15-epi-lipoxin A5 promotes neutrophil exit from exudates for clearance by splenic macrophages.

Specialized proresolving mediators (SPMs) promote local macrophage efferocytosis but excess leukocytes early in inflammation require additional leukocyte clearance mechanism for resolution. Here, neutrophil clearance mechanisms from localized acute inflammation were investigated in mouse dorsal air pouches. 15-HEPE (15-hydroxy-5Z,8Z,11Z,13E,17Z-eicosapentaenoic acid) levels were increased in the exudates. Activated human neutrophils converted 15-HEPE to lipoxin A5 (5S,6R,15S-trihydroxy-7E,9E,11Z,13E,17Z-eicosapentaenoic acid), 15-epi-lipoxin A5 (5S,6R,15R-trihydroxy-7E,9E,11Z,13E,17Z-eicosapentaenoic acid), and resolvin E4 (RvE4; 5S,15S-dihydroxy-6E,8Z,11Z,13E,17Z-eicosapentaenoic acid). Exogenous 15-epi-lipoxin A5, 15-epi-lipoxin A4 and a structural lipoxin mimetic significantly decreased exudate neutrophils and increased local tissue macrophage efferocytosis, with comparison to naproxen. 15-epi-lipoxin A5 also cleared exudate neutrophils faster than the apparent local capacity for stimulated macrophage efferocytosis, so the fate of exudate neutrophils was tracked with CD45.1 variant neutrophils. 15-epi-lipoxin A5 augmented the exit of adoptively transferred neutrophils from the pouch exudate to the spleen, and significantly increased splenic SIRPa+ and MARCO+ macrophage efferocytosis. Together, these findings demonstrate new systemic resolution mechanisms for 15-epi-lipoxin A5 and RvE4 in localized tissue inflammation, which distally engage the spleen to activate macrophage efferocytosis for the clearance of tissue exudate neutrophils.

Are secondary bacterial pneumonia mortalities increased because of insufficient pro-resolving mediators?

Respiratory viral infections, including respiratory syncytial virus (RSV), parainfluenza viruses and type A and B influenza viruses, can have severe outcomes. Bacterial infections frequently follow viral infections, and influenza or other viral epidemics periodically have higher mortalities from secondary bacterial pneumonias. Most secondary bacterial infections can cause lung immunosuppression by fatty acid mediators which activate cellular receptors to manipulate neutrophils, macrophages, natural killer cells, dendritic cells and other lung immune cells. Bacterial infections induce synthesis of inflammatory mediators including prostaglandins and leukotrienes, then eventually also special pro-resolving mediators, including lipoxins, resolvins, protectins and maresins, which normally resolve inflammation and immunosuppression. Concurrent viral and secondary bacterial infections are more dangerous, because viral infections can cause inflammation and immunosuppression before the secondary bacterial infections worsen inflammation and immunosuppression. Plausibly, the higher mortalities of secondary bacterial pneumonias are caused by the overwhelming inflammation and immunosuppression, which the special pro-resolving mediators might not resolve.

Lipoxin A4 ameliorates knee osteoarthritis progression in rats by antagonizing ferroptosis through activation of the ESR2/LPAR3/Nrf2 axis in synovial fibroblast-like synoviocytes.

BACKGROUND: Our previous studies have shown that lipoxin A4 (LXA4) can serve as a potential biomarker for assessing the efficacy of exercise therapy in knee osteoarthritis (KOA), and fibroblast-like synoviocytes (FLSs) may play a crucial role in KOA pain as well as in the progression of the pathology. OBJECTIVE: By analyzing the GSE29746 dataset and collecting synovial samples from patients with different Kellgren-Lawrence (KL) grades for validation, we focused on exploring the potential effect of LXA4 on ferroptosis in FLSs through the ESR2/LPAR3/Nrf2 axis to alleviate pain and pathological advancement in KOA. METHODS: The association between FLSs ferroptosis and chondrocyte matrix degradation was explored by cell co-culture. We overexpressed and knocked down LPAR3 in vitro to explore its potential mechanism in FLSs. A rat model of monosodium iodoacetate (MIA)-induced KOA was constructed and intervened with moderate-intensity treadmill exercise and intraperitoneal injection of PHTPP to investigate the effects of the LXA4 intracellular receptor ESR2 on exercise therapy. RESULTS: ESR2, LPAR3, and GPX4 levels in the synovium decreased with increasing KL grade. After LXA4 intervention in the co-culture system, GPX4, LPAR3, and ESR2 were upregulated in FLSs, collagen II was upregulated in chondrocytes, and MMP3 and ADAM9 were downregulated. LPAR3 overexpression upregulated the expression of GPX4, Nrf2, and SOD1 in FLSs, while downregulating the expression of MMP13 and MMP3; LPAR3 knockdown reversed these changes. Moderate-intensity platform training improved the behavioral manifestations of pain in KOA rats, whereas PHTPP treatment partially reversed the improvement in synovial and cartilage pathologies induced by platform training. CONCLUSION: LXA4 inhibited FLSs ferroptosis by activating the ESR2/LPAR3/Nrf2 axis, thereby alleviating the pain and pathological progression of KOA. This study brings a new target for the treatment of KOA and also leads to a deeper understanding of the potential mechanisms of exercise therapy for KOA.

Advances in the Chemistry and Biology of Specialised Pro-Resolving Mediators (SPMs).

This review article assembles key recent advances in the synthetic chemistry and biology of specialised pro-resolving mediators (SPMs). The major medicinal chemistry developments in the design, synthesis and biological evaluation of synthetic SPM analogues of lipoxins and resolvins have been discussed. These include variations in the top and bottom chains, as well as changes to the triene core, of lipoxins, all changes intended to enhance the metabolic stability whilst retaining or improving biological activity. Similar chemical modifications of resolvins are also discussed. The biological evaluation of these synthetic SPMs is also described in some detail. Original investigations into the biological activity of endogenous SPMs led to the pairing of these ligands with the FPR2/LX receptor, and these results have been challenged in more recent work, leading to conflicting results and views, which are again discussed.

Alterations in the pro-resolving lipid mediator machinery within first trimester maternal tissue: Implications in decidualization and miscarriage risk.

A pivotal event in uterine receptivity and human reproduction is the differentiation of endometrial stromal cells into decidual cells, known as decidualization. Decidualization is interlinked with its inflammatory environment. Our study aimed to investigate the presence and role of pro-resolving lipid mediators in first trimester maternal tissue. We assessed the levels of LXA4 and RvD1, along with their metabolic LOX enzymes, in elective (control) and sporadic miscarriage samples. We investigated the effects of LXA4 and RvD1 on decidualization using primary endometrial stromal cells and the immortalized endometrial stromal St-T1b cell line. The upregulation of 12- and 15-LOX expression was observed in pregnancy tissue after sporadic miscarriage, suggesting an inflammatory imbalance. Furthermore, incubation with these lipid mediators led to a decrease in decidualization biomarkers PRL and IGFBP-1, accompanied by morphological changes indicative of aberrant differentiation. The expression of LOX enzymes in decidual natural killer cells suggests their involvement in regulating the inflammatory surroundings and the extent of decidualization.

A signaling network map of Lipoxin (LXA4): an anti-inflammatory molecule.

Lipoxins (LXs) are a class of endogenous bioactive lipid mediators that are involved in the regulation of inflammation. They exert immunomodulatory effects by regulating the behaviour of various immune cells, including neutrophils, macrophages, and T and B cells, by promoting the clearance of apoptotic neutrophils. This helps to dampen inflammation and promote tissue repair. LXs regulate the expression of many inflammatory genes by modulating the levels of transcription factors, such as nuclear factor κB (NF-κB), activator protein-1 (AP-1), nerve growth factor-regulated factor 1A binding protein 1 (NGF), and peroxisome proliferator activated receptor γ (PPAR-γ), which are elevated in various diseases, such as respiratory tract diseases, renal diseases, cancer, neurodegenerative diseases, and viral infections. Lipoxin-mediated signaling is involved in chronic inflammation, cancer, diabetes-associated kidney disease, lung injury, liver injury, endometriosis, respiratory tract diseases, neurodegenerative diseases, chronic cerebral hypoperfusion, and retinal degeneration. In this study, we systematically investigated the intricate network of lipoxin signaling by analyzing the relevant literature. The resulting map comprised 467 molecules categorized as activation/inhibition, enzyme catalysis, gene and protein expression, molecular associations, and translocation events. This map serves as a valuable resource for understanding the complexity of lipoxin signaling and its impact on various cellular functions.

Lipoxins A4 and B4 inhibit glial cell activation via CXCR3 signaling in acute retinal neuroinflammation.

Lipoxins are small lipids that are potent endogenous mediators of systemic inflammation resolution in a variety of diseases. We previously reported that Lipoxins A4 and B4 (LXA4 and LXB4) have protective activities against neurodegenerative injury. Yet, lipoxin activities and downstream signaling in neuroinflammatory processes are not well understood. Here, we utilized a model of posterior uveitis induced by lipopolysaccharide endotoxin (LPS), which results in rapid retinal neuroinflammation primarily characterized by activation of resident macroglia (astrocytes and Müller glia), and microglia. Using this model, we observed that each lipoxin reduces acute inner retinal inflammation by affecting endogenous glial responses in a cascading sequence beginning with astrocytes and then microglia, depending on the timing of exposure; prophylactic or therapeutic. Subsequent analyses of retinal cytokines and chemokines revealed inhibition of both CXCL9 (MIG) and CXCL10 (IP10) by each lipoxin, compared to controls, following LPS injection. CXCL9 and CXCL10 are common ligands for the CXCR3 chemokine receptor, which is prominently expressed in inner retinal astrocytes and ganglion cells. We found that CXCR3 inhibition reduces LPS-induced neuroinflammation, while CXCR3 agonism alone induces astrocyte reactivity. Together, these data uncover a novel lipoxin-CXCR3 pathway to promote distinct anti-inflammatory and proresolution cascades in endogenous retinal glia.

BML-111, the agonist of lipoxin A4, suppresses epithelial-mesenchymal transition and migration of MCF-7 cells via regulating the lipoxygenase pathway.

Introduction: Aberrant epithelial-mesenchymal transition (EMT) and migration frequently occur during tumour progression. BML-111, an analogue of lipoxin A4, has been implicated in inflammation in cancer research. Methods: 3-(4,5-Dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay, western blot, Reverse Transcription Polymerase Chain Reaction (RT-PCR), transwell assay, immunofluorescence, and immunohistochemistry were conducted in this study. Results: In vitro experiments revealed that BML-111 inhibited EMT and migration in CoCl2-stimulated MCF-7 cells. These effects were achieved by inhibiting MMP-2 and MMP-9, which are downregulated by 5-lipoxygenase (5-LOX). Moreover, BML-111 inhibited EMT and migration of breast cancer cells in BALB/c nude mice inoculated with MCF-7 cells. Conclusion: Our results suggest that BML-111 may be a potential therapeutic drug for breast cancer and that blocking the 5-LOX pathway could be a possible approach for mining effective drug targets.

Effect of Alox-15 Polymorphism on GCF Levels of Lipoxin-A4 in Chronic Periodontitis: A Preliminary Study

Lipoxins play an important role in periodontal resolution, hence, investigation of genetic polymorphism of lipoxin gene may provide important information on the role of lipoxins in periodontal disease pathogenesis. The aim of this study was to investigate a polymorphism of C-to-T substitution at position c.-292 in ALOX15 (reticulocyte-type 15 lipoxygenase 1) gene in patients with chronic periodontitis and to associate the polymorphism with gingival crevicular fluid (GCF) lipoxin A4 (LXA4) levels. Forty-five chronic periodontitis and 45 periodontally healthy patients were included in this case-control study. Plaque index, calculus index, sulcus bleeding index, full mouth probing depth (PD) and clinical attachment loss (CAL) were recorded. GCF and blood samples were collected. GCF was analyzed for LXA4 levels by enzyme linked immunosorbant assay. Genotyping of ALOX15 polymorphism was studied using PCR. Mean LXA4 was lower in periodontitis group compared to the periodontally healthy group. There was a negative correlation between CAL and LXA4. The CC genotype was higher in the study group than in the control group. In the study group, mean CAL was significantly lower among individuals with the CT genotype. Mean LXA4 was significantly lower in CC genotype (45.0±7.11 ng/mL) compared to CT genotype (50.81±5.81 ng/mL) among the patients with periodontitis. The results suggest that LXA4 and c.-292T allele are associated with periodontal health. Polymorphisms in the ALOX15 gene may influence periodontal disease pathogenesis. Hence, investigation of such polymorphisms could benefit the evaluation of lipoxins role in periodontal disease.

Resumo Lipoxinas desempenham um papel importante na recuperação periodonta, portanto, a investigação do polimorfismo genético do gene da lipoxina pode fornecer informações importantes sobre o papel das lipoxinas na patogênese da doença periodontal. O objetivo deste estudo foi investigar um polimorfismo de substituição C-to-T na posição c-292 no gene ALOX15 (reticulócito-tipo 15 lipoxigenase 1) em pacientes com periodontite crônica e associar o polimorfismo com a lipoxina A4 (LXA4) do fluido gengival crevicular (FGC). Quarenta e cinco pacientes com periodontite crônica e 45 pacientes periodonalmente saudáveis foram incluídos neste estudo caso-controle. Índice de placa, índice de cálculo, índice de sangramento do sulco, profundidade de sondagem (PS) da boca toda e perda de inserção clínica (PIC) foram registrados. Amostras do FGC e de sangue foram coletadas. O FGC foi analisado quanto aos níveis de LXA4 por ensaio imunoadsorvente ligado à enzima (ELISA). A genotipagem do polimorfismo ALOX15 foi estudada por PCR. A média de LXA4 foi menor no grupo de periodontite em comparação com o grupo periodontalmente saudável. Houve uma correlação negativa entre PIC e LXA4. O genótipo CC foi maior no grupo de estudo do que no grupo controle. No grupo de estudo, a média de PIC foi significativamente menor entre os indivíduos com o genótipo CT. A média de LXA4 foi significativamente menor no genótipo CC (45,0 ± 7,11 ng / mL) em comparação com o genótipo CT (50,81 ± 5,81 ng / mL) entre os pacientes com periodontite. Os resultados sugerem que o alelo LXA4 e o alelo c-292T estão associados à saúde periodontal. Polimorfismos no gene ALOX15 podem influenciar a patogênese da doença periodontal. Assim, a investigação de tais polimorfismos pode beneficiar a avaliação do papel das lipoxinas na doença periodontal.