Carcinogenicity And Underlying Molecular Mechanism Of Heavy Metal Nickel Nanoparticle

Objective: This research explored the carcinogenicity and underlying molecular mechanismof heavy metal nickel (Ni) nanoparticle, and antioxidant epigallocatechin gallate (EGCG) was usedto inhibit its toxicity in vitro experiments using JB6cells (a mice epithelial cell line). This studycould provide scientific clues for evaluating the carcinogenic effects, preventing the toxicity of Ninanoparticles and the development of antagonist drug.Method:1. MTT test was used to detect the cell viability under different concentrations(0-10μg/cm2) Ni nanoparticle alone or supplemented with10μM antioxidant EGCG on JB6cells.2. Flow cytometry was used to evaluate the cell cycle and apoptosis.3. Cell microfilament structure and oxidative stress level were observed after fluorescent dyestaining under the laser scanning confocal microscope.4. Luciferase assay was employed to detect the expression level of two transcription factorsAP-1and NF-κB.5. Protein expression of the MAPK signaling pathway was evaluated by Western.Results:1. MTT assay showed that the viability of JB6cells decreased gradually with theincrease of Ni nanoparticle concentrations after24hour treatment. EGCG showed some inhibitiveeffects on the toxicity induced by Ni nanoparticle especially under the concentrations of7.5and10μg/cm2.2. Ni nanoparticle induced cell death mainly through apoptosis. Under low concentration ofNi nanoparticle, JB6cells were mainly arrested at the phase of G0/G1, but at the phase of G2/Munder the high Ni nanoparticle concentrations. EGCG showed inhibition effects on cell apoptosisinduced by Ni nanoparticles and an enhancement on the cell proportion of G0/G1phase under highNi nanoparticle concentrations.3. The normal structure of actin filaments disappeared and density beam appeared around thenucleus in JB6cells under the high concentration of Ni nanoparticle exposure (7.5and10μg/cm2).EGCG showed some inhibitive effects on the microfilament structure damage induced by Ninanoparticles but could not prevent the formation of density beam.4. EGCG could obviously decrease ROS and O2-level in JB6cells under Ni nanoparticleexposure.5. Ni Nanoparticle could increase transcription factors (Ap-1and NF-κB) level in JB6cells and EGCG showed certain inhibition effects on this effect.6. Ni Nanoparticle showed up-regulation of the phosphorylation level of MAPK signalingpathway, antioxidant EGCG could inhibit this effect.Conclusion:1. JB6cell apoptosis induced by Ni nanoparticle could be inhibited by antioxidant EGCG.2. Ni nanoparticle could induce the apoptosis under the low concentration and the DNAdamage at high concentration in JB6cells, and EGCG showed certain inhibition effects on thiseffect.3. The toxicity of Ni nanoparticle on JB6cells might be induced by oxidative stress, andinhibitive effect induced by EGCG on this effect might be through down regulation of the level ofintracellular oxidative stress.4. Carcinogenicity of Ni nanoparticle could be achieved by increasing the AP-1and NF-κBtranscription factors level in JB6cells, and antioxidants might antagonize this effect.5. The carcinogenicity of Ni nanoparticle could up-regulate the MAPK signaling pathwayespecially the phosphorylation levels of P38, ERK1/2while the antioxidant EGCG played aninhibitive effect through down-regulating the phosphorylation levels of this signaling pathway.