Phototoxicity and cytotoxicity of fullerol in human retinal pigment epithelial cells.
The water-soluble nanoparticle hydroxylated fullerene [fullerol, nano-C60(OH)(22-26)] has several clinical applications including use as a drug carrier to bypass the blood ocular barriers. We have previously found that fullerol is both cytotoxic and phototoxic to human lens epithelial cells (HLE B-3) and that the endogenous antioxidant lutein blocked some of this phototoxicity. In the present study we have found that fullerol induces cytotoxic and phototoxic damage to human retinal pigment epithelial cells. Accumulation of nano-C60(OH)(22-26) in the cells was confirmed spectrophotometrically at 405 nm, and cell viability, cell metabolism and membrane permeability were estimated using trypan blue, MTS and LDH assays, respectively. Fullerol was cytotoxic toward hRPE cells maintained in the dark at concentrations higher than 10 microM. Exposure to an 8.5 J x cm(-2) dose of visible light in the presence of >5 microM fullerol induced TBARS formation and early apoptosis, indicating phototoxic damage in the form of lipid peroxidation. Pretreatment with 10 and 20 microM lutein offered some protection against fullerol photodamage. Using time resolved photophysical techniques, we have now confirmed that fullerol produces singlet oxygen with a quantum yield of Phi=0.05 in D2O and with a range of 0.002-0.139 in various solvents. As our previous studies have shown that fullerol also produces superoxide in the presence of light, retinal phototoxic damage may occur through both type I (free radical) and type II (singlet oxygen) mechanisms. In conclusion, ocular exposure to fullerol, particularly in the presence of sunlight, may lead to retinal damage.
Laboratory of Pharmacology, National Institute of Environmental Health Sciences, Research Triangle Park, NC 27709, USA.
Albert R
AR
Wielgus
Baozhong
B
Zhao
Colin F
CF
Chignell
Dan-Ning
DN
Hu
Joan E
JE
Roberts
D017209:Apoptosis / Q000187:drug effects; D053148:Caspase 3 / Q000378:metabolism; D002460:Cell Line; D002462:Cell Membrane / Q000187:drug effects / Q000473:pathology; D017484:Dermatitis, Phototoxic / Q000473:pathology*; D004847:Epithelial Cells / Q000187:drug effects* / Q000528:radiation effects; D037741:Fullerenes / Q000633:toxicity*; D006801:Humans; D006860:Hydrogen Bonding; D007202:Indicators and Reagents; D053758:Nanoparticles; D009336:Necrosis; D010100:Oxygen / Q000032:analysis / Q000378:metabolism; D010316:Particle Size; D055213:Retinal Pigment Epithelium / Q000166:cytology / Q000473:pathology*; D017392:Thiobarbituric Acid Reactive Substances / Q000378:metabolism
D037741:Fullerenes; D007202:Indicators and Reagents; D017392:Thiobarbituric Acid Reactive Substances; C496652:fullerol C60(OH)22; D053148:Caspase 3; D010100:Oxygen