Cell growth inhibition and apoptosis by SDS-solubilized single-walled carbon nanotubes in normal rat kidney epithelial cells

Carbon nanotubes (CNTs), promising novel nanomaterials, have been applied to drug delivery and bio-imaging; however, their potential harmful effects on human health and environment have gained much attention recently. In the present study, we investigated cytotoxic effect of solubilized single-walled CNTs (SWCNTs), which were dispersed in water by sodium dodesyl sulfate (SDS), in normal rat kidney epithelial cells (NRK-52E). SDS-SWCNT (0.125-10 μg/mL)-treated NRK-52E cells showed decreased cell viability and enhanced cytotoxicity marker levels following 24-48 h incubation. In addition, SDS-SWCNT treatment evoked the cell growth inhibition: 8 μg/mL SDS-SWCNT induced the growth arrest at G(0)/G(1) phase and levels of cell cycle-related proteins such as CDK2, CDK6 and phosphorylated-retinoblastoma (pRB) were significantly reduced by CNT. Whereas, at higher concentration of SDS-SWCNT, the percentage of cell numbers in apoptotic sub-G(1) phase was substantially increased. Along with these changes, SDS-SWCNT treatment elevated protein levels for p53 and p21 with a concomitant increase in the single strand DNA breakage. Taken together, these results suggest that SDS-solubilized SWCNTs exert genotoxic effect in renal epithelial cells, and p53-dependent signaling can be associated with the growth arrest and apoptosis events upon CNT-induced DNA damage.