Са2+- and NF-κB-dependent generation of NO in the photosensitized neurons and satellite glial cells

Abstract

Photodynamic therapy (PDT) is used for killing of malignant cells in tumors including brain cancer. It can also damage normal neurons and glial cells. Nitric oxide (NO) is known to control PDT-induced cell death. To study the mechanisms that regulate NO generation in photosensitized neurons and glial cells, we used a simple model object - isolated crayfish mechanoreceptor that consists of a single sensory neuron surrounded by glial cells. PDT induced NO generation in glial cells, neuronal dendrites, and, less, in soma and axon. Using modulators of the cytosolic Ca²⁺ level and nuclear factor-kappa B (NF-κB) activity, we showed that Ca²⁺ and NF-κB regulate NO generation in the photosensitized neurons and glia. Actually, NO production was stimulated by 4-fold cadmium chloride (CdCl₂) concentration in the saline, Ca²⁺ ionophore ionomycine, or inhibition of Ca²⁺-ATPase in the endoplasmic reticulum by 2,5-ditert-butylbenzene-1,4-diol (tBuBHQ). Oppositely, CdCl₂ or nifedipine, blockers of Ca²⁺ channels in the plasma membrane, decreased NO generation. NO production was also inhibited by S-methylthiouronium sulfate (SMT), inhibitor of Ca²⁺-independent inducible NO synthase. SMT also prevented the stimulation of PDT-induced NO generation by NF-κB activator prostratin. This suggests the involvement of both Ca²⁺-dependent neuronal NO synthase and Ca²⁺-independent inducible NO synthase, which is regulated by NF-κB, in NO production in the crayfish neurons and glia.

Keywords: Ca(2+); Glia; NF-κB; Neuron; Nitric oxide; PDT.