| Objective Microplastics(MPs)is defined as plastic particles smaller than 5 mm,include nanoplastics(NPs)which defined as plastic particles with sizes ranging from 1 nm to 1000 nm.MPs and NPs are derived from the breakdown of waste plastics through mechanical,chemical and biological processes,as well as the direct input of MPs and NPs in various industrial and personal care products.MPs are present in extensively consumed foods,which may be due to animal intake of MPs in the environment,as well as the contamination with MPs during the production and packaging procedure.Studies have evidenced that MPs could be absorbed by the human body and enter the blood circulation and tissues.Studies on aquatic organisms have shown that the nervous system is an sensitive toxic target of MPs,but it remains unclear whether MPs can penetrate the blood-brain barrier and cause neurotoxicity in mammals.In this study,50 nm polystyrene nanoplastics(PS-NPs)was employed as the representative of MPs to observe the damage of MPs to blood-brain barrier(BBB)in mice,as well as to microglia and neuronal cells.At the same time,the potential neurotoxicity mechanism of MPs was clarified by in vitro cell experiment,so as to provide reference for the potential threat of MPs to mammals and human health.Methods In the in vivo experiment,C57 mice were orally exposed to PS-NPs for 7 days.Firstly,the changes in the permeability of blood-brain barrier were observed.The in vivo biofluorescence imaging system was employed to observe the accumulation of PS-NPs in brain tissue of mice.Secondly,histopathological staining of brain tissue slices was performed to observe microglia activation and neuronal damage.In vitro experiments were conducted to explore the potential mechanism of PS-NPs damage to BBB by immortalized human cerebral microvascular endothelial cell(hCMEC/D3).At the same time,the effects of PS-NPs on microglia and neuronal cells were observed using murine microglia BV2 cell and murine hippocampal neuron HT-22 cell as well as the adverse effects of activated microglia to neurons.Results The in vivo studies showed that PS-NPs(0.5-50 mg/kg.bw)significantly increased BBB permeability.The PS-NPs could penetrated BBB and accumulated in the brain of mice in a dose-dependent manner.In addition,PS-NPs were found to exist in microglia and induced the activation of microglia as well as neuron damage in the brain of mice.The in vitro studies showed that PS-NPs could be endocytosed by hCMEC/D3 cell and accumulated in cells,induced the decrease of cell viability,reactive oxygen species(ROS)production,nuclear factor kappa-B(NF-κB)activation,tumor necrosis factor α(TNF-α)secretion and cell programmed necrosis(necroptosis).In addition,PS-NPs readily penetrate through monolayer formed by hCMEC/D3 cells.PS-NPs exposure led to the disorder of tight junction(TJ)formed by hCMEC/D3 cells,which was manifested as the decrease of transendothelial electrical resistance(TEER)and the decrease of Occludin expression.There was no obvious corelatioship between the permeability of PS-NPs and TJ damage.Besides,PSNPs led to the activation of BV2 cells,caused large production of ROS and release of TNF-αand IL-1β.HT-22 was cultured in BV2-activated conditional medium,and it was observed that the neurotoxic substances released by activated microglia led to the morphological changes and the decrease of cell viability in HT-22 cells.Conclusion PS-NPs could increase BBB permeability in mice,enter and accumulate in brain tissue,activate microglia and induce neuronal degeneration.PS-NPs could penetrate the monolayer of cerebral microvascular endothelial cells through paracellular pathway and endocytosis pathway,leading to endothelial cell necroptosis.Besides,BV2 cells phagocytosis PS-NPs and significantly activated,released inflammatory factors,resulting in the morphological changes and cell viability decreased of HT-22 cells,suggesting that microplastics may damage neurons by activating microglia. |
PDF Full Text Request