Epithelial cell signaling responses to enterohemorrhagic Escherichia coli infection

The cellular basis of organ failure in sepsis-signaling during damage and repair processes

Sepsis is defined as life-threatening organ dysfunction caused by a dysregulated host response to infection. This definition, updated in 2016, shifted the conceptual focus from exclusive attention to the systemic inflammatory response toward the multifactorial tissue damage that occurs during the progression of infection to sepsis and shock. Whereas targeting the inflammatory host response to infection did not translate into improved clinical management of sepsis, recent findings might shed new light on the maladaptive host–pathogen interaction in sepsis and pave the way for “theranostic” interventions. In addition to the well-known resistance responses of the immune system that result in pathogen clearance, “disease tolerance” has recently been acknowledged as a coping mechanism of presumably equal importance. We propose that both defense mechanisms, “resistance” and “disease tolerance”, can get out of control in sepsis. Whereas excessive activation of resistance pathways propagates tissue damage via immunopathology, an inappropriate “tolerance” might entail immunoparalysis accompanied by fulminant, recurrent or persisting infection. The review introduces key signaling processes involved in infection-induced “resistance” and “tolerance”. We propose that elaboration of these signaling pathways allows novel insights into sepsis-associated tissue damage and repair processes. Moreover theranostic opportunities for the specific treatment of sepsis-related hyperinflammation or immunoparalysis will be introduced. Agents specifically affecting either hyperinflammation or immunoparalysis in the course of sepsis might add to the therapeutic toolbox of personalized care in the field of organ dysfunction caused by infection. (This article is freely available.)

Resveratrol and some glucosyl, glucosylacyl, and glucuronide derivatives reduce Escherichia coli O157:H7, Salmonella Typhimurium, and Listeria monocytogenes Scott A adhesion to colonic epithelial cell lines

The efficacy of resveratrol and some glucosyl, glucosylacyl, and glucuronide derivatives in inhibiting the adhesion of Salmonella Typhimurium, Escherichia coli O157:H7, and Listeria monocytogenes Scott A to Caco-2 and HT-29 colonic cells was investigated. The three bacteria strains were capable of adhering to both colonic epithelial cell lines, which responded by producing the pro-inflammatory interleukin 8 (IL-8). Adhesion inhibition of E. coli O157:H7 and S. Typhimurium to colonic cells was ≥60 and ≥40%, respectively, when resveratrol and most of the resveratrol derivatives were applied. Lower adhesion inhibition was observed for the bacteria with higher adherence potential, L. monocytogenes (≥20%). Resveratrol-3-O-(6'-O-butanoyl)-β-D-glucopyranoside (BUT) (50 and 100 μM) and resveratrol-3-O-(6'-O-octanoyl)-β-D-glucopyranoside (OCT) (50 μM) reduced IL-8 secretion by 100%. These results suggest that one mechanism for the beneficial attributes of resveratrol and especially the derivatives BUT and OCT could be the ability to reduce the adhesion and consequent pro-inflammatory cytokine production in intestinal epithelial cells in response to pathogen adhesion. The potential use of these compounds in the prevention of foodborne infections, intestinal homeostasis loss, and inflammatory bowel diseases could be another step in finding coadjuvants or alternatives to antibiotic treatments.

Verotoxin-2 activates mitogen-activated protein kinases in bovine adherent peripheral blood mononuclear cells

The effects of verotoxin (VT) on the mitogen-activated protein (MAP) kinase signalling pathways were investigated in bovine adherent peripheral blood mononuclear cells (PBMCs). VT2 stimulated a transient activation of both p38 MAP kinase and extracellular-regulated kinase (ERK) and stimulated an increase in tumour necrosis factor-α release from PBMCs. Bovine PBMCs react with very similar kinetics to human peripheral blood monocytes, despite the gross differences in disease outcome of the two species on infection with verotoxigenic Escherichia coli.

Surface-layer protein extracts from Lactobacillus helveticus inhibit enterohaemorrhagic Escherichia coli O157:H7 adhesion to epithelial cells

Adherence of intestinal pathogens, including Escherichia coli O157:H7, to human intestinal epithelial cells is a key step in pathogenesis. Probiotic bacteria, including Lactobacillus helveticus R0052 inhibit the adhesion of E. coli O157:H7 to epithelial cells, a process which may be related to specific components of the bacterial surface. Surface-layer proteins (Slps) are located in a paracrystalline layer outside the bacterial cell wall and are thought to play a role in tissue adherence. However, the ability of S-layer protein extract derived from probiotic bacteria to block adherence of enteric pathogens has not been investigated. Human epithelial (HEp-2 and T84) cells were treated with S-layer protein extract alone, infected with E. coli O157:H7, or pretreated with S-layer protein extract prior to infection to determine their importance in the inhibition of pathogen adherence. The effects of S-layer protein extracts were characterized by phase-contrast and immunofluorescence microscopy and measurement of the transepithelial electrical resistance of polarized monolayers. Pre-treatment of host epithelial cells with S-layer protein extracts prior to E. coli O157:H7 infection decreased pathogen adherence and attaching-effacing lesions in addition to preserving the barrier function of monolayers. These in vitro studies indicate that a non-viable constituent derived from a probiotic strain may prove effective in interrupting the infectious process of an intestinal pathogen.