Effect of indirubin on the expression of proinflammatory cytokines in keratinocytes

Objective: To investigate the effect of indirubin on the expression of proinflammatory cytokines in HaCaT cells, and to elucidate the mechanisms of Diqing ointment in the treatment of psoriasis. Methods: The human immortalized keratinocyte cell line, HaCaT cells, were used to observe the changes in the expression levels of IL-1β, IL-6, and TNF-α in HaCaT cells after treatment with different concentrations of indirubin. HaCaT cells were divided into 4 groups. The secretion levels of IL-1β, IL-6, and TNF-α in the culture supernatants were detected by enzyme-linked immunosorbent assay ELISA, and the expression levels of IL-1β, IL-6, and TNF-α mRNA were detected by real-time PCR (RT-qPCR). Results: Expression levels of both mRNA and protein of IL-1β, IL-6, and TNF-α were significantly and dose-dependently decreased after treatment with indirubin. Conclusion: Indirubin, the main component of Qingdai ointment, can lower expression levels of pro-inflammatory cytokines such as IL-1β, IL-6, and TNF-α in keratinocytes, leading to the improvements of psoriasis.