Authors’ reply: looking beyond the mucosa in ulcerative colitis

The distribution of binding sites for three lectins labeled with rhodamine was studied by using immunofluorescence microscopy in the colonic mucosa in ulcerative colitis.Binding sites for Dolichos biflorus agglutinin (DBA), a lectin specific to terminal α-N-acetylgalactosamine residue, and soy bean agglutinin (SBA), specific to teminal α or β-N-acetylgalactosamine residue of surface glycoprotein in the endoscopically uninvolved mucosa in ulcerative colitis were almost equal in distribution to those of normal human colon. These two lectins were markedly decreased in distribution in the endoscopically involved mucosa, whereas they were also decreased in the boundary zone which was considered as locating between the involved and the uninvolved portion. On the other hand, there was no definite difference in binding sites for concanavalin A (Con A), a lectin specific to terminal α-mannopyranoside, α-glucopyranoside, between normal colon and ulcerative colitis.These results suggest that a quantitative and/or qualitative alteration in the colonic mucin has an important role in the colonic mucosa in ulcerative colitis. And lectins may be developed into a powerful probe for the detection of biochemical change in the colonic mucosa in ulcerative colitis.

Mucosal hypoxia is detected in the mucosa of ulcerative colitis (UC), however the mechanism and the cause of hypoxia is not fully understood, while a dense infiltration of plasma cells is observed in the inflamed mucosa of UC. When differentiating from a B cell to a plasma cell, the energy metabolism dramatically shifts from glycolysis to oxidative phosphorylation, which results in a large amount of oxygen consumption of the plasma cell. We hypothesized that the plasma cell infiltration into the inflamed mucosa contributes to the mucosal hypoxia in UC in part. We examined the association between mucosal hypoxia and plasma cell infiltration in UC. More IgG plasma cells (but not IgA plasma cells) were distributed, and the nuclear and cell sizes were enlarged in hypoxic mucosa compared to normoxic mucosa in UC. Oxidative phosphorylation signature genes of these IgG plasma cells were markedly upregulated compared to those of other lymphoid cells infiltrating the lamina propria of inflamed mucosa of UC. Enlarged IgG plasma cells, which increase in number in the inflamed mucosa of UC, can be related to the hypoxic state of the inflamed mucosa of UC.

Background: Ulcerative colitis (UC) is a chronic inflammatory bowel disease in which the colonic mucosa is infiltrated with plasma cells producing IgG autoantibodies. It is not known whether this represents...

There is an increased influx of activated eosinophils to the intestinal mucosa in active ulcerative colitis, and an increased release of eosinophil-derived proteins, such as ECP, has also been observed. These findings indicate that eosinophils may contribute to tissue damage and intestinal inflammation in this disease. The relative importance of different chemotactic factors and the impact of steroid treatment on their effect in active ulcerative colitis are not known. We measured the eosinophil chemotactic activity in perfusion fluids from 11 patients with ulcerative colitis before and after steroid treatment and from 7 control patients. The effect of neutralizing antibodies to IL-5 and -8, RANTES, eotaxin, MCP-3, TNF-alpha, GM-CSF was investigated. The chemotactic activity was higher in perfusion fluids from patients than from controls (P = 0.0043). Anti-IL-5 (P = 0.005) and -TNF-alpha (P = 0.017) inhibited the activity in perfusion fluids obtained before treatment. Steroid treatment prevented the effect of all antibodies but had no significant effect on the chemotactic activity. The chemotactic activity correlated with the levels of eosinophil granule proteins in the perfusion fluids. In conclusion, in ulcerative colitis, eosinophils are attracted to the intestinal tissue by chemotactic factors, of which IL-5 and TNF-alpha may be the most prominent steroid-sensitive ones. The steroid-insensitive chemotactic activities remain unidentified.

Involvement of the IL-22/REG Iα axis in ulcerative colitis

There is conflicting evidence regarding the significance of vasoactive intestinal peptide (VIP) in inflammatory bowel disease (IBD). Involvement of the VIP receptor in IBD has not been reported. We examined the expression and localization of the VIP receptor in IBD. We determined the location of VIP receptor 1 (VIPR1) immunohistologically in surgically resected intestinal samples from 10 controls, 15 patients with ulcerative colitis, and 10 patients with Crohn's disease. A fluorescein-linked immunohistological study was performed using anti-VIPR1 antibody, with double-staining with antibodies to CD3, CD19, and CD68. Correlations with interleukin (IL)-4 and TNF-alpha expression were also investigated. Results showed that the number of VIPR1-positive cells was significantly increased in the inflammatory mucosa. VIPR1 was expressed in CD3-, CD19-, and CD68-positive cells. The proportion of VIPR1-positive cells among CD3-positive cells was significantly higher in the lamina propria of patients with ulcerative colitis than in those with Crohn's disease and the controls. The proportion of VIPR1-positive cells among CD68-positive cells was significantly higher in patients with ulcerative colitis and Crohn's disease than in the controls. A correlation between the numbers of VIPR1- and IL-4-positive cells was found in patients with ulcerative colitis, and between the numbers of VIPR1- and TNF-alpha-positive cells in patients with Crohn's disease. In conclusion, VIPR1 was widely expressed in infiltrating inflammatory cells, especially CD3- and CD68-positive cells in ulcerative colitis mucosa and CD68-positive cells in Crohn's disease mucosa. The differential expression of VIPR1 in ulcerative colitis and Crohn's disease mucosa suggests that the VIP system plays different roles in the pathogenesis of IBD.

Group II phospholipase A2 is involved in the pathogenesis of various inflammatory diseases and in the host defence against bacteria. The enzyme is expressed in the epithelial cells of colonic mucosa in ulcerative colitis. In this study, we measured the concentration of group II phospholipase A2 in serum and colonic mucosa of patients with ulcerative colitis of different severity and of control patients without any inflammatory disease. The activity of ulcerative colitis was assessed by endoscopy. The concentration of group II phospholipase A2 was measured with an immunoassay. The concentrations of group II phospholipase A2 in serum and colonic mucosa were significantly higher in patients with active and inactive ulcerative colitis than in controls. However, the group II phospholipase A2 levels did not separate patients with different disease activity. The concentration of group II phospholipase A2 in colonic mucosa corresponded with the mucosal inflammatory activity (higher in active colonic areas) intra-individually, but not between different patients with ulcerative colitis. Serum group II phospholipase A2 values were above the normal reference range more often than the values of 11 standard laboratory blood tests widely used for the follow-up of inflammatory activity in ulcerative colitis. These results indicate that the concentration of group II phospholipase A2 is increased in serum and colonic mucosa of patients with ulcerative colitis. The clinical value of the measurement of group II phospholipase A2 in the follow-up of ulcerative colitis remains to be clarified.

: Interleukin-8 (IL-8) is a chemotactic cytokine (chemokine), which both attracts and activates granulocytes. IL-8 could have a central function in the initiation and perpetuation of the inflammatory bowel diseases (IBD), due to its relative resistance to inactivation and long half-life in vivo. Using a quantitative reverse transcriptase polymerase chain reaction (RT-PCR) assay, we have observed elevated levels of IL-8 mRNA in colonic mucosal sections obtained from surgically resected specimens from ulcerative colitis (UC) and Crohn's disease (CD) patients with actively inflamed mucosa. The level of IL-8 mRNA expression in the intestinal mucosal biopsies from UC and CD patients was much greater in involved as opposed to noninvolved mucosal sections. The highest expression of IL-8 mRNA detected by RT-PCR was in UC mucosa and in isolated intestinal epithelial cells from UC patients. Increased IL-8 production by cells in IBD intestinal mucosa as well as IBD epithelial cells may be involved in the continuous attraction and activation of granulocytes in the inflamed intestine in both UC and CD patients. Chemokines, such as IL-8, are potent chemoattractant molecules and may have a central role in the augmentation and perpetuation of inflammation in IBD.

Ulcerative colitis: moving beyond the mucosal dogma.

Colorectal neoplasias (CRN)s developing from the ulcerative colitis (UC) mucosa include both colitic and sporadic neoplasias. Although several genomic analyses of advanced colitis-associated cancer are available, such studies do not distinguish between colitic and sporadic cases, and the early-stage genomic alterations involved in the onset of colitic cancer remain unclear. To address this, we performed a genomic analysis of early-stage CRN developing from the UC mucosa (CRNUC). We extracted DNA from 36 early-stage CRNUCs (T1 cancer, 10; dysplasia, 26) from 32 UC patients and performed targeted sequencing of 43 genes commonly associated with colitis-associated cancer and compared the results with sequencing data from the Japanese invasive colitis-associated cancer. The most frequently mutated gene in the CRNUC cohort was APC (mutated in 47.2% of the cases), followed by TP53 (44.4%), KRAS (27.8%), and PRKDC (27.8%). None of the TP53 mutations occurred at any of the hotspot codons. Although the TP53 mutations in The Cancer Genome Atlas of Colorectal Cancer were dispersed throughout the gene, those detected here in CRNUC cases were concentrated in the amino terminal part of the DNA-binding domain. Interestingly, the mutations in KRAS and TP53 were mutually exclusive in CRNUC, and CRNUCs with KRAS mutations had histologically serrated lesions in the gland duct. Mayo endoscopic subscore was higher in TP53-mutated CRNUCs and lower in KRAS-mutated CRNUCs. Our findings suggest that early-stage CRNUC can be classified into 2 groups: those developing through the carcinogenic pathway via TP53 mutations and those developing through the carcinogenic pathway via KRAS mutations.

Reduced butyrate-production capacity has been reported in fecal microbial communities in patients with active ulcerative colitis. However, the butyrate-production capacity of the mucosal microbiome from active vs quiescent mucosa in ulcerative colitis has been unexplored. We sought to determine the diversity and relative abundance of mucosal bacterial and fungal communities from endoscopically active vs quiescent mucosa in patients with UC, and aimed to predict contributions of mucosal microbial communities to butyrate synthesis. Systematic, segmental right- and left-sided biopsies were obtained from endoscopically active (n = 13) or quiescent (n = 17) colonic mucosa, among 15 patients with pan-colonic ulcerative colitis. Dietary fiber intake of patients was performed using the validated five-item FiberScreen questionnaire. Amplicon sequencing of mucosal bacteria and fungi was performed. The diversity and relative abundance of mucosal bacterial and fungal taxa were quantified, and predicted contributions to butyrate synthesis were ascertained. Bacterial alpha and beta diversity were similar between active vs quiescent mucosa. Butyrogenic taxa were significantly increased in quiescence, including Butyricimonas, Subdoligranulum, and Alistipes. Predicted butyrate kinase activity was significantly and concomitantly increased in quiescent mucosa. Fiber intake was positively correlated with butyrogenic microbes. Compared to mucosal bacterial prevalence, mucosal fungi were detected in low prevalence. Butyrogenic microbes are relatively increased in quiescent mucosa in ulcerative colitis, and may be related to increased fiber intake during quiescence. Manipulation of the mucosal microbiome towards butyrate-producing bacteria may be associated with endoscopic quiescence.

No available test objectively measures impairment of function of the inflamed colonic mucosa in ulcerative colitis. To study function we assessed rectal bicarbonate output by rectal dialysis in the presence of water and bacterial fatty acid (n-butyrate) in 21 controls, 18 patients with acute ulcerative colitis, 12 patients with ulcerative colitis in remission, and 12 patients with other forms of colitis. In acute ulcerative colitis, compared with controls, bicarbonate output and pH was reduced (p less than 0.001); stimulated bicarbonate output with bacterial fatty acid (incremental bicarbonate output) was reduced by 80% in acute ulcerative colitis (p less than 0.01). Results indicate that bicarbonate output is a useful and selective test of mucosal function in acute ulcerative colitis. A diminished incremental bicarbonate output with n-butyrate supports the view of inadequate oxidation of bacterial fatty acids in vivo by the mucosa in ulcerative colitis. Whether the test will prove to be an index of prognosis or will aid choice between medical or surgical therapy requires further study.

Crohn's disease (CD) is a condition characterized by excessive numbers of activated T cells in the mucosa. We investigated whether a defect in apoptosis could prolong T cell survival and contribute to their accumulation in the mucosa. Apoptotic, Bcl-2+, and Bax+ cells in tissue sections were detected by the TUNEL method and immunohistochemistry. T cell apoptosis was induced by IL-2 deprivation, Fas Ag ligation, and exposure to TNF-alpha and nitric oxide. TUNEL+ leukocytes were few in control, CD, and ulcerative colitis (UC) mucosa, with occasional CD68+ and myeloperoxidase+, but no CD45RO+, apoptotic cells. Compared with control and UC, CD T cells grew remarkably more in response to IL-2 and were significantly more resistant to IL-2 deprivation-induced apoptosis. CD T cells were also more resistant to Fas- and nitric oxide-mediated apoptosis, whereas TNF-alpha failed to induce cell death in all groups. Compared with control, CD mucosa contained similar numbers of Bcl-2+, but fewer Bax+, cells, while UC mucosa contained fewer Bcl-2+, but more Bax+, cells. Hence, the Bcl-2/Bax ratio was significantly higher in CD and lower in UC. These results indicate that CD may represent a disorder where the rate of T cell proliferation exceeds that of cell death. Insufficient T cell apoptosis may interfere with clonal deletion and maintenance of tolerance, and result in inappropriate T cell accumulation contributing to chronic inflammation.

CpG island hypermethylation (CIHM) is frequently observed in the colonic mucosa in ulcerative colitis (UC) and is deeply involved in UC-associated colorectal carcinogenesis. We evaluated the influence of common polymorphisms related to DNA repair or xenobiotic pathway (XRCC1, GSTP1, GSTT1, and GSTM1) on the individual susceptibility to CIHM status in the non-neoplastic rectal mucosa in UC patients. XRCC1 Arg399Gln and Arg194Trp, GSTP1 Ile104Val, and GSTT1, GSTM1 null polymorphisms were genotyped in 84 UC patients without neoplastic lesions, in relation to CIHM in the rectal mucosa of three candidate CpG loci (p14, p16, and CDH1) assessed by methylation-specific polymerase chain reaction. XRCC1 codon 399 Arg/Gln genotype (odds ratio (OR) = 0.31, 95%CI = 0.12-0.81, p = 0.017) and 399 Gln carrier (GlnGln+Arg/Gln: OR = 0.30, 95%CI = 0.12-0.76, p = 0.01) were significantly associated with reduced susceptibility to CIHM of the CDH1 promoter. GSTP1 Val carrier (Ile Val+Val/Val) also held a significantly lower susceptibility to CIHM of the p16 promoter (OR = 0.26, 95%CI = 0.08-0.86, p = 0.028). In contrast, GSTT1 present genotype (OR = 3.16, 95%CI = 1.27-7.89, p = 0.01) was significantly associated with increased susceptibility to CIHM of the same gene. XRCC1 codon 399 Gln/Gln genotype was significantly associated with lower mean number of CIHM when compared to the Arg/Arg genotype (1.53 ± 1.01 vs. 0.63 ± 1.06, p = 0.024). In addition, the GSTP1 Ile/Val carrier (Ile/Val+Val/Val) was also significantly associated with lower mean number of CIHM (1.43 ± 1.03 vs. 0.84 ± 1.07, p = 0.03). XRCC1 Arg399Gln and GSTP1 Ile104Val polymorphisms may influence the CIHM status in the rectal mucosa of UC patients and may be substantially involved in UC-associated carcinogenesis.

In 7 patients with ulcerative colitis, the energy level in the large intestinal mucosa was investigated. ATP and energy charge in the intestinal mucosa in ulcerative colitis showed lower levels than those of control subjects. Therefore, energy-deficit may exist in the large intestinal mucosa in ulcerative colitis.