Surfactin（從自然中產生之胜肽），是一種生物界面活性劑並被廣泛的運用在生物醫學上。雖然Surfactin在生物醫學領域應用上極具潛力，但Surfactin對人體生物相容性與人體內之安定性的相關資訊上仍是有限的。根據過去文獻中報導，Surfactin具有溶血的作用，另外，由於Surfactin屬於胜肽類，其體內被胜肽分解作用的安定性，必須進行充分的被研究，以印證在人體的使用。由於Surfactin類似於微粒狀的外來物，當進入人體時，主要由單核吞噬細胞系統（MPS）所吞噬。因此Surfactin與巨噬細胞的相互作用是很重要的，因為巨噬細胞是一個很重要的防禦系統，並且提供一個給藥目標的途徑，也是評估Surfactin對巨噬細胞的毒性的機會。因此，本研究目的在探討人類巨噬細胞（U-937）加入Surfactin後細胞所產生之各種變化以及Surfactin在細胞培養環境中之安定性。本研究中使用U-937人類巨噬細胞與Surfactin交互作用，並評估去氫酶的活性以做為細胞存活率之分析。我們還研究了U-937人類巨噬細胞內的各項反應－活性氧（ROS）的含量、線粒體膜電位、細胞週期分析。在試管外（in vitro）安定性方面，則利用基質輔助雷射脫附游離飛行時間質譜儀（MALDI – TOF）作分析。U-937細胞加入Surfactin後對細胞存活率會呈現劑量和時間依賴性的影響。而Surfactin對HeLa（人類卵巢癌細胞）與NIH/3T3（老鼠纖維母細胞）也有相同細胞毒性效應。經過Surfactin作用後的巨噬細胞相對於未加入Surfactin的對照組（0.5和1小時）並沒有產生H2O2的增加，但在O2-含量上卻有明顯的上升。Surfactin相對於對照組，除了在劑量為 5μM有明顯的上升外，在其他使用劑量上，會使線粒體膜電位緩慢上升。在Surfactin劑量為10μM作用時間 4小時細胞有明顯的凋亡現象產生。在體外（in vitro）安定性上，Surfactin可以在細胞環境培養中穩定達24小時之久。從我們的研究中可以更深入且有助於了解Surfactin在人體中運行狀況。 Surfactin, a kind of natural lipopeptide, is an interesting and powerful biosurfactant and is widely used in biomedical applications. Although there is an increasing potential for the application of surfactin in the biomedical field, the information on its biocompatibility and stability towards human systems still remains limited. Surfactin has been reported to exhibit hemolytic action. Also, due to its peptide character, the in vivo proteolytic stability of surfactin must be fully investigated to validate the use in human body. Similar to particulate foreign bodies, surfactin is primarily captured by the mononuclear phagocyte system (MPS) after administration into human body. The interactions between surfactin and macrophages are important because macrophages are central in the host defense system and provide opportunities for crucial evaluating cytotoxicity of surfactin. Hence, the objective of this study was to examine the changes macrophages undergo with treatment of surfactin and the stability of surfactin under the cell culture conditions. Here U-937 human macrophages cells were treated with surfactin, and the activity of dehydrogenases in those cells, an indicator of cell viability, was assessed. We also examined the intracellular responses—reactive oxygen species (ROS) content, mitochondria membrane potential, and cell cycle profiles—in U-937 human macrophages treated with surfactin. The in vitro stability of surfactin was conducted using Matrix-Assisted Laser Desorption and Ionization with Time-of-Flight (MALDI-TOF) mass spectrometry. Surfactin exhibited dose- and time-dependent toxic effects on U-937 cell proliferation. Surfactin treatment also damaged the HeLa (human cervical cancer), and NIH/3T3 (mouse fibroblast) cells. H2O2 production in surfactin-treated macrophages was unstable. However, there was a significant rise in the O2 content relative to untreated control cells over the incubation times (0.5 and 1 h). Surfactin caused a steady rise in the mitochondrial membrane potential relative to untreated control cells for every dose and culture period, except that significant increases were demonstrated at dose of 5 M. Apoptosis had developed at higher doses after 4 h of incubation time at 10 M. Surfactin was stable up to 24 h incubation. Our findings could be helpful for a better understanding of the action of surfactin in human systems.
