Dihydrocapsaicin (DHC), a saturated structural analog of capsaicin, induces autophagy in human cancer cells in a catalase-regulated manner.
Although capsaicin, a pungent component of red pepper, is known to induce apoptosis in several types of cancer cells, the mechanisms underlying capsaicin-induced cytotoxicity are unclear. Here, we showed that dihydrocapsaicin (DHC), an analog of capsaicin, is a potential inducer of autophagy. DHC was more cytotoxic than capsaicin in HCT116, MCF-7 and WI38 cell lines. Capsaicin and DHC did not affect the sub-G(1) apoptotic peak, but induced G(0)/G(1) arrest in HCT116 and MCF-7 cells. DHC caused the artificial autophagosome marker GFP-LC3 to redistribute and upregulated expression of autophagy-related proteins. Blocking of autophagy by 3-methyladenine (3MA) as well as siRNA Atg5 induced a high level of caspase-3 activation. Although pretreatment with zVAD completely inhibited caspase-3 activation by 3MA, it did not prevent cell death. DHC-induced autophagy was enhanced by zVAD pretreatment, as shown by increased accumulation of LC3-II protein. DHC attenuated basal ROS levels through catalase induction; this effect was enhanced by antioxidants, which increased both LC3-II expression and caspase-3 activation. The catalase inhibitor 3-amino-1,2,4-triazole (3AT) abrogated DHC-induced expression of LC3-II, overexpression of the catalase gene increased expression of LC3-II protein, and knockdown decreased it. Additionally, DHC-induced autophagy was independent of p53 status. Collectively, DHC activates autophagy in a p53-independent manner and that may contribute to cytotoxicity of DHC.
Oh
Seon Hee
SH
DNA Repair Research Center, Dong-Gu, Gwangju, Korea.
Kim
Young Soon
YS
Lim
Sung Chul
SC
Hou
Yi Feng
YF
Chang
In Youb
IY
You
Ho Jin
HJ
D000225:Adenine / Q000031:analogs & derivatives / Q000494:pharmacology; D000640:Amitrole / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects; D001343:Autophagy / Q000187:drug effects; D000071187:Autophagy-Related Protein 5; D002211:Capsaicin / Q000031:analogs & derivatives* / Q000737:chemistry / Q000494:pharmacology; D053148:Caspase 3 / Q000378:metabolism; D002374:Catalase / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D045744:Cell Line, Tumor; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D008869:Microtubule-Associated Proteins / Q000037:antagonists & inhibitors / Q000235:genetics; D009369:Neoplasms / Q000201:enzymology*; D034741:RNA, Small Interfering / Q000235:genetics; D017382:Reactive Oxygen Species / Q000378:metabolism
C502778:ATG5 protein, human; D000071187:Autophagy-Related Protein 5; D004791:Enzyme Inhibitors; D008869:Microtubule-Associated Proteins; D034741:RNA, Small Interfering; D017382:Reactive Oxygen Species; C025946:3-methyladenine; D002374:Catalase; D053148:Caspase 3; D000225:Adenine; D002211:Capsaicin; C012906:dihydrocapsaicin; D000640:Amitrole