Role of tumor necrosis factor and nitric oxide in the cytotoxic effects of Clostridium difficile toxin A and toxin B on macrophages
Role of tumor necrosis factor and nitric oxide in the cytotoxic effects of Clostridium difficile toxin A and toxin B on macrophages
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DOI：
10.1016/s0041-0101(96)00172-9
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发表时间：
1997-05-01
期刊：
影响因子：
2.8
通讯作者：
Ribeiro, RA
中科院分区：
文献类型：
--
作者：
Melo, AA;Souza, MHLP;Ribeiro, RA
艰难梭菌是与结肠炎相关的细菌，它产生两种外毒素，毒素A（TxA）和毒素B（TxB）。虽然这些毒素被公认为对几种哺乳动物细胞类型具有细胞毒性，但所涉及的机制尚未完全了解。本研究的目的是检查TxA和TxB对培养的腹腔巨噬细胞的细胞毒性，并研究肿瘤坏死因子-α（TNF-α）和一氧化氮（NO）是否参与该过程。作为对照，E. coliLPS进行了研究。TxA、TxB和LPS对巨噬细胞单层具有剂量依赖性的细胞毒性，其中TxB的毒性最强。所有毒素都刺激了巨噬细胞释放TNF-α。TxB在诱导这种反应方面再次最活跃。释放的TNF-α似乎参与LPS和TxA的作用，但不参与TxB的作用，因为抗TNF-α的mAb抑制前两者的细胞毒性，但对后者没有影响。NO不参与TxA和TxB的作用，因为即使在IFN-γ存在下，这些毒素也不诱导巨噬细胞中产生这种介质。此外，L-亚氨基-乙基-L-鸟氨酸（L-NIO），一种NO合成酶抑制剂，并没有改变由TxA或TxB引起的巨噬细胞死亡。虽然LPS能够诱导产生大量的NO，但NO并不介导LPS的细胞毒性，因为L-NIO不影响LPS引起的巨噬细胞死亡的程度。因此，TxA和TxB似乎通过不同的机制对培养的巨噬细胞产生细胞毒性作用。TNF-α参与TxA和LPS介导的细胞毒性，但不参与TxB引起的毒性。NO不参与任何这些毒素的杀伤作用。(C)1997 Elsevier Science Ltd.
Clostridium difficile, the bacterium involved in antibiotic-associated colitis, produces two exotoxins, toxin A (TxA) and toxin B (TxB). Although these toxins are well recognized as being cytotoxic to several mammalian cell types, the mechanisms involved are not fully understood. The aim of the present investigation was to examine the cytotoxicity of TxA and TxB to peritoneal macrophages in culture and to investigate whether tumor necrosis factor-alpha (TNF-alpha) and nitric oxide (NO) are involved in the process. As a control, the effect of E. coli LPS was also investigated. TxA, TxB and LPS were dose-dependently cytotoxic to macrophage monolayers, with TxB being the most potent. All of the toxins stimulated the release of TNF-alpha from macrophages. TxB was again the most active in inducing this response. The TNF-alpha released appears to be involved in the action of LPS and TxA, but not of TxB, since a mAb against TNF-alpha inhibited the cytotoxicity of the former two but had no effect on the latter. NO is not involved in the effects of TxA and TxB since these toxins did not induce the production of this mediator in macrophages, even in the presence of IFN-gamma. In addition, L-imino-ethyl-L-ornithine (L-NIO), a NO synthase inhibitor, did not modify the macrophage death caused by TxA or TxB. Although LPS was able to induce the production of high amounts of NO, NO did not mediate the LPS cytotoxicity since L-NIO did not influence the degree of macrophage death caused by LPS. TxA and TxB therefore appear to exert cytotoxic effects on cultured macrophages by different mechanisms. TNF-alpha is involved in TxA and LPS-mediated cytotoxicity but not in the toxicity caused by TxB. NO is not involved in the killing action of any of these toxins. (C) 1997 Elsevier Science Ltd.