Drp1-Dependent Mitochondrial Fission Mediates Toxicity of Positively Charged Graphene in Microglia

Abstract

The unique physicochemical properties of graphene and its derivatives enable their application in the diagnostics and therapy of central nervous system (CNS) diseases.However, the potential impacts of surface properties of functionalized graphene on microglia remain poorly understood. Herein, we used graphene oxides (GO), polyethylene glycol (PEG)-and polyethylenimine (PEI)-functionalized GO, which possess different surface charges, to investigate their effects on microglia by focusing on mitochondrial dynamics. The positively charged GO-PEI was found to promote mitochondrial fission as observed in BV-2 cells with mitochondria labeled by DsRed2-mito, indicating that alterations in mitochondrial dynamics depend on the surface properties of graphene. Concurrent to mitochondrial fragmentation, treatment with positively charged GO-PEI induced an increase in mitochondrial recruitment of dynamin-related protein (Drp1). Additionally, GO-PEI treatment also led to apoptotic and autophagic cell death. However, Drp1 silencing by small interfering RNA (siRNA) could effectively attenuate GO-PEI-induced apoptotic and autophagic cell death, indicating that mitochondrial fragmentation occurs upstream of GO-PEI-mediated toxicity in microglia. Overall, our study indicated that positively charged GO-PEI might cause deleterious influence on the central immune homeostasis by Drp1-dependent mitochondrial fragmentation, and provide the strategies for the rational design of graphene-based materials in neuroscience.

Gold nanoparticles enhance TRAIL sensitivity through Drp1-mediated apoptotic and autophagic mitochondrial fission in NSCLC cells

“…36 Briefly, cells were seeded in a 96-well plate at a density of 5.0×10 4 cells/well for 24 h and then treated with TRAIL with or without AuNPs for 24 h. For the combination treatment, the cells were pretreated with 50 µg/mL AuNPs for 6 h, followed by incubation with 20 ng/mL TRAIL for an additional 24 h. After incubation with 0.5 mg/mL MTT (Sigma) for 4 h, the MTT-formazan crystals were subsequently dissolved in dimethyl sulfoxide. Absorbance at 570 nm was measured with a Model 680 microplate reader (Bio-Rad, Hercules, CA, USA).…”

“…Likewise, we obtained similar results in cells by inhibiting mitochondrial fission using Mdivi-1 ( Figure 6E), which supported the notion that mitochondrial fragmentation constitutes a critical upstream event that mediates mitochondrial dysfunction such as Δψm loss, ATP depletion, and mitochondrial ROS generation, as observed previously. 36 …”

Multivalent Interactions between 2D Nanomaterials and Biointerfaces

“…Positively charged NPs exhibit higher uptake efficacy than their negatively charged or neutral counterparts, which could be attributed to their stronger affinity to the negatively charged cell membrane. The study about the role of surface charge in biological interactions of graphene derivatives was taken by Ma and co‐workers and Ren and co‐workers . They fabricated GO modified with different surface moieties including polyethylene glycol (PEG), bovine serum albumin (BSA), and polyethylenimine (PEI) to obtain graphene sheets with different functionalities and charges.…”

“…They fabricated GO modified with different surface moieties including polyethylene glycol (PEG), bovine serum albumin (BSA), and polyethylenimine (PEI) to obtain graphene sheets with different functionalities and charges. Compared with pristine GO, PEG, and BSA coverage reduced endocytosis while positively charged GO‐PEI facilitated their cellular internalization …”

“…Several studies have revealed that graphene derivatives localize not only in endosomes or lysosomes but also mitochondria . Interestingly, some other reports showed graphene sheets with positively charged PEI coatings could target and accumulate in mitochondria, which is attributed to electrostatic interactions with the negatively charged mitochondrial membrane ( Figure ) . Graphene modified with pyropheophorbide‐a (PPa) and integrin αvβ3 monoclonal antibody (mAb) can also escape from endosomes and then translocate to the mitochondria …”