Increase of CD26/dipeptidyl peptidase IV expression on human gingival fibroblasts upon stimulation with cytokines and bacterial components

Interleukin 13-Induced Inflammation Increases DPP4 Abundance but Does Not Enhance Middle East Respiratory Syndrome Coronavirus Replication in Airway Epithelia

BACKGROUND

Chronic pulmonary conditions such as asthma and chronic obstructive pulmonary disease increase the risk of morbidity and mortality during infection with the Middle East respiratory syndrome coronavirus (MERS-CoV). We hypothesized that individuals with such comorbidities are more susceptible to MERS-CoV infection due to increased expression of its receptor, dipeptidyl peptidase 4 (DPP4).

METHODS

We modeled chronic airway disease by treating primary human airway epithelia with the Th2 cytokine interleukin 13 (IL-13), examining how this affected DPP4 protein levels with MERS-CoV entry and replication.

RESULTS

IL-13 exposure for 3 days led to greater DPP4 protein abundance, while a 21-day treatment raised DPP4 levels and caused goblet cell metaplasia. Surprisingly, despite this increase in receptor availability, MERS-CoV entry and replication were not significantly affected by IL-13 treatment.

CONCLUSIONS

Our results suggest that greater DPP4 abundance is likely not the primary mechanism leading to increased MERS severity in the setting of Th2 inflammation. Transcriptional profiling analysis highlighted the complexity of IL-13-induced changes in airway epithelia, including altered expression of genes involved in innate immunity, antiviral responses, and maintenance of the extracellular mucus barrier. These data suggest that additional factors likely interact with DPP4 abundance to determine MERS-CoV infection outcomes.

Study of Plasma Anti-CD26 Autoantibody Levels in a Cohort of Treatment-Naïve Early Arthritis Patients

In rheumatoid arthritis (RA), the identification of biomarkers to adjust treatment intensity and to correctly diagnose the disease in early stages still constitutes a challenge and, as such, novel biomarkers are needed. We proposed that autoantibodies (aAbs) against CD26 (DPP4) might have both etiological importance and clinical value. Here, we perform a prospective study of the potential diagnostic power of Anti-CD26 aAbs through their quantification in plasmas from 106 treatment-naïve early and undifferentiated AR. Clinical antibodies, Anti-CD26 aAbs, and other disease-related biomarkers were measured in plasmas obtained in the first visit from patients, which were later classified as RA and non-RA according to the American College of Rheumatology criteria. Two different isotype signatures were found among ten groups of patients, one for Anti-CD26 IgA and other for Anti-CD26 IgG and IgM isotypes, both converging in patients with arthritis (RA and Unresolved Undifferentiated Arthritis: UUA), who present elevated levels of all three isotypes. The four UUA patients, unresolved after two years, were ACPA and rheumatic factor (RF) negatives. In the whole cohort, 51.3% of ACPA/RF seronegatives were Anti-CD26 positives, and a similar frequency was observed in the seropositive RA patients. Only weak associations of the three isotypes with ESR, CRP and disease activity parameters were observed. Anti-CD26 aAbs are present in treatment-naïve early arthritis patients, including ACPA and RF seronegative individuals, suggestive of a potential pathogenic and/or biomarker role of Anti-CD26 aAbs in the development of rheumatic diseases.

Nature of the Interplay Between Periodontal Diseases and COVID-19

The coronavirus disease 2019 (COVID-19) is mostly a mild condition, however, in some patients, it could progress into a severe and even fatal disease. Recent studies have shown that COVID-19 infection and severity could be associated with the presence of periodontitis, one of the most prevalent chronic diseases. This association could be explained by the fact that periodontitis and COVID-19 share some common risk factors that included chronic diseases, such as diabetes and hypertension as well as conditions such as age, sex, and genetic variants. Another possible explanation could be the systemic inflammation and the aspiration of periodontopathogens seen in patients with periodontitis, which could have a synergism with the virus or compromise the reaction of the body against COVID-19. This narrative review explores the nature of these associations, the evidence behind them, and their implications.

A molecular link between diabetes and breast cancer: Therapeutic potential of repurposing incretin-based therapies for breast cancer

Female breast cancer recently surpassed lung cancer and became the most commonly diagnosed cancer worldwide. As per the recent data from WHO, breast cancer accounts for one out of every 8 cancer cases diagnosed among an estimated 2.3 million new cancer cases. Breast cancer is the most prevailing cancer type among women causing the highest number of cancer-related mortality. It has been estimated that in 2020, 68,5000 women died due to this disease. Breast cancers have varying degrees of molecular heterogeneity; therefore, they are divided into various molecular clinical sub types. Recent reports suggest that type 2 diabetes (one of the common chronic diseases worldwide) is linked to the higher incidence, accelerated progression, and aggressiveness of different cancers; especially breast cancer. Breast cancer is hormone-dependent in nature and has a cross-talk with metabolism. A number of antidiabetic therapies are known to exert beneficial effects on various types of cancers, including breast cancer. However, only a few reports are available on the role of incretin-based antidiabetic therapies in cancer as a whole and in breast cancer in particular. The present review sheds light on the potential of incretin based therapies on breast cancer and explores the plausible underlying mechanisms. Additionally, we have also discussed the sub types of breast cancer as well as the intricate relationship between diabetes and breast cancer.

DPP-4 inhibition: А novel therapeutic approach to the treatment of pulmonary hypertension?

Pulmonary hypertension (PH) is a progressive disorder characterized by alterations of the vascular structure and function in the lungs. Despite the success in its stabilisation by targeting pulmonary vascular tone and endothelial dysfunction, the prognosis remains poor and new therapeutic approaches via neglected macromolecular targets are needed. In the pathophysiology of PH the early stages of vascular remodelling are considered to be reversible, while endothelial to mesenchymal transition and proliferation/migration of fibroblasts play a critical role in staging the irreversible phase. Dipeptidyl peptidase-4 (DPP-4)/CD26 is present and active in the lungs and is expressed constitutively on lung fibroblasts, on which it exerts proliferative effects. Further, it is a marker of migrating fibroblasts and of their functional activation, including collagen synthesis and inflammatory cytokine secretion. Inhibiting DPP-4 improves the reversible phases of vascular dysfunction in PH, but is also highly likely to attenuate endothelial to mesenchymal transition and decrease the proliferation and migration of fibroblasts, preventing fibrosis and, consequently, should prolong or even inhibit entrance to the potentially irreversible phase of PH. Proposed mechanisms that support the multifaceted aspects of DPP-4 inhibition in terms of improving PH, involve pathways and mediators in pulmonary vascular and connective tissue remodelling. The latter are affected by the inhibition of this protease resulting in the synergistic beneficial antioxidative, anti-inflammatory and antifibrotic effects. We offer here an evidence-supported hypothesis that DPP-4 inhibitors are likely to be effective in the irreversible phase of remodelling in PH. Accordingly, we propose PH as a possible novel therapeutic indication for existing and new DPP-4 inhibitors.

Stress Hyperglycemia in Critically Ill Patients: Insight Into Possible Molecular Pathways

Severe sepsis, systemic inflammatory response syndrome (SIRS), and traumatic brain injury are frequently associated with hyperglycemia in non-diabetic patients. In patients suffering from any of these conditions, hyperglycemia at admission to an intensive care unit (ICU) is directly correlated with increased mortality or morbidity. Although there was initial enthusiasm for insulin treatment to blood glucose levels below 110 mg/dL in these patients, recent understanding suggests that the potential for hypoglycemic complications make this approach potentially dangerous. More moderate glucose control seems to be more beneficial than the aggressive glucose lowering initially suggested. An important publication has shown that hyperlactatemia accompanying hyperglycemia could be the real culprit in bad outcomes. This suggests that coupling moderate glucose lowering with therapeutic agents which might treat the underlying metabolic disturbances in these conditions may be a better strategy. The key metabolic disturbance in these three conditions seems to be persistent glycolysis as an energy source even in the presence of adequate tissue oxygenation (the Warburg Effect). We look at recent advances in understanding aerobic glycolysis and possibly the action of DPP4 on incretins resulting in insulin dysregulation and suggest key metabolic pathways involved in hyperglycemia regulation.

Dipeptidyl peptidase-4 inhibition: insights from the bench and recent clinical studies

PURPOSE OF REVIEW

Atherosclerosis is the leading cause of death globally. The pathophysiology of atherosclerosis is not fully understood. Recent studies suggest dipeptidyl peptidase-4 (DPP4), a regulator of inflammation and metabolism, may be involved in the development of atherosclerotic diseases. Recent advances in the understanding of DPP4 function in atherosclerosis will be discussed in this review.

RECENT FINDINGS

Multiple preclinical and clinical studies suggest DPP4/glucagon-like peptide-1 axis is involved in the development of atherosclerotic disease. However, several recent trials assessing the cardiovascular effects of DPP4 inhibition indicate enzymatic inhibition of DPP4 lacks beneficial effects on cardiovascular disease.

SUMMARY

Catalytic inhibition of DPP4 with DPP4 inhibitors alters pathways that could favor cardioprotection. Glucagon-like peptide-1 receptor-independent aspects of DPP4 function may contribute to the overall neutral effects on cardiovascular outcome seen in the outcome trials.

Dipeptidyl peptidase 4 promotes epithelial cell transformation and breast tumourigenesis via induction of PIN1 gene expression

BACKGROUND AND PURPOSE

Dipeptidyl peptidase 4 (DPP4) is an aminopeptidase that is widely expressed in different cell types. Recent studies suggested that DPP4 plays an important role in tumour progression in several human malignancies. Here we have examined the mechanisms by which up-regulation of DPP4 expression causes epithelial transformation and mammary tumourigenesis.

EXPERIMENTAL APPROACH

Expression of DPP4 and the peptidylprolyl cis/trans isomerase, NIMA-interacting 1 (PIN1), and the cytotoxic effects of combined treatment with sitagliptin and juglone were investigated by immunohistochemistry, immunoblotting, real-time PCR, TUNEL and soft agar assays, using MCF7 cells. The effects of sitagliptin on tumour development in vivo were studied in the syngeneic 4T1 metastatic breast cancer model.

KEY RESULTS

Activity of the transcription factor E2F1 induced by EGF was enhanced by DPP4, thus increasing PIN1 expression. Furthermore, DPP4 enhanced MEK/ERK and JNK/c-Jun signalling induced by EGF, inducing AP-1 activity and epithelial cell transformation. In contrast, DPP4 silencing or DPP4 inhibition in MCF7 cells inhibited PIN1 expression via E2F1 activity induced by EGF, decreasing colony formation and inducing DNA fragmentation. In the syngeneic 4T1 metastatic breast cancer model, DPP4 overexpression increased tumour development, whereas treatment with sitagliptin and/or juglone suppressed it. Consistent with these observations, DPP4 levels were positively correlated with PIN1 expression in human breast cancer.

CONCLUSIONS AND IMPLICATIONS

DPP4 promoted EGF-induced epithelial cell transformation and mammary tumourigenesis via induction of PIN1 expression, suggesting that sitagliptin targeting of DPP4 could be a treatment strategy in patients with breast cancer.

Dipeptidyl peptidase 4 promotes epithelial cell transformation and breast tumourigenesis via induction of PIN1 gene expression

BACKGROUND AND PURPOSE

Dipeptidyl peptidase 4 (DPP4) is an aminopeptidase that is widely expressed in different cell types. Recent studies suggested that DPP4 plays an important role in tumour progression in several human malignancies. Here we have examined the mechanisms by which up-regulation of DPP4 expression causes epithelial transformation and mammary tumourigenesis.

EXPERIMENTAL APPROACH

Expression of DPP4 and the peptidylprolyl cis/trans isomerase, NIMA-interacting 1 (PIN1), and the cytotoxic effects of combined treatment with sitagliptin and juglone were investigated by immunohistochemistry, immunoblotting, real-time PCR, TUNEL and soft agar assays, using MCF7 cells. The effects of sitagliptin on tumour development in vivo were studied in the syngeneic 4T1 metastatic breast cancer model.

KEY RESULTS

Activity of the transcription factor E2F1 induced by EGF was enhanced by DPP4, thus increasing PIN1 expression. Furthermore, DPP4 enhanced MEK/ERK and JNK/c-Jun signalling induced by EGF, inducing AP-1 activity and epithelial cell transformation. In contrast, DPP4 silencing or DPP4 inhibition in MCF7 cells inhibited PIN1 expression via E2F1 activity induced by EGF, decreasing colony formation and inducing DNA fragmentation. In the syngeneic 4T1 metastatic breast cancer model, DPP4 overexpression increased tumour development, whereas treatment with sitagliptin and/or juglone suppressed it. Consistent with these observations, DPP4 levels were positively correlated with PIN1 expression in human breast cancer.

CONCLUSIONS AND IMPLICATIONS

DPP4 promoted EGF-induced epithelial cell transformation and mammary tumourigenesis via induction of PIN1 expression, suggesting that sitagliptin targeting of DPP4 could be a treatment strategy in patients with breast cancer.

Dpp4 inhibition as a therapeutic strategy in cardiometabolic disease: Incretin-dependent and -independent function

Cardiometabolic disorders including obesity, diabetes and cardiovascular disease are among the most severe health problems worldwide. DPP4 enzymatic inhibitors were first developed as anti-diabetic reagents which preserve incretin hormones and promote post-prandial insulin secretion. It's been shown in animal studies that incretin-based therapy has a beneficial effect on cardiovascular disease. Recent studies demonstrated novel non-catalytic functions of DPP4 that may play a role in cardiometabolic disease. Although the role of DPP4 inhibition-mediated incretin effects has been well-reviewed, little information of its incretin-independent actions was introduced in cardiometabolic disease. In the current review, we will summarize the catalytic dependent and independent effects of DPP4 inhibition on cardiometabolic disease.

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Discuss the findings from recent large scale clinical trials (EXAMINE and SAVOR-TIMI 53)

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Summarize the catalytic dependent and independent effects of DPP4 inhibition on cardiometabolic disease

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Focus on recent evidence linking DPP4 inhibition therapy with cardiovascular disease

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Provide mechanistic insights into the cardiovascular effect of DPP4

Recent Advances in Dipeptidyl-Peptidase-4 Inhibition Therapy: Lessons from the Bench and Clinical Trials

DPP4 inhibitors (DPP4i) are a class of newly developed antidiabetic drugs which preserve incretin hormones and promote postprandial insulin secretion. Although the cardiovascular effect of DPP4 inhibition has been substantially studied, the exact role of DPP4 in cardiovascular disease especially in humans remains elusive. Previous small studies and meta-analyses have suggested a benefit in both surrogate outcomes and cardiovascular events for these agents. However, there was growing evidence in recent years questioning the cardioprotective effect of DPP4i. Further, a signal of heart failure hospitalization in a recent large scale clinical trial SAVOR-TIMI 53 has called into question the safety of these agents and their utility in the treatment of cardiovascular disease. In this review, we will revisit the physiologic function of DPP4 and discuss its role in cardiometabolic disease based on recent experimental and clinical studies.

DPP4 in cardiometabolic disease: recent insights from the laboratory and clinical trials of DPP4 inhibition

The discovery of incretin-based medications represents a major therapeutic advance in the pharmacological management of type 2 diabetes mellitus (T2DM), as these agents avoid hypoglycemia, weight gain, and simplify the management of T2DM. Dipeptidyl peptidase-4 (CD26, DPP4) inhibitors are the most widely used incretin-based therapy for the treatment of T2DM globally. DPP4 inhibitors are modestly effective in reducing HbA1c (glycated hemoglobin) (≈0.5%) and while these agents were synthesized with the understanding of the role that DPP4 plays in prolonging the half-life of incretins such as glucagon-like peptide-1 and gastric inhibitory peptide, it is now recognized that incretins are only one of many targets of DPP4. The widespread expression of DPP4 on blood vessels, myocardium, and myeloid cells and the nonenzymatic function of CD26 as a signaling and binding protein, across a wide range of species, suggest a teleological role in cardiovascular regulation and inflammation. Indeed, DPP4 is upregulated in proinflammatory states including obesity, T2DM, and atherosclerosis. Consistent with this maladaptive role, the effects of DPP4 inhibition seem to exert a protective role in cardiovascular disease at least in preclinical animal models. Although 2 large clinical trials suggest a neutral effect on cardiovascular end points, current limitations of performing trials in T2DM over a limited time horizon on top of maximal medical therapy must be acknowledged before rendering judgment on the cardiovascular efficacy of these agents. This review will critically review the science of DPP4 and the effects of DPP4 inhibitors on the cardiovascular system.

Dipeptidyl peptidase IV activity in commercial solutions of human serum albumin

Due to the heterogeneous nature of commercial human serum albumin (cHSA), other components, such as the protease dipeptidyl peptidase IV (DPP-IV), possibly contribute to the therapeutic effect of cHSA. Here, we provide evidence for the first time that DPP-IV activity contributes to the formation of aspartate-alanine diketopiperazine (DA-DKP), a known immunomodulatory molecule from the N terminus of human albumin. cHSA was assayed for DPP-IV activity using a specific DPP-IV substrate and inhibitor. DPP-IV activity was assayed at 37 and 60°C because cHSA solutions are pasteurized at 60°C. DPP-IV activity in cHSA was compared with other sources of albumin such as a recombinant albumin (rHSA). In addition, the production of DA-DKP was measured by negative electrospray ionization/liquid chromatography mass spectrometry (ESI(-)/LCMS). Significant levels of DPP-IV activity were present in cHSA. This activity was abolished using a specific DPP-IV inhibitor. Fully 70 to 80% DPP-IV activity remained at 60°C compared with the 37°C incubate. No DPP-IV activity was present in rHSA, suggesting that DPP-IV activity is present only in HSA produced using the Cohn fractionation process. The formation of DA-DKP at 60°C was observed with the DPP-IV inhibitor significantly decreasing this formation. DPP-IV activity in cHSA results in the production of DA-DKP, which could account for some of the clinical effects of cHSA.

Extracellular β-NAD(+) inhibits interleukin-1-induced matrix metalloproteinase-1 and -3 expression on human gingival fibroblasts

There is increasing evidence to show that extracellular β-nicotinamide adenine dinucleotide (β-NAD(+)) modulates various biological functions in inflammatory/immune regions. The aim of this study was to determine the effect of β-NAD(+) on matrix metalloproteinase (MMP) expression on human gingival fibroblasts (hGF), the excess production of which leads to the matrix degradation associated with the pathological processes of periodontitis. The expression of MMP-1 and MMP-3 on hGF was determined by real-time polymerase chain reaction (PCR) and an enzyme-linked immunosorbent assay. The phosphorylated status of mitogen-activated protein (MAP) kinases, extracellular signal-regulated kinase 1/2 (ERK), c-Jun N-terminal kinase (JNK), and p38 and the expression of inhibitor κB (IκB)α were determined by Western blotting. β-NAD(+) inhibited the expression of MMP-1 and MMP-3 triggered by IL-1α at gene and protein levels. β-NAD(+) had no significant effect on the IL-1α-induced phosphorylation of ERK1/2, JNK, and p38 and also had no effect on the IL-1α-induced degradation of IκBα relative to the control, suggesting that inhibition by β-NAD(+) was independent of the MAP kinase and the nuclear factor-κB signaling pathways. Transcripts of NAD(+)-metabolizing enzymes, such as NAD(+)-glycohydrolase, adenosine diphosphate (ADP)-ribosylcyclase, and ADP-ribosyltransferase, were expressed by hGF as assessed by RT-PCR. Experiments using α-NAD(+), which is not a substrate for ADP-ribosylcyclase or ADP-ribosyltransferase, revealed the possible contribution of NAD(+)-glycohydrolase to the inhibition of MMP. This is consistent with the finding that ADP-ribose, an NAD(+)-metabolite by NAD(+)-glycohydrolase, exhibited MMP inhibition similar to β-NAD(+). The present findings may provide an additional viewpoint to clarify a natural feedback mechanism during the inflammatory process in periodontal tissue.

Upregulation of CD26 expression in epithelial cells and stromal cells during wound-induced skin tumour formation

We have previously described InvEE transgenic mice in which non-dividing, differentiating epidermal cells express oncogenically activated MAPK kinase 1 (MEK1). Skin wounding triggers tumour formation in InvEE mice via a mechanism that involves epidermal release of IL-1α and attraction of a pro-tumorigenic inflammatory infiltrate. To look for potential effects on the underlying connective tissue, we screened InvEE and wild-type epidermis for differential expression of cytokines and immune modulators. We identified a single protein, CD26 (dipeptidyl peptidase-4). CD26 serum levels were not increased in InvEE mice. In contrast, CD26 was upregulated in keratinocytes expressing mutant MEK1 and in the epithelial compartment of InvEE tumours, where it accumulated at cell-cell borders. CD26 expression was increased in dermal fibroblasts following skin wounding but was downregulated in tumour stroma. CD26 activity was stimulated by calcium-induced intercellular adhesion in keratinocytes, suggesting that the upregulation of CD26 in InvEE epidermis is due to expansion of the differentiated cell layers. IL-1α treatment of dermal fibroblasts stimulated CD26 activity, and therefore epidermal IL-1α release may contribute to the upregulation of CD26 expression in wounded dermis. Pharmacological blockade of CD26, via Sitagliptin, reduced growth of InvEE tumours, while combined inhibition of IL-1α and CD26 delayed tumour onset and reduced tumour incidence. Our results demonstrate that inappropriate activation of MEK1 in the epidermis leads to changes in dermal fibroblasts that, like the skin inflammatory infiltrate, contribute to tumour formation.

The expression of dipeptidyl peptidase IV (DPPIV/CD26) is associated with enhanced chemosensitivity to paclitaxel in epithelial ovarian carcinoma cells

Dipeptidyl peptidase IV (DPPIV/CD26) is a multifunctional cell surface aminopeptidase that is widely expressed in different cell types. Recent studies have suggested that DPPIV plays an important role in tumor progression in several human malignancies. In the current study, we investigated the role of DPPIV in paclitaxel resistance in epithelial ovarian carcinoma (EOC) cells. We first examined the correlation between expression levels of DPPIV and sensitivity to paclitaxel in various EOC cell lines. Subsequently, to clarify the cellular functions of DPPIV, we investigated the role of this molecule in the sensitivity of EOC to paclitaxel in vitro and in vivo using stably DPPIV-transfected EOC cells. We identified a positive correlation between DPPIV expression and paclitaxel sensitivity in various EOC cell lines. In addition, we observed a significant increase in the paclitaxel sensitivity of DPPIV-overexpressing EOC cells. Furthermore, no apparent alteration in paclitaxel sensitivity was noted by the addition of a specific inhibitor of DPPIV activity in DPPIV-transfected or natively DPPIV-overexpressing EOC cells. In a subcutaneous murine model treated with paclitaxel, on Day 39, the tumor size of the DPPIV-transfected cell-inoculated group was as large as that of the vector-transfected cell-inoculated group. In contrast, on Day 61, the former was smaller than the latter. The present findings show that DPPIV may be involved in the increased sensitivity to paclitaxel of EOC cells regardless of the involvement of DPPIV activity.

The Role of Neuropeptide Endopeptidases in Cutaneous Immunity

Proteolytic processing and degradation plays an important role in modulating the generation and bioactivity of neuroendocrine peptide mediators, a class of key molecules in cutaneous biology.

Accordingly, the cellular localization and expression, and the molecular biology and structural properties of selected intracellular prohormone convertases and ectopically expressed zinc-binding metalloendoproteases are discussed.

A special reference will be made to the physiologic and pathophysiologic significance of these endopeptidases in cutaneous immunobiology.

Because of the number of pathologically relevant changes in inflammation and tumor progression that can be directly attributed to neprilysin and angiotensin-converting enzyme, a particular focus will be on the role of these enzymes in modulating innate and adaptive immune responses in the skin.

Essential role of placental leucine aminopeptidase in gynecologic malignancy

The M1 aminopeptidase family is important for the maturation or degradation of bioactive peptides by hydrolyzing their N-terminal amino acids. Some investigators have studied aminopeptidase in the maintenance of homeostasis including maintenance of normal pregnancy, memory retention, blood pressure regulation and antigen presentation. However, there are a few reports on the relation between the M1 aminopeptidase family and carcinoma. In addition to its capacity to degrade a range of peptides, placental-leucine aminopeptidase (P-LAP) has novel functions that impact on normal cells and neoplastic cells. P-LAP is the focus of this review.

Coexpression and interaction of CXCL10 and CD26 in mesenchymal cells by synergising inflammatory cytokines: CXCL8 and CXCL10 are discriminative markers for autoimmune arthropathies

Leukocyte infiltration during acute and chronic inflammation is regulated by exogenous and endogenous factors, including cytokines, chemokines and proteases. Stimulation of fibroblasts and human microvascular endothelial cells with the inflammatory cytokines interleukin-1beta (IL-1beta) or tumour necrosis factor alpha (TNF-alpha) combined with either interferon-alpha (IFN-alpha), IFN-beta or IFN-gamma resulted in a synergistic induction of the CXC chemokine CXCL10, but not of the neutrophil chemoattractant CXCL8. In contrast, simultaneous stimulation with different IFN types did not result in a synergistic CXCL10 protein induction. Purification of natural CXCL10 from the conditioned medium of fibroblasts led to the isolation of CD26/dipeptidyl peptidase IV-processed CXCL10 missing two NH2-terminal residues. In contrast to intact CXCL10, NH2-terminally truncated CXCL10(3-77) did not induce extracellular signal-regulated kinase 1/2 or Akt/protein kinase B phosphorylation in CXC chemokine receptor 3-transfected cells. Together with the expression of CXCL10, the expression of membrane-bound CD26/dipeptidyl peptidase IV was also upregulated in fibroblasts by IFN-gamma, by IFN-gamma plus IL-1beta or by IFN-gamma plus TNF-alpha. This provides a negative feedback for CXCL10-dependent chemotaxis of activated T cells and natural killer cells. Since TNF-alpha and IL-1beta are implicated in arthritis, synovial concentrations of CXCL8 and CXCL10 were compared in patients suffering from crystal arthritis, ankylosing spondylitis, psoriatic arthritis and rheumatoid arthritis. All three groups of autoimmune arthritis patients (ankylosing spondylitis, psoriatic arthritis and rheumatoid arthritis) had significantly increased synovial CXCL10 levels compared with crystal arthritis patients. In contrast, compared with crystal arthritis, only rheumatoid arthritis patients, and not ankylosing spondylitis or psoriatic arthritis patients, had significantly higher synovial CXCL8 concentrations. Synovial concentrations of the neutrophil chemoattractant CXCL8 may therefore be useful to discriminate between autoimmune arthritis types.

Effect of IL-1 on the hydrolysis of the tumor antigen epitope gp100280–288 by fibroblast-expressed enzymes

The role of proinflammatory cytokines in increasing the activity of specific proteases suggests the hypothesis that, by altering the expression of these mediators, adjuvants may modulate the effectiveness of peptides used as vaccines. The possible effect of IL-1 on fibroblast-expressed, peptidases was, thus, investigated by analyzing the degradation of a tumor antigen epitope (gp100(280-288), YLEPGPVTA) in the presence of cultured human fibroblasts. The data obtained indicate an increase of substrate hydrolysis after IL-1 treatment as compared with non-treated controls. Hydrolysis increase was accompanied by defined changes in the population of the by-products formed: specifically, the amount of peptidic by-products increased more than the amount of single amino acids, and the amount of the C-terminal by-products increased more than the amount of their N-terminal counterpart. These data appear to indicate that the positive effect of IL-1 on the activity of substrate-active enzymes is function of modified expression of a number of these enzymes by fibroblasts. From these data it can be inferred that the use of IL-1-inducing adjuvants, increasing the activity of peptidases expressed by bystander cells, may reduce the bio-availability of peptides used for immunization.

Expression of CD13/aminopeptidase N on human gingival fibroblasts and up-regulation upon stimulation with interleukin-4 and interleukin-13

BACKGROUND AND OBJECTIVES

Aminopeptidase N (APN)/CD13 is a multifunctional ectoenzyme that is involved in anti-inflammatory reactions, control of immune reactions and differentiation of many cellular systems. Here, we hypothesized that CD13/APN would be expressed on human gingival fibroblasts (hGF) and would contribute to the regulation of immune responses in periodontal tissue.

METHODS AND RESULTS

CD13/APN was expressed on hGF at the mRNA and protein levels as determined by reverse transcriptase-polymerase chain reaction (RT-PCR) and flow cytometry, respectively. Enzymatic activities accompanying the expression were assessed by colorimetrical analysis using the synthetic substrate Leu-p-nitroanilide. We examined the possible regulation of CD13/APN expression on hGF in response to T cell-derived cytokines. T helper (Th) 2 cell type cytokines such as interleukin-4 and interleukin-13, but not interleukin-2 or interleukin-15, preferentially increased the expression of proteins as well as the enzymatic activities of CD13/APN in a dose-dependent manner. Receptors for these cytokines, the interleukin-4 receptor alpha chain, interleukin-13 receptor alpha1 chain, and interleukin-2R common gamma chain, were expressed on hGF assessed by RT-PCR or flow cytometry. hGF exhibited inhibitory effects for formyl-methionyl-leucyl-phenylalanine (FMLP)-induced polymorphonuclear leukocyte-activation that was evaluated by Mac-1 expression, and this inhibitory effect was partially recovered by pre-treatment with the APN-specific inhibitor bestatin.

CONCLUSIONS

These findings suggested that CD13/APN expressed by hGF could contribute to the anti-inflammatory response in periodontal tissue, and may be involved in disease processes mediated by Th2 cells.

Dipeptidyl peptidase IV in tumor progression

Dipeptidyl peptidase IV (DPPIV) is a 110-kDa glycoprotein with ubiquitous expression. Several recent studies have shown that DPPIV affects tumor progression in several human malignancies. We found that ovarian carcinoma cell lines with higher DPPIV expression showed less invasive potential. Furthermore, introduction of DPPIV cDNA into SKOV3 cells (SKDPIV), derived from serous cystadenocarcinoma showing little DPPIV expression, caused a significant decrease in both migration and invasive potential. In addition, nude mice inoculated with SKDPIV cells showed significantly less peritoneal dissemination and longer survival time than those inoculated with parental or vector-transfected cells. We further examined the mechanisms of anti-invasive ability of DPPIV. The expression of E-cadherin was positively correlated with DPPIV expression among five independent ovarian carcinoma cell lines. The SKDPIV cells showed enhanced expression of E-cadherin with a cellular morphological change from a fibroblastic and motile phenotype to an epithelial phenotype compared to parental and MOCK cells. In addition, matrix metalloproteinase 2 (MMP-2) and membrane type 1 matrix metalloprotease (MT1-MMP), which are important markers associated with invasive and metastatic potential, were remarkably reduced in SKDPIV cells. In contrast, tissue inhibitors of matrix metalloproteinases (TIMPs) were enhanced by DPPIV transfection. These findings imply that DPPIV may functionally suppress peritoneal dissemination and progression of ovarian carcinoma by regulating the expression levels of several molecules associated with carcinoma cell invasion and progression.

Stromal cell-derived factor-1alpha-induced cell proliferation and its possible regulation by CD26/dipeptidyl peptidase IV in endometrial adenocarcinoma

CD26/dipeptidylpeptidase IV (DPPIV) is a 110 kD membrane-bound extracellular peptidase with ubiquitous expressions, and has a variety of functional properties in the development of human malignancies as well as T-cell biology. According to recent reports, stromal cell derived factor-1alpha (SDF-1alpha), which is a good substrate for CD26/DPPIV, is expressed in various solid tumors and is involved in tumor development or metastasis. We investigated the expression of SDF-1alpha and its corresponding receptor, CXCR4, in human endometrial carcinoma (EMCA) tissues and the function of SDF-1alpha on EMCA cells with its regulation by CD26/DPPIV. We demonstrated that SDF-1alpha and CXCR4 were expressed in human EMCA, and these immunoreactivities were significantly low in Grade 3 EMCA, which was similar to that of CD26/DPPIV, compared to those in Grade 1 and Grade 2. Additionally, exogenous SDF-1alpha concentration was significantly lower in CD26/DPPIV-transfected EMCA cells than that in vector-transfected cells. Moreover, exogenous SDF-1alpha significantly stimulated cell proliferation in vector-transfected cells in a concentration dependent manner. In contrast, in CD26/DPPIV-transfected cells, there was no apparent effect on proliferation shown by the addition of exogenous SDF-1alpha. This is the first report showing a direct link between the SDF-1alpha/CXCR4 pathway with CD26/DPPIV in solid tumors, suggesting that CD26/DPPIV is likely to directly modulate various SDF-1alpha induced functions.

Dipeptidyl-peptidase IV from bench to bedside: an update on structural properties, functions, and clinical aspects of the enzyme DPP IV

Dipeptidyl-peptidase IV/CD26 (DPP IV) is a cell-surface protease belonging to the prolyloligopeptidase family. It selectively removes the N-terminal dipeptide from peptides with proline or alanine in the second position. Apart from its catalytic activity, it interacts with several proteins, for instance, adenosine deaminase, the HIV gp120 protein, fibronectin, collagen, the chemokine receptor CXCR4, and the tyrosine phosphatase CD45. DPP IV is expressed on a specific set of T lymphocytes, where it is up-regulated after activation. It is also expressed in a variety of tissues, primarily on endothelial and epithelial cells. A soluble form is present in plasma and other body fluids. DPP IV has been proposed as a diagnostic or prognostic marker for various tumors, hematological malignancies, immunological, inflammatory, psychoneuroendocrine disorders, and viral infections. DPP IV truncates many bioactive peptides of medical importance. It plays a role in glucose homeostasis through proteolytic inactivation of the incretins. DPP IV inhibitors improve glucose tolerance and pancreatic islet cell function in animal models of type 2 diabetes and in diabetic patients. The role of DPP IV/ CD26 within the immune system is a combination of its exopeptidase activity and its interactions with different molecules. This enables DPP IV/CD26 to serve as a co-stimulatory molecule to influence T cell activity and to modulate chemotaxis. DPP IV is also implicated in HIV-1 entry, malignant transformation, and tumor invasion.

Cleavage of CD14 on human gingival fibroblasts cocultured with activated neutrophils is mediated by human leukocyte elastase resulting in down-regulation of lipopolysaccharide-induced IL-8 production

Activated polymorphonuclear leukocytes (PMNs) release various types of proteases and express them on the cell surface. The proteases play important roles in PMN-mediated events. In the present study, flow cytometric analysis revealed that CD14 expression on human gingival fibroblasts (HGF) was markedly reduced by PMA-activated PMNs in a coculture system. We found that this reduction was caused by both secreted and cell surface proteases produced by activated PMNs. A protease responsible for the reduction was found to be human leukocyte elastase (HLE) secreted from the activated PMNs by use of various protease inhibitors, although HLE was only partially involved in CD14 reduction caused by cell-bound molecule(s) on fixed PMNs. Analysis with purified HLE revealed a time- and dose-dependent reduction of CD14 on HGF, and complete reduction was observed by 20 microg/ml HLE treatment for 30-60 min, but the other molecules such as CD26, CD59, CD157, and MHC class I on HGF were only slightly reduced. This reduction of CD14 resulted from direct proteolysis by HLE on the cell surface, because HLE reduced CD14 on fixed HGF and also on purified cell membranes. As a result of CD14 proteolysis, IL-8 production by HGF was suppressed when triggered by 10 ng/ml LPS, but not by IL-1alpha, indicating that HLE inhibited a CD14-dependent cell activation. These findings suggested that activated PMNs have a potential negative feedback mechanism for HGF function at the inflammatory site, particularly in periodontal tissues.