Endothelial cell adhesion molecules in inflammation and postischemic reperfusion injury

Glycine-nitronyl nitroxide conjugate protects human umbilical vein endothelial cells against hypoxia/reoxygenation injury via multiple mechanisms and ameliorates hind limb ischemia/reperfusion injury in rats

Oxidative stress and inflammation play important roles in the pathogenesis of ischemia/reperfusion (I/R)-injury. The administration of antioxidants and anti-inflammatory agents has been applied to prevent I/R-injury for several decades. Of the numerous compounds administrated therapeutically in anti-oxidative stress, nitronyl nitroxide has gained increasing attention due to its continuous ability to scavenge active oxygen radicals. However, its effect is not ideal in clinical therapy. In previous study, we linked the anti-inflammatory amino acid glycine to nitronyl nitroxide and developed a novel glycine-nitronyl nitroxide (GNN) conjugate, which showed a synergetic protection against renal ischemia/reperfusion injury. However, the underlying mechanism remains unclear. In this study, a hypoxia/reoxygenation (H/R) injury model was established in human umbilical vein endothelial cells (HUVECs) and we found that the GNN conjugate significantly elevated the cell viability via reducing the apoptosis rate in H/R-treated HUVECs. Meanwhile, GNN conjugate attenuated H/R induced mitochondrial fragmentation, mitochondrial membrane potential reduction, Cytochrome c release and autophagy. To determine the extensive applicability of GNN conjugate in different I/R models and its effect in remote organs, an in vivo hind limb I/R model was established. As expected, GNN conjugate ameliorated damages of muscle and remote organs. These results demonstrate that GNN conjugate may be an effective agent against ischemia/reperfusion injury in clinical therapy.

Win 55212-2, a cannabinoid receptor agonist, attenuates leukocyte/endothelial interactions in an experimental autoimmune encephalomyelitis model

Multiple sclerosis (MS) is the most common of the immune demyelinating disorders of the central nervous system (C NS). Leukocyte/endothelial interactions are important steps in the progression of the disease and substances that interfere with these activities have been evaluated as potential therapeutic agents. C annabinoid receptor agonists have been shown to downregulate immune responses and there is preliminary evidence that they may slow the progress of MS. The purpo se of this investigation was to determine how cannabinoid recepto r agonists interfere with leukocyte rolling and adhesion. This was investigated in an experimental autoimmune encephalo myelitis (EAE) model using six to eight week old C 57BL/6 mice. Mouse myelin oligodendrocyte protein and pertussis toxin were used to induce EAE. WIN 55212-2, C B1 and C B2 antagonist were given. By use of in vivo intravital microscopy, leukocyte/endothelial interactio ns were evaluated via a cranial window implanted two days before. The results demonstrated that EAE increases leukocyte rolling and firm adhesion in the brain, and that this increased leukocyte/endothelial interactio n can be attenuated by administration of WIN 55212-2. Furthermore, use of the selective antagonists for the C B1 recepto r (SR 141716A) and the C B2 receptor (SR144528) in this study demonstrated that the cannabinoid’s inhibitory effects on leukocyte/endothelial interactions can be mediated by activating C B2 receptor.

Inflammation Modulates RLIP76/RALBP1 Electrophile-Glutathione Conjugate Transporter and Housekeeping Genes in Human Blood-Brain Barrier Endothelial Cells

Endothelial cells are often present at inflammation sites. This is the case of endothelial cells of the blood-brain barrier (BBB) of patients afflicted with neurodegenerative disorders such as Alzheimer's, Parkinson's, or multiple sclerosis, as well as in cases of bacterial meningitis, trauma, or tumor-associated ischemia. Inflammation is a known modulator of gene expression through the activation of transcription factors, mostly NF-κB. RLIP76 (a.k.a. RALBP1), an ATP-dependent transporter of electrophile-glutathione conjugates, modulates BBB permeability through the regulation of tight junction function, cell adhesion, and exocytosis. Genes and pathways regulated by RLIP76 are transcriptional targets of tumor necrosis factor alpha (TNF-α) pro-inflammatory molecule, suggesting that RLIP76 may also be an inflammation target. To assess the effects of TNF-α on RLIP76, we faced the problem of choosing reference genes impervious to TNF-α. Since such genes were not known in human BBB endothelial cells, we subjected these to TNF-α, and measured by quantitative RT-PCR the expression of housekeeping genes commonly used as reference genes. We find most to be modulated, and analysis of several inflammation datasets as well as a metaanalysis of more than 5000 human tissue samples encompassing more than 300 cell types and diseases show that no single housekeeping gene may be used as a reference gene. Using three different algorithms, however, we uncovered a reference geneset impervious to TNF-α, and show for the first time that RLIP76 expression is induced by TNF-α and follows the induction kinetics of inflammation markers, suggesting that inflammation can influence RLIP76 expression at the BBB. We also show that MRP1 (a.k.a. ABCC1), another electrophile-glutathione transporter, is not modulated in the same cells and conditions, indicating that RLIP76 regulation by TNF-α is not a general property of glutathione transporters. The reference geneset uncovered herein should aid in future gene expression studies in inflammatory conditions of the BBB.

Involvement of the nuclear factor-κB pathway in the adhesion of neutrophils to renal tubular cells after injury induced by neonatal postasphyxial serum

Nuclear factor κB (NF-κB) plays an important role in the regulation of inflammatory proteins. However, it is unclear whether the NF-κB/intercellular adhesion molecule-1 (ICAM-1) pathway is involved in the adhesion of neutrophils and renal injury after hypoxia-ischemia (HI) in neonates. In this report we investigated whether NF-κB and its downstream molecule ICAM-1 were involved in renal injury induced by postasphyxial serum (PS) from neonates. Human renal proximal tubular (HK-2) cells were preincubated with 10 % fetal calf serum (control), 20 % neonatal PS, or 20 % PS plus pyrolidine dithiocarbamate (PDTC). The expression of IκBα, NF-κB p65, and ICAM-1 in HK-2 cells was determined by Western blot and/or immunohistochemistry. Nuclear translocation of NF-κB p65 in HK-2 cells was detected by immunofluorescence and Western blot. The ICAM-1 mRNA was determined by RT-PCR. Then HK-2 cells were cultured with neutrophils from neonates with asphyxia. After HK-2 cells had been cultured with neutrophils, we detected myeloperoxidase (MPO) activity, the leakage rate of lactate dehydrogenase (LDH), and cell viability. We found that PS preincubation resulted in significantly decreased IκBα expression and increased expression of NF-κB and ICAM-1, and facilitated the nuclear translocation of NF-κB in HK-2 cells. PS preincubation increased MPO activity, leading to elevated leakage rates of LDH and decreased cell viability after neutrophil exposure. Furthermore, the inhibition of NF-κB activity by PDTC significantly upregulated IκBα expression, decreased NF-κB and ICAM-1 expression, downregulated the nuclear translocation of NF-κB, and decreased MPO activity. This leads to decreased leakage rates of LDH and increased cell viability after neutrophil exposure. Our findings suggest that NF-κB/ICAM-1 pathway may be involved in neutrophil-endothelial interactions and neonatal renal injury after HI.

Chlamydia pneumoniae heat shock protein 60 enhances expression of ERK, TLR-4 and IL-8 in atheromatous plaques of coronary artery disease patients

Chlamydia pneumoniae heat shock protein (cHSP) 60 is produced during chronic chlamydial infection and activate innate immune and inflammatory responses thereby contributing to atherogenesis. However, to date there is no apparent signaling cascade delineated in human atherosclerotic plaques in C. pneumoniae positive coronary artery disease (CAD) patients. Atherosclerotic plaques were obtained from 40 CAD patients (28 men, 12 women) attending Department of Cardio Thoracic and Vascular Surgery Safdarjung Hospital, New Delhi. Atherosclerotic plaques were used for gene expression studies at RNA level by real-time PCR and to study expression of ERK1/2, JNK1/2, NF-kB, IkkB and MCP-1 at protein level by immunoblotting. Significantly higher (p < 0.001) RNA expression was found for IL-8, TLR-2/4, TGF-β, ICAM1, VCAM1 and MAPKinase genes, whereas significantly lower (p < 0.001) RNA expression for SMAD4, IkkB, BRCA1 and IL-10 was detected in cHSP60-positive atheromatous plaque of CAD patients. Moreover, at proteins level pERK1/2 (p = 0.05), NF-kB (p = 0.017), MCP-1 (p = 0.011) was higher and IkkB expression was lower (p = 0.038) in cHSP60-positive atheromatous plaque of CAD patients. This study by using human atheromatous plaques at RNA and protein levels demonstrated higher expression of TLR-2/4, IL-8, ICAM1, VCAM1, ERK1/2 and NF-kB in cHSP60-positive CAD patients.

Sirtinol treatment reduces inflammation in human dermal microvascular endothelial cells

Histone deacetylases (HDAC) are key enzymes in the epigenetic control of gene expression. Recently, inhibitors of class I and class II HDAC have been successfully employed for the treatment of different inflammatory diseases such as rheumatoid arthritis, colitis, airway inflammation and asthma. So far, little is known so far about a similar therapeutic effect of inhibitors specifically directed against sirtuins, the class III HDAC. In this study, we investigated the expression and localization of endogenous sirtuins in primary human dermal microvascular endothelial cells (HDMEC), a cell type playing a key role in the development and maintenance of skin inflammation. We then examined the biological activity of sirtinol, a specific sirtuin inhibitor, in HDMEC response to pro-inflammatory cytokines. We found that, even though sirtinol treatment alone affected only long-term cell proliferation, it diminishes HDMEC inflammatory responses to tumor necrosis factor (TNF)α and interleukin (IL)-1β. In fact, sirtinol significantly reduced membrane expression of adhesion molecules in TNFã- or IL-1β-stimulated cells, as well as the amount of CXCL10 and CCL2 released by HDMEC following TNFα treatment. Notably, sirtinol drastically decreased monocyte adhesion on activated HDMEC. Using selective inhibitors for Sirt1 and Sirt2, we showed a predominant involvement of Sirt1 inhibition in the modulation of adhesion molecule expression and monocyte adhesion on activated HDMEC. Finally, we demonstrated the in vivo expression of Sirt1 in the dermal vessels of normal and psoriatic skin. Altogether, these findings indicated that sirtuins may represent a promising therapeutic target for the treatment of inflammatory skin diseases characterized by a prominent microvessel involvement.

Applying New Science for Old Medicines: Targeting Leukocyte-Endothelial Adhesions by Antiinflammatory Herbal Drugs

During the last two decades, considerable progress has been made in understanding the molecular mechanisms of the various leukocytes and endothelial cell adhesion molecules (cell adhesion molecules - CAMs) involved in cell-cell and cell matrix interactions. This understanding has opened up a new avenue of novel chemotherapeutic targets and bioassay models for inflammatory diseases. Recently developed In Vitro bioassays on leukocyte/endothelial cell adhesions can now offer rapid and inexpensive assessment methods for herbal medicines with claimed antiinflammatory uses. Through the use of these robust in vitro methods, active principles of herbal drugs can also be isolated thereby providing the opportunity of standardizations based on a known chemical standard(s) and pharmacology. This review highlights relevant leukocyte/endothelial CAMs targets, available in vitro methods and our strategic approach for herbal standardizations.

Plasma circulatory markers in male and female patients with coronary artery disease

OBJECTIVE

Inflammatory processes play a role in the pathogenesis of atherosclerosis, and plasma circulatory markers have been associated with cardiovascular risk. There is no single report in which adhesion molecule and circulatory cytokines have been evaluated in a single population set with coronary artery disease (CAD) on the basis of gender. Thus, we evaluated plasma circulatory markers in patients with CAD and in controls that were divided by gender (because functioning of circulatory markers and response toward conventional factors are not identical in men and women) and by conventional risk factors such as smoking and alcohol intake.

METHODS

A total of 192 patients with CAD (148 male and 44 female) and 192 controls with no symptoms of CAD (142 male and 50 female) were enrolled. Detection of concentration to high-sensitivity C-reactive protein (hsCRP), interleukin (IL)-2, IL-4, IL-6, IL-8, IL-10, IL-13, interferon (IFN)-gamma, tumor necrosis factor (TNF)-alpha, and adhesion molecules (intercellular adhesion molecule [ICAM]-1 and vascular adhesion molecule [VCAM]-1) was performed using enzyme-linked immunosorbent assay kits.

RESULTS

In male patients with CAD, levels of IL-4, IL-6, IL-8, IL-13, ICAM-1, VCAM-1, hsCRP (P < .001), and IFN-gamma (P = .003) were significantly higher compared with controls; however, levels of IL-10 were significantly lower (P < .001). In female patients with CAD, levels of IL-4, hsCRP, VCAM-1 (P = .001), and IL-13 (P = .028) were significantly higher and IL-10 levels were significantly lower (P < .001) compared with controls. In addition, levels of circulatory markers were strongly associated with male smokers and imperceptibly associated with male alcoholics and female smokers and alcoholics.

CONCLUSION

This study compared the plasma circulatory markers between patients with CAD and healthy controls, between patients with CAD who smoke and controls, and between alcoholic patients with CAD and controls divided by gender. Moreover, among circulatory markers studied, higher levels were found for IL-4, IL-13, hsCRP, and VCAM-1, and lower levels were found for IL-10 in male and female patients with CAD compared with healthy controls.

Staphylococcal peptidoglycan initiates an inflammatory response and procoagulant activity in human vascular endothelial cells: a comparison with highly purified lipoteichoic acid and TSST-1

Staphylococcus aureus is one of the most significant pathogens in human sepsis and endocarditis. A hallmark of these endovascular S. aureus infections is that the coagulation system is triggered by a tissue factor (TF)-dependent pathway. This study demonstrates that highly purified S. aureus peptidoglycan, lipoteichoic acid (LTA) and TSST-1 increase TF mRNA and TF surface protein in human umbilical vein endothelial cells (ECs). Concomitantly, peptidoglycan- and LTA-activated ECs express significant TF-dependent procoagulant activity (TF PCA). In addition peptidoglycan, but not LTA or TSST-1, induced surface expression of the EC inflammation markers ICAM-1 and VCAM-1, which supported the adhesion of monocytes to these ECs. During the coculture of peptidoglycan-activated ECs and adherent monocytes, a marked additional increase of TF PCA was observed. Marginal increases in TF PCA were observed in cocultures of monocytes with LTA- or TSST-1-activated ECs. This study defines in particular staphylococcal peptidoglycan, previously known as a potent initiator of TF PCA in monocytes, as also being an activator of a coagulant response in human ECs that is further intensified by the presence of surface-bound monocytes.

Gamma interferon confers resistance to infection with Staphylococcus aureus in human vascular endothelial cells by cooperative proinflammatory and enhanced intrinsic antibacterial activities

Vascular endothelium is an exposed target in systemic endovascular Staphylococcus aureus infections. We reported earlier that the proinflammatory and procoagulant activities of primary human umbilical vein endothelial cells (ECs) after binding and ingestion of S. aureus organisms provide the cells effective means for leukocyte-mediated bacterial elimination. Expanding on this, we now show that these ECs exhibit a modest intrinsic capacity for eliminating intracellular S. aureus that was influenced by cytokines relevant to S. aureus infections. Using various EC infection assays, we showed that gamma interferon (IFN-gamma), applied to cultures of ECs prior to or after infection with S. aureus, markedly reduced the level of infection, illustrated by lower percentages of S. aureus-infected ECs and less intracellular bacteria per infected cell. IFN-gamma-activated ECs had unaltered abilities to bind S. aureus and processed ingested bacteria by a seemingly conventional phagocytic pathway. IFN-gamma treatment rescued EC monolayers from severe injury by virulent clinical S. aureus strains or excessive bacterial numbers. Mechanistically, IFN-gamma controls S. aureus infection via IFN-gamma receptor, most likely through stimulation of intrinsic endothelial antibacterial mechanisms but independent of processes that deprive bacteria of intracellular L-tryptophan or iron. The antibacterial activity of IFN-gamma-stimulated ECs coincided with sustained or slightly elevated endothelial proinflammatory responses that supported monocyte recruitment. In conclusion, we identify IFN-gamma as a potent regulatory Th1 cytokine possessing exclusive abilities to augment intrinsic antistaphylococcal effector mechanisms in human ECs without ablating the S. aureus-induced proinflammatory EC responses and, as such, coordinating a protective efficacy of ECs against blood-borne S. aureus infection.

Variable adhesion of different red blood cell products to activated vascular endothelium under flow conditions

Red blood cells (RBCs) that have been stored prior to transfusion show increased adherence to vascular endothelium in vitro, which suggests a potential for stored blood transfusion to impede blood flow in some patients. Transfusion is often required in patients with sepsis or inflammation; however, whether activation of endothelium affects stored RBC-endothelial cell (EC) interactions is unknown. We investigated whether storage time and leukocyte content of RBC products influences the adhesion of RBCs to activated ECs. RBCs from nonleukocyte-reduced (S-RBCs), buffy-coat-poor (BCP-RBCs), and leukocyte-filtered (LF-RBCs) products and cultured EC layers were pretreated with endotoxin, tumor necrosis factor-alpha (TNF-alpha), or medium alone prior to perfusion of the RBCs across the EC layer in a continuous flow microchamber. After a single day of RBC storage, the number of adherent RBCs was increased in the endotoxin and TNF-alpha pretreated groups compared to the unactivated-control group. These differences were statistically significant for S-RBCs and LF-RBC products (P < 0.05). In contrast, there was no significant difference in RBC adherence to activated and unactivated endothelium at other time-points of RBC product storage. The strength of adhesion of stored RBCs from S-RBC products to activated ECs was not altered following treatment; however, endotoxin significantly increased the adhesive strength of LF-RBCs to endothelium. These results demonstrate that while fresh RBCs show increased adhesion to activated endothelium, storage of RBCs did not promote increased adhesion to activated endothelium. However, inflammatory conditions promote stronger adhesion of stored RBCs to ECs, which may contribute to impaired tissue perfusion in some transfusion recipients.

Human microvascular endothelial cell activation by IL-1 and TNF-alpha stimulates the adhesion and transendothelial migration of circulating human CD14+ monocytes that develop with RANKL into functional osteoclasts

Circulating pre-OCs may be recruited to locally inflamed sites through specific interactions with activated microvasculature. We found that HMVECs stimulated the adhesion and TEM of circulating pre-OCs, in an ICAM-1- and CD44-dependent manner, leading to greater RANKL-induced OC formation and bone pit resorption.

INTRODUCTION

Inflammation is critical for healing processes but causes severe tissue destruction when chronic. Local osteoclast (OC) formation and bone resorption may increase at inflammatory sites through multiple mechanisms, including direct stimulation by inflamed microvasculature of circulating OC precursor (pre-OC) migration through a blood vessel barrier into bone or joint tissue. How this might occur is not yet well understood.

MATERIALS AND METHODS

Cytokine-activated human microvascular endothelial cell (HMVEC) monolayers, with or without IL-1 and TNF-alpha preactivation (24 h), were incubated in adhesion (1-3 h) or porous transwell transendothelial migration (TEM; 3 h) assays with human peripheral blood mononuclear cells (hPBMCs) or CD14+ monocyte or CD14- lymphocyte subsets. The number of cells that adhered or transmigrated, and their ability to thereafter develop with macrophage-colony stimulating factor (M-CSF) + RANKL into bone pit-resorbing OCs, were analyzed. Immunostaining and neutralizing antibodies to key cell adhesion molecules were used to determine their potential involvement in stimulated CD14+ monocyte TEM.

RESULTS

M-CSF + RANKL caused OC and bone pit formation only from hPBMCs and CD14+ cells but not CD14- cells. Adhesion of hPBMCs or CD14+ cells but not CD14- cells was stimulated by cytokine preactivation of HMVECs and led to the full capture of all circulating pre-OCs capable of developing into OCs. Cytokine-preactivated HMVECs also promoted the postadhesion TEM of hPBMCs and CD14+ populations, resulting in markedly greater OC formation and bone pit resorption by transmigrated cells. Immunodetectable vascular cell adhesion molecule (VCAM-1), intercellular adhesion molecule (ICAM-1), and CD44 levels increased on cytokine-treated HMVEC surfaces, and neutralizing antibodies to ICAM-1 or CD44, but not VCAM-1 or platelet endothelial cell adhesion molecule (PECAM-1), inhibited stimulated CD14+ cell TEM through activated HMVECs.

CONCLUSIONS

This is the first demonstration that cytokine-activated HMVECs efficiently capture and promote the TEM of circulating pre-OCs capable of differentiating into bone-resorbing OCs. Thus, direct pre-OC recruitment by activated microvasculature at inflammatory sites may significantly contribute to normal OC bone remodeling during fracture healing or exacerbate pathological bone loss in various chronic inflammatory disorders.

Prevention of neutrophil extravasation by hepatocyte growth factor leads to attenuations of tubular apoptosis and renal dysfunction in mouse ischemic kidneys

Ischemia and reperfusion (I/R) injuries occur in numerous organs under pathophysiological conditions. In this process, neutrophils play important roles in eliciting parenchymal injuries. Using a murine model of renal I/R, we show that hepatocyte growth factor (HGF) is a natural ligand that inhibits endothelial injuries and neutrophil extravasation. In mice after renal I/R, plasma HGF levels increased, along with c-Met/HGF receptor phosphorylation in the vascular endothelium. However, this c-Met activation was transient, associated with a decrease in endogenous HGF level, and followed by neutrophil infiltration and renal dysfunction. Suppression of endothelial c-Met phosphorylation by anti-HGF IgG led to rapid progressions of neutrophil extravasation, tubular apoptosis, and renal dysfunction. Inversely, enhancement of the c-Met activation by exogenous HGF blocked endothelial/tubular apoptotic injuries and acute renal failure. In this process, HGF prevented endothelial nuclear factor kappaB activation and inhibited induction of an adhesion molecule (ICAM-1), resulting in attenuated vascular edema and neutrophil infiltration. Thus, we conclude that 1) the HGF/c-Met system of endothelial cells confers an initial barrier to block neutrophil infiltration, and 2) transient and insufficient HGF production allows manifestation of postischemic renal failure. Our study provides a rationale for why HGF supplementation elicits therapeutic effects in ischemic kidneys.

Effect of maternal anti-HPA-1a antibodies and polyclonal IVIG on the activation status of vascular endothelial cells

Maternal anti-HPA-1a antibodies can cause severe fetal and neonatal alloimmune thrombocytopenia (FNAIT), complicated by intracranial haemorrhage (ICH). Antenatal treatment with maternal intravenous immunoglobulin (IVIG) seems to protect against ICH even when thrombocytopenia persists. The aim of this study was to investigate if anti-HPA-1a antibodies and IVIG potentially affect vascular endothelial cells (ECs) in order to identify susceptibility for ICH. Human umbilical cord endothelial cells (HUVEC) were incubated with anti-HPA-1a antibodies with or without polyclonal IVIG and evaluated for EC activation. Maternal sera with anti-HPA-1a antibodies affected neither the EC expression of intracellular adhesion molecule-1 (ICAM-1), vascular adhesion molecule-1 (VCAM-1) and tissue factor (TF) nor the release of van Willebrand factor (vWF) or interleukin (IL)-8 nor the integrity of ECs. Maternal sera obtained after IVIG treatment and polyclonal IVIG decrease constitutive and cytokine-induced ICAM-1 and VCAM-1 expression on ECs. The results show that maternal anti-HPA-1a antibodies cause no activation or damage of ECs in this model. The clinical relevance of the de-activating properties of IVIG on EC activation with respect to ICH deserves further investigation.

Irradiation of mechanically-injured human arterial endothelial cells leads to increased gene expression and secretion of inflammatory and growth promoting cytokines

Radiation therapy is applied to inhibit neointima formation after percutaneous transluminal coronary angioplasty (PTCA). In this study, we evaluated the effect of irradiation on re-endothelialisation of circular denuded tracks made in post-confluent cultures of arterial endothelial cells (ECs) and on cellular factors involved in this process. Image analysis and time-lapse microcinematography revealed cell migration into denuded areas starting 4h after injury. Fifty percent coverage was achieved at 14.8 +/- 2.0 h. Using competitive PCR and flow cytometry techniques, no significant changes in mRNA expression of interleukin-1beta (IL-1beta), interleukin-8 (IL-8), basic fibroblast growth factor (bFGF or FGF-2), transforming growth factor-beta1 (TGF-beta1), platelet-derived growth factor A (PDGF-A), platelet-derived growth factor B (PDGF-B) and tissue factor (TF), and surface molecule expression of anti-intercellular adhesion molecule-1 (ICAM-1), anti-vascular cell adhesion molecule-1 (VCAM-1), anti-platelet/endothelial cell adhesion molecule-1 (PECAM-1), MHC-1, TF and Fas were observed. However, injury did significantly (P < 0.05) elevate the release of IL-8 and FGF-2 protein in the cell culture supernatant, as assessed by ELISA. Radiation (15Gy) given immediately after injury did not affect the kinetics of re-endothelialisation up to 48 h, in spite of the fact that no cell divisions were observed. Thereafter cell density decreased and cultures deteriorated. Compared to cultures exposed to injury alone, radiation induced significant (P < 0.05) increases in mRNA levels of IL-8 (1.35 +/- 0.10-fold increase at 4h), FGF-2 (1.62 +/- 0.10-fold at 4h; 1.76 +/- 0.33-fold at 24h) and IL-1beta (2.76 +/- 0.40-fold at 24h), whereas mRNA levels of TGF-beta1, PDGF-A and PDGF-B increased about 1.2-fold. IL-8 and FGF-2 protein concentrations in the media were higher than those observed in non-irradiated injured cell cultures; however, this difference was not significant. Radiation induced a 2.3 +/- 0.3-fold increase (P < 0.05) in Fas surface expression only. In conclusion, irradiation of mechanically-injured human EC leads to increased gene expression and protein secretion of inflammatory and growth promoting cytokines.

Targeted deletion of CD44v7 exon leads to decreased endothelial cell injury but not tumor cell killing mediated by interleukin-2-activated cytolytic lymphocytes

In the current study, we investigated the nature and role of CD44 variant isoforms involved in endothelial cell (EC) injury and tumor cell cytotoxicity mediated by IL-2-activated killer (LAK) cells. Treatment of CD44 wild-type lymphocytes with IL-2 led to increased gene expression of CD44 v6 and v7 variant isoforms and to significant induction of vascular leak syndrome (VLS). CD44v6-v7 knockout (KO) and CD44v7 KO mice showed markedly reduced levels of IL-2-induced VLS. The decreased VLS in CD44v6-v7 KO and CD44v7 KO mice did not result from differential activation and expansion of CD8+ T cells, NK, and NK-T cells or from altered degree of perivascular lymphocytic infiltration in the lungs. LAK cells from CD44v7 KO mice showed a significant decrease in their ability to adhere to and mediate lysis of EC but not lysis of P815 tumor cells in vitro. CD44v7-mediated lysis of EC by LAK cells was dependent on the activity of phosphatidylinositol 3-kinase and tyrosine kinases. Interestingly, IL-2-activated LAK cells expressing CD44hi but not CD44lo were responsible for EC lysis. Furthermore, lysis of EC targets could be blocked by addition of soluble or enzymatic cleavage of CD44v6-v7-binding glycosaminoglycans. Finally, anti-CD44v7 mAbs caused a significant reduction in the adherence to and killing of EC and led to suppression of IL-2-induced VLS. Together, this study suggests that the expression of CD44v7 on LAK cells plays a specific role in EC injury and that it may be possible to reduce EC injury but not tumor cell killing by specifically targeting CD44v7.

Changes of tissue factor-dependent coagulant activity mediated by adhesion between polymorphonuclear leukocytes and endothelial cells

The purpose of this study was to examine whether polymorphonuclear leukocytes (PMNs) facilitate a tissue factor, a physiologic initiator of coagulation in endothelial cells, -dependent coagulant activity (TF activity). The TF activity in bovine endothelial cells (BAECs) was significantly increased in a concentration-dependent manner by PMNs (1 x 10(5) - 1 x 10(7) cells/ml) without affecting the treatment of N-formyl-methionyl-leucyl-phenylalanine, a selective activator of PMNs, and the addition of PMNs finally resulted in cell damage as evaluated by the lactate dehydrogenase leakage method. In the same conditions, an increase of adhesion between PMNs and BAECs was also observed in a time-dependent manner. However, since direct adhesion of PMNs to BAECs was impossible by using the transwell, PMNs failed to induce any changes in the TF activity. Hence, the change of TF activity found here might be closely related to the PMNs adhesion to BAECs. Indeed, anti-intercellular adhesion molecule-1 (anti-ICAM-1) antibody blocked the increase of TF activity in BAECs. These findings suggest that PMNs could increase TF activity in endothelial cells, which is triggered by adhesion to endothelial cells through ICAM-1.

Monocytes augment bacterial species- and strain-dependent induction of tissue factor activity in bacterium-infected human vascular endothelial cells

In bacterial endocarditis (BE), intravascular infection with Staphylococcus aureus, Streptococcus sanguis, or Staphylococcus epidermidis can lead to formation of a fibrin clot on the inner surface of the heart and cause heart dysfunction. The events that start the coagulation in the early stage of the disease are largely unknown. We have recently shown that human endothelial cells (EC) upon binding and internalization of S. aureus, but not S. sanguis or S. epidermidis, express tissue factor (TF)-dependent procoagulant activity (TFA). The present study shows that infection of EC with these three pathogens induces surface expression of intracellular adhesion molecule 1 (ICAM-1) and vascular cell adhesion molecule 1 (VCAM-1) and monocyte adhesion. Subsequent coculture of these cells synergistically enhanced TFA, which was exclusively dependent on TF molecules that were expressed on EC during coculture. TFA induction required direct contact between monocytes and bacterium-infected EC, but the signals for this response were not generated by the binding of monocytes through their beta(2)- or alpha(4)-integrins to ICAM-1 or VCAM-1, respectively, on infected EC. The mechanism by which monocytes induce TFA in bacterium-infected EC was partly mediated by the proinflammatory cytokine interleukin-1 produced by the cells during coculture. Endogenous tumor necrosis factor alpha was not involved. This modulating effect of monocytes on species- and strain-dependent TFA of bacterium-infected EC supports our hypothesis that in an early stage in the pathogenesis of BE, as well as other intravascular infections that lead to detrimental fibrin formation, the coagulation cascade can be activated on the surfaces of EC as a consequence of specific interactions between pathogenic bacteria, EC, and monocytes.

Clinical significance of anti-endothelial cell antibody in renal transplant recipients

In order to evaluate the role of anti-endothelial cell antibody (AECA) in acute rejection in renal transplantation, serum AECA IgG titers were measured in 68 healthy controls, 111 chronic hemodialysis (HD) patients and 58 first renal transplant recipients. The AECA titer in hemodialysis patients was higher than in healthy controls (13.9 +/- 5.0 vs. 4.8 +/- 2.3 U/mL, p < 0.01). In transplant recipients, AECA titers were not affected by dialysis mode (HD vs. CAPD vs. non-dialysis; 9.6 +/- 7.6 vs. 7.9 +/- 3.9 vs. 11.9 +/- 3.1 U/mL, p > 0.05). After renal transplantation, AECA titer was decreased significantly (vs. 4.7 +/- 3.6 U/mL. p < 0.01). The serum AECA IgG titers increased significantly in recipients with acute rejection (6.9 +/- 3.1 vs. 13.5 +/- 9.9 U/mL, p < 0.01), but decreased to 5.6 +/- 3.0 U/mL (p < 0.01) after formal rejection therapy. In the recipients with acute rejection (n = 27), the pre-renal transplant AECA titer was higher than in that without acute rejection (14.0 +/- 8.6 vs. 7.7 +/- 3.8 U/mL, p < 0.01). The results of this study lead us to conclude that pre- and post-renal transplant AECA titer might be a useful predictor for acute rejection and useful for monitoring acute rejection in renal transplant recipients.

Renal ischemia--reperfusion injury: an inescapable event affecting kidney transplantation outcome

Ischemia--reperfusion (I-R) injury has been shown to be a common cause of late and irreversible complications during a variety of standard medical and surgical procedures. The pathogenesis of events which follow the I-R involves both injured endothelium and activated leukocytes and their interaction. In kidney transplantation, an I-R injury occurs in situations such as graft harvesting, cold storage and surgery. Clinical consequences of I-R injury have been considered to be delayed graft function and acute rejection in the short term and chronic rejection late after transplantation. Here we focused on current knowledge of pathophysiology of renal I-R injury in kidney transplantation and on possibilities of experimental therapy.

Bacterial species- and strain-dependent induction of tissue factor in human vascular endothelial cells

A cardinal process in bacterial endocarditis (BE) is the activation of the clotting system and the formation of a fibrin clot on the inner surface of the heart, the so-called endocardial vegetation. The processes that lead to the activation of the clotting system on endothelial surfaces upon exposure to bacteria are largely unknown. In the present study, we investigated in an in vitro model whether infection of human endothelial cells (EC) with bacteria that are relevant to BE, such as Staphylococcus aureus, Streptococcus sanguis, and Staphylococcus epidermidis, leads to induction of tissue factor (TF)-dependent procoagulant activity (TFA) and whether this process is influenced by host factors, such as interleukin-1 (IL-1), that are produced in response to the bacteremia in vivo. The results show that S. aureus binds to and is internalized by EC, resulting in expression of TF mRNA and TF surface protein as well as generation of TFA within 4 to 8 h after infection. No TFA was found when EC were exposed to UV-irradiated S. aureus or bacterial cell wall fragments. S. sanguis and S. epidermidis, although also binding to EC, did not induce endothelial TFA. This indicates a species and strain dependency. EC also expressed TFA after exposure to IL-1. The enhanced TFA of EC after exposure to S. aureus was not prevented by IL-1 receptor antagonist, arguing against an auto- or paracrine contribution of endogenous IL-1. When IL-1 was applied together with bacteria, this had a synergistic effect on the induction of EC TFA. This was found in particular with S. aureus but also, although to a lesser degree, with S. sanguis and S. epidermidis. This influence of IL-1 on the species- and strain-dependent induction of EC TFA suggests that bacterial factors as well as host factors orchestrate the induction of coagulation in an early stage in the pathogenesis of endovascular disease, such as BE.