Localization and mechanism of secretion of B-type natriuretic peptide in comparison with those of A-type natriuretic peptide in normal subjects and patients with heart failure

BACKGROUND

B-type or brain natriuretic peptide (BNP) is a novel natriuretic peptide secreted from the heart that forms a peptide family with A-type or atrial natriuretic peptide (ANP), and its plasma level has been shown to be increased in patients with congestive heart failure. This study was designed to examine the sources and mechanisms of the secretion of BNP in comparison with those of ANP in control subjects and in patients with heart failure.

METHODS AND RESULTS

We measured the plasma levels of BNP as well as ANP in 16 patients with dilated cardiomyopathy (11 men and 5 women; mean age, 59 years) and 18 control subjects (9 men and 9 women; mean age, 54 years) by sampling blood from the femoral vein, the aortic root, the anterior interventricular vein (AIV), and the coronary sinus using the newly developed immunoradiometric assay systems. In the control subjects, there was no significant difference in the plasma ANP level between the aortic root and the AIV (24.0 +/- 5.2 pg/mL versus 32.2 +/- 17.0 pg/mL), but there was a highly significant step-up of the level between the AIV and the coronary sinus (32.2 +/- 17.0 pg/mL versus 371.4 +/- 111.1 pg/mL, P < .001). In contrast, there was a significant step-up of the plasma BNP level between the aortic root and the AIV (8.6 +/- 6.4 pg/mL versus 19.0 +/- 11.5 pg/mL, P < .01) but not between the AIV and the coronary sinus (19.0 +/- 11.5 pg/mL versus 28.8 +/- 14.0 pg/mL). On the other hand, in patients with dilated cardiomyopathy, there was a significant step-up in the plasma ANP level between the aortic root and the AIV (280.6 +/- 183.7 pg/mL versus 612.3 +/- 431.6 pg/mL, P < .01) and between the AIV and the coronary sinus (612.3 +/- 431.6 pg/mL versus 1229.0 +/- 772.7 pg/mL, P < .01). There was a significant step-up in the plasma BNP level between the aortic root and the AIV (268.4 +/- 293.2 pg/mL versus 511.6 +/- 458.1 pg/mL, P < .01) but not between the AIV and the coronary sinus (511.6 +/- 458.1 pg/mL versus 529.7 +/- 455.3 pg/mL) in patients with dilated cardiomyopathy. The arteriovenous difference at the AIV of the plasma level of BNP had a significant positive correlation with left ventricular end-systolic volume index (r = 0.859, P < .001) and a significant negative correlation with left ventricular ejection fraction (r = -.735, P < .001).

CONCLUSIONS

We conclude that (1) BNP is secreted mainly from the left ventricle in normal adult humans as well as in patients with left ventricular dysfunction, whereas ANP is secreted from atria in normal adult humans and also from the left ventricle in patients with left ventricular dysfunction; (2) secretion of BNP as well as ANP from the left ventricle increases in proportion to the severity of the left ventricular dysfunction, suggesting that the secretions of ANP and BNP from the left ventricle are regulated mainly by wall tension of the left ventricle; and (3) the peripheral plasma levels of ANP and BNP reflect the secretion rate of these hormones from the left ventricle and may be used as a marker of the degree of left ventricular dysfunction in patients with left ventricular dysfunction.

B70 antigen is a second ligand for CTLA-4 and CD28

The membrane antigen B7/BB1 (refs 1, 2) is expressed on activated B cells, macrophages and dendritic cells, and binds to a counter-receptor, CD28, expressed on T lymphocytes and thymocytes. Interaction between CD28 and B7 results in potent costimulation of T-cell activation initiated through the CD3/T-cell receptor complex. Discrepancies between results with anti-CD28 and anti-B7 antibodies have suggested the existence of a second ligand for CD28 and CTLA-4 (refs 3, 6-8). We have generated a monoclonal antibody, IT2, that reacts with a 70K glycoprotein (B70). B70 complementary DNA was cloned from a B-lymphoblastoid cell line library and encodes a new protein of the immunoglobulin superfamily with limited homology to B7. B70 is expressed on resting monocytes and dendritic cells and on activated, but not resting, T, NK and B lymphocytes. IT2 substantially inhibited the binding of a CTLA4-immunoglobulin fusion protein to human B-lymphoblastoid cell lines and, together with anti-B7 antibody, completely blocked CTLA-4 binding. Further IT2 efficiently inhibited primary allogeneic mixed lymphocyte responses. These findings indicate that B70 is a second ligand for CD28 and CTLA-4 and may play an important role for costimulation of T cells in a primary immune response.

Metalloproteinase-mediated release of human Fas ligand

Fas ligand (FasL) is a type II integral membrane protein homologous with tumor necrosis factor (TNF). Recent studies indicate that TNF is processed to yield the soluble cytokine by metalloproteinases at the cell surface of activated macrophages and T cells. In the present study, we investigated whether FasL is also released by metalloproteinases. Treatment with hydroxamic acid inhibitors of matrix metalloproteinases specifically led to accumulation of membrane-type FasL (p40) on the surface of human FasL cDNA transfectants and activated human T cells, as estimated by surface immunofluorescence and immunoprecipitation with newly established anti-human FasL monoclonal antibodies. This surface accumulation of mFasL was associated with the decrease of soluble FasL (p27) in the supernatant as estimated by quantitative ELISA and immunoprecipitation with anti-human FasL monoclonal antibodies. These results indicate that human FasL is efficiently released from the cell surface by metalloproteinases like TNF.

Specific acceptance of cardiac allograft after treatment with antibodies to ICAM-1 and LFA-1

An indefinite survival of cardiac allografts between fully incompatible mice strains was observed when monoclonal antibodies (MAbs) to intercellular adhesion molecule-1 (ICAM-1) and leukocyte function-associated antigen-1 (LFA-1) were simultaneously administered after the transplantation for 6 days. Mice with long-term surviving cardiac allografts accepted skin grafts from the donor-strain but rejected skin grafts from a third-party strain. Because MAbs to ICAM-1 or LFA-1 alone were insufficient for prolonged tolerance, the two MAbs probably acted synergistically to induce specific unresponsiveness. Thus, ICAM-1----LFA-1 adhesion participates in the induction of allograft rejection and MAbs may be useful as therapeutic agents.

Involvement of tumor necrosis factor-related apoptosis-inducing ligand in surveillance of tumor metastasis by liver natural killer cells

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) induces apoptosis in various tumor cells in vitro, but its physiological role in tumor surveillance remains unknown. Here, we report that TRAIL is constitutively expressed on murine natural killer (NK) cells in the liver and plays a substantial role in suppressing tumor metastasis. Freshly isolated NK cells, but not natural killer T cells or ordinary T cells, from the liver expressed cell surface TRAIL, which was responsible for spontaneous cytotoxicity against TRAIL-sensitive tumor cells in vitro along with perforin and Fas ligand (FasL). Administration of neutralizing monoclonal antibody against TRAIL significantly increased experimental liver metastases of several TRAIL-sensitive tumor cell lines. Such an anti-metastatic effect of TRAIL was not observed in NK cell-depleted mice or interferon-gamma-deficient mice, the latter of which lacked TRAIL on liver NK cells. These findings provide the first evidence for the physiological function of TRAIL as a tumor suppressor.

The natural killer T (NKT) cell ligand alpha-galactosylceramide demonstrates its immunopotentiating effect by inducing interleukin (IL)-12 production by dendritic cells and IL-12 receptor expression on NKT cells

The natural killer T (NKT) cell ligand alpha-galactosylceramide (alpha-GalCer) exhibits profound antitumor activities in vivo that resemble interleukin (IL)-12-mediated antitumor activities. Because of these similarities between the activities of alpha-GalCer and IL-12, we investigated the involvement of IL-12 in the activation of NKT cells by alpha-GalCer. We first established, using purified subsets of various lymphocyte populations, that alpha-GalCer selectively activates NKT cells for production of interferon (IFN)-gamma. Production of IFN-gamma by NKT cells in response to alpha-GalCer required IL-12 produced by dendritic cells (DCs) and direct contact between NKT cells and DCs through CD40/CD40 ligand interactions. Moreover, alpha-GalCer strongly induced the expression of IL-12 receptor on NKT cells from wild-type but not CD1(-/-) or Valpha14(-/-) mice. This effect of alpha-GalCer required the production of IFN-gamma by NKT cells and production of IL-12 by DCs. Finally, we showed that treatment of mice with suboptimal doses of alpha-GalCer together with suboptimal doses of IL-12 resulted in strongly enhanced natural killing activity and IFN-gamma production. Collectively, these findings indicate an important role for DC-produced IL-12 in the activation of NKT cells by alpha-GalCer and suggest that NKT cells may be able to condition DCs for subsequent immune responses. Our results also suggest a novel approach for immunotherapy of cancer.

The tissue distribution of the B7-2 costimulator in mice: abundant expression on dendritic cells in situ and during maturation in vitro

B7-2 is a recently discovered, second ligand for the CTLA-4/CD28, T cell signaling system. Using the GL-1 rat monoclonal antibody (mAb), we monitored expression of B7-2 on mouse leukocytes with an emphasis on dendritic cells. By cytofluorography, little or no B7-2 was detected on most cell types isolated from spleen, thymus, peritoneal cavity, skin, marrow, and blood. However, expression of B7-2 could be upregulated in culture. In the case of epidermal and spleen dendritic cells, which become highly immunostimulatory for T cells during a short period of culture, the upregulation of B7-2 was dramatic and did not require added stimuli. Lipopolysaccharide did not upregulate B7-2 levels on dendritic cells, in contrast to macrophages and B cells. By indirect immunolabeling, the level of staining with GL-1 mAb exceeded that seen with rat mAbs to several other surface molecules including intercellular adhesion molecule 1, B7-1, CD44, and CD45, as well as new hamster mAbs to CD40, CD48, and B7-1/CD80. Of these accessory molecules, B7-2 was a major species that increased in culture, implying a key role for B7-2 in the functional maturation of dendritic cells. B7-2 was the main (> 90%) CTLA-4 ligand on mouse dendritic cells. When we applied GL-1 to tissue sections of a dozen different organs, clear-cut staining with B7-2 antigen was found in many. B7-2 staining was noted on liver Kupffer cells, interstitial cells of heart and lung, and profiles in the submucosa of the esophagus. B7-2 staining was minimal in the kidney and in the nonlymphoid regions of the gut, and was not observed at all in the brain. In the tongue, only rare dendritic cells in the oral epithelium were B7-2+, but reactive cells were scattered about the interstitial spaces of the muscle. In all lymphoid tissues, Gl-1 strongly stained certain distinct regions that are occupied by dendritic cells and by macrophages. For dendritic cells, these include the thymic medulla, splenic periarterial sheaths, and lymph node deep cortex; for macrophages, the B7-2-rich regions included the splenic marginal zone and lymph node subcapsular cortex. Splenic B7-2+ cells were accessible to labeling with GL-1 mAb given intravenously. Dendritic cell stimulation of T cells (DNA synthesis) during the mixed leukocyte reaction was significantly (35-65%) blocked by GL-1.(ABSTRACT TRUNCATED AT 400 WORDS)

Critical contribution of liver natural killer T cells to a murine model of hepatitis

Natural killer T (NKT) cells constitute a distinct subpopulation of T cells with a unique antigen specificity, prompt effector functions, and an unusual tissue distribution. NKT cells are especially abundant in the liver, but their physiological function in this organ remains unclear. In the present study, we examined the possible contribution of NKT cells to a murine model of hepatitis induced by i.v. injection of Con A. CD1-deficient mice lacking NKT cells were highly resistant to Con A-induced hepatitis. Adoptive transfer of hepatic NKT cells isolated from wild-type mice, but not from FasL-deficient gld mice, sensitized CD1-deficient mice to Con A-induced hepatitis. Furthermore, adoptive transfer of hepatic mononuclear cells from wild-type mice, but not from CD1-deficient mice, sensitized gld mice to Con A-induced hepatitis. Upon Con A administration, hepatic NKT cells rapidly up-regulated cell surface FasL expression and FasL-mediated cytotoxicity. At the same time, NKT cells underwent apoptosis leading to their rapid disappearance in the liver. These results implicated FasL expression on liver NKT cells in the pathogenesis of Con A-induced hepatitis, suggesting a similar pathogenic role in human liver diseases such as autoimmune hepatitis.

Differential regulation of IkappaB kinase alpha and beta by two upstream kinases, NF-kappaB-inducing kinase and mitogen-activated protein kinase/ERK kinase kinase-1

NF-kappaB is activated by various stimuli including inflammatory cytokines and stresses. A key step in the activation of NF-kappaB is the phosphorylation of its inhibitors, IkappaBs, by an IkappaB kinase (IKK) complex. Recently, two closely related kinases, designated IKKalpha and IKKbeta, have been identified to be the components of the IKK complex that phosphorylate critical serine residues of IkappaBs for degradation. A previously identified NF-kappaB-inducing kinase (NIK), which mediates NF-kappaB activation by TNFalpha and IL-1, has been demonstrated to activate IKKalpha. Previous studies showed that mitogen-activated protein kinase/ERK kinase kinase-1 (MEKK1), which constitutes the c-Jun N-terminal kinase/stress-activated protein kinase pathway, also activates NF-kappaB by an undefined mechanism. Here, we show that overexpression of MEKK1 preferentially stimulates the kinase activity of IKKbeta, which resulted in phosphorylation of IkappaBs. Moreover, a catalytically inactive mutant of IKKbeta blocked the MEKK1-induced NF-kappaB activation. By contrast, overexpression of NIK stimulates kinase activities of both IKKalpha and IKKbeta comparably, suggesting a qualitative difference between NIK- and MEKK1-mediated NF-kappaB activation pathways. Collectively, these results indicate that NIK and MEKK1 independently activate the IKK complex and that the kinase activities of IKKalpha and IKKbeta are differentially regulated by two upstream kinases, NIK and MEKK1, which are responsive to distinct stimuli.

Different secretion patterns of atrial natriuretic peptide and brain natriuretic peptide in patients with congestive heart failure

BACKGROUND

The plasma levels of atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) are increased in relation to the severity of congestive heart failure (CHF). This study was designed to examine whether the secretion patterns of ANP and BNP vary with underlying cardiac disorders of CHF with different degrees of overload in atria and ventricles.

METHODS AND RESULTS

We measured plasma levels of ANP and BNP in the aorta in 20 patients with mitral stenosis (MS) in whom atria are mainly overloaded, 30 patients with dilated cardiomyopathy (DCM) in whom both atria and ventricles are overloaded, and 20 control subjects during cardiac catheterization. Pulmonary capillary wedge pressure (PCWP) was significantly higher in the MS and DCM groups (16.7 +/- 4.7 mm Hg and 15.1 +/- 7.7 mm Hg, respectively) than in the control group (7.2 +/- 1.1 mm Hg, p < 0.01), whereas there was no significant difference between the MS and DCM groups. Left ventricular end-diastolic pressure (LVEDP) was significantly higher in the DCM group than in the MS group (16.4 +/- 7.8 mm Hg versus 7.6 +/- 2.0 mm Hg, p < 0.01), and the level was comparable between the MS and control groups (7.6 +/- 2.0 mm Hg versus 6.8 +/- 1.2 mm Hg, p = NS). The plasma ANP level was significantly higher in the MS and DCM groups (356 +/- 169 pg/ml and 331 +/- 323 pg/ml, respectively) than in the control group (98 +/- 41 pg/ml, p < 0.01), whereas there was no significant difference between the MS and DCM groups. The plasma BNP level was significantly higher in the DCM group than in the MS group (333 +/- 405 pg/ml versus 147 +/- 54 pg/ml, p < 0.01), and the level was significantly higher in the MS group than in the control group (147 +/- 54 pg/ml versus < 10 pg/ml, p < 0.01). The plasma levels of ANP and BNP had a highly positive correlation with PCWP in the DCM group (p < 0.01). On the other hand, in the MS group, the plasma ANP level had a highly significant correlation with PCWP (p < 0.01) but the plasma BNP level did not.

CONCLUSIONS

We conclude that plasma levels of BNP mainly reflect the degree of ventricular overload and that the secretion patterns of ANP and BNP vary with underlying cardiac disorders of CHF with different degrees of overload in atria and ventricles.

A glycolipid on the surface of mouse natural killer cells

Cytotoxic treatment with rabbit antiserum raised against purified glycosphingolipid "asialo GM1" was capable of eliminating natural killer (NK) activity of spleen cells from different inbred mouse strains including CBA/J, C57BL/6, BALB/c, AKR, and athymic nude mice. The anti-asialo GM1 antiserum showed little cross-reactivity with structurally related glycolipids, e.g. GM), GD 1 b and asialo GM2 in the microflocculation test. The specific reactivity of this antiserum with NK cells was confirmed by the quantitative absorption of anti-NK activity with graded amounts of asialo GM1 but not with other glycosphingolipids. The absorption of anti-brain-associated T cell antigen (anti-BAT) with asialo GM1 also effectively diminished its anti-NK activity, leaving the ability to kill T cells intact. This suggests that the antibody to asialo GM1 is responsible for the anti-NK activity contained in the anti-BAT antiserum. In contrast to the extreme sensitivity of NK cells to anti-asialo GM1, alloreactive cytotoxic T killer cells generated in the mixed lymphocyte culture were not killed by anti-asialo GM1 and complement. These results indicate that asialo GM1 is expressed on mouse NK cells in a high concentration.

Angiographic no-reflow phenomenon as a predictor of adverse long-term outcome in patients treated with percutaneous transluminal coronary angioplasty for first acute myocardial infarction

OBJECTIVES

We sought to elucidate the long-term prognostic importance of angiographic no-reflow phenomenon after percutaneous transluminal coronary angioplasty (PTCA) for acute myocardial infarction (AMI).

BACKGROUND

Angiographic no-reflow phenomenon, a reduced coronary antegrade flow (Thrombolysis in Myocardial Infarction [TIMI] flow grade < or =2) without mechanical obstruction after recanalization, predicts poor left ventricular (LV) functional recovery and survival in the early phase of AMI. We hypothesized that angiographic no-reflow phenomenon also predicts long-term clinical outcome.

METHODS

We studied 120 consecutive patients with their first AMI treated by PTCA without flow-restricting lesions. The patients were classified as either no-reflow (n = 30) or reflow (TIMI-3) (n = 90) based on post-PTCA cineangiograms to follow up (5.8 +/- 1.2 years) for cardiac death and nonfatal events.

RESULTS

Patients with no-reflow had congestive heart failure (p < 0.0001), malignant arrhythmia (p = 0.038), and cardiac death (p = 0.002) more often than did those with reflow. Kaplan-Meier curves showed lower cardiac survival and cardiac event-free survival (p < 0.0001) in patients with no-reflow than in those with reflow. Multivariate analyses disclosed that no-reflow phenomenon was an independent predictor of long-term cardiac death (relative risk [RR] 5.25, 95% confidence interval [CI] 1.85 to 14.9, p = 0.002) and cardiac events (RR 3.71, 95% CI 1.79 to 7.69, p = 0.0004). At follow-up, survivors with no-reflow had higher end-diastolic and end-systolic LV volume indices and plasma brain natriuretic peptide levels, and lower LV ejection fractions (p = 0.0002, p < 0.0001, p = 0.002, p < 0.0001, respectively) than did those with reflow, indicating that no-reflow may be involved in LV remodeling.

CONCLUSIONS

Angiographic no-reflow phenomenon strongly predicts long-term cardiac complications after AMI; these complications are possibly associated with LV remodeling.

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) contributes to interferon gamma-dependent natural killer cell protection from tumor metastasis

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is expressed by in vitro activated natural killer (NK) cells, but the relevance of this observation to the biological function of NK cells has been unclear. Herein, we have demonstrated the in vivo induction of mouse TRAIL expression on various tissue NK cells and correlated NK cell activation with TRAIL-mediated antimetastatic function in vivo. Expression of TRAIL was only constitutive on a subset of liver NK cells, and innate NK cell control of Renca carcinoma hepatic metastases in the liver was partially TRAIL dependent. Administration of therapeutic doses of interleukin (IL)-12, a powerful inducer of interferon (IFN)-gamma production by NK cells and NKT cells, upregulated TRAIL expression on liver, spleen, and lung NK cells, and IL-12 suppressed metastases in both liver and lung in a TRAIL-dependent fashion. By contrast, alpha-galactosylceramide (alpha-GalCer), a powerful inducer of NKT cell IFN-gamma and IL-4 secretion, suppressed both liver and lung metastases but only stimulated NK cell TRAIL-mediated function in the liver. TRAIL expression was not detected on NK cells from IFN-gamma-deficient mice and TRAIL-mediated antimetastatic effects of IL-12 and alpha-GalCer were strictly IFN-gamma dependent. These results indicated that TRAIL induction on NK cells plays a critical role in IFN-gamma-mediated antimetastatic effects of IL-12 and alpha-GalCer.

Type I interferons (IFNs) regulate tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) expression on human T cells: A novel mechanism for the antitumor effects of type I IFNs

Tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) is a proapoptotic member of the TNF family of type II membrane proteins, which constitutes one component of T cell cytotoxicity. In this study, we investigated the expression and function of TRAIL in human peripheral blood T (PBT) cells. Although freshly isolated PBT cells did not express a detectable level of TRAIL on their surface, a remarkable TRAIL expression was rapidly induced on the surface of both CD4(+) and CD8(+) PBT cells upon stimulation with anti-CD3 monoclonal antibody and type I interferons (IFNs). This enhancement of TRAIL expression was a unique feature of type I IFNs (IFN-alpha and IFN-beta), and neither type II IFN (IFN-gamma) nor various other cytokines enhanced TRAIL expression on anti-CD3-stimulated PBT cells. Type I IFNs have been used for clinical treatment of renal cell carcinomas (RCCs), and we found that most RCC cell lines were susceptible to TRAIL-induced apoptosis. Type I IFNs substantially augmented cytotoxic activity of anti-CD3-stimulated PBT cells against RCC cell lines in a TRAIL-dependent manner. These results indicate a unique feature of type I IFNs to regulate TRAIL-mediated T cell cytotoxicity, which may be involved in the antitumor effects of type I IFNs against various tumors.

Cloning and characterization of a novel human phosphodiesterase that hydrolyzes both cAMP and cGMP (PDE10A)

cDNA encoding a novel phosphodiesterase (PDE) was isolated from a human fetal lung cDNA library and designated PDE10A. The deduced amino acid sequence contains 779 amino acids, including a putative cGMP binding sequence in the amino-terminal portion of the molecule and a catalytic domain that is 16-47% identical in amino acid sequence to those of other PDE families. Recombinant PDE10A transfected and expressed in COS-7 cells hydrolyzed cAMP and cGMP with Km values of 0.26 and 7.2 microM, respectively, and Vmax with cGMP was almost twice that with cAMP. Of the PDE inhibitors tested, dipyridamole was most effective, with IC50 values of 1.2 and 0.45 microM for inhibition of cAMP and cGMP hydrolysis, respectively. cGMP inhibited hydrolysis of cAMP, and cAMP inhibited cGMP hydrolysis with IC50 values of 14 and 0.39 microM, respectively. Thus, PDE10A exhibited properties of a cAMP PDE and a cAMP-inhibited cGMP PDE. PDE10A transcripts were particularly abundant in the putamen and caudate nucleus regions of brain and in thyroid and testis, and in much lower amounts in other tissues. The PDE10A gene was located on chromosome 6q26 by fluorescent in situ hybridization analysis. PDE10A represents a new member of the PDE superfamily, exhibiting unique kinetic properties and inhibitor sensitivity.

A new I subregion (I-J) marked by a locus (Ia-4) controlling surface determinants on suppressor T lymphocytes

In an accompanying publication we show that a subpopulation of T lymphocytes, which includes allotype suppressor T cells, selectively expresses I-region determinants. In this report, we show that these determinants are controlled by a new locus, Ia-4. Unlike the classically defined Ia antigens, they are not found on B lymphocytes. Antibody against Ia-4 determinants cannot be detected by conventional dye exclusion cytoxicity assays, suggesting that they are present on a small subpopulation (less than 10%) of peripheral T lymphocytes. The Ia-4 locus marks a new I subregion, provisionally designated I-J. This chromosomal segment is defined by the crossover positions in strains B10.A(5R) (K-end boundary) and B10.HTT (D-end boundary), and maps between the I-B and I-C subregions.

Reactive oxygen species mediate crosstalk between NF-κB and JNK

The activation of NF-kappaB inhibits apoptosis via a mechanism involving upregulation of various antiapoptotic genes, such as cellular FLICE-inhibitory protein (c-FLIP), Bcl-xL, A1/Bfl-1, and X chromosome-liked inhibitor of apoptosis (XIAP). In contrast, the activation of c-Jun N-terminal kinase (JNK) promotes apoptosis in a manner that is dependent on the cell type and the context of the stimulus. Recent studies have indicated that one of the antiapoptotic functions of NF-kappaB is to downregulate JNK activation. Further studies have also revealed that NF-kappaB inhibits JNK activation by suppressing accumulation of reactive oxygen species (ROS). In this review, we will focus on the signaling crosstalk between the NF-kappaB and JNK cascades via ROS.

Cloning, expression and chromosome locations of the human DNMT3 gene family

DNA methylation plays an important role in animal development and gene regulation. In mammals, several genes encoding DNA cytosine methyltransferases have been identified. DNMT1 is constitutively expressed and is required for the maintenance of global methylation after DNA replication. In contrast, the murine Dnmt3 family genes appear to be developmentally regulated and behave like de novo DNA methyltransferases in vitro. In this study, we have cloned human DNMT3A and DNMT3B that encode full-length DNMT3A and DNMT3B proteins with 98% and 94% amino acid sequence identity to their murine homologues. The DNMT3A and DNMT3B show high homology in the carboxy terminal catalytic domain and contain a conserved cysteine-rich region, which shares homology with the X-linked ATRX gene of the SNF2/SWI family. We have mapped human DNMT3A and DNMT3B to chromosomes 2p23 and 20q11.2 respectively, and determined the DNMT3B genomic structure. We further show that DNMT3A expression is ubiquitous and can be readily detected in most adult tissues, whereas DNMT3B is expressed at very low levels in most tissues except testis, thyroid and bone marrow. Significantly, both DNMT3A and DNMT3B expression is elevated in several tumor cell lines to levels comparable to DNMT1. The cloning of the human DNMT3 genes will facilitate further biochemical and genetic studies of their functions in establishment of DNA methylation patterns, regulation of gene expression and tumorigenesis.

TRAF5, an activator of NF-kappaB and putative signal transducer for the lymphotoxin-beta receptor

Tumor necrosis factor (TNF) receptor-associated factors (TRAFs) are signal transducers for several members of the TNF receptor superfamily. We have identified a novel member of the TRAF family by degenerate oligonucleotide polymerase chain reaction amplification that contains a zinc RING finger and zinc finger motifs, a coiled-coil region, and a C-terminal "TRAF" homology domain. In vitro translated TRAF5 binds to the cytoplasmic region of the lymphotoxin-beta receptor (LT-betaR) but not to several other related receptors including CD40, both TNF receptors, Fas, and nerve growth factor receptor. TRAF5 and LT-betaR coimmunoprecipitate when overexpressed in COS7 cells. TRAF5 mRNA expression is found in all visceral organs and overlaps with LT-betaR. These features distinguish TRAF5 from the other members of the TRAF family. The transcription factor NF-kappaB is activated in HEK293 cells by overexpression of full-length TRAF5 but not a truncated form lacking the zinc binding region. Furthermore, overexpression of LT-betaR in HEK293 cells also results in activation of NF-kappaB, which is partially inhibited by the truncated TRAF5 mutant. These results show TRAF5 is functionally similar to TRAF2 in that both mediate activation NF-kappaB and implicate TRAF5 as a signal transducer for LT-betaR.

4-1BB ligand induces cell division, sustains survival, and enhances effector function of CD4 and CD8 T cells with similar efficacy

A costimulatory member of the TNFR family, 4-1BB, is expressed on activated T cells. Although some reports have suggested that 4-1BB is primarily involved in CD8 T cell activation, in this report we demonstrate that both CD4 and CD8 T cells respond to 4-1BB ligand (4-1BBL) with similar efficacy. CD4 and CD8 TCR transgenic T cells up-regulate 4-1BB, OX40, and CD27 and respond to 4-1BBL-mediated costimulation during a primary response to peptide Ag. 4-1BBL enhanced proliferation, cytokine production, and CTL effector function of TCR transgenic T cells. To compare CD4 vs CD8 responses to 4-1BBL under similar conditions of antigenic stimulation, we performed MLRs with purified CD4 or CD8 responders from CD28(+/+) and CD28(-/-) mice. We found that CD8 T cells produced IL-2 and IFN-gamma in a 4-1BBL-dependent manner, whereas under the same conditions the CD4 T cells produced IL-2 and IL-4. 4-1BBL promoted survival of CD4 and CD8 T cells, particularly at late stages of the MLR. CD4 and CD8 T cells both responded to anti-CD3 plus s4-1BBL with a similar cytokine profile as observed in the MLR. CD4 and CD8 T cells exhibited enhanced proliferation and earlier cell division when stimulated with anti-CD3 plus anti-CD28 compared with anti-CD3 plus 4-1BBL, and both subsets responded comparably to anti-CD3 plus 4-1BBL. These data support the idea that CD28 plays a primary role in initial T cell expansion, whereas 4-1BB/4-1BBL sustains both CD4 and CD8 T cell responses, as well as enhances cell division and T cell effector function.

B70/B7-2 is identical to CD86 and is the major functional ligand for CD28 expressed on human dendritic cells

Dendritic cells comprise a system of highly efficient antigen-presenting cells involved in the initiation of T cell responses. Herein, we investigated the role of the CD28 pathway during alloreactive T cell proliferation induced by dendritic-Langerhans cells (D-Lc) generated by culturing human cord blood CD34+ progenitor cells with granulocyte/macrophage colony-stimulating factor and tumor necrosis factor alpha. In addition to expressing CD80 (B7/BB1), a subset of D-Lc expressed B70/B7-2. Binding of the CTLA4-Ig fusion protein was completely inhibited by a combination of monoclonal antibodies (mAbs) against CD80 and B70/B7-2, indicating the absence of expression of a third ligand for CD28/CTLA-4. It is interesting to note that mAbs against CD86 completely prevented the binding of CTLA4-Ig in the presence of mAbs against CD80 and bound to a B70/B7-2-transfected fibroblast cell line, demonstrating that the B70/B7-2 antigen is identical to CD86. CD28 triggering was essential during D-Lc-induced alloreaction as it was inhibited by mAbs against CD28 (9 out of 11 tested). However, none of six anti-CD80 mAbs demonstrated any activity on the D-Lc-induced alloreaction, though some were previously described as inhibitory in assays using CD80-transfected cell lines. In contrast, a mAb against CD86 (IT-2) was found to suppress the D-Lc-dependent alloreaction by 70%. This inhibitory effect was enhanced to > or = 90% when a combination of anti-CD80 and anti-CD86 mAbs was used. The present results demonstrate that D-Lc express, in addition to CD80, the other ligand for CTLA-4, CD86 (B70/B7-2), which plays a primordial role during D-Lc-induced alloreaction.

Protective roles of mast cells against enterobacterial infection are mediated by Toll-like receptor 4

Toll-like receptors (TLRs) are mammalian homologues of the Drosophila Toll receptors and are thought to have roles in innate recognition of bacteria. We demonstrated that TLR 2, 4, 6, and 8 but not TLR5 were expressed on mouse bone marrow-derived mast cells (BMMCs). Using BMMCs from the genetically TLR4-mutated strain C3H/HeJ, we demonstrated that functional TLR4 was required for a full responsiveness of BMMCs to produce inflammatory cytokines (IL-1beta, TNF-alpha, IL-6, and IL-13) by LPS stimulation. TLR4-mediated stimulation of mast cells by LPS was followed by activation of NF-kappaB but not by stress-activated protein kinase/c-Jun NH2-terminal kinase signaling. In addition, in the cecal ligation and puncture-induced acute septic peritonitis model, we demonstrated that genetically mast cell-deficient W/W(v) mice that were reconstituted with TLR4-mutated BMMCs had significantly higher mortality than W/W(v) mice reconstituted with TLR4-intact BMMCs. Higher mortality of TLR4-mutated BMMC-reconstituted W/W(v) mice was well correlated with defective neutrophil recruitment and production of proinflammatory cytokines in the peritoneal cavity. Taken together, these observations provide definitive evidence that mast cells play important roles in exerting the innate immunity by releasing inflammatory cytokines and recruitment of neutrophils after recognition of enterobacteria through TLR4 on mast cells.

Nitric oxide activity is deficient in spasm arteries of patients with coronary spastic angina

BACKGROUND

Coronary spasm can be induced by acetylcholine, serotonin, ergonovine, or histamine, all of which cause vasodilation when the endothelium is intact by releasing nitric oxide (NO). Coronary spasm is promptly relieved by nitroglycerin, which vasodilates through its conversion to NO. It is thus possible that NO release may be deficient in the spasm arteries in patients with coronary spastic angina (CSA). The aim of this study was to determine whether NO release is deficient in coronary arteries of patients with CSA.

METHODS AND RESULTS

NG-monomethyl-L-arginine (L-NMMA), an inhibitor of NO synthase, was infused into coronary arteries in 21 patients with coronary spastic angina (CSA) and in 28 control patients. Coronary spasm was induced by intracoronary injection of acetylcholine and was documented angiographically in all patients with CSA. L-NMMA dose-dependently decreased basal luminal diameter of coronary arteries in control patients, whereas it had no effect on basal diameter of the spasm arteries in patients with CSA. L-NMMA abolished the dilator response to acetylcholine and enhanced the constrictor response to acetylcholine in control arteries, whereas it had no effect on the constrictor response to acetylcholine in spasm arteries. Intracoronary infusion of L-arginine did not affect the diameter of spasm or control arteries. The dilator response to nitroglycerin was increased markedly in spasm arteries compared with control arteries, whereas response to diltiazem did not differ between them.

CONCLUSIONS

There is a deficiency in endothelial NO activity in spasm arteries, which leads to the supersensitivity of the artery to the vasodilator effect of nitroglycerin and to the vasoconstrictor effect of acetylcholine in patients with CSA. This deficient endothelial NO activity plays an important role in the pathogenesis of coronary spasm.

Long-term prognosis for patients with variant angina and influential factors

Two hundred forty-five patients with variant angina were followed for an average of 80.5 months (range, 36-184 months). Survival rate at 1, 3, 5, and 10 years was 98%, 97%, 97%, and 93%, respectively. Survival rate without myocardial infarction at 1, 3, 5, and 10 years was 86%, 85%, 83%, and 81%, respectively. By univarite analysis, ST segment elevation in both the anterior and inferior electrocardiographic leads was the most important factor influencing survival, followed by use of calcium antagonists, left ventricular function, smoking, and alcohol intake. The variables that significantly correlated with survival without myocardial infarction were use of calcium antagonists, left ventricular function, extent and severity of coronary artery disease, coronary artery bypass surgery, and disease activity. Multivariate analysis using the Cox proportional hazards model showed that intake of calcium antagonists, extent and severity of coronary artery disease, and ST segment elevation in both the anterior and inferior leads were significant independent predictors of survival without myocardial infarction. We conclude that long-term prognosis for patients with variant angina is relatively good and that use of calcium antagonists improves it.

Nasal mast cells in perennial allergic rhinitics exhibit increased expression of the Fc epsilonRI, CD40L, IL-4, and IL-13, and can induce IgE synthesis in B cells

Cross-linking of allergen specific IgE bound to the high affinity IgE receptor (FC epsilonRI) on the surface of mast cells with multivalent allergens results in the release of both pre-formed and newly generated mediators, and in the manifestation of allergic symptoms. The expression of Fc epsilonRI, and the synthesis of IgE are therefore critical for the development of allergic diseases. In this study, we report that nasal mast cells (NMC) from patients with perennial allergic rhinitis (PAR) expressed significantly greater levels of the Fc epsilonRI, CD40L, IL-4, and IL-13 as compared to NMC from patients with chronic infective rhinitis (CIR). The level of Fc epsilonRI expression in NMC of PAR patients strongly correlated with the levels of serum total (r = 0.8, P < 0.003) and specific IgE (r = 0.89, P < 0.0004) antibodies. In addition, stimulation of NMC with IL-4, upregulated the Fc epsilonRIalpha chain expression both at the protein and mRNA levels, as detected by flow cytometry and reverse transcriptase-polymerase chain reaction. Furthermore, NMC from PAR, but not CIR, patients induced IgE synthesis by purified B cells in the presence of Der fII (mite antigen). These results suggest novel and critical roles for mast cells in promoting the allergic reaction through the increased expression of Fc epsilonRI and by enhancing and amplifying the IgE production, within the local microenvironment.