Targeting Reperfusion Injury in the Age of Mechanical Thrombectomy

Posthypoxic behavioral impairment and mortality of Drosophila melanogaster are associated with high temperatures, enhanced predeath activity and oxidative stress

Hypoxia is an underlying pathophysiological condition of a variety of devastating diseases, including acute ischemic stroke (AIS). We are faced with limited therapeutic options for AIS patients, and even after successful restoration of cerebral blood flow, the poststroke mortality is still high. More basic research is needed to explain mortality after reperfusion and to develop adjunct neuroprotective therapies. Drosophila melanogaster (D.m.) is a suitable model to analyze hypoxia; however, little is known about the impacts of hypoxia and especially of the subsequent reperfusion injury on the behavior and survival of D.m. To address this knowledge gap, we subjected two wild-type D.m. strains (Canton-S and Oregon-R) to severe hypoxia (<0.3% O₂) under standardized environmental conditions in a well-constructed hypoxia chamber. During posthypoxic reperfusion (21% O₂), we assessed fly activity (evoked and spontaneous) and analyzed molecular characteristics (oxidative stress marker abundance, reactive oxygen species (ROS) production, and metabolic activity) at various timepoints during reperfusion. First, we established standard conditions to induce hypoxia in D.m. to guarantee stable and reproducible experiments. Exposure to severe hypoxia under defined conditions impaired the climbing ability and reduced the overall activity of both D.m. strains. Furthermore, a majority of the flies died during the early reperfusion phase (up to 24 h). Interestingly, the flies that died early exhibited elevated activity before death compared to that of the flies that survived the entire reperfusion period. Additionally, we detected increases in ROS and stress marker (Catalase, Superoxide Dismutase and Heat Shock Protein 70) levels as well as reductions in metabolic activity in the reperfusion phase. Finally, we found that changes in environmental conditions impacted the mortality rate. In particular, decreasing the temperature during hypoxia or the reperfusion phase displayed a protective effect. In conclusion, our data suggest that reperfusion-dependent death might be associated with elevated temperatures, predeath activity, and oxidative stress.

A new fruit fly model of reperfusion injury, the tissue damage commonly seen in stroke that occurs when an organ is starved of oxygen and then exposed to oxygen again, opens new possibilities for understanding stroke pathology. Pardes Habib from Aachen University, Germany, and colleagues subjected flies to extremely low oxygen levels for up to six hours before returning them to a normal oxygen environment. Most flies died after re-exposure to oxygen, but not before showing a ‘last gasp’ burst of physical activity compared to individuals that survived the treatment. The return to normal oxygen levels led to an increase in signs of cellular stress and reduced metabolic activity, especially among those flies kept at warmer temperatures. The findings lay the groundwork for better understanding of reperfusion injury and how to treat it.

Neutrophil-to-Lymphocyte Ratio Predicts Cerebral Edema and Clinical Worsening Early After Reperfusion Therapy in Stroke

BACKGROUND AND PURPOSE

The mechanisms linking systemic inflammation to poor outcome in ischemic stroke are not fully understood. The authors investigated if peripheral inflammation following reperfusion therapy leads to an increase in cerebral edema (CED), thus hindering the clinical recovery.

METHODS

We designed a single-center study conducted at Centro Hospitalar Universitário São João between 2017 and 2019. Inclusion criteria were being adult, having an anterior circulation acute ischemic stroke, and receiving reperfusion therapy. Neutrophil-to-lymphocyte, platelet-to-lymphocyte ratios, and the systemic inflammatory response syndrome criteria were determined. The presence and grade of CED were evaluated on the computed tomography performed 24 hours following event. The clinical outcomes included early neurological deterioration and functional dependence at 90 days. Adjusted odds ratio and 95% CI were obtained by ordinal and logistic regression models. Optimal cutoff values were defined using receiver operating characteristic analysis in the training cohort and validated in an independent data set.

RESULTS

Five hundred fifty-three patients were included. Neutrophil-to-lymphocyte increased with higher degrees of CED at 24 hours (adjusted odds ratio, 1.34 [1.09-1.68], P<0.01) and was associated with early neurological deterioration (adjusted odds ratio, 1.30 [1.04-1.63], P<0.05) and poor functional status at 90 days (adjusted odds ratio, 1.79 [1.28-2.48], P<0.01). Platelet-to-lymphocyte was not associated with the outcomes. Systemic inflammatory response syndrome was related to CED due to altered white blood cell counts. Neutrophil-to-lymphocyte was the best predictor with an area under the curve around 0.7. Neutrophil-to-lymphocyte ≥7 had and accuracy, sensitivity, and specificity around 60%.

CONCLUSIONS

Increased systemic inflammation is linked to the severity of CED early after reperfusion therapy in stroke. Easily obtained inflammatory markers convey early warning alerts for patients at risk of severe neurological complications with an impact on long-term functional outcome. CED quantification should be included as an end point in proof-of-concept trials in immunomodulation in stroke.

Sappanone A Protects Against Inflammation, Oxidative Stress and Apoptosis in Cerebral Ischemia-Reperfusion Injury by Alleviating Endoplasmic Reticulum Stress

Endoplasmic reticulum stress is an important contributor to the cerebral ischemic injury. Sappanone A (SA), a kind of natural homoisoflavanone extracted from Caesalpinia sappan L, has been evidenced to exhibit anti-inflammatory and antioxidative properties. The present study aimed to investigate the potential neuroprotective effects of SA in cerebral ischemia-reperfusion injury. The potential neuroprotective effect of SA was tested in a rat model of middle cerebral artery occlusion (MCAO) allowing reperfusion and PC12 cell model of oxygen-glucose deprivation and reperfusion (OGD/R). Post-ischemic neuronal injury was evaluated by 2, 3, 5-triphenyltetrazolium chloride (TTC) and hematoxylin-eosin (H&E) staining. The levels of inflammatory factors and oxidative stress-related markers were detected using corresponding kits. Cell apoptosis was evaluated by terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) or flow cytometry, and the expression of apoptosis-associated proteins was determined using western blot analysis. Subsequently, endoplasmic reticulum stress-related proteins were detected through western blot analysis, and CCAAT/enhancer binding protein (C/EBP) homologous protein (CHOP) was overexpressed to confirm the contribution of endoplasmic reticulum stress inhibition by SA to the neuroprotective effects post OGD/R. Results revealed that SA was effective in ameliorating cerebral infarction and pathological injuries post-reperfusion following MCAO, which is associated with reduced inflammation, oxidative stress, and cell apoptosis by SA in the brain. Consistently, these neuroprotective effects of SA post ischemia-reperfusion were also observed in a PC12 cell model of OGD/R. Importantly, endoplasmic reticulum stressors, including the CHOP, the 78 kDa glucose-regulated protein 78 (GRP78), and phosphorylated eukaryotic initiation factors 2α (EIF-2α), were significantly downregulated by SA, while CHOP overexpression attenuated the beneficial effects of SA on inflammation, oxidative stress, and apoptosis in OGD/R-induced PC12 cells. These results demonstrated that SA alleviates endoplasmic reticulum stress, ameliorating inflammation, oxidative stress, and apoptosis, and thereby serves as therapeutic potential for protection against cerebral ischemia-reperfusion injury in ischemic stroke.

Emerging neuroprotective strategies for the treatment of ischemic stroke: An overview of clinical and preclinical studies

Stroke is the leading cause of disability and thesecond leading cause of death worldwide. With the global population aged 65 and over growing faster than all other age groups, the incidence of stroke is also increasing. In addition, there is a shift in the overall stroke burden towards younger age groups, particularly in low and middle-income countries. Stroke in most cases is caused due to an abrupt blockage of an artery (ischemic stroke), but in some instances stroke may be caused due to bleeding into brain tissue when a blood vessel ruptures (hemorrhagic stroke). Although treatment options for stroke are still limited, with the advancement in recanalization therapy using both pharmacological and mechanical thrombolysis some progress has been made in helping patients recover from ischemic stroke. However, there is still a substantial need for the development of therapeutic agents for neuroprotection in acute ischemic stroke to protect the brain from damage prior to and during recanalization, extend the therapeutic time window for intervention and further improve functional outcome. The current review has assessed the past challenges in developing neuroprotective strategies, evaluated the recent advances in clinical trials, discussed the recent initiative by the National Institute of Neurological Disorders and Stroke in USA for the search of novel neuroprotectants (Stroke Preclinical Assessment Network, SPAN) and identified emerging neuroprotectants being currently evaluated in preclinical studies. The underlying molecular mechanism of each of the neuroprotective strategies have also been summarized, which could assist in the development of future strategies for combinational therapy in stroke treatment.

CD84 Links T Cell and Platelet Activity in Cerebral Thrombo-Inflammation in Acute Stroke

RATIONALE

Ischemic stroke is a leading cause of morbidity and mortality worldwide. Recanalization of the occluded vessel is essential but not sufficient to guarantee brain salvage. Experimental and clinical data suggest that infarcts often develop further due to a thromboinflammatory process critically involving platelets and T cells, but the underlying mechanisms are unknown.

OBJECTIVE

We aimed to determine the role of CD (cluster of differentiation)-84 in acute ischemic stroke after recanalization and to dissect the underlying molecular thromboinflammatory mechanisms.

METHODS AND RESULTS

Here, we show that mice lacking CD84-a homophilic immunoreceptor of the SLAM (signaling lymphocyte activation molecule) family-on either platelets or T cells displayed reduced cerebral CD4+ T-cell infiltration and thrombotic activity following experimental stroke resulting in reduced neurological damage. In vitro, platelet-derived soluble CD84 enhanced motility of wild-type but not of Cd84-/- CD4+ T cells suggesting homophilic CD84 interactions to drive this process. Clinically, human arterial blood directly sampled from the ischemic cerebral circulation indicated local shedding of platelet CD84. Moreover, high platelet CD84 expression levels were associated with poor outcome in patients with stroke.

CONCLUSIONS

These results establish CD84 as a critical pathogenic effector and thus a potential pharmacological target in ischemic stroke.

Mesenchymal Stem Cell-Mediated Mitochondrial Transfer: a Therapeutic Approach for Ischemic Stroke

Stroke is the leading cause of death and adult disability worldwide. Mitochondrial dysfunction is one of the hallmarks of stroke-induced neuronal death, and maintaining mitochondrial function is essential in cell survival and neurological progress following ischemic stroke. Stem cell-mediated mitochondrial transfer represents an emerging therapeutic approach for ischemic stroke. Accumulating evidence suggests that mesenchymal stem cells (MSCs) can directly transfer healthy mitochondria to damaged cells, and rescue mitochondrial damage-provoked tissue degeneration. This review summarizes the research on MSCs-mediated mitochondrial transfer as a therapeutic strategy against ischemic stroke.

Immunothrombosis and thromboinflammation in host defense and disease

Platelets are increasingly being recognized for playing roles beyond thrombosis and hemostasis. Today we know that they mediate inflammation by direct interactions with innate immune cells or secretion of cytokines/chemokines. Here we review their interactions with neutrophils and monocytes/macrophages in infection and sepsis, stroke, myocardial infarction and venous thromboembolism. We discuss new roles for platelet surface receptors like GPVI or GPIb and also look at platelet contributions to the formation of neutrophil extracellular traps (NETs) as well as to deep vein thrombosis during infection, e.g. in COVID-19 patients.

Mitochondrial Transfer as a Therapeutic Strategy Against Ischemic Stroke

Stroke is a debilitating disease that remains the second leading cause of death and disability worldwide. Despite accumulating knowledge of the disease pathology, treatments for stroke are limited, and clinical translation of the neuroprotective agents has not been a complete success. Accumulating evidence links mitochondrial dysfunction to brain impairments after stroke. Recent studies have implicated the important roles of healthy mitochondria in neuroprotection and neural recovery following ischemic stroke. New and convincing studies have shown that mitochondrial transfer to the damaged cells can help revive cells energetic in the recipient cells. Hence, mitochondrial transplantation has shown to replace impaired or dysfunctional mitochondria with exogenous healthy mitochondria after ischemic stroke. We highlight the potential of mitochondrial transfer by stem cells as a therapeutic strategy for the treatment of ischemic stroke. This review captures the recent advances in the mitochondrial transfer as a novel and promising treatment for ischemic stroke.

Matrix Metalloproteinase-9 Relationship With Infarct Growth and Hemorrhagic Transformation in the Era of Thrombectomy

Objective: To assess the relationship between matrix metalloproteinase 9 (MMP-9), a proteolytic enzyme involved in the breakdown of the blood-brain barrier, and infarct growth and hemorrhagic transformation in acute ischemic stroke (AIS) with large vessel occlusion (LVO) in the era of mechanical thrombectomy (MT) using the kinetics of MMP-9 and sequential magnetic resonance imaging (MRI).

Methods: HIBISCUS-STROKE is a cohort study including AIS patients with LVO treated with MT following admission MRI. Patients underwent sequential assessment of MMP-9, follow-up CT at day 1, and MRI at day 6. The CT scan at day 1 classified any hemorrhagic transformation according to the European Co-operative Acute Stroke Study-II (ECASS II) classification. Infarct growth was defined as the difference between final Fluid-Attenuated Inversion Recovery volume and baseline diffusion-weighted imaging volume. Conditional logistic regression analyses were adjusted for main confounding variables including reperfusion status.

Results: One hundred and forty-eight patients represent the study population. A high MMP-9 level at 6 h from admission (H6) (p = 0.02), a high glucose level (p = 0.01), a high temperature (p = 0.04), and lack of reperfusion (p = 0.02) were associated with infarct growth. A high MMP-9 level at H6 (p = 0.03), a high glucose level (p = 0.03) and a long delay from symptom onset to groin puncture (p = 0.01) were associated with hemorrhagic transformation.

Conclusions: In this MT cohort study, MMP-9 level at H6 predicts infarct growth and hemorrhagic transformation.

A Pre-Intervention 4-Item Scale for Predicting Poor Outcome Despite Successful Recanalization in Basilar Artery Occlusion

Poor outcome despite successful recanalization is a relatively common occurrence after endovascular therapy (EVT) in acute intracranial large vessel occlusion. We aimed to develop a simple pre-intervention scale with readily available indicators for predicting the 90-day poor outcome in acute basilar artery occlusion (BAO) patients with successful recanalization after EVT. A prospectively registered consecutive cohort of acute BAO patients treated with EVT in a tertiary stroke center during a 6-year period was reviewed. Poor outcome despite successful recanalization was defined as a 90-day mRS of > 3 despite a post-intervention mTICI of ≥ 2b. A logistic regression analysis was employed to develop the predictive scale. The performance of the scale was estimated by ROC curve and Hosmer-Lemeshow test. Poor outcome was observed in 48 of 109 patients included in this study. The proposed scale consisted of four selected pre-intervention predictors, including the NIHSS score, Pons-Midbrain Index (PMI), bilateral thalamic infarction, and Basilar Artery on Computed Tomography Angiography (BATMAN) collateral score. The 4-item scale revealed good discrimination with an area under curve of 0.83 (95% CI = 0.75-0.90) and acceptable calibration assessed by Hosmer-Lemeshow test (P = 0.48). The optimal cutoff value of the scale (range 0-5 points) was ≥ 3 points with 77% sensitivity, 80% specificity, and 79% accuracy. As a pre-intervention predictive model, the 4-item scale has promising predictive value for poor outcome despite successful recanalization in BAO patients treated with EVT. Nevertheless, external validation with blinded outcome is still needed to confirm its performance before clinical application.

Effect of blood pressure parameters on functional independence in patients with acute ischemic stroke in the first 6 hours after endovascular thrombectomy

BACKGROUND AND PURPOSE

Studies have suggested that blood pressure (BP) levels after endovascular thrombectomy (EVT) are correlated with clinical outcomes. The aim of our study was to investigate the effect of BP in different time intervals within the first 24 hours after EVT on functional outcomes.

METHODS

Data of patients who received EVT for acute ischemic stroke at two institutions were reviewed. After EVT, hourly BP data were collected and divided into four time intervals: 1-6 hours, 7-12 hours, 13-18 hours, and 19-24 hours. The mean, maximum, and standard deviation (SD) of BP were calculated and compared with the outcome of interest in patients with successful recanalization. The outcome of interest was functional independence, which was defined as a 3-month modified Rankin Scale score of ≤2.

RESULTS

Of 224 patients with stroke who received EVT, 166 (74.1%) (mean age 70.2±13.1 years; 49.4% men) achieved successful recanalization and 82 (49.4%) exhibited functional independence. After adjustment for possible confounders, lower mean, maximum, and SD values of systolic and diastolic BP observed in the first 6 hours after EVT were independently associated with functional independence. Furthermore, the area under the receiver operating characteristic curve values observed for BP parameters for outcome prediction in the first 6 hours were the highest across the 24-hour period following EVT.

CONCLUSION

In patients with stroke who achieved successful recanalization, the first 6 hours after EVT was the key period influencing the correlation between BP and functional outcome.

Safety and Efficacy of Otaplimastat in Patients with Acute Ischemic Stroke Requiring tPA (SAFE-TPA): A Multicenter, Randomized, Double-Blind, Placebo-Controlled Phase 2 Study

Objective

Otaplimastat is a neuroprotectant that inhibits matrix metalloprotease pathway, and reduces edema and intracerebral hemorrhage induced by recombinant tissue plasminogen activator (rtPA) in animal stroke models. We aimed to assess the safety and efficacy of otaplimastat in patients receiving rtPA.

Methods

This was a phase 2, 2‐part, multicenter trial in stroke patients (19–80 years old) receiving rtPA. Intravenous otaplimastat was administered <30 minutes after rtPA. Stage 1 was a single‐arm, open‐label safety study in 11 patients. Otaplimastat 80 mg was administered twice daily for 3 days. Stage 2 was a randomized, double‐blind, placebo‐controlled study involving 69 patients, assigned (1:1:1) to otaplimastat 40 mg, otaplimastat 80 mg, or a placebo. The primary endpoint was the occurrence of parenchymal hematoma (PH) on day 1. Secondary endpoints included serious adverse events (SAEs), mortality, and modified Rankin scale (mRS) distribution at 90 days (http://clinicaltrials.gov identifier: NCT02787278).

Results

No safety issues were encountered in stage 1. The incidence of PH during stage 2 was comparable: 0 of 22 with the placebo, 0 of 22 with otaplimastat 40 mg, and 1 of 21 with the 80 mg dose. No differences in SAEs (13%, 17%, 14%) or death (8.3%, 4.2%, 4.8%) were observed among the 3 groups. Three adverse events (chills, muscle rigidity, hepatotoxicity) were judged to be related to otaplimastat.

Interpretation

Intravenous otaplimastat adjunctive therapy in patients receiving rtPA is feasible and generally safe. The functional efficacy of otaplimastat needs to be investigated with further large trials. ANN NEUROL 2020;87:233–245

Time-dependent infarct volume affects the benefit of recanalization

Objectives

The benefit threshold of infarct volume from recanalization remains unclear. We assumed that the threshold decreased over time, and then investigated the benefit curve of infarct volume during different time periods.

Methods

We reviewed prospectively collected clinical and imaging data from acute ischemic stroke patients with internal carotid artery and M1 occlusion who underwent angiography before and 24 h after reperfusion therapy. Ordinal analyses of modified Rankin Scale scores were performed and curves were fitted.

Results

Of the included 445 patients, the median age was 71 years and 157 (35.3%) were women. The mean time from onset to treatment (OTT) was 248 ± 142 min. The median baseline infarct core volume was 49 (IQR 22–85) ml. Follow-up angiography revealed recanalization in 265 (59.6%) patients. The fitting curves showed that patients with an OTT ≤3 h would benefit from recanalization no matter how large the infarct volume was, whereas patients with an OTT between 3 and 4.5 h and with an infarct volume ≥ 125 ml, and those with an OTT ≥ 4.5 h and with an infarct volume ≥ 80 ml did not benefit from recanalization.

Conclusions

We established a time-dependent benefit threshold of infarct volume from recanalization, and thus suggested to estimate infarct core volume to select patients for reperfusion therapy in those with an OTT beyond 3 h.

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The benefit of recanalization within 3 h is independent of infarct volume.

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The benefit threshold of infarct volume decreases over time if beyond 3 h.

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Infarct volume is recommended to aid in patient selection for reperfusion therapy.

A new era for stroke therapy: Integrating neurovascular protection with optimal reperfusion

Recent advances in stroke reperfusion therapies have led to remarkable improvement in clinical outcomes, but many patients remain severely disabled, due in part to the lack of effective neuroprotective strategies. In this review, we show that 95% of published preclinical studies on "neuroprotectants" (1990-2018) reported positive outcomes in animal models of ischemic stroke, while none translated to successful Phase III trials. There are many complex reasons for this failure in translational research, including that the majority of clinical trials did not test early delivery of neuroprotectants in combination with successful reperfusion. In contrast to the clinical trials, >80% of recent preclinical studies examined the neuroprotectant in animal models of transient ischemia with complete reperfusion. Furthermore, only a small fraction of preclinical studies included long-term functional assessments, aged animals of both genders, and models with stroke comorbidities. Recent clinical trials demonstrate that 70%-80% of patients treated with endovascular thrombectomy achieve successful reperfusion. These successes revive the opportunity to retest previously failed approaches, including cocktail drugs that target multiple injury phases and different cell types. It is our hope that neurovascular protectants can be retested in future stroke research studies with specific criteria outlined in this review to increase translational successes.