Platelet-derived chemokines: pathophysiology and therapeutic aspects

How to explain the beneficial effects of platelet-rich plasma

Platelet-rich plasma (PRP) is the platelet and leukocyte-containing plasmatic fraction of anticoagulated autologous blood. While evidence supporting the clinical use of PRP in dentistry is low, PRP is widely used in sports medicine, orthopedics, and dermatology. Its beneficial activity is commonly attributed to the growth factors released from platelets accumulating in PRP; however, evidence is indirect and not comprehensive. There is thus a demand to revisit PRP with respect to basic and translational science. This review is to (i) recapitulate protocols and tools to prepare PRP; (ii) to discuss the cellular and molecular composition of PRP with a focus on platelets, leukocytes, and the fibrin-rich extracellular matrix of coagulated plasma; and finally (iii) to discuss potential beneficial effects of PRP on a cellular and molecular level with an outlook on its current use in dentistry and other medical fields.

Extracellular vesicles purified from serum-converted human platelet lysates offer strong protection after cardiac ischaemia/reperfusion injury

Extracellular vesicles (EVs) from cultured cells or bodily fluids have been demonstrated to show therapeutic value following myocardial infarction. However, challenges in donor variation, EV generation and isolation methods, and material availability have hindered their therapeutic use. Here, we show that human clinical-grade platelet concentrates from a blood establishment can be used to rapidly generate high concentrations of high purity EVs from sero-converted platelet lysate (SCPL-EVs) with minimal processing, using size-exclusion chromatography. Processing removed serum carrier proteins, coagulation factors and complement proteins from the original platelet lysate and the resultant SCPL-EVs carried a range of trophic factors and multiple recognised cardioprotective miRNAs. As such, SCPL-EVs protected rodent and human cardiomyocytes from hypoxia/re-oxygenation injury and stimulated angiogenesis of human cardiac microvessel endothelial cells. In a mouse model of myocardial infarction with reperfusion, SCPL-EV delivery using echo-guided intracavitary percutaneous injection produced large improvements in cardiac function, reduced scar formation and promoted angiogenesis. Since platelet-based biomaterials are already widely used clinically, we believe that this therapy could be rapidly suitable for a human clinical trial.

Thrombocytopenia is associated with a dysregulated host response in severe COVID-19

BACKGROUND

Thrombocytopenia is associated with increased mortality in COVID-19 patients.

OBJECTIVE

To determine the association between thrombocytopenia and alterations in host response pathways implicated in disease pathogenesis in patients with severe COVID-19.

PATIENTS/METHODS

We studied COVID-19 patients admitted to a general hospital ward included in a national (CovidPredict) cohort derived from 13 hospitals in the Netherlands. In a subgroup, 43 host response biomarkers providing insight in aberrations in distinct pathophysiological domains (coagulation and endothelial cell function; inflammation and damage; cytokines and chemokines) were determined in plasma obtained at a single time point within 48 h after admission. Patients were stratified in those with normal platelet counts (150-400 × 109/L) and those with thrombocytopenia (<150 × 109/L).

RESULTS

6.864 patients were enrolled in the national cohort, of whom 1.348 had thrombocytopenia and 5.516 had normal platelets counts; the biomarker cohort consisted of 429 patients, of whom 85 with thrombocytopenia and 344 with normal platelet counts. Plasma D-dimer levels were not different in thrombocytopenia, although patients with moderate-severe thrombocytopenia (<100 × 109/L) showed higher D-dimer levels, indicating enhanced coagulation activation. Patients with thrombocytopenia had lower plasma levels of many proinflammatory cytokines and chemokines, and antiviral mediators, suggesting involvement of platelets in inflammation and antiviral immunity. Thrombocytopenia was associated with alterations in endothelial cell biomarkers indicative of enhanced activation and a relatively preserved glycocalyx integrity.

CONCLUSION

Thrombocytopenia in hospitalized patients with severe COVID-19 is associated with broad host response changes across several pathophysiological domains. These results suggest a role of platelets in the immune response during severe COVID-19.

Platelet-rich plasma in the pathologic processes of tendinopathy: a review of basic science studies

Tendinopathy is a medical condition that includes a spectrum of inflammatory and degenerative tendon changes caused by traumatic or overuse injuries. The pathological mechanism of tendinopathy has not been well defined, and no ideal treatment is currently available. Platelet-rich plasma (PRP) is an autologous whole blood derivative containing a variety of cytokines and other protein components. Various basic studies have found that PRP has the therapeutic potential to promote cell proliferation and differentiation, regulate angiogenesis, increase extracellular matrix synthesis, and modulate inflammation in degenerative tendons. Therefore, PRP has been widely used as a promising therapeutic agent for tendinopathy. However, controversies exist over the optimal treatment regimen and efficacy of PRP for tendinopathy. This review focuses on the specific molecular and cellular mechanisms by which PRP manipulates tendon healing to better understand how PRP affects tendinopathy and explore the reason for the differences in clinical trial outcomes. This article has also pointed out the future direction of basic research and clinical application of PRP in the treatment of tendinopathy, which will play a guiding role in the design of PRP treatment protocols for tendinopathy.

Platelet Response to Allergens, CXCL10, and CXCL5 in the Context of Asthma

Asthma is a chronic respiratory disease initiated by a variety of factors, including allergens. During an asthma attack, the secretion of C-X-C-motif chemokine 10 (CXCL10) and chemokine ligand 5 (CCL5) causes the migration of immune cells, including platelets, into the lungs and airway. Platelets, which contain three classes of chemical messenger-filled granules, can secrete vasodilators (adenosine diphosphate and adenosine triphosphate), serotonin (a vasoconstrictor and a vasodilator, depending on the biological system), platelet-activating factor, N-formylmethionyl-leucyl-phenylalanine ((fMLP), a bacterial tripeptide that stimulates chemotaxis), and chemokines (CCL5, platelet factor 4 (PF4), and C-X-C-motif chemokine 12 (CXCL12)), amplifying the asthma response. The goal of this work was threefold: (1) to understand if and how the antibody immunoglobulin E (IgE), responsible for allergic reactions, affects platelet response to the common platelet activator thrombin; (2) to understand how allergen stimulation compares to thrombin stimulation; and (3) to monitor platelet response to fMLP and the chemokines CXCL10 and CCL5. Herein, high-pressure liquid chromatography with electrochemical detection and/or carbon-fiber microelectrode amperometry measured granular secretion events from platelets with and without IgE in the presence of the allergen 2,4,6-trinitrophenyl-conjugated ovalbumin (TNP-Ova), thrombin, CXCL10, or CCL5. Platelet adhesion and chemotaxis were measured using a microfluidic platform in the presence of CXCL10, CCL5, or TNP-OVA. Results indicate that IgE binding promotes δ-granule secretion in response to platelet stimulation by thrombin in bulk. Single-cell results on platelets with exogenous IgE exposure showed significant changes in the post-membrane-granule fusion behavior during chemical messenger delivery events after thrombin stimulation. In addition, TNP-Ova allergen stimulation of IgE-exposed platelets secreted serotonin to the same extent as thrombin platelet stimulation. Enhanced adhesion to endothelial cells was demonstrated by TNP-Ova stimulation. Finally, only after incubation with IgE did platelets secrete chemical messengers in response to stimulation with fMLP, CXCL10, and CCL5.

Fashionable, but What is Their Real Clinical Usefulness? NLR, LMR, and PLR as a Promising Indicator in Colorectal Cancer Prognosis: A Systematic Review

The link between inflammation and cancer is still an attractive subject of many studies because systemic inflammatory response has been proven to play a pivotal role in cancer progression and metastasis. The strongest relationship between chronic inflammation and cancer development is observed in colorectal cancer (CRC). The evaluation of ratios derived from the routinely performed inflammatory biomarkers shows limited performances and limited clinical utility when individually used as prognostic factors for patients with CRC. In this review, we would like to summarize the latest knowledge about the diagnostic utility of systemic inflammatory ratios: neutrophil/lymphocyte (NLR), lymphocyte/monocyte (LMR), and platelet/lymphocyte (PLR) in CRC. We focused on the papers that assessed the diagnostic utility of blood cell parameters on the basis of the area under the ROC curve published in the recent 6 years. Identification of biomarkers that are significantly associated with prognostic in cancer would help the selection of patients with a high risk of poor outcomes.

Analyzing the Systems Biology Effects of COVID-19 mRNA Vaccines to Assess Their Safety and Putative Side Effects

COVID-19 vaccines have been instrumental tools in reducing the impact of SARS-CoV-2 infections around the world by preventing 80% to 90% of hospitalizations and deaths from reinfection, in addition to preventing 40% to 65% of symptomatic illnesses. However, the simultaneous large-scale vaccination of the global population will indubitably unveil heterogeneity in immune responses as well as in the propensity to developing post-vaccine adverse events, especially in vulnerable individuals. Herein, we applied a systems biology workflow, integrating vaccine transcriptional signatures with chemogenomics, to study the pharmacological effects of mRNA vaccines. First, we derived transcriptional signatures and predicted their biological effects using pathway enrichment and network approaches. Second, we queried the Connectivity Map (CMap) to prioritize adverse events hypotheses. Finally, we accepted higher-confidence hypotheses that have been predicted by independent approaches. Our results reveal that the mRNA-based BNT162b2 vaccine affects immune response pathways related to interferon and cytokine signaling, which should lead to vaccine success, but may also result in some adverse events. Our results emphasize the effects of BNT162b2 on calcium homeostasis, which could be contributing to some frequently encountered adverse events related to mRNA vaccines. Notably, cardiac side effects were signaled in the CMap query results. In summary, our approach has identified mechanisms underlying both the expected protective effects of vaccination as well as possible post-vaccine adverse effects. Our study illustrates the power of systems biology approaches in improving our understanding of the comprehensive biological response to vaccination against COVID-19.

Vitamin D Supplementation Modulates Platelet-Mediated Inflammation in Subjects With Type 2 Diabetes: A Randomized, Double-Blind, Placebo-Controlled Trial

Background

Recently, our group identified increased platelet-mediated inflammation in type 2 diabetes (T2DM) patients, and it is a well-established risk factor for diabetes complications, particularly for the development of cardiovascular diseases (CVD). Furthermore, vitamin D is reported to play an important role in the modulation of platelet hyperactivity and immune function, although the effect of vitamin D on platelet-mediated inflammation is not well studied. Hence, we aimed to investigate the effect of vitamin D supplementation on platelet-mediated inflammation in T2DM patients.

Methods

After screening a total of 201 subjects, our randomized, double-blind, placebo-controlled trial included 59 vitamin-D-deficient T2DM subjects, and the participants were randomly assigned to placebo (n = 29) or vitamin D3 (n = 30) for 6 months. Serum vitamin D metabolite levels, immunome profiling, platelet activation, and platelet-immune cell aggregate formation were measured at baseline and at the end of the study. Similarly, the serum levels of inflammatory cytokines/chemokines were assessed by a multiplex assay.

Results

Six months of vitamin D supplementation increases the serum vitamin D3 and total 25(OH)D levels from the baseline (p < 0.05). Vitamin D supplementation does not improve glycemic control, and no significant difference was observed in immune cells. However, platelet activation and platelet immune cell aggregates were altered after the vitamin D intervention (p < 0.05). Moreover, vitamin D reduces the serum levels of IL-18, TNF-α, IFN-γ, CXCL-10, CXCL-12, CCL-2, CCL-5, CCL-11, and PF-4 levels compared to the baseline levels (p < 0.05). Our ex vivo experiment confirms that a sufficient circulating level of vitamin D reduces platelet activation and platelet intracellular reactive oxygen species.

Conclusion

Our study results provide evidence that vitamin D supportive therapy may help to reduce or prevent the disease progression and cardiovascular risk in T2DM patients by suppressing oxidative stress and platelet-mediated inflammation.

Clinical Trial Registration

Clinical Trial Registry of India: CTRI/2019/01/016921.

An Insight into Recent Advances on Platelet Function in Health and Disease

Platelets play a variety of roles in vascular biology and are best recognized as primary hemostasis and thrombosis mediators. Platelets have a large number of receptors and secretory molecules that are required for platelet functionality. Upon activation, platelets release multiple substances that have the ability to influence both physiological and pathophysiological processes including inflammation, tissue regeneration and repair, cancer progression, and spreading. The involvement of platelets in the progression and seriousness of a variety of disorders other than thrombosis is still being discovered, especially in the areas of inflammation and the immunological response. This review represents an integrated summary of recent advances on the function of platelets in pathophysiology that connects hemostasis, inflammation, and immunological response in health and disease and suggests that antiplatelet treatment might be used for more than only thrombosis.

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.

Evaluation of Immune Response and Haematological Parameters in Infected Male Albino Rats by Giardiasis

The present work aimed to study the effects of G. lamblia infection on immunological, haematological studies and to evaluate immunoglobulins and some cytokines. Fifty male albino rats were divided into six groups. The control group including 20 rats and the infected group includes 30 rats. All the estimations were checked all over five checkpoints (CP) (7, 14, 21, 28, and 35 days post-infection). Serum levels of IgA, IgG, IgM and IgE. Cytokines INF-γ, TNF-alpha, IL-4, IL-10, and haematological parameters were determined. Cyst and trophozoite were counted. A considerable increase in the level of immunoglobulins and cytokines in all infected groups compared to the control group was documented. Furthermore, a significant decrease in red blood corpuscles, haemoglobin, and mean corpuscular haemoglobin concentration levels, whereas substantial increases in mean corpuscular volume, mean corpuscular haemoglobin and platelets were observed. Moreover, infected rats had a substantial rise in WBCs, lymphocytes, and eosinophil counts compared to the control group, whereas neutrophils and monocytes had a significant decrease. Number of trophozoites and cysts were significantly increased in infected groups before diminishing after day 28. The current results showed that Th1 and Th2 immune responses, which are characterized by the production of TNF-α, IFN-γ, IL-4 and IL-10, are important for protection against Giardia infections and also verified the balance between these cytokines and the timing of their production was crucial in G. lamblia immune response. Giardia lamblia, Immunity, Antibodies, cytokines, eosinophil.

Exosomes Recovered From the Plasma of COVID-19 Patients Expose SARS-CoV-2 Spike-Derived Fragments and Contribute to the Adaptive Immune Response

Coronavirus disease 2019 (COVID-19) is an infectious disease caused by beta-coronavirus severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) that has rapidly spread across the globe starting from February 2020. It is well established that during viral infection, extracellular vesicles become delivery/presenting vectors of viral material. However, studies regarding extracellular vesicle function in COVID-19 pathology are still scanty. Here, we performed a comparative study on exosomes recovered from the plasma of either MILD or SEVERE COVID-19 patients. We show that although both types of vesicles efficiently display SARS-CoV-2 spike-derived peptides and carry immunomodulatory molecules, only those of MILD patients are capable of efficiently regulating antigen-specific CD4+ T-cell responses. Accordingly, by mass spectrometry, we show that the proteome of exosomes of MILD patients correlates with a proper functioning of the immune system, while that of SEVERE patients is associated with increased and chronic inflammation. Overall, we show that exosomes recovered from the plasma of COVID-19 patients possess SARS-CoV-2-derived protein material, have an active role in enhancing the immune response, and possess a cargo that reflects the pathological state of patients in the acute phase of the disease.

The Effects of Lower vs Higher Cell Number of Platelet-Rich Plasma (PRP) on Hair Density and Diameter in Androgenetic Alopecia (AGA): A Randomized, Double-Blinded, Placebo, Parallel-Group Half-Scalp IRB-Approved Study

BACKGROUND

Androgenetic alopecia (AGA) is a common disorder in both males and females and may be improved by platelet-rich plasma (PRP) treatment.

OBJECTIVES

The aim of this study was to compare safety, efficacy, and satisfaction following treatment with a lower or higher number of platelets over 6 months.

METHODS

This was a prospective randomized, double-blinded, placebo, parallel-group, half-scalp IRB-approved study involving 8 subjects with moderate AGA. Participants received intradermal PRP injections (baseline and Month 3), according to 2 treatment protocols (high vs low platelet numbers) to the frontal and crown portions of the hemiscalp and normal saline to control sites. Phototrichoscans were recorded at baseline and at 6 months, and global photography and subject and investigator satisfaction questionnaires were obtained at baseline, 3, and 6 months.

RESULTS

At the end of 6-month evaluation period, both groups demonstrated absolute increases in total hair density, follicle diameter, and terminal hair density, as well as absolute and percentage changes at the frontal and crown targeted sites compared with baseline. These improvements tended to occur more often in areas treated with higher platelet numbers than with lower numbers. Vellus hair densities did not exhibit any significant changes with either PRP dosages. The investigator and 6 of the subjects were "satisfied" with the results at 3 months and no adverse reactions were associated with the treatments.

CONCLUSIONS

Intradermal injections with 2 therapeutic quantities of platelets were equally safe and efficacious for treating men and women with AGA. Higher numbers of platelets may have a greater effect than lower numbers of platelets in regard to hair density, follicle diameter, and terminal hair density but exhibited minimal effects on vellus hair densities at the 6-month evaluation point. Further studies are required to determine whether any significant advantages occur when delivering either lower or higher numbers of platelets in AGA treatments as long as therapeutic levels are administered.

LEVEL OF EVIDENCE: 2

Role of Neurons and Glia Cells in Wound Healing as a Novel Perspective Considering Platelet as a Conventional Player

Wound healing is a complex physiological process in which the damaged or injured tissue is replaced or regenerated by new cells or existing cells respectively in their synthesized and secreted matrices. Several cells modulate the process of wound healing including macrophages, fibroblasts, and keratinocytes. Apart from these cells, platelet has been considered as a major cellular fragment to be involved in wound healing at several stages by secreting its granular contents including growth factors, thus resulting in coagulation, inflammation, and angiogenesis. A distant cell, which is gaining significant attention nowadays due to its resemblance with platelet in several aspects, is the neuron. Not only neurons but also glia cells are also confirmed to regulate wound healing at different stages in an orchestrated manner. Furthermore, these neurons and glia cells mediate wound healing inducing tissue repair and regeneration apart from hemostasis, angiogenesis, and inflammation by secreting various growth factors, coagulation molecules, immunomodulatory molecules as well as neurohormones, neuropeptides, and neurotrophins. Therefore, in wound healing platelets, neurons and glia cells not only contribute to tissue repair but are also responsible for establishing the wound microenvironment, thus affecting the proliferation of immune cells, fibroblast, and keratinocytes. Here in this review, we will enlighten the physiological roles of neurons and glia cells in coordination with platelets to understand various cellular and molecular mechanism in brain injury and associated neurocognitive impairments.

Effects of Nutrients on Platelet Function: A Modifiable Link between Metabolic Syndrome and Neurodegeneration?

Metabolic syndrome increases the risk of vascular dementia and other neurodegenerative disorders. Recent studies underline that platelets play an important role in linking peripheral with central metabolic and inflammatory mechanisms. In this narrative review, we address the activation of platelets in metabolic syndrome, their effects on neuronal processes and the role of the mediators (e.g., serotonin, platelet-derived growth factor). Emerging evidence shows that nutritional compounds and their metabolites modulate these interactions-specifically, long chain fatty acids, endocannabinoids and phenolic compounds. We reviewed the role of activated platelets in neurovascular processes and nutritional compounds in platelet activation.

A case of resistant multiple plantar warts cured with combined autologous platelet-rich plasma injection and topical salicylic acid 30

BACKGROUND

Plantar warts are common benign cutaneous lesions affecting the plantar aspects of the feet; they are caused by infection of the keratinocytes by the human papillomavirus (HPV). The effective treatment of plantar warts is still a therapeutic challenge.

AIM

This study aimed to assess the possible clinical efficacy and safety of the combined intralesional autologous platelet-rich plasma (PRP) injection with local application of salicylic acid 30% solution in the treatment of multiple resistant plantar warts.

METHOD

In the present case, a 54-year-old immunocompetent male patient presented with multiple, bilateral resistant plantar warts.

RESULTS

A complete clearance of the plantar warts was observed after three sessions of intralesional autologous PRP injections with one-month interval, combined with twice-daily local application of salicylic acid 30% solution between sessions. No recurrence was recorded after a nine-month follow-up from the last session. There were no reported side effects during or after the sessions.

CONCLUSION

The combined intralesional autologous PRP injection with topical salicylic acid is an effective, economic, and safe modality of treatment for multiple resistant plantar warts.

Possible clinical efficacy and tolerability of platelet-rich plasma in the treatment of patients with recalcitrant plane warts: The first clinical study

BACKGROUND

Plane warts are prevalent cutaneous diseases, caused by different serotypes of human papillomavirus.

AIMS

This study aimed to assess the possible clinical efficacy and tolerability of platelet-rich plasma (PRP) in the treatment of patients with multiple recalcitrant plane warts.

METHODS

This prospective cohort clinical study was carried out on 25 patients with clinical and dermoscopic evident multiple recalcitrant plane warts. The patients were treated with autologous intralesional PRP injections every month until a complete clearance or for a maximum of two sessions. Then, patients were clinically evaluated one month after every session and after a six-month follow-up from the last injection.

RESULTS

Of the included patients, 20 (80%) patients had facial plane warts, 3 (12%) patients had plane warts in the dorsum of hands, and 2 (8%) patients had plane warts in the dorsal aspect of feet. 60% of the patients have more than 100 plane warts, and all the patients had plane warts than 1 cm in size. The complete improvement was observed in 20% and 100% of the patients after the first and second sessions, respectively. No recurrence was detected after a six-month follow-up. No side effects were recorded after the treatment sessions.

CONCLUSION

Intralesional injection of PRP could be potentially effective and well-tolerated immunotherapy for the treatment of multiple recalcitrant plane warts. Whatever, more studies are needed with a larger sample size and a longer period of follow-up. Also, randomized and controlled studies are required to evaluate its efficacy in treating different clinical types of warts.

Role of Platelet Cytokines in Dengue Virus Infection

Platelets are anucleated blood cells derived from bone marrow megakaryocytes and play a crucial role in hemostasis and thrombosis. Platelets contain specialized storage organelles, called alpha-granules, contents of which are rich in cytokines such as C-X-C Motif Chemokine Ligand (CXCL) 1/4/7, (C-C motif) ligand (CCL) 5/3, CXCL8 (also called as interleukin 8, IL-8), and transforming growth factor β (TGF-β). Activation of platelets lead to degranulation and release of contents into the plasma. Platelet activation is a common event in many viral infections including human immunodeficiency virus (HIV), H1N1 influenza, Hepatitis C virus (HCV), Ebola virus (EBV), and Dengue virus (DENV). The cytokines CXCL8, CCL5 (also known as Regulated on Activation, Normal T Expressed and Secreted, RANTES), tumor necrosis factor α (TNF-α), CXCL1/5 and CCL3 released, promote development of a pro-inflammatory state along with the recruitment of other immune cells to the site of infection. Platelets also interact with Monocytes and Neutrophils and facilitate their activation to release different cytokines which further enhances inflammation. Upon activation, platelets also secrete factors such as CXCL4 (also known as platelet factor, PF4), CCL5 and fibrinopeptides which are critical regulators of replication and propagation of several viruses in the host. Studies suggest that CXCL4 can both inhibit as well as enhance HIV1 infection. Data from our lab show that CXCL4 inhibits interferon (IFN) pathway and promotes DENV replication in monocytes in vitro and in patients significantly. Inhibition of CXCL4 mediated signaling results in increased IFN production and suppressed DENV and JEV replication in monocytes. In this review, we discuss the role of platelets in viral disease progression with a focus on dengue infection.

A Relationship Between Clinical and Laboratory Characteristics in Children With Severe Scorpion Envenomation in Çukurova, Turkey

OBJECTIVE

Scorpion stings are an important health problem in many parts of the world. The aim of this study was to retrospectively examine cases of scorpion stings to evaluate their epidemiological, clinical, and laboratory features and to determine strategies that can reduce morbidity and mortality in these cases.

METHODS

Scorpion stings experienced by children between 2007 and 2013 were retrospectively reviewed. The patients were categorized into groups based on severities of toxicities, and demographic, clinical, and laboratory features were compared between the groups.

RESULTS

The mean ± SD age of the 189 patients with scorpion stings was 83.43 ± 59.62 months. There was a significant difference between the clinical stages and the age distribution of the cases (P < 0.05). White blood cell counts differed significantly between the groups (P < 0.05). There was not a significant difference in mean platelet volume and platelet distribution width between the groups, but plateletcrit and low platelet count were significantly different between stage 1 and stage 3 cases (P < 0.05). Glucose, creatinine kinase-myoglobin binding, and troponin I were also significantly different (P < 0.05). The mortality rate was 0%.

CONCLUSIONS

People living in regions where scorpion stings are frequent should be informed about preventive measures against these stings, cases of scorpion stings should be monitored in appropriate centers, and staff offering care to these cases should be educated about treatment methods. In addition, treatment protocols should be determined in accordance with regions where the stings occur and studies should be performed to describe prognostic indicators.

Platelets: emerging facilitators of cellular crosstalk in rheumatoid arthritis

Rheumatoid arthritis (RA) is an autoimmune disease in which a variety of circulating pro-inflammatory cells and dysregulated molecules are involved in disease aetiology and progression. Platelets are an important cellular element in the circulation that can bind several dysregulated molecules (such as collagen, thrombin and fibrinogen) that are present both in the synovium and the circulation of patients with RA. Platelets not only respond to dysregulated molecules in their environment but also transport and express their own inflammatory mediators, and serve as regulators at the boundary between haemostasis and immunity. Activated platelets also produce microparticles, which further convey signalling molecules and receptors to the synovium and circulation, thereby positioning these platelet-derived particles as strategic regulators of inflammation. These diverse functions come together to make platelets facilitators of cellular crosstalk in RA. Thus, the receptor functions, ligand binding potential and dysregulated signalling pathways in platelets are becoming increasingly important for treatment in RA. This Review aims to highlight the role of platelets in RA and the need to closely examine platelets as health indicators when designing effective pharmaceutical targets in this disease.

How do chemokines navigate neutrophils to the target site: Dissecting the structural mechanisms and signaling pathways

Chemokines play crucial roles in combating microbial infection and initiating tissue repair by recruiting neutrophils in a timely and coordinated manner. In humans, no less than seven chemokines (CXCL1, CXCL2, CXCL3, CXCL5, CXCL6, CXCL7, and CXCL8) and two receptors (CXCR1 and CXCR2) mediate neutrophil functions but in a context dependent manner. Neutrophil-activating chemokines reversibly exist as monomers and dimers, and their receptor binding triggers conformational changes that are coupled to G-protein and β-arrestin signaling pathways. G-protein signaling activates a variety of effectors including Ca2+ channels and phospholipase C. β-arrestin serves as a multifunctional adaptor and is coupled to several signaling hubs including MAP kinase and tyrosine kinase pathways. Both G-protein and β-arrestin signaling pathways play important non-overlapping roles in neutrophil trafficking and activation. Functional studies have established many similarities but distinct differences for a given chemokine and between chemokines at the level of monomer vs. dimer, CXCR1 vs. CXCR2 activation, and G-protein vs. β-arrestin pathways. We propose that two forms of the ligand binding two receptors and activating two signaling pathways enables fine-tuned neutrophil function compared to a single form, a single receptor, or a single pathway. We summarize the current knowledge on the molecular mechanisms by which chemokine monomers/dimers activate CXCR1/CXCR2 and how these interactions trigger G-protein/β-arrestin-coupled signaling pathways. We also discuss current challenges and knowledge gaps, and likely advances in the near future that will lead to a better understanding of the relationship between the chemokine-CXCR1/CXCR2-G-protein/β-arrestin axis and neutrophil function.

Platelet chemokines in health and disease

In recent years, it has become clear that platelets and platelet-derived chemokines, beyond their role in thrombosis and haemostasis, are important mediators affecting a broad spectrum of (patho)physiological conditions. These biologically active proteins are released from α-granules upon platelet activation, most probably even during physiological conditions. In this review, we give a concise overview and an update on the current understanding of platelet-derived chemokines in a context of health and disease.

Note: The review process for this manuscript was fully handled by G. Y. H. Lip, Editor in Chief.

Platelet-Derived Chemokine CXCL7 Dimer Preferentially Exists in the Glycosaminoglycan-Bound Form: Implications for Neutrophil-Platelet Crosstalk

Platelet-derived chemokine CXCL7 (also known as NAP-2) plays a crucial role in orchestrating neutrophil recruitment in response to vascular injury. CXCL7 exerts its function by activating the CXC chemokine receptor 2 (CXCR2) receptor and binding sulfated glycosaminoglycans (GAGs) that regulate receptor activity. CXCL7 exists as monomers, dimers, and tetramers, and previous studies have shown that the monomer dominates at lower and the tetramer at higher concentrations. These observations then raise the question: what, if any, is the role of the dimer? In this study, we make a compelling observation that the dimer is actually the favored form in the GAG-bound state. Further, we successfully characterized the structural basis of dimer binding to GAG heparin using solution nuclear magnetic resonance (NMR) spectroscopy. The chemical shift assignments were obtained by exploiting heparin binding-induced NMR spectral changes in the WT monomer and dimer and also using a disulfide-linked obligate dimer. We observe that the receptor interactions of the dimer are similar to the monomer and that heparin-bound dimer is occluded from receptor interactions. Cellular assays also show that the heparin-bound CXCL7 is impaired for CXCR2 activity. We conclude that the dimer–GAG interactions play an important role in neutrophil–platelet crosstalk, and that these interactions regulate gradient formation and the availability of the free monomer for CXCR2 activation and intrathrombus neutrophil migration to the injury site.

Current Evidence for Clinical Efficacy of Platelet Rich Plasma in Aesthetic Surgery: A Systematic Review

Background

Platelet rich plasma (PRP) has attracted attention in a number of surgical fields due to a wide variety of potential clinical benefits. Yet PRP has not gained wide popularity in aesthetic surgery as a result of uncertainty surrounding objective clinical evidence.

Objectives

We aim to describe the current applications, define preparation and activation, explore effectiveness, and propose a classification system to facilitate comparisons across studies.

Methods

A comprehensive review of the literature regarding the use of platelet rich plasma in aesthetic surgery was performed. Data gathered included: PRP application, study type, subject number, centrifugation, anticoagulation, activation, PRP composition, and outcomes.

Results

Thirty-eight reports were identified. Applications included injection into aging skin (29%), scalp alopecia (26%), lipofilling (21%), fractional laser (13%), and facial surgery (11%). The majority of studies (53%) were case series without controls. Leucocytes were sparsely defined (32%). The concentration of injected and/or baseline platelets was rarely clarified (18%). The mechanism of activation was described in 27 studies (71%), while anticoagulation was uncommonly elucidated (47%). While most studies (95%) claim effectiveness, objective measures were only utilized in 17 studies (47%).

Conclusions

Current studies produce context-dependent results with a lack of consistent reporting of PRP preparation, composition, and activation in aesthetic applications, making meaningful meta-analysis unrealistic. Thus the method of PRP preparation warrants increased attention. We recommend a set of descriptors, FIT PAAW (described below), to produce scientifically grounded conclusions, facilitating a clearer understanding of the situations in which PRP is effective.

Level of Evidence

4

Effects of purified anthocyanin supplementation on platelet chemokines in hypocholesterolemic individuals: a randomized controlled trial

Background

It is becoming increasingly evident that platelet chemokines are involved in distinct aspects of atherosclerosis. The aim of this study was to examine the effects of long-term supplementation with purified anthocyanins on platelet chemokines in hypercholesterolemic individuals and to identify correlations of decreased platelet chemokine levels with serum lipid and inflammatory marker levels.

Methods

A total of 146 hypercholesterolemic individuals were recruited and treated with 320 mg of purified anthocyanins (n = 73) or a placebo (n = 73) daily for 24 weeks in this randomized, double-blind, placebo-controlled trial.

Results

Anthocyanin supplementation for 24 weeks significantly decreased the plasma CXCL7 (–12.32% vs. 4.22%, P = 0.001), CXCL5 (–9.95% vs. 1.93%, P = 0.011), CXCL8 (–6.07% vs. 0.66%, P = 0.004), CXCL12 (–8.11% vs. 5.43%, P = 0.023) and CCL2 levels (–11.63% vs. 12.84%, P = 0.001) compared with the placebo. Interestingly, the decreases in the CXCL7 and CCL2 levels were both positively correlated with the decreases in the serum low-density lipoprotein-cholesterol (LDL-C), high-sensitivity C-reactive protein (hsCRP) and interleukin-1β (IL-1β) levels after anthocyanin supplementation for 24 weeks. The decrease in the CXCL8 level was negatively correlated with the increase in the how-density lipoprotein-cholesterol (HDL-C) level and was positively correlated with the decrease in the soluble P-selectin (sP-selectin) level in the anthocyanin group. In addition, a positive correlation was observed between the decreases in the CXCL12 and tumornecrosis factor-α (TNF-α) levels after anthocyanin supplementation. However, the plasma CXCL4L1, CXCL1, macrophage migration inhibitory factor (MIF) and human plasminogen activator inhibitor 1 (PAI-1) levels did not significantly change following anthocyanin supplementation.

Conclusions

The present study supports the notion that platelet chemokines are promising targets of anthocyanins in the prevention of atherosclerosis.

Trial registration

ChiCTR-TRC-08000240. Registered: 10 December 2008.

Reduction in mean platelet volume in children with acute bronchiolitis

AIM

Platelets which are known to play a role in inflamation change their shapes when they are activated and this change is reflected in mean platelet volume and platelet distribution width values. Therefore, the mean platelet volume and platelet distribution width values are considered to be beneficial parameters for the diagnosis and treatment of many inflammatory diseases. The aim of the study was to evaluate platelet volume indices in children with acute bronchiolitis.

MATERIAL AND METHODS

A total of 514 infants who were below the age of 2 years old were evaluated in this study. Three hundred thirteen of these infants were diagnosed with acute bronchiolitis patients and 201 were healthy children. The patients were separated into four groups as mild, moderate, severe bronchiolitis and the control patient group. The groups were evaluated in terms of significant differences in the values of mean platelet volume and platelet distribution width. A p value of <0.05 was considered statistically significant for all results.

RESULTS

The mean platelet volume was found to be 6.8±0.6 fL in the patients with mild bronchiolitis attack, 6.7±0.6 fL in the patients with moderate bronchiolitis attack, 6.5±0.5 fL in the patients with severe bronchiolitis attack and 7.3±1.1 fL in the control group. The mean platalet volume was statistically significantly lower in the mild, moderate and severe bronchiolitis attack groups compared to the control group (p=0.000). The platelet distribution width was found to be 17.2%±0.83 in the mild bronchiolitis attack group, 17.1%±0.96 in the moderate bronchiolitis attack group, 17.3%±0.87 in the severe bronchiolitis attack group and 16.9±1.6% in the control patient group. This difference was not statistically significant (p=0.159). The platelet count was statistically significantly higher in the mild, moderate and severe bronchiolitis attack groups compared to the control group (p=0.000).

CONCLUSIONS

The mean platalet volume is decreased in patients with acute bronchiolitis. It is not a useful criterion in determining the severity of bronchiolitis attack. It is important that clinicians evaluating hemogram results to also interprete this variable.

Utilização de plasma rico em plaquetas de coelhos com poucos leucócitos e hemácias para a consolidação de ossos

Objetivou-se utilizar o plasma rico em plaquetas, obtido por técnica capaz de produzir um produto autólogo, com reduzido número de leucócitos e hemácias, e avaliar, por meio de radiografias, a capacidade de cicatrização de uma falha óssea induzida no rádio de coelhos. Foram coletados 10,5mL de sangue por via intracardíaca, o qual foi distribuído em três tubos de hemossedimentação contendo citrato de sódio. Os tubos contendo as amostras foram submetidos a uma centrifugação a 2.000rpm (670,8G) por 20 minutos, e da coluna de sedimentação foram aspirados de cada tubo 1.000µL de plasma para a redução do volume sobrenadante. Aspirou-se o plasma acima do anel de leucócitos e transferiu-se para outro tubo para centrifugação a 2.000rpm por 10 minutos. O conteúdo plaquetário no fundo do tubo foi ressuspendido e homogeneizado a 1.000µL do plasma sobrenadante para formar o PRP líquido. Uma falha de 1,0cm foi realizada no rádio esquerdo de cada coelho. O tempo de consolidação foi observado por meio de exame radiográfico aos 45 e 90 dias de pós-operatório (PO). As imagens foram comparadas entre o grupo controle (G1) e o grupo que recebeu o implante de PRP por via transdérmica (G2). A evolução da cicatrização foi verificada com auxílio do programa Adobe Photoshop CC e em uma escala de cinza que representa o contraste. No G2 foi verificada média de 63% de contraste aos 45 dias de PO e de 65% aos 90 dias de PO. No G2, aos 45 dias de PO, a média encontrada foi de 42,7%, e aos 90 dias de PO, 31,25%, indicando que houve evolução do processo de reparação óssea em comparação ao grupo que não recebeu o implante de PRP. O método de obtenção de plasma rico em plaqueta autólogo de coelhos reduziu o número de leucócitos e hemácias e recuperou o número de plaquetas, sendo este maior ou igual aos valores fisiológicos para a espécie. O PRP obtido foi capaz de acelerar o processo de consolidação óssea em coelhos.

Association between aspirin therapy and the outcome in critically ill patients: a nested cohort study

Background

Antiplatelet therapy may attenuate the undesirable effects of platelets on the inflammatory cascades in critical illness. The objective of this study was to evaluate the association between aspirin therapy during intensive care unit (ICU) stay and all-cause mortality.

Methods

This was a nested cohort study within two randomized controlled trials in which all enrolled patients (N = 763) were grouped according to aspirin intake during ICU stay. The primary endpoints were all-cause ICU mortality and hospital mortality. Secondary endpoints included the development of severe sepsis during the ICU stay, ICU and hospital length of stay and the duration of mechanical ventilation. Propensity score was used to adjust for clinically and statistically relevant variables.

Results

Of the 763 patients, 154 patients (20 %) received aspirin. Aspirin therapy was not associated with a reduction in ICU mortality (adjusted OR 1.18, 95 % CI 0.69–2.02, P = 0.55) nor with hospital mortality (adjusted OR 0.95, 95 % CI 0.61–1.50, P = 0.82). Aspirin use had no preferential association with mortality among any of the study subgroups. Additionally, aspirin therapy was associated with higher risk of ICU-acquired severe sepsis, and increased mechanical ventilation duration and ICU length of stay.

Conclusion

Our study showed that the use of aspirin in critically ill patients was not associated with lower mortality, but rather with an increased morbidity.

Trial Registration Number

ISRCTN07413772 and ISRCTN96294863.

Platelet mass index in very preterm infants: can it be used as a parameter for neonatal morbidities?

OBJECTIVE

Platelet mass index (PMI) is related to the platelet functionality. The aim of this study was to evaluate the correlation between PMI and the occurrence of various inflammation-related morbidities of prematurity, such as bronchopulmonary dysplasia (BPD), necrotizing enterocolitis (NEC), retinopathy of prematurity (ROP), intraventricular hemorrhage (IVH) and sepsis in very low-birth weight (VLBW) infants.

METHODS

This retrospective analysis of VLBW infants admitted to a level 3 neonatal intensive care unit from October 2012 and 2014, n = 330. Platelet mass was calculated and recorded on the day of birth and between 3 and 7 days (second measure) for each patient. Statistical analysis included analysis of paired samples t test and independent samples t test.

RESULT

Among VLBW neonates, PMI values were lower in infants with ROP (p = 0.016), BPD (p = 0.002), IVH (p = 0.018) and NEC (p = 0.011) when compared with the control group in the second measurement.

CONCLUSIONS

In this study, we found that premature infants with BPD, NEC, ROP, IVH and sepsis had lower PMI levels in early postnatal life than infants without these diseases. This might be associated with the inflammatory process.

Platelet secretion of CXCL4 is Rac1-dependent and regulates neutrophil infiltration and tissue damage in septic lung damage

BACKGROUND AND PURPOSE

Platelets are potent regulators of neutrophil accumulation in septic lung damage. We hypothesized that platelet-derived CXCL4 might support pulmonary neutrophilia in a murine model of abdominal sepsis.

EXPERIMENTAL APPROACH

Polymicrobial sepsis was triggered by coecal ligation and puncture (CLP) in C57BL/6 mice. Platelet secretion of CXCL4 was studied by using confocal microscopy. Plasma and lung levels of CXCL4, CXCL1 and CXCL2 were determined by elisa. Flow cytometry was used to examine surface expression of Mac-1 on neutrophils.

KEY RESULTS

CLP increased CXCL4 levels in plasma, and platelet depletion reduced plasma levels of CXCL4 in septic animals. Rac1 inhibitor NSC23766 decreased the CLP-enhanced CXCL4 in plasma by 77%. NSC23766 also abolished PAR4 agonist-induced secretion of CXCL4 from isolated platelets. Inhibition of CXCL4 reduced CLP-evoked neutrophil recruitment, oedema formation and tissue damage in the lung. However, immunoneutralization of CXCL4 had no effect on CLP-induced expression of Mac-1 on neutrophils. Targeting CXCL4 attenuated plasma and lung levels of CXCL1 and CXCL2 in septic mice. CXCL4 had no effect on neutrophil chemotaxis in vitro, indicating it has an indirect effect on pulmonary neutrophilia. Intratracheal CXCL4 enhanced infiltration of neutrophils and formation of CXCL2 in the lung. CXCR2 antagonist SB225002 markedly reduced CXCL4-provoked neutrophil accumulation in the lung. CXCL4 caused secretion of CXCL2 from isolated alveolar macrophages.

CONCLUSIONS AND IMPLICATIONS

Rac1 controls platelet secretion of CXCL4 and CXCL4 is a potent stimulator of neutrophil accumulation in septic lungs via generation of CXCL2 in alveolar macrophages. Platelet-derived CXCL4 plays an important role in lung inflammation and tissue damage in polymicrobial sepsis.

Rac1-dependent secretion of platelet-derived CCL5 regulates neutrophil recruitment via activation of alveolar macrophages in septic lung injury

Accumulating evidence suggest that platelets play an important role in regulating neutrophil recruitment in septic lung injury. Herein, we hypothesized that platelet-derived CCL5 might facilitate sepsis-induced neutrophil accumulation in the lung. Abdominal sepsis was induced by CLP in C57BL/6 mice. CLP increased plasma levels of CCL5. Platelet depletion and treatment with the Rac1 inhibitor NSC23766 markedly reduced CCL5 in the plasma of septic mice. Moreover, Rac1 inhibition completely inhibited proteasePAR4-induced secretion of CCL5 in isolated platelets. Immunoneutralization of CCL5 decreased CLP-induced neutrophil infiltration, edema formation, and tissue injury in the lung. However, inhibition of CCL5 function had no effect on CLP-induced expression of Mac-1 on neutrophils. The blocking of CCL5 decreased plasma and lung levels of CXCL1 and CXCL2 in septic animals. CCL5 had no effect on neutrophil chemotaxis in vitro, suggesting an indirect effect of CCL5 on neutrophil recruitment. Intratracheal challenge with CCL5 increased accumulation of neutrophils and formation of CXCL2 in the lung. Administration of the CXCR2 antagonist SB225002 abolished CCL5-induced pulmonary recruitment of neutrophils. Isolated alveolar macrophages expressed significant levels of the CCL5 receptors CCR1 and CCR5. In addition, CCL5 triggered significant secretion of CXCL2 from isolated alveolar macrophages. Notably, intratracheal administration of clodronate not only depleted mice of alveolar macrophages but also abolished CCL5-induced formation of CXCL2 in the lung. Taken together, our findings suggest that Rac1 regulates platelet secretion of CCL5 and that CCL5 is a potent inducer of neutrophil recruitment in septic lung injury via formation of CXCL2 in alveolar macrophages.

Vesicular trafficking and signaling for cytokine and chemokine secretion in mast cells

Upon activation mast cells (MCs) secrete numerous inflammatory compounds stored in their cytoplasmic secretory granules by a process called anaphylactic degranulation, which is responsible for type I hypersensitivity responses. Prestored mediators include histamine and MC proteases but also some cytokines and growth factors making them available within minutes for a maximal biological effect. Degranulation is followed by the de novo synthesis of lipid mediators such as prostaglandins and leukotrienes as well as a vast array of cytokines, chemokines, and growth factors, which are responsible for late phase inflammatory responses. While lipid mediators diffuse freely out of the cell through lipid bilayers, both anaphylactic degranulation and secretion of cytokines, chemokines, and growth factors depends on highly regulated vesicular trafficking steps that occur along the secretory pathway starting with the translocation of proteins to the endoplasmic reticulum. Vesicular trafficking in MCs also intersects with endocytic routes, notably to form specialized cytoplasmic granules called secretory lysosomes. Some of the mediators like histamine reach granules via specific vesicular monoamine transporters directly from the cytoplasm. In this review, we try to summarize the available data on granule biogenesis and signaling events that coordinate the complex steps that lead to the release of the inflammatory mediators from the various vesicular carriers in MCs.

Rac1 regulates platelet shedding of CD40L in abdominal sepsis

Matrix metalloproteinase-9 (MMP-9) regulates platelet shedding of CD40L in abdominal sepsis. However, the signaling mechanisms controlling sepsis-induced shedding of CD40L from activated platelets remain elusive. Rac1 has been reported to regulate diverse functions in platelets; we hypothesized herein that Rac1 might regulate platelet shedding of CD40L in sepsis. The specific Rac1 inhibitor NSC23766 (N6-[2-[[4-(diethylamino)-1-methylbutyl] amino]-6-methyl-4-pyrimidinyl]-2 methyl-4, 6-quinolinediamine trihydrochloride) was administered to mice undergoing cecal ligation and puncture (CLP). Levels of CD40L and MMP-9 in plasma, platelets, and neutrophils were determined by use of ELISA, western blot, and confocal microscopy. Platelet depletion abolished the CLP-induced increase in plasma levels of CD40L. Rac1 activity was significantly increased in platelets from septic animals. Administration of NSC23766 abolished the CLP-induced enhancement of soluble CD40L levels in the plasma. Moreover, Rac1 inhibition completely inhibited proteinase-activated receptor-4-induced surface mobilization and secretion of CD40L in isolated platelets. CLP significantly increased plasma levels of MMP-9 and Rac1 activity in neutrophils. Treatment with NSC23766 markedly attenuated MMP-9 levels in the plasma from septic mice. In addition, Rac1 inhibition abolished chemokine-induced secretion of MMP-9 from isolated neutrophils. Finally, platelet shedding of CD40L was significantly reduced in response to stimulation with supernatants from activated MMP-9-deficient neutrophils compared with supernatants from wild-type neutrophils, indicating a direct role of neutrophil-derived MMP-9 in regulating platelet shedding of CD40L. Our novel data suggest that sepsis-induced platelet shedding of CD40L is dependent on Rac1 signaling. Rac1 controls surface mobilization of CD40L on activated platelets and MMP-9 secretion from neutrophils. Thus, our findings indicate that targeting Rac1 signaling might be a useful way to control pathologic elevations of CD40L in the systemic circulation in abdominal sepsis.

Neutrophil extracellular traps (NETs) and the role of platelets in infection

In addition to playing a central role in normal haemostasis, platelets make important contributions to host inflammatory and immune responses to injury or infection. Under pathophysiological conditions where platelet function is not tightly controlled, platelets also play critical roles in pathogenic processes underlying cardiovascular disease, uncontrolled inflammation, coagulopathy and in tumour metastasis. Neutrophil extracellular traps (NETs) are webs of histone-modified nuclear material extruded from activated neutrophils during inflammatory responses and these degranulation events can be directly triggered by platelet/neutrophil engagement. Emerging research describes how NETs influence platelet function, particularly in the setting of infection and inflammation. Especially intriguing is the potential for platelet-driven coagulation to be modulated by NETs in plasma and interstitial spaces. These findings also reveal new perspectives related to improved therapy for venous thrombosis.

Neutrophil extracellular traps (NETs) and the role of platelets in infection

In addition to playing a central role in normal haemostasis, platelets make important contributions to host inflammatory and immune responses to injury or infection. Under pathophysiological conditions where platelet function is not tightly controlled, platelets also play critical roles in pathogenic processes underlying cardiovascular disease, uncontrolled inflammation, coagulopathy and in tumour metastasis. Neutrophil extracellular traps (NETs) are webs of histone-modified nuclear material extruded from activated neutrophils during inflammatory responses and these degranulation events can be directly triggered by platelet/neutrophil engagement. Emerging research describes how NETs influence platelet function, particularly in the setting of infection and inflammation. Especially intriguing is the potential for platelet-driven coagulation to be modulated by NETs in plasma and interstitial spaces. These findings also reveal new perspectives related to improved therapy for venous thrombosis.

Platelet-rich plasma: underlying biology and clinical correlates

Platelet-rich plasma (PRP) has recently become the focus of intensive interest and discussion, in part because of the expanding understanding of platelet function. Anucleate platelets within PRP release a myriad of growth factors and cytokines while contributing to plasma coagulation and fibrin development; the latter acts as vehicle for the local delivery. The biological effects of PRP are largely attributed to the platelet secretome and plasma signaling proteins. Clinical data suggest that PRPs may exploit different regenerative mechanisms under diverse disease conditions, including hemostasis, inflammation, angiogenesis and the synthesis of extracellular matrix. The success of PRP therapies depends on current tissue healing research and the translation of this knowledge into clinical developments.

The role of chemokines in hepatitis C virus-mediated liver disease

The hepatitis C virus (HCV) is a global health problem affecting more than 170 million people. A chronic HCV infection is associated with liver fibrosis, liver cirrhosis and hepatocellular carcinoma. To enable viral persistence, HCV has developed mechanisms to modulate both innate and adaptive immunity. The recruitment of antiviral immune cells in the liver is mainly dependent on the release of specific chemokines. Thus, the modulation of their expression could represent an efficient viral escape mechanism to hamper specific immune cell migration to the liver during the acute phase of the infection. HCV-mediated changes in hepatic immune cell chemotaxis during the chronic phase of the infection are significantly affecting antiviral immunity and tissue damage and thus influence survival of both the host and the virus. This review summarizes our current understanding of the HCV-mediated modulation of chemokine expression and of its impact on the development of liver disease. A profound knowledge of the strategies used by HCV to interfere with the host's immune response and the pro-fibrotic and pro-carcinogenic activities of HCV is essential to be able to design effective immunotherapies against HCV and HCV-mediated liver diseases.

Clopidogrel enhances periodontal repair in rats through decreased inflammation

AIM

We hypothesized that platelet inactivation induced by drugs might interfere with periodontal repair in experimental periodontitis by suppressing the release of biological mediators from platelets at the site of injury.

MATERIAL AND METHODS

Sixty rats were randomly assigned to six groups (n = 10) and ligatures were placed around lower first molars of three groups. The other three groups were used as negative controls. Ligatures were removed after 10 days of periodontitis induction and all groups were submitted to treatment with aspirin (Asp) (30 mg/kg), clopidogrel (Clop) (75 mg/kg) or NaCl 0.9% intra-gastrically once daily for 3 days. Periodontal tissue was assessed by the measurement of CXCL12, CXCL4, CCL5 and platelet-derived growth factor (PDGF) by enzyme-linked immunosorbent assay; histomorphometrical analysis of polymorphonuclear (PMN) infiltration, attachment loss, bone loss and osteoclast numbers and quantification of blood vessels by imunnohistochemistry.

RESULTS

During periodontal repair and treatment with NaCl 0.9%, CCL5 was decreased and CXCL12 increased when compared with negative control groups. Asp and Clop did not affect CCL5 expression, decreased CXCL12 but only Clop decreased CXCL4 and PDGF content compared with saline-treated animals. Clop increased blood vessel number, reduced PMN count and decreased attachment and bone loss, also decreased osteoclast number in animals submitted or not to periodontal repair.

CONCLUSION

Systemic administration of Clop for 3 days improved the repair process associated with experimental periodontal disease, suggesting that it may have therapeutic value under situations where tissues undergo a transition from inflammation to repair.

Gateway to understanding microparticles: standardized isolation and identification of plasma membrane-derived vesicles

Microparticles (MPs) are small plasma membrane-derived vesicles that can expose molecules originating from their parental cells. As vectors of biological information they are likely to play an active role in both homeostasis and pathogenesis, making them promising biomarkers and nanomedicine tools. Therefore, there is an urgent need for standardization of MP isolation and analysis protocols to propel our understanding of MP biology to the next level. Based on current methodology and recent insights, this review proposes an optimized protocol for the isolation and biochemical characterization of MPs.

Platelet-rich plasma for managing pain and inflammation in osteoarthritis

Osteoarthritis (OA) is a common disease involving joint damage, an inadequate healing response and progressive deterioration of the joint architecture. Autologous blood-derived products, such as platelet-rich plasma (PRP), are key sources of molecules involved in tissue repair and regeneration. These products can deliver a collection of bioactive molecules that have important roles in fundamental processes, including inflammation, angiogenesis, cell migration and metabolism in pathological conditions, such as OA. PRP has anti-inflammatory properties through its effects on the canonical nuclear factor κB signalling pathway in multiple cell types including synoviocytes, macrophages and chondrocytes. PRP contains hundreds of different molecules; cells within the joint add to this milieu by secreting additional biologically active molecules in response to PRP. The net results of PRP therapy are varied and can include angiogenesis, the production of local conditions that favour anabolism in the articular cartilage, or the recruitment of repair cells. However, the molecules found in PRP that contribute to angiogenesis and the protection of joint integrity need further clarification. Understanding PRP in molecular terms could help us to exploit its therapeutic potential, and aid the development of novel treatments and tissue-engineering approaches, for the different stages of joint degeneration.

Platelets and autoimmunity

Vascular injury is the initial manifestation of inflammation resulting in the recruitment and activation of various cell types. The integrity of the vascular wall is monitored by platelets that become activated in the presence of exposed subendothelium. Besides their well-established role in haemostasis, ample data are now emerging on the many immunoregulatory functions of platelets. Platelets store and release a large plethora of cytokines, chemokines and growth factors. They also represent the largest circulating pool of many inflammatory mediators like P-selectin, CD40L and non-neuronal serotonin. Furthermore, complement activation occurs on the platelet surface and deposition of complement results in platelet activation. Overall, platelets have multiple functions in both innate and adaptive immunity. Further insight into the multifaceted role of platelets could therefore provide important clues into how we could implement current platelet therapy to reduce both platelet-induced thrombosis and inflammation. In this review, we discuss the current perceptions of platelet involvement in various autoimmune diseases like rheumatoid arthritis, systemic lupus erythematosus, systemic sclerosis and multiple sclerosis.

Alternative C-terminal helix orientation alters chemokine function: structure of the anti-angiogenic chemokine, CXCL4L1

BACKGROUND

CXCL4L1 is a highly potent anti-angiogenic and anti-tumor chemokine, and its structural information is unknown.

RESULTS

CXCL4L1 x-ray structure is determined, and it reveals a previously unrecognized chemokine structure adopting a novel C-terminal helix conformation.

CONCLUSION

The alternative helix conformation enhances the anti-angiogenic activity of CXCL4L1 by reducing the glycosaminoglycan binding ability.

SIGNIFICANCE

Chemokine C-terminal helix orientation is critical in regulating their functions. Chemokines, a subfamily of cytokines, are small, secreted proteins that mediate a variety of biological processes. Various chemokines adopt remarkable conserved tertiary structure comprising an anti-parallel β-sheet core domain followed by a C-terminal helix that packs onto the β-sheet. The conserved structural feature has been considered critical for chemokine function, including binding to cell surface receptor. The recently isolated variant, CXCL4L1, is a homologue of CXCL4 chemokine (or platelet factor 4) with potent anti-angiogenic activity and differed only in three amino acid residues of P58L, K66E, and L67H. In this study we show by x-ray structural determination that CXCL4L1 adopts a previously unrecognized structure at its C terminus. The orientation of the C-terminal helix protrudes into the aqueous space to expose the entire helix. The alternative helix orientation modifies the overall chemokine shape and surface properties. The L67H mutation is mainly responsible for the swing-out effect of the helix, whereas mutations of P58L and K66E only act secondarily. This is the first observation that reports an open conformation of the C-terminal helix in a chemokine. This change leads to a decrease of its glycosaminoglycan binding properties and to an enhancement of its anti-angiogenic and anti-tumor effects. This unique structure is recent in evolution and has allowed CXCL4L1 to gain novel functional properties.

Hyperreactive platelet phenotypes: relationship to altered serotonin transporter number, transport kinetics and intrinsic response to adrenergic co-stimulation

The mechanism underlying a hyperreactive platelet phenotype remains unknown. Since serotonin has been shown to influence platelet biology and atherothrombosis, we sought to investigate the association of platelet serotonin transporter number, binding affinity, and uptake kinetics with platelet aggregation. A total of 542 healthy volunteers had light transmittance platelet aggregometry measured in response to varying concentrations of epinephrine, serotonin, epinephrine plus serotonin, ADP and collagen. Transporter-dependent serotonin uptake rate was determined (Vmax), as were serotonin transporter number (Bmax) and binding affinity (Kd) using 3H paroxetine binding in a homologous displacement assay, nonlinear regression and validated algorithms for kinetic modelling. Stimulation with submaximal (2μM) epinephrine concentration elicited a distinct, bimodal pattern of platelet aggregation in this population. In contrast, subjects exhibited minimal aggregation in response to serotonin alone. Co-stimulation with submaximal epinephrine and serotonin induced platelet aggregation to a level beyond that observed with either agonist alone and maintained a bimodal response distribution. Subjects with heightened (>60%) platelet aggregation to both epinephrine alone and epinephrine plus serotonin exhibited increased platelet serotonin uptake, and transporter number and affinity. In a population of healthy subjects, co-stimulation with submaximal concentrations of epinephrine and serotonin identifies a subset of individuals with a hyperreactive platelet aggregation profile that is associated with changes in platelet serotonin function.

The chemokine superfamily revisited

The chemokine superfamily consists of a large number of ligands and receptors. At first glance, this family appears redundant and their ligand-receptor relationships promiscuous, making its study challenging. However, analyzing this family from the evolutionary perspective greatly simplifies understanding both the organization and function of this apparently complex system. In particular, the functions of a subgroup of chemokines (designated homeostatic chemokines) have played pivotal roles in advancing our understanding of the organization and function of the cellular networks that shape the immune system. Here, we update the full scope of the human and mouse chemokine superfamilies and their relationships and summarize several important roles that homeostatic chemokines play in the immune system.

The heterodimerization of platelet-derived chemokines

Chemokines encompass a large family of proteins that act as chemoattractants and are involved in many biological processes. In particular, chemokines guide the migration of leukocytes during normal and inflammatory conditions. Recent studies reveal that the heterophilic interactions between chemokines significantly affect their biological activity, possibly representing a novel regulatory mechanism of the chemokine activities. The co-localization of platelet-derived chemokines in vivo allows them to interact. Here, we used nano-spray ionization mass spectrometry to screen eleven different CXC and CC platelet-derived chemokines for possible interactions with the two most abundant chemokines present in platelets, CXCL4 and CXCL7. Results indicate that many screened chemokines, although not all of them, form heterodimers with CXCL4 and/or CXCL7. In particular, a strong heterodimerization was observed between CXCL12 and CXCL4 or CXCL7. Compared to other chemokines, the main structural difference of CXCL12 is in the orientation and packing of the C-terminal alpha-helix in relation to the beta-sheet. The analysis of one possible structure of the CXCL4/CXCL12 heterodimer, CXC-type structure, using molecular dynamics (MD) trajectory reveals that CXCL4 may undergo a conformational transition to alter the alpha helix orientation. In this new orientation, the alpha-helix of CXCL4 aligns in parallel with the CXCL12 alpha-helix, an energetically more favorable conformation. Further, we determined that CXCL4 and CXCL12 physically interact to form heterodimers by co-immunoprecipitations from human platelets. Overall, our results highlight that many platelet-derived chemokines are capable of heterophilic interactions and strongly support future studies of the biological impact of these interactions.