Induction of tumor necrosis factor alpha in cultured glial cells by trimethyltin

Within the central nervous system, cytokines are thought to play an active role in pathophysiological changes seen in various neurodegenerative diseases and trauma. Previous studies in our laboratory demonstrated that systemic administration of the neurotoxicant trimethyltin (TMT) produced a rapid and sustained elevation of CNS TNF alpha mRNA levels. In order to examine the effects of TMT on glial cultures in the absence of a neuronal component, primary glial cultures were exposed to TMT. Cultured glial cells undergo distinct morphological changes within 6 h of exposure to 10 microM TMT. This is characterized by an initial retraction of astrocytic processes revealing long, thin GFAP-dense processes and enlarged cell bodies, progressing to distinct retraction of plasmalemmna processes by 24 h. Prior to morphological changes, mRNA levels for the astrocyte-specific protein, glial fibrillary acidic protein (GFAP), increased within 3 h, as determined by Northern blot hybridization. Approximately a four-fold increase in TNF alpha mRNA levels was observed after 6 h as determined by competitive RT-PCR. This stimulation resulted in a 10-fold increase in the biologically active form of TNF alpha protein. These results suggest that a direct stimulation of glial cells may produce an early and critical response of the nervous system in chemical-induced neurotoxicity.