Purpose

Neutrophils play a critical role in defending against threats such as microbial infection, yet their activation during innate immune response incites collateral damage to healthy tissues. We have previously shown that corneal injury induces mast cells to express the neutrophil chemoattractant CXCL2. Here we delineate the mechanism of injury-induced, non-IgE-mediated mast cell activation at the ocular surface.

Methods

Corneal injury was induced by mechanical removal of the epithelium and anterior stroma in mast cell deficient (cKit^W-sh) and C57BL/6 mice using Algerbrush II. Corneas were analyzed for frequencies of total CD45⁺ inflammatory cells, CD11b⁺Ly6G⁺ neutrophils, and cKit⁺FcεR1⁺ mast cells using flow cytometry. Mast cells were stimulated with different inflammatory factors known to increase during corneal injury (IL-33, IL-1β, IL-36γ, IL-6, SDF1α and Substance P) and assessed for the secretion of β-hexosaminidase, tryptase and CXCL2 using ELISA. IL-33 neutralizing antibody (1 mg/ml) was administered locally for mast cell inhibition in vivo.

Results

Mast cell deficient mice failed to recruit early neutrophils to the injured corneas. IL-33 stimulation upregulated CXCL2 secretion by mast cells. Corneal injury resulted in amplified expression of IL-33 at the cornea and epithelium was identified as its primary source. Topical neutralization of IL-33 at the ocular surface inhibited mast cell activation, limited neutrophil infiltration, and reduced corneal inflammatory haze, normalizing tissue architecture following ocular injury.

Conclusions

These data implicate IL-33 in mast cell activation and early neutrophil recruitment in non-allergic inflammation, suggesting IL-33 as a potential therapeutic target in inflammatory disorders of the ocular surface.

中文翻译：

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上皮衍生的 IL-33 激活肥大细胞以在角膜损伤后启动中性粒细胞募集。

目的

中性粒细胞在抵御微生物感染等威胁方面发挥着关键作用，但它们在先天免疫反应过程中的激活会引发对健康组织的附带损害。我们之前已经表明，角膜损伤会诱导肥大细胞表达中性粒细胞趋化因子 CXCL2。在这里，我们描述了眼表损伤诱导的、非 IgE 介导的肥大细胞激活的机制。

方法

使用 Algerbrush II机械去除肥大细胞缺陷 (cKit ^W-sh ) 和 C57BL/6 小鼠的上皮和前基质，诱导角膜损伤。使用流式细胞术分析角膜的总 CD45 ⁺炎症细胞、CD11b ⁺ Ly6G ⁺中性粒细胞和 cKit ⁺ FcεR1 ⁺肥大细胞的频率。用已知在角膜损伤期间增加的不同炎症因子（IL-33、IL-1β、IL-36γ、IL-6、SDF1α 和物质 P）刺激肥大细胞，并使用以下方法评估 β-氨基己糖苷酶、类胰蛋白酶和 CXCL2 的分泌ELISA。局部施用IL-33中和抗体(1mg/ml)用于体内肥大细胞抑制。

结果

肥大细胞缺陷小鼠未能将早期中性粒细胞募集到受伤的角膜。IL-33 刺激可上调肥大细胞的 CXCL2 分泌。角膜损伤导致角膜上 IL-33 的表达扩增，上皮细胞被确定为其主要来源。在眼表局部中和 IL-33 可抑制肥大细胞活化、限制中性粒细胞浸润并减少角膜炎症混浊，使眼部损伤后的组织结构正常化。

结论

这些数据表明 IL-33 参与非过敏性炎症中的肥大细胞活化和早期中性粒细胞募集，表明 IL-33 是眼表炎症性疾病的潜在治疗靶点。