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 different 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 by rhIFN-γ was also suppressed by triptolide at the concentrations of 10-9 mol/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-γ;Interferon-γ receptor;Janus kinase;Suppressor of cytokine signaling