甲型烯醇化酶於發炎反應中調節巨噬細胞與嗜中性球活化之角色

Abstract

甲型烯醇化酶為多功能的蛋白，其功能不同取決於在細胞中之位置。單核球及巨噬細胞發現，發炎過程中甲型烯醇化酶易位至細胞表面並當做纖溶酶原受體，促進細胞外基質降解和細胞遷移。甲型烯醇化酶也會在發炎過程釋放到細胞外，透過類鐸受體4刺激巨噬細胞活化。在這項研究中我們探討嗜中性球於發炎過程其甲型烯醇化酶是否會易位至細胞表面外，也探討甲型烯醇化酶於發炎反應中對於巨噬細胞活化扮演之角色。以脂多醣體內刺激小鼠嗜中性球顯示甲型烯醇化酶於細胞表面表現上升，並增強離體纖溶酶原活化，這個結果被抗甲型烯醇化酶單株克隆抗體阻斷。當小鼠肺泡巨噬細胞MH-S細胞和人類PMA-THP-1巨噬細胞被脂多醣刺激時，也觀察到同樣的現象。此外，抗甲型烯醇化酶單株克隆還可以分別抑制脂多醣和重組甲型烯醇化酶刺激巨噬細胞之活化。此外，脂多醣刺激巨噬細胞活化被傳明酸所阻斷，傳明酸與纖溶酶原結合併阻止其活化。這些數據表明，在脂多醣刺激巨噬細胞後，甲型烯醇化酶介導之纖溶酶活化可以增強發炎反應。總之，結果顯示嗜中性球與巨噬細胞受到脂多醣刺激，其表面甲型烯醇化酶表現增加，促使這些白血球的遷移與活化。因此，通過抗甲型烯醇化酶單株克隆抗體來阻斷這些現象可能被用於治療敗血症等發炎相關之疾病。

The glycolytic enzyme alpha-enolase (enolase-1, ENO1) is a multifunctional protein with various activities depending on its cellular and extracellular localization. In monocytes/macrophages, ENO1 has been shown to translocate to the cell surface and serve as a plasminogen receptor (PLGR), which facilitates extracellular matrix degradation and cell migration during inflammation. ENO1 can also be released to the extracellular space to stimulate macrophages activation via TLR4 during inflammation. In this study, we investigated whether cell surface translocation of ENO1 also occurs in neutrophils, and we also examined whether ENO1 may modulate the activation of macrophages during inflammation. Neutrophils isolated from LPS-challenged mice showed elevated surface expression of ENO1 and enhanced PLG activation ex vivo, which was effectively blocked by anti-ENO1 mAbs. The same phenomenon was also observed when the murine alveolar macrophage MH-S cells and human PMA-THP-1 macrophages cells were stimulated by LPS. In addition, anti-ENO1 mAbs could also inhibit the activation of macrophages stimulated by LPS and recombinant ENO1, respectively. Furthermore, LPS-triggered macrophage activation was blocked by tranexamic acid (TXA), which binds PLG and prevents its activation. These data indicated that upon LPS stimulation of macrophages, ENO1-mediated activation of plasmin could enhance the inflammatory response. Overall, our results indicate that during LPS-stimulated inflammation, upregulated ENO1 expression on the cell surface of neutrophils and macrophages may facilitate the migration and activation of these leukocytes, hence, blocking these events by inhibited by anti-ENO1 mAbs can potentially be used to suppress inflammation in diseases such as sepsis.