The Antitumor Activity And The Toxicity On Lung Tissue Of AgNPs

Silver nanoparticles(AgNPs)is widely used in biomedicine because of its unique physical and chemical properties and antibacterial activity.Recently,some studies have shown that AgNPs have strong antitumor activity in some animal models.The exact molecular mechanism of AgNPs inducing cancer cell death remains to be further explored.The wide application of AgNPs in various fields leads to its accumulation in the environment,and its biosafety has attracted much attention.In this study,tumor cells were taken as the research object to explore the anti-tumor activity and biological mechanism of AgNPs;human lung normal cells and mice were taken as the research objects to explore the lung tissue damage and molecular mechanism of low-dose AgNPs for long-term exposure.The results are as follows:1.AgNPs induced tumor cell proliferation inhibition and cell death through telomerase/telomere:The telomerase activity,telomere length,cell proliferation and related protein expression of tumor cells were detected after exposure to AgNPs.The results showed that AgNPs could not only inhibit telomerase activity in cell extracts,but also induce telomerase activity down-regulation in tumor cells.The inhibition of telomerase activity in small-sized AgNPs(25 nm)was significantly higher than that in large-sized AgNPs(75 nm)The decrease of telomerase activity is related to the inhibition of telomerase catalytic subunit(hTERT)protein expression by AgNPs;further exploration found that the continuous inhibition of telomerase activity and the down-regulation of telomere binding protein by AgNPs lead to telomere shortening and dysfunction,interfere with the stability of tumor cell chromosome,and form a anaphase bridge during cell division.Through the construction of telomerase overexpression cells,telomerase knockdown cells,enzyme activity mutant cells and TRF2 mutant cells,it was found that overexpression of telomerase catalytic subunit can reduce the anticancer activity of AgNPs,and down-regulation of telomerase activity or telomere interference can enhance the cytotoxicity of AgNPs to HeLa cells.These results indicate that the telomere dysfunction and telomerase activity inhibition induced by AgNPs are closely related to the anticancer effect of AgNPs,which provides a new insight into the anticancer mechanism of AgNPs.2.The effect of AgNPs on lung cellular senescence and tissue fibrosis:Cellular senescence and the expression of related proteins were detected to study the damage of AgNPs on normal lung cells and tissues.The results showed that the activity of senescence related ?-galactosidase,abnormal condensation of chromatin in nucleus and the expression of senescence related secretory factor genes were up-regulated in normal lung cells exposed to sub-toxic doses of AgNPs for a long time.These aging biomarkers increased,indicating that AgNPs exposure induced cellular senescence.The results of flow cytometry showed that the cell cycle was arrested in G2/M phase,and the number of apoptotic cells increased from 3.3%to 74.3%.The fluorescence analysis revealed that the apoptosis induced by AgNPs was related to senescence.Excessive prostaglandin E2(PGE2)was synthesized by up regulating the expression of nuclear transcription factor NF?B and cyclooxygenase-2(COX2),leading to senescence of lung cells.Inhibition of COX2 can reduce cellular senescence induced by AgNPs to normal level.In mice,the expression of COX2 protein,the activity of ?-galactosidase,the expression of ?-SMA and the accumulation of collagen were up-regulated in the lung tissue exposed to AgNPs.In summary,AgNPs induced senescence by activating NF?B signaling pathway,up-regulating expression and synthese of COX2/PGE2,and removing senescent cells by apoptosis.Exposure to AgNPs accelerated the senescence of mouse lung cells and caused lung tissue inflammation and slight pulmonary fibrosis...