Cellular interaction of nontypeable Haemophilus influenzae triggers cytotoxicity of infected type II alveolar cells via apoptosis
Cellular interaction of nontypeable Haemophilus influenzae triggers cytotoxicity of infected type II alveolar cells via apoptosis
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DOI：
10.1111/2049-632x.12215
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发表时间：
2015-03-01
影响因子：
3.3
通讯作者：
Chakraborti, Anuradha
中科院分区：
文献类型：
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作者：
Goyal, Manu;Singh, Meenu;Chakraborti, Anuradha
无法分型的流感嗜血杆菌（NTHi）是下呼吸道感染的重要原因，导致慢性阻塞性肺疾病（COPD）恶化。尽管其致病潜力，很少有人知道的作用，细胞内NTHi在肺部感染的发病机制。使用庆大霉素保护测定研究NTHi内化的动力学。从COPD患者分离的NTHi菌株有效地粘附并侵入II型肺泡（A549）细胞。在早期阶段，也就是说，6小时感染后，我们注意到大量增加的NTHi入侵细胞内复制没有证据。电子显微镜显示，大多数的内化NTHi居住在膜结合的酸性内吞空泡。然而，在后期阶段，也就是说，8小时感染后，观察到细胞内的NTHi活性显着减少，空泡被发现是空的NTHi逃逸到胞质溶胶。到12 h，细胞病变明显，细胞质大量空泡化，染色质浓缩，质膜完整。此外，凋亡标志物的分析证实，感染的A549细胞在后期发生凋亡。此外，通过细胞松弛素D抑制NTHi的内化防止细胞凋亡。总的来说，这些发现表明，NTHi的内化和其从空泡隔室的逃逸在感染过程中通过细胞凋亡触发肺泡细胞的细胞毒性。
Nontypeable Haemophilus influenzae (NTHi) is an important cause of lower respiratory tract infections, resulting in exacerbations of chronic obstructive pulmonary disease (COPD). Despite its pathogenic potential, little is known regarding the role of intracellular NTHi in pathogenesis of pulmonary infection. Kinetics of NTHi internalization was studied using gentamicin protection assays. NTHi strains isolated from COPD patients efficiently adhere to and invade type II alveolar (A549) cells. During early stages, that is, 6 h postinfection, we noted a substantial increase in NTHi invasion with no evidence of intracellular replication. Electron microscopy revealed that the majority of internalized NTHi resided within membrane bound acidic endocytic vacuoles. However, at later stages, that is, 8 h postinfection, significant reduction in viable intracellular NTHi was observed and vacuoles were found to be empty with NTHi escape into the cytosol. By 12 h, cytopathic changes of cells were evident with massive vacuolization of cytoplasm, intense chromatin condensation, and intact plasma membrane. Furthermore, analysis of apoptotic markers confirmed that infected A549 cells underwent apoptosis at later stages. In addition, inhibition of internalization of NTHi by cytochalasin D prevented apoptosis of cells. Collectively, these findings suggest that internalization of NTHi and its escape from vacuolar compartments triggers cytotoxicity of alveolar cells via apoptosis during the infection process.