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Increased iNOS activity is essential for intestinal epithelial tight junction dysfunction in endotoxemic mice
Xiaonan Han1, Mitchell P Fink, Runkuan Yang
1Department of Critical Care Medicine, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, 15261, USA.
Shock (Augusta, Ga.)
|February 11, 2004
Summary
Systemic inflammation from lipopolysaccharide (LPS) increases nitric oxide (NO) production, disrupting gut barrier function by altering tight junction proteins. Inhibiting inducible NO synthase (iNOS) protects against these effects.
Area of Science:
- Gastroenterology
- Immunology
- Molecular Biology
Background:
- Systemic inflammation, often induced by lipopolysaccharide (LPS), can compromise gastrointestinal epithelial integrity.
- Nitric oxide (NO) production is elevated during inflammation, but its specific role in altering gut barrier function is not fully understood.
- Tight junction (TJ) proteins are crucial for maintaining the intestinal barrier.
Purpose of the Study:
- To investigate if increased nitric oxide (NO) production during LPS-induced systemic inflammation alters the expression and localization of key tight junction (TJ) proteins in the ileal and colonic epithelium.
- To determine if inducible NO synthase (iNOS) is involved in LPS-induced gut epithelial dysfunction.
- To assess the therapeutic potential of inhibiting iNOS in preventing barrier disruption.
Main Methods:
- Mice were injected with LPS to induce systemic inflammation.
- Inducible NO synthase (iNOS) was inhibited using a pharmacologic inhibitor (L-NIL) or by using iNOS knockout mice.
- Expression and localization of TJ proteins (ZO-1, ZO-2, ZO-3, occludin) were analyzed using immunoblotting and immunohistochemistry.
- Gut mucosal permeability and bacterial translocation were measured.
Main Results:
- LPS injection decreased the expression and TJ localization of ZO-1, ZO-2, ZO-3, and occludin in the ileal and colonic mucosa.
- Immunohistochemistry revealed disrupted distribution of ZO-1 and occludin in endotoxemic mice.
- LPS-induced endotoxemia increased ileal mucosal permeability and bacterial translocation to mesenteric lymph nodes.
- Inhibition or genetic ablation of iNOS ameliorated LPS-induced changes in TJ protein expression and gut barrier function.
Conclusions:
- Increased inducible NO synthase (iNOS)-dependent nitric oxide (NO) production contributes to the pathogenesis of gastrointestinal epithelial dysfunction during systemic inflammation.
- Altered expression and localization of key tight junction (TJ) proteins are mechanisms underlying this dysfunction.
- Targeting iNOS activity may be a viable strategy to protect the gut barrier during systemic inflammatory conditions.