EX4 stabilizes and activates Nrf2 via PKCδ, contributing to the prevention of oxidative stress-induced pancreatic beta cell damage

Journal Article · Sat Jan 14 23:00:00 EST 2017 · Toxicology and Applied Pharmacology

DOI:https://doi.org/10.1016/J.TAAP.2016.12.005· OSTI ID:22690903

Kim, Mi-Hwi; Kim, Eung-Hwi ^[1]; Jung, Hye Seung ^[2]; Yang, Dongki ^[3]; Park, Eun-Young ^[4]; Jun, Hee-Sook ^[1]

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1. College of Pharmacy, Gachon Institute of Pharmaceutical Science, Gachon University, Yeonsu-ku, Incheon (Korea, Republic of)
2. Department of Internal Medicine, Seoul National University College of Medicine, Seoul (Korea, Republic of)
3. Department of Physiology, Gachon University College of Medicine, Incheon (Korea, Republic of)
4. College of Pharmacy, Natural Medicine Research Institute, Mokpo National University, Muan-gun, Jeonnam (Korea, Republic of)

Oxidative stress in pancreatic beta cells can inhibit insulin secretion and promote apoptotic cell death. Exendin-4 (EX4), a glucagon-like peptide-1 receptor agonist, can suppress beta cell apoptosis, improve beta cell function and protect against oxidative damage. In this study, we investigated the molecular mechanisms for antioxidative effects of EX4 in pancreatic beta cells. INS-1 cells, a rat insulinoma cell line, were pretreated with EX4 and exposed to palmitate or H{sub 2}O{sub 2}. Reactive oxygen species (ROS) production, and glutathione and insulin secretion were measured. The mRNA and protein expression levels of antioxidant genes were examined. The level of nuclear factor erythroid 2-related factor 2 (Nrf2), its binding to antioxidant response element (ARE), and its ubiquination in the presence of EX4 were determined. The Nrf2 signaling pathway was determined using rottlerin (protein kinase [PK]Cδ inhibitor), H89 (PKA inhibitor) and LY294002 (phosphatidylinositide 3-kinase [PI3K] inhibitor). EX4 treatment decreased ROS production, recovered cellular glutathione levels and insulin secretion in the presence of oxidative stress in INS-1 cells. The expression levels of glutamate-cysteine ligase catalytic subunit and heme oxygenase-1 were increased by EX4 treatment. EX4 promoted Nrf2 translocation, ARE binding activity and enhanced stabilization of Nrf2 by inhibition of ubiquitination. Knockdown of Nrf2 abolished the effect of EX4 on increased insulin secretion. Inhibition of PKCδ attenuated Nrf2 translocation and antioxidative gene expression by EX4 treatment. We suggest that EX4 activates and stabilizes Nrf2 through PKCδ activation, contributing to the increase of antioxidant gene expression and consequently improving beta cell function in the presence of oxidative stress. - Highlights: • EX4 protects against oxidative stress-induced pancreatic beta cell dysfunction. • EX4 increases antioxidant gene expression. • Antioxidative effect of EX4 is mediated by Nrf2. • EX4 increases Nrf2 level by stabilizing Nrf2 protein. • EX4 stabilizes Nrf2 by activation of PKCδ.

• OSTI ID: 22690903
• Journal Information: Toxicology and Applied Pharmacology, Journal Name: Toxicology and Applied Pharmacology Vol. 315; ISSN TXAPA9; ISSN 0041-008X
• Country of Publication: United States
• Language: English

Related Subjects

60 APPLIED LIFE SCIENCES
ANTIOXIDANTS
APOPTOSIS
CYCLOHEXIMIDE
CYSTEINE
DAMAGE
ECR HEATING
GLUCAGON
GLUTATHIONE
HEME
HEXADECANOIC ACID
HYDROGEN PEROXIDE
INSULIN
LIGASES
MESSENGER-RNA
NAD
OXIDATION
OXYGENASES
PANCREAS
PHOSPHOTRANSFERASES
POLYMERASE CHAIN REACTION
POLYMERASES
QUININE
RATS
RECEPTORS
SECRETION