Background Systemic sclerosis (SSc) is a collagen disease that exhibits intractable fibrosis and vascular injury of the skin and internal organs. Transforming growth factor-β (TGF-β)/Smad signaling plays a central role in extracellular matrix (ECM) production by α-SMA-positive myofibroblasts. Myofibroblasts may be partially derived from various precursor cells in addition to resident fibroblasts. Recently, our high-throughput in vitro screening discovered a small compound, LG283, that may disrupt the differentiation of epithelial cells into myofibroblasts. This compound was originally generated as a curcumin derivative. Methods In this study, we investigated the effect of LG283 on inhibiting fibrosis and its mechanism. The action of LG283 on TGF-β-dependent fibrogenic activity and epithelial-mesenchymal transition (EMT) was analyzed in vitro. The effects of LG283 were also examined in a bleomycin-induced skin fibrosis mouse model. Results LG283 suppressed TGF-β-induced expression of ECM, α-SMA, and transcription factors Snail 1 and 2, and Smad3 phosphorylation in cultured human dermal fibroblasts. LG283 was also found to block EMT induction in cultured human epithelial cells. During these processes, Smad3 phosphorylation and/or expression of Snail 1 and 2 were inhibited by LG283 treatment. In the bleomycin-induced skin fibrosis model, oral administration of LG283 efficiently protected against the development of fibrosis and decrease of capillary vessels without significantly affecting cell infiltration or cytokine concentrations in the skin. No apparent adverse effects of LG283 were found. LG283 treatment remarkably inhibited the enhanced expression of α-SMA and phosphorylated Smad3, as well as those of Snail 1 and 2, in the bleomycin-injected skin. Conclusions The LG283 compound exhibits antagonistic activity on fibrosis and vascular injury through inhibition of TGF-β/Smad/Snail mesenchymal transition pathways and thus, may be a candidate therapeutic for the treatment of SSc. Although the involvement of EMT in the pathogenesis of SSc remains unclear, the screening of EMT regulatory compounds may be an attractive approach for SSc therapy.

BackgroundTransforming growth factor-β (TGF-β)/Smad signaling is well known to play a critical role in the pathogenesis of systemic sclerosis (SSc). We previously developed an artificial molecule, the histidine-pyridine-histidine ligand derivative HPH-15, which may have an antifibrotic effect. The purpose of the present study was to clarify the effects of this drug in human skin fibroblasts and in a preclinical model of SSc.MethodsThe effects of HPH-15 on expression of extracellular matrix components and TGF-β signaling in human dermal fibroblasts were analyzed. The antifibrotic properties of HPH-15 and its mechanisms were also examined in a bleomycin-induced skin fibrosis mouse model.ResultsHPH-15 suppressed the TGF-β-induced phosphorylation of Smad3 and inhibited the expression of collagen I, fibronectin 1, connective tissue growth factor, and α-smooth muscle actin induced by TGF-β in cultured human skin fibroblasts. In the bleomycin-induced skin fibrosis model, oral administration of HPH-15 protected against the development of skin fibrosis and ameliorated established skin fibrosis. Additionally, HPH-15 suppressed the phosphorylation of Smad3 in various cells, including macrophages in the bleomycin-injected skin. Further, in the treated mice, dermal infiltration of proinflammatory macrophages (CD11b+Ly6Chi) and M2 profibrotic macrophages (CD11b+CD204+ or CD11b+CD206+) was significantly decreased during the early and late stages, respectively. HPH-15 treatment resulted in decreased messenger RNA (mRNA) expression of the M2 macrophage markers arginase 1 and Ym-1 in the skin, whereas it inversely augmented expression of Friend leukemia integration 1 and Krüppel-like factor 5 mRNAs, the transcription factors that repress collagen synthesis. No apparent adverse effects of HPH-15 were found during the treatment.ConclusionsHPH-15 may inhibit skin fibrosis by inhibiting the phosphorylation of Smad3 in dermal fibroblasts and possibly in macrophages. Our results demonstrate several positive qualities of HPH-15, including oral bioavailability, a good safety profile, and therapeutic effectiveness. Thus, this TGF-β/Smad inhibitor is a potential candidate therapeutic for SSc clinical trials.Electronic supplementary materialThe online version of this article (10.1186/s13075-018-1534-y) contains supplementary material, which is available to authorized users.

Dermokine is a chiefly skin-specific secreted glycoprotein localized in the upper epidermis, and its family consists of three splice variants in mice and five in humans. To investigate the pathophysiological impact of dermokine, we generated mice deficient for two (bg) or all dermokine isoforms (abg). Both variants, especially dermokine abg-deficient mice exhibited scale and wrinkle formation resembling ichthyosis accompanied by transepidermal water imbalance at the neonatal stage. Several dermokine abg-deficient mice died by postnatal day 21 when reared under low humidity. Moreover, the cornified envelope was vulnerable, and skin barrier lipid ceramides were reduced in the epidermis of dermokine abg-deficient mice. cDNA microarray and quantitative reverse transcriptaseePCR assays of the epidermis revealed the upregulation of small proline-rich protein and late cornified envelope family members, as well as antimicrobial peptides in the dermokine abg-deficient mice. These barrier gene signatures were similar to that seen in psoriasis, whereas recent studies demonstrated that congenital ichthyosis has gene profiles resembling psoriasis. In line with these findings, adult dermokine abg-deficient mice exhibited aggravated phenotypes in psoriasis-like dermatitis models but not in allergic dermatitis models. Dermokine may play a regulatory role in inflammatory dyskeratotic diseases, such as congenital ichthyosis and psoriasis, in the crosstalk between barrier dysfunction and inflammation.

Objective To assess the preclinical efficacy and mechanism of action of an anti‐CX3CL1 monoclonal antibody (mAb) in systemic sclerosis (SSc). Methods Cultured human dermal fibroblasts were used to evaluate the direct effect of anti‐CX3CL1 mAb on fibroblasts. In addition, bleomycin‐induced and growth factor–induced models of SSc were used to investigate the effect of anti‐CX3CL1 mAb on leukocyte infiltration, collagen deposition, and vascular damage in the skin. Results Anti‐CX3CL1 mAb treatment significantly inhibited Smad3 phosphorylation (P < 0.05) and expression of type I collagen and fibronectin 1 (P < 0.01) in dermal fibroblasts stimulated with transforming growth factor β1 (TGFβ1). In the bleomycin model, daily subcutaneous bleomycin injection increased serum CX3CL1 levels (P < 0.05) and augmented lesional CX3CL1 expression. Simultaneous administration of anti‐CX3CL1 mAb or CX3CR1 deficiency significantly suppressed the dermal thickness, collagen content, and capillary loss caused by bleomycin (P < 0.05). Injection of bleomycin induced expression of pSmad3 and TGFβ1 in the skin, which was inhibited by anti‐CX3CL1 mAb. Further, the dermal infiltration of CX3CR1+ cells, macrophages (inflammatory and alternatively activated [M2‐like] subsets), and CD3+ cells significantly decreased following anti‐CX3CL1 mAb therapy (P < 0.05), as did the enhanced skin expression of fibrogenic molecules, such as thymic stromal lymphopoietin and secreted phosphoprotein 1 (P < 0.05). However, the treatment did not significantly reduce established skin fibrosis. In the second model, simultaneous anti‐mCX3CL1 mAb therapy significantly diminished the skin fibrosis induced by serial subcutaneous injection of TGFβ and connective tissue growth factor (P < 0.01). Conclusion Anti‐CX3CL1 mAb therapy may be a novel approach for treating early skin fibrosis in inflammation‐driven fibrotic skin disorders such as SSc.