Photodynamic Inactivation of Isolated Crayfish Mechanoreceptor Neuron: Different Death Modes Under Different Photosensitizer Concentrations¶

Abstract

To study the mechanism of photodynamic nerve cell killing, isolated crayfish mechanoreceptor neurons were photosensitized by the sulfonated aluminum ophthalocyanine Photosens. Neuron activity was continuously recorded until irreversible abolition. Intense (10(-5) M Photosens) or weak (10(-7) M Photosens) photosensitization induced different bioelectric neuron responses: firing activation followed by irreversible depolarization block or gradual inhibition until firing abolition, respectively. These bioelectric responses were accompanied by different biochemical and morphological changes. In the case of intense photosensitization, neuron nuclei swelled and then shrank. Succinate dehydrogenase (SDH) was inhibited, and the plasma membrane was compromised just after firing cessation. Weak photosensitization did not induce these changes but caused swelling of the endoplasmic reticulum and destruction of the matrix, cristae and membranes in some of the mitochondria. Other mitochondria, however, retained the normal structure. Plasma membrane damage, SDH inhibition, nucleus shrinkage and impairment of the nuclear border occurred after 2-4 h. It is concluded that intense photosensitization induced necrotic processes during irradiation, whereas weaker impact caused delayed necrosis 2-4 h later. The observed electrophysiological neuron responses to photodynamic therapy may be considered as early hallmarks of different modes of forthcoming cell death.

Protection of Crayfish Glial Cells but not Neurons from Photodynamic Injury by Nerve Growth Factor

“…4b-9b and 4c-9c, respectively). Nucleus fragmentation or chromatin clumping into big dense masses characteristic of apoptosis were never observed in isolated, photosensitized, or chemically treated SN like in our previous experiments (Uzdensky et al 2002. Unlike SN, apoptosis of untreated SGC was sometimes registered within 8 h after isolation (Figs.…”

“…We did not observe apoptosis of crayfish SN treated by PDT or chemical pro-apoptotic agents (Uzdensky et al 2002. It could be intrinsically blocked like in various adult vertebrate neurons (Benn and Woolf 2004).…”

“…3). The mean duration of such neuronal response called "neuron lifetime" as in our previous works (Uzdensky et al 2002 varied from 7 to 25 min in different experimental series. At 8 h after PDT, neuronal and glial nuclei shrank.…”

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

“…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].…”

“…After following 30-min incubation in the dark, cells were irradiated for 30 min by a helium-neon (633 nm) or diode laser (670 nm) until irreversible firing abolition that occurred typically within 15-25 min. 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].…”