Activity of fosfomycin against nosocomial multiresistant bacterial pathogens from Croatia: a multicentric study

Aim

To determine in vitro susceptibility of multiresistant bacterial isolates to fosfomycin.

Methods

In this prospective in vitro study (local non-random sample, level of evidence 3), 288 consecutively collected multiresistant bacterial isolates from seven medical centers in Croatia were tested from February 2014 until October 2016 for susceptibility to fosfomycin and other antibiotics according to Clinical and Laboratory Standards Institute methodology. Susceptibility to fosfomycin was determined by agar dilution method, while disc diffusion were performed for in vitro testing of other antibiotics. Polymerase chain reaction and sequencing was performed for the majority of extended spectrum β-lactamase (ESBL)-producing Klebsiella pneumoniae (K. pneumoniae) and carbapenem-resistant isolates.

Results

The majority of 288 multiresistant bacterial isolates (82.6%) were susceptible to fosfomycin. The 236 multiresistant Gram-negative isolates showed excellent susceptibility to fosfomycin. Susceptibility rates were as follows: Escherichia coli ESBL 97%, K. pneumoniae ESBL 80%, Enterobacter species 85.7%, Citrobacter freundii 100%, Proteus mirabilis 93%, and Pseudomonas aeruginosa 60%. Of the 52 multiresistant Gram-positive isolates, methicillin-resistant Staphylococcus aureus showed excellent susceptibility to fosfomycin (94.4%) and vancomycin-resistant enterococcus showed low susceptibility to fosfomycin (31%). Polymerase chain reaction analysis of 36/50 ESBL-producing K. pneumoniae isolates showed that majority of isolates had CTX-M-15 beta lactamase (27/36) preceded by ISEcp insertion sequence. All carbapenem-resistant Enterobacter and Citrobacter isolates had bla_VIM-1 metallo-beta-lactamase gene.

Conclusion

With the best in vitro activity among the tested antibiotics, fosfomycin could be an effective treatment option for infections caused by multiresistant Gram-negative and Gram-positive bacterial strains in the hospital setting.

MAPK regulation of IL-4/IL-13 receptors contributes to the synergistic increase in CCL11/eotaxin-1 in response to TGF-β1 and IL-13 in human airway fibroblasts

CCL11/eotaxin-1 is a potent eosinophilic CC chemokine expressed by primary human fibroblasts. The combination of TGF-β1 and IL-13 synergistically increases CCL11 expression, but the mechanisms behind the synergy are unclear. To address this, human airway fibroblast cultures from normal and asthmatic subjects were exposed to IL-13 alone or TGF-β1 plus IL-13. Transcriptional (nuclear run-on) and posttranscriptional (mRNA stability) assays confirmed that transcriptional regulation is critical for synergistic expression of CCL11. TGF-β1 plus IL-13 synergistically increased STAT-6 phosphorylation, nuclear translocation, and binding to the CCL11 promoter as compared with IL-13 alone. STAT-6 small interfering RNA significantly knocked down both STAT-6 mRNA expression and phosphorylation and inhibited CCL11 mRNA and protein expression. Regulation of the IL-4Rα complex by TGF-β1 augmented IL-13 signaling by dampening IL-13Rα2 expression, overcoming IL-13's autoregulation of its pathway and enhancing the expression of CCL11. Our data suggest that TGF-β1 induced activation of the MEK/ERK pathway reduces IL-13Rα2 expression induced by IL-13. Thus, TGF-β1, a pleiotropic cytokine upregulated in asthmatic airways, can augment eosinophilic inflammation by interfering with IL-13's negative feedback autoregulatory loop under MEK/ERK-dependent conditions.

Mast cell phenotype, location, and activation in severe asthma. Data from the Severe Asthma Research Program

RATIONALE

Severe asthma (SA) remains poorly understood. Mast cells (MC) are implicated in asthma pathogenesis, but it remains unknown how their phenotype, location, and activation relate to asthma severity.

OBJECTIVES

To compare MC-related markers measured in bronchoscopically obtained samples with clinically relevant parameters between normal subjects and subjects with asthma to clarify their pathobiologic importance.

METHODS

Endobronchial biopsies, epithelial brushings, and bronchoalveolar lavage were obtained from subjects with asthma and normal subjects from the Severe Asthma Research Program (N = 199). Tryptase, chymase, and carboxypeptidase A (CPA)3 were used to identify total MC (MC(Tot)) and the MC(TC) subset (MCs positive for both tryptase and chymase) using immunostaining and quantitative real-time polymerase chain reaction. Lavage was analyzed for tryptase and prostaglandin D2 (PGD2) by ELISA.

MEASUREMENTS AND MAIN RESULTS

Submucosal MC(Tot) (tryptase-positive by immunostaining) numbers were highest in "mild asthma/no inhaled corticosteroid (ICS) therapy" subjects and decreased with greater asthma severity (P = 0.002). In contrast, MC(TC) (chymase-positive by immunostaining) were the predominant (MC(TC)/MC(Tot) > 50%) MC phenotype in SA (overall P = 0.005). Epithelial MC(Tot) were also highest in mild asthma/no ICS, but were not lower in SA. Instead, they persisted and were predominantly MC(TC). Epithelial CPA3 and tryptase mRNA supported the immunostaining data (overall P = 0.008 and P = 0.02, respectively). Lavage PGD2 was higher in SA than in other steroid-treated groups (overall P = 0.02), whereas tryptase did not differentiate the groups. In statistical models, PGD2 and MC(TC)/MC(Tot) predicted SA.

CONCLUSIONS

Severe asthma is associated with a predominance of MC(TC) in the airway submucosa and epithelium. Activation of those MC(TC) may contribute to the increases in PGD2 levels. The data suggest an altered and active MC population contributes to SA pathology.

Role of insulin-like growth factor binding protein-3 in allergic airway remodeling

RATIONALE

The hallmarks of allergic asthma are airway inflammation, obstruction, and remodeling. Airway remodeling may lead to irreversible airflow obstruction with increased morbidity and mortality. Despite advances in the treatment of asthma, the mechanisms underlying airway remodeling are still poorly understood. We reported that insulin-like growth factor (IGF) binding proteins (IGFBPs) contribute to extracellular matrix deposition in idiopathic pulmonary fibrosis; however, their contribution to airway remodeling in asthma has not been established.

OBJECTIVES

We hypothesized that IGFBP-3 is overexpressed in asthma and contributes to airway remodeling.

METHODS

We evaluated levels of IGFBP-3 in tissues and bronchoalveolar lavage fluid from patients with asthma at baseline and 48 hours after allergen challenge, in reparative epithelium in an in vitro wounding assay, and in conditioned media from cytokine- and growth factor-stimulated primary epithelial cells.

MEASUREMENTS AND MAIN RESULTS

IGFBP-3 levels and distribution were evaluated by Western blot, ELISA, and immunofluorescence. IGFBP-3 is increased in vivo in the airway epithelium of patients with asthma compared with normal control subjects. The concentration of IGFBP-3 is increased in the bronchoalveolar lavage fluid of patients with asthma after allergen challenge, its levels are increased in reparative epithelium in an in vitro wounding assay and in the conditioned medium of primary airway epithelial cell cultures stimulated with IGF-I.

CONCLUSIONS

Our results suggest that one mechanism of allergic airway remodeling is through the secretion of the profibrotic IGFBP-3 from IGF-I-stimulated airway epithelial cells during allergic inflammation.

Interleukin-13-induced MUC5AC is regulated by 15-lipoxygenase 1 pathway in human bronchial epithelial cells

RATIONALE

15-Lipoxygenase-1 (15LO1) and MUC5AC are highly expressed in asthmatic epithelial cells. IL-13 is known to induce 15LO1 and MUC5AC in human airway epithelial cells in vitro. Whether 15LO1 and/or its product 15-HETE modulate MUC5AC expression is unknown.

OBJECTIVES

To determine the expression of 15LO1 in freshly harvested epithelial cells from subjects with asthma and normal control subjects and to determine whether IL-13-induced 15LO1 expression and activation regulate MUC5AC expression in human bronchial epithelial cells in vitro.

METHODS

Human airway epithelial cells from subjects with asthma and normal subjects were evaluated ex vivo for 15LO1 and MUC5AC expression. The impact of 15LO1 on MUC5AC expression in vitro was analyzed by inhibiting 15LO1 through pharmacologic (PD146176) and siRNA approaches in human bronchial epithelial cells cultured under air-liquid interface. We analyzed 15 hydroxyeicosatetraenoic acid (15-HETE) by liquid chromatography/UV/mass spectrometry. MUC5AC and 15LO1 were analyzed by real-time RT-PCR, immunofluoresence, and Western blot.

MEASUREMENTS AND MAIN RESULTS

Epithelial 15LO1 expression increased with asthma severity (P < 0.0001). 15LO1 significantly correlated with MUC5AC ex vivo and in vitro. IL-13 increased 15LO1 expression and stimulated formation of two molecular species of 15-HETE esterified to phosphotidylethanolamine (15-HETE-PE). Inhibition of 15LO1 suppressed 15-HETE-PE and decreased MUC5AC expression in the presence of IL-13 stimulation. The addition of exogenous 15-HETE partially restored MUC5AC expression.

CONCLUSIONS

Epithelial 15LO1 expression increases with increasing asthma severity. IL-13 induction of 15-HETE-PE enhances MUC5AC expression in human airway epithelial cells. High levels of 15LO1 activity could contribute to the increases of MUC5AC observed in asthma.

Cell-specific activation profile of extracellular signal-regulated kinase 1/2, Jun N-terminal kinase, and p38 mitogen-activated protein kinases in asthmatic airways

BACKGROUND

Many airway cells manifest signs of chronic activation in asthma. The mechanism of this chronic activation is unknown.

OBJECTIVES

We sought to study the activation of the mitogen-activated protein kinase (MAPK) signaling pathway in airway cells.

METHODS

Endobronchial biopsy specimens from patients with severe and mild asthma (n = 17 in each group) and healthy control subjects (n = 15) were analyzed for the phosphorylated MAPKs extracellular signal-regulated kinase (ERK) 1/2, p38, and Jun N-terminal kinase (JNK) and their downstream effectors by means of immunofluorescence staining. Airway epithelial activation of ERK1/2 and p38 was studied by using Western blotting. Epithelial function was studied by means of real-time PCR, ELISA, and the thymidine incorporation assay.

RESULTS

We detected strong phospho-ERK1/2 staining in airway epithelium and smooth muscle cells in biopsy specimens from asthmatic patients. Fluorescent areas per image, as well as mean fluorescence intensity, were significantly (P < .0001) different among the 3 study groups (patients with severe asthma, patients with mild asthma, and healthy control subjects). Patients with severe asthma also demonstrated strong phospho-p38 staining, mostly in epithelial cells, which was significantly different from that in patients with mild asthma (P = .0001) and healthy control subjects (P = .02). Phospho-JNK primarily stained airway smooth muscle cells. Healthy subjects showed the highest intensity of phospho-JNK staining compared with that seen in patients with severe (P = .004) and mild asthma (P = .003). Inhibition of ERK1/2 and p38 in primary airway epithelial cells blocked their proliferation and expression of select, but not all, chemokines.

CONCLUSIONS

Significant phosphorylation of ERK1/2 and p38 and their correlation with disease severity suggests that the foregoing signaling pathways play an important role in asthma. The ERK1/2 and p38 pathways regulate epithelial cell secretory function and proliferation.

IL-13 induced increases in nitrite levels are primarily driven by increases in inducible nitric oxide synthase as compared with effects on arginases in human primary bronchial epithelial cells

BACKGROUND

Exhaled nitric oxide is increased in asthma, but the mechanisms controlling its production, including the effects of T-helper type 2 (Th2) cytokines, are poorly understood. In mouse and submerged human epithelial cells, Th2 cytokines inhibit expression of inducible nitric oxide synthase (iNOS). Arginases have been proposed to contribute to asthma pathogenesis by limiting the arginine substrate available to NOS enzymes, but expression of any of these enzymes has not been extensively studied in primary human cells.

OBJECTIVES

We hypothesized that primary human airway epithelial cells in air-liquid interface (ALI) culture would increase iNOS expression and activity in response to IL-13, while decreasing arginase expression.

METHODS

iNOS and arginase mRNA (real-time PCR) and protein expression (Western blot and immunofluorescence) as well as iNOS activity (nitrite levels) were measured in ALI epithelial cells cultured from bronchial brushings of normal and asthmatic subjects following IL-13 stimulation.

RESULTS

IL-13 up-regulated iNOS mRNA primarily at a transcriptional level in epithelial cells. iNOS protein and activity also increased, arginase1 protein expression decreased while arginase 2 expression did not change. The changes in iNOS protein correlated strongly with changes in nitrites, and inclusion of arginase (1 or 2) did not substantially change the relationship. Interestingly, iNOS mRNA and protein were not correlated.

CONCLUSIONS

These results contrast with many previous results to confirm that Th2 stimuli enhance iNOS expression and activity. While arginase 1 protein decreases in response to IL-13, neither arginase appears to substantially impact nitrite levels in this system.

Mechanisms of tissue inhibitor of metalloproteinase 1 augmentation by IL-13 on TGF-beta 1-stimulated primary human fibroblasts

BACKGROUND

TGF-beta induces expression of tissue inhibitor of metalloproteinase 1 (TIMP-1), a potent inhibitor of matrix metalloproteinases that controls extracellular matrix metabolism and deposition. IL-13 alone does not induce TIMP-1, but in combination with TGF-beta it augments TIMP-1 expression. Although these interactions have implications for remodeling in asthma, little is understood regarding the mechanisms controlling TIMP-1 product.

OBJECTIVE

To explore the role of Smads and mitogen-activated protein kinase kinase (MEK)-extracellular signal-regulated kinase (ERK) in the TIMP-1 augmentation by IL-13+TGF-beta1 in primary human airway fibroblasts.

METHODS

Real-time PCR, Western blot, ELISA, and transient transfection were used to evaluate the mechanisms of TIMP-1 augmentation.

RESULTS

IL-13 enhanced TGF-beta1-induced Smad-2 and Smad-3 phosphorylation, transient transfection with dominant-negative Smad-2 or Smad-3 decreased TIMP-1 mRNA expression in the presence of TGF-beta1 and IL-13+TGF-beta1 through inhibition of Smad-2 or Smad-3 phosphorylation. ERK phosphorylation was increased by IL-13 and IL-13+TGF-beta1. MEK-ERK inhibition decreased TIMP-1 mRNA/protein to a greater degree after IL-13+TGF-beta1 stimulation versus TGF-beta1 alone. MEK-ERK inhibition also significantly increased Akt phosphorylation under all conditions and decreased Smad-3 phosphorylation in the presence of IL-13+TGF-beta1. In contrast, phosphoinositide-3 kinase-Akt inhibition increased phosphorylation of ERK and Smads, leading to increased TIMP-1.

CONCLUSION

These results indicate that IL-13 augments TGF-beta1-induced TIMP-1 expression through increased Smad phosphorylation. These increases occur as TGF-beta1 downregulates IL-13-induced phosphoinositide-3 kinase activation while leaving the positive effect of IL-13-induced ERK on Smad signaling.

CLINICAL IMPLICATIONS

This augmentation of TGF-beta1-induced TIMP-1 by IL-13 could contribute to the fibrosis and airway remodeling seen in the presence of T(H)2 inflammation in asthma.

IgE expression pattern in lung: relation to systemic IgE and asthma phenotypes

BACKGROUND

IgE-mediated responses contribute to allergy and asthma. Little is understood regarding the relationship of tissue IgE to systemic IgE, inflammation or clinical outcomes.

OBJECTIVES

To evaluate local IgE expression and cellular inflammation in the proximal and distal lung of normal subjects and subjects with asthma of varying severity and relate those tissue parameters to systemic IgE levels, atopy, lung function, and history of severe exacerbations of asthma.

METHODS

Tissue from more than 90 subjects with eosinophilic (SAeo(+)) and noneosinophilic (SAeo(-)) severe asthma, mild asthma and normal subjects were immunostained for IgE, signal-amplifying isoform of IgE receptor (FcepsilonRIbeta) and markers of mast cells, eosinophils, and lymphocytes. Tissue expression of IgE, FcepsilonRIbeta, cellular inflammation, serum IgE, and atopy were compared. Regression models were used to determine the relationship of local and systemic IgE to lung function and severe exacerbations of asthma.

RESULTS

Mast cell-bound IgE was present along airways but absent in lung parenchyma. Although the groups were similar in systemic/serum IgE and atopy, local/tissue IgE was highest in SAeo(+) and correlated with eosinophils and lymphocytes (r(s) = 0.52, P < .0001; and r(s) = 0.23, P = .03, respectively). Higher local IgE was associated with better lung function, but also with more severe exacerbations of asthma.

CONCLUSION

Local IgE appears to be primarily a component of responses within the mucosal immune compartment and is related to cellular inflammation, lung function, and clinical outcomes in asthma.

CLINICAL IMPLICATIONS

Local/airway IgE-related processes rather than systemic markers of atopy may be relevant in determining clinical outcomes in asthma.

IL4R alpha mutations are associated with asthma exacerbations and mast cell/IgE expression

BACKGROUND

Severe asthma has been associated with severe exacerbations, lower lung function and greater tissue inflammation. Previous studies have suggested that mutations in interleukin-4 receptor alpha (IL4Ralpha) are associated with lower lung function, higher IgE, and a gain in receptor function. However, an effect on exacerbations and tissue inflammation has not been shown.

HYPOTHESIS

Allelic substitutions in IL4Ralpha are associated with asthma exacerbations, lower lung function, and tissue inflammation, in particular to mast cells and IgE.

METHODS

Two well-characterized cohorts of subjects with severe asthma were analyzed for five single nucleotide polymorphisms (SNPs) in IL4Ralpha. These polymorphisms were compared with the history of severe asthma exacerbations and lung function. In the primary (National Jewish) cohort, these polymorphisms were also compared with endobronchial tissue inflammatory cells and local IgE.

RESULTS

In both cohorts, the presence of the minor alleles at E375A and Q551R, which were more common in African Americans, was associated with a history of severe exacerbations and lower lung function. In the National Jewish cohort, the C allele at E375A was associated with higher tissue mast cells and higher levels of IgE bound to mast cells. The significance for most of these associations remained when whites (the larger racial subgroup) were analyzed separately.

CONCLUSIONS

SNPs in IL4Ralpha, which are more common in African Americans, are associated with severe asthma exacerbations, lower lung function, and increased mast cell-related tissue inflammation. Further studies of the impact of these mutations in African Americans and on receptor function are indicated.

Subtle immunodeficiency in severe asthma: IgA and IgG2 correlate with lung function and symptoms

BACKGROUND

Atopy, increased serum IgE and eosinophilic airway inflammation are common in asthma and may indicate aberrant immune responses, but the cause(s) are unknown. It was hypothesized that differences in serum immunoglobulins, immunoglobulin free light chains (FLC) and secretory IgA (sIgA) would exist between subjects with asthma of varying severity and normal subjects, and the levels would correlate with lung function, symptoms and airway inflammation.

METHODS

Serum IgG, IgA, IgE and IgM, IgG subclasses and FLC, and bronchoalveolar lavage sIgA were evaluated from 15 normal subjects, 9 mild and 22 severe asthmatics with similar atopic status. Asthma symptoms were obtained by questionnaire, and airway inflammation was assessed by immunostaining for five inflammatory cell types.

RESULTS

Immunoglobulin levels in all groups were generally within the normal range. However, IgA and IgG were lower in severe asthmatics than normal subjects (overall p = 0.006 and 0.02, respectively). IgA, but not IgG, correlated with lung function and asthma symptoms (r-values >0.58; p-values <0.009). Although similar among the groups, higher sIgA and IgG(2) also positively correlated with lung function and negatively with asthma symptoms (r-values >0.63; p-values <0.009). IgA and IgG/IgG(1) positively correlated with tissue mast cells.

CONCLUSIONS

Subtle alterations in IgA- and IgG(2)-mediated responses in asthma may be disease-related. As their levels are generally normal, it is possible that the quality/repertoire of immune protection provided by these isotypes, perhaps against carbohydrate epitopes, may be altered in asthma.

Exhaled nitric oxide identifies the persistent eosinophilic phenotype in severe refractory asthma

BACKGROUND

The fractional concentration of exhaled nitric oxide (FENO) is increased in asthma, correlates with eosinophilic inflammation, and decreases after steroid therapy.

OBJECTIVE

We sought to examine whether persistent eosinophilia would be accompanied by an increased FENO level despite steroid therapy in patients with severe refractory asthma (SRA) as manifestations of steroid resistance.

METHODS

Subjects with SRA, subjects with mild-moderate asthma, and healthy control subjects had FENO measured, followed by endobronchial biopsy and bronchoalveolar lavage. Tissue and bronchoalveolar lavage inflammatory cells were assessed for all subjects, and eosinophil status (EOS+/EOS-) was determined for subjects with SRA.

RESULTS

Twenty-four subjects with SRA, 15 subjects with moderate-mild asthma, and 17 healthy control subjects were studied. Subjects with EOS+ SRA had significantly higher median FENO levels compared with levels in subjects with EOS- SRA (P = .0084) and all other groups. In subjects with SRA, FENO levels correlated with tissue eosinophils (r(s) = 0.54, P = .007), lymphocytes (r(s) = 0.40, P = .003), and mast cells (r(s) = 0.44, P = .05). FENO levels of greater than 72.9 ppb were associated with a sensitivity of 0.56 and a specificity of 1.0 for EOS+ status in subjects with SRA.

CONCLUSION

FENO measurement identified the subgroup of subjects with SRA with persistent eosinophilia despite steroid therapy. Further studies are needed on the use of FENO to monitor response to therapy over time in subjects with SRA.

Relationship of Small Airway Chymase-Positive Mast Cells and Lung Function in Severe Asthma

Distal lung inflammation may be important in asthma pathophysiology. The goal of this study was to measure cellular inflammation in the large airway and four distal lung regions (small airway inner and outer wall, alveolar attachments, and peripheral alveolar tissue) and to correlate the specific inflammatory cells with several lung function parameters. Sections of concurrently obtained endobronchial and transbronchial/surgical biopsy tissue from 20 individuals with severe asthma were immunostained for T-lymphocyte, eosinophil, monocyte/macrophage, neutrophil, and two mast cell markers (tryptase and chymase). Specific cell distributions were determined and correlated with lung function measures. The number of inflammatory cells generally increased toward the periphery, but the percentage of T-lymphocytes, eosinophils, monocytes/macrophages, and neutrophils remained similar or decreased from large to small airways. In contrast, mast cell number, percentage, and the chymase-positive phenotype increased in small airway regions. After the analysis was adjusted for multiple comparisons, only chymase-positive mast cells significantly and positively correlated with lung function. Such a relationship was seen only in the small airway/alveolar attachments lung region (r(s) = 0.61-0.89; p </= 0.001 for all correlations). These data suggest that induction of chymase-positive mast cells, particularly in the small airway outer wall/alveolar attachments region, may be protective for lung function in severe asthma.

Increased TGF-beta2 in severe asthma with eosinophilia

BACKGROUND

Airway eosinophilia and thickened subepithelial basement membrane have previously been reported to increase with increases in TGF-beta expression. However, little is known regarding the expression of specific TGF-beta isoforms (TGF-beta1, TGF-beta2, and TGF-beta3) in asthma, despite recent evidence suggesting that isoforms may have differing biologic activities.

OBJECTIVE

This study examined airway tissue expression of the 3 TGF-beta isoforms and several downstream pathway elements in 48 patients with severe asthma with or without persistent eosinophilia, 14 patients with mild asthma, and 21 normal subjects.

METHODS

Immunochemistry/immunofluorescence, quantitative real-time PCR and enzyme immunoassay were used to evaluate the 3 TGF-beta isoforms, their receptors, collagen I deposition, connective tissue growth factor expression, and tissue inhibitor of metalloproteinases 1 levels.

RESULTS

Of the isoforms, only TGF-beta2 was different among the groups and increased in severe asthma (overall P < .0001). The increase was due to severe asthma tissue eosinophils which, unlike eosinophils in other groups, expressed high amounts of TGF-beta2. Subjects with severe asthma also had the thickest subbasement membrane and highest tissue inhibitor of metalloproteinases 1 levels. In contrast, TGF-beta receptor 1 and connective tissue growth factor were both consistently downregulated in asthma, regardless of severity.

CONCLUSION

TGF-beta2, expressed mainly by eosinophils, is the predominant isoform expressed in severe asthma, and is associated with increased profibrotic responses. Decreased expression of TGF-beta receptor 1 and connective tissue growth factor in all asthma severity groups suggests a degree of activation of the TGF-beta pathway in airway tissue of all asthmatic compared with normal airways.

Transforming growth factor-beta2 induces bronchial epithelial mucin expression in asthma

The transforming growth factor (TGF)-beta family is important for tissue repair in pathological conditions including asthma. However, little is known about the impact of either TGF-beta1 or TGF-beta2 on asthmatic airway epithelial mucin expression. We evaluated bronchial epithelial TGF-beta1 and TGF-beta2 expression and their effects on mucin expression, and the role of TGF-beta1 or TGF-beta2 in interleukin (IL)-13-induced mucin expression. Epithelial TGF-beta1, TGF-beta2, and mucin expression were evaluated in endobronchial biopsies from asthmatics and normal subjects. The effects of TGF-beta1 or TGF-beta2 on mucin MUC5AC protein and mRNA expression, and the impact of IL-13 on epithelial TGF-beta1, TGF-beta2, and MUC5AC were determined in cultured bronchial epithelial cells from endobronchial brushings of both subject groups. In biopsy tissue, epithelial TGF-beta2 expression levels were higher than TGF-beta1 in both asthmatics and normals. TGF-beta2, but not TGF-beta1, was increased in asthmatics compared with normals, and significantly correlated with mucin expression. TGF-beta2, but not TGF-beta1, increased mucin expression in cultured epithelial cells from both subject groups. IL-13 increased the release of TGF-beta2, but not TGF-beta1, from epithelial cells. A neutralizing TGF-beta2 antibody partially inhibited IL-13-induced mucin expression. These data suggest that TGF-beta2 production by asthmatic bronchial epithelial cells may increase airway mucin expression. IL-13-induced mucin expression may occur in part through TGF-beta2 up-regulation.

Distinguishing severe asthma phenotypes: role of age at onset and eosinophilic inflammation

BACKGROUND

Asthma is a heterogeneous process, yet little is understood regarding phenotypes.

OBJECTIVE

To determine whether phenotypic differences exist between early-onset, severe asthma as compared with late-onset disease and whether the presence or absence of eosinophilia influences the phenotypes.

METHODS

Cross-sectional analysis of integrated clinical, physiologic, and pathologic data collected from 80 subjects with severe asthma. Subjects were divided into those with asthma onset before age 12 years (n = 50) versus after age 12 (n = 30) and by the presence or absence of lung eosinophils.

RESULTS

Subjects with early-onset, severe asthma had significantly more allergen sensitivity (skin test positivity, 98% vs 76%, P <.007) and more allergic symptoms (P values all <or=.02) than subjects with late-onset asthma. In contrast, subjects with late-onset asthma had lower lung function (P values =.05 to.07) than early-onset, despite a shorter (P <.0001) duration of illness. Both groups had a high degree of general asthma symptoms, but those with persistent eosinophils from either age at onset group had significantly more (multiple P values <.05). Similarly, the presence of eosinophils in either age at onset group was associated with the lowest lung function (P <or=.02). Although late-onset asthma was associated with the highest numbers of lung eosinophils (P <.007), only early-onset severe asthma was associated with a lymphocytic/mast cell inflammatory process. Finally, subjects with late-onset asthma without eosinophils had no subepithelial basement membrane thickening, suggesting a different pathologic process.

CONCLUSIONS

Differentiating severe asthma by age at onset and presence or absence of eosinophils identifies phenotypes of asthma, which could benefit subsequent genetic and therapeutic studies.

Subepithelial basement membrane immunoreactivity for matrix metalloproteinase 9: association with asthma severity, neutrophilic inflammation, and wound repair

BACKGROUND

Asthma likely involves an active injury and repair process, including components such as neutrophils and matrix metalloproteinase 9 (MMP-9). Although MMP-9 is increased in lavage fluid and sputum in patients with asthma, controversy exists as to the role of tissue MMP-9.

OBJECTIVE

The purpose of this study was to determine whether increases in submucosal cellular MMP-9, matrix MMP-9 (subepithelial basement membrane [SBM]), or both would be associated with severe asthma, neutrophilic inflammation, and wound repair.

METHODS

Immunohistochemical staining and analyses of MMP-9, inflammatory cells, transforming growth factor beta, and collagen I were performed in endobronchial biopsy specimens, bronchoalveolar lavage fluid, or both from 38 patients with severe asthma and compared with results in 10 patients with mild asthma, 8 patients with moderate asthma, and 10 healthy control subjects.

RESULTS

A significantly greater proportion of patients with severe asthma demonstrated MMP-9 staining of the SBM than control subjects (P =.02). Bronchoalveolar lavage MMP-9 levels were also increased in patients with severe asthma (P =.0004). The numbers of submucosal neutrophils and macrophages, but not eosinophils, were significantly higher in asthmatic individuals with MMP-9 staining of the SBM (P =.004 and P =.01, respectively). However, the presence of SBM MMP-9 was associated with a high correlation between lavage and tissue eosinophils (r = 0.58, P =.009). Although the SBM thickness did not differ between groups, higher numbers of transforming growth factor beta-positive cells were seen in subjects with SBM MMP-9 staining. Pulmonary function was significantly lower in those asthmatic subjects with SBM staining.

CONCLUSIONS

These results suggest that localized tissue MMP-9 might play an important role in wound repair and cell trafficking.

Expression and activation of 15-lipoxygenase pathway in severe asthma: relationship to eosinophilic phenotype and collagen deposition

BACKGROUND

Although 15(S)-hydroxyeicosatetraenoic acid (15(S)-HETE), a product of 15-lipoxygenase (15-LO), may be involved in mild to moderate asthma, little is known about its potential roles in severe asthma.

OBJECTIVES

This study was performed to evaluate 15(S)-HETE levels in bronchoalveolar lavage fluid (BALF) from severe asthmatics with and without airway eosinophils and from the control groups. In addition, 15-LO protein expression was examined in endobronchial biopsy, while its expression and activation were evaluated in BAL cells.

RESULTS

While 15(S)-HETE levels in BALF were significantly higher in all severe asthmatics than normal subjects, severe asthmatics with airway eosinophils had the highest levels compared with mild, moderate asthmatics and normal subjects. 15(S)-HETE levels were associated with tissue eosinophil numbers, sub-basement membrane thickness and BALF tissue inhibitor of metalloproteinase-1 levels, and were accompanied by increased 15-LO expression in bronchial epithelium. In addition, activation of 15-LO was suggested by the increased proportion of 15-LO in the cytoplasmic membrane of alveolar macrophages from severe asthmatics.

CONCLUSION

The data suggest that severe asthmatics with persistent airway eosinophils manifest high levels of 15(S)-HETE in BALF, which may be associated with airway fibrosis. It is likely that 15-LO expression and activation by airway cells explain the increased 15(S)-HETE levels.

Transbronchial biopsy as a tool to evaluate small airways in asthma

Small airway (SA) inflammation in asthmatics is poorly understood. Surgical biopsies to obtain peripheral lung tissue are seldom justified in asthmatics. Therefore, the authors hypothesised that transbronchial biopsy could be an alternative approach to evaluate SA in asthma. Transbronchial and endobronchial biopsy tissue samples (TBBX and EBBX) from 12 severe asthmatics were evaluated for airway and parenchymal total inflammatory cell count expressed as the sum of immunostained T-cells (CD3), macrophages (CD68), mast cells (tryptase AAI), neutrophils (neutrophil elastase) and eosinophils (EG2) per mm2. The large airways (LA) were evaluated in EBBXs, while SA, medium airways (MA) and alveolar tissue (AT) were evaluated in TBBXs. When cell counts from SA, MA, LA and AT were compared, SA had a significantly higher cell count than MA or LA (SA 1011 x mm(-2) (539-1,290), MA 346 x mm(-2) (223-415), LA 332 x mm(-2) (189-416), AT 464 x mm(-2) (298-834)). The cell density and pattern of the inflammatory cell distribution in subjects with TBBXs appeared similar to those in three severe asthmatics whose inflammatory cells were analysed in surgical tissue samples. This study suggests that small airway may be identified and analysed in transbronchial biopsy tissue samples and therefore transbronchial biopsy tissue samples could expand the analysis of inflammation and tissue remodelling in asthma.

Persistent wheezing in very young children is associated with lower respiratory inflammation

Despite advances in understanding the pathophysiology of asthma, morbidity and mortality in pediatrics continue to rise. Little is known about the initiation and chronicity of inflammation resulting in asthma in this young population. We evaluated 20 "wheezing" children (WC) (median age 14.9 mo) with a minimum of two episodes of wheezing or prolonged wheezing > or = 2 mo in a 6-mo period with bronchoscopy and bronchoalveolar lavage (BAL). Comparisons were made with six normal controls (NC) (median age 23.3 mo) undergoing general anesthesia for elective surgery. BAL fluid cell counts and differentials were determined. The eicosanoids, leukotriene (LT) B(4), LTE(4), prostaglandin (PG)E(2), and 15-hydroxyeicosatetraenoic acid (HETE) and the mast cell mediators, beta-tryptase and PGD(2), were evaluated by enzyme immunoassay (EIA). WC had significant elevations in total BAL cells/ml (p = 0.01), as well as, lymphocytes (LYMPH, p = 0.007), macrophages/monocytes (M&M, p = 0.02), polymorphonuclear cells (PMN, p = 0.02), epithelial cells (EPI, p = 0.03), and eosinophils (EOS, p = 0.04) compared with NC. Levels of PGE(2) (p = 0.0005), 15-HETE (p = 0.002), LTE(4) (p = 0.04), and LTB(4) (p = 0.05) were also increased in WC compared with NC, whereas PGD(2) and beta-tryptase were not. This study confirms that inflammation is present in the airways of very young WC and may differ from patterns seen in adults with asthma.

Peripheral blood and airway tissue expression of transforming growth factor beta by neutrophils in asthmatic subjects and normal control subjects

BACKGROUND

Airway remodeling may play an important role in asthma pathophysiology. Transforming growth factor beta (TGF-beta) has a critical role in the remodeling process. Although cellular sources for TGF-beta have been previously investigated in asthma airways, the expression, release, or both of TGF-beta from asthmatic airways and blood neutrophils has not been reported.

OBJECTIVE

The current study evaluated the TGF-beta protein and messenger (m)RNA expression by airway and peripheral blood neutrophils in asthmatic and normal subjects.

METHODS

TGF-beta protein expression by airway and peripheral blood neutrophils was detected by using immunocytochemistry. TGF-beta protein levels in blood neutrophil supernatant were measured by using an enzyme immunoassay. TGF-beta mRNA expression was evaluated by using reverse transcription-PCR.

RESULTS

Higher numbers of TGF-beta(+) cells and neutrophils were found in airway tissue of asthmatic (n = 15) compared with normal subjects (n = 10). Although neutrophils in both asthmatic and normal airway tissue expressed TGF-beta protein and the percentage of neutrophils expressing TGF-beta was similar between the two groups, the total number of TGF-beta(+) neutrophils was higher in the asthmatic subjects (P =.01). Peripheral blood neutrophils from asthmatic (n = 5) and normal subjects (n = 7) also expressed TGF-beta protein and mRNA. Blood neutrophils from asthmatic subjects spontaneously released significantly higher levels of TGF-beta than those from normal subjects (P =.007).

CONCLUSION

These data suggest that airway and blood neutrophils from both asthmatic and normal subjects can express and release TGF-beta. Higher levels of TGF-beta expression-release from asthmatic neutrophils indicate that neutrophils may be involved in the airway remodeling process of asthmatic subjects.