scholarly journals Curcumin prevents As3+-induced carcinogenesis through regulation of GSK3β/Nrf2

2021 ◽  
Vol 16 (1) ◽  
Author(s):  
Yuan-Ye Dang ◽  
Hua Luo ◽  
Yong-Mei Li ◽  
Yang Zhou ◽  
Xiu Luo ◽  
...  
Keyword(s):  
Molecular Docking ◽  
Signaling Pathway ◽  
Cell Apoptosis ◽  
Cell Transformation ◽  
Autophagic Flux ◽  
Related Factor ◽  
Antioxidant Genes ◽  
Nrf2 Signaling Pathway ◽  
Ubiquitination Pathway ◽  
Gsk 3Β

Abstract Background Arsenic (As3+) is a carcinogen with considerable environmental and occupational relevancy. Its mechanism of action and methods of prevention remain to be investigated. Previous studies have demonstrated that ROS is responsible for As3+-induced cell transformation, which is considered as the first stage of As3+ carcinogenesis. The NF-E2 p45-related factor-2 (Nrf2) signaling pathway regulates the cellular antioxidant response, and activation of Nrf2 has recently been shown to limit oxidative damage following exposure to As3+ Methods and results In this study, molecular docking was used to virtually screen natural antioxidant chemical databases and identify molecules that interact with the ligand-binding site of Keap1 (PDB code 4L7B). The cell-based assays and molecular docking findings revealed that curcumin has the best inhibitory activity against Keap1-4L7B. Co-immunoprecipitation (Co-IP) results indicated that curcumin is a potent Keap1 Kelch domain-dependent Nrf2 activator that stabilizes Nrf2 by hindering its ubiquitination. The increased activation of Nrf2 and its target antioxidant genes by curcumin could significantly decrease As3+-generated ROS. Moreover, curcumin induced autophagy in As3+-treated BEAS-2B via inducing autophagy by the formation of a p62/LC-3 complex and increasing autophagic flux by promoting transcription factor EB (TFEB) and lysosome-associated membrane protein 1 (LAMP1) expression. Knockdown of Nrf2 abolished curcumin-induced autophagy and downregulated ROS. Further studies showed that inhibition of autophagosome and lysosome fusion with bafilomycin a1 (BafA1) could block curcumin and prevented As3+-induced cell transformation. These results demonstrated that curcumin prevents As3+-induced cell transformation by inducing autophagy via the activation of the Nrf2 signaling pathway in BEAS-2B cells. However, overexpression of Keap-1 showed a constitutively high level of Nrf2 in As3+-transformed BEAS-2B cells (AsT) is Keap1-independent regulation. Overexpression of Nrf2 in AsT demonstrated that curcumin increased ROS levels and induced cell apoptosis via the downregulation of Nrf2. Further studies showed that curcumin decreased the Nrf2 level in AsT by activating GSK-3β to inhibit the activation of PI3K/AKT. Co-IP assay results showed that curcumin promoted the interaction of Nrf2 with the GSK-3β/β-TrCP axis and ubiquitin. Moreover, the inhibition of GSK-3β reversed Nrf2 expression in curcumin-treated AsT, indicating that the decrease in Nrf2 is due to activation of the GSK-3β/β-TrCP ubiquitination pathway. Furthermore, in vitro and in vivo results showed that curcumin induced cell apoptosis, and had anti-angiogenesis and anti-tumorigenesis effects as a result of activating the GSK-3β/β-TrCP ubiquitination pathway and subsequent decrease in Nrf2. Conclusions Taken together, in the first stage, curcumin activated Nrf2, decreased ROS, and induced autophagy in normal cells to prevent As3+-induced cell transformation. In the second stage, curcumin promoted ROS and apoptosis and inhibited angiogenesis via inhibition of constitutive expression of Nrf2 in AsT to prevent tumorigenesis. Our results suggest that antioxidant natural compounds such as curcumin can be evaluated as potential candidates for complementary therapies in the treatment of As3+-induced carcinogenesis.

scholarly journals Cytoprotective Effect of Ligustrum robustum Polyphenol Extract against Hydrogen Peroxide-Induced Oxidative Stress via Nrf2 Signaling Pathway in Caco-2 Cells

2019 ◽  
Vol 2019 ◽  
pp. 1-8 ◽  
Author(s):  
Jiayi Chen ◽  
Fangting He ◽  
Sijing Liu ◽  
Tao Zhou ◽  
Saira Baloch ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Hydrogen Peroxide ◽  
Signaling Pathway ◽  
Total Phenolic ◽  
Heme Oxygenase 1 ◽  
Related Factor ◽  
Cytoprotective Effect ◽  
Quinone Oxidoreductase ◽  
Antioxidant Genes ◽  
Nrf2 Signaling Pathway

Ligustrum robustum is a traditional herbal tea that is widely distributed in southwest China. The health effects of L. robustum are characteristics of clearing heat, antioxidant, inducing resurgence, and improving digestion. However, the molecular mechanisms related to these effects, particularly the antioxidant mechanism, have been seldom reported. The objective of this study was to assess antioxidative capacity of L. robustum, and its protective effects and mechanisms against hydrogen peroxide (H2O2) - induced toxicity in Caco-2 cells. Total phenolic contents, free radical scavenging activity, and reducing capacity of L. robustum were measured. The effects of L. robustum on the cell viability and antioxidant defense system were explored. The expression of nuclear factor E2 related factor 2 (Nrf2) and antioxidant genes: quinone oxidoreductase 1 (NQO1), heme oxygenase-1 (HO-1), and glutamate cysteine ligase (GCL) were analyzed by western blot and qPCR. Pretreatment of L. robustum could significantly reduce H2O2-induced toxicity, decrease the level of reactive oxygen species (ROS) and malondialdehyde (MDA), and increase the activities of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px), and glutathione reductase (GR). By activating the expression of Nrf2 and antioxidant genes (NQO1, HO-1, and GCL), L. robustum exerts cytoprotective effect in Caco-2 cells dealt with H2O2. Therefore, the well-established model of Caco-2 cells demonstrates that L. robustum may modulate the cytoprotective effect against the H2O2-induced oxidative stress through the Nrf2 signaling pathway.

scholarly journals MitoQ Modulates Lipopolysaccharide-Induced Intestinal Barrier Dysfunction via Regulating Nrf2 Signaling

2020 ◽  
Vol 2020 ◽  
pp. 1-9 ◽  
Author(s):  
Shengfeng Zhang ◽  
Qingniao Zhou ◽  
Youcheng Li ◽  
Yunli Zhang ◽  
Yinmei Wu
Keyword(s):  
Oxidative Stress ◽  
Inflammatory Response ◽  
Signaling Pathway ◽  
Related Factor ◽  
Barrier Dysfunction ◽  
Gut Barrier ◽  
Mucosal Permeability ◽  
Antioxidant Genes ◽  
Lps Challenge ◽  
Nrf2 Signaling Pathway

Background. Gut barrier dysfunction with alterant mucosal permeability during sepsis is a challenge problem in clinical practice. Intestinal epithelial cells (IECs) are strongly involved in mucosal oxidative stress and inflammatory response. The current study aimed at investigating the effect of MitoQ, a mitochondrial targeted antioxidant, in the treatment of intestinal injury and its potential mechanism during sepsis. Methods. 30 minutes before sepsis induction by lipopolysaccharide (LPS) treatment, mice were treated with MitoQ. Intestinal histopathology, mucosal permeability, inflammatory cytokines, and mucosal barrier proteins were evaluated in the present study. Results. MitoQ pretreatment significantly decreased the levels of plasma diamine oxidase, D-lactate, and intestinal histological damage and markedly restored the levels of tight junction proteins (ZO-1 and occludin) following LPS challenge. Furthermore, MitoQ inhibited the LPS-induced intestinal oxidative stress and inflammatory response, evidenced by increased levels of intestinal superoxide dismutase and glutathione, and decreased levels of intestinal IL-1, IL-6, TNF-α, and nitric oxide levels. Mechanically, we found that MitoQ inhibited the oxidative stress via activating nuclear factor E2-related factor 2 (Nrf2) signaling pathway and its downstream antioxidant genes, including HO-1, NQO-1, and GCLM. Conclusions. MitoQ exerts antioxidative and anti-inflammatory effects against sepsis-associated gut barrier injury by promoting Nrf2 signaling pathway.

scholarly journals Nrf2 Activation Attenuates Acrylamide-Induced Neuropathy in Mice

2021 ◽  
Vol 22 (11) ◽  
pp. 5995
Author(s):  
Chand Basha Davuljigari ◽  
Frederick Adams Ekuban ◽  
Cai Zong ◽  
Alzahraa A. M. Fergany ◽  
Kota Morikawa ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Signaling Pathway ◽  
Messenger Rna ◽  
Hepatic Necrosis ◽  
Related Factor ◽  
Necrosis Factor Alpha ◽  
Adult Mice ◽  
Nrf2 Signaling Pathway ◽  
Antioxidant Proteins ◽  
Oxide Synthase

Acrylamide is a well characterized neurotoxicant known to cause neuropathy and encephalopathy in humans and experimental animals. To investigate the role of nuclear factor erythroid 2-related factor 2 (Nrf2) in acrylamide-induced neuropathy, male C57Bl/6JJcl adult mice were exposed to acrylamide at 0, 200 or 300 ppm in drinking water and co-administered with subcutaneous injections of sulforaphane, a known activator of the Nrf2 signaling pathway at 0 or 25 mg/kg body weight daily for 4 weeks. Assessments for neurotoxicity, hepatotoxicity, oxidative stress as well as messenger RNA-expression analysis for Nrf2-antioxidant and pro-inflammatory cytokine genes were conducted. Relative to mice exposed only to acrylamide, co-administration of sulforaphane protected against acrylamide-induced neurotoxic effects such as increase in landing foot spread or decrease in density of noradrenergic axons as well as hepatic necrosis and hemorrhage. Moreover, co-administration of sulforaphane enhanced acrylamide-induced mRNA upregulation of Nrf2 and its downstream antioxidant proteins and suppressed acrylamide-induced mRNA upregulation of tumor necrosis factor alpha (TNF-α) and inducible nitric oxide synthase (iNOS) in the cerebral cortex. The results demonstrate that activation of the Nrf2 signaling pathway by co-treatment of sulforaphane provides protection against acrylamide-induced neurotoxicity through suppression of oxidative stress and inflammation. Nrf2 remains an important target for the strategic prevention of acrylamide-induced neurotoxicity.

scholarly journals Sulforaphane induces colorectal cancer cell proliferation through Nrf2 activation in a p53-dependent manner

2020 ◽  
Vol 63 (1) ◽  
Author(s):  
Yunjeong Gwon ◽  
Jisun Oh ◽  
Jong-Sang Kim
Keyword(s):  
Colon Cancer ◽  
Cell Proliferation ◽  
Signaling Pathway ◽  
Cancer Cell ◽  
Related Factor ◽  
Mild Stress ◽  
Dependent Manner ◽  
Cancer Cell Proliferation ◽  
Nrf2 Signaling Pathway ◽  
Dose Dependent

AbstractSulforaphane is a well-known phytochemical that stimulates nuclear factor erythroid 2-related factor 2 (Nrf2)-mediated antioxidant cellular response. In this study, we found that sulforaphane promoted cell proliferation in HCT116 human colon cancer cells expressing a normal p53 gene in a dose-dependent but biphasic manner. Since p53 has been reported to contribute to cell survival by regulating various metabolic pathways to adapt to mild stress, we further examined cellular responses in both p53-wild-type (WT) and p53-knockout (KO) HCT116 cells exposed to sulforaphane in vitro and in vivo. Results demonstrated that sulforaphane treatment activated Nrf2-mediated antioxidant enzymes in both p53-WT and p53-KO cells, decreased apoptotic protein expression in WT cells but increased in KO cells in a dose-dependent manner, and increased the expression of a mitochondrial biogenesis marker PGC1α in WT cells but decreased in KO cells. Moreover, a low dose of sulforaphane promoted tumor growth, upregulated the Nrf2 signaling pathway, and decreased apoptotic cell death in p53-WT HCT116 xenografts compared to that in p53-KO HCT116 xenografts in BALB/c nude mice. These findings suggest that sulforaphane can influence colon cancer cell proliferation and mitochondrial function through a crosstalk between the Nrf2 signaling pathway and p53 axis.

Downregulation of Sulfiredoxin (Srx) Suppressed Cell Proliferation Migration and Invasion Through Inhibiting Extracellular Signal-Regulated Kinase/Nrf2 Pathway in Hepatocellular Carcinoma

2021 ◽  
Vol 11 (11) ◽  
pp. 2137-2145
Author(s):  
Xuejuan Zhu ◽  
Danqian Lu
Keyword(s):  
Cell Proliferation ◽  
Western Blot ◽  
Signaling Pathway ◽  
Cell Lines ◽  
Colony Formation ◽  
Migration And Invasion ◽  
Related Factor ◽  
Extracellular Signal Regulated Kinase ◽  
Extracellular Signal ◽  
Nrf2 Signaling Pathway

Background: Sulfiredoxin (Srx) has been identified to play important roles in the development of various cancers. However, the precise effects and underlying mechanism of Srx on the progression of HCC are far from being fully understood. Materials and Methods: The abundances of Srx in THLE-2 cell and HCC cell lines were determined by western blot and RT-qPCR. Next, SK-Hep-1 cells were transfected with shRNA-Srx or shRNA-NC and treated with TBHQ (an extracellular signal-regulated kinase (ERK) activator) for functional experiments. Then, CCK8 and colony formation assays were used to determine cell proliferation and clone-forming abilities in vitro. Cell migration and invasion were assessed via wound healing and transwell assays. The expression of MMP2, MMP9 and key members in ERK/nuclear factor E2 related factor (Nrf2) signaling pathway was detected by performing western blot analysis. Results: We reported evidence that Srx was frequently up-regulated in HCC cell lines. Srx interference constrained cell proliferation, colony formation rate, migration and invasion of SK-Hep-1 cells. Moreover, mechanistic investigations indicated that Srx interference significantly inhibited the activation of ERK/Nrf2 signaling pathway, and ERK activator TBHQ can reverse the functions of Srx interference in SK-Hep-1 cells. Conclusion: Overall, Downregulation of Srx might impede HCC progression by suppressing ERK/Nrf2 signaling pathway. Findings in the current study reported the functional involvement and molecular mechanism of Srx in HCC, suggesting that Srx might have a potential therapeutic value in HCC treatment.

scholarly journals Hepatoprotective Effect of Polysaccharides Isolated from Dendrobium officinale against Acetaminophen-Induced Liver Injury in Mice via Regulation of the Nrf2-Keap1 Signaling Pathway

2018 ◽  
Vol 2018 ◽  
pp. 1-10 ◽  
Author(s):  
Guosheng Lin ◽  
Dandan Luo ◽  
Jingjing Liu ◽  
Xiaoli Wu ◽  
Jinfen Chen ◽  
...  
Keyword(s):  
Liver Injury ◽  
Signaling Pathway ◽  
Nuclear Translocation ◽  
Hepatoprotective Effect ◽  
Dendrobium Officinale ◽  
Regulatory Subunit ◽  
Heme Oxygenase 1 ◽  
Related Factor ◽  
Glutamate Cysteine Ligase ◽  
Nrf2 Signaling Pathway

The effect of polysaccharides isolated from Dendrobium officinale (DOP) on acetaminophen- (APAP-) induced hepatotoxicity and the underlying mechanisms involved are investigated. Male Institute of Cancer Research (ICR) mice were randomly assigned to six groups: (1) control, (2) vehicle (APAP, 230 mg/kg), (3) N-acetylcysteine (100 mg/kg), (4) 50 mg/kg DOP, (5) 100 mg/kg DOP, and (6) 200 mg/kg DOP. Alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels in the serum and glutathione (GSH), malondialdehyde (MDA), catalase (CAT), total antioxidant capacity (T-AOC), myeloperoxidase (MPO), and reactive oxygen species (ROS) levels in the liver were determined after the death of the mice. The histological examination of the liver was also performed. The effect of DOP on the Kelch-like ECH-associated protein 1- (Keap1-) nuclear factor erythroid 2-related factor 2 (Nrf2) signaling pathway was evaluated using Western blot analysis and real-time polymerase chain reaction (PCR). The results showed that DOP treatment significantly alleviated the hepatic injury. The decrease in ALT and AST levels in the serum and ROS, MDA, and MPO contents in the liver, as well as the increases in GSH, CAT, and T-AOC in the liver, were observed after DOP treatment. DOP treatment significantly induced the dissociation of Nrf2 from the Nrf2−Keap1 complex and promoted the Nrf2 nuclear translocation. Subsequently, DOP-mediated Nrf2 activation triggered the transcription and expressions of the glutamate–cysteine ligase catalytic (GCLC) subunit, glutamate–cysteine ligase regulatory subunit (GCLM), heme oxygenase-1 (HO-1), and NAD(P)H dehydrogenase quinone 1 (NQO1) in APAP-treated mice. The present study revealed that DOP treatment exerted potentially hepatoprotective effects against APAP-induced liver injury. Further investigation about mechanisms indicated that DOP exerted the hepatoprotective effect by suppressing the oxidative stress and activating the Nrf2−Keap1 signaling pathway.

scholarly journals Ganoderic Acid D Protects Human Amniotic Mesenchymal Stem Cells against Oxidative Stress-Induced Senescence through the PERK/NRF2 Signaling Pathway

2020 ◽  
Vol 2020 ◽  
pp. 1-18
Author(s):  
Yan Xu ◽  
Huan Yuan ◽  
Yi Luo ◽  
Yu-Jie Zhao ◽  
Jian-Hui Xiao
Keyword(s):  
Oxidative Stress ◽  
Stem Cells ◽  
Signaling Pathway ◽  
Adult Stem Cells ◽  
Telomerase Activity ◽  
Related Factor ◽  
Dependent Manner ◽  
Ganoderic Acid ◽  
Nrf2 Signaling Pathway

Aging is an important risk factor in the occurrence of many chronic diseases. Senescence and exhaustion of adult stem cells are considered as a hallmark of aging in organisms. In this study, a senescent human amniotic mesenchymal stem cell (hAMSC) model subjected to oxidative stress was established in vitro using hydrogen peroxide. We investigated the effects of ganoderic acid D (GA-D), a natural triterpenoid compound produced from Ganoderma lucidum, on hAMSC senescence. GA-D significantly inhibited β-galactosidase (a senescence-associated marker) formation, in a dose-dependent manner, with doses ranging from 0.1 μM to 10 μM, without inducing cytotoxic side-effects. Furthermore, GA-D markedly inhibited the generation of reactive oxygen species (ROS) and the expression of p21 and p16 proteins, relieved the cell cycle arrest, and enhanced telomerase activity in senescent hAMSCs. Furthermore, GA-D upregulated the expression of phosphorylated protein kinase R- (PKR-) like endoplasmic reticulum kinase (PERK), peroxidase III (PRDX3), and nuclear factor-erythroid 2-related factor (NRF2) and promoted intranuclear transfer of NRF2 in senescent cells. The PERK inhibitor GSK2656157 and/or the NRF2 inhibitor ML385 suppressed the PERK/NRF2 signaling, which was activated by GA-D. They induced a rebound for the generation of ROS and β-galactosidase-positive cells and attenuated the differentiation capacity. These findings suggest that GA-D retards hAMSC senescence through activation of the PERK/NRF2 signaling pathway and may be a promising candidate for the discovery of antiaging agents.

Effect of fluoride on PERK-Nrf2 signaling pathway in mouse ameloblasts

2019 ◽  
Vol 38 (7) ◽  
pp. 833-845
Author(s):  
X Zhou ◽  
Z Chen ◽  
W Zhong ◽  
R Yu ◽  
L He
Keyword(s):  
Oxidative Stress ◽  
Er Stress ◽  
Signaling Pathway ◽  
Nuclear Import ◽  
Target Genes ◽  
Dental Fluorosis ◽  
Related Factor ◽  
Dependent Manner ◽  
Nrf2 Signaling Pathway ◽  
Glutamylcysteine Synthetase

In the development of dental fluorosis, oxidative stress is considered as the key mechanism. Endoplasmic reticulum (ER) stress can induce oxidative stress and activate the important antioxidative factor nuclear factor erythroid 2-related factor 2 (Nrf2) in a PKR-like ER kinase (PERK)-dependent manner, but combining ER stress and oxidative stress, the role of PERK-Nrf2 signaling pathway involved in fluoride-regulated ameloblasts is not fully defined. Here, we studied the effect of fluoride on PERK-Nrf2 signaling pathway in mouse ameloblasts. We found that low-dose and continuous fluoride exposure increased binding immunoglobulin protein expression and activated PERK–activating transcription factor 4 signaling pathway. Meanwhile, the expression of Nrf2 and its target genes (glutamylcysteine synthetase and glutathione S-transferase-P1) enhanced following ER stress. Tunicamycin increased the expression of PERK, leading to Nrf2 nuclear import, and tauroursodeoxycholate suppressed Nrf2 activation through PERK during ER stress, indicating that PERK activation is required for Nrf2 nuclear entry. Furthermore, tert-butylhydroquinone triggered the overexpression of Nrf2 to reduce ER stress, but luteolin inhibited Nrf2 nuclear localization to elevate ER stress. In summary, this study proved that fluoride under certain dose can induce ER stress and promote Nrf2 nuclear import via PERK activation and suggested that antioxidation mechanism mediated by PERK-Nrf2 can alleviate fluoride-induced ER stress effectively.

scholarly journals Bovine Herpesvirus 1 Productive Infection Led to Inactivation of Nrf2 Signaling through Diverse Approaches

2019 ◽  
Vol 2019 ◽  
pp. 1-14
Author(s):  
Xiaotian Fu ◽  
Dongmei Chen ◽  
Yan Ma ◽  
Weifeng Yuan ◽  
Liqian Zhu
Keyword(s):  
Signaling Pathway ◽  
Bovine Herpesvirus ◽  
Productive Infection ◽  
Heme Oxygenase 1 ◽  
Related Factor ◽  
Quinone Oxidoreductase ◽  
Herpesvirus Type ◽  
Nrf2 Signaling Pathway ◽  
Mdbk Cells ◽  
Bovine Herpesvirus Type 1

Bovine herpesvirus type 1 (BoHV-1) is a significant cofactor for bovine respiratory disease complex (BRDC), the most important inflammatory disease in cattle. BoHV-1 infection in cell cultures induces overproduction of pathogenic reactive oxygen species (ROS) and the depletion of nuclear factor erythroid 2 p45-related factor 2 (Nrf2), a master transcriptional factor regulating a panel of antioxidant and cellular defense genes in response to oxidative stress. In this study, we reported that the virus productive infection in MDBK cells at the later stage significantly decreased the expression levels of heme oxygenase-1 (HO-1) and NAD(P)H quinone oxidoreductase-1 (NQO1) proteins, the canonical downstream targets regulated by Nrf2, inhibited Nrf2 acetylation, reduced the accumulation of Nrf2 proteins in the nucleus, and relocalized nuclear Nrf2 proteins to form dot-like staining patterns in confocal microscope assay. The differential expression of Kelch-like ECH associated protein 1 (KEAP1) and DJ-1 proteins as well as the decreased association between KEAP1 and DJ-1 promoted Nrf2 degradation through the ubiquitin proteasome pathway. These data indicated that the BoHV-1 infection may significantly suppress the Nrf2 signaling pathway. Moreover, we found that there was an association between Nrf2 and LaminA/C, H3K9ac, and H3K18ac, and the binding ratios were altered following the virus infection. Taken together, for the first time, we provided evidence showing that BoHV-1 infection inhibited the Nrf2 signaling pathway by complicated mechanisms including promoting Nrf2 degradation, relocalization of nuclear Nrf2, and inhibition of Nrf2 acetylation.

l-carnitine protects human hepatocytes from oxidative stress-induced toxicity through Akt-mediated activation of Nrf2 signaling pathway

2016 ◽  
Vol 94 (5) ◽  
pp. 517-525 ◽  
Author(s):  
Jinlian Li ◽  
Yanli Zhang ◽  
Haiyun Luan ◽  
Xuehong Chen ◽  
Yantao Han ◽  
...  
Keyword(s):  
Protective Effect ◽  
Signaling Pathway ◽  
Nuclear Translocation ◽  
Cell Damage ◽  
Binding Activity ◽  
Akt Pathway ◽  
Heme Oxygenase 1 ◽  
Related Factor ◽  
Akt Inhibitor ◽  
Nrf2 Signaling Pathway

In our previous study, l-carnitine was shown to have cytoprotective effect against hydrogen peroxide (H2O2)-induced injury in human normal HL7702 hepatocytes. The aim of this study was to investigate whether the protective effect of l-carnitine was associated with the nuclear factor erythroid 2 (NFE2)-related factor 2 (Nrf2) pathway. Our results showed that pretreatment with l-carnitine augmented Nrf2 nuclear translocation, DNA binding activity and heme oxygenase-1 (HO-1) expression in H2O2-treated HL7702 cells, although l-carnitine treatment alone had no effect on them. Analysis using Nrf2 siRNA demonstrated that Nrf2 activation was involved in l-carnitine-induced HO-1 expression. In addition, l-carnitine-mediated protection against H2O2 toxicity was abrogated by Nrf2 siRNA, indicating the important role of Nrf2 in l-carnitine-induced cytoprotection. Further experiments revealed that l-carnitine pretreatment enhanced the phosphorylation of Akt in H2O2-treated cells. Blocking Akt pathway with inhibitor partly abrogated the protective effect of l-carnitine. Moreover, our finding demonstrated that the induction of Nrf2 translocation and HO-1 expression by l-carnitine directly correlated with the Akt pathway because Akt inhibitor showed inhibitory effects on the Nrf2 translocation and HO-1 expression. Altogether, these results demonstrate that l-carnitine protects HL7702 cells against H2O2-induced cell damage through Akt-mediated activation of Nrf2 signaling pathway.

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