Sunčica Buljević

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.

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.

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.

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.

Wound Healing Process, Diabetes and Implications of Dipeptidyl Peptidase IV (DPP IV/CD26)

Dipeptidyl Peptidase IV or molecule CD26 (DPP IV/CD26) is a multifunctional protein, identified as a therapeutic target for type 2 diabetes, due to its ability to degrade incretins, insulin secretagogues. Delayed wound healing is a significant complication in diabetic patients that represents a major socio-economic health problem. It has been proposed that DPP IV/CD26 inhibition accelerates healing of chronic diabetic ulcers in those patients, through the induction of a histological pattern consistent with enhanced angiogenesis. Studies on mice models of diabetesdisturbed wound healing also suggested that the inhibition of DPP IV enzymatic activity may improve tissue regeneration processes. However, further research is needed to elucidate the role of DPP IV/CD26 in diabetic wound healing. The objective of this work was to discuss recent findings on the implications of DPP IV/CD26 in tissue regeneration and reparation in diabetic environment.

Role of Dipeptidyl Peptidase IV/CD26 in Inflammatory Bowel Disease

Inflammatory bowel disease (IBD) comprises two main chronic pathologies of the gastrointestinal tract (GIT): ulcerative colitis (UC) and Crohn’s disease (CD), both characterized by alternating phases of active inflammation and clinical remission with different complications and extraintestinal manifestations. The ethiopathogenesis of IBD has still not been elucidated, but it has been suggested that inflammatory processes emerge in genetically susceptible individuals as a result of an irregular, over-expressed immunological reaction to some undefined food antigens or some other agents of microbial origin. Given the complexity of etiological factors in human IBD, a lot of current knowledge regarding IBD pathogenesis has arisen from the study of various animal models. Although no ideal model of IBD has been accomplished so far, they resemble different important clinical, histopathological and immunological aspects of human IBD. Chemically induced murine models by oral administration of dextran sodium sulfate (DSS) and intrarectal aplication of 2, 4, 6-trinitrobenzene sulfonic acid (TNBS) are the most commonly used due to their onset and duration of colonic inflammation which is immediate, reproducible and shares a lot of similarities with human IBD. TNBS-induced colitis is one of the most accepted and used Crohn-like disease while DSS model is clinically and histologically similar to human ulcerative colitis. These models, together with other animal models of IBD, have given insight in different processes at the molecular level and have revealed the importance of different molecules involved in IBD etiology, representing therefore essential tools in investigating different mechanisms underlying acute or chronic inflammation in the IBD. Growing body of knowledge proposes proteases as key factors in the occurrence of inflammatory processes due to their ability to metabolize different biologically active molecules implicated in maintaining the integrity of mucosal barrier (8). Dipeptidyl-peptidase IV, known also as CD26 molecule (DPP IV/CD26) is one of them (9). DPP IV/CD26 is also T-cell differentiation antigen, expressed on various cell types, having numerous functions in a variety of biological processes, as well as immunological mechanisms. It is also present in a soluble form circulating in body fluids in living organisms with specific peptidase function having unique features in substrate processing: it cleaves dipeptides from the N terminus of polypeptides having proline or alanin at the penultimate position. Since Xaa-Pro peptides are not easily metabolized by other proteases, the action of DPP IV/CD26 is an essential step in the degradation of many polypeptides. Numerous biologically important cytokines, chemokines and neuropeptides with potential and/or confirmed role in IBD ethiopathogenesis are effective DPP IV/CD26 substrates. Previous studies including patients affected with IBD showed a correlation between disease severity and serum DPP IV/CD26 activity. Furthermore, a potential role of DPP IV/CD26 in the pathogenesis of IBD, given its involvement in immune regulations via its expression on immune cells and capability to cleave biologically active molecules has been proposed. Additionally, DPP IV/CD26 inhibitors have been pointed out as therapeutic agents in ameliorating inflammatory processes in immunologically mediated diseases such as IBD. Given the potential role of DPP IV/CD26 and possible involvement in the pathogenesis of IBD, the aim of this study was to investigate and review does it and in which manner the deficiency of DPP IV/CD26 affect the neuroimmune response during development, progression and resolution of inflammatory events in two models of IBD in mice.