Difference in phototoxicity of cyclodextrin complexed fullerene [(gamma-CyD)2/C60] and its aggregated derivatives toward human lens epithelial cells.
The water-soluble fullerene derivative gamma-cyclodextrin bicapped C(60) [(gamma-CyD)(2)/C(60), CDF0] has several clinical applications, including use as a drug carrier to bypass the blood ocular barriers or a photosensitizer to treat tumors in photodynamic therapy. We have assessed the potential ocular toxicity of (gamma-CyD)(2)/C(60) and its aggregated derivatives induced by UVA and visible light in vitro in human lens epithelial cells (HLE B-3). Cell viability using the MTS assay demonstrated that 2 microM (gamma-CyD)(2)/C(60) was highly phototoxic to HLE B-3 cells with UVA irradiation, while no effect was observed in the presence of visible light or when maintained in the dark. In contrast, the aggregated derivative (CDF150) showed neither cytotoxicity nor any phototoxic effect even at 30 microM with either UVA or visible light irradiation. In lens cells treated with (gamma-CyD)(2)/C(60), phototoxicity was manifested as apoptosis. Singlet oxygen production measurement using the EPR/TEMP trapping technique determined that (gamma-CyD)(2)/C(60) (CDF0) efficiently produced singlet oxygen. The rate of singlet oxygen production decreased with increased aggregation, with no production by the fully aggregated sample formed after 150 min of heating (CDF150). UVA irradiation of HLE B-3 in the presence of (gamma-CyD)(2)/C(60) resulted in a significant rise in intracellular protein-derived peroxides. The singlet oxygen quenchers sodium azide and histidine each significantly protected lens cells against (gamma-CyD)(2)/C(60) photodamage, but lutein and Trolox (vitamin E) did not. Clearly, singlet oxygen is an important intermediate in the phototoxicity of monomeric (gamma-CyD)(2)/fullerene. Our results also demonstrate that UVA-blocking sunglasses can limit the ocular phototoxicity of this nanomaterial, while nontoxic endogenous antioxidants like lutein or Trolox cannot provide adequate protection.
Zhao
Baozhong
B
Laboratory of Pharmacology, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina 27709, USA.
He
Yu-Ying
YY
Chignell
Colin F
CF
Yin
Jun-Jie
JJ
Andley
Usha
U
Roberts
Joan E
JE
D002460:Cell Line; D004578:Electron Spin Resonance Spectroscopy; D004847:Epithelial Cells / Q000187:drug effects*; D037741:Fullerenes / Q000494:pharmacology / Q000633:toxicity*; D006801:Humans; D007908:Lens, Crystalline / Q000166:cytology / Q000187:drug effects*; D010544:Peroxidases / Q000378:metabolism; D017319:Photosensitizing Agents / Q000494:pharmacology / Q000633:toxicity*; D026082:Singlet Oxygen / Q000378:metabolism; D013696:Temperature; D014466:Ultraviolet Rays; D047408:gamma-Cyclodextrins / Q000494:pharmacology / Q000633:toxicity*
C541824:(gamma-CyD)2 C60; D037741:Fullerenes; D017319:Photosensitizing Agents; D047408:gamma-Cyclodextrins; D026082:Singlet Oxygen; D010544:Peroxidases; C023792:gamma-cyclodextrin