Possible involvement of neutrophil elastase in impaired mucosal repair in patients with ulcerative colitis

Neutrophil Elastase and Elafin in Inflammatory Bowel Diseases: Urinary Biomarkers Reflecting Intestinal Barrier Dysfunction and Proteolytic Activity

Background: Inflammatory bowel disease (IBD), including ulcerative colitis (UC) and Crohn's disease (CD), is a chronic inflammatory disorder driven by a complex interplay of immune and proteolytic mechanisms. Neutrophil elastase (NE), released at sites of inflammation, plays a central role by promoting inflammation, degrading the extracellular matrix (ECM), and disturbing intestinal barrier integrity via NF-κB activation and E-cadherin degradation. Elafin, an endogenous NE inhibitor, mitigates proteolytic damage, reinforces the intestinal barrier, and exerts anti-inflammatory effects by suppressing NF-κB and reducing pro-inflammatory cytokines. Since the NE/elafin balance is critical in IBD, assessing their ratio may provide a more precise measure of proteolytic dysregulation. This study aimed to evaluate the diagnostic and prognostic utility of urinary NE, elafin, and their ratio in IBD patients. Methods: Urinary concentrations of NE and elafin were measured by immunoassay in 88 subjects including ulcerative colitis and Crohn's disease patients and healthy individuals. The diagnostic accuracy of these biomarkers was assessed using receiver operating characteristic (ROC) curve analysis. Results: Urinary NE levels were significantly elevated in both UC and CD patients compared to controls, with a 17-fold increase in the UC patients and a 28-fold increase in the CD patients (p < 0.0001). Elafin levels were also increased in IBD patients. The NE/elafin ratio was significantly increased in both disease groups, with a 4.5-fold increase in the UC and 5.6-fold increase in the CD patients compared to healthy controls. The ROC curve analysis demonstrated that the NE/elafin ratio is the most effective biomarker for distinguishing CD patients from healthy individuals (AUC = 0.896), with a high sensitivity (92.9%) and specificity (69.7%), making it a strong diagnostic tool. NE also showed an excellent diagnostic performance both in CD (AUC = 0.842) and UC (AUC = 0.880). The elafin urinary profile had a high diagnostic value, with a better accuracy in the UC patients (AUC = 0.772) than the CD patients (AUC = 0.674), though it was inferior to NE and NE/elafin. Conclusions: Our findings indicate that urinary NE, elafin, the and NE/elafin ratio have significant diagnostic value in differentiating IBD patients from healthy controls. The NE/elafin ratio and NE proved to be the most reliable urinary biomarkers in both CD and UC diagnosis, with a high predictive value and strong discriminatory power.

The Potential of Molecular Remission: Tissue Neutrophil Elastase Is Better Than Histological Activity for Predicting Long-Term Relapse in Patients With Ulcerative Colitis in Endoscopic Remission

BACKGROUND

Growing interest exists in deep remission, beyond clinical and endoscopic remission, to enhance long-term prognosis in patients with ulcerative colitis (UC). Our study aimed to evaluate the risk of relapse according to tissue expression levels of calprotectin and neutrophil elastase (NE) in patients with quiescent UC.

METHODS

Rectal biopsies were performed on 218 patients with UC in clinical and endoscopic remission. Histological activity was prospectively scored using the Robarts Histological Index. Tissue calprotectin and NE levels were evaluated using immunohistochemistry. Optimal tissue calprotectin and NE cutoffs for relapse were determined using log-rank analysis. Cox proportional hazard analyses evaluated relapse risk factors.

RESULTS

Tissue calprotectin and NE levels were significantly higher in patients with histological activity than in those in histological remission (P < .001). The optimal cutoffs of tissue calprotectin and NE for relapse were 10.61 and 22.08 per mm2, respectively. The 3-year clinical relapse risk was significantly lower in the low-tissue NE group than in the high-tissue NE group (P = .009); however, it did not differ between the low- and high-tissue calprotectin group (P = .094). In multivariate analyses, a low level of tissue NE expression was independently associated with a lower risk of 3-year clinical relapse (adjusted hazard ratio = 0.453, 95% confidence interval = 0.225-0.911, P = .026), unlike histological index and tissue calprotectin.

CONCLUSIONS

In patients with UC who have achieved clinical and endoscopic remission, tissue expression of NE is a better predictor of long-term relapse than histological activity.

Neutrophils: From Inflammatory Bowel Disease to Colitis-Associated Colorectal Cancer

Inflammatory bowel disease (IBD) is a non-specific inflammatory disease of digestive tract, primarily manifesting as ulcerative colitis (UC) and Crohn's disease (CD). The precise etiology of IBD remains elusive. The interplay of genetic factors, environmental influences, and intestinal microbiota contributes to the establishment of an uncontrolled immune environment within the intestine, which can progressively lead to atypical hyperplasia and ultimately to malignancy over a long period. This colorectal malignant tumor that arises from chronic IBD is referred to as colitis-associated colorectal cancer (CAC). Dysregulation in the quantity and functionality of neutrophils plays a significant role in the onset, progression, and recurrence of IBD, as well as in the transition from IBD to CAC. Neutrophils affect the pathophysiology of IBD through various mechanisms, including the production of reactive oxygen species (ROS), degranulation, the release of inflammatory mediators and chemokines, and the formation of neutrophil extracellular traps (NETs). These processes can induce DNA mutations, thereby facilitating the development of colon cancer. Given the incomplete understanding of the disease mechanisms underlying IBD and CAC, effective treatment and prevention strategies remain challenging. Consequently, a comprehensive review of the functional roles of neutrophils in IBD and CAC is essential for advancing our understanding of IBD pathogenesis and identifying potential therapeutic targets.

The role of neutrophils in autoimmune diseases

Historically, neutrophils have been primarily regarded as short-lived immune cells that act as initial responders to antibacterial immunity by swiftly neutralizing pathogens and facilitating the activation of adaptive immunity. However, recent evidence indicates that their roles are considerably more complex than previously recognized. Neutrophils comprise distinct subpopulations and can interact with various immune cells, release granular proteins, and form neutrophil extracellular traps. These functions are increasingly recognized as contributing factors to tissue damage in autoimmune diseases. This review comprehensively examines the physiological functions and heterogeneity of neutrophils, their interactions with other immune cells, and their significance in autoimmune diseases, including systemic lupus erythematosus, rheumatoid arthritis, antiphospholipid syndrome, antineutrophil cytoplasmic antibody-associated vasculitis, multiple sclerosis, and others. This review aims to provide a deeper understanding of the function of neutrophils in the development and progression of autoimmune disorders.

Neutrophils in Inflammatory Diseases: Unraveling the Impact of Their Derived Molecules and Heterogeneity

Inflammatory diseases involve numerous disorders and medical conditions defined by an insufficient level of self-tolerance. These diseases evolve over the course of a multi-step process through which environmental variables play a crucial role in the emergence of aberrant innate and adaptive immunological responses. According to experimental data accumulated over the past decade, neutrophils play a significant role as effector cells in innate immunity. However, neutrophils are also involved in the progression of numerous diseases through participation in the onset and maintenance of immune-mediated dysregulation by releasing neutrophil-derived molecules and forming neutrophil extracellular traps, ultimately causing destruction of tissues. Additionally, neutrophils have a wide variety of functional heterogeneity with adverse effects on inflammatory diseases. However, the complicated role of neutrophil biology and its heterogeneity in inflammatory diseases remains unclear. Moreover, neutrophils are considered an intriguing target of interventional therapies due to their multifaceted role in a number of diseases. Several approaches have been developed to therapeutically target neutrophils, involving strategies to improve neutrophil function, with various compounds and inhibitors currently undergoing clinical trials, although challenges and contradictions in the field persist. This review outlines the current literature on roles of neutrophils, neutrophil-derived molecules, and neutrophil heterogeneity in the pathogenesis of autoimmune and inflammatory diseases with potential future therapeutic strategies.

Hyaluronic Acid in Synovial Fluid Prevents Neutrophil Activation in Spondyloarthritis

Spondyloarthritis (SpA) patients suffer from joint inflammation resulting in tissue damage, characterized by the presence of numerous neutrophils in the synovium and synovial fluid (SF). As it is yet unclear to what extent neutrophils contribute to the pathogenesis of SpA, we set out to study SF neutrophils in more detail. We analyzed the functionality of SF neutrophils of 20 SpA patients and 7 disease controls, determining ROS production and degranulation in response to various stimuli. In addition, the effect of SF on neutrophil function was determined. Surprisingly, our data show that SF neutrophils in SpA patients have an inactive phenotype, despite the presence of many neutrophil-activating stimuli such as GM-CSF and TNF in SF. This was not due to exhaustion as SF neutrophils readily responded to stimulation. Therefore, this finding suggests that one or more inhibitors of neutrophil activation may be present in SF. Indeed, when blood neutrophils from healthy donors were activated in the presence of increasing concentrations of SF from SpA patients, degranulation and ROS production were dose-dependently inhibited. This effect was independent of diagnosis, gender, age, and medication in the patients from which the SF was isolated. Treatment of SF with the enzyme hyaluronidase strongly reduced the inhibitory effect of SF on neutrophil activation, indicating that hyaluronic acid that is present in SF may be an important factor in preventing SF neutrophil activation. This finding provides novel insights into the role of soluble factors in SF regulating neutrophil function and may lead to the development of novel therapeutics targeting neutrophil activation via hyaluronic acid or associated pathways.

PR1P, a VEGF-stabilizing peptide, reduces injury and inflammation in acute lung injury and ulcerative colitis animal models

Acute Respiratory Distress Syndrome (ARDS) and Ulcerative Colitis (UC) are each characterized by tissue damage and uncontrolled inflammation. Neutrophils and other inflammatory cells play a primary role in disease progression by acutely responding to direct and indirect insults to tissue injury and by promoting inflammation through secretion of inflammatory cytokines and proteases. Vascular Endothelial Growth Factor (VEGF) is a ubiquitous signaling molecule that plays a key role in maintaining and promoting cell and tissue health, and is dysregulated in both ARDS and UC. Recent evidence suggests a role for VEGF in mediating inflammation, however, the molecular mechanism by which this occurs is not well understood. We recently showed that PR1P, a 12-amino acid peptide that binds to and upregulates VEGF, stabilizes VEGF from degradation by inflammatory proteases such as elastase and plasmin thereby limiting the production of VEGF degradation products (fragmented VEGF (fVEGF)). Here we show that fVEGF is a neutrophil chemoattractant in vitro and that PR1P can be used to reduce neutrophil migration in vitro by preventing the production of fVEGF during VEGF proteolysis. In addition, inhaled PR1P reduced neutrophil migration into airways following injury in three separate murine acute lung injury models including from lipopolysaccharide (LPS), bleomycin and acid. Reduced presence of neutrophils in the airways was associated with decreased pro-inflammatory cytokines (including TNF-α, IL-1β, IL-6) and Myeloperoxidase (MPO) in broncho-alveolar lavage fluid (BALF). Finally, PR1P prevented weight loss and tissue injury and reduced plasma levels of key inflammatory cytokines IL-1β and IL-6 in a rat TNBS-induced colitis model. Taken together, our data demonstrate that VEGF and fVEGF may each play separate and pivotal roles in mediating inflammation in ARDS and UC, and that PR1P, by preventing proteolytic degradation of VEGF and the production of fVEGF may represent a novel therapeutic approach to preserve VEGF signaling and inhibit inflammation in acute and chronic inflammatory diseases.

Elafin and its precursor trappin-2: What is their therapeutic potential for intestinal diseases?

Elafin and its precursor trappin-2 are known for their contribution to the physiological mucosal shield against luminal microbes. Such a contribution seems to be particularly relevant in the gut, where the exposure of host tissues to heavy loads of microbes is constant and contributes to mucosa-associated pathologies. The expression of trappin-2/elafin has been shown to be differentially regulated in diseases associated with gut inflammation. Accumulating evidence has demonstrated the protective effects of trappin-2/elafin in gut intestinal disorders associated with acute or chronic inflammation, or with gluten sensitization disorders. The protective effects of trappin-2/elafin in the gut are discussed in terms of their pleiotropic modes of action: acting as protease inhibitors, transglutaminase substrates, antimicrobial peptides or as a regulator of pro-inflammatory transcription factors. Further, the question of the therapeutic potential of trappin-2/elafin delivery at the intestinal mucosa surface is raised. Whether trappin-2/elafin mucosal delivery should be considered to ensure intestinal tissue repair is also discussed.

Polyphenols and Maillard Reaction Products in Dried Prunus spinosa Fruits: Quality Aspects and Contribution to Anti-Inflammatory and Antioxidant Activity in Human Immune Cells Ex Vivo

Dried Prunus spinosa fruits (sloes) are folk phytotherapeutics applied to treat chronic inflammatory disorders. However, their pharmacological potential, activity vectors, and drying-related changes in bioactive components remain unexplored. Therefore, the present research aimed to evaluate the anti-inflammatory and antioxidant effects of dried sloes in ex vivo models of human neutrophils and peripheral blood mononuclear cells (PMBCs) and establish their main active components. It was revealed that the fruit extracts significantly and dose-dependently inhibited the respiratory burst, downregulated the production of elastase (ELA-2) and TNF-α, and upregulated the IL-10 secretion by immune cells under pro-inflammatory and pro-oxidant stimulation. The slightly reduced IL-6 and IL-8 secretion was also observed. The structural identification of active compounds, including 45 phenolics and three Maillard reaction products (MRPs) which were formed during drying, was performed by an integrated approach combining LC-MS/MS, preparative HPLC isolation, and NMR studies. The cellular tests of four isolated model compounds (chlorogenic acid, quercetin, procyanidin B2, and 5-hydroxymethylfurfural), supported by statistical correlation studies, revealed a significant polyphenolic contribution and a slight impact of MRPs on the extracts’ effects. Moreover, a substantial synergy was observed for phenolic acids, flavonoids, condensed proanthocyanidins, and MPRs. These results might support the phytotherapeutic use of dried P. spinosa fruits to relieve inflammation and establish the quality control procedure for the extracts prepared thereof.

Neutrophil Extracellular Trap Density Increases With Increasing Histopathological Severity of Crohn's Disease

BACKGROUND

Intestinal neutrophil recruitment is a characteristic feature of the earliest stages of inflammatory bowel disease (IBD). Neutrophil elastase (NE) and myeloperoxidase (MPO) mediate the formation of neutrophil extracellular traps (NETs); NETs produce the bactericidal oxidant hypochlorous acid (HOCl), causing host tissue damage when unregulated. The project aim was to investigate the relationship between NET formation and clinical IBD in humans.

METHODS

Human intestinal biopsies were collected from Crohn's disease (CD) patients, endoscopically categorized as unaffected, transitional, or diseased, and assigned a histopathological score.

RESULTS

A significant linear correlation was identified between pathological score and cell viability (TUNEL+). Immunohistochemical analysis revealed the presence of NET markers NE, MPO, and citrullinated histone (CitH3) that increased significantly with increasing histopathological score. Diseased specimens showed greater MPO+-immunostaining than control (P < .0001) and unaffected CD (P < .0001), with transitional CD specimens also showing greater staining than controls (P < .05) and unaffected CD (P < .05). Similarly, NE+-immunostaining was elevated significantly in diseased CD than controls (P < .0001) and unaffected CD (P < .0001) and was significantly higher in transitional CD than in controls (P < .0001) and unaffected CD (P < .0001). The CitH3+-immunostaining of diseased CD was significantly higher than controls (P < .05), unaffected CD (P < .0001) and transitional CD (P < .05), with transitional CD specimens showing greater staining than unaffected CD (P < .01). Multiplex immunohistochemistry with z-stacking revealed colocalization of NE, MPO, CitH3, and DAPI (cell nuclei), confirming the NET assignment.

CONCLUSION

These data indicate an association between increased NET formation and CD severity, potentially due to excessive MPO-mediated HOCl production in the extracellular domain, causing host tissue damage that exacerbates CD.

Polyphenol-Enriched Extracts of Prunus spinosa Fruits: Anti-Inflammatory and Antioxidant Effects in Human Immune Cells Ex Vivo in Relation to Phytochemical Profile

The fresh fruits of Prunus spinosa L., a wild plum species, are traditionally used for dietary purposes and medicinal applications in disorders related to inflammation and oxidative stress. This study aimed to investigate the phytochemical composition of the fruits in the function of fractionated extraction and evaluate the biological potential of the extracts as functional products in two models of human immune cells ex vivo. Fifty-seven phenolic components were identified in the extracts by UHPLC-PDA-ESI-MS3, including twenty-eight new for the analysed fruits. Fractionation enabled the enrichment of polyphenols in the extracts up to 126.5 mg gallic acid equivalents/g dw total contents, 91.3 mg/g phenolic acids (caffeoyl-, coumaroyl-, and feruloylquinic acids), 41.1 mg/g flavonoids (mostly quercetin mono-, di- and triglycosides), 44.5 mg/g condensed proanthocyanidins, and 9.2 mg/g anthocyanins (cyanidin and peonidin glycosides). The hydroalcoholic extract and phenolic-enriched fractions of the fruits revealed significant ability to modulate pro-oxidant, pro-inflammatory, and anti-inflammatory functions of human neutrophils and peripheral blood mononuclear cells (PBMCs): they strongly downregulated the release of reactive oxygen species, TNF-α, and neutrophils elastase, upregulated the secretion of IL-10, and slightly inhibited the production of IL-8 and IL-6 in the cells stimulated by fMLP, fMLP+cytochalasin B, and LPS, depending on the test. Correlation studies and experiments on the pure compounds indicated a significant contribution of polyphenols to these effects. Moreover, cellular safety was confirmed for the extracts by flow cytometry in a wide range of concentrations. The results support the traditional use of fresh blackthorn fruits in inflammatory disorders and indicate extracts that are most promising for functional applications.

Cells and mediators of inflammation as effectors of epithelial repair in the inflamed intestine

Mucosal and histological healing have become the gold standards for assessing the efficacy of therapy in patients living with inflammatory bowel diseases (IBD). Despite these being the accepted goals in therapy, the mechanisms that underlie the healing of the mucosa after an inflammatory insult are not well understood, and many patients fail to meet this therapeutic endpoint. Here we review the emerging evidence that mediators (e.g., prostaglandins, cytokines, proteases, reactive oxygen, and nitrogen species) and innate immune cells (e.g., neutrophils and monocytes/macrophages), that are involved in the initiation of the inflammatory response, are also key players in the mechanisms underlying mucosal healing to resolve chronic inflammation in the colon. The dual function mediators comprise an inflammation/repair program that returns damaged tissue to homeostasis. Understanding details of the dual mechanisms of these mediators and cells may provide the basis for the development of drugs that can help to stimulate epithelial repair in patients affected by IBD.

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.

Estrogen-related receptor alpha (ERRα) is a key regulator of intestinal homeostasis and protects against colitis

The estrogen-related receptor alpha (ERRα) is a primary regulator of mitochondrial energy metabolism, function and dynamics, and has been implicated in autophagy and immune regulation. ERRα is abundantly expressed in the intestine and in cells of the immune system. However, its role in inflammatory bowel disease (IBD) remains unknown. Here, we report a protective role of ERRα in the intestine. We found that mice deficient in ERRα were susceptible to experimental colitis, exhibiting increased colon inflammation and tissue damage. This phenotype was mediated by impaired compensatory proliferation of intestinal epithelial cells (IEC) following injury, enhanced IEC apoptosis and necrosis and reduced mucus-producing goblet cell counts. Longitudinal analysis of the microbiota demonstrated that loss of ERRα lead to a reduction in microbiome α-diversity and depletion of healthy gut bacterial constituents. Mechanistically, ERRα mediated its protective effects by acting within the radio-resistant compartment of the intestine. It promoted disease tolerance through transcriptional control of key genes involved in intestinal tissue homeostasis and repair. These findings provide new insights on the role of ERRα in the gut and extends our current knowledge of nuclear receptors implicated in IBD.

Lycium barbarum mitigates radiation injury via regulation of the immune function, gut microbiota, and related metabolites

Previous studies have suggested that Lycium barbarum (L. barbarum) has a radioprotective function, although more in-depth investigation is still required. We investigated the radioprotective efficacy of extract of the fruits of L. barbarum (LBE) and its radioprotective mechanisms. Mice were exposed to 8.5 Gy, 5.5 Gy, or 6.0 Gy total body irradiation (TBI), and the survival rate, lymphocyte percentage, amount of cytokines, and viability of the irradiated cells, as well as the gut microbiome and fecal metabolomics were studied. LBE enhanced the survival of the mice exposed to 8.5 Gy γ-ray TBI or 5.5 Gy X-ray TBI. After 6.0 Gy γ-ray TBI, LBE exhibited good immunomodulatory properties, mainly characterized by the accelerated recovery of lymphocyte percentages, and the enhanced expression of immune-related cytokines. LBE reconstituted the gut microbiota of irradiated mice, increased the relative abundance of potentially beneficial genera (e.g., Turicibacter, Akkermansia), and decreased the relative abundance of potentially harmful bacterial genera (e.g., Rikenellaceae_RC9_gut_group). Beneficial regulatory effects of LBE on the host metabolites were also noted, and the major upregulated metabolites induced by LBE, such as Tetrahydrofolic acid and N-ornithyl-L-taurine, were positively correlated with the immune factor interleukin (IL)-6. In vitro, LBE also increased the vitality of rat small intestinal epithelial cells (IEC-6) after 4.0 Gy γ-ray irradiation and promoted the growth of Akkermansia muciniphila. These results confirmed a radioprotective function of LBE and indicated that the radioprotective mechanism may be due to immunomodulation and the synergistically modulating effect on the gut microbiota and related metabolites.

High circulating elafin levels are associated with Crohn's disease-associated intestinal strictures

Background

Antimicrobial peptide expression is associated with disease activity in inflammatory bowel disease (IBD) patients. IBD patients have abnormal expression of elafin, a human elastase-specific protease inhibitor and antimicrobial peptide. We determined elafin expression in blood, intestine, and mesenteric fat of IBD and non-IBD patients.

Methods

Serum samples from normal and IBD patients were collected from two UCLA cohorts. Surgical resection samples of human colonic and mesenteric fat tissues from IBD and non-IBD (colon cancer) patients were collected from Cedars-Sinai Medical Center.

Results

High serum elafin levels were associated with a significantly elevated risk of intestinal stricture in Crohn’s disease (CD) patients. Microsoft Azure Machine learning algorithm using serum elafin levels and clinical data identified stricturing CD patients with high accuracy. Serum elafin levels had weak positive correlations with clinical disease activity (Partial Mayo Score and Harvey Bradshaw Index), but not endoscopic disease activity (Mayo Endoscopic Subscore and Simple Endoscopic Index for CD) in IBD patients. Ulcerative colitis (UC) patients had high serum elafin levels. Colonic elafin mRNA and protein expression were not associated with clinical disease activity and histological injury in IBD patients, but stricturing CD patients had lower colonic elafin expression than non-stricturing CD patients. Mesenteric fat in stricturing CD patients had significantly increased elafin mRNA and protein expression, which may contribute to high circulating elafin levels. Human mesenteric fat adipocytes secrete elafin protein.

Conclusions

High circulating elafin levels are associated with the presence of stricture in CD patients. Serum elafin levels may help identify intestinal strictures in CD patients.

Near infrared readouts offer sensitive and rapid assessments of intestinal permeability and disease severity in inflammatory bowel disease models

Intestinal permeability and neutrophil activity are closely linked to inflammatory bowel disease (IBD) pathophysiology. Here we discuss two techniques for assessing permeability and neutrophil activity in mouse IBD models using near infrared (NIR) detection. To address the limitation of visible light readouts-namely high background-IRDye 800CW was used to enable rapid, non-terminal measurements of intestinal permeability. The increased sensitivity of NIR readouts for colon permeability is shown using dextran sulfate sodium (DSS) and anti-CD40 murine colitis models in response to interleukin-22 immunoglobulin Fc (IL22Fc) fusion protein and anti-p40 monoclonal antibody treatments, respectively. In addition to enhanced permeability, elevated levels of neutrophil elastase (NE) have been reported in inflamed colonic mucosal tissue. Activatable NIR fluorescent probes have been extensively used for disease activity evaluation in oncologic animal models, and we demonstrate their translatability using a NE-activatable reagent to evaluate inflammation in DSS mice. Confocal laser endomicroscopy (CLE) and tissue imaging allow visualization of spatial NE activity throughout diseased colon as well as changes in disease severity from IL22Fc treatment. Our findings with the 800CW dye and the NE probe highlight the ease of their implementation in preclinical IBD research.

Application of a chemical probe to detect neutrophil elastase activation during inflammatory bowel disease

Neutrophil elastase is a serine protease that has been implicated in the pathogenesis of inflammatory bowel disease. Due to post-translational control of its activation and high expression of its inhibitors in the gut, measurements of total expression poorly reflect the pool of active, functional neutrophil elastase. Fluorogenic substrate probes have been used to measure neutrophil elastase activity, though these tools lack specificity and traceability. PK105 is a recently described fluorescent activity-based probe, which binds to neutrophil elastase in an activity-dependent manner. The irreversible nature of this probe allows for accurate identification of its targets in complex protein mixtures. We describe the reactivity profile of PK105b, a new analogue of PK105, against recombinant serine proteases and in tissue extracts from healthy mice and from models of inflammation induced by oral cancer and Legionella pneumophila infection. We apply PK105b to measure neutrophil elastase activation in an acute model of experimental colitis. Neutrophil elastase activity is detected in inflamed, but not healthy, colons. We corroborate this finding in mucosal biopsies from patients with ulcerative colitis. Thus, PK105b facilitates detection of neutrophil elastase activity in tissue lysates, and we have applied it to demonstrate that this protease is unequivocally activated during colitis.

Neutrophil Extracellular Traps Sustain Inflammatory Signals in Ulcerative Colitis

BACKGROUND AND AIMS

In ulcerative colitis [UC], mucosal damage occurs in areas that are infiltrated with neutrophils. The antimicrobial function of neutrophils relies in part on the formation of extracellular web-like structures, named neutrophil extracellular traps [NETs]. The formation and/or clearance of aberrant NETs have been associated with several immune diseases. Here we investigated the role of NETs in UC-related inflammation.

METHODS

The expression of NET-associated proteins was evaluated in colonic biopsies of patients with Crohn's disease [CD], UC and in normal controls [NC] by Western blotting, immunofluorescence and immunohistochemistry. Colonic biopsies of UC patients were analysed before and after anti-tumour necrosis factor α [anti-TNF-α] treatment. The capacity of neutrophils to produce NETs upon activation was tested in vitro. UC lamina propria mononuclear cells [LPMCs] were cultured with NETs in the presence or absence of an extracellular signal-regulated kinase-1/2 [ERK1/2] inhibitor and inflammatory cytokine induction was assessed by real-time polymerase chain reaction and enzyme-linked immunosorbent assay. We also characterized the contribution of NETs in dextran sodium sulfate [DSS]-induced colitis.

RESULTS

NET-associated proteins were over-expressed in inflamed colon of UC patients as compared to CD patients and NC. Circulating neutrophils of UC patients produced NETs in response to TNF-α stimulation, and reduced expression of NET-related proteins and diminished NET formation were seen in patients receiving successful treatment with anti-TNF-α. Treatment of UC LPMCs with NETs activated ERK1/2, thus enhancing TNF-α and interleukin-1β [IL-1β] production. NETs were induced in mice with DSS-colitis and in vivo inhibition of NET release attenuated colitis.

CONCLUSIONS

Our data show that NET release occurs in UC and suggest a role for NETs in sustaining mucosal inflammation in this disorder.

Understanding the Multifaceted Role of Neutrophils in Cancer and Autoimmune Diseases

Neutrophils are one of the first immune cell types that are recruited to injury and infection site. As a vital component of the immune system, neutrophils are heterogeneous immune cells known to have phagocytic property and function in inflammation. Recent studies revealed that neutrophils play dual roles in tumor initiation, development, and progression. The multifunctional roles of neutrophils in diseases are mainly due to their production of different effector molecules under different conditions. N1 and N2 neutrophils or high density neutrophils (HDNs) and low density neutrophils (LDNs) have been used to distinguish neutrophils subpopulations with pro- vs. anti-tumor activity, respectively. Indeed, N1 and N2 neutrophils also represent immunostimulating and immunosuppressive subsets, respectively, in cancer. The emerging studies support their multifaceted roles in autoimmune diseases. Although such subsets are rarely identified in autoimmune diseases, some unique subsets of neutrophils, including low density granulocytes (LDGs) and CD177⁺ neutrophils, have been reported. Given the heterogeneity and functional plasticity of neutrophils, it is necessary to understand the phenotypical and functional features of neutrophils in disease status. In this article, we review the multifaceted activates of neutrophils in cancer and autoimmune diseases, which may support new classification of neutrophils to help understand their important functions in immune homeostasis and pathologies.

The use of selected neutrophil protein plasma concentrations in the diagnosis of Crohn's disease and ulcerative colitis - a preliminary report

BACKGROUND

Difficulties in diagnosis of inflammatory bowel disease (IBD) motivate the search for new diagnostic tools, including laboratory tests. The aim of this study was to evaluate concentrations of the neutrophil (NEU) proteins leukocyte elastase (HLE-α1AT), lactoferrin and calprotectin as potential biomarkers used in the diagnosis and assessment of clinical activity of Crohn's disease (CD) and ulcerative colitis (UC).

MATERIAL/METHODS

The study included 27 patients with CD, 33 patients with UC and 20 healthy controls. Plasma concentrations of calprotectin, lactoferrin and HLE-α1AT were measured using ELISA.

RESULTS

In patients with CD higher concentrations of HLE-α1AT (64.3±43.1 vs. 30.1±7.7 ng/l, P<0.001), calprotectin (151.6±97.8 vs. 69.9±22.1 ng/l, P<0.001) and lactoferrin (243.2±102.0 vs. 129.7±32.7 ng/l, P<0.001) than in the control group were found. In patients with UC higher plasma concentrations of HLE-α1AT (62.0±30.9 vs. 30.1±7.7 ng/l, P<0.001), calprotectin (149.6±72.3 vs. 69.9±22.1 ng/l, P<0.001) and lactoferrin (242.6±107.5 vs 129.7±32.7 ng/l, P<0.001) than in the control group were found. HLE-α1AT/NEU and lactoferrin/NEU ratios in patients with UC were significantly higher compared with patients with CD. Calprotectin (P=0.010) and lactoferrin (P=0.023) levels were higher in patients with the active compared with inactive phase of CD.

CONCLUSIONS

The diagnostic characteristics of plasma granulocyte protein concentrations indicate the usefulness of these tests in the diagnosis of IBD. Higher HLE-α1AT and lactoferrin/NEU ratios in patients with UC than with CD may suggest the usefulness of these ratios in differential diagnostics. Plasma calprotectin and lactoferrin levels may be useful in CD activity assessment.

Neutrophils in ulcerative colitis: a review of selected biomarkers and their potential therapeutic implications

OBJECTIVES

This review article describes the role of neutrophils in mucosal injury and the resulting crypt abscesses characteristic of ulcerative colitis. We also review selected biomarkers for monitoring neutrophil presence and activity in the mucosa as well as their potential as therapeutic targets.

MATERIAL

We have collated and selectively reviewed data on the most prominent well-established and emerging neutrophil-related biomarkers and potential therapeutic targets (calprotectin, lactoferrin, CXCR1, CXCR2, MMP-9, NGAL, elafin, HNE, pANCAs, MPO, CD16, CD177, CD64, HNPs, SLPI and PTX3) in ulcerative colitis.

RESULTS

Systemic and intestinal neutrophil activity increases substantially in active ulcerative colitis, driving tissue damage and extra-intestinal manifestations. Calprotectin is a robust neutrophil and disease biomarker, and a few neutrophil-related targets are being clinically explored as therapeutic targets.

CONCLUSION

We propose that targeting neutrophils and their inflammatory mediators per se is an opportunity that should be explored to identify new effective medical therapies. The overall clinical goal for neutrophil-targeted therapy will be to modulate, but not completely silence, neutrophil activity, thereby abolishing the destructive inflammation with associated acute and chronic tissue damage without compromising host-defense.

The Dual Role of Neutrophils in Inflammatory Bowel Diseases

Inflammatory bowel diseases (IBD), including Crohn’s disease and ulcerative colitis, are characterised by aberrant immunological responses leading to chronic inflammation without tissue regeneration. These two diseases are considered distinct entities, and there is some evidence that neutrophil behaviour, above all other aspects of immunity, clearly separate them. Neutrophils are the first immune cells recruited to the site of inflammation, and their action is crucial to limit invasion by microorganisms. Furthermore, they play an essential role in proper resolution of inflammation. When these processes are not tightly regulated, they can trigger positive feedback amplification loops that promote neutrophil activation, leading to significant tissue damage and evolution toward chronic disease. Defective chemotaxis, as observed in Crohn’s disease, can also contribute to the disease through impaired microbe elimination. In addition, through NET production, neutrophils may be involved in thrombo-embolic events frequently observed in IBD patients. While the role of neutrophils has been studied in different animal models of IBD for many years, their contribution to the pathogenesis of IBD remains poorly understood, and no molecules targeting neutrophils are used and validated for the treatment of these pathologies. Therefore, it is crucial to improve our understanding of their mode of action in these particular conditions in order to provide new therapeutic avenues for IBD.

Current overview of extrinsic and intrinsic factors in etiology and progression of inflammatory bowel diseases

Inflammatory bowel diseases (IBD) are chronic, relapsing disorders affecting gastrointestinal (GI) tract and associated with intestinal mucosa damage and inflammation. The principal therapeutic goals in IBD include control of the intestinal inflammation and treatment of the major symptoms, mainly abdominal pain and diarrhea. Current therapeutic strategies for IBD rely on the use of non-specific anti-inflammatory agents and immunosuppressive drugs (e.g. aminosalicylates, monoclonal antibodies, and antibiotics), which cause severe side effects, and - in a significant number of patients - do not induce long-term benefits. In this review, we summarize the epidemiology and the most important risk factors of IBD, including genetic, immunological and environmental. Our main focus is to discuss pharmacological targets for current and future treatments of IBD.

Alpha-1-antitrypsin therapy ameliorates acute colitis and chronic murine ileitis

BACKGROUND

Fecal alpha-1-antitrypsin (AAT) clearance has been a marker of clinical disease severity in inflammatory bowel diseases (IBDs) for many years. Although AAT deficiency is more often associated with lung and liver pathologies, AAT-deficient patients with concomitant IBD have been shown to develop more aggressive disease and rapid progression to surgery. Although recent studies have highlighted the pleiotropic anti-inflammatory functions of AAT, including reducing proinflammatory cytokine production and suppressing immune cell activation, its potential therapeutic role in IBD has not been described.

METHODS

The therapeutic potential of human AAT administration was assessed in murine models of IBD including new-onset and established chemically induced colitis and spontaneous chronic murine ileitis. Histological assessment of inflammation, cytokine secretion profiling, and flow cytometric evaluation of inflammatory infiltrate were performed in each model. The effect of AAT on intestinal barrier function was also examined both in vitro and in vivo.

RESULTS

AAT attenuated inflammation in small and large intestinal IBD models through reduced secretion of proinflammatory cytokines, inflammatory cell infiltration, and reduced tissue injury. AAT also increased intestinal restitution after chemically induced colitis. AAT significantly decreased intestinal permeability in vitro and in vivo as part of a protective mechanism for both acute and chronic models of IBD.

CONCLUSIONS

Our findings describe a beneficial role for AAT in IBD models through suppression of cytokine production and enhanced intestinal barrier function. This raises the possibility that AAT supplementation, which has a long history of proven safety, may have a therapeutic effect in human IBD.

Rebamipide enema therapy as a treatment for patients with active distal ulcerative colitis

BACKGROUND

The clinical efficacy of corticosteroids in the treatment of ulcerative colitis (UC) is well-established. However, prolonged usage of these drugs can result in serious complications. Rebamipide {2-(4-chlorobenzoylamino)-3[2-(1H)-quinolinon-4-yl] propionic acid}, a cytoprotective agent, has been reported to have anti-inflammatory activity and to repair mucosal injury in animal colitis models. The aim of the present study was to assess the clinical efficacy and safety of a novel Rebamipide enema therapy in UC patients.

METHODS

Twenty patients with the active distal type of UC in whom corticosteroid treatment had been unsuccessful were treated with rectal administration of Rebamipide twice a day for 3 weeks, during which corticosteroid dosage was kept constant. The efficacy of treatment was assessed from clinical symptoms and endoscopic findings. The anti-inflammatory effect of Rebamipide was also examined by monitoring changes in the intensity of histological inflammation and levels of cytokine activity in the rectal mucosa.

RESULTS

At 3 weeks after the initiation of Rebamipide enema therapy, 11 patients (55%) achieved clinical remission. Sixteen (80%) were colonoscopically judged to be responders, with decreased levels of interleukin (IL)-1beta but not of IL-8, and an increased ratio of IL-1 receptor antagonist/IL-1beta in organ cultures of mucosal tissues. The change in the number of infiltrating neutrophils was not significantly correlated with the clinical response to this therapy. No side-effects were noted in any patients.

CONCLUSION

Rebamipide enema therapy proved to be safe and useful in corticosteroid-refractory patients with the active distal type of UC.

Inhibition of neutrophil elastase prevents the development of murine dextran sulfate sodium-induced colitis

BACKGROUND

Neutrophil elastase (NE) is a major secretory product from activated neutrophils and a major contributor to tissue destruction. However, little is known about the pathogenic contribution of NE to ulcerative colitis (UC). This study was designed to investigate the contribution of NE by measuring NE activity in plasma and colonic mucosal tissue from UC patients and a murine acute colitis model, and to elucidate the therapeutic effect of the NE-specific inhibitor ONO-5046.

METHODS

The NE enzyme activities in plasma and colonic mucosal tissue from UC patients were directly measured using an enzyme-substrate reaction. Acute colitis was induced in mice by administration of 1.5% dextran sulfate sodium (DSS) for 5 days. DSS-induced colitis mice were then treated with ONO-5046 (50 mg/kg body weight) intraperitoneally twice a day.

RESULTS

In UC patients, the NE enzyme activity was significantly elevated in both the plasma and colonic mucosal tissue compared with healthy controls. In DSS-induced colitis mice, the NE enzyme activity increased in parallel with the disease development. ONO-5046 showed therapeutic effects in DSS-treated mice by significantly reducing weight loss and histological score. ONO-5046 suppressed the NE enzyme activities in both plasma and culture supernatant of colonic mucosa from DSS-induced colitis mice.

CONCLUSIONS

ONO-5046, a specific NE inhibitor, prevented the development of DSS-induced colitis in mice. NE therefore represents a promising target for the treatment of UC patients.

Inflammatory gene signature in ulcerative colitis with cDNA macroarray analysis

BACKGROUND

Most array analyses of ulcerative colitis have focused on identifying susceptibility genes for ulcerative colitis.

AIM

To clarify the changes in gene expression during inflammation in ulcerative colitis colon mucosa using cDNA macroarray.

METHODS

From 23 ulcerative colitis patients, 16 each of inflamed and non-inflamed specimens (total 32 samples for individual analysis) were obtained by colonoscopic biopsy. Eighteen of the 32 samples, used for pairwise analysis, consisted of nine sample pairs, each pair being from the same patient. We examined expression profiles of approximately 1300 genes with cDNA macroarray. Comparisons were made using two kinds of statistics, t-test and significance analysis of microarray in both analyses. The reproducibility of significant genes from the macroarray analysis was confirmed by real-time ploymerase chain reaction.

RESULTS

We detected five upregulated genes, categorized into proinflammatory genes (MRP14, GRO gamma and SAA1) and anti-inflammatory genes (TIMP1 and Elafin) in inflamed mucosa, and one upregulated gene (L-FABP) in non-inflamed mucosa.

CONCLUSIONS

As the cDNA macroarray analysis in this study exactly reflects the total profile of gene expression in the clinical setting of ulcerative colitis, the genes identified will be directly applicable to diagnostics or as novel therapeutic targets in active ulcerative colitis.