Aeromonas sobria serine protease decreases epithelial barrier function in T84 cells and accelerates bacterial translocation across the T84 monolayer in vitro

Abstract

Aeromonas sobria is a pathogen causing food-borne illness. In immunocompromised patients and the elderly, A . sobria can leave the intestinal tract, and this opportunistically leads to severe extraintestinal diseases including sepsis, peritonitis, and meningitis. To cause such extraintestinal diseases, A . sobria must pass through the intestinal epithelial barrier. The mechanism of such bacterial translocation has not been established. Herein we used intestinal (T84) cultured cells to investigate the effect of A . sobria serine protease (ASP) on junctional complexes that maintain the intercellular adhesion of the intestinal epithelium. When several A . sobria strains were inoculated into T84 monolayer grown on Transwell inserts, the strain with higher ASP production largely decreased the value of transepithelial electrical resistance exhibited by the T84 monolayer and markedly caused bacterial translocation from the apical surface into the basolateral side of T84 monolayer. Further experiments revealed that ASP acts on adherens junctions (AJs) and causes the destruction of both nectin-2 and afadin, which are protein components constituting AJs. Other studies have not revealed the bacterial pathogenic factors that cause the destruction of both nectin-2 and afadin, and our present results thus provide the first report that the bacterial extracellular protease ASP affects these molecules. We speculate that the destruction of nectin-2 and afadin by the action of ASP increases the ability of A . sobria to pass through intestinal epithelial tissue and contributes to the severity of pathological conditions.

Aeromonas sobria Induces Proinflammatory Cytokines Production in Mouse Macrophages via Activating NLRP3 Inflammasome Signaling Pathways

“…recognize the exogenous PAMPs or its released DAMPs. Previous studies on A. sobria were mainly focused on the case reports in humans, and several studies were about the characteristics and functions of virulence factor serine protease in colonic epithelial cells (Kobayashi, 2011;Kobayashi et al, 2019;Song et al, 2019). However, the interactions between A. sobria and host cells' innate immunity have not been clarified.…”

Pathogenic profile and cytotoxic activity of Aeromonas spp. isolated from Pectinatella magnifica and surrounding water in the South Bohemian aquaculture region

“…Serine proteases (SP) are associated with liquefaction of muscle tissue resulting in lesion formation (Whitby, Landon, & Coleman, 1992). It has also been suggested that SP could be involved in the development of extraintestinal diseases such as sepsis, peritonitis and meningitis because of their ability to decrease epithelial barrier function and accelerate bacterial translocation (Kobayashi et al., 2019). After penetration, SP could contribute to septic shock through interaction with plasma proteins and increase haemorrhagic tendencies in sepsis (Imamura, Nitta, Wada, Kobayashi, & Okamoto, 2008).…”

Aeromonas sobria Serine Protease Degrades Several Protein Components of Tight Junctions and Assists Bacterial Translocation Across the T84 Monolayer

“…We added bacterial cells (MOI = 5) suspended in HBSS containing 15 mM HEPES (pH 7.4) to the apical side of T84 cells cultured in 12-well microplates. In our earlier study, the degradation of the protein components constituting the junctional complexes was observed to start early (Kobayashi et al, 2019). As in that study, we analyzed the degradation of the protein components constituting TJs at 2 hr post-infection.…”

“…To test this hypothesis, we performed an in vitro analysis using cultured T84 cells ( Kobayashi et al., 2019 ), and we observed that ASP acts on AJs and causes the destruction of both nectin-2 and afadin (protein components constituting AJs). We suspect that the destruction of nectin-2 and afadin by the action of ASP ( i ) increases the ability of A. sobria to pass through intestinal epithelial tissue, and ( ii ) contributes to the severity of pathological conditions.…”