The Contribution of LIGHT to the Development of Systemic Sclerosis by Modulating IL-6 and T Helper Type 1 Chemokine Expression in Dermal Fibroblasts

Systemic sclerosis (SSc) is an autoimmune and vascular disease resulting in multiple organ fibrosis, in which IL-6 and T helper (Th)2/Th17 cytokines serve as critical disease drivers. LIGHT is a proinflammatory cytokine promoting IL-6 production in lung fibroblasts and Th1 chemokine expression in dermal fibroblasts (DFs) stimulated with IFN-γ. In this study, we investigated the potential contribution of LIGHT to SSc development using clinical samples and animal models. In SSc-involved skin, LIGHT was upregulated in inflammatory cells, whereas herpesvirus entry mediator (HVEM), a receptor of LIGHT, was downregulated in DFs. Similar expression profiles of LIGHT and HVEM were reproduced in bleomycin-treated mice. Transcription factor FLI1 bound to the HVEM promoter, and FLI1 small interfering RNA suppressed HVEM expression in normal DFs. In SSc DFs, LIGHT significantly increased IL-6 production, whereas IFN-γ/LIGHT-dependent Th1 chemokine induction was decreased compared with that in normal DFs. Importantly, LIGHT small interfering RNA significantly attenuated bleomycin-induced skin fibrosis, and serum LIGHT levels were elevated in patients with diffuse cutaneous SSc and positively correlated with clinical parameters reflecting skin and pulmonary fibrosis. Taken together, these results suggest that altered response of DFs to LIGHT, namely increased IL-6 production and decreased Th1 chemokine expression, contributes to the development of skin fibrosis in SSc.

Altered Properties of Endothelial Cells and Mesenchymal Stem Cells Underlying the Development of Scleroderma-like Vasculopathy in KLF5+/- ;Fli-1+/- Mice

OBJECTIVE

In prevous studies, we established a new animal model, KLF5^+/- ;Fli-1^+/- mice, in which fundamental pathologic features of systemic sclerosis (SSc) are broadly recapitulated. SSc vasculopathy is believed to occur as a result of impaired vascular remodeling, but its detailed mechanism of action remains unknown. To address this, the present study investigated the properties of dermal microvascular endothelial cells (DMECs), bone marrow-derived endothelial progenitor cells (BM-EPCs), and bone marrow-derived mesenchymal stem cells (BM-MSCs), a precursor of pericytes, in KLF5^+/- ;Fli-1^+/- mice.

METHODS

Neovascularization and angiogenesis were assessed in KLF5^+/- ;Fli-1^+/- mice by in vivo Matrigel plug assay and in vitro tube formation assay, respectively. The properties of mouse BM-EPCs and BM-MSCs were assessed with in vitro studies. Dermal vasculature was visualized in vivo by injecting the mice with fluorescein isothiocyanate-conjugated dextran.

RESULTS

Neovascularization was diminished in skin-embedded Matrigel plugs from KLF5^+/- ;Fli-1^+/- mice. DMECs from KLF5^+/- ;Fli-1^+/- mice showed defective tubulogenic activity, decreased expression of VE-cadherin and CD31, and an imbalance in the expression of Notch1/Dll4, suggesting that angiogenesis and anastomosis are disturbed. KLF5^+/- ;Fli-1^+/- mouse BM-MSCs exhibited enhanced proliferation and migration and increased collagen production following stimulation with transforming growth factor β1, indicating that these cells differentiate preferentially into myofibroblasts rather than pericytes. KLF5^+/- ;Fli-1^+/- mouse BM-EPCs displayed a transition toward mesenchymal cells, suggesting that vasculogenesis is impaired. Wound healing was delayed in KLF5^+/- ;Fli-1^+/- mice (mean ± SD healing time 15.67 ± 0.82 days versus 13.50 ± 0.84 days; P = 0.0017), and the vascular network was poorly developed in wound scar tissue.

CONCLUSION

The characteristics observed in the KLF5^+/- ;Fli-1^+/- mouse model - specifically, impaired neovascularization and vascular maturation - are similar to those observed in human SSc, and could be at least partially attributable to the induction of SSc-like properties in DMECs, BM-EPCs, and BM-MSCs. These findings indicate the critical contribution of Klf5 and Fli1 deficiency in vascular cells and related cell precursors to the development of SSc vasculopathy.

Regulation of skin fibrosis by RALDH1-producing dermal dendritic cells via retinoic acid-mediated regulatory T cell induction: A role in scleroderma

BACKGROUND

Skin fibrosis of systemic sclerosis (SSc) is believed to be driven by complex processes including immune abnormalities, but the underlying immune response remains enigmatic. In particular, the role of dermal dendritic cells (DCs) is totally unknown.

OBJECTIVE

We investigated the impact of CD103 loss on bleomycin-induced skin fibrosis because CD103 is a critical molecule determining DC phenotypes.

METHODS

Bleomycin-induced skin fibrosis was generated with Cd103^-/- mice. The alterations of tissue fibrosis and related inflammation were investigated by histologic examination, hydroxyproline assay, quantitative reverse transcription PCR and flow cytometry. SSc skin samples were evaluated by immunofluorescence.

RESULTS

CD103 loss decreased bleomycin-induced dermal thickness and collagen contents, along with TGF-β1 and CTGF suppression. Treg proportion was increased, while Th1/Th2/Th17 cell proportions were decreased in the skin of bleomycin-treated Cd103^-/- mice. Bleomycin injection enhanced CD11b^-CD103^- DC proportion in wild-type mice, which was further augmented in Cd103^-/- mice. Importantly, RALDH1/ALDH1A1 enzyme oxidizing retinaldehyde to retinoic acid, an inducer of Tregs, was preferentially expressed by CD11b^-CD103^- DCs and its expression levels were elevated in bleomycin-injected skin lesions, to a greater extent in Cd103^-/- mice than in wild-type mice. Importantly, the number of RALDH1-positive DCs was decreased in the lesional skin of SSc patients and tended to inversely correlate with skin fibrosis severity.

CONCLUSION

This study identified a critical role of dermal DCs as a regulator of Treg development through RALDH1 in bleomycin-treated mice and possibly in human SSc. This finding sheds new light on dermal DCs as a new therapeutic target of SSc.

Prediction of therapeutic response before and during i.v. cyclophosphamide pulse therapy for interstitial lung disease in systemic sclerosis: A longitudinal observational study

There have been no established parameters to predict responsiveness to i.v. cyclophosphamide (IVCY) pulse therapy in combination with corticosteroids in patients with interstitial lung disease (ILD) related to systemic sclerosis (SSc). This retrospective study was conducted to determine predictive factors for efficacy of IVCY at the time of before and during the treatment. Thirty-two Japanese SSc patients, ever treated for ILD with IVCY in combination with prednisolone, were analyzed retrospectively. We performed detailed time-course analyses of parameters derived from blood samples and pulmonary function tests. With the exclusion of eight unclassified patients, 24 patients were classified into 14 good responders (GR) or 10 poor responders (PR) on the basis of changes in percent predicted diffusing capacity for carbon monoxide (DLco). Pretreatment percent predicted DLco was significantly reduced in PR compared with GR. In addition, serum parameters such as Krebs von den Lungen-6 (KL-6), surfactant protein D (SP-D) and C-reactive protein were significantly higher in PR than in GR. Furthermore, our time-course analyses revealed a transient increase in serum KL-6 levels with a peak at 3 months after the first infusion of cyclophosphamide, which showed no relation to therapeutic efficacy. Moreover, continuously high serum KL-6 levels (>2000 U/mL) and rapid decrease in SP-D levels (<200 ng/mL) during IVCY were remarkably characteristic of PR and GR, respectively. ILD severity/activity before treatment and variability of serum KL-6 and SP-D levels during treatment may be useful to predict therapeutic effects of IVCY on SSc-ILD.

Increased expression of aquaporin-1 in dermal fibroblasts and dermal microvascular endothelial cells possibly contributes to skin fibrosis and edema in patients with systemic sclerosis

BACKGROUND

Aquaporin-1 (AQP1), a water channel protein controlling the water contents of cells and tissues, exerts pleiotropic effects on various biological activities, including inflammation, angiogenesis, and extracellular matrix remodeling, by regulating cell behaviors and tissue water balance.

OBJECTIVE

To investigate AQP1 roles in systemic sclerosis (SSc) which is characterized by autoimmune inflammation, vasculopathy, and tissue fibrosis.

METHODS

AQP1 expression was evaluated by immunohistochemistry and quantitative reverse transcription PCR in skin samples from human and animal models and by immunoblotting in cultured cells. Fli1 binding to the AQP1 promoter was evaluated by chromatin immunoprecipitation. Cell migration was assessed by scratch assay.

RESULTS

Dermal fibroblasts and endothelial cells highly expressed AQP1 in SSc lesional skin, and AQP1 expression in dermal fibroblasts and endothelial cells positively correlated with the degrees of tissue fibrosis and edema, respectively. Consistently, SSc dermal fibroblasts up-regulated AQP1 compared with normal dermal fibroblasts in vitro. Furthermore, TGF-β stimulation induced AQP1 expression in normal dermal fibroblasts, while TGF-β1 antisense oligonucleotide suppressed AQP1 expression in SSc dermal fibroblasts. In endothelial cells, Fli1 deficiency resulted in AQP1 up-regulation in vivo and in vitro and Fli1 bound to the AQP1 promoter. Importantly, SSc dermal fibroblasts and FLI1 siRNA-treated endothelial cells had a pro-migratory property, which was remarkably diminished by gene silencing of AQP1.

CONCLUSION

AQP1 is up-regulated in SSc dermal fibroblasts and SSc endothelial cells at least partially due to autocrine TGF-β stimulation and Fli1 deficiency, respectively, possibly contributing to inflammation, vasculopathy, and tissue fibrosis by regulating tissue edema and cell migration.

Assessment of endothelial function during the loading phase of infliximab in psoriasis: a potential predictor of its drug survival

BACKGROUND

Tumor necrosis factor inhibitors decrease the risk of cardiovascular events in moderate to severe psoriasis, but the association between their effects on endothelial function and those on skin lesions has not been well studied. We investigated the association between infliximab effects on endothelial function during the loading phase and those on skin lesions in patients with psoriasis.

METHODS

We evaluated endothelial function with reactive hyperemia-peripheral arterial tonometry index (RHI) in 15 patients with psoriasis before the first and third infusions of infliximab. Patients were stratified into two groups; those who maintained Psoriasis Area and Severity Index (PASI) 75 response for more than 6 months (defined as responders) and the others (defined as nonresponders).

RESULTS

Six weeks after the initiation of infliximab (before the third infusion), PASI scores were significantly improved compared with baseline, while RHI values were not altered in the whole patient group. However, when the responders and the nonresponders were analyzed separately, RHI values tended to be decreased before the third infusion compared with baseline in the nonresponders, while being unchanged in the responders. Importantly, the difference in ∆RHI reached a statistical significance between the two groups, and the cutoff value (mean - 2 standard deviation of RHI values in the responders) identified the nonresponders with 67% of sensitivity and 100% of specificity.

CONCLUSIONS

The decrease in RHI values before the third infusion may serve as a predictor for the long-term unfavorable effect of infliximab on psoriatic skin lesions.

CXCL13 produced by macrophages due to Fli1 deficiency may contribute to the development of tissue fibrosis, vasculopathy and immune activation in systemic sclerosis

CXCL13, a chemokine for B cells, follicular T cells, T helper 17 cells, and regulatory T cells, is reported to contribute to the development of systemic sclerosis (SSc), reflecting aberrant activation of immune system. To better understand the role of CXCL13 in SSc, we investigated the influence of Fli1 deficiency, a potential predisposing factor of this disease, on CXCL13 expression and assessed the clinical correlation of serum CXCL13 levels by multivariate regression analysis. Haploinsufficient loss of Fli1 remarkably induced CXCL13 expression in murine peritoneal macrophages, while gene silencing of FLI1 did not affect the expression of CXCL13 in human dermal fibroblasts and human dermal microvascular endothelial cells. Serum CXCL13 levels were elevated in SSc patients compared with healthy controls and correlated positively with skin score and negatively with pulmonary function test results. SSc patients with elevated serum CXCL13 levels had longer disease duration, diffuse cutaneous involvement, interstitial lung disease (ILD), heart involvement, pulmonary arterial hypertension, Raynaud's phenomenon, pitting scars, digital ulcers, telangiectasia, and high serum IgG levels more frequently than the other patients. In particular, serum CXCL13 levels were associated with ILD and digital ulcers by multivariate regression analysis. Taken together, these results indicate that CXCL13 expression is upregulated by Fli1 deficiency in macrophages, potentially contributing to the development of tissue fibrosis, vasculopathy and immune activation in SSc, especially ILD and digital ulcers.

Possible pro-inflammatory role of heparin-binding epidermal growth factor-like growth factor in the active phase of systemic sclerosis

Heparin-binding epidermal growth factor (EGF)-like growth factor (HB-EGF) is a member of the EGF family growth factors, which affects multiple aspects of the wound healing process such as epithelialization, wound contraction and angiogenesis. In our study, we measured the serum HB-EGF levels of 51 systemic sclerosis (SSc) patients, which showed a significant increase compared with those of 20 normal subjects. Further analysis revealed a positive correlation between the HB-EGF level and pulmonary ground-glass score but no correlation between the former and pulmonary fibrosis score. Other findings include: a significant increase of serum sialylated carbohydrate antigen KL-6 levels and significant shortness of disease duration in the diffuse cutaneous SSc patients with elevated HB-EGF levels; and significantly higher HB-EGF levels in the presence of Raynaud's phenomenon, in that of telangiectasia, and in the absence of contracture of phalanges in all SSc patients. We then evaluated HB-EGF mRNA levels of fibroblasts harvested from skin samples of the SSc patients and those of foreskin-derived fibroblasts treated with transforming growth factor-β, both of which were significantly higher than each control. In conclusion, we speculate that HB-EGF plays a pro-inflammatory role in the active skin and lung lesions of SSc.

The impact of transcription factor Fli1 deficiency on the regulation of angiogenesis

The insufficiency of Friend leukaemia virus integration 1 (Fli1), a member of the Ets family transcription factors, is implicated in the pathogenesis of vasculopathy associated with systemic sclerosis (SSc). Fli1 deficiency accelerates early steps of angiogenesis, including detachment of pre-existing pericytes and extracellular matrix degradation by endothelial proteinases, but the impact of Fli1 deficiency on the other steps of angiogenesis has not been investigated. Therefore, we evaluated the effect of Fli1 deficiency on migration, proliferation, cell survival and tube formation of human dermal microvascular endothelial cells (HDMECs). HDMECs transfected with FLI1 siRNA exhibited a greater migratory property in scratch assay and transwell migration assay and a higher proliferation rate in BrdU assay than HDMECs transfected with non-silencing scrambled RNA. In flow cytometry-based apoptosis assay, FLI1 siRNA-transduced HDMECs revealed the decreased number of annexin and propidium iodide-double-positive apoptotic cells compared with control cells, reflecting the promotion of cell survival. On the other hand, tubulogenic activity on Matrigel was remarkably suppressed in Fli1-deficient HDMECs relative to control cells. These results indicate that Fli1 deficiency promotes migration, proliferation and cell survival, while abating tube formation of endothelial cells, suggesting that Fli1 deficiency is potentially attributable to the development of both proliferative obliterative vasculopathy (occlusion of arterioles and small arteries) and destructive vasculopathy (loss of small vessels) characteristic of SSc vasculopathy.

Systemic Sclerosis Dermal Fibroblasts Suppress Th1 Cytokine Production via Galectin-9 Overproduction due to Fli1 Deficiency

Dermal fibroblasts promote skin-localized transdifferentiation of regulatory T cells to T helper (Th) type 2-like cells in systemic sclerosis (SSc). However, the entire effect of SSc dermal fibroblasts on immune cells still remains unknown. Because galectin-9 induces Th2 cytokine-predominant immune imbalance by negatively regulating Th1/Th17 cells in inflammatory diseases, we investigated the contribution of galectin-9 to Th immune balance in SSc lesional skin. We used human clinical samples and Fli1^+/- mice because Fli1 deficiency induces SSc-like phenotypes in various cell types. Galectin-9 was overexpressed in SSc dermal fibroblasts in vivo and in vitro. Serum galectin-9 levels were significantly elevated in SSc patients and positively correlated with skin score. Galectin-9 was up-regulated by autocrine endothelin stimulation and Fli1 deficiency, and Fli1 occupied the LGALS9 promoter in dermal fibroblasts. Co-culture of splenic CD4⁺ T cells with Fli1^+/- dermal fibroblasts significantly increased IL-4-producing cell proportion, and this effect was cancelled in parallel with the increased interferon-γ production when Fli1^+/- dermal fibroblasts were transfected with Lgals9 small interfering RNA. Furthermore, Lgals9 small interfering RNA suppressed dermal collagen deposition by increasing interferon-γ production of skin-infiltrating CD4⁺ T cells in bleomycin-treated mice. These results suggest that SSc dermal fibroblasts suppress interferon-γ expression of skin-infiltrating CD4⁺ T cells through galectin-9 overproduction, promoting skin fibrosis development.

Fli1 Deficiency Induces CXCL6 Expression in Dermal Fibroblasts and Endothelial Cells, Contributing to the Development of Fibrosis and Vasculopathy in Systemic Sclerosis

Objective.

CXCL6, a chemokine with proangiogenic property, is reported to be involved in vasculopathy associated with systemic sclerosis (SSc). We investigated the contribution of CXCL6 to SSc development by focusing on the association of friend leukemia virus integration 1 (Fli1) deficiency, a potential predisposing factor of SSc, with CXCL6 expression and clinical correlation of serum CXCL6 levels.

Methods.

mRNA levels of target genes and the binding of Fli1 to the CXCL6 promoter were evaluated by quantitative reverse transcription-PCR and chromatin immunoprecipitation, respectively. Serum CXCL6 levels were determined by ELISA.

Results.

FLI1 siRNA significantly enhanced CXCL6 mRNA expression in human dermal fibroblasts and human dermal microvascular endothelial cells, while Fli1 haploinsufficiency significantly suppressed CXCL6 mRNA expression in murine peritoneal macrophages stimulated with lipopolysaccharide. Supporting a critical role of Fli1 deficiency to induce SSc-like phenotypes, CXCL6 mRNA expression was higher in SSc dermal fibroblasts than in normal dermal fibroblasts. Importantly, Fli1 bound to the CXCL6 promoter in dermal fibroblasts, endothelial cells, and THP-1 cells. In patients with SSc, serum CXCL6 levels correlated positively with the severity of dermal and pulmonary fibrosis and were elevated in association with cardiac and pulmonary vascular involvement and cutaneous vascular symptoms, including Raynaud phenomenon, digital ulcers (DU)/pitting scars, and telangiectasia. Especially, serum CXCL6 levels were associated with DU/pitting scars and heart involvement by multiple regression analysis.

Conclusion.

CXCL6 expression is upregulated by Fli1 deficiency in fibroblasts and endothelial cells, potentially contributing to the development of fibrosis and vasculopathy in the skin, lung, and heart of SSc.

Epithelial Fli1 deficiency drives systemic autoimmunity and fibrosis: Possible roles in scleroderma

Systemic sclerosis (SSc), or scleroderma, is a multisystem autoimmune disorder characterized by vasculopathy and fibrosis in the skin and internal organs, most frequently in the esophagus and lungs. Hitherto, studies on SSc pathogenesis centered on immune cells, vascular cells, and fibroblasts. Although dysregulated keratinocytes in SSc have been recently reported, the contribution of epithelial cells to pathogenesis remains unexplored. In this study, we demonstrated the induction of SSc-like molecular phenotype in keratinocytes by gene silencing of transcription factor Friend leukemia virus integration 1 (Fli1), the deficiency of which is implicated in SSc pathogenesis. Keratin 14-expressing epithelial cell-specific Fli1 knockout mice spontaneously developed dermal and esophageal fibrosis with epithelial activation. Furthermore, they developed remarkable autoimmunity with interstitial lung disease derived from thymic defects with down-regulation of autoimmune regulator (Aire). Importantly, Fli1 directly regulated Aire expression in epithelial cells. Collectively, epithelial Fli1 deficiency might be involved in the systemic autoimmunity and selective organ fibrosis in SSc. This study uncovers unidentified roles of dysregulated epithelial cells in SSc pathogenesis.

Plasma plasmin-α2-plasmin inhibitor complex levels may predict the effect of cyclophosphamide for systemic sclerosis-related interstitial lung disease

OBJECTIVES

Intravenous pulse cyclophosphamide (IVCY) is the first-line treatment for systemic sclerosis-associated interstitial lung disease (SSc-ILD). So far, there is no useful predictive marker for IVCY efficacy against SSc-ILD, although potential candidates are parameters reflecting vascular activation. Since plasma levels of plasmin-α2-plasmin inhibitor complex (PIC) serve as a potential biomarker of SSc vasculopathy, we evaluated the usefulness of plasma PIC levels as an indicator for IVCY efficacy against SSc-ILD.

METHODS

We measured plasma PIC levels in 23 patients with active SSc-ILD and 20 patients with stabilized SSc-ILD, and also retrospectively studied traceable data of patients with active SSc-ILD during IVCY therapy.

RESULTS

Plasma PIC levels were significantly elevated in patients with active SSc-ILD as compared to patients with stabilized SSc-ILD. Among patients with active SSc-ILD, baseline plasma PIC concentrations were significantly higher in patients responsive to IVCY than in those refractory to IVCY. After the entire six infusions, plasma PIC levels were significantly decreased compared with baseline in the responders, while not in the nonresponders. In the responders, plasma PIC levels were remarkably decreased after a couple of infusions. Regarding the changes of parameters by the entire infusions, Δ plasma PIC levels correlated positively with Δ serum KL-6 levels and inversely with Δ the percentage of predicted vital capacity.

CONCLUSIONS

The elevation of baseline plasma PIC levels and the rapid decrease in plasma PIC levels during a couple of infusions may predict the efficacy of the entire IVCY therapy against SSc-ILD.

A potential contribution of antimicrobial peptide LL-37 to tissue fibrosis and vasculopathy in systemic sclerosis

BACKGROUND

LL-37 is an antimicrobial peptide with pleiotropic effects on the immune system, angiogenesis and tissue remodelling. These are cardinal pathological events in systemic sclerosis (SSc).

OBJECTIVES

To elucidate the potential role of LL-37 in SSc.

METHODS

The expression of target molecules was evaluated by immunostaining and quantitative reverse-transcription real-time polymerase chain reaction in human and murine skin. The mechanisms regulating LL-37 expression in endothelial cells were examined by gene silencing and chromatin immunoprecipitation. Serum LL-37 levels were determined by enzyme-linked immunosorbent assay.

RESULTS

In SSc lesional skin, LL-37 expression was increased in dermal fibroblasts, perivascular inflammatory cells, keratinocytes and, particularly, dermal small vessels. Expression positively correlated with interferon-α expression, possibly reflecting LL-37-dependent induction of interferon-α. In SSc animal models, bleomycin-treated skin exhibited the expression pattern of CRAMP, a murine homologue of LL-37, similar to that of LL-37 in SSc lesional skin. Furthermore, Fli1^+/- mice showed upregulated expression of CRAMP in dermal small vessels. Fli1 binding to the CAMP (LL-37 gene) promoter and Fli1 deficiency-dependent induction of LL-37 were also confirmed in human dermal microvascular endothelial cells. In the analysis of sera, patients with SSc had serum LL-37 levels significantly higher than in healthy controls. Furthermore, serum LL-37 levels positively correlated with skin score and the activity of alveolitis and were significantly elevated in patients with digital ulcers compared with those without.

CONCLUSIONS

LL-37 upregulation, induced by Fli1 deficiency at least in endothelial cells, potentially contributes to the development of skin sclerosis, interstitial lung disease and digital ulcers in SSc.

Progranulin Overproduction Due to Fli-1 Deficiency Contributes to the Resistance of Dermal Fibroblasts to Tumor Necrosis Factor in Systemic Sclerosis

OBJECTIVE

Progranulin is a growth factor that is active in wound repair and is an antagonist of tumor necrosis factor (TNF) receptors, regulating fibroblast activation, angiogenesis, and inflammation. Because long-standing activation of gene programs related to wound healing is a hallmark of systemic sclerosis (SSc), we sought to investigate the role of progranulin in SSc.

METHODS

Progranulin expression levels in human and murine skin samples were determined by immunohistochemical analysis and quantitative reverse transcription-polymerase chain reaction. The role of progranulin in fibroblast activation was examined using a gene-silencing technique. Progranulin levels in serum obtained from 60 patients with SSc and 16 healthy control subjects were determined by enzyme-linked immunosorbent assay.

RESULTS

Progranulin expression was increased in SSc dermal fibroblasts compared with normal dermal fibroblasts, both in vivo and in vitro. Transcription factor Fli-1, a deficiency of which is involved in the activation of SSc dermal fibroblasts, served as a potent repressor of the progranulin gene, and Fli-1(+/-) mice and bleomycin-treated wild-type mice exhibited up-regulated expression of progranulin in dermal fibroblasts. SSc dermal fibroblasts were resistant to the antifibrotic effect of TNF, but this resistance was reversed by gene silencing of progranulin. Serum progranulin levels were elevated in patients with early diffuse cutaneous SSc (dcSSc), especially in those with inflammatory skin symptoms, and were positively correlated with the C-reactive protein level.

CONCLUSION

Progranulin overproduction due to Fli-1 deficiency may contribute to the constitutive activation of SSc dermal fibroblasts by antagonizing the antifibrotic effect of TNF. Progranulin may also be involved in the inflammatory process associated with progressive skin sclerosis in early dcSSc.

Association of anti-RNA polymerase III antibody and silicone breast implants in patients with systemic sclerosis

Systemic sclerosis (SSc) is believed to be caused by a complex interplay between genetic factors and environmental influences. Although silicone has been considered to be a candidate of environmental agents, clinical data presented so far fail to show a significant association between silicone breast implant (SBI) and the development of SSc. Because we recently experienced two consecutive SSc patients with anti-RNA polymerase III (RNAP III) antibody who underwent SBI, we here investigated the association of SBI history with the development of SSc positive for anti-RNAP III antibody. Among 262 Japanese SSc patients, of note, the frequency of SBI history was significantly higher in the anti-RNAP III antibody group (16.0% [4/25]) than in the anti-topoisomerase I antibody group (0% [0/87], P < 0.005) and in the anticentromere antibody group (1.2% [2/150], P < 0.005). These results suggest that SBI could influence the development of SSc in a certain subset of patients with anti-RNAP III antibody.

Serum levels of interleukin-18-binding protein isoform a: Clinical association with inflammation and pulmonary hypertension in systemic sclerosis

Systemic sclerosis (SSc) is a chronic autoimmune inflammatory disease characterized by extensive tissue fibrosis and various vascular complications. A wealth of evidence suggests the substantial contribution of pro-inflammatory cytokines to the development of SSc, but the role of interleukin (IL)-18 signaling in this disease still remains elusive. To address this issue, we herein determined serum levels of IL-18-binding protein isoform a (IL-18BPa), a soluble decoy receptor for IL-18, by enzyme-linked immunosorbent assay in 57 SSc patients and 20 healthy controls and evaluated their clinical correlation. Serum IL-18BPa levels were higher in SSc patients than in healthy controls, while comparable between diffuse cutaneous SSc and limited cutaneous SSc patients. Although serum IL-18BPa levels were not associated with dermal and pulmonary fibrotic parameters in SSc patients, there was a significant positive correlation between serum IL-18BPa levels and right ventricular systolic pressure estimated by echocardiography. Furthermore, in 24 SSc patients who underwent right heart catheterization, serum IL-18BPa levels positively correlated with mean pulmonary arterial pressure. As for systemic inflammatory markers, significant positive correlations of circulating IL-18BPa levels with erythrocyte sedimentation rate and C-reactive protein were noted. These results suggest that the inhibition of IL-18 signaling by IL-18BPa may be involved in the development of pulmonary vascular involvement leading to pulmonary hypertension and modulate the systemic inflammation in SSc.

Tamibarotene Ameliorates Bleomycin-Induced Dermal Fibrosis by Modulating Phenotypes of Fibroblasts, Endothelial Cells, and Immune Cells

Tamibarotene (Am80) is a synthetic retinoid that modulates the pathologic processes of various autoimmune and inflammatory diseases and their animal models. We here investigated the therapeutic potential of Am80 against systemic sclerosis using its animal models. Am80 significantly attenuated dermal and hypodermal fibrosis in bleomycin (BLM)-treated mice and tight skin 1 mice, respectively. Consistently, Am80 significantly suppressed the expression of various molecules related to tissue fibrosis, including transforming growth factor-β1, connective tissue growth factor, IL-4, IL-10, IL-13, IL-17A, tumor necrosis factor-α, IFN-γ, and monocyte chemotactic protein 1 in the lesional skin of BLM-treated mice. Furthermore, Am80 decreased the proportion of effector T cells, while increasing that of naïve T cells among CD4+ T cells in the draining lymph nodes of BLM-treated mice. Moreover, a series of BLM-induced pathologic events, including endothelial-to-mesenchymal transition; ICAM-1 expression in endothelial cells; the infiltration of macrophages, mast cells, and lymphocytes; and M2 macrophage differentiation, were attenuated by Am80. Importantly, Am80 directly reversed the profibrotic phenotype of transforming growth factor-β1-treated dermal fibroblasts, suppressed ICAM-1 expression in endothelial cells, and promoted M1 macrophage differentiation in vitro. Collectively, Am80 inhibits the development of experimental dermal fibrosis by reversing the profibrotic phenotype of various cell types and would be a candidate for therapeutic drugs against dermal fibrosis of systemic sclerosis.

Endothelin receptor blockade ameliorates vascular fragility in endothelial cell-specific Fli-1-knockout mice by increasing Fli-1 DNA binding ability

OBJECTIVE

It is generally accepted that blockade of endothelin receptors has potentially beneficial effects on vasculopathy associated with systemic sclerosis (SSc). The aim of this study was to clarify the molecular mechanism underlying these effects using endothelial cell-specific Fli-1-knockout (Fli-1 ECKO) mice, an animal model of SSc vasculopathy.

METHODS

Levels of messenger RNA for target genes and the expression and phosphorylation levels of target proteins were determined in human and murine dermal microvascular endothelial cells by real-time quantitative reverse transcription-polymerase chain reaction and immunoblotting, respectively. The binding of Fli-1 to the target gene promoters was evaluated using chromatin immunoprecipitation. Expression levels of Fli-1 and α-smooth muscle actin in murine skin were evaluated using immunohistochemistry. Vascular structure and permeability were evaluated in mice injected with fluorescein isothiocyanate-dextran and Evans blue dye, respectively.

RESULTS

In human dermal microvascular endothelial cells, endothelin 1 induced phosphorylation of Fli-1 at Thr(312) through the sequential activation of c-Abl and protein kinase Cδ, leading to a decrease in Fli-1 protein levels as well as a decrease in binding of Fli-1 to the target gene promoters, whereas bosentan treatment reversed those effects. In Fli-1 ECKO mice, 4 weeks of treatment with bosentan increased endothelial Fli-1 expression, resulting in vascular stabilization and the restoration of impaired leaky vessels.

CONCLUSION

The vascular fragility of Fli-1 ECKO mice was improved by bosentan through the normalization of Fli-1 protein levels and activity in endothelial cells, which may explain, in part, the mechanism underlying the beneficial effects of endothelin receptor blockade on SSc vasculopathy.

A possible contribution of lipocalin-2 to the development of dermal fibrosis, pulmonary vascular involvement and renal dysfunction in systemic sclerosis

BACKGROUND

Lipocalin-2 is an adipocytokine implicated in apoptosis, innate immunity, angiogenesis, and the development of chronic kidney disease.

OBJECTIVES

To investigate the role of lipocalin-2 in systemic sclerosis (SSc).

MATERIALS AND METHODS

Serum lipocalin-2 levels were determined by enzyme-linked immunosorbent assay in 50 patients with SSc and 19 healthy subjects. Lipocalin-2 expression was evaluated in the skin of patients with SSc and bleomycin (BLM)-treated mice and in Fli1-deficient endothelial cells by reverse transcriptase-real time polymerase chain reaction, immunoblotting and/or immunohistochemistry.

RESULTS

Although serum lipocalin-2 levels were comparable between patients with SSc and healthy controls, the prevalence of scleroderma renal crisis was significantly higher in patients with SSc with elevated serum lipocalin-2 levels than in those with normal levels. Furthermore, serum lipocalin-2 levels inversely correlated with estimated glomerular filtration rate in patients with SSc with renal dysfunction. Among patients with SSc with normal renal function, serum lipocalin-2 levels positively correlated with skin score in patients with diffuse cutaneous SSc with disease duration of < 3 years and inversely correlated with estimated right ventricular systolic pressure in total patients with SSc. Importantly, in SSc lesional skin, lipocalin-2 expression was increased in dermal fibroblasts and endothelial cells. In BLM-treated mice, lipocalin-2 was highly expressed in dermal fibroblasts, but not in endothelial cells. On the other hand, the deficiency of transcription factor Fli1, which is implicated in SSc vasculopathy, induced lipocalin-2 expression in cultivated endothelial cells.

CONCLUSIONS

Lipocalin-2 may be involved in renal dysfunction and dermal fibrosis of SSc. Dysregulated matrix metalloproteinase-9/lipocalin-2-dependent angiogenesis due to Fli1 deficiency may contribute to the development of pulmonary arterial hypertension associated with SSc.

Successful experience of rituximab therapy for systemic sclerosis-associated interstitial lung disease with concomitant systemic lupus erythematosus

Previous studies have demonstrated that B cells play critical roles in autoimmune disorders including systemic sclerosis (SSc) and systemic lupus erythematosus (SLE). However, the effectiveness of rituximab (RTX), a chimeric anti-CD20 antibody, for SSc-associated interstitial lung disease (ILD) or SLE disease activity remains controversial. We herein report an SSc patient with severely progressed ILD and concomitant SLE treated by two cycles of RTX at baseline and half a year later. This treatment improved ILD and SLE activities, along with reduction of dermal sclerosis and serum anti-topoisomerase I antibody levels. In addition, our detailed time-course data indicate that half a year may be appropriate as an interval between each cycle of RTX therapy aimed at SSc-associated ILD or SLE. Overall, the current report could pave the way to establish RTX as a disease-modifying drug for patients with SSc and/or SLE showing resistance to other already approved medications.

Fibrosis, vascular activation, and immune abnormalities resembling systemic sclerosis in bleomycin-treated Fli-1-haploinsufficient mice

OBJECTIVE

Fli-1, a potential predisposing factor for systemic sclerosis (SSc), is constitutively down-regulated in the lesional skin of patients with SSc by an epigenetic mechanism. To investigate the impact of Fli-1 deficiency on the induction of an SSc phenotype in various cell types, we generated bleomycin-induced skin fibrosis in Fli-1(+/-) mice and investigated the molecular mechanisms underlying its phenotypic alterations.

METHODS

Messenger RNA (mRNA) levels and protein expression of target molecules were examined by quantitative reverse transcription-polymerase chain reaction and immunostaining. Transforming growth factor β (TGFβ) bioassay was used to evaluate the activation of latent TGFβ. The binding of Fli-1 to the target gene promoters was assessed with chromatin immunoprecipitation.

RESULTS

Bleomycin induced more severe dermal fibrosis in Fli-1(+/-) mice than in wild-type mice. Fli-1 haploinsufficiency activated dermal fibroblasts via the up-regulation of αvβ3 and αvβ5 integrins and activation of latent TGFβ. Dermal fibrosis in Fli-1(+/-) mice was also attributable to endothelial-to-mesenchymal transition, which is directly induced by Fli-1 deficiency and amplified by bleomycin. Th2/Th17-skewed inflammation and increased infiltration of mast cells and macrophages were seen, partly due to the altered expression of cell adhesion molecules in endothelial cells as well as the induction of the skin chemokines. Fli-1(+/-) mouse macrophages preferentially differentiated into an M2 phenotype upon stimulation with interleukin-4 (IL-4) or IL-13.

CONCLUSION

Our findings provide strong evidence for the fundamental role of Fli-1 deficiency in inducing SSc-like phenotypic alterations in dermal fibroblasts, endothelial cells, and macrophages in a manner consistent with human disease.

Serum omentin levels: A possible contribution to vascular involvement in patients with systemic sclerosis

Adipokines have been shown to be potentially involved in various pathological processes of systemic sclerosis (SSc), including inflammation, vasculopathy and fibrosis, through their pleiotropic effects. Omentin is a member of the adipokines, and has a protective effect against vascular inflammation and pathological remodeling leading to atherosclerosis as well as a vasodilatory effect. To assess the potential role of omentin in the development of SSc, we determined serum omentin levels by enzyme-linked immunosorbent assay in 66 SSc and 21 control subjects and evaluated their clinical correlation. Serum omentin levels were significantly decreased in diffuse cutaneous SSc patients compared with limited cutaneous SSc patients, while comparable between total SSc patients and healthy controls. In diffuse cutaneous (dc)SSc, patients with a disease duration of 5 years or less had serum omentin levels significantly lower than those with a disease duration of more than 5 years. In total SSc, serum omentin levels were significantly higher in patients with elevated right ventricular systolic pressure than in the others, while serum omentin levels did not correlate with fibrotic and systemic inflammatory parameters. These results suggest that a loss of omentin-dependent protection against vascular inflammation and remodeling may be related to pathological vascular events of early dcSSc. The elevation of serum omentin levels may serve as a marker of vascular involvement leading to pulmonary arterial hypertension in SSc, which is possibly due to the compensatory induction of omentin against the increased pulmonary vascular tone.