Concentration Of Lipoxin A4 Research Articles

Lipoxin A4 Ameliorates Imiquimod-Induced Psoriasis-Like Dermatitis via Promoting the Regression of Inflammation.

As a mediator of inflammation resolution, lipoxin A4 (LXA4) mainly plays an anti-inflammatory role and promotes inflammation resolution. LXA4 plays an inhibiting inflammatory role in a variety of diseases, tissues and cells, including keratinocytes. Psoriasis is a chronic inflammatory skin disease mediated by dysregulation of inflammation of immune cells and keratinocytes. However, the expression and role of LXA4 in psoriasis-like mouse models are still unclear. Imiquimod (IMQ) topical treatment of dorsal skin induces psoriasis-like dermatitis in BALB/c mice, pretreated intraperitoneally with or without LXA4 prior to IMQ application. Severity of dorsal lesions is assessed by using a modified human scoring system and histopathology. The concentration of LXA4 and the expression of ALOX15 (a key gene in LXA4 metabolic synthesis) in lesional skins were detected by ELISA and Western blot. Quantitative PCR and ELISA were conducted to detect the mRNA and secretion levels of inflammatory cytokines. The proportion of IL-17A-producing γδT cells in skin and skin draining cervical lymph nodes and helper (Th) 17 cells in spleens was evaluated by flow cytometry. Western blotting was used to analyze the expressions of p-STAT3 and TRAF6. The concentration of LXA4 and the expression of ALOX15 were decreased in IMQ-induced lesional skin. LXA4 significantly relieved psoriasis-like lesions in IMQ-induced mouse models. Furthermore, LXA4 decreased IMQ-induced systemic inflammation, including reduced the proportion of IL-17A-producing gdT cells in skin and skin draining cervical lymph nodes and Th17 cells in spleens, the secretion and expression of CCL20, IL-17A, IL-1β, and TNF-α in skin and serum. LXA4 markedly inhibited IMQ-induced expression of TRAF6 and p-STAT3. LXA4 significantly ameliorates IMQ-induced psoriasis-like inflammation, and LXA4 can be used as a target for psoriasis treatment.

Decreased Gene Expression of Lipoxin A4 Receptor May Contribute to Nonallergic Rhinitis Pathogenesis

Background: Rhinitis is a prevalent chronic inflammatory illness of the nasal mucosa. Arachidonic acid-derived lipoxin A4 (LXA4) has long been recognized to exert crucial antiinflammatory and pro-resolving effects on inflammatory responses through a specific receptor named LXA4 receptor/formyl peptide receptor-2 (ALX/FPR2). This study aimed to determine the serum level of LXA4 and the relative mRNA expression level of FPR2 in peripheral blood cells of patients with rhinitis (allergic and nonallergic) compared to healthy individuals. Materials And Methods: The study groups consisted of 37 patients with Allergic Rhinitis (AR), 16 patients with Nonallergic Rhinitis (NAR), and 20 sex- and age-matched healthy individuals. The measurement of LXA4 serum level was performed by the Enzyme-Linked Immunosorbent Assay (ELISA) technique, and the analysis of FPR2 mRNA expression level was performed by quantitative real-time PCR method. Results: The serum concentrations of LXA4 decreased in AR and NAR patients compared to healthy controls; however, this difference was not statistically significant (P>0.05). Besides, the mRNA expression level of FPR2 in peripheral blood cells of patients with nonallergic rhinitis was significantly lower than that in allergic rhinitis (P<0.05). Conclusion: Our results suggest that reduced gene expression of FPR2 may contribute to developing persistent and chronic nasal mucosa inflammation seen in NAR patients. Therefore, stable analogs of LXA4 and its receptor agonist may help develop new therapeutic approaches for rhinitis.

Salivary levels of specialized pro‐resolving lipid mediators as indicators of periodontal health/disease status

This cross-sectional case-control study aimed to determine if salivary levels of lipoxin A4 (LXA4), protectin D1 (PD1), resolvin E1 (RvE1) and maresin 1 (MaR1) might constitute a reflection of periodontal health/disease status. One hundred and two periodontitis patients and 61 healthy controls were recruited. Periodontal clinical status was determined by criteria based on full-mouth clinico-radiographical data. Salivary concentration of the analytes was calculated by enzyme-linked immunosorbent assay. The association between the biomarkers with disease status was assessed individually and adjusted for confounding using multivariate binary logistic regression models. Significantly decreased LXA4 and increased PD1/MaR1 salivary levels were detected in periodontitis patients in comparison with healthy controls. However, no significant differences were observed for RvE1 levels between clinical groups. Clinical parameters such as probing depth, clinical attachment loss and extent were negatively correlated with LXA4, positively correlated with PD1/MaR1 and not correlated with RvE1 salivary levels. Logistic regression analyses revealed a strong/independent association of LXA4, PD1 and MaR1 salivary levels regarding disease status. Interaction effects between demographic predictor variables and salivary concentration of LXA4, PD1 and MaR1 were also identified. The results of this study demonstrated a strong/independent association between reduced LXA4 and increased PD1/MaR1 salivary levels with periodontitis suggesting an imbalance in the specialized pro-resolving lipid mediators (SPMs) in periodontal disease.

Effects of the ALX/FPR2 receptors of lipoxin A4 on lung injury induced by fat embolism syndrome in rats

This study was designed to investigate the inflammatory responses in fat embolism syndrome (FES) and the relationship of ALX/FPR2 receptors and lipoxin A4 (LXA4) in FES models. In this model, lung injury score, lung tissue wet-to-dry (W/D) ratio and total protein concentration in bronchoalveolar lavage fluid (BALF) were increased compared with those of the control group. Meanwhile, the number of leukocytes and neutrophils was significantly increased in the FES group, as was the myeloperoxidase (MPO) activity and mRNA expression. In addition, the release of TNF-α and IL-1β was increased. Then, we explored whether LXA4 and ALX/FPR2 were involved in the pathological process of FES. The LXA4 concentration in the experimental groups was markedly higher than that in the control group. At the same time, the protein and mRNA levels of ALX/FPR2 were upregulated in the rat model of FES. Moreover, rats treated with BML-111, an agonist for the ALX/FPR2 receptor of LXA4, showed a lower inflammatory response than mice treated with fat alone. However, the role of BML-111 in fat emboli (FE)-induced acute lung injury (ALI) was attenuated by BOC-2, an antagonist of the ALX/FPR2 receptor of LXA4. Our results demonstrated that the inflammatory response may play an important role in the pathogenesis of FES and that the activation of the ALX/FPR2 receptor for LXA4 can decrease the inflammatory response and may be a therapeutic target for FE-induced ALI.

Lipoxin A4 inhibits the invasion and migration of endometrial stromal cells by down-regulating NF-κB signaling-mediated autophagy

Objective: To investigate whether the suppressive effects of lipoxin A4 (LXA4) on endometriosis are mediated by the regulation of autophagic activity, and to further explore the actual molecular mechanism. Methods: (1) Eutopic and ectopic endometria were obtained from 13 patients with endometriosis, and 10 eutopic endometria collected from non-endometriosis patients were used as control. The expression of the autophagy-related biochemical markers [microtubule-associated protein 1 light chain 3 (LC3) and p62] were detected by western blot. Levels of LXA4 in the biopsies were measured by ELISA. (2) Primary human endometrial stromal cells (ESC) were isolated and cultured in vitro from eutopic endometria of infertility patients with endometriosis. After treatment with exogenous LXA4 or autophagy inhibitor 3-methyladenine (3-MA) or autophagy inducer rapamycin, cell migration and invasion were evaluated by transwell assay, and autophagy was detected by western blot. (3) ESC were treated with LXA4, the gene expressions of nuclear factor kappa B (NF-κB) etc. were examined by quantitative real-time PCR, and the activation of NF-κB signaling was detected by western blot. (4) ESC were incubated with 10 μmol/L NF-κB inhibitor BAY11-7080, the autophagic activation was detected by western blot. Results: (1) Autophagy-related marker, LC3-Ⅱ and LC3-Ⅱ/LC3-Ⅰ ratio, showed a significant up-regulation in ectopic lesions of endometriosis compared with eutopic endometria of affected or healthy women (all P<0.05) . However, the LXA4 level significantly decreased in ectopic tissue (P<0.05) . There was a significant negative correlation between LXA4 concentration and relative expression of LC3-Ⅱ in ectopic lesions (r= -0.780, P=0.002) . (2) 10 and 100 nmol/L exogenous LXA4 could significantly down-regulate the LC3-Ⅱ protein expression and up-regulate the p62 protein expression (all P<0.05) . LXA4 markedly inhibited the invasion and migration of ESC (P<0.05) ;while the reactivation of autophagy by rapamycin almost reversed the anti-invasion and anti-migration effects of LXA4. (3) After LXA4 treatment, the expression level of NF-κB gene significantly decreased (P<0.05) . Furthermore, the results of western blot analysis showed that the nuclear translocation of NF-κB p65 was markedly down-regulated under LXA4 treatment (P<0.05) . (4) The NF-κB inhibitor BAY11-7080 markedly suppressed the autophagic activation of LXA4 (P<0.05) . Conclusion: LXA4 could inhibit the invasion and migration of ESC by down-regulating the NF-κB signaling-mediated autophagy.

Physiological levels of lipoxin A4 inhibit ENaC and restore airway surface liquid height in cystic fibrosis bronchial epithelium.

In cystic fibrosis (CF), the airway surface liquid (ASL) is depleted. We previously demonstrated that lipoxin A4 (LXA4) can modulate ASL height (ASLh) through actions on Cl− transport. Here, we report novel effects of lipoxin on the epithelial Na+ channel ENaC in this response. ASL dynamics and ion transport were studied using live‐cell confocal microscopy and short‐circuit current measurements in CF (CuFi‐1) and non‐CF (NuLi‐1) cell cultures. Low physiological concentrations of LXA4 in the picomolar range produced an increase in ASLh which was dependent on inhibition of an amiloride‐sensitive Na+ current and stimulation of a bumetanide‐sensitive Cl− current. These ion transport and ASLh responses to LXA4 were blocked by Boc‐2 an inhibitor of the specific LXA4 receptor ALX/FPR2. LXA4 affected the subcellular localization of its receptor and enhanced the localization of ALX/FPR2 at the apical membrane of CF cells. Our results provide evidence for a novel effect of low physiological concentrations of LXA4 to inhibit airway epithelial Na+ absorption that results in an ASL height increase in CF airway epithelia.

Lipoxygenase-Derived Arachidonic Acid Metabolites in Chronic Obstructive Pulmonary Disease

Chronic obstructive pulmonary disease (COPD) is characterized by a persistence of inflammation in large and small airways. We hypothesized that this could be caused by the inability of an inflammatory process to resolve. In the resolution of inflammation, a switching of arachidonic acid metabolism from the production of proinflammatory leukotriene B(4) (LtB(4)) to the synthesis of anti-inflammatory lipoxins plays an important role. The aim of our study was to determine the content of lipoxin A(4) (LXA(4)) and LtB(4) in induced sputum of patients with exacerbated COPD and to compare it to healthy controls, as well as to analyze the relationship between proinflammatory and anti-inflammatory mediators and an inflammatory cell spectrum in induced sputum. Induced sputum from 17 COPD patients and 7 healthy controls were analyzed for LXA(4) and LtB(4) content and inflammatory cell spectrum. COPD patients had a significantly lower sputum LXA(4) concentration and LtB(4)/LXA(4) ratio compared with healthy controls. A significant negative correlation was found between the LXA(4) concentration and the relative neutrophil count and between the LtB(4)/LXA(4) ratio and the relative macrophage count. COPD patients during the late phase of exacerbation had a suppressed production of LXA(4) and an elevated LtB(4)/LXA(4) ratio in induced sputum demonstrating a proinflammatory imbalance. The correction of a balance between proinflammatory and anti-inflammatory eicosanoids by the administration of stable analogues of lipoxins could improve the treatment of chronic obstructive pulmonary disease in the future.

Effect of lipoxin A4 on interleukin-1β production of human monocytes from severe preeclamptic women and its relationship with cytoplasm free calcium concentration-an in vitro study

Objective To investigate the effect of lipoxin A4(LXA4) on interleukin-1β(IL-1β)production of monocytes in maternal peripheral blood from severe preeelampsia women and its relationship with cytosolic free calcium([Ca2+]i)concentration. Methods Peripheral venous blood was drawn from 15 women with severe preeelampsia(SPE group)and 20 normal pregnant women (control group)who were admitted to the First Affiliated Hospital of Wenzhou Medical College from October 2008 to May 2009.Monoeytes were obtained from peripheral blood with Ficolt density gradient centrifugation and then were suspended in RPMI-1640 culture supplemented with LXA4 at the final concentrations of 0,10 and 100 nmol/L,respectively.IL-1β levels in monocytes supernatant were detected by enzyme-linked immunosorbent assay.The cytoplasma[Ca2+]i of cultured monocytes and its variations affected by LXA4 were measured by laser scanning confocal microscope. Results (1) After incubation with different concentrations of LXA4(0,10,100 nmol/L)for 24 h,the levels of IL-1β in SPE group were(63.16±8.20)pg/L,(53.71±8.08)pg/L and(43.16±6.89)pg/L,respectively, indicating a significant inhibition effect on IL-1β level in a dose-dependent manner (P 0.05). (2) Without LXA4, the [Ca2+ ]i concentrations of monocytes in the SPE group were higher than that of the control (1028.09 ± 160. 52 vs 323.61 ±87.86, P<0. 05). After treatment with 100 nmol/L LXA4, the [Ca2+ ]i concentration of monocytes significantly decreased in the SPE group (409.67± 116.73, P<0. 05). Conclusions In vitro LXA4 may inhibit the IL-1β production in monoeytes of SPE patients through decrease of the cytoplama [Ca2+ ]i concentration. Key words: Lipoxins; Pre-eclampsia; Monocytes; Interleukin-lbeta; Calcium

Effects of lipoxin A4 on chemotaxis and degranulation of human eosinophils stimulated by platelet‐activating factor and N‐formyl‐L‐methionyl‐L‐leucyl‐L‐phenylalanine

Lipoxins are trihydroxytetraene metabolites derived through a double lipoxygenation of arachidonic acid. Lipoxin A4 (LXA4) was prepared by total chemical synthesis, and its capacity to modulate eosinophil migration has been evaluated. LXA4 is a weak and partial chemotactic agent; at 10(-6) M, it achieved about 20% of the response of 10(-6) M platelet-activating factor (PAF). Preincubation of eosinophils with increasing doses of LXA4 (10(-10)-10(-5) M) resulted in a concentration-dependent inhibition of cell migration induced by 10(-6) M formyl-methionyl-leucyl-phenylalanine (FMLP) and 10(-6) M PAF. The concentration of LXA4 which produced 50% inhibition (IC50) of eosinophil migration was approximately 10(-6) M. LXA4 (10(-10)-10(-6) M) did not elicit ECP release or modulate ECP release induced by 10(-6) M FMLP. LXA4 may have antiallergic properties in preventing eosinophilic migration.

Identification of Lipoxin A4and Its Relationship to the Sulfidopeptide Leukotrienes C4, D4, and E4in the Bronchoalveolar Lavage Fluids Obtained from Patients with Selected Pulmonary Diseases

Lipoxins are biologically active trihydroxytetraene containing products derived from arachidonic acid that are formed by interactions between lipoxygenases. Although the lipoxins have been generated from mixed cell suspensions in vitro, it has not been established whether these products are synthesized in vivo. We have performed bronchoalveolar lavage (BAL) in 12 patients with lung disease (sarcoid, six; pneumonia, two; asthma, two; carcinoma, one; alveolitis of unknown cause, one) and in six normal control subjects. The BAL fluid was analyzed for lipoxin A4 (LXA4) using gas chromatography mass spectrometry with selective ion monitoring, and the levels of the sulfidopeptide leukotrienes were determined using reverse-phase high-performance liquid chromatography and radioimmunoassay. LXA4 was detected in BAL fluid from nine of the 12 patients studied. The levels of LXA4 ranged from 0.4 to 2.8 ng/ml. LXA4 was not detected in any of the six normal subjects. Sulfidopeptide leukotrienes were detected in all the BAL samples, ranging from 0.04 to 0.7 ng/ml, and there was no significant difference between the patients and the normal subjects. In patients with detectable LXA4 in BAL fluid, the ratio of the concentrations of LXA4 to those of the sulfidopeptide leukotrienes ranged from 1.9 to 62 (mean, 19.0). This is the first demonstration of the presence of LXA4 in disease.

Lipoxin A4 and Lipoxin B4 Inhibit Chemotactic Responses of Human Neutrophils Stimulated by Leukotriene B4 and N-Formyl-l-Methionyl-l-Leucyl-l-Phenylalanine

1. Lipoxin A4 (LXA4) and lipoxin B4 (LXB4) have been evaluated for their capacities to modulate neutrophil (PMN) migration and endothelial cell adherence using compounds prepared by total chemical synthesis. 2. Increased PMN migration was seen with concentrations of LXA4 from 10(-9) mol/l to 10(-7) mol/l. LXA4 was 100-fold less potent than leukotriene B4 (LTB4) and it elicited only one-half of the maximal response of LTB4. 3. The (5S,6S,15S)-isomer of LXA4 induced only a weak migratory response and LXB4 was inactive, suggesting that the activity of LXA4 was stereospecific. 4. Modified chequerboard analysis indicated that LXA4 was a chemokinetic agent. 5. Preincubation of PMN with increasing concentrations of LXA4 induced a very similar dose- and time-dependent inhibition of the subsequent response to 10(-7) mol/l LTB4 or 10(-7) mol/l N-formyl-L-methionyl-L-leucyl-L-phenylalanine (FMLP). The inhibition was observed at 10(-10) mol/l LXA4; the concentration which produced 50% inhibition was 10(-8) mol/l and 100% inhibition of PMN locomotion occurred at 10(-6) mol/l LXA4. 6. The (5S,6S,15S)-isomers of LXA4 and LXB4 were 5- and 100-fold less potent than LXA4, respectively, in suppressing LTB4- or FMLP-induced PMN migration. 7. Preincubation of PMN with LXA4 led to a suppression of calcium mobilization, as assessed by Quin2-AM fluorescence, when the cells were subsequently stimulated under optimal conditions by LTB4 or FMLP. 8. These results suggest that the inhibitory activity of lipoxins may be related to the capacity of these molecules to regulate calcium ion mobilization.