Resolution of inflammation in neuromyelitis optica spectrum disorders

BACKGROUND

Neuromyelitis optica spectrum disorders (NMOSD) are a spectrum of neuroinflammatory disorders associated with autoimmune antibodies against aquaporin-4 (AQP4). Accumulating evidence suggests that inflammation is involved in NMOSD pathogenesis. Resolution of inflammation, which is a highly regulated process mediated by specialized pro-resolving lipid mediators (SPMs) is important to prevent over-responsive inflammation. Deficiency in resolution of inflammation may lead to or accelerates inflammatory diseases. However, whether resolution of inflammation is impaired in NMOSD is not known. The objective of this study was to analyze the levels of SPMs in the serum and cerebrospinal fluid (CSF) of NMOSD patients, and to explore the roles of SPMs in clinical features of NMOSD.

METHODS

Thirty-five patients with NMOSD, 34 patients with multiple sclerosis, and 36 patients with non-inflammatory neurological diseases were enrolled in this study. Pro-resolving mediators including Annexin A1 (ANXA1) and resolvin D1 (RvD1), as well as pro-inflammatory lipid mediator leukotriene B4 (LTB4) levels were analyzed by enzyme-linked immunosorbent assay. Pro- and anti-inflammatory cytokines as well as chemokine levels were analyzed using cytometric beads array (CBA).

RESULTS

Our results showed RvD1 levels were significantly decreased, whereas LTB4 levels were significantly increased in the CSF of NMOSD patients. AQP4-IgG titer was negatively correlated with RvD1 levels in the CSF of NMOSD patients.

CONCLUSIONS

Decreased RvD1 levels indicate impaired resolution of inflammation in NMOSD patients. AQP4-IgG may contribute to increased inflammation and lead to unresolved inflammation in NMOSD.

Lipoxin A4 attenuates LPS-induced mouse acute lung injury via Nrf2-mediated E-cadherin expression in airway epithelial cells

A fundamental element of acute lung injury (ALI) is the inflammation that is part of the body's immune response to a variety of local or systemic stimuli. Lipoxins (LXs) are important endogenous lipids that mediate resolution of inflammation. Previously, we demonstrated that LXA4 reduced the LPS inhalation-induced pulmonary edema, neutrophil infiltration and TNF-α production in mice. With the same model, the current investigation focused on the role of the airway epithelium, a first-line barrier and a prime target of inhaled toxicants. We report that LXA4 strongly inhibited LPS-induced ALI in mice, in part by protecting the airway epithelium and preserving the E-cadherin expression and airway permeability. Using a cryo-imaging assay and fluorescence detection, LXA4 was shown to block LPS-induced ROS generation and preserve mitochondrial redox status both in vivo and in vitro. To further assess whether and how NF-E2-related factor 2 (Nrf2) was involved in the protective effect of LXA4, fluorescence resonance energy transfer (FRET) analysis was employed in human epithelial cell line (16HBE), to determine the relative distance between Nrf2 and its negative regulator or cytosolic inhibitor, Kelch-like ECH-associated protein 1 (Keap1). It provided us the evidence that LXA4 further promoted the dissociation of Nrf2 and Keap1 in LPS-treated 16HBE cells. The results also showed that LXA4 activates Nrf2 by phosphorylating it on Ser40 and triggering its nuclear translocation. Moreover, when the plasmid expression dominant negative mutation of Nrf2 was transfected as an inhibitor of wild-type Nrf2, the protective effect of LXA4 on E-cadherin expression was almost completely blocked. These results provide a new mechanism by which LXA4 inhibits LPS-induced ALI through Nrf2-mediated E-cadherin expression.

Low blood and vitreal BDNF, LXA4 and altered Th1/Th2 cytokine balance are potential risk factors for diabetic retinopathy

OBJECTIVE

The study was conducted to observe the serum and vitreous levels of LXA4, BDNF and Th1/Th2 cytokines in type 2 diabetes mellitus (DM) and changes associated with diabetic retinopathy (DR). Further, the in vitro study was performed to analyze the exposure of BDNF and LXA4 on LPS-induced pro-inflammatory state in ARPE 19 cells.

MATERIALS AND METHODS

Totally 114 individuals were recruited in a prospective case control study. Of these, 27 were type 2 DM cases with no complications, 30 cases were type 2 DM with non proliferative diabetic retinopathy (NPDR), 30 were type 2 DM with proliferative diabetic retinopathy (PDR), and 27 were healthy control. ELISA was done to estimate the serum and vitreous levels of BDNF, VEGF and PEDF. FACS cytometric Bead Array system was used to analyze the serum cytokines.

RESULTS

The serum BDNF and LXA4 levels were significantly reduced in both NPDR and PDR cases compared to control (p=0.005, 0.01; p=0.033, 0.015). Serum IL-6 was significantly increased in the PDR group (p=0.04). BDNF showed a significant negative correlation with VEGF levels (r=-0.522, p<0.01) and positive correlation with IL-10 (r=0.67, p<0.05) in serum. A significant odds ratio for the serum BDNF (OR: 3.20, p=0.025) as well as serum IL-6 (OR: 1.244, p=0.042) indicated them as potential risk factors for progression of type 2 DM to DR. A significant decrease in both the LXA4 (p=0.013) and BDNF (p=0.0008) with increase in cytokines IL-6 and IL-10 levels were observed in the vitreous of PDR cases ((p=0.04, 0.01). In vitro studies showed that both LXA4 (10 nmol/L) and BDNF (500 pg) decreased the IL-6 levels (p=0.036, 0.0002), in LPS induced pro-inflammatory condition in ARPE 19 cells, thereby their anti-inflammatory effect.

CONCLUSIONS

This study reports that low serum BDNF and higher IL-6 levels are potential risk factors for DR in type 2 DM. This study supports the role of BDNF in modulating the pro- and anti-inflammatory cytokines, and low level of BDNF is associated with development of diabetic retinopathy.

Lipoxin A4 regulates expression of the estrogen receptor and inhibits 17β-estradiol induced p38 mitogen-activated protein kinase phosphorylation in human endometriotic stromal cells

OBJECTIVE

To study the role of lipoxin A4 (LXA4) in endometriosis.

DESIGN

Molecular analysis in human samples and primary human endometriotic stromal cells (ESCs).

SETTING

University hospital.

PATIENT(S)

Forty-nine premenopausal women (30 patients with endometriosis and 19 controls).

INTERVENTION(S)

Normal and ectopic endometrial biopsies obtained during surgery performed during the proliferative phase of the menstrual cycle; ESCs used for in vitro studies.

MAIN OUTCOME MEASURE(S)

Levels of LXA4 measured by enzyme-linked immunosorbent assay (ELISA); mRNA levels of the estrogen receptor (ER), progestogen receptor (PR), tumor necrosis factor α (TNF-α), and interleukin 6 (IL-6) quantified by quantitative reverse-transcription polymerase chain reaction (qRT-PCR); and p38 mitogen-activated protein kinase (p38 MAPK) phosphorylation evaluated by Western blotting.

RESULT(S)

The LXA4 expression level decreased in ectopic tissue as well as ERα and PR, although the expression of ERβ increased in ectopic endometrium compared with the controls. Investigations with correlation analysis revealed the expression of LXA4 was positively correlated with ERα and negatively correlated with ERβ in vivo. Moreover, administering LXA4 could augment ERβ expression in ESCs and inhibit the 17β-estradiol-induced phosphorylation of p38 MAPK very likely through ERβ.

CONCLUSION(S)

Our findings indicate that LXA4 regulates ERβ expression and inhibits 17β-estradiol-induced phosphorylation of p38 MAPK, very likely through ERβ in ESCs.

The eosinophil chemoattractant 5-oxo-ETE and the OXE receptor

5-Oxo-ETE (5-oxo-6,8,11,14-eicosatetraenoic acid) is formed from the 5-lipoxygenase product 5-HETE (5S-hydroxy-6,8,11,14-eicosatetraenoic acid) by 5-hydroxyeicosanoid dehydrogenase (5-HEDH). The cofactor NADP(+) is a limiting factor in the synthesis of 5-oxo-ETE because of its low concentrations in unperturbed cells. Activation of the respiratory burst in phagocytic cells, oxidative stress, and cell death all dramatically elevate both intracellular NADP(+) levels and 5-oxo-ETE synthesis. 5-HEDH is widely expressed in inflammatory, structural, and tumor cells. Cells devoid of 5-lipoxygenase can synthesize 5-oxo-ETE by transcellular biosynthesis using inflammatory cell-derived 5-HETE. 5-Oxo-ETE is a chemoattractant for neutrophils, monocytes, and basophils and promotes the proliferation of tumor cells. However, its primary target appears to be the eosinophil, for which it is a highly potent chemoattractant. The actions of 5-oxo-ETE are mediated by the highly selective OXE receptor, which signals by activating various second messenger pathways through the release of the βγ-dimer from Gi/o proteins to which it is coupled. Because of its potent effects on eosinophils, 5-oxo-ETE may be an important mediator in asthma, and, because of its proliferative effects, may also contribute to tumor progression. Selective OXE receptor antagonists, which are currently under development, could be useful therapeutic agents in asthma and other allergic diseases.

Dual role of lipoxin A4 in pneumosepsis pathogenesis

Lipoxin A4 (LXA4) is an endogenous lipid mediator with potent anti-inflammatory actions but its role in infectious processes is not well understood. We investigated the involvement of LXA4 and its receptor FPR2/ALX in the septic inflammatory dysregulation. Pneumosepsis was induced in mice by inoculation of Klebsiella pneumoniae. LXA4 levels and FPR2/ALX expression in the infectious focus as well as the effects of treatment with receptor agonists (LXA4 and BML-111) and antagonists (BOC-2 and WRW(4)) in early (1h) and late (24h) sepsis were studied. Sepsis induced an early increase in LXA4, FPR2/ALX lung expression, local and systemic infection and inflammation, and mortality. Treatment with BOC-2 in early sepsis increased leukocyte migration to the focus, and reduced bacterial load and dissemination. Inhibition of 5- and 15-lipoxygenase in early sepsis also increased leukocyte migration. Early treatment with WRW(4) and BOC-2 improved survival. Treatment with authentic LXA4 or BML-111 in early sepsis decreased cell migration and worsened the infection. In late sepsis, treatment with BOC-2 had no effect, but LXA4 improved the survival rate by reducing the excessive inflammatory response, this effect being abolished by pretreatment with BOC-2. Thus, the anti-inflammatory and pro-resolution mediator LXA4 and its receptor FPR2/ALX levels were increased in the early phase of sepsis, contributing to the septic inflammatory dysregulation. In addition, LXA4 has a dual role in sepsis and that its beneficial or harmful effects are critically dependent on the time. Therefore, a proper interference with LXA4 system may be a new therapeutic avenue to treat sepsis.

Exhaled breath condensate eicosanoid levels associate with asthma and its severity

BACKGROUND

The relationship between anti-inflammatory lipoxins and proinflammatory leukotrienes might be important in the pathobiology and severity of asthma.

OBJECTIVE

We sought to investigate whether exhaled breath condensate (EBC) lipoxin and leukotriene measurements can noninvasively characterize the asthmatic diathesis and its severity.

METHODS

We measured lipoxin A4 (LXA4) and leukotriene B4 (LTB4) levels in EBC collected from patients with asthma of different severities and from healthy control subjects.

RESULTS

EBC LXA4 and LTB4 levels are increased in asthmatic patients compared with those seen in healthy control subjects (LXA4: 31.40 vs 2.41 pg/mL EBC, respectively [P < .001]; LTB4: 45.62 vs 3.82 pg/mL EBC, respectively [P < .001]). Although levels of both eicosanoids are increased in asthmatic patients, the LXA4/LTB4 ratio decreases with increasing asthma severity. It is 41% lower in patients with severe versus moderate asthma (0.52 vs 0.88, P = .034). EBC LXA4 levels correlate with the degree of airflow obstruction measured by using FEV1 (r = 0.28, P = .018). An LXA4 cutoff value of 7 pg/mL EBC provides 90% sensitivity and 92% specificity for the diagnosis of asthma (area under the curve, 0.96; P < .001). An LTB4 cutoff value of 11 pg/mL EBC provides 100% sensitivity and 100% specificity for the diagnosis of asthma (area under the curve, 1; P < .001).

CONCLUSIONS

Proresolving and proinflammatory eicosanoids are generated in the airways of all asthmatic patients. The proportion of proresolving compounds decreases with asthma severity. These findings support the role for EBC eicosanoid measurements in the noninvasive diagnosis of asthma and suggest that proresolving eicosanoid pathways are dysregulated in patients with severe asthma.