Blood-brain barrier permeability and monocyte infiltration in experimental allergic encephalomyelitis: a quantitative MRI study

Upregulation of C-X-C motif chemokine 12 in the spinal cord alleviated the symptoms of experimental autoimmune encephalomyelitis in Lewis rats

Background

C-X-C motif chemokine 12 (CXCL12) is a chemokine that performs many functions. Studies have shown that CXCL12 can aggravate inflammatory symptoms in the central nervous system (CNS). Evidence also indicates that CXCL12 can promote the repair of myelin sheaths in the CNS in experimental autoimmune encephalomyelitis (EAE). Here, we investigated the function of CXCL12 in CNS inflammation by upregulating CXCL12 in the spinal cord and subsequently inducing EAE.

Materials and methods

CXCL12 upregulation in the spinal cords of Lewis rats was induced by the injection of adeno-associated virus 9 (AAV9)/eGFP-P2A-CXCL12 after intrathecal catheter implantation. Twenty-one days after AAV injection, EAE was induced and clinical score was collected; Immunofluorescence staining, WB and LFB-PAS staining were used to evaluate the effect of CXCL12 upregulation. In the in vitro study, oligodendrocyte precursor cells (OPCs) were harvested, cultured with CXCL12 and AMD3100, and subjected to immunofluorescence staining for functional assessment.

Results

CXCL12 was upregulated in the lumbar enlargement of the spinal cord by AAV injection. In each stage of EAE, upregulation of CXCL12 significantly alleviated clinical scores by inhibiting leukocyte infiltration and promoting remyelination. In contrast, the addition of AMD3100, which is a CXCR4 antagonist, inhibited the effect of CXCL12. In vitro, 10 ng/ml CXCL12 promoted the differentiation of OPCs into oligodendrocytes.

Conclusion

AAV-mediated upregulation of CXCL12 in the CNS can alleviate the clinical signs and symptoms of EAE and significantly decrease the infiltration of leukocytes in the peak stage of EAE. CXCL12 can promote the maturation and differentiation of OPCs into oligodendrocytes in vitro. These data indicate that CXCL12 effectively promotes remyelination in the spinal cord and decreases the signs and symptoms of EAE.

Morphine-mediated release of astrocyte-derived extracellular vesicle miR-23a induces loss of pericyte coverage at the blood-brain barrier: Implications for neuroinflammation

Opioids such as morphine are the most potent and efficacious drugs currently available for pain management. Paradoxically, opioids have also been implicated in inducing neuroinflammation and associated neurocognitive decline. Pericytes, a critical component of the neurovascular unit (NVU), are centrally positioned between endothelial cells and astrocytes, maintaining function of the blood-brain barrier (BBB) nd regulating neuroinflammation by controlling monocyte influx under various pathological conditions. The role of pericytes in morphine-mediated neuroinflammation however, has received less attention, especially in the context of how pericytes crosstalk with other central nervous system (CNS) cells. The current study was undertaken to examine the effect of miRNAs released from morphine-stimulated human primary astrocyte-derived extracellular vesicles (morphine-ADEVs) in mediating pericyte loss at the blood-brain barrier, leading, in turn, to increased influx of peripheral monocytes. Our findings suggest that the heterogeneous nuclear ribonucleoprotein complex A2/B1 (hnRNP A2/B1) plays role in morphine-mediated upregulation and release of miR-23a in ADEVs, and through action of morphine via mu opioid receptor.We further demonstrated that miR-23a in morphine-ADEVs could be taken up by pericytes, resulting in downregulation of PTEN expression, ultimately leading to increased pericyte migration. Furthermore, both overexpression of PTEN and blocking the miR-23a target site at PTEN 3UTR (by transfecting miR-23a-PTEN target protector), attenuated morphine-ADEV-mediated pericyte migration. We also demonstrated that in the microvessels isolated from morphine-administered mice, there were fewer PDGFβR + pericytes co-localizing with CD31+ brain endothelial cells compared with those from saline mice. In line with these findings, we also observed increased loss of pericytes and a concomitantly increased influx of monocytes in the brains of morphine-administered pericyte-labeled NG2-DsRed mice compared with saline mice. In conclusion, our findings indicate morphine-ADEVs mediated loss of pericyte coverage at the brain endothelium, thereby increasing the influx of peripheral monocytes in the central nervous system, leading to neuroinflammation.

Endothelial ETS1 inhibition exacerbate blood-brain barrier dysfunction in multiple sclerosis through inducing endothelial-to-mesenchymal transition

Blood-brain barrier (BBB) dysfunction has been recognized as an early pathological feature and contributing factor in multiple sclerosis. Endothelial-to-mesenchymal transition is a process associated with endothelial dysfunction leading to the disruption of vessel stability and barrier function, yet its functional consequence in multiple sclerosis remains unclear. Here, we demonstrated that endothelial-to-mesenchymal transition accompanied the blood-brain barrier dysfunction in several neurological disorders, especially in multiple sclerosis. The activity of transcription factor ETS1, which is highly expressed in endothelial cells (ECs) and responded to an inflammatory condition, is suppressed in the central nervous system (CNS) ECs in MS and its animal model experimental autoimmune encephalomyelitis. We identify ETS1 as a central regulator of endothelial-to-mesenchymal transition (EndMT) associated with the compromise of barrier integrity. These phenotypical and functional alterations can further induce high permeability, immune infiltration, and organ fibrosis in multiple sclerosis, thus promoting disease progression. Together, these results demonstrate a functional role of EndMT in blood-brain barrier dysfunction and propose ETS1 as a potential transcriptional switch of EndMT to target the development of multiple sclerosis.

Immune Modulation by Antigenic Peptides and Antigenic Peptide Conjugates for Treatment of Multiple Sclerosis

The immune system defends our body by fighting infection from pathogens utilizing both the innate and adaptive immune responses. The innate immune response is generated rapidly as the first line of defense. It is followed by the adaptive immune response that selectively targets infected cells. The adaptive immune response is generated more slowly, but selectively, by targeting a wide range of foreign particles (i.e., viruses or bacteria) or molecules that enter the body, known as antigens. Autoimmune diseases are the results of immune system glitches, where the body's adaptive system recognizes self-antigens as foreign. Thus, the host immune system attacks the self-tissues or organs with a high level of inflammation and causes debilitation in patients. Many current treatments for autoimmune diseases (i.e., multiple sclerosis (MS), rheumatoid arthritis (RA)) have been effective but lead to adverse side effects due to general immune system suppression, which makes patients vulnerable to opportunistic infections. To counter these negative effects, many different avenues of antigen specific treatments are being developed to selectively target the autoreactive immune cells for a specific self-antigen or set of self-antigens while not compromising the general immune system. These approaches include soluble antigenic peptides, bifunctional peptide inhibitors (BPI) including IDAC and Fc-BPI, polymer conjugates, and peptide-drug conjugates. Here, various antigen-specific methods of potential treatments, their efficacy, and limitations will be discussed along with the potential mechanisms of action.

Recent advancements in nanoparticle-mediated approaches for restoration of multiple sclerosis

Multiple Sclerosis (MS) is an autoimmune disease with complicated immunopathology which necessitates considering multifactorial aspects for its management. Nano-sized pharmaceutical carriers named nanoparticles (NPs) can support impressive management of disease not only in early detection and prognosis level but also in a therapeutic manner. The most prominent initiator of MS is the domination of cellular immunity to humoral immunity and increment of inflammatory cytokines. The administration of several platforms of NPs for MS management holds great promise so far. The efforts for MS management through in vitro and in vivo (experimental animal models) evaluations, pave a new way to a highly efficient therapeutic means and aiding its translation to the clinic in the near future.

Lowering blood cholesterol does not affect neuroinflammation in experimental autoimmune encephalomyelitis

Background

Multiple sclerosis (MS) is a chronic disabling disease of the central nervous system (CNS) commonly affecting young adults. There is increasing evidence that environmental factors are important in the development and course of MS. The metabolic syndrome (MetS) which comprises dyslipidemia has been associated with a worse outcome in MS disease. Furthermore, the lipid-lowering drug class of statins has been proposed to improve MS disease course. However, cholesterol is also rate-limiting for myelin biogenesis and promotes remyelination in MS animal models. Thus, the impact of circulating blood cholesterol levels during the disease remains debated and controversial.

Methods

We assessed the role of circulating cholesterol on the murine model of MS, the experimental autoimmune encephalomyelitis (EAE) disease using two different approaches: (1) the mouse model of familial hypercholesterolemia induced by low-density lipoprotein receptor (LDLr) deficiency, and (2) the use of the monoclonal anti-PCSK9 neutralizing antibody alirocumab, which reduces LDLr degradation and consequently lowers blood levels of cholesterol.

Results

Elevated blood cholesterol levels induced by LDLr deficiency did not worsen clinical symptoms of mice during EAE. In addition, we observed that the anti-PCSK9 antibody alirocumab did not influence EAE disease course, nor modulate the immune response in EAE.

Conclusions

These findings suggest that blood cholesterol level has no direct role in neuro-inflammatory diseases and that the previously shown protective effects of statins in MS are not related to circulating cholesterol.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-022-02409-x.

Efferocytosis in the Central Nervous System

The effective clearance of apoptotic cells is essential for maintaining central nervous system (CNS) homeostasis and restoring homeostasis after injury. In most cases of physiological apoptotic cell death, efferocytosis prevents inflammation and other pathological conditions. When apoptotic cells are not effectively cleared, destruction of the integrity of the apoptotic cell membrane integrity, leakage of intracellular contents, and secondary necrosis may occur. Efferocytosis is the mechanism by which efferocytes quickly remove apoptotic cells from tissues before they undergo secondary necrosis. Cells with efferocytosis functions, mainly microglia, help to eliminate apoptotic cells from the CNS. Here, we discuss the impacts of efferocytosis on homeostasis, the mechanism of efferocytosis, the associations of efferocytosis failure and CNS diseases, and the current clinical applications of efferocytosis. We also identify efferocytosis as a novel potential target for exploring the causes and treatments of CNS diseases.

An insight into the role of liposomal therapeutics in the reversion of Multiple Sclerosis

INTRODUCTION

Multiple Sclerosis (MS), as an autoimmune disease, has complicated immunopathology, which makes its management relevant to various factors. Novel pharmaceutical vehicles, especially liposomes, can support efficacious handling of this disease both in early detection and prognosis and also in a therapeutic manner. The most well-known trigger of MS onset is the predominance of cellular to humoral immunity and enhancement of inflammatory cytokines level. The installation of liposomes as nanoparticles to control this disease holds great promise up to now.

AREAS COVERED

Various types of liposomes with different properties and purposes have been formulated and targeted immune cells with their surface manipulations. They may be encapsulated with anti-inflammatory, MS-related therapeutics, or immunodominant myelin-specific peptides for attaining a higher therapeutic efficacy of the drugs or tolerance induction. Cationic liposomes are also highly applicable for gene delivery of the anti-inflammatory cytokines or silencing the inflammatory cytokines. Liposomes have also been used as biotools for comprehending MS pathomechanisms or as diagnostic agents.

EXPERT OPINION

The efforts to manage MS through nanomedicine, especially liposomal therapeutics, pave a new avenue to a high-throughput medication of this autoimmune disease and their translation to the clinic in the future for overcoming the challenges that MS patients confront.

Dysregulation of Blood-Brain Barrier and Exacerbated Inflammatory Response in Cx47-Deficient Mice after Induction of EAE

Induction of experimental autoimmune encephalomyelitis (EAE), an animal model of multiple sclerosis (MS), in connexin 32 (Cx32) or Cx47 knockout (KO) mice with deficiency in oligodendrocyte gap junctions (GJs) results in a more severe disease course. In particular, Cx47 KO EAE mice experience an earlier EAE onset and more pronounced disease severity, accompanied by dysregulated pro-inflammatory responses preceding the disease manifestations. In this study, analysis of relevant pro-inflammatory cytokines in wild type EAE, Cx32 KO EAE, and Cx47 KO EAE mice revealed altered expression of Vcam-1 preceding EAE [7 days post injection (dpi)], of Ccl2 at the onset of EAE (12 dpi), and of Gm-csf at the peak of EAE (24 dpi) in Cx47 KO EAE mice. Moreover, Cx47 KO EAE mice exhibited more severe blood-spinal cord barrier (BSCB) disruption, enhanced astrogliosis with defects in tight junction formation at the glia limitans, and increased T-cell infiltration prior to disease onset. Thus, Cx47 deficiency appears to cause dysregulation of the inflammatory profile and BSCB integrity, promoting early astrocyte responses in Cx47 KO EAE mice that lead to a more severe EAE outcome. Further investigation into the role of oligodendrocytic Cx47 in EAE and multiple sclerosis pathology is warranted.

Trends of Chitosan Based Delivery Systems in Neuroregeneration and Functional Recovery in Spinal Cord Injuries

Spinal cord injury (SCI) is one of the most complicated nervous system injuries with challenging treatment and recovery. Regenerative biomaterials such as chitosan are being reported for their wide use in filling the cavities, deliver curative drugs, and also provide adsorption sites for transplanted stem cells. Biomaterial scaffolds utilizing chitosan have shown certain therapeutic effects on spinal cord injury repair with some limitations. Chitosan-based delivery in stem cell transplantation is another strategy that has shown decent success. Stem cells can be directed to differentiate into neurons or glia in vitro. Stem cell-based therapy, biopolymer chitosan delivery strategies, and scaffold-based therapeutic strategies have been advancing as a combinatorial approach for spinal cord injury repair. In this review, we summarize the recent progress in the treatment strategies of SCI due to the use of bioactivity of chitosan-based drug delivery systems. An emphasis on the role of chitosan in neural regeneration has also been highlighted.

Predictive Markers of Immunogenicity and Efficacy for Human Vaccines

Vaccines represent one of the major advances of modern medicine. Despite the many successes of vaccination, continuous efforts to design new vaccines are needed to fight "old" pandemics, such as tuberculosis and malaria, as well as emerging pathogens, such as Zika virus and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Vaccination aims at reaching sterilizing immunity, however assessing vaccine efficacy is still challenging and underscores the need for a better understanding of immune protective responses. Identifying reliable predictive markers of immunogenicity can help to select and develop promising vaccine candidates during early preclinical studies and can lead to improved, personalized, vaccination strategies. A systems biology approach is increasingly being adopted to address these major challenges using multiple high-dimensional technologies combined with in silico models. Although the goal is to develop predictive models of vaccine efficacy in humans, applying this approach to animal models empowers basic and translational vaccine research. In this review, we provide an overview of vaccine immune signatures in preclinical models, as well as in target human populations. We also discuss high-throughput technologies used to probe vaccine-induced responses, along with data analysis and computational methodologies applied to the predictive modeling of vaccine efficacy.

Screening for Interacting Proteins with Peptide Biomarker of Blood-Brain Barrier Alteration under Inflammatory Conditions

Neurodegenerative diseases are characterized by increased permeability of the blood-brain barrier (BBB) due to alterations in cellular and structural components of the neurovascular unit, particularly in association with neuroinflammation. A previous screening study of peptide ligands to identify molecular alterations of the BBB in neuroinflammation by phage-display, revealed that phage clone 88 presented specific binding affinity to endothelial cells under inflammatory conditions in vivo and in vitro. Here, we aimed to identify the possible target receptor of the peptide ligand 88 expressed under inflammatory conditions. A cross-link test between phage-peptide-88 with IL-1β-stimulated human hCMEC cells, followed by mass spectrometry analysis, was used to identify the target of peptide-88. We modeled the epitope-receptor molecular interaction between peptide-88 and its target by using docking simulations. Three proteins were selected as potential target candidates and tested in enzyme-linked immunosorbent assays with peptide-88: fibronectin, laminin subunit α5 and laminin subunit β-1. Among them, only laminin subunit β-1 presented measurable interaction with peptide-88. Peptide-88 showed specific interaction with laminin subunit β-1, highlighting its importance as a potential biomarker of the laminin changes that may occur at the BBB endothelial cells under pathological inflammation conditions.

Links between Immune Cells from the Periphery and the Brain in the Pathogenesis of Epilepsy: A Narrative Review

Accumulating evidence has demonstrated that the pathogenesis of epilepsy is linked to neuroinflammation and cerebrovascular dysfunction. Peripheral immune cell invasion into the brain, along with these responses, is implicitly involved in epilepsy. This review explored the current literature on the association between the peripheral and central nervous systems in the pathogenesis of epilepsy, and highlights novel research directions for therapeutic interventions targeting these reactions. Previous experimental and human studies have demonstrated the activation of the innate and adaptive immune responses in the brain. The time required for monocytes (responsible for innate immunity) and T cells (involved in acquired immunity) to invade the central nervous system after a seizure varies. Moreover, the time between the leakage associated with blood–brain barrier (BBB) failure and the infiltration of these cells varies. This suggests that cell infiltration is not merely a secondary disruptive event associated with BBB failure, but also a non-disruptive event facilitated by various mediators produced by the neurovascular unit consisting of neurons, perivascular astrocytes, microglia, pericytes, and endothelial cells. Moreover, genetic manipulation has enabled the differentiation between peripheral monocytes and resident microglia, which was previously considered difficult. Thus, the evidence suggests that peripheral monocytes may contribute to the pathogenesis of seizures.

Recent advances in nano delivery systems for blood-brain barrier (BBB) penetration and targeting of brain tumors

Gliomas constitute about 80% of brain tumors and have a meager two-year survival rate. The treatment options available are very few because of poor prognosis and a lack of targeted nanodelivery systems that can cross the blood-brain barrier (BBB) and the blood-tumor barrier. This short review attempts to clarify the challenges for delivery systems designed to cross the BBB, and provides a brief description of the different types of targeted nanodelivery system that have shown potential for success in delivering drugs to the brain. Further, this review describes the most recent studies that have developed nanoparticles for brain delivery in the past five years. We also provide an insight into the most recent clinical trials designed to assess the efficacy of these nanodelivery systems for glioma.

Longitudinal imaging of T-cells and inflammatory demyelination in a preclinical model of multiple sclerosis using 18F-FAraG PET and MRI

Lymphocytes and innate immune cells are key drivers of multiple sclerosis (MS) and are the main target of MS disease-modifying therapies (DMT). Ex vivo analyses of MS lesions have revealed cellular heterogeneity and variable T cell levels, which may have important implications for patient stratification and choice of DMT. Although MRI has proven valuable to monitor DMT efficacy, its lack of specificity for cellular subtypes highlights the need for complementary methods to improve lesion characterization. Here, we evaluated the potential of 2′-deoxy-2′-¹⁸F-fluoro-9-β-d-arabinofuranosylguanine (¹⁸F-FAraG) PET imaging to noninvasively assess infiltrating T cells and to provide, in combination with MRI, a novel tool to determine lesion types. Methods: We used a novel MS mouse model that combines cuprizone and experimental autoimmune encephalomyelitis to reproducibly induce 2 brain inflammatory lesion types, differentiated by their T cell content. ¹⁸F-FAraG PET imaging, T2-weighted MRI, and T1-weighted contrast-enhanced MRI were performed before disease induction, during demyelination with high levels of innate immune cells, and after T cell infiltration. Fingolimod immunotherapy was used to evaluate the ability of PET and MRI to detect therapy response. Ex vivo immunofluorescence analyses for T cells, microglia/macrophages, myelin, and blood–brain barrier (BBB) integrity were performed to validate the in vivo findings. Results:¹⁸F-FAraG signal was significantly increased in the brain and spinal cord at the time point of T cell infiltration. ¹⁸F-FAraG signal from white matter (corpus callosum) and gray matter (cortex, hippocampus) further correlated with T cell density. T2-weighted MRI detected white matter lesions independently of T cells. T1-weighted contrast-enhanced MRI indicated BBB disruption at the time point of T cell infiltration. Fingolimod treatment prevented motor deficits and decreased T cell and microglia/macrophage levels. In agreement, ¹⁸F-FAraG signal was decreased in the brain and spinal cord of fingolimod-treated mice; T1-weighted contrast-enhanced MRI revealed intact BBB, whereas T2-weighted MRI findings remained unchanged. Conclusion: The combination of MRI and ¹⁸F-FAraG PET enables detection of inflammatory demyelination and T cell infiltration in an MS mouse model, providing a new way to evaluate lesion heterogeneity during disease progression and after DMT. On clinical translation, these methods hold great potential for stratifying patients, monitoring MS progression, and determining therapy responses.

Exosomal miR-155 from M1-polarized macrophages promotes EndoMT and impairs mitochondrial function via activating NF-κB signaling pathway in vascular endothelial cells after traumatic spinal cord injury

Pathologically, blood-spinal-cord-barrier (BSCB) disruption after spinal cord injury (SCI) leads to infiltration of numerous peripheral macrophages into injured areas and accumulation around newborn vessels. Among the leaked macrophages, M1-polarized macrophages are dominant and play a crucial role throughout the whole SCI process. The aim of our study was to investigate the effects of M1-polarized bone marrow-derived macrophages (M1-BMDMs) on vascular endothelial cells and their underlying mechanism. Microvascular endothelial cell line bEnd.3 cells were treated with conditioned medium or exosomes derived from M1-BMDMs, followed by evaluations of endothelial-to-mesenchymal transition (EndoMT) and mitochondrial function. After administration, we found conditioned medium or exosomes from M1-BMDMs significantly promoted EndoMT of vascular endothelial cells in vitro and in vivo, which aggravated BSCB disruption after SCI. In addition, significant dysfunction of mitochondria and accumulation of reactive oxygen species (ROS) were also detected. Furthermore, bioinformatics analysis demonstrated that miR-155 is upregulated in both M1-polarized macrophages and microglia. Experimentally, exosomal transfer of miR-155 participated in M1-BMDMs-induced EndoMT and mitochondrial ROS generation in bEnd.3 cells, and subsequently activated the NF-κB signaling pathway by targeting downstream suppressor of cytokine signaling 6 (SOCS6), and suppressing SOCS6-mediated p65 ubiquitination and degradation. Finally, a series of rescue assay further verified that exosomal miR155/SOCS6/p65 axis regulated the EndoMT process and mitochondrial function in vascular endothelial cells. In summary, our work revealed a potential mechanism describing the communications between macrophages and vascular endothelial cells after SCI which could benefit for future research and aid in the development of potential therapies for SCI.

Detection of Monocyte/Macrophage and Microglia Activation in the TMEV Model of Chronic Demyelination Using USPIO-Enhanced Ultrahigh-Field Imaging

BACKGROUND AND PURPOSE

Blood-derived monocytes/macrophages can be labeled with ultrasmall superparamagnetic iron oxides (USPIO) at periphery and subsequently migrate into areas of inflammation in the brain. We investigated temporal pattern of migration of peripheral immune cells in Theiler's murine encephalomyelitis virus (TMEV) model of chronic demyelination by USPIO-enhanced imaging.

METHODS

Fifteen SJL mice (Envigo, Indianapolis, IN) were injected with TMEV (n = 12) or saline (n = 3) at 7 weeks of age. Brain MRI of 9.4 T was performed at 3 months postinfection (mpi) (the peak of inflammatory phase), at 4, 5, and 7 mpi (throughout neurodegenerative phase) using T2*-weighted gradient echo MRI, and performed 24 hours after USPIO injection. Contrast enhancing lesion (CEL) number and volume were measured and development of brain atrophy was assessed across serial time points. Clinical disability scale and rotarod score assessed disease progression.

RESULTS

CEL was detected in a total of eight (66.7%) TMEV-infected animals and none of the Controls. The CEL was present in four (33.3%) TMEV-infected animals at 3 mpi, two (16.7%) at 4 mpi, six (54.5%) at 5 mpi, and four (44.4%) at 7 mpi, respectively. In TMEV-infected animals, the CEL number and volume increased significantly from 3 to 7 mpi (P < .01 for both). The correlation between total CEL number and volume with clinical and MRI outcomes was trending (P < .05). On histopathology analysis, CEL showed increased density of Iba1 staining for microglia activity.

CONCLUSIONS

Serial USPIO imaging is a promising biomarker for investigating the effect of therapeutic interventions on monocytes/macrophages and microglia activation and neurodegeneration in TMEV-infected animals.

Protection of Fecal Microbiota Transplantation in a Mouse Model of Multiple Sclerosis

Given the growing evidence of a link between gut microbiota (GM) dysbiosis and multiple sclerosis (MS), fecal microbiota transplantation (FMT), aimed at rebuilding GM, has been proposed as a new therapeutic approach to MS treatment. To evaluate the viability of FMT for MS treatment and its impact on MS pathology, we tested FMT in mice with experimental autoimmune encephalomyelitis (EAE), a mouse model of MS. We provide evidence that FMT can rectify altered GM to some extent with a therapeutic effect on EAE. We also found that FMT led to reduced activation of microglia and astrocytes and conferred protection on the blood-brain barrier (BBB), myelin, and axons in EAE. Taken together, our data suggest that FMT, as a GM-based therapy, has the potential to be an effective treatment for MS.

Neuroimmune interaction in seizures and epilepsy: focusing on monocyte infiltration

Epilepsy is a major neurological condition that affects millions of people globally. While a number of interventions have been developed to mitigate this condition, a significant number of patients are refractory to these treatments. Consequently, other avenues of research are needed. One such avenue is modulation of the immune system response to this condition, which has mostly focused on microglia, the resident immune cells of the central nervous system (CNS). However, other immune cells can impact neurological conditions, principally blood-borne monocytes that can infiltrate into brain parenchyma after seizures. As such, this review will first discuss how monocytes can be recruited to the CNS and how they can be distinguished from there immunological cousins, microglia. Then, we will explore what is known about the role monocytes have within seizure pathogenesis and epilepsy. Considering how little is known about monocyte function in seizure- and epilepsy-related pathologies, further studies are warranted that investigate infiltrated blood-borne monocytes as a potential therapeutic target for epilepsy treatment.

In vivo imaging of CNS microglial activation/macrophage infiltration with combined [18F]DPA-714-PET and SPIO-MRI in a mouse model of relapsing remitting experimental autoimmune encephalomyelitis

Purpose

To evaluate the feasibility and sensitivity of multimodality PET/CT and MRI imaging for non-invasive characterization of brain microglial/macrophage activation occurring during the acute phase in a mouse model of relapsing remitting multiple sclerosis (RR-MS) using [¹⁸F]DPA-714, a selective radioligand for the 18-kDa translocator protein (TSPO), superparamagnetic iron oxide particles (SPIO), and ex vivo immunohistochemistry.

Methods

Experimental autoimmune encephalomyelitis (EAE) was induced in female SJL/J mice by immunization with PLP_139–151. Seven symptomatic EAE mice and five controls underwent both PET/CT and MRI studies between 11 and 14 days post-immunization. SPIO was injected i.v. in the same animals immediately after [¹⁸F]DPA-714 and MRI acquisition was performed after 24 h. Regional brain volumes were defined according to a mouse brain atlas on co-registered PET and SPIO-MRI images. [¹⁸F]DPA-714 standardized uptake value (SUV) ratios (SUVR), with unaffected neocortex as reference, and SPIO fractional volumes (SPIO-Vol) were generated. Both SUVR and SPIO-Vol values were correlated with the clinical score (CS) and among them. Five EAE and four control mice underwent immunohistochemical analysis with the aim of identifying activated microglia/macrophage and TSPO expressions.

Results

SUVR and SPIO-Vol values were significantly increased in EAE compared with controls in the hippocampus (p < 0.01; p < 0.02, respectively), thalamus (p < 0.02; p < 0.05, respectively), and cerebellum and brainstem (p < 0.02), while only SPIO-Vol was significantly increased in the caudate/putamen (p < 0.05). Both SUVR and SPIO-Vol values were positively significantly correlated with CS and among them in the same regions. TSPO/Iba1 and F4/80/Prussian blue staining immunohistochemistry suggests that increased activated microglia/macrophages underlay TSPO expression and SPIO uptake in symptomatic EAE mice.

Conclusions

These preliminary results suggest that both activated microglia and infiltrated macrophages are present in vulnerable brain regions during the acute phase of PLP-EAE and contribute to disease severity. Both [¹⁸F]DPA-714-PET and SPIO-MRI appear suitable modalities for preclinical study of neuroinflammation in MS mice models.

A receptor-binding radiopharmaceutical for imaging of traumatic brain injury in a rodent model: [99mTc]Tc-tilmanocept

INTRODUCTION

Blood-brain barrier (BBB) disruption and subsequent neuro-inflammation occur following traumatic brain injury (TBI), resulting in a spectrum of human nervous system disorders. [^99mTc]Tc-tilmanocept is a receptor-binding radiopharmaceutical FDA-approved for sentinel lymph node mapping. We hypothesize that after an intravenous (i.v.) injection, [^99mTc]Tc-tilmanocept, will traverse a disrupted BBB and bind to CD206-bearing microglial cells.

METHODS

Age-matched mice were divided into three groups: 5-days post TBI (n = 4), and 5-days post sham (n = 4), and naïve controls (n = 4). IRDye800CW-labeled [^99mTc]Tc-tilmanocept (0.15 nmol per gram body weight) and FITC-labeled bovine serum albumin (FITC-BSA) were injected (i.v.) into each mouse. Mice were imaged with a high-resolution gamma camera for 45 min. Immediately after imaging, the brains were perfused with fixative, excised, imaged with a fluorescence scanner, assayed for radioactivity, and prepared for histology.

RESULTS

In vivo nuclear imaging, ex vivo fluorescence imaging, ex vivo gamma well counting, and histo-microscopy demonstrated enhanced tilmanocept uptake in the TBI region. The normalized [^99mTc]Tc-tilmanocept uptake value from nuclear imaging and the maximum pixel intensity from fluorescence imaging of the TBI group (1.12 ± 0.12 and 2288 ± 278 a.u., respectively) were significantly (P < 0.04) higher than the sham group (0.64 ± 0.28 and 1708 ± 101 a.u., respectively) and the naive group (0.76 ± 0.24 and 1643 ± 391 a.u., respectively). The mean [^99mTc]Tc-tilmanocept scaled uptake in the TBI brains (0.058 ± 0.013%/g) was significantly (P < 0.010) higher than the scaled brain uptake of the sham group (0.031 ± 0.011%/g) and higher (P = 0.04) than the uptake of the naïve group (0.020 ± 0.002%/g). Fluorescence microscopy demonstrated increased uptake of the IRDye800CW-tilmanocept and FITC-BSA in the TBI brain regions.

CONCLUSION

[^99mTc]Tc-tilmanocept traverses disrupted blood-brain barrier and localizes within the injured region. ADVANCES IN KNOWLEDGE AND IMPLICATIONS FOR PATIENT CARE: [^99mTc]Tc-tilmanocept could serve as an imaging biomarker for TBI-associated neuroinflammation and any disease process that involves a disruption of the blood-brain barrier.

Using antifibrinolytics to tackle neuroinflammation

Plasmin is generally known as a promotor of inflammation. Recent advancement suggests that it has a complex role as immunity modulator. Pharmacological inhibition of plasmin production and activity has been proven to improve neurological outcomes in traumatic brain injury and subarachnoid hemorrhage, most probably by preventing re-bleeding. The immune-modulatory properties of antifibrinolytics, however, suggest that they probably have effects unrelated to fibrinolysis inhibition, which are currently not adequately harnessed. The present work aims to give an account of the existing data regarding antifibrinolytics as agents influencing neuroinflammation. Preclinical and clinical studies on the possible influence of antifibrinolytics on neuroinflammation are scarce. However, the emerging evidence suggests that inhibition of plasmin(ogen) activity can ameliorate neuroinflammation to some extent. This data demonstrate that plasmin(ogen) is not exclusively involved in fibrinolysis, but also has other substrates and can precipitate in inflammatory processes. Investigation on the role of plasmin as the factor for the development of neuroinflammation shows the significant potential of antifibrinolytics as pharmacotherapy of neuroinflammationm, which is worthy of further exploration.

Monitoring diffuse injury during disease progression in experimental autoimmune encephalomyelitis with on resonance variable delay multiple pulse (onVDMP) CEST MRI

Multiple sclerosis (MS) is an autoimmune disorder that targets myelin proteins and results in extensive damage in the central nervous system in the form of focal lesions as well as diffuse molecular changes. Lesions are currently detected using T1-weighted, T2-weighted, and gadolinium-enhanced magnetic resonance imaging (MRI); however, monitoring such lesions has been shown to be a poor predictor of disease progression. Chemical exchange saturation transfer (CEST) MRI is sensitive to many of the biomolecules in the central nervous system altered in MS that cannot be detected using conventional MRI. We monitored disease progression in an experimental autoimmune encephalomyelitis (EAE) model of MS using on resonance variable delay multiple pulse (onVDMP) CEST MRI. Alterations in onVDMP signal were observed in regions responsible for hindlimb function throughout the central nervous system. Histological analysis revealed glial activation in areas highlighted in onVDMP CEST MRI. onVDMP signal changes in the 3rd ventricle preceded paralysis onset that could not be observed with conventional MRI techniques. Hence, the onVDMP CEST MRI signal has potential as a novel imaging biomarker and predictor of disease progression in MS.

Analysis of magnetization transfer (MT) influence on quantitative mapping of T2 relaxation time

PURPOSE

Multi-echo spin-echo (MESE) protocol is the most effective tool for mapping T₂ relaxation in vivo. Still, MESE extensive use of radiofrequency pulses causes magnetization transfer (MT)-related bias of the water signal, instigated by the presence of macromolecules (MMP). Here, we analyze the effects of MT on MESE signal, alongside their impact on quantitative T₂ measurements.

METHODS

Study used 3 models: in vitro urea phantom, ex vivo horse brain, and in vivo human brain. MT ratio (MTR) was measured between single-SE and MESE protocols under different scan settings including varying echo train lengths, number of slices, and inter-slice gap. MTR and T₂ values were extracted for each model and protocol.

RESULTS

MT interactions biased MESE signals, and in certain settings, the corresponding T₂ values. T₂ underestimation of up to 4.3% was found versus single-SE values in vitro and up to 13.8% ex vivo, correlating with the MMP content. T₂ bias originated from intra-slice saturation of the MMP, rather than from indirect saturation in multi-slice acquisitions. MT-related signal attenuation was caused by slice crosstalk and/or partial T₁ recovery, whereas smaller contribution was caused by MMP interactions. Inter-slice gap had a similar effect on in vivo MTR (21.2%), in comparison to increasing the number of slices (18.9%).

CONCLUSIONS

MT influences MESE protocols either by uniformly attenuating the entire echo train or by cumulatively attenuating the signal along the train. Although both processes depend on scan settings and MMP content, only the latter will cause underestimation of T₂ .

Effects of Statin Treatment on Outcomes after Traumatic Brain Injury

Neuroprotective treatments that have shown promise in reducing secondary injury and improving recovery in animal models of traumatic brain injury (TBI) have not been found effective to date in humans. One reason may be the delay after injury in initiating treatment. Statin medications are among the promising neuroprotective agents in animal models, and their presence in the bloodstream of many individuals at the time of injury might optimize their clinical impact. This observational study conducted by a subset of centers participating in the National Institute on Disability, Independent Living, and Rehabilitation Research (NIDILRR)-funded TBI Model System program sought to examine the effects of taking statin medication at the time injury on functional outcomes. Participants >50 years of age were prospectively enrolled during patient rehabilitation. Demographic data, cardiovascular history, and brain injury history were obtained through chart abstraction and interview. Prescription medication use in the year prior to enrollment was determined from a national pharmacy search service. Propensity scoring was used to create 49 pairs of participants who were well matched on demographic and clinical attributes but discordant for statin use. The treated and untreated participants did not differ on initial Glasgow Coma Score, time until commands were followed, duration of post-traumatic amnesia, or Functional Independence Measure (FIM) scores at rehabilitation admission, discharge, or 1 year post-injury, or on acute or rehabilitation hospital lengths of stay. Evidence of greater and lesser statin compliance was not associated with outcome. This study did not provide support for a clinically important benefit of statin use at the time of moderate to severe TBI.

Superparamagnetic iron oxide nanocolloids in MRI studies of neuroinflammation

Iron oxide (IO) nanocolloids are being increasingly used to image cellular contribution to neuroinflammation using MRI, as these particles are capable of labeling circulating cells with phagocytic activity, allowing to assess cell trafficking from the blood to neuroinflammation sites. The use of IOs relies on the natural phagocytic properties of immune cells, allowing their labeling either in vitro or directly in vivo, following intravenous injection. Despite concerns on the specificity of the latter approach, the widespread availability and relatively low cost of these techniques, coupled to a sensitivity that allows to reach single cell detection, have promoted their use in several preclinical and clinical studies. In this review, we discuss the results of currently available preclinical and clinical IO-enhanced MRI studies of immune cell trafficking in neuroinflammation, examining the specificity of the existing findings, in view of the different possible mechanisms underlying IO accumulation in the brain. From this standpoint, we assess the implications of the temporal and spatial differences in the enhancement pattern of IOs, compared to gadolinium-based contrast agents, a clinically established MRI marker blood-brain barrier breakdown. While concerns on the specificity of cell labeling obtained using the in-vivo labeling approach still need to be fully addressed, these techniques have indeed proved able to provide additional information on neuroinflammatory phenomena, as compared to conventional Gadolinium-enhanced MRI.

Bilateral carotid artery stenosis causes unexpected early changes in brain extracellular matrix and blood-brain barrier integrity in mice

Bilateral carotid artery stenosis (BCAS) is one experimental model of vascular dementia thought to preferentially impact brain white matter. Indeed, few studies report hippocampal and cortical pathology prior to 30 days post-stenosis; though it is unclear whether those studies examined regions outside the white matter. Since changes in the blood-brain barrier (BBB) permeability precede more overt brain pathology in various diseases, we hypothesized that changes within the BBB and/or BBB-associated extracellular matrix (ECM) could occur earlier after BCAS in the hippocampus, cortex and striatum and be a precursor of longer term pathology. Here, C57Bl/6 mice underwent BCAS or sham surgeries and changes in the BBB and ECM were analyzed by collagen IV (vascular basement membrane component), α5 integrin (marker of endothelial activation), claudin-5 and occludin (tight junction proteins), Evans blue (permeability marker), Ki-67 (cell proliferation marker), and GFAP and CD11b (glial cell markers) immunohistochemistry after 14 days. Significant changes in markers of cerebrovascular integrity and glial activation were detected, not only in the striatum, but also in the hippocampus and cortex. In conclusion, this study demonstrates for the first time that changes in the BBB/ECM occur shortly after BCAS and within multiple brain regions and suggests such changes might underlie the gradual development of BCAS non-white matter pathology.

Immunological effects of iron oxide nanoparticles and iron-based complex drug formulations: Therapeutic benefits, toxicity, mechanistic insights, and translational considerations

Nanotechnology offers several advantages for drug delivery. However, there is the need for addressing potential safety concerns regarding the adverse health effects of these unique materials. Some such effects may occur due to undesirable interactions between nanoparticles and the immune system, and they may include hypersensitivity reactions, immunosuppression, and immunostimulation. While strategies, models, and approaches for studying the immunological safety of various engineered nanoparticles, including metal oxides, have been covered in the current literature, little attention has been given to the interactions between iron oxide-based nanomaterials and various components of the immune system. Here we provide a comprehensive review of studies investigating the effects of iron oxides and iron-based nanoparticles on various types of immune cells, highlight current gaps in the understanding of the structure-activity relationships of these materials, and propose a framework for capturing their immunotoxicity to streamline comparative studies between various types of iron-based formulations.

USPIO-positive MS lesions are associated with greater tissue damage than gadolinium-positive-only lesions during 3-year follow-up

Background:

Identifying in vivo the processes that determine lesion severity in multiple sclerosis (MS) remains a challenge.

Objectives:

To describe the dynamics of ultrasmall superparamagnetic iron oxide (USPIO) enhancement in MS lesions and the relationship between USPIO enhancement and microstructural changes over 3 years.

Methods:

Lesion development was assessed at baseline, Months 3, 6, and 9, using magnetic resonance imaging (MRI) with gadolinium and USPIO. Microstructural changes were assessed at baseline, Months 3, 6, 9, 12, 18, 24, and 36, using relaxometry, magnetization transfer, and diffusion-weighted imaging.

Results:

We included 15 patients with clinically isolated syndrome. In the 52 MRI scans acquired with USPIO, 22 lesions were USPIO and gadolinium positive, and 44 were USPIO negative but gadolinium positive. Lesions no longer exhibited sustained USPIO enhancement 3 months later. At baseline, lesions that were both USPIO and gadolinium positive had lower magnetization transfer ratio values (common language effect size = 0.84, p = 0.0005) and lower fractional anisotropy values (0.83, p = 0.001) than gadolinium-positive-only lesions. USPIO-positive lesions remained associated with greater damage than gadolinium-positive-only lesions throughout the 3-year follow-up.

Conclusion:

USPIO enhancement, mainly reflecting monocyte infiltration, is transient and is associated with persistent tissue damage after 3 years.

MRI monitoring of monocytes to detect immune stimulating treatment response in brain tumor

Background

Glioblastoma (GBM) is an aggressive brain cancer with a poor prognosis. The use of immune therapies to treat GBM has become a promising avenue of research. It was shown that amphotericin B (Amp B) can stimulate the innate immune system and suppress the growth of brain tumor initiating cells (BTICs). However, it is not feasible to use histopathology to determine immune activation in patients. We developed an MRI technique that can rapidly detect a therapeutic response in animals treated with drugs that stimulate innate immunity. Ultra-small iron oxide nanoparticles (USPIOs) are MRI contrast agents that have been widely used for cell tracking. We hypothesized that the increased monocyte infiltration into brain tumors due to Amp B can be detected using USPIO-MRI, providing an indicator of early drug response.

Methods

We implanted human BTICs into severe combined immunodeficient mice and allowed the tumor to establish before treating the animals with either Amp B or vehicle and then imaged them using MRI with USPIO (ferumoxytol) contrast.

Results

After 7 days of treatment, there was a significantly decreased T2* in the tumor of Amp B but not vehicle animals, suggesting that USPIO is carried into the tumor by monocytes. We validated our MRI results with histopathology and confirmed that Amp B-treated animals had significantly higher levels of macrophage/microglia that were colocalized with iron staining in their brain tumor compared with vehicle mice.

Conclusion

USPIO-MRI is a promising method of rapidly assessing the efficacy of anticancer drugs that stimulate innate immunity.

The beneficial effects of HMG-CoA reductase inhibitors in the processes of neurodegeneration

Statins, cholesterol lowering drugs, have been demonstrated to exert beneficial effects in other conditions such as primary and progressing neurodegenerative diseases beyond their original role. Observation that statins ameliorate the neurodegenerative diseases such as Parkinson's disease (PD), Alzheimer's disease (AD), multiple sclerosis (MS) and cerebral ischemic stroke, the neuroprotective effects of these drugs are thought to be linked to their anti-inflammatory, anti-oxidative, and anti-excitotoxic properties. Despite the voluminous literature on the clinical advantages of 3-hydroxy-3-methylglutaryl Co-enzyme A reductase (HMGCR) inhibitors (statins) in cardiovascular system, the neuroprotective effects and the underlying mechanisms are little understood. Hence, the present review tries to provide a critical overview on the statin-induced neuroprotection, which are presumed to be associated with the ability to reduce cholesterol, Amyloid-β and apolipoprotein E (ApoE) levels, decrease reactive oxygen and nitrogen species (ROS and RNS) formation, inhibit excitotoxicity, modulate matrix metalloproteinases (MMPs), stimulate endothelial nitric oxide synthase (eNOS), and increase cerebral blood perfusion. This review is also aimed to illustrate that statins protect neurons against the neuro-inflammatory processes through balancing pro-inflammatory/anti-inflammatory cytokines. Ultimately, the beneficial role of statins in ameliorating the development of PD, AD, MS and cerebral ischemic stroke has been separately reviewed.

Virus entry and replication in the brain precedes blood-brain barrier disruption during intranasal alphavirus infection

Viral infections of the central nervous system (CNS) are often associated with blood-brain barrier (BBB) disruption, yet the impact of virus replication and immune cell recruitment on BBB integrity are incompletely understood. Using two-photon microscopy, we demonstrate that Venezuelan equine encephalitis virus (VEEV) strain TC83-GFP, a GFP expressing, attenuated strain with a G3A mutation within the 5' UTR that is associated with increased sensitivity to type I interferons (IFNs), does not directly impact BBB permeability. Following intranasal infection of both wild-type and IFN-induced protein with tetratricopeptide repeats 1 (IFIT1)-deficient mice, which fail to block TC83-specific RNA translation, virus spreads to the olfactory bulb and cortex via migration along axonal tracts of neurons originating from the olfactory neuroepithelium. Global dissemination of virus in the CNS by 2days post-infection (dpi) was associated with increased BBB permeability in the olfactory bulb, but not in the cortex or hindbrain, where permeability only increased after the recruitment of CX3CR1⁺ and CCR2⁺ mononuclear cells on 6 dpi, which corresponded with tight junction loss and claudin 5 redistribution. Importantly, despite higher levels of viral replication, similar results were obtained in IFIT1-deficient mice. These findings indicate that TC83 gains CNS access via anterograde axonal migration without directly altering BBB function and that mononuclear and endothelial cell interactions may underlie BBB disruption during alphavirus encephalitis.

Staining of HLA-DR, Iba1 and CD68 in human microglia reveals partially overlapping expression depending on cellular morphology and pathology

HLA-DR, Iba1 and CD68 are widely used microglia markers in human tissue. However, due to differences in gene regulation, they may identify different activation stages of microglia. Here, we directly compared the expression of HLA-DR, Iba1 and CD68 in microglia with different phenotypes, ranging from ramified to amoeboid, to foamy phagocytizing macrophages, in adjacent sections immunocytochemically double stained for two of the markers. Material was used from patients diagnosed with multiple sclerosis (MS) and Alzheimer's disease (AD) patients and control subjects because together they contain all the microglia activation stages in an acute and a chronic inflammatory setting. We found a similar, yet not identical, overall expression pattern. All three markers were expressed by ramified/amoeboid microglia around chronic active MS lesions, but overlap between HLA-DR and Iba1 was limited. Foamy macrophages in the demyelinating rims of active MS lesions of MS expressed more HLA-DR and CD68 than Iba1. All markers were expressed by small microglia accumulations (nodules) in MS NAWM. Dense core AD plaques in the hippocampus were mostly associated with microglia expressing HLA-DR. Diffuse AD plaques were not specifically associated with microglia at all. These results indicate that microglia markers have different potential for neuropathological analysis, with HLA-DR and CD68 reflecting immune activation and response to tissue damage, and Iba1 providing a marker more suited for structural studies in the absence of pathology.

Plasminogen Deficiency Delays the Onset and Protects from Demyelination and Paralysis in Autoimmune Neuroinflammatory Disease

Multiple sclerosis (MS) is a neuroinflammatory, demyelinating disease of the CNS. Fibrinogen deposition at sites of blood-brain barrier breakdown is a prominent feature of neuroinflammatory disease and contributes to disease severity. Plasminogen, the primary fibrinolytic enzyme, also modifies inflammatory processes. We used a murine model of MS, experimental autoimmune encephalomyelitis (EAE), to evaluate the hypothesis that the loss of plasminogen would exacerbate neuroinflammatory disease. However, contrary to initial expectations, EAE-challenged plasminogen-deficient (Plg^-) mice developed significantly delayed disease onset and reduced disease severity compared with wild-type (Plg⁺) mice. Similarly, pharmacologic inhibition of plasmin activation with tranexamic acid also delayed disease onset. The T-cell response to immunization was similar between genotypes, suggesting that the contribution of plasminogen was downstream of the T-cell response. Spinal cords from EAE-challenged Plg^- mice demonstrated significantly decreased demyelination and microglial/macrophage accumulation compared with Plg⁺ mice. Although fibrinogen-deficient mice or mice with combined deficiencies of plasminogen and fibrinogen had decreased EAE severity, they did not exhibit the delay in EAE disease onset, as seen in mice with plasminogen deficiency alone. Together, these data suggest that plasminogen and plasmin-mediated fibrinolysis is a key modifier of the onset of neuroinflammatory demyelination.SIGNIFICANCE STATEMENT Multiple sclerosis is a severe, chronic, demyelinating disease. Understanding the pathobiology related to the autoreactive T-cell and microglial/macrophage demyelinating response is critical to effectively target therapeutics. We describe for the first time that deficiency of plasminogen, the key fibrinolytic enzyme, delays disease onset and protects from the development of the paralysis associated with a murine model of multiple sclerosis, experimental autoimmune encephalomyelitis (EAE). Administration of a widely used, pharmacologic inhibitor of plasminogen activation, tranexamic acid, also delays the onset of neuroinflammation associated with EAE.

Endothelial Wnt/β-catenin signaling reduces immune cell infiltration in multiple sclerosis

Disruption of the blood-brain barrier (BBB) is a defining and early feature of multiple sclerosis (MS) that directly damages the central nervous system (CNS), promotes immune cell infiltration, and influences clinical outcomes. There is an urgent need for new therapies to protect and restore BBB function, either by strengthening endothelial tight junctions or suppressing endothelial vesicular transcytosis. Although wingless integrated MMTV (Wnt)/β-catenin signaling plays an essential role in BBB formation and maintenance in healthy CNS, its role in BBB repair in neurologic diseases such as MS remains unclear. Using a Wnt/β-catenin reporter mouse and several downstream targets, we demonstrate that the Wnt/β-catenin pathway is up-regulated in CNS endothelial cells in both human MS and the mouse model experimental autoimmune encephalomyelitis (EAE). Increased Wnt/β-catenin activity in CNS blood vessels during EAE progression correlates with up-regulation of neuronal Wnt3 expression, as well as breakdown of endothelial cell junctions. Genetic inhibition of the Wnt/β-catenin pathway in CNS endothelium before disease onset exacerbates the clinical presentation of EAE, CD4⁺ T-cell infiltration into the CNS, and demyelination by increasing expression of vascular cell adhesion molecule-1 and the transcytosis protein Caveolin-1 and promoting endothelial transcytosis. However, Wnt signaling attenuation does not affect the progressive degradation of tight junction proteins or paracellular BBB leakage. These results suggest that reactivation of Wnt/β-catenin signaling in CNS vessels during EAE/MS partially restores functional BBB integrity and limits immune cell infiltration into the CNS.

Early monitoring and quantitative evaluation of macrophage infiltration after experimental traumatic brain injury: A magnetic resonance imaging and flow cytometric analysis

The inflammatory response following traumatic brain injury (TBI) is regulated by phagocytic cells. These cells comprising resident microglia and infiltrating macrophages play a pivotal role in the interface between early detrimental and delayed beneficial effects of inflammation. The aim of the present study was to monitor the early effect of monocyte/phagocytic accumulation and further to explore its kinetics in TBI mice. Localized macrophage population was monitored using ultrasmall superparamagnetic iron oxide (USPIO) nanoparticle enhanced in vivo serial magnetic resonance imaging (MRI). Flow cytometry based gating study was performed to discriminate between resident microglia (Ly6G^-CD11b⁺CD45^low) and infiltrating macrophages (Ly6G^-CD11b⁺CD45^high) at the injury site. The T₂* relaxation analysis revealed that maximum macrophage infiltration occurs between 66 and 72h post injury (42-48h post administration of USPIO) at the site of inflammation. This imaging data was well supported by iron oxide specific Prussian blue staining and macrophage specific F4/80 immunohistochemistry (IHC) analysis. Quantitative real-time PCR analysis found significant expression of monocyte chemoattractant protein-1 (MCP-1) at 72h post injury. Also, we found that flow cytometric analysis demonstrated a 7-fold increase in infiltrating macrophages around 72h post injuries as compared to control. The MR imaging in combination with flow cytometric analysis enabled the dynamic measurement of macrophage infiltration at the injury site. This study may help in setting an optimal time window to intervene and prevent damage due to inflammation and to increase the therapeutic efficacy.

Monocyte behaviour and tissue transglutaminase expression during experimental autoimmune encephalomyelitis in transgenic CX3CR1gfp/gfp mice

Leukocyte infiltration into the central nervous system (CNS) is a key pathological feature in multiple sclerosis (MS) and the MS animal model experimental autoimmune encephalomyelitis (EAE). Recently, preventing leukocyte influx into the CNS of MS patients is the main target of MS therapies and insight into cell behaviour in the circulation is needed for further elucidation of such therapies. In this study, we aimed at in vivo visualization of monocytes in a time-dependent manner during EAE. Using intravital two-photon microscopy (IVM), we imaged CX3CR1^gfp/gfp mice during EAE, visualizing CX3CR1-GFP⁺ monocytes and their dynamics in the spinal cord vasculature. Our observations showed that intraluminal crawling of CX3CR1-GFP⁺ monocytes increased even before the clinical onset of EAE due to immunization of the animals. Furthermore, intraluminal crawling remained elevated during ongoing clinical disease. Besides, the displacement of these cells was larger during the peak of EAE compared to the control animals. In addition, we showed that the enzyme tissue transglutaminase (TG2), which is present in CNS-infiltrated cells in MS patients, is likewise found in CX3CR1-GFP⁺ monocytes in the spinal cord lesions and at the luminal side of the vasculature during EAE. It might thereby contribute to adhesion and crawling of monocytes, facilitating extravasation into the CNS. Thus, we put forward that interference with monocyte adhesion, by e.g. inhibition of TG2, should be applied at a very early stage of EAE and possibly MS, to effectively combat subsequent pathology.

Intracerebral GM-CSF contributes to transendothelial monocyte migration in APP/PS1 Alzheimer's disease mice

Although tight junctions between human brain microvascular endothelial cells in the blood-brain barrier prevent molecules or cells in the bloodstream from entering the brain, in Alzheimer's disease, peripheral blood monocytes can "open" these tight junctions and trigger subsequent transendothelial migration. However, the mechanism underlying this migration is unclear. Here, we found that the CSF2RB, but not CSF2RA, subunit of the granulocyte-macrophage colony-stimulating factor receptor was overexpressed on monocytes from Alzheimer's disease patients. CSF2RB contributes to granulocyte-macrophage colony-stimulating factor-induced transendothelial monocyte migration. Granulocyte-macrophage colony-stimulating factor triggers human brain microvascular endothelial cells monolayer tight junction disassembly by downregulating ZO-1 expression via transcription modulation and claudin-5 expression via the ubiquitination pathway. Interestingly, intracerebral granulocyte-macrophage colony-stimulating factor blockade abolished the increased monocyte infiltration in the brains of APP/PS1 Alzheimer's disease model mice. Our results suggest that in Alzheimer's disease patients, high granulocyte-macrophage colony-stimulating factor levels in the brain parenchyma and cerebrospinal fluid induced blood-brain barrier opening, facilitating the infiltration of CSF2RB-expressing peripheral monocytes across blood-brain barrier and into the brain. CSF2RB might be useful as an Alzheimer's disease biomarker. Thus, our findings will help to understand the mechanism of monocyte infiltration in Alzheimer's disease pathogenesis.

Liposomal nano-drugs based on amphipathic weak acid steroid prodrugs for treatment of inflammatory diseases

BACKGROUND

Steroids are the most efficacious anti-inflammatory agents. However, their toxicities and side-effects compromise their clinical application. Various strategies and major efforts were dedicated for formulating viable liposomal glucocorticosteroids (GCs), so far none of these were approved.

OBJECTIVES

To evaluate these approaches for formulating GC-delivery systems, especially liposomes, and with focus on the Barenholz Lab experience.

METHODS

We developed PEGylated nano-liposomes (NSSL) remotely loaded with water-soluble amphipathic weak acid GC-prodrugs. Their remote loading results in high, efficient and stable loading to the level that enables human clinical use. We characterized them for their physical chemistry and stability. We demonstrated their therapeutic efficacy in relevant animal models and studied their pharmacokinetics (PK), biodistribution (BD) and pharmacodynamics advantages over the free pro-drugs.

RESULTS

Our steroidal nano-drugs demonstrate much superior PK, BD, tolerability and therapeutic efficacies compared to the free pro-drugs and to most drugs currently used to treat these diseases. These nano-drugs act as robust immune-suppressors, affecting cytokines secretion and diminishing hemorrhage and edema.

CONCLUSIONS

The combination of improved physical-chemistry, PK, BD, tolerability and therapeutic efficacy of these steroidal nano-drugs over the pro-drugs "as-is" support their further clinical development as potential therapeutic agents for treating inflammatory diseases.

Nanoparticle Technologies in the Spinal Cord

Nanoparticles are increasingly being studied within experimental models of spinal cord injury (SCI). They are used to image cells and tissue, move cells to specific regions of the spinal cord, and deliver therapeutic agents locally. The focus of this article is to provide a brief overview of the different types of nanoparticles being studied for spinal cord applications and present data showing the capability of nanoparticles to deliver the chondroitinase ABC (chABC) enzyme locally following acute SCI in rats. Nanoparticles releasing chABC helped promote axonal regeneration following injury, and the nanoparticles also protected the enzyme from rapid degradation. In summary, nanoparticles are viable materials for diagnostic or therapeutic applications within experimental models of SCI and have potential for future clinical use.

Research review on the pharmacological effects of astragaloside IV

Astragalus membranaceus Bunge has been used to treat numerous diseases for thousands of years. As the main active substance of Astragalus membranaceus Bunge, astragaloside IV (AS-IV) also demonstrates the potent protective effect on focal cerebral ischemia/reperfusion, cardiovascular disease, pulmonary disease, liver fibrosis, and diabetic nephropathy. Based on studies published during the past several decades, the current state of AS-IV research and the pharmacological effects are detailed, elucidated, and summarized. This review systematically summarizes the pharmacological effects, metabolism mechanism, and the toxicity of AS-IV. AS-IV has multiple pharmacologic effects, including anti-inflammatory, antifibrotic, antioxidative stress, anti-asthma, antidiabetes, immunoregulation, and cardioprotective effect via numerous signaling pathways. According to the existing studies and clinical practices, AS-IV possesses potential for broad application in many diseases.

Neuroendothelial NMDA receptors as therapeutic targets in experimental autoimmune encephalomyelitis

Multiple sclerosis is among the most common causes of neurological disability in young adults. Here we provide the preclinical proof of concept of the benefit of a novel strategy of treatment for multiple sclerosis targeting neuroendothelial N-methyl-D-aspartate glutamate receptors. We designed a monoclonal antibody against N-methyl-D-aspartate receptors, which targets a regulatory site of the GluN1 subunit of N-methyl-D-aspartate receptor sensitive to the protease tissue plasminogen activator. This antibody reverted the effect of tissue plasminogen activator on N-methyl-D-aspartate receptor function without affecting basal N-methyl-D-aspartate receptor activity (n = 21, P < 0.01). This antibody bound N-methyl-D-aspartate receptors on the luminal surface of neurovascular endothelium in human tissues and in mouse, at the vicinity of tight junctions of the blood-spinal cord barrier. Noteworthy, it reduced human leucocyte transmigration in an in vitro model of the blood-brain barrier (n = 12, P < 0.05). When injected during the effector phase of MOG-induced experimental autoimmune encephalomyelitis (n = 24), it blocked the progression of neurological impairments, reducing cumulative clinical score (P < 0.001) and mean peak score (P < 0.001). This effect was observed in wild-type animals but not in tissue plasminogen activator knock-out animals (n = 10). This therapeutic effect was associated to a preservation of the blood-spinal cord barrier (n = 6, P < 0.001), leading to reduced leucocyte infiltration (n = 6, P < 0.001). Overall, this study unveils a critical function of endothelial N-methyl-D-aspartate receptor in multiple sclerosis, and highlights the therapeutic potential of strategies targeting the protease-regulated site of N-methyl-D-aspartate receptor.

DNA Subtraction of In Vivo Selected Phage Repertoires for Efficient Peptide Pathology Biomarker Identification in Neuroinflammation Multiple Sclerosis Model

To streamline in vivo biomarker discovery, we developed a suppression subtractive DNA hybridization technique adapted for phage-displayed combinatorial libraries of 12 amino acid peptides (PhiSSH). Physical DNA subtraction is performed in a one-tube-all-reactions format by sequential addition of reagents, producing the enrichment of specific clones of one repertoire. High-complexity phage repertoires produced by in vivo selections in the multiple sclerosis rat model (experimental autoimmune encephalomyelitis, EAE) and matched healthy control rats were used to evaluate the technique. The healthy repertoire served as a physical DNA subtractor from the EAE repertoire to produce the subtraction repertoire. Full next-generation sequencing (NGS) of the three repertoires was performed to evaluate the efficiency of the subtraction technique. More than 96% of the clones common to the EAE and healthy repertoires were absent from the subtraction repertoire, increasing the probability of randomly selecting various specific peptides for EAE pathology to about 70%. Histopathology experiments were performed to confirm the quality of the subtraction repertoire clones, producing distinct labeling of the blood–brain barrier (BBB) affected by inflammation among healthy nervous tissue or the preferential binding to IL1-challenged vs. resting human BBB model. Combining PhiSSH with NGS will be useful for controlled in vivo screening of small peptide combinatorial libraries to discover biomarkers of specific molecular alterations interspersed within healthy tissues.