Inhibition of nitric oxide with aminoguanidine reduces bacterial translocation after endotoxin challenge in vivo.
BACKGROUND
Administration of lipopolysaccharide (LPS) has been shown to increase bacterial translocation (BT) in vivo and in vitro. In addition, LPS upregulates inducible nitric oxide synthase expression in the intestinal epithelium-a phenomenon that can either enhance microbial killing, or alternatively, promote BT by impairing the gut barrier.


OBJECTIVE
To determine the effect, if any, of an inhibitor of nitric oxide synthase, namely, aminoguanidine (AG), on BT after LPS challenge.


METHODS
Sprague-Dawley rats were randomized to receive either AG or normal saline solution via subcutaneously placed osmotic pumps (Alzet), followed 18 hours later by LPS injection (5 mg/kg or 20 mg/kg intraperitoneally). Quantitative cultures of the cecum, mesenteric lymph nodes, liver, and spleen were obtained, and plasma nitrite and nitrate levels were measured at 24 hours. Transmembrane potential difference and mucosal permeability to fluorescein isothiocyanate-labeled dextran and fluorescein isothiocyanate-labeled Escherichia coli C25 were measured in the Using chamber. The intestinal membrane was examined by light, transmission electron, and confocal laser microscopy.


RESULTS
Rats that were given high-dose LPS had elevated levels of nitrite and nitrate and a 100% incidence of BT. In contrast, AG infusion significantly reduced both BT (22%) and nitrite and nitrate levels. Animals that received LPS and normal saline solution had a significantly lower transmembrane potential difference than those that received LPS and AG. High-dose LPS resulted in sloughing of the apical enterocytes at the villus tips where bacterial entry seemed to occur, as seen with confocal laser microscopy.


CONCLUSIONS
Inhibition of nitric oxide production with AG decreases BT after high-dose LPS challenge. The mechanism may involve increased cellular viability and decreased damage to the gut mucosal barrier in rats that receive AG.
Department of Surgery, University of Pittsburgh School of Medicine, Pa., USA.
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Sorrells
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Friend
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Koltuksuz
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Courcoulas
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Boyle
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Garrett
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Watkins
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Rowe
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Ford
D000818:Animals; D018988:Bacterial Translocation / Q000187:drug effects*; D002432:Cecum / Q000382:microbiology; D002463:Cell Membrane Permeability / Q000187:drug effects; D004731:Endotoxins / Q000009:adverse effects*; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D004848:Epithelium / Q000187:drug effects / Q000201:enzymology; D004926:Escherichia coli / Q000502:physiology*; D016650:Fluorescein-5-isothiocyanate; D005456:Fluorescent Dyes; D006146:Guanidines / Q000494:pharmacology*; D007413:Intestinal Mucosa / Q000187:drug effects / Q000201:enzymology / Q000648:ultrastructure; D008070:Lipopolysaccharides / Q000009:adverse effects*; D008099:Liver / Q000382:microbiology; D008198:Lymph Nodes / Q000382:microbiology; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D008643:Mesentery; D009566:Nitrates / Q000097:blood; D009569:Nitric Oxide / Q000037:antagonists & inhibitors*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors*; D009573:Nitrites / Q000097:blood; D011897:Random Allocation; D051381:Rats; D017207:Rats, Sprague-Dawley; D013154:Spleen / Q000382:microbiology; D015854:Up-Regulation
D004731:Endotoxins; D004791:Enzyme Inhibitors; D005456:Fluorescent Dyes; D006146:Guanidines; D008070:Lipopolysaccharides; D009566:Nitrates; D009573:Nitrites; D009569:Nitric Oxide; D019001:Nitric Oxide Synthase; D016650:Fluorescein-5-isothiocyanate; C004479:pimagedine