Limits...
Activation of NF-E2-related factor-2 reverses biochemical dysfunction of endothelial cells induced by hyperglycemia linked to vascular disease.

Xue M, Qian Q, Adaikalakoteswari A, Rabbani N, Babaei-Jadidi R, Thornalley PJ - Diabetes (2008)

Bottom Line: The effects of sulforaphane on multiple pathways of biochemical dysfunction, increased reactive oxygen species (ROS) formation, hexosamine pathway, protein kinase C (PKC) pathway, and increased formation of methylglyoxal were assessed.Activation of nrf2 by sulforaphane induced nuclear translocation of nrf2 and increased ARE-linked gene expression, for example, three- to fivefold increased expression of transketolase and glutathione reductase.This also abolished the counteracting effect of sulforaphane, suggesting mediation by nrf2 and related increase of transketolase expression.

View Article: PubMed Central - PubMed

Affiliation: Clinical Sciences Research Institute, Warwick Medical School, University of Warwick, University Hospital, Coventry, UK.

ABSTRACT

Objective: Sulforaphane is an activator of transcription factor NF-E2-related factor-2 (nrf2) that regulates gene expression through the promoter antioxidant response element (ARE). Nrf2 regulates the transcription of a battery of protective and metabolic enzymes. The aim of this study was to assess whether activation of nrf2 by sulforaphane in human microvascular endothelial cells prevents metabolic dysfunction in hyperglycemia.

Research design and methods: Human microvascular HMEC-1 endothelial cells were incubated in low and high glucose concentrations (5 and 30 mmol/l, respectively), and activation of nrf2 was assessed by nuclear translocation. The effects of sulforaphane on multiple pathways of biochemical dysfunction, increased reactive oxygen species (ROS) formation, hexosamine pathway, protein kinase C (PKC) pathway, and increased formation of methylglyoxal were assessed.

Results: Activation of nrf2 by sulforaphane induced nuclear translocation of nrf2 and increased ARE-linked gene expression, for example, three- to fivefold increased expression of transketolase and glutathione reductase. Hyperglycemia increased the formation of ROS-an effect linked to mitochondrial dysfunction and prevented by sulforaphane. ROS formation was increased further by knockdown of nrf2 and transketolase expression. This also abolished the counteracting effect of sulforaphane, suggesting mediation by nrf2 and related increase of transketolase expression. Sulforaphane also prevented hyperglycemia-induced activation of the hexosamine and PKC pathways and prevented increased cellular accumulation and excretion of the glycating agent methylglyoxal.

Conclusions: We conclude that activation of nrf2 may prevent biochemical dysfunction and related functional responses of endothelial cells induced by hyperglycemia in which increased expression of transketolase has a pivotal role.

Show MeSH

Related in: MedlinePlus

Nrf2 activation and transketolase expression in human HMEC-1 endothelial cells in vitro. A: Schematic diagram showing activation of nrf2 and dynamic nuclear-cytoplasmic shuttling of nrf2 for ARE-linked expression. B: Multiple pathways of biochemical dysfunction induced by hyperglycemia in microvascular endothelial cells and effect of nrf2 activated, ARE-mediated induction of transketolase expression. Other mechanisms of biochemical dysfunction may be involved.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC2551693&req=5

f1: Nrf2 activation and transketolase expression in human HMEC-1 endothelial cells in vitro. A: Schematic diagram showing activation of nrf2 and dynamic nuclear-cytoplasmic shuttling of nrf2 for ARE-linked expression. B: Multiple pathways of biochemical dysfunction induced by hyperglycemia in microvascular endothelial cells and effect of nrf2 activated, ARE-mediated induction of transketolase expression. Other mechanisms of biochemical dysfunction may be involved.

Mentions: Under basal conditions, nrf2 is complexed with Kelch-like ECH-associated protein 1 (Keap1), a BTB-Kelch protein. Keap1 is a substrate adaptor protein for a Cul 3–dependent E3 ubiquitin ligase complex, directing nrf2 for proteasomal degradation (19). Oxidative stress, electrophiles, and sulforaphane-like inducers disrupt the Keap1-nrf2 complex: nrf2 translocates to the nucleus and, combining with small maf protein (20), induces ARE-linked gene expression (21). Sulforaphane releases nrf2 from Keap1 by modification of critical cysteine thiol residues (22). Keap1 has concurrent increased susceptibility to degradation but also has ARE-linked gene expression and may be induced by nrf2 activation, providing an autoregulatory feedback loop (23). Nrf2 also undergoes nuclear export, establishing cytoplasmic/nuclear dynamic shuttling (24). Recent research has suggested that the serine/threonine kinase CK2 has a role in nuclear import of nrf2 and that both CK2 and tyrosine kinase Fyn influence nuclear export and degradation of nrf2 (25,26) (Fig. 1A). There is an active nrf2–Keap-1 system in vascular endothelial cells (27).


Activation of NF-E2-related factor-2 reverses biochemical dysfunction of endothelial cells induced by hyperglycemia linked to vascular disease.

Xue M, Qian Q, Adaikalakoteswari A, Rabbani N, Babaei-Jadidi R, Thornalley PJ - Diabetes (2008)

Nrf2 activation and transketolase expression in human HMEC-1 endothelial cells in vitro. A: Schematic diagram showing activation of nrf2 and dynamic nuclear-cytoplasmic shuttling of nrf2 for ARE-linked expression. B: Multiple pathways of biochemical dysfunction induced by hyperglycemia in microvascular endothelial cells and effect of nrf2 activated, ARE-mediated induction of transketolase expression. Other mechanisms of biochemical dysfunction may be involved.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2551693&req=5

f1: Nrf2 activation and transketolase expression in human HMEC-1 endothelial cells in vitro. A: Schematic diagram showing activation of nrf2 and dynamic nuclear-cytoplasmic shuttling of nrf2 for ARE-linked expression. B: Multiple pathways of biochemical dysfunction induced by hyperglycemia in microvascular endothelial cells and effect of nrf2 activated, ARE-mediated induction of transketolase expression. Other mechanisms of biochemical dysfunction may be involved.
Mentions: Under basal conditions, nrf2 is complexed with Kelch-like ECH-associated protein 1 (Keap1), a BTB-Kelch protein. Keap1 is a substrate adaptor protein for a Cul 3–dependent E3 ubiquitin ligase complex, directing nrf2 for proteasomal degradation (19). Oxidative stress, electrophiles, and sulforaphane-like inducers disrupt the Keap1-nrf2 complex: nrf2 translocates to the nucleus and, combining with small maf protein (20), induces ARE-linked gene expression (21). Sulforaphane releases nrf2 from Keap1 by modification of critical cysteine thiol residues (22). Keap1 has concurrent increased susceptibility to degradation but also has ARE-linked gene expression and may be induced by nrf2 activation, providing an autoregulatory feedback loop (23). Nrf2 also undergoes nuclear export, establishing cytoplasmic/nuclear dynamic shuttling (24). Recent research has suggested that the serine/threonine kinase CK2 has a role in nuclear import of nrf2 and that both CK2 and tyrosine kinase Fyn influence nuclear export and degradation of nrf2 (25,26) (Fig. 1A). There is an active nrf2–Keap-1 system in vascular endothelial cells (27).

Bottom Line: The effects of sulforaphane on multiple pathways of biochemical dysfunction, increased reactive oxygen species (ROS) formation, hexosamine pathway, protein kinase C (PKC) pathway, and increased formation of methylglyoxal were assessed.Activation of nrf2 by sulforaphane induced nuclear translocation of nrf2 and increased ARE-linked gene expression, for example, three- to fivefold increased expression of transketolase and glutathione reductase.This also abolished the counteracting effect of sulforaphane, suggesting mediation by nrf2 and related increase of transketolase expression.

View Article: PubMed Central - PubMed

Affiliation: Clinical Sciences Research Institute, Warwick Medical School, University of Warwick, University Hospital, Coventry, UK.

ABSTRACT

Objective: Sulforaphane is an activator of transcription factor NF-E2-related factor-2 (nrf2) that regulates gene expression through the promoter antioxidant response element (ARE). Nrf2 regulates the transcription of a battery of protective and metabolic enzymes. The aim of this study was to assess whether activation of nrf2 by sulforaphane in human microvascular endothelial cells prevents metabolic dysfunction in hyperglycemia.

Research design and methods: Human microvascular HMEC-1 endothelial cells were incubated in low and high glucose concentrations (5 and 30 mmol/l, respectively), and activation of nrf2 was assessed by nuclear translocation. The effects of sulforaphane on multiple pathways of biochemical dysfunction, increased reactive oxygen species (ROS) formation, hexosamine pathway, protein kinase C (PKC) pathway, and increased formation of methylglyoxal were assessed.

Results: Activation of nrf2 by sulforaphane induced nuclear translocation of nrf2 and increased ARE-linked gene expression, for example, three- to fivefold increased expression of transketolase and glutathione reductase. Hyperglycemia increased the formation of ROS-an effect linked to mitochondrial dysfunction and prevented by sulforaphane. ROS formation was increased further by knockdown of nrf2 and transketolase expression. This also abolished the counteracting effect of sulforaphane, suggesting mediation by nrf2 and related increase of transketolase expression. Sulforaphane also prevented hyperglycemia-induced activation of the hexosamine and PKC pathways and prevented increased cellular accumulation and excretion of the glycating agent methylglyoxal.

Conclusions: We conclude that activation of nrf2 may prevent biochemical dysfunction and related functional responses of endothelial cells induced by hyperglycemia in which increased expression of transketolase has a pivotal role.

Show MeSH
Related in: MedlinePlus