以小鼠搔癢動物模式探討綠豆皮水萃取物之皮膚保護性與免疫調節效果

Abstract

皮膚是一種獨特的器官，可保護生物體免受外部損傷，而屏障功能受損與許多不適症狀有關，包括乾燥、泛紅、脫屑、瘙癢和發炎，此時又稱為皮膚炎 (濕疹)，這些症狀往往十分擾人、影響生活品質，是個值得重視的議題。噁唑酮 (oxazolone) 是一種常用於動物模式上誘導皮膚炎化合物，會誘發紅腫、瘙癢、表皮增生和發炎細胞浸潤等症狀，且近年隨著腸道菌研究的興起，也將目光轉移至皮膚炎與腸道的關係，其中腸道菌相也參與著許多皮膚發炎性疾病的生理狀態，然而固醇類藥物如：地塞松 (dexamethasone) 雖能有效緩解症狀與減緩發炎，但易有副作用且實質難以根治，自古至今已有各種食物和草藥被發現具有抗發炎和皮膚保護作用之潛力，因此透過食療的角度或許是一個緩解皮膚炎的可行方法。綠豆 (Vigna radiata) 是一種應用性廣泛的傳統食材，具有許多生理活性及保健功效，基於 LC-MS 的初步結果發現，綠豆皮水萃取物 (mung bean skin water extract, MSE) 主要活性成分為牡荊素 (vitexin) 和異牡荊素 (isovitexin)；根據先前研究指出含有vitexin萃取物於細胞模式中能促進皮膚傷口修復，並且vitexin與isovitexin於動物模型中均表現出抗發炎和抗過敏作用，然而尚未有 MSE 對於皮膚炎和免疫調節以及腸道菌之關聯的研究，因此本研究旨在探討 MSE 於oxazolone誘導的小鼠搔癢模式中其皮膚保護和免疫調節活性，並分析腸道菌相與其作用之連結。實驗結果顯示，MSE 具有減緩皮膚脫皮、結痂、泛紅之現象，並可以通過減少表皮層與真皮層厚度和肥大細胞浸潤來減緩表皮增生、降低皮膚炎分數以及降低抓癢次數， MSE 的作用方向可能主要抑制血漿中與瘙癢相關和促發炎細胞激素含量，包括 IL-4、IL-5、IL-13、IL-25、IL-31 和 TNF-⍺，並有提升皮膚屏障蛋白表現的趨勢，MSE亦能影響腸道菌相組成，增加Lactobacillus等益菌相對豐富度、降低UCG-003潛在有害菌之相對豐富度，並且也指出Lactobacillus與皮膚炎表徵嚴重度呈負相關、UCG-003則呈正相關。總言之，MSE對皮膚瘙癢與發炎具有潛在的保護作用，或許能作為預防皮膚炎的飲食療法之一。

The human skin is the largest organ that provides defensive functions against harmful chemicals and pathogens. Impaired skin barrier function has been associated with undesirable symptoms, including dryness, redness, flaking, itching, and inflaming, also called eczema. Oxazolone has been developed to induce dermatitis in mice models with pruritic, epidermal hyperplasia, and inflammatory cell infiltration. Studies linked inflammatory skin diseases to an imbalanced gut microbiome; hence, the modulation of the gut microbiota to improve skin condition seems feasible. Steroids such as dexamethasone can effectively relieve symptoms and reduce inflammation. Still, they are prone to side effects and difficult to cure. There is a growing interest in natural products as alternatives to synthetic drugs. Mung bean (Vigna radiata) is a typical food and Chinese medicine with numerous beneficial effects. Our preliminary results based on LC-MS found that the mung bean skin water extract (MSE) contained vitexin and isovitexin as major compounds. According to previous studies, it is pointed out that the extracts containing vitexin can promote skin wound repair in vitro—both exhibit anti-inflammation as well as anti-allergic function in vivo models. However, there is no research on the association of MSE with dermatitis, immune modulation, and gut microbiota. Therefore, this study aimed to investigate the skin protection, immune and gut microbiota modulation of MSE in an oxazolone-induced pruritus mice model and to analyze the relationship between dermatitis and gut microbiota. The results showed that MSE alleviated peeling, scabbing, and redness of the skin. Besides, MSE could reduce scratching behavior and dermatitis score by reducing epidermis, dermis thickness, and mast cell infiltration. The mechanism of action of MSE might primarily suppress plasma itch-related and pro-inflammatory cytokine levels, including IL-4, IL-13, IL-25, IL-31, and TNF-ɑ, with a trend toward increasing the gene expression of skin barrier proteins. MSE can also affect gut microbiota composition, elevating the relative abundance of beneficial bacteria such as Lactobacillus and reducing the relative abundance of harmful bacteria UCG-003. It also pointed out that Lactobacillus was negatively correlated with the severity of appearance characterization, and UCG-003 was positively associated with severe appearance. In conclusion, MSE exhibited potential skin protection against pruritus and could be used as a dietary therapy for dermatitis prevention.