The Involvement of Autophagy in the Response of Neurons and Glial Cells to Photodynamic Treatment

Abstract

Photodynamic therapy is used for selective destruction of pathological tissue in oncology; this method is also employed for ablation of brain tumors. Cell death upon photodynamic treatment results from oxidative stress that develops in photosensitized cells upon exposure to light in the presence of oxygen. We studied the development of autophagy during photo-induced oxidative stress in a crayfish stretch receptor that consists of two sensory neurons in a glial envelope by measuring the number and distribution of lysosomes using a LysoTracker Red fluorescent probe. Photodynamic treatment with radachlorin (500 nM) for 15 min decreased the number of lysosomes, probably due to their photodestruction. However, 1 h after the photodynamic treatment with radachlorin (250 nM) the LysoTracker Red fluorescence increased with larger granules occurring, which may be indicative of autophagic processes in the cell. Photodynamic treatment is capable of inducing necrosis of neurons and glial cells and glial apoptosis in a crayfish stretch receptor. Modulation of autophagy by application of specific inhibitors and activators of AMPK (AICAR, dorsomorphin) and mTOR (rapamycin, KU0063794) revealed that autophagy could protect glia against photo-induced cell death.