HOME
Return to Table of Contents
VASOACTIVE INTESTINAL PEPTIDE AMELIORATES BARRIER DYSFUNCTION ASSOCIATED WITH ATTACHING EFFACING PATHOGENS
X Wu, BA Vallance, J Walker, K Madsen, A Buchan, K Jacobson
Attaching and effacing pathogens enterohaemorrhagic Escherichia coli (EHEC), enteropathogenic E. coli (EPEC) and C. rodentium cause severe diarrhea in humans and animals. Vasoactive intestinal peptide (VIP), an important regulator of barrier function is likely involved. While the actions of VIP on barrier function have focused primarily on transcellular permeability, effects on paracellular permeability has received limited attention. The aim of the present study was to examine the amelioratory effects of VIP on intestinal paracellular barrier integrity induced my A/E pathogens in vivo and in vitro.
METHODS: C57BL/6 mice received 2.5 × 108 C. rodentium by gavage on day 0. VIP was administered by daily i.p. injection (0.5 nmol/per mouse) from day 1 up until and including day 10, the day of sacrifice. Animal weights were monitored daily and animals were sacrificed on day 10. The colons were removed and assessed for epithelial barrier function, histology, expression and distribution of tight junction proteins ZO-1, claudin-3 and occludin. In addition, human polarized colonic epithelial cell monolayer (Caco-2) was infected with EPEC. Transepithelial resistance, 3Hmannitol flux and expression and distribution of tight junction protein (ZO-1 and occludin) were examined during infection with or without VIP (10–8 M) treatment.
RESULTS: Treatment with VIP significantly attenuated the weight loss (13% vs. 31% decrease from baseline at day 4) and was associated with full recovery by day 10. Moreover, VIP treatment ameliorated the histological damage score (0.94±0.20 vs. 1.66±0.33), attenuated the increase in mannitol flux (20.3±1.1 nm/cm2/hr vs. 31.2±3.3 nm/cm2/hr) and normalized the response to forskolin (95.7±5.8 µA/cm2 vs. 63.2±8.3 µA/cm2). In parallel VIP diminished the relocation of tight junction proteins away to the cytoplasm. When tested in vitro, VIP treatment was associated with a significant, but partial reduction in increased unidirectional mannitol flux at 4 hours post-infection with EPEC. The disruption of tight junction structure in Caco-2 monolayers induced by EPEC infection was also abrogated by VIP.
CONCLUSION: This study demonstrated that VIP ameliorated mouse colon colitis induced by C. rodentium and maintained colonic epithelial cell barrier integrity by regulating tight junction proteins through mechanisms not limited to its immunomodulatory actions.
Supported by CCFC (Canada)