The Role of Probiotics in Lipopolysaccharide-Induced Autophagy in Intestinal Epithelial Cells

Abstract

Background/Aims: Dysfunction of autophagy has been associated with loss of intestinal homeostasis. Lipopolysaccharide (LPS) from Gram-negative bacteria is known to be a major initiator of intestinal epithelial cell (IEC) autophagy. Although probiotics have been recognized to be involved in many therapeutic properties and participate in host defense responses, the molecular mechanisms by which probiotics exert these positive effects remain unknown. This study assessed the effect of probiotics on LPS-induced physical barrier dysfunction and the underlying mechanism of probiotic action in IECs with a focus on autophagy. Methods: A LPS-induced autophagic model was established in rat IEC18 cells wherein cells were treated with culture medium supernatants of Bifidobacteria following LPS intervention at indicated times. Autophagosomes in IEC18 cells were visualized by confocal microscopy after transfection with a tandem GFP-mCherry-LC3 construct and also by transmission electron microscopy. Autophagy-associated protein levels were analyzed by western blot and transepithelial electrical resistance (TEER) was measured using an epithelial voltohmmeter. Results: Probiotic treatment could effectively inhibit LPS-induced autophagy, as evidenced by the decreased ratio of microtubule-associated light chain 3 (LC3)-II/LC3-I, fewer autophagic vacuoles, and reduced punctate distribution of GFP-mCherry-LC3. In addition, probiotics prevented chloroquine (CQ) inhibition of autophagic flux and autophagolysosomal fusion as indicated by a failure to recruit LAMP1 and cathepsin D to lysosomes. Interestingly, ATG16L1 knockdown did not inhibit the effect of probiotics on LPS-induced autophagy. Furthermore, the diminished barrier function could be prevented by probiotics. Conclusions: We provide evidence that autophagy mediation by probiotics may be involved in enteroprotection against LPS-induced intestinal epithelial toxicity, and could serve as a novel mechanism through which probiotics promote and maintain gut homeostasis.

Rebeccamycin Attenuates TNF-α-Induced Intestinal Epithelial Barrier Dysfunction by Inhibiting Myosin Light Chain Kinase Production

“…Whether the dysfunction of intestinal epithelial barrier function in inflammatory bowel disease is the cause or consequence of mucosal inflammation remains unclear. However, the development of strategies that address the damage to intestinal epithelial barrier function in IBD would be of value to overall therapeutic strategies for IBD [11, 45-48]. We showed here that rebeccamycin inhibits the TNF-α-induced upregulation of MLC phosphorylation mediated by MLCK via Chk1 activation; this might be the molecular mechanism of the protective action of rebeccamycin against the intestinal epithelial barrier dysfunction triggered by TNF-α.…”

Acetyl-CoA Synthetase 2 Promotes Cell Migration and Invasion of Renal Cell Carcinoma by Upregulating Lysosomal-Associated Membrane Protein 1 Expression

“…Cellular Physiology and Biochemistry [30][31][32], especially in cancer metastasis [33]. Therefore, our results are important for the understanding of autophagy abnormalities and RCC development and metastasis.…”

Polymyxin B Attenuates LPS-Induced Death but Aggravates Radiation-Induced Death via TLR4-Myd88-IL-6 Pathway

“…PMB is widely used to eliminate the effects of endotoxin contamination, both in vitro and in vivo . The involved mechanism is that PMB is the TLR signaling inhibitor and could block the biological effects of LPS through binding to lipid A, the toxic component of LPS, which is negatively charged [15-17]. Moreover, the neutralizing effect of PMB on LPS is dose-related and specific for LPS [18].…”