The Protective Effect And Mechanism Of Polysaccharide From Broussonetia Papyrifera Flower On Uv-induced Skin Photodamage

Objective:Photodamage is a special type of damage to skin tissue caused by ultraviolet radiation,which can cause epidermal cell death,dermal collagen degradation,and lead to solar dermatitis,photoaging,skin cancer and other photodermatosis.Broussonetia papyrifera flower was studied to show a protective effect on skin aging and inflammation,thus has a potential protective effect on photodamage.The aim of this study is to clarify the antioxidant activity of polysaccharides from Broussonetia papyrifera flower in vitro and explore the protective effect and mechanism on photodamage in vitro using UVA-induced mouse skin photodamage model,after optimizing the extraction conditions of the polysaccharides,and to provide scientific basis for the application of polysaccharides from Broussonetia papyrifera flower on clinical skin care of photodermatosis and development of natural antioxidants with low toxicity and high effectivity.Methods:1.Optimization of the extraction process and physicochemical properties of polysaccharide from Broussonetia papyrifera flowerIn this stud the extraction rate of polysaccharide was selected as the index to optimize the ultrasonic-assisted extraction process of polysaccharide from Broussonetia papyrifera flower by single factor test and Box-Behnken response surface method.The polysaccharide content of Broussonetia papyrifera flower was determined by phenol-sulfuric acid method.The molecular weight and monosaccharide composition of polysaccharide from Broussonetia papyrifera flower were analyzed by HPLC and HPGPC.2.Antioxidant activity of polysaccharide from Broussonetia papyrifera flower in vitroIn vitro antioxidant activity studies of polysaccharide from Broussonetia papyrifera flower was evaluated by determining DPPH radical、ABTS~+radical、hydroxyl radical、super-oxide radical scavenging rates and total reducing power ascorbic acid(Vc)as positive control.3.The protective effect and mechanism of polysaccharide from Broussonetia papyrifera flower on UV-induced mice skin photodamageTo investigate the protective effect of polysaccharide from Broussonetia papyrifera flower on skin photodamage,a total of 56 female Kunming mice were randomly divided into 7 groups:control group,model group,matrix gel group,vitamin A group,and polysaccharide low-dose,medium-dose and high-dose groups.The exposed back skin of mice was irradiated by UVA to induce skin photodamage model,drugs were applied to the skin 1 hour before irradiation.After 8 weeks of continuous irradiation,the back skin was scored,and its moisture was measured.The effects of polysaccharide from Broussonetia papyrifera flower on back skin morphology,skin thickness and changes collagen fibers were investigated by hematoxylin-eosin and Masson staining.The contents of skin hydroxyproline,SOD,GSH-Px,CAT,MDA,TNF-α,IL-1β,IL-6 were determined by enzyme-linked immunosorbent assay.The expression of MMP-1/3,proteins related to Nrf2/HO-1 and NF-κB pathway in mouse skin was determined by Western blot.Results:1.Optimization of the extraction process and physicochemical properties of polysaccharide from Broussonetia papyrifera flowerThe optimal ultrasonic-assisted extraction method of polysaccharide from Broussonetia papyrifera flower was as follows:the ratio of liquid to solid was 1:44,the ultrasonic power was 85 W,the extraction temperature was 65℃,and the extraction time was 45 min,with the extraction yield as high as 6.70%.The polysaccharide was composed of three monosaccharides,mannose,glucose and galactose,and with a molecular weight of 0.58～341.37k Da.2.Antioxidant activity of polysaccharide from Broussonetia papyrifera flower in vitroIn this study,polysaccharide from Broussonetia papyrifera flower showed a certain deoxidizing ability,the IC 50 of DPPH radical、ABTS~+radical、hydroxyl radical、super-oxide radical were 3.28 mg/m L、0.47 mg/m L、0.76 mg/m L、2.47 mg/m L,respectively,indicated that the polysaccharide from Broussonetia papyrifera flower had good antioxidant activity in vitro.3.The protective effect and mechanism of polysaccharide from Broussonetia papyrifera flower on UV-induced mice skin photodamageThe results showed that compared with the control group,the mouse back skin of mice in UVA group and UVA matrix gel group was dry,rough,and hardened,with leather-like changes,erythema ulceration and decreased skin moisture.The epidermal thickness was increased significantly,and the dermal collagen content was decreased,associated with disordered arrangement of elastic fibers.The activities of SOD,GSH-Px and CAT in skin tissue were determined decreased,the contents of proinflammatory cytokine TNF-α,IL-1βand IL-6 were increased significantly.Pretreated skin with 4%,6%and 8%of polysaccharide gel 1 hour before UVA irradiation can improve roughness and ulceration of back skin to different degrees,ameliorate skin thickening,and damage to dermal collagen.At the same time,the activities of SOD,GSH-Px and CAT in skin tissue were increased,and the content of MDA was decreased.The contents of proinflammatory cytokine TNF-α,IL-1βand IL-6 were decreased.Western blot results showed that compared with the UVA matrix gel group,the contents of MMP-1 and MMP-3 were decreased significantly,and the expression of Nrf2/HO-1protein were increased and p-p65/p65 protein were decreased significantly in the mouse back skin by pretreatment with polysaccharide gel.Conclusion:The optimized ultrasonic extraction process was applied to extract the polysaccharide from Broussonetia papyrifera flower,which had a strong antioxidant activity in vitro,and a protective effect on UVA-induced mice skin photodamage in vivo.The mechanism may be related to the activation of Nrf2/HO-1 and inhibition of NF-κB signaling pathway,leading to the regulation of antioxidative enzyme SOD and improvement of inflammatory response.The results can provide theoretical basis for exploring the utilization of Broussonetia papyrifer flower on UV induced photodermatosis.