Effect of Cu²⁺ on the Nucleoli of Cultured Astrocytes from the Rat Cerebral Cortex

Cultured astrocytes were incubated with CuCl₂, which caused dose-dependent cell death (25-200 μM, 24 h). Immunocytochemical detection of the nucleolar protein nucleophosmin/B23 (NPM/B23) demonstrated that exposure to Cu²⁺ (100 μM, 24 h) caused a significant increase in the surface area of NPM/B23 clusters, which was accompanied by the changes in the nucleolar ultrastructure characteristic of nucleolar stress. Longer incubation of astrocytes with Cu²⁺ (100 μM, 48 h) led to accumulation of the endoplasmic reticulum (ER) stress marker GRP78, which was accompanied by the increase in nucleolar size and migration of the nucleolar material into the nucleoplasm.