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Mariusz Duda, Olga Krzysztynska-Kuleta, Magdalena Olchawa, Tadeusz Jan Sarna; Comparison of the efficiency of photoreceptor outer segments to photogenerate singlet oxygen after their pre-irradiation with green or blue light.. Invest. Ophthalmol. Vis. Sci. 2018;59(9):3077.
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Although phototoxic potential of short-wavelength visible light has been well documented in numerous studies involving systems of complexity different, the exact mechanism of cytotoxicity of violet-blue light remains only partially understood. We addressed this issue by measuring photogeneration of singlet oxygen by photoreceptor outer segments under selected experimental condition.
Photoreceptor outer segments, isolated from horse eyes (hrPOS) were pre-irradiated with selected wavelengths (400-500 nm, 32 mJ/cm2) using nanosecond light pulses generated by Nd-YAG laser equipped with optical parametric oscillator, their absorption spectra were examined immediately after the irradiation and after second exposure to irradiation at 380 nm. The ability of hrPOS to photogenerate singlet oxygen after excitation at 370-510 nm was tested before and after irradiation at 500nm (32 mJ/cm2). The release of retinal from hrPOS was analyzed in samples irradiated with blue light (420 nm, 6mW/cm2) or green light (500-580 nm, 6mW/cm2) using LED light sources. Singlet oxygen (SO) was detected by time-resolved phosphorescence in 1270 nm.
Irradiation of hrPOS in the range of 460-500 nm decreased their absorbance at 500 nm and increased absorbance at 380 nm. Exposure to 400-440 nm light increased absorbance below 340 nm while no increase at 380 nm was observed. The action spectra of SO photogeneration showed a higher efficiency to generate SO by the irradiated hrPOS when excited below 450 nm. SO photogeneration was also observed in Folch’s extracts of hrPOS after their pre-irradiation.
The results suggest that pre-irradiation of hrPOS with 460-500 nm light induces reversible release of retinal, which upon activation with short-wavelength visible light generates potentially cytotoxic singlet oxygen. On the other hand, pre-irradiation of hrPOS by 400-440 nm light, may induce irreversible modifications of the retinal. Both processes could contribute to the formation of reactive oxygen species and possible cytotoxicity.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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