Objective

Asthma, a well-known disease with high morbidity, is characterized by chronic airway inflammation. However, the allergic inflammation mechanisms of follistatin-like protein 1 (FSTL1) have not been elucidated. This study aims to investigate the effects of FSTL1 in ovalbumin (OVA)-induced mice and macrophages on nucleotide-binding domain and leucine-rich repeat protein 3 (NLRP3)/interleukin-1β (IL-1β) signaling pathway.

Methods

Mice were randomly divided into control-WT, OVA-WT, control-Fstl1^±, OVA-Fstl1^±. Histological changes were assessed by HE and PAS staining. The protein levels of Muc-5AC, FSTL1, NLRP3, and IL-1β in lung tissue were detected by immunohistochemistry and ELISA. The bronchoalveolar lavage fluid (BALF) in mice and human serum samples were detected by ELISA. Then, mice were grouped into control, FSTL1, MCC950 + FSTL1 to further investigate the relationship between FSTL1 and NLRP3/IL-1β. Alveolar macrophage cells (MH-S cells) were separated into control, OVA, FSTL1, OVA + FSTL1, OVA + siNC, OVA + siFSTL1, MCC950, and FSTL1 + MCC950 groups to explore the effect of FSTL1 on the NLRP3/IL-1β signaling. The protein expression of NLRP3 and IL-1β in MH-S cells was detected by Western blot analysis.

Results

The present results uncovered that Fstl1^± significantly ameliorated OVA-induced Muc-5AC production and mucus hypersecretion. Fstl1^± was also found to decrease the production of inflammatory cytokines and inflammatory cell infiltration in OVA-induced asthmatic mice. Meanwhile, the serum concentrations of FSTL1 and IL-1β were higher in asthma subjects than the health subjects, and Fstl1^± ameliorated the production of NLRP3 and IL-1β in OVA-induced asthmatic mice. Furthermore, mice by injected FSTL1 substantially stimulated the expression of NLRP3 and IL-1β, while pretreatment with MCC950 in mice significantly weakened the production of NLRP3 and IL-1β induced by injection FSTL1. Pretreatment with siFSTL1 or MCC950 significantly reduced the production of NLRP3 and IL-1β induced by OVA or FSTL1 in MH-S cells.

Conclusions

The study results showed that FSTL1 played an important role in allergic airway inflammation by activating NLRP3/IL-1β. Hence, inhibition FSTL1 could be applied as a therapeutic agent against asthma.

中文翻译：

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FSTL1通过激活小鼠和巨噬细胞中的NLRP3/IL-1β信号通路加重OVA诱导的炎症反应

 客观的

哮喘是一种众所周知的高发病率疾病，其特征是慢性气道炎症。然而，卵泡抑素样蛋白1（FSTL1）的过敏性炎症机制尚未阐明。本研究旨在探讨卵清蛋白（OVA）诱导的小鼠和巨噬细胞中FSTL1对核苷酸结合域和富含亮氨酸重复蛋白3（NLRP3）/白细胞介素1β（IL-1β）信号通路的影响。

 方法

将小鼠随机分为对照-WT、OVA-WT、对照-Fstl1 ^± 、OVA- Fstl1 ^± 。通过HE和PAS染色评估组织学变化。采用免疫组化和ELISA法检测肺组织中Muc-5AC、FSTL1、NLRP3、IL-1β的蛋白水平。采用ELISA法检测小鼠支气管肺泡灌洗液（BALF）和人血清样本。然后将小鼠分为对照组、FSTL1、MCC950+FSTL1，以进一步研究FSTL1与NLRP3/IL-1β之间的关系。将肺泡巨噬细胞（MH-S细胞）分为对照、OVA、FSTL1、OVA+FSTL1、OVA+siNC、OVA+siFSTL1、MCC950和FSTL1+MCC950组，探讨FSTL1对NLRP3/IL-1β的影响发信号。 Western blot分析检测MH-S细胞中NLRP3和IL-1β的蛋白表达。

 结果

目前的结果表明， Fstl1^显着改善了 OVA 诱导的 Muc-5AC 产生和粘液分泌过多。还发现Fstl1 ^±可以减少 OVA 诱导的哮喘小鼠中炎症细胞因子的产生和炎症细胞浸润。同时，哮喘受试者的 FSTL1 和 IL-1β 血清浓度高于健康受试者，并且Fstl1 ^±改善了 OVA 诱导的哮喘小鼠中 NLRP3 和 IL-1β 的产生。此外，注射FSTL1的小鼠显着刺激了NLRP3和IL-1β的表达，而用MCC950预处理小鼠显着减弱了注射FSTL1诱导的NLRP3和IL-1β的产生。用siFSTL1或MCC950预处理显着减少了MH-S细胞中由OVA或FSTL1诱导的NLRP3和IL-1β的产生。

 结论

研究结果表明，FSTL1通过激活NLRP3/IL-1β在过敏性气道炎症中发挥重要作用。因此，抑制FSTL1可以用作治疗哮喘的药物。