Abstract: Objective To investigate whether Lactobacillus rhamnosus GG conditioned medium（LGG-CM）has preventive effect
against E. coli K1-induced neuropathogenicity in vitro by inhibiting nuclear factor-κB (NF-κB) signaling pathway. Methods An
in vitro blood-brain barrier (BBB) model was constructed using human brain microvascular endothelial cells (HBMECs). The
effect of LGG-CM on E. coli-actived NF-κB signaling pathway was assayed using Western blotting. Invasion assay and
polymorphonuclear leukocyte (PMN) transmigration assay were performed to explore whether LGG-CM could inhibit E. coli
invasion and PMN transmigration across the BBB in vitro. The expressions of ZO-1 and CD44 were detected using Western
blotting and immunofluorescence. The changes of trans-epithelial electric resistance (TEER) and bacterial translocation were
determined to evaluate the BBB permeability. Results Pre-treament with LGG-CM inhibited E. coli-activated NF-κB signaling
pathway in HBMECs and decreased the invasion of E. coli K1 and transmigration of PMN. Western blotting showed that
LGG-CM could alleviate E. coli-induced up-regulation of CD44 and down-regulation of ZO-1 expressions in HBMECs. In
addition, pre-treatment with LGG-CM alleviated E. coli K1-induced reduction of TEER and suppressed bacterial translocation
across the BBB in vitro. Conclusion LGG-CM can block E. coli-induced activation of NF-κB signaling pathway and thereby
prevents E. coli K1-induced neuropathogenicity by decreasing E. coli K1 invasion rates and PMN transmigration.