A disintegrin and metalloprotease 17 promotes microglial cell survival via epidermal growth factor receptor signalling following spinal cord injury

Tumour necrosis factor-α (TNF-α) converting enzyme (TACE), also termed a disintegrin and metallopro-tease 17 (ADAM17), is involved in multiple cell signalling pathways. Through the secretion of epidermal growth factor receptor (EGFR) ligands, ADAM17 can activate the EGFR and is involved in various downstream signalling pathways. The present study aimed to investigate whether ADAM17-induced EGFR transactivation is involved in microglial cell survival following spinal cord injury (SCI). Reverse transcription quantitative polymerase chain reaction and western blot analysis revealed that ADAM17 was overexpressed in a mouse model following SCI. A 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay demonstrated that the viability of human microglia and oligodendrocytes were significantly reduced in a time- and dose-dependent manner following treatment with the ADAM17 antagonist, TNF protease inhibitor 2. Hoechst 33258 staining and flow cytometric analysis revealed that inhibiting ADAM17 increased the rate of cellular apoptosis in neuronal and glial cell cultures, which was accompanied by increased cleavage of caspase-3. Western blot analysis demonstrated that inhibiting ADAM17 resulted in a reduction in the phosphorylation of the EGFR signalling pathway components and thereby impaired functional recovery, inhibited cell viability and prompted microglial apoptosis following SCI. Pre-treatment with the EGFR inhibitor, AG1478, rescued the ADAM17-mediated proliferation of microglial cells. These data demonstrated that ADAM17 contributed to microglial cell survival, predominantly by EGFR signalling, following SCI.