Johnson Amber M, Kaushik Radhey S, Rotella Nicholas J, Hardwidge Philip R
Center for Infectious Disease Research and Vaccinology, South Dakota State University, Brookings, South Dakota 57007, USA.
Infect Immun. 2009 Jan;77(1):341-7. doi: 10.1128/IAI.01097-08. Epub 2008 Oct 20.
Enterotoxigenic Escherichia coli (ETEC) is a common cause of travelers' and postweaning diarrhea in humans and swine, respectively. The extent to which ETEC damages host cells is unclear. Experiments are presented that probe the ability of porcine ETEC isolates to induce apoptosis and cell death in porcine intestinal epithelial cells. Quantification of host phosphatidylserine exposure following ETEC infection suggested that ETEC induced changes in plasma membrane asymmetry, independent of the expression of the heat-labile enterotoxin. Significant host cell death was not observed. ETEC infection also caused a drastic inhibition of host esterase activity, as measured by calcein fluorescence. While ETEC infection resulted in activation of host caspase 3, terminal deoxynucleotidyltransferase-mediated dUTP-biotin nick end labeling of DNA double-strand breakage, indicative of late stages of apoptosis, was not observed. Camptothecin-induced apoptosis markedly increased subsequent ETEC adherence. Transfer of cell-free supernatants from apoptotic cells to bacterial inocula prior to infection of naïve cells increased the transcriptional activity of the regulatory region upstream of the K88ac operon and promoted subsequent adherence to host cells.
产肠毒素大肠杆菌（ETEC）分别是人类旅行者腹泻和猪断奶后腹泻的常见病因。ETEC对宿主细胞的损伤程度尚不清楚。本文展示了一些实验，这些实验探究了猪ETEC分离株在猪肠道上皮细胞中诱导凋亡和细胞死亡的能力。ETEC感染后宿主磷脂酰丝氨酸暴露的定量分析表明，ETEC诱导了质膜不对称性的变化，这与不耐热肠毒素的表达无关。未观察到明显的宿主细胞死亡。通过钙黄绿素荧光测量发现，ETEC感染还导致宿主酯酶活性的显著抑制。虽然ETEC感染导致宿主半胱天冬酶3激活，但未观察到DNA双链断裂的末端脱氧核苷酸转移酶介导的dUTP生物素缺口末端标记，这是凋亡后期的指标。喜树碱诱导的凋亡显著增加了随后ETEC的黏附。在感染未接触过ETEC的细胞之前，将凋亡细胞的无细胞上清液转移到细菌接种物中，增加了K88ac操纵子上游调控区域的转录活性，并促进了随后对宿主细胞的黏附。
