Lactobacillus johnsonii L531 Ameliorates Escherichia coli-Induced Cell Damage via Inhibiting NLRP3 Inflammasome Activity and Promoting ATG5/ATG16L1-Mediated Autophagy in Porcine Mammary Epithelial Cells

Abstract

<i>Escherichia coli</i> (<i>E. coli</i>), a main mastitis-causing pathogen in sows, leads to mammary tissue damage. Here, we explored the effects of <i>Lactobacillus johnsonii</i> L531 on attenuating <i>E. coli</i>-induced inflammatory damage in porcine mammary epithelial cells (PMECs). <i>L. johnsonii</i> L531 pretreatment reduced <i>E. coli</i> adhesion to PMECs by competitive exclusion and the production of inhibitory factors and decreased <i>E. coli</i>-induced destruction of cellular morphology and ultrastructure. <i>E. coli</i> induced activation of NLRP3 inflammasome associated with increased expression of NLRP3, ASC, and cleaved caspase-1, however, <i>L. johnsonii</i> L531 inhibited <i>E. coli</i>-induced activation of NLRP3 inflammasome. Up-regulation of interleukin <i>(Il)-1β</i>, <i>Il-6</i>, <i>Il-8</i>, <i>Il-18</i>, tumor necrosis factor alpha, and chemokine <i>Cxcl2</i> expression after <i>E. coli</i> infection was attenuated by <i>L. johnsonii</i> L531. <i>E. coli</i> infection inhibited autophagy, whereas <i>L. johnsonii</i> L531 reversed the inhibitory effect of <i>E. coli</i> on autophagy by decreasing the expression of autophagic receptor SQSTM1/p62 and increasing the expression of autophagy-related proteins ATG5, ATG16L1, and light chain 3 protein by Western blotting analysis. Our findings suggest that <i>L. johnsonii</i> L531 pretreatment restricts NLRP3 inflammasome activity and induces autophagy through promoting ATG5/ATG16L1-mediated autophagy, thereby protecting against <i>E. coli</i>-induced inflammation and cell damage in PMECs.