Effect Of Graphene Oxide(GO) On Lipid In Key Cells Of Atherosclerosis

Graphene oxide(GO)has been widely used in biotechnology and nanomedicine due to its excellent biocompatibility,solubility and high drug loading capacity.Due to the application of GO in biomedicine,it has become one of the nano materials that contact human artery.At present,the toxic effect of GO on the key cells of arterial wall and the mechanism of atherosclerosis process have not been fully confirmed.Therefore,to evaluate the unique physical and chemical properties of GO and the mechanism of adverse health effects in the vascular circulation system is to ensure the safety of GO in biomedicine.The research contents of this paper were concluded as follows:1.The interactions between THP-1macrophages and GO of different sizes(GO of size 500–5000 nm,denoted as GO-L;GO of size < 500 nm,denoted as GO-S).,TEM results showed that the internalization of GO appeared to be minimal after 24 h exposure.Whereas up to 50 ?g/m L of GO-L but not GO-S reduced lipid accumulation,accompanying with a significantly reduced release of soluble monocyte chemoattractant protein-1(MCP-1)but not interleukin-6(IL-6).Moreover,lipidomic data showed that GO-L decreased the levels of 17 lipid classes,whereas GO-S only decreased the levels of 5 lipid classes.For comparison,50 ?g/m L carbon black(CB)significantly increased lipid accumulation with considerable particle internalization.GO-reduced lipid accumulation was not related with increase of reactive oxygen species(ROS)or induction of autophagy,and modulation of autophagy by chemicals showed no significant effect to alter the effects of GO-L on lipid accumulation.However,exposure to GO reduced the m RNAand protein levels of key components in peroxisome proliferators-activated receptor(PPAR)signaling pathway,a pathway that is related with lipid droplet biogenesis,and the modulation of PPAR? by chemicals altered the effects of GO-L on lipid accumulation.In conclusion,our results suggested that GO size-dependently altered lipid profiles in THP-1 macrophages that might be related with PPAR signaling pathway.2.Human umbilical vein endothelial cells(HUVECs)were exposed to GO with large size(denoted as GO-L)or small size(denoted as GO-S),and transcriptomics were used to understand the mechanisms of cytotoxicity of GO at systemic levels.It was shown that GO-L more significantly induced cytotoxicity compared with GO-S.Transcriptomic analysis revealed that compared with GO-S,GO-L had larger impact on gene ontology terms related with mitochondrial function as well as Kyoto Encyclopedia of Genes and Genomes(KEGG)pathways related with cell death and growth.But GO-S showed greater influence on KEGG pathways related with lipid metabolism.Both types of GO showed minimal impact on oxidative stress but increased de novo lipogenesis protein fatty acid synthase(FASN).However,only GO-S significantly promoted acyl-Co A synthetase 3(ACSL3),a key enzyme responsible for esterification of free fatty acids and lipid droplet biogenesis.Not surprisingly,GO-L but not GO-S impaired lipid droplet biogenesis,and increasing lipid levels by oleic acid or ?-linolenic acid reduced the cytotoxicity of GO-L to HUVECs.Combined,the results from this study suggested that impaired lipid droplet biogenesis was involved in GO-induced cytotoxicity in HUVECs,and inducing lipid droplet biogenesis could prevent the cytotoxicity of GO.3.The interaction between graphene oxide and vascular smooth muscle cells(VSMCs)led to the cytotoxicity and morphological changes of cells,such as membrane damage.Transcriptomics data suggested that graphene oxide decreased anti-viral signaling due to the decrease of Toll-like receptor 3(TLR3).This study further verified that graphene oxide decreased interferon induced protein with tetratricopeptide repeats 1(IFIT1)and radical S-adenosyl methionine domain containing 2(RSDA2),TLR3-downstream genes involved in anti-viral responses.As RSAD2 proteins are also involved in lipid dysfunction,this study further analyzed the influence of graphene oxide on lipid metabolism genes,and verified the increase of adipose triglyceride lipase(ATGL),although the increase of diacylglycerol O-acyltransferase 1(DGAT1)was only modest.Adding TLR3 agonist polyinosinic:polycytidylic acid(Poly IC)partially increased TLR3-downstream protein interleukin-8(IL-8)and some lipid classes,particularly lysophosphatidylcholine(LPC)and lysophosphatidylethano-lamine(LPE),in graphene oxide-exposed cells,indicating a relationship between TLR3-mediated immune response and lipid metabolism.In mice receiving repeated intravenous injection of graphene oxide,significantly decreased TLR3,IFIT1 and RSAD2 but increased ATGL proteins were observed in aortas.It is concluded that graphene oxide could alter anti-viral signaling pathways and lipid metabolism via decreasing TLR3 in VSMCs.