The Vascular Health Effects And Mechanism Of Multi-Walled Carbon Nanotubes (MWCNTs):Role Of Length And Functionalization Of MWCNTs

Multi-walled carbon nanotubes(MWCNTs)have excellent physicochemical properties and have been widely used in biotechnology,biomedicine and other fields.The application of MWCNTs in biomedicine has increased the chance of contact with human blood vessels.The mechanism of toxic effects of MWCNTs on vascular endothelial cells and the development of cardiovascular disease is still unclear.To ensure the safe use of MWCNTs,it is necessary to evaluate the physicochemical properties of MWCNTs and their effects on the adverse effects of vascular system in vivo and its mechanism of action.The main contents were summarized as below:1.The physicochemical properties of two different lengths of MWCNTs(XFM19 and XFM22)were characterized by BET(Brunauer-Emmett-Teller)specific surface area,transmission electron microscopy(TEM),dynamic light scattering(DLS)and Raman spectroscopy.Human umbilical vein endothelial cells(HUVECs)were used as models in vitro.Toxicity and mechanism of MWCNTs on HUVECs were determined by measuring a series of biological indicators of cytotoxicity,oxidative stress,inflammatory response,endoplasmic reticulum(ER)stress and expression of their biomarkers.TEM observations indicate that MWCNTs can be internalized into HUVECs and localized in the nucleus and mitochondria.The longer MWCNTs(XFM19)are more cytotoxic to HUVECs.Both MWCNTs significantly increased intracellular reactive oxygen species(ROS)levels and adhesion of THP-1 monocytes to HUVECs,accompanied by increased release of interleukin-6(IL-6),The biomarker of ER stress,DDIT3 expression,but not XBP-1s expression or BiP protein level,was significantly induced by the exposure of longer MWCNTs(XFM19).The experimental results indicate that the length dependence of MWCNTs on the toxic effects of HUVECs may be related to the activation of oxidative stress and ER stress.2.The changes in diameter,morphology,hydrated particle size and Zeta potential caused by the adsorption of MWCNTs(XFM19 and XFM21)by serum proteins were determined by atomic force microscope(AFM)and DLS,respectively.The cell model is HUVECs.we investigated the influence of pre-incubation with bovine serum albumin(BSA)on internalization,cytotoxicity,oxidative stress and inflammation induced by pristine/carboxylated MWCNTs to HUVECs.AFM indicated the adsorption of proteins onto the surface of MWCNTs,which consequently increased the diameter.TEM indicated the internalization of both types of MWCNTs into HUVECs,whereas preincubation with BSA appeared to enhance the internalization.MWCNT exposure induced cytotoxicity and oxidative stress as well as moderate inflammatory responses.MWCNTs-BSA is less cytotoxic to HUVECs,and the release of IL-6 and TNF? induced by MWCNTs-BSA and THP-1 adhesion to HUVECs are enhanced.The above results indicate that it is necessary to consider the interaction between MWCNTs and serum proteins when assessing the biological effects of MWCNTs in circulation.3.The morphological structure,hydrated particle size and zeta potential of pristine MWCNTs(p-MWCNTs),hydroxylated MWCNTs(h-MWCNTs)and carboxylated MWCNTs(c-MWCNTs)were characterized by TEM and DLS.THP-1 macrophages and co-culture model consisting of human bronchial epithelial cells(16HBE)and THP-1 macrophages were used as cell models.Biological indicators such as cytotoxicity,oxidative stress,inflammatory response,lipid accumulation,ER stress markers,and apoptosis-related genes were analyzed.The results showed that the three MWCNTs could be internalized into vesicles with a monolayer membrane,and associated with a modest increase of cytotoxicity,and could induce oxidative stress.All types of MWCNTs significantly induced lipid accumulation in THP-1 macrophages and more modestly in the co-culture model consisting of 16 HBE and THP-1 macrophages.MWCNT-induced lipid accumulation in THP-1 macrophages was decreased modestly by antioxidant(N-Acetyl-L-cysteine,NAC)and more effectively by ER stress inhibitor(4-phenylbutyric acid,4-PBA).Moreover,MWCNTs exposure promoted the mRNA level of ER stress marker DDIT3,protein level of p-chop and the expression of scavenger receptor(CD36,MSR1).In conclusion,this study suggested that MWCNTs exposure could promote lipid accumulation in THP-1 macrophages,which could be related with the modulation of ER stress leading to up-regulation of scavenger receptors.