Endogenous Protease Nexin-1 Protects against Cerebral Ischemia

Abstract

The serine protease thrombin plays a role in signalling ischemic neuronal death in the brain. Paradoxically, endogenous neuroprotective mechanisms can be triggered by preconditioning with thrombin (thrombin preconditioning, TPC), leading to tolerance to cerebral ischemia. Here we studied the role of thrombin’s endogenous potent inhibitor, protease nexin-1 (PN-1), in ischemia and in tolerance to cerebral ischemia induced by TPC. Cerebral ischemia was modelled in vitro in organotypic hippocampal slice cultures from rats or genetically engineered mice lacking PN-1 or with the reporter gene lacZ knocked into the PN-1 locus PN-1HAPN-1-lacZ/HAPN-1-lacZ (PN-1 KI) exposed to oxygen and glucose deprivation (OGD). We observed increased thrombin enzyme activity in culture homogenates 24 h after OGD. Lack of PN-1 increased neuronal death in the CA1, suggesting that endogenous PN-1 inhibits thrombin-induced neuronal damage after ischemia. OGD enhanced β-galactosidase activity, reflecting PN-1 expression, at one and 24 h, most strikingly in the stratum radiatum, a glial cell layer adjacent to the CA1 layer of ischemia sensitive neurons. TPC, 24 h before OGD, additionally increased PN-1 expression 1 h after OGD, compared to OGD alone. TPC failed to induce tolerance in cultures from PN-1−/− mice confirming PN-1 as an important TPC target. PN-1 upregulation after TPC was blocked by the c-Jun N-terminal kinase (JNK) inhibitor, L-JNKI1, known to block TPC. This work suggests that PN-1 is an endogenous neuroprotectant in cerebral ischemia and a potential target for neuroprotection.

Expression pattern of human SERPINE2 in a variety of human tumors

“…As a glia-derived nexin, SERPINE2 is involved in regulating astrocyte proliferation, neurite outgrowth, neuron migration and localization, contributing to the development of brain, and the regeneration and reconstruction of neurons (38)(39)(40)(41). Our studies of EST profile showed that SERPINE2 expression begins to climb at early as the fetus stage, reaches a peak at the neonate and plateaus after the juvenile stage (Fig.…”

“…Indeed, SERPINE2 may contribute to the development of the brain by modulating the proliferation and differentiation of cerebellar granular neuron precursors via the major mitogen SHH, as well as via granule neuron migration and positioning (41). SERPINE2 may exert protective activity in the pathalogical progression of intracranial hemorrhage (42), cerebral ischemia (40), and Alzheimer's disease (43). Again, the role of SERPINE2 in tumor progression in the brain seems to be a paradox.…”

Organotypic Hippocampal Slices as Models for Stroke and Traumatic Brain Injury

“…The molecular mechanism by which thrombin causes injury may relate to FXa (perinuclear activated factor X), which catalyzes the conversion of prothrombin to thrombin in neural tissue after ischemia [112]. Protease nexin-1 and L-JNKI1 were able to prevent the neuronal injury caused by thrombin [113,114]. …”

Neuron‐generated thrombin induces a protective astrocyte response via protease activated receptors

“…Circulating serum proteases, notably thrombin, fibrinogen, plasmin, kallikreins, and activated protein C (APC), enter the central nervous system (CNS) via injured blood brain barrier (De Luca et al, ; Petersen, Ryu, & Akassoglou, ; Radulovic et al, ). The action of thrombin on PAR1 is limited by endogenous antagonists, including protease nexin‐1(PN‐1) (Choi, Suzuki, Kim, Wagner, & Cunningham, ; Mirante et al, ).…”

“…(CNS) via injured blood brain barrier (De Luca et al, 2017;Petersen, Ryu, & Akassoglou, 2018;Radulovic et al, 2015). The action of thrombin on PAR1 is limited by endogenous antagonists, including protease nexin-1(PN-1) (Choi, Suzuki, Kim, Wagner, & Cunningham, 1990;Mirante et al, 2013).…”