Function of exudative neutrophilic granulocytes in patients with Crohn's disease or ulcerative colitis

Role of CD34 in inflammatory bowel disease

Inflammatory bowel disease (IBD) is caused by a variety of pathogenic factors, including chronic recurrent inflammation of the ileum, rectum, and colon. Immune cells and adhesion molecules play an important role in the course of the disease, which is actually an autoimmune disease. During IBD, CD34 is involved in mediating the migration of a variety of immune cells (neutrophils, eosinophils, and mast cells) to the inflammatory site, and its interaction with various adhesion molecules is involved in the occurrence and development of IBD. Although the function of CD34 as a partial cell marker is well known, little is known on its role in IBD. Therefore, this article describes the structure and biological function of CD34, as well as on its potential mechanism in the development of IBD.

Changes in leukocytes and CRP in different stages of major depression

Background

We recently reported increased levels of neutrophils, monocytes and C-reactive protein (CRP) correlated with symptom severity in acute schizophrenia. Here, we investigated if a similar pattern of innate immune system activation occurs in major depression (MD).

Methods

We assessed differential blood counts, CRP, depression symptoms (HAMD-21) and psychosocial functioning (GAF) in controls (n = 129) and patients with first (FEMD: n = 82) or recurrent (RMD: n = 47) disease episodes of MD at baseline (T0; hospital admission) and after 6-weeks treatment (T6).

Results

Considering smoking, BMI and gender as covariates, neutrophils (FEMD: p = 0.034, RMD: p = 0.034) and CRP (FEMD: p < 0.001, RMD: p = 0.021) were higher, and eosinophils (FEMD: p = 0.005, RMD: p = 0.004) lower in patients versus controls at T0. Baseline lymphocyte counts were elevated in RMD (p = 0.003) but not FEMD. Results were confirmed by analyses of nonsmokers. At follow-up, eosinophils rose significantly in FEMD (p = 0.011) but no significant changes were observed in RMD. Improvement in HAMD-21 correlated with T0–T6 changes of neutrophil counts in FEMD (r = 0.364, p = 0.024). Compared with our previous schizophrenia study, raised baseline neutrophil and reduced eosinophil counts in MD had smaller effect sizes and treatment had a weaker association with T0-T6 changes in neutrophils. In addition, lymphocytes were elevated at T0 in recurrent MD but not in schizophrenia patients.

Conclusions

These findings suggest that innate immunity may be involved in early stages of MD, and adaptive immunity may be involved in chronic disease. Thus, further studies may lead to new disease stage-dependent MD treatment strategies targeting different aspects of immune system activation.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-022-02429-7.

Dichotomous roles of neutrophils in modulating pathogenic and repair processes of inflammatory bowel diseases

Neutrophils are considered as complex innate immune cells and play a critical role in maintaining intestinal mucosal homeostasis. They exert robust pro-inflammatory effects and recruit other immune cells in the acute phase of pathogen infection and intestinal inflammation, but paradoxically, they also limit exogenous microbial invasion and facilitate mucosal restoration. Hyperactivation or dysfunction of neutrophils results in abnormal immune responses, leading to multiple autoimmune and inflammatory diseases including systemic lupus erythematosus, rheumatoid arthritis, and inflammatory bowel diseases (IBD). As a refractory intestinal inflammatory disease, the pathogenesis and progression of IBD are associated with complicated immune response processes in which neutrophils are profoundly involved. However, the consensus on potential roles of neutrophils in modulating pathogenic and repair processes of IBD remains not fully understood. Accumulated infiltrating neutrophils cross the epithelial barrier and contribute to microbial dysbiosis, aggravated intestinal architectural damage, compromised resolution of intestinal inflammation and increased risk of thrombosis during IBD. Paradoxically, activated neutrophils are also associated with effective elimination of invaded microbiota, promoted angiogenesis and tissue restoration of gut mucosa in IBD. Here, we discuss the beneficial and detrimental roles of neutrophils in the onset and resolution of intestinal mucosal inflammation, hoping to provide a precise overview of neutrophil functions in the pathogenesis of IBD.

The role of neutrophils during intestinal inflammation

Polymorphonuclear leukocytes or neutrophils play a critical role in the maintenance of intestinal homeostasis. They have elegant defense mechanisms to eliminate microbes that have translocated across a single layer of mucosal epithelial cells that form a critical barrier between the gut lumen and the underlying tissue. During the inflammatory response, neutrophils also contribute to the recruitment of other immune cells and facilitate mucosal healing by releasing mediators necessary for the resolution of inflammation. Although the above responses are clearly beneficial, excessive recruitment and accumulation of activated neutrophils in the intestine under pathological conditions such as inflammatory bowel disease is associated with mucosal injury and debilitating disease symptoms. Thus, depending on the circumstances, neutrophils can be viewed as either good or bad. In this article, we summarize the beneficial and deleterious roles of neutrophils in the intestine during health and disease and provide an overview of what is known about neutrophil function in the gut.

New treatment options in the management of IBD - focus on colony stimulating factors

Inflammatory bowel disease (IBD) is characterized by inflammation of the gastrointestinal tract, typically with a relapsing and remitting clinical course. The intestinal inflammation in IBD is controlled by a complex interplay of innate and adaptive immune mechanisms. Innate immunity comprises a set of distinct elements, which includes circulating cells such as neutrophils, monocytes, and resident intestinal immune cells (dendritic and Paneth cells), as well as intestinal epithelium and cellular products, including antimicrobial peptides such as defensins and cathelicidins. Different components of innate immunity in IBD have been suggested to be defective or impaired. The human granulocyte-macrophage colony-stimulating factor (GM-CSF) and the human granulocyte colony-stimulating factor (G-CSF) have emerged as potential tools for the modulation of intestinal inflammation and repair. The greatest evidence supporting the use of colony-stimulating factors in intestinal inflammation comes from studies conducted in active Crohn’s disease (CD) patients treated with sargramostim and filgrastim, but evidence for its recommendation as treatment remains weak, as the majority of studies are open label, nonrandomized, and with a small number of patients.

Growth factors as treatment for inflammatory bowel disease: a concise review of the evidence toward their potential clinical utility

In the process of inflammation and repair of the intestinal mucosa in inflammatory bowel disease (IBD), there occurs a complex and an unknown interplay of innate and adaptive immune mechanisms. This interaction of factors may explain why IBD is characterized by a relapsing and remitting clinical course. Different components of innate immunity, hormones and interleukins in IBD have been suggested to be impaired. The growth hormone, epidermal growth factor, keratinocyte growth factor and colony-stimulating factors have emerged as potential tools for the modulation of intestinal inflammation and repair. Despite promising results of initial studies, the evidence that justify treatment of patients in clinical practice is not enough as some of the trials are nonrandomized or included a small number of patients. In this concise review, we provide a summary of the most recent and relevant evidence regarding the potential therapeutic effects of growth factors in IBD.

Phlebotomine salivas inhibit immune inflammation-induced neutrophil migration via an autocrine DC-derived PGE2/IL-10 sequential pathway

In the present study, we investigated whether saliva from Phlebotomus papatasi and Phlebotomus duboscqi inhibited antigen-induced neutrophil migration and the mechanisms involved in these effects. The pretreatment of immunized mice with salivary gland extracts (SGE) of both phlebotomines inhibited OVA challenge-induced neutrophil migration and release of the neutrophil chemotactic mediators, MIP-1alpha, TNF-alpha, and leukotriene B4 (LTB4). Furthermore, SGE treatment enhanced the production of anti-inflammatory mediators, IL-10 and PGE2. SGE treatments failed to inhibit neutrophil migration and MIP-1alpha and LTB4 production in IL-10-/- mice, also failing in mice treated with nonselective (indomethacin) or selective (rofecoxibe) cyclooxygenase (COX) inhibitors. COX inhibition resulted in diminished SGE-induced IL-10 production, and PGE2 release triggered by SGE remained increased in IL-10-/- mice, suggesting that prostanoids are acting through an IL-10-dependent mechanism. SGE treatments in vivo reduced the OVA-induced lymphoproliferation of spleen-derived cells. Further, the in vitro incubation of bone marrow-derived dendritic cells (DC) with SGE inhibited the proliferation of CD4+T cells from OVA-immunized mice, which was reversed by indomethacin and anti-IL-10 antibody treatments. Supporting these results, SGE induced the production of PGE2 and IL-10 by DC, which were blocked by COX inhibition. These effects were associated with the reduction of DC-membrane expression of MHC-II and CD86 by SGE treatment. Altogether, the results showed that Phlebotomine saliva inhibits immune inflammation-induced neutrophil migration by an autocrine DC sequential production of PGE2/IL-10, suggesting that the saliva constituents might be promising therapeutic molecules to target immune inflammatory diseases.

Crohn’s disease: Innate immunodeficiency?

In the past, Crohn’s disease (CD) has been understood primarily as an immunologic disorder characterized by an abnormal T-cell response. Recent in vitro and in vivo data suggests that CD may instead be precipitated by innate immune dysfunction resulting from a combination of genetic and environmental factors. Some reports have demonstrated a defective immune response in a variety of other cellular components, including neutrophils, monocytes and dendritic cells. Recent studies of granulocyte-macrophage colony-stimulating factor (GM-CSF) in CD, aiming to stimulate the innate immune system with the conception that an innate immune defect underlies the development of the disease, have been demonstrated a clinical benefit and reinforce this evolving understanding of the disease.

Impaired neutrophil chemotaxis in Crohn's disease relates to reduced production of chemokines and can be augmented by granulocyte-colony stimulating factor

BACKGROUND

Defective neutrophil recruitment has been described as a primary pathogenic abnormality in Crohn's disease. Cantharidin-induced blisters provide a novel investigative tool to assess cellular influx and inflammatory mediator production during acute inflammation and allows the effects of therapy on these parameters to be measured.

AIMS

To determine whether reduced neutrophil tissue penetration in Crohn's disease relates to impaired production of inflammatory mediators, and whether it can be reversed by granulocyte-colony stimulating factor (G-CSF).

METHODS

Neutrophil and monocyte/macrophage populations and inflammatory mediators were measured in cantharidin blisters at 24 h. Neutrophil chemotaxis was assessed in vitro using blister fluid as the chemoattractant. The effect of s.c. G-CSF on blister phenotype was determined.

RESULTS

Significantly fewer neutrophils migrated into blisters in Crohn's patients. The production of neutrophil chemokines, but not other inflammatory mediators, was reduced. This significantly correlated with reduced chemotaxis in vitro. Differences were unrelated to caspase-recruitment domain 15 genotype. G-CSF significantly increased blister neutrophil concentrations in control subjects and Crohn's patients.

CONCLUSIONS

Reduced neutrophil migration during acute inflammation in Crohn's disease is associated with impaired production of appropriate chemoattractants. G-CSF therapy increases neutrophil tissue migration, which may partially account for its observed therapeutic effect.

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 migration in inflammation: nitric oxide inhibits rolling, adhesion and induces apoptosis

There is controversy in the literature over whether nitric oxide (NO) released during the inflammatory process has a pro- or inhibitory effect on neutrophil migration. The aim of the present investigation was to clarify this situation. Treatment of rats with non-selective, NG-nitro-L-arginine (nitro), or selective inducible NO synthase (iNOS), aminoguanidine (amino) inhibitors enhanced neutrophil migration 6h after the administration of low, but not high, doses of carrageenan (Cg) or Escherichia coli endotoxin (LPS). The neutrophil migration induced by N-formyl-methionyl-leucyl-phenylalanine (fMLP) was also enhanced by nitro or amino treatments. The enhancement of Cg-induced neutrophil migration by NOS inhibitor treatments was reversed by co-treatment with L-arginine, suggesting an involvement of the L-arginine/NOS pathway in the process. The administration of Cg in iNOS deficient (iNOS(-/-)) mice also enhanced the neutrophil migration compared with wild type mice. This enhancement was markedly potentiated by treatment of iNOS(-/-) mice with nitro. Investigating the mechanisms by which NOS inhibitors enhanced the neutrophil migration, it was observed that they promoted an increase in Cg-induced rolling and adhesion of leukocytes to endothelium and blocked the apoptosis of emigrated neutrophils. Similar results were observed in iNOS(-/-) mice, in which these mechanisms were potentiated and reverted by nitro and L-arginine treatments, respectively. In conclusion, these results suggest that during inflammation, NO released by either constitutive NOS (cNOS) or iNOS down-modulates the neutrophil migration. This NO effect seems to be a consequence of decreased rolling and adhesion of the neutrophils on endothelium and also the induction of apoptosis in migrated neutrophils.

Tumour necrosis factor-α mediates neutrophil migration to the knee synovial cavity during immune inflammation

Tumour necrosis factor (TNF)-alpha, interleukin-1beta, interleukin-8 and leukotriene B4 have an important role on neutrophil recruitment during immune-inflammation. Here we evaluated the participation of several inflammatory mediators on ovalbumin-induced neutrophil recruitment in the knee articular space of immunized rats. Ovalbumin administration in immunized, but not in control, rats induced a dose- and time-dependent neutrophil accumulation, which was inhibited by dexamethasone, pentoxifylline or thalidomide, but not by selective inhibitors of nitric oxide (nitro-L-arginine), platelet-activating factor (BN50730 or UK74505), prostaglandins (indomethacin), histamine (meclisine) or leukotriene B4 (MK 886 and CP105,696). Anti-TNF-alpha antiserum, but not anti-interleukin-1beta or anti-CINC-1 (cytokine-induced neutrophil chemoattractant 1) antisera, impaired ovalbumin-induced neutrophil accumulation. High amounts of TNF-alpha were detected in the exudates, which was inhibited by dexamethasone, pentoxifylline and thalidomide. These results suggest a specific role for TNF-alpha in this model, and the ability of pentoxifylline and thalidomide to inhibit both neutrophil influx and TNF-alpha release may have therapeutic implications in arthritis.

Leukocyte elastase induces epithelial apoptosis: role of mitochondial permeability changes and Akt

During acute inflammation, neutrophil-mediated injury to epithelium may lead to disruption of epithelial function, including the induction of epithelial apoptosis. Herein, we report the effects of neutrophil transmigration and of purified leukocyte elastase on epithelial cell survival. Neutrophil transmigration induced apoptosis of epithelial cells [control monolayers: 5 +/- 1 cells/25 high-power fields (HPF) vs. neutrophil-treated monolayers: 29 +/- 10 cells/HPF, P < 0.05, n = 3 as determined by terminal deoxynucleotidyl transferase dUTP nick-end labeling assay] as did low concentrations (0.1 U/ml) of purified leukocyte elastase (control monolayers: 6.4 +/- 2.5% apoptotic vs. elastase: 26.2 +/- 2.9% apoptotic, P < 0.05, as determined by cytokeratin 18 cleavage). Treatment with elastase resulted in decreased mitochondrial membrane potential, release of cytochrome c to the cytosol, and cleavage of caspases-9 and -3 as determined by Western blot analysis, implicating altered mitochondrial membrane permeability as a primary mechanism for elastase-induced apoptosis. Additionally, incubation of epithelial cells with leukocyte elastase resulted in an early increase followed by a decrease in the phosphorylation of epithelial Akt, a serine/threonine kinase important in cell survival. Inhibition of epithelial Akt before elastase treatment potentiated epithelial cell apoptosis, suggesting that the initial activation of Akt represents a protective response by the epithelial cells to the proapoptotic effects of leukocyte elastase. Taken together, these observations suggest that epithelial cells exhibit a dual response to cellular stress imposed by leukocyte elastase with a proapoptotic response mediated via early alterations in mitochondrial membrane permeability countered by activation of the survival pathway involving Akt.

Subclinical intestinal inflammation: an inherited abnormality in Crohn's disease relatives?

BACKGROUND & AIMS

One approach to unraveling the genetics of complex inherited disease, such as Crohn's disease, is to search for subclinical disease markers among unaffected family members. We assessed the possible presence, prevalence, and inheritance pattern of subclinical intestinal inflammation in apparently healthy relatives of patients with Crohn's disease.

METHODS

A total of 49 patients with Crohn's disease, 16 spouses, and 151 (58%) of 260 available first-degree relatives underwent a test for intestinal inflammation (fecal calprotectin concentration). The mode of inheritance was assessed from 36 index patients (by variance component analysis) when more than 50% of relatives were studied.

RESULTS

Fecal calprotectin concentrations in patients with Crohn's disease (47 mg/L; confidence interval [CI], 27-95 mg/L) and relatives (11 mg/L; CI, 9-14 mg/L) differed significantly (P < 0.0001) from controls (4 mg/L; CI, 3-5 mg/L), whereas that of the spouses did not (4 mg/L; CI, 3-6 mg/L; P > 0.5). Fecal calprotectin concentration was increased in 49% of all relatives studied. The increased fecal calprotectin concentration among the relatives of the 36 index patients had an inheritance pattern that was most consistent with an additive inheritance pattern.

CONCLUSIONS

There is a high prevalence of subclinical intestinal inflammation in first-degree relatives of patients with Crohn's disease that conforms best to an additive inheritance pattern. The genetic basis for this abnormality may represent a risk factor for Crohn's disease.

The role of ATP-sensitive potassium channels in neutrophil migration and plasma exudation

Neutrophil activation and migration during an inflammatory response is preceded or accompanied by plasma membrane electrical changes. Besides changes in calcium currents, neutrophils have a high permeability to potassium, mainly through potassium channels. However, the significance of potassium channels in neutrophil physiology is still unclear. Here, we show that the treatment of rats with the ATP-sensitive potassium channel blocker glibenclamide (4, 20, or 40 micromol/kg) dose dependently decreased carrageenan-, N-formyl-methionyl-leucyl-phenylalanine (fMLP)-, and lipopolysaccharide-induced neutrophil influx and fluid leakage into the interpleural space. On the other hand, minoxidil (an ATP-sensitive potassium channel opener; 25, 50, and 100 micromol/kg) increased both neutrophil influx and fluid leakage induced by a submaximal dose of carrageenan. In addition, in vitro human neutrophil chemotaxis induced by leukotriene B4 or fMLP (both 1 microM) was fully blocked by glibenclamide (10, 30, and 100 microM) or tetraethylammonium (a nonselective potassium channel blocker; 1, 3, and 10 mM). Thus, our results disclose the possibility that ATP-sensitive potassium channels may have a role in neutrophil migration and chemotaxis and plasma exudation in the inflammatory response.

Protein-tyrosine phosphatase MEG2 is expressed by human neutrophils. Localization to the phagosome and activation by polyphosphoinositides

Signaling pathways involving reversible tyrosine phosphorylation are essential for neutrophil antimicrobial responses. Using reverse transcriptase PCR, expression of the protein-tyrosine phosphatase MEG2 by peripheral neutrophilic polymorphonuclear leukocytes (PMN) was identified. Polyclonal antibodies against MEG2 were developed that confirmed expression of MEG2 protein by PMN. Through a combination of immunofluorescence and cell fractionation followed by immunoblotting, we determined that MEG2 is predominantly cytosolic with components present in secondary and tertiary granules and secretory vesicles. MEG2 activity, as determined by immunoprecipitation and in vitro phosphatase assays, is inhibited after exposure of cells to the particulate stimulant opsonized zymosan or to phorbol 12-myristate 13-acetate but largely unaffected by the chemoattractant N-formyl-methionyl-leucyl-phenyalanine. Studies using bacterially expressed glutathione S-transferase MEG2 fusion protein indicate that cysteine 515 is essential for catalytic activity, whereas the noncatalytic (N-terminal) domain of MEG2 negatively regulates the enzymatic activity of the C-terminal phosphatase domain. The activity of MEG2 is enhanced by specific polyphosphoinositides with the order of potency being phosphatidylinositol (PI) 4,5-diphosphate > PI 3,4,5-triphosphate > PI 4-phosphate. MEG2 associates at an early stage with nascent phagosomes. Taken together, our results indicate that MEG2 is a polyphosphoinositide-activated tyrosine phosphatase that may be involved in signaling events regulating phagocytosis, an essential antimicrobial function in the innate immune response.

Tumour necrosis factor-alpha and leukotriene B(4) mediate the neutrophil migration in immune inflammation

1. We investigated the mediators responsible for neutrophil migration induced by ovalbumin (OVA) in immunized mice and the mechanisms involved in their release. 2. OVA administration promoted dose- and time-dependent neutrophil migration in immunized, but not in non-immunized mice, which was mediated by leukotriene B(4) (LTB(4)) and tumour necrosis factor (TNF)alpha, since it was inhibited by LTB(4) synthesis inhibitor (MK 886) or by LTB(4) receptor antagonist (CP 105,696), by dexamethasone and by antiserum to TNFalpha (82, 85, 63 and 87%, respectively). Confirming TNFalpha involvement, OVA challenge in immunized p55 TNF receptor deficient mice (p55(-/-)) did not promote neutrophil migration (control: 2.90 +/- 0.68; p55(-/-): 0.92+/-0.23 x 10(6) neutrophils cavity(-1)). 3. OVA-stimulated peritoneal cells from immunized mice released a neutrophil chemotactic factor which mimicked, in naive mice, neutrophil migration induced by OVA. 4. Supernatant chemotactic activity is due to TNFalpha and LTB(4), since its release was inhibited by MK 886 (93%) and dexamethasone (90%), and significant amounts of these mediators were detected. 5. TNFalpha and LTB(4) released by OVA challenge seem to act through a sequential mechanism, since MK 886 inhibited (88%) neutrophil migration induced by TNFalpha. Moreover, peritoneal cells stimulated with TNFalpha released LTB(4). 6. CD(4)(+) T cells are responsible for TNFalpha release, because the depletion of this subset prevented the release of TNFalpha (control: 400 +/- 25; immunized: 670 +/- 40; CD(4)(+) depleted: 435 +/- 18 pg ml(-1)). 7. In conclusion, neutrophil migration induced by OVA depends on TNFalpha released by CD(4)(+) cells, which acts through an LTB(4)-dependent mechanism.

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.

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

The activation of circulating polymorphonuclear leukocytes was determined in terms of superoxide radical generation and granulocyte elastase release in untreated patients with ulcerative colitis (N = 10) and Crohn's disease (N = 9) in remission and in control subjects (N = 10). Superoxide radical generation was determined by monitoring spectrophotometrically the reduction of ferricytochrome, after stimulation of cells with phorbol myristate acetate. Plasma elastase concentration was measured by a solid-phase enzyme immunoassay technique as the complex with alpha-1-proteinase inhibitor. Superoxide formation by polymorphonuclear leukocytes from patients with ulcerative colitis and Crohn's disease was significantly lower compared with controls [median (range) nmol/min/mg protein: Crohn's disease 7.8 (7.1-9.6); ulcerative colitis 8.25 (7.4-10.3); controls 14.7 (13.6-15.8)] (P < 0.001), while no difference was found between the two groups of patients. In contrast plasma elastase levels in patients with ulcerative colitis and Crohn's disease were similar to that of controls. This defective respiratory burst of polymorphonuclear leukocytes in patients with inflammatory bowel disease in remission, in absence of an altered degranulation, could represent an important factor for the pathogenesis of these diseases.

Endothelial serpins--protectors of the vasculature?

Vascular damage, initiated by host inflammatory cells, is a component of the pathophysiology of many acute and chronic inflammatory disorders. Neutrophil-mediated tissue damage is mediated primarily by proteinases, particularly elastase and cathepsin G. In this study we have identified endothelial binding of two key serine proteinase inhibitors (serpins), alpha 1-antitrypsin, the inhibitor of elastase, and alpha 1-antichymotrypsin, the inhibitor of cathepsin G. These serpins are shed from the endothelium into the supernatant when neutrophils adherent to the endothelium are activated. Endothelium activated by lipopolysaccharide (LPS) augments this process. Serpin-proteinase complexes activate neutrophils and induce further cytokine release, thereby amplifying inflammatory processes. Strategies aimed at preventing endothelial serpin depletion may help minimize vascular damage during inflammation.

Induction of lymphocyte proliferation by antigen-pulsed human neutrophils

We have investigated whether purified antigen-pulsed human neutrophils can induce a proliferative response in purified resting blood lymphocytes. Neutrophils were pulsed with soluble tetanus toxoid (dose range 25-250 Lf/ml) and co-cultured with autologous lymphocytes that had been depleted of MHC class II expressing cells. The antigen-pulsed neutrophils induced an increase of lymphocyte proliferation which was dependent on the antigen dose and the neutrophil/lymphocyte ratios. Neutrophils were less potent than autologous monocytes in stimulating lymphocyte proliferation. Blocking with a monoclonal antibody to a common determinant of the human MHC class II complex failed to reduce the lymphoproliferative effects and allogenic antigen-pulsed neutrophils were also able to elicit lymphocyte proliferation similar to autologous neutrophils. We conclude that antigen-pulsed neutrophils are able to induce lymphocyte proliferation in a non-MHC-restricted fashion.

Increased neutrophil receptors for and response to the proinflammatory bacterial peptide formyl-methionyl-leucyl-phenylalanine in Crohn's disease

Neutrophils have an important role in mediating tissue injury in inflammatory bowel disease. The proinflammatory peptide formyl-methionyl-leucyl-phenylalanine (FMLP), which is produced by intestinal bacteria, is a potent chemotactic factor for human neutrophils and has been used experimentally to induce acute colitis in animal models. Its action involves specific receptors on the surface of the neutrophil. Increased mucosal permeability, which has been described in Crohn's disease, might contribute to the pathogenesis of the intestinal lesions in this disease by means of increased absorption of FMLP and other gut-derived bacterial products. To evaluate the interaction between FMLP and neutrophils in patients with inflammatory bowel disease, we have studied the binding characteristics and responsiveness of circulating neutrophils to this peptide. Neutrophils from patients with Crohn's disease but not those with ulcerative colitis were found to have significantly increased numbers of receptors for FMLP with similar affinity constants. This was associated with a significantly increased functional response to FMLP in chemiluminescence assays. Differences in neutrophils between Crohn's disease and ulcerative colitis are probably not intrinsic to the neutrophil but reflect their conditioning by the different inflammatory milieu of these diseases.

Phase II trial of copper zinc superoxide dismutase (CuZnSOD) in treatment of Crohn's disease

Bovine CuZnSOD was used during an 8-year period as an anti-inflammatory drug in 26 patients with severe Crohn's disease, usually after failure of corticotherapy, or when this drug was avoided because of side-effects or abscesses. This was a Phase II trial during which doses, routes of administration and concomitant therapies were progressively modified. The acceptability was excellent with the free enzyme. We obtained 19/26 very good short term responses, and 82% good results on long term evolution. The efficacy of SOD as an anti-inflammatory drug in Crohn's disease needs to be confirmed by controlled trials.