Department of Respiratory Medicine, The Second Hospital, Cheeloo College of Medicine, Shandong University, Jinan, Shandong 250033, China.
Cheeloo College of Medicine, Shandong University, Jinan, Shandong 250033, China.
J Healthc Eng. 2022 Mar 16;2022:7355485. doi: 10.1155/2022/7355485. eCollection 2022.
is one of the most pathogenic invasive fungi, and its interaction with the host's natural immunity, especially the role of the inflammasome family, has not been fully elucidated. As an important member of the inflammasome family, NOD-like receptor (NLR) family caspase recruitment domain (CARD) containing 4 (NLRC4) has been proven to protect lungs from damage from a variety of pathogens. In this study, we investigated the protective effect and mechanism of NLRC4 on cryptococcal pulmonary infection using NLRC4-/-mice in vivo and NLRC4-/-macrophages in vitro models stimulated by cryptococcal cells. We apply small animal fluorescence imaging to detect the fungal burden in the lungs and living body micro-CT scans of mice and in vitro tissue micro-CT scans to compare differences in infection foci nodules and histopathological lesions, and the activation of caspase-1 and downstream cytokines were detected by Western bolt and ELISA, etc. The results demonstrated that cryptococcal infection can activate the Nod-like receptors of caspase-1 activation and NLRC4 inflammasomes in macrophages and dendritic cells and affect downstream IL-1 and IL-18 release. After cryptococcal infection, the survival rate, lung fungal burden, and histopathological damage of NLRC4 mice were significantly impaired. NLRC4 macrophages showed a lower release of inflammatory factors, reactive oxygen species (ROS), and lactate dehydrogenase (LDH). Collectively, our results demonstrated that the activation of caspase-1 and downstream cytokines mediated by NLRC4 inflammasome in immune cells during infection can enhance pyroptosis of macrophages, affect the phagocytic ability of macrophages, and inhibit the intracellular parasitism of cryptococcus, eventually reducing the burden of fungi.
新型隐球菌是最具致病性的侵袭性真菌之一，其与宿主天然免疫的相互作用，尤其是模式识别受体（pattern recognition receptor，PRR）家族中的炎症小体的作用，尚未完全阐明。作为炎症小体家族的重要成员，NOD 样受体（NLR）家族含 caspase 募集结构域（caspase recruitment domain，CARD）4（NLRC4）已被证明可保护肺部免受多种病原体的损伤。在本研究中，我们通过体内 NLRC4-/-小鼠和体外 NLRC4-/-巨噬细胞模型刺激新型隐球菌细胞，研究 NLRC4 对新型隐球菌肺部感染的保护作用及其机制。我们应用小动物荧光成像检测肺部真菌负荷和活体小鼠 micro-CT 扫描以及体外组织 micro-CT 扫描，比较感染灶结节和组织病理学损伤的差异，并通过 Western blot 和 ELISA 等方法检测 caspase-1 和下游细胞因子的激活。结果表明，新型隐球菌感染可激活巨噬细胞和树突状细胞中的 Nod 样受体（caspase-1 激活）和 NLRC4 炎症小体，并影响下游 IL-1 和 IL-18 的释放。新型隐球菌感染后，NLRC4 小鼠的存活率、肺部真菌负荷和组织病理学损伤明显受损。NLRC4 巨噬细胞炎症因子、活性氧（reactive oxygen species，ROS）和乳酸脱氢酶（lactate dehydrogenase，LDH）的释放水平较低。综上所述，我们的研究结果表明，感染过程中免疫细胞中 NLRC4 炎症小体介导的 caspase-1 和下游细胞因子的激活可增强巨噬细胞的细胞焦亡，影响巨噬细胞的吞噬能力，抑制新型隐球菌的细胞内寄生，从而减轻真菌负担。
