| Due to the excellent physical and chemical properties,nanomaterias have attaracted widespread attention at the beginning of their birth.Now,with the rapid development of nanotechnology,more and more nanomaterials are applied to the catalyzer,electronic devices,food,cosmetics,biomedicine and other fields of goods.Because of increasing contact with human body and the environment in daily life,the biological effects and toxicity of nanoparticles on human body and the environment have received considerable attention.At present,the researches on biological effects of nanomaterials are mainly focused on the biological effects of nanomaterials from the surface phenomena such as cell metabolic activity and cell death on the cellular level,little is known about the change of biological processes and the biological effects of nanomaterials on environmental microorganisms,especially eukaryotic ones,and biological individuals.Therefore,the biological effects of nanomaterials on eukaryotic microorganism Saccharomyces cerevisiae,animal cells HeLa and rat individuals were studied base on autophagic dysfuction induced by nanomaterials.The role of autophagy in its various levels of biological effects and toxicity was also discussed.In Saccharomyces cerevisiae,the biological effects of cadmium telluride quantum dots were studied on population and cellular levels,and blockade of autophagic flux was proved as a novel toxicity mechanism of cadmium telluride quantum dots.The effect of cadmium telluride quantum dots on the growth of yeast was evaluated by OD600 and colony-forming units(CFU).The result indicated that cadmium telluride quantum dots inhibited the growth of yeast in a dose-dependent manner.Moreover,the half maximal inhibitory concentration(IC50)of G-CdTe obtained by these methods were 318.2 ± 63.2 and 186.6 ± 19.7 nmol/L,while those of O-CdTe were 84.0 ± 13.1 and 59.4 ± 12.0 nmol/L.This indicated that cadmium telluride quantum dots inhibited the growth of yeast in a size-dependent manner.To study the mechanism of growth inhibition induced by cadmium telluride quantum dots,the cell cycle and cell death of yeast were evaluated.Cadmium telluride quantum dots could increase the proporation of cells in G2/M phase by 15.34%and change the cell death ratio unsignificantly,indicating that cadmium telluride quantum dots mainly affected the yeast growth by inducing the cell cycle arrest.The cellular effect of cadmium telluride quantum dots was studied by scanning electron microscopy,biochemical and molecular methods.We found that cadmium telluride quantum dots induced the accumulation of autophagy-related vesicles in cytoplasm and a significant decrease in ratio of GFP/GFP-Atg8(p<0.01).Futher study demonstrated that cadmium telluride quantum dots induced the accumulation of autophagy-related vesicles was caused by blocking autophagic flux(p<0.05).Moreover,recovering autophagic flux could reduce the toxicity of cadmium telluride quantum dots in yeast,indicting that inducing blockade of autophagic flux is the toxicity mechanism of cadmium telluride quantum dots.The role of cadmium ions in the toxicity of quantum dots was also studied and the result indiated that cadmium ions play an important role in blockade of autophagic flux and toxicity caused by quantum dots.Taking together,these suggested that cadmium telluride quantum dots induced blockade of autophagic flux,which may result in cell cycle arrest and inhibit cell growth,and finally exhibited the toxicity on Saccharomyces cerevisiae.In the human cervical cancer HeLa cells,gadolinium oxide nanoparticles were demonstrated to induce blockade of autophagic flux,which acts as a potential toxicity mechanism.The effect of gadolinium oxide nanoparticles on the viability of HeLa cells was evaluated by MTT assay.After treatment for 24 h,gadolinium oxide nanoparticles did not decrease the cell viability significantly,but the cellular effect of gadolinium oxide nanoparticles in HeLa cells was observed by monodansylcadaverine(MDC)staining and immunofluorescence.The result showed that gadolinium nanoparticles induced autophagosomes accumulation,which was caused by blocking autophagic flux after further study.Under the stress induced by cisplatin,gadolinium nanoparticles could decrease the cellular viability from 90.3%to 70.9%significantly(p<0.001)and increase the proportion of apoptosis cells from 14.11%to 27.53%,while recovering of autophagic flux by rapamycin could reduce the enhancement induced by gadolinium oxide nanoparticles(p<0.05).This indicated that blockade of autophagic flux is a potential toxicity mechanism of gadolinium oxide nanoparticles.In addition,the ability of nuclear magnetic contrast and chemotherapic enhancement made gadolinium nanoparticles to be a potential material for cancer diagnosis and treatment.In the Sprague-Dawley rats,the biological effects of titanium dioxide nanoparticles on individual,intestinal cells and intestinal microecological levels were determined,and the role of autophagic flux blockade on the biological effects and toxicity induced of titanium dioxide nanoparticles was also discussed.We evaluated the effect of titanium dioxide nanoparticles on rat and found the weight gain was significantly decreased by about 58 g after intragastric administrating low concentration(200 mg/kg body weight,p<0.01)and high concentration(1 g/kg body weight,p<0.001)of titanium dioxide nanoparticles for 4 weeks.To explore the reasons,the weight of rat organ and the function of liver and kidney were detected.The result showed that titanium dioxide nanoparticles had no significant effect on the weight of heart,liver,spleen,lung and kidney,so as the function of liver and kidney(p>0.05).These indicated that titanium dioxide nanoparticles did not cause obvious damage on rat organs.Futhermore,immunofluorescence and d-xylose test were performed to detect the structure and function of rat intestinal cells,which contacted with titanium dioxide nanoparticles directly.The reslt showed that titanium dioxide nanoparticles could block the autophagic flux of small intestine and colon cells,and induce small intestinal absorption decreased and colonic lesions.It is speculated that the blockade of autophagic flux may be the cause of reduced intestinal absorption and colonic lesions.The high-throughput sequencing method was used to evaluate the effect of titanium dioxide nanoparticles on gut microbiota.The results showed that titanium dioxide nanoparticles could increase the proportion of proteobacteria from 3.3%to 4.49%and the proportion of bacteria in the genus Rhizoctonia(from 0.93%to 3.75%,p<0.001)and Rumenococcus(from 0.26%to 3.43%,p<0.001).These changes in gut microbiota were similar with those in patients with inflammatory bowel disease,indicating that titanium dioxide nanoparticles had a negative impact on gut microbiota.Taking together,these suggested that titanium dioxide nanoparticles induced blockade of autophagic flux led to reduced intestinal absorption and colonic lesions,which decreased weight gain in rats.In this paper,the role of nanomaterias induced autophagic flux blockade in their biological effects and toxicity was discussed in the eukaryotic microorganism Saccharomyces cerevisiae,animal cell HeLa and rat individuals.It provides experimental and theoretical basis for the better understanding of the biological effects and toxicity of nanomaterials. |
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