Anti-inflammatory and glial response maintain normal colon function in trimethyltin-treated rats

Studies on the contribution of enteric neuropathy and intestinal homeostasis to central nervous system degeneration using animal models have reported varying results. Recently, colonic myenteric plexus degeneration was observed in trimethyltin-treated rats. Further characterization of this animal model is necessary to determine its potential for investigating the relationship between the enteric nervous system and central nervous system degeneration. In this study, trimethyltin-treated rats (8 mg/kg body weight, i.p.) were used to measure colonic function, structure, and possible colon abnormalities. The colonic function was assessed by measuring fecal pellet output and transit time. Hematoxylin and eosin staining and immunohistochemistry were performed to evaluate inflammatory profiles and intestinal epithelial cell homeostasis. The expression of mRNA encoding tight junction proteins was quantified with quantitative PCR to determine colon permeability. Histological examination of the colon revealed mucosal immune cell infiltration, crypt damage, and high iNOS and arginase-1 expression in the mucosal layer of trimethyltin-treated rats. At the same time, trimethyltin induced high expression of iNOS, arginase-1, and GFAP and increased cell death in the colonic myenteric plexus. The low cell proliferation and low goblet cell distribution suggested altered intestinal epithelial cell homeostasis in trimethyltin-treated rats. Trimethyltin also upregulated claudin 1 expression. However, normal colon function was preserved. In conclusion, the results show that trimethyltin induces colon inflammation and cell death in the colonic myenteric plexus, and disrupts intestinal epithelial cell homeostasis. However, the balance between anti-inflammatory and pro-inflammatory responses maintains normal colon function in trimethyltin-treated rats.