Specificity of indium-111 granulocyte scanning and fecal excretion measurement in inflammatory bowel disease--an autoradiographic study

Flagellin hypervariable region determines symbiotic properties of commensal Escherichia coli strains

Escherichia coli represents a classical intestinal gram-negative commensal. Despite this commensalism, different E. coli strains can mediate disparate immunogenic properties in a given host. Symbiotic E. coli strains such as E. coli Nissle 1917 (EcN) are attributed beneficial properties, e.g., promotion of intestinal homeostasis. Therefore, we aimed to identify molecular features derived from symbiotic bacteria that might help to develop innovative therapeutic alternatives for the treatment of intestinal immune disorders. This study was performed using the dextran sodium sulphate (DSS)-induced colitis mouse model, which is routinely used to evaluate potential therapeutics for the treatment of Inflammatory Bowel Diseases (IBDs). We focused on the analysis of flagellin structures of different E. coli strains. EcN flagellin was found to harbor a substantially longer hypervariable region (HVR) compared to other commensal E. coli strains, and this longer HVR mediated symbiotic properties through stronger activation of Toll-like receptor (TLR)5, thereby resulting in interleukin (IL)-22–mediated protection of mice against DSS-induced colitis. Furthermore, using bone-marrow–chimeric mice (BMCM), CD11c+ cells of the colonic lamina propria (LP) were identified as the main mediators of these flagellin-induced symbiotic effects. We propose flagellin from symbiotic E. coli strains as a potential therapeutic to restore intestinal immune homeostasis, e.g., for the treatment of IBD patients.

A flagellum renders bacteria motile, but this study reveals another property important for symbiosis: the hypervariable region of Escherichia coli flagellin strongly determines activation of TLR5, mediating benefits for the host such as protection against colitis.

Proteomics and metabolomics in inflammatory bowel disease

Genome-wide studies in inflammatory bowel disease (IBD) have allowed us to understand Crohn's disease and ulcerative colitis as forms of related autoinflammatory disorders that arise from a multitude of pathogenic origins. Proteomics and metabolomics are the offspring of genomics that possess unprecedented possibilities to characterize unknown pathogenic pathways. It has been about a decade since proteomics was first applied to IBD, and 5 years for metabolomics. These techniques have yielded novel and potentially important findings, but turning these results into beneficial patient outcomes remains challenging. This review recounts the history and context of clinical IBD developments before and after proteomics and metabolomics IBD in this field, discusses the challenges in consolidating high complexity data with physiological understanding, and provides an outlook on the emerging principles that will help interface the bioanalytical laboratory with IBD prognosis.

Induction and activation of adaptive immune populations during acute and chronic phases of a murine model of experimental colitis

BACKGROUND

Dextran sodium sulphate (DSS) is commonly used to induce intestinal inflammation in rodents. Despite its continuing importance as a model system for examining IBD pathogenesis, the mucosal and systemic immune responses have not been comprehensively documented.

AIMS

The purpose of this study was to dissect functional and phenotypic changes in both immune compartments associated with acute and chronic DSS-induced colitis.

METHODS

C57BL/6 mice were exposed to 3% DSS for 6 days followed by 20 days of water, and organs (spleens, MLN and colons) were harvested during both acute and chronic phases of colitis to examine innate and adaptive cell populations.

RESULTS

As early as 1 day post DSS, significant changes in the percentage, distribution and activation status of all innate cell populations examined were noted. These striking differences continued in systemic and mucosal lymphoid tissues throughout the acute phase (days 5-12). Significantly, during the late acute and chronic phases T and B cells accumulated in the colon. In contrast, in the spleens of chronically inflamed mice T and B cells were significantly decreased whereas neutrophils, macrophages, and IL-6 and IL-17 positive cells were increased.

CONCLUSIONS

Our data provides important insights into the mucosal and systemic immune responses induced by DSS administration. Notably, we show that adaptive immune responses are induced during both acute and chronic colitis. This will facilitate a more informed and sophisticated use of this model both for investigating basic mechanisms of intestinal inflammation and for the evaluation of potential new therapeutic agents for IBD.

Advanced oxidation protein products: a novel marker of oxidative stress in ulcerative colitis

BACKGROUND/GOALS

The etiology and pathogenesis of chronic inflammatory bowel diseases are still poorly understood. Oxidative stress takes place in the pathogenesis of ulcerative colitis (UC) and advanced oxidation protein products (AOPP) are accepted as a novel marker of oxidative stress. There are no data concerning whether AOPP may be used as a simple serum marker to assess the disease activity, predict severity of the disease course in UC.

STUDY

In this study, we determine the importance of neutrophil activation and the role of oxidative stress in the pathogenesis of UC, by quantification of AOPP and total thiol levels as markers of oxidative protein damage, malondialdehyde levels as a marker of lipid peroxidation, and myeloperoxidase activity as a marker of neutrophil activation in patients with UC.

RESULTS

Serum levels of AOPP, thiol, myeloperoxidase activity, and malondialdehyde were found as increased in UC group compared with controls (P=0.004, 0.047, 0.001, and 0.001 respectively).

CONCLUSIONS

Our finding of increased levels of plasma AOPP levels supports the presence of oxidative stress and protein oxidation in UC and this marker may be used as a simple serum marker to assess disease activity, predict the severity of disease course, and perhaps response to therapy.

Increased interleukin-8 (IL-8) in rectal dialysate from patients with ulcerative colitis: evidence for a biological role for IL-8 in inflammation of the colon

OBJECTIVE

Infiltration of neutrophils and their release of toxic reactive oxygen species (ROS) in the colonic mucosa are associated with tissue damage in ulcerative colitis (UC). This neutrophil migration may be induced by chemoattractants, such as cytokines, in the colonic milieu. One such chemoattractant is interleukin-8 (IL-8), a neutrophil chemokine that is present at high concentrations in inflamed mucosa. However, the functional significance of IL-8 in neutrophil attraction and activation in UC has not been established. We hypothesized that IL-8 in the colonic lumen of patients with UC primes neutrophils, leading to their attraction and activation.

METHODS

The colonic milieu was sampled by rectal dialysis. Using a semi-permeable membrane with a molecular weight cut-off of 12 kDa, dialysis solution was placed in the rectum and allowed to equilibrate over a 4-h period with the colonic milieu of controls or of patients with UC. IL-8 concentrations were measured by ELISA. Two functions of healthy neutrophils (PMN) were measured: expression of CD11-b surface adhesion molecules (by flow cytometry), and production of ROS (by both chemiluminescence and cytochrome C reduction assays). Neutrophil functions after exposure to rectal dialysates or n-formyl-methionyl-leucyl-phenylalanine (fMLP) were assessed before and after adding anti-IL-8 antibody or the fMLP blocker BMLP.

RESULTS

IL-8 concentrations in dialysates from patients with active UC were significantly higher than in controls and correlated with disease activity. UC dialysates significantly increased ROS production and CD11-b expression by neutrophils and anti-IL-8 antibody partially (50%) inhibited these stimulatory effects of UC dialysates. Preincubation of neutrophils with UC dialysates significantly potentiated the fMLP-induced rise in ROS and anti-IL-8 antibody completely abolished this priming effect.

CONCLUSIONS

The colonic milieu, sampled by rectal dialysis, from patients with active UC can both activate and prime neutrophils in vitro. High concentrations of IL-8 in the colonic lumen of UC patients are partially responsible for the activating effects of rectal dialysates, and account for all of its priming effects. These findings provide direct evidence for a role for IL-8 in inflammatory bowel disease.

Labelling of leucocytes with technetium-99m exametazime causes in vitro upregulation of granulocyte CD11b without correlation to tissue uptake in vivo

The aims of this study were to investigate whether labelling with technetium-99m exametazime alters the expression of adhesion molecule CD11b on granulocytes and monocytes, and to study whether the expression of CD11b on unlabelled or labelled cells correlates with uptake of the labelled cells in the inflamed bowel, in the lungs or in the reticuloendothelial system. Leucocytes were obtained from 25 patients with inflammatory bowel disease who underwent leucocyte scan. The cellular expression of CD11b was analysed using flow cytometry. Labelling with 99mTc-exametazime induced an increased surface expression of CD11b on granulocytes (P<0.01), but not on monocytes. The increase in CD11b expression on granulocytes was lower than the spontaneous mobilization that occurred at 37 degrees C and correlated neither with this, nor with N-formyl-methionyl-phenylalanine induced expression of the same receptor. Basal expression of CD11b on unlabelled granulocytes, but not on monocytes, correlated with bowel and lung uptake 45 min after reinjection of labelled cells, but not with uptake on later images. No correlation was found between the CD11b expression on labelled granulocytes or monocytes and scintigraphic uptake. Our findings show that labelling with 99mTc-exametazime increases the expression of adhesion protein CD11b on granulocytes. The increase in surface expression of CD11b does not correlate with the scintigraphic uptake of labelled cells in the bowel, in the lungs or in the reticuloendothelial system.

Circulating neutrophils from patients with ulcerative colitis have a normal respiratory burst

The hallmark of ulcerative colitis is a diffuse infiltration of neutrophils from the circulation into the colonic mucosa. The underlying mechanism for neutrophil tissue infiltration is unknown. One possible hypothesis is abnormal circulating neutrophils. This hypothesis has been previously tested with conflicting results. The aim of our study was to re-evaluate circulating neutrophil function in the absence of several possible confounding factors. To this end, we measured the respiratory burst of circulating neutrophils in response to two different stimuli by chemiluminescence in patients with active and inactive ulcerative colitis being off all medications. Our results show no significant difference between ulcerative colitis patients and controls in peak chemiluminescence, area-under-the-curve and time to peak comparisons. However, 27% of patients with active ulcerative colitis had an abnormally elevated chemiluminescence to stimuli. In addition, no correlations were seen between disease activity and peak chemiluminescence. Thus circulating neutrophils in the majority of patients with ulcerative colitis do not appear to be either "primed" or hyperactive. This may suggest the presence of local colonic factors that lead to neutrophil tissue infiltration and activation.

111Indium labeling of hepatocytes for analysis of short-term biodistribution of transplanted cells

Hepatocyte transplantation is useful for ex vivo gene therapy and liver repopulation. Methods for hepatic reconstitution have recently been developed but optimization of hepatocyte transplantation systems is necessary. To develop systems for noninvasive assessment of the biodistribution of transplanted cells, we labeled hepatocytes with 111indium-oxine. Our initial studies showed that hepatocytes incorporated 111indium-oxine with an efficiency of approximately 20%. After labeling, cell viability was unchanged and 111indium was present in hepatocytes after overnight culture, as well as after intrasplenic transplantation. Transplanted cells were successfully localized by means of scintigraphic imaging. The scintigraphic patterns of cell distribution were different when hepatocytes were transplanted by means of either spleen or internal jugular vein, which deposit cells into separate vascular beds. Quantitative analysis of the biodistribution of 111indium-labeled hepatocytes indicated that within 2 hr of intrasplenic transplantation, cells were predominantly localized in liver and spleen, and occasionally in lungs. To determine whether the rate of intrasplenic cell injection influenced translocation of hepatocytes, we transplanted cells in normal rats. Despite intrasplenic cell injection at a variety of rates, organ-specific distribution of 111indium-labeled hepatocytes remained unchanged. Labeling with 111indium did not affect long-term survival of transplanted hepatocytes. These results indicate that 111indium-labeling of hepatocytes should greatly assist noninvasive analysis in the short-term of the biodistribution of transplanted hepatocytes.

Technetium-99m hexamethyl propylene amine oxime granulocyte scintigraphy in Crohn's disease: diagnostic and clinical relevance

Scintigraphy with autologous granulocytes labelled by technetium-99m hexamethyl, propylene amine oxime (99mTc-HMPAO) was performed in 103 Crohn's disease patients and 52 healthy controls. In 31 patients endoscopic and histologic activity was compared with scan activity index. In the 98 patients with a positive scan, the extent of Crohn's disease, assessed by scintigraphy, was compared with that evaluated by small bowel x ray or colonoscopy with biopsies. In 48 patients, Crohn's disease activity index, activity index, simple index, erythrocyte sedimentation rate, C-reactive protein were correlated with the scan results. In 16 patients the five parameters and scan were repeated after treatment with methyl-prednisolone (10 cases), enteral nutrition (3), and 5-acetylsalicylic acid (3). The results showed that 99mTc-HMPAO granulocyte scan had a 95% sensitivity and 100% specificity to detect active inflammation; it correctly showed an abscess or a fistula in all the 24 cases found. The correlation between histological inflammatory activity and scan activity index was highly significant (r = 0.85; p < 0.01), less significant (r = 0.65; p < 0.01) between endoscopy and scan activity index. The evaluation for the extent of Crohn's disease by scan was completely correct in the small bowel (100%) and 93% correct in the large bowel. No correlation was seen between the three clinical activity parameters and scanning; in more than 80% of the cases in remission on the basis of a clinical or laboratory index, scintigraphy remained positive. Medical treatment was effective on the clinical indices but not on the active inflammation in the ileum, whereas it led to a negative scan in 5/11 cases in the large intestine. Scintigraphy with 99mTc-HMPAO granulocyte plays an important part in Crohn's disease for the diagnosis of complications, for activity and assessment of the extent, and for the treatment results evaluation.

Influence of sulphasalazine and mesalazine on cellular and biochemical oxygen metabolite production. Effect of in vivo administration and an in vitro analysis

Oxidative damage has been implicated in the pathogenesis of inflammatory bowel disease. In the present study sulphasalazine and mesalazine (5-aminosalicylic acid) in vitro were shown to possess scavenging activity and to attenuate the production of oxygen metabolites by neutrophils. In a double-blind randomized crossover study, with five patients with inflammatory bowel disease in remission and four healthy controls, we evaluated the influence of in vivo administration of sulphasalazine and mesalazine on the neutrophil oxygen metabolite production in vitro. Apart from a small but significant increase in the neutrophil H2O2 and O2 production by sulphasalazine, in particular in controls, in vivo administration of both drugs hardly affected the oxygen metabolite-producing capacity of the cells. This observation was confirmed by in vitro preincubation of neutrophils with the drugs and subsequent oxygen metabolite production analysis. It is concluded that sulphasalazine and mesalazine do not influence the oxidative capacity of neutrophils, but scavenge and attenuate the production of oxygen metabolites when present in the immediate surroundings of the cells. Thus, protection against oxidative damage is definitely one of the modes of action of these drugs.

Indium 111-labeled granulocyte scan in the diagnosis and management of acute inflammatory bowel disease

The indium 111 granulocyte scan was used to evaluate 39 individuals known to have or suspected of having inflammatory bowel disease. Twenty-three of these individuals had positive scans and 16 had negative scans. Eighty-seven confirmatory studies, which consisted of barium radiography, endoscopy, operative findings, and histopathology, were performed in 37 of these individuals. The remaining two negative scans corroborated only by clinical course, CBC, and erythrocyte sedimentation rate. In addition, 10 follow-up scans were performed in six of the 39 patients to monitor therapy or investigate a change in symptoms. As an anatomic indicator of acute granulocytic infiltration of the intestinal lamina propria and crypts, the authors found that this scan had a 97 percent rate of sensitivity and 100 percent specificity. Specific indications for the use of the indium 111-labeled granulocyte scan are described. For the authors, in general, this test has become a vital adjunct to endoscopy and radiography in the diagnosis and management of patients with symptoms of inflammatory bowel disease.

Are activity indices helpful in assessing active intestinal inflammation in Crohn's disease?

We have investigated the correlation of 24 h and 48 h faecal Indium-111 excretion with each other and with several clinical activity indices for Crohn's disease (CD): Crohn's disease activity index (CDAI), activity index (AI), simple index (SI), Oxford score, and laboratory parameters, such as ESR, serum albumin, orosomucoid, C-reactive protein, alpha-l-antitrypsin (alpha 1-AT) faecal concentration, and alpha 1-AT clearance in 58 CD patients (37 with small bowel and 21 with colonic disease). A significant correlation was found between 24 and 48 h faecal Indium-111 excretion for small bowel (r = 0.708, p less than 0.0001) and colonic disease (r = 0.994, p less than 0.0001). The median faecal Indium-111 excretion for colonic involvement (4%; 0.15-50% median and range) was significantly (p less than 0.005) higher than that for small bowel disease (0.45%; 0.03-2.9%). No significant correlation was found between faecal Indium-111 excretion and any activity index in the patients with small bowel disease, while in the group of patients with colonic localisation only the AI showed a significant correlation (r = 0.593, p less than 0.02). Faecal Indium-111 excretion was significantly correlated with alpha 1-AT clearance (r = 0.712, p less than 0.0001) and faecal alpha 1-AT concentration (r = 0.750, p less than 0.0001) in small bowel and in colonic localisation (r = 0.530, p less than 0.02 and r = 0.444, p less than 0.05). Serum albumin was significantly correlated only in the group of patients with colonic disease (r = -0.593, p less than 0.05). The present study shows poor agreement between activity indices, serum parameters of activity and faecal Indium-111 excretion. As a good correlation was found with the alpha1-clearance, which reflects losses into the gut, these results may suggest that faecal Indium excretion does not only reflect activity of inflammation, but my relate to the extent of intestinal ulceration.

Advances in the assessment of disease activity in inflammatory bowel disease

Knowledge of the severity and extent of the inflammation in inflammatory bowel diseases provides a means of determining rational therapeutic strategies in affected patients. During the past 3 decades, several clinical, laboratory, and combined indices have been proposed for the assessment of inflammatory bowel disease; refinements in radiologic methods and the availability of endoscopy and biopsy have facilitated the accurate assessment of the extent and severity of the disease. In relapsing conditions such as inflammatory bowel disease, however, the use of such procedures is limited by the radiation exposure or the relatively invasive nature of the technique. In this article, we review the proposed methods and recent advances in assessment of patients with inflammatory bowel disease; we also discuss possible strategies at the time of diagnosis, during recurrence, and in evaluation of the efficacy of drug or dietic therapy.

Assessment of inflammatory bowel disease activity by technetium 99m phagocyte scanning

Autologous technetium 99m-labeled phagocyte scanning has been used to assess disease activity in inflammatory bowel disease in 51 consecutive patients. Strong correlations were found between the 24-h fecal excretion of isotope and the histologic score of mucosal biopsy specimens (rS = 0.84, p less than 0.001, where rS is Spearman's rank correlation coefficient), and between the 24-h fecal excretion of isotope and a clinical inflammatory bowel disease activity index based on the Crohn's disease activity index (rS = 0.87, p less than 0.001). To develop a clinically useful and objective measure of inflammatory bowel disease activity that did not require a 24-h stool collection, the intensity of bowel uptake on scanning was graded visually from 0 to 4, a ratio of count rates for the region of interest to the iliac crest reference region was calculated, and the rapidity of labeled phagocyte uptake into inflamed bowel was measured as the peak uptake time. Visual grading of disease activity on the scans was validated by comparing it with the ratio of count rates from inflamed bowel regions of interest and those from the iliac crest reference region. The ratio of count rates showed a significant correlation with the clinical disease activity index (r = 0.75, p less than 0.001). The visual scan grade also correlated well with the clinical activity index (r = 0.87, p less than 0.001). Count rates from hourly scans were also used to calculate the time of peak uptake of counts for a given region of interest. There was a strong negative correlation between this peak uptake time and the fecal excretion of isotope (rS = -0.81, p less than 0.001), a clinical activity index (r = -0.60, p less than 0.001), and the histologic score of the mucosal biopsy specimens (r = -0.84, p less than 0.001). These results indicate that the technetium 99m-labeled phagocyte scan provides an objective assessment of disease activity in inflammatory bowel disease using the visual scan grade, ratio of count rates for the region of inflamed bowel, or by the peak uptake time, thereby avoiding the problems associated with fecal collections. This scanning test may prove to be of significant value in clinical management and in the assessment of treatment response.

Diminished neutrophil function in Crohn's disease and ulcerative colitis identified by decreased oxidative metabolism and low superoxide dismutase content

Features of the neutrophil oxidative metabolism and enzyme activity in peripheral blood neutrophils were studied in 43 patients with Crohn's disease, 13 with ulcerative colitis and 33 healthy controls. The production of superoxide anion (O2-.) by phorbol-myristate-acetate stimulated neutrophils from patients with Crohn's disease and ulcerative colitis was significantly diminished compared with controls mean (SE) = 47.1 (3.6) and 38.0 (3.8) v 67.4 (7.5) nmol/10(7) cells/min, p less than or equal to 0.02, respectively, while the production of hydrogen peroxide was normal. The neutrophil content of superoxide dismutase (SOD), a cytoprotective enzyme, was also markedly diminished in Crohn's disease mean (SE) = 7.11 (0.23) ng SOD/micrograms DNA, p less than 0.05, and ulcerative colitis mean (SE) = 5.74 (0.42) compared with controls 7.84 (0.27), p less than 0.001. In contrast, the concentration of neutrophil elastase, a neutral protease, was found to be normal when compared with neutrophils from controls. The neutrophil O2-. production and the SOD concentrations were significantly and negatively correlated with the disease activity in Crohn's disease and ulcerative colitis. The results indicate diminished neutrophil function in peripheral blood of patients with Crohn's disease and ulcerative colitis as illustrated by a diminished oxidative system, which correlates with the disease activity.

Laboratory assessment of inflammatory bowel disease

Presently there are no specific laboratory tests to diagnose inflammatory bowel disease (IBD). Nonspecific tests to differentiate diarrhea due to mucosal injury from that occurring in patients with normal bowel mucosa (eg, fecal occult blood, leukocytes, etc) are not helpful. Tests to exclude infections agents are very important, since the clinical and radiological appearance of these may mimic IBD, and patients with IBD may suffer from superinfection. There are no laboratory tests which can differentiate Crohn's colitis from ulcerative colitis (UC). The tests used in the assessment and management of severely ill patients (Hgb, WBC, electrolytes, etc) are important, since abnormalities need to be corrected on an ongoing basis. The tests used to assess nutritional status are of little clinical value, since "clinical assessment" is as good as the laboratory assessment. Estimation of disease activity by tests is rarely better than the judgment of the clinician. Workup for malabsorption in Crohn's disease and the assessment of absorptive capacity of the terminal ileum are important for proper planning of management. Laboratory tests are also useful in clarifying the nature of some complications (eg, anemias and joint diseases).

Indium-111-labelled granulocyte accumulation in respiratory tract of patients with bronchiectasis

18 patients with severe bronchiectasis and persistent purulent sputum production were investigated, by the use of gamma scans, between acute exacerbations of their symptoms to determine localisation and traffic of 111In-labelled granulocytes in the lungs. Labelled granulocytes appeared in the respiratory tract of 16 patients within 24 h of their injection. Uptake occurred almost exclusively in areas demonstrated by computed tomography (CT) to be bronchiectatic. However, 111In uptake was not demonstrated in 21 of the 55 segments showing bronchiectasis on CT, and these were therefore thought to be not actively inflamed. The whole-body loss of radioactivity up to 4-7 days following injection of the labelled cells ranged from 0 to 53% and correlated with 24 h purulent sputum volume (r = 0.45, p less than 0.01) and with CT extent of moderate and severe bronchiectasis (r = 0.40, p less than 0.05), but not with overall CT extent of bronchiectasis, age, forced expiratory volume in one second, or duration of purulent sputum production in years.

Intestinal accumulation of 111In-granulocytes in patients studied because of occult infection

111In-granulocyte scintigraphy was performed on 245 patients in whom a localized infection was suspected. In 123 patients scintigraphy was positive and of these 35 (28%) had intestinal accumulations of 111In-granulocytes. Specific local causes for the intestinal uptake of radioactivity were antibiotic associated colitis (eight patients), local pyogenic bowel infection (four patients), systemic disease (two patients), bowel necrosis (two patients), colonic cancer (one patient) and Stevens-Johnson's syndrome (one patient). Nonspecific mechanisms of bowel accumulation were desquamation of labelled granulocytes (12 patients) and bleeding (two patients). In three cases the mechanism of colonic accumulation of granulocytes was not revealed. These results show that unexpected accumulations of labelled granulocytes in the gut is not a rare phenomenon and is often due to clinically significant intestinal inflammation or other disease, especially in patients who do not have signs of respiratory, pancreatic or oesophageal inflammation causing desquamated granulocytes to accumulate in the gut.