Ke Xiaojing, Lei Lang, Li Huang, Li Houxuan, Yan Fuhua
Nanjing Stomatological Hospital, Medical School of Nanjing University, China.
Nanjing Stomatological Hospital, Medical School of Nanjing University, China.
Mol Immunol. 2016 Sep;77:8-13. doi: 10.1016/j.molimm.2016.07.010. Epub 2016 Jul 21.
To eliminate invading pathogens and keep homeostasis, host employs multiple approaches such as the non-inflammation associated-apoptosis, inflammation associated-necroptosis and pyroptosis, etc. Necroptosis is known as a highly pro-inflammatory form of cell death due to the release of massive damage-associated molecular patterns (DAMPs). For the first time, we reported that Porphyromonas gingivalis induced cellular necroptosis through receptor-interacting protein 1 (RIP1)/RIP3/mixed lineage kinase domain-like (MLKL) signaling pathway in monocytes. Necroptosis in THP-1 cells was induced by MLKL phosphorylation in vitro. P. gingivalis treated-THP-1 cells exhibited lower cell death rate with pretreatment of inhibitors RIP1 and MLKL, accompanied with attenuated TNF-α and IL-6 expressions. Moreover, the necroptosis risk was also reduced via gene silencing by RIP3 or MLKL in the P. gingivalis treated-THP-1 cell lines. We further explored P. gingivalis-induced necroptosis in animal models in vivo. Firstly, C57BL/6 mice were injected with P. gingivalis in the subcutaneous chamber model. Animals pretreated with MLKL inhibitor exhibited significantly enhanced P. gingivalis clearance; in addition, levels of TNF-α and IL-6 were notably decreased by 60% via MLKL inhibition. Secondly, P. gingivalis-induced periodontitis was utilized to investigate necroptosis related-periodontopathogensis. Positive staining of phosphorylated MLKL in mice periodontitis biopsies was detected to a higher degree, while larger amount of alveolar bone loss was observed in MLKL (-) group comparing to those in the MLKL (+) group. These findings may suggest that P. gingivalis play essential roles in necroptosis process during periodontitis, and our research may shed light on the further work on the related periodontopathogenesis investigation.
为了清除入侵的病原体并维持体内平衡，宿主采用多种方式，如非炎症相关凋亡、炎症相关坏死性凋亡和焦亡等。坏死性凋亡因其释放大量损伤相关分子模式（DAMPs）而被认为是一种高度促炎的细胞死亡形式。我们首次报道牙龈卟啉单胞菌通过单核细胞中的受体相互作用蛋白1（RIP1）/RIP3/混合谱系激酶结构域样蛋白（MLKL）信号通路诱导细胞坏死性凋亡。体外实验中，MLKL磷酸化可诱导THP-1细胞发生坏死性凋亡。用RIP1和MLKL抑制剂预处理牙龈卟啉单胞菌处理的THP-1细胞，其细胞死亡率降低，同时TNF-α和IL-6表达减弱。此外，在牙龈卟啉单胞菌处理的THP-1细胞系中，通过RIPⅢ或MLKL基因沉默也降低了坏死性凋亡风险。我们进一步在体内动物模型中探究牙龈卟啉单胞菌诱导的坏死性凋亡。首先，在皮下腔室模型中给C57BL/6小鼠注射牙龈卟啉单胞菌。用MLKL抑制剂预处理的动物表现出牙龈卟啉单胞菌清除能力显著增强；此外，通过抑制MLKL，TNF-α和IL-6水平显著降低了60%。其次，利用牙龈卟啉单胞菌诱导的牙周炎来研究坏死性凋亡相关的牙周发病机制。在小鼠牙周炎活检中检测到磷酸化MLKL的阳性染色程度更高，而与MLKL(+)组相比，MLKL(-)组观察到更多的牙槽骨吸收。这些发现可能表明牙龈卟啉单胞菌在牙周炎坏死性凋亡过程中起重要作用，我们的研究可能为进一步研究相关牙周发病机制提供思路。
