| Objective Psoriasis is commom, chronic inflammatory disease has a high relapse,affects approximately0.1-4%of worldwide population. However, the specificpathogenesis of psoriasis is still unknow. K17is overexpressed in psoriatic skin comparedwith normal skin. Our previous investigations have demonstated a K17/T-cell/cytokineautoimmune loop in the pathogenesis of psoriasis. NB-UVB which could induce Tlymphocytes apoptosis and reduce psoriasis-related inflammatory cytokines productionwas effective in the treatment of psoriasis, expecially in psoriasis vulgaris. NB-UVB coulddirectly degrade inflammatory cytokines. However, whether NB-UVB could directlyaffect K17is still unknown. The purpose of our study is to investigate the effects ofNB-UVB on the expression of K17in human keratinocytes.Methods HaCaT cell line was cultured in DMEM/F12. When cells at70%confluence exposure to different dose of NB-UVB. CCK-8andAnnexin V/PI were used to detected cell proliferation and cell apoptosis. Cell cytoskeleton changes were deteted byElectroscopy. To clarify the relationship between different dose of NB-UVB and K17expression, real-time PCR and Western-blot were employed to detect the K17mRNAandK17protein level after (50,100,200and400mJ/cm2) NB-UVB exposure. Western blotwas performed to detect K17, Erk1/2, Phospho-Erk1/2, Stat3, phosphor-Stat3, P38,Phospho-P38, P65, Phospho-P65,AKT, Phospho-AKT,STAT1, Phospho-STAT1, β-actinexpression of keratinocytes before and after exposed to NB-UVB. Furthermore, primaryhuman keratinocytes and psoriatic dermatitis animal model were cultured to detect theK17mRNAand K17protein level in KCs and mice skin. HE staining was applied toobserve the pathological changes in mice skin tissue after NB-UVB exposedandimmnofluorescence and immunohistochemical was aplied to detect K17proteinexpression in mice skin tissue.Results Flowcytometry usingAnnexin-V/PI showed0-400mJ/cm2NB-UVB is themaximum dose to endure keratinocytes. Cellullar proliferation usingCCK-8indicatedthat keratinocytes proliferation was increased after exposingto50or100mJ/cm2dose ofNB-UVB. However,200or400mJ/cm2dose of NB-UVB was of the contrary result. Forfurther explanation, we examined mRNAand protein of K17at this dose range. K17expression is consistent with keratinocytes proliferation. Through the screening ofsignaling pathway, we found that100mJ/cm2dose of NB-UVB could induce STAT3andErk1/2phosphorylation and increase K17expression, while400mJ/cm2dose ofNB-UVB inhibit STAT3and Erk1/2phosphorylation and decrease K17expression. WhenErk1/2phosphorylation was blocked, the K17expression induced by100mJ/cm2dose ofNB-UVB was inhibited. To determine whether this phenomenon is exclusive for HaCaTcells, we reperformed this expemiment in normal human epidermal keratinocyte (NHEK).The results were similar to HaCaT cells. In vivo experiment was performed to confirmwhether NB-UVB could regulate K17expression in keratinocytes. We examined whetherNB-UVB could increase K17protein expression in mouse skin. HE staining of biopsiesfrom mice ears after13daily IMQ treatment, and high dose of NB-UVB (accumulate doseachieved1500mJ/cm2) and low dose of NB-UVB (100mJ/cm2qid). The immunofluorescence analyses showed that the expression of K17protein after low dose ofNB-UVB irradiated was higher than that of the control group, and K17expression in highdose group was down regulate than control group. These results indicated that NB-UVBcan also regulate K17expression in vivo.Conclusions Our study suggested that low doses of NB-UVB could increase K17expression, while high doses of NB-UVB could inhibit K17expression. Different dose ofNB-UVB exposure could cause biologicalchanges in human keratinocytes, which isassociated with the state of the signal pathway. NB-UVB treatment for psoriasis wasperformed with the minimum erythema dose (MED) in clinical practice initially. When thedose is higher than the initial clinical dose, cell proliferation and K17expression wasinhibited. When the dose is lower than the initial clinical dose, keratinocytes proliferationand K17expression was promoted. Certain dose of NB-UVB could inhibit K17expressionin keratinocytes. Thus, NB-UVB played an important role in treatment of psoriasis. Themechanism may be associated with the phosphorylation of STAT3and ERK1/2pathway.Thus, we can infer that NB-UVB caned block partialy the ‘K17/T-cell/cytokines’loop,prevent the formation of positive feedback loop and relieve the clinical symptoms ofpsoriatic. |
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