Concentrations Of Leukotriene B4 Research Articles

Stepwise phosphorylation of BLT1 defines complex assemblies with β-arrestin serving distinct functions.

G protein-coupled receptors (GPCRs) utilize complex cellular systems to respond to diverse ligand concentrations. By taking BLT1, a GPCR for leukotriene B4 (LTB4 ), as a model, our previous work elucidated that this system functions through the modulation of phosphorylation status on two specific residues: Thr308 and Ser310 . Ser310 phosphorylation occurs at a lower LTB4 concentration than Thr308 , leading to a shift in ligand affinity from a high-to-low state. However, the implications of BLT1 phosphorylation in signal transduction processes or the underlying mechanisms have remained unclear. Here, we identify the sequential BLT1-engaged conformations of β-arrestin and subsequent alterations in signal transduction. Stimulation of the high-affinity BLT1 with LTB4 induces phosphorylation at Ser310 via the ERK1/2-GRK pathway, resulting in a β-arrestin-bound low-affinity state. This configuration, referred to as the "low-LTB4 -induced complex," necessitates the finger loop region and the phosphoinositide-binding motif of β-arrestins to interact with BLT1 and deactivates the ERK1/2 signaling. Under high LTB4 concentrations, the low-affinity BLT1 again binds to the ligand and triggers the generation of the low-LTB4 -induced complex into a different form termed "high-LTB4 -induced complex." This change is propelled by The308 -phosphorylation-dependent basal phosphorylation by PKCs. Within the high-LTB4 -induced complex, β-arrestin adapts a unique configuration that involves additional N domain interaction to the low-affinity BLT1 and stimulates the PI3K/AKT pathway. We propose that the stepwise phosphorylation of BLT1 defines the formation of complex assemblies, wherein β-arrestins perform distinct functions.

NLRP3 is essential for neutrophil polarization and chemotaxis in response to leukotriene B4 gradient

Neutrophil recruitment to sites of infection and inflammation is an essential process in the early innate immune response. Upon activation, a subset of neutrophils rapidly assembles the multiprotein complex known as the NLRP3 inflammasome. The NLRP3 inflammasome forms at the microtubule organizing center, which promotes the formation of interleukin (IL)-1β and IL-18, essential cytokines in the immune response. We recently showed that mice deficient in NLRP3 (NLRP3-/-) have reduced neutrophil recruitment to the peritoneum in a model of thioglycolate-induced peritonitis. Here, we tested the hypothesis that this diminished recruitment could be, in part, the result of defects in neutrophil chemotaxis. We find that NLRP3-/- neutrophils show loss of cell polarization, as well as reduced directionality and velocity of migration toward increasing concentrations of leukotriene B4 (LTB4) in a chemotaxis assay in vitro, which was confirmed through intravital microscopy of neutrophil migration toward a laser-induced burn injury of the liver. Furthermore, pharmacologically blocking NLRP3 inflammasome assembly with MCC950 in vitro reduced directionality but preserved nondirectional movement, indicating that inflammasome assembly is specifically required for polarization and directional chemotaxis, but not cell motility per se. In support of this, pharmacological breakdown of the microtubule cytoskeleton via nocodazole treatment induced cell polarization and restored nondirectional cell migration in NLRP3-deficient neutrophils in the LTB4 gradient. Therefore, NLRP3 inflammasome assembly is required for establishment of cell polarity to guide the directional chemotactic migration of neutrophils.

Elevated leukotriene B4 and 8-isoprostane in exhaled breath condensate from preterm-born infants

BackgroundInflammation and oxidative stress play a key role in the development of bronchopulmonary dysplasia (BPD), possibly contributing to persistent respiratory morbidity after preterm birth. We aimed to assess if inflammatory markers were elevated in exhaled breath condensate (EBC) of infants born very prematurely (< 32 weeks gestation) at 12–16 corrected months of age, and if increased levels were associated with BPD diagnosis and respiratory morbidity.MethodsEBC samples and respiratory questionnaires were collected from 15 term-born infants and 33 preterm-born infants, 12 with a neonatal BPD diagnosis. EBC samples were analysed for leukotriene B4 (inflammation) and 8-isoprostane (oxidative stress) concentrations using enzyme-linked immune-assays. Differences between groups were analysed by Kruskal-Wallis Test with post-hoc comparisons, independent samples t-test or Mann-Whitney U test depending on normality of the data.ResultsLeukotriene B4 and 8-isoprostane levels were elevated in exhaled breath condensate of preterm-born infants compared to those born at term (mean difference [95% CI]; 1.52 [0.45, 2.59], p = 0.02; 0.77 [0.52, 1.02], p < 0.001, respectively). Leukotriene B4 and 8-isoprostane levels were independent of BPD diagnosis and respiratory morbidity over the first year of life.ConclusionsInfants born very prematurely exhibit elevated markers of airway neutrophilic inflammation and oxidative stress beyond the first year of life, regardless of a neonatal diagnosis of chronic lung disease or respiratory morbidity during infancy. These findings may have implications for future lung health.Trial RegistrationN/A.

Peripheral blood leukotriene B4 and E4 as biomarkers in Alzheimer’s disease

AbstractBackgroundWe showed recently that use of leukotriene receptor antagonists, typically used in asthma therapy, was associated with preserved executive function among people with Alzheimer’s disease (AD) dementia. The aim of this study was to determine if leukotriene B4 (LTB4) and E4 (LTE4) would be associated with longitudinal changes in cognitive performance and cerebrovascular disease markers in people with AD.MethodParticipants with clinical AD or mild cognitive impairment were identified from the Ontario Neurodegenerative Disease Research Initiative. LTB4 and LTE4 were extracted from fasting serum and quantified using ultra‐high performance liquid chromatography‐tandem mass spectrometry (UPLC‐MS/MS). Concentrations below the limit of detection were imputed using quantile regression imputation of left‐censored data. Cognition was assessed using composite scores for executive function (Trails Making Test B, Symbol Digit Modalities Test, Stroop switching task, and verbal fluency) and memory (Rey Auditory Verbal Learning Test and Brief Visuospatial Memory Test). White matter hyperintensities (WMH), lacunes, and perivascular spaces (PVS) were quantified using T2‐weighted structural magnetic resonance imaging (MRI). Longitudinal associations between baseline LTB4 or LTE4 and cognition and imaging markers at baseline and 1‐year‐follow‐up were assessed using mixed‐effects linear regression models, controlling for baseline demographic factors, medication use, and vascular comorbidities. Findings were corrected for multiple comparisons using a 5% false discovery rate.ResultAmong 158 participants (mean age = 69.22 years, 51% female, mean education = 14.61 years), higher baseline concentrations of LTB4 were not associated with performance in executive function or memory over time nor with changes in WMH, lacunes, or PVS over time. Higher baseline concentrations of LTE4 were associated with better performance in memory over time (β = 0.153 [95% CI = 0.026, 0.287]; however, this finding did not survive correction for multiple comparisons (adjusted p = 0.260; Table 1).ConclusionIn a group of patients with AD, higher LTB4 and LTE4 in serum were not associated with changes in cognitive performance nor markers of cerebrovascular disease. These findings suggest very little potential for serum leukotrienes as biomarkers for cognitive decline of cerebrovascular disease progression in AD.

THE LEVEL OF LEUKOTRIENE B4 IN PATIENTS WITH ARTERIAL HYPERTENSION AND CORONAVIRUS DISEASE

Relevance. Patients with comorbid pathology, including arterial hypertension (AH), coronary artery disease, type 2 diabetes, and cerebrovascular disease have been shown to be at risk for coronavirus disease (COVID-19). Currently, among the pathogenetic mechanisms of vascular endothelial damage are considered direct effects of SARS-COV-2 virus, as well as proinflammatory cytokines, which lead to a «cytokine storm» with unpredictable consequences for the patient. In this aspect, the role of leukotriene B4 (LTB4) – one of the first candidates to provoke a hyperimmune inflammatory response in the progression of COVID-19 – was insufficiently elucidated.&#x0D; Objective: to investigate the level of leukotriene B4 (LTB4) in patients with AH with and without coronavirus disease 2019.&#x0D; Methods. 78 people with AH and overweight or obesity who were treated at the Lviv Emergency Hospital were examined. All patients were divided into 2 groups: group 1 (n=37) – persons with AH (stage І-ІІІ, grade 1-3); group 2 (n=41) – patients with AH (stage І-ІІІ, grade 1-3), COVID -19 and interstitial lung disease.&#x0D; Anthropometric measurements with a determination of body mass index (BMI), echocardiography, a blood test, biochemical blood test with determination of glucose, alanine aminotransferase, aspartate aminotransferase, creatinine, and urea were performed. Serum blood samples for the examination of LTB4 (Elabscience Elisa Kit) were taken and processed using ELISA method.&#x0D; Results. Saturation was significantly lower in patients of group 2, while heart rate and body temperature were higher (p &lt; 0,01) compared to group 1. There was a significant decrease in hemoglobin level, increase in ESR, glucose, and LTB4 in individuals with AH and COVID-19, which is probably due to the presence of inflammation in the lung tissue in coronavirus infection. The concentration of LTB4 ranged from 370 to 3600 pg/l in patients of group 2. 19 individuals (46,3%) of group 2 had a higher level of LTB4 than the median value, which is probably associated with a more severe course of coronavirus infection. A positive correlation between LTB4 and BMI (rs= 0,369; p &lt; 0,05) was found in individuals with AH.&#x0D; Conclusions. The level of LTB4 is higher in patients with AH and COVID – 19 than in individuals with AH, due to the severity of the inflammation process in this comorbid pathology.

Gram-Negative Bacteria Salmonella typhimurium Boost Leukotriene Synthesis Induced by Chemoattractant fMLP to Stimulate Neutrophil Swarming.

Leukotriene synthesis in neutrophils is critical for host survival during infection. In particular, leukotriene B4 (LTB4) is a powerful neutrophil chemoattractant that plays a crucial role in neutrophil swarming. In this work, we demonstrated that preincubation of human neutrophils with Salmonella typhimurium strongly stimulated LTB4 production induced by the bacterial chemoattractant, peptide N-formyl-L-methionyl-L-leucyl-l-phenylalanine (fMLP), while the reverse sequence of additions was ineffective. Preincubation with bacterial lipopolysaccharide or yeast polysaccharide zymosan particles gives weaker effect on fMLP-induced LTB4 production. Activation of 5-lipoxygenase (5-LOX), a key enzyme in leukotrienes biosynthesis, depends on rise of cytosolic concentration of Ca2+ and on translocation of the enzyme to the nuclear membrane. Both processes were stimulated by S. typhimurium. With an increase in the bacteria:neutrophil ratio, the transformation of LTB4 to ω-OH-LTB4 was suppressed, which further supported increased concentration of LTB4. These data indicate that in neutrophils gathered around bacterial clusters, LTB4 production is stimulated and at the same time its transformation is suppressed, which promotes neutrophil swarming and elimination of pathogens simultaneously.

Effect of halometasone cream combined with Simiao pill on the therapeutic effect and expression of serum leukotriene B4 (LTB4) and thymic stromal lymphopoietin (TSLP) in patients with eczema, and the factors influencing its clinical efficacy.

Chronic eczema has the characteristics of a long treatment cycle and repeated attacks, which seriously affects the daily life and work of patients. Topical glucocorticoids are the first-line treatment for chronic eczema. This study aimed to retrospectively analyze the effects of halometasone cream combined with Simiao pill on the efficacy and expression of serum leukotriene B4 (LTB4) and thymic stromal lymphopoietin (TSLP) in patients with eczema, and identify the factors influencing its clinical efficacy. We retrospectively collected the medical records of 195 patients with chronic eczema treated in the dermatology department from January 2020 to May 2021, and divided them into two groups according to medication: 98 cases were treated with halometasone cream (control group) and 97 cases were treated with halometasone ointment combined with Simiao pill (observation group). The severity of eczema, quality of life, clinical efficacy, LTB4 and TSLP levels, and safety were compared between the two groups. Multivariate logistic regression analysis was used to determine the independent factors affecting clinical efficacy. After treatment, the Eczema area and severity index (EASI) and Dermatology Life Quality Index (DLQI) scores in the observation group were markedly lower than those of the control group (P<0.05). The total clinical effective rate of the observation group was 88.8%, which was notably higher than that of the control group 70.1% (P=0.001). The concentrations of serum LTB4 and TSLP in the observation group were markedly lower than those in the control group (P<0.05). Logistic regression analysis showed that the treatment regimen, digestive system symptoms, heavy aching limbs, and damp-heat tongue and pulse were independent factors affecting the curative effect of the patients (P<0.05). Simiao pill combined with halometasone cream can effectively improve chronic eczema and enhance the clinical efficacy of treatment, which may be related to the reduction of serum LTB4 and TSLP levels. The treatment plan, digestive system symptoms, heavy aching limbs, and damp-heat tongue and pulse are the main factors that affecting the clinical curative effect. Thus, clinical intervention programs should be made according to the above factors to improve the quality of life of patients.

Increased leukotriene B4 plasma concentration in type 2 diabetes individuals with cardiovascular autonomic neuropathy

Background and aimA low-grade inflammation is associated with cardiac autonomic neuropathy (CAN) and increased concentration of leukotriene B4 (LTB4) was found in individuals with type 1 diabetes and definitive CAN. This cross-sectional study evaluated plasma concentration of LTB4 and of other inflammatory mediators, namely, tumor necrosis factor (TNF), interleukin (IL)1B, and IL10 in individuals with type 2 diabetes (T2D) and different degrees of CAN, and correlated these inflammatory mediators with the degree of glycemic control and with a surrogate marker of insulin resistance.MethodsTNF, IL1B, IL10 and LTB4 plasma concentrations were measured in 129 T2D subjects (62% women with [median] age of 63 years, disease duration of 8 years and HbA1c of 7.3%) with or without CAN. The Lipid accumulation product index was used as a surrogate marker of insulin resistance.ResultsLTB4 concentration was significantly higher in those presenting incipient CAN (69.7 ± 16.6 pg mL-1) and definitive CAN (71.5 ± 15.7 pg mL-1) versus those without CAN (57.0 ± 13.9 pg mL-1). The groups without CAN and with incipient CAN were pooled (group without definitive CAN) and compared to those with definitive CAN. LTB4 concentration was higher in the latter group, as well as TNF concentration, while IL10 concentration was lower in this group. After adjustment for confounding variables, only LTB4 concentration remained significantly different between the groups with and without definitive CAN. Plasma concentration of LTB4 did not correlate with the degree of glycemic control. After sorting the participants by sex, a borderline weak correlation was found between LTB4 and the Lipid accumulation product index in women.ConclusionIn the T2D setting, circulating LTB4 concentration seems to be associated with cardiovascular dysautonomia.

Pathogenic role leukotriene B4 in lung injury induced by lung-protective mechanical ventilation in rabbits

To elucidate the pathogenic role of leukotriene B4 (LTB4) in pulmonary hyper-permeability and inflammation induced by lung-protective mechanical ventilation (LPMV) in rabbits. Thirty-two healthy Japanese white rabbits were randomized into 4 groups for treatment with vehicle or bestatin (a leukotriene A4 hydrolase inhibitor that inhibits LTB4 production) administered intragastrically at the daily dose of 8 mg/kg for 5 days, followed by sham operation (group S and group BS, respectively, in which the rabbits were anesthetized only) or LPMV (group PM and group BPM, respectively, in which the rabbits received ventilation with 50% oxygen at a tidal volume of 8 mL/kg for 5 h). The concentrations of LTB4 and cyclic adenosine monophosphate (cAMP) in the lung tissues were analyzed by ELISA. cAMP content, protein kinase A (PKA) protein expression and the Rap1-GTP protein to total Rap1 protein ratio were determined to assess the activities of cAMP/PKA and Rap1 signaling pathways. The lung injury was evaluated by assessing lung permeability index, lung wet/dry weight ratio, polymorphonuclear leukocyte (PMN) count in bronchoalveolar lavage fluid (BALF), pulmonary myeloperoxidase (MPO) activity and lung histological scores. None of the examined parameters differed significantly between group S and group BS. All the parameters with the exception of lung histological score increased significantly in group PM and group BPM as compared to those in group S (P < 0.05). Compared with those in PM group, the rabbits in group BPM showed significantly reduced LTB4 production in the lungs (P < 0.05), up-regulated cAMP/ PKA and Rap1 signaling pathway activities (P < 0.05), and alleviated lung hyper-permeability and inflammation (P < 0.05). LPMV can induce LTB4 overproduction to down-regulate cAMP/PKA and Rap1 signaling pathways in the lungs of rabbits, which results in lung hyper-permeability and inflammation. Bestatin can inhibit LTB4 production in the lungs to protect against LPMV-induced lung hyper-permeability and inflammation.

Microglia-released leukotriene B4 promotes neutrophil infiltration and microglial activation following intracerebral hemorrhage

Intracerebral hemorrhage (ICH) from blood vessel rupture results in parenchymal hematoma formation and neuroinflammation, ultimately leading to neurodegeneration. Several lines of evidence suggest that the severity of ICH-induced neural damage is exacerbated by infiltration of T-cells, monocytes, and especially neutrophils into the hematoma. Neutrophil migration is regulated by chemokines, formyl peptides, and leukotriene B4 (LTB4), a metabolite of arachidonic acid. In this study, we demonstrate that LTB4 is a key signaling factor promoting microglial activity and leukocyte infiltration into hematoma and thus a potentially critical determinant of ICH pathogenesis and clinical outcome. Lipidomic analysis revealed markedly increased LTB4 concentration in the hematoma-containing brain tissues 6–24 h after experimental ICH in mice. Expression of 5-lipoxygenase, a rate-limiting enzyme for LTB4 production, was upregulated in activated microglia and neutrophils within the hematoma following ICH. Treatment of cultured BV-2 microglia with thrombin, which is abundant in hematoma, promoted activation, proinflammatory cytokine expression, and LTB4 secretion. Further, conditioned medium from thrombin-stimulated BV-2 cells potentiated the transwell migration of neutrophil-like cells, a response blocked by a LTB4 receptor antagonist. These results suggest that arachidonic acid conversion to LTB4 following ICH contributes to neuroinflammation and ensuing neural tissue damage by inducing microglial activation and neutrophil recruitment.

LTB4 and 5-oxo-ETE from extracellular vesicles stimulate neutrophils in granulomatosis with polyangiitis

Activation of neutrophils is an important mechanism in the pathology of granulomatosis with polyangiitis (GPA). In this study, we evaluated whether extracellular vesicles (EVs) circulating in the plasma of GPA patients could contribute to this process. EVs from the plasma of GPA patients in the active stage of the disease (n = 10) and healthy controls (n = 10) were isolated by ultracentrifugation and characterized by flow cytometry (CD63, CD8) and nanoparticle tracking analysis. Targeted oxylipin lipidomics of EVs was performed by HPLC-MS/MS. EV/oxylipin-induced neutrophil extracellular traps (NETs) were analyzed by confocal microscopy, and released double-stranded DNA (dsDNA) was quantified by PicoGreen fluorescent dye. Reactive oxygen species (ROS) production and neutrophils' EV binding/uptake were evaluated by flow cytometry. Brief priming with granulocyte-macrophage colony-stimulating factor was required for EV-mediated ROS production and dsDNA release. It was observed that priming also increased EV binding/uptake by neutrophils only for EVs from GPA patients. EVs from GPA patients had higher concentrations of leukotriene (LT)B4 and 5-oxo-eicosatetraenoic acid (5-oxo-ETE) as compared with EVs from healthy controls. Moreover, neutrophils stimulated with LTB4 or 5-oxo-ETE produced ROS and released dsDNA in a concentration-dependent manner. These results reveal the potential role of EVs containing oxylipin cargo on ROS production and NET formation by activated neutrophils.

Leukotriene B4 in equine asthma syndrome: what do we know so far?

ABSTRACT: The term “equine asthma syndrome” (EAS) was recently proposed due to the resemblance of the equine disease to human asthma. Leukotrienes cause constriction of the bronchi, especially in the lower airways and increase mucus secretion in the respiratory system. Leukotriene B4 (LTB4) has been discovered as a strong chemotactic factor, which plays a role in neutrophil migration. The immunologic background of EAS remains not fully elucidated despite many studies on the pathogenesis. This study aimed to evaluate the LTB4 concentration in the bronchoalveolar lavage fluid (BALF) of horses with and without pulmonary inflammatory disease. Thirty-five mixed breed horses were studied and LTB4 was determined by using specific ELISA Kit. The horses were grouped by 2 different criteria for statistical analysis of data: 1) according to the values for BALF citology and 2) according to the detection of LTB4 in BALF. There was significant difference of effect of age on the LTB4 detection in equine BALF. Younger animals were the majority where it was possible to detect LTB4 values in LBA. In conclusion, there was an effect of age on the detection of LTB4 in equine BALF, where LTB4 levels were more easily detected in younger animals than older animals and the results of this study raise the possibility of considering future studies with the objective of establishing the real role and the best moment to detect LTB4 in BALF of the equine asthma syndrome.

Arachidonic Acid and Docosahexaenoic Acid Metabolites in the Airways of Adults With Cystic Fibrosis: Effect of Docosahexaenoic Acid Supplementation.

Cystic fibrosis (CF) is an autosomal recessive disorder, caused by genetic mutations in CF transmembrane conductance regulator protein. Several reports have indicated the presence of specific fatty acid alterations in CF patients, most notably decreased levels of plasmatic and tissue docosahexaenoic acid (DHA), the precursor of specialized pro-resolving mediators. We hypothesized that DHA supplementation could restore the production of DHA-derived products and possibly contribute to a better control of the chronic pulmonary inflammation observed in CF subjects. Sputum samples from 15 CF and 10 chronic obstructive pulmonary disease (COPD) subjects were collected and analyzed by LC/MS/MS, and blood fatty acid were profiled by gas chromatography upon lipid extraction and transmethylation. Interestingly, CF subjects showed increased concentrations of leukotriene B4 (LTB4), prostaglandin E2 (PGE2), and 15-hydroxyeicosatetraenoic acid (15-HETE), when compared with COPD patients, whereas the concentrations of DHA metabolites did not differ between the two groups. After DHA supplementation, not only DHA/arachidonic acid (AA) ratio and highly unsaturated fatty acid index were significantly increased in the subjects completing the study (p < 0.05) but also a reduction in LTB4 and 15-HETE was observed, together with a tendency for a decrease in PGE2, and an increase in 17-hydroxy-docosahexaenoic acid (17OH-DHA) levels. At the end of the washout period, LTB4, PGE2, 15-HETE, and 17OH-DHA showed a trend to return to baseline values. In addition, 15-HETE/17OH-DHA ratio in the same sample significantly decreased after DHA supplementation (p < 0.01) when compared with baseline. In conclusion, our results show here that in CF patients, an impairment in fatty acid metabolism, characterized by increased AA-derived metabolites and decreased DHA-derived metabolites, could be partially corrected by DHA supplementation.

Inhibition of LTA4H by bestatin in human and mouse colorectal cancer

BackgroundOur preclinical data showed that the leukotriene A4 hydrolase (LTA4H) pathway plays a role in colorectal cancer (CRC). High expression of LTA4H and leukotriene B4 receptor type 1 (BLT1) were also associated with CRC survival probability. Clinical samples were evaluated to determine whether LTA4H could serve as a therapeutic target and whether leukotriene B4 (LTB4) could be used as a biomarker for evaluating the efficacy of bestatin in CRC. MethodsPatients with Stage I-III CRC did or did not receive bestatin prior to surgery. Evaluable pairwise CRC patient blood samples were collected to evaluate LTB4 concentration. Tissues were processed by immunohistochemistry to detect the LTA4H pathway and Ki-67 expression. We also determined whether LTA4H or BLT1 was associated with CRC survival probability and explored the mechanism of bestatin action in CRC. FindingsSamples from 13 CRC patients showed a significant decrease in LTB4, the LTA4H signaling pathway, and Ki-67 in the bestatin-treated group compared with the untreated group. LTA4H and BLT1 are overexpressed in CRC and associated with CRC survival probability. Bestatin effectively inhibited LTB4 and tumorigenesis in the ApcMin/+ and CRC patient-derived xenograft mouse model. InterpretationThese results demonstrate that LTB4 could serve as a biomarker for evaluating bestatin efficacy in CRC and the antitumor effects of bestatin through its targeting of LTA4H and support further studies focusing on LTA4H inhibition in CRC.

Serum leukotriene B4 levels, tonsillar hypertrophy and sleep-disordered breathing in childhood

ObjectivesIn children with snoring, increased production of leukotriene B4 (LTB4) may promote tonsillar hypertrophy and sleep-disordered breathing (SDB) or conversely SDB may enhance LTB4 synthesis. We explored whether: i) high LTB4 serum levels predict tonsillar hypertrophy; and ii) SDB severity correlates with LTB4 serum concentration. MethodsNormal-weight children with SDB or controls underwent polysomnography and measurement of LTB4 serum concentration. Tonsillar hypertrophy was the main outcome measure and high LTB4 serum level (>75 t h percentile value in controls) was the primary explanatory variable. Odds ratio (OR) and the corresponding 95% confidence intervals (CI) for tonsillar hypertrophy in children with versus without high LTB4 level were calculated. The control subgroup and subgroups of subjects with increasing SDB severity were compared regarding LTB4 concentration by Kruskal-Wallis test. Spearman's correlation co-efficient was applied to assess the association of LTB4 concentration with SDB severity. ResultsA total of 104 children with SDB and mean obstructive apnea-hypopnea index-AHI of 4.8 ± 5.3 episodes/h (primary snoring: n = 19; mild SDB: n = 49; moderate/severe SDB: n = 36) and 13 controls (no snoring; AHI: 0.4 ± 0.2 episodes/h) were recruited. The four study subgroups were similar regarding LTB4 serum concentration (P = 0.64). High LTB4 (>170.3 pg/mL) was a significant predictor of tonsillar hypertrophy after adjustment for age and gender (OR 3.0 [1.2–7.2]; P = 0.01). There was no association between AHI or desaturation index and LTB4 serum concentration (r = −0.08; P = 0.37 and r = −0.1; P = 0.30, respectively). ConclusionNo association was identified between SDB severity and LTB4 levels, but high LTB4 concentration predicted tonsillar hypertrophy.

Exhaled breath condensate hydrogen peroxide, pH and leukotriene B4 are associated with lower airway inflammation and airway cytology in the horse.

Exhaled breath condensate (EBC) analysis is a noninvasive method to assess the lower respiratory tract. In human subjects, EBC hydrogen peroxide (H2 O2 ), pH and leukotriene B4 (LTB4 ) are useful for detection and monitoring of inflammatory lung diseases, including asthma. To determine associations between EBC biomarkers and cytological and endoscopic definitions of lower airway inflammation (LAI) while controlling for sampling and environmental variables. Prospective, cross-sectional study. Clinical, endoscopic and airway cytological findings from 47 horses were compared with EBC pH and concentrations of H2 O2 and LTB4 by univariate and multivariable analyses. Dichotomous (presence/absence of airway inflammation) and continuous outcome variables (differential cell counts in tracheal aspirate and bronchoalveolar lavage fluid, BALF) were evaluated and potential effects of collection and methodological factors were included. EBC pH and H2 O2 concentrations were higher in horses with LAI and both were positively associated with the percentage of neutrophils in BALF (P<0.05). Mast cell percentage in BALF was negatively associated with EBC pH, and BALF eosinophil percentage was positively associated with EBC LTB4 (P<0.05). Ambient temperature, relative humidity and assay methodology significantly impacted some analytes. LAI is challenging to categorise due to a variety of clinical and cytological phenotypes. Although the study was designed to overcome this limitation, numbers of horses were small in some categories. EBC pH and H2 O2 concentrations are altered by airway inflammation, suggesting a role for these biomarkers in the diagnosis and monitoring of airway disease. Environmental and methodological factors can influence these biomarkers and should be considered in the interpretation of results.

Endocervical and Neutrophil Lipoxygenases Coordinate Neutrophil Transepithelial Migration to Neisseria gonorrhoeae.

Infection with Neisseria gonorrhoeae (GC) is characterized by robust neutrophil influx that is insufficient to clear the bacteria. Sustained neutrophilic inflammation contributes to serious clinical sequelae that particularly affect women, including pelvic inflammatory disease and infertility. We established a 3-component system using GC, End1 polarized human endocervical cells, and primary human neutrophils to investigate neutrophil transepithelial migration following infection. Neutrophil migration across endocervical monolayers increased with the infectious dose and required GC-epithelial cell contact. Epithelial protein kinase C, cytosolic phospholipase A2, 12R-lipoxygenase (LOX), and eLOX3 hepoxilin synthase were required for neutrophil transmigration to GC, and migration was abrogated by blocking the MRP2 efflux pump and by adding recombinant soluble epoxide hydrolase. These results are all consistent with epithelial cell production of the neutrophil chemoattractant hepoxilin A3 (HXA3). Neutrophil transmigration was also accompanied by increasing apical concentrations of leukotriene B4 (LTB4). Neutrophil 5-lipoxygenase and active BLT1 receptor were required for apical LTB4 and neutrophil migration. Our data support a model in which GC-endocervical cell contact infection stimulates HXA3 production, driving neutrophil migration that is amplified by neutrophil-derived LTB4. Therapeutic targeting of these pathways could limit inflammation and deleterious clinical sequelae in women with gonorrhea.

Effects of leukotriene B4 on interleukin-32, interferon-γ and chemokines in rats with rheumatoid arthritis.

The objective of this study was to investigate the effects of leukotriene B4 (LTB4) on the expression of interleukin-32 (IL-32) interferon-γ (IFN-γ) and chemokine monocyte chemoattractant protein (MCP-1) and macrophage inhibitory protein (MIP-1α) in rheumatoid arthritis (RA). The rat model of RA collagen induced-arthritis (CIA) was established. The levels of LTB4, interleukin-32, IFN-γ and chemokines MCP-1 and MIP-1α in CIA rats were detected by ELISA. After the rat synovial cells were isolated and treated with different concentrations of LTB4, the effect of LTB4 the expression of IL-32, IFN-γ and chemokines MCP-1 and MIP-1α mRNA in synovial cells was detected by real-time quantitative PCR, the effect of LTB4 on protein expression was detected by immunoblotting. The effects of different concentrations of LTB4 on the viability and apoptosis of synovial cells were detected by LDH and cell proliferation reagent WST-1. Compared with the control group, the levels of LTB4, IL-32, IFN-γ and chemokines MCP-1 and MIP-1α were significantly increased in the serum of the CIA group. After treatment of CIA rat synovial cells with different concentrations of LTB4, the expression of IL-32, IFN-γ and chemokines MCP-1 and MIP-1α mRNA and protein were increased with significant differences among groups. WST-1 and flow cytometry showed that LTB4 had significant toxic effects on synovial cells and promoted apoptosis. In conclusion, LTB4 promotes the expression of interleukin-32, IFN-γ and chemokines MCP-1 and MIP-1α in synovial cells and facilitates apoptosis of synovial cells.

LTB4 and montelukast in transplantation-related bronchiolitis obliterans in rats

BackgroundLung transplantation is the only effective treatment for end-stage lung diseases. Bronchiolitis obliterans, which is known as non-infectious chronic lung allograft dysfunction (CLAD) in the new classification, is the greatest threat to long-term survival after lung transplantation. This study investigated the role of leukotriene B4 (LTB4) and montelukast in transplantation-related bronchiolitis obliterans and discussed the pathophysiological significance of LTB4 in chronic rejection.MethodsRats were randomly divided into an experimental group (montelukast), a positive control group (dexamethasone), and a blank control group (normal saline solution; NS). Each piece of trachea removed from a F344 rat was transplanted into a Lewis rat through a 5-mm incision at the episternum by subcutaneous embedding. The recipients were treated with gastric lavage with 3 mg/kg · d montelukast suspension, 1 mg/kg · d dexamethasone, and 1 mL/kg · d NS, respectively, in each group. On Day 28, peripheral blood was drawn to measure the white blood cell counts and plasma LTB4 levels. The donor specimens were stained by H-E and Masson, and their organizational structure and extent of fibrosis were visually assessed. The measurement data were compared using one-way analysis of variance, and the categorical data were compared using the chi-square test. A P value of less than 0.05 was considered to indicate statistical significance.ResultsThe white blood cell counts of the montelukast, dexamethasone, and NS groups were (16.0 ± 4.2) × 109/L, (19.5 ± 11.6) × 109/L, and (25.8 ± 3.6) × 109/L; no statistical significance was found (P = 0.101). The concentrations of LTB4 were 2230 ± 592 pg/mL, 1961 ± 922 pg/mL, and 3764 ± 1169 pg/mL, and statistical significance was found between the NS group and each of the others (P = 0.009). The percentages of tracheal occlusion were 73.6% ± 13.8%, 23.4% ± 3.2%, and 89.9% ± 11.3%, and statistical significance was found among the three groups (P = 0.000).ConclusionsThe study established a model to simulate bronchiolitis obliterans after clinical lung transplantation. Oral administration of montelukast reduced plasma LTB4 levels in rats and played a preventive role against tracheal fibrosis after transplantation. This suggests that LTB4 may be involved in bronchiolitis obliterans after pulmonary transplantation. This study indicates a new direction for research into the prevention and treatment of bronchiolitis obliterans after lung transplantation.

The leukotriene B4 receptors BLT1 and BLT2 form an antagonistic sensitizing system in peripheral sensory neurons

Sensitization of the heat-activated ion channel transient receptor potential vanilloid 1 (TRPV1) through lipids is a fundamental mechanism during inflammation-induced peripheral sensitization. Leukotriene B4 is a proinflammatory lipid mediator whose role in peripheral nociceptive sensitization is not well understood to date. Two major G-protein-coupled receptors for leukotriene B4 have been identified: the high-affinity receptor BLT1 and the low-affinity receptor BLT2. Transcriptional screening for the expression G-protein-coupled receptors in murine dorsal root ganglia showed that both receptors were among the highest expressed in dorsal root ganglia. Calcium imaging revealed a sensitization of TRPV1-mediated calcium increases in a relative narrow concentration range for leukotriene B4 (100-200 nm). Selective antagonists and neurons from knock-out mice demonstrated a BLT1-dependent sensitization of TRPV1-mediated calcium increases. Accordingly, leukotriene B4-induced thermal hyperalgesia was mediated through BLT1 and TRPV1 as shown using the respective knock-out mice. Importantly, higher leukotriene B4 concentrations (>0.5 μm) and BLT2 agonists abolished sensitization of the TRPV1-mediated calcium increases. Also, BLT2 activation inhibited protein kinase C- and protein kinase A-mediated sensitization processes through the phosphatase calcineurin. Consequently, a selective BLT2-receptor agonist increased thermal and mechanical withdrawal thresholds during zymosan-induced inflammation. In accordance with these data, immunohistochemical analysis showed that both leukotriene B4 receptors were expressed in peripheral sensory neurons. Thus, the data show that the two leukotriene B4 receptors have opposing roles in the sensitization of peripheral sensory neurons forming a self-restricting system.