Search PubMed⌕ Search

Biomedical subjects

J W Lammers

Publications and source records attributed to J W Lammers.

At least 37 records · Page 2Linked to original sources
PubMed1999

A composite C/EBP binding site is essential for the activity of the promoter of the IL-3/IL-5/granulocyte-macrophage colony-stimulating factor receptor beta c gene.

The common beta-chain (beta c) is the main signaling component of the heterodimeric receptors for IL-3, IL-5, and GM-CSF and is primarily expressed on myeloid cells. The proximal beta c promoter is regulated by GGAA binding proteins, including PU.1, a hemopoietic specific member of the Ets family. However, it is not likely that PU.1 alone accounts for the myeloid-restricted expression of the beta c subunit. Here we describe the identification of a C/EBP binding enhancer that is located 2 kb upstream of the transcription start site. The enhancer contains two elements that bind C/EBP alpha and -beta in U937 cells, while C/EBP epsilon is also bound in extracts of HL-60 cells. Importantly, deletion of the enhancer or mutation of either of one of the C/EBP sites results in a complete loss of promoter activity in cell lines as well as in primary cells, showing the importance of C/EBP members in beta c gene activation. We further show that PU.1 has to cooperate with C/EBP proteins to induce beta c transcription. Since the beta c is already expressed on CD34+ cells, these results demonstrate that both C/EBP and PU.1 are not only important for the myeloid-specific gene regulation at later stages of myeloid differentiation.

Animals↗
PubMed1999

STAT5 activation by BCR-Abl contributes to transformation of K562 leukemia cells.

Signal transducers and activators of transcription (STATs) belong to a family of transcription factors that were originally identified as mediators of cytokine-induced gene expression. Recent evidence, however, has shown that certain members of the STAT family, including STAT3, are also involved in cellular transformation. Here we show that STAT5 also plays a role in cellular transformation by the BCR-Abl oncogene. In BCR-Abl transformed K562 cells, STAT5A and 5B are constitutively phosphorylated on tyrosine and are transcriptionally active. Moreover, expression of a dominant negative form of STAT5 shows that active STAT5 is necessary for the growth in soft agar of these cells. These results show that besides STAT3, STAT5 can also be involved in cellular transformation.

Cell Transformation, Neoplastic↗
PubMed1999

Regulation of p21rac activation in human neutrophils.

The small guanosine triphosphate (GTPase) p21rac is highly expressed in human neutrophils where it is thought to play a role in cytoskeletal reorganization and superoxide production. Using the p21rac binding domain of PAK (PAK-RBD) as an activation-specific probe, we have investigated agonist-stimulated activation of p21rac. Stimulation of neutrophils with the chemoattractants fMet-Leu-Phe (fMLP) or platelet-activating factor (PAF) induced an extremely rapid and transient p21rac activation, being optimal within 5 seconds. This activation correlates with the rapid changes of intracellular free Ca(2+) ([Ca(2+)](i)) stimulated by fMLP; however, changes in [Ca(2+)](i) were neither sufficient nor required for p21rac activation. Furthermore, fMLP-induced p21rac activation was not inhibited by broad tyrosine kinase inhibitors or specific inhibitors of ERK, p38 mitogen activated protein kinase, Src, or phosphatidylinositol 3-kinases. Surprisingly, the cytokines granulocyte-macrophage colony-stimulating factor (GM-CSF) and tumor necrosis factor-alpha did not cause p21rac activation or modulate fMLP-induced p21rac activation. AlF(-), a potent activator of heterotrimeric G-protein alpha-subunits, however, was found to activate p21rac. Stimulation of neutrophils with phorbol myristate acetate (PMA) strongly activated the respiratory burst, but did not induce p21rac activation, suggesting that superoxide production per se can occur independently of p21rac activation. These data suggest that in human granulocytes, G-protein coupled receptors, but not cytokine receptors, activate p21rac via a rapid, novel exchange-mechanism independently of changes in [Ca(2+)](i), tyrosine phosphorylation, or PI3K.

Calcium↗
PubMed1999

Characterization of eosinophil adhesion to TNF-alpha-activated endothelium under flow conditions: alpha 4 integrins mediate initial attachment, and E-selectin mediates rolling.

The multistep model of leukocyte adhesion reveals that selectins mediate rolling interactions and that integrins mediate firm adhesion processes. In this study, the interaction between eosinophils and TNF-alpha-activated HUVEC (second or third passage) was studied under flow conditions (0.8 and 3.2 dynes/cm2). Especially the role of alpha 4 integrins on eosinophils and E-selectin on HUVEC was studied. Inhibition of the integrin alpha 4 chain on eosinophils reduced the number of firmly adhered resting eosinophils to TNF-alpha-stimulated endothelium by 43% whereas the percentage rolling cells increased 2.2-fold compared with untreated control eosinophils. Blocking of E-selectin on the endothelium reduced the number of adherent eosinophils by only 23% and 16%. In this situation, however, hardly any rolling adhesion was observed, and the few rolling cells showed a low rolling velocity. Blocking both alpha 4 integrin on eosinophils and E-selectin on HUVEC reduced the number of adhered eosinophils by 95%. P-selectin did not significantly participate in eosinophil adhesion to TNF-alpha-activated HUVEC. Inhibition of both alpha 4 integrins and beta 2 integrins on eosinophils resulted in a reduction of adhered cells by 65% and a 3-fold increase in percentage rolling cells. Taken together, these results clearly show that resting eosinophils preferentially use constitutively active alpha 4 integrins (alpha 4 beta 1, alpha 4 beta 7) for the first attachment to TNF-alpha-activated HUVEC. In addition, alpha 4 integrins and E-selectin work synergistically in eosinophil adherence to TNF-alpha-activated HUVEC. Although E-selectin is important for eosinophil rolling under these conditions, P-selectin plays only a minor role.

Antigens, CD↗
PubMed1999

Regulation and function of protein kinase B and MAP kinase activation by the IL-5/GM-CSF/IL-3 receptor.

Interleukin (IL)-3, IL-5 and granulocyte-macrophage colony-stimulating factor (GM-CSF) regulate proliferation, differentiation and apoptosis of target cells. Receptors for these cytokines consist of a cytokine-specific alpha subunit and a common shared beta c subunit. Tyrosine phosphorylation of the beta c is thought to play a critical role in mediating signal transduction events. We have examined the effect of mutation of beta c tyrosines on the activation of multiple signal transduction pathways. Activation of protein kinase B (PKB) required JAK2 and was inhibited by dominant-negative phosphatidylinositol 3-kinase (P13K). Overexpression of JAK2 was sufficient to activate both protein kinase B (PKB) and extracellular regulated kinase-1 (ERK1). Tyrosine 577 and 612 were found to be critical for the activation of PKB and ERK1, but not activation of STAT transcription factors. Activation of both PKB and ERK have been implicated in the regulation of proliferation and apoptosis. We generated GM-CSFR stable cell lines expressing receptor mutants to evaluate their effect on these processes. Activation of both PKB and ERK was perturbed, while STAT activation remained unaffected. Tyrosines 577 and 612 were necessary for optimal proliferation, however, mutation of these tyrosine residues did not affect GM-CSF mediated rescue from apoptosis. These data demonstrate that while phosphorylation of beta c tyrosine residues 577 and 612 are important for optimal cell proliferation, rescue from apoptosis can be mediated by alternative signalling routes apparently independent of PKB or ERK activation.

Animals↗
PubMed1999

[The place of long-acting beta 2 adrenergic agonists in the treatment of asthma and chronic obstructive lung disease (COPD)].

At the introduction of long-acting beta 2-adrenergic agonists physicians were reluctant to prescribe them for prolonged use, as they might increase mortality due to asthma. In national and international guidelines beta 2-agonists are reserved for moderate to severe asthma. Well-controlled studies have shown, however, that long-acting beta 2-agonists are effective bronchodilators, able to improve symptoms and lung function and to decrease the number of exacerbations. As long as these bronchodilators are combined with inhaled steroids, they may be beneficial in early stages of asthma of low severity. In the treatment of COPD the place of long-acting beta 2-agonists is not clear yet. First experiences show, however, that these drugs deserve a place in the treatment of COPD, notably against nocturnal dyspnoea. Use of long-acting beta 2-agonists is often associated with clear improvement in quality of life and walking distance of COPD patients, which does not appear to be accompanied by distinct improvement in pulmonary function (FEV1), however.

Adrenal Cortex Hormones↗
PubMed1999

Lineage-specific activation of STAT3 by interferon-gamma in human neutrophils.

Binding of interferon-gamma (IFN-gamma) to its heterodimeric receptor induces activation of the tyrosine kinases JAK1 and JAK2 followed by tyrosine phosphorylation of STAT1alpha. Selective activation of STAT1alpha at the IFN-gamma receptor is achieved by specific interaction between a cytosolic tyrosine motif including Y440 in the IFN-gamma receptor alpha-chain and the SH2 domain of STAT1alpha. We demonstrate that, in addition to STAT1alpha, STAT3 is also activated by IFN-gamma in human neutrophils. The activation of STAT3 was not found in human eosinophils, monocytes, and HL-60 cells, although the STAT3 protein was expressed in these cells. The cell type-specific activation of STAT3 by IFN-gamma was also observed in neutrophils that are differentiated in vitro from human CD34+ hematopoietic stem cells. These results indicate that a single cytokine receptor can activate different STAT family members in a cell-specific manner, which might result in cell-specific gene transcription.

Antiviral Agents↗
PubMed1999

C/EBP regulates the promoter of the eosinophil-derived neurotoxin/RNS2 gene in human eosinophilic cells.

The eosinophil-derived neurotoxin (EDN), a member of the mammalian ribonuclease family, is found in the large specific granules of human eosinophilic leukocytes. We have investigated the role of the C/EBP transcription factor family in the regulation of EDN promoter activity. Here we show that the C/EBP family is involved in intrinsic regulation of EDN promoter activity. We have identified a C/EBP binding site located at -124 in the proximal promoter of the EDN gene. Mutation of this C/EBP site results in a decrease of promoter activity in HL-60-eos cells as well as in eosinophils differentiated in vitro from CD34+ cells. Different C/EBP proteins are able to bind to the C/EBP site as shown by gel shift assay. Our results indicate the importance of the C/EBP family in the regulation of the EDN gene in eosinophils.

Animals↗
PubMed1999

Activation of a functionally distinct 80-kDa STAT5 isoform by IL-5 and GM-CSF in human eosinophils and neutrophils.

Interleukin-5 (IL-5), IL-3, and granulocyte macrophage colony-stimulating factor (GM-CSF) are hematopoietic cytokines which signal through a common beta subunit (betac) of a heterodimeric receptor. Among the intracellular signaling pathways activated via betac is the JAK/STAT pathway. We show that different STAT5 isoforms are activated by IL-5 and GM-CSF in eosinophils, neutrophils, and differentiated eosinophilic HL-60 cells. Whereas IL-5 activated the wild-type STAT5A and STAT5B proteins in HL60-eos cells, a carboxyl-terminally truncated 80-kDa STAT5 isoform was activated in mature eosinophils and neutrophils. Surprisingly, while both isoforms bind strongly to an element from the beta-casein promoter, only p80 STAT5 binds to the ICAM1-IRE. Consequently, a carboxyl-terminal truncated STAT5 is capable of blocking STAT3-mediated transcription of an IREtkCAT reporter construct. The cell type-specific expression of these functionally distinct STAT5 isoforms might contribute to the pleiotropic effects of IL-5 and GM-CSF on different target cells.

Cell Extracts↗
PubMed1999

Type of lymph node involvement and survival in pathologic N1 stage III non-small cell lung carcinoma.

BACKGROUND: Survival of patients with stage II non-small lung cancer by the 1986 classification depends on the type of lymph node involvement (by direct extension or by metastases in lobar or hilar lymph nodes). The influence of these types of lymph node involvement on survival was investigated in pathologic N1 stage III patients. METHODS: Of 2,009 patients having operation from 1977 through 1993, the cases of 123 patients with pathologic N1 stage III disease (80 T3 N1 and 43 T4 N1) were reviewed. The N1 status was refined by the specific type of lymph node involvement. RESULTS: The cumulative 5-year survival rate of all hospital survivors (n = 111) was 27.2%. A significant difference in mean 5-year survival rate was observed between patients who underwent complete resection and those with incomplete resection (34.4% versus 11.4%; p = 0.0001). Further analysis was performed with hospital survivors having complete resection only (n = 76). The cumulative 5-year survival rate was 34.4%. Type of lymph node involvement did not relate to survival for the group as a whole or for the T3 and T4 subsets. Survival was not related to age, histology, type of resection, or tumor size. CONCLUSIONS: Moderately good results can be obtained with surgical resection for stage III patients with pathologic N1 disease. In contrast with stage II, complete resection of pathologic N1 higher-stage non-small cell lung carcinoma is not influenced by type of lymph node involvement.

Adult↗
PubMed1999

Guidelines for severe community-acquired pneumonia in the western world.

BACKGROUND: Recently, several guidelines (ATS 1993/IDSA 1998; ERS 1998; SWAB 1998) have been issued for the initial therapy of patients with community-acquired pneumonia. In patients who fulfil the criteria for severe community-acquired pneumonia (SCAP), it was advised to start with a macrolide (active against Legionella spp. and Mycoplasma pneumoniae) in combination with an agent active against both pneumococci and Pseudomonas aeruginosa by the ATS/IDSA guidelines, while the ERS suggested starting with a second or third generation cephalosporin, in combination with either a macrolide or second generation quinolon plus or minus rifampicin. In the SWAB guidelines, no recommendations for SCAP were made. METHODS: Sixty-two cases admitted to the intensive care units of a tertiary-care university hospital with SCAP between 1992 and 1996 were studied retrospectively. The causative pathogens, clinical and laboratory characteristics of severity, antibiotic therapy and mortality were analysed. Immunocompromised patients, patients using immunosuppressive agents and patients with a malignancy were excluded. RESULTS: Indices of severe illness were widely seen and 37% developed shock while 45% required vasoactive drugs. Bilobular or multilobular abnormalities were seen in 34% of the patients. Forty-five patients (73%) required artificial respiration and 54 (87%) had an underlying disease. The overall mortality was 42%. In 41 patients (66%), a pathogen was isolated. The most frequent causes of SCAP in this study were Streptococcus pneumoniae (22 cases or 35%), Haemophilus influenzae (seven cases or 11%), Pseudomonas aeruginosa (four cases or 7%), and other Enterobacteriaceae (twice in combination with pneumococci and once with H. influenzae). Legionella pneumophila was identified in three cases. In patients with severe chronic obstructive pulmonary disease (COPD), pneumococci were the most important pathogens six cases or 27%), followed by P. aeruginosa (14%) and H. influenzae (14%). CONCLUSIONS: The guidelines for the management of SCAP issued by the ATS and IDSA in 1993 are only partially adequate in the Dutch setting. Coverage of P. aeruginosa would seem useful, given the fact that isolation of this pathogen has been shown to be a predictor of mortality, but only in patients with severe COPD or structural disease of the lung, and especially in patients in whom the Gram stain reveals Gram-negative rods, as is also suggested in the revised IDSA guidelines (1998). Risk factors for P. aeruginosa could be added to the ERS guidelines. Including SCAP as a separate entity in the SWAB guidelines may be useful.

Adult↗
PubMed1999

Prescription and usage of long-term oxygen therapy in patients with chronic obstructive pulmonary disease in The Netherlands.

Long-term oxygen therapy (LTOT) has been shown to improve survival in hypoxaemic patients with chronic obstructive pulmonary disease (COPD). This has resulted in recommending the prescription of oxygen for at least 15 h day-1 in most European countries. In order to examine the prescription and usage of LTOT and to assess the adherence to international recommendations for its prescription, a survey was set up in a random sample of clients of the largest oxygen company in the Netherlands. After patients had been visited for an interview, additional postal surveys were sent to the physician who had prescribed LTOT and to the oxygen company. For 175 COPD patients the mean oxygen prescription and mean oxygen usage were 15.6 +/- 5.8 and 14.1 +/- 6.8 h day-1, respectively. In 62 patients (35%) oxygen was prescribed < 15 h day-1, more often by non-chest physicians than by chest physicians (P < 0.0001), and 91 patients (52%) used oxygen < 15 h day-1. Of 113 patients with a prescription > or = 15 h day-1, 39 (35%) used oxygen < 15 h day-1 and 74 for > or = 15 h day-1. The latter were prescribed oxygen for more h day-1, had been longer on LTOT, had a higher resting flow rate, were prescribed a concentrator, employed portable cylinders and used oxygen in public significantly more often than the former. We conclude that in a selected group of LTOT patients with COPD both oxygen prescription and usage were often inadequate, particularly if LTOT was prescribed by non-chest physicians.

Aged↗
PubMed1999

Asthma exacerbations during first therapy with long acting beta 2-agonists.

Long-acting beta 2-agonists (LBA) have become an important therapeutic strategy in the treatment of asthma. There is, however, debate whether LBA increase the risk of asthma exacerbations (AE). We studied whether the risk of AE was increased in patients starting LBA therapy and whether the risk was associated with severity. Patients, aged 5-49 years, who were firstly prescribed LBA between 1992 and 1995, and who had at least two consecutive prescriptions of LBA, were selected from the PHARMO-RLS database. The exposure period was the interval between the first and last dispensing of the first exposure episode. The year before the onset was the control period. Single short courses of oral glucocorticosteroids or antibiotics were used as proxy indicators for AE. Severity indicators, assessed in the 6 months before initiation of LBA, were used to classify patients' severity. A total of 788 patients met the inclusion criteria (men: 45.1%, median age: 35). The incidence rate of AE increased significantly (p < 0.001) with severity from 1.7 to 2.4 and 1.1 to 2.7 AE per person year in index and control period, respectively. The risk was merely elevated among patients who start LBA therapy without being treated with other anti-asthma drugs before (RR 1.4, 95% CI 1.0-2.2). First starters of LBA showed no overall change in incidence of AE when compared with the year before starting treatment. A total of 6.9% of patients used LBA as step-one therapy. These patients suffer, in contrast to the whole population, a 40% increased risk of having AE. Although this could be due to confounding, we recommend being reluctant to prescribe LBA to patients who have not been treated before with other anti-asthma drugs.

Adolescent↗
PubMed1999

Asthma therapy modulates priming-associated blood eosinophil responsiveness in allergic asthmatics.

Eosinophils play an important role in the pathogenesis of asthma. Several pro-inflammatory responses of eosinophils are primed in vivo in this disease. The aim of the present study was to investigate whether regular antiasthma treatment could modulate priming-sensitive cytotoxic mechanisms of human eosinophils. In a randomized, two-centre, double-blind parallel group study, the effect of 8 weeks of treatment with salmeterol xinafoate 50 microg b.i.d., beclomethasone dipropionate 400 microg b.i.d. or both on pulmonary function and the activation of priming-sensitive cytotoxic mechanisms of eosinophils, i.e. degranulation of eosinophil cationic protein (ECP) in serum, and activation of isolated eosinophils in the context of induction of the respiratory burst and release of platelet-activating factor (PAF) were tested. These effects were evaluated in 40 allergic asthmatics before and 24 h after allergen inhalation challenge. Whereas baseline forced expiratory volume in one second (FEV1) improved in all treatment groups, only treatment with a combination of salmeterol and beclomethasone significantly inhibited the allergen-induced increase in serum ECP, and (primed/unprimed) PAF-release, suggesting inhibition of eosinophil priming after allergen challenge. In contrast to the combination therapy, monotherapy with beclomethasone had no influence on allergen-induced PAF-release, suggesting an additional anti-inflammatory effect of salmeterol during combination therapy. Monotherapy with beclomethasone inhibited the prechallenge serum-treated zymosan (STZ) (0.1 mg mL(-1))-induced respiratory burst and the allergen-induced increase in serum ECP levels, reflecting pre- and postchallenge anti-inflammatory effects. During monotherapy with salmeterol, an allergen-induced increase in serum ECP concentration and STZ (0.1 mg x mL(-1))-induced respiratory burst was observed, suggesting that treatment with salmeterol alone had no effect on priming-sensitive eosinophil cytotoxic mechanisms. In conclusion, this study shows that standard asthma therapy leads to inhibition of eosinophil priming of cytotoxic mechanisms in vivo.

Adrenergic beta-Agonists↗
PubMed1999

Reducing adverse effects of inhaled fenoterol through optimization of the aerosol formulation.

We compared the adverse effects of 160 micrograms of fenoterol in the form of a 2.8-micron monodisperse aerosol with those of 800 micrograms of fenoterol as a conventional metered dose inhaler (MDI) aerosol plus spacer. Previously, a monodisperse aerosol was shown to elicit equivalent degrees of bronchodilation at an 80% lower dose using a standard MDI. A total of 12 healthy volunteers (8 women and 4 men) participated in this study and inhaled in random order a placebo, the monodisperse aerosol, and the MDI aerosol. Changes in serum potassium level, finger tremor, blood pressure, heart rate, and specific airway conductance were measured before and 15 minutes after administration. Compared with placebo, the active aerosols elicited a significant improvement in airway conductance and adverse effects. Serum potassium level decreased by 0.27 mmol/L after the monodisperse aerosol, and the MDI lowered it by 0.67 mmol/L (P = 0.001). Finger tremor also increased less: 0.07 versus 0.29 V (P = 0.029). Changes in cardiovascular parameters were not significantly different from those elicited by the placebo. There were no significant specific airway conductance differences between the two active aerosols. By changing the formulation of MDI aerosols, the occurrence of adverse effects can be reduced.

Absorption↗
PubMed1999

Staging of lymph nodes with FDG dual-headed PET in patients with non-small-cell lung cancer.

Accurate assessment of mediastinal lymph node involvement in patients with non-small-cell lung cancer (NSCLC) is necessary to select patients for direct surgical treatment. The aims of the present study were to assess the feasibility of staging NSCLC with FDG using a dual-headed positron emission tomographic (PET) camera and to compare this non-invasive technique with computed tomography (CT) and lymph node sampling, since both modalities are currently used for staging NSCLC. Thirty-three patients (29 men and 4 women, mean age 60 years) with newly diagnosed NSCLC were studied. In all patients, CT, FDG dual-headed PET and mediastinoscopy were performed within 4 weeks. The results of mediastinoscopy were used to select patients for thoracotomy. For both the assessment of individual lymph node involvement and the patient-based classification, the results of FDG dual-headed PET and CT were compared using the McNemar test. Thirty-one of 187 lymph nodes studied contained tumour metastases. FDG dual-headed PET showed a significantly higher sensitivity (P < 0.001) and specificity (P < 0.001) than CT. FDG dual-headed PET and CT correctly staged 27 and 20 patients, respectively. Due to the significantly higher negative predictive value of FDG dual-headed PET versus CT (P = 0.012), it was a better non-invasive diagnostic tool for selecting patients for surgery. In seven of eight patients, additional intrapulmonary sites of increased uptake were found, which revealed malignancy on histological examination. CT was false-negative in three of these patients. In one patients, increased FDG uptake was caused by an infection. In conclusion, it is possible to stage mediastinal lymph nodes in patients with NSCLC using a dual-headed PET camera. The high negative predictive value of FDG dual-headed PET suggests that mediastinoscopy may be omitted in patients with NSCLC.

Aged↗
PubMed1998

Analysis of signal transduction pathways regulating cytokine-mediated Fc receptor activation on human eosinophils.

Igs can be potent stimulants of eosinophil activation since interaction with IgA or IgG-coated particles can lead to eosinophil degranulation. We have investigated the comparative roles of mitogen-activated protein (MAP) kinases (MAPKs; ERK1/2 and p38) and phosphatidylinositol-3 kinase (PI3K) in the priming and regulation of Fc receptor functioning on human eosinophils utilizing a MAPK kinase (MEK) inhibitor (PD98059), a p38 inhibitor SB203580, and the widely used PI3K inhibitors wortmannin and LY294002. We demonstrate that priming of human eosinophils with Th2-derived cytokines, IL-4 and IL-5, differentially activate phosphotyrosine-associated PI3K and ERK and p38 MAP kinases. This activation can be inhibited by pre-incubation with wortmannin or LY294002, PD98059, and SB203580, respectively. Analysis of the effects of the inhibitors on rosette formation between human eosinophils and IgA- or IgG-coated beads revealed that activation of MEK was not required for IgA binding after priming with IL-4 or IL-5. However, inhibition of MEK did inhibit IL-5-primed binding of IgG-beads. The rosette formation of primed eosinophils with IgA-beads could be completely inhibited by wortmannin and LY294002 treatment, demonstrating a critical role for PI3K. Interestingly, inhibition of the p38 pathway also resulted in a complete blockade of IgA rosette formation. This work demonstrates regulatory control by inside-out signaling of Fc receptors by various cytokines on human eosinophils. Thus in vivo the local production of Th2-derived cytokines will regulate the effector functions of Fc receptors.

Androstadienes↗