Platelet CD36 signaling through ERK5 promotes caspase-dependent procoagulant activity and fibrin deposition in vivo

Abstract Dyslipidemia is a risk factor for clinically significant thrombotic events. In this condition, scavenger receptor CD36 potentiates platelet reactivity through recognition of circulating oxidized lipids. CD36 promotes thrombosis by activating redox-sensitive signaling molecules, such as the MAPK extracellular signal-regulated kinase 5 (ERK5). However, the events downstream of platelet ERK5 are not clear. In this study, we report that oxidized low-density lipoprotein (oxLDL) promotes exposure of procoagulant phosphatidylserine (PSer) on platelet surfaces. Studies using pharmacologic inhibitors indicate that oxLDL-CD36 interaction–induced PSer exposure requires apoptotic caspases in addition to the downstream CD36-signaling molecules Src kinases, hydrogen peroxide, and ERK5. Caspases promote PSer exposure and, subsequently, recruitment of the prothrombinase complex, resulting in the generation of fibrin from the activation of thrombin. Caspase activity was observed when platelets were stimulated with oxLDL. This was prevented by inhibiting CD36 and ERK5. Furthermore, oxLDL potentiates convulxin/glycoprotein VI–mediated fibrin formation by platelets, which was prevented when CD36, ERK5, and caspases were inhibited. Using 2 in vivo arterial thrombosis models in apoE-null hyperlipidemic mice demonstrated enhanced arterial fibrin accumulation upon vessel injury. Importantly, absence of ERK5 in platelets or mice lacking CD36 displayed decreased fibrin accumulation in high-fat diet–fed conditions comparable to that seen in chow diet–fed animals. These findings suggest that platelet signaling through CD36 and ERK5 induces a procoagulant phenotype in the hyperlipidemic environment by enhancing caspase-mediated PSer exposure.

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Scavenger receptor BI modulates platelet reactivity and thrombosis in dyslipidemia

Blood ◽

10.1182/blood-2010-02-268508 ◽

2010 ◽

Vol 116 (11) ◽

pp. 1932-1941 ◽

Cited By ~ 46

Author(s):

Yi Ma ◽

Mohammad Z. Ashraf ◽

Eugene A. Podrez

Keyword(s):

Platelet Reactivity ◽

Scavenger Receptor ◽

Density Lipoprotein ◽

Cholesterol Content ◽

Type I ◽

Dual Roles ◽

Scavenger Receptor Bi ◽

Class B ◽

Plasma High Density

Abstract Hypercholesterolemia is associated with increased platelet sensitivity to agonists and a prothrombotic phenotype. Mechanisms of platelet hypersensitivity are poorly understood; however, increased platelet cholesterol levels associated with hypercholesterolemia were proposed as leading to hypersensitivity. Scavenger receptor class B type I (SR-BI) in the liver controls plasma high-density lipoprotein (HDL) levels, and SR-BI–deficient mice display a profound dyslipoproteinemia. SR-BI is also expressed on platelets, and recent studies have suggested a role for SR-BI in platelet function; however, its role in hemostasis is unknown. Our present studies demonstrated that non-bone marrow–derived SR-BI deficiency and the dyslipidemia associated with it lead to platelet hyperreactivity that was mechanistically linked to increased platelet cholesterol content. Platelet-specific deficiency of SR-BI, on the other hand, was associated with resistance to hyperreactivity induced by increased platelet cholesterol content. Intravital thrombosis studies demonstrated that platelet SR-BI deficiency protected mice from prothrombotic phenotype in 2 types of dyslipidemia associated with increased platelet cholesterol content. These novel findings demonstrate that SR-BI plays dual roles in thrombosis and may contribute to acute cardiovascular events in vivo in hypercholesterolemia.

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Scavenger Receptor CD36 Directs Nonclassical Monocyte Patrolling Along the Endothelium During Early Atherogenesis

Arteriosclerosis Thrombosis and Vascular Biology ◽

10.1161/atvbaha.117.309123 ◽

2017 ◽

Vol 37 (11) ◽

pp. 2043-2052 ◽

Cited By ~ 31

Author(s):

Paola M. Marcovecchio ◽

Graham D. Thomas ◽

Zbigniew Mikulski ◽

Erik Ehinger ◽

Karin A.L. Mueller ◽

...

Keyword(s):

Low Density Lipoprotein ◽

Scavenger Receptor ◽

Density Lipoprotein ◽

Adaptor Protein ◽

Fold Increase ◽

Vascular Wall ◽

Western Diet ◽

Oxidized Lipoprotein

Objective— Nonclassical monocytes (NCM) function to maintain vascular homeostasis by crawling or patrolling along the vessel wall. This subset of monocytes responds to viruses, tumor cells, and other pathogens to aid in protection of the host. In this study, we wished to determine how early atherogenesis impacts NCM patrolling in the vasculature. Approach and Results— To study the role of NCM in early atherogenesis, we quantified the patrolling behaviors of NCM in ApoE −/− (apolipoprotein E) and C57BL/6J mice fed a Western diet. Using intravital imaging, we found that NCM from Western diet–fed mice display a 4-fold increase in patrolling activity within large peripheral blood vessels. Both human and mouse NCM preferentially engulfed OxLDL (oxidized low-density lipoprotein) in the vasculature, and we observed that OxLDL selectively induced NCM patrolling in vivo. Induction of patrolling during early atherogenesis required scavenger receptor CD36, as CD36 −/− mice revealed a significant reduction in patrolling activity along the femoral vasculature. Mechanistically, we found that CD36-regulated patrolling was mediated by a SFK (src family kinase) through DAP12 (DNAX activating protein of 12KDa) adaptor protein. Conclusions— Our studies show a novel pathway for induction of NCM patrolling along the vascular wall during early atherogenesis. Mice fed a Western diet showed increased NCM patrolling activity with a concurrent increase in SFK phosphorylation. This patrolling activity was lost in the absence of either CD36 or DAP12. These data suggest that NCM function in an atheroprotective manner through sensing and responding to oxidized lipoprotein moieties via scavenger receptor engagement during early atherogenesis.

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Prothrombotic Platelet Signaling by the Scavenger Receptor, CD36.

Blood ◽

10.1182/blood.v110.11.3642.3642 ◽

2007 ◽

Vol 110 (11) ◽

pp. 3642-3642

Author(s):

Kan Chen ◽

Maria Febbraio ◽

Roy Silverstein

Keyword(s):

Platelet Activation ◽

Tyrosine Kinases ◽

Kinase Inhibitor ◽

Low Density Lipoprotein ◽

Scavenger Receptor ◽

Density Lipoprotein ◽

Adenosine Diphosphate ◽

Mapk Signaling ◽

Signaling Cascade

Abstract The scavenger receptor CD36 binds a broad array of ligands, including oxidized low density lipoprotein (oxLDL), thrombospondin-1, fatty acids and apoptotic cells. CD36 was first isolated and characterized structurally from platelets, but the functional role of CD36 on platelets remains relatively obscure. We previously determined that treating platelets with oxLDL activated platelets and that activation was not seen in CD36-null platelets. Using a pharmacological inhibitor we now show that inhibition of JNK MAP kinase abrogated the activation of platelets by oxLDL. This effect was specific to oxLDL-mediated activation because this inhibitor had minimal effect on platelet activation by other classic agonists as exemplified by adenosine diphosphate (ADP). We demonstrated by immunoblotting that JNK2 and its upstream activator MKK4 were phosphorylated in the presence of oxLDL. We also found that the increase of JNK2 phosphorylation by oxLDL was diminished in CD36-null platelets. We showed that a src family kinase inhibitor (AG1879) blocked both platelet activation and JNK2 phosphorylation upon oxLDL treatment. By co-immunoprecipitation we demonstrated that CD36 recruited “active” fyn and lyn in platlets upon oxLDL treatment. These studies suggest that CD36 ligands can activate platelets through a signaling cascade involving src family tyrosine kinases and MAPK signaling molecules such as MKK4 and JNK2. OxLDL forms in the setting of hyperlipidemia and inflammation and plays an important role in atherosclerosis. A common characteristic of atherosclerosis is a prothrombotic state. Our results suggested that a specific signaling cascade activated by CD36 ligands generated in pathological states may contribute to a prothrombotic phenotype in vivo.

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Lipoprotein Glomerulopathy-Like Lesions in Atherosclerotic Mice Defected With HDL Receptor SR-B1

Frontiers in Cardiovascular Medicine ◽

10.3389/fcvm.2021.734824 ◽

2021 ◽

Vol 8 ◽

Author(s):

Jiawei Liao ◽

Jie Bai ◽

Xiangbo An ◽

Yang Liu ◽

Yuhui Wang ◽

...

Keyword(s):

Cardiovascular Diseases ◽

Low Density Lipoprotein ◽

Scavenger Receptor ◽

Density Lipoprotein ◽

Chow Diet ◽

Loss Of Function ◽

Lipoprotein Glomerulopathy ◽

Class B ◽

Density Lipoprotein Receptor ◽

Accelerate Atherosclerosis

High-density lipoprotein (HDL) homeostasis is important in maintaining both cardiovascular and renal health. Scavenger receptor class B type 1 (SR-B1), the major HDL receptor in mammals, plays a crucial role in reverse cholesterol transport and HDL metabolism. Evidence from mouse study has well demonstrated that HDL disorders caused by Srb1 inactivation accelerate atherosclerosis and even induce lethal cardiovascular diseases. However, the renal consequences of Srb1 dysfunction are still unknown. Here we explored this issue in both Srb1 knockout (Srb1-/-) mice and atherosclerotic low-density lipoprotein receptor knockout (Ldlr-/-) mice with Srb1 deletion. Our data showed that no apparent renal damage was observed in 5-month-old Srb1-/- mice fed on standard rodent chow diet as well as Srb1-/- mice fed on a high-fat diet (HFD) for 12 weeks. However, 5-month-old Srb1/Ldlr-/- mice fed on rodent chow had increased urinary albumin excretion and developed spontaneous intraglomerular Oil-red O (ORO)-positive lipoprotein deposition that is similar to lesions observed in human lipoprotein glomerulopathy (LPG). HFD feeding accelerated LPG-like lesions in Srb1/Ldlr-/- mice, inducing severe proteinuria and significantly promoting intraglomerular ORO-positive lipoprotein deposition. Interestingly, probucol reversed HFD-induced HDL disorders and almost fully abrogated LPG-like lesions in Srb1/Ldlr-/- mice. In conclusion, the present study demonstrates that SR-B1 dysfunction leads to LPG-like lesions in atherosclerotic mice, which could be rescued by probucol. SR-B1 loss-of-function mutant carriers therefore might be susceptible to developing metabolic nephropathy in addition to cardiovascular diseases, and probucol might be a potential therapeutics.

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Abstract 646: Redox Control of Macropinocytosis; An Unexplored Target in Atherosclerosis

Arteriosclerosis Thrombosis and Vascular Biology ◽

10.1161/atvb.36.suppl_1.646 ◽

2016 ◽

Vol 36 (suppl_1) ◽

Author(s):

Pushpankur Ghoshal ◽

Bhupesh Singla ◽

Douglas Feck ◽

Nadiezhda Cantu-Medellin ◽

Eric Kelley ◽

...

Keyword(s):

Lipid Accumulation ◽

Oxidized Ldl ◽

Low Density Lipoprotein ◽

Scavenger Receptor ◽

Density Lipoprotein ◽

Actin Binding ◽

Lipid Uptake ◽

Signaling Mechanism ◽

Membrane Ruffling

Aims: Early studies established the paradigm that oxidation of low density lipoprotein (LDL) is necessary for scavenger receptor-mediated LDL uptake and lipid accumulation in macrophages. In addition to this “classical” mode of lipid internalization, scavenger receptor-independent uptake of native, non-oxidized LDL (nLDL) via macropinocytosis has been demonstrated to contribute to lipid uptake by macrophages. Despite this previous information the precise signaling mechanisms regulating macropinocytosis of nLDL and the relative contribution of lipid macropinocytosis to atherosclerosis remain unknown. This study was designed to examine the role of phagocyte NADPH oxidase (a.k.a. Nox2) in macropinocytosis and to investigate macropinocytotic uptake of lipids in hypercholesterolemic ApoE -/- mice in vivo . Results: Phorbol myristate acetate (4β-PMA) activation of human and murine macrophages stimulated membrane ruffling, macropinosome formation, and subsequent uptake of nLDL by macropinocytosis. FACS data indicated that 4β-PMA stimulates lipid accumulation following nLDL treatment in macrophages lacking scavenger receptor CD36. Mechanistically, we found that pharmacological blockade of protein kinase C (PKC), inhibition of flavoenzymes by diphenyleneiodonium, and scavenging intracellular superoxide anion abolished phorbol ester-induced macropinocytosis. Transcriptional knockdown of Nox2 using siRNA inhibited 4β-PMA-induced macropinocytosis in THP-1 macrophages. Delving further into the mechanism, we found that Nox2 via redox inactivation of PTEN and activation of the PI3K/Akt pathway dephosphorylates the actin-binding protein cofilin, stimulates membrane ruffling, and induces macropinocytosis. Finally, peritoneal chimera experiments indicate that macropinocytotic uptake of lipids in hypercholesterolemic ApoE -/- mice was attenuated in Nox2 y/- macrophages compared to wild type controls. Innovation and Conclusion: These findings suggest a previously undescribed redox-sensitive signaling pathway leading to internalization of nLDL by macropinocytosis. The signaling mechanism described herein may identify new targets in atherosclerosis and other disease conditions involving macropinocytosis.

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Oxidation of Plasma Low-Density Lipoprotein Accelerates Its Accumulation and Degradation in the Arterial Wall In Vivo

Circulation ◽

10.1161/01.cir.94.7.1698 ◽

1996 ◽

Vol 94 (7) ◽

pp. 1698-1704 ◽

Cited By ~ 46

Author(s):

Klaus Juul ◽

Lars B. Nielsen ◽

Klaus Munkholm ◽

Steen Stender ◽

Børge G. Nordestgaard

Keyword(s):

Arterial Wall ◽

Low Density Lipoprotein ◽

Density Lipoprotein ◽

Low Density

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Interaction of 4-hydroxynonenal-modified low-density lipoproteins with the fibroblast apolipoprotein B/E receptor

Biochemical Journal ◽

10.1042/bj2340245 ◽

1986 ◽

Vol 234 (1) ◽

pp. 245-248 ◽

Cited By ~ 31

Author(s):

W Jessup ◽

G Jurgens ◽

J Lang ◽

H Esterbauer ◽

R T Dean

Keyword(s):

Apolipoprotein B ◽

Negative Charge ◽

Low Density Lipoprotein ◽

Ldl Receptor ◽

Density Lipoprotein ◽

Low Density ◽

Lipid Peroxidation Product ◽

Modified Low Density Lipoproteins ◽

Peroxidation Product

The incorporation of the lipid peroxidation product 4-hydroxynonenal into low-density lipoprotein (LDL) increases the negative charge of the particle, and decreases its affinity for the fibroblast LDL receptor. It is suggested that this modification may occur in vivo, and might promote atherogenesis.

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