Leukocyte integrin very late antigen-4/vascular cell adhesion molecule-1 adhesion pathway in splanchnic artery occlusion shock

We investigated the role played by the very late antigen-4 (VLA-4)/vascular cell adhesion molecule-1 (VCAM-1) interaction in the pathogenesis of splanchnic artery occlusion shock. Splanchnic artery occlusion shock was induced in anaesthetized rats by clamping splanchnic arteries for 45 min. Sham operated animals were used as controls. Survival time, serum tumour necrosis factor (TNF-alpha), monocyte and lymphocyte cell count and the responsiveness to acetylcholine of aortic rings were studied. Furthermore we investigated the VCAM-1 expression on vessel endothelium and the percentage of VLA-4 positive leukocytes. Splanchnic artery occlusion shocked rats had a decreased survival time (76 +/- 10 min, while sham shocked rats survived more than 4 h), increased serum levels of TNF-alpha (328 +/- 11 U/ml), a decreased number of both monocytes and lymphocytes and reduced responsiveness to acetylcholine (10 nM-10 mu M) of aortic rings, In addition we found an increased expression of endothelial VCAM-1 on aortic rings and a reduced percentage of VLA-4 positive lymphocytes and monocytes. Passive immunization with specific antibodies raised against either VCAM-1 or VLA-4 (2 mg/kg, i.v., 3 h before splanchnic artery occlusion shock) increased survival, improved monocyte and lymphocyte count and restored the responsiveness of aortic rings to acetylcholine (P < 0.01). Finally, inhibition of TNF-alpha biosynthesis reversed the increased endothelial expression of VCAM-1 and the reduced percentage of integrin VLA-4 positive leukocytes. Our findings suggest that (i) VLA-4/VCAM-1 interaction has a role in the pathogenesis of circulatory shock; (ii) this interaction might be a target for new therapeutic approaches to the therapy of low-flow states.