Tibial slope in the posterolateral quadrant with and without ACL injury

INTRODUCTION

An increased tibial slope is a risk factor for rupture of the anterior cruciate ligament. In addition, a tibial bone bruise or posterior lateral impression associated with slope changes also poses chronic ligamentous instability of the knee joint associated with an anterior cruciate ligament (ACL) injury. In the majority of cases, the slope is measured in one plane X-ray in the lateral view. However, this does not sufficient represent the complex anatomy of the tibial plateau and especially for the posterolateral quadrant. Normal values from a "healthy" population are necessary to understand if stability of the knee joint is negatively affected by an increasing slope in the posterolateral area. Until now there are no data about the physiological slope in the posterolateral quadrant of the tibial plateau.

MATERIALS AND METHODS

In 116 MRI scans of patients without ligamentous lesions and 116 MRI scans with an ACL rupture, tibial slope was retrospectively determined using the method described by Hudek et al. Measurements were made in the postero-latero-lateral (PLL) and postero-latero-central (PLC) segments using the 10-segment classification. In both segments, the osseous as well as the cartilaginous slope was measured. Measurements were performed by two independent surgeons.

RESULTS

In the group without ligamentous injury the mean bony PLL slope was 5.8° ± 4.8° and the cartilaginous PLL slope was 6.7° ± 4.8°. In the PLC segment the mean bony slope was 6.6° ± 5.0° and the cartilaginous slope was 9.4° ± 5.7°. In the cohort with ACL rupture, the bony and cartilaginous slope in both PLL and PCL were significantly higher (P < 0.001) than in the group without ACL injury (bony PLL 9.8° ± 4.8°, cartilage PLL 10.4° ± 4.7°, bony PLC 10.3° ± 4.8°, cartilage PLL 12.8° ± 4.3°). Measurements were performed independently by two experienced surgeons. There were good inter- (CI 87-98.7%) and good intraobserver (CI 85.8-99.6%) reliability.

CONCLUSION

The bony and the cartilaginous slope in the posterolateral quadrant of the tibial plateau are different but not independent. Patients with an anterior cruciate ligament injury have a significantly steeper slope in the posterolateral quadrant compared to a healthy group. Our data indicate that this anatomic feature might be a risk factor for a primary ACL injury which has not been described yet.

LEVEL OF EVIDENCE

III.

Observing many researchers using the same data and hypothesis reveals a hidden universe of uncertainty

This study explores how researchers' analytical choices affect the reliability of scientific findings. Most discussions of reliability problems in science focus on systematic biases. We broaden the lens to emphasize the idiosyncrasy of conscious and unconscious decisions that researchers make during data analysis. We coordinated 161 researchers in 73 research teams and observed their research decisions as they used the same data to independently test the same prominent social science hypothesis: that greater immigration reduces support for social policies among the public. In this typical case of social science research, research teams reported both widely diverging numerical findings and substantive conclusions despite identical start conditions. Researchers' expertise, prior beliefs, and expectations barely predict the wide variation in research outcomes. More than 95% of the total variance in numerical results remains unexplained even after qualitative coding of all identifiable decisions in each team's workflow. This reveals a universe of uncertainty that remains hidden when considering a single study in isolation. The idiosyncratic nature of how researchers' results and conclusions varied is a previously underappreciated explanation for why many scientific hypotheses remain contested. These results call for greater epistemic humility and clarity in reporting scientific findings.

Analysis of low-dose estrogen on callus BMD as measured by pQCT in postmenopausal women

Background

Osteoporosis affects elderly patients of both sexes. It is characterized by an increased fracture risk due to defective remodeling of the bone microarchitecture. It affects in particular postmenopausal women due to their decreased levels of estrogen. Preclinical studies with animals demonstrated that loss of estrogen had a negative effect on bone healing and that increasing the estrogen level led to a better bone healing. We asked whether increasing the estrogen level in menopausal patients has a beneficial effect on bone mineral density (BMD) during callus formation after a bone fracture.

Methods

To investigate whether estrogen has a beneficial effect on callus BMD of postmenopausal patients, we performed a prospective double-blinded randomized study with 76 patients suffering from distal radius fractures. A total of 31 patients (71.13 years ±11.99) were treated with estrogen and 45 patients (75.62 years ±10.47) served as untreated controls. Calculated bone density as well as cortical bone density were determined by peripheral quantitative computed tomography (pQCT) prior to and 6 weeks after the surgery. Comparative measurements were performed at the fractured site and at the corresponding position of the non-fractured arm.

Results

We found that unlike with preclinical models, bone fracture healing of human patients was not improved in response to estrogen treatment. Furthermore, we observed no dependence between age-dependent bone tissue loss and constant callus formation in the patients.

Conclusions

Transdermally applied estrogen to postmenopausal women, which results in estrogen levels similar to the systemic level of premenopausal women, has no significant beneficial effect on callus BMD as measured by pQCT, as recently shown in preclinical animal models.

Trial registration

Low dose estrogen has no significant effect on bone fracture healing measured by pQCT in postmenopausal women, DRKS00019858. Registered 25th November 2019 - Retrospectively registered. Trial registration number DRKS00019858.

Supplementary information

The online version contains supplementary material available at 10.1186/s12891-020-03713-4.

Visualizing GeoData with R

The processment of information related to a geographic location has long been difficult due to lacking data sources and processing power. The recent changes in the rise of web-based technologies like OpenStreetMap (OSM) and Google Maps change the picture.With R it is possible to execute a large amount of data and to produce appropriate visualisations. The challenge is to find the necessary spatial information. In this paper an overview is given to reflect the possibilities spatial visualisations in the context of social sciences. Moreover, it provides an introduction to spatial visualisation.Sources for spatial data and methods of data collection are described and examples of visualisations are presented. 

Cement augmentation of the proximal femoral nail antirotation for the treatment of osteoporotic pertrochanteric fractures--a biomechanical cadaver study

INTRODUCTION

Proximal femoral fractures will gain increasing importance in the future due to the epidemiological development. Osteoporosis is often a limiting factor in the achievement of implant stability. New nailing systems offer the possibility of augmentation of the femoral neck component with cement. The aim of this study was to perform a biomechanical comparison of implant stability in osteoporotic pertrochanteric fractures using the proximal femoral nail antirotation (PFNA, Synthes GmbH, Umkirch, Germany) with cement augmented and non-augmented blades.

MATERIALS AND METHODS

Bone mineral density (BMD) was measured by dual-energy X-ray absorptiometry (DEXA) in six pairs of fresh-frozen human femurs. Standardised pertrochanteric fractures (AO31-A2.3) were treated with a PFNA. Cement augmentation was performed in six constructs. Axial loading was applied according to a single-leg-stance model using a hydraulic testing machine increasing to 1400N over 10,000 cycles. Biomechanical comparisons between the two groups that were comparable concerning BMD, tip-apex-distance and native stiffness were made with regard to postoperative stiffness, survived cycles, load to failure, failure mechanism and axial displacement.

RESULTS

The stiffness of all stabilised femurs was significantly lower than for native specimens (native 702.5±159.6N/mm vs. postoperative 275.4±53.8N/mm, p<0.001). Stiffness after instrumentation was significantly greater for the cement augmented group than for the non-augmented group (300.6±46.7N/mm vs. 250.3±51.6N/mm, respectively, p=0.001). Five of the twelve constructs survived cyclic testing. Statistically significant differences of the BMD were detected between survived and failed constructs (0.79±0.17g/cm(2) vs. 0.45±0.12g/cm(2), respectively, p=0.028). The failure loads for specimens surviving 10,000 cycles were 4611.9±2078.9N in the cement augmented group (n=3) and 4516.3N and 3253.5N in the non-augmented group (n=2). Postoperative stiffness was found to be a positive predictor of maximum force to failure (R(2)=0.83, p=0.02).

CONCLUSIONS

The results of this biomechanical study show that cement augmentation of the PFNA increases the implant stability in osteoporotic pertrochanteric fractures. Further studies are necessary to evaluate this procedure in providing long term clinical results.

Calcium homeostasis influences radiological fracture healing in postmenopausal women

INTRODUCTION

Recent studies suggest that calcium and 25-[OH]-cholecalciferol represent substantial co-factors in fracture healing. However, there still seems to be no sustainable consensus regarding the influence on fracture healing patterns. In this study, the influence of calcium and vitamin D levels on fracture callus formation was prospectively analysed using pQCT scan.

METHODS

94 postmenopausal females with distal radius fractures and consecutive surgery were included. Calcium, 25-[OH]-cholecalciferol, parathyroid hormone and bone-specific alkaline phosphatase levels were obtained prior surgical treatment and after 6 weeks. A pQCT scan was performed on both sites. Bone mineral density and fracture callus area were determined after detecting the outer border contour at a threshold of 280 mg/ccm. Patients received daily supplements of 1000 mg calcium and 880 IU 25-[OH]-cholecalciferol.

RESULTS

Mean 25-[OH]-cholecalciferol level was 19.61 ± 21.87 ng/ml, mean parathyroid hormone level was 52.6 ± 58.9 ng/l and mean Ca level was 2.23 ± 0.35 mmol/l. After 6 weeks of supplementation a significant increase of calcium (p < 0.001) and 25-[OH]-cholecalciferol (p < 0.001), and a significant decrease of parathyroid hormone (p < 0.001) levels were observed. Sixth week follow-up fracture callus area correlated significantly with postoperative normal range calcium levels on the fractured site (p = 0.006). Bone mineral density correlated with age (p < 0.001), but not with calcium and 25-[OH]-cholecalciferol levels after 6 weeks. All fractures presented timely adequate callus formation.

CONCLUSION

Calcium and parathyroid hormone serum levels influence fracture callus area interpreted as fracture callus formation patterns. Calcium levels within physiological range accounted for highest fracture callus area. Therefore, a balanced calcium homeostasis is required for appropriate callus formation.

Pupil evaluation in addition to Glasgow Coma Scale components in prediction of traumatic brain injury and mortality

Background

Early diagnosis and prediction of traumatic brain injury (TBI) is essential for determining treatment strategies and allocating resources. This study evaluated the predictive accuracy of Glasgow Coma Scale (GCS) verbal, motor and eye components alone, or in addition to pupil size and reactivity, for TBI.

Methods

A retrospective cohort analysis of data from 51 425 severely injured patients registered in the Trauma Registry of the German Society for Trauma Surgery from 1993 to 2009 was undertaken. Only directly admitted patients alive on admission and with complete data on GCS, pupil size and pupil reactivity were included. The unadjusted predictive roles of GCS components and pupil parameters, alone or in combination, were modelled using area under the receiver operating characteristic (AUROC) curve analyses and multivariable logistic regression regarding presence of TBI and death.

Results

Some 24 115 patients fulfilled the study inclusion criteria. Best accuracy for outcome prediction was found for pupil reactivity (AUROC 0·770, 95 per cent confidence interval 0·761 to 0·779) and GCS motor component (AUROC 0·797, 0·788 to 0·805), with less accuracy for GCS eye and verbal components. The combination of pupil reactivity and GCS motor component (AUROC 0·822, 0·814 to 0·830) outmatched the predictive accuracy of GCS alone (AUROC 0·808, 0·800 to 0·815). Pupil reactivity and size were significantly correlated (rs = 0·56, P &lt; 0·001). Patients displaying both unequal pupils and fixed pupils were most likely to have TBI (95·1 per cent of 283 patients). Good outcome (Glasgow Outcome Scale score 4 or more) was documented for only 1929 patients (8·0 per cent) showing fixed and bilateral dilated pupils.

Conclusion

The best predictive accuracy for presence of TBI was obtained using the GCS components. Pupil reactivity together with the GCS motor component performed best in predicting death.

Apoptotic effects on B-cell chronic lymphocytic leukemia (B-CLL) cells of heterocyclic compounds isolated from Guttiferaes

A series of 10 heterocyclic compounds purified from Allanblackia were tested on two B cell lines, ESKOL and EHEB, and on cells from B-CLL patients. Several molecules inhibited the proliferation of both cell lines and promoted apoptosis of B-CLL cells through different mechanisms, some of them elicited a dissipation of the mitochondrial transmembrane potential, other triggered caspase-3 activation and cleavage of the inducible nitric oxide synthase. Blood mononuclear cells and B-lymphocytes from healthy donors appeared less sensitive than B-CLL cells. These results indicate that these molecules may be of interest in the development of new therapies for B-CLL.

Hyperforin, a new lead compound against the progression of cancer and leukemia?

Extracts of the plant St John's wort, Hyperforin perforatum L., have been used for centuries in traditional medicine, notably for the treatment of depression. One of their main lipophilic components, a natural prenylated phloroglucinol termed hyperforin (HF), has been identified as the major molecule responsible for the antidepressant effects of this plant. Within the last few years, a number of studies have demonstrated that HF displays, in addition, several other biological properties of potential pharmacological interest. They include an antibacterial capacity and inhibitory effects on inflammatory mediators. It is worth noting that HF also promotes apoptosis of various cancer cells from solid tumors and hematological malignancies, including B-cell chronic lymphocytic leukemia. In addition, HF inhibits the capacity of migration and invasion of different tumor cells, as well as exhibiting antiangiogenic effects. Altogether, these properties qualify HF as a lead structure for the development of new therapeutic molecules in the treatment of various diseases, including some malignant tumors.

[Pro- and anti-apoptotic role of nitric oxide, NO]

NO displays both pro- and anti-apoptotic properties. The parameters governing these effects begin to be elucidated. Among these figure the nature of the cells, their redox state, the flow and concentration of NO, its possibility to react with superoxide generated at the level of mitochondria. The targets of NO include molecules involved in DNA repair, such as PARP, the DNA-dependent protein kinase (DNA-PK) and p53 which control the transcription of various genes involved in the apoptotic process (bax, cdk inhibitors), and the proteasome which control the degradation of several apoptotic proteins. The inhibition by NO of caspases through S-nitrosylation of their active sites provides a rationale for our understanding of the anti-apoptotic effect of NO, but other mechanisms are involved, such as a regulation of the mitochondrial permeability. A better knowledge of the various steps of the apoptotic process that are affected by NO would allow the design of new pharmacological tools.

Contribution of nitric oxide to the apoptotic process in human B cell chronic lymphocytic leukaemia

B cell chronic lymphocytic leukaemia (B-CLL) is characterised by defective apoptosis that cannot be explained solely on the basis of the known chromosomal abnormalities. We and other have now reported that the leukemic cells spontaneously display the inducible isoform of nitric oxide synthase, iNOS. Inhibition of the iNOS pathway leads to increased apoptosis of the tumoral cells in vitro, indicating that the endogenous release of NO contributes to their resistance to the normal apoptotic process. The factors that induce the expression of iNOS in vivo in the leukemic cells are not yet identified. Yet, as interaction of B-CLL leukemic cells with bone marrow stromal cells promotes their survival, the involvement of adhesion molecules and integrins may be suspected. The engagement of CD23 stimulates iNOS activation in the tumoral cells, suggesting that in vivo interaction of CD23 with one of its recognised ligands may contribute to iNOS induction. A role for CD40-CD40 ligand interaction may also be hypothesised. The mechanisms involved in the anti-apoptotic role of NO are not fully understood, but may implicate the inhibition of caspase activity, hence the impairment of the Fas pathway. In addition, the mitochondrial membrane potential disruption appears to be a NO-sensitive step in the apoptosis cascade. The presence of a NOS displaying anti-apoptotic properties has now been recognised in different cell types, including various leukaemia. A better knowledge of the mechanisms governing the ultimate fate of NO, anti- versus pro-apoptotic would allow the development of new therapeutic approaches for the treatment of these diseases.

Mechanisms involved in the pro- and anti-apoptotic role of NO in human leukemia

Nitric oxide (NO) exerts contrasting effects on apoptosis, depending on its concentration, flux and cell type. In some situations, NO activates the transduction pathways leading to apoptosis, whereas in other cases NO protects cells against spontaneous or induced apoptosis. The redox state of the cells appears to be a crucial parameter for the determination of the ultimate action of NO on cell multiplication and survival. Apoptosis is mostly associated with the delivery of NO by chemical donors and with myelomonocytic cells, whereas antiapoptotic effects seem to be related to the endogenous production of NO by NO synthases and is observed more frequently in cells of the B lymphocyte lineage. Pro-apoptotic effects are often observed when NO reacts with superoxide to produce the highly toxic peroxynitrite. Through the induction of damages to DNA, NO stimulates the expression of enzymes and transcription factors involved in DNA repair and modulation of apoptosis, such as the tumor suppressor p53. The latter molecule transactivates the expression of pro-apoptotic genes, such as bax, and that of the cyclin-dependent kinase inhibitor p21, whereas it down-regulates the expression of the anti-apoptotic protein bcl-2. On the other hand, NO inactivates caspases through oxidation and S-nitrosylation of the active cystein, providing an efficient means to block apoptosis. Other protective effects of NO on apoptosis rely on the stimulation of cGMP-dependent protein kinase (PKG), modulation of the members of the bcl-2/bax family that control the mitochondrial pore transition permeability, induction of the heat shock protein HSP 70 and interaction with the ceramide pathway. A defect in the apoptotic process contributes to the accumulation of tumoral cells in leukemia, notably in B-CLL. A better knowledge of the targets of NO would provide efficient means to control cell apoptosis, and hence would possibly lead to the development of new therapeutic approaches for diseases where an alteration of apoptosis is involved.

Expression of a functional inducible nitric oxide synthase in hairy cell leukaemia and ESKOL cell line

The expression of nitric oxide synthase (NOS) isoforms was investigated in the established ESKOL hairy cell line and in leukemic cells of patients with hairy cell leukemia (HCL). By reverse transcription-polymerase chain reaction (RT-PCR), these cells were found to spontaneously express inducible NOS (iNOS)-specific mRNA, but not endothelial constitutive NOS (ecNOS) mRNA. The iNOS protein was detected by immunofluorescence in the cytoplasm of permeabilized leukemic cells and ESKOL cells, using different anti-iNOS monoclonal antibodies. A protein of 135 kDa was identified by Western blotting in ESKOL and HCL lysates, confirming the presence of an iNOS in these cells. Cytosolic homogenates displayed NOS catalytic activity, as measured by the conversion of 14C-labelled L-arginine into 14C L-citrulline and by detection in situ using the DAF-2DA (diaminofluorescein diacetate) NO-sensitive fluorescent probe. Ligation of CD23 (low affinity IgE receptor) was found to increase iNOS expression in ESKOL and conversely to decrease the percentage of cells undergoing apoptosis, as measured by the percentage of cells expressing annexin V. These results indicate that, as in chronic B cell lymphocytic leukemia cells (B-CLL) a functional iNOS is expressed constitutively in hairy cells that contributes to protecting these tumoral cells from apoptosis.

Regulation of ICAM-1/CD54 expression on human endothelial cells by hydrogen peroxide involves inducible NO synthase

Expression of the inducible isoform of nitric oxide synthase (iNOS) is stimulated by cytokines in human epithelial cells. This work indicates that incubation of human umbilical cord endothelial cells with combinations of interleukin-1beta, tumor necrosis factor alpha, and interferon-gamma stimulated the synthesis of iNOS mRNA, as detected by reverse transcriptase-polymerase chain reaction. It is important to note that 50, 100, and 200 microM hydrogen peroxide was able to stimulate iNOS directly. Furthermore, 100 microM H2O2 enhanced synthesis of the oxidation products, nitrite (NO2-) and nitrate (NO3-) at 12 and 36 h. iNOS protein, detected by Western blot analysis, as well as L-citrulline levels, were also increased. When endothelial cell monolayers were incubated for 1 h with 100 microM H2O2 and subsequently with cytokines, iNOS mRNA was further augmented. Under the same conditions, we regularly observed an inhibition (25%) of intercellular adhesion molecule-1 (ICAM-1/CD54) expression. The latter was reversed when the NOS inhibitor N(G)-monomethyl-L-arginine was added, as shown by flow cytometry. These data suggest a specific effect of endogenous hydroperoxides on the biosynthesis and processing of the human endothelial iNOS isoform. We propose that H2O2 induces a temporary NO-dependent modulation of adhesion molecule expression to limit the tissue destruction that accompanies the vascular recruitment of leukocytes.

Functional properties of soluble CD21

Soluble receptors may display immunoregulatory properties by blocking interactions between ligands and their membrane receptors or by triggering specific biologic responses through interaction with counter part membrane receptors. A natural soluble form of CD21 that is cleaved from lymphocyte membrane CD21 circulates in normal human serum. Soluble CD21 retains the capacity to bind iC3b and CD23, the known ligands of membrane CD21. In a similar fashion to IgE complexes, another ligand of CD23, the soluble CD21 was shown to efficiently trigger CD23-signalling pathways in human monocytes. By inducing release of proinflammatory cytokines and upregulating expression of molecules involved in antigen presentation, soluble CD21 modulates critical monocyte functions that may be relevant to allergic and inflammatory disorders.

Soluble CD21 induces activation and differentiation of human monocytes through binding to membrane CD23

Interactions between CD23, the low-affinity receptor for IgE, and CD21, the C3d/EBV receptor, modulate several intracellular events in lymphocytes. A soluble form of CD21 (sCD21) corresponding to the extracellular domain of the receptor circulates in normal plasma. We now demonstrate that purified sCD21 acts as a functional ligand for CD23-expressing monocytes. Soluble CD21 induced an increase in intracellular cGMP levels and the production of IL-6 and TNF-alpha in IL-4-pretreated monocytes induced to express CD23 but not in unstimulated CD23- monocytes. The accumulation of cGMP and the production of TNF-alpha were inhibited by NG-monomethyl-L-arginine (L-NMMA), indicating that sCD21 activates the L-arginine pathway of NO production. We demonstrated that sCD21 activates NO synthase (NOS) since it was found to enhance the conversion of L-arginine into L-citrulline and induce the intracellular expression of inducible NOS in CD23+ monocytes. In addition, sCD21 was shown to up-regulate the expression of HLA-DR and CD40 and decrease that of CD14 on cultured CD23+ monocytes. Thus, in a fashion similar to IgE complexes, sCD21 is able to efficiently trigger CD23 signaling pathways, inducing the release of pro-inflammatory mediators by human monocytes. Soluble CD21 up-regulates the expression of molecules involved in antigen presentation, further suggesting a potential immunoregulatory function for the soluble molecule.

The induction of nitric oxide by interleukin-12 and tumor necrosis factor-alpha in human natural killer cells: relationship with the regulation of lytic activity

We have investigated the interleukin-12 (IL-12) and tumor necrosis factor-alpha (TNFalpha)-induced regulation of human natural killer (NK) cell function and their relationship with nitric oxide (NO) generation. We demonstrate that both cytokines were efficient to trigger the transcription of the inducible nitric oxide synthase (iNOS) mRNA, as detected by reverse transcriptase-polymerase chain reaction (RT-PCR). Western blot analysis and intracytoplasmic fluorescence showed that iNOS protein was also induced by both cytokines. However, our data indicate that NO does not play a significant role in the effector phase of the cytotoxic activity mediated by NK-stimulated cells, inasmuch as the lytic activity was not affected in the presence of specific NO synthase inhibitors. When aminoguanidine (AMG), an inhibitor of iNOS, was added during the afferent phase of NK stimulation with IL-12 and TNFalpha, a subsequent increase in the lytic potential of the effector cells towards the NK-sensitive target cells (K562) and lymphokine-activated killer (LAK) target cells (Daudi) was observed. Conversely, the addition of chemical NO donors during the afferent step resulted in a dose-dependent inhibition of the NK and LAK cytotoxicity. Our data suggest that the enhancement of NK-cell cytotoxic activity resulting from iNOS inhibition may be correlated, at least in part, to an increase in interferon-gamma production and granzyme B expression.

Regulation by endogenous INTERLEUKIN-10 of the expression of nitric oxide synthase induced after ligation of CD23 in human macrophages

The possible role of interleukin 10 (IL-10) as an endogenous inhibitor of CD23-driven inducible nitric oxide synthase (iNOS) expression in human macrophages was investigated. Cross-linking of CD23 by a monoclonal antibody induced iNOS mRNA, as detected by RT-PCR, and the production of NO measured as the stable derivative, nitrite. A linear correlation was observed between CD23 expression and iNOS activity or NO2- production. The iNOS activity reached a maximum 48 h after ligation of CD23, then declined rapidly until 72 h. In parallel, nitrite production was detected after 24 h and reached a maximum after 48 h. In addition, ligation of the CD23 molecule induced, in a time-dependent manner, the production of IL-10. As this cytokine is known to regulate iNOS induction and activity, we evaluated the effect of a neutralizing mAb to IL-10 on CD23-induced iNOS activity and nitrite production by CD23-bearing macrophages and found that both were significantly enhanced. Furthermore, the addition of exogenous IL-10 suppressed CD23-driven iNOS mRNA expression, iNOS activity and production of nitrite. These data suggest that, after CD23-ligation at the cell surface of human phagocytes, the secretion of IL-10 downregulates the CD23-induced NO production at the transcriptional level, thus providing an efficient feed-back mechanism.

B-cell chronic lymphocytic leukemia cells express a functional inducible nitric oxide synthase displaying anti-apoptotic activity

The expression of different isoforms of nitric oxide synthase (NOS) was investigated in B-cell chronic lymphocytic leukemia (B-CLL) to delineate a possible role for nitric oxide (NO) in the control of apoptosis of the tumoral cells. By reverse transcription-polymerase chain reaction (RT-PCR), all B-CLL cells were found to express spontaneously inducible NOS (iNOS) mRNA, whereas endothelial constitutive NOS (ecNOS) mRNA was undetectable. The iNOS protein was detected by immunofluorescence in the cytoplasm of permeabilized leukemic cells and identified by Western blotting, using different anti-iNOS antibodies, as a protein of 135 kD in B-CLL cytoplasmic extracts. B-CLL cell lysates also displayed basal NOS enzymatic activity, as measured by the conversion of 14C-labeled L-arginine into 14C-L-citrulline. Ligation of CD23, expressed on the vast majority of B-CLL cells, resulted in increased iNOS expression and activity. The NO released exerted an anti-apoptotic effect on B-CLL cells that was counteracted by NOS inhibitors and engagement of the APO-1/Fas pathway. Therefore, the existence of a functional iNOS in B-CLL cells will provide further insights into the mechanisms that control proliferation and apoptosis in these tumor cells.

Nitric oxide production in human macrophagic cells phagocytizing opsonized zymosan: direct characterization by measurement of the luminol dependent chemiluminescence

When differentiated into mature macrophages by the combination of all-trans retinoic acid and 1,25-dihydroxyvitamin D3, the human promonocytic cell lines U937 and THP-1 expressed inducible nitric oxide synthase (iNOS) transcripts. During their differentiation, the cells acquired the capacity to produce not only superoxide anion (O2.-) but also nitric oxide (.NO) in response to IgG (or IgE)-opsonized zymosan. The inhibitors of the iNOS pathway, aminoguanidine and NG-monomethyl-L-arginine (L-NMMA), suppressed the production of .NO and enhanced the steady-state concentration of O2.- determined. Conversely, superoxide dismutase (SOD) scavenged the O2.- released and increased the .NO-derived nitrite concentration detected. These data suggested a possible interaction between O2.- and .NO. In differentiated U937 (or THP-1) cells, IgG or IgE-opsonized zymosan induced a strong time-dependent luminol-dependent chemiluminescence (LDCL), which was abrogated by SOD and partially inhibited by aminoguanidine or L-NMMA. Since the iNOS inhibitors did not directly scavenge O2.-, LDCL determination in the presence or absence of SOD and/or iNOS inhibitors demonstrated a concomitant production of O2.- and .NO. These radicals induced the formation of a .NO-derived product(s), probably peroxynitrite (ONOO-), which was required to elicit maximal LDCL. Finally, LDCL measurement provided a convenient tool to characterize iNOS triggering and demonstrated an interaction between NADPH oxidase and iNOS products in human macrophagic cells phagocytizing opsonized-zymosan. These findings show that in activated macrophages, iNOS activity can be involved in LDCL and support the debated hypothesis of iNOS participation to the microbicidal activity of human macrophages.

Characterization of a constitutive type III nitric oxide synthase in human U937 monocytic cells: stimulation by soluble CD23

The soluble cleavage fragment of the low-affinity immunoglobulin E (IgE) receptor/CD23 (sCD23 25000 MW) and antibodies directed against their receptors on monocytes, CD11b and CD11c, stimulate the production of nitric oxide (NO) by these cells and we have suggested that the enzyme involved could be related to the endothelial constitutive type III nitric oxide synthase (ecNOS). In the present work, we have analysed the characteristic properties of this NOS isoform in the model of the human promonocytic cells U937 By reverse-transcription polymerase chain reaction (RT-PCR), the presence of an mRNA coding for type III NOS was found in U937 cells and the corresponding protein was detected by immunofluorescence in permeabilized cells with a specific anti-ecNOS monoclonal antibody (mAb). Membrane extracts displayed a NOS activity dependent on the presence of calcium and calmodulin in the reaction medium and that was abrogated in the presence of EGTA. Recombinant soluble CD23 (25000 MW) was found to trigger an NO-dependent cGMP accumulation in these cells, which was abrogated by calcium chelators and inhibitors of the calcium/calmodulin complex. Moreover, sCD23 elicited a transient augmentation of intracytoplasmic free calcium concentration [Ca2+]i that was dependent on the presence of calcium in the external buffer and was prevented in the presence of EGTA, indicating that it was due to a calcium influx. In conclusion, human promonocytic cells such as U937 exhibit a functional type III NOS that can be stimulated by calcium-raising agents, such as sCD23.

The 25-kDa soluble CD23 activates type III constitutive nitric oxide-synthase activity via CD11b and CD11c expressed by human monocytes

CD23, a low-affinity receptor for IgE, was recently shown to bind to CD11b and CD11c molecules on human monocytes. The 25-kDa soluble fragment of CD23 (sCD23), was tested for its capacity to elicit various signaling pathways in human monocytes. sCD23 was found to trigger an early increase in cGMP accumulation, through the generation of nitric oxide. This was a result of activating the L-arginine pathway, since the sCD23-mediated effect was inhibited in the presence of substituted nonmetabolizable L-arginine analogues. In addition, the increase in cGMP was suppressed by calcium chelators and inhibitors of the calcium/calmodulin complex, suggesting the involvement of a constitutive, calcium-dependent nitric oxide synthase (NOS). Indeed, the presence of an endothelial constitutive type III NOS mRNA was detected in nonactivated human monocytes, and the corresponding protein has been detected by flow cytometry. Moreover, sCD23 was shown to induce a calcium influx in monocytes, in accordance with an activation of a constitutive NOS through a transient increase in [Ca2+]i. As expected, these events were mimicked by mAbs against CD11b and CD11c, the macrophage receptors for CD23. In addition to these early events, sCD23 and the agonistic anti-CD11b and CD11c mAbs, which all trigger the release of proinflammatory mediators such as TNF-alpha, were shown to act through an NO-dependent process.

The 25-kDa soluble CD23 activates type III constitutive nitric oxide-synthase activity via CD11b and CD11c expressed by human monocytes

CD23, a low-affinity receptor for IgE, was recently shown to bind to CD11b and CD11c molecules on human monocytes. The 25-kDa soluble fragment of CD23 (sCD23), was tested for its capacity to elicit various signaling pathways in human monocytes. sCD23 was found to trigger an early increase in cGMP accumulation, through the generation of nitric oxide. This was a result of activating the L-arginine pathway, since the sCD23-mediated effect was inhibited in the presence of substituted nonmetabolizable L-arginine analogues. In addition, the increase in cGMP was suppressed by calcium chelators and inhibitors of the calcium/calmodulin complex, suggesting the involvement of a constitutive, calcium-dependent nitric oxide synthase (NOS). Indeed, the presence of an endothelial constitutive type III NOS mRNA was detected in nonactivated human monocytes, and the corresponding protein has been detected by flow cytometry. Moreover, sCD23 was shown to induce a calcium influx in monocytes, in accordance with an activation of a constitutive NOS through a transient increase in [Ca2+]i. As expected, these events were mimicked by mAbs against CD11b and CD11c, the macrophage receptors for CD23. In addition to these early events, sCD23 and the agonistic anti-CD11b and CD11c mAbs, which all trigger the release of proinflammatory mediators such as TNF-alpha, were shown to act through an NO-dependent process.

Role of leukotriene B4 in the interleukin-4-induced human mononuclear phagocyte activation

Interleukin-4 (IL-4) induced a time- and dose-dependent production of leukotriene B4 (LTB4) by human resting monocytes indicating that IL-4 induced the activation of the 5-lipoxygenase pathway in resting human monocytes. Maximal effect was observed in the presence of 10 ng/ml IL-4, and in kinetics experiments LTB4 production plateaued 40 min after the onset of stimulation. When stimulated for 48 hr with IL-4, resting human monocytes expressed and released the low-affinity receptor for IgE (CD23) and were partially inhibited in the presence of a highly non-redox 5-lipoxygenase inhibitor (BW B70C), suggesting that the production of LTB4 partially contributed to the IL-4-induced CD23 expression and release. This hypothesis was strengthened by the fact that exogenous LTB4 (10 nM) was found to increase the effect of a suboptimal dose of IL-4 (1 ng/ml). In addition to these phenotypical changes, IL-4 primed the phorbol-12-myristate-13-acetate (PMA)-induced luminol-dependent chemiluminescence response (LDCL) by normal human monocytes, this priming effect being abrogated in the presence of BW B70C. Taken together, these data indicated that IL-4 induced the production of LTB4 by activation of the 5-lipoxygenase pathway in human monocytes, and that the activation of this pathway could upregulate the expression and release of CD23 and the respiratory burst of these cells.

Triggering of CD23b antigen by anti-CD23 monoclonal antibodies induces interleukin-10 production by human macrophages

The aim of this study was to evaluate the capacity of human macrophages to produce interleukin (IL)-10 upon stimulation of membrane CD23. An anti-CD23 monoclonal antibody (mAb) was found to elicit the expression of the specific mRNA for IL-10 in CD23-bearing macrophages, and to induce a time-dependent production of this cytokine with a maximal effect reached after 12 h. Inasmuch as we previously reported that CD23 ligation evoked the generation of nitric oxide and of cAMP, the effect of the Rp diastereoisomer of adenosine 3', 5'-cyclic phosphorothioate (Rp-cAMP, an inhibitor of the cAMP pathway) and of NG-monomethyl-L-arginine (L-NMMA, an inhibitor of the nitric oxide pathway) were evaluated on CD23-induced IL-10 production. In the presence of Rp-cAMP, the CD23-induced production of IL-10 and of the pro-inflammatory cytokine tumor necrosis factor-alpha (TNF-alpha) was totally abrogated, whereas, in the presence of L-NMMA, IL-10 production was enhanced and TNF-alpha production was suppressed. In addition, neutralization of IL-10 with an anti-IL-10 mAb increased both the magnitude and duration of CD23-driven TNF-alpha production. Such an inducing effect was observed with different anti-CD23 mAb (clone 135, MHM6 and 25), indicating that the triggering of the CD23 molecule at the surface of human macrophages induced the generation of IL-10 through a cAMP-dependent mechanism. Concomitantly this generation of IL-10 was down-regulated by nitric oxide, which was also produced after triggering of the CD23 antigen. Taken together these data indicated that human macrophages produced IL-10 after triggering of the CD23 molecule and that this production could regulate the inflammatory state of these cells.

Granulocyte macrophage colony stimulating factor induces Fc epsilon RII/CD23 expression on normal human polymorphonuclear neutrophils

Three major molecules have been recognized as IgE-binding structures on hematopoietic cells: the heterotrimeric high-affinity receptor for IgE (Fc epsilon RI), the low-affinity receptor for IgE (Fc epsilon RII/CD23) and the Mac-2/IgE-binding protein (epsilon BP). The latter has been shown to be expressed on polymorphonuclear neutrophils (PMN), where it regulates IgE-dependent activation. Experiments were undertaken to determine whether the IgE-binding capacity of PMN is mediated exclusively by this molecule. No detectable binding of human myeloma IgE to unstimulated PMN from normal volunteers could be evidenced. In contrast, PMN stimulated with granulocyte macrophage colony stimulating factor (GM-CSF) (500 U/ml) for 24 h displayed positive IgE binding. This binding was significantly inhibited in the presence of mAb directed against Mac-2/epsilon BP and also in the presence of anti-CD23 mAb, but not of anti-Fc epsilon RI mAb or isotype-matched controls. By flow cytometry, CD23 expression was detected on GM-CSF-primed PMN by several anti-CD23 mAb, including EBVCS-5, BB10 or Mab135, which recognize different epitopes. CD23 was also evidenced by immunocytochemistry in GM-CSF-primed PMN. By in situ hybridization, GM-CSF-treated PMN exhibited a hybridization signal for CD23 mRNA and the presence of the CD23b isoform-specific mRNA was detected by RT-PCR. These findings indicate that PMN can synthesize CD23 molecules under GM-CSF induction. This strong CD23 expression might be of physiopathological relevance in IgE-dependent activation during allergic processes.

Nitric oxide production by human monocytes: evidence for a role of CD23

Nitric oxide (NO) appears to be an important and pleiotropic bioregulator of immune responses. The existence of the NO synthase (NOS) pathway in human monocytes/macrophages remains a subject of controversy, despite an increasing number of reports suggesting that human monocytes produce NO in vitro in response to various stimuli. Here, Bernard Dugas and colleagues consider the arguments supporting these conclusions, with particular emphasis on the results obtained by ligation of the low-affinity IgE receptor (Fcepsilon RIIb/CD23b).

Evidence for a role of Fc epsilon RII/CD23 in the IL-4-induced nitric oxide production by normal human mononuclear phagocytes

IL-4 stimulates NO production by human monocytes. After 6 days of culture with IL-4, human monocytes released detectable amounts of nitrite and L-citrulline that were inhibited in the presence of nitro-L-arginine (1 mM). Incubation with an anti-CD23 mAb Fab fragment that suppressed the biological effect of CD23 led to a strong reduction (50 to 70%) of the IL-4-induced nitrite and L-citrulline production. Ligation of membrane-associated CD23 or stimulation with recombinant soluble CD23 elicited monocytes to release nitrite and L-citrulline that was suppressed by nitro-L-arginine. Preactivation of human monocytes with IFN-gamma led to subsequent increased IL-4- and CD23-driven nitrite and L-citrulline productions that were also suppressed in the presence of either nitro-L-arginine or the anti-CD23 mAb Fab fragment. The CD23 molecule under its membrane or soluble form thus regulates NO generation by human monocytes. In addition, the IL-4-induced NO production could be mediated, at least in part, by CD23.

Involvement of CD23/Fc epsilon RII in the homotypic and heterotypic cytoadhesion of the human eosinophilic cell line Eol-3

A subclone of the EoL-3 human eosinophilic leukemia cell line (EoL-3.12) was selected for its high inducibility of CD23 (low affinity IgE receptor/Fc epsilon RII) by IL-4. Maximum membrane CD23 expression was detected after 16 h of incubation with IL-4, then gradually returned to basal level after 48 h. Membrane expression of CD23 on EoL-3.12 cells was found to parallel their homotypic aggregation. Extending the time of incubation with IL-4 to 48 h or more resulted in a de-aggregation of cells of cells with a shedding of membrane CD23 and an increase of its soluble form, sCD23. The IL-4-induced aggregation of EoL-3.12 cells was inhibited with anti-CD23 antibody or human myeloma IgE protein, indicating that it was mediated through the engagement of CD23. EoL3.12 incubated with IL-4 displayed morphological changes associated with differentiation, such as an increased number of lobulated nuclei with prominent nucleoli, increased ratio of cytoplasm and distinct cytoplasmic processes. EoL-3.12 cells incubated with IL-4 also displayed an enhanced adherence to human umbilical vein endothelial cells (HUVEC), which was reverted when the IL-4 incubation time extended. Furthermore, the transendothelial migration of EoL-3.12 cells toward a chemokinetic gradient of soluble CD23 (sCD23; 29 kDa fragment) closely paralleled the density of membrane CD23 expressed on EoL-3.12 cells. Additionally, the engagement of CD23 led to the activation of the L-arginine-dependent pathway of nitric oxide (NO) production, as detected by the increase in intracytoplasmic cGMP concentration. The capacity of EoL-3.12 cells to form homotypic as well as heterotypic adhesion appears therefore to be regulated, at least in part, by the level of CD23 expression.

Ligation of CD23 activates soluble guanylate cyclase in human monocytes via an L-arginine-dependent mechanism

Transduction through Fc epsilon R2/CD23 was analyzed in normal human monocytes using immunoglobulin E (IgE)-anti-IgE immune complexes (IgE ICs) and monoclonal antibodies (mAbs) to CD23. Anti-CD23 mAb and IgE IC triggered a time-dependent increase in cGMP and cAMP in interleukin-4-preincubated (CD23+) but not in unstimulated (CD23-) monocytes. Maximal cGMP and cAMP accumulations were observed 10 and 20 min, respectively, after the onset of CD23 ligation. The increase in cGMP was inhibited with N omega-monomethyl-L-arginine (L-NMMA), which also partially affected cAMP accumulation. Addition of an anti-CD23 mAb Fab fragment inhibited the IgE IC- and the anti-CD23 mAb-induced cGMP and cAMP accumulation, confirming the engagement of CD23. In addition, IgE IC and anti-CD23 mAb induced, at least in some donors, a production of nitrite that was inhibited in the presence of L-NMMA. Taken together, these findings suggest a possible involvement of the nitric oxide synthase pathway in IgE IC-mediated activation of CD23+ monocytes.

[Role of interleukin-4 in the regulation of nitric oxide production by normal human monocytes]

Resting normal human monocytes were found to produce small amounts of cGMP in response to IL-4. This production was inhibited in the presence of LNMMA suggesting an association with activation of the NO synthase (NOS) pathway. In addition, this cGMP generation was abrogated in the presence of either a Ca2+ chelator, EGTA, or a calcium/calmodulin inhibitor, W7, suggesting that IL-4 stimulates the constitutive NOS (cNOS). An enhanced response was observed when monocytes were preincubated with IFN-gamma and whether the cGMP accumulation was still abrogated in the presence of LNMMA it was not affected by either EGTA or W7 suggesting, in that case, the activation of an inducible NOS (iNOS). Taken together these data suggest that IL-4 could stimulate a cNOS in resting and an iNOS in the IFN-gamma-treated human monocytes, indicating that the generation of NO is highly dependent on the maturation state of these cells.

Growth arrest and terminal differentiation of leukemic myelomonocytic cells induced through ligation of surface CD23 antigen

Acute myelogenous leukemia (AML) cells express CD23 surface antigen after in vitro treatment with various cytokines, including interleukin-4 (IL-4) and interferon gamma. Subsequent ligation of CD23 by specific monoclonal antibody (MoAb) induces substantial morphologic and functional modifications in these cells. In the present study, we investigated the role of CD23 in the proliferation and the maturation of leukemic cells from AML patients or the U937 cell line. CD23+ cell treatment with CD23 MoAb inhibited the proliferation of leukemic cells. This correlated with their terminal differentiation after 7 to 9 days incubation because they (1) definitively lost their growth capacity; (2) adhered to culture flasks and became monocyte/macrophage-like; and (3) expressed mature monocyte markers including nonspecific esterases. Intracellular mechanism of this antitumoral effect was then analyzed in U937 cells. Induction of high-density surface CD23 expression by IL-4 or granulocyte-macrophage colony-stimulating factor coincided with a transient decrease of U937 cell proliferation. CD23 ligation during this low-proliferative phase induced a rapid activation of L-arginine-dependent pathway and the intracellular accumulation of cyclic guanosine monophosphate and cyclic adenosine monophosphate (cAMP). Induction of these early messengers was followed by the activation of nuclear factor-kB transcription factor and the modulation of proto-oncogene expression by U937 cells. Whereas U937 cell treatment with IL-4 decreased c-fos/c-jun expression, CD23 MoAb reinduced c-fos/c-jun and promoted the expression of cell maturation-associated proto-oncogenes junB and c-fms, during the first 24 hours. Both IL-4 and CD23 MoAb downregulated the expression of c-myb. CD23 ligation also induced the production of TNF alpha by U937 cells. Inhibitors of cAMP and nitric oxide reversed CD23-mediated modification in U937 cells. These data evidence the ability of CD23 surface antigen to mediate terminal differentiation of early leukemic myelomonocytic cells.

Regulatory role of nitric oxide in the IL-4-induced IgE production by normal human peripheral blood mononuclear cells

An in vitro study was performed in order to assess a possible regulatory role of nitric oxide (NO), a short-lived biologic mediator that displays immunoregulatory properties, in the IL-4-driven synthesis of IgE by normal human peripheral blood mononuclear cells (PBMC). In addition to induce IgE production, IL-4 was found to elicit nitrite (NO2-) release by PBMC. A marked correlation was observed between IgE secretion and nitrite release by PBMC stimulated with an optimal concentration of IL-4. The IL-4-dependent IgE production was significantly reduced (p < 0.001) in the presence of N omega-monomethyl-L-arginine (LNMMA), an inhibitor of the NO-synthase pathway; this inhibition was partially reverted with an excess of L-arginine. Addition to PBMC cultures of the chemical NO donor Sin-1, inactive alone, was found to result, depending on the concentration of IL-4, in either potentiation (suboptimal concentration of IL-4, 10 ng/ml) or inhibition (optimal concentration of IL-4, 50 ng/ml) of IgE synthesis. The potentiating effect of Sin-1 was dose dependent, with a maximal effect for 300 microM, whereas its metabolite Sin-1c was inactive. In both cases, Sin-1 markedly reduced the IL-4-induced release of the soluble form of the low affinity IgE receptor (sCD23). Together, these data strongly suggest that NO may display biphasic immunoregulatory properties on the IL-4-induced IgE production by PBMC.

Heterogenous nitrite production by IL-4-stimulated human monocytes and peripheral blood mononuclear cells

The capacity of human peripheral blood mononuclear cells and monocytes to generate nitrites, spontaneously or in response to Interleukin-4 was evaluated in vitro. Peripheral blood mononuclear cells and monocytes were found to release significant amounts of nitrites after 8 to 12 days in culture. This spontaneous production of nitrites was inhibited in the presence of 1 mM NG monomethyl-L-arginine, suggesting that this process was dependent upon the L-arginine metabolism. The present data also indicated that addition of Interleukin-4 generally resulted in an increased nitrite production, that was potentiated by IFN-gamma, inactive alone. The response of human monocytes to Interleukin-4 was more heterogenous than that observed with unfractionated peripheral blood mononuclear cells. These results suggest that cell/cell interactions could play an important role in the activation of the nitric oxide synthase pathway in human.

Heterogeneous spontaneous and interleukin-4-induced nitric oxide production by human monocytes

The generation of nitric oxide by human monocytes has long been a subject of controversy because of the difficulty of rationalizing this production. In this work we evaluated the capacity of human monocytes to produce nitric oxide (NO) as measured by nitrite (NO2-) release. Resting unstimulated monocytes (2 x 10(6) cells/ml) were found to produce significant amounts of NO2- after 8 to 12 days in culture. This production appeared to be highly heterogeneous. Indeed, approximately, 75% of monocytes from the different donors produced up to 10 microM NO2- and were considered low producers; the last 25% produced higher amounts of NO2- (from 10 to 110 microM) and were considered high producers. In any case the spontaneous production of NO2- by monocytes was overcome in the presence of 1 mM N omega-monomethyl-L-arginine (LNMMA). This inhibitory effect was reversed in the presence of an excess of L-arginine (5 mM), indicating that this process is effectively dependent on L-arginine metabolism. Because interleukin-4 (IL-4) is considered an important NO-regulatory cytokine, its regulatory effect on this spontaneous production of NO was also evaluated. In the presence of a defined dose of IL-4 (1 to 100 ng/ml) the spontaneous production of the high-producing population of monocytes was abrogated, whereas IL-4 stimulated the production by the low-producing population of monocytes, which was suppressed in the presence of LNMMA. The present data indicate that NO production by human monocytes is heterogeneous and that IL-4 can be a potent inducer or inhibitor of this production, suggesting a variability in the activation state of these cells.

Involvement of Fc epsilon RII/CD23 and L-arginine-dependent pathway in IgE-mediated stimulation of human monocyte functions

Elevated IgE levels are commonly observed during the inflammatory responses in allergy and a variety of infections. This Ig activates the release of multiple mediators from monocytes/macrophages. In the present work, we attempted to clarify the IgE-dependent events involved in the activation of monocyte functions. IgE-anti-IgE immune complexes induce the production of tumor necrosis factor-alpha, oxygen radicals, IL-6 and thromboxane B2 from normal human purified monocytes. Expression and cross-linkage of Fc epsilon RII/CD23 were essential for these IgE-mediated effects. Cytokine production following CD23 ligation depended on nitric oxide transduction pathway, as it was inhibited by NG-monomethyl-L-arginine, a competitive inhibitor of the conversion of L-arginine to L-citroline by nitric oxide synthase. Furthermore, addition of the nitric oxide chemical donator, Sin-1, enhanced IgE-induced monokine release. CD23-ligation also induced the production of nitrites by these cells. This work linked CD23 to the L-arginine-dependent transduction pathway and shows their involvement in IgE-mediated stimulation of human monocytes.

Leukotriene B4 enhances IL-4-induced IgE production from normal human lymphocytes

Interleukin 4 (IL-4)-induced IgE production by normal peripheral blood mononuclear cells (PBMC) and E- cells (PBMC partially depleted of T cells) was significantly enhanced by leukotriene B4(LTB4) in a dose-dependent manner, whereas LTB4 by itself was not effective for IgE production. The potentiating effect of LTB4 was strictly dependent on IL-4. When PBMC or E- cells were primed with IL-4 (300 U/ml) for 48 hr, then recultured with LTB4 alone (10(-10) to 10(-8) M), increased IgE production was observed. Maximum enhancement of IgE production after IL-4 priming was achieved using a combination of IL-4 and LTB4, acting additively. Moreover, the potentiating effect of LTB4 on IL-4-induced IgE production was completely dependent on the presence of a monocyte/macrophage population. This effect of LTB4 was completely abolished by depletion of monocytes and recovered by reconstitution with autologous monocytes. From the study of IL-4 receptor (IL-4R) expression determined by flow cytometry, IL-4 was found to upregulate the biotinylated-IL-4 (B-IL-4)/streptavidin binding to both T- and B-cell populations. A further increase of B-IL-4 binding was obtained when the cells were incubated with IL-4 and LTB4. Finally, LTB4 can induce soluble CD23 (sCD23) release by E- cells tested either alone or in the presence of IL-4. Taken together, these data suggest that LTB4 can influence the IL-4-induced IgE production through, at least, a bimodal action, i.e., increase of IL-4R positive cells and release of sCD23. These findings may be a specific feature of LTB4 which provides a crucial role in IL-4-linked allergic inflammatory process.

Interleukin-4 stimulates cGMP production by IFN-gamma-activated human monocytes. Involvement of the nitric oxide synthase pathway

Resting human blood monocytes from some donors were found to produce a small amount of 3'-5' guanine cyclic monophosphate (cGMP) in response to interleukin 4 (IL-4). A much higher response was observed when monocytes were preincubated with interferon (IFN-gamma), which alone was ineffective. Preincubation of monocytes with IL-4 led, in contrast, to their subsequent incapacity to generate cGMP in response to IL-4. The accumulation of cGMP induced by IL-4 in IFN-gamma preincubated monocytes was dose-dependent and peaked about 15 min after its addition. It was inhibited in the presence of NG-mono-methyl-L-arginine (L-NMMA), an inhibitor of the nitric oxide synthase pathway. This suppressive effect of L-NMMA was reverted by an excess of L- but not of D-arginine. Accumulation of cGMP was significantly reduced by addition of soluble guanylyl cyclase inhibitors, such as LY83583 [correction of LY83853] and methylene blue, but was not impaired in the presence of EGTA, suggesting that the pathway involved is calcium independent. In addition, IL-4 induced an increased secretion of nitrite by monocytes, that was potentiated by IFN-gamma and inhibited by L-NMMA. Taken together, these results suggest that the sequential exposure of monocytes to IFN-gamma and IL-4 elicits the release of NO from L-arginine, which in turn is capable to stimulate soluble guanylyl cyclase.

Purified excretory-secretory component of filarial parasite enhances Fc epsilon RII/CD23 expression on human splenic B and T cells and IgE synthesis while potentiating T-helper type 2-related cytokine generation from T cells

The CD23-bearing cells are known to be involved in multiple biological activities, including IgE synthesis and IgE-dependent cytotoxicity to parasites. The factors that regulate interleukin-4 (IL-4)-induced IgE synthesis in helminthic infection were analysed by using an excretory-secretory component (ESC) of Dirofilaria immitis (DI). Human splenic B and T cells significantly enhanced the expression of low-affinity Fc receptors for IgE (Fc epsilon RII/CD23) by stimulation with ESC, either acting alone or in synergy with IL-4. On B cells, ESC potentiated the CD23 expression in synergy with IL-4, whereas ESC alone was unable to modulate CD23 expression. In contrast, ESC directly induced CD23 expression on T cells by acting alone and no further enhancement was observed in the presence of IL-4. Furthermore, IL-4-induced IgE synthesis by splenic mononuclear cells (SMNC) was greatly enhanced in the presence of ESC. Of particular interest, T cells primed by ESC significantly produced a set of cytokines including IL-3, IL-4, IL-5 and IL-6. Inasmuch, IL-4-induced IgE synthesis in helminthic infection may be selectively modulated by parasite protein(s) acting on the generation of T-helper type 2 (Th2)-related cytokines.

Beta 2-adrenoceptor agonists regulate the IL-4-induced phenotypical changes and IgE-dependent functions in normal human monocytes

The beta 2-adrenoceptor agonists salbutamol and fenoterol were tested for their regulatory effects on human monocyte phenotype and functions, either alone or in combination with interleukin-4 (IL-4). These drugs enhanced in a dose-dependent manner the IL-4-induced membrane and mRNA expression of the low-affinity receptor for immunoglobulin E (IgE) (CD23), as well as the release of its soluble form, sCD23. Salbutamol and fenoterol alone elicited expression of the monomorphic beta 2-chain (CD18) of the leukocyte functional antigen (LFA1) family. This effect appeared to be restricted to CD11b (CR3) and CD11c (gp 150-95), because CD11a (LFA-1 alpha chain) was not modified. beta 2-Adrenoceptor stimulation was also found to potentiate the effect of IL-4 on CD11b, CD11c, and CD18 expression. In contrast, these agents alone did not alter the level of major histocompatibility complex class II and CD14 antigens or modify their respective up- and down-regulation by IL-4. Ligation of CD23 on IL-4-preincubated (CD23+) monocytes with IgE/anti-IgE immune complexes induced the release of free radicals nitric oxide and of the proinflammatory mediators IL-6 and thromboxane B2 (TxB2). Addition of salbutamol, inactive alone, potentiated the generation of superoxide anion and of nitric oxide generation, as well as the production of IL-6 and TxB2 triggered by CD23 ligation. These results indicate that beta 2-adrenoceptor stimulation potentiates in vitro the IL-4-induced phenotypical and functional changes on monocytes and suggest that such an interaction could occur in IgE-dependent immune reactions.

CD23-mediated cell signalling

Signal transduction through ligation of the CD23 (Fc epsilon RII) molecule was analysed in human B cells and monocytes. Monoclonal antibodies directed against the IgE binding site of CD23 were found to trigger phosphoinositide hydrolysis and calcium mobilization in B cells, but not in monocytes. These early events were also obtained with an IgE+anti-IgE complex, which supposedly mimicks the physiological situation of a multivalent antigen inducing the cross-linking of cell-bound IgE. Redistribution of CD23 was also found to evoke cAMP accumulation both in B lymphocytes and monocytes. Moreover, we present evidence indicating a possible cross-talk between the IL-4- and CD23-induced second messengers. We suggest that the alternative transduction pathways elicited by ligation of CD23 are linked to the CD23 isoform(s) expressed by these cells and may result from their association with different sets of molecules.

CD23 and IgE expression during the human immune response to cutaneous leishmaniasis: possible role in monocyte activation

Leishmania brasiliensis causes cutaneous leishmaniasis (CL) in humans. During this infection, a variety of inflammatory mediators are produced by T cells and monocytes/macrophages. In the present study, we analysed serum IgE levels and their correlation with in situ expression of the low affinity receptor for IgE (Fc epsilon RII/CD23) in patients infected with L. brasiliensis before and following therapy. These analyses were compared to in situ expression of tumour necrosis factor-alpha (TNF alpha), interleukin 3 (IL3), interferon-gamma (IFN gamma) and IL4. Disease-free individuals from the same endemic area sensitized with L. brasiliensis antigens were also included in this work. Our data indicate that during infection, serum levels of IgE and TNF alpha increased and correlated with elevated in situ expression of CD23, IL4 and TNF alpha mRNA. This expression disappeared following successful treatment, but persisted in patients resistant to anti-leishmania therapy. Patients resistant to therapy differed from other cases by a dramatic decrease in their in vivo expression of IFN gamma protein. Analysis of CD23 function in purified human monocytes indicated that this antigen mediates IgE/anti-IgE-dependent TNF alpha production. These data suggest a possible in vivo role of CD23 in acute immune responses in human CL.

1,1'-Ethylidenebis(tryptophan) (Peak E) induces functional activation of human eosinophils and interleukin 5 production from T lymphocytes: association of eosinophilia-myalgia syndrome with a L-tryptophan contaminant

This study was designed to clarify the important association between eosinophilia-myalgia syndrome (EMS) and the L-tryptophan contaminant, "Peak E." To determine the functional activation of eosinophils induced by Peak E, eosinophil cationic protein (ECP) release was examined. Peak E augumented the release of ECP from peripheral blood normodense eosinophils by degranulation. Proliferative analysis using the human eosinophilic leukemia cell line EoL-3 showed prominent cellular replication in the presence of Peak E. Moreover, Peak E upregulated interleukin 5 (IL-5) receptor levels on normodense eosinophils. Of particular interest, Peak E-stimulated human splenic T cells produced bioactive and immunoreactive IL-5. Marked induction of IL-5 mRNA in Peak E-stimulated T cells was also shown by reverse-transcriptase polymerase chain reaction (RT-PCR). In contrast, L-tryptophan without the contaminant showed none of these effects. Thus, these data suggest that Peak E might be involved in the pathogenesis of EMS through bimodal mechanism including IL-5 generation by T cells and potentiation of eosinophil functional activation.

Inhibitors of protein tyrosine kinases and protein tyrosine phosphatases suppress IL-4-induced CD23 expression and release by human B lymphocytes

The pleiotropic lymphokine IL-4 is a growth and differentiation factor for human B cells. IL-4 induces the expression of the CD23 (Fc epsilon RII) molecule on B lymphocytes and promotes the release of its soluble form (sCD23); the cleavage fragments of the latter have been reported to modulate IL-4-dependent IgE biosynthesis. In the present work, we have tested the effects of inhibitors of protein tyrosine kinases (PTK) and protein phosphatases (PP) on the induction by IL-4 of the membrane and soluble forms of CD23. The PTK inhibitors genistein and lavendustin A were found to suppress, in a dose-dependent way, the induction by IL-4 of CD23 membrane expression as well as CD23 release by resting and SAC-preactivated B lymphocytes. No such suppression was detected with inhibitors of serine and threonine kinases. The addition of the protein tyrosine phosphatase (PTP) inhibitor sodium orthovanadate also resulted in a marked decrease in CD23 induction by IL-4. Cell viability was little affected by these inhibitors. However, a diminution of the large activated B cell population was observed, which correlated with an inhibition of the entry in the S phase. Partial inhibition of sCD23 release was also observed with okadaic acid and calyculin A, two inhibitors of serine/threonine PP, but only at concentrations which block PP1 in addition to PP2A. These results suggest that protein tyrosine phosphorylation and dephosphorylation may play a major role in IL-4 signalling. This conclusion was strengthened by the observation that a mAb anti-CD45, a membrane tyrosine phosphatase, inhibited IL-4-induced sCD23 release by B lymphocytes.

Biochemical and functional alterations induced by CD23 ligation in the human promonocytic cell line U937

The early events triggered in interleukin-4 (IL-4)-stimulated U937 cells by ligation of CD23/Fc epsilon RII with specific monoclonal antibodies (mAb) were analysed, as a model of the action of this molecule on the differentiation of promonocytic cells. As well as IL-4-activated human monocytes, addition of anti-CD23 mAb to IL-4-treated U937 cells triggered cAMP accumulation but did not evoke significant polyphosphoinositide hydrolysis. However, by a microspectrofluorometric technique allowing single cell analysis, anti-CD23 mAb was found to elicit calcium mobilization in these cells. In addition, the treatment induced phenotypic alterations in these cells, as evidenced by the acquisition of the monocyte marker CD14 and the increase of the alpha-chain (CD11a) and of the common beta-chain (CD18) of the leucocyte function-associated antigen 1 (LFA-1) family antigens. Although weaker than in monocytes, CD23 ligation evoked a small secretion of the pro-inflammatory mediators IL-6 and thromboxane B2. These data suggest that a significant maturation of promonocytic cells towards a more mature monocytic phenotype can be achieved through successive exposure to IL-4 and CD23 ligation.

Leukotriene B4 induces interleukin 5 generation from human T lymphocytes

Leukotriene B4 (LTB4) has been shown to affect several interleukin (IL)-linked functions of human lymphocytes. In this study, we investigated whether LTB4 regulates IL-5 generation from human T cells and subsequently modulates eosinophil functions. Preincubation of T cells with very low concentrations (10(-12) to 10(-8) M) of LTB4 induced concentration-dependent IL-5 production, the event occurring after the first 24 h of cultivation. However, direct action of LTB4 to IL-5 generation is strictly dependent on a preincubation with appropriate concentration of LTB4. In contrast, the stereoisomer of LTB4, 5S,12S-dihydroxy-6,8,10,14-eicosatetraenoic acid showed no enhancement of IL-5 production. IL-5 released from LTB4-primed T cells elicited sustained viability of mature eosinophils and reduced the content of eosinophil cationic protein in their crystalloid matrix by degranulation. These data suggest that LTB4 induces bioactive IL-5 production from T cells and that the released IL-5 modulates eosinophil functions which might play a crucial role in eosinophil-linked allergic inflammatory process.