Mechanism by which lycium barbarum polysaccharides inhibit keratinocyte apoptosis in burn wounds via autophagy
BACKGROUND:Lycium barbarum polysaccharide has many biological activities and has been found to have potential effects on promoting wound healing.OBJECTIVE:To investigate the mechanism of lycium barbarum polysaccharide in tumor necrosis factor-α-mediated keratinocyte apoptosis and its effect on the healing of burn wounds.METHODS:(1)In vitro experiment:Keratinocytes were divided into four groups:cells were cultured in the α-MEM medium(complete medium)containing 15%fetal bovine serum and 1%glutamine in normal group,cultured in the complete medium containing lycium barbarum polysaccharide in positive control group,cultured in the complete medium containing tumor necrosis factor-α in model group,and cultured in the complete medium containing lycium barbarum polysaccharide and tumor necrosis factor-α in experimental group.After 24 hours of culture,cell proliferation was detected using cell counting kit-8 assay;Cleaved caspase-8,TNF R1,FADD,and LC3 were detected using western blot.Then an autophagy inhibitor group(the complete medium containing 3-methyladenine)and an autophagy inhibitor+lycium barbarum polysaccharide group(the complete medium containing lycium barbarum polysaccharide,tumor necrosis factor-α,and 3-methyladenine)were set up.After 24 hours of culture,keratinocyte apoptosis was detected by flow cytometry.(2)In vivo experiment:Six Sprague-Dawley rats were randomly divided into a control group and an experimental group,with three rats in each group.Four deep Ⅱ degree burn wounds with a diameter of 2 cm were made on the back of each rat.At 24 hours after modeling,mice in the control and experimental groups were coated with normal saline and lycium barbarum polysaccharide solution,respectively,once a day.Wound healing was observed regularly after treatment.Samples were taken 28 days after treatment and the pathologic pattern of the wound was observed.RESULTS AND CONCLUSION:(1)In vitro experiment:Addition of lycium barbarum polysaccharide alone did not affect cell proliferation and apoptosis and the expression of apoptotic and autophagic proteins in keratinocytes.After the addition of tumor necrosis factor α,the proliferation of keratinocytes was inhibited,the apoptotic rate increased,and the expression of apoptotic and autophagic proteins was elevated,while lycium barbarum polysaccharide could antagonize the above effects of tumor necrosis factor-α.Lycium barbarum polysaccharide combined with autophagy inhibitors further reduced the apoptotic rate of keratinocytes.(2)In vivo experiment:The wound healing rate of rats in the experimental group was higher than that of the control group at 12,16,20,24,and 28 days after treatment(P＜0.05,P＜0.01).Hematoxylin-eosin staining results at 28 days after treatment showed an intact and well-defined epidermis of the wound in the experimental group compared with the control group.To conclude,lycium barbarum polysaccharide protects the integrity of skin epidermal tissue and promotes wound healing by inhibiting autophagy and apoptosis of keratinocytes.
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