Role of cytokine-induced neutrophil chemoattractant-2 (CINC-2) alpha in a rat model of chronic bronchopulmonary infections with Pseudomonas aeruginosa

Characteristics of inflammatory response and repair after experimental blast lung injury in rats

BACKGROUND AND OBJECTIVES

Blast-induced lung injury is associated with inflammatory, which are characterised by disruption of the alveolar-capillary barrier, haemorrhage, pulmonary infiltrateration causing oedema formation, pro-inflammatory cytokine and chemokine release, and anti-inflammatory counter-regulation. The objective of the current study was to define sequence of such alterations in with establishing blast-induced lung injury in rats using an advanced blast generator.

METHODS

Rats underwent a standardized blast wave trauma and were euthanised at defined time points. Non-traumatised animals served as sham controls. Obtained samples from bronchoalveolar lavage fluid (BALF) at each time-point were assessed for histology, leukocyte infiltration and cytokine/chemokine profile.

RESULTS

After blast lung injury, significant haemorrhage and neutrophil infiltration were observed. Similarly, protein accumulation, lactate dehydrogenase activity (LDH), alveolar eicosanoid release, matrix metalloproteinase (MMP)-2 and -9, pro-Inflammatory cytokines, including tumour necrosis factor (TNF) and interleukin (IL) -6 raised up. While declining in the level of anti-inflammatory cytokine IL-10 occurred. Ultimately, pulmonary oedema developed that increased to its maximum level within the first 1.5 h, then recovered within 24 h.

CONCLUSION

Using a stablished model, can facilitate the study of inflammatory response to blast lung injury. Following the blast injury, alteration in cytokine/chemokine profile and activity of cells in the alveolar space occurs, which eventuates in alveolar epithelial barrier dysfunction and oedema formation. Most of these parameters exhibit time-dependent return to their basal status that is an indication to resilience of lungs to blast-induced lung injury.

L-arginine Improves Plasma Lipid Profile and Muscle Inflammatory Response in Trained Rats After High-Intense Exercise

Purpose: This study aimed to evaluate whether supplementation with L-arginine alone or in combination with physical exercise training can modulate rats' lipid and inflammatory profiles after a single intense exercise session. Methods: Male Wistar rats were divided into four different groups: control (C), trained (T), supplemented with L-arginine (C + A) and trained and supplemented (T + A). Animals from supplemented groups (C + A and T + A groups) received 300 mg/kg animal body weight L-arginine diluted in 30 mL of drinking water for 8 weeks. Exercise training protocol (moderate intensity-70% achieved in the maximum effort test) was held 5 days/week for 8 weeks. Results: Exercise training induced a decrease in the amount of plasma, cholesterol and triglyceride totals, and skeletal muscle VEGF and CINC. Supplementation alone showed a benefit by reducing LDL levels. Conclusion: Training combined with supplementation showed a pronounced reduction in skeletal muscle VEGF and CINC amount. L-arginine supplementation, especially when associated with the regular aerobic physical exercise at moderate intensity was able to improve not only plasma lipid profile but also the inflammatory response of skeletal muscle immediately after an exhaustive physical exercise session.

Assessment of Cytokine-Induced Neutrophil Chemoattractants as Biomarkers for Prediction of Pulmonary Toxicity of Nanomaterials

This work determines whether cytokine-induced neutrophil chemoattractants (CINC)-1, CINC-2 and CINC-3 can be markers for predicting high or low pulmonary toxicity of nanomaterials (NMs). We classified NMs of nickel oxide (NiO) and cerium dioxide (CeO₂) into high toxicity and NMs of two types of titanium dioxides (TiO₂ (P90 and rutile)) and zinc oxide (ZnO) into low toxicity, and we analyzed previous data of CINCs in bronchoalveolar lavage fluid (BALF) of rats from three days to six months after intratracheal instillation (0.2 and 1.0 mg) and inhalation exposure (0.32–10.4 mg/m³) of materials (NiO, CeO₂, TiO₂ (P90 and rutile), ZnO NMs and micron-particles of crystalline silica (SiO₂)). The concentration of CINC-1 and CINC-2 in BALF had different increase tendency between high and low pulmonary toxicity of NMs and correlated with the other inflammatory markers in BALF. However, CINC-3 increased only slightly in a dose-dependent manner compared with CINC-1 and CINC-2. Analysis of receiver operating characteristics for the toxicity of NMs by CINC-1 and CINC-2 showed the most accuracy of discrimination of the toxicity at one week or one month after exposure and CINC-1 and CINC-2 in BALF following intratracheal instillation of SiO₂ as a high toxicity could accurately predict the toxicity at more than one month after exposure. These data suggest that CINC-1 and CINC-2 may be useful biomarkers for the prediction of pulmonary toxicity of NMs relatively early in both intratracheal instillation and inhalation exposure.

Circulating cytokine portraits can differentiate between allograft rejection and pulmonary infection in cardiac transplant rats

OBJECTIVES

Cardiac rejection and infection are the leading causes of morbidity and mortality after transplant representing with similar non-specific symptoms. Early discrimination is crucial yet challenging. We proposed that aberrant serum cytokine portraits exist in pulmonary infection and allograft rejection, and such profiles might aid in timely differential diagnosis.

METHODS

Lewis rat received Wistar rat heart allografts. Allograft rejection (n = 5) and pulmonary infection (n = 7) were induced via cessation of cyclosporine injection and intratracheal inoculation of Pseudomonas aeruginosa, respectively, and pathologically confirmed. A non-rejection and non-infection group (n = 5) was served as healthy controls. The circulating cytokine profiles of the study objects were then simultaneously measured using a multiplex quantitative cytokine array.

RESULTS

Thirteen cytokines [B7-2, β-nerve growth factor (NGF), chemokine (C-X3-C motif) ligand 1 (Fractalkine), granulocyte-macrophage colony-stimulating factor (GM-CSF), interferon gamma (IFN-γ), interleukin beta (IL-β), IL-2, IL-4, IL-10, chemokine (C-X-C motif) ligand 5 (LIX), L-selectin, chemokine (C-C motif) ligand 2 (MCP-1), brain creatine kinase (TCK-1) and tumour necrosis factor alpha (TNF-α)] were up-regulated in allograft rejecting animals. Among them, B7-2, β-NGF, Fractalkine, GM-CSF, IFN-γ, IL-β, IL-2, IL-4, LIX, MCP-1 and TCK-1 were significantly increased compared with infection rats (all P-values <0.05). B7-2, CNIC-1 and CNIC-2 were increased in infection animals when compared with healthy controls (900.85 ± 259.30 vs 175.04 ± 161.07 pg/ml, 319.68 ± 264.91 vs 13.50 ± 0.00 pg/ml and 51.424 ± 29.51 vs 5.24 ± 1.30 pg/ml, respectively, all P-values <0.05).

CONCLUSIONS

The present study demonstrated fluctuations in circulating cytokine portraits in cardiac allograft rejection and bacterial pulmonary infection after transplant. Such disease-specific cytokine patterns might facilitate early discrimination between rejection and infection.

Pulmonary toxicity of well-dispersed titanium dioxide nanoparticles following intratracheal instillation

In order to investigate the pulmonary toxicity of titanium dioxide (TiO₂) nanoparticles, we performed an intratracheal instillation study with rats of well-dispersed TiO₂ nanoparticles and examined the pulmonary inflammation and histopathological changes in the lung. Wistar Hannover rats were intratracheally administered 0.2 mg (0.66 mg/kg) and 1.0 mg (3.3 mg/kg) of well-dispersed TiO₂ nanoparticles (P90; diameter of agglomerates: 25 nm), then the pulmonary inflammation responses were examined from 3 days to 6 months after the instillation, and the pathological features were examined up to 24 months. Transient inflammation and the upregulation of chemokines in the broncho-alveolar lavage fluid were observed for 1 month. No respiratory tumors or severe fibrosis were observed during the recovery time. These data suggest that transient inflammation induced by TiO₂ may not lead to chronic, irreversible legions in the lung, and that TiO₂ nanoparticles may not have a high potential for lung disorder.

Pulmonary toxicity of well-dispersed titanium dioxide nanoparticles following intratracheal instillation

In order to investigate the pulmonary toxicity of titanium dioxide (TiO₂) nanoparticles, we performed an intratracheal instillation study with rats of well-dispersed TiO₂ nanoparticles and examined the pulmonary inflammation and histopathological changes in the lung. Wistar Hannover rats were intratracheally administered 0.2 mg (0.66 mg/kg) and 1.0 mg (3.3 mg/kg) of well-dispersed TiO₂ nanoparticles (P90; diameter of agglomerates: 25 nm), then the pulmonary inflammation responses were examined from 3 days to 6 months after the instillation, and the pathological features were examined up to 24 months. Transient inflammation and the upregulation of chemokines in the broncho-alveolar lavage fluid were observed for 1 month. No respiratory tumors or severe fibrosis were observed during the recovery time. These data suggest that transient inflammation induced by TiO₂ may not lead to chronic, irreversible legions in the lung, and that TiO₂ nanoparticles may not have a high potential for lung disorder.

Assessing Pseudomonas aeruginosa virulence and the host response using murine models of acute and chronic lung infection

Murine models of acute and chronic lung infection have been used in studying Pseudomonas aeruginosa for assessing in vivo behavior and for monitoring of the host response. These models provide an important resource for studies of the initiation and maintenance of bacterial infection, identify bacterial genes essential for in vivo maintenance and for the development and testing of new therapies. The rat has been used extensively as a model of chronic lung infection, whereas the mouse has been a model of acute and chronic infection. Intratracheal administration of planktonic bacterial cells in the mouse provides a model of acute pneumonia. Bacteria enmeshed in agar beads can be used in the rat and mouse to reproduce the lung pathology of cystic fibrosis patients with advanced chronic pulmonary disease. Here, we describe the methods to assess virulence of P. aeruginosa using prototype and clinical strains in the Sprague-Dawley rat and the C57BL/6NCrlBR mouse by monitoring several measurable read-outs including weight loss, mortality, in vivo growth curves, the competitive index of infectivity, and the inflammatory response.

Expression of cytokine-induced neutrophil chemoattractant in rat lungs following an intratracheal instillation of micron-sized nickel oxide nanoparticle agglomerates

OBJECTIVE

In our previous study, we reported that the micron-sized nickel oxide nanoparticle agglomerates induced neutrophil infiltration and the gene expression of the cytokine-induced neutrophil chemoattractant (CINC)-2αβ in a rat lung. In this study, we examined the expression of the CINCs family in the lung using the same rat model exposed to micron-sized nickel oxide nanoparticle agglomerates.

METHODS

The count median diameter of nickel oxide nanoparticle agglomerates suspended in saline was 1.34 μm (primary diameter: 8.41 nm). Male Wistar rats received an intratracheal instillation of 1 mg (3.3 mg/kg) of nickel oxide nanoparticles and were dissected at 3 days, 1 week, 1 month, 3 months, and 6 months after the instillation. The negative control group received an instillation of saline. The concentration of CINC-1 in the lung and the bronchoalveolar lavage fluid (BALF), CINC-2αβ in the BALF, and CINC-3 in the lung and the BALF was examined.

RESULTS

The concentration of CINC-1 was elevated at 3 days, 3 months, and 6 months in the lung tissue and from 3 days to 6 months in the BALF. The concentration of CINC-2αβ was elevated from 3 days to 3 months in the BALF. The concentration of CINC-3 was also elevated at 3 days, 1 week, 3 months, and 6 months in the lung tissue. Infiltration of neutrophil and alveolar macrophage was observed mainly in the alveoli during the observed time period.

CONCLUSION

These results suggest that CINC-1 to -3 were totally involved in the lung injury caused by micron-sized nickel oxide nanoparticle agglomerates.

Identification and characterization of a novel CXC chemokine in xenograft tumor induced by mas-overexpressing cells

Overexpressions of G protein-coupled receptor (GPCR) with elevated downstream signaling events have been reported in various tumors. However, the cellular mechanism that GPCR overexpression leads to tumor formation is largely unknown. The orphan GPCR mas was originally isolated from a human epidermoid carcinoma. In vivo studies of mas-overexpressing cells suggested that xenograft tumor formation was positively correlated with the levels of mas expression. Histochemical analysis indicated that xenograft tumor consisted of mas-transfected and stromal cells. Biochemical analyses revealed that cells overexpressing mas exhibited significantly increased anchorage-independent growth, whereas there was no significant difference in cell proliferation in comparison with empty vector-transfected control cells. Expression profiling using mRNA differential display and Northern analysis indicated an elevated expression of GRO and a novel CXC chemokines, tumor-induced factor (TIF), in mas-transfected cells and xenograft tumor. Bacterially expressed recombinant TIF was found to act as a neutrophil chemoattractant in a chemotactic assay. These results suggest that mas overexpression enables anchorage-independent growth of transformed cells, and interplays of secreted chemokines with stromal cells modulate xenograft tumor formation. Importantly, a novel CXC chemokine, TIF, was identified in the xenograft tumor tissues.

Animal models of chronic lung infection with Pseudomonas aeruginosa: useful tools for cystic fibrosis studies

Cystic fibrosis (CF) is caused by a defect in the transmembrane conductance regulator (CFTR) protein that functions as a chloride channel. Dysfunction of the CFTR protein results in salty sweat, pancreatic insufficiency, intestinal obstruction, male infertility and severe pulmonary disease. In most patients with CF life expectancy is limited due to a progressive loss of functional lung tissue. Early in life a persistent neutrophylic inflammation can be demonstrated in the airways. The cause of this inflammation, the role of CFTR and the cause of lung morbidity by different CF-specific bacteria, mostly Pseudomonas aeruginosa, are not well understood. The lack of an appropriate animal model with multi-organ pathology having the characteristics of the human form of CF has hampered our understanding of the pathobiology and chronic lung infections of the disease for many years. This review summarizes the main characteristics of CF and focuses on several available animal models that have been frequently used in CF research. A better understanding of the chronic lung infection caused particularly by P. aeruginosa, the pathophysiology of lung inflammation and the pathogenesis of lung disease necessitates animal models to understand CF, and to develop and improve treatment.

Spiral ligament fibrocytes release chemokines in response to otitis media pathogens

CONCLUSION

Spiral ligament fibrocytes (SLFs) may be involved in the innate immune response of the inner ear by producing chemoattractants for recruiting inflammatory cells such as neutrophils and monocytes.

OBJECTIVE

The purpose of this study was to investigate the cellular responses of SLFs when challenged by inflammatory stimuli such as components of otitis media pathogens or proinflammatory cytokines.

MATERIALS AND METHODS

To detect released inflammatory cytokines and chemokines, cells were treated for 48 h with whole lysates of nontypable Haemophilus influenzae (NTHi), Streptococcus pneumoniae, or with interleukin 1 alpha (IL-1alpha). The culture medium was then collected and applied to protein arrays. To compare mRNA levels of chemokines, total RNA was extracted after 3 h of treatment with the above agents, and quantitative real-time PCR was performed.

RESULTS

Protein array analysis showed that in response to NTHi or S. pneumoniae, rat SLFs released monocyte chemotactic protein 1, macrophage inflammatory protein 3 alpha, TNF-alpha, and cytokine-induced neutrophil chemoattractant 2 and 3. Treatment with IL-1alpha, on the other hand, resulted in release of MCP-1 but not the other molecules. Tissue inhibitor of metalloproteinase 1 and vascular endothelial growth factor were released regardless of the inflammatory stimulus used.

Inflammatory mechanisms underlying the rat pulmonary neutrophil influx induced by airway exposure to staphylococcal enterotoxin type A

Association between staphylococcal infection and pathogenesis of upper airways disease has been reported. This study aimed to investigate the mechanisms underlying the rat pulmonary inflammation induced by airway exposure to staphylococcal enterotoxin A (SEA). SEA (0.3-10 ng trachea(-1)) caused dose-dependent neutrophil accumulation in BAL fluid, reaching maximal responses at 4 h (25-fold increase for 3 ng trachea(-1)). Significant accumulation of both lymphocytes and macrophages in BAL fluid was also observed at 4 h (2.1- and 1.9-fold increase, respectively, for 3 ng trachea(-1)). At later times (16 h), neutrophil counts in bone marrow (immature forms) and peripheral blood increased by 63 and 81%, respectively. SEA failed to directly induce chemotaxis and adhesion of isolated neutrophils. Analysis of mRNA expression for iNOS, COX-2 and CINC-2 in lung tissue showed an upregulation of these enzymes, which paralleled elevated levels of LTB4, PGE2, TNF-alpha, IL-6 and NO2- in BAL fluid. Expression of CINC-1 was unchanged, whereas CINC-3 was reduced in SEA-treated rats. Incubation of isolated alveolar macrophages with SEA (3 microg ml(-1)) resulted in significant elevations of TNF-alpha and NO2- levels in the cell supernatants. Dexamethasone (0.5 mg kg(-1)), celecoxib (3 mg kg(-1)) and compound 1400 W (5 mg kg(-1)) markedly reduced SEA-induced lung neutrophil influx and NO2- levels in BAL fluid. The lipoxygenase inhibitor AA-861 (100 microg kg(-1)) partly inhibited the neutrophil influx in SEA-treated rats without modifying the NO2- levels. None of these treatments reduced the number of mononuclear cells in BAL fluid (except of dexamethasone, which abolished the increased lymphocyte counts). Our study shows that airways exposure to SEA results in marked neutrophil influx through mechanisms involving increased expressions of CINC-2, iNOS and COX-2, as well as enhanced production of NO, PGE2, LTB4, TNF-alpha and IL-6.

Expression of CINC-2beta is related to the state of differentiation of alveolar epithelial cells

Alveolar epithelial cells are among the first cells to encounter inhaled particles or organisms. These cells likely participate in the initiation and modulation of the inflammatory response by production of chemokines. However, there is little information on the extent or regulation of chemokine production by these cells. Rat type II cells were studied under differentiated and dedifferentiated conditions to determine their ability to express and secrete CXC chemokines. Both differentiated and dedifferentiated type II cells secreted MIP-2, MCP-1, and CINC-2 in response to a cytokine mixture of IL-1beta, TNF-alpha, and IFN-gamma or to IL-1beta alone. The cytokine mixture also induced iNOS expression and nitrite secretion. Both differentiated and dedifferentiated type II cells expressed CINC-1 (GRO), CINC-2alpha, CINC-3 (MIP-2), and MCP-1 mRNA, and their expression was increased by the cytokine mixture or by IL-1beta alone. However, CINC-2beta, a splice variant of CINC-2, was only expressed under differentiated conditions stimulated by KGF and was not increased by the cytokine mixture or by IL-1beta. In situ hybridization of normal lung and lung instilled with Ad-KGF demonstrated that CINC-2beta was expressed by alveolar and bronchiolar epithelial cells in vivo. We conclude that CINC-2beta is regulated differently from most other chemokines and that its expression is related to the state of alveolar type II cell differentiation.

Chronic pneumonia with Pseudomonas aeruginosa and impaired alveolar fluid clearance

Background

While the functional consequences of acute pulmonary infections are widely documented, few studies focused on chronic pneumonia. We evaluated the consequences of chronic Pseudomonas lung infection on alveolar function.

Methods

P. aeruginosa, included in agar beads, was instilled intratracheally in Sprague Dawley rats. Analysis was performed from day 2 to 21, a control group received only sterile agar beads. Alveolar-capillary barrier permeability, lung liquid clearance (LLC) and distal alveolar fluid clearance (DAFC) were measured using a vascular (¹³¹I-Albumin) and an alveolar tracer (¹²⁵I-Albumin).

Results

The increase in permeability and LLC peaked on the second day, to return to baseline on the fifth. DAFC increased independently of TNF-α or endogenous catecholamine production. Despite the persistence of the pathogen within the alveoli, DAFC returned to baseline on the 5^th day. Stimulation with terbutaline failed to increase DAFC. Eradication of the pathogen with ceftazidime did not restore DAFC response.

Conclusions

From these results, we observe an adequate initial alveolar response to increased permeability with an increase of DAFC. However, DAFC increase does not persist after the 5^th day and remains unresponsive to stimulation. This impairment of DAFC may partly explain the higher susceptibility of chronically infected patients to subsequent lung injury.

Control of inflammatory pain by chemokine-mediated recruitment of opioid-containing polymorphonuclear cells

Opioid-containing leukocytes can counteract inflammatory hyperalgesia. Under stress or after local injection of corticotropin releasing factor (CRF), opioid peptides are released from leukocytes, bind to opioid receptors on peripheral sensory neurons and mediate antinociception. Since polymorphonuclear cells (PMN) are the predominant opioid-containing leukocyte subpopulation in early inflammation, we hypothesized that PMN and their recruitment by chemokines are important for peripheral opioid-mediated antinociception at this stage. Rats were intraplantarly injected with complete Freund's adjuvant (CFA). Using flow cytometry, immunohistochemistry, and ELISA, leukocyte subpopulations, chemokine receptor (CXCR2) expression on opioid-containing leukocytes and the CXCR2 ligands keratinocyte-derived chemokine (KC), macrophage inflammatory protein-2 (MIP-2) and cytokine-induced neutrophil chemoattractant-2 (CINC-2) were quantified. Paw pressure threshold (PPT) was determined before and after intraplantar and subcutaneous injection of CRF with or without naloxone. PMN depletion was achieved by intravenous injection of an antiserum. Chemokines were blocked by intraplantar injection of anti-MIP-2 and/or anti-KC antiserum. We found that at 2 h post CFA (i) intraplantar but not subcutaneous injection of CRF produced dose-dependent and naloxone-reversible antinociception (P<0.05, ANOVA). (ii) Opioid-containing leukocytes in the paw and CRF-induced antinociception were reduced after PMN depletion (P<0.05, t-test). (iii) Opioid-containing leukocytes mostly expressed CXCR2. MIP-2 and KC, but not CINC-2 were detectable in inflamed but not in noninflamed tissue (P<0.05, ANOVA). (iv) Combined but not single blockade of MIP-2 and KC reduced the number of opioid-containing leukocytes and peripheral opioid-mediated antinociception (P<0.05, t-test; P>0.05, ANOVA). In summary, in early inflammation peripheral opioid-mediated antinociception is critically dependent on PMN and their recruitment by CXCR2 chemokines.

Change in location of cytokine-induced neutrophil chemoattractants (CINCs) in pulmonary silicosis

Rat cytokine-induced neutrophil chemoattractants (CINCs), which belong to the interleukin-8 family, are known to be induced by treatment with lipopolysaccharide (LPS). Recently, CINCs were grouped into four subtypes-CINC-1, CINC-2alpha, CINC-2beta, and CINC-3-and CINC-1 was considered to be a major isoform among the four CINCs in LPS-induced acute lung inflammation in rats. The purpose of this study was to investigate the change in location of CINCs with chronic inflammation induced by experimental pulmonary silicosis. Administration of silica particles induced lung granulomas. Immunohistochemical staining for CINCs showed that the number of cells positive for CINC-2alpha, CINC-2beta, and CINC-3 was increased, peaking at 1 day after treatment with silica particles, whereas CINC-1 was almost undetectable. We suggest that CINC-2alpha, CINC-2beta, and CINC-3 are the most important chemoattractants in the formation of granulomas in chronic inflammation.

Altered chemokine expression in the spinal cord and brain contributes to differential interleukin-1beta-induced neutrophil recruitment

The pattern of neutrophil recruitment that accompanies inflammation in the CNS depends on the site of injury and the stage of development. The adult brain parenchyma is refractory to neutrophil recruitment and associated damage as compared to the spinal cord or juvenile brain. Using quantitative Taqman RT-PCR and enzyme-liked immunosorbent assay (ELISA), we compared mRNA and protein expression of the rat neutrophil chemoattractant chemokines (CINC) in spinal cord and brain of adult and juvenile rats to identify possible association with the observed differences in neutrophil recruitment. Interleukin-1beta (IL-1beta) injection resulted in up-regulated chemokine expression in both brain and spinal cord. CINC-3 mRNA was elevated above CINC-1 and CINC-2alpha, with expression levels for each higher in spinal cord than in brain. By ELISA, IL-1beta induced greater CINC-1 and CINC-2alpha expression compared to CINC-3, with higher protein levels in spinal cord than in brain. In the juvenile brain, significantly higher levels of CINC-2alpha protein were observed in response to IL-1beta injection than in the adult brain following an equivalent challenge. Correspondingly, neutrophil recruitment was observed in the juvenile brain and adult spinal cord, but not in the adult brain. No expression of CINC-2beta mRNA was detected. Thus differential chemokine induction may contribute to variations in neutrophil recruitment in during development and between the different CNS compartments.

Expression and function of the C5a receptor in rat alveolar epithelial cells

Although alveolar epithelial cells (AEC) form an important barrier for host defenses in the lung, there is limited information about ways in which AEC can directly participate in the lung inflammatory response. In the current studies, primary cultures of rat AEC (RAEC) have been shown to specifically bind recombinant rat C5a at high affinity and in a saturable manner. This binding was enhanced in a time-dependent manner by pre-exposure of RAEC to LPS, IL-6, or TNF-alpha, the increased binding of C5a being associated with increased levels of mRNA for the C5a receptor (C5aR). Exposure of RAEC to C5a also caused increased expression of mRNA for C5aR. As compared with exposure of RAEC to LPS or to C5a alone, exposure to the combination caused enhanced production of TNF-alpha, macrophage inflammatory protein-2, and cytokine-induced neutrophil chemoattractant-1, as well as increased intracellular levels of IL-1beta. These data indicate that RAEC, when activated, have enhanced binding of C5a in association with increased mRNA for C5aR. The functional outcome is enhanced release of proinflammatory mediators. These data underscore the phlogistic potential of RAEC and the ability of C5a to enhance the phlogistic responses of RAEC.

Dexamethasone impairs pulmonary defence against Pseudomonas aeruginosa through suppressing iNOS gene expression and peroxynitrite production in mice

To elucidate the in vivo mechanisms involved in the impairment in pulmonary defence as the result of treatment with glucocorticoids, we established fatal pneumonia with bacteraemia in dexamethasone (DEX)-treated mice by means of an intratracheal challenge of Pseudomonas aeruginosa. An increased neutrophil influx was observed in bronchoalveolar lavage (BAL) fluids from both untreated and DEX-treated mice. The complete suppression of an inducible isoform of nitric oxide synthase (iNOS) mRNA expression and tumour necrosis factor alpha (TNF-alpha) production during the early phase of pneumonia, but not CXC chemokine production, were found in the case of the DEX-treated mice. An immunohistochemical study with a specific antibody also revealed negative staining for nitrotyrosine in the lung tissue of DEX-treated mice, while the formation of nitrotyrosine, which indirectly indicates the generation of peroxynitrite with a potent bactericidal activity, was detected clearly in the bronchial epithelium as well as alveolar phagocytic cells of lung tissue from untreated mice. Furthermore, an intraperitoneal administration of S-methyl-isothiourea (SMT), a potent inhibitor of NOS, significantly decreased the survival and increased bacterial density in the case of untreated mice. In contrast, no significant effects on the survival and bacterial density in the lung and blood were found as the result of treatment with SMT in DEX-treated mice. Collectively, a complete repression of iNOS gene expression and a lack of the generation of peroxynitrite as well as an inhibition of TNF-alpha production in the lung appeared to be responsible for the progression of the fatal pneumonia due to P. aeruginosa in DEX-treated mice.