Dijana Detel

Neuroimmunomodulative properties of dipeptidyl peptidase IV/CD26 in a TNBS‐induced model of colitis in mice

Causal connections between dipeptidyl peptidase IV, also known as CD26 molecule (DPP IV/CD26) and inflammatory bowel disease (IBD) have been shown, but mechanisms of these interactions are unclear. Our hypothesis was that DPP IV/CD26 could affect the neuroimmune response during inflammatory events. Therefore, we aimed to evaluate its possible role and the relevance of the gut–brain axis in a model of IBD in mice. Trinitrobenzenesulfonic acid‐induced (TNBS) colitis was induced in CD26‐deficient (CD26−/−) and wild‐type (C57BL/6) mice. Pathohistological and histomorphometrical measurements were done. Concentrations and protein expressions of DPP IV/CD26 substrates neuropeptide Y (NPY) and vasoactive intestinal peptide (VIP) were determined. Concentrations of IL‐6 and IL‐10 were evaluated. Investigations were conducted at systemic and local levels. Acute inflammation induced increased serum NPY concentrations in both mice strains, more enhanced in CD26−/− mice. Increased NPY concentrations were found in colon and brain of C57BL/6 mice, while in CD26−/− animals only in colon. VIP and IL‐6 serum and tissue concentrations were increased in both mice strains in acute inflammation, more pronouncedly in CD26−/− mice. IL‐10 concentrations, after a decrease in serum of both mice strains, increased promptly in CD26−/− mice. Decreased IL‐10 concentration was found in brain of C57BL/6 mice, while it was increased in colon of CD26−/− mice in acute inflammation. DPP IV/CD26 deficiency affects the neuroimmune response at systemic and local levels during colitis development and resolution in mice. Inflammatory changes in the colon reflected on investigated parameters in the brain, suggesting an important role of the gut–brain axis in IBD pathogenesis. J. Cell. Biochem. 112: 3322–3333, 2011.

Serum and intestinal dipeptidyl peptidase IV (DPP IV/CD26) activity in children with celiac disease.

Objective: Dipeptidyl peptidase IV (DPP IV/CD26) is involved in the degradation of proline-rich proteins such as gliadin and in modulation of the immune response. The aim of this study was to examine the possible causal connection between DPP IV enzyme activities and celiac disease (CD) in children. Patients and Methods: Intestinal mucosal biopsy specimens were obtained from 97 patients. The patients were divided into 3 groups: patients with active CD (n = 38), patients with malabsorption syndrome (MS) of other causes (n = 37), and control patients (n = 22). In addition, blood samples were collected from 48 patients with active CD and 50 control patients without gastrointestinal diseases. DPP IV enzyme activity was measured in the intestinal mucosal biopsy specimens and in the serum samples. Results: DPP IV activity in the small intestine correlated inversely with the grade of mucosal damage in the CD (r = −0.92, P < 0.001) and MS groups (r = −0.90, P < 0.001). Intestinal DPP IV activity was statistically significantly lower in the CD and MS groups than in the control group (P < 0.001). By contrast, serum DPP IV activity was not significantly different between the CD and control groups. Conclusions: Our results suggest that the decrease in intestinal DPP IV activity is not specific to CD because it correlates with the level of mucosal damage in both patients with CD and those with MS. In addition, it seems that serum DPP IV activity cannot be used as a specific noninvasive diagnostic or prognostic marker of CD.

THE INFLUENCE OF AGE ON INTESTINAL DIPEPTIDYL PEPTIDASE IV (DPP IV/CD26), DISACCHARIDASES, AND ALKALINE PHOSPHATASE ENZYME ACTIVITY IN C57BL/6 MICE

The objective of this study was to determine and describe the age-related changes in intestinal brush border membrane enzyme activities that occur in C57Bl/6 mice. Specifically, jejunal, duodenal, and ileal dipeptidyl peptidase IV/CD26, disaccharidase (lactase, sucrase, and maltase), and alkaline phosphatase activities were determined. A significant correlation between analyzed intestinal brush border membrane enzyme activities and animal age was found. Our study revealed that intestinal dipeptidyl peptidase IV/CD26, lactase, sucrase, maltase, and alkaline phosphatase activities decline significantly with age (p < .05). Nevertheless, the horizontal (duodenum to ileum) enzyme activity patterns are not affected by age.

Decreased soluble dipeptidyl peptidase IV activity as a potential serum biomarker for COPD.

OBJECTIVES The objective of this study was to measure soluble dipeptidyl peptidase IV (sDPPIV) activity in sera of patients with stable chronic obstructive pulmonary disease (COPD) in comparison to healthy controls. The main goal was to assess changes in the enzyme activity in relation to severity of the disease, age and smoking history and to evaluate diagnostic accuracy for prediction of COPD by level of serum sDPPIV activity. DESIGN AND METHODS The study included 106 patients with stable COPD (GOLD II-GOLD IV stages) and 38 healthy controls. Serum sDPPIV activity as well as some inflammatory markers (CRP, total and differential leukocyte counts) was measured. Multivariate logistic regression models were applied to analyze association of sDPPIV activity and inflammatory markers in risk estimation for COPD development. RESULTS sDPPIV activity in COPD patients was significantly reduced when compared to healthy controls. Decrease was observed already in GOLD II stage. Age and smoking history did not influence sDPPIV activity. Very good diagnostic accuracy (AUC=0.833; sensitivity and specificity of 85.7% and 78.9%, respectively) for GOLD II and good diagnostic accuracy (AUC=0.801; sensitivity and specificity of 65.1% and 86.8%, respectively) for total cohort of COPD patients were found. The multivariate logistic regression model showed that the use of sDPPIV in combination with CRP and lymphocyte proportion improved diagnostic strength and gave an AUC of 0.933. CONCLUSIONS sDPPIV activity is decreased in COPD patients as early as in GOLD II stage. Very good diagnostic accuracy of sDPPIV activity suggests it as a candidate biomarker for early diagnosis of COPD.

Development and resolution of colitis in mice with target deletion of dipeptidyl peptidase IV.

A role for dipeptidyl peptidase IV (DPP IV/CD26) in the pathogenesis of inflammatory bowel disease has been proposed owing to its involvement in immune regulation via its expression on immune cells and ability to cleave biologically active molecules. The aim of this study was to investigate the influence of DPP IV/CD26 deficiency on development and resolution of dextran sulfate sodium‐induced colitis in CD26‐deficient (CD26‐/‐) and wild‐type (C57BL/6) mice. Colitis was characterized by clinical and histological changes and infiltration of immune cells in the colonic mucosa. In the acute phase of colitis, loss of body mass and disease activity in C57BL/6 mice was more intensive than in CD26‐/‐ mice, in spite of similar histopathological changes at the local level. Although acute inflammation induced a significant increase in the number of macrophages and dendritic cells in both mouse strains, in CD26‐/‐ mice the increase of macrophages was twice that in C57BL/6 animals (18.0 ± 4.5 versus 41.3 ± 5.8), whereas the increase in dendritic cells was more pronounced in C57BL/6 mice. In the acute phase of colitis, colonic DPP IV/CD26 activity was significantly decreased in C57BL/6 mice compared with healthy animals. The results of our study reveal that DPP IV/CD26 deficiency affects the onset of clinical symptoms and the specific cells infiltrating at the site of inflammation in CD26‐/‐ animals, suggesting a pathophysiological role of DPP IV/CD26 and providing new insights into the nature of the immune response activated during the development of colitis.

Involvement of Dpp IV/CD26 in Cutaneous Wound Healing Process in Mice

Dipeptidyl peptidase IV (DPP IV/CD26) is a widely distributed multifunctional protein that plays a significant role in different physiological as well as pathological processes having a broad spectrum of bioactive substrates and immunomodulative properties. It has potential influence on different processes crucial for wound healing, including cell adhesion, migration, apoptosis, and extracellular matrix degradation. However, despite its known enzymatic and immunomodulative functions, limited data characterize the role of DPP IV/CD26 in cutaneous wound healing mechanisms. The aim of this study was to investigate the process of wound healing in conditions of CD26 deficiency in order to obtain better insights on the role of DPP IV/CD26 in cutaneous regeneration. Experimental wounds were made on the dorsal part of CD26 deficient (CD26−/−) and wild‐type mice (C57BL/6). The process of cutaneous wound healing was monitored on defined time schedule postwounding by macroscopic, microscopic, and biochemical analyses. Obtained results revealed a better rate of wound closure, revascularization and cell proliferation in CD26−/− mice, with enhanced local expression of hypoxia‐inducible factor 1α and vascular endothelial growth factor. CD26 deficiency induced prompt macrophage recruitment at the site of skin damage but did not influence mobilization of T‐cells in comparison with wild‐type mice. CD26−/− mice have significantly higher values of IP‐10 in serum and control skins compared with wild‐type mice but values in wounds did not differ significantly on days 2, 4, and 7 of wound healing. DPP IV/CD26 activity was found to be decreased 4 days postwounding in serum and 2, 4, and 7 days postwounding in wounds of wild‐type animals compared with control skins. These findings contribute to better understanding of wound healing mechanisms and could give a support in finding new therapeutic approaches for wound healing and tissue regeneration.

Influence of CD26/dipeptidyl peptidase IV deficiency on immunophenotypic changes during colitis development and resolution

A lot of evidence for the importance of CD26/dipeptidyl peptidase IV (CD26/DPP IV) in immunoactivation has been reported; however, its involvement in colitis remains unclear. The aim of this study was to investigate the influence of CD26/DPP IV deficiency on immunophenotypic changes associated with dextran sulfate sodium (DSS)-induced colitis in wild-type (WT) and CD26-deficient mice. Development of clinical symptoms of colitis and animal health status parameters were assessed; the expression of the nuclear factor (NF)-κB p65 subunit was measured by quantitative real-time PCR, while cell characterization was determined by flow cytometry and immunohistochemical staining. DSS treatment induced loss of body weight and colon length shortening in both mouse strains. An increase of myeloperoxidase activity in CD26-deficient mice was more intensive than in WT mice, in spite of similar histopathological changes. Furthermore, a significant increase in the expression of NF-κB p65 subunit in the colon of CD26-deficient mice was determined. The percentage of splenic CD4+ and CD8+ cells in the acute phase of colitis was significantly decreased in WT mice, while in the same period, an increase in the percentage of splenic CD8+ cells was present in CD26-deficient mice. Development of colitis was accompanied by a significant increase in the percentage of intrahepatic NKT cells in both mouse strains, but their percentage in spleen was increased only in CD26-deficient mice. CD26 deficiency was associated with a heightened response to DSS accompanied by increased expression of NF-κB p65 subunit and distinct changes in leukocyte trafficking. These results provide new insights into the role of CD26/DPP IV during the development of colitis.

[Dipeptidyl peptidase IV in inflammatory bowel diseases (DPP IV/CD26)].

Dipeptidil-peptidaza IV (DPP IV/CD26) i upalne bolesti crijeva Upalne bolesti crijeva (Crohnova bolest, ulcerozni kolitis, nedeterminirani kolitis) skupina su kroničnih autoimunosnih upalnih bolesti obilježenih ponavljanim upalama različitih dijelova gastrointestinalnog trakta koje su važan javnozdravstveni problem današnjice. Unatoč brojnim temeljnim i kliničkim istraživanjima etiologija ovih bolesti, kao i sama patogeneza upale ostaju nedovoljno razjašnjene. Dosadašnja su istraživanja potvrdila uzročno-posljedičnu vezu između medijatora upalnog odgovora i molekula uključenih u regulaciju njihove biološke aktivnosti, osobito proteaza. Cilj ovoga preglednog rada jest sažeti prikaz dosadašnjih saznanja o različitim aspektima upalnih bolesti crijeva, s posebnim naglaskom na potencijalnu ulogu i uključenost dipeptidil-peptidaze IV, odnosno molekule CD26 (DPP IV/CD26) u mehanizme nastanka upalnih procesa u probavnom sustavu. Dan je i pregled životinjskih modela kolitisa koji su znatno pridonijeli razumijevanju i terapiji ovih bolesti, s osobitim naglaskom na mišji model ulceroznog kolitisa (DSS-kolitis) te Crohnove bolesti (TNBS-kolitis). Dipeptidyl Peptidase IV in Inflammatory Bowel Diseases (DPP IV/CD26) Inflammatory bowel diseases (Crohns disease, ulcerative colitis, undetermined colitis) are a group of chronic autoimmune inflammatory diseases distinguished by recurrent inflammation of various parts of the gastrointestinal (GI) system and presenting a significant public health problem. Despite large basic and clinical research, the aetiology of these diseases and the pathogenesis of inflammation itself remain elusive. Previous studies have confirmed a causal relationship between mediators of inflammatory response and molecules involved in the regulation of their biological activity, especially proteases. The aim of this review is to summarise earlier findings on different aspects of inflammatory bowel diseases, paying particular attention to the involvement of dipeptidyl peptidase IV (CD26 molecule, DPP IV/CD26) in the etiopathogenesis of inflammatory processes in the GI tract. Animal studies of colitis have significantly contributed to the understanding and treatment of these diseases, investigations of ulcerative colitis (DSS-colitis) and Crohns disease (TNBS-colitis) on the murine model in particular.

The effect of CD26‐deficiency on dipeptidyl peptidase 8 and 9 expression profiles in a mouse model of Crohn's disease

The involvement of dipeptidyl peptidase (DP) IV/CD26 (DPP IV/CD26) family members in the pathogenesis of Crohns disease (CD), an autoimmune inflammatory condition of the gut, is effected mainly through proteolytic cleavage of immunomodulatory substrates and DPP IV/CD26s costimulatory function. DP8 and DP9 are proteases with diverse functions including cell interactions, apoptosis, and immune response but their localization remains to be clarified. We assessed the impact of DPP IV/CD26 deficiency (CD26−/−) on the expression profiles of DP8 and DP9 by qPCR and immunodetection as well as quantified DP8/9 enzyme activity in distinctive phases of a chemically‐induced CD model in mice. CD26−/− did not affect colon DP8 mRNA expression, while the physiological concentration of DP8 protein is decreased in CD26−/− mice but rises in inflammation (P < 0.05). On the other hand, DP9 mRNA level is significantly increased in CD26−/− mice in inflammation as well as healing with the DP9 concentration being almost twofold increased (P < 0.05) in all experimental points in CD26−/− mice compared to wild‐type indicating the expected up‐regulation in CD26−/− conditions. Surprisingly, dominantly intracellular DP8 and DP9 were found in abundance in serum. DP8/9 activity is decreased in the inflamed colon, whereas its contribution to the overall serum DPP IV/CD26‐like activity is negligible, suggesting the importance of their extra‐enzymatic functions. To summarize, CD induction generated gene, protein and enzymatic changes of DP8 and DP9 so their involvement in inflammation development and/or healing process is implicated, especially in CD26−/−, and the question of their subcellular localization should be revised.

Chlorogenic acid ameliorates experimental colitis in mice by suppressing signaling pathways involved in inflammatory response and apoptosis

Chlorogenic acid (ChA) exhibits a multitude of positive health effects, however, the signaling mechanisms by which ChA could influence the inflammatory response in experimental colitis are unknown. To answer this question, we induced colitis in mice by administration of 2.5% dextran sulfate sodium (DSS) in drinking water for seven days. Oral administration of ChA significantly ameliorated clinical symptoms, improved disease activity index and colon shortening induced by DSS. Furthermore, ChA administration resulted in a suppression of phosphorylated extracellular signal-regulated kinases 1 and 2 (ERK1/2), c-Jun N-terminal kinases 1 and 2 (JNK1/2), Akt and signal transducer and activator of transcription 3 (STAT3) with concomitant upregulation of phosphatase and tensin homolog (PTEN) expression. Immunohistochemical analysis showed a dose-dependent decrease in expression and nuclear translocation of nuclear factor-kappa B (NF-κB) p65 subunit, which was accompanied by suppression of pro-inflammatory cytokine tumor necrosis factor-alpha (TNF-α) expression. Induction of apoptosis and oxidative stress was attenuated in a dose-dependent manner by suppressing Bax, caspase-8, caspase-9 and heme oxygenase-1 (HO-1) protein expression in mice administrated with ChA. The results of the current study suggest that ChA could be useful for the treatment of inflammation and attenuating colitis severity by suppressing activation of pro-inflammatory and apoptotic signaling pathways.