Lobar pneumonia, one of the community-acquired pneumonia (CAP), is a common pediatric low respiratory tract infection. Calpains are Ca~(2+)-activated cysteine proteases whose activation mechanism is elusive. The present study was undertaken to detect the role and mechanism of calpains in pediatric lobar pneumonia. The human acute lung infection model (ALIM) was constructed and infected by Streptococcus . Enzyme-linked immunosorbent assay (ELISA) was used to measure interleukin (IL)-6, IL-8 and tumor necrosis factor (TNF)-α. We observed the lactate dehydrogenase (LDH) release, calpains activity and calpain inhibitor effects in ALIM. The expression of proliferating cell nuclear antigen (PCNA) protein was quantified by western blotting. Then the effects of calpain 1 and 2 knockdown on expressions of inflammation factors and PCNA protein, LDH release and apoptosis were evaluated in lung MRC-5 cells. In constructed ALIM, expressions of IL-6 (P 0.01), IL-8 (P 0.01), TNF-α (P 0.05) and PCNA protein (P 0.05) were significantly reduced by the calpain inhibitor. Expressions of IL-6, IL-8, TNF-α, PCNA protein and relative LDH release were statistically reduced by the small interfering (si) RNA-calpain 1 and 2 in MRC-5 cells (P 0.05). Calpains silence increased apoptotic cells from 5% (negative control) to more than 20% in MRC-5 cells. The present study suggests that calpains possess a significant effect on inflammations, cell proliferation and apoptosis. Suppression of calpains may provide a potential therapeutic target of lobar pneumonia.
展开▼
机译：大叶性肺炎是社区获得性肺炎（CAP）之一，是一种常见的小儿下呼吸道感染。钙蛋白酶是Ca〜（2 +）-活化的半胱氨酸蛋白酶，其活化机制尚不清楚。本研究旨在检测钙蛋白酶在小儿大叶性肺炎中的作用和机制。构建了人急性肺部感染模型（ALIM），并被链球菌感染。酶联免疫吸附试验（ELISA）用于测量白介素（IL）-6，IL-8和肿瘤坏死因子（TNF）-α。我们在ALIM中观察到了乳酸脱氢酶（LDH）释放，钙蛋白酶活性和钙蛋白酶抑制剂的作用。通过蛋白质印迹定量增殖细胞核抗原（PCNA）蛋白的表达。然后评估了钙蛋白酶1和2的敲低对肺MRC-5细胞中炎症因子和PCNA蛋白表达，LDH释放和凋亡的影响。在构建的ALIM中，IL-6（ P <0.01），IL-8（ P <0.01），TNF-α（ P <0.05）和PCNA蛋白（ P < 0.05）被钙蛋白酶抑制剂显着降低。 IL-6，IL-8，TNF-α，PCNA蛋白的表达和相对LDH的释放在MRC-5细胞中被小干扰（si）RNA-钙蛋白酶1和2统计学地降低了（P <0.05）。钙蛋白酶沉默使MRC-5细胞中的凋亡细胞从5％（阴性对照）增加到20％以上。本研究表明钙蛋白酶对炎症，细胞增殖和凋亡具有重要作用。抑制钙蛋白酶可能提供大叶性肺炎的潜在治疗靶点。
展开▼
