Functional analysis of the human vascular cell adhesion molecule 1 promoter

(Homo-)harringtonine prevents endothelial inflammation through IRF-1 dependent downregulation of VCAM1 mRNA expression and inhibition of cell adhesion molecule protein biosynthesis

The plant alkaloid homoharringtonine (HHT) is a Food and Drug Administration (FDA)-approved drug for the treatment of hematologic malignancies. In addition to its well-established antitumor activity, accumulating evidence attributes anti-inflammatory effects to HHT, which have mainly been studied in leukocytes to date. However, a potential influence of HHT on inflammatory activation processes in endothelial cells, which are a key feature of inflammation and a prerequisite for the leukocyte-endothelial cell interaction and leukocyte extravasation, remains poorly understood. In this study, the anti-inflammatory potential of HHT and its derivative harringtonine (HT) on the TNF-induced leukocyte-endothelial cell interaction was assessed, and the underlying mechanistic basis of these effects was elucidated. HHT affected inflammation in vivo in a murine peritonitis model by reducing leukocyte infiltration and proinflammatory cytokine expression as well as ameliorating abdominal pain behavior. In vitro, HT and HHT impaired the leukocyte-endothelial cell interaction by decreasing the expression of the endothelial cell adhesion molecules intracellular adhesion molecule -1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1). This effect was mediated by a bipartite mechanism. While HHT did not affect the prominent TNF-induced pro-inflammatory NF-ĸB signaling cascade, the compound downregulated the VCAM1 mRNA expression in an IRF-1-dependent manner and diminished active ICAM1 mRNA translation as determined by polysome profiling. This study highlights HHT as an anti-inflammatory compound that efficiently hampers the leukocyte-endothelial cell interaction by targeting endothelial activation processes.

A20 regulates lymphocyte adhesion in murine neuroinflammation by restricting endothelial ICOSL expression in the CNS

A20 is a ubiquitin-modifying protein that negatively regulates NF-κB signaling. Mutations in A20/TNFAIP3 are associated with a variety of autoimmune diseases, including multiple sclerosis (MS). We found that deletion of A20 in central nervous system (CNS) endothelial cells (ECs) enhances experimental autoimmune encephalomyelitis (EAE), a mouse model of MS. A20ΔCNS-EC mice showed increased numbers of CNS-infiltrating immune cells during neuroinflammation and in the steady state. While the integrity of the blood-brain barrier (BBB) was not impaired, we observed a strong activation of CNS-ECs in these mice, with dramatically increased levels of the adhesion molecules ICAM-1 and VCAM-1. We discovered ICOSL to be expressed by A20-deficient CNS-ECs, which we found to function as adhesion molecules. Silencing of ICOSL in CNS microvascular ECs partly reversed the phenotype of A20ΔCNS-EC mice without reaching statistical significance and delayed the onset of EAE symptoms in WT mice. In addition, blocking of ICOSL on primary mouse brain microvascular ECs impaired the adhesion of T cells in vitro. Taken together, we propose that CNS EC-ICOSL contributes to the firm adhesion of T cells to the BBB, promoting their entry into the CNS and eventually driving neuroinflammation.

Nuciferine induces autophagy to relieve vascular cell adhesion molecule 1 activation via repressing the Akt/mTOR/AP1 signal pathway in the vascular endothelium

Pro-inflammatory factor-associated vascular cell adhesion molecule 1 (VCAM1) activation initiates cardiovascular events. This study aimed to explore the protective role of nuciferine on TNFα-induced VCAM1 activation. Nuciferine was administrated to both high-fat diet (HFD)-fed mice and the TNFα-exposed human vascular endothelial cell line. VCAM1 expression and further potential mechanism(s) were explored. Our data revealed that nuciferine intervention alleviated VCAM1 activation in response to both high-fat diet and TNFα exposure, and this protective effect was closely associated with autophagy activation since inhibiting autophagy by either genetic or pharmaceutical approaches blocked the beneficial role of nuciferine. Mechanistical studies revealed that Akt/mTOR inhibition, rather than AMPK, SIRT1, and p38 signal pathways, contributed to nuciferine-activated autophagy, which further ameliorated TNFα-induced VCAM1 via repressing AP1 activation, independent of transcriptional regulation by IRF1, p65, SP1, and GATA6. Collectively, our data uncovered a novel biological function for nuciferine in protecting VCAM1 activation, implying its potential application in improving cardiovascular events.

Phosphorylation of USP20 on Ser334 by IRAK1 promotes IL-1β-evoked signaling in vascular smooth muscle cells and vascular inflammation

Reversible lysine-63 (K63) polyubiquitination regulates proinflammatory signaling in vascular smooth muscle cells (SMCs) and plays an integral role in atherosclerosis. Ubiquitin-specific peptidase 20 (USP20) reduces NFκB activation triggered by proinflammatory stimuli, and USP20 activity attenuates atherosclerosis in mice. The association of USP20 with its substrates triggers deubiquitinase activity; this association is regulated by phosphorylation of USP20 on Ser334 (mouse) or Ser333 (human). USP20 Ser333 phosphorylation was greater in SMCs of atherosclerotic segments of human arteries as compared with nonatherosclerotic segments. To determine whether USP20 Ser334 phosphorylation regulates proinflammatory signaling, we created USP20-S334A mice using CRISPR/Cas9-mediated gene editing. USP20-S334A mice developed ∼50% less neointimal hyperplasia than congenic WT mice after carotid endothelial denudation. WT carotid SMCs showed substantial phosphorylation of USP20 Ser334, and WT carotids demonstrated greater NFκB activation, VCAM-1 expression, and SMC proliferation than USP20-S334A carotids. Concordantly, USP20-S334A primary SMCs in vitro proliferated and migrated less than WT SMCs in response to IL-1β. An active site ubiquitin probe bound to USP20-S334A and USP20-WT equivalently, but USP20-S334A associated more avidly with TRAF6 than USP20-WT. IL-1β induced less K63-linked polyubiquitination of TRAF6 and less downstream NFκB activity in USP20-S334A than in WT SMCs. Using in vitro phosphorylation with purified IRAK1 and siRNA-mediated gene silencing of IRAK1 in SMCs, we identified IRAK1 as a novel kinase for IL-1β-induced USP20 Ser334 phosphorylation. Our findings reveal novel mechanisms regulating IL-1β-induced proinflammatory signaling: by phosphorylating USP20 Ser334, IRAK1 diminishes the association of USP20 with TRAF6 and thus augments NFκB activation, SMC inflammation, and neointimal hyperplasia.

Homocysteine, Vitamins B6 and Folic Acid in Experimental Models of Myocardial Infarction and Heart Failure—How Strong Is That Link?

Cardiovascular diseases are the leading cause of death and the main cause of disability. In the last decade, homocysteine has been found to be a risk factor or a marker for cardiovascular diseases, including myocardial infarction (MI) and heart failure (HF). There are indications that vitamin B6 plays a significant role in the process of transsulfuration in homocysteine metabolism, specifically, in a part of the reaction in which homocysteine transfers a sulfhydryl group to serine to form α-ketobutyrate and cysteine. Therefore, an elevated homocysteine concentration (hyperhomocysteinemia) could be a consequence of vitamin B6 and/or folate deficiency. Hyperhomocysteinemia in turn could damage the endothelium and the blood vessel wall and induce worsening of atherosclerotic process, having a negative impact on the mechanisms underlying MI and HF, such as oxidative stress, inflammation, and altered function of gasotransmitters. Given the importance of the vitamin B6 in homocysteine metabolism, in this paper, we review its role in reducing oxidative stress and inflammation, influencing the functions of gasotransmitters, and improving vasodilatation and coronary flow in animal models of MI and HF.

VCAM1, HMOX1 and NOS3 differential endothelial expression may impact sickle cell anemia vasculopathy

Endothelial dysfunction plays a major role in sickle cell anemia (SCA) systemic vasculopathy, with upregulation of adhesion molecules (e.g., VCAM-1), decreased nitric oxide bioavailability, and oxidative stress. We aimed to assess the modulation role of pro-inflammatory and pro-oxidative stimuli on endothelial VCAM1, NOS3, and HMOX1 expression. We also evaluated the effect of the main SCA therapeutic agent, hydroxyurea, on that modulation. Our results showed that two VCAM1 promoter haplotypes, we previously associated with pediatric cerebral vasculopathy and severe hemolysis in SCA, increased promoter activity in TNF-α-stimulated transfected EA.hy926 and HBEC cell lines, consistent with a higher VCAM1 expression in macro and microvascular settings. In non-transfected cells, we also observed TNF-α-induced VCAM1 overexpression as well as heme-induced overexpression of HMOX1 in both cell models. Heme did not affect VCAM1 nor NOS3 expression and the latter was also not affected by TNF-α stimulus. Hydroxyurea treatment lowered TNF-induced VCAM1 and NOS3 expression but did not affect heme-induced HMOX1 expression. These data further indicate that VCAM1 haplotypes we studied lead to higher VCAM1 expression affecting not only cerebral but also systemic vasculopathy risk. The differential endothelial expression of VCAM1, NOS3, and HMOX1 also confirms their genetic modulation role in SCA systemic vasculopathy.

Mechanosensitive molecular interactions in atherogenic regions of the arteries: development of atherosclerosis

A terrible disease of the cardiovascular system, atherosclerosis, develops in the areas of bends and branches of arteries, where the direction and modulus of the blood flow velocity vector change, and consequently so does the mechanical effect on endothelial cells in contact with the blood flow. The review focuses on topical research studies on the development of atherosclerosis – mechanobiochemical events that transform the proatherogenic mechanical stimulus of blood flow – low and low/oscillatory arterial wall shear stress in the chains of biochemical reactions in endothelial cells, leading to the expression of specific proteins that cause the progression of the pathological process. The stages of atherogenesis, systemic risk factors for atherogenesis and its important hemodynamic factor, low and low/oscillatory wall shear stress exerted by blood flow on the endothelial cells lining the arterial walls, have been described. The interactions of cell adhesion molecules responsible for the development of atherosclerosis under low and low/oscillating shear stress conditions have been demonstrated. The activation of the regulator of the expression of cell adhesion molecules, the transcription factor NF-κB, and the factors regulating its activation under these conditions have been described. Mechanosensitive signaling pathways leading to the expression of NF-κB in endothelial cells have been described. Studies of the mechanobiochemical signaling pathways and interactions involved in the progression of atherosclerosis provide valuable information for the development of approaches that delay or block the development of this disease. Key words: atherogenesis; shear stress; transcription factor NF-κB; RelA expression; mechanosensitive receptors; cell adhesion molecules; signaling pathways; mechanotransduction.

Bortezomib enhances G-CSF-induced hematopoietic stem cell mobilization by decreasing CXCL12 levels and increasing vascular permeability

Bortezomib (BTZ) is known to enhance the mobilization of hematopoietic stem and progenitor cells (HSPCs) induced by granulocyte colony-stimulating factor (G-CSF). However, the most effective time at which to administer BTZ to produce this enhancing effect remains debatable, and the precise mechanism underlying the effect of BTZ is poorly understood. We addressed these questions in this article by performing animal experiments. First, in agreement with previous studies, BTZ administration 12 hours before blood collection was most effective for HSPC mobilization; in contrast, BTZ administration 3 days before blood collection negatively affected HSPC harvesting. Next, in terms of the mechanism of action, G-CSF, but not BTZ, downregulated the expression of very late antigen-4 on HSPCs and vascular cell adhesion molecule-1 on bone marrow (BM) stromal cells; however, intriguingly, both G-CSF and BTZ downregulated CXCL12 chemokine expression in BM. Notably, BTZ treatment also increased BM vascular permeability. These results suggest that the pro-mobilization effect of BTZ could involve the dissociation of HSPCs from BM stromal cells triggered by G-CSF, vascular hyperpermeability elicited by BTZ, and downregulation of CXCL12 concomitantly induced by G-CSF and BTZ.

Drebrin attenuates atherosclerosis by limiting smooth muscle cell transdifferentiation

AIMS

The F-actin-binding protein Drebrin inhibits smooth muscle cell (SMC) migration, proliferation and pro-inflammatory signaling. Therefore, we tested the hypothesis that Drebrin constrains atherosclerosis.

METHODS AND RESULTS

SM22-Cre+/Dbnflox/flox/Ldlr-/- (SMC-Dbn-/-/Ldlr-/-) and control mice (SM22-Cre+/Ldlr-/-, Dbnflox/flox/Ldlr-/-, and Ldlr-/-) were fed a Western diet for 14-20 weeks. Brachiocephalic arteries of SMC-Dbn-/-/Ldlr-/- mice exhibited 1.5- or 1.8-fold greater cross-sectional lesion area than control mice at 14 or 20 wk, respectively. Aortic atherosclerotic lesion surface area was 1.2-fold greater in SMC-Dbn-/-/Ldlr-/- mice. SMC-Dbn-/-/Ldlr-/- lesions comprised necrotic cores that were two-fold greater in size than those of control mice. Consistent with their bigger necrotic core size, lesions in SMC-Dbn-/- arteries also showed more transdifferentiation of SMCs to macrophage-like cells: 1.5- to 2.5-fold greater, assessed with BODIPY or with CD68, respectively. In vitro data were concordant: Dbn-/- SMCs had 1.7-fold higher levels of KLF4 and transdifferentiated to macrophage-like cells more readily than Dbnflox/flox SMCs upon cholesterol loading, as evidenced by greater up-regulation of CD68 and galectin-3. Adenovirally mediated Drebrin rescue produced equivalent levels of macrophage-like transdifferentiation in Dbn-/- and Dbnflox/flox SMCs. During early atherogenesis, SMC-Dbn-/-/Ldlr-/- aortas demonstrated 1.6-fold higher levels of reactive oxygen species than control mouse aortas. The 1.8-fold higher levels of Nox1 in Dbn-/- SMCs was reduced to WT levels with KLF4 silencing. Inhibition of Nox1 chemically or with siRNA produced equivalent levels of macrophage-like transdifferentiation in Dbn-/- and Dbnflox/flox SMCs.

CONCLUSIONS

We conclude that SMC Drebrin limits atherosclerosis by constraining SMC Nox1 activity and SMC transdifferentiation to macrophage-like cells.

TRANSLATIONAL PERSPECTIVE

Drebrin is abundantly expressed in vascular smooth muscle cells (SMCs) and is up-regulated in human atherosclerosis. A hallmark of atherosclerosis is the accumulation of foam cells that secrete pro-inflammatory cytokines and contribute to plaque instability. A large proportion of these foam cells in humans derive from SMCs. We found that SMC Drebrin limits atherosclerosis by reducing SMC transdifferentiation to macrophage-like foam cells in a manner dependent on Nox1 and KLF4. For this reason, strategies aimed at augmenting SMC Drebrin expression in atherosclerotic plaques may limit atherosclerosis progression and enhance plaque stability by bridling SMC-to-foam-cell transdifferentiation.

VCAM1 Labels a Subpopulation of Neural Stem Cells in the Adult Hippocampus and Contributes to Spatial Memory

Active neural stem cells (aNSCs) and quiescent neural stem cells (qNSCs) are two distinct subpopulations found in the adult hippocampal dentate gyrus (DG). However, to date, no cell surface marker has been established to identify and profile qNSCs in the adult hippocampus. Here, we identified expression of vascular cell adhesion molecule 1 (VCAM1) on the cell surface of NSCs, through which we identified a previously unrecognized subpopulation of NSCs in the adult mouse DG. Interestingly, most VCAM1-expressing NSCs were largely quiescent. By injecting virus into Ai14 reporter mice to conduct lineage tracing in the adult DG, we confirmed that VCAM1-expressing cells were multipotent and capable of generating neurons and astrocytes. Furthermore, depletion of Vcam1 during the embryonic or adult stage impaired spatial learning and memory in mice, accompanied by a reduced number of radial glial-like cells and proliferating NSCs in the subgranular zone of Vcam1 knockout mice.

Heat therapy: mechanistic underpinnings and applications to cardiovascular health

Cardiovascular diseases (CVD) are the leading cause of death worldwide, and novel therapies are drastically needed to prevent or delay the onset of CVD to reduce the societal and healthcare burdens associated with these chronic diseases. One such therapy is "heat therapy," or chronic, repeated use of hot baths or saunas. Although using heat exposure to improve health is not a new concept, it has received renewed attention in recent years as a growing number of studies have demonstrated robust and widespread beneficial effects of heat therapy on cardiovascular health. Here, we review the existing literature, with particular focus on the molecular mechanisms that underscore the cardiovascular benefits of this practice.

TRIM65 E3 ligase targets VCAM-1 degradation to limit LPS-induced lung inflammation

Although the adhesion molecules-mediated leukocyte adherence and infiltration into tissues is an important step of inflammation, the post-translational regulation of these proteins on the endothelial cells is poorly understood. Here, we report that TRIM65, an ubiquitin E3 ligase of tripartite protein family, selectively targets vascular cell adhesion molecule 1 (VCAM-1) and promotes its ubiquitination and degradation, by which it critically controls the duration and magnitude of sepsis-induced pulmonary inflammation. TRIM65 is constitutively expressed in human vascular endothelial cells. During TNFα-induced endothelial activation, the protein levels of TRIM65 and VCAM-1 are inversely correlated. Expression of wild-type TRIM65, but not expression of a TRIM65 mutant that lacks E3 ubiquitin ligase function in endothelial cells, promotes VCAM-1 ubiquitination and degradation, whereas small interference RNA-mediated knockdown of TRIM65 attenuates VCAM-1 protein degradation. Further experiments show that TRIM65 directly interacts with VCAM-1 protein and directs its polyubiquitination, by which TRIM65 controls monocyte adherence and infiltration into tissues during inflammation. Importantly, TRIM65-deficient mice are more sensitive to lipopolysaccharide-induced death, due to sustained and severe pulmonary inflammation. Taken together, our studies suggest that TRIM65-mediated degradation of VCAM-1 represents a potential mechanism that controls the duration and magnitude of inflammation.

Glycocalyx sialic acids regulate Nrf2-mediated signaling by fluid shear stress in human endothelial cells

Activation of the nuclear factor erythroid 2-related factor 2 (Nrf2) pathway is critical for vascular endothelial redox homeostasis in regions of high, unidirectional shear stress (USS), however the underlying mechanosensitive mediators are not fully understood. The endothelial glycocalyx is disrupted in arterial areas exposed to disturbed blood flow that also exhibit enhanced oxidative stress leading to atherogenesis. We investigated the contribution of glycocalyx sialic acids (SIA) to Nrf2 signaling in human endothelial cells (EC) exposed to atheroprotective USS or atherogenic low oscillatory shear stress (OSS). Cells exposed to USS exhibited a thicker glycocalyx and enhanced turnover of SIA which was reduced in cells cultured under OSS. Physiological USS, but not disturbed OSS, enhanced Nrf2-mediated expression of antioxidant enzymes, which was attenuated following SIA cleavage with exogenous neuraminidase. SIA removal disrupted kinase signaling involved in the nuclear accumulation of Nrf2 elicited by USS and promoted mitochondrial reactive oxygen species accumulation. Notably, knockdown of the endogenous sialidase NEU1 potentiated Nrf2 target gene expression, directly implicating SIA in regulation of Nrf2 signaling by USS. In the absence of SIA, deficits in Nrf2 responses to physiological flow were also associated with a pro-inflammatory EC phenotype. This study demonstrates that the glycocalyx modulates endothelial redox state in response to shear stress and provides the first evidence of an atheroprotective synergism between SIA and Nrf2 antioxidant signaling. The endothelial glycocalyx therefore represents a potential therapeutic target against EC dysfunction in cardiovascular disease and redox dyshomeostasis in ageing.

A Novel STAT3-Mediated GATA6 Pathway Contributes to tert-Butylhydroquinone- (tBHQ-) Protected TNFα-Activated Vascular Cell Adhesion Molecule 1 (VCAM-1) in Vascular Endothelium

The activation of vascular cell adhesion molecule 1 (VCAM-1) in vascular endothelial cells has been well considered implicating in the initiation and processing of atherosclerosis. Oxidative stress is mechanistically involved in proatherosclerotic cytokine-induced VCAM-1 activation. tert-Butylhydroquinone (tBHQ), a synthetic phenolic antioxidant used for preventing lipid peroxidation of food, possesses strongly antioxidant capacity against oxidative stress-induced dysfunction in various pathological process. Here, we investigated the protective role of tBHQ on tumor necrosis factor alpha- (TNFα-) induced VCAM-1 activation in both aortic endothelium of mice and cultured human vascular endothelial cells and uncovered its potential mechanisms. Our data showed that tBHQ treatment significantly reversed TNFα-induced activation of VCAM-1 at both transcriptional and protein levels. The mechanistic study revealed that inhibiting neither nuclear factor (erythroid-derived 2)-like 2 (Nrf2) nor autophagy blocked the beneficial role of tBHQ. Alternatively, tBHQ intervention markedly alleviated TNFα-increased GATA-binding protein 6 (GATA6) mRNA and protein expressions and its translocation into nucleus. Further investigation indicated that tBHQ-inhibited signal transducer and activator of transcription 3 (STAT3) but not mitogen-activated protein kinase (MAPK) pathway contributed to its protective role against VCAM-1 activation via regulating GATA6. Collectively, our data demonstrated that tBHQ prevented TNFα-activated VCAM-1 via a novel STAT3/GATA6-involved pathway. tBHQ could be a potential candidate for the prevention of proatherosclerotic cytokine-caused inflammatory response and further dysfunctions in vascular endothelium.

Zinc Oxide Exerts Anti-Inflammatory Properties on Human Placental Cells

Background: An aberrant and persistent inflammatory state at the fetal-maternal interface is considered as a key contributor in compromised pregnancies. Decidual endothelial cells (DECs) play a pivotal role in the control of the local decidual inflammation. The aim of the current study was to determine whether dietary supplement with zinc oxide (ZnO), due to its very low adverse effects, may be useful for modulating the inflammatory response in the first trimester of pregnancy. Methods: The anti-inflammatory properties of ZnO in pregnancy were evaluated by in vitro tests on endothelial cells isolated from normal deciduas and on a trophoblast cell line (HTR8/Svneo). The effects of this treatment were analyzed in terms of adhesion molecule expression and inflammatory cytokine secretion, by real time-quantitative PCR (RT-qPCR) and enzyme-linked immunosorbent assay (ELISA). Results: Our data showed that ZnO was able to reduce the inflammatory response of DECs, in terms of vascular cell adhesion molecule-1 (VCAM-1), interleukin (IL)-8, IL-6, tumor necrosis factor-α (TNF-α) and monocyte chemoattractant protein-1 (MCP-1) expression induced by TNF-α stimulation. This compound exerted no effect on intracellular adhesion molecule-1 (ICAM-1) exocytosis induced by TNF-α on stimulated trophoblast cells, but significantly reduced their IL-6 expression. Conclusion: According to these results, it can be suggested that the ZnO supplement, through its modulation of the pro-inflammatory response of DECs, can be used in pregnancy for the prevention of local decidual inflammation.

Drebrin regulates angiotensin II-induced aortic remodelling

Aims

The actin-binding protein Drebrin is up-regulated in response to arterial injury and reduces smooth muscle cell (SMC) migration and proliferation through its interaction with the actin cytoskeleton. We, therefore, tested the hypothesis that SMC Drebrin inhibits angiotensin II-induced remodelling of the proximal aorta.

Methods and results

Angiotensin II was administered via osmotic minipumps at 1000 ng/kg/min continuously for 28 days in SM22-Cre+/Dbnflox/flox (SMC-Dbn-/-) and control mice. Blood pressure responses to angiotensin II were assessed by telemetry. After angiotensin II infusion, we assessed remodelling in the proximal ascending aorta by echocardiography and planimetry of histological cross sections. Although the degree of hypertension was equivalent in SMC-Dbn-/- and control mice, SMC-Dbn-/- mice nonetheless exhibited 60% more proximal aortic medial thickening and two-fold more outward aortic remodelling than control mice in response to angiotensin II. Proximal aortas demonstrated greater cellular proliferation and matrix deposition in SMC-Dbn-/- mice than in control mice, as evidenced by a higher prevalence of proliferating cell nuclear antigen-positive nuclei and higher levels of collagen I. Compared with control mouse aortas, SMC-Dbn-/- aortas demonstrated greater angiotensin II-induced NADPH oxidase activation and inflammation, evidenced by higher levels of Ser-536-phosphorylated NFκB p65 subunits and higher levels of vascular cell adhesion molecule-1, matrix metalloproteinase-9, and adventitial macrophages.

Conclusions

We conclude that SMC Drebrin deficiency augments angiotensin II-induced inflammation and adverse aortic remodelling.

Passing the Vascular Barrier: Endothelial Signaling Processes Controlling Extravasation

A central function of the vascular endothelium is to serve as a barrier between the blood and the surrounding tissue of the body. At the same time, solutes and cells have to pass the endothelium to leave or to enter the bloodstream to maintain homeostasis. Under pathological conditions, for example, inflammation, permeability for fluid and cells is largely increased in the affected area, thereby facilitating host defense. To appropriately function as a regulated permeability filter, the endothelium uses various mechanisms to allow solutes and cells to pass the endothelial layer. These include transcellular and paracellular pathways of which the latter requires remodeling of intercellular junctions for its regulation. This review provides an overview on endothelial barrier regulation and focuses on the endothelial signaling mechanisms controlling the opening and closing of paracellular pathways for solutes and cells such as leukocytes and metastasizing tumor cells.

Aronia berry extract inhibits TNF-α-induced vascular endothelial inflammation through the regulation of STAT3

Background

Inflammation in endothelial cells induces production of inflammatory cytokines and monocytes adhesion, which are crucial events in the initiation of atherosclerosis. Aronia berry (Aronia meranocalpa), also called black chokeberry, contains abundant anthocyanins that have received considerable interest for their possible relations to vascular health.

Objective

The aim of this study was to investigate whether an anthocyanin-rich extract obtained from aronia berry can attenuate inflammatory responses in vascular endothelial cells.

Methods

As a model of vascular endothelial inflammation, human umbilical vein endothelial cells (HUVECs) pretreated with aronia berry extract were stimulated with tumor necrosis factor-alpha (TNF-α). The expression levels of cytokines and adhesion molecules were analyzed. To investigate the effects of aronia berry extract on the adhesion of THP-1 monocytic cell, the static adhesion assay was carried out. The possible molecular mechanisms by which aronia berry extract regulated vascular inflammatory responses were explored.

Results

The mRNA expressions of interleukins (IL-1β, IL-6, and IL-8) and monocyte chemoattractant protein-1 (MCP-1) upregulated by TNF-α were significantly suppressed by pretreatment with aronia berry extract. Aronia berry extract decreased TNF-α-induced monocyte/endothelial adhesion and suppressed vascular cell adhesion molecule-1 (VCAM-1) expression, but did not affect intercellular adhesion molecule-1 (ICAM-1) expression. Moreover, aronia berry extract decreased the phosphorylation of signal transducer and activator of transcription 3 (STAT3) and the nuclear levels of STAT3 and interferon regulatory transcription factor-1 (IRF1). The nuclear translocation of nuclear factor-kappa B (NF-κB) was not inhibited by aronia berry extract.

Conclusion

Aronia berry extract could exert anti-atherosclerotic effects on TNF-α-induced inflammation through inhibition of STAT3/IRF1 pathway in vascular endothelial cells.

Galangin Prevents Increased Susceptibility to Pentylenetetrazol-Stimulated Seizures by Prostaglandin E2

Epilepsy is one of the most common chronic neurological diseases. It is characterized by recurrent epileptic seizures, where one-third of patients are refractory to existing treatments. Evidence revealed the association between neuroinflammation and increased susceptibility to seizures since there is a pronounced increase in the expression of key inflammatory mediators, such as prostaglandin E₂ (PGE₂), during seizures. The purpose of this study was to investigate whether PGE₂ increases susceptibility to pentylenetetrazol-induced (PTZ) seizures. Subsequently, we evaluated if the flavonoid isolated from the plant Piper aleyreanum (galangin) presented any anticonvulsive effects. Our results demonstrated that the group treated with PGE₂ increased susceptibility to PTZ and caused myoclonic and generalized seizures, which increased seizure duration and electroencephalographic wave amplitudes. Furthermore, treatment with PGE₂ and PTZ increased IBA-1 (microglial marker), GFAP (astrocytic marker), 4-HNE (lipid peroxidation marker), VCAM-1 (vascular cell adhesion molecule 1), and p-PKAIIα (phosphorylated cAMP-dependent protein kinase) immunocontent. Indeed, galangin prevented behavioral and electroencephalographic seizures, reactive species production, decreased microglial and astrocytic immunocontent, as well as decreased VCAM-1 immunocontent and p-PKA/PKA ratio induced by PGE₂/PTZ. Therefore, this study suggests galangin may have an antagonizing role on PGE₂-induced effects, reducing cerebral inflammation and protecting from excitatory effects evidenced by administrating PGE₂ and PTZ. However, further studies are needed to investigate the clinical implications of the findings and their underlying mechanisms.

Curcumin-galactomannoside complex inhibits pathogenesis in Ox-LDL-challenged human peripheral blood mononuclear cells

Oxidised low-density lipoprotein (ox-LDL) is a pro-atherogenic molecule, which induces inflammatory response and contributes to the pathogenesis of vascular dysfunction to atherosclerosis. The aim of the present study was to explore the anti-inflammatory effect of a novel bioavailable formulation of curcumin as 'curcumagalactomannosides' (CGM) against ox-LDL-induced inflammatory responses in human peripheral blood mononuclear cells (hPBMCs). Curcumagalactomannosides was made from natural curcumin using the soluble dietary fibre (galactomannans) derived from fenugreek seeds (Trigonella foenumgracum) and the hPBMCs were isolated from healthy human volunteers. The cells were cultured in collagen-coated plates at 37 °C and grouped as Group I (Control), Group II (ox-LDL treated) and Group III (ox-LDL + CGM treated). Further analysis of inflammatory markers, reactive oxygen species and mRNA expression levels indicated significantly increased expressions of iNOS, TNF-α, IL-6 and VCAM-1 in ox-LDL-treated group along with the nuclear translocation of NF-κB. Other inflammatory markers such as LOX, PGE2, total COX and lipid peroxidation level were also found to be significantly (p < 0.05) increased upon ox-LDL treatment. The treatment with CGM on the other hand was found to down-regulate and reverse the ox-LDL-induced alterations indicating its potential anti-inflammatory effect on hPBMCs via. NF-κB signalling pathway.

Selective inhibition of endothelial NF-κB signaling attenuates chronic intermittent hypoxia-induced atherosclerosis in mice

BACKGROUND AND AIMS

Chronic intermittent hypoxia (CIH) exposure causes atherosclerosis, although the underlying mechanisms are poorly understood. This study defines the role of endothelial intrinsic NF-κB signaling in the atherogenic response to CIH.

METHODS

We created ApoE-EC^I-κBmt mice that are deficient in the apolipoprotein E gene (ApoE^-/-) and overexpress an I-κBα mutant (I-κBmt) selectively in endothelial cells. ApoE^-/- and ApoE-EC^I-κBmt mice were fed a normal chow diet (NCD) or high cholesterol diet (HCD) and exposed to sham or CIH, and atherosclerotic lesions were quantified.

RESULTS

CIH exposure activated NF-κB in aortas, and induced the expression of endothelial-specific and NF-κB-dependent genes, E-selectin and vascular cell adhesion molecule (VCAM)-1, in the aortas and hearts. Endothelial I-κBmt overexpression in ApoE-EC^I-κBmt mice significantly inhibited CIH-induced NF-κB activity, and suppressed E-selectin and VCAM-1 expressions, confirming endothelial NF-κB inhibition in ApoE-EC^I-κBmt mice. ApoE^-/- mice, on NCD, developed mild atherosclerotic lesions spontaneously, and developed advanced and larger areas of atherosclerotic plaques when exposed to CIH. ApoE^-/- mice also developed advanced atherosclerotic lesions when fed an HCD alone. The HCD-induced atherosclerotic plaques became more advanced, and plaque area was doubled in mice exposed to HCD + CIH. Endothelial I-κBmt overexpression in ApoE-EC^I-κBmt mice attenuated spontaneously developed atherosclerotic lesions, abrogated CIH-induced atherosclerosis and mitigated CIH-mediated facilitation of HCD-induced atherosclerosis.

CONCLUSIONS

These results suggest that endothelial intrinsic NF-kB signaling may play a pivotal role in CIH-induced atherosclerosis.

Molecular Regulation of Sprouting Angiogenesis

The term angiogenesis arose in the 18th century. Several studies over the next 100 years laid the groundwork for initial studies performed by the Folkman laboratory, which were at first met with some opposition. Once overcome, the angiogenesis field has flourished due to studies on tumor angiogenesis and various developmental models that can be genetically manipulated, including mice and zebrafish. In addition, new discoveries have been aided by the ability to isolate primary endothelial cells, which has allowed dissection of various steps within angiogenesis. This review will summarize the molecular events that control angiogenesis downstream of biochemical factors such as growth factors, cytokines, chemokines, hypoxia-inducible factors (HIFs), and lipids. These and other stimuli have been linked to regulation of junctional molecules and cell surface receptors. In addition, the contribution of cytoskeletal elements and regulatory proteins has revealed an intricate role for mobilization of actin, microtubules, and intermediate filaments in response to cues that activate the endothelium. Activating stimuli also affect various focal adhesion proteins, scaffold proteins, intracellular kinases, and second messengers. Finally, metalloproteinases, which facilitate matrix degradation and the formation of new blood vessels, are discussed, along with our knowledge of crosstalk between the various subclasses of these molecules throughout the text. Compr Physiol 8:153-235, 2018.

A function-blocking CD47 antibody modulates extracellular vesicle-mediated intercellular signaling between breast carcinoma cells and endothelial cells

Tumor cells release extracellular vesicles (EVs) into the tumor microenvironment that may facilitate malignant progression and metastasis. Breast carcinoma EVs express high levels of the thrombospondin-1 and signal regulatory protein-α receptor CD47, which is the target of several experimental therapeutics currently in clinical trials. We analyzed changes in gene expression and function in human umbilical vein endothelial cells (HUVEC) induced by treatment with EVs derived from breast carcinoma cells and the effects of the function-blocking CD47 antibody B6H12 on the resulting intercellular communication. CD47⁺ EVs exhibited greater uptake by HUVEC compared to CD47^- EVs, but the CD47 antibody did not inhibit their uptake. Global and targeted analyses of transcripts demonstrated that treatment of HUVEC with EVs derived from MDA-MB-231 breast carcinomas cells altered pathways associated with tumor necrosis factor-α signaling, angiogenesis, lymphangiogenesis, endothelial-mesenchymal transition, and extracellular matrix. EVs from triple-negative MDA-MB-231 cells were more active than EVs from less metastatic breast carcinoma cell lines. Treatment with MDA-MB-231 EVs down-regulated VEGFR2 mRNA expression and tyrosine phosphorylation while enhancing phosphorylation of the tyrosine phosphatase SHP2. VEGFR2 expression and phosphorylation in HUVEC was further inhibited by the CD47 antibody. Consistent with the observed changes in endothelial-mesenchymal transition genes and SHP2, treatment with MDA-MB-231-derived EVs decreased Zeb1 protein levels in HUVEC, whereas the CD47 antibody increased Zeb1 levels. The induction of E-selectin and other known targets of tumor necrosis factor-α signaling by EVs was also enhanced by the CD47 antibody, and E-selectin was the most up-regulated transcript following CD47 antibody treatment alone. These studies reveal several mechanisms by which therapeutics targeting CD47 could modulate tumor growth by altering the cross talk between cancer-derived EVs and nonmalignant cells in the tumor stroma.

The critical role of SENP1-mediated GATA2 deSUMOylation in promoting endothelial activation in graft arteriosclerosis

Data from clinical research and our previous study have suggested the potential involvement of SENP1, the major protease of post-translational SUMOylation, in cardiovascular disorders. Here, we investigate the role of SENP1-mediated SUMOylation in graft arteriosclerosis (GA), the major cause of allograft failure. We observe an endothelial-specific induction of SENP1 and GATA2 in clinical graft rejection specimens that show endothelial activation-mediated vascular remodelling. In mouse aorta transplantation GA models, endothelial-specific SENP1 knockout grafts demonstrate limited neointima formation with attenuated leukocyte recruitment, resulting from diminished induction of adhesion molecules in the graft endothelium due to increased GATA2 SUMOylation. Mechanistically, inflammation-induced SENP1 promotes the deSUMOylation of GATA2 and IκBα in endothelial cells, resulting in increased GATA2 stability, promoter-binding capability and NF-κB activity, which leads to augmented endothelial activation and inflammation. Therefore, upon inflammation, endothelial SENP1-mediated SUMOylation drives GA by regulating the synergistic effect of GATA2 and NF-κB and consequent endothelial dysfunction.

Endothelial MAPKs Direct ICAM-1 Signaling to Divergent Inflammatory Functions

Lymphocyte transendothelial migration (TEM) is critically dependent on intraendothelial signaling triggered by adhesion to ICAM-1. Here we show that endothelial MAPKs ERK, p38, and JNK mediate diapedesis-related and diapedesis-unrelated functions of ICAM-1 in cerebral and dermal microvascular endothelial cells (MVECs). All three MAPKs were activated by ICAM-1 engagement, either through lymphocyte adhesion or Ab-mediated clustering. MAPKs were involved in ICAM-1-dependent expression of TNF-α in cerebral and dermal MVECs, and CXCL8, CCL3, CCL4, VCAM-1, and cyclooxygenase 2 (COX-2) in cerebral MVECs. Endothelial JNK and to a much lesser degree p38 were the principal MAPKs involved in facilitating diapedesis of CD4⁺ lymphocytes across both types of MVECs, whereas ERK was additionally required for TEM across dermal MVECs. JNK activity was critical for ICAM-1-induced F-actin rearrangements. Furthermore, activation of endothelial ICAM-1/JNK led to phosphorylation of paxillin, its association with VE-cadherin, and internalization of the latter. Importantly ICAM-1-induced phosphorylation of paxillin was required for lymphocyte TEM and converged functionally with VE-cadherin phosphorylation. Taken together we conclude that during lymphocyte TEM, ICAM-1 signaling diverges into pathways regulating lymphocyte diapedesis, and other pathways modulating gene expression thereby contributing to the long-term inflammatory response of the endothelium.

Hemorheological alterations in sickle cell anemia and their clinical consequences - The role of genetic modulators

Sickle cell anemia (SCA) is an autosomal recessive disease caused by the HBB:c.20A>T mutation that leads to hemoglobin S synthesis. The disease presents with high clinical heterogeneity characterized by chronic hemolysis, recurrent episodes of vaso-oclusion and infection. This work aimed to characterize by in silico studies some genetic modulators of severe hemolysis and stroke risk in children with SCA, and understand their consequences at the hemorheological level.Association studies were performed between hemolysis biomarkers as well as the degree of cerebral vasculopathy and the inheritance of several polymorphic regions in genes related with vascular cell adhesion and vascular tonus in pediatric SCA patients. In silico tools (e.g. MatInspector) were applied to investigate the main variant consequences.Variants in vascular adhesion molecule-1 (VCAM1) gene promoter and endothelial nitric oxide synthase (NOS3) gene were significantly associated with higher degree of hemolysis and stroke events. They potentially modify transcription factor binding sites (e.g. VCAM1 rs1409419_T allele may lead to an EVI1 gain) or disturb the corresponding protein structure/function. Our findings emphasize the relevance of genetic variation in modulating the disease severity due to their effect on gene expression or modification of protein biological activities related with sickled erythrocyte/endothelial interactions and consequent hemorheological abnormalities.

Mobilization of human immature hematopoietic progenitors through combinatory use of bortezomib and immunomodulatory drugs

Combination use of the proteasome inhibitor bortezomib and the immunomodulatory drugs lenalidomide or thalidomide has provided superior outcomes in multiple myeloma over their single use; however, these combinations can produce significant toxicities. Unexpectedly, we found a small but significant increase in the population of immature granulocytes and erythrocytes/megakaryocytes in peripheral blood in 16 of 22 patients (73%) treated with dexamethasone in combination with bortezomib and immunomodulatory drugs (triplet), but not in any of 25 patients treated with either bortezomib or immunomodulatory drugs with dexamethasone (doublet). These immature cells gradually increased to a peak level (mean 2.6% per white blood cells) with triplet therapy, and disappeared immediately after therapy cessation. The numbers of circulating CD34⁺ cells and colony-forming cells derived from peripheral blood mononuclear cells increased after triplet therapy compared with those in patients treated by either bortezomib or immunomodulatory drugs plus dexamethasone. Furthermore, triplet regimen downregulated the expression of CXCR4, a chemokine receptor essential for bone marrow retention, on CD34⁺ cells, suggesting an unexpected effect on normal hematopoietic stem/progenitor cells through the reduced interaction with the bone marrow microenvironment. Our observations suggest that combination use should be carefully evaluated to exert synergistic anti-myeloma effects while avoiding unexpected adverse events.

Protein Kinase CK2 Regulates Leukocyte-Endothelial Cell Interactions during Ischemia and Reperfusion in Striated Skin Muscle

BACKGROUND

Ischemia and reperfusion (I/R) causes tissue injury by inflammatory processes. This involves the upregulation of endothelial surface proteins by phospho-regulated signaling pathways, resulting in enhanced interactions of leukocytes with endothelial cells. Recently, we found that protein kinase CK2 is a crucial regulator of leukocyte-mediated inflammation. Therefore, in this study we investigated the involvement of CK2 in leukocyte-endothelial cell interactions during I/R injury.

METHODS

We first analyzed the inhibitory action of (E)-3-(2,3,4,5-tetrabromophenyl)acrylic acid (TBCA) and CX-4945 on CK2 kinase activity and the viability of human dermal microvascular endothelial cells (HDMEC). To mimic I/R conditions in vitro, HDMEC were exposed to hypoxia and reoxygenation and the expression of adhesion molecules was analyzed by flow cytometry. Moreover, we analyzed in vivo the effect of CK2 inhibition on leukocyte-endothelial cell interactions in the dorsal skinfold chamber model of I/R injury by means of repetitive intravital fluorescence microscopy and immunohistochemistry.

RESULTS

We found that TBCA and CX-4945 suppressed the activity of CK2 in HDMEC without affecting cell viability. This was associated with a significant downregulation of E-selectin and intercellular adhesion molecule (ICAM)-1 after in vitro hypoxia and reoxygenation. In vivo, CX-4945 treatment significantly decreased the numbers of adherent and transmigrated leukocytes in striated muscle tissue exposed to I/R.

CONCLUSION

Our findings indicate that CK2 is involved in the regulation of leukocyte-endothelial cell interactions during I/R by mediating the expression of E-selectin and ICAM-1.

Ubiquitin-specific Protease 20 Regulates the Reciprocal Functions of β-Arrestin2 in Toll-like Receptor 4-promoted Nuclear Factor κB (NFκB) Activation

Toll-like receptor 4 (TLR4) promotes vascular inflammatory disorders such as neointimal hyperplasia and atherosclerosis. TLR4 triggers NFκB signaling through the ubiquitin ligase TRAF6 (tumor necrosis factor receptor-associated factor 6). TRAF6 activity can be impeded by deubiquitinating enzymes like ubiquitin-specific protease 20 (USP20), which can reverse TRAF6 autoubiquitination, and by association with the multifunctional adaptor protein β-arrestin2. Although β-arrestin2 effects on TRAF6 suggest an anti-inflammatory role, physiologic β-arrestin2 promotes inflammation in atherosclerosis and neointimal hyperplasia. We hypothesized that anti- and proinflammatory dimensions of β-arrestin2 activity could be dictated by β-arrestin2's ubiquitination status, which has been linked with its ability to scaffold and localize activated ERK1/2 to signalosomes. With purified proteins and in intact cells, our protein interaction studies showed that TRAF6/USP20 association and subsequent USP20-mediated TRAF6 deubiquitination were β-arrestin2-dependent. Generation of transgenic mice with smooth muscle cell-specific expression of either USP20 or its catalytically inactive mutant revealed anti-inflammatory effects of USP20in vivoandin vitro Carotid endothelial denudation showed that antagonizing smooth muscle cell USP20 activity increased NFκB activation and neointimal hyperplasia. We found that β-arrestin2 ubiquitination was promoted by TLR4 and reversed by USP20. The association of USP20 with β-arrestin2 was augmented when β-arrestin2 ubiquitination was prevented and reduced when β-arrestin2 ubiquitination was rendered constitutive. Constitutive β-arrestin2 ubiquitination also augmented NFκB activation. We infer that pro- and anti-inflammatory activities of β-arrestin2 are determined by β-arrestin2 ubiquitination and that changes in USP20 expression and/or activity can therefore regulate inflammatory responses, at least in part, by defining the ubiquitination status of β-arrestin2.

Protective effects of monomethyl fumarate at the inflamed blood-brain barrier

BACKGROUND

Reactive oxygen species play a key role in the pathogenesis of multiple sclerosis as they induce blood-brain barrier disruption and enhance transendothelial leukocyte migration. Thus, therapeutic compounds with antioxidant and anti-inflammatory potential could have clinical value in multiple sclerosis. The aim of the current study was to elucidate the therapeutic effects of monomethyl fumarate on inflammatory-mediated changes in blood-brain barrier function and gain insight into the underlying mechanism.

METHODS

The effects of monomethyl fumarate on monocyte transendothelial migration across and adhesion to inflamed human brain endothelial cells (hCMEC/D3) were quantified using standardized in vitro migration and adhesion assays. Flow cytometry analysis and qPCR were used to measure the concomitant effects of monomethyl fumarate treatment on protein expression of cell adhesion molecules. Furthermore, the effects of monomethyl fumarate on the expression and nuclear localization of proteins involved in the activation of antioxidant and inflammatory pathways in human brain endothelial cells were elucidated using nuclear fractionation and Western blotting. Statistical analysis was performed using one-way ANOVA followed by the Bonferroni post-hoc test.

RESULTS

Our results show that monomethyl fumarate induced nuclear translocation of nuclear factor (erythroid-derived 2)-like 2 and concomitant production of the antioxidant enzymes heme oxygenase-1 and NADPH:quinone oxidoreductase-1 in brain endothelial cells. Importantly, monomethyl fumarate treatment markedly decreased monocyte transendothelial migration across and adhesion to inflamed human brain endothelial cells. Treatment of brain endothelial cells with monomethyl fumarate resulted in a striking reduction of vascular cell adhesion molecule expression. Surprisingly, monomethyl fumarate did not affect nuclear translocation of nuclear factor-кB suggesting that monomethyl fumarate potentially affects activity of nuclear factor-ĸB downstream of nuclear translocation.

CONCLUSIONS

Taken together, we show that monomethyl fumarate, the primary metabolite of dimethyl fumarate, which is currently used in the clinics for the treatment of relapsing-remitting multiple sclerosis, demonstrates beneficial therapeutic effects at the inflamed blood-brain barrier.

Growth arrest-specific 6 regulates thrombin-induced expression of vascular cell adhesion molecule-1 through forkhead box O1 in endothelial cells

BACKGROUND

Growth arrest-specific 6 (Gas6)-deficient mice are protected against venous thromboembolism (VTE), suggesting a role for Gas6 in this disorder. We previously demonstrated that Gas6 induces forkhead box O1 (FoxO-1) phosphorylation through the phosphoinositide 3-kinase-Akt pathway. FoxO-1 regulates the expression of vascular cell adhesion molecule-1 (VCAM-1), a molecule that has been implicated in VTE.

OBJECTIVES

To assess the role of FoxO-1 in Gas6-dependent VCAM-1 expression.

METHODS

Thrombin was used to stimulate endothelial cells (ECs). Wild-type (WT) and Gas6(-/-) ECs were transfected with small interfering RNA targeting Axl or FoxO-1, a luciferase-coupled plasmid containing the FoxO-1 consensus sequence, and a phosphorylation-resistant FoxO-1 mutant, or treated with an Akt inhibitor. VCAM-1 mRNA expression was measured by real time-qPCR. VCAM-1 protein expression and FoxO-1 and Akt phosphorylation were assessed by western blot analysis. FoxO-1 localization was assessed by immunofluorescence. Adhesion of bone marrow mononuclear cells (BM-MCs) on ECs was assessed by fluorescence.

RESULTS AND CONCLUSIONS

Thrombin induces both VCAM-1 expression and FoxO-1 phosphorylation and nuclear exclusion in WT ECs only. Silencing of FoxO-1 enhances VCAM-1 expression in both WT and Gas6(-/-) ECs. Inhibition of Akt or FoxO-1 phosphorylation prevents VCAM-1 expression in WT ECs. These data show that Gas6 induces FoxO-1 phosphorylation, leading to derepression of VCAM-1 expression. BM-MC-EC adhesion is increased by thrombin in WT ECs. BM-MC-EC adhesion is further increased when FoxO-1 is silenced, but decreased when FoxO-1 phosphorylation is inhibited. These results demonstrate that the Gas6-FoxO-1 signaling axis plays an important role in VCAM-1 expression in the context of VTE by promoting BM-MC-EC adhesion.

Crossing the Vascular Wall: Common and Unique Mechanisms Exploited by Different Leukocyte Subsets during Extravasation

Leukocyte extravasation is one of the essential and first steps during the initiation of inflammation. Therefore, a better understanding of the key molecules that regulate this process may help to develop novel therapeutics for treatment of inflammation-based diseases such as atherosclerosis or rheumatoid arthritis. The endothelial adhesion molecules ICAM-1 and VCAM-1 are known as the central mediators of leukocyte adhesion to and transmigration across the endothelium. Engagement of these molecules by their leukocyte integrin receptors initiates the activation of several signaling pathways within both leukocytes and endothelium. Several of such events have been described to occur during transendothelial migration of all leukocyte subsets, whereas other mechanisms are known only for a single leukocyte subset. Here, we summarize current knowledge on regulatory mechanisms of leukocyte extravasation from a leukocyte and endothelial point of view, respectively. Specifically, we will focus on highlighting common and unique mechanisms that specific leukocyte subsets exploit to succeed in crossing endothelial monolayers.

A hot water extract of Curcuma longa inhibits adhesion molecule protein expression and monocyte adhesion to TNF-α-stimulated human endothelial cells

The recruitment of arterial leukocytes to endothelial cells is an important step in the progression of various inflammatory diseases. Therefore, its modulation is thought to be a prospective target for the prevention or treatment of such diseases. Adhesion molecules on endothelial cells are induced by proinflammatory cytokines, including tumor necrosis factor-α (TNF-α), and contribute to the recruitment of leukocytes. In the present study, we investigated the effect of hot water extract of Curcuma longa (WEC) on the protein expression of adhesion molecules, monocyte adhesion induced by TNF-α in human umbilical vascular endothelial cells (HUVECs). Treatment of HUVECs with WEC significantly suppressed both TNF-α-induced protein expression of adhesion molecules and monocyte adhesion. WEC also suppressed phosphorylation and degradation of nuclear factor of kappa light polypeptide gene enhancer in B-cells inhibitor, alpha (IκBα) induced by TNF-α in HUVECs, suggesting that WEC inhibits the NF-κB signaling pathway.

Differential role of an NF-κB transcriptional response element in endothelial versus intimal cell VCAM-1 expression

RATIONALE

Human and murine Vcam1 promoters contain 2 adjacent nuclear factor-κB (NF-κB)-binding elements. Both are essential for cytokine-induced transcription of transiently transfected promoter-reporter constructs. However, the relevance of these insights to regulation of the endogenous Vcam1 gene and to pathophysiological processes in vivo remained unknown.

OBJECTIVE

Determine the role of the 5' NF-κB-binding element in expression of the endogenous Vcam1 gene.

METHODS AND RESULTS

Homologous recombination in embryonic stem cells was used to inactivate the 5' NF-κB element in the Vcam1 promoter and alter 3 nucleotides in the 5' untranslated region to allow direct comparison of wild-type versus mutant allele RNA expression and chromatin configuration in heterozygous mice. Systemic treatment with inflammatory cytokines or endotoxin (lipopolysaccharide) induced lower expression of the mutant allele relative to wild-type by endothelial cells in the aorta, heart, and lungs. The mutant allele also showed lower endothelial expression in 2-week atherosclerotic lesions in Vcam1 heterozygous/low-density lipoprotein receptor-deficient mice fed a cholesterol-rich diet. In vivo chromatin immunoprecipitation assays of heart showed diminished lipopolysaccharide-induced association of RNA polymerase 2 and NF-κB p65 with the mutant promoter. In contrast, expression of mutant and wild-type alleles was comparable in intimal cells of wire-injured carotid artery and 4- to 12-week atherosclerotic lesions.

CONCLUSIONS

This study highlights differences between in vivo and in vitro promoter analyses, and reveals a differential role for a NF-κB transcriptional response element in endothelial vascular cell adhesion molecule-1 expression induced by inflammatory cytokines or a cholesterol-rich diet versus intimal cell expression in atherosclerotic lesions and injured arteries.

L-tetrahydropalamatine inhibits tumor necrosis factor-α-induced monocyte-endothelial cell adhesion through downregulation of intercellular adhesion molecule-1 and vascular cell adhesion molecule-1 involving suppression of nuclear factor-κ B signaling pathway

OBJECTIVE

To investigate whether I-tetrahydropalmatine (I-THP), an alkaloid mainly present in Corydalis family, could ameliorate early vascular inflammatory responses in atherosclerotic processes.

METHODS

Fluorescently labeled monocytes were co-incubated with human umbilical vein endothelial cells (HUVECs), which were pretreated with I-THP and then simulated with tumor necrosis factor (TNF)-α in absence of I-THP to determine if I-THP could reduce thecytokine-induced adhesion of monocytes to HUVECs. Then I-THP were further studied the underlying mechanisms through observing the transcriptional and translational level of intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) and the nuclear translocation of nuclear factor (NF)-κ B in HUVECs.

RESULTS

L-THP could block TNF-α-induced adhesion of monocytes to HUVECs and could significantly inhibited the expression of ICAM-1 and VCAM-1 on cell surface by 31% and 36% at 30 μ mol/L. L-THP pretreatment could also markedly reduce transcriptional and translational level of VCAM-1 as well as mildly reduce the total protein and mRNA expression levels of ICAM-1. Furthermore, I-THP attenuated TNF-α-stimulated NF-κ B nuclear translocation.

CONCLUSION

These results provide evidences supporting that I-THP could be a promising compound in the prevention and treatment of the early vascular inflammatory reaction in atherosclerosis by inhibiting monocyte adhesion to vascular endothelial cell through downregulating ICAM-1 and VCAM-1 in vascular endothelial cell based on suppressing NF-κ B.

TNF-induced endothelial barrier disruption: beyond actin and Rho

The decrease of endothelial barrier function is central to the long-term inflammatory response. A pathological alteration of the ability of endothelial cells to modulate the passage of cells and solutes across the vessel underlies the development of inflammatory diseases such as atherosclerosis and multiple sclerosis. The inflammatory cytokine tumour necrosis factor (TNF) mediates changes in the barrier properties of the endothelium. TNF activates different Rho GTPases, increases filamentous actin and remodels endothelial cell morphology. However, inhibition of actin-mediated remodelling is insufficient to prevent endothelial barrier disruption in response to TNF, suggesting that additional molecular mechanisms are involved. Here we discuss, first, the pivotal role of Rac-mediated generation of reactive oxygen species (ROS) to regulate the integrity of endothelial cell-cell junctions and, second, the ability of endothelial adhesion receptors such as ICAM-1, VCAM-1 and PECAM-1, involved in leukocyte transendothelial migration, to control endothelial permeability to small molecules, often through ROS generation. These adhesion receptors regulate endothelial barrier function in ways both dependent on and independent of their engagement by immune cells, and orchestrate the crosstalk between leukocyte transendothelial migration and endothelial permeability during inflammation.

C/EBP-α, involvement of a novel transcription factor in leptin-induced VCAM-1 production in mouse chondrocytes

Leptin and vascular cell adhesion molecules-1 (VCAM-1) are two important mediators in obesity-related osteoarthritis, while the molecular mechanism linking leptin to VCAM-1 production is still obscure. Here we show that leptin upregulates VCAM-1 mRNA and protein levels in a time- and dose-dependent manner. Mechanistically, leptin induces VCAM-1 promoter activity by increasing the expression of C/EBP-α and facilitating its binding to a newly identified element in the VCAM-1 gene. Gain or loss of function studies reveal a regulatory role of C/EBP-α on VCAM-1 expression. Finally, elevated plasma leptin level correlates to increased C/EBP-α and VCAM-1 production in chondrocytes from obese mice.

Copper induces--and copper chelation by tetrathiomolybdate inhibits--endothelial activation in vitro

Endothelial activation with increased expression of cellular adhesion molecules and chemokines critically contributes to vascular inflammation and atherogenesis. Redox-active transition metal ions play an important role in vascular oxidative stress and inflammation. Therefore, the goal of the present study was to investigate the role of copper in endothelial activation and the potential anti-inflammatory effects of copper chelation by tetrathiomolybdate (TTM) in human aortic endothelial cells (HAECs). Incubating HAECs with cupric sulfate dose- and time-dependently increased mRNA and protein expression of vascular cell adhesion molecule-1 (VCAM-1), intercellular adhesion molecule-1 (ICAM-1), and monocyte chemotactic protein-1 (MCP-1). Copper also activated the redox-sensitive transcription factors, nuclear factor kappa B (NF-κB) and activator protein-1 (AP-1), which was inhibited by pretreatment of the cells with TTM. Furthermore, TTM dose-dependently inhibited tumor necrosis factor α (TNFα)-induced activation of NF-κB and AP-1, as well as mRNA and protein expression of VCAM-1, ICAM-1, and MCP-1, which was abolished by preincubating the cells with 5 µM TTM and 15 µM cupric sulfate. The inhibitory effect of TTM on TNFα-induced NF-κB activation was associated with decreased phosphorylation and degradation of IκBα. These data suggest that intracellular copper causes activation of redox-sensitive transcription factors and upregulation of inflammatory mediators in endothelial cells. Copper chelation by TTM may attenuate TNFα-induced endothelial activation and, hence, inhibit vascular inflammation and atherosclerosis.

Multiple antioxidants improve cardiac complications and inhibit cardiac cell death in streptozotocin-induced diabetic rats

Diabetic cardiomyopathy, a disorder of the heart muscle in diabetic patients, is one of the major causes of heart failure. Since diabetic cardiomyopathy is now known to have a high prevalence in the asymptomatic diabetic patient, prevention at the earliest stage of development by existing molecules would be appropriate in order to prevent the progression of heart failure. In this study, we investigated the protective role of multiple antioxidants (MA), on cardiac dysfunction and cardiac cell apoptosis in streptozotocin (STZ)-induced diabetic rat. Diabetic cardiomyopathy in STZ-treated animals was characterized by declined systolic, diastolic myocardial performance, oxidative stress and apoptosis in cardiac cells. Diabetic rats on supplementation with MA showed decreased oxidative stress evaluated by the content of reduced levels of lipid per-oxidation and decreased activity of catalase with down-regulation of heme-oxygenase-1 mRNA. Supplementation with MA also resulted in a normalized lipid profile and decreased levels of pro-inflammatory transcription factor NF-kappaB as well as cytokines such as TNF-α, IFN-γ, TGF-β, and IL-10. MA was found to decrease the expression of ROS-generating enzymes like xanthine oxidase, monoamine oxidase-A along with 5-Lipoxygenase mRNA and/or protein expression. Further, left ventricular function, measured by a microtip pressure transducer, was re-established as evidenced by increase in ±dp/dtmax, heart rate, decreased blood pressure, systolic and diastolic pressure as well as decrease in the TUNEL positive cardiac cells with increased Bcl-2/Bax ratio. In addition, MA supplementation decreased cell death and activation of NF-kappaB in cardiac H9c2 cells. Based on our results, we conclude that MA supplementation significantly attenuated cardiac dysfunction in diabetic rats; hence MA supplementation may have important clinical implications in terms of prevention and management of diabetic cardiomyopathy.

Testosterone: a vascular hormone in health and disease

Coronary heart disease is a leading cause of premature death in men. Epidemiological studies have shown a high prevalence of low serum testosterone levels in men with cardiovascular disease (CVD). Furthermore, a low testosterone level is associated in some but not in all observational studies with an increase in cardiovascular events and mortality. Testosterone has beneficial effects on several cardiovascular risk factors, which include cholesterol, endothelial dysfunction and inflammation: key mediators of atherosclerosis. A bidirectional relationship between low endogenous testosterone levels and concurrent illness complicates attempts to validate causality in this association and potential mechanistic actions are complex. Testosterone is a vasoactive hormone that predominantly has vasodilatory actions on several vascular beds, although some studies have reported conflicting effects. In clinical studies, acute and chronic testosterone administration increases coronary artery diameter and flow, improves cardiac ischaemia and symptoms in men with chronic stable angina and reduces peripheral vascular resistance in chronic heart failure. Although the mechanism of the action of testosterone on vascular tone in vivo is not understood, laboratory research has found that testosterone is an L-calcium channel blocker and induces potassium channel activation in vascular smooth muscle cells. Animal studies have consistently demonstrated that testosterone is atheroprotective, whereas testosterone deficiency promotes the early stages of atherogenesis. The translational effects of testosterone between in vitro animal and human studies, some of which have conflicting effects, will be discussed in this review. We review the evidence for a role of testosterone in vascular health, its therapeutic potential and safety in hypogonadal men with CVD, and some of the possible underlying mechanisms.

IL-17 induces expression of vascular cell adhesion molecule through signalling pathway of NF-κB, but not Akt1 and TAK1 in vascular smooth muscle cells

Interleukin-17 (IL-17) plays an important role in several autoimmune diseases. IL-17 can induce the expression of vascular cell adhesion molecule (VCAM-1) in aortic vascular smooth muscle cells (SMCs), which is important for the development of atherosclerosis. However, the signalling pathway of IL-17-induced VCAM-1 expression remains unclear. In this study, we reported that IL-17-induced expression of VCAM-1 in SMCs is dependent on NF-κB, but independent of Akt1 and TAK1. This is because knocking down Akt1 or TAK1 by siRNA did not reduce IL-17-induced activation of NF-κB and expression of VCAM-1, whereas knocking down NF-κB by siRNA markedly inhibited IL-17-mediated upregulation of VCAM-1 expression. In addition, IL-17-induced expression of VCAM-1 is partially dependent on activation of ERK1/2. Therefore, these signalling pathways of IL-17-mediated upregulation of VCAM-1 expression might be therapeutic targets for treatment of IL-17-mediated inflammation.

An in vitro evaluation of the anti-inflammatory effects of platelet-rich plasma, ketorolac, and methylprednisolone

PURPOSE

The purpose of this study was to quantify the extent of the anti-inflammatory effect of platelet-rich plasma (PRP) in a controlled in vitro environment.

METHODS

Through the stimulation of human umbilical vein endothelial cells with inflammatory cytokines (tumor necrosis factor α and interferon γ), cell adhesion molecule expression (E-selectin, vascular cell adhesion molecule, and human leukocyte antigen DR) and PRP's anti-inflammatory effect can be measured. PRP was produced from 3 individuals using a single-spin (PRPLP) process. Treatment groups include negative (unstimulated) controls, positive (stimulated) controls, ketorolac tromethamine, methylprednisolone, PRP, ketorolac-PRP, and methylprednisolone-PRP. A fluorescence assay of the cellular inflammation markers was measured by the BioTek Synergy HT plate reader (BioTek Instruments, Winooski, VT) at 0, 1, 2, and 5 days.

RESULTS

At days 2 and 5, methylprednisolone treatment showed a 2.1- to 5.8-fold reduction (P < .05) in inflammation markers over PRP. In addition, PRP and ketorolac showed a 1.4- to 2.5-fold reduction (P < .05) in cellular inflammation markers over the control. There was no statistically significant difference between ketorolac and PRP.

CONCLUSIONS

Although PRP and ketorolac reduced cellular inflammation markers (E-selectin, vascular cell adhesion molecule, and human leukocyte antigen DR) compared with control, neither caused as great a reduction as methylprednisolone.

CLINICAL RELEVANCE

Although PRP and ketorolac did not produce as significant a reduction in cellular inflammation markers as methylprednisolone, they reduced cellular inflammation compared with the control. These agents may have clinical application as injectable anti-inflammatory medications.

Isoforms of Vitamin E Differentially Regulate PKC α and Inflammation: A Review

Vitamin E regulation of disease has been extensively studied but most studies focus on the α-tocopherol isoform of vitamin E. These reports indicate contradictory outcomes for anti-inflammatory functions of the α-tocopherol isoform of vitamin E with regards to animal and clinical studies. These seemingly disparate results are consistent with our recent studies demonstrating that purified natural forms of vitamin E have opposing regulatory functions during inflammation. In this review, we discuss that α-tocopherol inhibits whereas γ-tocopherol elevates allergic inflammation, airway hyperresponsiveness, leukocyte transendothelial migration, and endothelial cell adhesion molecule signaling through protein kinase Cα. Moreover, we have demonstrated that α-tocopherol is an antagonist and γ-tocopherol is an agonist of PKCα through direct binding to a regulatory domain of PKCα. In summary, we have determined mechanisms for opposing regulatory functions of α-tocopherol and γ-tocopherol on inflammation. Information from our studies will have significant impact on the design of clinical studies and on vitamin E consumption.

Tanshinone IIA inhibits TNF-α-mediated induction of VCAM-1 but not ICAM-1 through the regulation of GATA-6 and IRF-1

The goal of this study was to investigate the differential effect of tanshinone IIA on the induction of intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) by TNF-α and the possible molecular mechanisms by which it regulates ICAM-1 and VCAM-1 expression differentially. Stimulation of human umbilical vein endothelial cells (HUVEC) with TNF-α increased ICAM-1 and VCAM-1 expressions, and the pretreatment with tanshinone IIA concentration dependently inhibited VCAM-1 expression but not ICAM-1 expression. In previous study, PI3K/Akt, PKC and Jak/STAT-3 pathways were involved in the TNF-α-mediated induction of VCAM-1 but not ICAM-1. Thus, we examined the effect of tanshinone IIA on TNF-α-mediated activations of PI3K/Akt, PKC and Jak/STAT-3 pathways. Tanshinone IIA efficiently inhibited the phosphorylations of Akt, PKC and STAT-3 by TNF-α. Moreover, we determined the effect of tanshinone IIA on IRF-1 or GATAs induction and binding activity to VCAM-1 promoter since the upstream promoter region of VCAM-1 but not ICAM-1 contains IRF-1 and GATA binding motifs. Western blot analysis and ChIP assay showed that tanshinone IIA efficiently inhibited TNF-α-increased nuclear level of IRF-1 and GATA-6 and their binding affinity to VCAM-1 promoter region. Taken together, tanshinone IIA selectively inhibits TNF-α-mediated expression of VCAM-1 but not ICAM-1 through modulation of PI3/Akt, PKC and Jak/STAT-3 pathway as well as IRF-1 and GATA-6 binding activity.

IRF-1 and miRNA126 modulate VCAM-1 expression in response to a high-fat meal

RATIONALE

A high-fat diet accompanied by hypertriglyceridemia increases an individual's risk for development of atherosclerosis. An early event in this process is monocyte recruitment through binding to vascular cell adhesion molecule 1 (VCAM-1) upregulated on inflamed arterial endothelium. Diets high in polyunsaturated fatty acids (PUFAs) may provide athero-protection by ameliorating this effect.

OBJECTIVE

We investigated the acute regulation of VCAM-1 expression in human aortic endothelial cells (HAEC) in response to triglyceride-rich lipoproteins (TGRL) isolated from subjects after consumption of a high-fat meal.

METHODS AND RESULTS

Postprandial TGRL isolated from 38 subjects were categorized as proatherogenic or antiatherogenic according to their capacity to alter the inflammatory response of HAEC. Proatherogenic TGRL increased expression of VCAM-1, intercellular adhesion molecule 1 (ICAM-1), and E-selectin by ≈20% compared with stimulation with tumor necrosis factor-α alone, whereas antiatherogenic TGRL decreased VCAM-1 expression by ≈20% while still upregulating ICAM-1. The relative atherogenicity of TGRL positively correlated with particle density of TG, apolipoprotein (Apo)CIII, ApoE, and cholesterol. Ω3-PUFA mimicked the effect of antiatherogenic TGRL by downregulating VCAM-1 expression. TGRL exerted this differential regulation of VCAM-1 by reciprocally modulating expression and activity of the transcription factor interferon regulatory factor 1 (IRF-1) and expression of microRNA 126 (miR-126). Overexpression or silencing of IRF-1 or miR-126 expression recapitulated the proatherogenic or antiatherogenic regulation of VCAM-1.

CONCLUSIONS

In response to a high-fat meal, TGRL bias the inflammatory response of endothelium via transcriptional and posttranscriptional editing of VCAM-1. Subjects with an anti-inflammatory response to a meal produced TGRL that was enriched in nonesterified fatty acids, decreased IRF-1 expression, increased miR-126 activity, and diminished monocyte arrest.

MicroRNA-181b regulates NF-κB-mediated vascular inflammation

EC activation and dysfunction have been linked to a variety of vascular inflammatory disease states. The function of microRNAs (miRNAs) in vascular EC activation and inflammation remains poorly understood. Herein, we report that microRNA-181b (miR-181b) serves as a potent regulator of downstream NF-κB signaling in the vascular endothelium by targeting importin-α3, a protein that is required for nuclear translocation of NF-κB. Overexpression of miR-181b inhibited importin-α3 expression and an enriched set of NF-κB-responsive genes such as adhesion molecules VCAM-1 and E-selectin in ECs in vitro and in vivo. In addition, treatment of mice with proinflammatory stimuli reduced miR-181b expression. Rescue of miR-181b levels by systemic administration of miR-181b "mimics" reduced downstream NF-κB signaling and leukocyte influx in the vascular endothelium and decreased lung injury and mortality in endotoxemic mice. In contrast, miR-181b inhibition exacerbated endotoxin-induced NF-κB activity, leukocyte influx, and lung injury. Finally, we observed that critically ill patients with sepsis had reduced levels of miR-181b compared with control intensive care unit (ICU) subjects. Collectively, these findings demonstrate that miR-181b regulates NF-κB-mediated EC activation and vascular inflammation in response to proinflammatory stimuli and that rescue of miR-181b expression could provide a new target for antiinflammatory therapy and critical illness.

FoxOs integrate pleiotropic actions of insulin in vascular endothelium to protect mice from atherosclerosis

Atherosclerotic cardiovascular disease is the leading cause of death in insulin-resistant (type 2) diabetes. Vascular endothelial dysfunction paves the way for atherosclerosis through impaired nitric oxide availability, inflammation, and generation of superoxide. Surprisingly, we show that ablation of the three genes encoding isoforms of transcription factor FoxO in endothelial cells prevents atherosclerosis in low-density lipoprotein receptor knockout mice by reversing these subphenotypes. Paradoxically, the atheroprotective effect of FoxO deletion is associated with a marked decrease of insulin-dependent Akt phosphorylation in endothelial cells, owing to reduced FoxO-dependent expression of the insulin receptor adaptor proteins Irs1 and Irs2. These findings support a model in which FoxO is the shared effector of multiple atherogenic pathways in endothelial cells. FoxO ablation lowers the threshold of Akt activity required for protection from atherosclerosis. The data demonstrate that FoxO inhibition in endothelial cells has the potential to mediate wide-ranging therapeutic benefits for diabetes-associated cardiovascular disease.