, according to investigators.
These findings suggest that restoring EEC function could alleviate some of the more general abdominal symptoms associated with IBD, reported lead author Zachariah Raouf, MD, of Johns Hopkins University School of Medicine, Baltimore, and colleagues.
“The symptoms experienced by patients with IBD, especially ulcerative colitis, may include those that are colonic in nature, such as bloody stools, abdominal pain, and weight loss, as well as those that are more general in nature, such as severe nausea and abdominal bloating,” the investigators wrote in Cellular and Molecular Gastroenterology and Hepatology . “Although the first set of symptoms may be attributable to the effects of colonic inflammation itself, those that are more vague seem to overlap with the symptoms that patients with small intestinal dysmotility experience, such as occur in response to medications, or diabetes.”
Supporting this notion, several previous studies have reported the onset of intestinal dysmotility in experimental models of colitis, which is believed to be caused by impaired enteric nervous system function. But the precise mechanisms behind the impaired intestinal motility observed in colitis patients remain unclear.
To learn more, Dr. Raouf and colleagues conducted experiments involving three groups of mice: wild-type mice, mice genetically engineered to overexpress EECs, and mice lacking EECs.
To induce colitis, the mice were administered dextran sulfate sodium (DSS) in drinking water at concentrations of 2.5% or 5% for 7 days. Small intestinal motility was evaluated by measuring the transit of fluorescein isothiocyanate (FITC)-dextran. Immunohistochemical analyses were conducted to assess EEC number and differentiation, while quantitative reverse-transcriptase polymerase chain reaction was used to examine the expression of genes related to serotonin synthesis and transport.
The researchers examined colon length and signs of colonic inflammation, monitored weight loss, and measured the expression of proinflammatory cytokines. Histological analyses of colon and small intestine tissues were performed to further understand the effects of colitis. The presence and number of EEC cells was evaluated using chromogranin A (ChgA) staining, while apoptosis in EECs was measured via TUNEL staining. The expression of serotonin-related genes was also assessed.
These experiments revealed that DSS-induced colitis led to significant small-bowel hypomotility and a reduction in EEC density. Of note, genetic overexpression of EECs or treatment with prucalopride, a 5-hydroxytryptamine receptor 4 agonist, improved small intestinal motility.
“It is noteworthy that there were no significant changes in the density of other intestinal epithelial cells, or in other cell types that are linked to motility, such as enteric glia and neurons, suggesting the specificity of the effect,” the investigators wrote. “Importantly, treatment with a serotonin agonist ameliorated the colitis-induced, small-bowel hypomotility and attenuated the severity of colitis, providing potential clinical relevance of the current findings. Taken together, these results identify mechanisms to explain the intestinal hypomotility observed in the setting of colitis.”Dr. Raouf and colleagues called for human clinical trials to their findings. Specifically, they suggested exploring therapies targeting enteroendocrine cells or serotonin pathways and examining the role of different EEC types in gut motility during inflammation. The study was supported by the National Institutes of Health. The investigators disclosed no conflicts of interest.
