The relationship between plasma cystatin C, mortality and acute respiratory distress syndrome subphenotype in the HARP-2 trial

Objective: To evaluate the performance of cystatin C as a prognostic and predictive marker in a trial of patients with acute respiratory distress syndrome (ARDS). Design, patients and setting: A retrospective analysis was performed on plasma samples from patients included in the HARP-2 (hydroxymethylglutaryl-CoA reductase inhibition with simvastatin in acute lung injury to reduce pulmonary dysfunction) trial - a multicentre, phase 2b trial carried out in general intensive care units across 40 hospitals in the United Kingdom and Ireland. Cystatin C concentrations in plasma obtained from 466 patients with ARDS (before they were randomly assigned in the trial) were quantified by ELISA (enzyme-linked immunosorbent assay). Results: In a univariate analysis, plasma cystatin C concentrations were significantly higher in patients with ARDS who did not survive past 28 days (odds ratio [OR], 1.39 [95% CI, 1.12-1.72]; P = 0.002). In a multivariate model adjusted for selected covariates, cystatin C concentrations remained higher among patients with ARDS who did not survive, although this did not reach statistical significance (OR, 1.28 [95% CI, 0.96-1.71]; P = 0.090). Cystatin C concentration was also significantly associated with hyperinflammatory ARDS (OR, 2.64 [95% CI, 1.83-3.89]; P < 0.001). In multivariate models adjusted for both cystatin C concentration and ARDS subphenotype, hyperinflammatory ARDS was prognostic for mortality (OR, 2.06 [95% CI, 1.16-3.64]; P = 0.013) but cystatin C concentration was not (OR, 1.16 [95% CI, 0.85-1.57]; P = 0.346). In a multivariate analysis, hyperinflammatory ARDS was predictive of a beneficial effect of simvastatin on mortality (OR, 2.05 [95% CI, 1.16-3.62]; P = 0.014) but cystatin C concentration was not (OR, 1.10 [95% CI, 0.77-1.56]; P = 0.614). Conclusion: The association between cystatin C concentration and mortality in ARDS may be dependent on inflammatory subphenotype. Cystatin C concentration does not appear to add to existing prognostic or predictive approaches.

Schistosoma mansoni immunomodulatory molecule Sm16/SPO-1/SmSLP is a member of the trematode-specific helminth defence molecules (HDMs)

BACKGROUND

Sm16, also known as SPO-1 and SmSLP, is a low molecular weight protein (~16kDa) secreted by the digenean trematode parasite Schistosoma mansoni, one of the main causative agents of human schistosomiasis. The molecule is secreted from the acetabular gland of the cercariae during skin invasion and is believed to perform an immune-suppressive function to protect the invading parasite from innate immune cell attack.

METHODOLOGY/PRINCIPAL FINDINGS

We show that Sm16 homologues of the Schistosomatoidea family are phylogenetically related to the helminth defence molecule (HDM) family of immunomodulatory peptides first described in Fasciola hepatica. Interrogation of 69 helminths genomes demonstrates that HDMs are exclusive to trematode species. Structural analyses of Sm16 shows that it consists predominantly of an amphipathic alpha-helix, much like other HDMs. In S. mansoni, Sm16 is highly expressed in the cercariae and eggs but not in adult worms, suggesting that the molecule is of importance not only during skin invasion but also in the pro-inflammatory response to eggs in the liver tissues. Recombinant Sm16 and a synthetic form, Sm16 (34-117), bind to macrophages and are internalised into the endosomal/lysosomal system. Sm16 (34-117) elicited a weak pro-inflammatory response in macrophages in vitro but also suppressed the production of bacterial lipopolysaccharide (LPS)-induced inflammatory cytokines. Evaluation of the transcriptome of human macrophages treated with a synthetic Sm16 (34-117) demonstrates that the peptide exerts significant immunomodulatory effects alone, as well as in the presence of LPS. Pathways most significantly influenced by Sm16 (34-117) were those involving transcription factors peroxisome proliferator-activated receptor (PPAR) and liver X receptors/retinoid X receptor (LXR/RXR) which are intricately involved in regulating the cellular metabolism of macrophages (fatty acid, cholesterol and glucose homeostasis) and are central to inflammatory responses.

CONCLUSIONS/SIGNIFICANCE

These results offer new insights into the structure and function of a well-known immunomodulatory molecule, Sm16, and places it within a wider family of trematode-specific small molecule HDM immune-modulators with immuno-biotherapeutic possibilities.

Preclinical Evaluation of Dose-Volume Effects and Lung Toxicity Occurring In and Out-of-Field

PURPOSE

The aim of this study was to define the dose and dose-volume relationship of radiation-induced pulmonary toxicities occurring in and out-of-field in mouse models of early inflammatory and late fibrotic response.

MATERIALS AND METHODS

Early radiation-induced inflammation and fibrosis were investigated in C3H/NeJ and C57BL/6J mice, respectively. Animals were irradiated with 20 Gy delivered to the upper region of the right lung as a single fraction or as 3 consecutive fractions using the Small Animal Radiation Research Platform (Xstrahl Inc, Camberley, UK). Cone beam computed tomography was performed for image guidance before irradiation and to monitor late toxicity. Histologic sections were examined for neutrophil and macrophage infiltration as markers of early inflammatory response and type I collagen staining as a marker of late-occurring fibrosis. Correlation was evaluated with the dose-volume histogram parameters calculated for individual mice and changes in the observed cone beam computed tomography values.

RESULTS

Mean lung dose and the volume receiving over 10 Gy (V10) showed significant correlation with late responses for single and fractionated exposures in directly targeted volumes. Responses observed outside the target volume were attributed to nontargeted effects and showed no dependence on either mean lung dose or V10.

CONCLUSIONS

Quantitative assessment of normal tissue response closely correlates early and late pulmonary response with clinical parameters, demonstrating this approach as a potential tool to facilitate clinical translation of preclinical studies. Out-of-field effects were observed but did not correlate with dosimetric parameters, suggesting that nontargeted effects may have a role in driving toxicities outside the treatment field.

Inhibition of ataxia telangiectasia related-3 (ATR) improves therapeutic index in preclinical models of non-small cell lung cancer (NSCLC) radiotherapy

BACKGROUND AND PURPOSE

To evaluate the impact of ATR inhibition using AZD6738 in combination with radiotherapy on the response of non-small cell lung cancer (NSCLC) tumour models and a murine model of radiation induced fibrosis.

MATERIALS AND METHODS

AZD6738 was evaluated as a monotherapy and in combination with radiation in vitro and in vivo using A549 and H460 NSCLC models. Radiation induced pulmonary fibrosis was evaluated by cone beam computed tomography (CBCT) and histological staining.

RESULTS

AZD6738 specifically inhibits ATR kinase and enhanced radiobiological response in NSCLC models but not in human bronchial epithelial cells (HBECs) in vitro. Significant tumour growth delay was observed in cell line derived xenografts (CDXs) of H460 cells (p<0.05) which were less significant in A549 cells. Combination of AZD6738 with radiotherapy showed no significant change in lung tissue density by CBCT (p>0.5) and histological scoring of radiation induced fibrosis (p>0.5).

CONCLUSION

Inhibition of ATR with AZD6738 in combination with radiotherapy increases tumour growth delay without observable augmentation of late radiation induced toxicity further underpinning translation towards clinical evaluation in NSCLC.

A secretory leukocyte protease inhibitor variant with improved activity against lung infection

Secretory leukocyte protease inhibitor (SLPI) is an important respiratory tract host defense protein, which is proteolytically inactivated by excessive neutrophil elastase (NE) during chronic Pseudomonas infection in the cystic fibrosis (CF) lung. We generated two putative NE-resistant variants of SLPI by site-directed mutagenesis, SLPI-A16G and SLPI-S15G-A16G, with a view to improving SLPI's proteolytic stability. Both variants showed enhanced resistance to degradation in the presence of excess NE as well as CF patient sputum compared with SLPI-wild type (SLPI-WT). The ability of both variants to bind bacterial lipopolysaccharides and interact with nuclear factor-κB DNA binding sites was also preserved. Finally, we demonstrate increased anti-inflammatory activity of the SLPI-A16G protein compared with SLPI-WT in a murine model of pulmonary Pseudomonas infection. This study demonstrates the increased stability of these SLPI variants compared with SLPI-WT and their therapeutic potential as a putative anti-inflammatory treatment for CF lung disease.

Respiratory syncytial virus infections enhance cigarette smoke induced COPD in mice

Respiratory syncytial viral (RSV) infections are a frequent cause of chronic obstructive pulmonary disease (COPD) exacerbations, which are a major factor in disease progression and mortality. RSV is able to evade antiviral defenses to persist in the lungs of COPD patients. Though RSV infection has been identified in COPD, its contribution to cigarette smoke-induced airway inflammation and lung tissue destruction has not been established. Here we examine the long-term effects of cigarette smoke exposure, in combination with monthly RSV infections, on pulmonary inflammation, protease production and remodeling in mice. RSV exposures enhanced the influx of macrophages, neutrophils and lymphocytes to the airways of cigarette smoke exposed C57BL/6J mice. This infiltration of cells was most pronounced around the vasculature and bronchial airways. By itself, RSV caused significant airspace enlargement and fibrosis in mice and these effects were accentuated with concomitant smoke exposure. Combined stimulation with both smoke and RSV synergistically induced cytokine (IL-1α, IL-17, IFN-γ, KC, IL-13, CXCL9, RANTES, MIF and GM-CSF) and protease (MMP-2, -8, -12, -13, -16 and cathepsins E, S, W and Z) expression. In addition, RSV exposure caused marked apoptosis within the airways of infected mice, which was augmented by cigarette smoke exposure. RSV and smoke exposure also reduced protein phosphatase 2A (PP2A) and protein tyrosine phosphates (PTP1B) expression and activity. This is significant as these phosphatases counter smoke-induced inflammation and protease expression. Together, these findings show for the first time that recurrent RSV infection markedly enhances inflammation, apoptosis and tissue destruction in smoke-exposed mice. Indeed, these results indicate that preventing RSV transmission and infection has the potential to significantly impact on COPD severity and progression.

Glucocorticoid receptor β and histone deacetylase 1 and 2 expression in the airways of severe asthma

RATIONALE

Upregulation of glucocorticoid receptor β (GRβ) has been implicated in steroid resistance in severe asthma, although previous studies are conflicting. GRβ has been proposed as a dominant negative isoform of glucocorticoid receptor α (GRα) but it has also been suggested that GRβ can cause steroid resistance via reduced expression of histone deacetylase 2 (HDAC2), a key regulator of steroid responsiveness in the airway.

OBJECTIVES

To examine GRβ, GRα, HDAC1 and HDAC2 expression at transcript and protein levels in bronchial biopsies from a large series of patients with severe asthma, and to compare the findings with those of patients with mild to moderate asthma and healthy volunteers.

METHODS

Bronchoscopic study in two UK centres with real-time PCR and immunohistochemistry performed on biopsies, western blotting of bronchial epithelial cells and immunoprecipitation with anti-GRβ antibody.

MEASUREMENTS AND MAIN RESULTS

Protein and mRNA expression for GRα and HDAC2 did not differ between groups. GRβ mRNA was detected in only 13 of 73 samples (seven patients with severe asthma), however immunohistochemistry showed widespread epithelial staining in all groups. Western blotting of bronchial epithelial cells with GRβ antibody detected an additional 'cross-reacting' protein, identified as clathrin. HDAC1 expression was increased in patients with severe asthma compared with healthy volunteers.

CONCLUSIONS

GRβ mRNA is expressed at low levels in a minority of patients with severe asthma. HDAC1 and HDAC2 expression was not downregulated in severe asthma. These data do not support upregulated GRβ and resultant reduced HDAC expression as the principal mechanism of steroid resistance in severe asthma. Conflicting GRβ literature may be explained in part by clathrin cross-reactivity with commercial antibodies.

Elafin, an elastase-specific inhibitor, is cleaved by its cognate enzyme neutrophil elastase in sputum from individuals with cystic fibrosis

Elafin is a neutrophil serine protease inhibitor expressed in lung and displaying anti-inflammatory and anti-bacterial properties. Previous studies demonstrated that some innate host defense molecules of the cystic fibrosis (CF) and chronic obstructive pulmonary disease airways are impaired due to increased proteolytic degradation observed during lung inflammation. In light of these findings, we thus focused on the status of elafin in CF lung. We showed in the present study that elafin is cleaved in sputum from individuals with CF. Pseudomonas aeruginosa-positive CF sputum, which was found to contain lower elafin levels and higher neutrophil elastase (NE) activity compared with P. aeruginosa-negative samples, was particularly effective in cleaving recombinant elafin. NE plays a pivotal role in the process as only NE inhibitors are able to inhibit elafin degradation. Further in vitro studies demonstrated that incubation of recombinant elafin with excess of NE leads to the rapid cleavage of the inhibitor. Two cleavage sites were identified at the N-terminal extremity of elafin (Val-5-Lys-6 and Val-9-Ser-10). Interestingly, purified fragments of the inhibitor (Lys-6-Gln-57 and Ser-10-Gln-57) were shown to still be active for inhibiting NE. However, NE in excess was shown to strongly diminish the ability of elafin to bind lipopolysaccharide (LPS) and its capacity to be immobilized by transglutamination. In conclusion, this study provides evidence that elafin is cleaved by its cognate enzyme NE present at excessive concentration in CF sputum and that P. aeruginosa infection promotes this effect. Such cleavage may have repercussions on the innate immune function of elafin.

The role of secretory leucoprotease inhibitor in the resolution of inflammatory responses

Chronic lung disease is one of the most common causes of death and disability worldwide. This group of diseases is characterized by a protease burden, an infective process and a dominant pro-inflammatory profile. While SLPI (secretory leucoprotease inhibitor) was initially identified as a serine protease inhibitor, it has since been shown that SLPI possesses other properties distinct from those associated with its antiprotease capabilities that play an important role in protecting the host from infection and injury. In the course of this review, we will highlight the findings from a range of studies that illustrate the multiple functions of SLPI and its role in the resolution of the immune response.

Secretory leucoprotease inhibitor binds to NF-kappaB binding sites in monocytes and inhibits p65 binding

Secretory leucoprotease inhibitor (SLPI) is a nonglycosylated protein produced by epithelial cells. In addition to its antiprotease activity, SLPI has been shown to exhibit antiinflammatory properties, including down-regulation of tumor necrosis factor α expression by lipopolysaccharide (LPS) in macrophages and inhibition of nuclear factor (NF)-κB activation in a rat model of acute lung injury. We have previously shown that SLPI can inhibit LPS-induced NF-κB activation in monocytic cells by inhibiting degradation of IκBα without affecting the LPS-induced phosphorylation and ubiquitination of IκBα. Here, we present evidence to show that upon incubation with peripheral blood monocytes (PBMs) and the U937 monocytic cell line, SLPI enters the cells, becoming rapidly localized to the cytoplasm and nucleus, and affects NF-κB activation by binding directly to NF-κB binding sites in a site-specific manner. SLPI can also prevent p65 interaction with the NF-κB consensus region at concentrations commensurate with the physiological nuclear levels of SLPI and p65. We also demonstrate the presence of SLPI in nuclear fractions of PBMs and alveolar macrophages from individuals with cystic fibrosis and community-acquired pneumonia. Therefore, SLPI inhibition of NF-κB activation is mediated, in part, by competitive binding to the NF-κB consensus-binding site.

Sodium depletion in conscious cynomolgus monkeys attenuates baroreflex sensitivity independently of prostaglandins

We tested the hypothesis that baroreflex attenuation during sodium depletion is due to increased prostaglandin (PG) levels. We studied baroreflex sensitivity before and after PG synthesis inhibition in conscious cynomolgus monkeys. Arterial pressure and pulse interval (PI) were measured during intravenous infusions of phenylephrine (1-20 micrograms.kg-1.min-1, n = 6) and nitroprusside (1-10 micrograms.kg-1.min-1, n = 7). Infusions were repeated 30 min after indomethacin (Indo, 6 mg/kg iv). The slope (in ms/mmHg) of the mean arterial blood pressure-PI plot was used as an index of baroreflex sensitivity. Plasma renin activity (PRA) was elevated (47.9 +/- 9.7 vs. 8.8 +/- 3.3 ng angiotensin I.ml-1.h-1) after sodium depletion (P < 0.05). Baroreflex sensitivity to hypotension and hypertension was significantly (P < 0.05) attenuated by sodium depletion (3.69 +/- 0.9 vs. 0.9 +/- 0.1 ms/mmHg and 7.38 +/- 0.6 vs. 5.04 +/- 0.9 ms/mmHg, respectively). Indo decreased PRA to 28.6 +/- 5.7 ng angiotensin I.ml-1.h-1 (P < 0.05) in sodium-depleted monkeys and decreased heart rate -21 +/- 3.7 from a baseline of 166 +/- 9.40 beats/min in normal monkeys and -22 +/- 2.9 from a baseline of 191 +/- 7.9 beats/min in low-sodium monkeys (P < 0.05). Indo did not significantly change baroreflex sensitivity in either group. Thus the baroreflex was attenuated in conscious nonhuman primates during sodium depletion; acute PG synthesis blockade did not improve baroreflex sensitivity. Indo decreased heart rate without changing arterial pressure; suggesting that PGs caused a downward resetting of the pressure-heart rate relationship.

The site and mechanism of dioxygen reduction in bovine heart cytochrome c oxidase

The site and mechanism of dioxygen reduction in cytochrome c oxidase from bovine heart muscle have been investigated. The rate of cytochrome c2+ oxidation by O2 is shown to be affected by several factors: 1) pH, with optima at 5.65 and 6.0, 2) temperature between 0 and 29 degrees C, with E alpha = 13 kcal mol-1, 3) D2O exchange, with a reduction in rate of 50% or more at the pH optima, and 4) the addition of ethylene glycol or glycerol, which significantly lowers the rate. The extremely narrow (delta vCO approximately 4 cm-1) infrared stretch bands at approximately 1964 and approximately 1959 cm-1 for liganded CO are only slightly affected by factors 1-4 or by changes in the oxidation state of metals other than the heme alpha 3 iron. These results indicate a stable, unusually immobile O2 reduction site well-isolated from the external medium, a characteristic expected to be important for oxidase function. Precise stereochemical positioning of hydrogen donors adjacent to O2 liganded to heme alpha 3 iron can be expected in order to achieve the optimization of the time/distance relationships required for enzyme catalysis. These findings support a novel mechanism of O2 reduction via a hydroperoxide intermediate within a reaction pocket that experiences little change in conformation during the hydrogen and electron transfer steps.