Kurita-Ochiai T, Fukushima K, Ochiai K
Department of Microbiology, Nihon University School of Dentistry at Matsudo, Chiba, Japan.
Infect Immun. 1999 Jan;67(1):22-9. doi: 10.1128/IAI.67.1.22-29.1999.
We previously reported that butyric acid, an extracellular metabolite from periodontopathic bacteria, induced apoptosis in murine thymocytes, splenic T cells, and human Jurkat T cells. In this study, we examined the ability of butyric acid to induce apoptosis in peripheral blood mononuclear cells (PBMC) and the effect of bacterial lipopolysaccharide (LPS) on this apoptosis. Butyric acid significantly inhibited the anti-CD3 monoclonal antibody- and concanavalin A-induced proliferative responses in a dose-dependent fashion. This inhibition of PBMC growth by butyric acid depended on apoptosis in vitro. It was characterized by internucleosomal DNA digestion and revealed by gel electrophoresis followed by a colorimetric DNA fragmentation assay to occur in a concentration-dependent fashion. Butyric acid-induced PBMC apoptosis was accompanied by caspase-3 protease activity but not by caspase-1 protease activity. LPS potentiated butyric acid-induced PBMC apoptosis in a dose-dependent manner. Flow-cytometric analysis revealed that LPS increased the proportion of sub-G1 cells and the number of late-stage apoptotic cells induced by butyric acid. Annexin V binding experiments with fractionated subpopulations of PBMC in flow cytometory revealed that LPS accelerated the butyric acid-induced CD3(+)-T-cell apoptosis followed by similar levels of both CD4(+)- and CD8(+)-T-cell apoptosis. The addition of LPS to PBMC cultures did not cause DNA fragmentation, suggesting that LPS was unable to induce PBMC apoptosis directly. These data suggest that LPS, in combination with butyric acid, potentiates CD3(+) PBMC T-cell apoptosis and plays a role in the apoptotic depletion of CD4(+) and CD8(+) cells.
我们之前报道过，丁酸作为牙周病原菌的一种细胞外代谢产物，可诱导小鼠胸腺细胞、脾T细胞和人Jurkat T细胞凋亡。在本研究中，我们检测了丁酸诱导外周血单核细胞（PBMC）凋亡的能力以及细菌脂多糖（LPS）对这种凋亡的影响。丁酸以剂量依赖的方式显著抑制抗CD3单克隆抗体和刀豆球蛋白A诱导的增殖反应。丁酸对PBMC生长的这种抑制作用在体外依赖于凋亡。其特征为核小体间DNA消化，并通过凝胶电泳随后进行比色DNA片段化分析显示以浓度依赖的方式发生。丁酸诱导的PBMC凋亡伴随着caspase-3蛋白酶活性，但不伴随着caspase-1蛋白酶活性。LPS以剂量依赖的方式增强丁酸诱导的PBMC凋亡。流式细胞术分析显示，LPS增加了亚G1期细胞的比例以及丁酸诱导的晚期凋亡细胞的数量。在流式细胞术中对PBMC亚群进行Annexin V结合实验显示，LPS加速了丁酸诱导的CD3(+) - T细胞凋亡，随后CD4(+)和CD8(+) - T细胞凋亡水平相似。向PBMC培养物中添加LPS不会导致DNA片段化，这表明LPS不能直接诱导PBMC凋亡。这些数据表明，LPS与丁酸联合可增强CD3(+) PBMC T细胞凋亡，并在CD4(+)和CD8(+)细胞的凋亡性耗竭中起作用。
