title: Lactobacillus acidophilus S-layer protein-mediated inhibition of Salmonella-induced apoptosis in Caco-2 cells.
abstract: Surface layer (S-layer) proteins are crystalline arrays of proteinaceous subunits present as the outermost component of the cell wall in several Lactobacillus species. The underlying mechanism for how S-layer proteins inhibit pathogen infections remains unclear. To gain insights into the mechanism of the antimicrobial activity of Lactobacillus S-layer proteins, we examined how Lactobacillus S-layer proteins impact Salmonella Typhimurium-induced apoptosis in vitro in Caco-2 human colon epithelial cells. When Caco-2 cells infected with Salmonella Typhimurium SL1344, we found that apoptosis was mediated by activation of caspase-3, but not caspase-1. When Salmonella Typhimurium SL1344 and S-layer proteins were coincubated simultaneously, Caco-2 cell apoptosis was markedly decreased and the cell damage was modified, as evaluated by flow cytometry and microscopy. Detailed analyses showed that the S-layer proteins inhibited the caspase-3 activity and activated the extracellular signal-regulated kinases 1 and 2 (ERK1/2) signaling pathway. Taken together, these findings suggest that Lactobacillus S-layer proteins protected against Salmonella-induced apoptosis through reduced caspase-3 activation. In addition, Salmonella-induced apoptotic cell damage was modified by S-layer proteins through the ERK1/2 signaling pathway. This mechanism may represent a novel approach for antagonizing Salmonella infection.
authors.affiliation: College of Veterinary Medicine, Nanjing Agricultural University, China.
authors.forename: Pengcheng
authors.initials: P
authors.lastname: Li
authors.forename: Yinyan
authors.initials: Y
authors.lastname: Yin
authors.forename: Qinghua
authors.initials: Q
authors.lastname: Yu
authors.forename: Qian
authors.initials: Q
authors.lastname: Yang
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D018938:Caco-2 Cells; D053148:Caspase 3 / Q000378:metabolism; D006801:Humans; D007413:Intestinal Mucosa / Q000382:microbiology*; D007779:Lactobacillus acidophilus; D008562:Membrane Glycoproteins / Q000494:pharmacology*; D012486:Salmonella typhimurium / Q000187:drug effects*
chemical_list: D000900:Anti-Bacterial Agents; D008562:Membrane Glycoproteins; C055764:S-layer proteins; D053148:Caspase 3