Increase in circulating microparticles in inflammatory bowel disease patients induces vascular alterations

Alterations of vascular function participate to the development of the inflammatory bowel disease (IBD). We have previously reported the presence of inflammation-related vasoactive factors in small mesenteric arteries from Crohn’s disease patients (Tabernero et al., Circulation, 2003). Microparticles (MPs) are membrane vesicles released during cell activation and apoptosis whose circulating levels have been shown to be increased in patients with IBD, including MPs from platelets and activated platelets, endothelial, leukocyte and erythrocyte origins (Leonetti et al., Archives of Cardiovascular Diseases, Tome 102-Supplement 1-Mars 2009.).Here, we investigated whether MPs from IBD patients (IBD-MPs) play a role in the regulation of endothelial function and vascular reactivity in this disease. Male Swiss mice were injected intravenously with IBD-MPs or saline solution and sacrificed 24 h after. Endothelial function and vascular reactivity were studied on aortic rings by myography. The involvement of nitric oxide (NO), cyclooxygenase (COX) metabolites and superoxide anion (O2- ) was also assessed using the following inhibitors: NG-L-Nitro-arginine (NO synthase inhibitor, L-NA); indomethacin (non-selective COX inhibitor); SC-560 (selective COX-1 inhibitor), NS-398 (selective COX-2 inhibitor) and MnTMPyP (permeable superoxide dismutase mimetic). In aorta, IBD-MPs significantly reduced both endothelium-dependent induced by acetylcholine and the NO donor, sodium nitroprusside, respectively. IBD-MPs decreased the contraction to serotonin (5-HT) compared to saline that was completely prevented in the presence of L-NA. Moreover, aorta from mice treated with IBD-MPs displayed increase NO production. Interestingly, the ability of NS-398 to reduce 5-HT-induced contraction in control mice was abolished in vessels taken from mice treated with IBD-MPs. Although IBD-MPs decreased O2- production in the aorta, the O2- scavenger MnTMPyP reduced the contraction to 5-HT in an identical manner in aorta from both control and IBD-MPs treated mice. The present study provides evidence of the capacity of IBD-MPs to induce endothelial dysfunction and vascular hyporeactivity. These effects result from a subtle alteration of the balance between NO, reactive oxygen species and metabolites from COX-2. They underscore the participation of MPs in the course of vascular alterations in this disease. (Partially supported by Ferring France Laboratories)

Increase in circulating microparticles in inflammatory bowel disease patients induces vascular alterations

Among the proposed hypothesis for inflammatory bowel disease (IBD) pathogenesis, a vascular cause has been suggested, mostly in reference to anatomic and pathological studies. We previously reported in small mesenteric arteries from Crohn's disease patients a balance between vasoconstrictor products from cyclooxygenase and unidentified vasodilatory products that maintained vascular reactivity in a physiological range despite an increase of circulatory cytokines in these patients (Tabernero et al., Circulation, 2003). Microparticles (MPs) are membrane vesicles released during cell activation and apoptosis. Elevated levels of circulating MPs have been detected in pathologic conditions and their increase has been associated with disease activity and/or prognosis. We investigated whether MPs from IBD patients may play a role in the regulation of endothelial function and vascular reactivity in this disease. Blood samples were obtained either from IBD patients as well as age and sex-matched healthy subjects. MPs concentration and origin were assessed by flow cytometry using specific antibodies. Male Swiss mice were injected intravenously with MPs from IBD patients or with saline solution and sacrified after 24hours. Endothelial function and vascular reactivity were studied on aortic rings and small mesenteric resistance arteries (SMA) by myography and arteriography, respectively. Patients with IBD displayed increased circulating levels of MPs compared to healthy subjects including those from procoagulant, platelet and activated platelet, endothelial, leukocyte and erythrocyte origins. In aorta, MPs from IBD patients compared to saline significantly reduced both endothelium-dependent relaxation to acetylcholine and contraction to serotonin. In SMA, although MPs from IBD patients did not affect flow-induced dilation, a reduced NO-component that was completely compensated by the endothelium-derived hyperpolarizing factor-component of the response was highlighted. Besides, MPs from IBD did not affect myogenic tone in SMA. These results provide further evidence of increased circulating levels of MPs in patients with IBD. MPs origin may play a role in enhanced coagulation and inflammatory states reported in IBD patients. Finally, MPs from IBD patients influence both endothelial dysfunction and vascular hyporeactivity in the experimental model used.(Partially supported by Ferring France Laboratories)

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