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Free Radical Biology and Medicine (FRBM)

Downregulation of glycine decarboxylase enhanced cofilin-mediated migration in hepatocellular carcinoma cells

Publication date: 20 May 2018 Source:Free Radical Biology and Medicine, Volume 120 Author(s): Hao Zhuang, Qiang Li, Xinran Zhang, Xuda Ma, Zun Wang, Yun Liu, Xianfu Yi, Ruibing Chen, Feng Han, Ning Zhang, Yongmei Li Metabolic reprogramming is a hallmark of cancer. Glycine decarboxylase (GLDC), an oxidoreductase, plays an important role in amino acid metabolism. While GLDC promotes tumor initiation and proliferation in non-small cell lung cancer and glioma and it was reported as a putative tumor suppressor gene in gastric cancer, the role of GLDC in hepatocellular carcinoma (HCC) is unknown. In the current study, microarray-based analysis suggested that GLDC expression was low in highly malignant HCC cell lines, and clinicopathological analysis revealed a decrease in GLDC in HCC tumor samples. While the knockdown of GLDC enhanced cancer cell migration and invasion, GLDC overexpression inhibited them. Mechanistic studies revealed that GLDC knockdown increased the levels of reactive oxygen species (ROS) and decreased the ratio of glutathione/oxidized glutathione (GSH/GSSG), which in turn dampened the ubiquitination of cofilin, a key regulator of actin polymerization. Consequently, the protein level of cofilin was elevated, which accounted for the increase in cell migration. The overexpression of GLDC reversed the phenotype. Treatment with N-acetyl-L-cysteine decreased the protein level of cofilin while treatment with H2O2 increased it, further confirming the role of ROS in regulating cofilin degradation. In a tumor xenographic transplant nude mouse model, the knockdown of GLDC promoted intrahepatic metastasis of HCC while GLDC overexpression inhibited it. Our data indicate that GLDC downregulation decreases ROS-mediated ubiquitination of cofilin to enhance HCC progression and intrahepatic metastasis. Graphical abstract

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An evolving understanding of the S-glutathionylation cycle in pathways of redox regulation

Publication date: 20 May 2018 Source:Free Radical Biology and Medicine, Volume 120 Author(s): Jie Zhang, Zhi-wei Ye, Shweta Singh, Danyelle M. Townsend, Kenneth D. Tew By nature of the reversibility of the addition of glutathione to low pKa cysteine residues, the post-translational modification of S-glutathionylation sanctions a cycle that can create a conduit for cell signaling events linked with cellular exposure to oxidative or nitrosative stress. The modification can also avert proteolysis by protection from over-oxidation of those clusters of target proteins that are substrates. Altered functions are associated with S-glutathionylation of proteins within the mitochondria and endoplasmic reticulum compartments, and these impact energy production and protein folding pathways. The existence of human polymorphisms of enzymes involved in the cycle (particularly glutathione S-transferase P) create a scenario for inter-individual variance in response to oxidative stress and a number of human diseases with associated aberrant S-glutathionylation have now been identified. Graphical abstract

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Nrf2 inhibits oxaliplatin-induced peripheral neuropathy via protection of mitochondrial function

Publication date: 20 May 2018 Source:Free Radical Biology and Medicine, Volume 120 Author(s): Yang Yang, Lan Luo, Xueting Cai, Yuan Fang, Jiaqi Wang, Gang Chen, Jie Yang, Qian Zhou, Xiaoyan Sun, Xiaolan Cheng, Huaijiang Yan, Wuguang Lu, Chunping Hu, Peng Cao Oxaliplatin-induced peripheral neuropathy (OIPN) is a severe, dose-limiting toxicity associated with cancer chemotherapy. The efficacy of antioxidant administration in OIPN is debatable, as the promising preliminary results obtained with a number of antioxidants have not been confirmed in larger clinical trials. Besides its antioxidant activity, the transcription factor, nuclear factor-erythroid 2 (NF-E2) p45-related factor 2 (Nrf2) plays a crucial role in the maintenance of mitochondrial homeostasis, and mitochondrial dysfunction is a key contributor to OIPN. Here, we have investigated the protective properties of Nrf2 in OIPN. Nrf2 -/- mice displayed severe mechanical allodynia and cold sensitivity and thus experienced increased peripheral nervous system injury compared to Nrf2 +/+ mice. Furthermore, Nrf2 knockout aggravated oxaliplatin-induced reactive oxygen species production, decreased the mitochondrial membrane potential, led to abnormal intracellular calcium levels, and induced cytochrome c-related apoptosis and overexpression of the TRP protein family. Sulforaphane-induced activation of the Nrf2 signaling pathway alleviated morphological alterations, mitochondrial dysfunction in dorsal root ganglion neurons, and nociceptive sensations in mice. Our findings reveal that Nrf2 may play a critical role in ameliorating OIPN, through protection of mitochondrial function by alleviating oxidative stress and inhibiting TRP protein family expression. This suggests that pharmacological or therapeutic activation of Nrf2 may be used to prevent or slow down the progression of OIPN. Graphical abstract

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Nitrite exerts antioxidant effects, inhibits the mTOR pathway and reverses hypertension-induced cardiac hypertrophy

Publication date: 20 May 2018 Source:Free Radical Biology and Medicine, Volume 120 Author(s): Danielle A. Guimaraes, Madla A. dos Passos, Elen Rizzi, Lucas C. Pinheiro, Jefferson H. Amaral, Raquel F. Gerlach, Michele M. Castro, Jose E. Tanus-Santos Cardiac hypertrophy is a common consequence of chronic hypertension and leads to heart failure and premature death. The anion nitrite is now considered as a bioactive molecule able to exert beneficial cardiovascular effects. Previous results showed that nitrite attenuates hypertension-induced increases in reactive oxygen species (ROS) production in the vasculature. Whether antioxidant effects induced by nitrite block critical signaling pathways involved in cardiac hypertrophy induced by hypertension has not been determined yet. The Akt/mTOR signaling pathway is responsible to activate protein synthesis during cardiac remodeling and is activated by increased ROS production, which is commonly found in hypertension. Here, we investigated the effects of nitrite treatment on cardiac remodeling and activation of this hypertrophic signaling pathway in 2 kidney-1 clip (2K1C) hypertension. Sham and 2K1C rats were treated with oral nitrite at 1 or 15 mg/kg for four weeks. Nitrite treatment (15 mg/kg) reduced systolic blood pressure and decreased ROS production in the heart tissue from hypertensive rats. This nitrite dose also blunted hypertension-induced activation of mTOR pathway and cardiac hypertrophy. While the lower nitrite dose (1 mg/kg) did not affect blood pressure, it exerted antioxidant effects and tended to attenuate mTOR pathway activation and cardiac hypertrophy induced by hypertension. Our findings provide strong evidence that nitrite treatment decreases cardiac remodeling induced by hypertension as a result of its antioxidant effects and downregulation of mTOR signaling pathway. This study may help to establish nitrite as an effective therapy in hypertension-induced cardiac hypertrophic remodeling. Graphical abstract

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Macrophage-derived superoxide production and antioxidant response following skeletal muscle injury

Publication date: 20 May 2018 Source:Free Radical Biology and Medicine, Volume 120 Author(s): Emmeran Le Moal, Gaëtan Juban, Anne Sophie Bernard, Tamas Varga, Clotilde Policar, Bénédicte Chazaud, Rémi Mounier Macrophages are key players of immunity that display different functions according to their activation states. In a regenerative context, pro-inflammatory macrophages (Ly6Cpos) are involved in the mounting of the inflammatory response whereas anti-inflammatory macrophages (Ly6Cneg) dampen the inflammation and promote tissue repair. Reactive oxygen species (ROS) production is a hallmark of tissue injury and of subsequent inflammation as described in a bacterial challenge context. However, whether macrophages produce ROS following a sterile tissue injury is uncertain. In this study, we used complementary in vitro, ex vivo and in vivo experiments in mouse to show that macrophages do not release ROS following a sterile injury in skeletal muscle. Furthermore, expression profiles of genes involved in the response to oxidative stress in Ly6Cpos and Ly6Cneg macrophage subsets did not indicate any antioxidant response in this context. Finally, in vivo, pharmacological antioxidant supplementation with N-Acetyl-cysteine (NAC) following skeletal muscle injury did not alter macrophage phenotype during skeletal muscle regeneration. Overall, these results indicate that following a sterile injury, macrophage-derived ROS release is not involved in the regulation of the inflammatory response in the regenerating skeletal muscle. Graphical abstract

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Redox Biology

PARP1 promoter links cell cycle progression with adaptation to oxidative environment

Publication date: September 2018 Source:Redox Biology, Volume 18 Author(s): Julita Pietrzak, Corinne M. Spickett, Tomasz Płoszaj, László Virág, Agnieszka Robaszkiewicz Although electrophiles are considered as detrimental to cells, accumulating recent evidence indicates that proliferating non-cancerous and particularly cancerous cells utilize these agents for pro-survival and cell cycle promoting signaling. Hence, the redox shift to mild oxidant release must be balanced by multiple defense mechanisms. Our latest findings demonstrate that cell cycle progression, which dictates oxidant level in stress-free conditions, determines PARP1 transcription. Growth modulating factors regulate CDK4/6-RBs-E2Fs axis. In cells arrested in G1 and G0, RB1-E2F1 and RBL2-E2F4 dimers recruit chromatin remodelers such as HDAC1, SWI/SNF and PRC2 to condense chromatin and turn off transcription. Release of retinoblastoma-based repressive complexes from E2F-dependent gene promoters in response to cell transition to S phase enables transcription of PARP1. This enzyme contributes to repair of oxidative DNA damage by supporting several strand break repair pathways and nucleotide or base excision repair pathways, as well as acting as a co-activator of transcription factors such as NRF2 and HIF1a, which control expression of antioxidant enzymes involved in removal of electrophiles and secondary metabolites. Furthermore, PARP1 is indispensible for transcription of the pro-survival kinases MAP2K6, ERK1/2 and AKT1, and for maintaining MAPK activity by suppressing transcription of the MAPK inhibitor, MPK1. In summary, cell cycle controlled PARP1 transcription helps cells to adapt to a pro-oxidant redox shift. Graphical abstract

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Neuroprotection against 6-OHDA toxicity in PC12 cells and mice through the Nrf2 pathway by a sesquiterpenoid from Tussilago farfara

Publication date: September 2018 Source:Redox Biology, Volume 18 Author(s): Joohee Lee, Kwangho Song, Eugene Huh, Myung Sook Oh, Yeong Shik Kim Oxidative stress plays a key role in neurodegenerative diseases such as Alzheimer's and Parkinson's diseases. Therefore, the nuclear factor-E2-related factor 2 (Nrf2), a key regulator of the antioxidative response, is considered to be important as a therapeutic target for neurodegenerative diseases. We investigated the underlying mechanism of Nrf2-mediated neuroprotective effects against oxidative stress in the PC12 cell line by 7β-(3-ethyl-cis-crotonoyloxy)-1α-(2-methylbutyryloxy)-3,14-dehydro-Z-notonipetranone (ECN), one of the sesquiterpenoids in Farfarae Flos. Pretreatment of PC12 cells with ECN had a protective effect against hydrogen peroxide (H2O2)- or 6-hydroxydopamine (6-OHDA)-induced cytotoxicity. ECN upregulated the ARE-luciferase activity and induced the mRNA expression of Nrf2 and antioxidant enzyme heme oxygenase-1 (HO-1). Knockdown of Nrf2 by small, interfering RNA (siRNA) abrogated the upregulation of HO-1, indicating that ECN had induced HO-1 via the Nrf2 pathway. Pretreatment with the thiol reducing agents, N-acetylcysteine (NAC) or dithiothreitol (DTT), attenuated Nrf2 activation and HO-1 expression. However, the non-thiol reducing antioxidant, Trolox, failed to inhibit HO-1 induction by ECN. These results suggest that ECN may directly interact with Kelch-like ECH-associated protein 1 (Keap1) and modify critical cysteine thiols present in the proteins responsible for Nrf2-mediated upregulation of HO-1. In a 6-OHDA-induced mouse model of PD, administration of ECN ameliorated motor impairments and dopaminergic neuronal damage. Taken together, ECN exerts neuroprotective effects by activating the Nrf2/HO-1 signaling pathway in both PC12 cells and mice. Thus, ECN, as an Nrf2 activator, could be an attractive therapeutic candidate for the neuroprotection or treatment of neurodegenerative diseases. Graphical abstract

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Adropin regulates pyruvate dehydrogenase in cardiac cells via a novel GPCR-MAPK-PDK4 signaling pathway

Publication date: September 2018 Source:Redox Biology, Volume 18 Author(s): Dharendra Thapa, Michael W. Stoner, Manling Zhang, Bingxian Xie, Janet R. Manning, Danielle Guimaraes, Sruti Shiva, Michael J. Jurczak, Iain Scott Mitochondria supply ~90% of the ATP required for contractile function in cardiac cells. While adult cardiomyocytes preferentially utilize fatty acids as a fuel source for oxidative phosphorylation, cardiac mitochondria can switch to other substrates when required. This change is driven in part by a combination of extracellular and intracellular signal transduction pathways that alter mitochondrial gene expression and enzymatic activity. The mechanisms by which extracellular metabolic information is conveyed to cardiac mitochondria are not currently well defined. Recent work has shown that adropin – a liver-secreted peptide hormone – can induce changes in mitochondrial fuel substrate utilization in skeletal muscle, leading to increased glucose use. In this study, we examined whether adropin could regulate mitochondrial glucose utilization pathways in cardiac cells. We show that stimulation of cultured cardiac cells with adropin leads to decreased expression of the pyruvate dehydrogenase (PDH) negative regulator PDK4, which reduces inhibitory PDH phosphorylation. The downregulation of PDK4 expression by adropin is lost when GPR19 – a putative adropin receptor – is genetically depleted in H9c2 cells. Loss of GRP19 expression alone increased PDK4 expression, leading to a reduction in mitochondrial respiration. Finally, we show that adropin-mediated GPR19 signaling relies on the p44/42 MAPK pathway, and that pharmacological disruption of this pathway blocks the effects of adropin on PDK4 in cardiac cells. These findings suggest that adropin may be a key regulator of fuel substrate utilization in the heart, and implicates an orphan G-protein coupled receptor in a novel signaling pathway controlling mitochondrial fuel metabolism. Graphical abstract

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Cyanidin and delphinidin modulate inflammation and altered redox signaling improving insulin resistance in high fat-fed mice

Publication date: September 2018 Source:Redox Biology, Volume 18 Author(s): Elena Daveri, Eleonora Cremonini, Angela Mastaloudis, Shelly N. Hester, Steven M. Wood, Andrew L. Waterhouse, Mauri Anderson, Cesar G. Fraga, Patricia I. Oteiza Consumption of diets high in fat and/or fructose content promotes tissue inflammation, oxidative stress, and insulin resistance, activating signals (e.g. NF-κB/JNK) that downregulate the insulin cascade. Current evidence supports the concept that select flavonoids can mitigate obesity and type 2 diabetes (T2D). This work investigated if supplementation with the anthocyanidins (AC) cyanidin and delphinidin could attenuate the adverse consequences of consuming a high fat diet (HFD) in mice. Consumption of an AC-rich blend mitigated HFD-induced obesity, dyslipidemia and insulin resistance (impaired responses to insulin and glucose). HFD-fed mice were characterized by increased liver lipid deposition and inflammation, which were also attenuated upon AC supplementation. HFD caused liver oxidative stress showing an increased expression of NADPH oxidases, generators of superoxide and H2O2, and high levels of oxidized lipid-protein adducts. This was associated with the activation of the redox sensitive signals IKK/NF-κB and JNK1/2, and increased expression of the NF-κB-regulated PTP1B phosphatase, all known inhibitors of the insulin pathway. In agreement with an improved insulin sensitivity, AC supplementation inhibited oxidative stress, NF-κB and JNK activation, and PTP1B overexpression. Thus, cyanidin and delphinidin consumption either through diet or by supplementation could be a positive strategy to control the adverse effects of Western style diets, including overweight, obesity, and T2D. Modulation of inflammation, oxidative stress, and NF-κB/JNK activation emerge as relevant targets of AC beneficial actions. Graphical abstract

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Redox mechanism of levobupivacaine cytostatic effect on human prostate cancer cells

Publication date: September 2018 Source:Redox Biology, Volume 18 Author(s): Caroline Jose, Etienne Hebert-Chatelain, Nivea Dias Amoedo, Emmanuel Roche, Emilie Obre, Didier Lacombe, Hamid Reza Rezvani, Philippe Pourquier, Karine Nouette-Gaulain, Rodrigue Rossignol Anti-cancer effects of local anesthetics have been reported but the mode of action remains elusive. Here, we examined the bioenergetic and REDOX impact of levobupivacaine on human prostate cancer cells (DU145) and corresponding non-cancer primary human prostate cells (BHP). Levobupivacaine induced a combined inhibition of glycolysis and oxidative phosphorylation in cancer cells, resulting in a reduced cellular ATP production and consecutive bioenergetic crisis, along with reactive oxygen species generation. The dose-dependent inhibition of respiratory chain complex I activity by levobupivacaine explained the alteration of mitochondrial energy fluxes. Furthermore, the potency of levobupivacaine varied with glucose and oxygen availability as well as the cellular energy demand, in accordance with a bioenergetic anti-cancer mechanism. The levobupivacaine-induced bioenergetic crisis triggered cytostasis in prostate cancer cells as evidenced by a S-phase cell cycle arrest, without apoptosis induction. In DU145 cells, levobupivacaine also triggered the induction of autophagy and blockade of this process potentialized the anti-cancer effect of the local anesthetic. Therefore, our findings provide a better characterization of the REDOX mechanisms underpinning the anti-effect of levobupivacaine against human prostate cancer cells.

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