Jones N L, Islur A, Haq R, Mascarenhas M, Karmali M A, Perdue M H, Zanke B W, Sherman P M
Research Institute, Hospital for Sick Children, University of Toronto, Toronto M5G 1X8, Canada L8N 3Z5.
Am J Physiol Gastrointest Liver Physiol. 2000 May;278(5):G811-9. doi: 10.1152/ajpgi.2000.278.5.G811.
Human intestinal cells lack globotriaosylceramide (Gb(3)), the receptor for Shiga toxin-1 (Stx1) and Shiga toxin-2 (Stx2). Therefore, the role of these toxins in mediating intestinal disease during infection with Shiga toxin-producing Escherichia coli is unclear. The aims of this study were to determine whether Stx1 and Stx2 induce apoptosis in epithelial cells expressing (HEp-2, Caco-2) or lacking (T84) Gb(3) and to characterize the role of the Bcl-2 family. Stx1 (12.5 ng/ml) induced apoptosis in both HEp-2 (21.9 +/- 7.9% vs. 0.8 +/- 0.3%, P = 0.01) and Caco-2 (10.1 +/- 1.2% vs. 3.1 +/- 0.4%, P = 0.006) cells but not in Gb(3)-deficient T84 cells. Toxin-mediated apoptosis of HEp-2 cells was associated with enhanced expression of the proapoptotic protein Bax. Inhibition of caspase activation prevented toxin-stimulated apoptosis. In addition, overexpression of Bcl-2 by transient transfection blocked Stx1-stimulated cell death. These findings indicate that Shiga toxins produced by E. coli signal Gb(3)-expressing epithelial cells to undergo apoptosis in association with enhanced Bax expression, thereby resulting in activation of the caspase cascade.
人类肠道细胞缺乏作为志贺毒素1（Stx1）和志贺毒素2（Stx2）受体的球三糖神经酰胺（Gb(3)）。因此，这些毒素在产志贺毒素大肠杆菌感染期间介导肠道疾病中的作用尚不清楚。本研究的目的是确定Stx1和Stx2是否能诱导表达Gb(3)（HEp-2、Caco-2）或缺乏Gb(3)（T84）的上皮细胞发生凋亡，并阐明Bcl-2家族的作用。Stx1（12.5 ng/ml）可诱导HEp-2细胞（21.9 +/- 7.9%对0.8 +/- 0.3%，P = 0.01）和Caco-2细胞（10.1 +/- 1.2%对3.1 +/- 0.4%，P = 0.006）发生凋亡，但不能诱导缺乏Gb(3)的T84细胞凋亡。毒素介导的HEp-2细胞凋亡与促凋亡蛋白Bax的表达增强有关。抑制半胱天冬酶激活可阻止毒素刺激的凋亡。此外，通过瞬时转染过表达Bcl-2可阻断Stx1刺激的细胞死亡。这些发现表明，大肠杆菌产生的志贺毒素可使表达Gb(3)的上皮细胞发生凋亡，同时Bax表达增强，从而导致半胱天冬酶级联反应的激活。
