ER-Dependent Ca++-mediated Cytosolic ROS as an Effector for Induction of Mitochondrial Apoptotic and ATM-JNK Signal Pathways in Gallic Acid-treated Human Oral Cancer Cells

• Published in: Anticancer research 2016-02, Vol.36 (2), p.697-705
• Main Authors: Lu, Yao-Cheng, Lin, Meng-Liang, Su, Hong-Lin, Chen, Shih-Shun
• Format: Article
• Language: English
• Subjects: Antineoplastic Agents - pharmacology; Antioxidants - pharmacology; Apoptosis - drug effects; Ataxia Telangiectasia Mutated Proteins - antagonists & inhibitors; Ataxia Telangiectasia Mutated Proteins - genetics; Ataxia Telangiectasia Mutated Proteins - metabolism; Calcium Signaling - drug effects; Cell Line, Tumor; Cytosol - metabolism; Endoplasmic Reticulum - drug effects; Endoplasmic Reticulum - enzymology; Enzyme Activation; Gallic Acid - pharmacology; Humans; JNK Mitogen-Activated Protein Kinases - antagonists & inhibitors; JNK Mitogen-Activated Protein Kinases - metabolism; Membrane Potential, Mitochondrial - drug effects; Mitochondria - drug effects; Mitochondria - enzymology; Mitochondria - pathology; Mouth Neoplasms - drug therapy; Mouth Neoplasms - enzymology; Mouth Neoplasms - genetics; Mouth Neoplasms - pathology; Oxidative Stress - drug effects; Phosphorylation; Protein Kinase Inhibitors - pharmacology; Reactive Oxygen Species - metabolism; RNA Interference; Time Factors; Transfection
• ISSN: 1791-7530

Release of calcium (Ca(++)) from the endoplasmic reticulum (ER) has been proposed to be involved in induction of apoptosis by oxidative stress. Using inhibitor of ER Ca(++) release dantrolene and inhibitor of mitochondrial Ca(++) uptake Ru-360, we demonstrated that Ca(++) release from the ER was associated with generation of reactive oxygen species (ROS), loss of mitochondrial membrane potential, and apoptosis of human oral cancer (OC) cells induced by gallic acid (GA). Small interfering RNA-mediated suppression of protein kinase RNA-like endoplasmic reticulum kinase inhibited tunicamycin-induced induction of 78 kDa glucose-regulated protein, C/EBP homologous protein, pro-caspase-12 cleavage, cytosolic Ca(++) increase and apoptosis, but did not attenuate the increase in cytosolic Ca(++) level and apoptosis induced by GA. Ataxia telangiectasia mutated (ATM)-mediated c-Jun N-terminal kinase (JNK) phosphorylation and apoptosis by GA was blocked by dantrolene. The specificity of ROS-mediated ATM-JNK activation was confirmed by treatment with N-acetylcysteine, a ROS scavenger. Blockade of ATM activation by specific inhibitor KU55933, short hairpin RNA, or kinase-dead ATM overexpression suppressed JNK phosphorylation but did not completely inhibit cytosolic ROS production, mitochondrial cytochrome c release, pro-caspase-3 cleavage, and apoptosis induced by GA. Taken together, these results indicate that GA induces OC cell apoptosis by inducing the activation of mitochondrial apoptotic and ATM-JNK signal pathways, likely through ER Ca(++)-mediated ROS production.