Low-dose carbon ion irradiation effects on DNA damage and oxidative stress in the mouse testis

https://doi.org/10.1016/j.asr.2010.08.037Get rights and content

Abstract

To investigate the effects of low-dose carbon ion irradiation on reproductive system of mice, the testes of outbred Kunming strain mice were whole-body irradiated with 0, 0.05, 0.1, 0.5 and 1 Gy, respectively. We measured DNA double-strand breaks (DNA DSBs) and oxidative stress parameters including malondialdehyde (MDA) content, superoxide dismutase (SOD) activity, and testis weight and sperm count at 12 h, 21 d and 35 d after irradiation in mouse testis. At 12 h postirradiation, a significant increase in DNA DSB level but no pronounced alterations in MDA content or SOD activity were observed in 0.5 and 1 Gy groups compared with the control group. At 21 d postirradiation, there was a significant reduction in sperm count and distinct enhancements of DSB level and MDA content in 0.5 and 1 Gy groups in comparison with control. At 35 d postirradiation, the levels of DNA DSBs and MDA, and SOD activity returned to the baseline except for the MDA content in 1 Gy (P < 0.05), while extreme falls of sperm count were still observed in 0.5 (P < 0.01) and 1 Gy (P < 0.01) groups. For the 0.05 or 0.1 Gy group, no differences were found in DNA DSB level and MDA content between control and at 12 h, 21 d and 35 d after irradiation, indicating that lower doses of carbon ion irradiation have no significant influence on spermatogenesis processes. In this study, male germ cells irradiated with over 0.5 Gy of carbon ions are difficult to repair completely marked by the sperm count. Furthermore, these data suggest that the deleterious effects may be chronic or delayed in reproductive system after whole-body exposure to acute high-dose carbon ions.

Introduction

Irradiation has been widely reported to damage organisms by attacking proteins, nucleic acid and lipids in cells.

Heavy ions, an important component of galactic cosmic rays, have high linear energy transfer (LET) and high relative biological effectiveness (RBE), and consequently are much more deleterious on the cellular or molecular level than low-LET irradiation such as X-rays or gamma(γ)-rays (Li et al., 2005). For example, heavy ions produce more irreparable DNA breaks (Ritter et al., 1997), chromosomal breakage and rearrangements and a greater degree of abnormal differentiation (Sekine et al., 2008) than low-LET irradiation. Due to the favorite characteristics of heavy-ion beams such as an energy deposition peak (Bragg peak) at the end of its range and an increased RBE within the peak, heavy-ion cancer therapy is attracting growing interest all over the world (Ji et al., 2008). However, heavy-ion irradiation not only destroys the tumor but could potentially damage the normal tissue around the tumor. In recent years, hormesis/adaptive response induced with low-dose ionizing irradiation to harmful effects of subsequent high-dose has become the focus of research in radiotherapy (Liu et al., 1987). Therefore, it is essential to monitor and evaluate the effects of heavy ion of low doses for human space exploration and heavy-ion cancer therapy.

The testis is one of the most radiosensitive organs in the body. There is abundant evidence from the animals that exposure of male germ cells to ionizing radiation cause detrimental influence (Hamer et al., 2003, Santra and Manna, 2009). Epidemiological data have suggested that the male germ damage induced by ionizing radiation may result in low reproductive ability and the presence of mutations due to pre-term pregnancy loss and various pathologies in offspring, including childhood cancer (Haines et al., 2002). Our previous findings also showed that heavy ions can lead to prominent morphological damage (Liu et al., 2009), and destroy poly (ADP-ribose) polymerase (PARP) activity and its expression linked with DNA repair (Zhang et al., 2008), and increase spermatocyte chromosomal aberrations (Zhang et al., 1998) in mouse testis.

Here, we investigated the dose- and time-response of low-dose heavy-ion irradiation on DNA double-strand breaks (DNA DSBs), oxidative stress index in mouse testes for better evaluation of the radiation risks in space and providing guidelines to protect gonad during radiotherapy.

Section snippets

Animals

A total of 105 immature male Kunming strain mice (from Institute of Lanzhou Biological Products, China) weighing 16–18 g (about 3.5 week) were used in this study. All animals were housed in cages with free access to drinking water and diet. Cages were kept at 20–22 °C with 12 h light/dark cycle. Animals were randomly divided into six groups including control (0 Gy), 0.05, 0.1, 0.5 or 1 Gy group, each group constituted 21 male mice.

Irradiation procedure

Mice were restrained in containers fixed on the irradiation equipment

Testis weight and sperm count

Slight changes in testis weights and ratios of testis weight to body-weight were detected at 12 h after the exposure, and no mature sperm was observed in immature mice according to the classification described by Zuo and Ning (2001) and Shen et al. (1991). Significant declines in 0.5 Gy group (p < 0.01) and 1 Gy group (p < 0.05) was observed at the 21st day in the ratio of testis weight to body-weight as well as sperm count of the epididymis. At the 35th day, the testis weight tended to return to the

Discussion

The testis is an extremely radiosensitive organ in the body. Owing that the duration of germ cell development from spermatogonia to spermatozoa in mouse is needed 35 d, the sperm collected from the epididymis was derived specifically from the irradiated spermatocytes (21 d) and from the irradiated differentiating spermatogonial stem cells (35 d) Shen et al., 1991 in our experiment. Hence, it can reflect the repair status of different types of germ cells in testes and the damage arising in

Acknowledgment

This work was supported by grants from the National Basic Research Program of China (2010CB834202), the National Natural Science Foundation of China (10835011, 10675151, 10805064), the Scientific Technology Research Projects of Gansu Province (0702NKDA045, 0806RJYA020) and the Western Talent Program of Chinese Academy of Sciences (0760160XBO, 0860260XBO). We express our thanks to the accelerator crew at the HIRFL, National Laboratory of Heavy Ion Accelerator in Lanzhou.

References (27)

  • H. Zhang et al.

    Chromosomal aberrations induced by 12C6+ heavy ion irradiation in spermatogonia and spermatocytes of mice

    Mutat. Res.

    (1998)
  • H. Zhang et al.

    Induction of cytogenetic adaptive response in spermatogonia and spermatocytes by pre-exposure of mouse testis to low-dose 12C6+ ions

    Mutat Res

    (2008)
  • R.G. Ahmed

    Is there a balance between oxidative stress and antioxidant defense system during development

    Med. J. Islamic World Academy Sci.

    (2005)
  • Cited by (11)

    • Induction of reproductive cell death in Caenorhabditis elegans across entire linear-energy-transfer range of carbon-ion irradiation

      2018, DNA Repair
      Citation Excerpt :

      Acute carbon-ion irradiation was carried out at the Heavy Ion Research Facility in Lanzhou (HIRFL, Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou, China). The beam production and dosimetry have been described previously [29]. In this study, the energy of carbon ions measured 80 MeV/nucleon, dose rate was 0.17 Gy/s, and beam diameter was 50 mm.

    • The developmental toxicity and apoptosis in zebrafish eyes induced by carbon-ion irradiation

      2015, Life Sciences
      Citation Excerpt :

      They have also demonstrated potency with single particle tracks, producing major lesions in DNA [50]. When compared to low-linear energy transfer (LET) irradiation, heavy ions can induce even more serious damage, such as cell death, oxidative stress, carcinogenesis and DNA damage in mammalian cells and tissues [13,30,31]. It is worth noting that the presence of oxygen was not required for heavy ions to produce their effects [7,16].

    • Mutagenic effects of heavy ion irradiation on rice seeds

      2012, Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms
      Citation Excerpt :

      The embryos of the seeds were kept on top to compensate for the short penetration distance of low-energy heavy ion beams (Fig. 1). The medium-energy heavy ion beam irradiation equipment was identical to that used by Liu et al. [22]. The parameters used in the present study were as follows: the ion energy was 80 MeV; the dose of 20Ne10+ was 80 Gy and approximately 2,000 rice seeds from each variety were treated.

    • Homologous recombination in Arabidopsis seeds along the track of energetic carbon ions

      2012, Mutation Research - Fundamental and Molecular Mechanisms of Mutagenesis
      Citation Excerpt :

      The exposure of Arabidopsis seeds (S0) to carbon irradiation was carried out with the Heavy Ion Research Facility in Lanzhou (HIRFL, Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou, China). The beam production and dosimetry has been described previously [37]. In this study, the energy of carbon ions was 87.5 MeV/nucleon at the entrance into seeds.

    • Protective effects of melatonin against <sup>12</sup> C <sup>6+</sup> beam irradiation-induced oxidative stress and DNA injury in the mouse brain

      2012, Advances in Space Research
      Citation Excerpt :

      The changes in TM and the rates of tailing cells in irradiated brains were also prevented in a dose-dependent manner in brains pretreated with melatonin. These data are consistent with other in vitro and in vivo studies in other organs and animals (Kaya et al., 1999; Liu et al., 2010; Vijayalaxmi et al., 2004), and suggest that melatonin can effectively alleviate the G0/G1 phase arrest, reduce DNA damage, and induce adaptive response in brain cells. We also observed that melatonin pretreatment caused a dose-dependent decrease in MDA levels and an increase in T-SOD and SOD2 activity compared with irradiation-only groups.

    View all citing articles on Scopus
    View full text