Matsuwaki Yoshinori, Wada Kota, White Thomas A, Benson Linda M, Charlesworth M Cristine, Checkel James L, Inoue Yoshinari, Hotta Kyoko, Ponikau Jens U, Lawrence Christopher B, Kita Hirohito
Department of Medicine and Immunology, Mayo Clinic, Rochester, MN 55905, USA.
J Immunol. 2009 Nov 15;183(10):6708-16. doi: 10.4049/jimmunol.0901220. Epub 2009 Oct 28.
Eosinophils are multifunctional leukocytes implicated in the pathogenesis of asthma and in immunity to certain organisms. Associations between exposure to an environmental fungus, such as Alternaria, and asthma have been recognized clinically. Protease-activated receptors (PARs) are G protein-coupled receptors that are cleaved and activated by serine proteases, but their roles in innate immunity remain unknown. We previously found that human eosinophils respond vigorously to Alternaria organisms and to the secretory product(s) of Alternaria with eosinophils releasing their proinflammatory mediators. In this study, we investigated the roles of protease(s) produced by Alternaria and of PARs expressed on eosinophils in their immune responses against fungal organisms. We found that Alternaria alternata produces aspartate protease(s) and that human peripheral blood eosinophils degranulate in response to the cell-free extract of A. alternata. Eosinophils showed an increased intracellular calcium concentration in response to Alternaria that was desensitized by peptide and protease ligands for PAR-2 and inhibited by a PAR-2 antagonistic peptide. Alternaria-derived aspartate protease(s) cleaved PAR-2 to expose neo-ligands; these neo-ligands activated eosinophil degranulation in the absence of proteases. Finally, treatment of Alternaria extract with aspartate protease inhibitors, which are conventionally used for HIV-1 and other microbes, attenuated the eosinophils' responses to Alternaria. Thus, fungal aspartate protease and eosinophil PAR-2 appear critical for the eosinophils' innate immune response to certain fungi, suggesting a novel mechanism for pathologic inflammation in asthma and for host-pathogen interaction.
嗜酸性粒细胞是多功能白细胞，与哮喘的发病机制以及对某些生物体的免疫有关。临床上已认识到接触环境真菌（如链格孢属）与哮喘之间的关联。蛋白酶激活受体（PARs）是G蛋白偶联受体，可被丝氨酸蛋白酶切割并激活，但其在固有免疫中的作用尚不清楚。我们之前发现，人类嗜酸性粒细胞对链格孢属生物体及其分泌产物有强烈反应，嗜酸性粒细胞会释放其促炎介质。在本研究中，我们调查了链格孢属产生的蛋白酶以及嗜酸性粒细胞上表达的PARs在其针对真菌生物体的免疫反应中的作用。我们发现链格孢产生天冬氨酸蛋白酶，并且人类外周血嗜酸性粒细胞会因链格孢的无细胞提取物而脱颗粒。嗜酸性粒细胞对链格孢的反应表现为细胞内钙浓度升高，该反应被PAR - 2的肽和蛋白酶配体脱敏，并被PAR - 2拮抗肽抑制。链格孢属来源的天冬氨酸蛋白酶切割PAR - 2以暴露新配体；这些新配体在没有蛋白酶的情况下激活嗜酸性粒细胞脱颗粒。最后，用传统上用于治疗HIV - 1和其他微生物的天冬氨酸蛋白酶抑制剂处理链格孢提取物，减弱了嗜酸性粒细胞对链格孢的反应。因此，真菌天冬氨酸蛋白酶和嗜酸性粒细胞PAR - 2似乎对嗜酸性粒细胞对某些真菌的固有免疫反应至关重要，这提示了哮喘病理炎症和宿主 - 病原体相互作用的一种新机制。
