Transfusion of Resting Platelets Reduces Brain Hemorrhage After Intracerebral Hemorrhage and tPA-Induced Hemorrhage After Cerebral Ischemia

Inhibition of Anaplastic Lymphoma Kinase Protects From Ischemic Stroke

BACKGROUND

Ischemic stroke is often accompanied by oxidative stress and inflammatory response, both of which work synergistically to exacerbate the disruption of the blood-brain barrier and ischemic brain injury. ALK (anaplastic lymphoma kinase), a cancer-associated receptor tyrosine kinase, was found to play a role in oxidative stress and inflammation. In this study, we investigated the role of ALK inhibition in a murine model of ischemic stroke.

METHODS

Focal cerebral ischemia was induced by temporary occlusion of the right middle cerebral artery in mice with a filament. The ALK inhibitor alectinib was administered following the stroke. ALOX15 (arachidonic acid 15-lipoxygenase) was overexpressed by adenovirus injection. The immunohistochemistry, Western blot, oxidative stress, inflammation, blood-brain barrier leakage, infarct volume, and functional outcomes were determined.

RESULTS

We found that the expression of ALK was markedly increased in the neurovascular unit after cerebral ischemia. Treatment with the ALK inhibitor alectinib reduced the accumulation of reactive oxygen species, lipid peroxidation, and oxidative DNA, increased the vascular levels of antioxidant enzymes, inactivated the vascular NLRP3 (nucleotide-binding oligomerization domain-like receptor protein 3) inflammasome pathway, and reduced vascular inflammation (ICAM-1 [intercellular adhesion molecule-1] and MCP-1 [monocyte chemoattractant protein-1]) after ischemia. Moreover, alectinib reduced the loss of cerebrovascular integrity and blood-brain barrier damage, consequently decreasing brain infarction and neurological deficits. Furthermore, alectinib reduced stroke-evoked ALOX15 expression, whereas virus-mediated overexpression of ALOX15 abolished alectinib-dependent inhibition of oxidative stress and vascular inflammation, blood-brain barrier protection, and neuroprotection, suggesting the protective effects of alectinib for stroke may involve ALOX15.

CONCLUSIONS

Our findings demonstrated that alectinib protects from stroke by regulating ischemic signaling cascades and suggest that ALK may be a novel therapeutic target for ischemic stroke.

The role of platelets in the blood-brain barrier during brain pathology

Platelets play critical roles in maintaining hemostasis. The blood brain barrier (BBB), a significant physical and metabolic barrier, helps maintain physiological stability by limiting transportations between the blood and neural tissues. When the brain undergoes inflammation, tumor, trauma, or bleeding, the platelet responses to help with maintaining BBB homeostasis. In the traditional point of view, activated platelets aggregate to form thrombi which cover the gaps of the blood vessels to protect BBB. However, increasing evidences indicate that platelets may harm BBB by enhancing vascular permeability. Hereby, we reviewed recently published articles with a special focus on the platelet-mediated damage of BBB. Factors released by platelets can induce BBB permeability, which involve platelet-activating factors (PAF), P-selectin, ADP, platelet-derived growth factors (PDGF) superfamily proteins, especially PDGF-AA and PDGF-CC, etc. Platelets can also secrete Amyloid-β (Aβ), which triggers neuroinflammation and downregulates the expression of tight junction molecules such as claudin-5 to damage BBB. Additionally, platelets can form aggregates with neutrophils to release reactive oxygen species (ROS), which can destroy the DNA, proteins, and lipids of endothelial cells (ECs). Moreover, platelets participate in neuroinflammation to affect BBB. Conversely, some of the platelet released factors such as PDGF-BB, protects BBB. In summary, platelets play dual roles in BBB integrity and the related mechanisms are reviewed.

Platelet-to-Neutrophil Ratio is Related to Hemorrhagic Transformation in Patients With Acute Cerebral Infarction

BACKGROUND

As a common complication of cerebral infarction, hemorrhagic transformation (HT) often indicates a worse clinical outcome. The aim of this study was to explore the relationship between the platelet-to-neutrophil ratio (PNR) and HT in patients with acute cerebral infarction.

METHODS

Patients with HT after acute cerebral infarction were enrolled in the HT group. Matched patients with acute cerebral infarction without HT were enrolled at the same time. All patients included in this study did not receive reperfusion therapy. The PNR was obtained on the second day of admission. Multivariate logistic analysis was used to evaluate the relationship between the PNR and HT.

RESULTS

We collected data from a total of 137 patients: 61 patients with HT and 76 patients without HT. After adjusting for confounders, the PNR was independently associated with HT (odds ratio=0.922, 95% confidence interval: 0.891-0.955, P <0.05). The receiver operating characteristic curve demonstrated that the PNR could better predict HT (area under the curve=0.808, 95% confidence interval: 0.735-0.882, P <0.05). When the cut-off value of the PNR was 50.4765, the sensitivity was 70.5%, and the specificity was 82.9%. After stratifying the PNR to 50.4765, logistic analysis was performed again. The risk of HT in patients with a low PNR was 12.995 times that of patients with a high PNR. In patients without atrial fibrillation, the PNR was still independently related to HT.

CONCLUSIONS

The PNR is a predictor of HT, and patients with a low PNR have a higher risk of HT.

Targeting Oxidative Stress and Inflammatory Response for Blood-Brain Barrier Protection in Intracerebral Hemorrhage

Significance: Blood-brain barrier (BBB) disruption is a major pathological change after intracerebral hemorrhage (ICH) and is both the cause and result of oxidative stress and of the immune response post-ICH. These processes contribute to ICH-induced brain injury. Recent Advances: After the breakdown of cerebral vessels, blood components, including erythrocytes and their metabolites, thrombin, and fibrinogen, can access the cerebral parenchyma through the compromised BBB, triggering oxidative stress and inflammatory cascades. These aggravate BBB disruption and contribute to further infiltration of blood components, resulting in a vicious cycle that exacerbates brain edema and neurological injury after ICH. Experimental and clinical studies have highlighted the role of BBB disruption in ICH-induced brain injury. Critical Issues: In this review, we focus on the strategies to protect the BBB in ICH. Specifically, we summarize the evidence and the underlying mechanisms, including the ICH-induced process of oxidative stress and inflammatory response, and we highlight the potential therapeutic targets to protect BBB integrity after ICH. Future Directions: Future studies should probe the mechanism of ferroptosis as well as oxidative stress-inflammation coupling in BBB disruption after ICH and investigate the effects of antioxidants and immunomodulatory agents in more ICH clinical trials. Antioxid. Redox Signal. 37, 115-134.

Contribution of Various Types of Transfusion to Acute and Delayed Intracerebral Hemorrhage Injury

Intracerebral hemorrhage (ICH) is the second most prevalent type of stroke, after ischemic stroke, and has exceptionally high morbidity and mortality rates. After spontaneous ICH, one primary goal is to restrict hematoma expansion, and the second is to limit brain edema and secondary injury. Various types of transfusion therapies have been studied as treatment options to alleviate the adverse effects of ICH etiopathology. The objective of this work is to review transfusions with platelets, fresh frozen plasma (FFP), prothrombin complex concentrate (PCC), and red blood cells (RBCs) in patients with ICH. Furthermore, tranexamic acid infusion studies have been included due to its connection to ICH and hematoma expansion. As stated, the first line of therapy is limiting bleeding in the brain and hematoma expansion. Platelet transfusion is used to promote recovery and mitigate brain damage, notably in patients with severe thrombocytopenia. Additionally, tranexamic acid infusion, FFP, and PCC transfusion have been shown to affect hematoma expansion rate and volume. Although there is limited available research, RBC transfusions have been shown to cause higher tissue oxygenation and lower mortality, notably after brain edema, increases in intracranial pressure, and hypoxia. However, these types of transfusion have varied results depending on the patient, hemostasis status/blood thinner, hemolysis, anemia, and complications, among other variables. Inconsistencies in published results on various transfusion therapies led us to review the data and discuss issues that need to be considered when establishing future guidelines for patients with ICH.

Matrix metalloproteinase-2 on activated platelets triggers endothelial PAR-1 initiating atherosclerosis

AIMS 

Platelets participate in atherogenesis with mechanisms not yet fully clarified. Vascular wall MMP-2 is involved in the arterial remodelling accompanying atherosclerosis. Platelets contain and release MMP-2 but no informations are available on its role in atherosclerotic lesion formation.

METHODS AND RESULTS 

We generated double knockout mice lacking the LDL receptor and MMP-2 only in circulating blood cells showing that they develop significantly lesser femoral intima thickening after photochemical-induced arterial damage and atherosclerotic lesions in the aorta, measured by the en face method, after 4 months of atherogenic diet. Moreover, repeated transfusions of autologous-activated platelets in LDLR-/- mice on atherogenic diet significantly enhanced the extension of aortic atherosclerotic lesions while transfusion of activated platelets from MMP-2-/- mice did not. In vitro coincubation studies showed that platelet-derived MMP-2 plays a pivotal role in the development and progression of atherosclerosis through a complex cross-talk between activated platelets, monocyte/macrophages, and endothelial cells. Translational studies in patients with CAD and chronic HIV infection showed that platelet surface expression of MMP-2 highly significantly correlated with the degree of carotid artery stenosis.

CONCLUSION 

We show a previously unknown mechanism of the pathway through which platelets expressing MMP-2 trigger the initial phases of atherosclerosis and provide a mechanism showing that they activate endothelial PAR-1 triggering endothelial p38MAPK signalling and the expression of adhesion molecules. The development of drugs blocking selectively platelet MMP-2 or its expression may represent a new approach to the prevention of atherosclerosis.

Platelets as drivers of ischemia/reperfusion injury after stroke

Ischemic stroke is a leading cause of morbidity and mortality worldwide and, despite reperfusion either via thrombolysis or thrombectomy, stroke patients often suffer from lifelong disabilities. These persistent neurological deficits may be improved by treating the ischemia/reperfusion (I/R) injury that occurs following ischemic stroke. There are currently no approved therapies to treat I/R injury, and thus it is imperative to find new targets to decrease the burden of ischemic stroke and related diseases. Platelets, cell fragments from megakaryocytes, are primarily known for their role in hemostasis. More recently, investigators have studied the nonhemostatic role of platelets in inflammatory pathologies, such as I/R injury after ischemic stroke. In this review, we seek to provide an overview of how I/R can lead to platelet activation and how activated platelets, in turn, can exacerbate I/R injury after stroke. We will also discuss potential mechanisms by which platelets may ameliorate I/R injury.

Hemorrhagic Transformation After Tissue Plasminogen Activator Treatment in Acute Ischemic Stroke

Hemorrhagic transformation (HT) is a common complication after thrombolysis with recombinant tissue-type plasminogen activator (rt-PA) in ischemic stroke. In this article, recent research progress of HT in vivo and in vitro studies was reviewed. We have discussed new potential mechanisms and possible experimental models of HT development, as well as possible biomarkers and treatment methods. Meanwhile, we compared and analyzed rodent models, large animal models and in vitro BBB models of HT, and the limitations of these models were discussed. The molecular mechanism of HT was investigated in terms of BBB disruption, rt-PA neurotoxicity and the effect of neuroinflammation, matrix metalloproteinases, reactive oxygen species. The clinical features to predict HT were represented including blood biomarkers and clinical factors. Recent progress in neuroprotective strategies to improve HT after stroke treated with rt-PA is outlined. Further efforts need to be made to reduce the risk of HT after rt-PA therapy and improve the clinical prognosis of patients with ischemic stroke.

Rosiglitazone ameliorates tissue plasminogen activator-induced brain hemorrhage after stroke

Objective

Delayed thrombolytic therapy with recombinant tissue plasminogen activator (tPA) may exacerbate blood‐brain barrier (BBB) breakdown after ischemic stroke and lead to catastrophic hemorrhagic transformation (HT). Rosiglitazone(RSG), a widely used antidiabetic drug that activates peroxisome proliferator‐activated receptor‐γ (PPAR‐γ), has been shown to protect against cerebral ischemia through promoting poststroke microglial polarization toward the beneficial anti‐inflammatory phenotype. However, whether RSG can alleviate HT after delayed tPA treatment remains unknown. In this study, we sort to examine the role of RSG on tPA‐induced HT after stroke.

Methods and results

We used the murine suture middle cerebral artery occlusion (MCAO) models of stroke followed by delayed administration of tPA (10 mg/kg, 2 hours after suture occlusion) to investigate the therapeutic potential of RSG against tPA‐induced HT. When RSG(6 mg/kg) was intraperitoneally administered 1 hour before MCAO in tPA‐treated MCAO mice, HT in the ischemic territory was significantly attenuated 1 day after stroke. In the tPA‐treated MCAO mice, we found RSG significantly mitigated BBB disruption and hemorrhage development compared to tPA‐alone‐treated stroke mice. Using flow cytometry and immunostaining, we confirmed that the expression of CD206 was significantly upregulated while the expression of iNOS was down‐regulated in microglia of the RSG‐treated mice. We further found that the expression of Arg‐1 was also upregulated in those tPA and RSG‐treated stroke mice and the protection against tPA‐induced HT and BBB disruption in these mice were abolished in the presence of PPAR‐γ antagonist GW9662 (4 mg/kg, 1 hour before dMCAO through intraperitoneal injection).

Conclusions

RSG treatment protects against BBB damage and ameliorates HT in delayed tPA‐treated stroke mice by activating PPAR‐γ and favoring microglial polarization toward anti‐inflammatory phenotype.

Biomimetic drug-delivery systems for the management of brain diseases

Acting as a double-edged sword, the blood-brain barrier (BBB) is essential for maintaining brain homeostasis by restricting the entry of small molecules and most macromolecules from blood. However, it also largely limits the brain delivery of most drugs. Even if a drug can penetrate the BBB, its accumulation in the intracerebral pathological regions is relatively low. Thus, an optimal drug-delivery system (DDS) for the management of brain diseases needs to display BBB permeability, lesion-targeting capability, and acceptable safety. Biomimetic DDSs, developed by directly utilizing or mimicking the biological structures and processes, provide promising approaches for overcoming the barriers to brain drug delivery. The present review summarizes the biological properties and biomedical applications of the biomimetic DDSs including the cell membrane-based DDS, lipoprotein-based DDS, exosome-based DDS, virus-based DDS, protein template-based DDS and peptide template-based DDS for the management of brain diseases.