Bacterial endotoxin: molecular relationships of structure to activity and function

Endotoxins of Gram-negative microbes fulfill as components of the outer membrane a vital function for bacterial viability and, if set free, induce in mammalians potent pathophysiological effects. Chemically, they are lipopolysaccharides (LPS) consisting of an O-specific chain, a core oligosaccharide, and a lipid component, termed lipid A. The latter determines the endotoxic activities and, together with the core constituent Kdo, essential functions for bacteria. The primary structure of lipid A of various bacterial origin has been elucidated and lipid A of Escherichia coli has been chemically synthesized. The biological analysis of synthetic lipid A partial structures proved that the expression of endotoxic activity depends on a unique primary structure and a peculiar endotoxic conformation. The biological lipid A effects are mediated by macrophage-derived bioactive peptides such as tumor necrosis factor alpha (TNF). Macrophages possess LPS receptors, and the lipid A regions involved in specific binding and cell activation have been characterized. Synthetic lipid A partial structures compete the specific binding of LPS or lipid A and antagonistically inhibit the production of LPS-induced TNF. LPS toxicity, in general, and the ability of LPS to induce TNF are also suppressed by a recently developed monoclonal antibody (IgG2a), which is directed against an epitope located in the core oligosaccharide. At present we determine molecular and submolecular details of the specificity of the interaction of lipid A with responsive host cells with the ultimate aim to provide pharmacological or immunological therapeutics that reduce or abolish the fatal inflammatory consequences of endotoxicosis.

Analysis of the synovial cell infiltrate in early rheumatoid synovial tissue in relation to local disease activity

OBJECTIVE

To define variations in the cellular infiltrate and in the expression of monokines in synovial tissue (ST) from rheumatoid arthritis (RA) patients with different durations of disease and different levels of disease activity.

METHODS

The immunohistologic features of synovial biopsy specimens from 31 patients with early RA (< 1 year) and 35 patients with longstanding RA (> 5 years) were compared. The possible associations between these features and local disease activity, as measured by the score for pain in the biopsied knee joint were also evaluated.

RESULTS

The immunohistologic features were not dependent on disease duration. We found a positive correlation between the scores for knee pain and the semiquantitative scores for the number of macrophages, as well as the expression of interleukin-6 and tumor necrosis factor alpha, whereas the correlation with the scores for CD4+ T cells was negative. Multivariate analysis showed that these correlations were highly statistically significant (P < 0.003).

CONCLUSION

The results do not support the view that inflammatory mechanisms in the synovial tissues of RA patients differ between early and late stages of the disease. The findings presented here are consistent with the concept that early RA is the result of a synovitis process of longer duration and that macrophage-derived cytokines play an important role in maintaining the clinical signs of inflammation.

Cytokine production by normal human monocytes: inter-subject variation and relationship to an IL-1 receptor antagonist (IL-1Ra) gene polymorphism

Monocytes from different individuals show variable cytokine production in response to a variety of stimuli. We wished to determine the sets of conditions (cytokine combinations) that would enable us to demonstrate stable inter-individual differences in the production of IL-1 alpha, IL-1 beta, IL-1Ra, on-6 and tumour necrosis factor-alpha (TNF-alpha) by monocytes. We assessed the ability of a number of recombinant human cytokines (granulocyte-macrophage colony-stimulating factor (GM-CSF), interferon-gamma (IFN-gamma), TNF-alpha, IL-4, IL-6, transforming growth factor-beta (TGF-beta), IL-10 and IL-1Ra)) to stimulate or inhibit the production of one or more of these monocyte products. GM-CSF was found to stimulate the production of all five of these cytokines in a highly reproducible manner. TNF-alpha also up-regulated production of IL-1 alpha, IL-1 beta, IL-1Ra and IL-6 by monocytes, but the variability in the results of cells cultured from the same individuals on different occasions was greater. Other cytokines either stimulated production of only some of the five cytokine products tested, or stimulated the production of some cytokine products while inhibiting production of others. This was especially evident when cytokines were used in combination with GM-CSF: IFN-gamma down-regulated production of IL-1Ra while up-regulating the production of IL-1 alpha/beta, IL-6 and TNF-alpha, while IL-4 had the exact opposite effect. Polymorphisms in regions of cytokine genes that affect transcription may account for some of the interindividual variation in cytokine production. We have shown that a stable estimate of cytokine production phenotype can be obtained when monocytes collected on at least two separate occasions are stimulated by GM-CSF in vitro. We have looked for a relationship between IL-1 production and an 86-bp variable repeat polymorphism in intron 2 of the IL-1Ra gene. A less common allele of this polymorphism (allele 2) was associated with increased production of IL-1Ra protein, and also reduced production of IL-1 alpha protein by monocytes.

Instillation of six different ultrafine carbon particles indicates a surface area threshold dose for acute lung inflammation in mice

Increased levels of particulate air pollution are associated with increased respiratory and cardiovascular mortality and morbidity. Some epidemiologic and toxicologic research suggests ultrafine particles (UFPs) (< 100 nm) to be more harmful per unit mass than larger particles. Our study was aimed at a quantitative comparison of acute adverse effects of different types of carbonaceous UFPs at a dose range that causes a moderate inflammatory response in lungs. We used six different particle types (primary particle size 10-50 nm, specific surface area 30-800 m2/g, and organic content 1-20%): PrintexG, Printex90, flame soot particles with different organic content (SootL, SootH), spark-generated ultrafine carbon particles (ufCP), and the reference diesel exhaust particles (DEP) SRM1650a. Mice were instilled with 5, 20, and 50 microg of each particle type, and bronchoalveolar lavage was analyzed 24 hr after instillation for inflammatory cells and the level of proinflammatory cytokines. At respective mass-doses, particle-caused detrimental effects ranked in the following order: ufCP > SootL > or = SootH > Printex90 > PrintexG > DEP. Relating the inflammatory effects to the particle characteristics--organic content, primary particle size, or specific surface area--demonstrates the most obvious dose response for particle surface area. Our study suggests that the surface area measurement developed by Brunauer, Emmett, and Teller is a valuable reference unit for the assessment of causative health effects for carbonaceous UFPs. Additionally, we demonstrated the existence of a threshold for the particle surface area at an instilled dose of approximately 20 cm2, below which no acute proinflammatory responses could be detected in mice.

Alveolar macrophage-mediated killing of Pneumocystis carinii f. sp. muris involves molecular recognition by the Dectin-1 beta-glucan receptor

Innate immune mechanisms against Pneumocystis carinii, a frequent cause of pneumonia in immunocompromised individuals, are not well understood. Using both real time polymerase chain reaction as a measure of organism viability and fluorescent deconvolution microscopy, we show that nonopsonic phagocytosis of P. carinii by alveolar macrophages is mediated by the Dectin-1 β-glucan receptor and that the subsequent generation of hydrogen peroxide is involved in alveolar macrophage–mediated killing of P. carinii. The macrophage Dectin-1 β-glucan receptor colocalized with the P. carinii cyst wall. However, blockage of Dectin-1 with high concentrations of anti–Dectin-1 antibody inhibited binding and concomitant killing of P. carinii by alveolar macrophages. Furthermore, RAW 264.7 macrophages overexpressing Dectin-1 bound P. carinii at a higher level than control RAW cells. In the presence of Dectin-1 blockage, killing of opsonized P. carinii could be restored through FcγRII/III receptors. Opsonized P. carinii could also be efficiently killed in the presence of FcγRII/III receptor blockage through Dectin-1–mediated phagocytosis. We further show that Dectin-1 is required for P. carinii–induced macrophage inflammatory protein 2 production by alveolar macrophages. Taken together, these results show that nonopsonic phagocytosis and subsequent killing of P. carinii by alveolar macrophages is dependent upon recognition by the Dectin-1 β-glucan receptor.

Human immunodeficiency virus type 1 infection alters chemokine beta peptide expression in human monocytes: implications for recruitment of leukocytes into brain and lymph nodes

Two chemokine (chemoattractant cytokines) beta peptides, macrophage inflammatory proteins 1 alpha and 1 beta (MIP-1 alpha and MIP-1 beta), were induced in human monocyte cultures following infection with the human immunodeficiency virus type 1 (HIV-1). Induction depended on productive viral infection: not only did the kinetics of MIP-1 peptide induction closely follow those of viral replication, but monocyte cultures inoculated with heat-inactivated virus or infected in the presence of AZT failed to produce these chemokine beta peptides. In addition, HIV infection markedly altered the pattern of beta chemokine expression elicited by tumor necrosis factor (TNF), itself a potent proinflammatory cytokine upregulated during the development of AIDS. Reverse transcription (RT)-PCR and RT-in situ PCR studies on brain tissue from patients with AIDS dementia demonstrated elevated MIP-1 alpha and MIP-1 beta mRNA expression relative to comparable samples from HIV-1-infected patients without dementia. Cells expressing chemokines in HIV-1-infected brains were identified morphologically as microglia and astrocytes. As MIP-1 alpha and MIP-1 beta are potent chemoattractants for both monocytes and specific subpopulations of lymphocytes, this dysregulation of beta chemokine expression may influence the trafficking of leukocytes during HIV infection. These data, taken together, suggest a mechanism by which HIV-1-infected monocytes might recruit uninfected T cells and monocytes to sites of active viral replication or inflammation, notably the brain and lymph nodes.

Cytokine expression by neutrophils and macrophages in vivo: endotoxin induces tumor necrosis factor-alpha, macrophage inflammatory protein-2, interleukin-1 beta, and interleukin-6 but not RANTES or transforming growth factor-beta 1 mRNA expression in acute lung inflammation

Using a rat model of acute lung inflammation induced by intratracheal instillation of lipopolysaccharide (LPS), we investigated the kinetics of mRNA expression and the potential cellular sources of tumor necrosis factor-alpha (TNF-alpha), macrophage inflammatory protein-2 (MIP-2), interleukin (IL)-1 beta, IL-6, RANTES, and transforming growth factor-beta 1 (TGF-beta 1). By Northern blot analysis, TNF-alpha and MIP-2 mRNAs in total lung tissue increased markedly by 30 min and peaked by 1 h after LPS exposure, whereas expression of IL-1 beta and IL-6 was not detected until 1 h and peaked within 6 h. In contrast, neither RANTES nor TGF-beta 1 mRNA was induced by LPS throughout 72 h, although a basal expression was detected in both saline- and LPS-treated lung tissues. At 1 h after LPS, the bronchoalveolar lavage (BAL) fluid contained about 98% alveolar macrophages (AM), whereas by 6 or 12 h, 88% of BAL cells were polymorphonuclear neutrophils (PMN). Upon extraction of total RNA after separation of AM from PMN in BAL, Northern analysis showed that at 1 h, AM expressed pronounced signals for TNF-alpha, MIP-2, IL-1 beta, and IL-6. At 6 and 12 h, however, while cytokine transcripts decreased in AM, PMN exhibited strong signals for these cytokines. A low basal noninducible signal for TGF-beta 1 but not RANTES was detected in both AM and PMN. Finally, by in situ hybridization techniques, PMN in the lung tissue, particularly those located in the vicinity of the bronchiole and vasculature, were demonstrated to localize MIP-2 mRNA.(ABSTRACT TRUNCATED AT 250 WORDS)

Inhibition of mannose-binding lectin reduces postischemic myocardial reperfusion injury

BACKGROUND

Complement consists of a complex cascade of proteins involved in innate and adaptive immunity. The cascade can be activated through 3 distinct mechanisms, designated the classical, alternative, and lectin pathways. Although complement is widely accepted as participating in the pathophysiology of ischemia-reperfusion injury, the specific role of the lectin pathway has not been addressed.

METHODS AND RESULTS

Monoclonal antibodies (mAbs; P7E4 and 14C3.74, IgG1kappa isotypes) were raised against rat mannose-binding lectin (rMBL). Both mAbs recognized rMBL-A by Western analysis or surface plasmon resonance. P7E4, but not 14C3.74, exhibited a concentration-dependent inhibition of the lectin pathway, with maximal effect at 10 microg/mL. In vivo, rats were subjected to 30 minutes of left coronary artery occlusion and 4 hours of reperfusion. Complement C3 deposition was greatly attenuated in hearts pretreated with P7E4 compared with 14C3.74-treated hearts. Pretreatment with P7E4 (1 mg/kg) significantly reduced myocardial creatine kinase loss (48%), infarct size (39%), and neutrophil infiltration (47%) compared with 14C3.74-treated animals. In addition, P7E4 pretreatment significantly attenuated the expression of proinflammatory genes (intercellular adhesion molecule-1, vascular cell adhesion molecule-1, and interleukin-6) after ischemia-reperfusion.

CONCLUSIONS

The lectin complement pathway is activated after myocardial ischemia-reperfusion and leads to tissue injury. Blockade of the lectin pathway with inhibitory mAbs protects the heart from ischemia-reperfusion by reducing neutrophil infiltration and attenuating proinflammatory gene expression.

Enhanced immune responses in females, as opposed to decreased responses in males following haemorrhagic shock and resuscitation

Although haemorrhagic shock produces immunodepression in both humans and experimental animals, no information is available concerning gender differences in the immune and endocrine response to shock. To study this, male and female (proestrus and diestrus) C3H/HeN mice (25 g body weight) were bled and maintained at a mean arterial blood pressure of 35 +/- 5 mmHg for 1 h and then adequately resuscitated. The animals were killed at 2 h after resuscitation to obtain splenocytes, macrophages (M phi, peritoneal and splenic), as well as whole blood. IL-1 release by M phi, splenocyte proliferative capacity and splenocyte IL-3 release in female mice was significantly increased. Male mice, however, showed decreased release of all interleukins (IL-1, 2, 3, 6) as well as splenocyte proliferative capacity after shock. Plasma corticosterone levels decreased in proestrus female mice, as opposed to increased levels in males following shock. Corticosterone may therefore, be in part responsible for the observed gender differences. To the authors' knowledge, this is the first study which shows that immune responsiveness in female mice is enhanced after haemorrhagic shock, as opposed to decreased responsiveness in males. Thus, unlike males which exhibit increased susceptibility to sepsis/infections, females should be able to better tolerate the deleterious effects of shock.

Neutralization of macrophage inflammatory protein-2 attenuates neutrophil recruitment and bacterial clearance in murine Klebsiella pneumonia

The role of macrophage inflammatory protein-2 (MIP-2) in bacterial pneumonia was characterized. Mice were challenged with Klebsiella pneumoniae intratracheally, and organs were harvested at 8, 24, and 48 h. Inoculation with K. pneumoniae resulted in the time-dependent expression of MIP-2 mRNA and protein within the lung, which was maximal 48 h after inoculation. Mice were then passively immunized with rabbit anti-murine MIP-2 serum intraperitoneally 2 h before administration of K. pneumoniae. Treatment with anti-MIP-2 serum resulted in a 60% decrease in lung neutrophil (PMNL) influx and a significant increase in K. pneumoniae colony-forming units in both lung and liver homogenates. Finally, treatment with anti-MIP-2 serum decreased early (48-72 h) but not late (after 72 h) survival in animals with Klebsiella pneumonia. This study indicates that MIP-2 is produced during Klebsiella pneumonia and inhibition of MIP-2 bioactivity in vivo results in decreased PMNL influx and lung bacterial clearance in murine Klebsiella pneumonia. MIP-2 is produced during Klebsiella pneumonia and inhibition of MIP-2 bioactivity in vivo results in decreased PMNL influx and lung bacterial clearance in murine Klebsiella pneumonia.

Complement factor C5a mediates renal ischemia-reperfusion injury independent from neutrophils

The complement system has been shown to mediate renal ischemia-reperfusion (I/R) injury. However, the contribution of complement factor C5a to I/R injury, in particular in the kidney, remains to be established. In this study, we investigated the impact of blocking the C5aR pathway on the inflammatory response and on the renal function in a murine model of I/R injury. First, we analyzed C5aR expression in kidneys of healthy mice. Intriguingly, we found expression on mesangial, as well as on tubular epithelial, cells. After I/R injury, C5aR expression was up-regulated in tubular epithelial cells. In addition, mRNA levels of CXC chemokines and TNF-alpha increased significantly and kidneys were heavily infiltrated by neutrophils. Blocking the C5aR pathway by a specific C5a receptor antagonist (C5aRA) abrogated up-regulation of CXC chemokines but not of TNF-alpha and reduced neutrophil infiltration by >50%. Moreover, application of the C5aRA significantly reduced loss of renal function. This improvement of function was independent of the presence of neutrophils because neutrophil depletion by mAb NIMP-R14 did not affect the protective effect of C5aRA treatment. Furthermore, blocking of the C5aR pathway had no influence on renal apoptosis. These data provide evidence that C5a is crucially involved in the pathogenesis of renal I/R injury by modulation of neutrophil-dependent as well as neutrophil-independent pathways, which include the regulation of CXC chemokines but not TNF-alpha or apoptotic pathways.

Chemokine gene expression in the brains of mice with lymphocytic choriomeningitis

Chemokines are pivotal in the trafficking of leukocytes. In the present study, we examined the expression of multiple chemokine genes during the course of lymphocytic choriomeningitis (LCM) in mice. In noninfected mice, no detectable chemokine gene expression was found in the brain; however, by day 3 postinfection, the induction of a number of chemokine mRNAs was observed as follows (in order from the greatest to the least): cytokine responsive gene-2 or interferon-inducible 10-kDa protein (Crg-2/IP-10), RANTES, monocyte chemotactic protein-1 (MCP-1), macrophage inflammatory protein-1 (MIP-1beta), and MCP-3. At day 6 postinfection, the expression of these chemokine mRNAs was increased, and low expression of lymphotactin, C10, MIP-2, and MIP-1alpha mRNAs was detectable. Transcript for T-cell activation-3 was not detectable in the brain at any time following LCM virus (LCMV) infection. With some exceptions, a pattern of chemokine gene expression similar to that in the brain was observed in the peripheral organs of LCMV-infected mice. Mice that lacked expression of gamma interferon developed LCM and had a qualitatively similar but quantitatively reduced cerebral chemokine gene expression profile. In contrast, little or no chemokine gene expression was detectable in the brains of LCMV-infected athymic mice which did not develop LCM. Expression of Crg-2/IP-10 RNA was localized to predominantly resident cells of the central nervous system (CNS) and overlapped with sites of viral infection and immune cell infiltration. These findings demonstrate the expression of a number of chemokine genes in the brains of mice infected with LCMV. The pattern of chemokine gene expression in LCM may profoundly influence the characteristic phenotype and response of leukocytes in the brain and contribute to the immunopathogenesis of this fatal CNS infection.

The murine neutrophil-chemoattractant chemokines LIX, KC, and MIP-2 have distinct induction kinetics, tissue distributions, and tissue-specific sensitivities to glucocorticoid regulation in endotoxemia

Lipopolysaccharide-induced CXC chemokine (LIX) is a novel murine neutrophil-chemoattractant CXC chemokine cloned as a glucocorticoid-attenuated response gene. We investigated LIX message expression in an acute endotoxemia model. LIX message peaks later than KC or macrophage inflammatory protein-2 (MIP-2) and remains elevated longer in almost all tissues. Induced LIX message expression in heart is 5- to 6-fold greater than in lung and spleen, and 20-fold greater than in liver. In contrast, KC expression is equal in heart, lung, and liver, whereas MIP-2 expression is strongest in the lung. Glucocorticoid regulation of these genes also differs. Endotoxemia-induced LIX message expression in the lung is markedly enhanced in adrenalectomized mice and strongly attenuated by dexamethasone, whereas lung KC and MIP-2 expression are unaffected by glucocorticoids. It is surprising to note that endotoxemia-induced brain expression of LIX (but not KC or MIP-2) is increased by dexamethasone. These observations suggest that LIX may have biological roles distinct from KC and MIP-2.

Expression and regulation of human neutrophil-derived macrophage inflammatory protein 1 alpha

Neutrophil (polymorphonuclear leukocyte [PMN]) sequestration is one of the histologic hallmarks of an acute inflammatory response. During the natural evolution of an inflammatory response, PMNs are often replaced by mononuclear cells. This shift in the elicitation of specific leukocyte populations usually occurs as the inflammatory lesion enters either the repair/resolution stage or progresses to a chronic inflammation. To elucidate a potential mechanism for the temporal change from predominantly PMN recruitment to the presence of monocytes, we postulated that PMNs could be a rich source of monocyte chemotactic factors. In our studies, we have identified a dose-dependent induction of monocyte chemotactic activity by PMNs treated with lipopolysaccharide (LPS; 1-100 ng/ml). Interestingly, this monocyte chemotactic activity was significantly attenuated in the presence of neutralizing anti-human macrophage inflammatory protein 1 alpha (MIP-1 alpha) antibodies. Moreover, immunolocalization studies demonstrated the expression of MIP-1 alpha by stimulated PMNs. These findings showed that a significant amount of PMN-derived monocyte chemotactic activity was attributable to MIP-1 alpha. Subsequent characterization of MIP-1 alpha steady-state mRNA and antigen expression demonstrated both a dose- and time-dependent production by LPS-treated PMNs. Granulocyte/macrophage colony-stimulating factor (GM-CSF), a potent PMN activator, failed to induce the expression of MIP-1 alpha over a wide range of concentrations. However, PMNs stimulated in the presence of both LPS and GM-CSF resulted in a synergistic expression pattern for MIP-1 alpha. PMNs stimulated in the presence of both GM-CSF and LPS demonstrated an enhanced and prolonged expression for both MIP-1 alpha mRNA and antigen, as compared with LPS alone. Messenger RNA stabilization analyses demonstrated that MIP-1 alpha mRNA isolated from PMNs stimulated in the presence of GM-CSF and LPS had a prolonged mRNA t1/2, as compared with LPS alone. These findings support the notion that PMNs are capable of producing MIP-1 alpha in the presence of LPS, and that GM-CSF can influence this production through prolongation of MIP-1 alpha mRNA t1/2. The production of PMN-derived MIP-1 alpha, in association with the expression of appropriate adhesion molecules at a site of inflammation, may be one of the central events that contributes to the temporal shift from predominantly PMNs to monocytes during the evolution of inflammation.

Macrophage inflammatory proteins 1 and 2: expression by rat alveolar macrophages, fibroblasts, and epithelial cells and in rat lung after mineral dust exposure

Macrophage inflammatory proteins 1 alpha and 2 (MIP-1 alpha, MIP-2) are members of a growing family of cytokines thought to play a role in host defense. MIP-1 alpha and MIP-2 were previously identified in the mouse and shown to stimulate inflammatory cell recruitment. To better understand the potential role of MIP-1 alpha and MIP-2 in lung defense, we investigated the ability of rat lung cells to express mRNA for and/or secrete MIP-1 alpha and MIP-2 proteins in vitro and characterized expression of these cytokines in rat lung after in vivo exposure to silica (SiO2) or titanium dioxide (TiO2). In response to lipopolysaccharide, rat alveolar macrophages expressed increased levels of MIP-1 alpha and MIP-2 mRNA and secreted proteins (identified by N-terminal sequencing) homologous to mouse MIP-1 alpha and MIP-2. Rat alveolar macrophage MIP-1 alpha and MIP-2 mRNA expression was also increased by tumor necrosis factor-alpha (TNF) and adherence to plastic. Studies with a rat fibroblast and epithelial cell line demonstrated that MIP-2, but not MIP-1 alpha, expression can be detected in these cells after stimulation with TNF. Intratracheal instillation studies with SiO2 and TiO2 showed that inflammatory doses of these dusts increase MIP-1 alpha and MIP-2 mRNA expression in whole lung and that increased gene expression preceded the accumulation of inflammatory cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Excessive in vitro bacterial lipopolysaccharide-induced production of monokines in cirrhosis

The objective of this study was to analyze monokine production by peripheral blood mononuclear cells from patients with alcoholic cirrhosis. The capacity of peripheral blood mononuclear cells and purified monocytes from these patients to produce tumor necrosis factor alpha, interleukin 1 beta, and interleukin 6 was investigated. Spontaneous production of tumor necrosis factor alpha, interleukin 6 and interleukin 1 beta was similar in cirrhotic and healthy subjects, but serum levels of interleukin 6 (less than 2 U/ml vs. 9.5 +/- 3 U/ml) and tumor necrosis factor alpha (3.1 +/- 1.2 pg/ml vs. 12.0 +/- 1.2 pg/ml) were significantly higher in cirrhotic patients. However, peripheral blood mononuclear cells or purified monocytes from patients with alcoholic liver cirrhosis, stimulated in vitro with Escherichia coli lipopolysaccharide, displayed a marked increase of tumor necrosis factor alpha, interleukin 1 beta and interleukin 6 secretions compared with healthy controls. A striking feature of this overproduction was its reversibility as assessed by allowing cells to rest in vitro without lipopolysaccharide for 1 to 7 days before stimulation. In such conditions, tumor necrosis factor alpha and interleukin 6 secretions declined to levels present in healthy subjects in whom production remained stable, whereas interleukin 1 beta secretion markedly decreased in both groups to the point where no difference could be seen. This reversible oversecretion of cytokines after lipopolysaccharide stimulation, along with the lack of abnormality of spontaneous cytokine secretion, suggests that monocytes in these patients may have undergone an in vivo activation process analogous to a priming phenomenon. The in vitro activation with lipopolysaccharide may represent the correlate of in vivo endotoxemia observed during acute events such as sepsis.(ABSTRACT TRUNCATED AT 250 WORDS)

Proteolytic activation of alternative CCR1 ligands in inflammation

Although chemokines CCL3/MIP-1alpha and CCL5/RANTES are considered to be primary CCR1 ligands in inflammatory responses, alternative CCR1 ligands have also been described. Indeed, four such chemokines, CCL6/C10/MIP-related protein-1, CCL9/MIP-1gamma/MIP-related protein-2, CCL15/MIP-1delta/hemofiltrate CC chemokine-2/leukotactin-1, and CCL23/CKbeta8/myeloid progenitor inhibitory factor-1, are unique in possessing a separately encoded N-terminal domain of 16-20 residues and two additional precisely positioned cysteines that form a third disulfide bridge. In vitro, these four chemokines are weak CCR1 agonists, but potency can be increased up to 1000-fold by engineered or expression-associated N-terminal truncations. We examined the ability of proinflammatory proteases, human cell supernatants, or physiological fluids to perform N-terminal truncations of these chemokines and thereby activate their functions. Remarkably, most of the proteases and fluids removed the N-terminal domains from all four chemokines, but were relatively unable to cleave the truncated forms further. The truncated chemokines exhibited up to 1000-fold increases in CCR1-mediated signaling and chemotaxis assays in vitro. In addition, N-terminally truncated CCL15/MIP-1delta and CCL23/CKbeta8, but not CCL3/MIP-1alpha or CCL5/RANTES, were detected at relatively high levels in synovial fluids from rheumatoid arthritis patients. These data suggest that alternative CCR1 ligands are converted into potent chemoattractants by proteases released during inflammatory responses in vivo.

Modulation of neutrophil influx in glomerulonephritis in the rat with anti-macrophage inflammatory protein-2 (MIP-2) antibody

The role of the chemokine, macrophage inflammatory protein-2 (MIP-2), during anti-glomerular basement membrane (GBM) antibody (Ab) glomerulonephritis (GN) was studied. Rat MIP-2 cDNA had been cloned previously. Recombinant rat MIP-2 (rMIP-2) from Escherichia coli exhibited neutrophil chemotactic activity and produced neutrophil influx when injected into the rat bladder wall. By using a riboprobe derived from the cDNA and an anti-rMIP-2 polyclonal Ab, MIP-2 was found to be induced in glomeruli with anti-GBM Ab GN as mRNA by 30 min and protein by 4 h, with both disappearing by 24 h. The expression of MIP-2 correlated with glomerular neutrophil influx. A single dose of the anti-MIP-2 Ab 30 min before anti-GBM Ab was effective in reducing neutrophil influx (40% at 4 h, P < 0.01) and periodic acid-Schiff deposits containing fibrin (54% at 24 h, P < 0.01). The anti-rMIP-2 Ab had no effect on anti-GBM Ab binding (paired-label isotope study). Functional improvement in the glomerular damage was evidenced by a reduction of abnormal proteinuria (P < 0.05). These results suggest that MIP-2 is a major neutrophil chemoattractant contributing to influx of neutrophils in Ab-induced glomerular inflammation in the rat.

Pulmonary inflammatory, chemokine, and mutagenic responses in rats after subchronic inhalation of carbon black

Chronic inhalation of carbon black can produce carcinomas in rat lungs. At present the mechanisms underlying the rat lung tumor response to carbon black are unknown, although a significant role for inflammation and cell proliferation has been postulated. To investigate the processes which may contribute to development of rat lung tumors after carbon black exposure, we characterized the effects of subchronic inhalation of carbon black by rats on mutagenesis in alveolar epithelial cells, pulmonary inflammation, inflammatory cytokine/growth factor expression, and lung histopathology. Briefly, rats were exposed for 6 hr/day, 5 days/week for up to 13 weeks to 1.1, 7.1, and 52.8 mg/m3 carbon black and the effects on the lung were characterized after 6.5 and 13 weeks of exposure and 3 and 8 months of recovery. Endpoints characterized after carbon black exposure included mutation in the hprt gene of alveolar epithelial cells, changes in bronchoalveolar lavage fluid markers of lung injury and inflammation, expression of mRNA for the chemokines, MIP-2 and MCP-1, and lung histopathology. Lung burdens of carbon black were also determined. After 13 weeks of exposure to 1.1, 7.1, and 52.8 mg/m3 carbon black, lung burdens were 354, 1826, and 7861 micrograms carbon black, respectively. The lung clearance of carbon black appeared impaired after exposure to 7.1 and 52.8 mg/m3 carbon black, with the effects being more pronounced at the higher exposure level. Subchronic inhalation of 1.1 mg/m3 carbon black did not elicit any detectable adverse lung effects. A significant increase in hprt mutation frequency in alveolar epithelial cells was detected immediately after 13 weeks of exposure to 7.1 and 52.8 mg/m3 carbon black as well as after 3- and 8-month recovery periods for the group exposed to 52.8 mg/m3. No increase in hprt mutation frequency was observed for epithelial cells obtained from rats exposed to 1.1 mg/m3 carbon black. The observation that genotoxic effects (i.e., mutations) on alveolar epithelial cells occurred only after carbon black exposures which resulted in significant inflammation and epithelial hyperplasia supports the hypothesis that inflammatory cell-derives oxidants and increased cell proliferation play a role in the pathogenesis of rat lung tumors in response to carbon black.

Soluble peptidoglycan-induced monokine production can be blocked by anti-CD14 monoclonal antibodies and by lipid A partial structures

We have investigated the interaction of soluble peptidoglycan (sPG), in comparison with lipopolysaccharide (LPS), with human mononuclear cells (MNC) by determining the capacity of sPG to induce interleukin-6 (IL-6) and IL-1 release. In addition, we investigated the modulation of their interaction by anti-CD14 monoclonal antibody and by partial structures of LPS. We found that sPG, like LPS, was able to induce IL-6 and IL-1 production by MNC. However, dose-response experiments revealed that at least 3,000 ng of sPG per ml was necessary for induction, whereas the optimal LPS concentration was 1 ng/ml. Anti-CD14 monoclonal antibody reduced sPG- and LPS-induced IL-6 and IL-1 production. Moreover, partial structures of LPS were able to reduce monokine production induced by sPG and LPS. We conclude that sPG constitutes, like LPS, an inflammatory cytokine inducer and that CD14 is involved in the activation of human monocytes not only by LPS but also by sPG.

Interactions of lung stretch, hyperoxia, and MIP-2 production in ventilator-induced lung injury

The use of positive pressure mechanical ventilation can cause ventilator-induced lung injury (VILI). We hypothesized that hyperoxia in combination with large tidal volumes (VT) would accentuate noncardiogenic edema and neutrophil infiltration in VILI and be dependent on stretch-induced macrophage inflammatory protein-2 (MIP-2) production. In rats ventilated with VT 20 ml/kg, there was pulmonary edema formation that was significantly increased by hyperoxia. Total lung neutrophil infiltration and MIP-2 in bronchoalveolar lavage (BAL) fluid were significantly elevated, in animals exposed to high VT both on room air (RA) and with hyperoxia. Hyperoxia markedly augmented the migration of neutrophils into the alveoli. Anti-MIP-2 antibody blocked migration of neutrophils into the alveoli in RA by 51% and with hyperoxia by 65%. We concluded that neutrophil migration into the alveoli was dependent on stretch-induced MIP-2 production. Hyperoxia significantly increased edema formation and neutrophil migration into the alveoli with VT 20 ml/kg, although BAL MIP-2 levels were nearly identical to VT 20 ml/kg with RA, suggesting that other mechanisms may be involved in hyperoxia-augmented neutrophil alveolar content in VILI.

Involvement of mannose receptor in cytokine interleukin-1beta (IL-1beta), IL-6, and granulocyte-macrophage colony-stimulating factor responses, but not in chemokine macrophage inflammatory protein 1beta (MIP-1beta), MIP-2, and KC responses, caused by attachment of Candida albicans to macrophages

The production of chemotactic cytokines (chemokines) and other cytokines by macrophages in response to fungal infection is thought to be critical during the course of candidiasis. However, the mechanism of cytokine synthesis by macrophages in response to fungi is not well understood. Therefore, the response of macrophages to Candida albicans was examined in terms of receptor-mediated chemokine and other cytokine mRNA induction. Attachment of C. albicans to murine thioglycollate-elicited peritoneal macrophages induced increased mRNA levels of the cytokines interleukin-1beta (IL-1beta), IL-6, and granulocyte-macrophage colony-stimulating factor (GM-CSF) and the chemokines macrophage inflammatory protein 1beta (MIP-1beta), MIP-2, and KC (a member of the platelet factor 4 neutrophil chemoattractant family), as determined by quantitative reverse transcription-PCR. However, treatment of macrophages with alpha-methyl-D-mannoside significantly reduced the cytokine GM-CSF response to C. albicans but did not affect the chemokine MIP-2 response. Antisense oligodeoxynucleotide (ODN) to mannose receptor (MR) mRNA inhibited the expression and function of MR in macrophages as determined by Western blot analysis and 125I-labeled mannose-bovine serum albumin (BSA) binding, and also inhibited the elevation of cytokine IL-1beta, IL-6, and GM-CSF mRNA levels induced by C. albicans attachment. Elevation of chemokine MIP-1beta, MIP-2, and KC mRNA levels induced by C. albicans was not affected in macrophages whose MR expression was suppressed by antisense ODN treatment. Furthermore, IL-4 treatment of macrophages, which up-regulated MR expression as determined by Western blot analysis and fluorescein isothiocyanate-labeled mannose-BSA uptake, enhanced the level of cytokine GM-CSF mRNA induced by C. albicans but not the level of the chemokine MIP-2 mRNA. These results indicate that selected cytokine responses of macrophages to C. albicans are mediated by MR, while some chemokine responses may be mediated by other receptors.

Chemokine expression in rheumatoid arthritis (RA): evidence of RANTES and macrophage inflammatory protein (MIP)-1 beta production by synovial T cells

Earlier studies from this laboratory provided evidence for restricted cytokine expression in the T cell population in RA tissues. Specifically, IL-2, IL-4, IL-6 and interferon-gamma (IFN-gamma) gene expression levels were low. The selective chemoattractant and activation effects of chemokines on leucocytes identify them as potentially ideal candidates in mediating selective inflammatory processes in RA. Accordingly, we undertook studies to examine constitutive chemokine gene expression in RA tissues. RANTES, monocyte chemotactic protein-1 (MCP-1) and MIP-1 beta gene expression was examined in both the T and non-T cell populations in RA peripheral blood (PB), synovial fluid (SF) and synovial tissues (ST). Our results identified elevated levels of both RANTES and MIP-1 beta gene expression in circulating RA PB and SF T cells. By contrast, MCP-1 expression was virtually absent in RA PB, yet elevated MCP-1 mRNA levels were detected primarily in the non-T cell populations of the SF and ST samples. Histological examination of affected rheumatoid joints revealed extensive RANTES and MIP-1 beta expression in sites of lymphocyte infiltration and cell proliferation, namely the synovial lining and sublining layers. Fractionation or RA ST patient samples revealed that RANTES expression was restricted to the T cells, whereas MIP-1 beta expression was detected in both T and non-T fractions. These data suggest that MCP-1, MIP-1 beta and RANTES may have a central role in the trafficking of reactive molecules involved in immunoregulation and in the inflammatory processes in RA.

Pulmonary and systemic effects of short-term inhalation exposure to ultrafine carbon black particles

While environmental particles are associated with mortality and morbidity related to pulmonary and cardiovascular (CV) disease, the mechanisms involved in CV health effects are not known. Changes in systemic clotting factors have been associated with pulmonary inflammation. We hypothesized that inhaled ultrafine particles result in an inflammatory response which may stimulate systemic clotting factor release. Adult male Wistar rats were exposed to either fine or ultrafine carbon black (CB) for 7 h. The attained total suspended particle concentrations were 1.66 mg/m(3) for ultrafine CB and 1.40 mg/m(3) for fine CB. Particle concentration of ultrafine particles was more than 10 times greater than that of fine particles and the count median aerodynamic diameter averaged 114 nm for the ultrafine and 268 nm for the fine carbon particles. Data were collected immediately, 16 and 48 h following exposure. Only ultrafine CB caused an increase in total bronchoalveolar lavage (BAL) leukocytes, whereas both fine (2-fold) and ultrafine (4-fold) carbon particles caused an increase in BAL neutrophils at 16 h postexposure. Exposure to the ultrafine, but not fine, carbon was also associated with significant increases in the total numbers of blood leukocytes. Plasma fibrinogen, factor VII and von Willebrand factor (vWF) were unaffected by particle treatments as was plasma Trolox equivalent antioxidant status (TEAC). Macrophage inflammatory protein-2 mRNA was significantly increased in BAL cells 48 h following exposure to ultrafine CB. The data show that there is a small but consistent significant proinflammatory effect of this exposure to ultrafine particles that is greater than the effect of the same exposure to fine CB.

Essential role of alveolar macrophages in intrapulmonary activation of NF-kappaB

Acute inflammatory injury in rat lung induced by deposition of immunoglobulin G immune complexes requires expression of cytokines and chemokines as well as activation of the transcription factor nuclear factor (NF)-kappaB. There is little direct evidence regarding the role of alveolar macrophages in these activation events. In the present studies, rat lungs were depleted of alveolar macrophages by airway instillation of liposome-encapsulated dichloromethylene diphosphonate. These procedures, which greatly reduced the number of retrievable alveolar macrophages, suppressed activation of lung NF-kappaB in the inflammatory model. In addition, bronchoalveolar lavage levels of tumor necrosis factor-alpha (TNF-alpha) and the CXC chemokine, macrophage inflammatory protein-2, were substantially reduced. In parallel, upregulation of the lung vascular adhesion molecule, intercellular adhesion molecule-1, was greatly reduced by intrapulmonary instillation of phosphonate-containing liposomes. Neutrophil accumulation and development of lung injury were also substantially diminished. Lung instillation of TNF-alpha in alveolar macrophage-depleted rats restored the NF-kappaB activation response in whole lung. These data suggest that, in this inflammatory model, initial activation of NF-kappaB occurs in alveolar macrophages and the ensuing production of TNF-alpha may propagate NF-kappaB activation to other cell types in the lung.