Effect And Mechanism Of Centella Asiatica On HaCaT Cells And Imiquimod Induced Psoriasis Mice

Psoriasis is a skin disease affected by many factors,such as heredity,diet and environment.Its main pathological features are excessive proliferation of keratinocytes and infiltration of inflammatory cells.Psoriasis patients with severe skin itching,affect sleep,severe chills,high fever and other symptoms,accompanied by a series of psychological problems,quality of life decline.Traditional drugs have poor efficacy and many side effects,so it is urgent to develop more ideal anti-psoriasis drugs.Modern pharmacological studies have shown that Centella asiatica（L.）urban has anti-oxidation,anti-fibrosis,promoting wound healing,analgesia and anti-tumor effects,and its application field has gradually expanded to the treatment of skin diseases.In this study,the effects of different components of Centella asiatica on oxidative stress,inflammation level and skin barrier function of HaCaT cell induced by lipopolysaccharide（LPS）were systematically evaluated.Combined with imiquimod induced psoriasis mice model,the best active component of Centella asiatica in relieving psoriasis was identified,and its possible mechanism of action was explored.The results of this study can provide experimental support for the application of Centella asiatica in functional food and skin care products,and have certain theoretical significance and application value.The main contents and conclusions are as follows:（1）Antioxidant activity of different components of Centella asiatica.Different components of Centella asiatica were extracted and the contents of total flavonoids and total polyphenols were determined.It was found that the ethyl acetate component of Centella asiatica had the highest content of total flavonoids and total polyphenols,followed by n-butanol component.DPPH（1,1-Diphenyl-2-picrylhydrazyl radicals）,ABTS（2,2′-Azino-bis-3-ethylbenzo-thiazoline-6-sulfonic acid diammonium salt）and FRAP（Ferric ion reducing antioxidant power）experiments showed that the anti-oxidant capacity of n-butanol and ethyl acetate was significantly better than that of other components.The results showed that the contents of total flavonoids and total polyphenols in different components were closely related to their anti-oxidant capacity in vitro.（2）Effects of different components of Centella asiatica on inflammation and barrier function of HaCaT cell.HaCaT cells were induced by 20μg·m L^-1 LPS to establish an inflammatory injury model,and the effects of different components of Centella asiatica on intracellular GSH（Glutathione）,SOD（Superoxide dismutase）and ROS（Reactive oxygen species）contents were investigated.The results showed that the five components of Centella asiatica could effectively increase the content of GSH and SOD and reduce the level of intracellular ROS,and the ethyl acetate component was the best.In addition,ELISA result showed that different components of Centella asiatica significantly inhibited the secretion of IL-6（Interleukin 6）and MMP1（Matrix metalloproteinase 1）.The five components of Centella asiatica components can effectively down regulate inflammatory factors IFN-γ（Interferon-γ）,CCL20（CC chemokine ligand-20）,IL-6 and TNF-α（Tumor necrosis factor-α）,reduce collagenase degradation related factors（MMP1 and MMP3）and improve the gene expression level of barrier protective factors AQP3（Aquaporin 3）and FLG（Filaggrin）,and the ethyl acetate and n-hexane components have the best effect.Flow cytometry was used to detect the effects of ethyl acetate and n-hexane on apoptosis and cell cycle of Centella asiatica.Western blot analysis showed that the ethyl acetate fraction and n-hexane fraction of Centella asiatica could exert anti-inflammatory effect by inhibiting the expression of NF-κB（Nuclear factor kappa-B）and JAK1-STAT3（Janus kinase 1-signal transducer and activator 3）related pathway proteins,and the ethyl acetate fraction had the best regulatory effect in a dose-dependent manner.（3）To investigate the intervention effect of Centella asiatica ethyl acetate on psoriasis mice.The psoriasis mice model was established by 5%imiquimod cream,and the regulation of ethyl acetate in Centella asiatica was evaluated at animal level.The results showed that the erythema and wrinkles of skin in the ethyl acetate group were reduced,and part of the skin was smooth and elastic.At the same time,ethyl acetate can inhibit the secretion of inflammatory factors in serum and skin lesions.These results indicate that ethyl acetate has therapeutic effect on psoriasis.