Simulated Microplastic Release from Cutting Boards and Evaluation of Intestinal Inflammation and Gut Microbiota in Mice.

Background: Plastic cutting boards are commonly used in food preparation, increasing human exposure to microplastics (MPs). However, the health implications are still not well understood.

Objectives: The objective of this study was to assess the impacts of long-term exposure to MPs released from cutting boards on intestinal inflammation and gut microbiota.

Methods: MPs were incorporated into mouse diets by cutting the food on polypropylene (PP), polyethylene (PE), and willow wooden (WB) cutting boards, and the diets were fed to mice over periods of 4 and 12 wk. Serum levels of C-reactive protein (CRP), tumor necrosis factor-$\alpha$ (TNF-$\alpha$), interleukin-10 (IL-10), lipopolysaccharide (LPS, an endotoxin), and carcinoembryonic antigen (CEA), along with ileum and colon levels of interleukin-1$\beta$ (IL-$1\beta$), TNF-$\alpha$, malondialdehyde (MDA), superoxide dismutase (SOD), secretory immunoglobulin A (sIgA), and myosin light chain kinase (MLCK), were measured using mouse enzyme-linked immunosorbent assay (ELISA) kits. The mRNA expression of mucin 2 and intestinal tight junction proteins in mouse ileum and colon tissues was quantified using real-time quantitative reverse transcription polymerase chain reaction. Fecal microbiota, fecal metabolomics, and liver metabolomics were characterized.

Results: PP and PE cutting boards released MPs, with concentrations reaching $\mathrm{1,088}\pm 95.0$ and $\mathrm{1,211}\pm 322\mu g/g$ in diets, respectively, and displaying mean particle sizes of $10.4\pm 0.96$ vs. $27.4\pm 1.45\mu m$. Mice fed diets prepared on PP cutting boards for 12 wk exhibited significantly higher serum levels of LPS, CRP, TNF-$\alpha$, IL-10, and CEA, as well as higher levels of IL-1$\beta$, TNF-$\alpha$, MDA, SOD, and MLCK in the ileum and colon compared with mice fed diets prepared on WB cutting boards. These mice also showed lower relative expression of Occludin and Zonula occludens-1 in the ileum and colon. In contrast, mice exposed to diets prepared on PE cutting boards for 12 wk did not show evident inflammation; however, there was a significant decrease in the relative abundance of Firmicutes and an increase in Desulfobacterota compared with those fed diets prepared on WB cutting boards, and exposure to diets prepared on PE cutting boards over 12 wk also altered mouse fecal and liver metabolites compared with those fed diets prepared on WB cutting boards.

Discussion: The findings suggest that MPs from PP cutting boards impair intestinal barrier function and induce inflammation, whereas those from PE cutting boards affect the gut microbiota, gut metabolism, and liver metabolism in the mouse model. These findings offer crucial insights into the safe use of plastic cutting boards. https://doi.org/10.1289/EHP15472.