Respiratory burst of circulating polymorphonuclear leukocytes and plasma elastase levels in patients with inflammatory bowel disease in remission

Neutrophil anti-neutrophil cytoplasmic autoantibody proteins: bactericidal increasing protein, lactoferrin, cathepsin, and elastase as serological markers of inflammatory bowel and other diseases

Inflammatory bowel disease (IBD) is a chronic inflammatory disorder of the gastrointestinal tract comprising Crohn's disease and ulcerative colitis. Although the pathogenesis of the disease is not clearly defined yet, environmental, genetic and other factors contribute to the onset of the disease. Apart from the clinical and histopathological findings, several serological biomarkers are also employed to detect IBD. One of the most thoroughly studied biomarker is anti-neutrophil cytoplasmic autoantibody (ANCA). We herein provide an overview of the current knowledge on the use of ANCA and certain ANCA proteins, such as bactericidal increasing protein, lactoferrin, cathepsin G and elastase, as serological markers for IBD and other diseases.

Peripheral neutrophil functions and cell signalling in Crohn`s disease

The role of the innate immunity in the pathogenesis of Crohn's disease (CD), an inflammatory bowel disease, is a subject of increasing interest. Neutrophils (PMN) are key members of the innate immune system which migrate to sites of bacterial infection and initiate the defence against microbes by producing reactive oxygen species (ROS), before undergoing apoptosis. It is believed that impaired innate immune responses contribute to CD, but it is as yet unclear whether intrinsic defects in PMN signal transduction and corresponding function are present in patients with quiescent disease. We isolated peripheral blood PMN from CD patients in remission and healthy controls (HC), and characterised migration, bacterial uptake and killing, ROS production and cell death signalling. Whereas IL8-induced migration and signalling were normal in CD, trans-epithelial migration was significantly impaired. Uptake and killing of E. coli were normal. However, an increased ROS production was observed in CD PMN after stimulation with the bacterial peptide analogue fMLP, which was mirrored by an increased fMLP-triggered ERK and AKT signal activation. Interestingly, cleavage of caspase-3 and caspase-8 during GMCSF-induced rescue from cell-death was decreased in CD neutrophils, but a reduced survival signal emanating from STAT3 and AKT pathways was concomitantly observed, resulting in a similar percentage of end stage apoptotic PMN in CD patients and HC. In toto, these data show a disturbed signal transduction activation and functionality in peripheral blood PMN from patients with quiescent CD, which point toward an intrinsic defect in innate immunity in these patients.

p40phox expression regulates neutrophil recruitment and function during the resolution phase of intestinal inflammation

NADPH oxidase is a multisubunit complex that assembles during phagocytosis to generate reactive oxygen species. Several components of this complex have been implicated in chronic granulomatous disease and Crohn's disease, highlighting the importance of reactive oxygen species in regulating host immune response. In this study, we use genetically deficient mice to elucidate how p40(phox), one subunit of the NADPH oxidase complex, functions during intestinal inflammation. We show that p40(phox) deficiency enhances inflammation in both dextran sulfate sodium-induced and innate immune-mediated murine colitis models. This inflammation is characterized by severe colonic tissue injury, increased proinflammatory cytokines, and increased neutrophil recruitment. We demonstrate that neutrophils are essential during the recovery phase of intestinal inflammation and that p40(phox) expression is necessary for this restitution. Lastly, using an integrative bioinformatic approach, we show that p40(phox) deficiency leads to upregulation of chemokine receptor 1 and downregulation of enzymes involved in glycan modifications, including fucosyltransferases and sialyltransferases, during inflammation. We propose that p40(phox) deficiency enhances intestinal inflammation through the dysregulation of these two pathways in neutrophils.

The neutrophil respiratory burst and bacterial digestion in Crohn's disease

BACKGROUND

Neutrophils are a key part of the innate immune defence against microbes, using the respiratory burst (RB) to optimise killing and digestion. Previous studies of the neutrophil RB in Crohn's disease (CD) have yielded conflicting results.

METHODS

Superoxide production in response to phorbol-myristyl acetate (PMA) was measured in neutrophils from 100 patients with CD compared to 50 healthy controls (HCs) and 50 patients with ulcerative colitis (UC). A further 22 CD and 10 HCs were studied using f-Met-Leu-Phe (fMLP), and digestion of E. coli by neutrophils was also evaluated.

RESULTS

The mean ± SEM PMA-stimulated RB (nmol O(2)/10(6) cells/min) was 10.86 ± 0.26 in HCs, 9.76 ± 0.23 in CD (P=0.02) and 10.04 ± 0.28 in UC (P=0.09 vs HC and 0.47 vs CD). No significant effect of age, gender or medication was observed. The RB in three patients with presumed CD was found to be in the range expected in patients with inherited neutrophil disorders. Stimulation with fMLP was calcium dependent and attenuated in patients on 5-ASA. Digestion of E. coli by neutrophils was not different in HC vs CD (21.6 vs 20.53%, P=0.60).

CONCLUSION

The significant reduction in neutrophil RB in CD does not appear to result in defective bacterial digestion and is therefore unlikely play a major role in pathogenesis. Three patients in this cohort of patients with presumed idiopathic CD were found to have a profound defect of the neutrophil RB. A high index of suspicion for such patients is prudent, as their prognosis can be improved by altering or augmenting the conventional treatment regimens employed for CD.

An open-labelled study of granulocyte colony-stimulating factor in the treatment of active Crohn's disease

BACKGROUND

Immunodeficiency syndromes associated with a Crohn's-like illness suggest innate immune defects may lead to Crohn's disease. Anecdotal cases using haemopoietic colony-stimulating factors report improvement in intestinal disease associated with these syndromes.

AIM

To test the safety and efficacy of recombinant human granulocyte colony-stimulating factor in active Crohn's disease.

METHODS

In an open-labelled 12-week trial, patients with a Crohn's Disease Activity Index between 220 and 450 were treated with recombinant human granulocyte colony-stimulating factor (filgrastim, Neupogen). Concomitant immunosuppressants were prohibited except prednisone < or =20 mg/day. Patient's received recombinant human granulocyte colony-stimulating factor 300 mcg daily subcutaneously adjusted to achieve an absolute neutrophil count between 25 and 35 x 10(9)/L.

RESULTS

Twenty patients were enrolled with a mean initial Crohn's Disease Activity Index of 307 (range: 234-428). Fifteen patients (75%) completed 8 weeks; 13 patients (65%) completed 12 weeks with the mean Crohn's Disease Activity Index for patients continuing through those times of 196 (range: 36-343) and 162 (range: 20-308), respectively. At week 12, 11 patients (55%) demonstrated a decrease of at least 70 points; five (25%) achieved a sustained remission. The mean decrease was statistically significant at each assessment time-point. Three of four patients with fistulae had a positive response. Adverse effects included bone pain, mostly mild resolving with continued treatment. One patient was hospitalized with a viral-like syndrome but it is uncertain if this was treatment related.

CONCLUSION

Recombinant human granulocyte colony-stimulating factor is safe and potentially effective therapy for active Crohn's disease.

Neutrophil elastase: a determinant of endothelial damage and reperfusion injury after liver transplantation?

Reperfusion injury has been implicated in the development of primary graft dysfunction (PGD) after liver transplantation. Neutrophil migration and activation may be involved in the pathogenesis of this injury. We studied neutrophil activation and its role in the etiology of PGD by measuring neutrophil elastase by radioimmunoassay, in serial blood samples of 19 patients before, during, and for 24 hr after transplantation. In a subgroup of patients, we also measured soluble thrombomodulin at the same time points as a marker of endothelial damage. The pretransplant elastase level was significantly raised (40.13+/-4.84 ng/ml, mean+/-SEM) compared with levels of healthy controls (18.7+/-5.6 ng/ml, P<0.05). A marked increase in elastase activity followed reperfusion, with a peak at 2 hr (370+/-50.5 ng/ml, P<0.01). Thereafter, there was a decline, but elastase remained elevated at 24 hr (186+/-60.94 ng/ml). The mean increase in neutrophil elastase after reperfusion correlated significantly with markers of graft function (P<0.05) and with the mean rise in soluble thrombomodulin (P=0.042), which increased from a pretransplant level of 81.2+/-11.32 to 186+/-50.4 ng/ml, 6 hr after reperfusion (P<0.05). The results of this study indicate that marked neutrophil activation and endothelial cell damage occurs after graft reperfusion during orthotopic liver transplantation, and the degree of activation correlates with markers of graft function, which may suggest a role in the etiology of PGD.