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The reactive oxygen species as pathogenic factors of fragmented microplastics to macrophages
Soyeon Jeon1, Dong-Keun Lee1, Jiyoung Jeong1
1Lab of Toxicology, Department of Health Sciences, The Graduate School of Dong-A University, 37, Nakdong-daero 550 Beon-gil, Saha-gu, Busan, 49315, Republic of Korea.
Abstract:
The presence of microplastics in the various food web raised concerns on human health, but little is known about the target cells and mechanism of toxicity of microplastics. In this study, we evaluated the toxicity of microplastics using relevant cell lines to the oral route of exposure. Approximately 100 μm-sized fragment-type polypropylene (PP) and polystyrene (PS) particles were prepared by sieving after pulverization and further applied the accelerated weathering using ultraviolet and heat. Thus, the panel of microplastics includes fresh PP (f-PP), fresh PS (f-PS), weathered PP (w-PP), and weathered PS (w-PS). The spherical PS with a similar size was used as a reference particle. Treatment of all types of PP and PS did not show any toxic effects to the Caco-2 cells and HepG2 cells. However, the treatment of microplastics to THP-1 macrophages showed significant toxicity in the order of f-PS > f-PP > w-PS > w-PP. The weathering process significantly reduced the reactive oxygen species (ROS) generation potential of both microplastics because the weathered microplastics have an increased affinity to bind serum protein which acts as a ROS scavenger. The intrinsic ROS generation potential of microplastics showed a good correlation with the toxicity endpoints including cytotoxicity and pro-inflammatory cytokines in THP-1 macrophages. In conclusion, the results of this study suggest that the target cell type of microplastics via oral administration can be macrophages and the pathogenic factor to THP-1 macrophages is the intrinsic ROS generation potential of microplastics. Nevertheless, the toxic effect of microplastics tested in this study was much less than that of nano-sized particles.
Insights
Microplastics pose health risks, primarily targeting macrophages via oral exposure. Their toxicity is linked to reactive oxygen species (ROS) generation, which decreases with weathering. Further research is needed.
Area of Science:
- Environmental Health
- Toxicology
- Cell Biology
Background:
- Microplastics are prevalent in food webs, raising human health concerns.
- Limited knowledge exists regarding microplastic target cells and toxicity mechanisms via oral exposure.
Purpose of the Study:
- To evaluate the toxicity of microplastics using cell lines relevant to oral exposure.
- To identify target cells and understand the mechanism of microplastic toxicity.
Main Methods:
- Prepared 100 μm polypropylene (PP) and polystyrene (PS) microplastics, including fresh and weathered forms.
- Exposed Caco-2, HepG2, and THP-1 macrophage cell lines to microplastics.
- Assessed cytotoxicity, reactive oxygen species (ROS) generation, and pro-inflammatory cytokine release.
Main Results:
- Microplastics showed no toxicity in Caco-2 and HepG2 cells.
- THP-1 macrophages exhibited significant toxicity, ordered as fresh PS > fresh PP > weathered PS > weathered PP.
- Weathering reduced ROS generation potential due to increased serum protein binding, correlating with toxicity.
Conclusions:
- Macrophages are identified as a key target cell type for orally administered microplastics.
- The intrinsic ROS generation potential of microplastics is a primary pathogenic factor for macrophages.
- The tested microplastics exhibited lower toxicity compared to nano-sized particles.
