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Nε-carboxymethyllysine-mediated endoplasmic reticulum stress promotes endothelial cell injury through Nox4/MKP-3

Wen-Jane Lee1, Wayne Huey-Herng Sheu2, Shing-Hwa Liu3

  • 1Department of Medical Research, Taichung Veterans General Hospital, Taichung, Taiwan; Department of Social Work, Tunghai University, Taichung, Taiwan.

Free Radical Biology & Medicine
|July 12, 2014
PubMed

Insights

N(ε)-carboxymethyllysine (CML) drives diabetic vascular issues. This study reveals that MAPK phosphatase-3 (MKP-3) inactivation of ERK via Nox4 contributes to CML-induced endothelial cell injury in diabetes.

Area of Science:

  • Endocrinology
  • Cell Biology
  • Vascular Biology

Background:

  • N(ε)-carboxymethyllysine (CML) is a key factor in diabetic vascular complications and endothelial dysfunction.
  • The precise cellular mechanisms by which CML induces these effects, particularly the roles of protein tyrosine phosphatases and ERK phosphorylation, are not fully understood.

Purpose of the Study:

  • To investigate the critical role of endoplasmic reticulum (ER) localization of MAPK phosphatase-3 (MKP-3) in regulating ERK inactivation and promoting NADPH oxidase-4 (Nox4) activation in CML-induced endothelial cell injury.
  • To elucidate the pathway linking CML, ER stress, MKP-3, Nox4, and ERK dephosphorylation in diabetic vascular complications.

Main Methods:

  • Quantification of serum CML levels in type 2 diabetes patients and diabetic animals.
  • In vitro studies using human umbilical vein endothelial cells (HUVECs) and SVECs to assess CML effects on ER stress, apoptosis, ERK activation, and MKP-3 activity.
  • siRNA-mediated knockdown of MKP-3, MKP-1, and MKP-2 to determine specific phosphatase involvement.
  • Investigation of the interaction between MKP-3, ERK, and Nox4.
  • Assessment of antioxidant effects on CML-induced changes.
  • In vivo immunohistochemical analysis of aortic endothelium in diabetic mouse models.

Main Results:

  • Serum CML levels were elevated in diabetic patients and animals.
  • CML exposure increased ER stress, apoptosis, MKP-3 activity, and Nox4-mediated activation, while reducing ERK activation in endothelial cells.
  • MKP-3, but not MKP-1 or MKP-2, was essential for CML's effects.
  • MKP-3 mediated ERK dephosphorylation through Nox4 and increased its integration with ERK.
  • Antioxidants reversed CML-induced MKP-3 activity and expression.
  • Diabetic mouse aortas showed increased MKP-3 and CML, with decreased phospho-ERK staining.

Conclusions:

  • The study identifies a critical pathway involving Nox4-mediated activation of MKP-3 in regulating ERK dephosphorylation during CML-induced endothelial cell dysfunction.
  • These findings suggest that targeting the Nox4/MKP-3 interaction or MKP-3 activation may offer therapeutic strategies for diabetic vascular complications.
Keywords:
AGEsCMLERKFree radicalsHuman endothelial cellsMKP-3Nox4

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