Microplastics alter gut serotonin levels in the absence of overt intestinal inflammation 4808

Abstract Description Humans are estimated to consume 5 grams of microplastics (MP) each week. MP are known to alter the gut microbiota; however, it is unclear what leads to this disruption. Thus, we sought to examine how MP alter mucosal immune and epithelial responses. Therefore, we exposed mice to MP by incorporated various sizes of polystyrene (0.5, 1, 2, 3, 5 µM) MPs into the AIN93M (Research Diets Inc) chow. C57BL/6J, 3-week old mice, were put on AIN93M without MP for 1 week and then separated into two groups being fed AIN93M or AIN93M plus MP for 12 weeks. Baseline, 3-, 6-, 9- and 12-week stool was collected to measure lipocalin-2 (LCN-2) and secretory IgA (sIgA). Serum TNFα and serotonin were measured at 12-weeks. We observed no difference in fecal LCN-2, fecal sIgA or serum TNFα levels. We did observe increased serum and colonic serotonin in mice exposed to MPs. Gut serotonin is thought to regulate gut immune responses and the microbiota. When CD4+ T cells were enriched from secondary lymphoid tissues from unexposed mice, and stimulated ex vivo, serotonin priming significantly reduced IFNγ production. Overall, our study shows MP alter serotonin levels that likely dampens gut immune responses. It is likely this increase in serotonin has systemic consequences as serotonin affects a wide range of tissues including the liver, cardiac muscle, adipose tissue, and skeletal muscle systems. Topic Categories Mucosal and Regional Immunology (MUC)