Enterocyte Microvillus-Derived Vesicles Detoxify Bacterial Products and Regulate Epithelial-Microbial Interactions
David A. Shifrin, Jr., Russell E. McConnell, Rajalakshmi Nambiar, James N. Higginbotham, Robert J. Coffey, and Matthew J. Tyska
Current Biology; April 10, 2012
The continuous monolayer of intestinal epithelial cells (IECs) lining the gut lumen functions as the site of nutrient absorption and as a physical barrier to prevent the transloca- tion of microbes and associated toxic compounds into the peripheral vasculature . IECs also express host defense proteins such as intestinal alkaline phosphatase (IAP), which detoxify bacterial products and prevent intestinal inflammation [2–5]. Our laboratory recently showed that IAP is enriched on vesicles that are released from the tips of IEC microvilli and accumulate in the intestinal lumen [6, 7]. Here, we show that these native ‘‘lumenal vesicles’’ (LVs) (1) contain catalytically active IAP that can dephos- phorylate lipopolysaccharide (LPS), (2) cluster on the surface of native lumenal bacteria, (3) prevent the adherence of enteropathogenic E. coli (EPEC) to epithelial monolayers, and (4) limit bacterial population growth. We also find that IECs upregulate LV production in response to EPEC and other Gram-negative pathogens. Together, these results suggest that microvillar vesicle shedding represents a novel mechanism for distributing host defense machinery into the intestinal lumen and that microvillus-derived LVs modulate epithelial-microbial interactions.
Enteropathogenic E. coli intimately attached to the surface of Caco2BBE intestinal epithelial cells (Image selected for cover of Current Biology)
Immunofluorescence of Enteropathogenic E. coli intimately attached to the surface of HT-29 intestinal epithelial cells reveal actin pedestal formation and enrichment of intestinal alkaline phosphatase at sites of bacterial attachment. DNA (bacteria and HT-29) marked with DAPI in blue, IAP in green, actin marked with phalloidin in red.