Background/Purpose:  Systemic sclerosis (SSc) is a multisystem autoimmune disease characterized by vasculopathy and fibrosis of the skin and various internal organs. Glycyrrhizin, a triterpenoid saponin glycoside from the roots of licorice, is a clinically approved for the treatment of chronic hepatic diseases and itching dermatitis and has also been used for Kampo in the Orient from ancient times. Importantly, glycyrrhizin has been shown to modulate the pathological processes of fibrosis, inflammation, and vasculopathy in some experimental disease models. Based on these backgrounds, we investigated the effect of glycyrrhizin on the three cardinal pathological features of SSc, including tissue fibrosis, inflammation, and vasculopathy, utilizing bleomycin (BLM)-treated mice recapitulating the fibrotic and inflammatory aspects of SSc and endothelial cell-specific Fli1 knockout (Fli1ECKO) mice mimicking SSc vasculopathy.

Methods: Wild type C57BL/6 mice were subcutaneously injected with BLM or phosphate buffered saline (PBS) for the indicated period of time together with daily intraperitoneal injection of glycyrrhizin (30mg/kg) or PBS. mRNA and/or protein levels of target molecules were determined by quantitative reverse transcription-PCR, immunostaining, and/or immunoblotting in the skin samples and cultivated cells. Th1/Th2/Th17 polarization of immune response and macrophages polarization were evaluated by flow cytometry. Vascular permeability was evaluated by Evans blue dye injection in Fli1ECKO mice.

Results: Glycyrrhizin significantly ameliorated dermal thickness and collagen contents and decreased the number of myofibroblasts in BLM-treated mice. Consistent with these findings, glycyrrhizin significantly suppressed mRNA levels of the Col1a1, Col1a2, and Col3a1 genes, while not those of the Ctgf and Tgfb genes in the lesional skin of BLM-treated mice. Since mRNA levels of the Thbs1 gene, encoding thrombospondin 1 which activates latent form of TGF-Β, were significantly reduced under the same condition, glycyrrhizin is likely to prevent the development of BLM-induced dermal fibrosis at least partially by blocking autocrine TGF-Β signaling in dermal fibroblasts. As for the expression profiles of cytokines and chemokines, the reduction of IL-4 and IL-6 was noted in the lesional skin of BLM-treated mice administered glycyrrhizin. Consistently, glycyrrhizin attenuated the BLM-dependent induction of Th2 cells in draining lymph nodes and spleen, partially contributing to the prevention of BLM-induced dermal fibrosis. Relevant to this finding, the expression levels of M2 macrophage markers were decreased by glycyrrhizin in the lesional skin of BLM-treated mice. With respect to the pathological vascular aspects, glycyrrhizin prevented the BLM-dependent induction of endothelial-to-mesenchymal transition, also associated with the reduction of dermal fibrosis by this agent, and improved the leaky vascular phenotype of Fli1ECKO mice.

Conclusion: Glycyrrhizin has potential preventive and/or therapeutic effects on the pathological dermal fibrosis and vasculopathy similar to SSc by acting on fibroblasts, endothelial cells, and immune cells.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/glycyrrhizin-ameliorates-fibrosis-vasculopathy-and-immune-abnormalities-in-animal-models-of-systemic-sclerosis/