Bacterial translocation is inhibited in inducible nitric oxide synthase knockout mice after endotoxin challenge but not in a model of bacterial overgrowth

Arch Surg. 1997 Nov;132(11):1190-5. doi: 10.1001/archsurg.1997.01430350040007.

Abstract

Background: Studies have shown that nitric oxide (NO) and NO synthase (NOS) inhibitors injure and protect organs after endotoxin (lipopolysaccharide [LPS]) challenge.

Objective: To test the hypothesis that LPS-induced gut injury and bacterial translocation (BT) are mediated through activation of inducible NOS (iNOS).

Design: A randomized, controlled study using genetically altered, iNOS gene knockout mice.

Setting: University research laboratory.

Methods: Forty-five wild-type (iNOS+/+) or homozygous mutant (iNOS-/-) mice weighing 25 to 35 g were challenged with Escherichia coli LPS or saline (10 mg/ kg) intraperitoneally (n = 8/group). In a second set of experiments, a bacterial overgrowth model of BT (E coli monoassociation) was tested (n = 6-7/group). The mesenteric lymph nodes and cecums were cultured, and liver, ileal, and blood nitrite and nitrate levels measured 24 hours after LPS or E coli monoassociation.

Results: After LPS challenge, 87.5% of the iNOS+/+ mice but 0% of the iNOS-/- mice had BT to their mesenteric lymph nodes (P < .01; chi 2 analysis). Nitrite and nitrate levels of the liver, ileum, and blood were higher in the iNOS+/+ mice (P < .05). In the E coli overgrowth model, BT to mesenteric lymph nodes occurred in 100% of iNOS-/- and iNOS+/+ mice.

Conclusions: In this limited study, LPS-induced BT did not occur in iNOS-deficient mice, suggesting that LPS induction of increased iNOS activity is necessary for LPS-induced BT to occur. In contrast, iNOS activation does not seem to be necessary in a bacterial overgrowth model of BT.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Bacterial Translocation / physiology*
  • Escherichia coli
  • Lipopolysaccharides / administration & dosage
  • Mice
  • Mice, Knockout
  • Nitric Oxide Synthase / physiology*

Substances

  • Lipopolysaccharides
  • Nitric Oxide Synthase