We have discovered that clinically tested inhibitors of matrix metalloproteinases can control the functional activity of T cell membrane type-1 matrix metalloproteinase (MT1-MMP) and the onset of disease in a rodent model of type 1 diabetes in non-obese diabetic mice. We determined that MT1-MMP proteolysis of the T cell surface CD44 adhesion receptor affects the homing of T cells into the pancreas. We also determined that both the induction of the intrinsic T cell MT1-MMP activity and the shedding of cellular CD44 follow the adhesion of insulin-specific, CD8-positive, K d -restricted T cells to the matrix. Conversely, inhibition of these events by AG3340 (a potent hydroxamate inhibitor that was widely used in clinical trials in cancer patents) impedes the transmigration of diabetogenic T cells into the pancreas and protects non-obese diabetic mice from diabetes onset. Overall, our studies have divulged a previously unknown function of MT1-MMP and identified a promising novel drug target in type I diabetes.
Insulin-dependent diabetes mellitus (IDDM)1 (type I diabetes) is a T cell-mediated, autoimmune disease. The pathogenesis of IDDM involves the activation of autoimmune T cells followed by their homing into the pancreatic islets (1). In the islets, T cells destroy insulin-producing †cells (2). The CD44 surface receptor is elevated in activated T cells and, via its interactions with endothelial hyaluronan, contributes to T cell adhesion on the endothelium and the subsequent transmigration events (3). MT1-MMP, a multifunctional membrane-tethered enzyme, functions in cancer cells as one of the main mediators of pericellular proteolytic events and directly cleaves cell receptors (4, 5). CD44, a major hyaluronan receptor, is a well-established target of MT1-MMP in tumor cells (6 -9). MT1-MMP cleavage releases the extracellular domain of CD44 from the cell surfaces and inactivates the functionality of the CD44 adhesion receptor. Evidence suggests that MT1-MMP proteolysis of CD44 significantly affects the adhesion and migration of malignant cells (6, 9, 10).Consistently, we hypothesized that MT1-MMP also targets CD44 in T cells and that these proteolytic events regulate transmigration of the diabetogenic T cells into the pancreatic islets. In agreement with our hypothesis, we have determined here that pharmacological inhibition of T cell MT1-MMP enhances adhesion of the diabetogenic T cells to the pancreatic endothelium. Conversely, the enhanced adhesion of T cells significantly diminishes their subsequent homing into the pancreatic islets. Our results also imply that the inhibition of T cell MT1-MMP is key to the delay of the onset of diabetes in non-obese diabetic (NOD) mice, a well-accepted rodent model of IDDM.
EXPERIMENTAL PROCEDURESMice and Cells-NOD mice of NOD/LtJ strain were obtained from the Jackson Laboratory. IS-CD8 Ï© T cells (insulin-specific, CD8-positive, K d -restricted T cells of the TGNFC8 clone from the pancreas of NOD mouse) (11) were maintained in Click's medium supplemented with 5% fetal calf ser...