Adhesion molecules in inflammatory diseases

Selective intracellular delivery of dexamethasone into activated endothelial cells using an E-selectin-directed immunoconjugate

In chronic inflammatory diseases, the endothelium is an attractive target for pharmacological intervention because it plays an important role in leukocyte recruitment. Hence, inhibition of endothelial cell activation and consequent leukocyte infiltration may improve therapeutic outcome in these diseases. We report on a drug targeting strategy for the selective delivery of the anti-inflammatory drug dexamethasone to activated endothelial cells, using an E-selectin-directed drug-Ab conjugate. Dexamethasone was covalently attached to an anti-E-selectin Ab, resulting in the so-called dexamethasone-anti-E-selectin conjugate. Binding of the conjugate to E-selectin was studied using surface plasmon resonance and immunohistochemistry. Furthermore, internalization of the conjugate was studied using confocal laser scanning microscopy and immuno-transmission electron microscopy. It was demonstrated that the dexamethasone-anti-E-selectin conjugate, like the unmodified anti-E-selectin Ab, selectively bound to TNF-alpha-stimulated endothelial cells and not to resting endothelial cells. After binding, the conjugate was internalized and routed to multivesicular bodies, which is a lysosome-related cellular compartment. After intracellular degradation, pharmacologically active dexamethasone was released, as shown in endothelial cells that were transfected with a glucocorticoid-responsive reporter gene. Furthermore, intracellularly delivered dexamethasone was able to down-regulate the proinflammatory gene IL-8. In conclusion, this study demonstrates the possibility to selectively deliver the anti-inflammatory drug dexamethasone into activated endothelial cells, using an anti-E-selectin Ab as a carrier molecule.

High efficiency transient transfection of genes in human umbilical vein endothelial cells by electroporation

Endothelial cells derived from the human umbilical vein (HUVEC) are used to study the mechanisms involved in EC response to various stimuli as well as to investigate the basis of pathological conditions of the vascular system such as altered endothelium permeability, tumor-induced angiogenesis, atherosclerosis and leukocyte extravasation in chronic inflammatory responses. However, investigations of gene involvement related to these conditions have progressed slowly because of the difficulty of transfecting HUVEC with high efficiency. Whereas several technical approaches have been described, they usually result in low levels of transfected cells or they require several steps or sophisticated instrumentation. We describe here a straightforward protocol of transfection of freshly isolated HUVEC that is based on the simple technique of electroporation. Efficiencies of gene transfection greater than 40% were routinely obtained by using a combination of optimized conditions of HUVEC isolation, composition of the electroporation medium and homogeneity of the plasmids. The protocol has been applied to the functional transient transfection of functional genes in HUVEC as illustrated in the case of the cDNA encoding GFP, protein kinase C (alpha and epsilon isotypes) and beta-galactosidase.

Immunophenotypic characterisation of carotid plaque: increased amount of inflammatory cells as an independent predictor for ischaemic symptoms

OBJECTIVES

To investigate the inflammatory response within intact carotid plaques from carotid eversion endarterectomy (CEE) to determine the relationship between immunohistological plaque morphology and ischaemic cerebrovascular symptoms.

MATERIAL AND METHODS

Intact CEE plaques from 71 patients with high-grade (>70%) stenosis undergoing CEE (group I, symptomatic, n=42; group II, asymptomatic, n =29) and 12 normal postmortem arteries (control group) were analysed with specific antibodies to inflammatory cells (T-Lymphocytes (CD3, CD4), cytotoxic T-cells (CD8), B-lymphocytes (CD20), natural killer cells (CD57), macrophages (CD68)), endothelial adhesion molecules (ICAM-1 (CD54), P-selectin (CD62P), E-selectin (CD62E), VCAM-1 (CD106) and T-lymphocyte co-stimulatory molecule (CD40)) and procoagulatory modulators (thrombomodulin (CD141), tissue factor (CD142)). Both groups were matched for gender, age, risk factors, degree of carotid artery stenosis. Plaques were measured using a semiquantitative score system in a blinded fashion by two observers. Statistical analysis of the group differences were performed by using the Kruskal-Wallis test and the Multitest Procedure with Permutation-Testing. Significance was taken as a p<0.05.

RESULTS

There were significantly more inflammatory cells, an overexpression of P-selectin and the procoagulatory markers thrombomodulin and tissue factor in symptomatic compared to both asymptomatic plaques and the ones of the control group. In both groups there was no significance for ICAM-1, VCAM-1, macrophages and co-stimulatory molecule CD40. There was also no significance for any factor between the asymptomatic and the control group. However, the differences between the symptomatic and the asymptomatic group were highly significant for all factors.

CONCLUSION

These data suggest that structural changes and inflammatory damage within the individual plaque seems to be a critical step in promoting plaque rupture with embolic sequelae.

Selective immunointervention in autoimmune diseases: lessons from multiple sclerosis

Activation of peripheral T cells by foreign and self antigens is under stringent control by different mechanisms, both thymic and peripheral. Control of T cell reactivity is accomplished by three major types of mechanisms: 1) deletion, the physical elimination of T cells specific for a given antigen, 2) anergy, the functional incapacity of T cells to respond to antigen, 3) suppression, the inhibition of T cell function by a regulatory (suppressor) cell. Their failure may lead to autoimmune diseases. The progress in understanding T cell activation, inactivation and modulation is being translated into strategies able to induce selective immunosuppression to treat different pathological situations, notably autoimmune diseases, allergies, and allograft rejection. The medical need for selective immunosuppression is very high, as the available immunosuppressive drugs are substantially inadequate because of limited efficacy, modest selectivity, and considerable toxicity. Key attack points for selective immunointervention have been identified: modulation of antigen recognition, co-stimulation blockade, induction of regulatory cells, deviation to non-pathogenic or protective responses, neutralization of proinflammatory cytokines, induction or administration of anti-inflammatory cytokines, and modulation of leukocyte trafficking. All these forms of immunointervention have been successfully used to prevent and sometimes treat experimental autoimmune diseases. Based on these results, expectations have been raised for exploiting the same strategies to inhibit the activation of human autoreactive T cells. In this overview, we will examine recent advances towards immunointervention in multiple sclerosis (MS) as a paradigm for successes and failures of current immunotherapeutic approaches in human autoimmune diseases.

Immunoglobulin and cytokine expression in mixed lymphocyte cultures is reduced by disruption of gap junction intercellular communication

Connexins (Cx), the protein subunits assembled into gap junction intercellular communication channels, are expressed in primary lymphoid organs and by circulating leukocytes. Human tonsil-derived T and B lymphocytes express Cx40 and 43; circulating human T, B, and NK lymphocytes express Cx43 and directly transfer between each other a low molecular dye indicative that functional gap junctions exist. We now identify specific properties in the immune system underwritten by gap junctions. Mixed lymphocytes cultured in the presence of two reagents with independent inhibitory action on gap junction communication, a connexin mimetic peptide and 18-alpha-glycyrrhetinic acid, markedly reduced the secretion of IgM, IgG, and IgA. The secretion of these immunoglobulins by purified B cells was also reduced by the two classes of gap junction inhibitors. Complex temporal inhibitory effects on the expression of mRNA encoding interleukins, especially IL-10, were also observed. The results indicate that intercellular signaling across gap junctions is an important component of the mechanisms underlying metabolic cooperation in the immune system.

Humic acid suppresses the LPS-induced expression of cell-surface adhesion proteins through the inhibition of NF-kappaB activation

Humic acid (HA), a potential toxin when penetrating the drinking well water of blackfoot disease-endemic areas in Taiwan, has been implicated as one of the etiological factors of this disease. In this study, we investigated the effects of HA on the expression of human vascular endothelial-leukocyte adhesion molecules and the activation of nuclear factor kappa B (NF-kappaB) in cultured human umbilical vein endothelial cells (HUVECs). The expression of intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), and E-selectin was monitored by flow cytometry. Pretreatment of HUVECs with HA inhibited the lipopolysaccharide (LPS)-induced expression of these three adhesion molecules in a dose- and time-dependent manner. Since NF-kappaB can regulate the expression of these adhesion molecules, NF-kappaB activation was assessed by electrophoretic mobility shift assay (EMSA). Our results reveal that the activation of NF-kappaB by LPS is suppressed by HA in a dose- and time-dependent manner. Furthermore, HA reduces NF-kappaB binding to DNA slightly, but completely inhibits the degradation of IkappaBalpha at a concentration of 100 microg/ml. Thus, all our data demonstrate that HA can inhibit the LPS-induced expression of adhesion molecules through the inhibition of NF-kappaB activation. HA may also suppress the immune or inflammatory reaction of HUVECs responsible for endotoxin, which could be one possible explanation for the causes of the infection and inflammation observed for patients with blackfoot disease. Our results also suggest that immune or inflammatory disturbance occurs for patients with blackfoot disease and that NF-kappaB may be a critical molecule in the pathogenesis of this disease.

Periodontal disease and atherosclerotic cardiovascular disease: confounding effects or epiphenomenon?

Recent evidence suggests that periodontal disease may predispose to atherosclerotic cardiovascular disease. Data support mechanisms of host-derived local and systemic proinflammatory responses similar to atherosclerosis, consisting of monocytic-derived cytokines and other inflammatory mediators, which are induced by periodontal pathogens and its endotoxin, lipopolysaccharide. These mechanisms may contribute to the start of vascular endothelial dysfunction and further sequelae leading to atherosclerosis. Experimental evidence and biologic plausibility appear to support this proposal. However, clinical evidence from a MEDLINE search from January 1966-December 1999 proposed a weak or no correlation primarily due to confounding factors. The aim of care is to reduce vulnerable pathogens from the infected periodontium by standard treatment; however, new approaches appear promising. Increased awareness of a potential link among infective agents, immunoinflammatory processes, and atherosclerosis may clarify clinical implications.

Inhibition by nitric oxide-releasing compounds of E-selectin expression in and neutrophil adhesion to human endothelial cells

The effects of two chemically unrelated nitric oxide (NO)-releasing compounds were studied on adhesion molecule expression in and neutrophil adhesion to human umbilical vein endothelial cells. Incubation of confluent monolayers of endothelial cells with increasing concentrations of lipopolysaccharide stimulated the adhesion of polymorphonuclear leukocytes to endothelial cells. Flow cytometric analysis showed that lipopolysaccharide treatment upregulated the expression of adhesion molecules E-selectin and intercellular adhesion molecule-1 (ICAM-1) in human umbilical vein endothelial cells. A novel NO-releasing compound GEA 3175 (1,2,3, 4-oxatriazolium, -3-(3-chloro-2-methylphenyl)-5-[[(4-methylphenyl)sulfonyl]amino]-, hydroxide inner salt) inhibited lipopolysaccharide-induced adhesion being more potent than the earlier known NO donor S-nitroso-N-acetylpenicillamine. The increased E-selectin expression induced by lipopolysaccharide was significantly attenuated by the two NO donors tested whereas ICAM-1 expression remained unaltered. The present data show that NO donors inhibit E-selectin expression in and neutrophil adhesion to lipopolysaccharide-stimulated vascular endothelial cells. Thus, by inhibiting leukocyte adhesion NO donors may reduce leukocyte infiltration and leukocyte-mediated tissue injury in inflammation and ischemia-reperfusion injury.

Effects of diet and of dietary components on endothelial leukocyte adhesion molecules

Endothelial-leukocyte adhesion molecules are involved in processes regulating the selective attachment of leukocytes to the vessel wall, which participate in tissue inflammation, atherogenesis, and immunity. There has been recent appreciation that diet or specific dietary components may modulate such processes. Highly unsaturated-- particularly omega-3 -- fatty acids and antioxidants are receiving increasing attention in this regard as potential antiatherogenic and anti-inflammatory agents. The vascular surface expression of endothelial leukocyte molecules can also be reflected by plasma levels of "soluble" adhesion molecules, thus allowing the assessment of the effects of diet and selected dietary components on these processes in vivo.

Presence of activated lymphocytes in the peripheral blood of patients with halo nevi

BACKGROUND

The involution of the central pigmented lesion in halo nevus (HN) seems to be mediated by an immune response against self antigens expressed by melanocytes.

OBJECTIVE

We assessed the presence of activated lymphocytes in the peripheral blood lymphocytes from patients with HN.

METHODS

Peripheral blood was obtained from patients with HN associated with benign pigmented lesions (5) or melanoma (2) as well as from patients with melanoma without HN (5) and healthy subjects (10). Activated lymphocytes were detected by flow cytometry analysis using monoclonal antibodies (mAb) against CD69, CD71, CD98, HLA-DR, and activated beta(1) integrins (HUTS-21 mAb).

RESULTS

The peripheral blood lymphocytes from patients with HN, associated with either benign or malignant lesions, exhibited a significantly higher expression of all activation markers studied compared with patients with melanoma without HN or compared with healthy subjects. Therefore the peripheral blood of HN patients contained a significant fraction of lymphocytes with an activated (CD69(+), HLA-DR(+), CD98(bright)), cell proliferating (CD71( bright)), and high adhesive (HUTS-21(bright)) phenotype. These activated cells disappeared from peripheral blood after the surgical resection of the skin lesion.

CONCLUSION

Our findings further support the involvement of immune activation in HN phenomenon.