探討靈芝蛋白對於腸道表皮細胞完整性的影響

Abstract

靈芝蛋白 (Ling-Zhi 8, LZ-8) 為一種蕈菇類免疫調節蛋白 (fungal immunomodulatory protein, FIP)，根據研究已知LZ-8對於免疫細胞有活化、調控及增生的作用，LZ-8可促使調節性T細胞的增生，而這群調節性T細胞有助於延緩葡聚糖硫酸 (dextran sulfate sodium, DSS) 後所誘發的腸炎情況。除了在免疫細胞上的研究，發現LZ-8亦對於腸細胞有一定的影響，例如：研究發現LZ-8有助於保護腸道細胞的完整性，免於化療藥物剋癌易所造成腸道細胞的破壞。因此不只是對於免疫細胞有作用，LZ-8對於腸道表皮細胞亦可能有影響。在發炎性腸道疾病 (inflammatory bowel disease, IBD) 中，眾多促炎性細胞因子 (pro-inflammatory cytokines) 會使腸道表皮細胞凋亡，造成細胞間的緊密連接蛋白 (tight junction) 破壞，進而改變腸細胞通透性及完整性。腸道細胞間通透性增加會使原本位於固有層的免疫細胞直接接觸共生菌或是抗原等，促使免疫細胞活化、分泌過多促延性細胞因子，導致發炎情形不斷。根據研究結果，我們發現LZ-8在促炎性細胞因子破壞腸道表皮細胞的情況下，LZ-8對於腸細胞緊密連接蛋白有強化作用，可增進腸細胞完整性，又腸道表皮細胞完整性對於發炎性腸道疾病具有重要的角色，我們認為LZ-8對於發炎性腸道疾病可能具有延緩發炎的效果，可能透過影響緊密接連蛋白而延緩腸道細胞損傷。結果顯示其中LZ-8對於緊密連接蛋白的機轉是透過降低肌球蛋白輕鏈激酶(myosin light chain kinase) 合成，進而降低促炎性細胞因子對腸道表皮細胞的破壞。

Ling-Zhi 8 (LZ-8), known as a fungal immunomodulatory protein (FIP), is isolated from Ganoderma lucidium. LZ-8 has ability to activate, expand and regulate immune cells. Recently, LZ-8 has been shown to induce regulatory T cell (Treg) expansion and these Treg cells alleviate intestinal inflammation in mouse colitis model. In addition, LZ-8 may inhibit the growth of some types of cancer cell. While many LZ-8 studies have been done in immune and cancer cells, the researches of LZ-8 in epithelial cells are rare. In this study, we explore the effect of LZ-8 on intestinal epithelial cells (IECs) and focus on tight junctions, which form intestinal barrier between lumen and lamina propia. According to our preliminary data, LZ-8 may increase the expression of tight junction proteins such as occludin and ZO-1 and protect IECs against pro-inflammatory cytokine-induced barrier dysfunction. The mechanism for this effect is through downregulating synthesis of myosin light chain kinase which further inhibits tight junction protein from damaging. Since the integrity of IECs is critical in the pathogenesis of IBD, we will examine the possible function of LZ-8 on IECs in a mouse IBD model.