Maintenance Of Endothelial Integrity Research Articles

Endothelial progenitor cells and neovasculogenesis

It is has been established that endothelial progenitor cells EPC are of great interest in the maintenance of endothelial integrity and postnatal neovascularization of the adult organism’s tissues. It is shown that the formation of new blood vessels can be carried out both by angiogenesis and vasculogenesis from EPC. In this review, data are presented on the heterogeneity of the EPC in population. These cells are indentified by different markers and have different proliferative and functional capacities. They not only activate the neovascularization of tissues after damage, but also they are potential candidates for therapeutic angiogenesis.

Urotensin II promotes the proliferation of endothelial progenitor cells through p38 and p44/42 MAPK activation

Urotensin II (UII) is a vasoactive peptide with many potent effects in the cardiorenovascular system and is also possibly involved in the pathogenesis of atherosclerosis. Endothelial progenitor cells (EPCs) are involved in angiogenesis and vascular homeostasis and may be important in the maintenance of endothelial integrity. The aim of this study was to investigate whether UII has an effect on the proliferation of bone marrow-derived EPCs and the possible signaling mechanisms involved. Bone marrow-derived EPCs were isolated from male Sprague-Dawley rats and cultured in medium containing 5% fetal bovine serum. Cells were incubated with UII for 24 h. The proliferation of EPCs was analyzed by MTT assay. Western blotting was performed to determine the phosphorylation levels of mitogen-activated protein kinases (MAPKs). The results demonstrated that UII promoted the proliferation of EPCs in a concentration-dependent manner in a certain range, and the proliferation was largely suppressed by inhibitors of GPR14 and MAPKs (p38 and p44/42). UII significantly increased the phosphorylation levels of p38MAPK and p44/42MAPK, and these effects were significantly inhibited by respective inhibitors. These findings indicate that UII promotes the proliferation of rat bone marrow-derived EPCs through a process that involves MAPK activation, and provides novel insights regarding the role of UII in the EPC-mediated repair of atherosclerotic injury.

Circulating Endothelial Progenitor Cells as Biomarkers for Prediction of Cardiovascular Outcomes

Experimental studies suggest that bone marrow-derived endothelial progenitor cells (EPCs) play an important role in the maintenance of endothelial integrity and hemostasis. The number of circulating EPC has been shown to be inversely correlated with cardiovascular risk factors and vascular function and to predict cardiovascular events independent of both traditional and non-traditional risk factors. Thus, EPCs provide a clinical advantage over the use of other biomarkers as their measurement is directly associated with endothelial function, and available evidence suggests that they are consistently and significantly associated with a spectrum of cardiovascular complications, such as acute coronary syndromes and coronary artery disease. However, many issues in the field of EPC isolation and identification, particularly in regards to the effective and unequivocal molecular characterization of these cells still remain unresolved. In addition, simple EPC counts do not adequately describe cardiovascular disease risk. This limitation is attributable to variation in the definition of EPCs, the number of existing cardiovascular risk factors in different patients as well as a difference in the interaction between EPCs and other hematopoietic progenitor, inflammatory cells or platelets.

AKAP12 regulates vascular integrity in zebrafish

The integrity of blood vessels controls vascular permeability and extravasation of blood cells, across the endothelium. Thus, the impairment of endothelial integrity leads to hemorrhage, edema, and inflammatory infiltration. However, the molecular mechanism underlying vascular integrity has not been fully understood. Here, we demonstrate an essential role for A-kinase anchoring protein 12 (AKAP12) in the maintenance of endothelial integrity during vascular development. Zebrafish embryos depleted of akap12 (akap12 morphants) exhibited severe hemorrhages. In vivo time-lapse analyses suggested that disorganized interendothelial cell-cell adhesions in akap12 morphants might be the cause of hemorrhage. To clarify the molecular mechanism by which the cell-cell adhesions are impaired, we examined the cell-cell adhesion molecules and their regulators using cultured endothelial cells. The expression of PAK2, an actin cytoskeletal regulator, and AF6, a connector of intercellular adhesion molecules and actin cytoskeleton, was reduced in AKAP12-depleted cells. Depletion of either PAK2 or AF6 phenocopied AKAP12-depleted cells, suggesting the reduction of PAK2 and AF6 results in the loosening of intercellular junctions. Consistent with this, overexpression of PAK2 and AF6 rescued the abnormal hemorrhage in akap12 morphants. We conclude that AKAP12 is essential for integrity of endothelium by maintaining the expression of PAK2 and AF6 during vascular development.

Fractalkine Expression Induces Endothelial Progenitor Cell Lysis by Natural Killer Cells

BackgroundCirculating CD34+ cells, a population that includes endothelial progenitors, participate in the maintenance of endothelial integrity. Better understanding of the mechanisms that regulate their survival is crucial to improve their regenerative activity in cardiovascular and renal diseases. Chemokine-receptor cross talk is critical in regulating cell homeostasis. We hypothesized that cell surface expression of the chemokine fractalkine (FKN) could target progenitor cell injury by Natural Killer (NK) cells, thereby limiting their availability for vascular repair.Methodology/Principal FindingsWe show that CD34+-derived Endothelial Colony Forming Cells (ECFC) can express FKN in response to TNF-α and IFN-γ inflammatory cytokines and that FKN expression by ECFC stimulates NK cell adhesion, NK cell-mediated ECFC lysis and microparticles release in vitro. The specific involvement of membrane FKN in these processes was demonstrated using FKN-transfected ECFC and anti-FKN blocking antibody. FKN expression was also evidenced on circulating CD34+ progenitor cells and was detected at higher frequency in kidney transplant recipients, when compared to healthy controls. The proportion of CD34+ cells expressing FKN was identified as an independent variable inversely correlated to CD34+ progenitor cell count. We further showed that treatment of CD34+ circulating cells isolated from adult blood donors with transplant serum or TNF-α/IFN-γ can induce FKN expression.ConclusionsOur data highlights a novel mechanism by which FKN expression on CD34+ progenitor cells may target their NK cell mediated killing and participate to their immune depletion in transplant recipients. Considering the numerous diseased contexts shown to promote FKN expression, our data identify FKN as a hallmark of altered progenitor cell homeostasis with potential implications in better evaluation of vascular repair in patients.

Shear stress mechanotransduction in Endothelial Progenitor Cells (EPC) using a cone plate rheometer

Objectives: Endothelial progenitor cells (EPC) play an important role in the maintenance of endothelial integrity. Endothelial cell responses to shear stress are thought to play a critical role in blood flow dependent phenomena, including angiogenesis, vascular remodelling and arteriosclerosis.

Concerns and Hopes for Stem Cell Therapy in Cardiology: Focus on Endothelial Progenitor Cells

The crucial role played by the endothelium in cardiovascular disorders has been repetitively recognised. Endothelium injury has been implicated in atherosclerosis, thrombosis, hypertension and other cardiovascular diseases. Recently, however, research has undertaken a new avenue. As mature endothelial cells posses limited regenerative capacities, the interest has been switched to the circulating endothelial progenitor cells (EPCs). Indeed, the scientific community has made progress in understanding the role of EPCs in the maintenance of endothelial integrity and function as well as post natal neovascularisation. It has been suggested that these cells are able to home in the site of heart injury / damage and that they might take part in angiogenesis, giving hope for new treatment opportunities. There is evidence that reduced availability of EPCs or impairment of their function is associated with more severe CV disease and to comorbid risk factors. Different current drug regimes are able to influence bone marrow production and release of EPCs and several growth factors are considered for possible useful new therapeutic approaches. Thus, many studies into the potential use of EPCs in the clinical setting have recently been conducted with conflicting results. The goal of this review article is to discuss current therapies to regenerate new vessels and therefore to enhance myocardial function. The article overviews the search strategy and the pathophysiological aspects behind this therapy, consider the target currently under investigation and set the stage for new ideas.

BAS/BSCR26 Histone deacetylase 3 protects endothelial cells from inflammation via regulation of galectin 9 expression

Histone deacetylase 3 (HDAC3), a member of the class I histone deacetylases, is known to have a crucial role in endothelial cell differentiation1 2 and maintenance of endothelial integrity in...

Abstract 5219: Reduced Number of CD34+ Circulating Progenitor Cells Predict Long-term Cardiovascular Outcome in Chronic Kidney Disease Patients With Hemodialysis

Background: Patients with chronic kidney disease(CKD) on hemodialysis (HD) are the highest risk population for cardiovascular (CV) disease, and endothelial dysfunction is regarded as an important cause of CV risk in this population. Circulating endothelial progenitor cells (EPCs) are believed to be involved in maintenance of endothelial integrity, and are close proximity to CD34+ circulating progenitor cells (CPCs). We prospectively examined whether reduced number of CD34+ CPCs would predict long-term CV outcome in HD patients. Methods: The number of CD34+ CPCs was determined with the use of flow-cytometry in blood sample before dialysis session in 216 outer HD patients. To avoid the influence of body fluid overload, the ratio of CD34+ CPCs to peripheral mononuclear cells (CD34+/PMNCs) were calculated. The patients were divided into tertiles according to CD34+/PMNCs levels; tertile 1 (T1): <0.012, T2: 0.013–0.022 and T3: >0.023 (n=72 each), and were prospectively followed for 4 years. Results: During 42±10months, 67 CV events and 35 deaths (21 CV deaths) occurred. Four-year event-free survival were 54%, 68% and 82% for CV events (p=0.0013), 78%, 92% and 98% for CV death (p=0.0009) and 73%, 84% and 93% for all-cause death (p=0.0058) in T1, T2 and T3, respectively. On Cox multivariate analysis, reduced CD34+CPCs levels were independent predictor for CV events (HR 2.40, 95%CI 1.25–4.62, p=0.028 for T1 vs. T3), for CV death (HR 5.46, 95%CI 1.18–25.26, p=0.029 for T1 vs. T3) and for all-cause death (HR 3.72, 95%CI 1.37–10.09, p=0.030 for T1 vs. T3), respectively. Conclusion: These data suggest that reduced number of CD34+ CPCs predicts long-term CVoutcome in CKD patients with HD.

Endothelial progenitor cells in patients with coronary artery disease and left ventricular dysfunction

Endothelial progenitor cells (EPCs) play a key role in maintenance of endothelial integrity and postnatal neovascularization. We verified whether the number of subpopulations of EPCs is different in patients with coronary artery disease (CAD) and normal or impaired left ventricular (LV) function. Sixty-eight consecutive patients (37 men, age 60+/-18 years) with CAD were studied. All patients underwent quantitative coronary angiography and flow cytometric analysis. Patients with LV ejection fraction <45% (n=22) were compared with those with normal function (n=46). The two groups had similar age, sex, cardiovascular risk factors, medical therapy, LV dimension, and number of diseased vessels. Patients with LV dysfunction, by study design, were more symptomatic and had a lower LV ejection fraction. The two groups had similar white cell count and mononuclear cells. The absolute number of CD34 and CD133 cells was significantly (P<0.05) higher in patients with LV dysfunction as compared with patients with normal function or healthy participants. In contrast, CD14 cells were significantly (P=0.005) lower in the former patients than in the latter, whereas no significant difference was noted in the number of cells positive for CD105 among groups. Subpopulations of EPCs have a discordant behavior in CAD patients with or without LV dysfunction, with cells positive for the endothelial markers CD34 and CD133 being increased and cells that promote vasculogenesis and microvascular development being significantly reduced.

Different mechanisms of saturated versus polyunsaturated FFA-induced apoptosis in human endothelial cells

Apoptosis and underlying mechanisms were evaluated in human umbilical vein endothelial cells (HUVECs), in target tissues of late diabetic vascular complications [human aortic endothelial cells (HAECs) and human retinal endothelial cells (HRECs)], and in endothelial progenitor cells (EPCs) exposed to FFAs, which are elevated in obesity and diabetes. Saturated stearic acid concentration dependently induced apoptosis that could be mediated via reduced membrane fluidity, because both apoptosis and membrane rigidity are counteracted by eicosapentaenoic acid. PUFAs triggered apoptosis at a concentration of 300 micromol/l in HUVECs, HAECs, and EPCs, but not HRECs, and, in contrast to stearic acid, involved caspase-8 activation. PUFA-induced apoptosis, but not stearic acid-induced apoptosis, strictly correlated (P < 0.01) with protein expression of E2F-1 (r = 0.878) and c-myc (r = 0.966). Lack of c-myc expression and activity owing to quiescence or transfection with dominant negative In373-Myc, respectively, renders HUVECs resistant to PUFA-induced apoptosis. Because c-myc is abundant in growing cells only, apoptosis triggered by PUFAs, but not by saturated stearic acid, obviously depends on the growth/proliferation status of the cells. Finally, this study shows that FFA-induced apoptosis depends on the vascular origin and growth/proliferation status of endothelial cells, and that saturated stearic acid-induced apoptosis and PUFA-induced apoptosis are mediated via different mechanisms.

Vascular Endothelial Growth Factor Receptor-1 Regulates Postnatal Angiogenesis Through Inhibition of the Excessive Activation of Akt

Vascular endothelial growth factor (VEGF) binds both VEGF receptor-1 (VEGFR-1) and VEGF receptor-2 (VEGFR-2). Activation of VEGFR-2 is thought to play a major role in the regulation of endothelial function by VEGF. Recently, specific ligands for VEGFR-1 have been reported to have beneficial effects when used to treat ischemic diseases. However, the role of VEGFR-1 in angiogenesis is not fully understood. In this study, we showed that VEGFR-1 performs "fine tuning" of VEGF signaling to induce neovascularization. We examined the effects of retroviral vectors expressing a small interference RNA that targeted either the VEGFR-1 gene or the VEGFR-2 gene. Deletion of either VEGFR-1 or VEGFR-2 reduced the ability of endothelial cells to form capillaries. Deletion of VEGFR-1 markedly reduced endothelial cell proliferation and induced premature senescence of endothelial cells. In contrast, deletion of VEGFR-2 significantly impaired endothelial cell survival. When VEGFR-1 expression was blocked, VEGF constitutively activated Akt signals and thus induced endothelial cell senescence via a p53-dependent pathway. VEGFR-1(+/-) mice exhibited an increase of endothelial Akt activity and showed an impaired neovascularization in response to ischemia, and this impairment was ameliorated in VEGFR-1(+/-) Akt1(+/-) mice. These results suggest that VEGFR-1 plays a critical role in the maintenance of endothelial integrity by modulating the VEGF/Akt signaling pathway.

Increasing Evidence That Estrogen Is an Important Modulator of Bone Marrow–Mediated Cardiac Repair After Acute Infarction

Extensive experimental and clinical evidence accumulated over the past several years indicates that the infarcted heart can be repaired by endogenous as well as exogenous stem/progenitor cells. Experimental studies from several laboratories have reported that bone marrow–derived endothelial progenitor cells (EPCs) are mobilized after acute myocardial infarction (MI), home to the infarcted myocardium, and improve left ventricular (LV) perfusion and function.1 Although EPCs have been shown to differentiate into a cardiomyocytic phenotype in vitro, EPC-induced beneficial effects appear to stem primarily from myocardial neovascularization. In an effort to enhance EPC-mediated cardiovascular reparative benefits, current studies are focused on the molecular mechanistic aspects of this phenomenon and on the modulation of EPC kinetics. Article p 2261 Clinical evidence also supports an important role for EPCs in atherosclerotic cardiovascular disease. Lower numbers of colony-forming circulating EPCs are associated with an increased Framingham risk factor score and endothelial dysfunction,2 and the number of circulating EPCs predicts the severity of coronary artery disease.3 These observations underscore the fact that EPCs participate not only in tissue repair after injury but also in the maintenance of endothelial integrity and function. After a stressful event such as acute MI or myocardial ischemia, additional EPCs are mobilized from the bone marrow, home to the injured tissue, and participate in neovascularization. Taken together, these considerations suggest that enhanced cardiac repair after MI may potentially be achieved by augmenting mobilization, myocardial homing, and functionality of EPCs. Elucidation of the signaling mechanisms involved in these processes is therefore important to the development of therapeutic strategies for cardiac repair. Although the role of EPCs in cardiac repair is a relatively new field of investigation, the influence of estrogen on cardiovascular health has been studied for decades. Estrogen exerts multifaceted effects on the heart and blood vessels via genomic and …

Effects of Fluid Shear Stress on eNOS mRNA Expression and NO Production in Human Endothelial Progenitor Cells

The increases in physiological levels of fluid shear stress have beneficial effects on vascular homeostasis. Endothelial progenitor cells (EPCs) play an important role in the maintenance of endothelial integrity. We hypothesized that shear stress-mediated vascular protection is related to the upregulation of endothelial nitric oxide synthase expression in EPCs. The human EPCs exposed to in vitro shear stress levels of 5, 15 and 25 dyn/cm² for 4 h. In vitro shear stress, in a dose-dependent fashion, increased the endothelial nitric oxide synthase mRNA expression and the nitric oxide production in human EPCs. The present findings for the first time provide novel insights into the mechanisms of the physiological levels of fluid shear stress on the regulation of human EPC biologic phenotype as a potential factor, which might contribute to vascular protective activities in humans although evidence is indirect.

Sirolimus accelerates senescence of endothelial progenitor cells through telomerase inactivation

Background Sirolimus-eluting stent (SES) is commonly used to prevent in-stent restenosis but is not infrequently complicated by late angiographic stent thrombosis (LAST). On the other hand, circulating endothelial progenitor cells (EPCs) play a significant role in the maintenance of endothelial integrity. Aim We examined whether sirolimus affects differentiation, proliferative activity, senescence, colony formation, and network formation in EPCs originated from mononuclear cells (MNCs). Methods and results MNCs were isolated from peripheral blood of healthy volunteers. EPCs outgrew from the culture of MNCs in the presence of vascular endothelial growth factor. When MNCs were incubated with sirolimus at 0.01, 0.1, and 1 ng/ml for 4 days, sirolimus dose-dependently reduced the number of differentiated, adherent EPCs, as assessed by an in vitro culture assay. After ex-vivo cultivation, EPCs became senescent as determined by acidic β-galactosidase staining. When MNCs were treated with sirolimus, sirolimus dose-dependently accelerated the onset of EPCs senescence. RT-PCR analysis demonstrated that FK506-binding protein 12 (FKBP12), a receptor of sirolimus, was expressed in MNCs. To obtain an insight into the underlying downstream effects of sirolimus, we measured telomerase activity and the expression of p27 kip1. Sirolimus decreased telomerase activity dose-dependently, which was accompanied with down-regulation of the catalytic subunit, telomerase reverse transcriptase (TERT). Furthermore, sirolimus up-regulated the cell cycle inhibitor p27 kip1. Having demonstrated that sirolimus accelerated the onset of senescence, we examined whether that translated into a decrease in proliferative activity and clonal expansion. Both MTS assay and BrdU incorporation assay have shown that sirolimus treatment significantly diminished the proliferative activity in EPCs. In addition, colony forming unit assay revealed that sirolimus dramatically decreased colony formation as compared to control (no treatment). Finally, in a Matrigel assay, EPCs treated with sirolimus were shown to be less integrated into the network formation than control (no treatment). Conclusion The inhibitory effects of sirolimus on circulating EPCs potently may affect re-endotheliazation after SES implantation.

EGFL7 Is a Chemoattractant for Endothelial Cells and Is Up-Regulated in Angiogenesis and Arterial Injury

The endothelium of the adult vasculature is normally quiescent, with the exception of the vasculature of the female reproductive system. However, in response to appropriate stimuli (ie, wound healing, atherosclerosis, tumor growth and metastasis, arthritis) the vasculature becomes activated and grows new capillaries through angiogenesis. We have recently identified a novel endothelial-restricted gene, Egfl7, that encodes a 41-kd secreted protein (Fitch MJ, Campagnolo L, Kuhnert F, Stuhlmann H: Egfl7, a novel epidermal growth factor-domain gene expressed in endothelial cells. Dev Dyn 2004, 230:316-324). Egfl7 is expressed at high levels early during mouse embryonic development and is strictly associated with the vascular bed. In this study, we investigated Egfl7 expression in the quiescent adult vasculature, in the pregnant uterus, and in two different models of arterial injury, namely ballooning and ferric chloride injury. By RNA in situ hybridization, Egfl7 expression in the vasculature was found to be restricted to the endothelium of the capillaries and mature vessels. In the pregnant uterus, increased vascularization was accompanied by up-regulation of Egfl7. On arterial injury, Egfl7 expression was up-regulated in the regenerating endothelium, but not in the neointima. Importantly, the EGFL7 protein acted as a chemoattractant for embryonic endothelial cells and fibroblasts in a cell migration assay. Together, these results suggest that Egfl7 functions in the formation and maintenance of endothelial integrity and that its up-regulation may be a critical component in the reorganization of the vascular bed in response to angiogenic stimuli.

RANKL regulates endothelial cell survival through the phosphatidylinositol 3'-kinase/Akt signal transduction pathway.

The maintenance of endothelial integrity is important for prevention of vascular diseases. Several growth factors, such as bFGF and angiopoietin-1, have been shown to suppress endothelial cell apoptosis and thus help to maintain endothelial integrity. Several studies suggested that receptor activator of NF-kappaB (RANK) and its ligand (RANKL) could be involved in endothelial physiology. Using immunofluorescence and reverse transcriptase-polymerse chain reaction, we found that RANK was expressed by endothelial cells, and RANKL was expressed by arterial smooth muscle cells. Furthermore, RANKL suppressed apoptosis of primary cultured endothelial cells. The RANKL-induced survival appeared to be dependent on PI 3'-kinase activity, because wortmannin and LY294002, PI 3'-kinase-specific inhibitors, blocked the RANKL-induced survival effect. RANKL elicited the phosphorylation of the serine-threonine kinase Akt at Ser473 in a PI 3'-kinase-dependent manner. The expression of a dominant-negative form of Akt or pretreatment of Akt-specific inhibitor in endothelial cells reversed the RANKL-induced survival effect. Tumor necrosis factor-alpha, which causes endothelial cell apoptosis, induced endothelial cells to express osteoprotegerin, a decoy receptor that inhibits RANK-RANKL signaling. These findings indicate that RANK, in response to the paracrine stimulus of RANKL, may play an important role in maintaining endothelial cell integrity through the PI 3'-kinase/Akt signal transduction pathway.

Fibroblast growth factor-2, but not vascular endothelial growth factor, upregulates telomerase activity in human endothelial cells.

Telomerase plays a major role in the control of replicative capacity, a critical property for successful angiogenesis and maintenance of endothelial integrity. In this study, we examined the relationship between telomerase activity and endothelial cell proliferation as well as the regulation of this enzyme by fibroblast growth factor-2 (FGF-2) and vascular endothelial growth factor-A (VEGF). Telomerase was repressed in endothelial cells freshly derived from intact endothelium, whereas activity was present during logarithmic growth in culture. In cultured human umbilical vein endothelial cells (HUVECs), mRNA levels of hTERT-the catalytic subunit of telomerase-and enzyme activity decreased reversibly on induction of quiescence. Treatment of quiescent HUVECs with FGF-2 restored telomerase activity in a time- and dose-dependent manner, whereas VEGF had no such effect, although both factors induced comparable mitogenic responses. FGF-2, but not VEGF, upregulated the mRNA levels for hTERT and for the hTERT gene transactivation factor Sp1. Serial passage in the presence of individual growth factors accelerated the accumulation of senescent cells in VEGF-treated cultures compared with cultures treated with FGF-2. FGF-2, but not VEGF, restores telomerase activity and maintains the replicative capacity of endothelial cells.

Zinc attenuates tumor necrosis factor-mediated activation of transcription factors in endothelial cells.

The objective of the study was to test the hypothesis that zinc can protect against endothelial dysfunction by interfering with oxidative stress-mediated cellular signaling and subsequent inhibition of an endothelial cell inflammatory response. Our approach was to compare alterations on molecular and biochemical levels with changes in endothelial barrier function that occur in zinc deficient conditions.To investigate our hypothesis, endothelial cells were exposed to zinc deficient media for 2 to 10 days to deplete cellular zinc stores. Following this, half of the groups received zinc supplementation (9.2 microM) for 48 hours. The other half served as zinc deficient controls. These cells were then challenged with tumor necrosis factor-alpha (TNF) for varying time periods. Nuclear extracts were prepared from cells and analyzed for nuclear factor kappa B (NF-kappa B) and activator protein-1 (AP-1) binding. Media from cells were analyzed for interleukin 8 (IL-8) production, and cellular proteins were determined.Zinc supplementation resulted in a 74% increase in cellular zinc content. It was also shown that a 1.5 hour exposure to TNF (100 U/mL medium) significantly increased NF-kappa B and AP-1 binding, which was lowered considerably when cells were supplemented with physiological levels of zinc. Zinc supplementation also caused a marked attenuation in IL-8 expression by endothelial cells in response to TNF-mediated cell activation.Our previous data clearly show that zinc is a protective and critical nutrient for maintenance of endothelial integrity. The present data suggest that zinc may protect against cytokine-mediated activation of oxidative stress sensitive transcription factors, upregulation of inflammatory cytokines and endothelial cell dysfunction. This may have implications in understanding mechanisms of atherosclerosis.

Endothelial structural integrity is maintained during endotoxic shock in an interleukin-1 type 1 receptor knockout mouse.

The derangement of arterial endothelial cell morphology is a good indicator of a severe shock state. Because interleukin (IL)-1 has been implicated in this process, we examined the structural integrity of aortic endothelial cells in conjunction with serum IL-6 concentrations and nitric oxide levels, which are known to increase during endotoxemia in animals genetically devoid of the type 1 IL-1 receptor. Endotoxin (10 mg/kg Escherichia coli, injected intraperitoneally) (LD100) or saline vehicle was administered to adult male C57BL/129J wild-type control mice and C57BL/129J knockout mice possessing a homozygous deletion of the type 1 IL-1 receptor. The integrity of the aortic endothelium was determined by comparisons of ultrastructure. Mice injected with sterile vehicle showed normal endothelial ultrastructure with intact membranes. Wild-type and knockout control animals receiving saline vehicle showed a complete aortic endothelium (29.11 +/- .27 and 30.85 +/- .21 intact endothelial cells per millimeter of internal elastic lamina (IEL), respectively, p = N.S.). Endotoxin-treated wild-type animals showed extensive endothelial damage with most sections showing only denuded IEL on the luminal surface (1.83 +/- .38 cells/mm IEL, p < .001 vs. control). Knockout animals treated with endotoxin showed complete maintenance of endothelial structural integrity (34.08 +/- .57 cells/mm IEL, p < .001 vs. endotoxin-treated wild type) with ultrastructural morphology appearing identical to those given saline vehicle. Also, no apparent correlation was observed between serum IL-6 concentrations or serum nitric oxide levels and aortic endothelial damage. The maintenance of endothelial integrity in animals devoid of the IL-1 receptor confirms earlier observations of endothelial cell protection with IL-1 receptor antagonism and suggests that IL-1 contributes significantly to sepsis-induced endothelial damage.