Fyn Inhibition by Cycloalkane-Fused 1,2-Dithiole-3-thiones Enhances Antioxidant Capacity and Protects Mitochondria from Oxidative Injury

Koo, Ja Hyun; Lee, Woo Hyung; Lee, Chan Gyu; Kim, Sang Geon

doi:10.1124/mol.111.077149

Cited by 22 publications

(13 citation statements)

References 52 publications

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“…Our study using LY294002, a PI3K inhibitor, reveals that the role of Akt in cell survival is linked to the promotion of Nrf2/ARE transcriptional regulation, which is brought to effect by checking GSK3 β -mediated Fyn kinase activation. Fyn kinase, which is said to have key role in promoting Nrf2 degradation, 13, 15, 23 has been implicated in oxidative stress-associated functional insufficiencies 24, 25 as well as apoptosis. 26, 27, 28 We observed that Fyn kinase inhibition using PP1 suppressed the endogenous ROS levels along with enhancement in stability and functional capacity of Nrf2.…”

Section: Discussionmentioning

confidence: 99%

Essential role of PH domain and leucine-rich repeat protein phosphatase 2 in Nrf2 suppression via modulation of Akt/GSK3β/Fyn kinase axis during oxidative hepatocellular toxicity

2014

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Instances of sustained oxidative activity have been shown to involve dysregulation of Nrf2-mediated transcriptional induction; however, mechanisms warranting Nrf2-repression remain unclear. In this study, using primary rat hepatocytes, we have attempted to identify factors that may negatively influence Nrf2 survival pathway. Though studies indicate a conspicuous association between Akt and Nrf2, a confirmatory link between the two is unaddressed. On inhibiting PI3K/Akt pathway, we observed compromised activities of antioxidant and detoxification enzymes culminating in oxidative cytotoxicity. This was accompanied by reduced nuclear retention of Nrf2 and its ARE binding affinity, increased Nrf2 ubiquitination and concurrent decline in its downstream targets. Moreover, Akt inhibition enhanced nuclear translocation as well as phosphorylation of Fyn kinase, an enzyme linked to Nrf2 degradation, by relieving GSK3β from phosphorylation-mediated repression. The involvement of Akt and Fyn kinase in influencing Nrf2 signaling was further confirmed in oxidatively stressed hepatocytes by using tert-butyl hydroperoxide (tBHP). tBHP-induced decrease in Nrf2 levels was associated with enhanced Fyn kinase phosphorylation, Fyn kinase nuclear translocation and decreased levels of phosphorylated GSK3β(Ser9) in a time-dependent manner. Interestingly, tBHP induced site-specific deactivation of Akt as only Akt(Ser473) phosphorylation was observed to be affected. Further, protein expression as well as nuclear localization of PHLPP2, a phosphatase specific for Akt(Ser473), was found to be significantly enhanced in tBHP-stressed hepatocytes. Silencing of PHLPP2 not only resulted in considerable restoration of Nrf2 signaling, enhanced Nrf2-ARE binding and reduced Nrf2 ubiquitination but also significantly suppressed tBHP-induced ROS generation and alterations in mitochondrial permeability. We infer that cellular PHLPP2 levels may aggravate oxidative toxicity by suppressing Nrf2/ARE transcriptional regulation via Akt(Se473)/GSK3β/Fyn kinase axis. The study indicates that PHLPP2 could serve as a new target for developing strategies to manage pathological conditions exacerbated due to oxidative stress.

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Section: Discussionmentioning

confidence: 99%

Essential role of PH domain and leucine-rich repeat protein phosphatase 2 in Nrf2 suppression via modulation of Akt/GSK3β/Fyn kinase axis during oxidative hepatocellular toxicity

2014

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“…After washing with PBS containing 1% fetal bovine serum, the cells were stained with 5 μl fluorescein isothiocyanate-Annexin V and 2 μg ml −1 PI. Cell cycle analysis was done using PI48. Fluorescence intensity in the cells was assessed using BD FACSCalibur II flow cytometer and the CellQuest software (BD Biosciences, San Jose, CA, USA).…”

Section: Methodsmentioning

confidence: 99%

Hepcidin inhibits Smad3 phosphorylation in hepatic stellate cells by impeding ferroportin-mediated regulation of Akt

et al. 2016

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Hepatic stellate cell (HSC) activation on liver injury facilitates fibrosis. Hepatokines affecting HSCs are largely unknown. Here we show that hepcidin inhibits HSC activation and ameliorates liver fibrosis. We observe that hepcidin levels are inversely correlated with exacerbation of fibrosis in patients, and also confirm the relationship in animal models. Adenoviral delivery of hepcidin to mice attenuates liver fibrosis induced by CCl4 treatment or bile duct ligation. In cell-based assays, either hepcidin from hepatocytes or exogenous hepcidin suppresses HSC activation by inhibiting TGFβ1-mediated Smad3 phosphorylation via Akt. In activated HSCs, ferroportin is upregulated, which can be prevented by hepcidin treatment. Similarly, ferroportin knockdown in HSCs prohibits TGFβ1-inducible Smad3 phosphorylation and increases Akt phosphorylation, whereas ferroportin over-expression has the opposite effect. HSC-specific ferroportin deletion also ameliorates liver fibrosis. In summary, hepcidin suppresses liver fibrosis by impeding TGFβ1-induced Smad3 phosphorylation in HSCs, which depends on Akt activated by a deficiency of ferroportin.

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“…With high degree of differentiation, HepG2 cells retain many biological characteristics of hepatocytes and could synthesize nearly all human plasma proteins. It has been widely used as a cellular model to investigate the oxidative injury of hepatocytes elicited by H 2 O 2 [36–40], arachidonic acid and iron [41], hepatocytes toxicity induced by alcohol [42] or CYP2E1 [43], and hepatocellular injury by Hepatitis C virus [44]. HepG2 cells were cultured in a humidified atmosphere of 95% air plus 5% CO 2 in a 37°C incubator in Dulbecco's modified Eagle's medium supplemented with 10% heat-inactivated fetal bovine serum, 100 μ M streptomycin, and 100 U/mL penicillin.…”

Section: Methodsmentioning

confidence: 99%

N-Acetyl-Serotonin Protects HepG2 Cells from Oxidative Stress Injury Induced by Hydrogen Peroxide

Jiang

et al. 2014

Oxidative Medicine and Cellular Longevity

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Oxidative stress plays an important role in the pathogenesis of liver diseases. N-Acetyl-serotonin (NAS) has been reported to protect against oxidative damage, though the mechanisms by which NAS protects hepatocytes from oxidative stress remain unknown. To determine whether pretreatment with NAS could reduce hydrogen peroxide- (H2O2-) induced oxidative stress in HepG2 cells by inhibiting the mitochondrial apoptosis pathway, we investigated the H2O2-induced oxidative damage to HepG2 cells with or without NAS using MTT, Hoechst 33342, rhodamine 123, Terminal dUTP Nick End Labeling Assay (TUNEL), dihydrodichlorofluorescein (H2DCF), Annexin V and propidium iodide (PI) double staining, immunocytochemistry, and western blot. H2O2 produced dramatic injuries in HepG2 cells, represented by classical morphological changes of apoptosis, increased levels of malondialdehyde (MDA) and intracellular reactive oxygen species (ROS), decreased activity of superoxide dismutase (SOD), and increased activities of caspase-9 and caspase-3, release of cytochrome c (Cyt-C) and apoptosis-inducing factor (AIF) from mitochondria, and loss of membrane potential (ΔΨm). NAS significantly inhibited H2O2-induced changes, indicating that it protected against H2O2-induced oxidative damage by reducing MDA levels and increasing SOD activity and that it protected the HepG2 cells from apoptosis through regulating the mitochondrial apoptosis pathway, involving inhibition of mitochondrial hyperpolarization, release of mitochondrial apoptogenic factors, and caspase activity.

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Fyn Inhibition by Cycloalkane-Fused 1,2-Dithiole-3-thiones Enhances Antioxidant Capacity and Protects Mitochondria from Oxidative Injury

Cited by 22 publications

References 52 publications

Essential role of PH domain and leucine-rich repeat protein phosphatase 2 in Nrf2 suppression via modulation of Akt/GSK3β/Fyn kinase axis during oxidative hepatocellular toxicity

Essential role of PH domain and leucine-rich repeat protein phosphatase 2 in Nrf2 suppression via modulation of Akt/GSK3β/Fyn kinase axis during oxidative hepatocellular toxicity

Hepcidin inhibits Smad3 phosphorylation in hepatic stellate cells by impeding ferroportin-mediated regulation of Akt

N-Acetyl-Serotonin Protects HepG2 Cells from Oxidative Stress Injury Induced by Hydrogen Peroxide

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