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.

Association between arachidonate lipoxygenase 15,c.-292 C > T gene polymorphism and non-cystic fibrosis bronchiectasis in children: a pilot study on the effects on airway lipoxin A4 and disease phenotype.

BACKGROUND: Persistent airway inflammation is a central feature of bronchiectasis. Arachidonate 15-lipoxygenase (ALOX-15) controls production of endogenous lipid mediators, including lipoxins that regulate airway inflammation. Mutations at various positions in ALOX-15 gene can influence airway disease development. We investigated association between ALOX-15,c.-292 C > T gene polymorphism and bronchiectasis unrelated to cystic fibrosis in Egyptian children. Also, lipoxin A4 (LXA4) level in bronchoalveolar lavage (BAL) was studied in relation to polymorphism genotypes and disease phenotypes determined by clinical, pulmonary functions, and radiological severity parameters. METHODS: This was an exploratory study that included 60 participants. Thirty children with non-cystic fibrosis bronchiectasis (NCFB) were compared with 30 age and sex-matched controls. ALOX-15,c.-292 C > T polymorphism was genotyped using TaqMan-based Real-time PCR. LXA4 was measured in BAL using ELISA method. RESULTS: There was no significant difference between patients and controls regarding ALOX-15,c.-292 C > T polymorphism genotypes and alleles (OR = 1.75; 95% CI (0.53-5.7), P = 0.35) (OR = 1; 95% CI (0.48-2), p = 1). BAL LXA4 level was significantly lower in patients, median (IQR) of 576.9 (147.6-1510) ng/ml compared to controls, median (IQR) of 1675 (536.8-2542) (p = 0.002). Patients with severe bronchiectasis had a significantly lower LXA4 level (p < 0.001). There were significant correlations with exacerbations frequency (r=-0.54, p = 0.002) and FEV1% predicted (r = 0.64, p = 0.001). Heterozygous CT genotype carriers showed higher LXA4 levels compared to other genotypes(p = 0.005). CONCLUSIONS: Low airway LXA4 in children with NCFB is associated with severe disease phenotype and lung function deterioration. CT genotype of ALOX-15,c.-292 C > T polymorphism might be a protective genetic factor against bronchiectasis development and/or progression due to enhanced LXA4 production.

Dysregulation of neuroprotective lipoxin pathway in astrocytes in response to cytokines and ocular hypertension​.

Glaucoma leads to vision loss due to retinal ganglion cell death. Astrocyte reactivity contributes to neurodegeneration. Our recent study found that lipoxin B4 (LXB4), produced by retinal astrocytes, has direct neuroprotective actions on retinal ganglion cells. In this study, we aimed to investigate how the autacoid LXB4 influences astrocyte reactivity in the retina under inflammatory cytokine-induced activation and during ocular hypertension. The protective activity of LXB4 was investigated in vivo using the mouse silicone-oil model of chronic ocular hypertension. By employing a range of analytical techniques, including bulk RNA-seq, RNAscope in-situ hybridization, qPCR, and lipidomic analyses, we discovered the formation of lipoxins and expression of the lipoxin pathway in rodents (including the retina and optic nerve), primates (optic nerve), and human brain astrocytes, indicating the presence of this neuroprotective pathway across various species. Findings in the mouse retina identified significant dysregulation of the lipoxin pathway in response to chronic ocular hypertension, leading to an increase in 5-lipoxygenase (5-LOX) activity and a decrease in 15-LOX activity. This dysregulation was coincident with a marked upregulation of astrocyte reactivity. Reactive human brain astrocytes also showed a significant increase in 5-LOX. Treatment with LXB4 amplified the lipoxin biosynthetic pathway by restoring and amplifying the generation of another member of the lipoxin family, LXA4, and mitigated astrocyte reactivity in mouse retinas and human brain astrocytes. In conclusion, the lipoxin pathway is functionally expressed in rodents, primates, and human astrocytes, and is a resident neuroprotective pathway that is downregulated in reactive astrocytes. Novel cellular targets for LXB4's neuroprotective action are inhibition of astrocyte reactivity and restoration of lipoxin generation. Amplifying the lipoxin pathway is a potential target to disrupt or prevent astrocyte reactivity in neurodegenerative diseases, including retinal ganglion cell death in glaucoma.

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.

LXA4 protected mice from renal ischemia/reperfusion injury by promoting IRG1/Nrf2 and IRAK-M-TRAF6 signal pathways.

Excessive inflammatory response and increased oxidative stress play an essential role in the pathophysiology of ischemia/reperfusion (I/R)-induced acute kidney injury (IRI-AKI). Emerging evidence suggests that lipoxin A4 (LXA4), as an endogenous negative regulator in inflammation, can ameliorate several I/R injuries. However, the mechanisms and effects of LXA4 on IRI-AKI remain unknown. In this study, A bilateral renal I/R mouse model was used to evaluate the role of LXA4 in wild-type, IRG1 knockout, and IRAK-M knockout mice. Our results showed that LXA4, as well as 5-LOX and ALXR, were quickly induced, and subsequently decreased by renal I/R. LXA4 pretreatment improved renal I/R-induced renal function impairment and renal damage and inhibited inflammatory responses and oxidative stresses in mice kidneys. Notably, LXA4 inhibited I/R-induced the activation of TLR4 signal pathway including decreased phosphorylation of TAK1, p36, and p65, but did not affect TLR4 and p-IRAK-1. The analysis of transcriptomic sequencing data and immunoblotting suggested that innate immune signal molecules interleukin-1 receptor-associated kinase-M (IRAK-M) and immunoresponsive gene 1 (IRG1) might be the key targets of LXA4. Further, the knockout of IRG1 or IRAK-M abolished the beneficial effects of LXA4 on IRI-AKI. In addition, IRG1 deficiency reversed the up-regulation of IRAK-M by LXA4, while IRAK-M knockout had no impact on the IRG1 expression, indicating that IRAK-M is a downstream molecule of IRG1. Mechanistically, we found that LXA4-promoted IRG1-itaconate not only enhanced Nrf2 activation and increased HO-1 and NQO1, but also upregulated IRAK-M, which interacted with TRAF6 by competing with IRAK-1, resulting in deactivation of TLR4 downstream signal in IRI-AKI. These data suggested that LXA4 protected against IRI-AKI via promoting IRG1/Itaconate-Nrf2 and IRAK-M-TRAF6 signaling pathways, providing the rationale for a novel strategy for preventing and treating IRI-AKI.

Lipoxin A4 levels predict site-specific clinical improvements post scaling and root planing and correlate negatively with periodontal pathogens in severe periodontitis.

BACKGROUND: Serving as a stop signal of inflammation, the role of lipoxin A4 (LXA4) in periodontitis remains to be clarified. This study is aimed to examine the changes in LXA4 levels in gingival crevicular fluid (GCF) after scaling and root planing (SRP) and to determine the relationship between LXA4 levels and treatment outcomes and periodontal pathogens in severe periodontitis. METHODS: A total of 74 GCF samples were collected from 21 severe periodontitis participants at the deepest affected sites. These sites were re-sampled at 1, 3, and 6 months after SRP. Besides, GCF samples were also collected from 25 periodontally healthy participants. Clinical parameters including probing depth (PD) and clinical attachment level (CAL) in periodontitis group were recorded. LXA4 levels and periodontal pathogens in the GCF were analyzed by ELISA and PCR, respectively. Correlations between GCF LXA4 levels and treatment effect and periodontal pathogens were assessed. RESULTS: LXA4 levels in GCF significantly increased after SRP (p < 0.05), but remained lower than those observed in healthy individuals (p < 0.05). Sites with lower baseline LXA4 concentrations were more likely to experience greater improvements in PD at 6 months post-SRP (area under the curve [AUC] = 0.792), and the improvements were positively correlated with the increase of LXA4 at these sites post-treatment (p < 0.05). Furthermore, more elevated LXA4 levels were observed in sites that became negative for Prevotella intermedia or Tannerella forsythia after SRP. CONCLUSION: Baseline LXA4 in GCF has the potential to predict the site-specific response of severe periodontal lesions to SRP. The increase of LXA4 levels after treatment was positively correlated with clinical improvements and negatively correlated with the presence of Prevotella intermedia or Tannerella forsythia.

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.

Remodelación vascular como modelo in vitro para el estudio del síndrome antifosfolipídico obstétrico / Vascular remodeling as in vitro model for the study of the obstetrical antiphospholipid syndrome

Introducción y Objetivo: Los anticuerpos antifosfolípidos (aAFL) se pueden unir a las células trofoblásticas o a las endoteliales, alterando la remodelación vascular y consecuentemente la placentación normal. El objetivo fue evaluar el efecto del suero de pacientes con síndrome antifosfolipídico (SAF) obstétrico en la interacción endotelio-trofoblasto utilizando un modelo in vitro tridimensional de remodelación vascular. Métodos: Las pacientes con aAFL fueron clasificadas en dos grupos: morbilidad gestacional y trombosis (MG/TV, n=7) y morbilidad gestacional sola (MG, n=8). Como control, se incluyeron mujeres sin aAFL con MG (MG/ aAFL-, n=10), y mujeres sanas (SHN, n=7). Células endoteliales HUVEC fueron cultivadas en Matrigel™ hasta formar estructuras tubulares (angiogénesis) y luego se adicionaron células trofoblásticas HTR8; estas células invaden las estructuras tubulares de las células endoteliales mejorando su estabilidad. Se evaluó el efecto de 10% del suero de las mujeres del estudio sobre esta interacción.

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.

Suplementos dietarios en periodoncia: revisión bibliográfica narrativa / Additives in periodontics: a narrative review of the literature

Se realizó la revisión de los trabajos de investigación relacionados con la utilización de resolvinas y probióticos como complementos dietarios en la terapia periodontal, tanto en animales de experimentación como en humanos, describiendo el origen, la composición y los posibles mecanismos de acción. A partir de los trabajos revisados, se concluyó que las aludidas sustencias son, en la actualidad, un tema de investigación no traspolable a la clínica y que en el mediano plano, podrían potenciar las terapias actuales para patologías periodontales específicas.

Papel da Lipoxina A4 na fisiologia do sistema nervoso central e no dano cognitivo associado à neuroinflamação / Lipoxin A4 paper of the central nervous system physiology and cognitive impairment associated with neuroinflammation

O papel da lipoxina A4 (LXA4) no sistema imunológico é bem estudado, mas o papeldessa molécula na fisiologia do sistema nervoso central (SNC) só foi abordado recentemente.Como um modulador alostérico positivo, a LXA4 produz efeitos canabimiméticos e pode, dessaforma, estar envolvida em vßrios aspectos de funções fisiológicas reguladas pelo sistemaendocanabinóide (eCB). Nós investigamos essa hipótese analisando o comportamento decamundongos knockout (5-LO-/-) para a enzima 5-lipoxigenase (5-LO), que participa da síntesede LXA4. Ansiedade, consumo de ßgua e alimento, locomoção, nocicepção e memórias aversivassão comportamentos reconhecidos como sob controle do sistema eCB e foram avaliados nesteestudo. Nenhuma alteração foi observada no comportamento de 5-LO-/-em relação ao consumode ßgua e alimento e locomoção no teste de campo aberto. No entanto, o tratamento com LXA4produziu efeito ansiolítico no labirinto em cruz elevada. Além disso, inibição farmacológica da 5-LO demonstrou um efeito ansiogênico em animais idosos, mas não em adultos jovens, indicandoque a LXA4 endógena exerce um efeito regulatório sobre ansiedade de forma idade-dependente.Os animais 5-LO-/-apresentaram um aumento na sensibilidade e redução na tolerância à dor noteste de sensibilidade ao choque. Ainda, uma disfunção em memória de curto prazo e extinção dememória no teste de esquiva inibitória foi observada nos animais 5-LO-/-, indicando que a LXA4pode agir na facilitação do aprendizado...

The role of lipoxin A4 (LXA4) in the immune system is well studied, however the part thismolecule plays in central nervous system (CNS) physiology has only recently been addressed.LXA4, as a CB1 allosteric enhancer, has a cannabimimetic effect and may therefore be involvedin various aspects of endocannabinoid system (eCB) physiological functions. We investigatedthis reasoning by analyzing the behavior of 5-lipoxygenase (5-LO) knockout mice (5-LO-/-).Anxiety-like behavior, appetitive behavior, locomotion, nociception and learning and memory areall known to be under control of the eCB system and were assessed in this study. No alterationwas observed in the behavior of 5-LO knockout mice regarding appetitive behavior, measured byfood and water intake, or locomotion in the open field test. However, treatment with LXA4produced an anxiolytic-like effect on the elevated plus maze. Further, pharmacological inhibitionof 5-LO showed an anxiogenic-like effect in aged, but not adult mice, indicating that endogenousLXA4 has an age-dependent effect on the modulation of anxiety-like behavior. 5-LO-/- micepresented an increase in pain sensitivity and a decrease in pain tolerance in the foot shocksensitivity test. Interestingly, the animals also presented impairment in short-term memory andextinction learning in the step-down inhibitory avoidance task, pointing out that LXA4 may act inthe facilitation of fear learning. These data are of great importance to the possible use of LXA4 astreatment to neuroinflammation induced cognitive impairment.The study of sepsis reveals that an inflammatory stimulus can induce the exacerbatedproduction of pro-inflammatory cytokines in the CNS, which causes neuroinflammation andcognitive impairment...

Efeito do veneno de Crotalus durissus terrificus no edema crônico induzido na pata de camundongos pela injeção de bacilo Calmette-Guérin (BCG) / Effect of the Crotalus durissus terrificus in edema chronic induced in mice paw by the injection of bacilo Calmette-Guérin (BCG)

Diferentemente do observado em outros envenenamentos por serpentes da família Viperidae, nos causados pela Cdt não se observam sinais inflamatórios significativos no local da picada. Estudos prévios mostram que o VCdt inibe a resposta inflamatória aguda e algumas atividades biológicas de macrófagos, principal célula do processo inflamatório crônico. Nesse trabalho verificou-se o efeito do VCdt sobre o edema de pata crônico induzido pela injeção intraplantar de BCG em camundongos. Na concentração utilizada, o BCG evoca um edema crônico que é significativamente inibido pelo pré-tratamento dos animais com o VCdt (s.c.). Essa inibição persistiu por todo o período estudado (15 dias). O grupo que recebeu o veneno 1 h após a injeção de BCG também apresentou perfil de edema inibido em relação ao grupo controle, de forma semelhante ao observado no grupo pré-tratado com o veneno. Os grupos tratados com o VCdt 6 ou 11 dias após a injeção do BCG apresentavam edema de magnitude semelhante até o dia da injeção do veneno, sendo observada uma inibição significativa desse edema no dias subseqüentes à injeção do veneno. Uma vez constatado esse efeito inibitório do VCdt sobre o edema inflamatório crônico induzido pelo BCG, estudou-se qual a fração do veneno seria responsável por esse efeito. Os resultados indicam que a crotoxina, e não outros componentes deste veneno seja a responsável por essa inibição. Estudando-se possíveis mecanismos envolvidos nessa inibição, a reversão da inibição induzida pelo VCdt observada em grupos pré-tratados com dexametazona e zileuton, sugerem fortemente a participação de mediadores originados na via das lipoxigenases, no efeito inibitório do VCdt sobre esse modelo de inflamação crônica. Em conclusão, os resultados indicam que a crotoxina do VCdt possua uma significativa ação inibitória sobre o edema crônico induzido pelo BCG, possivelmente pela geração de mediadores antiinflamatórios da via das lipoxigenases.

Papel da endotelina-1 na inflamação articular / Role of endothelin-1 in the joint inflammation

As endotelinas (ET) são peptídeos produzidos por uma grande variedade de células e exercem seus efeitos através da sua ligação aos seus receptores de superfície ETA e ETB. Foi demonstrado que os níveis de ET-1 estão aumentados no plasma e no líquido sinovial de pacientes com artrite reumatóide (AR), uma doença autoimune crônica caracterizada por influxo celular, formação de edema e destruição articular. No entanto, apesar do aumento na produção de ET-1, o papel destes peptídeos durante a AR permanece pouco compreendido. O objetivo central deste estudo foi avaliar o papel das ET na migração celular e na formação de edema utilizando o modelo murino de artrite induzida por zymosan (AIZ). Nós observamos que a expressão de RNAm prepro-ET-1 encontra-se aumentada durante a AIZ e que o bloqueio dos receptores ETA e ETB reduziu significativamente a formação de edema, o recrutamento de neutrófilos para articulação e a produção de TNF-alfa, CXCL-1 e LTB4. Nós ainda demonstramos que o estímulo in vivo com ET-1 foi capaz de induzir a formação de edema, o recrutamento de neutrófilos e a produção de TNF-alfa, enquanto nossos dados in vitro demonstraram que a ET-1 é um potente estímulo quimiotático para neutrófilos. Em seguida, nós avaliamos os efeitos da lipoxina A4 (LXA4), um mediador lipídico pró-resolutivo e anti-inflamatório, durante a AIZ, focando nos efeitos da LXA4 sobre a expressão de ET-1 e sobre os efeitos próinflamatórios induzidos por ET-1 tanto in vivo quanto in vitro. O pré-tratamento com LXA4 reduziu a formação de edema, o influxo de neutrófilos, a expressão de RNAm para prepro-ET-1 e a produção articular de CXCL-1, LTB4 e TNF-alfa na articulação durante a AIZ. De acordo, o BML-111 (agonista do receptor LXA4) e o ácido acetil salicílico (AAS; responsável pela produção endógena de 15-epilipoxina) inibiram significativamente a formação de edema e o recrutamento de neutrófilos para a articulação estimulada com zymosan. Observamos também que o pré-tratamento in vivo com LXA4 durante a inflamação articular induzida por ET-1 inibiu o influxo celular, a formação de edema e a produção de TNF-alfa no lavado articular, enquanto o estímulo in vitro com LXA4 inibiu a ativação e a migração de neutrófilos induzida por ET-1. Resultados prévios obtidos durante a minha dissertação de mestrado demonstraram que uma fração enriquecida em tetranortriterpenóides obtida a partir da semente de Carapa guianensis Aublet apresentava um importante efeito anti-inflamatório na AIZ. No presente trabalho, nós demonstramos que a gedunina, uma das substâncias presentes na semente de C. guianensis, reduziu significativamente o influxo e a ativação celular induzidos por zymosan no líquido sinovial, que foi acompanhado pela diminuição da hipernocicepção e da produção de importantes mediadores inflamatórios envolvidos na AR, dentre eles a ET-1. Estudos in vitro demonstraram ainda que o tratamento com a gedunina foi capaz de impedir a ativação e a quimiotaxia de neutrófilos estimulados com ET-1. Tomados em conjunto, nossos dados demonstram que i) as ET exercem um papel pró-inflamatório central durante a AIZ, através da indução da produção de mediadores inflamatórios, formação de edema e migração de neutrófilos para as articulações inflamadas; ii) a LXA4 exerce importantes efeitos anti-inflamatórios durante a AIZ através da regulação da expressão e dos efeitos pró-inflamatórios in vitro e in vivo induzidos pela ET-1; iii) a gedunina exerce efeitos antiinflamatórios e anti-nociceptivos durante a AIZ e é capaz de inibir a expressão e a atividade de ET-1.

Mecanismos inatos de regulação da IL-12 durante a infecção por Mycobacterium tuberculosis / Innate mechanisms of regulation of IL-12 during Mycobacterium tuberculosis infection

A citocina IL-12 desempenha um papel importante na indução de uma rede de genes da resposta imune envolvidos na resistência a infecções por patógenos intracelulares. IL-12, citocina produzida principalmente por células dendríticas (DCs) e fagócitos, é uma das citocinas responsáveis pela ativação de uma resposta do tipo Thl, levando à produção de IFN-y e subsequente ativação de macrófagos, que se tornará um ambiente desfavorável para o sobrevivência de agentes invasores. Um exemplo desses microorganismos é o Mycobacterium tuberculosis, um importante patógeno humano causador da tuberculose. O M tuberculosis induz a produção de IL-12 em células apresentadoras de antígeno profissionais, entretanto, os mecanismos envolvidos na regulação dessa citocina durante o curso da infecção pelo bacilo não são complementamente entendidos. O objetivo geral desse projeto de tese é investigar os mecanismos imunes inatos que controlam a produção de IL-12 em resposta ao M tuberculosis. A hipótese testada foi que os receptores do tipo Tol! (TLR) e as lipoxinas são mediadores centrais da regulação de IL-12 influenciando a resistência/susceptibilidade ao bacilo. Um modelo experimental de infecção pulmonar e um modelo de infecção in vitro foram usados para esse propósito. amundongos deficientes em MyD88 se mostraram altamente susceptíveis à infecção via aerosol com M tuberculosis, implicando assim, a sinalização via TLR/IL-IR como um determinante da resposta do hospedeiro contra esse importante patógeno humano. Associado ao aumento de susceptibilidade, pulmões dos animais deficientes em MyD88 infectados com o bacilo apresentaram um significativa redução na indução de IL-12 e células T CD4+ secretoras de IFN-y. Observou-se também, que DCs de camundongos deficientes em MyD88 apresentaram uma falha na produção de IL-12 em resposta ao M tuberculosis in vitro. Apesar de trabalhos recentes indicarem que M tuberculosis contêm diversos ligantes como PIMs e DNA, os quais, podem...

New insights into the anti-inflammatory actions of aspirin- induction of nitric oxide through the generation of epi-lipoxins

Aspirin has always remained an enigmatic drug. Not only does it present with new benefits for treating an ever-expanding list of apparently unrelated diseases at an astounding rate but also because aspirin enhances our understanding of the nature of these diseases processe. Originally, the beneficial effects of aspirin were shown to stem from its inhibition of cyclooxygenase-derived prostaglandins, fatty acid metabolites that modulate host defense. However, in addition to inhibiting cyclooxygenase activity aspirin can also inhibit pro-inflammatory signaling pathways, gene expression and other factors distinct from eicosanoid biosynthesis that drive inflammation as well as enhance the synthesis of endogenous protective anti-inflammatory factors. Its true mechanism of action in anti-inflammation remains unclear. Here the data from a series of recent experiments proposing that one of aspirin's predominant roles in inflammation is the induction of nitric oxide, which potently inhibits leukocyte/endothelium interaction during acute inflammation, will be discussed. It will be argued that this nitric oxide-inducing effects are exclusive to aspirin due to its unique ability, among the family of traditional anti-inflammatory drugs, to acetylate the active site of inducible cyclooxygenase and generate a family of lipid mediators called the epi-lipoxins that are increasingly being shown to have profound roles in a range of host defense responses.