Blood coagulation protein fibrinogen promotes autoimmunity and demyelination via chemokine release and antigen presentation

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.

Hemostasis components in cerebral amyloid angiopathy and Alzheimer's disease

Increased cerebrovascular amyloid-β (Aβ) deposition represents the main pathogenic mechanisms characterizing Alzheimer's disease (AD) and cerebral amyloid angiopathy (CAA). Whereas an increasing number of studies define the contribution of fibrin(ogen) to neurodegeneration, how other hemostasis factors might be pleiotropically involved in the AD and CAA remains overlooked. Although traditionally regarded as pertaining to hemostasis, these proteins are also modulators of inflammation and angiogenesis, and exert cytoprotective functions. This review discusses the contribution of hemostasis components to Aβ cerebrovascular deposition, which settle the way to endothelial and blood-brain barrier dysfunction, vessel fragility, cerebral bleeding, and the associated cognitive changes. From the primary hemostasis, the process that refers to platelet aggregation, we discuss evidence regarding the von Willebrand factor (vWF) and its regulator ADAMTS13. Then, from the secondary hemostasis, we focus on tissue factor, which triggers the extrinsic coagulation cascade, and on the main inhibitors of coagulation, i.e., tissue factor pathway inhibitor (TFPI), and the components of protein C pathway. Last, from the tertiary hemostasis, we discuss evidence on FXIII, involved in fibrin cross-linking, and on components of fibrinolysis, including tissue-type plasminogen activator (tPA), urokinase-type plasminogen activator (uPA) and its receptor uPA(R), and plasminogen activator inhibitor-1 (PAI-1). Increased knowledge on contributors of Aβ-related disease progression may favor new therapeutic approaches for early modifiable risk factors.

Endothelial Tpl2 regulates vascular barrier function via JNK-mediated degradation of claudin-5 promoting neuroinflammation or tumor metastasis

Increased vascular permeability and leakage are hallmarks of several pathologies and determine disease progression and severity by facilitating inflammatory/metastatic cell infiltration. Using tissue-specific genetic ablation in endothelial cells, we have investigated in vivo the role of Tumor progression locus 2 (Tpl2), a mitogen-activated protein kinase kinase kinase (MAP3K) member with pleiotropic effects in inflammation and cancer. In response to proinflammatory stimuli, endothelial Tpl2 deletion alters tight junction claudin-5 protein expression through inhibition of JNK signaling and lysosomal degradation activation, resulting in reduced vascular permeability and immune cell infiltration. This results in significantly attenuated disease scores in experimental autoimmune encephalomyelitis and fewer tumor nodules in a hematogenic lung cancer metastasis model. Accordingly, pharmacologic inhibition of Tpl2 or small interfering RNA (siRNA)-mediated Tpl2 knockdown recapitulates our findings and reduces lung metastatic tumor invasions. These results establish an endothelial-specific role for Tpl2 and highlight the therapeutic potential of blocking the endothelial-specific Tpl2 pathway in chronic inflammatory and metastatic diseases.

Imaging meningeal inflammation in CNS autoimmunity identifies a therapeutic role for BTK inhibition

Leptomeningeal inflammation in multiple sclerosis is associated with worse clinical outcomes and greater cortical pathology. Despite progress in identifying this process in multiple sclerosis patients using post-contrast fluid-attenuated inversion recovery imaging, early trials attempting to target meningeal inflammation have been unsuccessful. There is a lack of appropriate model systems to screen potential therapeutic agents targeting meningeal inflammation. We utilized ultra-high field (11.7 T) MRI to perform post-contrast imaging in SJL/J mice with experimental autoimmune encephalomyelitis induced via immunization with proteolipid protein peptide (PLP139-151) and complete Freund's adjuvant. Imaging was performed in both a cross-sectional and longitudinal fashion at time points ranging from 2 to 14 weeks post-immunization. Following imaging, we euthanized animals and collected tissue for pathological evaluation, which revealed dense cellular infiltrates corresponding to areas of contrast enhancement involving the leptomeninges. These areas of meningeal inflammation contained B cells (B220+), T cells (CD3+) and myeloid cells (Mac2+). We also noted features consistent with tertiary lymphoid tissue within these areas, namely the presence of peripheral node addressin-positive structures, C-X-C motif chemokine ligand-13 (CXCL13)-producing cells and FDC-M1+ follicular dendritic cells. In the cortex adjacent to areas of meningeal inflammation we identified astrocytosis, microgliosis, demyelination and evidence of axonal stress/damage. Since areas of meningeal contrast enhancement persisted over several weeks in longitudinal experiments, we utilized this model to test the effects of a therapeutic intervention on established meningeal inflammation. We randomized mice with evidence of meningeal contrast enhancement on MRI scans performed at 6 weeks post-immunization, to treatment with either vehicle or evobrutinib [a Bruton tyrosine kinase (BTK) inhibitor] for a period of 4 weeks. These mice underwent serial imaging; we examined the effect of treatment on the areas of meningeal contrast enhancement and noted a significant reduction in the evobrutinib group compared to vehicle (30% reduction versus 5% increase; P = 0.003). We used ultra-high field MRI to identify areas of meningeal inflammation and to track them over time in SJL/J mice with experimental autoimmune encephalomyelitis, and then used this model to identify BTK inhibition as a novel therapeutic approach to target meningeal inflammation. The results of this study provide support for future studies in multiple sclerosis patients with imaging evidence of meningeal inflammation.

Blood Coagulation Factor Fibrinogen in Tumor Pathogenesis of Central Nervous System B-Cell Lymphoma

Central nervous system (CNS) lymphoma is an extranodal non-Hodgkin B-cell lymphoma characterized by malignant lymph tissue arising in the brain or spinal cord, associated with inflammation and blood-brain barrier (BBB) disruption. Although BBB disruption is known to occur in patients with CNS lymphoma, a direct link between these two has not been shown. Herein, abundant deposition of the blood coagulation protein fibrinogen around B-cell lymphoma was detected in CNS lymphoma patients and in the CNS parenchyma in an orthotopic mouse model. Functional enrichment analysis of unbiased cerebrospinal fluid proteomics of CNS B-cell lymphoma patients showed that coagulation protein networks were highly connected with tumor-associated biological signaling pathways. In vivo two-photon imaging demonstrated that lymphoma growth was associated with BBB disruption, and in vitro experiments identified a role for fibrinogen in promoting lymphoma cell adhesion. Overall, these results identify perivascular lymphoma clustering at sites of fibrinogen deposition, and suggest that fibrinogen may be a target for pharmacologic intervention in metastatic B-cell lymphoma associated with BBB disruption.

Changes in blood-spinal cord barrier permeability and neuroimmune interactions in the underlying mechanisms of chronic pain

Advancing our understanding of the underlying mechanisms of chronic pain is instrumental to the identification of new potential therapeutic targets. Neuroimmune communication throughout the pain pathway is of crucial mechanistic importance and has been a major focus of preclinical chronic pain research over the last 2 decades. In the spinal cord, not only do dorsal horn neurons partake in mechanistically important bidirectional communication with resident immune cells such as microglia, but in some cases, they can also partake in bidirectional crosstalk with immune cells, such as monocytes/macrophages, which have infiltrated into the spinal cord from the circulation. The infiltration of immune cells into the spinal cord can be partly regulated by changes in permeability of the blood-spinal cord barrier (BSCB). Here, we discuss evidence for and against a mechanistic role for BSCB disruption and associated changes in neuroimmune crosstalk in preclinical chronic pain. We also consider recent evidence for its potential involvement in the vincristine model of chemotherapy-induced painful neuropathy. We conclude that current knowledge warrants further investigation to establish whether preventing BSCB disruption, or targeting the changes associated with this disruption, could be used for the development of novel approaches to treating chronic pain.

Thrombin generation and activity in multiple sclerosis

The coagulation cascade and immune system are intricately linked, highly regulated and respond cooperatively in response to injury and infection. Increasingly, evidence of hyper-coagulation has been associated with autoimmune disorders, including multiple sclerosis (MS). The pathophysiology of MS includes immune cell activation and recruitment to the central nervous system (CNS) where they degrade myelin sheaths, leaving neuronal axons exposed to damaging inflammatory mediators. Breakdown of the blood-brain barrier (BBB) facilitates the entry of peripheral immune cells. Evidence of thrombin activity has been identified within the CNS of MS patients and studies using animal models of experimental autoimmune encephalomyelitis (EAE), suggest increased thrombin generation and activity may play a role in the pathogenesis of MS as well as inhibit remyelination processes. Thrombin is a serine protease capable of cleaving multiple substrates, including protease activated receptors (PARs), fibrinogen, and protein C. Cleavage of all three of these substrates represent pathways through which thrombin activity may exert immuno-regulatory effects and regulate permeability of the BBB during MS and EAE. In this review, we summarize evidence that thrombin activity directly, through PARs, and indirectly, through fibrin formation and activation of protein C influences neuro-immune responses associated with MS and EAE pathology.

Blood-brain barrier resealing in neuromyelitis optica occurs independently of astrocyte regeneration

Approximately 80% of neuromyelitis optica spectrum disorder (NMOSD) patients harbor serum anti-aquaporin-4 autoantibodies targeting astrocytes in the CNS. Crucial for NMOSD lesion initiation is disruption of the blood-brain barrier (BBB), which allows the entrance of Abs and serum complement into the CNS and which is a target for new NMOSD therapies. Astrocytes have important functions in BBB maintenance; however, the influence of their loss and the role of immune cell infiltration on BBB permeability in NMOSD have not yet been investigated. Using an experimental model of targeted NMOSD lesions in rats, we demonstrate that astrocyte destruction coincides with a transient disruption of the BBB and a selective loss of occludin from tight junctions. It is noteworthy that BBB integrity is reestablished before astrocytes repopulate. Rather than persistent astrocyte loss, polymorphonuclear leukocytes (PMNs) are the main mediators of BBB disruption, and their depletion preserves BBB integrity and prevents astrocyte loss. Inhibition of PMN chemoattraction, activation, and proteolytic function reduces lesion size. In summary, our data support a crucial role for PMNs in BBB disruption and NMOSD lesion development, rendering their recruitment and activation promising therapeutic targets.

The Immune System's Role in the Consequences of Mild Traumatic Brain Injury (Concussion)

Mild traumatic brain injury (mild TBI), often referred to as concussion, is the most common form of TBI and affects millions of people each year. A history of mild TBI increases the risk of developing emotional and neurocognitive disorders later in life that can impact on day to day living. These include anxiety and depression, as well as neurodegenerative conditions such as chronic traumatic encephalopathy (CTE) and Alzheimer's disease (AD). Actions of brain resident or peripherally recruited immune cells are proposed to be key regulators across these diseases and mood disorders. Here, we will assess the impact of mild TBI on brain and patient health, and evaluate the recent evidence for immune cell involvement in its pathogenesis.

Development of Proteomic Prediction Models for Transition to Psychotic Disorder in the Clinical High-Risk State and Psychotic Experiences in Adolescence

IMPORTANCE

Biomarkers that are predictive of outcomes in individuals at risk of psychosis would facilitate individualized prognosis and stratification strategies.

OBJECTIVE

To investigate whether proteomic biomarkers may aid prediction of transition to psychotic disorder in the clinical high-risk (CHR) state and adolescent psychotic experiences (PEs) in the general population.

DESIGN, SETTING, AND PARTICIPANTS

This diagnostic study comprised 2 case-control studies nested within the European Network of National Schizophrenia Networks Studying Gene-Environment Interactions (EU-GEI) and the Avon Longitudinal Study of Parents and Children (ALSPAC). EU-GEI is an international multisite prospective study of participants at CHR referred from local mental health services. ALSPAC is a United Kingdom-based general population birth cohort. Included were EU-GEI participants who met CHR criteria at baseline and ALSPAC participants who did not report PEs at age 12 years. Data were analyzed from September 2018 to April 2020.

MAIN OUTCOMES AND MEASURES

In EU-GEI, transition status was assessed by the Comprehensive Assessment of At-Risk Mental States or contact with clinical services. In ALSPAC, PEs at age 18 years were assessed using the Psychosis-Like Symptoms Interview. Proteomic data were obtained from mass spectrometry of baseline plasma samples in EU-GEI and plasma samples at age 12 years in ALSPAC. Support vector machine learning algorithms were used to develop predictive models.

RESULTS

The EU-GEI subsample (133 participants at CHR (mean [SD] age, 22.6 [4.5] years; 68 [51.1%] male) comprised 49 (36.8%) who developed psychosis and 84 (63.2%) who did not. A model based on baseline clinical and proteomic data demonstrated excellent performance for prediction of transition outcome (area under the receiver operating characteristic curve [AUC], 0.95; positive predictive value [PPV], 75.0%; and negative predictive value [NPV], 98.6%). Functional analysis of differentially expressed proteins implicated the complement and coagulation cascade. A model based on the 10 most predictive proteins accurately predicted transition status in training (AUC, 0.99; PPV, 76.9%; and NPV, 100%) and test (AUC, 0.92; PPV, 81.8%; and NPV, 96.8%) data. The ALSPAC subsample (121 participants from the general population with plasma samples available at age 12 years (61 [50.4%] male) comprised 55 participants (45.5%) with PEs at age 18 years and 61 (50.4%) without PEs at age 18 years. A model using proteomic data at age 12 years predicted PEs at age 18 years, with an AUC of 0.74 (PPV, 67.8%; and NPV, 75.8%).

CONCLUSIONS AND RELEVANCE

In individuals at risk of psychosis, proteomic biomarkers may contribute to individualized prognosis and stratification strategies. These findings implicate early dysregulation of the complement and coagulation cascade in the development of psychosis outcomes.

Precisely Structured Nitric-Oxide-Releasing Copolymer Brush Defeats Broad-Spectrum Catheter-Associated Biofilm Infections In Vivo

Gram-negative bacteria cannot be easily eradicated by antibiotics and are a major source of recalcitrant infections of indwelling medical devices. Among various device-associated infections, intravascular catheter infection is a leading cause of mortality. Prior approaches to surface modification, such as antibiotics impregnation, hydrophilization, unstructured NO-releasing, etc., have failed to achieve adequate infection-resistant coatings. We report a precision-structured diblock copolymer brush (H(N)-b-S) composed of a surface antifouling block of poly(sulfobetaine methacrylate) (S) and a subsurface bactericidal block (H(N)) of nitric-oxide-emitting functionalized poly(hydroxyethyl methacrylate) (H) covalently grafted from the inner and outer surfaces of a polyurethane catheter. The block copolymer architecture of the coating is important for achieving good broad-spectrum anti-biofilm activity with good biocompatibility and low fouling. The coating procedure is scalable to clinically useful catheter lengths. Only the block copolymer brush coating ((H(N)-b-S)) shows unprecedented, above 99.99%, in vitro biofilm inhibition of Gram-positive and Gram-negative bacteria, 100-fold better than previous coatings. It has negligible toxicity toward mammalian cells and excellent blood compatibility. In a murine subcutaneous infection model, it achieves >99.99% biofilm reduction of Gram-positive and Gram-negative bacteria compared with <90% for silver catheter, while in a porcine central venous catheter infection model, it achieves >99.99% reduction of MRSA with 5-day implantation. This precision coating is readily applicable for long-term biofilm-resistant and blood-compatible copolymer coatings covalently grafted from a wide range of medical devices.

Data mining of human plasma proteins generates a multitude of highly predictive aging clocks that reflect different aspects of aging

We previously identified 529 proteins that had been reported by multiple different studies to change their expression level with age in human plasma. In the present study, we measured the q-value and age coefficient of these proteins in a plasma proteomic dataset derived from 4263 individuals. A bioinformatics enrichment analysis of proteins that significantly trend toward increased expression with age strongly implicated diverse inflammatory processes. A literature search revealed that at least 64 of these 529 proteins are capable of regulating life span in an animal model. Nine of these proteins (AKT2, GDF11, GDF15, GHR, NAMPT, PAPPA, PLAU, PTEN, and SHC1) significantly extend life span when manipulated in mice or fish. By performing machine-learning modeling in a plasma proteomic dataset derived from 3301 individuals, we discover an ultra-predictive aging clock comprised of 491 protein entries. The Pearson correlation for this clock was 0.98 in the learning set and 0.96 in the test set while the median absolute error was 1.84 years in the learning set and 2.44 years in the test set. Using this clock, we demonstrate that aerobic-exercised trained individuals have a younger predicted age than physically sedentary subjects. By testing clocks associated with 1565 different Reactome pathways, we also show that proteins associated with signal transduction or the immune system are especially capable of predicting human age. We additionally generate a multitude of age predictors that reflect different aspects of aging. For example, a clock comprised of proteins that regulate life span in animal models accurately predicts age.

Fibrinogen/AKT/Microfilament Axis Promotes Colitis by Enhancing Vascular Permeability

BACKGROUND & AIMS

Increased vascular permeability (VP) has been indicated to play an important role in the pathogenesis of inflammatory bowel disease (IBD). However, the pathological causes of increased intestinal VP in IBD remain largely unknown.

METHOD

Fibrinogen level was measured in dextran sulphate sodium (DSS)-induced colitis and patients with ulcerative colitis. Gly-Pro-Arg-Pro acetate (GPRP), an Fg inhibitor, was used to detect the effect of Fg inhibition on the pathogenesis of DSS-induced colitis, as indicated by tissue damage, cytokine release and inflammatory cell infiltration. Miles assay was used to detect vascular permeability.

RESULTS

Through tandem mass tag-based quantitative proteomics, fibrinogen (Fg) was found to be upregulated in the colon of DSS-treated mice, which was consistent with increased Fg level in colon sample of patients with ulcerative colitis. Gly-Pro-Arg-Pro acetate (GPRP), an Fg inhibitor, significantly alleviated DSS-induced colitis as indicated by improvement of body weight loss and mortality. GPRP decreased colonic inflammation and VP in DSS-treated mice. In vivo, Fg enhanced VP as indicated by Miles assay, which was significantly inhibited by GRPR, AKT (serine/threonine kinase 1) inhibitors and low doses of Jasplakinolide which induced actin polymerization, while was dramatically enhanced by Cytochalasin D (an actin polymerization inhibitor). Moreover, activation of AKT was found in vessels of DSS-treated mice. In vitro, Fg induced activation of AKT and depolymerization of microfilament and promoted cell-to-cell disaggregation. Furthermore, inhibition of AKT decreased Fg-induced microfilament depolymerization.

CONCLUSIONS

Our findings highlight the importance of Fg in regulating colitis by modulation of VP via activating AKT and subsequent depolymerization of microfilament and suggest Fg as an attractive target for anti-colitis treatment.

The Role of Thrombin in Brain Injury After Hemorrhagic and Ischemic Stroke

Thrombin is increased in the brain after hemorrhagic and ischemic stroke primarily due to the prothrombin entry from blood either with a hemorrhage or following blood-brain barrier disruption. Increasing evidence indicates that thrombin and its receptors (protease-activated receptors (PARs)) play a major role in brain pathology following ischemic and hemorrhagic stroke (including intracerebral, intraventricular, and subarachnoid hemorrhage). Thrombin and PARs affect brain injury via multiple mechanisms that can be detrimental or protective. The cleavage of prothrombin into thrombin is the key step of hemostasis and thrombosis which takes place in every stroke and subsequent brain injury. The extravascular effects and direct cellular interactions of thrombin are mediated by PARs (PAR-1, PAR-3, and PAR-4) and their downstream signaling in multiple brain cell types. Such effects include inducing blood-brain-barrier disruption, brain edema, neuroinflammation, and neuronal death, although low thrombin concentrations can promote cell survival. Also, thrombin directly links the coagulation system to the immune system by activating interleukin-1α. Such effects of thrombin can result in both short-term brain injury and long-term functional deficits, making extravascular thrombin an understudied therapeutic target for stroke. This review examines the role of thrombin and PARs in brain injury following hemorrhagic and ischemic stroke and the potential treatment strategies which are complicated by their role in both hemostasis and brain.

Impact of fibrinogen level on the prognosis of patients with traumatic brain injury: a single-center analysis of 2570 patients

Background

Fibrinogen may play an important role in the survival of trauma patients; however, its role in traumatic brain injury (TBI) and its correlation with disease prognosis remain poorly understood. The aims of this study were to determine the incidence of TBI-associated hypofibrinogenemia in patients with TBI and to evaluate the prognostic value of fibrinogen level with respect to mortality and clinical outcomes.

Methods

A total of 2570 consecutive TBI patients were retrospectively studied. Prognostic evaluations were determined using the Glasgow Outcome Score (GOS) assessment 3 months after injury. The shape of the relationship between fibrinogen level and mortality or outcome was examined using cubic spline functions. Logistic regression analyses were conducted to identify the association between fibrinogen level and 3-month functional outcomes.

Results

Fibrinogen concentrations < 2 g/L were observed in 992 (38.6%) patients at the time of admission. Multivariate analyses showed that for patients with fibrinogen levels < 2.0 g/L, those levels were an independent prognostic factor for 3-month mortality (odds ratio [OR], 0.91; 95% confidence interval [CI], 0.89–0.93; P < .001). By contrast, for patients with fibrinogen levels < 2.5 g/L, the levels were an independent prognostic factor for favorable outcomes at 3 months (OR, 1.654; 95% CI, 1.186–2.306; P = .003). Similar results were also seen for patients with fibrinogen levels > 3.0 g/L, with the levels being an independent prognostic factor for favorable outcomes at 3 months (OR, 0.771; 95% CI, 0.607–0.979; P = .033).

Conclusions

Fibrinogen is an independent prognostic factor for clinical outcomes in TBI patients. Maintaining the level of fibrinogen between 2.5 and 3 g/L may improve clinical outcomes in patients with TBI.

Inflammatory Activation of Astrocytes Facilitates Melanoma Brain Tropism via the CXCL10-CXCR3 Signaling Axis

Melanoma is the deadliest skin cancer due to its high rate of metastasis, frequently to the brain. Brain metastases are incurable; therefore, understanding melanoma brain metastasis is of great clinical importance. We used a mouse model of spontaneous melanoma brain metastasis to study the interactions of melanomas with the brain microenvironment. We find that CXCL10 is upregulated in metastasis-associated astrocytes in mice and humans and is functionally important for the chemoattraction of melanoma cells. Moreover, CXCR3, the receptor for CXCL10, is upregulated in brain-tropic melanoma cells. Targeting melanoma expression of CXCR3 by nanoparticle-mediated siRNA delivery or by shRNA transduction inhibits melanoma cell migration and attenuates brain metastasis in vivo. These findings suggest that the instigation of pro-inflammatory signaling in astrocytes is hijacked by brain-metastasizing tumor cells to promote their metastatic capacity and that the CXCL10-CXCR3 axis may be a potential therapeutic target for the prevention of melanoma brain metastasis.

A Geroscience Approach to Preventing Pathologic Consequences of COVID-19

The essential scope of the coronavirus infectious disease 2019 (COVID-19) pandemic is focused on developing effective treatments and vaccines for acute SARS-CoV-2 infection. There is also a critical need to develop interventions to prevent the complications of COVID-19, which occur with an alarming frequency in older adults. Since severe pathologic effects of infection occur with increasing age, COVID-19 falls under the geroscience concept that all diseases in older adults have a common and major underlying cause of declining function and resilience. Geroscience posits that manipulation of aging will simultaneously delay the appearance or severity of major diseases because they share the same risk factor: aging and the multiple processes involved in aging. Drug combinations that target multiple aging processes and the cytokine networks associated with them would not necessarily limit SARS-CoV-2 infection rates but would prevent severe pathologic consequences of the disease in older adults by maintaining a more youthful-like resilience to infection-related complications. A drug cocktail aimed at controlling cytokine actions would complement current clinical treatments and vaccine effectiveness for COVID-19 and serve as a prototype for future age-related infectious disease pandemics wherein the elderly population is especially vulnerable.

Differentially expressed proteins in the intestine of Cynoglossus semilaevis Günther following a Shewanella algae challenge

Fish intestine is an important constituent of the mucosal immune system. The gut and gut-associated lymphoid tissue construct a local immune environment. A Shewanella algae strain was previously reported to be a pathogen causing ascitic disease accompanied with intestinal inflammation in Cynoglossus semilaevis. This study aimed to investigate the intestine immune response in C. semilaevis to S. algae infection at the protein level. Two-dimensional electrophoresis coupled with mass spectrometry proteomics was utilized to compare protein expression in the intestines from normal and S. algae-infected C. semilaevis. A total of 70 differentially expressed proteins (DEPs), consisting of 16 upregulated and 54 downregulated proteins, were identified in the intestine tissue of C. Semilaevis. These protein expression changes were further validated using western blot analysis and quantitative real-time PCR. Gene ontology enrichment analysis showed that these 70 DEPs could be assigned across three categories: "cellular components", "molecular function", and "biological process". Forty-one DEPs (six up-regulated and 35 down-regulated proteins) related to metabolic processes were identified. In addition, 20 DEPs (eight up-regulated and 12 down-regulated proteins) related to stress and immune responses were identified. A protein-protein interaction network generated by the STRING (Search Tool for the Retrieval of Interacting Genes/protein) revealed that 30 DEPs interacted with one another to form an integrated network. Among them, 29 DEPs were related to stress, immune, and metabolism processes. In the network, some of the immune related proteins (C9, FGB, KNG1, apolipoprotein A-IV-like, and PDIA3) were up-regulated and most DEPs involved in metabolism processes were down-regulated. These results indicate that the immune defense response of the intestine was activated and the intestinal function associated with metabolism processes was disturbed. This study provides valuable information for further research into the functions of these DEPs in fish.

Metformin as a Potential Agent in the Treatment of Multiple Sclerosis

Metformin, a synthetic derivative of guanidine, is commonly used as an oral antidiabetic agent and is considered a multi-vector application agent in the treatment of other inflammatory diseases. Recent studies have confirmed the beneficial effect of metformin on immune cells, with special emphasis on immunological mechanisms. Multiple Sclerosis (MS) is an autoimmune disease of the central nervous system (CNS) characterized by various clinical courses. Although the pathophysiology of MS remains unknown, it is most likely a combination of disturbances of the immune system and biochemical pathways with a disruption of blood-brain barrier (BBB), and it is strictly related to injury of intracerebral blood vessels. Metformin has properties which are greatly desirable for MS therapy, including antioxidant, anti-inflammatory or antiplatelet functions. The latest reports relating to the cardiovascular disease confirm an increased risk of ischemic events in MS patients, which are directly associated with a coagulation cascade and an elevated pro-thrombotic platelet function. Hence, this review examines the potential favourable effects of metformin in the course of MS, its role in preventing inflammation and endothelial dysfunction, as well as its potential antiplatelet role.

Reelin depletion protects against autoimmune encephalomyelitis by decreasing vascular adhesion of leukocytes

Neuroinflammation as a result of immune cell recruitment into the central nervous system (CNS) is a key pathogenic mechanism of multiple sclerosis (MS). However, current anti-inflammatory interventions depleting immune cells or directly targeting their trafficking into the CNS can have serious side effects, highlighting a need for better immunomodulatory strategies. We detected increased Reelin concentrations in the serum of patients with MS, resulting in increased endothelial permeability to leukocytes through increased nuclear factor κB-mediated expression of vascular adhesion molecules. We thus investigated the prophylactic and therapeutic potential of Reelin immunodepletion in experimental autoimmune encephalomyelitis (EAE) and further validated the results in Reelin knockout mice. Removal of plasma Reelin by either approach protected against neuroinflammation and largely abolished the neurological consequences by reducing endothelial permeability and immune cell accumulation in the CNS. Our findings suggest Reelin depletion as a therapeutic approach with an inherent good safety margin for the treatment of MS and other diseases where leukocyte extravasation is a major driver of pathogenicity.

Inflammation: major denominator of obesity, Type 2 diabetes and Alzheimer's disease-like pathology?

Adipose tissue is an active metabolic organ that contributes to processes such as energy storage and utilization and to the production of a number of metabolic agents, such as adipokines, which play a role in inflammation. In this review, we try to elucidate the connections between peripheral inflammation at obesity and Type 2 diabetes and the central inflammatory process. Multiple lines of evidence highlight the importance of peripheral inflammation and its link to neuroinflammation, which can lead to neurodegenerative diseases such as dementia, Alzheimer's disease (AD) and Parkinson's disease. In addition to the accumulation of misfolded amyloid beta (Aβ) peptide and the formation of the neurofibrillary tangles of hyperphosphorylated tau protein in the brain, activated microglia and reactive astrocytes are the main indicators of AD progression. They were found close to Aβ plaques in the brains of both AD patients and rodent models of Alzheimer's disease-like pathology. Cytokines are key players in pro- and anti-inflammatory processes and are also produced by microglia and astrocytes. The interplay of seemingly unrelated pathways between the periphery and the brain could, in fact, have a common denominator, with inflammation in general being a key factor affecting neuronal processes in the brain. An increased amount of white adipose tissue throughout the body seems to be an important player in pro-inflammatory processes. Nevertheless, other important factors should be studied to elucidate the pathological processes of and the relationship among obesity, Type 2 diabetes and neurodegenerative diseases.

Endothelial-specific Crif1 deletion induces BBB maturation and disruption via the alteration of actin dynamics by impaired mitochondrial respiration

Cerebral endothelial cells (ECs) require junctional proteins to maintain blood-brain barrier (BBB) integrity, restricting toxic substances and controlling peripheral immune cells with a higher concentration of mitochondria than ECs of peripheral capillaries. The mechanism underlying BBB disruption by defective mitochondrial oxidative phosphorylation (OxPhos) is unclear in a mitochondria-related gene-targeted animal model. To assess the role of EC mitochondrial OxPhos function in the maintenance of the BBB, we developed an EC-specific CR6-interactin factor1 (Crif1) deletion mouse. We clearly observed defects in motor behavior, uncompacted myelin and leukocyte infiltration caused by BBB maturation and disruption in this mice. Furthermore, we investigated the alteration in the actin cytoskeleton, which interacts with junctional proteins to support BBB integrity. Loss of Crif1 led to reorganization of the actin cytoskeleton and a decrease in tight junction-associated protein expression through an ATP production defect in vitro and in vivo. Based on these results, we suggest that mitochondrial OxPhos is important for the maturation and maintenance of BBB integrity by supplying ATP to cerebral ECs.

Leveraging the Dynamic Blood-Brain Barrier for Central Nervous System Nanoparticle-based Drug Delivery Applications

Neurological diseases and injuries have profound impact on a patient's lifespan and functional capabilities, but often lack effective intervention strategies to address the underlying neuropathology. The blood-brain barrier (BBB) is a major hurdle in the effective delivery of therapeutics to the brain. Recent discoveries in BBB maintenance reveal a dynamic system where time of day, disease progression, and even biological variables all strongly influence its permeability and flux of molecules. Nanoparticles can be used to improve the efficacy of therapeutics by increasing circulation time, bioavailability, selectivity, and controlling the rate of payload release. Considering these recent findings, the next generation of pharmacological paradigms are evolving to leverage nanotechnology to turn therapeutic intervention to meet the needs of a specific patient (i.e. personalized medicine).

Brain Microvascular Pericytes in Vascular Cognitive Impairment and Dementia

Pericytes are unique, multi-functional mural cells localized at the abluminal side of the perivascular space in microvessels. Originally discovered in 19th century, pericytes had drawn less attention until decades ago mainly due to lack of specific markers. Recently, however, a growing body of evidence has revealed that pericytes play various important roles: development and maintenance of blood–brain barrier (BBB), regulation of the neurovascular system (e.g., vascular stability, vessel formation, cerebral blood flow, etc.), trafficking of inflammatory cells, clearance of toxic waste products from the brain, and acquisition of stem cell-like properties. In the neurovascular unit, pericytes perform these functions through coordinated crosstalk with neighboring cells including endothelial, glial, and neuronal cells. Dysfunction of pericytes contribute to a wide variety of diseases that lead to cognitive impairments such as cerebral small vessel disease (SVD), acute stroke, Alzheimer’s disease (AD), and other neurological disorders. For instance, in SVDs, pericyte degeneration leads to microvessel instability and demyelination while in stroke, pericyte constriction after ischemia causes a no-reflow phenomenon in brain capillaries. In AD, which shares some common risk factors with vascular dementia, reduction in pericyte coverage and subsequent microvascular impairments are observed in association with white matter attenuation and contribute to impaired cognition. Pericyte loss causes BBB-breakdown, which stagnates amyloid β clearance and the leakage of neurotoxic molecules into the brain parenchyma. In this review, we first summarize the characteristics of brain microvessel pericytes, and their roles in the central nervous system. Then, we focus on how dysfunctional pericytes contribute to the pathogenesis of vascular cognitive impairment including cerebral ‘small vessel’ and ‘large vessel’ diseases, as well as AD. Finally, we discuss therapeutic implications for these disorders by targeting pericytes.

Transcriptional profiling and therapeutic targeting of oxidative stress in neuroinflammation

Oxidative stress is a central part of innate-immune induced neurodegeneration. However, the transcriptomic landscape of the central nervous system (CNS) innate immune cells contributing to oxidative stress is unknown, and therapies to target their neurotoxic functions are not widely available. Here, we provide the oxidative stress innate immune cell atlas in neuroinflammatory disease, and report the discovery of new druggable pathways. Transcriptional profiling of oxidative stress-producing CNS innate immune cells (Tox-seq) identified a core oxidative stress gene signature coupled to coagulation and glutathione pathway genes shared between a microglia cluster and infiltrating macrophages. Tox-seq followed by a microglia high-throughput screen (HTS) and oxidative stress gene network analysis, identified the glutathione regulating compound acivicin with potent therapeutic effects decreasing oxidative stress and axonal damage in chronic and relapsing multiple sclerosis (MS) models. Thus, oxidative stress transcriptomics identified neurotoxic CNS innate immune populations and may enable the discovery of selective neuroprotective strategies.

Ex vivo interaction between blood components and hormone-dependent breast cancer cells induces alterations associated with epithelial-mesenchymal transition and thrombosis

The prevalence of breast cancer is steadily increasing with metastasis and thromboembolic complications identified as the most common causes of death. The acquisition of an aggressive phenotype by hormone-dependent breast cancers is mediated by Transforming Growth Factor Beta 1 (TGF-β₁) expression and is associated with epithelial-mesenchymal transition (EMT) and, potentially, increased propensity for thrombosis. We investigated this phenomenon by assessing the effect of platelet-rich plasma (PRP) and whole blood (WB) on parameters of EMT and hypercoagulation in vitro. MCF-7 breast cancer cells were cultured under standard conditions, followed by co-culture with PRP or WB. Cells were processed for real-time PCR (TGF-β₁ and vimentin), electron microscopy or immunocytochemistry (TGF-β₁). Micrographs were qualitatively assessed, and real-time PCR data analyzed with PAST Statistical Software. The addition of blood components heightened TGF-β₁ immunolocalization and significantly increased corresponding gene expression. Both PRP and WB significantly increased vimentin expression and induced a shape change from a typical epithelial phenotype to a spindle-shape morphology, indicative of EMT. Fibrin fiber, network and plaque formation indicated a hypercoagulatory environment. The results thus show that in preparation for hematogenous metastasis, hormone-dependent breast cancer cells assume an aggressive phenotype associated with EMT, simultaneously increasing the propensity for the formation of thrombo-emboli.

C-X-C Motif Chemokine 10 Contributes to the Development of Neuropathic Pain by Increasing the Permeability of the Blood-Spinal Cord Barrier

Neuropathic pain is among the most debilitating forms of chronic pain. Studies have suggested that chronic pain pathogenesis involves neuroimmune interactions and blood-spinal cord barrier (BSCB) disruption. However, the underlying mechanisms are poorly understood. We modeled neuropathic pain in rats by inducing chronic constriction injury (CCI) of the sciatic nerve and analyzed the effects on C-X-C motif chemokine 10 (CXCL10)/CXCR3 activation, BSCB permeability, and immune cell migration from the circulation into the spinal cord. We detected CXCR3 expression in spinal neurons and observed that CCI induced CXCL10/CXCR3 activation, BSCB disruption, and mechanical hyperalgesia. CCI-induced BSCB disruption enabled circulating T cells to migrate into the spinal parenchyma. Intrathecal administration of an anti-CXCL10 antibody not only attenuated CCI-induced hyperalgesia, but also reduced BSCB permeability, suggesting that CXCL10 acts as a key regulator of BSCB integrity. Moreover, T cell migration may play a critical role in the neuroimmune interactions involved in the pathogenesis of CCI-induced neuropathic pain. Our results highlight CXCL10 as a new potential drug target for the treatment of nerve injury-induced neuropathic pain.

ADAMTS13 ameliorates inflammatory responses in experimental autoimmune encephalomyelitis

BACKGROUND

ADAMTS13 (a disintegrin and metalloprotease with a thrombospondin type 1 motif, member 13) plays a vital role in preventing microvascular thrombosis and inflammation. Reduced ADAMTS13 levels in plasma have been detected in multiple sclerosis (MS) patients. In the present study, we have determined the role of ADAMTS13 in the disease progression of MS using a mouse model of experimental autoimmune encephalomyelitis (EAE).

METHODS

Female C57BL/6 mice were immunized with MOG_35-55 peptide and then treated with ADAMTS13 or vehicle in preventive and therapeutic settings. Mice were analyzed for clinical deficit, white matter demyelination and inflammatory cell infiltration. To explore the underlying mechanism, VWF expression and blood-spinal cord barriers (BSCB) were determined.

RESULTS

Plasma ADAMTS13 activity was suppressed in EAE mice. ADAMTS13-treated EAE mice exhibited an ameliorated disease course, reduced demyelination, and decreased T lymphocyte, neutrophil and monocyte infiltration into the spinal cord. Consistently, ADAMTS13 treatment reduced VWF levels and inhibited BSCB breakdown in the spinal cords of EAE mice. However, leukocytes in the blood and spleen of EAE mice remained unaffected by ADAMTS13 administration.

CONCLUSION

Our results demonstrate that ADAMTS13 treatment ameliorates inflammatory responses, demyelination and disease course in EAE mice. Therefore, our study suggests that ADAMTS13 may represent a potential therapeutic strategy for MS patients.

An Integrated View on Vascular Dysfunction in Alzheimer's Disease

BACKGROUND

Cerebrovascular disease is a common comorbidity in patients with Alzheimer's disease (AD). It is believed to contribute additively to the cognitive impairment and to lower the threshold for the development of dementia. However, accumulating evidence suggests that dysfunction of the cerebral vasculature and AD neuropathology interact in multiple ways. Vascular processes even proceed AD neuropathology, implicating a causal role in the etiology of AD. Thus, the review aims to provide an integrated view on vascular dysfunction in AD.

SUMMARY

In AD, the cerebral vasculature undergoes pronounced cellular, morphological and structural changes, which alters regulation of blood flow, vascular fluid dynamics and vessel integrity. Stiffening of central blood vessels lead to transmission of excessive pulsatile energy to the brain microvasculature, causing end-organ damage. Moreover, a dysregulated hemostasis and chronic vascular inflammation further impede vascular function, where its mediators interact synergistically. Changes of the cerebral vasculature are triggered and driven by systemic vascular abnormalities that are part of aging, and which can be accelerated and aggravated by cardiovascular diseases. Key Messages: In AD, the cerebral vasculature is the locus where multiple pathogenic processes converge and contribute to cognitive impairment. Understanding the molecular mechanism and pathophysiology of vascular dysfunction in AD and use of vascular blood-based and imaging biomarker in clinical studies may hold promise for future prevention and therapy of the disease.

Fibrin(ogen) in human disease: both friend and foe

Fibrinogen is an abundant protein synthesized in the liver, present in human blood plasma at concentrations ranging from 1.5-4 g/L in healthy individuals with a normal half-life of 3-5 days. With fibrin, produced by thrombin-mediated cleavage, fibrinogen plays important roles in many physiological processes. Indeed, the formation of a stable blood clot, containing polymerized and cross-linked fibrin, is crucial to prevent blood loss and drive wound healing upon vascular injury. A balance between clotting, notably the conversion of fibrinogen to fibrin, and fibrinolysis, the proteolytic degradation of the fibrin mesh, is essential. Disruption of this equilibrium can cause disease in distinct manners. While some pathological conditions are the consequence of altered levels of fibrinogen, others are related to structural properties of the molecule. The source of fibrinogen expression and the localization of fibrin(ogen) protein also have clinical implications. Low levels of fibrinogen expression have been detected in extra-hepatic tissues, including carcinomas, potentially contributing to disease. Fibrin(ogen) deposits at aberrant sites including the central nervous system or kidney, can also be pathological. In this review, we discuss disorders in which fibrinogen and fibrin are implicated, highlighting mechanisms that may contribute to disease.

Considerations for Soluble Protein Biomarker Blood Sample Matrix Selection

Blood-based soluble protein biomarkers provide invaluable clinical information about patients and are used as diagnostic, prognostic, and pharmacodynamic markers. The most commonly used blood sample matrices are serum and different types of plasma. In drug development research, the impact of sample matrix selection on successful protein biomarker quantification is sometimes overlooked. The sample matrix for a specific analyte is often chosen based on prior experience or literature searches, without good understanding of the possible effects on analyte quantification. Using a data set of 32 different soluble protein markers measured in matched serum and plasma samples, we examined the differences between serum and plasma and discussed how platelet or immune cell activation can change the quantified concentration of the analyte. We have also reviewed the effect of anticoagulant on analyte quantification. Finally, we provide specific recommendations for biomarker sample matrix selection and propose a systematic and data-driven approach for sample matrix selection. This review is intended to raise awareness of the impact and considerations of sample matrix selection on biomarker quantification.

Systemic factors as mediators of brain homeostasis, ageing and neurodegeneration

A rapidly ageing population and a limited therapeutic toolbox urgently necessitate new approaches to treat neurodegenerative diseases. Brain ageing, the key risk factor for neurodegeneration, involves complex cellular and molecular processes that eventually result in cognitive decline. Although cell-intrinsic defects in neurons and glia may partially explain this decline, cell-extrinsic changes in the systemic environment, mediated by blood, have recently been shown to contribute to brain dysfunction with age. Here, we review the current understanding of how systemic factors mediate brain ageing, how these factors are regulated and how we can translate these findings into therapies for neurodegenerative diseases.

The FDP/FIB Ratio and Blood FDP Level May Be Related to Seizures After Fever in Young Children

Objective: To evaluate the relationship of the blood fibrinogen (FIB) degradation product (FDP) level and FDP/FIB ratio with seizure in young children with fever. Methods: A total of 35 children with simple febrile seizures and 80 children with fever but no seizure were selected. First, the differences in white blood cell (WBC), platelets (PLT), prothrombin time (PT), activated partial thromboplastin time (APTT), thrombin time (TT), FIB, FDP, FDP/FIB ratio, and C-reactive protein (CRP) between 35 children with simple febrile seizures and 40 randomly selected children with fever but no seizure were retrospectively analyzed. Then, an ROC curve was used to determine the diagnostic utility of the FDP level, FDP/FIB ratio, and FDP+FDP/FIB ratio, and the best diagnostic cutoff points were selected. Finally, the diagnostic specificities of the three diagnostic indicators were verified by comparison with the results of all 80 children with fever but no seizure. Results: The FDP level and FDP/FIB ratio were significantly different between the two groups (P < 0.0001) and there was a positive correlation between the FDP and FIB levels. Both the FDP level and FDP/FIB ratio had good diagnostic value. An FDP ≥ 2.0 mg/L and FDP/FIB ratio ≥ 0.5 had good diagnostic specificities. Combined application of an FDP ≥ 2.0 mg/L and FDP/FIB ratio ≥ 0.5 improved the diagnostic power. Conclusions: The blood FDP level and FDP/FIB ratio may be related to seizures after fever, and an FDP ≥ 2.0 mg/L + FDP/FIB ratio ≥ 0.5 has good diagnostic specificity.

Short-term inhibition of fibrinolytic system restores locomotor function after spinal cord injury in mice

Spinal cord injury (SCI) is caused by an initial mechanical insult followed by a series of deleterious events that promote the progressive damage of affected tissues. Fibrinolysis, the process by which plasmin degrades cross-linked fibrin clots, has numerous functions in the central nervous system. However, the roles of the fibrinolytic system in SCI pathophysiology remain unknown. We investigated the roles of fibrinolysis in SCI, and explored therapeutic applications targeting fibrinolysis. Plasminogen-deficient (Plg^-/-) mice exhibited significantly improved locomotor function in the early phase of SCI (the first 7 days post injury), with significant inhibition of bleeding and vascular permeability, but failed to demonstrate conclusive functional recovery. Consistent with these findings, the short-term administration of tranexamic acid (TXA) in wild-type mice over the first 3 days post injury significantly improved locomotor function after SCI, whereas prolonged TXA administration did not. Prolonged TXA administration resulted in significantly lower levels of matrix metalloproteinase activities in the spinal cord, suggesting that inhibition of the fibrinolytic system impaired tissue remodeling. Our results indicate that the fibrinolytic system has time-dependent biphasic actions following SCI. The temporally optimised modulation of fibrinolytic activity may thus be a novel therapeutic strategy to improve functional outcomes after SCI.

Iron homeostasis, complement, and coagulation cascade as CSF signature of cortical lesions in early multiple sclerosis

Objective

Intrathecal inflammation, compartmentalized in cerebrospinal fluid (CSF) and in meningeal infiltrates, has fundamental role in inflammation, demyelination, and neuronal injury in cerebral cortex in multiple sclerosis (MS). Since the exact link between intrathecal inflammation and mechanisms of cortical pathology remains unknown, we aimed to investigate a detailed proteomic CSF profiling which is able to reflect cortical damage in early MS.

Methods

We combined new proteomic method, TRIDENT, CSF analysis, and advanced 3T magnetic resonance imaging (MRI), in 64 MS patients at the time of diagnosis and 26 controls with other neurological disorders. MS patients were stratified according to cortical lesion (CL) load.

Results

We identified 227 proteins differently expressed between the patients with high and low CL load. These were mainly related to complement and coagulation cascade as well as to iron homeostasis pathway (30 and 6% of all identified proteins, respectively). Accordingly, in the CSF of MS patients with high CL load at diagnosis, significantly higher levels of sCD163 (P < 0.0001), free hemoglobin (Hb) (P < 0.05), haptoglobin (P < 0.0001), and fibrinogen (P < 0.01) were detected. By contrast, CSF levels of sCD14 were significantly (P < 0.05) higher in MS patients with low CL load. Furthermore, CSF levels of sCD163 positively correlated (P < 0.01) with CSF levels of neurofilament, fibrinogen, and B cell‐related molecules, such as CXCL13, CXCL12, IL10, and BAFF.

Interpretation

Intrathecal dysregulation of iron homeostasis and coagulation pathway as well as B‐cell and monocyte activity are strictly correlated with cortical damage at early disease stages.

Inflaming the Brain

Exactly how cerebrovascular alterations contribute to Alzheimer's disease (AD) is still unknown. Merlini et al. (2019) show that blood-derived fibrinogen leads to dendritic spine elimination and cognitive deficit via microglial CD11b/CD18. Fibrinogen may be a significant contributor to AD pathogenesis.

Modification of primary amines to higher order amines reduces in vivo hematological and immunotoxicity of cationic nanocarriers through TLR4 and complement pathways

For decades, cationic polymer nanoparticles have been investigated for nucleic acid delivery. Despite promising in vitro transfection results, most formulations have failed to translate into the clinic due to significant in vivo toxicity - especially when delivered intravenously. To address this significant problem, we investigated the detailed mechanisms that govern the complex in vivo systemic toxicity response to common polymeric nanoparticles. We determined that the toxicity response is material dependent. For branched polyethylenimine (bPEI) nanoparticles - toxicity is a function of multiple pathophysiological responses - triggering of innate immune sensors, induction of hepatic toxicity, and significant alteration of hematological properties. In contrast, for chitosan-based nanoparticles - systemic toxicity is primarily driven through innate immune activation. We further identified that modification of primary amines to secondary and tertiary amines using the small molecule imidazole-acetic-acid (IAA) ameliorates in vivo toxicity from both nanocarriers by different, material-specific mechanisms related to Toll-like receptor 4 activation (for bPEI) and complement activation driven neutrophil infiltration (for chitosan), respectively. Our results provide a detailed roadmap for evaluating in vivo toxicity of nanocarriers and identifies potential opportunities to reduce toxicity for eventual clinical translation.

Endothelial Targets in Stroke: Translating Animal Models to Human

Cerebral ischemia (stroke) induces injury to the cerebral endothelium that may contribute to parenchymal injury and worsen outcome. This review focuses on current preclinical studies examining how to prevent ischemia-induced endothelial dysfunction. It particularly focuses on targets at the endothelium itself. Those include endothelial tight junctions, transcytosis, endothelial cell death, and adhesion molecule expression. It also examines how such studies are being translated to the clinic, especially as adjunct therapies for preventing intracerebral hemorrhage during reperfusion of the ischemic brain. Identification of endothelial targets may prove valuable in a search for combination therapies that would specifically protect different cell types in ischemia.

Imaging the dynamic interactions between immune cells and the neurovascular interface in the spinal cord

Imaging the dynamic interactions between immune cells, glia, neurons and the vasculature in living rodents has revolutionized our understanding of physiological and pathological mechanisms of the CNS. Emerging microscopy and imaging technologies have enabled longitudinal tracking of structural and functional changes in a plethora of different cell types in the brain. The development of novel methods also allowed stable and longitudinal optical access to the spinal cord with minimum tissue perturbation. These important advances facilitated the application of in vivo imaging using two-photon microscopy for studies of the healthy, diseased, or injured spinal cord. Indeed, decoding the interactions between peripheral and resident cells with the spinal cord vasculature has shed new light on neuroimmune and vascular mechanisms regulating the onset and progression of neurological diseases. This review focuses on imaging studies of the interactions between the vasculature and peripheral immune cells or microglia, with emphasis on their contribution to neuroinflammation. We also discuss in vivo imaging studies highlighting the importance of neurovascular changes following spinal cord injury. Real-time imaging of blood-brain barrier (BBB) permeability and other vascular changes, perivascular glial responses, and immune cell entry has revealed unanticipated cellular mechanisms and novel molecular pathways that can be targeted to protect the injured or diseased CNS. Imaging the cell-cell interactions between the vasculature, immune cells, and neurons as they occur in real time, is a powerful tool both for testing the efficacy of existing therapeutic approaches, and for identifying new targets for limiting damage or enhancing the potential for repair of the affected spinal cord tissue.

Aging Neurovascular Unit and Potential Role of DNA Damage and Repair in Combating Vascular and Neurodegenerative Disorders

Progressive neurological deterioration poses enormous burden on the aging population with ischemic stroke and neurodegenerative disease patients, such as Alzheimers’ disease and Parkinson’s disease. The past two decades have witnessed remarkable advances in the research of neurovascular unit dysfunction, which is emerging as an important pathological feature that underlies these neurological disorders. Dysfunction of the unit allows penetration of blood-derived toxic proteins or leukocytes into the brain and contributes to white matter injury, disturbed neurovascular coupling and neuroinflammation, which all eventually lead to cognitive dysfunction. Recent evidences suggest that aging-related oxidative stress, accumulated DNA damage and impaired DNA repair capacities compromises the genome integrity not only in neurons, but also in other cell types of the neurovascular unit, such as endothelial cells, astrocytes and pericytes. Combating DNA damage or enhancing DNA repair capacities in the neurovascular unit represents a promising therapeutic strategy for vascular and neurodegenerative disorders. In this review, we focus on aging related mechanisms that underlie DNA damage and repair in the neurovascular unit and introduce several novel strategies that target the genome integrity in the neurovascular unit to combat the vascular and neurodegenerative disorders in the aging brain.

Spatiotemporal distribution of fibrinogen in marmoset and human inflammatory demyelination

Multiple sclerosis is an inflammatory demyelinating disease of the central nervous system. Although it has been extensively studied, the proximate trigger of the immune response remains uncertain. Experimental autoimmune encephalomyelitis in the common marmoset recapitulates many radiological and pathological features of focal multiple sclerosis lesions in the cerebral white matter, unlike traditional experimental autoimmune encephalomyelitis in rodents. This provides an opportunity to investigate how lesions form as well as the relative timing of factors involved in lesion pathogenesis, especially during early stages of the disease. We used MRI to track experimental autoimmune encephalomyelitis lesions in vivo to determine their age, stage of development, and location, and we assessed the corresponding histopathology post-mortem. We focused on the plasma protein fibrinogen-a marker for blood-brain barrier leakage that has also been linked to a pathogenic role in inflammatory demyelinating lesion development. We show that fibrinogen has a specific spatiotemporal deposition pattern, apparently deriving from the central vein in early experimental autoimmune encephalomyelitis lesions <6 weeks old, and preceding both demyelination and visible gadolinium enhancement on MRI. Thus, fibrinogen leakage is one of the earliest detectable events in lesion pathogenesis. In slightly older lesions, fibrinogen is found inside microglia/macrophages, suggesting rapid phagocytosis. Quantification demonstrates positive correlation of fibrinogen deposition with accumulation of inflammatory cells, including microglia/macrophages and T cells. The peak of fibrinogen deposition coincides with the onset of demyelination and axonal loss. In samples from chronic multiple sclerosis cases, fibrinogen was found at the edge of chronic active lesions, which have ongoing demyelination and inflammation, but not in inactive lesions, suggesting that fibrinogen may play a role in sustained inflammation even in the chronic setting. In summary, our data support the notion that fibrinogen is a key player in the early pathogenesis, as well as sustained inflammation, of inflammatory demyelinating lesions.

Biomimetic Strategies To Treat Traumatic Brain Injury by Leveraging Fibrinogen

There were over 27 million new cases of traumatic brain injuries (TBIs) in 2016 across the globe. TBIs are often part of complicated trauma scenarios and may not be diagnosed initially because the primary clinical focus is on stabilizing the patient. Interventions used to stabilize trauma patients may inadvertently impact the outcomes of TBIs. Recently, there has been a strong interest in the trauma community toward administrating fibrinogen-containing solutions intravenously to help stabilize trauma patients. While this interventional shift may benefit general trauma scenarios, fibrinogen is associated with potentially deleterious effects for TBIs. Here, we deconstruct what components of fibrinogen may be beneficial as well as potentially harmful following TBI and extrapolate this to biomimetic approaches to treat bleeding and trauma that may also lead to better outcomes following TBI.

Intracerebroventricular administration of lupus serum induces microglia activation and leukocyte adhesion in the cerebromicrovasculature of mice

BACKGROUND

Central nervous system (CNS) involvement is commonly seen in the patients with system lupus erythematosus (SLE). Mechanisms underlying CNS damage in SLE remain largely unknown. Accumulating evidence suggest that activation of microglia in CNS plays an important role in the inflammatory responses in neurological diseases. The aim of this study is to examine the involvement of microglia in the CNS inflammatory responses induced by circulating serum of SLE patients.

METHODS

We performed intracerebroventricular (ICV) injection of serums collected from SLE patients or healthy controls to mice, and examined phenotypic changes of microglia, the levels of cytokines, chemokine and adhesion molecules in the brain. Intravital microscopy was used to observe leukocyte rolling and adhesion in the cerebromicrovasculature. We further examined whether minocycline can block inflammatory responses induced by SLE serum. In vitro experiments were conducted to examine whether IgGs from the sera of SLE patients or healthy control can activate the primary cultured microglia.

RESULTS

We found that ICV injection of SLE serum increases morphological activation of microglia in the cortex and hippocampus. Inflammatory mediators including pro-inflammatory cytokines (IL-1, IL-6 and TNF-α), chemokine (CCL2 and CCL5) and adhesion molecules (P-selectin and ICAM-1) were significantly elevated in the brains of SLE-serum-treated mice. Using intravital microscopy, we demonstrated that SLE serum promotes leukocyte rolling and adhesion. Furthermore, suppression of microglia activation by systemically using minocycline could decrease the levels of inflammatory molecular, and prevent leukocyte rolling and adhesion. The in vitro experiments revealed that IgG from SLE sera could be engulfed by microglia and stimulated the microglia to secret pro-inflammatory cytokines.

CONCLUSION

Our data suggest that the activation of microglia, which promotes leukocyte adhesion to the brain microvasculature, is an important pathological mechanism of CNS involvement in SLE.

A high-fat diet promotes depression-like behavior in mice by suppressing hypothalamic PKA signaling

Obesity is associated with an increased risk of depression. The aim of the present study was to investigate whether obesity is a causative factor for the development of depression and what is the molecular pathway(s) that link these two disorders. Using lipidomic and transcriptomic methods, we identified a mechanism that links exposure to a high-fat diet (HFD) in mice with alterations in hypothalamic function that lead to depression. Consumption of an HFD selectively induced accumulation of palmitic acid in the hypothalamus, suppressed the 3', 5'-cyclic AMP (cAMP)/protein kinase A (PKA) signaling pathway, and increased the concentration of free fatty acid receptor 1 (FFAR1). Deficiency of phosphodiesterase 4A (PDE4A), an enzyme that degrades cAMP and modulates stimulatory regulative G protein (Gs)-coupled G protein-coupled receptor signaling, protected animals either from genetic- or dietary-induced depression phenotype. These findings suggest that dietary intake of saturated fats disrupts hypothalamic functions by suppressing cAMP/PKA signaling through activation of PDE4A. FFAR1 inhibition and/or an increase of cAMP signaling in the hypothalamus could offer potential therapeutic targets to counteract the effects of dietary or genetically induced obesity on depression.

Vascular aspects of multiple sclerosis: emphasis on perfusion and cardiovascular comorbidities

INTRODUCTION

Multiple sclerosis (MS) is a chronic inflammatory, demyelinating, and neurodegenerative disease of the central nervous system. Over the last two decades, more favorable MS long-term outcomes have contributed toward increase in prevalence of the aged MS population. Emergence of age-associated pathology, such as cardiovascular diseases, may interact with the MS pathophysiology and further contribute to disease progression. Areas covered: This review summarizes the cardiovascular involvement in MS pathology, its disease activity, and progression. The cardiovascular health, the presence of various cardiovascular diseases, and their effect on MS cognitive performance are further explored. In similar fashion, the emerging evidence of a higher incidence of extracranial arterial pathology and its association with brain MS pathology are discussed. Finally, the authors outline the methodologies behind specific perfusion magnetic resonance imaging (MRI) and ultrasound Doppler techniques, which allow measurement of disease-specific and age-specific vascular changes in the aging population and MS patients. Expert opinion: Cardiovascular pathology significantly contributes to worse clinical and MRI-derived disease outcomes in MS. Global and regional cerebral hypoperfusion may be associated with poorer physical and cognitive performance. Prevention, improved detection, and treatment of the cardiovascular-based pathology may improve the overall long-term health of MS patients.

Extracellular vesicle fibrinogen induces encephalitogenic CD8+ T cells in a mouse model of multiple sclerosis

In this report, we show that fibrinogen, identified by proteomics to be present in blood plasma extracellular vesicles (EVs), is sufficient and required for autoimmune-mediated spontaneous relapsing disease activity in a murine model of multiple sclerosis (MS). Unique to this model is that plasma EVs induced CD8-mediated disease. Analysis of human plasma EVs identified fibrinogen in MS patient samples, thereby providing a compelling translational association between our experimental findings and the perpetuation of CD8-mediated autoimmunity in human MS. Hence, these findings provide evidence for EVs as means by which to model an important aspect of spontaneous CD8+ T cell development related to autoimmunity in MS.

Extracellular vesicles (EVs) are emerging as potent mediators of intercellular communication with roles in inflammation and disease. In this study, we examined the role of EVs from blood plasma (pEVs) in an experimental autoimmune encephalomyelitis mouse model of central nervous system demyelination. We determined that pEVs induced a spontaneous relapsing−remitting disease phenotype in MOG_35–55-immunized C57BL/6 mice. This modified disease phenotype was found to be driven by CD8+ T cells and required fibrinogen in pEVs. Analysis of pEVs from relapsing−remitting multiple sclerosis patients also identified fibrinogen as a significant portion of pEV cargo. Together, these data suggest that fibrinogen in pEVs contributes to the perpetuation of neuroinflammation and relapses in disease.