Autophagy is induced upon platelet activation and is essential for hemostasis and thrombosis

Mesenchymal Stem Cell-Derived Exosomes as Drug Carriers for Delivering miRNA-29b to Ameliorate Inflammation in Corneal Injury Via Activating Autophagy

Purpose

Corneal injury (CI) resulting in corneal opacity remains a clinical challenge. Exosomes (Exos) derived from bone marrow mesenchymal stem cells (BMSCs) have been proven effective in repairing various tissue injuries and are also considered excellent drug carriers due to their biological properties. Recently, microRNA-29b (miR-29b) was found to play an important role in the autophagy regulation which correlates with cell inflammation and fibrosis. However, the effects of miR-29b and autophagy on CI remain unclear. To find better treatments for CI, we used Exos to carry miR-29b and investigated its effects in the treatment of CI.

Methods

BMSCs were transfected with miR-29b-3p agomir/antagomir and negative controls (NCs) to obtain Exos-29b-ago, Exos-29b-anta, and Exos-NC. C57BL/6J mice that underwent CI surgeries were treated with Exos-29b-ago, Exos-29b-anta, Exos-NC, or PBS. The autophagy, inflammation, and fibrosis of the cornea were estimated by slit-lamp, hematoxylin and eosin (H&E) staining, immunofluorescence, RT‒qPCR, and Western blot. The effects of miR-29b-3p on autophagy and inflammation in immortalized human corneal epithelial cells (iHCECs) were also investigated.

Results

Compared to PBS, Exos-29b-ago, Exos-29b-anta, and Exos-NC all could ameliorate corneal inflammation and fibrosis. However, Exos-29b-ago, which accumulated a large amount of miR-29b-3p, exerted excellent potency via autophagy activation by inhibiting the PI3K/AKT/mTOR pathway and further inhibited corneal inflammation via the mTOR/NF-κB/IL-1β pathway. After Exos-29b-ago treatment, the expressions of collagen type III, α-smooth muscle actin, fibronectin, and vimentin were significantly decreased than in other groups. In addition, overexpression of miR-29b-3p prevented iHCECs from autophagy impairment and inflammatory injury.

Conclusions

Exos from BMSCs carrying miR-29b-3p can significantly improve the therapeutic effect on CI via activating autophagy and further inhibiting corneal inflammation and fibrosis.

Regulation of platelet activation and thrombus formation in acute non-ST segment elevation myocardial infarction: Role of Beclin1

This study aims to investigate the mechanism of platelet activation-induced thrombosis in patients with acute non-ST segment elevation myocardial infarction (NSTEMI) by detecting the expression of autophagy-associated proteins in platelets of patients with NSTEMI. A prospective study was conducted on 121 patients with NSTEMI who underwent emergency coronary angiography and optical coherence tomography. The participants were divided into two groups: the ST segment un-offset group (n = 64) and the ST segment depression group (n = 57). We selected a control group of 60 patients without AMI during the same period. The levels of autophagy-associated proteins and the expression of autophagy-associated proteins in platelets were measured using immunofluorescence staining and Western blot. In NSTEMI, the prevalence of red thrombus was higher in the ST segment un-offset myocardial infarction (STUMI) group, whereas white thrombus was more common in the ST segment depression myocardial infarction (STDMI) group. Furthermore, the platelet aggregation rate was significantly higher in the white thrombus group compared with the red thrombus group. Compared with the control group, the autophagy-related protein expression decreased, and the expression of αIIbβ3 increased in NSTEMI. The overexpression of Beclin1 could activate platelet autophagy and inhibit the expression of αIIbβ3. The results suggested that the increase in platelet aggregation rate in patients with NSTEMI may be potentially related to the change in autophagy. And the overexpression of Beclin1 could reduce the platelet aggregation rate by activating platelet autophagy. Our findings demonstrated that Beclin1 could be a potential therapeutic target for inhibiting platelet aggregation in NSTEMI.

Autophagy, a double-edged sword for oral tissue regeneration

BACKGROUND

Oral health is of fundamental importance to maintain systemic health in humans. Stem cell-based oral tissue regeneration is a promising strategy to achieve the recovery of impaired oral tissue. As a highly conserved process of lysosomal degradation, autophagy induction regulates stem cell function physiologically and pathologically. Autophagy activation can serve as a cytoprotective mechanism in stressful environments, while insufficient or over-activation may also lead to cell function dysregulation and cell death.

AIM OF REVIEW

This review focuses on the effects of autophagy on stem cell function and oral tissue regeneration, with particular emphasis on diverse roles of autophagy in different oral tissues, including periodontal tissue, bone tissue, dentin pulp tissue, oral mucosa, salivary gland, maxillofacial muscle, temporomandibular joint, etc. Additionally, this review introduces the molecular mechanisms involved in autophagy during the regeneration of different parts of oral tissue, and how autophagy can be regulated by small molecule drugs, biomaterials, exosomes/RNAs or other specific treatments. Finally, this review discusses new perspectives for autophagy manipulation and oral tissue regeneration.

KEY SCIENTIFIC CONCEPTS OF REVIEW

Overall, this review emphasizes the contribution of autophagy to oral tissue regeneration and highlights the possible approaches for regulating autophagy to promote the regeneration of human oral tissue.

Structural analysis of platelet fragments and extracellular vesicles produced by apheresis platelets during storage

ABSTRACT

Platelets (PLTs) for transfusion can be stored for up to 7 days at room temperature (RT). The quality of apheresis PLTs decreases over storage time, which affects PLT hemostatic functions. Here, we characterized the membranous particles produced by PLT storage lesion (PSLPs), including degranulated PLTs, PLT ghosts, membrane fragments, and extracellular membrane vesicles (PEVs). The PSLPs generated in apheresis platelet units were analyzed on days 1, 3, 5, and 7 of RT storage. A differential centrifugation and a sucrose density gradient were used to separate PSLP populations. PSLPs were characterized using scanning and transmission electron microscopy (EM), flow cytometry (FC), and nanoparticle tracking analysis (NTA). PSLPs have different morphologies and a broad size distribution; FC and NTA showed that the concentration of small and large PSLPs increases with storage time. The density gradient separated 3 PSLP populations: (1) degranulated PLTs, PLT ghosts, and large PLT fragments; (2) PEVs originated from PLT activation and organelles released by necrotic PLTs; and (3) PEV ghosts. Most PSLPs expressed phosphatidyl serine and induced thrombin generation in the plasma. PSLPs contained extracellular mitochondria and some had the autophagosome marker LC3. PSLPs encompass degranulated PLTs, PLT ghosts, large PLT fragments, large and dense PEVs, and low-density PEV ghosts. The activation-related PSLPs are released, particularly during early stage of storage (days 1-3), and the release of apoptosis- and necrosis-related PSLPs prevails after that. No elevation of LC3- and TOM20-positive PSLPs indicates that the increase of extracellular mitochondria during later-stage storage is not associated with PLT mitophagy.

Changes in inflammatory responses and autophagy during apheresis platelet preservation and their correlation with platelet transfusion refractoriness in patients with acute lymphoblastic leukemia

Acute lymphoblastic leukemia (ALL) is a common hematopoietic malignancy, and platelet transfusion plays a crucial role in its treatment. This study aimed to investigate the changes in inflammatory response and autophagy during the preservation of apheresis platelets (AP) and their correlation with platelet transfusion refractoriness (PTR) in ALL. ALL patients were included, and APs were categorized based on the preservation period (day 0, day 1, days 2-3, and days 4-5). The activation factors procaspase-activating compound 1 (PAC-1) and P-selectin (CD62P), AP aggregation function, inflammation levels (interleukin 1 beta [IL-1β], interleukin 6 [IL-6], tumor necrosis factor alpha [TNF-α] and NOD-like receptor thermal protein domain associated protein 3 [NLRP3]), and autophagy-related genes (p62) during AP preservation were assessed. Following co-culturing APs with peripheral blood mononuclear cells (PBMCs), specific activation markers were studied to observe APs influence on immune cells activation. The effectiveness of platelet transfusion was assessed, and risk factors for PTR were analyzed. As the storage duration of AP increased, the activation factors, coagulation factor activity, inflammation levels, and the activation of immune cells in AP increased, while fibrinogen levels and AP aggregation function decreased. The expression levels of autophagy-related genes (the autophagy marker light chain 3B gene [LC3B] and Beclin 1 gene) decreased with prolongation preservation. The effective rate of AP transfusion in ALL patients was 68.21%. AP preservation time, IL-6, p62, and Beclin 1 were identified as independent risk factors affecting PTR in ALL patients. In conclusion, during AP preservation, inflammation, autophagy, and activation of immune cells were observed to increase. AP preservation time, IL-6, p62, and Beclin 1 were independent risk factors for PTR.

Autophagy in sepsis-induced acute lung injury: Friend or foe?

Sepsis-induced acute lung injury (ALI) is a life-threatening syndrome with high mortality and morbidity, resulting in a heavy burden on family and society. As a key factor that maintains cellular homeostasis, autophagy is regarded as a self-digesting process by which damaged organelles and useless proteins are recycled for cell metabolism, and it thus plays a crucial role during physiological and pathological processes. Recent studies have indicated that autophagy is involved in the pathophysiological process of sepsis-induced ALI, including cell apoptosis, inflammation, and mitochondrial dysfunction, which indicates that regulating autophagy may be beneficial for this disease. However, the role of autophagy in the etiology and treatment of sepsis-induced ALI is not well characterized. This review summarizes the autophagy-related signaling pathways in sepsis-induced ALI, as well as focuses on the dual role of autophagy and its regulation by non-coding RNAs during disease progression, for the development of potential therapeutic strategies in this disease.

Autophagy and its consequences for platelet biology

Autophagy, the continuous recycling of intracellular building blocks, molecules, and organelles is necessary to preserve cellular function and homeostasis. In this context, it was demonstrated that autophagy plays an important role in megakaryopoiesis, the development and differentiation of hematopoietic progenitor cells into megakaryocytes. Furthermore, in recent years, autophagic proteins were detected in platelets, anucleate cells generated by megakaryocytes, responsible for hemostasis, thrombosis, and a key cell in inflammation and host immune responses. In the last decade studies have indicated the occurrence of autophagy in platelets. Moreover, autophagy in platelets was subsequently demonstrated to be involved in platelet aggregation, adhesion, and thrombus formation. Here, we review the current knowledge about autophagy in platelets, its function, and clinical implications. However, at the advent of platelet autophagy research, additional discoveries derived from evolving work will be required to precisely define the contributions of autophagy in platelets, and to expand the ever increasing physiologic and pathologic roles these remarkable and versatile blood cells play.

High Autophagy Patterns in Swelling Platelets During Apheresis Platelet Storage

Platelets undergo remarkable morphological changes during storage. Platelets change into different sizes and densities and differ in their biochemistry and functions. However, the correlation between structural heterogeneity and platelet autophagy is largely unknown. The aim of this study was to investigate the autophagy process in vitro, such as routine storage of platelets, and explore the role of reactive oxygen species (ROS) involved in the regulation of platelet autophagy. The ROS and autophagy levels of platelet concentrates from apheresis platelets were evaluated through flow cytometry. The expression levels of autophagy-associated proteins (LC3I, LC3II, Beclin1, Parkin, and PINK1) were measured via Western blot. All biomarkers were dynamically monitored for seven days. Moreover, the morphological characteristics of platelet morphology during storage were analyzed through transmission electron microscopy (TEM). Flow cytometry showed that the levels of total cell ROS and mitochondria ROS increased in the stored platelets. Together with the increase in mitochondrial ROS, the autophagy signal LC3 in the platelets was strongly amplified. The number of swollen platelets (large platelets) considerably increased, and that of autophagy signal LC3 was remarkably higher than that of the normal platelets. Western blot revealed that the expression levels of Beclin1 and LC3 II/LC3 I ratio were enhanced, whereas those of Parkin and PINK1 almost did not change during the seven days of storage. The existence of autophagosomes or autophagolysosomes in the platelets at the middle stage of platelet storage was observed via TEM. Our data demonstrated that the subpopulation of large (swollen) platelets exhibited different autophagy patterns. Furthermore, increased platelet autophagy was associated with mitochondrial ROS. These preliminary results suggest that swelling platelets have a higher autophagy pattern than normal platelets during storage.

The platelet transcriptome and proteome in Alzheimer's disease and aging: an exploratory cross-sectional study

Introduction: Alzheimer's disease (AD) and aging are associated with platelet hyperactivity. However, the mechanisms underlying abnormal platelet function in AD and aging are yet poorly understood. Methods: To explore the molecular profile of AD and aged platelets, we investigated platelet activation (i.e., CD62P expression), proteome and transcriptome in AD patients, non-demented elderly, and young individuals as controls. Results: AD, aged and young individuals showed similar levels of platelet activation based on CD62P expression. However, AD and aged individuals had a proteomic signature suggestive of increased platelet activation compared with young controls. Transcriptomic profiling suggested the dysregulation of proteolytic machinery involved in regulating platelet function, particularly the ubiquitin-proteasome system in AD and autophagy in aging. The functional implication of these transcriptomic alterations remains unclear and requires further investigation. Discussion: Our data strengthen the evidence of enhanced platelet activation in aging and provide a first glimpse of the platelet transcriptomic changes occurring in AD.

Advances in Understanding the Links between Metabolism and Autophagy in Acute Myeloid Leukemia: From Biology to Therapeutic Targeting

Autophagy is a highly conserved cellular degradation process that regulates cellular metabolism and homeostasis under normal and pathophysiological conditions. Autophagy and metabolism are linked in the hematopoietic system, playing a fundamental role in the self-renewal, survival, and differentiation of hematopoietic stem and progenitor cells, and in cell death, particularly affecting the cellular fate of the hematopoietic stem cell pool. In leukemia, autophagy sustains leukemic cell growth, contributes to survival of leukemic stem cells and chemotherapy resistance. The high frequency of disease relapse caused by relapse-initiating leukemic cells resistant to therapy occurs in acute myeloid leukemia (AML), and depends on the AML subtypes and treatments used. Targeting autophagy may represent a promising strategy to overcome therapeutic resistance in AML, for which prognosis remains poor. In this review, we illustrate the role of autophagy and the impact of its deregulation on the metabolism of normal and leukemic hematopoietic cells. We report updates on the contribution of autophagy to AML development and relapse, and the latest evidence indicating autophagy-related genes as potential prognostic predictors and drivers of AML. We review the recent advances in autophagy manipulation, combined with various anti-leukemia therapies, for an effective autophagy-targeted therapy for AML.

Thymic stromal lymphopoietin induces platelet mitophagy and promotes thrombosis in Kawasaki disease

Kawasaki disease (KD) is an acute systemic vasculitis primarily affecting infants and children. Activated platelets predispose patients to coronary artery structural lesions that may lead to thrombotic cardiovascular events. To discover potential proteins underlying platelet activation in KD, we conducted a protein chip assay of 34 cytokines and discovered thymic stromal lymphopoietin (TSLP) was aberrantly expressed, which remained elevated after intravenous immunoglobulin G (IVIG) treatment and during convalescence in KD patients in comparison to healthy controls. Enzyme-linked immunosorbent assay (ELISA) corroborated the upregulation of TSLP in KD patients, which was exacerbated in convalescent patients complicated with thrombosis. TSLP receptors on platelets were also significantly upregulated in KD patients complicated with thrombosis. Platelet activation, apoptosis, and mitochondrial autophagy (mitophagy) were increased in convalescence KD patients complicated with thrombosis. In vitro, TSLP induced platelet activation and platelet mitophagy in healthy blood donors, as observed in KD patients. TSLP, similar to mitophagy agonist carbonyl cyanide 3-chlorophenyl hydrazone (CCCP), promoted thrombosis, which was attenuated by the mitophagy inhibitor Mdivi-1. Co-immunoprecipitation in TSLP-treated platelets revealed TSLP receptor (TSLPR) bound to mitophagy regulators, Parkin and Voltage Dependent Anion Channel Protein 1 (VDAC1).Thus, our results demonstrated that TSLP induced platelet mitophagy via a novel TSLPR/Parkin/VDAC1 pathway that promoted thrombosis in KD. These results suggest TSLP as a novel therapeutic target against KD-associated thrombosis.

Platelets, Protean Cells with All-Around Functions and Multifaceted Pharmacological Applications

Platelets, traditionally known for their roles in hemostasis and coagulation, are the most prevalent blood component after erythrocytes (150,000-400,000 platelets/μL in healthy humans). However, only 10,000 platelets/μL are needed for vessel wall repair and wound healing. Increased knowledge of the platelet's role in hemostasis has led to many advances in understanding that they are crucial mediators in many other physiological processes, such as innate and adaptive immunity. Due to their multiple functions, platelet dysfunction is involved not only in thrombosis, mediating myocardial infarction, stroke, and venous thromboembolism, but also in several other disorders, such as tumors, autoimmune diseases, and neurodegenerative diseases. On the other hand, thanks to their multiple functions, nowadays platelets are therapeutic targets in different pathologies, in addition to atherothrombotic diseases; they can be used as an innovative drug delivery system, and their derivatives, such as platelet lysates and platelet extracellular vesicles (pEVs), can be useful in regenerative medicine and many other fields. The protean role of platelets, from the name of Proteus, a Greek mythological divinity who could take on different shapes or aspects, is precisely the focus of this review.

Histone deacetylation-regulated cell surface Siglec-7 expression promoted megakaryocytic maturation and enhanced platelet-like particle release

BACKGROUND

Functioning as important hematologic cells for hemostasis, wound healing and immune defense platelets are produced before being released into the blood by cytoplasmic fragmentation at the end of the megakaryocyte (MK) differentiation, during which the involvement of both apoptosis and autophagy has been reported. Inhibitory sialic acid-binding immunoglobulin-like lectin-7 gene (Siglec-7) can be expressed on platelets and induce apoptosis on activation for uncharacterized function.

OBJECTIVE

We aimed to investigate the regulatory mechanism for Siglec-7 activation along MK differentiation and its physiologic role during the MK maturation and platelet formation.

METHODS

By using 2 well-established MK differentiation models (HEL and K562) and human primary CD34⁺ cell, we examined the upregulations of transcript and protein levels of Siglec-7 during MK differentiation, and the effect of Siglec-7 surface presence on MK differentiation and platelet-like particles (PLPs) release.

RESULTS

We show that both transcripts and surface Siglec-7 were elevated during MK differentiation, and the histone deacetylase 1 (HDAC1) acted as a negative regulator for Siglec-7 activation. By increasing Siglec-7 surface expression, we found that increased presence of Siglec-7 not only enhanced MK maturation but also the release of PLPs by activating caspase 3-dependent signaling, as evidenced in the observation of more CD41, polyploidy, and platelet factor 4 transcript formations.

CONCLUSION

In this study, we demonstrated that Siglec-7 activation was subjected to epigenetic regulation, and the resulting induced expression of surface Siglec-7 played an important regulatory role in promoting MK differentiation, maturation, and PLP formation.

The Function and Regulation of Platelet P2Y12 Receptor

In addition to the key role in hemostasis and thrombosis, platelets have also been wildly acknowledged as immune regulatory cells and involving in the pathogenesis of inflammation-related diseases. Since purine receptor P2Y12 plays a crucial role in platelet activation, P2Y12 antagonists such as clopidogrel, prasugrel, and ticagrelor have been widely used in cardiovascular diseases worldwide in recent decades due to their potent antiplatelet and antithrombotic effects. Meanwhile, the role of P2Y12 in inflammatory diseases has also been extensively studied. Relatively, there are few studies on the regulation of P2Y12. This review first summarizes the various roles of P2Y12 in the process of platelet activation, as well as downstream effects and signaling pathways; then introduces the effects of P2Y12 in inflammatory diseases such as sepsis, atherosclerosis, cancer, autoimmune diseases, and asthma; and finally reviews the current researches on P2Y12 regulation.

The Use of Triphenyl Phosphonium Cation Enhances the Mitochondrial Antiplatelet Effect of the Compound Magnolol

Although platelets are anucleated cells, they have fully functional mitochondria, and currently, it is known that several processes that occur in the platelet require the action of mitochondria. There are plenty of mitochondrial-targeted compounds described in the literature related to cancer, however, only a small number of studies have approached their interaction with platelet mitochondria and/or their effects on platelet activity. Recent studies have shown that magnolia extract and mitochondria-targeted magnolol can inhibit mitochondrial respiration and cell proliferation in melanoma and oral cancer cells, respectively, and they can also induce ROS and mitophagy. In this study, the effect of triphenylphosphonium cation, linked by alkyl chains of different lengths, to the organic compound magnolol on human-washed platelets was evaluated. We demonstrated that the addition of triphenylphosphonium by a four-carbon linker to magnolol (MGN4) considerably enhanced the Magnolol antiplatelet effect by a 3-fold decrease in the IC50. Additionally, platelets exposed to MGN4 5 µM showed several differences from the control including increased basal respiration, collagen-induced respiration, ATP-independent respiration, and reduced ATP-dependent respiration and non-mitochondrial respiration.

Autophagy Is Required to Sustain Increased Intestinal Cell Proliferation during Phenotypic Plasticity Changes in Honey Bee (Apis mellifera)

Tissue phenotypic plasticity facilitates rapid adaptation of organisms to biotic and/or abiotic pressure. The reproductive capacity of honey bee workers (Apis mellifera) is plastic and responsive to pheromones produced by broods and the queen. Egg laying workers (ELWs), which could reactivate their ovaries and lay haploid eggs upon queen lost, have been commonly discussed from many aspects. However, it remains unclear whether midgut homeostasis in ELWs is affected during plastic changes. Here, we found that the expression of nutrition- and autophagy-related genes was up-regulated in the midguts of ELWs, compared with that in nurse workers (NWs) by RNA-sequencing. Furthermore, the area and number of autophagosomes were increased, along with significantly increased cell death in the midguts of ELWs. Moreover, cell cycle progression in the midguts of ELWs was increased compared with that in NWs. Consistent with the up-regulation of nutrition-related genes, the body and midgut sizes, and the number of intestinal proliferation cells of larvae reared with royal jelly (RJ) obviously increased more than those reared without RJ in vitro. Finally, cell proliferation was dramatically suppressed in the midguts of ELWs when autophagy was inhibited. Altogether, our data suggested that autophagy was induced and required to sustain cell proliferation in ELWs' midguts, thereby revealing the critical role of autophagy played in the intestines during phenotypic plasticity changes.

Autophagy and Its Lineage-Specific Roles in the Hematopoietic System

Autophagy is a dynamic process that regulates the selective and nonselective degradation of cytoplasmic components, such as damaged organelles and protein aggregates inside lysosomes to maintain tissue homeostasis. Different types of autophagy including macroautophagy, microautophagy, and chaperon-mediated autophagy (CMA) have been implicated in a variety of pathological conditions, such as cancer, aging, neurodegeneration, and developmental disorders. Furthermore, the molecular mechanism and biological functions of autophagy have been extensively studied in vertebrate hematopoiesis and human blood malignancies. In recent years, the hematopoietic lineage-specific roles of different autophagy-related (ATG) genes have gained more attention. The evolution of gene-editing technology and the easy access nature of hematopoietic stem cells (HSCs), hematopoietic progenitors, and precursor cells have facilitated the autophagy research to better understand how ATG genes function in the hematopoietic system. Taking advantage of the gene-editing platform, this review has summarized the roles of different ATGs at the hematopoietic cell level, their dysregulation, and pathological consequences throughout hematopoiesis.

Understanding Long COVID; Mitochondrial Health and Adaptation-Old Pathways, New Problems

Many people infected with the SARS-CoV-2 suffer long-term symptoms, such as "brain fog", fatigue and clotting problems. Explanations for "long COVID" include immune imbalance, incomplete viral clearance and potentially, mitochondrial dysfunction. As conditions with sub-optimal mitochondrial function are associated with initial severity of the disease, their prior health could be key in resistance to long COVID and recovery. The SARs virus redirects host metabolism towards replication; in response, the host can metabolically react to control the virus. Resolution is normally achieved after viral clearance as the initial stress activates a hormetic negative feedback mechanism. It is therefore possible that, in some individuals with prior sub-optimal mitochondrial function, the virus can "tip" the host into a chronic inflammatory cycle. This might explain the main symptoms, including platelet dysfunction. Long COVID could thus be described as a virally induced chronic and self-perpetuating metabolically imbalanced non-resolving state characterised by mitochondrial dysfunction, where reactive oxygen species continually drive inflammation and a shift towards glycolysis. This would suggest that a sufferer's metabolism needs to be "tipped" back using a stimulus, such as physical activity, calorie restriction, or chemical compounds that mimic these by enhancing mitochondrial function, perhaps in combination with inhibitors that quell the inflammatory response.

Exosomes, autophagy and ER stress pathways in human diseases: Cross-regulation and therapeutic approaches

Exosomal release pathway and autophagy together maintain homeostasis and survival of cells under stressful conditions. Autophagy is a catabolic process through which cell entities, such as malformed biomacromolecules and damaged organelles, are degraded and recycled via the lysosomal-dependent pathway. Exosomes, a sub-type of extracellular vesicles (EVs) formed by the inward budding of multivesicular bodies (MVBs), are mostly involved in mediating communication between cells. The unfolded protein response (UPR) is an adaptive response that is activated to sustain survival in the cells faced with the endoplasmic reticulum (ER) stress through a complex network that involves protein synthesis, exosomes secretion and autophagy. Disruption of the critical crosstalk between EVs, UPR and autophagy may be implicated in various human diseases, including cancers and neurodegenerative diseases, yet the molecular mechanism(s) behind the coordination of these communication pathways remains obscure. Here, we review the available information on the mechanisms that control autophagy, ER stress and EV pathways, with the view that a better understanding of their crosstalk and balance may improve our knowledge on the pathogenesis and treatment of human diseases, where these pathways are dysregulated.

Current therapeutic strategies and perspectives in refractory ITP: What have we learned recently?

Immune thrombocytopenia (ITP) is an acquired autoimmune bleeding disorder featured by increased platelet destruction and deficient megakaryocyte maturation. First-line treatments include corticosteroids, intravenous immunoglobulin and intravenous anti-D immunoglobulin. Second-line treatments consist of rituximab, thrombopoietin receptor agonists and splenectomy. Although most patients benefit from these treatments, an individualized treatment approach is warranted due to the large heterogeneity among ITP patients. In addition, ITP patients may relapse and there remains a subset of patients who become refractory to treatments. The management of these refractory patients is still a challenge. This review aims to summarize emerging therapeutic approaches for refractory ITP in several categories according to their different targets, including macrophages, platelets/megakaryocytes, T cells, B cells, and endothelial cells. Moreover, current management strategies and combination regimens of refractory ITP are also discussed.

Unfolded Protein Response Differentially Modulates the Platelet Phenotype

BACKGROUND

Unfolded protein response (UPR) is a multifaceted signaling cascade that alleviates protein misfolding. Although well studied in nucleated cells, UPR in absence of transcriptional regulation has not been described. Intricately associated with cardiovascular diseases, platelets, despite being anucleate, respond rapidly to stressors in blood. We investigate the UPR in anucleate platelets and explore its role, if any, on platelet physiology and function.

METHODS

Human and mouse platelets were studied using a combination of ex vivo and in vivo experiments. Platelet lineage-specific knockout mice were generated independently for each of the 3 UPR pathways, PERK (protein kinase RNA [PKR]-like endoplasmic reticulum kinase), XBP1 (X-binding protein), and ATF6 (activating transcription factor 6). Diabetes patients were prospectively recruited, and platelets were evaluated for activation of UPR under chronic pathophysiological disease conditions.

RESULTS

Tunicamycin induced the IRE1α (inositol-requiring enzyme-1alpha)-XBP1 pathway in human and mouse platelets, while oxidative stress predominantly activated the PERK pathway. PERK deletion significantly increased platelet aggregation and apoptosis and phosphorylation of PLCγ2, PLCβ3, and p38 MAPK. Deficiency of XBP1 increased platelet aggregation, with higher PLCβ3 and PKCδ activation. ATF6 deletion mediated a relatively modest effect on platelet phenotype with increased PKA (protein kinase A). Platelets from diabetes patients exhibited a positive correlation between disease severity, platelet activation, and protein aggregation, with only IRE1α-XBP1 activation. Moreover, IRE1α inhibition increased platelet aggregation, while clinically approved chemical chaperone, sodium 4-phenylbutyrate reduced the platelet hyperactivation.

CONCLUSIONS

We show for the first time, that UPR activation occurs in platelets and can be independent of genomic regulation, with selective induction being specific to the source and severity of stress. Each UPR pathway plays a key role and can differentially modulate the platelet activation pathways and phenotype. Targeting the specific arms of UPR may provide a new antiplatelet strategy to mitigate thrombotic risk in diabetes and other cardiovascular diseases.

Platelet activation and partial desensitization are associated with viral xenophagy in patients with severe COVID-19

During severe COVID-19, platelets get activated and become partly desensitized through mechanisms involving glycoprotein shedding.

Platelets from patients with severe COVID-19 internalize SARS-CoV-2 and develop viral xenophagy.

Mild thrombocytopenia, changes in platelet gene expression, enhanced platelet functionality, and presence of platelet-rich thrombi in the lung have been associated with thromboinflammatory complications of patients with COVID-19. However, whether severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) gets internalized by platelets and directly alters their behavior and function in infected patients remains elusive. Here, we investigated platelet parameters and the presence of viral material in platelets from a prospective cohort of 29 patients with severe COVID-19 admitted to an intensive care unit. A combination of specific assays, tandem mass spectrometry, and flow cytometry indicated high levels of protein and lipid platelet activation markers in the plasma from patients with severe COVID-19 associated with an increase of proinflammatory cytokines and leukocyte-platelets interactions. Platelets were partly desensitized, as shown by a significant reduction of αIIbβ3 activation and granule secretion in response to stimulation and a decrease of surface GPVI, whereas plasma from patients with severe COVID-19 potentiated washed healthy platelet aggregation response. Transmission electron microscopy indicated the presence of SARS-CoV-2 particles in a significant fraction of platelets as confirmed by immunogold labeling and immunofluorescence imaging of Spike and nucleocapsid proteins. Compared with platelets from healthy donors or patients with bacterial sepsis, platelets from patients with severe COVID-19 exhibited enlarged intracellular vesicles and autophagolysosomes. They had large LC3-positive structures and increased levels of LC3II with a co-localization of LC3 and Spike, suggesting that platelets can digest SARS-CoV-2 material by xenophagy in critically ill patients. Altogether, these data show that during severe COVID-19, platelets get activated, become partly desensitized, and develop a selective autophagy response.

TLR4 inhibitor alleviates sepsis-induced organ failure by inhibiting platelet mtROS production, autophagy, and GPIIb/IIIa expression

Thrombocytopenia and impaired platelet function are associated with sepsis-induced organ failure. Numerous studies have shown that mitochondrial ROS (mtROS) and autophagy are related to organ injury in sepsis. However, the relationships between platelet mtROS, autophagy and sepsis organ failure remain unclear. Herein, we explored whether toll like receptor 4 (TLR4) inhibitor alleviates sepsis organ failure by inhibiting platelet mtROS production, autophagy, and GPIIb/IIIa expression.Mice were administrated with LPS, LPS + TAK242 or vehicle. The lungs and kidneys were harvested and analyzed using hematoxylin and eosin staining assay. Platelet rich plasma (PRP) was isolated from blood and platelets aggregation and TLR4 expression were analyzed using flow cytometer and western blot. PRP from healthy volunteers was treated with saline, LPS, or LPS + TAK242, and then mitoSOX and calcium were detected using flow cytometer, and NOX2 and LC3B were tested using western blot.Results showed that TAK242 effectively alleviated LPS-induced acute kidney and lung injury in mice, and decreased CD41 expression more significantly than CD62P. In vitro, by inhibiting TLR4, TAK242 suppressed Ca²⁺, mitoSOX fluorescence, NOX2 expression and LC3BII/LC3BI ratio in LPS treated platelets.TLR4 inhibitor TAK242 may effectively alleviate mouse lung and kidney injury by inhibition of mouse platelet GPIIb/IIIa, and reduce LPS-induced mtROS generation related to Ca²⁺ influx, thus reducing platelet activation.

Redox Mechanisms of Platelet Activation in Aging

Aging is intrinsically linked with physiologic decline and is a major risk factor for a broad range of diseases. The deleterious effects of advancing age on the vascular system are evidenced by the high incidence and prevalence of cardiovascular disease in the elderly. Reactive oxygen species are critical mediators of normal vascular physiology and have been shown to gradually increase in the vasculature with age. There is a growing appreciation for the complexity of oxidant and antioxidant systems at the cellular and molecular levels, and accumulating evidence indicates a causal association between oxidative stress and age-related vascular disease. Herein, we review the current understanding of mechanistic links between oxidative stress and thrombotic vascular disease and the changes that occur with aging. While several vascular cells are key contributors, we focus on oxidative changes that occur in platelets and their mediation in disease progression. Additionally, we discuss the impact of comorbid conditions (i.e., diabetes, atherosclerosis, obesity, cancer, etc.) that have been associated with platelet redox dysregulation and vascular disease pathogenesis. As we continue to unravel the fundamental redox mechanisms of the vascular system, we will be able to develop more targeted therapeutic strategies for the prevention and management of age-associated vascular disease.

Autophagy Ameliorates Reactive Oxygen Species-Induced Platelet Storage Lesions

Platelet transfusion is a life-saving therapy to prevent bleeding; however, the availability of platelets for transfusion is limited by the markedly short shelf life owing to the development of platelet storage lesions (PSLs). The mechanism of PSLs remains obscure. Dissection of the intracellular biological changes in stored platelets may help to reduce PSLs and improve platelet transfusion efficiency. In the present study, we explore the changes of stored platelets at room temperature under constant agitation. We found that platelets during storage showed an increased reactive oxygen species (ROS) generation accompanied with receptor shedding, apoptosis, and diminished platelet aggregation. ROS scavenger reduced platelet shedding but also impaired platelet aggregation. Autophagy is a conserved catabolic process that sequesters protein aggregates and damaged organelles into lysosomes for degradation and platelets’ own intact autophagic system. We revealed that there exist a stable autophagic flux in platelets at the early stage of storage, and the autophagic flux in platelets perished after long-term storage. Treatment stored platelets with rapamycin, which stimulates autophagy in eukaryotic cells, markedly ameliorated PSLs, and improved platelet aggregation in response to extracellular stimuli.

Human platelets display dysregulated sepsis-associated autophagy, induced by altered LC3 protein-protein interaction of the Vici-protein EPG5

Platelets mediate central aspects of host responses during sepsis, an acute profoundly systemic inflammatory response due to infection. Macroautophagy/autophagy, which mediates critical aspects of cellular responses during inflammatory conditions, is known to be a functional cellular process in anucleate platelets, and is essential for normal platelet functions. Nevertheless, how sepsis may alter autophagy in platelets has never been established. Using platelets isolated from septic patients and matched healthy controls, we show that during clinical sepsis, the number of autophagosomes is increased in platelets, most likely due to an accumulation of autophagosomes, some containing mitochondria and indicative of mitophagy. Therefore, autophagy induction or early-stage autophagosome formation (as compared to decreased later-stage autophagosome maturation or autophagosome-late endosome/lysosome fusion) is normal or increased. This was consistent with decreased fusion of autophagosomes with lysosomes in platelets. EPG5 (ectopic P-granules autophagy protein 5 homolog), a protein essential for normal autophagy, expression did increase, while protein-protein interactions between EPG5 and MAP1LC3/LC3 (which orchestrate the fusion of autophagosomes and lysosomes) were significantly reduced in platelets during sepsis. Furthermore, data from a megakaryocyte model demonstrate the importance of TLR4 (toll like receptor 4), LPS-dependent signaling for regulating this mechanism. Similar phenotypes were also observed in platelets isolated from a patient with Vici syndrome: an inherited condition caused by a naturally occurring, loss-of-function mutation in EPG5. Together, we provide evidence that autophagic functions are aberrant in platelets during sepsis, due in part to reduced EPG5-LC3 interactions, regulated by TLR4 engagement, and the resultant accumulation of autophagosomes.Abbreviations: ACTB: beta actin; CLP: cecal ligation and puncture; Co-IP: co-immunoprecipitation; DAP: death associated protein; DMSO: dimethyl sulfoxide; EPG5: ectopic P-granules autophagy protein 5 homolog; ECL: enhanced chemiluminescence; HBSS: Hanks' balanced salt solution; HRP: horseradish peroxidase; ICU: intensive care unit; LPS: lipopolysaccharide; LAMP1: lysosomal associated membrane protein 1; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; MTOR: mechanistic target of rapamycin kinase; MKs: megakaryocytes; PFA: paraformaldehyde; PBS: phosphate-buffered saline; PLA: proximity ligation assay; pRT-PCR: quantitative real-time polymerase chain reaction; RT: room temperature; SQSTM1/p62: sequestosome 1; SDS-PAGE: sodium dodecyl sulfate-polyacrylamide gel electrophoresis; TLR4: toll like receptor 4; TEM: transmission electron microscopy; WGA: wheat germ agglutinin.

Quantitative LC-MS/MS uncovers the regulatory role of autophagy in immune thrombocytopenia

BACKGROUND

Immune thrombocytopenia (ITP) is an autoimmune haemorrhagic disease whose pathogenesis is associated with bone marrow megakaryocyte maturation disorder and destruction of the haematopoietic stem cell microenvironment.

METHODS

In this study, we report the qualitative and quantitative profiles of the ITP proteome. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) was conducted to elucidate the protein profiles of clinical bone marrow mononuclear cell (BMMC) samples from ITP patients and healthy donors (controls). Gene Ontology (GO) and Kyoto Encyclopaedia Genes and Genome (KEGG) pathway analyses were performed to annotate the differentially expressed proteins. A protein-protein interaction (PPI) network was constructed with the BLAST online database. Target proteins associated with autophagy were quantitatively identified by parallel reaction monitoring (PRM) analysis.

RESULTS

Our approaches showed that the differentially expressed autophagy-related proteins, namely, HSPA8, PARK7, YWHAH, ITGB3 and CSF1R, were changed the most. The protein expression of CSF1R in ITP patients was higher than that in controls, while other autophagy-related proteins were expressed at lower levels in ITP patients than in controls.

CONCLUSION

Bioinformatics analysis indicated that disruption of the autophagy pathway is a potential pathological mechanism of ITP. These results can provide a new direction for exploring the molecular mechanism of ITP.

Involvement of autophagy in diosgenin‑induced megakaryocyte differentiation in human erythroleukemia cells

Natural agents have been used to restart the process of differentiation that is inhibited during leukemic transformation of hematopoietic stem or progenitor cells. Autophagy is a housekeeping pathway that maintains cell homeostasis against stress by recycling macromolecules and organelles and plays an important role in cell differentiation. In the present study, an experimental model was established to investigate the involvement of autophagy in the megakaryocyte differentiation of human erythroleukemia (HEL) cells induced by diosgenin [also known as (25R)‑Spirosten‑5‑en‑3b‑ol]. It was demonstrated that Atg7 expression was upregulated from day 1 of diosgenin‑induced differentiation and was accompanied by a significant elevation in the conversion of light chain 3 A/B (LC3‑A/B)‑I to LC3‑A/B‑II. Autophagy was modulated before or after the induction of megakaryocyte differentiation using 3‑methyladenine (3‑MA, autophagy inhibitor) and metformin (Met, autophagy initiation activator). 3‑MA induced a significant accumulation of the LC3 A/B‑II form at day 8 of differentiation. It was revealed that 3‑MA had a significant repressive effect on the nuclear (polyploidization) and membrane glycoprotein V [(GpV) expression] maturation. On the other hand, autophagy activation increased GpV genomic expression, but did not change the nuclear maturation profile after HEL cells treatment with Met. It was concluded that autophagy inhibition had a more prominent effect on the diosgenin‑differentiated cells than autophagy activation.

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

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

Usnic Acid and Usnea barbata (L.) F.H. Wigg. Dry Extracts Promote Apoptosis and DNA Damage in Human Blood Cells through Enhancing ROS Levels

Nowadays, numerous biomedical studies performed on natural compounds and plant extracts aim to obtain highly selective pharmacological activities without unwanted toxic effects. In the big world of medicinal plants, Usnea barbata (L) F.H. Wigg (U. barbata) and usnic acid (UA) are well-known for their therapeutical properties. One of the most studied properties is their cytotoxicity on various tumor cells. This work aims to evaluate their cytotoxic potential on normal blood cells. Three dry U. barbata extracts in various solvents: ethyl acetate (UBEA), acetone (UBA), and ethanol (UBE) were prepared. From UBEA we isolated usnic acid with high purity by semipreparative chromatography. Then, UA, UBA, and UBE dissolved in 1% dimethyl sulfoxide (DMSO) and diluted in four concentrations were tested for their toxicity on human blood cells. The blood samples were collected from a healthy non-smoker donor; the obtained blood cell cultures were treated with the tested samples. After 24 h, the cytotoxic effect was analyzed through the mechanisms that can cause cell death: early and late apoptosis, caspase 3/7 activity, nuclear apoptosis, autophagy, reactive oxygen species (ROS) level and DNA damage. Generally, the cytotoxic effect was directly proportional to the increase of concentrations, usnic acid inducing the most significant response. At high concentrations, usnic acid and U. barbata extracts induced apoptosis and DNA damage in human blood cells, increasing ROS levels. Our study reveals the importance of prior natural products toxicity evaluation on normal cells to anticipate their limits and benefits as potential anticancer drugs.

Curcumin at Low Doses Potentiates and at High Doses Inhibits ABT-737-Induced Platelet Apoptosis

Curcumin is a natural bioactive component derived from the turmeric plant Curcuma longa, which exhibits a range of beneficial activities on human cells. Previously, an inhibitory effect of curcumin on platelets was demonstrated. However, it is unknown whether this inhibitory effect is due to platelet apoptosis or procoagulant platelet formation. In this study, curcumin did not activate caspase 3-dependent apoptosis of human platelets, but rather induced the formation of procoagulant platelets. Interestingly, curcumin at low concentration (5 µM) potentiated, and at high concentration (50 µM) inhibited ABT-737-induced platelet apoptosis, which was accompanied by inhibition of ABT-737-mediated thrombin generation. Platelet viability was not affected by curcumin at low concentration and was reduced by 17% at high concentration. Furthermore, curcumin-induced autophagy in human platelets via increased translocation of LC3I to LC3II, which was associated with activation of adenosine monophosphate (AMP) kinase and inhibition of protein kinase B activity. Because curcumin inhibits P-glycoprotein (P-gp) in cancer cells and contributes to overcoming multidrug resistance, we showed that curcumin similarly inhibited platelet P-gp activity. Our results revealed that the platelet inhibitory effect of curcumin is mediated by complex processes, including procoagulant platelet formation. Thus, curcumin may protect against or enhance caspase-dependent apoptosis in platelets under certain conditions.

Super-resolution imaging of platelet-activation process and its quantitative analysis

Understanding the platelet activation molecular pathways by characterizing specific protein clusters within platelets is essential to identify the platelet activation state and improve the existing therapies for hemostatic disorders. Here, we employed various state-of-the-art super-resolution imaging and quantification methods to characterize the platelet spatiotemporal ultrastructural change during the activation process due to phorbol 12-myristate 13-acetate (PMA) stimuli by observing the cytoskeletal elements and various organelles at nanoscale, which cannot be done using conventional microscopy. Platelets could be spread out with the guidance of actin and microtubules, and most organelles were centralized probably due to the limited space of the peripheral thin regions or the close association with the open canalicular system (OCS). Among the centralized organelles, we provided evidence that granules are fused with the OCS to release their cargo through enlarged OCS. These findings highlight the concerted ultrastructural reorganization and relative arrangements of various organelles upon activation and call for a reassessment of previously unresolved complex and multi-factorial activation processes.

Electrospun Polydioxanone Loaded With Chloroquine Modulates Template-Induced NET Release and Inflammatory Responses From Human Neutrophils

The implantation of a biomaterial quickly initiates a tissue repair program initially characterized by a neutrophil influx. During the acute inflammatory response, neutrophils release neutrophil extracellular traps (NETs) and secrete soluble signals to modulate the tissue environment. In this work, we evaluated chloroquine diphosphate, an antimalarial with immunomodulatory and antithrombotic effects, as an electrospun biomaterial additive to regulate neutrophil-mediated inflammation. Electrospinning of polydioxanone was optimized for rapid chloroquine elution within 1 h, and acute neutrophil-biomaterial interactions were evaluated in vitro with fresh human peripheral blood neutrophils at 3 and 6 h before quantifying the release of NETs and secretion of inflammatory and regenerative factors. Our results indicate that chloroquine suppresses NET release in a biomaterial surface area–dependent manner at the early time point, whereas it modulates signal secretion at both early and late time points. More specifically, chloroquine elution down-regulates interleukin 8 (IL-8) and matrix metalloproteinase nine secretion while up-regulating hepatocyte growth factor, vascular endothelial growth factor A, and IL-22 secretion, suggesting a potential shift toward a resolving neutrophil phenotype. Our novel repurposing of chloroquine as a biomaterial additive may therefore have synergistic, immunomodulatory effects that are advantageous for biomaterial-guided in situ tissue regeneration applications.

Platelet autophagic machinery involved in thrombosis through a novel linkage of AMPK-MTOR to sphingolipid metabolism

Basal macroautophagy/autophagy has recently been found in anucleate platelets. Platelet autophagy is involved in platelet activation and thrombus formation. However, the mechanism underlying autophagy in anucleate platelets require further clarification. Our data revealed that LC3-II formation and SQSTM1/p62 degradation were noted in H₂O₂-activated human platelets, which could be blocked by 3-methyladenine and bafilomycin A₁, indicating that platelet activation may cause platelet autophagy. AMPK phosphorylation and MTOR dephosphorylation were also detected, and block of AMPK activity by the AMPK inhibitor dorsomorphin reversed SQSTM1 degradation and LC3-II formation. Moreover, autophagosome formation was observed through transmission electron microscopy and deconvolution microscopy. These findings suggest that platelet autophagy was induced partly through the AMPK-MTOR pathway. In addition, increased LC3-II expression occurred only in H₂O₂-treated Atg5^f/f platelets, but not in H₂O₂-treated atg5^-/- platelets, suggesting that platelet autophagy occurs during platelet activation. atg5^-/- platelets also exhibited a lower aggregation in response to agonists, and platelet-specific atg5^-/- mice exhibited delayed thrombus formation in mesenteric microvessles and decreased mortality rate due to pulmonary thrombosis. Notably, metabolic analysis revealed that sphingolipid metabolism is involved in platelet activation, as evidenced by observed several altered metabolites, which could be reversed by dorsomorphin. Therefore, platelet autophagy and platelet activation are positively correlated, partly through the interconnected network of sphingolipid metabolism. In conclusion, this study for the first time demonstrated that AMPK-MTOR signaling could regulate platelet autophagy. A novel linkage between AMPK-MTOR and sphingolipid metabolism in anucleate platelet autophagy was also identified: platelet autophagy and platelet activation are positively correlated.Abbreviations: 3-MA: 3-methyladenine; A.C.D.: citric acid/sod. citrate/glucose; ADP: adenosine diphosphate; AKT: AKT serine/threonine kinase; AMPK: AMP-activated protein kinase; ANOVA: analysis of variance; ATG: autophagy-related; B4GALT/LacCS: beta-1,4-galactosyltransferase; Baf-A1: bafilomycin A₁; BECN1: beclin 1; BHT: butylate hydrooxytoluene; BSA: bovine serum albumin; DAG: diacylglycerol; ECL: enhanced chemiluminescence; EDTA: ethylenediamine tetraacetic acid; ELISA: enzyme-linked immunosorbent assay; GALC/GCDase: galactosylceramidase; GAPDH: glyceraldehyde-3-phosphate dehydrogenase; GBA/GluSDase: glucosylceramidase beta; GPI: glycosylphosphatidylinositol; H₂O₂: hydrogen peroxide; HMDB: human metabolome database; HRP: horseradish peroxidase; IF: immunofluorescence; IgG: immunoglobulin G; KEGG: Kyoto Encyclopedia of Genes and Genomes; LAMP1: lysosomal associated membrane protein 1; LC-MS/MS: liquid chromatography-tandem mass spectrometry; mAb: monoclonal antibody; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; MPV: mean platelet volume; MTOR: mechanistic target of rapamycin kinase; ox-LDL: oxidized low-density lipoprotein; pAb: polyclonal antibody; PC: phosphatidylcholine; PCR: polymerase chain reaction; PI3K: phosphoinositide 3-kinase; PLS-DA: partial least-squares discriminant analysis; PRP: platelet-rich plasma; Q-TOF: quadrupole-time of flight; RBC: red blood cell; ROS: reactive oxygen species; RPS6KB/p70S6K: ribosomal protein S6 kinase B; SDS: sodium dodecyl sulfate; S.E.M.: standard error of the mean; SEM: scanning electron microscopy; SGMS: sphingomyelin synthase; SM: sphingomyelin; SMPD/SMase: sphingomyelin phosphodiesterase; SQSTM1/p62: sequestosome 1; TEM: transmission electron microscopy; UGT8/CGT: UDP glycosyltransferase 8; UGCG/GCS: UDP-glucose ceramide glucosyltransferase; ULK1: unc-51 like autophagy activating kinase 1; UPLC: ultra-performance liquid chromatography; PIK3C3/VPS34: phosphatidylinositol 3-kinase catalytic subunit type 3; PtdIns3P: phosphatidylinositol-3-phosphate; WBC: white blood cell; WT: wild type.

Impact of platelet-rich plasma versus selenium in ameliorating induced toxicity in rat testis: histological, immunohistochemical, and molecular study

This study was conducted on forty adult rats divided into four groups: Group I (control) that is divided into subgroups A, B, and C and Group II (methotrexate (MTX)-treated); the rats were injected intraperitoneally with MTX at a dose of 1 mg/kg/week, for 8 weeks. Group III (MTX-Se co-treated) was injected with MTX like Group II plus an oral administration of selenium at a dose of 10 μg/kg b.w/day, for 8 weeks. Group IV (MTX-PRP co-treated), rats were injected intraperitoneally with MTX like Group II plus platelet-rich plasma (PRP) injection under the scrotum, three times with 2-week intervals (volume-0.1 ml per injection) and euthanized after 8 weeks. Histological, immunohistochemical, and genetic expression using qPCR and western blotting technique were conducted. There was improvement in histological structure of testes in most specimens of Group IV. The latter group revealed a significant decrease in Bax and an increase in Bcl-2. The regeneration of testicular tissue was more observed in Group IV as measured by an increase in mean number of PCNA. Moreover, Group IV revealed an increased genetic level of FSCN3, GCNF, UBQLN3, and DAZL. Both MTX-Se and MTX-PRP have an anti-inflammatory effect as measured by a reduction in NF-κb. The anti-oxidative effect of selenium and PRP was noticed by a decrease in the level of the iNos and an increase in eNos protein and the autophagy marker LC3. PRP has ameliorative effects on induced rat testicular toxicity as evaluated by morphological changes and confirmed by immunohistochemical reactions, genetic expression, and western blotting analyses including oxidative and anti- oxidative markers.

Inflammation, Nitro-Oxidative Stress, Impaired Autophagy, and Insulin Resistance as a Mechanistic Convergence Between Arterial Stiffness and Alzheimer's Disease

The average age of the world's elderly population is steadily increasing. This unprecedented rise in the aged world population will increase the prevalence of age-related disorders such as cardiovascular disease (CVD) and neurodegeneration. In recent years, there has been an increased interest in the potential interplay between CVDs and neurodegenerative syndromes, as several vascular risk factors have been associated with Alzheimer's disease (AD). Along these lines, arterial stiffness is an independent risk factor for both CVD and AD. In this review, we discuss several inflammaging-related disease mechanisms including acute tissue-specific inflammation, nitro-oxidative stress, impaired autophagy, and insulin resistance which may contribute to the proposed synergism between arterial stiffness and AD.

Autophagy attenuates high glucose-induced oxidative injury to lens epithelial cells

Purpose: Autophagic dysfunction and abnormal oxidative stress are associated with cataract. The purpose of the present study was to investigate the changes of cellular autophagy and oxidative stress and their association in lens epithelial cells (LECs) upon exposure to high glucose.

Methods: Autophagy and oxidative stress-related changes were detected in streptozotocin-induced Type 1 diabetic mice and normal mouse LECs incubated in high glucose conditions. Rapamycin at a concentration of 100 nm/l or 50 μM chloroquine was combined for analysis of the relationship between autophagy and oxidative stress. The morphology of LECs during autophagy was observed by transmission electron microscopy. The expressions of autophagy markers (LC3B and p62) were identified, as well as the key factors of oxidative stress (SOD2 and CAT) and mitochondrial reactive oxygen species (ROS) generation.

Results: Transmission electron microscopy indicated an altered autophagy activity in diabetic mouse lens tissues with larger autophagosomes and multiple mitochondria. Regarding the expressions, LC3B was elevated, p62 was decreased first and then increased, and SOD2 and CAT were increased before a decrease during 4 months of follow-up in diabetic mice and 72 h of culture under high glucose for mouse LECs. Furthermore, rapamycin promoted the expressions of autophagy markers but alleviated those of oxidative stress markers, whereas chloroquine antagonized autophagy but enhanced oxidative stress by elevating ROS generation in LECs exposed to high glucose.

Conclusions: The changes in autophagy and oxidative stress were fluctuating in the mouse LECs under constant high glucose conditions. Autophagy might attenuate high glucose-induced oxidative injury to LECs.

Thrombocytopathy and endotheliopathy: crucial contributors to COVID-19 thromboinflammation

The core pathology of coronavirus disease 2019 (COVID-19) is infection of airway cells by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) that results in excessive inflammation and respiratory disease, with cytokine storm and acute respiratory distress syndrome implicated in the most severe cases. Thrombotic complications are a major cause of morbidity and mortality in patients with COVID-19. Patients with pre-existing cardiovascular disease and/or traditional cardiovascular risk factors, including obesity, diabetes mellitus, hypertension and advanced age, are at the highest risk of death from COVID-19. In this Review, we summarize new lines of evidence that point to both platelet and endothelial dysfunction as essential components of COVID-19 pathology and describe the mechanisms that might account for the contribution of cardiovascular risk factors to the most severe outcomes in COVID-19. We highlight the distinct contributions of coagulopathy, thrombocytopathy and endotheliopathy to the pathogenesis of COVID-19 and discuss potential therapeutic strategies in the management of patients with COVD-19. Harnessing the expertise of the biomedical and clinical communities is imperative to expand the available therapeutics beyond anticoagulants and to target both thrombocytopathy and endotheliopathy. Only with such collaborative efforts can we better prepare for further waves and for future coronavirus-related pandemics.

ECM-regulation of autophagy: The yin and the yang of autophagy during wound healing

Wound healing is a complex sequence of tissue protection, replacement, and reorganization leading to regenerated tissue. Disruption of any of these steps results in the process being incomplete as an ulcer or over-exuberant as a hypertrophic scar. Over the past decade, it has become evident that the extracellular matrix and associated components orchestrate this process. However, the cellular events that are induced by the extracellular matrix to accomplish wound healing remain to be defined. Herein we propose that matrix-regulated cellular macro-autophagy is key to both the tissue replacement and resolution stages of healing by directing cellular function or apoptosis. Further, disruptions in matrix turnover alter autophagic function leading to chronic wounds or scarring. While the literature that directly investigates autophagy during wound healing is sparse, the emerging picture supports our proposing a model of the centrality of the matrix-autophagy modulation as central to physiologic and pathologic healing.

Guidelines for the use and interpretation of assays for monitoring autophagy (4th edition)1

In 2008, we published the first set of guidelines for standardizing research in autophagy. Since then, this topic has received increasing attention, and many scientists have entered the field. Our knowledge base and relevant new technologies have also been expanding. Thus, it is important to formulate on a regular basis updated guidelines for monitoring autophagy in different organisms. Despite numerous reviews, there continues to be confusion regarding acceptable methods to evaluate autophagy, especially in multicellular eukaryotes. Here, we present a set of guidelines for investigators to select and interpret methods to examine autophagy and related processes, and for reviewers to provide realistic and reasonable critiques of reports that are focused on these processes. These guidelines are not meant to be a dogmatic set of rules, because the appropriateness of any assay largely depends on the question being asked and the system being used. Moreover, no individual assay is perfect for every situation, calling for the use of multiple techniques to properly monitor autophagy in each experimental setting. Finally, several core components of the autophagy machinery have been implicated in distinct autophagic processes (canonical and noncanonical autophagy), implying that genetic approaches to block autophagy should rely on targeting two or more autophagy-related genes that ideally participate in distinct steps of the pathway. Along similar lines, because multiple proteins involved in autophagy also regulate other cellular pathways including apoptosis, not all of them can be used as a specific marker for bona fide autophagic responses. Here, we critically discuss current methods of assessing autophagy and the information they can, or cannot, provide. Our ultimate goal is to encourage intellectual and technical innovation in the field.

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.

Parkin Coordinates Platelet Stress Response in Diabetes Mellitus: A Big Role in a Small Cell

Increased platelet activation and apoptosis are characteristic of diabetic (DM) platelets, where a Parkin-dependent mitophagy serves a major endogenous protective role. We now demonstrate that Parkin is highly expressed in both healthy platelets and diabetic platelets, compared to other mitochondria-enriched tissues such as the heart, muscle, brain, and liver. Abundance of Parkin in a small, short-lived anucleate cell suggest significance in various key processes. Through proteomics we identified 127 Parkin-interacting proteins in DM platelets and compared them to healthy controls. We assessed the 11 highest covered proteins by individual IPs and confirmed seven proteins that interacted with Parkin; VCP/p97, LAMP1, HADHA, FREMT3, PDIA, ILK, and 14-3-3. Upon further STRING analysis using GO and KEGG, interactions were divided into two broad groups: targeting platelet activation through (1) actions on mitochondria and (2) actions on integrin signaling. Parkin plays an important role in mitochondrial protection through mitophagy (VCP/p97), recruiting phagophores, and targeting lysosomes (with LAMP1). Mitochondrial β-oxidation may also be regulated by the Parkin/HADHA interaction. Parkin may regulate platelet aggregation and activation through integrin signaling through interactions with proteins like FREMT3, PDIA, ILK, and 14-3-3. Thus, platelet Parkin may regulate the protection (mitophagy) and stress response (platelet activation) in DM platelets. This study identified new potential therapeutic targets for platelet mitochondrial dysfunction and hyperactivation in diabetes mellitus.

Role of long noncoding RNA MEG3/miR-378/GRB2 axis in neuronal autophagy and neurological functional impairment in ischemic stroke

Autophagy has been shown to maintain neural system homeostasis during stroke. However, the molecular mechanisms underlying neuronal autophagy in ischemic stroke remain poorly understood. This study aims to investigate the regulatory mechanisms of the pathway consisting of MEG3 (maternally expressed gene 3), microRNA-378 (miR-378), and GRB2 (growth factor receptor-bound protein 2) in neuronal autophagy and neurological functional impairment in ischemic stroke. A mouse model of the middle cerebral artery occluded-induced ischemic stroke and an in vitro model of oxygen-glucose deprivation-induced neuronal injury were developed. To understand the role of the MEG3/miR-378/GRB2 axis in the neuronal regulation, the expression of proteins associated with autophagy in neurons was measured by Western blotting analysis, and neuron death was evaluated using a lactate dehydrogenase leakage rate test. First, it was found that the GRB2 gene, up-regulated in middle cerebral artery occluded-operated mice and oxygen-glucose deprivation-exposed neurons, was a target gene of miR-378. Next, miR-378 inhibited neuronal loss and neurological functional impairment in mice, as well as neuronal autophagy and neuronal death by silencing of GRB2. Confirmatory in vitro experiments showed that MEG3 could specifically bind to miR-378 and subsequently up-regulate the expression of GRB2, which in turn suppressed the activation of Akt/mTOR pathway. Taken together, these findings suggested that miR-378 might protect against neuronal autophagy and neurological functional impairment and proposed that a MEG3/miR-378/GRB2 regulatory axis contributed to better understanding of the pathophysiology of ischemic stroke.

Platelets Endocytose Viral Particles and Are Activated via TLR (Toll-Like Receptor) Signaling

OBJECTIVE

Thrombocytopenia is associated with many viral infections suggesting virions interact with and affect platelets. Consistently, viral particles are seen inside platelets, and platelet activation markers are detected in viremic patients. In this article, we sought mechanistic insights into these virion/platelet interactions by examining how platelets endocytose, traffic, and are activated by a model virion. Approach and Results: Using fluorescently tagged HIV-1 pseudovirions, 3-dimensional structured illumination microscopy, and transgenic mouse models, we probed the interactions between platelets and virions. Mouse platelets used known endocytic machinery, that is, dynamin, VAMP (vesicle-associated membrane protein)-3, and Arf6 (ADP-ribosylation factor 6), to take up and traffic HIV-1 pseudovirions. Endocytosed HIV-1 pseudovirions trafficked through early (Rab4⁺) and late endosomes (Rab7⁺), and then to an LC3⁺ (microtubule-associated protein 1A/1B-light chain 3) compartment. Incubation with virions induced IRAK4 (interleukin 1 receptor-associated kinase 4), Akt (protein kinase B), and IKK (IκB kinase) activation, granule secretion, and platelet-leukocyte aggregate formation. This activation required TLRs (Toll-like receptors) and MyD88 (myeloid differentiation primary response protein 88) but was less extensive and slower than activation with thrombin. In vivo, HIV-1 pseudovirions injection led to virion uptake and platelet activation, as measured by IKK activation, platelet-leukocyte aggregate formation, and mild thrombocytopenia. All were decreased in VAMP-3^-/- and, megakaryocyte/platelet-specific, Arf6^-/- mice. Similar platelet activation profiles (increased platelet-leukocyte aggregates, plasma platelet factor 4, and phospho-IκBα) were detected in newly diagnosed and antiretroviral therapy-controlled HIV-1⁺ patients.

CONCLUSIONS

Collectively, our data provide mechanistic insights into the cell biology of how platelets endocytose and process virions. We propose a mechanism by which platelets sample the circulation and respond to potential pathogens that they take up.

Rapamycin induces megakaryocytic differentiation through increasing autophagy in Dami cells

: Autophagy is a conserved cellular process that involves the degradation of cytoplasmic components in eukaryotic cells. However, the correlation between autophagy and megakaryocyte development is unclear. This study aims to explore the role of autophagy in megakaryocyte differentiation. To test our hypothesis, we used the Dami cell line in-vitro experiments. Rapamycin and Bafilomycin A1 were used to stimulate Dami cells. CD41 expression and apoptosis were analysed by flow cytometry. Autophagy-related proteins were detected by Western blotting. 12-O-Tetradecanoylphorbol 13-acetate-treated Dami cells can simulate endomitosis of megakaryocytes in vitro. Rapamycin-induced autophagic cell death was verified by LC3-II conversion upregulation. Meanwhile, Bafilomycin A1 blocked endomitosis and autophagy of Dami cells. Our results provide evidence that autophagy is involved in megakaryocyte endomitosis and platelet development. Rapamycin inhibited cell viability and induced multiple cellular events, including apoptosis, autophagic cell death, and megakaryocytic differentiation, in human Dami cells. Upregulated autophagy triggered by rapamycin can promote the differentiation of Dami cells, while endomitosis is accompanied by enhanced autophagy.

LncRNA GUSBP5-AS promotes EPC migration and angiogenesis and deep vein thrombosis resolution by regulating FGF2 and MMP2/9 through the miR-223-3p/FOXO1/Akt pathway

Long non-coding RNAs (lncRNAs) play an essential role in multitudinous physiological and pathological processes, including vascular disease. We previously showed that lncRNA GUSBP5-AS (enst00000511042) is upregulated in endothelial progenitor cells (EPCs) of deep veni thrombosis (DVT) patients. Here, we investigate the role and mechanism of GUSBP5-AS in EPCs and DVT. Using the DVT model, we found that GUSBP5-AS significantly reduced the thrombus size and weight and enhanced the homing ability of EPC to DVT sites to promote resolution and recanalization of thrombus. GUSBP5-AS promoted cell cycle progression, proliferation, migration and invasion in EPCs, enhanced EPC angiogenesis in vitro and in vivo, and inhibited apoptosis. Strikingly, this study showed that GUSBP5-AS was unbalanced and modulated Forkhead Box Protein O1 (FOXO1) in EPCs in patients with DVT by interacting with miR-223-3p. Mechanistically, GUSBP5-AS functions as a sponge of miR-223-3p, which targets FOXO1. Both GUSBP5-AS knockdown and miR-223-3p overexpression remarkably inhibited angiogenesis, migration and invasion in EPCs. Additionally, our data suggested that GUSBP-AS activated the Akt pathway and enhanced fibroblast growth factor 2 (FGF2), matrix metalloproteinase-2/9 (MMP2/9) and F-actin expression. Taken together, this study indicates that GUSBP5-AS modulates angiogenesis, proliferation and homing ability of EPCs via regulating FGF2 and MMP2/9 expression through the miR-223-3p/FOXO1/Akt pathway, which may provide a new direction for the development of DVT therapeutics.

Metabolic pathways mediate pathogenesis and offer targets for treatment in rheumatic diseases

PURPOSE OF REVIEW

The cause of autoimmune diseases remains incompletely understood. Here, we highlight recent advances in the role of proinflammatory metabolic pathways in autoimmune disease, including treatment with antioxidants and mechanistic target of rapamycin (mTOR) inhibitors.

RECENT FINDINGS

Recent studies show that mTOR pathway activation, glucose utilization, mitochondrial oxidative phosphorylation, and antioxidant defenses play critical roles in the pathogenesis of autoimmune diseases, including rheumatoid arthritis, immune thrombocytopenia, Sjögren's syndrome, large vessel vasculitis, and systemic lupus erythematosus. mTOR activity leads to Th1 and Th17 cell proliferation, Treg depletion, plasma cell differentiation, macrophage dysfunction, and increased antibody and immune complex production, ultimately resulting in tissue inflammation. mTOR also affects the function of connective tissue cells, including fibroblast-like synoviocytes, endothelial cells, and podocytes. mTOR inhibition via rapamycin and N-acetylcysteine, and blockade of glucose utilization show clinical efficacy in both mouse models and clinical trials, such as systemic lupus erythematosus.

SUMMARY

The mTOR pathway is a central regulator of growth and survival signals, integrating environmental cues to control cell proliferation and differentiation. Activation of mTOR underlies inflammatory lineage specification, and mTOR blockade-based therapies show promising efficacy in several autoimmune diseases.