Summary auto-generated
This study investigates how thermolabile direct hemolysin (TDH) from Vibrio parahaemolyticus affects intestinal barrier function using cultured epithelial cells (Caco-2 and T84) and isolated rat intestinal tissue (18Co cells). TDH is a virulence factor produced by pathogenic V. parahaemolyticus strains. The researchers exposed differentiated epithelial monolayers to TDH and measured barrier integrity through transepithelial electrical resistance, permeability assays, and enzyme activities. TDH caused a rapid, dose-dependent increase in intestinal permeability and disruption of tight junctions, accompanied by increased intracellular calcium levels. The toxin induced morphological changes in epithelial cells and altered the localization of tight junction proteins. These effects were partially prevented by blocking calcium signaling. The study demonstrates that TDH damages the intestinal epithelial barrier through calcium-dependent mechanisms, which likely contributes to the pathogenesis of V. parahaemolyticus gastroenteritis. The findings provide mechanistic insight into how this bacterial toxin compromises intestinal barrier function.
Key findings
- TDH rapidly disrupted intestinal epithelial barrier function in cultured cells and tissue, increasing permeability and decreasing transepithelial electrical resistance in a dose-dependent manner
- TDH-induced barrier damage was accompanied by increased intracellular calcium concentration and required calcium signaling for its effects
- The toxin caused morphological changes in epithelial cells and altered the localization of tight junction proteins, consistent with direct damage to cell-cell junctions
- Blocking calcium signaling pathways partially prevented TDH-induced barrier disruption, indicating calcium-dependent mechanisms are critical to toxin action
- These findings suggest TDH contributes to V. parahaemolyticus pathogenesis by directly damaging the intestinal epithelial barrier through calcium-mediated mechanisms
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Abstract
Vibrio parahaemolyticus produces a thermostable direct haemolysin (TDH) that has been implicated in the pathogenesis of diarrhoeal disease caused by this organism. In previous work, TDH induced Cl- secretion in human colonic epithelial cells that was dependent on the intracellular Ca2+ concentration, [Ca2+]in. This study investigated whether Cl- secretion induced by TDH is influenced by the stage of maturation of intestinal epithelial cells. Two different human colonic cell lines, villus cell-like Caco-2 cells and crypt cell-like T84 cells, cultured by different methods to obtain differentiated samples, were used. When these cells were exposed to butyrate, a transcriptional regulator of differentiation genes, or co-cultured with 18Co cells, a human colonic fibroblast cell line, they showed increased trans-epithelial resistance and villus cell marker enzyme activity. In Caco-2 cells, exposure to butyrate or co-culturing with 18Co cells resulted in increased TDH binding, higher short-circuit currents (Isc) and greater [Ca2+]in. These results suggest that sensitivity to TDH is affected by the stage of cellular differentiation of cultured intestinal epithelial cells.