The Expression of Antimicrobial Peptide Lysozyme is Increased by Treatment with Silver Nanoparticle (Atomyball S®) in Mammalian Epithelial Cells

In recent years, the use of silver nanoparticles (SNPs) is gaining ground especially on its use as disinfectant or antiseptic. The application of SNPs in the manufacture of medical devices and products is attributed to its high antibacterial efficacy. But while most of the studies on SNPs focus on its direct effect on bacteria, investigations have not been done on the effect of SNPs on mammalian innate immune molecules that possess bacterial killing capacity. Thus, in this report, we determined whether SNPs could affect naturally occurring antimicrobial molecules. We used here a silver nanoparticle, termed S (Atomyball S (R)), which has a size of 5 nanometers; (nm), and treated it to lung epithelial cell lines A549 and Calu-3. A low concentration of nanoparticle S (5 mu g/ml) did not induce cell toxicity as determined by lactate dehydrogenase assay. Interestingly, we observed that S increased the mRNA and protein expression levels of the antimicrobial peptide lysozyme, which is considered as one of the most important host immune defense molecules in human epithelial tissues. Quantification of the secreted lysozyme in the apical surface fluid obtained from air-liquid interface cultures of Calu-3 cells also revealed a significant increase of lysozyme in cells treated with nanoparticle S. Although the mechanism of its action on lysozyme is yet to be elucidated, these findings firstly suggest that the silver nanoparticle S (Atomyball S (R)) positively regulated the expression of antimicrobial peptide lysozyme in mammalian cells.