Multiple expression of matrix metalloproteinases in murine neurocysticercosis: Implications for leukocyte migration through multiple central nervous system barriers

During the course of murine neurocysticercosis (NCC), disruption of the unique protective barriers in the central nervous system (CNS) is evidenced by extravasation of leukocytes. This process varies according to the anatomical sites and diverse vascular beds analyzed. To examine mechanisms involved in the observed differences, the expression and activity of eight matrix metalloproteinases (MMPs) were analyzed in a murine model of NCC. The mRNA expression of the MMPs studied was upregulated as a result of infection, and active MMPs were mainly detected in leukocytes migrating into the brain. Polarized expression and gelatinolytic activity of several MMPs were identified in immune cells extravasating pial vessels as early as 1 day post infection. In contrast, leukocytes expressing active MMPs and extravasating parenchymal vessels were not observed until 5 weeks post infection. In ventricular areas, most of the MMP activity was detected in leukocytes traversing the ependyma from leptomeningeal infiltrates. In addition, immune cells continued to express active MMPs after exiting vessels suggesting that enzymatic activity of MMPs is not just required for diapedesis. These results correlate with our previous studies showing differential kinetics in the disruption of the CNS barriers upon infection and help document the important role of MMPs during leukocyte infiltration and inflammation.