蕈菇類免疫調節蛋白LZ-8對調節性樹突細胞與腸道表皮細胞的影響

Abstract

LZ-8 (Ling-Zhi 8)是屬於蕈菇類免疫調節蛋白(Fungal immunomodulatory protein, FIP)的一種，由日本學者Kino博士從靈芝 (Ganoderma lucidium) 菌絲體 (mycelia) 分離純化出來的小分子蛋白，分子量大約為12.4kD，其構造與人類免疫球蛋白重鏈區之可變區域的胺基酸序列及二級結構有高度的相似性。根據目前研究報告顯示，LZ-8具備有抗過敏、抗發炎、降低移植排斥等效果；同時，LZ-8也被發現有刺激免疫細胞引發免疫反應之能力，例如提升清除及抑制腫瘤細胞蔓延的效果等，故能定義LZ-8為免疫調節蛋白。由先前餵食小鼠LZ-8的初步實驗結果發現，小鼠體內的CD25+ FOXP3+調節性T細胞比例在脾臟以及腸隙膜淋巴結有顯著的增加，而這其中的機制仍是未知的；由前人文獻指出，腸道中FOXP3+ 調節性T細胞的產生，與A酸(Retinoic acid)增強CD11c+ CD103+ 調節性樹突細胞抗原呈現功能有關，由我們添加LZ-8於體外培養的調節性樹突細胞實驗結果得到，LZ-8能顯著提升此細胞的乙醛脫氫酶 (Aldehyde dehydrogenase1 family1, member 2, ALDH1A2) 訊息核醣核酸 (messenger ribonucleic acid, mRNA)的表現，將LZ-8培養後的調節性樹突細胞與T細胞共培養後能使FOP3+ 調節性T細胞生成比例提升，在小鼠腸炎模式的實驗中，在引發腸炎之前和引發腸炎過程中持續餵食小鼠LZ-8能夠顯著減緩小鼠腸炎的症狀。綜合以上體內與體外的初步結果，顯示口服LZ-8或許能在腸胃道具有抑制發炎的功能。另外在初步添加LZ-8於小鼠腸道表皮細胞株的實驗中，LZ-8有促使它生長的情形，這可能代表LZ-8可以透過調控腸胃道表皮細胞以讓腸胃道維持恆定(homeostasis)。故探討LZ-8腸胃道之中的機制對於治療人類發炎性腸道疾病 (Inflammatory bowel disease, IBD) 方面或許有開發潛力存在。

LZ-8, a bioactive protein isolated from Ganoderma lucidium, it has been reported that has several immunomodulatory function on immune cells. In our preliminary data showed that orally administering LZ-8 to mice would enhance the increase of CD25+ FOPX3+ regulatory T cell population both in the MLN and spleen. But the mechanism underlying this outcome was remained unknown. In addition, our in vitro data showed that treating LZ-8 to bone marrow-derived regulatory dendritic cells would upregulate the mRNA expression of aldehyde dehydrogenase family 1, subfamily 2 (ALDH1A2), a rate-limiting enzyme that helps dendritic cells synthesis more retinoic acid to exert regulatory function. In the experiment of co-culturing LZ-8-treated regDCs with CD4+ T cells showed higher ratio of FOXP3+ regulatory T cell production. Furthermore, in mice IBD model, LZ-8- fed mice had reduction of criteria for IBD evaluation including weight loss and inflammatory cytokine production. Taken together, these data demonstrated that LZ-8 might activate regulatory dendritic cells residing in intestine (CD103+ DCs), and then promote downstream CD25+ FOXP3+ regulatory T cells development. Furthermore, another source of RA was intestinal epithelial cells (IECs) which express ALDH1A1 and ALDH1A3 to produce RA. In our recent experiment found that adding LZ-8 to mouse IEC cell line, CMT-93, would promote its growth. If LZ-8 could also upregulate the enzymatic activity of ALDH on IECs, it is another good explaination that LZ-8 could attenuate IBD. In conclusion, administration of LZ-8 might mediate the homeostasis in the intestine and have a therapeutic potential to inflammatory disease, such as inflammatory bowel disease.