The Effects Of Hsp27 Against UVB-induced Photoaging In Rat Skin

Background: Ultraviolet irradiation is one of the most important factors lead to skin photoaging.Long exposure under ultraviolet irradiatin can cause a variety of skin lesions.In response to ultraviolet radiation,the skin has produced some natural resistance mechanisms.Besides,some studies suggest that heat shock protein 27(hsp27)plays an important role in protecting cells from various environmental damage,including ultraviolet irradiation.However,modulation in hsp27 expression toward skin protection against UVB treatment has not been investigated clearly.The specific regulation mechanism of hsp27 on UVB-induced skin photoaging needs to be further clarified.Objective:To explore the hsp27 lead to rat skin photoaging by UVB radiation protection,and analyzes the possible mechanism,this study down-regulated the expression of hsp27 in skin photoaing rat and detected oxidative stress related index ? aging markers ? apoptosis markers and morphology in rats.Further verification of the transcriptional regulation of hsp27 on UVB-induced skin photoaging was conducted.Methods:Rats received injection of the adeno-associated virus(AAV)containing interfering-hsp27 vector into the skin through intradermal injection.After stable expression of the virus,a chronic photoaging model of UVB-irradiated rats was established.HE staining and Masson staining were used to observe histopathology.?-galactose staining was used to observe cell aging.The content of superoxide dismutase(SOD)was determined by xanthine oxidase method,malondialdehyde(MDA)was determined by thiobarbituric acid method,and hydroxyproline(HYP)was determined by alkaline hydrolysis method.Immunohistochemistry was used to detect the expression of hsp27,ki76,bax,bcl-2.TUNEL assay was used to detect cell apoptosis.Western blot was used to detect the protein expression of hsp27,p53,p16,p21,bax,bcl2,and caspase3.mRNA expressions of bax and bcl-2 were detected by RT-PCR.Results: After intragerical injection of hsp27 virus,the protein and RNA expression levels of hsp27 were significantly lower than those in the control group(p <0.01).Compared with the UVB group,the UVB-AAV group had thickened epidermis,disordered cell arrangement,increased glands,disordered collagenous fiber arrangement and elastic fiber deformation;The content of MDA was significantly increased(p<0.01)and the content of HYP was significantly decreased(p<0.05);the positive rate of SA-gal staining was significantly increased(p<0.05),and the expression of aging related pathway marker protein p53 and p16 was significantly increased(p<0.05);the positive rate of TUNEL staining was significantly increased(p<0.05),and the expression of anti-apoptotic factor bcl-2 was decreased,while the expression of apoptotic factor bax was increased(p<0.05).Conclusion:1.Down-regulating the expression of hsp27 in rat skin can seriously damage the normal structure of skin tissue and collagen fibers and enhance the oxidative stress.2.The level of hsp27 is closely related to cell senescence.Down-regulation of hsp27 in skin tissue may aggravate UVB-induced skin photoaging,mainly characterized by the significantly increased positive rate of SA-?-gal and the increased expression of p16,p53 and other cell senescence related proteins.3.Down-regulation of hsp27 can increase the apoptosis rate after UVB irradiation and regulate the proportion of bcl-2 and bax in tissues,thus making apoptosis more severe.