EZH2 as a major histone methyltransferase in PDGF-BB-activated orbital fibroblast in the pathogenesis of Graves' ophthalmopathy

Graves' ophthalmopathy (GO) is an extra-thyroidal complication of Graves' disease which can lead to vision loss in severe cases. Currently, treatments of GO are not sufficiently effective, so novel therapeutic strategies are needed. As platelet-derived growth factor (PDGF)-BB induces several effector mechanisms in GO orbital fibroblasts including cytokine production and myofibroblast activation, this study aims to investigate the roles of histone lysine methyltransferases (HKMTs) in PDGF-BB-activated GO orbital fibroblasts by screening with HKMTs inhibitors library. From the total of twelve selective HKMT inhibitors in the library, EZH2, G9a and DOT1L inhibitors, DZNeP, BIX01294 and Pinometostat, respectively, prevented PDGF-BB-induced proliferation and hyaluronan production by GO orbital fibroblasts. However, only EZH2 inhibitor, DZNeP, significantly blocked pro-inflammatory cytokine production. For the HKMTs expression in GO orbital fibroblasts, PDGF-BB significantly and time-dependently induced EZH2, G9a and DOT1L mRNA expression. To confirm the role of EZH2 in PDGF-BB-induced orbital fibroblast activation, EZH2 silencing experiments revealed suppression of PDGF-BB-induced collagen type I and α-SMA expression along with decreasing histone H3 lysine 27 trimethylation (H3K27me3) level. In a more clinically relevant model than orbital fibroblast culture experiments, DZNeP treated GO orbital tissues significantly reduced pro-inflammatory cytokine production while slightly reduced ACTA2 mRNA expression. Our data is the first to demonstrate that among all HKMTs EZH2 dominantly involved in the expression of myofibroblast markers in PDGF-BB-activated orbital fibroblast from GO presumably via H3K27me3. Thus, EZH2 may represent a novel therapeutics target for GO.

Regulation of dermal fibroblasts by human neutrophil peptides

Human neutrophil peptides (HNPs) can induce cell proliferation and activation so their growth promoting activities may have potential clinical benefit. This study investigated the effects of HNPs on human dermal fibroblasts. Differential gene expression in HNP-treated cells and genes involved in regulating intracellular pathways were explored. Dermal fibroblasts were isolated from healthy neonatal foreskin and treated with HNPs in 2D and 3D cell culture systems. The expression of cell proliferation (Ki-67) gene and cell activation (COL1A1) gene plus their proteins was measured. Differential gene expression was determined using RNA-seq, and upregulated and downregulated genes were mapped onto intracellular pathways by KEGG analysis and Gene Ontology databases. HNPs significantly increased cell proliferation without cytotoxicity whilst HNP1 enhanced expression of COL1A1 and type I collagen production in 2D cells and 3D spheroids. RNA-sequencing analysis showed gene clustering with clear separation between HNP1-treated and control groups. A heatmap of top 50 differentially expressed genes was consistent among HNP1-treated samples. Most upregulated genes were associated with cell proliferation and activation as mapped into intracellular pathways whilst most downregulated genes belonged to steroid/arachidonic acid metabolism and inflammatory signaling pathways. HNP1 increased cell proliferation and activation but reduced lipid metabolism and inflammation.

Histone Deacetylase 4 Controls Extracellular Matrix Production in Orbital Fibroblasts from Graves' Ophthalmopathy Patients

Background: Graves' ophthalmopathy (GO) is an autoimmune eye disease with the characteristic symptoms of eyelid retraction and proptosis. Orbital fibroblast activation induced by platelet-derived growth factor-BB (PDGF-BB) stimulation plays a crucial role in GO pathogenesis, leading to excessive proliferation and extracellular matrix production by orbital fibroblasts. Currently, GO treatment options remain limited and novel therapies including targeted drugs are needed. Histone deacetylases (HDACs) are associated with the development and progression of several cancers and autoimmune diseases by epigenetically controlling gene transcription, and HDAC inhibitors (HDACis) may have therapeutic potential. Nevertheless, the role of HDACs in orbital fibroblasts from GO is unknown. Therefore, we studied the expression of HDACs as well as their contribution to extracellular matrix production in orbital fibroblasts. Methods: Orbital tissues were obtained from GO patients (n = 18) who underwent decompression surgery with approval from the Institutional Review Board of the Faculty of Medicine (Protocol number 401/61), Chulalongkorn University (Bangkok, Thailand). Furthermore, orbital tissue was obtained from control patients (n = 3) without inflammatory or thyroid disease who underwent surgery for cosmetic reasons. Orbital fibroblast cultures were established from the orbital tissues. HDAC mRNA and protein expression in orbital fibroblasts was analyzed by reverse transcription-quantitative real-time PCR and Western blot. PDGF-BB-activated orbital fibroblast and orbital tissues were treated with HDACis or HDAC4 small-interfering RNA. Results: PDGF-BB-stimulated orbital fibroblasts had upregulated HDAC4 mRNA and protein expression. HDAC4 mRNA expression was significantly higher in GO compared with healthy control orbital fibroblasts. Histone H3 lysine 9 acetylation (H3K9ac) decreased upon PDGF-BB stimulation. Treatment with HDAC4i (tasquinimod) and HDAC4/5i (LMK-235) significantly decreased both proliferation and hyaluronan production in PDGF-BB-stimulated orbital fibroblasts. HDAC4 silencing reduced mRNA expression of hyaluronan synthase 2 (HAS2), collagen type I alpha 1 chain (COL1A1), Ki67, and α-smooth muscle actin (α-SMA), as well as hyaluronan production in PDGF-BB-stimulated orbital fibroblasts. Tasquinimod significantly reduced HAS2 and α-SMA mRNA expression in whole orbital tissue. Conclusion: Our data indicated, for the first time, that altered HDAC4 regulation along with H3K9 hypoacetylation might represent a mechanism that contributes to excessive proliferation and extracellular matrix production by orbital fibroblasts in GO. HDAC4 might represent a novel target for GO therapy.

Role of antimicrobial peptides in atopic dermatitis

Host defense peptides (HDPs) or antimicrobial peptides (AMPs) are short cationic amphipathic peptides of divergent sequences, which are part of the innate immune system and produced by various types of cells and tissues. The predominant role of HDPs is to respond to and protect humans against infection and inflammation. Common human HDPs include defensins, cathelicidin, psoriasin, dermcidin, and ribonucleases, but these peptides may be dysregulated in the skin of patients with atopic dermatitis (AD). Current evidence suggests that the antimicrobial properties and immunomodulatory effects of HDPs are involved in AD pathogenesis, making HDPs research a promising area for predicting disease severity and developing novel treatments for AD. In this review, we describe a potential role for human HDPs in the development, exacerbation, and progression of AD and propose their potential therapeutic benefits.

The Inhibitory Effect of Human Beta-defensin-3 on Candida Glabrata Isolated from Patients with Candidiasis

Candida glabrata is a common non-albicans Candida species found in patients with candidiasis and it sometimes develops antifungal resistance. Human beta-defensin-3 (hBD-3) is an antimicrobial peptide of immune system active against various types of microbes including Candida spp. This study investigated antifungal activity of hBD-3 and its synergistic effect with a first-line antifungal agent on C. glabrata clinical isolates. Candida spp. were characterised in patients with candidiasis. The antifungal activities of hBD-3 and fluconazole against C. glabrata were evaluated using Broth microdilution assay. The synergistic activity of these two agents was determined by checkerboard microdilution and time-killing assays. The cytotoxicity of hBD-3 was evaluated using LDH-cytotoxicity colorimetric assay. Of 307 episodes from 254 patients diagnosed with candidiasis, C. glabrata was found in 21 clinical isolates. Antifungal susceptibility tests of C. glabrata were performed, fluconazole demonstrated an inhibitory effect at concentrations of 0.25-8 μg/ml, but one antifungal resistant strain was identified (>64 μg/ml). hBD-3 showed an inhibitory effect against all selected strains at concentrations of 50-75 μg/ml and exhibited a synergistic effect with fluconazole at the fractional inhibitory concentration index (FICI) of 0.25-0.50. A concentration of 25 μg/ml of hBD-3 alone showed no cytotoxicity but synergistic activity was seen with fluconazole. In conclusion, hBD-3 has antifungal activity against C. glabrata and synergistic effects with fluconazole at concentrations that alone, have no cytotoxicity. hBD-3 could be used as an adjunctive therapy with first-line antifungal agents for patients with C. glabrata infection particularly those infected with fluconazole-resistant strains.

Integrative Analysis of Proteomics and DNA Methylation in Orbital Fibroblasts From Graves' Ophthalmopathy

BACKGROUND

Graves' ophthalmopathy (GO) is a frequent extrathyroidal complication of Graves' hyperthyroidism. Orbital fibroblasts contribute to both orbital tissue inflammation and remodeling in GO, and as such are crucial cellular elements in active GO and inactive GO. However, so far it is largely unknown whether GO disease progression is associated with functional reprogramming of the orbital fibroblast effector function. Therefore, the aim of this study was to compare both the proteome and global DNA methylation patterns between orbital fibroblasts isolated from active GO, inactive GO and healthy controls.

METHODS

Orbital fibroblasts from inactive GO (n=5), active GO (n=4) and controls (n=5) were cultured and total protein and DNA was isolated. Labelled and fractionated proteins were analyzed with a liquid chromatography tandem-mass spectrometer (LC-MS/MS). Data are available via ProteomeXchange with identifier PXD022257. Furthermore, bisulphite-treated DNA was analyzed for methylation pattern with the Illumina Infinium Human Methylation 450K beadchip. In addition, RNA was isolated from the orbital fibroblasts for real-time quantitative (RQ)-PCR. Network and pathway analyses were performed.

RESULTS

Orbital fibroblasts from active GO displayed overexpression of proteins that are typically involved in inflammation, cellular proliferation, hyaluronan synthesis and adipogenesis, while various proteins associated with extracellular matrix (ECM) biology and fibrotic disease, were typically overexpressed in orbital fibroblasts from inactive GO. Moreover, orbital fibroblasts from active GO displayed hypermethylation of genes that linked to inflammation and hypomethylated genes that linked to adipogenesis and autoimmunity. Further analysis revealed networks that contained molecules to which both hypermethylated and hypomethylated genes were linked, including NF-κB, ERK1/2, Alp, RNA polymerase II, Akt and IFNα. In addition, NF-κB, Akt and IFNα were also identified in networks that were derived from the differentially expressed proteins. Generally, poor correlation between protein expression, DNA methylation and mRNA expression was observed.

CONCLUSIONS

Both the proteomics and DNA methylation data support that orbital fibroblasts from active GO are involved in inflammation, adipogenesis, and glycosaminoglycan production, while orbital fibroblasts from inactive disease are more skewed towards an active role in extracellular matrix remodeling. This switch in orbital fibroblast effector function may have therapeutic implications and further studies into the underlying mechanism are thus warranted.

Basic Fibroblast Growth Factor Induces Adipogenesis in Orbital Fibroblasts: Implications for the Pathogenesis of Graves' Orbitopathy

BACKGROUND

Basic fibroblast growth factor (bFGF) has been implicated in the pathogenesis of Graves' orbitopathy (GO). It stimulates several processes, including hyaluronan synthesis, involved in orbital tissue volume expansion and may act synergistically with platelet-derived growth factor (PDGF)-BB. PDGF-BB is known to stimulate adipogenesis in orbital fibroblasts, but the effect of bFGF on adipogenesis in orbital fibroblasts is so far unknown. This study was conducted to determine whether (i) bFGF induces adipogenesis in orbital fibroblasts, (ii) bFGF and PDGF-BB together exert an additive or synergistic effect on adipogenesis, and (iii) treatment directed at bFGF- and PDGF-BB signaling may potentially be of interest for the treatment of GO.

METHODS

Orbital fibroblasts from GO patients and controls were cultured in adipocyte differentiation medium with or without bFGF and/or PDGF-BB at different concentrations. Adipogenesis was determined by Oil Red O staining and messenger RNA expression of the late adipocyte differentiation markers cell death-inducing DFFA-like effector C (CIDEC) and adiponectin (ADIPOQ). To demonstrate involvement of FGF-receptor and PDGF-receptor signaling, experiments were also conducted in the presence of dasatinib (inhibitor of PDGF-receptor) or nintedanib (inhibitor of PDGF-receptor and FGF-receptor).

RESULTS

bFGF significantly stimulated adipogenesis by orbital fibroblasts, as shown by increased Oil Red O staining and CIDEC and ADIPOQ expression after 14 days of differentiation. Furthermore, an additive effect of bFGF/PDGF-BB co-stimulation on adipogenesis was observed at the lowest concentration (12.5 ng/mL) of the growth factors tested. Nintedanib completely inhibited bFGF-, PDGF-BB-, and bFGF/PDGF-BB-induced adipogenesis, while dasatinib only fully abrogated PDGF-BB-induced adipogenesis.

CONCLUSION

bFGF induces adipogenesis in orbital fibroblasts and as such may contribute to GO. The additive effect of bFGF and PDGF-BB on adipogenesis, along with the observed inhibitory effects of dasatinib and nintedanib, point at independent receptor-mediated effects. This supports the hypothesis that multi-target directed therapy might be more efficient in the treatment of GO.

Basic FGF and PDGF-BB synergistically stimulate hyaluronan and IL-6 production by orbital fibroblasts

Orbital fibroblast activation is a central pathologic feature of Graves' Ophthalmopathy (GO). Basic fibroblast growth factor (bFGF) and vascular endothelial growth factor (VEGF) have been proposed to contribute to GO, but their effects on orbital fibroblasts are largely unknown. We found that bFGF stimulated proliferation and hyaluronan production, but not IL-6 production by orbital fibroblasts, while VEGF hardly affected orbital fibroblast activity. Remarkably, co-stimulation of orbital fibroblasts with bFGF and PDGF-BB synergistically enhanced IL-6 and hyaluronan production and displayed an additive effect on proliferation compared to either bFGF or PDGF-BB stimulation. Nintedanib, a FGF- and PDGF-receptor targeting drug, more efficiently blocked bFGF + PDGF-BB-induced IL-6 and hyaluronan production than dasatinib that only targets PDGF-receptor. In conclusion, bFGF may contribute to orbital inflammation and tissue remodeling in GO, especially through synergistic interaction with PDGF-BB. Multi-target therapy directed at the bFGF and PDGF pathways may potentially be of interest for the treatment of GO.

Histamine induces NF-κB controlled cytokine secretion by orbital fibroblasts via histamine receptor type-1

Mast cells and their products are likely to be involved in regulating orbital fibroblast activity in Graves' Ophthalmopathy (GO). Histamine is abundantly present in granules of mast cells and is released upon mast cell activation. However, the effect of histamine on orbital fibroblasts has not been examined so far. Orbital tissues from GO patients and controls were analyzed for the presence of mast cells using toluidine blue staining and immunohistochemical detection of CD117 (stem cell factor receptor). Orbital fibroblasts were cultured from GO patients and healthy controls, stimulated with histamine and cytokines (IL-6, IL-8, CCL2, CCL5, CCL7, CXCL10 and CXCL11) were measured in culture supernatants. Also hyaluronan levels were measured in culture supernatants and hyaluronan synthase (HAS) and hyaluronidase (HYAL) gene expression levels were determined. In addition, histamine receptor subtype gene expression levels were examined as well as the effect of the histamine receptor-1 (HRH1) antagonist loratadine and NF-κB inhibitor SC-514 on histamine-induced cytokine production. Mast cell numbers were increased in GO orbital tissues. Histamine stimulated the production of IL-6, IL-8 and CCL2 by orbital fibroblasts, while it had no effect on the production of CCL5, CCL7, CXCL10, CXCL11 and hyaluronan. Orbital fibroblasts expressed HRH1 and loratadine and SC-514 both blocked histamine-induced IL-6, IL-8 and CCL2 production by orbital fibroblasts. In conclusion, this study demonstrates that histamine can induce the production of NF-κB controlled-cytokines by orbital fibroblasts, which supports a role for mast cells in GO.

Current perspectives on the role of orbital fibroblasts in the pathogenesis of Graves' ophthalmopathy

Graves' ophthalmopathy (GO) is an extra-thyroidal complication of Graves' disease (GD; Graves' hyperthyroidism) characterized by orbital tissue inflammation, expansion, remodeling and fibrosis. Although the initiating trigger of GO is still indistinct, excessive orbital fibroblast activity is at the heart of its pathogenesis. Orbital fibroblasts are activated by cellular interactions with immune cells and the soluble factors they secrete. Orbital fibroblasts, especially from GO patients, express the thyrotropin receptor (TSH-receptor; TSHR), and activation of the orbital fibroblast population by stimulatory autoantibodies directed against the TSHR may provide an important link between GD and GO. Furthermore, stimulatory autoantibodies directed against the insulin-like growth factor-1 receptor have been proposed to contribute to orbital fibroblast activation in GO. Activated orbital fibroblasts produce inflammatory mediators thereby contributing to the orbital inflammatory process in GO. Moreover, orbital fibroblasts exhibit robust proliferative activity and extracellular matrix (especially hyaluronan) synthesizing capacity and can differentiate into adipocytes and myofibroblasts with disease progression, thereby contributing to tissue expansion/remodeling and fibrosis in GO. Orbital fibroblasts, especially those from GO patients, exhibit a hyper-responsive phenotype when compared to fibroblasts from other anatomical regions, which may further contribute to GO pathogenesis. Fibrocytes have been identified as additional source of orbital fibroblasts in GO, where they may contribute to orbital tissue inflammation, adipogenesis and remodeling/fibrosis. This review addresses our current view on the role that orbital fibroblasts fulfill in GO pathogenesis and both established as well as less established not fully crystallized concepts that need future studies will be discussed.

Platelet-Derived Growth Factor-BB Enhances Adipogenesis in Orbital Fibroblasts

PURPOSE

Platelet-derived growth factor (PDGF)-BB has been identified as important factor in pathogenesis of Graves' ophthalmopathy (GO). It stimulates proliferation, cytokine, and hyaluronan production, and thyrotropin receptor expression by orbital fibroblasts. Therefore, the PDGF-pathway has been proposed as a target for pharmacological intervention in GO. However, increased adipogenesis is another major pathological characteristic of GO and it is unknown whether this is affected by PDGF-BB. The aim of this study was to investigate the effect of PDGF-BB on adipocyte differentiation by orbital fibroblasts.

METHODS

Orbital fibroblasts from five healthy controls and nine GO patients were collected. Adipogenesis was induced by culturing orbital fibroblasts in differentiation medium, either in the presence or absence of PDGF-BB. Adipogenesis was determined by Oil-Red-O staining, triglyceride measurement, and peroxisome proliferator-activated receptor (PPAR)-γ mRNA expression.

RESULTS

Platelet-derived growth factor-BB significantly enhanced adipocyte differentiation by orbital fibroblasts (Oil-Red-O staining [P < 0.0001], triglyceride measurement [P < 0.05], and PPAR-γ mRNA expression [P < 0.05]). It enhanced IL-6 production early during differentiation, but the effect of PDGF-BB on adipogenesis was independent of autocrine IL-6 signaling as it was not abrogated by IL-6-receptor-α neutralizing antibody. The clinically applicable tyrosine kinase inhibitor dasatinib and tyrphostin AG1296, which both block PDGF receptor tyrosine kinase activity, inhibited PDGF-BB-enhanced adipogenesis (P < 0.05) in orbital fibroblasts. Moreover, dasatinib reduced PPAR-γ mRNA expression in cultured GO orbital tissue.

CONCLUSIONS

Platelet-derived growth factor-BB enhances adipogenesis in orbital fibroblasts, and, thus, may contribute to adipose tissue expansion in GO. Therefore, the PDGF-signaling cascade may represent a target of therapy to interfere with adipogenesis in GO.

Platelet-derived growth factor: a key factor in the pathogenesis of graves' ophthalmopathy and potential target for treatment

Activation of orbital fibroblasts resulting in excessive proliferation, cytokine and hyaluronan production and differentiation into adipocytes, is a main determinant of orbital tissue inflammation and tissue expansion in Graves' ophthalmopathy (GO). During the last years we have shown that the platelet-derived growth factor (PDGF) isoforms PDGF-AA, PDGF-AB and PDGF-BB are increased in orbital tissue from GO patients with active and inactive disease. These PDGF isoforms exhibit the capacity to stimulate proliferation, hyaluronan and cytokine/chemokine production by orbital fibroblasts. Moreover, PDGF-AB and PDGF-BB increase thyroid stimulating hormone receptor (TSHR) expression by orbital fibroblasts, which enhances the orbital fibroblast activating capacity of the THSR stimulatory autoantibodies present in Graves' disease (GD) patients. Of these PDGF isoforms PDGF-BB exhibits the strongest orbital fibroblast activating effects, which is likely related to its ability to bind both the PDGF-receptor (PDGF-R)α and PDGF-Rβ chains. Thus the PDGF-system fulfills important roles in orbital fibroblast activation in both active and inactive GO, which supports a therapeutic rationale for blocking PDGF signaling in GO. Tyrosine kinase inhibitors (TKIs) may be candidates to target PDGF signaling. Of several TKIs tested dasatinib exhibited the highest potency to block PDGF-R signaling in orbital fibroblasts and may represent a promising compound for the treatment of GO as it was effective at low dosage and is associated with less side effects compared to imatinib mesylate and nilotinib. In this review the contribution of PDGF to the pathophysiology of GO as well as therapeutic approaches to target this PDGF-system will be addressed.

The tyrosine kinase inhibitor dasatinib effectively blocks PDGF-induced orbital fibroblast activation

BACKGROUND

Graves' ophthalmopathy (GO) remains hard to treat. Excessive orbital fibroblast activation by platelet-derived growth factor (PDGF)-BB contributes to GO. The tyrosine kinase inhibitors (TKIs) imatinib mesylate and dasatinib both target PDGF-receptor tyrosine kinase activity, albeit with a different potency. We compared the efficacy of these TKIs on PDGF-BB-induced proliferation, and on cytokine and hyaluronan production by orbital fibroblasts. Also the capacity of dasatinib to suppress GO-associated gene expression in orbital tissue was examined.

METHODS

Orbital fibroblasts from four GO patients and five control subjects were used. The efficacy of the two TKIs was tested by: 1) pre-incubating orbital fibroblasts overnight with different TKI concentrations, followed by 24 h stimulation with PDGF-BB, 2) adding TKI and PDGF-BB simultaneously to the orbital fibroblasts in 24 h cultures. Proliferation was assessed by colorimetric assay. Hyaluronan and cytokine production were measured by ELISA. Furthermore, orbital tissue was obtained from a patient with active GO, and the effect of dasatinib on the expression levels of HAS2-, CCL2-, IL6-, and IL8-mRNA expression was examined by real-time quantitative PCR.

RESULTS

Pre-incubation of orbital fibroblasts with imatinib mesylate or dasatinib resulted in significant and dose-dependent inhibition of PDGF-BB-induced orbital fibroblast proliferation, and hyaluronan and cytokine production. Dasatinib exhibited these effects at far lower concentrations. The same results were observed in the setting where TKI and PDGF-BB treatments were commenced simultaneously. In orbital tissue from active GO, dasatinib significantly suppressed HAS2-, CCL2-, IL6- and IL8-mRNA levels.

CONCLUSION

Dasatinib may be a promising alternative to high-dose steroids in the treatment of GO.

A nested sequence-specific primer-polymerase chain reaction for the detection of HLA-B*15:02

In this study, we reported a new technique in detecting HLA-B*15:02 by using a nested sequence-specific primer-polymerase chain reaction (SSP-PCR) that can be used on genomic DNA and whole blood for carbamazepine hypersensitivity prediction. We tested a total of 200 blind samples with known human leukocyte antigen (HLA)-B allelic types (44 positive for HLA-B*15:02 and 156 negative for HLA-B*15:02) with this new nested SSP-PCR technique and compared its efficacy to that of commercial sequence-specific oligonucleotide probe-polymerase chain reaction (SSOP-PCR). Using starting materials from DNA and whole blood, we were able to detect HLA-B*15:02 in 44 of our samples correctly. The test is very sensitive and is highly reproducible.