Chumbler Nicole M, Farrow Melissa A, Lapierre Lynne A, Franklin Jeffrey L, Lacy D Borden
Department of Pathology, Microbiology and Immunology, Vanderbilt University School of Medicine, Nashville, Tennessee, USA.
Department of Surgery, Vanderbilt University School of Medicine, Nashville, Tennessee, USA The Veterans Affairs Tennessee Valley Healthcare System, Nashville, Tennessee, USA Epithelial Biology Center, Vanderbilt University, Nashville, Tennessee, USA.
Infect Immun. 2016 Sep 19;84(10):2871-7. doi: 10.1128/IAI.00583-16. Print 2016 Oct.
As the major cause of antibiotic-associated diarrhea, Clostridium difficile is a serious problem in health care facilities worldwide. C. difficile produces two large toxins, TcdA and TcdB, which are the primary virulence factors in disease. The respective functions of these toxins have been difficult to discern, in part because the cytotoxicity profiles for these toxins differ with concentration and cell type. The goal of this study was to develop a cell culture model that would allow a side-by-side mechanistic comparison of the toxins. Conditionally immortalized, young adult mouse colonic (YAMC) epithelial cells demonstrate an exquisite sensitivity to both toxins with phenotypes that agree with observations in tissue explants. TcdA intoxication results in an apoptotic cell death that is dependent on the glucosyltransferase activity of the toxin. In contrast, TcdB has a bimodal mechanism; it induces apoptosis in a glucosyltransferase-dependent manner at lower concentrations and glucosyltransferase-independent necrotic death at higher concentrations. The direct comparison of the responses to TcdA and TcdB in cells and colonic explants provides the opportunity to unify a large body of observations made by many independent investigators.
作为抗生素相关性腹泻的主要病因，艰难梭菌是全球医疗机构面临的一个严重问题。艰难梭菌产生两种大毒素，即TcdA和TcdB，它们是疾病中的主要毒力因子。这些毒素各自的功能一直难以辨别，部分原因是这些毒素的细胞毒性特征随浓度和细胞类型而不同。本研究的目的是建立一种细胞培养模型，以便对这些毒素进行并行的机制比较。条件永生化的年轻成年小鼠结肠（YAMC）上皮细胞对这两种毒素均表现出极高的敏感性，其表型与组织外植体中的观察结果一致。TcdA中毒导致依赖于毒素葡糖基转移酶活性的凋亡性细胞死亡。相比之下，TcdB具有双峰机制；它在较低浓度下以葡糖基转移酶依赖性方式诱导凋亡，在较高浓度下诱导葡糖基转移酶非依赖性坏死性死亡。在细胞和结肠外植体中对TcdA和TcdB反应的直接比较为统一许多独立研究者所做的大量观察提供了机会。
