Exendin-4 inhibits high glucose-induced oxidative stress in retinal pigment epithelial cells by modulating the expression and activation of p⁶⁶Shc

Abstract

Purpose

Activation of p⁶⁶Sch, an adaptor protein, is associated with oxidative stress and apoptosis and has been implicated in the pathogenesis of diabetes-induced retinal pigment epithelial cell damage and diabetic retinopathy. Exendin-4 is a glucagon-like protein that protects against diabetic retinopathy, but the mechanism of action is not well understood. This study aimed to investigate whether Exendin-4 could protect against high glucose-induced oxidative stress and apoptosis in the adult human retinal pigment epithelial-19 cell line by modulating levels and activation of p⁶⁶Shc and to study the underlying mechanisms.

Materials and Methods

Adult human retinal pigment epithelial-19 cells were cultured under low (5 µM) or high glucose (100 µM) conditions in the presence or absence of Exendin-4 and with or without pre-incubation with Exendin-9-39, a glucagon-like peptide-1 receptor antagonist.

Results

In a dose-dependent manner, Exendin-4 inhibited high glucose-induced cell death and decreased levels of reactive oxygen species, lactate dehydrogenase release, and single single-stranded DNA. At the most effective concentration (100 µM), Exendin-4 reduced mitochondrial levels of phospho-p⁶⁶Shc (Ser³⁶), cytoplasmic levels of cleaved caspase-3 and cytochrome-c, and NADPH oxidase levels in high glucose-treated cells. It also increased levels of glutathione and magnesium superoxide dismutase and protein levels of magnesium superoxide dismutase but downregulated total protein levels of protein kinase-β and p⁶⁶Shc and inhibited c-Jun N-terminal kinase phosphorylation in both low- and high glucose-treated cells. All these Exendin-4 effects, however, were inhibited by Exendin-9-39.

Conclusions

Exendin-4 protects against high glucose-induced adult human retinal pigment epithelial-19 cell damage by increasing antioxidants, downregulating NADPH, and inhibiting mitochondria-mediated apoptosis, effects that are associated with the inhibition of c-Jun N-terminal kinase and downregulation of protein kinase-β and p⁶⁶Shc.

Keywords:

• Exendin-4
• high glucose
• retina
• oxidative stress
• p66Shc

Acknowledgement

The author wishes to thanks the technical staff at the laboratories of King Khalid University for their help in measuring some biochemical parameters of this study and wishes to thank the deanship of scientific research for their continuous help.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

The author wishes to thank the deanship of scientific research at King Khalid University for their continuous support to this study.