Silibinin induces mitochondrial NOX4-mediated endoplasmic reticulum stress response and its subsequent apoptosis

Abstract

BackgroundSilibinin, a biologically active compound of milk thistle, has chemopreventive effects on cancer cell lines. Recently it was reported that silibinin inhibited tumor growth through activation of the apoptotic signaling pathway. Although various evidences showed multiple signaling pathways of silibinin in apoptosis, there were no reports to address the clear mechanism of ROS-mediated pathway in prostate cancer PC-3 cells. Several studies suggested that reactive oxygen species (ROS) play an important role in various signaling cascades, but the primary source of ROS was currently unclear.MethodsThe effect of silibinin was investigated on cell growth of prostate cell lines by MTT assay. We examined whether silibinin induced apoptosis through production of ROS using flow cytometry. Expression of apoptosis-, endoplasmic reticulum (ER)-related protein and gene were determined by western blotting and RT-PCR, respectively.ResultsResults showed that silibinin triggered mitochondrial ROS production through NOX4 expression and finally led to induce apoptosis. In addition, mitochondrial ROS caused ER stress through disruption of Ca2+ homeostasis. Co-treatment of ROS inhibitor reduced the silibinin-induced apoptosis through the inhibition of NOX4 expression, resulting in reduction of both Ca2+ level and ER stress response.ConclusionsTaken together, silibinin induced mitochondrial ROS-dependent apoptosis through NOX4, which is associated with disruption of Ca2+ homeostasis and ER stress response. Therefore, the regulation of NOX4, mitochondrial ROS producer, could be a potential target for the treatment of prostate cancer.Electronic supplementary materialThe online version of this article (doi:10.1186/s12885-016-2516-6) contains supplementary material, which is available to authorized users.

The novel resveratrol derivative 3,5-diethoxy-3′,4′-dihydroxy-trans-stilbene induces mitochondrial ROS-mediated ER stress and cell death in human hepatoma cells in vitro

“…Until now, there have been no reports that ROS accumulation caused by Res or Res derivatives can elicit ER stress, but the role of other drug-mediated mitochondrial ROS in ER stress induction has been demonstrated in a variety of cell types [39,55] . Drug-mediated ROS generation precedes UPR induction and is efficiently blocked by ROS scavengers [55] .…”

“…Drug-mediated ROS generation precedes UPR induction and is efficiently blocked by ROS scavengers [55] . In terms of mechanisms, the drugs trigger mitochondrial ROS production through the regulation of gene expression or enzyme activity of mitochondrial ROS-producing proteins, such as NADPH oxidase 4 or cytochrome c reductase (complex III), respectively [39] .…”

“…In terms of mechanisms, the drugs trigger mitochondrial ROS production through the regulation of gene expression or enzyme activity of mitochondrial ROS-producing proteins, such as NADPH oxidase 4 or cytochrome c reductase (complex III), respectively [39] . Although the precise mechanism of how mitochondrial ROS induce ER stress requires further investigation, it is proposed that oxidative protein damage and/or its mediated ER calcium release may trigger ER stress [39,55] . However, Res-006-mediated mitochondrial ROS may not induce ER stress through the disruption of ER calcium homeostasis because treatment with the intracellular calcium chelator BAPTA/AM could not inhibit Res-006-mediated cell death ( Figure 2D).…”

Monensin Induces PC-3 Prostate Cancer Cell Apoptosis via ROS Production and Ca2+ Homeostasis Disruption

“…Apoptosis, one of the chemotherapeutic strategies, is an evolutionary-conserved and highly regulated process that involves activation of a series of molecular events (1,2) Several reports have shown that apoptosis is induced via various extracellular stresses, including reactive oxygen species (ROS) (3). ROS play vital roles in apoptosis and some other cellular events (4,5).…”

Natural Compounds in Prostate Cancer Prevention and Treatment: Mechanisms of Action and Molecular Targets

“…In this setting, proteostasis disruption appears to play a key role in the modulation of the nutraceutical-related apoptotic cell death. Indeed, while apigenin, luteolin, genistein, and celastrol inhibited the proteasomal activity and caused ubiquitinated protein accumulation in different PCa cell lines [154][155][156], quercetin, curcumin, silibinin, and tannic acid induced endoplasmic reticulum (ER) stress [157][158][159][160], a condition where unfolded/misfolded proteins accumulate in the ER lumen and promote the activation of distinct pro-death cascades, including the double-stranded RNA-dependent protein kinase PKR-like ER kinase (PERK)/eukaryotic initiation factor 2α (eIF2α)/activating transcription factor 4 (ATF4)/C/EBP homologous protein (CHOP) pathway and the inositol-requiring enzyme 1α (IRE1)/c-Jun N-terminal kinase (JNK)/p38 MAPK cascade [161]. Notably, curcumin-and silibinin-mediated ER stress was associated with generation of reactive oxygen species (ROS) and redox homeostasis alteration [159,162], which were also observed in resveratrol-and sulforaphane-treated PCa cells [163][164][165][166].…”