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

Epigenetic Regulation of Matrix Metalloproteinase-1 and -3 Expression in Mycobacterium tuberculosis Infection.

In pulmonary tuberculosis (TB), the inflammatory immune response against Mycobacterium tuberculosis (Mtb) is associated with tissue destruction and cavitation, which drives disease transmission, chronic lung disease, and mortality. Matrix metalloproteinase (MMP)-1 is a host enzyme critical for the development of cavitation. MMP expression has been shown to be epigenetically regulated in other inflammatory diseases, but the importance of such mechanisms in Mtb-associated induction of MMP-1 is unknown. We investigated the role of changes in histone acetylation in Mtb-induced MMP expression using inhibitors of histone deacetylases (HDACs) and histone acetyltransferases (HAT), HDAC siRNA, promoter-reporter constructs, and chromatin immunoprecipitation assays. Mtb infection decreased Class I HDAC gene expression by over 50% in primary human monocyte-derived macrophages but not in normal human bronchial epithelial cells (NHBEs). Non-selective inhibition of HDAC activity decreased MMP-1/-3 expression by Mtb-stimulated macrophages and NHBEs, while class I HDAC inhibition increased MMP-1 secretion by Mtb-stimulated NHBEs. MMP-3 expression, but not MMP-1, was downregulated by siRNA silencing of HDAC1. Inhibition of HAT activity also significantly decreased MMP-1/-3 secretion by Mtb-infected macrophages. The MMP-1 promoter region between -2,001 and -2,942 base pairs from the transcriptional start site was key in control of Mtb-driven MMP-1 gene expression. Histone H3 and H4 acetylation and RNA Pol II binding in the MMP-1 promoter region were increased in stimulated NHBEs. In summary, epigenetic modification of histone acetylation via HDAC and HAT activity has a key regulatory role in Mtb-dependent gene expression and secretion of MMP-1 and -3, enzymes which drive human immunopathology. Manipulation of epigenetic regulatory mechanisms may have potential as a host-directed therapy to improve outcomes in the era of rising TB drug resistance

The Protease Inhibitor Alpha-2-Macroglobuline-Like-1 Is the p170 Antigen Recognized by Paraneoplastic Pemphigus Autoantibodies in Human

Paraneoplastic pemphigus (PNP) is a devastating autoimmune blistering disease, involving mucocutaneous and internal organs, and associated with underlying neoplasms. PNP is characterized by the production of autoantibodies targeting proteins of the plakin and cadherin families involved in maintenance of cell architecture and tissue cohesion. Nevertheless, the identity of an antigen of Mr 170,000 (p170), thought to be critical in PNP pathogenesis, has remained unknown

Mitoxantrone, pixantrone, and mitoxantrone (2-hydroxyethyl)piperazine are toll-like receptor 4 antagonists, inhibit NF-κB activation, and decrease TNF-alpha secretion in primary microglia

Toll-like receptor 4 (TLR4) recognizes various endogenous and microbial ligands and is an essential part in the innate immune system. TLR4 signaling initiates transcription factor NF-κB and production of proinflammatory cytokines. TLR4 contributes to the development or progression of various diseases including stroke, neuropathic pain, multiple sclerosis, rheumatoid arthritis and cancer, and better therapeutics are currently sought for these conditions. In this study, a library of 140 000 compounds was virtually screened and a resulting hit-list of 1000 compounds was tested using a cellular reporter system. The topoisomerase II inhibitor mitoxantrone and its analogues pixantrone and mitoxantrone (2-hydroxyethyl)piperazine were identified as inhibitors of TLR4 and NF-κB activation. Mitoxantrone was shown to bind directly to the TLR4, and pixantrone and mitoxantrone (2- hydroxyethyl)piperazine were shown to inhibit the production of proinflammatory cytokines such as tumor necrosis factor alpha (TNFα) in primary microglia. The inhibitory effect on NF-κB activation or on TNFα pro-duction was not mediated through cytotoxity at ≤ 1 μM concentration for pixantrone and mitoxantrone (2- hydroxyethyl)piperazine treated cells, as assessed by ATP counts. This study thus identifies a new mechanism of action for mitoxantrone, pixantrone, and mitoxantrone (2-hydroxyethyl)piperazine through the TLR4.Peer reviewe

Innate immunity, epigenetics and autoimmunity in rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic inflammatory autoimmune disease characterized by the progressive and irreversible destruction of joints. RA remains an incurable condition, although a new class of drugs, biologicals, have made a major breakthrough in targeting and/or eliminating the immune cells, including T cells, B cells and monocytes/macrophages from the joints. That we cannot (yet?) cure the disease is most likely due to the lack of therapeutic targeting the endogenously activated RA synovial fibroblasts (RASF). Most interestingly, RASF express Toll-like receptors (TLRs) 1-6 rendering them prone to activation by exogenous and endogenous TLR ligands and resulting in the production of numerous powerful chemokines and cytokines. These factors are responsible for the repopulation of immune cells in the joints after ceasing cell depleting therapies. To characterize the molecular mechanisms of synovial activation, a new approach studying the epigenetic characteristics of RASF has been recently undertaken. Thereby, the pattern of histone acetylation, DNA methylation and gene expression regulating microRNA are being explored. Since auto-antibodies have the most predictive and diagnostic value for RA, it is challenging to study more comprehensively the contribution of auto-antibodies to the disease. A new screening technique, serological analysis of recombinant human cDNA expression library (SEREX), adapted from cancer research allowed for the identification of novel auto-antibodies in RA, including anti-serpin E2 auto-antibodies. The serpin E2 auto-antibodies were found to inhibit the activity of serpin E2 and have potentially a functional role in the disease. The recent findings in the field of innate immunity, epigenetics and autoimmunity related to the pathogenesis of RA are in the scope of this review

Protein Tyrosine Phosphatase Nonreceptor Type 2 (PTPN2), an Important Regulator of IL-6 Production in Rheumatoid Arthritis Synovial Fibroblasts

Objective This article is protected by copyright. All rights reserved. Methods Synovial tissues from RA and osteoarthritis (OA) were stained for PTPN2. Synovial fibroblasts (SF), were stimulated with TNF and IL1β, LPS, TRAIL or thapsigargin. Expression of PTPN2 in SF or PBMCs was analyzed by Real-time PCR and Western blotting. Cell death, the release of IL-6 and IL-8 and the induction of autophagy were analyzed after PTPN2 silencing. MeDIP analysis was used to check DNA methylation-regulated gene expression of PTPN2. Results PTPN2 was significantly overexpressed in synovial tissues of RA compared to OA. Patients treated with anti-TNF therapy showed significantly reduced staining for PTPN2 compared with patients treated with non-biologics. In RASF, PTPN2 expression was higher compared to OASF. This differential expression is not regulated by DNA methylation. PTPN2 was further upregulated after stimulation with TNF, TNF combined with IL1β and LPS. There was no significant difference in basal PTPN2 expression in PBMCs from patients with RA, ankylosing spondylitis, systemic lupus erythematosus and healthy controls. Most interestingly, PTPN2 silencing in RASF significantly increased the production of the inflammatory cytokine IL-6 but did not affect levels of IL-8. Moreover, functional analysis showed that high PTPN2 levels contribute to the increased apoptosis resistance of RASF and increased autophagy. Conclusion This is the first study on PTPN2 in RASF showing that PTPN2 regulates IL-6 production, cell death and autophagy. This indicates that PTPN2 is linked to the pathogenesis of RA via synovial fibroblasts. This article is protected by copyright. All rights reserved

Citrullination enhances the pro-inflammatory response to fibrin in rheumatoid arthritis synovial fibroblasts

OBJECTIVE: Fibrin deposits are characteristic of the synovial tissues in rheumatoid arthritis (RA). Once citrullinated, fibrin becomes an autoantigen and is thought to contribute in this way to perpetuate the disease. Our study aimed to analyse the responses of RA synovial fibroblasts (RASF) to native and citrullinated fibrin. METHODS: The transcriptome induced by fibrin in RASF was approached with whole-genome-based gene expression arrays. The upregulation of selected pro-inflammatory genes by fibrin was confirmed in additional primary cell cultures using quantitative PCR and ELISA. Citrullination reactions were carried out with recombinant human peptidylarginine deiminases (PAD) 2 and 4. RESULTS: In the whole-genome array native fibrin was found to modulate the gene expression profile of RASF, particularly upregulating mRNA levels of several pro-inflammatory cytokines. The induction of interleukin (IL)-6 and IL-8 by fibrin was confirmed in additional samples at both the mRNA and the protein level. Blocking and knockdown experiments showed the participation of toll-like receptor (TLR)4 in the induction of both cytokines. As compared with the native macromolecule, PAD2-citrullinated fibrin induced significantly higher expression of the pro-inflammatory cytokines in these cells. CONCLUSIONS: Our results suggest that fibrin mediates inflammatory responses in RASF via a TLR4 pathway. In this way, fibrin and particularly its citrullinated form may contribute to sustain the cytokine burst in RA