Normal human alveolar macrophages obtained by bronchoalveolar lavage have a limited capacity to release interleukin-1

Flagellin-modulated inflammasome pathways characterize the human alveolar macrophage response to Burkholderia pseudomallei, a lung-tropic pathogen

Melioidosis is an emerging tropical infection caused by inhalation, inoculation, or ingestion of the flagellated, facultatively intracellular pathogen Burkholderia pseudomallei. The melioidosis case fatality rate is often high, and pneumonia, the most common presentation, doubles the risk of death. The alveolar macrophage is a sentinel pulmonary host defense cell, but the human alveolar macrophage in B. pseudomallei infection has never been studied. The objective of this study was to investigate the host-pathogen interaction of B. pseudomallei infection with the human alveolar macrophage and to determine the role of flagellin in modulating inflammasome-mediated pathways. We found that B. pseudomallei infects primary human alveolar macrophages but is gradually restricted in the setting of concurrent cell death. Electron microscopy revealed cytosolic bacteria undergoing division, indicating that B. pseudomallei likely escapes the alveolar macrophage phagosome and may replicate in the cytosol, where it triggers immune responses. In paired human blood monocytes, uptake and intracellular restriction of B. pseudomallei are similar to those observed in alveolar macrophages, but cell death is reduced. The alveolar macrophage cytokine response to B. pseudomallei is characterized by marked interleukin (IL)-18 secretion compared to monocytes. Both cytotoxicity and IL-18 secretion in alveolar macrophages are partially flagellin dependent. However, the proportion of IL-18 release that is driven by flagellin is greater in alveolar macrophages than in monocytes. These findings suggest differential flagellin-mediated inflammasome pathway activation in the human alveolar macrophage response to B. pseudomallei infection and expand our understanding of intracellular pathogen recognition by this unique innate immune lung cell.

Chikungunya virus infection induces differential inflammatory and antiviral responses in human monocytes and monocyte-derived macrophages

Chikungunya virus (CHIKV) is a zoonotic arthropod-borne virus that has caused several outbreaks in tropical and subtropical areas worldwide during the last 50 years. The virus is known to target different human cell types throughout the course of infection including epithelial and endothelial cells, fibroblasts, primary monocytes and monocyte-derived macrophages (MDMs). The two latter are phagocytic cell populations of the innate immune system which are involved in some aspects of CHIKV pathogenesis. However, monocytes and macrophages also potentially contribute to the control of viral replication through the expression of different pattern recognition receptors sensing viral pathogens and subsequently, inducing an type I interferone (IFN-I)-dependent antiviral immune response. The aim of this study was to determine the modulation of the expression of Toll-like receptors (TLRs), cytokine secretion capabilities and antiviral factor production in monocytes and MDMs following infection with CHIKV. Moreover, we sought to determine the replication kinetics of CHIKV in these two cell populations. We found that the maximum peak of CHIKV replication was observed between 18- and 24-hours post-infection (hpi), while after that the is strongly reduced. Furthermore, CHIKV infection induced the pro-inflammatory cytokine production starting from the first 6 hpi in both monocytes and MDMs, with similar kinetics but different protein levels. In contrast, the kinetics of transcriptional expression of some TLRs were different between both cell types. In addition, IFN-I, 2',5'-oligoadenylate synthetase 1 (OAS1), and double-stranded RNA-activated protein kinase R (PKR) mRNA levels were detected in response to CHIKV infection of monocytes and MDMs, resulting the highest expression levels at 48 hpi. In conclusion, our data provides evidence that CHIKV infection activates the TLR pathways in primary monocytes and MDMs, which play a crucial role in CHIKV pathogenesis and/or host defense, differentially. However, additional studies are required to determine the functional role of TLRs in monocytes and MDMs.

Vpr Is a VIP: HIV Vpr and Infected Macrophages Promote Viral Pathogenesis

HIV infects several cell types in the body, including CD4+ T cells and macrophages. Here we review the role of macrophages in HIV infection and describe complex interactions between viral proteins and host defenses in these cells. Macrophages exist in many forms throughout the body, where they play numerous roles in healthy and diseased states. They express pattern-recognition receptors (PRRs) that bind viral, bacterial, fungal, and parasitic pathogens, making them both a key player in innate immunity and a potential target of infection by pathogens, including HIV. Among these PRRs is mannose receptor, a macrophage-specific protein that binds oligosaccharides, restricts HIV replication, and is downregulated by the HIV accessory protein Vpr. Vpr significantly enhances infection in vivo, but the mechanism by which this occurs is controversial. It is well established that Vpr alters the expression of numerous host proteins by using its co-factor DCAF1, a component of the DCAF1-DDB1-CUL4 ubiquitin ligase complex. The host proteins targeted by Vpr and their role in viral replication are described in detail. We also discuss the structure and function of the viral protein Env, which is stabilized by Vpr in macrophages. Overall, this literature review provides an updated understanding of the contributions of macrophages and Vpr to HIV pathogenesis.

Age-related dynamics of pro-inflammatory cytokines in equine bronchoalveolar lavage (BAL) fluid and peripheral blood from horses managed on pasture

The objectives of this study were to evaluate the natural age-related variation and compare the level of pro-inflammatory cytokines in the peripheral blood and lower airways of horses. The mRNA expression of IL-1β, IL-6, IL-8 TNF-α TLR-4 in bronchoalveolar lavage (BAL) fluid and peripheral blood mononuclear cells (PBMC) were studied by quantitative real time polymerase chain reaction (PCR) and differential cell count cytology from 44 horses of different ages. A significant age-related increase was found for the mRNA expression of IL-6, IL-8, TLR-4 and TNF-α in stimulated BAL cells and for TNF-α in stimulated PBMC. Furthermore, a significant decrease was found in the mRNA expression of IL-1β and TNF-α in stimulated BAL cells compared to stimulated PBMC. In conclusion, continued low antigen exposure of horses in the pasture environment could lead to a tight regulation of mRNA gene expression in the airway space compared to the peripheral blood and favour an age-related accumulation of mRNA genes.

House Dust Mite Allergens and the Induction of Monocyte Interleukin 1β Production That Triggers an IκBζ-Dependent Granulocyte Macrophage Colony-Stimulating Factor Release from Human Lung Epithelial Cells

Asthma is a chronic lung disease characterized by inflammation centered upon bronchial epithelium. House dust mite is one of the most common respiratory allergens that trigger exacerbations of asthma. IκBζ (gene NFKBIZ) is a recently recognized member of the NF-κB family that can be induced in mononuclear phagocytes and lung epithelial cells and has been shown to play a prominent role in epithelial cell function. We therefore analyzed the role of IκBζ in regulating lung epithelial cell cytokine responses to house dust mite mix (HDM). We found that human bronchial epithelial cells express IκBζ and release IL-6 and granulocyte macrophage colony-stimulating factor (GMCSF) when cocultured with human monocytes and HDM. This response is blocked in the presence of IL-1 receptor antagonist (IL-1Ra), indicating that it is IL-1 mediated. Neither HDM-stimulated macrophages nor dendritic cells release IL-1β and subsequently induce cytokine release from the bronchial epithelial cells. Rhodobacter sphaeroides LPS (RS-LPS), a TLR4 antagonist, blocks the ability of HDM to induce IκBζ and release GMCSF from epithelial cells cocultured with monocytes. Additionally, human bronchial epithelial cells show no induction of IκBζ or cytokine responses to direct HDM stimulation. Finally, NFKBIZ small interfering RNA-mediated knockdown in the bronchial epithelial cells suppresses the release of IL-1-induced IL-6 and GMCSF. Our findings indicate a possible role for monocyte recruitment and lung epithelial cell IκBζ in mediating asthma associated inflammation. Thus, IκBζ, IL-1Ra, and RS-LPS deserve future study as potential modulators of house dust mite-induced asthma.

A review of the equine age-related changes in the immune system: comparisons between human and equine aging, with focus on lung-specific immune-aging

The equine aging process involves many changes to the immune system that may be related to genetics, the level of nutrition, the environment and/or an underlying subclinical disease. Geriatric horses defined as horses above the age of 20, exhibit a decline in body condition, muscle tone and general well-being. It is not known whether these changes contribute to decreased immune function or are the result of declining immune function. Geriatric years are characterized by increased susceptibility to infections and a reduced antibody response to vaccination as a result of changes in the immune system. Humans and horses share many of these age-related changes, with only a few differences. Thus, inflamm-aging and immunosenescence are well-described phenomena in both human and equine research, particularly in relation to the peripheral blood and especially the T-cell compartment. However, the lung is faced with unique challenges because of its constant interaction with the external environment and thus may not share similarities to peripheral blood when considering age-related changes in immune function. Indeed, recent studies have shown discrepancies in cytokine mRNA and protein expression between the peripheral blood and bronchoalveolar lavage immune cells. These results provide important evidence that age-related immune changes or 'dys-functions' are organ-specific.

Cytokine BAFF released by Helicobacter pylori-infected macrophages triggers the Th17 response in human chronic gastritis

BAFF is a crucial cytokine that affects the activity of both innate and adaptive immune cells. It promotes the expansion of Th17 cells in autoimmune disorders. With this study, we investigated the BAFF/Th17 responses in Helicobacter pylori-induced gastritis in humans. Our results show that the mucosa from Helicobacter(+) patients with chronic gastritis is enriched in IL-17 and BAFF, whereas the two cytokines are weakly expressed in Helicobacter(-) patients with chronic gastritis; moreover, the expression of both BAFF and IL-17 decreases after bacteria eradication. We demonstrate that BAFF accumulates in macrophages in vivo and that it is produced by monocyte-derived macrophages in vitro, after Helicobacter stimulation. Application of BAFF on monocytes triggers the accumulation of reactive oxygen species that are crucial for the release of pro-Th17 cytokines, such as IL-23, IL-1β, and TGF-β. Moreover, BAFF directly promotes the differentiation of Th17 cells. In conclusion, our results support the notion that an axis BAFF/Th17 exists in chronic gastritis of Helicobacter(+) patients and that its presence strictly depends on the bacterium. Moreover, we demonstrated that BAFF is able to drive Th17 responses both indirectly, by creating a pro-Th17 cytokine milieu through the involvement of innate immune cells, and directly, via the differentiation of T cells toward the specific profile. The results obtained in this study are of great interest for Helicobacter-related diseases and the development of novel therapeutic strategies based on the inhibition of the BAFF/IL-17 response.

Bordetella parapertussis survives inside human macrophages in lipid raft-enriched phagosomes

Bordetella parapertussis is a human pathogen that causes whooping cough. The increasing incidence of B. parapertussis has been attributed to the lack of cross protection induced by pertussis vaccines. It was previously shown that B. parapertussis is able to avoid bacterial killing by polymorphonuclear leukocytes (PMN) if specific opsonic antibodies are not present at the site of interaction. Here, we evaluated the outcome of B. parapertussis innate interaction with human macrophages, a less aggressive type of cell and a known reservoir of many persistent pathogens. The results showed that in the absence of opsonins, O antigen allows B. parapertussis to inhibit phagolysosomal fusion and to remain alive inside macrophages. The O antigen targets B. parapertussis to lipid rafts that are retained in the membrane of phagosomes that do not undergo lysosomal maturation. Forty-eight hours after infection, wild-type B. parapertussis bacteria but not the O antigen-deficient mutants were found colocalizing with lipid rafts and alive in nonacidic compartments. Taken together, our data suggest that in the absence of opsonic antibodies, B. parapertussis survives inside macrophages by preventing phagolysosomal maturation in a lipid raft- and O antigen-dependent manner. Two days after infection, about 15% of macrophages were found loaded with live bacteria inside flotillin-enriched phagosomes that had access to nutrients provided by the host cell recycling pathway, suggesting the development of an intracellular infection. IgG opsonization drastically changed this interaction, inducing efficient bacterial killing. These results highlight the need for B. parapertussis opsonic antibodies to induce bacterial clearance and prevent the eventual establishment of cellular reservoirs of this pathogen.

Double impact of cigarette smoke and mechanical ventilation on the alveolar epithelial type II cell

INTRODUCTION

Ventilator-induced lung injury (VILI) impacts clinical outcomes in acute respiratory distress syndrome (ARDS), which is characterized by neutrophil-mediated inflammation and loss of alveolar barrier function. Recent epidemiological studies suggest that smoking may be a risk factor for the development of ARDS. Because alveolar type II cells are central to maintaining the alveolar epithelial barrier during oxidative stress, mediated in part by neutrophilic inflammation and mechanical ventilation, we hypothesized that exposure to cigarette smoke and mechanical strain have interactive effects leading to the activation of and damage to alveolar type II cells.

METHODS

To determine if cigarette smoke increases susceptibility to VILI in vivo, a clinically relevant rat model was established. Rats were exposed to three research cigarettes per day for two weeks. After this period, some rats were mechanically ventilated for 4 hours. Bronchoalveolar lavage (BAL) and differential cell count was done and alveolar type II cells were isolated. Proteomic analysis was performed on the isolated alveolar type II cells to discover alterations in cellular pathways at the protein level that might contribute to injury. Effects on levels of proteins in pathways associated with innate immunity, oxidative stress and apoptosis were evaluated in alveolar type II cell lysates by enzyme-linked immunosorbent assay. Statistical comparisons were performed by t-tests, and the results were corrected for multiple comparisons using the false discovery rate.

RESULTS

Tobacco smoke exposure increased airspace neutrophil influx in response to mechanical ventilation. The combined exposure to cigarette smoke and mechanical ventilation significantly increased BAL neutrophil count and protein content. Neutrophils were significantly higher after smoke exposure and ventilation than after ventilation alone. DNA fragments were significantly elevated in alveolar type II cells. Smoke exposure did not significantly alter other protein-level markers of cell activation, including Toll-like receptor 4; caspases 3, 8 and 9; and heat shock protein 70.

CONCLUSIONS

Cigarette smoke exposure may impact ventilator-associated alveolar epithelial injury by augmenting neutrophil influx. We found that cigarette smoke had less effect on other pathways previously associated with VILI, including innate immunity, oxidative stress and apoptosis.

Macrophages in tuberculosis: friend or foe

Tuberculosis (TB) remains one of the greatest threats to human health. The causative bacterium, Mycobacterium tuberculosis (Mtb), is acquired by the respiratory route. It is exquisitely human adapted and a prototypic intracellular pathogen of macrophages, with alveolar macrophages (AMs) being the primary conduit of infection and disease. The outcome of primary infection is most often a latently infected healthy human host, in whom the bacteria are held in check by the host immune response. Such individuals can develop active TB later in life with impairment in the immune system. In contrast, in a minority of infected individuals, the host immune response fails to control the growth of bacilli, and progressive granulomatous disease develops, facilitating spread of the bacilli via infectious aerosols coughed out into the environment and inhaled by new hosts. The molecular details of the Mtb-macrophage interaction continue to be elucidated. However, it is clear that a number of complex processes are involved at the different stages of infection that may benefit either the bacterium or the host. Macrophages demonstrate tremendous phenotypic heterogeneity and functional plasticity which, depending on the site and stage of infection, facilitate the diverse outcomes. Moreover, host responses vary depending on the specific characteristics of the infecting Mtb strain. In this chapter, we describe a contemporary view of the behavior of AMs and their interaction with various Mtb strains in generating unique immunologic lung-specific responses.

Seoul virus-infected rat lung endothelial cells and alveolar macrophages differ in their ability to support virus replication and induce regulatory T cell phenotypes

Hantaviruses cause a persistent infection in reservoir hosts that is attributed to the upregulation of regulatory responses and downregulation of proinflammatory responses. To determine whether rat alveolar macrophages (AMs) and lung microvascular endothelial cells (LMVECs) support Seoul virus (SEOV) replication and contribute to the induction of an environment that polarizes CD4(+) T cell differentiation toward a regulatory T (Treg) cell phenotype, cultured primary rat AMs and LMVECs were mock infected or infected with SEOV and analyzed for viral replication, cytokine and chemokine responses, and expression of cell surface markers that are related to T cell activation. Allogeneic CD4(+) T cells were cocultured with SEOV-infected or mock-infected AMs or LMVECs and analyzed for helper T cell (i.e., Treg, Th17, Th1, and Th2) marker expression and Treg cell frequency. SEOV RNA and infectious particles in culture media were detected in both cell types, but at higher levels in LMVECs than in AMs postinfection. Expression of Ifnβ, Ccl5, and Cxcl10 and surface major histocompatibility complex class II (MHC-II) and MHC-I was not altered by SEOV infection in either cell type. SEOV infection significantly increased Tgfβ mRNA in AMs and the amount of programmed cell death 1 ligand 1 (PD-L1) in LMVECs. SEOV-infected LMVECs, but not AMs, induced a significant increase in Foxp3 expression and Treg cell frequency in allogeneic CD4(+) T cells, which was virus replication and cell contact dependent. These data suggest that in addition to supporting viral replication, AMs and LMVECs play distinct roles in hantavirus persistence by creating a regulatory environment through increased Tgfβ, PD-L1, and Treg cell activity.

The identification of markers of macrophage differentiation in PMA-stimulated THP-1 cells and monocyte-derived macrophages

Differentiated macrophages are the resident tissue phagocytes and sentinel cells of the innate immune response. The phenotype of mature tissue macrophages represents the composite of environmental and differentiation-dependent imprinting. Phorbol-12-myristate-13-acetate (PMA) and 1,25-dihydroxyvitamin D3 (VD₃) are stimuli commonly used to induce macrophage differentiation in monocytic cell lines but the extent of differentiation in comparison to primary tissue macrophages is unclear. We have compared the phenotype of the promonocytic THP-1 cell line after various protocols of differentiation utilising VD₃ and PMA in comparison to primary human monocytes or monocyte-derived macrophages (MDM). Both stimuli induced changes in cell morphology indicative of differentiation but neither showed differentiation comparable to MDM. In contrast, PMA treatment followed by 5 days resting in culture without PMA (PMAr) increased cytoplasmic to nuclear ratio, increased mitochondrial and lysosomal numbers and altered differentiation-dependent cell surface markers in a pattern similar to MDM. Moreover, PMAr cells showed relative resistance to apoptotic stimuli and maintained levels of the differentiation-dependent anti-apoptotic protein Mcl-1 similar to MDM. PMAr cells retained a high phagocytic capacity for latex beads, and expressed a cytokine profile that resembled MDM in response to TLR ligands, in particular with marked TLR2 responses. Moreover, both MDM and PMAr retained marked plasticity to stimulus-directed polarization. These findings suggest a modified PMA differentiation protocol can enhance macrophage differentiation of THP-1 cells and identify increased numbers of mitochondria and lysosomes, resistance to apoptosis and the potency of TLR2 responses as important discriminators of the level of macrophage differentiation for transformed cells.

MAIL regulates human monocyte IL-6 production

IL-6 is a pleiotropic cytokine implicated in the pathogenesis of disorders such as sepsis and cancer. We noted that human monocytes are excellent producers of IL-6 as compared with monocyte-derived macrophages. Because macrophages from molecule containing ankyrin repeats induced by LPS (MAIL) knockout animals have suppressed IL-6 production, we hypothesized that regulation of MAIL is key to IL-6 production in humans and may explain the differences between human monocytes and macrophages. To test this hypothesis fresh human monocytes and monocyte-derived macrophages were compared for MAIL expression in response to LPS. LPS-induced monocyte MAIL expression was highly inducible and transient. Importantly for our hypothesis MAIL protein expression was suppressed during differentiation of monocytes to macrophages. Of note, the human MAIL protein detected was the 80 kDa MAIL-L form and human MAIL showed nuclear localization. Human MAIL-L bound to p50 subunit of the NF-kappaB and increased IL-6 luciferase promoter activity in a cEBPbeta, NF-kappaB, and AP-1-dependent fashion. Like the differences in MAIL induction, monocytes produced 6-fold more IL-6 compared with macrophages (81.7 +/- 29.7 vs 12.6 +/- 6.8 ng/ml). Furthermore, suppression of MAIL by small interfering RNA decreased the production of IL-6 significantly in both THP-1 cells and in primary monocytes. Costimulation of monocytes with LPS and muramyl dipeptide induced an enhanced IL-6 response that was suppressed by siMAIL. Our data suggests that MAIL is a key regulator of IL-6 production in human monocytes and plays an important role in both TLR and NOD-like receptor ligand induced inflammation.

Pyrin critical to macrophage IL-1beta response to Francisella challenge

Relative to monocytes, human macrophages are deficient in their ability to process and release IL-1beta. In an effort to explain this difference, we used a model of IL-1beta processing and release that is dependent upon bacterial escape into the cytosol. Fresh human blood monocytes were compared with monocyte-derived macrophages (MDM) for their IL-1beta release in response to challenge with Francisella novicida. Although both cell types produced similar levels of IL-1beta mRNA and intracellular pro-IL-1beta, only monocytes readily released processed mature IL-1beta. Baseline mRNA expression profiling of candidate genes revealed a remarkable deficiency in the pyrin gene, MEFV, expression in MDM compared with monocytes. Immunoblots confirmed a corresponding deficit in MDM pyrin protein. To determine whether pyrin levels were responsible for the monocyte/MDM difference in mature IL-1beta release, pyrin expression was knocked down by nucleofecting small interfering RNA against pyrin into monocytes or stably transducing small interfering RNA against pyrin into the monocyte cell line, THP-1. Pyrin knockdown was associated with a significant drop in IL-1beta release in both cell types. Importantly, M-CSF treatment of MDM restored pyrin levels and IL-1beta release. Similarly, the stable expression of pyrin in PMA-stimulated THP-1-derived macrophages induces caspase-1 activation, associated with increased IL-1beta release after infection with F. novicida. In summary, intracellular pyrin levels positively regulate MDM IL-1beta responsiveness to Francisella challenge.

P2X(7) receptor and macrophage function

Macrophages are unique innate immune cells that play an integral role in the defense of the host by virtue of their ability to recognize, engulf, and kill pathogens while sending out danger signals via cytokines to recruit and activate inflammatory cells. It is becoming increasingly clear that purinergic signaling events are essential components of the macrophage response to pathogen challenges and disorders such as sepsis may be, at least in part, regulated by these important sensors. The activation of the P2X(7) receptor is a powerful event in the regulation of the caspase-1 inflammasome. We provide evidence that the inflammasome activation requires "priming" of macrophages prior to ATP activation of the P2X(7)R. Inhibition of the inflammasome activation by the tyrosine kinase inhibitor, AG126, suggests regulation by phosphorylation. Finally, the P2X(7)R may also be activated by other elements of the host response such as the antimicrobial peptide LL-37, which adds a new, physiologically relevant agonist to the P2X(7)R pathway. Therapeutic approaches to inflammation and sepsis will certainly be enhanced by an increased understanding of how purinergic receptors modulate the inflammasomes.

Pulmonary surfactant protein A regulates TLR expression and activity in human macrophages

The pulmonary innate immune system responds to various airborne microbes. Although its specificity is broad and based on the recognition of pathogen-associated molecular patterns, it is uniquely regulated to limit inflammation and thereby prevent damage to the gas-exchanging alveoli. Macrophages, critical cell determinants of this system, recognize microbes through pattern recognition receptors such as TLRs, which typically mediate proinflammatory responses. The lung collectin, surfactant protein A (SP-A), has emerged as an important innate immune determinant that regulates microbe-macrophage interactions in this environment. In this study, we report the basal and SP-A-induced transcriptional and posttranslational regulation of TLR2 and TLR4 expression during the differentiation of primary human monocytes into macrophages. Despite SP-A's ability to up-regulate TLR2 expression on human macrophages, it dampens TLR2 and TLR4 signaling in these cells. SP-A decreases the phosphorylation of IkappaBalpha, a key regulator of NF-kappaB activity, and nuclear translocation of p65 which result in diminished TNF-alpha secretion in response to TLR ligands. SP-A also reduces the phosphorylation of TLR signaling proteins upstream of NF-kappaB, including members of the MAPK family. Finally, we report for the first time that SP-A decreases the phosphorylation of Akt, a major cell regulator of NF-kappaB and potentially MAPKs. These data identify a critical role for SP-A in modulating the lung inflammatory response by regulating macrophage TLR activity.

Pyrin levels in human monocytes and monocyte-derived macrophages regulate IL-1beta processing and release

Macrophages and their precursors, monocytes, are key cells involved in the innate immune response. Although both monocytes and macrophages produce caspase-1, the key enzyme responsible for pro-IL-1beta processing; macrophages are limited in their ability to activate the enzyme and release functional IL-1beta. In this context, because mutations in the pyrin gene (MEFV) cause the inflammatory disorder familial Mediterranean fever, pyrin is believed to regulate IL-1beta processing. To determine whether variations in pyrin expression explain the difference between monocytes and macrophages in IL-1beta processing and release, pyrin was studied in human monocytes and monocyte-derived macrophages. Although monocytes express pyrin mRNA and protein, which is readily inducible by endotoxin, monocyte-derived macrophages express significantly less pyrin mRNA and protein. Pyrin levels directly correlated with IL-1beta processing in monocytes and macrophages; therefore, we asked whether pyrin might promote IL-1beta processing and release. HEK293 cells were transfected with pyrin, caspase-1, apoptotic speck protein with a caspase recruitment domain, and IL-1beta. Pyrin induced IL-1beta processing and release in a dose-dependent manner. Conversely, pyrin small interference RNA suppressed pro-IL-1beta processing in both THP-1 cells and fresh human monocytes. In summary, both pyrin expression and IL-1beta processing and release are diminished upon the maturation of monocytes to macrophages. When pyrin is ectopically expressed or silenced, IL-1beta processing and release parallels the level of pyrin. In conclusion, in the context of endotoxin-induced activation of mononuclear phagocytes, pyrin augments IL-1beta processing and release.

Chronic inflammation: importance of NOD2 and NALP3 in interleukin-1beta generation

Inflammation is part of the non-specific immune response that occurs in reaction to any type of bodily injury. In some disorders, the inflammatory process - which under normal conditions is self-limiting - becomes continuous and chronic inflammatory diseases might develop subsequently. Pattern recognition molecules (PRMs) represent a diverse collection of molecules responsible for sensing danger signals, and together with other immune components they are involved in the first line of defence. NALP3 and NOD2, which belong to a cytosolic subgroup of PRMs, dubbed Nod-like-receptors (NLRs), have been associated recently with inflammatory diseases, specifically Crohn's disease and Blau syndrome (NOD2) and familial cold autoinflammatory syndrome, Muckle-Wells syndrome and chronic infantile neurological cutaneous and articular syndrome (NALP3). The exact effects of the defective proteins are not fully understood, but activation of nuclear factor (NF)-kappaB, transcription, production and secretion of interleukin (IL)-1beta and activation of the inflammasome are some of the processes that might hold clues, and the present review will provide a thorough update in this area.

Peripheral injection of lipopolysaccharide enhances expression of inflammatory cytokines in murine locus coeruleus: possible role of increased norepinephrine turnover

Cytokines and catecholamines are known to constitute a significant portion of the regulatory neuroimmune networks involved in maintaining homeostasis in the central nervous system (CNS). Although we have already reported an increase in norepinephrine (NE) turnover within the locus coeruleus (LC) at 2 and 4 h after the intraperitoneal (i.p.) injection of lipopolysaccharide (LPS), the implication of this increase remains unclear. In view of evidence that norepinephrine (NE) acts in an anti-inflammatory manner by way of negatively regulating pro-inflammatory cytokine expression, we examined the inflammatory cytokine expression levels in the LC of C3H/HeN mice (male, 8 weeks old) after an i.p. LPS injection. The mRNA expression levels of the genes encoding IL-1beta and TNF-alpha within the LC increased during the first 2 h, and showed two peaks, the first at 4 h and the second lesser one at 15 h after the LPS injection. Microglia, which are one of the major cell types that produce pro-inflammatory cytokines in the CNS, were isolated from mouse neonate brains in order to clarify more precisely the relationship between the changes in NE content and the up-regulation of inflammatory cytokines in the LC. Simultaneous incubation of microglia with LPS and NE enhanced the expression of IL-1beta at both mRNA and protein levels, but reduced the mRNA and protein levels of TNF-alpha. These data support the hypothesis that NE negatively regulates the expression of pro-inflammatory cytokine expression, at least in the case of TNF-alpha, which action could contribute to the observed anti-inflammatory properties of NE. This report, based on the results of both in vivo and in vitro experiments, is the first to suggest a relationship between NE content and cytokine expression levels in the CNS.

ATP-stimulated release of interleukin (IL)-1beta and IL-18 requires priming by lipopolysaccharide and is independent of caspase-1 cleavage

Interleukin (IL)-1beta and IL-18 are structurally similar proteins that require caspase-1 processing for activation. Both proteins are released from the cytosol by unknown pathway(s). To better characterize the release pathway(s) for IL-1beta and IL-18 we evaluated the role of lipopolysaccharide priming, of interleukin-1beta-converting enzyme (ICE) inhibition, of human purinergic receptor (P2X(7)) function, and of signaling pathways in human monocytes induced by ATP. Monocytes rapidly processed and released both IL-1beta and IL-18 after exogenous ATP. Despite its constitutive cytosolic presence, IL-18 required lipopolysaccharide priming for the ATP-induced release. Neither IL-1beta nor IL-18 release was prevented by ICE inhibition, and IL-18 release was not induced by ICE activation itself. Release of both cytokines was blocked completely by a P2X7 receptor antagonist, oxidized ATP, and partially by an antibody to P2X(7) receptor. In evaluating the signaling components involved in the ATP effect, we identified that the protein-tyrosine kinase inhibitor, AG126, produced a profound inhibition of both ICE activation as well as release of IL-1beta/IL-18. Taken together, these results suggest that, although synthesis of IL-1beta and IL-18 differ, ATP-mediated release of both cytokines requires a priming step but not proteolytically functional caspase-1.

Transforming growth factor-beta is involved in the pathogenesis of dialysis-related amyloidosis

BACKGROUND

Advanced glycation end product-modified beta2-microglobulin (AGE-beta2m) is an important component of dialysis-related amyloidosis (DRA). Its presence induces monocyte chemotaxis and the release of the proinflammatory cytokines through macrophage activation. Transforming growth factor-beta (TGF-beta) is a multifunctional cytokine that also has chemotactic activity for monocytes at very low (0.1 to 10 pg/mL) concentrations and inhibits proinflammatory cytokine production of macrophages. In this study, we investigated the role of TGF-beta in the pathogenesis of DRA.

METHODS

We performed an immunohistochemical study of DRA tissues (8 cases) to confirm the existence of TGF-betas and their receptors; we also performed a chemotaxis assay of human monocytes as well as enzyme-linked immunosorbent assay (ELISA) of TGF-beta1, tumor necrosis factor-alpha (TNF-alpha), interleukin-1beta (IL-1beta), and interleukin-1 receptor antagonist (IL-1Ra) in the supernatant of human monocyte-derived macrophage cell culture under varying conditions of incubation with TGF-beta1, AGE-beta2m, and TGF-beta1 antibody additions.

RESULTS

There was positive staining for TGF-betas (types 1, 2, and 3) and their receptors (types I, II, and III) in infiltrated macrophages (CD68+), synovial lining cell, as well as vascular walls around amyloid deposition. AGE-beta2m also induced TGF-beta1 production by macrophages in a dose-dependent manner (410 +/- 80 pg/mL at 12.5 microg/mL, 621 +/- 62 pg/mL at 25 microg/mL, and 776 +/- 62 pg/mL at 50 microg/mL of AGE-beta2m). AGE-beta2m induced significant TNF-alpha and IL-1Ra production by macrophage. The addition of exogenous TGF-beta1 (0.1 to 10 ng/mL) decreased AGE-beta2m-induced TNF-alpha production and increased IL-1Ra production in a dose-dependent fashion. IL-1beta production was not effected by any experimental conditions. In chemotaxis assay, anti-TGF-beta1 antibody (0.1 to 10 microg/mL) attenuated AGE-beta2m-induced monocyte chemotaxis.

CONCLUSIONS

These results provide the first evidence to our knowledge for the presence of TGF-beta in DRA tissue, as well as the stimulatory action of AGE-beta2m on tissue macrophages. In turn, TGF-beta suppresses the proinflammatory activation of macrophages, suggesting a dual role for TGF-beta in the inflammatory process of DRA. These observations may provide a pathophysiologic link between TGF-beta and DRA.

Interleukin-1 expression during hyperoxic lung injury in the mouse

An important component of the pathophysiologic response to hyperoxia (O2) is pulmonary inflammation, although the roles of specific inflammatory mediators during pulmonary O2 toxicity are not completely known. Interleukin-1 (IL-1) is an early inflammatory mediator and is sufficient to elicit many of the responses associated with acute injury. The IL-1 family comprises two bioactive proteins, IL-1alpha and IL-1beta, and their natural antagonist IL-1ra. Here we report studies of IL-1 regulation during hyperoxic lung injury in the adult mouse. When assayed by Northern blot, increases in IL-1beta mRNA were seen after 2 days of hyperoxia. In contrast, IL-1alpha mRNA was barely detectable before 4 days of hyperoxia. To further understand the cellular origin of IL-1beta expression in lungs, in situ hybridization and immunohistochemical analyses were performed. IL-1beta mRNA or protein was not detected in the lungs of unexposed animals. At 3 days, we observed the accumulation of IL-1beta transcripts in pulmonary interstitial macrophages and in a subset of neutrophils, and immunodetectable IL-1beta protein was co-localized in adjacent sections. At 4 days of exposure, IL-1beta transcripts were widespread in lung tissue, but many areas rich in IL-1beta mRNA were devoid of immunodetectable IL-1beta. However, it is not known whether increased synthesis of IL-1beta or the uncoupling of IL-1beta protein and mRNA accumulation has a role in pathophysiology of pulmonary O2 toxicity.

Different pattern of local and systemic release of proinflammatory and anti-inflammatory mediators in severely injured patients with chest trauma

BACKGROUND

Excessive release of proinflammatory cytokines has been involved in pathogenesis of acute respiratory distress syndrome.

DESIGN

Since injured patients with chest trauma reveal a high risk for posttraumatic acute respiratory distress syndrome, local and systemic release of proinflammatory cytokines and their naturally occurring inhibitors were determined in the early posttraumatic period.

MATERIALS AND METHODS

Proinflammatory and anti-inflammatory mediators were measured in plasma and bronchoalveolar lavage fluid (BALF) from 16 patients with multiple injuries including severe chest injury (Injury Severity Score of 34.4 +/- 2.3 points) and compared with healthy volunteers (n = 17).

RESULTS

Tumor necrosis factor-alpha was detectable neither in plasma nor in BALF. Interleukin-1beta and interleukin-8 were significantly increased in BALF from injured patients, while plasma levels were similar in both groups. Soluble tumor necrosis factor receptors p55 and p75 and interleukin-1ra were markedly elevated in plasma (p < or = 0.01) and BALF (p < or = 0.001) from injured patients compared with controls.

CONCLUSION

Highly increased concentrations of proinflammatory cytokines in BALF, but not in circulation, indicate a strong local inflammatory response early after multiple injuries combined with chest injury rather than severe systemic inflammation. In contrast, anti-inflammatory mechanisms seem to be activated locally and systemically.

Role of macrophages in pulmonary late-phase reaction in guinea pigs

To examine the role of macrophages in pulmonary late-phase reaction (LPR), macrophages were reduced in sensitized guinea pigs by an intravenous injection of liposome-encapsulated dichloromethylene diphosphonate (Cl2MDP). Macrophage reduction was evaluated by bronchoalveolar lavage (BAL) fluid analysis. In Cl2MDP liposome-treated animals, the number of macrophages in BAL fluid significantly decreased by 56% compared with PBS liposome-treated animals (1.6 +/- 0.1 vs. 3.6 +/- 0.4 x 10(6) cells, p < 0.01). The number of neutrophils, eosinophils, or lymphocytes in BAL fluid showed no significant changes in these two groups. Both PBS and Cl2MDP liposome-treated sensitized guinea pigs were challenged with an inhalation of antigen, and respiratory resistance (Rrs) was measured. PBS liposome-treated animals (control) exhibited both immediate (IPR) and late (LPR) increases in Rrs. The maximal increases in Rrs at IPR and LPR were 217 +/- 19 and 187 +/- 20% of baseline values, respectively (n = 9). On the other hand, Cl2MDP liposome-treated animals showed an immediate increase in Rrs (IPR); however, the late increase in Rrs (LPR) was significantly suppressed (p < 0.05). The maximal increases in Rrs at IPR and LPR were 200 +/- 13 and 134 +/- 11% of baseline values, respectively (n = 8). In Cl2MDP liposome-treated animals, the numbers of macrophages and neutrophils in BAL fluid 4 hr after antigen challenge decreased by 45% and 54%, respectively, compared with PBS liposome-treated animals (p < 0.05). In Cl2MDP liposome-treated animals, neutrophil chemotactic activity in BAL fluid 4 hr after antigen challenge decreased by 59% compared with PBS liposome-treated animals (p < 0.05). These results suggest that macrophages play an important role in the development of pulmonary LPR through the induction of neutrophil accumulation in the airways.

Antigen expression of alveolar macrophages in smokers and patients with lung diseases

Alveolar macrophage function was studied immunocytochemically using three monoclonal antibodies--macrophage CD 68 KP 1 (M), protein CD 11C (P), and anti-elastin (EL)--and three polyclonal antibodies--lysozyme (LZ), alpha-1-antitrypsin (AAT), and alpha-1-antichymotrypsin (AACT). The material for study was smears obtained from bronchial washings from 15 healthy persons and 60 patients with respiratory infections or primary or secondary malignant lung infiltration. Eight of the healthy group and 40 of the patient group were smokers (SM). The percentage of cells obtained from the washings which were macrophages was also measured. The intensity of staining reactions for each of the six antigens was noted and in general more intense staining was noted in smokers than in non-smokers. More intense staining was observed in patients with pulmonary infections (group II PI) and metastatic pulmonary infiltrations (group IV MP Ca) than in controls (group IC), while patients with primary lung cancer (group III PP Ca) had highly reduced staining reactions. The number of macrophages was similarly increased in all groups in comparison with the IC group for non-smokers and in all groups except III PP Ca for smokers. It is concluded that smoking, pulmonary infections, and metastatic infiltration of the lung are associated with an increase in the number and activity of alveolar macrophages, while patients with primary lung cancer have an increase in the number of macrophages which are functionally incompetent.

Increased levels of tumor necrosis factor alpha (TNF-alpha) and interleukin 1 beta (IL-1 beta) in tracheal aspirates of newborns with pneumonia

Pneumonia is one of the major sites of infection in ventilated newborns. We investigated whether the cytokines IL-1 beta and TNF-alpha are detectable in tracheal aspirates of newborns with pneumonia as a diagnostic marker. All 12 infants with pneumonia had elevated levels of IL-1 beta (range 30-300 pg/ml) and TNF-alpha (range 60-680 pg/ml), whereas control infants (n = 21; respiratory distress syndrome, very low birth weight or infants intubated preoperatively) had no detectable levels of IL-1 beta or TNF-alpha. In vitro investigations with mononuclear cells of umbilical cord blood were performed to rule out that exogenously added surfactant influences IL-1 beta and TNF-alpha production. It is concluded that IL-1 beta and TNF-alpha are important and specific mediators of neonatal pneumonia which may be of diagnostic importance.

Endotoxin administration to humans primes alveolar macrophages for increased production of inflammatory mediators

To elucidate potential mechanisms of the acute lung injury associated with endotoxemia, we evaluated the effect of intravenously administered endotoxin on the ability of alveolar macrophages isolated by bronchoalveolar lavage from normal subjects to produce inflammatory mediators. Within 1 hr of endotoxin (4 ng/kg body weight) administration, all 12 study subjects developed constitutional symptoms and leukopenia, and within 3 hr, low-grade fever. Resolution of symptoms and fever by 6 hr was accompanied by systemic granulocytosis. Although intravenously administered endotoxin appeared to activate a subset of circulating monocytes, it did not alter the bronchoalveolar lavage cell number, phenotype (95% macrophages), or constitutively expressed high levels of surface HLA-DR and O2-. In contrast, intravenous endotoxin primed the alveolar macrophages for enhanced lipopolysaccharide-induced secretion of interleukin-1 (11.8 to 25.8 U/ml; P = 0.04), tumor necrosis factor-alpha (titer, 6.8 to 13.6; P = 0.20), and prostaglandin E2 (38.4 to 116.3 ng/ml; P = 0.035). These results demonstrate that low-dose intravenous endotoxin primes human alveolar macrophages, which are already differentiated in situ, for enhanced secretion of inflammatory mediators. Such mediators may contribute to the pulmonary changes associated with endotoxemia and acute lung injury.

Expression and modulation of a mononuclear phagocyte differentiation antigen (PAM-1) during in vitro maturation of peripheral blood monocytes

Human macrophages obtained by in vitro maturation of peripheral blood monocytes express a surface antigen, PAM-1, recognized by a monoclonal antibody and typical of pulmonary alveolar and tissue macrophages. PAM-1, undetectable in freshly isolated peripheral blood monocytes, was expressed in monocyte-derived macrophages after 3 days of in vitro adherent culture and was maximal after 14-15 days (50%-60% of positive cells). Similar levels of PAM-1 positivity were observed in non-adherent monocyte-derived macrophages suggesting that cell adhesion was not a critical requisite for the expression of this antigen. Bacterial lipopolysaccharide and a monocyte chemotactic protein preparation respectively suppressed and upregulated PAM-1 expression in monocyte-derived macrophages. In contrast, interferon-gamma, although enhancing the levels of class II HLA-DR antigen in monocyte-derived macrophages, did not influence the kinetics of appearance and the levels of PAM-1 in these cells. Thus, expression of PAM-1, which is restricted to certain stages of the monocyte-macrophage differentiation pathway, is also differentially modulated by activation signals, which can be present in the micro-environment of inflammed tissues.

Quantification of interleukin-1 in nasal polyps from patients with chronic sinusitis

We have measured interleukin-1 alpha (IL-1 alpha) and beta levels in nasal polyps (NP) from patients with chronic sinusitis (CS) in order to determine their significance in the pathogenesis of NP. NP in ten cases (five male and five female; age range, 17-63 years) were removed to separate mononuclear (M) and polymorphonuclear (PMN) fractions through Ficoll-Paque separation media. ELISA measurements of the M fraction showed that the mean value of IL-1 beta was 17.8 pg/ml per gram, which was significantly higher than that of IL-1 alpha (7.04 pg/ml per gram, P < 0.01, Wilcoxon test). In the PMN fraction, the mean value of IL-1 alpha was 8.79 pg/ml per gram and that of IL-beta was 7.85 pg/ml per gram, which was not significantly different. Mononuclear leukocytes, particularly activated monocytes, seem to be a major source of IL-1 in the NP taken from patients with CS.

Localization of intestinal interleukin 1 activity and protein and gene expression to lamina propria cells

BACKGROUND

Interleukin 1 (IL-1) is a key mediator of bowel inflammation, but there is limited knowledge about the amount and site of production of this cytokine in the gastrointestinal tract under physiological or pathological conditions.

METHODS

Epithelial and lamina propria mononuclear cells were isolated from control, and Crohn's disease- and ulcerative colitis-involved mucosa to investigate the capacity of these cells to generate IL-1 bioactivity, IL-1 alpha and IL-1 beta immunoreactivity, and gene expression.

RESULTS

Control lamina propria mononuclear cells produced substantial amounts of IL-1 alpha and IL-1 beta, which increased dramatically when inflammatory bowel disease cells were used. Epithelial cells from control, Crohn's disease, and ulcerative colitis intestine displayed no IL-1 bioactivity or immunoreactivity. Lamina propria mononuclear cells contained moderate to large quantities of IL-1 alpha and IL-1 beta messenger RNA (mRNA), respectively, whereas epithelial cells had none. The absence of IL-1 transcripts in epithelial cells was selective, because mRNA for HLA-DR antigens was present in control and inflammatory bowel disease cells.

CONCLUSIONS

In normal and inflamed human intestine there is a distinct compartmentalization of IL-1, as mononuclear but not epithelial cells generate this cytokine. The high levels of IL-1 in inflammatory bowel disease may explain several of its local and systemic manifestations, and blockade by specific antagonists could have important therapeutic effects.

ELISA detection of IL-1 beta in human sera needs independent confirmation. False positives in hospitalized patients

The detection of cytokines in human sera has become an accepted index of disease activity in various diseases, including sepsis. However, little attention has been paid to the specificity of these measurements. Using a sensitive sandwich enzyme-linked immunoassay (ELISA), we studied IL-1 beta detectability in sera from 419 serum samples randomly obtained from our clinical laboratory. In initial studies, 6.7% of samples were positive (n = 24, 0.1 to 1.0 ng/ml, and n = 5, 1 to 80 ng/ml). However, attempts to further characterize positive samples revealed that over 90% were falsely positive. For example, samples fractionated on Sephadex G-75 demonstrated IL-1 beta "detectability" near the void volume, and negative samples, spiked with rIL-1 beta, eluted at approximately 17 kD. To determine if this detectability was due to heterophillike antibodies, 23 of 29 "positive" samples were retested in the presence of nonimmune mouse serum. Only 2 of 23 previously positive samples were still positive. Importantly, mouse serum had no effect upon normal human serum spiked with rIL-1 beta. Furthermore, blinded samples sent to a reference laboratory also demonstrated false positive IL-1 beta detection in selected samples. Taken together, these data demonstrate that the presence of nonspecific immunoactivity in sera may confound cytokine assays of human biologic material and suggest that, when possible, a second means of confirming ELISA-positive samples be used.

Abnormal fibroblast clone--an alternative hypothesis for pathogenesis of rheumatic heart disease

Fibrosis is an ubiquitous process. Any tissue injury can culminate in fibroblast accumulation and multiplication with collagen synthesis and deposition. A large number of chronic disease states such as rheumatic heart disease, constrictive pericarditis, cirrhosis of the liver, renal interstitial fibrosis, chronic interstitial lung disease are characterized by extensive fibrosis. In many of these patients, when there is no clinical or laboratory evidence of previous injury, it is presumed that the initiating insult/injury had been 'subclinical'. I propose that 1) the fibroblasts can be activated even in the absence of preceding inflammation, 2) it is the type of 'fibroblast clone' in a given individual together with the 'milieu' in a particular tissue/organ which decides the occurrence and severity of subsequent fibrosis. This fibroblast clonal theory adds a new dimension to the pathogenesis of various disease states and may help in identifying those at high-risk and in evolving a unified therapeutic strategy for amelioration of various disorders characterized by extensive fibrosis.

Production of interleukin 1 by rat pleural leucocytes in culture after intratracheal instillation of crocidolite asbestos

This study was undertaken to investigate the production of interleukin 1 (IL-1) by pleural leucocytes in culture and to evaluate the influence of intratracheal instillation of crocidolite asbestos on this production. Normal pleural leucocytes spontaneously released IL-1 in culture and stimulation with lipopolysaccharide (LPS) dramatically increased production. Intratracheal instillation with crocidolite asbestos induced recruitment of pleural leucocytes in the longer term and changed IL-1 production by the leucocytes. Reduced production of IL-1 was found by one day after instillation of asbestos and this was correlated with the dose of asbestos. With increasing time after instillation, however, release of IL-1 by pleural leucocytes gradually recovered to normal until, one month after asbestos injection, the leucocytes produced augmented IL-1 in culture compared with control pleural leucocytes. Our data show that pleural leucocytes possess the potential to produce IL-1 in vitro and this capability is altered by intratracheal instillation of crocidolite asbestos. This may be relevant to development of pleural diseases associated with inhalation of asbestos.

Lipopolysaccharide binding protein enhances the responsiveness of alveolar macrophages to bacterial lipopolysaccharide. Implications for cytokine production in normal and injured lungs

A plasma lipopolysaccharide (LPS)-binding protein (LBP) has been shown to regulate the response of rabbit peritoneal macrophages and human blood monocytes to endotoxin (LPS). We investigated whether LBP is present in lung fluids and the effects of LBP on the response of lung macrophages to LPS. Immunoreactive LBP was detectable in the lavage fluids of patients with the adult respiratory distress syndrome by immunoprecipitation followed by Western blotting, and also by specific immunoassay. In rabbits, the LBP appeared to originate outside of the lungs, inasmuch as mRNA transcripts for LBP were identified in total cellular RNA from liver, but not from lung homogenates or alveolar macrophages. Purified LBP enhanced the response of human and rabbit alveolar macrophages to both smooth form LPS (Escherichia coli O111B:4) and rough form LPS (Salmonella minnesota Re595). In the presence of LBP and LPS, the onset of tumor necrosis factor-alpha (TNF alpha) production occurred earlier and at an LPS threshold dose that was as much as 1,000-fold lower for both types of LPS. In rabbit alveolar macrophages treated with LBP and LPS, TNF alpha mRNA appeared earlier, reached higher levels, and had a prolonged half-life as compared with LPS treatment alone. Neither LPS nor LPS and LBP affected pHi or [Cai++] in alveolar macrophages. Specific monoclonal antibodies to CD14, a receptor that binds LPS/LBP complexes, inhibited TNF alpha production by human alveolar macrophages stimulated with LPS alone or with LPS/LBP complexes, indicating the importance of CD14 in mediating the effects of LPS on alveolar macrophages. Thus, immunoreactive LBP accumulates in lung lavage fluids in patients with lung injury and enhances LPS-stimulated TNF alpha gene expression in alveolar macrophages by a pathway that depends on the CD14 receptor. LBP may play an important role in augmenting TNF alpha expression by alveolar macrophages within the lungs.

Fibroblast growth factors in connective tissue disease associated interstitial lung disease

Fibrosis is a major cause of morbidity and mortality in chronic inflammatory diseases, especially interstitial pulmonary disorders. Fibroproliferation is an important part of this fibrotic response, and is mediated largely through growth factors such as platelet-derived growth factor (PDGF), insulin-like growth factor (IGF) I and tumour necrosis factor-alpha (TNF-alpha). Although there is some evidence implicating these cytokines in fibrotic disorders, strong evidence in vivo is almost nonexistent. In order to ascertain the role that these factors play in inflammatory lung disorders associated with connective tissue diseases, alveolar mononuclear cells have been obtained from subjects by bronchoalveolar lavage and assessed for the spontaneous release of fibroblast growth factors. The study population consisted of subjects with a variety of different connective tissue disorders, both with and without inflammatory pulmonary complications. It was found that lavage cells spontaneously secreted fibroblast growth factor activity over 24 h with maximum activity detected at 6 to 12 h. Growth factor activity could be detected in most subjects with connective tissue disease-associated inflammatory lung disease and some normal subjects, but the amount of growth factor activity was much higher in the former than in the latter. By means of antibody depletion experiments all growth factor activity from lavage cells of normal patients was attributable to TNF-alpha while patients with interstitial lung disease secreted large amounts of PDGF and fibronectin in addition to TNF-alpha. Approximately 40-50% of the total released growth factor activity could be accounted for by PDGF, and 100% by the combination of PDGF, TNF-alpha and fibronectin. While TNF-alpha is released from the bronchoalveolar lavage cells of many subjects, in addition, many patients with interstitial lung disease also release spontaneously, large amounts of fibroblast growth factor activity attributable to PDGF and fibronectin.

Accessory function of human mononuclear phagocytes for lymphocyte responses to the superantigen staphylococcal enterotoxin B

The role of the cytokines IL-1 alpha, IL-1 beta, and IL-6 and the cell adhesion molecules ICAM-1, LFA-1 (alpha and beta), and Mac-1 as accessory molecules for stimulation of T cells by the superantigen staphylococcal enterotoxin B (SEB) was examined. Both blood monocytes and alveolar macrophages were used as accessory cells because these cells differ in patterns of cytokine expression and thus potentially in accessory cell function for superantigens. The blastogenic response of highly purified T cells to SEB was reconstituted with either monocytes or alveolar macrophages. IL-1 secretion was increased comparably in monocytes and alveolar macrophages by SEB, but IL-6 was not stimulated by SEB. IL-1 alpha plus IL-1 beta reconstituted the response of T cells to SEB but required the addition of accessory cells. The cell adhesion molecules ICAM-1 and LFA-1 but not Mac-1 also functioned as accessory molecules for SEB-induced cluster formation and lymphocyte blastogenesis. Thus, not only must this superantigen bind to Class II MHC on accessory cells as is well known, but also SEB requires at least certain cytokines (IL-1 alpha and IL-1 beta) produced by accessory cells and cell adhesion molecules (ICAM-1 and LFA-1) for activation of T lymphocytes.

Processing of interleukin-1 in cells of monocytic lineage is differentiation-dependent

The interleukin-1 (IL-1) alpha and beta precursor proteins are processed and released from several cell types in the absence of a canonical signal peptide. To gain some insight into the mechanisms that allow the production of IL-1 alpha and beta, we have investigated by immunoprecipitation the synthesis, their release and processing in a promyeloblastic cell line of tumoral origin, U937, and in peripheral blood monocytes. We show that U937 monocytic cells, on induction with a tumor-promoting agent, synthesize and release into the culture medium proIL-1 beta but do not process it. Similarly, peripheral blood monocytes left in adherence for 24 h or longer, prior to addition of lipopolysaccharide, synthesize and release proIL-1 alpha and beta without detectable processing of either cytokine. Processing and release of IL-1 alpha and beta by peripheral blood monocytes can be observed when monocytes are left to adhere for periods less than 15 h before lipopolysaccharide addition. IL-1 alpha and beta show similar kinetics of release from the cells, suggesting the existence of a common mechanism regulating their secretion. Since peripheral blood monocytes left in adherence in the presence of lipopolysaccharide differentiate into macrophages, we conclude that release and processing of IL-1 can occur independently and that processing depends on the stage of differentiation of monocytes, i.e. only the monocytes at an early stage of differentiation produce 17-kDa IL-1 alpha and beta.

Characterization of IL-1 inhibitory factor released from human alveolar macrophages as IL-1 receptor antagonist

IL-1 possesses pleiotropic properties on various cells and its activity may be stringently regulated in several ways. We have previously reported that both IL-1 and its inhibitory factor are concomitantly released from alveolar macrophages in both healthy subjects and patients with chronic inflammatory lung diseases. An increase in IL-1 activities and a decrease in inhibitory activities are characteristics found in both healthy smokers and patients with interstitial lung diseases. In this study, we further examined the biological properties of IL-1 inhibitory factor. The inhibitor exhibited a dose-dependent specific inhibition of an augmentation by IL-1 of PHA-induced murine thymocyte proliferation, while no inhibition of the augmentation by IL-2, IL-4, IL-6, or tumour necrosis factor (TNF) was found. 125I-labelled IL-1 alpha binding on PHA-stimulated murine thymocytes revealed two types of IL-1 binding sites, 44 sites/cell with a Kd of 2.7 x 10(-10) M and 230 sites/cell with a Kd of 2.5 x 10(-9) M. Alveolar macrophage culture supernatants blocked the binding of labelled IL-1 to the IL-1 receptor in a dose-dependent fashion. Scatchard plot analysis revealed that the inhibitory factor in the supernatants blocked the binding competitively. These results indicate that alveolar macrophages produce a specific IL-1 inhibitory factor, functioning as an IL-1 receptor antagonist.

In vitro desensitization to lipopolysaccharide suppresses tumour necrosis factor, interleukin-1 and interleukin-6 gene expression in a similar fashion

Like blood monocytes, the human monocytic cell line Mono Mac 6 can be stimulated by lipopolysaccharide (LPS) at 1 microgram/ml to produce high levels of cytokines. When Mono Mac 6 cells are stimulated for 4-6 hr at 1 x 10(6)/ml, supernatants contain tumour necrosis factor (TNF) at an average of 60 U/ml and interleukin-6 (IL-6) at an average of 1000 U/ml. IL-1 is not detected in the supernatant, but after three freeze-thaw cycles cell-associated IL-1 can be detected (100 U/ml) and with similar amounts of IL-alpha and -beta. Preculture of Mono Mac 6 cells with LPS at 10 ng/ml for 3 days results in cells refractory to subsequent stimulation by LPS at 1 microgram/ml. In the refractory desensitized cells, production of all three cytokines is down-regulated, with a more than 10-fold reduction in protein production. For all three cytokines, this desensitization appears to be regulated at the transcript level, with a strong reduction in specific mRNA as detected by Northern blot analysis. Furthermore, Mono Mac 6 cells can be stimulated by Staphylococcus aureus (LPS contamination less than 10 pg/ml) to produce cytokines. This type of stimulus is unable to overcome desensitization, in that the secretion of TNF in LPS-precultured Mono Mac 6 cells was 10- to 100-fold lower than in Mono Mac 6 cells without LPS preculture. These data show that desensitization in Mono Mac 6 cells affects all three cytokines tested and that it extends to other activating signals, such as staphylococci.

Pulmonary response to inhaled silica or titanium dioxide

The pulmonary response to mineral dust inhalation was investigated by characterizing markers of lung injury and inflammation, macrophage activation, dust clearance, and histopathology. Rats were exposed (6 hr/day x 5 days) to air or 50 mg/m3 crystalline silica (SiO2) or titanium dioxide (TiO2). At 7, 14, 28, and 63 days after exposure, bronchoalveolar lavage fluid (BALF) was analyzed for lactate dehydrogenase (LDH), total protein, and N-acetylglucosaminidase, as well as cell number, type, and viability. Alveolar macrophages (AM) obtained in BALF were cultured with or without LPS and release of interleukin-1 (IL-1) and fibronectin was determined. Histopathology was conducted at 28 and 63 days. The exposure protocol resulted in 1.8-1.9 mg of mineral dust being deposited in the pulmonary region. Clearance of SiO2 was significantly less than TiO2. SiO2 increased BALF neutrophils (Days 14, 28, and 63), total protein (Days 28 and 63), and LDH and lymphocytes (Day 63). SiO2 increased AM-derived fibronectin release (Day 63) and LPS-induced IL-1 release (all time points), but not spontaneous release of IL-1. TiO2 did not change BALF biochemical or cellular parameters or AM secretory activity. Histopathology revealed minimal interstitial inflammation with SiO2 and no significant response in control or TiO2 rats. These results demonstrate the pulmonary response to inhaled SiO2 can be differentiated from the relatively innocuous TiO2 by changes in BALF markers of injury and inflammation further supporting the use of BALF analysis to make relative assessments of pulmonary toxicity. The stimulation of macrophage fibronectin release by the fibrogenic dust SiO2 and not TiO2 is consistent with a role for this glycoprotein in lung injury and repair. Last, the early and persistent effect of SiO2 on LPS-induced AM IL-1 release indicates this response may represent a sensitive early marker of dust-induced changes in the AM population.

Interleukin-4 downregulates interleukin-6 production by human alveolar macrophages at protein and mRNA levels

Effects of interleukin-4 (IL-4) on IL-6 production by human alveolar macrophages (AM) obtained by bronchoalveolar lavage from healthy donors was examined at the protein and gene levels. IL-6 production was quantitated by enzyme immunoassay (EIA) and bioassay using the IL-6 dependent murine hybridoma cell line MH60.BSF2. Results showed that when activated with LPS, AM released significantly more biologically active IL-6 than blood monocytes. Human rIL-4 significantly suppressed IL-6 production by AM and monocytes stimulated with LPS. Northern blot analysis revealed that IL-4 reduced the expression of IL-6 mRNA in LPS-stimulated AM and monocytes. The inhibitory effect was most pronounced when IL-4 was added with LPS or within the first 4 hr after LPS to AM or monocytes. The suppressive effect of IL-4 was completely neutralized by pretreatment with anti-IL-4 antibody. IL-4 also showed a suppressive effect on IL-6 production by macrophages generated in vitro by maturation of blood monocytes with granulocyte-macrophage colony stimulating factor (GM-CSF). These observations suggest that IL-4 may play a critical role in in situ regulation of immune responses through suppression of IL-6 production.

Cooperation between accessory cells and T lymphocytes in patients with tuberculous pleurisy

We studied interleukin 1 (IL-1) activity of pleural fluid macrophages and peripheral blood monocytes obtained from ten patients with tuberculous pleurisy and ten patients with malignant pleurisy, using purified protein derivative (PPD) as a stimulating agent. Tuberculous pleural fluid macrophages and peripheral blood monocytes tended to produce higher IL-1 activity than malignant pleural fluid macrophages and blood monocytes and showed significantly more IL-1 activity than healthy control monocytes. However, no significant difference in IL-1 activity was observed between tuberculous pleural macrophages and blood monocytes. With the cooperation of these accessory cells, pleural fluid T lymphocytes in patients with tuberculous pleurisy showed a significant level of interleukin 2 (IL-2) activity in the presence of PPD. Tuberculous pleural fluid macrophages promoted greater IL-2 production than blood monocytes from either tuberculous pleural fluid or blood T lymphocytes despite relative equivalence in measured IL-1 production. Combination of tuberculous pleural fluid macrophages and pleural fluid T lymphocytes was the most effective for increasing IL-2 activity when compared with other combinations. These results suggest that tuberculous pleural fluid macrophages and T lymphocytes may contribute to the immunopathogenesis of tuberculosis at a local site of disease.

Cytotoxic tumor necrosis factor activity produced by equine alveolar macrophages: preliminary characterization

Blood monocytes and alveolar macrophages (AM) were harvested from foals (aged 46 days to 6 months) and cultured in either medium alone or medium containing 10 micrograms/ml bacterial lipopolysaccharide (LPS). After 24 h, culture supernates were collected and analyzed for cytotoxic activity on sensitized L929 cells. Both monocytes and AM that had been treated with LPS produced significantly more cytotoxic activity than the same cell type exposed to medium lacking LPS. LPS-treated macrophages secreted significantly more cytotoxic activity (120 +/- 17.8 U/ml) than did LPS-treated monocytes (47.3 +/- 17.0 U/ml); however, constitutive production of cytotoxin by monocytes was higher (16.7 +/- 4.1 versus 1.2 +/- 1.2 U/ml). The identification of the cytotoxin as tumor necrosis factor (TNF) was strongly suggested by its reactivity with a rabbit antiserum directed against the N-terminal 15 amino acids of human TNF. TNF secretion by AM increased in a dose-dependent manner between LPS concentrations of 0.0001 and 1 microgram/ml, then leveled off. Most of the cytotoxic TNF activity produced by AM was secreted within the first 8 h after initial contact with LPS. Macrophage supernatant TNF was stable over a pH range of 6-11, but lost activity when kept at a pH less than 6. Equine TNF also was destroyed by exposure for 1 h to temperatures more than 60 degrees C. TNF bioactivity was recovered as a single peak after crude macrophage supernate was subjected to analysis by either anion exchange or gel filtration chromatography (molecular weight approximately 56,000).