Safety and efficacy of natalizumab in patients with acute ischaemic stroke (ACTION): a randomised, placebo-controlled, double-blind phase 2 trial

Pre-clinical to Clinical Translational Failures and Current Status of Clinical Trials in Stroke Therapy: A Brief Review

In stroke (cerebral ischemia), despite continuous efforts both at the experimental and clinical level, the only approved pharmacological treatment has been restricted to tissue plasminogen activator (tPA). Stroke is the leading cause of functional disability and mortality throughout worldwide. Its pathophysiology starts with energy pump failure, followed by complex signaling cascade that ultimately ends in neuronal cell death. Ischemic cascade involves excessive glutamate release followed by raised intracellular sodium and calcium influx along with free radicals' generation, activation of inflammatory cytokines, NO synthases, lipases, endonucleases and other apoptotic pathways leading to cell edema and death. At the pre-clinical stage, several agents have been tried and proven as an effective neuroprotectant in animal models of ischemia. However, these agents failed to show convincing results in terms of efficacy and safety when the trials were conducted in humans following stroke. This article highlights the various agents which have been tried in the past but failed to translate into stroke therapy along with key points that are responsible for the lagging of experimental success to translational failure in stroke treatment.

Aging and Neurodegenerative Disease: Is the Adaptive Immune System a Friend or Foe?

Neurodegenerative diseases of the central nervous system (CNS) are characterized by progressive neuronal death and neurological dysfunction, leading to increased disability and a loss of cognitive or motor functions. Alzheimer's disease, Parkinson's disease and amyotrophic lateral sclerosis have neurodegeneration as a primary feature. However, in other CNS diseases such as multiple sclerosis, stroke, traumatic brain injury, and spinal cord injury, neurodegeneration follows another insult, such as demyelination or ischaemia. Although there are different primary causes to these diseases, they all share a hallmark of neuroinflammation. Neuroinflammation can occur through the activation of resident immune cells such as microglia, cells of the innate and adaptive peripheral immune system, meningeal inflammation and autoantibodies directed toward components of the CNS. Despite chronic inflammation being pathogenic in these diseases, local inflammation after insult can also promote endogenous regenerative processes in the CNS, which are key to slowing disease progression. The normal aging process in the healthy brain is associated with a decline in physiological function, a steady increase in levels of neuroinflammation, brain shrinkage, and memory deficits. Likewise, aging is also a key contributor to the progression and exacerbation of neurodegenerative diseases. As there are associated co-morbidities within an aging population, pinpointing the precise relationship between aging and neurodegenerative disease progression can be a challenge. The CNS has historically been considered an isolated, "immune privileged" site, however, there is mounting evidence that adaptive immune cells are present in the CNS of both healthy individuals and diseased patients. Adaptive immune cells have also been implicated in both the degeneration and regeneration of the CNS. In this review, we will discuss the key role of the adaptive immune system in CNS degeneration and regeneration, with a focus on how aging influences this crosstalk.

A year-long immune profile of the systemic response in acute stroke survivors

Stroke is a leading cause of cognitive impairment and dementia, but the mechanisms that underlie post-stroke cognitive decline are not well understood. Stroke produces profound local and systemic immune responses that engage all major innate and adaptive immune compartments. However, whether the systemic immune response to stroke contributes to long-term disability remains ill-defined. We used a single-cell mass cytometry approach to comprehensively and functionally characterize the systemic immune response to stroke in longitudinal blood samples from 24 patients over the course of 1 year and correlated the immune response with changes in cognitive functioning between 90 and 365 days post-stroke. Using elastic net regularized regression modelling, we identified key elements of a robust and prolonged systemic immune response to ischaemic stroke that occurs in three phases: an acute phase (Day 2) characterized by increased signal transducer and activator of transcription 3 (STAT3) signalling responses in innate immune cell types, an intermediate phase (Day 5) characterized by increased cAMP response element-binding protein (CREB) signalling responses in adaptive immune cell types, and a late phase (Day 90) by persistent elevation of neutrophils, and immunoglobulin M+ (IgM+) B cells. By Day 365 there was no detectable difference between these samples and those from an age- and gender-matched patient cohort without stroke. When regressed against the change in the Montreal Cognitive Assessment scores between Days 90 and 365 after stroke, the acute inflammatory phase Elastic Net model correlated with post-stroke cognitive trajectories (r = -0.692, Bonferroni-corrected P = 0.039). The results demonstrate the utility of a deep immune profiling approach with mass cytometry for the identification of clinically relevant immune correlates of long-term cognitive trajectories.

Platelets as Modulators of Cerebral Ischemia/Reperfusion Injury

Ischemic stroke is among the leading causes of disability and death worldwide. In acute ischemic stroke, the rapid recanalization of occluded cranial vessels is the primary therapeutic aim. However, experimental data (obtained using mostly the transient middle cerebral artery occlusion model) indicates that progressive stroke can still develop despite successful recanalization, a process termed "reperfusion injury." Mounting experimental evidence suggests that platelets and T cells contribute to cerebral ischemia/reperfusion injury, and ischemic stroke is increasingly considered a thrombo-inflammatory disease. The interaction of von Willebrand factor and its receptor on the platelet surface, glycoprotein Ib, as well as many activatory platelet receptors and platelet degranulation contribute to secondary infarct growth in this setting. In contrast, interference with GPIIb/IIIa-dependent platelet aggregation and thrombus formation does not improve the outcome of acute brain ischemia but dramatically increases the susceptibility to intracranial hemorrhage. Here, we summarize the current understanding of the mechanisms and the potential translational impact of platelet contributions to cerebral ischemia/reperfusion injury.

Ischaemic stroke

Stroke is the second highest cause of death globally and a leading cause of disability, with an increasing incidence in developing countries. Ischaemic stroke caused by arterial occlusion is responsible for the majority of strokes. Management focuses on rapid reperfusion with intravenous thrombolysis and endovascular thrombectomy, which both reduce disability but are time-critical. Accordingly, improving the system of care to reduce treatment delays is key to maximizing the benefits of reperfusion therapies. Intravenous thrombolysis reduces disability when administered within 4.5 h of the onset of stroke. Thrombolysis also benefits selected patients with evidence from perfusion imaging of salvageable brain tissue for up to 9 h and in patients who awake with stroke symptoms. Endovascular thrombectomy reduces disability in a broad group of patients with large vessel occlusion when performed within 6 h of stroke onset and in patients selected by perfusion imaging up to 24 h following stroke onset. Secondary prevention of ischaemic stroke shares many common elements with cardiovascular risk management in other fields, including blood pressure control, cholesterol management and antithrombotic medications. Other preventative interventions are tailored to the mechanism of stroke, such as anticoagulation for atrial fibrillation and carotid endarterectomy for severe symptomatic carotid artery stenosis.

Immune Responses and Anti-inflammatory Strategies in a Clinically Relevant Model of Thromboembolic Ischemic Stroke with Reperfusion

The poor clinical relevance of experimental models of stroke contributes to the translational failure between preclinical and clinical studies testing anti-inflammatory molecules for ischemic stroke. Here, we (i) describe the time course of inflammatory responses triggered by a thromboembolic model of ischemic stroke and (ii) we examine the efficacy of two clinically tested anti-inflammatory drugs: Minocycline or anti-CD49d antibodies (tested in stroke patients as Natalizumab) administered early (1 h) or late (48 h) after stroke onset. Radiological (lesion volume) and neurological (grip test) outcomes were evaluated at 24 h and 5 days after stroke. Immune cell responses peaked 48 h after stroke onset. Myeloid cells (microglia/macrophages, dendritic cells, and neutrophils) were already increased 24 h after stroke onset, peaked at 48 h, and remained increased-although to a lesser extent-5 days after stroke onset. CD8⁺ and CD4⁺ T-lymphocytes infiltrated the ipsilateral hemisphere later on (only from 48 h). These responses occurred together with a progressive blood-brain barrier leakage at the lesion site, starting 24 h after stroke onset. Lesion volume was maximal 24-48 h after stroke onset. Minocycline reduced both lesion volume and neurological deficit only when administered early after stroke onset. The blockade of leukocyte infiltration by anti-CD49d had no impact on lesion volume or long-term neurological deficit, independently of the timing of treatment. Our data are in accordance with the results of previous clinical reports on the use of Minocycline and Natalizumab on ischemic stroke. We thus propose the use of this clinically relevant model of thromboembolic stroke with recanalization for future testing of anti-inflammatory strategies for stroke.

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.

Systemic inflammatory response syndrome and long-term outcome after intracerebral hemorrhage

Objective

To investigate whether the systemic inflammatory response syndrome (SIRS) without infection as surrogate of a systemic immune response is associated with poor long-term functional outcome in patients with spontaneous intracerebral hemorrhage (ICH).

Methods

We analyzed consecutive patients with spontaneous ICH from our prospective cohort study (2018-2015). SIRS was defined according to standard criteria: i.e., 2 or more of the following parameters during hospitalization: body temperature <36°C or >38°C, respiratory rate >20 per minute, heart rate >90 per minute, or white blood cell count <4,000/μL or >12,000/μL in the absence of infection. The primary outcome consisted of the modified Rankin Scale (mRS) at 3 and 12 months investigated by adjusted ordinal shift analyses. Bias and confounding were addressed by propensity score matching and multivariable regression models.

Results

Of 780 patients with ICH, 21.8% (n = 170) developed SIRS during hospitalization. Patients with SIRS showed more severe ICH compared with those without; i.e., larger ICH volumes (18.3 cm3, interquartile range [IQR 4.6-47.2 cm3] vs 7.4 cm3, IQR [2.4-18.6 cm3]; p < 0.01), increased intraventricular hemorrhage (57.6%, n = 98/170 vs 24.8%, n = 79/319; p < 0.01), and poorer neurologic admission status (NIH Stroke Scale score 16, IQR [7-30] vs 6, IQR [3-12]; p < 0.01). ICH severity-adjusted analyses revealed an independent association of SIRS with poorer functional outcome after 3 (OR 1.80, 95% CI [1.08-3.00]; p = 0.025) and 12 months (OR 1.76, 95% CI [1.04-2.96]; p = 0.034). Increased ICH volumes on follow-up imaging (OR 1.38, 95% CI [1.01-1.89]; p = 0.05) and previous liver dysfunction (OR 3.01, 95% CI [1.03-10.19]; p = 0.04) were associated with SIRS.

Conclusions

In patients with ICH, we identified SIRS to be predictive of poorer long-term functional outcome over the entire range of mRS estimates. Clinically relevant associations with SIRS were documented for previous liver dysfunction and hematoma enlargement.

Therapeutic Modulation of the Complement Cascade in Stroke

Stroke is a leading cause of death and disability worldwide and an increasing number of ischemic stroke patients are undergoing pharmacological and mechanical reperfusion. Both human and experimental models of reperfused ischemic stroke have implicated the complement cascade in secondary tissue injury. Most data point to the lectin and alternative pathways as key to activation, and C3a and C5a binding of their receptors as critical effectors of injury. During periods of thrombolysis use to treat stroke, acute experimental complement cascade blockade has been found to rescue tissue and improves functional outcome. Blockade of the complement cascade during the period of tissue reorganization, repair, and recovery is by contrast not helpful and in fact is likely to be deleterious with emerging data suggesting downstream upregulation of the cascade might even facilitate recovery. Successful clinical translation will require the right clinical setting and pharmacologic strategies that are capable of targeting the key effectors early while not inhibiting delayed repair. Early reports in a variety of disease states suggest that such pharmacologic strategies appear to have a favorable risk profile and offer substantial hope for patients.

Global brain inflammation in stroke

Stroke, including acute ischaemic stroke and intracerebral haemorrhage, results in neuronal cell death and the release of factors such as damage-associated molecular patterns (DAMPs) that elicit localised inflammation in the injured brain region. Such focal brain inflammation aggravates secondary brain injury by exacerbating blood-brain barrier damage, microvascular failure, brain oedema, oxidative stress, and by directly inducing neuronal cell death. In addition to inflammation localised to the injured brain region, a growing body of evidence suggests that inflammatory responses after a stroke occur and persist throughout the entire brain. Global brain inflammation might continuously shape the evolving pathology after a stroke and affect the patients' long-term neurological outcome. Future efforts towards understanding the mechanisms governing the emergence of so-called global brain inflammation would facilitate modulation of this inflammation as a potential therapeutic strategy for stroke.

Immunomodulatory Therapeutic Strategies in Stroke

The role of immunity in all stages of stroke is increasingly being recognized, from the pathogenesis of risk factors to tissue repair, leading to the investigation of a range of immunomodulatory therapies. In the acute phase of stroke, proposed therapies include drugs targeting pro-inflammatory cytokines, matrix metalloproteinases, and leukocyte infiltration, with a key objective to reduce initial brain cell toxicity. Systemically, the early stages of stroke are also characterized by stroke-induced immunosuppression, where downregulation of host defences predisposes patients to infection. Therefore, strategies to modulate innate immunity post-stroke have garnered greater attention. A complementary objective is to reduce longer-term sequelae by focusing on adaptive immunity. Following stroke onset, the integrity of the blood–brain barrier is compromised, exposing central nervous system (CNS) antigens to systemic adaptive immune recognition, potentially inducing autoimmunity. Some pre-clinical efforts have been made to tolerize the immune system to CNS antigens pre-stroke. Separately, immune cell populations that exhibit a regulatory phenotype (T- and B- regulatory cells) have been shown to ameliorate post-stroke inflammation and contribute to tissue repair. Cell-based therapies, established in oncology and transplantation, could become a strategy to treat the acute and chronic stages of stroke. Furthermore, a role for the gut microbiota in ischaemic injury has received attention. Finally, the immune system may play a role in remote ischaemic preconditioning-mediated neuroprotection against stroke. The development of stroke therapies involving organs distant to the infarct site, therefore, should not be overlooked. This review will discuss the immune mechanisms of various therapeutic strategies, surveying published data and discussing more theoretical mechanisms of action that have yet to be exploited.

The Inflammatory Response After Ischemic Stroke: Targeting β2 and β1 Integrins

Ischemic stroke is a leading cause of death and disability with limited therapeutic options. Resulting inflammatory mechanisms after reperfusion (removal of the thrombus) result in cytokine activation, calcium influx, and leukocytic infiltration to the area of ischemia. In particular, leukocytes migrate toward areas of inflammation by use of integrins, particularly integrins β1 and β2. Integrins have been shown to be necessary for leukocyte adhesion and migration, and thus are of immediate interest in many inflammatory diseases, including ischemic stroke. In this review, we identify the main integrins involved in leukocytic migration following stroke (α L β2, αDβ2, α4β1, and α5β1) and targeted clinical therapeutic interventions.

Repurposing multiple sclerosis drugs: a review of studies in neurological and psychiatric conditions

Treatment options for multiple sclerosis (MS) have improved in the past 20 years, with new oral disease-modifying drugs and monoclonal antibodies becoming available. The success seen with these drugs in MS, and their various mechanisms of action, has led to them being investigated in other neurological and psychiatric disorders. This review article summarises the ongoing and completed studies of MS drugs in neurological and psychiatric conditions other than MS. The most promising results are for interferon beta in human T cell leukaemia virus 1 associated myelopathy/tropical spastic paraparesis and glioma, and for fingolimod in acute ischaemic stroke and intracerebral haemorrhage. The coming years could see the arrival of exciting new therapies for disorders that neurologists have historically found difficult to treat and that represent a significant unmet clinical need.

Electrical Stimulation of the Mesencephalic Locomotor Region Attenuates Neuronal Loss and Cytokine Expression in the Perifocal Region of Photothrombotic Stroke in Rats

Deep brain stimulation of the mesencephalic locomotor region (MLR) improves the motor symptoms in Parkinson’s disease and experimental stroke by intervening in the motor cerebral network. Whether high-frequency stimulation (HFS) of the MLR is involved in non-motor processes, such as neuroprotection and inflammation in the area surrounding the photothrombotic lesion, has not been elucidated. This study evaluates whether MLR-HFS exerts an anti-apoptotic and anti-inflammatory effect on the border zone of cerebral photothrombotic stroke. Rats underwent photothrombotic stroke of the right sensorimotor cortex and the implantation of a microelectrode into the ipsilesional MLR. After intervention, either HFS or sham stimulation of the MLR was applied for 24 h. The infarct volumes were calculated from consecutive brain sections. Neuronal apoptosis was analyzed by TUNEL staining. Flow cytometry and immunohistochemistry determined the perilesional inflammatory response. Neuronal apoptosis was significantly reduced in the ischemic penumbra after MLR-HFS, whereas the infarct volumes did not differ between the groups. MLR-HFS significantly reduced the release of cytokines and chemokines within the ischemic penumbra. MLR-HFS is neuroprotective and it reduces pro-inflammatory mediators in the area that surrounds the photothrombotic stroke without changing the number of immune cells, which indicates that MLR-HFS enables the function of inflammatory cells to be altered on a molecular level.

Post-Stroke Blood-Brain Barrier Disruption and Poor Functional Outcome in Patients Receiving Thrombolytic Therapy

BACKGROUND AND PURPOSE

The role played by post-stroke inflammation after an ischemic event in limiting functional recovery remains unclear. One component of post-stroke inflammation is disruption of the blood-brain barrier (BBB). This study examines the relationship between post-stroke BBB disruption and functional outcome.

METHODS

Acute stroke patients treated with thrombolysis underwent magnetic resonance imaging scanning 24 h and 5 days after their initial event. BBB permeability maps were generated from perfusion weighted imaging. Average permeability was calculated in the affected hemisphere. Good functional outcome, defined as a modified Rankin score of 0 or 1, was compared with average permeability using logistic regression.

RESULTS

Of the 131 patients enrolled, 76 patients had the necessary data to perform the analysis at 24 h, and 58 -patients had data for the 5-day assessment. Higher BBB permeability measured at 24 h (OR 0.57; 95% CI 0.33-0.99, p = 0.045) and at 5 days (OR 0.24; 95% CI 0.09-0.66, p = 0.005) was associated with worse functional outcome 1-3 months after the acute ischemic stroke. For every percentage increase in BBB disruption at 5 days, there was a 76% decrease in the chance of achieving a good functional outcome after stroke. Multivariate analysis found this to be independent of age, stroke volume, or clinical stroke severity.

CONCLUSIONS

Post-stroke BBB disruption appears to be predictive of functional outcome irrespective of stroke size.

Shared Gene Expression Between Multiple Sclerosis and Ischemic Stroke

Patients with multiple sclerosis (MS) appear to have an increased risk of ischemic stroke (IS). Although MS and IS have very different phenotypes, gene-based and pathway-based analyses of large-scale genome-wide association studies (GWAS) have increasingly enhanced our understanding of these two diseases. Whether there are common molecular mechanisms connecting MS and IS is still unclear. Here, we describe the outcome of gene-based test and pathway-based analysis of GWAS datasets that explored potential gene expression links between MS and IS. After identifying significant gene sets individually of MS and IS, we performed pathway-based analysis in four biological pathway databases (KEGG, PANTHER, REACTOME, and WikiPathways) and GO categories. We discovered that there were 9 shared pathways between MS and IS in KEGG, 2 in PANTHER, 14 in REACTOME, 1 in WikiPathways, and 194 in GO annotations (p < 0.05). These results provide an improved understanding about possible shared mechanisms and treatments strategies for MS and IS. They also provide some basis for further studies of how these two diseases are linked at the molecular level.

Inflammation and neural repair after ischemic brain injury

Stroke causes neuronal cell death and destruction of neuronal circuits in the brain and spinal cord. Injury to the brain tissue induces sterile inflammation triggered by the extracellular release of endogenous molecules, but cerebral inflammation after stroke is gradually resolved within several days. In this pro-resolving process, inflammatory cells adopt a pro-resolving or repairing phenotype in the injured brain, activating endogenous repairing programs. Although the mechanisms involved in the transition from inflammation to neural repair after stroke remain largely unknown to date, some of the mechanisms for inflammation and neural repair have been clarified in detail. This review focuses on the molecular or cellular mechanisms involved in sterile inflammation and neural repair after stroke. This accumulation of evidence may be helpful for speculating about the endogenous repairing mechanisms in the brain and identifying therapeutic targets for improving the functional prognoses of stroke patients.

Role of polymorphonuclear neutrophils in the reperfused ischemic brain: insights from cell-type-specific immunodepletion and fluorescence microscopy studies

Polymorphonuclear neutrophil granulocytes (PMNs) are part of the early post-ischemic immune response that orchestrates the removal of infarcted brain tissue. PMNs contribute to secondary brain injury in experimental stroke models. In human patients, high PMN-to-lymphocyte ratios in peripheral blood are predictive of poor stroke outcome. Following earlier studies indicating that the cerebral microvasculature forms an efficient barrier that impedes PMN brain entry even under conditions of ischemia, more recent studies combining intravital two-photon microscopy and ex vivo immunohistochemistry unequivocally demonstrated the accumulation of PMNs in the ischemic brain parenchyma. In the meantime, transgenic mouse lines, such as mice expressing Cre-recombinase and the red fluorescent reporter protein tdTomato under the highly granulocyte-specific locus for the gene Ly6G (so-called Catchup mice), have become available that allow study of dynamic interactions of PMNs with brain parenchymal cells. These mice will further help us understand how PMNs promote brain injury and disturb brain remodeling and plasticity.

Ischemia-reperfusion injury in stroke: impact of the brain barriers and brain immune privilege on neutrophil function

Reperfusion injury following ischemic stroke is a complex pathophysiological process involving numerous mechanisms ranging from the release of excitatory amino acids and ion disequilibrium to the induction of apoptosis and necrosis, to oxidative stress and inflammation. The migration of neutrophils into the brain parenchyma and release of their abundant proteases are generally considered the main cause of neuronal cell death and acute reperfusion injury following ischemic stroke. Recent findings in experimental and human stroke have challenged this view, as the majority of neutrophils were rather found to accumulate within the neurovascular unit (NVU) and the subarachnoid space (SAS) where they remain separated from the brain parenchyma by the glia limitans. The brain parenchyma is an immune-privileged site that is not readily accessible to immune cells and does not elicit stereotypic adaptive or innate immune responses. Understanding brain immune privilege requires intimate knowledge of its unique anatomy in which the brain barriers, that include the glia limitans, establish compartments that differ remarkably with regard to their accessibility to the immune system. We here propose that the brain immune privilege also extends to an ischemic insult, where the brain parenchyma does not evoke a rapid infiltration of neutrophils as observed in ischemic events in peripheral organs. Rather, neutrophil accumulation in the NVU and SAS could have a potential impact on cerebrospinal fluid (CSF) drainage from the central nervous system (CNS) and thus on edema formation and reperfusion injury after ischemic stroke. Integrating the anatomical and functional implications of the brain immune privilege with the unquestionable role of neutrophils in reperfusion injury is a prerequisite to exploit appropriate strategies for therapeutic interventions aiming to reduce neuronal cell death after ischemic stroke.

Inflammatory molecules might become both biomarkers and therapeutic targets for stroke management

Stroke is the fifth leading cause of death and the most frequent cause of disability worldwide. Currently, stroke diagnosis is based on neuroimaging; therefore, the lack of a rapid tool to diagnose stroke is still a major concern. In addition, therapeutic approaches to combat ischemic stroke are still scarce, since the only approved therapies are directed toward restoring blood flow to the affected brain area. However, due to the reduced time window during which these therapies are effective, few patients benefit from them; therefore, alternative treatments are urgently needed to reduce stroke brain damage in order to improve patients' outcome. The inflammatory response triggered after the ischemic event plays an important role in the progression of stroke; consequently, the study of inflammatory molecules in the acute phase of stroke has attracted increasing interest in recent decades. Here, we provide an overview of the inflammatory processes occurring during ischemic stroke, as well as the potential for these inflammatory molecules to become stroke biomarkers and the possibility that these candidates will become interesting neuroprotective therapeutic targets to be blocked or stimulated in order to modulate inflammation after stroke.

Anti-inflammatory treatments for stroke: from bench to bedside

So far, intravenous tissue-type plasminogen activator (tPA) and mechanical removal of arterial blood clot (thrombectomy) are the only available treatments for acute ischemic stroke. However, the short therapeutic window and the lack of specialized stroke unit care make the overall availability of both treatments limited. Additional agents to combine with tPA administration or thrombectomy to enhance efficacy and improve outcomes associated with stroke are needed. Stroke-induced inflammatory processes are a response to the tissue damage due to the absence of blood supply but have been proposed also as key contributors to all the stages of the ischemic stroke pathophysiology. Despite promising results in experimental studies, inflammation-modulating treatments have not yet been translated successfully into the clinical setting. This review will (a) describe the timing of the stroke immune pathophysiology; (b) detail the immune responses to stroke sift-through cell type; and (c) discuss the pitfalls on the translation from experimental studies to clinical trials testing the therapeutic pertinence of immune modulators.

Potentially Common Therapeutic Targets for Multiple Sclerosis and Ischemic Stroke

Ischemic stroke (IS) and multiple sclerosis (MS) are two pathologies of the central nervous system (CNS). At the first look, this appears to be the only similarity between the two diseases, as they seem quite different. Indeed IS has an acute onset compared to MS which develops chronically; IS is consecutive to blood clot migrating to cerebral blood vessels or decrease in cerebral blood flow following atherosclerosis or decreases in cardiac output, whereas MS is an immune disease associated with neurodegeneration. However, both pathologies share similar pathologic pathways and treatments used in MS have been the object of studies in IS. In this mini-review we will discuss similarities between IS and MS on astrocytes and neuroinflammation hallmarks emphasizing the potential for treatments.

Spinal Cord Injury Scarring and Inflammation: Therapies Targeting Glial and Inflammatory Responses

Deficits in neuronal function are a hallmark of spinal cord injury (SCI) and therapeutic efforts are often focused on central nervous system (CNS) axon regeneration. However, secondary injury responses by astrocytes, microglia, pericytes, endothelial cells, Schwann cells, fibroblasts, meningeal cells, and other glia not only potentiate SCI damage but also facilitate endogenous repair. Due to their profound impact on the progression of SCI, glial cells and modification of the glial scar are focuses of SCI therapeutic research. Within and around the glial scar, cells deposit extracellular matrix (ECM) proteins that affect axon growth such as chondroitin sulfate proteoglycans (CSPGs), laminin, collagen, and fibronectin. This dense deposition of material, i.e., the fibrotic scar, is another barrier to endogenous repair and is a target of SCI therapies. Infiltrating neutrophils and monocytes are recruited to the injury site through glial chemokine and cytokine release and subsequent upregulation of chemotactic cellular adhesion molecules and selectins on endothelial cells. These peripheral immune cells, along with endogenous microglia, drive a robust inflammatory response to injury with heterogeneous reparative and pathological properties and are targeted for therapeutic modification. Here, we review the role of glial and inflammatory cells after SCI and the therapeutic strategies that aim to replace, dampen, or alter their activity to modulate SCI scarring and inflammation and improve injury outcomes.

Targeting vascular inflammation in ischemic stroke: Recent developments on novel immunomodulatory approaches

Ischemic stroke is a devastating and debilitating medical condition with limited therapeutic options. However, accumulating evidence indicates a central role of inflammation in all aspects of stroke including its initiation, the progression of injury, and recovery or wound healing. A central target of inflammation is disruption of the blood brain barrier or neurovascular unit. Here we discuss recent developments in identifying potential molecular targets and immunomodulatory approaches to preserve or protect barrier function and limit infarct damage and functional impairment. These include blocking harmful inflammatory signaling in endothelial cells, microglia/macrophages, or Th17/γδ T cells with biologics, third generation epoxyeicosatrienoic acid (EET) analogs with extended half-life, and miRNA antagomirs. Complementary beneficial pathways may be enhanced by miRNA mimetics or hyperbaric oxygenation. These immunomodulatory approaches could be used to greatly expand the therapeutic window for thrombolytic treatment with tissue plasminogen activator (t-PA). Moreover, nanoparticle technology allows for the selective targeting of endothelial cells for delivery of DNA/RNA oligonucleotides and neuroprotective drugs. In addition, although likely detrimental to the progression of ischemic stroke by inducing inflammation, oxidative stress, and neuronal cell death, 20-HETE may also reduce susceptibility of onset of ischemic stroke by maintaining autoregulation of cerebral blood flow. Although the interaction between inflammation and stroke is multifaceted, a better understanding of the mechanisms behind the pro-inflammatory state at all stages will hopefully help in developing novel immunomodulatory approaches to improve mortality and functional outcome of those inflicted with ischemic stroke.

The meningeal and choroidal infiltration routes for leukocytes in stroke

Stroke is a major health burden as it is a leading cause of morbidity and mortality worldwide. Blood flow restoration, through thrombolysis or endovascular thrombectomy, is the only effective treatment but is restricted to a limited proportion of patients due to time window constraint and accessibility to technology. Over the past two decades, research has investigated the basic mechanisms that lead to neuronal death following cerebral ischemia. However, the use of neuroprotective paradigms in stroke has been marked by failure in translation from experimental research to clinical practice. In the past few years, much attention has focused on the immune response to acute cerebral ischemia as a major factor to the development of brain lesions and neurological deficits. Key inflammatory processes after stroke include the activation of resident glial cells as well as the invasion of circulating leukocytes. Recent research on anti-inflammatory strategies for stroke has focused on limiting the transendothelial migration of peripheral immune cells from the compromised vasculature into the brain parenchyma. However, recent trials testing the blockage of cerebral leukocyte infiltration in patients reported inconsistent results. This emphasizes the need to better scrutinize how immune cells are regulated at the blood-brain interface and enter the brain parenchyma, and particularly to also consider alternative cerebral infiltration routes for leukocytes, including the meninges and the choroid plexus. Understanding how immune cells migrate to the brain via these alternative pathways has the potential to develop more effective approaches for anti-inflammatory stroke therapies.

Immunotherapy of experimental and human stroke with agents approved for multiple sclerosis: a systematic review

Background

'Thromboinflammation' describes a novel concept in stroke pathophysiology that has opened up the possibility of immunotherapeutic approaches which could become promising strategies for targeted stroke therapies in the future.

Methods

We reviewed current evidence for agents approved for multiple sclerosis in preclinical and clinical stroke studies. A systematic review was performed in accordance with the PRISMA statement, searching MEDLINE, the Cochrane Central Register of Controlled Trials, and reference lists of articles published until 16 October 2017.

Results

The review included 52 of 629 identified studies, consisting of 5 clinical and 47 preclinical trials. Most of the studies showed beneficial effects of the evaluated immunotherapeutic drugs in terms of reduction in morphological lesion size and improvement in functional outcome. Nevertheless, the significance of these findings is limited due to the high degree of heterogeneity.

Conclusions

Immunotherapy of stroke might be effective and could become a promising treatment strategy, but larger clinical trials with standardized interventions and outcome measures are needed.

Hypothermia and brain inflammation after cardiac arrest

The cessation (ischemia) and restoration (reperfusion) of cerebral blood flow after cardiac arrest (CA) induce inflammatory processes that can result in additional brain injury. Therapeutic hypothermia (TH) has been proven as a brain protective strategy after CA. In this article, the underlying pathophysiology of ischemia-reperfusion brain injury with emphasis on the role of inflammatory mechanisms is reviewed. Potential targets for immunomodulatory treatments and relevant effects of TH are also discussed. Further studies are needed to delineate the complex pathophysiology and interactions among different components of immune response after CA and identify appropriate targets for clinical investigations.

Paradigm Shift to Neuroimmunomodulation for Translational Neuroprotection in Stroke

The treatment of acute ischemic stroke is still an unresolved clinical problem since the only approved therapeutic intervention relies on early blood flow restoration through pharmacological thrombolysis, mechanical thrombus removal, or a combination of both strategies. Due to their numerous complications and to the narrow time-window for the intervention, only a minority of stroke patients can actually benefit from revascularization procedures, highlighting the urgent need of identifying novel strategies to prevent the progression of an irreversible damage in the ischemic penumbra. During the past three decades, the attempts to target the pathways implicated in the ischemic cascade (e.g., excitotoxicity, calcium channels overactivation, reactive oxygen species (ROS) production) have failed in the clinical setting. Based on a better understanding of the pathobiological mechanisms and on a critical reappraisal of most failed trials, numerous findings from animal studies have demonstrated that targeting the immune system may represent a promising approach to achieve neuroprotection in stroke. In particular, given the dualistic role of distinct components of both the innate and adaptive arms of the immune system, a strategic intervention should be aimed at establishing the right equilibrium between inflammatory and reparative mechanisms, taking into consideration their spatio-temporal recruitment after the ischemic insult. Thus, the application of immunomodulatory drugs and their ability to ameliorate outcomes deserve validation in patients with acute ischemic stroke.

Emerging Role of Immunity in Cerebral Small Vessel Disease

Cerebral small vessel disease (CSVD) is one of the main causes of vascular dementia in older individuals. Apart from risk containment, efforts to prevent or treat CSVD are ineffective due to the unknown pathogenesis of the disease. CSVD, a subtype of stroke, is characterized by recurrent strokes and neurodegeneration. Blood-brain barrier (BBB) impairment, chronic inflammatory responses, and leukocyte infiltration are classical pathological features of CSVD. Understanding how BBB disruption instigates inflammatory and degenerative processes may be informative for CSVD therapy. Antigens derived from the brain are found in the peripheral blood of lacunar stroke patients, and antibodies and sensitized T cells against brain antigens are also detected in patients with leukoaraiosis. These findings suggest that antigen-specific immune responses could occur in CSVD. This review describes the neurovascular unit features of CSVD, the immune responses to specific neuronal and glial processes that may be involved in a distinct mechanism of CSVD, and the current evidence of the association between mechanisms of inflammation and interventions in CSVD. We suggest that autoimmune activity should be assessed in future studies; this knowledge would benefit the development of effective therapeutic interventions in CSVD.

2017 Yearbook of Neurorestoratology

In 2016 we published the first Yearbook of Neurorestoratology, which summarized pathogenesis in nervous system disease and damage, as well as neurorestorative mechanisms and neurorestorative therapeutic results. Given the progress and achievements occurring in 2017, we have put together those major progresses as the “2017 Yearbook of Neurorestoratology”, which can help readers to easily follow the latest developments in Neurorestoratology.

Dominant role of microglial and macrophage innate immune responses in human ischemic infarcts

Inflammatory mechanisms, involving granulocytes, T‐cells, B‐cells, macrophages and activated microglia, have been suggested to play a pathogenic role in experimental models of stroke and may be targets for therapeutic intervention. However, knowledge on the inflammatory response in human stroke lesions is limited. Here, we performed a quantitative study on the inflammatory reaction in human ischemic infarct lesions. We found increased numbers of T‐lymphocytes, mainly CD8⁺ cells, but not of B‐lymphocytes. Their number was very low in comparison to that seen in inflammatory diseases of the central nervous system and they did not show signs of activation. Polymorphonuclear leukocytes were present in meninges and less prominently in the perivascular space in early lesions, but their infiltration into the lesioned tissue was sparse with the exception of a single case. Microglia were lost in the necrotic core of fresh lesions, their number was increased in the surrounding penumbra, apparently due to proliferation. Using TMEM119 as a marker for the resident microglia pool, macrophages in lesions were in part derived from the original microglia pool, depending on the lesion stage. Most microglia and macrophages revealed a pro‐inflammatory activation pattern, expressing molecules involved in phagocytosis, oxidative injury, antigen presentation and iron metabolism and had partially lost the expression of P2RY12, an antigen expressed on homeostatic (“resting”) microglia in rodents. At later lesion stages, the majority of macrophages showed intermediate activation patterns, expressing pro‐inflammatory and anti‐inflammatory markers. Microglia in the normal white matter of controls and stroke patients were already partly activated toward a pro‐inflammatory phenotype. Our data suggest that the direct contribution of lymphocytes and granulocytes to active tissue injury in human ischemic infarct lesions is limited and that stroke therapy that targets pro‐inflammatory microglia and macrophage activation may be effective.

Systemic inflammatory response syndrome, infection, and outcome in intracerebral hemorrhage

Objective:

Systemic inflammatory response syndrome (SIRS) may be related to poor outcomes after intracerebral hemorrhage (ICH).

Methods:

The Ethnic/Racial Variations of Intracerebral Hemorrhage study is an observational study of ICH in whites, blacks, and Hispanics throughout the United Sates. SIRS was defined by standard criteria as 2 or more of the following on admission: (1) body temperature <36°C or >38°C, (2) heart rate >90 beats per minute, (3) respiratory rate >20 breaths per minute, or (4) white blood cell count <4,000/mm³ or >12,000/mm³. The relationship among SIRS, infection, and poor outcome (modified Rankin Scale [mRS] 3–6) at discharge and 3 months was assessed.

Results:

Of 2,441 patients included, 343 (14%) met SIRS criteria at admission. Patients with SIRS were younger (58.2 vs 62.7 years; p < 0.0001) and more likely to have intraventricular hemorrhage (IVH; 53.6% vs 36.7%; p < 0.0001), higher admission hematoma volume (25.4 vs 17.5 mL; p < 0.0001), and lower admission Glasgow Coma Scale (GCS; 10.7 vs 13.1; p < 0.0001). SIRS on admission was significantly related to infections during hospitalization (adjusted odds ratio [OR] 1.36, 95% confidence interval [CI] 1.04–1.78). In unadjusted analyses, SIRS was associated with poor outcomes at discharge (OR 1.96, 95% CI 1.42–2.70) and 3 months (OR 1.75, 95% CI 1.35–2.33) after ICH. In analyses adjusted for infection, age, IVH, hematoma location, admission GCS, and premorbid mRS, SIRS was no longer associated with poor outcomes.

Conclusions:

SIRS on admission is associated with ICH score on admission and infection, but it was not an independent predictor of poor functional outcomes after ICH.

Cortisol is More Important than Metanephrines in Driving Changes in Leukocyte Counts after Stroke

BACKGROUND

There are notable changes in the number of white blood cells (WBCs) after stroke, but the primary mediators of these changes are unclear. In this study, we assessed the role of the neuroendocrine and sympathetic nervous systems in stroke-induced changes of WBCs within distinct leukocyte subsets, as well as the effect of these changes on stroke outcomes.

METHODS

Patients were recruited within 72 hours after ischemic stroke; complete blood count with differential was obtained at set time points. The relationships among leukocyte numbers, cortisol, adrenocorticotropic hormone, interleukin-6, and metanephrines were assessed at 72 hours after stroke. Associations between abnormal leukocyte counts at 72 hours, poststroke infection, and 3-month outcomes were determined.

RESULTS

A total of 114 subjects were enrolled. Severe stroke was associated with leukocytosis, neutrophilia, monocytosis, lymphopenia, and eosinopenia. At 72 hours after stroke, increased serum cortisol was independently associated with neutrophilia and lymphopenia. Abnormal leukocyte counts were not independently predictive of poststroke infection, but lymphopenia was associated with poor outcome (modified Rankin score >3) at 3 months after stroke (odds ratio = 22.86 [1.95, 267.65]; P = .01).

CONCLUSIONS

Increased serum cortisol is independently associated with neutrophilia and lymphopenia after stroke. Lymphopenia is not an independent predictor of infections but is independently associated with worse outcome.

Anti-Inflammatory Targets for the Treatment of Reperfusion Injury in Stroke

While the mainstay of acute stroke treatment includes revascularization via recombinant tissue plasminogen activator or mechanical thrombectomy, only a minority of stroke patients are eligible for treatment, as delayed treatment can lead to worsened outcome. This worsened outcome at the experimental level has been attributed to an entity known as reperfusion injury (R/I). R/I is occurred when revascularization is delayed after critical brain and vascular injury has occurred, so that when oxygenated blood is restored, ischemic damage is increased, rather than decreased. R/I can increase lesion size and also worsen blood barrier breakdown and lead to brain edema and hemorrhage. A major mechanism underlying R/I is that of poststroke inflammation. The poststroke immune response consists of the aberrant activation of glial cell, infiltration of peripheral leukocytes, and the release of damage-associated molecular pattern (DAMP) molecules elaborated by ischemic cells of the brain. Inflammatory mediators involved in this response include cytokines, chemokines, adhesion molecules, and several immune molecule effectors such as matrix metalloproteinases-9, inducible nitric oxide synthase, nitric oxide, and reactive oxygen species. Several experimental studies over the years have characterized these molecules and have shown that their inhibition improves neurological outcome. Yet, numerous clinical studies failed to demonstrate any positive outcomes in stroke patients. However, many of these clinical trials were carried out before the routine use of revascularization therapies. In this review, we cover mechanisms of inflammation involved in R/I, therapeutic targets, and relevant experimental and clinical studies, which might stimulate renewed interest in designing clinical trials to specifically target R/I. We propose that by targeting anti-inflammatory targets in R/I as a combined therapy, it may be possible to further improve outcomes from pharmacological thrombolysis or mechanical thrombectomy.

Integrins as Therapeutic Targets: Successes and Cancers

Integrins are transmembrane receptors that are central to the biology of many human pathologies. Classically mediating cell-extracellular matrix and cell-cell interaction, and with an emerging role as local activators of TGFβ, they influence cancer, fibrosis, thrombosis and inflammation. Their ligand binding and some regulatory sites are extracellular and sensitive to pharmacological intervention, as proven by the clinical success of seven drugs targeting them. The six drugs on the market in 2016 generated revenues of some US$3.5 billion, mainly from inhibitors of α4-series integrins. In this review we examine the current developments in integrin therapeutics, especially in cancer, and comment on the health economic implications of these developments.

Therapeutic Potential of Intravenous Immunoglobulin in Acute Brain Injury

Acute ischemic and traumatic injury of the central nervous system (CNS) is known to induce a cascade of inflammatory events that lead to secondary tissue damage. In particular, the sterile inflammatory response in stroke has been intensively investigated in the last decade, and numerous experimental studies demonstrated the neuroprotective potential of a targeted modulation of the immune system. Among the investigated immunomodulatory agents, intravenous immunoglobulin (IVIg) stand out due to their beneficial therapeutic potential in experimental stroke as well as several other experimental models of acute brain injuries, which are characterized by a rapidly evolving sterile inflammatory response, e.g., trauma, subarachnoid hemorrhage. IVIg are therapeutic preparations of polyclonal immunoglobulin G, extracted from the plasma of thousands of donors. In clinical practice, IVIg are the treatment of choice for diverse autoimmune diseases and various mechanisms of action have been proposed. Only recently, several experimental studies implicated a therapeutic potential of IVIg even in models of acute CNS injury, and suggested that the immune system as well as neuronal cells can directly be targeted by IVIg. This review gives further insight into the role of secondary inflammation in acute brain injury with an emphasis on stroke and investigates the therapeutic potential of IVIg.