Pioglitazone restores IGFBP-3 levels through DNA PK in retinal endothelial cells cultured in hyperglycemic conditions

Shalini Thakran, Qiuhua Zhang, Vanessa Morales-Tirado, Jena J. Steinle

Research output: Contribution to journalArticle

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Abstract

Purpose: Previously, we reported that pioglitazone prevented insulin resistance and cell death in type 2 diabetic retina by reducing TNFa and suppressor of cytokine signaling 3 (SOCS3) levels. Numerous reports suggest prominent vasoprotective effects of insulin growth factor binding protein–3 (IGFBP-3) in diabetic retinopathy. We hypothesized that pioglitazone protects against retinal cell apoptosis by regulating IGFBP-3 levels, in addition to reducing TNFa. The current study explored potential IGFBP-3 regulatory pathways by pioglitazone in retinal endothelial cells cultured in high glucose.

Methods: Primary human retinal endothelial cells (REC) were grown in normal (5 mM) and high glucose (25 mM) and treated with pioglitazone for 24 hours. Cell lysates were processed for Western blotting and ELISA analysis to evaluate IGFBP-3, TNFα, and cleaved caspase 3 protein levels.

Results: Our results show that treatment with pioglitazone restored the high glucose–induced decrease in IGFBP-3 levels. This regulation was independent of TNFα actions, as reducing TNFα levels with siRNA did not prevent pioglitazone from increasing IGFBP-3 levels. Pioglitazone required protein kinase A (PKA) and DNA-dependent protein kinase (DNA PK) activity to regulate IGFBP-3, as specific inhibitors for each protein prevented pioglitazonemediated normalization of IGFBP-3 in high glucose. Insulin growth factor binding protein–3 activity was increased and apoptosis decreased by pioglitazone, which was eliminated when serine site 156 of IGFBP-3 was mutated suggesting a key role of this phosphorylation site in pioglitazone actions.

Conclusions: Our findings suggest that pioglitazone mediates regulation of IGFBP-3 via activation of PKA/DNA PK pathway in hyperglycemic retinal endothelial cells.

Original languageEnglish (US)
Pages (from-to)177-184
Number of pages8
JournalInvestigative Ophthalmology and Visual Science
Volume56
Issue number1
DOIs
StatePublished - Dec 18 2015

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pioglitazone
DNA-Activated Protein Kinase
Intercellular Signaling Peptides and Proteins
Endothelial Cells
Insulin
Cyclic AMP-Dependent Protein Kinases
Glucose
Apoptosis

All Science Journal Classification (ASJC) codes

  • Ophthalmology
  • Sensory Systems
  • Cellular and Molecular Neuroscience

Cite this

Pioglitazone restores IGFBP-3 levels through DNA PK in retinal endothelial cells cultured in hyperglycemic conditions. / Thakran, Shalini; Zhang, Qiuhua; Morales-Tirado, Vanessa; Steinle, Jena J.

In: Investigative Ophthalmology and Visual Science, Vol. 56, No. 1, 18.12.2015, p. 177-184.

Research output: Contribution to journalArticle

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