?-Lipoic acid prevents against cisplatin cytotoxicity via activation of the NRF2/HO-1 antioxidant pathway.
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ABSTRACT:
SUBMITTER: Lee J
PROVIDER: S-EPMC6932784 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:Nrf2 antioxidant signaling is involved in liver protection, but this generalization overlooks conflicting studies indicating that Nrf2 effects are not necessarily hepatoprotective. The role of Nrf2/HO-1 in cholestatic liver injury (CLI) remains poorly defined. Here, we report that Nrf2/HO-1 activation exacerbates liver injury rather than exerts a protective effect in CLI. Inhibiting HO-1 or ameliorating bilirubin transport alleviates liver injury in CLI models. Nrf2 knockout confers hepatoprotection in CLI mice, whereas in non-CLI mice, Nrf2 knockout aggravates liver damage. In the CLI setting, oxidative stress activates Nrf2/HO-1, leads to bilirubin accumulation, and impairs mitochondrial function. High levels of bilirubin reciprocally upregulate the activation of Nrf2 and HO-1, while antioxidant and mitochondria-targeted SOD2 overexpression attenuate the toxicity of bilirubin. Additionally, the expression of Nrf2 and HO-1 is significantly elevated in serum of patients with CLI. These results reveal an unrecognized function of Nrf2 signaling in exacerbating liver injury in cholestatic disease.
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Project description:The citric acid cycle (CAC) metabolite fumarate has been proposed to be cardioprotective; however, its mechanisms of action remain to be determined. To augment cardiac fumarate levels and to assess fumarate's cardioprotective properties, we generated fumarate hydratase (Fh1) cardiac knockout (KO) mice. These fumarate-replete hearts were robustly protected from ischemia-reperfusion injury (I/R). To compensate for the loss of Fh1 activity, KO hearts maintain ATP levels in part by channeling amino acids into the CAC. In addition, by stabilizing the transcriptional regulator Nrf2, Fh1 KO hearts upregulate protective antioxidant response element genes. Supporting the importance of the latter mechanism, clinically relevant doses of dimethylfumarate upregulated Nrf2 and its target genes, hence protecting control hearts, but failed to similarly protect Nrf2-KO hearts in an in vivo model of myocardial infarction. We propose that clinically established fumarate derivatives activate the Nrf2 pathway and are readily testable cytoprotective agents.
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Project description:Prevention of hepatic fat accumulation may be an important approach for liver diseases due to the increased relevance of hepatic steatosis in this field. This study was conducted to investigate the effects of the antioxidant ?-lipoic acid (?-LA) on hepatic steatosis, hepatocellular function, and oxidative stress in a model of type 2 diabetes fed with a high fat diet (HFD). Goto-Kakizaki rats were randomly divided into four groups. The first group received only a standard rat diet (control GK) including groups 2 (HFD), 3 (vehicle group), and 4 (?-LA group), which were given HFD, ad libitum during three months. Wistar rats are the non-diabetic control group. Carbohydrate and lipid metabolism, liver function, plasma and liver tissue malondialdehyde (MDA), liver GSH, tumor necrosis factor-? (TNF-?) and nuclear factor E2 (erythroid-derived 2)-related factor-2 (Nrf2) levels were assessed in the different groups. Liver function was assessed using quantitative hepatobiliary scintigraphy, serum aspartate, and alanine aminotransferases (AST, ALT), alkaline phosphatase, gamma-glutamyltranspeptidase, and bilirubin levels. Histopathologically steatosis and fibrosis were evaluated. Type 2 diabetic animals fed with HFD showed a marked hepatic steatosis and a diminished hepatic extraction fraction and both were fully prevented with ?-LA. Plasma and liver tissue MDA and hepatic TNF-? levels were significantly higher in the HFD group when compared with the control group and significantly lower in the ?-LA group. Systemic and hepatic cholesterol, triglycerides, and serum uric acid levels were higher in hyperlipidemic GK rats and fully prevented with ?-LA. In addition, nuclear Nrf2 activity was significantly diminished in GK rats and significantly augmented after ?-LA treatment. In conclusion, ?-LA strikingly ameliorates steatosis in this animal model of diabetes fed with HFD by decrementing the inflammatory marker TNF-? and reducing oxidative stress. ?-LA might be considered a useful therapeutic tool to prevent hepatic steatosis by incrementing antioxidant defense systems through Nrf2 and consequently decreasing oxidative stress and inflammation in type 2 diabetes.
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