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Praditi C, Bozonet SM, Dachs GU, Vissers MCM. Ascorbate Uptake and Retention by Breast Cancer Cell Lines and the Intracellular Distribution of Sodium-Dependent Vitamin C Transporter 2. Antioxidants (Basel) 2023; 12:1929. [PMID: 38001782 PMCID: PMC10669237 DOI: 10.3390/antiox12111929] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2023] [Revised: 10/26/2023] [Accepted: 10/26/2023] [Indexed: 11/26/2023] Open
Abstract
Ascorbate plays a vital role as a co-factor for a superfamily of enzymes, the 2-oxoglutarate dependent dioxygenases (2-OGDDs), which govern numerous pathways in cancer progression, including the hypoxic response and the epigenetic regulation of gene transcription. Ascorbate uptake into most cells is through active transport by the sodium-dependent vitamin C transporter 2 (SVCT2). The aims of this study were to determine the kinetics of ascorbate uptake and retention by breast cancer cell lines under various oxygen conditions, and to investigate the role of SVCT2 in mediating ascorbate uptake and intracellular trafficking. Human MDA-MB231 cells accumulated up to 5.1 nmol ascorbate/106 cells, human MCF7 cells 4.5 nmol/106 cells, and murine EO771 cells 26.7 nmol/106 cells. Intracellular ascorbate concentrations decreased rapidly after reaching maximum levels unless further ascorbate was supplied to the medium, and there was no difference in the rate of ascorbate loss under normoxia or hypoxia. SVCT2 was localised mainly to subcellular compartments, with the nucleus apparently containing the most SVCT2 protein, followed by the mitochondria. Much less SVCT2 staining was observed on the plasma membrane. Our data showed that careful management of the doses and incubation times with ascorbate in vitro allows for an approximation of in vivo conditions. The localisation of SVCT2 suggests that the distribution of ascorbate to intracellular compartments is closely aligned to the known function of ascorbate in supporting 2-OGDD enzymatic functions in the organelles and with supporting antioxidant protection in the mitochondria.
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Affiliation(s)
- Citra Praditi
- Mātai Hāora—Centre for Redox Biology and Medicine, Department of Pathology and Biomedical Science, University of Otago Christchurch, Christchurch 8011, New Zealand; (C.P.); (S.M.B.)
| | - Stephanie M. Bozonet
- Mātai Hāora—Centre for Redox Biology and Medicine, Department of Pathology and Biomedical Science, University of Otago Christchurch, Christchurch 8011, New Zealand; (C.P.); (S.M.B.)
| | - Gabi U. Dachs
- Mackenzie Cancer Research Group, Department of Pathology and Biomedical Science, University of Otago Christchurch, Christchurch 8011, New Zealand;
| | - Margreet C. M. Vissers
- Mātai Hāora—Centre for Redox Biology and Medicine, Department of Pathology and Biomedical Science, University of Otago Christchurch, Christchurch 8011, New Zealand; (C.P.); (S.M.B.)
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2
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Bozonet SM, Magon NJ, Schwartfeger AJ, Konigstorfer A, Heath SG, Vissers MCM, Morris VK, Göbl C, Murphy JM, Salvesen GS, Hampton MB. Oxidation of caspase-8 by hypothiocyanous acid enables TNF-mediated necroptosis. J Biol Chem 2023:104792. [PMID: 37150321 DOI: 10.1016/j.jbc.2023.104792] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2023] [Revised: 04/18/2023] [Accepted: 04/19/2023] [Indexed: 05/09/2023] Open
Abstract
Necroptosis is a form of regulated cell death triggered by various host and pathogen-derived molecules during infection and inflammation. The essential step leading to necroptosis is phosphorylation of the mixed lineage kinase domain-like protein (MLKL) by receptor-interacting protein kinase 3 (RIPK3). Caspase 8 cleaves RIPKs to block necroptosis, so synthetic caspase inhibitors are required to study this process in experimental models. However, it is unclear how caspase-8 activity is regulated in a physiological setting. The active site cysteine of caspases is sensitive to oxidative inactivation, so we hypothesized that oxidants generated at sites of inflammation can inhibit caspase-8 and promote necroptosis. Here, we discovered that hypothiocyanous acid (HOSCN), an oxidant generated in vivo by heme peroxidases including myeloperoxidase and lactoperoxidase, is a potent caspase-8 inhibitor. We found HOSCN was able to promote necroptosis in mouse fibroblasts treated with tumor necrosis factor (TNF). We also demonstrate purified caspase-8 was inactivated by low concentrations of HOSCN, with the predominant product being a disulfide-linked dimer between Cys360 and Cys409 of the large and small catalytic subunits. We show oxidation still occurred in the presence of reducing agents, and reduction of the dimer was slow, consistent with HOSCN being a powerful physiological caspase inhibitor. While the initial oxidation product is a dimer, further modification also occurred in cells treated with HOSCN, leading to higher molecular weight caspase-8 species. Taken together, these findings indicate major disruption of caspase-8 function, and suggest a novel mechanism for the promotion of necroptosis at sites of inflammation.
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Affiliation(s)
- S M Bozonet
- Mātai Hāora - Centre for Redox Biology and Medicine, Department of Pathology and Biomedical Science, University of Otago, Christchurch, New Zealand
| | - N J Magon
- Mātai Hāora - Centre for Redox Biology and Medicine, Department of Pathology and Biomedical Science, University of Otago, Christchurch, New Zealand
| | - A J Schwartfeger
- School of Biological Sciences, University of Canterbury, Christchurch, New Zealand
| | - A Konigstorfer
- Mātai Hāora - Centre for Redox Biology and Medicine, Department of Pathology and Biomedical Science, University of Otago, Christchurch, New Zealand
| | - S G Heath
- Mātai Hāora - Centre for Redox Biology and Medicine, Department of Pathology and Biomedical Science, University of Otago, Christchurch, New Zealand
| | - M C M Vissers
- Mātai Hāora - Centre for Redox Biology and Medicine, Department of Pathology and Biomedical Science, University of Otago, Christchurch, New Zealand
| | - V K Morris
- School of Biological Sciences, University of Canterbury, Christchurch, New Zealand
| | - C Göbl
- Mātai Hāora - Centre for Redox Biology and Medicine, Department of Pathology and Biomedical Science, University of Otago, Christchurch, New Zealand; School of Biological Sciences, University of Canterbury, Christchurch, New Zealand
| | - J M Murphy
- The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia; Department of Medical Biology, University of Melbourne, Parkville, Victoria, Australia
| | - G S Salvesen
- Sanford Burnham Prebys Medical Discovery Institute, La Jolla, CA, USA
| | - M B Hampton
- Mātai Hāora - Centre for Redox Biology and Medicine, Department of Pathology and Biomedical Science, University of Otago, Christchurch, New Zealand.
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Tang JS, Bozonet SM, McKenzie JL, Anderson RF, Melton LD, Vissers MCM. Back Cover: Physiological Concentrations of Blueberry‐Derived Phenolic Acids Reduce Monocyte Adhesion to Human Endothelial Cells. Mol Nutr Food Res 2019. [DOI: 10.1002/mnfr.201970047] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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4
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Talla U, Bozonet SM, Parker HA, Hampton MB, Vissers MCM. Prolonged exposure to hypoxia induces an autophagy-like cell survival program in human neutrophils. J Leukoc Biol 2019; 106:1367-1379. [PMID: 31412152 DOI: 10.1002/jlb.4a0319-079rr] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2019] [Revised: 07/14/2019] [Accepted: 07/14/2019] [Indexed: 12/13/2022] Open
Abstract
Neutrophils contribute to low oxygen availability at inflammatory sites through the generation of reactive oxidants. They are also functionally affected by hypoxia, which delays neutrophil apoptosis. However, the eventual fate of neutrophils in hypoxic conditions is unknown and this is important for their effective clearance and the resolution of inflammation. We have monitored the survival and function of normal human neutrophils exposed to hypoxia over a 48 h period. Apoptosis was delayed, and the cells remained intact even at 48 h. However, hypoxia promoted significant changes in neutrophil morphology with the appearance of many new cytoplasmic vesicles, often containing cell material, within 5 hours of exposure to low O2 . This coincided with an increase in LC3B-II expression, indicative of autophagosome formation and an autophagy-like process. In hypoxic conditions, neutrophils preferentially lost myeloperoxidase, a marker of azurophil granules. Short-term (2 h) hypoxic exposure resulted in sustained potential to generate superoxide when O2 was restored, but the capacity for oxidant production was lost with longer periods of hypoxia. Phagocytic ability was unchanged by hypoxia, and bacterial killing by neutrophils in both normoxic and hypoxic conditions was substantially diminished after 24 hours. However, pre-exposure to hypoxia resulted in an enhanced ability to kill bacteria by oxidant-independent mechanisms. Our data provide the first evidence for hypoxia as a driver of neutrophil autophagy that can influence the function and ultimate fate of these cells, including their eventual clearance and the resolution of inflammation.
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Affiliation(s)
- Usharani Talla
- Centre for Free Radical Research, Department of Pathology and Biomedical Science, University of Otago, Christchurch, New Zealand
| | - Stephanie M Bozonet
- Centre for Free Radical Research, Department of Pathology and Biomedical Science, University of Otago, Christchurch, New Zealand
| | - Heather A Parker
- Centre for Free Radical Research, Department of Pathology and Biomedical Science, University of Otago, Christchurch, New Zealand
| | - Mark B Hampton
- Centre for Free Radical Research, Department of Pathology and Biomedical Science, University of Otago, Christchurch, New Zealand
| | - Margreet C M Vissers
- Centre for Free Radical Research, Department of Pathology and Biomedical Science, University of Otago, Christchurch, New Zealand
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5
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Tang JS, Bozonet SM, McKenzie JL, Anderson RF, Melton LD, Vissers MCM. Physiological Concentrations of Blueberry-Derived Phenolic Acids Reduce Monocyte Adhesion to Human Endothelial Cells. Mol Nutr Food Res 2019; 63:e1900478. [PMID: 31216087 DOI: 10.1002/mnfr.201900478] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2019] [Indexed: 12/12/2022]
Abstract
SCOPE Blueberry polyphenols are thought to confer cardiovascular health benefits, but have limited bioavailability. They undergo extensive metabolism and their phenolic acid metabolites are likely to be the mediators of bioactivity. The effect of blueberry-derived phenolic acids on one aspect of inflammation, monocyte adhesion to vascular endothelial cells, is investigated. METHODS AND RESULTS The major blueberry-derived phenolic acids in human plasma are identified and quantified. Three test mixtures representing compounds present at 0-4 h (Early), 4-24 h (Late), or 0-24 h (Whole) are used to investigate the effect on adhesion of monocytes to tumor necrosis factor alpha (TNFα)-activated endothelial cells. The Late mixture reduces monocyte adhesion, but there is no effect of the Early or Whole mixtures. Exclusion of syringic acid from each mixture results in inhibition of monocyte adhesion. Exposure to the phenolic acid mixtures has no effect on the endothelial surface expression of adhesion molecules intercellular cell adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), or E-selectin, suggesting that other molecular mechanisms are responsible for the observed effect. CONCLUSION This study shows that physiological concentrations of blueberry polyphenol metabolites can help maintain cardiovascular health by regulating monocyte adhesion to the vascular endothelium.
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Affiliation(s)
- Jeffry S Tang
- School of Chemical Sciences, University of Auckland, Auckland, 1142, New Zealand.,Centre for Free Radical Research, Department of Pathology and Biomedical Science, University of Otago, Christchurch, 8011, New Zealand
| | - Stephanie M Bozonet
- Centre for Free Radical Research, Department of Pathology and Biomedical Science, University of Otago, Christchurch, 8011, New Zealand
| | - Judith L McKenzie
- Hematology Research Group, Department of Pathology & Biomedical Science, University of Otago, Christchurch, 8011, New Zealand
| | - Robert F Anderson
- School of Chemical Sciences, University of Auckland, Auckland, 1142, New Zealand.,Faculty of Medical and Health Sciences, Auckland Cancer Society Research Centre, University of Auckland, Auckland, 1023, New Zealand
| | - Laurence D Melton
- School of Chemical Sciences, University of Auckland, Auckland, 1142, New Zealand.,Riddet Centre of Research Excellence for Food Research, Palmerston North, 4442, New Zealand
| | - Margreet C M Vissers
- Centre for Free Radical Research, Department of Pathology and Biomedical Science, University of Otago, Christchurch, 8011, New Zealand
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6
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Tang JS, Vissers MCM, Anderson RF, Sreebhavan S, Bozonet SM, Scheepens A, Melton LD. Bioavailable Blueberry-Derived Phenolic Acids at Physiological Concentrations Enhance Nrf2-Regulated Antioxidant Responses in Human Vascular Endothelial Cells. Mol Nutr Food Res 2018; 62. [PMID: 29278300 DOI: 10.1002/mnfr.201700647] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2017] [Revised: 12/15/2017] [Indexed: 12/13/2022]
Abstract
SCOPE Blueberry consumption is believed to confer a cardiovascular health advantage, but the active compounds and effects require characterization. This study aims to identify the polyphenol metabolites in plasma after blueberry juice intake and determine their bioactivity on endothelial cells. METHODS AND RESULTS Three healthy individuals are recruited to obtain profiles of bioavailable plasma polyphenol metabolites following intake of blueberry juice. Of 33 phenolic compounds screened, 12 aglycone phenolic acids are detected and their maximum plasma concentrations and circulation time determined. Using this information, the effect of three physiologically relevant mixtures of blueberry-derived phenolic acids is investigated for their ability to induce nuclear factor erythroid 2-related factor 2 (Nrf2)-nuclear translocation and downstream gene expression in human endothelial cells. Pretreatment with the phenolic acids for 18 h results in a significant upregulation of the Nrf2-regulated antioxidant response proteins heme oxygenase 1 (HO-1) and glutamate-cysteine ligase modifier subunit (GCLM), following 6 h exposure to 2.5 μm H2 O2 . CONCLUSION Physiologically relevant concentrations of blueberry-derived aglycone phenolic acids can induce Nrf2-regulated antioxidant response proteins in vascular endothelial cells in response to low μm concentrations of H2 O2 . Our results represent an advance over previous studies that have used single compounds or high concentrations in cell-based investigations.
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Affiliation(s)
- Jeffry S Tang
- School of Chemical Sciences, University of Auckland, Auckland, New Zealand
| | - Margreet C M Vissers
- Centre for Free Radical Research, Department of Pathology, University of Otago, Christchurch, New Zealand
| | - Robert F Anderson
- School of Chemical Sciences, University of Auckland, Auckland, New Zealand.,Auckland Cancer Society Research Centre, Faculty of Medical and Health Sciences, University of Auckland, Aukland, New Zealand
| | - Sreevalsan Sreebhavan
- Auckland Cancer Society Research Centre, Faculty of Medical and Health Sciences, University of Auckland, Aukland, New Zealand
| | - Stephanie M Bozonet
- Centre for Free Radical Research, Department of Pathology, University of Otago, Christchurch, New Zealand
| | - Arjan Scheepens
- School of Biological Sciences, University of Auckland, Auckland, New Zealand
| | - Laurence D Melton
- School of Chemical Sciences, University of Auckland, Auckland, New Zealand.,Riddet Centre of Research Excellence for Food Research, Palmerston North, New Zealand
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7
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Campbell EJ, Vissers MCM, Wohlrab C, Hicks KO, Strother RM, Bozonet SM, Robinson BA, Dachs GU. Pharmacokinetic and anti-cancer properties of high dose ascorbate in solid tumours of ascorbate-dependent mice. Free Radic Biol Med 2016; 99:451-462. [PMID: 27567539 DOI: 10.1016/j.freeradbiomed.2016.08.027] [Citation(s) in RCA: 44] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/24/2016] [Revised: 08/23/2016] [Accepted: 08/23/2016] [Indexed: 12/18/2022]
Abstract
Despite recent evidence for an anti-tumour role for high-dose ascorbate, potential mechanisms of action are still unclear. At mM concentrations that are achieved with high-dose intravenous administration, autoxidation of ascorbate can generate cytotoxic levels of H2O2. Ascorbate is also a required co-factor for the hydroxylases that suppress the transcription factor hypoxia-inducible factor (HIF-1). HIF-1 supports an aggressive tumour phenotype and is associated with poor prognosis, and previous studies have shown that optimizing intracellular ascorbate levels down-regulates HIF-1 activation. In this study we have simultaneously measured ascorbate concentrations and the HIF-1 pathway activity in tumour tissue following high dose ascorbate administration, and have studied tumour growth and physiology. Gulo-/- mice, a model of the human ascorbate dependency condition, were implanted with syngeneic Lewis lung tumours, 1g/kg ascorbate was administered into the peritoneum, and ascorbate concentrations were monitored in plasma, liver and tumours. Ascorbate levels peaked within 30min, and although plasma and liver ascorbate returned to baseline within 16h, tumour levels remained elevated for 48h, possibly reflecting increased stability in the hypoxic tumour environment. The expression of HIF-1 and its target proteins was down-regulated with tumour ascorbate uptake. Elevated tumour ascorbate levels could be maintained with daily administration, and HIF-1 and vascular endothelial growth factor protein levels were reduced in these conditions. Increased tumour ascorbate was associated with slowed tumour growth, reduced tumour microvessel density and decreased hypoxia. Alternate day administration of ascorbate resulted in lower tumour levels and did not consistently decrease HIF-1 pathway activity. Levels of sodium-dependent vitamin C transporters 1 and 2 were not clearly associated with ascorbate accumulation by murine tumour cells in vitro or in vivo. Our results support the suppression of the hypoxic response by ascorbate as a plausible mechanism of action of its anti-tumour activity, and this may be useful in a clinical setting.
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MESH Headings
- Animals
- Antineoplastic Agents/blood
- Antineoplastic Agents/pharmacokinetics
- Antineoplastic Agents/pharmacology
- Antioxidants/metabolism
- Antioxidants/pharmacokinetics
- Antioxidants/pharmacology
- Ascorbic Acid/blood
- Ascorbic Acid/pharmacokinetics
- Ascorbic Acid/pharmacology
- Carcinoma, Lewis Lung/drug therapy
- Carcinoma, Lewis Lung/genetics
- Carcinoma, Lewis Lung/metabolism
- Carcinoma, Lewis Lung/pathology
- Drug Administration Schedule
- Female
- Gene Expression Regulation, Neoplastic
- Hypoxia-Inducible Factor 1, alpha Subunit/antagonists & inhibitors
- Hypoxia-Inducible Factor 1, alpha Subunit/genetics
- Hypoxia-Inducible Factor 1, alpha Subunit/metabolism
- Injections, Intraperitoneal
- Isoenzymes/genetics
- Isoenzymes/metabolism
- Mice
- Mice, Knockout
- Signal Transduction
- Sodium-Coupled Vitamin C Transporters/genetics
- Sodium-Coupled Vitamin C Transporters/metabolism
- Vascular Endothelial Growth Factor A/antagonists & inhibitors
- Vascular Endothelial Growth Factor A/genetics
- Vascular Endothelial Growth Factor A/metabolism
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Affiliation(s)
- Elizabeth J Campbell
- Mackenzie Cancer Research Group, Department of Pathology, University of Otago, Christchurch 8011, New Zealand
| | - Margreet C M Vissers
- Centre for Free Radical Research, Department of Pathology, University of Otago, Christchurch 8011, New Zealand
| | - Christina Wohlrab
- Mackenzie Cancer Research Group, Department of Pathology, University of Otago, Christchurch 8011, New Zealand
| | - Kevin O Hicks
- Auckland Cancer Society Research Centre, University of Auckland, Auckland 1142, New Zealand
| | - R Matthew Strother
- Canterbury Regional Cancer and Haematology Service, Canterbury District Health Board, Christchurch 8011, New Zealand
| | - Stephanie M Bozonet
- Centre for Free Radical Research, Department of Pathology, University of Otago, Christchurch 8011, New Zealand
| | - Bridget A Robinson
- Mackenzie Cancer Research Group, Department of Pathology, University of Otago, Christchurch 8011, New Zealand; Canterbury Regional Cancer and Haematology Service, Canterbury District Health Board, Christchurch 8011, New Zealand; Department of Medicine, University of Otago, Christchurch 8011, New Zealand
| | - Gabi U Dachs
- Mackenzie Cancer Research Group, Department of Pathology, University of Otago, Christchurch 8011, New Zealand.
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8
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Campbell EJ, Bozonet SM, Robinson BA, Vissers MCM, Dachs GU. Abstract 229: Restoring physiological levels of ascorbate alleviates HIF-1 activation and reduces tumour growth in Gulo-/- mice. Cancer Res 2014. [DOI: 10.1158/1538-7445.am2014-229] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Abstract
Background: Hypoxia-inducible factor-1 (HIF-1) upregulates the expression of hundreds of genes involved in adaption of tumours to the hypoxic microenvironment. HIF-1 levels and transcriptional activity are regulated by hydroxylase enzymes, which require ascorbate as a cofactor. Adequate supplementation of cells with ascorbate has been shown to reduce HIF-1 activation in vitro, and we hypothesise that a similar activity could affect tumour growth in vivo. In this study we investigated the effect of dietary ascorbate on tumour growth in Gulo-/- mice, a model of the human ascorbate deficiency condition.
Methods: C57/Bl6 Gulo-/- mice were supplemented with 3300 mg/L, 330 mg/L or 33mg/L of ascorbate in their drinking water for one month before subcutaneous, syngeneic tumour implantation with either B16-F10 melanoma, or Lewis lung carcinoma (LL/2), and then for duration of the experiment. Levels of HIF-1α, and its targets, carbonic anhydrase-IX (CA-IX), and glucose transporter-1 (GLUT-1) were analysed by western blotting, and vascular endothelial growth factor (VEGF) levels by ELISA. Ascorbate concentrations of tissue, plasma and tumours were measured using high pressure liquid chromatography with electrochemical detection (HPLC-EC).
Results: Across all organs and plasma samples, ascorbate content was in the physiological range (up to levels seen in wild-type mice) and was correlated with dietary ascorbate intake. Tumour ascorbate also reflected ascorbate intake and optimal ascorbate levels (3300 mg/L) significantly increased the time for LL/2 tumours to reach 200 mm3 (lag growth) (13.3±2.6 days), compared to these same tumours in mice supplemented with either 330 mg/L (9.1±2.6 days) or 33 mg/L (9.8±1.39 days) of ascorbate (p<0.001). Similarly, tumours took significantly longer to grow from 200-800 mm3 (log phase) when mice were supplemented with 3300 mg/L compared to lower supplementation (p<0.05). B16-F10 tumours showed no difference in the lag growth period between ascorbate treatments (p=0.49). However, supplementing mice with 3300 mg/mL of ascorbate lead to a significant reduction in the tumour growth rate during log phase (3.9±1.1 days), compared to mice supplemented with either 330 mg/L (2.0±0.90 days) or 33mg/L (2.1±0.71 days) (p<0.001). Levels of HIF-1α protein in tumours decreased as dietary ascorbate supplementation increased for both LL/2 (p<0.001) and B16F10 (p<0.001). Tumour ascorbate was significantly correlated with low levels of CA-IX, GLUT-1 and VEGF levels in both LL/2 and B16 tumours (all p<0.05).
Conclusions: The data from the current study support the hypothesis that restoration of optimal intracellular ascorbate levels is associated with reduced HIF-1 levels and slower tumour growth. This data may have implications for the management of cancer, although clinical trials are required to assess whether human tumour levels of ascorbate can similarly be manipulated.
Citation Format: Elizabeth J. Campbell, Stephanie M. Bozonet, Bridget A. Robinson, Margreet CM Vissers, Gabi U. Dachs. Restoring physiological levels of ascorbate alleviates HIF-1 activation and reduces tumour growth in Gulo-/- mice. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 229. doi:10.1158/1538-7445.AM2014-229
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Carr AC, Bozonet SM, Vissers MCM. A randomised cross-over pharmacokinetic bioavailability study of synthetic versus kiwifruit-derived vitamin C. Nutrients 2013; 5:4451-61. [PMID: 24284610 PMCID: PMC3847741 DOI: 10.3390/nu5114451] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2013] [Revised: 10/08/2013] [Accepted: 10/24/2013] [Indexed: 11/17/2022] Open
Abstract
Kiwifruit are a rich source of vitamin C and also contain numerous phytochemicals, such as flavonoids, which may influence the bioavailability of kiwifruit-derived vitamin C. The aim of this study was to compare the relative bioavailability of synthetic versus kiwifruit-derived vitamin C using a randomised cross-over pharmacokinetic study design. Nine non-smoking males (aged 18–35 years) received either a chewable tablet (200 mg vitamin C) or the equivalent dose from gold kiwifruit (Actinidia chinensis var. Sungold). Fasting blood and urine were collected half hourly to hourly over the eight hours following intervention. The ascorbate content of the plasma and urine was determined using HPLC with electrochemical detection. Plasma ascorbate levels increased from 0.5 h after the intervention (P = 0.008). No significant differences in the plasma time-concentration curves were observed between the two interventions (P = 0.645). An estimate of the total increase in plasma ascorbate indicated complete uptake of the ingested vitamin C tablet and kiwifruit-derived vitamin C. There was an increase in urinary ascorbate excretion, relative to urinary creatinine, from two hours post intervention (P < 0.001). There was also a significant difference between the two interventions, with enhanced ascorbate excretion observed in the kiwifruit group (P = 0.016). Urinary excretion was calculated as ~40% and ~50% of the ingested dose from the vitamin C tablet and kiwifruit arms, respectively. Overall, our pharmacokinetic study has shown comparable relative bioavailability of kiwifruit-derived vitamin C and synthetic vitamin C.
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Affiliation(s)
- Anitra C Carr
- Centre for Free Radical Research, Department of Pathology & Biomedical Science, University of Otago, Christchurch, P.O. Box 4345, Christchurch 8140, New Zealand.
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10
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Carr AC, Bozonet SM, Pullar JM, Simcock JW, Vissers MCM. A randomized steady-state bioavailability study of synthetic versus natural (kiwifruit-derived) vitamin C. Nutrients 2013; 5:3684-95. [PMID: 24067392 PMCID: PMC3798928 DOI: 10.3390/nu5093684] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2013] [Revised: 08/15/2013] [Accepted: 08/26/2013] [Indexed: 01/07/2023] Open
Abstract
Whether vitamin C from wholefoods has equivalent bioavailability to a purified supplement remains unclear. We have previously showed that kiwifruit provided significantly higher serum and tissue ascorbate levels than synthetic vitamin C in a genetically vitamin C-deficient mouse model, suggesting a synergistic activity of the whole fruit. To determine if these results are translatable to humans, we carried out a randomized human study comparing the bioavailability of vitamin C from kiwifruit with that of a vitamin C tablet of equivalent dosage. Thirty-six young non-smoking adult males were randomized to receive either half a gold kiwifruit (Actinidia Chinensis var. Hort 16A) per day or a comparable vitamin C dose (50 mg) in a chewable tablet for six weeks. Ascorbate was monitored weekly in fasting venous blood and in urine, semen, leukocytes, and skeletal muscle (vastus lateralis) pre- and post-intervention. Dietary intake of vitamin C was monitored using seven day food and beverage records. Participant ascorbate levels increased in plasma (P < 0.001), urine (P < 0.05), mononuclear cells (P < 0.01), neutrophils (P < 0.01) and muscle tissue (P < 0.001) post intervention. There were no significant differences in vitamin C bioavailability between the two intervention groups in any of the fluid, cell or tissue samples tested. Overall, our study showed comparable bioavailability of synthetic and kiwifruit-derived vitamin C.
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Affiliation(s)
- Anitra C. Carr
- Centre for Free Radical Research, Department of Pathology & Biomedical Science, University of Otago, Christchurch, PO Box 4345, Christchurch 8140, New Zealand; E-Mails: (S.M.B.); (J.M.P.); margreet.vissers@otag (M.C.M.V.)
- Author to whom correspondence should be addressed; E-Mail: ; Tel.: +64-3-378-6498; Fax: +64-3-378-6540
| | - Stephanie M. Bozonet
- Centre for Free Radical Research, Department of Pathology & Biomedical Science, University of Otago, Christchurch, PO Box 4345, Christchurch 8140, New Zealand; E-Mails: (S.M.B.); (J.M.P.); margreet.vissers@otag (M.C.M.V.)
| | - Juliet M. Pullar
- Centre for Free Radical Research, Department of Pathology & Biomedical Science, University of Otago, Christchurch, PO Box 4345, Christchurch 8140, New Zealand; E-Mails: (S.M.B.); (J.M.P.); margreet.vissers@otag (M.C.M.V.)
| | - Jeremy W. Simcock
- Department of Plastic and Reconstructive Surgery, University of Otago, Christchurch, PO Box 4345, Christchurch 8140, New Zealand; E-Mail:
| | - Margreet C. M. Vissers
- Centre for Free Radical Research, Department of Pathology & Biomedical Science, University of Otago, Christchurch, PO Box 4345, Christchurch 8140, New Zealand; E-Mails: (S.M.B.); (J.M.P.); margreet.vissers@otag (M.C.M.V.)
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Carr AC, Bozonet SM, Pullar JM, Simcock JW, Vissers MC. Human skeletal muscle ascorbate is highly responsive to changes in vitamin C intake and plasma concentrations. Am J Clin Nutr 2013; 97:800-7. [PMID: 23446899 PMCID: PMC3607654 DOI: 10.3945/ajcn.112.053207] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
BACKGROUND Vitamin C (ascorbate) is likely to be essential for skeletal muscle structure and function via its role as an enzyme cofactor for collagen and carnitine biosynthesis. Vitamin C may also protect these metabolically active cells from oxidative stress. OBJECTIVE We investigated the bioavailability of vitamin C to human skeletal muscle in relation to dietary intake and plasma concentrations and compared this relation with ascorbate uptake by leukocytes. DESIGN Thirty-six nonsmoking men were randomly assigned to receive 6 wk of 0.5 or 2 kiwifruit/d, an outstanding dietary source of vitamin C. Fasting blood samples were drawn weekly, and 24-h urine and leukocyte samples were collected before intervention, after intervention, and after washout. Needle biopsies of skeletal muscle (vastus lateralis) were carried out before and after intervention. RESULTS Baseline vastus lateralis ascorbate concentrations were ~16 nmol/g tissue. After intervention with 0.5 or 2 kiwifruit/d, these concentrations increased ~3.5-fold to 53 and 61 nmol/g, respectively. There was no significant difference between the responses of the 2 groups. Mononuclear cell and neutrophil ascorbate concentrations increased only ~1.5- and ~2-fold, respectively. Muscle ascorbate concentrations were highly correlated (P < 0.001) with dietary intake (R = 0.61) and plasma concentrations (R = 0.75) in the range from 5 to 80 μmol/L. CONCLUSIONS Human skeletal muscle is highly responsive to vitamin C intake and plasma concentrations and exhibits a greater relative uptake of ascorbate than leukocytes. Thus, muscle appears to comprise a relatively labile pool of ascorbate and is likely to be prone to ascorbate depletion with inadequate dietary intake. This trial was registered at the Australian New Zealand Clinical Trials Registry (www.anzctr.org.au) as ACTRN12611000162910.
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Affiliation(s)
- Anitra C Carr
- Centre for Free Radical Research, Department of Pathology, University of Otago, Christchurch, Christchurch, New Zealand.
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Vissers MCM, Bozonet SM, Pearson JF, Braithwaite LJ. Dietary ascorbate intake affects steady state tissue concentrations in vitamin C-deficient mice: tissue deficiency after suboptimal intake and superior bioavailability from a food source (kiwifruit). Am J Clin Nutr 2011; 93:292-301. [PMID: 21123463 DOI: 10.3945/ajcn.110.004853] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
BACKGROUND Humans acquire vitamin C (ascorbate) from their diet, and optimal tissue concentrations are required to maintain its enzyme cofactor and antioxidant activities. How dietary intake affects tissue concentrations is difficult to monitor and has generally been based on the measurement of plasma concentrations. OBJECTIVE We aimed to determine the effect of various ascorbate intakes on tissue concentrations in the Gulo mouse model of vitamin C deficiency and to compare the effectiveness of delivery when ascorbate was added to the drinking water or obtained through a fruit source (kiwifruit). DESIGN Gulo(-/-) mice were fed various amounts of ascorbate for 1 mo, either in their drinking water or as a kiwifruit gel. Tissue vitamin C content was measured and compared with concentrations in wild-type mice. RESULTS Ascorbate concentrations in serum, liver, kidney, heart, and white blood cells were extremely labile and were well below concentrations observed in the wild-type mice when serum concentrations were below saturation. All tissues except for brain were rapidly depleted when intake was stopped. Consumption of a preparation of fresh kiwifruit (either green or gold varieties) resulted in up to 5 times more effective delivery to tissues than when ascorbate was administered via the drinking water. CONCLUSIONS Subsaturation concentrations of plasma ascorbate resulted in severe deficiency in many tissues, and saturating amounts were required to achieve tissue concentrations similar to those found in wild-type animals. It is possible that the bioavailability of ascorbate is superior from some foods, such as kiwifruit. These results have important implications for human nutrition.
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Bozonet SM, Scott-Thomas AP, Nagy P, Vissers MCM. Hypothiocyanous acid is a potent inhibitor of apoptosis and caspase 3 activation in endothelial cells. Free Radic Biol Med 2010; 49:1054-63. [PMID: 20615463 DOI: 10.1016/j.freeradbiomed.2010.06.028] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/22/2010] [Accepted: 06/18/2010] [Indexed: 11/29/2022]
Abstract
Hypothiocyanous acid (HOSCN) is a common, thiol-specific oxidant with strong antibacterial activity. It is thought to be nontoxic to mammalian cells, although its ability to specifically target intracellular thiols may potentially cause cellular dysfunction. In this study we demonstrate specific effects of HOSCN on human endothelial cells, with exposure to high concentrations resulting in morphology changes unlike those seen with other oxidants. Effects were time- and dose-dependent and were accompanied by loss of total cell thiols and GSH and by inactivation of glyceraldehyde-3-phosphate dehydrogenase. High-dose exposure was cytotoxic, but lesser doses did not cause cell death, and apoptosis was not initiated by any concentration of HOSCN. In fact, initiation of apoptosis was blocked by minimal HOSCN exposure, with activation of caspase 3 and cleavage of the proenzyme being prevented. This was unlikely to be due to direct oxidation of the caspase 3 active-site cysteine and suggests alternative targeting of the caspase pathway. The survival of endothelial cells when HOSCN is present together with an inducer of apoptosis suggests that HOSCN differs from most other oxidants and could affect endothelial cell survival pathways in a way that may have an impact on vascular function.
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Affiliation(s)
- Stephanie M Bozonet
- Free Radical Research Group, Pathology Department, University of Otago at Christchurch, Christchurch 8140, New Zealand.
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Bozonet SM, Findlay VJ, Day AM, Cameron J, Veal EA, Morgan BA. Oxidation of a eukaryotic 2-Cys peroxiredoxin is a molecular switch controlling the transcriptional response to increasing levels of hydrogen peroxide. J Biol Chem 2005; 280:23319-27. [PMID: 15824112 DOI: 10.1074/jbc.m502757200] [Citation(s) in RCA: 126] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Although activation of the AP-1-like transcription factor Pap1 in Schizosaccharomyces pombe is important for oxidative stress-induced gene expression, this activation is delayed at higher concentrations of peroxide. Here, we reveal that the 2-Cys peroxiredoxin (2-Cys Prx) Tpx1 is required for the peroxide-induced activation of Pap1. Tpx1, like other eukaryotic 2-Cys Prxs, is highly sensitive to oxidation, which inactivates its thioredoxin peroxidase activity. Our data suggest that the reduced thioredoxin peroxidase-active form of Tpx1 is required for the peroxide-induced oxidation and nuclear accumulation of Pap1. Indeed, in contrast to the previously described role for Tpx1 in the activation of the Sty1 stress-activated protein kinase by peroxide, we find that both catalytic cysteines of Tpx1 are required for Pap1 activation. Moreover, overexpression of the conserved sulfiredoxin Srx1, which interacts with and reduces Tpx1, allows rapid activation of Pap1 at higher concentrations of H(2)O(2). Conversely, loss of Srx1 prevents the reduction of oxidized Tpx1 and prolongs the inhibition of Pap1 activation. Collectively, these data suggest that redox regulation of the thioredoxin peroxidase activity of Tpx1 acts as a molecular switch controlling the transcriptional response to H(2)O(2). Furthermore, they reveal that a single eukaryotic 2-Cys Prx regulates peroxide signaling by multiple independent mechanisms.
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Affiliation(s)
- Stephanie M Bozonet
- Institute of Cell and Molecular Biosciences, Faculty of Medical Sciences, University of Newcastle upon Tyne, UK
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Veal EA, Findlay VJ, Day AM, Bozonet SM, Evans JM, Quinn J, Morgan BA. A 2-Cys Peroxiredoxin Regulates Peroxide-Induced Oxidation and Activation of a Stress-Activated MAP Kinase. Mol Cell 2004; 15:129-39. [PMID: 15225554 DOI: 10.1016/j.molcel.2004.06.021] [Citation(s) in RCA: 173] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2003] [Revised: 03/18/2004] [Accepted: 05/04/2004] [Indexed: 01/27/2023]
Abstract
Oxidative stress-induced cell damage is an important component of many diseases and ageing. In eukaryotes, activation of JNK/p38 stress-activated protein kinase (SAPK) signaling pathways is critical for the cellular response to stress. 2-Cys peroxiredoxins (2-Cys Prx) are highly conserved, extremely abundant antioxidant enzymes that catalyze the breakdown of peroxides to protect cells from oxidative stress. Here we reveal that Tpx1, the single 2-Cys Prx in Schizosaccharomyces pombe, is required for the peroxide-induced activation of the p38/JNK homolog, Sty1. Tpx1 activates Sty1, downstream of previously identified redox sensors, by a mechanism that involves formation of a peroxide-induced disulphide complex between Tpx1 and Sty1. We have identified conserved cysteines in Tpx1 and Sty1 that are essential for normal peroxide-induced Tpx1-Sty1 disulphide formation and Tpx1-dependent regulation of peroxide-induced Sty1 activation. Thus we provide new insight into the response of SAPKs to diverse stimuli by revealing a mechanism for SAPK activation specifically by oxidative stress.
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Affiliation(s)
- Elizabeth A Veal
- Institute of Cell and Molecular Biosciences, Faculty of Medical Sciences, University of Newcastle upon Tyne, Newcastle upon Tyne, NE2 4HH, United Kingdom.
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