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NLRC5, the largest member of the Nod-like receptor (NLR) family, has been reported to play a pivotal role in regulating inflammatory responses. Recent evidence suggests that NLRC5 participates in Toll-like receptor (TLR) signaling pathways and negatively modulates nuclear factor-κB (NF-κB) activation. In this study, we investigated the interaction between NLRC5 and TLR2 in the NF-κB inflammatory signaling pathway and the involvement of NLRC5 in TLR2-mediated allergic airway inflammation. We knocked down TLR2 and NLRC5, respectively in the RAW264.7 macrophage cell line by small interfering RNA (siRNA) and then stimulated the knockdown cells with lipoteichoic acid (LTA). In comparison with the negative siRNA group, the level of NLRC5 expression was lower in the TLR2 siRNA group, with a reduction in the NF-κB-related inflammatory response. Conversely, in the NLRC5 knockdown cells, after LTA-treated the level of TLR2 expression did not change but the expression levels of both NF-κB pp65 and NLRP3 increased remarkably. Thus, we hypothesize that NLRC5 participates in the LTA-induced inflammatory signaling pathway and regulates the inflammation via TLR2/NF-κB. Similarly, in subsequent in vivo experiments, we demonstrated that the expression level of NLRC5 was significantly increased in the ovalbumin-induced allergic airway inflammation. However, this effect disappeared in TLR2-deficient (TLR2 -/- ) mice and was accompanied by reduced levels of NF-κB expression and airway inflammation. In conclusion, NLRC5 negatively regulates LTA-induced inflammatory response via a TLR2/NF-κB pathway in macrophages and also participates in TLR2-mediated allergic airway inflammation., (© 2019 Wiley Periodicals, Inc.)

Unresolved inflammation underpins the pathogenesis of allergic airway diseases, such as asthma. Ketamine, accepted as a promising therapy for resistant asthma, has been demonstrated to attenuate allergic airway inflammation. However, the anti-inflammatory mechanism by ketamine in this setting is largely unknown. We aimed to investigate whether autophagy was involved in the protective effect of ketamine on allergic airway inflammation. Female C57BL/6 mice were sensitized to ovalbumin (OVA) and treated with ketamine at 25, 50, or 100 mg/kg prior to OVA challenge. In this model, the pulmonary morphological findings and airway inflammation were significantly inhibited at 50 mg/kg but not at 25 or 100 mg/kg. Moreover, 50 mg/kg ketamine abrogated the increased concentrations of inflammatory cytokines in bronchoalveolar lavage fluid (BALF) of allergic mice, as well as activated the expression of phosphorylated mammalian target of rapamycin (p-MTOR) and inhibited autophagy in allergic mice. To confirm whether the effect of 50 mg/kg ketamine on asthma was mediated by inhibiting autophagy, rapamycin was administered to mice sensitized to OVA and exposed to 50 mg/kg ketamine. All of the effect of 50 mg/kg ketamine was reversed by rapamycin treatment, including increased p-MTOR and decreased autophagy. Taken together, the present study demonstrates that 50 mg/kg ketamine inhibits allergic airway inflammation by suppressed autophagy, and this effect is mediated by the activation of MTOR in the lungs of allergic mice.

Background: Estrogen has been suggested to play a protective role against airway inflammations, such as asthma. In these processes, the inflammasome nucleotide-binding oligomerization domain, leucine-rich repeat and pyrin domain containing 3 (NLRP3) partly accounts for the activation of pro-inflammatory factors. The aim of the present study was to investigate whether NLRP3 was involved in the protective effect of estrogen against allergic airway inflammation. Methods: An ovariectomy was performed on female C57BL/6 mice; some were sham-operated (sham). We then sensitized and challenged them with ovalbumin (OVA) to establish an airway inflammation model. Meanwhile, some mice were treated with 17β-estradiol (E2) for 28 days. Results: The expression of NLRP3 inflammasome and its downstream products, caspase-1 and the pro-inflammatory cytokine interleukin (IL)-1β (IL-1β), increased concomitantly with OVA-challenged airway inflammation and decreased with the expression of estrogen receptor β (ERβ). In addition, treating ovariectomized (OVX) mice with E2 dramatically ameliorated airway inflammation via such mechanisms as leukocyte recruitment, mucus production, and secretion of pro-inflammatory cytokines other than IL-18 in bronchoalveolar lavage (BAL) fluid (BALF). Furthermore, E2 suppressed both the mRNA expression and protein expression of NLRP3, caspase-1, and IL-1β. In summary, our study showed that NLRP3 inflammasome activation and pro-inflammatory cytokine production markedly increased in OVA-induced airway inflammation, and E2 effectively abrogated such inflammation by regulating the activation of NLRP3., (© 2018 The Author(s).)

Background: Our colleagues have demonstrated an impressive therapeutic role of sevoflurane in a murine allergic airway inflammation model, but the mechanisms underlying this effect remain undefined. In this study, we tried to investigate the effect of sevoflurane on the resolution of allergic airway inflammation and to assess whether NLRP3 or the NLRP3 inflammasome is involved in this process., Methods: Female (C57BL/6) mice were sensitized and challenged with ovalbumin (OVA). Then, some of the mice received MCC950 (10 mg/kg; i.p.) or 3% sevoflurane. Total and differential inflammatory cell numbers, proinflammatory cytokines in bronchoalveolar lavage fluid (BALF), the peribronchial inflammation density, and mucus production were evaluated. In addition, we analysed the protein levels of NLRP3, the apoptosis-associated speck-like protein containing the caspase activation and recruitment domain (ASC), pro-caspase-1, and caspase-1 in the lung tissue., Results: We found that OVA-induced inflammatory cell recruitment to peribronchial regions, goblet cell hyperplasia, the serum levels of IgE, inflammatory cells, and the Th2 cytokine secretion in BALF was potently suppressed by sevoflurane with an efficacy comparable with that suppressed by MCC950 treatment. Furthermore, sevoflurane, similar to MCC950, clearly inhibited the OVA-induced activity of NLRP3 in the lungs. In addition, we found that OVA challenge failed to increase the expression of ASC, pro-caspase-1, and caspase-1 in the lungs and the levels of IL-18 and IL-1 β in BALF., Conclusion: Taken together, our data showed that sevoflurane ameliorated allergic airway inflammation by inhibiting Th2 responses and NLRP3 expression. The NLRP3 independent of inflammasomes participated in the pathogenesis of allergic asthma in this model.

Nebulized lidocaine has been suggested to be beneficial in asthma therapy, but the underlying mechanisms are little known. We aimed to investigate whether Toll-like receptor (TLR) 2 was involved in the protective effect of lidocaine on allergic airway inflammation. Female C57BL/6 mice were sensitized and challenged with ovalbumin (OVA). Meanwhile, some of the mice were treated with TLR2 agonist (Pam3CSK4, 100 μg) intraperitoneally in combination with OVA on day 0. Just after allergen provocation, mice were treated with inhaled lidocaine or vehicle for 30 min. In this model, we found that lidocaine markedly attenuated OVA-evoked airway inflammation, leukocyte recruitment and mucus production. Moreover, lidocaine abrogated the increased concentrations of T cytokines and TNF-α in bronchoalveolar lavage fluid (BALF) of allergic mice, as well as reducing the expression of phosphorylated nuclear factor (P-NF)-κBp65 and the NOD-like receptor pyridine containing 3 (NLRP3), which are important for the production of pro-inflammatory cytokines. In addition, our study showed that lidocaine dramatically decreased OVA-induced increased expression of TLR2 in the lung tissues. Furthermore, activation of TLR2 aggravated OVA-challenged airway inflammation, meanwhile, it also elevated OVA-induced expression of P-NF-κBp65 and NLRP3 in the lungs. However, lidocaine effectively inhibited airway inflammation and counteracted the expression of P-NF-κBp65 and NLRP3 in allergic mice pretreated with Pam3CSK4. Taken together, the present study demonstrated that lidocaine prevented allergic airway inflammation via TLR2 in an OVA-induced murine allergic airway inflammation model. TLR2/NF-κB/NLRP3 pathway may serve as a promising therapeutic strategy for allergic airway inflammation., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Mer receptor tyrosine kinase (MerTK) expressed in macrophages is essential for phagocytosis of apoptotic cells. Here, we investigate whether MerTK is involved in the phagocytosis of Staphylococcus aureus (S. aureus) and regulation of staphylococcal lipoteichoic acid (LTA)-induced inflammatory response in macrophages. We found that stimulating RAW264.7 macrophages with S. aureus activated multiple signaling pathways including toll-like receptor 2 (TLR2), scavenger receptor A (SR-A), and MerTK. Meanwhile, S. aureus stimulation also induced activation of proteins focal adhesion kinase (FAK) and Rac1, which are related to phagocytosis. Pretreatment with a specific Mer-blocking antibody significantly inhibited S. aureus-induced phosphorylation of MerTK, while it had no effect on S. aureus-induced activation of FAK and Rac1. Moreover, by confocal laser microscope, we observed that the antibody blockade of MerTK had little impact on the phagocytosis of S. aureus by RAW264.7 macrophages. Additionally, pretreatment with this antibody further promoted LTA-induced phosphorylation of nuclear factor κB (NF-κB) p65 subunit and production of pro-inflammatory cytokines, such as TNF-α, IL-6, IL-1β, and macrophage inflammatory protein-2 (MIP-2). Collectively, these results suggest that MerTK does not play an essential role in the phagocytosis of S. aureus but attenuates inflammation induced by staphylococcal LTA through blocking NF-κB activation.

Objective To investigate the molecular mechanisms of Toll-like receptor 2 (TLR2) taking part in inflammatory response in Staphylococcus aureus (SA)-induced asthma. Methods We established the cell inflammatory response model through stimulating mouse RAW264.7 macrophages with SA. The TLR2, myeloid differentiation factor 88 (MyD88), phosphoinositide-3 kinase (PI3K), nuclear factor κBp65 (NF-κBp65), phospho-NF-κBp65, beclin-1 and microtubule-associated protein 1 light chain 3B (LC3B) were detected by Western blot analysis after treatment with TLR2 small interfering RNA (siRNA) and 3-methyladenine (3-MA), and the tumor necrosis factor α (TNF-α) and interleukin 6 (IL-6) were determined by ELISA. In addition, the number of autolysosomes was observed by the laser scanning confocal microscope. Results SA-stimulated macrophages activated various signaling pathways including TLR2. TLR2 siRNA markedly repressed the expressions of PI3K, phospho-NF-κBp65, the autophagy protein beclin-1 and LC3B as well as the number of autolysosomes and the production of TNF- and IL-6. We also demonstrated that 3-MA had the same effect on autophagy and inflammation as TLR2 siRNA did. Conclusion TLR2 modulates SA-induced inflammatory response and autophagy in macrophages through PI3K signaling pathway.

Toll-like receptors (TLRs) are innate pattern recognition receptors that play a critical role in allergic inflammation, yet their contribution to autophagy in asthma remains poorly defined. Here, we investigate the role of Toll-like receptor 2 (TLR2) in phosphoinositide 3-kinases/protein kinase B (PI3K/Akt) pathway-mediated autophagy in ovalbumin-induced airway inflammation in mice. Wild-type (WT) and TLR2-knockout (TLR2 -/- ) C57BL/6 mice were ovalbumin-sensitized and ovalbumin-challenged. In ovalbumin-challenged WT mice, enhanced expression of TLR2 in lung tissue, remarkable inflammatory cell infiltrates, goblet cell hyperplasia, and increased mucus production were observed. The number of inflammatory cells and interleukin-13 (IL-13) levels increased, while interferon-gamma (IFN-γ) levels decreased in bronchoalveolar lavage fluid. Expression of PI3K, phospho-Akt, Beclin-1 and LC3-II was enhanced significantly. These changes were mitigated dose-dependently in 3-methyl adenine-treated mice. In contrast, similar but weaker changes were found in ovalbumin-challenged TLR2 -/- mice, and the changes were not significantly attenuated by 3-methyl adenine treatment. These results indicate that TLR2 confers a pivotal role in allergic airway inflammation via regulating the PI3K/Akt signaling pathway-related autophagy in mice.

Galectin-1 (Gal-1) has immunomodulatory activities in various allergic inflammatory disorders, but its potential anti-inflammatory properties on allergic airway diseases have not been confirmed. We explored the pharmacological effects of Gal-1 on the progression of allergic airway inflammation and investigated the underlying mechanism. Female C57BL/6 mice were sensitized on day 0 and challenged with ovalbumin (OVA) on days 14-17 to establish an allergic airway inflammation model. In the challenge phase, a subset of mice was treated intraperitoneally with recombinant Gal-1 (rGal-1) or dexamethasone (Dex). We found that rGal-1 inhibited pulmonary inflammatory cell recruitment, mucus secretion, bronchoalveolar lavage fluid (BALF) inflammatory cell infiltration, and cytokine production. The treatment also suppressed the infiltration of eosinophils into the allergic lung as indicated by decreased expression levels of eotaxin and eosinophil peroxidase (EPX). However, only the expression levels of IL-25, neither IL-33 nor TSLP, were significantly decreased in the lung by rGal-1 treatment. These immunomodulatory effects in the allergic lung were correlated with the activation of extracellular signal-regulated kinase (ERK) signaling pathway and downregulation of endogenous Gal-1. In addition, rGal-1 reduced the plasma concentrations of anti-OVA immunoglobulin E (IgE) and IL-17. Our findings suggest that rGal-1 is an effective therapy for allergic airway inflammation in a murine model and may be a potential pharmacological target for allergic airway inflammatory diseases. [ABSTRACT FROM AUTHOR]