bims-noxint 2021-04-25 papers

Issue of 2021–04–25
five papers selected by
Laia Caja Puigsubira, Uppsala University

Exp Mol Med. 2021 Apr 19.

MD2 blockade prevents modified LDL-induced retinal injury in diabetes by suppressing NADPH oxidase-4 interaction with Toll-like receptor-4.

Huaicheng Chen, Tao Yan, Zongming Song, Shilong Ying, Beibei Wu, Xin Ju, Xi Yang, Jia Qu, Wencan Wu, Zongduan Zhang, Yi Wang.

Modified LDL-induced inflammation and oxidative stress are involved in the pathogenesis of diabetic retinopathy. Recent studies have also shown that modified LDL activates Toll-like receptor 4 (TLR4) to mediate retinal injury. However, the mechanism by which modified LDL activates TLR4 and the potential role of the TLR4 coreceptor myeloid differentiation protein 2 (MD2) are not known. In this study, we inhibited MD2 with the chalcone derivatives L2H17 and L6H21 and showed that MD2 blockade protected retinal Müller cells against highly oxidized glycated-LDL (HOG-LDL)-induced oxidative stress, inflammation, and apoptosis. MD2 inhibition reduced oxidative stress by suppressing NADPH oxidase-4 (NOX4). Importantly, HOG-LDL activated TLR4 and increased the interaction between NOX4 and TLR4. MD2 was required for the activation of these pathways, as inhibiting MD2 prevented the association of NOX4 with TLR4 and reduced NOX4-mediated reactive oxygen species production and TLR4-mediated inflammatory factor production. Furthermore, treatment of diabetic mice with L2H17 significantly reduced LDL extravasation in the retina and prevented retinal dysfunction and apoptosis by suppressing the TLR4/MD2 pathway. Our findings provide evidence that MD2 plays a critical role in mediating modified LDL-induced cell injury in the retina and suggest that targeting MD2 may be a potential therapeutic strategy.

DOI: https://doi.org/10.1038/s12276-021-00607-w

Br J Pharmacol. 2021 Apr 04.

Apocynin prevents cigarette smoking-induced loss of skeletal muscle mass and function by preserving proteostatic signalling.

Stanley M H Chan, Ivan Bernardo, Chanelle Mastronado, Kevin Mou, Simone N De Luca, Huei Jiunn Seow, Aleksandar Dobric, Kurt Brassington, Stavros Selemidis, Steven Bozinovski, Ross Vlahos.

BACKGROUND AND PURPOSE: Skeletal muscle dysfunction is a major comorbidity of COPD. It has been postulated that this type of muscle dysfunction may be a direct consequence of oxidative insults evoked by CS exposure. The present study examined the effect of a potent Nox inhibitor and ROS scavenger, apocynin on CS-induced muscle dysfunction.
EXPERIMENTAL APPROACH: Male BALB/c mice were exposed to either room air (sham) or CS generated from 9 cigarettes per day, 5 days a week for 8 weeks with or without apocynin treatment (5 mg·kg-1 w/v, intraperitoneal injection). C2C12 myotubes exposed to either hydrogen peroxide (H2 O2 ) or water-soluble cigarette smoke extract (CSE) with or without apocynin (500 nM), was set up as an experimental model in vitro.
KEY RESULTS: Eight weeks of CS exposure caused muscle dysfunction in mice; evidenced by a 10% loss in muscle mass and 54% loss in strength of tibialis anterior which were prevented by apocynin administration. In C2C12 myotubes, direct exposure to H2 O2 or CSE caused myofiber wasting, which was associated with ~50% loss in muscle-derived insulin-like growth factor (IGF)-1 and 2-fold induction of Nox2, independent of cellular inflammation. The expression of myostatin and MAFbx, negative regulator of muscle mass, were upregulated under H2 O2 but not CSE conditions. Apocynin treatment completely attenuated CSE-induced Nox2 expression, preserving muscle-derived IGF-1 expression and signaling pathway downstream of mammalian target of rapamycin (mTOR), thereby preventing myofiber wasting.
CONCLUSION AND IMPLICATIONS: Targeted pharmacological inhibition of Nox-derived ROS may alleviate the lung and systemic manifestations in smokers with COPD.

Keywords: Antioxidants; Chronic Obstructive Pulmonary Disease; IGF-1; NADPH oxidase; Protein carbonylation

DOI: https://doi.org/10.1111/bph.15482

Free Radic Biol Med. 2021 Apr 20. pii: S0891-5849(21)00208-2. [Epub ahead of print]

Nrf2 inhibition sensitizes breast cancer stem cells to ionizing radiation via suppressing DNA repair.

Shenghui Qin, Xiaoyuan He, Houmin Lin, Bradley A Schulte, Mingfeng Zhao, Kenneth D Tew, Gavin Y Wang.

Radiation is widely used for cancer treatment but the radioresistance properties of cancer stem cells (CSCs) pose a significant challenge to the success of cancer therapy. Nuclear factor erythroid-2-related factor 2 (Nrf2) has emerged as a prominent regulator of cellular antioxidant responses and its over-activation is associated with drug resistant in cancer cells. However, the role of Nrf2 signaling in regulating the response of CSCs to irradiation has yet to be defined. Here, we show that exposure of triple-negative breast cancer (TNBC) cells to ionizing radiation (IR) upregulates Nrf2 expression and promotes its nuclear translocation in a reactive oxygen species (ROS)-dependent manner. Ectopic overexpression of Nrf2 attenuates, whereas knockdown of Nrf2 potentiates IR-induced killing of TNBC CSCs. Mechanistically, we found that Nrf2 knockdown increases IR-induced ROS production and impedes DNA repair at least in part via inhibition of DNA-PK. Furthermore, activation of Nrf2 by sulforaphane diminishes, whereas inhibition of Nrf2 by ML385 enhances IR-induced killing of TNBC CSCs. Collectively, these results demonstrate that IR-induced ROS production can activate Nrf2 signaling, which in turn counteracts the killing effect of irradiation. Therefore, pharmacological inhibition of IR-induced Nrf2 activation by ML385 could be a new therapeutic approach to sensitize therapy-resistant CSCs to radiotherapy.

Keywords: Breast cancer stem cells; DNA repair; DNA-PK; Ionizing radiation; Nrf2; Reactive oxygen species

DOI: https://doi.org/10.1016/j.freeradbiomed.2021.04.006

Front Immunol. 2021 ;12 638381

Microglial Nox2 Plays a Key Role in the Pathogenesis of Experimental Autoimmune Encephalomyelitis.

Chih-Fen Hu, San-Pin Wu, Gu-Jiun Lin, Chi-Chang Shieh, Chih-Sin Hsu, Jing-Wun Chen, Shih-Heng Chen, Jau-Shyong Hong, Shyi-Jou Chen.

While oxidative stress has been linked to multiple sclerosis (MS), the role of superoxide-producing phagocyte NADPH oxidase (Nox2) in central nervous system (CNS) pathogenesis remains unclear. This study investigates the impact of Nox2 gene ablation on pro- and anti-inflammatory cytokine and chemokine production in a mouse experimental autoimmune encephalomyelitis (EAE) model. Nox2 deficiency attenuates EAE-induced neural damage and reduces disease severity, pathogenic immune cells infiltration, demyelination, and oxidative stress in the CNS. The number of autoreactive T cells, myeloid cells, and activated microglia, as well as the production of cytokines and chemokines, including GM-CSF, IFNγ, TNFα, IL-6, IL-10, IL-17A, CCL2, CCL5, and CXCL10, were much lower in the Nox2-/- CNS tissues but remained unaltered in the peripheral lymphoid organs. RNA-seq profiling of microglial transcriptome identified a panel of Nox2 dependent proinflammatory genes: Pf4, Tnfrsf9, Tnfsf12, Tnfsf13, Ccl7, Cxcl3, and Cxcl9. Furthermore, gene ontology and pathway enrichment analyses revealed that microglial Nox2 plays a regulatory role in multiple pathways known to be important for MS/EAE pathogenesis, including STAT3, glutathione, leukotriene biosynthesis, IL-8, HMGB1, NRF2, systemic lupus erythematosus in B cells, and T cell exhaustion signaling. Taken together, our results provide new insights into the critical functions performed by microglial Nox2 during the EAE pathogenesis, suggesting that Nox2 inhibition may represent an important therapeutic target for MS.

Keywords: NADPH oxidase; chemotaxis; experimental autoimmune encephalomyelitis; microglia; reactive oxygen species

DOI: https://doi.org/10.3389/fimmu.2021.638381

Front Physiol. 2021 ;12 642752

Long-Term Angiotensin II Infusion Induces Oxidative and Endoplasmic Reticulum Stress and Modulates Na+ Transporters Through the Nephron.

Bruna Bezerra Lins, Fernando Augusto Malavazzi Casare, Flávia Ferreira Fontenele, Guilherme Lopes Gonçalves, Maria Oliveira-Souza.

High plasma angiotensin II (Ang II) levels are related to many diseases, including hypertension, and chronic kidney diseases (CKDs). Here, we investigated the relationship among prolonged Ang II infusion/AT1 receptor (AT1R) activation, oxidative stress, and endoplasmic reticulum (ER) stress in kidney tissue. In addition, we explored the chronic effects of Ang II on tubular Na+ transport mechanisms. Male Wistar rats were subjected to sham surgery as a control or prolonged Ang II treatment (200 ng⋅kg-1⋅min-1, 42 days) with or without losartan (10 mg⋅kg-1⋅day-1) for 14 days. Ang II/AT1R induced hypertension with a systolic blood pressure of 173.0 ± 20 mmHg (mmHg, n = 9) compared with 108.0 ± 7 mmHg (mmHg, n = 7) in sham animals. Under these conditions, gene and protein expression levels were evaluated. Prolonged Ang II administration/AT1R activation induced oxidative stress and ER stress with increased Nox2, Nox4, Cyba and Ncf1 mRNA expression, phosphorylated PERK and eIF2α protein expression as well as Atf4 mRNA expression. Ang II/AT1R also raised Il1b, Nfkb1 and Acta2 mRNA expression, suggesting proinflammatory, and profibrotic effects. Regarding Na+ tubular handling, Ang II/AT1R enhanced cortical non-phosphorylated and phospho/S552/NHE3, NHE1, ENaC β, NKCC2, and NCC protein expression. Our results also highlight the therapeutic potential of losartan, which goes beyond the antihypertensive effect, playing an important role in kidney tissue. This treatment reduced oxidative stress and ER stress signals and recovered relevant parameters of the maintenance of renal function, preventing the progression of Ang II-induced CKD.

Keywords: angiotensin II; endoplasmic reticulum stress; inflammation; kidney sodium transporters; oxidative stress

DOI: https://doi.org/10.3389/fphys.2021.642752