A Comparison of the Morphologic Effects ofSerpulina hyodysenteriaeor its Beta-hemolysin on the Murine Cecal Mucosa

Abstract

Abstract. Studies were carried out to compare the early morphologic changes in the cecal mucosa of mice either infected with Serpulina hyodysenteriae or exposed to the ␤-hemolysin of S. hyodysenteriae. Sixty-five 12-24-week-old C3H/HeOuJ mice were infected with S. hyodysenteriae by gastric intubation. Two mice were necropsied every hour for 30 hours following infection. S. hyodysenteriae was isolated from the cecal contents of each mouse at all time points. Macroscopic lesions were first apparent at 14 hours postinfection (PI), and light microscopic lesions were first apparent at 10 hours PI, earlier than has been previously reported. Ultrastructural changes, first evident at 6 hours PI, included disarray and loss of microvilli and terminal web, with dilatation of intercellular spaces. Luminal bacteria were translocated through epithelial cells to the lamina propria, where capillaries exhibited changes indicative of increased permeability. In another experiment, solutions containing between 2,500 and 25,000 hemolytic units of purified S. hyodysenteriae hemolysin were placed within the lumen of surgically closed murine ceca (n ϭ 10); ceca were collected for examination 3 hours following treatment. Ultrastructural changes consisted of loss of microvilli and terminal web and marked vacuolation and exfoliation of epithelial cells. Significant numbers of necrotic and apoptotic epithelial cells were present, and epithelial cells internalized moderate numbers of bacteria. The hemolysin of S. hyodysenteriae induces some of the same early ultrastructural changes in the cecal epithelium of mice as occur following infection with S. hyodysenteriae. Based on the observed bacterial translocation, luminal bacteria also appear to play a unique role in lesion development in this model.

Emergence of DiverseHelicobacterSpecies in the Pathogenesis of Gastric and Enterohepatic Diseases

“…Davis et al also noted the occasional penetration of EHS into the epithelium of the rat cecum (66). More recently, invasion into the lamina propria of the cecum by EHS in mice following challenge with the spirochete Serpulina hyodysenteriae has been reported (212). The significance of cell entry and/or tissue invasion by EHS and the conditions under which these events take place have not been fully elucidated.…”

Cloning of a Beta-Hemolysin Gene ofBrachyspira(Serpulina)hyodysenteriaeand Its Expression inEscherichia coli

“…Whether the previously described tly genes (18,25) code for other hemolysins or serve as regulatory proteins in B. hyodysenteriae can be answered only by more defined biochemical and genetic studies. The biologic activity of purified HlyA, however, has been shown to induce murine colonic lesions similar to those caused by B. hyodysenteriae and to disrupt the integrity of epithelial cell monolayers (9,26).…”

“…Studies with osmoprotectants indicated that a pore with a diameter of 1.0 to 1.1 nm was formed by the beta-hemolysin (10). Additional studies from this laboratory have indicated that purified beta-hemolysin affects the integrity of epithelial cell monolayers and induces colonic epithelial cell damage similar to that caused by infection with B. hyodysenteriae (9,26).…”

α-Haemolysin ofEscherichia coliin IBD: a potentiator of inflammatory activity in the colon

“…Haemolysins are pore-forming toxins (PFTs), E coli α-haemolysin (HlyA) belonging to the β-barrel-PFT (β-PFT) group. It forms small cation-permeable channels in the host cell membrane with an inner diameter of approximately 10 Å. Haemolytic bacteria have been shown to induce intestinal malabsorption,17 secretion18 and epithelial lesions via necrosis and/or apoptosis 19. We previously showed that HlyA induced ‘focal leaks’ in colonic HT-29/B6 cells, within which E coli accumulated before undergoing translocation 20.…”