Anti-inflammatory treatments for stroke: from bench to bedside

Anti-inflammatory therapy for preventing stroke and other vascular events after ischaemic stroke or transient ischaemic attack

BACKGROUND

An increasing body of evidence suggests that inflammation plays a key role in stroke, in particular stroke of atherosclerotic origin. Anti-inflammatory medications are a widely heterogeneous group of drugs that are used to suppress the innate inflammatory pathway and thus prevent persistent or recurrent inflammation. Anti-inflammatory agents have the potential to stabilise atherosclerotic plaques by impeding the inflammatory pathway. By targeting specific cytokines, the inflammatory pathway may be interrupted at various stages.

OBJECTIVES

To assess the benefits and harms of anti-inflammatory medications plus standard care versus standard care with or without placebo for prevention of vascular events (stroke, myocardial infarction (MI), non-fatal cardiac arrest, unstable angina requiring revascularisation, vascular death) and all-cause mortality in people with a prior history of ischaemic stroke or transient ischaemic attack (TIA).

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL; last searched 29 May 2019); MEDLINE (1948 to 29 May 2019); Embase (1980 to 29 May 2019); the Cumulative Index to Nursing and Allied Health Literature (CINAHL; 1982 to 29 May 2019); and Scopus (1995 to 29 May 2019). In an effort to identify additional published, unpublished, and ongoing trials, we searched several grey literature sources (last searched 30 May 2019). We incorporated all identified studies into the results section. We applied no restrictions with respect to language, date of publication, or study setting.

SELECTION CRITERIA

We considered randomised controlled trials (RCTs) and cluster-randomised controlled trials that evaluated anti-inflammatory medications for prevention of major cardiovascular events following ischaemic stroke or TIA.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed for inclusion titles and abstracts of studies identified by the search. Two review authors independently reviewed full-text articles for inclusion in this review. We planned to assess risk of bias and to apply the GRADE method.

MAIN RESULTS

We identified no studies that met the inclusion criteria.

AUTHORS' CONCLUSIONS

There is currently a paucity of evidence on the use of anti-inflammatory medications for prevention of major cardiovascular events following ischaemic stroke or TIA. RCTs are needed to assess whether use of anti-inflammatory medications in this setting is beneficial.

Predictive value of inflammatory markers for functional outcomes in patients with ischemic stroke

Background: Inflammatory processes have been proposed in the pathophysiology of ischemic stroke. The present study was designed to evaluate the relationship between tumor necrosis factor-alpha (TNF-α), interleukin 6 (IL-6), IL 1 beta (IL-1β), and high sensitivity C-reactive protein (hsCRP) with the prognosis and functional outcome in patients with less severe ischemic stroke. Methods: We measured the level of IL-1β, IL-6, hsCRP, and TNF-α on days 1 and 5 after stroke onset by enzyme-linked immunosorbent assay (ELISA). The infarct volume was assessed using Alberta Stroke Program Early CT Score (ASPECTS) and posterior circulation ASPECTS (pcASPECTS) score in brain computed tomography (CT) scan and magnetic resonance imaging (MRI). The severity of stroke was assessed by applying the National Institutes of Health Stroke Scale (NIHSS) and Modified Rankin Scale (MRS) in 24 hours on day 5 and after 3 months from stroke onset. Good outcome was defined as the third month MRS ≤ 2. The association of inflammatory markers and the course of stroke symptoms over time was examined. Results: Forty-four first-ever stroke patients without concurrent inflammatory diseases with a mean age of 65 years were included. The mean NIHSS and MRS in admission time were 6.5 ± 3.5 and 3.07, respectively. The day 1 and the day 5 levels of IL-1β, IL-6, hsCRP, and TNF-α were not significantly different in good and poor outcome groups (all P-values > 0.05). In addition, they were not significantly associated with the ASPECTS, pcASPECTS, and changes of NIHSS and MRS over time. Conclusion: The levels of hsCRP, IL-1β, IL-6, and TNF-α are not reliable predictors of functional outcomes in patients with less severe acute ischemic stroke (AIS).

NF-κB Inhibitors Attenuate MCAO Induced Neurodegeneration and Oxidative Stress-A Reprofiling Approach

Stroke is the leading cause of morbidity and mortality worldwide. About 87% of stroke cases are ischemic, which disrupt the physiological activity of the brain, thus leading to a series of complex pathophysiological events. Despite decades of research on neuroprotectants to probe for suitable therapies against ischemic stroke, no successful results have been obtained, and new alternative approaches are urgently required in order to combat this pathological torment. To address these problems, drug repositioning/reprofiling is explored extensively. Drug repurposing aims to identify new uses for already established drugs, and this makes it an attractive commercial strategy. Nuclear factor-kappa beta (NF-κB) is reported to be involved in many physiological and pathological conditions, such as neurodegeneration, neuroinflammation, and ischemia/reperfusion (I/R) injury. In this study, we examined the neuroprotective effects of atorvastatin, cephalexin, and mycophenolate against the NF-κB in ischemic stroke, as compared to the standard NF-κB inhibitor caeffic acid phenethyl ester (CAPE). An in-silico docking analysis was performed and their potential neuroprotective activities in the in vivo transient middle cerebral artery occlusion (t-MCAO) rat model was examined. The percent (%) infarct area and 28-point composite neuro score were examined, and an immunohistochemical analysis (IHC) and enzyme-linked immunosorbent assay (ELISA) were further performed to validate the neuroprotective role of these compounds in stroke as well as their potential as antioxidants. Our results demonstrated that these novels NF-κB inhibitors could attenuate ischemic stroke-induced neuronal toxicity by targeting NF-κB, a potential therapeutic approach in ischemic stroke.

Salidroside Reduces Inflammation and Brain Injury After Permanent Middle Cerebral Artery Occlusion in Rats by Regulating PI3K/PKB/Nrf2/NFκB Signaling Rather than Complement C3 Activity

Salidroside, an active constituent of Rhodiola rosea, is neuroprotective after transient middle cerebral artery occlusion (tMCAO). However, its effects in other experimental stroke models are less understood. Here, we investigated the effect of daily intraperitoneal injections of salidroside in rats after permanent MCAO (pMCAO). Cerebral infarct volumes at 1 day after pMCAO were significantly reduced by treatment with 100 mg/kg/day salidroside, but not by 25 or 50 mg/kg/day, and this benefit of salidroside increased significantly over at least 7 days of treatment, when it was also accompanied by decreased neurological deficit scores. These observations led us to investigate the underlying mechanism of action of salidroside. 100 mg/kg salidroside for 1 day increased NeuN, Nrf2, and its downstream mediator HO-1, while it reduced nuclear NFκB p50, IL-6, and TNFα. Brusatol, a Nrf2 inhibitor, blocked the actions of salidroside on Nrf2, NFκB p50, IL-6, and TNFα. Salidroside also increased the ratio of p-PKB/PKB at 1 day after pMCAO even in the presence of brusatol. LY294002, a PI3K inhibitor, prevented all these effects of salidroside, including those on NeuN, p-PKB/PKB, Nrf2, HO-1, and pro-inflammatory mediators. In contrast, salidroside had no significant effect on the level of cerebral complement C3 after pMCAO, or on the activity of C3 as measured by the expression of cerebral Egr1. Our findings therefore suggest that salidroside reduces neuroinflammation and neural damage by regulating the PI3K/PKB/Nrf2/NFκB signaling pathway after pMCAO, and that this neuroprotective effect does not involve modulation of complement C3 activity.

Post-stroke remodeling processes in animal models and humans

After cerebral ischemia, events like neural plasticity and tissue reorganization intervene in lesioned and non-lesioned areas of the brain. These processes are tightly related to functional improvement and successful rehabilitation in patients. Plastic remodeling in the brain is associated with limited spontaneous functional recovery in patients. Improvement depends on the initial deficit, size, nature and localization of the infarction, together with the sex and age of the patient, all of them affecting the favorable outcome of reorganization and repair of damaged areas. A better understanding of cerebral plasticity is pivotal to design effective therapeutic strategies. Experimental models and clinical studies have fueled the current understanding of the cellular and molecular processes responsible for plastic remodeling. In this review, we describe the known mechanisms, in patients and animal models, underlying cerebral reorganization and contributing to functional recovery after ischemic stroke. We also discuss the manipulations and therapies that can stimulate neural plasticity. We finally explore a new topic in the field of ischemic stroke pathophysiology, namely the brain-gut axis.

Biochanin A Provides Neuroprotection Against Cerebral Ischemia/Reperfusion Injury by Nrf2-Mediated Inhibition of Oxidative Stress and Inflammation Signaling Pathway in Rats

Background

Oxidative stress and neuroinflammation are 2 pivotal mechanisms in the progression of cerebral ischemia/reperfusion injury. Biochanin A, a natural phytoestrogen, has been reported to protect against ischemic brain injury in animal experiments, but the possible pharmacological mechanisms of its neuroprotection remain elusive. In this research, we sought to investigate the neuroprotective effects of biochanin A in experimental stroke rats and the probable mechanisms underlying oxidative stress and inflammation signaling pathways.

Material/Methods

An ischemic stroke model was induced by inserting thread into the middle cerebral artery. Rats were pre-administered intraperitoneally with a vehicle solution or biochanin A (10, 20, or 40 mg·kg·d⁻¹) for 14 days prior to ischemic stroke. Neurological score, infarct volume, and cerebral edema were assessed after 2 h of ischemia and 24 h of reperfusion. The activities of SOD and GSH-Px and MDA content were measured. The expressions of Nrf2, HO-1, and NF-κB and the activity of phosphor-IκBα were detected by Western blotting.

Results

Biochanin A pretreatment significantly improved neurological deficit and decreased infarct size and brain edema. Biochanin A also enhanced SOD and GSH-Px activities and suppressed the production of MDA. Additionally, biochanin A promoted Nrf2 nuclear translocation, promoted the expression of HO-1, and inhibited NF-κB activation in ischemic brain injury.

Conclusions

The results indicated that biochanin A protected the brain against ischemic injury in rats by anti-oxidative and anti-inflammatory actions. The activation of the Nrf2 pathway and the inhibition of the NF-κB pathway may contribute to the neuroprotective effects of biochanin A.

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.

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.

Myeloid Cell and Transcriptome Signatures Associated With Inflammation Resolution in a Model of Self-Limiting Acute Brain Inflammation

Inflammation contributes to tissue repair and restoration of function after infection or injury. However, some forms of inflammation can cause tissue damage and disease, particularly if inappropriately activated, excessive, or not resolved adequately. The mechanisms that prevent excessive or chronic inflammation are therefore important to understand. This is particularly important in the central nervous system where some effects of inflammation can have particularly harmful consequences, including irreversible damage. An increasing number of neurological disorders, both acute and chronic, and their complications are associated with aberrant neuroinflammatory activity. Here we describe a model of self-limiting acute brain inflammation optimized to study mechanisms underlying inflammation resolution. Inflammation was induced by intracerebral injection of lipopolysaccharide (LPS) and the temporal profile of key cellular and molecular changes were defined during the progression of the inflammatory response. The kinetics of accumulation and loss of neutrophils in the brain enabled well-demarcated phases of inflammation to be operatively defined, including induction and resolution phases. Microglial reactivity and accumulation of monocyte-derived macrophages were maximal at the onset of and during the resolution phase. We profiled the transcriptome-wide gene expression changes at representative induction and resolution timepoints and used gene coexpression network analysis to identify gene clusters. This revealed a distinct cluster of genes associated with inflammation resolution that were induced selectively or maximally during this phase and indicated an active programming of gene expression that may drive resolution as has been described in other tissues. Induction of gene networks involved in lysosomal function, lipid metabolism, and a comparative switch to MHC-II antigen presentation (relative to MHC-I during induction) were prominent during the resolution phase. The restoration and/or further induction of microglial homeostatic signature genes was notable during the resolution phase. We propose the current model as a tractable reductionist system to complement more complex models for further understanding how inflammation resolution in the brain is regulated and as a platform for in vivo testing/screening of candidate resolution-modifying interventions. Our data highlight how resolution involves active cellular and transcriptome reprogramming and identify candidate gene networks associated with resolution-phase adaptations that warrant further study.

Efficacy and Mechanism of Panax Ginseng in Experimental Stroke

Stroke is one of the leading causes of death and long-term disability worldwide. However, effective therapeutic approaches are still limited. The disruption of blood supply triggers complicated temporal and spatial events involving hemodynamic, biochemical, and neurophysiologic changes, eventually leading to pathological disturbance and diverse clinical symptoms. Ginseng (Panax ginseng), a popular herb distributed in East Asia, has been extensively used as medicinal and nutritional supplements for a variety of disorders worldwide. In recent years, ginseng has displayed attractive beneficial effects in distinct neurological disorders including stroke, involving multiple protective mechanisms. In this article, we reviewed the literature on ginseng studies in the experimental stroke field, particularly focusing on the in vivo evidence on the preventive or therapeutic efficacy and mechanisms of ginseng and ginsenosides in various stroke models of mice and rats. We also summarized the efficacy and underlying mechanisms of ginseng and ginsenosides on short- and long-term stroke outcomes.

Modulation of the Endocannabinoid System Following Central Nervous System Injury

Central nervous system (CNS) injury, such as stroke or trauma, is known to increase susceptibility to various infections that adversely affect patient outcomes (CNS injury-induced immunodepression-CIDS). The endocannabinoid system (ECS) has been shown to have immunoregulatory properties. Therefore, the ECS might represent a druggable target to overcome CIDS. Evidence suggests that cannabinoid type 2 receptor (CB₂R) activation can be protective during the early pro-inflammatory phase after CNS injury, as it limits neuro-inflammation and, therefore, attenuates CIDS severity. In the later phase post CNS injury, CB₂R inhibition is suggested as a promising pharmacologic strategy to restore immune function in order to prevent infection.

Elevated Tumor Necrosis Factor-a-induced Protein 8-like 2 mRNA from Peripheral Blood Mononuclear Cells in Patients with Acute Ischemic Stroke

Background: Tumor necrosis factor-a-induced protein 8-like 2 (TIPE2) is a novel regulator of immunity and protects against experimental stroke. However, the expression and function of TIPE2 in patients with acute ischemic stroke has not been well demonstrated. Methods: A total of 182 consecutive patients with acute ischemic stroke and 40 healthy controls were included during November 2015 to June 2016. The mRNA levels of TIPE2, interleukin(IL)-1β, IL-10, IL-6, nuclear factor(NF)-κβ, activator protein(AP)-1, interferon(IFN)-γ and tumor necrosis factor(TNF)-α from peripheral blood mononuclear cells were determined using real time quantitative reverse transcriptase polymerase chain reaction. The severity of stroke was assessed using the National Institutes of Health Stroke Scale (NIHSS) score. Results: The median mRNA levels of TIPE2, TNF-α, AP-1, IFN-γ and NF-κβ in patients with acute ischemic stroke were significantly higher than healthy controls (all P<0.001, respectively). Of note, TIPE2 mRNA showed an increasing trend on a time-dependent manner after the onset of stroke. Furthermore, TIPE2 mRNA was negatively associated with lesion volumes (r=-0.23, P<0.01), NIHSS(r=-0.15, P<0.05), TNF-α(r=-0.33,P<0.001), AP-1(r=-0.28,P<0.001), IFN-γ (r=-0.16, P<0.05) and NF-κβ (r=-0.13, P<0.05), but positively associated with IL-6(r=0.14, P<0.05) and IL-10(r=-0.31, P<0.001). Hierarchy cluster analysis showed that TIPE2 mRNA has nearest membership with TNF-α, followed by IL-6, NF-κβ, AP-1, IL-10, IL-1β and IFN-γ. In addition, TIPE2 mRNA in survivals (n=149) was significantly higher than nonsurvivals (n=33) (P<0.001), and showed a great odd ratio (0.52, 95% confidence interval: 0.349-0.760, P<0.001) on 3-month mortality. Conclusions: TIPE2 mRNA contributed to the immune response of stroke and might be a potential biomarker for the mortality of acute ischemic stroke.