The role of the tumor necrosis factor (TNF)-α convertase (TACE/ADAM17) in the adult nervous system remains poorly understood. The authors have previously demonstrated that TACE is upregulated in rat forebrain slices exposed to oxygen–glucose deprivation (OGD). They have now used rat mixed cortical cultures exposed to OGD or glutamate to study (1) TACE expression and localization, and (2) the effects of TNF-α release on cell viability. OGD- or glutamate-caused TNF-α release, an effect that was blocked by the TACE inhibitor BB3103 (BB) (0.1–1 μmol/L; control: 1.67 ± 0.59; OGD: 6.59 ± 1.52; glutamate: 3.38 ± 0.66; OGD ± BB0.1: 3.23 ± 0.67; OGD ± BB1: 1.33 ± 0.22 pg/mL, n = 6, P < 0.05). Assay of TACE activity as well as Western blot showed that TACE expression is increased in OGD- or glutamate-exposed cells. In control cultures, TACE immunoreactivity was present in some microglial cells, whereas, after OGD or glutamate, TACE immunostaining appeared in most microglial cells and in some astrocytes. Conversely, BB3103 (0.1 μmol/L) caused apoptosis after glutamate exposure as shown by annexin and Hoechst 33342 staining and caspase-3 activity, an effect mimicked by the proteasome inhibitor MG-132 (caspase activity: glutamate: 5.1 ± 0.1; glutamate + BB: 7.8 ± 0.8; glutamate + MG: 11.9 ± 0.5 pmol · min−1 mg−1 protein, n = 4, P < 0.05), suggesting that translocation of the transcription factor NF-κB mediates TNF-α–induced antiapoptotic effect. Taken together, these data demonstrate that, in rat mixed neuronal–glial cortical cultures exposed to OGD or glutamate, (1) TACE/ADAM17 activity accounts for the majority of TNF-α shedding, (2) an increase in glial TACE expression contributes to the rise in TNF-α, and (3) TNF-α release in this setting inhibits apoptosis via activation of the transcription factor NF-κB.
The individual and combined neuroprotective effects of propofol and ketamine on rat mixed cortical cultures exposed to oxygen-glucose deprivation-reperfusion injury
