bims-noxint 2019-05-26 papers

Issue of 2019–05–26
five papers selected by
Laia Caja Puigsubira, Uppsala University

Biomed Res Int. 2019 ;2019 1484736

Bromodomain and Extraterminal (BET) Protein Inhibition Restores Redox Balance and Inhibits Myofibroblast Activation.

Carmel J W Stock, Charalambos Michaeloudes, Patricia Leoni, Andrew L Durham, Sharon Mumby, Athol U Wells, Kian Fan Chung, Ian M Adcock, Elisabetta A Renzoni, Gisela E Lindahl.

Background and Objective: Progressive pulmonary fibrosis is the main cause of death in patients with systemic sclerosis (SSc) with interstitial lung disease (ILD) and in those with idiopathic pulmonary fibrosis (IPF). Transforming growth factor-β (TGF-β) and NADPH oxidase- (NOX-) derived reactive oxygen species (ROS) are drivers of lung fibrosis. We aimed to determine the role of the epigenetic readers, bromodomain and extraterminal (BET) proteins in the regulation of redox balance in activated myofibroblasts.
Methods: In TGF-β-stimulated fibroblasts, we investigated the effect of the BET inhibitor JQ1 on the mRNA expression of the prooxidant gene NOX4 and the antioxidant gene superoxide dismutase (SOD2) by quantitative RT-PCR, the antioxidant transcription factor NF-E2-related factor 2 (Nrf2) activity by a reporter assay, and intracellular ROS levels by dichlorofluorescein staining. Myofibroblast activation was determined by α-smooth muscle actin immunocytochemistry. The role of specific BET protein isoforms in NOX4 gene regulation was studied by siRNA silencing and chromatin-immunoprecipitation.
Results and Conclusions: Affymetrix gene array analysis revealed increased NOX4 and reduced SOD2 expression in SSc and IPF fibroblasts. SOD2 silencing in non-ILD control fibroblasts induced a profibrotic phenotype. TGF-β increased NOX4 and inhibited SOD2 expression, while increasing ROS production and myofibroblast differentiation. JQ1 reversed the TGF-β-mediated NOX4/SOD2 imbalance and Nrf2 inactivation and attenuated ROS production and myofibroblast differentiation. The BET proteins Brd3 and Brd4 were shown to bind to the NOX4 promoter and drive TGF-β-induced NOX4 expression. Our data indicate a critical role of BET proteins in promoting redox imbalance and pulmonary myofibroblast activation and support BET bromodomain inhibitors as a potential therapy for fibrotic lung disease.

DOI: https://doi.org/10.1155/2019/1484736

Cancer Biol Med. 2019 Feb;16(1): 38-54

The PI3K/Akt/GSK-3β/ROS/eIF2B pathway promotes breast cancer growth and metastasis via suppression of NK cell cytotoxicity and tumor cell susceptibility.

Fengjiao Jin, Zhaozhen Wu, Xiao Hu, Jiahui Zhang, Zihe Gao, Xiao Han, Junfang Qin, Chen Li, Yue Wang.

Objective: To examine the effect of pSer9-GSK-3β on breast cancer and to determine whether the underlying metabolic and immunological mechanism is associated with ROS/eIF2B and natural killer (NK) cells.
Methods: We employed TWS119 to inactivate GSK-3β by phosphorylating Ser9 and explored its effect on breast cancer and NK cells. The expression of GSK-3β, natural killer group 2 member D (NKG2D) ligands, eIF2B was quantified by PCR and Western blot. We measured intracellular reactive oxygen species (ROS) and mitochondrial ROS using DCFH-DA and MitoSOXTM probe, respectively, and conducted quantitative analysis of cellular respiration on 4T1 cells with mitochondrial respiratory chain complex I/III kits.
Results: Our investigation revealed that TWS119 downregulated NKG2D ligands (H60a and Rae1), suppressed the cytotoxicity of NK cells, and promoted the migration of 4T1 murine breast cancer cells. Nevertheless, LY290042, which attenuates p-GSK-3β formation by inhibiting the PI3K/Akt pathway, reversed these effects. We also found that higher expression of pSer9-GSK-3β induced higher levels of ROS, and observed that abnormality of mitochondrial respiratory chain complex I/III function induced the dysfunction of GSK-3β-induced electron transport chain, naturally disturbing the ROS level. In addition, the expression of NOX3 and NOX4 was significantly up-regulated, which affected the generation of ROS and associated with the metastasis of breast cancer. Furthermore, we found that the expression of pSer535-eIF2B promoted the expression of NKG2D ligands (Mult-1 and Rae1) following by expression of pSer9-GSK-3β and generation of ROS.
Conclusions: The PI3K/Akt/GSK-3β/ROS/eIF2B pathway could regulate NK cell activity and sensitivity of tumor cells to NK cells, which resulted in breast cancer growth and lung metastasis. Thus, GSK-3β is a promising target of anti-tumor therapy.

Keywords: GSK-3β; NK cells; NKG2D/NKG2DLs; ROS; breast cancer; eIF2B

DOI: https://doi.org/10.20892/j.issn.2095-3941.2018.0253

Redox Biol. 2019 May 09. pii: S2213-2317(19)30379-9. [Epub ahead of print]24 101209

IL-1 beta-mediated macrophage-hepatocyte crosstalk upregulates hepcidin under physiological low oxygen levels.

Inês Silva, Teresa Peccerella, Sebastian Mueller, Vanessa Rausch.

In mammals, the iron masterswitch hepcidin efficiently controls iron recycling by the macrophage-liver axis but the exact interplay between macrophages and hepatocytes remains poorly understood. We here study hepcidin response during macrophage differentiation as well as the macrophage-hepatocyte crosstalk and its subsequent effects on hepatocyte hepcidin using an in vitro co-culture model that mimics the physiological liver microenvironment. We show that macrophage differentiation strongly induces hepcidin by 60-fold both in THP1 macrophages and primary isolated monocyte-derived macrophages. Removal of H2O2 by catalase or inhibition of NOX2 efficiently blocked hepcidin induction. After differentiation, macrophage hepcidin accounted for 10% of total hepatocyte hepcidin and did not respond to low oxygen levels. In contrast, co-culture of differentiated macrophages with Huh7 cells significantly induced hepatocyte hepcidin, which was further potentiated under low oxygen levels. Hepatocyte hepcidin was also upregulated when Huh7 cells were solely exposed to macrophage-conditioned hypoxic medium. A cytokine screen identified macrophage secreted IL-1β as major inducer of hepcidin in hepatocytes. In confirmation, treatment of Huh7 cells with the IL-1 receptor antagonist (anakinra) completely blunted macrophage-mediated hepcidin transcription in hepatocytes. Finally, detailed analysis of potentially involved signaling pathways points toward STAT3 and CEBPδ-mediated hepcidin induction independent of IL-6. In conclusion, our study demonstrates a strong NOX2-mediated hepcidin induction during macrophage differentiation. These differentiated macrophages are able to efficiently induce hepatocyte hepcidin mainly through secretion of IL-1β. Our data highlight a hitherto unrecognized role of macrophage-hepatocyte crosstalk for a joint and oxygen-dependent hepcidin production through STAT3 and CEBPδ.

Keywords: Cytokines; Hydrogen peroxide; Hypoxia; Iron metabolism/hepcidin; NADPH oxidase; STAT3

DOI: https://doi.org/10.1016/j.redox.2019.101209

Mol Cancer. 2019 May 22. 18(1): 98

Circular RNA F-circSR derived from SLC34A2-ROS1 fusion gene promotes cell migration in non-small cell lung cancer.

Ke Wu, Xun Liao, Youling Gong, Juan He, Jian-Kang Zhou, Shuangyan Tan, Wenchen Pu, Canhua Huang, Yu-Quan Wei, Yong Peng.

Cancer-associated chromosomal translocations are reported to generate oncogenic circular RNA (circRNA), contributing to tumorigenesis. The fusion gene SLC34A2-ROS1 (solute carrier family 34 member 2 and ROS proto-oncogene 1) plays an important role in non-small cell lung cancer (NSCLC) progression. However, whether SLC34A2-ROS1 gene can produce circRNA remains unknown. Here, we identified two novel circRNAs (F-circSR1 and F-circSR2) generated from SLC34A2-ROS1 fusion gene, while F-circSR1 has higher expression than F-circSR2. Functional studies through gain- and loss-of-function strategies showed that both F-circSRs promote cell migration in lung cancer cells, whereas they have little effect on cell proliferation. Using the minigene GFP reporter assay, we verified that the flanking complementary sequences with canonical splicing sites are essential for F-circSR biogenesis. Therefore, our findings demonstrate the oncogenic role of F-circSR in NSCLC and highlight its therapeutic potential.

Keywords: Cell migration; Circular RNA; NSCLC; SLC34A2-ROS1

DOI: https://doi.org/10.1186/s12943-019-1028-9

Cancer Lett. 2019 May 16. pii: S0304-3835(19)30292-7. [Epub ahead of print]

A feedforward relationship between active Rac1 and phosphorylated Bcl-2 is critical for sustaining Bcl-2 phosphorylation and promoting cancer progression.

Stephen Jun Fei Chong, Jolin Xiao Hui Lai, Jianhua Qu, Jayshree Hirpara, Jia Kang, Kunchithapadam Swaminathan, Thomas Loh, Ansu Kumar, Shireen Vali, Taher Abbasi, Shazib Pervaiz.

Active GTPase-Rac1 is associated with cellular processes involved in carcinogenesis and expression of Bcl-2 endows cells with the ability to evade apoptosis. Here we provide evidence that active Rac1 and Bcl-2 work in a positive feedforward loop to promote sustained phosphorylation of Bcl-2 at serine-70 (S70pBcl-2), which stabilizes its anti-apoptotic activity. Pharmacological and genetic inactivation of Rac1 prevent interaction with Bcl-2 and reduces S70pBcl-2. Similarly, BH3-mimetic inhibitors of Bcl-2 could disrupt Rac1-Bcl-2 interaction and reduce S70pBcl-2. This effect of active Rac1 could also be rescued by scavengers of intracellular superoxide (O2-.), thus implicating NOX-activating activity of Rac1 in promoting S70pBcl-2. Moreover, active Rac1-mediated redox-dependent S70pBcl-2 involves the inhibition of phosphatase PP2A holoenzyme assembly. Sustained S70pBcl-2 in turn secures Rac1-Bcl-2 interaction. Importantly, inhibiting Rac1 activity, scavenging O2-. or employing BH3-mimetic inhibitor significantly reduced S70pBcl-2-mediated survival in cancer cells. Notably, Rac1 expression, and its interaction with Bcl-2, positively correlate with S70pBcl-2 levels in patient-derived lymphoma tissues and with advanced stage lymphoma and melanoma. Together, we provide evidence of a positive feedforward loop involving active Rac1, S70pBcl-2 and PP2A, which could have potential diagnostic, prognostic and therapeutic implications.

Keywords: Active Rac1; Bcl-2 phosphorylation; Cancer; Chemo-resistance; Reactive Oxygen Species

DOI: https://doi.org/10.1016/j.canlet.2019.05.009