Mitochondrial Reactive Oxygen Species Generation and Calcium Increase Induced by Visible Light in Astrocytes

: Mitochondria contain photosensitive chromophores that can be activated or inhibited by light in the visible range. Rather than utilizing light energy, however, mitochondrial electron transport oxidation‐reduction reaction and energy coupling could be stimulated or damaged by visible light. Our pre...

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Bibliographic Details
Published in:Annals of the New York Academy of Sciences 2004-04, Vol.1011 (1), p.45-56
Main Authors: JOU, MEI-JIE, JOU, SHUO-BIN, GUO, MEI-JIN, WU, HONG-YUEH, PENG, TSUNG-I
Format: Article
Language:English
Subjects:
Animals
Astrocytes - cytology
Astrocytes - metabolism
calcium
Calcium - metabolism
Cell Line
Fluorescent Dyes - metabolism
Hydrogen Peroxide - metabolism
Light
mitochondria
Mitochondria - metabolism
Oxidants - metabolism
photoirradiation
Rats
reactive oxygen species
Reactive Oxygen Species - metabolism
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Summary:: Mitochondria contain photosensitive chromophores that can be activated or inhibited by light in the visible range. Rather than utilizing light energy, however, mitochondrial electron transport oxidation‐reduction reaction and energy coupling could be stimulated or damaged by visible light. Our previous work demonstrated that reactive oxygen species (ROS) were generated in cultured astrocytes after visible laser irradiation. With confocal fluorescence microscopy, we found that ROS were generated mostly from mitochondria. This mitochondrial ROS (mROS) formation plays a critical role in photoirradiation‐induced phototoxicity and apoptosis. In this study, we measured changes of mitochondrial calcium level ([Ca2+]m) in cultured astrocytes (RBA‐1 cell line) irradiated with blue light and examined the association between mROS formation and [Ca2+]m level changes. Changes of intracellular ROS and [Ca2+]m were visualized using fluorescent probes 2′,7′‐dichlorodihydrofluorescein (DCF), and rhod‐2 After exposure to visible light irradiation, RBA‐1 astrocytes showed a rapid increase in ROS accumulation particularly in the mitochondrial area. Increase in [Ca2+]m was also induced by photoirradiation. The levels of increase in DCF fluorescence intensity varied among different astrocytes. Some of the cells generated much higher levels of ROS than others. For those cells that had high ROS levels, mitochondrial Ca2+ levels were also high. In cells that had mild ROS levels, mitochondrial Ca2+ levels were only slightly increased. The rate of increase in DCF fluorescence seemed to be close to the rate of rhod‐2 fluorescence increase. There is a positive and close correlation between mitochondrial ROS levels and mitochondrial Ca2+ levels in astrocytes irradiated by visible light.
ISSN:0077-8923
1749-6632
DOI:10.1196/annals.1293.005