Increased thrombin inhibition in experimental autoimmune encephalomyelitis

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 (PN-1) in the brain. We measured the capacity of brain homogenates to inhibit exogenous thrombin and the CNS levels of ATIII and PN-1 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 post-immunization, inhibition of exogenous thrombin activity was measured by a recently developed fluorimetric assay. PN-1 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 (2.5-fold 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, PN-1 elevations were more pronounced at the preclinical stage on Day 8 (3-fold higher than controls, P=0.01) than on Day 13 (1.4-fold higher, P=0.005). Increased brain thrombin inhibition at the clinical peak of EAE probably reflects increased influx of plasma thrombin inhibitors. Early PN-1 changes represent a potential target for thrombin modulating drugs in EAE and MS.

Thrombin Induces Long-Term Potentiation of Reactivity to Afferent Stimulation and Facilitates Epileptic Seizures in Rat Hippocampal Slices: Toward Understanding the Functional Consequences of Cerebrovascular Insults

“…Once across the BBB, active thrombin is inhibited by endogenous serpins in the brain (Beilin et al, 2001), which are saturated when the levels rise above the buffering capacity of these inhibitors. In inflammatory models such as experimental autoimmune encephalomyelitis, there is widespread deposition of fibrin and activation of thrombin (Paterson et al, 1987;Inaba et al, 2001), as well as greatly elevated levels of thrombin inhibitors (Beilin et al, 2005). The importance of the BBB in protecting against epilepsy is further supported by the observation that in most of the central diseases that cause epilepsy, such as inflammation, tumors, trauma, and stroke, there is breakdown of the BBB.…”

The Multiple Sclerosis Degradome: Enzymatic Cascades in Development and Progression of Central Nervous System Inflammatory Disease

“…Moreover, batroxobin, a thrombin-like defibrinogenating enzyme, reduces clinical signs of disease but not perivascular monocular cell infiltration [119]. The important relationship between thrombin and serpins in disease pathogenesis is suggested by studies showing elevated endogenous inhibitors of thrombin, PN1 and ATIII in CNS of mice with EAE, with PN1 being most abundant prior to clinical disease and ATIII levels paralleling the peak of clinical disease [18,117].…”

Thrombotic Processes in Multiple Sclerosis as Manifestation of Innate Immune Activation

“…The activity of thrombin in the brain is regulated by thrombin inhibitors such as serum antithrombin III and brain protease nexin-1 secreted by glial cells and neurons that confirms the relevance of thrombin regulation in the brain (42, 43). An increase of brain protease nexin-1 levels was shown at early pre-clinical stages in EAE (45) while the plasma thrombin–antithrombin complexes increased immediately prior to EAE symptoms and decreased in relation to their improvement (46). …”