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Deletion of thioredoxin interacting protein (TXNIP) augments hyperoxia-induced vaso-obliteration in a mouse model of oxygen induced-retinopathy.

Abdelsaid MA, Matragoon S, Ergul A, El-Remessy AB - PLoS ONE (2014)

Bottom Line: Exposure of TKO to hyperoxia significantly decreased the anti-apoptotic thioredoxin protein (∼ 50%) level compared with WT.This effect was associated with a significant increase in activation of the apoptotic ASK-1, PARP and caspase-3 pathway.Our results showed that despite comparable VEGF level and signal in TKO, exposure to hyperoxia significantly decreased Trx expression compared to WT.

View Article: PubMed Central - PubMed

Affiliation: Clinical and Experimental Therapeutics, University of Georgia, Augusta, Georgia, United States of America; Department of Physiology, Georgia Regents University, Augusta, Georgia, United States of America; Charlie Norwood VA Medical Center, Augusta, Georgia, United States of America.

ABSTRACT
We have recently shown that thioredoxin interacting protein (TXNIP) is required for VEGF-mediated VEGFR2 receptor activation and angiogenic signal. Retinas from TXNIP knockout mice (TKO) exhibited higher cellular antioxidant defense compared to wild type (WT). This study aimed to examine the impact of TXNIP deletion on hyperoxia-induced vaso-obliteration in ischemic retinopathy. TKO and WT pups were subjected to oxygen-induced retinopathy model. Retinal central capillary dropout was measured at p12. Retinal redox and nitrative state were assessed by reduced-glutathione (GSH), thioredoxin reductase activity and nitrotyrosine formation. Western blot and QT-PCR were used to assess VEGF, VEGFR-2, Akt, iNOS and eNOS, thioredoxin expression, ASK-1 activation and downstream cleaved caspase-3 and PARP in retinal lysates. Retinas from TKO mice exposed to hyperoxia showed significant increases (1.5-fold) in vaso-obliteration as indicated by central capillary drop out area compared to WT. Retinas from TKO showed minimal nitrotyrosine levels (10% of WT) with no change in eNOS or iNOS mRNA expression. There was no change in levels of VEGF or activation of VEGFR2 and its downstream Akt in retinas from TKO and WT. In comparison to WT, retinas from TKO showed significantly higher level of GSH and thioredoxin reductase activity in normoxia but comparable levels under hyperoxia. Exposure of TKO to hyperoxia significantly decreased the anti-apoptotic thioredoxin protein (∼ 50%) level compared with WT. This effect was associated with a significant increase in activation of the apoptotic ASK-1, PARP and caspase-3 pathway. Our results showed that despite comparable VEGF level and signal in TKO, exposure to hyperoxia significantly decreased Trx expression compared to WT. This effect resulted in liberation and activation of the apoptotic ASK-1 signal. These findings suggest that TXNIP is required for endothelial cell survival and homeostasis especially under stress conditions including hyperoxia.

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Deletion of TXNIP augments hyperoxia-induced vaso-obliteration compared to WT.Wild type (WT) and TXNIP knockout (TKO) mice were subjected to hyperoxia (75% O2, p7–p12). Retinas were fixed and stained with iso-lectin B4 to quantify oxygen induced vaso-obliteration. A–C) Retinas from TKO mice exposed to hyperoxia showed significant increases in vaso-obliteration compared to WT. (*P<0.05 vs WT, n = 12). D) Hyperoxia stimulates TXNIP expression mRNA in WT but not in TKO mice. (*P<0.05 vs WT normoxia, n = 4)
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pone-0110388-g001: Deletion of TXNIP augments hyperoxia-induced vaso-obliteration compared to WT.Wild type (WT) and TXNIP knockout (TKO) mice were subjected to hyperoxia (75% O2, p7–p12). Retinas were fixed and stained with iso-lectin B4 to quantify oxygen induced vaso-obliteration. A–C) Retinas from TKO mice exposed to hyperoxia showed significant increases in vaso-obliteration compared to WT. (*P<0.05 vs WT, n = 12). D) Hyperoxia stimulates TXNIP expression mRNA in WT but not in TKO mice. (*P<0.05 vs WT normoxia, n = 4)

Mentions: Exposure of the developing rodent retina (post-natal day p7 to p12) to high levels of oxygen causes vascular cell death as indicated by central capillary dropout [26]. Increases in oxidative stress and peroxynitrite have been shown to cause vascular cell loss in ischemic retinopathy model [27], [29]–[31]. Retinas from TKO demonstrate comparable vascular density to their WT littermates at normal oxygen level at p7 (Fig. S1) and at p12 as recently characterized by our group [23]. We and others have previously showed that deletion of TXNIP enhanced antioxidant defense and decreased oxidative stress [8], [23], [24]. Therefore, TKO mice were predicted to show higher vascular protection against hyperoxia compared to wild type (WT) mice. In contrast, deletion of TXNIP aggravated hyperoxia-induced vaso-obliteration as indicated by significant increase (1.6-fold) in central capillary dropout areas compared to WT at p12 (Fig. 1A–C). Of note, hyperoxia drives retinal TXNIP mRNA expression (1.5-fold) in WT mice but not TKO (Fig. 1D).


Deletion of thioredoxin interacting protein (TXNIP) augments hyperoxia-induced vaso-obliteration in a mouse model of oxygen induced-retinopathy.

Abdelsaid MA, Matragoon S, Ergul A, El-Remessy AB - PLoS ONE (2014)

Deletion of TXNIP augments hyperoxia-induced vaso-obliteration compared to WT.Wild type (WT) and TXNIP knockout (TKO) mice were subjected to hyperoxia (75% O2, p7–p12). Retinas were fixed and stained with iso-lectin B4 to quantify oxygen induced vaso-obliteration. A–C) Retinas from TKO mice exposed to hyperoxia showed significant increases in vaso-obliteration compared to WT. (*P<0.05 vs WT, n = 12). D) Hyperoxia stimulates TXNIP expression mRNA in WT but not in TKO mice. (*P<0.05 vs WT normoxia, n = 4)
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4199686&req=5

pone-0110388-g001: Deletion of TXNIP augments hyperoxia-induced vaso-obliteration compared to WT.Wild type (WT) and TXNIP knockout (TKO) mice were subjected to hyperoxia (75% O2, p7–p12). Retinas were fixed and stained with iso-lectin B4 to quantify oxygen induced vaso-obliteration. A–C) Retinas from TKO mice exposed to hyperoxia showed significant increases in vaso-obliteration compared to WT. (*P<0.05 vs WT, n = 12). D) Hyperoxia stimulates TXNIP expression mRNA in WT but not in TKO mice. (*P<0.05 vs WT normoxia, n = 4)
Mentions: Exposure of the developing rodent retina (post-natal day p7 to p12) to high levels of oxygen causes vascular cell death as indicated by central capillary dropout [26]. Increases in oxidative stress and peroxynitrite have been shown to cause vascular cell loss in ischemic retinopathy model [27], [29]–[31]. Retinas from TKO demonstrate comparable vascular density to their WT littermates at normal oxygen level at p7 (Fig. S1) and at p12 as recently characterized by our group [23]. We and others have previously showed that deletion of TXNIP enhanced antioxidant defense and decreased oxidative stress [8], [23], [24]. Therefore, TKO mice were predicted to show higher vascular protection against hyperoxia compared to wild type (WT) mice. In contrast, deletion of TXNIP aggravated hyperoxia-induced vaso-obliteration as indicated by significant increase (1.6-fold) in central capillary dropout areas compared to WT at p12 (Fig. 1A–C). Of note, hyperoxia drives retinal TXNIP mRNA expression (1.5-fold) in WT mice but not TKO (Fig. 1D).

Bottom Line: Exposure of TKO to hyperoxia significantly decreased the anti-apoptotic thioredoxin protein (∼ 50%) level compared with WT.This effect was associated with a significant increase in activation of the apoptotic ASK-1, PARP and caspase-3 pathway.Our results showed that despite comparable VEGF level and signal in TKO, exposure to hyperoxia significantly decreased Trx expression compared to WT.

View Article: PubMed Central - PubMed

Affiliation: Clinical and Experimental Therapeutics, University of Georgia, Augusta, Georgia, United States of America; Department of Physiology, Georgia Regents University, Augusta, Georgia, United States of America; Charlie Norwood VA Medical Center, Augusta, Georgia, United States of America.

ABSTRACT
We have recently shown that thioredoxin interacting protein (TXNIP) is required for VEGF-mediated VEGFR2 receptor activation and angiogenic signal. Retinas from TXNIP knockout mice (TKO) exhibited higher cellular antioxidant defense compared to wild type (WT). This study aimed to examine the impact of TXNIP deletion on hyperoxia-induced vaso-obliteration in ischemic retinopathy. TKO and WT pups were subjected to oxygen-induced retinopathy model. Retinal central capillary dropout was measured at p12. Retinal redox and nitrative state were assessed by reduced-glutathione (GSH), thioredoxin reductase activity and nitrotyrosine formation. Western blot and QT-PCR were used to assess VEGF, VEGFR-2, Akt, iNOS and eNOS, thioredoxin expression, ASK-1 activation and downstream cleaved caspase-3 and PARP in retinal lysates. Retinas from TKO mice exposed to hyperoxia showed significant increases (1.5-fold) in vaso-obliteration as indicated by central capillary drop out area compared to WT. Retinas from TKO showed minimal nitrotyrosine levels (10% of WT) with no change in eNOS or iNOS mRNA expression. There was no change in levels of VEGF or activation of VEGFR2 and its downstream Akt in retinas from TKO and WT. In comparison to WT, retinas from TKO showed significantly higher level of GSH and thioredoxin reductase activity in normoxia but comparable levels under hyperoxia. Exposure of TKO to hyperoxia significantly decreased the anti-apoptotic thioredoxin protein (∼ 50%) level compared with WT. This effect was associated with a significant increase in activation of the apoptotic ASK-1, PARP and caspase-3 pathway. Our results showed that despite comparable VEGF level and signal in TKO, exposure to hyperoxia significantly decreased Trx expression compared to WT. This effect resulted in liberation and activation of the apoptotic ASK-1 signal. These findings suggest that TXNIP is required for endothelial cell survival and homeostasis especially under stress conditions including hyperoxia.

Show MeSH
Related in: MedlinePlus