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Mucosal healing determined by endoscopy is currently the remission standard for ulcerative colitis (UC). However, new criteria for remission are emerging, such as histologic normalization, which appears to correlate better to the risk of relapse. Here, we study mucosal healing on a molecular and functional level in quiescent UC. We obtained endoscopic biopsies from 33 quiescent UC patients and from 17 controls. Histology was assessed using Geboes score. Protein and mRNA levels were evaluated for the tight junction proteins claudin-2, claudin-4, occludin, and tricellulin, as well as Cl−/HCO3− exchanger DRA, and cyclo-oxygenase enzymes (COX-1, COX-2). The mucosal activity of COX-1 and COX-2 enzymes was assessed in modified Ussing chambers, measuring electrogenic ion transport (short-circuit current, SCC). Chronic inflammation was present in most UC patients. The protein level of claudin-4 was reduced, while mRNA-levels of claudin-2 and claudin-4 were upregulated in UC patients. Surprisingly, the mRNA level of COX-1 was downregulated, but was unaltered for COX-2. Basal ion transport was not affected, while COX-2 inhibition induced a two-fold larger decrease in SCC in UC patients. Despite being in clinical and endoscopic remission, quiescent UC patients demonstrated abnormal mucosal barrier properties at the molecular and functional level. Further exploration of mucosal molecular signature for revision of current remission standards should be considered.

Background: Cyclooxygenase (COX) activity is increased in endoscopic normal colonic mucosa from patients with colorectal neoplasia (CRN). COX-2 is thought to be the predominant COX isozyme involved in neoplasia. Meanwhile, relative contributions of COX-1 and COX-2 isoforms are unknown. Knowledge about their mutual activity in colonic mucosa is important for diagnostics and targeted therapy for CRN. The aim of this study was to assess the relative function, expression and localization of COX-1 and COX-2 enzymes in colonic non-neoplastic human mucosa and thereby to potentially reveal a mucosal disease predisposition for better treatment. Methods: Biopsies were pinched from normal appearing colonic mucosa in patients undergoing endoscopy. Ussing chamber technique was applied for an indirect assessment of epithelial activity, RT-qPCR for expression and immunohistochemistry for localization of COX-1 and COX-2 enzymes in patients without (ctrls) and with a history of CRN (CRN-pts). Results: Combined COX-1 and COX-2 activity was higher in CRN-pts, p=0.036. COX-2 was primarily localized in absorptive cells, while COX-1 appeared to be restricted to nonenteroendocrine tuft cells of the colonic epithelium. Conclusions: In biopsies from endoscopic normal appearing colonic mucosa, combined activity of COX-1 and COX-2 enzymes is increased in CRN-pts compared with ctrls. This indicates that COX-1 and COX-2 together contribute to an increased proliferation process. Of note, in colonic epithelial cell lining, the COX-1 enzyme seems localized in tuft cells.

The pathogenesis of colorectal neoplasia (CRN) has been associated with altered non-neuronal acetylcholine (ACh) metabolism. The aim of this study was to characterize expression, function and cellular location of ACh-related proteins in biopsies obtained from endoscopic normal appearing sigmoid colon in patients with and without CRN. Messenger-RNA (mRNA) levels of 17 ACh-related proteins were quantified by rt-qPCR. Functional responses to ACh, measured as electrogenic transepithelial short circuit current (SCC), were recorded using the Ussing chamber technique. Finally, cellular localization of choline transporter-like proteins (CTLs) and butyryl-cholinesterase enzyme (BChE) was determined by immunohistochemistry. mRNA expression of CTL1 and CTL4 was increased in patients with CRN (p = 0.002 and p = 0.04, respectively). In functional experiments, baseline SCC was increased in CRN patients. ACh induced rapid biphasic changes in SCC. An initial decreasing phase was observed in the minority of CRN patients vs. the majority of controls (25% vs. 69%, respectively, p = 0.031). For the second increasing phase of SCC, data indicated ACh-activation of two receptors. For both parts of the biphasic response, the half maximal effective concentration and maximal responses showed no difference between patient groups. Immunohistochemistry demonstrated CTL1, 3 and 4 and BChE to be localized to colonic crypt cells. We conclude that CRN is associated with increased expression of CTL1 and CTL4, augmented basal prostaglandin-dependent secretion, and altered functional channel response to ACh in human endoscopic normal appearing colonic mucosa. The immunohistochemical findings support CTL1, CTL3, CTL4 and BChE to be involved in non-neuronal mucosal ACh metabolism. This article is protected by copyright. All rights reserved

Background Intracellular signaling through cyclic nucleotides, both cyclic AMP and cyclic GMP, is altered in colorectal cancer. Accordingly, it is hypothesized that an underlying mechanism for colorectal neoplasia involves altered function of phosphodiesterases (PDEs), which affects cyclic nucleotide degradation. Here we present an approach to evaluate the function of selected cyclic nucleotide-PDEs in colonic endoscopic biopsies from non-neoplastic appearing mucosa. Methods Biopsies were obtained from patients with and without colorectal neoplasia. Activities of PDEs were characterized functionally by measurements of transepithelial ion transport and their expression and localization by employing real-time qPCR and immunohistochemistry. Results In functional studies PDE subtype-4 displayed lower activity in colorectal neoplasia patients (p = 0.006). Furthermore, real-time qPCR analysis showed overexpression of subtype PDE4B (p = 0.002) and subtype PDE5A (p = 0.02) in colorectal neoplasia patients. Finally, immunohistochemistry for 7 PDE isozymes demonstrated the presence of all 7 isozymes, albeit with weak reactions, and with no differences in localization between colorectal neoplasia and control patients. Of note, quantification of PDE subtype immunostaining revealed a lower amount of PDE3A (p = 0.04) and a higher amount of PDE4B (p = 0.02) in samples from colorectal neoplasia patients. Conclusion In conclusion, functional data indicated lower activity of PDE4 subtypes while expressional and abundance data indicated a higher expression of PDE4B in patients with colorectal neoplasia. We suggest that cyclic nucleotide-PDE4B is overexpressed as a malfunctioning protein in non-neoplastic appearing colonic mucosa from patients with colorectal neoplasia. If a predisposition of reduced PDE4B activity in colonic mucosa from colorectal neoplasia patients is substantiated further, this subtype could be a potential novel early diagnostic risk marker and may even be a target for future medical preventive treatment of colorectal cancer. Electronic supplementary material The online version of this article (doi:10.1186/s12885-016-2980-z) contains supplementary material, which is available to authorized users.