Overexpression of the neurotrophic cytokine S100 beta in human temporal lobe epilepsy.

Neuritic sprouting and disturbances of calcium homeostasis are well described in epilepsy. S100 beta is an astrocyte-derived cytokine that promotes neurite growth and induces increases in levels of intracellular calcium in neurons. In sections of neocortex of surgically resected temporal lobe tissue from patients with intractable epilepsy, we found that the number of S100 beta-immunoreactive astrocytes was approximately threefold higher than that found in control patients (p < 0.001). These astrocytes were activated, i.e., enlarged, and had prominent processes. Temporal lobe tissue levels of S100 beta were shown by ELISA to be fivefold higher in 21 epileptics than in 12 controls (p < 0.001). The expression of the astrocyte intermediate filament protein, glial fibrillary acidic protein, was not significantly elevated in epileptics, suggesting a selective up-regulation of S100 beta expression. Our findings, together with established functions of S100 beta, suggest that this neurotrophic cytokine may be involved in the pathophysiology of epilepsy.