Photodynamic treatment that causes intense oxidative stress and cell death is currently used in neurooncology. However, along with tumor cells, it may damage healthy neurons and glia. To study the involvement of signaling processes in photodynamic injury or protection of neurons and glia, we used crayfish mechanoreceptor consisting of a single neuron surrounded by glial cells. It was photosensitized with alumophthalocyanine Photosens. Application of specific inhibitors showed that phosphatidylinositol 3-kinase did not participate in photoinduced death of neurons and glia. Akt was involved in photoinduced necrosis but not in apoptosis of neurons and glia. Glycogen synthase kinase-3β participated in photoinduced apoptosis of glial cells and in necrosis of neurons. Therefore, phosphatidylinositol 3-kinase/protein kinase Akt/glycogen synthase kinase-3β pathway was not involved as a whole in photodynamic injury of crayfish neurons and glia but its components, Akt and glycogen synthase kinase-3β, independently and cell specifically regulated death of neurons and glial cells. According to these data, necrosis in this system was a controlled but not a non-regulated cell death mode. The obtained results may be used for the search of pharmacological agents selectively modulating death and survival of normal neurons and glial cells during photodynamic therapy of brain tumors.

Photodynamic therapy based on photogeneration of cytotoxic singlet oxygen and following oxidative stress is currently used in neuro-oncology for destruction of brain tumors. However, along with a tumor, it damages healthy neurons and glial cells. We studied the involvement of the glutamate-related signaling pathway in photodynamic damage to normal glial cells in the crayfish stretch receptor. This model object consists of a single neuron surrounded by glial cells. It was photosensitized with alumophthalocyanine Photosens and irradiated by the diode laser (670 nm). Application of enzyme inhibitors and ion channels modulators showed that exogenous L-glutamate decreased photoinduced apoptosis of crayfish glial cells. The natural neuroglial mediator N-acetylaspartylglutamate, which releases glutamate after splitting by glutamate carboxypeptidase II, also inhibited photoinduced apoptosis. Inhibition of glutamate carboxypeptidase II, oppositely, enhanced glial apoptosis. This confirmed the antiapoptotic activity of glutamate. Glutamate agonist NMDA or inhibitor of NMDA receptors MK801 did not influence photodynamic death of glial cells, i.e., these receptors did not participate in glial apoptosis. Inhibition of metabotropic glutamate receptors mGluRI with AP-3 reduced PDT-induced apoptosis of glial cells. Thus, chemical modifiers of various signaling processes can modulate photoinduced necrosis or apoptosis of glial cells and thus modify efficiency of photodynamic therapy.

Photodynamic treatment causes intense oxidative stress and kills cells. It is currently used in neurooncology. However, along with tumor it damages surrounding healthy neuronal and glial cells. In order to study the possible role of the phosphatidylinositol 3-kinase/protein kinase Akt/glycogen synthase kinase-3β signaling pathway in photodynamic damage to normal neurons and glia, we used isolated crayfish stretch receptor that consists only of a single neuron surrounded by glial cells. It was photosensitized with alumophthalocyanine Photosens (100 nM). The laser diode (670nm, 0.4W/cm 2 ) was used as a light source. Application of specific inhibitors of the enzymes involved in this pathway showed that phosphatidylinositol 3-kinase did not participate in photoinduced death of neurons and glia. Protein kinase Akt was involved in photoinduced necrosis but not in apoptosis of neurons and glia. Glycogen synthase kinase-3β participated in photoinduced apoptosis of glial cells and in necrosis of neurons. Therefore, the phosphatidylinositol 3-kinase/protein kinase Akt/glycogen synthase kinase-3β pathway was not involved as a whole in photodynamic injury of crayfish neurons and glial cells but its components, protein kinase Akt and glycogen synthase kinase-3β, independently and cell-specifically regulated photoinduced death of neurons and glial cells. These data showed that in this system necrosis was not non-regulated and catastrophic mode of cell death. It was controlled by some signaling proteins. The obtained results may be used for search of pharmacological agents that selectively modulate injury of normal neurons and glial cells during photodynamic therapy of brain tumors.