Cytokine-induced VCAM-1 and ICAM-1 expression in different organs of the mouse

The dual radiolabeled mAb technique was used to quantify the constitutive and induced expression of intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) in the microvasculature of different organs of the mouse. The constitutive expression of both adhesion molecules varied significantly between tissues, with ICAM-1 levels consistently higher than VCAM-1 in all tissues studied. Following systemic administration of endotoxin (LPS), an increased surface expression of both adhesion molecules occurred in most organs, with the largest increases for ICAM-1 (2 to 3x increase) noted in the heart, small intestine, and brain, while heart and small intestine exhibited the largest increases in LPS-induced VCAM-1 expression (2 to 5x increase). These responses occurred in the face of an unaltered expression of platelet endothelial cell adhesion molecule-1 (PECAM-1) in all tissues. TNF-alpha also elicited an increased expression of both adhesion molecules, with initial increases noted at 2 to 5 h, peak levels at 5 to 9 h, and a sustained elevation above baseline at 24 h. The TNF-alpha-induced increases in both ICAM-1 and VCAM-1 were dose dependent, with significant up-regulation noted at 5 microg/kg and maximal increases occurring at 10 to 25 microg/kg. These studies indicate that while there are significant quantitative differences in constitutive and induced expression of murine ICAM-1 and VCAM-1, the kinetics and dose-response characteristics of the two adhesion molecules to TNF-alpha are qualitatively similar.