Melatonin prevents the injury-induced decline of Akt/forkhead transcription factors phosphorylation.
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.
Koh
Phil-Ok
PO
Department of Anatomy, College of Veterinary Medicine, Research Institute of Life Science, Gyeongsang National University, Jinju, South Korea. pokoh@gsnu.ac.kr
D048948:14-3-3 Proteins / Q000378:metabolism; D000818:Animals; D000975:Antioxidants / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects*; D015153:Blotting, Western; D051858:Forkhead Transcription Factors / Q000378:metabolism*; D047468:Immunoprecipitation; D020287:In Situ Nick-End Labeling; D066298:In Vitro Techniques; D020244:Infarction, Middle Cerebral Artery / Q000503:physiopathology; D008297:Male; D008550:Melatonin / Q000494:pharmacology*; D009419:Nerve Tissue Proteins / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D000081382:Pyruvate Dehydrogenase Acetyl-Transferring Kinase; D051381:Rats; D017207:Rats, Sprague-Dawley; D000071161:Forkhead Box Protein O1
D048948:14-3-3 Proteins; D000975:Antioxidants; D051858:Forkhead Transcription Factors; D008550:Melatonin; D009419:Nerve Tissue Proteins; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D000081382:Pyruvate Dehydrogenase Acetyl-Transferring Kinase; C000631434:Pdk1 protein, rat; C074639:Foxo1 protein, rat; D000071161:Forkhead Box Protein O1