Induction of DNA Damage and G2 Cell Cycle Arrest by Diepoxybutane through the Activation of the Chk1-Dependent Pathway in Mouse Germ Cells

Abstract

1,2:3,4-Diepoxybutane (DEB) is a major carcinogenic metabolite of 1,3-butadiene (BD), which has been shown to cause DNA strand breaks in cells through its potential genotoxicity. The adverse effect of DEB on male reproductive cells in response to DNA damage has not been thoroughly studied, and the related mechanism is yet to be elucidated. Using mouse spermatocyte-derived GC-2 cells, we demonstrated in the present study that DEB caused the proliferation inhibition and marked cell cycle arrest at the G2 phase but not apoptosis. DEB also induced DNA damage as evidenced by γ-H2AX expression, the comet assay, and the cytokinesis-block micronucleus assay. Meanwhile, DEB triggered the Chk1/Cdc25c/Cdc2 signal pathway, which could be abated in the presence of UCN-01 or Chk1 siRNA. GC-2 cells exposed to DEB experienced ROS generation and pretreatment of N-acetyl-l-cysteine, partly attenuated DEB-induced DNA damage, and G2 arrest. Furthermore, measurement of testicular cells showed an increased proportion of tetraploid cells in mice administrated with DEB, alongside the enhanced expression of p-Chk1. Also, the defective reproductive phenotypes, including reduced sperm motility, increased sperm malformation, and histological abnormality of testes, were observed. In conclusion, these results suggest DEB induces DNA damage and G2 cell cycle arrest by activating the Chk1-dependent pathway, while oxidative stress may be associated with eliciting toxicity in male reproductive cells.