Adhesion of peripheral blood mononuclear cells to vascular endothelium in patients with systemic sclerosis (scleroderma)

Kidney transplantation in systemic sclerosis: Advances in graft, disease, and patient outcome

Systemic sclerosis (SSc) is an immune-mediated rheumatic disease characterized by vascular abnormalities, tissue fibrosis, and inflammation. Renal disease occurring in patients with SSc may have a variable clinicopathological picture. However, the most specific renal condition associated with this disease is the scleroderma renal crisis (SRC), characterized by acute onset of renal failure and severe hypertension. SRC develops in about 20% of cases of SSc, especially in those patients with diffuse cutaneous disease. The prognosis of this condition is often negative, with a rapid progression to end-stage renal disease (ESRD). The advent of the antihypertensive angiotensin-converting enzyme inhibitors in 1980 was associated with a significant improvement in patients’ survival and recovery of renal function. However, the prognosis of these patients can still be improved. The dialytic condition is associated with early death, and mortality is significantly higher than among patients undergoing renal replacement therapy (RRT) due to other conditions. Patients with SRC who show no signs of renal functional recovery despite timely blood pressure control are candidates for kidney transplantation (KT). In this review, we reported the most recent advances in KT in patients with ESRD due to SSc, with a particular overview of the risk of disease recurrence after transplantation and the evolution of other disease manifestations.

Differential expression of junctional adhesion molecules in different stages of systemic sclerosis

OBJECTIVE

Systemic sclerosis (SSc) is characterized by early perivascular inflammation, microvascular endothelial cell (MVEC) activation/damage, and defective angiogenesis. Junctional adhesion molecules (JAMs) regulate leukocyte recruitment to sites of inflammation and ischemia-reperfusion injury, vascular permeability, and angiogenesis. This study was undertaken to investigate the possible role of JAMs in SSc pathogenesis.

METHODS

JAM-A and JAM-C expression levels in skin biopsy samples from 25 SSc patients and 15 healthy subjects were investigated by immunohistochemistry and Western blotting. Subcellular localization of JAMs in cultured healthy dermal MVECs and SSc MVECs was assessed by confocal microscopy. Serum levels of soluble JAM-A (sJAM-A) and sJAM-C in 64 SSc patients and 32 healthy subjects were examined by enzyme-linked immunosorbent assay.

RESULTS

In control skin, constitutive JAM-A expression was observed in MVECs and fibroblasts. In early-stage SSc skin, JAM-A expression was strongly increased in MVECs, fibroblasts, and perivascular inflammatory cells. In late-stage SSc, JAM-A expression was decreased compared with controls. JAM-C was weakly expressed in control and late-stage SSc skin, while it was strongly expressed in MVECs, fibroblasts, and inflammatory cells in early-stage SSc. Surface expression of JAM-A was higher in early-stage SSc MVECs and increased in healthy MVECs stimulated with early-stage SSc sera. JAM-C was cytoplasmic in resting healthy MVECs, while it was recruited to the cell surface upon challenge with early-stage SSc sera. Early-stage SSc MVECs exhibited constitutive surface JAM-C expression. In SSc, increased levels of sJAM-A and sJAM-C correlated with early disease and measures of vascular damage.

CONCLUSION

Our findings indicate that JAMs may participate in MVEC activation, inflammatory processes, and impaired angiogenesis in different stages of SSc.

[Cytokines and T cell differentiation in systemic sclerosis]

The physiopathology of systemic sclerosis remains unclear within a complex interaction between vasculopathy, perivascular inflammatory infiltrate, extensive tissue fibrosis and auto-immune manifestations. Chronology between vascular disease and adjacent inflammatory cell infiltration is still not yet clarified. There is growing evidence that T cell activation and its cytokine expression play a key role in vascular impairment occurrence and collagen dysregulation. Nevertheless, cytokine descriptions are mainly limited to blood and tissue measurement and the T cells differentiation analysis restricted to the Th1/Th2 balance. The purpose of this review is to establish an exhaustive cartography of cytokines involved in T cell differentiation, regarding the recent advance in T lymphocyte differentiation, including Th9, Th17, Th22 and regulatory T cells (Treg) pathways. This review will focus on Th17, Th22 and Treg differentiation, corresponding to the equilibrium between inflammation and tolerance. Finally, regarding published results in systemic sclerosis, T cells participation appears to be more a Th1/Th2 co-expression than an exclusive Th1 or Th2 polarization. Also, a possible Th22/Treg imbalance is suggested, leading to a Th22 overexpression and likely to tissue inflammation genesis.

Junctional adhesion molecule-A is abnormally expressed in diffuse cutaneous systemic sclerosis skin and mediates myeloid cell adhesion

OBJECTIVE

To investigate the role of junctional adhesion molecule-A (JAM-A) in the pathogenesis of systemic sclerosis (SSc).

METHODS

Biopsy specimens from proximal and distal arm skin and serum were obtained from patients with SSc and normal volunteers. To determine the expression of JAM-A on SSc dermal fibroblasts and in SSc skin, cell surface ELISAs and immunohistology were performed. An ELISA was designed to determine the amount of soluble JAM-A (sJAM-A) in serum. Myeloid U937 cell-SSc dermal fibroblast and skin adhesion assays were performed to determine the role of JAM-A in myeloid cell adhesion.

RESULTS

The stratum granulosum and dermal endothelial cells (ECs) from distal arm SSc skin exhibited significantly decreased expression of JAM-A in comparison with normal volunteers. However, sJAM-A was increased in the serum of patients with SSc compared with normal volunteers. Conversely, JAM-A was increased on the surface of SSc compared with normal dermal fibroblasts. JAM-A accounted for a significant portion of U937 binding to SSc dermal fibroblasts. In addition, JAM-A contributed to U937 adhesion to both distal and proximal SSc skin.

CONCLUSIONS

JAM-A expression is dysregulated in SSc skin. Decreased expression of JAM-A on SSc ECs may result in a reduced response to proangiogenic basic fibroblast growth factor. Increased JAM-A expression on SSc fibroblasts may serve to retain myeloid cells, which in turn secrete angiogenic factors.

The proadhesive phenotype of systemic sclerosis skin promotes myeloid cell adhesion via ICAM-1 and VCAM-1

OBJECTIVE

SSc is characterized by microvascular abnormalities and leucocyte infiltration. Previous studies have suggested a proadhesive phenotype in SSc skin, but the functional consequences of this phenotype are not fully understood. Molecules known to mediate leucocyte adhesion include those present at intracellular junctions, such as junctional adhesion molecule-B (JAM-B), JAM-C and CD99, as well as intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1). The aim of this study was to examine adhesive interactions in SSc skin.

METHODS

The expression of JAM-B, JAM-C, CD99, ICAM-1 and VCAM-1 in SSc skin was determined by immunohistology and cell surface ELISA. Myeloid U937 cell-SSc dermal fibroblast adhesion assays or in situ adhesion assays to SSc skin were performed.

RESULTS

JAM-C and CD99 expression on endothelial cells (ECs) in SSc skin was decreased compared with expression on normal ECs. CD99 was overexpressed on mononuclear cells in SSc skin and on SSc dermal fibroblasts. Neutralizing ICAM-1 inhibited the binding of U937 cells to SSc dermal fibroblasts. In addition, blocking both ICAM-1 and VCAM-1 inhibited U937 cell adhesion to either proximal (less involved) or distal (more involved) SSc skin.

CONCLUSIONS

These studies show that JAM-C and CD99 are aberrantly expressed in SSc skin. However, these adhesion molecules do not mediate myeloid cell-SSc skin adhesion. In contrast, we demonstrate an important role for ICAM-1 and VCAM-1 in the retention of myeloid cells in SSc skin, suggesting that targeting these molecules may be useful SSc therapies.

Polymorphism of the fractalkine receptor CX3CR1 and systemic sclerosis-associated pulmonary arterial hypertension

Fractalkine (FKN) and its receptor CX3CR1 are critical mediators in the vascular and tissue damage of several chronic diseases, including systemic sclerosis (SSc) and pulmonary arterial hypertension (PAH). Interestingly, the V249I and T280M genetic polymorphisms influence CX3CR1 expression and function. We investigated whether these polymorphisms are associated with PAH secondary to SSc. CX3CR1 genotypes were analyzed by PCR and sequencing in 76 patients with limited SSc and 204 healthy controls. PAH was defined by colorDoppler echocardiography. Homozygosity for 249II as well as the combined presence of 249II and 280MM were significantly more frequent in patients with SSc compared to controls (17 vs 6%, p = 0.0034 and 5 vs 1%, p = 0.0027, respectively). The 249I and 280M alleles were associated with PAH (odd ratio [OR] 2.2, 95% confidence interval [CI] 1.01-4.75, p = 0.028 and OR 7.37, 95%CI: 2.45-24.60, p = 0.0001, respectively). In conclusion, the increased frequencies of 249I and 280M CX3CR1 alleles in a subgroup of patients with SSc-associated PAH suggest a role for the fractalkine system in the pathogenesis of this condition. Further, the 249I allele might be associated with susceptibility to SSc.

Prolactin synthesis by lymphocytes from patients with systemic sclerosis

Systemic sclerosis (SSc) is an autoimmune disease characterized by fibrosis of the skin and internal organs. It has been demonstrated that serum prolactin levels are increased in patients with various connective tissue diseases. The aim of this study was to investigate the possible source of excessive prolactin synthesis in SSc and its effects on immune cells. The study group consisted of 52 patients with diffuse SSc (44 women and eight men) and 52 age and sex matched healthy controls. The methods used were: ELISA and indirect immunofluorescence. Our results show significantly elevated level of prolactin in male and female patients with SSc and increased prolactin production by SSc lymphocytes as compared to healthy donors X lymphocytes (25.4+/-11.0 vs. 13.4+/-5.0 absorbance units). Patients X and healthy controls X lymphocytes, showed equal presence of prolactin receptors. Soluble interleukin 2 receptor (CD25) concentration, was significantly higher in supernatants of prolactin stimulated lymphocytes, as compared to non-stimulated lymphocytes. We conclude that lymphocytes might contribute to elevated prolactin levels in patients with SSc and that these cells themselves may be sensitive to prolactin stimulation. Therefore, a pharmacologic attempt to lower prolactin levels in patients with SSc could proof beneficial.

Long-term therapy with plasma exchange in systemic sclerosis: effects on laboratory markers reflecting disease activity

Plasma exchange (PEX) is a technique that has been applied to the treatment of many immunological disorders, including connective tissue diseases. The crucial role of some humoral factors in the pathogenesis of systemic sclerosis (SSc) could explain the good clinical results obtained in terms of slowing down the disease progression, but the efficacy of PEX in the treatment of SSc is not yet well defined, owing to the lack of controlled studies and validated parameters of disease activity. To demonstrate the long-term efficacy of PEX in the treatment of SSc we treated a group of 28 SSc patients affected with recent onset and/or rapidly progressive disease. Most of these had a diffuse form of SSc, with anti-Sc170 antibody as a disease marker. Before and after long-term PEX treatment we evaluated disease activity parameters including the serum levels of interleukin 2 soluble receptor (sIL-2R) and aminoterminal type III procollagen peptide (PIIINP), plus the percentage of DR+ T cells in the peripheral blood. We also assessed clinical parameters of total skin score and total visceral score. The same parameters were evaluated in 25 SSc patients who did not satisfy the admission criteria for PEX, treated long-term with drugs only. At baseline, serum PIIINP and sIL-2R levels and the percentage of DR+ T cells were significantly increased in PEX patients as compared to others. Following long-term PEX treatment, all the laboratory parameters significantly decreased and the clinical scores showed a slight but not significant improvement. Conversely, in the other group of SSc patients treated for the same period with drugs only, no significant change of laboratory parameters was detected and the clinical scores slightly worsened. Our data suggest that long-term PEX therapy seems to be effective in slowing down the clinical course of patients with severe and rapidly progressive SSc.

Characterization of autoantibodies to endothelial cells in systemic sclerosis (SSc): association with pulmonary fibrosis

To determine the prevalence and the characterization of antibodies to endothelial cells in patients with SSc, serum samples from 80 patients with SSc, 20 patients with systemic lupus erythematosus (SLE), and 20 healthy control subjects were examined by ELISA using cultured human umbilical vein endothelial cells (HUVEC), indirect immunofluorescence analysis (IIF), and immunoblotting using cytoplasmic extract of HUVEC. IgG and/or IgM isotype anti-endothelial cell antibodies (AECA) were demonstrated by ELISA in 43 of 80 patients with SSc (54%), in 15 of 20 patients with SLE (75%), and in none of 20 healthy control subjects. Immunofluorescence analysis on HUVEC substrate showed homogeneous cytoplasmic staining. Immunoblotting demonstrated that these patients had antibodies directed to one or several antigens of approximately 60, 90, 110 and 140 kD, and the most common responses were to the 90-kD antigen. By the immunofluorescence method using HUVEC, affinity-purified anti-90-kD antibodies showed identical cytoplasmic staining to that produced by sera positive for AECA. Furthermore, AECA were closely correlated with pulmonary fibrosis in patients with SSc. These findings suggest that patients with SSc have abnormal antibodies to endothelial cell antigens, and support the hypothesis that endothelial dysfunction is involved in the development of this disease.

Immunopathogenesis of systemic sclerosis

The information outlined above can be used to generate a model of the immunopathogenesis of SSc (Fig. 3). This model includes a susceptible host, with age greater than 25 and female gender being risk factors. The model also includes exposure to exogenous agents, which could be different in different individuals and may include inhaled or ingested chemicals or infectious agents. An early event is T-cell activation, with infiltration in the skin and internal organs. Activation of the T cells is a selective process that appears to be influenced by antigen in SSc patients. The importance of a particular T-cell subpopulation may depend upon the organ involved and the stage of the disease. CD4+ T cells predominate in the skin. In contrast, CD8+ T cells are increased in the lungs of patients with alveolitis, where they are oligoclonal, showing evidence of antigen-driven selection. V delta 1+ gamma/delta T cells are increased in both the blood and lungs of SSc patients and also show evidence of selection by antigen. B cells are activated early, with polyclonal activation leading to hypergammaglobulinemia. SSc-specific autoantibodies target DNA topoisomerase I, centromeric proteins, and RNA polymerases I and III. Characteristics of autoantibodies in SSc suggest that the target antigens are presented to the immune system as native molecules or even part of a multiunit complex. There is some homology between viruses and autoantibody targets in SSc, which suggests that molecular mimicry may play a role in initiating the antibody response. Many nonspecific inflammatory cells infiltrate the tissues and show evidence of activation. These include macrophages and monocytes, mast cells, eosinophils, basophils, and natural killer cells. Soluble mediators made by these T cells, B cells, and nonspecific inflammatory cells can activate and damage fibroblasts, endothelial cells, and other vascular cells. The relative importance of the various candidate cytokines, the temporal sequence of their production, and their cellular sources remain largely to be defined. There may be some contribution of direct T-cell cytotoxicity or antibody-dependent cellular cytoxicity to the tissue damage that occurs.

IgG antiendothelial cell autoantibodies from scleroderma patients induce leukocyte adhesion to human vascular endothelial cells in vitro. Induction of adhesion molecule expression and involvement of endothelium-derived cytokines

IgG autoantibodies that bind human endothelial cells (AECA) were detected by ELISA in 30 of 42 samples of sera from patients with scleroderma. Pretreatment of human umbilical vein endothelial cells with AECA-positive scleroderma sera, or IgG purified from these sera, led to a dose- and time-dependent increase in the ability of the cells to bind human U937 monocytic cells. Threshold-active IgG concentrations were 1-10 micrograms/ml; effects were significant after 3 h and maximal after 6-12 h. IgG from AECA-negative sera or normal sera were without effect. Increased adhesion of U937 cells was accompanied by increased expression of endothelial intercellular adhesion molecule-1, vascular cell adhesion molecule-1, and E-selectin. Transfer of endothelial cell-conditioned media after pretreatment with AECA and immunodepletion of IgG demonstrated the presence of transferable activity that mimicked the effects of AECA. Treatment with neutralizing anticytokine antibodies indicated that IL-1, generated by the endothelial cells in response to AECA, was involved in the upregulation of adhesion molecules and U937 cell adhesion. We conclude that AECA can play a pathogenic role in scleroderma by activating endothelial cells, in part due to autocrine or paracrine actions of IL-1.

HLA and ethnic associations among systemic sclerosis patients with anticentromere antibodies

SSc with ACAs is characterized by limited cutaneous involvement and, in most patients, a mild protracted course. We have studied 104 SSc patients, 47 with ACAs and 57 who were negative for both ACAs and anti-topo I antibodies, for HLA-DR and -DQ associations using DNA typing techniques. Normal controls consisted of 181 healthy individuals. A significant association was observed in the ACA-positive patients with DQB1-0501 (p = 0.001, RR 2.6). There was also a significant decrease in the frequency of DQB1-0201 (p = 0.01, RR 0.33). In addition, the ACA-positive SSc patients were significantly different ethnically from both the other SSc patients and the normal controls (p = 0.004). When patients were stratified according to their ethnic origin and the analysis of HLA associations was repeated, the HLA associations persisted. These results strongly suggest that the development of SSc with ACAs is associated with particular DQB1 alleles, and also that ethnic origin plays a role in disease susceptibility.