Cyclooxygenase-2 expression and role of vasoconstrictor prostanoids in small mesenteric arteries from patients with Crohn's disease.

BACKGROUND: The present study investigates the vascular reactivity and the involvement of nitric oxide and prostanoids in regulating vasoconstriction of small mesenteric arteries from patients with Crohn's disease (CD) to understand the vascular component of this pathology. METHODS AND RESULTS: An increased production of proinflammatory cytokines (tumor necrosis factor-alpha and interleukins 1beta, 6, and 8) has been observed in biopsy specimens of inflammatory intestinal mucosa. However, contractile responses of small mesenteric arteries from CD patients in response to norepinephrine were not changed ex vivo when compared with controls. Exposure to either the nitric oxide synthase inhibitor N(G)-nitro-L-arginine or the cyclooxygenase (COX) inhibitor indomethacin did not modify contractions induced by norepinephrine in either control or CD patients. However, in the latter, the specific COX-2 inhibitor N-(2-cyclohexyloxy-4-nitrophenyl) methanesulfonamide significantly attenuated norepinephrine-induced vasoconstriction. Furthermore, immunohistochemical analysis showed marked COX-2 expression in the whole arterial wall of vessels from CD patients. Vessels from control patients exhibited weak COX-2 staining in the adventitial and endothelial layers only. CONCLUSIONS: The above results provide direct evidence for COX-2 expression in small mesenteric arteries from CD patients. They also shed new light on the involvement of vasoconstrictor metabolites of COX in regulating contraction of these arteries. Of particular interest is the balance between vasoconstrictor products from COX-2 and unidentified vasodilatory products that maintained vascular reactivity in a physiological range despite an increase of circulatory cytokines in patients with CD.

Cyclooxygenase-2 and inducible nitric oxide synthase in omental arteries harvested from patients with severe liver diseases: immuno-localization and influence on vascular tone.

OBJECTIVE: To investigate the expression of inducible cyclooxygenase (COX-2) and inducible nitric oxide synthase (iNOS) and the role of vasodilatory prostanoids and endogenous nitric oxide (NO) in small omental arteries harvested from patients with severe liver diseases. DESIGN: Ex vivo study of resistance arteries. SETTING. Intensive care unit. PATIENTS: Twenty patients undergoing liver transplantation for fulminant hepatic failure (FHF, n=6), cirrhogenous viral hepatitis (CH, n=6) and limited hepatocarcinoma (controls, n=8). INTERVENTIONS: Western blot and immunohistochemical labeling for assessment of COX-2 and iNOS expression and localization and ex vivo vascular reactivity studies. MEASUREMENTS AND RESULTS: Significant upregulation of COX-2 and iNOS expressions were detected in arteries from FHF and CH patients with a greater increase in the former than in the latter. Ex vivo contractile responses to norepinephrine and the thromboxane A(2) analog, U46619, were not significantly different between patients with severe liver dysfunction and controls. Exposure to either the NO-synthase inhibitor, N(G)-nitro-L-arginine methyl ester (L-NAME), the cyclooxygenase inhibitor, indomethacin, or their combination did not significantly modify contractions of agonists in controls and CH patients. In FHF, the specific COX-2 inhibitor, N-(2-cyclohexyloxy-4-nitrophenyl) methanesulfonamide (1 micro m/l), but not L-NAME, significantly enhanced the maximal effect ( p<0.01) and the sensitivity ( p<0.01) to norepinephrine. CONCLUSIONS: COX-2 and iNOS are upregulated in omental arteries from patients with cirrhogenous hepatitis and fulminant hepatic failure. Whereas neither NO nor vasodilatory prostaglandins seem to play a major role in counteracting arterial contractility of arteries from control patients, COX-2 derivatives are involved in lowering the arterial contractility of vessels harvested from FHF patients.