Interactions of lymphocytes from patients with psoriatic arthritis or healthy controls and cultured endothelial cells

Insights Into Leukocyte Trafficking in Inflammatory Arthritis - Imaging the Joint

The inappropriate accumulation and activation of leukocytes is a shared pathological feature of immune-mediated inflammatory diseases (IMIDs), such as rheumatoid arthritis (RA) and psoriatic arthritis (PsA). Cellular accumulation is therefore an attractive target for therapeutic intervention. However, attempts to modulate leukocyte entry and exit from the joint have proven unsuccessful to date, indicating that gaps in our knowledge remain. Technological advancements are now allowing real-time tracking of leukocyte movement through arthritic joints or in vitro joint constructs. Coupling this technology with improvements in analyzing the cellular composition, location and interactions of leukocytes with neighboring cells has increased our understanding of the temporal dynamics and molecular mechanisms underpinning pathological accumulation of leukocytes in arthritic joints. In this review, we explore our current understanding of the mechanisms leading to inappropriate leukocyte trafficking in inflammatory arthritis, and how these evolve with disease progression. Moreover, we highlight the advances in imaging of human and murine joints, along with multi-cellular ex vivo joint constructs that have led to our current knowledge base.

Adhesion of peripheral blood mononuclear cells and CD4+ T cells from patients with psoriasis to cultured endothelial cells via the interaction between lymphocyte function-associated antigen type 1 and intercellular adhesion molecule 1

BACKGROUND

The adhesion of CD4+ T cells to endothelial cells and their subsequent migration to skin tissue are essential to develop the psoriatic skin lesion. However, few studies have examined the role of adhesion molecules in the binding of T cells from patients with chronic plaque psoriasis to endothelial cells in vitro; thus, the adhesion molecules responsible for the development of skin lesions are still unclear.

OBJECTIVES

To identify the responsible adhesion molecules in the interaction between CD4+ T cells in patients with chronic plaque psoriasis and cytokine-stimulated endothelial cells.

METHODS

An in vitro adhesion assay between Calcein-labelled peripheral blood mononuclear cells (PBMC) and cytokine-stimulated human endothelial cultures, which exhibit a higher adhesion capacity to PBMC, was established, and the adhesion-inhibitory effects of a panel of antiadhesion molecule antibodies on the adhesion of PBMC from patients with psoriasis to endothelial cells were examined. Then, the inhibitory effects of selected antibodies acting on the interaction between CD4+ T cells from patients with psoriasis (purified by negative magnetic cell sorting) and cultured endothelial cells were examined.

RESULTS

A significant increase (P < 0.01) in the adhesion of psoriatic PBMC to both endothelial cultures, human skin microvascular endothelial cells from adults (HMVEC-Ad) and human coronary arterial endothelial cells (HCAEC), compared with healthy PBMC, was demonstrated in our in vitro cell adhesion assay. Pretreatment of both endothelial cultures with tumour necrosis factor (TNF)-alpha (1000 U mL(-1)) induced the most frequent adhesion of PBMC from patients with psoriasis among the three inflammatory cytokines examined, i.e. TNF-alpha, interleukin-1beta and interferon-gamma [TNF-alpha-treated vs. nontreated: P < 0.001 (in both HMVEC-Ad and HCAEC)]. In both endothelial cultures treated with TNF-alpha, PBMC from patients with psoriasis exhibited significantly more frequent adhesion compared with those from healthy individuals (P < 0.001). The TNF-alpha-stimulated HMVEC-Ad, which exhibited the most frequent adhesion of PBMC, were selected for adhesion-inhibition experiments using monoclonal antibodies (mAbs) to adhesion molecules that are upregulated in psoriatic lesions, and the combination of antilymphocyte function-associated antigen type 1 (LFA-1) and anti-intercellular adhesion molecule 1 (ICAM-1) mAbs gave the greatest reduction of adhesion of PBMC from patients with psoriasis (approximately 69% reduction; P < 0.01). This combination of mAbs significantly reduced also the adhesion of CD4+ T cells from patients with psoriasis to TNF-alpha-stimulated HMVEC-Ad (approximately 62% reduction), compared with pretreatment with isotype control mAbs (P < 0.01).

CONCLUSIONS

These findings indicate that the LFA-1/ICAM-1 interaction plays a major role in the adhesion of CD4+ T cells to endothelial cells and that TNF-alpha might play an important role for the induction of adhesion molecules on endothelial cells at psoriatic skin lesions.

Psoriasis Arthritis

This article presents an overview of psoriatic arthritis, including the origin, genetic influence and immunologic factors involved in its evolution. The clinical features of psoriatic arthritis are also reviewed in this article, and a discussion of the diagnosis and treatment is included. We have highlighted the current psoriasis treatments, new biological therapies, and their use in practice. This paper reviews the efficacy of these agents, and the importance of their early appliance. The available published data on the efficacy of antimalarials, sulfasalazine, methotrexate, azathioprine and ciclosporin are described, as well as new data on leflunomide and other novel agents.

Increased Neutrophil Adherence in Psoriasis: Role of the Human Endothelial Cell Receptor Thy-1 (CD90)

The chronic inflammatory skin disease psoriasis is characterized by prominent skin infiltration by neutrophils and microabscess formation. The adhesion of leukocytes and subsequent transmigration through the activated endothelium is one prerequisite for the accumulation of these cells in skin. In recent studies, the human Thy-1 (CD90) was characterized as an adhesion molecule on activated endothelial cells (ECs) mediating the adhesion of neutrophils via the interaction with the beta2-integrin Mac-1. Based on these novel findings, we compared the roles of Thy-1 and ICAM-1 in the adhesion of neutrophils from patients with psoriasis to activated ECs. The adhesion of peripheral blood neutrophils of patients suffering from psoriasis to Thy-1-transfected cells as well as to activated, Thy-1-expressing human dermal microvascular ECs (HDMECs) is distinctly increased in comparison to the adhesion of neutrophils from healthy controls. In contrast, adherence of psoriatic neutrophils to ICAM-1 transfectants is, if at all, only slightly enhanced compared to healthy controls. The interaction of healthy as well as psoriatic polymorphonuclear cells to Thy-1 transfectants and HDMECs was significantly inhibited by blocking Thy-1 on ECs or its receptor Mac-1 on neutrophils, indicating the importance of this interaction for the adhesion of neutrophils to activated endothelium. In conclusion, our data indicate that the adhesion of neutrophils to activated ECs mediated by Thy-1/Mac-1 interaction is an important attachment mechanism facilitating their subsequent migration into lesional psoriatic skin.

Current concepts in psoriatic arthritis

This review summarizes articles written about psoriatic arthritis in the past year. It concentrates on clinical and epidemiologic issues, pathogenesis and treatment, and updates the reader regarding new concepts in psoriatic arthritis.

Regulation of chemokine expression in atherosclerosis

(1) Chemokines play a central role in the pathogenesis of atherosclerosis, contributing to leukocyte recruitment, angiogenesis and also proliferation and migration of smooth muscle cells into atherosclerotic plaques. (2) Leukocytes and endothelial cells are an important source of chemokines, and many of the risk factors associated with atherosclerosis increase chemokine expression. There is now a body of evidence to suggest that interactions between cells such as leukocytes and endothelial cells amplify chemokine release, and this may contribute to sustained chemokine generation in inflammatory conditions. (3) This article summarises, briefly, what is currently known about chemokines release. A number of important pharmacological strategies used in the treatment of atherosclerosis inhibit chemokine release and the extent to which this may contribute to their therapeutic effect will be discussed. Understanding the mechanisms controlling chemokine expression is essential for the design of specific therapeutic interventions in atherosclerosis.

Disease mechanisms in psoriasis and psoriatic arthritis

Any hypothesis that tries to explain disease mechanisms in psoriasis and psoriatic arthritis (PsA) must take into account the containment of the inflammatory process to three specific sites: the skin, synovium, and enthesis. This article reviews the recent literature that advances our understanding of disease mechanisms at these specific sites. Additional progress will be achieved by research that focuses on common pathogenic pathways at these sites, in particular when searching for foreign candidates or auto-antigens triggering the T-cell-mediated immune response.

Interaction of monocytes from patients with psoriatic arthritis with cultured microvascular endothelial cells

The aim of this study was to investigate the interaction of monocytes of the peripheral blood of patients with psoriatic arthritis with cultured human dermal microvascular endothelial cells (HDMEC) compared to monocytes from control persons. The surface expression of adhesion molecules (ADM) and other cell surface molecules in psoriatic arthritis and control monocytes was investigated by quantitative flow cytometry. The receptor densities of these molecules were determined in terms of monoclonal antibody (mAb) binding sites. Cocultivation experiments including peripheral blood mononuclear cells and HDMEC were performed to determine the adhesion to and transmigration through activated or resting endothelial cell monolayers. In order to achieve optimal responses of cellular functions, activation for adhesion experiments was induced by lipopolysaccharide (LPS), while in transmigration experiments the endothelial cells were activated by TNF-alpha. For transendothelial migration studies HDMEC cultivated on collagen gels were used. In the supernatants of cocultivated cells the cytokines IL-6 and IL-8 were determined by ELISA. A significantly reduced expression of CD11b in nonactivated psoriatic arthritis peripheral blood monocytes compared to control monocytes was verified (mean number of adhesion molecules/cell: 33,756 +/- 10,138 vs 61,023 +/- 6925). In agreement with these findings, adhesion to, as well as transendothelial migration through, activated HDMEC was found to be significantly reduced in psoriatic arthritis monocytes. Transendothelial migration engendered an enrichment of monocytes in the migrated cell fraction for both control and psoriatic arthritis peripheral blood mononuclear cells. The activation of HDMEC by LPS induced a highly significantly enhanced cytokine release for IL-6 and IL-8, irrespective of the origin of monocytes (psoriatic arthritis vs. controls). However, IL-8 production in the supernatants of nonactivated monocytes/HDMEC cocultures was significantly reduced in the case of monocytes from psoriatic arthritis patients (6650 +/- 2489.32 pg/ml) vs 9280.00 +/- 3209.51 pg/ml in control patients. Impaired adhesion as well as transendothelial migration of monocytes derived from peripheral blood of psoriatic arthritis patients can be explained by the reduced expression of adhesion molecules MAC-1 (CD11b/CD18) at the surface of monocytes. The reduced IL-8 production also corresponds to a diminished cellular interaction under nonflow conditions. These results support the view that there are systemic immunological alterations in psoriatic arthritis patients.