Photodynamic damage of glial cells in crayfish ventral nerve cord

Abstract

Photodynamic therapy (PDT) is a promising method for treatment of brain tumors, the most of which are of glial origin. In the present work we studied PDT-mediated injury of glial cells in nerve tissue, specifically, in abdominal connectives in the crayfish ventral nerve cord. The preparation was photosensitized with alumophthalocyanine Photosens and irradiated 30 min with the diode laser (670 nm, 0.1 or 0.15 W/cm 2 ). After following incubation in the darkness during 1-10 hours it was fluorochromed with Hoechst 33342 and propidium iodide to reveal nuclei of living, necrotic and apoptotic cells. The chain-like location of the glial nuclei allowed visualization of those enveloping giant axons and blood vessels. The level of glial necrosis in control preparations was about 2-5 %. Apoptosis was not observed in control preparations. PDT significantly increased necrosis of glial cells to 52 or 67 % just after irradiation with 0.1 or 0.15 W/cm 2 , respectively. Apoptosis of glial cells was observed only at 10 hours after light exposure. Upper layers of the glial envelope of the connectives were injured stronger comparing to deep ones: the level of glial necrosis decreased from 100 to 30 % upon moving from the connective surface to the plane of the giant axon inside the connective. Survival of glial cells was also high in the vicinity of blood vessels. One can suggest that giant axons and blood vessels protect neighboring glial cells from photodynamic damage. The mechanism of such protective action remains to be elucidated.

Assessment of Neuroglial Relationships under Photodynamic Treatment Using Fluorescent Visualization of Giant Axons in Crayfish Ventral Nerve Cord

“…Observed phenomenon of increased survival of the glial cells in the direct proximity from neurons' axons may have several suppositional reasons. In our previous work with slightly different design of experiment [13], where we had seen the same effect in the crayfish ventral nerve cord under photo oxidation, we excluded such possible reasons of the phenomena as lack of photosensitizer and light power in the deep nerve tissue layers near the axons. Therefore the observed effect of increased survival of the glial cells as one approached to the giant axons, could be consequence of glia protective neuroglial interactions in the crayfish VNC.…”