Tumor-infiltrating DCs suppress nucleic acid-mediated innate immune responses through interactions between the receptor TIM-3 and the alarmin HMGB1.

The mechanisms by which tumor microenvironments modulate nucleic acid-mediated innate immunity remain unknown. Here we identify the receptor TIM-3 as key in circumventing the stimulatory effects of nucleic acids in tumor immunity. Tumor-associated dendritic cells (DCs) in mouse tumors and patients with cancer had high expression of TIM-3. DC-derived TIM-3 suppressed innate immune responses through the recognition of nucleic acids by Toll-like receptors and cytosolic sensors via a galectin-9-independent mechanism. In contrast, TIM-3 interacted with the alarmin HMGB1 to interfere with the recruitment of nucleic acids into DC endosomes and attenuated the therapeutic efficacy of DNA vaccination and chemotherapy by diminishing the immunogenicity of nucleic acids released from dying tumor cells. Our findings define a mechanism whereby tumor microenvironments suppress antitumor immunity mediated by nucleic acids.

Thrombin cleavage of osteopontin controls activation of hepatic stellate cells and is essential for liver fibrogenesis.

Liver biopsy is the current reliable way of evaluating liver fibrosis. However, no specific sera biomarker could be applied in clinical diagnosis. As the pivotal role of osteopontin (OPN) reported in numerous liver diseases, thrombin-cleaved OPN (Thr-OPN) exposes an integrin-binding motif that promoted biological functions. Herein, we investigated the potential of Thr-OPN in liver fibrosis. Using patient samples, mouse models and hepatic stellate cells (HSCs), we analyzed the involvement of Thr-OPN in liver fibrosis. The result showed that, first, Thr-OPN level was significantly higher in patients with liver cirrhosis than that in patients with chronic hepatitis B and healthy controls. Thr-OPN level was positively correlated with liver fibrosis degree in clinical samples. Then in mouse models, it showed a similar correlation between hepatic Thr-OPN levels and liver fibrosis degree. Thr-OPN peptides exacerbated liver fibrosis in OPN-deficient mice, whereas the neutralization of Thr-OPN alleviated liver fibrosis in wild-type mice. Furthermore, when compared with full-length OPN (FL-OPN), Thr-OPN exhibited a greater ability to promote HSC activation, proliferation, and migration via mitogen-activated protein (MAP) kinase and nuclear factor (NF)-κB pathways. In conclusion, Thr-OPN, not FL-OPN, was critically involved in the exacerbation of liver fibrosis by α9 and α4 integrins via MAP kinase and NF-κB signaling pathway, thus representing a novel diagnostic biomarker and treatment target for liver cirrhosis.

G-CSF-induced sympathetic tone provokes fever and primes antimobilizing functions of neutrophils via PGE2.

Granulocyte colony-stimulating factor (G-CSF) is widely used for peripheral blood stem/progenitor mobilization. G-CSF causes low-grade fever that is ameliorated by nonsteroidal anti-inflammatory drugs (NSAIDs), suggesting the activation of arachidonic acid (AA) cascade. How G-CSF regulated this reaction was assessed. G-CSF treatment in mice resulted in fever, which was canceled in prostaglandin E synthase (mPGES-1)-deficient mice. Mobilization efficiency was twice as high in chimeric mice lacking mPGES-1, specifically in hematopoietic cells, suggesting that prostaglandin E2 (PGE2) from hematopoietic cells modulated the bone marrow (BM) microenvironment. Neutrophils from steady-state BM constitutively expressed mPGES-1 and significantly enhanced PGE2 production in vitro by ß-adrenergic stimulation, but not by G-CSF, which was inhibited by an NSAID. Although neutrophils expressed all ß-adrenergic receptors, only ß3-agonist induced this phenomenon. Liquid chromatography-tandem mass spectrometry traced ß-agonist-induced PGE2 synthesis from exogenous deuterium-labeled AA. Spontaneous PGE2 production was highly efficient in Gr-1high neutrophils among BM cells from G-CSF-treated mice. In addition to these in vitro data, the in vivo depletion of Gr-1high neutrophils disrupted G-CSF-induced fever. Furthermore, sympathetic denervation eliminated both neutrophil priming for PGE2 production and fever during G-CSF treatment. Thus, sympathetic tone-primed BM neutrophils were identified as one of the major PGE2 producers. PGE2 upregulated osteopontin, specifically in preosteoblasts, to retain progenitors in the BM via EP4 receptor. Thus, the sympathetic nervous system regulated neutrophils as an indispensable PGE2 source to modulate BM microenvironment and body temperature. This study provided a novel mechanistic insight into the communication of the nervous system, BM niche components, and hematopoietic cells.

A Novel α9 Integrin Ligand, XCL1/Lymphotactin, Is Involved in the Development of Murine Models of Autoimmune Diseases.

The integrin α9ß1 is a key receptor involved in the development of autoimmune diseases. However, the detailed mechanism for the association of α9ß1 integrin with its ligands remains unclear. In this study, we introduce XCL1/lymphotactin, a member of the chemokine family, as a novel ligand for α9 integrin. Using α9 integrin-overexpressing NIH3T3 cells and endogenously α9 integrin-expressing human rhabdomyosarcoma cells, the interaction between XCL1 and α9 integrin was confirmed by pull-down assays. XCL1 enhanced α9 integrin-dependent cell migration of these cells, thus acting on α9 integrin as a chemoattractant. We also analyzed the in vivo function of XCL1 in the development of anti-type II collagen Ab-induced inflammatory arthritis (CAIA) in BALB/c mice and experimental autoimmune encephalomyelitis in C57BL/6 mice, because α9 integrin is involved in these autoimmune disease models. In CAIA, recombinant XCL1 aggravated the disease and this exacerbation was inhibited by an anti-α9 integrin Ab. An XCL1-neutralizing Ab produced in this study also ameliorated CAIA. Furthermore, the XCL1-neutralizing Ab abrogated the disease progression in experimental autoimmune encephalomyelitis. Therefore, to our knowledge this study provides the first in vitro and in vivo evidence that the interaction between XCL1 and α9 integrin has an important role for autoimmune diseases.

Implication of Soluble Forms of Cell Adhesion Molecules in Infectious Disease and Tumor: Insights from Transgenic Animal Models.

Cell adhesion molecules (CAMs) are surface ligands, usually glycoproteins, which mediate cell-to-cell adhesion. They play a critical role in maintaining tissue integrity and mediating migration of cells, and some of them also act as viral receptors. It has been known that soluble forms of the viral receptors bind to the surface glycoproteins of the viruses and neutralize them, resulting in inhibition of the viral entry into cells. Nectin-1 is one of important CAMs belonging to immunoglobulin superfamily and herpesvirus entry mediator (HVEM) is a member of the tumor necrosis factor (TNF) receptor family. Both CAMs also act as alphaherpesvirus receptor. Transgenic mice expressing the soluble form of nectin-1 or HVEM showed almost complete resistance against the alphaherpesviruses. As another CAM, sialic acid-binding immunoglobulin-like lectins (Siglecs) that recognize sialic acids are also known as an immunoglobulin superfamily member. Siglecs play an important role in the regulation of immune cell functions in infectious diseases, inflammation, neurodegeneration, autoimmune diseases and cancer. Siglec-9 is one of Siglecs and capsular polysaccharide (CPS) of group B Streptococcus (GBS) binds to Siglec-9 on neutrophils, leading to suppress host immune response and provide a survival advantage to the pathogen. In addition, Siglec-9 also binds to tumor-produced mucins such as MUC1 to lead negative immunomodulation. Transgenic mice expressing the soluble form of Siglec-9 showed significant resistance against GBS infection and remarkable suppression of MUC1 expressing tumor proliferation. This review describes recent developments in the understanding of the potency of soluble forms of CAMs in the transgenic mice and discusses potential therapeutic interventions that may alter the outcomes of certain diseases.

Comparison of the antiviral potential among soluble forms of herpes simplex virus type-2 glycoprotein D receptors, herpes virus entry mediator A, nectin-1 and nectin-2, in transgenic mice.

Herpesvirus entry mediator A (HVEM), nectin-1 and nectin-2 are cellular receptors of glycoprotein D (gD) of herpes simplex virus type-2 (HSV-2). It has been shown that soluble forms of HSV gD receptors have the antiviral potential in cultured cells and transgenic mice. Here, to compare antiviral potential of soluble forms of HVEM, nectin-1 and nectin-2 against HSV-2 infections in vivo, transgenic mice expressing fusion proteins consisting of the entire ectodomain of HVEM, nectin-1 or nectin-2 and the Fc portion of human IgG (HVEMIg, nectin-1Ig and nectin-2Ig, respectively) were intraperitoneally infected with HSV-2. In the infection with 3 MLD50 (50 % mouse lethal dose), effective resistance was not observed in transgenic mice expressing nectin-2Ig. In a transgenic mouse line with high expression of nectin-1Ig, significant protection from the infection with 30 and 300 MLD50 was observed (survival rate of 100 and 71 %, respectively). On the other hand, transgenic mice expressing HVEMIg showed a complete resistance to the lethal infection even with 300 MLD50 (survival rate of 100 %). These results demonstrated that HVEMIg could exert effective antiviral activities against HSV-2 infections in vivo as compared with other soluble forms of HSV gD receptors.

Osteopontin attenuates acute gastrointestinal graft-versus-host disease by preventing apoptosis of intestinal epithelial cells.

BACKGROUND AND AIMS: Acute graft-versus-host disease (GVHD) is a major complication after allogeneic hematopoietic stem cell transplantation, which often targets gastrointestinal (GI) tract. Osteopontin (OPN) plays an important physiological role in the efficient development of Th1 immune responses and cell survival by inhibiting apoptosis. The role of OPN in acute GI-GVHD is poorly understood. In the present study, we investigated the role of OPN in donor T cells in the pathogenicity of acute GI-GVHD. METHODS: OPN knockout (KO) mice and C57BL/6 (B6) mice were used as donors, and (C57BL/6 × DBA/2) F1 (BDF1) mice were used as allograft recipients. Mice with acute GI-GVHD were divided into three groups: the control group (BDF1→BDF1), B6 group (B6→BDF1), and OPN-KO group (OPN-KO→BDF1). Bone marrow cells and spleen cells from donors were transplanted to lethally irradiated recipients. Clinical GVHD scores were assessed daily. Recipients were euthanized on day 7 after transplantation, and colons and small intestines were collected for various analyses. RESULTS: The clinical GVHD score in the OPN-KO group was significantly increased compared with the B6 and control groups. We observed a difference in the severity of colonic GVHD between the OPN-KO group and B6 group, but not small intestinal-GVHD between these groups. Interferon-γ, Tumor necrosis factor-α, Interleukin-17A, and Interleukin-18 gene expression in the OPN-KO group was differed between the colon and small intestine. Flow cytometric analysis revealed that the fluorescence intensity of splenic and colonic CD8 T cells expressing Fas Ligand was increased in the OPN-KO group compared with the B6 group. CONCLUSION: We demonstrated that the importance of OPN in T cells in the onset of acute GI-GVHD involves regulating apoptosis of the intestinal cell via the Fas-Fas Ligand pathway.

A CD153+CD4+ T follicular cell population with cell-senescence features plays a crucial role in lupus pathogenesis via osteopontin production.

Immune aging results in diminished adaptive immunity and increased risk for autoimmunity. We previously reported a unique PD-1(+) CD44(high)CD4(+) T cell population that increases with age in normal mice. In this study, we indicate that the age-dependent PD-1(+) CD44(high)CD4(+) T cells develop as unique T follicular (TF) cells in a B cell-dependent manner and consist of two subpopulations, as follows: CD153(+) cells preferentially secreting abundant osteopontin on TCR stimulation and CD153(-) cells that are apparently TCR anergic. These unique TF cells with essentially similar features increase much earlier and are accumulated in the spontaneous germinal centers (GCs) in lupus-prone female BWF1 (f-BWF1) mice. These TF cells showed characteristic cell-senescence features and developed in association with extensive CD4(+) T cell proliferation in vivo, suggesting replicative senescence. Although the CD153(+) TF cells were defective in proliferation capacity, they were quite stable and specifically responded to self GC-B cells to secret abundant osteopontin, which inhibited B cell receptor-induced GC-B cell apoptosis in f-BWF1 mice. Transfer of CD153(+) PD-1(+) CD4(+) T cells promoted the growth of spontaneous GCs, whereas administration of anti-osteopontin Ab suppressed GC enlargement and anti-nuclear Ab production and ameliorated clinical lupus nephritis of f-BWF1 mice. Current results suggest that senescent CD153(+) TF cells generated as a consequence of extensive endogenous CD4(+) T cell proliferation play an essential, if not sufficient, role in lupus pathogenesis in lupus-prone genetic background and may also contribute to an increased autoimmunity risk with age.

Syndecan 4 Mediates Nrf2-dependent Expansion of Bronchiolar Progenitors That Protect Against Lung Inflammation.

The use of lung progenitors for regenerative medicine appears promising, but their biology is not fully understood. Here, we found anti-inflammatory attributes in bronchiolar progenitors that were sorted as a multipotent subset of mouse club cells and found to express secretory leukocyte protease inhibitor (SLPI). Notably, the impaired expression of SLPI in mice increased the number of bronchiolar progenitors and decreased the lung inflammation. We determined a transcriptional profile for the bronchiolar progenitors of Slpi-deficient mice and identified syndecan 4, whose expression was markedly elevated as compared to that of wild-type mice. Systemic administration of recombinant syndecan 4 protein caused a substantial increase in the number of bronchiolar progenitors with concomitant attenuation of both airway and alveolar inflammation. The syndecan 4 administration also resulted in activation of the Keap1-Nrf2 antioxidant pathway in lung cells, which is critically involved in the therapeutic responses to the syndecan 4 treatment. Moreover, in 3D culture, the presence of syndecan 4 induced differentiated club cells to undergo Nrf2-dependent transition into bronchiolar progenitors. Our observations reveal that differentiative switches between bronchiolar progenitors and club cells are under the Nrf2-mediated control of SLPI and syndecan 4, suggesting the possibility of new therapeutic approaches in inflammatory lung diseases.

Integrin α9 on lymphatic endothelial cells regulates lymphocyte egress.

Sphingosine 1-phosphate (S1P) plays a role in lymphocyte egress from lymphoid organs. However, it remains unclear how S1P production and secretion are regulated. We show that under inflammatory conditions, α9 integrin, which is closely associated with activated ß1 integrin, and its ligand, tenascin-C, colocalize on medullary and cortical sinuses of draining lymph nodes (dLNs), which is a gate for lymphocyte exit, and that inhibition of lymphocyte egress is evident by blockade of α9 integrin-mediated signaling at dLNs. Based on in vitro analysis using lymphatic endothelial cells obtained from mice embryos, we suggested the possibility that stimulation of lymphatic endothelial cells by tenascin-C enhances S1P secretion in an α9 integrin-dependent manner without affecting S1P synthesis and/or degradation. Blockade of α9 integrin-mediated signaling reduced lymphocyte egress from dLNs in several models, including experimental autoimmune encephalomyelitis, where it improved clinical scores and pathology. Therefore, manipulating α9 integrin function may offer a therapeutic strategy for treating various inflammatory disorders.

Osteopontin-integrin interaction as a novel molecular target for antibody-mediated immunotherapy in adult T-cell leukemia.

BACKGROUND: Adult T-cell leukemia (ATL) is a CD4(+) T-cell neoplasm with a poor prognosis. A previous study has shown that there is a strong correlation between the secreted matricellular protein osteopontin (OPN) level and disease severity in ATL patients. Here, we investigated the role of OPN in ATL pathogenesis and the possible application of anti-OPN monoclonal antibody (mAb) for ATL immunotherapy in NOD/Shi-scid,IL-2Rg (null) (NOG) mice. RESULTS: Subcutaneous inoculation of ATL cell lines into NOG mice increased the plasma level of OPN, which significantly correlated with metastasis of the inoculated cells and survival time. Administration of an SVVYGLR motif-recognizing anti-OPN mAb resulted in inhibition not only of tumor growth but also of tumor invasion and metastasis. The number of fibroblast activating protein-positive fibroblasts was also reduced by this mAb. We then co-inoculated mouse embryonic fibroblasts (MEFs) isolated from wild-type (WT) or OPN knockout mice together with ATL-derived TL-OmI cells into the NOG mice. The mice co-inoculated with WT MEFs displayed a significant decrease in survival relative to those injected with TL-OmI cells alone and the absence of OPN in MEFs markedly improved the survival rate of TL-OmI-inoculated mice. In addition, tumor volume and metastasis were also reduced in the absence of OPN. CONCLUSION: We showed that the xenograft NOG mice model can be a useful system for assessment of the physiological role of OPN in ATL pathogenesis. Using this xenograft model, we found that fibroblast-derived OPN was involved in tumor growth and metastasis, and that this tumor growth and metastasis was significantly suppressed by administration of the anti-OPN mAbs. Our findings will lead to a novel mAb-mediated immunotherapeutic strategy targeting against the interaction of OPN with integrins on the tumor of ATL patients.

Regular Exercise Enhances the Immune Response Against Microbial Antigens Through Up-Regulation of Toll-like Receptor Signaling Pathways.

BACKGROUND/AIMS: Regular physical exercise can enhance resistance to many microbial infections. However, little is known about the mechanism underlying the changes in the immune system induced by regular exercise. METHODS: We recruited members of a university badminton club as the regular exercise (RE) group and healthy sedentary students as the sedentary control (SC) group. We investigated the distribution of peripheral blood mononuclear cell (PBMC) subsets and functions in the two groups. RESULTS: There were no significant differences in plasma cytokine levels between the RE and SC groups in the true resting state. However, enhanced levels of IFN-γ, TNF-α, IL-6, IFN-α and IL-12 were secreted by PBMCs in the RE group following microbial antigen stimulation, when compared to the SC group. In contrast, the levels of TNF-α and IL-6 secreted by PBMC in the RE group were suppressed compared with those in SC group following non-microbial antigen stimulation (concanavalin A or α-galactosylceramide). Furthermore, PBMC expression of TLR2, TLR7 and MyD88 was significantly increased in the RE group in response to microbial antigen stimulation. CONCLUSION: Regular exercise enhances immune cell activation in response to pathogenic stimulation leading to enhanced cytokine production mediated via the TLR signaling pathways.

Decreased Osteopontin Expression as a Reliable Prognostic Indicator of Improvement in Pulmonary Tuberculosis: Impact of the Level of Interferon-gamma-Inducible Protein 10.

BACKGROUND/AIMS: Osteopontin (OPN) expression is increased during the course of various chronic inflammatory diseases, including tuberculosis (TB). However, its prognostic value in TB management remains unclear. This study aimed to determine whether OPN could associate with other cytokines serving as a reliable biomarker for evaluating the effectiveness of early anti-TB treatments. METHODS: Smear-positive pulmonary TB patients (n = 20) were recruited, and the plasma levels of OPN, IP-10, TNF-α, and IL-12 were measured by ELISA before initiation of anti-TB therapy and after sputum smear conversion. The C-reactive protein (CRP) levels and erythrocyte sedimentation rate (ESR) were also tracked during anti-TB treatment. RESULTS: OPN expression was significantly elevated in patients with smear-positive pulmonary TB, and was closely related with disease severity. Monitoring during the treatment course revealed that its expression, along with that of IFN-x03B3;-induced protein 10 (IP-10), decreased significantly only after sputum smear conversion. Moreover, OPN levels positively correlated with CRP levels before and after anti-TB treatment. Furthermore, OPN markedly promoted IP-10 expression in peripheral blood mononuclear cells. CONCLUSION: Association between OPN and IP-10 may serve as a reliable prognostic indicator for improvement during the early treatment of pulmonary TB, and may help clinicians in tailoring an effective TB treatment regimen.

Functions and development of red pulp macrophages.

Macrophages are extremely heterogeneous mononuclear phagocytes widely distributed throughout the body. They play unique roles in each organ where they reside. Among macrophage subsets, red pulp macrophages (RPMs) that localize in the splenic red pulp, are critical for maintenance of blood homeostasis by actively phagocytosing injured and senescent erythrocytes and blood-borne particulates. Recent evidence indicates that RPMs are mainly generated during embryogenesis and are maintained during adult life. Furthermore, the cell-intrinsic and -extrinsic factors (namely, Spi-C, IRF8/4, heme oxygenase-1, and M-CSF) that regulate the development and survival of RPMs have been identified. Although the immunological properties of RPMs have yet to be elucidated fully, pioneering studies have demonstrated that these cells are capable of inducing differentiation of regulatory T cells via expression of transforming growth factor-ß and secrete a large amount of type I interferons during parasitic infections. In this review, we describe recent advances in understanding of the functions and development of RPMs.

Osteopontin has a crucial role in osteoclast-like multinucleated giant cell formation.

The osteoclast (OC) is a major player in the pathogenic bone destruction of inflammatory bone diseases such as rheumatoid arthritis and Langerhans cell histiocytosis. Recently, it was shown that immature dendritic cells (iDC) fuse faster and more efficiently than monocytes in forming OC-like multinucleated giant cells (MGCs), and that osteopontin (OPN) is involved in the pathogenesis of inflammatory bone diseases. In this study, we hypothesized that OPN is a key factor for generation of OC-like MGCs from iDCs. We used an in vitro culture system to differentiate iDCs, derived from monocytes obtained from the blood of healthy donors, into OC-like MGCs. We evaluated OPN levels and expression of OPN receptors during the course of differentiation. OPN has an arginine-glycine-aspartic acid (RGD) motif, and protease cleavage reveals a SVVYGLR motif. The concentrations of both full-length and cleaved forms of OPN increased during the course of OC-like MGC formation. Expression of OPN RGD- and SVVYGLR-recognizing receptors also increased at later stages. We analyzed whether blocking OPN binding to its receptors affected OC-like MGC formation. Monocytes treated with OPN siRNA were able to differentiate into iDCs effectively; however, differentiation of these iDCs into OC-like MGCs was significantly reduced. The formation of OC-like MGCs was not significantly reduced by RGD synthetic peptide. By contrast, SVVYGLR synthetic peptide caused a significant reduction. These data suggest that the cleaved form of OPN plays a critical role in driving iDC differentiation into OC-like MGCs in the early phase of differentiation, in an autocrine and/or paracrine fashion.

α9ß1 integrin acts as a critical intrinsic regulator of human rheumatoid arthritis.

OBJECTIVE: The role of the joint tissue microenvironment in the pathogenesis of human RA has recently attracted much attention. The present study investigated the roles of α9ß1 integrin and its ligands in synovial specimens of human RA patients in generating the unique human arthritic tissue microenvironment. METHODS: Synovial fibroblasts and macrophages were isolated from the synovial tissue of patients with RA or OA. The expression of α9ß1 integrin was analysed using FACS with multicolour staining. The production of MMPs and proinflammatory cytokines was analysed in cultures of synovial fibroblasts and macrophages with α9ß1 integrin ligands. RESULTS: Synovial fibroblasts and macrophages derived from arthritic joints spontaneously secreted tenascin-C and osteopontin. Synovial fibroblasts and macrophages obtained from patients with RA expressed α9ß1 integrins, a common receptor for osteopontin and tenascin-C. In the synovial fibroblasts of RA, the amount of tenascin-C protein produced was much greater than that of osteopontin in synovial fibroblasts of RA. Importantly, autocrine and paracrine interactions of α9ß1 integrin and tenascin-C induced the expression of MMPs and IL-6 in synovial fibroblasts, as well as TNF-α and IL-1ß in synovial macrophages. CONCLUSION: These findings indicate that autocrine and paracrine interaction of α9ß1 integrin and tenascin-C in the joint tissue microenvironment contributes to the pathogenesis of RA. Therefore α9ß1 integrin may become a potential therapeutic target for RA.

Extracellular matrix protein tenascin-C is required in the bone marrow microenvironment primed for hematopoietic regeneration.

The BM microenvironment is required for the maintenance, proliferation, and mobilization of hematopoietic stem and progenitor cells (HSPCs), both during steady-state conditions and hematopoietic recovery after myeloablation. The ECM meshwork has long been recognized as a major anatomical component of the BM microenvironment; however, the molecular signatures and functions of the ECM to support HSPCs are poorly understood. Of the many ECM proteins, the expression of tenascin-C (TN-C) was found to be dramatically up-regulated during hematopoietic recovery after myeloablation. The TN-C gene was predominantly expressed in stromal cells and endothelial cells, known as BM niche cells, supporting the function of HSPCs. Mice lacking TN-C (TN-C(-/-)) mice showed normal steady-state hematopoiesis; however, they failed to reconstitute hematopoiesis after BM ablation and showed high lethality. The capacity to support transplanted wild-type hematopoietic cells to regenerate hematopoiesis was reduced in TN-C(-/-) recipient mice. In vitro culture on a TN-C substratum promoted the proliferation of HSPCs in an integrin α9-dependent manner and up-regulated the expression of the cyclins (cyclinD1 and cyclinE1) and down-regulated the expression of the cyclin-dependent kinase inhibitors (p57(Kip2), p21(Cip1), p16(Ink4a)). These results identify TN-C as a critical component of the BM microenvironment that is required for hematopoietic regeneration.

Syndecan-4 prevents cardiac rupture and dysfunction after myocardial infarction.

RATIONALE: Syndecan-4 (Syn4), a cell-surface heparan sulfate proteoglycan, has been detected in the infarct region after myocardial infarction (MI), but its functional significance has not been elucidated. OBJECTIVE: We examined whether and how Syn4 regulates the cardiac healing process after MI. METHODS AND RESULTS: Although the heart in Syn4-deficient (Syn4(-/-)) mice was morphologically and functionally normal, Syn4(-/-) mice exhibited impaired heart function and increased mortality rate as a result of cardiac ruptures after MI. Cardiac ruptures in Syn4(-/-) mice were associated with reduced inflammatory reaction and impaired granulation tissue formation during the early phase of MI, as evidenced by reduced numbers of leukocytes, fibroblasts, myofibroblasts, macrophages, and capillary vessels, along with reduced extracellular matrix protein deposition in the infarct region after MI. Transforming growth factor-ß1-dependent cell signaling was preserved, whereas cell migration, fibronectin-induced cell signaling, and differentiation into myofibroblasts were defective in Syn4(-/-) cardiac fibroblasts. We also found that Syn4 was involved in basic fibroblast growth factor-dependent endothelial cell signaling, cell proliferation, and tube formation. Finally, overexpression of the shed form of Syn4 before MI creation led to an increase in mortality due to cardiac rupture via its action as a dominant-negative inhibitor of endogenous Syn4 signaling, which suggested a protective role of Syn4 signaling in MI. CONCLUSIONS: These results suggest that Syn4 plays an important role in the inflammatory response and granulation tissue formation, thereby preventing cardiac rupture and dysfunction after MI.

Interleukin-17A deficiency accelerates unstable atherosclerotic plaque formation in apolipoprotein E-deficient mice.

OBJECTIVE: Interleukin(IL)-17A, an inflammatory cytokine, has been implicated in atherosclerosis, in which inflammatory cells within atherosclerotic plaques express IL-17A. However, its role in the development of atheroscelrosis remains to be controversial. METHODS AND RESULTS: To directly examine the role of IL-17A in atherosclerosis, we generated apolipoprotein E (ApoE)/IL-17A double-deficient (ApoE(-/-)IL-17A(-/-)) mice. Mice were fed with high-fat diet (HFD) for either 8 or 16 weeks, both starting at ages of 6 to 8 weeks. We found that splenic CD4(+) T-cells produced high amounts of IL-17A in ApoE(-/-) mice after HFD feeding for 8 weeks. Atherosclerosis was significantly accelerated in HFD-fed ApoE(-/-)IL-17A(-/-) mice compared with ApoE(-/-) mice. Splenic CD4(+) T-cells of ApoE(-/-)IL-17A(-/-) mice after HFD feeding for 8 weeks, but not for 16 weeks, exhibited increased interferon gamma and decreased IL-5 production. Importantly, formation of vulnerable plaque as evidenced by reduced numbers of vascular smooth muscle cells and reduced type I collagen deposition in the plaque was detected in ApoE(-/-)IL-17A(-/-) mice after HFD feeding for 8 weeks. CONCLUSIONS: These results suggest that IL-17A regulates the early phase of atherosclerosis development after HFD feeding and plaque stability, at least partly if not all by modulating interferon gamma and IL-5 production from CD4(+) T-cells.

Osteopontin modulates the generation of memory CD8+ T cells during influenza virus infection.

The adaptive immune system generates memory cells, which induce a rapid and robust immune response following secondary Ag encounter. Memory CD8(+) T cells are a critical component of protective immunity against infections and cancers. Therefore, understanding the mechanism whereby memory CD8(+) T cells are generated and maintained is important for inducing effective memory CD8(+) T cell response. Recent studies have demonstrated that the inflammatory cytokine IL-12 favors the generation of terminal effector CD8(+) T cells rather than memory precursor effector CD8(+) T cells by regulating the expression of the transcription factor T-bet. In this study, we report that the inflammatory cytokine osteopontin (Opn) modulates memory CD8(+) T cell generation during influenza virus infection. Although Opn wild-type and Opn knockout (KO) mice had similar numbers of virus-specific effector CD8(+) T cells, virus-specific effector CD8(+) T cells generated in Opn KO mice showed low levels of T-bet expression and an increased memory precursor cell population compared with cells generated in Opn wild-type mice. This resulted in the persistently increased number of memory CD8(+) T cells in Opn KO mice. Studies with bone marrow-derived dendritic cells demonstrated that Opn deficiency in bone marrow-derived dendritic cells results in low levels of IL-12 production in response to the stimulation with influenza virus. Thus, we hypothesize that Opn modulates the generation of memory precursor effector CD8(+) T cells by regulating cytokine milieu during the acute phase of virus infection. This finding may provide new insight into the role of Opn in adaptive immune response.