Azithromycin selectively reduces tumor necrosis factor alpha levels in cystic fibrosis airway epithelial cells

Azithromycin (AZM) ameliorates lung function in cystic fibrosis (CF) patients. This macrolide has been suggested to have anti-inflammatory properties as well as other effects potentially relevant for therapy of CF. In this study, we utilized three CF (IB3-1, 16HBE14o- AS3, and 2CFSMEo-) and two isogenic non-CF (C38 and 16HBE14o- S1) airway epithelial cell lines to investigate whether AZM could reduce tumor necrosis factor alpha (TNF-alpha) mRNA and protein levels by real-time quantitative PCR analysis and an enzyme-linked immunosorbent assay (ELISA), respectively. We studied the effects on the DNA binding of NF-kappaB and specificity protein 1 (Sp1) by an ELISA. Non-CF cells express significantly lower TNF-alpha mRNA and protein levels than an isogenic CF cell line. In CF cells, AZM treatment causes a 30% reduction of TNF-alpha mRNA levels (P < 0.05) and a 45% decrease in TNF-alpha secretion (P < 0.05), reaching approximately the levels of the untreated isogenic non-CF cells. In CF cells, NF-kappaB and Sp1 DNA binding activities were also significantly decreased (about 45 and 60%, respectively; P < 0.05) after AZM treatment. Josamycin, a macrolide lacking clinically described anti-inflammatory effects, was ineffective. Finally, AZM did not alter the mRNA expression levels of interleukin-6, a proinflammatory molecule not differentially expressed in CF and isogenic non-CF cells. The results of our study support the anti-inflammatory activities of this macrolide, since we show that AZM reduced the levels of TNF-alpha and propose inhibitions of NF-kappaB and Sp1 DNA binding as possible mechanisms of this effect.     

Genotypic analysis of respiratory mucous sulfation defects in cystic fibrosis.

Intracellular dysfunction of the cystic fibrosis transmembrane conductance regulator (CFTR) has been proposed to alter endosomal acidification. The most widely studied consequence of this defect has been alterations in the biochemical properties of cystic fibrosis (CF) respiratory mucus glycoproteins. However, studies confirming the existence of mucous processing defects in CF have been hindered by the lack of in vivo animal models by which to test these hypotheses in the absence of secondary effects of chronic bacterial infection. The human bronchial xenograft model has been useful in evaluating the pathophysiologic differences between CF and non-CF airway epithelium, in the absence of secondary disease effects such as goblet cell hyperplasia. In this study we sought to compare the extent of sulfation within secreted mucus glycoproteins from CF and non-CF human bronchial xenografts. Cumulative results of xenografts generated from 13 independent CF tissue samples demonstrated a statistically significant higher level of sulfation (1.7 +/- 0.18, P < 0.026) as compared to non-CF paired controls. Such findings add to the growing body of knowledge that primary defects in sulfation exist in CF respiratory mucin. Correlation of genotype with the extent of mucus sulfation revealed two categories of CF tissues with statistically different mucus sulfation profiles. Results from these studies demonstrated a 2.0 +/- 0.15-fold higher level of mucus sulfation produced from xenografts of five defined CF genotypes as compared to non-CF controls (P < 0.004, n= 10). Interestingly, three CF samples for which one mutant allele remained undefined (deltaoff8/unknown or G551D/unknown) demonstrated no statistical difference in the level of sulfation as compared with matched non-CF controls (n= 3). This as yet unknown allele was not identified within a screen for the 26 most common CF mutations. These results provide preliminary evidence for allelic variation within the CF population which may begin to elucidate the structure-function of CFTR with regards to intracellular mucus processing defects.     

The amiloride-inhibitable Na+ conductance is reduced by the cystic fibrosis transmembrane conductance regulator in normal but not in cystic fibrosis airways.

Cystic fibrosis (CF) airway cells, besides their well-known defect in cAMP-dependent Cl- conductance, are characterized by an enhanced Na+ conductance. In this study we have examined the Na+ conductance in human respiratory tract by measuring transepithelial voltage and resistance (Vte, Rte) and by assessing membrane voltages (Vm) of freshly isolated airway epithelial cells from CF and non-CF patients. Basal amiloride inhibitable (10 micromol/liter) equivalent short circuit current (Isc = Vte/Rte) was significantly increased in CF compared with non-CF tissues. After stimulation by forskolin (10 micromol/liter) a significant depolarization of Vm corresponding to the cAMP-dependent activation of a Cl- conductance was observed in non-CF but not in CF airway cells. In non-CF tissue but not in CF tissue the effects of amiloride and N-methyl-D-glucamine on Vm were attenuated in the presence of forskolin. Also the amiloride-inhibitable Isc was significantly reduced by forskolin (1 micromol/liter) and isobutylmethylxanthine (IBMX; 100 micromol/liter) only in non-CF tissue. We conclude that cystic fibrosis transmembrane conductance regulator acts as a downregulator of epithelial Na+ channels in human airways. This downregulation of epithelial Na+ channels is absent in CF airways, leading to hyperabsorption and to the characteristic increase in mucus viscosity.     

Inflammatory cytokines TNF-α and IL-17 enhance the efficacy of cystic fibrosis transmembrane conductance regulator modulators

Without cystic fibrosis transmembrane conductance regulator–mediated (CFTR-mediated) HCO₃^– secretion, airway epithelia of newborns with cystic fibrosis (CF) produce an abnormally acidic airway surface liquid (ASL), and the decreased pH impairs respiratory host defenses. However, within a few months of birth, ASL pH increases to match that in non-CF airways. Although the physiological basis for the increase is unknown, this time course matches the development of inflammation in CF airways. To learn whether inflammation alters CF ASL pH, we treated CF epithelia with TNF-α and IL-17 (TNF-α+IL-17), 2 inflammatory cytokines that are elevated in CF airways. TNF-α+IL-17 markedly increased ASL pH by upregulating pendrin, an apical Cl^–/HCO₃^– exchanger. Moreover, when CF epithelia were exposed to TNF-α+IL-17, clinically approved CFTR modulators further alkalinized ASL pH. As predicted by these results, in vivo data revealed a positive correlation between airway inflammation and CFTR modulator–induced improvement in lung function. These findings suggest that inflammation is a key regulator of HCO₃^– secretion in CF airways. Thus, they explain earlier observations that ASL pH increases after birth and indicate that, for similar levels of inflammation, the pH of CF ASL is abnormally acidic. These results also suggest that a non-cell-autonomous mechanism, airway inflammation, is an important determinant of the response to CFTR modulators.     

Cyclic adenosine monophosphate-dependent kinase in cystic fibrosis tracheal epithelium.

Cl-impermeability in cystic fibrosis (CF) tracheal epithelium derives from a deficiency in the beta-adrenergic regulation of apical membrane Cl- channels. To test the possibility that cAMP-dependent kinase is the cause of this deficiency, we assayed this kinase in soluble fractions from cultured airway epithelial cells, including CF human tracheal epithelial cells. Varying levels of cAMP were used in these assays to derive both a Vmax and apparent dissociation constant (Kd) for the enzymes in soluble extracts. The cAMP-dependent protein kinase from CF human tracheal epithelial cells has essentially the same Vmax and apparent Kd as non-CF human, bovine, and dog tracheal epithelial cells. Thus, the total activity of the cAMP-dependent kinases and their overall responsiveness to cAMP are unchanged in CF.     

Anti-inflammatory effects of moxifloxacin on activated human monocytic cells: inhibition of NF-kappaB and mitogen-activated protein kinase activation and of synthesis of proinflammatory cytokines

We previously showed that moxifloxacin (MXF) exerts protective anti-inflammatory effects in immunosuppressed mice infected with Candida albicans by inhibiting interleukin-8 (IL-8) and tumor necrosis factor alpha (TNF-alpha) production in the lung. Immunohistochemistry demonstrated inhibition of nuclear factor (NF)-kappaB translocation in lung epithelium and macrophages in MXF-treated mice. In the present study we investigated the effects of MXF on the production of proinflammatory cytokines (i.e., IL-8, TNF-alpha, and IL-1beta) by activated human peripheral blood monocytes and THP-1 cells and analyzed the effects of the drug on the major signal transduction pathways associated with inflammation: NF-kappaB and the mitogen-activated protein kinases ERK and c-Jun N-terminal kinase (JNK). The levels of IL-8, TNF-alpha, and IL-1beta secretion rose 20- and 6.7-fold in lipopolysaccharide (LPS)-activated monocytes and THP-1 cells, respectively. MXF (5 to 20 microg/ml) significantly inhibited cytokine production by 14 to 80% and 15 to 73% in monocytes and THP-1 cells, respectively. In THP-1 cells, the level of NF-kappaB nuclear translocation increased fourfold following stimulation with LPS-phorbol myristate acetate (PMA), and this was inhibited (38%) by 10 microg of MXF per ml. We then assayed the degradation of inhibitor (I)-kappaB by Western blotting. LPS-PMA induced degradation of I-kappaB by 73%, while addition of MXF (5 microg/ml) inhibited I-kappaB degradation by 49%. Activation of ERK1/2 and the 46-kDa p-JNK protein was enhanced by LPS and LPS-PMA and was significantly inhibited by MXF (54 and 42%, respectively, with MXF at 10 microg/ml). We conclude that MXF suppresses the secretion of proinflammatory cytokines in human monocytes and THP-1 cells and that it exerts its anti-inflammatory effects in THP-1 cells by inhibiting NF-kappaB, ERK, and JNK activation. Its anti-inflammatory properties should be further assessed in clinical settings.     

Clarithromycin suppresses lipopolysaccharide-induced interleukin-8 production by human monocytes through AP-1 and NF-kappa B transcription factors

Erythromycin and other macrolides are effective for the treatment of chronic inflammatory airway diseases such as diffuse panbronchiolitis (DPB) and chronic sinusitis. The effect of macrolides in DPB is suggested to be anti-inflammatory rather than antibacterial. We investigated the effects of clarithromycin on interleukin-8 (IL-8) production using human peripheral monocytes and the human monocytic leukaemia cell line, THP-1. Bacterial extracts from Escherichia coli, Pseudomonas aeruginosa and Helicobacter pylori, as well as E. coli-derived lipopolysaccharide (LPS), induced IL-8 production. Clarithromycin suppressed this production in a dose-dependent manner in both monocytes and THP-1 cells (49.3-75.0% inhibition at 10 mg/L). A luciferase reporter gene assay with plasmids containing a serially deleted IL-8 promoter fragment showed that both the activator protein-1 (AP-1) and/or the nuclear factor-kappa B (NF-kapp aB) binding sequences were responsible for the LPS and clarithromycin responsiveness of the IL-8 promoter. Consistently, in an electromobility shift assay, LPS increased the specific binding of both AP-1 and NF-kappaB, whereas clarithromycin suppressed it. Moreover, LPS and clarithromycin regulated three other promoters that have either the NF-kappa B or the AP-1 binding sequences: two synthetic (pAP-1-Luc and pNF-kappa B-Luc) and one naturally occurring (ELAM-Luc). Our results indicate that clarithromycin modified inflammation by sup-pressing IL-8 production and that clarithromycin may affect the expression of other genes through AP-1 and NF-kappa B. In addition to treatment of airway diseases, the anti-inflammatory effect of macrolides may be beneficial for the treatment of other inflammatory diseases such as chronic gastritis caused by H. pylori.     

Mercaptoethylguanidine inhibits the inflammatory response in a murine model of chronic infection with Pseudomonas aeruginosa

Chronic airway inflammation induced by Pseudomonas aeruginosa is the eventual cause of respiratory failure in most people affected by cystic fibrosis. Recent evidence implicates the involvement of free radical and oxidant stress in the pathogenesis of the inflammatory injury. Here we report the efficacy of a novel experimental therapeutic, mercaptoethylguanidine (MEG), which has combined actions as a selective inhibitor of the inducible nitric oxide synthase and as a scavenger of peroxynitrite, a potent oxidant formed in the reaction of nitric oxide and superoxide radical. Chronic pulmonary infection was established in FVB/N mice by intratracheal administration of 10(5) colony-forming units of P. aeruginosa in agar beads. Treatment with MEG (10 mg/kg/dose every 8 h i.p.) inhibited weight loss in the first 3 days and reduced histologic injury at 8 days postinfection. MEG also reduced myeloperoxidase activity, a marker of neutrophil infiltration, at 8 days and concentrations of the proinflammatory cytokines interleukin-1beta, tumor necrosis factor-alpha, and macrophage inflammatory protein 2 in whole lung homogenates. MEG-treated animals and controls had similar perioperative mortality and comparable colony counts of P. aeruginosa at 8 days, indicating that MEG did not exacerbate infection. Our data suggest that MEG may be an effective immunomodulatory therapy of pulmonary inflammation induced by chronic infection.     

Vagus nerve stimulation inhibits activation of coagulation and fibrinolysis during endotoxemia in rats

BACKGROUND: Sepsis and endotoxemia are associated with concurrent activation of inflammation and the hemostatic mechanism, which both contribute to organ dysfunction and death. Electrical vagus nerve stimulation (VNS) has been found to inhibit tumor necrosis factor (TNF)-alpha release during endotoxemia in rodents. OBJECTIVE: To determine the effect of VNS on activation of coagulation and fibrinolysis. METHODS: Rats received a sublethal i.v. dose of lipopolysaccharide (LPS) after electrical VNS or sham stimulation. Activation of coagulation and fibrinolysis, as well as cytokine release, was measured before LPS injection and 2, 4 and 6 h thereafter. Results: LPS induced activation of the coagulation system (increases in the plasma concentrations of thrombin-antithrombin complexes and D-dimer, and a decrease in antithrombin) and biphasic changes in the fibrinolytic system [early rises of plasminogen activator activity and tissue-type plasminogen activator, followed by a delayed increase in plasminogen activator inhibitor type 1 (PAI-1)]. VNS strongly inhibited all LPS-induced procoagulant responses and more modestly attenuated the fibrinolytic response. In addition, VNS attenuated the LPS-induced increases in plasma and splenic concentrations of the proinflammatory cytokines TNF-alpha and interleukin-6 (IL-6), while not influencing the release of the anti-inflammatory cytokine IL-10. CONCLUSION: These data illustrate a thus far unrecognized effect of VNS and suggest that the cholinergic anti-inflammatory pathway not only impacts on inflammation but also on the coagulant-anticoagulant balance.     

Macrolide antibiotics protect against endotoxin-induced vascular leakage and neutrophil accumulation in rat trachea.

We studied the effects of macrolides on lipopolysaccharide (LPS)-induced airway inflammation in the rat tracheal mucosa. Erythromycin and roxithromycin dose dependently inhibited microvascular leakage and neutrophil recruitment induced by LPS. This inhibitory action on vascular permeability was abolished by neutrophil depletion.     

Transfer of a cathelicidin peptide antibiotic gene restores bacterial killing in a cystic fibrosis xenograft model

Recent studies suggest that the gene defect in cystic fibrosis (CF) leads to a breach in innate immunity. We describe a novel genetic strategy for reversing the CF-specific defect of antimicrobial activity by transferring a gene encoding a secreted cathelicidin peptide antibiotic into the airway epithelium grown in a human bronchial xenograft model. The airway surface fluid (ASF) from CF xenografts failed to kill Pseudomonas aeruginosa or Staphylococcus aureus. Partial reconstitution of CF transmembrane conductance regulator expression after adenovirus-mediated gene transfer restored the antimicrobial activity of ASF from CF xenografts to normal levels. Exposure of CF xenografts to an adenovirus expressing the human cathelicidin LL-37/hCAP-18 increased levels of this peptide in the ASF three- to fourfold above the normal concentrations, which were equivalent in ASF from CF and normal xenografts before gene transfer. The increase of LL-37 was sufficient to restore bacterial killing to normal levels. The data presented describe an alternative genetic approach to the treatment of CF based on enhanced expression of an endogenous antimicrobial peptide and provide strong evidence that expression of antimicrobial peptides indeed protects against bacterial infection.     

Relative cytokine and cytokine inhibitor production by mononuclear cells and neutrophils

Mononuclear cells represent the major source of cytokines in blood; however, it has been postulated that neutrophils may produce and/or release modest amounts of cytokines. In this study, we compared the production of cytokines and cytokine inhibitors in lipopolysaccharide (LPS)-stimulated whole blood, peripheral blood mononuclear cells (PBMCs), and neutrophils (PMNs) separated by density gradient centrifugation. Contamination of PBMCs in the isolated PMNs was less than 0.1% as determined by morphological analysis and flow cytometry. LPS (50 ng/mL) induced a strong increase of the proinflammatory cytokines tumor necrosis factor, interleukin (IL)-1beta, IL-8, and IL-6 in whole blood. In the isolated cell preparations, proinflammatory cytokine production was significantly greater in the PBMCs compared with the PMNs. On a per cell basis, PMNs produced less than 1.5% of these cytokines compared with PBMCs. For cytokine inhibitors, TNF-soluble receptor type II and IL-1 receptor antagonist were increased by LPS stimulation in whole blood, PBMCs, and PMNs. On a per cell basis, LPS-induced TNF-soluble receptor type II and IL-1 receptor antagonist production by PMNs was 9.8% and 15.4% of those of PBMCs, respectively. These data show that a highly purified population of PMNs makes a relatively minor to nonexistent contribution to the production of proinflammatory cytokines.     

IL10 Released by a New Inflammation-regulated Lentiviral System Efficiently Attenuates Zymosan-induced Arthritis

Administration of anti-inflammatory cytokines is a common therapeutic strategy in chronic inflammatory diseases. Gene therapy is an efficient method for delivering therapeutic molecules to target cells. Expression of the cell adhesion molecule E-selectin (ESEL), which is expressed in the early stages of inflammation, is controlled by proinflammatory cytokines, making its promoter a good candidate for the design of inflammation-regulated gene therapy vectors. This study describes an ESEL promoter (ESELp)-based lentiviral vector (LV) that drives localized transgene expression during inflammation. Mouse matrigel plug assays with ESELp-transduced endothelial cells showed that systemic lipopolysaccharide (LPS) administration selectively induces ESELp-controlled luciferase expression in vivo. Inflammation-specific induction was confirmed in a mouse model of arthritis, showing that this LV is repeatedly induced early in acute inflammation episodes and is downregulated during remission. Moreover, the local acute inflammatory response in this animal model was efficiently blocked by expression of the anti-inflammatory cytokine interleukin-10 (IL10) driven by our LV system. This inflammation-regulated expression system has potential application in the design of new strategies for the local treatment of chronic inflammatory diseases such as cardiovascular and autoimmune diseases.     

Phosphodiesterase type 4 inhibitors cause proinflammatory effects in vivo

Phosphodiesterase type 4 (PDE(4)) inhibitors are currently being evaluated as potential therapies for inflammatory airway diseases. However, this class of compounds has been shown to cause an arteritis/vasculitis of unknown etiology in rats and cynomolgus monkeys. Studies in rodents have demonstrated the anti-inflammatory effects of PDE(4) inhibitors on lipopolysaccharide (LPS)-induced airway inflammation. The aim of this work was to assess the direct effects of PDE(4) inhibitors on inflammatory cells and cytokine levels in the lung in relation to therapeutic effects. The effects of the PDE(4) inhibitors 3-cyclo-propylmethoxy-4-difluoromethoxy-N-[3,5-di-chloropyrid-4-yl]-benzamide (roflumilast) and 3-(cyclopentyloxy)-N-(3,5-dichloro-4-pyridyl)-4-methoxybenzamide (piclamilast) were assessed in vivo, using BALB/c mice, and in vitro, in unstimulated human endothelial and epithelial cell lines. In BALB/c mice, LPS challenge caused an increase in neutrophils in bronchoalveolar lavage (BAL) and lung tissue and BAL tumor necrosis factor-alpha levels, which were inhibited by treatment with either roflumilast or piclamilast (30-100 mg/kg subcutaneously). However, roflumilast and piclamilast alone (100 mg/kg) caused a significant increase in plasma and lung tissue keratinocyte-derived chemokine (KC) levels, and lung tissue neutrophils. In vitro, both piclamilast and roflumilast caused an increase in interleukin (IL)-8 release from human umbilical vein endothelial cells but not BEAS-2B cells, suggesting that one source of the increased KC may be endothelial cells. At doses that antagonized an LPS-induced inflammatory response, the PDE(4) inhibitors possessed proinflammatory activities in the lung that may limit their therapeutic potential. The proinflammatory cytokines KC and IL-8 therefore may provide surrogate biomarkers, both in preclinical animal models and in the clinic, to assess potential proinflammatory effects of this class of compounds.     

Inducible nitric oxide synthase expression is reduced in cystic fibrosis murine and human airway epithelial cells.

It has been reported that exhaled nitric oxide levels are reduced in cystic fibrosis (CF) patients. We have examined the inducible isoform of nitric oxide synthase (iNOS) in the airways by immunostaining and found that iNOS is constitutively expressed in the airway epithelia of non-CF mouse and human tissues but essentially absent in the epithelium of CF airways. We explored potential consequences of lost iNOS expression and found that iNOS inhibition significantly increases mouse nasal trans-epithelial potential difference, and hindered the ability of excised mouse lungs to prevent growth of Pseudomonas aeruginosa. The absence of continuous nitric oxide production in epithelial cells of CF airways may play a role in two CF-associated characteristics: hyperabsorption of sodium and susceptibility to bacterial infections.     

Novel neutrophil-derived proteins in bronchoalveolar lavage fluid indicate an exaggerated inflammatory response in pediatric cystic fibrosis patients

BACKGROUND: Airway inflammation in cystic fibrosis (CF) is exaggerated and characterized by neutrophil-mediated tissue destruction, but its genesis and mechanisms remain poorly understood. To further define the pulmonary inflammatory response, we conducted a proteome-based screen of bronchoalveolar lavage fluid (BALF) collected from young children with and without CF experiencing endobronchial infection. METHODS: We collected BALF samples from 45 children younger than 5 years and grouped them according to the presence of respiratory pathogens: > or = 1 x 10(5) colony-forming units (CFU)/mL BALF (18 and 12 samples with and without CF, respectively) and <1 x 10(5) CFU/mL (23 and 15 samples). BALF proteins were analyzed with SELDI-TOF mass spectrometry (MS) and H4 ProteinChips. Proteins were identified and characterized using trypsin digestion, tandem MS, Fourier transform ion cyclotron resonance MS, immunoblotting, and ELISA. RESULTS: The SELDI-TOF MS BALF profiles contained 53 unique, reliably detected proteins. Peak intensities of 24 proteins differed significantly between the CF and non-CF samples. They included the neutrophil proteins, alpha-defensin 1 and 2, S100A8, S100A9, and S100A12, as well as novel forms of S100A8 and S100A12 with equivalent C-terminal deletions. Peak intensities of these neutrophil proteins and immunoreactive concentrations of selected examples were significantly higher in CF than non-CF samples. CONCLUSIONS: Small neutrophil-derived BALF proteins, including novel C-terminal truncated forms of S100A proteins, are easily detected with SELDI-TOF MS. Concentrations of these molecules are abnormally high in early CF lung disease. The data provide new insights into CF lung disease and identify novel proteins strongly associated with CF airway inflammation.     

Effect of Systemic Infection Induced by Pseudomonas aeruginosa on the Brain Uptake of Colistin in Mice

In view of reports of colistin-induced neurotoxicity in infected patients, the aim of this study was to assess whether the integrity of the blood-brain barrier (BBB) and the brain uptake of colistin are altered in the presence of systemic Pseudomonas aeruginosa infection. Bacteremia was confirmed 8 h after intramuscular administration of P. aeruginosa ATCC 27853 to Swiss Outbred mice, at which time a single subcutaneous dose of colistin sulfate (40 mg/kg of body weight) or an intravenous dose of [(14)C]sucrose (2 μCi) was administered. Despite a substantial elevation in plasma levels of the proinflammatory cytokines tumor necrosis factor alpha, interleukin-1β, and interleukin-6 during bacterial infection, the brain uptake of colistin was similar between infected and noninfected mice with AUC(brain)/AUC(plasma) (where AUC(brain) is the area under the brain concentration-time curve and AUC(plasma) is the area under the plasma concentration-time curve) ratios of 0.023 and 0.024, respectively. Similarly, the brain-to-plasma ratios of [(14)C]sucrose were no different between infected and noninfected mice, consistent with a lack of effect of bacteremia on BBB integrity. To further correlate any relationship between BBB disruption and plasma levels of proinflammatory cytokines, BBB integrity, colistin brain uptake, and plasma proinflammatory cytokines were measured following the administration of Salmonella enterica lipopolysaccharide (LPS), an agent known to induce BBB disruption. Despite LPS inducing a 4-fold increase in colistin brain uptake and a significant (P < 0.05) 1.2-fold increase in [(14)C]sucrose BBB penetration, plasma cytokine levels were lower with LPS treatment relative to those obtained with bacterial infection with P. aeruginosa. This study demonstrates that the brain uptake of colistin is not increased in mice during P. aeruginosa-induced systemic bacteremia despite a significant increase in plasma levels of three proinflammatory cytokines.     

Immunomodulatory indications of azithromycin in respiratory disease: a concise review for the clinician

Azithromycin has a well-characterized bacteriostatic activity. However, it also has a robust immunomodulatory effect that has proven beneficial in a variety of chronic illnesses. This effect results in decreased production of pro-inflammatory cytokines in the acute phase and promotes resolution of chronic inflammation in the later phases. Specifically, azithromycin has direct activity on airway epithelial cells to maintain their function and reduce mucus secretion. These characteristics have resulted in the use of azithromycin in the management of a variety of chronic lung diseases including chronic obstructive pulmonary disease, cystic fibrosis (CF), non-CF bronchiectasis, bronchiolitis obliterans syndrome, diffuse panbronchiolitis, and asthma. In this review, we present the evidence supporting the role of azithromycin in these conditions with an emphasis on the clinical aspects for the practicing physician.     

Recipient iNOS but not eNOS deficiency reduces luminal narrowing in tracheal allografts

Chronic airway rejection is characterized by prolonged inflammation, epithelial damage, and eventual luminal obliterative bronchiolitis (OB). In cardiac allografts, the inducible nitric oxide synthase (iNOS) promotes acute rejection but paradoxically reduces neointimal formation, the hallmark of chronic rejection. The specific roles of NOS isoforms in modulating lymphocyte traffic and airway rejection are not known. Using a double lumen mouse tracheal transplant model, tracheal grafts from B10.A (allo) or C57BL/6J (iso) mice were transplanted into cyclosporine-treated wild-type (WT) iNOS(-/-) or endothelial NOS (eNOS)(-/-) recipients. OB was observed in WT tracheal allografts at 3 weeks (53 +/- 2% luminal occlusion vs. 17 +/- 1% for isografts, P < 0.05) with sites of obstructive lesion formation coinciding with areas of CD3(+) CD8(+) T cell-rich lymphocytic bronchitis. In contrast, allografts in iNOS(-/-) recipients exhibited reductions in local expression of proinflammatory chemokines and cytokines, graft T cell recruitment and apoptosis, and luminal obliteration (29 +/- 2%, P < 0.05 vs. WT allografts). Recipient eNOS deficiency, however, suppressed neither chemokine expression, lymphocyte infiltration, nor airway occlusion (54 +/- 2%). These data demonstrate that iNOS exacerbates luminal obliteration of airway allografts in contrast with the known suppression by iNOS of cardiac allograft vasculopathy. Because iNOS(-/-) airways transplanted into WT allograft hosts are not protected from rejection, these data suggest that iNOS expressed by graft-infiltrating leukocytes exerts the dominant influence on airway rejection.