Quantifying intraepithelial lymphocytes and subepithelial collagen band in microscopic colitis, extracting insights into the interrelationship of lymphocytic and collagenous colitis.

Microscopic colitis (MC) is the umbrella term for the conditions termed lymphocytic colitis (LC) and collagenous colitis (CC). LC with thickening of the subepithelial collagen band or CC with increased number of intraepithelial T- lymphocytes (IELs) is often seen in MC and may lead to difficulties in correct histological classification. We investigated the extent of overlapping features of CC and LC in 60 cases of MC by measuring the exact thickness of the subepithelial collagen band in Van Gieson stained slides and quantifying number of IELs in CD3 stained slides by digital image analysis. A thickened collagen band was observed in nine out of 29 cases with LC (31%) and an increased number of IELs in all 23 cases of CC (100%). There was no correlation between the thickness of the collagen band and number of IELs. Due to the increased number of IELs in all cases of CC we consider the lymphocytic inflammatory infiltration of the mucosa to be the essential histopathological feature of MC. However, although LC and CC are related due to the lymphocytic inflammation, the non-linear correlation of number of IELs and thickness of the collagenous band indicate differences in their pathogenesis.

The Water Channel Aquaporin 8 is a Critical Regulator of Intestinal Fluid Homeostasis in Collagenous Colitis.

BACKGROUND AND AIMS: Diarrhoea is a common, debilitating symptom of gastrointestinal disorders. Pathomechanisms probably involve defects in trans-epithelial water transport, but the role of aquaporin [AQP] family water channels in diarrhoea-predominant diseases is unknown. We investigated the involvement of AQPs in the pathobiology of collagenous colitis [CC], which features chronic, watery diarrhoea despite overtly normal intestinal epithelial cells [IECs]. METHODS: We assessed the expression of all AQP family members in mucosal samples of CC patients before and during treatment with the corticosteroid drug budesonide, steroid-refractory CC patients and healthy controls. Samples were analysed by genome-wide mRNA sequencing [RNA-seq] and quantitative real-time PCR [qPCR]. In some patients, we performed tissue microdissection followed by RNA-seq to explore the IEC-specific CC transcriptome. We determined changes in the protein levels of the lead candidates in IEC by confocal microscopy. Finally, we investigated the regulation of AQP expression by corticosteroids in model cell lines. RESULTS: Using qPCR and RNA-seq, we identified loss of AQP8 expression as a hallmark of active CC, which was reverted by budesonide treatment in steroid-responsive but not refractory patients. Consistently, decreased AQP8 mRNA and protein levels were observed in IECs of patients with active CC, and steroid drugs increased AQP8 expression in model IECs. Moreover, low APQ8 expression was strongly associated with higher stool frequency in CC patients. CONCLUSION: Down-regulation of epithelial AQP8 may impair water resorption in active CC, resulting in watery diarrhoea. Our results suggest that AQP8 is a potential drug target for the treatment of diarrhoeal disorders.

Expression Profiling of Inflammatory and Immunological Genes in Collagenous Colitis.

BACKGROUND: Collagenous colitis [CC] is a common idiopathic cause of chronic watery diarrhoea. We investigated its pathogenesis by means of gene expression analysis. METHODS: We analysed the expression of genes implicated in immunological and inflammatory pathways in paired colonic biopsies of histologically involved and uninvolved mucosa from five patients with histologically patchy CC, in pooled colonic biopsies of eight other patients with diffuse CC, and in pooled biopsies of eight normal controls. Analyses were performed with the Nanostring nCounter system. Expression ratios were generated and confirmed by quantitative reverse transcription PCR. RESULTS: CC mucosa was characterized by enhanced expression of nitric oxide synthase 2; of matrix metalloproteinases 3 and 9 and tissue inhibitor of metalloproteinase 1, but not transforming growth factor ß1; of mediators of T-helper 1 immunity including interleukins 12A [IL12A], 12B, IL12 receptor B1 and interferon γ; of immune mediators of the leukocyte immunoglobulin-like receptor subfamily B; and of multiple T cell cytokines and their receptors. The mitogen-activated protein kinase signalling pathway was unchanged. There were no increases in IL22, IL22RA2 or tumour necrosis factor α, which are reportedly elevated in chronic inflammatory bowel disease. In four of five patients with patchy CC, similar gene expression profiles were observed in histologically involved and uninvolved mucosa. CONCLUSIONS: CC is characterized by altered expression of a limited repertoire of genes involved in nitric oxide synthesis, extracellular matrix remodelling, T-helper 1 immunity and immune modulation. The abnormal gene expression in patchy CC may be expressed in mucosa with and without histological disease manifestations.

Collagenous colitis development occurs after long standing mucosal healing in IBD with TNF-α inhibitors, and could be due to exaggerated healing response from excess TNF-α inhibition.

Collagenous colitis is a relatively rare disorder affecting mainly middle-aged women where they present with chronic non-bloody diarrhea. Both with lymphocytic colitis they compose microscopic colitis. The exact cause of collagenous colitis is still unknown however; many potential pathophysiologic mechanisms have been proposed but no convincing mechanism has been identified. Collagenous colitis has been linked to medications mainly NSAIDs, SSRIs, and PPIs. It is also believed that collagenous colitis is autoimmune disease and there are weak believe it could have some genetic inheritance. We reported before two cases of collagenous colitis developed in patients with Crohn's disease and ulcerative colitis while they were in complete mucosal remission after being treated with tumor necrosis factors-α inhibitors. In this article we will try to explain how collagenous colitis can develop in patients with inflammatory bowel disease especially those on tumor necrosis factors-α inhibitors.

Proton pump inhibitor induced collagen expression in colonocytes is associated with collagenous colitis.

AIM: To elucidate the role of proton pump inhibitors (PPIs) in collagenous disease, direct effect of PPI on colonocytes was examined. METHODS: Collagenous colitis is a common cause of non-bloody, watery diarrhea. Recently, there has been increasing focus on the use of proton PPIs as a risk factor for developing collagenous colitis. Mouse CT26 colonic cells were treated with PPI and/or PPI-induced alkaline media. Expression of fibrosis-associated genes was examined by RT-PCR. In human materials, collagen expression was examined by immunohistochemistry. RESULTS: CT26 cells expressed a Na+-H+ exchanger gene (solute carrier family 9, member A2). Treatment with PPI and/or PPI-induced alkaline media caused growth inhibition and oxidative stress in CT26 cells. The treatment increased expression of fibrosis inducing factors, transforming growth factor ß and fibroblast growth factor 2. The treatment also decreased expression of a negative regulator of collagen production, replication factor C1, resulting in increased expression of collagen types III and IV in association with lipid peroxide. In biopsy specimens from patients with collagenous colitis, type III and IV collagen were increased. Increase of type III collagen was more pronounced in PPI-associated collagenous colitis than in non-PPI-associated disease. CONCLUSION: From these findings, the reaction of colonocytes to PPI might participate in pathogenesis of collagenous colitis.

Fecal stream diversion and mucosal cytokine levels in collagenous colitis: A case report.

In this case report, we examined the levels of cytokines expressed before and during fecal stream diversion and after intestinal continuity was restored in a patient with collagenous colitis. We report the case of a 46-year-old woman with chronic, active collagenous colitis who either failed to achieve clinical remission or experienced adverse effects with the following drugs: loperamide, cholestyramine, budesonide, methotrexate and adalimumab. Due to the intractable nature of the disease and because the patient was having up to 15 watery bowel movements per day, she underwent a temporary ileostomy. Colonic biopsies were analyzed for mucosal cytokine protein levels before and during fecal stream diversion and after intestinal continuity was restored. Mucosal protein levels of interleukin (IL)-1ß, IL-2, IL-6, IL-12, IL-17 A, IL-23, TNF, IFN-γ, IL-4, IL-5, IL-10 and IL-13 were all higher during active disease and decreased to non-detectable or considerably lower levels during fecal stream diversion. One month after the restoration of bowel continuity, when the patient experienced a relapse of symptoms, IL-2, IL-23 and IL-21 levels were again increased. Our results indicate that fecal stream diversion in this patient suppressed the levels of all cytokines analyzed in colonic biopsies. With the recurrence of clinical symptoms and histological changes after bowel reconstruction, the levels of primarily proinflammatory cytokines increased. Our findings support the hypothesis that a luminal factor triggers the inflammation observed in collagenous colitis.

Increased fecal levels of chromogranin A, chromogranin B, and secretoneurin in collagenous colitis.

Interactions between the enteric nervous system and the immune system are suggested to play an important role in the pathophysiology of inflammatory bowel disease (IBD). This study aims to determine if chromogranin A (CgA), chromogranin B (CgB), and secretoneurin (SN) are detectable in feces (F) from patients with collagenous colitis (CC) and to compare the levels found in patients with ulcerative colitis (UC) and Crohn's disease (CD) before and during treatment. Patients with CC (n = 12) were studied before and after 3, 7, 28, and 56 days of treatment. Patients with IBD (UC, n = 21; CD, n = 11) were studied before and after 28 and 56 days of treatment. Clinical data were recorded, and fecal samples were collected at each occasion. F-CgA, F-CgB, and F-SN were measured by RIA. Eleven patients with CC, 21 with UC, and 10 with CD achieved remission. On inclusion, CC patients had higher levels of F-CgA, F-CgB, and F-SN than patients with IBD and controls. Patients with IBD expressed markedly lower levels of F-SN than controls. During treatment, F-SN in CC patients decreased to control levels but remained low in IBD patients. No change was found in F-CgA or F-CgB in any of the groups. In conclusion, CgA, CgB, and SN are detectable in feces, and CC patients express higher values than patients with IBD and controls. During treatment, F-SN decreased to control levels in CC. These findings suggest that the enteric nervous system is clearly involved in the pathophysiology of CC.

An easy method to quantify plasma cells/plasma cell precursors in normal colonic mucosa, collagenous colitis and Crohn's colitis.

BACKGROUND: The number of round cells that should normally be present in the colonic mucosa remains disputed. Biopsies from patients with chronic diarrhoea, having a slightly increased number of round cells in the lamina propria mucosa (lpm) may be diagnosed as slight chronic colitis by some pathologists, while others may regard these biopsies as being normal. MATERIALS AND METHODS: The numbers of plasma cells/plasma cell precursors (PC-PCP) were assessed in colonic biopsies from 35 patients by the aid of MUM1 immunostaining. MUM1 (multiple myeloma oncogene 1) is a member of the interferon regulatory family of transcription factors (interferon regulatory factor 4 gene, IRF4). RESULTS: Many of the round cells considered, as lymphocytes in H&E staining were in fact MUM1-positive PCP. In 6 patients having a priori, a slightly increased number of round cells, the mean number of MUM1-labelled cells was 40.8, in 5 patients with collagenous colitis, it was 81.4 and in 12 patients with Crohn's colitis, 87.6, whereas in 12 normal individuals it was 23.3 (MUM1-positive cells in collagenous-Crohn's colitis vs. normal mucosa, p<0.05). CONCLUSION: MUM1 was of value in recording a significant increase of PC-PCP in collagenous colitis and Crohn's colitis. The subjective impression of increased cellularity in some colonic biopsies from patients with chronic diarrhoea was substantiated in mathematical terms, by demonstrating that the number of PC-PCP was increased.

Fecal eosinophil cationic protein as a marker of active disease and treatment outcome in collagenous colitis: a pilot study.

BACKGROUND AND AIMS: Fecal calprotectin (FC) is used as a marker for intestinal inflammation in inflammatory bowel disease (IBD) but there is no reliable marker for collagenous colitis (CC). We have previously demonstrated that the mucosal inflammation in CC is characterized by eosinophil activation, which is restored during budesonide treatment, but there is no enhanced neutrophil activity. The aim of this study was to evaluate the use of fecal eosinophil cationic protein (F-ECP) and eosinophil protein X (F-EPX) compared with the neutrophil-derived myeloperoxidase (F-MPO) and FC in patients treated for active CC. METHODS: Patients with active CC (n = 12) were studied before and after 3, 7, 28 and 56 days of budesonide treatment. Clinical symptoms and stool frequency were recorded, fecal samples were collected, and F-ECP, F-EPX, F-MPO and FC were measured at each occasion. RESULTS: All but one patient achieved remission. On inclusion 92%, 67%, 67% and 75% of the patients had elevated F-ECP, F-EPX, F-MPO and FC levels, respectively. All markers decreased during the treatment, particularly F-ECP and F-EPX, which decreased after only 3 days. At the end of the study 100%, 92%, 83% and 75% of the patients had normal F-ECP, F-EPX, F-MPO and FC values, respectively. CONCLUSION: F-ECP demonstrated the best discriminating capacity in detecting active CC. A normalized F-ECP and F-EPX may further be studied as a marker for successful treatment. During budesonide treatment there is a rapid fall in F-ECP and F-EPX, accompanied by clinical improvement, indicating an essential role for the eosinophil participating in the pathophysiology of CC.

Low levels of bile acids increase bacterial uptake in colonic biopsies from patients with collagenous colitis in remission.

BACKGROUND: Patients with collagenous colitis have an impaired mucosal barrier. Moreover, collagenous colitis is associated with bile acid malabsorption. Bile acids can increase bacterial mucosal uptake in humans. Mucosal barrier function was investigated by exposing colonic biopsies to chenodeoxycholic acid (CDCA) or deoxycholic acid (DCA) in Ussing chamber experiments. AIM: To find if low levels of bile acids increase bacterial uptake in colonic biopsies from collagenous colitis patients. METHODS: The study comprised 33 individuals; 25 with collagenous colitis (14 in clinical remission without treatment, 11 with active disease and 10 examined in clinical remission resulting from treatment with 6 mg budesonide); eight healthy individuals undergoing screening colonoscopy served as controls. Endoscopic biopsies from the sigmoid colon were mounted in modified Ussing chambers and assessed for short-circuit current (Isc), potential difference, trans-epithelial resistance and transmucosal passage of Escherichia coli K12 after adding 100 µmol/L CDCA or DCA. RESULTS: When adding 100 µmol/L CDCA or DCA, bacterial uptake increased fourfold in biopsies of patients in remission; CDCA 6.5 units [2.5-9.8] and DCA 6.2 units [2.1-22] (median [IQR]), compared with uptake in biopsies without added bile acids 1.6 units [1.1-3] (P=0.004 and P=0.01 respectively). In active disease and in patients in remission due to budesonide treatment, bile acids did not affect bacterial uptake. Confocal microscopy revealed trans-epithelial passage of E. coli K12 within 30 min. CONCLUSIONS: Low concentrations of dihydroxy-bile acids exacerbate mucosal barrier dysfunction in colonic biopsies of patients with collagenous colitis in remission. This allows a substantially increased bacterial uptake, which may contribute to recurrence of inflammation.

Connective tissue growth factor expression is increased in collagenous colitis and coeliac disease.

AIMS: Subepithelial collagen deposition is a classical feature of collagenous colitis (CC), but is also seen in untreated coeliac disease. The end-stage mediator of excess cellular collagen production is connective tissue growth factor (CTGF). The aim of this study was to investigate CTGF expression by in situ hybridization (ISH) and polymerase chain reaction (PCR) in CC and coeliac disease as well as lymphocytic colitis (LC), Crohn's colitis and ulcerative colitis (UC). METHODS AND RESULTS: For coeliac disease we analysed fresh frozen material by quantitative reverse transcription-polymerase chain reaction (RT-PCR) and archival material for ISH. PCR transcripts in coeliac disease were moderately elevated and labelled cells were significantly increased in the subepithelial zone. For CC, LC and UC we investigated archival material because of the rarity of the first two conditions. There was a marked increase in CTGF expression in the subepithelial zone in CC, localizing to cells with the morphology of smooth muscle cells, which was not seen in LC. CONCLUSIONS: The colocalization of CTGF transcripts with areas of excessive collagen deposition in coeliac disease and CC suggest that it might be the end-stage mediator of local fibrosis in these conditions.

Is increased colon subepithelial collagen layer thickness in diabetic patients related to collagenous colitis? An immunohistochemical study.

In this study, we evaluated immunohistochemically whether increased thickness of the colon subepithelial collagen layer in diabetic patients relates to collagenous colitis. A total of 100 patients (25 in each group) were included in this study. There were diabetic patients with chronic diarrhea in the first group, diabetic patients without chronic diarrhea in the second group, non-diabetic patients with chronic diarrhea in the third group, and control patients in the fourth group. The endoscopic biopsy specimens were obtained from the rectum, sigmoid colon, and descending colon. The thickness of the subepithelial collagen layer was measured using the ocular micrometer method. The immunohistochemical staining was performed with type 1 collagen and fibronectin antibody. The thickness of the colon subepithelial collagen layer in diabetic patients with or without diarrhea was significantly greater than that in control patients. This thickened subepithelial collagen layer in diabetic patients was stained with fibronectin antibody, but not with type 1 collagen antibody in the immunohistochemical study. These immunohistochemical staining characteristics were not similar to those in collagenous colitis, but were similar to those in normal subjects. Increased colon subepithelial collagen layer thickness in diabetic patients does not relate to collagenous colitis.

Metabolic and inflammatory faecal markers in collagenous colitis.

OBJECTIVES: To evaluate the excretion of the inflammatory and metabolic faecal markers calprotectin, lactoferrin, and short-chain fatty acids in symptomatic and quiescent collagenous colitis. METHODS: Faecal samples from 21 patients with active collagenous colitis, 12 patients retested in remission, and 13 controls were analysed. Calprotectin was determined using an enzyme-linked immunosorbent assay. Lactoferrin was estimated by a latex agglutination test. Short-chain fatty acids were determined by steam distillation followed by gas-liquid chromatography. RESULTS: Calprotectin was increased in patients with active collagenous colitis [80 microg/g (6.25-1899)] (median and range) compared with patients with quiescent collagenous colitis [26 microg/g (6.25-340)], P=0.025 and controls [6.25 microg/g (6.25-99)], P=0.002. Eight patients (38%) with active collagenous colitis had normal levels of calprotectin. Lactoferrin was detected in one patient only. Concentrations of total short-chain fatty acids did not differ in patients with active collagenous colitis compared with quiescent collagenous colitis or controls (P=0.75), whereas concentrations of the branched-chain fatty acids were decreased in patients with active collagenous colitis versus controls (P<0.005). In-vitro incubations demonstrated increased ratios of acetate in patients with active and quiescent collagenous colitis compared with controls (P<0.05), with a corresponding decrease in branched-chain fatty acids ratios (P<0.05). CONCLUSION: Faecal calprotectin was increased in collagenous colitis; however, increased excretion was not a universal finding limiting the use of calprotectin as an inflammatory marker in collagenous colitis. Faecal lactoferrin was almost undetectable. Luminal fermentative conditions are altered in collagenous colitis. Fermentative alterations could be secondary to changes in substrate availability and intestinal transit time.

Steroids reduce local inflammatory mediator secretion and mucosal permeability in collagenous colitis patients.

AIM: To study the effect of oral steroids upon clinical response and rectal mucosa secretion of eosinophil cationic protein (ECP), myeloperoxidase (MPO), basic fibroblast growth factor (bFGF), vascular endothelial growth factor (VEGF) and albumin in patients with collagenous colitis (CC). METHODS: A segmental perfusion technique was used to collect perfusates from rectum of CC patients once before and twice (one and four weeks) after the start of steroid treatment. Clinical data was monitored and ECP, MPO, bFGF, VEGF and albumin concentrations were analyzed by immunochemical methods in perfusates and in serum. RESULTS: Steroids reduced the number of bowel movements by more than five times within one week and all patients reported improved subjective well-being at wk 1 and 4. At the same time, the median concentrations of ECP, bFGF, VEGF and albumin in rectal perfusates decreased significantly. MPO values were above the detection limit in only 3 patients before treatment and in none during treatment. VEGF, bFGF, ECP and albumin concentrations correlated with each other with the exception of ECP and albumin. A decrease of serum ECP and VEGF concentrations was also seen even if the overtime reduction was not significant. CONCLUSION: Oral steroid treatment in CC patients induced a simultaneous reduction of bowel movements and rectal release of ECP, bFGF, VEGF and albumin, suggesting that these polypeptides and increased mucosal permeability are important components of the pathophysiology in collagenous colitis.

Small-bowel permeability in collagenous colitis.

OBJECTIVE: Collagenous colitis (CC) is a chronic inflammatory bowel disease that affects the colon. However, some patients with CC present with accompanying pathologic small-bowel manifestations such as coeliac disease, defects in bile acid absorption and histopathologic changes in small-intestinal biopsies, indicating that CC is a pan-intestinal disease. In small-intestinal disease, the intestinal barrier function may be impaired, and the permeability of the small intestine altered. The purpose of this research was to study small-bowel function in patients with CC as expressed by intestinal permeability. MATERIAL AND METHODS: Ten patients with CC and chronic diarrhoea participated in the study. Coeliac disease was excluded by small-bowel biopsy and/or serology. Intestinal permeability was assessed as urinary excretion (ratios) 2, 4 and 6 h after ingestion of 14C-labelled mannitol (14C-mannitol) and 99mTc-labelled diethylenetriamine-pentaacetic acid (99mTc-DTPA). Data were compared with the results from healthy controls. RESULTS: No difference was found between groups in urinary excretion of 14C-mannitol and 99mTc-DTPA after 2, 4 or 6 h, respectively. Likewise, no significant differences in the 99mTc-DTPA/14C-mannitol ratios between patients and controls were detected after 2 h: 0.030 (0.008-0.130) versus 0.020 (0.007-0.030), p = 0.19, after 4 h: 0.040 (0.009-0.180) versus 0.020 (0.008-0.040), p = 0.14 or after 6 h: 0.040 (0.012-0.180) versus 0.020 (0.010-0.040), p = 0.17. CONCLUSIONS: No alterations in intestinal permeability in patients with CC could be demonstrated. Impairment of the integrity of the mucosa of the small bowel and the presence of a general dysfunction of the small intestine in patients with CC seem unlikely.

Detection of inflammatory markers in stools from patients with irritable bowel syndrome and collagenous colitis.

OBJECTIVE: Irritable bowel syndrome (IBS) and collagenous colitis (CC) share chronically recurring symptoms of altered bowel habits associated with abdominal pain or discomfort. The aims of the present study were to investigate whether inflammatory markers could be detected in faeces from patients with IBS and CC, and to elucidate whether such analyses could be used as non-invasive tools to distinguish between these disorders. MATERIAL AND METHODS: Stool samples were obtained from 18 patients with CC, 46 patients with IBS and 20 healthy controls (HC). Eosinophil protein X (EPX), myeloperoxidase (MPO), tryptase, interleukin-1 beta (IL-1beta) and tumour necrosis factor alpha (TNFalpha) were measured in supernatants from processed faeces using immunoassays. RESULTS: EPX levels were enhanced in faeces from CC patients (median 3.8 microg/g (0.47-16.2)) compared to patients with IBS (0.44 microg/g (0.25-1.8)), p<0.001, and HC (0.46 microg/g (0.21-1.3)), p<0.001. In addition, MPO was increased in CC patients (11.7 microg/g (2.0-124)) compared to IBS patients (1.7 microg/g (0.81-5.2)), p<0.01, and HC (2.5 microg/g (1.1-6.3)), p<0.05. Tryptase was found in 9/18 patients with CC, 6/46 with IBS and 1/19 HC. IL-1beta was only enhanced in 2/11 CC patients and TNFalpha was not detected in any sample. CONCLUSIONS: Increased levels of EPX, MPO and tryptase were observed in stools from collagenous colitis patients, whereas the levels in IBS patients did not differ from healthy controls. Our data suggest that faecal markers could be used as part of the clinical work-up to determine which patients should be biopsied and evaluated for collagenous colitis.

Rectal mucosal nitric oxide in differentiation of inflammatory bowel disease and irritable bowel syndrome.

BACKGROUND & AIMS: Differentiating patients with functional bowel disorders from those with inflammatory bowel disease (IBD) can be difficult. Rectal luminal levels of nitric oxide (NO) are greatly increased in IBD. To further evaluate this disease marker, we compared NO in patients with irritable bowel syndrome (IBS) with those found in patients with active IBD and in healthy control subjects. METHODS: Rectal NO was measured with chemiluminescence technique by using a tonometric balloon method in 28 healthy volunteers, 39 patients with IBS, 86 with IBD (Crohn's disease and ulcerative colitis), and 12 patients with collagenous colitis. In addition, NO was measured before and after a 4-week treatment period in patients with active ulcerative colitis and repeatedly during 2 weeks in healthy volunteers. RESULTS: NO was low in healthy control subjects (median, 45; 25th-75th percentile, 34-64 parts per billion [ppb]), and variations over time were small. In IBS patients NO was slightly increased (150, 53-200 ppb; P < .001), whereas patients with active IBD or collagenous colitis had greatly increased NO levels (3475, 575-8850 ppb, and 9950, 4475-19,750 ppb, respectively; P < .001). With a cutoff level of 250 ppb, NO had a sensitivity of 95% and a specificity of 91% in discriminating between active bowel inflammation and IBS. Rectal NO correlated with disease activity in IBD and collagenous colitis and decreased markedly in IBD patients responding to anti-inflammatory treatment. CONCLUSIONS: Rectal NO is a minimally invasive and rapid tool for discriminating between active bowel inflammation and IBS and a possibly useful add-on for monitoring patients with IBD.

Atypical forms of microscopic colitis: morphological features and review of the literature.

Microscopic colitis is defined as a syndrome of chronic watery diarrhea with a chronic inflammatory cell infiltrate in the colonic mucosa but without significant abnormalities at colonoscopy. It encompasses at least two histopathologic entities (ie, collagenous and lymphocytic colitis). The recognition and characterization of microscopic colitis has markedly changed the approach to the evaluation and management of chronic diarrhea. The histologic features of collagenous and lymphocytic colitis are well known to most pathologists. By considering the clinical history and symptoms, the pathologist should be able to reach the correct diagnosis in most cases. However, the spectrum of morphologic changes associated with watery diarrhea syndrome appears to be broader than originally thought. Morphologic changes more often associated with chronic inflammatory bowel disease or even chronic ischemic or infectious colitis have been noted in patients with clinically established microscopic colitis. The data presented in this article suggest that microscopic colitis is a heterogeneous entity, which includes both classic and "atypical" forms. Problems arise when cases do not fit the usual pattern or lack some of the findings that are expected. Pathologists should be aware of the presence of atypical forms of microscopic colitis.

Activation of nuclear factor kappaB in colonic mucosa from patients with collagenous and ulcerative colitis.

BACKGROUND AND AIMS: Expression of inducible nitric oxide synthase (iNOS) is greatly upregulated in the colonic mucosa of patients with collagenous and ulcerative colitis. As the transcription factor nuclear factor kappaB (NFkappaB) is a major inducer of iNOS gene expression, we compared activation and transcriptional activity of NFkappaB in colonic mucosal biopsies from these patients. PATIENTS: Eight patients with collagenous colitis, six with relapsing ulcerative colitis, and eight with uninflamed bowel were studied. METHODS: NFkappaB DNA binding activity was assessed by electrophoretic mobility shift assay and inhibitor of NFkappaB (IkappaB) kinase (IKK) activity by immunocomplex kinase assay. In vivo recruitment of NFkappaB to the iNOS promoter was determined by chromatin immunoprecipitation analysis and transcriptional activity by NFkappaB gene expression profiling arrays. Cells showing NFkappaB activation were identified by immunohistochemistry. RESULTS: In collagenous and ulcerative colitis, as opposed to uninflamed bowel, IKKbeta activity and strong NFkappaB DNA binding gave rise to activation of identical NFkappaB subunits and recruitment of transcriptionally active p65 to the iNOS promoter. In collagenous colitis, activated NFkappaB was observed only in epithelial cells while up to 10% of lamina propria macrophages showed activation in ulcerative colitis. CONCLUSIONS: In collagenous and ulcerative colitis, colonic mucosal NFkappaB is activated and recruited to the iNOS promoter in vivo via an IKKbeta mediated pathway. As collagenous colitis is not associated with tissue injury, these data challenge the prevailing view that activation of NFkappaB per se mediates tissue injury. Our results suggest that downstream inflammatory reactions leading to tissue damage originate in lamina propria immune cells, as increased NFkappaB activity in collagenous colitis was localised solely in epithelial cells, but present also in macrophages in ulcerative colitis.