Signaling properties of CD38 in the mouse immune system: enzyme-dependent and -independent roles in immunity

Advances and challenges of immunotherapies in NK/T cell lymphomas

Natural killer (NK)/T cell lymphoma (NKTCL) is a rare subtype of Epstein-Barr virus (EBV)-associated non-Hodgkin lymphoma characterized by poor clinical outcomes. It is more common in East Asian and Latin American countries. Despite the introduction of asparaginase/pegaspargase-based chemotherapy, the prognosis of patients with advanced NKTCL needs to be improved, and few salvage treatment options are available for relapsed/refractory patients who fail chemotherapy. Although many unknowns remain, novel treatment strategies to further improve outcomes are urgently needed. Immunotherapy has emerged and shown favorable antitumor activity in NKTCL, including monoclonal antibodies targeting immune checkpoint inhibitors, other receptors on the cellular membrane, and cellular immunotherapy, which could enhance immune cells attack on tumor cells. In this review, we provide an overview of recent immunotherapy in NKTCL, focusing on programmed cell death-1 (PD-1)/programmed cell death-ligand 1 (PD-L1), cytotoxic T lymphocyte-associated protein 4 (CTLA-4), chimeric antigen receptor (CAR) T cells, EBV-specific cytotoxic T lymphocytes, immunomodulatory agents, and other targeted agents, as well as the current progress and challenges in the field.

Mouse CD38-Specific Heavy Chain Antibodies Inhibit CD38 GDPR-Cyclase Activity and Mediate Cytotoxicity Against Tumor Cells

CD38 is the major NAD⁺-hydrolyzing ecto-enzyme in most mammals. As a type II transmembrane protein, CD38 is also a promising target for the immunotherapy of multiple myeloma (MM). Nanobodies are single immunoglobulin variable domains from heavy chain antibodies that naturally occur in camelids. Using phage display technology, we isolated 13 mouse CD38-specific nanobodies from immunized llamas and produced these as recombinant chimeric mouse IgG2a heavy chain antibodies (hcAbs). Sequence analysis assigned these hcAbs to five distinct families that bind to three non-overlapping epitopes of CD38. Members of families 4 and 5 inhibit the GDPR-cyclase activity of CD38. Members of families 2, 4 and 5 effectively induce complement-dependent cytotoxicity against CD38-expressing tumor cell lines, while all families effectively induce antibody dependent cellular cytotoxicity. Our hcAbs present unique tools to assess cytotoxicity mechanisms of CD38-specific hcAbs in vivo against tumor cells and potential off-target effects on normal cells expressing CD38 in syngeneic mouse tumor models, i.e. in a fully immunocompetent background.

Novel Insights in Anti-CD38 Therapy Based on CD38-Receptor Expression and Function: The Multiple Myeloma Model

Multiple myeloma (MM) is a hematological disease characterized by the proliferation and accumulation of malignant plasmacells (PCs) in the bone marrow (BM). Despite widespread use of high-dose chemotherapy in combination with autologous stem cell transplantation (ASCT) and the introduction of novel agents (immunomodulatory drugs, IMiDs, and proteasome inhibitors, PIs), the prognosis of MM patients is still poor. CD38 is a multifunctional cell-surface glycoprotein with receptor and ectoenzymatic activities. The very high and homogeneous expression of CD38 on myeloma PCs makes it an attractive target for novel therapeutic strategies. Several anti-CD38 monoclonal antibodies have been, or are being, developed for the treatment of MM, including daratumumab and isatuximab. Here we provide an in-depth look at CD38 biology, the role of CD38 in MM progression and its complex interactions with the BM microenvironment, the importance of anti-CD38 monoclonal antibodies, and the main mechanisms of antibody resistance. We then review a number of multiparametric flow cytometry techniques exploiting CD38 antigen expression on PCs to diagnose and monitor the response to treatment in MM patients.

CD38 in cancer-associated fibroblasts promotes pro-tumoral activity

Primary and metastatic melanoma progression are supported by a local microenvironment comprising, inter alia, of cancer-associated fibroblasts (CAFs). We previously reported in orthotropic/syngeneic mouse models that the stromal ectoenzyme CD38 participates in melanoma growth and metastasis. The results presented here suggest that CD38 is a novel regulator of CAFs' pro-tumorigenic functions. Orthotopic co-implantation of CD38 deficient fibroblasts and B16F10 melanoma cells limited tumor size, compared with CD38-expressing fibroblasts. Intrinsically, CAF-CD38 promoted migration of primary fibroblasts toward melanoma cells. Further, in vitro paracrine effects of CAF-CD38 fostered tumor cell migration and invasion as well as endothelial cell tube formation. Mechanistically, we report that CAF-CD38 drives the protein expression of an angiogenic/pro-metastatic signature, which includes VEGF-A, FGF-2, CXCL-12, MMP-9, and HGF. Data suggest that CAF-CD38 fosters tumorigenesis by enabling the production of pro-tumoral factors that promote cell invasion, migration, and angiogenesis.

The Circular Life of Human CD38: From Basic Science to Clinics and Back

Monoclonal antibodies (mAbs) were initially considered as a possible “magic bullet” for in vivo elimination of tumor cells. mAbs represented the first step: however, as they were murine in nature (the earliest experience on the field), they were considered unfit for human applications. This prompted the development of techniques for cloning the variable regions of conventional murine antibodies, genetically mounted on human IgG. The last step in this years-long process was the design for the preparation of fully human reagents. The choice of the target molecule was also problematic, since cancer-specific targets are quite limited in number. To overcome this obstacle in the planning phases of antibody-mediated therapy, attention was focused on a set of normal molecules, whose quantitative distribution may balance a tissue-dependent generalized expression. The results and clinical success obtained with anti-CD20 mAbs revived interest in this type of strategy. Using multiple myeloma (MM) as a tumor model was challenging first of all because the plasma cells and their neoplastic counterpart eluded the efforts of the Workshop on Differentiation Antigens to find a target molecule exclusively expressed by these cells. For this reason, attention was turned to surface molecules which fulfill the requisites of being reasonably good targets, even if not specifically restricted to tumor cells. In 2009, we proposed CD38 as a MM target in virtue of its expression: it is absent on early hematological progenitors, has variable but generalized limited expression by normal cells, but is extremely high in plasma cells and in myeloma. Further, regulation of its expression appeared to be dependent on a variety of factors, including exposure to all-trans retinoic acid (ATRA), a potent and highly specific inducer of CD38 expression in human promyelocytic leukemia cells that are now approved for in vivo use. This review discusses the history of human CD38, from its initial characterization to its targeting in antibody-mediated therapy of human myeloma.

CD38: A Potential Therapeutic Target in Cardiovascular Disease

Substantial research has demonstrated the association between cardiovascular disease and the dysregulation of intracellular calcium, ageing, reduction in nicotinamide adenine dinucleotide NAD+ content, and decrease in sirtuin activity. CD38, which comprises the soluble type, type II, and type III, is the main NADase in mammals. This molecule catalyses the production of cyclic adenosine diphosphate ribose (cADPR), nicotinic acid adenine dinucleotide phosphate (NAADP), and adenosine diphosphate ribose (ADPR), which stimulate the release of Ca²⁺, accompanied by NAD+ consumption and decreased sirtuin activity. Therefore, the relationship between cardiovascular disease and CD38 has been attracting increased attention. In this review, we summarize the structure, regulation, function, targeted drug development, and current research on CD38 in the cardiac context. More importantly, we provide original views about the as yet elusive mechanisms of CD38 action in certain cardiovascular disease models. Based on our review, we predict that CD38 may serve as a novel therapeutic target in cardiovascular disease in the future.

Paving the Way toward Successful Multiple Myeloma Treatment: Chimeric Antigen Receptor T-Cell Therapy

Despite the significant progress of modern anticancer therapies, multiple myeloma (MM) is still incurable for the majority of patients. Following almost three decades of development, chimeric antigen receptor (CAR) T-cell therapy now has the opportunity to revolutionize the treatment landscape and meet the unmet clinical need. However, there are still several major hurdles to overcome. Here we discuss the recent advances of CAR T-cell therapy for MM with an emphasis on future directions and possible risks. Currently, CAR T-cell therapy for MM is at the first stage of clinical studies, and most studies have focused on CAR T cells targeting B cell maturation antigen (BCMA), but other antigens such as cluster of differentiation 138 (CD138, syndecan-1) are also being evaluated. Although this therapy is associated with side effects, such as cytokine release syndrome and neurotoxicity, and relapses have been observed, the benefit–risk balance and huge potential drive the ongoing clinical progress. To fulfill the promise of recent clinical trial success and maximize the potential of CAR T, future efforts should focus on the reduction of side effects, novel targeted antigens, combinatorial uses of different types of CAR T, and development of CAR T cells targeting more than one antigen.

Current advances in chimeric antigen receptor T-cell therapy for refractory/relapsed multiple myeloma

Multiple myeloma (MM), considered an incurable hematological malignancy, is characterized by its clonal evolution of malignant plasma cells. Although the application of autologous stem cell transplantation (ASCT) and the introduction of novel agents such as immunomodulatory drugs (IMiDs) and proteasome inhibitors (PIs) have doubled the median overall survival to eight years, relapsed and refractory diseases are still frequent events in the course of MM. To achieve a durable and deep remission, immunotherapy modalities have been developed for relapsed/refractory multiple myeloma (RRMM). Among these approaches, chimeric antigen receptor (CAR) T-cell therapy is the most promising star, based on the results of previous success in B-cell neoplasms. In this immunotherapy, autologous T cells are engineered to express an artificial receptor which targets a tumor-associated antigen and initiates the T-cell killing procedure. Tisagenlecleucel and Axicabtagene, targeting the CD19 antigen, are the two pacesetters of CAR T-cell products. They were approved by the US Food and Drug Administration (FDA) in 2017 for the treatment of acute lymphocytic leukemia (ALL) and diffuse large B-cell lymphoma (DLBCL). Their development enabled unparalleled efficacy in combating hematopoietic neoplasms. In this review article, we summarize six promising candidate antigens in MM that can be targeted by CARs and discuss some noteworthy studies of the safety profile of current CAR T-cell therapy.

CD38 Is Robustly Induced in Human Macrophages and Monocytes in Inflammatory Conditions

Macrophages and their monocyte precursors mediate innate immune responses and can promote a spectrum of phenotypes from pro-inflammatory to pro-resolving. Currently, there are few markers that allow for robust dissection of macrophage phenotype. We recently identified CD38 as a marker of inflammatory macrophages in murine in vitro and in vivo models. However, it is unknown whether CD38 plays a similar marker and/or functional role in human macrophages and inflammatory diseases. Here, we establish that CD38 transcript and protein are robustly induced in human macrophages exposed to LPS (±IFN-γ) inflammatory stimuli, but not with the alternative stimulus, IL-4. Pharmacologic and/or genetic CD38 loss-of-function significantly reduced the secretion of inflammatory cytokines IL-6 and IL-12p40 and glycolytic activity in human primary macrophages. Finally, monocyte analyses in systemic lupus erythematosus patients revealed that, while all monocytes express CD38, high CD38 expression in the non-classical monocyte subpopulation is associated with disease. These data are consistent with an inflammatory marker role for CD38 in human macrophages and monocytes.

Liver X Receptor Nuclear Receptors Are Transcriptional Regulators of Dendritic Cell Chemotaxis

The liver X receptors (LXRs) are ligand-activated nuclear receptors with established roles in the maintenance of lipid homeostasis in multiple tissues. LXRs exert additional biological functions as negative regulators of inflammation, particularly in macrophages. However, the transcriptional responses controlled by LXRs in other myeloid cells, such as dendritic cells (DCs), are still poorly understood. Here we used gain- and loss-of-function models to characterize the impact of LXR deficiency on DC activation programs. Our results identified an LXR-dependent pathway that is important for DC chemotaxis. LXR-deficient mature DCs are defective in stimulus-induced migration in vitro and in vivo Mechanistically, we show that LXRs facilitate DC chemotactic signaling by regulating the expression of CD38, an ectoenzyme important for leukocyte trafficking. Pharmacological or genetic inactivation of CD38 activity abolished the LXR-dependent induction of DC chemotaxis. Using the low-density lipoprotein receptor-deficient (LDLR^-/-) LDLR^-/- mouse model of atherosclerosis, we also demonstrated that hematopoietic CD38 expression is important for the accumulation of lipid-laden myeloid cells in lesions, suggesting that CD38 is a key factor in leukocyte migration during atherogenesis. Collectively, our results demonstrate that LXRs are required for the efficient emigration of DCs in response to chemotactic signals during inflammation.

CD38 promotes pristane-induced chronic inflammation and increases susceptibility to experimental lupus by an apoptosis-driven and TRPM2-dependent mechanism

In this study, we investigated the role of CD38 in a pristane-induced murine model of lupus. CD38-deficient (Cd38-/-) but not ART2-deficient (Art2-/-) mice developed less severe lupus compared to wild type (WT) mice, and their protective phenotype consisted of (i) decreased IFN-I-stimulated gene expression, (ii) decreased numbers of peritoneal CCR2hiLy6Chi inflammatory monocytes, TNF-α-producing Ly6G+ neutrophils and Ly6Clo monocytes/macrophages, (iii) decreased production of anti-single-stranded DNA and anti-nRNP autoantibodies, and (iv) ameliorated glomerulonephritis. Cd38-/- pristane-elicited peritoneal exudate cells had defective CCL2 and TNF-α secretion following TLR7 stimulation. However, Tnf-α and Cxcl12 gene expression in Cd38-/- bone marrow (BM) cells was intact, suggesting a CD38-independent TLR7/TNF-α/CXCL12 axis in the BM. Chemotactic responses of Cd38-/- Ly6Chi monocytes and Ly6G+ neutrophils were not impaired. However, Cd38-/- Ly6Chi monocytes and Ly6Clo monocytes/macrophages had defective apoptosis-mediated cell death. Importantly, mice lacking the cation channel TRPM2 (Trpm2-/-) exhibited very similar protection, with decreased numbers of PECs, and apoptotic Ly6Chi monocytes and Ly6Clo monocytes/macrophages compared to WT mice. These findings reveal a new role for CD38 in promoting aberrant inflammation and lupus-like autoimmunity via an apoptosis-driven mechanism. Furthermore, given the implications of CD38 in the activation of TRPM2, our data suggest that CD38 modulation of pristane-induced apoptosis is TRPM2-dependent.

CD38/cADPR Signaling Pathway in Airway Disease: Regulatory Mechanisms

Asthma is an inflammatory disease in which proinflammatory cytokines have a role in inducing abnormalities of airway smooth muscle function and in the development of airway hyperresponsiveness. Inflammatory cytokines alter calcium (Ca²⁺) signaling and contractility of airway smooth muscle, which results in nonspecific airway hyperresponsiveness to agonists. In this context, Ca²⁺ regulatory mechanisms in airway smooth muscle and changes in these regulatory mechanisms encompass a major component of airway hyperresponsiveness. Although dynamic Ca²⁺ regulation is complex, phospholipase C/inositol tris-phosphate (PLC/IP3) and CD38-cyclic ADP-ribose (CD38/cADPR) are two major pathways mediating agonist-induced Ca²⁺ regulation in airway smooth muscle. Altered CD38 expression or enhanced cyclic ADP-ribosyl cyclase activity associated with CD38 contributes to human pathologies such as asthma, neoplasia, and neuroimmune diseases. This review is focused on investigations on the role of CD38-cyclic ADP-ribose signaling in airway smooth muscle in the context of transcriptional and posttranscriptional regulation of CD38 expression. The specific roles of transcription factors NF-kB and AP-1 in the transcriptional regulation of CD38 expression and of miRNAs miR-140-3p and miR-708 in the posttranscriptional regulation and the underlying mechanisms of such regulation are discussed.

Nociceptive Roles of TRPM2 Ion Channel in Pathologic Pain

Pain is a protective mechanism that enables us to avoid potentially harmful environments. However, when pathologically persisted and aggravated under severely injured or inflamed conditions, pain often reduces the quality of life and thus is considered as a disease to eliminate. Inflammatory and/or neuropathic mechanisms may exaggerate interactions between damaged tissues and neural pathways for pain mediation. Similar mechanisms also promote the communication among cellular participants in synapses at spinal or higher levels, which may amplify nociceptive firing and subsequent signal transmission, deteriorating the pain sensation. In this pathology, important cellular players are afferent sensory neurons, peripheral immune cells, and spinal glial cells. Arising from damage of injury, overloaded interstitial and intracellular reactive oxygen species (ROS) and intracellular Ca²⁺ are key messengers in the development and maintenance of pathologic pain. Thus, an ROS-sensitive and Ca²⁺-permeable ion channel that is highly expressed in the participant cells might play a critical role in the pathogenesis. Transient receptor potential melastatin subtype 2 (TRPM2) is the unique molecule that satisfies all of the requirements: the sensitivity, permeability, and its expressing cells. Notable progress in delineating the role of TRPM2 in pain has been achieved during the past decade. In the present review, we summarize the important findings in the key cellular components that are involved in pathologic pain. This overview will help to understand TRPM2-mediated pain mechanisms and speculate therapeutic strategies by utilizing this updated information.

CD38 in the pathogenesis of allergic airway disease: Potential therapeutic targets

CD38 is an ectoenzyme that catalyzes the conversion of β-nicotinamide adenine dinucleotide (β-NAD) to cyclic adenosine diphosphoribose (cADPR) and adenosine diphosphoribose (ADPR) and NADP to nicotinic acid adenine dinucleotide phosphate (NAADP) and adenosine diphosphoribose-2'-phosphate (ADPR-P). The metabolites of NAD and NADP have roles in calcium signaling in different cell types including airway smooth muscle (ASM) cells. In ASM cells, inflammatory cytokines augment CD38 expression and to a greater magnitude in cells from asthmatics, indicating a greater capacity for the generation of cADPR and ADPR in ASM from asthmatics. CD38 deficient mice develop attenuated airway responsiveness to inhaled methacholine following allergen sensitization and challenge compared to wild-type mice indicating its potential role in asthma. Regulation of CD38 expression in ASM cells is achieved by mitogen activated protein kinases, specific isoforms of PI3 kinases, the transcription factors NF-κB and AP-1, and post-transcriptionally by microRNAs. This review will focus on the role of CD38 in intracellular calcium regulation in ASM, contribution to airway inflammation and airway hyperresponsiveness in mouse models of allergic airway inflammation, the transcriptional and post-transcriptional mechanisms of regulation of expression, and outline approaches to inhibit its expression and activity.

CD38 is expressed on inflammatory cells of the intestine and promotes intestinal inflammation

The enzyme CD38 is expressed on a variety of hematopoietic and non-hematopoietic cells and is involved in diverse processes such as generation of calcium-mobilizing metabolites, cell activation, and chemotaxis. Here, we show that under homeostatic conditions CD38 is highly expressed on immune cells of the colon mucosa of C57BL/6 mice. Myeloid cells recruited to this tissue upon inflammation also express enhanced levels of CD38. To determine the role of CD38 in intestinal inflammation, we applied the dextran sulfate sodium (DSS) colitis model. Whereas wild-type mice developed severe colitis, CD38-/- mice had only mild disease following DSS-treatment. Histologic examination of the colon mucosa revealed pronounced inflammatory damage with dense infiltrates containing numerous granulocytes and macrophages in wild-type animals, while these findings were significantly attenuated in CD38-/- mice. Despite attenuated histological findings, the mRNA expression of inflammatory cytokines and chemokines was only marginally lower in the colons of CD38-/- mice as compared to wild-type mice. In conclusion, our results identify a function for CD38 in the control of inflammatory processes in the colon.

CD38 expression in early B-cell precursors contributes to extracellular signal-regulated kinase-mediated apoptosis

CD38 is a 45,000 molecular weight transmembrane protein that is expressed in immature and mature lymphocytes. However, the expression and function of CD38 during B-cell differentiation in mice is poorly understood. Here, we report that CD38 is expressed from the earliest stages of B-cell development. Pre-pro-B, pro-B, pre-B and immature B cells from murine bone marrow all stained positive for CD38. Interestingly, CD38 expression increases with B-cell maturation. To assess the role of CD38 during B-cell maturation, CD38-deficient mice were analysed. CD38(-/-) mice showed a significant increase in both the frequency of B-lineage cells and the absolute numbers of pre-pro-B cells in bone marrow; however, no other differences were observed at later stages. CD38 cross-linking in Ba/F3 cells promoted apoptosis and marked extracellular signal-regulated kinase (ERK) phosphorylation, and these effects were reduced by treatment with the mitogen-activated protein kinase/ERK kinase inhibitor PD98059, and similar effects were observed in B-cell precursors from bone marrow. These data demonstrate that B-cell precursors in mouse bone marrow express functional CD38 and implicate the early ligation of CD38 in the ERK-associated regulation of the B-lineage differentiation pathway.

Airway responsiveness in CD38-deficient mice in allergic airway disease: studies with bone marrow chimeras

CD38 is a cell-surface protein involved in calcium signaling and contractility of airway smooth muscle. It has a role in normal airway responsiveness and in airway hyperresponsiveness (AHR) developed following airway exposure to IL-13 and TNF-α but appears not to be critical to airway inflammation in response to the cytokines. CD38 is also involved in T cell-mediated immune response to protein antigens. In this study, we assessed the contribution of CD38 to AHR and inflammation to two distinct allergens, ovalbumin and the epidemiologically relevant environmental fungus Alternaria. We also generated bone marrow chimeras to assess whether Cd38(+/+) inflammatory cells would restore AHR in the CD38-deficient (Cd38(-/-)) hosts following ovalbumin challenge. Results show that wild-type (WT) mice develop greater AHR to inhaled methacholine than Cd38(-/-) mice following challenge with either allergen, with comparable airway inflammation. Reciprocal bone marrow transfers did not change the native airway phenotypic differences between WT and Cd38(-/-) mice, indicating that the lower airway reactivity of Cd38(-/-) mice stems from Cd38(-/-) lung parenchymal cells. Following bone marrow transfer from either source and ovalbumin challenge, the phenotype of Cd38(-/-) hosts was partially reversed, whereas the airway phenotype of the WT hosts was preserved. Airway inflammation was similar in Cd38(-/-) and WT chimeras. These results indicate that loss of CD38 on hematopoietic cells is not sufficient to prevent AHR and that the magnitude of airway inflammation is not the predominant underlying determinant of AHR in mice.

Ectoenzymes in leukocyte migration and their therapeutic potential

Inflammation causes or accompanies a huge variety of diseases. Migration of leukocytes from the blood into the tissues, in the tissues, and from the tissues to lymphatic vasculature is crucial in the formation and resolution of inflammatory infiltrates. In addition to classical adhesion and activation molecules, several other molecules are known to contribute to the leukocyte traffic. Several of them belong to ectoenzymes, which are cell surface molecules having catalytically active sites outside the cell. We will review here how several ectoenzymes present on leukocytes or endothelial cell surface function as adhesins and/or modulate the extravasation cascade through their enzymatic activities. Moreover, their therapeutic potential as immune modulators in different experimental inflammation models and in clinical trials will be discussed.

Structure-based design of 2-aminopyridine oxazolidinones as potent and selective tankyrase inhibitors

Aberrant activation of the Wnt pathway has been implicated in the development and formation of many cancers. TNKS inhibition has been shown to antagonize Wnt signaling via Axin stabilization in APC mutant colon cancer cell lines. We employed structure-based design to identify a series of 2-aminopyridine oxazolidinones as potent and selective TNKS inhibitors. These compounds exhibited good enzyme and cell potency as well as selectivity over other PARP isoforms. Co-crystal structures of these 2-aminopyridine oxazolidinones complexed to TNKS reveal an induced-pocket binding mode that does not involve interactions with the nicotinamide binding pocket. Oral dosing of lead compounds 3 and 4 resulted in significant effects on several Wnt-pathway biomarkers in a three day DLD-1 mouse tumor PD model.

CD38 controls the innate immune response against Listeria monocytogenes

CD38, adenosine-5'-diphosphate-ribosyl cyclase 1, is a multifunctional enzyme, expressed on a wide variety of cell types. CD38 has been assigned diverse functions, including generation of calcium-mobilizing metabolites, cell activation, and chemotaxis. Using a murine Listeria monocytogenes infection model, we found that CD38 knockout (KO) mice were highly susceptible to infection. Enhanced susceptibility was already evident within 3 days of infection, suggesting a function of CD38 in the innate immune response. CD38 was expressed on neutrophils and inflammatory monocytes, and especially inflammatory monocytes further upregulated CD38 during infection. Absence of CD38 caused alterations of the migration pattern of both cell types to sites of infection. We observed impaired accumulation of cells in the spleen but surprisingly similar or even higher accumulation of cells in the liver. CD38 KO and wild-type mice showed similar changes in the composition of neutrophils and inflammatory monocytes in blood and bone marrow, indicating that mobilization of these cells from the bone marrow was CD38 independent. In vitro, macrophages of CD38 KO mice were less efficient in uptake of listeria but still able to kill the bacteria. Dendritic cells also displayed enhanced CD38 expression following infection. However, absence of CD38 did not impair the capacity of mice to prime CD8(+) T cells against L. monocytogenes, and CD38 KO mice could efficiently control secondary listeria infection. In conclusion, our results demonstrate an essential role for CD38 in the innate immune response against L. monocytogenes.

Loss of TRPM2 function protects against irradiation-induced salivary gland dysfunction

Xerostomia as a result of salivary gland damage is a permanent and debilitating side effect of radiotherapy for head and neck cancers. Effective treatments for protecting, or restoring, salivary gland function are not available. Here we report that irradiation treatment leads to activation of the calcium-permeable channel, transient potential melastatin-like 2 (TRPM2), via stimulation of poly-ADP-ribose polymerase. Importantly, irradiation induced an irreversible loss of salivary gland fluid secretion in TRPM2+/+ mice while a transient loss was seen in TRPM2-/- mice with >60% recovery by 30 days after irradiation. Treatment of TRPM2+/+ mice with the free radical scavenger Tempol or the PARP1 inhibitor 3-aminobenzamide attenuated irradiation-induced activation of TRPM2 and induced significant recovery of salivary fluid secretion. Furthermore, TPL (4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl) induced complete recovery of function in irradiated TRPM2-/- mice. These novel data demonstrate that TRPM2 is activated by irradiation, via PARP1 activation, and contributes to irreversible loss of salivary gland function.

Altered CD38/Cyclic ADP-Ribose Signaling Contributes to the Asthmatic Phenotype

CD38 is a transmembrane glycoprotein expressed in airway smooth muscle cells. The enzymatic activity of CD38 generates cyclic ADP-ribose from β-NAD. Cyclic ADP-ribose mobilizes intracellular calcium during activation of airway smooth muscle cells by G-protein-coupled receptors through activation of ryanodine receptor channels in the sarcoplasmic reticulum. Inflammatory cytokines that are implicated in asthma upregulate CD38 expression and increase the calcium responses to contractile agonists in airway smooth muscle cells. The augmented intracellular calcium responses following cytokine exposure of airway smooth muscle cells are inhibited by an antagonist of cyclic ADP-ribose. Airway smooth muscle cells from CD38 knockout mice exhibit attenuated intracellular calcium responses to agonists, and these mice have reduced airway response to inhaled methacholine. CD38 also contributes to airway hyperresponsiveness as shown in mouse models of allergen or cytokine-induced inflammatory airway disease. In airway smooth muscle cells obtained from asthmatics, the cytokine-induced CD38 expression is significantly enhanced compared to expression in cells from nonasthmatics. This differential induction of CD38 expression in asthmatic airway smooth muscle cells stems from increased activation of MAP kinases and transcription through NF-κB, and altered post-transcriptional regulation through microRNAs. We propose that increased capacity for CD38 signaling in airway smooth muscle in asthma contributes to airway hyperresponsiveness.

The NAD+-dependent histone deacetylase SIRT6 promotes cytokine production and migration in pancreatic cancer cells by regulating Ca2+ responses

Cytokine secretion by cancer cells contributes to cancer-induced symptoms and angiogenesis. Studies show that the sirtuin SIRT6 promotes inflammation by enhancing TNF expression. Here, we aimed to determine whether SIRT6 is involved in conferring an inflammatory phenotype to cancer cells and to define the mechanisms linking SIRT6 to inflammation. We show that SIRT6 enhances the expression of pro-inflammatory cyto-/chemokines, such as IL8 and TNF, and promotes cell migration in pancreatic cancer cells by enhancing Ca(2+) responses. Via its enzymatic activity, SIRT6 increases the intracellular levels of ADP-ribose, an activator of the Ca(2+) channel TRPM2. In turn, TRPM2 and Ca(2+) are shown to be involved in SIRT6-induced TNF and IL8 expression. SIRT6 increases the nuclear levels of the Ca(2+)-dependent transcription factor, nuclear factor of activated T cells (NFAT), and cyclosporin A, a calcineurin inhibitor that reduces NFAT activity, reduces TNF and IL8 expression in SIRT6-overexpressing cells. These results implicate a role for SIRT6 in the synthesis of Ca(2+)-mobilizing second messengers, in the regulation of Ca(2+)-dependent transcription factors, and in the expression of pro-inflammatory, pro-angiogenic, and chemotactic cytokines. SIRT6 inhibition may help combat cancer-induced inflammation, angiogenesis, and metastasis.

TRPM2 cation channels modulate T cell effector functions and contribute to autoimmune CNS inflammation

TRPM2, a highly Ca²⁺-permeable member of the transient receptor potential melastatin-related (TRPM) family of cation channels, is expressed in cells of the immune system. We demonstrate firstly that TRPM2 cation channels on T cells critically influence T cell proliferation and proinflammatory cytokine secretion following polyclonal T cell receptor stimulation. Consistently, trpm2-deficient mice exhibited an attenuated clincal phenotype of experimental autoimmune encephalomyelitis (EAE) with reduced inflammatory and demyelinating spinal cord lesions. Importantly, trmp2-deficient T cells were as susceptible as wildtype T cells to oxidative stress-induced cell death as it occurs in inflammatory CNS lesions. This supports the notion that the attenuated EAE phenotype is mainly due to reduced T cell effector functions but unaffected by potential modulation of T cell survival at the site of inflammation. Our findings suggest TRPM2 cation channels as a potential target for treating autoimmune CNS inflammation.

Mice deficient in CD38 develop an attenuated form of collagen type II-induced arthritis

CD38, a type II transmembrane glycoprotein expressed in many cells of the immune system, is involved in cell signaling, migration and differentiation. Studies in CD38 deficient mice (CD38 KO mice) indicate that this molecule controls inflammatory immune responses, although its involvement in these responses depends on the disease model analyzed. Here, we explored the role of CD38 in the control of autoimmune responses using chicken collagen type II (col II) immunized C57BL/6-CD38 KO mice as a model of collagen-induced arthritis (CIA). We demonstrate that CD38 KO mice develop an attenuated CIA that is accompanied by a limited joint induction of IL-1β and IL-6 expression, by the lack of induction of IFNγ expression in the joints and by a reduction in the percentages of invariant NKT (iNKT) cells in the spleen. Immunized CD38 KO mice produce high levels of circulating IgG1 and low of IgG2a anti-col II antibodies in association with reduced percentages of Th1 cells in the draining lymph nodes. Altogether, our results show that CD38 participates in the pathogenesis of CIA controlling the number of iNKT cells and promoting Th1 inflammatory responses.

Enhancement of humoral immunity in mice by coupling pUCpGs10 and aluminium to the HCV recombinant immunogen

Aim

To investigate the enhancement of humoral immunity when CpG ODN (cytidine phosphate guanosine oligodeoxynucleotides) and aluminium adjuvants are complexed with the HCV (Hepatitis C virus) recombinant immunogen in mice.

Methods

After immunizing Balb/c mice with the recombination HCV antigen adjuvanted with pUCpGs10 and/or aluminium(antigen+CpG+alum, antigen+CpG, antigen+alum, antigen+PBS), enzyme-linked immunosorbent assay (ELISA) was used to measure the specific serum antibody titers of IgG, to determine the neutralization response to various peptide genotypes, and to determine the concentration of IL-6 and IL-10 in supernatants of in vitro cultured splenic lymphocytes. Enzyme-linked immunospot assay (ELISPOT) was used to quantify the non-specific and specific splenic antibody-secreting cells (ASCs), and flow cytometry (FCM) determined the ratio of different splenic lymphocytes. The serum of rabbits immunized with the recombinant pBVGST/HVR1 antigen immunoprecipitated the HCV isolated from 12 patients' serum.

Results

The sera antibody titers were 1:51200, 1:9051, 1:18102, 1:6400 respectively after the final immunization and demonstrated good neutralization responses to the six gene peptide containing 1a, 1b, 2a, 3a, 4a and 6a. The aluminum adjuvant increased the population of both specific ASCs (P < 0.01) and total ASCs(P < 0.05), with a proportional rise in concentrations of CD19⁺CD27⁺ (P < 0.05), as well as levels of IL-6, IL-10 (P < 0.05) in splenic lymphocytes. The results clearly indicated a significantly higher number of CD19⁺CD38⁺ splenic lymphocytes with the aluminum and pUCpGs10 adjuvant present compared to the control group(P < 0.05). Anti-HVR1 antibody in induced mice can cross-reactively capture HCV particles (10/12).

Conclusions

1. The aluminum adjuvant induces a potent Th2-biased immune response by increasing both the populations of specific and total ASCs and the ratio of CD19⁺CD27⁺ cells. 2. The pUCpGs10 complexed with the aluminum adjuvant boosts the population of plasma cells and increase the efficiency of the immune response. 3. The two adjuvants have synergistic effects on humoral immunity. 4. The recombinant HVR1 protein has the possibility of generating broadly reactive anti-HVR1 antibody.

CD38 and chronic lymphocytic leukemia: a decade later

This review highlights a decade of investigations into the role of CD38 in CLL. CD38 is accepted as a dependable marker of unfavorable prognosis and as an indicator of activation and proliferation of cells when tested. Leukemic clones with higher numbers of CD38(+) cells are more responsive to BCR signaling and are characterized by enhanced migration. In vitro activation through CD38 drives CLL proliferation and chemotaxis via a signaling pathway that includes ZAP-70 and ERK1/2. Finally, CD38 is under a polymorphic transcriptional control after external signals. Consequently, CD38 appears to be a global molecular bridge to the environment, promoting survival/proliferation over apoptosis. Together, this evidence contributes to the current view of CLL as a chronic disease in which the host's microenvironment promotes leukemic cell growth and also controls the sequential acquisition and accumulation of genetic alterations. This view relies on the existence of a set of surface molecules, including CD38, which support proliferation and survival of B cells on their way to and after neoplastic transformation. The second decade of studies on CD38 in CLL will tell if the molecule is an effective target for antibody-mediated therapy in this currently incurable leukemia.

CD38 exacerbates focal cytokine production, postischemic inflammation and brain injury after focal cerebral ischemia

BACKGROUND

Converging evidence suggests that inflammatory processes significantly influence brain injury and clinical impairment in ischemic stroke. Although early studies suggested a key role of lymphocytes, recent data has emphasized the orchestrating function of innate immunity, i.e., macrophages and microglia. The bifunctional receptor and ectoenzyme CD38 synthesizes calcium-mobilizing second messengers (e.g., cyclic ADP-ribose), which have been shown to be necessary for activation and migration of myeloid immune cells. Therefore, we investigated the dynamics of CD38 in stroke and the impact of CD38-deficiency on cytokine production, inflammation and cerebral damage in a mouse model of cerebral ischemia-reperfusion.

METHODOLOGY/PRINCIPAL FINDINGS

We show that the local expression of the chemokine MCP-1 was attenuated in CD38-deficient mice compared with wildtype mice after focal cerebral ischemia and reperfusion. In contrast, no significant induction of MCP-1 expression was observed in peripheral blood after 6 hours. Flow cytometry analysis revealed less infiltrating macrophages and lymphocytes in the ischemic hemisphere of CD38-deficient mice, whereas the amount of resident microglia was unaltered. An up-regulation of CD38 expression was observed in macrophages and CD8(+) cells after focal cerebral ischemia in wildtype mice, whereas CD38 expression was unchanged in microglia. Finally, we demonstrate that CD38-deficiency decreases the cerebral ischemic injury and the persistent neurological deficit after three days of reperfusion in this murine temporary middle cerebral artery occlusion (tMCAO) model.

CONCLUSION/SIGNIFICANCE

CD38 is differentially regulated following stroke and its deficiency attenuates the postischemic chemokine production, the immune cell infiltration and the cerebral injury after temporary ischemia and reperfusion. Therefore CD38 might prove a therapeutic target in ischemic stroke.

The PI3K p110δ regulates expression of CD38 on regulatory T cells

The PI3K pathway has emerged as a key regulator of regulatory T cell (Treg) development and homeostasis and is required for full Treg-mediated suppression. To identify new genes involved in PI3K-dependent suppression, we compared the transcriptome of WT and p110δ^D910A Tregs. Among the genes that were differentially expressed was the gene for the transmembrane cyclic ADP ribose hydrolase CD38. Here we show that CD38 is expressed mainly by a subset of Foxp3⁺CD25⁺CD4⁺ T cells originating in the thymus and on Tregs in the spleen. CD38^high WT Tregs showed superior suppressive activity to CD38^low Tregs, which failed to upregulate CD73, a surface protein which is important for suppression. However, Tregs from heterozygous CD38^+/− mice were unimpaired despite lower levels of CD38 expression. Therefore, CD38 can be used as a marker for Tregs with high suppressive activity and the impaired Treg function in p110δ^D910A mice can in part be explained by the failure of CD38^high cells to develop.

ATRA-induced HL-60 myeloid leukemia cell differentiation depends on the CD38 cytosolic tail needed for membrane localization, but CD38 enzymatic activity is unnecessary

Leukocyte antigen CD38 expression is an early marker of all-trans retinoic acid (ATRA) stimulated differentiation in the leukemic cell line HL-60. It promotes induced myeloid maturation when overexpressed, whereas knocking it down is inhibitory. It is a type II membrane protein with an extracellular C-terminal enzymatic domain with NADase/NADPase and ADPR cyclase activity and a short cytoplasmic N-terminal tail. Here we determined whether CD38 enzymatic activity or the cytoplasmic tail is required for ATRA-induced differentiation. Neither a specific CD38 ectoenzyme inhibitor nor a point mutation that cripples enzymatic activity (CD38 E226Q) diminishes ATRA-induced differentiation or G1/0 arrest. In contrast a cytosolic deletion mutation (CD38 Δ11-20) prevents membrane expression and inhibits differentiation and G1/0 arrest. These results may be consistent with disrupting the function of critical molecules necessary for membrane-expressed CD38 signal transduction. One candidate molecule is the Src family kinase Fgr, which failed to undergo ATRA-induced upregulation in CD38 Δ11-20 expressing cells. Another is Vav1, which also showed only basal expression after ATRA treatment in CD38 Δ11-20 expressing cells. Therefore, the ability of CD38 to propel ATRA-induced myeloid differentiation and G1/0 arrest is unimpaired by loss of its ectoenzyme activity. However a cytosolic tail deletion mutation disrupted membrane localization and inhibited differentiation. ATRA-induced differentiation thus does not require the CD38 ectoenzyme function, but is dependent on a membrane receptor function.

TRPM2: a multifunctional ion channel for calcium signalling

The transient potential receptor melastatin-2 (TRPM2) channel has emerged as an important Ca(2+) signalling mechanism in a variety of cells, contributing to cellular functions that include cytokine production, insulin release, cell motility and cell death. Its ability to respond to reactive oxygen species has made TRPM2 a potential therapeutic target for chronic inflammation, neurodegenerative diseases, and oxidative stress-related pathologies. TRPM2 is a non-selective, calcium (Ca(2+))-permeable cation channel of the melastatin-related transient receptor potential (TRPM) ion channel subfamily. It is activated by intracellular adenosine diphosphate ribose (ADPR) through a diphosphoribose hydrolase domain in its C-terminus and regulated through a variety of factors, including synergistic facilitation by [Ca(2+)](i), cyclic ADPR, H(2)O(2), NAADP, and negative feedback regulation by AMP and permeating protons (pH). In addition to its role mediating Ca(2+) influx into the cells, TRPM2 can also function as a lysosomal Ca(2+) release channel, contributing to cell death. The physiological and pathophysiological context of ROS-mediated events makes TRPM2 a promising target for the development of therapeutic tools of inflammatory and degenerative diseases.

Role of 4-1BB receptor in the control played by CD8(+) T cells on IFN-gamma production by Mycobacterium tuberculosis antigen-specific CD4(+) T Cells

Background

Antigen-specific IFN-γ producing CD4⁺ T cells are the main mediators of protection against Mycobacterium tuberculosis infection both under natural conditions and following vaccination. However these cells are responsible for lung damage and poor vaccine efficacy when not tightly controlled. Discovering new tools to control nonprotective antigen-specific IFN-γ production without affecting protective IFN-γ is a challenge in tuberculosis research.

Methods and Findings

Immunization with DNA encoding Ag85B, a candidate vaccine antigen of Mycobacterium tuberculosis, elicited in mice a low but protective CD4⁺ T cell-mediated IFN-γ response, while in mice primed with DNA and boosted with Ag85B protein a massive increase in IFN-γ response was associated with loss of protection. Both protective and non-protective Ag85B-immunization generated antigen-specific CD8⁺ T cells which suppressed IFN-γ-secreting CD4⁺ T cells. However, ex vivo ligation of 4-1BB, a member of TNF-receptor super-family, reduced the massive, non-protective IFN-γ responses by CD4⁺ T cells in protein-boosted mice without affecting the low protective IFN-γ-secretion in mice immunized with DNA. This selective inhibition was due to the induction of 4-1BB exclusively on CD8⁺ T cells of DNA-primed and protein-boosted mice following Ag85B protein stimulation. The 4-1BB-mediated IFN-γ inhibition did not require soluble IL-10, TGF-β, XCL-1 and MIP-1β. In vivo Ag85B stimulation induced 4-1BB expression on CD8⁺ T cells and in vivo 4-1BB ligation reduced the activation, IFN-γ production and expansion of Ag85B-specific CD4⁺ T cells of DNA-primed and protein-boosted mice.

Conclusion/Significance

Antigen-specific suppressor CD8⁺ T cells are elicited through immunization with the mycobacterial antigen Ag85B. Ligation of 4-1BB receptor further enhanced their suppressive activity on IFN-γ-secreting CD4⁺ T cells. The selective expression of 4-1BB only on CD8⁺ T cells in mice developing a massive, non-protective IFN-γ response opens novel strategies for intervention in tuberculosis pathology and vaccination through T-cell co-stimulatory-based molecular targeting.

Mammalian sirtuins: biological insights and disease relevance

Aging is accompanied by a decline in the healthy function of multiple organ systems, leading to increased incidence and mortality from diseases such as type II diabetes mellitus, neurodegenerative diseases, cancer, and cardiovascular disease. Historically, researchers have focused on investigating individual pathways in isolated organs as a strategy to identify the root cause of a disease, with hopes of designing better drugs. Studies of aging in yeast led to the discovery of a family of conserved enzymes known as the sirtuins, which affect multiple pathways that increase the life span and the overall health of organisms. Since the discovery of the first known mammalian sirtuin, SIRT1, 10 years ago, there have been major advances in our understanding of the enzymology of sirtuins, their regulation, and their ability to broadly improve mammalian physiology and health span. This review summarizes and discusses the advances of the past decade and the challenges that will confront the field in the coming years.

Nicotinamide mononucleotide adenylyl transferase-mediated axonal protection requires enzymatic activity but not increased levels of neuronal nicotinamide adenine dinucleotide

Axonal degeneration is a hallmark of many neurological disorders. Studies in animal models of neurodegenerative diseases indicate that axonal degeneration is an early event in the disease process, and delaying this process can lead to decreased progression of the disease and survival extension. Overexpression of the Wallerian degeneration slow (Wld(s)) protein can delay axonal degeneration initiated via axotomy, chemotherapeutic agents, or genetic mutations. The Wld(s) protein consists of the N-terminal portion of the ubiquitination factor Ube4b fused to the nicotinamide adenine dinucleotide (NAD(+)) biosynthetic enzyme nicotinamide mononucleotide adenylyl transferase 1 (Nmnat1). We previously showed that the Nmnat1 portion of this fusion protein was the critical moiety for Wld(s)-mediated axonal protection. Here, we describe the development of an automated quantitative assay for assessing axonal degeneration. This method successfully showed that Nmnat1 enzymatic activity is important for axonal protection as mutants with reduced enzymatic activity lacked axon protective activity. We also found that Nmnat enzymes with diverse sequences and structures from various species, including Drosophila melanogaster, Saccharomyces cerevisiae, and archaebacterium Methanocaldococcus jannaschii, which encodes a protein with no homology to eukaryotic Nmnat enzymes, all mediate robust axonal protection after axotomy. Besides the importance of Nmnat enzymatic activity, we did not observe changes in the steady-state NAD(+) level, and we found that inhibition of nicotinamide phosphoribosyltransferase (Nampt), which synthesizes substrate for Nmnat in mammalian cells, did not affect the protective activity of Nmnat1. These results provide the possibility of a role for new Nmnat enzymatic activity in axonal protection in addition to NAD(+) synthesis.

Mechanism-based small molecule probes for labeling CD38 on live cells

CD38 is a type II transmembrane glycoprotein with multiple functions. It acts as an ecto-enzyme as well as a receptor. The enzymatic activity catalyzes the formation of two potent Ca(2+) releasing agents: cyclic adenosine diphosphate ribose (cADPR) from nicotinamide adenine dinucleotide (NAD) and nicotinic acid adenine dinucleotide phosphate (NAADP) from NAD phosphate (NADP). The receptor function of CD38 leads to the phosphorylation of intracellular signaling proteins and the up-regulation of cytokine production in immune cells. These two functions of CD38 underlie its involvement in various biological processes, such as hormone secretion, immune cell differentiation, and immune responses. Clinically, CD38 is used as a negative prognosis marker for chronic lymphatic leukemia (CLL). However, a clear molecular understanding of CD38's role in physiology and pathology is still lacking. To facilitate the study of CD38 at cellular and molecular levels, here we report a mechanism-based method for fluorescently labeling CD38 on live cells. This labeling method does not interfere with the receptor function of CD38 and the downstream signaling. The labeling method is thus a useful tool to study the receptor function of CD38 in live cells. In addition, since the mechanism-based labeling also inhibits the enzymatic activity of CD38, it should be useful for dissecting the receptor function of CD38 without interference from its enzyme function in complicated biological processes.

CD38 plays a dual role in allergen-induced airway hyperresponsiveness

The multifunctional surface protein CD38 acts as a receptor with ecto-enzymatic activity, hydrolyzing NAD to generate several products known to exhibit Ca2+-mobilizing properties. Although CD38 is a convenient marker of immune cell development, and an indicator of progression for several diseases, it is not restricted to the immune compartment. To determine the potentially multilayered involvement of CD38 in allergen-induced airway inflammation and hyperreactivity, we dissected the potential role of CD38 as a regulator of immunity, but also pulmonary function. CD38-deficient and wild-type (WT) mice were sensitized and airway challenged with ovalbumin, and subsequently analyzed regarding their level of airway hyperresponsiveness (AHR) in response to methacholine. Parameters of lung inflammation were also analyzed. Similar sets of measurements were obtained from reciprocal bone marrow swapping experiments between CD38(-/-) and WT mice. Mice lacking CD38 exhibit strongly reduced AHR, which is accompanied by a decrease in typical hallmarks of pulmonary inflammation, including eosinophilia and lymphocytic lung infiltrates, as well as Th2-cytokine levels (IL-4, -5, and -13). Antigen-specific immunoglobulin (Ig)E and IgG1 antibody titers are substantially reduced, consistent with CD38 being crucial for mounting a primary humoral systemic immune response. Reconstitution of lethally irradiated, lung-shielded, CD38-deficient mice with WT bone marrow does not restore WT levels of airway hyperreactivity, nor mucus secretion. The opposite experiment, transferring CD38(-/-) bone marrow into WT mice, also shows reduced AHR levels. These studies demonstrate that CD38 not only acts as a key modulator of the immune response, but also plays an equally important role as an intrinsic pulmonary component.

Augmentation of antibody responses by retinoic acid and costimulatory molecules

Antibody production is crucial for a successful vaccine response. Beyond the ability of vitamin A (VA) and its active metabolite, all-trans-retinoic acid (RA) to restore growth in VA-deficient animals, supplementation with VA and/or treatment with RA can augment antibody responses in both VA-deficient and VA-adequate animals. RA alone, and in combination with stimuli that are ligands for the Toll-like receptor family, can augment the adaptive immune response leading to a heightened primary antibody response, and a stronger recall response upon restimulation. Mechanisms may include regulation of cell populations, type 1/type 2 cytokines, and B cell-related transcription factors, leading to accelerated B cell maturation.

Poly (ADP-ribose) polymerases (PARPs) 1-3 regulate astrocyte activation

Besides their traditional role in maintaining CNS homeostasis, astrocytes also participate in innate immune responses. Indeed, we have previously demonstrated that astrocytes are capable of recognizing bacterial pathogens such as Staphylococcus aureus, a common etiologic agent of CNS infections, and respond with the robust production of numerous proinflammatory mediators. Suppression of Poly (ADP-ribose) polymerase-1 (PARP-1), a DNA repair enzyme, has been shown to attenuate inflammatory responses in several cell types including mixed glial cultures. However, a role for PARP-1 in regulating innate immune responses in purified astrocytes and the potential for multiple PARP family members to cooperatively regulate astrocyte activation has not yet been examined. The synthetic PARP-1 inhibitor PJ-34 attenuated the production of several proinflammatory mediators by astrocytes in response to S. aureus stimulation including nitric oxide, interleukin-1 beta, tumor necrosis factor-alpha, and CCL2. The release of all four mediators was partially reduced in PARP-1 knockout (KO) astrocytes compared to wild-type cells. The residual inflammatory mediator expression detected in PARP-1 KO astrocytes was further blocked with PJ-34, suggesting either non-specific effects of the drug or actions on alternative PARP isoforms. Reduction in PARP-2 or PARP-3 expression by siRNA knock down revealed that these isoforms also contributed to inflammatory mediator regulation in response to S. aureus. Interestingly, the combined targeting of either PARP-1/PARP-2 or PARP-2/PARP-3 attenuated astrocyte inflammatory responses more effectively compared to knock down of either PARP alone, suggesting cooperativity between PARP isoforms. Collectively, these findings suggest that PARPs influence the extent of S. aureus-induced astrocyte activation.

CD38 and CD157: biological observations to clinical therapeutic targets

The application of molecular knowledge for developing new medical technologies is the goal of molecular medicine. Success in this area is highly dependent on the interaction of investigators from fields as diverse as biochemistry, cell biology, immunology, physiology, epidemiology, and physics, with an eye toward applying their insights and discoveries to improving human health. Such interdisciplinary approaches rarely find the common ground and language necessary to achieve this goal. Recently, a meeting of researchers studying the ectoenzymes CD38 and CD157 brought together insights into the regulation of calcium signaling, the metabolism of pyridine nucleotides by CD38 and CD157, and subsequent effects on immune function. Together, these discoveries were being applied to the development of novel therapeutics and diagnostics for myeloma and chronic lymphocytic leukemia. This issue of Molecular Medicine, featuring several short reviews based on a conference held in Turin, Italy, 10-12 June 2006, showcases the current state of this field and highlights some recent progress in molecular medicine.

CD38 and CD157: biological observations to clinical therapeutic targets

The application of molecular knowledge for developing new medical technologies is the goal of molecular medicine. Success in this area is highly dependent on the interaction of investigators from fields as diverse as biochemistry, cell biology, immunology, physiology, epidemiology, and physics, with an eye toward applying their insights and discoveries to improving human health. Such interdisciplinary approaches rarely find the common ground and language necessary to achieve this goal. Recently, a meeting of researchers studying the ectoenzymes CD38 and CD157 brought together insights into the regulation of calcium signaling, the metabolism of pyridine nucleotides by CD38 and CD157, and subsequent effects on immune function. Together, these discoveries were being applied to the development of novel therapeutics and diagnostics for myeloma and chronic lymphocytic leukemia. This issue of Molecular Medicine, featuring several short reviews based on a conference held in Turin, Italy, 10-12 June 2006, showcases the current state of this field and highlights some recent progress in molecular medicine.