Elsevier

Theriogenology

Volume 72, Issue 5, 15 September 2009, Pages 599-611
Theriogenology

Beta-cypermethrin impairs reproductive function in male mice by inducing oxidative stress

https://doi.org/10.1016/j.theriogenology.2009.04.016Get rights and content

Abstract

Cypermethrin (CYP), an insecticide, has deleterious effects on male reproductive function. The objective was to identify whether the effects of beta-CYP on male reproductive organs were associated with oxidative stress. Three doses of beta-CYP (1, 10, and 20 mg/kg) were administered to male mice for 35 d, with or without vitamin E (20 mg/kg). The moderate (10 mg/kg) and high (20 mg/kg) doses of beta-CYP not only decreased body weight and the weight of the testes, epididymides, seminal vesicles, and prostate (P < 0.05) but also reduced serum testosterone concentration and the expression of steroidogenic acute regulatory protein (P < 0.05), in addition to damaging the seminiferous tubules and sperm development. Furthermore, moderate and high doses of beta-CYP administration decreased sperm number, sperm motility, and intact acrosome rate (P < 0.05). Based on ultrastructural analyses, high doses of beta-CYP produced swelling and degeneration of mitochondria and the smooth endoplasmic reticulum of Leydig cells and caused the formation of concentric circles. These toxic effects of beta-CYP may be mediated by increasing oxidative stress, as the moderate and high doses of this compound increased malondialdehyde and nitric oxide in testes (P < 0.05); reduced the activity of catalase, glutathione peroxidase (GSH-Px), and superoxide dismutase (P < 0.05); and activated ERK1/2 (P < 0.05). Vitamin E reversed the effects of beta-CYP on testosterone production and testis damage (P < 0.05 vs. the high-dose group). Therefore, we inferred that beta-CYP damaged the structure of testes and decreased sperm output by inducing oxidative stress.

Introduction

Cypermethrin (CYP) is a synthetic pyrethroid insecticide that has been widely used over the past 30 yr in China and other countries against pests, particularly Lepidoptera, cockroaches, and termites. In animals, cypermethrin has been used as a chemotherapeutic agent against ectoparasite infestations [1]. Beta-CYP is a mixture of the alpha and theta forms of the insecticide. Its activity is lower than that of alpha-CYP but higher than other CYPs. Beta-CYP has been applied widely for agricultural pest control in China and comprises more than 50% of the total pyrethroid market production [2]. Although cypermethrin was considered safe and was widely used on agricultural crops and forests as well as in public and animal health [3], there is accumulating evidence that chronic exposure or high-dose CYP has toxic effects on humans and animals.

Cypermethrin can be found in trace amounts or at higher concentrations in soil and air. In mammals, CYP can accumulate in body fat, skin, liver, kidneys, adrenal glands, ovaries, lung, blood, and heart [4], [5], [6]. However, the main target for CYP is the central nervous system. Symptoms of CYP toxicity in laboratory animals include pawing, burrowing, salivation, tremors, writhing, and seizures. In humans, high doses of CYP result in twitching, drowsiness, coma, and seizures [7]. Cypermethrin exerts its neurotoxic effect through voltage-dependent sodium channels and integral protein ATPases in the neuronal membrane [8], [9].

In addition to neurons, reproductive organs are another toxic target of CYP [10], [11]. Cypermethrin decreases the weight of testosterone-sensitive organs, increases the height of seminal gland epithelium, and reduces sperm count and motility in male mice [11], [12], [13], [14], [15]. Moreover, CYP significantly reduced serum concentrations of testosterone, follicle-stimulating hormone (FSH), and luteinizing hormone (LH) [11], in addition to decreasing the number of implantation sites and viable fetuses in females mated with these male mice [11]. Taken together, it is evident that CYP disrupted male reproductive function.

The mechanism by which CYP affects male reproduction is unclear: Pyrethroids are rapidly metabolized in mammals, and several studies have shown that CYP damages the brain, liver, and erythrocytes by causing oxidative stress [16], [17], [18]. However, there are no studies that have investigated how oxidative stress mediates CYP-induced deficits in male reproduction. Consequently, the current study examined the role of oxidative stress in beta-CYP–induced damage to the testes and the possible protective effects of vitamin E. Vitamin E is a fat-soluble vitamin with potent antioxidant properties that scavenges intracellular free radicals and maintains cell membrane integrity by inhibiting lipid peroxidation induced by reactive oxygen species (ROS) [19].

Section snippets

Materials

Beta-CYP (>99% pure) was obtained from Nanjing Panfeng Chem Ltd. (Nanjing, Jiangsu, China). The steroidogenic acute regulatory protein (StAR) antibody was kindly provided by Professor D.M. Stocco (Texas Tech University Science Center, Lubbock, TX, USA), and antibodies for phosphorylated (p)-ERK (E-4) and ERK were purchased from Santa Cruz Biotechnology, Inc. (Santa Cruz, CA, USA). The 125I-testosterone radioimmunoassay (RIA) kit was purchased from the China Institute of Atomic Energy (Beijing,

Effect of beta-CYP on body weight and testosterone-sensitive organ weights

The three doses of beta-CYP decreased body weight gain and weight of testosterone-sensitive organs, such as testes, epididymides, seminal vesicles, and prostate. These measures were reduced in mice given 10 or 20 mg/kg beta-CYP compared with that for the vehicle control (P < 0.05). Vitamin E ameliorated the effect of CYP; body and testosterone-sensitive organ weight was higher in the 20 mg/kg beta-CYP group that received vitamin E than that in the 20 mg/kg beta-CYP group that did not receive vitamin

Discussion

In this study, beta-CYP had profound negative effects on male reproductive function; however, these changes were prevented by administering an antioxidant. The high dose (20 mg/kg) of beta-CYP significantly reduced the weight of the reproductive organs including testes, epididymides, seminal vesicles, and prostate and diminished sperm number, development, and quality. Beta-CYP also reduced serum testosterone concentrations, possibly by reducing StAR expression and damaging the seminiferous

Acknowledgments

We thank Dr. Zhong-Xian Lu for his valuable and constructive criticism and Mr. J. Hodo Bedell for editorial assistance with the manuscript. This study was supported by a grant from the National Natural Science Foundation of China (No. 30270955).

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