Xiao-Peng Hu

Advanced research on acteoside for chemistry and bioactivities

Acteoside is one kind of phenylethanoid glycoside, which has shown a lot of biological activities. This article reviewed the study progress of acteoside, such as distribution, preparation, identification, and bioactivities.

Inhibition of autophagosome-lysosome fusion by ginsenoside Ro via the ESR2-NCF1-ROS pathway sensitizes esophageal cancer cells to 5-fluorouracil-induced cell death via the CHEK1-mediated DNA damage checkpoint

ABSTRACT Modulation of autophagy has been increasingly regarded as a promising cancer therapeutic approach. In this study, we screened several ginsenosides extracted from Panax ginseng and identified ginsenoside Ro (Ro) as a novel autophagy inhibitor. Ro blocked the autophagosome-lysosome fusion process by raising lysosomal pH and attenuating lysosomal cathepsin activity, resulting in the accumulation of the autophagosome marker MAP1LC3B/LC3B and SQSTM1/p62 (sequestosome 1) in various esophageal cancer cell lines. More detailed studies demonstrated that Ro activated ESR2 (estrogen receptor 2), which led to the activation of NCF1/p47PHOX (neutrophil cytosolic factor 1), a subunit of NADPH oxidase, and subsequent reactive oxygen species (ROS) production. Treatment with siRNAs or inhibitors of the ESR2-NCF1-ROS axis, such as N-acetyl-L-cysteine (NAC), diphenyleneiodonium chloride (DPI), apocynin (ACN), Tiron, and Fulvestrant apparently decreased Ro-induced LC3B-II, GFP-LC3B puncta, and SQSTM1, indicating that ROS instigates autophagic flux inhibition triggered by Ro. More importantly, suppression of autophagy by Ro sensitized 5-fluorouracil (5-Fu)-induced cell death in chemoresistant esophageal cancer cells. 5-Fu induced prosurvival autophagy, and by inhibiting such autophagy, siRNAs against BECN1/beclin 1, ATG5, ATG7, and LC3B enhanced 5-Fu-induced autophagy-associated and apoptosis-independent cell death. We observed that Ro potentiates 5-Fu cytotoxicity via delaying CHEK1 (checkpoint kinase 1) degradation and downregulating DNA replication process, resulting in the delayed DNA repair and the accumulation of DNA damage. In summary, these data suggest that Ro is a novel autophagy inhibitor and could function as a potent anticancer agent in combination therapy to overcome chemoresistance.

Gypenoside L inhibits autophagic flux and induces cell death in human esophageal cancer cells through endoplasm reticulum stress-mediated Ca 2+ release

Esophageal cancer is one of the leading cause of cancer mortality in the world. Due to the increased drug and radiation tolerance, it is urgent to develop novel anticancer agent that triggers nonapoptotic cell death to compensate for apoptosis resistance. In this study, we show that treatment with gypenoside L (Gyp-L), a saponin isolated from Gynostemma pentaphyllum, induced nonapoptotic, lysosome-associated cell death in human esophageal cancer cells. Gyp-L-induced cell death was associated with lysosomal swelling and autophagic flux inhibition. Mechanistic investigations revealed that through increasing the levels of intracellular reactive oxygen species (ROS), Gyp-L triggered protein ubiquitination and endoplasm reticulum (ER) stress response, leading to Ca2+ release from ER inositol trisphosphate receptor (IP3R)-operated stores and finally cell death. Interestingly, there existed a reciprocal positive-regulatory loop between Ca2+ release and ER stress in response to Gyp-L. In addition, protein synthesis was critical for Gyp-L-mediated ER stress and cell death. Taken together, this work suggested a novel therapeutic option by Gyp-L through the induction of an unconventional ROS-ER-Ca2+-mediated cell death in human esophageal cancer.

NOX2-Mediated TFEB Activation and Vacuolization Regulate Lysosome-Associated Cell Death Induced by Gypenoside L, a Saponin Isolated from Gynostemma pentaphyllum

Downregulation of apoptotic signal pathway and activation of protective autophagy mainly contribute to the chemoresistance of tumor cells. Therefore, exploring efficient chemotherapeutic agents or isolating novel natural products that can trigger nonapoptotic and nonautophagic cell death such as lysosome-associated death is emergently required. We have recently extracted a saponin, gypenoside L (Gyp-L), from Gynostemma pentaphyllum and showed that Gyp-L was able to induce nonapoptotic cell death of esophageal cancer cells associated with lysosome swelling. However, contributions of vacuolization and lysosome to cell death remain unclear. Herein, we reveal a critical role for NADPH oxidase NOX2-mediated vacuolization and transcription factor EB (TFEB) activation in lysosome-associated cell death. We found that Gyp-L initially induced the abnormal enlarged and alkalized vacuoles, which were derived from lipid rafts dependent endocytosis. Besides, NOX2 was activated to promote vacuolization and mTORC1-independent TFEB-mediated lysosome biogenesis. Finally, raising lysosome pH could enhance Gyp-L induced cell death. These findings suggest a protective role of NOX2-TFEB-mediated lysosome biogenesis in cancer drug resistance and the tight interaction between lipid rafts and vacuolization. In addition, Gyp-L can be utilized as an alternative option to overcome drug-resistance though inducing lysosome associated cell death.