Kerryn McCluskie

Resveratrol, an extract of red wine, inhibits lipopolysaccharide induced airway neutrophilia and inflammatory mediators through an NF-κB-independent mechanism

Consumption of a naturally occurring polyphenol, resveratrol, in particular through drinking moderate amounts of red wine, has been suggested to be beneficial to health. A plethora of in vitro studies published demonstrate various anti‐inflammatory actions of resveratrol. The aim of this research was to determine whether any of these anti‐inflammatory effects translate in vivo in a rodent model of LPS induced airway inflammation. Resveratrol reduced lung tissue neutrophilia to a similar magnitude as that achieved by treatment with budesonide. This was associated with a reduction in pro‐inflammatory cytokines and prostanoid levels. Interestingly, the reduction did not appear to be due to an impact on NF‐κB activation or the expression of the respective genes as suggested by various in vitro publications. These results suggest that resveratrol may possess anti‐inflammatory properties via a novel mechanism. Elucidation of this mechanism may lead to potential new therapies for the treatment of chronic inflammation.

PPAR‐γ agonists as therapy for diseases involving airway neutrophilia

Peroxisome proliferator-activated receptors (PPARs) are a family of ligand-activated nuclear hormone receptors belonging to the steroid receptor superfamily. Previously, the present authors have shown that PPAR‐γ agonists inhibit the release of inflammatory cell survival factors and induce apoptosis in vitro. The aim of this study was to determine the effect of two structurally different PPAR agonists in an in vivo model of lipopolysaccharide (LPS)-induced airway inflammation. Mice were treated with PPAR agonists, rosiglitazone or SB 219994, prior to exposure to aerosolised LPS, and the extent of airway inflammation was assessed 3 h later. In these experiments, the PPAR ligands inhibited LPS-induced airway neutrophilia and associated chemoattractants/survival factors (keratinocyte-derived chemokine and granulocyte-colony stimulating factor) in the mouse lung. The present authors postulate that if a peroxisome proliferator-activated receptor agonist has the same effect in man, and neutrophils are important in the progression of respiratory diseases, such as chronic obstructive pulmonary disease, then this class of compounds could be a potential therapy. Furthermore, several peroxisome proliferator-activated receptor‐γ agonists have been shown to be clinically effective for the treatment of type II diabetes, suggesting that any benefit of peroxisome proliferator-activated receptor‐γ ligands in the progression of respiratory diseases, which may involve airway neutrophilia, could be explored relatively quickly.

Role of p38 MAP kinase in LPS‐induced airway inflammation in the rat

We investigated the effect of the p38 kinase inhibitor SB 203580 on airway inflammation induced by aerosolized lipopolysaccharide (LPS) in male Wistar rats. SB 203580 significantly inhibited (ED50=15.8 mg kg−1) plasma levels of TNF‐α in rats challenged with LPS (1.5 mg kg−1, i.p.). Aerosolized LPS induced a peak in TNF‐α levels and the initiation of a neutrophilic response in bronchoalveolar lavage (BAL) fluid at the 2 h time point. Furthermore, the 4 h time point was associated with the peak in IL‐1β levels and the initial plateau of neutrophilia observed in the BAL fluid. SB 203580 (100 mg kg−1), had no effect on peak TNF‐α levels or the associated neutrophilia in the BAL. Interestingly, the PDE 4 inhibitor RP 73401 (100 mg kg−1) significantly reduced both TNF‐α levels and neutrophilic inflammation. However, the BAL fluid from rats pre‐treated with either compound significantly inhibited TNF‐α release from cultured human monocytes 18 h after LPS treatment (83.6 and 44.5% inhibition, respectively). Alternatively, SB 203580 (100 mg kg−1) produced dose‐related inhibition of BAL IL‐1β levels (67.5% inhibition, P<0.01) and BAL neutrophilia (45.9% inhibition, P<0.01) 4 h after LPS challenge. P38 protein was present in lung tissue and the level of expression was not affected by LPS treatment. P38 kinase appears to be involved in the release of IL‐1β and the sustained neutrophilic response in the BAL fluid. This data may suggest a role for p38 inhibitors in the treatment of airway inflammatory diseases in which neutrophilia is a feature of the lung pathology.

IκB kinase-2 independent and dependent inflammation in airway disease models: relevance of IKK- 2 inhibition to the clinic

Nuclear factor κB (NF-κB) is a transcription factor believed to be central in the expression of numerous inflammatory genes and the pathogenesis of many respiratory diseases. We have previously demonstrated increased NF-κB pathway activation in a steroid-sensitive animal model of lipopolysaccharide (LPS)-driven airway inflammation. It is noteworthy that this phenomenon was not observed in a steroid-insensitive model of elastase-induced inflammation in the rat. The aim of this study was to gather further evidence to suggest that these similar profiles of neutrophilic inflammation can be NF-κB-dependent or -independent by determining the impact of an IκB kinase-2 (IKK-2) inhibitor, 2-[(aminocarbonyl)amino]-5-(4-fluorophenyl)-3-thiophenecarboxamide (TPCA-1). In the LPS model, TPCA-1 blocked the increase in NF-κB DNA binding, a marker of NF-κB pathway activation. This inhibition was associated with a reduction in inflammatory mediator release [tumor necrosis factor α (TNFα)/interleukin-1β (IL-1β)/matrix metalloproteinase-9 (MMP-9)] and lung inflammatory cell burden (neutrophilia/eosinophilia). These data were paralleled with a steroid and in human cell based assays. In the elastase-driven inflammation model, in which our group has previously failed to measure an increase in NF-κB DNA binding, neither TPCA-1 nor the steroid, affected mediator release (IL-1β/MMP-9) or cellular burden (neutrophilia/lymphomononuclear cells). This is the first study to examine the effect of an IKK-2 inhibitor in well validated models that mimic aspects of the inflammatory lesion evident in diseases such as COPD. In conclusion, we have demonstrated that animal models with similar profiles of airway inflammation can be IKK-2 inhibitor/steroid-sensitive or -insensitive. If both profiles of inflammation exist in the clinic, then this finding is extremely exciting and may lead to greater understanding of disease pathology and the discovery of novel anti-inflammatory targets.

Novel role for the Liver X nuclear receptor in the suppression of lung inflammatory responses

The liver X receptors (LXRα/β) are part of the nuclear receptor family and are believed to regulate cholesterol and lipid homeostasis. It has also been suggested that LXR agonists possess anti-inflammatory properties. The aim of this work was to determine the effect of LXR agonists on the innate immune response in human primary lung macrophages and a pre-clinical rodent model of lung inflammation. Before profiling the impact of the agonist, we established that both the human macrophages and the rodent lungs expressed LXRα/β. We then used two structurally distinct LXR agonists to demonstrate that activation of this transcription factor reduces cytokine production in THP-1 cells and lung macrophages. Then, using the expression profile of ATP binding cassettes A1 (ABCA-1; a gene directly linked to LXR activation) as a biomarker for lung exposure of the compound, we demonstrated an LXR-dependent reduction in lung neutrophilia rodents in vivo. This inhibition was not associated with a suppression of c-Fos/c-Jun mRNA expression or NF-κB/AP-1 DNA binding, suggesting that any anti-inflammatory activity of LXR agonists is not via inhibition of NF-κB/AP-1 transcriptional activity. These data do not completely rule out an impact of these agonists on these two prominent transcription factors. In summary, this study is the first to demonstrate anti-inflammatory actions of LXRs in the lung. Chronic innate inflammatory responses observed in some airway diseases is thought to be central to disease pathogenesis. Therefore, data suggest that LXR ligands have utility in the treatment of lung diseases that involves chronic inflammation mediated by macrophages and neutrophils.

Dissociation by steroids of eosinophilic inflammation from airway hyperresponsiveness in murine airways

BackgroundThe link between eosinophils and the development of airway hyperresponsiveness (AHR) in asthma is still controversial. This question was assessed in a murine model of asthma in which we performed a dose ranging study to establish whether the dose of steroid needed to inhibit the eosinophil infiltration correlated with that needed to block AHR.MethodsThe sensitised BALB/c mice were dosed with vehicle or dexamethasone (0.01–3 mg/kg) 2 hours before and 6 hours after each challenge (once daily for 6 days) and 2 hours before AHR determination by whole-body plethysmography. At 30 minutes after the AHR to aerosolised methacholine the mice were lavaged and differential white cell counts were determined. Challenging with antigen caused a significant increase in eosinophils in the bronchoalveolar lavage (BAL) fluid and lung tissue, and increased AHR.ResultsDexamethasone reduced BAL and lung tissue eosinophilia (ED50 values of 0.06 and 0.08 mg/kg, respectively), whereas a higher dose was needed to block AHR (ED50 of 0.32 mg/kg at 3 mg/ml methacholine. Dissociation was observed between the dose of steroid needed to affect AHR in comparison with eosinophilia and suggests that AHR is not a direct consequence of eosinophilia.ConclusionThis novel pharmacological approach has revealed a clear dissociation between eosinophilia and AHR by using steroids that are the mainstay of asthma therapy. These data suggest that eosinophilia is not associated with AHR and questions the rationale that many pharmaceutical companies are adopting in developing low-molecular-mass compounds that target eosinophil activation/recruitment for the treatment of asthma.

Utility of exhaled nitric oxide as a noninvasive biomarker of lung inflammation in a disease model

There is a great deal of interest in developing less invasive markers for monitoring airway inflammation and the effect of possible novel anti-inflammatory therapies that may take time to impact on disease pathology. Exhaled nitric oxide (eNO) has been shown to be a reproducible, noninvasive indicator of the inflammatory status of the airway in the clinic. The aim of the present study was to determine the usefulness of measuring eNO as a marker of the anti-inflammatory impact of glucocorticoid and an inhibitor of κB kinase-2 (IKK-2) inhibitor 2-[(aminocarbonyl)amino]-5-(4-fluorophenyl)-3-thiophenecarboxamide (TPCA-1), in a pre-clinical model of airway inflammation. Rats were given vehicle, budesonide or TPCA-1 prior to exposure to lipopolysaccharide, previously shown to induce an increase in eNO and airway neutrophilia/eosinophilia. Comparison of the effect of the two compounds on inflammatory components demonstrated a significant correlation between the impact on eNO and inflammatory cell burden in the airway. The current study demonstrates the usefulness of profiling potential disease-modifying therapies on exhaled nitric oxide levels and the way in which an effect on this noninvasive biomarker relates to effects on pathological parameters such as lung cellularity. Information from studies such as the current one would suggest that the measurement of exhaled nitric oxide has potential for monitoring inflammatory status in lung tissue.

Functional characterization and biomarker identification in the Brown Norway model of allergic airway inflammation

The antigen‐induced inflammatory response in the Brown Norway rat is a model commonly used to assess the impact of novel compounds on airway eosinophilia. A detailed functional, cellular and molecular characterization of this model has not yet been performed within a single study. This information together with the temporal changes in this phenomenon should be known before this model can be used, with confidence, to elucidate the mechanisms of action of novel anti‐inflammatory drugs. Antigen challenge caused an accumulation of eosinophils in lung tissue 24 h after challenge. Accumulation of CD2+ T cells was not apparent until after 72 h. Interestingly, mRNA for the Th2 type cytokines interleukin (IL)‐4, IL‐5 and IL‐13 and eotaxin were elevated in lung tissue after challenge and the expression of IL‐13 and eotaxin protein increased at around 8–12 h. The temporal changes in both the biomarker production and the functional responses are important factors to consider in protocol design prior to initiating a compound screening program. A neutralising antibody (R73) against αβ‐TCR caused a significant reduction in T cell numbers accompanied by a significant suppression of eosinophil accumulation. Airway hyperreactivity (AHR) was not apparent in this specific Brown Norway model in sensitized animals after a single or multiple challenges although eosinophil influx was seen in the same animals. In conclusion, this is a convenient pre‐clinical model (incorporating the measurement of biomarkers and functional responses) for screening novel small molecule inhibitors and/or biotherapeutics targeted against T cell/eosinophil infiltration/activation.

Critical Role for T Cells in Sephadex-Induced Airway Inflammation: Pharmacological and Immunological Characterization and Molecular Biomarker Identification

Intratracheal instillation of Sephadex particles is a convenient model for assessing the impact of potential anti-inflammatory compounds on lung eosinophilia thought to be a key feature in asthma pathophysiology. However, the underlying cellular and molecular mechanisms involved are poorly understood. We have studied the time course of Sephadex-induced lung eosinophilia, changes in pulmonary T cell numbers, and gene and protein expression as well as the immunological and pharmacological modulation of these inflammatory indices in the Sprague Dawley rat. Sephadex increased T cell numbers (including CD4+ T cells) and evoked a pulmonary eosinophilia that was associated with an increase in gene/protein expression of the Th2-type cytokines IL-4, IL-5, and IL-13 and eotaxin in lung tissue. Sephadex instillation also induced airway hyperreactivity to acetylcholine and bradykinin. A neutralizing Ab (R73) against the αβ-TCR caused 54% depletion of total (CD2+) pulmonary T cells accompanied by a significant inhibition of IL-4, IL-13 and eotaxin gene expression together with suppression (65% inhibition) of eosinophils in lung tissue 24 h after Sephadex treatment. Sephadex-induced eosinophilia and Th2 cytokine gene and/or protein expression were sensitive to cyclosporin A and budesonide, compounds that inhibit T cell function, suggesting a pivotal role for T cells in orchestrating Sephadex-induced inflammation in this model.

Effect of the p38 kinase inhibitor, SB 203580, on sephadex induced airway inflammation in the rat

SB 203580 is a pyridinyl imidazole compound which inhibits the release of pro-inflammatory cytokines, such as tumour necrosis factor-alpha (TNF-alpha) and interleukin-1beta (IL-1beta), in vitro and in vivo by inhibiting p38 mitogen-activated protein kinase (MAPK). The present study investigated the effects of SB 203580 in a model of airway inflammation induced by the topical administration of Sephadex into the rat airways. This inflammatory response is characterized by the development of lung oedema, airway tissue inflammatory cell recruitment and an increase in lung TNF-alpha and IL-1beta levels. Sephadex-induced lung oedema was accompanied by a significant increase in lung tissue TNF-alpha but not IL-1beta levels. There was also a significant increase in lung tissue macrophages and an increase in eosinophils which did not reach significance. SB 203580 administration significantly inhibited lung oedema (ED50=18 mg x kg(-1)) in a dose-related manner but was without significant effect on lung tissue cell recruitment or cytokine levels. These data suggest that the increase in tumour necrosis factor-alpha and lung oedema are separate processes which both contribute to Sephadex pathology. Furthermore, the inhibitory effect of SB 203580 on Sephadex-induced lung oedema suggests that p38 kinase inhibitors may be of use in pulmonary pathologies in which lung oedema is a feature.