NLRP3 inflammasome expression in lipopolysaccharide-induced otitis media

Abstract

Background: The nucleotide-binding oligomerization domain-like receptor protein 3 (NLRP3) inflammasome is a critical molecule mediating interleukin-1β (IL-1β) responses. However, the role of the NLRP3 inflammasome in otitis media has not been fully examined.

Aims/Objectives: The purpose of this study is to assess the expression of NLRP3, ASC (apoptosis-associated speck-like protein containing a caspase recruitment domain and a pyrin domain), and caspase-1 in lipopolysaccharide-induced otitis media.

Materials and methods: BALB/c mice received a transtympanic injection of either lipopolysaccharide or phosphate-buffered saline. The mice were sacrificed 24 h after injection. Concentrations of IL-1β, NLRP3, ASC, and caspase-1 in the middle ear effusions were measured by enzyme-linked immunosorbent assay. Temporal bones were processed for histologic examination and immunohistochemistry.

Results: The transtympanic injection of lipopolysaccharide significantly upregulated levels of IL-1β, NLRP3, ASC, and caspase-1 in the middle ear as compared with the control mice. The proteins of NLRP3, ASC, and caspase-1 were observed in infiltrating inflammatory cells induced by lipopolysaccharide in the middle ear cavity.

Conclusions and significance: Lipopolysaccharide induces NLRP3 inflammasome components in the middle ear. The NLRP3 inflammasome may play an important role in the pathogenesis of otitis media. Modulation of inflammasome-mediated inflammation may be a novel therapeutic strategy for otitis media.

Chinese abstract

背景：集核苷酸齐聚化域样受体蛋白3（NLRP3）炎症小体是介导白细胞介素-1β（IL-1β）反应的关键分子。然而, NLRP3炎症小体在中耳炎中的作用尚未得到充分研究。

目的：本研究的目的是评估脂多糖诱导的中耳炎中NLRP3、ASC（含半胱天冬酶募集域和嘧啶域的凋亡相关的斑点样蛋白）和半胱天冬酶-1的表达。

材料和方法：对BALB/C小鼠经鼓室注射脂多糖或磷酸盐缓冲盐水。注射24小时后将其处死。采用酶联免疫吸附法测定中耳积液中IL-1β、NLRP3、ASC和caspase-1的浓度。对颞骨进行处理以便对其进行组织学检查和免疫组化检查。

结果：与对照组相比, 经鼓室注射脂多糖能显著提高中耳IL-1β、NLRP3、ASC和半胱天冬酶-1的含量。在脂多糖诱导的中耳腔炎性细胞浸润中观察到NLRP3、ASC和半胱天冬酶-1蛋白。

结论与意义：脂多糖诱导中耳NLRP3炎症成分。NLRP3炎症小体可能在中耳炎的发病机制中发挥重要作用。调节炎症小体介导的炎症可能是一种治疗中耳炎的新疗法。

Keywords:

• Infection
• toll-like receptor
• NOD-like receptor
• cytokine
• interleukin
• inflammation

Acknowledgements

This work was supported by JSPS KAKENHI (Grants-in-Aid for Scientific Research from The Ministry of Education, Culture, Sports, Science and Technology of Japan) under Grant (Grant Numbers, JP16K20249 and JP17K11329).

Disclosure statement

No potential conflict of interest was reported by the authors.