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.

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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.

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. K E Y W O R D Sallergic airway inflammation, macrophage, negative regulation, NLRC5, TLR2

BackgroundThe purpose of this study was to explore the function and mechanism of peroxisome proliferator activated receptor agonist (PPARγ) in the toll-like receptor 2 (TLR2)/nod-like receptor with pyrin domain containing 3 (NLRP3) inflammatory corpuscle pathway of asthmatic mice.Material/MethodsEighteen female mice (C57) were randomly divided into 4 groups: the control group, the asthma model group challenged by ovalbumin (OVA), the rosiglitazone group, and the PPARγ agonist rosiglitazone treatment group. The infiltration of peribronchial inflammatory cells as well as the proliferation and mucus secretion of bronchial epithelial goblet cells were observed by hematoxylin and eosin and periodic acid-Schiff staining. Western blots were employed to detect the expression levels of TLR2, PPARγ, nuclear factor-kappa B (NF-kappaB), NLRP3, and ASC [apoptosis-associated speck-like protein containing C-terminal caspase recruitment domain [CARD]).ResultsThe number of inflammatory cells and eosinophils, and the levels of OVAs IgE, interleukin-4 (IL-4), and IL-13 were significantly higher in the C57 asthma group compared to the C57 control group and the treatment group (P<0.05). The infiltration of peribronchiolar inflammatory cells, wall thickening, goblet cell hyperplasia, and mucus secretion in the treatment group were all significantly decreased compared to those in the asthma group. PPARγ expression in the treatment group was significantly higher compared to the asthma group and the control group (P<0.05). The protein expression levels of TLR2, NF-kappaB, NLRP3, and ASC were significantly lower compared to the asthma group but were higher compared to the control group (P<0.05).ConclusionsPPARγ rosiglitazone ameliorates airway inflammation by inhibiting NF-kappaB expression in asthmatic mice, and further inhibits the activation of TLR2/NLRP3 inflammatory corpuscles.