Effects of triptolide on interferon-γ signaling in a human keratmocyte cell line HaCaT.

Abstract

Objective To investigate the effects of triptolide on the expression of a series of proteins associated with interferon-γ (IFN-γ)signaling in HaCaT keratinocytes.Methods After pretreatment with difrerent dosages of triptolide(10-10-10-7 mol/L),HaCaT cells were stimulated by recombinant human IFN-γ(rhIFN-γ,500 U/mL)for various periods followed by the collection of cells.Then,total protein was extracted from these cells and subjected to Western blotting for the detection of expression of interferon-γ receptor α(IFN-γRα),phosphorylated Janus kinase 2(pJAK2)and suppressor of cytokine signaling (SOCS1).Results Triptolide at the concentrations of 10-8 mol/L and 10-7 mol/L significantly inhibited the IFN-γRα expression upregulated by rhIFN-γ(both P＜0.05).The expression of pJAK2 induced bv rhIFN-γ was also suppressed by triptolide at the concentrations of 10-9 moI/L and 10-8 mol/L(both P＜0.05).The inhibition of triptolide on IFN-γRα and pJAK2 expression was dose-dependent and the 50%inhibitory concentrations(IC50 value)were 1.37×10-8 mol/L and 2.83×10-9 mol/L,respectively.On the contrary,triptolide upregulated the expression of SOCS1 stimulated by rhIFN-γ at the concentrations of 10-10,10-9 and 10-8 mol/L(P＜0.05,0.05,0.01,respectively)with the 50%effective dosage(ED50 value)at 3.32 × 10-11 mol/L.Conclusions By inhibiting the expression of IFN-γRα as well as phosphorylation of JAK2 and upregulating the expression of SOCS1,triptolide inhibits the phosphorylation of STAT-1,resulting in the inhibition of genetic transcription of multiple inflammatory factors induced by IFN-γ signaling in HaCaT keratinocytes,and the inhibition probably contributes to the efficacy of triptolide in the treatment of IFN-γ-dependent inflammatory skin disorders,such as psoriasis. Key words: Triptolide; Interferon type Ⅱ; Receptors,interferon; Janus kinase 2:Suppressor of cytokine signaling proteins