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Size-dependent deleterious effects of nano- and microplastics on sperm motility
Ziyi Lin1, Zijie Li2, Shuqin Ji2
1The Brain Cognition and Brain Disease Institute, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen, China; University of Chinese Academy of Sciences, Beijing, China.
Introduction:
Growing concerns regarding the reproductive toxicity associated with daily life exposure to micro-/nano-plastics (abbreviated as MNPs) have become increasingly prevalent. In reality, MNPs exposure involves a heterogeneous mixture of MNPs of different sizes rather than a single size.
Methods:
In this study, an oral exposure mouse model was used to evaluate the effects of MNPs of four size ranges: 25-30 nm, 1-5 µm, 20-27 µm, and 125-150 µm. Adult male C57BL/6 J mice were administered environmentally relevant concentrations of 0.1 mg MNPs/day for 21 days. After that, open field test and computer assisted sperm assessment (CASA) were conducted. Immunohistochemical analyses of organ and cell type localization of MNPs were evaluated. Testicular transcriptome analysis was carried out to understand the molecular mechanisms.
Results:
Our result showed that MNPs of different size ranges all impaired sperm motility, with a decrease in progressive sperm motility, linearity and straight-line velocity of sperm movement. Alterations did not manifest in animal locomotion, body weight, or sperm count. Noteworthy effects were most pronounced in the smaller MNPs size ranges (25-30 nm and 1-5 µm). Linear regression analysis substantiated a negative correlation between the size of MNPs and sperm curvilinear activity. Immunohistochemical analysis unveiled the intrusions of 1-5 µm MNPs, but not 20-27 µm and 125-150 µm MNPs, into Leydig cells and testicular macrophages. Further testicular transcriptomic analysis revealed perturbations in pathways related to spermatogenesis, oxidative stress, and inflammation. Particularly within the 1-5 µm MNPs group, a heightened perturbation in pathways linked to spermatogenesis and oxidative stress was observed.
Conclusions:
Our data support the size-dependent impairment of MNPs on sperm functionality, underscoring the pressing need for apprehensions about and interventions against the escalation of environmental micro-/nano-plastics contamination. This urgency is especially pertinent to small-sized MNPs.
Insights
Micro-/nano-plastics (MNPs) exposure impairs sperm motility, with smaller sizes causing more pronounced effects. This highlights the urgent need to address environmental MNPs contamination, especially concerning smaller particles.
Area of Science:
- Environmental Science
- Toxicology
- Reproductive Biology
Background:
- Growing concerns exist regarding the reproductive toxicity of micro-/nano-plastics (MNPs) from daily life exposure.
- MNPs exposure typically involves heterogeneous mixtures of various sizes, not single sizes.
Purpose of the Study:
- To evaluate the effects of different micro-/nano-plastic (MNP) sizes on male mouse reproductive parameters.
- To investigate the underlying molecular mechanisms of MNP-induced reproductive toxicity.
Main Methods:
- An oral exposure mouse model using four MNP size ranges (25-30 nm, 1-5 µm, 20-27 µm, 125-150 µm) at environmentally relevant concentrations for 21 days.
- Assessment of sperm motility via Computer Assisted Sperm Analysis (CASA), open field tests, and immunohistochemical analysis for MNP localization.
- Testicular transcriptome analysis to identify molecular pathway alterations.
Main Results:
- All tested MNP sizes impaired sperm motility, with smaller sizes (25-30 nm, 1-5 µm) showing the most significant effects.
- Smaller MNPs (1-5 µm) were found within Leydig cells and testicular macrophages, while larger sizes were not detected in these tissues.
- Transcriptomic analysis revealed disruptions in pathways related to spermatogenesis, oxidative stress, and inflammation, particularly in the 1-5 µm MNP group.
Conclusions:
- Micro-/nano-plastic exposure demonstrates a size-dependent impairment of sperm functionality.
- The findings underscore the urgent need for interventions against environmental MNP contamination, with a particular focus on smaller-sized particles due to their pronounced effects.
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