eNOS involved in colitis-induced mucosal blood flow increase.

Area of Science:

• Gastroenterology
• Physiology
• Pharmacology

Background:

• The role of nitric oxide (NO) in inflammatory bowel disease (IBD) pathogenesis remains debated.
• Endothelial nitric oxide synthase (eNOS) may offer mucosal protection during colonic inflammation.

Purpose of the Study:

• To investigate the role of NO in regulating colonic mucosal blood flow in rat models of colitis.
• To determine the specific nitric oxide synthase (NOS) isoforms involved in colitis-associated hyperemia.

Main Methods:

• Induction of colitis using trinitrobenzene sulfonic acid (TNBS) or dextran sulfate sodium (DSS) in rats.
• Continuous monitoring of colonic mucosal blood flow and arterial blood pressure using laser-Doppler flowmetry.
• Administration of NOS inhibitors (l-NNA, l-NIL) and analysis of NOS mRNA expression (iNOS, eNOS, nNOS) via real-time RT-PCR.

Main Results:

• Colitic rats exhibited significantly higher colonic mucosal blood flow compared to controls.
• Non-selective NOS inhibition (l-NNA) reduced blood flow in colitis models but not in controls, indicating NO-dependent hyperemia.
• Increased expression of iNOS and eNOS mRNA was observed in both colitis models, while nNOS remained unchanged.
• Inhibition of inducible NOS (iNOS) with l-NIL did not affect blood flow, suggesting eNOS is the primary contributor.

Conclusions:

• TNBS- and DSS-induced colitis lead to increased colonic mucosal blood flow.
• This hyperemia is likely mediated by enhanced endothelial nitric oxide synthase (eNOS) activity, suggesting a protective role in IBD.