Localization of Vibrio vulnificus infection in dendritic cells and its effects on the cytoskeleton / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>Vibrio vulnificus (Vv) is an estuarine bacterium that can cause primary septicemia as well as serious wound infections. However, little is known about the mechanisms by which Vv infects dendritic cells (DCs) and its effects on cytoskeleton. In this study, we aimed to investigate the invasion, internalization, and the organelles damage of the cultured dendritic cells (a DC 2.4 strain) during Vv infection.</p><p><b>METHODS</b>The study model was the cultured DCs infected by a Vv 1.758 strain. Electron microscopy was used to observe the localization of bacteria at the different time points of infection, cell morphology, and the process of organelles changes. The cytoskeleton structure including the microfilaments and the microtubules rearrangement was examined under a fluorescence microscope.</p><p><b>RESULTS</b>The Vv were pinocytosised into the DC cells through double-sides, and localized at 1 - 2 mm of the inner side membrane. It took 1.3, 1.9, and 3.4 hours to reach the infection ratio of 25%, 50%, and 75%, respectively. Using electron microscopy, the DCs had been observed to have developed chromatin aggregation within 4.0 hours, and significant cytoskeleton structure disruption was noted within 6.0 hours.</p><p><b>CONCLUSION</b>The high lethality of Vv infection may be associated with the direct disruption of the DCs cytoskeleton structure.</p>

Effects of Mycobacterium tuberculosis on apoptosis of mouse dendritic cells and activation of caspase-3, caspase-8 / 浙江大学学报·医学版

<p><b>OBJECTIVE</b>To investigate the effects of Mycobacterium tuberculosis on apoptosis of mouse dendritic cells (DC 2. 4) and the activation of caspase-3, caspase-8.</p><p><b>METHODS</b>Mycobacterium tuberculosis H37Rv strain was co-cultured with DC 2. 4 cells. The morphological changes of DC 2. 4 cells were observed with fluorescence microscope after DAPI staining and transmission electron microscope. The apoptosis of DC 2. 4 cells were examined by DNA agarose gel electrophoresis. The activities of caspase-3 and caspase-8 were detected by colorimetric assay.</p><p><b>RESULTS</b>Bacterial invasion was observed while DC 2. 4 cells and H37Rv were co-cultured for 2 h; and the rates of invasion were (16.1 ± 4.3)%, (35.8 ± 5.1)%, (50.2 ± 5.7)%, (58.3 ± 6.2)% and(65.9 ± 6.9)% at 4, 6, 8,10, 12 h, respectively. The phenomenon of nuclear condensation and marginalization were shown by DAPI staining and transmission electron microscope in DC 2. 4 cells at 6 h of co-cultivation with H37Rv. The characteristic bands of apoptosis by DNA electrophoresis were detected. The activities of caspase-3 and caspase-8 were increased in a time-dependent manner. The rates of DC 2. 4 cell apoptosis were (6.4 ± 2.5)%, (11.8 ± 5.3)% and (31.1 ± 8.7)% at 6 h,12 h and 24 h after co-cultivation with H37Rv, respectively. The maximal activities of intracellular caspase-3 and caspase-8 at 10 h and 6 h were (2.01 ± 0.09) U/μg and (2.40 ± 0.07)U/μg, respectively, which was significantly different compared with the control groups(P<0.05). The activation of caspase-8 was earlier than that of caspase-3.</p><p><b>CONCLUSION</b>Mycobacterium tuberculosis can induce the apoptosis of DC 2. 4 cells, which is associated with the activation of intracellular caspase-3 and caspase-8.</p>