Department of Microbiology, Institute of Biomedical Sciences, University of São Paulo, São Paulo, Brazil.
Department of Microbiology, Institute of Biomedical Sciences, University of São Paulo, São Paulo, Brazil.
Cytokine. 2014 Mar;66(1):46-53. doi: 10.1016/j.cyto.2013.12.014. Epub 2014 Jan 14.
Aggregatibacter actinomycetemcomitans is an important periodontal pathogen that can participate in periodontitis and other non-oral infections. The cytolethal distending toxin (Cdt) is among the virulence factors produced by this bacterium. The Cdt is also secreted by several mucosa-associated Gram-negative pathogens and may play a role in perpetuating the infection by modulating the immune response. Although the toxin targets a wide range of eukaryotic cell types little is known about its activity on macrophages which play a key part in alerting the rest of the immune system to the presence of pathogens and their virulence factors. In view of this, we tested the hypothesis that the A. actinomycetemcomitans Cdt (AaCdt) disrupts macrophage function by inhibiting phagocytic activity as well as affecting the production of cytokines. Murine macrophages were co-cultured with either wild-type A. actinomycetemcomitans or a Cdt(-) mutant. Viable counts and qPCR showed that phagocytosis of the wild-type strain was significantly reduced relative to that of the Cdt(-) mutant. Addition of recombinant Aa(r)Cdt to co-cultures along with the Cdt(-) mutant diminished the phagocytic activity similar to that observed with the wild type strain. High concentrations of Aa(r)Cdt resulted in decreased phagocytosis of fluorescent bioparticles. Nitric oxide production was modulated by the presence of Cdt and the levels of IL-1β, IL-12 and IL-10 were increased. Production of TNF-α did not differ in the co-culture assays but was increased by the presence of Aa(r)Cdt. These data suggest that the Cdt may modulate macrophage function in A. actinomycetemcomitans infected sites by impairing phagocytosis and modifying the pro-inflammatory/anti-inflammatory cytokine balance.
伴放线聚集杆菌是一种重要的牙周病原体，可参与牙周炎和其他非口腔感染。细胞致死扩张毒素 (Cdt) 是该细菌产生的毒力因子之一。该毒素也由几种粘膜相关的革兰氏阴性病原体分泌，可能通过调节免疫反应在持续感染中发挥作用。尽管该毒素靶向广泛的真核细胞类型，但对其在巨噬细胞中的活性知之甚少，巨噬细胞在向免疫系统其他部分发出病原体及其毒力因子存在的警报方面起着关键作用。鉴于此，我们测试了以下假设：伴放线聚集杆菌 Cdt (AaCdt) 通过抑制吞噬活性以及影响细胞因子的产生来破坏巨噬细胞功能。用野生型伴放线聚集杆菌或 Cdt(-)突变体共培养小鼠巨噬细胞。活菌计数和 qPCR 显示，与 Cdt(-)突变体相比，野生型菌株的吞噬作用明显降低。在共培养物中添加重组 Aa(r)Cdt 以及 Cdt(-)突变体，可使吞噬活性类似于观察到的野生型菌株。高浓度的 Aa(r)Cdt 导致荧光生物颗粒的吞噬作用减少。Cdt 的存在可调节一氧化氮的产生，且 IL-1β、IL-12 和 IL-10 的水平增加。共培养物测定中 TNF-α 的产生没有差异，但 Aa(r)Cdt 的存在会增加其产生。这些数据表明，Cdt 可能通过损害吞噬作用和改变促炎/抗炎细胞因子平衡来调节感染伴放线聚集杆菌的部位的巨噬细胞功能。
