Lipoteichoic acid acts as an antagonist and an agonist of lipopolysaccharide on human gingival fibroblasts and monocytes in a CD14-dependent manner. (49/9413)

CD14 has been implicated as a receptor of lipoteichoic acid (LTA) and other bacterial components as well as lipopolysaccharide (LPS). Since the structures of LTAs from various gram-positive bacteria are heterogeneous, we analyzed the effects of LTAs on the secretion of interleukin-8 (IL-8) by high- and low-CD14-expressing (CD14(high) and CD14(low)) human gingival fibroblasts (HGF). While Bacillus subtilis LTA had an IL-8-inducing effect on CD14(high) HGF which was considerably weaker than that of LPS, Streptococcus sanguis and Streptococcus mutans LTAs had practically no effect on the cells. B. subtilis LTA had only a weak effect on CD14(low) HGF, as did LPS. S. sanguis and S. mutans LTAs at a 1,000-fold excess each completely inhibited the IL-8-inducing activities of both LPS and a synthetic lipid A on CD14(high) HGF. The effect of LPS was also inhibited by the presence of an LPS antagonist, synthetic lipid A precursor IVA (LA-14-PP), with a 100-fold higher potency than S. sanguis and S. mutans LTAs and by anti-CD14 monoclonal antibody (MAb). S. sanguis and S. mutans LTAs, LA-14-PP, and anti-CD14 MAb had no significant effect on phorbol myristate acetate-stimulated IL-8 secretion by HGF. These LTAs also inhibited the IL-8-inducing activity of B. subtilis LTA on CD14(high) HGF, as did LA-14-PP and anti-CD14 MAb. The antagonistic and agonistic functions of LTAs were also observed with human monocytes. Binding of fluorolabeled LPS to human monocytes was inhibited by S. sanguis LTA, although the inhibition was 100 times weaker than that of LPS itself, and anti-CD14 MAb inhibited fluorolabeled LPS and S. sanguis LTA binding. Binding of LTAs to CD14 was also observed with nondenaturing polyacrylamide gel electrophoresis. These results indicate that LTAs act as antagonists or agonists via a CD14-dependent mechanism, probably due to the heterogeneous structure of LTAs, and that an antagonistic LTA might be a useful agent for suppressing the periodontal disease caused by gram-negative bacteria.  (+info)

High mobility group-I(Y) protein facilitates nuclear factor-kappaB binding and transactivation of the inducible nitric-oxide synthase promoter/enhancer. (50/9413)

Nitric oxide (NO), a free radical gas whose production is catalyzed by the enzyme NO synthase, participates in the regulation of multiple organ systems. The inducible isoform of NO synthase (iNOS) is transcriptionally up-regulated by inflammatory stimuli; a critical mediator of this process is nuclear factor (NF)-kappaB. Our objective was to determine which regulatory elements other than NF-kappaB binding sites are important for activation of the iNOS promoter/enhancer. We also wanted to identify transcription factors that may be functioning in conjunction with NF-kappaB (subunits p50 and p65) to drive iNOS transcription. Deletion analysis of the iNOS promoter/enhancer revealed that an AT-rich sequence (-61 to -54) downstream of the NF-kappaB site (-85 to -76) in the 5'-flanking sequence was important for iNOS induction by interleukin-1beta and endotoxin in vascular smooth muscle cells. This AT-rich sequence, corresponding to an octamer (Oct) binding site, bound the architectural transcription factor high mobility group (HMG)-I(Y) protein. Electrophoretic mobility shift assays showed that HMG-I(Y) and NF-kappaB subunit p50 bound to the iNOS promoter/enhancer to form a ternary complex. The formation of this complex required HMG-I(Y) binding at the Oct site. The location of an HMG-I(Y) binding site typically overlaps that of a recruited transcription factor. In the iNOS promoter/enhancer, however, HMG-I(Y) formed a complex with p50 while binding downstream of the NF-kappaB site. Furthermore, overexpression of HMG-I(Y) potentiated iNOS promoter/enhancer activity by p50 and p65 in transfection experiments, suggesting that HMG-I(Y) contributes to the transactivation of iNOS by NF-kappaB.  (+info)

Nuclear retention of IkappaBalpha protects it from signal-induced degradation and inhibits nuclear factor kappaB transcriptional activation. (51/9413)

Transcriptional activation of nuclear factor kappaB (NF-kappaB) is mediated by signal-induced phosphorylation and degradation of its inhibitor, IkappaBalpha. However, NF-kappaB activation induces rapid resynthesis of IkappaBalpha, which is responsible for post-induction repression of transcription. Newly synthesized IkappaBalpha translocates to the nucleus, where it dissociates NF-kappaB from DNA and transports NF-kappaB from the nucleus to the cytoplasm in a nuclear export sequence-dependent process that is sensitive to leptomycin B (LMB). In the present study, LMB was used as a tool to inhibit nuclear export sequence-mediated nuclear protein export and evaluate the consequences for regulation of NF-kappaB-dependent transcriptional activity. Pretreatment of cells with LMB inhibits NF-kappaB-dependent transcriptional activation mediated by interleukin 1beta or tumor necrosis factor alpha. This is a consequence of the inhibition of signal-induced degradation of IkappaBalpha. Although LMB treatment does not affect the signal transduction pathway leading to IkappaBalpha degradation, it blocks IkappaBalpha nuclear export. IkappaBalpha is thus accumulated in the nucleus, and in this compartment it is resistant to signal-induced degradation. These results indicate that the signal-induced degradation of IkappaBalpha is mainly, if not exclusively, a cytoplasmic process. An efficient nuclear export of IkappaBalpha is therefore essential for maintaining a low level of IkappaBalpha in the nucleus and allowing NF-kappaB to be transcriptionally active upon cell stimulation.  (+info)

Glucocorticoid enhances interleukin-1-induced pressor response in freely moving rats through its effect on nitric oxide release. (52/9413)

We investigated whether changes in nitric oxide (NO) release might be responsible for the modulation by glucocorticoids of the pressor response to i.p. injection of interleukin-1beta (IL-1beta) in freely moving rats. In such rats, IL-1beta (10 microgram/kg) induced a biphasic pressor response, with a rise in the plasma concentration of NOx (NO2(-) and NO3(-): metabolites of NO) during the second phase. Systemic pretreatment with an exogenous glucocorticoid, dexamethasone (0.5 mg/kg), enhanced the second phase of the pressor response and completely suppressed the increase in plasma NOx. Treatment with Nomega-nitro-L-arginine methyl ester (L-NAME, a nonspecific NO synthase inhibitor), enhanced the pressor response while attenuating the increase in plasma NOx. After bilateral adrenalectomy, IL-1beta induced a smaller pressor response, but a larger increase in plasma NOx; dexamethasone reversed these changes. Our results suggest that endogenous NO moderates the pressor response to IL-1beta in freely moving rats, and that glucocorticoids enhance the IL-1beta-induced pressor response at least in part by reducing endogenous NO release.  (+info)

Interleukin-1beta in immune cells of the abdominal vagus nerve: a link between the immune and nervous systems? (53/9413)

Intraperitoneal administration of the cytokine interleukin-1beta (IL-1beta) induces brain-mediated sickness symptoms that can be blocked by subdiaphragmatic vagotomy. Intraperitoneal IL-1beta also induces expression of the activation marker c-fos in vagal primary afferent neurons, suggesting that IL-1beta is a key component of vagally mediated immune-to-brain communication. The cellular sources of IL-1beta activating the vagus are unknown, but may reside in either blood or in the vagus nerve itself. We assayed IL-1beta protein after intraperitoneal endotoxin [lipopolysaccharide (LPS)] injection in abdominal vagus nerve, using both an ELISA and immunohistochemistry, and in blood plasma using ELISA. IL-1beta levels in abdominal vagus nerve increased by 45 min after LPS administration and were robust by 60 min. Plasma IL-1beta levels increased by 60 min, whereas little IL-1beta was detected in cervical vagus or sciatic nerve. IL-1beta-immunoreactivity (IR) was expressed in dendritic cells and macrophages within connective tissues associated with the abdominal vagus by 45 min after intraperitoneal LPS injection. By 60 min, some immune cells located within the nerve and vagal paraganglia also expressed IL-1beta-IR. Thus, intraperitoneal LPS induced IL-1beta protein within the vagus in a time-frame consistent with signaling of immune activation. These results suggest a novel mechanism by which IL-1beta may serve as a molecular link between the immune system and vagus nerve, and thus the CNS.  (+info)

Vasculitis in the Palmerston North mouse model of lupus: phenotype and cytokine production profile of infiltrating cells. (54/9413)

OBJECTIVE: To define the phenotype of cells in the perivascular and vascular infiltrates of Palmerston North (PN) mice and the cytokines that those cells produce. METHODS: Immunohistologic analysis, flow cytometric analysis, and reverse transcriptase-polymerase chain reaction (RT-PCR) studies were performed on tissues and cells from female PN mice and age-matched and sex-matched DBA/2 mice. RESULTS: With aging, PN mice developed a female-predominant, lupus-like disease, with a severe systemic mononuclear cell perivasculitis and vasculitis. The perivasculitis involved arteries and veins in kidney, liver, brain, and lung; the vasculitis predominantly involved veins and venules. The perivascular and vascular infiltrates in female PN mice were composed mainly of an unusual cell type that expressed phenotypic markers characteristic of both T cells (Thy1+, CD3+, CD4+, T cell receptor + [TCR+]) and B cells (B220+). In addition, the infiltrates contained a smaller number of conventional CD4+,B220- T cells and macrophages. Very few CD8+ T cells or surface Ig+ B cells were seen. Unlike the Thy1+,B220+ T cells present in MRL/lpr mice, most of which were CD4-,CD8- and TCRalpha/beta+, the majority of the Thy1+,B220+ T cells in the perivascular/vascular infiltrates of PN mice were CD4+ and expressed either TCRalpha/beta or TCRgamma/delta. By immunohistologic staining, the cells in the perivascular and vascular infiltrates in the kidneys of older PN mice were shown to produce interleukin-4 (IL-4), IL-6, and IL-10, but not IL-2, interferon-gamma, transforming growth factor beta, tumor necrosis factor alpha, or IL-1beta. By RT-PCR, the kidneys of older PN mice were found to express high levels of IL-4, IL-6, and IL-10 messenger RNA. CONCLUSION: The vascular and perivascular infiltrates in PN mice are composed predominantly of an unusual subpopulation of T cells that are Thy1+,B220+,CD4+,CD8-, express either TCRalpha/beta or TCRgamma/delta, and produce mainly type 2 cytokines. The exact role of these cells in the immunopathogenesis of lupus-like disease in PN mice remains to be elucidated.  (+info)

Regulation of cyclooxygenase-2 expression in human mesangial cells--transcriptional inhibition by IL-13. (55/9413)

Activated mesangial cells may play an important part in glomerulonephritis. Cytokines can modulate the release of prostanoids by human mesangial cells (HMC). We have investigated the effects of pro-inflammatory stimuli on COX-2 expression in HMC and its potential modulation by interleukin (IL)-13. HMC released increased amounts of prostaglandin E2 (PGE2) after treatment with several combinations of IL-1 beta, tumor necrosis factor (TNF)-alpha and/or lipopolysaccharide. Increases in PGE2 correlated with the induction of COX-2 protein expression. The accumulation of PGE2 elicited by a combination of IL-1 beta/TNF-alpha correlated closely with the temporal pattern of COX-2 protein expression, which reflected the induction of COX-2 mRNA. IL-13 inhibited IL-1 beta/TNF-alpha-elicited PGE2 production, as well as COX-2 protein and mRNA expression in a concentration-dependent fashion. With 50 ng.mL-1 IL-13 these parameters were inhibited by 90, 80 and 84%, respectively. In HMC transfected with the 5' regulatory region of the COX-2 gene, IL-13 suppressed cytokine-induced promoter activation. Our results suggest that COX-2 expression is a major target for IL-13-mediated abrogation of prostaglandin release by HMC and support that this process takes place by transcriptional inhibition of the COX-2 gene.  (+info)

Inflammatory cytokines provide a third signal for activation of naive CD4+ and CD8+ T cells. (56/9413)

The effects of inflammatory cytokines on naive T cells have been studied using MHC protein/peptide complexes on microspheres, thus avoiding the use of APCs whose functions may be affected by the cytokines. IL-1, but not IL-12, increased proliferation of CD4+ T cells in response to Ag and IL-2, which is consistent with effects on in vivo priming of CD4+ cells. In contrast, proliferation of CD8+ T cells to Ag and IL-2 required IL-12, and IL-12 replaced adjuvant in stimulating an in vivo response to peptide. These results support a model in which distinct inflammatory cytokines act directly on naive CD4+ and CD8+ T cells to provide a third signal, along with Ag and IL-2, to optimally activate differentiation and clonal expansion.  (+info)