Mitochondrial Respiratory Chain Inhibitors Involved in ROS Production Induced by Acute High Concentrations of Iodide and the Effects of SOD as a Protective Factor.

Lingyan Wang,Lanying Li,Mohamed Ahmed,Tingting Wang,Xiaomei Yao,Yongmei Li,Na Zhang,Qi Duan

doi:10.1155/2015/217670

Abstract

A major source of reactive oxygen species (ROS) generation is the mitochondria. By using flow cytometry of the mitochondrial fluorescent probe, MitoSOX Red, western blot of mitochondrial ROS scavenger Peroxiredoxin (Prx) 3 and fluorescence immunostaining, ELISA of cleaved caspases 3 and 9, and TUNEL staining, we demonstrated that exposure to 100 μM KI for 2 hours significantly increased mitochondrial superoxide production and Prx 3 protein expression with increased expressions of cleaved caspases 3 and 9. Besides, we indicated that superoxide dismutase (SOD) at 1000 unit/mL attenuated the increase in mitochondrial superoxide production, Prx 3 protein expression, and lactate dehydrogenase (LDH) release and improved the relative cell viability at 100 μM KI exposure. However, SOD inhibitor diethyldithiocarbamic acid (DETC) (2 mM), Rotenone (0.5 μM), a mitochondrial complex I inhibitor, and Antimycin A (10 μM), a complex III inhibitor, caused an increase in mitochondrial superoxide production, Prx 3 protein expression, and LDH release and decreased the relative cell viability. We conclude that the inhibitors of mitochondrial respiratory chain complex I or III may be involved in oxidative stress caused by elevated concentrations of iodide, and SOD demonstrates its protective effect on the Fischer rat thyroid cell line (FRTL) cells.

Highlights

Reactive oxygen species (ROS) are required for normal physiologic function and are linked to thyroid hormone synthesis, yet they become toxic when produced in excessive amounts [1]
We conclude that the inhibitors of mitochondrial respiratory chain complex I or III may be involved in oxidative stress caused by elevated concentrations of iodide, and superoxide dismutase (SOD) demonstrates its protective effect on the Fischer rat thyroid cell line (FRTL) cells
We discovered that a significant decrease of lactate dehydrogenase (LDH) release was detected in SOD and in KI + SOD group when compared to KI group (P < 0.05), while the increased LDH release instigated by KI (100 μM) could be further increased by diethyldithiocarbamic acid (DETC), Rotenone, and Antimycin A in FRTL cells (Figure 2(b)), with significant increase being observed in KI + DETC group, KI + Rotenone group, and KI + Antimycin A group (P < 0.05)

Summary

Introduction

Reactive oxygen species (ROS) are required for normal physiologic function and are linked to thyroid hormone synthesis, yet they become toxic when produced in excessive amounts [1]. Adequate iodide intake is required for normal thyroid function, but ROS production due to the elevated concentrations of iodide may disturb the redox equilibrium and may become toxic for intracellular macromolecules, such as DNA, proteins, lipids, and nucleic acids [1,2,3,4,5]. Thyroid hormone receptors have been detected in mitochondria which are involved in the regulation of energy mechanism and apoptosis [6]. One of the major sources of ROS are mitochondria, especially superoxide anions, which are highly involved in mitochondrial dysfunction [6, 7]. Complex III can generate ROS and release ROS into the inner membrane space or mitochondrial matrix [14,15,16]

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