Cardioprotection by resveratrol: a novel mechanism via autophagy involving the mTORC2 pathway.
OBJECTIVE
On the basis of our previous reports that cardioprotection induced by ischaemic preconditioning induces autophagy and that resveratrol, a polyphenolic antioxidant present in grapes and red wine induces preconditioning-like effects, we sought to determine if resveratrol could induce autophagy.


RESULTS
Resveratrol at lower doses (0.1 and 1 microM in H9c2 cardiac myoblast cells and 2.5 mg/kg/day in rats) induced cardiac autophagy shown by enhanced formation of autophagosomes and its component LC3-II after hypoxia-reoxygenation or ischaemia-reperfusion. The autophagy was attenuated with the higher dose of resveratrol. The induction of autophagy was correlated with enhanced cell survival and decreased apoptosis. Treatment with rapamycin (100 nM), a known inducer of autophagy, did not further increase autophagy compared with resveratrol alone. Autophagic inhibitors, wortmannin (2 microM) and 3-methyladenine (10 mM), significantly attenuated the resveratrol-induced autophagy and induced cell death. The activation of mammalian target of rapamycin (mTOR) was differentially regulated by low-dose resveratrol, i.e. the phosphorylation of mTOR at serine 2448 was inhibited, whereas the phosphorylation of mTOR at serine 2481 was increased, which was attenuated with a higher dose of resveratrol. Although resveratrol attenuated the activation of mTOR complex 1, low-dose resveratrol significantly induced the expression of Rictor, a component of mTOR complex 2, and activated its downstream survival kinase Akt (Ser 473). Resveratrol-induced Rictor was found to bind with mTOR. Furthermore, treatment with Rictor siRNA attenuated the resveratrol-induced autophagy.


CONCLUSIONS
Our results indicate that at lower dose, resveratrol-mediated cell survival is, in part, mediated through the induction of autophagy involving the mTOR-Rictor survival pathway.
Gurusamy
Narasimman
N
Cardiovascular Research Center, University of Connecticut School of Medicine, Farmington, CT 06030-1110, USA.
Lekli
Istvan
I
Mukherjee
Subhendu
S
Ray
Diptarka
D
Ahsan
Md Kaimul
MK
Gherghiceanu
Mihaela
M
Popescu
Lawrence M
LM
Das
Dipak K
DK
D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D001343:Autophagy / Q000187:drug effects* / Q000502:physiology; D002316:Cardiotonic Agents / Q000494:pharmacology*; D002352:Carrier Proteins / Q000378:metabolism*; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism*; D008297:Male; D032386:Myoblasts, Cardiac / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D009206:Myocardium / Q000166:cytology; D010766:Phosphorylation / Q000187:drug effects; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D000076226:Rapamycin-Insensitive Companion of mTOR Protein; D051381:Rats; D017207:Rats, Sprague-Dawley; D000077185:Resveratrol; D013267:Stilbenes / Q000494:pharmacology*; D058570:TOR Serine-Threonine Kinases; D014157:Transcription Factors / Q000378:metabolism
D002316:Cardiotonic Agents; D002352:Carrier Proteins; C519510:Crtc1 protein, rat; D047908:Intracellular Signaling Peptides and Proteins; D000076226:Rapamycin-Insensitive Companion of mTOR Protein; D013267:Stilbenes; D014157:Transcription Factors; C550254:rictor protein, rat; C546845:mTOR protein, rat; D017346:Protein Serine-Threonine Kinases; D058570:TOR Serine-Threonine Kinases; D000077185:Resveratrol