Lung Bacterial Clearance Research Articles

Cathelicidin-Related Antimicrobial Peptide Is Required for Effective Lung Mucosal Immunity in Gram-Negative Bacterial Pneumonia

Cathelicidins are a family of endogenous antimicrobial peptides that exert diverse immune functions, including both direct bacterial killing and immunomodulatory effects. In this study, we examined the contribution of the murine cathelicidin, cathelicidin-related antimicrobial peptide (CRAMP), to innate mucosal immunity in a mouse model of Gram-negative pneumonia. CRAMP expression is induced in the lung in response to infection with Klebsiella pneumoniae. Mice deficient in the gene encoding CRAMP (Cnlp(-/-)) demonstrate impaired lung bacterial clearance, increased bacterial dissemination, and reduced survival in response to intratracheal K. pneumoniae administration. Neutrophil influx into the alveolar space during K. pneumoniae infection was delayed early but increased by 48 h in CRAMP-deficient mice, which was associated with enhanced expression of inflammatory cytokines and increased lung injury. Bone marrow chimera experiments indicated that CRAMP derived from bone marrow cells rather than structural cells was responsible for antimicrobial effects in the lung. Additionally, CRAMP exerted bactericidal activity against K. pneumoniae in vitro. Similar defects in lung bacterial clearance and delayed early neutrophil influx were observed in CRAMP-deficient mice infected with Pseudomonas aeruginosa, although this did not result in increased bacterial dissemination, increased lung injury, or changes in lethality. Taken together, our findings demonstrate that CRAMP is an important contributor to effective host mucosal immunity in the lung in response to Gram-negative bacterial pneumonia.

Stroke‐induced activation of the α7 nicotinic receptor increasesPseudomonas aeruginosalung injury

Infectious complications, predominantly pneumonia, are the most common cause of death in the postacute phase of stroke, although the mechanisms underlying the corresponding immunosuppression are not fully understood. We tested the hypothesis that activation of the α7 nicotinic acetylcholine receptor (α7nAChR) pathway is important in the stroke-induced increase in lung injury caused by Pseudomonas aeruginosa pneumonia in mice. Prior stroke increased lung vascular permeability caused by P. aeruginosa pneumonia and was associated with decreased lung neutrophil recruitment and bacterial clearance in mice. Pharmacologic inhibition (methyllycaconitine IC(50): 0.2-0.6 nM) or genetic deletion of the α7nAChR significantly (P<0.05) attenuates the effect of prior stroke on lung injury and mortality caused by P. aeruginosa pneumonia in mice. Finally, pretreatment with PNU-282987, a pharmacologic activator of the α7nAChR (EC(50): 0.2 μM), significantly (P<0.05) increased lung injury caused by P. aeruginosa pneumonia, significantly (P<0.05) decreased the release of KC, a major neutrophil chemokine, and significantly (P<0.05) decreased intracellular bacterial killing by a mouse alveolar macrophage cell line and primary mouse neutrophils. In summary, the α7 nicotinic cholinergic pathway plays an important role in mediating the systemic immunosuppression observed after stroke and directly contributes to more severe lung damage induced by P. aeruginosa.

Zinc supplementation restores PU.1 and Nrf2 nuclear binding in alveolar macrophages and improves redox balance and bacterial clearance in the lungs of alcohol-fed rats.

Chronic alcohol abuse causes oxidative stress, impairs alveolar macrophage immune function, and increases the risk of pneumonia and acute lung injury. Recently we determined that chronic alcohol ingestion in rats decreases zinc levels and macrophage function in the alveolar space; provocative findings in that zinc is essential for normal immune and antioxidant defenses. Alveolar macrophage immune function depends on stimulation by granulocyte/monocyte colony-stimulating factor, which signals via the transcription factor PU.1. In parallel, the antioxidant response element signals via the transcription factor Nrf2. However, the role of zinc bioavailability on these signaling pathways within the alveolar space is unknown. To determine the efficacy of dietary zinc supplementation on lung bacterial clearance and oxidative stress, we tested 3 different groups of rats: control-fed, alcohol-fed, and alcohol-fed with zinc supplementation. Rats were then inoculated with intratracheal Klebsiella pneumoniae, and lung bacterial clearance was determined 24 hours later. Isolated alveolar macrophages were isolated from uninfected animals and evaluated for oxidative stress and signaling through PU.1 and Nrf2. Alcohol-fed rats had a 5-fold decrease in lung bacterial clearance compared to control-fed rats. Dietary zinc supplementation of alcohol-fed rats normalized bacterial clearance and mitigated oxidative stress in the alveolar space, as reflected by the relative balance of the thiol redox pair cysteine and cystine, and increased nuclear binding of both PU.1 and Nrf2 in alveolar macrophages from alcohol-fed rats. Dietary zinc supplementation prevents alcohol-induced alveolar macrophage immune dysfunction and oxidative stress in a relevant experimental model, suggesting that such a strategy could decrease the risk of pneumonia and lung injury in individuals with alcohol use disorders.

Cooperative Interactions between TLR4 and TLR9 Regulate Interleukin 23 and 17 Production in a Murine Model of Gram Negative Bacterial Pneumonia

Toll like receptors play an important role in lung host defense against bacterial pathogens. In this study, we investigated independent and cooperative functions of TLR4 and TLR9 in microbial clearance and systemic dissemination during Gram-negative bacterial pneumonia. To access these responses, wildtype Balb/c mice, mice with defective TLR4 signaling (TLR4lps-d), mice deficient in TLR9 (TLR9−/−) and TLR4/9 double mutant mice (TLR4lps-d/TLR9−/−) were challenged with K. pneumoniae, then time-dependent lung bacterial clearance and systemic dissemination determined. We found impaired lung bacterial clearance in TLR4 and TLR9 single mutant mice, whereas the greatest impairment in clearance was observed in TLR4lps-d/TLR9−/− double mutant mice. Early lung expression of TNF-α, IL-12, and chemokines was TLR4 dependent, while IFN-γ production and the later expression of TNF-α and IL-12 was dependent on TLR9. Classical activation of lung macrophages and maximal induction of IL-23 and IL-17 required both TLR4 and TLR9. Finally, the i.t. instillation of IL-17 partially restored anti-bacterial immunity in TLR4lps-d/TLR9−/− double mutant mice. In conclusion, our studies indicate that TLR4 and TLR9 have both non-redundant and cooperative roles in lung innate responses during Gram-negative bacterial pneumonia and are both critical for IL-17 driven antibacterial host response.

Intrapulmonary Administration of Leukotriene B4Enhances Pulmonary Host Defense against Pneumococcal Pneumonia

Leukotriene B(4) (LTB(4)) is a potent lipid mediator of inflammation formed by the 5-lipoxygenase (5-LO)-catalyzed oxidation of arachidonic acid. We have previously shown that (i) LTB(4) is generated during infection, (ii) its biosynthesis is essential for optimal antimicrobial host defense, (iii) LT deficiency is associated with clinical states of immunocompromise, and (iv) exogenous LTB(4) augments antimicrobial functions in phagocytes. Here, we sought to determine whether the administration of LTB(4) has therapeutic potential in a mouse model of pneumonia. Wild-type and 5-LO knockout mice were challenged with Streptococcus pneumoniae via the intranasal route, and bacterial burdens, leukocyte counts, and cytokine levels were determined. LTB(4) was administered via the intraperitoneal, intravenous, and intranasal routes prior to pneumococcal infection and by aerosol 24 h following infection. Leukocytes recovered from mice given S. pneumoniae and treated with aerosolized LTB(4) were evaluated for expression levels of the p47phox subunit of NADPH oxidase. Intrapulmonary but not systemic pretreatment with LTB(4) significantly reduced the lung S. pneumoniae burden in wild-type mice. Aerosolized LTB(4) was effective at improving lung bacterial clearance when administered postinoculation in animals with established infection and exhibited greater potency in 5-LO knockout animals, which also exhibited greater baseline susceptibility. Augmented bacterial clearance in response to LTB(4) was associated with enhanced monocyte recruitment and leukocyte expression of p47phox. The results of the current study in an animal model serve as a proof of concept for the potential utility of treatment with aerosolized LTB(4) as an immunostimulatory strategy in patients with bacterial pneumonia.

Lipocalin 2 Is Required for Pulmonary Host Defense against Klebsiella Infection

Antimicrobial proteins comprise a significant component of the acute innate immune response to infection. They are induced by pattern recognition receptors as well as by cytokines of the innate and adaptive immune pathways and play important roles in infection control and immunomodulatory homeostasis. Lipocalin 2 (siderocalin, NGAL, 24p3), a siderophore-binding antimicrobial protein, is critical for control of systemic infection with Escherichia coli; however, its role in mucosal immunity in the respiratory tract is unknown. In this study, we found that lipocalin 2 is rapidly and robustly induced by Klebsiella pneumoniae infection and is TLR4 dependent. IL-1beta and IL-17 also individually induce lipocalin 2. Mucosal administration of IL-1beta alone could reconstitute the lipocalin 2 deficiency in TLR4 knockout animals and rescue them from infection. Lipocalin 2-deficient animals have impaired lung bacterial clearance in this model and mucosal reconstitution of lipocalin 2 protein in these animals resulted in rescue of this phenotype. We conclude that lipocalin 2 is a crucial component of mucosal immune defense against pulmonary infection with K. pneumoniae.

In vivo effect of adhesion inhibitor heparin on Legionella pneumophila pathogenesis in a murine pneumonia model

To examine the effect of intratracheal heparin instillation on Legionella pneumophila-related acute lung injury (ALI) and systemic dissemination. Prospective, controlled experimental study. University research laboratory. A/J mice received 5 microg of sulfated heparin intratracheally co-instilled with 10(6) or 10(8) colony-forming units (CFU) of a virulent isolate of L. pneumophila. ALI was assessed in control groups (PBS and PBS-heparin) and on days 1, 2 and 3 post-infection, in terms of the lung wet-to-dry (W/D) weight ratios and of lung endothelial permeability to radio-labeled albumin (Perm-I(125)). Lung bacterial loads were measured and systemic spread was assessed by blood and target organ culture. The alveolar inflammatory response was evaluated by measuring the cytokine levels (TNF-alpha, IFN-gamma, IL-6 and IL-12p70) in bronchoalveolar lavage fluids (BALF). Co-instilled heparin improved mouse survival after the 10(8) CFU challenge (p < 0.01). On day 2, heparin co-instillation significantly reduced the W/D ratio and Perm-I(125) (p < 0.01 and p < 0.001 respectively), improved lung bacterial clearance (p < 0.001), prevented systemic dissemination (blood, liver, spleen, kidneys and brain cultures, all p < 0.05) and significantly increased IFN-gamma and IL-12p70 levels in BALF (p < 0.05). Heparin co-instillation during intratracheal L. pneumophila challenge has a protective effect on the alveolar-capillary barrier and prevents bacterial dissemination. These results tend to confirm the competitive inhibition by heparin of L. pneumophila attachment to lung epithelium in vivo, and point to the possible involvement of a heparan-sulfate adhesin in L. pneumophila binding to pneumocytes.

Toll-like Receptor 2 Down-regulation in Established Mouse Allergic Lungs Contributes to Decreased Mycoplasma Clearance

Respiratory Mycoplasma pneumoniae (Mp) infection is involved in asthma pathobiology, but whether the established allergic airway inflammation compromises lung innate immunity and subsequently predisposes patients with asthma to Mp infection remains unknown. To test whether the established allergic airway inflammation compromises host innate immunity (e.g., Toll-like receptor 2 [TLR2]) to hinder the elimination of Mp from the lungs. We used mouse models of ovalbumin (OVA)-induced allergic airway inflammation with an ensuing Mp infection, and cultures of mouse primary lung dendritic cells (DCs) and bone marrow-derived DCs. Lung Mp clearance in allergic mice and TLR2 and IL-6 levels in lung cells, including DCs as well as cultured primary lung DCs and bone marrow-derived DCs, were assessed. The established OVA-induced allergic airway inflammation, or the prominent Th2 cytokines IL-4 and IL-13, inhibited TLR2 expression and IL-6 production in lung cells, including lung DCs, and eventually led to impaired host defense against Mp. Studies in IL-6 knockout mice indicated that IL-6 directly promoted Mp clearance from the lungs. IL-4- and IL-13-induced suppression of TLR2 was mediated by inhibiting nuclear factor-kappaB activation through signal transducer and activator of transcription 6 (STAT6) signaling pathway. The established OVA-induced allergic airway inflammation impairs TLR2 expression and host defense cytokine (e.g., IL-6) production, and subsequently delays lung bacterial clearance. This could offer novel therapeutic strategies to reinstate TLR2 activation by using TLR2 ligands and/or blocking IL-4 and IL-13 to ameliorate persisting respiratory bacterial infections in allergic lungs.

139 Involvement of Nod-Rip2 Pathway in Lung Inflammation, Bacterial Clearance and Survival in a Mouse Model of Pulmonary Infection with Chlamydia pneumoniae

139 Involvement of Nod-Rip2 Pathway in Lung Inflammation, Bacterial Clearance and Survival in a Mouse Model of Pulmonary Infection with Chlamydia pneumoniae

Accumulation of gamma/delta T cells in the lungs and their roles in neutrophil-mediated host defense against pneumococcal infection

The present study was designed to elucidate the role of Vγ4 + γδ T cells, a major subset of pulmonary γδ T cells, in host defense against infection with Streptococcus pneumoniae. The proportion and number of whole γδ T cells, identified as CD3 + and TCR-δ + cells, and Vγ4 + γδ T cells, identified as CD3 + and TCR-Vγ4 + cells, increased in the lungs at 3, 6 and 12 h post-infection. Survival of infected mice and lung bacterial clearance were severely impaired in TCR-Vγ4 −/− mice compared with control wild-type (WT) mice. The impaired host protection in TCR-Vγ4 −/− mice correlated well with attenuated recruitment of neutrophils in lungs. MIP-2 and TNF-α synthesis in the infected tissues was significantly reduced in TCR-Vγ4 −/− mice compared with WT mice. Similar results were noted in the synthesis of TNF-α, but not clearly of MIP-2, by lung leukocytes stimulated with live bacteria. Our results demonstrate that Vγ4 + γδ T cells play an important role in the neutrophil-mediated host defense against S. pneumoniae infection by promoting the synthesis of TNF-α and possibly of MIP-2 in the lungs.

Effect of Concentrated Ambient Particles on Macrophage Phagocytosis and Killing of Streptococcus pneumoniae

Particulate air pollution is linked to increased pneumonia epidemiologically and diminished lung bacterial clearance experimentally. We investigated the effect of concentrated ambient particles (CAPs, </= PM(2.5)) on the interaction of murine primary alveolar macrophages (AMs) and the murine macrophage cell line, J774 A.1, with Streptococcus pneumoniae. We found that CAPs increased binding of bacteria by both primary AMs and J774 cells (66.7 +/- 10.6% and 58.9 +/- 4.0%, respectively, n = 4). In contrast to bacterial binding, CAPs decreased internalization in both AMs and J774 (55.4 +/- 8.5% and 54.7 +/- 5.1%, respectively, n = 4). The rate of killing of internalized bacteria was similar, but CAPs caused a decrease in the absolute number of bacteria killed by macrophages, mainly due to decreased internalization. Additional analyses showed that soluble components of CAPs mediated the enhanced binding and decreased internalization of S. pneumoniae. Chelation of iron in soluble CAPs substantially reversed, while addition of iron as ferric ammonium citrate restored inhibition of phagocytosis of S. pneumoniae in vitro. The results identify phagocytic internalization as a specific target for toxic effects of air pollution particles on AMs.

Synthetic furanones inhibit quorum-sensing and enhance bacterial clearance in Pseudomonas aeruginosa lung infection in mice.

Antibiotics are used to treat bacterial infections by killing the bacteria or inhibiting their growth, but resistance to antibiotics can develop readily. The discovery that bacterial quorum-sensing regulates bacterial virulence as well as the formation of biofilms opens up new ways to control certain bacterial infections. Furanone compounds capable of inhibiting bacterial quorum-sensing systems have been isolated from the marine macro alga Delisea pulchra. Two synthetic furanones were tested for their ability to attenuate bacterial virulence in the mouse models of chronic lung infection by targeting bacterial quorum-sensing without directly killing bacteria or inhibiting their growth. Study I. Mice with Escherichia coli MT102 [luxR-PluxI-gfp(ASV)] lung infection were injected intravenously with N-acyl homoserine lactones with or without furanones to test the interference of furanones with quorum-sensing. Study II. Mice with lung infection by Pseudomonas aeruginosa PAO1 [dsred, lasR-PlasB-gfp(ASV)] were injected intravenously with furanones to evaluate their inhibiting effects on quorum-sensing. Study III. Mice with P. aeruginosa PAO1 lung infection were treated with different doses of furanones to evaluate the therapeutic effects of furanones on the lung infection. Furanones successfully interfered with N-acyl homoserine lactone and suppressed bacterial quorum-sensing in lungs, which resulted in decreases in expression of green fluorescent protein. Furanones accelerated lung bacterial clearance, and reduced the severity of lung pathology. In a lethal P. aeruginosa lung infection, treatment with furanone significantly prolonged the survival time of the mice. Synthetic furanone compounds inhibited bacterial quorum-sensing in P. aeruginosa and exhibited favourable therapeutic effects on P. aeruginosa lung infection.

Metal composition and solubility determine lung toxicity induced by residual oil fly ash collected from different sites within a power plant.

Residual oil fly ash (ROFA) is a particulate pollutant comprised of soluble and insoluble metals and is produced by the combustion of fossil fuels. The objective was to examine the pulmonary responses to chemically distinct ROFA samples collected from either a precipitator or air heater within the same power plant. The collected ROFA samples were suspended in saline (total sample), incubated for 24 h at 37 degrees C, centrifuged, separated into soluble and insoluble fractions, and the metal composition was determined. In addition, electron spin resonance (ESR) was used to detect short-lived free radical intermediates produced by the ROFA samples and the different fractions. On day 0, Male Sprague-Dawley rats were intratracheally instilled with saline (vehicle control) or the ROFA samples (1 mg/100 g body wt). At day 1, bronchoalveolar lavage was performed, and lung inflammation was assessed. On day 3, additional rats that had been treated with ROFA were intratracheally inoculated with 5 x 10(5) Listeria monocytogenes, and pulmonary bacterial clearance was measured at days 6, 8, and 10. The precipitator ROFA was found to be more soluble and acidic with a significantly greater mass of each metal compared with the air heater ROFA. A prominent hydroxyl radical signal was measured for the total and soluble precipitator ROFA after the addition of H2O2, whereas the air heater ROFA and its fractions did not produce a signal. Precipitator ROFA induced a greater inflammatory response than air heater ROFA illustrated by a significant elevation in lung neutrophils. In addition, pulmonary clearance of L. monocytogenes was greatly diminished in the rats treated with the soluble and total precipitator ROFA samples. None of the air heater ROFA samples had an effect on lung bacterial clearance. In conclusion, precipitator ROFA, particularly the soluble fraction, generated a metal-dependent hydroxyl radical as measured by ESR and was shown to cause more inflammation and result in reduced lung defense against infection compared with air heater ROFA. These results are most likely due to differences in metal composition and solubility of the ROFA samples.

Nonpeptide antagonists of AT1 receptor for angiotensin II delay the onset of acute respiratory distress syndrome.

We have previously reported that losartan, a selective antagonist of AT1 receptors for angiotensin II (AII), strongly suppresses the activation of neutrophils by N-formylmethionyl-leucyl-phenylalanine (fMLP) through a mechanism that does not involve inhibition of AT1 receptors. Herein, we analyze whether losartan would prevent the development of the acute respiratory distress syndrome (ARDS) triggered by lung bacterial infection. We found that losartan (0.2-200 microg/kg/min) delays the onset of ARDS in Wistar rats challenged by i.t. instillation of Bordetella bronchiseptica. Although this effect was associated with a significant inhibition of lung-neutrophil recruitment, lung bacterial clearance was not impaired but rather, it was significantly improved. We also found that another nonpeptide AT1 receptor blocker, irbesartan, exerted similar effects to losartan, i.e., it was also able to inhibit neutrophil activation by fMLP and to delay the onset of ARDS in B. bronchiseptica-challenged rats. Neither the inhibitor of angiotensin-converting enzyme captopril, nor the nonselective peptide inhibitor of AII receptors saralasin reproduced these effects. Our data are consistent with the possibility that nonpeptide AT1 receptor blockers delay the onset of ARDS triggered by bacterial infection through a mechanism dependent, at least in part, on their ability to prevent neutrophil activation by N-formyl-peptides.

Role of NADPH oxidase in the mechanism of lung neutrophil sequestration and microvessel injury induced by Gram-negative sepsis: studies in p47phox-/- and gp91phox-/- mice.

We addressed the role of O(2) generated by the NADPH oxidase complex in the mechanism of polymorphonuclear leukocyte (PMN) accumulation and transalveolar migration and lung microvascular injury. Studies were made in mice lacking the p47(phox) and gp91(phox) subunits of NADPH oxidase (p47(phox-/-) and gp91(phox-/-)) in which PMN are incapable of the respiratory burst. The mice were challenged i.p. with live Escherichia coli to induce sepsis. We observed time-dependent increases in PMN sequestration and migration from 1 to 6 h after challenge with 2 x 10(8) E. coli. The responses in knockout mice were greater post-E. coli challenge compared with control mice; i.e., transalveolar PMN migration post-E. coli challenge increased by approximately 50% in the null mice above values in wild type. The increased PMN infiltration was associated with decreased lung bacterial clearance. The generation of the chemoattractant macrophage-inflammatory protein-2 in lung tissue was greater in NADPH oxidase-defective mice after E. coli challenge than control mice; moreover, macrophage-inflammatory protein-2 Ab pretreatment prevented the PMN infiltration. We also observed that E. coli failed to increase lung microvascular permeability in p47(phox-/-) and gp91(phox-/-) mice despite the greater lung PMN sequestration. Thus, O(2) production is required for the induction of sepsis-induced lung microvascular injury. We conclude that NADPH oxidase-derived O(2) generation has an important bactericidal role, such that an impairment in bacterial clearance in NADPH oxidase-defective mice results in increased chemokine generation and lung tissue PMN infiltration.

Role of the type 1 TNF receptor in lung inflammation after inhalation of endotoxin or Pseudomonas aeruginosa.

To determine the roles of the type 1 tumor necrosis factor (TNF) receptor (TNFR1) in lung inflammation and antibacterial defense, we exposed transgenic mice lacking TNFR1 [TNFR1(-/-)] and wild-type control mice to aerosolized lipopolysaccharide or Pseudomonas aeruginosa. After LPS, bronchoalveolar lavage fluid (BALF) from TNFR1(-/-) mice contained fewer neutrophils and less macrophage inflammatory protein-2 than BALF from control mice. TNF-alpha, interleukin-1beta, and total protein levels in BALF as well as tissue intercellular adhesion molecule-1 expression did not differ between the two groups. In contrast, lung inflammation and bacterial clearance after infection were augmented in TNFR1(-/-) mice. BALF from infected TNFR1(-/-) mice contained more neutrophils and TNF-alpha and less interleukin-1beta and macrophage inflammatory protein-2 than that from control mice, but protein levels were similarly elevated in both groups. Lung inflammation and bacterial clearance were also augmented in mice lacking both TNF receptors. Thus TNFR1 facilitates neutrophil recruitment after inhalation of lipopolysaccharide, in part by augmenting chemokine induction. In contrast, TNFR1 attenuates lung inflammation in response to live bacteria but does not contribute to increased lung permeability and is not required for the elimination of P. aeruginosa.

IL-10 Is a Major Mediator of Sepsis-Induced Impairment in Lung Antibacterial Host Defense

To explore the mechanism of immunosuppression associated with sepsis, we developed a murine model of sepsis-induced Pseudomonas aeruginosa pneumonia. CD-1 mice underwent either cecal ligation and 26-gauge needle puncture (CLP) or sham surgery, followed by the intratracheal (i.t.) administration of P. aeruginosa or saline. Survival in mice undergoing CLP followed 24 h later by the i.t. administration of saline or P. aeruginosa was 58% and 10%, respectively, whereas 95% of animals undergoing sham surgery followed by P. aeruginosa administration survived. Increased mortality in the CLP/P. aeruginosa group was attributable to markedly impaired lung bacterial clearance and the early development of P. aeruginosa bacteremia. The i.t. administration of bacteria to CLP-, but not sham-, operated mice resulted in an impressive intrapulmonary accumulation of neutrophils. Furthermore, P. aeruginosa challenge in septic mice resulted in a relative shift toward enhanced lung IL-10 production concomitant with a trend toward decreased IL-12. The i.p., but not i.t., administration of IL-10 Abs given just before P. aeruginosa challenge in septic mice significantly improved both survival and clearance of bacteria from the lungs of septic animals administered P. aeruginosa. Finally, alveolar macrophages isolated from animals undergoing CLP displayed a marked impairment in the ability to ingest and kill P. aeruginosa ex vivo, and this defect was partially reversed by the in vivo neutralization of IL-10. Collectively, these observations indicate that the septic response substantially impairs lung innate immunity to P. aeruginosa, and this effect is mediated primarily by endogenously produced IL-10.

Lung-Specific Transgenic Expression of KC Enhances Resistance toKlebsiella pneumoniaein Mice

AbstractA vigorous host response is required to effectively clear pathogenic bacteria from the lungs and is dependent upon the recruitment and activation of neutrophils and macrophages. A family of chemotactic cytokines, referred to as chemokines, have been shown to participate in this complex protective response. In this study, we assessed the role of the C-X-C chemokine KC in lung antibacterial host defense using wild-type (wt) B6D2 mice or transgenic mice that had been bred on a B6D2 background expressing KC under the control of a Clara cell-specific promoter within the lung. The administration of Klebsiella pneumoniae to both wt and KC-transgenic mice resulted in a time-dependent expression of KC protein within the lung that peaked at 24 to 48 h postinoculation. When infected with K. pneumoniae, the KC-transgenic mice showed a striking improvement in survival compared with wt control mice. This improved survival was due to an increase in bacterial clearance, which occurred in association with a vigorous recruitment of neutrophils in the KC-transgenic mice compared with their wt control counterparts. No differences in the lung levels of the specific cytokines TNF-α, IFN-γ, IL-12, and IL-10 were noted. However, inducible macrophage inflammatory protein-2 levels were significantly decreased in the KC-transgenic mice compared with the wt mice. This study indicates that the compartmentalized overexpression of KC in vivo results in increased lung bacterial clearance and improved survival, which occurs in association with enhanced polymorphonuclear leukocyte influx to the lung.

Ethanol Feeding Impairs Innate Immunity and Alters the Expression of Th1- and Th2-Phenotype Cytokines in Murine Klebsiella Pneumonia

The prolonged and excessive consumption of alcohol has been shown to predispose the host to a variety of infectious complications, which may be due, in part, to the inability to produce important activating cytokines. In this study, we assessed the effect of chronic alcohol ingestion on bacterial clearance, survival, and cytokine mRNA and protein expression in mice with Klebsiella pneumonia. Two-week ethanol feeding resulted in substantial impairment in the clearance of K. pneumoniae and decreased survival, compared with CD-1 mice receiving an isocaloric diet without ethanol. No differences were noted between control and ethanol groups in the total numbers or percent of bronchoalveolar lavage fluid neutrophils or macrophages at 24 and 48 hr post-intratracheal K. pneumoniae. Importantly, the lungs of alcohol-fed mice with Klebsiella pneumonia displayed a decrease or delay in the expression of interleukin (IL)-12 p35 and p40 mRNA and interferon-γ mRNA, respectively, as well as reduced IL-12 and interferon-γ protein levels, compared with controls. Conversely, a time-dependent increase in lung IL-10 mRNA and protein was noted in ethanol-fed animals, compared with control animals challenged with K. pneumoniae. In summary, our studies indicate that ethanol ingestion results in a profound suppression of lung bacterial clearance and decreased survival in Klebsiella pneumonia, which occurs in association with a shift in the balance of lung cytokine mRNA and protein expression favoring Th2- rather than Th1-phenotype cytokines.

Ethanol feeding impairs innate immunity and alters the expression of Th1- and Th2-phenotype cytokines in murine Klebsiella pneumonia.

The prolonged and excessive consumption of alcohol has been shown to predispose the host to a variety of infectious complications, which may be due, in part, to the inability to produce important activating cytokines. In this study, we assessed the effect of chronic alcohol ingestion on bacterial clearance, survival, and cytokine mRNA and protein expression in mice with Klebsiella pneumonia. Two-week ethanol feeding resulted in substantial impairment in the clearance of K. pneumoniae and decreased survival, compared with CD-1 mice receiving an isocaloric diet without ethanol. No differences were noted between control and ethanol groups in the total numbers or percent of bronchoalveolar lavage fluid neutrophils or macrophages at 24 and 48 hr post-intratracheal K. pneumoniae. Importantly, the lungs of alcohol-fed mice with Klebsiella pneumonia displayed a decrease or delay in the expression of interleukin (IL)-12 p35 and p40 mRNA and interferon-gamma mRNA, respectively, as well as reduced IL-12 and interferon-gamma protein levels, compared with controls. Conversely, a time-dependent increase in lung IL-10 mRNAand protein was noted in ethanol-fed animals, compared with control animals challenged with K. pneumoniae. In summary, our studies indicate that ethanol ingestion results in a profound suppression of lung bacterial clearance and decreased survival in Klebsiella pneumonia, which occurs in association with a shift in the balance of lung cytokine mRNA and protein expression favoring Th2- rather than Th1-phenotype cytokines.