Study On The Mechanism Of Activation Of Microglia Induced By Quantum Dots Leading To Inflammatory Response In Hippocampus

CdTe QDs(CdTe quantum dots)is considered to be the most luminous quantum dots due to its simple synthesis,high quantum yield,good monochromatism and obvious quantum confining effect.It is widely used in various fields and has a good application prospect for targeted drug delivery as well as biomedical imaging.This study mainly explored the mechanism of cadmium-based quantum dots(CdTe QDs and CdTe@ZnS QDs)inducing microglia activation to induce hippocampal inflammatory response and the mechanism of Ag2Se QDs inducing inflammatory response in mouse hippocampus.The specific research content is divided into the following four parts:1.Preparation and characterization of quantum dots(QDs).The CdTe QDs and CdTe@ZnS QDs used in this study were prepared by our research group.Firstly,the previous characterization results of these two kinds of quantum dots by ourselves were summarized.Secondly,the Ag2Se QDs were generously provided by Wuhan University.The characterizations of CdTe QDs,CdTe@ZnS QDs and Ag2Se QDs were carried out by use of TEM,Malvern size analyzer,potential particle size analyzer,fluorescence spectrophotometer,ultraviolet-visible light spectrophotometer,including the particle size,morphology,hydrated particle size,Zeta potential and maximum emission fluorescence wavelength.Finally,the toxicity of the above quantum dots to the microglia cells was evaluated on purpose of determining the exposure concentrations in the later experiment.2.The neurotoxicity and mechanism of CdTe and CdTe@ZnS QDs to model animals.Firstly,the lifespan as well as the expression of inflammation-related genes was selected to explore the inflammation response of Caenorhabditis elegans(C.elegans or nematode for short)after exposure to CdTe and CdTe@ZnS QDs,so as to indirectly reflects the effects of these two quantum dots on the function of the nervous system.Several behavioral indicators of Caenorhabditis elegans were recorded to evaluate the neurotoxic effects of CdTe and CdTe@ZnS QDs from a behavioral perspective,including forward locomotion,body bends and head thrashes.Then the inflammatory response mechanism of CdTe and CdTe@ZnS QDs on mouse hippocampus was investigated by detecting the microglia activation and IL-1?-mediated inflammation.3.The mechanism of inflammatory response in BV2 cells induced by NLRP3 inflammasome activation owing to CdTe and CdTe@ZnS QDS.The experimental results of C.elegans and mice in the first two chapters clarified the neurotoxicity of CdTe and CdTe@ZnS QDs.On this basis,the neuroglial BV2 cells were selected to further explore the possible neurotoxicity mechanism of CdTe and CdTe@ZnS QDs focusing on the microglia activation and IL-1?-mediated inflammation.4.Research on the neurotoxic effect and mechanism of Ag2Se QDs.We compared the neurotoxic effect of Ag2Se QDs with that of CdTe and CdTe@ZnS QDs in this section.The results in the first two chapters showed that CdTe and CdTe@ZnS QDs would cause neurological behavioral defects in Caenorhabditis elegans and inflammatory damage to the hippocampus of mice.And the NLRP3 inflammasome activation played a crucial role in the toxic mechanism of the induced neuroinflammation.Therefore,we hoped to evaluate whether Ag2Se QDS owned the same toxic effects.Firstly,we tested whether Ag2Se QDs had any effect on the neurological function of Caenorhabditis elegans,and then explored the potential inflammatory response of Ag2Se QDs on the hippocampus of mice.Subsequently,BV2 microglia were selected to study the pro-inflammatory mechanism of Ag2Se QDs.The main findings are as follows:1.Preparation and characterization of QDs:The characterization results of several QDs showed that all QDs exhibited uniform particle size distribution,obvious lattice structure and good stability,which could meet the experimental requirements of this research.According to the MTT experiment results,(1.25,2.5 and 5 nM)were determined as the exposure concentrations of CdTe QDs,CdTe@ZnS QDs and Ag2Se QDs.2.The neurotoxicity and mechanism of CdTe and CdTe@ZnS QDs to model animals:Firstly,CdTe and CdTe@ZnS QDs both changed the movement behavior of nematodes in an unfavorable way,especially CdTe QDs.When the exposure concentration and time were the same,CdTe QDs could damage the lifespan and behavior of nematodes more seriously than CdTe@ZnS QDs.And both QDs could cause inflammation response and nervous system damage in C.elegans,which might be related to oxidative stress from elevated ROS.Secondly,the microglial activation and IL-1?-mediated inflammatory response were observed in the mice hippocampus exposed to these two QDs.In general,the inflammatory response caused by CdTe@ZnS QDs was lighter than that of CdTe QDs,indicating that the ZnS shell had a certain protective effect.However,two kinds of QDs both activated NLRP3 inflammasome to varying degrees,suggesting that the ZnS shell cannot completely prevent the adverse effects by CdTe QDs.3.The mechanism of inflammatory response in BV2 cells induced by NLRP3 inflammasome activation owing to CdTe and CdTe@ZnS QDS:The results indicated that exposure of CdTe and CdTe@ZnS QDs could cause IL-1?-mediated inflammation and inflammatory cell death in BV2 cells.When exploring the molecular mechanism of these two QDs inducing the release of IL-1? and further causing cell inflammatory death,we found that the NLRP3 inflammasome activation was involved.Firstly,these two QDs activated the NF-?B pathway,which not only led to the priming of NLRP3 inflammasomes but also promoted the expression of pro-IL-1? in the cells.Secondly,QDs exposure led to excessive ROS production that triggered the NLRP3 inflammasomes activation,which in turn activated caspase-1 to cut pro-IL-1? into mature IL-1? that then was released outside the cell.Furthermore,when caspase-1 or NF-?B or ROS was inhibited by specific inhibitors,the increased IL-1? secretion and cell inflammatory death caused by CdTe and CdTe@ZnS QDs was effectively alleviated in BV2 cells.4.Research on the neurotoxic effect and mechanism Ag2Se QDs.The results showed that Ag2Se-PEG QDs could cause neurological deficits in Caenorhabditis elegans and activation of microglia and further led to the inflammatory response in the mice hippocampus as well as the NLRP3 inflammasome activation,resulting in the inflammatory response mediated by the pro-inflammatory cytokine IL-1?.On the one hand,Ag2Se QDs activated the NF-?B pathway,leading to the initiation of NLRP3 inflammasomes and promoting the expression of pro-IL-1? in BV2 cells.On the other hand,the excessive ROS generation(especially mtROS)induced by Ag2Se QDs triggered the NLRP3 inflammasomes activation,which led to the activation of caspase-1.And activated caspase-1 cut the pro-IL-1? from NF-?B activation into clevead-IL-1?,which was secreted outside the cell and resulting in the inflammation.This study mainly explored the mechanism of cadmium-based quantum dots(CdTe QDs and CdTe@ZnS QDs)inducing microglia activation to induce hippocampal inflammatory response,and the mechanism of Ag2Se QDs inducing inflammatory response in mouse hippocampus.Our research aims to find effective methods to alleviate or even eliminate the central inflammation caused by QDs.We believe that our research will provide a theoretical basis for the subsequent optimization of the neurobiological safety application of QDs.