Melatonin plays a neuroprotective role against
brain injury through the activation of Akt and the inhibition of apoptotic cell death. This study investigated whether
melatonin modulates the anti-apoptotic signal through the activation of Akt and its downstream targets, FKHR, AFX, and 14-3-3. Adult male rats were treated with
melatonin (5 mg/kg) prior to
middle cerebral artery occlusion (MCAO) and brain tissues were collected at 24 hr after MCAO. This study confirmed that
melatonin significantly reduces
infarct volume and decreases the number of TUNEL-positive cells in the cerebral cortex. Potential activation was measured by phosphorylation of PDK1 at Ser(241), Akt at Ser(473), FKHR at Ser(256), and AFX at Ser(193) using Western blot analysis.
Melatonin prevented the injury-induced reduction of pPDK1, pAkt, pFKHR, and pAFX. However,
melatonin did not affect the level of 14-3-3, which acts as an anti-apoptotic factor through interaction of pFKHR. Further, in the presence of
melatonin, the interaction of pFKHR and 14-3-3 increased, compared with that of control animals. This study suggests that
melatonin plays a potent protective role against
brain injury and that Akt activation and FKHR phosphorylation by
melatonin mediated these protective effects.