Abstract
Purpose: :
Cerium oxide nanoparticles (CNPs) possess regenerative radical scavenging activities that mimic the catalytic functions of superoxide dismutase and catalase in vitro. At concentrations as low as 0.000516 µg/ml, CNPs significantly reduced reactive oxygen species (ROS) generation in primary retinal cell cultures challenged with hydrogen peroxide. Presently, we investigated whether the CNPs at concentrations up to 33000X higher, had any cytotoxic effect on five different cell lines.
Methods: :
We assessed the viability of five cell lines after exposure to CNPs at a number of concentrations and durations. These were mouse cone photoreceptor precursor tumor cells (661W, from M.R. Al-Ubaidi), human retinal pigment epithelial cells (ARPE19, from American Type Culture Collection (ATCC): cat. # CRL-2302), human corneal epithelial cells (THE, from J. Chodosh), primary human umbilical vein endothelial cells (HUVEC, from M.A. Ihnat), and human microvascular endothelial cells (HMEC, from M.A. Ihnat). All were adherent cells with specific culture conditions. Cell viability was determined using either the CellQuanti-MTTTMCell Viability Assay Kit (BioAssay Systems) or CellTiter 96® AQueous One Solution Cell Proliferation Assay Kit (Promega). Apoptosis assessment by flow cytometry was performed using the Annexin V-PE Apoptosis Detection Kit I (BD Biosciences). Reagents for ROS detection (5-(and-6)-carboxy-2’,7’-dichlorodihydrofluorescein diacetate, dihydroethidium, and 3’-p-aminophenyl fluorescein) for flow cytometry were from Invitrogen.
Results: :
At maximum concentration examined, 17.2 µg/ml of CNPs for 48 hours, there was no cytotoxicity observed in four of the cell lines. However, 661W cells were uniquely sensitive to CNPs and showed reduction in viability at 8.6 µg/ml after incubation for 72 hours. This result paralleled the increase in apoptosis and production of ROS observed under these conditions.
Conclusions: :
At 1.72 µg/ml, 3300X higher than the concentration observed to be effective for radical scavenging activity, CNPs are not cytotoxic. However, they do facilitate the production of ROS, specifically superoxide anions and hydroxyl radicals in 661W cells at concentrations at or above 8.6 µg/ml after incubation for 72 hours. Under these conditions, CNPs cause an increase in apoptosis in 661W cells most likely due to oxidative damage.
Keywords: oxidation/oxidative or free radical damage • antioxidants • retinal culture