Elsevier

Toxicology Letters

Volume 138, Issue 3, 3 March 2003, Pages 185-192
Toxicology Letters

Short communication
Zearalenone induces male germ cell apoptosis in rats

https://doi.org/10.1016/S0378-4274(02)00405-8Get rights and content

Abstract

Zearalenone (ZEA), a nonsteroidal estrogenic mycotoxin, is known to cause toxicity of testis in male rats. To investigate whether apoptosis is involved in ZEA-induced testicular toxicity and to identify the stage and target germ cell type, 10-week-old Sprague–Dawley male rats were treated with a single intraperitoneal (i.p.) dose of ZEA (5 mg/kg) and euthanized at 3, 6, 12, 24, or 48 h subsequently. Histopathologically, germ cell degeneration was found at stages I–VI 12 h after dosing. Degenerating germ cells were shown to undergo apoptosis as revealed by in situ terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL). The frequency of TUNEL-labeled germ cells increased in a stage-specific manner, the peak frequency gradually progressing at stages I–VI of seminiferous tubules with time after dosing, suggesting that the damaged germ cells, especially spermatogonia and spermatocytes, gradually underwent the processes leading to apoptosis. DNA laddering on gel electrophoresis was apparent 12 h after dosing. The results demonstrated that a single dose of ZEA induces testicular germ cell apoptosis in a time-dependent and stage-specific pattern. This study has established that apoptosis is the principal mechanism contributing to germ cell depletion and testicular atrophy following ZEA exposure.

Introduction

Zearalenone (ZEA) is a naturally occurring estrogenic substance produced by Fusarium fungi growing on grains, mainly corn and hay exposed to high moisture during storage (Miricha et al., 1968, Miricha and Christensen, 1974). ZEA causes alterations in the reproductive tract of laboratory animals and domestic animals. In addition, various estrogenic effects like decreased fertility, increased fetal resorptions, reduced litter size, changed weight of endocrine glands and changed serum hormone levels have been observed (Kuiper-Goodman et al., 1987). However, no teratogenic effects were found in mice, rats, guinea pigs or rabbits (Kuiper-Goodman et al., 1987). Hematological toxicity of ZEA also has been reported after a single intraperitoneal (i.p.) dose (Maaroufi et al., 1996).

Apoptosis is a way for the body to remove damaged or unnecessary cells (Kerr et al., 1972, Thompson, 1995). Cell death through apoptosis is distinct from pathological cell death, or necrosis (Farber, 1994). Apoptosis is characterized morphologically by chromatin condensation, cytoplasmic shrinkage, and membrane blebbing, while necrosis involves disruption of membrane integrity, subsequent cellular swelling and lysis (Saraste, 1999). Spontaneous cell death of spermatogenic germ cells appears to be a constant feature of normal spermatogenesis in variety of mammalian species (Blanco-Rodriguez and Martinez-Garcia, 1996, Kerr, 1992). On the other hand, germ cell apoptosis can also be induced by pathological conditions and toxic chemicals such as mono-(2-ethylhexyl)phthalate (Richburg and Boekelheide, 1996), cyclophosphamide (Cai et al., 1997), 1,3-dinitrobenzene (Strandgaard and Miller, 1998), ethane dimethane sulfonate (Nandi et al., 1999), nitrofurazone (Shoda et al., 2001) and 2-bromopropane (Yu et al., 2001) in the seminiferous tubules.

There has, to our knowledge, been no specific study on the processes leading to the type of cell death caused by ZEA. In the present study, we assessed germ cell death in the testes of rats given a single i.p. dose of ZEA, using methods including histology, in situ terminal deoxynucleotidyl transferase (TdT)-mediated dUTP nick end-labeling (TUNEL) and DNA gel electrophoresis. We examined whether or not ZEA induced apoptosis in the male germ cells, and if so, whether the apoptosis was correlated with any particular stage of germ cell differentiation.

Section snippets

Animals and treatments

Adult male Sprague–Dawley rats at 10 weeks of age obtained from Charles River Breeding Laboratories (Bio Genomics, Korea) were housed in wire cages with filter tops at 23±1 °C, 55±5% of humidity and a 12 h light/12 h dark cycle, and given rodent chow (PMI, USA) and water ad libitum. The animals were given a single i.p. dose of 5 mg/kg of ZEA (Sigma-Aldrich, USA) in the vehicle at a total volume of 1ml/kg of body weight and were euthanized under ether anesthesia after 3, 6, 12, 24, or 48 h after

Histopathological analysis

Germ cell degeneration was first found in spermatogonia in seminiferous tubules at stages I–VI at 6 h after ZEA treatment, characterized by pyknotic nuclei and eosinophilic cytoplasm. The change was also observed in tubules in stages I–VI at 12 h after dosing (Fig. 1C). Such degenerative changes were not found in the control testes (Fig. 1A).

In situ TUNEL analysis

Quantitative data from TUNEL-labeled germ cells are shown in Fig. 2. In the testes from the control rats, a few TUNEL-labeled cells were found in

Discussion

In this study, we showed that ZEA induces apoptosis in male rat germ cells in a time-dependent and stage specific pattern. This is the first report that ZEA induces apoptotic death of male rat germ cells. TUNEL-labeled germ cells induced by ZEA reached a maximum in number at 12 h after dosing. On the gel electrophoresis for DNA ladders, a significant increase in DNA fragmentation was observed at 12 h after ZEA treatment when TUNEL-labeled germ cells increased significantly. Apoptosis is a

Acknowledgements

This work was supported by Korea Research Foundation Grant (KRF-2001-003-G00052).

References (28)

  • E. Farber

    Programmed cell death: necrosis versus apoptosis

    Modern Pathol.

    (1994)
  • IARC, 1993. Some naturally occurring substances: Food items and constituents, Heterocyclic aromatic amines and...
  • J.B. Kerr

    Spontaneous degeneration of germ cells in rat testis: assessment of cell types and frequency during the spermatogenic cycle

    J. Reprod. Fertil.

    (1992)
  • J.F. Kerr et al.

    Apoptosis: a basic biological phenomenon with wide-ranging implications in tissue kinetics

    Br. J. Cancer

    (1972)
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