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Adverse effects of pristine and aged polystyrene microplastics in mice and their Nrf2-mediated defense mechanisms
Haiyan Cui1, Weishu Yang1, Yongshun Cui1
1State Key Laboratory of Pollution Control and Resource Reuse, School of Environment, Nanjing University, 163 Xianlin Ave, Nanjing, 210023, China.
Abstract:
Health hazards associated with microplastics (MPs) remain largely unknown, and the effects of aged MPs, one of their persistent forms, are poorly characterized. Male ICR mice were intratracheally instilled with 0.01 and 1 mg/day pristine and ultraviolet (UV)-aged polystyrene microplastics (PS and APS) with an average diameter of 4 - 5 μm daily for 1 week. UV irradiation caused the PS to have a rough surface, become fragmented, and increase their carbonyl groups. Both PS and APS caused structural damage to the mouse gut, liver, spleen, and testis. Inflammatory infiltration in liver, swollen and congested gut, and loose spleen globules, as well as the loose interstitium of the seminiferous tubules in testis were found in 1 mg/day APS group. Increases in serum alanine aminotransferase and immunoglobulin A levels in 1 mg/day APS group (p < 0.05) demonstrated that APS exposure could induce greater liver and spleen functional damage than PS. Meanwhile, triglyceride and total cholesterol levels in liver were enhanced in 1 mg/day APS group (p < 0.05). Superoxide dismutase and glutathione contents in 0.01 and 1 mg/day APS groups significantly decreased (p < 0.05), which suggesting that PS and APS could interfere with the antioxidant capacity in mice. Nuclear factor erythroid 2-related factor 2 (Nrf2) and heme oxygenase-1 (HO-1) levels in the PS and APS groups showed significant increases in the liver and testis (p < 0.05), and a significant decrease in the spleen (p < 0.05), which were analyzed to get a first survey for Nrf2/HO-1-mediated tissue-specific defense mechanisms. In conclusion, acute exposure to PS and APS induced potential metabolic disorders, and APS could produce more serious immune damage and reproductive toxicity. These findings provide new insights in health risk assessment of aged MPs.
Insights
Aged microplastics cause gut, liver, spleen, and testis damage in mice. Ultraviolet-aged polystyrene microplastics (APS) induced more severe immune and reproductive toxicity than pristine polystyrene microplastics (PS).
Area of Science:
- Environmental Science
- Toxicology
- Materials Science
Background:
- Microplastic (MP) health hazards are largely unknown.
- Effects of aged MPs, a persistent form, are poorly characterized.
Purpose of the Study:
- To investigate the health effects of pristine and UV-aged polystyrene microplastics (PS and APS) in mice.
- To characterize the damage caused by MPs to various organs and assess the role of aging in MP toxicity.
Main Methods:
- Male ICR mice were intratracheally instilled with 0.01 and 1 mg/day of PS and APS (4-5 μm diameter) for one week.
- UV irradiation altered PS surface characteristics, causing fragmentation and increased carbonyl groups.
- Organ damage, serum enzyme levels, lipid profiles, antioxidant capacity, and Nrf2/HO-1 pathway markers were analyzed.
Main Results:
- Both PS and APS caused structural damage to the gut, liver, spleen, and testis.
- APS exposure led to greater liver and spleen functional damage, indicated by increased ALT and IgA levels.
- APS exposure also elevated liver triglyceride and total cholesterol, decreased antioxidant capacity (SOD, glutathione), and affected the Nrf2/HO-1 pathway in a tissue-specific manner.
Conclusions:
- Acute exposure to PS and APS induces potential metabolic disorders.
- APS causes more severe immune damage and reproductive toxicity compared to PS.
- Findings offer insights into the health risk assessment of aged MPs.
