Oxymatrine Sensitizes the HaCaT Cells to the IFN-γ Pathway and Downregulates MDC, ICAM-1, and SOCS1 by Activating p38, JNK, and Akt

Abstract

Decreased interferon (IFN)-γ levels and increased levels of macrophage-derived chemokine (MDC) and intercellular adhesion molecule (ICAM)-1 are known to be involved in allergic skin diseases, such as eczema and atopic dermatitis. Activation of the IFN-γ and its downstream interleukin-12 (IL-12) pathway can correct these diseases. Suppressor of cytokine signaling 1 (SOCS1) is a cytokine signaling inhibitor that blocks downstream pathways of IFN-γ by blocking the mitogen-activated protein kinase (MAPK) and protein kinase B (Akt) signaling pathways. Oxymatrine (OMT), a quinolizidine alkaloid extracted from the herbal medicine Radix Sophorae flavescentis, is used to treat allergic skin diseases in China. The non-cytotoxic concentrations of OMT in HaCaT cells were determined through 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assays. Tumor necrosis factor (TNF)-α and IFN-γ were used to stimulate HaCaT cells, and OMT was added to this system with tacrolimus (FK506) as a positive control. The mRNAs of cytokines, MDC, ICAM-1, IL-12p35, IL-12p40, and IFN-γ receptor (IFN-γR)α were detected by RT-PCR. Western blot analyses were performed to assess activation of the MAPK (p38, Jun N-terminal kinase, and extracellular signal-regulated kinase) and Akt signaling pathways. OMT increased the mRNA levels of the IL-12 and IFN-γRα, reduced the mRNA levels of ICAM-1, MDC, and SOCS1. But FK506 increased the mRNA levels of IL12 and inhibited the expression of ICAM-1 mRNAs and had no effects on the IFN-γRα, MDC, and SOCS1 mRNA in HaCaT cells stimulated with TNF-α and IFN-γ. Thus, the mechanisms through which OMT and FK506 ameliorate allergic skin diseases differ.

Keywords: IFN-γ; MAPKs; SOCS1; allergic skin diseases; atopic dermatitis; oxymatrine.