| Project/Area Number |
11670139
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Pathological medical chemistry
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| Research Institution | The University of Tokyo |
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Principal Investigator |
IMAJOH-OHMI Shinobu Medical Science, Basic Medical Sciences, The University of Tokyo Associate Professor, 医科学研究所, 助教授 (20160046)
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| Co-Investigator(Kenkyū-buntansha) |
NONAKA Takashi Medical Science, Basic Medical Sciences, JSPS Fellow, 医科学研究所, 日本学術振興会特別研究員
SASAKAWA Chihiro Medical Science, Microbiology and Immunology, The University of Tokyo Professor, 医科学研究所, 教授 (70114494)
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| Project Period (FY) |
1999 – 2000
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| Project Status |
Completed (Fiscal Year 2000)
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| Budget Amount *help |
¥3,600,000 (Direct Cost: ¥3,600,000)
Fiscal Year 2000: ¥1,600,000 (Direct Cost: ¥1,600,000)
Fiscal Year 1999: ¥2,000,000 (Direct Cost: ¥2,000,000)
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| Keywords | Shigella / Bacterial infection / Apoptosis / Cell death / Ipa protein / Cell differentiation / macrophage / caspase / アポトーシス / 細胞感染 / 食細胞 / U937 / 単球 / 病原性因子 |
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| Research Abstract |
Upon invasion into tissues bacterial phathogens are phagocytosed by resident macrophages to be killed and digested. Some bacteria can escape into the cytosol and induce cell death of the host cell.
Shigella flexneri is also reported to induce apoptosis in murine macrophages where a bacterial invasion plasmid antigen B (IpaB) activates a cellular protease triggering apoptotic cell death. However, other investigators observed necrotic cell death in Shigella-infected human macrophages derived from peripheral monocytes. Cell death of macrophages caused by bacterial invasion remains to be characterized on the basis of molecular interaction.
We employed here a human monoblastic cell line U937 that is poteittially differentiated into cells resembling mature monocytes in the peripheral blood. Cultured with IFNgamma or RA, U937 cells become superoxide anion-producible. When S.flexneri was introduced into thus differentiated cells, cell death occurred regardless of differentiation stateas as judge
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d by the dye exclusion viability test. Cell death was also observed in undifferentiated U937 cells, but was strongly promoted in RA-differentiated cells. On the other hand, an avirulent mutant strain deficient in Ipa proteins did not induce cell death, probably because bacteria could not enter the cell. These results clearly indicate that bacterial invasion induces cell death in monocyte-like U937 cells. However, undifferentiated and RA-differentiated U937 cells died exhibiting cytoplasmic swelling but not nuclear condensation and fragmentation, suggesting that these cells underwent necrosis. Surprisingly, IFNgamma-differentiated U937 cells showed morphological features typical of apoptosis, though these cells were as sensitive as undifferentiated U937 to virulent Shigella. These observations were confirmed by DNA fragmentation assay on an agarose gel where chromosomal DNA from IFNgamma-treated cells was electrophoresed in a ladder-like manner upon Shigella infection but that from U937 cells of different differentiation state was not. Furthermore, cleavage of PARP was seen only when IFNgamma-differentiated cells were infected with pathgenic Shigella. These findings suggest that vilulent Shigella induces distinct types of cell death in U937 cells depending on their differentiation state. Less
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