Histamine receptor 2 is required to suppress innate immune responses to bacterial ligands in patients with inflammatory bowel disease

BACKGROUND: Histamine is a key immunoregulatory mediator in immediate-type hypersensitivity reactions and chronic inflammatory responses, in particular histamine suppresses proinflammatory responses to bacterial ligands, through histamine receptor 2 (H2R). The aim of this study was to investigate the effects of histamine and H2R on bacteria-induced inflammatory responses in patients with IBD. METHODS: Peripheral blood mononuclear cells (PBMCs) were obtained from patients with Crohn's disease, patients with ulcerative colitis, and healthy controls. PBMC histamine receptor expression was evaluated by flow cytometry. Cytokine secretion following Toll-like receptor (TLR)-2, TLR-4, TLR-5, or TLR-9 stimulation in the presence or absence of histamine or famotidine (H2R antagonist) was quantified. Biopsy histamine receptor gene expression was evaluated using reverse transcription-polymerase chain reaction. The in vivo role of H2R was evaluated in the T-cell transfer murine colitis model. RESULTS: The percentage of circulating H2R monocytes was significantly reduced in patients with IBD. Histamine effectively suppressed TLR-induced cytokine secretion from healthy volunteer PBMCs but not for PBMCs from patients with IBD. Famotidine reversed this suppressive effect. H1R, H2R, and H4R gene expression was increased in inflamed gastrointestinal mucosa compared with noninflamed mucosa from the same patient and expression levels correlated with proinflammatory cytokine gene expression. Mice receiving lymphocytes from H2R donors, or treated with famotidine, displayed more severe weight loss, higher disease scores and increased numbers of mucosal IFN-γ and IL-17 T cells. CONCLUSION: Patients with IBD display dysregulated expression of histamine receptors, with diminished anti-inflammatory effects associated with H2R signaling. Deliberate manipulation of H2R signaling may suppress excessive TLR responses to bacteria within the gut

Irritable bowel syndrome-type symptoms in patients with inflammatory bowel disease: a real association or reflection of occult inflammation?

OBJECTIVES: Do gastrointestinal symptoms in patients with inflammatory bowel disease (IBD) in apparent remission reflect the coexistence of irritable bowel syndrome (IBS) or subclinical inflammation? The aims of this study were as follows: (i) to prospectively determine the prevalence of IBS symptoms in IBD patients in remission; and (ii) to determine whether IBS symptoms correlate with levels of fecal calprotectin. METHODS: Remission was defined by physician assessment: Crohn's disease (CD) activity index <or=150 and ulcerative colitis disease activity index <or=3, and serum C-reactive protein <10, while off corticosteroids or biologics. Quality of life (QOL) (by inflammatory bowel disease questionnaire), the hospital anxiety and depression scale (HAD), and fecal calprotectin were measured. RESULTS: Rome II criteria for IBS were fulfilled in 37/62 (59.7%) of CD patients and by 17/44 (38.6%) of those with ulcerative colitis (UC). However, fecal calprotectin was significantly elevated above the upper limit of normal in both IBD patient groups, indicating the presence of occult inflammation. Furthermore, calprotectin levels were significantly higher in CD and UC patients with criteria for IBS than in those without IBS-type symptoms. QOL scores were lower and HAD scores higher among UC patients with IBS symptoms in comparison to those who did not have IBS symptoms. CONCLUSIONS: IBS-like symptoms are common in patients with IBD who are thought to be in clinical remission, but abnormal calprotectin levels suggest that the mechanism in most cases is likely to be occult inflammation rather than coexistent IBS

Mycobacterium avium subsp. Paratuberculosis (MAP) as a modifying factor in Crohn's disease

BACKGROUND: Crohn's disease (CD) is a multifactorial syndrome with genetic and environmental contributions. Mycobacterium avium subspecies paratuberculosis (MAP) has been frequently isolated from mucosal tissues of patients with CD but the cellular immune response to this bacterium has been poorly described. Our aim was to examine the influence of MAP on T-cell proliferation and cytokine responses in patients with inflammatory bowel disease (IBD). METHODS: Peripheral blood mononuclear cells (PBMCs) and mesenteric lymph node cells (MLNCs) were obtained from IBD patients and non-IBD controls. PBMC T-cell proliferation in response to MAP was determined using CFSE labeling and flow cytometry. The specificity of cytokine responses to MAP was controlled by parallel exposure to Listeria monocytogenes (LM) or Salmonella typhimurium (ST). RESULTS: Coincubation of PBMCs with MAP induced significantly more T-cell proliferation (P < 0.0001) in PBMCs isolated from CD patients compared to PBMCs obtained from ulcerative colitis (UC) patients or healthy volunteers. In addition, PBMCs from CD patients secreted significantly higher (P < 0.05) levels of tumor necrosis factor-alpha (TNF-alpha; 2302 +/- 230 pg/mL) and interleukin (IL)-10 (299 +/- 48 pg/mL) in response to MAP compared to UC patients (TNF-alpha: 1219 +/- 411 pg/mL; IL-10: 125 +/- 19 pg/mL) and controls (TNF-alpha: 1447 +/- 173 pg/mL; IL-10: 127 +/- 12 pg/mL). No difference in cytokine responses was observed in response to LM or ST. MLNCs from both CD and UC patients secreted significantly more TNF-alpha and IL-8 in response to MAP compared to MLNCs from non-IBD control patients. CONCLUSIONS: Increased proliferation of T cells and an altered cytokine response suggest that prior exposure to MAP and engagement of the immune system is common in patients with CD. This does not imply causation but does support further examination of this bacterium as an environmental modifying factor