Thrombin and prothrombin are expressed by neurons and glial cells and accumulate in neurofibrillary tangles in Alzheimer disease brain

Review of the potential pharmacological role of erucic acid: a monounsaturated omega-9 fatty acid

This comprehensive review aims to provide an overview of the pharmacological properties of erucic acid (EA) and highlight areas that require further research. EA is an omega-9 fatty acid found in certain vegetable oil, such as rapeseed oil has demonstrated favourable effects in rodents, including ameliorating myocardial lipidosis (fat accumulation in the heart muscle), congestive heart disease, hepatic steatosis (fat accumulation in the liver), and memory impairments. These findings have prompted regulatory bodies to establish limits on EA content in food oils. The studies were performed on rodents and led to caution on ingesting the EA at high levels. Moreover, EA is frequently utilized as a nutritional supplement for the treatment of adrenoleukodystrophy, myocardial disease, and memory improvement. The review of the article indicated that EA improves cognitive function, has a part in Huntington's disease, interacts with peroxisome proliferator-activated receptors, inhibits elastase and thrombin, has anti-inflammatory, antioxidant, and anti-tumour properties, and inhibits influenza A virus. This article elucidates the pharmacological effects of EA, an omega-9 fatty acid.

Argatroban promotes recovery of spinal cord injury by inhibiting the PAR1/JAK2/STAT3 signaling pathway

Argatroban is a synthetic thrombin inhibitor approved by U.S. Food and Drug Administration for the treatment of thrombosis. However, whether it plays a role in the repair of spinal cord injury is unknown. In this study, we established a rat model of T10 moderate spinal cord injury using an NYU Impactor Moder III and performed intraperitoneal injection of argatroban for 3 consecutive days. Our results showed that argatroban effectively promoted neurological function recovery after spinal cord injury and decreased thrombin expression and activity in the local injured spinal cord. RNA sequencing transcriptomic analysis revealed that the differentially expressed genes in the argatroban-treated group were enriched in the JAK2/STAT3 pathway, which is involved in astrogliosis and glial scar formation. Western blotting and immunofluorescence results showed that argatroban downregulated the expression of the thrombin receptor PAR1 in the injured spinal cord and the JAK2/STAT3 signal pathway. Argatroban also inhibited the activation and proliferation of astrocytes and reduced glial scar formation in the spinal cord. Taken together, these findings suggest that argatroban may inhibit astrogliosis by inhibiting the thrombin-mediated PAR1/JAK2/STAT3 signal pathway, thereby promoting the recovery of neurological function after spinal cord injury.

A novel target-triggered signal chemiluminescence kit for thrombin detection based on fusiform Au/MIL-53(Fe)

In this work, a fusiform Au/MIL-53(Fe) catalyst was used to construct a chemiluminescence (CL) kit for the sensitive and rapid detection of thrombin (THR). The porous silica microspheres encapsulated with luminol in holes by thrombin aptamer (THR-APT/Luminol/SPSiO2) and the fusiform Au/MIL-53(Fe) modified with thrombin aptamer complementary chains (Au/MIL-53(Fe)-SSDNA) were prepared. Then, a CL kit for THR detection was constructed by using the prepared composites. When thrombin is added to the reaction system, it binds to its aptamer (THR-APT) to open the holes of SPSiO2, which cause luminol and Au/MIL-53(Fe) release. Released luminol enters the detection system and triggers the reaction of luminol-H2O2-NaOH with the catalyst of Au/MIL-53(Fe), and produces a CL signal. The detection limit and the linear range of the kit were 4.7 × 10-15 M and 1.5 × 10-14 - 3.5 × 10-10 M, respectively. The CL kit also showed high stability, selectivity and reproducibility, and was successfully applied to the determination of THR in serum samples. Therefore, the proposed method for detecting THR has great application potential in the diagnosis of blood-related disease markers.

Intrinsic SERS Fingerprints of Aptamer-Peptide Conjugates for Direct High-Specific Profiling Abnormal Protein Levels in Cancer Patients

Surface-enhanced Raman spectroscopy (SERS) with ultrasensitive vibrational fingerprints enables quick identification and trace detection of various kinds of molecules. But proteins usually have low Raman cross sections and are difficult to generate recognizable signals in direct SERS detection. Recently, nucleic acid-peptide conjugates are emerging with great potential in structuring, assembling, catalyzing, sensing, etc., and the coupling of aptamers further enables superior biological recognition and programmability. Here, we develop the aptamer-peptide conjugates as a new kind of SERS probe for direct high-specific profiling abnormal protein levels in cancer patients. The aptamer conjugated with glutathione (GSH) functions as both the recognition element and the SERS reporters that can simultaneously generate SERS fingerprints of both peptides and nucleic acids. This kind of biocompatible probe appears to have excellent performance in high-salt environments and realizes rapid, simple, and multisignal detection of thrombin (TB). Data-driven soft independent modeling of class analogy (DD-SIMCA) is used to distinguish SERS profiles of actual blood samples and realize the identification and classification of cancer patients. Furthermore, the effect of low-temperature storage time on blood samples is analyzed by tracking the changes of SERS profiles; the results hint that plasma samples stored under 4 °C for more than 2 days could generate false negative results due to TB hydrolysis, which has important implications for clinical sample analysis. This kind of nucleic acid-peptide conjugate provides new ideas for SERS sensing strategy in the future.

Bioinformatic analysis of the SPs and NFTs proteomes unravel putative biomarker candidates for Alzheimer's disease

Aging is the main risk factor for the appearance of age-related neurodegenerative diseases, including Alzheimer's disease (AD). AD is the most common form of dementia, characterized by the presence of senile plaques (SPs) and neurofibrillary tangles (NFTs), the main histopathological hallmarks in AD brains. The core of these deposits are predominantly amyloid fibrils in SPs and hyperphosphorylated Tau protein in NFTs, but other molecular components can be found associated with these pathological lesions. Herein, an extensive literature review was carried out to obtain the SPs and NFTs proteomes, followed by a bioinformatic analysis and further putative biomarker validation. For SPs, 857 proteins were recovered, and, for NFTs, 627 proteins of which 375 occur in both groups and represent the common proteome. Gene Ontology (GO) enrichment analysis permitted the identification of biological processes and the molecular functions most associated with these lesions. Analysis of the SPs and NFTs common proteins unraveled pathways and molecular targets linking both histopathological events. Further, validation of a putative phosphotarget arising from the in silico analysis was performed in serum-derived extracellular vesicles from AD patients. This bioinformatic approach contributed to the identification of putative molecular targets, valuable for AD diagnostic or therapeutic intervention.

Whey protein powder with milk fat globule membrane attenuates Alzheimer's disease pathology in 3×Tg-AD mice by modulating neuroinflammation through the peroxisome proliferator-activated receptor γ signaling pathway

Whey protein powder (PP), which is mainly derived from bovine milk, is rich in milk fat globule membrane (MFGM). The MGFM has been shown to play a role in promoting neuronal development and cognition in the infant brain. However, its role in Alzheimer's disease (AD) has not been elucidated. Here, we showed that the cognitive ability of 3×Tg-AD mice (a triple-transgenic mouse model of AD) could be improved by feeding PP to mice for 3 mo. In addition, PP ameliorated amyloid peptide deposition and tau hyperphosphorylation in the brains of AD mice. We found that PP could alleviate AD pathology by inhibiting neuroinflammation through the peroxisome proliferator-activated receptor γ (PPARγ)-nuclear factor-κB signaling pathway in the brains of AD mice. Our study revealed an unexpected role of PP in regulating the neuroinflammatory pathology of AD in a mouse model.

C/EBPβ/AEP Signaling Drives Alzheimer's Disease Pathogenesis

Alzheimer's disease (AD) is the most common type of dementia. Almost two-thirds of patients with AD are female. The reason for the higher susceptibility to AD onset in women is unclear. However, hormone changes during the menopausal transition are known to be associated with AD. Most recently, we reported that follicle-stimulating hormone (FSH) promotes AD pathology and enhances cognitive dysfunctions via activating the CCAAT-enhancer-binding protein (C/EBPβ)/asparagine endopeptidase (AEP) pathway. This review summarizes our current understanding of the crucial role of the C/EBPβ/AEP pathway in driving AD pathogenesis by cleaving multiple critical AD players, including APP and Tau, explaining the roles and the mechanisms of FSH in increasing the susceptibility to AD in postmenopausal females. The FSH-C/EBPβ/AEP pathway may serve as a novel therapeutic target for the treatment of AD.

Pathophysiological Role of Microglial Activation Induced by Blood-Borne Proteins in Alzheimer's Disease

The blood-brain barrier (BBB) restricts entry of neurotoxic plasma components, blood cells, and pathogens into the brain, leading to proper neuronal functioning. BBB impairment leads to blood-borne protein infiltration such as prothrombin, thrombin, prothrombin kringle-2, fibrinogen, fibrin, and other harmful substances. Thus, microglial activation and release of pro-inflammatory mediators commence, resulting in neuronal damage and leading to impaired cognition via neuroinflammatory responses, which are important features observed in the brain of Alzheimer's disease (AD) patients. Moreover, these blood-borne proteins cluster with the amyloid beta plaque in the brain, exacerbating microglial activation, neuroinflammation, tau phosphorylation, and oxidative stress. These mechanisms work in concert and reinforce each other, contributing to the typical pathological changes in AD in the brain. Therefore, the identification of blood-borne proteins and the mechanisms involved in microglial activation and neuroinflammatory damage can be a promising therapeutic strategy for AD prevention. In this article, we review the current knowledge regarding the mechanisms of microglial activation-mediated neuroinflammation caused by the influx of blood-borne proteins into the brain via BBB disruption. Subsequently, the mechanisms of drugs that inhibit blood-borne proteins, as a potential therapeutic approach for AD, along with the limitations and potential challenges of these approaches, are also summarized.

PARIN5, a Novel Thrombin Receptor Antagonist Modulates a Streptozotocin Mice Model for Diabetic Encephalopathy

Diabetic encephalopathy (DE) is an inflammation-associated diabetes mellitus (DM) complication. Inflammation and coagulation are linked and are both potentially modulated by inhibiting the thrombin cellular protease-activated receptor 1 (PAR1). Our aim was to study whether coagulation pathway modulation affects DE. Diabetic C57BL/6 mice were treated with PARIN5, a novel PAR1 modulator. Behavioral changes in the open field and novel object recognition tests, serum neurofilament (NfL) levels and thrombin activity in central and peripheral nervous system tissue (CNS and PNS, respectively), brain mRNA expression of tumor necrosis factor α (TNF-α), Factor X (FX), prothrombin, and PAR1 were assessed. Subtle behavioral changes were detected in diabetic mice. These were accompanied by an increase in serum NfL, an increase in central and peripheral neural tissue thrombin activity, and TNF-α, FX, and prothrombin brain intrinsic mRNA expression. Systemic treatment with PARIN5 prevented the appearance of behavioral changes, normalized serum NfL and prevented the increase in peripheral but not central thrombin activity. PARIN5 treatment prevented the elevation of both TNF-α and FX but significantly elevated prothrombin expression. PARIN5 treatment prevents behavioral and neural damage in the DE model, suggesting it for future clinical research.

pKr-2 induces neurodegeneration via upregulation of microglial TLR4 in the hippocampus of AD brain

We recently demonstrated that prothrombin kringle-2 (pKr-2) derived from blood-brain barrier (BBB) disruption could induce hippocampal neurodegeneration and object recognition impairment through neurotoxic inflammatory responses in the five familial Alzheimer's disease mutation (5XFAD) mice. In the present study, we aimed to determine whether pKr-2 induces microglial activation by stimulating toll-like receptor 4 (TLR4) upregulation and examine whether this response contributes to pKr-2-induced neuroinflammatory damage in the hippocampi of mice models. We observed that inflammatory responses induced by pKr-2 administration in the hippocampi of wild-type mice were significantly abrogated in TLR4-deficient mice (TLR4^-/-), and caffeine supply or rivaroxaban treatment that inhibits the overexpression of hippocampal pKr-2 reduced TLR4 upregulation in 5XFAD mice, resulting in the inhibition of neuroinflammatory responses. Similar to the expression patterns of pKr-2, TLR4, and the TLR4 transcription factors, PU.1 and p-c-Jun, seen in the postmortem hippocampal tissues of Alzheimer's disease (AD) patients, our results additionally showed the influence of transcriptional regulation on TLR4 expression following pKr-2 expression in triggering the production of neurotoxic inflammatory mediators. Therefore, we conclude that pKr-2 may play a role in initiating upregulation of microglial TLR4, consequently inducing hippocampal neurodegeneration. Furthermore, the control of pKr-2-induced microglial TLR4 could be a useful therapeutic strategy against hippocampal neurodegeneration in AD.

Key brain cell interactions and contributions to the pathogenesis of Alzheimer's disease

Alzheimer's disease (AD) is the most common neurodegenerative disease worldwide, with the two major hallmarks being the deposition of extracellular β-amyloid (Aβ) plaques and of intracellular neurofibrillary tangles (NFTs). Additionally, early pathological events such as cerebrovascular alterations, a compromised blood-brain barrier (BBB) integrity, neuroinflammation and synaptic dysfunction, culminate in neuron loss and cognitive deficits. AD symptoms reflect a loss of neuronal circuit integrity in the brain; however, neurons do not operate in isolation. An exclusively neurocentric approach is insufficient to understand this disease, and the contribution of other brain cells including astrocytes, microglia, and vascular cells must be integrated in the context. The delicate balance of interactions between these cells, required for healthy brain function, is disrupted during disease. To design successful therapies, it is critical to understand the complex brain cellular connections in AD and the temporal sequence of their disturbance. In this review, we discuss the interactions between different brain cells, from physiological conditions to their pathological reactions in AD, and how this basic knowledge can be crucial for developing new therapeutic strategies.

Accumulation of high molecular weight kininogen in the brains of Alzheimer's disease patients may affect microglial function by altering phagocytosis and lysosomal cathepsin activity

Increased activation of the contact system protein high molecular weight kininogen (HK) has been shown in plasma and cerebrospinal fluid of Alzheimer's disease (AD) patients, but its potential role in the brain has not been explored. We assessed HK levels in brain tissue from 20 AD patients and controls and modeled the effects of HK on microglia-like cells in culture. We show increased levels of HK in the hippocampus of AD patients, which colocalized with amyloid beta (Aβ) deposits and activated microglia. Treatment of microglia with HK led to cell clustering and elevated levels of phagocytosed Aβ. We demonstrate that microglia internalize HK and traffic it to lysosomes, which is accompanied by reduced activity of lysosomal cathepsins L and S. Our results suggest that HK accumulation in the AD hippocampus may alter microglial uptake and degradation of Aβ fibrils, possibly contributing to microglial dysfunction in AD.

Current understanding of the interactions between metal ions and Apolipoprotein E in Alzheimer's disease

Alzheimer's disease (AD), the most common type of dementia in the elderly, is a chronic and progressive neurodegenerative disorder with no effective disease-modifying treatments to date. Studies have shown that an imbalance in brain metal ions, such as zinc, copper, and iron, is closely related to the onset and progression of AD. Many efforts have been made to understand metal-related mechanisms and therapeutic strategies for AD. Emerging evidence suggests that interactions of brain metal ions and apolipoprotein E (ApoE), which is the strongest genetic risk factor for late-onset AD, may be one of the mechanisms for neurodegeneration. Here, we summarize the key points regarding how metal ions and ApoE contribute to the pathogenesis of AD. We further describe the interactions between metal ions and ApoE in the brain and propose that their interactions play an important role in neuropathological alterations and cognitive decline in AD.

Blood-brain barrier leakage in Alzheimer's disease: From discovery to clinical relevance

Alzheimer's disease (AD) is the most common form of dementia. AD brain pathology starts decades before the onset of clinical symptoms. One early pathological hallmark is blood-brain barrier dysfunction characterized by barrier leakage and associated with cognitive decline. In this review, we summarize the existing literature on the extent and clinical relevance of barrier leakage in AD. First, we focus on AD animal models and their susceptibility to barrier leakage based on age and genetic background. Second, we re-examine barrier dysfunction in clinical and postmortem studies, summarize changes that lead to barrier leakage in patients and highlight the clinical relevance of barrier leakage in AD. Third, we summarize signaling mechanisms that link barrier leakage to neurodegeneration and cognitive decline in AD. Finally, we discuss clinical relevance and potential therapeutic strategies and provide future perspectives on investigating barrier leakage in AD. Identifying mechanistic steps underlying barrier leakage has the potential to unravel new targets that can be used to develop novel therapeutic strategies to repair barrier leakage and slow cognitive decline in AD and AD-related dementias.

The Role of Extracellular Matrix Components in the Spreading of Pathological Protein Aggregates

Several neurodegenerative diseases are characterized by the accumulation of aggregated misfolded proteins. These pathological agents have been suggested to propagate in the brain via mechanisms similar to that observed for the prion protein, where a misfolded variant is transferred from an affected brain region to a healthy one, thereby inducing the misfolding and/or aggregation of correctly folded copies. This process has been characterized for several proteins, such as α-synuclein, tau, amyloid beta (Aβ) and less extensively for huntingtin and TDP-43. α-synuclein, tau, TDP-43 and huntingtin are intracellular proteins, and their aggregates are located in the cytosol or nucleus of neurons. They have been shown to spread between cells and this event occurs, at least partially, via secretion of these protein aggregates in the extracellular space followed by re-uptake. Conversely, Aβ aggregates are found mainly extracellularly, and their spreading occurs in the extracellular space between brain regions. Due to the inherent nature of their spreading modalities, these proteins are exposed to components of the extracellular matrix (ECM), including glycans, proteases and core matrix proteins. These ECM components can interact with or process pathological misfolded proteins, potentially changing their properties and thus regulating their spreading capabilities. Here, we present an overview of the documented roles of ECM components in the spreading of pathological protein aggregates in neurodegenerative diseases with the objective of identifying the current gaps in knowledge and stimulating further research in the field. This could potentially lead to the identification of druggable targets to slow down the spreading and/or progression of these pathologies.

Thrombin induces morphological and inflammatory astrocytic responses via activation of PAR1 receptor

Spinal cord injury (SCI) will result in the significant elevation of thrombin production at lesion site via either breakage of blood-spinal cord barrier or upregulated expression within nerve cells. Thrombin-induced activation of the protease activated receptors (PARs) evokes various pathological effects that deteriorate the functional outcomes of the injured cord. The cellular consequences of thrombin action on the astrocytes, as well as the underlying mechanism are not fully elucidated by far. In the present study, SCI model of rats was established by contusion, and primary astrocytes were isolated for culture from newborn rats. The expression levels of thrombin and PAR1 receptor at lesion sites of the spinal cord were determined. The primary astrocytes cultured in vitro were stimulated with different concentration of thrombin, and the resultant morphological changes, inflammatory astrocytic responses, as well as PAR1-activated signal pathway of astrocytes were accordingly examined using various agonists or antagonists of the receptor. Thrombin was found to reverse astrocytic stellation, promote proliferation but inhibit migration of astrocytes. Furthermore, the serine protease was shown to facilitate inflammatory response of astrocytes through regulation of MAPKs/NFκB pathway. Our results have provided the morphological evidence of astrocytic reactivity in response to thrombin stimulation and its neuroinflammatory effects following SCI, which will be indicative for the fundamental insights of thrombin-induced neuropathology.

Are apolipoprotein E fragments a promising new therapeutic target for Alzheimer’s disease?

Human apolipoprotein E (ApoE) is a 299-amino acid secreted glycoprotein that binds cholesterol and phospholipids. ApoE exists as three common isoforms (ApoE2, ApoE3, and ApoE4) and heterozygous carriers of the ε4 allele of the gene encoding ApoE (APOE) have a fourfold greater risk of developing Alzheimer’s disease (AD). The enzymes thrombin, cathepsin D, α-chymotrypsin-like serine protease, and high-temperature requirement serine protease A1 are responsible for ApoE proteolytic processing resulting in bioactive C-terminal-truncated fragments that vary depending on ApoE isoforms, brain region, aging, and neural injury. The objectives of the present narrative review were to describe ApoE processing, discussing current hypotheses about the potential role of various ApoE fragments in AD pathophysiology, and reviewing the current development status of different anti-ApoE drugs. The exact mechanism by which APOE gene variants increase/decrease AD risk and the role of ApoE fragments in the deposition are not fully understood, but APOE is known to directly affect tau-mediated neurodegeneration. ApoE fragments co-localize with neurofibrillary tangles and amyloid β (Aβ) plaques, and may cause neurodegeneration. Among anti-ApoE approaches, a fascinating strategy may be to therapeutically overexpress ApoE2 in APOE ε4/ε4 carriers through vector administration or liposomal delivery systems. Another approach involves reducing ApoE4 expression by intracerebroventricular antisense oligonucleotides that significantly decreased Aβ pathology in transgenic mice. Differences in the proteolytic processing of distinct ApoE isoforms and the use of ApoE fragments as mimetic peptides in AD treatment are also under investigation. Treatment with peptides that mimic the structural and biological properties of native ApoE may reduce Aβ deposition, tau hyperphosphorylation, and glial activation in mouse models of Aβ pathology. Alternative strategies involve the use of ApoE4 structure correctors, passive immunization to target a certain form of ApoE, conversion of the ApoE4 aminoacid sequence into that of ApoE3 or ApoE2, and inhibition of the ApoE-Aβ interaction.

Neurocoagulation from a Mechanistic Point of View in the Central Nervous System

Coagulation mechanisms are critical for maintaining homeostasis in the central nervous system (CNS). Thrombin, an important player of the coagulation cascade, activates protease activator receptors (PARs), members of the G-protein coupled receptor family. PAR1 is located on neurons and glia. Following thrombin activation, PAR1 signals through the extracellular signal-regulated kinase pathway, causing alterations in neuronal glutamate release and astrocytic morphological changes. Similarly, the anticoagulation factor activated protein C (aPC) can cleave PAR1, following interaction with the endothelial protein C receptor. Both thrombin and aPC are expressed on endothelial cells and pericytes in the blood-brain barrier (BBB). Thrombin-induced PAR1 activation increases cytosolic Ca²⁺ concentration in brain vessels, resulting in nitric oxide release and increasing F-actin stress fibers, damaging BBB integrity. aPC also induces PAR1 activation and preserves BBB vascular integrity via coupling to sphingosine 1 phosphate receptors. Thrombin-induced PAR1 overactivation and BBB disruption are evident in CNS pathologies. During epileptic seizures, BBB disruption promotes thrombin penetration. Thrombin induces PAR1 activation and potentiates N-methyl-D-aspartate receptors, inducing glutamate-mediated hyperexcitability. Specific PAR1 inhibition decreases status epilepticus severity in vivo. In stroke, the elevation of brain thrombin levels further compromises BBB integrity, with direct parenchymal damage, while systemic factor Xa inhibition improves neurological outcomes. In multiple sclerosis (MS), brain thrombin inhibitory capacity correlates with clinical presentation. Both thrombin inhibition by hirudin and the use of recombinant aPC improve disease severity in an MS animal model. This review presents the mechanisms underlying the effects of coagulation on the physiology and pathophysiology of the CNS.

A Fluorescence Kinetic-Based Aptasensor Employing Stilbene Isomerization for Detection of Thrombin

It is important to detect thrombin due to its physiological and pathological roles, where rapid and simple analytical approaches are needed. In this study, an aptasensor based on fluorescence attenuation kinetics for the detection of thrombin is presented, which incorporates the features of stilbene and aptamer. We designed and synthesized an aptasensor by one-step coupling of stilbene compound and aptamer, which employed the adaptive binding of the aptamer with thrombin to cause a change in stilbene fluorescence attenuation kinetics. The sensor realized detection of thrombin by monitoring the variation in apparent fluorescence attenuation rate constant (k_app), which could be further used for probing of enzyme–aptamer binding. In comprehensive studies, the developed aptasensor presented satisfactory performance on repeatability, specificity, and regeneration capacity, which realized rapid sensing (10 s) with a limit of detection (LOD) of 0.205 μM. The strategy was successful across seven variants of thrombin aptasensors, with tunable k_app depending on the SITS (4-Acetamido-4′-isothiocyanato-2,2′-stilbenedisulfonic acid disodium salt hydrate) grafting site. Analyte detection mode was demonstrated in diluted serum, requiring no separation or washing steps. The new sensing mode for thrombin detection paves a way for high-throughput kinetic-based sensors for exploiting aptamers targeted at clinically relevant proteins.

Thrombin Signaling Contributes to High Glucose-Induced Injury of Human Brain Microvascular Endothelial Cells

BACKGROUND

Diabetes is one of the strongest disease-related risk factors for Alzheimer's disease (AD). In diabetics, hyperglycemia-induced microvascular complications are the major cause of end-organ injury, contributing to morbidity and mortality. Microvascular pathology is also an important and early feature of AD. The cerebral microvasculature may be a point of convergence of both diseases. Several lines of evidence also implicate thrombin in AD as well as in diabetes.

OBJECTIVE

Our objective was to investigate the role of thrombin in glucose-induced brain microvascular endothelial injury.

METHODS

Cultured Human brain microvascular endothelial cells (HBMVECs) were treated with 30 mM glucose±100 nM thrombin and±250 nM Dabigatran or inhibitors of PAR1, p38MAPK, MMP2, or MMP9. Cytotoxicity and thrombin activity assays on supernatants and western blotting for protein expression in lysates were performed.

RESULTS

reatment of HBMVECs with 30 mM glucose increased thrombin activity and expression of inflammatory proteins TNFα, IL-6, and MMPs 2 and 9; this elevation was reduced by the thrombin inhibitor dabigatran. Direct treatment of brain endothelial cells with thrombin upregulated p38MAPK and CREB, and induced TNFα, IL6, MMP2, and MMP9 as well as oxidative stress proteins NOX4 and iNOS. Inhibition of thrombin, thrombin receptor PAR1 or p38MAPK decrease expression of inflammatory and oxidative stress proteins, implying that thrombin may play a central role in glucose-induced endothelial injury.

CONCLUSION

Since preventing brain endothelial injury would preserve blood-brain barrier integrity, prevent neuroinflammation, and retain intact functioning of the neurovascular unit, inhibiting thrombin, or its downstream signaling effectors, could be a therapeutic strategy for mitigating diabetes-induced dementia.

The Effects of Fibrinogen's Interactions with Its Neuronal Receptors, Intercellular Adhesion Molecule-1 and Cellular Prion Protein

Neuroinflammatory diseases, such as Alzheimer's disease (AD) and traumatic brain injury (TBI), are associated with the extravascular deposition of the fibrinogen (Fg) derivative fibrin and are accompanied with memory impairment. We found that during the hyperfibrinogenemia that typically occurs during AD and TBI, extravasated Fg was associated with amyloid beta and astrocytic cellular prion protein (PrPC). These effects coincided with short-term memory (STM) reduction and neurodegeneration. However, the mechanisms of a direct Fg-neuron interaction and its functional role in neurodegeneration are still unclear. Cultured mouse brain neurons were treated with Fg in the presence or absence of function-blockers of its receptors, PrPC or intercellular adhesion molecule-1 (ICAM-1). Associations of Fg with neuronal PrPC and ICAM-1 were characterized. The expression of proinflammatory marker interleukin 6 (IL-6) and the generation of reactive oxygen species (ROS), mitochondrial superoxide, and nitrite in neurons were assessed. Fg-induced neuronal death was also evaluated. A strong association of Fg with neuronal PrPC and ICAM-1, accompanied with overexpression of IL-6 and enhanced generation of ROS, mitochondrial superoxide, and nitrite as well as the resulting neuronal death, was found. These effects were reduced by blocking the function of neuronal PrPC and ICAM-1, suggesting that the direct interaction of Fg with its neuronal receptors can induce overexpression of IL-6 and increase the generation of ROS, nitrite, and mitochondrial superoxide, ultimately leading to neuronal death. These effects can be a mechanism of neurodegeneration and the resultant memory reduction seen during TBI and AD.

Control of hippocampal prothrombin kringle-2 (pKr-2) expression reduces neurotoxic symptoms in five familial Alzheimer's disease mice

Background and Purpose

There is a scarcity of information regarding the role of prothrombin kringle‐2 (pKr‐2), which can be generated by active thrombin, in hippocampal neurodegeneration and Alzheimer's disease (AD).

Experimental Approach

To assess the role of pKr‐2 in association with the neurotoxic symptoms of AD, we determined pKr‐2 protein levels in post‐mortem hippocampal tissues of patients with AD and the hippocampi of five familial AD (5XFAD) mice compared with those of age‐matched controls and wild‐type (WT) mice, respectively. In addition, we investigated whether the hippocampal neurodegeneration and object memory impairments shown in 5XFAD mice were mediated by changes to pKr‐2 up‐regulation.

Key Results

Our results demonstrated that pKr‐2 was up‐regulated in the hippocampi of patients with AD and 5XFAD mice, but was not associated with amyloid‐β aggregation in 5XFAD mice. The up‐regulation of pKr‐2 expression was inhibited by preservation of the blood–brain barrier (BBB) via addition of caffeine to their water supply or by treatment with rivaroxaban, an inhibitor of factor Xa that is associated with thrombin production. Moreover, the prevention of up‐regulation of pKr‐2 expression reduced neurotoxic symptoms, such as hippocampal neurodegeneration and object recognition decline due to neurotoxic inflammatory responses in 5XFAD mice.

Conclusion and Implications

We identified a novel pathological mechanism of AD mediated by abnormal accumulation of pKr‐2, which functions as an important pathogenic factor in the adult brain via blood brain barrier (BBB) breakdown. Thus, pKr‐2 represents a novel target for AD therapeutic strategies and those for related conditions.

Emerging pathogenic role of peripheral blood factors following BBB disruption in neurodegenerative disease

The responses of central nervous system (CNS) cells such as neurons and glia in neurodegenerative diseases (NDs) suggest that regulation of neuronal and glial functions could be a strategy for ND prevention and/or treatment. However, attempts to develop such therapeutics for NDs have been hindered by the challenge of blood-brain barrier (BBB) permeability and continued constitutive neuronal loss. These limitations indicate the need for additional perspectives for the prevention/treatment of NDs. In particular, the disruption of the blood-brain barrier (BBB) that accompanies NDs allows brain infiltration by peripheral factors, which may stimulate innate immune responses involved in the progression of neurodegeneration. The accumulation of blood factors like thrombin, fibrinogen, c-reactive protein (CRP) and complement components in the brain has been observed in NDs and may activate the innate immune system in the CNS. Thus, strengthening the integrity of the BBB may enhance its protective role to attenuate ND progression and functional loss. In this review, we describe the innate immune system in the CNS and the contribution of blood factors to the role of the CNS immune system in neurodegeneration and neuroprotection.

Thrombin: A Pivotal Player in Hemostasis and Beyond

The serine protease thrombin, a naturally derived enzyme, plays a key role in hemostasis by converting fibrinogen to fibrin and activating coagulation factor XIII whereby the fibrin clot is stabilized. Furthermore, thrombin activates platelets through protease-activated receptors on the platelet surface. Conversely, thrombin also exerts anticoagulant effects, enhancing the protein C activity while complexed with thrombomodulin. During recent years, it has become evident that thrombin has significant effects beyond hemostasis, as it contributes also to modulation of the endothelium, promotes inflammation and angiogenesis, and plays a role in tumor progression. Yet, due to the very short half-life and almost immediate inhibition in fluid phase by antithrombin, thrombin itself remains elusive, and only indirect measurement of thrombin generation is possible. This review provides a description of structure and mechanisms of action of thrombin both in physiological and pathological processes. Furthermore, it summarizes laboratory tests that measure in vivo or ex vivo thrombin generation, and presents knowledge on the value of these biomarkers in bleeding disorders, cardiopulmonary bypass surgery, and thromboembolic risk assessment in different patient populations. Finally, this review outlines further perspectives on using thrombin generation biomarkers for research purposes and in clinical practice.

Inhibition of protease-activated receptor 1 (PAR1) ameliorates cognitive performance and synaptic plasticity impairments in animal model of Alzheimer's diseases

INTRODUCTION

Alzheimer's disease (AD) is a progressive brain disorder accompanied with synaptic failures and decline in cognitive and learning processes. Protease-activated receptor 1 (PAR1) is the major thrombin receptor in the brain that is implicated in synaptic plasticity and memory formation. In the current study, we hypothesized that inhibition of PAR1 would theoretically prevent amyloid beta (Aβ) accumulation in the brain and then contribute to reduce risk of AD. The aim of the present study was to evaluate the effect of PAR1 inhibition by using SCH (as an inhibitor of PAR1) on spatial learning, memory, and synaptic plasticity in the CA1 region of the hippocampus in rat model of Alzheimer's disease.

METHODS

For the induction of Alzheimer's disease, amyloid beta (Aβ) 1-42 was injected in the CA1 region of the hippocampus. The rats were divided into four groups: group I (surgical sham); group II rat mode of Alzheimer's disease (AD); group III (SCH) (25 μg/kg) intraperitoneally (i.p.), and group IV (AD + SCH). After 14 days of protocol, the rats in group III received SCH and 30 min after injection behavioral and electrophysiological tests were performed. Learning and memory ability was assessed by Morris water maze and novel object recognition tests. Extracellular evoked field excitatory postsynaptic potentials (fEPSP) were recorded in the stratum radiatum of the CA1 area.

RESULTS

Our results showed that AD rats showed impairments in learning and memory, and long-term potentiation (LTP) was not induced in these rats. However, injection of SCH overcame the AD-induced impairment in LTP generation in the CA1 area of the hippocampus and improved learning and memory impairment.

Alzheimer's Disease-Rationales for Potential Treatment with the Thrombin Inhibitor Dabigatran

Alzheimer's disease (AD) is caused by neurodegenerative, but also vascular and hemostatic changes in the brain. The oral thrombin inhibitor dabigatran, which has been used for over a decade in preventing thromboembolism and has a well-known pharmacokinetic, safety and antidote profile, can be an option to treat vascular dysfunction in early AD, a condition known as cerebral amyloid angiopathy (CAA). Recent results have revealed that amyloid-β proteins (Aβ), thrombin and fibrin play a crucial role in triggering vascular and parenchymal brain abnormalities in CAA. Dabigatran blocks soluble thrombin, thrombin-mediated formation of fibrin and Aβ-containing fibrin clots. These clots are deposited in brain parenchyma and blood vessels in areas of CAA. Fibrin-Aβ deposition causes microvascular constriction, occlusion and hemorrhage, leading to vascular and blood-brain barrier dysfunction. As a result, blood flow, perfusion and oxygen and nutrient supply are chronically reduced, mainly in hippocampal and neocortical brain areas. Dabigatran has the potential to preserve perfusion and oxygen delivery to the brain, and to prevent parenchymal Aβ-, thrombin- and fibrin-triggered inflammatory and neurodegenerative processes, leading to synapse and neuron death, and cognitive decline. Beneficial effects of dabigatran on CAA and AD have recently been shown in preclinical studies and in retrospective observer studies on patients. Therefore, clinical studies are warranted, in order to possibly expand dabigatran approval for repositioning for AD treatment.

The pleiotropic effects of antithrombotic drugs in the metabolic-cardiovascular-neurodegenerative disease continuum: impact beyond reduced clotting

Antithrombotic drugs are widely used for primary and secondary prevention, as well as treatment of many cardiovascular disorders. Over the past few decades, major advances in the pharmacology of these agents have been made with the introduction of new drug classes as novel therapeutic options. Accumulating evidence indicates that the beneficial outcomes of some of these antithrombotic agents are not solely related to their ability to reduce thrombosis. Here, we review the evidence supporting established and potential pleiotropic effects of four novel classes of antithrombotic drugs, adenosine diphosphate (ADP) P2Y12-receptor antagonists, Glycoprotein IIb/IIIa receptor Inhibitors, and Direct Oral Anticoagulants (DOACs), which include Direct Factor Xa (FXa) and Direct Thrombin Inhibitors. Specifically, we discuss the molecular evidence supporting such pleiotropic effects in the context of cardiovascular disease (CVD) including endothelial dysfunction (ED), atherosclerosis, cardiac injury, stroke, and arrhythmia. Importantly, we highlight the role of DOACs in mitigating metabolic dysfunction-associated cardiovascular derangements. We also postulate that DOACs modulate perivascular adipose tissue inflammation and thus, may reverse cardiovascular dysfunction early in the course of the metabolic syndrome. In this regard, we argue that some antithrombotic agents can reverse the neurovascular damage in Alzheimer's and Parkinson's brain and following traumatic brain injury (TBI). Overall, we attempt to provide an up-to-date comprehensive review of the less-recognized, beneficial molecular aspects of antithrombotic therapy beyond reduced thrombus formation. We also make a solid argument for the need of further mechanistic analysis of the pleiotropic effects of antithrombotic drugs in the future.

Role of Thrombin in Central Nervous System Injury and Disease

Thrombin is a Na+-activated allosteric serine protease of the chymotrypsin family involved in coagulation, inflammation, cell protection, and apoptosis. Increasingly, the role of thrombin in the brain has been explored. Low concentrations of thrombin are neuroprotective, while high concentrations exert pathological effects. However, greater attention regarding the involvement of thrombin in normal and pathological processes in the central nervous system is warranted. In this review, we explore the mechanisms of thrombin action, localization, and functions in the central nervous system and describe the involvement of thrombin in stroke and intracerebral hemorrhage, neurodegenerative diseases, epilepsy, traumatic brain injury, and primary central nervous system tumors. We aim to comprehensively characterize the role of thrombin in neurological disease and injury.

Discovery of Screening Biomarkers for Major Depressive Disorder in Remission by Proteomic Approach

Major depressive disorder (MDD) is a common disorder involving depressive mood and decreased motivation. Due to its high heterogeneity, novel biomarkers are required to diagnose MDD. In this study, a proteomic method was used to identify a new MDD biomarker. Using sequential window acquisition of all theoretical mass spectra acquisitions and multiple reaction monitoring analysis via mass spectrometry, relative and absolute quantification of proteins in the sera was performed. The results of the relative quantitation by sequential window acquisition for all theoretical mass spectra data showed that seven proteins were significantly differently expressed between MDD patients and other patients with remission status. However, absolute quantification by multiple reaction monitoring analysis identified prothrombin as the only significantly upregulated protein in the depressive state compared to remission (p < 0.05) and was, thus, subsequently selected as an MDD biomarker. The area under the curve for prothrombin was 0.66. Additionally, increased prothrombin/thrombin induced hyper-activation of platelets via activating protease-activated receptors, a feature associated with MDD; specifically, activated platelets secrete various molecules related to MDD, including brain-derived neurotropic factors and serotonin. Therefore, prothrombin is a potential screening, prognostic, and diagnostic marker for MDD.

Short-term treatment with dabigatran alters protein expression patterns in a late-stage tau-based Alzheimer's disease mouse model

Proteins that regulate the coagulation cascade, including thrombin, are elevated in the brains of Alzheimer's disease (AD) patients. While studies using amyloid-based AD transgenic mouse models have implicated thrombin as a protein of interest, the role of thrombin in tau-based animal models has not been explored. The current study aims to determine how inhibiting thrombin could alter oxidative stress, inflammation, and AD-related proteins in a tau-based mouse model, the Tg4510. Aged Tg4510 mice were treated with the direct thrombin inhibitor dabigatran or vehicle for 7 days, brains collected, and western blot and data-independent proteomics using mass spectrometry with SWATH-MS acquisition performed to evaluate proteins related to oxidative stress, intracellular signaling, inflammation, and AD pathology. Dabigatran reduced iNOS, NOX4, and phosphorylation of tau (S396, S416). Additionally, dabigatran treatment increased expression of several signaling proteins related to cell survival and synaptic function. Increasing evidence supports a chronic procoagulant state in AD, highlighting a possible pathogenic role for thrombin. Our data demonstrate that inhibiting thrombin produces alterations in the expression of proteins involved in oxidative stress, inflammation, and AD-related pathology, suggesting that thrombin-mediated signaling affects multiple AD-related pathways providing a potential future therapeutic target.

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Thrombin inhibition with dabigatran reduces markers of oxidative stress in vivo.

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Dabigatran treatment reduces tau pathology in vivo.

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Dabigatran treatment promotes factors related to cell survival, synaptic function.

A review on neuropharmacological role of erucic acid: an omega-9 fatty acid from edible oils

Neurodegenerative diseases (ND) are characterised by loss of neurons in the brain and spinal cord. For the normal functioning of the brain, divers group of fatty acids in the form of glycerophospholipids, glycerol ether lipids, cerebrosides, sulfatides, and gangliosides are essential. They are present abundantly in the nervous system and are actively involved in both the development and maintenance of the nervous system. A dietary deficiency of essential fatty acid during development results in hypomyelination state which affects various neuronal functions. Several studies suggested that age remains the primary risk factor for almost all neurodegenerative disorders. The potential contribution of these fatty acids in the progression of neurodegenerative disorders is indispensable. Erucic acid an omega 9 fatty acid, which is obtained from edible oils has proven to cause myocardial lipidosis, heart lesions and hepatic steatosis in animals therefore, its content in edible oils is restricted to certain levels by regulatory agencies. However, erucic acid in the form of a mixture with oleic acid is often used as a dietary treatment for the management of adrenoleukodystrophy without any cardiotoxicity. Our literature search revealed that, erucic acid reported to enhance cognitive function, interact with peroxisome proliferator activated receptors (PPARs), inhibit elastase and thrombin. In this review first we have attempted to describe the relationship between fatty acids and neurodegeneration followed by a description on the pharmacology of erucic acid. The overall purpose of this review is to analyse toxic and beneficial neuropharmacological effects of erucic acid.

Delta-secretase cleavage of Tau mediates its pathology and propagation in Alzheimer's disease

Alzheimer’s disease (AD) is a progressive neurodegenerative disease with age as a major risk factor. AD is the most common dementia with abnormal structures, including extracellular senile plaques and intraneuronal neurofibrillary tangles, as key neuropathologic hallmarks. The early feature of AD pathology is degeneration of the locus coeruleus (LC), which is the main source of norepinephrine (NE) supplying various cortical and subcortical areas that are affected in AD. The spread of Tau deposits is first initiated in the LC and is transported in a stepwise manner from the entorhinal cortex to the hippocampus and then to associative regions of the neocortex as the disease progresses. Most recently, we reported that the NE metabolite DOPEGAL activates delta-secretase (AEP, asparagine endopeptidase) and triggers pathological Tau aggregation in the LC, providing molecular insight into why LC neurons are selectively vulnerable to developing early Tau pathology and degenerating later in the disease and how δ-secretase mediates the spread of Tau pathology to the rest of the brain. This review summarizes our current understanding of the crucial role of δ-secretase in driving and spreading AD pathologies by cleaving multiple critical players, including APP and Tau, supporting that blockade of δ-secretase may provide an innovative disease-modifying therapeutic strategy for treating AD.

The identification of an enzyme that plays a critical role in the progression of Alzheimer’s disease (AD) could lead to novel therapeutic interventions. In the earliest stage of AD, the build-up of Tau protein aggregates causes degeneration of a site in the brainstem. These abnormal Tau accumulations then spread to other parts of the brain. Recent research suggests that an enzyme called delta-secretase cleaves Tau and other key molecules, making Tau more prone to forming aggregates and thus facilitating disease progression. Keqiang Ye and co-workers at Emory University School of Medicine in Atlanta, USA, reviewed current understanding of the role of delta-secretase in AD pathology. Studies show that delta-secretase expression levels are high in aged mice and AD brains. Inhibiting delta-secretase could therefore limit neurodegeneration and alleviate cognitive deficits in patients.

Introduction of a thrombin sensor based on its interaction with dabigatran as an oral direct thrombin inhibitor

Dabigatran (DAB) is a direct thrombin inhibitor used for preventing blood clots and emboli after orthopedic surgery. The DAB - thrombin interaction was followed by fluorescence and UV-Vis spectroscopic methods. The binding of DAB to thrombin was also modeled by the molecular docking method. The obtained experimental results were consistent with theoretical results. The voltammetric method was also tested for DAB - thrombin interaction. Based on voltammetric findings, carbon paste electrode containing graphite powder, paraffin oil, MWCNTs, and DAB was constructed and used for thrombin monitoring after investigation of the DAB oxidation mechanism for the first time. The decrease in the linear sweep voltammetric (LSV) peak current of DAB in the presence of thrombin was utilized for the thrombin analysis. The calibration plot was linear in the concentration range of 1 to 70 nM (R² = 0.9992) by LSV technique with a detection limit of 0.3 nM. The applicability of the proposed sensor was evaluated by the determination of thrombin in human serum as a real sample.

Truncation of Tau selectively facilitates its pathological activities

Neurofibrillary tangles of abnormally hyperphosphorylated Tau are a hallmark of Alzheimer's disease (AD) and related tauopathies. Tau is truncated at multiple sites by various proteases in AD brain. Although many studies have reported the effect of truncation on the aggregation of Tau, these studies mostly employed highly artificial conditions, using heparin sulfate or arachidonic acid to induce aggregation. Here, we report for the first time the pathological activities of various truncations of Tau, including site-specific phosphorylation, self-aggregation, binding to hyperphosphorylated and oligomeric Tau isolated from AD brain tissue (AD O-Tau), and aggregation seeded by AD O-Tau. We found that deletion of the first 150 or 230 amino acids (aa) enhanced Tau's site-specific phosphorylation, self-aggregation, and binding to AD O-Tau and aggregation seeded by AD O-Tau, but deletion of the first 50 aa did not produce a significant effect. Deletion of the last 50 aa was found to modulate Tau's site-specific phosphorylation, promote its self-aggregation, and cause it to be captured by and aggregation seeded by AD O-Tau, whereas deletion of the last 20 aa had no such effects. Among the truncated Taus, Tau_151-391 showed the highest pathological activities. AD O-Tau induced aggregation of Tau_151-391 in vitro and in cultured cells. These findings suggest that the first 150 aa and the last 50 aa protect Tau from pathological characteristics and that their deletions facilitate pathological activities. Thus, inhibition of Tau truncation may represent a potential therapeutic approach to suppress Tau pathology in AD and related tauopathies.

Thrombin, a Mediator of Coagulation, Inflammation, and Neurotoxicity at the Neurovascular Interface: Implications for Alzheimer's Disease

The societal burden of Alzheimer’s disease (AD) is staggering, with current estimates suggesting that 50 million people world-wide have AD. Identification of new therapeutic targets is a critical barrier to the development of disease-modifying therapies. A large body of data implicates vascular pathology and cardiovascular risk factors in the development of AD, indicating that there are likely shared pathological mediators. Inflammation plays a role in both cardiovascular disease and AD, and recent evidence has implicated elements of the coagulation system in the regulation of inflammation. In particular, the multifunctional serine protease thrombin has been found to act as a mediator of vascular dysfunction and inflammation in both the periphery and the central nervous system. In the periphery, thrombin contributes to the development of cardiovascular disease, including atherosclerosis and diabetes, by inducing endothelial dysfunction and related inflammation. In the brain, thrombin has been found to act on endothelial cells of the blood brain barrier, microglia, astrocytes, and neurons in a manner that promotes vascular dysfunction, inflammation, and neurodegeneration. Thrombin is elevated in the AD brain, and thrombin signaling has been linked to both tau and amyloid beta, pathological hallmarks of the disease. In AD mouse models, inhibiting thrombin preserves cognition and endothelial function and reduces neuroinflammation. Evidence linking atrial fibrillation with AD and dementia indicates that anticoagulant therapy may reduce the risk of dementia, with targeting thrombin shown to be particularly effective. It is time for “outside-the-box” thinking about how vascular risk factors, such as atherosclerosis and diabetes, as well as the coagulation and inflammatory pathways interact to promote increased AD risk. In this review, we present evidence that thrombin is a convergence point for AD risk factors and as such that thrombin-based therapeutics could target multiple points of AD pathology, including neurodegeneration, vascular activation, and neuroinflammation. The urgent need for disease-modifying drugs in AD demands new thinking about disease pathogenesis and an exploration of novel drug targets, we propose that thrombin inhibition is an innovative tactic in the therapeutic battle against this devastating disease.

PPARδ and its ligand erucic acid may act anti-tumoral, neuroprotective, and myelin protective in neuroblastoma, glioblastoma, and Parkinson's disease

In this review study, we focus on potential benefits of the transcription factor PPARδ and its ligand erucic acid (EA) in management of neuroectodermal tumors and Parkinson's Disease. PPARδ is a nuclear receptor and transcription factor that induces myelination, promotes oligodendroglial and neuronal differentiation, and possess anti-neuroinflammatory properties. While both pro-tumorigenic and anti-tumorigenic effects have been described for PPARδ, we propose that PPARδ may perform a predominantly anticancer role in tumors originating from the neuroectoderm. PPARδ ligand-activation via oleic acid and GW501516, or overexpression of PPARδ, elicits profound antitumor actions in neuroblastoma and melanoma. In glioblastomas, there is evidence indicating a differentiation failure of O2A (oligodendroglial-astrocytic biprogenitor) cells and it has been shown that EA reduced DNA synthesis in C6 rat glioblastoma spheroid cultures in clinically achievable concentrations. EA is a ω9 fatty acid which is being used in the treatment of adrenoleukodystrophy. EA is widely consumed in Asian countries via ingestion of cruciferous vegetables including mustard and rapeseed oil. EA also exerts antioxidant and anti-inflammatory activities. Recent studies of Parkinson's Disease (PD) have implicated demyelination, white matter pathology, oligodendroglial injury, and neural inflammation in the underlying pathophysiology. In the rotenone PD model in rats, PPARδ ligand GW501516 saves dopaminergic neurons during injury induced by chemical toxins and improves behavioral functioning in PD via alleviation of endoplasmic reticulum stress. PPARδ agonists also reduce the NLRP3 inflammasome-associated neural inflammation in the MPTP PD model in mice. Herein, we propose that PPARδ and its ligand EA highly deserve to be studied in animal models of neuroblastoma, glioblastoma, and PD.

Dissecting the Structural Organization of Multiprotein Amyloid Aggregates Using a Bottom-Up Approach

Deposition of fibrillar amyloid β (Aβ) in senile plaques is a pathological signature of Alzheimer's disease. However, senile plaques also contain many other components, including a range of different proteins. Although the composition of the plaques can be analyzed in post-mortem tissue, knowledge of the molecular details of these multiprotein inclusions and their assembly processes is limited, which impedes the progress in deciphering the biochemical mechanisms associated with Aβ pathology. We describe here a bottom-up approach to monitor how proteins from human cerebrospinal fluid associate with Aβ amyloid fibrils to form plaque particles. The method combines flow cytometry and mass spectrometry proteomics and allowed us to identify and quantify 128 components of the captured multiprotein aggregates. The results provide insights into the functional characteristics of the sequestered proteins and reveal distinct interactome responses for the two investigated Aβ variants, Aβ(1-40) and Aβ(1-42). Furthermore, the quantitative data is used to build models of the structural organization of the multiprotein aggregates, which suggests that Aβ is not the primary binding target for all the proteins; secondary interactions account for the majority of the assembled components. The study elucidates how different proteins are recruited into senile plaques and establishes a new model system for exploring the pathological mechanisms of Alzheimer's disease from a molecular perspective.

The Cerebral Thrombin System Is Activated after Intracerebral Hemorrhage and Contributes to Secondary Lesion Growth and Poor Neurological Outcome in C57Bl/6 Mice

With increasing evidence for the existence of a cerebral thrombin system, coagulation factor IIa (thrombin) is suspected to influence the pathogenesis of secondary injury progression after intracerebral hemorrhage (ICH). We hypothesized that mechanisms associated with local volume expansion after ICH, rather than blood constituents, activate the cerebral thrombin system and are responsible for detrimental neurological outcome. To test this hypothesis, we examine the local thrombin expression after ICH in a C57BL/6N mouse model in the presence and absence of blood constituents. ICH was established using stereotaxic orthotopic injection of utologous blood (n = 10) or silicone oil as inert volume substance (n = 10) into the striatum. Intracranial pressure (ICP), cerebral blood flow (CBF), and mean arterial blood pressure (MAP) were monitored during and 30 min after the procedure. No significant differences between ICP, CBF, and MAP were found between both groups. Prothrombin messenger RNA expression was upregulated early after ICH. Immunohistochemistry showed an increase of perilesional thrombin in both groups (blood, 4.24-fold; silicone, 3.10-fold), whereas prothrombin fragment (F1.2) was elevated only in the absence of whole blood. Thrombin expression is colocalized with neuronal antigen expression. After 24 h, lesion size and neuronal loss were similar. Perihematomal thrombin correlated with increased neuronal loss and detrimental neurological outcome in vivo. In our study, we demonstrate, for the first time, that the local cerebral thrombin system is activated after ICH and that this activation is independent of the presence of whole-blood constituents. In our study, neuronal damage is driven by local thrombin expression and leads to an adverse clinical outcome.

Novel Chemiluminescence Sensor for Thrombin Detection Based on Dual-Aptamer Biorecognition and Mesoporous Silica Encapsulated with Iron Porphyrin

Thrombin is a marker of blood-related diseases, and its detection is of great significance in the fields of medical and biological research. Herein, a novel chemiluminescence (CL) sensor for thrombin detection was prepared based on dual-aptamer biorecognition and mesoporous silica encapsulated with iron porphyrin. Mesoporous silica encapsulated with hematin by aptamer1 (Apt1/hematin/M-SiO₂) and magnetic microspheres modified with aptamer2 (Apt2/NH₂-MS) were successfully prepared, and the two materials were used to construct a CL sensor to detect thrombin. Primarily, Apt2/NH₂-MS is used for pretreatment separation of thrombin samples by the biorecognition effect between the aptamer (Apt2) and target (thrombin). Then, thrombin/Apt2/NH₂-MS is again recognized with Apt1 on the surface of Apt1/hematin/M-SiO₂ and Apt1/thrombin/Apt2/NH₂-MS is formed, so dual-aptamer biorecognition is realized. Meanwhile, the generated Apt1/thrombin/Apt2/NH₂-MS makes Apt1 shed off the surface of M-SiO₂ and release hematin. The released hematin can catalyze the luminol-H₂O₂ CL reaction. Therefore, a sandwich-type CL sensor was constructed based on dual-aptamer biorecognition and hematin catalysis for the detection of thrombin. The sensor has a linear range of 7.5 × 10^-15 to 2.5 × 10^-10 mol·L^-1 and a detection limit of 2.2 × 10^-15 mol·L^-1 and also exhibits excellent selectivity, reproducibility, and stability. The sensor was successfully used for the detection of thrombin in serum samples, which makes it possible to apply the sensor in the detection of thrombin in actual samples.

Erucic acid, a nutritional PPARδ-ligand may influence Huntington's disease pathogenesis

Increasing recent evidence suggests a key role of oligodendroglial injury and demyelination in the pathophysiology of Huntington's Disease (HD) and the transcription factor PPARδ is critical for oligodendroglial regeneration and myelination. PPARδ directly involves in the pathogenesis of HD and treatment with a brain-permeable PPARδ-agonist (KD3010) alleviates its severity in mice. Erucic acid (EA) is also a PPARδ-ligand ω9 fatty acid which is highly consumed in Asian countries through ingesting cruciferous vegetables such as rapeseed (Brassica napus) and indian mustard (Brassica juncea). EA is also an ingredient of Lorenzo's oil employed in the medical treatment of adrenoleukodystrophy and can be converted to nervonic acid, a component of myelin. HD pathogenesis also involves oxidative and inflammatory injury and EA exerts antioxidative and antiinflammatory efficacies including inhibition of thrombin and elastase. Consumption of rapeseed, indian mustard, and Canola oils (containing EA) improves cognitive parameters in animal models, as well as treatment with pure EA. Moreover, erucamide, an endogenous EA-amide derivative regulating angiogenesis and water balance, exerts antidepressive and anxiolytic effects in mice. Hitherto, no study has investigated the therapeutic potential of EA in HD and we believe that it strongly merits to be studied in animal models of HD as a potential therapeutic.

Anticoagulants for Treatment of Alzheimer's Disease

Alzheimer's disease (AD) is a multifactorial syndrome with a plethora of progressive, degenerative changes in the brain parenchyma, but also in the cerebrovascular and hemostatic system. A therapeutic approach for AD is reviewed, which is focused on the role of amyloid-β protein (Aβ) and fibrin in triggering intra-brain vascular dysfunction and connected, cognitive decline. It is proposed that direct oral anticoagulants (DOACs) counteract Aβ-induced pathological alterations in cerebral blood vessels early in AD, a condition, known as cerebral amyloid angiopathy (CAA). By inhibiting thrombin for fibrin formation, anticoagulants can prevent accumulations of proinflammatory thrombin and fibrin, and deposition of degradation-resistant, Aβ-containing fibrin clots. These fibrin-Aβ clots are found in brain parenchyma between neuron cells, and in and around cerebral blood vessels in areas of CAA, leading to decreased cerebral blood flow. Consequently, anticoagulant treatment could reduce hypoperfusion and restricted supply of brain tissue with oxygen and nutrients. Concomitantly, hypoperfusion-enhanced neurodegenerative processes, such as progressive Aβ accumulation via synthesis and reduced perivascular clearance, neuroinflammation, and synapse and neuron cell loss, could be mitigated. Given full cerebral perfusion and reduced Aβ- and fibrin-accumulating and inflammatory milieu, anticoagulants could be able to decrease vascular-driven progression in neurodegenerative and cognitive changes, present in AD, when treated early, therapeutically, or prophylactically.

Competitive aptasensor with gold nanoparticle dimers and magnetite nanoparticles for SERS-based determination of thrombin

It is known that the intensity of surface-enhanced Raman scattering (SERS) of monomeric gold nanoparticles (GNPs) is insufficient for ultrasensitive analysis. The authors describe dimeric GNPs for use in a competitive SERS and aptamer based assay for thrombin. The reagent 1,2-bis(4-pyridyl) ethylene serves as both the coupling agent and the Raman reporter on the GNP dimers. In the presence of thrombin, the hybridization of two aptamers, one attached to the GNP dimers, the other to magnetic nanoparticles, is competitively prevented. This method takes advantage of the unique "hot spots" of the GNP dimers to amplify the Raman signal. This results in an ultra-sensitive thrombin assay when compared to assays using GNP monomers. The limit of detection is as low as 1 fM of thrombin. The Raman intensity, best measured at 1612 cm^-1, increases linearly in the 1 fM to 10 nM thrombin concentration range. The method was applied to the determinaiton of thrombin in spiked simulated body fluid and human serum. Graphical abstract This method takes advantage of the unique "hot spots" of the gold nanoparticle dimers to amplify the Raman signal. The dimers are linked to the magnetic nanoparticles via an aptamer. The use of both competitive displacement and magnetic separation greatly improves the sensitivity of the thrombin assay.

Coagulation Pathways in Neurological Diseases: Multiple Sclerosis

Significant progress has been made in understanding the complex interactions between the coagulation system and inflammation and autoimmunity. Increased blood-brain-barrier (BBB) permeability, a key event in the pathophysiology of multiple sclerosis (MS), leads to the irruption into the central nervous system of blood components that include virtually all coagulation/hemostasis factors. Besides their cytotoxic deposition and role as a possible trigger of the coagulation cascade, hemostasis components cause inflammatory response and immune activation, sustaining neurodegenerative events in MS. Early studies showing the contribution of altered hemostasis in the complex pathophysiology of MS have been strengthened by recent studies using methodologies that permitted deeper investigation. Fibrin(ogen), an abundant protein in plasma, has been identified as a key contributor to neuroinflammation. Perturbed fibrinolysis was found to be a hallmark of progressive MS with abundant cortical fibrin(ogen) deposition. The immune-modulatory function of the intrinsic coagulation pathway still remains to be elucidated in MS. New molecular details in key hemostasis components participating in MS pathophysiology, and particularly involved in inflammatory and immune responses, could favor the development of novel therapeutic targets to ameliorate the evolution of MS. This review article introduces essential information on coagulation factors, inhibitors, and the fibrinolytic pathway, and highlights key aspects of their involvement in the immune system and inflammatory response. It discusses how hemostasis components are (dys)regulated in MS, and summarizes histopathological post-mortem human brain evidence, as well as cerebrospinal fluid, plasma, and serum studies of hemostasis and fibrinolytic pathways in MS. Studies of disease-modifying treatments as potential modifiers of coagulation factor levels, and case reports of autoimmunity affecting hemostasis in MS are also discussed.

Thrombin and the Coag-Inflammatory Nexus in Neurotrauma, ALS, and Other Neurodegenerative Disorders

This review details our current understanding of thrombin signaling in neurodegeneration, with a focus on amyotrophic lateral sclerosis (ALS, Lou Gehrig's disease) as well as future directions to be pursued. The key factors are multifunctional and involved in regulatory pathways, namely innate immune and the coagulation cascade activation, that are essential for normal nervous system function and health. These two major host defense systems have a long history in evolution and include elements and regulators of the coagulation pathway that have significant impacts on both the peripheral and central nervous system in health and disease. The clotting cascade responds to a variety of insults to the CNS including injury and infection. The blood brain barrier is affected by these responses and its compromise also contributes to these detrimental effects. Important molecules in signaling that contribute to or protect against neurodegeneration include thrombin, thrombomodulin (TM), protease activated receptor 1 (PAR1), damage associated molecular patterns (DAMPs), such as high mobility group box protein 1 (HMGB1) and those released from mitochondria (mtDAMPs). Each of these molecules are entangled in choices dependent upon specific signaling pathways in play. For example, the particular cleavage of PAR1 by thrombin vs. activated protein C (APC) will have downstream effects through coupled factors to result in toxicity or neuroprotection. Furthermore, numerous interactions influence these choices such as the interplay between HMGB1, thrombin, and TM. Our hope is that improved understanding of the ways that components of the coagulation cascade affect innate immune inflammatory responses and influence the course of neurodegeneration, especially after injury, will lead to effective therapeutic approaches for ALS, traumatic brain injury, and other neurodegenerative disorders.

Regulation of myelin structure and conduction velocity by perinodal astrocytes

The speed of impulse transmission is critical for optimal neural circuit function, but it is unclear how the appropriate conduction velocity is established in individual axons. The velocity of impulse transmission is influenced by the thickness of the myelin sheath and the morphology of electrogenic nodes of Ranvier along axons. Here we show that myelin thickness and nodal gap length are reversibly altered by astrocytes, glial cells that contact nodes of Ranvier. Thrombin-dependent proteolysis of a cell adhesion molecule that attaches myelin to the axon (neurofascin 155) is inhibited by vesicular release of thrombin protease inhibitors from perinodal astrocytes. Transgenic mice expressing a dominant-negative fragment of VAMP2 in astrocytes, to reduce exocytosis by 50%, exhibited detachment of adjacent paranodal loops of myelin from the axon, increased nodal gap length, and thinning of the myelin sheath in the optic nerve. These morphological changes alter the passive cable properties of axons to reduce conduction velocity and spike-time arrival in the CNS in parallel with a decrease in visual acuity. All effects were reversed by the thrombin inhibitor Fondaparinux. Similar results were obtained by viral transfection of tetanus toxin into astrocytes of rat corpus callosum. Previously, it was unknown how the myelin sheath could be thinned and the functions of perinodal astrocytes were not well understood. These findings describe a form of nervous system plasticity in which myelin structure and conduction velocity are adjusted by astrocytes. The thrombin-dependent cleavage of neurofascin 155 may also have relevance to myelin disruption and repair.