Four types of B ifidobacteria trigger autophagy response in intestinal epithelial cells

Objectives To investigate the influence of gut microbiota on autophagy activation in intestinal epithelial cells ( IEC ) and to evaluate the IEC autophagy response to different types of Bifidobacteria .Methods IEC ‐18 cells were treated with lipopolysaccharide ( LPS ) derived from enteropathogenic E scherichia coli ( EPEC ) O 127: B 8 and culture medium supernatants of four types of B ifidobacteria . Transepithelial electrical resistance ( TEER ) was measured using an epithelial voltohmmeter. Autophagy was determined by transmission electron microscopy ( TEM ), the ratio of LC 3‐ II to LC 3‐ I and the persistence of both green fluorescent protein ( GFP ) and m C herry signals using a tandem m C herry‐ GFP ‐ LC 3 construct. The expression of A tg12– A tg5– A tg16 complex was measured by quantitative real‐time polymerase chain reaction. Results EPEC‐LPS significantly diminished the TEER of IEC compared with untreated controls by 45–55%. This reduction was not observed after treated with B ifidobacteria at all time points. B ifidobacteria could initiate the activation of autophagy in IEC , based on both the ratio of LC3‐II to LC3‐I and TEM . There was no difference in the influence of the four types of Bifidobacteria on the autophagy response. Compared with Bifidobacteria , IEC reacted to EPEC‐LPS much more intensively by autophagy accumulation. More m C herry + LC 3 autophagic puncta and increased expressions of autophagy genes Atg5 , Atg12 and Atg16 could be detected after being treated with B ifidobacteria and EPEC‐LPS . Conclusions B ifidobacteria initiate autophagy activation in IEC . The A tg12– A tg5– A tg16 multimeric complex might participate in the activation of B ifidobacteria ‐induced cell autophagy.