Leukocyte migration from the blood into tissues is vital for immune surveillance and inflammation. Specificity for the site of leukocyte migration is determined by the combination of adhesion molecules, cytokines and chemokines in the microenvironment.
We have focused on the function of the endothelial cell adhesion molecule VCAM-1. VCAM-1 is expressed on endothelial cells during atherosclerosis, allograft rejection, infection, and asthmatic responses. Furthermore, disruption of the mouse VCAM-1 gene impairs placentation and cardiac development resulting in embryo death. Thus, VCAM-1 has important functions in development and disease. As little was known regarding VCAM-1 signaling, we studied the molecular mechanisms for VCAM-1 signal transduction in endothelial cells in vitro and in vivo.
Although it has traditionally been thought that VCAM-1 simply serves as a scaffold for leukocyte binding to endothelium, we have reported that it activates endothelial cell intracellular signal transduction pathways which result in endothelial cell shape changes and leukocyte passage. VCAM-1 activates endothelial cell NADPH oxidase resulting in the generation of low non-toxic levels of reactive oxygen species (ROS). These ROS rapidly stimulate endothelial cell-associated matrix metalloproteinases (MMP) which are required for VCAM-1-dependent lymphocyte migration. We have also demonstrated that in vivo administration of the antioxidant bilirubin blocks VCAM-1-dependent leukocyte migration into the lung in experimental asthma.
Currently, there are two main research directions.
1. We are examining mechanisms for VCAM-1-stimulated activation of endothelial cell NADPH oxidase, including studies of the structure/function of the cytoplasmic tail of VCAM-1. We are also examining the mechanisms for ROS function in regulating endothelial cell intracellular signals.
2. To further determine whether these VCAM-1 signals function in vivo, we are utilizing knockout and transgenic mouse models to examine VCAM-1-dependent infiltration of eosinophils in experimental asthma. Pulmonary eosinophilia is one of the most consistent hallmarks of asthma.
Information about the mechanisms that control leukocyte infiltration will provide a basis towards proposing interventions in VCAM-1-mediated processes in disease. Moreover, limiting VCAM-1 dependent inflammation in chronic disease may be an advantageous target as it would spare VCAM-1-independent inflammation such as neutrophil clearance of infections
Tudor, K-S. R.S., Deem, T.L. and Cook-Mills, J. 2000. Novel b-4-integrin Ligands on an Endothelial Cell Line. Biochem. Cell Biol. 78:99-113.
Matheny, H., Deem, T.L. and Cook-Mills, J. 2000. Lymphocyte Migration Through Monolayers of Endothelial Cell Lines Involves VCAM-1 Signaling Via Endothelial Cell NADPH Oxidase. J. Immunology 164:6550-6559.
Hess, K. L., J. D. Johnson and Cook-Mills, J. 2001. Different Orders for Acquisition of Apoptotic Characteristics by Leukocytes. J. Leuk. Biol. 70:405-412.
Tudor, K-S. R.S., Hess, K.L. and Cook-Mills, J. 2001. Cytokines Modulate Endothelial Cell Intracellular Signal Transduction Required for VCAM-1-dependent Lymphocyte Transendothelial Migration. Cytokine 15:196-211.
Cook-Mills, J.M. 2002. VCAM-1 Signaling During Lymphocyte Migration: Role of Reactive Oxygen Species. Molecular Immunology. 39:498-508.
Johnson, J., Hess, K.L., and Cook-Mills, J. 2003. CD44, _4-integrin and Fuciodin Receptors Mediate Endothelial Cell Phagocytosis of Apoptotic Leukocytes. J. Leuk. Biol. 74:810-820.
Cook-Mills, J.M., Johnson, J.D., Ochi, A., Wang, L., and Zhang, Y. 2004. Calcium Mobilization and Rac1 Activation are Required for VCAM-1 Mediated Endothelial Cell NADPH Oxidase Activity During Lymphocyte Migration. Biochem. J. 378:539-547.
Deem, T.L. and Cook-Mills, J.M. 2004. Vascular Cell Adhesion Molecule-1 (VCAM-1) Activation of Endtohelial Cell Matrix Metalloproteinases: Role of Reactive Oxygen Species. Blood 104:2385-2393.
Cook-Mills, J.M and Deem, T.L. 2005. Active Endothelial Cell Function During Inflammation. J. Leuk. Biol. 77:487-495.
Keshavan, P., Deem, T.L., Cook-Mills, J.M. and Zucker, S.D. 2005. Unconjugated Bilirubin Inhibits Lymphocyte Migration Across Endothelial Monolayers. J. Immunol. 174:3709-3718.
