Stroke is the leading cause of morbidity and mortality worldwide. Inflammatory cascades have a major impact on outcome and regeneration after ischemic stroke. High-mobility group box 1 (HMGB1) has ...come into the focus of experimental and clinical stroke research because it is released from necrotic brain tissue and its differential redox forms attract and activate immune cells after ischemic brain injury. HMGB1 is a potent inducer of inflammatory cascades, and thereby, secondary deterioration of neurological outcome.
The role of HMGB1 in sterile inflammation is well established. Emerging evidence suggests that HMGB1 modulates neuroinflammation after experimental brain ischemia and that it may be a useful prognostic biomarker for stroke patients.
HMGB1 is instantly released from necrotic cells in the ischemic core and activates an early inflammatory response. In addition, brain-released HMGB1 can be redox modified in the circulation and activate peripheral immune cells. HMGB1 concentrations correlate with disease severity and outcome after brain injury. This is the first review depicting the crucial role of HMGB1 in the initiation and perpetuation of secondary immune alterations after experimental and clinical stroke.
HMGB1-dependent signaling pathways are on the verge and have the potential to become a central topic in experimental stroke research. Current and upcoming projects in this field will be paving the way for future translational approaches targeting the center of poststroke inflammation to improve stroke recovery and long-term outcome.
Acute brain lesions induce profound alterations of the peripheral immune response comprising the opposing phenomena of early immune activation and subsequent immunosuppression. The mechanisms ...underlying this brain-immune signaling are largely unknown. We used animal models for experimental brain ischemia as a paradigm of acute brain lesions and additionally investigated a large cohort of stroke patients. We analyzed release of HMGB1 isoforms by mass spectrometry and investigated its inflammatory potency and signaling pathways by immunological in vivo and in vitro techniques. Features of the complex behavioral sickness behavior syndrome were characterized by homecage behavior analysis. HMGB1 downstream signaling, particularly with RAGE, was studied in various transgenic animal models and by pharmacological blockade. Our results indicate that the cytokine-inducing, fully reduced isoform of HMGB1 was released from the ischemic brain in the hyperacute phase of stroke in mice and patients. Cytokines secreted in the periphery in response to brain injury induced sickness behavior, which could be abrogated by inhibition of the HMGB1-RAGE pathway or direct cytokine neutralization. Subsequently, HMGB1-release induced bone marrow egress and splenic proliferation of bone marrow-derived suppressor cells, inhibiting the adaptive immune responses in vivo and vitro. Furthermore, HMGB1-RAGE signaling resulted in functional exhaustion of mature monocytes and lymphopenia, the hallmarks of immune suppression after extensive ischemia. This study introduces the HMGB1-RAGE-mediated pathway as a key mechanism explaining the complex postischemic brain-immune interactions.
Summary Background Haematoma expansion is a major cause of mortality in intracranial haemorrhage related to vitamin K antagonists (VKA-ICH). Normalisation of the international normalised ratio (INR) ...is recommended, but optimum haemostatic management is controversial. We assessed the safety and efficacy of fresh frozen plasma (FFP) versus prothrombin complex concentrate (PCC) in patients with VKA-ICH. Methods We did an investigator-initiated, multicentre, prospective, randomised, open-label, blinded-endpoint trial. Patients aged at least 18 years with VKA-ICH who presented within 12 h after symptom onset with an INR of at least 2·0 were randomly assigned (1:1) by numbered sealed envelopes to 20 mL/kg of intravenous FFP or 30 IU/kg of intravenous four-factor PCC within 1 h after initial cerebral CT scan. The primary endpoint was the proportion of patients with INR 1·2 or lower within 3 h of treatment initiation. Masking of treatment was not possible, but the primary analysis was observer masked. Analyses were done using a treated-as-randomised approach. This trial is registered with EudraCT, number 2008-005653-37, and ClinicalTrials.gov , number NCT00928915. Findings Between Aug 7, 2009, and Jan 9, 2015, 54 patients were randomly assigned (26 to FFP and 28 to PCC) and 50 received study drug (23 FFP and 27 PCC). The trial was terminated on Feb 6, 2015, after inclusion of 50 patients after a safety analysis because of safety concerns. Two (9%) of 23 patients in the FFP group versus 18 (67%) of 27 in the PCC group reached the primary endpoint (adjusted odds ratio 30·6, 95% CI 4·7–197·9; p=0·0003). 13 patients died: eight (35%) of 23 in the FFP group (five from haematoma expansion, all occurring within 48 h after symptom onset) and five (19%) of 27 in the PCC group (none from haematoma expansion), the first of which occurred on day 5 after start of treatment. Three thromboembolic events occurred within 3 days (one in the FFP group and two in the PCC group), and six after day 12 (one and five). 43 serious adverse events (20 in the FFP group and 23 in the PCC group) occurred in 26 patients. Six serious adverse events were judged to be FFP related (four cases of haematoma expansion, one anaphylactic reaction, and one ischaemic stroke) and two PCC related (ischaemic stroke and pulmonary embolism). Interpretation In patients with VKA-related intracranial hemorrhage, four-factor PCC might be superior to FFP with respect to normalising the INR, and faster INR normalisation seemed to be associated with smaller haematoma expansion. Although an effect of PCC on clinical outcomes remains to be shown, our data favour the use of PCC over FFP in intracranial haemorrhage related to VKA. Funding Octapharma.
Neuroinflammatory processes contribute to secondary neuronal damage after intracerebral hemorrhage. We aimed to characterize the time course of brain immigration of different leukocyte subsets after ...striatal injection of either autologous blood or collagenase in mice.
Intracerebral hemorrhage was induced by injection of either autologous blood (20 μL) or collagenase (0.03 U) in C57Bl/6J mice. Hematoma volumetry was performed on cryosections. Blood volume was measured by hemoglobin spectrophotometry. Leukocytes were isolated from hemorrhagic hemisphere 1, 3, 5, and 14 days after intracerebral hemorrhage, stained for leukocyte markers, and measured by flow cytometry. Heterologous blood injection from CD45.1 mice was used to investigate the origin of brain-invading leukocytes.
Collagenase injection induced a larger hematoma volume but a similar blood content compared with blood injection. Cerebral leukocyte infiltration in the hemorrhagic hemisphere was similar in both models. The majority of leukocytes isolated from the brain originated from the circulation. CD4+ T lymphocytes were the predominant brain leukocyte population in both models. However, cerebral granulocyte counts were higher after collagenase compared with blood injection.
Brain infiltration of systemic immune cells is similar in both murine intracerebral hemorrhage models. The pathophysiological impact of invading leukocytes and, in particular, of T cells requires further investigation.
Summary Background In animal models of acute ischaemic stroke, blocking of the leukocyte-endothelium adhesion by antagonism of α4 integrin reduces infarct volumes and improves outcomes. We assessed ...the effect of one dose of natalizumab, an antibody against the leukocyte adhesion molecule α4 integrin, in patients with acute ischaemic stroke. Methods In this double-blind, phase 2 study, patients with acute ischaemic stroke (aged 18–85 years) from 30 US and European clinical sites were randomly assigned (1:1) to 300 mg intravenous natalizumab or placebo with stratification by treatment window and baseline infarct size. Patients, investigators, and study staff were masked to treatment assignments. The primary endpoint was the change in infarct volume from baseline to day 5 and was assessed in the modified intention-to-treat population. Secondary endpoints were the change in infarct volume from baseline to day 30, and from 24 h to days 5 and 30; the National Institute of Health Stroke Scale (NIHSS) at baseline, 24 h, and at days 5 (or discharge), 30, and 90; and modified Rankin Scale (mRS) and Barthel Index (BI) at days 5 (or discharge), 30, and 90. This trial is registered with ClinicalTrials.gov , number NCT01955707. Findings Between Dec 16, 2013, and April 9, 2015, 161 patients were randomly assigned to natalizumab (n=79) or placebo (n=82). Natalizumab did not reduce infarct volume growth from baseline to day 5 compared with placebo (median absolute growth 28 mL range −8 to 303 vs 22 mL −11 to 328; relative growth ratio 1·09 90% CI 0·91–1·30, p=0·78) or to day 30 (4 mL −43 to 121 vs 4 mL −28 to 180; 1·05 0·88–1·27, p=0·68), from 24 h to day 5 (8 mL −30 to 177 vs 7 mL −13 to 204; 1·00 0·89–1·12, p=0·49), and from 24 h to day 30 (−5 mL −93 to 81 vs −5 mL −48 to 48; 0·98 0·87–1·11, p=0·40). No difference was noted between the natalizumab and placebo groups in the NIHSS (score ≤1 or ≥8 point improvement) from baseline at 24 h, day 5 (or discharge), day 30 (27 35% vs 36 44%; odds ratio 0·69 90% CI 0·39–1·21, p=0·86), and day 90 (36 47% vs 37 46%; 1·10 0·63–1·93, p=0·39). More patients in the natalizumab group than in the placebo group had mRS scores of 0 or 1 at day 30 (13 18% vs seven 9%; odds ratio 2·88 90% CI 1·20–6·93, p=0·024) and day 90 (18 25% vs 16 21%; 1·48 0·74–2·98, p=0·18); and BI (score ≥95) at day 90 (34 44% vs 26 33%; 1·91 1·07–3·41, p=0·033) but not significantly at day 5 or day 30 (26 34% vs 26 32%; 1·13 0·63–2·00, p=0·37). Natalizumab and placebo groups had similar incidences of adverse events (77 99% of 78 patients vs 81 99% of 82 patients), serious adverse events (36 46% vs 38 46%), and deaths (14 18% vs 13 16%). Two patients in the natalizumab group died because of adverse events assessed as related to treatment by the investigator (pneumonia, and septic shock and multiorgan failure). Interpretation Natalizumab administered up to 9 h after stroke onset did not reduce infarct growth. Treatment-associated benefits on functional outcomes might warrant further investigation. Funding Biogen.
Intracerebral hemorrhage (ICH) is the most devastating adverse event in patients receiving oral anticoagulation. There is only sparse evidence regarding ICH related to the use of non-vitamin K ...antagonist oral anticoagulant (NOAC) agents.
To evaluate the early clinical and radiological course, acute management, and outcome of ICH related to NOAC use.
Prospective investigator-initiated, multicenter observational study. All diagnostic and treatment decisions, including administration of hemostatic factors (eg, prothrombin complex concentrate), were left to the discretion of the treating physicians. The setting was 38 stroke units across Germany (February 1, 2012, to December 31, 2014). The study included 61 consecutive patients with nontraumatic NOAC-associated ICH, of whom 45 (74%) qualified for the hematoma expansion analysis.
Hematoma expansion, intraventricular hemorrhage, and reversal of anticoagulation during the acute phase. Recorded were the 3-month functional outcome, factors associated with an unfavorable outcome (modified Rankin Scale score, 3-6), any new intraventricular extension or an increase in the modified Graeb score by at least 2 points, and the frequency of substantial hematoma expansion (defined as relative ≥ 33% or absolute ≥ 6-mL volume increase).
In total, 41% (25 of 61) of patients with NOAC-associated ICH were female, and the mean (SD) patient age was 76.1 (11.6) years. At admission, the median National Institutes of Health Stroke Scale score was 10 (interquartile range, 4-18). The mean (SD) baseline hematoma volume was 23.7 (31.3) mL. In patients with sequential imaging for the hematoma expansion analysis, substantial hematoma expansion occurred in 38% (17 of 45). New or increased intraventricular hemorrhage was observed in 18% (8 of 45). Overall mortality was 28% (17 of 60 follow-up data were missing in 1 patient) at 3 months, and 65% (28 of 43) of survivors had an unfavorable outcome (modified Rankin Scale score, 3-6). Overall, 57% (35 of 61) of the patients received prothrombin complex concentrate, with no statistically significant effect on the frequency of substantial hematoma expansion (43% 12 of 28 for prothrombin complex concentrate vs 29% 5 of 17 for no prothrombin complex concentrate, P = .53), or on the occurrence of an unfavorable outcome (modified Rankin Scale score, 3-6) (odds ratio, 1.20; 95% CI, 0.37-3.87; P = .76).
Non-vitamin K antagonist oral anticoagulant-associated ICH has a high mortality and an unfavorable outcome, and hematoma expansion is frequent. Larger-scale prospective studies are needed to determine whether the early administration of specific antidotes can improve the poor prognosis of NOAC-associated ICH.
T lymphocytes are increasingly recognized as key modulators of detrimental inflammatory cascades in acute ischaemic stroke, but the potential of T cell-targeted therapy in brain ischaemia is largely ...unexplored. Here, we characterize the effect of inhibiting leukocyte very late antigen-4 and endothelial vascular cell adhesion molecule-1-mediated brain invasion-currently the most effective strategy in primary neuroinflammatory brain disease in murine ischaemic stroke models. Very late antigen-4 blockade by monoclonal antibodies improved outcome in models of moderate stroke lesions by inhibiting cerebral leukocyte invasion and neurotoxic cytokine production without increasing the susceptibility to bacterial infections. Gene silencing of the endothelial very late antigen-4 counterpart vascular cell adhesion molecule-1 by in vivo small interfering RNA injection resulted in an equally potent reduction of infarct volume and post-ischaemic neuroinflammation. Furthermore, very late antigen-4-inhibition effectively reduced the post-ischaemic vascular cell adhesion molecule-1 upregulation, suggesting an additional cross-signalling between invading leukocytes and the cerebral endothelium. Dissecting the specific impact of leukocyte subpopulations showed that invading T cells, via their humoral secretion (interferon-γ) and immediate cytotoxic mechanisms (perforin), were the principal pathways for delayed post-ischaemic tissue injury. Thus, targeting T lymphocyte-migration represents a promising therapeutic approach for ischaemic stroke.
Stroke is the third most common cause of death and a main cause of acquired adult disability in developed countries. Only very limited therapeutical options are available for a small proportion of ...stroke patients in the acute phase. Current research is intensively searching for novel therapeutic strategies and is increasingly focusing on the sub-acute and chronic phase after stroke because more patients might be eligible for therapeutic interventions in a prolonged time window. These delayed mechanisms include important pathophysiological pathways such as post-stroke inflammation, angiogenesis, neuronal plasticity and regeneration. In order to analyze these mechanisms and to subsequently evaluate novel drug targets, experimental stroke models with clinical relevance, low mortality and high reproducibility are sought after. Moreover, mice are the smallest mammals in which a focal stroke lesion can be induced and for which a broad spectrum of transgenic models are available. Therefore, we describe here the mouse model of transcranial, permanent coagulation of the middle cerebral artery via electrocoagulation distal of the lenticulostriatal arteries, the so-called "coagulation model". The resulting infarct in this model is located mainly in the cortex; the relative infarct volume in relation to brain size corresponds to the majority of human strokes. Moreover, the model fulfills the above-mentioned criteria of reproducibility and low mortality. In this video we demonstrate the surgical methods of stroke induction in the "coagulation model" and report histological and functional analysis tools.
Cardioembolism in paroxysmal atrial fibrillation (pxAF) is a frequent cause of ischemic stroke. Sensitive detection of pxAF after stroke is crucial for adequate secondary stroke prevention; the ...optimal diagnostic modality to detect pxAF on stroke units is unknown. We compared 24-hour Holter electrocardiography (ECG) with continuous stroke unit ECG monitoring (CEM) for pxAF detection.
Patients with acute ischemic stroke or transient ischemic attack were prospectively enrolled. After a 12-channel ECG on admission, all patients received 24-hour Holter ECG and CEM. Additionally, ECG monitoring data underwent automated analysis using dedicated software to identify pxAF. Patients with a history of atrial fibrillation or with atrial fibrillation on the admission ECG were excluded.
Four hundred ninety-six patients (median age, 69 years; 61.5% male) fulfilled all inclusion criteria (ischemic stroke: 80.4%; transient ischemic attack: 19.6%). Median stroke unit stay lasted 88.8 hours (interquartile range, 65.0-122.0). ECG data for automated CEM analysis were available for a median time of 64.0 hours (43.0-89.8). Paroxysmal AF was documented in 41 of 496 patients (8.3%). Of these, Holter detected pxAF in 34.1%; CEM in 65.9%; and automated CEM in 92.7%. CEM and automated CEM detected significantly more patients with pxAF than Holter (P<0.001), and automated CEM detected more patients than CEM (P<0.001).
Automated analysis of CEM improves pxAF detection in patients with stroke on stroke units compared with 24-hour Holter ECG. The comparative usefulness of prolonged or repetitive Holter ECG recordings requires further evaluation.
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