Abstract
Taraxacum officinale has been consumed as a folk remedy due to its diverse physiological activities. This study aimed to investigate the antioxidative potential of T. officinale water extract (TOWE) and ethanol extract (TOEE) against oxidative stress and compare their molecular mechanism via the induction of heme oxygenase-1 (HO-1) in RAW 264.7 cells. The antioxidative activity was evaluated through the radical scavenging assay, the cytoprotection assay against oxidative damage, and Western blot analysis. Both extracts dose-dependently induced HO-1 expression without any cytotoxicity in accordance with the activation of a transcription factor, nuclear factor-erythroid 2 p45-related factor 2 (Nrf2). In addition, TOWE induced HO-1 expression through the phosphorylation of phosphoinositide 3-kinase (PI3K)/Akt and c-Jun NH2-terminal kinase (JNK), while TOEE activated HO-1 by PI3K/Akt phosphorylation. In order to identify the antioxidative potential by HO-1 induction, oxidative damage-caused cell death by tert-butyl hydroperoxide (t-BHP) was significantly attenuated by both extracts. Their antioxidative potential was confirmed by HO-1 selective inducer and inhibitor, cobalt protoporphyrin (CoPP), and tin protoporphyrin (SnPP), respectively. These results indicate that TOWE and TOEE potently alleviated oxidative damage via the induction of Nrf2/MAPK/PI3K mediated HO-1 induction in RAW 264.7 cells.
Highlights
Excess generation of intracellular reactive oxygen species (ROS) in response to xenobiotics, drugs, cytokines, and environmental stress can cause damage through the modification or degradation of cellular components, including DNA, protein, lipids, and carbohydrates, which contributes to the tissue injury in the context of a variety of disease state [1]
These results indicate that T. officinale water extract (TOWE) and T. officinale ethanol extract (TOEE) potently alleviated oxidative damage via the induction of nuclear factor-erythroid 2 p45-related factor 2 (Nrf2)/mitogen-activated protein kinase (MAPK)/phosphoinositide 3-kinase (PI3K)
heme oxygenase-1 (HO-1) is regulated by a nuclear factor-erythroid 2 p45-related factor 2 (Nrf2), which can be activated in response to oxidative stress [4]
Summary
Excess generation of intracellular reactive oxygen species (ROS) in response to xenobiotics, drugs, cytokines, and environmental stress can cause damage through the modification or degradation of cellular components, including DNA, protein, lipids, and carbohydrates, which contributes to the tissue injury in the context of a variety of disease state [1]. Oxidative stress is highly related to the progress of diverse diseases, such as age-related macular degeneration, Parkinson’s disease, alcoholic hepatitis, and cardiovascular diseases [2]. In order to eliminate the oxidative stress, cells have developed their own defensive mechanisms through the induction of antioxidative enzymes, such as superoxide dismutase (SOD), heme oxygenase-1 (HO-1), and NAD(P)H: quinone oxidoreductase (NQO1). HO-1 is one of the metabolizing enzymes and converts heme to biliverdin, carbon monoxide, and free iron. These catabolites have exhibited potent protective activities against oxidative stress and inflammation [3]. HO-1 is regulated by a nuclear factor-erythroid 2 p45-related factor 2 (Nrf2), which can be activated in response to oxidative stress [4]. Activated Nrf can translocate into the nucleus and bind the antioxidant response element (ARE), which can lead the gene expression of various antioxidative
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