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Michael L. Denton, C.D. Clark, III, Gary D. Noojin, Larry E. Estlack, Curtis W. Burney, Adam Schenk, Robert J. Thomas; Transition Between Photothermal And Photochemical Damage Mechanisms In Cultured Rpe Cells Depends Upon The Degree Of Pigmentation And Ambient Temperature. Invest. Ophthalmol. Vis. Sci. 2011;52(14):4426.
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© ARVO (1962-2015); The Authors (2016-present)
Investigate the effects of varying ambient temperature on laser damage thresholds at 413 nm and photo-oxidative rates in an in vitro retinal model.
Pigmented hTERT-RPE1 cells were used to determine threshold ED50 irradiance thresholds for laser damage (fluorescence staining with calcein AM and ethidium homodimer1) at 413 nm. We defined damage trends (ED50 radiant exposure vs exposure duration) for both photothermal (shortest exposure durations) and photochemical (longest exposure durations) mechanisms, and determined the exposure duration range in which the damage mechanism transitioned. We also measured the temperature dependence of the photo-oxidation rate in either non-pigmented or pigmented cultured RPE cells at ambient temperatures in the range of 25-50 °C. Microthermography of the cells during laser exposure provided temperature rise information that was related to damage efficiencies. A computational model was used to simulate the temperature-dependent shift in damage thresholds.
Lowering ambient temperature from 35 °C to 25 °C caused a shift in the transition between photothermal and photochemical damage mechanisms. Thermal inactivation of photo-oxidation occurred at a lower ambient temperature in pigmented cells as compared with non-pigmented cells, indicating the slight temperature rise due to melanin absorption can influence photo-oxidative rates. Microthermography provided a thermally-based dose response curve that was superior to that of laser dose. Our computer-based model correctly predicts the exposure duration at which the damage mechanisms transitions, even though our data cannot distinguish between a temperature-dependent loss of function (oxidative enzymes) or a temperature-dependent efficiency of removal of reactive oxygen species.
The accumulation of photo-oxidation and photochemical damage in an RPE system was found to depend upon both the ambient temperature and the degree of pigmentation.
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