Expression of EMMPRIN (CD147) on circulating platelets in vivo

Preferential and sustained platelet activation in COVID-19 survivors with mental disorders

Pre-existing mental disorders are considered a risk factor for severe COVID-19 outcomes, possibly because of higher vascular burden. Moreover, an unconventional platelet activation characterizes COVID-19 and contributes to inflammatory and thrombotic manifestations. In the light of the inflammation theory of mental disorders, we hypothesized that patients with mental disorders could be sensitive to the SARS-CoV-2 elicited platelet activation. We investigated platelet activation in 141 COVID-19 survivors at one month after clearance of the virus, comparing subjects with or without an established pre-existing diagnosis of mental disorder according to the DSM-5. We found that platelets from patients with a positive history of psychiatric disorder underwent unconventional activation more frequently than conventional activation or no activation at all. Such preferential activation was not detected when platelets from patients without a previous psychiatric diagnosis were studied. When testing the effects of age, sex, and psychiatric history on the platelet activation, GLZM multivariate analysis confirmed the significant effect of diagnosis only. These findings suggest a preferential platelet activation during acute COVID-19 in patients with a pre-existing psychiatric disorder, mediated by mechanisms associated with thromboinflammation. This event could have contributed to the higher risk of severe outcome in the psychiatric population.

A Perspective on How Fibrinaloid Microclots and Platelet Pathology May be Applied in Clinical Investigations

Microscopy imaging has enabled us to establish the presence of fibrin(ogen) amyloid (fibrinaloid) microclots in a range of chronic, inflammatory diseases. Microclots may also be induced by a variety of purified substances, often at very low concentrations. These molecules include bacterial inflammagens, serum amyloid A, and the S1 spike protein of severe acute respiratory syndrome coronavirus 2. Here, we explore which of the properties of these microclots might be used to contribute to differential clinical diagnoses and prognoses of the various diseases with which they may be associated. Such properties include distributions in their size and number before and after the addition of exogenous thrombin, their spectral properties, the diameter of the fibers of which they are made, their resistance to proteolysis by various proteases, their cross-seeding ability, and the concentration dependence of their ability to bind small molecules including fluorogenic amyloid stains. Measuring these microclot parameters, together with microscopy imaging itself, along with methodologies like proteomics and imaging flow cytometry, as well as more conventional assays such as those for cytokines, might open up the possibility of a much finer use of these microclot properties in generative methods for a future where personalized medicine will be standard procedures in all clotting pathology disease diagnoses.

In Situ Endothelial SARS-CoV-2 Presence and PROS1 Plasma Levels Alteration in SARS-CoV-2-Associated Coagulopathies

BACKGROUND

Coagulation decompensation is one of the complications most frequently encountered in COVID-19 patients with a poor prognosis or long-COVID syndrome, possibly due to the persistence of SARS-CoV-2 infection in the cardiovascular system. To date, the mechanism underlying the alteration of the coagulation cascade in COVID-19 patients remains misunderstood and the anticoagulant protein S (PROS1) has been described as a potential risk factor for complications related to COVID-19, due to PLpro SARS-CoV-2 enzyme proteolysis.

METHODS

Biopsies and blood samples were collected from SARS-CoV-2 positive and negative swab test subjects with coagulopathies (peripheral arterial thrombosis), and SARS-CoV-2 presence, ACE2 and CD147 expression, and plasmatic levels of PROS1 were evaluated.

RESULTS

We reported a significant decrease of plasmatic PROS1 in the coagulopathic SARS-CoV-2 swab positive cohort, in association with SARS-CoV-2 in situ infection and CD147 peculiar expression. These data suggested that SARS-CoV-2 associated thrombotic/ischemic events might involve PROS1 cleavage by viral PLpro directly in the site of infection, leading to the loss of its anticoagulant function.

CONCLUSIONS

Based on this evidence, the identification of predisposing factors, such as CD147 increased expression, and the use of PLpro inhibitors to preserve PROS1 function, might be useful for COVID-19 coagulopathies management.

Platelets and SARS-CoV-2 During COVID-19: Immunity, Thrombosis, and Beyond

COVID-19 is characterized by dysregulated thrombosis and coagulation that can increase mortality in patients. Platelets are fast responders to pathogen presence, alerting the surrounding immune cells and contributing to thrombosis and intravascular coagulation. The SARS-CoV-2 genome has been found in platelets from patients with COVID-19, and its coverage varies according to the method of detection, suggesting direct interaction of the virus with these cells. Antibodies against Spike and Nucleocapsid have confirmed this platelet-viral interaction. This review discusses the immune, prothrombotic, and procoagulant characteristics of platelets observed in patients with COVID-19. We outline the direct and indirect interaction of platelets with SARS-CoV-2, the contribution of the virus to programmed cell death pathway activation in platelets and the consequent extracellular vesicle release. We discuss platelet activation and immunothrombosis in patients with COVID-19, the effect of Spike on platelets, and possible activation of platelets by classical platelet activation triggers as well as contribution of platelets to complement activation. As COVID-19-mediated thrombosis and coagulation are still not well understood in vivo, we discuss available murine models and mouse adaptable strains.

Elevated EMMPRIN Serum Levels Indicate Plaque Vulnerability in Patients With Asymptomatic High Grade Carotid Stenosis

OBJECTIVE

Carotid atherosclerosis is an important cause of cerebral ischaemic stroke. Sonographic plaque characteristics are inappropriate for exact prediction of possible future ischaemic events. Additional markers are needed to predict the clinical outcome in high grade carotid stenosis. This study aimed to test extracellular matrix metalloproteinase inducer (EMMPRIN), due to its involvement in plaque formation and destabilisation, as a potential marker of high risk vulnerable plaques.

METHODS

EMMPRIN was analysed in pre-operative serum samples from patients with symptomatic and asymptomatic carotid artery stenosis by a specific ELISA. Pre-operative duplex sonography classified the atherosclerotic plaque due to echogenicity. Histopathological analysis of vulnerable and non-vulnerable plaques was based on the American Heart Association (AHA) classification.

RESULTS

The study included 265 patients undergoing carotid endarterectomy: 90 (m:f, 69:21) patients with symptomatic and 175 (m:f, 118:57) with asymptomatic disease. Analysis of circulating EMMPRIN revealed significantly higher levels in patients with echolucent plaques (4 480; IQR 3 745, 6 144 pg/mL) compared with echogenic plaques (4 159; IQR 3 418, 5 402 pg/mL; p = .025). Asymptomatic patients with vulnerable plaques had significantly higher levels of EMMPRIN (4 875; IQR 3 850, 7 016 pg/mL) compared with non-vulnerable plaques (4 109; IQR 3 433, 5 402 pg/mL; p < .001). In logistic regression analysis, duplex sonography combined with age, gender, and clinical risk factors predicted vulnerable plaques in asymptomatic patients with an AUC of 0.71 (95% CI 0.61 - 0.80). EMMPRIN significantly improved the AUC in asymptomatic patients (AUC 0.79; 95% CI 0.71 - 0.87; p = .014).

CONCLUSION

Patients with high risk plaques according to ultrasound and histopathological characteristics demonstrated increased serum EMMPRIN levels. EMMPRIN on top of clinical risk factors, including age, gender, and duplex sonography may be used for pre-operative risk stratification in asymptomatic patients.

Platelet-leukocyte crosstalk in COVID-19: How might the reciprocal links between thrombotic events and inflammatory state affect treatment strategies and disease prognosis?

Platelet-leukocyte crosstalk is commonly manifested by reciprocal links between thrombosis and inflammation. Platelet thrombus acts as a reactive matrix that recruits leukocytes to the injury site where their massive accumulation, activation and migration promote thrombotic events while triggering inflammatory responses. As a life-threatening condition with the associations between inflammation and thrombosis, COVID-19 presents diffuse alveolar damage due to exaggerated macrophage activity and cytokine storms. These events, together with direct intracellular virus invasion lead to pulmonary vascular endothelialitis, cell membranes disruption, severe endothelial injury, and thrombosis. The developing pre-alveolar thrombus provides a hyper-reactive milieu that recruits circulating leukocytes to the injury site where their activation contributes to thrombus stabilization and thrombosis propagation, primarily through the formation of Neutrophil extracellular trap (NET). NET fragments can also circulate and deposit in further distance where they may disseminate intravascular thrombosis in severe cases of disease. Thrombi may also facilitate leukocytes migration into alveoli where their accumulation and activation exacerbate cytokine storms and tissue damage, further complicating the disease. Based on these mechanisms, whether an effective anti-inflammatory protocol can prevent thrombotic events, or on the other hand; efficient antiplatelet or anticoagulant regimens may be associated with reduced cytokine storms and tissue damage, is now of interests for several ongoing researches. Thus shedding more light on platelet-leukocyte crosstalk, the review presented here discusses the detailed mechanisms by which platelets may contribute to the pathogenesis of COVID-19, especially in severe cases where their interaction with leukocytes can intensify both inflammatory state and thrombosis in a reciprocal manner.

Unconventional CD147-dependent platelet activation elicited by SARS-CoV-2 in COVID-19

BACKGROUND

Platelet activation and thrombotic events characterizes COVID-19.

OBJECTIVES

To characterize platelet activation and determine if SARS-CoV-2 induces platelet activation.

PATIENTS/METHODS

We investigated platelet activation in 119 COVID-19 patients at admission in a university hospital in Milan, Italy, between March 18 and May 5, 2020. Sixty-nine subjects (36 healthy donors, 26 patients with coronary artery disease, coronary artery disease, and seven patients with sepsis) served as controls.

RESULTS

COVID-19 patients had activated platelets, as assessed by the expression and distribution of HMGB1 and von Willebrand factor, and by the accumulation of platelet-derived (plt) extracellular vesicles (EVs) and HMGB1+ plt-EVs in the plasma. P-selectin upregulation was not detectable on the platelet surface in a fraction of patients (55%) and the concentration of soluble P-selectin in the plasma was conversely increased. The plasma concentration of HMGB1+ plt-EVs of patients at hospital admission remained in a multivariate analysis an independent predictor of the clinical outcome, as assessed using a 6-point ordinal scale (from 1 = discharged to 6 = death). Platelets interacting in vitro with SARS-CoV-2 underwent activation, which was replicated using SARS-CoV-2 pseudo-viral particles and purified recombinant SARS-CoV-2 spike protein S1 subunits. Human platelets express CD147, a putative coreceptor for SARS-CoV-2, and Spike-dependent platelet activation, aggregation and granule release, release of soluble P-selectin and HMGB1+ plt-EVs abated in the presence of anti-CD147 antibodies.

CONCLUSIONS

Hence, an early and intense platelet activation, which is reproduced by stimulating platelets in vitro with SARS-CoV-2, characterizes COVID-19 and could contribute to the inflammatory and hemostatic manifestations of the disease.

The probable role and therapeutic potential of the PI3K/AKT signaling pathway in SARS-CoV-2 induced coagulopathy

Coronavirus disease 2019 (COVID-19), which is caused by severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), is associated with a high mortality rate. The majority of deaths in this disease are caused by ARDS (acute respiratory distress syndrome) followed by cytokine storm and coagulation complications. Although alterations in the level of the number of coagulation factors have been detected in samples from COVID-19 patients, the direct molecular mechanism which has been involved in this pathologic process has not been explored yet. The PI3K/AKT signaling pathway is an intracellular pathway which plays a central role in cell survival. Also, in recent years the association between this pathway and coagulopathies has been well clarified. Therefore, based on the evidence on over-activity of the PI3K/AKT signaling pathway in SARS-CoV-2 infection, in the current review, the probable role of this cellular pathway as a therapeutic target for the prevention of coagulation complications in patients with COVID-19 is discussed.

Rapid Release of Interleukin-1β from Human Platelets Is Independent of NLRP3 and Caspase

OBJECTIVE

 Platelets are critical in mediating both rapid responses to injury and the development and progression of coronary disease. Several studies have shown that, after prolonged exposure to agonists, they produce and release inflammatory mediators including interleukin-1β (IL-1β), via the classical pathway (NLRP3 inflammasome and caspase-1 cleavage to release active IL-1β) as described for leukocytes. This study aimed to determine whether there is rapid release of IL-1β in response to soluble platelet agonists and whether such rapid release is NLRP3- and caspase-1-dependent.

METHODS AND RESULTS

 Using flow cytometry to detect platelet activation (and release of α and dense granule contents) and the combination of Western blotting, enzyme-linked-immunosorbent assay, and immunogold labeling transmission electron and immunofluorescence microscopy, we identified that resting human platelets contain mature IL-1β. Platelets release IL-1β within minutes in response to adenosine diphosphate (ADP), collagen, and thrombin receptor agonists, but not in response to conventional NLRP3 inflammasome agonists-lipopolysaccharide and adenosine triphosphate. The rapid release of IL-1β in response to ADP and thrombin receptor agonists was independent of caspases (including caspase-1) and NLRP3. Immature and mature IL-1β were identified as low-abundance proteins on transmission electron microscopy of human platelets, and were localized to the platelet cytosol, open canalicular system, and the periphery of α granules.

CONCLUSION

 Unlike monocytes and neutrophils, human platelets are capable of rapid agonist- and time-dependent release of IL-1β by a mechanism which is independent of caspase-1 and NLRP3.

Colchicine inhibits ROS generation in response to glycoprotein VI stimulation

Colchicine inhibits coronary and cerebrovascular events in patients with coronary artery disease (CAD), and although known to have anti-inflammatory properties, its mechanisms of action are incompletely understood. In this study, we investigated the effects of colchicine on platelet activation with a particular focus on its effects on activation via the collagen glycoprotein (GP)VI receptor, P2Y₁₂ receptor, and procoagulant platelet formation. Therapeutic concentrations of colchicine in vitro (equivalent to plasma levels) significantly decreased platelet aggregation in whole blood and in platelet rich plasma in response to collagen (multiplate aggregometry) and reduced reactive oxygen species (ROS) generation (H₂DCF-DA, flow cytometry) in response to GPVI stimulation with collagen related peptide-XL (CRP-XL, GPVI specific agonist). Other platelet activation pathways including P-selectin expression, GPIIb/IIIa conformational change and procoagulant platelet formation (GSAO⁺/CD62P⁺) (flow cytometry) were inhibited with higher concentrations of colchicine known to inhibit microtubule depolymerization. Pathway specific mechanisms of action of colchicine on platelets, including modulation of the GPVI receptor pathway at low concentrations, may contribute to its protective role in CAD.

Agranulocytosis Following COVID-19 Recovery

Clinicians have continued to report on the clinical behavior and characteristics of patients with coronavirus disease 2019 (COVID-19) as our knowledge of the virus continues to mature. Herein, we report the case of a 39-year-old male with multiple comorbidities who became critically ill with COVID-19 infection, requiring mechanical ventilation and vasopressors, and then developed agranulocytosis following clinical improvement and resolution of symptoms of COVID infection. The period of agranulocytosis coincided with the development of thrombocytosis, and following resolution of agranulocytosis, the platelet count also normalized, suggesting a possible related mechanism. Interestingly, the patient was treated with TBO-filgrastim 480 mcg daily with a rapid reconstitution of neutrophils. While the mechanism of agranulocytosis remains unknown, we report, to our knowledge, the first known case of agranulocytosis following COVID-19 infection and its successful treatment with granulocyte colony-stimulating factor.

Remote ischemic preconditioning inhibits platelet αIIb β3 activation in coronary artery disease patients receiving dual antiplatelet therapy: A randomized trial

OBJECTIVES

We investigated whether remote ischemic preconditioning (RIPC) inhibits agonist-induced conformational activation of platelet αIIb β3 in patients with coronary artery disease already receiving conventional antiplatelet therapy.

PATIENTS/METHODS

Consecutive patients with angiographically confirmed coronary artery disease were randomized to RIPC or sham treatment. Venous blood was collected before and immediately after RIPC/sham. Platelet aggregometry (ADP, arachidonic acid) and whole blood platelet flow cytometry was performed for CD62P, CD63, active αIIb β3 (PAC-1 binding) before and after stimulation with ADP, thrombin ± collagen, or PAR-1 thrombin receptor agonist.

RESULTS

Patients (25 RIPC, 23 sham) were well matched, 83% male, age (mean ± standard deviation) 63.3 ± 13.2 years, 95% aspirin, 81% P2Y12 inhibitor. RIPC did not affect platelet aggregation, nor agonist-induced expression of CD62P, but selectively and significantly decreased αIIb β3 activation after stimulation with either PAR-1 agonist peptide or the combination of thrombin + collagen, but not after ADP nor thrombin alone. The effect of RIPC on platelet αIIb β3 activation was evident in patients receiving both aspirin and P2Y12 inhibitor, and was not associated with an increase in vasodilator-stimulated phosphoprotein phosphorylation.

CONCLUSIONS

Remote ischemic preconditioning inhibits conformational activation of platelet αIIb β3 in response to exposure to thrombin and collagen in patients with coronary artery disease receiving dual antiplatelet therapy. These findings indicate agonist-specific inhibition of platelet activation by RIPC in coronary artery disease that is not obviated by the prior use of P2Y12 inhibitors.

Evaluation of CD147 gene expression, lipid peroxidation, and antioxidants in cases of acute coronary syndrome in Egyptian population

Background

The main mechanism of acute coronary syndrome (ACS) is the rupture of atherosclerotic plaques. Matrix metalloproteinases (MMPs) play an important role in the rupture of the vulnerable plaques. MMP secretion is stimulated by CD147, one of the immunoglobulin families. Malondialdehyde is an important marker of oxidative damage, which is related to the atherosclerotic process. Superoxide dismutase normally prevents the oxidative process. This study was conducted to evaluate the association of ACS with CD147 gene expression, lipid peroxidation, and antioxidants in Egyptian population. The study included 124 people, 62 ACS patients and 62 healthy controls.

Results

CD147 gene expression in the ACS group was significantly increased compared to the control group (p < 0.001). The ACS was 9.71 ± 3.56-fold; the control group was 0.94 ± 0.19-fold. Also, the SOD activity in the ACS group was significantly increased when compared to the control group (t = 16.023, p < 0.001). There was a highly significant increase in the MDA level in ACS groups when compared to the control group (t = 35.536, p < 0.001). There was a highly significant increase in the creatine kinase-MB (CK-MB) and high sensitive troponin I levels in ACS groups when compared to the control group (p < 0.001).

Conclusion

There is a highly significant positive correlation between CK-MB and CD147 in both control and ACS groups (p = <0.001**); also, there is highly significant positive correlation between high sensitive troponin I and CD 147 in both control and ACS groups (p = <0.001**), but we did not find significant correlation between SOD and CD147 or between MDA and CD 147 in both control and ACS groups.

Platelets as Potent Signaling Entities in Type 2 Diabetes Mellitus

Type 2 diabetes mellitus (T2DM) is a multifactorial disease with a dysregulated circulating inflammatory molecule tendency. T2DM is closely associated with systemic inflammation, endothelial dysfunction, cardiovascular risk, and increased clotting susceptibility. Platelets have fundamental roles in the development and propagation of inflammation and cardiovascular risk. They signal through membrane receptors, resulting in (hyper)activation and release of inflammatory molecules from platelet compartments. This review highlights how circulating inflammatory molecules, acting as platelet receptor ligands, interact with platelets, causing platelets to be potent drivers of systemic inflammation. We conclude by suggesting that focused platelet research in T2DM is an important avenue to pursue to identify novel therapeutic targets, and that platelets could be used as cellular activity sensors themselves.

Effects of exercise training on markers of adipose tissue remodeling in patients with coronary artery disease and type 2 diabetes mellitus: sub study of the randomized controlled EXCADI trial

BACKGROUND

Investigate effects of long-term exercise on the remodeling markers MMP-9, TIMP-1, EMMPRIN and Galectin-3 in combined type 2 diabetes mellitus (T2DM) and coronary artery disease (CAD) patients. Any associations between these biomarkers and glucometabolic variables were further assessed at baseline.

METHODS

137 patients (age 41-81 years, 17.2% females) were included and randomized to a 12-months exercise program or to a control group. Fasting blood samples and subcutaneous adipose tissue (AT) samples were taken at inclusion and after 12-months. The intervention was a combination of aerobic and strength training for a minimum of 150 min per week. Circulating protein levels were measured by ELISA methods and RNA was extracted from AT and circulating leukocytes. Expression levels were relatively quantified by PCR.

RESULTS

After 12 months of intervention, both AT-expression and circulating levels of EMMPRIN were increased in the exercise group (p < 0.05, both) with significant difference in change between the two groups (p < 0.05 both). No significant effect was observed on MMP-9, TIMP-1 and Galectin-3. Levels of TIMP-1 (AT-expression and circulating) were significantly correlated to insulin, and HOMA2- after Bonferroni correction (p = 0.001, by 48 performed correlations).

CONCLUSION

The increase in levels of EMMPRIN after long-term exercise training, might indicate some degree of AT remodeling in these patients after 12-months of exercise, whether beneficial or not. The remodeling markers were to some extent associated with glucometabolic variables in our population with the combined disease.Trial registration clinicaltrials.gov, NCT01232608. Registered 2 November 2010.

Role of COX-2/PGE2 Mediated Inflammation in Oral Squamous Cell Carcinoma

A significant amount of research indicates that the cyclooxygenase/prostaglandin E2 (PGE2) pathway of inflammation contributes to the development and progression of a variety of cancers, including squamous cell carcinoma of the oral cavity and oropharynx (OSCC). Although there have been promising results from studies examining the utility of anti-inflammatory drugs in the treatment of OSCC, this strategy has been met with only variable success and these drugs are also associated with toxicities that make them inappropriate for some OSCC patients. Improved inflammation-targeting therapies require continued study of the mechanisms linking inflammation and progression of OSCC. In this review, a synopsis of OSCC biology will be provided, and recent insights into inflammation related mechanisms of OSCC pathobiology will be discussed. The roles of prostaglandin E2 and cluster of differentiation factor 147 (CD147) will be presented, and evidence for their interactions in OSCC will be explored. Through continued investigation into the protumourigenic pathways of OSCC, more treatment modalities targeting inflammation-related pathways can be designed with the hope of slowing tumour progression and improving patient prognosis in patients with this aggressive form of cancer.

Novel assay demonstrates that coronary artery disease patients have heightened procoagulant platelet response

Essentials Procoagulant platelets can be detected using GSAO in human whole blood. Stable coronary artery disease is associated with a heightened procoagulant platelet response. Agonist-induced procoagulant platelet response is not inhibited by aspirin alone. Collagen plus thrombin induced procoagulant platelet response is partially resistant to clopidogrel.

SUMMARY

Background Procoagulant platelets are a subset of highly activated platelets with a critical role in thrombin generation. Evaluation of their clinical utility in thrombotic disorders, such as coronary artery disease (CAD), has been thwarted by the lack of a sensitive and specific whole blood assay. Objectives We developed a novel assay, utilizing the cell death marker, GSAO [(4-(N-(S-glutathionylacetyl)amino)phenylarsonous acid], and the platelet activation marker, P-selectin, to identify procoagulant platelets in whole blood by flow cytometry. Patients/Methods Using this assay, we characterized the procoagulant platelet population in healthy controls and a cohort of patients undergoing elective coronary angiography. Results In patients with CAD, compared with patients without CAD, there was a heightened procoagulant platelet response to thrombin (25.2% vs. 12.2%), adenosine diphosphate (ADP) (7.8% vs. 2.7%) and thrombin plus collagen (27.2% vs. 18.3%). The heightened procoagulant platelet potential in CAD patients was not associated with other markers of platelet function, including aggregation, dense granule release and activation of α2b β3 integrin. Although dual antiplatelet therapy (DAPT) was associated with partial suppression of procoagulant platelets, this inhibitory effect on a patient level could not be predicted by aggregation response to ADP and was not fully suppressed by clopidogrel. Conclusions We report for the first time that procoagulant platelets can be efficiently detected in a few microliters of whole blood using the cell death marker, GSAO, and the platelet activation marker, P-selectin. A heightened procoagulant platelet response may provide insight into the thrombotic risk of CAD and help identify a novel target for antiplatelet therapies in CAD.

Extracellular Matrix Metalloproteinase Inducer EMMPRIN (CD147) in Cardiovascular Disease

The receptor EMMPRIN is involved in the development and progression of cardiovascular diseases and in the pathogenesis of myocardial infarction. There are several binding partners of EMMPRIN mediating the effects of EMMPRIN in cardiovascular diseases. EMMPRIN interaction with most binding partners leads to disease progression by mediating cytokine or chemokine release, the activation of platelets and monocytes, as well as the formation of monocyte-platelet aggregates (MPAs). EMMPRIN is also involved in atherosclerosis by mediating the infiltration of pro-inflammatory cells. There is also evidence that EMMPRIN controls energy metabolism of cells and that EMMPRIN binding partners modulate intracellular glycosylation and trafficking of EMMPRIN towards the cell membrane. In this review, we systematically discuss these multifaceted roles of EMMPRIN and its interaction partners, such as Cyclophilins, in cardiovascular disease.

Platelets and matrix metalloproteinases

Matrix metalloproteinases (MMPs) and their inhibitors essentially contribute to a variety of pathophysiologies by modulating cell migration, tissue degradation and inflammation. Platelet-associated MMP activity appears to play a major role in these processes. First, platelets can concentrate leukocyte-derived MMP activity to sites of vascular injury by leukocyte recruitment. Second, platelets stimulate MMP production in e.g. leukocytes, endothelial cells, or tumour cells by direct receptor interaction or/and by paracrine pathways. Third, platelets synthesise and secrete a variety of MMPs including MMP-1, MMP-2, MMP-3, and MMP-14 (MT1-MMP), and potentially MMP-9 as well as the tissue inhibitors of metalloproteinase (TIMPs). This review focuses on platelet-derived and platelet-induced MMPs and their inhibitors.

Focusing on plasma glycoprotein VI

New methods for analysing both platelet and plasma forms of the platelet-specific collagen receptor, glycoprotein VI (GPVI) in experimental models or human clinical samples, and the development of the first therapeutic compounds based on dimeric soluble GPVI-Fc or anti-GPVI antibody-based constructs, coincide with increased understanding of the potential pathophysiological role of GPVI ligand binding and shedding. Platelet GPVI not only mediates platelet activation at the site of vascular injury where collagen is exposed, but is also implicated in the pathogenesis of other diseases, such as atherosclerosis and coagulopathy, rheumatoid arthritis and tumour metastasis. Here, we describe some of the critical mechanisms for generating soluble GPVI from platelets, and future avenues for exploiting this unique platelet-specific receptor for diagnosis and/or disease prevention.

Association Study between an SNP in CD147 and Its Expression With Acute Coronary Syndrome in a Jiangsu Chinese Population

CD147 is an important molecule in the inflammation and proteolysis process. This molecule crucially contributes to the initial and progression of atherosclerotic lesions. A single nucleotide polymorphism in CD147 gene, the rs8259 T/A in the 3'-untranslated region, is responsible for its expression in various cells. This study assessed whether the genetic variation rs8259 is associated with acute coronary syndrome (ACS) and CD147. A total of 943 ACS subjects and 439 stable angina subjects, and 851 controls were genotyped for rs8259 polymorphism by polymerase chain reaction restriction fragment length polymorphism and DNA-sequencing method. Plasma soluble CD147 (sCD147) level was measured by enzyme-linked immunosorbent assay. CD147 mRNA and protein expression in peripheral blood mononuclear cells were tested by real-time quantitative polymerase chain reaction and western blot, respectively. We found that TT genotype and T-allele frequency of CD147 rs8259 in ACS patients were much lower than the other patient groups. Significant difference was not observed between stable angina and controls. CD147 T allele was negatively related to ACS. ACS patients exhibited the highest CD147 expression in peripheral blood mononuclear cells and plasma sCD147 level. The plasma sCD147 levels in the culprit vessel were higher than those in the radial artery. In ACS patients, AA gene carriers had the highest CD147 levels, whereas TT gene carriers had the lowest CD147 levels. Linear regression analysis showed that genotypes and disease conditions contributed 49% to the change of the plasma CD147 level. These results suggested that the single nucleotide polymorphism of CD147 gene rs8259 T/A was associated with ACS susceptibility. Allele T gene may decrease the relative risk of suffering from ACS through downregulation of CD147 expression.

Function of CD147 in atherosclerosis and atherothrombosis

CD147, a member of the immunoglobulin super family, is a well-known potent inducer of extracellular matrix metalloproteinases. Studies show that CD147 is upregulated in inflammatory diseases. Atherosclerosis is a chronic inflammatory disease of the artery wall. Further understanding of the functions of CD147 in atherosclerosis and atherothrombosis may provide a new strategy for preventing and treating cardiovascular disease. In this review, we discuss how CD147 contributes to atherosclerosis and atherothrombosis.

Cyclophilin A and EMMPRIN (CD147) in cardiovascular diseases

Cyclophilin A (CyPA) is an abundantly expressed intracellular protein. It exerts a variety of functions due to its peptidyl-prolyl cis-trans isomerase (PPIase) activity. When released into the extracellular space, CyPA binds to its extracellular receptor CD147 (EMMPRIN) and thereby initiates a cascade of inflammatory processes. Recent data indicate that both extra- and intracellular CyPA significantly contribute to cardiovascular inflammation, myocardial ischaemia and reperfusion injury, and myocardial remodelling processes. Thus, CyPA appears to represent a novel target to treat vascular and myocardial inflammation.

Circulating levels of soluble EMMPRIN (CD147) correlate with levels of soluble glycoprotein VI in human plasma

Extracellular matrix metalloproteinase inducer (EMMPRIN; CD147), which binds to the platelet-specific collagen receptor glycoprotein (GP) VI, is expressed in a range of cell types including platelets and leukocytes, and has been implicated in neoplastic disease and atherosclerotic coronary disease. Both CD147 and GPVI can be shed from cell membranes and detected in plasma. However, while the relationship between soluble CD147 (sCD147), soluble GPVI (sGPVI) and standard markers of platelet activation has received little attention, such analysis may help reveal pathways mediating release of sCD147. We investigated the relationship between sCD147 and platelet markers including sGPVI, soluble and platelet-bound CD62P (P-selectin), active αIIbβ3 (assessed by PAC-1 binding) and platelet CD147 in 25 patients with stable angina pectoris (SAP), 13 patients with no coronary artery disease (CAD) and 10 healthy donors. Plasma levels of sCD147 significantly correlated with sGPVI (r = 0.46, p = .004), but did not correlate with any other platelet markers examined. Linear regression analysis identified that sCD147 levels could be predicted by sGPVI levels (β = .445, p = 0.003) and age (β = 0.304, p = 0.038), but were independent of potential clinical confounders such as CAD, diabetes and medication usage. As sCD147 strongly correlates with platelet-specific sGPVI, a common platelet source and/or mechanism of release may contribute to sCD147 levels in vivo.

Oxidized low-density lipoprotein-induced CD147 expression and its inhibition by high-density lipoprotein on platelets in vitro

INTRODUCTION

Matrix metalloproteinases (MMPs) are believed to progressively degrade the collagenous components of the protective fibrous cap, leading to atherosclerotic plaque rupture or destabilization. Oxidized low-density lipoprotein (ox-LDL) enhances the release of CD147, known as the extracellular MMP inducer, from coronary smooth muscle cells. However, whether ox-LDL can induce platelet CD147 expression is unknown. Therefore, we investigated the influence of ox-LDL and high-density lipoprotein (HDL) on CD147 expression on human platelets.

MATERIALS AND METHODS

Washed platelets were incubated with ox-LDL (or native LDL) and HDL or anti-LOX-1 monoclonal antibody prior to incubation with ox-LDL. In parallel, buffer (PBS) was added to washed platelets as a control. The expression levels of CD147, CD62P, CD63 and Annexin V were assessed by flow cytometry, and soluble CD147 from the platelets was assessed by an enzyme-linked immunosorbent assay. Laser scanning microscopy (LSM) and transmission electron microscopy (TEM) were used to visualize the morphological changes and granule release, respectively, from the platelets.

RESULTS

Platelets treated with ox-LDL exhibited a significant increase in the expression of CD147 (or Annexin V), followed by increases in CD62P and CD63, compared with the control group. In contrast, HDL or anti-LOX-1 monoclonal antibody decreased these effects. The expression of soluble CD147 increased as the concentration of ox-LDL used to treat the platelets increased. After exposure to ox-LDL, morphological changes and granule release in the platelets were visualized by LSM and TEM. Additionally, the TEM revealed that HDL inhibits alpha-granule release.

CONCLUSIONS

In platelets, ox-LDL stimulates the release of CD147 via binding to LOX-1, whereas HDL inhibits this effect. This finding could provide new insights concerning the influence of ox-LDL and HDL on plaque stability by the up-regulation of CD147 on platelets.

EMMPRIN (CD147/basigin) mediates platelet-monocyte interactions in vivo and augments monocyte recruitment to the vascular wall

BACKGROUND

Platelets play a central role in hemostasis, in inflammatory diseases such as atherosclerosis, and during thrombus formation following vascular injury. Thereby, platelets interact intensively with monocytes and enhance their recruitment to the vascular wall.

OBJECTIVES

To investigate the role of the extracellular matrix metalloproteinase inducer (EMMPRIN) in platelet-monocyte interactions.

METHODS AND RESULTS

Isolated human monocytes were perfused in vitro over firmly adherent platelets to allow investigation of the role of EMMPRIN in platelet-monocyte interactions under flow conditions. Monocytes readily bound to surface-adherent platelets. Both antibody blockade and gene silencing of monocyte EMMPRIN substantially attenuated firm adhesion of monocytes to platelets at arterial and venous shear rates. In vivo, platelet interactions with the murine monocyte cell line ANA-1 were significantly decreased when ANA-1 cells were pretreated with EMMPRIN-silencing small interfering RNA prior to injection into wild-type mice. Using intravital microscopy, we showed that recruitment of EMMPRIN-silenced ANA-1 to the injured carotid artery was significantly reduced as compared with control cells. Further silencing of EMMPRIN resulted in significantly fewer ANA-1-platelet aggregates in the mouse circulation as determined by flow cytometry. Finally, we identified glycoprotein (GP)VI as a critical corresponding receptor on platelets that mediates interaction with monocyte EMMPRIN. Thus, blocking of GPVI inhibited the effect of EMMPRIN on firm monocyte adhesion to platelets under arterial flow conditions in vitro, and abrogated EMMPRIN-mediated platelet-monocyte aggregate formation in vivo.

CONCLUSIONS

EMMPRIN supports platelet-monocyte interactions and promotes monocyte recruitment to the arterial wall. Therefore, EMMPRIN might represent a novel target to reduce vascular inflammation and atherosclerotic lesion development.

Human T cell microparticles circulate in blood of hepatitis patients and induce fibrolytic activation of hepatic stellate cells

Microparticles (MPs) are small cell membrane vesicles that are released from cells during apoptosis or activation. Although circulating platelet MPs have been studied in some detail, the existence and functional role of T cell MPs remain elusive. We show that blood from patients with active hepatitis C (alanine aminotransferase [ALT] level >100 IU/mL) contains elevated numbers of T cell MPs compared with patients with mild hepatitis C (ALT <40 IU/mL) and healthy controls. T cell MPs fuse with cell membranes of hepatic stellate cells (HSCs), the major effector cells for excess matrix deposition in liver fibrosis and cirrhosis. MP uptake is partly intercellular adhesion molecule 1-dependent and leads to activation of nuclear factor kappa B and extracellular signal-regulated kinases 1 and 2 and subsequent up-regulation of fibrolytic genes in HSCs, down-regulation of procollagen α1(I) messenger RNA, and blunting of profibrogenic activities of transforming growth factor β1. Ex vivo, the induced fibrolytic activity is evident in MPs derived from activated CD4+ T cells and is highest in MPs derived from activated and apoptotic CD8+ T cells. Mass spectrometry, fluorescence-activated cell sorting analysis, and function blocking antibodies revealed CD147/Emmprin as a candidate transmembrane molecule in HSC fibrolytic activation by CD8+ T cell MPs.

CONCLUSION

Circulating T cell MPs are a novel diagnostic marker for inflammatory liver diseases, and in vivo induction of T cell MPs may be a novel strategy to induce regression of liver fibrosis.

Intracoronary shear-related up-regulation of platelet P-selectin and platelet-monocyte aggregation despite the use of aspirin and clopidogrel

Recent in vitro studies have shown that shear stress can cause platelet activation by agonist-independent pathways. However, no studies have assessed the extent of shear-induced platelet activation within human coronary arteries. We sampled blood from the coronary arteries proximal and distal to coronary lesions and from the coronary sinus in humans with stable coronary disease who were taking both aspirin and clopidogrel. A novel, computationally based technique for estimating shear stress from 3-dimensional coronary angiographic images of these arteries was developed, and the effect of stenosis severity and calculated shear stress on in vivo platelet and related leukocyte activation pathways were determined. We provide evidence of intracoronary up-regulation of platelet P-selectin, platelet-monocyte aggregation, and monocyte CD11b without platelet glycoprotein IIb-IIIa activation or soluble P-selectin up-regulation. This correlates with intracoronary stenosis severity and calculated shear stress and occurs despite the concurrent use of aspirin and clopidogrel. Our results show for the first time shear-related platelet and monocyte activation in human coronary arteries and suggest this as a potential therapeutic target that is resistant to conventional antiplatelet agents.

Monocyte CD147 is induced by advanced glycation end products and high glucose concentration: possible role in diabetic complications

CD147 is a highly glycosylated transmembrane protein that is known to play a role in regulation of many protein families. It has the unique ability to maintain functional activity in both the membrane bound state and in the soluble form. CD147 is known to play a role in regulation of matrix metalloproteinase (MMP) expression, but whether its expression is affected by the diabetic milieu is not known, and its role in regulation of monocyte MMPs in this environment has not been investigated. Therefore, in this study we investigated the effect of advanced glycation end products (AGEs) and high glucose (HG; 25 mM), on monocyte CD147 expression. Culture of THP-1 monocytes in the presence of AGEs or HG significantly increased CD147 at the gene and protein level. THP-1 cell results were confirmed using freshly isolated monocytes from human volunteers. The effect of AGEs and HG on CD147 expression was also mimicked by addition of proinflammatory cytokines. Addition of AGEs or HG also increased expression of monocyte MMP-1 and MMP-9 but not MMP-2. This increase in MMPs was significantly attenuated by inhibition of CD147 using either a small interfering RNA or an anti-CD147 antibody. Inhibition of NF-κB or addition of antibodies to either TNF-α or the receptor for AGE (RAGE) each significantly prevented in a dose-dependent manner the induction of CD147 gene and protein by AGE and also decreased MMP-1 and MMP-9. This novel result shows that AGEs can induce monocyte CD147 expression, an effect mediated by inflammatory pathways and RAGE. Because MMPs play a role in monocyte migration, inhibition of their regulator CD147 may assist in the prevention of diabetic complications, particularly those where monocyte infiltration is an early initiating event.