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Jana Stankova

Publications and source records attributed to Jana Stankova.

17 recordsLinked to original sources
PubMed2006

CysLT1 receptor engagement induces activator protein-1- and NF-kappaB-dependent IL-8 expression.

Because cysteinyl-leukotrienes (cysLTs) are major protagonists in the pathophysiology of human asthma, and because neutrophils are involved in the more severe form of asthma, we studied the potential for leukotriene (LT) D(4) to induce synthesis of the chemokine IL-8 through activation of the CysLT1 receptor. We found LTD(4) to induce IL-8 gene expression in monocytic THP-1 cells and human dendritic cells with complete abrogation by selective CysLT1 antagonists. Human embryonic kidney-293 cells stably transfected with CysLT1 were used to better study the transcriptional regulation of the IL-8 promoter. Stimulation of the cells with graded concentrations of LTD(4) resulted in a time- and concentration-dependent induction of IL-8 transcription and protein synthesis. Use of IL-8 promoter mutants with substitutions in their NF-kappaB, activator protein (AP)-1, and NF-IL-6 binding elements revealed a requirement for NF-kappaB and AP-1, but not NF-IL-6, in LTD(4)-induced activation of the IL-8 promoter. Overexpression of dominant-negative IkappaBalpha inhibited the IL-8 transactivation induced by LTD(4). NF-kappaB DNA binding activity was induced by LTD(4), as determined by electrophoretic mobility shift assays, and could be supershifted by antibodies against p50 and p65. Supershift assays after LTD(4) stimulation also indicated the formation of a c-Jun/c-Fos complex. Moreover, our results demonstrate that LTD(4) upregulates the expression of c-fos and c-jun at the mRNA level. Our data show for the first time that LTD(4), via the CysLT1 receptor, can transcriptionally activate IL-8 production, with involvement of the transcription factors p50, p65, Fos, and Jun. These findings provide mechanistic and potentially therapeutic elements for modulation of the inflammatory component of asthma.

Asthma↗
PubMed2006

Toll-like receptor agonists differentially regulate cysteinyl-leukotriene receptor 1 expression and function in human dendritic cells.

BACKGROUND: Dendritic cells (DCs) acquire, during their maturation, the expression of the chemokine receptor CCR7 and the ability to migrate to lymph nodes in response to CC chemokine ligand 19 (CCL19). This migration is impaired in mice lacking the leukotriene (LT) C4 transporter and restored by addition of exogenous LTC4. OBJECTIVE: To define the role of LT in human DC function, we studied the expression and function of the cysteinyl-leukotriene (CysLT) receptors during DC differentiation from monocytes and subsequent maturation. METHODS: Receptor expression was measured by flow cytometry and real-time PCR. Responsiveness to LTD4 stimulation was assessed by calcium flux and chemotaxis. RESULTS: Maturation of DC with LPS, a classic Toll-like receptor 4 agonist, reduced CysLT receptor 1 (CysLT1) expression by 50%, whereas CysLT receptor 2 expression was increased. In contrast, the Toll-like receptor 3 agonist poly inosinic and cytidylic acid (polyI:C) had no effect on receptor expression. Downregulation of CysLT1 expression by LPS could not be mimicked by TNF-alpha alone or in combination with IL-1beta or IL-6. It was, however, prevented by inhibitors of COX and could be reproduced by a combination of TNF-alpha and prostaglandin E2. Immature DCs and DCs matured with polyI:C, but not with LPS, responded to LTD4 with a robust cytosolic calcium flux, which was prevented by the CysLT1 antagonist montelukast. LTD4 induced DC chemotaxis and enhanced DC migration in response to CCL19 in DCs matured with polyI:C, but only weakly in DCs matured with LPS. CONCLUSION: Our data suggest that human DCs may differentially respond to leukotriene, depending on their maturational stimuli. CLINICAL IMPLICATIONS: Our study demonstrates that some microbial agents can reduce the migration of dendritic cells in response to leukotrienes, with potential for differential involvement of these cells in allergic inflammation.

Calcium↗
PubMed2006

Leukotriene D4 enhances immunoglobulin production in CD40-activated human B lymphocytes.

BACKGROUND: Cysteinyl-leukotrienes (cysLTs) are lipid mediators recognized for their role in asthma and allergic inflammation. CysLT1, one of the receptors for cysLTs, is expressed, among others, in bronchial smooth muscle cells, phagocytes, and B lymphocytes. The potential role of CysLT1 in B lymphocytes remains unexplored. OBJECTIVE: We examined the modulation of expression and function of CysLT1 in human B lymphocytes. METHODS: Human B lymphocytes were purified from peripheral blood and analyzed by means of RT-PCR and flow cytometry, after culture with IL-4 and anti-CD40 antibody or CD154-transfected fibroblasts. Functional responses to leukotriene (LT) D4 in terms of cytosolic calcium flux, proliferation, and immunoglobulin production were also examined. RESULTS: B lymphocytes expressed CysLT1 at both the mRNA and protein levels. Two-fold to 3-fold enhancement of CysLT1 expression was observed after B-cell exposure to a combination of activating anti-CD40 antibody and IL-4. The expression of CysLT1 was also enhanced when B lymphocytes were cocultured with CD154-transfected fibroblasts in the presence of IL-4. Moreover, IL-4 and CD40-activated B lymphocytes showed an increased responsiveness to LTD4 in terms of cytosolic calcium flux, which was totally prevented by the selective CysLT1 antagonist montelukast. Stimulation of IL-4 and CD40-activated B lymphocytes with picomolar concentrations of LTD4 induced mature epsilon transcripts and upregulated IgE and IgG production 2-fold to 3-fold. CONCLUSION: We have demonstrated that expression of CysLT1 can be upregulated in B lymphocytes after stimulation with CD154, with consequent increased responsiveness of the cells to LTD4 in terms of immunoglobulin production. CLINICAL IMPLICATIONS: This study provides evidence that cysLTs generated during allergic reactions can affect B-cell function and enhance IgE and IgG production, which may further contribute to the allergic process.

B-Lymphocytes↗
PubMed2006

Fibroblast growth factor 2 and transforming growth factor beta1 synergism in human bronchial smooth muscle cell proliferation.

Bronchial smooth muscle cell (BSMC) hyperplasia is a typical feature of airway remodeling and contributes to airway obstruction and hyperresponsiveness in asthma. Fibroblast growth factor 2 (FGF-2) and transforming growth factor beta1 (TGF-beta1) are sequentially upregulated in asthmatic airways after allergic challenge. Whereas FGF-2 induces BSMC proliferation, the mitogenic effect of TGF-beta1 remains controversial, and the effect of sequential FGF-2 and TGF-beta1 co-stimulation on BSMC proliferation is unknown. This study aimed to assess the individual and sequential cooperative effects of FGF-2 and TGF-beta1 on human BSMC proliferation and define the underlying mechanisms. Mitogenic response was measured using crystal violet staining and [3H]-thymidine incorporation. Steady-state mRNA and protein levels were measured by semiquantitative RT-PCR, Western blot, and ELISA, respectively. TGF-beta1 (0.1-20 ng/ml) alone had no effect on BSMC proliferation, but increased the proliferative effect of FGF-2 (2 ng/ml) in a concentration-dependent manner (up to 6-fold). Two distinct platelet-derived growth factor receptor (PDGFR) inhibitors, AG1296 and Inhibitor III, as well as a neutralizing Ab against PDGFRalpha, partially blocked the synergism between these two growth factors. In this regard, TGF-beta1 increased PDGF-A and PDGF-C mRNA expression as well as PDGF-AA protein expression. Moreover, FGF-2 pretreatment increased the mRNA and protein expression of PDGFRalpha and the proliferative effect of exogenous PDGF-AA (140%). Our data suggest that FGF-2 and TGF-beta1 synergize in BSMC proliferation and that this synergism is partially mediated by a PDGF loop, where FGF-2 and TGF-beta1 upregulate the receptor (PDGFRalpha) and the ligands (PDGF-AA and PDGF-CC), respectively. This powerful synergistic effect may thus contribute to the hyperplastic phenotype of BSMC in remodeled asthmatic airways.

Adult↗
PubMed2005

The anti-apoptotic effect of leukotriene B4 in neutrophils: a role for phosphatidylinositol 3-kinase, extracellular signal-regulated kinase and Mcl-1.

The constitutive commitment of neutrophils to apoptosis is a key process for the control and resolution of inflammation and it can be delayed by various inflammatory mediators including leukotriene B4 (LTB4). The mechanisms by which LTB4 contributes to neutrophil survival are still unclear and the present work aims at identifying intracellular pathways underlying this effect. Inhibition of human neutrophil apoptosis by LTB4 was abrogated by the phosphatidylinositol 3-kinase (PI3-K) inhibitor wortmannin and by the specific MEK inhibitor PD98059. In contrast, inhibitors of p38 MAPK, Jak2/3 and Src did not hinder the anti-apoptotic effect of LTB4. We also investigated the effects of members of the Bcl-2 family as they play a crucial role in the regulation of programmed cell death. When neutrophils were incubated with LTB4 for 1 to 6 h, the mRNA levels of the anti-apoptotic protein Mcl-1 were upregulated approximately 2-fold, while those of the pro-apoptotic protein Bax were downregulated 3- to 4-fold, as determined by real-time PCR. Accordingly, Western blot analysis revealed that the expression of Mcl-1 was upregulated in presence of LTB4, while flow cytometric analysis revealed that Bax protein was downregulated. Furthermore, the modulatory effects of LTB4 on Mcl-1 and Bax proteins were abolished in the presence of either wortmannin or PD98059. Taken together, these results demonstrate the participation of PI3-K and MEK/ERK kinases, as well as regulatory apoptotic proteins such as Mcl-1 and Bax, in the anti-apoptotic effects of LTB4 in human neutrophils.

Androstadienes↗
PubMed2005

Involvement of BLT1 endocytosis and Yes kinase activation in leukotriene B4-induced neutrophil degranulation.

One of the important biological activities of human neutrophils is degranulation, which can be induced by leukotriene B4 (LTB4). Here we investigated the intracellular signaling events involved in neutrophil degranulation mediated by the high affinity LTB4 receptor, BLT1. Peripheral blood neutrophils as well as the promyeloid PLB-985 cell line, stably transfected with BLT1 cDNA and differentiated into a neutrophil-like cell phenotype, were used throughout this study. LTB4-induced enzyme release was inhibited by 50-80% when cells were pretreated with the pharmacological inhibitors of endocytosis sucrose, Con A and NH4Cl. In addition, transient transfection with a dominant negative form of dynamin (K44A) resulted in approximately 70% inhibition of ligand-induced degranulation. Pretreating neutrophils or BLT1-expressing PLB-985 cells with the Src family kinase inhibitor PP1 resulted in a 30-60% inhibition in BLT1-mediated degranulation. Yes kinase, but not c-Src, Fgr, Hck, or Lyn, was found to exhibit up-regulated kinase activity after LTB4 stimulation. Moreover, BLT1 endocytosis was found to be necessary for Yes kinase activation in neutrophils. LTB4-induced degranulation was also sensitive to inhibition of PI3K. In contrast, it was not affected by inhibition of the mitogen-activated protein kinase MEK kinase, the Janus kinases, or the receptor tyrosine kinase epidermal growth factor receptor or platelet-derived growth factor receptor. Taken together, our results suggest an essential role for BLT1 endocytosis and Yes kinase activation in LTB4-mediated degranulation of human neutrophils.

Calcium Signaling↗
PubMed2005

Involvement of leukotriene B4 receptor 1 signaling in platelet-activating factor-mediated neutrophil degranulation and chemotaxis.

Platelet-activating factor (PAF) is a potent lipid mediator of inflammation that can act on human neutrophils. When neutrophils are stimulated with PAF at concentrations greater than 10 nM, a double peak of intracellular calcium mobilization is observed. The second calcium peak observed in PAF-treated neutrophils has already been suggested to come from the production of endogenous leukotriene B4 (LTB4). Here we demonstrate the involvement of endogenous LTB4 production and subsequent activation of the high affinity LTB4 receptor (BLT1) in this second calcium mobilization peak observed after stimulation with PAF. We also show that the second, but not the first peak, could be desensitized by prior exposure to LTB4. Moreover, when neutrophils were pre-treated with pharmacological inhibitors of LTB4 production or with the specific BLT1 antagonist, U75302, PAF-mediated neutrophil degranulation was inhibited by more than 50%. On the other hand, pre-treating neutrophils with the PAF receptor specific antagonist (WEB2086) did not prevent any LTB4-induced degranulation. Also, when human neutrophils were pre-treated with U75302, PAF-mediated chemotaxis was reduced by more than 60%. These data indicate the involvement of BLT1 signaling in PAF-mediated neutrophil activities.

Calcium Signaling↗
PubMed2003

Trafficking, ubiquitination, and down-regulation of the human platelet-activating factor receptor.

Platelet-activating factor (PAF) is a potent phospholipid mediator involved in various disease states such as allergic asthma, atherosclerosis and psoriasis. The human PAF receptor (PAFR) is a member of the G protein-coupled receptor family. Following PAF stimulation, cells become rapidly desensitized; this refractory state can be maintained for hours and is dependent on PAFR phosphorylation, internalization, and down-regulation. In this report, we characterized ligand-induced, long term PAFR desensitization, and pathways leading to its degradation. Some GPCRs are known to be targeted to proteasomes for degradation while others traffic via the early/late endosomes toward lysosomes. Specific inhibitors of lysosomal proteases and inhibitors of the proteasome were effective in reducing the ligand-induced PAFR down-regulation by 40 and 25%, respectively, indicating the importance of receptor targeting to both lysosomes and proteasomes in long term cell desensitization to PAF. The effects of the proteasome and lysosomal protease inhibitors were additive and, together, completely blocked ligand-induced degradation of PAFR. Using dominant-negative Rab5 and 7 and colocalization of the PAFR with the early endosome autoantigen I (EEAI) or transferrin, we confirmed that ligand-induced PAFR down-regulation was Rab5/7-dependent and involved lysosomal degradation. In addition, we also demonstrated that PAFR was ubiquitinated in an agonist-independent manner. However, a dominant negative ubiquitin ligase (NCbl) reduced PAFR ubiquitination and inhibited ligand-induced but not basal receptor degradation. Our results indicate that PAFR degradation can occur via both the proteasome and lysosomal pathways and ligand-stimulated degradation is ubiquitin-dependent.

Animals↗
PubMed2003

Agonist-independent desensitization and internalization of the human platelet-activating factor receptor by coumermycin-gyrase B-induced dimerization.

Platelet-activating factor (PAF) is a phospholipid with potent and diverse physiological actions, particularly as a mediator of inflammation. We have reported previously that mutant G protein-coupled receptors (GPCRs) affect the functional properties of coexpressed wild-type human PAF receptor (hPAFR) (Le Gouill, C., Parent, J. L., Caron, C. A., Gaudreau, R., Volkov, L., Rola-Pleszczynski, M., and Stankova, J. (1999) J. Biol. Chem. 274, 12548-12554). Increasing evidence suggests that dimerization of GPCRs may play an important role in the regulation of their biological activity. Additional data have also suggested that dimerization may be important in the subsequent internalization of the delta-opioid receptor. To investigate the specific role of dimerization in the internalization process of GPCRs, we generated a fusion protein of hPAFR and bacterial DNA gyrase B (GyrB), dimerized through the addition of coumermycin. We found that dimerization potentiates PAF-induced internalization of hPAFR-GyrB in Chinese hamster ovary cells stably expressing c-Myc-hPAFR-GyrB. Coumermycin-driven dimerization was also sufficient to induce an agonist-independent sequestration process in an arrestin- and clathrin-independent manner. Moreover, the protein kinase C inhibitors staurosporine and GF109203X blocked the coumermycin-induced desensitization of hPAFR-GyrB, suggesting the implication of protein kinase C in the molecular mechanism mediating the agonist-independent desensitization of the receptor. Taken together, these findings suggest a novel mechanism of GPCR desensitization and internalization triggered by dimerization.

Aminocoumarins↗
PubMed2003

Activation of ERK1/2 by platelet-activating factor receptor is independent of receptor internalisation and G-protein activation.

Platelet-activating factor (PAF) is a potent pro-inflammatory phospholipid mediator involved in a broad range of physiological and pathophysiological processes. The receptor of PAF (PAFR) is a heptahelical G-protein-coupled receptor. We have shown previously that upon agonist stimulation, PAFR internalised through clathrin-coated vesicles in an arrestin-dependent, but G-protein-coupling-independent manner. In the current report, we demonstrate that PAF stimulates Erk1/2 phosphorylation and: (1). dominant negative mutants of arrestins and dynamin do not influence Erk1/2 activation, (2). hypertonic conditions do not decrease the extent of Erk1/2 phosphorylation, (3). internalisation-deficient and/or G-protein-coupling-deficient mutants of PAFR activate Erk1/2 as efficiently as the wild-type PAFR, and (4). inhibition of epidermal growth factor receptor (EGFR) does not block Erk1/2 activation. Taken together, our results suggest that PAFR-mediated activation of mitogen-activated protein kinases Erk1/2 does not require receptor endocytosis, receptor tyrosine kinase transactivation or G-protein activation. In addition, our studies reveal that PAFR-mediated signals of G-protein activation, receptor internalisation and MAPK activation are differentially regulated by receptor structure and/or conformation.

Animals↗
PubMed2003

CysLT1 receptor upregulation by TGF-beta and IL-13 is associated with bronchial smooth muscle cell proliferation in response to LTD4.

BACKGROUND: Airway remodeling is a feature of chronic asthma. It involves a number of structural changes, including bronchial smooth muscle cell (BSMC) hyperplasia and hypertrophy. Cysteinyl leukotrienes (cysLTs) have been suggested to play a role in airway remodeling in addition to their numerous other physiopathologic effects. OBJECTIVES: This work was aimed at characterizing the potential modulation of CysLT1 receptor expression by cytokines and the eventual functional relevance of this modulation. METHODS: Expression of CysLT1 receptor was measured by flow cytometry and immunofluorescence microscopy. Transcripts were measured by RT-PCR and BSMC proliferation by crystal violet staining. RESULTS: When human BSMC were exposed to transforming growth factor (TGF)-beta, IL-13, or IFN-gamma, their expression of CysLT1 receptor was significantly augmented in a time- and concentration-dependent manner. Interestingly, IL-4 had no significant effect on CysLT1 receptor expression in BSMC. Moreover, IL-13 and IFN-gamma but not TGF-beta were able to increase CysLT1 mRNA levels. Finally, when BSMC were pretreated with TGF-beta or IL-13 but not IFN-gamma, their responsiveness to LTD(4) was markedly enhanced in terms of BSMC proliferation. Whereas TGF-beta, IL-13, or LTD(4) alone had little effect on BSMC proliferation, preexposure of the cells to TGF-beta or IL-13 for 24 hours resulted in a significant increase in proliferation in response to LTD(4). The enhanced proliferation was totally prevented by pretreating the cytokine-primed BSMC with the selective CysLT1 receptor antagonist Montelukast. CONCLUSIONS: Taken together, our findings indicate a synergy between certain cytokines and cysLTs, mediated by the augmented expression of the CysLT1 receptor and subsequent LTD(4)-triggered BSMC proliferation. These findings support a role for cysLTs in the airway remodeling observed in asthmatic patients and may provide a rationale for preventive and therapeutic intervention.

Bronchi↗
PubMed2003

Upregulation of expression of the chemokine receptor CCR5 by hydrogen peroxide in human monocytes.

The objective of this study was to test the hypothesis that an oxidative stress can serve as a signal to regulate the expression of CCR5. When human monocytes were exposed to graded concentration of hydrogen peroxide (H(2)O(2)), CCR5 mRNA levels increased maximally at 4 h of exposure to 200 microM of H(2)O(2) and decreased by 24 h of treatment. Pretreatment of monocytes with the NF-kappaB inhibitor BAY 11-8072 blocked the H(2)O(2)-induced augmentation of CCR5 mRNA expression, suggesting a role for this transcription factor in the regulation of CCR5 expression. CCR5 protein expression on the plasma membrane was also increased by treatment with H(2)O(2,) as assessed by flow cytometry. This was accompanied by enhanced responsiveness of H(2)O(2)-pretreated monocytes to the CCR5 ligand MIP-1beta in terms of chemotaxis and c-fos gene activation. Our results suggest that oxidative stress may indeed modulate the expression of chemokine receptors and thus contribute to regulation of the inflammatory process.

Catalase↗
PubMed2002

Proinflammatory gene induction by platelet-activating factor mediated via its cognate nuclear receptor.

It has been postulated that intracellular binding sites for platelet-activating factor (PAF) contribute to proinflammatory responses to PAF. Isolated nuclei from porcine cerebral microvascular endothelial cells (PCECs) produced PAF-molecular species in response to H(2)O(2). Using FACS analysis, we demonstrated the expression of PAF receptors on cell and nuclear surfaces of PCECs. Confocal microscopy studies performed on PCECs, Chinese hamster ovary cells stably overexpressing PAF receptors, and isolated nuclei from PCECs also showed a robust nuclear distribution of PAF receptors. Presence of PAF receptors at the cell nucleus was further revealed in brain endothelial cells by radioligand binding experiments, immunoblotting, and in situ in brain by immunoelectron microscopy. Stimulation of nuclei with methylcarbamate-PAF evoked a decrease in cAMP production and a pertussis toxin-sensitive rise in nuclear calcium, unlike observations in plasma membrane, which exhibited a pertussis toxin-insensitive elevation in inositol phosphates. Moreover, on isolated nuclei methylcarbamate-PAF evoked the expression of proinflammatory genes inducible nitric oxide synthase and cyclooxygenase-2 (COX-2) and was associated with augmented extracellular signal-regulated kinase 1/2 phosphorylation and NF-kappaB binding to the DNA consensus sequence. COX-2 expression was prevented by mitogen-activated protein kinase kinase/extracellular signal-regulated kinase 1/2 and NF-kappaB inhibitors. This study describes for the first time the nucleus as a putative organelle capable of generating PAF and expresses its receptor, which upon stimulation induces the expression of the proinflammatory gene COX-2.

Animals↗
PubMed2002

Threonine 308 within a putative casein kinase 2 site of the cytoplasmic tail of leukotriene B(4) receptor (BLT1) is crucial for ligand-induced, G-protein-coupled receptor-specific kinase 6-mediated desensitization.

Desensitization of G-protein-coupled receptors may involve phosphorylation of serine and threonine residues. The leukotriene B(4) (LTB(4)) receptor (BLT1) contains 14 intracellular serines and threonines, 8 of which are part of consensus target sequences for protein kinase C (PKC) or casein kinase 2. In this study, we investigated the importance of PKC and GPCR-specific kinase (GRK) phosphorylation in BLT1 desensitization. Pretreatment of BLT1-transfected COS-7 cells with PKC activators caused a decrease of LTB(4)-induced inositol phosphate (IP) accumulation. This reduction was prevented with the PKC inhibitor, staurosporine, and not observed in cells expressing a BLT1 deletion mutant (G291stop) lacking the cytoplasmic tail. Moreover LTB(4)-induced IP accumulation was significantly inhibited by overexpression of GRK2, GRK5, and especially GRK6, in cells expressing wild type BLT1 but not in those expressing G291stop. GRK6-mediated desensitization correlated with increased phosphorylation of BLT1. The G319stop truncated BLT1 mutant displayed functional characteristics comparable with wild type BLT1 in terms of desensitization by GRK6, but not by PKC. Substitution of Thr(308) within a putative casein kinase 2 site to proline or alanine in the full-length BLT1 receptor prevented most of GRK6-mediated inhibition of LTB(4)-induced IP production but only partially affected LTB(4)-induced BLT1 phosphorylation. Our findings thus suggest that Thr(308) is a major residue involved in GRK6-mediated desensitization of BLT1 signaling.

Amino Acid Sequence↗
PubMed2002

Modulation of leukotriene B4 receptor-1 expression by dexamethasone: potential mechanism for enhanced neutrophil survival.

Glucocorticoids can down-regulate many inflammatory and immune responses and constitute a powerful therapeutic tool in a number of diseases. However, they have a somewhat paradoxical effect on neutrophils, in that they prolong their survival. Because leukotriene B(4) (LTB(4)) can also extend neutrophil survival, we proposed that glucocorticoids could prevent neutrophil apoptosis by up-regulating their expression of the high-affinity LTB(4) receptor (BLT1). Here we show that, indeed, dexamethasone (DEX) up-regulates the steady-state levels of BLT1 mRNA in human neutrophils. The effect was time and concentration dependent, being maximal at 4 h and at 10-100 nM DEX. The effect was also dependent on transcriptional activity, whereas BLT1 mRNA stability was not affected. DEX-induced up-regulation of BLT1 expression was prevented by pretreatment with the LTB(4) antagonist LY255283. Moreover, LTB(4) itself up-regulated the expression of BLT1 mRNA. BLT1 protein expression on neutrophils exposed to DEX for 24 h was also up-regulated 2- to 3-fold, and DEX-treated as well as LTB(4)-treated cells showed enhanced responsiveness to LTB(4) in terms of intracellular Ca(2+) mobilization and chemotaxis. Whereas DEX and LTB(4) alone decreased neutrophil apoptosis by approximately 50%, neutrophils treated with both LTB(4) and DEX showed >90% survival at 24 h. Moreover, BLT1 antagonists prevented the increased neutrophil survival induced by DEX as well as by LTB(4). Taken together, our results suggest that DEX-induced up-regulation of BLT1 expression in neutrophils may be one mechanism through which glucocorticoids can prolong neutrophil survival, namely by enhancing cell responses to the antiapoptotic effect of LTB(4).

Adjuvants, Immunologic↗
PubMed2002

Endothelins regulate mediator production of rat tissue-cultured mucosal mast cells. Up-regulation of Th1 and inhibition of Th2 cytokines.

Mast cells have been shown to produce endothelin-1 (ET-1) and to express ET receptors. Thus, we postulated that ETs modulate mast cell mediator production in an autocrine manner. Rat tissue-cultured mast cells (RCMC-1) were incubated with exogenous ET-1 or ET-3, and beta-hexosaminidase release and TNF, IL-4, IL-10, IL-12, IL-13, macrophage inflammatory protein-1alpha (MIP-1alpha), and nitric oxide (NO) production were investigated. ET-1 and -3 induced the release of beta-hexosaminidase and TNF and of mRNA expression. An antagonist of the ET(B) receptor subtype abrogated ET-stimulated TNF release, although ET(A) and ET(B) receptors have been identified by immunocytochemistry. It is interesting that ET-1 and ET-3 inhibited (25-30%) mRNA expression of Th2-type cytokines (IL-4, IL-10, and IL-13) and increased IL-12 release (39% and 41%, respectively) without affecting MIP-1alpha and NO production. Thus, our data suggest that ETs may play an important role in modulating the cytokine network by regulating Th1/Th2 cytokine production by mast cells.

Animals↗