Chunhui Wang

Transcriptional inhibition of intestinal NHE8 expression by glucocorticoids involves Pax5

Sodium/hydrogen exchangers (NHEs) are a family of proteins that transport sodium ions into the cells by moving protons out of the cells. They play a major role in sodium absorption, cell volume regulation, and intracellular pH regulation. Three out of nine identified NHEs (NHE2, NHE3, and NHE8) are expressed on the apical membrane of intestinal epithelial cells. Glucocorticoids have been found to regulate NHE3 function in the intestine, but it is unknown if they have a similar function on NHE8 expression. Interestingly, high glucocorticoid levels in the intestine coincide chronologically with the change from high expression of NHE8 to high expression of NHE3. Studies were performed to explore the role of glucocorticoids on NHE8 expression during intestinal maturation. Brush-border membrane vesicles were isolated from intestinal epithelia, and Western blotting was performed to determine NHE8 protein expression of suckling male rats treated with methylpredisolone. Real-time PCR was used to quantitate NHE8 mRNA expression in rats and Caco-2 cells. Human NHE8 promoter activity was characterized through transfection of Caco-2 cells. Gel mobility shift assays (GMSAs) were used to identify the promoter sequences and the transcription factors involved in glucocorticoid-mediated regulation. Our results showed that the expression of NHE8 mRNA and protein was decreased in glucocorticoid-treated rats and human intestinal epithelial cells (Caco-2). The activity of the human NHE8 gene promoter transfected in Caco-2 cells was also reduced by glucocorticoid treatment. GMSAs suggested that the reduction in promoter activity in the presence of glucocorticoids was due to enhanced transcription factor Pax5 binding on the NHE8 proximal promoter region. In conclusion, this study showed that glucocorticoids inhibit NHE8 gene expression by increasing Pax5 binding on NHE8 gene promoter, suggesting an important role for Pax5 during intestinal maturation.

Somatostatin regulates NHE8 protein expression via the ERK1/2 MAPK pathway in DSS-induced colitis mice

Previous studies reported that administration of somatostatin (SST) to human patients mitigated their diarrheal symptoms. Octreotide (an analog of SST) treatment in animals resulted in upregulation of sodium/hydrogen exchanger 8 (NHE8). NHE8 is important for water/sodium absorption in the intestine, and loss of NHE8 function results in mucosal injury. Thus we hypothesized that NHE8 expression is inhibited during colitis and that SST treatment during pathological conditions can restore NHE8 expression. Our data showed for the first time that NHE8 is expressed in the human colonic tissue and that NHE8 expression is decreased in ulcerative colitis (UC) patients. We also found that octreotide could stimulate colonic NHE8 expression in colitic mice. Furthermore, the somatostatin receptor 2 (SSTR2) agonist seglitide and the somatostatin receptor 5 (SSTR5) agonist L-817,818 could restore NHE8 expression via its role in suppressing ERK1/2 phosphorylation. Our study uncovered a novel mechanism of SST stimulation of NHE8 expression in colitis.

Endoscopic management of foreign bodies in the upper gastrointestinal tract: a retrospective study of 1294 cases

Abstract Objective: To report our endoscopic outcomes and explore the effects of duration of impaction and anesthetic methods on the endoscopic removal of foreign bodies in the upper gastrointestinal tract. Methods: All consecutive patients with suspected foreign body (FB) ingestion between January 2013 and June 2016 were enrolled. Demographic, clinical and endoscopic data were collected and analyzed. Results: A total of 1294 patients aged seven months to 94 years were enrolled. Odynophagia (415 cases, 32.1%), FB sensation (340 cases, 26.3%) and sore throat (267 cases, 20.1%) were the most frequent complaints. The duration of FB impaction ranged from 4 h to over two years. Anatomically, foreign bodies were most commonly located in the esophagus (n = 1025, 86.9%). Bony foreign bodies comprised the majority of identified foreign bodies. The most common underlying pathology was esophageal stricture (38 cases, 53.5%). Nearly half of the patients (49.9%) developed complications. As the duration of impaction increased, the success rate by endoscopy decreased (p < .001), and the complication rate increased (p < .001). Endoscopic management under general anesthesia didn’t improve the success rate or lower the complication rate compared with topical pharyngeal anesthesia (p = .793 and p = .085). Age ≥60, duration of impaction longer than one day, impaction in the esophagus, and sharp foreign bodies were identified as risk factors for complications. Conclusions: Delayed flexible endoscopy in patients, especially elderly patients, with sharp FB impactions in the esophagus results in worse endoscopic outcomes. Endoscopic management under general anesthesia did not improve the therapeutic results compared with topical pharyngeal anesthesia.

Up-regulation of NHE8 by somatostatin ameliorates the diarrhea symptom in infectious colitis mice model

Na+/H+ exchangers (NHEs) have been shown to be involved in regulating cell volume and maintaining fluid and electrolyte homeostasis. Pooled evidences have suggested that loss of Na+/H+ exchanger isoform 8 (NHE8) impairs intestinal mucosa. Whether NHE8 participates in the pathology of infectious colitis is still unknown. Our previous study demonstrated that somatostatin (SST) could stimulate the expression of intestinal NHE8 so as to facilitate Na+ absorption under normal condition. This study further explored whether NHE8 participates in the pathological processes of infectious colitis and the effects of SST on intestinal NHE8 expression in the setting of infectious colitis. Our data showed that NHE8 expression was reduced in Citrobacter rodentium (CR) infected mice. Up-regulation of NHE8 improved diarrhea symptom and mucosal damage induced by CR. In vitro, a similar observation was also seen in Enteropathogenic E. coli (EPEC) infected Caco-2 cells. Seglitide, a SST receptor (SSTR) 2 agonist, partly reversed the inhibiting action of EPEC on NHE8 expression, but SSTR5 agonist (L-817,818) had no effect on the expression of NHE8. Moreover, SST blocked the phosphorylation of p38 in EPEC-infected Caco-2 cells. Taken together, these results suggest that enhancement of intestinal NHE8 expression by SST could ameliorate the symptoms of mice with infectious colitis.

Molecular mechanisms of somatostatin-mediated intestinal epithelial barrier function restoration by upregulating claudin-4 in mice with DSS-induced colitis

Intestinal barrier dysfunction plays a crucial role in the pathogenesis of ulcerative colitis (UC). Previous studies have shown somatostatin (SST) can protect intestinal barrier structure possibly through upregulating tight junction (TJ) protein expression, but the mechanisms of this upregulation remain undefined. This study aimed to investigate the molecular mechanisms of interaction of SST with its downstream regulatory elements in DSS-induced colitis mice. In DSS-induced colitis mice, exogenous SST supplement (octreotide) effectively ameliorated disease progression, restored colonic barrier structure and function, and stimulated claudin-4 expression. Similar effects were also observed for SST on Caco-2 cells intervened by TNF-α. SST receptor 5 (SSTR5) agonist L-817,818 upregulated the claudin-4 expression whereas the SSTR2 agonist seglitide could not reverse TNF-α-induced reduction of claudin-4. SST treatment significantly decreased the phosphorylation levels of ERK1/2 and p38 induced by TNF-α. PD-98059 (ERK1/2 pathway inhibitor) but not SB-202190 (p38 pathway inhibitor) could reverse TNF-α-induced suppression of claudin-4 expression. Both inhibitors could improve the TJ barrier function damaged by TNF-α. Our studies suggest that the protective effect of SST on intestinal barrier achieved by upregulating claudin-4 expression through activation of SSTR5 and suppression of the ERK1/2 pathways. These findings will benefit the development of novel treatment regimens for UC.

Tu1397 Somatostatin Regulates NHE8 Protein Expression via the MAPK -ERK1/2 Pathway in Colitis Mice

Background and aim:diarrhea is a common disease in gastroenterology which is caused by various affects such as intestinal infection, non-infectious inflammation, tumors and so on. The imbalance of fluid/sodium absorption and secretion is considered playing a crucial role in diarrhea. Sodium, as an important electrolyte, involves three mechanisms to transport. Of note, sodium/hydrogen exchanger (NHE) may occupy a crucial position in modulating intestinal water and sodium absorption. Previous study had shown that somatostatin (SST) could stimulate NHE8 expression in physiological intestine. To determine the benefical effect of SST on NHE8 protein expression in colitis mice and its mechanisms, experimental colitis was induced in mice utilizing dextran sulfate sodium (DSS), models of Caco-2 cells intervened by TNF-α were also established to further explore the mechanism of somatostatin modulating NHE8 expression. Methods: To induce diarrhea via intestinal inflammation, mice were fed with 3% Dextran sulfate sodium (DSS) water for seven days. On the eighth day, treatment groups were administrated with octreotide at dose of 50 μg/ kg body weight three times a day for three days. On the eleventh day, mice were euthanized and colonic tissues were collected. Diarrheal symptoms were assessed every other day. Diarrheal score was recorded based on fecal shape, color and hardness. For the TNF-α study, Caco-2 cells were incubated with TNF-α for 18 hours before adding somatostatin. Cells were exposed to somatostatin for 1 hour before harvest. To further explore the mechanism of somatostatin modulating NHE8 expression, Caco-2 cells were incubated with TNF-α for 18 hours. Subsequently, Caco-2 cells pretreated with MAPKK inhibitor (PD98059) were administratedwith SST for 1 hour before harvest.Results: For DSS colitis mice, the expression of somatostatin in colon were decreased in DSS colitis mice compared with the control mice. Moreover, SST could not only ameliorate diarrhea in inflammatory colitis (diarrheal score: 1.7 ± 0.78 vs. 3.6 ± 0.16, n = 3, P<0.05) but also stimulate NHE8 expression in proximal and distal colon compared with DSS colitis mice (proximal colon: 0.61±0.08 vs. 0.31±0.04, n=3, P<0.05; distal colon: 0.74±0.1 vs. 0.36±0.06, n=3, P<0.05). For TNF-α intervened Caco-2 cells, SST could stimulate NHE8 expression compared with TNF-α intervened cells (0.5 ± 0.04 vs. 0.25 ± 0.01; n=3, P<0.05). Furthermore, compared with TNF-α intervened cells, SST could decline the phosphorylation of ERK1/2 (P<0.05). conclusions :In conclusion, the present study suggested that somatostatin could up-regulate the expression of NHE8 protein in both DSS colitis mice and TNF-α intervened Caco-2 cells by blocking the activation of the MAPK-ERK1/2 pathway.