Responses of astrocyte to simultaneous glutamate and arachidonic acid treatment.

After cellular injury many endogenous toxins are released from injured cells and result in secondary injury. To elucidate mechanisms of such injury many of these toxins have been studied individually. However, the data obtained is only useful for reference and does not accurately represent the multifactorial situation under pathophysiological conditions. Primary astrocytic cultures were treated individually and simultaneously with two well-studied toxins, glutamate (Glu) and arachidonic acid (AA). Both are simultaneously released from neural cells during injury. Measurements of cellular protein content, intracellular water space, lactate dehydrogenase release, and malondialdehyde formation indicated that Glu and AA act through different mechanisms. Glu+AA applied together had a synergistic effect on the levels of Caspase-3 gene expression, and Bcl-2 and Hsp70 protein. Atomic force microscopy observed that Glu caused cell membrane roughness and nuclear swelling, while AA induced pores in the cell membrane and nuclear shrinkage. Glu+AA accelerated nuclear shrinkage and resulted in more serious cell damage. This study not only distinguishes the different responses of astrocytes to Glu and AA, but also provides a new view into the synergistic effect of these biochemicals; highlighting the need to be cautious in applying single factor experimental data to interpret complex physiological and pathological conditions in animals. Two or more factors may act not only on different targets but also on the same target synergistically.