Iguratimod Treated Scleroderma with Interrupted Egr1/TGF-β Loop

Qingran Yan¹, Lichong Shen ¹, Xiaoxiang Chen ¹ and Liangjing Lu ¹, ¹Department of Rheumatology, Renji Hospital, Shanghai Jiaotong University School of medicine, Shanghai, China (People's Republic)

Meeting: 2019 ACR/ARP Annual Meeting

Keywords: Egr1 and tissue growth factor (TGF), Iguratimod, Scleredema

Session Information

Date: Tuesday, November 12, 2019

Title: 5T095: Systemic Sclerosis & Related Disorder – Basic Science (2744–2749)

Session Type: ACR Abstract Session

Session Time: 2:30PM-4:00PM

Background/Purpose: Iguratimod is a novel disease modifying anti-rheumatic drug that has been approved for treating rheumatoid arthritis in East Asia. Transcription factor early growth response 1 (Egr1) is one the most down-regulated genes in with iguratimod treatment. Egr1 forms a positive feedback loop with TGFβ and is overexpressed in lesional skin from systemic sclerosis (SSc) patients. This study is aim to investigate the anti-fibrotic effect of iguratimod in scleroderma models and patient skin grafts.

Methods: We used iguratimod to treat TGFβ-stimulated human skin fibroblast, bleomycin induced mice, tight skin 1 (TSK-1) mice and SSc skin grafts. The bleomycin model contained pre-establish fibrosis and late onset treatment. The skin grafts came from three SSc patients and was planted into irradiated nude mice.

Results: Iguratimod strongly inhibited egr1 expression in human skin fibroblast, with moderate down-regulation of Egr2/3. Iguratimod neutralized effects of TGFβ on 232/327 Egr1 inducible genes according to transcriptome sequencing. Further protein interaction analysis showed that Egr1 was one of the hub genes of iguratimod working network. Collagen production and α-SMA production were decreased by iguratimod. Knocking down Egr1 using siRNA could mimic these effects. Both oral and topical iguratimod could treat dermal thickening and collagen deposition in bleomycin induced skin fibrosis. α-SMA (+) myofibroblast counts, as well as Egr1 (+) and TGFβ (+) fibroblast counts were significantly reduced by iguratimod. Similarly, topical iguratimod ameliorated dermal fibrosis in TSK-1 mice. Of note, 5-week iguratimod local injection remarkably reduced collagen content in skin grafts from three SSc patients, with simultaneous inhibited Egr1 and TGFβ staining.

Conclusion: We found the potential of iguratimod to treat SSc, which was characterized as the interruption of Egr1/TGFβ loop. Further clinical investigations for its safety and efficacy is warranted.

Iguratimod inhibited Egr1 expression in primary human dermal fibroblast. Human fibroblast were stimulated by TGF-β and treated with 0.1% DMSO -T- or 100μM iguratimod -TI-. -A- Iguratimod treatment suppressed multiple egr genes, particularly egr1. RNA was isolated and sequenced to Illumina Hiseq. Each line represents an independent experiment. -B- Iguratimod inhibited egr1 mRNA expression in dose dependent manner. N = 3 per group. *P<0.05, **P<0.01, ANOVA. -C, D- Iguratimod significantly reduced egr-1 protein synthesis at 100μM. -E- Analysis of 327 Egr1 response gene expression -genes with FDR < 0.05; fold change ≥ 1.5 in NC vs T comparison-. Iguratimod could largely neutralize the effects of TGF-β on Egr-1 response genes. -F- Gene interaction analysis on the top 50 regulated genes between T and IGT groups using STRINGS data base. Egr1 was in the center of the network.

Iguratimod treated fibrosis of skin grafts from systemic sclerosis -SSc- patients with interrupted Egr1/TGF-β loop. Lesional skin tissue from each SSc patient were transplanted subcutaneously into two irradiated nude mice. The grafts were injected with 0.1mg/ml iguratimod or vehicle every day for 5 weeks. -A- Sirius red staining for each graft. The red parts represent collagen and green parts represent total protein. -B- The collagen content of each skin tissue was quantified by eluting the dye and colorimetric assay. -C and D- Representative images of Egr1 and TGFβ staining.

Disclosure: Q. Yan, None; L. Shen, None; X. Chen, None; L. Lu, None.

To cite this abstract in AMA style:

Yan Q, Shen L, Chen X, Lu L. Iguratimod Treated Scleroderma with Interrupted Egr1/TGF-β Loop [abstract]. Arthritis Rheumatol. 2019; 71 (suppl 10). https://acrabstracts.org/abstract/iguratimod-treated-scleroderma-with-interrupted-egr1-tgf-%ce%b2-loop/. Accessed .

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