bims-noxint 2019-08-25 papers

bims-noxint

Biomed News

on NADPH oxidases in tumorigenesis

Issue of 2019–08–25
twelve papers selected by
Laia Caja Puigsubira, Uppsala University

High nuclear NADPH oxidase 4 expression levels are correlated with cancer development and poor prognosis in hepatocellular carcinoma.
NOX4 modulates macrophage phenotype and mitochondrial biogenesis in asbestosis.
Apocynin alleviates lung injury by suppressing NLRP3 inflammasome activation and NF-κB signaling in acute pancreatitis.
Does Pioglitazone Lead to Neutrophil Extracellular Traps Formation in Chronic Granulomatous Disease Patients?
Serum response factor (SRF) promotes ROS generation and hepatic stellate cell activation by epigenetically stimulating NCF1/2 transcription.
Curcumin enhances cisplatin sensitivity by suppressing NADPH oxidase 5 expression in human epithelial cancer.
Reactive Oxygen Species (ROS), Intimal Thickening, and Subclinical Atherosclerotic Disease.
The detrimental effect of asymmetric dimethylarginine on cholesterol efflux of macrophage foam cells: Role of the NOX/ROS signaling.
Hydroxytyrosol promotes autophagy by regulating SIRT1 against advanced oxidation protein product‑induced NADPH oxidase and inflammatory response.
The synergistic effect between hydrogen peroxide and nitrite, two long-lived molecular species from cold atmospheric plasma, triggers tumor cells to induce their own cell death.
Neutrophil Extracellular Traps Initiate Gallstone Formation.
Vitamin D receptor activation regulates microglia polarization and oxidative stress in spontaneously hypertensive rats and angiotensin II-exposed microglial cells: Role of renin-angiotensin system.

Pathology. 2019 Aug 20. pii: S0031-3025(19)30332-0. [Epub ahead of print]

High nuclear NADPH oxidase 4 expression levels are correlated with cancer development and poor prognosis in hepatocellular carcinoma.

Hyuk Soo Eun, Kwangsik Chun, In-Sang Song, Cheong-Hae Oh, In-Ock Seong, Min-Kyung Yeo, Kyung-Hee Kim.

  NADPH oxidase (NOX) is a key source of reactive oxygen species (ROS). This study aimed to verify NOX2 and NOX4 expression levels in hepatocellular carcinoma (HCC). A total of 134 matched pairs of HCC cells and non-tumour hepatocytes from 134 patients were examined by immunohistochemical staining, and the association of NOX2 and NOX4 expression with clinicopathological parameters was analysed. Western blotting in four HCC cell lines and reverse transcription digital droplet polymerase chain reaction (RT-ddPCR) in 20 pairs of HCC and non-tumour tissue samples were also performed to detect NOX4. Cytoplasmic NOX2 and nuclear NOX4 expression levels were shown by immunohistochemistry to be higher in HCC cells than in non-tumour hepatocytes (p<0.001 each). The western blotting results for NOX4 in four HCC cell lines were consistent with the immunohistochemical results. Increased cytoplasmic expression of NOX2 and NOX4 in HCC cells was significantly correlated with liver cirrhosis (p<0.001 and p<0.031, respectively). However, decreased cytoplasmic expression of NOX2 and NOX4 was significantly correlated with advanced pathological TNM stage (p<0.029 and p<0.007, respectively). Multivariate analysis with clinicopathological parameters showed that high nuclear and low cytoplasmic NOX4 expression levels are correlated with short overall survival (p=0 .021). Our findings imply that cytoplasmic NOX2 and nuclear NOX4 expression is upregulated during HCC development. In particular, NOX4 translocation into the nucleus may affect the development and progression of HCC. NOX2 and NOX4 could be diagnostic markers and have therapeutic implications in HCC.

Keywords:  NADPH oxidase 2; NADPH oxidase 4; diagnosis; hepatocellular carcinoma; prognosis

DOI:  https://doi.org/10.1016/j.pathol.2019.05.004
JCI Insight. 2019 Aug 22. pii: 126551. [Epub ahead of print]4(16):

NOX4 modulates macrophage phenotype and mitochondrial biogenesis in asbestosis.

Chao He, Jennifer L Larson-Casey, Dana Davis, Vidya Sagar Hanumanthu, Ana Leda F Longhini, Victor J Thannickal, Linlin Gu, A Brent Carter.

  Macrophage activation is implicated in the development of pulmonary fibrosis by generation of profibrotic molecules. Although NADPH oxidase 4 (NOX4) is known to contribute to pulmonary fibrosis, its effects on macrophage activation and mitochondrial redox signaling are unclear. Here, we show that NOX4 is crucial for lung macrophage profibrotic polarization and fibrotic repair after asbestos exposure. NOX4 was elevated in lung macrophages from subjects with asbestosis, and mice harboring a deletion of NOX4 in lung macrophages were protected from asbestos-induced fibrosis. NOX4 promoted lung macrophage profibrotic polarization and increased production of profibrotic molecules that induce collagen deposition. Mechanistically, NOX4 further augmented mitochondrial ROS production and induced mitochondrial biogenesis. Targeting redox signaling and mitochondrial biogenesis prevented the profibrotic polarization of lung macrophages by reducing the production of profibrotic molecules. These observations provide evidence that macrophage NOX4 is a potentially novel therapeutic target to halt the development of asbestos-induced pulmonary fibrosis.

Keywords:  Bioenergetics; Immunology; Macrophages; Mitochondria; Pulmonology

DOI:  https://doi.org/10.1172/jci.insight.126551
Int Immunopharmacol. 2019 Aug 19. pii: S1567-5769(19)30507-7. [Epub ahead of print]75 105821

Apocynin alleviates lung injury by suppressing NLRP3 inflammasome activation and NF-κB signaling in acute pancreatitis.

Hong-Zhong Jin, Xiao-Jia Yang, Kai-Liang Zhao, Fang-Chao Mei, Yu Zhou, Yun-Dong You, Wei-Xing Wang.

  Mounting evidence has demonstrated that acute pancreatitis (AP) is one of the causes of multiple organ damage. NADPH (nicotinamide adenine dinucleotide phosphate) act as a substrate of NADPH oxidase (NOX) to generate reactive oxygen species (ROS), but the role NADPH oxidase signaling pathway plays in AP-induced acute lung injury remains unclear. Apocynin, an inhibitor of NOX, is highly effective in suppressing the production of ROS. Here, we used rat model of severe acute pancreatitis (SAP) to explore whether the NOX inhibitor apocynin produced protective effects in against SAP-induced lung injury via inhibition of inflammation and oxidation. We observed that apocynin significantly attenuated severe acute pancreatitis-induced increase of NOX2, NOX4 and ROS expressions in lung tissues. In addition, the phosphorylation and degradation of IκBα, and the nuclear localization of NF-κB p65 in SAP-induced lung injury were also inhibited after using apocynin. Simultaneously, down-regulation of NOX suppressed the levels of inflammasome proteins including NLRP3, ASC, pro-Caspase-1 and cleaved-Caspase-1 in the lung. Serum levels of TNF-α, interleukin (IL)-1β and IL-6 were also reduced. Our findings suggest that beyond anti-oxidative effects, apocynin may also have anti-inflammatory effects by suppressing NLRP3 inflammasome activation and NF-κB signaling in acute pancreatitis. Therefore, apocynin may have therapeutic potential in the treatment of SAP and SAP-induced lung injury.

Keywords:  Apocynin; Lung injury; NADPH oxidases; NLRP3 inflammasome; Pancreatitis

DOI:  https://doi.org/10.1016/j.intimp.2019.105821
Front Immunol. 2019 ;10 1739

Does Pioglitazone Lead to Neutrophil Extracellular Traps Formation in Chronic Granulomatous Disease Patients?

Gouri P Hule, Umair Ahmed Bargir, Manasi Kulkarni, Priyanka Kambli, Prasad Taur, Mukesh Desai, Manisha Rajan Madkaikar.

  Nicotinamide adenine dinucleotide phosphate (NADPH) oxidase, the enzyme complex responsible for reactive oxygen species (ROS) production, is defective in chronic granulomatous disease (CGD) patients. This enzyme helps in antimicrobial host defense by phagocytes. CGD patients are unable to form neutrophil extracellular traps (NETs), which are composed of granule-derived proteins from neutrophils decorated with decondensed chromatin. Mitochondria have gained attention, being a rich source of flavochrome enzymes due to the presence of several sites for superoxide production. Recently, PPARγ agonists, a mitochondrial ROS inducer, induce mitochondrial ROS formation post-treatment in murine NADPH oxidase knockout models. Mitochondrial ROS is also essential for NOX-independent NETosis. Our study for the first time detects induction of NETosis independent of NADPH oxidase post-treatment with agonists such as pioglitazone and rosiglitazone in CGD subjects. Neutrophils isolated from CGD subjects were treated with pioglitazone and rosiglitazone. After treatment, qualitative analysis of NET formation was done using confocal microscopy after staining with DAPI. Quantitative estimation of extracellular DNA was performed using Sytox green. Mitochondrial ROS production with PPARγ agonist-treated/untreated neutrophils was detected using MitoSOX red. Pioglitazone and rosiglitazone induce significant NET formation in CGD patients. Our data clearly signify the effect of PPARγ agonists in induction of NET formation in CGD cases. Apart from the proposed experimental studies regarding the detailed mechanism of action, controlled trials could provide valuable information regarding the clinical use of pioglitazone in CGD patients as curative HSCT remains challenging in developing countries.

Keywords:  MitoSOX red; NOX independnent NETosis; chronic granulomatous disease; mitochondrial ROS; neutrophil extracellular traps; peroxisome proliferator-activated receptor gamma agonists; pioglitazone; reactive oxygen species

DOI:  https://doi.org/10.3389/fimmu.2019.01739
Redox Biol. 2019 Aug 15. pii: S2213-2317(19)30757-8. [Epub ahead of print]26 101302

Serum response factor (SRF) promotes ROS generation and hepatic stellate cell activation by epigenetically stimulating NCF1/2 transcription.

Ming Kong, Xuyang Chen, Fangqiao Lv, Haozhen Ren, Zhiwen Fan, Hao Qin, Liming Yu, Xiaolei Shi, Yong Xu.

  Activation of hepatic stellate cells (HSC) is a hallmark event in liver fibrosis. Accumulation of reactive oxygen species (ROS) serves as a driving force for HSC activation. The regulatory subunits of the NOX complex, NCF1 (p47phox) and NCF2 (p67phox), are up-regulated during HSC activation contributing to ROS production and liver fibrosis. The transcriptional mechanism underlying NCF1/2 up-regulation is not clear. In the present study we investigated the role of serum response factor (SRF) in HSC activation focusing on the transcriptional regulation of NCF1/2. We report that compared to wild type littermates HSC-conditional SRF knockout (CKO) mice exhibited a mortified phenotype of liver fibrosis induced by thioacetamide (TAA) injection or feeding with a methionine-and-choline deficient diet (MCD). More importantly, SRF deletion attenuated ROS levels in HSCs in vivo. Similarly, SRF knockdown in cultured HSCs suppressed ROS production in vitro. Further analysis revealed that SRF deficiency resulted in repression of NCF1/NCF2 expression. Mechanistically, SRF regulated epigenetic transcriptional activation of NCF1/NCF2 by interacting with and recruiting the histone acetyltransferase KAT8 during HSC activation. In conclusion, we propose that SRF integrates transcriptional activation of NCF1/NCF2 and ROS production to promote liver fibrosis.

Keywords:  Hepatic stellate cell; Liver fibrosis; Neutrophil cytosolic factor; Reactive oxygen species; Serum response factor; Transcriptional regulation

DOI:  https://doi.org/10.1016/j.redox.2019.101302
Oncol Lett. 2019 Aug;18(2): 2132-2139

Curcumin enhances cisplatin sensitivity by suppressing NADPH oxidase 5 expression in human epithelial cancer.

Siqi Chen, Wei Gao, Min-Juan Zhang, Jimmy Yu-Wai Chan, Thian-Sze Wong.

  Cisplatin-based chemotherapy regimens serve a pivotal role in human cancer treatment. Nevertheless, treatment failure may occur if the cancer is inherently resistant to cisplatin or acquires a resistant phenotype during the course of treatment. Although cisplatin resistance can hinder the efficacy of cisplatin treatment for human cancer, the underlying mechanism remains poorly understood. The current study established a cisplatin-resistant human epithelial cancer cell line. Notably, differential upregulation of NADPH oxidase 5 (NOX5) was identified in this resistant cell line. Furthermore, cisplatin treatment induced cancer cells to express NOX5 and cells that overexpressed NOX5 exhibited greater resistance to cisplatin via the activation of Akt. Treatment with curcumin may suppress NOX5 expression in cancer cells and enhance sensitivity to cisplatin treatment. In a xenograft model, a combined regimen of cisplatin with low-dose curcumin significantly reduced malignant tumor growth. These data demonstrate that curcumin has a chemosensitizing effect on cisplatin-resistant epithelial cancer types. Therefore, the use of curcumin in addition to a cisplatin-based treatment regimen may improve treatment outcomes in human patients with epithelial cancer.

Keywords:  NADPH oxidase 5; cancer; cisplatin; curcumin; sensitivity

DOI:  https://doi.org/10.3892/ol.2019.10479
Front Cardiovasc Med. 2019 ;6 89

Reactive Oxygen Species (ROS), Intimal Thickening, and Subclinical Atherosclerotic Disease.

Denise Burtenshaw, Michael Kitching, Eileen M Redmond, Ian L Megson, Paul A Cahill.

  Arteriosclerosis causes significant morbidity and mortality worldwide. Central to this process is the development of subclinical non-atherosclerotic intimal lesions before the appearance of pathologic intimal thickening and advanced atherosclerotic plaques. Intimal thickening is associated with several risk factors, including oxidative stress due to reactive oxygen species (ROS), inflammatory cytokines and lipid. The main ROS producing systems in-vivo are reduced nicotinamide dinucleotide phosphate (NADPH) oxidase (NOX). ROS effects are context specific. Exogenous ROS induces apoptosis and senescence, whereas intracellular ROS promotes stem cell differentiation, proliferation, and migration. Lineage tracing studies using murine models of subclinical atherosclerosis have revealed the contributory role of medial smooth muscle cells (SMCs), resident vascular stem cells, circulating bone-marrow progenitors and endothelial cells that undergo endothelial-mesenchymal-transition (EndMT). This review will address the putative physiological and patho-physiological roles of ROS in controlling vascular cell fate and ROS contribution to vascular regeneration and disease progression.

Keywords:  NAPDH oxidase; NOX; adventitial cells; arteriosclerosis; endothelial cells; intimal thickening; smooth muscle (physiology); stem cells

DOI:  https://doi.org/10.3389/fcvm.2019.00089
Free Radic Biol Med. 2019 Aug 19. pii: S0891-5849(19)30818-4. [Epub ahead of print]

The detrimental effect of asymmetric dimethylarginine on cholesterol efflux of macrophage foam cells: Role of the NOX/ROS signaling.

Chia-Hui Chen, Jin-Feng Zhao, Chiao-Po Hsu, Yu Ru Kou, Tse-Min Lu, Tzong-Shyuan Lee.

   BACKGROUND: Asymmetric dimethylarginine (ADMA) is an endogenous nitric oxide synthase inhibitor and has been proposed to be an independent risk factor for cardiovascular diseases. However, little is known about its role in the regulation of lipid metabolism. In this study, we investigated the effect of ADMA on cholesterol metabolism and its underlying molecular mechanism.
METHODS: Oxidized low-density lipoprotein (oxLDL)-induced macrophage foam cells were used as an in vitro model. Apolipoprotein E-deficient (apoE-/-) hyperlipidemic mice were used as an in vivo model. Western blot analysis was used to evaluate protein expression. Luciferase reporter assays were used to assess the activity of promoters and transcription factors. Conventional assay kits were used to measure the levels of ADMA, cholesterol, triglycerides, and cytokines.
RESULTS: Treatment with oxLDL decreased the protein expression of dimethylarginine dimethylaminohydrolase-2 (DDAH-2) but not DDAH-1. Incubation with ADMA markedly increased oxLDL-induced lipid accumulation in macrophages. ADMA impaired cholesterol efflux following oxLDL challenge and downregulated the expression of ATP-binding cassette transporter A1 (ABCA1) and ABCG1 by interfering with liver X receptor α (LXRα) expression and activity. Additionally, this inhibitory effect of ADMA on cholesterol metabolism was mediated through the activation of the NADPH oxidase/reactive oxygen species pathway. In vivo experiments revealed that chronic administration of ADMA for 4 weeks exacerbated systemic inflammation, decreased the aortic protein levels of ABCA1 and ABCG1, and impaired the capacity of reverse cholesterol transport, ultimately, leading to the progression of atherosclerosis in apoE-/- mice.
CONCLUSION: Our findings suggest that the ADMA/DDAH-2 axis plays a crucial role in regulating cholesterol metabolism in macrophage foam cells and atherosclerotic progression.

Keywords:  ATP-Binding cassette transporter; Asymmetric dimethylarginine; Atherosclerosis; Cholesterol metabolism; Liver X receptor α; Macrophage foam cell

DOI:  https://doi.org/10.1016/j.freeradbiomed.2019.08.016
Int J Mol Med. 2019 Aug 05.

Hydroxytyrosol promotes autophagy by regulating SIRT1 against advanced oxidation protein product‑induced NADPH oxidase and inflammatory response.

Tian Sun, Qian Chen, Si-Yuan Zhu, Qian Wu, Cong-Rui Liao, Zheng Wang, Xiao-Hu Wu, Hang-Tian Wu, Jian-Ting Chen.

Advanced oxidation protein products (AOPPs) can trigger NADPH oxidase (NOX) and lead to the production of reactive oxygen species (ROS) in the pathophysiology of rheumatoid arthritis (RA). Hydroxytyrosol (HT) is a phenolic composite in olive oil that has antioxidant and anti‑inflammatory effects and enhances autophagy. Early research has revealed that HT can activate the silent information regulator 1 (SIRT1) pathway to induce autophagy and alleviate the cartilage inflammatory response caused by H2O2. However, whether HT can attenuate AOPP‑induced NOX and inflammatory responses remains to be elucidated. The present study aimed to investigate how HT can alleviate the damage caused by AOPPs. In cell experiments, chondrocytes were pre‑stimulated with HT and then exposed to AOPPs. First, it was found that HT promoted autophagy through the SIRT1 pathway, increased the expression of autophagy‑related proteins including microtubule‑associated protein 1 light chain 3, autophagy related (ATG)5 and ATG7, and decreased the expression of P62. Furthermore, HT reduced the expression of NOX, which was affected by AOPPs in chondrocytes through the SIRT1 pathway. Finally, the expression of inflammatory cytokines caused by AOPPs was downregulated following HT treatment. In conclusion, it was found that HT reduced the expression of NOX and inhibited the inflammatory response caused by AOPPs in chondrocytes through the SIRT1 pathway.

DOI: https://doi.org/10.3892/ijmm.2019.4300
Redox Biol. 2019 Aug 08. pii: S2213-2317(19)30798-0. [Epub ahead of print]26 101291

The synergistic effect between hydrogen peroxide and nitrite, two long-lived molecular species from cold atmospheric plasma, triggers tumor cells to induce their own cell death.

Georg Bauer.

  Nitrite and H2O2 are long-lived species in cold atmospheric plasma and plasma-activated medium. It is known that their synergistic interaction is required for selective apoptosis induction in tumor cells that are treated with plasma-activated medium. This study shows that the interaction between nitrite and H2O2 leads to the formation of peroxynitrite, followed by singlet oxygen generation through the interaction between peroxynitrite and residual H2O2. This primary singlet oxygen causes local inactivation of few catalase molecules on the surface of tumor cells. As a consequence, H2O2 and peroxynitrite that are constantly produced by tumor cells and are usually decomposed by their protective membrane-associated catalase, are surviving at the site of locally inactivated catalase. This leads to the generation of secondary singlet oxygen through the interaction between tumor cell-derived H2O2 and peroxynitrite. This selfsustained process leads to autoamplification of secondary singlet oxygen generation and catalase inactivation. Inactivation of catalase allows the influx of H2O2 through aquaporins, leading to intracellular glutathione depletion and sensitization of the cells for apoptosis induction through lipid peroxidation. It also allows to establish intercellular apoptosis-inducing HOCl signaling, driven by active NOX1 and finalized by lipid peroxidation through hydroxyl radicals that activates the mitochondrial pathway of apoptosis. This experimentally established model is based on a triggering function of CAP and PAM-derived H2O2/nitrite that causes selective cell death in tumor cells based on their own ROS and RNS. This model explains the selectivity of CAP and PAM action towards tumor cells and is in contradiction to previous models that implicated that ROS/RNS from CAP or PAM were sufficient to directly cause cell death of tumor cells.

Keywords:  Apoptosis; Catalase; Cold atmospheric plasma; Hydrogen peroxide; Nitrite; Singlet oxygen

DOI:  https://doi.org/10.1016/j.redox.2019.101291
Immunity. 2019 Aug 09. pii: S1074-7613(19)30318-8. [Epub ahead of print]

Neutrophil Extracellular Traps Initiate Gallstone Formation.

Luis E Muñoz, Sebastian Boeltz, Rostyslav Bilyy, Christine Schauer, Aparna Mahajan, Navena Widulin, Anika Grüneboom, Irmgard Herrmann, Edgyda Boada, Manfred Rauh, Veit Krenn, Mona H C Biermann, Malgorzata J Podolska, Jonas Hahn, Jasmin Knopf, Christian Maueröder, Solomiya Paryzhak, Tetiana Dumych, Yi Zhao, Markus F Neurath, Markus H Hoffmann, Tobias A Fuchs, Moritz Leppkes, Georg Schett, Martin Herrmann.

  The presence of gallstones (cholelithiasis) is a highly prevalent and severe disease and one of the leading causes of hospital admissions worldwide. Due to its substantial health impact, we investigated the biological mechanisms that lead to the formation and growth of gallstones. We show that gallstone assembly essentially requires neutrophil extracellular traps (NETs). We found consistent evidence for the presence of NETs in human and murine gallstones and describe an immune-mediated process requiring activation of the innate immune system for the formation and growth of gallstones. Targeting NET formation via inhibition of peptidyl arginine deiminase type 4 or abrogation of reactive oxygen species (ROS) production, as well as damping of neutrophils by metoprolol, effectively inhibit gallstone formation in vivo. Our results show that after the physicochemical process of crystal formation, NETs foster their assembly into larger aggregates and finally gallstones. These insights provide a feasible therapeutic concept to prevent cholelithiasis in patients at risk.

Keywords:  NOX2; PADi4; calcium carbonate crystals; cholesterol crystals; gallstone growth; gallstones; lisosomal leakage; lithogenic diet; neutrophil extracellular traps; neutrophils

DOI:  https://doi.org/10.1016/j.immuni.2019.07.002
Redox Biol. 2019 Aug 08. pii: S2213-2317(19)30694-9. [Epub ahead of print]26 101295

Vitamin D receptor activation regulates microglia polarization and oxidative stress in spontaneously hypertensive rats and angiotensin II-exposed microglial cells: Role of renin-angiotensin system.

Changmeng Cui, Pengfei Xu, Gongying Li, Yi Qiao, Wenxiu Han, Chunmei Geng, Dehua Liao, Mengqi Yang, Dan Chen, Pei Jiang.

  Hypertension is one of the major predisposing factors for neurodegenerative disease characterized with activated renin-angiotensin system (RAS) in both periphery and brain. Vitamin D (VitD) is recently recognized as a pleiotropic hormone with strong neuroprotective properties. While multiple lines of evidence suggest that VitD can act on RAS, the evidence concerning the crosstalk between VitD and RAS in the brain is limited. Therefore, this study aims to evaluate whether VitD can modulate brain RAS to trigger neuroprotective actions in the brain of spontaneously hypertensive rats (SHR). Our data showed that calcitriol treatment induced VDR expression and inhibited neural death in the prefrontal cortex of SHR. Sustained calcitriol administration also inhibited microglia M1 polarization, but enhanced M2 polarization, accompanied with decreased expression of proinflammatory cytokines. We then further explored the potential mechanisms and showed that SHR exhibited overactivated classical RAS with increased expression of angiotensin II (Ang II) receptor type 1 (AT1), angiotensin converting enzyme (ACE) and Ang II production, whereas the counteracting arm of traditional RAS, ACE2/Ang(1-7)/MasR, was impaired in the SHR brain. Calcitriol nonsignificantly suppressed AT1 and ACE but markedly reduced Ang II formation. Intriguingly, calcitriol exerted pronouncedly impact on ACE2/Ang(1-7)/MasR axis with enhanced expression of ACE2, MasR and Ang(1-7) generation. Meanwhile, calcitriol ameliorated the overactivation of NADPH-oxidase (Nox), the downstream of RAS, in SHR, and also mitigated oxidative stress. In microglial (BV2) cells, we further found that calcitriol induced ACE2 and MasR with no significant impact on ACE and AT1. In accordance, calcitriol also attenuated Ang II-induced Nox activation and ROS production, and shifted the microglia polarization from M1 to M2 phenotype. However, co-treatment with A779, a specific MasR antagonist, abrogated the antioxidant and neuroimmune modulating actions of VitD. These findings strongly indicate the involvement of ACE2/Ang(1-7)/MasR pathway in the neuroprotective mechanisms of VitD in the hypertensive brain.

Keywords:  ACE2/Ang(1–7)/MasR axis; Neuroinflammation; Oxidative stress; Renin-angiotensin system; Vitamin D

DOI:  https://doi.org/10.1016/j.redox.2019.101295