Modulation of hypoxia-inducible factor-1 alpha in cultured primary cells by intracellular ascorbate

Vissers, Margreet C.M.; Gunningham, Sarah P.; Morrison, Mary J.; Dachs, Gabi U.; Currie, Margaret J.

doi:10.1016/j.freeradbiomed.2006.11.023

Cited by 105 publications

(90 citation statements)

References 51 publications

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“…Similar results have been reported for HIFa in cells treated with cobalt chloride or DFO (at the same doses as here), or exposed to 0.4% O 2 [35]. Others, however, found that ascorbate effectively blocks HIFa stabilization under 1% O 2 , and attributed the discrepancies to the variable degrees of hypoxia that were used in the different experimental settings [36]. The failure of ascorbate to destabilize IRP2 in DFO-treated cells emphasizes the essential role of iron for IRP2 degradation.…”

Section: Discussionsupporting

confidence: 88%

Redox control of iron regulatory protein 2 stability

2011

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Edited by Stuart Ferguson Keywords:Iron metabolism Iron regulatory protein 2 Proteasome Oxidative stress Hypoxia a b s t r a c t Iron regulatory protein 2 (IRP2) is a critical switch for cellular and systemic iron homeostasis. In iron-deficient or hypoxic cells, IRP2 binds to mRNAs containing iron responsive elements (IREs) and regulates their expression. Iron promotes proteasomal degradation of IRP2 via the F-box protein FBXL5. Here, we explored the effects of oxygen and cellular redox status on IRP2 stability. We show that iron-dependent decay of tetracycline-inducible IRP2 proceeds efficiently under mild hypoxic conditions (3% oxygen) but is compromised in severe hypoxia (0.1% oxygen). A treatment of cells with exogenous H 2 O 2 protects IRP2 against iron and increases its IRE-binding activity. IRP2 is also stabilized during menadione-induced oxidative stress. These data demonstrate that the degradation of IRP2 in iron-replete cells is not only oxygen-dependent but also sensitive to redox perturbations.

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Section: Discussionsupporting

confidence: 88%

Redox control of iron regulatory protein 2 stability

2011

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“…ROS activates NF-κB, and antioxidants reduce the NF-κB-dependent transcription of pro-inflammatory cytokines (Janssen-Heininger et al, 2000;Schubert et al, 2002). Furthermore, antioxidants destabilize HIF-1 and reduce the expression of HIF-1 target genes (Gao et al, 2007;Vissers et al, 2007). In the present study, we confirmed that hypoxia increased ROS production and the expression of proinflammatory cytokines.…”

Section: Discussionsupporting

confidence: 83%

“…Antioxidants decrease the transcriptional activity of HIF-1 Recent reports have shown that antioxidants diminish the protein level of hypoxia-induced HIF-1 by destabilization (Gao et al, 2007;Vissers et al, 2007). Because HIF-1 is an important transcription factor for the expression of hypoxia-induced target genes, we examined whether antioxidants decrease the transcriptional activity of HIF-1 in PDLFs (Loboda et al, 2010;Storz and Imlay, 1999).…”

Section: Resultsmentioning

confidence: 98%

The Effect of Antioxidants on the Production of Pro-Inflammatory Cytokines and Orthodontic Tooth Movement

Chae

Park

Hwang

et al. 2011

Molecules and Cells

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Orthodontic force causes gradual compression of the periodontal ligament tissues, which leads to local hypoxia in the compression side of the tissues. In this study, we investigated whether antioxidants exert a regulatory effect on two factors: the expression of pro-inflammatory cytokines in human periodontal ligament fibroblasts (PDLFs) that were exposed to mechanical compression and hypoxia and the rate of orthodontic tooth movement in rats. Exposure of PDLFs to mechanical compression (0.5-3.0 g/cm 2 ) or hypoxic conditions increased the production of intracellular reactive oxygen species. Hypoxic treatment for 24 h increased the mRNA levels of IL-1β, IL-6 and IL-8 as well as vascular endothelial growth factor (VEGF) in PDLFs. Resveratrol (10 nM) or N-acetylcysteine (NAC, 20 mM) diminished the transcriptional activity of hypoxiainducible factor-1 and hypoxia-induced expression of VEGF. Combined treatment with mechanical compression and hypoxia significantly increased the expression levels of IL-1β, IL-6, IL-8, TNF-α and VEGF in PDLFs. These levels were suppressed by NAC and resveratrol. The maxillary first molars of rats were moved mesially for seven days using an orthodontic appliance. NAC decreased the amount of orthodontic tooth movement compared to the vehicletreated group. The results from immunohistochemical staining demonstrated that NAC suppressed the expression of IL-1β and TNF-α in the periodontal ligament tissues compared to the vehicle-treated group. These results suggest that antioxidants have the potential to negatively regulate the rate of orthodontic tooth movement through the down-regulation of pro-inflammatory cytokines in the compression sides of periodontal ligament tissues.

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“…Following treatment with ascorbate in culture, SVCT2 protein showed a biphasic response (Fig. 5), in that it increased almost 2-fold in cells treated with a low physiologic concentration of ascorbate (25 µM), but decreased as the concentration of ascorbate was further increased, such that there was a suppression of SVCT2 expression of about 40% at 200 µM ascorbate.Since ascorbate is known to be involved in the regulation of the transcription factor HIF-1α in endothelial cells (Vissers et al, 2007), we tested whether cobalt, which increases HIF-1α in most cells, could also regulate the SVCT2. When primary endothelial cells were exposed to cobalt chloride (250 µM) for 48 h in culture, a marked increase in SVCT2 was observed (Fig.…”

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confidence: 99%

Development of ascorbate transporters in brain cortical capillary endothelial cells in culture

Qiao

May

2008

Brain Research

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Ascorbic acid in its reduced form is not transported across the capillary endothelial cell blood-brain barrier. This is thought to be due to absence of the SVCT2, a specific transporter for ascorbate. To assess this directly we prepared primary cultures of mouse cortical microvascular endothelial cells. When still in the capillaries, these cells did not express the SVCT2 protein as assessed by immunocytochemistry and by immunoblotting. However, during several days in culture, they developed SVCT2 expression and showed ascorbate transport rates comparable to those in immortalized endothelial cell lines. SVCT2 expression was inversely proportional to cell density, was enhanced by culture at low physiologic plasma ascorbate concentrations, was inhibited by ascorbate concentrations expected in the brain interstitium, and was stimulated by cobalt ions. Expression of the SVCT2 was associated with ascorbate-dependent maturation and release of type IV collagen by the cells in culture. Although the SVCT2 is induced by culture of cortical capillary endothelial cells, its absence in vivo remains perplexing, given the need for intracellular ascorbate to facilitate type IV collagen maturation and release by endothelial cells. SectionStructural Organization of the Brain Keywords SVCT2; ascorbate transport; cobalt, collagen; cortical capillary endothelial cells Vitamin C, or ascorbic acid, is an important antioxidant and enzyme co-factor in the central nervous system, where it has several functions, including antioxidant protection (Rice2000), peptide amidation (Eipper et al., 1983), myelin formation (Eldridge et al., 1987), enhancement of synaptic activity (Qiu et al., 2007), and protection against glutamate toxicity (Rebec et al., 1994). In contrast to other organs, however, very little ascorbate appears to enter the brain directly across capillary endothelial cells forming the blood-brain barrier (BBB). Rather, the vitamin is transported from the blood into the cerebrospinal fluid through the choroid plexus (Agus et al., 1997;Spector1977) and by specialized cells lining the third ventricle . Plasma concentrations of ascorbate are 30-60 µM, and these are increased to 200-400 µM in the cerebrospinal fluid through this mechanism (Reiber et al., 1993;Spector et al., 1973). Transport of ascorbate into neurons further increases the gradient, since neurons contain *Corresponding author: Dr. James May, 7465 Medical Research Building IV, Vanderbilt University School of Medicine, Nashville, TN 37232-0475. Tel. (615) 936-1653; Fax: (615) 936-1667. E-mail: james.may@vanderbilt.edu. Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal d...

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Modulation of hypoxia-inducible factor-1 alpha in cultured primary cells by intracellular ascorbate

Cited by 105 publications

References 51 publications

Redox control of iron regulatory protein 2 stability

Redox control of iron regulatory protein 2 stability

The Effect of Antioxidants on the Production of Pro-Inflammatory Cytokines and Orthodontic Tooth Movement

Development of ascorbate transporters in brain cortical capillary endothelial cells in culture

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