Multiwalled Carbon Nanotubes Inhibit Steroidogenesis by Disrupting Steroidogenic Acute Regulatory Protein Expression and Redox Status

Ovarian granulosa cells play crucial roles in the processes of follicle development, ovulation, luteinization and steroid hormone secretion or steroidogenesis. In this study, we used preovulatory rat granulosa cells to investigate the effects of multiwall carbon nanotubes on ovarian endocrine function, especially in regulating progesterone secretion, steroidogenic acute regulatory protein, as well as the potential mechanisms. By using cytotoxicity assays, radioimmunoassay, western blotting and fluorescence quantitative analysis and imaging methods, multiwall carbon nanotubes were found to inhibit the progesterone secretion of preovulatory ovarian granulosa cells by inhibiting the steroidogenic acute regulatory protein expression, and the influence could be restored after the removal of multiwall carbon nanotubes. The underlying mechanisms were related to the cytotoxicity, oxidative stress and mitochondria damages due to the MWCNTs. There were no obvious differences shown due to the distinct tube lengths. Both long and short MWCNTs share the same trends in all the above assays. Our findings provide important insights to the regulatory effects of multiwalled carbon nanotubes on granulosa cell steroidogenesis and subsequent safety evaluation of nanomaterials on reproductive toxicity.