1. Melatonin, a novel selective ATF-6 inhibitor, induces human hepatoma cell apoptosis through COX-2 downregulation.
- Author
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Bu LJ, Yu HQ, Fan LL, Li XQ, Wang F, Liu JT, Zhong F, Zhang CJ, Wei W, Wang H, and Sun GP
- Subjects
- Activating Transcription Factor 6 genetics, Down-Regulation, Hep G2 Cells, Humans, In Situ Nick-End Labeling, Liver Neoplasms, Proto-Oncogene Proteins c-bcl-2 metabolism, RNA Interference, RNA, Messenger metabolism, RNA, Small Interfering, Reverse Transcriptase Polymerase Chain Reaction, Signal Transduction, Tunicamycin pharmacology, bcl-2-Associated X Protein metabolism, Activating Transcription Factor 6 antagonists & inhibitors, Antioxidants pharmacology, Apoptosis drug effects, CCAAT-Enhancer-Binding Proteins metabolism, Cyclooxygenase 2 metabolism, Endoplasmic Reticulum Stress drug effects, Melatonin pharmacology, Unfolded Protein Response drug effects
- Abstract
Aim: To clarify the mechanisms involved in the critical endoplasmic reticulum (ER) stress initiating unfolded protein response pathway modified by melatonin., Methods: Hepatoma cells, HepG2, were cultured in vitro . Flow cytometry and TUNEL assay were used to measure HepG2 cell apoptosis. Western blotting and quantitative reverse transcription-polymerase chain reaction methods were used to determine the protein and messenger RNA levels of ER stress and apoptosis related genes' expression, respectively. Tissue microarray construction from patients was verified by immunohistochemical analysis., Results: In the present study, we first identified that melatonin selectively blocked activating transcription factor 6 (ATF-6) and then inhibited cyclooxygenase-2 (COX-2) expression, leading to enhanced liver cancer cell apoptosis under ER stress condition. Dramatically increased CCAAT-enhancer-binding protein homologous protein level, suppressed COX-2 and decreased Bcl-2/Bax ratio by melatonin or ATF-6 siRNA contributed the enhanced HepG2 cell apoptosis under tunicamycin (an ER stress inducer) stimulation. In clinical hepatocellular carcinoma patients, the close relationship between ATF-6 and COX-2 was further confirmed., Conclusion: These findings indicate that melatonin as a novel selective ATF-6 inhibitor can sensitize human hepatoma cells to ER stress inducing apoptosis., Competing Interests: Conflict-of-interest statement: No conflicts of interest exist for any of the authors.
- Published
- 2017
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