Induction Of Adhesion Molecules Research Articles

Activation of Nrf2 in Endothelial Cells Protects Arteries From Exhibiting a Proinflammatory State

Proinflammatory mediators influence atherosclerosis by inducing adhesion molecules (eg, VCAM-1) on endothelial cells (ECs) via signaling intermediaries including p38 MAP kinase. Regions of arteries exposed to high shear stress are protected from inflammation and atherosclerosis, whereas low-shear regions are susceptible. Here we investigated whether the transcription factor Nrf2 regulates EC activation in arteries. En face staining revealed that Nrf2 was activated in ECs at an atheroprotected region of the murine aorta where it negatively regulated p38-VCAM-1 signaling, but was expressed in an inactive form in ECs at an atherosusceptible site. Treatment with sulforaphane, a dietary antioxidant, activated Nrf2 and suppressed p38-VCAM-1 signaling at the susceptible site in wild-type but not Nrf2(-/-) animals, indicating that it suppresses EC activation via Nrf2. Studies of cultured ECs revealed that Nrf2 inactivates p38 by suppressing an upstream activator MKK3/6 and by enhancing the activity of the negative regulator MKP-1. Nrf2 prevents ECs at the atheroprotected site from exhibiting a proinflammatory state via the suppression of p38-VCAM-1 signaling. Pharmacological activation of Nrf2 reduces EC activation at atherosusceptible sites and may provide a novel therapeutic strategy to prevent or reduce atherosclerosis.

Role of Intercellular Adhesion Molecule-1 (ICAM-1) of Community Acquired Pneumonia in Mansoura University Hospitals (MUHs)

Background:Pneumonia is an inflammation of the lung that is most often caused by infection with bacteria, viruses, or other organisms. Occasionally, inhaled chemicals that irritate the lungs can cause pneumonia, Community-acquired pneumonia (CAP) is defined as pneumonia not acquired in a hospital or a long-term care facility. Despite the availability of potent new antimicrobials and effective vaccines, ICAM-1 is a cytokine inducible adhesion molecule expressed on the cells of multiple lineages at sites of inflammation.

Retinal Endothelial Cell Apoptosis Stimulates Recruitment of Endothelial Progenitor Cells

Bone marrow-derived endothelial progenitor cells (EPCs) contribute to vascular repair although it is uncertain how local endothelial cell apoptosis influences their reparative function. This study was conducted to determine how the presence of apoptotic bodies at sites of endothelial damage may influence participation of EPCs in retinal microvascular repair. Microlesions of apoptotic cell death were created in monolayers of retinal microvascular endothelial cells (RMECs) by using the photodynamic drug verteporfin. The adhesion of early-EPCs to these lesions was studied before detachment of the apoptotic cells or after their removal from the wound site. Apoptotic bodies were fed to normal RMECs and mRNA levels for adhesion molecules were analyzed. Endothelial lesions where apoptotic bodies were left attached at the wound site showed a fivefold enhancement in EPC recruitment (P < 0.05) compared with lesions where the apoptotic cells had been removed. In intact RMEC monolayers exposed to apoptotic bodies, expression of ICAM, VCAM, and E-selectin was upregulated by 5- to 15-fold (P < 0.05-0.001). EPCs showed a characteristic chemotactic response (P < 0.05) to conditioned medium obtained from apoptotic bodies, whereas analysis of the medium showed significantly increased levels of VEGF, IL-8, IL-6, and TNF-alpha when compared to control medium; SDF-1 remained unchanged. The data indicate that apoptotic bodies derived from retinal capillary endothelium mediate release of proangiogenic cytokines and chemokines and induce adhesion molecule expression in a manner that facilitates EPC recruitment.

The immunobiology of primary sclerosing cholangitis

Primary sclerosing cholangitis (PSC) is a chronic cholestatic liver disease histologically characterized by the presence of intrahepatic and/or extrahepatic biliary duct concentric, obliterative fibrosis, eventually leading to cirrhosis. Approximately 75% of patients with PSC have inflammatory bowel disease. The male predominance of PSC, the lack of a defined, pathogenic autoantigen, and the potential role of the innate immune system suggest that it may be due to dysregulation of immunity rather than a classic autoimmune disease. However, PSC is associated with several classic autoimmune diseases, and the strongest genetic link to PSC identified to date is with the human leukocyte antigen DRB01*03 haplotype. The precise immunopathogenesis of PSC is largely unknown but likely involves activation of the innate immune system by bacterial components delivered to the liver via the portal vein. Induction of adhesion molecules and chemokines leads to the recruitment of intestinal lymphocytes. Bile duct injury results from the sustained inflammation and production of inflammatory cytokines. Biliary strictures may cause further damage as a result of bile stasis and recurrent secondary bacterial cholangitis. Currently, there is no effective therapy for PSC and developing a rational therapeutic strategy demands a better understanding of the disease.

Th17 and natural Treg cell population dynamics in systemic lupus erythematosus

To investigate the relative abundance and activities of Th17 cells and natural Treg cells in systemic lupus erythematosus (SLE). Blood samples were collected from 50 adult patients with SLE. Samples were processed to detect Th17 cells and natural Treg cells by flow cytometry, and related gene expression was assessed by real-time reverse transcription-polymerase chain reaction. Skin biopsy specimens were collected for histologic assessment. The function of Th17 cells in relation to human umbilical vein endothelial cells (HUVECs) was studied in vitro. Th17 cells were also examined in lupus-prone MRL/Mp-lpr/lpr (MRL/lpr) mice. We demonstrated the presence of Th17 cells among the peripheral blood mononuclear cells (PBMCs) and in the involved organs of patients with active SLE. Both the percentage of circulating Th17 cells and the ability to produce interleukin-17A (IL-17A) were increased in samples derived from patients with active SLE. The number of Th17 cells increased during SLE flare, especially in patients with vasculitis, and decreased following certain treatments. We observed that IL-17A from patients with SLE could induce adhesion molecule messenger RNA expression in HUVECs and adhesion of T cells to HUVECs. An increase in the percentage of Th17 cells was correlated with natural Treg cell depletion during disease flare. Finally, expansion of the Th17 cell population was detected in MRL/lpr mice. SLE flare might be linked to the expansion of the Th17 cell population and the depletion of natural Treg cell subpopulations. Expansion of the Th17 cell population might be related to a distinct cytokine environment in active SLE. Th17 cells and microenvironmental IL-17A are involved in vascular inflammation in SLE. Antagonism of Th17 cells by IL-17A-blocking antibodies should be explored as a treatment of SLE.

LTβR Signaling Induces Cytokine Expression and Up-Regulates Lymphangiogenic Factors in Lymph Node Anlagen

The formation of lymph nodes is a complex process crucially controlled through triggering of LTbetaR on mesenchymal cells by LTalpha(1)beta(2) expressing lymphoid tissue inducer (LTi) cells. This leads to the induction of chemokines to attract more hematopoietic cells and adhesion molecules to retain them. In this study, we show that the extravasation of the first hematopoietic cells at future lymph node locations occurs independently of LTalpha and that these cells, expressing TNF-related activation-induced cytokine (TRANCE), are the earliest LTi cells. By paracrine signaling the first expression of LTalpha(1)beta(2) is induced. Subsequent LTbetaR triggering on mesenchymal cells leads to their differentiation to stromal organizers, which now also start to express TRANCE, IL-7, as well as VEGF-C, in addition to the induced adhesion molecules and chemokines. Both TRANCE and IL-7 will further induce the expression of LTalpha(1)beta(2) on newly arrived immature LTi cells, resulting in more LTbetaR triggering, generating a positive feedback loop. Thus, LTbetaR triggering by LTi cells during lymph node development creates a local environment to which hematopoietic precursors are attracted and where they locally differentiate into fully mature, LTalpha(1)beta(2) expressing, LTi cells. Furthermore, the same signals may regulate lymphangiogenesis to the lymph node through induction of VEGF-C.

Advanced Glycation End Products Subspecies-Selectively Induce Adhesion Molecule Expression and Cytokine Production in Human Peripheral Blood Mononuclear Cells

Advanced glycation end products (AGEs) are proteins or lipids that become glycated after exposure to diverse reducing sugars. Accumulation of AGEs induces diabetes complications. Microinflammation is a common major mechanism in the pathogenesis of diabetic vascular complications. Activation of monocytes/macrophages and T cells plays roles in the pathogenesis of atherosclerosis. The activation of T cells requires the enhanced expression of adhesion molecules on monocytes. AGEs activate monocytes by engaging the receptor for AGE (RAGE); however, little is known about the profile of agonist activity of diverse AGE moieties on monocytes. We investigated the effect of four distinct AGE subtypes (AGE-modified bovine serum albumin; AGE-2, AGE-3, AGE-4, and AGE-5) at concentrations ranging from 0.1 to 100 microg/ml on the expression of intercellular adhesion molecule-1, B7.1, B7.2, and CD40 on monocytes and its impact on the production of interferon-gamma and tumor necrosis factor-alpha in human peripheral blood mononuclear cells. Among the AGEs examined, AGE-2 and AGE-3 selectively induced adhesion molecule expression and cytokine production. Antagonism experiments using antibodies against adhesion molecules demonstrated that cell-to-cell interaction between monocytes and T/natural killer cells was involved in AGE-2- and AGE-3-induced cytokine production. AGE-2 and AGE-3 up-regulated the expression of RAGE on monocytes. The effects of AGE-2 and AGE-3 were inhibited by nuclear factor-kappaB and p38 mitogen-activated protein kinase inhibitors. These results indicated that AGE-2 and AGE-3 activated monocytes via RAGE, leading to the up-regulation of adhesion molecule expression and cytokine production.

Immunogenic properties of renal cell carcinoma and the pathogenesis of osteolytic bone metastases

The immunogenic properties of renal cell carcinoma (RCC) on bone osteolysis were investigated. mRNA expression of three proinflammatory cytokines, monocyte chemotactic protein-1 (MCP-1), interleukin-6 (IL-6) and interleukin-8 (IL-8), were determined in a panel of RCC lines (CRBM 1990, ACHN and Caki-1). Moreover proinflammatory cytokine mRNA expression and protein levels of adhesion molecules, intercellular adhesion molecule-1 (ICAM-1) and E-selectin, on human umbilical vein endothelial cells (HUVEC) incubated with the conditioned media from RCC lines were evaluated. RCC express mRNA of MCP-1, IL-6 and IL-8 that may induce a proinflammatory phenotype in endothelial cells. mRNA expression of IL-6, and IL-8 was induced on HUVEC treated with the conditioned media from RCC lines and mRNA and protein levels of ICAM-1 and E-selectin were also increased. This study demonstrates the immunogenic properties of renal cell carcinoma, such as pro-inflammatory cytokine secretion and the induction of adhesion molecules (ICAM-1 and E-Sel) by endothelial cells. ICAM-1 binds lymphocyte function-associated antigen-1 (LFA-1), which is expressed by pre-osteoclasts, so that, the observed proinflammatory phenotype in HUVEC may also favour osteoclast recruitment in bone metastases microenvironment. Osteolysis in bone metastases, mediated by this pathway, may be further potentiated by the pro-angiogenic properties of RCC.

High Pulsatility Flow Induces Adhesion Molecule and Cytokine mRNA Expression in Distal Pulmonary Artery Endothelial Cells

Arterial stiffening or reduced compliance of proximal pulmonary vessels has been shown to be an important predictor of outcomes in patients with pulmonary hypertension. Though current evidence indicates that arterial stiffening modulates flow pulsatility in downstream vessels and is likely related to microvascular damage in organs without extensive distributing arteries, the cellular mechanisms underlying this relationship in the pulmonary circulation are unexplored. Thus, this study was designed to examine the responses of the microvascular pulmonary endothelium to changes in flow pulsatility. A flow system was developed to reproduce arterial-like pulse flow waves with the capability of modulating flow pulsatility through regulation of upstream compliance. Pulmonary microvascular endothelial cells (PMVECs) were exposed to steady flow and pulse flow waves of varied pulsatility with varied hemodynamic energy (low: pulsatility index or PI = 1.0; medium: PI = 1.7; high: PI = 2.6) at flow frequency of 1 or 2 Hz for different durations (1 and 6 h). The mean flow rates in all the conditions were kept the same with shear stress at 14 dynes/cm(2). Gene expression was evaluated by analyzing mRNA levels of adhesion molecules (ICAM-1, E-selectin), chemokine (MCP-1) and growth factor/receptor (VEGF, Flt-1) in PMVECs. Functional changes were observed with monocyte adhesion assay. 1) Compared to either steady flow or low pulsatility flow, increased flow pulsatility for 1 h induced significant increases in mRNA levels of ICAM-1, E-selectin and MCP-1. 2) Sustained high pulsatility flow perfusion induced increases in ICAM, E-selectin, MCP-1, VEGF and its receptor Flt-1 expression. 3) Flow pulsatility effects on PMVECs were frequency-dependent with greater responses at 2 Hz and likely associated with the hemodynamic energy level. 4) Pulse flow waves with high flow pulsatility at 2 Hz induced leukocyte adhesion and recruitment to PMVECs. Increased upstream pulmonary arterial stiffness increases flow pulsatility in distal arteries and induces inflammatory gene expression, leukocyte adhesion and cell proliferation in the downstream PMVECs.

Inhibition of adhesion molecules expression by allicin in TNF‐α‐ and LPS‐treated MOVAS via downregulation of NF‐κB

Allicin is a precursor of a number of secondary products formed in garlic preparations. Since the upregulation of adhesion molecules in response to numerous inducing factors is associated with inflammation, interfering with the expression of adhesion molecules may be an important therapeutic target of inflammatory diseases. We examined the effect of allicin on the expression of adhesion molecules induced by TNF‐α or LPS in cultured mouse vascular smooth muscle cells (MOVAS) by ELISA, Western blot and Luciferase analysis, respectively. MOVAS were pretreated for 20 h with allicin (0.01‐1 μg/ml) and then exposed to TNF‐α or LPS for 4 and 8 h to measure the expression of E‐selectin, VCAM‐1 and ICAM‐1, respectively. Allicin significantly inhibited surface expression of adhesion molecules in a dose dependent manner. Specifically, the most significant reduction was observed in ICAM‐1 expression. In addition, allicin treatment resulted in the decrease of NF‐κB activation, whereas phosphorylation of AKT and ERK induced by LPS but not TNF‐α was inhibited. These results suggest that allicin downregulates TNF‐α‐ or LPS‐induced adhesion molecules expression via inhibition of NF‐κB activity and LPS‐mediated induction of adhesion molecules by inhibiting AKT and ERK signaling. Moreover, the data indicate that allicin may be considered in therapeutic strategies for the management of vascular inflammatory diseases

TNF‐α induces VCAM‐1 expression via PKCδ/Src/EGFR transactivation linking to AP‐1 and NF‐¿B in human renal mesangial cells

In glomerular cells, TNF‐α can induce adhesion molecule expression and then attracts monocytes adhesion. However, the mechanisms underlying TNF‐α ‐induced VCAM‐1 expression in human renal mesangial cells (HRMCs) remain unclear. Western blot, RT‐PCR, and monocytes adhesion analyses showed that in HRMCs, TNF‐α induced VCAM‐1 mRNA and protein expression in a time‐dependent manner, which were attenuated by the inhibitors of PKC (GF109203X and rottlerin), c‐Src (PP1), EGF receptor (AG1478), PI3K (LY294002), p38 MAPK (SB202190) and JNK (SP600125), or transfection with siRNA of c‐Src, Akt, p38 MAPK, and JNK2. These results suggest that EGFR transactivation participates in VCAM‐1 expression induced by TNF‐α. Accordingly, TNF‐α ‐stimulated phosphorylation of p38 MAPK and JNK was inhibited by pretreatment with GF109203X, rottlerin, PP1, AG1478, LY294002, SB202190, or SP600125. TNF‐α induced VCAM‐1 expression was blocked by selective inhibitors of AP‐1 (tanshinone IIA) and NF‐¿B (Bay11‐7082). Moreover, TNF‐α ‐stimulated activation of VCAM‐1 promoter activity was blocked by these selective inhibitors. Taken together, these results suggest that in HRMCs, PKCδ/c‐Src‐dependent EGFR transactivation, PI3K/Akt, p38 MAPK, JNK activation linking to AP‐1 and NF‐¿B is involved in TNF‐α‐induced VCAM‐1 expression and monocytes adhesion.

A long-acting glucagon-like peptide-1 analogue attenuates induction of plasminogen activator inhibitor type-1 and vascular adhesion molecules

Glucagon-like peptide-1 (GLP-1) administration attenuates endothelial cell dysfunction in diabetic patients and inhibits tumour necrosis factor alpha (TNF)-mediated plasminogen activator inhibitor type-1 (PAI-1) induction in human vascular endothelial cells. The short half-life of GLP-1 mediated via degradation by the enzyme dipeptidyl peptidase 4 mandates the clinical use of long-acting GLP-1 analogues. The effects of a long-acting GLP-1 analogue on PAI-1 and vascular adhesion molecule expression in vascular endothelial cells are unknown. In this report, we demonstrate for the first time that the treatment with liraglutide, a long-acting GLP-1 analogue, inhibited TNF or hyperglycaemia-mediated induction of PAI-1, intercellular adhesion molecule-1 and vascular cell adhesion molecule-1 mRNA and protein expression in a human vascular endothelial cell line. In addition, treatment attenuated TNF- or hyperglycaemia-mediated induction of the orphan nuclear receptor Nur77 mRNA expression. Taken together, these observations indicate that liraglutide inhibits TNF- or glucose-mediated induction of PAI-1 and vascular adhesion molecule expression, and this effect may involve the modulation of NUR77. These effects suggest that liraglutide may potentially improve the endothelial cell dysfunction associated with premature atherosclerosis identified in type 2 diabetic patients.

Endothelial Cell-Specific NF-κB Inhibition Protects Mice from Atherosclerosis

Atherosclerosis is a progressive disorder of the arterial wall and the underlying cause of cardiovascular diseases such as heart attack and stroke. Today, atherosclerosis is recognized as a complex disease with a strong inflammatory component. The nuclear factor-kappaB (NF-kappaB) signaling pathway regulates inflammatory responses and has been implicated in atherosclerosis. Here, we addressed the function of NF-kappaB signaling in vascular endothelial cells in the pathogenesis of atherosclerosis in vivo. Endothelium-restricted inhibition of NF-kappaB activation, achieved by ablation of NEMO/IKKgamma or expression of dominant-negative IkappaBalpha specifically in endothelial cells, resulted in strongly reduced atherosclerotic plaque formation in ApoE(-/-) mice fed with a cholesterol-rich diet. Inhibition of NF-kappaB abrogated adhesion molecule induction in endothelial cells, impaired macrophage recruitment to atherosclerotic plaques, and reduced expression of cytokines and chemokines in the aorta. Thus, endothelial NF-kappaB signaling orchestrates proinflammatory gene expression at the arterial wall and promotes the pathogenesis of atherosclerosis.

Endothelial effects of emission source particles: Acute toxic response gene expression profiles

Air pollution epidemiology has established a strong association between exposure to ambient particulate matter (PM) and cardiovascular outcomes. Experimental studies in both humans and laboratory animals support varied biological mechanisms including endothelial dysfunction as potentially a central step to the elicitation of cardiovascular events. We therefore hypothesized that relevant early molecular alterations on endothelial cells should be assessable in vitro upon acute exposure to PM components previously shown to be involved in health outcomes. Using a model emission PM, residual oil fly ash and one of its predominant constituents (vanadium-V), we focused on the development of gene expression profiles to fingerprint that particle and its constituents to explore potential biomarkers for PM-induced endothelial dysfunction. Here we present differential gene expression and transcription factor activation profiles in human vascular endothelial cells exposed to a non-cytotoxic dose of fly ash or V following semi-global gene expression profiling of approximately 8000 genes. Both fly ash and it's prime constituent, V, induced alterations in genes involved in passive and active transport of solutes across the membrane; voltage-dependent ion pumps; induction of extracellular matrix proteins and adhesion molecules; and activation of numerous kinases involved in signal transduction pathways. These preliminary data suggest that cardiovascular effects associated with exposure to PM may be mediated by perturbations in endothelial cell permeability, membrane integrity; and ultimately endothelial dysfunction.

Zinc fingers protect the kidney from ischemia/reperfusion injury

A pivotal transcription factor influencing both gene expression and apoptosis is the nuclear factor-kappa B (NF-κB). NF-κB is a central regulator of inflammation by inducing adhesion molecules and other pro-inflammatory components. In ischemia/reperfusion injury, NF-κB upregulates the genes encoding these molecules. Attenuating the process could be important in decreasing myocardial infarct size or diminishing the likelihood of acute renal failure when the heart or kidneys are subject to ischemia. In this issue, Lutz et al. [1] show that an endogenous protector can suppress the pro-inflammatory activation of NF-κB. This protector is the NF-κB-induced zinc finger regulator, termed A20. The authors first studied human endothelial cells that were exposed to 1% O2 for 4 h followed by reoxygenation. They observed that E-selectin, vascular cell adhesion molecule, and interleukin (IL-8) expression were transiently increased, accompanied by sustained A20 expression. The authors next used an adenovirus to introduce A20 and found that the endothelial cells exhibited blunted NF-κB activation of the above-mentioned genes in response to hypoxia/re-oxygenation. They next subjected rats to renal ischemia/reperfusion by 45-min renal pedicle clamping. Pretreatment of the animals with adenovirus carrying A20 reduced renal inflammation and injury. The authors concluded that A20 maintains homeostasis in kidneys exposed to ischemia/reperfusion, a form of endogenous damage control. What is A20 [2]? A20 is a cytoplasmic protein that contains an N-terminal ovarian tumor (OTU) domain and seven novel zinc finger structures with a characteristic CysXaa2–4-Cys-Xaa11-Cys-Xaa2–Cys motif. What are zinc fingers? A zinc finger is a protein domain that can bind to DNA. A zinc finger consists of two anti-parallel β sheets and an α-helix. The zinc ion is crucial for the stability of this domain type; in the absence of the metal ion the domain unfolds, since it is too small to have a hydrophobic core. Zinc fingers are important in regulation because, when interacted with DNA and zinc ion, they provide a unique structural motif for DNA-binding proteins. The structure of each individual finger is highly conserved and consists of about 30 amino acid residues, constructed as a ββα-fold and held together by a zinc ion. The α-helix occurs at the C-terminal part of the finger, while the β-sheet occurs at the N-terminal part. Many transcription factors, regulatory proteins, and other proteins that interact with DNA contain zinc fingers, as does A20. These proteins typically interact with the major groove along the double helix of DNA in which case the zinc fingers are arranged around the DNA strand in such a way that the α-helix of each finger contacts the DNA, forming an almost continuous stretch of α-helices around the DNA molecule. How does A20 regulate NF-κB and influence apoptosis [2, 3]? To deal with this complicated question, a prototype model of NF-κB and common activators should be presented first (Fig. 1). Perhaps, the best model of NF-κB activation, although by no means the only model, is via tumor necrosis factor (TNF) and members of the IL-1/toll receptor family. TNF binds to its receptor (TNFR1) and activates the recruitment of TNF-receptor-associated factor (TRAF2) and the receptor-interacting protein (RIP). This combination binds to the TNFR via the adapter protein known as TNFRSF1A-associated via death domain (TRADD). TRADD in turn recruits Fas-associated protein with death domain (FADD), which is an adaptor molecule J Mol Med (2008) 86:1297–1300 DOI 10.1007/s00109-008-0411-6

Large tumors too slippery for T cells?

On page 2125, Quezada et al. find that big tumors might evade T cell destruction by shutting down adhesion molecules. Figure 1 Boosting adhesion molecule expression in tumor blood vessels (red) allows more tumor-killing T cells (green) to gain access. Tumor-fighting T cells work better when suppressive regulatory T (T reg) cells are not lurking. But treatments that either deplete T reg cells or boost anti-tumor T cell activity aren't enough to destroy tumors, as Quezada et al. now show. As seen in other tumor models, skin tumors in mice were destroyed when the group depleted T reg cells before tumor implantation. But if they depleted T reg cells after tumors had already developed, the treatment failed, even if the animals were given T cell–boosting drugs. Plenty of potential tumor-killing T cells were available, but they did not seem to infiltrate the tumors. Small tumors, at least, were sensitive to T cells. When T reg cell depletion was combined with T cell–boosting drugs, small, newly implanted tumors were destroyed. But well-established tumors resisted the effects of this regimen. Established tumors, the group found, had fewer adhesion molecules on surrounding blood vessels. To determine whether these adhesives might help T cells invade bigger tumors, the group induced adhesion molecules in mice using irradiation. Zapped mice that were then injected with anti-tumor T cells along with activity-enhancing drugs fought off tumors. But irradiated mice that were also injected with T reg cells put up a weak fight. How tumors dial down adhesion molecules as they grow and whether T reg cells coerce them into doing so remain to be seen. The findings might explain why treatments that deplete T reg cells and enhance killer T cell activity haven't fared well in clinical trials. Perhaps combining them with irradiation might make them more effective.

Increased Endothelial Mitogen-Activated Protein Kinase Phosphatase-1 Expression Suppresses Proinflammatory Activation at Sites That Are Resistant to Atherosclerosis

Atherosclerosis is a chronic inflammatory disease of arteries. It is triggered by proinflammatory mediators which induce adhesion molecules (eg, vascular cell adhesion molecule [VCAM]-1) in endothelial cells (ECs) by activating p38 and c-Jun N-terminal kinase (JNK) mitogen-activated protein (MAP) kinases by phosphorylation. Blood flow influences atherosclerosis by exerting shear stress (mechanical drag) on the inner surface of arteries, a force that alters endothelial physiology. Regions of the arterial tree exposed to high shear are protected from endothelial activation, inflammation, and atherosclerosis, whereas regions exposed to low or oscillatory shear are susceptible. We examined whether MAP kinase phosphatase (MKP)-1, a negative regulator of p38 and JNK, mediates the antiinflammatory effects of shear stress. We observed that expression of MKP-1 in cultured ECs was elevated by shear stress, whereas the expression of VCAM-1 was reduced. MKP-1 induction was shown to be necessary for the antiinflammatory effects of shear stress because gene silencing of MKP-1 restored VCAM-1 expression in sheared ECs. Immunostaining revealed that MKP-1 is preferentially expressed by ECs in a high-shear, protected region of the mouse aorta and is necessary for suppression of EC activation at this site, because p38 activation and VCAM-1 expression was enhanced by genetic deletion of MKP-1. We conclude that MKP-1 induction is required for the antiinflammatory effects of shear stress. Thus, our findings reveal a novel molecular mechanism contributing to the spatial distribution of vascular inflammation and atherosclerosis.

The 15-Lipoxygenase-Modified High Density Lipoproteins 3 Fail to Inhibit the TNF-α-Induced Inflammatory Response in Human Endothelial Cells

Endothelial dysfunction represents one of the earliest events in vascular atherogenesis. Proinflammatory stimuli activate endothelial cells, resulting in an increased expression of adhesion molecules and chemoattractants that mediate leukocyte and monocyte adhesion, migration, and homing. High density lipoproteins (HDL) inhibit endothelial cell expression of adhesion molecules in response to proinflammatory stimuli. In the present work, we demonstrate that the modification of HDL(3) (the major and the most antiatherogenic HDL subfraction) by 15-lipoxygenase (15-LO), an enzyme overexpressed in the atherosclerotic lesions, impairs the anti-inflammatory activity of this lipoprotein. The 15-LO-modified HDL(3) failed to inhibit TNF-alpha-mediated mRNA and protein induction of adhesion molecules and MCP-1 in several models of human endothelial cells, and promoted inflammatory response by up-regulating the expression of such mediators of inflammation and by increasing monocyte adhesion to endothelial cells. Moreover, 15-LO-modified HDL(3) were unable to contrast the formation of reactive oxygen species in cells incubated with TNF-alpha, and increased the reactive oxygen species content in unstimulated cells. Activation of NF-kappaB and AP-1 was mainly involved in the expression of adhesion molecules and MCP-1 induced by 15-LO-HDL(3). Altogether, these results demonstrate that enzymatic modification induced by 15-LO impaired the protective role of HDL(3), generating a dysfunctional lipoprotein endowed with proinflammatory characteristics.

Regulation of Neutral Sphingomyelinase-2 (nSMase2) by Tumor Necrosis Factor-α Involves Protein Kinase C-δ in Lung Epithelial Cells

Neutral sphingomyelinases (N-SMases) are major candidates for stress-induced ceramide production, but there is still limited knowledge of the regulatory mechanisms of the cloned N-SMase enzyme-nSMase2. We have reported that p38 mitogen-activated protein kinase (MAPK) was upstream of nSMase2 in tumor necrosis-alpha (TNF-alpha)-stimulated A549 cells ( J Biol Chem 282: 1384-1396, 2007 ). Here, we report a role for protein kinase C (PKC) in mediating TNF-induced translocation of nSMase2 from the Golgi to the plasma membrane (PM). Pharmacological inhibition of PKCs prevented TNF-stimulated nSMase2 translocation to the PM in A549 cells. Using phorbol 12-myristate 13-acetate (PMA) as a tool to dissect PKC responses, we found that PMA induced nSMase2 translocation to the PM in a time- and dose-dependent manner. Pharmacological inhibitors and specific siRNA implicated the novel PKCs, specifically PKC-delta, in both TNF and PMA-stimulated nSMase2 translocation. However, PMA did not increase in vitro N-SMase activity and PKC-delta did not regulate TNF-induced N-SMase activity. Furthermore, PKC-delta and nSMase2 did not coimmunoprecipitate, suggesting that other signaling proteins may be involved. PMA-stimulated nSMase2 translocation was independent of p38 MAPK, and neither PKC inhibitors nor small interfering RNA had significant effects on TNF-stimulated p38 MAPK activation, indicating that PKC-delta does not act through p38 MAPK in regulating nSMase2. Finally, down-regulation of PKC-delta inhibited induction of vascular cell and intercellular adhesion molecules, previously identified as downstream of nSMase2 in A549 cells. Taken together, these data implicate PKC-delta as a regulator of nSMase2 and, for the first time, identify nSMase2 as a point of cross-talk between the PKC and sphingolipid pathways.

Impact of Omega-3 and Trans Fatty Acids on Vascular Remodeling:Opposing Roles in Cardiovascular Health

Omega-3 polyunsaturated fatty acids (n-3 PUFAs) have well-recognized cardio-beneficial effects that include reductions in atherosclerotic lesions and mortality from myocardial infarction, stroke, and sudden cardiac death. In contrast, evidence suggests that more than 30,000 premature coronary deaths per year in the US alone are associated with consumption of high levels of trans isomers of unsaturated fatty acids, or trans fatty acids (TFAs). Epidemiological evidence from four large cohort studies overwhelmingly supports the conclusion that TFAs are linked to coronary heart disease (CHD). CHD in patients is associated with pathological vascular remodeling (PVR) and impaired compensatory vascular remodeling (CVR). PVR is characterized by thickening of vessel walls, reduction in elasticity, and occlusion of vessels, resulting in restricted blood flow. CVR represents a physiological process whereby vessels from a pre-existing arteriolar network develop into collateral arteries, effectively bypassing the site of arterial occlusion. The structure and function of vascular endothelial cell membranes are altered by both PVR and CVR. Oxidative stress and the induction of endothelial adhesion molecules promote PVR and inhibit CVR. It is known that n-3 PUFAs inhibit the release of soluble adhesion molecules and proinflammatory cytokines whereas TFA consumption has been linked to an increased release of these proinflammatory mediators. However, it is not known whether the changes in cell membrane composition induced by n-3 PUFAs or TFAs impact development of PVR and CVR directly or whether the changes result indirectly from altered expression and/or release of proinflammatory mediators. This review summarizes studies suggesting that n-3 PUFAs and TFAs have opposing effects on endothelial cells and that their effects on the endothelium might play an important role in vascular remodeling.