Department of Chemical Engineering, National Tsing Hua University, Hsinchu 300, Taiwan.
Biomaterials. 2012 Sep;33(27):6559-69. doi: 10.1016/j.biomaterials.2012.05.064. Epub 2012 Jun 15.
Graphene oxide (GO) nanosheets have sparked growing interests in biological and medical applications. This study examined how macrophage, the primary immune cell type engaging microbes, responded to GO treatment. We uncovered that incubation of macrophage cell RAW264.7 with GO elicited autophagy in a concentration-dependent manner, as evidenced by the appearance of autophagic vacuoles and activation of autophagic marker proteins. Such GO-induced autophagy was observed in various cell lines and in macrophage treated with GO of different sizes. Strikingly, GO treatment of macrophage provoked the toll-like receptor (TLR) signaling cascades and triggered ensuing cytokine responses. Molecular analysis identified that TLR4 and TLR9 and their downstream signaling mediators MyD88, TRAF6 and NF-κB played pivotal roles in the GO-induced inflammatory responses. By silencing individual genes in the signaling pathway, we further unveiled that the GO-induced autophagy was modulated by TLR4, TLR9 and was dependent on downstream adaptor proteins MyD88, TRIF and TRAF6. Altogether, we demonstrated that GO treatment of cells simultaneously triggers autophagy and TLR4/TLR9-regulated inflammatory responses, and the autophagy was at least partly regulated by the TLRs pathway. This study thus suggests a mechanism by which cells respond to nanomaterials and underscores the importance of future safety evaluation of nanomaterials.
氧化石墨烯（GO）纳米片在生物和医学应用中引起了越来越多的关注。本研究探讨了主要与微生物相互作用的免疫细胞类型——巨噬细胞对 GO 处理的反应。我们发现，巨噬细胞 RAW264.7 与 GO 孵育会以浓度依赖的方式引发自噬，这表现在自噬小体的出现和自噬标记蛋白的激活。这种 GO 诱导的自噬在各种细胞系和用不同大小的 GO 处理的巨噬细胞中都观察到。引人注目的是，GO 处理巨噬细胞会引发 Toll 样受体（TLR）信号级联反应，并引发随后的细胞因子反应。分子分析确定 TLR4 和 TLR9 及其下游信号转导介质 MyD88、TRAF6 和 NF-κB 在 GO 诱导的炎症反应中发挥关键作用。通过沉默信号通路中的单个基因，我们进一步揭示 TLR4、TLR9 调节 GO 诱导的自噬，并且该自噬依赖于下游衔接蛋白 MyD88、TRIF 和 TRAF6。总之，我们证明了细胞同时对 GO 处理触发自噬和 TLR4/TLR9 调节的炎症反应，并且自噬至少部分受到 TLR 途径的调节。因此，本研究提出了细胞对纳米材料的反应机制，并强调了对纳米材料进行未来安全性评估的重要性。
