Platelet necrosis mediates ischemic stroke outcome in mice

The LPS-inactivating enzyme acyloxyacyl hydrolase protects the brain from experimental stroke

Blood-brain-barrier (BBB) disruption is a pathological hallmark of ischemic stroke, and inflammation occurring at the BBB contributes to the pathogenesis of ischemic brain injury. Lipopolysaccharide (LPS), a cell wall component of Gram-negative bacteria, is elevated in patients with acute stroke. The activity of LPS is controlled by acyloxyacyl hydrolase (AOAH), a host enzyme that deacylates LPS to inactivated forms. However, whether AOAH influences the pathogenesis of ischemic stroke remain elusive. We performed in vivo experiments to explore the role and mechanism of AOAH on neutrophil extravasation, BBB disruption, and brain infarction. We found that AOAH was upregulated in neutrophils in peri-infarct areas from mice with transient focal cerebral ischemia. AOAH deficiency increased neutrophil extravasation into the brain parenchyma and proinflammatory cytokine production, broke down the BBB and worsened stroke outcomes in mice. These effects require Toll-like receptor 4 (TLR4) because absence of TLR4 or pharmacologic inhibition of TLR4 signaling prevented the exacerbated inflammation and BBB damage in Aoah-/- mice after ischemic stroke. Importantly, neutrophil depletion or inhibition of neutrophil trafficking by blocking LFA-1 integrin dramatically reduced stroke-induced BBB breakdown in Aoah-/- mice. Furthermore, virus-mediated overexpression of AOAH induced a substantial decrease in neutrophil recruitment that was accompanied by reducing BBB damage and stroke volumes. Our findings show the importance of AOAH in regulating neutrophil-dependent BBB breakdown and cerebral infarction. Consequently, strategies that modulate AOAH may be a new therapeutic approach for treatment of ischemic stroke.

Systemic immune-inflammation index is associated with cardiac complications following acute ischemic stroke: A retrospective single-center study

BACKGROUND

Stroke-induced heart syndrome is a feared complication of ischemic stroke, that is commonly encountered and has a strong association with unfavorable prognosis. More research is needed to explore underlying mechanisms and inform clinical decision making. This study aims to explore the relationship between the early systemic immune-inflammation (SII) index and the cardiac complications after acute ischemic stroke.

METHODS

Consecutive patients with acute ischemic stroke were prospectively collected from January 2020 to August 2022 and retrospectively analyzed. We included subjects who presented within 24 hours after symptom onset and were free of detectable infections or cancer on admission. SII index [(neutrophils × platelets/ lymphocytes)/1000] was calculated from laboratory data at admission.

RESULTS

A total of 121 patients were included in our study, of which 24 (19.8 %) developed cardiac complications within 14 days following acute ischemic stroke. The SII level was found higher in patients with stroke-heart syndrome (p<.001), which was an independent predictor of stroke-heart syndrome (adjusted odds ratio 5.089, p=.002).

CONCLUSION

New-onset cardiovascular complications diagnosed following a stroke are very common and are associated with early SII index.

Mitofusin-2 Regulates Platelet Mitochondria and Function

BACKGROUND

Single-nucleotide polymorphisms linked with the rs1474868 T allele (MFN2 [mitofusin-2] T/T) in the human mitochondrial fusion protein MFN2 gene are associated with reduced platelet MFN2 RNA expression and platelet counts. This study investigates the impact of MFN2 on megakaryocyte and platelet biology.

METHODS

Mice with megakaryocyte/platelet deletion of Mfn2 (Mfn2-/- [Mfn2 conditional knockout]) were generated using Pf4-Cre crossed with floxed Mfn2 mice. Human megakaryocytes were generated from cord blood and platelets isolated from healthy subjects genotyped for rs1474868. Ex vivo approaches assessed mitochondrial morphology, function, and platelet activation responses. In vivo measurements included endogenous/transfused platelet life span, tail bleed time, transient middle cerebral artery occlusion, and pulmonary vascular permeability/hemorrhage following lipopolysaccharide-induced acute lung injury.

RESULTS

Mitochondria was more fragmented in megakaryocytes derived from Mfn2-/- mice and from human cord blood with MFN2 T/T genotype compared with control megakaryocytes. Human resting platelets of MFN2 T/T genotype had reduced MFN2 protein, diminished mitochondrial membrane potential, and an increased rate of phosphatidylserine exposure during ex vivo culture. Platelet counts and platelet life span were reduced in Mfn2-/- mice accompanied by an increased rate of phosphatidylserine exposure in resting platelets, especially aged platelets, during ex vivo culture. Mfn2-/- also decreased platelet mitochondrial membrane potential (basal) and activated mitochondrial oxygen consumption rate, reactive oxygen species generation, calcium flux, platelet-neutrophil aggregate formation, and phosphatidylserine exposure following dual agonist activation. Ultimately, Mfn2-/- mice showed prolonged tail bleed times, decreased ischemic stroke infarct size after cerebral ischemia-reperfusion, and exacerbated pulmonary inflammatory hemorrhage following lipopolysaccharide-induced acute lung injury. Analysis of MFN2 SNPs in the iSPAAR study (Identification of SNPs Predisposing to Altered ALI Risk) identified a significant association between MFN2 and 28-day mortality in patients with acute respiratory distress syndrome.

CONCLUSIONS

Mfn2 preserves mitochondrial phenotypes in megakaryocytes and platelets and influences platelet life span, function, and outcomes of stroke and lung injury.

Neutrophil activation in patients treated with endovascular therapy is associated with unfavorable outcomes and mitigated by intravenous thrombolysis

BACKGROUND

Accumulating evidence indicates that neutrophil activation (NA) contributes to microvascular thromboinflammation in acute ischemic stroke (AIS) due to a large vessel occlusion. Preclinical data have suggested that intravenous thrombolysis (IVT) before endovascular therapy (EVT) could dampen microvascular thromboinflammation. In this study we investigated the association between NA dynamics and stroke outcome, and the impact of IVT on NA in patients with AIS treated with EVT.

METHODS

A single-center prospective study was carried out, including patients treated with EVT for whom three blood samples (before, within 1 hour, 24 hours post-EVT) were drawn to measure plasma myeloperoxidase (MPO) concentration as a marker of NA. Unfavorable outcome was defined as a modified Rankin score of 3-6 at 3 months.

RESULTS

Between 2016 and 2020, 179 patients were included. The plasma MPO concentration peaked significantly 1 hour post-EVT (median increase 21.0 ng/mL (IQR -2.1-150)) and returned to pre-EVT baseline values 24 hours after EVT (median change from baseline -0.8 ng/mL (IQR -7.6-6.7)). This peak was strongly associated with unfavorable outcomes at 3 months (aOR 0.53 (95% CI 0.34 to 0.84), P=0.007). IVT before EVT abolished this 1 hour post-EVT MPO peak. Changes in plasma MPO concentration (baseline to 1 hour post-EVT) were associated with unfavorable outcomes only in patients not treated with IVT before EVT (aOR 0.54 (95% CI 0.33 to 0.88, P=0.013). However, we found no significant heterogeneity in the associations between changes in plasma MPO concentration and outcomes.

CONCLUSIONS

A peak in plasma MPO concentration occurs early after EVT and is associated with unfavorable outcomes. IVT abolished the post-EVT MPO peak and may modulate the association between NA and outcomes.

Immunothrombosis versus thrombo-inflammation: platelets in cerebrovascular complications

A State-of-the Art lecture titled "Thrombo-Neuroinflammatory Disease" was presented at the International Society on Thrombosis and Haemostasis Congress in 2023. First, we would like to advocate for discrimination between immunothrombosis and thrombo-inflammation, as immunothrombosis describes an overshooting inflammatory reaction that results in detrimental thrombotic activity. In contrast, thrombo-inflammation describes the interplay of platelets and coagulation with the immunovascular system, resulting in the recruitment of immune cells and loss of barrier function (hence, hallmarks of inflammation). Both processes can be observed in the brain, with cerebral venous thrombosis being a prime example of immunothrombosis, while infarct progression in response to ischemic stroke is a paradigmatic example of thrombo-inflammation. Here, we review the pathomechanisms underlying cerebral venous thrombosis and ischemic stroke from a platelet-centric perspective and discuss translational implications. Finally, we summarize relevant new data on this topic presented during the 2023 International Society on Thrombosis and Haemostasis Congress.

Immunothrombosis in neurovascular disease

A State of the Art lecture titled "Immunothrombosis in Neurovascular Diseases" was presented at the International Society on Thrombosis and Haemostasis Congress in 2023. Despite significant clinical advancements in stroke therapy, stroke remains a prominent contributor to both mortality and disability worldwide. Brain injury resulting from an ischemic stroke is a dynamic process that unfolds over time. Initially, an infarct core forms due to the abrupt and substantial blockage of blood flow. In the subsequent hours to days, the surrounding tissue undergoes gradual deterioration, primarily driven by sustained hypoperfusion, programmed cell death, and inflammation. While anti-inflammatory strategies have proven highly effective in experimental models of stroke, their successful translation to clinical use has proven challenging. To overcome this translational hurdle, a better understanding of the distinct immune response driving ischemic stroke brain injury is needed. In this review article, we give an overview of current knowledge regarding the immune response in ischemic stroke and the contribution of immunothrombosis to this process. We discuss therapeutic approaches to overcome detrimental immunothrombosis in ischemic stroke and how these can be extrapolated to other neurovascular diseases, such as Alzheimer's disease and multiple sclerosis. Finally, we summarize relevant new data on this topic presented during the 2023 International Society on Thrombosis and Haemostasis Congress.

Regulated necrosis pathways: a potential target for ischemic stroke

Globally, ischemic stroke causes millions of deaths per year. The outcomes of ischemic stroke are largely determined by the amount of ischemia-related and reperfusion-related neuronal death in the infarct region. In the infarct region, cell injuries follow either the regulated pathway involving precise signaling cascades, such as apoptosis and autophagy, or the nonregulated pathway, which is uncontrolled by any molecularly defined effector mechanisms such as necrosis. However, numerous studies have recently found that a certain type of necrosis can be regulated and potentially modified by drugs and is nonapoptotic; this type of necrosis is referred to as regulated necrosis. Depending on the signaling pathway, various elements of regulated necrosis contribute to the development of ischemic stroke, such as necroptosis, pyroptosis, ferroptosis, pathanatos, mitochondrial permeability transition pore-mediated necrosis and oncosis. In this review, we aim to summarize the underlying molecular mechanisms of regulated necrosis in ischemic stroke and explore the crosstalk and interplay among the diverse types of regulated necrosis. We believe that targeting these regulated necrosis pathways both pharmacologically and genetically in ischemia-induced neuronal death and protection could be an efficient strategy to increase neuronal survival and regeneration in ischemic stroke.

A Machine Learning-Based Classification of Immunogenic Cell Death Regulators and Characterisation of Immune Microenvironment in Acute Ischemic Stroke

Immunogenic cell death (ICD) regulators exert a crucial part in quite a few in numerous biological processes. This study aimed to determine the function and diagnostic value of ICD regulators in acute ischemic stroke (AIS). 31 significant ICD regulators were identified from the gene expression omnibus (GEO) database in this work (the combination of the GSE16561 dataset and the GSE37587 dataset in the comparison of non-AIS and AIS patients). The random forest model was applied and 15 potential ICD regulators were screened to forecast the probability of AIS. A nomogram, on the basis of 11 latent ICD regulators, was performed. The resolution curve analysis indicated that patients can gain benefits from the nomogram. The consensus clustering approach was applied, and AIS patients were divided into 2 ICD clusters (cluster A and cluster B) based on the identified key ICD regulatory factors. To quantify the ICD pattern, 181 ICD-related dissimilarly expressed genes (DEGs) were selected for further investigation. The expression levels of NFKB1, NFKB2, and PARP1 were greater in gene cluster A than in gene cluster B. In conclusion, ICD regulators exerted a crucial part in the progress of AIS. The investigation made by us on ICD patterns perhaps informs prospective immunotherapeutic methods for AIS.

CypD induced ROS output promotes intracranial aneurysm formation and rupture by 8-OHdG/NLRP3/MMP9 pathway

Reactive Oxygen Species (ROS) are widely accepted as a pernicious factor in the progression of intracranial aneurysm (IA), which is eminently related to cell apoptosis and extracellular matrix degradation, but the mechanism remains to be elucidated. Recent evidence has identified that enhancement of Cyclophilin D (CypD) under stress conditions plays a critical role in ROS output, thus accelerating vascular destruction. However, no study has confirmed whether cypD is a detrimental mediator of cell apoptosis and extracellular matrix degradation in the setting of IA development. Our data indicated that endogenous cypD mRNA was significantly upregulated in human IA lesions and mouse IA wall, accompanied by higher level of ROS, MMPs and cell apoptosis. CypD-/- remarkably reversed vascular smooth muscle cells (VSMCs) apoptosis and elastic fiber degradation, and significantly decreased the incidence of aneurysm and ruptured aneurysm, together with the downregulation of ROS, 8-OHdG, NLRP3 and MMP9 in vivo and vitro. Furthermore, we demonstrated that blockade of cypD with CsA inhibited the above processes, thus preventing IA formation and rupture, these effects were highly dependent on ROS output. Mechanistically, we found that cypD directly interacts with ATP5B to promote ROS release in VSMCs, and 8-OHdG directly bind to NLRP3, which interacted with MMP9 to increased MMP9 level and activity in vivo and vitro. Our data expound an unexpected role of cypD in IA pathogenesis and an undescribed 8-OHdG/NLRP3/MMP9 pathway involved in accelerating VSMCs apoptosis and elastic fiber degradation. Repressing ROS output by CypD inhibition may be a promising therapeutic strategy for prevention IA development.

Alterations in the megakaryocyte transcriptome impacts platelet function in sepsis and COVID-19 infection

Platelets and their parent cell, the megakaryocyte (MK), are increasingly recognized for their roles during infection and inflammation. The MK residing in the bone marrow or arising from precursors trafficked to other organs for development go on to form platelets through thrombopoiesis. Infection, by direct and indirect mechanisms, can alter the transcriptional profile of MKs. The altered environment, whether mediated by inflammatory cytokines or other signaling mechanisms results in an altered platelet transcriptome. Platelets released into the circulation, in turn, interact with each other, circulating leukocytes and endothelial cells and contribute to the clearance of pathogens or the potentiation of pathophysiology through such mechanisms as immunothrombosis. In this article we hope to identify key contributions that explore the impact of an altered transcriptomic landscape during severe, systemic response to infection broadly defined as sepsis, and viral infections, including SARS-CoV2. We include current publications that outline the role of MKs from bone-marrow and extra-medullary sites as well as the circulating platelet. The underlying diseases result in thrombotic complications that exacerbate organ dysfunction and mortality. Understanding the impact of platelets on the pathophysiology of disease may drive therapeutic advances to improve the morbidity and mortality of these deadly afflictions.

The predominant PAR4 variant in individuals of African ancestry worsens murine and human stroke outcomes

Protease-activated receptor 4 (PAR4) (gene F2RL3) harbors a functional dimorphism, rs773902 A/G (encoding Thr120/Ala120, respectively) and is associated with greater platelet aggregation. The A allele frequency is more common in Black individuals, and Black individuals have a higher incidence of ischemic stroke than White individuals. However, it is not known whether the A allele is responsible for worse stroke outcomes. To directly test the in vivo effect of this variant on stroke, we generated mice in which F2rl3 was replaced by F2RL3, thereby expressing human PAR4 (hPAR4) with either Thr120 or Ala120. Compared with hPAR4 Ala120 mice, hPAR4 Thr120 mice had worse stroke outcomes, mediated in part by enhanced platelet activation and platelet-neutrophil interactions. Analyses of 7,620 Black subjects with 487 incident ischemic strokes demonstrated the AA genotype was a risk for incident ischemic stroke and worse functional outcomes. In humanized mice, ticagrelor with or without aspirin improved stroke outcomes in hPAR4 Ala120 mice, but not in hPAR4 Thr120 mice. P selectin blockade improved stroke outcomes and reduced platelet-neutrophil interactions in hPAR4 Thr120 mice. Our results may explain some of the racial disparity in stroke and support the need for studies of nonstandard antiplatelet therapies for patients expressing PAR4 Thr120.

Blood-brain crosstalk: the roles of neutrophils, platelets, and neutrophil extracellular traps in neuropathologies

Systemic inflammation, neurovascular dysfunction, and coagulopathy often occur concurrently in neuropathologies. Neutrophils and platelets have crucial synergistic roles in thromboinflammation and are increasingly suspected as effector cells contributing to the pathogenesis of neuroinflammatory diseases. In this review, we summarize the roles of platelet-neutrophil interactions in triggering complex pathophysiological events affecting the brain that may lead to the disruption of brain barriers, infiltration of toxic factors into the parenchyma, and amplification of neuroinflammation through the formation of neutrophil extracellular traps (NETs). We highlight the clinical significance of thromboinflammation in neurological disorders and examine the contributions of damage-associated molecular patterns (DAMPs) derived from platelets and neutrophils. These DAMPs originate from both infectious and non-infectious risk factors and contribute to the activation of inflammasomes during brain disorders. Finally, we identify knowledge gaps in the molecular mechanisms underlying neurodegenerative disease pathogenesis and emphasize the potential of interventions targeting platelets and neutrophils to treat neuroinflammatory diseases.

Prognostic value of inflammatory markers for in-hospital mortality in intensive care patients with acute ischemic stroke: a retrospective observational study based on MIMIC-IV

Background

Acute ischemic stroke (AIS) is a primary cause of death and disability worldwide. Four markers that can be readily determined from peripheral blood, namely, the systemic immune-inflammation index (SII), neutrophil-to-lymphocyte ratio (NLR), platelet-to-lymphocyte ratio (PLR), and total bilirubin, were measured in this study. We examined the relationship between the SII and in-hospital mortality after AIS and evaluated which of the above four indicators was most accurate for predicting in-hospital mortality after AIS.

Methods

We selected patients from the Medical Information Mart for Intensive Care-IV (MIMIC-IV) database who were aged >18 years and who were diagnosed with AIS on admission. We collected the patients' baseline characteristics, including various clinical and laboratory data. To investigate the relationship between the SII and in-hospital mortality in patients with AIS, we employed the generalized additive model (GAM). Differences in in-hospital mortality between the groups were summarized by the Kaplan-Meier survival analysis and the log-rank test. The receiver operating characteristic (ROC) curve analysis was used to assess the accuracy of the four indicators (SII, NLR, PLR, and total bilirubin) for predicting in-hospital mortality in patients with AIS.

Results

The study included 463 patients, and the in-hospital mortality rate was 12.31%. The GAM analysis showed a positive correlation between the SII and in-hospital mortality in patients with AIS, but the correlation was not linear. Unadjusted Cox regression identified a link between a high SII and an increased probability of in-hospital mortality. We also found that patients with an SII of >1,232 (Q2 group) had a considerably higher chance of in-hospital mortality than those with a low SII (Q1 group). The Kaplan-Meier analysis demonstrated that patients with an elevated SII had a significantly lower chance of surviving their hospital stay than those with a low SII. According to the results of the ROC curve analysis, the in-hospital mortality of patients with AIS predicted by the SII had an area under the ROC curve of 0.65, which revealed that the SII had a better discriminative ability than the NLR, PLR, and total bilirubin.

Conclusion

The in-hospital mortality of patients with AIS and the SII were positively correlated, but not linearly. A high SII was associated with a worse prognosis in patients with AIS. The SII had a modest level of discrimination for forecasting in-hospital mortality. The SII was slightly better than the NLR and significantly better than the PLR and total bilirubin for predicting in-hospital mortality in patients with AIS.

Small-Molecule Cyclophilin Inhibitors Potently Reduce Platelet Procoagulant Activity

Procoagulant platelets are associated with an increased risk for thrombosis. Procoagulant platelet formation is mediated via Cyclophilin D (CypD) mediated opening of the mitochondrial permeability transition pore. Inhibiting CypD activity could therefore be an interesting approach to limiting thrombosis. In this study, we investigated the potential of two novel, non-immunosuppressive, non-peptidic small-molecule cyclophilin inhibitors (SMCypIs) to limit thrombosis in vitro, in comparison with the cyclophilin inhibitor and immunosuppressant Cyclosporin A (CsA). Both cyclophilin inhibitors significantly decreased procoagulant platelet formation upon dual-agonist stimulation, shown by a decreased phosphatidylserine (PS) exposure, as well as a reduction in the loss of mitochondrial membrane potential. Furthermore, the SMCypIs potently reduced procoagulant platelet-dependent clotting time, as well as fibrin formation under flow, comparable to CsA. No effect was observed on agonist-induced platelet activation measured by P-selectin expression, as well as CypA-mediated integrin α_IIbβ₃ activation. Importantly, whereas CsA increased Adenosine 5'-diphosphate (ADP)-induced platelet aggregation, this was unaffected in the presence of the SMCypIs. We here demonstrate specific cyclophilin inhibition does not affect normal platelet function, while a clear reduction in procoagulant platelets is observed. Reducing platelet procoagulant activity by inhibiting cyclophilins with SMCypIs forms a promising strategy to limit thrombosis.

QiShen YiQi and its components attenuate acute thromboembolic stroke and carotid thrombosis by inhibition of CD62P/PSGL-1-mediated platelet-leukocyte aggregate formation

BACKGROUND

QiShen YiQi (QSYQ) dropping pill, a component-based Chinese medicine consisting of benefiting Qi (YQ) and activating blood (HX) components, has been reported to exert a beneficial effect on cerebral ischemia-induced stroke. However, its efficacy and pharmacological mechanism on acute thromboembolic stroke is not clear.

PURPOSE

This study is to explore the preventative effect and pharmacological mechanism of QSYQ and its YQ/HX components on the formation of platelet-leukocyte aggregation (PLA) in acute thromboembolic stroke.

STUDY DESIGN AND METHODS

In vivo thromboembolic stroke model and FeCl₃-induced carotid arterial occlusion models were used. Immunohistochemistry, Western blot, RT-qPCR, and flow cytometry experiments were performed to reveal the pharmacological mechanisms of QSYQ and its YQ/HX components.

RESULTS

In thromboembolic stroke rats, QSYQ significantly attenuated infarct area, improved neurological recovery, reduced PLA formation, and inhibited P-selection (CD62P)/ P-selectin glycoprotein ligand-1 (PSGL-1) expressions. The YQ component preferentially down-regulated PSGL-1 expression in leukocyte, while the HX component preferentially down-regulated CD62P expression in platelet. In carotid arterial thrombosis mice, QSYQ and its YQ/HX components inhibited thrombus formation, prolonged vessel occlusion time, reduced circulating leukocytes and P-selectin expression. PLA formation and platelet/leukocyte adhesion to endothelial cell were also inhibited by QSYQ and its YQ/HX components in vitro.

CONCLUSION

QSYQ and YQ/HX components attenuated thromboembolic stroke and carotid thrombosis by decreasing PLA formation via inhibiting CD62P/PSGL-1 expressions. This study shed a new light on the prevention of thromboembolic stroke.

DIAGNOSTIC VALUE OF SYSTEMIC IMMUNE–INFLAMMATION INDEX (SIII) IN ACUTE ISCHEMIC STROKE

Background: Calculated based on platelet, neutrophil and lymphocyte counts, the systemic immune-inflammation index is thought to be associated with many malignancies in the literature. Despite the existing investigations on its diagnostic value, there have been no clear results reported regarding its diagnostic value in stroke patients. The current study is therefore intended to demonstrate the diagnostic value of the systemic immune-inflammation index and its prognostic value in cases of acute ischemic stroke. Materials and Methods: A total of 150 cases of acute stroke and a control group of 150 individuals were retrospectively examined. The data recorded for each case included age, gender, history, vital findings, NIHSS, SIII, and outcome. Results: In the current study, the group of stroke patients had significantly higher SIII than the control group. According to the diagnostic examinations, in stroke, the diagnostic value of SIII was greater than that of neutrophil-to-lymphocyte ratio at a statistically significant level. The present study also found that, compared to the SIII, the (Lymphocyte x Platelet)/Neutrophil ratio (called the novel SIII) had a higher statistical significance in diagnosing the stroke and predicting early hospital mortality. Conclusions: The SIII can be a good marker for both diagnostic evaluation and for predicting early hospital mortality in stroke cases. Additionally, it is approved to be a useful index since it can be calculated inexpensively and easily.

An update on the molecular mechanism and pharmacological interventions for Ischemia-reperfusion injury by regulating AMPK/mTOR signaling pathway in autophagy

AMP-activated protein kinase (5'-adenosine monophosphate-activated protein kinase, AMPK)/mammalian target of rapamycin (mTOR) is an important signaling pathway maintaining normal cell function and homeostasis in vivo. The AMPK/mTOR pathway regulates cellular proliferation, autophagy, and apoptosis. Ischemia-reperfusion injury (IRI) is secondary damage that frequently occurs clinically in various disease processes and treatments, and the exacerbated injury during tissue reperfusion increases disease-associated morbidity and mortality. IRI arises from multiple complex pathological mechanisms, among which cell autophagy is a focus of recent research and a new therapeutic target. The activation of AMPK/mTOR signaling in IRI can modulate cellular metabolism and regulate cell proliferation and immune cell differentiation by adjusting gene transcription and protein synthesis. Thus, the AMPK/mTOR signaling pathway has been intensively investigated in studies focused on IRI prevention and treatment. In recent years, AMPK/mTOR pathway-mediated autophagy has been found to play a crucial role in IRI treatment. This article aims to elaborate the action mechanisms of AMPK/mTOR signaling pathway activation in IRI and summarize the progress of AMPK/mTOR-mediated autophagy research in the field of IRI therapy.

Neutrophil extracellular trap inhibition improves survival in neonatal mouse infectious peritonitis

BACKGROUND

Treatment of neonatal peritonitis and sepsis is challenging. Following infection, neutrophils elaborate neutrophil extracellular traps (NETs)-extracellular lattices of decondensed chromatin decorated with antimicrobial proteins. NETs, however, can augment pathogenic inflammation causing collateral damage. We hypothesized that NET inhibition would improve survival in experimental neonatal infectious peritonitis.

METHODS

We induced peritonitis in 7 to 10-day-old mice by intraperitoneal injection with cecal slurry. We targeted NETs by treating mice with neonatal NET-Inhibitory Factor (nNIF), an endogenous NET-inhibitor; Cl-amidine, a PAD4 inhibitor; DNase I, a NET degrading enzyme, or meropenem (an antibiotic). We determined peritoneal NET and cytokine levels and circulating platelet-neutrophil aggregates. Survival from peritonitis was followed for 6 days.

RESULTS

nNIF, Cl-amidine, and DNase I decreased peritoneal NET formation and inflammatory cytokine levels at 24 h compared to controls. nNIF, Cl-amidine, and DNase I decreased circulating platelet-neutrophil aggregates, and NET-targeting treatments significantly increased survival from infectious peritonitis compared to controls. Finally, nNIF administration significantly improved survival in mice treated with sub-optimal doses of meropenem even when treatment was delayed until 2 h after peritonitis induction.

CONCLUSIONS

NET inhibition improves survival in experimental neonatal infectious peritonitis, suggesting that NETs participate pathogenically in neonatal peritonitis and sepsis.

IMPACT

1. Neutrophil extracellular trap formation participates pathogenically in experimental neonatal infectious peritonitis. 2. NET-targeting strategies improve outcomes in a translational model of neonatal infectious peritonitis. 3. NET inhibition represents a potential target for drug development in neonatal sepsis and infectious peritonitis.

Platelet-Neutrophil Crosstalk in Thrombosis

Platelets are essential for the formation of a haemostatic plug to prevent bleeding, while neutrophils are the guardians of our immune defences against invading pathogens. The interplay between platelets and innate immunity, and subsequent triggering of the activation of coagulation is part of the host system to prevent systemic spread of pathogen in the blood stream. Aberrant immunothrombosis and excessive inflammation can however, contribute to the thrombotic burden observed in many cardiovascular diseases. In this review, we highlight how platelets and neutrophils interact with each other and how their crosstalk is central to both arterial and venous thrombosis and in COVID-19. While targeting platelets and coagulation enables efficient antithrombotic treatments, they are often accompanied with a bleeding risk. We also discuss how novel approaches to reduce platelet-mediated recruitment of neutrophils could represent promising therapies to treat thrombosis without affecting haemostasis.

Increased Systemic Immune-Inflammation Index Predicts Disease Severity and Functional Outcome in Acute Ischemic Stroke Patients

BACKGROUND

Systemic immune-inflammation index (SII) and system inflammation response index (SIRI) have been recently investigated as novel inflammatory and prognostic markers. Our study aimed to investigate the relationship between SII and SIRI index and severity of stroke, and to analyze the prognostic value in acute ischemic stroke (AIS) patients.

METHODS

The SII is defined as platelet×(neutrophil count/lymphocyte count), SIRI is defined as neutrophil count×(monocyte count/lymphocyte count). We plotted receiver operating characteristic curves of SII and SIRI for poor outcomes and calculated area under the curve (AUC) values and cutoff values. Multivariate logistic regression analysis was performed to analyze the association between SII/SIRI index and poor functional outcome.

RESULTS

We included 234 AIS patients [mean age 69 (57-78) years; 50.4% male]. Both SII and SIRI were higher in the moderate-to-severe stroke group than in the mild stroke group [932.73 (569.84-1610.90) vs. 581.21 (386.98-1015.59), P <0.001 and 2.00 (1.24-3.13) vs. 1.35 (0.83-1.92), P <0.001]. The area under the receiver operating characteristic curve (area under the curve) value of SII (0.678, 0.608-0.748, P <0.001) tested a similar discriminatory ability compared with SIRI (0.682, 95% CI (0.612-0.751), P <0.001). Multivariate logistic regression analyses showed that SII was significantly associated with poor prognosis at discharge of AIS patients [adjusted odds ratio (95% confidence interval): 2.350 (1.149-4.803), P =0.019)], conversely, SIRI had no prognostic value.

CONCLUSIONS

Higher SII and SIRI indexes were correlated with greater risk of stroke severity, meanwhile SII could be useful for predicting adverse clinical outcomes after AIS.

The HALP (hemoglobin, albumin, lymphocyte, and platelet) score is associated with early-onset post-stroke cognitive impairment

BACKGROUND

The HALP score (hemoglobin, albumin, lymphocyte, and platelet) is a novel indicator that measures systemic inflammation and nutritional status. The goal of this study was to look into the relationship between the HALP score and post-stroke cognitive impairment (PSCI) in people who had an acute ischemic stroke (AIS).

METHODS

A total of 592 individuals with ischemic stroke were included in the research, and the PSCI (n = 382) and non-PSCI (n = 210) groups were determined using the Mini-Mental State Examination scale 2 weeks following the stroke. HALP score was computed by the formula: hemoglobin (g/L) × albumin (g/L) × lymphocytes (/L) / platelets (/L), and was split into three layers according to the tertiles. The connection between the HALP and cognitive results was investigated by binary logistic regression.

RESULTS

The PSCI group's HALP score was much lower than the non-PSCI group's (p < 0.001). The HALP score was divided into three layers: T1 ≤ 34.0, T2 34.1-49.4, and T3 ≥ 49.5, respectively. In the binary regression analysis, taking the T3 layer as the reference, the T1 layer showed the highest risk of PSCI after adjusting for confounding factors (odds ratio (OR) = 1.965, 95% confidence interval (CI) = 1.237-3.122, p = 0.004), while there was no increased risk of PSCI in the T2 layer (OR = 1.538, 95%CI = 0.983-2.404, p = 0.059).

CONCLUSION

Low HALP score at admission was found to be correlated with early-onset PSCI and may help clinicians in the early identification of high-risk patients.

Markers of neutrophil mediated inflammation associate with disturbed continuous electroencephalogram after out of hospital cardiac arrest

BACKGROUND

Achieving an acceptable neurological outcome in cardiac arrest survivors remains challenging. Ischemia-reperfusion injury induces inflammation, which may cause secondary neurological damage. We studied the association of ICU admission levels of inflammatory biomarkers with disturbed 48-hour continuous electroencephalogram (cEEG), and the association of the daily levels of these markers up to 72 h with poor 6-month neurological outcome.

METHODS

This is an observational, post hoc sub-study of the COMACARE trial. We measured serum concentrations of procalcitonin (PCT), high-sensitivity C-reactive protein (hsCRP), osteopontin (OPN), myeloperoxidase (MPO), resistin, and proprotein convertase subtilisin/kexin type 9 (PCSK9) in 112 unconscious, mechanically ventilated ICU-treated adult OHCA survivors with initial shockable rhythm. We used grading of 48-hour cEEG monitoring as a measure for the severity of the early neurological disturbance. We defined 6-month cerebral performance category (CPC) 1-2 as good and CPC 3-5 as poor long-term neurological outcome. We compared the prognostic value of biomarkers for 6-month neurological outcome to neurofilament light (NFL) measured at 48 h.

RESULTS

Higher OPN (p = .03), MPO (p < .01), and resistin (p = .01) concentrations at ICU admission were associated with poor grade 48-hour cEEG. Higher levels of ICU admission OPN (OR 3.18; 95% CI 1.25-8.11 per ln[ng/ml]) and MPO (OR 2.34; 95% CI 1.30-4.21) were independently associated with poor 48-hour cEEG in a multivariable logistic regression model. Poor 6-month neurological outcome was more common in the poor cEEG group (63% vs. 19% p < .001, respectively). We found a significant fixed effect of poor 6-month neurological outcome on concentrations of PCT (F = 7.7, p < .01), hsCRP (F = 4.0, p < .05), and OPN (F = 5.6, p < .05) measured daily from ICU admission to 72 h. However, the biomarkers did not have independent predictive value for poor 6-month outcome in a multivariable logistic regression model with 48-hour NFL.

CONCLUSION

Elevated ICU admission levels of OPN and MPO predicted disturbances in cEEG during the subsequent 48 h after cardiac arrest. Thus, they may provide early information about the risk of secondary neurological damage. However, the studied inflammatory markers had little value for long-term prognostication compared to 48-hour NFL.

Ntrk1 promotes mesangial cell proliferation and inflammation in rat glomerulonephritis model by activating the STAT3 and p38/ERK MAPK signaling pathways

BACKGROUND

Mesangial proliferative glomerulonephritis (MsPGN) accounts for a main cause of chronic kidney disease (CKD), chronic renal failure and uremia. This paper aimed to examine the effect of Ntrk1 on MsPGN development, so as to identify a novel therapeutic target for MsPGN.

METHODS

The MsPGN rat model was constructed by single injection of Thy1.1 monoclonal antibody via the tail vein. Additionally, the Ntrk1 knockdown rat model was established by injection of Ntrk1-RNAi lentivirus via the tail vein. Periodic acid-schiff staining and immunohistochemistry (IHC) were performed on kidney tissues. Moreover, the rat urinary protein was detected. Mesangial cells were transfected and treated with p38 inhibitor (SB202190) and ERK inhibitor (PD98059). Meanwhile, the viability and proliferation of mesangial cells were analyzed by cell counting kit-8 (CCK-8) and 5-Ethynyl-2'-deoxyuridine assays. Gene expression was detected by quantitative real-time polymerase chain reaction (qRT-PCR) and Western-blot (WB) assays.

RESULTS

The proliferation of mesangial cells was enhanced in glomerulus and Ki67 expression was up-regulated in renal tubule of MsPGN rats. The urine protein level increased in MsPGN rats. Pro-inflammatory factors and Ntrk1 expression were up-regulated in glomerulus of MsPGN rats. Ntrk1 up-regulation promoted the viability, proliferation, expression of pro-inflammatory factors and activation of the STAT3, p38 and ERK signaling pathways in mesangial cells. Ntrk1 knockdown reduced mesangial cell proliferation, urine protein, pro-inflammatory factors, activation of STAT3, p38 and ERK signaling pathways in glomerulus, and decreased Ki67 expression in renal tubule of MsPGN rats. Treatment with SB202190 and PD98059 reversed the effect of Ntrk1 on promoting the viability, proliferation and inflammatory response of mesangial cells.

CONCLUSION

Ntrk1 promoted mesangial cell proliferation and inflammation in MsPGN rats by activating the STAT3 and p38/ERK MAPK signaling pathways.

Association of the systemic immune-inflammation index (SII) and clinical outcomes in patients with stroke: A systematic review and meta-analysis

Introduction

A novel systemic immune-inflammation index (SII) has been proven to be associated with outcomes in patients with cancer. Although some studies have shown that the SII is a potential and valuable tool to diagnose and predict the advise outcomes in stroke patients. Nevertheless, the findings are controversial, and their association with clinical outcomes is unclear. Consequently, we conducted a comprehensive review and meta-analysis to explore the relationship between SII and clinical outcomes in stroke patients.

Methods

A search of five English databases (PubMed, Embase, Cochrane Library, Scopus, and Web of Science) and four Chinese databases (CNKI, VIP, WanFang, and CBM) was conducted. Our study strictly complied with the PRISMA (the Preferred Reporting Items for Systematic Reviews and Meta-Analyses). We used the NOS (Newcastle-Ottawa Scale) tool to assess the possible bias of included studies. The endpoints included poor outcome (the modified Rankin Scale [mRS] ≥ 3 points or > 3 points), mortality, the severity of stroke (according to assessment by the National Institute of Health stroke scale [NIHSS] ≥ 5 points), hemorrhagic transformation (HT) were statistically analyzed.

Results

Nineteen retrospective studies met the eligibility criteria, and a total of 18609 stroke patients were included. Our study showed that high SII is significantly associated with poor outcomes (odds ratio [OR] 1.06, 95% confidence interval [CI] 1.02-1.09, P = 0.001, I² = 93%), high mortality (OR 2.16, 95% CI 1.75-2.67, P < 0.00001, I² = 49%), and the incidence of HT (OR 2.09, 95% CI 1.61-2.71, P < 0.00001, I² = 42%). We also investigated the difference in SII levels in poor/good outcomes, death/survival, and minor/moderate-severe stroke groups. Our analysis demonstrated that the SII level of the poor outcome, death, and moderate-severe stroke group was much higher than that of the good outcome, survival, and minor stroke group, respectively (standard mean difference [SMD] 1.11, 95% CI 0.61-1.61, P < 0.00001 [poor/good outcome]; MD 498.22, 95% CI 333.18-663.25, P < 0.00001 [death/survival]; SMD 1.35, 95% CI 0.48-2.23, P = 0.002 [severity of stroke]). SII, on the other hand, had no significant impact on recanalization (OR 1.50, 95% CI 0.86-2.62, P = 0.16).

Discussion

To the best of our knowledge, this may be the first meta-analysis to look at the link between SII and clinical outcomes in stroke patients. The inflammatory response after a stroke is useful for immunoregulatory treatment. Stroke patients with high SII should be closely monitored, since this might be a viable treatment strategy for limiting brain damage after a stroke. As a result, research into SII and the clinical outcomes of stroke patients is crucial. Our preliminary findings may represent the clinical condition and aid clinical decision-makers. Nonetheless, further research is needed to better understand the utility of SII through dynamic monitoring. To generate more robust results, large-sample and multi-center research are required.

Systematic review registration

https://www.crd.york.ac.uk/prospero/, identifier CRD42022371996.

HJ11 decoction restrains development of myocardial ischemia-reperfusion injury in rats by suppressing ACSL4-mediated ferroptosis

HJ11 is a novel traditional Chinese medicine developed from the appropriate addition and reduction of Si-Miao-Yong-An decoction, which has been commonly used to treat ischemia-reperfusion (I/R) injury in the clinical setting. However, the mechanism of action of HJ11 components remains unclear. Ferroptosis is a critical factor that promotes myocardial I/R injury, and the pathophysiological ferroptosis-mediated lipid peroxidation causes I/R injury. Therefore, this study explored whether HJ11 decoction ameliorates myocardial I/R injury by attenuating ACSL4-mediated ferroptosis. This study also explored the effect of ACSL4 expression on iron-dependent programmed cell death by preparing a rat model of myocardial I/R injury and oxygen glucose deprivation/reperfusion (OGD/R)-induced H9c2 cells. The results showed that HJ11 decoction improved cardiac function; attenuated I/R injury, apoptosis, oxidative stress, mitochondrial damage, and iron accumulation; and reduced infarct size in the myocardial I/R injury rat model. Additionally, HJ11 decoction suppressed the expression of ferroptosis-promoting proteins [Acyl-CoA synthetase long-chain family member 4 (ACSL4) and cyclooxygenase-2 (COX2)] but promoted the expression of ferroptosis-inhibiting proteins [ferritin heavy chain 1 (FTH1) and glutathione-dependent lipid hydroperoxidase glutathione peroxidase 4 (GPX4)] in the myocardial tissues of the I/R injury rat model. Similar results were found with the OGD/R-induced H9c2 cells. Interestingly, ACSL4 knockdown attenuated iron accumulation, oxidative stress, and ferroptosis in the OGD/R-treated H9c2 cells. However, ACSL4 overexpression counteracted the inhibitory effect of the HJ11 decoction on OGD/R-triggered oxidative stress and ferroptosis in H9c2 cells. These findings suggest that HJ11 decoction restrained the development of myocardial I/R injury by regulating ACSL4-mediated ferroptosis. Thus, HJ11 decoction may be an effective medication to treat myocardial I/R injury.

Procoagulant platelets: novel players in thromboinflammation

Platelets play a key role in maintaining hemostasis. However, dysregulated platelet activation can lead to pathological thrombosis or bleeding. Once a platelet gets activated, it will either become an aggregatory platelet or eventually a procoagulant platelet with both types playing distinct roles in thrombosis and hemostasis. Although aggregatory platelets have been extensively studied, procoagulant platelets have only recently come into the spotlight. Procoagulant platelets are a subpopulation of highly activated platelets that express phosphatidylserine and P-selectin on their surface, allowing for coagulation factors to bind and thrombin to be generated. In recent years, novel roles for procoagulant platelets have been identified and they have increasingly been implicated in thromboinflammatory diseases. Here, we provide an up-to-date review on the mechanisms resulting in the formation of procoagulant platelets and how they contribute to hemostasis, thrombosis, and thromboinflammation.

PD-L1 Regulates Platelet Activation and Thrombosis via Caspase-3/GSDME Pathway

Platelets play a central role in hemostasis and thrombosis, regulating the occurrence and development of thrombotic diseases, including ischemic stroke. Programmed death ligand 1 (PD-L1) has recently been detected in platelet, while the function of PD-L1 in platelets remain elusive. Our data reveal a novel mechanism for the role of PD-L1 on platelet activation and arterial thrombosis. PD-L1 knockout does not affect platelet morphology, count, and mean volume under homeostasis and without risk of bleeding, which inhibits platelet activation by suppressing outside-in-activation of integrin by downregulating the Caspase-3/GSDME pathway. Platelet adoptive transfer experiments demonstrate that PD-L1 knockout inhibits thrombosis. And the absence of PD-L1 improves ischemic stroke severity and increases mice survival. Immunohistochemical staining of the internal structure of the thrombus proves that PD-L1 enhances the seriousness of the thrombus by inhibiting platelet activation. This work reveals a regulatory role of PD-L1 on platelet activation and thrombosis while providing novel platelet intervention strategies to prevent thrombosis.

Neutrophil extracellular traps regulate ischemic stroke brain injury

Ischemic stroke prompts a strong inflammatory response, which is associated with exacerbated outcomes. In this study, we investigated mechanistic regulators of neutrophil extracellular trap (NET) formation in stroke and whether they contribute to stroke outcomes. NET-forming neutrophils were found throughout brain tissue of ischemic stroke patients, and elevated plasma NET biomarkers correlated with worse stroke outcomes. Additionally, we observed increased plasma and platelet surface-expressed high-mobility group box 1 (HMGB1) in stroke patients. Mechanistically, platelets were identified as the critical source of HMGB1 that caused NETs in the acute phase of stroke. Depletion of platelets or platelet-specific knockout of HMGB1 significantly reduced plasma HMGB1 and NET levels after stroke, and greatly improved stroke outcomes. We subsequently investigated the therapeutic potential of neonatal NET-inhibitory factor (nNIF) in stroke. Mice treated with nNIF had smaller brain infarcts, improved long-term neurological and motor function, and enhanced survival after stroke. nNIF specifically blocked NET formation without affecting neutrophil recruitment after stroke. Importantly, nNIF also improved stroke outcomes in diabetic and aged mice and was still effective when given 1 hour after stroke onset. These results support a pathological role for NETs in ischemic stroke and warrant further investigation of nNIF for stroke therapy.

Procoagulant platelet sentinels prevent inflammatory bleeding through GPIIBIIIA and GPVI

Impairment of vascular integrity is a hallmark of inflammatory diseases. We recently reported that single immune-responsive platelets migrate and re-position themselves to sites of vascular injury to prevent bleeding. However, it remains unclear how single platelets preserve vascular integrity once encountering endothelial breaches. Here we demonstrate by intravital microscopy combined with genetic mouse models that procoagulant activation (PA) of single platelets and subsequent recruitment of the coagulation cascade are crucial for the prevention of inflammatory bleeding. Using a novel lactadherin-based compound we detect phosphatidylserine (PS)-positive procoagulant platelets in the inflamed vasculature. We identify exposed collagen as the central trigger arresting platelets and initiating subsequent PA in a CypD- and TMEM16F-dependent manner both in vivo and in vitro. Platelet PA promotes binding of the prothrombinase complex to the platelet membrane, greatly enhancing thrombin activity resulting in fibrin formation. PA of migrating platelets is initiated by co-stimulation via integrin αIIbβ3 (GPIIBIIIA)/Gα13-mediated outside-in-signaling and GPVI signaling, leading to an above-threshold intracellular calcium release. This effectively targets the coagulation cascade to breaches of vascular integrity identified by patrolling platelets. Platelet-specific genetic loss of either CypD or TMEM16F as well as combined blockade of platelet GPIIBIIIA and GPVI reduce platelet PA in vivo and aggravate pulmonary inflammatory hemorrhage. Our findings illustrate a novel role of procoagulant platelets in the prevention of inflammatory bleeding and provide evidence that PA of patrolling platelet sentinels effectively targets and confines activation of coagulation to breaches of vascular integrity.

Thromboinflammation in Brain Ischemia: Recent Updates and Future Perspectives

Despite decades of promising preclinical validation and clinical translation, ischemic stroke still remains as one of the leading causes of death and disability worldwide. Within its complex pathophysiological signatures, thrombosis and inflammation, that is, thromboinflammation, are highly interconnected processes leading to cerebral vessel occlusion, inflammatory responses, and severe neuronal damage following the ischemic event. Hence, we here review the most recent updates on thromboinflammatory-dependent mediators relevant after stroke focusing on recent discoveries on platelet modulation, a potential regulation of the innate and adaptive immune system in thromboinflammation, utterly providing a thorough up-to-date overview of all therapeutic approaches currently undergoing clinical trial.

Measurement of procoagulant platelets provides mechanistic insight and diagnostic potential in heparin-induced thrombocytopenia

BACKGROUND

Heparin-induced thrombocytopenia (HIT) is a prothrombotic, immune-mediated adverse drug reaction associated with high rates of thrombosis-related morbidity and mortality caused by FcγRIIa-activating pathogenic antibodies to PF4-heparin. Procoagulant platelets are a platelet subset that promote thrombin generation, are clinically relevant in prothrombotic diseases, and are formed when platelet G-protein-coupled receptor (GPCR) and ITAM-linked receptors are co-stimulated.

OBJECTIVES

We examined the procoagulant platelet response of healthy donors to platelet agonists in the presence of HIT plasma and determined the contribution of FcγRIIa.

PATIENTS/METHODS

Our previously established flow cytometry-based procoagulant platelet assay was modified to incorporate plasma samples, performed using FcγRIIa-responsive donor platelets. Plasma samples were serotonin-release assay-confirmed HIT (HIT+), or negative on HIT screening.

RESULTS

In response to GPCR stimulation, only HIT+ plasma produced a heparin-dependent sensitization that required active FcγRIIa. As a potential diagnostic tool, the procoagulant platelet assay achieved 98% accuracy in identifying clinically verified HIT when performed blinded to the diagnoses of a validation cohort. Samples inducing a higher procoagulant platelet response were more likely from patients with thrombotic complications. Thrombin stimulation markedly increased the procoagulant platelet response with HIT+ plasma that was heparin independent and only partially reversed by FcγRIIa blockade, possibly reflecting ongoing thrombotic risk after heparin cessation.

CONCLUSIONS

We demonstrate that HIT plasma together with platelet agonists increased the procoagulant platelet proportions, which may contribute to thrombotic risk in HIT. Targeting procoagulant platelet activation may represent a novel treatment strategy. This assay may be a rapid, clinically relevant functional assay for accurately detecting pathological HIT antibodies.

Beyond Hemostasis: Platelet Innate Immune Interactions and Thromboinflammation

There is accumulating evidence that platelets play roles beyond their traditional functions in thrombosis and hemostasis, e.g., in inflammatory processes, infection and cancer, and that they interact, stimulate and regulate cells of the innate immune system such as neutrophils, monocytes and macrophages. In this review, we will focus on platelet activation in hemostatic and inflammatory processes, as well as platelet interactions with neutrophils and monocytes/macrophages. We take a closer look at the contributions of major platelet receptors GPIb, α_IIbβ₃, TLT-1, CLEC-2 and Toll-like receptors (TLRs) as well as secretions from platelet granules on platelet-neutrophil aggregate and neutrophil extracellular trap (NET) formation in atherosclerosis, transfusion-related acute lung injury (TRALI) and COVID-19. Further, we will address platelet-monocyte and macrophage interactions during cancer metastasis, infection, sepsis and platelet clearance.

Nitrate Metabolism and Ischemic Cerebrovascular Disease: A Narrative Review

Inorganic and organic nitrates are present in vivo and in vitro. Inorganic nitrate is considered a pool of nitric oxide (NO), but it can be converted into nitrite and NO through various mechanisms. It plays an important role in the regulation of complex physiological and biochemical reactions, such as anti-inflammatory processes and the inhibition of platelet aggregation, which are closely related to the pathology and treatment of cerebrovascular disease. Ischemic cerebrovascular disease is characterized by high incidence, recurrence, and disability rates. Nitrate, nitrite, and NO were recently found to be involved in cerebrovascular disease. In this review, we describe the relationship between cerebrovascular disease and nitrate metabolism to provide a basis for further advances in laboratory and clinical medicine.

Dual antiplatelet therapy improves functional recovery and inhibits inflammation after cerebral ischemia/reperfusion injury

Background

Dual antiplatelet therapy with aspirin and clopidogrel (ASA + CPG) during the first 21 days has been shown to reduce the risk of major ischemic events in patients with transient ischemic attack (TIA) or minor stroke. However, the mechanisms underlying combination treatment with ASA + CPG in experimental ischemic stroke has not been fully elucidated.

Methods

Minor cerebral ischemia was induced in mice by transient distal middle cerebral artery occlusion (tdMCAO). Two doses of ASA + CPG (12 and 24 mg/kg/day) or vehicle were administered by gavage daily. Neurological behaviors were assessed using the modified Garcia scores, Rotarod test, Y maze, and open field test. Platelet function was assessed in vitro by flow cytometry and in vivo by bleeding and clotting time. The neutrophil ratio and the levels of inflammatory cytokines were measured by flow cytometry and the Meso Scale Discovery (MSD) electrochemilunimescence, respectively.

Results

Sensorimotor function was partially recovered with ASA + CPG treatment after ischemia. Anxiety levels and cognitive functions showed improvement in the ASA + CPG group at 12 mg/kg/day after 21 days. Both tail bleeding time and flow cytometry showed significantly decreased platelet function after ASA + CPG treatment. Notably, ASA + CPG at 12 mg/kg/day prolonged clotting time at 28 days after injury. Furthermore, the ratio of neutrophils, an indicator of inflammation, was reduced with 12 mg/kg/day ASA + CPG treatment in the bone marrow (BM) at 21 days and in the peripheral blood (PB) at 21 and 28 days after tdMCAO. Both doses of ASA + CPG decreased pro-inflammatory cytokine interleukin (IL)-6 expression 21 days after stroke. Taken together, these results demonstrated that combination treatment with ASA + CPG improved long-term neurological function after stroke and may inhibit platelet-neutrophil interaction by decreasing the concentration of pro-inflammatory cytokine, IL-6.

Conclusions

These findings indicate a neuroprotective effect of combination treatment with ASA + CPG for a duration of 21 days in an experimental acute minor stroke model. These findings provide further evidence that dual antiplatelet therapy may be a viable neuroprotective treatment to decrease the recurrence of stroke.

Neutrophil-Platelet Interactions as Novel Treatment Targets in Cardiovascular Disease

Neutrophils and platelets are among the most abundant cell types in peripheral blood and characterized by high plasticity and a readily available reservoir of surface proteins and secretable granule contents. Receptor-mediated activation and granule release predispose both cell types for rapid responses to various stimuli. While neutrophils provide the first line of defense to microbial infections and platelets are known for their aggregatory functions in hemostasis and thrombosis, research of the past decade has highlighted that both cell types jointly shape local and systemic immune responses and clot formation alike. Concomitant activation of neutrophils and platelets has been observed in a variety of cardiovascular diseases, including arterial and venous thrombosis, atherosclerosis as well as myocardial infarction and ischemia-reperfusion injury. In this review, we describe the mechanisms by which neutrophils and platelets interact physically, how release of granule contents and soluble molecules by either cell type affects the other and how this mutual activation supports the efficacy of immune responses. We go on to describe how activated platelets contribute to host defense by triggering neutrophil extracellular trap (NET) formation in a process termed immunothrombosis, which in turn promotes local platelet activation and coagulation. Further, we review current evidence of hazardous overactivation of either cell type and their respective role in cardiovascular disease, with a focus on thrombosis, myocardial infarction and ischemia-reperfusion injury, and describe how neutrophils and platelets shape thromboinflammation in COVID-19. Finally, we provide an overview of therapeutic approaches targeting neutrophil-platelet interactions as novel treatment strategy in cardiovascular disease.

Hsp47 Inhibitor Col003 Attenuates Collagen-Induced Platelet Activation and Cerebral Ischemic-Reperfusion Injury in Rats

Ischemic stroke is a major type of stroke worldwide currently without effective treatment, although antiplatelet therapy is an existing option for it. In previous studies, heat shock protein 47 (Hsp47) was found to be expressed on the surface of human and mice platelets and to strengthen the interaction between platelets and collagen. In recent years, Col003 was discovered to inhibit the interaction of Hsp47 with collagen. We evaluated whether the Hsp47 inhibitor Col003 is a promising therapeutic agent for ischemic stroke. Here, we first verified that Hsp47 is also expressed on the surface of rat platelets, and its inhibitor Col003 significantly inhibited thrombus formation in the FeCl₃-induced rat carotid arterial thrombus model. Both Col003 and clopidogrel did not alter the bleeding time or coagulation parameters, while aspirin increased the tail-bleeding time (p < 0.05). The low cytotoxicity level of Col003 to rat platelets and human liver cells was similar to those of aspirin and clopidogrel. Col003 inhibited collagen-induced platelet aggregation, adhesion, [Ca²⁺]_i mobilization, P-selectin expression, reactive oxygen species production and the downstream signal pathway of collagen receptors. The results of the middle cerebral artery occlusion model indicated that Col003 has a protective effect against cerebral ischemic-reperfusion injury in rats. The Hsp47 inhibitor Col003 exerted antiplatelet effect and protective effect against brain damage induced by ischemic stroke through the inhibition of glycoprotein VI (GPVI)and mitogen-activated protein kinase (MAPK) signaling events, which might yield a new antiplatelet agent and strategy to treat ischemic stroke.

Targeting neutrophils as a novel therapeutic strategy after stroke

Stroke is followed by an intricate immune interaction involving the engagement of multiple immune cells, including neutrophils. As one of the first responders recruited to the brain, the crucial roles of neutrophils in the ischemic brain damage are receiving increasing attention in recent years. Notably, neutrophils are not homogenous, and yet there is still a lack of full knowledge about the extent and impact of neutrophil heterogeneity. The biological understanding of the neutrophil response to both innate and pathological conditions is rapidly evolving as single-cell-RNA sequencing uncovers overall neutrophil profiling across maturation and differentiation contexts. In this review, we scrutinize the latest research that points to the multifaceted role of neutrophils in different conditions and summarize the regulatory signals that may determine neutrophil diversity. In addition, we list several potential targets or therapeutic strategies targeting neutrophils to limit brain damage following ischemic stroke.

Brothers in arms: platelets and neutrophils in ischemic stroke

PURPOSE OF REVIEW

In this review, we will describe how the combined ability of platelets and neutrophils to interact with each other drives ischemic stroke brain injury.

RECENT FINDINGS

Neutrophils are one of the first cells to respond during ischemic stroke. Although animals stroke models have indicated targeting neutrophils improves outcomes, clinical trials have failed to yield successful strategies. Platelets play a critical role in recruiting neutrophils to sites of injury by acting as a bridge to the injured endothelium. After initial platelet adhesion, neutrophils can rapidly bind platelets through P-selectin and glycoprotein Ibα. In addition, recent data implicated platelet phosphatidylserine as a novel key regulator of platelet-neutrophil interactions in the setting of ischemic stroke. Inhibition of procoagulant platelets decreases circulating platelet-neutrophil aggregates and thereby reduces infarct size. Platelet binding alters neutrophil function, which contributes to the injury associated with ischemic stroke. This includes inducing the release of neutrophil extracellular traps, which are neurotoxic and pro-thrombotic, leading to impaired stroke outcomes.

SUMMARY

Platelet-neutrophil interactions significantly contribute to the pathophysiology of ischemic stroke brain injury. Better understanding the mechanisms behind their formation and the downstream consequences of their interactions will lead to improved therapies for stroke patients.

Platelet Activation and Chemokine Release Are Related to Local Neutrophil-Dominant Inflammation During Hyperacute Human Stroke

Experimental evidence has emerged that local platelet activation contributes to inflammation and infarct formation in acute ischemic stroke (AIS) which awaits confirmation in human studies. We conducted a prospective observational study on 258 consecutive patients undergoing mechanical thrombectomy (MT) due to large-vessel-occlusion stroke of the anterior circulation (08/2018–05/2020). Intraprocedural microcatheter aspiration of 1 ml of local (occlusion condition) and systemic arterial blood samples (self-control) was performed according to a prespecified protocol. The samples were analyzed for differential leukocyte counts, platelet counts, and plasma levels of the platelet-derived neutrophil-activating chemokine C-X-C-motif ligand (CXCL) 4 (PF-4), the neutrophil attractant CXCL7 (NAP-2), and myeloperoxidase (MPO). The clinical-biological relevance of these variables was corroborated by specific associations with molecular-cellular, structural-radiological, hemodynamic, and clinical-functional parameters. Seventy consecutive patients fulfilling all predefined criteria entered analysis. Mean local CXCL4 (+ 39%: 571 vs 410 ng/ml, P = .0095) and CXCL7 (+ 9%: 693 vs 636 ng/ml, P = .013) concentrations were higher compared with self-controls. Local platelet counts were lower (− 10%: 347,582 vs 383,284/µl, P = .0052), whereas neutrophil counts were elevated (+ 10%: 6022 vs 5485/µl, P = 0.0027). Correlation analyses revealed associations between local platelet and neutrophil counts (r = 0.27, P = .034), and between CXCL7 and MPO (r = 0.24, P = .048). Local CXCL4 was associated with the angiographic degree of reperfusion following recanalization (r =  − 0.2523, P = .0479). Functional outcome at discharge correlated with local MPO concentrations (r = 0.3832, P = .0014) and platelet counts (r = 0.288, P = .0181). This study provides human evidence of cerebral platelet activation and platelet-neutrophil interactions during AIS and points to the relevance of per-ischemic thrombo-inflammatory mechanisms to impaired reperfusion and worse functional outcome following recanalization.

Platelet Innate Immune Receptors and TLRs: A Double-Edged Sword

Platelets are hematopoietic cells whose main function has for a long time been considered to be the maintenance of vascular integrity. They have an essential role in the hemostatic response, but they also have functional capabilities that go far beyond it. This review will provide an overview of platelet functions. Indeed, stress signals may induce platelet apoptosis through proapoptotis or hemostasis receptors, necrosis, and even autophagy. Platelets also interact with immune cells and modulate immune responses in terms of activation, maturation, recruitment and cytokine secretion. This review will also show that platelets, thanks to their wide range of innate immune receptors, and in particular toll-like receptors, and can be considered sentinels actively participating in the immuno-surveillance of the body. We will discuss the diversity of platelet responses following the engagement of these receptors as well as the signaling pathways involved. Finally, we will show that while platelets contribute significantly, via their TLRs, to immune response and inflammation, these receptors also participate in the pathophysiological processes associated with various pathogens and diseases, including cancer and atherosclerosis.

New Insight Into Neutrophils: A Potential Therapeutic Target for Cerebral Ischemia

Ischemic stroke is one of the main issues threatening human health worldwide, and it is also the main cause of permanent disability in adults. Energy consumption and hypoxia after ischemic stroke leads to the death of nerve cells, activate resident glial cells, and promote the infiltration of peripheral immune cells into the brain, resulting in various immune-mediated effects and even contradictory effects. Immune cell infiltration can mediate neuronal apoptosis and aggravate ischemic injury, but it can also promote neuronal repair, differentiation and regeneration. The central nervous system (CNS), which is one of the most important immune privileged parts of the human body, is separated from the peripheral immune system by the blood-brain barrier (BBB). Under physiological conditions, the infiltration of peripheral immune cells into the CNS is controlled by the BBB and regulated by the interaction between immune cells and vascular endothelial cells. As the immune response plays a key role in regulating the development of ischemic injury, neutrophils have been proven to be involved in many inflammatory diseases, especially acute ischemic stroke (AIS). However, neutrophils may play a dual role in the CNS. Neutrophils are the first group of immune cells to enter the brain from the periphery after ischemic stroke, and their exact role in cerebral ischemia remains to be further explored. Elucidating the characteristics of immune cells and their role in the regulation of the inflammatory response may lead to the identification of new potential therapeutic strategies. Thus, this review will specifically discuss the role of neutrophils in ischemic stroke from production to functional differentiation, emphasizing promising targeted interventions, which may promote the development of ischemic stroke treatments in the future.

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.

Systemic Immune-Inflammation Index Predicts 3-Month Functional Outcome in Acute Ischemic Stroke Patients Treated with Intravenous Thrombolysis

Background and Purpose

Systemic immune-inflammation index (SII), a novel inflammation index derived from counts of circulating platelets, neutrophils and lymphocytes, has been studied in developing incident cancer. However, the clinical value of SII in acute ischemic stroke (AIS) patients had not been further investigated. Therefore, we aimed to explore the association between SII and severity of stroke as well as 3-month outcome of AIS patients.

Methods

A total of 216 AIS patients receiving intravenous thrombolysis (IVT) and 875 healthy controls (HCs) were retrospectively recruited. Blood samples were collected within 24h after admission. Severity of stroke was assessed by the National Institute of Health stroke scale (NIHSS) scores on admission and poor 3-month functional outcome was defined as Modified Rankin Scale (mRS) > 2.

Results

SII levels in AIS patients were higher than in HCs. The cut-off value of SII is 545.14×10⁹/L. Patients with SII > 545.14×10⁹/L had higher NIHSS scores (median: 5 vs 9, p < 0.001), a positive correlation between SII and NIHSS was observed (rs = 0.305, p < 0.001). Multivariate logistic regression analyses showed that high SII was one of the independent risk factors for poor prognosis at 3 months of AIS patients (OR = 3.953, 95% CI = 1.702-9.179, p = 0.001). The addition of SII to the conventional prognostic model improved the reclassification (but not discrimination) of the functional outcome (net reclassification index 39.3%, p = 0.007).

Conclusion

SII is correlated with stroke severity at admission and can be a novel prognostic biomarker for AIS patients treated with IVT.

Endogenous neuroprotective mechanism of ATP2B1 in transcriptional regulation of ischemic preconditioning

Ischemic stroke is the main cause of disability and mortality in the world. Clinical studies have shown that patients who undergo mild transient ischemic attack (TIA) before more severe ischemic stroke have lower clinical severity of stroke and better functional prognosis. This phenomenon is called ischemic preconditioning (IPC). IPC is a powerful intrinsic protection of the brain against ischemic injury, but the underlying mechanism of IPC-mediated endogenous protection of the brain is not clear.

METHODS

Using transcriptome method, we sequenced the serum of 3 stroke patients with progenitor TIA and 3 stroke patients without prodromal TIA. We explored the expression profiles of miRNAs and mRNAs in response to IPC, and predicted the regulatory pathway of IPC related genes and their expression in cerebral neurons. The methylation consistent expression of IPC-related gene ATP2B1 in blood and brain and alternative polyadenylate (APA) analysis were used to identify the pathway and molecular mechanism of endogenous neuroprotection of IPC.

RESULTS

We found that the brain protective effect of IPC was related to platelet homeostasis and Ca²⁺ concentration. IPC-related gene ATP2B1 was highly expressed in γ-aminobutyric acid (GABA)-containing neurons in the brain. From the mechanism, we speculated that ATP2B1 was representative of the same methylation in blood and brain and was affected by alternative polyadenylation.

CONCLUSION

We speculate that IPC can induce alternative polyadenylation of ATP2B1 and trigger the mechanism of brain endogenous neuroprotection by regulating the decrease of Ca²⁺ concentration in platelet homeostasis pathway and the activation of GABAB receptor.

The von Willebrand Factor A1 domain mediates thromboinflammation, aggravating ischemic stroke outcome in mice

von Willebrand factor (VWF) plays an important role in ischemic stroke. However, the exact mechanism by which VWF mediates progression of ischemic stroke brain damage is not completely understood. Using flow cytometric analysis of single cell suspensions prepared from brain tissue and immunohistochemistry, we investigated the potential inflammatory mechanisms by which VWF contributes to ischemic stroke brain damage in a mouse model of cerebral ischemia/reperfusion injury. Twenty-four hours after stroke, flow cytometric analysis of brain tissue revealed that overall white blood cell recruitment in the ipsilesional brain hemisphere of VWF KO mice was 2 times lower than WT mice. More detailed analysis showed a specific reduction of proinflammatory monocytes, neutrophils and T-cells in the ischemic brain of VWF KO mice compared to WT mice. Interestingly, histological analysis revealed a substantial number of neutrophils and T-cells still within the microcirculation of the stroke brain, potentially contributing to the no-reflow phenomenon. Specific therapeutic targeting of the VWF A1 domain in WT mice resulted in reduced immune cell numbers in the affected brain and protected mice from ischemic stroke brain damage. More specifically, recruitment of proinflammatory monocytes was reduced two-fold, neutrophil recruitment was reduced five-fold and T-cell recruitment was reduced two-fold in mice treated with a VWF A1-targeting nanobody compared to mice receiving a control nanobody. In conclusion, our data identify a potential role for VWF in the recruitment of proinflammatory monocytes, neutrophils and T-cells to the ischemic brain via a mechanism that is mediated by its A1 domain.

Thrombocytopathies: Not Just Aggregation Defects-The Clinical Relevance of Procoagulant Platelets

Platelets are active key players in haemostasis. Qualitative platelet dysfunctions result in thrombocytopathies variously characterized by defects of their adhesive and procoagulant activation endpoints. In this review, we summarize the traditional platelet defects in adhesion, secretion, and aggregation. In addition, we review the current knowledge about procoagulant platelets, focusing on their role in bleeding or thrombotic pathologies and their pharmaceutical modulation. Procoagulant activity is an important feature of platelet activation, which should be specifically evaluated during the investigation of a suspected thrombocytopathy.

Hyperglycemia exacerbates ischemic stroke outcome independent of platelet glucose uptake

OBJECTIVE

Hyperglycemia is a common comorbidity for ischemic stroke and is associated with worsened neurological outcomes. Platelets are central mediators of ischemic stroke and hyperglycemia mediates platelet hyperactivity. In this study, we investigated the contribution of platelet glucose metabolism to ischemic stroke.

METHODS

Mice lacking both Glut1 and Glut3 specifically in platelets (DKO) and their littermate controls (WT) were subjected to 1-hour transient middle cerebral artery occlusion under normoglycemic and streptozotocin-induced hyperglycemic conditions after which stroke outcomes, platelet activation, and platelet-neutrophil aggregate (PNA) formation were examined.

RESULTS

Under normoglycemic conditions, DKO mice were protected from ischemic stroke with smaller brain infarct volumes and improved cerebral blood flow. In addition, DKO mice had reduced platelet activation, PNA, and cerebral neutrophil recruitment after stroke. Hyperglycemia significantly increased infarct size and cerebral Evans blue extravasation and worsened neurological outcomes and cerebral blood flow in both WT and DKO mice, abolishing the protective effect witnessed under normoglycemic conditions. Flow cytometric analysis after stroke demonstrated increased platelet activation and neutrophil trafficking to the brain, independent of platelet glucose metabolism. Finally, platelets from healthy DKO mice were unable to become procoagulant upon dual agonist stimulation. Conversely, hyperglycemia increased platelet mitochondrial reactive oxygen species production which potentiated procoagulant platelet formation in WT mice and restored procoagulant platelet formation in DKO mice.

CONCLUSION

Hyperglycemia aggravates ischemic stroke outcome independent of platelet glucose uptake. Furthermore, we demonstrated that hyperglycemia primes procoagulant platelet formation. This underlines the therapeutic potential for strategies targeting procoagulant platelet formation for the treatment of acute ischemic stroke.

Dynamic capillary stalls in reperfused ischemic penumbra contribute to injury: A hyperacute role for neutrophils in persistent traffic jams

Ever since the introduction of thrombolysis and the subsequent expansion of endovascular treatments for acute ischemic stroke, it remains to be identified why the actual outcomes are less favorable despite recanalization. Here, by high spatio-temporal resolution imaging of capillary circulation in mice, we introduce the pathological phenomenon of dynamic flow stalls in cerebral capillaries, occurring persistently in salvageable penumbra after reperfusion. These stalls, which are different from permanent cellular plugs of no-reflow, were temporarily and repetitively occurring in the capillary network, impairing the overall circulation like small focal traffic jams. In vivo microscopy in the ischemic penumbra revealed leukocytes traveling slowly through capillary lumen or getting stuck, while red blood cell flow was being disturbed in the neighboring segments under reperfused conditions. Stall dynamics could be modulated, by injection of an anti-Ly6G antibody specifically targeting neutrophils. Decreased number and duration of stalls were associated with improvement in penumbral blood flow within 2-24 h after reperfusion along with increased capillary oxygenation, decreased cellular damage and improved functional outcome. Thereby, dynamic microcirculatory stall phenomenon can be a contributing factor to ongoing penumbral injury and is a potential hyperacute mechanism adding on previous observations of detrimental effects of activated neutrophils in ischemic stroke.