Isorhamnetin protects against oxidative stress by activating Nrf2 and inducing the expression of its target genes

Journal Article · Wed Jan 15 04:00:00 UTC 2014 · Toxicology and Applied Pharmacology

DOI:https://doi.org/10.1016/J.TAAP.2013.10.026· OSTI ID:22285581

Yang, Ji Hye; Shin, Bo Yeon; Han, Jae Yun; Kim, Mi Gwang; Wi, Ji Eun ^[1]; Kim, Young Woo; Cho, Il Je; Kim, Sang Chan ^[2]; Shin, Sang Mi ^[1]

---

1. College of Pharmacy, Chosun University, Gwangju, 501-759 (Korea, Republic of)
2. Medical Research Center for Globalization of Herbal Formulation, College of Korean Medicine, Daegu Haany University, Gyeongsan 712-715 (Korea, Republic of)

Isorhamentin is a 3′-O-methylated metabolite of quercetin, and has been reported to have anti-inflammatory and anti-proliferative effects. However, the effects of isorhamnetin on Nrf2 activation and on the expressions of its downstream genes in hepatocytes have not been elucidated. Here, we investigated whether isorhamnetin has the ability to activate Nrf2 and induce phase II antioxidant enzyme expression, and to determine the protective role of isorhamnetin on oxidative injury in hepatocytes. In HepG2 cells, isorhamnetin increased the nuclear translocation of Nrf2 in a dose- and time-dependent manner, and consistently, increased antioxidant response element (ARE) reporter gene activity and the protein levels of hemeoxygenase (HO-1) and of glutamate cysteine ligase (GCL), which resulted in intracellular GSH level increases. The specific role of Nrf2 in isorhamnetin-induced Nrf2 target gene expression was verified using an ARE-deletion mutant plasmid and Nrf2-knockout MEF cells. Deletion of the ARE in the promoter region of the sestrin2 gene, which is recently identified as the Nrf2 target gene by us, abolished the ability of isorhamnetin to increase luciferase activity. In addition, Nrf2 deficiency completely blocked the ability of isorhamnetin to induce HO-1 and GCL. Furthermore, isorhamnetin pretreatment blocked t-BHP-induced ROS production and reversed GSH depletion by t-BHP and consequently, due to reduced ROS levels, decreased t-BHP-induced cell death. In addition isorhamnetin increased ERK1/2, PKCδ and AMPK phosphorylation. Finally, we showed that Nrf2 deficiency blocked the ability of isorhamnetin to protect cells from injury induced by t-BHP. Taken together, our results demonstrate that isorhamnetin is efficacious in protecting hepatocytes against oxidative stress by Nrf2 activation and in inducing the expressions of its downstream genes. - Highlights: • We investigated the effect of isorhamnetin on Nrf2 activation. • Isorhamnetin increased Nrf2 activity and its target gene expression. • Isorhamnetin blocked t-BHP-induced ROS production and reversed GSH depletion. • Isorhamnetin increased ERK1/2, PKCδ and AMPK phosphorylation. • Isorhamnetin is efficacious in protecting hepatocytes against oxidative stress.

• OSTI ID: 22285581
• Journal Information: Toxicology and Applied Pharmacology, Journal Name: Toxicology and Applied Pharmacology Journal Issue: 2 Vol. 274; ISSN TXAPA9; ISSN 0041-008X
• Country of Publication: United States
• Language: English

Related Subjects

60 APPLIED LIFE SCIENCES
AMP
ANTIOXIDANTS
APOPTOSIS
CYSTEINE
GENES
INFLAMMATION
INJURIES
LIGASES
LIVER CELLS
LUCIFERASE
OXIDATION
QUERCETIN
TIME DEPENDENCE