Tumor necrosis factor-induced E-selectin expression on vascular endothelial cells

Glycans and Glycan-Binding Proteins as Regulators and Potential Targets in Leukocyte Recruitment

Leukocyte recruitment is a highly controlled cascade of interactions between proteins expressed by the endothelium and circulating leukocytes. The involvement of glycans and glycan-binding proteins in the leukocyte recruitment cascade has been well-characterised. However, our understanding of these interactions and their regulation has expanded substantially in recent years to include novel lectins and regulatory pathways. In this review, we discuss the role of glycans and glycan-binding proteins, mediating the interactions between endothelium and leukocytes both directly and indirectly. We also highlight recent findings of key enzymes involved in glycosylation which affect leukocyte recruitment. Finally, we investigate the potential of glycans and glycan binding proteins as therapeutic targets to modulate leukocyte recruitment and transmigration in inflammation.

Molecular mechanisms underlying synergistic adhesion of sickle red blood cells by hypoxia and low nitric oxide bioavailability

The molecular mechanisms by which nitric oxide (NO) bioavailability modulates the clinical expression of sickle cell disease (SCD) remain elusive. We investigated the effect of hypoxia and NO bioavailability on sickle red blood cell (sRBC) adhesion using mice deficient for endothelial NO synthase (eNOS) because their NO metabolite levels are similar to those of SCD mice but without hypoxemia. Whereas sRBC adhesion to endothelial cells in eNOS-deficient mice was synergistically upregulated at the onset of hypoxia, leukocyte adhesion was unaffected. Restoring NO metabolite levels to physiological levels markedly reduced sRBC adhesion to levels seen under normoxia. These results indicate that sRBC adherence to endothelial cells increases in response to hypoxia prior to leukocyte adherence, and that low NO bioavailability synergistically upregulates sRBC adhesion under hypoxia. Although multiple adhesion molecules mediate sRBC adhesion, we found a central role for P-selectin in sRBC adhesion. Hypoxia and low NO bioavailability upregulated P-selectin expression in endothelial cells in an additive manner through p38 kinase pathways. These results demonstrate novel cellular and signaling mechanisms that regulate sRBC adhesion under hypoxia and low NO bioavailability. Importantly, these findings point us toward new molecular targets to inhibit cell adhesion in SCD.

Which factors are related to the presence of atherosclerosis in rheumatoid arthritis?

OBJECTIVE

An accelerated progression of atherosclerosis may contribute to the increased mortality due to cardiovascular disease reported in rheumatoid arthritis (RA). The aim of this study was to identify variables, related to disease onset as well as to disease progression, of importance for the presence of atherosclerosis, as diagnosed by B-mode ultrasonography, in patients with medium-term RA. The results are based on the co-analysis of retrospective data as well as cross-sectional data. The impact of RA per se on atherosclerosis was evaluated relative to age- and sex-matched controls.

METHODS

Thirty-nine RA patients, with a maximum age of 65 years, who had previously been included in a large retrospective cohort study, were assessed by duplex scanning after a disease duration of 19-23 years. In the present study, factors identified in the two earlier studies were assessed for their potential relationship with intima-media wall thickness (IMT) of the common carotid artery (CCA), and the presence and grade of atherosclerotic plaques of the CCA and the common femoral artery, in regression models. The candidate co-variates were: variables reflecting inflammatory activity at disease onset and at the time of ultrasound assessment, established cardiovascular risk factors, pharmacological treatment [corticosteroids, disease-modifying anti-rheumatic drugs (DMARDs)], and the presence of complications and co-morbidity identified during disease progression, as well as lipid levels, anti-lipid antibodies, haemostatic factors, and markers of immune activation measured at ultrasound assessment.

RESULTS

In patients with RA, analysis of simple linear regression models revealed those variables significantly associated with IMT-CCA to be age, tissue plasminogen activator (tPA) antigen, cholesterol, low density lipoprotein (LDL)-cholesterol, triglycerides, and atherosclerotic plaques while neither inflammatory status at disease onset, traditional cardiovascular risk factors, or pharmacological treatment during disease had any significant impact on IMT. In an estimated multiple linear regression model, variables associated with increasing log of IMT-CCA were the log of cholesterol and of soluble intracellular adhesion molecule 1 (sICAM-1), while methotrexate treatment tended to have a decreasing effect. In simple binary logistic regression, atherosclerotic plaques were associated with age, IMT-CCA, smoking, and the levels of sICAM-1, sE-selectin, interleukin-2 soluble receptor alpha (IL-2sRalpha), plasminogen activator inhibitor-1 (PAI-1) mass, cholesterol, LDL-cholesterol, and the LDL/high density lipoprotein (HDL) ratio. A multiple approach indicated that plaques were associated with age, cholesterol, and sE-selectin. Severe plaques were associated with LDL-cholesterol and disease duration. Logistic regression in the age- and sex-matched case-control study revealed that IMT-CCA was, together with the D-dimer, associated with RA per se.

CONCLUSION

Levels of lipids and adhesion molecules were associated with the presence of atherosclerosis in RA. IMT-CCA was associated with RA per se. Disease duration could predict severe atherosclerotic plaques. Treatment with methotrexate seemed to decrease the IMT-CCA.

Visualizing the acute effects of vascular-targeted therapy in vivo using intravital microscopy and magnetic resonance imaging: correlation with endothelial apoptosis, cytokine induction, and treatment outcome

The acute effects of the vascular-disrupting agent 5,6-dimethylxanthenone-4-acetic acid (DMXAA) were investigated in vivo using intravital microscopy (IVM) and magnetic resonance imaging (MRI). Changes in vascular permeability and blood flow of syngeneic CT-26 murine colon adenocarcinomas were assessed at 4 and 24 hours after DMXAA treatment (30 mg/kg, i.p.) and correlated with induction of tumor necrosis factor-alpha (TNF-alpha), endothelial damage [CD31/terminal deoxynucleotidyl transferase (TdT)], and treatment outcome. Intravital imaging revealed a marked increase in vascular permeability 4 hours after treatment, consistent with increases in intratumoral mRNA and protein levels of TNF-alpha. Parallel contrast-enhanced MRI studies showed a approximately 4-fold increase in longitudinal relaxation rates (DeltaR(1)), indicative of increased contrast agent accumulation within the tumor. Dual immunostained tumor sections (CD31/TdT) revealed evidence of endothelial apoptosis at this time point. Twenty-four hours after treatment, extensive hemorrhage and complete disruption of vascular architecture were observed with IVM, along with a significant reduction in DeltaR(1); and virtual absence of CD31 immunostaining. DMXAA-induced tumor vascular damage resulted in significant long-term (60-day) cures compared to untreated controls. Multimodality imaging approaches are useful in visualizing the effects of antivascular therapy in vivo. Such approaches allow cross validation and correlation of findings with underlying molecular changes contributing to treatment outcome.

Integrated neuroendocrine immune risk factors in relation to rheumatoid arthritis: should rheumatologists now adopt a model of a multiyear, presymptomatic phase?

An integrative perspective of neuroendocrine immune (NEI) and related risk factors for the onset of rheumatoid arthritis (RA) is presented, based upon studies of the long-term presymptomatic phase. Besides the recognized genetic markers and familial predisposition, multiple immunological precursors of RA have been identified many years before the clinical onset of inflammatory manifestations. Rheumatoid factors and related antibodies occur in approximately one-half of presymptomatic susceptibles. Cigarette smoking in sufficient amount and duration is a major risk factor for RA, particularly for postmenopausal-onset women and for men. In premenopausal-onset RA, subtle insufficiency of adrenal cortical function is less well recognized. In such women, cytokine imbalance may also precede inflammatory onset of RA. In males alone, multiple hormonal and cytokine correlations were found many years before the onset of RA, implying long-term activation or perturbation of this NEI system. The proposed physiopathogenetic model of RA requires further controlled, prospective studies for validation of the multiyear presymptomatic phase of RA. Such studies promise to clarify the currently unknown causal and sequential chains in this enigmatic disease.

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.

Tumor necrosis factor-alpha gene expression and release in cultured human dermal microvascular endothelial cells

Endothelial dysfunctions in the microcirculation are a common finding in the course of inflammatory disorders. These are, at least in part, mediated by endogenous agonists, e.g. tumor necrosis factor-alpha (TNF-alpha). As TNF-alpha mostly acts in an autocrine or paracrine fashion, it was tempting to speculate that microvascular endothelial cells synthesize and release this cytokine upon appropriate stimulation. In the present study, human dermal microvascular endothelial cells (HDMECs) expressed the TNF-alpha gene following incubation with interleukin-1beta (IL-1beta), lipopolysaccharids (LPSs), as well as a combination of IL-1beta, LPSs, and interferon-gamma (IFN-gamma), while IFN-gamma failed to exert an effect on TNF-alpha gene expression when given as a single stimulus. Transcription of the TNF-alpha gene was accompanied by an increase in TNF-alpha protein secretion into the cellular supernatant. As HDMECs were found to be a target of TNF-alpha, production of this cytokine by HDMECs may result in an autocrine activation loop that contributes to the deterioration of microcirculatory functions in infectious diseases and inflammatory skin disorders.

Tumour necrosis factor receptor I (p55) is upregulated on endothelial cells by exposure to the tumour-derived cytokine endothelial monocyte- activating polypeptide II (EMAP-II)

Endothelial monocyte activating polypeptide-II (EMAP-II) is an inflammatory cytokine known to have a role in neutrophil and macrophage chemotaxis and in apoptosis. It is a tumour-derived cytokine that sensitizes tumour vasculature to the effects of systemic TNF. In order to gain insight into the mechanism by which EMAP-II sensitizes vessels to TNF, we focused on its effects on TNF receptor expression. In human umbilical vein endothelial cells (HUVEC), TNF-R1 mRNA is increased four-fold following incubation with recombinant EMAP-II. Conditioned media from cell lines known to produce high levels of EMAP-II upregulated TNF-R1 but not TNF-R2 by up to twenty-fold compared to media controls and low expressing cell lines; this effect was blocked by anti-EMAP-II antibody. Recombinant EMAP-II upregulated TNF-R1 expression by approximately six-fold. Analysis of HUVEC lysates by ELISA showed increased expression of TNF-R1 within 2 h; TNF-R2 expression was unaffected by recombinant EMAP-II. Finally, immunohistochemistry of human melanomas in vivo showed that TNF-R1 staining is increased on the vessels of tumours known to express high levels of EMAP-II compared to low EMAP-II expressing tumours. These results suggest that EMAP-II upregulates TNF-R1 expression by endothelial cells both in vitro and in vivo. This induction of TNF-R1 expression may be the mechanism by which EMAP-II sensitizes tumour endothelium to the effects of TNF leading to haemorrhagic necrosis.

Human vascular endothelial cells produce tumor necrosis factor-alpha in response to proinflammatory cytokine stimulation

OBJECTIVE

To determine whether human vascular endothelial cells produce tumor necrosis factor-alpha (TNF-alpha) after stimulation with proinflammatory cytokines and bacterial lipopolysaccharides (LPS).

DESIGN

Prospective, in vitro repeated-measurements analysis of cellular responses.

SETTING

Research laboratory in an academic medical center.

SUBJECTS

Human umbilical vein endothelial cells (HUVECs).

INTERVENTIONS

HUVECs were incubated with interferon-gamma (IFN-gamma), interleukin-1beta (IL-1beta), and LPS, or their different combinations for 2 to 48 hrs.

MEASUREMENTS AND MAIN RESULTS

TNF-alpha was measured by time-resolved immunofluorometric assay. Unstimulated HUVECs did not produce detectable amounts of TNF-alpha, but IFN-gamma, IL-1beta, and LPS when added together induced TNF-alpha production of HUVECs in a time-dependent manner. Immunofluorescent staining confirmed that the TNF-alpha was produced by endothelial cells. IFN-gamma, IL-1beta, or LPS alone did not induce TNF-alpha production, whereas IFN-gamma and IL-1beta in combination were able to induce TNF-alpha production to some extent, and the production could be further increased with LPS. TNF-alpha messenger RNA expression was detected with reverse transcriptase-coupled polymerase chain reaction in stimulated, but not in unstimulated, HUVECs.

CONCLUSIONS

HUVECs are capable of producing TNF-alpha after proinflammatory cytokine stimulation and may therefore contribute to the increased amount of TNF-alpha found in pathologic states such as septic shock.

Plasma tumor necrosis factor-alpha soluble receptor p55 (sTNFp55) concentrations in eclamptic, preeclamptic and normotensive pregnant Zimbabwean women

We sought to examine the relationship between excessive tumor necrosis factor-alpha (TNF-alpha) release (as measured by sTNFp55 plasma concentrations) and risk of eclampsia and preeclampsia, respectively, among sub-Saharan African women delivering at Harare Maternity Hospital, Zimbabwe. In total, 33 pregnant women with eclampsia, 138 women with preeclampsia and 185 normotensive women were included in a case-control study conducted during the period, June 1995 through April 1996. Postpartum plasma sTNFp55 was measured by enzyme linked immunosorbent assay. Women with eclampsia had significantly higher sTNFp55 than normotensive controls (1.87 vs 1.35 ng/ml, P<0.001). Similarly, women with preeclampsia had sTNFp55 concentrations higher than normotensive controls (1.69 vs 1.35 ng/ml, P < 0.001). The odds ratio for eclampsia was 5.00 (adjusted odds ratio (OR) 5.00, 95% confidence interval (CI) 1.20-20.92) among women in the highest quartile of the control sTNFp55 distribution compared with women in the lowest quartile. The corresponding odds ratio and 95% CI for preeclampsia was 2.37 (1.11-5.06). Postpartum plasma sTNFp55 concentrations are increased among Zimbabwean women with eclampsia and preeclampsia as compared with their normotensive counterparts. These findings are consistent with the hypothesized role of cytokines in mediating endothelial dysfunction and the pathogenesis of preeclampsia/eclampsia. Additional work is needed to identify modifiable risk factors for the excessive synthesis and release of TNF-alpha in pregnancy; and to assess whether measurements of sTNFp55 early in pregnancy may be used to identify women likely to benefit from anti-inflammatory therapy.