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TXNIP links innate host defense mechanisms to oxidative stress and inflammation in retinal Muller glia under chronic hyperglycemia: implications for diabetic retinopathy.

Devi TS, Lee I, Hüttemann M, Kumar A, Nantwi KD, Singh LP - Exp Diabetes Res (2012)

Bottom Line: We also found in vivo that streptozocin-induced diabetic rats have higher retinal TXNIP and innate immune response gene expression than normal rats.Thus, our results show that HG sustains TXNIP up-regulation in Muller glia and evokes a program of cellular defense/survival mechanisms that ultimately lead to oxidative stress, ER stress/inflammation, autophagy and apoptosis.TXNIP is a potential target to ameliorate blinding ocular complications of diabetic retinopathy.

View Article: PubMed Central - PubMed

Affiliation: Department of Anatomy and Cell Biology, Wayne State University, Detroit, MI 48201, USA.

ABSTRACT
Thioredoxin Interacting Protein (TXNIP) mediates retinal inflammation, gliosis, and apoptosis in experimental diabetes. Here, we investigate the temporal response of Muller glia to high glucose (HG) and TXNIP expression using a rat Muller cell line (rMC1) in culture. We examined if HG-induced TXNIP expression evokes host defense mechanisms in rMC1 in response to metabolic abnormalities. HG causes sustained up-regulation of TXNIP (2 h to 5 days), ROS generation, ATP depletion, ER stress, and inflammation. Various cellular defense mechanisms are activated by HG: (i) NLRP3 inflammasome, (ii) ER stress response (sXBP1), (iii) hypoxic-like HIF-1α induction, (iv) autophagy/mitophagy, and (v) apoptosis. We also found in vivo that streptozocin-induced diabetic rats have higher retinal TXNIP and innate immune response gene expression than normal rats. Knock down of TXNIP by intravitreal siRNA reduces inflammation (IL-1β) and gliosis (GFAP) in the diabetic retina. TXNIP ablation in vitro prevents ROS generation, restores ATP level and autophagic LC3B induction in rMC1. Thus, our results show that HG sustains TXNIP up-regulation in Muller glia and evokes a program of cellular defense/survival mechanisms that ultimately lead to oxidative stress, ER stress/inflammation, autophagy and apoptosis. TXNIP is a potential target to ameliorate blinding ocular complications of diabetic retinopathy.

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HG induces TXNIP expression and evokes the host innate immune response in rat Muller glia. Quantitative RT-PCR for (a) TXNIP and (b) IL-1β mRNA expression in rMC1 is shown. HG increases TXNIP mRNA at 2–24 h (P < 0.05 versus time 0, n = 6) while pro-IL-1β mRNA is increased at 2 and 4 h (P < 0.05 versus time 0, n = 6) and then reduces at 24 h. (c) IHC detects a time-dependent accumulation of the p65 subunit of NF-κB in the nucleus in rMC1 under HG. (d) Active caspase-1 staining is increased in rMC1 using the caspase-1 FLICA probe. A representative of n = 3 is shown here.
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fig2: HG induces TXNIP expression and evokes the host innate immune response in rat Muller glia. Quantitative RT-PCR for (a) TXNIP and (b) IL-1β mRNA expression in rMC1 is shown. HG increases TXNIP mRNA at 2–24 h (P < 0.05 versus time 0, n = 6) while pro-IL-1β mRNA is increased at 2 and 4 h (P < 0.05 versus time 0, n = 6) and then reduces at 24 h. (c) IHC detects a time-dependent accumulation of the p65 subunit of NF-κB in the nucleus in rMC1 under HG. (d) Active caspase-1 staining is increased in rMC1 using the caspase-1 FLICA probe. A representative of n = 3 is shown here.

Mentions: We have shown previously that TXNIP expression and Muller glia activation occur early in the diabetic retina [9]. So far, a role for TXNIP in Muller cell activation and pro-inflammatory gene induction under HG exposure has not been investigated. Therefore, we undertook a series of experiments to examine the temporal response of rMC1 to chronic hyperglycemia in culture. We show that HG exposure in rMC1 induces a significant (P < 0.05, n = 6) increase in TXNIP mRNA expression (2–24 h) when compared with low glucose (5.5 mM, LG) indicated as time 0 control (Figure 2(a)). We have previously shown that TXNIP mediates pro-IL-1β expression in primary Schwann Cells via the NF-κB-dependent pathway [10]. Therefore, we examined if TXNIP expression correlates with pro-IL-1β induction in rMC1 under HG. As shown in Figure 2(b), HG increases IL-1β mRNA expression at 2 and 4 h (P < 0.01) and then reduces at 24 h to the level of the control at 0 time. Furthermore, nuclear NF-κB level is also enhanced by HG in rMC1 from 2 to 24 h (Figure 2(c)), which correlates with activation of caspase-1 in rMC1 (Figure 2(d)). Active caspase 1 is responsible for processing pro-IL-1β (34-kDa) to an active mature form of IL-1β (17-kDa).


TXNIP links innate host defense mechanisms to oxidative stress and inflammation in retinal Muller glia under chronic hyperglycemia: implications for diabetic retinopathy.

Devi TS, Lee I, Hüttemann M, Kumar A, Nantwi KD, Singh LP - Exp Diabetes Res (2012)

HG induces TXNIP expression and evokes the host innate immune response in rat Muller glia. Quantitative RT-PCR for (a) TXNIP and (b) IL-1β mRNA expression in rMC1 is shown. HG increases TXNIP mRNA at 2–24 h (P < 0.05 versus time 0, n = 6) while pro-IL-1β mRNA is increased at 2 and 4 h (P < 0.05 versus time 0, n = 6) and then reduces at 24 h. (c) IHC detects a time-dependent accumulation of the p65 subunit of NF-κB in the nucleus in rMC1 under HG. (d) Active caspase-1 staining is increased in rMC1 using the caspase-1 FLICA probe. A representative of n = 3 is shown here.
© Copyright Policy - open-access
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC3313582&req=5

fig2: HG induces TXNIP expression and evokes the host innate immune response in rat Muller glia. Quantitative RT-PCR for (a) TXNIP and (b) IL-1β mRNA expression in rMC1 is shown. HG increases TXNIP mRNA at 2–24 h (P < 0.05 versus time 0, n = 6) while pro-IL-1β mRNA is increased at 2 and 4 h (P < 0.05 versus time 0, n = 6) and then reduces at 24 h. (c) IHC detects a time-dependent accumulation of the p65 subunit of NF-κB in the nucleus in rMC1 under HG. (d) Active caspase-1 staining is increased in rMC1 using the caspase-1 FLICA probe. A representative of n = 3 is shown here.
Mentions: We have shown previously that TXNIP expression and Muller glia activation occur early in the diabetic retina [9]. So far, a role for TXNIP in Muller cell activation and pro-inflammatory gene induction under HG exposure has not been investigated. Therefore, we undertook a series of experiments to examine the temporal response of rMC1 to chronic hyperglycemia in culture. We show that HG exposure in rMC1 induces a significant (P < 0.05, n = 6) increase in TXNIP mRNA expression (2–24 h) when compared with low glucose (5.5 mM, LG) indicated as time 0 control (Figure 2(a)). We have previously shown that TXNIP mediates pro-IL-1β expression in primary Schwann Cells via the NF-κB-dependent pathway [10]. Therefore, we examined if TXNIP expression correlates with pro-IL-1β induction in rMC1 under HG. As shown in Figure 2(b), HG increases IL-1β mRNA expression at 2 and 4 h (P < 0.01) and then reduces at 24 h to the level of the control at 0 time. Furthermore, nuclear NF-κB level is also enhanced by HG in rMC1 from 2 to 24 h (Figure 2(c)), which correlates with activation of caspase-1 in rMC1 (Figure 2(d)). Active caspase 1 is responsible for processing pro-IL-1β (34-kDa) to an active mature form of IL-1β (17-kDa).

Bottom Line: We also found in vivo that streptozocin-induced diabetic rats have higher retinal TXNIP and innate immune response gene expression than normal rats.Thus, our results show that HG sustains TXNIP up-regulation in Muller glia and evokes a program of cellular defense/survival mechanisms that ultimately lead to oxidative stress, ER stress/inflammation, autophagy and apoptosis.TXNIP is a potential target to ameliorate blinding ocular complications of diabetic retinopathy.

View Article: PubMed Central - PubMed

Affiliation: Department of Anatomy and Cell Biology, Wayne State University, Detroit, MI 48201, USA.

ABSTRACT
Thioredoxin Interacting Protein (TXNIP) mediates retinal inflammation, gliosis, and apoptosis in experimental diabetes. Here, we investigate the temporal response of Muller glia to high glucose (HG) and TXNIP expression using a rat Muller cell line (rMC1) in culture. We examined if HG-induced TXNIP expression evokes host defense mechanisms in rMC1 in response to metabolic abnormalities. HG causes sustained up-regulation of TXNIP (2 h to 5 days), ROS generation, ATP depletion, ER stress, and inflammation. Various cellular defense mechanisms are activated by HG: (i) NLRP3 inflammasome, (ii) ER stress response (sXBP1), (iii) hypoxic-like HIF-1α induction, (iv) autophagy/mitophagy, and (v) apoptosis. We also found in vivo that streptozocin-induced diabetic rats have higher retinal TXNIP and innate immune response gene expression than normal rats. Knock down of TXNIP by intravitreal siRNA reduces inflammation (IL-1β) and gliosis (GFAP) in the diabetic retina. TXNIP ablation in vitro prevents ROS generation, restores ATP level and autophagic LC3B induction in rMC1. Thus, our results show that HG sustains TXNIP up-regulation in Muller glia and evokes a program of cellular defense/survival mechanisms that ultimately lead to oxidative stress, ER stress/inflammation, autophagy and apoptosis. TXNIP is a potential target to ameliorate blinding ocular complications of diabetic retinopathy.

Show MeSH
Related in: MedlinePlus