Lara Batičić Pučar

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.

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.