CD26-mediated signaling for T cell activation occurs in lipid rafts through its association with CD45RO

Disease-modifying pharmacological treatments of type 1 diabetes: Molecular mechanisms, target checkpoints, and possible combinatorial treatments

After a century of extensive scientific investigations, there is still no curative or disease-modifying treatment available that can provide long-lasting remission for patients diagnosed with type 1 diabetes (T1D). Although T1D has historically been regarded as a classic autoimmune disorder targeting and destroying pancreatic islet β-cells, significant research has recently demonstrated that β-cells themselves also play a substantial role in the disease's progression, which could explain some of the unfavorable clinical outcomes. We offer a thorough review of scientific and clinical insights pertaining to molecular mechanisms behind pathogenesis and the different therapeutic interventions in T1D covering over 20 possible pharmaceutical intervention treatments. The interventions are categorized as immune therapies, treatments targeting islet endocrine dysfunctions, medications with dual modes of action in immune and islet endocrine cells, and combination treatments with a broader spectrum of activity. We suggest that these collective findings can provide a valuable platform to discover new combinatorial synergies in search of the curative disease-modifying intervention for T1D. SIGNIFICANCE STATEMENT: This research delves into the underlying causes of T1D and identifies critical mechanisms governing β-cell function in both healthy and diseased states. Thus, we identify specific pathways that could be manipulated by existing or new pharmacological interventions. These interventions fall into several categories: (1) immunomodifying therapies individually targeting immune cell processes, (2) interventions targeting β-cells, (3) compounds that act simultaneously on both immune cell and β-cell pathways, and (4) combinations of compounds simultaneously targeting immune and β-cell pathways.

Toward a better understanding of T cell dysregulation in autism: An integrative review

Autism spectrum disorder (ASD) is a highly heterogeneous disorder characterized by impairments in social, communicative, and restrictive behaviors. Over the past 20 years, research has highlighted the role of the immune system in regulating neurodevelopment and behavior. In ASD, immune abnormalities are frequently observed, such as elevations in pro-inflammatory cytokines, alterations in immune cell frequencies, and dysregulated mechanisms of immune suppression. The adaptive immune system - the branch of the immune system conferring cellular immunity - may be involved in the etiology of ASD. Specifically, dysregulated T cell activity, characterized by altered cellular function and increased cytokine release, presence of inflammatory phenotypes and altered cellular signaling, has been consistently observed in several studies across multiple laboratories and geographic regions. Similarly, mechanisms regulating their activation are also disrupted. T cells at homeostasis coordinate the healthy development of the central nervous system (CNS) during early prenatal and postnatal development, and aid in CNS maintenance into adulthood. Thus, T cell dysregulation may play a role in neurodevelopment and the behavioral and cognitive manifestations observed in ASD. Outside of the CNS, aberrant T cell activity may also be responsible for the increased frequency of immune based conditions in the ASD population, such as allergies, gut inflammation and autoimmunity. In this review, we will discuss the current understanding of T cell biology in ASD and speculate on mechanisms behind their dysregulation. This review also evaluates how aberrant T cell biology affects gastrointestinal issues and behavior in the context of ASD.

Bidirectional relation between dipeptidyl peptidase 4 and angiotensin II type I receptor signaling

Cardiometabolic diseases are often associated with heightened levels of angiotensin II (Ang II), which accounts for the observed oxidative stress, inflammation, and fibrosis. Accumulating evidence indicates a parallel upregulation of dipeptidyl dipeptidase 4 (DPP4) activity in cardiometabolic diseases, with its inhibition shown to mitigate oxidative stress, inflammation, and fibrosis. These findings highlight an overlap between the pathophysiological mechanisms used by Ang II and DPP4. Recent evidence demonstrates that targeted inhibition of DPP4 prevents the rise in Ang II and its associated molecules in experimental models of cardiometabolic diseases. Similarly, inhibitors of the angiotensin I-converting enzyme (ACE) or Ang II type 1 receptor (AT1R) blockers downregulate DPP4 activity, establishing a bidirectional relationship between DPP4 and Ang II. Here, we discuss the current evidence supporting the cross talk between Ang II and DPP4, along with the potential mechanisms promoting this cross regulation. A comprehensive analysis of this bidirectional relationship across tissues will advance our understanding of how DPP4 and Ang II collectively promote the development and progression of cardiometabolic diseases.

Regulation of Peptidase Activity beyond the Active Site in Human Health and Disease

This comprehensive review addresses the intricate and multifaceted regulation of peptidase activity in human health and disease, providing a comprehensive investigation that extends well beyond the boundaries of the active site. Our review focuses on multiple mechanisms and highlights the important role of exosites, allosteric sites, and processes involved in zymogen activation. These mechanisms play a central role in shaping the complex world of peptidase function and are promising potential targets for the development of innovative drugs and therapeutic interventions. The review also briefly discusses the influence of glycosaminoglycans and non-inhibitory binding proteins on enzyme activities. Understanding their role may be a crucial factor in the development of therapeutic strategies. By elucidating the intricate web of regulatory mechanisms that control peptidase activity, this review deepens our understanding in this field and provides a roadmap for various strategies to influence and modulate peptidase activity.

Low levels of CD26 on certain cellular subtypes of donor harvest is associated with better clinical outcomes post allogeneic stem cell transplantation through regulation of NF-κB pathway and pro-inflammatory cytokines

BACKGROUND

We had previously reported significant association of immunoectoenzyme CD26 expression on donor harvest with acute Graft-versus-Host-Disease (aGVHD) in allogeneic stem cell transplantation (ASCT) patients. The current study was aimed at analysing CD26 signaling pathway molecules and understanding their impact on immune reconstitution and clinical outcomes post-ASCT.

SUBJECTS AND METHODOLOGY

The study cohort included 26 transplant donors/patients who underwent reduced intensity (n = 21), myeloablative (n = 4) and non-myeloablative (n = 1) ASCT for hematological malignancies. Donors were matched related donors (n = 19) and haploidentical donors (n = 7). Surface expression of CD26, CD73 and ADA, and various immune cell subtypes were assessed by multicolour-flow cytometry. Soluble CD26 (sCD26) and cytokine levels were measured in plasma samples by ELISA and Multiplex Luminex assay, respectively. Immune cells from healthy individuals were stimulated with phytohemagglutinin (PHA) in the presence or absence of CD26 inhibitor. Effect of CD26 inhibition on NF-κB localization in PHA stimulated cells was analysed by immunofluorescence and confocal microscopy. Pro-inflammatory cytokines from the culture supernatants were detected with Cytometric bead array flow cytometry. Association of all measured markers with clinical outcomes was evaluated using appropriate statistical tests.

RESULTS

CD26 surface expression on PBSC donor harvest cells showed increased risk of chronic GVHD (cGVHD, p = 0.055). Amongst the various immune cell subtypes, decreased B cells in harvest showed significant association with aGVHD (p = 0.022) whereas increased myeloid dendritic cells and CD3+T cells at Day100 in peripheral blood of transplant recipients correlated with cGVHD (p = 0.046) and aGVHD (p = 0.035), respectively. Further, high sCD26 in transplant recipients at Day100 exhibited association with reduced event-free survival (EFS) (p = 0.011). Higher CD26 expression on more & less mature NK cells, naïve & post-switched memory B cells and Treg cells in the donor harvest (p < 0.05) led to lower EFS in transplant recipients. Mechanistically, CD26 inhibitor caused dose-dependent reduction in CD26 enzyme activity and in pro-inflammatory cytokine production in post mitogen-stimulated T cell cultures.

CONCLUSION

Our study has implicated that lower CD26 expression on immune cell subtypes of the donor stem cell harvest is associated with reduced risk of GVHD and better survival. The underlying mechanism was found to be through NF-κB pathway and pro-inflammatory cytokines. Based on these observations, chemically designed or natural resources-based CD26 inhibitors can be explored further in clinical trials for improving ASCT outcomes.

CD26 CAR-T cells have attenuated mitochondrial and glycolytic metabolic profiling

BACKGROUND

Multiple targets of chimeric antigen receptor T cells (CAR-T cells) are shared expressed by tumor cells and T cells, these self-antigens may stimulate CAR-T cells continuously during the expansion. Persistent exposure to antigens is considered to cause metabolic reprogramming of T cells and the metabolic profiling is critical in determining the cell fate and effector function of CAR-T cells. However, whether the stimulation of self-antigens during CAR-T cell generation could remodel the metabolic profiling is unclear. In this study, we aim to investigate the metabolic characteristics of CD26 CAR-T cells, which expressed CD26 antigens themselves.

METHODS

The mitochondrial biogenesis of CD26 and CD19 CAR-T cells during expansion was evaluated by the mitochondrial content, mitochondrial DNA copy numbers and genes involved in mitochondrial regulation. The metabolic profiling was investigated by the ATP production, mitochondrial quality and the expression of metabolism-related genes. Furthermore, we assessed the phenotypes of CAR-T cells through memory-related markers.

RESULTS

We reported that CD26 CAR-T cells had elevated mitochondrial biogenesis, ATP production and oxidative phosphorylation at early expansion stage. However, the mitochondrial biogenesis, mitochondrial quality, oxidative phosphorylation and glycolytic activity were all weakened at later expansion stage. On the contrary, CD19 CAR-T cells did not exhibit such characteristics.

CONCLUSION

CD26 CAR-T cells showed distinctive metabolic profiling during expansion that was extremely unfavorable to cell persistence and function. These findings may provide new insights for the optimization of CD26 CAR-T cells in terms of metabolism.

Targeting cluster of differentiation 26 / dipeptidyl peptidase 4 (CD26/DPP4) in organ fibrosis

Cluster of differentiation 26 (CD26)/dipeptidyl peptidase 4 (DPP4) is an exopeptidase that is expressed as a transmembrane protein in many organs but also present in a circulating soluble form. Beyond its enzymatic and costimulatory activity, CD26/DPP4 is involved in the pathogenesis of chronic fibrotic diseases across many organ types, such as liver cirrhosis, kidney fibrosis and lung fibrosis. Organ fibrosis is associated with a high morbidity and mortality, and there are no causative therapies that can effectively attenuate the progress of the disease. Growing evidence suggests that inhibiting CD26/DPP4 can modulate the profibrotic tissue microenvironment and thus reduce fibrotic changes within affected organs. This review summarizes the role of CD26/DPP4 in fibroproliferative disorders and highlights new opportunities for an antifibrotic treatment by CD26/DPP4 inhibition. As a major advantage, CD26/DPP4 inhibitors have been in safe and routine clinical use in type 2 diabetes for many years and thus qualify for repurposing to repurpose as a promising therapeutic against fibrosis. LINKED ARTICLES: This article is part of a themed issue on Translational Advances in Fibrosis as a Therapeutic Target. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v180.22/issuetoc.

Dipeptidyl Peptidase 4 Inhibitor‒Associated Bullous Pemphigoid Is Characterized by an Altered Expression of Cytokines in the Skin

Dipeptidyl peptidase 4 inhibitors (DPP4is), commonly used drugs for treatment of type 2 diabetes, increase the risk for bullous pemphigoid (BP). Currently, the mechanism leading to the loss of immunological tolerance of the cutaneous adhesion molecule BP180 as well as similarities and differences in disease progression between DPP4i-associated BP (DPP4i-BP) and DPP4i-independent regular BP are largely unknown. We analyzed the expression of 32 cytokines and two proteases by Luminex and ELISA assays in samples taken from lesional and nonlesional skin of patients with regular BP or DPP4i-BP and healthy controls. Cytokines mediating B-cell survival and targeting such as BAFF, CCL4, CXCL12, and IL-6 were expressed at a higher level in the lesional regular BP skin than the levels in the lesional DPP4i-BP skin. The DPP4i-BP samples had increased levels of eosinophilic cytokines CCL1, CCL17, CCL26, and IL-5, which correlated with the serum level of anti-BP180 NC16A IgG autoantibodies. The mRNA expression of BAFF, IL6, CCL1, CCL17, CCL26, and IL5 measured by qPCR correlated with the protein levels. Taken together, the cutaneous cytokine profiles were found to provide distinctive molecular fingerprints between regular BP and DPP4i-BP.

Dipeptidyl Peptidase-4 Stabilizes Integrin α4β1 Complex to Promote Thyroid Cancer Cell Metastasis by Activating Transforming Growth Factor-Beta Signaling Pathway

Background: Metastatic disease is a major cause of thyroid cancer-related death. However, the mechanisms responsible for thyroid cancer metastasis are unclear. Dipeptidyl peptidase-4 (DPP4) is a multifunctional cell surface glycoprotein that has been reported to be a negative prognostic factor in thyroid cancer. We explored the molecular mechanism of the role of DPP4 in thyroid cancer cell metastasis. Methods: The effects of DPP4 on thyroid cancer cell migration/invasion in vitro were assessed by transwell assays. A lung metastatic mouse model was also established to determine the effect of DPP4 on tumor metastasis in vivo. DPP4 inhibitor sitagliptin was used to test its effect on thyroid cancer cell metastasis. The mechanism of which DPP4 promotes thyroid cancer cell metastasis was explored by a series of molecular and biochemical experiments. Results: We observed that DPP4 was significantly upregulated in papillary thyroid cancers compared with control subjects, and its expression was positively associated with lymph node metastasis and BRAF^V600E mutation. Functional studies showed that DPP4 knockdown significantly inhibited metastatic potential of thyroid cancer cells, and vice versa. However, DPP4 inhibitor sitagliptin did not affect the metastatic ability of thyroid cancer cells, indicating that the promoting effect of DPP4 on tumor metastasis was independent of its enzymatic activity. Mechanistically, DPP4 interacted with the α4 and β1 integrin subunits, and stabilized the formation of integrin α4β1 complex. DPP4-mediated integrin signal activation promoted the nuclear localization of c-Jun through the FAK/AKT pathway, thereby inducing the transcription of transforming growth factor-beta 1 (TGFB1 coding for protein TGF-β1). TGF-β1 then facilitated tumor metastasis by inducing the epithelial-mesenchymal transition. Conclusions: DPP4 promotes thyroid cancer cell metastasis through the integrins/FAK/AKT/c-Jun/TGF-β1 signaling axis. These findings may have implications for an alternative therapeutic strategy for thyroid cancer.

Role of Dipeptidyl Peptidase-4 (DPP4) on COVID-19 Physiopathology

DPP4/CD26 is a single-pass transmembrane protein with multiple functions on glycemic control, cell migration and proliferation, and the immune system, among others. It has recently acquired an especial relevance due to the possibility to act as a receptor or co-receptor for SARS-CoV-2, as it has been already demonstrated for other coronaviruses. In this review, we analyze the evidence for the role of DPP4 on COVID-19 risk and clinical outcome, and its contribution to COVID-19 physiopathology. Due to the pathogenetic links between COVID-19 and diabetes mellitus and the hyperinflammatory response, with the hallmark cytokine storm developed very often during the disease, we dive deep into the functions of DPP4 on carbohydrate metabolism and immune system regulation. We show that the broad spectrum of functions regulated by DPP4 is performed both as a protease enzyme, as well as an interacting partner of other molecules on the cell surface. In addition, we provide an update of the DPP4 inhibitors approved by the EMA and/or the FDA, together with the newfangled approval of generic drugs (in 2021 and 2022). This review will also cover the effects of DPP4 inhibitors (i.e., gliptins) on the progression of SARS-CoV-2 infection, showing the role of DPP4 in this disturbing disease.

Lipid rafts as viral entry routes and immune platforms: A double-edged sword in SARS-CoV-2 infection?

Lipid rafts are nanoscopic compartments of cell membranes that serve a variety of biological functions. They play a crucial role in viral infections, as enveloped viruses such as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) can exploit rafts to enter or quit target cells. On the other hand, lipid rafts contribute to the formation of immune synapses and their proper functioning is a prerequisite for adequate immune response and viral clearance. In this narrative review we dissect the panorama focusing on this singular aspect of cell biology in the context of SARS-CoV-2 infection and therapy. A lipid raft-mediated mechanism can be hypothesized for many drugs recommended or considered for the treatment of SARS-CoV-2 infection, such as glucocorticoids, antimalarials, immunosuppressants and antiviral agents. Furthermore, the additional use of lipid-lowering agents, like statins, may affect the lipid composition of membrane rafts and thus influence the processes occurring in these compartments. The combination of drugs acting on lipid rafts may be successful in the treatment of more severe forms of the disease and should be reserved for further investigation.

Emerging Role of Dipeptidyl Peptidase-4 in Autoimmune Disease

Dipeptidyl-peptidase IV (DPP4), originally identified as an aminopeptidase in 1960s, is an ubiquitously expressed protease presented as either a membrane-bound or soluble form. DPP4 cleaves dipeptide off from the N-terminal of its substrates, altering the bioactivity of its substrates. Subsequent studies reveal that DPP4 is also involved in various cellular processes by directly binding to a number of ligands, including adenosine deaminase, CD45, fibronectin, plasminogen, and caveolin-1. In recent years, many novel functions of DPP4, such as promoting fibrosis and mediating virus entry, have been discovered. Due to its implication in fibrotic response and immunoregulation, increasing studies are focusing on the potential role of DPP4 in inflammatory disorders. As a moonlighting protein, DPP4 possesses multiple functions in different types of cells, including both enzymatic and non-enzymatic functions. However, most of the review articles on the role of DPP4 in autoimmune disease were focused on the association between DPP4 enzymatic inhibitors and the risk of autoimmune disease. An updated comprehensive summary of DPP4's immunoregulatory actions including both enzymatic dependent and independent functions is needed. In this article, we will review the recent advances of DPP4 in immune regulation and autoimmune rheumatic disease.

CD26/DPP4 as a Therapeutic Target in Nonalcoholic Steatohepatitis Associated Hepatocellular Carcinoma

Simple Summary

CD26/DPP4 has been reported to attenuate anticancer immunity via chemokine cleavage and to promote insulin resistance and inflammation in the liver and/or adipose tissue via dysregulation of macrophage M1/M2 polarization. These results suggest the promotive roles of CD26/DPP4 especially in nonalcoholic steatohepatitis (NASH) associated hepatocellular carcinoma (HCC). In this review, we discuss the biological roles of CD26/DPP4 in the development and progression of NASH associated HCC and the potential of DPP4 inhibitors as therapeutic agents for HCC.

Abstract

Hepatocellular carcinoma (HCC) is generally considered an “immune-cold” cancer since T cells are not observed abundantly in HCC tumor tissue. Combination therapy with immune checkpoint inhibitors and vascular endothelial growth factor (VEGF) inhibitors is currently recognized as a first-line systemic treatment for advanced-stage HCC. Immunologically, immune checkpoint inhibitors influence the recognition of cancer cells by T cells, and VEGF inhibitors influence the infiltration of T cells into tumors. However, no drugs that facilitate the trafficking of T cells toward tumors have been developed. Chemokines are promising agents that activate T cell trafficking. On the other hand, metabolic factors such as obesity and insulin resistance are considered risk factors for HCC development. CD26/dipeptidyl peptidase 4 (DPP4) functions as a serine protease, selectively cleaving polypeptides with a proline or alanine at the penultimate N-terminal position, such as chemokines. Recently, CD26/DPP4 has been reported to attenuate anticancer immunity via chemokine cleavage and to promote insulin resistance and inflammation in the liver and/or adipose tissue via dysregulation of macrophage M1/M2 polarization. In this review, we discuss the promotive roles of CD26/DPP4 in HCC development and progression and the potential of DPP4 inhibitors as therapeutic agents for HCC.

Immune Profiling of COVID-19 in Correlation with SARS and MERS

Acute respiratory distress syndrome (ARDS) is a major complication of the respiratory illness coronavirus disease 2019, with a death rate reaching up to 40%. The main underlying cause of ARDS is a cytokine storm that results in a dysregulated immune response. This review discusses the role of cytokines and chemokines in SARS-CoV-2 and its predecessors SARS-CoV and MERS-CoV, with particular emphasis on the elevated levels of inflammatory mediators that are shown to be correlated with disease severity. For this purpose, we reviewed and analyzed clinical studies, research articles, and reviews published on PubMed, EMBASE, and Web of Science. This review illustrates the role of the innate and adaptive immune responses in SARS, MERS, and COVID-19 and identifies the general cytokine and chemokine profile in each of the three infections, focusing on the most prominent inflammatory mediators primarily responsible for the COVID-19 pathogenesis. The current treatment protocols or medications in clinical trials were reviewed while focusing on those targeting cytokines and chemokines. Altogether, the identified cytokines and chemokines profiles in SARS-CoV, MERS-CoV, and SARS-CoV-2 provide important information to better understand SARS-CoV-2 pathogenesis and highlight the importance of using prominent inflammatory mediators as markers for disease diagnosis and management. Our findings recommend that the use of immunosuppression cocktails provided to patients should be closely monitored and continuously assessed to maintain the desirable effects of cytokines and chemokines needed to fight the SARS, MERS, and COVID-19. The current gap in evidence is the lack of large clinical trials to determine the optimal and effective dosage and timing for a therapeutic regimen.

The Multiple Biological Functions of Dipeptidyl Peptidase-4 in Bone Metabolism

Dipeptidyl peptidase-4 (DPP4) is a ubiquitously occurring protease involved in various physiological and pathological processes ranging from glucose homeostasis, immunoregulation, inflammation to tumorigenesis. Recently, the benefits of DPP4 inhibitors as novel hypoglycemic agents on bone metabolism have attracted extensive attraction in many studies, indicating that DPP4 inhibitors may regulate bone homeostasis. The effects of DPP4 on bone metabolism are still unclear. This paper thoroughly reviews the potential mechanisms of DPP4 for interaction with adipokines, bone cells, bone immune cells, and cytokines in skeleton system. This literature review shows that the increased DPP4 activity may indirectly promote bone resorption and inhibit bone formation, increasing the risk of osteoporosis. Thus, bone metabolic balance can be improved by decreasing DPP4 activities. The substantial evidence collected and analyzed in this review supports this implication.

The Serine Protease CD26/DPP4 in Non-Transformed and Malignant T Cells

Simple Summary

The transmembrane serine protease CD26/Dipeptidylpeptidase 4 modulates T-cell activation, proliferation, and effector function. Due to their remarkable tumoricidal properties CD26-positive T cells are considered promising candidates for T cell-based immunotherapies while in cutaneous T cell lymphoma CD26/DPP4 expression patterns are established markers for diagnosis and possibly prognosis. With a focus on T cells, we review current knowledge on the regulation of CD26/DPP4 expression and release, its implication in T-cell effector function and the suitability CD26/DPP4 as a diagnostic and/or prognostic factor in T-cell malignancies.

Abstract

CD26/Dipeptidylpeptidase 4 is a transmembrane serine protease that cleaves off N-terminal dipeptides. CD26/DPP4 is expressed on several immune cell types including T and NK cells, dendritic cells, and activated B cells. A catalytically active soluble form of CD26/DPP4 can be released from the plasma membrane. Given its wide array of substrates and interaction partners CD26/DPP4 has been implicated in numerous biological processes and effects can be dependent or independent of its enzymatic activity and are exerted by the transmembrane protein and/or the soluble form. CD26/DPP4 has been implicated in the modulation of T-cell activation and proliferation and CD26/DPP4-positive T cells are characterized by remarkable anti-tumor properties rendering them interesting candidates for T cell-based immunotherapies. Moreover, especially in cutaneous T-cell lymphoma CD26/DPP4 expression patterns emerged as an established marker for diagnosis and treatment monitoring. Surprisingly, besides a profound knowledge on substrates, interaction partners, and associated signal transduction pathways, the precise role of CD26/DPP4 for T cell-based immune responses is only partially understood.

Structure-based study of immune receptors as eligible binding targets of coronavirus SARS-CoV-2 spike protein

One of the most important challenges in the battle against contagious SARS-CoV-2 is subtle identification of the virus pathogenesis. The broad range of COVID-19 clinical manifestations may indicate diversity of virus-host cells. Amongst key manifestations, especially in severe COVID-19 patients, reduction and/or exhaustion of lymphocytes, monocytes, basophils, and dendritic cells are seen.; therefore, it is required to recognize that how the virus infects the cells. Interestingly, angiotensin-converting enzyme 2 (ACE2) as the well-known receptor of SARS-CoV-2 is low or non-expressed in these cells. Using computational approach, several receptor candidates including leukocyte surface molecules and chemokine receptors that expressed in most lineages of immune cells were evaluated as the feasible receptor of spike receptor-binding domain (RBD) of SARS-CoV-2. The results revealed the higher binding affinity of CD26, CD2, CD56, CD7, CCR9, CD150, CD4, CD50, XCR1 and CD106 compared to ACE2. However, the modes of binding and amino acids involved in the interactions with the RBD domain of spike were various. Overall, the affinity of immune receptor candidates in binding to SARS-CoV-2 RBD may offer insight into the recognition of novel therapeutic targets in association with COVID-19.

The Role of Post-Translational Modifications of Chemokines by CD26 in Cancer

Chemokines are a large family of small chemotactic cytokines that fulfill a central function in cancer. Both tumor-promoting and -impeding roles have been ascribed to chemokines, which they exert in a direct or indirect manner. An important post-translational modification that regulates chemokine activity is the NH₂-terminal truncation by peptidases. CD26 is a dipeptidyl peptidase (DPPIV), which typically clips a NH₂-terminal dipeptide from the chemokine. With a certain degree of selectivity in terms of chemokine substrate, CD26 only recognizes chemokines with a penultimate proline or alanine. Chemokines can be protected against CD26 recognition by specific amino acid residues within the chemokine structure, by oligomerization or by binding to cellular glycosaminoglycans (GAGs). Upon truncation, the binding affinity for receptors and GAGs is altered, which influences chemokine function. The consequences of CD26-mediated clipping vary, as unchanged, enhanced, and reduced activities are reported. In tumors, CD26 most likely has the most profound effect on CXCL12 and the interferon (IFN)-inducible CXCR3 ligands, which are converted into receptor antagonists upon truncation. Depending on the tumor type, expression of CD26 is upregulated or downregulated and often results in the preferential generation of the chemokine isoform most favorable for tumor progression. Considering the tight relationship between chemokine sequence and chemokine binding specificity, molecules with the appropriate characteristics can be chemically engineered to provide innovative therapeutic strategies in a cancer setting.

Begelomab for severe refractory dermatomyositis: A case report

RATIONALE

Severe refractory idiopathic inflammatory myopathy (IIM) represents a challenge for the clinician. The lack of efficacy of available tools reflects our incomplete insight into the molecular events sustaining the inflammatory tissue damage in these patients. We present the first case of refractory IIM treated with anti-dipeptidyl peptidase-4 (DPP-4)/cluster of differentiation 26 (CD26) monoclonal antibody.

PATIENT CONCERNS

A 55-year old man presented with proximal muscle weakness, diffuse erythematous skin lesions which rapidly evolved into ulcerations, dysphagia and dysphonia.

DIAGNOSIS

Increased serum creatine kinase levels and histological findings at muscle and skin biopsies were compatible with the diagnosis of dermatomyositis (DM). Several lines of treatment failed to control the disease including steroids, mycophenolate mofetil, tacrolimus, intravenous immunoglobulins and rituximab. Despite therapy, the patient also had recurrent intestinal vasculitis causing bowel perforation. Concurrently, DPP-4/CD26 expression in the patient's skin and skeletal muscle was observed.

INTERVENTIONS

The patient was treated with begelomab, a murine immunoglobulin G2b monoclonal antibody against DPP-4/CD26.

OUTCOMES

Dysphagia, skin lesions and intestinal vasculitis resolved and the patient experienced a significant improvement of his quality of life.

CONCLUSION

Blockade of DPP-4/CD26, which is expressed on T cells and mediates T cell activation and function, is safe and might be effective in patients with refractory DM.

Epidemiology, virology, and history of Covid-19 infection

In this chapter, we will discuss the infection history and epidemiology, the viral structure of COVID 19 or SARS-CoV-2, mode of transmission, virulence, and pathogenesis of disease, and we also discuss how it was started and its relation to other coronaviruses. Then we will mention the relation to pregnancy, how it can affect pregnant female, sequelae on pregnancy course and labor, and effect on fetus and neonates.

SARS-CoV, MERS-CoV and SARS-CoV-2 infections in pregnancy and fetal development

Recently, in China, in 2019, a new type of disease has arisen caused by a new strain of coronavirus, the SARS-CoV-2 virus, considered extremely worrying due to its high infectivity power and the easy ability to spread geographically. For patients in general, the clinical features resulting from respiratory syndromes can trigger an asymptomatic condition. However, 25 % of patients infected by SARS-CoV-2 can progress to severity. Pregnant women are an unknown field in this complex process, and although they have symptoms similar to non-pregnant women, some points should be considered, such as complications during pregnancy and postpartum. Thus, the aim of this study was to understand the consequences of pregnancy and fetal development, caused by infections by the SARS-CoV, MERS-CoV and SARS-CoV-2 viruses. Among the aforementioned infections, MERS-CoV seems to be the most dangerous for newborns, inducing high blood pressure, pre-eclampsia, pneumonia, acute renal failure, and multiple organ failure in mother. This also causes a higher occurrence of emergency cesarean deliveries and premature births, in addition, some deaths of mothers and fetuses were recorded. Meanwhile, SARS-CoV and SARS-CoV-2 appear to have less severe symptoms. Furthermore, although a study found the ACE2 receptor, used by SARS-CoV-2, widely distributed in specific cell types of the maternal-fetal interface, there is no evidence of vertical transmission for any of the coronaviruses. Thus, the limited reported obstetric cases alert to the need for advanced life support for pregnant women infected with coronaviruses and to the need for further investigation for application in clinical practice.

Coronavirus membrane fusion mechanism offers a potential target for antiviral development

The coronavirus disease 2019 (COVID-19) pandemic has focused attention on the need to develop effective therapies against the causative agent, SARS-CoV-2, and also against other pathogenic coronaviruses (CoV) that have emerged in the past or might appear in future. Researchers are therefore focusing on steps in the CoV replication cycle that may be vulnerable to inhibition by broad-spectrum or specific antiviral agents. The conserved nature of the fusion domain and mechanism across the CoV family make it a valuable target to elucidate and develop pan-CoV therapeutics. In this article, we review the role of the CoV spike protein in mediating fusion of the viral and host cell membranes, summarizing the results of research on SARS-CoV, MERS-CoV, and recent peer-reviewed studies of SARS-CoV-2, and suggest that the fusion mechanism be investigated as a potential antiviral target. We also provide a supplemental file containing background information on the biology, epidemiology, and clinical features of all human-infecting coronaviruses, along with a phylogenetic tree of these coronaviruses.

Coronavirus membrane fusion mechanism offers a potential target for antiviral development

The coronavirus disease 2019 (COVID-19) pandemic has focused attention on the need to develop effective therapies against the causative agent, SARS-CoV-2, and also against other pathogenic coronaviruses (CoV) that have emerged in the past or might appear in future. Researchers are therefore focusing on steps in the CoV replication cycle that may be vulnerable to inhibition by broad-spectrum or specific antiviral agents. The conserved nature of the fusion domain and mechanism across the CoV family make it a valuable target to elucidate and develop pan-CoV therapeutics. In this article, we review the role of the CoV spike protein in mediating fusion of the viral and host cell membranes, summarizing the results of research on SARS-CoV, MERS-CoV, and recent peer-reviewed studies of SARS-CoV-2, and suggest that the fusion mechanism be investigated as a potential antiviral target. We also provide a supplemental file containing background information on the biology, epidemiology, and clinical features of all human-infecting coronaviruses, along with a phylogenetic tree of these coronaviruses.

Dipeptidyl Peptidase-4 at the Interface Between Inflammation and Metabolism

Dipeptidyl peptidase-4 (DPP4) is a serine protease that rapidly inactivates the incretin peptides, glucagon-like peptide-1, and glucose-dependent insulinotropic polypeptide to modulate postprandial islet hormone secretion and glycemia. Dipeptidyl peptidase-4 also has nonglycemic effects by controlling the progression of inflammation, which may be mediated more through direct protein-protein interactions than catalytic activity in the context of nonalcoholic fatty liver disease (NAFLD), obesity, and type 2 diabetes (T2D). Failure to resolve inflammation resulting in chronic subclinical activation of the immune system may influence the development of metabolic dysregulation. Thus, through both its cleavage and regulation of the bioactivity of peptide hormones and its influence on inflammation, DPP4 exhibits a diverse array of effects that can influence the progression of metabolic disease. Here, we highlight our current understanding of the complex biology of DPP4 at the intersection of inflammation, obesity, T2D, and NAFLD. We compare and review new mechanisms identified in basic laboratory and clinical studies, which may have therapeutic application and relevance to the pathogenesis of obesity and T2D.

Germline genetic patterns underlying familial rheumatoid arthritis, systemic lupus erythematosus and primary Sjögren's syndrome highlight T cell-initiated autoimmunity

OBJECTIVES

Familial aggregation of primary Sjögren's syndrome (pSS), systemic lupus erythematosus (SLE), rheumatoid arthritis (RA) and co-aggregation of these autoimmune diseases (ADs) (also called familial autoimmunity) is well recognised. However, the genetic predisposition variants that explain this clustering remains poorly defined.

METHODS

We used whole-exome sequencing on 31 families (9 pSS, 11 SLE, 6 RA and 5 mixed autoimmunity), followed by heterozygous filtering and cosegregation analysis of a family-focused approach to document rare variants predicted to be pathogenic by in silico analysis. Potential importance in immune-related processes, gene ontology, pathway enrichment and overlap analyses were performed to prioritise gene sets.

RESULTS

A range from 1 to 50 rare possible pathogenic variants, including 39 variants in immune-related genes across SLE, RA and pSS families, were identified. Among this gene set, regulation of T cell activation (p=4.06×10-7) and T cell receptor (TCR) signalling pathway (p=1.73×10-6) were particularly concentrated, including PTPRC (CD45), LCK, LAT-SLP76 complex genes (THEMIS, LAT, ITK, TEC, TESPA1, PLCL1), DGKD, PRKD1, PAK2 and NFAT5, shared across 14 SLE, RA and pSS families. TCR-interactive genes P2RX7, LAG3, PTPN3 and LAX1 were also detected. Overlap analysis demonstrated that the antiviral immunity gene DUS2 variant cosegregated with SLE, RA and pSS phenotypes in an extended family, that variants in the TCR-pathway genes CD45, LCK and PRKD1 occurred independently in three mixed autoimmunity families, and that variants in CD36 and VWA8 occurred in both RA-pSS and SLE-pSS families.

CONCLUSIONS

Our preliminary results define common genetic characteristics linked to familial pSS, SLE and RA and highlight rare genetic variations in TCR signalling pathway genes which might provide innovative molecular targets for therapeutic interventions for those three ADs.

Dopamine receptor D3 signalling in astrocytes promotes neuroinflammation

BACKGROUND

Neuroinflammation constitutes a pathogenic process leading to neurodegeneration in several disorders, including Alzheimer's disease, Parkinson's disease (PD) and sepsis. Despite microglial cells being the central players in neuroinflammation, astrocytes play a key regulatory role in this process. Our previous results indicated that pharmacologic-antagonism or genetic deficiency of dopamine receptor D3 (DRD3) attenuated neuroinflammation and neurodegeneration in two mouse models of PD. Here, we studied how DRD3-signalling affects the dynamic of activation of microglia and astrocyte in the context of systemic inflammation.

METHODS

Neuroinflammation was induced by intraperitoneal administration of LPS. The effect of genetic DRD3-deficiency or pharmacologic DRD3-antagonism in the functional phenotype of astrocytes and microglia was determined by immunohistochemistry and flow cytometry at different time-points.

RESULTS

Our results show that DRD3 was expressed in astrocytes, but not in microglial cells. DRD3 deficiency resulted in unresponsiveness of astrocytes and in attenuated microglial activation upon systemic inflammation. Furthermore, similar alterations in the functional phenotypes of glial cells were observed by DRD3 antagonism and genetic deficiency of DRD3 upon LPS challenge. Mechanistic analyses show that DRD3 deficiency resulted in exacerbated expression of the anti-inflammatory protein Fizz1 in glial cells both in vitro and in vivo.

CONCLUSIONS

These results suggest that DRD3 signalling regulates the dynamic of the acquisition of pro-inflammatory and anti-inflammatory features by astrocytes and microglia, finally favouring microglial activation and promoting neuroinflammation.

CD26 and Asthma: a Comprehensive Review

Asthma is a heterogeneous and chronic inflammatory family of disorders of the airways with increasing prevalence that results in recurrent and reversible bronchial obstruction and expiratory airflow limitation. These diseases arise from the interaction between environmental and genetic factors, which collaborate to cause increased susceptibility and severity. Many asthma susceptibility genes are linked to the immune system or encode enzymes like metalloproteases (e.g., ADAM-33) or serine proteases. The S9 family of serine proteases (prolyl oligopeptidases) is capable to process peptide bonds adjacent to proline, a kind of cleavage-resistant peptide bonds present in many growth factors, chemokines or cytokines that are important for asthma. Curiously, two serine proteases within the S9 family encoded by genes located on chromosome 2 appear to have a role in asthma: CD26/dipeptidyl peptidase 4 (DPP4) and DPP10. The aim of this review is to summarize the current knowledge about CD26 and to provide a structured overview of the numerous functions and implications that this versatile enzyme could have in this disease, especially after the detection of some secondary effects (e.g., viral nasopharyngitis) in type II diabetes mellitus patients (a subset with a certain risk of developing obesity-related asthma) upon CD26 inhibitory therapy.

Middle East Respiratory Syndrome Coronavirus (MERS-CoV): Infection, Immunological Response, and Vaccine Development

Middle East respiratory syndrome coronavirus (MERS-CoV) first emerged in late 2012. Since its emergence, a total of 2279 patients from 27 countries have been infected across the globe according to a World Health Organization (WHO) report (Feb. 12th, 2019). Approximately 806 patients have died. The virus uses its spike proteins as adhesive factors that are proinflammatory for host entry through a specific receptor called dipeptidyl peptidase-4 (DPP4). This receptor is considered a key factor in the signaling and activation of the acquired and innate immune responses in infected patients. Using potent antigens in combination with strong adjuvants may effectively trigger the activation of specific MERS-CoV cellular responses as well as the production of neutralizing antibodies. Unfortunately, to date, there is no effective approved treatment or vaccine for MERS-CoV. Thus, there are urgent needs for the development of novel MERS-CoV therapies as well as vaccines to help minimize the spread of the virus from infected patients, thereby mitigating the risk of any potential pandemics. Our main goals are to highlight and describe the current knowledge of both the innate and adaptive immune responses to MERS-CoV and the current state of MERS-CoV vaccine development. We believe this study will increase our understanding of the mechanisms that enhance the MERS-CoV immune response and subsequently contribute to the control of MERS-CoV infections.

Circulating Levels of Soluble Dipeptidyl Peptidase-4 Are Dissociated from Inflammation and Induced by Enzymatic DPP4 Inhibition

Dipeptidyl peptidase-4 (DPP-4) controls glucose homeostasis through enzymatic termination of incretin action. We report that plasma DPP-4 activity correlates with body weight and fat mass, but not glucose control, in mice. Genetic disruption of adipocyte Dpp4 expression reduced plasma DPP-4 activity in older mice but did not perturb incretin levels or glucose homeostasis. Knockdown of hepatocyte Dpp4 completely abrogated the obesity-associated increase in plasma DPP-4 activity, reduced liver cytokine expression, and partially attenuated inflammation in adipose tissue without changes in incretin levels or glucose homeostasis. In contrast, circulating levels of soluble DPP4 (sDPP4) were dissociated from inflammation in mice with endothelial-selective or global genetic inactivation of Dpp4. Remarkably, inhibition of DPP-4 enzymatic activity upregulated circulating levels of sDPP4 originating from endothelial or hematopoietic cells without inducing systemic or localized inflammation. Collectively, these findings reveal unexpected complexity in regulation of soluble versus enzymatic DPP-4 and control of inflammation and glucose homeostasis.

Association of CD26/dipeptidyl peptidase IV mRNA level in peripheral blood mononuclear cells with disease activity and bone erosion in rheumatoid arthritis

Dipeptidyl peptidase IV (DPP-IV, CD26) plays many roles in the pathogenesis of several autoimmune and inflammatory diseases. The current study evaluated the association of DPP-IV enzymatic activity and its gene expression with disease activity and bone erosion in rheumatoid arthritis. Blood samples were collected from 20 rheumatoid arthritis patients and 40 healthy volunteers. Patients were divided into four subgroups using DAS28 index. CD26 gene expression levels were analyzed in peripheral blood mononuclear cells by quantitative reverse transcription-polymerase chain reaction. Additionally, the enzymatic activity of this molecule in serum was determined using Gly-Pro-p-nitroanilide as substrate. Digital radiography was applied to obtain images for bone erosion assessment. No significant difference in serum DPP-IV activity level was seen between patients and controls (p = 0.140). However, patients exhibited an increase in CD26 mRNA expression (1.68 times) when compared to controls (p = 0.001). Moreover, a strong positive correlation between CD26 gene expression and DAS28 index as well as bone erosion in the hands was observed (r = 0.71, p = 0.002 and r = 0.61, p = 0.049, respectively). This study demonstrated that CD26 mRNA expression in rheumatoid arthritis patients is associated with disease activity and bone erosion, suggesting a potential role for this molecule in the immunopathology of rheumatoid arthritis and bone erosion.

Inhibition of DPP4 enhances inhibitory synaptic transmission through activating the GLP-1/GLP-1R signaling pathway in a rat model of febrile seizures

Dipeptidyl peptidase-IV (DPP4) is a cell surface serine peptidase widely expressed in the brain. Recent studies suggest that DPP4 contributes to the development of febrile seizures (FS); however, the underlying mechanism is still unclear. Thus, we investigated the role of DPP4 in the progression of FS at the molecular and electrophysiological levels using FS models in vivo and in vitro. Herein, we found that both the mRNA and protein levels of DPP4 were upregulated in the FS model. Administration of the pharmacological DPP4 inhibitor sitagliptin suppressed the hyperthermia-induced neuronal excitability as determined via whole-cell patch-clamp recordings in vitro. Interestingly, sitagliptin administration activated the glucagon-like peptide-1 (GLP-1)/GLP-1 receptor (GLP-1R) pathway by increasing the expression of GLP-1 and GLP-1R in a rat model of FS. Moreover, administration of the GLP-1R inhibitor exendin9-39 increased seizure severity, and sitagliptin reversed the effect, as shown in the electroencephalogram (EEG) and patch-clamp results in a rat model of FS. Furthermore, the GLP-1R-mediated reduction in GABAergic transmission was enhanced by sitagliptin and DPP4 knockdown through increasing miniature inhibitory post-synaptic currents (mIPSCs) in vitro accompanied by increased synaptic release of GABA in vivo. Taken together, our results demonstrate a role of DPP4 in regulating GABAergic transmission via the GLP-1/GLP-1R pathway. These findings indicated that DPP4 may represent a novel therapeutic strategy and target for FS.

Soluble CD26 is inversely Associated with Disease Severity in Patients with Chronic Eosinophilic Pneumonia

Backgrounds

CD26, a multifunctional T cell surface glycoprotein, is a type II transmembrane protein containing only six amino acid residues in its cytoplasmic region. In addition to its membrane form, CD26 exists in plasma in a soluble form (sCD26), which is thought to be the extracellular domain of the molecule cleaved from the cell surface. Recent studies indicated CD26 have an important role in the pathogenesis of asthma, known as Th2 like disease. The function of CD26 in the esosinophlic lung disease is not well understood.

Methods

Serum sCD26 was determined by enzyme-linked immunosorbent assay in patients with acute eosinophilic pneumonia, chronic eosinophilic pneumonia (CEP), and sarcoidosis, and in healthy volunteers, to establish its value for discriminating between disease entities and as marker of disease activity.

Results

Soluble CD26 was significantly reduced in CEP and was related to disease severity. In particular, sCD26 was inversely correlated with arterial oxygen tension in CEP.

Conclusion

Serum levels of sCD26 might appear to be useful as a new marker of CEP disease activity.

Regulation and roles of CD26/DPPIV in hematopoiesis and diseases

Dipeptidyl peptidase IV (DPPIV),¹ on the surface of certain cells, where it is also referred to as CD26, is involved in a vast majority of biological and pathological processes. CD26/DPPIV function contributes to cancer and tumor metastasis as well as inhibition of its expression which alters the expression of immune response-related genes. CD26/DPPIV is a widely distributed multifunctional integral membrane and secreted protein that is defined as early predictive biomarker in HIV, cancer and autoimmunity diseases like diabetes and multiple sclerosis. CD26/DPPIV-chemokine interaction may have a functional role in T-cells and overall immune function. It is expressed at low density on resting T cells, but is upregulated with T cell activation. In this review, we summarize valuable information about detailed biological aspects and pharmacokinetic characteristics of CD26/DPPIV and its clinical efficacy, focusing particularly on the role of CD26/DPPIV in immunological and non-immunological diseases. We also describe our recent work about umbilical cord blood (UCB)² hematopoietic stem cell transplantation strategies in which identified CD26+ cells can be differentiated to immune cells under certain culture condition.

The soluble cytoplasmic tail of CD45 (ct-CD45) in human plasma contributes to keep T cells in a quiescent state

The cytoplasmic tail of CD45 (ct‐CD45) is proteolytically cleaved and released upon activation of human phagocytes. It acts on T cells as an inhibitory, cytokine‐like factor in vitro. Here, we show that ct‐CD45 is abundant in human peripheral blood plasma from healthy adults compared with plasma derived from umbilical cord blood and plasma from patients with rheumatoid arthritis or systemic lupus erythematosus. Plasma depleted of ct‐CD45 enhanced T‐cell proliferation, while addition of exogenous ct‐CD45 protein inhibited proliferation and reduced cytokine production of human T lymphocytes in response to TCR signaling. Inhibition of T‐cell proliferation by ct‐CD45 was overcome by costimulation via CD28. T‐cell activation in the presence of ct‐CD45 was associated with an upregulation of the quiescence factors Schlafen family member 12 (SLFN12) and Krueppel‐like factor 2 (KLF2) as well as of the cyclin‐dependent kinase (CDK) inhibitor p27kip1. In contrast, positive regulators of the cell cycle such as cyclin D2 and D3 as well as CDK2 and CDK4 were found to be downregulated in response to ct‐CD45. In summary, we demonstrate that ct‐CD45 is present in human plasma and sets the threshold of T‐cell activation.

Cut to the chase: a review of CD26/dipeptidyl peptidase-4's (DPP4) entanglement in the immune system

CD26/DPP4 (dipeptidyl peptidase 4/DP4/DPPIV) is a surface T cell activation antigen and has been shown to have DPP4 enzymatic activity, cleaving-off amino-terminal dipeptides with either L-proline or L-alanine at the penultimate position. It plays a major role in glucose metabolism by N-terminal truncation and inactivation of the incretins glucagon-like peptide-1 (GLP) and gastric inhibitory protein (GIP). In 2006, DPP4 inhibitors have been introduced to clinics and have been demonstrated to efficiently enhance the endogenous insulin secretion via prolongation of the half-life of GLP-1 and GIP in patients. However, a large number of studies demonstrate clearly that CD26/DPP4 also plays an integral role in the immune system, particularly in T cell activation. Therefore, inhibition of DPP4 might represent a double-edged sword. Apart from the metabolic benefit, the associated immunological effects of long term DPP4 inhibition on regulatory processes such as T cell homeostasis, maturation and activation are not understood fully at this stage. The current data point to an important role for CD26/DPP4 in maintaining lymphocyte composition and function, T cell activation and co-stimulation, memory T cell generation and thymic emigration patterns during immune-senescence. In rodents, critical immune changes occur at baseline levels as well as after in-vitro and in-vivo challenge. In patients receiving DPP4 inhibitors, evidence of immunological side effects also became apparent. The scope of this review is to recapitulate the role of CD26/DPP4 in the immune system regarding its pharmacological inhibition and T cell-dependent immune regulation.

DPP-4 inhibitors and risk of infections: a meta-analysis of randomized controlled trials

BACKGROUND

To evaluate the risk of infections in the treatment of type 2 diabetes patients with dipeptidyl-peptidase 4 (DPP-4) inhibitors.

METHODS

A literature search was conducted through electronic databases. The inclusion criteria included study duration of no less than 12 weeks developed in type 2 diabetes patients, the use of a randomized control group receiving a DPP-4 inhibitor and the availability of outcome data for infections. Out of 2181 studies, 74 studies were finally included.

RESULTS

The risk of overall infection for DPP-4 inhibitors treatment was comparable to placebo (odds ratio (OR) = 0.97, 95% confidence interval (CI), 0.91 to 1.04, p = 0.40), metformin treatment (OR = 1.22, 95% CI, 0.95 to 1.56, p = 0.12), sulphonylurea treatment (OR = 1.09, 0.93 to 1.29, p = 0.29), thiazolidinedione treatment (OR = 0.86, 95% CI, 0.65 to 1.14, p = 0.29) and alpha glucosidase inhibitor treatment (OR = 1.03, 95% CI, 0.33 to 3.22, p = 0.96). When compared different DPP-4 inhibitors with placebo treatment, risks of infections were comparable for alogliptin, linagliptin, sitagliptin, saxagliptin and vildagliptin. Compared with placebo or active comparator treatment, risks of infection in different systems for DPP-4 inhibitors were all comparable.

CONCLUSIONS

The overall risk of infections of DPP-4 inhibitor was not increased compared with control groups.

Inhibition of VEGF-dependent angiogenesis by the anti-CD82 monoclonal antibody 4F9 through regulation of lipid raft microdomains

CD82 (also known as KAI1) belongs to the tetraspanin superfamily of type III transmembrane proteins, and is involved in regulating cell adhesion, migration and proliferation. In contrast to these well-established roles of CD82 in tumor biology, its function in endothelial cell (EC) activity and tumor angiogenesis is yet to be determined. In this study, we show that suppression of CD82 negatively regulates vascular endothelial growth factor (VEGF)-induced angiogenesis. Moreover, we demonstrate that the anti-CD82 mAb 4F9 effectively inhibits phosphorylation of VEGF receptor 2 (VEGFR2), which is the principal mediator of the VEGF-induced angiogenic signaling process in tumor angiogenesis, by regulating the organization of the lipid raft microdomain signaling platform in human EC. Our present work therefore suggests that CD82 on EC is a potential target for anti-angiogenic therapy in VEGFR2-dependent tumor angiogenesis.

Decreased Frequency and Secretion of CD26 Promotes Disease Progression in Indian Post Kala-azar Dermal Leishmaniasis

PURPOSE

Leishmania, the causative organisms for leishmaniasis, reside in host macrophages and survive by modulating the microbicidal pathways via attenuation of the oxidative burst and/or suppression of cell-mediated immunity. As post kala-azar dermal leishmaniasis (PKDL), the dermal sequela of visceral leishmaniasis, has no animal model, the underlying mechanism(s) that nullify the microbicidal effector mechanisms remain poorly understood. This study was aimed at assessing the status of dipeptidyl peptidase CD26, a co-stimulatory molecule that is essential for T-cell signal activation.

METHODS

The frequency/expression of CD26 and CD45RO/RA was evaluated by flow cytometry, while levels of soluble CD26 (sCD26), CXCL-10, RANTES, IL-10 and TGF-β along with adenosine deaminase (ADA) activity were measured using ELISA.

RESULTS

In patients with PKDL vis-à-vis healthy individuals, there was a significant decrease in the frequency and expression of CD26 on CD3(+)CD8(+) T-cells, which was accompanied by a significant lowering of plasma levels of sCD26. Furthermore, these patients showed a significant decrease in the frequency of CD45RO(+)/CD8(+) T-cells, concomitant with a significant increase in the proportion of CD45RA(+)/CD8(+) T-cells. This could collectively translate into reduced formation of the immunological synapse of CD26, CD45RO, and ADA, and lead to an attenuation of the Th1 responses. The decreased levels of CD26 and sCD26 correlated negatively with raised levels of Th2 cytokines, IL-10, and TGF-β along with the lesional parasite load, indicating disease specificity.

CONCLUSIONS

Taken together, the decreased expression and secretion of CD26 in patients with PKDL resulted in impairment of the CD26-ADA interaction, and thereby possibly contributed to T-cell unresponsiveness, emphasizing the need to develop immunomodulatory therapies against PKDL and by extension, the leishmaniases.

Synthetic lethal interaction of combined CD26 and Bcl-xL inhibition is a powerful anticancer therapy against hepatocellular carcinoma

AIM

CD26 is a membrane glycoprotein that has multiple functions, including dipeptidyl peptidase IV activity. CD26 expression varies in different tumor types, and its role in tumor growth in hepatocellular carcinoma (HCC) remains unclear.

METHODS

CD26 expression levels were examined in resected HCC and surrounding non-cancerous lesions. The effect of CD26 knockdown on the cellular proliferation of HepG2 or Huh7 cells, both of which highly express CD26, was studied in vitro.

RESULTS

CD26 mRNA expression levels were significantly increased in HCC compared with their surrounding non-cancerous lesions. We confirmed that various HCC cell lines, especially HepG2 and Huh7 cells, showed high expression levels of CD26. siRNA-mediated knockdown of CD26 suppressed hepatoma cell growth in vitro. CD26 knockdown induced cell cycle arrest through the upregulation of Cip/Kip family proteins, p21 in HepG2 cells and p27 in Huh7 cells. CD26 knockdown did not affect apoptosis, but it increased expressions of the pro-apoptotic proteins Bim and Bak and the anti-apoptotic protein Bcl-xL, suggesting an addiction of CD26 knockdown cells to Bcl-xL for survival. We thus treated CD26 knockdown cells with ABT-737, a Bcl-xL/-2/-w inhibitor, and observed that the synthetic lethal interaction of combined Bcl-xL and CD26 inhibition induced significant apoptosis and impaired cellular viability.

CONCLUSION

CD26 mRNA was overexpressed in HCC, and its inhibition suppressed cellular proliferation through cell cycle arrest. The combined use of CD26 knockdown with a Bcl-xL inhibitor further elicited substantial apoptosis and therefore may serve as a powerful anticancer combination therapy against HCC.

The Dipeptidyl Peptidase Family, Prolyl Oligopeptidase, and Prolyl Carboxypeptidase in the Immune System and Inflammatory Disease, Including Atherosclerosis

Research from over the past 20 years has implicated dipeptidyl peptidase (DPP) IV and its family members in many processes and different pathologies of the immune system. Most research has been focused on either DPPIV or just a few of its family members. It is, however, essential to consider the entire DPP family when discussing any one of its members. There is a substantial overlap between family members in their substrate specificity, inhibitors, and functions. In this review, we provide a comprehensive discussion on the role of prolyl-specific peptidases DPPIV, FAP, DPP8, DPP9, dipeptidyl peptidase II, prolyl carboxypeptidase, and prolyl oligopeptidase in the immune system and its diseases. We highlight possible therapeutic targets for the prevention and treatment of atherosclerosis, a condition that lies at the frontier between inflammation and cardiovascular disease.

Middle East Respiratory Syndrome Coronavirus Efficiently Infects Human Primary T Lymphocytes and Activates the Extrinsic and Intrinsic Apoptosis Pathways

Middle East respiratory syndrome (MERS) is associated with a mortality rate of >35%. We previously showed that MERS coronavirus (MERS-CoV) could infect human macrophages and dendritic cells and induce cytokine dysregulation. Here, we further investigated the interplay between human primary T cells and MERS-CoV in disease pathogenesis. Importantly, our results suggested that MERS-CoV efficiently infected T cells from the peripheral blood and from human lymphoid organs, including the spleen and the tonsil. We further demonstrated that MERS-CoV infection induced apoptosis in T cells, which involved the activation of both the extrinsic and intrinsic apoptosis pathways. Remarkably, immunostaining of spleen sections from MERS-CoV–infected common marmosets demonstrated the presence of viral nucleoprotein in their CD3⁺ T cells. Overall, our results suggested that the unusual capacity of MERS-CoV to infect T cells and induce apoptosis might partly contribute to the high pathogenicity of the virus.

Targeting CD13 (aminopeptidase-N) in turn downregulates ADAM17 by internalization in acute myeloid leukaemia cells

Secreted matrix metalloproteinases (MMP)-2 and MMP-9 and membrane-anchored aminopeptidase-N/CD13 are abnormally expressed in human acute myeloid leukaemia (AML). We previously showed that CD13 ligation by anti-CD13 monoclonal antibodies can induce apoptosis in AML cells. Here, we assessed ADAM17 expression in primary blood blasts CD13⁺CD33⁺ from patients with AML. Primary AML cells expressed ADAM17 transcript and its surface expression was higher in subtype M4 (myelomonocytic) and M5 (monocytic) AML specimens than in M0 and M1/M2 (early and granulocytic) specimens. In AML cell lines defining distinct AML subfamilies (HL-60/M2, NB4/M3, THP-1/M5, U937/M5) and primary AML cells cultured ex vivo, anti-CD13 antibodies downregulated surface CD13 and ADAM17 without affecting MMP-2/-9 release. Knockdown of CD13 by siRNA prevented anti-CD13-mediated ADAM17 downregulation, indicating that CD13 is required for ADAM17 downregulation. Soluble ADAM17 was not detected in the medium of anti-CD13 treated cells, suggesting that ADAM17 was not shed. After ligation by anti-CD13, CD13 and ADAM17 were internalized. Subsequently, we found that ADAM17 interacts with CD13. We postulate that the interaction of ADAM17 with CD13 and its downregulation following CD13 engagement has important implications in AML for the known roles of ADAM17 in tumour-associated cell growth, migration and invasion.

CD26-mediated induction of EGR2 and IL-10 as potential regulatory mechanism for CD26 costimulatory pathway

CD26 is associated with T cell signal transduction processes as a costimulatory molecule, and CD26(+) T cells have been suggested to be involved in the pathophysiology of diverse autoimmune diseases. Although the cellular and molecular mechanisms involved in CD26-mediated T cell activation have been extensively evaluated by our group and others, potential negative feedback mechanisms to regulate CD26-mediated activation still remain to be elucidated. In the present study, we examine the expression of inhibitory molecules induced via CD26-mediated costimulation. We show that coengagement of CD3 and CD26 induces preferential production of IL-10 in human CD4(+) T cells, mediated through NFAT and Raf-MEK-ERK pathways. A high level of early growth response 2 (EGR2) is also induced following CD26 costimulation, possibly via NFAT and AP-1-mediated signaling, and knockdown of EGR2 leads to decreased IL-10 production. Furthermore, CD3/CD26-stimulated CD4(+) T cells clearly suppress proliferative activity and effector cytokine production of bystander T cells in an IL-10-dependent manner. Taken together, our data suggest that robust CD26 costimulatory signaling induces preferential expression of EGR2 and IL-10 as a potential mechanism for regulating CD26-mediated activation.

Clinical significance of soluble CD26 in malignant pleural mesothelioma

There is no established single diagnostic marker for malignant pleural mesothelioma (MPM). CD26 is a 110 kDa, multifunctional, membrane-bound glycoprotein that has dipeptidyl peptidase IV (DPPIV) enzyme activity. The aim of this study was to evaluate the clinical significance of soluble CD26 (sCD26) in patients with MPM. The study included 80 MPM patients, 79 subjects with past asbestos exposure (SPE), and 134 patients with other benign pleural diseases (OPD) that were included as a control group. sCD26 levels and DPPIV activity in serum and/or pleural fluid were determined using an ELISA kit. Serum sCD26 levels and DPPIV enzyme activity in patients with MPM were significantly decreased compared with those in the SPE group (P = 0.000). The level of serum sCD26 was significantly decreased in patients with advanced stages of MPM compared with those with earlier stages (P = 0.047). The median OS of patients with MPM who had higher DPPIV enzyme activity was significantly longer than that of those with lower DPPIV enzyme activity (P = 0.032). The sCD26 levels in the pleural fluid of MPM patients with an epithelioid subtype were significantly increased compared with the OPD cohort (P = 0.012). Moreover, DPPIV enzyme activity in the pleural fluid of patients with MPM with an epithelioid subtype were significantly increased compared with those in the OPD cohort (P = 0.009). Patients with MPM who had lower specific DPPIV activity, determined as DPPIV/sCD26, showed significantly prolonged survival compared with those with higher specific DPPIV activity (P = 0.028). Serum sCD26 and DPPIV enzyme activity appear to be useful biomarkers for differentiating patients with MPM from SPE. The sCD26 levels or DPPIV enzyme activity in pleural fluid appear to be biomarkers in patients with an epithelioid subtype of MPM. DPPIV activity in serum or pleural fluid appears to be predictive for the prognosis of patients with MPM.

Design, Assessment, and in vivo Evaluation of a Computational Model Illustrating the Role of CAV1 in CD4(+) T-lymphocytes

Caveolin-1 (CAV1) is a vital scaffold protein heterogeneously expressed in both healthy and malignant tissue. We focus on the role of CAV1 when overexpressed in T-cell leukemia. Previously, we have shown that CAV1 is involved in cell-to-cell communication, cellular proliferation, and immune synapse formation; however, the molecular mechanisms have not been elucidated. We hypothesize that the role of CAV1 in immune synapse formation contributes to immune regulation during leukemic progression, thereby warranting studies of the role of CAV1 in CD4⁺ T-cells in relation to antigen-presenting cells. To address this need, we developed a computational model of a CD4⁺ immune effector T-cell to mimic cellular dynamics and molecular signaling under healthy and immunocompromised conditions (i.e., leukemic conditions). Using the Cell Collective computational modeling software, the CD4⁺ T-cell model was constructed and simulated under CAV1^+/+, CAV1^+/−, and CAV1^−/− conditions to produce a hypothetical immune response. This model allowed us to predict and examine the heterogeneous effects and mechanisms of CAV1 in silico. Experimental results indicate a signature of molecules involved in cellular proliferation, cell survival, and cytoskeletal rearrangement that were highly affected by CAV1 knock out. With this comprehensive model of a CD4⁺ T-cell, we then validated in vivo protein expression levels. Based on this study, we modeled a CD4⁺ T-cell, manipulated gene expression in immunocompromised versus competent settings, validated these manipulations in an in vivo murine model, and corroborated acute T-cell leukemia gene expression profiles in human beings. Moreover, we can model an immunocompetent versus an immunocompromised microenvironment to better understand how signaling is regulated in patients with leukemia.

Differential OVA-induced pulmonary inflammation and unspecific reaction in Dark Agouti (DA) rats contingent on CD26/DPPIV deficiency

Many disease models have shown that, within the species rat, different strains are differentially susceptible to asthma-induced inflammation depending on the genetic background. Likewise, CD26/DPPIV-deficiency in asthmatic F344 rats has been shown to result in a less pronounced inflammation and in increased Treg cell influx into the lung compared to wild-types. The aim of the present study was to investigate whether the genetic background of the animals interferes with CD26/DPPIV-deficiency in a model of allergic-like inflammation, or whether the deficiency per se is the predominant regulator of the inflammation. Therefore, we hypothesised that CD26/DPPIV-deficient Dark Agouti (DA) rats also exhibit a less pronounced ovalbumin (OVA)-induced inflammation compared to wild-types. After sensitisation with OVA, Al(OH)3 and heat-killed Bordetella pertussis bacilli, animals were challenged three times with 5% aerosolized OVA at intervals of 24h, i.e., on three consecutive days. 24h after the third challenge, animals were sacrificed and examined. In both wild-type and CD26/DPPIV-deficient rat groups, asthma induction led to (1) lung inflammation, (2) significantly increased eosinophil infiltration in the BALF, (3) significantly increased IgE serum levels, (4) a significant increase of inflammatory cytokines, (5) a significant increase of different T cell populations in the lungs and in their draining lymph nodes, as well as to (6) a significantly higher number of all T lymphocyte subtypes in the blood. Thus, the degree of the OVA-induced Th2-driven pulmonary inflammation was similarly pronounced in both wild-type and CD26/DPPIV-deficient DA rats.

The nonglycemic actions of dipeptidyl peptidase-4 inhibitors

A cell surface serine protease, dipeptidyl peptidase 4 (DPP-4), cleaves dipeptide from peptides containing proline or alanine in the N-terminal penultimate position. Two important incretin hormones, glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic peptide (GIP), enhance meal-stimulated insulin secretion from pancreatic β-cells, but are inactivated by DPP-4. Diabetes and hyperglycemia increase the DPP-4 protein level and enzymatic activity in blood and tissues. In addition, multiple other functions of DPP-4 suggest that DPP-4 inhibitor, a new class of antidiabetic agents, may have pleiotropic effects. Studies have shown that DPP-4 itself is involved in the inflammatory signaling pathway, the stimulation of vascular smooth cell proliferation, and the stimulation of oxidative stress in various cells. DPP-4 inhibitor ameliorates these pathophysiologic processes and has been shown to have cardiovascular protective effects in both in vitro and in vivo experiments. However, in recent randomized clinical trials, DPP-4 inhibitor therapy in high risk patients with type 2 diabetes did not show cardiovascular protective effects. Some concerns on the actions of DPP-4 inhibitor include sympathetic activation and neuropeptide Y-mediated vascular responses. Further studies are required to fully characterize the cardiovascular effects of DPP-4 inhibitor.