CD36 and ERK5 link dyslipidemia to apoptotic-like platelet procoagulant function

Influence of the Tissue Collection Procedure on the Adipogenic Differentiation of Human Stem Cells: Ischemic versus Well-Vascularized Adipose Tissue

Clinical and basic science applications using adipose-derived stem cells (ADSCs) are gaining popularity. The current adipose tissue harvesting procedures introduce nonphysiological conditions, which may affect the overall performance of the isolated ADSCs. In this study, we elucidate the differences between ADSCs isolated from adipose tissues harvested within the first 5 min of the initial surgical incision (well-vascularized, nonpremedicated condition) versus those isolated from adipose tissues subjected to medications and deprived of blood supply during elective free flap procedures (ischemic condition). ADSCs isolated from well-vascularized and ischemic tissues positively immunostained for several standard stem cell markers. Interestingly, the percent change in the CD36 expression for ADSCs isolated from ischemic versus well-vascularized tissue was significantly lower in males than females (p < 0.05). Upon differentiation and maturation to adipocytes, spheroids formed using ADSCs isolated from ischemic adipose tissue had lower triglyceride content compared to those formed using ADSCs isolated from the well-vascularized tissue (p < 0.05). These results indicate that ADSCs isolated from ischemic tissue either fail to uptake fatty acids or fail to efficiently convert those fatty acids into triglycerides. Therefore, more robust ADSCs suitable to establish in vitro adipose tissue models can be obtained by harvesting well-vascularized and nonpremedicated adipose tissues.

Is the suppression of CD36 a promising way for atherosclerosis therapy?

Atherosclerosis is the main underlying pathology of many cardiovascular diseases and is marked by plaque formation in the artery wall. It has posed a serious threat to the health of people all over the world. CD36 acts as a significant regulator of lipid homeostasis, which is closely associated with the onset and progression of atherosclerosis and may be a new therapeutic target. The abnormal overexpression of CD36 facilitates lipid accumulation, foam cell formation, inflammation, endothelial apoptosis, and thrombosis. Numerous natural products and lipid-lowering agents are found to target the suppression of CD36 or inhibit the upregulation of CD36 to prevent and treat atherosclerosis. Here, the structure, expression regulation and function of CD36 in atherosclerosis and its related pharmacological therapies are reviewed. This review highlights the importance of drugs targeting CD36 suppression in the treatment and prevention of atherosclerosis, in order to develop new therapeutic strategies and potential anti-atherosclerotic drugs both preclinically and clinically.

Activated platelets facilitate hematogenous metastasis of breast cancer by modulating the PDGFR-β/COX-2 axis

Platelets have been widely recognized as a bona fide mediator of malignant diseases, and they play significant roles in influencing various aspects of tumor progression. Paracrine interactions between platelets and tumor cells have been implicated in promoting the dissemination of malignant cells to distant sites. However, the underlying mechanisms of the platelet-tumor cell interactions for promoting hematogenous metastasis are not yet fully understood. We found that activated platelets with high expression of CD36 were prone to release a plethora of growth factors and cytokines, including high levels of PDGF-B, compared to resting platelets. PDGF-B activated the PDGFR-β/COX-2 signaling cascade, which elevated an array of pro-inflammatory factors levels, thereby aggravating tumor metastasis. The collective administration of CD36 inhibitor and COX-2 inhibitor resolved the interactions between platelets and tumor cells. Collectively, our findings demonstrated that targeting the crosstalk between platelets and tumor cells offers potential therapeutic strategies for inhibiting tumor metastasis.

Platelet mitochondria: the mighty few

PURPOSE OF REVIEW

Platelet mitochondrial dysfunction is both caused by, as well as a source of oxidative stress. Oxidative stress is a key hallmark of metabolic disorders such as dyslipidemia and diabetes, which are known to have higher risks for thrombotic complications.

RECENT FINDINGS

Increasing evidence supports a critical role for platelet mitochondria beyond energy production and apoptosis. Mitochondria are key regulators of reactive oxygen species and procoagulant platelets, which both contribute to pathological thrombosis. Studies targeting platelet mitochondrial pathways have reported promising results suggesting antithrombotic effects with limited impact on hemostasis in animal models.

SUMMARY

Targeting platelet mitochondria holds promise for the reduction of thrombotic complications in patients with metabolic disorders. Future studies should aim at validating these preclinical findings and translate them to the clinic.

Swimming improves platelet dysfunction in mice fed with a high-fat diet

BACKGROUND

We investigated the effects and mechanism of swimming on platelet function in mice fed with a high-fat diet.

MATERIAL AND METHODS

Mice were randomly divided into the control group (NC), high-fat group (HF), and high-fat diet combined with swimming group (FE). The FE group swam for 60 min a day, 5 days a week, for 8 weeks.

RESULTS

Compared with the NC group, the HF group had significant weight gain, dyslipidemia, abbreviated bleeding time after tail breakage, increased clot retraction, increased platelet aggregation rate, increased spread of platelets on fibrinogen, and increased pAKT level in platelets. Compared with the HF group, the FE group had lower body weight, improved dyslipidemia, prolonged bleeding time, reduced clot retraction, reduced platelet aggregation rate, decreased spread of platelets on fibrinogen, and decreased pAKT level in platelets.

CONCLUSIONS

By inhibiting the level of pAKT in platelets, swimming improves platelet dysfunction in mice fed with a high-fat diet.

Platelet CD36 links overweight and a prothrombotic phenotype in patients with non-valvular atrial fibrillation

Introduction

The pathophysiological mechanisms linking the overweight and prothrombotic state of non-valvular atrial fibrillation (NVAF) are incompletely understood. Our objective was to evaluate the effect of platelet CD36 on the risk of stroke associated with overweight in NVAF patients.

Methods

A cross-sectional study enrolled 182 subjects with NVAF in two groups: normal weight (18.5 &lt; body mass index(BMI) &lt; 25.0 kg/m2) and overweight (BMI ≥ 25.0 kg/m2). Clinical data, medical history, vital signs, transthoracic echocardiography parameters, and medication were recorded. Biochemical characteristics including blood glucose and serum lipid were analyzed in the Laboratory.

Results

The expression of platelet CD36 and integrin αIIbβ3 was detected by flow cytometry. Among the 182 patients with NVAF, 68 (37.36%) were classified as normal weight, 114 (62.64%) as overweight. With an increase in BMI, waist-hip ratio, cholesterol, triglycerides, left atrium diameters, and the ratio of mitral inflow E velocity to myocardial e' velocity in the mitral annulus (E/e') increased significantly (P &lt; 0.05). The mean fluorescent intensity of platelet CD36 increased significantly in overweight patients (P &lt; 0.01), in line with platelet activation biomarkers (platelet integrin αIIbβ3). Platelet CD36 was positively correlated with BMI and platelet integrin αIIbβ3, respectively (P &lt; 0.05). Additionally, platelet CD36 and BMI were independent risk factors for platelet activation in patients with NVAF.

Conclusions

Platelet CD36 is speculated to mediate the complex crosstalk between overweight and platelet hyperactivity, leading to the prothrombotic state in overweight patients with NVAF. Platelet CD36 could be a potential target for preventing the prothrombotic state in overweight patients with NVAF.

Platelet Redox Imbalance in Hypercholesterolemia: A Big Problem for a Small Cell

The imbalance between reactive oxygen species (ROS) synthesis and their scavenging by anti-oxidant defences is the common soil of many disorders, including hypercholesterolemia. Platelets, the smallest blood cells, are deeply involved in the pathophysiology of occlusive arterial thrombi associated with myocardial infarction and stroke. A great deal of evidence shows that both increased intraplatelet ROS synthesis and impaired ROS neutralization are implicated in the thrombotic process. Hypercholesterolemia is recognized as cause of atherosclerosis, cerebro- and cardiovascular disease, and, closely related to this, is the widespread acceptance that it strongly contributes to platelet hyperreactivity via direct oxidized LDL (oxLDL)-platelet membrane interaction via scavenger receptors such as CD36 and signaling pathways including Src family kinases (SFK), mitogen-activated protein kinases (MAPK), and nicotinamide adenine dinucleotide phosphate (NADPH) oxidase. In turn, activated platelets contribute to oxLDL generation, which ends up propagating platelet activation and thrombus formation through a mechanism mediated by oxidative stress. When evaluating the effect of lipid-lowering therapies on thrombogenesis, a large body of evidence shows that the effects of statins and proprotein convertase subtilisin/kexin type 9 inhibitors are not limited to the reduction of LDL-C but also to the down-regulation of platelet reactivity mainly by mechanisms sensitive to intracellular redox balance. In this review, we will focus on the role of oxidative stress-related mechanisms as a cause of platelet hyperreactivity and the pathophysiological link of the pleiotropism of lipid-lowering agents to the beneficial effects on platelet function.

Proprotein Convertase Subtilisin Kexin Type 9 (PCSK9) Beyond Lipids: The Role in Oxidative Stress and Thrombosis

Proprotein convertase subtilisin/kexin type 9 (PCSK9), mainly secreted in the liver, is a key regulator of cholesterol homeostasis inducing LDL receptors’ degradation. Beyond lipid metabolism, PCSK9 is involved in the development of atherosclerosis, promoting plaque formation in mice and human, impairing the integrity of endothelial monolayer and promoting the events that induce atherosclerosis disease progression. In addition, the PCSK9 ancillary role in the atherothrombosis process is widely debated. Indeed, recent evidence showed a regulatory effect of PCSK9 on redox system and platelet activation. In particular, the role of PCSK9 in the activation of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase (Nox2) system, of MAP-kinase cascades and of CD36 and LOX-1 downstream pathways, suggests that PCSK9 may be a significant cofactor in atherothrombosis development. This evidence suggests that the serum levels of PCSK9 could represent a new biomarker for the occurrence of cardiovascular events. Finally, other evidence showed that PCSK9 inhibitors, a novel pharmacological tool introduced in clinical practice in recent years, counteracted these phenomena. In this review, we summarize the evidence concerning the role of PCSK9 in promoting oxidative-stress-related atherothrombotic process.

Fatty acids and evolving roles of their proteins in neurological, cardiovascular disorders and cancers

The dysregulation of fat metabolism is involved in various disorders, including neurodegenerative, cardiovascular, and cancers. The uptake of long-chain fatty acids (LCFAs) with 14 or more carbons plays a pivotal role in cellular metabolic homeostasis. Therefore, the uptake and metabolism of LCFAs must constantly be in tune with the cellular, metabolic, and structural requirements of cells. Many metabolic diseases are thought to be driven by the abnormal flow of fatty acids either from the dietary origin and/or released from adipose stores. Cellular uptake and intracellular trafficking of fatty acids are facilitated ubiquitously with unique combinations of fatty acid transport proteins and cytoplasmic fatty acid-binding proteins in every tissue. Extensive data are emerging on the defective transporters and metabolism of LCFAs and their clinical implications. Uptake and metabolism of LCFAs are crucial for the brain's functional development and cardiovascular health and maintenance. In addition, data suggest fatty acid metabolic transporter can normalize activated inflammatory response by reprogramming lipid metabolism in cancers. Here we review the current understanding of how LCFAs and their proteins contribute to the pathophysiology of three crucial diseases and the mechanisms involved in the processes.

Antiplatelet Effects of PCSK9 Inhibitors in Primary Hypercholesterolemia

Proprotein convertase subtilisin-kexin type 9 (PCSK9) inhibitors are a novel group of hypolipidemic drugs that are recommended particularly for high-risk hypercholesterolemia patients, including those with primary hypercholesterolemia (PH), where lifelong exposure to high low-density lipoprotein (LDL) cholesterol levels results in an elevated risk of atherosclerosis at an early age. The onset and progression of atherosclerosis is significantly influenced by activated platelets. Oxidized LDL influences platelet activation by interacting with their surface receptors and remodeling the composition of their cell membrane. This results in platelet aggregation, endothelial cell activation, promotion of inflammation and oxidative stress, and acceleration of lipid accumulation in atherosclerotic plaques. PCSK9 inhibitors reduce platelet activation by both significantly lowering LDL levels and reducing the LDL receptor-mediated activation of platelets by PCSK9. They also work synergistically with other hypolipidemic and antithrombotic drugs, including statins, ezetimibe, acetylsalicylic acid, clopidogrel, and ticagrelor, which enhances their antiplatelet and LDL-lowering effects. In this review, we summarize the currently available evidence on platelet hyperreactivity in PH, the effects of PCSK9 inhibitors on platelets, and their synergism with other drugs used in PH therapy.

Cysteine sulfenylation by CD36 signaling promotes arterial thrombosis in dyslipidemia

Arterial thrombosis in the setting of dyslipidemia promotes clinically significant events, including myocardial infarction and stroke. Oxidized lipids in low-density lipoproteins (oxLDL) are a risk factor for athero-thrombosis and are recognized by platelet scavenger receptor CD36. oxLDL binding to CD36 promotes platelet activation and thrombosis by promoting generation of reactive oxygen species. The downstream signaling events initiated by reactive oxygen species in this setting are poorly understood. In this study, we report that CD36 signaling promotes hydrogen peroxide flux in platelets. Using carbon nucleophiles that selectively and covalently modify cysteine sulfenic acids, we found that hydrogen peroxide generated through CD36 signaling promotes cysteine sulfenylation of platelet proteins. Specifically, cysteines were sulfenylated on Src family kinases, which are signaling transducers that are recruited to CD36 upon recognition of its ligands. Cysteine sulfenylation promoted activation of Src family kinases and was prevented by using a blocking antibody to CD36 or by enzymatic degradation of hydrogen peroxide. CD36-mediated platelet aggregation and procoagulant phosphatidylserine externalization were inhibited in a concentration-dependent manner by a panel of sulfenic acid-selective carbon nucleophiles. At the same concentrations, these probes did not inhibit platelet aggregation induced by the purinergic receptor agonist adenosine diphosphate or the collagen receptor glycoprotein VI agonist collagen-related peptide. Selective modification of cysteine sulfenylation in vivo with a benzothiazine-based nucleophile rescued the enhanced arterial thrombosis seen in dyslipidemic mice back to control levels. These findings suggest that CD36 signaling generates hydrogen peroxide to oxidize cysteines within platelet proteins, including Src family kinases, and lowers the threshold for platelet activation in dyslipidemia.

CD36 in Atherosclerosis: Pathophysiological Mechanisms and Therapeutic Implications

PURPOSE OF REVIEW

Atherosclerosis is a chronic disease characterized by lipid retention and inflammation in the artery wall. The retention and oxidation of low-density lipoprotein (LDL) in sub-endothelial space play a critical role in atherosclerotic plaque formation and destabilization. Oxidized LDL (ox-LDL) and other modified LDL particles are avidly taken up by endothelial cells, smooth muscle cells, and macrophages mainly through several scavenger receptors, including CD36 which is a class B scavenger receptor and membrane glycoprotein.

RECENT FINDINGS

Animal studies performed on CD36-deficient mice suggest that deficiency of CD36 prevents the development of atherosclerosis, though with some debate. CD36 serves as a signaling hub protein at the crossroad of inflammation, lipid metabolism, and fatty acid metabolism. In addition, the level of soluble CD36 (unattached to cells) in the circulating blood was elevated in patients with atherosclerosis and other metabolic disorders. We performed a state-of-the-art review on the structure, ligands, functions, and regulation of CD36 in the context of atherosclerosis by focusing on the pathological role of CD36 in the dysfunction of endothelial cells, smooth muscle cells, monocytes/macrophages, and platelets. Finally, we highlight therapeutic possibilities to target CD36 expression/activity in atherosclerosis.