The brain-specific tissue-type plasminogen activator inhibitor, neuroserpin, protects neurons against excitotoxicity both in vitro and in vivo

Neuroserpin As an Adjuvant Therapy for Hypothermia on Brain Injury in Neonatal Hypoxic-Ischemic Rats

OBJECTIVE

We aimed to assess the effects of neuroserpin and its combination with hypothermia on hypoxic-ischemic (HI) brain injury in neonatal rats. Neuroserpin is an axon-secreted serine protease inhibitor and is important for brain development, neuronal survival, and synaptic plasticity.

STUDY DESIGN

Male Wistar-Albino rats on postnatal day 7 (P7) were randomly divided into five groups: sham group (n = 10), (HI; n = 10), hypoxic-ischemic hypothermia (HIH; n = 10), hypoxic-ischemic neuroserpin (HIN; n = 10), and hypoxic-ischemic neuroserpin-hypothermia (HINH; n = 10). The P7 rat brain's maturation is similar to a late preterm human brain at 34 to 36 weeks of gestation. HI was induced in rats on P7 as previously described. A single dose of 0.2 µM neuroserpin (HINH and HIN) or an equivalent volume of phosphate-buffered saline (sham, HIH, and HI) was administered intraventricularly by a Hamilton syringe immediately after hypoxia. In the follow-up, pups were subjected to systemic hypothermia or normothermia for 2 hours. Euthanasia was performed for histopathological evaluation on P10. Apoptosis was detected by caspase-3 activity and terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL) staining and was counted in the hippocampus.

RESULTS

In comparison to the HI group, the TUNEL-positive and caspase-3-positive neurons in the sham, HIN, HIH, and HINH groups were considerably lower (13.4 ± 1.0 vs. 1.9 ± 0.9, 6.0 ± 0.9, 5.3 ± 1.6, and 4.0 ± 1.1; p < 0.001) and (13.5 ± 1.7 vs. 1.2 ± 0.7, 9.1 ± 2.7, 4.8 ± 1.0, and 3.9 ± 1.6; p < 0.001). HIN, HIH, and HINH, compared to the sham group, showed more TUNEL-positive and caspase-3-positive neurons (6.0 ± 0.9, 5.3 ± 1.6, 4.0 ± 1.1 vs. 1.9 ± 0.9 and 9.1 ± 2.7, 4.8 ± 1.0, 3.9 ± 1.6 vs. 1.2 ± 0.7; p < 0.001). The HINH group (synergistic effect) had significantly fewer TUNEL-positive neurons and caspase-3-positive neurons than the HIN group (4.0 ± 1.1 vs. 6.0 ± 0.9 and 3.9 ± 1.6 vs. 9.1 ± 2.7; p < 0.001).

CONCLUSION

Our study showed that both neuroserpin alone and as an adjuvant treatment for hypothermia may have a neuroprotective effect on brain injury.

KEY POINTS

· Neuroserpin decreased brain injury.. · Neuroserpin showed a synergistic effect when used as an adjuvant treatment for hypothermia.. · The neuroprotective effect of neuroserpine was related to its antiapoptotic properties..

Acute Ischemic Stroke in the Clinic and the Laboratory: Targets for Translational Research

Ischemic stroke research has enabled significant advancements in diagnosis, treatment, and management of this debilitating disease, yet challenges remain standing in the way of better patient prognoses. In this narrative review, a fictional case illustrates challenges and uncertainties that medical professionals still face - penumbra identification, lack of neuroprotective agents, side-effects of tissue plasminogen activator, dearth of molecular biomarkers, incomplete microvascular reperfusion or no-reflow, post-recanalization hyperperfusion, blood pressure management and procedural anesthetic effects. The current state of the field is broadly reviewed per topic, with the aim to introduce a broad audience (scientist and clinician alike) to recent successes in translational stroke research and pending scientific queries that are tractable for preclinical assessment. Opportunities for co-operation between clinical and experimental stroke experts are highlighted to increase the size and frequency of strides the field makes to improve our understanding of this disease and ways of treating it.

The Janus face of endogenous neuronal tPA: promoting self-protection and worsening the death of neighboring neurons

Recombinant tissue-type plasminogen activator (r-tPA/Actilyse) stands as the prevailing pharmacological solution for treating ischemic stroke patients, of whom because their endogenous circulating tPA alone is not sufficient to rescue reperfusion and to promote favorable outcome. Beyond the tPA contributed by circulating endothelial cells and hepatocytes, neurons also express tPA, sparking debates regarding its impact on neuronal fate ranging from pro-survival to neurotoxic properties. In order to investigate the role of neuronal tPA during brain injuries, we developed models leading to its conditional deletion in neurons, employing AAV9-pPlat-GFP and AAV9-pPlat-Cre-GFP along with tPA floxed mice. These models were subjected to N-methyl-D-aspartate (NMDA)-induced excitotoxicity or thromboembolic ischemic stroke in mice. Initially, we established that our AAV9 constructs selectively transduce neurons, bypassing other brain cell types. Subsequently, we demonstrated that tPA-expressing neurons exhibit greater resistance against NMDA-induced excitotoxicity compared to tPA negative neurons. The targeted removal of tPA in neurons heightened the susceptibility of these neurons to cell death and prevented a paracrine neurotoxic effect on tPA non-expressing neurons. Under ischemic conditions, the self-neuroprotective influence of tPA encompassed both excitatory (GFP+/Tbr1+) and inhibitory (GFP+/GABA+) neurons. Our data indicate that endogenous neuronal tPA is a protective or deleterious factor against neuronal death in an excitotoxic/ischemic context, depending on whether it acts as an autocrine or a paracrine mediator.

The probable role of tissue plasminogen activator/neuroserpin axis in Alzheimer's disease: a new perspective

Alzheimer's disease (AD) is the most common type of dementia associated with amyloid beta (Aβ) deposition. Dysfunction of the neuronal clearance pathway promotes the accumulation of Aβ. The plasminogen-activating system (PAS) is controlled by various enzymes like tissue plasminogen activators (tPA). Neuronal tPA enhances the conversion of plasminogen to plasmin, which cleaves Aβ; this function is controlled by many inhibitors of PAS, including a plasminogen-activating inhibitor (PAI-1) and neuroserpin. Therefore, the objective of the present narrative review was to explore the potential role of tPA/neuroserpin in the pathogenesis of AD. PAI-1 activity is increased in AD, which is involved in accumulating Aβ. Progressive increase of Aβ level during AD neuropathology is correlated with the over-production of PAI-1 with subsequent reduction of plasmin and tPA activities. Reducing plasmin and tPA activities promote Aβ by reducing Aβ clearance. Neuroserpin plays a critical role in the pathogenesis of AD as it regulates the expression and accumulation of Aβ. Higher expression of neuroserpin inhibits the neuroprotective tPA and the generation of plasmin with subsequent reduction in the clearance of Aβ. These observations raise conflicting evidence on whether neuroserpin is neuroprotective or involved in AD progression. Thus, neuroserpin over-expression with subsequent reduction of tPA may propagate AD neuropathology.

The paradox of tPA in ischemic stroke: tPA knockdown following recanalization improves functional and histological outcomes

Previous studies have demonstrated that endogenous tissue-type plasminogen activator (tPA) is upregulated in the brain after an acute ischemic stroke (AIS). While mixed results were observed in genetic models, the pharmacological inhibition of endogenous tPA showed beneficial effects. Treatment with exogenous recombinant tPA exacerbated brain damage in rodent models of stroke. Despite the detrimental effects of tPA in ischemic stroke, recombinant tPA is administered to AIS patients to recanalize the occluded blood vessels because the benefits of its administration outweigh the risks associated with tPA upregulation and increased activity. We hypothesized that tPA knockdown following recanalization would ameliorate sensorimotor deficits and reduce brain injury. Young male and female rats (2-3 months old) were subjected to transient focal cerebral ischemia by occlusion of the right middle cerebral artery. Shortly after reperfusion, rats from appropriate cohorts were administered a nanoparticle formulation containing tPA shRNA or control shRNA plasmids (1 mg/kg) intravenously via the tail vein. Infarct volume during acute and chronic phases, expression of matrix metalloproteinases (MMPs) 1, 3, and 9, enlargement of cerebral ventricle volume, and white matter damage were all reduced by shRNA-mediated gene silencing of tPA following reperfusion. Additionally, recovery of somatosensory and motor functions was improved. In conclusion, our results provide evidence that reducing endogenous tPA following recanalization improves functional outcomes and reduces post-stroke brain damage.

Modeling and Correction of Protein Conformational Disease in iPSC-derived Neurons through Personalized Base Editing

Altered protein conformation can cause incurable neurodegenerative disorders. Mutations in SERPINI1 , the gene encoding neuroserpin, alter protein conformation resulting in cytotoxic aggregation in neuronal endoplasmic reticulum. Aggregates cause oxidative stress impairing function, leading to neuronal death. Familial encephalopathy with neuroserpin inclusion bodies (FENIB) is a rare autosomal dominant progressive myoclonic epilepsy. Patients present with seizures and cognitive impairments that progress to dementia and premature death. We developed HEK293T and induced pluripotent stem cell (iPSC) models of FENIB, harboring the patient's pathogenic SERPINI1 variant or stably overexpressing mutant neuroserpin fused to GFP (MUT NS-GFP). FENIB cells form neuroserpin inclusions which increase in size and number. Here, we utilized a personalized adenine base editor (ABE)-mediated approach to efficiently correct the pathogenic variant and to restore neuronal dendritic morphology. ABE-treated MUT NS-GFP cells demonstrated reduced inclusion size and number. Using an inducible MUT NS-GFP neuron system, we identified early prevention of toxic protein expression allowed aggregate clearance, while late prevention halted neuronal impairments. To address several challenges for clinical applications of gene correction, we developed a neuron-specific engineered virus-like particle to optimize neuronal ABE delivery. Preventing mutant protein with altered conformation production improved toxic protein clearance. Our findings provide a targeted strategy and may treat FENIB and potentially other neurodegenerative diseases due to altered protein conformation such as Alzheimer's and Huntington's diseases.

TMT proteomics analysis of cerebrospinal fluid from patients with cerebral venous sinus thrombosis

CVST is a type of venous stroke that mainly affects young adults with no reliable diagnostic markers and effective treatment strategies for secondary pathologies. However, the underlying pathological molecular mechanisms remain unclear. Here, we systematically analyzed the molecule profiling of the cerebrospinal fluid (CSF) in CVST patients via tandem mass tag (TMT)-based proteomics for the first time, aiming to reveal the pathogenesis and provide evidence for the diagnosis and treatment of CVST. Five CVST patients and five control patients were selected, and CSF samples were analyzed by TMT proteomics. Differentially expressed proteins (DEPs) were acquired and bioinformatics analysis was performed. Besides, parallel reaction monitoring (PRM) was utilized to validate the DEPs. 468 differentially expressed proteins were screened, 185 of which were up-regulated and 283 were down-regulated (fold change >1.2, P < 0.05). Bioinformatics analysis displayed that these proteins were significantly enriched in multiple pathways related to a variety of pathophysiological processes. PRM verification showed that apolipoprotein E, MMP-2, neuroserpin, clusterin, and several other molecules were down-regulated. These identified proteins reveal unique pathophysiological characteristics secondary to CVST. Further characterization of these proteins in future research could enable their application as potential therapeutic targets and biomarkers in CVST therapy. SIGNIFICANCE: Cerebral venous sinus thrombosis (CVST) is an underrated and potentially fatal cause of stroke with a reported mortality of 5-10% worldwide. Currently, in addition to anticoagulant and thrombolytic therapy, effective treatments targeting the injured brain parenchyma after CVST remain limited. Besides, accurate diagnostic markers are still sorely lacking. In the present study, we will detect the alterations of the CSF protein spectrum of CVST patients by TMT technique, screen differentially expressed proteins, analyze the functions of these signals through bioinformatics methods, and finally validate the key molecules through parallel reaction monitoring (PRM) technique. Collectively, the study aimed to offer a reference for the discovery of specific protein/pathway alterations in the CSF of CVST patients and further reveal the underlying pathogenesis, thereby providing evidence for the diagnosis and treatment of CVST.

Role of SERPINI1 pathogenic variants in familial encephalopathy with neuroserpin inclusion bodies: A case report and literature review

BACKGROUND

Familial encephalopathy with neuroserpin inclusion bodies (FENIB), a rare neurogenetic disease, is characterized by progressive cognitive decline and myoclonus and caused by pathogenic variants of the SERPINI1 gene that lead to the formation of neuroserpin inclusion bodies.

METHODS

We described the case of an Asian patient with FENIB associated with a pathogenic variant of SERPINI1 and summarized and analyzed the clinical characteristics of the case. In addition, we conducted a literature review of previously reported patients with this disease.

RESULTS

The patient, a 16-year-old Chinese girl, presented with progressive cognitive decline and myoclonus that had started at the age of 11 years. The girl was found to carry a de novo heterozygous c.1175G>A (p.G392E) variant of the SERPINI1 gene, which is a pathogenic variant according to the guidelines of the American College of Medical Genetics and Genomics. She had responded poorly to antiseizure medications (ASMs). At the last follow-up, her myoclonus was still out of control, and her self-care ability was poor. Our literature review revealed that 13 similar cases (including 9 cases in male patients) have been reported so far, in which six pathogenetic variations in SERPINI1, including G392E, were responsible for FENIB. All the patients presented with myoclonus, and 12 patients had experienced at least one other type of seizure. Further, as observed in our case, 9 out of 12 patients did not respond to ASMs. Progressive cognitive decline was observed in all the patients, and 10 out of 13 patients had dyskinesia. The median age of disease onset was 21 years, and the median age at the time of death was 33 years. Further, 9 out of 13 patients showed signs of cerebral and/or cerebellar atrophy. Finally, neuroserpin inclusion bodies were identified in six patients who underwent brain biopsy or autopsy.

CONCLUSIONS

Pathogenic variants of SERPINI1 should be suspected in children with progressive cognitive decline and myoclonus, especially in those with progressive myoclonus epilepsy. Further, gene detection and brain biopsy are important means for the diagnosis of FENIB.

Quantitative proteomics analysis of human vitreous in rhegmatogenous retinal detachment associated with choroidal detachment by data-independent acquisition mass spectrometry

The prognosis of rhegmatogenous retinal detachment (RRD) with choroidal detachment (RRDCD) is often poor and complicated. This study focused on the identification of the characteristic proteins and signal pathways associated with the etiology of RRDCD and to provide guidance for diagnosis and treatment of RRDCD. In this study, vitreous humor samples were obtained from 16 RRDCD patients, 14 with RRD, 12 with idiopathic epiretinal macular membrane (IEMM), and 5 healthy controls from donated corpse eyes. Data-independent acquisition mass spectrometry and bioinformatics analysis were employed to identify differentially expressed proteins (DEPs). In the vitreous humor, 14,842 peptides were identified. Patients with RRDCD had 249 DEPs (93 upregulated and 156 downregulated), with 89 in patients with RRD and 61 in patients with IEMM. Enrichment analysis of the GO and Kyoto Encyclopedia of Genes and Genomes DEP databases indicated functional clusters related to inflammation and immunity, protein degradation and absorption, cell adhesion molecules (CAMs), the hedgehog signaling pathway, and lipid metabolism. Weighted gene co-expression network analysis showed that DEPs with positive co-expression of RRDCD participated in immune-related pathways led by the complement and coagulation cascade, whereas DEPs with negative co-expression of RRDCD participated in protein degradation and absorption, CAMs, and the hedgehog signaling pathway. In summary, our study provides important clues and the theoretical basis for exploring the pathogenesis, progression, and prognosis of ocular fundus disease.

Neuroserpin, a crucial regulator for axogenesis, synaptic modelling and cell-cell interactions in the pathophysiology of neurological disease

Neuroserpin is an axonally secreted serpin that is involved in regulating plasminogen and its enzyme activators, such as tissue plasminogen activator (tPA). The protein has been increasingly shown to play key roles in neuronal development, plasticity, maturation and synaptic refinement. The proteinase inhibitor may function both independently and through tPA-dependent mechanisms. Herein, we discuss the recent evidence regarding the role of neuroserpin in healthy and diseased conditions and highlight the participation of the serpin in various cellular signalling pathways. Several polymorphisms and mutations have also been identified in the protein that may affect the serpin conformation, leading to polymer formation and its intracellular accumulation. The current understanding of the involvement of neuroserpin in Alzheimer's disease, cancer, glaucoma, stroke, neuropsychiatric disorders and familial encephalopathy with neuroserpin inclusion bodies (FENIB) is presented. To truly understand the detrimental consequences of neuroserpin dysfunction and the effective therapeutic targeting of this molecule in pathological conditions, a cross-disciplinary understanding of neuroserpin alterations and its cellular signaling networks is essential.

Low-intensity blast induces acute glutamatergic hyperexcitability in mouse hippocampus leading to long-term learning deficits and altered expression of proteins involved in synaptic plasticity and serine protease inhibitors

Neurocognitive consequences of blast-induced traumatic brain injury (bTBI) pose significant concerns for military service members and veterans with the majority of "invisible injury." However, the underlying mechanism of such mild bTBI by low-intensity blast (LIB) exposure for long-term cognitive and mental deficits remains elusive. Our previous studies have shown that mice exposed to LIB result in nanoscale ultrastructural abnormalities in the absence of gross or apparent cellular damage in the brain. Here we tested the hypothesis that glutamatergic hyperexcitability may contribute to long-term learning deficits. Using brain slice electrophysiological recordings, we found an increase in averaged frequencies with a burst pattern of miniature excitatory postsynaptic currents (mEPSCs) in hippocampal CA3 neurons in LIB-exposed mice at 1- and 7-days post injury, which was blocked by a specific NMDA receptor antagonist AP5. In addition, cognitive function assessed at 3-months post LIB exposure by automated home-cage monitoring showed deficits in dynamic patterns of discrimination learning and cognitive flexibility in LIB-exposed mice. Collected hippocampal tissue was further processed for quantitative global-proteomic analysis. Advanced data-independent acquisition for quantitative tandem mass spectrometry analysis identified altered expression of proteins involved in synaptic plasticity and serine protease inhibitors in LIB-exposed mice. Some were correlated with the ability of discrimination learning and cognitive flexibility. These findings show that acute glutamatergic hyperexcitability in the hippocampus induced by LIB may contribute to long-term cognitive dysfunction and protein alterations. Studies using this military-relevant mouse model of mild bTBI provide valuable insights into developing a potential therapeutic strategy to ameliorate hyperexcitability-modulated LIB injuries.

Neuroserpin: structure, function, physiology and pathology

Neuroserpin is a serine protease inhibitor identified in a search for proteins implicated in neuronal axon growth and synapse formation. Since its discovery over 30 years ago, it has been the focus of active research. Many efforts have concentrated in elucidating its neuroprotective role in brain ischemic lesions, the structural bases of neuroserpin conformational change and the effects of neuroserpin polymers that underlie the neurodegenerative disease FENIB (familial encephalopathy with neuroserpin inclusion bodies), but the investigation of the physiological roles of neuroserpin has increased over the last years. In this review, we present an updated and critical revision of the current literature dealing with neuroserpin, covering all aspects of research including the expression and physiological roles of neuroserpin, both inside and outside the nervous system; its inhibitory and non-inhibitory mechanisms of action; the molecular structure of the monomeric and polymeric conformations of neuroserpin, including a detailed description of the polymerisation mechanism; and the involvement of neuroserpin in human disease, with particular emphasis on FENIB. Finally, we briefly discuss the identification by genome-wide screening of novel neuroserpin variants and their possible pathogenicity.

Fibrinolytic Serine Proteases, Therapeutic Serpins and Inflammation: Fire Dancers and Firestorms

The making and breaking of clots orchestrated by the thrombotic and thrombolytic serine protease cascades are critical determinants of morbidity and mortality during infection and with vascular or tissue injury. Both the clot forming (thrombotic) and the clot dissolving (thrombolytic or fibrinolytic) cascades are composed of a highly sensitive and complex relationship of sequentially activated serine proteases and their regulatory inhibitors in the circulating blood. The proteases and inhibitors interact continuously throughout all branches of the cardiovascular system in the human body, representing one of the most abundant groups of proteins in the blood. There is an intricate interaction of the coagulation cascades with endothelial cell surface receptors lining the vascular tree, circulating immune cells, platelets and connective tissue encasing the arterial layers. Beyond their role in control of bleeding and clotting, the thrombotic and thrombolytic cascades initiate immune cell responses, representing a front line, "off-the-shelf" system for inducing inflammatory responses. These hemostatic pathways are one of the first response systems after injury with the fibrinolytic cascade being one of the earliest to evolve in primordial immune responses. An equally important contributor and parallel ancient component of these thrombotic and thrombolytic serine protease cascades are the serine protease inhibitors, termed serpins. Serpins are metastable suicide inhibitors with ubiquitous roles in coagulation and fibrinolysis as well as multiple central regulatory pathways throughout the body. Serpins are now known to also modulate the immune response, either via control of thrombotic and thrombolytic cascades or via direct effects on cellular phenotypes, among many other functions. Here we review the co-evolution of the thrombolytic cascade and the immune response in disease and in treatment. We will focus on the relevance of these recent advances in the context of the ongoing COVID-19 pandemic. SARS-CoV-2 is a "respiratory" coronavirus that causes extensive cardiovascular pathogenesis, with microthrombi throughout the vascular tree, resulting in severe and potentially fatal coagulopathies.

Deficiency in Neuroserpin Exacerbates CoCl2 Induced Hypoxic Injury in the Zebrafish Model by Increased Oxidative Stress

Protective strategy against hypoxic-ischemic (H/I) induced injury has been intensively discussed. Neuroserpin, an inhibitor for tissue plasminogen activator (tPA), has been proved a vital neuroprotective agent in cerebral ischemia mouse model and oxygen-glucose deprivation and reoxygenation (OGD/R) cell model. Neuroserpin is a promising therapeutic hint for neonatal hypoxic-ischemia injury. Here, we established a neuroserpin deficient zebrafish to study its role in CoCl₂ chemically induced hypoxic injury. CoCl₂ exposure was beginning at the embryonic stage. Development defects, neuronal loss, and vascular malformation was assessed by imaging microscopy. Neuroserpin deficient zebrafish showed more development defects, neuronal loss and vascular malformation compared to wide-type. Apoptosis and oxidative stress were evaluated to further identify the possible mechanisms. These findings indicate that neuroserpin could protective against CoCl₂ induced hypoxic injury by alleviating oxidative stress.

The Neuroprotective Role of Neuroserpin in Ischemic and Hemorrhagic Stroke

Tissue plasminogen activator (tPA) is commonly used to treat acute ischemic stroke within an appropriate therapeutic window. Its inhibitor, neuroserpin (NSP), is reported to exhibit neuroprotective effects on stroke. This review aims to summarize, from literature, the available evidence, potential mechanisms, and knowledge limitations regarding the neuroprotective role of NSP in stroke. All the available evidence indicates that the regulation of the inflammatory response may play a key role in the mechanisms of NSP, which involve all the constituents of the neuroimmune axis. The neuroinflammatory response triggered by stroke can be reversed by NSP, with complicated mechanisms such as maintenance and reconstruction of the structure and function of the blood-brain barrier (BBB), protection of the cells in the central nervous system, and suppression of cell death in both ischemic and hemorrhagic stroke. Moreover, available evidence strongly suggests a tPA-independent mechanism is involved in NSP. However, there are many important issues that are still unclear and need further investigation, such as the effects of NSP on hemorrhagic stroke, the role of the tPA-independent neuroprotective mechanisms, and the clinical application prospects of NSP. We believe our work will be helpful to further understand the neuroprotective role of NSP.

Neuroserpin extends the time window of tPA thrombolysis in a rat model of middle cerebral artery occlusion

Tissue-type plasminogen activator (tPA) is characterized as an effective drug for early thrombolytic therapy in acute cerebral infarction (ACI). However, tPA will increase the risk of hemorrhage if it is used beyond the treatment time window. The study aims to explore the effects of neuroserpin (NSP) on the time window of tPA thrombolysis in ACI and the underlying mechanism. The middle cerebral artery occlusion (MCAO) model was constructed in rats, which were randomly divided into six groups: sham operation group, infarction group, 1-hour thrombolysis group, 1-hour thrombolytic + NSP intervention group, 4-hour thrombolytic group, and 4-hour thrombolysis + NSP intervention group. The neurological changes in rats were evaluated by modified neurological severity scores and rota-rod test. The brain edema and cerebral infarction area were evaluated by dry-wet method and triphenyl tetrazolium chloride staining. The blood-brain barrier (BBB) integrity was examined by Evans blue method. The expressions of malondialdehyde, superoxide dismutase, and glutathione peroxidase in brain were also investigated. The expression of caspase-3 and Bcl-2 in brain tissue and apoptosis of neurons were examined by Western blot analysis and toluidine blue staining. tPA thrombolysis significantly attenuated the neurological impairment in rats with MCAO at 1 hour. Conversely, the effect of tPA thrombolysis at 4 hours after MCAO did not significantly help the recovery of neurological function. However, a combination of tPA treatment and NSP treatment at 4 hours after MCAO markedly ameliorated the neurological impairment, cerebral edema, cerebral infarction volume, BBB injury, oxidative stress products, and neuron apoptosis. NSP can probably expand the time window for tPA treatment to reduce neurological impairment in ACI.

Spinosin Attenuates Alzheimer's Disease-Associated Synaptic Dysfunction via Regulation of Plasmin Activity

Hippocampal synaptic dysfunction is a hallmark of Alzheimer’s disease (AD). Many agents regulating hippocampal synaptic plasticity show an ameliorative effect on AD pathology, making them potential candidates for AD therapy. In the present study, we investigated spinosin as a regulating agent of synaptic plasticity in AD. Spinosin attenuated amyloid β (Aβ)-induced long-term potentiation (LTP) impairment, and improved plasmin activity and protein level in the hippocampi of 5XFAD mice, a transgenic AD mouse model. Moreover, the effect of spinosin on hippocampal LTP in 5XFAD mice was prevented by 6-aminocaproic acid, a plasmin inhibitor. These results suggest that spinosin improves synaptic function in the AD hippocampus by regulating plasmin activity.

Neuroserpin expression during human brain development and in adult brain revealed by immunohistochemistry and single cell RNA sequencing

Neuroserpin is a serine-protease inhibitor mainly expressed in the CNS and involved in the inhibition of the proteolytic cascade. Animal models confirmed its neuroprotective role in perinatal hypoxia-ischaemia and adult stroke. Although neuroserpin may be a potential therapeutic target in the treatment of the aforementioned conditions, there is still no information in the literature on its distribution during human brain development. The present study provides a detailed description of the changing spatiotemporal patterns of neuroserpin focusing on physiological human brain development. Five stages were distinguished within our examined age range which spanned from the 7th gestational week until adulthood. In particular, subplate and deep cortical plate neurons were identified as the main sources of neuroserpin production between the 25th gestational week and the first postnatal month. Our immunohistochemical findings were substantiated by single cell RNA sequencing data showing specific neuronal and glial cell types expressing neuroserpin. The characterization of neuroserpin expression during physiological human brain development is essential for forthcoming studies which will explore its involvement in pathological conditions, such as perinatal hypoxia-ischaemia and adult stroke in human.

The role of endogenous tissue-type plasminogen activator in neuronal survival after ischemic stroke: friend or foe?

Endogenous protease tissue-type plasminogen activator (tPA) has highly efficient fibrinolytic activity and its recombinant variants alteplase and tenecteplase are established as highly effective thrombolytic drugs for ischemic stroke. Endogenous tPA is constituted of five functional domains through which it interacts with a variety of substrates, binding proteins and receptors, thus having enzymatic and cytokine-like effects to act on all cell types of the brain. In the past 2 decades, numerous studies have explored the clinical relevance of endogenous tPA in neurological diseases, especially in ischemic stroke. tPA is released from many cells within the brain parenchyma exposed to ischemia conditions in vitro and in vivo, which is believed to control neuronal fate. Some studies proved that tPA could induce blood-brain barrier disruption, neural excitotoxicity and inflammation, while others indicated that tPA also has anti-excitotoxic, neurotrophic and anti-apoptotic effects on neurons. Therefore, more work is needed to elucidate how tPA mediates such opposing functions that may amplify tPA from a therapeutic means into a key therapeutic target in endogenous neuroprotection after stroke. In this review, we summarize the biological characteristics and pleiotropic functions of tPA in the brain. Then we focus on possible hypotheses about why and how endogenous tPA mediates ischemic neuronal death and survival. Finally, we analyze how endogenous tPA affects neuron fate in ischemic stroke in a comprehensive view.

New thrombolytic strategy providing neuroprotection in experimental ischemic stroke: MMP10 alone or in combination with tissue-type plasminogen activator

Aims

Early reperfusion with tissue-type plasminogen activator (tPA) is an effective therapeutic strategy to treat acute ischemic stroke, but only 1/3 of tPA-treated patients recover and are free from disability. tPA has also shown neurotoxicity in experimental models of cerebral ischemia. Considering that MMP-10 improves stroke injury, we have examined the therapeutic and protective effect of MMP10 and tPA/MMP10 as clot-dissolving and neuroprotective agent in an experimental model of ischemic stroke and studied in vitro the molecular pathways involved in MMP10-mediated effects.

Methods and results

Cerebral ischemia was induced by the local injection of thrombin into the middle cerebral artery followed by reperfusion with MMP10 (6.5 µg/kg) and tPA (10 mg/kg) alone or in combination with MMP10. Cell cultures were also performed to determine the effect of MMP10 and tPA/MMP10 on brain endothelial cells and neurons. tPA/MMP10 significantly reduced the infarct size in the ischemic stroke model compared with tPA alone (P < 0.05). In vitro, MMP10 reduced the tPA-promoted endothelial ionic permeability, preserved the expression of claudin-5 and decreased ERK1/2 activation. Moreover, combination of tPA/MMP10 prevented tPA-mediated neuronal excitotoxicity and calcium influx. These effects were reversed by blocking MMP10 activity with a monoclonal antibody.

Conclusion

These results show that MMP10, either alone or in combination with tPA, might represent a new strategy for thrombolysis in ischemic stroke, providing higher protection against cerebrovascular damage.

Neuroprotective effect of neuroserpin in non-tPA-induced intracerebral hemorrhage mouse models

BACKGROUND

The neuroprotective effects of neuroserpin (NSP) have been well documented in both patients and animal models with cerebral ischemia; however, have never been investigated in hemorrhagic stroke. The aim of this study is to verify the neuroprotection of NSP in the non-tPA-induced intracerebral hemorrhage (ICH) mouse model.

METHODS

C57BL/6J male mice (n = 198) were involved in this study. ICH models were established with infusion of autologous blood into the brain parenchyma. We then detected NSP expression in ICH brains by morphological methods and western blotting analysis. We measured the brain water content and detected blood-brain barrier (BBB) permeability to verify the neuroprotective effects of NSP.

RESULTS

We found that NSP protein expression was upregulated in ICH models, with a peak at 48 h after ICH induction. NSP local administration reduced the brain edema and the BBB permeability in ICH models. The neurological deficits were also ameliorated. Thus, the neuroprotection of NSP in ICH state was confirmed. Additionally, we also found that the distribution pattern of occludin-expressing cells was obviously changed by the ICH procedure but partly recovered after NSP administration. This finding indicated that protecting and/or repairing the injured vascular endothelial cells may be a potential mechanism involved in NSP neuroprotection, which needs further verification.

CONCLUSIONS

Our results supported the fact that NSP may be considered as a potential therapy for ICH for the neuroprotective effects including amelioration of the edema.

Effects of neuroserpin on clinical outcomes and inflammatory markers in Chinese patients with acute ischemic stroke

OBJECTIVE

Neuroserpin (NSP) is known for its neuroprotective effects. The aim of this study was to investigate the relationship between NSP level and clinical outcomes and inflammatory markers in Chinese patients with acute ischemic stroke.

METHODS

A total of 133 patients with acute cerebral infarction (ischemia group) and 44 controls were recruited. The modified Rankin Scale (mRS) was used to determine the functional outcome three months after onset. We investigated the relationship between serum NSP levels [on admission and a decrease in NSP levels (10 days after admission versus on admission)] and serum levels of several inflammatory markers.

RESULTS

We confirmed that NSP levels on admission in the ischemia group were significantly higher than those in the control group. NSP levels in patients with good outcomes were significantly higher than those in patients with poor outcomes. NSP levels on admission were associated with having a good outcome in these patients. We found that a larger decrease in NSP levels (on admission vs. 10 days after admission) was correlated with lower serum levels of IL-6, IL-1β, and ICAM-1 10 days after admission.

CONCLUSIONS

A larger decrease in NSP levels related to lower levels of inflammatory marker, while higher NSP levels were associated with lower inflammatory markers and better functional outcomes. Decreasing the infarct size may play a role in this process. These results provide more evidence of the neuroprotective effect of NSP in cerebral ischemic patients. Decrease in the Serum NSP level and NSP level at admission may be considered as potential predictive factors for outcome of acute ischemic stroke.

Glaucoma is associated with plasmin proteolytic activation mediated through oxidative inactivation of neuroserpin

Neuroserpin is a serine protease inhibitor that regulates the activity of plasmin and its activators in the neuronal tissues. This study provides novel evidence of regulatory effect of the neuroserpin on plasmin proteolytic activity in the retina in glaucoma. Human retinal and vitreous tissues from control and glaucoma subjects as well as retinas from experimental glaucoma rats were analysed to establish changes in plasmin and neuroserpin activity. Neuroserpin undergoes oxidative inactivation in glaucoma which leads to augmentation of plasmin activity. Neuroserpin contains several methionine residues in addition to a conserved reactive site methionine and our study revealed enhanced oxidation of Met residues in the serpin under glaucoma conditions. Met oxidation was associated with loss of neuroserpin inhibitory activity and similar findings were observed in the retinas of superoxide dismutase (SOD) mutant mice that have increased oxidative stress. Treatment of purified neuroserpin with H2O2 further established that Met oxidation inversely correlated with its plasmin inhibitory activity. Dysregulation of the plasmin proteolytic system associated with increased degradation of the extracellular matrix (ECM) proteins in the retina. Collectively, these findings delineate a novel molecular basis of plasmin activation in glaucoma and potentially for other neuronal disorders with implications in disease associated ECM remodelling.

Can the benefits of rtPA treatment for stroke be improved?

Tissue-type plasminogen activator (tPA) is a serine protease well known to promote fibrinolysis. This is why: its recombinant form (rtPA) can be used, either alone or combined with thrombectomy, to promote recanalization/reperfusion following ischemic stroke. However, its overall benefits are counteracted by some of its side-effects, including incomplete lysis of clots, an increased risk of hemorrhagic transformation and the possibility of neurotoxicity. Nevertheless, better understanding of the mechanisms by which tPA influences brain function and promotes its alteration may help in the design of new strategies to improve stroke therapy.

Neonatal Hypoxia Ischaemia: Mechanisms, Models, and Therapeutic Challenges

Neonatal hypoxia-ischaemia (HI) is the most common cause of death and disability in human neonates, and is often associated with persistent motor, sensory, and cognitive impairment. Improved intensive care technology has increased survival without preventing neurological disorder, increasing morbidity throughout the adult population. Early preventative or neuroprotective interventions have the potential to rescue brain development in neonates, yet only one therapeutic intervention is currently licensed for use in developed countries. Recent investigations of the transient cortical layer known as subplate, especially regarding subplate's secretory role, opens up a novel set of potential molecular modulators of neonatal HI injury. This review examines the biological mechanisms of human neonatal HI, discusses evidence for the relevance of subplate-secreted molecules to this condition, and evaluates available animal models. Neuroserpin, a neuronally released neuroprotective factor, is discussed as a case study for developing new potential pharmacological interventions for use post-ischaemic injury.

Physiological and pathological functions of neuroserpin: Regulation of cellular responses through multiple mechanisms

It is 27 years since neuroserpin was first discovered in the nervous system and identified as a member of the serpin superfamily. Since that time potential roles for this serine protease inhibitor have been identified in neuronal and non-neuronal systems. Many are linked to inhibition of neuroserpin's principal enzyme target, tissue plasminogen activator (tPA), although some have been suggested to involve alternate non-inhibitory mechanisms. This review focuses mainly on the inhibitory roles of neuroserpin and discusses the evidence supporting tPA as the physiological target. While the major sites of neuroserpin expression are neural, endocrine and immune tissues, most progress on characterizing functional roles for neuroserpin have been in the brain. Roles in emotional behaviour, synaptic plasticity and neuroprotection in stroke and excitotoxicity models are discussed. Current knowledge on three neurological diseases associated with neuroserpin mutation or activity, Familial Encephalopathy with Neuroserpin Inclusion Bodies (FENIB), Alzheimer's disease and brain metastasis is presented. Finally, we consider mechanistic studies that have revealed a distinct inhibitory mechanism for neuroserpin and its possible implications for neuroserpin function.

Neuroserpin Attenuates H2O2-Induced Oxidative Stress in Hippocampal Neurons via AKT and BCL-2 Signaling Pathways

Oxidative stress plays a critical role in neuronal injury and is associated with various neurological diseases. Here, we explored the potential protective effect of neuroserpin against oxidative stress in primary cultured hippocampal neurons. Our results show that neuroserpin inhibits H2O2-induced neurotoxicity in hippocampal cultures as measured by WST, LDH release, and TUNEL assays. We found that neuroserpin enhanced the activation of AKT in cultures subjected to oxidative stress and that the AKT inhibitor Ly294002 blocked this neuroprotective effect. Neuroserpin increased the expression of the anti-apoptotic protein BCL-2 and blocked the activation of caspase-3. Neuroserpin did not increase the level of neuroprotection over levels seen in neurons transduced with a BCL-2 expression vector, and an inhibitor of Trk receptors, K252a, did not block neuroserpin's effect. Taken together, our study demonstrates that neuroserpin protects against oxidative stress-induced dysfunction and death of primary cultured hippocampal neurons through the AKT-BCL-2 signaling pathway through a mechanism that does not involve the Trk receptors and leads to inhibition of caspase-3 activation.

The story of an exceptional serine protease, tissue-type plasminogen activator (tPA)

The only acute treatment of ischemic stroke approved by the health authorities is tissue recombinant plasminogen activator (tPA)-induced thrombolysis. Under physiological conditions, tPA, belonging to the serine protease family, is secreted by endothelial and brain cells (neurons, astrocytes, microglia, oligodendrocytes). Although revascularisation induced by tPA is beneficial during a stroke, research over the past 20 years shows that tPA can also be deleterious for the brain parenchyma. Thus, in this review of the literature, after a brief history on the discovery of tPA, we reviewed current knowledge of mechanisms by which tPA can influence brain function in physiological and pathological conditions.

Impacts of tissue-type plasminogen activator (tPA) on neuronal survival

Tissue-type plasminogen activator (tPA) a serine protease is constituted of five functional domains through which it interacts with different substrates, binding proteins, and receptors. In the last years, great interest has been given to the clinical relevance of targeting tPA in different diseases of the central nervous system, in particular stroke. Among its reported functions in the central nervous system, tPA displays both neurotrophic and neurotoxic effects. How can the protease mediate such opposite functions remain unclear but several hypotheses have been proposed. These include an influence of the degree of maturity and/or the type of neurons, of the level of tPA, of its origin (endogenous or exogenous) or of its form (single chain tPA versus two chain tPA). In this review, we will provide a synthetic snapshot of our current knowledge regarding the natural history of tPA and discuss how it sustains its pleiotropic functions with focus on excitotoxic/ischemic neuronal death and neuronal survival.

Neuroprotective effect of neuroserpin in oxygen-glucose deprivation- and reoxygenation-treated rat astrocytes in vitro

Neuroserpin (NSP) reportedly exerts neuroprotective effects in cerebral ischemic animal models and patients; however, the mechanism of protection is poorly understood. We thus attempted to confirm neuroprotective effects of NSP on astrocytes in the ischemic state and then explored the relative mechanisms. Astrocytes from neonatal rats were treated with oxygen-glucose deprivation (OGD) followed by reoxygenation (OGD/R). To confirm the neuroprotective effects of NSP, we measured the cell survival rate, relative lactate dehydrogenase (LDH) release; we also performed morphological methods, namely Hoechst 33342 staining and Annexin V assay. To explore the potential mechanisms of NSP, the release of nitric oxide (NO) and TNF-α related to NSP administration were measured by enzyme-linked immunosorbent assay. The proteins related to the NF-κB, ERK1/2, and PI3K/Akt pathways were investigated by Western blotting. To verify the cause-and-effect relationship between neuroprotection and the NF-κB pathway, a NF-κB pathway inhibitor sc3060 was employed to observe the effects of NSP-induced neuroprotection. We found that NSP significantly increased the cell survival rate and reduced LDH release in OGD/R-treated astrocytes. It also reduced NO/TNF-α release. Western blotting showed that the protein levels of p-IKKBα/β and P65 were upregulated by the OGD/R treatment and such effects were significantly inhibited by NSP administration. The NSP-induced inhibition could be significantly reversed by administration of the NF-κB pathway inhibitor sc3060, whereas, expressions of p-ERK1, p-ERK2, and p-AKT were upregulated by the OGD/R treatment; however, their levels were unchanged by NSP administration. Our results thus verified the neuroprotective effects of NSP in ischemic astrocytes. The potential mechanisms include inhibition of the release of NO/TNF-α and repression of the NF-κB signaling pathways. Our data also indicated that NSP has little influence on the MAPK and PI3K/Akt pathways.

Tissue plasminogen activator-independent roles of neuroserpin in the central nervous system

A number of studies have confirmed the existence of tissue-type plasminogen activator-independent roles of neuroserpin, a member of the serine protease inhibitor superfamily. In this review article, we aim to clarify this role. These unique roles of neuroserpin are involved in its neuroprotective effect during ischemic brain injury, its regulation of tumorigenesis, and the mediation of emotion and cognition through the inhibition of urokinase-type plasminogen activator and fibrinolysin, modification of Th cells, reducing plaque formation, promoting process growth and intracellular adhesion, and altering the expression of cadherin and nuclear factor kappa B.

The calmodulin-dependent protein kinase II inhibitor KN-93 protects rat cerebral cortical neurons from N-methyl-D-aspartic acid-induced injury

In this study, primary cultured cerebral cortical neurons of Sprague-Dawley neonatal rats were treated with 0.25, 0.5, and 1.0 μM calmodulin-dependent protein kinase II inhibitor KN-93 after 50 μM N-methyl-D-aspartic acid-induced injury. Results showed that, compared with N-methyl-Daspartic acid-induced injury neurons, the activity of cells markedly increased, apoptosis was significantly reduced, leakage of lactate dehydrogenase decreased, and intracellular Ca(2+) concentrations in neurons reduced after KN-93 treatment. The expression of caspase-3, phosphorylated calmodulin-dependent protein kinase II and total calmodulin-dependent protein kinase II protein decreased after KN-93 treatment. And the effect was apparent at a dose of 1.0 μM KN-93. Experimental findings suggest that KN-93 can induce a dose-dependent neuroprotective effect, and that the underlying mechanism may be related to the down-regulation of caspase-3 and calmodulin- dependent protein kinase II expression.

Sterol metabolism regulates neuroserpin polymer degradation in the absence of the unfolded protein response in the dementia FENIB

Mutants of neuroserpin are retained as polymers within the endoplasmic reticulum (ER) of neurones to cause the autosomal dominant dementia familial encephalopathy with neuroserpin inclusion bodies or FENIB. The cellular consequences are unusual in that the ordered polymers activate the ER overload response (EOR) in the absence of the canonical unfolded protein response. We use both cell lines and Drosophila models to show that the G392E mutant of neuroserpin that forms polymers is degraded by UBE2j1 E2 ligase and Hrd1 E3 ligase while truncated neuroserpin, a protein that lacks 132 amino acids, is degraded by UBE2g2 (E2) and gp78 (E3) ligases. The degradation of G392E neuroserpin results from SREBP-dependent activation of the cholesterol biosynthetic pathway in cells that express polymers of neuroserpin (G392E). Inhibition of HMGCoA reductase, the limiting enzyme of the cholesterol biosynthetic pathway, reduced the ubiquitination of G392E neuroserpin in our cell lines and increased the retention of neuroserpin polymers in both HeLa cells and primary neurones. Our data reveal a reciprocal relationship between cholesterol biosynthesis and the clearance of mutant neuroserpin. This represents the first description of a link between sterol metabolism and modulation of the proteotoxicity mediated by the EOR.

Expression of neuroserpin, a selective inhibitor of tissue-type plasminogen activator in the human skin

Serine protease of the fibrinolytic system and their specific inhibitors, the serine protease inhibitors (SERPINs) are implicated in a number of physiological and pathological processes in skin. The main SERPIN is the plasminogen activator inhibitor-1 (or PAI-1), which is involved in wound healing and in pathogenesis of several diseases including skin fibrosis. Another member of SERPIN superfamily, the neuroserpin (NSP), is widely expressed in the central nervous system. It has been recently detected in different organs such as pancreas, heart, kidney and testis. In this study, we provided evidences for the presence of NSP in the skin, in 10 human skin samples (HSS) at mRNA level (RT-PCR) and protein level (Western blot and immunohistochemistry). The immunohistochemistry analysis showed that this expression was located in dermis around blood vessels.

Neuroprotection by urokinase plasminogen activator in the hippocampus

Tissue plasminogen activator (tPA) and urokinase plasminogen activator (uPA), which are both used for thrombolytic treatment of acute ischemic stroke, are serine proteases that convert plasminogen to active plasmin. Although recent experimental evidences have raised controversy about the neurotoxic versus neuroprotective roles of tPA in acute brain injury, uPA remains unexplored in this context. In this study, we evaluated the effect of uPA on neuronal death in the hippocampus of mice after kainate-induced seizures. In the normal brain, uPA was localized to both nuclei and cytosol of neurons. Following severe kainate-induced seizures, uPA completely disappeared in degenerating neurons, whereas uPA-expressing astrocytes substantially increased, suggesting reactive astrogliosis. uPA-knockout mice were more vulnerable to kainate-induced neuronal death than wild-type mice. Consistent with this, inhibition of uPA by intracerebral injection of the uPA inhibitor UK122 increased the level of neuronal death. In contrast, prior administration of recombinant uPA significantly attenuated neuronal death. Collectively, these results indicate that uPA renders neurons resistant to kainate-induced excitotoxicity. Moreover, recombinant uPA suppressed cell death in primary cultures of hippocampal neurons exposed to H2O2, zinc, or various excitotoxins, suggesting that uPA protects against neuronal injuries mediated by the glutamate receptor, or by oxidation- or zinc-induced death signaling pathways. Considering that tPA may facilitate neurodegeneration in acute brain injury, we suggest that uPA, as a neuroprotectant, might be beneficial for the treatment of acute brain injuries such as ischemic stroke.

Encephalopathy with neuroserpin inclusion bodies presenting as progressive myoclonus epilepsy and associated with a novel mutation in the Proteinase Inhibitor 12 gene

Neuroserpin encephalopathy is an autosomal-dominant degenerative disease associated with mutations in the Proteinase Inhibitor 12 (PI12) gene. A 26-year-old male presented with progressive myoclonus epilepsy and declining mental status. He had failed in university studies because of impaired attention, memory and concentration. Generalized seizures started to occur approximately once a month, and he developed myoclonus and progressive gait disturbances. Neuroimaging revealed mild atrophy and multiple periventricular white matter lesions, consistent with demyelination. He progressively declined and died at age 34. Neuropathologic examination revealed widespread involvement of the cerebral cortex by numerous round eosinophilic inclusions in neuronal perikarya and neuropil, predominantly within the deep cortical layers. Numerous inclusions were also found in the basal ganglia, thalamus, hippocampus, brain stem, spinal gray matter, and dorsal root ganglia. They were essentially absent from the cerebellum. The inclusions were immunopositive for antibodies raised against neuroserpin. The white matter lesions showed histologic features compatible with multiple sclerosis. Genetic analysis revealed a nucleotide substitution in codon 47 in one allele of the PI12 gene, resulting in a proline for leucine amino acid substitution (L47P). In summary, we report a case of neuroserpin encephalopathy associated with a novel PI12 mutation and complicated by coexistent multiple sclerosis.

Serine proteases, serine protease inhibitors, and protease-activated receptors: roles in synaptic function and behavior

Serine proteases, serine protease inhibitors, and protease-activated receptors have been intensively investigated in the periphery and their roles in a wide range of processes-coagulation, inflammation, and digestion, for example-have been well characterized (see Coughlin, 2000; Macfarlane et al., 2001; Molinari et al., 2003; Wang et al., 2008; Di Cera, 2009 for reviews). A growing number of studies demonstrate that these protein systems are widely expressed in many cell types and regions in mammalian brains. Accumulating lines of evidence suggest that the brain has co-opted the activities of these interesting proteins to regulate various processes underlying synaptic activity and behavior. In this review, we discuss emerging roles for serine proteases in the regulation of mechanisms underlying synaptic plasticity and memory formation.

Association between neuroserpin and molecular markers of brain damage in patients with acute ischemic stroke

BACKGROUND

Neuroserpin has shown neuroprotective effects in animal models of cerebral ischemia and has been associated with functional outcome after ischemic stroke. Our aim was to study whether neuroserpin serum levels could be associated to biomarkers of excitotoxicity, inflammation and blood brain barrier disruption.

METHODS

We prospectively included 129 patients with ischemic stroke (58.1% male; mean age, 72.4 ± 9.6 years) not treated with tPA within 12 hours (h) of symptoms onset (mean time, 4.7 ± 2.1 h). Poor functional outcome at 3 months was considered as a modified Rankin scale score >2. Serum levels of neuroserpin, Interleukin 6 (IL-6), Intercellular adhesion molecule-1 (ICAM-1), active Matrix metalloproteinase 9 (MMP-9), and cellular fibronectin (cFn) (determined by ELISA) and glutamate (determined by HPLC) were measured on admission, 24 and 72 h. The main variable was considered the decrease of neuroserpin levels within the first 24 h. ROC analysis was used to select the best predictive value for neuroserpin to predict poor functional outcome due to a lack of linearity.

RESULTS

The decrease of neuroserpin levels within the first 24 h was negatively correlated with serum levels at 24 hours of glutamate (r = -0.642), IL-6 (r = -0.678), ICAM-1 (r = -0.345), MMP-9 (r = -0.554) and cFn (r = -0.703) (all P < 0.0001). In the multivariate analysis, serum levels of glutamate (OR, 1.04; CI95%, 1.01-1.06, p = 0.001); IL-6 (OR, 1.4; CI95%, 1.1-1.7, p = 0.001); and cFn (OR, 1.3; CI95%, 1.1-1.6, p = 0.002) were independently associated with a decrease of neuroserpin levels <70 ng/mL at 24 h after adjusting for confounding factors.

CONCLUSIONS

These findings suggest that neuroprotective properties of neuroserpin may be related to the inhibition of excitotoxicity, inflammation, as well as blood brain barrier disruption that occur after acute ischemic stroke.

Neuroprotective effect of neuroserpin in rat primary cortical cultures after oxygen and glucose deprivation and tPA

Besides its role as a thrombolytic agent, tissue plasminogen activator (tPA) triggers harmful effects in the brain parenchyma after stroke, such as inflammation, excitotoxicity and basal lamina degradation. Neuroserpin, a natural inhibitor of tPA, has shown neuroprotective effects in animal models of brain infarct. However, the molecular mechanisms of neuroserpin-mediated neuroprotection after brain ischemia remain to be well characterized. Then, our aim was to investigate such mechanisms in primary mixed cortical cell cultures after oxygen and glucose deprivation (OGD). Primary rat mixed cortical cultures containing both astrocytes and neurons were subjected to OGD for 150min and subsequently treated with either tPA (5μg/mL), neuroserpin (0.125, 0.25, 0.5 or 1μM), and tPA together with neuroserpin at the mentioned doses. Twenty-four hours after treatment, LDH release, caspase-3 activity, MCP-1, MIP-2, active MMP-9, GRO/KC and COX-2 were measured. Statistical differences were analyzed using Student's t-test or one-way ANOVA as appropriate. Treatment with tPA after OGD increased LDH release, active MMP-9, MCP-1 and MIP-2 (all p≤0.05), but not caspase-3, GRO/KC or COX-2 compared to control. Treatment with neuroserpin after OGD decreased LDH release and active MMP-9 (all p≤0.05). It had no effect on caspase-3 activity, or on MCP-1, MIP-2, GRO/KC or COX-2 expression compared to control. Administration of tPA together with neuroserpin decreased LDH release, active MMP-9 and MIP-2 (all p≤0.05) and showed no effect on MCP-1, GRO/KC or COX-2 compared to control. Our results suggest that neuroprotective activity of neuroserpin involves attenuation on tPA-mediated mechanisms of inflammation and BBB disruption after brain ischemia.

Aprotinin confers neuroprotection by reducing apoptotic cell death

Aprotinin has been used in pediatric cardiac surgery for its antiinflammatory and hemostatic benefits. We have reported that aprotinin has a direct cellular neuroprotective effect through reduction of excitotoxicity. The purpose of this study was to investigate whether aprotinin is neuroprotective against apoptotic cell death. Near-pure neuronal cultures containing <5% astrocytes were obtained from fetal mice. Serum deprivation was initiated at 7 days by transferring the cultures, which are dependent on serum for survival, into growth medium lacking serum for 24 h. Neuronal cell death was assessed by phase-contrast cell counting after staining with 0.4% trypan blue dye. Aprotinin at a clinically relevant concentration of 100 KIU.mL(-1) significantly reduced apoptotic neuronal cell death from 84.4% to 51.8%. This result suggests that aprotinin has the potential to reduce brain injury resulting from apoptotic cell death induced by an ischemic insult. Additional studies are needed to evaluate the potential of aprotinin to reduce neurological injury in patients at high risk of cerebral injury, including those undergoing circulatory arrest.

Molecular insights and therapeutic targets for blood-brain barrier disruption in ischemic stroke: critical role of matrix metalloproteinases and tissue-type plasminogen activator

Blood-brain barrier (BBB) disruption, mediated through matrix metalloproteinases (MMPs) and other mechanisms, is a critical event during ischemic stroke. Tissue plasminogen activator (tPA) is the only FDA-approved thrombolytic therapy for acute ischemic stroke, but the efficacy and safety of its therapeutic application are limited by narrow treatment time windows and side effects. Thus, there is a pressing need to develop combinational therapy that could offset tPA side effects and improve efficacy in clinical practice. Recent experimental studies indicate that tPA has previously unidentified functions in the brain beyond its well-established thrombolytic activity, which might contribute to tPA-related side effects through MMPs (mainly MMP-9) and several signaling pathways involved in LDL receptor-related protein (LRP), activated protein C (APC) and protease-activated receptor 1 (PAR-1), platelet-derived growth factor C (PDGF-C), and N-methyl-d-aspartate (NMDA) receptor. Therapeutic targeting of MMPs and/or tPA-related signaling pathways might offer promising new approaches to combination therapies for ischemic stroke. This review provides an overview of the relationship between structural components and function of the BBB/neurovascular unit with respect to ischemic stroke. We discuss how MMPs and tPA contribute to BBB disruption during ischemic stroke and highlight recent findings of molecular signaling pathways involved in neurotoxicity of tPA therapy.

pH-dependent stability of neuroserpin is mediated by histidines 119 and 138; implications for the control of beta-sheet A and polymerization

Neuroserpin is a member of the serpin superfamily. Point mutations in the neuroserpin gene underlie the autosomal dominant dementia, familial encephalopathy with neuroserpin inclusion bodies. This is characterized by the retention of ordered polymers of neuroserpin within the endoplasmic reticulum of neurons. pH has been shown to affect the propensity of several serpins to form polymers. In particular, low pH favors the formation of polymers of both alpha(1)-antitrypsin and antithrombin. We report here opposite effects in neuroserpin, with a striking resistance to polymer formation at acidic pH. Mutation of specific histidine residues showed that this effect is not attributable to the shutter domain histidine as would be predicted by analogy with other serpins. Indeed, mutation of the shutter domain His338 decreased neuroserpin stability but had no effect on the pH dependence of polymerization when compared with the wild-type protein. In contrast, mutation of His119 or His138 reduced the polymerization of neuroserpin at both acidic and neutral pH. These residues are at the lower pole of neuroserpin and provide a novel mechanism to control the opening of beta-sheet A and hence polymerization. This mechanism is likely to have evolved to protect neuroserpin from the acidic environment of the secretory granules.

Regulation of matrix metalloproteinase-9 and tissue plasminogen activator activity by alpha-synuclein in rat primary glial cells

It is increasingly evident that neuroinflammatory response is involved in the pathogenesis of Parkinson's disease. In this study, we examined whether alpha-synuclein, a major components of Lewy body that has been implicated in the modulation of neuroinflammation, regulates MMP-9 and tPA activity, which plays important roles in neurodegeneration as well as regeneration processes, in cultured rat primary glial cells. Monomeric alpha-synuclein dose-dependently increased MMP-9 but not MMP-2 activity as well as mRNA level from cultured rat primary astrocytes and microglial cells. Maximal stimulation was observed at 50 nM alpha-synuclein. In contrast, the activity of tPA was decreased by alpha-synuclein with only marginal changes in the level of mRNA encoding tPA, if any. Interestingly, same concentration of alpha-synuclein aggregates did not induce MMP-9 activity. Overexpression of alpha-synuclein in rat primary astrocytes similarly increased MMP-9 activity. Treatment of alpha-synuclein increased the phosphorylation of ERK1/2 and the inhibition of ERK1/2 reversed the changes in MMP-9 and tPA activity. These results suggest further functional role of alpha-synuclein via regulation of protease systems through modulation of ERK1/2 activity in brain.

Aprotinin protects the cerebral microcirculation during cardiopulmonary bypass

BACKGROUND AND OBJECTIVE

We have previously reported that administration of aprotinin at a single dose protects the cerebral microcirculation. The current study was designed to identify the optimal dose for protecting the cerebral microcirculation with assessment of neurological and behavioral recovery as well as renal function after circulatory arrest and ultra-low-flow bypass.

METHODS

Twenty-four piglets were randomly assigned to three bypass groups at risk for postoperative cerebral and renal dysfunction. Cerebral microcirculation was assessed by intravital microscopy. Rhodamine-stained leukocytes were observed for adhesion and rolling. Animals were randomized to one of four aprotinin doses. Neurological deficit score, histological score, creatinine and blood urea nitrogen were analyzed, both independently for this study as well as in combination with 50 animals who were studied with the same protocol and near-infrared spectroscopy.

RESULTS

There was a dose-dependent relationship, resulting in fewer activated rolling leukocytes with a higher aprotinin dose. Aprotinin dose was an independent predictor of more rapid recovery of neurological and behavioral outcome. We present a linear regression model where aprotinin dose predicts neurological score. Aprotinin had no impact on renal function.

CONCLUSIONS

Aprotinin reduces cerebral leukocyte activation and accelerates neurologic recovery in a dose-dependent fashion. Aprotinin has no measurable impact on standard indices of renal function in young piglets. The current lack of availability of aprotinin is a serious disadvantage for pediatric patients undergoing cardiopulmonary bypass.

Conformational pathology of the serpins: themes, variations, and therapeutic strategies

Point mutations cause members of the serine protease inhibitor (serpin) superfamily to undergo a novel conformational transition, forming ordered polymers. These polymers characterize a group of diseases termed the serpinopathies. The formation of polymers underlies the retention of alpha(1)-antitrypsin within hepatocytes and of neuroserpin within neurons to cause cirrhosis and dementia, respectively. Point mutations of antithrombin, C1 inhibitor, alpha(1)-antichymotrypsin, and heparin cofactor II cause a similar conformational transition, resulting in a plasma deficiency that is associated with thrombosis, angioedema, and emphysema. Polymers of serpins can also form in extracellular tissues where they activate inflammatory cascades. This is best described for the Z variant of alpha(1)-antitrypsin in which the proinflammatory properties of polymers provide an explanation for both progressive emphysema and the selective advantage of this mutant allele. Therapeutic strategies are now being developed to block the aberrant conformational transitions and so treat the serpinopathies.

The 2.1-A crystal structure of native neuroserpin reveals unique structural elements that contribute to conformational instability

Neuroserpin is a selective inhibitor of tissue-type plasminogen activator (tPA) that plays an important role in neuronal plasticity, memory, and learning. We report here the crystal structure of native human neuroserpin at 2.1 A resolution. The structure has a helical reactive center loop and an omega loop between strands 1B and 2B. The omega loop contributes to the inhibition of tPA, as deletion of this motif reduced the association rate constant with tPA by threefold but had no effect on the kinetics of interaction with urokinase. Point mutations in neuroserpin cause the formation of ordered intracellular polymers that underlie dementia familial encephalopathy with neuroserpin inclusion bodies (FENIB). Wild-type neuroserpin is also unstable and readily forms polymers under near-physiological conditions in vitro. This is, in part, due to the substitution of a conserved alanine for serine at position 340. The replacement of Ser340 by Ala increased the melting temperature by 3 degrees C and reduced polymerization as compared to wild-type neuroserpin. Similarly, neuroserpin has Asn-Leu-Val at the end of helix F and thus differs markedly from the Gly-X-Ile consensus sequence of the serpins. Restoration of these amino acids to the consensus sequence increased thermal stability and reduced the polymerization of neuroserpin and its transition to the latent conformer. Moreover, introduction of the consensus sequence into S49P neuroserpin that causes FENIB increased the stability and inhibitory activity of the mutant, as well as blocked polymerization and increased the yield of protein during refolding. These data provide a molecular explanation for the inherent instability of neuroserpin and the effect of point mutations that underlie the dementia FENIB.

Optimal dose of aprotinin for neuroprotection and renal function in a piglet survival model

OBJECTIVE

The efficacy of aprotinin in reducing blood loss after cardiopulmonary bypass is well established, although its neuroprotective potential is less well known. Furthermore, there is controversy regarding optimal dosing and possible renal complications.

METHODS

Fifty-four piglets were randomized to one of 3 cardiopulmonary bypass groups designed to carry the risk of postoperative cerebral and renal dysfunction: circulatory arrest at 25 degrees C and ultra-low flow bypass (10 mL x kg(-1) x min(-1)) at either 25 degrees C or 34 degrees C. Animals were randomized to the following groups: control (no aprotinin), low dose (30,000 KIU/kg into prime only), standard full dose (30,000 KIU/kg bolus administered intravenously into prime plus 10,000 KIU/kg infusion), and double full dose. The tissue oxygenation index was monitored by means of near-infrared spectroscopy. Neurologic functional and histologic scores and creatinine and blood urea nitrogen values were outcomes of interest.

RESULTS

Aprotinin significantly improved neurologic scores on postoperative day 1 after ultra-low-flow bypass at 25 degrees C or 34 degrees C (P < .01) but not after hypothermic circulatory arrest (P = .57). Linear regression indicated a strong dose-response relationship, with higher aprotinin doses having the best neurologic scores. During low-flow bypass, a higher tissue oxygenation index was correlated with a higher aprotinin dose (P < .05). Aprotinin dose had no significant effect on creatinine or blood urea nitrogen values on day 1. Low body weight was the only predictor of high blood urea nitrogen values (r = -0.39, P < .01).

CONCLUSION

Aprotinin significantly improves neurologic recovery without compromising renal function in the young piglet.

Anti-Mullerian-hormone-dependent regulation of the brain serine-protease inhibitor neuroserpin

The balance between tissue-type plasminogen activator (tPA) and one of its inhibitors, neuroserpin, has crucial roles in the central nervous system, including the control of neuronal migration, neuronal plasticity and neuronal death. In the present study, we demonstrate that the activation of the transforming growth factor-beta (TGFbeta)-related BMPR-IB (also known as BMPR1B and Alk6)- and Smad5-dependent signalling pathways controls neuroserpin transcription. Accordingly, we demonstrate for the first time that anti-Mullerian hormone (AMH), a member of the TGFbeta family, promotes the expression of neuroserpin in cultured neurons but not in astrocytes. The relevance of these findings is confirmed by the presence of both AMH and AMH type-II receptor (AMHR-II) in brain tissues, and is supported by the observation of reduced levels of neuroserpin in the brain of AMHR-II-deficient mice. Interestingly, as previously demonstrated for neuroserpin, AMH protects neurons against N-methyl-D-aspartate (NMDA)-mediated excitotoxicity both in vitro and in vivo. This study demonstrates the existence of an AMH-dependent signalling pathway in the brain leading to an overexpression of the serine-protease inhibitor, neuroserpin, and neuronal survival.