Leukocyte trafficking: a special focus on VAP-1 and CLEVER-1

It is crucial that lymphocytes patrol the body against foreign intruders and that leukocytes invade inflamed tissues to ameliorate the infection or injury. The adhesion molecules in leukocytes and endothelial cells play an essential role in the immune response by directing the traffic of leukocytes. However, the same molecules that guide leukocyte traffic under physiological conditions are also involved in pathological situations, when an overly excessive or harmful inflammatory response leads to tissue destruction and organ dysfunction or tumor growth. Vascular adhesion protein-1 (VAP-1) and Common lymphatic endothelial and vascular endothelial receptor-1 (CLEVER-1) are endothelial molecules that participate in the adhesion of leukocytes to the endothelia. This study was designed to elucidate, using different inflammation models, the role of VAP-1 and CLEVER-1 in leukocyte migration to the inflamed tissue, and to evaluate the use of antibodies against these molecules as an anti-adhesive therapy. Also, the role of CLEVER-1 during tumorigenesis was studied. Blocking the function of VAP-1 with antibodies significantly decreased the accumulation of leukocytes in the inflamed tissue. Targeting CLEVER-1 prevented cell migration via lymphatic vessels, as well as leukocyte traffic during inflammation. Following the anti-CLEVER-1 antibody treatment the number of immune regulating leukocytes in tumors was reduced, which led to a decrease in tumor growth. However, the normal immune response towards immunization or bacterial infection was not compromised. Thus, VAP-1 and CLEVER-1 are both potential targets for antiinflammatory therapies for preventing the harmful accumulation of leukocytes in inflamed areas. Targeting CLEVER-1 may also inhibit tumor growth by reducing immunosuppressive leukocytes in tumorsVAP-1 ja CLEVER-1 tarttumismolekyylit valkosoluliikenteessä On elintärkeää, että lymfosyytit vartioivat elimistöä vierailta tunkeutujilta ja että valkosolut kulkeutuvat tulehtuneeseen kudokseen parantamaan infektion tai kudosvaurion. Valkosolujen kulkua elimistössä ohjaavat verisuonten ja valkosolujen pinnoilla olevat molekyylit, joita kutsutaan adheesio- eli tarttumismolekyyleiksi. Kuitenkin samat tarttumismolekyylit, jotka ohjaavat valkosolujen kulkua normaalitilanteessa, ovat myös osallisena liian voimakkaissa tai haitallisissa tulehdustilanteissa, jotka voivat johtaa kudoksen tuhoutumiseen ja toiminnan menetykseen tai syövän kasvuun. Verisuonen adheesioproteiini-1 (VAP-1) ja Yleinen lymfaattisen endoteelin ja verisuonen endoteelin reseptori-1 (CLEVER-1) ovat molekyylejä, jotka osallistuvat valkosolujen ja endoteelin väliseen tarttumistapahtumaan. Tämän tutkimuksen tarkoituksena oli selvittää erilaisten tulehdusmallien avulla VAP-1:n ja CLEVER-1:n merkitystä valkosolujen kulkeutumisessa tulehtuneeseen kudokseen ja arvioida VAP-1 ja CLEVER-1 vasta-aineiden käyttöä tulehdusta estävänä hoitona. Lisäksi tavoitteena oli tutkia CLEVER-1:n merkitystä syövän kasvussa. Estämällä VAP-1:n toiminta vasta-aineilla valkosolujen kulku tulehtuneeseen kudokseen väheni merkittävästi. CLEVER-1:n toiminnan esto rajoitti solujen kulkua imuteiden kautta imusolmukkeeseen sekä valkosolujen liikennettä tulehdusalueelle. CLEVER-1 vasta-ainehoito vähensi myös puolustusta säätelevien valkosolujen lukumäärää syöpäkudoksessa pienentäen syövän kasvua, kun taas immunisaation ja bakteeritulehduksen aikana immuunipuolustus toimi normaalisti. Tulosten perusteella sekä VAP-1 että CLEVER-1 ovat hyviä lääkekehityskohteita, sillä kohdistamalla vasta-ainehoito näihin molekyyleihin pystyttään estämään haitallista valkosolujen kerääntymistä tulehtuneeseen kudokseen. Lisäksi CLEVER-1:n toiminnan esto saattaa vähentää ns. immunosupressiivisten eli puolustuskykyä hillitsevien valkosolujen määrää syöpäkudoksessa ja täten edesauttaa syövän hoitoa.Siirretty Doriast

Compartmentalization of adenosine metabolism in cancer cells and its modulation during acute hypoxia.

Extracellular adenosine mediates diverse anti-inflammatory, angiogenic and vasoactive effects and becomes an important therapeutic target for cancer, which has been translated into clinical trials. This study was designed to comprehensively assess adenosine metabolism in prostate and breast cancer cells. We identified cellular adenosine turnover as a complex cascade, comprised of (a) the ectoenzymatic breakdown of ATP via sequential nucleotide pyrophosphatase/phosphodiesterase-1, ecto-5'-nucleotidase/CD73 and adenosine deaminase reactions, and ATP re-synthesis through counteracting adenylate kinase and nucleoside diphosphokinase; (b) the uptake of nucleotide-derived adenosine via equilibrative nucleoside transporters; and (c) the intracellular adenosine phosphorylation into ATP by adenosine kinase and other nucleotide kinases. The exposure of cancer cells to 1% O2 for 24 hours triggered ∼2-fold up-regulation of CD73, without affecting nucleoside transporters, adenosine kinase activity and cellular ATP content. The ability of adenosine to inhibit the tumor-initiating potential of breast cancer cells via receptor-independent mechanism was confirmed in vivo using a xenograft mouse model. The existence of redundant pathways controlling extracellular and intracellular adenosine provides a sufficient justification for reexamination of the current concepts of cellular purine homeostasis and signaling in cancer

Enhanced Antibody Production in Clever-1/Stabilin-1–Deficient Mice

Clever-1, encoded by the Stab1 gene, is a scavenger and leukocyte trafficking receptor expressed by subsets of vascular and lymphatic endothelial cells and immunosuppressive macrophages. Monocyte Clever-1 also modulates T cell activation. However, nothing is known about the possible links between B cell function and Clever-1. Here, we found that Stab1 knockout mice (Stab1−/−) lacking the Clever-1 protein from all cells present with abnormally high antibody levels under resting conditions and show enhanced humoral immune responses after immunization with protein and carbohydrate antigens. Removal of the spleen does not abolish the augmented basal and post-immunization antibody levels in Clever-1–deficient mice. The increased IgG production is also present in mice in which Clever-1 is selectively ablated from macrophages. When compared to wildtype macrophages, Clever-1–deficient macrophages show increased TNF-α synthesis. In co-culture experiments, monocytes/macrophages deficient of Clever-1 support higher IgM production by B cells, which is blocked by TNF-α depletion. Collectively, our data show that the excessive inflammatory activity of monocytes/macrophages in the absence of Clever-1 results in augmented humoral immune responses in vivo

Modeling Rare Human Disorders in Mice : The Finnish Disease Heritage

The modification of genes in animal models has evidently and comprehensively improved our knowledge on proteins and signaling pathways in human physiology and pathology. In this review, we discuss almost 40 monogenic rare diseases that are enriched in the Finnish population and defined as the Finnish disease heritage (FDH). We will highlight how gene-modified mouse models have greatly facilitated the understanding of the pathological manifestations of these diseases and how some of the diseases still lack proper models. We urge the establishment of subsequent international consortiums to cooperatively plan and carry out future human disease modeling strategies. Detailed information on disease mechanisms brings along broader understanding of the molecular pathways they act along both parallel and transverse to the proteins affected in rare diseases, therefore also aiding understanding of common disease pathologies.Peer reviewe

Vascular adhesion protein-1 defines a unique subpopulation of human hematopoietic stem cells and regulates their proliferation

Although the development of hematopoietic stem cells (HSC) has been studied in great detail, their heterogeneity and relationships to different cell lineages remain incompletely understood. Moreover, the role of Vascular Adhesion Protein-1 in bone marrow hematopoiesis has remained unknown. Here we show that VAP-1, an adhesin and a primary amine oxidase producing hydrogen peroxide, is expressed on a subset of human HSC and bone marrow vasculature forming a hematogenic niche. Bulk and single-cell RNAseq analyses reveal that VAP-1+ HSC represent a transcriptionally unique small subset of differentiated and proliferating HSC, while VAP-1− HSC are the most primitive HSC. VAP-1 generated hydrogen peroxide acts via the p53 signaling pathway to regulate HSC proliferation. HSC expansion and differentiation into colony-forming units are enhanced by inhibition of VAP-1. Contribution of VAP-1 to HSC proliferation was confirmed with mice deficient of VAP-1, mice expressing mutated VAP-1 and using an enzyme inhibitor. In conclusion, VAP-1 expression allows the characterization and prospective isolation of a new subset of human HSC. Since VAP-1 serves as a check point-like inhibitor in HSC differentiation, the use of VAP-1 inhibitors enables the expansion of HSC.Peer reviewe

Consequences of the Lack of CD73 and Prostatic Acid Phosphatase in the Lymphoid Organs

CD73, ecto-5&#39;-nucleotidase, is the key enzyme catalyzing the conversion of extracellular AMP to adenosine that controls vascular permeability and immunosuppression. Also prostatic acid phosphatase (PAP) possesses ecto-5&#39;-nucleotidase/AMPase activity and is present in leukocytes. However, its role related to immune system is unknown. Therefore, we analyzed enzymatic activities and leukocyte subtypes of CD73 and PAP knockouts and generated CD73/PAP double knockout mice to elucidate the contribution of CD73 and PAP to immunological parameters. Enzymatic assays confirmed the ability of recombinant human PAP to hydrolyze [H-3] AMP, although at much lower rate than human CD73. Nevertheless, 5&#39;-nucleotidase/AMPase activity in splenocytes and lymphocytes from PAP(-/-) mice tended to be lower than in wild-type controls, suggesting potential contribution of PAP, along with CD73, into lymphoid AMP metabolism ex vivo. Single knockouts had decreased number of CD4(+)/CD25(+)/FoxP(3)(+) regulatory T cells in thymus and CD73/PAP double knockouts exhibited reduced percentages of CD4(+) cells in spleen, regulatory T cells in lymph nodes and thymus, and CD4(+) and CD8(+) cells in blood. These findings suggest that PAP has a synergistic role together with CD73 in the immune system by contributing to the balance of leukocyte subpopulations and especially to the number of regulatory T cells in lymph nodes and thymus.</p

Modeling rare human disorders in mice: the finnish disease heritage

The modification of genes in animal models has evidently and comprehensively improved our knowledge on proteins and signaling pathways in human physiology and pathology. In this review, we discuss almost 40 monogenic rare diseases that are enriched in the Finnish population and defined as the Finnish disease heritage (FDH). We will highlight how gene-modified mouse models have greatly facilitated the understanding of the pathological manifestations of these diseases and how some of the diseases still lack proper models. We urge the establishment of subsequent international consortiums to cooperatively plan and carry out future human disease modeling strategies. Detailed information on disease mechanisms brings along broader understanding of the molecular pathways they act along both parallel and transverse to the proteins affected in rare diseases, therefore also aiding understanding of common disease pathologies.</p

SHARPIN regulates uropod detachment in migrating lymphocytes

Peer reviewe