Heat shock, but not the reactive state per se, induces increased expression of the small stress proteins hsp25 and αB-crystallin in glial cells in vitro

The stress proteins hsp25 and αB-crystallin are found in increased concentrations in reactive astrocytes of brains undergoing neurodegeneration. In order to characterize this reaction, we investigated the expression of hsp25 and αB-crystallin during growth and after stress (heat shock) in glial cells in vitro. In primary rat brain cultures, hsp25 was present in actively dividing astrocytes that were positive for glial fibrillary acidic protein. αB-crystallin was found predominantly in oligodendrocytes. Heat shock resulted in increased concentrations of hsp25 and αB-crystallin in astrocytes, without any detectable changes in intracellular localization, as detectable with confocal laser microscopy. These results indicate that a neurodegeneration-related increase of the small stress proteins in astrocytes is independent of gliosis per se, and may be a disease-related event.