CD40L Priming of Platelets via NF-κB Activation is CD40- and TAK1-Dependent

Modulating Immune Responses: The Double-Edged Sword of Platelet CD40L

The CD40-CD40L receptor ligand pair plays a fundamental role in the modulation of the innate as well as the adaptive immune response, regulating monocyte, T and B cell activation, and antibody isotype switching. Although the expression and function of the CD40-CD40L dyad is mainly attributed to the classical immune cells, the majority of CD40L is expressed by activated platelets, either in a membrane-bound form or shed as soluble molecules in the circulation. Platelet-derived CD40L is involved in the communication with different immune cell subpopulations and regulates their functions effectively. Thus, platelet CD40L contributes to the containment and clearance of bacterial and viral infections, and additionally guides leukocytes to sites of infection. However, platelet CD40L promotes inflammatory cellular responses also in a pathophysiological context. For example, in HIV infections, platelet CD40L is supportive of neuronal inflammation, damage, and finally HIV-related dementia. In sepsis, platelet CD40L can induce extensive endothelial and epithelial damage resulting in barrier dysfunction of the gut, whereby the translocation of microbiota into the circulation further aggravates the uncontrolled systemic inflammation. Nevertheless, a distinct platelet subpopulation expressing CD40L under septic conditions can attenuate systemic inflammation and reduce mortality in mice. This review focuses on recent findings in the field of platelet CD40L biology and its physiological and pathophysiological implications, and thereby highlights platelets as vital immune cells that are essential for a proper immune surveillance. In this context, platelet CD40L proves to be an interesting target for various inflammatory diseases. However, either an agonism or a blockade of CD40L needs to be well balanced since both the approaches can cause severe adverse events, ranging from hyperinflammation to immune deficiency. Thus, an interference in CD40L activities should be likely done in a context-dependent and timely restricted manner.

The critical role of neutrophil-endothelial cell interactions in sepsis: new synergistic approaches employing organ-on-chip, omics, immune cell phenotyping and in silico modeling to identify new therapeutics

Sepsis is a global health concern accounting for more than 1 in 5 deaths worldwide. Sepsis is now defined as life-threatening organ dysfunction caused by a dysregulated host response to infection. Sepsis can develop from bacterial (gram negative or gram positive), fungal or viral (such as COVID) infections. However, therapeutics developed in animal models and traditional in vitro sepsis models have had little success in clinical trials, as these models have failed to fully replicate the underlying pathophysiology and heterogeneity of the disease. The current understanding is that the host response to sepsis is highly diverse among patients, and this heterogeneity impacts immune function and response to infection. Phenotyping immune function and classifying sepsis patients into specific endotypes is needed to develop a personalized treatment approach. Neutrophil-endothelium interactions play a critical role in sepsis progression, and increased neutrophil influx and endothelial barrier disruption have important roles in the early course of organ damage. Understanding the mechanism of neutrophil-endothelium interactions and how immune function impacts this interaction can help us better manage the disease and lead to the discovery of new diagnostic and prognosis tools for effective treatments. In this review, we will discuss the latest research exploring how in silico modeling of a synergistic combination of new organ-on-chip models incorporating human cells/tissue, omics analysis and clinical data from sepsis patients will allow us to identify relevant signaling pathways and characterize specific immune phenotypes in patients. Emerging technologies such as machine learning can then be leveraged to identify druggable therapeutic targets and relate them to immune phenotypes and underlying infectious agents. This synergistic approach can lead to the development of new therapeutics and the identification of FDA approved drugs that can be repurposed for the treatment of sepsis.

LncRNA MSTRG.22719.16 mediates the reduction of enoxaparin sodium high-viscosity bone cement-induced thrombosis by targeting the ocu-miR-326-5p/CD40 axis

OBJECTIVE

Polymethylmethacrylate (PMMA) bone cement promotes the development of local thrombi. Our study found that a novel material, ES-PMMA bone cement, can reduce local thrombosis. We used a simple and reproducible animal model to confirm the reduction in local thrombosis and explored the associated molecular mechanism.

METHODS

New Zealand rabbits, which were used to model thrombosis using extracorporeal carotid artery shunts, were divided into the following two groups, with 3 rabbits in each group: the PMMA bone cement group and the ES-PMMA bone cement group. Four hours after modelling, experimental samples, including thrombotic and vascular tissues, were collected. Thrombotic samples from the PMMA group and ES-PMMA group were subjected to lncRNA sequencing, and a lncRNA microarray was used to screen the differentially expressed lncRNAs. The expression of thrombomodulin in endothelial cells was quantified in vascular tissue samples. Differences in the lncRNA expression profiles between the thrombotic samples of the PMMA group and ES-PMMA group were assessed by base-to-base alignment in the intergenic regions of genomes. The lncRNA-miRNA-mRNA competitive endogenous RNA (ceRNA) network was established in light of ceRNA theory. Thrombosis was observed in the PMMA group and ES-PMMA group.

RESULTS

The thrombotic weight was 0.00706 ± 0.00136 g/cm in the PMMA group and 0.00551 ± 0.00115 g/cm in the ES-PMMA group. Quantitative real-time polymerase chain reaction (RT-q-CR) and Western blotting revealed that the expression of CD40, which can regulate thrombosis in vascular endothelial cells, was significantly lower in the ES-PMMA group than in the PMMA group. High-throughput sequencing was used to identify 111 lncRNAs with lower expression in the ES-PMMA group than in the PMMA group. Through bioinformatics investigation, lncRNA MSTRG22719.16/ocu-miR-326-5p/CD40 binding sites were selected. Fluorescent in situ RNA hybridization (FISH) was performed to verify the lower expression of lncRNA MSTRG.22719.16 in vascular tissues from the ES-PMMA group. A dual-luciferase reporter gene assay was applied to verify that ocu-miR-326-5p binds the CD40 3'-UTR and targets lncRNA MSTRG.22719.16.

CONCLUSION

Compared with PMMA bone cement, ES-PMMA bone cement can reduce thrombosis through the lncRNA MSTRG.22719.16/ocu-miR-326-5p/CD40 axis.

Bazedoxifene attenuates intestinal injury in sepsis by suppressing the NF-κB/NLRP3 signaling pathways

Acute inflammatory injury is the primary cause of sepsis, leading to various organ failures. Bazedoxifene (BAZ) has been proven to have anti-inflammatory effects. However, its effects on sepsis-induced intestinal injury are unclear. Here, we demonstrated the beneficial effects of BAZ on intestinal injury and explored the underlying mechanisms using cecal ligation and perforation (CLP)-mediated sepsis mouse model and in vitro cultured intestinal epithelial MODE-K cells. We found that BAZ elevated the survival rate of septic mice and attenuated CLP-triggered intestinal damage. BAZ inhibited intestinal inflammation and restored the impaired intestinal barriers in CLP mice. The mechanistic study in lipopolysaccharide (LPS)/adenosine triphosphate (ATP)-stimulated MODE-K cells showed that BAZ significantly downregulated the expression of NOD-like receptor protein 3 (NLRP3), interleukin-1β (IL-1β), caspase-1, and gasdermin D (GSDMD), and markedly reduced the phosphorylation of molecules in the nuclear factor kappa B (NF-κB) pathway. Moreover, BAZ prominently rescued the decreased viability of MODE-K cells and reduced lactate dehydrogenase (LDH) release upon LPS/ATP challenge. However, BAZ did not affect the inflammasome assembly, as evidenced by the lack of changes in ASC (apoptosis speck-like protein containing a CARD) speck formation. Our results suggest that BAZ relieves inflammation and intestinal barrier function disruption by suppressing the NF-κB/NLRP3 signaling pathways. Therefore, BAZ is a potential therapeutic candidate for treating intestinal injury in sepsis.

Intracellular communication and immunothrombosis in sepsis

Inflammation and coagulation are the critical responses to infection that include leukocytes, platelets, and vascular endothelial cells responding in concert to eradicate the invading pathogen. In sepsis, a variety of cell surface receptors, including toll-like receptors, Fcγ-receptors, G-protein-coupled receptors, and adhesion receptors, detect the pathogens and elicit thromboinflammatory responses. Concurrently, the molecular patterns released from host damaged cells accelerate the immune responses through binding to the same pattern recognition receptors. Cytokines, chemokines, and extracellular vesicles are important mediators for amplifying the responses to distant cells as part of the systemic response to infections. At the same time, cells communicate with each other via direct contact, adhesion molecules, paracrine mediators, and tunneling nanotubes, which are important for regulating inflammation and thrombus formation. Despite increasing attention to immunothrombosis in sepsis, these close communication systems are less understood but play a critical role in host defense mechanisms. In this review, cellular activation and direct intercellular communication systems in sepsis with a focus on the coagulation response will be considered.

Platelets as Key Factors in Inflammation: Focus on CD40L/CD40

Platelets are anucleate cytoplasmic fragments derived from the fragmentation of medullary megakaryocytes. Activated platelets adhere to the damaged endothelium by means of glycoproteins on their surface, forming the platelet plug. Activated platelets can also secrete the contents of their granules, notably the growth factors contained in the α-granules, which are involved in platelet aggregation and maintain endothelial activation, but also contribute to vascular repair and angiogenesis. Platelets also have a major inflammatory and immune function in antibacterial defence, essentially through their Toll-like Receptors (TLRs) and Sialic acid-binding immunoglobulin-type lectin (SIGLEC). Platelet activation also contributes to the extensive release of anti- or pro-inflammatory mediators such as IL-1β, RANTES (Regulated on Activation, Normal T Expressed and Secreted) or CD154, also known as the CD40-ligand. Platelets are involved in the direct activation of immune cells, polynuclear neutrophils (PNNs) and dendritic cells via the CD40L/CD40 complex. As a general rule, all of the studies presented in this review show that platelets are capable of covering most of the stages of inflammation, primarily through the CD40L/CD40 interaction, thus confirming their own role in this pathophysiological condition.

Serum CD40L, ST2, IL-6, and CRP serving as biomarkers for acute coronary syndrome

To analyze the diagnostic value of CD40 ligand (CD40L), soluble growth stimulating expression gene 2 protein (ST2), interleukin-6 (IL-6), and C-reactive protein (CRP) are used in patients with acute coronary syndrome (ACS). Serum samples were collected from 259 ACS patients admitted to our hospital. Additionally, 119 healthy individuals who received physical examination in the hospital at the same time period were included as normal control. The levels of CD40L, ST2, IL-6, and CRP in 259 patients with ACS and 119 healthy subjects were detected by ELISA. The levels of CD40L, ST2, IL-6, and CRP were significantly increased in unstable angina (UA) patients, while ST2, CRP, and IL-6 were significantly elevated in acute myocardial infarction (AMI) patients. Pearson correlation analysis showed that ST2 was also closely related to CRP in ACS patients, while ST2 was positively correlated with creatine kinase (CK), creatine kinase isoenzyme (CK-MB), and troponin I (cTnI) in AMI patients. The levels of glucose (GLU) and low-density lipoprotein cholesterol (LDL-c) were significantly decreased, while the levels of high-density lipoprotein cholesterol (HDL-c) were significantly increased in AMI patients treated with stent implantation. Furthermore, the level of serum CD40 L was significantly elevated in coronary heart disease (CHD) patients treated with stent implantation, while the levels of ST2 and IL-6 in AMI patients treated with the stent implantation decreased significantly. The levels of inflammatory factors significantly changed in patients with ACS. These inflammatory factors may involve in the pathological progression of ACS and can be used as diagnostic indexes for ACS.

Clinical and Non-Clinical Determinants of the Effect of Mechanical Thrombectomy and Post-Stroke Functional Status of Patients in Short and Long-Term Follow-Up

To date, inconsistent results evaluating the effect of parameters on mechanical thrombectomy (MT) outcomes in stroke-patients have been published. This study aimed to identify the key parameters for functional status after MT in stroke-patients in short and long-term follow-up.

METHOD

The study analysis focused on the relevance of selected clinical and non-clinical parameters to the functional status of the patients after MT.

RESULTS

417 stroke-patients (mean age 67.8 ± 13.2 years) were qualified. Atrial fibrillation, and leukocytosis were significant for the neurological status on the first day of stroke (p = 0.036, and p = 0.0004, respectively). The parameters with the strongest effect on the functional status on day 10 were: age (p = 0.009), NIHSS (p = 0.002), hyperglycemia (p = 0.009), the result in TICI (p = 0.046), and first pass effect (p = 0.043). The parameters with the strongest effect on the functional status on day 365 were: age and NIHSS on the first day of stroke (p = 0.0002 and 0.002, respectively). Leukocytosis and the neurological status at baseline were key parameters associated with ICB after MT (p = 0.007 and p = 0.003, respectively).

CONCLUSIONS

Age and neurological status in the ultra-acute phase of stroke are crucial for the functional status in short and long-term observations of patients treated with mechanical thrombectomy. Atrial fibrillation, hyperglycemia, and inflammatory state are relevant to the short-term post-stroke functional status. First pass effect and the degree of post-interventional reperfusion are important technical parameters to the short-term functional status. Neurological status and white blood count during the acute phase are associated with a high rate of post-procedural intracranial bleeding.

Novel peripheral blood cell ratios: Effective 3-month post-mechanical thrombectomy prognostic biomarkers for acute ischemic stroke patients

BACKGROUND

Red blood cell distribution width to platelet ratio (RPR), Monocyte to high-density lipoprotein ratio (MHR), and Neutrophil to lymphocyte ratio (NLR) are novel inflammatory biomarkers in laboratory tests, which are associated with clinical outcomes in malignancy, cardiovascular and cerebrovascular diseases. This study aimed to determine their predictive value for the prognosis of acute ischemic stroke after mechanical thrombectomy (MT).

METHODS

A total of 286 patients with acute ischemic stroke (AIS) admitted to a tertiary stroke center in China between January 2018 and February 2020 were treated by MT. Demographic characteristics, risk factors, clinical data, laboratory parameters, and clinical outcomes were recorded. The clinical outcome was disability or death at discharge or 90 days (defined as a modified Rankin Scale score of 3-6). The relationship between RPR, MHR, and NLR and functional outcomes was investigated by binary Logistic regression analysis, and further assessed by receiver operating characteristic curve (ROC). The Kaplan-Meier method was used to analyze the survival rate of prognosis factors.

RESULTS

A total of 286 patients with AIS underwent MT (median age, 70.00; Interquartile range [IQR], 63.00-77.00; 41.6% female). Patients with unfavorable outcome showed higher RPR, MHR, and NLR than those with favorable outcome (RPR, [8.63; IQR, 6.30-10.78] vs [6.17; IQR, 5.11-7.35], P < 0.001; MHR, [0.40; IQR, 0.31-0.53] vs [0.34; IQR, 0.27-0.47], P = 0.005; NLR, [5.28; IQR, 3.63-8.02] vs [3.44; IQR, 2.63-4.63], P < 0.001). In multivariate and ROC curve analysis, higher RPR (>8.565) (odds ratio [OR], 1.671; 95% confidence interval [CI], 1.127-2.479; P = 0.011) and higher MHR (>0.368) (OR, 9.374; 95% CI, 1.160-75.767; P = 0.036), higher NLR (>4.030) (OR, 1.957; 95% CI, 1.382-2.770; P < 0.001) were independently associated with unfavorable outcome. The combined predictive value of the three indexes was higher than that of a single index. Kaplan-Meier survival curve analysis showed that the 90-day survival rate (82.1% vs 66.2%) was significantly different between the low RPR group and the high RPR group (χ² = 4.960, P = 0.026).

CONCLUSION

Higher RPR, MHR, and NLR might be independent risk factors for predicting 3-month poor prognosis in patients with AIS who underwent MT.

The Role of the Proteasome in Platelet Function

Platelets are megakaryocyte-derived acellular fragments prepped to maintain primary hemostasis and thrombosis by preserving vascular integrity. Although they lack nuclei, platelets harbor functional genomic mediators that bolster platelet activity in a signal-specific manner by performing limited de novo protein synthesis. Furthermore, despite their limited protein synthesis, platelets are equipped with multiple protein degradation mechanisms, such as the proteasome. In nucleated cells, the functions of the proteasome are well established and primarily include proteostasis among a myriad of other signaling processes. However, the role of proteasome-mediated protein degradation in platelets remains elusive. In this review article, we recapitulate the developing literature on the functions of the proteasome in platelets, discussing its emerging regulatory role in platelet viability and function and highlighting how its functional coupling with the transcription factor NF-κB constitutes a novel potential therapeutic target in atherothrombotic diseases.

Platelet Proteomes, Pathways, and Phenotypes as Informants of Vascular Wellness and Disease

Platelets rapidly undergo responsive transitions in form and function to repair vascular endothelium and mediate hemostasis. In contrast, heterogeneous platelet subpopulations with a range of primed or refractory phenotypes gradually arise in chronic inflammatory and other conditions in a manner that may indicate or support disease. Qualitatively distinguishable platelet phenotypes are increasingly associated with a variety of physiological and pathological circumstances; however, the origins and significance of platelet phenotypic variation remain unclear and conceptually vague. As changes in platelet function in disease exhibit many similarities to platelets following the activation of platelet agonist receptors, the intracellular responses of platelets common to hemostasis and inflammation may provide insights to the molecular basis of platelet phenotype. Here, we review concepts around how protein-level relations-from platelet receptors through intracellular signaling events-may help to define platelet phenotypes in inflammation, immune responses, aging, and other conditions. We further discuss how representing systems-wide platelet proteomics data profiles as circuit-like networks of causally related intracellular events, or, pathway maps, may inform molecular definitions of platelet phenotype. In addition to offering insights into platelets as druggable targets, maps of causally arranged intracellular relations underlying platelet function can also advance precision and interceptive medicine efforts by leveraging platelets as accessible, dynamic, endogenous, circulating biomarkers of vascular wellness and disease. Graphic Abstract: A graphic abstract is available for this article.

Biomarkers of Platelet Activation and Their Prognostic Value in Patients With Sepsis-Associated Disseminated Intravascular Coagulopathy

Sepsis-associated disseminated intravascular coagulation (DIC) is related to marked hemostatic changes such as transient thrombocytopenia secondary to the endogenous activation and consumption of platelets. This study measured markers of platelet function in 103 adult ICU patients with clinically established sepsis-associated DIC to determine the biomarker association with disease severity. Patients were categorized as having no DIC, nonovert DIC, or overt DIC using the International Society of Thrombosis and Hemostasis scoring system. Plasma levels of CD40L, platelet factor 4 (PF4), platelet-derived microparticles, and microparticle-associated tissue factor were quantified. Markers of platelet activation were significantly elevated in patients with DIC compared to healthy individuals. This increase was independent of platelet count. Levels of PF4 differed based on the severity of DIC and differentiated nonsurvivors and survivors. These findings suggest that the markers of platelet activation in DIC may not be regulated by the number of circulating platelets and may be independent of the factors leading to their consumption.

IL-1 and CD40/CD40L platelet complex: elements of induction of Crohn's disease and new therapeutic targets

Ulcerative colitis (UC) and Crohn's disease (CD) are chronic and multifactorial diseases that affect the intestinal tract, both characterized by recurrent inflammation of the intestinal mucosa, resulting in abdominal pain, diarrhea, vomiting and, rectal bleeding. Inflammatory bowel diseases (IBD) regroup these two disorders. The exact pathological mechanism of IBD remains ambiguous and poorly known. In genetically predisposed patients, defects in intestinal mucosal barrier are due to an uncontrolled inflammatory response to normal flora. In addition to the genetic predisposition, these defects could be triggered by environmental factors or by a specific lifestyle which is widely accepted as etiological hypothesis. The involvement of the CD40/CD40L platelet complex in the development of IBD has been overwhelmingly demonstrated. CD40L is climacteric in cell signalling in innate and adaptive immunity, the CD40L expression on the platelet cell surface gives them an immunological competence. The IL-1, a major inflammation mediator could be involved in different ways in the development of IBD. Here, we provide a comprehensive review regarding the role of platelet CD40/CD40L in the pathophysiological effect of IL-1 in the development of Crohn's disease (CD). This review could potentially help future approaches aiming to target these two pathways for therapeutic purposes and elucidate the immunological mechanisms driving gut inflammation.

Deciphering the Role of the Coagulation Cascade and Autophagy in Cancer-Related Thrombosis and Metastasis

Thrombotic complications are the second leading cause of death among oncology patients worldwide. Enhanced thrombogenesis has multiple origins and may result from a deregulation of megakaryocyte platelet production in the bone marrow, the synthesis of coagulation factors in the liver, and coagulation factor signaling upon cancer and the tumor microenvironment (TME). While a hypercoagulable state has been attributed to factors such as thrombocytosis, enhanced platelet aggregation and Tissue Factor (TF) expression on cancer cells, further reports have suggested that coagulation factors can enhance metastasis through increased endothelial-cancer cell adhesion and enhanced endothelial cell activation. Autophagy is highly associated with cancer survival as a double-edged sword, as can both inhibit and promote cancer progression. In this review, we shall dissect the crosstalk between the coagulation cascade and autophagic pathway and its possible role in metastasis and cancer-associated thrombosis formation. The signaling of the coagulation cascade through the autophagic pathway within the hematopoietic stem cells, the endothelial cell and the cancer cell are discussed. Relevant to the coagulation cascade, we also examine the role of autophagy-related pathways in cancer treatment. In this review, we aim to bring to light possible new areas of cancer investigation and elucidate strategies for future therapeutic intervention.

Aspirin Reduces the Potentiating Effect of CD40L on Platelet Aggregation via Inhibition of Myosin Light Chain

Background

Antiplatelet therapy with aspirin (acetylsalicylic acid [ASA]) is less efficient in some coronary patients, which increases their risk of developing thrombosis. Elevated blood levels of thromboinflammatory mediators, like soluble CD40L (sCD40L), may explain such variabilities. We hypothesized that in the presence of elevated levels of sCD40L, the efficacy of ASA may vary and aimed to determine the effects of ASA on CD40L signaling and aggregation of platelets.

Methods and Results

The effects of ASA on CD40L‐treated human platelets, in response to suboptimal concentrations of collagen or thrombin, were assessed at levels of aggregation, thromboxane A₂ secretion, and phosphorylation of p38 mitogen‐activated protein kinase, nuclear factor kappa B, transforming growth factor‐β–activated kinase 1, and myosin light chain. sCD40L significantly elevated thromboxane A₂ secretion in platelets in response to suboptimal doses of collagen and thrombin, which was reversed by ASA. ASA did not inhibit the phosphorylation of p38 mitogen‐activated protein kinase, nuclear factor kappa B, and transforming growth factor‐β–activated kinase 1, with sCD40L stimulation alone or with platelet agonists. sCD40L potentiated platelet aggregation, an effect completely reversed and partially reduced by ASA in response to a suboptimal dose of collagen and thrombin, respectively. The effects of ASA in sCD40L‐treated platelets with collagen were related to inhibition of platelet shape change and myosin light chain phosphorylation.

Conclusions

ASA does not affect platelet sCD40L signaling but prevents its effect on thromboxane A₂ secretion and platelet aggregation in response to collagen, via a mechanism implying inhibition of myosin light chain. Targeting the sCD40L axis in platelets may have a therapeutic potential in patients with elevated levels of sCD40L and who are nonresponsive or less responsive to ASA.

Role of NF-κB in Platelet Function

Platelets are megakaryocyte-derived fragments lacking nuclei and prepped to maintain primary hemostasis by initiating blood clots on injured vascular endothelia. Pathologically, platelets undergo the same physiological processes of activation, secretion, and aggregation yet with such pronouncedness that they orchestrate and make headway the progression of atherothrombotic diseases not only through clot formation but also via forcing a pro-inflammatory state. Indeed, nuclear factor-κB (NF-κB) is largely implicated in atherosclerosis and its pathological complication in atherothrombotic diseases due to its transcriptional role in maintaining pro-survival and pro-inflammatory states in vascular and blood cells. On the other hand, we know little on the functions of platelet NF-κB, which seems to function in other non-genomic ways to modulate atherothrombosis. Therein, this review will resemble a rich portfolio for NF-κB in platelets, specifically showing its implications at the levels of platelet survival and function. We will also share the knowledge thus far on the effects of active ingredients on NF-κB in general, as an extrapolative method to highlight the potential therapeutic targeting of NF-κB in coronary diseases. Finally, we will unzip a new horizon on a possible extra-platelet role of platelet NF-κB, which will better expand our knowledge on the etiology and pathophysiology of atherothrombosis.