Increased expression of chemerin in endothelial cells due to Fli1 deficiency may contribute to the development of digital ulcers in systemic sclerosis

Objectives. Chemerin is a member of adipocytokines with a chemoattractant effect on plasmacytoid dendritic cells and macrophages and pro-angiogenic properties. We investigated the potential role of chemerin in the development of SSc. Methods. Chemerin expression was evaluated by immunostaining and/or real-time quantitative RT-PCR in human and murine skin. The mechanisms regulating chemerin expression in dermal fibroblasts and endothelial cells were examined using the gene silencing technique and chromatin immunoprecipitation. Serum chemerin levels were determined by ELISA in 64 SSc patients and 19 healthy subjects. Results. In SSc lesional skin, chemerin was up-regulated in small blood vessels, while it was down-regulated in fibroblasts surrounded with thickened collagen bundles. The decreased expression of chemerin was significantly reversed by TGF-beta 1 antisense oligonucleotide in cultured SSc dermal fibroblasts and chemerin expression was markedly decreased in dermal fibroblasts of bleomycin-treated mice. Gene silencing of transcription factor Fli1, which binds to the chemerin promoter, induced chemerin expression in human dermal microvascular endothelial cells and Fli1(+/-) mice exhibited elevated chemerin expression in dermal blood vessels. Serum chemerin levels inversely correlated with estimated glomerular filtration rate in SSc patients with renal dysfunction. In SSc patients with normal renal function, patients with digital ulcers had higher serum chemerin levels than those without. Conclusion. Chemerin is down-regulated in SSc dermal fibroblasts by autocrine TGF-beta, while it is up-regulated in SSc dermal blood vessels through endothelial Fli1 deficiency. Increased chemerin expression in dermal blood vessels may be associated with the development of digital ulcers in SSc.