Endothelium-derived microparticles inhibit human cardiac valve endothelial cell function

Endothelial extracellular vesicles induce acute lung injury via follistatin-like protein 1

Cardiopulmonary bypass has been speculated to elicit systemic inflammation to initiate acute lung injury (ALI), including acute respiratory distress syndrome (ARDS), in patients after cardiac surgery. We previously found that post-operative patients showed an increase in endothelial cell-derived extracellular vesicles (eEVs) with components of coagulation and acute inflammatory responses. However, the mechanism underlying the onset of ALI owing to the release of eEVs after cardiopulmonary bypass, remains unclear. Plasma plasminogen-activated inhibitor-1 (PAI-1) and eEV levels were measured in patients with cardiopulmonary bypass. Endothelial cells and mice (C57BL/6, Toll-like receptor 4 knockout (TLR4-/-) and inducible nitric oxide synthase knockout (iNOS-/-)) were challenged with eEVs isolated from PAI-1-stimulated endothelial cells. Plasma PAI-1 and eEVs were remarkably enhanced after cardiopulmonary bypass. Plasma PAI-1 elevation was positively correlated with the increase in eEVs. The increase in plasma PAI-1 and eEV levels was associated with post-operative ARDS. The eEVs derived from PAI-1-stimulated endothelial cells could recognize TLR4 to stimulate a downstream signaling cascade identified as the Janus kinase 2/3 (JAK2/3)-signal transducer and activator of transcription 3 (STAT3)-interferon regulatory factor 1 (IRF-1) pathway, along with iNOS induction, and cytokine/chemokine production in vascular endothelial cells and C57BL/6 mice, ultimately contributing to ALI. ALI could be attenuated by JAK2/3 or STAT3 inhibitors (AG490 or S3I-201, respectively), and was relieved in TLR4-/- and iNOS-/- mice. eEVs activate the TLR4/JAK3/STAT3/IRF-1 signaling pathway to induce ALI/ARDS by delivering follistatin-like protein 1 (FSTL1), and FSTL1 knockdown in eEVs alleviates eEV-induced ALI/ARDS. Our data thus demonstrate that cardiopulmonary bypass may increase plasma PAI-1 levels to induce FSTL1-enriched eEVs, which target the TLR4-mediated JAK2/3/STAT3/IRF-1 signaling cascade and form a positive feedback loop, leading to ALI/ARDS after cardiac surgery. Our findings provide new insight into the molecular mechanisms and therapeutic targets for ALI/ARDS after cardiac surgery.

Effect of Thrombolysis on Circulating Microparticles in Patients with ST-Segment Elevation Myocardial Infarction

Objective

We demonstrated that circulating microparticles (MPs) are increased in patients with coronary heart disease (both chronic coronary syndrome (CCS) and acute coronary syndrome). Whether thrombolysis affects MPs in patients with ST-segment elevation myocardial infarction (STEMI) with or without percutaneous coronary intervention (PCI) is unknown.

Methods

This study was divided into three groups: STEMI patients with thrombolysis (n = 18) were group T, patients with chronic coronary syndrome (n = 20) were group CCS, and healthy volunteers (n = 20) were the control group. Fasting venous blood was extracted from patients in the CCS and control groups, and venous blood was extracted from patients in the T group before (pre-T) and 2 hours after (post-T) thrombolysis. MPs from each group were obtained by centrifugation. After determining the concentration, the effects of MPs on endothelial nitric oxide synthase (eNOS) and inducible nitric oxide synthase (iNOS) in rat myocardial tissue in vitro were detected by immunohistochemistry and western blotting. Changes in nitric oxide (NO) and oxygen free radicals (O2•-) were also detected. The effect of MPs on vasodilation in isolated rat thoracic aortae was detected.

Results

Compared with that in the control group (2.60 ± 0.38 mg/ml), the concentration of MPs was increased in patients with CCS (3.49 ± 0.72 mg/ml) and in STEMI patients before thrombolysis (4.17 ± 0.58 mg/ml). However, thrombolysis did not further increase MP levels (post-T, 4.23 ± 1.01 mg/ml) compared with those in STEMI patients before thrombolysis. Compared with those in the control group, MPs in both CCS and STEMI patients before thrombolysis inhibited the expression of eNOS (both immunohistochemistry and western blot analysis of phosphorylation at Ser1177), NO production in the isolated myocardium and vasodilation in vitro and stimulated the expression of iNOS (immunohistochemistry and western blot analysis of phosphorylation at Thr495), and the generation of O2•- in the isolated myocardium. The effects of MPs were further enhanced by MPs from STEMI patients 2 hours after thrombolysis.

Conclusion

Changes in MP function after thrombolysis may be one of the mechanisms leading to ischemia-reperfusion after thrombolysis.

Zhijing powder manages blood pressure by regulating PI3K/AKT signal pathway in hypertensive rats

Background

Zhijing Powder (ZJP) is a traditional Chinese medicine containing two kinds of Chinese medicine. Those studies analyze the molecular mechanism of ZJP in treating hypertension through network pharmacology, combined with animal experiments.

Methods

First, the effective ingredients and potential targets of the drug were obtained through drug databases, while the targets of disease obtained through disease target databases. The potential targets, cellular bioanalysis and signaling pathways were found in some platforms by analyzing collected targets. Further experiments were conducted to verify the effect and mechanism of drugs on cold and high salt in an induced-hypertension rat model.

Results

There are 17 effective components of centipedes and 10 of scorpions, with 464 drug targets obtained after screening. A total of 1263 hypertension targets were obtained after screening and integration, resulting in a protein-protein interaction network (PPI) with 145 points and 1310 edges. Gene ontology (GO) analysis shows that blood circulation regulation and activation of G protein-coupled receptors are mainly biological processes. The Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis shows that neuroactive ligand-receptor interaction, calcium signaling pathways, PI3K-AKT signaling pathways are the most abundant gene-enriched pathway. Animal experiments indicated that ZJP can reduce blood pressure (BP), affect expression of the PI3K-AKT signaling pathway, and improve oxidative stress in the body.

Conclusion

ZJP ameliorates oxidative stress and reduces BP in hypertensive rats caused by cold stimuli and high salt, revealing its effect on the expression of the PI3K/AKT signaling pathway in the rat aorta.

PTH-induced EndMT via miR-29a-5p/GSAP/Notch1 pathway contributed to valvular calcification in rats with CKD

Background

Endothelial‐to‐mesenchymal transition (EndMT) is a common pathophysiology in valvular calcification (VC) among non‐chronic kidney disease (CKD) patients. However, few studies were investigated in CKD‐induced VC. Parathyroid hormone (PTH) was considered to be an important component of EndMT in CKD‐induced cardiovascular diseases. Therefore, determining whether PTH could induce valvular EndMT and elucidating corresponding mechanism involved further study.

Methods

Performing a 5/6 nephrectomy with a high phosphorus diet was done to construct VC models in rats with CKD. miRNA sequencing was used to ascertain changes in microRNA in human umbilical vein endothelial cells (HUVECs) intervened by PTH. VC was observed by Von Kossa staining and scanning electron microscope.

Results

PTH induced valvular EndMT in VC. Global microRNA expression profiling of HUVECs was examined in PTH versus the control in vitro, in which miR‐29a‐5p was most notably decreased and was resumed by PTHrP(7‐34) (PTH‐receptor1 inhibitor). Overexpression of miR‐29a‐5p could inhibit PTH‐induced EndMT in vitro and valvular EndMT in vivo. The dual‐luciferase assay verified that γ‐secretase‐activating protein (GASP) served as the target of miR‐29a‐5p. miR‐29a‐5p‐mimics, si‐GSAP and DAPT (γ‐secretase inhibitor) inhibited PTH‐induced γ‐secretase activation, thus blocking Notch1 pathway activation to inhibit EndMT in vitro. Moreover, Notch1 pathway activation was observed in VC. Blocking Notch1 pathway activation via AAV‐miR‐29a and DAPT inhibited valvular EndMT. In addition, blocking Notch1 pathway activation was also shown to alleviate VC.

Conclusion

PTH activates valvular EndMT via miR‐29a‐5p/GSAP/Notch1 pathway, which can contribute to VC in CKD rats.

Artemisinin protects endothelial function and vasodilation from oxidative damage via activation of PI3K/Akt/eNOS pathway

INTRODUCTION

Previous studies showed that artemisinin (ART) may be useful in the protection against the early development of atherosclerosis, but the effects of ART on vasodilation and eNOS remained unclear.

OBJECTIVES AND METHODS

In the current study, we investigated the protective effect of ART on endothelial cell injury induced by oxidative stress and its underlying mechanism via MTT assay, Flow Cytometry Assay, Vasodilation study, Western blotting and vivo assay.

RESULTS

We found that pretreatment of human umbilical vein endothelial cells (HUVECs) with ART significantly suppressed H2O2-induced cell death by decreasing the extent of oxidation and MDA activity, activating SOD, increasing NO production and inhibiting caspase 3/7 activity. Meanwhile, we also found that ART was able to activate PI3K/Akt/eNOS pathway. PI3K inhibitor LY294002 or Akt kinase specific inhibitor Akt inhibitor VIII blocked the protective effect of ART. To explore the effect of ART in the damage of vasodilation induced by H2O2 in mice, we treated the aortic ring from C57BL/6 mice with H2O2 with or without ART, the results demonstrated that ART ameliorated endothelium-dependent vasodilation damage induced by H2O2.

CONCLUSION

Taken together, these data suggest that ART is able to protect endothelial function and vasodilation from oxidative damage, at least in part through activation of PI3K/Akt/eNOS pathway. Our findings indicate that artemisinin maybe as a potential therapeutic agent for patients with atherosclerosis.

Microparticles and cardiovascular diseases

Microparticles are a distinctive group of small vesicles, without nucleus, which are involved as significant modulators in several physiological and pathophysiological mechanisms. Plasma microparticles from various cellular lines have been subject of research. Data suggest that they are key players in development and manifestation of cardiovascular diseases and their presence, in high levels, is associated with chronic inflammation, endothelial damage and thrombosis. The strong correlation of microparticle levels with several outcomes in cardiovascular diseases has led to their utilization as biomarkers. Despite the limited clinical application at present, their significance emerges, mainly because their detection and enumeration methods are improving. This review article summarizes the evidence derived from research, related with the genesis and the function of microparticles in the presence of various cardiovascular risk factors and conditions. The current data provide a substrate for several theories of how microparticles influence various cellular mechanisms by transferring biological information.

Microparticles from Patients Undergoing Percutaneous Coronary Intervention Impair Vasodilatation by Uncoupling Endothelial Nitric Oxide Synthase

OBJECTIVES

Percutaneous coronary interventions (PCIs) save countless acute myocardial infarction (AMI) patients. However, endothelial injury is still an inevitable complication. Circulating microparticles (MPs) play important roles in vascular dysfunction. Whether PCI affects function of MPs remains unclear.

METHODS

MPs were obtained from AMI patients (n = 38) both preoperatively and 24 h after PCI, and healthy subjects (n = 20). MPs origins were tested by flow cytometry. Rat thoracic aortas were incubated with MPs to determine the effects of MPs on phosphorylation of endothelial nitric oxide synthase (eNOS), caveolin-1 expression, eNOS association with heat shock protein 90 (Hsp90), generation of nitric oxide (NO) and superoxide anion (O2), and endothelial-dependent vasodilatation.

RESULTS

Compared with healthy subjects, MP concentrations increased in AMI patients. Undergoing PCI had no further effect on MPs concentration, but it results in increased endothelial-derived MPs proportion and decreased platelet-derived MP ratio. MPs from AMI patients decreased eNOS phosphorylation at Ser1177, increased eNOS phosphorylation at T495 and caveolin-1 expression, decreased eNOS association with Hsp90, decreased NO production but increased (O2) generation, damaged endothelial-dependent vasodilatation. All of these effects of MPs were strengthened by PCI.

CONCLUSIONS

PCI further enhances the vascular injury effect of MPs. Circulating MPs may be a potential therapeutic target for patients undergoing PCI.

Review of the Association between Splenectomy and Chronic Thromboembolic Pulmonary Hypertension

Recent evidence suggests that there may be a link between splenectomy and the later development of pulmonary hypertension, in particular World Health Organization group IV pulmonary hypertension (chronic thromboembolic pulmonary hypertension). Epidemiological studies have demonstrated an odds ratio as high as 18 for the development of chronic thromboembolic pulmonary hypertension after splenectomy in comparison with matched control subjects who have not undergone splenectomy. The mechanisms governing the association between removal of the spleen and the subsequent development of chronic thromboembolic pulmonary hypertension remain incompletely understood; however, recent advances in understanding of coagulation homeostasis have shed some light on this association. Splenectomy increases the risk of venous thromboembolic disease, a necessary precursor of chronic thromboembolic pulmonary hypertension, by generating a prothrombotic state. This prothrombotic state likely results from a reduction in the removal of circulating procoagulant factors from the bloodstream after splenectomy. Although much is to be learned, circulating microparticles have emerged as the most likely mediator for the development of thrombosis after splenectomy. Apparently because of a reduction in reticuloendothelial cell clearance, microparticle levels are elevated in patients after splenectomy. Elevated circulating microparticle levels have been linked to thromboembolism and pulmonary hypertension in a dose-dependent fashion. It is important for health care providers to be aware of the link between splenectomy and chronic thromboembolic pulmonary hypertension. We are optimistic that clarification of the exact mechanisms that govern this association will yield clinical guidelines and potential treatments.

Endothelial vascular markers in coronary surgery

Coronary heart disease is associated with high morbidity and mortality. Endothelial dysfunction in affected patients is linked to long-term atherosclerotic disease progression and cardiovascular event rates. The present paper reports on changes in the levels of endothelial progenitor cells (VEGFR2/CD133/CD34), essential for endothelial repair, and of endothelial microvesicles (CD31/annexin V) as indicators of endothelial lesion, in patients undergoing coronary bypass surgery with respect both to baseline levels and to counts in healthy subjects. In an observational descriptive study, 31 patients scheduled for coronary revascularization surgery were compared with those of 25 healthy controls. In a subsequent longitudinal study, patients undergoing surgery were monitored at 5 timepoints up until 48 h after surgery. Endothelial progenitor cell (VEGFR2/CD133/CD34) and endothelial microvesicle (CD31/annexin V) levels were quantified by flow cytometry. Baseline endothelial progenitor cell counts in coronary patients were significantly lower than those of healthy controls (p < 0.001); however, after surgery, levels rose steadily over all 5 timepoints to 48 h  with statistically significant differences (p < 0.001) between intra-operative and 48 h after surgery (T5). Endothelial microvesicle levels were significantly higher in coronary patients prior to surgery than in healthy controls (p < 0.001), and despite declining at 48 h remained significantly higher than those of controls (p < 0.001). Coronary surgery has had a positive impact on the endothelium in the patients, prompting a decrease in signs of endothelial dysfunction and a considerable improvement in the endothelial repair mechanisms involved in angiogenesis, playing an important role in the inflammatory response and the remodelling process of ischemic myocardium in postoperative period.

Bubble-Induced Endothelial Microparticles Promote Endothelial Dysfunction

Decompression sickness is a systemic pathophysiological process caused by bubbles and endothelial microparticles (EMPs) are established markers reflecting competency of endothelial function and vascular biology. Here, we investigated the effects of bubble-induced EMPs on endothelial cells in vitro and vivo. Rat pulmonary microvascular endothelial cells (PMVECs) were isolated and stimulated by bubbles and bubble-induced EMPs were collected and incubated with normal PMVECs in vitro. Cell viability and apoptosis were detected using Cell Counting Kit-8 assay and Annexin V FITC/PI double staining, respectively. Cell permeability and pro-inflammatory cytokines were determined by electric cell substrate impedance sensing and enzyme-linked immunosorbent assay, respectively. Intracellular nitric oxide and reactive oxygen species production were analyzed microscopically. In vivo study, bubble-induced EMPs were intravenously injected to the rats and soluble thrombomodulin, intercellular adhesion molecule 1, and vascullar adhesion molecule 1 were involved in evaluating endothelial dysfunction. In our study, bubble stimulus resulted in a significant increase of EMPs release by 3 fold. Bubble-induced EMPs significantly decreased cell viability and increased cell apoptosis. Moreover, bubble-induced EMPs induced abnormal increase of cell permeability and over-expression of pro-inflammatory cytokines. Intracellular ROS production increased while NO production decreased. These negative effects caused by bubble-induced EMPs were remarkably suppressed when EMPs pretreated with surfactant FSN-100. Finally, intravenous injection of bubble-induced EMPs caused elevations of soluble thrombomodulin and pro-inflammatory cytokines in the circulation. Altogether, our results demonstrated that bubble-induced EMPs can mediate endothelial dysfunction in vitro and vivo, which can be attenuated by EMPs abatement strategy. These data expanded our horizon of the detrimental effects of bubble-induced EMPs, which may be of great concern in DCS.

Microparticles from Patients with the Acute Coronary Syndrome Impair Vasodilatation by Inhibiting the Akt/eNOS-Hsp90 Signaling Pathway

Objectives: Endothelial dysfunction is involved in the development of the acute coronary syndrome (ACS). Plasma microparticles (MPs) from other diseases have been demonstrated to initiate coagulation and endothelial dysfunction. However, whether MPs from ACS patients impair vasodilatation and endothelial function remains unclear. Methods: Patients (n = 62) with ACS and healthy controls (n = 30) were recruited for MP isolation. Rat thoracic aortas were incubated with MPs from ACS patients or healthy controls to determine the effects of MPs on endothelial-dependent vasodilatation, the phosphorylation of Akt and endothelial nitric oxide synthase (eNOS), the interaction of eNOS with heat shock protein 90 (Hsp90), and nitric oxide (NO) and superoxide anion (O2-) production. The origin of MPs was assessed by flow cytometry. Results: MP concentrations were increased in patients with ACS compared with healthy controls. They were positively correlated with the degree of coronary artery stenosis. MPs from ACS patients impair endothelial-dependent vasodilatation, decrease both Akt and eNOS phosphorylation, decrease the interaction between eNOS and Hsp90, and decrease NO production but increase O2- generation in rat thoracic aortas. Endothelial-derived MPs and platelet-derived MPs made up nearly 75% of MPs. Conclusions: Our data indicate that MPs from ACS patients negatively affect endothelial-dependent vasodilatation via Akt/eNOS-Hsp90 pathways.

Microparticles That Form Immune Complexes as Modulatory Structures in Autoimmune Responses

Microparticles (MPs) are induced during apoptosis, cell activation, and even “spontaneous” release. Initially MPs were considered to be inert cellular products with no biological function. However, an extensive research and functional characterization have shown that the molecular composition and the effects of MPs depend upon the cellular background and the mechanism inducing them. They possess a wide spectrum of biological effects on intercellular communication by transferring different molecules able to modulate other cells. MPs interact with their target cells through different mechanisms: membrane fusion, macropinocytosis, and receptor-mediated endocytosis. However, when MPs remain in the extracellular milieu, they undergo modifications such as citrullination, glycosylation, and partial proteolysis, among others, becoming a source of neoantigens. In rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE), reports indicated elevated levels of MPs with different composition, content, and effects compared with those isolated from healthy individuals. MPs can also form immune complexes amplifying the proinflammatory response and tissue damage. Their early detection and characterization could facilitate an appropriate diagnosis optimizing the pharmacological strategies, in different diseases including cancer, infection, and autoimmunity. This review focuses on the current knowledge about MPs and their involvement in the immunopathogenesis of SLE and RA.

Endurance capacity is not correlated with endothelial function in male university students

Background

Endurance capacity, assessed by 1000-meter (1000 m) run of male university students, is an indicator of cardiovascular fitness in Chinese students physical fitness surveillance. Although cardiovascular fitness is related to endothelial function closely in patients with cardiovascular diseases, it remains unclear whether endurance capacity correlates with endothelial function, especially with circulating endothelial microparticles (EMPs), a new sensitive marker of endothelial dysfunction in young students. The present study aimed to investigate the relationship between endurance capacity and endothelial function in male university students.

Methods

Forty-seven healthy male university students (mean age, 20.1±0.6 years; mean height, 172.4±6.3 cm; and mean weight, 60.0±8.2 kg) were recruited in this study. The measurement procedure of 1000 m run time was followed to Chinese national students Constitutional Health Criterion. Endothelium function was assessed by flow-mediated vasodilation (FMD) in the brachial artery measured by ultrasonic imaging, and the level of circulating EMPs was measured by flow cytometry. Cardiovascular fitness indicator - maximal oxygen uptake (VO2 max) - was also measured on a cycle ergometer using a portable gas analyzer.

Results

1000 m run time was correlated with VO₂max (r = −0.399, p<0.05). However, there were no correlations between VO₂max and FMD or levels of circulating CD31+/CD42- microparticles. Similarly, no correlations were found between 1000 m run time and FMD, and levels of circulating CD31+/CD42- microparticles in these male university students (p>0.05).

Conclusion

The correlations between endurance capacity or cardiovascular fitness and endothelial function were not found in healthy Chinese male university students. These results suggest that endurance capacity may not reflect endothelial function in healthy young adults with well preserved FMD and low level of circulating CD31+/CD42-EMPs.

Clinical CVVH model removes endothelium-derived microparticles from circulation

BACKGROUND

Endothelium-derived microparticles (EMPs) are submicron vesicles released from the plasma membrane of endothelial cells in response to injury, apoptosis or activation. We have previously demonstrated EMP-induced acute lung injury (ALI) in animal models and endothelial barrier dysfunction in vitro. Current treatment options for ALI are limited and consist of supportive therapies. We hypothesize that standard clinical continuous venovenous hemofiltration (CVVH) reduces serum EMP levels and may be adapted as a potential therapeutic intervention.

MATERIALS AND METHODS

EMPs were generated from plasminogen activation inhibitor-1 (PAI-1)-stimulated human umbilical vein endothelial cells (HUVECs). Flow cytometric analysis was used to characterize EMPs as CD31- and annexin V-positive events in a submicron size gate. Enumeration was completed against a known concentration of latex beads. Ultimately, a concentration of ~650,000 EMP/mL perfusate fluid (total 470 mL) was circulated through a standard CVVH filter (pore size 200 μm, flow rate 250 mL/hr) for a period of 70 minutes. 0.5 mL aliquots were removed at 5- to 10-minute intervals for flow cytometric analysis. EMP concentration in the dialysate was measured at the end of 4 hours to better understand the fate of EMPs.

RESULTS

A progressive decrease in circulating EMP concentration was noted using standard CVVH at 250 mL/hr (a clinical standard rate) from a 470 mL volume modelling a patient's circulation. A 50% reduction was noted within the first 30 minutes. EMPs entering the dialysate after 4 hours were 5.7% of the EMP original concentration.

CONCLUSION

These data demonstrate that standard CVVH can remove EMPs from circulation in a circuit modelling a patient. An animal model of hemofiltration with induction of EMP release is required to test the therapeutic potential of this finding and potential of application in early treatment of ALI.

Endothelial microparticles increase in mitral valve disease and impair mitral valve endothelial function

Mitral valve endothelial cells are important for maintaining lifelong mitral valve integrity and function. Plasma endothelial microparticles (EMPs) increased in various pathological conditions related to activation of endothelial cells. However, whether EMPs will increase in mitral valve disease and their relationship remains unclear. Here, 81 patients with mitral valve disease and 45 healthy subjects were analyzed for the generation of EMPs by flow cytometry. Human mitral valve endothelial cells (HMVECs) were treated with EMPs. The phosphorylation of Akt and endothelial nitric oxide synthase (eNOS), the association of eNOS and heat shock protein 90 (HSP90), and the generation of nitric oxide (NO) and superoxide anion (O(2)(∙-)) were measured. EMPs were increased significantly in patients with mitral valve disease compared with those in healthy subjects. EMPs were negatively correlated with mitral valve area in patients with isolated mitral stenosis. EMPs were significantly higher in the group with severe mitral regurgitation than those in the group with mild and moderate mitral regurgitation. Furthermore, EMPs were decreased dramatically in both Akt and eNOS phosphorylation and the association of HSP90 with eNOS in HMVECs. EMPs decreased NO production but increased O(2)(∙-) generation in HMVECs. Our data demonstrated that EMPs were significantly increased in patients with mitral valve disease. The increase of EMPs can in turn impair HMVEC function by inhibiting the Akt/eNOS-HSP90 signaling pathway. These findings suggest that EMPs may be a therapeutic target for mitral valve disease.

Evolving role of microparticles in the pathophysiology of endothelial dysfunction

BACKGROUND

Endothelial dysfunction is an early event in the development and progression of a wide range of cardiovascular diseases. Various human studies have identified that measures of endothelial dysfunction may offer prognostic information with respect to vascular events. Microparticles (MPs) are a heterogeneous population of small membrane fragments shed from various cell types. The endothelium is one of the primary targets of circulating MPs, and MPs isolated from blood have been considered biomarkers of vascular injury and inflammation.

CONTENT

This review summarizes current knowledge of the potential functional role of circulating MPs in promoting endothelial dysfunction. Cells exposed to different stimuli such as shear stress, physiological agonists, proapoptotic stimulation, or damage release MPs, which contribute to endothelial dysfunction and the development of cardiovascular diseases. Numerous studies indicate that MPs may trigger endothelial dysfunction by disrupting production of nitric oxide release from vascular endothelial cells and subsequently modifying vascular tone. Circulating MPs affect both proinflammatory and proatherosclerotic processes in endothelial cells. In addition, MPs can promote coagulation and inflammation or alter angiogenesis and apoptosis in endothelial cells.

SUMMARY

MPs play an important role in promoting endothelial dysfunction and may prove to be true biomarkers of disease state and progression.

Cell-derived microparticles in atherosclerosis: biomarkers and targets for pharmacological modulation?

Cardiovascular diseases remain an important cause of morbi-mortality. Atherosclerosis, which predisposes to cardiovascular disorders such as myocardial infarction and stroke, develops silently over several decades. Identification of circulating biomarkers to evaluate cardiovascular event risk and pathology prognosis is of particular importance. Microparticles (MPs) are small vesicles released from cells upon apoptosis or activation. Microparticles are present in blood of healthy individuals. Studies showing a modification of their concentrations in patients with cardiovascular risk factors and after cardiovascular events identify MPs as potential biomarkers of disease. Moreover, the pathophysiological properties of MPs may contribute to atherosclerosis development. In addition, pharmacological compounds, used in the treatment of cardiovascular disease, can reduce plasma MP concentrations. Nevertheless, numerous issues remain to be solved before MP measurement can be applied as routine biological tests to improve cardiovascular risk prediction. In particular, prospective studies to identify the predictive values of MPs in pathologies such as cardiovascular diseases are needed to demonstrate whether MPs are useful biomarkers for the early detection of the disease and its progression.

Role of receptor-mediated endocytosis in the antiangiogenic effects of human T lymphoblastic cell-derived microparticles

Microparticles possess therapeutic potential regarding angiogenesis. We have demonstrated the contribution of apoptotic human CEM T lymphocyte-derived microparticles (LMPs) as inhibitors of angiogenic responses in animal models of inflammation and tumor growth. In the present study, we characterized the antivascular endothelial growth factor (VEGF) effects of LMPs on pathological angiogenesis in an animal model of oxygen-induced retinopathy and explored the role of receptor-mediated endocytosis in the effects of LMPs on human retinal endothelial cells (HRECs). LMPs dramatically inhibited cell growth of HRECs, suppressed VEGF-induced cell migration in vitro experiments, and attenuated VEGF-induced retinal vascular leakage in vivo. Intravitreal injections of fluorescently labeled LMPs revealed accumulation of LMPs in retinal tissue, with more than 60% reductions of the vascular density in retinas of rats with oxygen-induced neovascularization. LMP uptake experiments demonstrated that the interaction between LMPs and HRECs is dependent on temperature. In addition, endocytosis is partially dependent on extracellular calcium. RNAi-mediated knockdown of low-density lipoprotein receptor (LDLR) reduced the uptake of LMPs and attenuated the inhibitory effects of LMPs on VEGF-A protein expression and HRECs cell growth. Intravitreal injection of lentivirus-mediated RNA interference reduced LDLR protein expression in retina by 53% and significantly blocked the antiangiogenic effects of LMPs on pathological vascularization. In summary, the potent antiangiogenic LMPs lead to a significant reduction of pathological retinal angiogenesis through modulation of VEGF signaling, whereas LDLR-mediated endocytosis plays a partial, but pivotal, role in the uptake of LMPs in HRECs.

Berberine improves endothelial function by reducing endothelial microparticles-mediated oxidative stress in humans

BACKGROUND

Circulating endothelial microparticles (EMPs) lead to endothelial dysfunction by increasing oxidative stress. Berberine has a beneficial effect on endothelial function, but no data are available on the EMP-mediated oxidative stress. The present study tests the hypothesis that berberine contributes to the improvement of endothelial function in humans via inhibiting EMP-mediated oxidative stress in vascular endothelium.

METHODS

Twelve healthy subjects received a 1-month berberine therapy and eleven healthy subjects served as control. Endothelium-dependent and -independent function in the brachial artery was assessed by flow-mediated vasodilation (FMD) and sublingual nitroglyceride-mediated vasodilation (NMD). Circulating EMPs and serum malondialdehyde (MDA) were measured before and after therapy. Furthermore, in vitro human umbilical vein endothelial cells (HUVECs) were stimulated by EMPs with or without presence of anti-oxidant compound apocynin or berberine. Intracellular reactive oxygen species (ROS), nitric oxide (NO) production and NADPH oxidase 4 (Nox4) protein expressions were examined, respectively.

RESULTS

The levels of serum MDA and circulating CD31+/CD42- MPs were significantly reduced in the berberine group compared with the control group, which were associated with improvement of FMD. The EMPs in vitro facilitated ROS production and Nox4 protein expression and reduced NO synthesis in HUVECs. These alterations can be reversed by the presence of apocynin or berberine, respectively.

CONCLUSION

The present study demonstrated for the first time that EMP-induced upregulation of Nox4 expression may enhance ROS production in HUVECs. Berberine treatment contributes to the amelioration of endothelial function through a partially reducing oxidative stress of vascular endothelium induced by circulating CD31+/CD42- microparticles in humans.

Microparticles, Vascular Function, and Atherothrombosis

Membrane-shed submicron microparticles (MPs) are released after cell activation or apoptosis. High levels of MPs circulate in the blood of patients with atherothrombotic diseases, where they could serve as a useful biomarker of vascular injury and a potential predictor of cardiovascular mortality and major adverse cardiovascular events. Atherosclerotic lesions also accumulate large numbers of MPs of leukocyte, smooth muscle cell, endothelial, and erythrocyte origin. A large body of evidence supports the role of MPs at different steps of atherosclerosis development, progression, and complications. Circulating MPs impair the atheroprotective function of the vascular endothelium, at least partly, by decreased nitric oxide synthesis. Plaque MPs favor local inflammation by augmenting the expression of adhesion molecule, such as intercellular adhesion molecule -1 at the surface of endothelial cell, and monocyte recruitment within the lesion. In addition, plaque MPs stimulate angiogenesis, a key event in the transition from stable to unstable lesions. MPs also may promote local cell apoptosis, leading to the release and accumulation of new MPs, and thus creating a vicious circle. Furthermore, highly thrombogenic plaque MPs could increase thrombus formation at the time of rupture, together with circulating MPs released in this context by activated platelets and leukocytes. Finally, MPs also could participate in repairing the consequences of arterial occlusion and tissue ischemia by promoting postischemic neovascularization.

Increased platelet, leukocyte and endothelial microparticles predict enhanced coagulation and vascular inflammation in pulmonary hypertension

Pulmonary hypertension (PH) is associated with platelet activation, vascular inflammation and endothelial dysfunction leading to often life threatening thrombo-embolic complications. Microparticles (MPs) are cell vesicles with strong coagulatory and inflammatory effects being released during cell activation and apoptosis. As there are currently no established surrogate markers predicting platelet activation and pro-coagulation in PH patients, the aim of the study was to analyze different pro-coagulatory MP populations that might be related to thrombo-embolic complications in PH patients. Circulating MPs from platelet- (PMP, CD31(+)/61(+)), leukocyte- (LMP, CD11b(+)) and endothelial- (EMP, CD62E(+)) origin were measured by flow cytometry in 19 PH patients and were compared to 16 controls. PH patients had increased levels of PMP (PH vs. control 1,016 ± 201 vs. 527 ± 59 counts per min [cpm], P = 0.032), LMP (PH vs. control 31 ± 3 cpm vs. 18 ± 2 cpm, P = 0.001) and EMP (PH vs. control 99 ± 14 cpm vs. 46 ± 6 cpm, P = 0.001). Furthermore, PMP correlated to LMP (PMP vs. LMP: r = 0.75, P < 0.001) and LMP correlated to EMP levels (LMP vs. EMP, r = 0.74, P < 0.001) indicating a functional interaction between the different types of MP. In comparison to non-embolic PH patients, patients with a thrombo-embolic PH suffered from enhanced endothelial cell dysfunction as represented by significantly increased EMP levels (thrombo-embolic PH vs. non-embolic PH 137 ± 27 vs. 72 ± 10, P = 0.02). PH patients have increased levels of platelet-, leukocyte- and endothelial MP indicating an increased vascular pro-coagulation and inflammation which might be related to thrombo-embolic complications as well as PH progression.

Endothelium-derived microparticles inhibit angiogenesis in the heart and enhance the inhibitory effects of hypercholesterolemia on angiogenesis

Therapeutic angiogenesis remains unsuccessful in coronary artery disease. It is known that plasma endothelium-derived microparticles (EMPs) are increased in coronary artery disease and that hypercholesterolemia can inhibit angiogenesis. We evaluated the relationship between EMPs and hypercholesterolemia in the impairment of angiogenesis. EMPs isolated from human umbilical vein endothelial cells were injected into low-density lipoprotein receptor-null (LDLr(-/-)) mice fed a Western diet for 2 wk and C57BL6 mice for 6 h or were directly added to the tissue culture media. Hearts isolated from mice were sectioned and cultured, and endothelial tube formation was measured. The expression and phosphorylation of endothelial NO synthase (eNOS) and the generation of NO in the hearts were determined. Angiogenesis was inhibited by pathophysiological concentrations of EMPs but not physiological concentrations of EMPs in hearts from C57BL6 mice. However, angiogenesis was inhibited by EMPs at both physiological and pathophysiological concentrations of EMPs in hearts from hypercholesterolemic LDLr(-/-) mice. Pathophysiological concentrations of EMPs decreased eNOS phosphorylation at Ser(1177) and NO generation without altering eNOS expression in hearts from C57BL6 mice. Both physiological and pathophysiological concentrations of EMPs decreased not only eNOS phosphorylation at Ser(1177) and NO generation, but eNOS expression in hypercholesterolemic hearts from LDLr(-/-) mice. These data demonstrated that pathophysiological concentrations of EMPs could inhibit angiogenesis in hearts by decreasing eNOS activity. EMPs and hypercholesterolemia mutually enhanced their inhibitory effect of angiogenesis by inducing eNOS dysfunction. Our findings suggest a novel mechanism by which hypercholesterolemia impairs angiogenesis.

Endothelial microparticles induce inflammation in acute lung injury

BACKGROUND

Previously, we have shown that endothelial microparticles (EMPs) injected into mice induce acute lung injury (ALI) [1]. In this study, we hypothesize that EMPs induce ALI by initiating cytokine release in the lung, leading to recruitment and activation of neutrophils.

MATERIALS AND METHODS

C57BL/6J male mice (8-10 wk old) were intravenously injected with EMPs (200,000/mL), LPS (2 mg/kg), or both. Bronchoalveolar lavage (BAL) and serum levels of IL-1β and TNF-α were analyzed by enzyme-linked immunoassay (ELISA). Morphometric analysis was performed on H and E stained lung sections. Myeloperoxidase (MPO) levels were determined via an enzymatic assay and immunofluorescence of stained sections.

RESULTS

EMPs led to significantly increased pulmonary and systemic IL-1β and TNF-α levels, which correlated with increased neutrophil recruitment to the lung. MPO levels in the lungs were increased significantly following injection of EMPs or LPS, compared to PBS. In mice treated with EMPs and LPS either simultaneously or successively, the cytokine and MPO levels were significantly increased over that of either treatment alone.

CONCLUSION

EMPs contribute to lung injury through the initiation of a cytokine cascade that increases recruitment of neutrophils and subsequent release of MPO. Furthermore, treatment of mice with both EMPs and LPS induced greater lung injury than either treatment alone, suggesting that EMPs prime the lung for increased injury by other pathogens. Therapies aimed at reducing or blocking EMPs may be a useful strategy for attenuating lung injury.

Protein composition of plasminogen activator inhibitor type 1-derived endothelial microparticles

Endothelial microparticles (EMPs) are small vesicles released from the plasma membrane of endothelial cells in response to cell injury, apoptosis, or activation. Low levels of MPs are shed into the blood from the endothelium, but in some pathologic states, the number of EMPs is elevated. The mechanism of MP formation and the wide-ranging effects of elevated EMPs are poorly understood. Here, we report the protein composition of EMPs derived from human umbilical cord endothelial cells stimulated with plasminogen activator inhibitor type 1 (PAI-1). Two-dimensional gel electrophoresis followed by mass spectrometry identified 58 proteins, of which some were verified by Western blot analysis. Gene Ontology database searches revealed that proteins identified on PAI-1-derived EMPs are highly diverse. Endothelial microparticles are composed of proteins from different cellular components that exhibit multiple molecular functions and are involved in a variety of biological processes. Important insight is provided into the generation and protein composition of PAI-1-derived EMPs.

Comparative proteomic analysis of PAI-1 and TNF-alpha-derived endothelial microparticles

Endothelium-derived microparticles (EMPs) are small vesicles released from endothelial cells in response to cell injury, apoptosis, or activation. Elevated concentrations of EMPs have been associated with many inflammatory and vascular diseases. EMPs also mediate long range signaling and alter downstream cell function. Unfortunately, the molecular and cellular basis of microparticle production and downstream cell function is poorly understood. We hypothesize that EMPs generated by different agonists will produce distinct populations of EMPs with unique protein compositions. To test this hypothesis, different EMP populations were generated from human umbilical vein endothelial cells by stimulation with plasminogen activator inhibitor type 1 (PAI-1) or tumor necrosis factor-alpha (TNF-alpha) and subjected to proteomic analysis by LC/MS. We identified 432 common proteins in all EMP populations studied. Also identified were 231 proteins unique to control EMPs, 104 proteins unique to PAI-1 EMPs and 70 proteins unique to TNF-alpha EMPs. Interestingly, variations in protein abundance were found among many of the common EMP proteins, suggesting that differences exist between EMPs on a relative scale. Finally, gene ontology (GO) and KEGG pathway analysis revealed many functional similarities and few differences between the EMP populations studied. In summary, our results clearly indicate that EMPs generated by PAI-1 and TNF-alpha produce EMPs with overlapping but distinct protein compositions. These observations provide fundamental insight into the mechanisms regulating the production of these particles and their physiological role in numerous diseases.

Estradiol-treated mesenchymal stem cells improve myocardial recovery after ischemia

BACKGROUND

Stem cell therapy is a promising treatment modality for injured cardiac tissue. A novel mechanism for this cardioprotection may include paracrine actions. Our lab has recently shown that gender differences exist in mesenchymal stem cell (MSC) paracrine function. Estrogen is implicated in the cardioprotection found in females. It remains unknown whether 17beta-estradiol (E2) affects MSC paracrine function and whether E2-treated MSCs may better protect injured cardiac tissue. We hypothesize that E2-exposed MSCs infused into hearts prior to ischemia may demonstrate increased vascular endothelial growth factor (VEGF) production and greater protection of myocardial function compared to untreated MSCs.

MATERIALS AND METHODS

Untreated and E2-treated MSCs were isolated, cultured, and plated and supernatants were harvested for VEGF assay (enzyme-linked immunosorbent assay). Adult male Sprague-Dawley rat hearts (n = 13) were isolated and perfused via Langendorff model and subjected to 15 min equilibration, 25 min warm global ischemia, and 40 min reperfusion. Hearts were randomly assigned to perfusate vehicle, untreated male MSC, or E2-treated male MSC. Transcoronary delivery of 1 million MSCs was performed immediately prior to ischemia in experimental hearts.

RESULTS

E2-treated MSCs provoked significantly more VEGF production than untreated MSCs (933.2 +/- 64.9 versus 595.8 +/- 10.7 pg/mL). Postischemic recovery of left ventricular developed pressure was significantly greater in hearts infused with E2-treated MSCs (66.9 +/- 3.3%) than untreated MSCs (48.7 +/- 3.7%) and vehicle (28.9 +/- 4.6%) at end reperfusion. There was also greater recovery of the end diastolic pressure with E2-treated MSCs than untreated MSCs and vehicle.

CONCLUSIONS

Preischemic infusion of MSCs protects myocardial function and viability. E2-treated MSCs may enhance this paracrine protection, which suggests that ex vivo modification of MSCs may improve therapeutic outcome.

Lymphocytic microparticles inhibit angiogenesis by stimulating oxidative stress and negatively regulating VEGF-induced pathways

Recent studies have demonstrated that lymphocyte-derived microparticles (LMPs) impair endothelial cell function. However, no data currently exist regarding the contribution of LMPs in the regulation of angiogenesis. In the present study, we investigated the effects of LMPs on angiogenesis in vivo and in vitro and demonstrated that LMPs strongly suppressed aortic ring microvessel sprouting and in vivo corneal neovascularization. In vitro, LMPs considerably diminished human umbilical vein endothelial cell survival and proliferation in a concentration-dependent manner. Mechanistically, the antioxidants U-74389G and U-83836E were partially protective against the antiproliferative effects of LMPs, whereas the NADPH oxidase (NOX) inhibitors apocynin and diphenyleneiodonium significantly abrogated these effects. Moreover, LMPs increased not only the expression of the NOX subunits gp91(phox), p22(phox), and p47(phox), but also the production of ROS and NOX-derived superoxide (O(2)(-)). Importantly, LMPs caused a pronounced augmentation in the protein expression of the CD36 antiangiogenic receptor while significantly downregulating the protein levels of VEGF receptor type 2 and its downstream signaling mediator, phosphorylated ERK1/2. In summary, LMPs potently suppress neovascularization in vivo and in vitro by augmenting ROS generation via NOX and interfering with the VEGF signaling pathway.

STEM CELL MECHANISMS AND PARACRINE EFFECTS

Heart disease remains the leading cause of death in the industrialized world. Stem cell therapy is a promising treatment modality for injured cardiac tissue. A novel mechanism for this cardioprotection may include paracrine actions. Cardiac surgery represents the unique situation where preischemia and postischemia treatment modalities exist that may use stem cell paracrine protection. This review (1) recalls the history of stem cells in cardiac disease and the unraveling of its mechanistic basis for protection, (2) outlines the pathways for stem cell-mediated paracrine protection, (3) highlights the signaling factors expressed, (4) explores the potential of using stem cells clinically in cardiac surgery, and (5) summarizes all human stem cell studies in cardiac disease to date.

Endothelium-derived microparticles induce endothelial dysfunction and acute lung injury

Acute lung injury (ALI) carries a high mortality in critically ill patients. Recent reports correlate elevated concentrations of endothelium-derived microparticles (EMPs) with diseases of endothelial dysfunction. Many of these diseases have ALI sequelae. We hypothesize that EMPs contribute to endothelial cell (EC) dysfunction and development of ALI. To test this hypothesis, we treated isolated vessels with EMPs and examined changes in vasodilation. Endothelial cell cultures were incubated with EMPs and examined for changes in stimulated nitric oxide (*NO) production and nitric oxide synthase (eNOS) activation. Finally, EMPs were injected into rats and mice and lungs examined for ALI. In both mouse and human ex vivo vessel preparations, we found a marked attenuation of endothelium-mediated vasodilation after EMP treatment (4 x 10(6)/mL). This dysfunction was not corrected by pretreatment of EMPs with free radical scavengers. Coincubation of EMPs with EC cultures yielded a three-fold reduction in A23187-stimulated *NO release. Western analysis of these cells showed a corresponding decrease in eNOS phosphorylation at Ser1179 and a decrease in hsp90 association. Measurements of lung permeability, myeloperoxidase activity, and histology of EMPs-treated Brown Norway rats demonstrated pulmonary edema, neutrophil recruitment, and compromise of the endothelial-alveolar barrier as a second hit phenomenon. In C57BL/6 mice, exogenous EMPs caused a significant rise in pulmonary capillary permeability both as a primary and secondary injury. These findings demonstrate EMPs are capable of inducing significant lung injury at pathophysiologically relevant concentrations. Endothelium-derived microparticles inhibit endothelium-mediated vasodilation and *NO generation from eNOS. Once elucidated, EMP mechanisms of inducing ALI and endothelial dysfunction may present new therapeutic targets.