Transforming Growth Factor-α Acting at the Epidermal Growth Factor Receptor Reduces Infarct Volume after Permanent Middle Cerebral Artery Occlusion in Rats

Transforming growth factor-alpha (TGF-alpha) is a ligand for the epidermal growth factor (EGF) receptor (EGFR), and is more abundant than EGF in the brain. The authors studied whether administration of exogenous TGF-alpha into the brain can protect neurons against ischemia in a model of permanent middle cerebral artery (MCA) occlusion in the rat, and whether any effect of TGF-alpha was mediated by EGFR by administering 4,5-dianilinophthalimide (DAPH), a protein-tyrosine kinase inhibitor with high selectivity for EGFR. Rats received either TGF-alpha (10 or 25 ng), DAPH (100 ng), DAPH plus TGF-alpha (25 ng), or vehicle in the ipsilateral first ventricle. Drugs were administered twice: 30 minutes before and 30 minutes after MCA occlusion, and infarct volume was evaluated 24 hours later. Transforming growth factor-alpha at the dose of 25 ng caused a statistically significant reduction of infarct volume (60%) in relation to ischemic rats administered vehicle. This reduction was no longer seen when TGF-alpha was administered in combination with DAPH. The present results show that TGF-alpha can protect neurons from ischemic damage, and that this effect is mediated by EGFR. It is suggested that activation of EGFR-mediated intracellular signalling pathways contributes to the survival of neural cells susceptible to ischemic injury.