Photodynamic effect of Radachlorin on nerve and glial cells

• Radachlorin is a promising photosensitizer for nervous tissue.
• Its absorption maximums 420 and 654 nm, fluorescence maximum 664 nm.
• It is accumulated in the nervous tissue within 30–60 min.
• It localizes mainly in glial cells and much less in neurons.
• Radachlorin-PDT kills neurons and glia at a concentration of 1 nM or less.

SummaryBackgroundRadachlorin, a chlorine-derived photosensitizer, is used currently in photodynamic therapy (PDT) of skin cancer. In this work we studied Radachlorin-PDT effect on peripheral nerve and glial cells that are damaged along with tumor tissue.MethodsWe used simple model objects – a crayfish stretch receptor that consists of a single sensory neuron surrounded by glial cells and crayfish nerve cord consisting of nerve fibers and ganglia. Radachlorin absorption and emission spectra were registered using spectrophotometer and spectrofluorimeter. Radachlorin accumulation and intracellular localization were studied using the fluorescence microscope. Necrotic and apoptotic cells were visualized using propidium iodide and Hoechst 33342. Neuronal activity was registered using standard electrophysiological methods.ResultsRadachlorin absorption spectrum in the physiological van Harreveld saline (pH 7.3) contained maximums at 420 and 654 nm. Its fluorescence band 620–700 nm had a maximum at 664 nm. In the crayfish stretch receptor Radachlorin localized predominantly to the glial envelope and penetrated slightly into the neuron body and axon. Radachlorin rapidly accumulated in the crayfish nerve cord tissue within 30 min. Its elimination in the dye-free solution occurred slower: 11% loss for 2 h. Radachlorin-PDT inactivated the neuron and induced necrosis of neurons and glial cells and glial apoptosis at concentrations as low as 10−10–10−9 M.ConclusionsRadachlorin rapidly accumulates in the nervous tissue, mainly in glial cells, and demonstrates very high photodynamic efficacy that characterize it as a promising photosensitizer.

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