Xanthohumol‐induced transient superoxide anion radical formation triggers cancer cells into apoptosis via a mitochondria‐mediated mechanism

Abstract

Oxidative stress and increased release of reactive oxygen species (ROS) are associated with apoptosis induction. Here we report ROS-mediated induction of apoptosis by xanthohumol (XN) from hops. XN at concentrations of 1.6-25 microM induced an immediate and transient increase in superoxide anion radical (O(2)(-*)) formation in 3 human cancer cell lines (average+/-SD EC(50) of maximum O(2)(-*) induction=3.1+/-0.8 microM), murine macrophages (EC(50)=4.0+/-0.3 microM), and BPH-1 benign prostate hyperplasia cells (EC(50)=4.3+/-0.1 microM), as evidenced by the O(2)(-*)-specific indicator dihydroethidium. MitoSOX Red costaining and experiments using isolated mouse liver mitochondria (EC(50)=11.4+/-1.8 microM) confirmed mitochondria as the site of intracellular O(2)(-*) formation. Antimycin A served as positive control (EC(50)=12.4+/-0.9 microM). XN-mediated O(2)(-*) release was significantly reduced in BPH-1 rho(0) cells harboring nonfunctional mitochondria (EC(50)>25 microM) and by treatment of BPH-1 cells with vitamin C, N-acetylcysteine (NAC), or the superoxide dismutase mimetic MnTMPyP. In addition, we demonstrated a rapid 15% increase in oxidized glutathione and a dose-dependent overall thiol depletion within 6 h (IC(50)=24.3+/-11 microM). Respiratory chain complexes I-III were weakly inhibited by XN in bovine heart submitochondrial particles, but electron flux from complex I and II to complex III was significantly inhibited in BPH-1 cells, with IC(50) values of 28.1 +/- 2.4 and 24.4 +/- 5.2 microM, respectively. Within 15 min, intracellular ATP levels were significantly reduced by XN at 12.5 to 50 microM concentrations (IC(50)=26.7+/-3.7 microM). Concomitantly, XN treatment caused a rapid breakdown of the mitochondrial membrane potential and the release of cytochrome c, leading to apoptosis induction. Pre- or coincubation with 2 mM NAC and 50 microM MnTMPyP at various steps increased XN-mediated IC(50) values for cytotoxicity in BPH-1 cells from 6.7 +/- 0.2 to 12.2 +/- 0.1 and 41.4 +/- 7.6 microM, and it confirmed XN-induced O(2)(-*) as an essential trigger for apoptosis induction. In summary, we have identified mitochondria as a novel cellular target of XN action, resulting in increased O(2)(-*) production, disruption of cellular redox balance and mitochondrial integrity, and subsequent apoptosis.

In vitro structure-toxicity relationship of chalcones in human hepatic stellate cells

“…Other studies reported, that XN (1) treatment induced the mitochondrial-mediated pathways of programmed cell death in human colon carcinoma cells and caused a rapid breakdown of the mitochondrial membrane potential, and the release of cytochrome c, leading to apoptosis induction in BPH-1 cells (Strathmann et al, 2010). Our results propose that apoptosis caused by XN (1) is mediated by a loss of mitochondrial membrane potential and subsequent cytochrome c release at concentrations as low as 10 μM, which is in good accordance with previous studies.…”

Dose-Dependent Protective and Inductive Effects of Xanthohumol on Oxidative DNA Damage in Saccharomyces cerevisiae

“…Anticarcinogenic and antioxidant properties of xanthohumol present in Humulus lupulus L. have been reported before (3,5,(9)(10)(11)(12)(13)(14)(37)(38)(39). However, scarce information is available on the eff ect of xanthohumol on yeast cells.…”

A Metabolomics-driven Elucidation of the Anti-obesity Mechanisms of Xanthohumol

“…Xanthohumol (XN) is a prenylated chalcone found in hops and beer and has an electrophilic group capable of inducing a stress response (10,15). XN is perhaps best known for its cancer chemopreventive properties and its ability to trigger apoptosis through ROS (16,17). Several reports are now starting to describe various anti-obesity properties of XN but with no well accepted mechanisms.…”