Feriotti Claudia, de Araújo Eliseu Frank, Loures Flavio Vieira, da Costa Tania Alves, Galdino Nayane Alves de Lima, Zamboni Dario Simões, Calich Vera Lucia Garcia
Department of Immunology, University of São Paulo, São Paulo, Brazil.
Department of Cell Biology, School of Medicine of Ribeirão Preto, University of São Paulo, São Paulo, Brazil.
Front Immunol. 2017 Jul 10;8:786. doi: 10.3389/fimmu.2017.00786. eCollection 2017.
The NOD-like receptor P3 (NLRP3) inflammasome is an intracellular multimeric complex that triggers the activation of inflammatory caspases and the maturation of IL-1β and IL-18, important cytokines for the innate immune response against pathogens. The functional NLRP3 inflammasome complex consists of NLRP3, the adaptor protein apoptosis-associated speck-like protein, and caspase-1. Various molecular mechanisms were associated with NLRP3 activation including the presence of extracellular ATP, recognized by the cell surface P2X7 receptor (P2X7R). Several pattern recognition receptors on innate immune cells recognize components resulting in diverse responses that influence adaptive immunity and disease outcome. However, the role of NLRP3 inflammasome was scantily investigated in pulmonary paracoccidioidomycosis (PCM), leading us to use an intratracheal (i.t.) model of infection to study the influence of this receptor in anti-fungal immunity and severity of infection. For studies, mice deficient for several NLRP3 inflammasome components (, , ) as well as deficient for ATP receptor () were infected i.t. with and several parameters of immunity and disease severity analyzed at the acute and chronic periods of infection. Pulmonary PCM was more severe in , , , and mice as demonstrated by the increased fungal burdens, mortality rates and tissue pathology developed. The more severe disease developed by NLRP3, ASC, and Caspase-1/11 deficient mice was associated with decreased production of IL-1β and IL-18 and reduced inflammatory reactions mediated by PMN leukocytes and activated CD4 and CD8 T cells. The decreased T cell immunity was concomitant with increased expansion of CD4CD25Foxp3 regulatory T (Treg) cells. Characterization of intracellular cytokines showed a persistent reduction of CD4 and CD8 T cells expressing IFN-γ and IL-17 whereas those producing IL-4 and TGF-β appeared in increased frequencies. Histopathological studies showed that all deficient mouse strains developed more severe lesions containing elevated numbers of budding yeast cells resulting in increased mortality rates. Altogether, these findings led us to conclude that the activation of the NLRP3 inflammasome has a crucial role in the immunoprotection against pulmonary PCM by promoting the expansion of Th1/Th17 immunity and reducing the suppressive control mediated by Treg cells.
核苷酸结合寡聚化结构域样受体P3（NLRP3）炎性小体是一种细胞内多聚体复合物，可触发炎性半胱天冬酶的激活以及白细胞介素-1β（IL-1β）和白细胞介素-18（IL-18）的成熟，这两种细胞因子是针对病原体的固有免疫反应中的重要细胞因子。功能性NLRP3炎性小体复合物由NLRP3、衔接蛋白凋亡相关斑点样蛋白和半胱天冬酶-1组成。多种分子机制与NLRP3的激活相关，包括细胞表面P2X7受体（P2X7R）识别的细胞外ATP的存在。固有免疫细胞上的几种模式识别受体识别相关成分，从而产生多种影响适应性免疫和疾病结局的反应。然而，NLRP3炎性小体在肺副球孢子菌病（PCM）中的作用研究较少，这促使我们使用气管内（i.t.）感染模型来研究该受体在抗真菌免疫和感染严重程度中的影响。在研究中，将几种NLRP3炎性小体成分缺陷（、、）以及ATP受体缺陷（）的小鼠经气管内感染，并在感染的急性期和慢性期分析免疫和疾病严重程度的几个参数。肺部PCM在、、、和小鼠中更为严重，表现为真菌负荷增加、死亡率升高以及组织病理学改变。NLRP3、ASC和半胱天冬酶-1/11缺陷小鼠病情更严重，这与IL-1β和IL-18的产生减少以及中性粒细胞和活化的CD4和CD8 T细胞介导的炎症反应减弱有关。T细胞免疫的降低与CD4CD25Foxp3调节性T（Treg）细胞的扩增增加同时出现。细胞内细胞因子的特征分析表明，表达干扰素-γ（IFN-γ）和白细胞介素-17（IL-17）的CD4和CD8 T细胞持续减少，而产生白细胞介素-4（IL-4）和转化生长因子-β（TGF-β）的细胞频率增加。组织病理学研究表明，所有缺陷小鼠品系均出现更严重的病变，其中含有数量增加的芽生酵母细胞，导致死亡率升高。总之，这些发现使我们得出结论，NLRP3炎性小体的激活通过促进Th1/Th17免疫的扩增和减少Treg细胞介导的抑制性控制，在针对肺部PCM的免疫保护中起关键作用。
