Abstract
Multiple sclerosis (MS) and its animal model, experimental autoimmune encephalomyelitis (EAE), are inflammatory diseases of the central nervous system (CNS). Activated coagulation factors are associated with inflammation and are elevated in the plasma of animals with EAE. Thrombin is a key coagulation factor and its major endogenous inhibitors are antithrombin III (ATIII) in the plasma and protease nexin 1 (PNβ1) in the brain. We measured the capacity of brain homogenates to inhibit exogenous thrombin and the CNS levels of ATIII and PNβ1 during the course of EAE. Acute EAE was induced in SJL/J mice by immunization with mouse spinal cord homogenates. On Days 8, 13, and 22 postβimmunization, inhibition of exogenous thrombin activity was measured by a recently developed fluorimetric assay. PNβ1 and ATIII were assayed both by immunohistochemistry and by immunoblots in the brain and spinal cord. Total brain thrombin inhibitory activity increased (32%) in EAE mice at the peak of clinical disease (Day 13, P = 0.04 compared to controls). Brain ATIII also increased at the peak of disease (2.5βfold higher than controls, P = 0.0001), and correlated significantly with clinical scores at all stages of disease (r = 0.72, P = 0.0068). In contrast, PNβ1 elevations were more pronounced at the preclinical stage on Day 8 (3βfold higher than controls, P = 0.01) than on Day 13 (1.4βfold higher, P = 0.005). Increased brain thrombin inhibition at the clinical peak of EAE probably reflects increased influx of plasma thrombin inhibitors. Early PNβ1 changes represent a potential target for thrombin modulating drugs in EAE and MS. Β© 2004 WileyβLiss, Inc.