Nrf2-Mediated HO-1 Induction Coupled with the ERK Signaling Pathway Contributes to Indirect Antioxidant Capacity of Caffeic Acid Phenethyl Ester in HepG2 Cells

Abstract

The objective of this study is to investigate the contributing effect of the nuclear transcription factor-erythroid 2-related factor 2 (Nrf2)-mediated signaling pathway on the indirect antioxidant capacity of caffeic acid phenethyl ester (CAPE) against oxidative stress in HepG2 cells. The result of an antioxidant response element (ARE)-luciferase assay showed that CAPE stimulated ARE promoter activity resulting in increased transcriptional and translational activities of heme oxygenase-1 (HO-1). In addition, CAPE treatment enhanced Nrf2 accumulation in the nucleus and the post-translational phosphorylation level of extracellular signal-regulated kinase (ERK) among several protein kinases tested. Treatment with ERK inhibitor U126 completely suppressed CAPE-induced ERK phosphorylation and HO-1 expression, but it only partly inhibited CAPE-induced Nrf2 accumulation and ARE promoter. Using the 2',7'-dichlorofluorescein-diacetate (DCFH-DA) method, the cellular antioxidant capacity of CAPE against 2,2'-azobis (2-amidinopropane) dihydrochloride (AAPH)- or H2O2-induced oxidative stress also was shown to be partially suppressed by the ERK inhibitor. From the overall results it is proposed that the indirect antioxidant activity of CAPE against oxidative stress in HepG2 cells is partially attributed to induction of HO-1, which is regulated by Kelch-like erythroid-cell-derived protein with CNC homology (ECH)-associated protein 1 (Keap1)-independent Nrf2 activation relying on post-translational phosphorylation of ERK.

Antioxidant efficacy and the upregulation of Nrf2-mediated HO-1 expression by (+)-lariciresinol, a lignan isolated from Rubia philippinensis, through the activation of p38

“…Cellular antioxidant capacity of antioxidants results from their direct capacity, defined as the capacity to quench free radicals, ROS and RNS either by donating hydrogen or electrons, whereas indirect capacity involves providing defense against oxidative stress through inducing the expression of phase II detoxifying and antioxidant enzymes4. ROS scavenging activity plays a pivotal role in cellular homeostasis during cell proliferation and maintenance.…”

“…Aerobic organisms have effective antioxidant networks to defend against oxidative stress, involving primary enzymes such as superoxide dismutase (SOD), glutathione peroxidase (GPx) and catalase (CAT) as well as inducible phase II detoxifying enzyme such as heme oxygenase-1 (HO-1), NAD(P)H dehydrogenase [quinone] 1 (NQO1), Glutamate-cysteine ligase catalytic subunit (GCLc), Glutamate-cysteine ligase regulatory subunit (GCLm) through the activation of nuclear transcription factor-erythroid 2 related factor (Nrf2)4. Under physiological conditions, Nrf2 is sequestered by binding to Kelch-like ECH-associated protein 1 (Keap1), which inhibits the translocation of Nrf2 into the nucleus.…”

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

“…In particular, the identification of a non-cytotoxic inducer of HO-1 may maximize the intrinsic antioxidative potential of cells. Many natural resources that scavenge free radicals have been identified and reported to induce HO-1 expression in a variety of cells, such as liver cells, retinal pigment epithelial cells and macrophage cells, and hence may function against oxidative stress [16][17][18].…”

Absorption properties and effects of caffeic acid phenethyl ester and its p-nitro-derivative on P-glycoprotein in Caco-2 cells and rats

“…Yeh and Yen (2006) demonstrated that polyphenols can induce the gene of drug metabolizing enzyme including P-gp through increasing the expression of Nrf2 protein. Kim and Jang (2014) recently proposed that CAPE exhibited the indirect antioxidant activity in HepG2 cells through enhancing the Nrf2 accumulation in the nucleus which is partially attributed to induction of HO-1. CAPE and CAPE-NO 2 were polyphenol-like compounds, and our studies also suggested that the two compounds might possess similar mechanisms with polyphenols in increasing P-gp expression, while identification of the specific mechanisms of the CAPE-and CAPE-NO 2 -mediated P-gp expression is still demanding.…”