On involvement of transcription factors nuclear factor kappa-light-chain-enhancer of activated B cells, activator protein-1 and signal transducer and activator of transcription-3 in photodynamic therapy-induced death of crayfish neurons and satellite glial cells.

Photodynamic therapy (PDT) is currently used in the treatment of brain tumors. However, not only malignant cells but also neighboring normal neurons and glial cells are damaged during PDT. In order to study the potential role of transcription factors-nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB), activator protein (AP-1), and signal transducer and activator of transcription-3 (STAT-3)-in photodynamic injury of normal neurons and glia, we photosensitized the isolated crayfish mechanoreceptor consisting of a single sensory neuron enveloped by glial cells. Application of different inhibitors and activators showed that transcription factors NF-κB (inhibitors caffeic acid phenethyl ester and parthenolide, activator betulinic acid), AP-1 (inhibitor SR11302), and STAT-3 (inhibitors stattic and cucurbitacine) influenced PDT-induced death and survival of neurons and glial cells in different ways. These experiments indicated involvement of NF-κB in PDT-induced necrosis of neurons and apoptosis of glial cells. However, in glial cells, it played the antinecrotic role. AP-1 was not involved in PDT-induced necrosis of neurons and glia, but mediated glial apoptosis. STAT-3 was involved in PDT-induced apoptosis of glial cells and necrosis of neurons and glia. Therefore, signaling pathways that regulate cell death and survival in neurons and glial cells are different. Using various inhibitors or activators of transcription factors, one can differently influence the sensitivity and resistance of neurons and glial cells to PDT.

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

Oxidative stress is the reason of diverse neuropathological processes. Photodynamic therapy (PDT), an effective inducer of oxidative stress, is used for cancer treatment, including brain tumors. We studied the role of various signaling pathways in photodynamic injury and protection of single neurons and satellite glial cells in the isolated crayfish mechanoreceptor. It was photosensitized with alumophthalocyanine Photosens in the presence of inhibitors or activators of various signaling proteins. PDT eliminated neuronal activity and killed neurons and glial cells. Inhibitory analysis showed the involvement of protein kinases Akt, glycogen synthase kinase-3ß (GSK-3ß), mammalian target of rapamycin (mTOR), mitogen-activated protein kinase kinases 1 and 2 (MEK1/2), calmodulin, calmodulin-dependent kinase II (CaMKII), adenylate cyclase, and nuclear factor NF-κB in PDT-induced necrosis of neurons. Nitric oxide (NO) and glial cell-derived neurotrophic factor (GDNF) reduced neuronal necrosis. In glial cells, protein kinases Akt, calmodulin, and CaMKII; protein kinases C and G, adenylate cyclase, and p38; and nuclear transcription factor NF-κB also mediated PDT-induced necrosis. In contrast, NO and neurotrophic factors nerve growth factor (NGF) and GDNF demonstrated anti-necrotic activity. Phospholipase Cγ, protein kinase C, GSK-3ß, mTOR, NF-κB, mitochondrial permeability transition pores, and NO synthase mediated PDT-induced apoptosis of glial cells, whereas protein kinase A, tyrosine phosphatases, and neurotrophic factors NGF, GDNF, and neurturin were involved in protecting glial cells from photoinduced apoptosis. Signaling pathways that control cell survival and death differed in neurons and glia. Inhibitors or activators of some signaling pathways may be used as potential protectors of neurons and glia from photooxidative stress and following death.

Involvement of nitric oxide in photodynamic injury of neurons and glial cells.

Photodynamic therapy (PDT) is a potential tool for treatment of brain tumors. However, not only malignant but also healthy neurons and glial cells may be damaged during PDT. Nitric oxide is an important modulator of cell viability and intercellular neuroglial communications. In order to study its role in photodynamic injury of normal neurons and surrounding glial cells, we used the crayfish stretch receptor that consists of only two identified sensory neurons enveloped by glial cells. Photodynamic treatment with alumophthalocyanine Photosens and diode laser (670 nm, 0.4 W/cm(2)) induced firing elimination, necrosis of neurons and glia, and apoptosis of glial cells. NO generated by exogenous generators NONOate or sodium nitroprussside protected neurons and glial cells from PDT-induced necrosis but enhanced PDT-induced apoptosis of glial cells. Application of various inhibitors of NO synthase showed that the anti-necrotic effect of NO could be related, at least in glial cells, to its production by neuronal rather than inducible isoform of this enzyme. Unlike, the pro-apoptotic effect of NO on glial cells could be, at least in part, associated with inducible NO synthase. The proapoptotic effect of NO on glial cells could be mediated by protein kinase G, which is activated by NO-dependent production of cGMP, because it inhibition reduced the PDT-induced glial apoptosis.

Protection effect of GDNF and neurturin on photosensitized crayfish neurons and glial cells.

Neurons and glial cells can protect each other from stress and following death by mutual exchange with neurotrophins. In order to examine involvement of different neurotrophic factors in neuroglial interactions in a photosensitized crayfish stretch receptor, a simple model object consisting of only two sensory neurons enveloped by glial cells, we studied the influence of glial cell line-derived neurotrophic factor (GDNF), neurturin, and ciliary neurotrophic factor (CNTF) on its photodynamic injury. Photodynamic treatment, which causes strong oxidative stress, induced firing abolition and necrosis of neurons, necrosis, and apoptosis of glial cells. GDNF significantly reduced photoinduced neuronal necrosis and neurturin but not CNTF showed a similar tendency. Both of them significantly reduced necrosis and apoptosis of glial cells. At the ultrastructural level, neurons and glial cells treated with GDNF in the darkness contained large mitochondria with well-developed cristae, numerous ribosomes, polysomes, rough endoplasmic reticulum (ER), and dictyosomes. This indicated the high level of bioenergetic, biosynthetic, and transport processes. Photodynamic treatment caused swelling and vacuolization of mitochondria, dictyosomes, and ER. It also impaired formation of glial protrusions and double membrane vesicles that transfer glial material into the neuron. GDNF prevented photoinduced mitochondria swelling that disturbed the cellular bioenergetics and cytoplasm vacuolization associated with injury of intracellular organelles. It also preserved the structures involved in protein synthesis and transport: rough ER, dictyosomes, polysomes, microtubule bundles, submembrane cisterns, and double membrane vesicles. GDNF-mediated maintenance of metabolism and ultrastructure of photosensitized neurons and glial cells may be the basis of its neuro- and glia protective effects.

On the role of phosphatidylinositol 3-kinase, protein kinase b/Akt, and glycogen synthase kinase-3ß in photodynamic injury of crayfish neurons and glial cells.

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-3ß participated in photoinduced apoptosis of glial cells and in necrosis of neurons. Therefore, phosphatidylinositol 3-kinase/protein kinase Akt/glycogen synthase kinase-3ß pathway was not involved as a whole in photodynamic injury of crayfish neurons and glia but its components, Akt and glycogen synthase kinase-3ß, 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.