Astrid Jüngel

MicroRNA-29, a key regulator of collagen expression in systemic sclerosis.

OBJECTIVE To investigate the role of microRNA (miRNA) as posttranscriptional regulators of profibrotic genes in systemic sclerosis (SSc). METHODS MicroRNA, which target collagens, were identified by in silico analysis. Expression of miRNA-29 (miR-29) was determined by TaqMan real-time polymerase chain reaction analysis of skin biopsy and fibroblast samples from SSc patients and healthy controls as well as in the mouse model of bleomycin-induced skin fibrosis. Cells were transfected with precursor miRNA (pre-miRNA)/anti-miRNA of miR-29 using Lipofectamine. Collagen gene expression was also studied in luciferase reporter gene assays. For stimulation, recombinant transforming growth factor beta (TGFbeta), platelet-derived growth factor B (PDGF-B), or interleukin-4 (IL-4) was used. The effects of inhibiting PDGF-B and TGFbeta signaling on the levels of miR-29 were studied in vitro and in the bleomycin model. RESULTS We found that miR-29a was strongly down-regulated in SSc fibroblasts and skin sections as compared with the healthy controls. Overexpression in SSc fibroblasts significantly decreased, and accordingly, knockdown in normal fibroblasts increased, the levels of messenger RNA and protein for type I and type III collagen. In the reporter gene assay, cotransfection with pre-miR-29a significantly decreased the relative luciferase activity, which suggests a direct regulation of collagen by miR-29a. TGFbeta, PDGF-B, or IL-4 reduced the levels of miR-29a in normal fibroblasts to those seen in SSc fibroblasts. Similar to human SSc, the expression of miR-29a was reduced in the bleomycin model of skin fibrosis. Inhibition of PDGF-B and TGFbeta pathways by treatment with imatinib restored the levels of miR-29a in vitro and in the bleomycin model in vivo. CONCLUSION These data add the posttranscriptional regulation of collagens by miR-29a as a novel aspect to the fibrogenesis of SSc and suggest miR-29a as a potential therapeutic target.

Platelet-derived serotonin links vascular disease and tissue fibrosis

Blocking 5-HT2B receptor provides a therapeutic target for fibrotic diseases caused by activated platelet release of serotonin during vascular damage.

Increased levels of circulating microparticles in primary Sjögren's syndrome, systemic lupus erythematosus and rheumatoid arthritis and relation with disease activity

IntroductionCell stimulation leads to the shedding of phosphatidylserine (PS)-rich microparticles (MPs). Because autoimmune diseases (AIDs) are characterized by cell activation, we investigated level of circulating MPs as a possible biomarker in primary Sjögrens syndrome (pSS), systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA).MethodsWe measured plasma levels of total, platelet and leukocyte MPs by prothrombinase capture assay and flow cytometry in 43 patients with pSS, 20 with SLE and 24 with RA and in 44 healthy controls (HCs). Secretory phospholipase A2 (sPLA2) activity was assessed by fluorometry. Soluble CD40 ligand (sCD40L) and soluble P-selectin (sCD62P), reflecting platelet activation, were measured by ELISA.ResultsPatients with pSS showed increased plasma level of total MPs (mean ± SEM 8.49 ± 1.14 nM PS equivalent (Eq), P < 0.0001), as did patients with RA (7.23 ± 1.05 n PS Eq, P = 0.004) and SLE (7.3 ± 1.25 nM PS Eq, P = 0.0004), as compared with HCs (4.13 ± 0.2 nM PS Eq). Patients with AIDs all showed increased level of platelet MPs (P < 0.0001), but only those with pSS showed increased level of leukocyte MPs (P < 0.0001). Results by capture assay and flow cytometry were correlated. In patients with high disease activity according to extra-glandular complications (pSS), DAS28 (RA) or SLEDAI (SLE) compared with low-activity patients, the MP level was only slightly increased in comparison with those having a low disease activity. Platelet MP level was inversely correlated with anti-DNA antibody level in SLE (r = -0.65; P = 0.003) and serum β2 microglobulin level in pSS (r = -0.37; P < 0.03). The levels of total and platelet MPs were inversely correlated with sPLA2 activity (r = -0.37, P = 0.0007; r = -0.36, P = 0.002, respectively). sCD40L and sCD62P concentrations were significantly higher in pSS than in HC (P ≤ 0.006).ConclusionsPlasma MP level is elevated in pSS, as well as in SLE and RA, and could be used as a biomarker reflecting systemic cell activation. Level of leukocyte-derived MPs is increased in pSS only. The MP level is low in case of more severe AID, probably because of high secretory phospholipase A2 (sPLA2) activity, which leads to consumption of MPs. Increase of platelet-derived MPs, sCD40L and sCD62P, highlights platelet activation in pSS.

Dual inhibition of c-abl and PDGF receptor signaling by dasatinib and nilotinib for the treatment of dermal fibrosis.

Abelson kinase (c‐abl) and platelet‐derived growth factor (PDGF) are key players in the pathogenesis of systemic sclerosis (SSc). The aim of the present study was to evaluate the antifibrotic potential of dasatinib and nilotinib, 2 novel inhibitors of c‐abl and PDGF, which are well tolerated and have recently been approved. Dasatinib and nilotinib dose‐dependently reduced the mRNA and protein levels of extracellular matrix proteins in human stimulated dermal fibroblasts from SSc patients (IC50 of 0.5–2.0 nM for dasatinib and 0.8–2.5 nM for nilotinib). In a mouse model of bleomycin‐induced dermal fibrosis, dasatinib and nilotinib potently reduced the dermal thickness, the number of myofibroblasts, and the collagen content of the skin in a dose‐dependent manner at well‐tolerated doses. These data indicate that dasatinib and nilotinib potently inhibit the synthesis of extracellular matrix in vitro and in vivo at biologically relevant concentrations. Thus, we provide the first evidence that dasatinib and nilotinib might be promising drugs for the treatment of patients with SSc.—Akhmetshina, A., Dees, C., Pileckyte, M., Maurer, B., Axmann, R., Jüngel, A., Zwerina, J., Gay, S., Schett, G., Distler, O., Distler, J. H. W. Dual inhibition of c‐abl and PDGF receptor signaling by dasatinib and nilotinib for the treatment of dermal fibrosis. FASEB J. 22, 2214–2222 (2008)

Down‐regulation of microRNA‐34a* in rheumatoid arthritis synovial fibroblasts promotes apoptosis resistance

OBJECTIVE To investigate the expression and effect of the microRNA-34 (miR-34) family on apoptosis in rheumatoid arthritis synovial fibroblasts (RASFs). METHODS Expression of the miR-34 family in synovial fibroblasts with or without stimulation with Toll-like receptor (TLR) ligands, tumor necrosis factor α (TNFα), interleukin-1β (IL-1β), hypoxia, or 5-azacytidine was analyzed by real-time polymerase chain reaction (PCR). Promoter methylation was studied by combined bisulfite restriction analysis. The effects of overexpression and silencing of miR-34a and miR-34a* on apoptosis were analyzed by annexin V/propidium iodide staining. Production of X-linked inhibitor of apoptosis protein (XIAP) was assessed by real-time PCR and immunohistochemistry analysis. Reporter gene assay was used to study the signaling pathways of miR-34a*. RESULTS Basal expression levels of miR-34a* were found to be reduced in synovial fibroblasts from RA patients compared to osteoarthritis patients, whereas levels of miR-34a, miR-34b/b*, and miR-34c/c* did not differ. Neither TNFα, IL-1β, TLR ligands, nor hypoxia altered miR-34a* expression. However, we demonstrated that the promoter of miR-34a/34a* was methylated and showed that transcription of the miR-34a duplex was induced upon treatment with demethylating agents. Enforced expression of miR-34a* led to an increased rate of FasL- and TRAIL-mediated apoptosis in RASFs. Moreover, levels of miR-34a* were highly correlated with expression of XIAP, which was found to be up-regulated in RA synovial cells. Finally, we identified XIAP as a direct target of miR-34a*. CONCLUSION Our data provide evidence of a methylation-specific down-regulation of proapoptotic miR-34a* in RASFs. Decreased expression of miR- 34a* results in up-regulation of its direct target XIAP, thereby contributing to resistance of RASFs to apoptosis.

Transcription Factor Fos-Related Antigen-2 Induces Progressive Peripheral Vasculopathy in Mice Closely Resembling Human Systemic Sclerosis

Background— Microvascular damage is one of the first pathological changes in systemic sclerosis. In this study, we investigated the role of Fos-related antigen-2 (Fra-2), a transcription factor of the activator protein-1 family, in the peripheral vasculopathy of systemic sclerosis and examined the underlying mechanisms. Methods and Results— Expression of Fra-2 protein was significantly increased in skin biopsies of systemic sclerosis patients compared with healthy controls, especially in endothelial and vascular smooth muscle cells. Fra-2 transgenic mice developed a severe loss of small blood vessels in the skin that was paralleled by progressive skin fibrosis at 12 weeks of age. The reduction in capillary density was preceded by a significant increase in apoptosis in endothelial cells at week 9 as detected by immunohistochemistry. Similarly, suppression of Fra-2 by small interfering RNA prevented human microvascular endothelial cells from staurosporine-induced apoptosis and improved both the number of tubes and the cumulative tube lengths in the tube formation assay. In addition, cell migration in the scratch assay and vascular endothelial growth factor–dependent chemotaxis in a modified Boyden chamber assay were increased after transfection of human microvascular endothelial cells with Fra-2 small interfering RNA, whereas proliferation was not affected. Conclusions— Fra-2 is present in human systemic sclerosis and may contribute to the development of microvasculopathy by inducing endothelial cell apoptosis and by reducing endothelial cell migration and chemotaxis. Fra-2 transgenic mice are a promising preclinical model to study the mechanisms and therapeutic approaches of the peripheral vasculopathy in systemic sclerosis.

Trichostatin A sensitises rheumatoid arthritis synovial fibroblasts for TRAIL-induced apoptosis

Background: Histone acetylation/deacetylation has a critical role in the regulation of transcription by altering the chromatin structure. Objective: To analyse the effect of trichostatin A (TSA), a streptomyces metabolite which specifically inhibits mammalian histone deacetylases, on TRAIL-induced apoptosis of rheumatoid arthritis synovial fibroblasts (RASF). Methods: Apoptotic cells were detected after co-treatment of RASF with TRAIL (200 ng/ml) and TSA (0.5, 1, and 2 μmol/l) by flow cytometry using propidium iodide/annexin-V-FITC staining. Cell proliferation was assessed using the MTS proliferation test. Induction of the cell cycle inhibitor p21Waf/Cip1 by TSA was analysed by western blot. Expression of the TRAIL receptor-2 (DR5) on the cell surface of RASF was analysed by flow cytometry. Levels of soluble TRAIL were measured in synovial fluid of patients with RA and osteoarthritis (OA) by ELISA. Results: Co-treatment of the cells with TSA and TRAIL induced cell death in a synergistic and dose dependent manner, whereas TRAIL and TSA alone had no effect or only a modest effect. RASF express DR5 (TRAIL receptor 2), but treatment of the cells with TSA for 24 hours did not change the expression level of DR5, as it is shown for cancer cells. TSA induced cell cycle arrest in RASF through up regulation of p21Waf1/Cip1. Levels of soluble TRAIL were significantly higher in RA than in OA synovial fluids. Conclusion: Because TSA sensitises RASF for TRAIL-induced apoptosis, it is concluded that TSA discloses sensitive sites in the cascade of TRAIL signalling and may represent a new principle for the treatment of RA.

Histone deacetylase 7, a potential target for the antifibrotic treatment of systemic sclerosis

OBJECTIVE We have recently shown a significant reduction in cytokine-induced transcription of type I collagen and fibronectin in systemic sclerosis (SSc) skin fibroblasts upon treatment with trichostatin A (TSA). Moreover, in a mouse model of fibrosis, TSA prevented the dermal accumulation of extracellular matrix. The purpose of this study was to analyze the silencing of histone deacetylase 7 (HDAC-7) as a possible mechanism by which TSA exerts its antifibrotic function. METHODS Skin fibroblasts from patients with SSc were treated with TSA and/or transforming growth factor beta. Expression of HDACs 1-11, extracellular matrix proteins, connective tissue growth factor (CTGF), and intercellular adhesion molecule 1 (ICAM-1) was analyzed by real-time polymerase chain reaction, Western blotting, and the Sircol collagen assay. HDAC-7 was silenced using small interfering RNA. RESULTS SSc fibroblasts did not show a specific pattern of expression of HDACs. TSA significantly inhibited the expression of HDAC-7, whereas HDAC-3 was up-regulated. Silencing of HDAC-7 decreased the constitutive and cytokine-induced production of type I and type III collagen, but not fibronectin, as TSA had done. Most interestingly, TSA induced the expression of CTGF and ICAM-1, while silencing of HDAC-7 had no effect on their expression. CONCLUSION Silencing of HDAC-7 appears to be not only as effective as TSA, but also a more specific target for the treatment of SSc, because it does not up-regulate the expression of profibrotic molecules such as ICAM-1 and CTGF. This observation may lead to the development of more specific and less toxic targeted therapies for SSc.

Association of circulating miR-223 and miR-16 with disease activity in patients with early rheumatoid arthritis

Background Identification of parameters for early diagnosis and treatment response would be beneficial for patients with early rheumatoid arthritis (ERA) to prevent ongoing joint damage. miRNAs have features of potential biomarkers, and an altered expression of miRNAs was shown in established rheumatoid arthritis (RA). Objective To analyse RA associated miRNAs in the sera of patients with ERA to find markers of early disease, clinical activity or predictors of disease outcome. Methods Total RNA was isolated from whole sera in ERA patients (prior to and after 3 and 12 months of therapy with disease modifying antirheumatic drugs), in patients with established RA and in healthy controls (HC) using phenol–chloroform extraction. Expression of miR-146a, miR-155, miR-223, miR-16, miR-203, miR-132 and miR-124a was analysed by TaqMan Real Time PCR. Results From all analysed miRNAs, levels of miR-146a, miR-155 and miR-16 were decreased in the sera of ERA patients in comparison with established RA. A change in circulating miR-16 in the first 3 months of therapy was associated with a decrease in DAS28 in long term follow-up in ERA (p=0.002). Levels of circulating miR-223 in treatment naïve ERA correlated with C reactive protein (p=0.008), DAS28 (p=0.031) and change in DAS28 after 3 months (p=0.003) and 12 months (p=0.011) of follow-up. However, neither miR-16 nor miR-223 could distinguish ERA from HC. Conclusions Differential expression of circulating miR-146a, miR-155 and miR-16 in the sera of ERA patients may characterise an early stage of the disease. We suggest miR-223 as a marker of disease activity and miR-16 and miR-223 as possible predictors for disease outcome in ERA.

Epigenetics and rheumatoid arthritis: The role of SENP1 in the regulation of MMP-1 expression☆

The aggressive phenotype of RA synovial fibroblasts (RASF) is characterised by the increased expression of matrix metalloproteinase (MMP)-1 as well as the small ubiquitin like modifier (SUMO)-1 and decreased expression of SUMO-specific protease SENP1. Since we showed an increased activity of acetyltransferases in this autoimmune disease, we wanted to analyze whether this affects the expression of MMP-1 and can be reversed by the reconstitution of SENP1. In RASF, the acetylation of histone H4 was significantly increased in the distal region of the MMP-1 promoter by 274 +/- 36% compared to OASF. Most interestingly, overexpression of SENP1 in RASF decreased acetylation specifically in this region by 51 +/- 0.5% and globally by 73 +/- 11%. Furthermore, the overexpression of SENP1 resulted in a downregulation of MMP-1 at both the mRNA (58 +/- 7%) and protein levels (28 +/- 6%), significantly reduced the invasiveness of RASF (from 34 +/- 9% to 2 +/- 2%) and led to an accumulation of histone deacetylase 4 (HDAC4) on the MMP-1 promoter (197 +/- 36%). Interestingly, SENP1 failed to modulate the expression of MMP-1 in the cells silenced for HDAC4. This is the first study linking the SUMOylation pathway and the production of MMP-1 to an epigenetic control mechanism mediated through histone acetylation which has a functional consequence for the invasiveness of RASF.