Fluorescence studies on radiation oxidative damage to membranes with implications to cellular radiosensitivity |
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Authors: | K P Mishra |
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Institution: | (1) Radiation Biology Division, Bhabha Atomic Research Centre, 400 085 Mumbai, India |
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Abstract: | Radiation oxidative damage to plasma membrane and its consequences to cellular radiosensitivity have received increasing attention
in the past few years. This review gives a brief account of radiation oxidative damage in model and cellular membranes with
particular emphasis on results from our laboratory. Fluorescence and ESR spin probes have been employed to investigate the
structural and functional alterations in membranes after y-irradiation. Changes in the lipid bilayer in irradiated unilamellar
liposomes prepared from egg yolk lecithin (EYL) were measured by using diphenylhexatriene (DPH) as a probe. The observed increase
in DPH polarization and decrease in fluorescence intensity after γ-irradiation of liposomes imply radiation-induced decrease
in bilayer fluidity. Inclusion of cholesterol in liposome was found to protect lipids against radiation damage, possibly by
modulation of bilayer organization e.g. lipid packing. Measurements on dipalmitoyl phosphatidylcholine (DPPC) liposomes loaded
with 6-carboxyfluorescein (CF) showed radiation dose-dependent release of the probe indicating radiation-induced increased
permeability. Changes in plasma membrane permeability of thymocytes were monitored by fluorescein diacetate (FDA) and induced
intracellular reactive oxygen species (ROS) were determined by 2,7-dichlorodihydro fluorescein diacetate (DCH-FDA). Results
suggest a correlation between ROS generation and membrane permeability changes induced by radiation within therapeutic doses
(0-10 Gy). It is concluded that increase in membrane permeability was the result of ROS-mediated oxidative reactions, which
might trigger processes leading to apoptotic cell death after radiation exposure. |
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Keywords: | Membrane oxidative damage cellular radiosensitivity DPH fluorescence lipid peroxidation liposomal membrane thymocyte membrane permeability |
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