Heat shock in cultured neurons and astrocytes: correlation of ultrastructure and heat shock protein synthesis

Abstract

Cultured cerebral cortical neurons and astrocytes were compared after a brief heat shock. Morphological findings were correlated with the synthesis of the 68 kD heat shock protein (HSP68). Heat shocked neurons demonstrated many severe morphological changes after exposure to temperatures of 43°C for 15 min and 45°C for 10 min. Nuclear membrane ‘blebbing’ with lysis of the membrane, chromatin clumping, and disappearance of the nucleolus were prominent after both conditions. Lysis of the cell membrane was noted in severely injured neurons; this was more prominent at the higher temperature. In addition, alterations to polyribosomes, Golgi apparatus, rough endoplasmic reticulum and mitochondria were noted in the cytoplasm of neurons after heat shock. In contrast, no significant changes were noted in either the nucleus or cytoplasm of heat shocked astrocytes. The severity of morphological changes in neurons directly correlated with the low level of induction of HSP68 in neurons. Neurons synthesized much less 68 kD heat shock protein than similarly heat shocked astrocytes. We conclude that cultured cerebral cortical neurons are more susceptible to injury after heat shock than heat resistant astrocytes and that one possible mechanism of injury is failure to synthesize adequate amounts of HSP68 after injury.