Cdte QDs-induced Hepatocyte Mitochondrial Dysfunction And Its Mechanism

Quantum dots（QDs）,as a kind of nanomaterials with potential applications,have wide application prospects in the fields of display,image sensing and biomedicine due to their fluorescent properties.Therefore,it is important to fully understand and evaluate their toxic effects and potential hazards.The liver is the main accumulation organ for QDs entering the body,but the potential adverse effects of QDs to the liver and the related mechanisms are still unclear.The liver,as the organ with strongest metabolic capacity in human body,is rich in mitochondria and many liver diseases are related to mitochondrial dysfunction.Currently,there are few studies on the role of mitochondrial dysfunction in QDs-induced hepatotoxicity,and the mechanisms of mitochondrial damage caused by QDs is not clear and need further research.Based on this,the liver toxic effects of the Cd Te QDs were first investigated in vivo in this study.Then,two hepatocytes were used as cell models to study the hepatotoxicity and mitochondrial dysfunction caused by Cd Te QDs,and the role of mitochondrial fission/fusion and mitophagy in Cd Te QDs-induced mitochondrial damage were preliminary explored.The main content and findings of the work described as follows:1.In this study,Cd Te QDs were synthesized by aqueous phase in the electrochemical workstation,and the QDs were characterized by fluorescence spectrophotometer,transmission electron microscope and Malvern laser particle size analyzer.The results found that Cd Te QDs showed similar size and uniform distribution under the electron microscope,and the average particle size was 2.62±0.37nm.The hydrated particle size of Cd Te QDs in normal saline and complete medium were 30.10±8.91 nm and 31.93±3.92,respectively.The Zeta potentials were-8.63±1.06 m V and-16.62±0.49 m V,respectively.2.ICR mice were exposed to Cd Te QDs via tail vein injection,the effects of Cd Te QDs on the body weight and liver coefficient of the mice were observed first.Then the accumulation of Cd Te QDs in the liver,the liver biochemical indicators and pathological changes caused by Cd Te QDs were detected.The expression of oxidative stress and apoptosis-related proteins were evaluated.The results showed that Cd Te QDs had no significant effect on the body weight and liver coefficient of mice,and the accumulation of cadmium in the liver increased with the increase of the exposure dose（P<0.05）.10μmol/kg of Cd Te QDs can cause a significant increase in AST（P<0.05）,and lead to liver spot necrosis and inflammatory cell infiltration around blood vessels.At the same time,Cd Te QDs can also cause liver tissue oxidative stress and overexpression of pro-apoptotic protein Bax（P<0.05）.3.Hep G2 cells and L02 cells were used as in vitro models to investigated the effects of Cd Te QDs on cell viability,morphology,membrane integrity,apoptosis rate and expression of apoptosis-related proteins.Then,we further study the effects of Cd Te QDs on intracellular reactive oxygen levels,ATP production,mitochondrial membrane potential,free Ca²⁺levels,and mitochondrial ultrastructure.The results showed that Cd Te QDs significantly reduced cell viability,increased intracellular LDH release and induced apoptosis in a concentration-dependent manner（P<0.05）.Under optical microscope,it was found that when exposed to higher concentrations of Cd Te QDs,the number of cells was significantly reduced,the cells were ruptured,and the intercellular connections were reduced.The detection results of apoptosis-related proteins showed that Cd Te QDs can significantly reduce the expression level of Bcl-2,leading to the release of cytochrome C from mitochondria,which further caused the cleavage of caspase3 precursors to cleaved caspase3,thereby inducing intrinsic apoptosis of cells.Mitochondrial toxicity studies found that the level of intracellular reactive oxygen species significantly increased,the mitochondrial transmembrane potential significantly decreased,the free Ca²⁺level increased and the ATP content significantly decreased（P<0.05）.The mitochondrial ultrastructure observation revealed that the mitochondrial cristae were broken.4.The effects of Cd Te QDs on mitochondrial fission/fusion and mitophagy were explored through confocal microscopy observation and the detection of mitochondrial fission/fusion and mitophagy related protein expression.Observation under a confocal microscope revealed that Cd Te QDs caused the dispersed distribution and reduced number of mitochondria in cells.The detection results of mitochondrial fission/fusion-related proteins showed that 100μM of Cd Te QDs can significantly reduce the expression of Drp1 on mitochondria（P<0.05）,which leads to the blockage of mitochondrial fission.At the same time,Cd Te QDs can also cause the decreased expression of Opal（P<0.05）,which affects mitochondrial inner membrane fusion and cristae formation.PINK1/Parkin-mediated mitochondrial autophagy-related proteins detection results showed that 100μM of Cd Te QDs can significantly reduce the expression of Parkin on mitochondria（P<0.05）.Mitophagy was observed under a confocal microscope by transfecting cells with GFP-LC3 plasmid and staining mitochondria.The quantitative results of colocalization showed that mitophagy was significantly reduced under the treatment of high-dose Cd Te QDs（P<0.05）.In summary,in vivo studies found that Cd Te QDs can accumulate in the liver after entering the mouse body,and cause liver damage,oxidative stress and abnormal expression of apoptosis proteins.In vitro studies found that Cd Te QDs have significant toxic effects on both hepatocytes and their mitochondria.Cd Te QDs can inhibit mitochondrial fission and mitochondrial inner membrane fusion,resulting in a reduction in the number of mitochondria and destruction of the mitochondrial cristae structure.Cd Te QDs can also inhibit mitophagy and affect the clearance of damaged mitochondria.This study revealed the role of mitochondrial fission/fusion and mitophagy in Cd Te QDs-induced mitochondrial dysfunction,and provided references for further studies on the mechanisms of Cd Te QDs-induced liver toxicity.