Monocyte-endothelial Interactions Research Articles

Alpha-1 antitrypsin inhibits fractalkine-mediated monocyte-lung endothelial cell interactions.

Chronic obstructive pulmonary disease (COPD) is characterized by nonresolving inflammation fueled by breach in the endothelial barrier and leukocyte recruitment into the airspaces. Among the ligand-receptor axes that control leukocyte recruitment, the full-length fractalkine ligand (CX3CL1)-receptor (CX3CR1) ensures homeostatic endothelial-leukocyte interactions. Cigarette smoke (CS) exposure and respiratory pathogens increase expression of endothelial sheddases, such as a-disintegrin-and-metalloproteinase-domain 17 (ADAM17, TACE), inhibited by the anti-protease α-1 antitrypsin (AAT). In the systemic endothelium, TACE cleaves CX3CL1 to release soluble CX3CL1 (sCX3CL1). During CS exposure, it is not known whether AAT inhibits sCX3CL1 shedding and CX3CR1+ leukocyte transendothelial migration across lung microvasculature. We investigated the mechanism of sCX3CL1 shedding, its role in endothelial-monocyte interactions, and AAT effect on these interactions during acute inflammation. We used two, CS and lipopolysaccharide (LPS) models of acute inflammation in transgenic Cx3cr1gfp/gfp mice and primary human endothelial cells and monocytes to study sCX3CL1-mediated CX3CR1+ monocyte adhesion and migration. We measured sCX3CL1 levels in plasma and bronchoalveolar lavage (BALF) of individuals with COPD. Both sCX3CL1 shedding and CX3CR1+ monocytes transendothelial migration were triggered by LPS and CS exposure in mice, and were significantly attenuated by AAT. The inhibition of monocyte-endothelial adhesion and migration by AAT was TACE-dependent. Compared with healthy controls, sCX3CL1 levels were increased in plasma and BALF of individuals with COPD, and were associated with clinical parameters of emphysema. Our results indicate that inhibition of sCX3CL1 as well as AAT augmentation may be effective approaches to decrease excessive monocyte lung recruitment during acute and chronic inflammatory states.NEW & NOTEWORTHY Our novel findings that AAT and other inhibitors of TACE, the sheddase that controls full-length fractalkine (CX3CL1) endothelial expression, may provide fine-tuning of the CX3CL1-CX3CR1 axis specifically involved in endothelial-monocyte cross talk and leukocyte recruitment to the alveolar space, suggests that AAT and inhibitors of sCX3CL1 signaling may be harnessed to reduce lung inflammation.

Immunological profiling in long COVID: overall low grade inflammation and T-lymphocyte senescence and increased monocyte activation correlating with increasing fatigue severity.

Many patients with SARS-CoV-2 infection develop long COVID with fatigue as one of the most disabling symptoms. We performed clinical and immune profiling of fatigued and non-fatigued long COVID patients and age- and sex-matched healthy controls (HCs). Long COVID symptoms were assessed using patient-reported outcome measures, including the fatigue assessment scale (FAS, scores ≥22 denote fatigue), and followed up to one year after hospital discharge. We assessed inflammation-related genes in circulating monocytes, serum levels of inflammation-regulating cytokines, and leukocyte and lymphocyte subsets, including major monocyte subsets and senescent T-lymphocytes, at 3-6 months post-discharge. We included 37 fatigued and 36 non-fatigued long COVID patients and 42 HCs. Fatigued long COVID patients represented a more severe clinical profile than non-fatigued patients, with many concurrent symptoms (median 9 [IQR 5.0-10.0] vs 3 [1.0-5.0] symptoms, p<0.001), and signs of cognitive failure (41%) and depression (>24%). Immune abnormalities that were found in the entire group of long COVID patients were low grade inflammation (increased inflammatory gene expression in monocytes, increased serum pro-inflammatory cytokines) and signs of T-lymphocyte senescence (increased exhausted CD8+ TEMRA-lymphocytes). Immune profiles did not significantly differ between fatigued and non-fatigued long COVID groups. However, the severity of fatigue (total FAS score) significantly correlated with increases of intermediate and non-classical monocytes, upregulated gene levels of CCL2, CCL7, and SERPINB2 in monocytes, increases in serum Galectin-9, and higher CD8+ T-lymphocyte counts. Long COVID with fatigue is associated with many concurrent and persistent symptoms lasting up to one year after hospitalization. Increased fatigue severity associated with stronger signs of monocyte activation in long COVID patients and potentially point in the direction of monocyte-endothelial interaction. These abnormalities were present against a background of immune abnormalities common to the entire group of long COVID patients.

Gynura procumbens (Lour.) Merr. extract attenuates monocyte adherence to endothelial cells through suppression of the NF-κB signaling pathway

Ethnopharmacological relevanceGynura procumbens (Lour.) Merr. (GP) is a herbaceous plant that grows in Malaysia and other parts of Southeast Asia. The herb is consumed as a remedy for various inflammatory-associated diseases, such as cancer, rheumatism, hypertension, diabetes mellitus and hyperlipidemia. Scientific studies demonstrate that GP extract possesses cardioprotective and anti-inflammatory effects. Cardiovascular disease is mainly caused by atherosclerosis, and inflammation plays a major role in all phases of atherosclerosis. The early inflammatory events in atherogenesis are the activation of endothelial cells and the recruitment of monocytes. Aim of the studyThis study aimed to evaluate the inhibitory effect of 80% ethanol extract of GP leaves (GPE) on the adherence of monocytes to the activated human endothelial cells and its underlying mechanism. Material and methodsQualitative and quantitative analyses of the extract were carried out by using a validated HPLC and UHPLC-MS/MS methods. The MTT test was used to select the range of concentration of extract for this study. The effect of GPE on TNF-α-induced monocyte-endothelial interaction was determined by the in vitro adhesion assay. Expression of cell surface proteins (ICAM-1, VCAM-1) and phosphorylation of nuclear factor kappa B (NF-κB) were determined by western blot, while expression of a chemokine (MCP-1) was identified by an enzyme-linked immunosorbent assay. ResultsHPLC and UHPLC-MS/MS analyses indicated that GPE contained chlorogenic acid, nicotiflorin and astragalin as the major compounds. GPE at 20, 40 and 60 μg/mL concentrations showed a significant reduction in monocyte adherence to endothelial cells and expression of ICAM-1 and MCP-1. However, only GPE at concentrations of 40 and 60 μg/mL was able to reduce VCAM-1 expression. Furthermore, GPE significantly inhibited IKKα/β, IκBα, NF-κB phosphorylation and NF-κB translocation. ConclusionIn conclusion, GPE may inhibit monocyte adherence to the activated endothelial cells and expression of ICAM-1, VCAM-1 and MCP-1, which are important proteins for monocyte-endothelial interaction, by suppressing the NF-κB signaling pathway. The results of this study support the traditional use of GPE to counteract inflammation-associated diseases and suggest that GP can be a potential source for bioactive compounds for the development of anti-inflammatory agents to prevent atherosclerosis.

Endothelial miR-199a-3p regulating cell adhesion molecules by targeting mTOR signaling during inflammation

BackgroundAdherence of monocytes to endothelial cells is the initial stage for development of coronary artery disease (CAD). MiRNAs have been reported to participate in this process by regulating the expression of cell adhesion molecules. This study aimed to explore the function of miR-199a-3p in endothelial inflammation and adhesion. MethodsWe assessed the expression of miR-199a-3p in CAD patients and ApoE-/- mice. The relationship between miR-199a-3p level and endothelial inflammation and adhesion was examined. ELISA was used to test the level of IL-6 and IL-8. Dual luciferase reporter assay was used to evaluate the binding between miR-199a-3p and mTOR. ResultsA decreased expression of miR-199a-3p was observed in the PBMCs and plasma of CAD patients, aorta of ApoE-/- mice and inflammatory HUVECs. MiR-199a-3p significantly suppressed the expression levels of pro-inflammatory cytokine (IL-6, IL-8), endothelial adhesion molecules (ICAM-1, VCAM-1) and monocyte-endothelial cells interaction. MiR-199a-3p directly targeted and repressed mTOR, and its suppression effect on ICAM-1 and VCAM-1 was abolished by mTOR inhibitor rapamycin, and rescued by mTOR activator MHY1485. Overexpression of miR-199a-3p promoted autophagy in HUVECs and inhibiting autophagy by chloroquine attenuated the effect of miR-199a-3p on ICAM-1 and VCAM-1 expression. Inhibition of autophagy promoted endothelial adhesion molecule expression and monocyte-EC interaction. ConclusionsOur results suggested that miR-199a-3p suppressed endothelial inflammation and adhesion by targeting mTOR signaling and increasing autophagy. Our findings point to an important role for miR-199a-3p in the early stage of cardiovascular disease.

Extracellular vesicle glucose transporter-1 and glycan features in monocyte-endothelial inflammatory interactions

Monocyte-induced endothelial cell inflammation is associated with multiple pathological conditions, and extracellular vesicles (EVs) are essential nanosized components of intercellular communication. EVs derived from endotoxin-stimulated monocytes were previously shown to carry pro-inflammatory proteins and RNAs. The role of glucose transporter-1 (GLUT-1) and glycan features in monocyte-derived EV-induced endothelial cell inflammation remains largely unexplored. This study demonstrates that EVs derived from endotoxin-stimulated monocytes activate inflammatory pathways in endothelial cells, which are partially attributed to GLUT-1. Alterations in glycan features and increased levels of GLUT-1 were observed in EVs derived from endotoxin-stimulated monocytes. Notably, inhibition of EV-associated GLUT-1, through the use of fasentin, suppressed EV-induced inflammatory cytokines in recipient endothelial cells.

Role and mechanism of action of butyrate in atherosclerotic diseases: a review.

Butyrate is a bioactive molecule produced by the intestinal flora and plays a major role in a variety of inflammatory diseases. Increasing evidence indicates that butyrate can regulate the occurrence and development of atherosclerosis (AS). Coincidentally, it reduces hyperlipidemia and hyperglycemia, which are major risk factors of AS. However, the mechanism by which butyrate regulates the development of AS remains unclear. In this article, we review the effect of butyrate treatment on AS with a focus on the mechanisms of butyrate-mediated modulation of several atherosclerotic processes. These include the improvement of monocyte-endothelial interactions, macrophage lipid accumulation, smooth muscle cell proliferation and migration, and lymphocyte differentiation and function. The existing research indicates that butyrate treatment may be a potentially effective strategy for the prevention of AS. Identity and underlying mechanisms of the molecular pathways of these interactions should be explored in the future to counter AS effectively.

Reactive oxygen species production by BP-1,6-quinone and its effects on the endothelial dysfunction: Involvement of the mitochondria

Strong epidemiological evidence supports the association between increased air pollution and the risk of developing atherosclerotic cardiovascular diseases (CVDs). However, the mechanism remains unclear. As an environmental air pollutant and benzo-a-pyrene (BP) metabolite, BP-1,6-quinone (BP-1,6-Q) is present in the particulate phase of air pollution. This study was undertaken to examine the redox activity of BP-1,6-Q and mechanisms associated with it using EA.hy926 endothelial cells. BP-1,6-Q at 0.01–1 μM significantly stimulated the production of reactive oxygen species (ROS)·in intact cells and isolated mitochondria. Furthermore, BP-1,6-Q-induced ROS was altered by mitochondrial electron transport chain (METC) inhibitors of complex I (rotenone) and complex III (antimycin A), denoting the involvement of mitochondrial electron transport chain (METC) in BP-1,6-Q mediated ROS production. In METC deficient cells, interestingly, BP-1,6-Q-mediated ROS production was enhanced, suggesting that overproduction of ROS by BP-1,6-Q is not only produced from mitochondria but can also be from the cell outside of mitochondria (extramitochondrial). BP-1,6-Q also triggered endothelial-monocyte interaction and stimulated expression of vascular adhesion molecule-1 (VCAM-1). In conclusion, these results demonstrate that BP-1,6-Q can generate ROS within both mitochondria and outside of mitochondria, resulting in stimulation of adhesion of monocytes to endothelial cells, a key event in the pathogenesis of atherosclerosis.

A novel 4-dimensional live-cell imaging system to study leukocyte-endothelial dynamics in ANCA-associated vasculitis

Neutrophils, monocytes and the endothelium are critical to ANCA-associated vasculitis (AAV) pathogenesis. This study aimed to develop a 4-dimensional (4D) live-cell imaging system that would enable investigation of spatial and temporal dynamics of these cells in health and disease. We further aimed to validate this system using autologous donor serum from AAV patients and polyclonal ANCA IgG, as well as exploring its potential in the pre-clinical testing of putative therapeutic compounds. Neutrophils and monocytes were isolated from peripheral venous blood of AAV patients or healthy controls and co-incubated on an endothelial monolayer in the presence of autologous serum. Alternatively, polyclonal ANCA IgG was used, following TNF-α priming, and imaged in 4-dimensions for 3 h using a spinning disc confocal microscope. Volocity 6.3® analysis software was used for quantification of leukocyte dynamics. The use of autologous serum resulted in increased neutrophil degranulation (p = .002), transmigration (p = .0096) and monocyte transcellular transmigration (p = .0013) in AAV patients. Polyclonal MPO-ANCA IgG induced neutrophil degranulation (p < .001) in this system. C5aR1 antagonism reduced neutrophil degranulation (p < .0002). We have developed a novel 4D in vitro system that allows accurate quantification of multiple neutrophil- and monocyte-endothelial interactions in AAV in a single assay. This system has the potential to highlight dynamics key to pathophysiology of disease, as well investigating the impact of potential therapeutics on these functions.

Exercise-associated prevention of adult cardiovascular disease in children and adolescents: monocytes, molecular mechanisms, and a call for discovery.

Atherosclerosis originates in childhood and adolescence. The goal of this review is to highlight how exercise and physical activity during childhood and adolescence, critical periods of growth and development, can prevent adult cardiovascular disease (CVD), particularly through molecular mechanisms of monocytes, a key cell of the innate immune system. Monocytes are heterogeneous and pluripotential cells that can, paradoxically, play a role in both the instigation and prevention of atherosclerosis. Recent discoveries in young adults reveal that brief exercise affects monocyte gene pathways promoting a cell phenotype that patrols the vascular system and repairs injuries. Concurrently, exercise inhibits pro-inflammatory monocytes, cells that contribute to vascular damage and plaque formation. Because CVD is typically asymptomatic in youth, minimally invasive techniques must be honed to study the subtle anatomic and physiologic evidence of vascular dysfunction. Exercise gas exchange and heart rate measures can be combined with ultrasound assessments of vascular anatomy and reactivity, and near-infrared spectroscopy to quantify impaired O2 transport that is often hidden at rest. Combined with functional, transcriptomic, and epigenetic monocyte expression and measures of monocyte-endothelium interaction, molecular mechanisms of early CVD can be formulated, and then translated into effective physical activity-based strategies in youth to prevent adult-onset CVD.

Hypoxia Enhances Endothelial Intercellular Adhesion Molecule 1 Protein Level Through Upregulation of Arginase Type II and Mitochondrial Oxidative Stress.

Hypoxia plays a crucial role in the pathogenesis of cardiovascular diseases. Mitochondrial enzyme arginase type II (Arg-II) is reported to lead to endothelial dysfunction and enhance the expression of endothelial inflammatory adhesion molecules such as intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1). In this study, we investigate the role of Arg-II in hypoxia-induced endothelial activation and the potential underlying mechanisms. Exposure of the human endothelial cells to hypoxia induced a time-dependent increase in Arg-II, HIF1α, HIF2α, and ICAM-1 protein level, whereas no change in the protein level of VCAM-1 and E-selectin was observed. Similar effects were obtained in cells treated with a hypoxia mimetic Dimethyloxaloylglycine (DMOG). Silencing HIF1α, but not HIF2α, reversed hypoxia-induced upregulation of Arg-II. Moreover, silencing Arg-II prevented the ICAM-1 upregulation induced by hypoxia or DMOG. Furthermore, the endothelial cells incubated under hypoxic condition or treated with DMOG or hypoxia enhanced monocyte adhesion, which was inhibited by silencing Arg-II. Lastly, silencing Arg-II prevented hypoxia-induced mitochondrial superoxide production in endothelial cells, and hypoxia-induced ICAM-1 upregulation was reversed by mitochondrial electron transport inhibitor rotenone. These data demonstrate that hypoxia enhances ICAM-1 protein level and monocyte-endothelial interaction through HIF1α-mediated increase in Arg-II protein level on leading to increased mitochondrial reactive oxygen species production. These effects of hypoxia on endothelial cells may play a key role in cardiovascular diseases. Our results suggest that Arg-II could be a promising therapeutic target to prevent hypoxia-induced vascular damage/dysfunction.

Anti-inflammatory Role of Carotenoids in Endothelial Cells Derived from Umbilical Cord of Women Affected by Gestational Diabetes Mellitus.

Diabetes is associated with vascular inflammation, endothelial dysfunction, and oxidative stress, promoting the development of cardiovascular diseases (CVD). Several studies showed that a carotenoid-rich diet is associated to a reduced cardiovascular risk in healthy and diabetic subjects, although the mechanisms of action are still unknown. Here, the potential role of β-carotene (BC) and lycopene (Lyc) in human endothelial cells isolated from human umbilical cord vein (HUVECs) of women with gestational diabetes (GD) and respective controls (C) has been investigated. Results showed that BC and Lyc reduced the tumor necrosis factor alpha- (TNF-α-) stimulated monocyte-endothelium interaction (adhesion assay), membrane exposure (flow cytometry), and total expression levels (Western blot) of VCAM-1 and ICAM-1 in both cell types. Moreover, the treatment with BC and Lyc reduced the TNF-α-induced nuclear translocation of NF-κB (image flow cytometry) by preserving bioavailability of nitric oxide (NO, flow cytometry, and cGMP EIA kit assay), a key vasoactive molecule. Notably, BC and Lyc pretreatment significantly reduced peroxynitrite levels (flow cytometry), contributing to the redox balance protection. These results suggest a new mechanism of action of carotenoids which exert vascular protective action in diabetic condition, thus reinforcing the importance of a carotenoid-rich diet in the prevention of diabetes cardiovascular complications.

Resolvin D1 blocks H2O2-mediated inhibitory crosstalk between SHP2 and PP2A and suppresses endothelial-monocyte interactions.

In recent years, various studies have demonstrated a role for endogenously derived specialized proresolving mediators such as resolvins in the resolution of inflammation. In exploring the signaling mechanisms, in the present study we show that Resolvin D1 (RvD1) reduces LPS-induced endothelial cell (EC)-monocyte interactions via blocking H2O2-mediated PP2A inactivation, NFκB activation and ICAM1 and VCAM1 expression. In addition, we found that H2O2-mediated SHP2 inhibition leads to tyrosine phosphorylation and inactivation of PP2A by LPS, which in turn, accounts for increased NFκB activation and ICAM1 and VCAM1 expression facilitating EC-monocyte interactions and all these LPS-mediated responses were reduced by RvD1. Furthermore, the suppression of NFκB activation, ICAM1 and VCAM1 expression and EC and monocyte interactions by RvD1 involved its receptors ALX/FPR2 and GPR32 as inhibition or neutralization of these receptors negated its effects. Besides, pertussis toxin completely prevented the effects of RvD1 on inhibition of LPS-induced H2O2 production, SHP2 and PP2A inactivation, NFκB activation, ICAM1 and VCAM1 expression and EC and monocyte interactions. Together, these observations suggest that RvD1 via activation of Gi-coupled ALX/FPR2 and GPR32 receptors blocks LPS-induced H2O2-mediated SHP2 and PP2A inactivation, NFκB activation, ICAM1 and VCAM1 expression and EC-monocyte interactions, which could be one of the several possible mechanisms underlying the anti-inflammatory actions of this specialized proresolving mediator.

Bone morphogenetic protein 9 (BMP9) and BMP10 enhance tumor necrosis factor-α-induced monocyte recruitment to the vascular endothelium mainly via activin receptor-like kinase 2

Bone morphogenetic proteins 9 and 10 (BMP9/BMP10) are circulating cytokines with important roles in endothelial homeostasis. The aim of this study was to investigate the roles of BMP9 and BMP10 in mediating monocyte–endothelial interactions using an in vitro flow adhesion assay. Herein, we report that whereas BMP9/BMP10 alone had no effect on monocyte recruitment, at higher concentrations both cytokines synergized with tumor necrosis factor-α (TNFα) to increase recruitment to the vascular endothelium. The BMP9/BMP10-mediated increase in monocyte recruitment in the presence of TNFα was associated with up-regulated expression levels of E-selectin, vascular cell adhesion molecule (VCAM-1), and intercellular adhesion molecule 1 (ICAM-1) on endothelial cells. Using siRNAs to type I and II BMP receptors and the signaling intermediaries (Smads), we demonstrated a key role for ALK2 in the BMP9/BMP10-induced surface expression of E-selectin, and both ALK1 and ALK2 in the up-regulation of VCAM-1 and ICAM-1. The type II receptors, BMPR-II and ACTR-IIA were both required for this response, as was Smad1/5. The up-regulation of cell surface adhesion molecules by BMP9/10 in the presence of TNFα was inhibited by LDN193189, which inhibits ALK2 but not ALK1. Furthermore, LDN193189 inhibited monocyte recruitment induced by TNFα and BMP9/10. BMP9/10 increased basal IκBα protein expression, but did not alter p65/RelA levels. Our findings suggest that higher concentrations of BMP9/BMP10 synergize with TNFα to induce the up-regulation of endothelial selectins and adhesion molecules, ultimately resulting in increased monocyte recruitment to the vascular endothelium. This process is mediated mainly via the ALK2 type I receptor, BMPR-II/ACTR-IIA type II receptors, and downstream Smad1/5 signaling.

In This Issue

HomeCirculation ResearchVol. 120, No. 11In This Issue Free AccessIn BriefPDF/EPUBAboutView PDFView EPUBSections ToolsAdd to favoritesDownload citationsTrack citationsPermissions ShareShare onFacebookTwitterLinked InMendeleyReddit Jump toFree AccessIn BriefPDF/EPUBIn This Issue Ruth Williams Ruth WilliamsRuth Williams Search for more papers by this author Originally published26 May 2017https://doi.org/10.1161/RES.0000000000000156Circulation Research. 2017;120:1687Therapeutic Potential of Synthetic Stem Cells (p 1768)Download figureDownload PowerPointLuo et al generate synthetic stem cells for cardiac therapies.Evidence indicates that the administration of stem cells, such as mesenchymal stem cells (MSCs), to patients with damaged hearts can improve myocardial function. It is currently believed that such reparative effects of MSCs are largely due to secreted factors. However, treating patients directly with such factors has been unsuccessful—possibly because the effects of the factors could not be sustained. Luo and colleagues reasoned that if such factors were enclosed in protective packaging, they might prove more effective. To find out, the team loaded MSC secretome proteins onto particles of poly(lactic-co-glycolic acid)—a biocompatible polymer that protects cytokines from degradation—and coated these particles with MSC membranes. Like regular MSCs, the repackaged synthetic MSCs (synMSCs), when cocultured with neonatal rat cardiac myocytes, synMSCs induced proliferation and contractility. And when given to mice with myocardial infarction, the reduced infarct size increased ventricle wall thickness and increased blood vessel density. Given these similar results, unpackaging and repackaging MSCs may seem unnecessary, but the defined composition of the synMSCs should provide a more uniform and predictable medication than cell-based approaches. Furthermore, the synMSCs exhibited superior stability to MSCs—suggesting synMSCs may be useful as an off-the-shelf treatment option.20-HETE–GPR75 Pairing and Hypertension (p 1776)Download figureDownload PowerPointGarcia et al identify a receptor for the potent inducer of hypertension 20-HETE.Hypertension is the leading cause of stroke and cardiovascular diseases, but because many different environmental and genetic factors contribute to the disorder, the underlying pathology is difficult to define. The complex etiology of hypertension could explain why, despite a range of treatment options, many patients have uncontrolled blood pressure (resistant hypertension). Among several hypertension-inducing factors is 20-hydroxyeicosatetraenoic acid (20-HETE)—a lipid produced by arachidonic acid hydrolysis. 20-HETE promotes vascular dysfunction—including inflammation and remodeling—and elevated blood levels of 20-HETE have been linked with hypertension, stroke, myocardial infarction, and vascular disease. To shed light on the mode of action of 20-HETE, Garcia and colleagues have now identified a 20-HETE receptor on endothelial and smooth muscle cells called G-protein receptor 75 (GPR75), which associates with G-protein–coupled receptor kinase interactor 1 (GIT1). The team showed that both GPR75 and GIT1 are required for 20-HETE-induced signaling activity. Moreover, genetic knockdown of GPR75 in mice prevented 20-HETE-dependent vascular dysfunction and hypertension. These findings open potential new avenues for developing treatments for resistant hypertension.Monocyte Patrolling in Arteries (p 1789)Download figureDownload PowerPointQuintar et al investigate monocyte patrolling behavior in arteries.Unlike classical inflammatory monocytes, nonclassical monocytes patrol blood vessel endothelium scavenging dead cells and debris. These patrolling cells were discovered in the microcirculation, and all subsequent studies have focused on these vessels. As a result, with the exception of monocyte recruitment to atherosclerotic plaques in arteries, little is known about monocyte-endothelial interactions in large vessels. Using a recently developed imaging technology, called intravital live cell triggered imaging system (ILTIS), Quintar and colleagues have now been able to monitor nonclassical monocytes in the arteries of healthy, hyperlipidemic, and atherosclerotic mice. They found that monocytes patrol healthy arteries—with each patrolling session lasting 5 to 10 minutes. In 2 different mouse models of hyperlipidemia, the patrolling behavior of these cells was increased by 8- to 9-fold. In atherogenic mice, patrolling increased by 22-fold, with each patrol lasting longer and proceeding more slowly. The number of patrolling cells directly correlated with the extent of endothelial damage, and mice with deficient patrolling monocytes exhibited greater atherosclerotic lesions. Together, the results suggest that the patrolling cells have a protective role in arteries and raise the possibility that therapeutically increasing monocyte patrolling behavior could help in reducing atherogenesis. Previous Back to top Next FiguresReferencesRelatedDetails May 26, 2017Vol 120, Issue 11 Advertisement Article InformationMetrics © 2017 American Heart Association, Inc.https://doi.org/10.1161/RES.0000000000000156 Originally publishedMay 26, 2017 PDF download Advertisement

Rutaecarpine Reverses the Altered Connexin Expression Pattern Induced by Oxidized Low-density Lipoprotein in Monocytes.

Adhesion of monocytes to the vascular endothelium is crucial in atherosclerosis development. Connexins (Cxs) which form hemichannels or gap junctions, modulate monocyte-endothelium interaction. We previously found that rutaecarpine, an active ingredient of the Chinese herbal medicine Evodia, reversed the altered Cx expression induced by oxidized low-density lipoprotein (ox-LDL) in human umbilical vein endothelial cells, and consequently decreases the adhesive properties of endothelial cells to monocytes. This study further investigated the effect of rutaecarpine on Cx expression in monocytes exposed to ox-LDL. In cultured human monocytic cell line THP-1, ox-LDL rapidly reduced the level of atheroprotective Cx37 but enhanced that of atherogenic Cx43, thereby inhibiting adenosine triphosphate release through hemichannels. Pretreatment with rutaecarpine recovered the expression of Cx37 but inhibited the upregulation of Cx43 induced by ox-LDL, thereby improving adenosine triphosphate-dependent hemichannel activity and preventing monocyte adhesion. These effects of rutaecarpine were attenuated by capsazepine, an antagonist of transient receptor potential vanilloid subtype 1. The antiadhesive effects of rutaecarpine were also attenuated by hemichannel blocker 18α-GA. This study provides additional evidence that rutaecarpine can modulate Cx expression through transient receptor potential vanilloid subtype 1 activation in monocytes, which contributes to the antiadhesive properties of rutaecarpine.

Selenium prevents microparticle-induced endothelial inflammation in patients after cardiopulmonary resuscitation.

IntroductionMicroparticles are elevated in patients after successful cardiopulmonary resuscitation (CPR) and may play a role in the development of endothelial dysfunction seen in post-cardiac arrest syndrome (PCAS), a life threatening disease with high mortality. To identify mechanisms of endothelial activation and to develop novel approaches in the therapy of PCAS, the impact of selenium, a trace element with antioxidative properties, was characterized in endothelial dysfunction induced by microparticles of resuscitated patients. Additionally, course of plasma selenium levels was characterized in the first 72 hours post-CPR.MethodsEndothelial cells were exposed to microparticles isolated of the peripheral blood of resuscitated patients, and leukocyte-endothelial interaction was measured by dynamic adhesion assay. Expression of adhesion molecules was assessed by immunoblotting and flow chamber. Blood samples were drawn 24, 48 and 72 hours after CPR for determination of plasma selenium levels in 77 resuscitated patients; these were compared to 50 healthy subjects and 50 patients with stable cardiac disease and correlated with severity of illness and outcome.ResultsMicroparticles of resuscitated patients enhance monocyte-endothelial interaction by up-regulation of ICAM-1 and VCAM-1. Selenium administration diminished ICAM-1 and VCAM-1-mediated monocyte adhesion induced by microparticles of resuscitated patients, suggesting that selenium has anti-inflammatory effects after CPR. Lowered selenium plasma levels were observed in resuscitated patients compared to controls and selenium levels immediately and 24 hours after CPR, inversely correlated with clinical course and outcome after resuscitation.ConclusionsEndothelial dysfunction is a pivotal feature of PCAS and is partly driven by microparticles of resuscitated patients. Administration of selenium exerted anti-inflammatory effects and prevented microparticle-mediated endothelial dysfunction. Decline of selenium was observed in plasma of patients after CPR and is a novel predictive marker of ICU mortality, suggesting selenium consumption promotes inflammation in PCAS.Electronic supplementary materialThe online version of this article (doi:10.1186/s13054-015-0774-3) contains supplementary material, which is available to authorized users.

Atraumatic Pulsatile Leukocyte Circulation for Long-Term In Vitro Dynamic Culture and Adhesion Assays.

Low flow rate pumping of cell suspensions finds current applications in bioreactors for short-term dynamic cell culture and adhesion assays. The aim of this study was to develop an atraumatic pump and hemodynamically adapted test circuit to allow operating periods of at least several hours. A computer-controlled mini-pump (MP) was constructed based on non-occlusive local compression of an elastic tube with commercial bi-leaflet valves directing the pulsatile flow into a compliant circuit. Cell damage and activation in the system were tested with whole blood in comparison with a set with a conventional peristaltic pump (PP). Activation of circulating THP-1 monocytes was tested by measuring the expression of CD54 (ICAM-1). Additionally, monocyte-endothelial interactions were monitored using a parallel-plate flow chamber with an artificial stenosis. The system required a priming volume of only 20 mL, delivering a peak pulsatile flow of up to 35 mL/min. After 8 h, blood hemolysis was significantly lower for MP with 11 ± 3 mg/dL compared with PP with 100 ± 16 mg/dL. CD142 (tissue factor) expression on blood monocytes was 50% lower for MP. With MP, THP-1 cells could be pumped for extended periods (17 h), with no enhanced expression of CD54 permitting the long-term co-culture of THP-1 with endothelial cells and the analysis of flow pattern effects on cell adhesion. A low-damage assay setup was developed, which allows the pulsatile flow of THP-1 cells and investigation of their interaction with other cells or surfaces for extended periods of time.

Role of Hic-5 in the formation of microvilli-like structures and the monocyte-endothelial interaction that accelerates atherosclerosis.

The adhesion of circulating monocytes to endothelial cells (ECs) is an early and critical event in the formation of atherosclerotic plaques. Hydrogen peroxide-inducible clone 5 (Hic-5) serves as an adaptor molecule in cell adhesion complexes. However, the role of endothelial Hic-5 in monocyte-EC interaction and atherogenesis remains unclear. We examined the roles of endothelial Hic-5 in monocyte-EC interaction and atherogenesis using mouse models of atherosclerosis and cultured human umbilical vein endothelial cells (HUVECs). Hic-5 was expressed in ECs, but not in monocytes/macrophages. An ex vivo monocyte adhesion assay revealed that adhesion of THP-1 monocytes to aortas isolated from Apoe(-/-) and LDLR(-/-) mice stimulated by TNF-α or oxidized LDL was suppressed by Hic-5 deficiency. Scanning electron microscopic observations of aortas harvested from Apoe(-/-) mice revealed that TNF-α- or oxidized LDL-induced microvilli-like structures were markedly suppressed by Hic-5 deficiency. Relative Hic-5 deficiency suppressed 60% of the atherosclerotic lesions in aortas from Apoe(-/-) and LDLR(-/-) mice. In contrast, overexpression of Hic-5 in HUVECs promoted induction of microvilli-like structures and adherence of THP-1 cells in an adhesion receptor such as intercellular adhesion molecule-1- and vascular cell adhesion molecule-1-dependent manner. Hic-5 in ECs plays an important role in the formation of microvilli-like structures and in the interaction between ECs and monocytes, leading to monocyte recruitment and subsequent development of atherosclerosis.

Milk-derived bioactive peptides inhibit human endothelial-monocyte interactions via PPAR-γ dependent regulation of NF-κB.

BackgroundMilk-derived bioactive peptides retain many biological properties and have therapeutic effects in cardiovascular disorders such as atherosclerosis. Under inflammatory conditions the expression of endothelial cells adhesion molecules is induced, increasing monocyte adhesion to human vessel wall, a critical step in the pathogenesis of atherosclerosis. In the present work we explored the effects of milk-derived bioactive peptides on the expression of the inflammatory phenotype of human endothelial cells and their effects on monocyte adherence to endothelial cells.ResultsTreatment of endothelial cells with milk-derived hydrolysate inhibited their production of inflammatory proteins MCP-1 and IL-8 and expression of VCAM-1, ICAM-1 and E-selectin. Milk derived hydrolysate also attenuated the adhesion of human monocytes to activated endothelial cells. The effect was similar to that obtained in endothelial cells treated with troglitazone, a ligand of peroxisome proliferators-activator receptor-gamma (PPAR-γ). PPAR-γ is a transcription factor which when activated antagonises the pro-inflammatory capability of nuclear factor κB (NF-κB). We further examined whether the effects of milk-derived hydrolysates on endothelial cells may be mediated through NF-κB activation via a PPAR-γ dependent mechanism. The specific PPAR-γ inhibitor, GW9662 blocked the effects of the hydrolysate on the NF-κB-mediated chemokines and adhesion molecules expression in endothelial cells.ConclusionsThese results suggest that milk-derived bioactive peptides work as anti-atherogenic agents through the inhibition of endothelial-dependent adhesive interactions with monocytes by inhibiting the NF-κB pathway through a PPAR-γ dependent mechanism.Electronic supplementary materialThe online version of this article (doi:10.1186/s12950-014-0044-1) contains supplementary material, which is available to authorized users.

Propofol protects human umbilical vein endothelial cells from cisplatin-induced injury

The anticancer drug cisplatin can up-regulate endothelial adhesion molecule expression, and trigger vascular endothelial injury. Propofol, an intravenous anesthetic, can inhibit endothelial adhesion molecule expression in some situations. Here, we explored whether and how propofol improved cisplatin-induced up-regulation of endothelial adhesion molecules in human umbilical vein endothelial cells. Compared with control group, cisplatin reduced endothelial nitric oxide synthase dimer/monomer ratio, activated protein kinase C and enhanced endothelial nitric oxide synthase-Thr495 phosphorylation, decreased nitric oxide production, augmented intercellular adhesion molecule 1 expression and monocyte-endothelial adhesion. These cisplatin-mediated effects were attenuated by propofol treatment. Nω-Nitro-L-arginine methyl ester hydrochloride, a nitric oxide synthase inhibitor, inhibited the effect of propofol on cisplatin-induced intercellular adhesion molecule 1 expression. Propofol improved cisplatin-mediated tetrahydrobiopterin reduction and nitrotyrosine overexpression. Compared with control group, cisplatin and PMA, a protein kinase C activator, both increased endothelial nitric oxide synthase-Thr495 phosphorylation, while propofol and GFX, a protein kinase C inhibitor, both decreased cisplatin-induced endothelial nitric oxide synthase-Thr495 phosphorylation. Our data indicated that propofol, via reducing cisplatin-induced endothelial nitric oxide synthase uncoupling and endothelial nitric oxide synthase-Thr495 phosphorylation, restored nitric oxide production, intercellular adhesion molecule 1 expression and monocyte-endothelial interaction.