Probiotics prevent enterohaemorrhagic Escherichia coli O157 : H7-mediated inhibition of interferon-γ-induced tyrosine phosphorylation of STAT-1

Abstract

Enterohaemorrhagic Escherichia coli (EHEC) O157 : H7 inhibits interferon (IFN)-γ-stimulated tyrosine phosphorylation of signal transducer and activator of transcription (STAT)-1 in epithelial cells. We determined the effects of probiotics on EHEC-mediated disruption of IFN-γ-stimulated STAT-1 activation in epithelial cell lines. Confluent Intestine 407, HEp-2 and Caco-2 epithelial cells were pre-treated (3 h) with either probiotics or surface-layer proteins derived from Lactobacillus helveticus R0052 prior to infection with EHEC O157 : H7 strain CL56 (m.o.i. 100 : 1, 6 h, 37 °C in 5 % CO2). Subsequently, cells were washed and stimulated with human recombinant IFN-γ (50 ng ml−1, 0.5 h, 37 °C) followed by whole-cell protein extraction and immunoblotting for tyrosine-phosphorylated STAT-1. Relative to uninfected cells, STAT-1-activation was reduced after EHEC O157 : H7 infection. Pre-incubation with the probiotic L. helveticus R0052 followed by EHEC infection abrogated pathogen-mediated disruption of IFN-γ–STAT-1 signalling. As determined using Transwell inserts, probiotic-mediated protection was independent of epithelial cell contact. In contrast, pre-incubation with boiled L. helveticus R0052, an equal concentration of viable Lactobacillus rhamnosus R0011, or surface-layer proteins (0.14 mg ml−1) did not restore STAT-1 signalling in EHEC-infected cells. The viable probiotic agent L. helveticus R0052 prevented EHEC O157 : H7-mediated subversion of epithelial cell signal transduction responses.