Clinical and Experimental Sciences Academic Unit, Faculty of Medicine, University of Southampton, Southampton, UK.
Faculty of Medicine, Suez Canal University, Ismailia, Egypt.
Clin Exp Allergy. 2018 May;48(5):555-567. doi: 10.1111/cea.13108.
Tryptase, the most abundant protease of the human mast cell, has been implicated as a key mediator of allergic inflammation that acts through activation of PAR2.
To investigate the contribution of PAR2 in the pro-inflammatory actions mediated by tryptase in a mice model.
We have injected recombinant human βII-tryptase into the peritoneum of PAR2-deficient and wild-type C57BL/6 mice. After 6, 12 and 24 hours, mice were killed, peritoneal lavage performed and inflammatory changes investigated.
Tryptase stimulated an increase in neutrophil numbers in the peritoneum, but responses did not differ between PAR2-deficient and wild-type mice. Heat inactivation of tryptase or pre-incubation with a selective tryptase inhibitor reduced neutrophilia, but neutrophil accumulation was not elicited with a peptide agonist of PAR2 (SLIGRL-NH ). Zymography indicated that tryptase stimulated the release of matrix metalloproteinases (MMP) 2 and 9 in the peritoneum of both mouse strains. Studies involving immunomagnetic isolation of neutrophils suggested that neutrophils represent the major cellular source of tryptase-induced MMP2 and MMP9. At 24 hours after tryptase injection, there was increased microvascular leakage as indicated by high levels of albumin in peritoneal lavage fluid, and this appeared to be partially abolished by heat-inactivating tryptase or addition of a protease inhibitor. There was no corresponding increase in levels of histamine or total protein. The extent of tryptase-induced microvascular leakage or gelatinase release into the peritoneum did not differ between PAR2-deficient and wild-type mice.
Our findings indicate that tryptase is a potent stimulus for neutrophil accumulation, MMP release and microvascular leakage. Although these actions required an intact catalytic site, the primary mechanism of tryptase in vivo would appear to involve processes independent of PAR2.
人肥大细胞中含量最丰富的蛋白酶——类胰蛋白酶，被认为是一种关键的过敏炎症介质，通过激活 PAR2 发挥作用。
在小鼠模型中研究 PAR2 在类胰蛋白酶介导的促炎作用中的作用。
我们将重组人βII-类胰蛋白酶注入 PAR2 缺陷型和野生型 C57BL/6 小鼠的腹腔内。6、12 和 24 小时后，处死小鼠，进行腹腔灌洗并研究炎症变化。
类胰蛋白酶刺激腹腔中性粒细胞数量增加，但 PAR2 缺陷型和野生型小鼠之间的反应没有差异。类胰蛋白酶热失活或与选择性类胰蛋白酶抑制剂预孵育可减少中性粒细胞增多，但 PAR2 肽激动剂 (SLIGRL-NH2) 不会引起中性粒细胞积聚。酶谱分析表明，类胰蛋白酶刺激两种小鼠品系腹腔中基质金属蛋白酶 (MMP) 2 和 9 的释放。涉及免疫磁分离中性粒细胞的研究表明，中性粒细胞是类胰蛋白酶诱导的 MMP2 和 MMP9 的主要细胞来源。在类胰蛋白酶注射后 24 小时，白蛋白在腹腔灌洗液中的高水平表明微血管通透性增加，而这种增加似乎部分被类胰蛋白酶热失活或添加蛋白酶抑制剂所消除。组胺或总蛋白水平没有相应增加。PAR2 缺陷型和野生型小鼠之间，类胰蛋白酶诱导的微血管渗漏或明胶酶释放到腹腔中的程度没有差异。
我们的发现表明，类胰蛋白酶是中性粒细胞聚集、MMP 释放和微血管渗漏的有力刺激物。尽管这些作用需要完整的催化位点，但类胰蛋白酶在体内的主要机制似乎涉及与 PAR2 无关的过程。
