受第六介白質抑制之巨噬細胞自噬作用在全身性紅斑狼瘡之意義

Abstract

背景：自噬作用是細胞分解自身細胞內的組成物以達到恆定的過程。自噬作用原先被視為是體內為了適應環境中營養缺乏的狀況而進行自我回收、再利用物質的機制，近年發現其在免疫以及發炎反應都佔有重要角色。細胞凋亡時，死亡細胞的清除及抗原呈現之異常，可能和自噬作用之異常有關，且可能與全身性紅斑狼瘡之致病機轉相關。細胞凋亡時，細胞核之蛋白質在分解的過程中會重新分配在細胞表面。在正常的生理狀況，這些蛋白質因巨噬細胞之迅速清除而不會引起自體免疫反應。因此巨噬細胞的功能異常，無法迅速清除自體抗原，也跟全身性紅斑狼瘡相關。第六介白質是一具有多重功能的細胞激素，可調控發炎反應，且可誘發B細胞成熟成漿細胞，在全身性紅斑狼瘡之致病機轉佔重要角色。巨噬細胞自噬作用與全身性紅斑狼瘡之致病機轉的關連現在仍不清楚。本研究探討第六介白質對於巨噬細胞自噬作用之影響。 實驗方法：THP-1細胞株衍生之巨噬細胞以及人類單核球衍生之巨噬細胞加入第六介白質或是第六介白質之受體阻抗劑培養。其自噬作用之功能由西方墨點法偵測LC3-II轉換試驗以及p62的量來衡量。 結果：由THP-1細胞株衍生之巨噬細胞上可見LC 3-II以及p62均升高，由此推論第六介白質抑制了正常的自噬作用。在使用rapamycin作為自噬作用之陽性對照組，亦呈現同樣結果。若預先加入第六介白質之受體阻抗劑，則可以抑制第六介白質對於巨噬細胞自噬作用的影響。使用人類單核球衍生之巨噬細胞進行實驗亦可以看到相似的結果。一個以關節炎以及尿中白血球增加為表現的全身性紅斑狼瘡病人其單核球衍生之巨噬細胞亦呈現自噬作用的缺陷。我們將進而探討第六介白質在全身性紅斑狼瘡對於巨噬細胞自噬作用的影響。

Background: Autophagy is a condition by which cells break down their own components to maintain homeostasis. Autophagy, initially viewed as a bulk-degradation mechanism in adaption to harsh environment, has been found to play a crucial role in immunity and inflammation. It has been proposed that defect in clearance of apoptotic cell debris and aberrant antigen presentation might be the link between autophagy and systemic lupus erythematosus (SLE). During apoptosis, nuclear proteins can be modified and redistributed on the cell surface. Under physiological conditions, these proteins are rapidly removed by macrophages and do not induce any autoimmunity. Therefore impaired macrophage function is also implicated in SLE. Interleukin-6 (IL-6) is a multifunctional cytokine, which plays a critical role in B cell hyperactivity and immunopathology of human SLE. The connection between impaired macrophage autophagy and SLE pathogenesis remains unclear. Here, we investigate the role of IL-6 in autophagy of macrophage. Methods: THP-1 cell line derived macrophages and primary human monocyte-derived macrophages were treated with IL-6 and IL-6 receptor antagonist (IL-6 RA). We detected autophagy function by LC3-II turnover assay and p62 level using Western blots. Results: Impaired autophagy of THP-1 macrophages after IL-6 treatment was demonstrated by elevated LC3-II and p62 on Western blots. Using rapamycin as positive control of autophagy, the results were consistent. After pre-treatment with IL-6 receptor antagonist, the effects of IL-6 on macrophage autophagy can be reversed. Similar results were seen on primary human monocyte-derived macrophages. Monocyte-derived macrophages of a SLE patient with arthritis and pyuria also showed impaired autophagy. The role of IL-6 in macrophage autophagy in SLE will be discussed.