Abstract
In our previous study, we showed that capsaicin induces autophagy in several cell lines. Here, we investigated the molecular mechanisms of capsaicin-induced autophagy in malignant (MCF-7 and MDA-MB-231) and normal (MCF10A) human breast cells. Capsaicin caused nonapoptotic cell cycle arrest of MCF-7 and MDA-MB-231 cells but induced apoptosis in MCF10A cells. In MCF-7 and MDA-MB-231 cells, capsaicin induced endoplasmic reticulum (ER) stress via inositol-requiring 1 and Chop and induced autophagy, as demonstrated by microtubule-associated protein 1 light chain-3 (LC3) conversion. Autophagy blocking by 3-methyladenine (3MA) or bafilomycin A1 (BaF1) activated caspase-4 and -7 and enhanced cell death. In MCF-7 and MDA-MB-231 cells, p38 was activated for more than 48 h by capsaicin treatment, but extracellular signal-regulated kinase (ERK) activation decreased after 12 h, and LC3II levels continuously increased. Furthermore, treatment with 3MA markedly down-regulated capsaicin-induced p38 activation and LC3 conversion, and BaF1 completely down-regulated ERK activation and led to LC3II accumulation. In addition, pharmacological blockade or knockdown of the p38 gene down-regulated Akt activation and LC3II levels but did not affect ERK, and pharmacological blockade or knockdown of the ERK gene up-regulated LC3II induction by capsaicin. Knockdown of inositol-requiring 1 down-regulated p38-Akt signaling. In MCF10A cells, capsaicin did not elicit p38 activation and LC3 conversion and caused the sustained activation of caspase-4. Collectively, capsaicin-induced autophagy is regulated by p38 and ERK; p38 controls autophagy at the sequestration step, whereas ERK controls autophagy at the maturation step, and that autophagy is involved in the retardation of cell death by blocking capsaicin-induced ER stress-mediated apoptosis in MCF-7 and MDA-MB-321 cells.
Footnotes
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↵ The online version of this article (available at http://molpharm.aspetjournals.org) contains supplemental material.
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This work was supported by the National Research Foundation of Korea, funded by the Ministry of Education, Science, and Technology through the Research Center for Resistant Cells [Grant R13-2003-009].
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Article, publication date, and citation information can be found at http://molpharm.aspetjournals.org.
doi:10.1124/mol.110.063495.
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ABBREVIATIONS:
- UPR
- unfolded protein response
- ER
- endoplasmic reticulum
- IRE1
- inositol-requiring enzyme 1
- LC3
- microtubule-associated protein 1 light chain-3
- MAPK
- mitogen-activated protein kinase
- 3MA
- 3-methyladenine
- BaF1
- bafilomycin A1
- ERK
- extracellular-regulated kinase
- MTT
- 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide
- DMSO
- dimethyl sulfoxide
- PBS
- phosphate-buffered saline
- JNK
- c-Jun N-terminal kinase
- siRNA
- short interfering RNA
- LY294002
- 2-(4-morpholinyl)-8-phenyl-1(4H)-benzopyran-4-one hydrochloride
- PD98059
- 2′-amino-3′-methoxyflavone
- SB203580
- 4-(4-fluorophenyl)-2-(4-methylsulfinylphenyl)-5-(4-pyridyl)1H-imidazole
- EB1089
- seocalcitol.
- Received January 7, 2010.
- Accepted April 6, 2010.
- Copyright © 2010 The American Society for Pharmacology and Experimental Therapeutics
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