Damage effect of combined noise and CO exposure on spermatogenesis in male rats

Abstract

Objective‍ ‍To analyze the detrimental effects of exposure to environmental noise alone and combined with carbon monoxide (CO) on spermatogenesis in male rats, investigate the underlying mechanisms involved in such damage, and evaluate the protective role of pterostilbene (PTE) against these adverse effects. Methods‍ ‍Sixty male SD rats (6~8 weeks old, weighing 200±10 g) were randomly divided normal control group (standard housing), sham-exposure control group (restraint stress only), noise exposure (85 dB), CO exposure (460 mg/m³), combined exposure (simultaneous exposure), and PTE intervention (80 mg/kg pretreatment), with 10 animals in each group. The rats were exposed daily for 2 h via a nose-only inhalation exposure system within a multifactorial environmental simulation chamber for 60 consecutive days. Sperm count and viability were measured after exposure. Histopathological changes of testicular tissues were observed with HE staining. qRT-PCR was used to measure stage-specific mRNA levels in germ cells. Serum sex hormone levels and adenosine triphosphate (ATP) concentrations in testes and sperm were detected. Transmission electron microscopy (TEM) was applied to observe the ultrastructural damage in the spermatocytes. Additionally, transcriptome sequencing was performed on testicular tissue, followed by bioinformatics analysis. Results‍ ‍Compared with the negative control group, the combined exposure group exhibited significant reductions in sperm viability and count (P<0.05), and developmental arrest of immature germ cells in the testicular tissue, with obviously less spermatogonia, spermatocytes, and round/elongated spermatids (P<0.01). Additionally, significantly reduced levels of reproductive-related hormones, such as gonadotropin-releasing hormone, follicle-stimulating hormone, luteinizing hormone and testosterone, and ATP levels in testes and sperm were observed in the mice after combined exposure (P<0.01), accompanied by mitochondrial rupture and cristae disruption in spermatocytes. Conversely, the PTE intervention group showed marked alleviation of these impairments, with parameters recovering almost to normal levels. Transcriptome sequencing identified biological processes related to reproductive development and ATP-dependent pathways as potential contributors to testicular injury induced by noise and CO exposure, with key genes including Nppa, Adm, Gnrh1, Ptafr, Atp13a5, Atp8b1, and LOC102555469. Conclusion‍ ‍Noise and CO exposure induce spermatogenic damage in rats, which may be related with energy metabolism and hormonal regulation, while PTE demonstrates significant protective effects against such reproductive impairments.

Keywords

• noise
• carbon monoxide
• combined exposure
• male reproductive toxicity
• spermatogenesis
• adenosine triphosphate
• pterostilbene