Biomol Ther.  2020 Sep;28(5):443-455. 10.4062/biomolther.2020.122.

Auranofin Enhances Sulforaphane-Mediated Apoptosis in Hepatocellular Carcinoma Hep3B Cells through Inactivation of the PI3K/Akt Signaling Pathway

Affiliations
  • 1Department of Molecular Biology, College of Natural Sciences, Pusan National University, Busan 46241, Republic of Korea
  • 2Anti-Aging Research Center, Dong-eui University, Busan 47340, Republic of Korea
  • 3Department of Pathology, Dong-eui University College of Korean Medicine, Busan 47227, Republic of Korea
  • 4Department of Biochemistry, Dong-eui University College of Korean Medicine, Busan 47227, Republic of Korea
  • 5Division of Basic Sciences, College of Liberal Studies, Dong-eui University, Busan 47340, Republic of Korea
  • 6Department of Marine Life Sciences, School of Marine Biomedical Sciences, Jeju National University, Jeju 63243, Republic of Korea
  • 7Department of Biological Science, College of Natural Sciences, Dong-A University, Busan 49315, Republic of Korea
  • 8Jeju National University School of Medicine and Jeju Research Center for Natural Medicine, Jeju 63243, Republic of Korea

Abstract

The thioredoxin (Trx) system plays critical roles in regulating intracellular redox levels and defending organisms against oxidative stress. Recent studies indicated that Trx reductase (TrxR) was overexpressed in various types of human cancer cells indicating that the Trx-TrxR system may be a potential target for anti-cancer drug development. This study investigated the synergistic effect of auranofin, a TrxR-specific inhibitor, on sulforaphane-mediated apoptotic cell death using Hep3B cells. The results showed that sulforaphane significantly enhanced auranofin-induced apoptosis by inhibiting TrxR activity and cell proliferation compared to either single treatment. The synergistic effect of sulforaphane and auranofin on apoptosis was evidenced by an increased annexin-V-positive cells and Sub-G1 cells. The induction of apoptosis by the combined treatment caused the loss of mitochondrial membrane potential (ΔΨm) and upregulation of Bax. In addition, the proteolytic activities of caspases (-3, -8, and -9) and the degradation of poly (ADP-ribose) polymerase, a substrate protein of activated caspase-3, were also higher in the combined treatment. Moreover, combined treatment induced excessive generation of reactive oxygen species (ROS). However, treatment with N-acetyl-L-cysteine, a ROS scavenger, reduced combined treatment-induced ROS production and apoptosis. Thereby, these results deduce that ROS played a pivotal role in apoptosis induced by auranofin and sulforaphane. Furthermore, apoptosis induced by auranofin and sulforaphane was significantly increased through inhibition of the phosphoinositide 3-kinase (PI3K)/Akt pathway. Taken together, the present study demonstrated that down-regulation of TrxR activity contributed to the synergistic effect of auranofin and sulforaphane on apoptosis through ROS production and inhibition of PI3K/Akt signaling pathway.

Keyword

Auranofin; Sulforaphane; TrxR; Apoptosis; ROS; PI3K/Akt
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