Piceatannol induces heme oxygenase-1 expression in human mammary epithelial cells through activation of ARE-driven Nrf2 signaling.

Piceatannol (3,4,3',5'-tetrahydroxy-trans-stilbene), derived from the seeds of Euphorbia lagascae, has been reported to have anti-proliferative, anti-inflammatory, and antioxidant properties. However, the mechanisms underlying its chemoprotective effects remain largely unresolved. In the present study, we found that piceatannol treatment (30 microM) significantly upregulated the expression of the antioxidant enzyme heme oxygenase-1 (HO-1) and its mRNA transcript at 6h and 3h, respectively in human breast epithelial (MCF10A) cells. A redox-sensitive transcription factor NF-E2-related factor (Nrf2) plays a pivotal role in induced expression of many cytoprotective enzymes including HO-1. Piceatannol induced translocation of Nrf2 into the nucleus and its transcriptional activities when treated to the MCF10A cells for 6h. Upregulation of HO-1 expression by piceatannol through direct binding of Nrf2 to antioxidant response element (ARE) was verified by the chromatin immunoprecipitation (ChIP) assay. siRNA knock down of Nrf2 gene abolished piceatannol-induced HO-1 expression. In addition, piceatannol-induced activation of Nrf2 and/or HO-1 expression was abrogated by the pharmacological inhibitor (LY294002) as well as the kinase-dead form of Akt. In an attempt to elucidate the molecular mechanisms underlying cytoprotective or chemoprotective activity exerted by piceatannol, we examined its effect on the signaling pathways responsible for induction of HO-1 expression. We hypothesize that an electrophilic quinone formed as a consequence of oxidation of piceatannol bearing the catechol moiety may bind directly to Kelch-like ECH-associated protein 1 (Keap1), an inhibitory protein that sequesters Nrf2 in the cytoplasm. This will diminish the affinity of Keap1 for Nrf2. The thiol reducing agents, dithiothreitol (100 microM) or beta-mercaptoethanol (1.4 microM), attenuated piceatannol-induced Nrf2 activation and HO-1 expression. It is hence likely that piceatannol modifies specific cysteine residues of Keap1, which allows Nrf2 to translocate into the nucleus and bind to ARE, leading to enhancement of the expression of HO-1. The characteristic catechol moiety of piceatannol appears to be critical for induction of Nrf2 activation and subsequent upregulation of HO-1.

Lee HH ，Park SA ，Almazari I ，Kim EH ，Na HK ，Surh YJ ... -  《-》

Guggulsterone induces heme oxygenase-1 expression through activation of Nrf2 in human mammary epithelial cells: PTEN as a putative target.

Almazari I ，Park JM ，Park SA ，Suh JY ，Na HK ，Cha YN ，Surh YJ ... -  《-》

The antioxidative potential of farrerol occurs via the activation of Nrf2 mediated HO-1 signaling in RAW 264.7 cells.

Farrerol, (S)-2,3-dihydro-5,7-dihydroxy-2-(4-hydroxyphenyl)-6,8-dimethyl-4-benzopyrone, isolated from rhododendron, has been shown to have antioxidative potential, but the molecular mechanism underlying this activity remains unclear. The inducible expression of heme oxygenase-1 (HO-1), a potent antioxidative and cytoprotective enzyme, is known to play an important role in cytoprotection in a variety of pathological models. In this study, we evaluated the antioxidative potential of farrerol against oxidative damage and investigated its antioxidative mechanism in RAW 264.7 cells. The molecular mechanism underlying the cytoprotective function of farrerol was determined by analyzing intracellular signaling pathways, transcriptional activation and the inhibitory effect of HO-1 on ROS production. Farrerol induced antioxidant enzymes mRNA expression, HO-1 protein expression and nuclear translocation of NF-E2-related factor 2 in RAW 264.7 macrophage cells. Farrerol down-regulated the expression of the Keap1 protein and the thiol reducing agents attenuated farrerol-induced HO-1 expression. Further investigation utilizing Western blotting and specific inhibitors of Akt, p38, JNK and ERK demonstrated that Akt, p38, and ERK axis of signaling pathway mediates HO-1 expression. Moreover, tert-butyl hydroperoxide (t-BHP)-induced oxidative damage was ameliorated by farrerol treatment in a dose-dependent manner, which was abolished by Akt, p38, ERK and HO-1 inhibitors (Snpp). It is hence likely that farrerol inactivated KEAP-1 or activated the Akt, p38 and ERK to facilitate the release of Nrf2 from Keap1 and subsequent reduced the intracellular production of reactive oxygen species via the induction of HO-1 expression. These results support the central role of HO-1 in the cytoprotective effect of farrerol.

Ci X ，Lv H ，Wang L ，Wang X ，Peng L ，Qin FX ，Cheng G ... -  《-》

Lansoprazole, a proton pump inhibitor, mediates anti-inflammatory effect in gastric mucosal cells through the induction of heme oxygenase-1 via activation of NF-E2-related factor 2 and oxidation of kelch-like ECH-associating protein 1.

Takagi T ，Naito Y ，Okada H ，Ishii T ，Mizushima K ，Akagiri S ，Adachi S ，Handa O ，Kokura S ，Ichikawa H ，Itoh K ，Yamamoto M ，Matsui H ，Yoshikawa T ... -  《-》

15-Keto prostaglandin E(2) induces heme oxygenase-1 expression through activation of Nrf2 in human colon epithelial CCD 841 CoN cells.

Prostaglandin E2 (PGE2) plays a key role in inflammation-associated carcinogenesis. NAD+-dependent 15-hydroxyprostaglandin dehydrogenase (15-PGDH) catalyzes the oxidation of the 15(S)-hydroxyl group of PGE2 to generate 15-keto PGE2. 15-PGDH has been known as a tumor suppressor in various malignancies including colon cancer. However, the molecular mechanisms underlying the tumor-suppressive function of 15-PGDH remain largely unresolved. In this study, we found that 15-keto PGE2 upregulated the expression of heme oxygenase-1 (HO-1), a representative antioxidative and anti-inflammatory enzyme, at both transcriptional and translational levels, in human colon epithelial CCD 841 CoN cells. A redox-sensitive transcription factor, NF-E2-related factor (Nrf2) plays a critical role in the regulation of HO-1 and other cytoprotective proteins. 15-Keto PGE2 induced translocation of Nrf2 into the nucleus and antioxidant response element-driven luciferase activity. Furthermore, the silencing of the Nrf2 gene abolished 15-keto PGE2-induced HO-1 expression in CCD 841 CoN cells. 15-Keto PGE2 activated AKT signaling, and the pharmacological AKT inhibitor, LY294002 suppressed the 15-keto PGE2-induced HO-1 expression. 15-Keto PGE2 generates the reactive oxygen species which is suppressed by the general antioxidant N-acetyl-l-cysteine. N-acetyl-l-cysteine treatment attenuated the 15-keto PGE2-induced phosphorylation of GSK3β, transcriptional activity of Nrf2, and subsequently HO-1 expression. However, 13,14-dihydro-15-keto PGE2 lacking the α,β-unsaturated carbonyl moiety failed to induce intracellular production of reactive oxygen species, HO-1 expression and nuclear translocation of Nrf2. In conclusion, 15-keto PGE2 induces HO-1 expression through Nrf2 activation in human colon epithelial cells.

Lee JE ，Zhong X ，Lee JY ，Surh YJ ，Na HK ... -  《-》