Differences in local versus systemic TNFalpha production in COPD: inhibitory effect of hyaluronan on LPS induced blood cell TNFalpha release

BACKGROUND

Chronic obstructive pulmonary disease (COPD) is characterised by both airway inflammation and systemic changes. To elucidate the relationship between local and systemic inflammation, tumour necrosis factor alpha (TNFalpha) production by sputum cells and blood cells of patients with COPD and controls was compared and the effect of the extracellular matrix compound hyaluronan (HA) on TNFalpha release was studied.

METHODS

Four study groups were included: 10 steroid free COPD patients, 8 steroid treated patients, 10 healthy smokers, and 11 healthy non-smokers. Sputum cells and blood were incubated for 24 hours with or without lipopolysaccharide (LPS) in the absence or presence of HA (122 kDa or HMW fragment). TNFalpha was measured by ELISA.

RESULTS

Sputum cells produced spontaneously high levels of TNFalpha but were unresponsive to LPS. Sputum cells from COPD patients (both steroid free and steroid treated) produced significantly less TNFalpha than cells from healthy non-smoking subjects (p=0.017 and p=0.001, respectively). In contrast, blood cells produced TNFalpha only in response to LPS. No differences were observed in TNFalpha production by blood cells between the patient groups and the control groups. HA (both fragments) partially blocked LPS (1 ng/ml) induced TNFalpha release by blood cells from all study groups, whereas TNFalpha production by sputum cells was not influenced by HA.

CONCLUSION

These data indicate a difference between local and systemic TNFalpha production. Sputum cells of patients with COPD produced less TNFalpha than controls, which could contribute to impaired local defence. An inhibitory effect of HA on TNFalpha release in blood cells was observed which was similar in both patients and controls.

Leptin as local inflammatory marker in COPD

INTRODUCTION

Chronic inflammation of the lung is a characteristic finding in chronic obstructive pulmonary disease (COPD). Leptin is a pleiotropic cytokine thought to play a role in host response to inflammation. As recent studies have shown that leptin receptors are present in the lung, this study aimed to determine if leptin is detectable in induced sputum of COPD patients and if there is a relationship between leptin and other inflammatory markers in sputum.

METHODS

Sputum was induced in 14 male patients with moderate COPD (FEV1: 56 (15) % pred.). Leptin, total tumour necrosis factor (TNF)-alpha, and C-reactive protein (CRP) were analyzed in induced sputum supernatant by ELISA. Leptin was also determined in EDTA plasma.

RESULTS

Leptin was detectable in induced sputum of 10 COPD patients. A significant relationship was found between sputum leptin and CRP (r = 0.943, P < 0.001) and total TNF-alpha (r = 0.690, P < 0.01). Plasma leptin and sputum leptin were inversely correlated (r = -0.643, P < 0.01).

CONCLUSION

The present study demonstrated that leptin is detectable in induced sputum of patients with moderate COPD and is related to other inflammatory markers. The observed correlations between leptin and inflammatory markers in sputum may indicate that leptin is involved in the local inflammatory response in COPD.

Enhanced levels of hyaluronan in lungs of patients with COPD: relationship with lung function and local inflammation

BACKGROUND

Chronic inflammation and airway remodelling are characteristics of chronic obstructive pulmonary disease (COPD). Hyaluronan (HA) is an extracellular matrix compound with proinflammatory activity. HA levels in induced sputum from patients with COPD were measured and related to local inflammation. The expression of hyaluronan synthase 2 (HAS2) and hyaluronidase 2 (HYAL2) was analysed in lung tissue.

METHODS

Sputum was obtained from 18 patients with COPD (forced expiratory volume in 1 second (FEV(1)) 62% predicted (range 20-76)) and 14 healthy smokers. HA and inflammatory markers were measured using ELISA assays. Lung sections were obtained from five patients with severe COPD (FEV(1) <30%) and from five smokers, and mRNA levels of HAS2 and HYAL2 were analysed by polymerase chain reaction.

RESULTS

HA levels were significantly higher in the sputum from patients with COPD than controls. The COPD population appeared to consist of two subpopulations with either high or moderate HA levels. The subgroup of patients with high HA levels had lower FEV(1) than the moderate HA group. In addition, neutrophil influx and levels of interleukin-8, and the soluble tumour necrosis factor receptors R55 and R75 were significantly higher in patients with high HA levels than in those with moderate HA levels and controls. Semiquantitative analysis revealed enhanced expression of HYAL2 in lung tissue of patients with severe COPD compared with control subjects.

CONCLUSION

These data indicate a relationship between HA levels, local inflammation and severity of disease, and suggest enhanced breakdown of HA in the lungs of patients with COPD.

Chronic obstructive pulmonary disease is associated with the -1055 IL-13 promoter polymorphism

IL-13 is strongly implicated in the development of asthma and chronic obstructive pulmonary disease (COPD). We previously identified an IL-13 promoter polymorphism (-1055 C to T) that is associated with allergic asthma. We now report an increased frequency of the -1055 T allele in COPD patients compared to healthy controls (P=0.002) and compared to a second control group consisting of smoking individuals with normal lung function (P=0.01). A closely linked IL-13 exon polymorphism is present at normal allelic frequencies (P=0.3 and 0.4, respectively). In addition, we observed a normal distribution of two IL-4 polymorphisms at positions -590 and +33 (P=0.2 and 0.9, respectively). These results could implicate a functional role for the IL-13 promoter polymorphism in the enhanced risk to develop COPD.

Systemic anti-inflammatory mediators in COPD: increase in soluble interleukin 1 receptor II during treatment of exacerbations

BACKGROUND

The aim of this study was to test the hypothesis that the chronic inflammatory process present in chronic obstructive pulmonary disease (COPD) is due to a defective endogenous anti-inflammatory mechanism.

METHODS

Systemic levels of the anti-inflammatory mediators soluble interleukin 1 receptor II (sIL-1RII), soluble tumour necrosis factor receptor p55 (sTNF-R55) and sTNF-R75, and of C reactive protein (CRP) and lipopolysaccharide binding protein (LBP) were analysed in 55 patients with stable COPD (median forced expiratory volume in one second (FEV1) 34% predicted (range 15–78)) and compared with levels in 23 control subjects. In addition, changes in these mediators were studied in 13 patients with COPD (median FEV1 34% predicted (range 19–51)) during the first 7 days in hospital with an exacerbation of the disease.

RESULTS

Patients with stable COPD were characterised by a systemic inflammatory process indicated by an increased leucocyte count (7.2 (4.7–16.4)v 4.8 (3.5–8.3) × 109/l), raised levels of CRP (11.8 (1.1–75.0) v 4.1 (0.6–75.0) μg/ml) and LBP (45.6 (8.1–200.0)v 27.9 (14.1–71.5) μg/ml), and moderate increases in both sTNF-Rs. In contrast, the sIL-1RII level did not differ between patients and controls (4.53 (2.09–7.60)v 4.63 (3.80–5.93) ng/ml). During treatment of disease exacerbations, systemic levels of both CRP (at day 3) and LBP (at day 7) were significantly reduced compared with day 1, whereas sIL-1RII levels increased.

CONCLUSIONS

These data suggest an imbalance in systemic levels of pro- and anti-inflammatory mediators in patients with stable COPD. The increase in the anti-inflammatory mediator sIL-1RII during treatment of exacerbations may contribute to the clinical improvement.

Systemic anti-inflammatory mediators in COPD: increase in soluble interleukin 1 receptor II during treatment of exacerbations

BACKGROUND

The aim of this study was to test the hypothesis that the chronic inflammatory process present in chronic obstructive pulmonary disease (COPD) is due to a defective endogenous anti-inflammatory mechanism.

METHODS

Systemic levels of the anti-inflammatory mediators soluble interleukin 1 receptor II (sIL-1RII), soluble tumour necrosis factor receptor p55 (sTNF-R55) and sTNF-R75, and of C reactive protein (CRP) and lipopolysaccharide binding protein (LBP) were analysed in 55 patients with stable COPD (median forced expiratory volume in one second (FEV(1)) 34% predicted (range 15-78)) and compared with levels in 23 control subjects. In addition, changes in these mediators were studied in 13 patients with COPD (median FEV(1) 34% predicted (range 19-51)) during the first 7 days in hospital with an exacerbation of the disease.

RESULTS

Patients with stable COPD were characterised by a systemic inflammatory process indicated by an increased leucocyte count (7.2 (4.7-16.4) v 4.8 (3.5-8.3) x 10(9)/l), raised levels of CRP (11.8 (1.1-75.0) v 4.1 (0.6-75.0) microg/ml) and LBP (45.6 (8.1-200.0) v 27.9 (14.1-71.5) microg/ml), and moderate increases in both sTNF-Rs. In contrast, the sIL-1RII level did not differ between patients and controls (4.53 (2.09-7.60) v 4.63 (3.80-5.93) ng/ml). During treatment of disease exacerbations, systemic levels of both CRP (at day 3) and LBP (at day 7) were significantly reduced compared with day 1, whereas sIL-1RII levels increased.

CONCLUSIONS

These data suggest an imbalance in systemic levels of pro- and anti-inflammatory mediators in patients with stable COPD. The increase in the anti-inflammatory mediator sIL-1RII during treatment of exacerbations may contribute to the clinical improvement.

Intratracheal instillation of lipopolysaccharide in mice induces apoptosis in bronchial epithelial cells: no role for tumor necrosis factor-alpha and infiltrating neutrophils

This study investigated apoptosis in lungs after local exposure to lipopolysaccharide (LPS). Mice were instilled intratracheally with 5 microg LPS, which corresponds to the amount acquired by smoking approximately 25 cigarettes, and killed at different time points after exposure. Our data demonstrate that local LPS exposure resulted in apoptosis in lungs from 2 h and peaked at 24 h, as detected by ligation-mediated polymerase chain reaction. Morphologic examination and terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end label staining demonstrated apoptosis in bronchial epithelial cells early after intratracheal (IT) LPS challenge, whereas infiltrating neutrophils displayed positive staining at 24 and 72 h after exposure. Apoptosis in lungs clearly preceded pulmonary neutrophil infiltration, confirming that neutrophils did not contribute to pulmonary apoptosis at early time points. Further, using three experimental approaches--namely, anti-tumor necrosis factor (TNF)-alpha treatment, IT TNF-alpha instillation, and TNF/lymphotoxin-alpha knockout mice--we demonstrate that TNF-alpha, which was elevated in lungs at both messenger RNA and protein levels after IT LPS challenge, was no primary mediator in LPS-induced apoptosis at early time points. Thus, local LPS exposure in mice resulted in early apoptosis of bronchial epithelial cells independent of infiltrating neutrophils and TNF-alpha, which suggests that apoptosis of bronchial epithelium may be involved in airway injury during exposure to LPS.

Disturbances in leptin metabolism are related to energy imbalance during acute exacerbations of chronic obstructive pulmonary disease

Previously we reported an impaired energy balance in patients with chronic obstructive pulmonary disease (COPD) during an acute disease exacerbation, but limited data are available on the underlying mechanisms. Experimental and clinical research supports the hypothesis of involvement of the hormone leptin in body weight and energy balance homeostasis. The aim of this study was to investigate the course of the energy balance in relation to leptin and the soluble tumor necrosis factor (TNF) receptors (sTNF-R) 55 and 75, plasma glucose, and serum insulin in patients with severe COPD during the first 7 d of hospitalization for an acute exacerbation (n = 17, 11 men, age mean [SD] 66 [10] yr, FEV(1) 36 [12] %pred). For reference values of the laboratory parameters, blood was collected from 23 (16 men) healthy, elderly subjects. On admission, the dietary intake/resting energy expenditure (REE) ratio was severely depressed (1.28 [0.57]), but gradually restored until Day 7 (1.65 [0. 45], p = 0.005 versus Day 1). Glucose and insulin concentrations were elevated on admission, but on Day 7 only plasma glucose was decreased. The sTNF-Rs were not different from healthy subjects and did not change. Plasma leptin, adjusted for fat mass expressed as percentage of body weight (%FM), was elevated on Day 1 compared with healthy subjects (1.82 [3.85] versus 0.32 [0.72] ng%/ml, p = 0.008), but decreased significantly until Day 7 (1.46 [3.77] ng%/ml, p = 0. 015 versus Day 1). On Day 7, sTNF-R55 was, independently of %FM, correlated with the natural logarithm (LN) of leptin (r = 0.65, p = 0.041) and with plasma glucose (r = 0.81, p = 0.015). In addition, the dietary intake/REE ratio was not only inversely related with LN leptin (-0.74, p = 0.037), but also with sTNF-R55 (r = -0.93, p = 0. 001) on day seven. In conclusion, temporary disturbances in the energy balance were seen during an acute exacerbation of COPD, related to increased leptin concentrations as well as to the systemic inflammatory response. Evidence was found that the elevated leptin concentrations were in turn under control of the systemic inflammatory response, and, presumably, the high-dose systemic glucocorticosteroid treatment.

Production of the acute-phase protein lipopolysaccharide-binding protein by respiratory type II epithelial cells: implications for local defense to bacterial endotoxins

This study demonstrates for the first time that respiratory epithelial cells are able to produce the acute phase protein lipopolysaccharide (LPS)-binding protein (LBP), which is known to play a central role in the defense to bacterial endotoxins (or LPS). Indications for local presence of LBP in human lung was obtained via reverse transcriptase/polymerase chain reaction that showed LBP messenger RNA (mRNA) expression. Therefore, LBP production by the human lung epithelial cell line A549, a human adenocarcinoma with features of type II pneumocytes, was studied. These cells produced LBP in response to interleukin (IL)-1beta, IL-6, and tumor necrosis factor- alpha, a response that was strongly enhanced by dexamethasone. In addition, LBP mRNA was detected in A549 cells, in increasing amounts as a result of stimulation. The pattern of cytokine-induced LBP production in A549 cells was similar to the pattern in the human liver epithelial cell line HuH-7. Moreover, the molecular weight of A549-derived LBP was approximately 60 kD, which is similar to HuH-7-derived LBP. Biologic activity of LBP produced by A549 cells was evaluated on the basis of its ability to interact with LPS. Further indications that type II alveolar epithelial cells are able to produce LBP were obtained from the observations that the murine lung type II epithelial cell line C10 produced murine LBP, and that isolated human primary type II pneumocytes expressed LBP mRNA, which was enhanced after stimulation of cells. The local production of this endotoxin binding protein by lung epithelial cells might contribute to a highly specific response at the site of exposure to bacteria and bacterial endotoxins.

Strong association of interleukin-6 and lipopolysaccharide-binding protein with severity of adverse reactions after diethylcarbamazine treatment of microfilaremic patients

To assess the involvement of inflammatory mediators in the development of adverse reactions in filarial patients undergoing treatment, 29 microfilaremic subjects were treated with diethylcarbamazine (DEC). Before and at serial time points after initiation of treatment, plasma levels of inflammatory mediators and DEC were measured, and adverse reactions were recorded. Patients experienced no or mild, moderate, or severe adverse reactions. Increasing pretreatment microfilarial counts were associated with escalating severity of adverse reactions. Plasma concentrations of DEC were not different among patients suffering from varying degrees of illness. Interleukin (IL)-6, IL-10, lipopolysaccharide-binding protein (LBP), and soluble tumor necrosis factor receptors (sTNF-Rs) increased after treatment. IL-6 and LBP, however, showed the strongest association with adverse reactions. Increasing levels of these molecules were closely correlated with the mounting severity of adverse reactions, which raises the possibility that they play an important role in systemic inflammation that arises after DEC treatment of filarial patients.

Release of endotoxin-binding proteins during major elective surgery: role of soluble CD14 in phagocytic activation

Our previous study demonstrated that soluble CD14 (sCD14) modulates the biologic activity of circulating endotoxin, which appears after surgery. In this study, we examined the behavior of endotoxin-binding proteins, such as sCD14, lipopolysaccharide-binding protein (LBP), and bactericidal/permeability-increasing protein (BPI), in patients' plasma after major abdominal surgery and the phagocytic secretion of sCD14 from peripheral blood mononuclear cells (PBMCs) throughout the observation period. In a prospective study, 15 patients undergoing major abdominal surgery (gastrectomy, n = 3; pancreatectomy, n = 10: colectomy, n = 2) were involved in this study. The endotoxin-binding proteins were perioperatively (preoperatively; postoperative hour 6; days 1, 2, 3, 4, 5, 7, and 10) measured by an enzyme-linked immunosorbent assay (ELISA). To exclude the hemodilution effect of samples, each parameter was corrected by dividing the respective value by the albumin concentration. The phagocytic activity at each time point was tested as an ex vivo sCD14 secretion from PBMCs in the presence and absence of exogenously added endotoxin, Escherichia coli 055B5 (1 ng/ml). Significant endotoxemia (0.35 +/- 0.13 EU/ml; p < 0.05) was observed 6 hours after the beginning of surgery. The sCD14/albumin value rapidly increased at 6 hours after surgery, peaked on day 1, and sequentially declined, whereas the BPI/albumin and LBP/albumin ratios increased more gradually and peaked on day 2. The secretion of sCD14 from 2 x 10(6) PBMCs was significantly enhanced from 6 hours after operation. The increased plasma level of sCD14 may be explained by the parallel-enhanced sCD14 PBMC production. Activated secretion of these endotoxin-binding proteins may play a role in regulating the biologic activity of circulating endotoxin.

Changes in endotoxin-binding proteins during major elective surgery: important role for soluble CD14 in regulation of biological activity of systemic endotoxin

Assessment of circulating endotoxin during the perioperative period, which is only demonstrated by the Limulus amebocyte lysate (LAL) test, may be modulated by several endotoxin-binding proteins. Endotoxin-neutralizing capacity (ENC) and the plasma levels of soluble CD14 (sCD14), lipopolysaccharide-binding protein, and bactericidal/permeability-increasing protein (BPI) were determined in 40 patients 6 h prior to skin incision for major abdominal surgery. The bioactivity of plasma endotoxin was tested by the polymyxin B-inhibited stimulatory activity of the plasma samples on healthy monocytes as measured by the release of tumor necrosis factor alpha. Plasma endotoxin levels in almost all patients increased from 0.05 +/- 0.01 to 0.23 +/- 0.03 experimental units (EU) per ml (P < 0.001); more specifically, 17 of 40 samples showed endotoxin levels of greater than 0.2 EU per ml and corresponding reductions in ENC. Soluble CD14 plasma levels were decreased from 5. 6 +/- 0.3 to 4.6 +/- 0.3 microg per ml (P < 0.05). ENC was strongly correlated with the sCD14 plasma concentration throughout the period of observation. The addition of sCD14-neutralizing monoclonal anti-sCD14 antibodies reduced ENC both pre- and postoperatively. No correlation could be established between ENC and the plasma levels of BPI, high-density lipoproteins, or low-density lipoproteins determined by measuring the concentrations of apoprotein A and apoprotein B. Biologically active endotoxin was found in only 6 of 17 samples with endotoxin levels greater than 0.2 EU per ml in the LAL test. These samples could be characterized by their perioperative loss of at least 35% of their sCD14. No change in sCD14 was detected in the remaining 11 samples. The perioperative loss of ENC is partly caused by the loss of sCD14 resulting from its consumption by endotoxin reaching the bloodstream. This study demonstrated the role of sCD14 on the bioactivity of circulating endotoxin in a human model of endotoxemia after major abdominal surgery.

Lipopolysaccharide binding protein and serum amyloid A secretion by human intestinal epithelial cells during the acute phase response

The acute phase proteins LPS binding protein (LBP) and serum amyloid A (SAA) are produced by the liver and are present in the circulation. Both proteins have been shown to participate in the immune response to endotoxins. The intestinal mucosa forms a large surface that is continuously exposed to these microbial products. By secretion of antimicrobial and immunomodulating agents, the intestinal epithelium contributes to the defense against bacteria and their products. The aim of this study was to explore the influence of the inflammatory mediators TNF-alpha, IL-6, and IL-1beta on the release of LBP and SAA by intestinal epithelial cells (IEC). In addition, the induction of LBP and SAA release by cell lines of intestinal epithelial cells and hepatic cells was compared. The data obtained show that in addition to liver cells, IEC also expressed LBP mRNA and released bioactive LBP and SAA upon stimulation. Regulation of LBP and SAA release by IEC and hepatocytes was typical for class 1 acute phase proteins, although differences in regulation between the cell types were observed. Endotoxin did not induce LBP and SAA release. Glucocorticoids were demonstrated to strongly enhance the cytokine-induced release of LBP and SAA by IEC, corresponding to hepatocytes. The data from this study, which imply that human IEC can produce LBP and SAA, suggest a role for these proteins in the local defense mechanism of the gut to endotoxin. Furthermore, the results demonstrate that tissues other than the liver are involved in the acute phase response.

Prediction of clinical severity and outcome of ventilator-associated pneumonia. Comparison of simplified acute physiology score with systemic inflammatory mediators

Systemic kinetics of three inflammatory mediators (bactericidal/permeability-increasing protein [BPI], soluble intercellular adhesion molecule [sICAM], and soluble E-selectin [sE-selectin]) were studied during the development of ventilator-associated pneumonia (VAP) (n = 42), diagnosed on quantitative cultures of bronchoscopic samples. From a pool of collected samples, nested samples were used to measure mediators on Days -4, -2, 0, and +2, relative to diagnosis. Correlations between systemic levels of mediators and clinical severity of infection (VAP with or without severe sepsis or septic shock) and patient outcome (mortality at Day 10 after diagnosis) were studied. Predictive values of inflammatory mediators were compared with daily Simplified Acute Physiology Score II (SAPS II) values and the logarithmic number of bacteria in bronchoscopic samples. During the development of VAP, increasing SAPS II scores and rising systemic mediator levels were only found in patients in whom VAP was accompanied with severe sepsis or septic shock. Values of SAPS II and plasma levels of BPI and sE-selectin, but not sICAM, increased from the day of diagnosis on in patients who died within 10 d of diagnosis. Systemic levels of inflammatory mediators did not better predict clinical severity or patient outcome than daily SAPS II scores. The logarithmic number of bacteria in bronchoscopic samples poorly correlated with circulating levels of inflammatory mediators, severity of infection, and patient outcome. Our findings show that a clinical scoring system (SAPS II score) is at least as good as a predictor for the clinical severity of infection and patient outcome, and provide new information on the kinetics of inflammatory mediators during the development of VAP.

The bactericidal/permeability-increasing protein (BPI) is present in specific granules of human eosinophils

Eosinophils participate in the inflammatory response seen in allergy and parasitic infestation, but a role in host defense against bacterial infection is not settled. The bactericidal/permeability-increasing protein (BPI) has been demonstrated in neutrophils and it exerts bacteriostatic and bactericidal effects against a wide variety of Gram-negative bacterial species. Using the Western blot technique, a 55-kD band, corresponding to BPI, was detected in lysates from both neutrophils and eosinophils. The localization of BPI in immature and mature eosinophils was investigated using immunoelectron microscopy. BPI was found in immature and mature specific granules of eosinophils and was detected in phagosomes as well, indicating release of the protein from the granules into the phagosomes. Using a specific enzyme-linked immunosorbent assay, eosinophils were shown to contain 179 ng of BPI/5 x 10(6) eosinophils compared with 710 ng BPI/5 x 10(6) neutrophils. The presence of BPI in eosinophils suggests a role for these cells in host defense against Gram-negative bacterial invasion or may suggest a role for BPI against parasitic infestation.

The enhanced inflammatory response in non-small cell lung carcinoma is not reflected in the alveolar compartment

An inflammatory response has been observed in lung cancer both locally and systemically. The aim of the present study was to investigate whether the alveolar compartment was involved in the inflammatory response in non-small cell lung carcinoma (NSCLC). Both inflammatory mediators in bronchoalveolar lavage fluid (BALF) and cytokines produced by alveolar macrophages (AM) were investigated. Twenty patients with newly detected NSCLC and nine control subjects were studied. The patients had not been treated with chemotherapy, radiotherapy or with systemic or inhaled corticosteroids. All patients and control subjects were current smokers or stopped smoking recently. BAL was performed in the affected lung as well as in the contralateral lung of NSCLC patients, and only unilaterally in control subjects. Comparable results were demonstrated for the levels of the of the inflammatory mediators TNF-a, Interleukin (IL)-6, IL-8, both soluble TNF receptors and the soluble adhesion molecules E-selectin and intercellular adhesion molecule (ICAM)-1 between the affected lung and the contralateral lung in the NSCLC population as well as between the NSCLC population and the control subjects. Moreover, no significant differences in cytokine profiles of AM were found between AM obtained from the affected lung and from the contralateral lung. Although BAL is a useful tool in the diagnostic procedure for NSCLC, the present findings suggest that BAL does not reflect the enhanced inflammatory state, as reported in plasma and in the interstitial compartment around the tumour cells in NSCLC.

Adenosine inhibits neutrophil degranulation in activated human whole blood: involvement of adenosine A2 and A3 receptors

Adenosine, acting via A2 receptors, is a potent inhibitor of neutrophil oxidative burst, but its effects and mechanisms of action on neutrophil degranulation have been less well characterized. We, therefore, investigated the effects of adenosine and its receptor-specific analogues on neutrophil degranulation in stimulated human whole blood. Adenosine dose-dependently inhibited the LPS- and TNF-alpha-induced release of the azurophilic granule proteins bactericidal/permeability-increasing protein, elastase, and defensins to approximately the same extent, with a maximum inhibition of 70 to 80% and an IC50 ranging from 14 to 24 microM. The inhibitory effects of adenosine were partially blocked by the A2 receptor antagonist 3,7-dimethyl-1-propargylxanthine, the A1/A2 antagonist 8(p-sulfophenyl)theophyline, and the A1/A3 antagonist xanthine amine congener, but not by the A1 antagonist 1,3-dipropyl-8-cyclopentylxanthine. The highly selective A3 agonist N6-(3-iodobenzyl)-adenosine-5'-N-methyluronamide and the nonselective agonist 2-chloroadenosine reduced degranulation more potently than the A1 agonist N6-cyclopentyladenosine. The inhibitory effects of N6-(3-iodobenzyl)-adenosine-5'-N-methyluronamide and 2-chloroadenosine were strongly reversed by xanthine amine congener, but were not affected by 8(p-sulfophenyl)theophyline. In addition, the adenosine kinase inhibitor GP515 attenuated degranulation via an adenosine-mediated mechanism. These data indicate that adenosine acts via A2 as well as A3 receptors to inhibit neutrophil degranulation and add to the anti-inflammatory potential of adenosine and adenosine-regulating agents in neutrophil-mediated tissue injury.

Adenosine inhibits neutrophil degranulation in activated human whole blood: involvement of adenosine A2 and A3 receptors

Adenosine, acting via A2 receptors, is a potent inhibitor of neutrophil oxidative burst, but its effects and mechanisms of action on neutrophil degranulation have been less well characterized. We, therefore, investigated the effects of adenosine and its receptor-specific analogues on neutrophil degranulation in stimulated human whole blood. Adenosine dose-dependently inhibited the LPS- and TNF-alpha-induced release of the azurophilic granule proteins bactericidal/permeability-increasing protein, elastase, and defensins to approximately the same extent, with a maximum inhibition of 70 to 80% and an IC50 ranging from 14 to 24 microM. The inhibitory effects of adenosine were partially blocked by the A2 receptor antagonist 3,7-dimethyl-1-propargylxanthine, the A1/A2 antagonist 8(p-sulfophenyl)theophyline, and the A1/A3 antagonist xanthine amine congener, but not by the A1 antagonist 1,3-dipropyl-8-cyclopentylxanthine. The highly selective A3 agonist N6-(3-iodobenzyl)-adenosine-5'-N-methyluronamide and the nonselective agonist 2-chloroadenosine reduced degranulation more potently than the A1 agonist N6-cyclopentyladenosine. The inhibitory effects of N6-(3-iodobenzyl)-adenosine-5'-N-methyluronamide and 2-chloroadenosine were strongly reversed by xanthine amine congener, but were not affected by 8(p-sulfophenyl)theophyline. In addition, the adenosine kinase inhibitor GP515 attenuated degranulation via an adenosine-mediated mechanism. These data indicate that adenosine acts via A2 as well as A3 receptors to inhibit neutrophil degranulation and add to the anti-inflammatory potential of adenosine and adenosine-regulating agents in neutrophil-mediated tissue injury.

Metabolism in patients with small cell lung carcinoma compared with patients with non-small cell lung carcinoma and healthy controls

BACKGROUND

Weight loss is a frequently occurring problem in patients with lung cancer due to an increased resting energy expenditure (REE) and a decreased energy intake. The aim of the present study was to compare the metabolic and inflammatory characteristics of patients with small cell lung carcinoma (SCLC) and non-small cell lung carcinoma (NSCLC). The metabolic parameters of the lung cancer population were compared with those of a healthy control group.

METHODS

REE was measured in 66 patients with lung cancer, subdivided according to their histology, and in 33 healthy controls matched for sex, age, and fat free mass (FFM). Inflammatory mediators were measured in the plasma of the patients with lung cancer.

RESULTS

An increased REE adjusted for FFM was found in the patients with lung cancer. Those with small cell lung carcinoma (SCLC) had an increased REE adjusted for FFM (mean 1925 kcal/day) compared with those with non-small cell lung carcinoma (NSCLC) (mean 1789 kcal/day, 95% CI for difference 36 to 236). FFM accounted for 69% and 48% of the inter-individual variation in REE in controls and those with NSCLC, respectively, while FFM accounted for only 25% of the variation in REE in patients with SCLC in whom the fat mass (FM) also contributed significantly (28%) to the variation in REE. Increased concentrations of soluble TNF-receptor 75 (sTNF-R75) and cortisol were found in patients with SCLC compared with those with NSCLC. Lipopolyasccharide binding protein (LBP) and sTNF-R55 were related to plasma levels of cortisol.

CONCLUSION

An enhanced REE adjusted for FFM occurred in patients with SCLC compared with those with NSCLC.

Bactericidal/permeability-increasing protein release in whole blood ex vivo: strong induction by lipopolysaccharide and tumor necrosis factor-alpha

In this study, the release of bactericidal/permeability-increasing protein (BPI), which is stored in polymorphonuclear leukocytes (PMNL), was analyzed in a whole blood ex vivo system. Of the microbial products tested, lipopolysaccharide (LPS) most potently induced BPI release; FMLP, serum-treated zymosan (STZ), and lipoteichoic acid (LTA) also induced BPI release. In addition, the inflammatory mediator tumor necrosis factor (TNF)-alpha potently activated PMNL in whole blood, via TNF receptor p55, to release BPI, whereas interleukin (IL)-1, IL-8, platelet activating factor, and C5a were poor inducers of BPI release. STZ and phorbol myristate acetate, but not LPS, FMLP, or LTA, stimulated isolated PMNL to release BPI. BPI was released in comparable magnitude with the azurophilic granule protein elastase. Furthermore, both proteins were released with similar kinetics, which started within 30 min after onset of stimulation and lasted 1-4 h.

The effects of treatment with chemotherapy on energy metabolism and inflammatory mediators in small-cell lung carcinoma

A disturbed energy balance has been demonstrated in lung cancer patients. Both an enhanced resting energy expenditure (REE) and a decreased energy intake contribute to weight loss. Enhanced systemic levels of inflammatory mediators were found to be related to the enhanced REE in lung cancer. The aim of the present study was to investigate energy metabolism and systemic levels of inflammatory mediators in small-cell lung carcinoma (SCLC) patients before and after treatment with chemotherapy. Hypermetabolism and an enhanced inflammatory response have already been demonstrated in SCLC by our group before. Twelve newly diagnosed SCLC patients were consecutively included in the study. REE was measured by indirect calorimetry and body composition was determined by bioelectrical impedance (BIA) before and 1 month after treatment. To assess the inflammatory state the acute-phase proteins, C-reactive protein (CRP) and lipopolysaccharide-binding protein (LBP), both soluble tumour necrosis factor (TNF) receptors, (sTNF-R)-55 and sTNF-R75, and soluble intercellular adhesion molecule (sICAM)-1 were measured in plasma before and 1 month after treatment. CRP was assessed by turbidemetry, whereas the other inflammatory parameters were measured by enzyme-linked immunosorbent assay (ELISA). A significant reduction in REE was found irrespective of therapeutic outcome, whereas body weight and body composition remained stable. The acute-phase proteins CRP and LBP were reduced significantly after treatment with chemotherapy, whereas both sTNF receptors and sICAM-1 remained enhanced. No correlation, however, existed between the decrease in REE and the decrease in the acute-phase proteins. In conclusion, chemotherapeutic treatment attenuates the tumour-related metabolic derangements and acute-phase response.

Evidence for a relation between metabolic derangements and increased levels of inflammatory mediators in a subgroup of patients with chronic obstructive pulmonary disease

BACKGROUND

An increase in resting energy expenditure (REE) commonly occurs in patients with chronic obstructive pulmonary disease (COPD), the cause of which is as yet unknown. The objective of this study was to assess the relationship between REE, acute phase proteins, and inflammatory mediators in patients with COPD.

METHODS

Thirty patients were studied and 26 healthy age-matched subjects served as controls. REE was measured by indirect calorimetry and adjusted for fat-free mass (FFM) by bioelectrical impedance analysis. Tumour necrosis factor alpha (TNF-alpha), soluble tumour necrosis receptor (sTNF-R)55 and sTNF-R75, interleukin (IL)-6, IL-8, and lipopolysaccharide binding protein (LBP) were measured by ELISA.

RESULTS

Fourteen patients had a normal REE and in 16 it was raised. The mean body mass index and fat mass were significantly lower in the latter but pulmonary function data were similar in the two groups. In the 30 patients with COPD the mean (SD) sTNF-R75 was 1.7 (1.0) ng/ml compared with 1.1 (0.4) ng/ml in the controls; C-reactive protein (CRP) was detectable (> 5 micrograms/ml) in eight patients compared with none of the control subjects, and LBP was 13.2 (7.7) micrograms/ml compared with 8.6 (3.1) micrograms/ml in the controls. The patients with a raised REE had increased mean levels of CRP compared with the patients with a normal REE (median 5.5 micrograms/ml (range 5-193) and < 5 micrograms/ml, respectively); the same was true for LBP (median 12.4 micrograms/ml (range 8.1-39.1) and 9.5 micrograms/ml (range 5.0-16.6), respectively), but sTNF-R55 and R75 and IL-8 were similar in the two groups. Of the 16 patients with a raised REE, the CRP level was increased in eight and normal in eight. In those with an increased level of CRP the FFM was decreased and LBP, IL-8, and sTNF-R55 and R75 were increased compared with those with normal CRP levels.

CONCLUSIONS

A subset of patients with COPD with an increased REE and decreased FFM have increased levels of acute phase reactant proteins and inflammatory cytokines in their serum; these phenomena may be causally related.

Bactericidal/permeability-increasing protein, a lipopolysaccharide-specific protein on the surface of human peripheral blood monocytes

Bactericidal/permeability-increasing protein (BPI), a cationic protein present in the azurophilic granule and on the surface of polymorphonuclear leukocytes, specifically interacts with lipopolysaccharide (LPS). This study demonstrates for the first time, using flow cytometry with specific anti-BPI monoclonal antibody (MAb), that human peripheral blood monocytes express BPI on their cell surface. The monocyte cell surface BPI was shown to bind to LPS, because binding of anti-BPI MAb 4E3 (which is known not to react with BPI to which LPS is bound) to cell surface BPI was strongly reduced after preincubation of cells with LPS. However, cell surface BPI did not quantitatively contribute to the interaction of LPS with the monocyte cell membrane, since preincubation of cells with 4E3 did not block binding of LPS-fluorescein isothiocyanate to monocytes. The origin of the monocyte cell surface BPI remains to be further elucidated.

Increased resting energy expenditure and weight loss are related to a systemic inflammatory response in lung cancer patients

PURPOSE

To determine whether an increased resting energy expenditure (REE) and weight loss in lung cancer patients are related to a systemic inflammatory response.

MATERIALS AND METHODS

REE was measured by indirect calorimetry using a ventilated hood system. Soluble tumor necrosis factor receptor 55 (sTNF-R55) and sTNF-R75, soluble intercellular adhesion molecule (sICAM)-1, soluble E (sE)-selectin, lipopolysaccharide (LPS)-binding protein (LBP), interleukin (IL)-6, and TNF-alpha were measured using sandwich enzyme-linked immunosorbent assay (ELISA), and C-reactive protein (CRP) was measured by turbidimetry. A cross-sectional study was performed to compare inflammatory mediators between hypermetabolic (REE/Harris Benedict [HB] equation > or = 110%) versus normometabolic (REE/HB < 110%) patients and between patients who lost weight (more than 10% loss of preillness weight) versus those whose weight remained stable.

RESULTS

Eighty-seven patients with primary non-small-cell lung cancer were consecutively entered onto the study. Mean REE expressed as a percentage of the HB reference values was 118% +/- 12%; 67 patients were considered hypermetabolic. Twenty-six patients had a substantial loss of more than 10% of their preillness weight. Hypermetabolic patients were found to have significantly increased levels of sTNF-R55, sE-selectin, LBP, and CRP compared with normometabolic patients. Weight loss was related with increased levels of the sTNF-Rs, sICAM-1, IL-6, LBP, and CRP.

CONCLUSION

Hypermetabolism and weight loss are related to the presence of a systemic inflammatory response as reflected by enhanced levels of inflammatory mediators and acute phase proteins in patients with primary non-small-cell lung cancer.

Lipopolysaccharide toxicity-regulating proteins in bacteremia

The toxicity of lipopolysaccharide (LPS) is modified by several proteins, such as bactericidal/permeability-increasing protein (BPI) and LPS-binding protein (LBP). BPI and LBP plasma levels were measured in patients with gram-negative (n = 36) or gram-positive (n = 28) bacteremia. Levels of BPI and LBP, which are proteins that neutralize and enhance LPS effects, respectively, were increased before bacteremia was first detected. The BPI/neutrophil ratio, reflecting neutrophil activation, was significantly associated with the presence of sepsis syndrome and death in bacteremic patients: 1.06 (0.11-6.49) versus 0.57 (0.06-3.82) in patients with and without sepsis syndrome (P < .01), respectively, and 0.64 (0.06-3.82) versus 1.02 (0.12-6.49) in survivors and nonsurvivors (P < .05), respectively (ratio in nanograms of BPI per 10(6) neutrophils). High LBP peak levels were significantly associated with the presence of sepsis syndrome (P < .01). No differences in BPI and LBP levels were observed in patients with gram-negative versus gram-positive bacteremia. BPI/neutrophil ratio, as a parameter of neutrophil activation, may be useful in monitoring infectious disease.

Presence of bactericidal/permeability-increasing protein in disease: detection by ELISA

A sandwich ELISA was developed specific for human bactericidal/permeability-increasing protein (BPI), using Mg++ ions to abrogate disturbance by lipopolysaccharide of BPI measurement and to prevent aspecific adherence of BPI to solid phase. In fresh EDTA or heparinized plasma of healthy volunteers BPI was not detectable, whereas in serum BPI was present, indicating that coagulation activates polymorphonuclear leukocytes to release BPI. Furthermore, BPI was present in plasma of critically ill intensive care unit (ICU) patients, in bronchoalveolar lavage fluid of patients suspected of having pneumonia, in wound fluid, and in pleural fluid. In sub-groups of samples with culture-proven bacteria, mean BPI levels were increased compared with subgroups without bacteria, although the differences were only significant in EDTA plasma of ICU patients. These findings indicate the presence of BPI during pathologic conditions. The physiologic role of the released BPI has to be further elucidated.

Characterization of two monoclonal antibodies directed against bactericidal/permeability-increasing protein

In this study the production and characterization of two monoclonal antibodies (MAbs), 4E3 and 5D7, against the bactericidal/permeability-increasing protein (BPI) were described. Using ELISAs, both 4E3 and 5D7 were shown to detect recombinant (r) BPI. Furthermore, natural BPI present in polymorphonuclear leukocytes (PMNL) was detected by both 4E3 and 5D7. The use of both MAbs in flow cytometry revealed that PMNL expressed low levels of cell-surface BPI. Lipopolysaccharide (LPS) was shown to block the interaction between anti-BPI MAb and rBPI. In addition, the MAbs blocked biologic activity of rBPI. The inhibition by BPI of LPS activation of the limulus amebocyte lysate assay and of LPS-induced tumor necrosis factor-alpha release by monocytes was prevented by 4E3 and 5D7. Both MAbs are specifically directed against BPI and can inhibit BPI bioactivity.

Lipopolysaccharide LPS-mediated soluble TNF receptor release and TNF receptor expression by monocytes. Role of CD14, LPS binding protein, and bactericidal/permeability-increasing protein

Previously we demonstrated that two soluble(s) tumor necrosis factor receptors, TNF-R55 as well as sTNF-R75, are constitutively released in vitro by monocytes, and that this release was markedly enhanced after activation. Because LPS is an important activator of monocytes, we investigated the effect of LPS on sTNF-R release by monocytes. It was found that release of sTNF-R75, but not (or minimally) release of sTNF-R55, was enhanced after activation with LPS, reaching plateau levels after approximately 2 days. CD14, one of the membrane receptors for LPS, is an intermediate in this process, as shown in experiments using mAb directed against CD14. Under serum-free conditions, LPS-induced sTNF-R75 release was less as compared with release in the presence of serum, suggesting involvement of serum proteins. Addition of LPS binding protein (LBP) enhanced the LPS-induced sTNF-R75 release under serum-free conditions, but had no effect in the presence of serum. On the other hand, bactericidal/permeability-increasing protein (BPI), known to possess LPS neutralizing activity, inhibited LPS-induced sTNF-R75 release. Furthermore, cell surface expression of both types of TNF-R was shown to be controlled by LPS, LBP, and BPI. LPS caused, within 1 h, a complete reduction of TNF-R55 as well as TNF-R75 expression, followed by enhanced re-expression of both receptors after 24 h. The down-modulation of expression was increased by LBP, whereas BPI counteracted the LPS-induced down-regulation. The LPS-enhanced release of sTNF-R75, capable of inactivation of TNF, as well as LPS-induced initial down-modulation of TNF-R expression leading to postulated temporary unresponsiveness to TNF may share in a physiological mechanism to carefully control the effects of TNF.

Lipopolysaccharide LPS-mediated soluble TNF receptor release and TNF receptor expression by monocytes. Role of CD14, LPS binding protein, and bactericidal/permeability-increasing protein

Previously we demonstrated that two soluble(s) tumor necrosis factor receptors, TNF-R55 as well as sTNF-R75, are constitutively released in vitro by monocytes, and that this release was markedly enhanced after activation. Because LPS is an important activator of monocytes, we investigated the effect of LPS on sTNF-R release by monocytes. It was found that release of sTNF-R75, but not (or minimally) release of sTNF-R55, was enhanced after activation with LPS, reaching plateau levels after approximately 2 days. CD14, one of the membrane receptors for LPS, is an intermediate in this process, as shown in experiments using mAb directed against CD14. Under serum-free conditions, LPS-induced sTNF-R75 release was less as compared with release in the presence of serum, suggesting involvement of serum proteins. Addition of LPS binding protein (LBP) enhanced the LPS-induced sTNF-R75 release under serum-free conditions, but had no effect in the presence of serum. On the other hand, bactericidal/permeability-increasing protein (BPI), known to possess LPS neutralizing activity, inhibited LPS-induced sTNF-R75 release. Furthermore, cell surface expression of both types of TNF-R was shown to be controlled by LPS, LBP, and BPI. LPS caused, within 1 h, a complete reduction of TNF-R55 as well as TNF-R75 expression, followed by enhanced re-expression of both receptors after 24 h. The down-modulation of expression was increased by LBP, whereas BPI counteracted the LPS-induced down-regulation. The LPS-enhanced release of sTNF-R75, capable of inactivation of TNF, as well as LPS-induced initial down-modulation of TNF-R expression leading to postulated temporary unresponsiveness to TNF may share in a physiological mechanism to carefully control the effects of TNF.

IL-6, IL-8 and TNF production by cytokine and lipopolysaccharide-stimulated human renal cortical epithelial cells in vitro

The capacity of renal epithelial cells to produce IL-6, IL-8 and TNF was investigated. Cultures of explanted human renal cortical epithelial cells (RCEC) were established, and cytokine-release and mRNA expression by these cells were measured. IL-6, IL-8 and TNF release were measured after stimulation with IL-1 beta TNF-alpha, LPS and the phorbol esther PMA. All these agents were found to induce increased release of the three cytokines. Whilst no spontaneous TNF-release occurred, IL-6 and IL-8 were continuously released by non-stimulated RCEC cultures. IL-1 beta was the most potent trigger, enhancing both RCEC cytokine release and expression of IL-6, IL-8 and TNF mRNA. Indomethacin, budesonide, cyclosporin and FK 506 were tested for their influence on RCEC cytokine release. Only the steroid budesonide appeared to reduce both spontaneous and IL-1 beta induced cytokine release. Our data demonstrate stimulus specific release of IL-6, IL-8 and TNF by RCEC, and suggest that cytokine cell-to-cell communication may be important in regulating inflammatory processes in the kidney.

Antagonistic effects of lipopolysaccharide binding protein and bactericidal/permeability-increasing protein on lipopolysaccharide-induced cytokine release by mononuclear phagocytes. Competition for binding to lipopolysaccharide

Serum proteins play an important role in LPS-induced cell activation. The LPS binding protein (LBP) enhances cellular responses to LPS, whereas the polymorphonuclear leukocyte product bactericidal/permeability-increasing protein (BPI) inhibits LPS-induced cell activation. In this study the influences of LBP and BPI, two proteins with opposite effects, but with considerable sequence homology, on LPS-induced mononuclear phagocytic cell cytokine release was studied. LBP was shown to enhance LPS-induced TNF-alpha, IL-6, and IL-8 release by mononuclear phagocytic cells, whereas BPI inhibited the release of these cytokines. Furthermore, the effects of LBP and BPI on LPS-induced cytokine release by mononuclear phagocytic cells were shown to be counteractive. BPI interfered with the enhancing effect of LBP on the LPS-induced cytokine release. At high LBP to BPI ratios, BPI could no longer inhibit LBP-induced enhancement. In accordance, increasing concentrations of BPI abrogated the LBP effect. Next, it was shown that LBP and BPI compete for binding to LPS by using an assay system that detects binding of free BPI to an anti-BPI mAb. LPS prevented binding of BPI to anti-BPI mAb, whereas preincubation of LPS with LBP prevented the LPS-induced inhibition. Also, it was observed that both BPI and LBP inhibited LPS activity in the chromogenic LAL assay. We conclude from this study that LBP and BPI have counteractive effects on LPS-induced mononuclear phagocytic cell cytokine release by competing for binding to LPS.

Antagonistic effects of lipopolysaccharide binding protein and bactericidal/permeability-increasing protein on lipopolysaccharide-induced cytokine release by mononuclear phagocytes. Competition for binding to lipopolysaccharide

Serum proteins play an important role in LPS-induced cell activation. The LPS binding protein (LBP) enhances cellular responses to LPS, whereas the polymorphonuclear leukocyte product bactericidal/permeability-increasing protein (BPI) inhibits LPS-induced cell activation. In this study the influences of LBP and BPI, two proteins with opposite effects, but with considerable sequence homology, on LPS-induced mononuclear phagocytic cell cytokine release was studied. LBP was shown to enhance LPS-induced TNF-alpha, IL-6, and IL-8 release by mononuclear phagocytic cells, whereas BPI inhibited the release of these cytokines. Furthermore, the effects of LBP and BPI on LPS-induced cytokine release by mononuclear phagocytic cells were shown to be counteractive. BPI interfered with the enhancing effect of LBP on the LPS-induced cytokine release. At high LBP to BPI ratios, BPI could no longer inhibit LBP-induced enhancement. In accordance, increasing concentrations of BPI abrogated the LBP effect. Next, it was shown that LBP and BPI compete for binding to LPS by using an assay system that detects binding of free BPI to an anti-BPI mAb. LPS prevented binding of BPI to anti-BPI mAb, whereas preincubation of LPS with LBP prevented the LPS-induced inhibition. Also, it was observed that both BPI and LBP inhibited LPS activity in the chromogenic LAL assay. We conclude from this study that LBP and BPI have counteractive effects on LPS-induced mononuclear phagocytic cell cytokine release by competing for binding to LPS.

Anti-CD14 antibodies reduce responses of cultured human endothelial cells to endotoxin

Lipopolysaccharide (LPS) activates both myeloid and endothelial cells. Whereas CD14 has been shown to be involved in LPS recognition by myeloid cells, the mechanism responsible for the strong response of endothelial cells to LPS remains to be elucidated. The role of CD14 in this process was studied using CD14-specific antibodies (Ab). Anti-CD14 Ab inhibited LPS-induced interleukin-6 (IL-6) release and E-selectin expression by cultured human umbilical vein endothelial cells (HUVEC). Messenger RNA encoding IL-6 and E-selectin was reduced in parallel. The inhibitory effect of anti-CD14 Ab was epitope dependent, maximal at low LPS concentrations and dropping with increasing LPS doses. Anti-CD14 Ab did not affect endothelial cell activation induced by IL-1 beta, tumour necrosis factor-alpha (TNF-alpha) and phorbol 12-myristate 13-acetate (PMA). IL-6 release and E-selectin expression of HUVEC were strongly reduced when LPS activation was performed in the absence of serum, indicating involvement of serum components in LPS activation of HUVEC. Nevertheless, anti-CD14 Ab also blocked LPS-induced HUVEC activation in the absence of serum. Although the role of serum components in LPS activation remains to be elucidated, CD14 seems to be a key mediator in LPS-induced activation of endothelial cells.

Involvement of CD14 in lipopolysaccharide-induced tumor necrosis factor-alpha, IL-6 and IL-8 release by human monocytes and alveolar macrophages

CD14 has been reported to function as a receptor for bacterial LPS complexed with serum proteins, transducing an activation signal for TNF-alpha production. We found that the anti-CD14 mAb MEM-18 inhibited not only LPS-induced release of TNF-alpha, but also LPS-induced, TNF-alpha independent release of IL-6 and IL-8 by human monocytes and alveolar macrophages. Inhibitory effect of MEM-18 was detected both in the presence of human or bovine calf serum and under serum-free conditions. In contrast, MEM-18 did not block release of these cytokines induced by IL-1 beta, TNF-alpha, PMA, and zymosan. We conclude that CD14 is involved in LPS-induced release of TNF-alpha, IL-6, and IL-8 by monocytes and alveolar macrophages and that this receptor appears to be able to recognize LPS directly in the absence of serum.

Involvement of CD14 in lipopolysaccharide-induced tumor necrosis factor-alpha, IL-6 and IL-8 release by human monocytes and alveolar macrophages

CD14 has been reported to function as a receptor for bacterial LPS complexed with serum proteins, transducing an activation signal for TNF-alpha production. We found that the anti-CD14 mAb MEM-18 inhibited not only LPS-induced release of TNF-alpha, but also LPS-induced, TNF-alpha independent release of IL-6 and IL-8 by human monocytes and alveolar macrophages. Inhibitory effect of MEM-18 was detected both in the presence of human or bovine calf serum and under serum-free conditions. In contrast, MEM-18 did not block release of these cytokines induced by IL-1 beta, TNF-alpha, PMA, and zymosan. We conclude that CD14 is involved in LPS-induced release of TNF-alpha, IL-6, and IL-8 by monocytes and alveolar macrophages and that this receptor appears to be able to recognize LPS directly in the absence of serum.

Role of tumour necrosis factor in the enhanced sensitivity of mice to endotoxin after exposure to lead

Heavy metals administered to animals, at doses which appear relatively innoxious by themselves, enhance susceptibility to endotoxin. The mechanisms which underly this phenomenon are not yet fully understood. In this study we investigated the role of the cytokine Tumour Necrosis Factor (TNF), an important mediator of the effects of endotoxin, in this phenomenon. First it was studied whether lead enhances sensitivity of mice to endotoxin and to TNF. Lead appeared to enhance sensitivity to both endotoxin and TNF resulting in mortality of mice at low endotoxin and TNF doses. Next we studied the influence of lead on serum TNF levels after stimulation by endotoxin. Lead treated mice showed lower TNF blood levels two hours after injection of endotoxin and lead. Six and eight hours after injection TNF levels of lead treated mice were higher compared to those of mice injected with endotoxin only. In the last part of our investigation, we studied the influence of a monoclonal hamster anti TNF antibody on the effect of combined lead-endotoxin exposure. Administration of the antibody prevents lethality completely. Our data indicate that TNF plays a central role in the phenomenon of the enhanced susceptibility of animals to endotoxin after exposure to lead. The enhanced susceptibility to endotoxin is caused by an enhanced susceptibility to TNF and possibly by a prolonged exposure to a higher level of TNF.