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Biomedical subjects

Joost J Oppenheim

Publications and source records attributed to Joost J Oppenheim.

At least 19 recordsLinked to original sources
PubMed2006

High mobility group box-1 protein induces the migration and activation of human dendritic cells and acts as an alarmin.

High mobility group box-1 (HMGB1) protein is a nonhistone, DNA-binding protein that plays a critical role in regulating gene transcription. Recently, HMGB1 has also been shown to act as a late mediator of endotoxic shock and to exert a variety of proinflammatory, extracellular activities. Here, we report that HMGB1 simultaneously acts as a chemoattractant and activator of dendritic cells (DCs). HMGB1 induced the migration of monocyte-derived, immature DCs (Mo-iDCs) but not mature DCs. The chemotactic effect of HMGB1 on iDCs was pertussis toxin-inhibitable and also inhibited by antibody against the receptor of advanced glycation end products (RAGE), suggesting that HMGB1 chemoattraction of iDCs is mediated by RAGE in a Gi protein-dependent manner. In addition, HMGB1 treatment of Mo-iDCs up-regulated DC surface markers (CD80, CD83, CD86, and HLA-A,B,C), enhanced DC production of cytokines (IL-6, CXCL8, IL-12p70, and TNF-alpha), switched DC chemokine responsiveness from CCL5-sensitive to CCL21-sensitive, and acquired the capacity to stimulate allogeneic T cell proliferation. Based on its dual DC-attracting and -activating activities as well as its reported capacity to promote an antigen-specific immune response, we consider HMGB1 to have the properties of an immune alarmin.

Cell Differentiation↗
PubMed2006

T cell lines from systemic sclerosis patients and healthy controls recognize multiple epitopes on DNA topoisomerase I.

Anti-DNA topoisomerase I (topo-I) antibodies are exclusively detected in patients with systemic sclerosis (SSc). Participation of this topo-I-specific autoimmune response in the pathogenesis of SSc has been actively investigated, but remains unproven. Here we characterized the peripheral T cell proliferative response to recombinant topo-I (rtopo-I) in 16 SSc patients with circulating anti-topo-I antibody. A low level (cpm < 2000) T cell proliferation (SI > 3) was detected in 6 (38%) of 16 patients. This low level response was similar to those previously observed in healthy controls. We established 56 topo-I-specific T cell lines recognizing 13 distinct T cell epitopes on topo-I from 4 SSc patients and 2 healthy controls. These T cell lines were established from in vitro activated PBMC (CD25(+)) by rtopo-I antigen. However they did not have the phenotype of regulatory T cells. Notably, 40 (71%) of the 56 T cell lines recognizing a common epitope were established from one patient. DNA sequencing of the T cell receptor cDNA produced an identical sequence indicating these T cells were from a single topo-I-specific T cell precursor. These results suggest that topo-I-specific T cells can become clonally expanded in some patients and may contribute to the pathogenesis of this disease.

Amino Acid Sequence↗
PubMed2006

Adenosine A2a receptors induce heterologous desensitization of chemokine receptors.

Adenosine, released by cells in an injurious or hypoxic environment, possesses potent anti-inflammatory effects by inhibiting the production of proinflammatory cytokines and superoxide anions (O2-). We hypothesized that adenosine compounds also induced heterologous desensitization of chemokine receptors, which played a critical role in leukocyte trafficking. Our studies using adenosine receptor subtype-specific agonists revealed that pretreatment with adenosine compounds suppressed RANTES-induced chemotaxis and Ca2+ flux through activation of A2a adenosine receptor. Adenosine compounds also desensitized IL-8- and MCP-1-induced chemotaxis, but not that induced by fMLP. Activation of protein kinase A (PKA), a component of the signaling pathway induced by the A2a receptor, was sufficient to desensitize RANTES-induced chemotaxis. Inhibition of PKA reversed the desensitization effects of adenosine compounds, suggesting that PKA was necessary for A2a receptor-mediated heterologous desensitization. In a mouse model, prior activation of A2a receptors blocked RANTES-induced recruitment of leukocytes in an air pouch. Moreover, the A2a receptor-induced cross-desensitization also reduced the susceptibility of monocytes to infection by an R5 strain of HIV-1. Our results suggest that activation of A2a adenosine receptors suppresses chemokine receptor function, and such receptor cross-talk was based on the simple mechanism of PKA-mediated heterologous desensitization, thus contributing to the antiinflammatory activity of adenosine.

Adenosine↗
PubMed2006

Pertussis toxin as an adjuvant suppresses the number and function of CD4+CD25+ T regulatory cells.

We observed a remarkable reduction in the frequency and immunosuppressive activity of splenic CD4+CD25+ T cells in C57BL/6 mice with MOG33-55-induced experimental autoimmune encephalomyelitis (EAE). Our study revealed that pertussis toxin (PTx), one component of the immunogen used to induce murine EAE, was responsible for down-regulating splenic CD4+CD25+ cells. Treatment of normal BALB/c mice with PTx in vivo reduced the frequency, suppressive activity and FoxP3 expression by splenic CD4+CD25+ T cells. However, PTx treatment did not alter the expression of characteristic phenotypic markers (CD45RB, CD103, GITR and CTLA-4) and did not increase the expression of CD44 and CD69 by the residual splenic and lymph node CD4+CD25+ T cells. This property of PTx was attributable to its ADP-ribosyltransferase activity. PTx did not inhibit suppressive activity of purified CD4+CD25+ T regulatory (Treg) cells in vitro, but did so in vivo, presumably due to an indirect effect. Although the exact molecular target of PTx that reduces Treg activity remains to be defined, our data suggests that alteration of both distribution and function of splenic immunocytes should play a role. This study concludes that an underlying cause for the immunological adjuvanticity of PTx is down-regulation of Treg cell number and function.

Adjuvants, Immunologic↗
PubMed2006

Glucocorticoid amplifies IL-2-dependent expansion of functional FoxP3(+)CD4(+)CD25(+) T regulatory cells in vivo and enhances their capacity to suppress EAE.

IL-2 is crucial for the production of CD4(+)CD25(+) T regulatory (Treg) cells while important for the generation of effective T cell-mediated immunity. How to exploit the capacity of IL-2 to expand Treg cells, while restraining activation of T effector (Teff) cells, is an important and unanswered therapeutic question. Dexamethasone (Dex), a synthetic glucocorticoid steroid, has been reported to suppress IL-2-mediated activation of Teff cells and increase the proportion of Treg cells. Thus, we hypothesized that glucocorticoids may be useful as costimulants to amplify IL-2-mediated selective expansion of Treg cells. We show in this study that short-term simultaneous administration of Dex and IL-2 markedly expanded functional suppressive Foxp3(+)CD4(+)CD25(+) T cells in murine peripheral lymphoid tissues. In a myelin oligodendrocyte glycoprotein-induced experimental autoimmune encephalomyelitis (EAE) mouse model, we observed that splenic CD4(+)CD25(+) T cells failed to suppress the proliferation of CD4(+)CD25(-) T cells. Pretreatment with Dex/IL-2 remarkably increased the proportion of CD4(+)FoxP3(+) cells and partially restored the function of splenic CD4(+)CD25(+) T cells, and inhibited the development of EAE. Therefore, the combination of glucocorticoid and IL-2, two currently used therapeutics, may provide a novel approach for the treatment of autoimmune diseases, transplant rejection and graft-vs.-host disease.

Animals↗
PubMed2006

Induction of dendritic cell maturation by pertussis toxin and its B subunit differentially initiate Toll-like receptor 4-dependent signal transduction pathways.

OBJECTIVE: Pertussis toxin (PT) has the capacity to activate dendritic cells (DCs) for the augmentation of cell-mediated immune responses. To investigate the mechanism(s) by which PT activates DCs, we investigated the effects of PT and its B-oligomer (PTB) on the maturation of human and mouse DCs and determined whether PT could act as a pathogen-associated molecular pattern to activate one of the Toll-like receptors (TLRs). METHODS: The effects of PT and PTB on the maturation of human and mouse DCs were analyzed in terms of surface marker expression, cytokine production, antigen-presenting capacity, and intracellular signaling. The participation of TLR4 in PT-induced signaling was determined by comparing the effect of PT on DCs derived from TLR4-deficient and wild-type mice, as well as by measuring PT-induced NF-kappaB activation in HEK293 cells transiently transfected to express various TLRs. RESULTS: Although both promoted phenotypic and functional maturation DCs, however, unlike PT that induced DC production of interleukin (IL)-6, tumor necrosis factor-alpha, IL-12, and interferon-inducible protein, PTB was capable of stimulating the production of interferon-inducible protein. Bone marrow-derived DCs from C3H/HeJ mice with defective TLR-4 alleles were unresponsive to PT and PTB, whereas DCs from C3H/HeN mice responded. In addition, PT induced NF-kappaB activation and IL-8 production in HEK293 cells transfected with a combination of TLR4 and MD2 but not in nontransfected or TLR2-transfected HEK293 cells. Comparison of the patterns of cytokine induction and intracellular signaling events in DCs treated by PT and PTB revealed that although PT, like lipopolysaccharide, triggered both MyD88-dependent and -independent pathways, PTB preferentially triggered MyD88-independent pathways. Interestingly, mouse splenocyte proliferation in response to PT and PTB was only partially dependent on TLR4. CONCLUSION: The data identify PT as another pathogen-associated molecular pattern that induces DC maturation in a TLR4-dependent manner. Unlike PT, which triggers both MyD88-dependent and -independent pathways, PTB only triggers the MyD88-independent pathway in DCs.

Animals↗
PubMed2006

IL-1 can act as number one.

Both interleukin-1 receptor (IL-1R) and toll-like receptor 2 (TLR2) signal via the adapter molecule MyD88. However, in response to a cutaneous infection challenge, the downstream signaling events diverge and IL-1R, but not TLR2, proves to be essential for host defense.

Adaptor Proteins, Signal Transducing↗
PubMed2005

Crosstalk between chemokines and neuronal receptors bridges immune and nervous systems.

Chemokine receptors, a family of Gi protein-coupled receptors responsible for cell migration, are widely expressed by cells of immune and nervous systems. Activation of receptors on the surface of leukocytes, such as opioid, vasoactive intestinal peptide, or adenosine receptors, often has inhibitory effects on chemokine receptors by a mechanism termed heterologous desensitization, resulting in suppression of immune responses. Conversely, activation of chemokine receptors also induces heterologous desensitization of mu-opioid receptors (MOR), a class of key analgesic receptors on neurons. Furthermore, prior exposure of neuronal cells to chemokine treatment enhances the sensitivity of transient receptor potential vanilloid 1 (TRPV1), a heat- and ligand-gated calcium channel, which is critical for sensing of pain. Consequently, during inflammation, activation of chemokine receptors on neurons contributes to hyperalgesia by inhibiting MOR and concomitantly sensitizing TRPV1 via Gi protein-mediated signaling pathways. These observations suggest that the crosstalk between chemokine receptors and neuropeptide membrane receptors serves as a bridge between the immune and nervous systems.

Animals↗
PubMed2005

Human tumor antigen MUC1 is chemotactic for immature dendritic cells and elicits maturation but does not promote Th1 type immunity.

The immunostimulatory outcome of the interactions of many pathogens with dendritic cells (DCs) has been well characterized. There are many fewer examples of similar interactions between DCs and self-molecules, especially the abnormal self-proteins such as many tumor Ags, and their effects on DC function and the immune response. We show that human epithelial cell Ag MUC1 mucin is recognized in its aberrantly glycosylated form on tumor cells by immature human myeloid DCs as both a chemoattractant (through its polypeptide core) and a maturation and activation signal (through its carbohydrate moieties). On encounter with MUC1, similar to the encounter with LPS, immature DCs increase cell surface expression of CD80, CD86, CD40, and CD83 molecules and the production of IL-6 and TNF-alpha cytokines but fail to make IL-12. When these DCs are cocultured with allogeneic CD4+ T cells, they induce production of IL-13 and IL-5 and lower levels of IL-2, thus failing to induce a type 1 response. Our data suggest that, in vivo in cancer patients, MUC1 attracts immature DCs to the tumor through chemotaxis and subverts their function by negatively affecting their ability to stimulate type 1 helper T cell responses important for tumor rejection.

Amino Acid Sequence↗
PubMed2005

Negative regulation of CXCR4-mediated chemotaxis by the lipid phosphatase activity of tumor suppressor PTEN.

Phosphatase and tensin homolog deleted on chromosome 10 (PTEN), a multifunctional tumor suppressor, has been shown to play a regulatory role in cell migration. Dictyostelium discoideum cells lacking PTEN exhibited impaired migration toward chemoattractant gradients. In the present study, we investigated the involvement of PTEN in chemotaxis of mammalian cells by examining PTEN-null Jurkat T cells. We observed that, in contrast to observations made in D discoideum, PTEN-null Jurkat T cells exhibited potent chemotactic responses to the chemokine stromal cell-derived factor 1alpha (SDF-1alpha), indicating that PTEN was not requisite for CXC chemokine receptor 4 (CXCR4)-mediated chemotaxis of Jurkat cells. Conversely, reconstitution of PTEN in Jurkat cells by using a tetracycline (Tet-on)-inducible expression system down-regulated CXCR4-mediated chemotaxis. Furthermore, we established the lipid phosphatase activity of PTEN as essential for its inhibitory effect on chemotaxis. In addition, using PTEN-expressing T-cell lines and primary T cells, we demonstrated that down-regulation of PTEN expression with vector-based small interfering RNAs (siRNAs) enhanced CXCR4-mediated chemotaxis. Based on these results, we conclude that PTEN expression negatively regulates chemotaxis of lymphoid mammalian cells via its lipid phosphatase activity. Our findings may account for the reported increase in metastatic activity of PTEN-null tumor cells.

Animals↗
PubMed2005

Triptolide, a constituent of immunosuppressive Chinese herbal medicine, is a potent suppressor of dendritic-cell maturation and trafficking.

Triptolide (TPT) is a chemically defined, potent immunosuppressive compound isolated from an anti-inflammatory Chinese herbal medicine. TPT has been reported to inhibit autoimmunity, allograft rejection, and graft-versus-host disease (GVHD), and its efficacy was previously attributed to the suppression of T cells. Since dendritic cells (DCs) play a major role in the initiation of T-cell-mediated immunity, we studied the effects of TPT on the phenotype, function, and migration of human monocyte-derived DCs. TPT treatment, over a pharmacologic concentration range, inhibited the lipopolysaccharide (LPS)-induced phenotypic changes, characteristic of mature DCs and the production of interleukin-12p70 (IL-12p70). Consequently, the allostimulatory functions of DCs were impaired by TPT treatment. Furthermore, the calcium mobilization and chemotactic responses of LPS-stimulated DCs to secondary lymphoid tissue chemokine (SLC)/CC chemokine ligand 21 (CCL21) were significantly lower in TPT-treated than untreated DCs, in association with lower chemokine receptor 7 (CCR7) and higher CCR5 expression. Egress of Langerhans cells (LCs) from explanted mouse skin in response to macrophage inflammatory protein-3beta (MIP-3beta)/CCL19 was arrested by TPT. In vivo administration of TPT markedly inhibited hapten (fluorescein isothiocyanate [FITC])-stimulated migration of mouse skin LCs to the draining lymph nodes. These data provide new insight into the mechanism of action of TPT and indicate that the inhibition of maturation and trafficking of DCs by TPT contributes to its immunosuppressive effects.

Animals↗
PubMed2005

Mouse cathelin-related antimicrobial peptide chemoattracts leukocytes using formyl peptide receptor-like 1/mouse formyl peptide receptor-like 2 as the receptor and acts as an immune adjuvant.

Mammalian antimicrobial proteins, such as defensins and cathelicidin, have stimulating effects on host leukocytes. Cathelin-related antimicrobial peptide (CRAMP), the orthologue of human cathelicidin/LL-37, is the sole identified murine cathelicidin. CRAMP has been shown to have both antimicrobial and angiogenic activities. However, whether CRAMP, like human cathelicidin/LL-37, also exhibits a direct effect on the migration and function of leukocytes is not known. We have observed that CRAMP, like LL-37, was chemotactic for human monocytes, neutrophils, macrophages, and mouse peripheral blood leukocytes. CRAMP also induced calcium mobilization and the activation of MAPK in monocytes. CRAMP-induced calcium flux in monocytes was desensitized by MMK-1, an agonistic ligand specific for formyl peptide receptor-like-1 (FPRL1), and vice versa, suggesting the use of FPRL1 by CRAMP as a receptor. Furthermore, CRAMP induced the chemotaxis of human embryonic kidney 293 cells transfected with either FPRL1 or mouse formyl peptide receptor-2, the mouse homologue of FPRL1, but not by untransfected parental human embryonic kidney 293 cells, confirming the use of FPRL1/mouse formyl peptide receptor-2 by CRAMP. Injection of CRAMP into mouse air pouches resulted in the recruitment predominantly of neutrophils and monocytes, indicating that CRAMP acts as a chemotactic factor in vivo. Finally, simultaneous administration of OVA with CRAMP to mice promoted both humoral and cellular Ag-specific immune responses. Thus, CRAMP functions as both a chemoattractant for phagocytic leukocytes and an enhancer of adaptive immune response.

Adjuvants, Immunologic↗
PubMed2005

BALB/c mice have more CD4+CD25+ T regulatory cells and show greater susceptibility to suppression of their CD4+CD25- responder T cells than C57BL/6 mice.

Increasing evidence indicates that CD4(+)CD25(+) T regulatory (Treg) cells control a wide spectrum of immune responses. The initial identification of CD4(+)CD25(+) Treg cell as a "professional suppressor" was based on observations made in BALB/c mice. This mouse strain is well known to preferentially develop T helper cell type 2 responses, to be more susceptible to intracellular parasite infection, to have a higher tumor incidence, and to be more resistant to the induction of autoimmune diseases, as compared with C57BL/6 (B6) mice. We therefore decided to compare Treg cell function of B6 and BALB/c mice. We observed that the frequency of CD4(+)CD25(+) T cells in the thymus and peripheral lymphoid organs of BALB/c mice was higher than in B6 mice. CD4(+)CD25(+) Treg cells from both mouse strains shared similar phenotypic properties, including expression of characteristic immunological markers and hyporesponsiveness to T cell receptor cross-linking and in their capacity to suppress proliferation of BALB/c CD4(+)CD25(-) T responder (Tres) cells. However, CD4(+)CD25(-) Tres cells from B6 mice were notably less susceptible to suppression by CD4(+)CD25(+) Treg cells from either mouse strain. Our data suggest that the number and the level of suppression of CD4(+)CD25(+) Treg cells for CD4(+)CD25(-) Tres cells may be dictated by genetic background. Our data also suggest that differences in the CD4(+)CD25(+) Treg cell number and the susceptibility of CD4(+)CD25(-) Tres cells may, at least in part, account for the differences in immune response between B6 and BALB/c strains of mice.

Animals↗
PubMed2005

A proinflammatory chemokine, CCL3, sensitizes the heat- and capsaicin-gated ion channel TRPV1.

Pain, a critical component of host defense, is one hallmark of the inflammatory response. We therefore hypothesized that pain might be exacerbated by proinflammatory chemokines. To test this hypothesis, CCR1 was cotransfected into human embryonic kidney (HEK)293 cells together with transient receptor potential vanilloid 1 (TRPV1), a cation channel required for certain types of thermal hyperalgesia. In these cells, capsaicin and anandamide induced Ca(2+) influx mediated by TRPV1. When CCR1:TRPV1/HEK293 cells were pretreated with CCL3, the sensitivity of TRPV1, as indicated by the Ca(2+) influx, was increased approximately 3-fold. RT-PCR analysis showed that a spectrum of chemokine and cytokine receptors is expressed in rat dorsal root ganglia (DRG). Immunohistochemical staining of DRG showed that CCR1 is coexpressed with TRPV1 in >85% of small-diameter neurons. CCR1 on DRG neurons was functional, as demonstrated by CCL3-induced Ca(2+) ion influx and PKC activation. Pretreatment with CCL3 enhanced the response of DRG neurons to capsaicin or anandamide. This sensitization was inhibited by pertussis toxin, U73122, or chelerythrine chloride, inhibitors of Gi-protein, phospholipase C, and protein kinase C, respectively. Intraplantar injection of mice with CCL3 decreased their hot-plate response latency. That a proinflammatory chemokine, by interacting with its receptor on small-diameter neurons, sensitizes TRPV1 reveals a previously undescribed mechanism of receptor cross-sensitization that may contribute to hyperalgesia during inflammation.

Animals↗
PubMed2005

Protein kinase C zeta is required for epidermal growth factor-induced chemotaxis of human breast cancer cells.

Chemotaxis plays an important role in cancer cell metastasis. In this study, we showed that epidermal growth factor (EGF) was a more potent chemoattractant than chemokine SDF-1alpha/CXCL12 for human breast cancer cell MDA-MB-231. Different inhibitors were used to evaluate the involvement of 12 protein kinase C (PKC) isotypes in the chemotactic signaling pathway. Chelerythrine chloride, an inhibitor of all PKC isotypes, blocked chemotaxis, whereas inhibitors of classic and novel PKC, such as Gö6976, Gö6850, or calphostin C, only impaired EGF-induced chemotaxis to a minor extent by not greater-than32% inhibition. These data suggested that atypical PKC were involved. The ligand-induced actin polymerization and cell adhesion were also similarly dependent on atypical PKC. Immunofluorescent staining showed an EGF-induced, LY294002-sensitive translocation of PKCzeta from the cytosol to the plasma membrane, indicating that EGF was capable of activating PKCzeta, probably via phosphoinositide 3 kinases. A myristoylated PKCzeta pseudosubstrate blocked the chemotaxis with an IC(50) of 20 mumol/L. To expand our investigation, we further showed that in MCF-7 and T47D, two additional human breast cancer cell lines, EGF-activated PKCzeta and the PKCzeta pseudosubstrate, inhibited chemotaxis. Taken together, our data suggest that PKCzeta is an essential component of the EGF-stimulated chemotactic signaling pathway in human breast cancer cells.

Alkaloids↗
PubMed2005

Autoantigens signal through chemokine receptors: uveitis antigens induce CXCR3- and CXCR5-expressing lymphocytes and immature dendritic cells to migrate.

We tested the hypothesis that interaction between autoantigens and chemoattractant receptors may be an important step in the development of autoimmunity. The retinal autoantigens S-antigen (S-Ag) and interphotoreceptor retinoid binding protein (IRBP) can induce autoimmune uveitis in rodent models. We evaluated the chemotactic activity of S-Ag and IRBP and found that both induced migration of human and mouse immature dendritic cells (iDCs) and lymphocytes, but not neutrophils, monocytes, or mature DCs. Cross-desensitization studies and single-receptor transfected cells revealed that subfamily of alpha chemokine receptors CXCR5 and CXCR3 mediated the chemotactic effect of IRBP, while only CXCR3 was required for the chemotactic response to S-Ag. Examination of the relationships between chemoattraction and the ability to elicit pathology at the protein or peptide levels in the mouse uveitis model revealed dissociation of the capacity to induce uveitis, lymphocyte proliferation, and chemoattraction. These studies suggest that IRBP and S-Ag can initiate innate and, in sensitive individuals, adaptive immune response by attracting iDCs and T and B cells expressing CXCR3 and CXCR5.

Arrestin↗
PubMed2005

Alarmins: chemotactic activators of immune responses.

The recruitment and activation of antigen-presenting cells are critical early steps in mounting an immune response. Many microbial components and endogenous mediators participate in this process. Recent studies have identified a group of structurally diverse multifunctional host proteins that are rapidly released following pathogen challenge and/or cell death and, most importantly, are able to both recruit and activate antigen-presenting cells. These potent immunostimulants, including defensins, cathelicidin, eosinophil-derived neurotoxin, and high-mobility group box protein 1, serve as early warning signals to activate innate and adaptive immune systems. We propose to highlight these proteins' unique activities by grouping them under the novel term 'alarmins', in recognition of their role in mobilizing the immune system.

Animals↗