Abstract
Indirect evidence has determined the possibility that microplastics (MP) induce constipation, although direct scientific proof for constipation induction in animals remains unclear. To investigate whether oral administration of polystyrene (PS)-MP causes constipation, an alteration in the constipation parameters and mechanisms was analyzed in ICR mice, treated with 0.5 μm PS-MP for 2 weeks. Significant alterations in water consumption, stool weight, stool water contents, and stool morphology were detected in MP treated ICR mice, as compared to Vehicle treated group. Also, the gastrointestinal (GI) motility and intestinal length were decreased, while the histopathological structure and cytological structure of the mid colon were remarkably altered in treated mice. Mice exposed to MP also showed a significant decrease in the GI hormone concentration, muscarinic acetylcholine receptors (mAChRs) expression, and their downstream signaling pathway. Subsequent to MP treatment, concentrations of chloride ion and expressions of its channel (CFTR and CIC-2) were decreased, whereas expressions of aquaporin (AQP)3 and 8 for water transportation were downregulated by activation of the mitogen-activated protein kinase (MAPK)/nuclear factor (NF)-κB signaling pathway. These results are the first to suggest that oral administration of PS-MP induces chronic constipation through the dysregulation of GI motility, mucin secretion, and chloride ion and water transportation in the mid colon.
Highlights
Due to increasing plastic wastes in oceans, MP have received great attention as pollutants of the marine environments [1]
Results of this study indicate that MP treatment is probably a novel cause for constipation, accompanied by decreased GI motility, mucin secretion, and ion/water channel expression in ICR mice
The current study evaluates the possibility of PS-MP administration as a novel cause of chronic constipation
Summary
Due to increasing plastic wastes in oceans, MP have received great attention as pollutants of the marine environments [1]. Alterations on several physiological responses, including oxidative stress, inflammatory cytokines secretion, cell cycle arrest, apoptosis, and histamine release, were detected in MP treated human cells [9,10,11]. Most MP treatments induce various alterations in the toxicology and physiology of mice and rats, changes were majorly accumulated in three major tissues, viz., liver, kidney, and gut [12,13]. Numerous pathological changes in lipid metabolism, inflammation, lipid profile, and lipid accumulation, were observed in the liver tissue of MP treated animals [12,14,15]. No significant physiological responses, including tissue damage, inflammation, oxidative stress, and behavior, were induced by MP administration for 28 days in mice, or for 5 weeks in Wistar rats [17,18]
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