肺炎链球菌感染早期IFN-β通过调节巨噬细胞炎症反应保护宿主

该文旨在探讨干扰素-β(interferon-β,IFN-β)在肺炎链球菌(Streptococcus pneumoniae,S.pn)感染早期对宿主炎症免疫的影响。使用外源重组IFN-β蛋白(recombinant IFN-β,rIFN-β)预处理WT小鼠及其腹腔渗出巨噬细胞(peritoneal exudate macrophages,PEMs),以培养基处理组作为对照。同时应用内源干扰素α/β受体(interferonα/βreceptor,IFNAR)缺陷的小鼠以及PEMs,以WT组为对照。各组分别暴露于D39菌株后,通过RT-PCR和ELISA检测白细胞介素-1β(interleukin-1β,IL-1β)、肿瘤坏死因子-α(tumor necrosis factor-α,TNF-α)的表达水平,并通过小鼠肺切片HE染色和肺干/湿重比评估其肺部炎症浸润和组织损伤,以分析IFN-β对宿主炎症反应的影响;为分析细菌清除率,对小鼠巨噬细胞系RAW264.7行吞噬实验、计数小鼠肺部细菌载量,最后通过小鼠生存率分析确认IFN-β对宿主抵抗S.pn的影响。结果表明,IFN-β抑制D39诱导的IL-1β和TNF-α的过度表达。与NC组比,rIFN-β预处理提高RAW264.7细胞对S.pn的吞噬能力(P<0.001),降低感染小鼠的肺部细菌负荷(P<0.01)和肺损伤评分(P<0.05)。而IFNAR–/–感染小鼠肺部菌载量相较于WT小鼠显著升高(P<0.001),持续更高水平的局部炎症反应导致其肺组织损伤加重且在9天内死亡率明显增加(P<0.05)。但各组小鼠体质量、肺干/湿重比和脾指数值差异无显著性(P>0.05)。可见,在S.pn感染早期,IFN-β通过调节巨噬细胞中促炎细胞因子的表达而维持适度的局部炎症反应,有助于宿主清除细菌,防止局部感染进展为致死性感染。

Interferon-βProtects Hosts through Modulating the Inflammatory Responses of Macrophages in the Early Stage of Streptococcus pneumoniae Infection

This study aimed to investigate the effect of IFN-β(interferon-β)on host inflammatory responses in the early stage of S.pn(Streptococcus pneumoniae)infection.WT(wild type)mice and their PEMs(peritoneal exudate macrophages)were pretreated with exogenous rIFN-β(recombinant IFN-β),and culture medium-treated groups serve as controls.Meanwhile,endogenous IFNAR(interferonα/βreceptor)deficient mice and PEMs were used,with WT counterparts as control groups.All the groups were exposed to strain D39,RT-PCR and ELISA were then used to measure the expression of IL-1β(interleukin-1β)and TNF-α(tumor necrosis factor-α).The pulmonary inflammatory infiltration and tissue injury were evaluated by HE-staining as well as dry/wet weight ratio in order to analyze the effect of IFN-βon host proinflammatory responses.To determine the bacterial clearance rate,phagocytosis analysis of RAW264.7 cells was carried out,and the bacterial load in lungs of infected mice was counted.Finally,the role of IFN-βon host resistance to S.pn was confirmed by survival rate analysis of mice.The results suggested that IFN-βinhibited the overexpression of IL-1βand TNF-αinduced by D39.Compared with the NC(negative control)groups,rIFN-βpretreatment increased the phagocytosis of S.pn by RAW264.7 cells(P<0.001)and reduced the bacterial burden in lungs(P<0.01)and lung injury score of infected mice(P<0.05).Consistently,the bacterial load in lungs of IFNAR–/–mice was significantly higher than that of WT mice(P<0.001).Persistent higher level of local inflammation caused aggravated lung tissue damage of IFNAR–/–mice and enhanced mortality within nine days(P<0.05).However,there were no significant differences in body weight,lung dry/wet weight ratio or spleen index among the groups.Overall,IFN-βcould maintain moderate local inflammatory responses by regulating the expression of proinflammatory cytokines in macrophages in the early stage of S.pn infection,which helped the host to clear bacteria,preventing local infection from developing into lethal infection.