Effects Of Salicylic Acid On The Expression Of Filaggrin (FLG) And Kallikrein7(KLK7) In Human Keratinocytes

Background and objective:Atopic dermatitis (AD) is a common, chronic, relapsing, inflammatory skindisease, with itchy skin, dryness and inflammation as the main characters. More andmore studies show that the abnormality of skin barrier function plays an important rolein the pathogenesis of AD. Filaggrin(FLG) is a differentiation protein indispensable forintegrated skin barrier and edpidermal hydration function. Deficiency and genemutation of FLG can damage the skin barrier, resulting in skin dryness and causing itch.Human kallikrein7(KLK7) is involved in cell shedding process of the skin and has arole in other pathophysiological processes of the skin such as keratinization andinflammation. In AD, the expression of KLK7significantly increases, causingdesquamation and itching.Via detecting the effects of salicylic acid at different concentrations on FLG andKLK7in human keratinocytes, this study probes into the impacts of salicylic acid onepidermal barrier function, to provide basic experimental data for clinical use ofsalicylic acid in treating AD.Methods:Keratinocytes were treated with different concentrations of salicylic acid for24h.MTT method was used to detect cell survival rate to determine the safety of salicylicacid. In the security concentration range, different concentrations of salicylic acid (500μg/ml,50μg/ml,5μg/ml,0.5μg/ml) were used in keratinocytes for24h. FLG and KLK7expressions were detected by immunohistochemical method, Elisa method and RT-PCR.One way ANOVA was used in statistical comparison.Results:1. The MTT results showed that treated with2000μg/ml and1000μg/ml of salicylic acid for24hours, cell survival rates were significantly decreased to28.37%and71.16%,respectively (P <0.01). In500μg/ml,50μg/ml,5μg/ml and0.5μg/ml groups, the survivalrates were98.04%,97.93%,98.28%,99.1%(all>95%). Therefore, the subsequentexperiment concentrations of salicylic acid were500μg/ml,50μg/ml,5μg/ml and0.5μg/ml.2.Immunohistochemical results showed that, compared with the control group(430.996±96.979), four concentrations (500μg/ml,50μg/ml,5μg/ml,0.5μg/ml) ofsalicylic acid increased FLG protein expression significantly (1520.476±37.807,3627.906±228.503,1590.677±166.396,808.073±154.108, P <0.01).3.RT-PCR results showed that, compared with the control group (7760±74.746),four concentrations (500μg/ml,50μg/ml,5μg/ml,0.5μg/ml) of salicylic acid increasedFLG mRNA expression significantly (13500±1014.193,16308±2034.382,137770±2255.839,11935±505.433, P <0.01).4. Elisa results showed that, compared with the control group (0.2325±0.1516),four concentrations (500μg/ml,50μg/ml,5μg/ml,0.5μg/ml) of salicylic acid inhibitedKLK7protein expression significantly (0.1017±0.01830,0.0787±0.01180,0.9570±0.19140,0.1120±0.02120,P<0.01).5. RT-PCR test indicated that, compared with the control group (10570±800.733),four concentrations (500μg/ml,50μg/ml,5μg/ml,0.5μg/ml) of salicylic acid inhibitedKLK7mRNA expression significantly (9556±512.000,7186±183.567,7571±235.119;8421±211.028,P<0.01).Among the four detection concentrations, effect of50μg/ml salicylic acid is themost obvious one.Conclusions：1. Salicylic acid at the concentrations of0.5μg/ml to500μg/ml can promote mRNAand protein levels of FLG, and inhibit mRNA and protein levels of KLK7. Among theseconcentrations,50μg/ml of salicylic acid exerted the most significant regulatory effects.2. Salicylic acid might improve skin barrier through upregulating levels of FLG anddownregulating levels of KLK7, which provided theoretical foundation for treating ADwith salicylic acid.