Role of Autophagy in Zinc Oxide Nanoparticles-Induced Apoptosis of Mouse LEYDIG Cells

Yuqian Wang,Xingfan Zhou,Rui Chen,Jiaxiang Chen,Hong Yin,Dan Yang,Jingcao Shen,Shichuan Tang,Jinglei Wang

doi:10.3390/ijms20164042

Abstract

Zinc oxide nanoparticles (ZnO NPs) have shown adverse health impact on the human male reproductive system, with evidence of inducing apoptosis. However, whether or not ZnO NPs could promote autophagy, and the possible role of autophagy in the progress of apoptosis, remain unclear. In the current study, in vitro and in vivo toxicological responses of ZnO NPs were explored by using a mouse model and mouse Leydig cell line. It was found that intragastrical exposure of ZnO NPs to mice for 28 days at the concentrations of 100, 200, and 400 mg/kg/day disrupted the seminiferous epithelium of the testis and decreased the sperm density in the epididymis. Furthermore, serum testosterone levels were markedly reduced. The induction of apoptosis and autophagy in the testis tissues was disclosed by up-regulating the protein levels of cleaved Caspase-8, cleaved Caspase-3, Bax, LC3-II, Atg 5, and Beclin 1, accompanied by down-regulation of Bcl 2. In vitro tests showed that ZnO NPs could induce apoptosis and autophagy with the generation of oxidative stress. Specific inhibition of autophagy pathway significantly decreased the cell viability and up-regulated the apoptosis level in mouse Leydig TM3 cells. In summary, ZnO NPs can induce apoptosis and autophagy via oxidative stress, and autophagy might play a protective role in ZnO NPs-induced apoptosis of mouse Leydig cells.

Highlights

Nanotechnology manipulates matters at the atomic, molecular, and supramolecular scales and has grown rapidly worldwide in the past decades
There was a significant decrease in sperm density of the epididymis after exposure to 100, 200, or 400 mg Zinc oxide nanoparticles (ZnO NPs)/kg/day compared to the vehicle control group (Figure 1B), indicating that ZnO NPs exposure significantly inhibited spermatogenesis
Apoptosis and autophagy were induced by ZnO NPs in the testis tissue with a decreased level of serum testosterone

Summary

Introduction

Nanotechnology manipulates matters at the atomic, molecular, and supramolecular scales and has grown rapidly worldwide in the past decades. With the development of nanotechnology, environmental exposure to nanoparticles (NPs) is increasing dramatically [1,2]. Zinc oxide nanoparticles (ZnO NPs) are used in various applications, such as cosmetics, rubber manufacture, pigments, food additives, biosensors, chemical fibers, bioimaging, and antibacterial agents, due to their low production cost and unique physicochemical properties [4]. ZnO NPs may enter human bodies by various routes, including inhalation, dermal penetration, injection, and ingestion [5]. These NPs can accumulate in various organs, such as the liver, spleen, lungs, kidney, and heart via circulation, and may produce adverse consequences, such as edema and degeneration of hepatocytes, inflammation of the pancreas, or damage to the stomach and spleen [6,7]. Toxicity research and health risk assessments of ZnO NPs have attracted tremendous attention recently [8]

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