Murine hepatic microvascular adhesion molecule expression is inducible and has a zonal distribution

The structural and functional heterogeneity of hepatocytes and non-parenchymal cells across the liver lobule or acinus has been well documented. The geographic distribution and potential for induced expression of adhesion molecules on murine hepatic microvascular cells has not been reported, although these molecules are able to influence the metastatic outcome of intravascular cancer cells. We have postulated that the expression of adhesion molecules on these cells is susceptible to regulation by environmental factors and that these molecules have a zonal distribution across the acinus. To test this hypothesis, we injected C57BL/6 mice with bacterial lipopolysaccharide, 1 microg/g body weight, i.p. At various time points (0-48 h) after stimulation, liver tissue sections were prepared for immunohistochemistry. Confocal microscopy was used to detect the expression of vascular cell adhesion molecule-1 (VCAM-1), E-selectin, intercellular adhesion molecule-1 (ICAM-1) and alpha v integrin. The expression patterns were quantitatively measured by histomorphometry. Under basal conditions, ICAM-1 was weakly expressed in terminal portal veins while minimal VCAM-1 and no E-selectin were detected. Following stimulation with lipopolysaccharide, VCAM-1 and E-selectin were expressed on the endothelium of terminal portal veins and on sinusoidal lining cells with significantly stronger expression in the periportal zone than midzone. VCAM-1 expression peaked at 4 h and decreased gradually by 48 h. E-selectin peaked at 2 h and disappeared by 12 h after stimulation. ICAM-1 expression showed a much stronger and more uniform expression across the acinus with the peak reached by 4 h and sustained for longer than 48 h after lipopolysaccharide administration. The alpha v integrin was not detected under basal conditions or after lipopolysaccharide stimulation. Expression of all these adhesion molecules (ICAM-1, VCAM-1, E-selectin and alpha v integrin) was induced by growth of B16F1 melanoma cells in the peritoneal cavity of the mouse. These results support the hypotheses that expression of microvascular adhesion molecules in the mouse liver is susceptible to regulation by environmental stimuli and has a zonal heterogeneity across the acinus.