Increased platelet sensitivity to collagen-induced aggregation in whole blood patients with systemic sclerosis

Platelet aggregation in whole blood was investigated in patients with Systemic sclerosis and age- and sex-matched controls. Dose-response curves for collagen, adrenaline and ADP-induced fall in platelet count were constructed. Aggregation to collagen at all concentrations was significantly greater (p less than 0.01) in the patients with systemic sclerosis than the normal controls, with a four-fold reduction in the ED50 for SS (0.044 +/- 0.03 mcg/1) compared with controls (0.12 +/- 0.008 mcg/1). No significant difference was observed in the response to the other aggregating agents, thus suggesting that in this disease a platelet abnormality exists which is specific for collagen. Increased platelet responsiveness to collagen and hence increased release of platelet-derived growth factors may provide a lin between endothelial damage and the connective tissue fibrosis of systemic sclerosis.     

Increased susceptibility to oxidation of low-density lipoproteins isolated from patients with systemic sclerosis

Objective. To examine the resistance to oxidation of low-density lipoproteins (LDL) from patients with systemic sclerosis (SSc) and primary Raynaud's phenomenon (RP) compared with healthy controls. Methods. Plasma LDL were isolated from patients with diffuse cutaneous and limited cutaneous SSc (dcSSc and lcSSc, respectively), patients with primary RP, and healthy control subjects. The lipoproteins were assessed for their resistance to oxidation in the presence of cupric ions, using spectrophotometric assays. Results. LDL from patients with dcSSc and lcSSc were more susceptible to oxidation than were those from healthy control subjects or patients with RP. Conclusion. Our findings suggest that free radicals may play a role in the pathology of SSc.     

Heterogeneity of collagen synthesis in normal and systemic sclerosis skin fibroblasts. Increased proportion of high collagen-producing cells in systemic sclerosis fibroblasts

Objective. The goal of this study was to quantitatively analyze the distribution of collagen synthesis in normal and systemic sclerosis (SSc) fibroblast populations in order to determine the extent of activation in SSc populations. Methods. We used quantitative in situ hybridization to assess the population distribution of type I collagen synthesis. Fibroblast cultures were derived from both clinically involved and uninvolved skin regions of patients with SSc, and from healthy adults, and assessed for levels of α1(I) procollagen messenger RNA (mRNA). Results. Dermal fibroblasts from both patients with SSc and normal adults were heterogeneous for distribution of α1(I) procollagen mRNA when assessed by in situ hybridization, with a wide range of grains per cell. In contrast, clones of neonatal fibroblasts showed a relatively homogeneous distribution of grain counts. Involved SSc skin fibroblasts had a larger proportion of cells in the high collagen-producing mRNA subpopulation (mean ± SEM 28.4 ± 6.85%), compared with normal fibroblasts (1.75 ± 1.44%) and uninvolved fibroblasts (9.6 ± 6.73%). Conversely, within the low collagen-producing mRNA subpopulation, involved fibroblasts had a smaller proportion of cells (mean ± SEM 14.0 ± 5.63%) than did uninvolved fibroblasts (37.8 ± 13.69%), while normal fibroblasts had a majority of the cells in this subpopulation (53.5 ± 8.68%). Conclusion. These results suggest that only a specific subset of fibroblasts are activated in SSc, as evidenced by an increased proportion of cells with high levels of α1(I) procollagen mRNA. Differences between the SSc and normal fibroblast populations appeared to be quantitative rather than qualitative. This may be a result of either clonal selection or selective activation in the pathogenesis of SSc.     

Antifibroblast antibodies from systemic sclerosis patients are internalized by fibroblasts via a caveolin-linked pathway

OBJECTIVE: Fibroblast activation is a crucial event in the development of systemic sclerosis (SSc). Antifibroblast autoantibodies (AFAs), detectable in the sera of SSc patients, are able to induce a proinflammatory phenotype on cultured fibroblasts. This study was undertaken to investigate the mechanisms of the interaction between AFAs and living fibroblasts. METHODS: We coupled to fluorescein 1) IgG purified from AFA-positive and AFA-negative SSc sera (as assessed by cellular enzyme-linked immunosorbent assay) and 2) single healthy donor and pooled normal IgG. The interaction of IgG with living cultured fibroblasts from healthy individuals and from a patient with SSc was visualized by real-time confocal microscopy. Intracellular colocalization of caveolin and internalized AFA-positive IgG was assessed by immunofluorescence. RESULTS: AFA-positive IgG bound to living fibroblasts and was internalized with a cytoplasmic fibrillar pattern, in contrast to AFA-negative IgG. In the IgG tested, no correlation with antinuclear antibody activity was found. Preincubation of fibroblasts with normal IgG did not affect internalization. Internalized AFA-positive IgG colocalized with caveolin, and internalization was entirely inhibited by disassembling fibroblast caveolae with filipin. CONCLUSION: The finding that both normal and pathologic fibroblasts specifically internalized AFA-positive, but not AFA-negative, IgG demonstrates that AFAs in SSc patient sera interact with constitutively expressed membrane molecules on fibroblasts, via an Fc-independent mechanism. The results of colocalization and inhibition experiments suggest that microdomains containing caveolin are involved in the interaction between AFAs and fibroblasts. These data, together with the reported ability of AFAs to activate fibroblasts, provide evidence for a role of AFAs in the pathogenesis of SSc.     

BALF-derived fibroblasts differ from biopsy-derived fibroblasts in systemic sclerosis.

Growth of fibroblasts from bronchoalveolar lavage fluid (BALF) in patients with systemic sclerosis (SSc) has previously been described. The purpose of the present study was to characterise fibroblasts from BALF and bronchial biopsies from SSc patients with alveolitis and from controls, to analyse fibroblast proliferation, migration, stress fibres and proteoglycan production. BALF and bronchial biopsies were collected from 10 patients with SSc and alveolitis and from 15 controls. Outgrowth of fibroblasts was observed from the BALF of four patients, particularly in those with a markedly increased percentage of eosinophils in BALF, but not in any member of the control group. Increased levels of granulocyte-macrophage colony-stimulating factor, correlating with the percentage of eosinophils in BALF, were found in patients when compared with controls. Fibroblasts from BALF showed an elongated, mobile phenotype and increased proteoglycan production compared to the corresponding biopsy fibroblasts. In conclusion, outgrowth of fibroblasts with an altered phenotype is reported from bronchoalveolar lavage fluid in systemic sclerosis patients with alveolitis and an increased percentage of eosinophils in the bronchoalveolar lavage fluid. These findings indicate a possible role for eosinophil-fibroblast interaction in pulmonary fibrosis in systemic sclerosis.     

Impaired collagen gel contraction with cultured skin fibroblasts from patients with systemic sclerosis

We investigated the capacity of skin fibroblasts, derived from 9 patients with systemic sclerosis (SSc), to contract collagen lattices in a three-dimensional culture system. In comparison with control fibroblasts (N = 8), more than 30% of SSc fibroblasts exhibited markedly impaired ability to contract collagen lattices. The expression of alpha2beta1 integrins and integrin-mediated signals were not significantly different between normal and SSc fibroblasts. Although the underlying mechanisms remain to be determined, our present data provide evidence that certain aspects of interaction with collagen are impaired in SSc fibroblasts.     

Increased serum interleukin 23 in patients with systemic sclerosis

OBJECTIVE: The relationship between systemic sclerosis (SSc) and interleukin 23 (IL-23), a cytokine associated with the differentiation of T lymphocytes, is unknown. We investigated serum IL-23 levels and their clinical association in patients with SSc. METHODS: Serum IL-23 levels were examined by ELISA in 63 patients with SSc, 15 patients with systemic lupus erythematosus (SLE), and 31 healthy individuals. SSc patients comprised 25 with limited cutaneous SSc and 38 with diffuse cutaneous SSc. RESULTS: Serum IL-23 levels were significantly elevated in SSc patients compared to patients with SLE (p < 0.05) and controls (p < 0.005). Elevated serum IL-23 levels were associated with the disease duration (p < 0.05) and the prevalence of pulmonary fibrosis (p < 0.05), although they were not associated with other clinical features, including the extent of skin sclerosis or the severity of pulmonary fibrosis. CONCLUSION: The results suggest that IL-23 is associated with induction of SSc and that blockade of IL-23 can be a potential therapeutic strategy in early SSc.     

Severe vascular complications in patients affected by systemic sclerosis cyclically treated with iloprost

The objective of this study was to evaluate the incidence of the most severe vascular complications, such as pulmonary arterial hypertension, scleroderma renal crisis, and digital necrosis requiring amputation, in a monocentric group of systemic sclerosis (SSc) patients cyclically treated with intravenous iloprost. We reviewed the record-charts of 115 patients affected by SSc (18 men and 97 women, mean age 58.9.1?±?14.2?years) regularly receiving iloprost for at least 3?years; the mean duration of the treatment was 98.8?±?37.5?months (a total of 946.8?years of therapy). Demographic and clinical features were recorded. None of the patients died of SSc-associated vascular complications. After iloprost administration digital gangrene requiring amputation developed in 2 patients who had concomitant peripheral arterial disease (a total of 3 episodes; annual incidence of 0.31 for 100?years of iloprost therapy). Four patients were diagnosed with pulmonary arterial hypertension during iloprost treatment (annual incidence of 0.42 for 100?years of drug therapy); in none of the cases did the complication show a progressive course. No cases of scleroderma renal crisis were observed. With the limits of an observational study and in the absence of a control group, our experience suggests that prolonged cyclic iloprost therapy may limit the incidence/progression of severe digital and visceral SSc-vasculopathy.     

Increased proto-oncogene expression in peripheral blood T lymphocytes from patients with systemic sclerosis

The expression of c-myc, c-myb, and c-ras proto-oncogenes, determined using RNA hybridization techniques (slot-blot), was significantly increased in peripheral blood T lymphocytes, but not in B cells, from 17 patients with systemic sclerosis with diffuse scleroderma, compared with the expression in normal control subjects. The magnitude of expression of c-myc and c-myb tended to be higher in patients with early, active disease. These results demonstrate an in vivo activation of T cells from systemic sclerosis patients, which may play an important role in the pathogenesis of the disease.     

Increased sensitivity of lymphocytes from patients with systemic autoimmune diseases to DNA alkylation by the methylating carcinogen N-methyl-N-nitrosourea.

Lymphocytes from patients with various diseases associated with autoimmunity showed both impaired capacity to repair O6-methylguanine (a powerful, promutagenic, directly miscoding base lesion) and increased sensitivity to the cytocidal effects of cellular methylation by N-methyl-N-nitrosourea (MNU) compared with normal controls and patients with other disorders. Defective repair of O6-methylguanine was significantly associated with arthritis and myositis in the group with systemic lupus erythematosus (SLE), and increased sensitivity to the toxic action of MNU was associated with the presence of immune complexes and the administration of steroids to patients with Behçet's syndrome. The results indicate that lymphocytes from patients with the autoimmune diseases studied are more susceptible to DNA damage with possible relevance to aetiopathogenesis.     

Increased sensitivity of cerebrohepatorenal syndrome fibroblasts to antimycin A

The effect of four mitochondrial electron transport inhibitors on the growth of normal and cerebrohepatorenal syndrome (CHRS) fibroblasts was studied. Compared to normal fibroblasts, CHRS cells demonstrated a fivefold greater sensitivity to antimycin A, an inhibitor of the cytochrome bc₁ complex (complex III), but equal inhibition by amytal, rotenone and 2-heptyl-4-hydroxyquinoline-N-oxide. The results suggest a primary or secondary functional deficiency at mitochondrial complex III in fibroblasts.     

Increased serum soluble OX40 in patients with systemic sclerosis

OBJECTIVE: To determine levels of serum soluble OX40 (also termed CD134, a member of the tumor necrosis factor receptor superfamily) and their clinical associations in patients with systemic sclerosis (SSc). METHODS: Serum soluble OX40 levels were examined by ELISA in 53 patients with SSc, 15 patients with systemic lupus erythematosus (SLE), and 32 healthy individuals. RESULTS: OX40 levels were significantly elevated in SSc patients (125.7 +/- 5.7 pg/ml) compared to patients with SLE (80.7 +/- 1.7 pg/ml; p < 0.005) and controls (88.2 +/- 3.0 pg/ml; p < 0.0001). Elevated OX40 levels were found to be associated with disease duration of less than 2 years (p < 0.05). CONCLUSION: Our results suggest that serum soluble OX40 levels correlate with the early-onset of SSc disease.     

Antifibroblast antibodies from systemic sclerosis patients are internalized by fibroblasts via a caveolin‐linked pathway

Objective

Fibroblast activation is a crucial event in the development of systemic sclerosis (SSc). Antifibroblast autoantibodies (AFAs), detectable in the sera of SSc patients, are able to induce a proinflammatory phenotype on cultured fibroblasts. This study was undertaken to investigate the mechanisms of the interaction between AFAs and living fibroblasts.

Methods

We coupled to fluorescein 1) IgG purified from AFA‐positive and AFA‐negative SSc sera (as assessed by cellular enzyme‐linked immunosorbent assay) and 2) single healthy donor and pooled normal IgG. The interaction of IgG with living cultured fibroblasts from healthy individuals and from a patient with SSc was visualized by real‐time confocal microscopy. Intracellular colocalization of caveolin and internalized AFA‐positive IgG was assessed by immunofluorescence.

Results

AFA‐positive IgG bound to living fibroblasts and was internalized with a cytoplasmic fibrillar pattern, in contrast to AFA‐negative IgG. In the IgG tested, no correlation with antinuclear antibody activity was found. Preincubation of fibroblasts with normal IgG did not affect internalization. Internalized AFA‐positive IgG colocalized with caveolin, and internalization was entirely inhibited by disassembling fibroblast caveolae with filipin.

Conclusion

The finding that both normal and pathologic fibroblasts specifically internalized AFA‐positive, but not AFA‐negative, IgG demonstrates that AFAs in SSc patient sera interact with constitutively expressed membrane molecules on fibroblasts, via an Fc‐independent mechanism. The results of colocalization and inhibition experiments suggest that microdomains containing caveolin are involved in the interaction between AFAs and fibroblasts. These data, together with the reported ability of AFAs to activate fibroblasts, provide evidence for a role of AFAs in the pathogenesis of SSc.

     

Mutant fibronectin gene in skin fibroblasts of sclerotic lesions from patients with progressive systemic sclerosis

A mutant fibronectin gene was identified in skin fibroblasts obtained from sclerotic lesions of 7 patients with progressive systemic sclerosis. We found 2 point mutations adjacent to the cell-attachment tetrapeptide DNA sequence in the cell-binding domain of the fibronectin gene. This observation suggests that the mutant fibronectin is related to an integral component of sclerotic pathogenesis through abnormal cellular interactions.     

Decreased susceptibility to Fas-induced apoptosis of systemic sclerosis dermal fibroblasts

OBJECTIVE: To determine whether dysregulated apoptosis of systemic sclerosis (SSc) fibroblasts contributes to progressive fibrosis by promoting fibroblast longevity. METHODS: We examined the pattern of fibroblast proliferation and apoptosis in SSc skin lesions and the susceptibility of cultured SSc dermal fibroblasts to apoptosis. Skin biopsy samples from SSc patients and control subjects were used to establish fibroblast cultures and were examined histologically. In skin sections, apoptosis was examined by TUNEL, and proliferation by immunostaining for proliferating cell nuclear antigen. Susceptibility of fibroblasts to apoptosis induced in vitro by different stimuli was studied by TUNEL. Expression of Bcl-2, Bcl-x, and Bax proteins in cultured fibroblasts was studied by Western blotting. RESULTS: Proliferation of dermal fibroblasts was not observed in normal skin but was present in skin from patients with SSc and other inflammatory skin diseases. Apoptosis of fibroblasts in SSc fibrotic skin lesions was not observed. In vitro, SSc fibroblasts were specifically resistant to apoptosis induced by Fas receptor stimulation but had normal susceptibility to apoptosis induced by nonspecific stimuli (protein kinase inhibition or serum withdrawal). Decreased susceptibility to Fas stimulation was not caused by decreased levels of surface Fas receptor. In SSc fibroblasts, quiescence induced by confluence and serum starvation was followed by an abnormal down-regulation of proapoptotic Bax protein. Up-regulation of the Bax:Bcl-2 ratio in SSc fibroblasts by Bcl-2 antisense oligonucleotides restored their susceptibility to Fas-mediated apoptosis. CONCLUSION: Our findings suggest that abnormal apoptotic regulation in fibroblasts can contribute to the pathogenesis of progressive fibrosis in SSc. Modulation of Bcl-2-related proteins appears to be a potential target for the development of apoptosis-based antifibrotic strategies.