Role of recruited neutrophils in interleukin-8 production in dog trachea after stimulation with Pseudomonas in vivo

Inhaled formulation and device selection: bridging the gap between preclinical species and first-in-human studies

The factors that influence inhaled first-in-human (FIH) device and formulation selection often differ significantly from the factors that have influenced the preceding preclinical experiments and inhalation toxicology work. In order to minimize the risk of delivery issues negatively impacting a respiratory pipeline program, the preclinical and FIH delivery systems must be considered holistically. This topic will be covered in more detail in this paper. Several examples will be presented that highlight how appropriate scientific strategy can help bridge the gap between delivering to preclinical species and human. Considerations for the FIH device selection (metered dose inhaler, dry powder inhaler and nebulizer) and formulation optimization for small molecules will be discussed in context with the preclinical delivery systems.

Phenazine-1-carboxylic acid, a secondary metabolite of Pseudomonas aeruginosa, alters expression of immunomodulatory proteins by human airway epithelial cells

Pseudomonas aeruginosa is a gram-negative bacterium that causes both acute and chronic lung disease in susceptible patient populations. P. aeruginosa secretes numerous proteins and secondary metabolites, many of which have biological effects that likely contribute to disease pathogenesis. An unidentified small-molecular-weight factor was previously reported to increase IL-8 release both in vitro and in vivo. To identify this factor, we subjected the <3-kDa fraction from P. aeruginosa-conditioned medium to HPLC analysis. A peak fraction that stimulated IL-8 release was found by mass spectrometry to have a molecular mass (MM) of 224 Da. On the basis of this MM and other biochemical properties, we hypothesized that the factor was phenazine-1-carboxylic acid (PCA). Subsequent studies and comparison with purified PCA confirmed this hypothesis. Purified PCA exhibited a number of biological effects in human airway epithelial cells, including increasing IL-8 release and ICAM-1 expression, as well as decreasing RANTES and monocyte chemoattractant protein-1 (MCP-1) release. PCA also increased intracellular oxidant formation as measured by electron paramagnetic resonance and by an intracellular oxidant-sensitive probe. Antioxidants inhibited PCA-dependent increases in IL-8 and ICAM-1, suggesting that oxidants contributed to these effects. However, in contrast to the related phenazine compound pyocyanin, PCA did not oxidize NAD(P)H at physiologically relevant pH, providing preliminary evidence that PCA and pyocyanin may have distinct redox chemistries within the cell. Thus PCA is a biologically active factor secreted by P. aeruginosa that has several activities that could alter the host immune and inflammatory response and thereby contribute to bacterial disease pathogenesis.

Small molecular weight secretory factors from Pseudomonas aeruginosa have opposite effects on IL-8 and RANTES expression by human airway epithelial cells

Pseudomonas aeruginosa is an opportunistic human pathogen that causes both an acute lung disease in patients with hospital-acquired pneumonia and a chronic lung disease in individuals with cystic fibrosis. Many of the pathophysiologic effects of P. aeruginosa infection are due to factors secreted by the bacterium. Conditioned media from cultures of P. aeruginosa increased interleukin-8 expression and decreased regulated on activation, normal T cells expressed and secreted (RANTES) expression by human airway epithelial cells. Both of these activities were present in heat-treated, protease-treated, small molecular weight fractions. The activities were not inhibited by polymyxin B and were not extracted into ethyl acetate, suggesting that they were not due to endotoxin or autoinducer. Conversely, results from chloroform extractions and studies with a phenazine-minus mutant suggested that the blue pigment pyocyanin contributes to these activities when present. In addition to the effects of small molecular weight factors on cytokine expression, proteases in bacterial-conditioned media further decreased levels of RANTES. By altering expression, release, and/or activity of inflammatory cytokines, secretory factors from P. aeruginosa could disrupt the delicate balance that constitutes the immune response to bacterial infection and thus could contribute to the lung damage that occurs in P. aeruginosa-infected airways.

Impairment of endotoxin-induced macrophage inflammatory protein 2 gene expression in alveolar macrophages in streptozotocin-induced diabetes in mice

To elucidate the mechanism of the high incidence of lower respiratory tract infections in patients with diabetes mellitus, we investigated the kinetics of production of macrophage inflammatory protein 2 (MIP-2), an important mediator of lung neutrophil recruitment, using mice with streptozotocin-induced diabetes. Intratracheal challenge with 1 mg of lipopolysaccharide (LPS), an endotoxin, per kg of body weight resulted in a time-dependent increase in the levels of MIP-2 protein in bronchoalveolar lavage (BAL) fluid, with the peak concentration (49.4 +/- 13 ng/ml) occurring at 3 h and significant neutrophil accumulation becoming apparent by 3 h in normal mice. In diabetic mice, the peak level of MIP-2 protein in BAL fluid did not occur until 6 h and was reduced to 21.9 +/- 10 ng/ml. Immunohistochemical studies using anti-MIP-2 antibody confirmed that the main cellular source of MIP-2 in the lung after LPS challenge was alveolar macrophages (AMs) in normal mice. The lungs in diabetic mice, however, showed no AMs staining for MIP-2 within 3 h after LPS challenge. PCR analysis using whole-lung RNA showed a time-dependent increase in MIP-2 mRNA levels after LPS instillation. The level of MIP-2 mRNA in diabetic mice was markedly decreased compared to that in normal mice. Our results indicate that impairment of MIP-2 mRNA expression in the AMs in diabetic mice resulted in delayed neutrophil recruitment in the lungs, and this may explain the development and progression of pulmonary infection in diabetes mellitus.

Chemotactic Migration Triggers IL-8 Generation in Neutrophilic Leukocytes

Neutrophils recovered from inflammatory exudates possess increased levels of IL-8, but exposure of neutrophils to chemoattractants results in only a modest stimulation of IL-8 generation. This study was undertaken to explore the hypothesis that IL-8 generation in these cells is dependent upon the process of migration. Neutrophils synthesized up to 30 times as much IL-8 during migration in response to a gradient of diverse chemoattractants than they did when stimulated directly by the attractants in the absence of a gradient. This IL-8 response was dependent on migration since it was not observed in cells exposed to concentration gradients of chemoattractants under conditions that prevented cell movement. While actinomycin-D (1 μg/ml) had little influence on the generation of IL-8 during chemotaxis, the protein synthesis inhibitor cycloheximide (10 μg/ml) markedly blunted the accumulation of cell-associated IL-8, suggesting that new protein synthesis from preexisting mRNA was responsible for the effect. Consistent with this interpretation, migrating cells incorporated over 10 times as much [3H]leucine into IL-8 as did nonmotile neutrophils exposed to chemoattractants. A substantial portion of the IL-8 generated during chemotaxis was released upon subsequent metabolic stimulation. Thus, the IL-8 synthesized during chemotaxis is uniquely positioned to exert a regulatory influence on inflammatory processes governed by neutrophilic leukocytes responding to inflammatory and infectious stimuli.

Mechanism of pyocyanin- and 1-hydroxyphenazine-induced lung neutrophilia in sheep airways

Pyocyanin (Pyo) and 1-hydroxyphenazine (1-HP) are extracellular products of Pseudomonas aeruginosa. To test whether these products were capable of producing an inflammatory response in the airways, combinations of Pyo and 1-HP at concentrations of 10(-4) and 10(-5) M were instilled into sheep airways, and indexes of inflammation were assessed by bronchoalveolar lavage (BAL) 24 h later. Challenge with the phenazines caused a significant dose-dependent increase in the number of cells and neutrophils recovered by BAL. Control challenges produced no such changes. The lung neutrophilia was accompanied by an increased concentration of albumin in BAL. The increases in BAL neutrophils and albumin could be blocked by treating the sheep with the 5-lipoxygenase inhibitor zileuton. Neither 1-HP nor Pyo was chemotactic to neutrophils when tested in vitro, but when alveolar macrophages (AM) were cultured in vitro in the presence of both Pyo and 1-HP (1 microM), the supernatants caused neutrophil chemotaxis. Analysis of AM culture supernatants incubated with the combination of pigments showed significant increases in leukotriene B4 and interleukin-8, and blocking these mediators separately or together reduced AM supernatant-induced neutrophil chemotaxis. We conclude that local instillation of Pyo and 1-HP can initiate an inflammatory response in the airways of sheep in vivo. This effect can be explained, in part, by the release of chemotactic factors produced by AM.

The effect of chloride concentration on human neutrophil functions: potential relevance to cystic fibrosis

Recently, some investigators have observed elevated concentrations of chloride in the airway surface fluid (ASF) overlying respiratory epithelia from cystic fibrosis (CF) patients compared with ASF overlying non-CF epithelia. Others have shown that this elevated ASF salt concentration can inactivate human beta-defensin-1, an antimicrobial peptide secreted by respiratory epithelia. This could impair the primary epithelial defense against bacteria in the CF airway, thereby forcing a greater reliance on polymorphonuclear leukocyte (PMN)-mediated defenses. Pseudomonas aeruginosa (Psa) flourishes in the CF airway despite the presence of abundant PMN. We therefore investigated whether elevated ASF chloride concentration in CF might also compromise PMN function. We employed a cell-culture model in which halide concentrations and osmolarity were varied independently. We examined the effects of chloride concentration on three aspects of PMN function: recruitment of PMN to the airway (production of interleukin-8 [IL-8]), PMN antimicrobial activity (killing of Psa), and PMN clearance from the airways (apoptosis and lysis). We found that exposure to elevated chloride concentration increased PMN synthesis of IL-8, decreased PMN killing of Psa, and accelerated PMN apoptosis and lysis. In CF airways, elevated chloride therefore could contribute to the increased number of PMN recruited into the airways, the increased survival of Psa, and the increased quantity of toxic mediators released by PMN into the airways. These effects of elevated chloride on PMN function may provide another causal link between loss of cystic fibrosis transmembrane conductance regulator function and CF lung disease.

Cytokine mRNA expression in whole blood samples from dogs with natural canine distemper virus infection

Cytokines are soluble polypeptides with many physiological functions and a special role during infection and inflammation. Little is known about cytokine regulation in naturally occurring viral diseases of animals. Especially the role of cytokines in the development and progression of lesions in canine distemper virus (CDV) infection in dogs is largely unknown. Whole blood samples from 14 dogs with CDV infection and three dogs suffering from non-distemper diseases were examined for mRNA of pro-inflammatory cytokines such as interleukin-1beta (IL-1), interleukin-6 (IL-6), interleukin-8 (IL-8), interleukin-12 (IL-12), tumor necrosis factor-alpha (TNF), interferon-gamma (IFN), and the anti-inflammatory transforming growth factor-beta1 (TGF) using reverse transcription polymerase chain reaction (RT-PCR). Blood samples from the three dogs that showed no clinical abnormalities during a pre-vaccination physical examination served as control. CDV infection was confirmed by post-mortem immunohistochemistry for CDV nucleoprotein. The degree of immunoreactivity and the number of virus antigen positive organs were expressed as antigen index. IFN transcripts were not identified in any dog and IL-8 transcripts were present in RNA isolates from all 20 dogs. None of the other cytokines was detected in control animals. IL-1 and IL-6 were each found in one non-distemper dog and TGF transcripts were amplified in two dogs with non-distemper disease. The following transcripts were found in variable numbers in distemper dogs: IL-1 (7/14 dogs), IL-6 (3/14 dogs), IL-12 (3/14 dogs), TNF (8/14 dogs), and TGF (10/14 dogs) with multiple cytokines in ten dogs. No cytokine transcripts were detected in three distemper dogs. There was no obvious correlation between cytokine mRNA expression and respiratory and gastrointestinal tract diseases. In the CNS, demyelination was frequently associated with IL-1, IL-12, TNF and TGF mRNA expression in the blood. IL-6 transcripts were found only in animals with early CNS lesions and TGF was the only detectable cytokine in an animal with chronic demyelination. Lack of detectable cytokine transcripts in whole blood samples was associated with a high antigen index and viremia, indicating that an overwhelming virus infection may suppress cytokine production, possibly due to paralysis of the immune system. Simultaneous occurrence of pro- and anti-inflammatory cytokines in whole blood preparation from most of the dogs with distemper, indicated a complex most likely disease stage dependent orchestrated cytokine expression.

Neutrophils Are Major Contributors to Intraparenchymal Lung IL-1β Expression After Hemorrhage and Endotoxemia

Acute lung injury and the acute respiratory distress syndrome (ARDS) are significant causes of morbidity and mortality following sepsis and hemorrhage. Increased IL-1β production in the lung is important in the development of acute inflammatory lung injury. Although neutrophils are an important component of the inflammatory response that characterizes acute lung injury, there is little information to suggest that they are capable of initiating cytokine-mediated immune responses in the lung. To explore the role of neutrophils in the early stages of acute lung injury, we examined IL-1β production by mouse lung neutrophils after hemorrhage and endotoxemia. There was a significant increase in IL-1β expression among intraparenchymal pulmonary neutrophil/mononuclear cells (IPNMC) 1 h after hemorrhage or endotoxemia. IL-1β was detected only in a neutrophil-rich fraction of the IPNMC, but not in T and B lymphocytes positively selected from the IPNMC. Cyclophosphamide (CTX)-treated neutropenic mice expressed significantly less IL-1β in IPNMC after hemorrhage or endotoxemia compared with CTX-untreated controls. Immunohistochemical analysis of lung sections from mice after hemorrhage or endotoxemia revealed IL-1β expression in infiltrating neutrophils. These data indicate that IL-1β-producing neutrophils traffic to the lungs rapidly in response to hemorrhage or endotoxemia and support the concept that proinflammatory cytokine production by lung neutrophils may contribute to the development of lung injury after blood loss and sepsis.

Inhibitory effect of macrolides on interleukin-8 secretion from cultured human nasal epithelial cells

The mechanism of macrolide therapy in chronic sinusitis patients is unclear. The authors studied the effect of macrolides on interleukin (IL)-8 secretion from cultured human nasal epithelial cells. Epithelial cells harvested from the nasal polyps of patients with chronic sinusitis were primary-cultured, and secreted IL-8 in culture media was measured by enzyme immunoassay. The cells secreted considerable amounts of IL-8 constitutively and in response to lipopolysaccharide. The secretion was significantly inhibited by 10(-5) M of erythromycin, clarithromycin, roxithromycin, and josamycin. 10(-6) M erythromycin still showed the inhibitory effect, whereas the same concentration of josamycin did not. These results indicate that macrolide antibiotics may act as an immunomodulator to reduce IL-8 in inflammatory sites and, at least partially, account for the clinically discrepant effects between 14- and 16-membered ring macrolides in long-term low-dose therapy for chronic sinusitis.

Nitrite reductase from Pseudomonas aeruginosa induces inflammatory cytokines in cultured respiratory cells

Persistent infection with Pseudomonas aeruginosa increases interleukin-8 (IL-8) levels and causes dense neutrophil infiltrations in the airway of patients with chronic airway diseases. To investigate the role of P. aeruginosa infection in IL-8 production in the airway of these patients, we examined whether cell lysates of P. aeruginosa could cause IL-8 production from human bronchial epithelial cells. Diluted sonicated supernatants of P. aeruginosa (SSPA) with a mucoid or nonmucoid phenotype stimulated human bronchial epithelial (BET-1A) cells to produce IL-8. In this study, we have purified a 59-kDa heat-stable protein with IL-8-inducing activity from the SSPA by sequential ion-exchange chromatography. The N-terminal sequence of this purified protein completely matched a sequence at the N-terminal part of the mature protein of nitrite reductase from P. aeruginosa. In addition, immunoblotting with a polyclonal immunoglobulin G (IgG) against recombinant Pseudomonas nitrite reductase demonstrated a specific binding to the purified protein. Furthermore, the immunoprecipitates of the SSPA with a polyclonal IgG against recombinant nitrite reductase induced a twofold-higher IL-8 production in the BET-1A cell culture than did the immunoprecipitates of the SSPA with a control IgG. These lines of evidence confirmed that Pseudomonas nitrite reductase was responsible for IL-8 production in the BET-1A cells. The purified nitrite reductase induced maximal expression of IL-8 mRNA in the BET-1A cells at 1 to 3 h after stimulation, and the IL-8 mRNA expression declined by 8 h after stimulation. New protein translation was not required for nitrite reductase-mediated IL-8 mRNA expression in the BET-1A cells. Nitrite reductase stimulated the BET-1A cells, as well as human alveolar macrophages, pulmonary fibroblasts, and neutrophils, to produce IL-8. In contrast, nitrite reductase induced significant levels of tumor necrosis factor alpha and IL-1beta protein only in human alveolar macrophages. These data support the notion that nitrite reductase from P. aeruginosa induces the production of inflammatory cytokines by respiratory cells and may contribute to the pathogenesis of chronic airway diseases and persistent P. aeruginosa infection.