Libertellenone H, a Natural Pimarane Diterpenoid, Inhibits Thioredoxin System and Induces ROS-Mediated Apoptosis in Human Pancreatic Cancer Cells.

Weirui Zhang,Yuping Zhu,Xiaoling Lu,Haobing Yu,Xiaoyu Liu,Binghua Jiao

doi:10.3390/molecules26020315

Abstract

Libertellenone H (LH), a marine-derived pimarane diterpenoid isolated from arctic fungus Eutypella sp. D-1, has shown effective cytotoxicity on a range of cancer cells. The present study is to explore the anticancer effect of LH on human pancreatic cancer cells and to investigate the intracellular molecular target and underlying mechanism. As shown, LH exhibited anticancer activity in human pancreatic cancer cells by promoting cell apoptosis. Mechanistic studies suggested that LH-induced reactive oxygen species (ROS) accumulation was responsible for apoptosis as antioxidant N-acetylcysteine (NAC) and antioxidant enzyme superoxide dismutase (SOD) antagonized the inhibitory effect of LH. Zymologic testing demonstrated that LH inhibited Trx system but had little effect on the glutathione reductase and glutaredoxin. Mass spectrometry (MS) analysis revealed that the mechanism of action was based on the direct conjugation of LH to the Cys32/Cys35 residue of Trx1 and Sec498 of TrxR, leading to a decrease in the cellular level of glutathione (GSH) and activation of downstream ASK1/JNK signaling pathway. Taken together, our findings revealed LH was a marine derived inhibitor of Trx system and an anticancer candidate.

Highlights

The thioredoxin system, composed of thioredoxin (Trx), thioredoxin reductase (TrxR), and nicotinamide adenine dinucleotide phosphate (NADPH), which is a critical antioxidant system in defensing against oxidative stress and maintaining cellular redox homeostasis by eliminating redundant reactive oxygen species (ROS) [1,2]
We evaluated the cytotoxicity of Libertellenone H (LH) in four pancreatic cancer cell lines, PANC-1, SW1990, AsPC-1, and BxPC-3 and human pancreatic duct epithelial cells HPDE6-C7 via the CCK8 assay
The results suggested LH significantly inhibited Trx1 and TrxR enzymes with IC50 value of 35.15 μM and 3.10 μM in Trx system (Figure 3A,B)

Summary

Introduction

The thioredoxin system, composed of thioredoxin (Trx), thioredoxin reductase (TrxR), and nicotinamide adenine dinucleotide phosphate (NADPH), which is a critical antioxidant system in defensing against oxidative stress and maintaining cellular redox homeostasis by eliminating redundant ROS [1,2]. Trx and TrxR1 were the dedicated isoforms of Trx and TrxR for predominantly cytosolic localization. The critical cysteine and selenocysteine motifs can modulate specific signal transduction cascades through its redox sensitive sulfhydryl switches [4]. The active reduced Trx (Trx-(SH)2) with vicinal dithiol can interact with downstream proteins via thiol–disulfide exchange reactions to form a disulfide bond and oxidized Trx (oxidized (Trx-S2)). The oxidized inactive disulfide of Trx-S2 is recycled to reduced Trx-(SH) by TrxR at the expense of NADPH [1,5]

Methods

Results

Conclusion