Endothelial reparative regeneration--a self-regulating process?

When investigating dynamics of reparative regeneration of the rat aorta endothelium after injuring a considerable area by means of cryogenic lesion, a certain tendency to cluster arrangement of proliferating endothelial cells (EC) has been revealed at the edge of the defect both at the beginning and at the end of the reparative process. This fact together with the data on mechanisms of migration and proliferation of EC makes it possible to suppose certain scheme of the mitotic reaction development in endothelium. It consists of centropetal movement of waves of interdependent acts of contraction and flattening of endotheliocytes. Some characteristics of the regenerative proliferation of endothelium make it possible to formulate a hypothesis on autowave character of its regulation.     

The mechanisms of reparative regeneration of venous endothelium

The reaction of endothelial cells of the inferior vena cava in response to freezing-induced lesions has been analysed in the experiments on 34 young adult Kyoto-Wistar normotensive rats. First the de-endothelialized surface is covered with flattened platelets and then, three days after surgery, the endothelium is restored as a result of migration and proliferation of endotheliocytes. The migrating endothelial cells removed the adhered platelets from de-endothelialized surface. The young endothelium was presented by a single layer of strongly elongated endothelial cells whose axis was parallel to the flow of blood. An immature endothelium is characterized by an increased number of endotheliocytes. No essential differences in the reaction of venous and aortic endothelium have been revealed in response to freezing-induced lesions.     

Damage and regeneration of the endothelium of the aorta in experimental hypercholesterolemia

In dynamics of the experimental hypercholesterolemia in rabbits, peculiarities of endothelial regeneration have been studied. Comparison of proliferative activity level in endotheliocytes with structural-functional state of the endothelial monolayer at atherogenesis makes it possible to consider, that the lesion of the endothelium cannot be regarded as an initiating factor for formation of atherosclerotic lesions. Formation of the lesions in the internal lining of the arteries is preceded by certain disorders in permeability of the endothelial barrier at increasing concentration of cholesterin in blood plasma, accompanying with a sharp activation of the cell proliferative activity. When lipid plates and atherosclerotic plaques are already formed, the processes of the endothelial damage and regeneration occur in parallel. The regeneration is ensured with an intensive proliferation and growth of endotheliocytes onto deendotheliolized areas of the damaged intima.     

Relevance of disease- and organ-specific endothelial cells for in vitro research

The endothelium is a dynamic, heterogeneous, disseminated organ that possesses vital secretory, synthetic, metabolic and immunological functions. Endothelial dysfunction has been implicated as a key factor in the development of organ-specific vascular diseases. This minireview gives a brief overview on EC (endothelial cell) biomarkers in arterial and venous endothelium and critically discusses the different sources of ECs that are most frequently applied in in vitro assays and research. The relevance of organ- and disease-specific endothelial cell cultures for studying cellular responses as a basis for improving therapeutic interventions is highlighted with particular emphasis on endothelial dysfunction in transplant-associated coronary artery disease, in atherosclerotic lesions and in response to diabetes mellitus.     

Endothelial dysfunction in acute and chronic coronary syndromes: evidence for a pathogenetic role of oxidative stress

The past two decades have highlighted the pivotal role of the endothelium in preserving vascular homeostasis. Among others, nitric oxide (NO) is currently believed to be the main component responsible for endothelium dependent vasorelaxation and therefore for endothelial function integrity. Reduced NO bioavailability causes the so-called "endothelial dysfunction," which seems to be the common molecular disorder comprising stable atherosclerotic narrowing lesions or acute plaque rupture causing unstable angina or myocardial infarction. Compelling evidence is accumulating, stressing the role of oxidative stress in causing reduced NO bioavailability and subsequently endothelial dysfunction (ED). More recently, the role of endothelial cell (EC) apoptosis as a possible final stage of ED and plaque activation has been suggested. In vitro and in vivo evidence suggests a role of oxidative stress also as a putative mechanism finally leading to plaque denudation and activation through increased EC apoptosis. Thus, oxidative stress, irrespective of atherosclerotic disease stages, seems to represent a key phenomenon in vascular disease progression and possible prevention.     

Participation of the endothelium in the development of the atherosclerotic plaque

In the past decade, initiated by the response-to-injury hypothesis of Ross and Glomset, the endothelium has been implicated in atherogenesis but as a passive participant--more involved through its absence than its presence. The hypothesis stated that endothelial desquamation due to an undefined injury led to platelet adhesion to the exposed basement membrane, and infiltration of serum lipoproteins. The subsequent release from the platelet alpha-granule of a potent smooth muscle cell mitogen and chemoattractant--the platelet-derived growth factor (PDGF)--was postulated to cause the intimal proliferative response that is known to be important in atherosclerotic plaque development. Recent evidence from several laboratories indicates that the endothelium has the potential to play a more active role in plaque development than simply contributing to pathological sequelae resulting from the loss of the nonthrombogenic surface provided by the endothelium. First, the endothelial cell (EC) is the site of attachment, and possibly activation, of blood-borne monocytes which enter the vessel wall as an early event in experimental atherogenesis. We have obtained in vitro evidence that the expression of monocyte binding sites on the surface of EC is a regulatable process and that increased EC turnover and certain exogenous agents acting on EC cause increased monocyte adhesion. Similar events may be responsible for focal adhesion of monocytes to the endothelium in vivo following hypercholesterolemia. Secondly, EC in culture are capable of chemically modifying low density lipoprotein (LDL) by a free radical oxidation process that renders the LDL toxic to proliferating cells and recognizable to the scavenger receptor of monocyte-derived macrophages. Thus, by oxidation of LDL, the EC have the potential to play an active role both in the formation of lipid-laden foam cells and in the accumulation of necrotic tissue which are hallmarks of the atherosclerotic lesion. Thirdly, cultured EC have been recently shown to secrete multiple mitogens for cultured smooth muscle cells. One of these mitogens appears to be closely related, if not identical, to PDGF using the criteria of receptor binding and biochemical and immunological similarity. Production of growth factors by EC is a regulatable process that is stimulated by exogenous agents such as endotoxin and phorbol esters which cause severe injury to cultured EC. Such a regulatory mechanism may participate in the in vivo proliferation of vascular SMC during the atherosclerotic process.(ABSTRACT TRUNCATED AT 400 WORDS)     

Mathematical modeling of vascular endothelial layer maintenance: the role of endothelial cell division, progenitor cell homing, and telomere shortening

Maintenance of the endothelial cell (EC) layer of the vessel wall is essential for proper functioning of the vessel and prevention of vascular disorders. Replacement of damaged ECs could occur through division of surrounding ECs. Furthermore, EC progenitor cells (EPCs), derived from the bone marrow and circulating in the bloodstream, can differentiate into ECs. Therefore, these cells might also play a role in maintenance of the endothelial layer in the vascular system. The proliferative potential of both cell types is limited by shortening of telomeric DNA. Accelerated telomere shortening might lead to senescent vascular wall cells and eventually to the inability of the endothelium to maintain a continuous monolayer. The aim of this study was to describe the dynamics of EC damage and repair and telomere shortening by a mathematical model. In the model, ECs were integrated in a two-dimensional structure resembling the endothelium in a large artery. Telomere shortening was described as a stochastic process with oxidative damage as the main cause of attrition. Simulating the model illustrated that increased cellular turnover or elevated levels of oxidative stress could lead to critical telomere shortening and senescence at an age of 65 yr. The model predicted that under those conditions the EC layer could display defects, which could initiate severe vascular wall damage in reality. Furthermore, simulations showed that 5% progenitor cell homing/yr can significantly delay the EC layer defects. This stresses the potential importance of EPC number and function to the maintenance of vascular wall integrity during the human life span.     

PROLIFERATION STUDIES OF THE ENDOTHELIAL AND SMOOTH MUSCLE CELLS OF THE MOUSE MESENTERY AFTER IRRADIATION

A continuous labelling technique was employed to study the effects of external β-radiation on the proliferation of endothelial cells and smooth muscle cells in the mesenteric arterioles of mice. Labelled and non-labelled cells of either type were determined by autoradiographic techniques in control animals and at different times (3, 12 and 48 weeks) after single doses of 20 and 45 Gy (2000 and 4500 rads). The fraction of cells labelled, even after 7 days of repeated injections was very low in all instances. Calculations showed very long turnover times for the two cell populations in control animals (>2 years for endothelium and >3 years for smooth muscle). After 20 and 45 Gy, no significant increase in endothelial proliferation was seen except at 3 weeks. No significant increase in labelling was observed in smooth muscle at any time after irradiation. These labelling data have been compared with the pattern of cell depletion of the irradiated endothelium. It was concluded that the depletion was much earlier than expected for a slowly proliferating tissue, if all the cells were cycling very slowly. Such an early depletion is, however, consistent with cell death resulting from a small proportion of the cells having a short cell cycle. The recovery of the endothelial cell numbers between 9 and 12 months was not accompanied by a rise in the fraction of labelled cells. It is suggested that repopulation may occur from outside the treated area.     

Proinflammatory and procoagulant effects of herpes simplex infection on human endothelium

Atherosclerotic lesions have been reported to contain herpes simplex virus (HSV) genomic material. This and other evidence suggests that latent viral infection may be an atherogenic trigger. Moreover, active HSV lesions manifest histologically marked fibrin deposition in microvessels. Our laboratory tested in vitro whether HSV infection would cause human umbilical vein endothelial cells to become procoagulant and attract inflammatory cells. Early infection of human endothelial cells with HSV-1 alters the surface conformation as detected by merocyanine 540 staining. The efficiency of prothrombinase complex assembly increases, resulting in a two- to threefold accelerated rate of thrombin generation on the cell surface of virally infected endothelium. HSV infection of endothelium results in a marked increase in thrombin-induced platelet adhesion with a concomitant decrease in prostacyclin secretion in response to thrombin. Viral infection enhances coagulation by decreasing endothelial thrombomodulin expression and subsequent activation of protein C. Viral infection also induces tissue factor in human endothelial cells within 4 hours of infection. Not only does the endothelial monolayer become procoagulant when infected with HSV, it also becomes a more adherent surface for granulocytes. Resting and stimulated granulocyte adherence is enhanced twofold on virally infected endothelium. Enhanced adhesion is accompanied by excessive granulocyte-mediated lysis of 51Cr-labeled HSV-infected endothelium and endothelial cell detachment from its substrate. Exaggerated endothelial detachment correlated with poor binding of infected endothelial cells to substratum matrix proteins. Resuspended virus-infected cells bound significantly less well to tissue culture containers coated with fibronectin, laminin, and type IV collagen. HSV-infected endothelium alters the anticoagulant properties of the endothelium causing it to become procoagulant.(ABSTRACT TRUNCATED AT 250 WORDS)     

Stimulation of endothelial cell binding of lymphocytes by tumor necrosis factor

Lymphokines and monokines have been reported to affect endothelial cell (EC) morphology and function. In experiments here described, we have demonstrated that recombinant tumor necrosis factor (TNF) stimulates the adhesion of T lymphocytes to confluent monolayers of human umbilical vein EC. The increase in adhesion induced by TNF was EC-specific inasmuch as preincubation of the lymphocytes with TNF did not alter binding, and preincubation of human dermal fibroblasts with TNF did not increase their inherently low adhesiveness for lymphocytes. Stimulation of T-EC binding occurred after treatment of the EC with as little as 0.01 U/ml (1 pg/ml) of TNF. In kinetic experiments, preincubation of EC with TNF for 4 hr resulted in optimal adhesion. TNF-treated EC retained their increased adhesiveness after fixation with paraformaldehyde, suggesting that TNF stimulated binding by increasing the expression or accessibility of EC surface receptors for lymphocytes. Although antibodies to the lymphocyte function-associated antigen 1 alpha- or beta-chains on the T cell markedly inhibited unstimulated T-EC binding, such antibodies had no effect on the increase in EC adhesiveness induced by TNF, indicating that the increased binding resulted from the generation of an alternate binding receptor on the EC membrane. These findings provide additional evidence that cytokines participate in the mobilization of mononuclear cells in the chronic inflammatory reaction by stimulation of the adhesiveness of endothelium for circulating lymphocytes.     

Role of LFA-1 and VLA-4 in the adhesion of cloned normal and LFA-1 (CD11/CD18)-deficient T cells to cultured endothelial cells. Indication for a new adhesion pathway.

Patients with the leukocyte adhesion deficiency (LAD) syndrome have a genetic defect in the common beta 2-chain (CD18) of the leukocyte integrins. This defect can result in the absence of cell surface expression of all three members of the leukocyte integrins. We investigated the capacity of T cell clones obtained from the blood of an LAD patient and of normal T cell clones to adhere to human umbilical vein endothelial cells (EC). Adhesion of the number of LAD T cells to unstimulated EC was approximately half of that of leukocyte function-associated antigen (LFA)-1+ T cells. Stimulation of EC with human rTNF-alpha resulted in an average 2- and 2.5-fold increase in adhesion of LFA-1+ and LFA-1- cells, respectively. This effect was maximal after 24 h and lasted for 48 to 72 h. The involvement of surface structures known to participate in cell adhesion (integrins, CD44) was tested by blocking studies with mAb directed against these structures. Adhesion of LFA-1+ T cells to unstimulated EC was inhibited (average inhibition of 58%) with mAb to CD11a or CD18. Considerably less inhibition of adhesion occurred with mAb to CD11a or CD18 (average inhibition, 20%) when LFA-1+ T cells were incubated with rTNF-alpha-stimulated EC. The adhesion of LFA-1- T cells to EC stimulated with rTNF-alpha, but not to unstimulated EC, was inhibited (average inhibition, 56%) by incubation with a mAb directed to very late antigen (VLA)-4 (CDw49d). In contrast to LAD T cell clones and the LFA-1+ T cell line Jurkat, mAb to VLA-4 did not inhibit adhesion of normal LFA-1+ T cell clones to EC, whether or not the EC had been stimulated with rTNF-alpha. We conclude that the adhesion molecule pair LFA-1/intercellular adhesion molecule (ICAM)-1 plays a major role in the adhesion of LFA-1+ T cell clones derived from normal individuals to unstimulated EC. Adhesion of LFA-1-T cells to TNF-alpha-stimulated EC is mediated by VLA-4/vascular cell adhesion molecule (VCAM)-1 interactions. Since we were unable to reduce significantly the adhesion of cultured normal LFA-1+ T cells to 24 h with TNF-alpha-stimulated endothelium with antibodies that block LFA-1/ICAM-1 or VLA-4/VCAM-1 interactions, and lectin adhesion molecule-1 and endothelial leukocyte adhesion molecule-1 appeared not to be implicated, other as yet undefined cell surface structures are likely to participate in T cell/EC interactions.     

Sympathetic nerve stimulation induces local endothelial Ca2+ signals to oppose vasoconstriction of mouse mesenteric arteries

It is generally accepted that the endothelium regulates vascular tone independent of the activity of the sympathetic nervous system. Here, we tested the hypothesis that the activation of sympathetic nerves engages the endothelium to oppose vasoconstriction. Local inositol 1,4,5-trisphosphate (IP(3))-mediated Ca(2+) signals ("pulsars") in or near endothelial projections to vascular smooth muscle (VSM) were measured in an en face mouse mesenteric artery preparation. Electrical field stimulation of sympathetic nerves induced an increase in endothelial cell (EC) Ca(2+) pulsars, recruiting new pulsar sites without affecting activity at existing sites. This increase in Ca(2+) pulsars was blocked by bath application of the α-adrenergic receptor antagonist prazosin or by TTX but was unaffected by directly picospritzing the α-adrenergic receptor agonist phenylephrine onto the vascular endothelium, indicating that nerve-derived norepinephrine acted through α-adrenergic receptors on smooth muscle cells. Moreover, EC Ca(2+) signaling was not blocked by inhibitors of purinergic receptors, ryanodine receptors, or voltage-dependent Ca(2+) channels, suggesting a role for IP(3), rather than Ca(2+), in VSM-to-endothelium communication. Block of intermediate-conductance Ca(2+)-sensitive K(+) channels, which have been shown to colocalize with IP(3) receptors in endothelial projections to VSM, enhanced nerve-evoked constriction. Collectively, our results support the concept of a transcellular negative feedback module whereby sympathetic nerve stimulation elevates EC Ca(2+) signals to oppose vasoconstriction.     

Characterisation of the interaction between circulating and in vitro cultivated endothelial progenitor cells and the endothelial barrier

In vitro cultured endothelial progenitor cells (cEPC) are used for intracoronary cell therapy in cardiac regeneration. The aim of this study was to investigate whether cEPC and circulating mononuclear cells (MNC), which include a small number of in vivo circulating EPC, are able to transmigrate through the endothelial barrier into the cardiac tissue. MNC and EPC were isolated from the peripheral blood from healthy male volunteers (n = 13, 25+/-6 years) and stained with a fluorescent marker. The cells were perfused in vitro through organs with endothelial layers of different phenotypes (rat aorta, human umbilical vein, isolated mouse heart). The endothelium and the basal lamina were then stained by immunofluorescence and the cryo-sections analysed using a confocal laser scanning microscope. After perfusion through the rat aorta, an adhesion/integration of MNC was observed at the endothelial layer and the basal lamina beneath endothelial cells. However, no migration of MNC over the endothelial barrier was found. This remained true even when the cell numbers were increased (from 0.5 to 10 million cells/h), when the time of perfusion was prolonged (1.5-4 h) and when the aorta was cultivated for 24 h. In the Langendorff-perfused mouse heart with intact endothelium, no migration of MNC (1 x 10(7)) or cEPC (1 x 10(6)) was observed after 0.5 and 2 h. In conclusion, MNC and cEPC do not possess any capacity to transmigrate the endothelial barrier. In the context of stem cell therapy, these cells may therefore serve as endothelial regenerators but not as cardiomyocyte substitutes.     

Have We Neglected the Role of Fetal Endothelium in Transplacental Transport?

Maternal‐to‐fetal transfer of nutrient and other substances occurs across the placental barrier (PB) which is made up of endothelial cells (EC) on the fetal side and the syncytiotrophoblast (STB) on the maternal side. Numerous studies were conducted to explore the transport characteristics across the STB layer, which is also considered as the major resistance for maternal‐to‐fetal exchange of materials. In contrast the layer of EC has received very little attention if at all. A recently developed viable co‐culture model of the PB revealed significant resistance of the EC layer for maternal‐to‐fetal transfer of glucose. This argues for a major contribution of the EC to overall transplacental transfer of nutrients. Accordingly, it is recommended to fill the void of knowledge and expand our understanding on the role of the feto‐placental endothelium for transplacental transport characteristics.     

The reparative regeneration of the endothelium of the aortic bifurcation in rats after cryodestruction

The dynamics of reparative regeneration of the rat abdominal aortic endothelium after cryodestruction was investigated in experiments on 27 rats. In the aortic bifurcation site as compared with its infrarenal region the marked differences in the reaction of blood cells with injured and repaired vascular wall, in increase of the proliferative activity of endothelial cells and heteromorphism of endothelial monolayer, accelerated growth of myointimal thickening are found. The mechanisms of local hemodynamic influence onto the velocity and pattern on endothelial restoration are under discussion.     

A scanning electron microscopic study of rat Masugi nephritis.

Changes in the glomerular capillaries in the first phase of rat Masugi nephritis were studied by scanning electron microscopy. The changes developed immediately after the injection of nephrotoxic rabbit IgG and early endothelial lesions (2 to 6 h) were characterized by an increase in microvilli and a decrease in endothelial pores. The microvilli were fused and produced abundant pored projections (cytofolds). The peripheral endothelium was then lifted off from the glomerular basement membrane (GBM), leaving scattered endothelial fragments on the GBM. The denuded GBM exhibited a rather uniform, thick carpet-like appearance with occasional crater formation. Depositon of fibrin strands was seen associated with endothelial exfoliation. These later dissolved and were converted to a fibrinoid material, consisting of a complex of fragmented, thin fibrils. A parallel study using the electron microscope revealed that the fibrinoid material was removed by emigrating monocytic macrophages. At the stage of resolution (24 to 72 h), the denuded GBM was covered mostly with a regenerating endothelial layer. A possible process of reorganization of the endothelial pores is discussed.     

Endothelial modulation and tolerance development in the vasorelaxant responses to nitrate of rabbit aorta

We investigated the endothelial modulations in nitrate tolerance in isolated rabbit aorta. Nitrate tolerance was induced by a 72-h treatment with transdermal nitroglycerin (NTG, 0.4 mg/h) in conscious rabbits, which was verified by a 20-fold increase in the EC50 values [NTG tolerance (6.1 +/- 0.8) x 10(-7) M vs control (3.0 +/- 0.6) x 10(-8) M]. The relaxations to NTG in tolerant and nontolerant aortic strips were enhanced when their endothelia were denuded [E(-)]. In the presence of endothelium [E(+)], NTG-tolerant vessels were not tolerant to acetylcholine (ACh), which can release endothelial nitric oxide (NO), exogenous NO or 8-bromo (Br)-cGMP. In NTG-tolerant and nontolerant vessels with endothelium, concentration-response curves for NO were the same as those in endothelium-absent tolerant vessels. In both NTG-tolerant and nontolerant vessels, treatment with superoxide dismutase (SOD, 20 units/ml), an O2-. scavenger, unaffected the responses to NTG reduced in the presence of endothelium, but treatment with NG-nitro-L-arginine methyl ester (L-NAME, 10(-4) M), an NO synthase (NOS) inhibitor, reversed these reductions. Thus, our data did not indicate that an increased endothelial superoxide O2-. production contributes to nitrate tolerance. Our study suggested that (i) an impaired biotransformation process from NTG to NO is responsible for the occurrence of nitrate tolerance and (ii) vascular response to NTG enhanced by endothelial removal is related to blocked endothelial NO release.     

Regulation of production of a platelet-derived growth factor-like protein by cultured bovine aortic endothelial cells

Platelet-derived growth factor (PDGF) is a potent mitogen for cultured cells of mesenchymal origin. Known sources of PDGF or PDGF-like protein are blood platelets, several transformed cell lines, and cultured endothelial cells (EC). We have examined the regulation of production of a PDGF-like protein in cultures of bovine aortic EC using a specific radioreceptor assay for PDGF. EC constitutively secreted PDGF-like protein into serum-containing or serum-free medium. The rate of production of PDGF-like protein was constant for at least 3 weeks and was not due to release of an internal store, since cell lysis by repeated freeze/thaw cycles did not relase significant amounts of the protein. Synthesis of PDGF-like protein was sensitive to changes in the pH of the media and was maximal at pH 8.5. Production of PDGF-like protein was independent of EC growth rate: rapidly dividing cells and confluent, quiescent cells produced equal amounts per cell. However, sparse, quiescent EC produced more PDGF-like protein per cell than did confluent, quiescent cells. Several phorbol esters stimulated production of PDGF-like protein. At a concentration of 10^?6 M, a twofold stimulation was observed upon addition of the tumor promoter 12-O-tetradecanoylphorbol 13-acetate (TPA) and nearly a fourfold stimulation upon addition of the nonpromoting analog, methyl TPA. Incubation of EC with endotoxin (10 μ/ml) resulted in a twofold stimulation of PDGF-like protein production. In all experiments with endotoxin and phorbol esters, an increase in the production of PDGF-like protein was accompanied by morphological changes in the EC cultures. The cells appeared elongated and fibroblastic and exhibited low viability. A mathematical model was developed in which PDGF-like protein production was shown to consist of two separate components—production at a constant rate by healthy cells and a large burst of synthesis and secretion by dying cells. These results suggest that injurious agents may be capable of stimulating production of a growth factor by the endothelium.     

Endothelial NADPH oxidase 4 protects ApoE-/- mice from atherosclerotic lesions

Vascular reactive oxygen species (ROS) are known to be involved in atherosclerosis development and progression. NADPH oxidase 4 (Nox4) is a constitutively active ROS-producing enzyme that is highly expressed in the vascular endothelium. Nox4 is unique in its biology and has been implicated in vascular repair, however, the role of Nox4 in atherosclerosis is unknown. Therefore, to determine the effect of endothelial Nox4 on development of atherosclerosis, Apoe E-/- mice +/- endothelial Nox4 (ApoE-/- + EC Nox4) were fed a high cholesterol/high fat (Western) diet for 24 weeks. Significantly fewer atherosclerotic lesions were observed in the ApoE-/- + EC Nox4 mice as compared to the ApoE-/- littermates, which was most striking in the abdominal region of the aorta. In addition, markers of T cell populations were markedly different between the groups; T regulatory cell marker (FoxP3) was increased whereas T effector cell marker (T-bet) was decreased in aorta from ApoE-/- + EC Nox4 mice compared to ApoE-/- alone. We also observed decreased monokine induced by gamma interferon (MIG; CXCL9), a cytokine known to recruit and activate T cells, in plasma and tissue from ApoE-/- + EC Nox4 mice. To further investigate the link between endothelial Nox4 and MIG expression, we utilized cultured endothelial cells from our EC Nox4 transgenic mice and human cells with adenoviral overexpression of Nox4. In these cultured cells, upregulation of Nox4 attenuated endothelial cell MIG expression in response to interferon-gamma. Together these data suggest that endothelial Nox4 expression reduces MIG production and promotes a T cell distribution that favors repair over inflammation, leading to protection from atherosclerosis.