Simultaneous induction of autophagy and toll-like receptor signaling pathways by graphene oxide.
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.
Department of Chemical Engineering, National Tsing Hua University, Hsinchu 300, Taiwan.
Guan-Yu
GY
Chen
Hong-Jie
HJ
Yang
Chia-Hsin
CH
Lu
Yu-Chan
YC
Chao
Shiaw-Min
SM
Hwang
Chiu-Ling
CL
Chen
Kai-Wei
KW
Lo
Li-Yu
LY
Sung
Wen-Yi
WY
Luo
Hsing-Yu
HY
Tuan
Yu-Chen
YC
Hu
D000818:Animals; D001343:Autophagy / Q000187:drug effects*; D002460:Cell Line; D016207:Cytokines / Q000378:metabolism; D020868:Gene Silencing / Q000187:drug effects; D006108:Graphite / Q000494:pharmacology*; D008264:Macrophages / Q000166:cytology / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure; D051379:Mice; D008954:Models, Biological; D053758:Nanoparticles / Q000737:chemistry; D015398:Signal Transduction / Q000187:drug effects*; D051193:Toll-Like Receptors / Q000378:metabolism*; D014617:Vacuoles / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure
D016207:Cytokines; D051193:Toll-Like Receptors; D006108:Graphite