Elucidation of Molecular Mechanisms of Streptozotocin-Induced Oxidative Stress, Apoptosis, and Mitochondrial Dysfunction in Rin-5F Pancreatic β-Cells.

Arwa M T Al Nahdi,Annie John,Haider Raza

doi:10.1155/2017/7054272

Abstract

Streptozotocin is a pancreatic beta-cell-specific cytotoxin and is widely used to induce experimental type 1 diabetes in rodent models. The precise molecular mechanism of STZ cytotoxicity is however not clear. Studies have suggested that STZ is preferably absorbed by insulin-secreting β-cells and induces cytotoxicity by producing reactive oxygen species/reactive nitrogen species (ROS/RNS). In the present study, we have investigated the mechanism of cytotoxicity of STZ in insulin-secreting pancreatic cancer cells (Rin-5F) at different doses and time intervals. Cell viability, apoptosis, oxidative stress, and mitochondrial bioenergetics were studied. Our results showed that STZ induces alterations in glutathione homeostasis and inhibited the activities of the respiratory enzymes, resulting in inhibition of ATP synthesis. Apoptosis was observed in a dose- and time-dependent manner. Western blot analysis has also confirmed altered expression of oxidative stress markers (e.g., NOS and Nrf2), cell signaling kinases, apoptotic protein-like caspase-3, PARP, and mitochondrial specific proteins. These results suggest that STZ-induced cytotoxicity in pancreatic cells is mediated by an increase in oxidative stress, alterations in cellular metabolism, and mitochondrial dysfunction. This study may be significant in better understanding the mechanism of STZ-induced β-cell toxicity/resistance and the etiology of type 1 diabetes induction.

Highlights

Streptozotocin (STZ), [N-(methylnitrosocarbamoyl)-α-Dglucosamine], is a broad spectrum antibiotic derived from the bacterium Streptomyces achromogenes [1]
The cytotoxicity of STZ is presumed to be mediated by reactive oxygen species (ROS), reactive nitric oxide species (NO/RNS), and induction of inflammatory responses [16, 17]. Using both in vitro cell culture and in vivo diabetic rodent models for STZ-induced toxicity, we have demonstrated that STZ induces cellular oxidative stress and mitochondrial respiratory dysfunction [18,19,20]
Our results demonstrate that the effects of STZ are dose and time dependent, causing oxidative stress-associated alterations in GSH redox metabolism and mitochondrial respiratory dysfunction leading to increased apoptosis in Rin-5F cells

Summary

Introduction

Streptozotocin (STZ), [N-(methylnitrosocarbamoyl)-α-Dglucosamine], is a broad spectrum antibiotic derived from the bacterium Streptomyces achromogenes [1]. It is a DNA alkylating agent and is often used as an antibacterial as well as anticancer agent [2, 3]. STZ is a glucose analogue that is selectively accumulated in pancreatic beta-cells via a GLUT 2 glucose transporter in the plasma membrane [7, 8]. STZ toxicity in beta-cells is dependent on GLUT 2 expression. After entering the beta-cells via the GLUT 2 transporter, it causes DNA damage due to the DNA alkylating activity of its methyl nitrosourea moiety [10, 11], which, in turn, results in DNA fragmentation [12].

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