Background: All known mechanisms of apoptosis induced by resveratrol act through cell cycle arrest and changes in mitochondrial membrane potential. It is currently unknown whether resveratrol-induced apoptosis is associated with other physiological processes, such as autophagy.
Methods: Apoptosis-related markers involved in the intrinsic and extrinsic apoptotic pathways, and autophagic markers were detected by using western blotting and immunofluorescence. Mitochondrial membrane potential was assayed by flow cytometry. Pharmaceutical or genetic inhibition of autophagy involved were carried by 3- methyladenine or knockdown of autophagy-related (Atg) genes by siRNA. Differences between two values were tested by Student's unpaired t test.
Results: We show that resveratrol-induced apoptosis occurs through both the intrinsic and extrinsic apoptotic pathways. Mitochondrial membrane potential and apoptosis-related markers, such as an increased Bax/Bcl-2 ratio, and cleaved forms of caspase-8 and caspase-3, arise following resveratrol addition. Moreover, we find that resveratrol increases both the levels of microtubule-associated protein 1 light chain 3-II and the number of autophagosomes, and further demonstrate that resveratrol-induced autophagy depends on the LKB1-AMPK-mTOR pathway. We next reveal that some apoptosis-related markers induced by resveratrol are further attenuated by the inhibition of autophagy with 3-methyladenine or knockdown of autophagy-related (Atg) genes by siRNA.
Conclusions: These results suggest that resveratrol induced apoptotic cell death of HL-60 cells depends on the autophagy activated through both the LKB1-AMPK and PI3K/AKT-regulated mTOR signaling pathways.
Keywords: AMPK-mTOR; Apoptosis; Autophagy; Cell death; HL-60; PI3K-Akt; Resveratrol.