Technical Innovation in Critical Care in a World of Constraints: Lessons from the COVID-19 Pandemic

The COVID-19 crisis was characterized by a massive need for respiratory support, which has unfortunately not been met globally. This situation mimicked those which gave rise to critical care in the past. Since the polio epidemic in the 50's, the technological evolution of respiratory support has enabled health professionals to save the lives of critically-ill patients worldwide every year. However, much of the current innovation work has turned around developing sophisticated, complex, and high-cost standards and approaches whose resilience is still questionable upon facing constrained environments or contexts, as seen in resuscitation work outside intensive care units, during pandemics, or in low-income countries. Ventilatory support is an essential life-saving tool for patients with respiratory distress. It requires an oxygen source combined to a ventilatory assistance device, an adequate monitoring system, and properly trained caregivers to operate it. Each of these elements can be subject to critical constraints, which we can no longer ignore. The innovation process should incorporate them as a prima materia, whilst focusing on the core need of the field using the concept of frugal innovation. Having a universal access to oxygen and respiratory support, irrespective of the context and constraints, necessitates: i) developing cost-effective, energy-efficient, and maintenance-free oxygen generation devices; ii) improving the design of non-invasive respiratory devices (for example, with oxygen saving properties); iii) conceiving fully frugal ventilators and universal monitoring systems; iv) broadening ventilation expertise by developing end-user training programs in ventilator assistance. The frugal innovation approach may give rise to a more resilient and inclusive critical care system. This paradigm shift is essential for the current and future challenges.

Epidural analgesia in ICU chest trauma patients with fractured ribs: retrospective study of pain control and intubation requirements

BACKGROUND

Nonintubated chest trauma patients with fractured ribs admitted to the intensive care unit (ICU) are at risk for complications and may require invasive ventilation at some point. Effective pain control is essential. We assessed whether epidural analgesia (EA) in patients with fractured ribs who were not intubated at ICU admission decreased the need for invasive mechanical ventilation (IMV). We also looked for risk factors for IMV.

STUDY DESIGN AND METHODS

This retrospective, observational, multicenter study conducted in 40 ICUs in France included consecutive patients with three or more fractured ribs who were not intubated at admission between July 2013 and July 2015.

RESULTS

Of the 974 study patients, 788 were included in the analysis of intubation predictors. EA was used in 130 (16.5%) patients, and 65 (8.2%) patients required IMV. Factors independently associated with IMV were chronic respiratory disease (P = 0.008), worse SAPS II (P < 0.0001), flail chest (P = 0.02), worse Injury Severity Score (P = 0.0003), higher respiratory rate at admission (P = 0.02), alcohol withdrawal syndrome (P < 0.001), and noninvasive ventilation (P = 0.04). EA was not associated with decreases in IMV requirements, median numerical rating scale pain score, or intravenous morphine requirements from day 1 to day 7.

CONCLUSIONS

EA was not associated with a lower risk of IMV in chest trauma patients with at least 3 fractured ribs, moderate pain, and no intubation on admission. Further studies are needed to clarify the optimal pain control strategy in chest trauma patients admitted to the ICU, notably those with severe pain or high opioid requirements.

Rovibrational hybrid fs/ps CARS using a volume Bragg grating for N₂ thermometry

Coherent anti-Stokes Raman scattering (CARS) spectra of N2 in the hybrid femtosecond/picosecond regime have been recorded with 0.7  cm(-1) resolution. The Q-branch rovibrational structure has been resolved, making it suitable for gas-phase simultaneous rotational and vibrational thermometry applications. Resolving this spectral structure requires synchronization of a narrowband picosecond probe pulse with a broadband femtosecond pair of pump and Stokes pulses. It is achieved using a single femtosecond ytterbium-laser source and a volume Bragg grating in a compact experimental arrangement.

Longwave infrared, single-frequency, tunable, pulsed optical parametric oscillator based on orientation-patterned GaAs for gas sensing

We demonstrate a nanosecond single-frequency nested cavity optical parametric oscillator (NesCOPO) based on orientation-patterned GaAs (OP-GaAs). Its low threshold energy of 10 μJ enables to pump it with a pulsed single-frequency Tm:YAP microlaser. Stable single-longitudinal-mode emission is obtained owing to Vernier spectral filtering provided by the dual-cavity doubly-resonant NesCOPO scheme. Crystal temperature tuning covers the 10.3-10.9 μm range with a quasi-phase-matching period of 72.6 μm. A first step toward the implementation of this device in a differential absorption lidar is demonstrated by carrying out short-range standoff detection of ammonia vapor around 10.4 μm. Owing to the single-frequency emission, interferences due to absorption by atmospheric water vapor can be discriminated from the analyte signal.

Spectrotemporal dynamics of a picosecond OPO based on chirped quasi-phase-matching

We report on the first experimental investigation of the spectral dynamics of a synchronously pumped optical parametric oscillator (OPO) by use of dispersive Fourier transformation. For standard pumping rates, we observe a reproducible steady-state pulse-to-pulse spectrum. However, at high pumping levels, the OPO delivers pulse trains with nontrivial oscillatory spectral patterns. So as to benefit from a tailored broadband gain spectrum, the investigated OPO contains a chirped quasi-phase matching (QPM) nonlinear crystal. We explore the specific impacts of using such a remarkable parametric amplification medium where nonlinearly coupled frequencies vary with position. Depending on the QPM chirp rate sign, a red- or blue-shift of the emitted wavelength occurs when the OPO is switched on, leading to different spectral steady-states. These singular spectrotemporal dynamics are evidenced and explained for the first time.

Multispecies high-energy emitter for CO₂, CH₄, and H₂O monitoring in the 2 μm range

We demonstrate the first emitter, based on a single optical source device, capable of addressing three species of interest (CO₂, CH₄, and H₂O) for differential absorption Lidar remote sensing of atmospheric greenhouse gases from space in the 2 μm region. It is based on an amplified nested cavity optical parametric oscillator. The single frequency source shows a total conversion efficiency of 37% and covers the 2.05-2.3 μm range.

[Impact of age on mortality in patients with acute traumatic spinal cord injury requiring intensive care]

OBJECTIVE

To evaluate the impact of age (<or≥65 ans) on hospital mortality in traumatic spinal cord injury requiring intensive care.

DESIGN

Retrospective, monocenter.

PATIENTS AND METHODS

A total of 131 patients greater or equal to 15 years (<65 years, n=109 and ≥65 years, n=22) was analyzed (cervical, n=71; thoracolumbar, n=60), over a 10 years period (1998-2008). The hospital and long-term mortality were studied. The risks factors of death were searched by a uni- and multivariate analysis. Intensive care unit (ICU) discharge and long-term neurological recovery, and long-term functional independence measure (FIM) were assessed.

RESULTS

Hospital mortality was increased in patients greater or equal to 65 years (41% vs 6%, P<0.001) and long term mortality was not different between the two groups (31% vs 12%, P=0.150). The risks factors of death were age (HR=3.44; IC 95%: 1.53-7.72, P=0.028), previous coronary disease (HR=3.64; IC 95%: 1.25-10.65; P=0.018) and fall injury (HR=2.40; IC 95%: 1.15-5.00, P=0.020). Among survivors, incompletes forms (Frankel B, C, D, E) were significantly more frequent in older patients at ICU discharge and long term follow up. At long term, FIM was similar in the two groups except a better sphincter control in patient greater or equal to 65 years.

CONCLUSION

Mortality rate of older people (≥65 years) were greater than those in younger people, mainly caused by an increased hospital mortality. Among survivors, the neurological recovery was better in patients' greater or equal to 65 years, and was associated with a functional status at least comparable than in the youngest patients.

Photon extrabunching in ultrabright twin beams measured by two-photon counting in a semiconductor

For many years twin beams originating from parametric down-converted light beams have aroused great interest and attention in the photonics community. One particular aspect of the twin beams is their peculiar intensity correlation functions, which are related to the coincidence rate of photon pairs. Here we take advantage of the huge bandwidth offered by two-photon absorption in a semiconductor to quantitatively determine correlation functions of twin beams generated by spontaneous parametric down-conversion. Compared with classical incoherent sources, photon extrabunching is unambiguously and precisely measured, originating from exact coincidence between down-converted pairs of photons, travelling in unison. These results strongly establish that two-photon counting in semiconductors is a powerful tool for the absolute measurement of light beam photon correlations at ultrashort timescales.

Compact, single-frequency, doubly resonant optical parametric oscillator pumped in an achromatic phase-adapted double-pass geometry

We report on a nested-cavity, doubly resonant optical parametric oscillator (NesCOPO) architecture for widely tunable, mid-IR, single-frequency generation. By use of an achromatic phase-adapted double-pass pumping scheme, this new, low-threshold, semimonolithic architecture only requires two free-standing cavity mirrors and a nonlinear crystal with a mirror coating deposited on its input facet while the other facet is antireflection coated. It is thus as simple and compact as any basic linear optical parametric oscillator cavity, is easily tunable, and displays low sensitivity to mechanical vibrations. Using a high-repetition-rate (4.8 kHz) microlaser as the pump source of the NesCOPO, we demonstrate a compact source that provides pulsed, stable single-frequency output over a wide spectral range (3.8-4.3 μm) with a high peak power (up to 50 W), which are properties well suited for practical gas sensing applications.

Passive mode locking of optical parametric oscillators: an efficient technique for generating sub-picosecond pulses

We show that optical parametric generation in a nonlinear crystal with a large group velocity mismatch between the pump and nearly-degenerate signal and idler is analogous to laser amplification in the medium with a gain recovery time comparable to the walk-off time. Based on this conclusion we propose to combine an OPO with a nonlinear saturable absorber or Kerr lens to generate directly high peak power sub-picosecond pulses using pump pulses ranging from tens of picoseconds to quasi-CW. Our analytical model predicts better than 80% photon conversion efficiency and pulse lengths that are of the order of a few hundred femtoseconds. Numerical simulations confirm our predictions and show that repetitive passive mode locking is feasible with a quasi-CW pump.

Loss of oncostatin M receptor beta in metastatic melanoma cells

Oncostatin M (OSM) is an interleukin-6 (IL-6) type cytokine originally described by its capacity to inhibit melanoma proliferation in vitro. Here, the mechanisms involved in resistance to growth inhibition by OSM were analysed for the first time on a large panel of metastatic melanoma cell lines. OSM resistance did not strictly correlate with IL-6, interferon-gamma or tumor necrosis factor-alpha resistance. Rather, it correlated with a specific loss of the OSM receptor-beta (OSMRbeta) subunit, in conjunction with a lower level of histone acetylation in the OSMRbeta promoter region. Treatment of various OSM-resistant melanoma cells with the histone deacetylase inhibitor Trichostatin A increased activity and histone acetylation of the OSMRbeta promoter as well as expression of OSMRbeta mRNA and protein, allowing OSM to activate the signal transducer and activator of transcription 3 (STAT3) and to inhibit proliferation. Other defects associated with OSM resistance were identified at the level of OSMRbeta transcription or protein expression, as well as downstream of or parallel to STAT3 activation. Altogether, our results suggest a role for OSM in the prevention of melanoma progression and that metastatic melanoma cells could escape this growth control by the epigenetic silencing of OSMRbeta.

Identification of agonistic and antagonistic antibodies against gp190, the leukemia inhibitory factor receptor, reveals distinct roles for its two cytokine-binding domains

The receptor for the cytokine leukemia inhibitory factor (LIF) associates the low affinity binding component gp190 and the high affinity converter gp130, both of which are members of the family of hematopoietic receptors characterized by the cytokine receptor homology (CRH) domain. The gp190 is among the very few members of this large family to contain two CRH domains. The membrane-distal one (herein called D1) is followed by an Ig-like domain, a membrane-proximal CRH domain called D2, and three type III fibronectin repeats. We raised a series of monoclonal antibodies specific for the human gp190. Among them was the blocking antibody 1C7, which was directed against the D1Ig region and which impaired the binding of LIF to gp190. Another blocking antibody, called 12D3, was directed against domain D2 and interfered with the reconstitution of the high affinity receptor complex, independently of the interaction between LIF and gp190. The blocking effect of these two antibodies concerned four cytokines known to use gp190, i.e. LIF, oncostatin M, ciliary neurotrophic factor, and cardiotrophin-1. Among 23 antibodies tested alone or in combination (two anti-D2 and 21 anti-D1Ig), only the mixture of the two anti-D2 antibodies displayed agonistic activity in the absence of the cytokine. Taken together, these results demonstrate that the two CRH domains of gp190 play different functions in ligand binding and receptor activation.

Relaxation of the alignment tolerances of a 1.55-mum extended-cavity semiconductor laser by use of an intracavity photorefractive filter

Commercial grating-tuned single-mode extended-cavity semiconductor lasers (ECLDs) can be tuned over 100 nm near 1.55mum . This continuous tuning with no mode hopping requires delicate factory adjustments and high mechanical stability so that the wavelength precision is kept as high as possible and the mismatch between the lasing wavelength and the wavelength of minimum loss remains as small as possible. The addition of a photorefractive crystal inside the cavity creates an adaptive spectral filter that decreases the loss of the lasing mode and thus enhances its stability. For what is to our knowledge the first time, we demonstrate the extension of the available wavelength-mismatch range without mode hopping by the addition of a CdTe photorefractive crystal inside the cavity of a single-mode grating-tuned ECLD.

Oncostatin M regulates the synthesis and turnover of gp130, leukemia inhibitory factor receptor alpha, and oncostatin M receptor beta by distinct mechanisms

The cytokine receptor subunits gp130, leukemia inhibitory factor receptor alpha (LIFRalpha), and oncostatin M receptor beta (OSMRbeta) transduce OSM signals that regulate gene expression and cell proliferation. After ligand binding and activation of the Janus protein-tyrosine kinase/STAT and mitogen-activated protein kinase signal transduction pathways, negative feedback processes are recruited. These processes attenuate receptor action by suppression of cytokine signaling and by down-regulation of receptor protein expression. This study demonstrates that in human fibroblasts or epithelial cells, OSM first decreases the level of gp130, LIFRalpha, and OSMRbeta by ligand-induced receptor degradation and then increases the level of the receptors by enhanced synthesis. The transcriptional induction of gp130 gene by OSM involves STAT3. Various cell lines expressing receptor subunits to the different interleukin-6 class cytokines revealed that only LIFRalpha degradation is promoted by activated ERK and that degradation of gp130, OSMRbeta, and a fraction of LIFRalpha involves mechanisms that are separate from signal transduction. These mechanisms include ligand-mediated dimerization, internalization, and endosomal/lysosomal degradation. Proteosomal degradation appears to involve a fraction of receptor subunit proteins that are ubiquitinated independently of ligand binding.

Ortho-directed metallation of π-deficient heterocycles in connection with palladium-catalyzed biaryl cross-coupling — Synthesis of marine alkaloids of the pyridoacridine series

Connection between ortho-directed metallation of π-deficient heterocycles and Suzuki cross-coupling reactions provides a very efficient and fruitful strategy to polycyclic molecules of biological interest. The methodology is used to synthesize alkaloids or precursors and analogues of natural compounds of the pyrido[2,3,4-k,l]acridine series.Key words: marine alkaloids, pyrido[2,3,4-k,l]acridines, metallation, cross-coupling.

Interleukin-15 expression in cutaneous T-cell lymphoma (mycosis fungoides and Sezary syndrome)

BACKGROUND

Cytokines are of potential importance in the pathogenesis of cutaneous T-cell mediated disorders, including cutaneous T-cell lymphoma (CTCL).

OBJECTIVES

To compare interleukin (IL)-15 expression in certain inflammatory cutaneous diseases, with that in CTCL (mycosis fungoides and Sézary syndrome).

METHODS

IL-15 mRNA and protein expression were examined by in situ hybridization and immunohistochemistry, respectively, on formalin-fixed, paraffin-embedded biopsies of normal human skin, atopic dermatitis, psoriasis, parapsoriasis and CTCL.

RESULTS

Despite similar expression of IL-15 mRNA, we found differences in IL-15 protein expression between normal human skin, atopic dermatitis and psoriasis on the one hand, and parapsoriasis and CTCL on the other. IL-15 protein expression was not detected in normal human skin, atopic dermatitis or psoriasis, but was detected, mainly at low levels but in a few patients at higher levels, in epidermal keratinocytes in parapsoriasis, mycosis fungoides and Sézary syndrome.

CONCLUSIONS

Induction of keratinocyte IL-15 expression appears to be a feature of CTCL. The factors stimulating such an expression remain unknown.

First total synthesis of phenylpyridine analogues of the antimitotic rhazinilam

The first synthesis of phenylpyridine analogues of rhazinilam and evaluation of these new structures as inhibitors of microtubule disassembly by interaction with tubulin are described. The synthesis is based on such key steps as picolinic metalation, hetero-ring cross-coupling and reduction of an acetyl group to an ethyl group. Elaboration of a quaternary picolinic carbon is one of the challenges of the synthesis. Biological evaluation of compounds bearing a quaternary picolinic carbon showed interactions with tubulin similar to (-)-rhazinilam but at a lower level.

New synthesis of benzo-delta-carbolines, cryptolepines, and their salts: in vitro cytotoxic, antiplasmodial, and antitrypanosomal activities of delta-carbolines, benzo-delta-carbolines, and cryptolepines

The paper describes, in its first part, a new synthesis of benzo-delta-carbolines, cryptolepines, and their salts. The strategy is based on the association between halogen-dance and hetero-ring cross-coupling. It is fully convergent and regioselective with interesting overall yields from 27% to 70%. A halogen-dance mechanism in quinoline series is also proposed. The formal synthesis of potential antimalarial compounds and the first total synthesis of 11-isopropylcryptolepine are also described. In the second part, cytotoxic activity against mammalian cells and activities against Plasmodium falciparum and Trypanosoma cruzi of benzo-delta-carbolines and delta-carbolines were evaluated in vitro to study the structure-activity relationships. For benzo-delta-carbolines, methylation at N-5 increases the cytotoxic and antiparasitic activities. A further alkylation on C-11 generally increases the cytotoxic activity but not the antiparasitic activity, cryptolepine and 11-methylcryptolepine being the most active on both parasites. Taking advantage of the fluorescence of the indoloquinoline chromophore, cryptolepine was localized by fluorescence microscopy in parasite DNA-containing structures suggesting that these compounds act through interaction with parasite DNA as proposed for cryptolepine on melanoma cells. For delta-carbolines, methylation at N-1 is essential for the antimalarial activity. 1-Methyl-delta-carboline specifically accumulates in the intracellular parasite. It has weak cytotoxic activity and can be considered as a potential antimalarial compound.

Stimulation of leukemia inhibitory factor receptor degradation by extracellular signal-regulated kinase

Leukemia inhibitory factor (LIF) signals via the heterodimeric receptor complex comprising the LIF receptor alpha subunit (LIFRalpha) and the common signal transducing subunit for interleukin-6 cytokine receptors, gp130. This study demonstrates that in different cell types, the level of LIFRalpha decreases during treatment with LIF or the closely related cytokine oncostatin M (OSM). Moreover, insulin and epidermal growth factor induce a similar LIFRalpha down-regulation. The regulated loss of LIFRalpha is specific since neither gp130 nor OSM receptor beta shows a comparable change in turnover. LIFRalpha down-regulation correlates with reduced cell responsiveness to LIF. Using protein kinase inhibitors and point mutations in LIFRalpha, we demonstrate that LIFRalpha down-regulation depends on activation of extracellular signal-regulated kinase 1/2 and phosphorylation of the cytoplasmic domain of LIFRalpha at serine 185. This modification appears to promote the endosomal/lysosomal pathway of the LIFRalpha. These results suggest that extracellular signal-regulated kinase-activating factors like OSM and growth factors have the potential to lower specifically LIF responsiveness in vivo by regulating LIFRalpha half-life.

Subunit structure of the high and low affinity human interleukin-15 receptors

Radio-iodinated cytokines and monoclonal antibodies directed at the IL-2R beta- and gamma-chains were used to analyze the structure of the cell-surface IL-15 and IL-2 receptors expressed by the human lymphoma cell clone YT-2C2. YT-2C2 cells are IL-2R alpha negative and express IL-2R gamma (15,000 molecules/cell) in excess of IL-2R beta (11,000 molecules/cell). Accordingly, they display a number of beta/gamma complexes of intermediate affinity for IL-2 and IL-15 which is equivalent to the number of beta-chains. Both cytokines compete for binding to this beta/gamma complex. There are about 800 high affinity IL-15 receptors, suggesting the presence of a similar number of IL-15R alpha-chains. Within the common intermediate affinity beta/gamma-complex, the anti-beta-chain A41 mAb defines an epitope which is similarly engaged in IL-2 and IL-15 binding, whereas the anti-beta-chain 284 mAb defines an epitope which does not display similar interaction with either cytokines. Thus, although IL-2 and IL-15 compete for binding to this beta/gamma-complex, they do not use similar binding areas. Cross-linking and immunoprecipitation experiments have shown that the high affinity IL-15 receptors comprises IL-2R beta/gamma, in association with IL-15R alpha and that the three chains can be efficiently cross-linked to IL-15 and co-immunoprecipitated. Contrary to the intermediate affinity situation, high affinity IL-15 binding and subunit cross-linking were not affected by excess amounts of IL-2, A41 or 284 mAb, suggesting that when engaged in the IL-15 high affinity complex, the beta- and gamma-chains adopt different conformations, at least with respect to IL-15 binding. Finally, we provide evidence for the participation of a novel 35 kDa component within the high affinity structure. This component is immunoprecipitated with anti-IL-2R gamma mAb but not with anti-IL-2R beta mAb and might correspond to a truncated form of IL-2R gamma-chain.

Effect of cytokines and lipid mediators on the synthesis of interleukin 1 beta by human bone marrow stromal cells

This study investigates the production of interleukin (IL-)1beta by cultured human bone marrow stromal cells. RT-PCR experiments indicate that two-thirds of cultures constitutively express IL-1beta mRNA transcripts. Their cell-associated IL-1beta levels are elevated after stimulation with tumour necrosis factor (TNF-)alpha but not with cytokines such as IL-1alpha, IL-3, IL-4, IL-6, IL-7, IL-10, SCF, G-CSF, M-CSF and TGF-beta or lipid mediators such as PGE2, LTB4, LXA4, LXB4, 12-HETE, 15-HETE and PAF. Addition of IL-4, but not IL-10 or TGF-beta, reduces the TNF-alpha-induced cell-associated IL-1beta. IL-1beta is never detected in bone marrow stromal cell supernatants whatever the stimulant added. In conclusion the pro-inflammatory molecule TNF-alpha stimulates bone marrow stromal cell-associated IL-1beta levels while the anti-inflammatory cytokine IL-4 reduces the TNF-alpha-induced effect. These results strengthen the key regulatory role of IL-4 on the production of haematopoietic cytokines by human bone marrow stromal cells.

Natural splicing of exon 2 of human interleukin-15 receptor alpha-chain mRNA results in a shortened form with a distinct pattern of expression

We report the existence of eight different interleukin-15 receptor alpha-chain (IL-15Ralpha) transcripts resulting from exon-splicing mechanisms within the IL-15Ralpha gene. Two main classes of transcripts can be distinguished that do or do not (Delta2 isoforms) contain the exon 2-coding sequence. Both classes were expressed in numerous cell lines and tissues (including peripheral blood lymphocytes) at comparable levels and could be transcribed in COS-7 cells, and the proteins were expressed at the cell surface. Both receptor forms displayed numerous glycosylation states, reflecting differential usage of a single N-glycosylation site as well as extensive O-glycosylations. Whereas IL-15Ralpha bound IL-15 with high affinity, Delta2IL-15Ralpha was unable to bind IL-15, thus revealing the indispensable role of the exon 2-encoded domain in cytokine binding. A large proportion of IL-15Ralpha was expressed at the nuclear membrane with some intranuclear localization, supporting a potential direct action of the IL-15.IL-15Ralpha complex at the nuclear level. In sharp contrast, Delta2IL-15Ralpha was found only in the non-nuclear membrane compartments, indicating that the exon 2-encoded domain (which is shown to contain a potential nuclear localization signal) plays an important role in receptor post-translational routing. Together, our data indicate that exon 2 splicing of human IL-15Ralpha is a natural process that might play regulatory roles at different levels.

Mannose 6-Phosphate/Insulin-like growth factor II receptor mediates internalization and degradation of leukemia inhibitory factor but not signal transduction

Leukemia inhibitory factor (LIF) is a multifunctional cytokine belonging to the interleukin-6 subfamily of helical cytokines, all of which use the glycoprotein (gp) 130 subunit for signal transduction. The specific receptor for LIF, gp190, binds this cytokine with low affinity and is also required for signal transduction. We have recently reported that glycosylated LIF produced by transfected Chinese hamster ovary cells also binds to a lectin-like receptor, mannose 6-phosphate/insulin-like growth factor II receptor (Man-6-P/IGFII-R) (Blanchard, F., Raher, S., Duplomb, L., Vusio, P., Pitard, V., Taupin, J. L., Moreau, J. F., Hoflack, B., Minvielle, S., Jacques, Y., and Godard, A. (1998) J. Biol. Chem. 273, 20886-20893). The present study shows that (i) mannose 6-phosphate-containing LIF is naturally produced by a number of normal and tumor cell lines; (ii) other cytokines in the interleukin-6 family do not bind to Man-6-P/IGFII-R; and (iii) another unrelated cytokine, macrophage-colony-stimulating factor, is also able to bind to Man-6-P/IGFII-R in a mannose 6-phosphate-sensitive manner. No functional effects or signal transductions mediated by this lectin-like receptor were observed in various biological assays after LIF binding, and mannose 6-phosphate-containing LIF was as active as non-glycosylated LIF. However, mannose 6-phosphate-sensitive LIF binding resulted in rapid internalization and degradation of the cytokine on numerous cell lines, which suggests that Man-6-P/IGFII-R plays an important role in regulating the amounts of LIF available in vivo.

Lipid mediators modulate the synthesis of interleukin 8 by human bone marrow stromal cells

Bone marrow stromal cells regulate marrow haematopoiesis by secreting interleukins (IL) such as IL-8. Lipid mediators modulate IL-8 synthesis in numerous cell types. We have investigated the effects of 5 lipid mediators (PAF, PGE(2), LTB(4), 12-HETE and 15-HETE) on the spontaneous and cytokine-induced IL-8 synthesis by human bone marrow stromal cells. By using reverse-transcriptase polymerase chain reaction (RT-PCR) we demonstrate that these cells constitutively express IL-8 transcripts. By using a specific ELISA, we found that the production of IL-8 by marrow stromal cells is enhanced after stimulation with 12-HETE (1 microM) both in serum-free and serum-containing culture medium. LTB(4)(1 microM) enhances IL-8 production only in serum-supplemented medium. PAF, PGE(2)and 15-HETE (1 microM to 0.1 nM) have no effect on the spontaneous and serum-induced production of IL-8 by human bone marrow stromal cells. PGE(2)(1 microM or 10 nM) reduces marrow stromal cell IL-8 synthesis in response to IL-1alpha or TNF-alpha. In contrast, PAF, 12-HETE, 15-HETE and LTB(4)have no effect. In conclusion, various lipid mediators modulate the spontaneous, serum- or cytokine-induced IL-8 synthesis by bone marrow stromal cells, highlighting, for the first time, their potential role in the regulation of IL-8 production within the human bone marrow.

Heterotaxy-neural tube defect and holoprosencephaly occuring independently in two sib fetuses

We report on two sib fetuses, products of a consanguineous union, who had multiple and apparently unrelated malformations. The first fetus, a female, had trilobed lungs, a single cardiac ventricle, asplenia, situs ambiguus of the liver, and a lumbosacral meningomyelocele. The brain of this fetus was normal. The second fetus, a male, had bilobed lungs, a single cardiac ventricle, situs solitus of the abdominal organs and spleen, and a semilobar holoprosencephaly. The occurrence of these malformations in sibs of different sexes and the parental consanguinity suggest a recessive mutation in a gene responsible for both heterotaxy and midline defects, including holoprosencephaly.

Binding of leukemia inhibitory factor (LIF) to mutants of its low affinity receptor, gp190, reveals a LIF binding site outside and interactions between the two cytokine binding domains

The gp190 transmembrane protein, the low affinity receptor for the leukemia inhibitory factor (LIF), belongs to the hematopoietin family of receptors characterized by the cytokine binding domain (CBD). gp190 is one of the very few members of this family to contain two such domains. The membrane-proximal CBD (herein called D2) is separated from the membrane-distal one (called D1) by an immunoglobulin-like (Ig) domain and is followed by three fibronectin type III repeats. We used truncated gp190 mutants and a blocking anti-gp190 monoclonal antibody to study the role of these repeats in low affinity receptor function. Our results showed that the D1Ig region was involved in LIF binding, while D2 appeared to be crucial for the proper folding of D1, suggesting functionally important interactions between the two CBDs in the wild-type protein. In addition, a point mutation in the carboxyl terminus of the Ig region strongly impaired ligand binding. These findings suggest that at least two distinct sites, both located within the D1Ig region, are involved in LIF binding to gp190, and more generally, that ligand binding sites on these receptors may well be located outside the canonical CBDs.

Presence of leukaemia inhibitory factor (LIF) and LIF-receptor chain (gp190) in osteoclast-like cells cultured from human giant cell tumour of bone. Ultrastructural distribution

The behaviour of multinucleated giant cells (MNC) obtained from a giant cell tumour of the tibia and cultured on glass coverslips or on devitalized dentin slices was investigated using light and electron microscopy. Cells were studied in the presence or absence of LIF a cytokine known to be involved in bone turnover and to act as a growth factor in some solid tumours. The direct effect of LIF on MNC was examined by a post-embedding colloidal gold immunocytochemistry process using human anti-LIF and anti-LIF-receptor (chain gp190) antibodies. After 7 days of culture, the MNC obtained displayed osteoclast immunocytochemical features. Moreover, these MNC were able to resorb large amounts of dentin and presented typical features of active osteoclasts. Immunolocalization of LIF and LIF-receptor revealed the presence of this cytokine and its receptor within the cytoplasm and nucleus of active resorbing MNC. LIF upmodulated MNC number and nucleation but decreased their ability to resorb dentin. The present study suggests that MNC obtained from human GCT, currently considered as osteoclast-like cells, are targets for LIF and may be a source of LIF production in this pathological condition.

Expression of leukemia inhibitory factor by cartilage-forming tumors of bone: an immunohistochemical study

Recent studies have implicated leukemia inhibitory factor in connective-tissue metabolism involving the remodeling of bone and the destruction of cartilage tissue. This cytokine, which has also been implicated in the proliferation of solid tumor, is expressed by osteotropic tumor cell lines. The present study investigated the presence of leukemia inhibitory factor in cartilage tissue harvested from cartilage-forming bone tumors. Immunohistochemical study showed that it was present in all benign enchondromas (n = 8) and malignant chondrosarcomas (n = 6) but not in control tissue (n = 3). The cytokine was localized in only cytoplasmic areas of cartilage cells. The number of stained cells ranged from less than 5% in enchondroma of the hand to more than 70% in grade-III chondrosarcoma. Moreover, high levels of leukemia inhibitory factor were found in the primary culture of tumor tissues (n = 7). These results question the significance of leukemia inhibitory factor in tumor-associated bone resorption and the potential role of this cytokine as a prognostic marker.

Interleukin-4 (IL-4), but not IL-10, regulates the synthesis of IL-6, IL-8 and leukemia inhibitory factor by human bone marrow stromal cells

Leukemia inhibitory factor (LIF), interleukin 6 (IL-6) and IL-8 are important regulators of inflammation and hematopoiesis. Human bone marrow stromal cells regulate marrow hematopoiesis by secreting cytokines. By using reverse-transcriptase polymerase chain reaction (RT-PCR), we demonstrate that human bone marrow stromal cells constitutively express LIF, IL-6 and IL-8 transcripts. By using specific ELISAs, we found that their spontaneous productions of LIF, IL-6 and IL-8 are elevated in response to serum and after stimulation with the pro-inflammatory cytokines IL-1alpha and TNF-alpha. The anti-inflammatory cytokine IL-4 reduces their serum- and cytokine-induced LIF secretion. By contrast, IL-4 stimulates their serum- and IL-1alpha-induced IL-6 synthesis. IL-4 has no effect on the serum-induced IL-8 synthesis by marrow stromal cells, but stimulates their cytokine-induced IL-8 production. The anti-inflammatory cytokine IL-10 has no effect on the serum- and cytokine-induced LIF, IL-6 and IL-8 synthesis by bone marrow stromal cells. RT-PCR experiments reveal the presence of IL-4 receptor alpha-chain mRNA and IL-10 receptor mRNA in cultured bone marrow stromal cells. The differential regulation by IL-4 of two related cytokines, such as LIF and IL-6, and the enhanced effect of this 'anti-inflammatory' cytokine on IL-6 and IL-8 synthesis highlight the tightly controlled regulation and the complexity of the cytokine production within the human bone marrow.

Leukemia inhibitory factor and oncostatin M influence the mineral phases formed in a murine heterotopic calcification model: a Fourier transform-infrared microspectroscopic study

The study of bone mineralization processes is of considerable interest in understanding bone diseases and developing new therapies for skeletal disorders, particularly since bone homeostasis requires numerous cell types and a large cytokine network. Cell culture models of mineralization have often been used to study the cellular mechanisms of mineralization, but few data have been reported concerning the influence of extracellular matrix components and cytokines on the physicochemical properties of mineral. The purpose of this study was to analyze the effects of two cytokines, leukemia inhibitory factor (LIF) and oncostatin M (OSM), involved in bone metabolism on the physicochemical properties of bone mineral formed in a murine in vivo mineralization model. Murine bone marrow cells implanted under the kidney capsule in the presence or absence of cytokines led to heterotopic ossicle formation. A scanning electron microscopic microprobe revealed that heterotopic calcification had a lower (approximately 20%) Ca/P ratio after cytokine treatment as compared with the control without cytokine. Transmission electron microscopic analysis of cytokine-treated ossicles showed numerous areas with low mineral density, whereas electron diffraction pattern revealed an apatitic phase. These areas were not observed in the absence of cytokine. Moreover, Fourier transform-infrared microspectroscopy showed at the molecular level that the presence of either cytokine induced many microscopic areas in which short-range order organization, such as incorporation of carbonate and crystallinity/maturity of ossicle mineral, were modified. LIF and OSM influenced mineral phase formation in the present model and may thus be key protagonists in bone mineral development and skeletal diseases.

The mannose 6-phosphate/insulin-like growth factor II receptor is a nanomolar affinity receptor for glycosylated human leukemia inhibitory factor

Comparison of the binding properties of non-glycosylated, glycosylated human leukemia inhibitory factor (LIF) and monoclonal antibodies (mAbs) directed at gp190/LIF-receptor beta subunit showed that most of the low affinity (nanomolar) receptors expressed by a variety of cell lines are not due to gp190. These receptors bind glycosylated LIF produced in Chinese hamster ovary cells (CHO LIF) (Kd = 6.9 nM) but not Escherichia coli-derived LIF or CHO LIF treated with endoglycosidase F. CHO LIF binding to these receptors is neither affected by anti-gp190 mAbs nor by anti-gp130 mAbs and is specifically inhibited by low concentrations of mannose 6-phosphate (Man-6-P) (IC50 = 40 microM), suggesting that they could be related to Man-6-P receptors. The identity of this LIF binding component with the Man-6-P/insulin-like growth factor-II receptor (Man-6-P/IGFII-R) was supported by several findings. (i) It has a molecular mass very similar to that of the Man-6-P/IGFII-R (270 kDa); (ii) the complex of LIF cross-linked to this receptor is immunoprecipitated by a polyclonal anti-Man-6-P/IGFII-R antibody; (iii) this antibody inhibits LIF and IGFII binding to the receptor with comparable efficiencies; (iv) soluble Man-6-P/IGFII-R purified from serum binds glycosylated LIF (Kd = 4.3 nM) but not E. coli LIF. The potential role of Man-6-P/IGFII-R in LIF processing and biological activity is discussed.