Nitric oxide promotes the internalization and passage of viable bacteria through cultured Caco-2 intestinal epithelial cells.

Abstract

Nitric oxide (NO) may play an important role in the pathophysiology of intestinal barrier disruption. Our purpose was to investigate the effects of NO donors on the internalization and passage of bacteria through cultured intestinal epithelial cells. Human intestinal epithelial cell line Caco-2 cells were grown on microtiter plastic plates. The cells were incubated with Escherichia coli and sodium nitroprusside (SNP) or S-nitroso-N-acetyl-penicillamine (SNAP), as NO donors, at several concentrations. The numbers of viable bacteria internalized into the epithelial cells were measured. Caco-2 cells were also grown to confluency on membranes of bicameral systems. The cells were incubated with E. coli and SNP. The numbers of viable bacteria passed through the epithelial layer were determined. Viability of the bacteria and the intestinal epithelial cells after culture with SNP or SNAP were also determined. Both SNP and SNAP at .1 or 1 mmol/L increased the number of viable bacteria internalized into the enterocytes. Both 1 or 10 mmol/L SNP promoted bacterial passage through the intestinal epithelial layer. However, 10 mmol/L SNP decreased the number of viable Caco-2 cells and failed to increase the bacterial internalization into Caco-2 cells. Incubation of E. coli with SNAP at 10 mmol/L slightly decreased the number of viable bacteria and failed to increase the bacterial internalization into Caco-2 cells. We conclude that NO donors promote both the viable bacterial uptake and passage through the intestinal epithelial layer.