Enteroinvasive bacteria directly activate expression of iNOS and NO production in human colon epithelial cells

Abstract

In these studies, we investigated whether bacterial infection of human colon epithelial cells is a sufficient stimulus to upregulate epithelial cell expression of inducible nitric oxide synthase (iNOS) and nitric oxide (NO) production. Human colon epithelial cells (Caco-2 and HT-29) rapidly upregulated iNOS mRNA and protein expression and NO production after infection with enteroinvasive Escherichia coli, Salmonella dublin, or Shigella flexneri but not after infection with noninvasive E. coli or an invasion-deficient mutant of S. dublin. Bacterial infection in the absence of added cytokines was as potent or more potent a stimulus of iNOS expression and NO production as stimulation of cells with combinations of cytokines known to strongly upregulate this epithelial cell response. Enteroinvasive E. coli increased epithelial NO production to a greater extent than S. dublin, although S. dublin was a stronger stimulus of epithelial cell interleukin-8 (IL-8) production. After enteroinvasive E. coli infection of polarized epithelial cell monolayers, nitrite, a stable NO end product, was released predominately into the apical compartment early after infection, whereas IL-8 was released in parallel into the basolateral compartment. These studies suggest NO and/or its redox products are an important component of the intestinal epithelial cell response to microbial infection.

Relative contributions of NOS isoforms during experimental colitis: endothelial-derived NOS maintains mucosal integrity

“…Because (28), epithelial-derived NO may also function in an antimicrobial role against enteric bacteria. This hypothesis is supported by studies in which enteroinvasive bacteria induce iNOS expression by cultured epithelial cells (59), similar to the effects of several proinflammatory cytokines (28). Moreover, we recently demonstrated that iNOS is strongly induced on colonic epithelial cells in mice infected with the gram-negative bacterial pathogen Citrobacter rodentium, a mouse-adapted version of enteropathogenic Escherichia coli.…”

Nitric Oxide Production by Human Intestinal Epithelial Cells and Competition for Arginine as Potential Determinants of Host Defense Against the Lumen-Dwelling Pathogen Giardia lamblia

“…NO is produced enzymatically from arginine through the action of NO synthase (NOS) 4 , which exists in three isoforms, neuronal NOS (NOS1), inducible NOS (iNOS; NOS2), and endothelial NOS (NOS3). In many cell types, the expression of iNOS is inducible by cytokines and microbial products, and iNOS is the major NOS isoform expressed by intestinal epithelial cells (21,22). Expression of iNOS in these cells can either be constitutive, as in mouse ileum (23) and isolated normal human duodenocytes (24), or inducible in vivo during colonic inflammation (25) or in vitro by cytokines (21) or in response to infection with invasive bacteria (22,26).…”

Analysis by High Density cDNA Arrays of Altered Gene Expression in Human Intestinal Epithelial Cells in Response to Infection with the Invasive Enteric BacteriaSalmonella

“…These chemokines can attract and activate neutrophils and monocytes/macrophages, which are important components of the acute inflammatory response initiated after enteric infection with invasive bacteria. Other epithelial genes induced after infection with invasive bacteria include cyclooxygenase-2, one of the crucial rate-limiting enzymes for prostaglandin production, and inducible NO synthase, which controls NO production (7)(8)(9). These genes are induced after infection with very different invasive bacteria, which have unique invasion strategies and reside in different intracellular compartments (1,10).…”