Activation and homologous desensitization of human endothelial cells by CD40 ligand, tumor necrosis factor, and interleukin 1

The causal role of intestinal microbiome in development of pre-eclampsia

The correlation of pre-eclampsia (PE) and intestinal microbiome has been widely demonstrated in existing research, whereas their causal relationship has been rarely explored. The causal relationship between intestinal microbiome and PE risk was examined using large-scale genome-wide association studies (GWAS) summary statistics. To be specific, the causal microbial taxa for PE were identified using the two-sample Mendelian randomization (MR) method. The results were verified to be robust through comprehensive sensitive analyses, and the independence of causal relationship was ensured through novel multivariable MR analyses. The possibility of reverse relationships was ruled out through reverse-direction MR analyses. Lastly, the biofunction was explored through enrichment analysis, and a series of validations of PE results in a second GWAS were performed to confirm the results. After correction, four microbial taxa, including Streptococcus genus for PE (FDR q = 0.085), Olsenella genus for PE (FDR q = 0.085), Enterobacteriales order for PE (FDR q = 0.0134), and Akkermansia genus for PE (FDR q = 0.015), had a causal relationship to diverse joint PE (FDR q < 0.15). Moreover, when three different methods were employed on basis of the nominal significance (P < 0.05), five suggestive microbial taxa took on significance. The effect of heterogeneity and horizontal pleiotropy was excluded through sensitive analysis, and the possibility of horizontal pleiotropy of BMI was ruled out through multivariable MR analysis. The protective mechanism of the identified taxa against PE was illustrated through GO enrichment analysis and KEGG pathways. A number of microbial taxa had a causal relationship to PE. The result of this study provides more insights into intestinal microbiome in the pathology of PE.

Identification and functional characterization of CD154 in T cell-dependent immune response in Nile tilapia (Oreochromis niloticus)

CD154, a member of the TNF superfamily, is a multifunctional molecule highly expressed in activated T cells, and plays important roles in T cell-dependent humoral immune response. In this study, CD154 of Nile tilapia (Oreochromis niloticus) was identified, and its functions in the T cell-dependent immune response were demonstrated. The open reading frame (ORF) of OnCD154 is 699 bp, encoding a protein of 232 amino acids with a 23 amino acid transmembrane region. Amino acid sequence of OnCD154 is highly homologous to that of other teleost fish, especially rainbow trout. Quantitative real-time PCR (qRT-PCR) demonstrated that mRNA of OnCD154 is highly expressed in immune organs, especially in spleen, thymus, gills, head kidney, etc. In addition, the anti-OnCD154 polyclonal antibody (anti-(r)OnCD154) was successfully prepared, and it can react with natural protein in head kidney leukocytes. Following two immunizations with keyhole limpet hemocyanin (KLH) in vivo, the significantly up-regulated expression level of OnCD154 mRNA appeared earlier (fifth day) and higher (42.9 folds) in the second challenge than the first on in head kidney. Further, after stimulation with KLH in vitro, the expressions of T cell-dependent immune response-related molecules (activated T cell specific surface molecules CD3ε and CD154) and B cell differentiation-related molecules (Blimp1 and sIgM) and CD40 were significantly up-regulated in head kidney leukocytes. Moreover, the up-regulated expressions of these molecules were blocked with the treatment of anti-(r)OnCD154 antibody. Taken together, these results indicate that OnCD154 might get involved in T cell-dependent immune response, and provide a new insight into the humoral immune response of teleost fish.

The human glomerular endothelial cells are potent pro-inflammatory contributors in an in vitro model of lupus nephritis

Juvenile-onset lupus nephritis (LN) affects up to 80% of juvenile-onset systemic lupus erythematosus patients (JSLE). As the exact role of human renal glomerular endothelial cells (GEnCs) in LN has not been fully elucidated, the aim of this study was to investigate their involvement in LN. Conditionally immortalised human GEnCs (ciGEnCs) were treated with pro-inflammatory cytokines known to be involved in LN pathogenesis and also with LPS. Secretion and surface expression of pro-inflammatory proteins was quantified via ELISA and flow cytometry. NF-κΒ and STAT-1 activation was investigated via immunofluorescence. Serum samples from JSLE patients and from healthy controls were used to treat ciGEnCs to determine via qRT-PCR potential changes in the mRNA levels of pro-inflammatory genes. Our results identified TNF-α, IL-1β, IL-13, IFN-γ and LPS as robust in vitro stimuli of ciGEnCs. Each of them led to significantly increased production of different pro-inflammatory proteins, including; IL-6, IL-10, MCP-1, sVCAM-1, MIP-1α, IP-10, GM-CSF, M-CSF, TNF-α, IFN-γ, VCAM-1, ICAM-1, PD-L1 and ICOS-L. TNF-α and IL-1β were shown to activate NF-κB, whilst IFN-γ activated STAT-1. JSLE patient serum promoted IL-6 and IL-1β mRNA expression. In conclusion, our in vitro model provides evidence that human GEnCs play a pivotal role in LN-associated inflammatory process.

Downregulation of GATA6 in mTOR-inhibited human aortic endothelial cells: effects on TNF-α-induced VCAM-1 expression and monocytic cell adhesion

Increased expression of vascular cell adhesion molecule 1 (VCAM-1) on the aortic endothelium is an early marker of atherogenesis, promoted in part by elevated levels of inflammatory cytokines such as TNF-α. Mammalian target of rapamycin (mTOR) is a ubiquitous signaling molecule that has been considered to contribute to diverse cellular processes through mTOR complex 1 (mTORC1) or complex 2 (mTORC2). This study aimed to elucidate the role of mTOR signaling in TNF-α-induced VCAM-1 expression by the arterial endothelium. Primary human aortic endothelial cells (HAECs) were treated with low-dose (0.1 ng/ml) TNF-α, and VCAM-1 expression was measured by real-time quantitative PCR, Western blot analysis, and flow cytometry. Inhibition of mTOR through siRNA-mediated depletion or treatment with chemical inhibitors rapamycin or torin 1 suppressed VCAM1 transcription, which translated to inhibition of VCAM-1 surface expression by HAECs and concomitant decreased adhesion of monocytes. A promoter luciferase assay and chromatin immunoprecipitation indicated that mTOR regulated VCAM1 transcription through a mechanism involving transcription factor GATA6. Activation of PKC-α and an increase in miR-200a-3p expression, caused by mTOR inhibition but not disruption of mTORC1 or mTORC2 singly or together, decreased TNF-α-induced GATA6 expression and its enrichment at the VCAM1 promoter. In conclusion, mTOR inhibition activates PKC-α independently of disruption of mTORC1 and/or mTORC2, which challenges the conventional wisdom regarding mTOR signaling. Moreover, mTOR signals through transcriptional and posttranscriptional mechanisms to elicit maximal cytokine-induced endothelial inflammation that precedes atherosclerosis. NEW & NOTEWORTHY Both mammalian target of rapamycin (mTOR) complex 1 (mTORC1) and mTORC2 contribute to PKC-α activation in the human aortic endothelium. Inhibition of mTOR is not equivalent to disruption of mTORC1 and/or mTORC2 in affecting human aortic endothelial cell signaling. Specifically, inhibition of mTOR causes PKC-α activation and miR-200a-3p upregulation, which independently suppresses TNF-α-induced transcription factor GATA6 expression and subsequently inhibits VCAM-1 expression and monocytic cell adhesion onto the aortic endothelium.

TNF inhibits catecholamine production from induced sympathetic neuron-like cells in rheumatoid arthritis and osteoarthritis in vitro

Synovial adipose stem cells (sASC) can be differentiated into catecholamine-expressing sympathetic neuron-like cells to treat experimental arthritis. However, the pro-inflammatory tumor necrosis factor (TNF) is known to be toxic to catecholaminergic cells (see Parkinson disease), and this may prevent anti-inflammatory effects in inflamed tissue. We hypothesized that TNF exhibits inhibitory effects on human differentiated sympathetic tyrosine hydroxylase-positive (TH+) neuron-like cells. For the first time, iTH+ neuron-like sympathetic cells were generated from sACSs of rheumatoid arthritis (RA) and osteoarthritis (OA) synovial tissue. Compared to untreated controls in both OA and RA, TNF-treated iTH+ cells demonstrated a weaker staining of catecholaminergic markers in cell cultures of RA/OA patients, and the amount of produced noradrenaline was markedly lower. These effects were reversed by etanercept. Exposure of iTH+ cells to synovial fluid of RA patients showed similar inhibitory effects. In mixed synovial cells, significant effects of TNF on catecholamine release were observed only in OA. This study shows that TNF inhibits iTH+ synovial cells leading to the decrease of secreted noradrenaline. This might be a reason why discovered newly appearing TH+ cells in the synovium are not able to develop their possible full anti-inflammatory role in arthritis.

Platelets and cancer angiogenesis nexus

There has been remarkable insight into the importance of platelets in a wide range of pathophysiologic events, including inflammation and cancer progression. Thrombocytosis in cancer patients is a common finding. Tumor cells induce platelet activation and subsequent aggregation through direct and indirect mechanisms. Platelets are recognized to contribute to metastatic dissemination. There is plenty of evidence that components of the hemostatic system contribute to the process of angiogenesis. Furthermore, there are accumulated data on the substantial influence of blood platelets in the process of blood vessel formation during malignancy. Platelets appear to be the main physiologic transporters of proangiogenic and antiangiogenic factors. Moreover, they influence the process of angiogenesis through platelet-derived microparticles, microRNA, lipids, and variety of surface receptors. Platelets contribute to early and late stages of angiogenesis. Available data support the overall stimulatory effect of platelets on tumor angiogenesis. It raises the possibility that interfering with platelet function may be an effective antineoplastic treatment strategy.

CD40L and TNF both activate the classical NF-κB pathway, which is not required for the CD40L induced alternative pathway in endothelial cells

CD40L and TNF signal through engagement of their respective receptors, which are both members of the TNF receptor family. They use partially common signaling molecules leading, among others, to activation of the NF-κB pathway. However, whereas TNF activates the classical, CD40L has been reported to activate the alternative NF-κB pathway, leading to the anticipation that differences in the pattern of inflammatory gene expression would occur. Here, we have compared the gene expression repertoire of CD40L (CD154) and TNF stimulated HUVEC and report that unexpectedly, apart from a stronger response to TNF, no major qualitative differences could be observed. This applies for the period of up to 6 h, a time where the alternative pathway has already been activated. Analysis of the early events after receptor engagement revealed that both TNF and CD40L activate the classical NF-κB pathway, and confirm activation of the alternative by the latter. Furthermore, using genetic and pharmacological inhibition of the classical pathway we show that activation of the alternative occurs independently of the former. This reveals novel insights into NF-κB signaling by CD40L and TNF in endothelial cells.

JNK and NADPH oxidase involved in fluoride-induced oxidative stress in BV-2 microglia cells

Excessive fluoride may cause central nervous system (CNS) dysfunction, and oxidative stress is a recognized mode of action of fluoride toxicity. In CNS, activated microglial cells can release more reactive oxygen species (ROS), and NADPH oxidase (NOX) is the major enzyme for the production of extracellular superoxide in microglia. ROS have been characterized as an important secondary messenger and modulator for various mammalian intracellular signaling pathways, including the MAPK pathways. In this study we examined ROS production and TNF-α, IL-1β inflammatory cytokines releasing, and the expression of MAPKs in BV-2 microglia cells treated with fluoride. We found that fluoride increased JNK phosphorylation level of BV-2 cells and pretreatment with JNK inhibitor SP600125 markedly reduced the levels of intracellular O₂^·− and NO. NOX inhibitor apocynin and iNOS inhibitor SMT dramatically decreased NaF-induced ROS and NO generations, respectively. Antioxidant melatonin (MEL) resulted in a reduction in JNK phosphorylation in fluoride-stimulated BV-2 microglia. The results confirmed that NOX and iNOS played an important role in fluoride inducing oxidative stress and NO production and JNK took part in the oxidative stress induced by fluoride and meanwhile also could be activated by ROS in fluoride-treated BV-2 cells.

TWEAK inhibits TRAF2-mediated CD40 signaling by destabilization of CD40 signaling complexes

We found recently that TNF-like weak inducer of apoptosis (TWEAK) and fibroblast growth factor-inducible-14 (Fn14) by virtue of their strong capability to reduce the freely available cytoplasmic pool of TNFR-associated factor (TRAF)2 and cellular inhibitors of apoptosis (cIAPs) antagonize the functions of these molecules in TNFR1 signaling, resulting in sensitization for apoptosis and inhibition of classical NF-κB signaling. In this study, we demonstrate that priming of cells with TWEAK also interferes with activation of the classical NF-κB pathway by CD40. Likewise, there was strong inhibition of CD40 ligand (CD40L)-induced activation of MAPKs in TWEAK-primed cells. FACS analysis and CD40L binding studies revealed unchanged CD40 expression and normal CD40L-CD40 interaction in TWEAK-primed cells. CD40L immunoprecipitates, however, showed severely reduced amounts of CD40 and CD40-associated proteins, indicating impaired formation or reduced stability of CD40L-CD40 signaling complexes. The previously described inhibitory effect of TWEAK on TNFR1 signaling has been traced back to reduced activity of the TNFR1-associated TRAF2-cIAP1/2 ubiquitinase complex and did not affect the stability of the immunoprecipitable TNFR1 receptor complex. Thus, the inhibitory effect of TWEAK on CD40 signaling must be based at least partly on other mechanisms. In line with this, signaling by the CD40-related TRAF2-interacting receptor TNFR2 was also attenuated but still immunoprecipitable in TWEAK-primed cells. Collectively, we show that Fn14 activation by soluble TWEAK impairs CD40L-CD40 signaling complex formation and inhibits CD40 signaling and thus identify the Fn14-TWEAK system as a potential novel regulator of CD40-related cellular functions.

β3-Adrenergic receptor stimulation induces E-selectin-mediated adipose tissue inflammation

Inflammation induced by wound healing or infection activates local vascular endothelial cells to mediate leukocyte rolling, adhesion, and extravasation by up-regulation of leukocyte adhesion molecules such as E-selectin and P-selectin. Obesity-associated adipose tissue inflammation has been suggested to cause insulin resistance, but weight loss and lipolysis also promote adipose tissue immune responses. While leukocyte-endothelial interactions are required for obesity-induced inflammation of adipose tissue, it is not known whether lipolysis-induced inflammation requires activation of endothelial cells. Here, we show that β(3)-adrenergic receptor stimulation by CL 316,243 promotes adipose tissue neutrophil infiltration in wild type and P-selectin-null mice but not in E-selectin-null mice. Increased expression of adipose tissue cytokines IL-1β, CCL2, and TNF-α in response to CL 316,243 administration is also dependent upon E-selectin but not P-selectin. In contrast, fasting increases adipose-resident macrophages but not neutrophils, and does not activate adipose-resident endothelium. Thus, two models of lipolysis-induced inflammation induce distinct immune cell populations within adipose tissue and exhibit distinct dependences on endothelial activation. Importantly, our results indicate that β(3)-adrenergic stimulation acts through up-regulation of E-selectin in adipose tissue endothelial cells to induce neutrophil infiltration.

Ferritin as a novel reporter gene for photoacoustic molecular imaging

Reporter genes may serve as endogenous contrast agents in the field of photoacoustic (PA) molecular imaging (PMI), enabling greater characterization of detailed cellular processes and disease progression. To demonstrate the feasibility of using ferritin as a reporter gene, human melanoma SK-24 (SK-MEL-24) cells were co-transfected with plasmid expressing human heavy chain ferritin (H-FT) and plasmid expressing enhanced green fluorescent protein (pEGFP-C1) using lipofectamine™ 2000. Nontransfected SK-MEL-24 cells served as a negative control. Fluorescent imaging of GFP confirmed transfection and transgene expression in co-transfected cells. To detect iron accumulation due to ferritin overexpression in SK-MEL-24 cells, a focused high-frequency ultrasonic transducer (60 MHz, f/1.5), synchronized to a pulsed laser (fluence < 5 mJ/cm(2)) was used to scan the PA signal at a wide range NIR wavelengths (850-950 nm). PA signal intensity from H-FT transfected SK-MEL-24 cells was about 5-9 dB higher than nontransfected SK-MEL-24 cells at 850-950 nm. Immunofluorescence and RT-PCR analysis both indicate high levels of ferritin expression in H-FT transfected SK-MEL24 cells, with little ferritin expression in nontransfected SK-MEL-24 cells. In this study, the feasibility of using ferritin as a reporter gene for PMI has been demonstrated in vitro. The use of ferritin as a reporter gene represents a novel concept for PMI using an endogenous contrast agent and may provide various opportunities for molecular imaging and basic science research.

Polymorphism G-308A in the promoter of the tumor necrosis factor-α gene and its association with the risk of venous thromboembolism

The main abnormalities associated with the increased risk of venous thrombosis are the inherited deficiencies of antithrombin, protein C, protein S, the point mutations known as factor V Leiden and factor II G20210A. The association of other specific genes with thrombotic risk is less known. G-308A polymorphism in the promoter area of the gene coding for tumor necrosis factor α (TNF-α) is associated with an increased transcription activity of this gene, increased TNF-α production and subsequent predisposition to some illnesses. The aim of this work was to study the link between this polymorphism and predisposition to deep venous thrombosis (DVT). The research determined the frequency of the variant allele -308A in the gene for TNF-α in a group of 67 patients diagnosed with DVT and in a group of 62 healthy volunteers. We confirmed statistically significant link between the occurrence of the variant allele -308A and DVT (P = 0.02). This mutation was associated with a 2.64-fold greater risk of venous thrombosis, 95% confidence interval (1.19-5.87). When excluding heterozygous and homozygous carriers of the Leiden mutation from both groups, the difference between the occurrence of the variant allele -308A in the groups of ill and healthy individuals remained statistically significant (P = 0.04). The statistical significance was also confirmed after the exclusion of patients with mutation in the gene for prothrombin (P = 0.02). The results of this work imply possible association between the variant allele -308A and the development of DVT.

Group B streptococcal colonization and the risk of pre-eclampsia

To determine if there was an association between recto-vaginal group B streptococcus (GBS) colonization and pre-eclampsia, two cross-sectional studies were conducted using statewide hospital databases. The first study analysed data from the state of Florida, USA, and included 190 645 women who were discharged in 2001. This dataset was used to generate the hypothesis that GBS colonization is associated with pre-eclampsia. The second study tested the GBS hypothesis using the records of 577 153 women who delivered in 2004 or 2005 in Texas, USA. Adjusted odds ratios (aOR) for the outcome of pre-eclampsia comparing GBS-positive to GBS-negative women were calculated using logistic regression. The aOR for the association between GBS carriage and pre-eclampsia was 0·71 [95% confidence interval (CI) 0·65–0·77] in the Florida dataset. In the Texas dataset, the overall prevalence of GBS carriage was 14·1% while the overall prevalence of pre-eclampsia was 4·0%. GBS carriers were 31% less likely than non-carriers to have pre-eclampsia (aOR 0·69, 95% CI 0·66–0·72) in Texas. In two large statewide analyses, GBS carriage was inversely associated with pre-eclampsia. A sensitivity analysis revealed that misclassification of GBS status is not a likely explanation of our findings.

Detection and monitoring of the multiple inflammatory responses by photoacoustic molecular imaging using selectively targeted gold nanorods

In vitro cell experiments have been performed to detect and monitor the upregulation of intercellular adhesion molecule-1 (ICAM-1) and E-selectin simultaneously by photoacoustic molecular imaging (PMI). Human umbilical vein endothelial cells (HUVECs) were grown on gelatin-coated glass slides and stimulated with inflammatory cytokines to induce the expression of the inflammatory biomarkers, ICAM-1 and E-selectin. Gold nanorods (GNRs) of aspect ratio (AR) 1:3 with absorption centered at 715 nm conjugated to anti-ICAM-1 antibody and GNRs of AR 1:3.5 with absorption centered at 800 nm conjugated to anti-E-selectin were exposed to HUVECs with different stimulation conditions. A focused high frequency ultrasonic transducer (60 MHz, f/1.5) was used to scan the photoacoustic (PA) signal over the top surface of the cell containing slides. Averaged PA signal intensity from the stimulated cells was about 3 folds higher (~10 dB) compared to the un-stimulated cells for both ICAM-1 and E-selectin. The strong binding of GNRs to the stimulated HUVEC cells was evidenced by fluorescence imaging. Exposure of HUVEC cells to GNRs conjugated to isotype control antibodies confirms a low level non-specific binding. Also, at 0, 2, 6, and 24 hours after inflammatory stimulation, the HUVECs were exposed to GNRs conjugated anti-ICAM-1 antibody and anti-E-selectin antibody. PA intensity at each stage of inflammation compares well with fluorescence imaging and rt-PCR quantification.

Mechanism of endothelial dysfunction in chronic kidney disease

Endothelium is the largest organ in the body strategically located between the wall of blood vessels and the blood stream. The human body contains approximately 10(13) endothelial cells weighing approximately 1kg, and covering a surface area of 4000 to 7000m(2) equivalent to the soccer playground. Hypertension and shear stress, inflammation, diabetes-associated factors such as advanced glycated end products, and uremic toxins are some of the prevalent risk factors of endothelial dysfunction in chronic kidney disease. In renal failure endothelial dysfunction and atherosclerosis are almost universal, as well as cardiovascular complications. Endothelial cell damage or injury is invariably associated with such clinical conditions as thrombosis, hypertension, renal failure and atherosclerosis and may be also responsible for accelerated atherosclerosis in patients with chronic renal failure. Traditional risk factor cannot explain the high prevalence and incidence of cardiovascular disease in chronic kidney disease, therefore other non-traditional risk factors such as endothelial dysfunction, oxidative stress or insulin resistance have increasingly been studied. In this review paper mechanism of endothelial dysfunction, including the role of nitric oxide pathway, adipocytokines and hemodialysis-induced endothelial dysfunction is discussed.

Signal transduction pathways involved in brain death-induced renal injury

Kidneys derived from brain death organ donors show an inferior survival when compared to kidneys derived from living donors. Brain death is known to induce organ injury by evoking an inflammatory response in the donor. Neuronal injury triggers an inflammatory response in the brain, leading to endothelial dysfunction and the release of cytokines in the circulation. Serum levels of interleukin-6, -8, -10, and monocyte chemoattractant protein-1 (MCP-1) are increased after brain death. Binding with cytokine-receptors in kidneys stimulates activation of nuclear factor-kappa B (NF-kappaB), selectins, adhesion molecules and production of chemokines leading to cellular influx. Mitogen-activated protein kinases (MAP-kinases) mediate inflammatory responses and together with NF-kappaB they seem to play an important role in brain death induced renal injury. Altering the activation state of MAP-kinases could be a promising drug target for early intervention to reduce cerebral injury related donor kidney damage and improve outcome after transplantation.

Vascular endothelium and graft-versus-host disease

Vascular endothelial cells are an exposed target tissue for immune-mediated injury during graft-versus-host disease (GVHD). However, widespread endothelial death resulting in multi-organ failure similar to that in hyperacute solid-organ transplant rejection is not observed during GVHD. The rather mild endothelial injury seen in histological samples from affected skin biopsies contrasts with severe epithelial injury observed sometimes simultaneously. The elucidation of the mechanisms that influence endothelial susceptibility to immune-mediated injury would explain this paradox and may help to separate GVHD from the beneficial graft-versus-leukaemia effect. Transplant-associated microangiopathy, veno-occlusive disease and accelerated arteriosclerosis are vascular injury syndromes that occur after allogeneic stem-cell transplantation. Biomarkers are needed to identify individuals at risk of developing these complications. Treatments that have been found to be particularly effective for these specific endothelial injury syndromes need to be tested in larger clinical trials.

Identification of a ligand-induced transient refractory period in nuclear factor-kappaB signaling

In response to a variety of extracellular ligands, nuclear factor-kappaB (NF-kappaB) signaling regulates inflammation, cell proliferation, and apoptosis. It is likely that cells are not continuously exposed to stimulating ligands in vivo but rather experience transient pulses. To study the temporal regulation of NF-kappaB and its major regulator, inhibitor of NF-kappaBalpha (IkappaBalpha), in real time, we utilized a novel transcriptionally coupled IkappaBalpha-firefly luciferase fusion reporter and characterized the dynamics and responsiveness of IkappaBalpha processing upon a short 30-s pulse of tumor necrosis factor alpha (TNFalpha) or a continuous challenge of TNFalpha following a 30-s preconditioning pulse. Strikingly, a 30-s pulse of TNFalpha robustly activated inhibitor of NF-kappaB kinase (IKK), leading to IkappaBalpha degradation, NF-kappaB nuclear translocation, and strong transcriptional up-regulation of IkappaBalpha. Furthermore, we identified a transient refractory period (lasting up to 120 min) following preconditioning, during which the cells were not able to fully degrade IkappaBalpha upon a second TNFalpha challenge. Kinase assays of IKK activity revealed that regulation of IKK activity correlated in part with this transient refractory period. In contrast, experiments involving sequential exposure to TNFalpha and interleukin-1beta indicated that receptor dynamics could not explain this phenomenon. Utilizing a well accepted computational model of NF-kappaB dynamics, we further identified an additional layer of regulation, downstream of IKK, that may govern the temporal capacity of cells to respond to a second proinflammatory insult. Overall, the data suggested that nuclear export of NF-kappaB.IkappaBalpha complexes represented another rate-limiting step that may impact this refractory period, thereby providing an additional regulatory mechanism.

Evolving functions of endothelial cells in inflammation

Inflammation is usually analysed from the perspective of tissue-infiltrating leukocytes. Microvascular endothelial cells at a site of inflammation are both active participants in and regulators of inflammatory processes. The properties of endothelial cells change during the transition from acute to chronic inflammation and during the transition from innate to adaptive immunity. Mediators that act on endothelial cells also act on leukocytes and vice versa. Consequently, many anti-inflammatory therapies influence the behaviour of endothelial cells and vascular therapeutics influence inflammation. This Review describes the functions performed by endothelial cells at each stage of the inflammatory process, emphasizing the principal mediators and signalling pathways involved and the therapeutic implications.

Divergent and convergent effects on gene expression and function in acute versus chronic endothelial activation

Activation of the vascular endothelium with cytokines such as TNF is widely used to study the role of the vasculature in proinflammatory disease. To gain insight into mechanisms of prolonged vascular endothelial activation we compared changes in gene expression induced by continuous activation in stable tmTNF-expressing cells with changes due to acute TNF challenge in vitro. Affymetrix Genechip analysis was performed on RNA from control, acute and continuous TNF-activated endothelial cells. Only 36% of the significant changes in gene expression were convergent between the acute and continuously activated endothelial cells compared with the control. From the divergently regulated genes, for example the cytokine ENA-78 was specifically induced in chronically activated cells, while E-selectin, a cell adhesion molecule, was upregulated only in acutely activated endothelial cells. Antioxidant SOD gene induction was noted in acute activation, while a regulatory NADPH oxidase subunit was selectively upregulated in continuously activated endothelium in accordance with significant reactive oxygen species induction occurred only in these cells. Accordingly, p38 and ERK1/2, two MAP kinases downstream of reactive oxygen species, were activated in stable transmembrane-spanning precursor (tm) TNF-expressing cells and were refractory to activation with soluble TNF or VEGF. In consequence, the increased p38 MAP kinase activity contributed to increased endothelial cell migration in tmTNF-expressing cells. These data suggest that continuous activation of endothelial cells leads to specific expression and functional changes, consistent with alterations observed in dysfunctional endothelium exposed to or involved in chronic inflammation.

Reactive oxygen species-induced activation of the MAP kinase signaling pathways

An abundance of scientific literature exists demonstrating that oxidative stress influences the MAPK signaling pathways. This review summarizes these findings for the ERK, JNK, p38, and BMK1 pathways. For each of these different MAPK signaling pathways, the following is reviewed: the proteins involved in the signaling pathways, how oxidative stress can activate cellular signaling via these pathways, the types of oxidative stress that are known to induce activation of the different pathways, and the specific cell types in which oxidants induce MAPK responses. In addition, the functional outcome of oxidative stress-induced activation of these pathways is discussed. The purpose of this review is to provide the reader with an overall understanding and appreciation of oxidative stress-induced MAPK signaling.

Eicosapentaenoic acid and docosahexaenoic acid modulate mitogen-activated protein kinase activity in endothelium

Omega-3 polyunsaturated fatty acids (PUFA) regulate inflammation and immunoreaction partially via affecting endothelial functions. However, the intracellular signaling mechanisms for inhibiting endothelial activation by omega-3 PUFA remain unclear. We investigated the effects of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) on mitogen-activated protein kinases (MAPK) of endothelium. We analyzed the expression of extracellular signal-related kinases (ERK1/2), Jun amino-terminal kinases (JNK), and p38 mRNA by real-time RT-PCR and the kinases activity by western blotting in tumor necrosis factor-alpha (TNF-alpha)-activated human umbilical vein endothelial cells (HUVEC). We observed that EPA or DHA alone significantly reduced the TNF-alpha-induced activation of p38 and JNK kinases at a concentration of 20 microM, but EPA is a more potent inhibitor than DHA. In contrast, both EPA and DHA significantly counteracted the TNF-alpha-mediated deactivation of ERK1/2 kinases. Meanwhile, both EPA and DHA significantly attenuated the TNF-alpha-induced expression of p38 and ERK1/2 mRNA, and DHA but not EPA also reduced the TNF-alpha-induced JNK mRNA expression. We present data show that both EPA and DHA alone diminish activation of p38 and JNK kinases, while maintaining the activation of ERK1/2 kinases of TNF-alpha-stimulated HUVEC. This may contribute to the inhibiting effects of omega-3 PUFA on endothelial activation by proinflammatory stimuli.

SOCS1 Inhibits Tumor Necrosis Factor-induced Activation of ASK1-JNK Inflammatory Signaling by Mediating ASK1 Degradation

We have previously shown that ASK1 undergoes ubiquitination and degradation in resting endothelial cells (EC) and that proinflammatory cytokine tumor necrosis factor (TNF) induces deubiquitination and stabilization, leading to ASK1 activation. However, the mechanism for the regulation of ASK1 stability is not known. In the present study, we have shown that SOCS1, a member of suppressor of cytokine signaling, induces ASK1 degradation. SOCS1 was constitutively expressed in EC and formed a labile complex with ASK1 that can be stabilized by proteasomal inhibitors. The phosphotyrosine-binding SH2 domain of SOCS1 was critical for its association with ASK1. Thus a SOCS1 mutant defective in phosphotyrosine binding failed to bind to and induce ASK1 degradation. Phosphotyrosine of ASK1 was induced in response to growth factors, and TNF induced dephosphorylation and dissociation of ASK1 from SOCS1. ASK1 with a mutation at Tyr-718 diminished the binding to SOCS1, suggesting that the phosphotyrosine-718 of ASK1 is critical for SOCS1 binding. Moreover, ASK1 expression and activity were up-regulated in SOCS1-deficient mice and derived EC, resulting in enhanced TNF-induced activation of JNK, expression of proinflammatory molecules, and apoptotic responses. We concluded that SOCS1 functions as a negative regulator in TNF-induced inflammation in EC, in part, by inducing ASK1 degradation.

Cell‐Based Assays Using Primary Endothelial Cells to Study Multiple Steps in Inflammation

Cell-based assays are powerful tools for drug discovery and provide insight into complex signal transduction pathways in higher eukaryotic cells. Information gleaned from assays that monitor a cellular phenotype can be used to elucidate the details of a single pathway and to establish patterns of cross talk between pathways. By selecting the appropriate cell model, cell-based assays can be used to understand the function of a specific cell type in a complex disease process such as inflammation. We have used human umbilical vein endothelial cells to establish three cell-based, phenotypic assays that query different stages of a major signaling pathway activated in inflammation. One assay analyzes the tumor necrosis factor alpha (TNFalpha)-induced translocation of the transcription factor NF-kappaB from the cytoplasm into the nucleus 20 min after stimulation with TNFalpha. Two more assays monitor the expression of E-selectin and VCAM-1, 4 and 24 h after stimulation with TNFalpha. Indirect immunofluorescence and high-throughput automated microscopy were used to analyze cells. Imaging was performed with the IN Cell Analyzer 3000. All assays proved to be highly robust. Z' values between 0.7 and 0.8 make each of the three assays well suited for use in high-throughput screening for drug or probe discovery.

Synergistic induction of tissue factor by coagulation factor Xa and TNF: evidence for involvement of negative regulatory signaling cascades

Enzymes of the blood coagulation pathway enhance the inflammatory response leading to endothelial dysfunction, accounting, in part, for the vascular complications occurring in sepsis and cardiovascular disease. The responses of endothelial cell activation include induction of the expression of tissue factor (TF), a membrane glycoprotein that promotes thrombosis, and of E-selectin, a cell adhesion molecule that promotes inflammation. In this report, we demonstrate synergistic interactions between the coagulation factor Xa (fXa) and the proinflammatory cytokines TNF, IL-1beta, and CD40L, leading to enhanced expression of TF and E-selectin in endothelial cells. A detailed analysis of the molecular pathways that could account for this activity of fXa showed that fXa inhibited the cytokine-induced expression of dual specificity phosphatases, MAP kinase phosphatase-L, -4, -5, and -7, blocking a negative regulatory effect on c-Jun N-terminal kinase. The synergistic interaction between fXa and TNF was also involved in the inhibition of A20 and IkappaBalpha expression in the IkappaB kinase-NF-kappaB pathway. The data indicate that inhibition of negative regulatory signaling accounts for the amplification of cytokine-induced endothelial cell activation by fXa.

Regulation of c-Jun N-terminal Kinase and p38 Kinase Pathways in Endothelial Cells

The rapid and transient induction of E-selectin gene expression by inflammatory tumor necrosis factor (TNF)-alpha in endothelial cells is mediated by signaling pathways which involve c-Jun N-terminal kinase (JNK) and p38 mitogen-activated protein kinase (MAPK) kinase pathways. To explore this regulation, we first observed that in the continuous presence of cytokine TNF, activation of JNK-1 in both nuclear and cytoplasmic compartments peaked at 15-30 min, with activity returning to uninduced levels by 60 min. Phosphorylation of both the p38 kinase and its molecular target, the nuclear transcription factor, activating transcription factor-2, were transient after TNF-alpha or interleukin (IL)-1beta induction. However, cycloheximide treatment prolonged the TNF-alpha-induced JNK-1 kinase activity beyond 60 min, suggesting that protein synthesis is required to limit this signaling cascade. We investigated the possible role of the dual-specificity phosphatases MAPK phosphatase (MKP)-1 and MKP-2 in limiting cytokine-induced MAPK signaling. Maximum induction of MKP-1 mRNA and nuclear protein levels by TNF-alpha or IL-1beta were noted at 60 min and their expression correlated with the termination of JNK kinase activity, whereas nuclear levels of MKP-2 were not significantly affected by treatment with TNF-alpha or IL-1beta. Transient overexpression of MKP-1 demonstrated significant specific inhibition of E-selectin promoter activity consistent with a regulatory role for dual-specificity phosphatases. Inhibition of MKP-1 expression through the use of small interfering RNAs prolonged the cytokine-induced p38 and JNK kinase phosphorylation. Our results suggest that endogenous inhibitors of the MAPK cascade, such as the dual-specificity phosphatases like MKP-1 may be important for the postinduction repression of MAPK activity and E-selectin transcription in endothelial cells. Thus, these inhibitors may play an important role in limiting the inflammatory effects of TNF-alpha and IL-1beta.

Requirement for Donor and Recipient CD40 Expression in Cardiac Allograft Rejection: Induction of Th1 Responses and Influence of Donor-Derived Dendritic Cells

Costimulation through the CD40-CD40 ligand (CD40L) pathway is critical to allograft rejection, in that anti-CD40L mAb therapy prolongs allograft survival. However, the majority of studies exploring CD40-CD40L interactions have targeted CD40L. Less is known about the requirement for donor- and/or host-derived CD40 during rejection. This study assessed the relative contributions of donor and recipient CD40 expression to the rejection process. As the effectiveness of costimulatory blockade may be mouse strain dependent, this study explored the requirement for donor and recipient CD40 expression in BALB/c and C57BL/6 mice. Wild-type (WT) and CD40(-/-) BALB/c recipients readily rejected WT and CD40(-/-) C57BL/6 allografts, and rejection was associated with a prominent Th1 response. In contrast, CD40(-/-) C57BL/6 recipients failed to reject WT or CD40(-/-) BALB/c allografts and did not mount Th1 or Th2 responses. However, injection of donor CD40(-/-) dendritic cells induced both Th1 and Th2 responses and allograft rejection in CD40(-/-) C57BL/6 recipients. Finally, WT C57BL/6 mice rejected CD40(-/-) allografts, but this rejection response was associated with muted Th1 responses. These findings demonstrate that 1) CD40 expression by the recipient or the graft may impact on the immune response following transplantation; 2) the requirement for CD40 is influenced by the mouse strain; and 3) the requirement for CD40 in rejection may be bypassed by donor DC. Further, as CD40 is not required for rejection in BALB/c recipients, but anti-CD40L mAb prolongs graft survival in these mice, these results suggest that anti-CD40L therapy functions at a level beyond disruption of CD40-CD40L interactions.

Endothelial cells present antigens in vivo

Background

Immune recognition of vascular endothelial cells (EC) has been implicated in allograft rejection, protection against pathogens, and lymphocyte recruitment. However, EC pervade nearly all tissues and predominate in none, complicating any direct test of immune recognition. Here, we examined antigen presentation by EC in vivo by testing immune responses against E. coli β-galactosidase (β-gal) in two lines of transgenic mice that express β-gal exclusively in their EC. TIE2-lacZ mice express β-gal in all EC and VWF-lacZ mice express β-gal in heart and brain microvascular EC.

Results

Transgenic and congenic wild type FVB mice immunized with β-gal expression vector DNA or β-gal protein generated high titer, high affinity antisera containing comparable levels of antigen-specific IgG1 and IgG2a isotypes, suggesting equivalent activation of T helper cell subsets. The immunized transgenic mice remained healthy, their EC continued to express β-gal, and their blood vessels showed no histological abnormalities. In response to β-gal in vitro, CD4⁺ and CD8⁺ T cells from immunized transgenic and FVB mice proliferated, expressed CD25, and secreted IFN-γ. Infection with recombinant vaccinia virus encoding β-gal raised equivalent responses in transgenic and FVB mice. Hearts transplanted from transgenic mice into FVB mice continued to beat and the graft EC continued to express β-gal. These results suggested immunological ignorance of the transgene encoded EC protein. However, skin transplanted from TIE2-lacZ onto FVB mice lost β-gal⁺ EC and the hosts developed β-gal-specific antisera, demonstrating activation of host immune effector mechanisms. In contrast, skin grafted from TIE2-lacZ onto VWF-lacZ mice retained β-gal⁺ EC and no antisera developed, suggesting a tolerant host immune system.

Conclusion

Resting, β-gal⁺ EC in transgenic mice tolerize specific lymphocytes that would otherwise respond against β-gal expressed by EC within transplanted skin. We conclude that EC effectively present intracellular "self" proteins to the immune system. However, antigen presentation by EC does not delete or anergize a large population of specific lymphocytes that respond to the same protein following conventional immunization with protein or expression vector DNA. These results clearly demonstrate striking context sensitivity in the immune recognition of EC, a subtlety that must be better understood in order to treat immune diseases and complications involving the vasculature.

Interleukin-4 increases the permeability of human endothelial cells in culture

BACKGROUND

IL-4 plays a key role in the induction of allergic inflammation, but its role as an effector molecule is less well-established. Although some observations suggest that IL-4 may mediate increased vascular permeability, which is a characteristic feature of allergic inflammation, evidence for a direct effect on endothelial cell permeability is lacking.

OBJECTIVE

To determine the effect of human IL-4 on the albumin permeability of cultured human endothelial cells.

METHODS

Human umbilical vein endothelial cells were cultured on permeable membranes and the albumin permeability of endothelial monolayers was measured with and without exposure to recombinant human IL-4. Endothelial cells were exposed to various concentrations of IL-4 (0.001-100 U/mL), for various durations (6-24 h), either in the presence or absence of anti-IL-4 antibody. Recovery of endothelial barrier function following exposure to IL-4 was also examined.

RESULTS

IL-4 induced a dose-dependent, reversible increase in endothelial permeability to albumin. Low concentrations of IL-4 (1 U/mL) induced a significant increase in endothelial permeability (P=0.004). IL-4-mediated endothelial leak occurred rapidly, within 6 h of exposure.

CONCLUSIONS

IL-4 has the capacity to induce vascular leak by a direct effect on cultured endothelial cells, suggesting a potential effector role for IL-4 in the pathogenesis of vascular leak in allergic diseases.

Abnormal germinal center reactions in systemic lupus erythematosus demonstrated by blockade of CD154-CD40 interactions

To determine the role of CD154-CD40 interactions in the B cell overactivity exhibited by patients with active systemic lupus erythematosus (SLE), CD19+ peripheral B cells were examined before and after treatment with humanized anti-CD154 mAb (BG9588, 5c8). Before treatment, SLE patients manifested activated B cells that expressed CD154, CD69, CD38, CD5, and CD27. Cells expressing CD38, CD5, or CD27 disappeared from the periphery during treatment with anti-CD154 mAb, and cells expressing CD69 and CD154 disappeared from the periphery during the post-treatment period. Before treatment, active-SLE patients had circulating CD38 (bright) Ig-secreting cells that were not found in normal individuals. Disappearance of this plasma cell subset during treatment was associated with decreases in anti-double-stranded DNA (anti-dsDNA) Ab levels, proteinuria, and SLE disease activity index. Consistent with this finding, peripheral B cells cultured in vitro spontaneously proliferated and secreted Ig in a manner that was inhibited by anti-CD154 mAb. Finally, the CD38(+/++)IgD(+), CD38(+++), and CD38(+)IgD(-) B cell subsets present in the peripheral blood also disappeared following treatment with humanized anti-CD154. Together, these results indicate that patients with active lupus nephritis exhibit abnormalities in the peripheral B cell compartment that are consistent with intensive germinal center activity, are driven via CD154-CD40 interactions, and may reflect or contribute to the propensity of these patients to produce autoantibodies.

Endothelial cell injury markers in chronic renal failure on conservative treatment and continuous ambulatory peritoneal dialysis

AIM

In chronic renal failure in dialyzed patients vascular damage is frequently observed and it is probable that disturbances in fibrinolytic activity and endothelial dysfunction may play a role in vascular complications such as stroke or ischemic heart disease. There have been a few data concerning hemostasis in chronic renal failure. Since hemostatic disturbances in nephrotic syndrome mimick those observed in patients maintained on chronic ambulatory peritoneal dialyses (CAPD), the aim of the study was to assess adhesion molecules (P-selectin, E-selectin, ICAM, VCAM and markers of endothelial cell injury), von Willebrand factor, thrombomodulin, and TFPI (tissue factor pathway inhibitor) in CAPD patients as well as in subjects with chronic renal failure (CRF) treated conservatively.

METHODS

The studies were performed on 23 CAPD patients, 24 patients with nephrotic syndrome and 24 sex- and age-matched healthy volunteers. TFPI total, full length, truncated, von Willebrand factor, trombomodulin, P-selectin, E-selectin, ICAM, VCAM and vascular endothelial growth factor (VEGF) and its receptor sFlt3 were assayed using commercially available kits. We evaluated also thrombin activity (thrombin-antithrombin complexes (TAT), prothrombin fragments 1 and 2) and the degree of plasmin generation.

RESULTS

In CAPD and CRF patients, concentrations of the adhesion molecules P-selectin, E-selectin, ICAM and VCAM were significantly higher when compared to the control group. Concentrations of total, free and truncated TFPI were significantly higher in CAPD and CRF patients when compared to the healthy volunteers. Concentrations of 'classical' markers of endothelial cell injury, von Willebrand factor and thrombomodulin, were significantly higher in CAPD and CRF patients when compared to the control group. In CAPD patients, VCAM and thrombomodulin were significantly elevated when compared to the CRF patients.

CONCLUSIONS

The elevated levels of adhesion molecules in CAPD patients probably reflect inadequate clearance as well as enhanced synthesis/release. They may also indicate endothelial cell injury as well as elevated levels of von Willebrand factor and trombomodulin and increased ICAM and VCAM in CAPD patients. Our studies indicate that in renal failure patients, particularly on CAPD, there is evidence of endothelial cell injury and a high degree of hypercoagulation relative to healthy subjects. It may lead to fibrin deposition in the vascular wall, thrombus formation, and development and progression of atherosclerosis with its complications.

Microarray analysis of cytokine and chemokine genes in the brains of macaques with SHIV-encephalitis

Human immunodeficiency virus (HIV)-encephalitis results from a cascade of viral-host interactions that lead to cytokine and chemokine imbalance, which then leads to neuropathologic manifestations of the disease. These include macrophage/microglia activation, astrocytosis and neuronal dysfunction or death. As the molecular mechanisms of this process are poorly understood, we used Atlas human cytokine or cytokine receptor microarray analysis to highlight gene expression profiles that accompanied encephalitis in Simian human immunodeficiency virus (SHIV) 89.6P-infected macaques. Of the 277 genes screened, marked upregulation of monocyte chemoattractant protein-1, interferon-inducible peptide IP-10 and interleukin-4 were observed specifically in the encephalitic brains. These genes are collectively known to promote macrophage infiltration and activation and virus replication. In contrast, genes regulating neurotrophic functions, such as brain-derived neurotrophic factor were downregulated. We also found that some of the apoptosis genes were up- or down-regulated. These data provide a comprehensive spectrum of gene expression that underscores the two major clinical manifestations of this unique syndrome: enhanced virus replication in brain macrophages and dystrophic changes in neurons.

TRAIL induces apoptosis and inflammatory gene expression in human endothelial cells

Human TRAIL can efficiently kill tumor cells in vitro and kill human tumor xenografts in mice with little effect on normal mouse cells or tissues. The effects of TRAIL on normal human tissues have not been described. In this study, we report that endothelial cells (EC), isolated from human umbilical veins or human dermal microvessels, express death domain-containing TRAIL-R1 and -R2. Incubation with TRAIL for 15 h causes approximately 30% of cultured EC to die, as assessed by propidium iodide uptake. Death is apoptotic, as assessed by Annexin V staining, 4',6'-diamidino-2-phenylindole staining, and DNA fragment ELISA. EC death is increased by cotreatment with cycloheximide but significantly reduced by caspase inhibitors or transduced dominant-negative Fas-associated death domain protein. In surviving cells, TRAIL activates NF-kappaB, induces expression of E-selectin, ICAM-1, and IL-8, and promotes adhesion of leukocytes. Injection of TRAIL into human skin xenografts promotes focal EC injury accompanied by limited neutrophil infiltration. These data suggest that TRAIL is an inducer of tissue injury in humans, an outcome that may influence antitumor therapy with TRAIL.

Ischemia-reperfusion of the murine testis stimulates the expression of proinflammatory cytokines and activation of c-jun N-terminal kinase in a pathway to E-selectin expression

Ischemia-reperfusion (IR) of the testis results in germ cell-specific apoptosis and can lead to aspermatogenesis. Germ cell-specific apoptosis after IR of the testis has been shown to be correlated with and dependent on neutrophil recruitment to the testis after IR. Studies that used E-selectin-deficient mice have demonstrated that E-selectin expression is critical for neutrophil recruitment to subtunical venules in the testis after IR and for the resultant germ cell-specific apoptosis. The present study investigates the in vivo signaling pathway that exists after IR that leads to neutrophil recruitment in the murine testis. Mice were subjected to a 2-h period of testicular ischemia followed by reperfusion. Results demonstrate that the proinflammatory cytokines, tumor necrosis factor alpha (TNFalpha) and interleukin 1beta (IL-1beta), are stimulated after IR as is the phosphorylation of c-jun N-terminal kinase (JNK). The downstream transcription factors of JNK, ATF-2 and c-jun are also phosphorylated at specific times after IR of the testis. Activation of the JNK stress-related kinase pathway is correlated with an increase in E-selectin expression and neutrophil recruitment to the testis after IR. Intratesticular injection of IL-1beta also caused JNK phosphorylation and neutrophil recruitment to the testis. These results suggest that testicular IR injury stimulates IL-1beta expression, which leads to activation of the JNK signaling pathway and ultimately E-selectin expression and neutrophil recruitment to the testis. This provides the first evidence of a cytokine/stress-related kinase signaling pathway to E-selectin expression in vivo.

Histamine antagonizes tumor necrosis factor (TNF) signaling by stimulating TNF receptor shedding from the cell surface and Golgi storage pool

Tumor necrosis factor (TNF) activates pro-inflammatory functions of vascular endothelial cells (EC) through binding to receptor type 1 (TNFR1) molecules expressed on the cell surface. The majority of TNFR1 molecules are localized to the Golgi apparatus. Soluble forms of TNFR1 (as well as of TNFR2) can be shed from the EC surface and inhibit TNF actions. The relationships among cell surface, Golgi-associated, and shed forms of TNFR1 are unclear. Here we report that histamine causes transient loss of surface TNFR1, TNFR1 shedding, and mobilization of TNFR1 molecules from the Golgi in cultured human EC. The Golgi pool of TNFR1 serves both to replenish cell surface receptors and as a source of shed receptor. Histamine-induced shedding is blocked by TNF-alpha protease inhibitor, an inhibitor of TNF-alpha-converting enzyme, and through the H1 receptor via a MEK-1/p42 and p44 mitogen-activated protein kinase pathway. Cultured EC with histamine-induced surface receptor loss become transiently refractory to TNF. Histamine injection into human skin engrafted on immunodeficient mice similarly caused shedding of TNFR1 and diminished TNF-mediated induction of endothelial adhesion molecules. These results both clarify relationships among TNFR1 populations and reveal a novel anti-inflammatory activity of histamine.

A short course of BG9588 (anti-CD40 ligand antibody) improves serologic activity and decreases hematuria in patients with proliferative lupus glomerulonephritis

OBJECTIVE

CD40-CD40 ligand (CD40L) interactions play a significant role in the production of autoantibodies and tissue injury in lupus nephritis. We performed an open-label, multiple-dose study to evaluate the safety, efficacy, and pharmacokinetics of BG9588, a humanized anti-CD40L antibody, in patients with proliferative lupus nephritis. The primary outcome measure was 50% reduction in proteinuria without worsening of renal function.

METHODS

Twenty-eight patients with active proliferative lupus nephritis were scheduled to receive 20 mg/kg of BG9588 at biweekly intervals for the first 3 doses and at monthly intervals for 4 additional doses. Safety evaluations were performed on all patients. Eighteen patients receiving at least 3 doses were evaluated for efficacy.

RESULTS

The study was terminated prematurely because of thromboembolic events occurring in patients in this and other BG9588 protocols (2 myocardial infarctions in this study). Of the 18 patients for whom efficacy could be evaluated, 2 had a 50% reduction in proteinuria without worsening of renal function. Mean reductions of 38.9% (P < 0.005), 50.1% (P < 0.005), and 25.3% (P < 0.05) in anti-double-stranded DNA (anti-dsDNA) antibody titers were observed at 1, 2, and 3 months, respectively, after the last treatment. There was a significant increase in serum C3 concentrations at 1 month after the last dose (P < 0.005), and hematuria disappeared in all 5 patients with significant hematuria at baseline. There were no statistically significant reductions in lymphocyte count or serum immunoglobulin, anticardiolipin antibody, or rubella IgG antibody concentrations after therapy.

CONCLUSION

A short course of BG9588 treatment in patients with proliferative lupus nephritis reduces anti-dsDNA antibodies, increases C3 concentrations, and decreases hematuria, suggesting that the drug has immunomodulatory action. Additional studies will be needed to evaluate its long-term effects.

CD40 expressed by human brain endothelial cells regulates CD4+ T cell adhesion to endothelium

Recent evidence suggests that interactions between CD40 on antigen presenting cells (APC) and CD40L on T cells generate signals that result in the activation of APC. In this study, the expression and function of CD40 was investigated in primary cultures of human brain microvessel endothelial cells (HBMEC). Results revealed constitutive expression of CD40 on untreated HBMEC. Stimulation with TNF-alpha, IFN-gamma, LPS or combination of TNF-alpha and IFN-gamma significantly upregulated CD40. The majority of CD40 molecules were localized on the apical surface of EC. Incubation of HBMEC with soluble CD40L resulted in increased expression of the adhesion molecules E-selectin, VCAM-1 and ICAM-1. Consequently, the adhesion of both resting and anti-CD3 activated CD4+ T lymphocytes to CD40L treated HBMEC was significantly increased compared to unstimulated EC. The expression of CD40 by cerebral endothelium, and endothelial cell activation following binding of CD40 to its ligand, CD40L, suggest a potential mechanism by which activated CD40L expressing T cells could enhance adhesion and migration of inflammatory cells across the blood-brain barrier (BBB) to sites of inflammation in the human central nervous system (CNS).

Upregulation of CD40 expression on endothelial cells infected with human cytomegalovirus

CD40 has been identified as an important molecule for a number of processes, such as immune responses, inflammation, and the activation of endothelia. We investigated CD40 in endothelial cells (EC) following infection with an endotheliotropic strain of human cytomegalovirus (HCMV). Between 8 and 72 h postinfection, we observed a significant increase in CD40 levels on the surface of infected EC, as measured by fluorescence-activated cell sorting analysis. As a consequence of CD40 upregulation, increased levels of E-selectin were found on infected EC after stimulation with CD154-expressing T cells. Enhanced expression of CD40 was specific for EC, since infection of fibroblasts did not result in the upregulation of CD40. The addition of neutralizing antibodies as well as UV inactivation of virus completely prevented the upregulation of CD40 on EC. Also, laboratory-adapted HCMV strain AD169 was not able to induce CD40 on EC. De novo protein synthesis was necessary for the increased surface expression. At early times (4 to 24 h) postinfection, this change was not accompanied by increased levels of CD40 protein or mRNA. At late times (48 to 96 h) postinfection, increased amounts of CD40 protein and mRNA were detected. Immunohistochemical analysis of infected tissues demonstrated elevated levels of CD40 on HCMV-infected EC in vivo. Thus, infection of EC by HCMV may result in the activation of endothelia and in the augmentation of inflammatory processes.

Markers of endothelial cell injury and thrombin activatable fibrinolysis inhibitor in nephrotic syndrome

Thromboembolic complications are often seen in patients with nephrotic syndrome. Markers of endothelial cell injury [thrombomodulin, intracellular adhesion molecule, vascular cell adhesion molecule, thrombin activatable fibrinolysis inhibitor (TAFI), protein Z, vascular endothelial growth factor, markers of thrombin and plasmin generation] were studied in 22 patients with nephrotic syndrome. All these parameters studied, except protein Z and D-dimers, were significantly higher in patients with nephrotic syndrome, whereas protein Z was significantly lower when compared with the healthy volunteers. None of the endothelial cell markers (thrombomodulin, P-selectin, E-selectin, intracellular adhesion molecule, vascular cell adhesion molecule), thrombin and plasmin generation markers (thrombin-antithrombin complexes, prothrombin fragments 1 + 2, plasmin-antiplasmin complexes, D-dimers), protein C, protein Z, vascular endothelial growth factor, and TAFI concentration and activity were directly correlated with the level of proteinuria, albumin, cholesterol, triglycerides or creatinine, except significant positive correlations between TAFI activity and serum creatinine, E-selectin and albumin as well as negative correlations between plasmin-antiplasmin complexes and proteinuria. In these patients, there is evidence of endothelial cell injury and probably secondary activation of the coagulation cascade. Elevated circulating TAFI antigen and activity might be a new link in the pathogenesis of impaired fibrinolysis and the progression of atherosclerosis in nephrotic syndrome. Protein Z deficiency might also contribute to the enhanced risk of thromboembolic complications in nephrotic syndrome.

Induction of cyclooxygenase-2 and enhanced release of prostaglandin E(2) and I(2) in human endothelial cells by engagement of CD40

OBJECTIVES

The hypothesis was tested that CD40-CD154 interaction is involved in the induction of cyclooxygenase-2 and the release of prostanoids in human endothelial cells.

METHODS AND RESULTS

In a coculture model of human endothelial cells and a transfected CD154 positive cell line, engagement of CD40 on endothelial cells dramatically increased the synthesis of prostacyclin, prostaglandin E(2) and thromboxane A(2). This upregulation was mediated through an induction of cyclooxygenase-2 (Cox-2), as it was blocked by Cox-2-selective inhibitors. Western blot analysis demonstrated that Cox-2 protein was markedly increased in endothelial cells following CD40 engagement, an effect that was inhibited by pretreatment of cells with an anti-CD154 antibody.

CONCLUSION

The data indicate that signaling via CD40 constitutes a major pathway in human endothelial cells for the induction of Cox-2 and release of prostanoids. The CD40-Cox-2 axis thus may represent an important pathway for initiating or maintaining an inflammatory process at the vessel wall.

Effects of testosterone and 17-beta-estradiol on TNF-alpha-induced E-selectin and VCAM-1 expression in endothelial cells. Analysis of the underlying receptor pathways

This study investigated the effects of testosterone and 17-beta-estradiol on tumor necrosis factor-alpha (TNF-alpha)-induced endothelial expression of E-selectin and vascular cell adhesion molecule-1 (VCAM-1) and the potential roles of hormone receptors involved in these actions. Human umbilical vein endothelial cells (HUVEC) were stimulated with TNF-alpha in the presence or absence of testosterone or 17-beta-estradiol, and the expression of E-selectin and VCAM-1 was investigated. As shown by Western blot analysis, co-administration with testosterone or 17-beta-estradiol increased the expression of E-selectin and VCAM-1 induced by TNF-alpha at 6 h and 3 h, respectively. Similarly, RT-PCR analysis revealed a significant increase in the amount of mRNA for E-selectin and VCAM-1 after co-administration with testosterone or 17-beta-estradiol in TNF-alpha-stimulated HUVEC. The presence of mRNA and proteins for androgen receptor and estrogen receptor alpha in HUVEC was verified by RT-PCR and Western blot. Flow cytometric analysis showed that preincubation with androgen receptor antagonist cyproterone and estrogen receptor antagonist tamoxifen completely abrogated the upregulating effects of testosterone and 17-beta-estradiol on TNF-alpha-induced E-selectin and VCAM-1 expression, respectively. Expression of TNF receptors in TNF-alpha-stimulated HUVEC was not influenced by testosterone and 17-beta-estradiol. The data indicate that both testosterone and 17-beta-estradiol increase TNF-alpha-induced E-selectin and VCAM-1 expression in endothelial cells via a receptor-mediated system, and expression of TNF receptors are not changed in these actions. The implications of these results for the facilitory effects of both sex hormones on immune reactions are discussed.