Reprogramming of monocytes by GM-CSF contributes to regulatory immune functions during intestinal inflammation.

Human and murine studies showed that GM-CSF exerts beneficial effects in intestinal inflammation. To explore whether GM-CSF mediates its effects via monocytes, we analyzed effects of GM-CSF on monocytes in vitro and assessed the immunomodulatory potential of GM-CSF-activated monocytes (GMaMs) in vivo. We used microarray technology and functional assays to characterize GMaMs in vitro and used a mouse model of colitis to study GMaM functions in vivo. GM-CSF activates monocytes to increase adherence, migration, chemotaxis, and oxidative burst in vitro, and primes monocyte response to secondary microbial stimuli. In addition, GMaMs accelerate epithelial healing in vitro. Most important, in a mouse model of experimental T cell-induced colitis, GMaMs show therapeutic activity and protect mice from colitis. This is accompanied by increased production of IL-4, IL-10, and IL-13, and decreased production of IFN-γ in lamina propria mononuclear cells in vivo. Confirming this finding, GMaMs attract T cells and shape their differentiation toward Th2 by upregulating IL-4, IL-10, and IL-13 in T cells in vitro. Beneficial effects of GM-CSF in Crohn's disease may possibly be mediated through reprogramming of monocytes to simultaneously improved bacterial clearance and induction of wound healing, as well as regulation of adaptive immunity to limit excessive inflammation.

The risk of colorectal cancer in patients with ulcerative colitis.

BACKGROUND AND AIM: Ulcerative colitis increases the risk of developing dysplasia and colitis-associated cancer (CAC). The purpose of this study was to determine the risk factors as well as protective measures for disease burden, need for colectomy and the development of CAC in ulcerative colitis (UC) patients. METHODS: A cohort of n = 434 UC patients was evaluated. Data analysis was performed by univariate and multivariate logistic regression. Odds ratios (OR) and 95 % confidence intervals (CI) were calculated, and significance was assessed by the likelihood ratio test. RESULTS: Mean patient age at UC diagnosis was 45.7 ± 15.1 years which manifested mainly as pancolitis (47 %) or left-sided colitis (45.2 %). CAC was detected in ten patients (2.3 %). UC disease duration was strongly associated with the risk of CAC (P < 0.0014); disease duration between 9 and 15 years: OR of 2.5 (95 % CI 0.2-41.1), more than 15 years: OR of 21.4 (95 % CI 2.6-173.6). The risk of developing dysplasia (low-grade intraepithelial neoplasia, LGIEN and high-grade intraepithelial neoplasia, HGIEN) or the need to undergo colectomy was also significantly related to disease duration (P = 0.006, P = 0.002, respectively). Established anti-inflammatory medication (e.g., 5-ASA, anti-TNF-α) significantly reduced the risk of both dysplasia and CAC (P = 0.02). CONCLUSIONS: Despite the use of modern therapies for UC, CAC rates remain high. In our study, risk factors included disease duration while anti-inflammatory therapies reduced the risk. Effective control of the intestinal inflammation also reduced the disease burden as indicated by decreased risk of requiring colectomy, underscoring the need for sufficient surveillance and anti-inflammatory therapies.

Immune suppression via glucocorticoid-stimulated monocytes: a novel mechanism to cope with inflammation.

Glucocorticoids (GCs) are used as first-line therapies for generalized suppression of inflammation (e.g., allergies or autoimmune diseases), but their long-term use is limited by severe side effects. Our previous work revealed that GCs induced a stable anti-inflammatory phenotype in monocytes, the GC-stimulated monocytes (GCsMs) that we exploited for targeted GC-mediated therapeutic effects. We demonstrate that GCsMs interact with T cells in suppressing proliferation, as well as cytokine release of CD8(+) and, especially, CD4(+) T cells in vitro, and that they support generation of Foxp3(+) cells. Therefore, we tested their immunosuppressive potential in CD4(+) T cell-induced colitis in vivo. We found that injection of GCsMs into mice with severe colitis abolished the inflammation and resulted in significant clinical improvement within a few days. T cells recovered from GCsM-treated mice exhibited reduced secretion of proinflammatory cytokines IFN-γ and IL-17. Furthermore, clusters of Foxp3(+) CD4(+) T cells were detectable at local sites of inflammation in the colon. Thus, GCsMs are able to modify T cell responses in vitro and in vivo, as well as to downregulate and clinically cure severe T cell-mediated colitis.

Nicotinamide treatment ameliorates the course of experimental colitis mediated by enhanced neutrophil-specific antibacterial clearance.

SCOPE: In previous studies, we could show that the B vitamin nicotinamide (NAM) enhanced antimicrobial activity of neutrophils. Here, we assessed the effects of NAM in two models of experimental colitis. METHODS AND RESULTS: Colitis was induced in C57BL/6 mice either by oral infection with Citrobacter rodentium or by DSS (dextran sodium sulphate) administration, and animals were systemically treated with NAM. Ex vivo bacterial clearance was assessed in murine and human whole blood, as well as isolated human neutrophils. In C. rodentium-induced colitis, NAM treatment resulted in markedly decreased systemic bacterial invasion, histological damage and increased fecal clearance of C. rodentium by up to 600-fold. In contrast, NAM had no effect when administered to neutrophil-depleted mice. Ex vivo stimulation of isolated human neutrophils, as well as murine and human whole blood with NAM led to increased clearance of C. rodentium and enhanced expression of antimicrobial peptides in neutrophils. Moreover, NAM treatment significantly ameliorated the course of DSS colitis, as assessed by body weight, histological damage and myeloperoxidase activity. CONCLUSION: Pharmacological application of NAM mediates beneficial effects in bacterial and chemically induced colitis. Future studies are needed to explore the clinical potential of NAM in the context of intestinal bacterial infections and human inflammatory bowel disease (IBD).

Translational 18F-FDG PET/CT imaging to monitor lesion activity in intestinal inflammation.

UNLABELLED: In patients with inflammatory bowel disease (IBD) and in murine IBD models, mucosal disease activity is routinely assessed by endoscopy and histologic evaluation. This information is valuable for monitoring treatment response, with mucosal healing being a major treatment goal. The aim of this study was to evaluate the translational potential of noninvasive (18)F-FDG PET/CT for the assessment of mucosal damage in murine dextran sodium sulfate (DSS) colitis and human IBD. METHODS: After induction of DSS colitis, (18)F-FDG uptake was serially assessed from colonic volumes of interest defined on PET/CT scans and intraindividually correlated to histologic findings and to infiltrating cell types. In addition, (18)F-FDG PET/CT scans of 25 Crohn disease patients were analyzed, and colonic (18)F-FDG uptake was correlated to endoscopically assessed damage. RESULTS: At days 4 and 7 after DSS induction, colonic (18)F-FDG uptake was significantly increased, with a distinct peak in the medial colon. (18)F-FDG uptake strongly correlated with histologic epithelial damage. Additionally, (18)F-FDG uptake increased in the bone marrow in the course of the disease, correlating with an increase in intestinal (18)F-FDG uptake. Histology and fluorescence-activated cell sorting analysis of the bone marrow of DSS mice revealed an increased number of immature neutrophils, whereas mucosal polymerase chain reaction suggested a correlation of (18)F-FDG uptake to T cell infiltration. In accordance with the results of (18)F-FDG PET/CT in DSS colitis, an increased (18)F-FDG uptake was found in 87% of deep mucosal ulcerations in IBD patients, whereas mild endoscopic lesions were detected only by (18)F-FDG PET/CT in about 50% of patients assessed. CONCLUSION: (18)F-FDG PET/CT is a noninvasive method for evaluation of both experimental colitis and Crohn disease patients and thereby offers promising translational potential.

Contrast-enhanced harmonic endoscopic ultrasound is able to discriminate benign submucosal lesions from gastrointestinal stromal tumors.

BACKGROUND: Although endoscopic ultrasound (EUS) has improved the diagnostic of potential malignancies, gastric lesions with suspicion of gastrointestinal stromal tumors (GIST) or benign lesions like lipoma or leiomyoma can often not be accurately differentiated by EUS, therefore, requiring tissue sampling with the risk of bleeding complications especially in GIST. As with the newest generation of EUS machines, contrast-enhanced harmonic endoscopic ultrasound (CEH-EUS) has become a new option to determine perfusion characteristics. The aim of this analysis was to evaluate whether CEH-EUS may help to discriminate various submucosal lesions. METHODS: Data sets of 17 patients with suspicious gastric or esophageal lesions, who were investigated with CEH-EUS were analyzed. Perfusion characteristics were classified by the investigator immediately and statistically analyzed after investigation. Samples from EUS-fine needle aspirates, biopsy samples after needle cut or surgical specimen served as gold standard. RESULTS: CEH-EUS showed nine lesions with reduced contrast enhancement (maximum intensity 6.2 ± 1.9 db) and eight lesions with hyperenhancement (47.3 ± 11.6 db). The latter eight lesions were all histologically identified as GIST, while the nine hypoenhanced lesions emerged to be four lipoma and five leiomyoma. Statistical analysis corresponded with initial perfusion classification in all cases. CONCLUSION: This is the first study showing that CEH-EUS can discriminate GIST from benign lesions with good accuracy. In the future, CEH-EUS-guided discrimination may lead to individualized diagnostic and therapeutic strategies in handling submucosal lesions.

Cytomegalovirus (CMV)-Specific Perforin and Granzyme B ELISPOT Assays Detect Reactivation of CMV Infection in Inflammatory Bowel Disease.

The role of cytomegalovirus (CMV) infection in the pathogenesis and exacerbation of Inflammatory Bowel Disease (IBD) has been unresolved. Typically, the CMV genome remains dormant in infected cells, but a breakdown of immune surveillance can lead to re-activation of viral replication in the gut mucosa, which is not necessarily associated with viremia or changes in antibody titers. We hypothesized that the detection of CMV-specific CD8 effector T cells should permit the distinction between dormant and active CMV infection. As CD8 effector T cells, unlike memory CD8 T cells, have perforin (PFN) and granzyme B (GzB) preformed in their cytoplasmic granules, we employed single cell resolution ELISPOT assays to measure the CMV antigen-triggered release of these molecules by CD8 T cells isolated from subjects with IBD, and age-matched healthy controls. The frequencies of CMV-specific (GzB) and PFN-producing CD8 T cells were increased in IBD patients compared to healthy controls. Furthermore, the increased CMV reactivity was associated with active IBD disease and with longer disease duration. Notably, PCR on serum frequently failed to detect CMV DNA during flares. The data show that during active IBD there is a flare of CD8 T cell activity against CMV in a substantial proportion of IBD patients, suggesting CMV reactivation that serum PCR does not detect. While it remains open whether CMV reactivation is a cause or consequence of IBD, our data suggest that monitoring CMV antigen-specific effector CD8 T cells with GzB and PFN ELISPOT analysis can provide novel insights into the role of CMV infection in IBD. Additionally, our data have implications for the fields of transplantation, HIV, cancer, and autoimmune diseases, in all of which patient care critically depends on sensitive and reliable detection of a reactivation of CMV infection.

Melanocortin-derived tripeptide KPV has anti-inflammatory potential in murine models of inflammatory bowel disease.

BACKGROUND: Despite some progress in recent years, the options for treating inflammatory bowel disease (IBD) are still dissatisfying, and surgery rates are still high. The anti-inflammatory effects of melanocortin peptides such as alpha-melanocyte-stimulating hormone (alpha-MSH) have been described recently in, for example, dextran sodium sulfate (DSS) colitis in mice. The aim of this study was to investigate the therapeutic potential of the melanocortin-derived tripeptide alpha-MSH(11-13) (KPV) and its mode of action in 2 models of intestinal inflammation. METHODS: The anti-inflammatory activity of KPV was analyzed in 2 well-described models of IBD: DSS colitis, and CD45RB(hi) transfer colitis. Furthermore, animals expressing a nonfunctional melanocortin-1 receptor (MC1Re/e) received DSS for induction of colitis and were treated with KPV. The course of inflammation was monitored by weight loss and histological changes in the colon as well as by myeloperoxidase (MPO) activity. RESULTS: In the DSS-colitis model, treatment with KPV led to earlier recovery and significantly stronger regain of body weight. Histologically, inflammatory infiltrates were significantly reduced in KPV-treated mice, which was confirmed by the significant reduction of MPO activity in colonic tissue after KPV treatment. Supporting these findings, KPV treatment of transfer colitis led to recovery, regain of body weight, and reduced inflammatory changes histologically. In MC1Re/e mice, KPV treatment rescued all animals in the treatment group from death during DSS colitis. CONCLUSIONS: The melanocortin-derived tripeptide KPV showed significant anti-inflammatory effects in 2 murine models of colitis. These effects seem to be at least partially independent of MC1R signaling. In conclusion, our data suggest KPV as an interesting therapeutic option for the treatment of IBD.