Abstract: BACKGROUND: Microplastics are a common environmental pollutant that can cause damage to the gastrointestinal tract, liver and kidney, and reproductive system. However, little is known about the effects of microplastics on the prostate.
OBJECTIVE: To investigate the effects of different charge-modified polystyrene microplastics on prostate tissues of male mice and its mechanism.
METHODS: A total of 48 male BALB/c mice were randomly divided into a control group, an unmodified microplastic group, a negatively charged microplastic group, and a positively charged microplastic group using a random number table, with 12 mice in each group. The mice in the control group were given ddH2O by gavage; the mice in the unmodified microplastic group were given unmodified polystyrene microplastics by gavage, and the mice in the negatively charged microplastic group and the positively charged microplastic group were given negatively charged polystyrene microplastics and positively charged polystyrene microplastics by gavage, respectively, once a day for 4 consecutive weeks. The body weight, drinking water, and food intake of the mice were detected every week. After gavage, the prostate mass, prostate coefficient, prostate histopathological morphology, inflammatory factor expression, microplastic accumulation in the prostate tissue of the mice, and the mRNA and protein expressions of hypoxia-inducible factor 1α and vascular endothelial growth factor were compared among the groups of mice.
RESULTS AND CONCLUSION: (1) With the prolongation of microplastic exposure time, the body weight of mice in the unmodified microplastics group and the positively charged microplastics exposure group was significantly suppressed. (2) After exposure to microplastics, they could enter the urinary system of mice, including prostate and bladder tissue. Among the mice in the positively charged microplastic group, the prostate mass and prostate coefficient increased most significantly. (3) Compared with the control group, the mass concentration and mRNA expression of interleukin 6, interleukin 1β, and tumor necrosis factor α were increased in the prostate tissue of the other three groups of mice (P < 0.05). Among them, the positively charged microplastic group exhibited most obvious increase. (4) Hematoxylin-eosin staining showed that the prostate tissue of mice in the unmodified microplastic group, negatively charged microplastic group, and positively charged microplastic group showed obvious proliferation of prostate epithelial cells and matrix, a significant increase in acini, and infiltration of a large number of inflammatory cells. Masson and Sirius red staining showed that compared with the control group, the prostate tissue of mice in the other three groups had obvious fibrosis. Immunohistochemical staining showed that compared with the control group, angiogenesis in the prostate tissue of mice increased in the other three groups (P < 0.05). (5) Compared with the control group, the mRNA and protein expressions of hypoxia-inducible factor 1α and vascular endothelial growth factor were increased in the prostate tissue of the other three groups of mice (P < 0.05), among which the negatively charged microplastic group and the positively charged microplastic group exhibited more significant increase. (6) The results show that polystyrene microplastics can enhance the release of inflammatory factors in mouse prostate tissue, promote angiogenesis in prostate tissue by activating the hypoxia-inducible factor 1α/vascular endothelial growth factor signaling pathway, and provide nutrition support for prostate hyperplasia and fibrosis.

Key words: polystyrene microplastics, prostate, inflammation, fibrosis, hyperplasia, angiogenesis, engineered material