Tissue accumulation of microplastics in mice and biomarker responses suggest widespread health risks of exposure

Abstract

Microplastics (MPs) are a significant environmental health issue and increasingly greater source of concern. MPs have been detected in oceans, rivers, sediments, sewages, soil and even table salts. MPs exposure on marine organisms and humans has been documented, but information about the toxicity of MPs in mammal is limited. Here we used fluorescent and pristine polystyrene microplastics (PS-MPs) particles with two diameters (5 μm and 20 μm) to investigate the tissue distribution, accumulation, and tissue-specific health risk of MPs in mice. Results indicated that MPs accumulated in liver, kidney and gut, with a tissue-accumulation kinetics and distribution pattern that was strongly depended on the MPs particle size. In addition, analyses of multiple biochemical biomarkers and metabolomic profiles suggested that MPs exposure induced disturbance of energy and lipid metabolism as well as oxidative stress. Interestingly, blood biomarkers of neurotoxicity were also altered. Our results uncovered the distribution and accumulation of MPs across mice tissues and revealed significant alteration in several biomarkers that indicate potential toxicity from MPs exposure. Collectively, our data provided new evidence for the adverse consequences of MPs.

Figure 1. Accumulation of different sizes of MPs in mice tissues after exposure for 28 days.

Figure 2. Concentration of MPs in 3 tissues of mice at different exposure times.

Figure 3. Representative images of H&E-stained liver sections from mice exposed for 4 weeks to 0.5 mg/day PS-MPs (5 μm and 20 μm).

Black arrows indicate liver inflammation and white arrows indicate lipid droplets.

Figure 4. Effects of MPs exposure on biological markers related to energy metabolism, lipid metabolism, oxidative stress and neurotoxicity.

(A) ATP levels; (B) LDH activities; (C) T-CHO levels; (D) TG levels; (E) CAT activities; (F) GSH-Px levels; (G) SOD activities and (H) AChE activities. *Means significant difference between MPs-treated groups and control group (P < 0.05). ^#Means significant difference between different MPs-treated groups (P < 0.05).

Figure 5. Metabolomic alterations due to MPs exposure.

Scores plots of PLS-DA for low (A), mid (B) and high (C) doses of MPs-treated groups and control group. (D) Number of differential metabolites among MPs-treated groups. M, 0.1 mg/day; H, 0.5 mg/day.

Figure 6. Heat map for the differential metabolites identified in different treatment groups calculated by z-scores.

M, 0.1 mg/day; H, 0.5 mg/day.

Figure 7. Summary of findings.