited the expression of ICAM-1 and E-selectin induced by phorbol 12-myristate 13-acetate, showing that inhibition occurred at a post-TNF-alpha receptor binding level. The 15-HPETE was found to inhibit the TNF-alpha-induced increase in adhesion molecule expression in the early stage of the incubation, but expression returned to normal after 18 hours. An effect of 15-HPETE on the early cell signaling system was demonstrated by the ability of this fatty acid to inhibit agonist-induced protein kinase C translocation.

Antineutrophil cytoplasmic autoantibodies interact with primary granule constituents on the surface of apoptotic neutrophils in the absence of neutrophil priming

The pathogenic role of antineutrophil cytoplasmic autoantibodies (ANCA) remains controversial because of the difficulty in explaining how extracellular ANCA can interact with intracellular primary granule constituents. It has been postulated that cytokine priming of neutrophils (PMN), as may occur during a prodromal infection, is an important trigger for mobilization of granules to the cell surface, where they may interact with ANCA. We show by electron microscopy that apoptosis of unprimed PMN is also associated with the translocation of cytoplasmic granules to the cell surface and alignment just beneath an intact cell membrane. Immunofluorescent microscopy and FACS analysis demonstrate reactivity of ANCA-positive sera and antimyeloperoxidase antibodies with apoptotic PMN, but not with viable PMN. Moreover, we show that apoptotic PMN may be divided into two subsets, based on the presence or absence of granular translocation, and that surface immunogold labeling of myeloperoxidase occurs only in the subset of PMN showing translocation. These results provide a novel mechanism that is independent of priming, by which ANCA may gain access to PMN granule components during ANCA-associated vasculitis.

The pathogenesis of chronic obstructive pulmonary disease of horses

Present evidence suggests that chronic obstructive pulmonary disease (COPD) of horses is a delayed hypersensitivity response to inhaled antigens, particularly the thermophilic moulds and actinomycetes that grow in damp hay. Within several hours of exposing COPD-susceptible horses to such hay, neutrophils invade the lung and accumulate in the lumens of airways, particularly bronchioles. The inflammatory response is accompanied by increased levels of histamine in bronchoalveolar lavage fluid, increased plasma levels of the inflammatory mediators thromboxane and 15-hydroxyeicosatetraenoic acid (15-HETE), and a decrease in the production of prostaglandin (PG) E2 by the airway mucosa. During acute exacerbations of COPD, airways exhibit nonspecific hyperresponsiveness and become obstructed as a result of bronchospasm and the accumulation of mucus and exudates. Bronchospasm is due largely to activation of smooth muscle muscarinic receptors by acetylcholine (ACh). Because the in vitro response of smooth muscle to ACh is unaltered, the increase in airway smooth muscle tone is probably a result of activation of airway reflexes by inflammatory mediators and decreases in inhibitory mechanisms such as the intrapulmonary nonadrenergic noncholinergic nervous system and the production of PGE2 in affected horses. The diffuse airway obstruction leads to uneven distribution of ventilation, ventilation/perfusion mismatching, and hypoxaemia. As a result of the increased respiratory drive caused by hypoxaemia and the presence of airway obstruction, horses adopt a characteristic breathing strategy in which very high peak flows at the start of exhalation rapidly diminish as exhalation proceeds.