Paternal ancestral gestational exposure to neonicotinoid thiacloprid induces transgenerational alteration in DNA methylation germline germline-specific genes in female ovaries
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Background
Neonicotinoids, a widely used class of insecticides, have raised concerns due to their potential role in the decline of bee populations. Accumulating pieces of evidence suggest that these chemicals may also pose risks to human and animal health.
Objectives
This study investigates the transgenerational effects of thiacloprid (Thia), a neonicotinoid, on the female reproductive system.
Methods
Pregnant outbred Swiss female mice were exposed to 0 and 6 mg/kg/day of thiacloprid from embryonic days E6.5 to E15.5. Adult female F1 and F3 progeny ovaries were examined for morphological abnormalities by using hematoxylin and eosin (H&E) staining of paraffin sections. Additionally, estradiol levels were assessed by ELISA using blood serum. A marker of mitosis, phosphorylated histone H3 at serine 10 (PhosphoHisH3ser10) levels, was analyzed by immunofluorescence, DNA methylation at some regions was analyzed by MeDIP, and RT-qPCR assessed gene expression.
Results
The gestational exposure to thiacloprid led to an increased formation of multi-oocyte follicles in directly exposed F1 generation ovaries but not in F3. We observed a reduction in serum estradiol levels in both F1 and F3 females. In direct F1 exposed progeny, we determined an increase in (PhosphoHisH3ser10) in granulosa cells. Additionally, alterations in DNA methylation were observed in germline reprogramming-responsive genes in embryonic ovaries, as well as the DNA methylation was altered at these genes in both the F1 and F3 ovaries. The modified DNA methylation was associated with changes in gene expression in adult ovaries of the F1 and F3 generations in genes encoding transcription and hormonal signaling factors.
Conclusion
Our findings demonstrate that ancestral gestational exposure to thiacloprid induces transgenerational effects on female reproductive health, potentially through epigenetic modifications of paternal germ cells.
