Dynamics of ultrastructural alterations in photosensitized crayfish glial and neuronal cells: Structures involved in transport processes and neuroglial interactions.

Photodynamic therapy (PDT) is used for cancer treatment, including brain tumors. To explore the dynamics of photodynamic injury of glial cells and neurons and corresponding neuroglial interactions, we studied ultrastructure of the PDT-treated crayfish stretch receptor that consists of a single sensory neuron enwrapped by glial cells. Just after PDT, swelling of some mitochondria, dictyosomes, and endoplasmic reticulum cisterns occurred in neurons and glial cells. Tubular lattices involved in intraglial transport became swollen and disintegrated. At 1 hr postirradiation, these alterations were expanded to the whole cells. Segregation of the neuronal cytoplasm by Nissl bodies, which were involved in protein synthesis and transport along neurites, was lost. Swelling of submembrane cisterns prevented formation of glial protrusions and double-wall vesicles involved in the glia-to-neuron transport. Five hours later, glial layers lost organelles, stuck together, or dilated locally as a result of edema. In the neuronal cytoplasm, only demises of ER and swollen mitochondria were present, but few mitochondria retained normal structure. Thus, swelling of intracellular organelles, the first sign of photodynamic injury, occurred simultaneously in neurons and glia, but glial organelles were eliminated more quickly. Therefore, glial cells were less resistant to PDT than neurons. Adjacent glial layers were damaged less than remote ones, suggesting their protection by the neuron. The structures involved in glia-to-neuron (neuronal submembrane cisterns, glial protrusions, double-wall vesicles), intraglial (tubular lattices), and intraneuronal (Nissl bodies, Golgi apparatus, microtubular bundles) transport were impaired at the earlier stages of stretch receptor damage.