Dihydroartemisinin Ameliorates Contact Hypersensitivity In Mice By Regulating TGF-β/Smad Signaling

Background:Contact hypersensitivity(CHS)is one of the most common skin diseases.It is an inflammatory skin reaction caused by an allergic semi-antigen and the approximately15%～20%of the global population are affected by CHS.Due to the variety of allergens are difficult to prevent in daily life and the traditional drug treatment has more side effects,relapse after withdrawal,and so on.It causes great distress to patients’life and psychology.In recent years,traditional Chinese medicine has shown better therapeutic effect in the treatment of CHS as a result of the characteristics of the low toxicity and multiple targets.As a derivative of Artemisinin,Dihydroartemisinin(DHA)has been shown to be effective in anti-inflammatory and immunomodulatory aspects.Therefore,we investigated the effect of DHA on the mouse model of CHS and its possible mechanism of action,providing new ideas and data for the treatment of CHS.Objectives:To investigate the effects of DHA on CHS in mice and its mechanisms.Methods:BALB/c mice were randomized into control group,model group,Dihydroartemisinin low group(50mg/kg/d)and Dihydroartemisinin high group(100mg/kg/d).Mice were sensitized with 0.5%2,4-dinitrofluorobenzene(DNFB)in acetone and olive oil,on shaved abdominal flank skin for two consecutive days.Five days later,CHS was elicited by applying 0.25%DNFB on the left ear.As a control,the right ear was treated with acetone/olive-oil alone.Two days before sensitization,the mice were treaded with DHA orally.During the modeling period,changes in mouse body weight and ear thickness were observed and recorded daily.H&E staining and immunohistochemistry staining were uesd to observe histopathological changes.The infiltration of inflammatory cells in skin and spleen was analyzed by flow cytometry.Enzyme-linked immunosorbent assays(ELISA)and immunoblot assays were used to detect inflammatory cytokines in serum and Smad-related proteins in skin.Results:The results showed that compared with control group,model group developed exaggerated CHS responses,which were normalized by DHA administration.DHA treatment could significantly inhibit the spleen index of CHS mice(p<0.05).Histopathological analysis also revealed that the degree of edema and cellular infiltration and the number of CD4~+T cells and CD8~+T cells were markedly decreased in DHA-treated mice compared with model mice.Moreover,DHA treatment significantly decreased CD4~+T cells,CD8~+T cells,dendritic cells and macrophages infiltration in the ear skin and spleen(p<0.05).DHA treatment also diminished level of IL-6,IFN-γ,TGF-βand MCP-1in the serum.Furthermore,Smad-2 and Smad-3 phosphorylation status was normalized by DHA treatment.Conclusion:DHA could obviously alleviate DNFB-induced CHS skin inflammation in mice.The possible mechanism might be that DHA suppressed infiltration of immune cells into skin and regulating TGF-β/Smad signaling pathway.Taken together,these results have important implications for the potential use of DHA in treatment of CHS.