On the Role of Phosphatidylinositol 3-Kinase, Protein Kinase B/Akt, and Glycogen Synthase Kinase-3β in Photodynamic Injury of Crayfish Neurons and Glial Cells

Abstract

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.

Protection of the Crayfish Mechanoreceptor Neuron and Glial Cells from Photooxidative Injury by Modulators of Diverse Signal Transduction Pathways

“…The results of our studies have demonstrated that diverse intercellular and intracellular signaling pathways control PDTinduced necrosis or apoptosis of isolated neurons and satellite glial cells [15,[27][28][29][30][31][32][33]59]. These data are summarized in the Table 1.…”

“…MRN has been used in classical studies of mechanisms of neuronal activity and its inhibition [19,20], relationship bet w e e n n e u r o n a l a c t i v i t y a n d m e t a b o l i s m [ 2 3 ] , mechanosensory transduction [21], neuroglial interactions [22], responses of neurons and glial cells to various physical and chemical impacts [15,[23][24][25][26], and signal transduction processes in neurons and glia [15,[27][28][29][30][31][32][33][34].…”

“…The methods of isolation of MRN, registration of neuronal activity, fluorescence microscopic and electron microscopic studies, and photosensitization have been described in detail earlier [22,[28][29][30][31][32][33][34]. Neurotrophic factors, inhibitors or activators of signaling proteins, were characterized in the papers [27][28][29][30][31][32][33][34][35]. In the recent research, we used also inhibitor of inducible NO synthase L-NIL (Sigma-Aldrich Co), MEK1/2 inhibitor U0126, and mammalian target of rapamycin (mTOR) inhibitor rapamycin (both from Alomone Labs, Israel).…”

“…The percent of propidium iodide-stained nuclei of necrotic cells were counted in the predetermined standard field around MRN soma. Fragmented apoptotic nuclei were counted around the proximal 2-mm axon fragment, where apoptosis was more significant [22,[27][28][29][30][31][32][33][34]. One-way ANOVA was used for statistical evaluations of significant differences between various experimental groups.…”

“…Akt and GSK-3β modulated PDT-induced death of MRN and glial cells in an uncoordinated manner, not as an integrated signaling pathway but separately. We have suggested that the pro-necrotic activity of Akt could be associated with its ability to inhibit anti-oxidant enzymes and stimulate generation of reactive oxygen species [27].…”