Interleukin 1 induces cultured human endothelial cell production of granulocyte-macrophage colony-stimulating factor

The Molecular and Genetic Mechanisms of Inherited Bone Marrow Failure Syndromes: The Role of Inflammatory Cytokines in Their Pathogenesis

Inherited bone marrow failure syndromes (IBMFSs) include Fanconi anemia, Diamond-Blackfan anemia, Shwachman-Diamond syndrome, dyskeratosis congenita, severe congenital neutropenia, and other rare entities such as GATA2 deficiency and SAMD9/9L mutations. The IBMFS monogenic disorders were first recognized by their phenotype. Exome sequencing has validated their classification, with clusters of gene mutations affecting DNA damage response (Fanconi anemia), ribosome structure (Diamond-Blackfan anemia), ribosome assembly (Shwachman-Diamond syndrome), or telomere maintenance/stability (dyskeratosis congenita). The pathogenetic mechanisms of IBMFSs remain to be characterized fully, but an overarching hypothesis states that different stresses elicit TP53-dependent growth arrest and apoptosis of hematopoietic stem, progenitor, and precursor cells. Here, we review the IBMFSs and propose a role for pro-inflammatory cytokines, such as TGF-β, IL-1β, and IFN-α, in mediating the cytopenias. We suggest a pathogenic role for cytokines in the transformation to myeloid neoplasia and hypothesize a role for anti-inflammatory therapies.

Diversity of Vascular Niches in Bones and Joints During Homeostasis, Ageing, and Diseases

The bones and joints in the skeletal system are composed of diverse cell types, including vascular niches, bone cells, connective tissue cells and mineral deposits and regulate whole-body homeostasis. The capacity of maintaining strength and generation of blood lineages lies within the skeletal system. Bone harbours blood and immune cells and their progenitors, and vascular cells provide several immune cell type niches. Blood vessels in bone are phenotypically and functionally diverse, with distinct capillary subtypes exhibiting striking changes with age. The bone vasculature has a special impact on osteogenesis and haematopoiesis, and dysregulation of the vasculature is associated with diverse blood and bone diseases. Ageing is associated with perturbed haematopoiesis, loss of osteogenesis, increased adipogenesis and diminished immune response and immune cell production. Endothelial and perivascular cells impact immune cell production and play a crucial role during inflammation. Here, we discuss normal and maladapted vascular niches in bone during development, homeostasis, ageing and bone diseases such as rheumatoid arthritis and osteoarthritis. Further, we discuss the role of vascular niches during bone malignancy.

Obesity-induced inflammation: The impact of the hematopoietic stem cell niche

Obesity and obesity-related diseases like type 2 diabetes (T2D) are prominent global health issues; therefore, there is a need to better understand the mechanisms underlying these conditions. The onset of obesity is characterized by accumulation of proinflammatory cells, including Ly6c^hi monocytes (which differentiate into proinflammatory macrophages) and neutrophils, in metabolic tissues. This shift toward chronic, low-grade inflammation is an obese-state hallmark and highly linked to metabolic disorders and other obesity comorbidities. The mechanisms that induce and maintain increased inflammatory myelopoiesis are of great interest, with a recent focus on how obesity affects more primitive hematopoietic cells. The hematopoietic system is constantly replenished by proper regulation of hematopoietic stem and progenitor (HSPC) pools in the BM. While early research suggests that chronic obesity promotes expansion of myeloid-skewed HSPCs, the involvement of the hematopoietic stem cell (HSC) niche in regulating obesity-induced myelopoiesis remains undefined. In this review, we explore the role of the multicellular HSC niche in hematopoiesis and inflammation, and the potential contribution of this niche to the hematopoietic response to obesity. This review further aims to summarize the potential HSC niche involvement as a target of obesity-induced inflammation and a driver of obesity-induced myelopoiesis.

Bone Angiogenesis and Vascular Niche Remodeling in Stress, Aging, and Diseases

The bone marrow (BM) vascular niche microenvironments harbor stem and progenitor cells of various lineages. Bone angiogenesis is distinct and involves tissue-specific signals. The nurturing vascular niches in the BM are complex and heterogenous consisting of distinct vascular and perivascular cell types that provide crucial signals for the maintenance of stem and progenitor cells. Growing evidence suggests that the BM niche is highly sensitive to stress. Aging, inflammation and other stress factors induce changes in BM niche cells and their crosstalk with tissue cells leading to perturbed hematopoiesis, bone angiogenesis and bone formation. Defining vascular niche remodeling under stress conditions will improve our understanding of the BM vascular niche and its role in homeostasis and disease. Therefore, this review provides an overview of the current understanding of the BM vascular niches for hematopoietic stem cells and their malfunction during aging, bone loss diseases, arthritis and metastasis.

Inflammatory bone marrow microenvironment

Self-renewing hematopoietic stem cells and their progeny, lineage-specific downstream progenitors, maintain steady-state hematopoiesis in the bone marrow (BM). Accumulating evidence over the last few years indicates that not only primitive hematopoietic stem and progenitor cells (HSPCs), but also cells defining the microenvironment of the BM (BM niche), sense hematopoietic stress signals. They respond by directing and orchestrating hematopoiesis via not only cell-intrinsic but also cell-extrinsic mechanisms. Inflammation has many beneficial roles by activating the immune system in tissue repair and as a defense mechanism. However, chronic inflammation can have detrimental effects by stressing HSPCs, leading to cell (DNA) damage resulting in BM failure or even to leukemia. Emerging data have demonstrated that the BM microenvironment plays a significant role in the pathogenesis of hematopoietic malignancies, in particular, through disrupted inflammatory signaling, specifically in niche (microenvironmental) cells. Clonal selection in the context of microenvironmental alterations can occur in the context of toxic insults (eg, chemotherapy), not only aging but also inflammation. In this review, we summarize mechanisms that lead to an inflammatory BM microenvironment and discuss how this affects normal hematopoiesis. We pay particular attention to the process of aging, which is known to involve low-grade inflammation and is also associated with age-related clonal hematopoiesis and potentially malignant transformation.

Impact of inflammation on early hematopoiesis and the microenvironment

Steady-state hematopoiesis is maintained by slowly dividing, self-renewing hematopoietic stem cells (HSCs) and their offspring, lineage-specified downstream progenitors in bone marrow (BM). It was previously thought that hematopoietic stresses such as infection or other inflammatory stimuli, are mostly recognized by terminally differentiated immune cells, i.e., front-line defenders at the local site of reaction, and that they produce factors that directly act on hematopoietic stem and progenitors (HSPCs) in BM and subsequently stimulate them to rebuild and sustain the hemato-lymphatic system. However, accumulating evidence now indicates that primitive HSPCs, as well as microenvironmental cells in BM are also able to sense systemically migrating hematopoietic stress signals, and respond by orchestrating on-site hematopoiesis via direct and indirect mechanisms. While inflammation has many beneficial roles in activating the immune system for defense or facilitating tissue repair, it also shows detrimental effects if sustained chronically, i.e., might lead to HSPC damage as bone marrow failure or leukemia. Thus, inflammation requires tight control of initiation and termination in time and space dependent manner.

Inflamm-Aging of Hematopoiesis, Hematopoietic Stem Cells, and the Bone Marrow Microenvironment

All hematopoietic and immune cells are continuously generated by hematopoietic stem cells (HSCs) and hematopoietic progenitor cells (HPCs) through highly organized process of stepwise lineage commitment. In the steady state, HSCs are mostly quiescent, while HPCs are actively proliferating and contributing to daily hematopoiesis. In response to hematopoietic challenges, e.g., life-threatening blood loss, infection, and inflammation, HSCs can be activated to proliferate and engage in blood formation. The HSC activation induced by hematopoietic demand is mediated by direct or indirect sensing mechanisms involving pattern recognition receptors or cytokine/chemokine receptors. In contrast to the hematopoietic challenges with obvious clinical symptoms, how the aging process, which involves low-grade chronic inflammation, impacts hematopoiesis remains undefined. Herein, we summarize recent findings pertaining to functional alternations of hematopoiesis, HSCs, and the bone marrow (BM) microenvironment during the processes of aging and inflammation and highlight some common cellular and molecular changes during the processes that influence hematopoiesis and its cells of origin, HSCs and HPCs, as well as the BM microenvironment. We also discuss how age-dependent alterations of the immune system lead to subclinical inflammatory states and how inflammatory signaling might be involved in hematopoietic aging. Our aim is to present evidence supporting the concept of “Inflamm-Aging,” or inflammation-associated aging of hematopoiesis.

Exogenous endothelial cells as accelerators of hematopoietic reconstitution

Despite the successes of recombinant hematopoietic-stimulatory factors at accelerating bone marrow reconstitution and shortening the neutropenic period post-transplantation, significant challenges remain such as cost, inability to reconstitute thrombocytic lineages, and lack of efficacy in conditions such as aplastic anemia. A possible means of accelerating hematopoietic reconstitution would be administration of cells capable of secreting hematopoietic growth factors. Advantages of this approach would include: a) ability to regulate secretion of cytokines based on biological need; b) long term, localized production of growth factors, alleviating need for systemic administration of factors that possess unintended adverse effects; and c) potential to actively repair the hematopoietic stem cell niche. Here we overview the field of hematopoietic growth factors, discuss previous experiences with mesenchymal stem cells (MSC) in accelerating hematopoiesis, and conclude by putting forth the rationale of utilizing exogenous endothelial cells as a novel cellular therapy for acceleration of hematopoietic recovery.

The potential role of recombinant hematopoietic colony-stimulating factors in preventing infections in the immunocompromised host

Hematopoietic colony-stimulating factors coordinate the proliferation and maturation of bone marrow and peripheral blood cells during normal hematopoiesis. Most of these factors are now available as recombinant human colony-stimulating factors, and preclinical and clinical testing is proceeding rapidly. Granulocyte and granulocyte/macrophage colony-stimulating factors have been the most extensively studied to date. In human clinical trials, granulocyte colony-stimulating factor improves neutrophil counts and function, reduces episodes of febrile neutropenia, improves neutrophil recovery after disease- or treatment-induced myelosuppression, and reduces the number of serious infections in several neutropenic disease states. Granulocyte/macrophage colony-stimulating factor has similar biological properties but may also improve eosinophil proliferation and function, and platelet cell recovery after myelotoxic bone marrow injury, Interleukin-1 boosts the effects of granulocyte colony-stimulating factor and granulocyte/macrophage colony-stimulating factor, but also may promote the resolution of established infections in conjunction with antibiotics. The therapeutic realities and future therapeutic implications of these agents for the therapy of infections, cancer and hemopoietic disorders are discussed.

Anti-inflammatory treatment increases angiogenesis during early fracture healing

OBJECTIVES

Both inflammation and angiogenesis are crucial for normal fracture healing. The goal of this work was to determine how anti-inflammatory treatment affects angiogenesis during early stages of fracture repair.

METHODS

Tibia fractures were created in adult mice and animals were treated with indomethacin (2 mg/kg/day), a non-steroidal anti-inflammatory drug, or PBS once a day beginning from 1 day before fracture and continuing to 6 days after fracture. Animals were killed at 7, 14, and 28 days after injury for histomorphometric analysis of fracture healing. A second group of animals were killed at 3 and 7 days after injury to measure tissue levels of VEGF and interleukin-1 beta (IL-1β). A third group of animals were killed at 3 and 7 days after injury for stereology analysis of macrophage and neutrophil infiltration and tissue vascularization.

RESULTS

Indomethacin significantly decreased bone and cartilage formation at 7 days after fracture compared to controls. Indomethacin decreased the tissue levels of IL-1β at 3 days after fracture but did not affect the recruitment of macrophages or neutrophils to injured limbs. Indomethacin-treated fractures had similar length density and surface density of vasculature as the controls at 3 days after injury. At 7 days after fracture, vasculature in indomethacin-treated fractures exhibited higher length density and surface density than that in controls. By 28 days after injury, indomethacin-treated fractures still exhibited defects in fracture repair.

CONCLUSIONS

Anti-inflammatory treatments using indomethacin impair bone and cartilage formation and increase tissue vascularization in the callus during early fracture healing.

Transcriptional profiling of the hematopoietic support of interleukin-stimulated human umbilical vein endothelial cells (HUVECs)

Endothelial cells can be successfully used to maintain or increase the number of hematopoietic stem cells in vitro. Previously we identified hematopoietic progenitor cell (HPC) expansion or survival benefit induced by IL-1β-, IL-3-, and IL-6-stimulated human umbilical vein endothelial cell (HUVEC) supernatants. In order to identify molecular mechanisms that support hematopoiesis, we examined the time-dependent expression profiles of IL-1β-, IL-3-, and IL-6-stimulated HUVECs via microarray. Here, we present 24 common upregulated elements and three common downregulated elements of IL-1β- and IL-3-stimulated HUVECs, with these factors exhibiting great potential for the observed HPC expansion. Furthermore, metabolic pathway analysis resulted in the identification of nonproteinogenic factors such as prostaglandin E(2) (PGE(2)) and nitric oxide (NO) and determined their HPC expansion potential via delta, methylcellulose, and cobblestone assays. We confirmed PGE(2) and spermine as hematopoietic expansion factors. Furthermore, we identified several factors such as SSAT, extracellular matrix components, microRNA21, and a microvesicle-mediated cross-talk between the endothelium and HPCs that may play a crucial role in determining stem cell fate. Our results suggest that microarray in combination with functional annotations is a convenient method to identify novel factors with great impact on HPC proliferation and differentiation.

Biologic and clinical significance of cytokine production in B-cell malignancies

Cytokines are a group of polypeptide hormones endowed with pleiotropic biological properties. Normal B lymphocytes produce a number of these factors that subserve important regulatory functions in the combined processes of proliferation and differentiation. Also neoplastic B cells can release cytokines and, simultaneously, respond to the same factors in an autocrine circuit that supports their malignant growth. In addition, tumor cells can make use of the factors released by normal cells, either spontaneously or under the influence of inductive signals from the neoplastic cells. Inappropriate or excessive release of cytokines may have an important role in the pathophysiology of some clinical features. Thus, neutralization of cytokine biologic activity in vivo could be a therapeutic strategy for treatment of human B-cell neoplasias.

Tumor necrosis factor-alpha and endothelial cells modulate Notch signaling in the bone marrow microenvironment during inflammation

OBJECTIVE

Homeostasis of the hematopoietic compartment is challenged and maintained during conditions of stress by mechanisms that are poorly defined. To understand how the bone marrow (BM) microenvironment influences hematopoiesis, we explored the role of Notch signaling and BM endothelial cells in providing microenvironmental cues to hematopoietic cells in the presence of inflammatory stimuli.

MATERIALS AND METHODS

The human BM endothelial cell line (BMEC) and primary human BM endothelial cells were analyzed for expression of Notch ligands and the ability to expand hematopoietic progenitors in an in vitro coculture system. In vivo experiments were carried out to identify modulation of Notch signaling in BM endothelial and hematopoietic cells in mice challenged with tumor necrosis factor-alpha (TNF-alpha) or lipopolysaccharide (LPS), or in Tie2-tmTNF-alpha transgenic mice characterized by constitutive TNF-alpha activation.

RESULTS

BM endothelial cells were found to express Jagged ligands and to greatly support progenitor's colony-forming ability. This effect was markedly decreased by Notch antagonists and augmented by increasing levels of Jagged2. Physiologic upregulation of Jagged2 expression on BMEC was observed upon TNF-alpha activation. Injection of TNF-alpha or LPS upregulated three- to fourfold Jagged2 expression on murine BM endothelial cells in vivo and resulted in increased Notch activation on murine hematopoietic stem/progenitor cells. Similarly, constitutive activation of endothelial cells in Tie2-tmTNF-alpha mice was characterized by increased expression of Jagged2 and by augmented Notch activation on hematopoietic stem/progenitor cells.

CONCLUSIONS

Our results provide the first evidence that BM endothelial cells promote expansion of hematopoietic progenitor cells by a Notch-dependent mechanism and that TNF-alpha and LPS can modulate the levels of Notch ligand expression and Notch activation in the BM microenvironment in vivo.

The effect of transendothelial migration on eosinophil function

In bronchial asthma, eosinophils found in the airways have an enhanced inflammatory capacity. We hypothesized that, at least in part, changes in functional phenotype are due to the effect of transendothelial migration. To model in vivo eosinophil trafficking to the lung, we cultured human pulmonary microvascular endothelial cell (HPMEC) monolayers on Transwell filters. The HPMECs were activated with interleukin (IL)-1beta to increase cell expression of intercellular adhesion molecule (ICAM)-1 and, hence, eosinophil transmigration. Peripheral blood eosinophils from allergic patients were added to HPMEC-covered Transwell filters and incubated for 3 h at 37 degrees C. The eosinophils were collected from below (migrated cells) and above (nonmigrated cells) the HPMEC monolayer to determine surface receptor expression, in vitro survival, and oxidative burst. Eosinophils never exposed to HPMECs were used as controls. Eosinophil cell surface expression of CD69, human leukocyte-associated antigen-DR (HLA-DR), and CD54 (ICAM-1) was significantly increased after transendothelial migration through IL-1beta-treated HPMECs compared with control cells (CD69: P<0.0005; HLA-DR and CD54: P<0.05) and nonmigrated eosinophils (CD69 and HLA-DR: P<0.05). Moreover, the percent in vitro survival (48 h) of migrated eosinophils was also significantly greater (P<0.0001 by trypan blue exclusion, P< 0.05 by flow cytometry) than that of control or nonmigrated eosinophils. Prolonged survival of migrated eosinophils was inhibited by addition of anti-granulocyte macrophage colony-stimulating factor (GM-CSF) antibodies (P<0.05) to the 48-h survival culture, suggesting that autocrine production of GM-CSF was, at least partially, responsible for increased eosinophil survival. Although GM-CSF protein was not measurable in survival culture supernates, GM-CSF messenger RNA (mRNA) was expressed in both nonmigrated and migrated eosinophils but not in control cells. Similarly, the eosinophils' oxidative burst induced by platelet-activating factor, formylmethionyl leucylphenylalanine, or phorbol myristate acetate was equally, and significantly, increased in both nonmigrated and migrated eosinophils (P<0.05 versus control). Therefore, whereas exposure of eosinophils to cytokine-activated HPMECs can increase surface receptor expression, in vitro survival, GM-CSF mRNA, and the respiratory burst, transendothelial migration can further potentiate receptor expression and survival in migrated cells. These results suggest that the process of transendothelial migration selectively participates in determining the eventual phenotype of airway eosinophils.

Positive and negative hematopoietic cytokines produced by bone marrow endothelial cells

Recently, cytokines and interleukins such as SCF, GM-CSF, G-CSF, TGF-beta, IL-6, IL-7, IL-8, IL-11 have been reported to be elaborated by endothelial cells. For further study, serum free bone marrow endothelial cell conditioned medium (BMEC-CM) was collected and ultrafiltrated by using a centriprep 10. The concentrated retentate (R-BMEC-CM) contained some substances whose molecular weight was more than 10 000 daltons. The filtrate (F-BMEC-CM) contained some substances whose molecular weight was less than 10 000 daltons. The effects of R-BMEC-CM and F-BMEC-CM on the growth of haematopoietic progenitors and the expression of cytokine and interleukin mRNAs of BMEC were investigated. The results showed that R-BMEC-CM stimulated the growth of CFU-GM, HPP-CFC, BFU-E, CFU-E, and CFU-Meg; while F-BMEC-CM inhibited the growth of these progenitors. Using the method of hybridizing to the Atlas cDNA Array, we were able to detect the presence of mRNAs of cytokines and interleukins in bone marrow endothelial cells. Our finding of the existence of mRNAs of SCF, GM-CSF, IL-6, TGF-beta, IL-1, and IL-11 in these cells was in agreement with the data reported previously. Furthermore, we detected mRNAs of MIP-2, Thymosion-beta4, PDGF, MSP-1, IFN-gamma, IL-13 and inhibin, which are related to haematopoiesis. Among these cytokines and interleukins, SCF, GM-CSF, IL-6, IL-1, and IL-11 are haematopoietic stimulators which may be responsible for the stimulative effects on the growth of haematopoietic progenitors. One of our new findings, the thymosin-beta4, is a small molecular haematopoietic inhibitor. It may be responsible for the inhibitory effect of F-BMEC-CM on haematopoietic progenitors. The presence of mRNAs of BMP, MSP-1, MIP-2, PDGF and IL-13 suggests that bone marrow endothelial cells might elaborate these substances. Their influence on haematopoietic progenitors needs further study.

Expression and secretion of vascular endothelial growth factor-A by cytokine-stimulated hematopoietic progenitor cells. Possible role in the hematopoietic microenvironment

In the hematopoietic microenvironment, bone marrow endothelial cells may play an important role in trafficking and maintenance of progenitor and stem cells due to adhesive interactions and paracrine secretion of hematopoietic growth factors. However, it is unknown whether progenitors in turn modulate endothelial proliferation and function. We analyzed mRNA expression (Northern blot) and release of vascular endothelial growth factor-A (VEGF-A), which specifically acts on endothelial cells, by cytokine-stimulated peripheral blood-derived CD34+ hematopoietic progenitor cells. While unstimulated CD34+ cells expressed VEGF-A mRNA weakly without cytokine release in vitro, incubation for 24 hours with a single cytokine (e.g., kit ligand [KL]) resulted in increased VEGF-A mRNA expression and significant secretion of VEGF-A into the supernatant. The amount of VEGF released was substantially augmented by incubation with a combination of cytokines (e.g., KL, IL-3, GM-CSF, G-CSF), or by exposure to hematopoietic cytokines for a longer time period. In addition, we show that VEGF induced the release of hematopoietic growth factors (GM-CSF) by bone marrow endothelial cells and that in vitro stromal cell-derived factor-1 (SDF-1) driven transendothelial progenitor cell migration was increased by the presence of VEGF, which might be due to pore formation (increased endothelial fenestration). In vivo, release of VEGF by progenitor cells may result in a paracrine loop supporting proliferation of both endothelium and progenitors and may facilitate transendothelial migration during cytokine-induced progenitor cell mobilization.

Cytokine profiles of cultured microvascular endothelial cells from the human intestine

BACKGROUND AND AIMS

Cytokine production by endothelial cells, has, for practical reasons, been chiefly studied in human umbilical vein endothelial cells (HUVEC) but, because tissue-specific differences apparently exist, the role of human intestinal microvascular endothelial cells (HIMEC) as a source of mucosal cytokines was also assessed.

METHODS

The expression of cytokine transcripts in HIMEC was screened by means of reverse transcription polymerase chain reaction (RT-PCR) and compared with cytokine profiles of HUVEC. Production of cytokines was investigated by bioassay and enzyme linked immunosorbent assay (ELISA).

RESULTS

In the basal unstimulated state, HIMEC and HUVEC cultures contained detectable mRNA for interleukin (IL)-3, IL-7, IL-8, IL-11, IL-14, IL-15, tumour necrosis factor (TNF)-alpha, transforming growth factor (TGF)-beta, and granulocytemacrophage colony stimulating factor (GM-CSF). However, message was undetectable for IL-2, IL-4, IL-5, IL-9, IL-10, IL-12p40, IL-13, and interferon (IFN)-gamma in the resting as well as the stimulated state. Stimulation of HIMEC and HUVEC with recombinant human (rh) IL-1 beta or rhTNF-alpha induced cell associated bioactive IL-1 alpha but not IL-1 beta, as well as enhanced secretion of both IL-6 and IL-8. Furthermore, transcript levels for GM-CSF and TNF-alpha were enhanced by rhIL-1 beta or rhTNF-alpha in both cell types. Supernatants from Th1-like or Th0-like gluten reactive intestinal T cell clones derived from patients with coeliac disease elicited cytokine profiles in both HIMEC and HUVEC similar to those revealed after rhIL-1 beta or rhTNF-alpha stimulation.

CONCLUSIONS

These data demonstrate that the intestinal microvascular endothelium may contribute to the cytokine network of the intestinal mucosa with the ability to respond to locally generated cytokines and to produce potent inflammatory mediators.

Platelet-activating factor stimulates interleukin-6 production by human endothelial cells and synergizes with tumor necrosis factor for enhanced production of granulocyte-macrophage colony stimulating factor

The interaction between human endothelial cells (EC) and leukocytes during inflammation is in part mediated through the release of soluble factors. Since platelet-activating factor (PAF) is a potent mediator of inflammatory responses, we investigated the potential of PAF to modulate IL-6 and GM-CSF production by EC. Exposure of these cells to PAF resulted in a concentration-dependent increase in IL-6 production, with a maximum at 10(-10) M PAF. Sequential incubation of EC with PAF and TNF alpha resulted in a synergistic increase of IL-6 production. This effect was specific for PAF since it was prevented by preincubation with the PAF receptor antagonist, WEB 2086. Northern blot analysis revealed enhanced IL-6 mRNA expression in PAF-treated EC. However, the synergy observed in protein synthesis between PAF and TNF alpha was not reflected in IL-6 mRNA accumulation, suggesting a post-translational modulation. Pretreatment of EC with the protein synthesis inhibitor cycloheximide before their exposure to PAF resulted, after washout of the cycloheximide, in a markedly augmented production of IL-6, suggesting a synergy between augmented IL-6 mRNA accumulation by PAF and IL-6 mRNA superinduction by cycloheximide. GM-CSF production by EC was also stimulated by the combined effects of PAF and TNF alpha, but PAF alone did not affect GM-CSF production. Taken together, our data suggest that PAF can stimulate EC to synthesize cytokines, including IL-6 and GM-CSF, which may contribute to local and, possibly, systemic responses during inflammation.

Protection from apoptosis in human neutrophils is determined by the surface of adhesion

Recent work suggests that various neutrophil agonists affect the rate of apoptosis in these cells. On the basis of these observations, we hypothesized that signals triggered in neutrophils via their adhesion receptors might also modify their life span. This hypothesis has been tested using human neutrophils adherent to tissue culture plastic, either untreated or coated with extracellular matrix (ECM) proteins or with monolayers of human umbilical vein endothelial cells. To detect and quantitate apoptotic changes in adherent cells, we developed a microtiter plate assay using a cell-permeable DNA-binding fluorescent dye, Hoechst 33342. Use of this assay demonstrated that 1) the number of apoptotic cells among neutrophils adherent to plastic after 6-20 h of incubation was significantly lower than that among neutrophils adherent to the ECM proteins fibronectin or laminin; 2) adhesion to interleukin-1-activated endothelial cells delayed apoptosis, whereas adhesion to nonactivated endothelium accelerated neutrophil death; and 3) monoclonal antibodies directed against intercellular adhesion molecule 1 or against the common beta 2-chain of the leukocyte integrins abolished the protective effect of interleukin-1-activated endothelial cells on apoptosis of adherent neutrophils. These results suggest that the life span of adherent neutrophils. depends on the activating signals triggered by the surface of adhesion.

Granulocyte macrophage colony stimulating factor produced in lesioned peripheral nerves induces the up-regulation of cell surface expression of MAC-2 by macrophages and Schwann cells

Peripheral nerve injury is followed by Wallerian degeneration which is characterized by cellular and molecular events that turn the degenerating nerve into a tissue that supports nerve regeneration. One of these is the removal, by phagocytosis, of myelin that contains molecules which inhibit regeneration. We have recently documented that the scavenger macrophage and Schwann cells express the galactose-specific lectin MAC-2 which is significant to myelin phagocytosis. In the present study we provide evidence for a mechanism leading to the augmented expression of cell surface MAC-2. Nerve lesion causes noneuronal cells, primarily fibroblasts, to produce the cytokine granulocyte macrophage-colony stimulating factor (GM-CSF). In turn, GM-CSF induces Schwann cells and macrophages to up-regulate surface expression of MAC-2. The proposed mechanism is based on the following novel observations. GM-CSF mRNA was detected by PCR in in vitro and in vivo degenerating nerves, but not in intact nerves. The GM-CSF molecule was detected by ELISA in medium conditioned by in vitro and in vivo degenerating peripheral nerves as of the 4th h after injury. GM-CSF activity was demonstrated by two independent bioassays, and repressed by activity blocking antibodies. Significant levels of GM-CSF were produced by nerve derived fibroblasts, but neither by Schwann cells nor by nerve derived macrophages. Mouse rGM-CSF enhanced MAC-2 production in nerve explants, and up-regulated cell surface expression of MAC-2 by Schwann cells and macrophages. Interleukin-1 beta up-regulated GM-CSF production thus suggesting that injury induced GM-CSF production may be mediated by interleukin-1 beta. Our findings highlight the fact that fibroblasts, by producing GM-CSF and thereby affecting macrophage and Schwann function, play a significant role in the cascade of molecular events and cellular interactions of Wallerian degeneration.

Adhesion-independent synergy of monocytes and endothelial cells in cytokine production: regulation of IL-6 and GM-CSF production by PAF

Co-Cultures of monocytes (MO) and endothelial cells (EC) were studied for their capacity to synergize in the production of interleukin-6 (IL-6) and granulocyte-macrophage colony-stimulating factor (GM–CSF), two cytokines potentially important in vascular physiopathology. Resting monocytes produced detectable amounts of IL-6 but no GM–CSF, whereas confluent EC produced significant quantities of GM–CSF, but minimal IL-6. In co-cultures without stimuli, additive synthesis of both cytokines was observed. When EC were pretreated, however, with either PAF, TNF or both stimuli, before addition of MO, synergistic production of IL-6 was observed. In contrast, GM–CSF production was not enhanced by coculture of monocytes with activated EC. When either cell population was fixed with paraformaldehyde or killed by freeze-thawing before addition to the co-culture, cytokine levels reverted to those produced by the unaffected population alone. On the other hand, separating the two cell populations by a cell-impermeable membrane in transwell cultures did not affect the synergistic production of the cytokines. Taken together, our data suggest that EC and MO can synergize in response to stimuli by producing IL-6 and that this synergy is dependent on the integrity of both cell populations, but independent of cell-cell contact.

Inhibition of GM-CSF production by recombinant human interleukin-4: negative regulator of hematopoiesis

Interleukin-4 (IL-4), also known as B-cell stimulatory factor-1 (BSF-1), was initially identified as a T-cell product that mediates anti-IgM-induced DNA synthesis in B-lymphocytes. Various aspects of this highly pleiotropic cytokine have been described, including those on hematopoietic progenitor cells. However, the role of IL-4 in the hematopoietic system has been given different interpretations. Normal human hematopoietic progenitor cells do not proliferate under control of the autocrine system and cytokines are needed for proliferation and differentiation. However, IL-4 in itself does not support proliferation of these cells and if this is the case, the effects of IL-4 on hematopoietic progenitor cells still need to be investigated from the point of view of synergism with other cytokines as well as the control of accessory cells in the production of cytokines. We describe here some properties of IL-4 in association with cytokine production, with special emphasis on granulocyte-macrophage colony-stimulating factor (GM-CSF) production.

Interleukin-1 and its inhibitors: implications for disease biology and therapy

IL-1 alpha and IL-1 beta are polypeptide hormones that exhibit a broad spectrum of beneficial and harmful biologic activities. Clinical trials designed to benefit from its stimulatory effects on human hematopoiesis and from its role in improving host defenses, are being currently conducted. Other in vivo studies, using IL-1 inhibitors with an attempts to block the detrimental effects of IL-1, are underway. Because of the multifunctional effects of IL-1 in human physiology and its pathogenetic role in several diseases, the capability to control the effects of IL-1 may prove to be a useful tool in medical practice.

GM-CSF activates regenerative epidermal growth and stimulates keratinocyte proliferation in human skin in vivo

Granulocyte/macrophage-colony-stimulating factor (GM-CSF), an immunomodulator of hematopoietic cells, has also been shown to stimulate human keratinocyte proliferation in vitro and speed healing of wounds in the skin of lepromatous leprosy patients. In this study we have examined the in vivo effects of recombinant human GM-CSF on epidermal keratinocyte proliferation and on expression of proteins marking regenerative epidermal growth. Skin biopsies from GM-CSF injected cutaneous sites were obtained between 1 and 6 d following administration of 7.5 or 15 micrograms of the growth factor. Activation of keratinocyte proliferation, quantified as the expression of the Ki67+ nuclear antigen, was noted 1 d following GM-CSF administration. A regenerative epidermal phenotype, demonstrated by immunohistochemical staining of cellular proteins involucrin, filaggrin, and keratin 16, was similarly noted as early as 1 d following GM-CSF injection. This phenotype persisted as late as 6 d post-injection. These results suggest that GM-CSF injection into human skin induces keratinocyte proliferation as well as regenerative differentiation of the epidermis. To date no other cytokine has been shown to be mitogenic for human keratinocytes both in vivo and in vitro or to alter keratinocyte differentiation along the "alternate" or regenerative pathway.

IL-1 alpha and TNF alpha act synergistically to stimulate production of myeloid colony-stimulating factors by cultured human bone marrow stromal cells and cloned stromal cell strains

Human bone marrow stromal cells respond to stimulation by the monokines IL-1 and TNF by producing colony-stimulating factors such as GM-CSF and G-CSF. In this study we show that IL-1 alpha and TNF alpha act synergistically to stimulate GM-CSF and G-CSF production by cultured marrow stromal cells. We further show that IL-1 alpha and TNF alpha synergistically stimulate production of GM-CSF and G-CSF by a clonal stroma-derived cell strain. Although IL-1 and TNF share many of the same biological activities, we show that IL-1 alpha and TNF alpha have an unequal ability to induce myeloid-CSF production by both cultures, with IL-1 alpha being the more potent inducer. We found that induction by IL-1 alpha and TNF alpha was independent of cell proliferation. The effect of IL-1 alpha and TNF alpha on production of the two myeloid-CSFs by the clonal cells was significantly greater than the unfractionated passaged stromal cultures, having the greater effect on G-CSF production. The clonally derived stromal cells constitutively produced colony-stimulating activity, in particular GM-CSF, at levels easily detected by ELISA. These findings show that, in addition to the overlapping and additive activities of IL-1 alpha and TNF alpha, they can interact synergistically. Our findings further suggest that a small subpopulation of stroma cells may be the major producer of G-CSF in the marrow microenvironment during immune response.

Endogenous production and peripheral blood levels of granulocyte-macrophage (GM-) and granulocyte (G-) colony-stimulating factors

Granulocyte-macrophage colony-stimulating factor (GM-CSF) and granulocyte colony-stimulating factor (G-CSF) are two important granulopoietic growth factors. This review will focus on the endogenous production of human GM-CSF and human G-CSF and its possible reflection in circulating levels in peripheral blood. When adequately stimulated a variety of cell-types such as monocytes/macrophages. T-lymphocytes, endothelial cells and fibroblasts can produce CSFs in vitro. G-CSF can increase to detectable levels in peripheral blood when there is a demand for granulocyte production such as acute neutropenic in conjunction with hematological disorders, chronic neutropenic conditions and acute infectious diseases in patients with or without underlying hematological disorders. G-CSF in peripheral blood is detected more often and in higher concentrations than GM-CSF. An independent regulation of GM-CSF and G-CSF secretion, quantitative differences in production and/or differences in elimination or distribution might be of importance.

Murine endothelial cell line cells, F-2: interaction with leukocytes and cytokines production

Flowcytometry demonstrated that murine endothelial cell line F-2 expresses MHC class I antigen, FcR II, Mac-1 and vascular cell adhesion molecule-1 (VCAM-1), but not intercellular adhesion molecule-1 (ICAM-1) and class II antigen. However, co-culturing with TNF-alpha for 24 hr resulted in the increased expression of ICAM-1, and the decreased expression of VCAM-1. IL-1 alpha and IFN-gamma exerted this regulatory effect on VCAM-1 but not on ICAM-1. T (Con A blast) and B (LPS blast) cells adhered to F-2 cells at almost equal levels, and the adhesion was enhanced 20 to 50% when the cells were precultured with TNF-alpha for 24 hr. The inhibition assay using either (anti-ICAM-1 + anti-LFA-1, lymphocyte function-associated antigen-1) or (anti-VCAM-1 + anti-VLA-4, very late antigen-4) mAbs demonstrated that the ICAM-1 system was utilized more preferentially by T than B blasts when F-2 cells were stimulated with TNF-alpha, and the VCAM-1 system was vice versa under the unstimulated and stimulated conditions. Granulocytes also adhered to F-2 cells, but no mAbs could inhibit the adhesion. Although F-2 cells produced a considerable amount of IL-6, GM-CSF and neutrophil chemotactic activity, a 24 hr incubation with TNF-alpha resulted in an increase of 12 fold in IL-6 and 3 fold in neutrophil chemotactic activity production.

Molecular regulation of the human IL-3 gene: inducible T cell-restricted expression requires intact AP-1 and Elf-1 nuclear protein binding sites

Interleukin 3 (IL-3) is a hematopoietic stem-cell growth and differentiation factor that is expressed solely in activated T and NK cells. Studies to date have identified elements 5' to the IL-3 coding sequences that regulate its transcription, but the sequences that confer T cell-specific expression remain to be clearly defined. We have now identified DNA sequences that are required for T cell-restricted IL-3 gene transcription. A series of transient transfections performed with human IL-3-chloramphenicol acetyltransferase (CAT) reporter plasmids in T and non-T cells revealed that a plasmid containing 319 bp of 5' flanking sequences was active exclusively in T cells. Deletion analysis revealed that T cell specificity was conferred by a 49-bp fragment (bp -319 to -270) that included a potential binding site for AP-1 transcription factors 6 bp upstream of a binding site for Elf-1, a member of the Ets family of transcription factors. DNaseI footprint and electrophoretic mobility shift assay analyses performed with MLA-144 T cell nuclear extracts demonstrated that this 49-bp region contains a nuclear protein binding region that includes consensus AP-1 and Elf-1 binding sites. In addition, extracts prepared from purified human T cells contained proteins that bound to synthetic oligonucleotides corresponding to the AP-1 and Elf-1 binding sites. In vitro-transcribed and -translated Elf-1 protein bound specifically to the Elf-1 site, and Elf-1 antisera competed and super shifted nuclear protein complexes present in MLA-144 nuclear extracts. Moreover, addition of anti-Jun family antiserum in electrophoretic mobility shift assay reactions completely blocked formation of the AP-1-related complexes. Transient transfection studies in MLA-144 T cells revealed that constructs containing mutations in the AP-1 site almost completely abolished CAT activity while mutation of the Elf-1 site or the NF-IL-3 site, a previously described nuclear protein binding site (bp. -155 to -148) in the IL-3 promoter, reduced CAT activity to < 25% of the activity given by wild-type constructs. We conclude that expression of the human IL-3 gene requires the AP-1 and Elf-1 binding sites; however, unlike other previously characterized cytokine genes such as IL-2, the AP-1 and Elf-1 factors can bind independently in the IL-3 gene.(ABSTRACT TRUNCATED AT 400 WORDS)

Role of interleukin-1 inhibitory molecules in therapy of acute and chronic myelogenous leukemia

The poor outcome of conventional therapy of acute and chronic myelogenous leukemias (AML and CML) has prompted several groups to investigate new therapeutic directions. Data from various laboratories, including our own, indicate that both normal and leukemia precursors proliferate in response to growth factors. Furthermore, it has been shown that AML blasts, low-density cells from CML patients with advanced disease, and cultured bone marrow-adherent layers from CML blast crisis patients produce interleukin 1 (IL-1); this molecule may play a pivotal role in driving leukemia cell proliferation through autocrine or paracrine pathways. We have therefore hypothesized that interruption of the IL-1-mediated growth-stimulatory mechanism may suppress leukemia precursor multiplication. In searching for IL-1-inhibitory molecules that may be used clinically, we have investigated the in vitro effects of various IL-1 inhibitors including IL-1 receptor antagonist, soluble IL-1 receptors, and interleukin 4. Our studies suggest that IL-1 inhibitors can suppress clonogenic growth of cultured AML and CML progenitors and may hence be exploitable in clinical trials.

Evidence that granulocyte macrophage-colony-stimulating factor regulates the distribution and differentiated state of dendritic cells/Langerhans cells in human lung and lung cancers

GM-CSF has been shown to be important for the survival and function of cells of dendritic cell/Langerhans cell (LC) lineage in vitro. Since these cells have been demonstrated to infiltrate human lung and some lung carcinomas, we hypothesized that the production of GM-CSF in the lung could be important in their recruitment and differentiation. Using both immunohistochemistry and in situ hybridization, we have shown that: (a) GM-CSF was produced by normal bronchiolar epithelium, the only site were CD1a+ LC are observed in the normal lung, whereas neither GM-CSF production nor LC were identified in normal alveolar epithelium. (b) In inflamed pulmonary tissue, hyperplastic alveolar cells produced GM-CSF, and CD1a+ LC accumulated adjacent to these cells. (c) Some, but not all, lung carcinomas produced this cytokine, and a close correlation was found between the production of GM-CSF and the number of CD1a+ LC infiltrating these tumors. Since GM-CSF was produced at all sites where CD1a+ LC are known to accumulate, but not at other locations within the lung, these data suggest that the local production of GM-CSF by certain lung cells may play an important role in determining the distribution and differentiated state of dendritic cell/LC in the human lung.

Haemopoietic growth factors in acute myeloblastic and lymphoblastic leukaemia

Acute leukaemia blast cells fail to mature into terminally differentiated cells and accumulate in the haemopoietic tissues. In analogy with normal haemopoiesis, the leukaemic mass is largely non-dividing and descends from a small pool of leukaemic progenitor cells with high proliferative activity. In vitro culture methods have become powerful instruments to analyse human leukaemia progenitor cells. These techniques have in recent years been considerably improved as the result of the availability of the recombinant HGFs. Here we have summarized the current insights in the growth properties of acute leukaemia progenitor cells, derived from the application of fully defined in vitro assays. We have discussed the proliferation and maturation abilities in relation to cytogenetic abnormalities, status of growth factor receptors and the property of autocrine growth stimulation and evaluated the significance of these findings for the understanding of the pathogenesis of acute myeloblastic leukaemia and acute lymphoblastic leukaemia.

Hematopoietic growth factors. A promising future for use in bone marrow dysfunction

The clinical future of hematopoietic growth factors appears promising. They will probably achieve broad clinical application in a wide variety of hematologic disorders. Their use in infectious diseases associated with granulocytopenia and in cancer-treatment regimens as adjuvant agents against myelosuppression and perhaps as stimulants of the natural anti-cancer effects of host cells also seems appropriate.

The biology of granulocyte-macrophage colony-stimulating factor: effects on hematopoietic and nonhematopoietic cells

Granulocyte-macrophage colony-stimulating factor (GM-CSF) is one of a family of glycoprotein cytokines that have potent effects in stimulating the proliferation, maturation, and function of hematopoietic cells. Deriving its name from its ability to stimulate the formation of macroscopic colonies containing neutrophils, eosinophils, macrophages, or mixtures of these cell types, GM-CSF stimulates the proliferation and maturation of myeloid progenitors, as well as functionally activating mature neutrophils, eosinophils, and macrophages. As most of the effects observed using GM-CSF in vitro have been shown to occur in vivo either in animal models or in human subjects, it is important to consider that GM-CSF may also exert some biological effects on nonhematopoietic cells. In response to immunologic stimuli, immunologic surveillance cells and cells of the microenvironment are capable of producing GM-CSF. In vitro experiments indicate that GM-CSF production is tightly regulated. In that regard, GM-CSF is not present in measurable quantities in normal serum, but little is known about the in vivo process of GM-CSF production and regulation. The biologic capabilities of GM-CSF have triggered its widespread clinical use in situations where hematopoiesis is compromised. GM-CSF can act as a potent growth factor in vivo, increasing the number and enhancing the function of hematopoietic progenitors and mature cells. However, the precise in vivo effect that GM-CSF may have on normal and neoplastic cells of nonhematopoietic origin remains undefined. The full range of GM-CSF bioactivity is mediated following binding to its receptor. The presence of specific receptors for GM-CSF has been demonstrated in all responsive cells of hematopoietic lineage, as well as in nonhematopoietic cells, both responsive and unresponsive. In conclusion, a large body of work from a number of laboratories has defined the biology of GM-CSF. Currently available reagents and technology will provide additional insights into the biology of this molecule, thereby expanding our present definition and allowing us to explore the mechanisms regulating hematopoiesis.

Interleukin 1 beta improves survival following cecal ligation and puncture

Despite antibiotic therapy intra-abdominal sepsis following major surgery is a significant cause of mortality. We sought to determine if interleukin-1 beta (IL-1) could improve survival in a murine model of intra-abdominal infection. Groups of 10 BDF1 mice received a single subcutaneous (sc) injection of recombinant human IL-1 beta 24 hr prior to cecal ligation and puncture (CLP) and were assessed twice daily for survival. Mice that received a single injection of IL-1 beta 24 hr prior to CLP had a dose-dependent improval in survival compared to controls. The beneficial effect of IL-1 treatment may have been related to its ability to stimulate myelopiesis. The addition of indomethacin, in an effort to limit possible toxicity of IL-1, did not further improve survival. Appropriate timing of specific immunomodulators may provide an additional strategy for the treatment of infections.

Selective eosinophil leukocyte recruitment by transendothelial migration and not by leukocyte-endothelial cell adhesion

Eosinophil infiltration is the hallmark of allergic inflammatory events. However, the mechanisms governing the influx of eosinophils into the tissue at a site of an allergic reaction remains unclear. We have examined the interactions of eosinophils and neutrophils isolated from the same atopic donor with cultured human umbilical vein endothelial cell (EC) monolayers in the search for a mechanism for this selective eosinophil recruitment. First, the adherence of eosinophils and neutrophils to ECs stimulated with lipopolysaccharide, interleukin (IL)-1 alpha, and tumor necrosis factor-alpha were compared. Each mediator induced a similar dose-dependent enhancement of eosinophil adhesiveness for both eosinophils and neutrophils. Thus, although cytokine activation of ECs in the vasculature adjacent to an inflammatory site probably serves as an important focusing mechanism for the extravasation of inflammatory cells at this site, there does not appear to be any selective EC-dependent mechanism for eosinophil recruitment. Little or no effect on eosinophil and neutrophil adherence was observed with IL-3, IL-5, granulocyte/macrophage colony-stimulating factor, platelet-activating factor (PAF), leukotriene B4, or histamine. Second, the migration of eosinophils and neutrophils through an EC monolayer in response to chemoattractants was examined. PAF was found to selectively enhance eosinophil transendothelial migration at doses of 10(-7) to 10(-10) M, with optimal effect at 10(-8) M. This effect was gradient dependent and could be inhibited by WEB 2086, a specific PAF inhibitor. These results suggest that localized production of PAF may be a prime factor in the events leading to eosinophil accumulation at allergic inflammatory sites, and that selectivity for eosinophil recruitment occurs at the stage of transendothelial cell migration under the influence of cell-specific chemoattractants.

Human endothelial cells transfected by SV40 T antigens: characterization and potential use as a source of normal endothelial factors

A putative role for the vascular endothelium as target for autoantibodies has been suggested in several autoimmune disorders and connective-tissue diseases. However, there are some difficulties linked to the use of cultured endothelial cells (EC) that limit considerably the extensive studies on the nature of endothelial target antigens involved. To overcome this problem, human EC, derived from umbilical veins, were transfected with recombinant plasmid pSV1 which contained the early genes of simian virus SV40. These transfected cells, called EC-pSV1, are able to grow without EC growth supplement and demonstrate a population doubling time of about 50 h. Among the EC properties, EC-pSV1 retain intracellular content of angiotensin-converting enzyme activity, exhibit constitutive production of interleukin 6 and of a growth-promoting activity on early passage EV, express intercellular adhesion molecule 1 (ICAM-1) and its up-regulation by tumor necrosis factor alpha, but have lost the expression of factor VIII-related antigen. Moreover, EC-pSV1 express a 55-kDa antigen found on EC and human platelets, and presumably acting as an antibody target in some cases of non-allergic asthma. However, at the 50-55th generation, morphological changes and altered growth behavior were visible. This work demonstrates that transfection of EC with SV40 T antigens may be of interest, particularly in areas of research including the study of EC targets involved in different human diseases.

Granulocyte-macrophage colony stimulating factor potentiates human polymorphonuclear leukocyte aggregation responses to formyl-methionyl-leucyl-phenylalanine

Polymorphonuclear leukocytes (PMN) are known to be activated by several lymphokines and can be induced to release lysosomal enzymes, prostaglandins (PG), thromboxanes (TX) and lipoxygenase products that may be involved in PMN aggregation responses during inflammatory reactions. Granulocyte-macrophage colony stimulating factor (GM-CSF), a glycoprotein cytokine released by immunocompetent cells, has been found to prime neutrophil responses, such as increased cell aggregation after exposure to various biological stimulants. In this study, we examined the effects of the cytokine GM-CSF on human neutrophilic aggregation stimulated by N-formyl-methionyl-leucyl-phenylalanine (FMLP) and its influence on the production of various arachidonic acid metabolites. Neutrophil aggregation of purified PMNs was measured by the percent change in light transmission in a standard aggregometer, and the arachidonic acid products leukotriene B4 (LTB4) and thromboxane A2 (TXA2) were quantified by radioimmunoassay. We found that GM-CSF and other cytokines, used alone, did not cause any significant increase in aggregation of the PMN. However, prior exposure of PMN to GM-CSF markedly increased the aggregation induced by FMLP as opposed to that detected with PMN stimulated with only FMLP. This priming effect was not observed with PMN preincubated with interleukin-1 (IL-1), tumor necrosis factor (TNF) or interleukin-6 (IL-6). In addition, GM-CSF and IL-6 both failed to stimulate the production of LTB4 and TXA2, products which are known to induce PMN aggregation. These findings provide new evidence suggesting that GM-CSF facilitates the action of FMLP on the adhesion dependent cellular functions of the inflammatory response, serving as an important co-factor in neutrophil aggregation.

The effect of immune mediators (cytokines) on the release of endothelium-derived relaxing factor (EDRF) and of prostacyclin by freshly harvested endothelial cells

The effect of recombinant tumor necrosis factor and other cytokines stimulated by LPS (lipopolysaccharide), on the release of endothelial-derived relaxing factor and of prostacyclin was investigated using freshly harvested endothelial cells attached to plastic microcarrier beads. The results show that the cytokines failed to interfere with the release of EDRF and prostacyclin under the conditions of these experiments.

Biochemical properties of vascular endothelial cells

Present knowledge in the field of vascular endothelial cells is reviewed. The role of endothelial cells in the synthesis of matrix proteins and glycosaminoglycans is described. Endothelial cells play a considerable role in the processes of coagulation and fibrinolysis. They also interact with neurotransmitters and vasomotoric substances, and participate in inflammation and immunological responses. They produce several different growth factors. Their role in lipoprotein metabolism is of special importance to research into atherosclerosis.

Eosinophil hematopoietins antagonize the programmed cell death of eosinophils. Cytokine and glucocorticoid effects on eosinophils maintained by endothelial cell-conditioned medium

Granulocyte-macrophage colony-stimulating factor (GM-CSF) was established as the constitutive and elicited human umbilical vein endothelial cell-derived eosinophil viability-sustaining factor. Stimulation of endothelium cell monolayers with IL-1 alpha (5 U/ml) increased the 48-h elaboration of GM-CSF from a mean of 3.2 to a mean of 8.2 pM (P less than 0.05). Dexamethasone (100 nM) decreased the constitutive GM-CSF elaboration by 49% (P less than 0.001) but did not diminish production by IL-1 alpha-stimulated endothelium. However, eosinophil viability decreased by 21% in dexamethasone-pretreated IL-1 alpha-stimulated endothelial cell-conditioned medium (P less than 0.05), which suggested viability antagonism by glucocorticoids. After 24 h of culture, eosinophil viability for replicate cells in enriched medium alone or with 1 pM GM-CSF decreased from means of 43 and 75% to means of 21 and 54%, respectively, when dexamethasone was included (P less than 0.05). However, 10 pM GM-CSF, IL-3, or IL-5 protected the cells against dexamethasone and against endonuclease-specific DNA fragmentation. In this model system of eosinophil-tissue interactions, dexamethasone prevents the endothelial cells from inducing a pathobiologic phenotypic change in the eosinophil by suppression of GM-CSF elaboration to concentrations that are not cytoprotective. Cytokine priming by GM-CSF, IL-3, or IL-5 may account for the differential responsiveness of select eosinophilic disorders to glucocorticoids.

Signal requirements for the generation of CD4+ and CD8+ T-cell responses to human allogeneic microvascular endothelium

Microvascular endothelium has been implicated as a major target in the rejection of vascularized allografts. In an attempt to dissect the stepwise generation of the T-cell-mediated immune response to microvascular endothelial cells (ECs), we analyzed the requirements for the two major T-cell subsets, CD4+ and CD8+, in the triggering of proliferative and cytotoxic responses to allogeneic ECs in vitro. Results demonstrate that resting ECs are unable to stimulate a functional response by purified T, CD4+, and CD8+ cells in the absence of costimulatory signals. T cells and CD8+ cells develop both proliferative and cytotoxic anti-EC responses by the addition of as little as 2 units/ml interleukin-2, 10 units/ml interleukin-1, or irradiated monocytes autologous to the responder lymphocytes, whereas only autologous monocytes are capable of triggering CD4+ T-cell precursors to proliferate and become anti-EC-specific effector cytotoxic T lymphocytes. CD8+ cell-mediated anti-EC cytotoxicity is directed toward allogeneic major histocompatibility complex (MHC) class I determinants on ECs and involves recognition by the CD3/T-cell receptor complex and the CD8 molecule on the effector T cells. CD4+ cells can be driven to proliferate, produce interleukin-2, and become anti-EC-specific cytotoxic T lymphocytes despite the lack of detectable membrane MHC class II determinants on the target cells. Chloroquine inhibition experiments demonstrate that autologous monocytes/macrophages are required by CD4+ T-cell precursors for the processing of EC-derived alloantigens and their subsequent presentation in the context of self-MHC molecules. These results are in agreement with the adoptive transfer experiments in experimental allograft models and suggest that the coordinate engagement of cells of the CD4, CD8, and monocyte/macrophage series is more effective than the individual cell subsets in the

The mechanism responsible for diminished neutrophil production in neonates delivered of women with pregnancy-induced hypertension

The neonatal neutropenia after pregnancy-induced hypertension is a function of diminished neutrophil production. These studies test the hypothesis that this diminution is due to decreased production of neutrophilic growth factors, reduced responsiveness of neutrophil progenitors to these factors, or the presence of an inhibitor. While the concentrations of placentally derived colony-stimulating factors were similar in normotensive and hypertensive gestations, bioassay demonstrated less colony-stimulating activity in placental conditioned media from hypertensive gestations. Evaluation of the responsiveness of progenitors to recombinant factors revealed no differences between those from normotensive and hypertensive gestations. However, neutrophilic colony formation in vitro was significantly inhibited after the addition of conditioned media or sera from hypertensive gestations, whereas the addition of these from normotensive gestations had no inhibitory effect. Thus this common maternal-fetal disorder is associated with an inhibitor of neutrophil production, which is elaborated by the placenta and present in cord blood serum.