Abstract
BackgroundPsoriasis is a common inflammatory skin disease. Abnormal proliferation of keratinocytes is one of the psoriatic histopathological features. Indirubin has an essential effect on the proliferation and activation of keratinocytes; however, in psoriasis, the specific mechanism of action of indirubin on keratinocytes is unclear. In the present study, we revealed the effects of indirubin on DNA methyltransferase 1 (DNMT1), wnt inhibitory factor 1 (wif-1), and wnt/β-catenin signal pathway, in the meantime, we explored the effects of indirubin on proliferation, cell cycle and the apoptosis of HaCaT cells.MethodsThe expression of DNMT1, wif-1, Frizzled2, Frizzled5, and β-catenin in HaCaT cells treated with different concentrations of indirubin were detected by Western blotting and quantitative real-time polymerase chain reaction (qRT-PCR). The expression levels of DNMT1 and wif-1 were observed after treated with different concentrations of indirubin by enzyme-linked immunosorbent assay (ELISA). The wif-1 promoter methylation status was detected by DNA methylation-specific PCR (MSP). The transcriptional activities of wif-1 and β-catenin were discovered by a luciferase reporter gene system. Cell viability was determined by Cell Counting Kit-8 (CCK8) method. The cell cycle was detected by flow cytometry. The apoptotic cells were surveyed by the apoptosis kit. The expression of Inolucrin, Loricrin, Filaggrin, Keratin 17, and transcriptional activation of transglutaminase 1(TGase1) were detected by Western blotting.ResultsIndirubin inhibited the expression of DNMT1 and the methylation of the wif-1 promoter. In the wnt signal pathway, indirubin restored the protein expression of wif-1 and inhibited expression of Frizzled2, Frizzled5, and β-catenin. Besides, indirubin inhibited the proliferation of HaCaT cells, induced apoptosis, and arrest cell cycle. We also reported that indirubin could down-regulate the expression of Involucrin, TGase 1, and keratin 17, but the expression of Filaggrin and Loricrin had no significant effect.ConclusionOur research showed that indirubin promoted the demethylation of wif-1 and suppressed the wnt/β-catenin signal pathway, thereby exerted an anti-proliferative effect. This study reveals the anti-proliferation mechanism of indirubin, which may provide an effective option for the treatment of proliferative diseases.
Highlights
Psoriasis is a common inflammatory skin disease
We observed the mRNA expression of wif-1 was recovered by quantitative real-time polymerase chain reaction (qRT-PCR) (Fig.1b), and protein expression of wif-1 was recovered by enzyme-linked immunosorbent assay (ELISA) (Fig.1f)
Indirubin inhibits the expression of DNA methyltransferase 1 (DNMT1) and suppresses the expression of wnt/β-catenin signal pathway related proteins DNMT1 expression is higher in psoriatic peripheral blood mononuclear cells (PBMCs) than in normal controls [16]
Summary
Psoriasis is a common inflammatory skin disease. Abnormal proliferation of keratinocytes is one of the psoriatic histopathological features. Psoriasis is a chronic inflammatory skin disease, which is characterized as erythema or plaques with silvery-white scales, abnormal keratinocyte proliferation, dermal angiogenesis, and immune cell infiltration [1]. It is usually accompanied with multifaceted diseases, such as cardiovascular disease, non-alcoholic fatty liver disease, Crohn’s disease, depression, and metabolic syndrome [2]. A bis-indole alkaloid used in traditional Chinese medicine, has long been used to treat various inflammatory disease and dermatosis [3], it has a variety of biological functions that have a vital impact on cell proliferation, activation, and migration [4]. It is presently used to treat psoriasis and is safe [7]
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