Effects of Short-Term Silver Nanoparticle Exposure on Proliferative Signaling Pathway in Human Skin Keratinocyte

Abstract

The growing usage of silver nanoparticles in healthcare products, household appliances, textile and agriculture in recent years has increased skin exposure to these particles. However, there is limited number of studies available on the safety and effects of silver nanoparticles on human skin in short time of contact. Human skin keratinocytes (HaCaT) cell line were used in the present experiments because they traditionally represent normal keratinocyte function. Objective: This study aimed to determine the effects of silver nanoparticles on proliferation of human skin keratinocytes after 24-hour exposure. Methods: Silver nanoparticles were synthesized by chemical reduction method to get average particle size of about 20 nm. Human skin keratinocytes cells were treated with various concentrations of silver nanoparticles (1, 3, 5 and 10 μg/ml) for 24 hours. Then the cells were grown in DMEM culture medium without silver nanoparticles. The cell number was compared between silver nanoparticles-treated keratinocytes and untreated cells. Changes in expression and phosphorylation of proteins involved in cell proliferation signaling pathway (ERK1/2 and p38 MAPK) were determined by immunoblot. Results: Silver nanoparticles were successfully synthesized with a size range of 18-26 nm. Proliferation of HaCaT cells decreased with increasing concentration of silver nanoparticles (24-hour exposure). After seven days in culture medium without silver nanoparticles, the number of HaCaT cells was nearly the same as the control group, except cells that had been treated with 10 μg/ml silver nanoparticles. Proteins involved in cell proliferation signaling pathways were determined by immunoblot. Immunoblot of HaCaT cells that were exposed to silver nanoparticles for 24 hours showed that phosphorylation of the ERK1/2 was increased, but no significant change was found in the phosphorylation of p38. Conclusion: Silver nanoparticles of about 20 nm could decrease HaCaT cell proliferation via ERK1/2 rather than p38 signaling pathway.