Clare O’Connor

Systemic and pulmonary oxidative stress in idiopathic pulmonary fibrosis.

An oxidant/antioxidant imbalance has been proposed in patients with idiopathic pulmonary fibrosis (IPF). We tested this hypothesis by measuring various parameters of the oxidant/antioxidant balance in the plasma of 12 patients with IPF (7 nonsmokers and 5 smokers); in the bronchoalveolar lavage fluid (BALF) of 24 patients with IPF (17 nonsmokers and 7 smokers) and 31 healthy subjects (23 nonsmokers and 8 smokers). The trolox equivalent antioxidant capacity (TEAC) in plasma and BALF was lower in nonsmoking patients with IPF (plasma 0.55+/-0.1 mM, p<.001; BALF 4.8+/-1.2 microM, mean +/-SEM, p<.01), compared with healthy nonsmokers (plasma 1.33+/-0.03 mM; BALF 10+/-2 microM). Similar trends in plasma and BALF TEAC were observed in smoking patients with IPF in comparison with healthy smokers. The decrease in BALF TEAC was concomitant with a decrease in BALF protein thiol levels, but the decrease TEAC levels in plasma in IPF patients was not accompanied by a decrease in protein thiol levels. Reduced glutathione (GSH) was lower in BALF in nonsmoking patients with IPF (1.0+/-0.1 microM) compared with healthy nonsmokers (2.3+/-0.2 microM, p<.001). In contrast, GSH levels were higher in smoking patients with IPF (5.2+/-1.1 microM, p<.001) than in nonsmoking patients. GSSG levels were not different in any of the groups. The levels of products of lipid peroxidation measured as thiobarbituric acid reactive substances (TBARS) in plasma and BALF were significantly increased in both smoking (plasma 2.2+/-0.5 microM, p<.01; BALF 0.18+/-0.04 microM, p<.001), and nonsmoking (plasma 2.1+/-0.3 microM, p<.01; BALF 0.22+/-0.05 microM, p<.001) IPF patients, compared with healthy nonsmokers (plasma 1.4+/-0.3 microM; BALF 0.05+/-0.004 microM). These data show evidence of oxidant/antioxidant imbalance in the lungs of patients with IPF, which is also reflected as systemic oxidant stress.

Sustained hypercapnic acidosis during pulmonary infection increases bacterial load and worsens lung injury

Objective:Hypercapnic acidosis is commonly permitted in patients with acute respiratory distress syndrome during the use of protective ventilation strategies. Hypercapnic acidosis is also a common complication of multiple lung diseases and is associated with a poor prognosis, although the mechanisms by which it leads to increased mortality is not known. Previous studies using noninfective models of lung injury show that acute (<6 hrs) hypercapnic acidosis reduced lung damage by an anti-inflammatory effect. We hypothesized that this anti-inflammatory effect would be detrimental in vivo in the presence of untreated bacterial infection and sustained hypercapnia (>48 hrs) and, furthermore, that if bacterial reproduction were controlled by antibiotic therapy, then the anti-inflammatory effects of hypercapnic acidosis would no longer prove detrimental. Design:This study was a prospective, randomized animal study. Setting:This study was conducted at a university research laboratory. Subjects:Study subjects were adult male Wistar-Kyoto rats. Interventions:After intratracheal instillation of Escherichia coli under general anesthesia, rats were housed in normocapnic (21% O2, 0% CO2) or hypercapnic (21% O2, 5% CO2) environments for 2 days. Rats were then reanesthetized for assessment of physiological and quantitative stereologic indices of lung damage, quantitative bacterial counts, and neutrophil phagocytosis. Measurements and Main Results:Hypercapnic acidosis was associated with higher lung bacterial colony counts, more structural damage, and lower static lung compliance than normocapnia. Neutrophils isolated from hypercapnic rats demonstrated impaired phagocytosis. In a further separate series of experiments, in which rats were given antibiotic therapy, lung damage was not different between normocapnic and hypercapnic acidosis groups. Conclusions:Prolonged hypercapnic acidosis worsened bacterial infection-induced lung injury. Our findings suggest an immunosuppressive effect of hypercapnic acidosis and have important implications for protective ventilation strategies that permit hypercapnic acidosis in patients with adult respiratory distress syndrome and in the management of hypercapnic acidosis during infective exacerbations of chronic obstructive pulmonary disease and other lung diseases.

The SERPINE2 Gene and Chronic Obstructive Pulmonary Disease

To the Editor: In the February 2006 issue of the Journal, DeMeo et al.1 identified SERPINE2 as a positional candidate gene for susceptibility to chronic obstructive pulmonary disease (COPD [MIM 606963]) and reported on the association of polymorphic variants of this gene with early-onset disease in a family-based study and with severe disease in a case-control study. With early prior information provided by the authors, we have independently tested for an association of the SERPINE2 gene with COPD in the largest case-control study reported to date. Our study consists of 1,018 COPD cases and 911 controls prospectively recruited from six European centers. We have provided details about the patients elsewhere.2 The study population was screened for genotypes at the Medical Research Council (United Kingdom) Gene Services Unit for five SNPs (table 1) in the SERPINE2 gene. All the SNPs evaluated were reported in the study by DeMeo et al. as associated with disease, with three of the five associated with disease in both the family and case-control study cohorts they assessed. Table 1.  LD between SERPINE2 SNPs Expressed as r2[Note] We examined linkage disequilibrium (LD) between the SNPs (table 1) and evaluated SNP and haplotype associations as described elsewhere.2 DeMeo et al. did not report specific LD values between SNPs or noncontiguous SNPs contributing to haplotypes. SNPs and genotype frequencies in the study population are shown in table 2. We found no significant deviation from Hardy-Weinberg equilibrium in frequencies for any of the SNPs. Table 2.  SERPINE2 Genotype and Allele Frequencies in Controls and COPD Cases We found no association between any of the SERPINE2 SNPs and disease, in examining both the allelic and genotype distributions, although our study was well powered to detect associations of the magnitude observed by DeMeo et al., and we would have expected to see these frequency differences with the SNPs that we studied. We also failed to find a relationship between any haplotypes of these SNPs and disease (data not shown). It was of interest that the allele and genotype frequencies observed in our control and patient groups were virtually identical to those observed in control subjects by DeMeo et al., indicating a common distribution of SERPINE2 variants in the European and North American populations studied. Our previous study has also shown that there is no evidence of population stratification in our sample. Patients evaluated in both the family-based and case-control studies reported by DeMeo et al. represent a severe subset of the disease spectrum. To determine whether the association with SERPINE2 noted by DeMeo et al. was related to disease severity, we also analyzed SNP allele and genotype frequencies in the subgroup of our patients with forced expiratory volume at 1 s ⩽45% (n=388), a group that represents severe disease, but we failed to observe any association. Our inability to replicate the observations of DeMeo et al. in a more highly powered case-control study may be related to differences in the disease phenotype of the patients studied, because our patients included those with and without emphysema. The possibility, however, that the associations reported by DeMeo et al. represent false-positive results must also be considered. In this respect, it is of note that, in the study by DeMeo et al., different associations were reported for SNPs that are in linkage disequilibrium with one another. For example, rs3795879 and rs3795877 have an r2 value of 1 in HapMap, yet different associations with quantitative spirometric phenotypes were reported for the family study. Similarly, rs1438831 and rs920251 are in complete LD, with an r2 value of 1 in HapMap and 0.95 in our study; however, in DeMeo et al.’s case-control study, the allele and genotype frequencies of rs920251 were found to be significantly associated with disease (P values of 0.015 and 0.011, respectively), whereas no similar association was observed for rs1438831. In both instances, the almost complete linkage between these pairs of SNPs would be expected to result in similar associations. These results underline the importance of replication in other large independent studies before SERPINE2 can be unequivocally assigned as a candidate gene for COPD. It is becoming apparent that, to detect modest genetic effects for complex diseases, several independent studies may be required and the data may need to be subjected to meta-analysis. For example, this approach has been used to study Alzheimer disease (see Alzheimers Association Web site). Similar approaches need to be adopted for COPD. It would also be helpful to have similar criteria adapted for phenotypic selection and to plan prospective studies on this basis.

CD18 Dependency of Transendothelial Neutrophil Migration Differs During Acute Pulmonary Inflammation

Neutrophil extravasation during inflammation can occur either by a mechanism that requires the neutrophil integrin complex, CD18, or by an alternative CD18-independent route. Which of the two pathways is used has been shown to depend on the site and nature of the inflammatory insult. More recent evidence suggests that selection may also depend on whether inflammation is chronic or acute, but why this is the case remains unknown. Using an in vitro model that supports both migratory mechanisms, we examined the CD18 dependency of migration of neutrophils isolated from patients with either chronic or acute pulmonary infection. Chronic neutrophils were found to behave like normal neutrophils by migrating to IL-8 and leukotriene B4 using the CD18-independent pathway, but to the bacterial product, FMLP, using the CD18-dependent route. In contrast, migration of acute neutrophils to all of these stimuli was CD18 dependent. Normal neutrophils could be manipulated to resemble acute neutrophils by exposing them to FMLP before migration, which resulted in a “switch” from the CD18-independent to -dependent mechanism during migration to IL-8 or leukotriene B4. Although treatment of normal neutrophils with FMLP caused selective down-regulation of the IL-8 receptor, CXCR2, and acute neutrophils were found to have less CXCR2 than normal, a functional relationship between decreased CXCR2 and selection of CD18-dependent migration was not demonstrated. Results indicate that selection of the CD18-dependent or -independent migration mechanism can be controlled by the neutrophil and suggest that the altered CD18 requirements of acute neutrophils may be due to priming in the circulation during acute infection.

Prediction of outcome in twin pregnancy with first and early second trimester ultrasound

Abstract Objective: To establish if first or second trimester biometry is a useful adjunct in the prediction of adverse perinatal outcome in twin pregnancy. Methods: A consecutive cohort of 1028 twin pregnancies was enrolled for the Evaluation of Sonographic Predictors of Restricted growth in Twins (ESPRiT) study, a prospective study conducted at eight academic centers. Outcome data was recorded for 1001 twin pairs that completed the study. Ultrasound biometry was available for 960 pregnancies. Biometric data obtained between 11 and 22 weeks were evaluated as predictors of a composite of adverse perinatal outcome (mortality, hypoxic ischemic encephalopathy, periventricular leukomalacia, necrotizing enterocolitis, respiratory distress, or sepsis), preterm delivery (PTD) and birthweight discordance greater than 18% (18% BW). Outcomes were adjusted for chorionicity and gestational age using Cox Proportional Hazards regression. Results: Differences in crown-rump length (CRL) were not predictive of adverse perinatal outcome. Between 14 and 22 weeks, a difference in abdominal circumference (AC) of more than 10% was the most useful predictor of adverse outcome, PTD and 18% or more BW discordance in all twins. Overall the strongest correlation was observed for intertwin differences in biometry between 18 and 22 weeks. Conclusion: Biometry in the early second trimester can successfully identify twin pregnancies at increased risk. Intertwin AC difference of greater than 10% between 14 and 22 weeks gestation was the best individual predictor of perinatal risk in all twins. Sonographic biometry in the early second trimester should therefore be utilized to establish perinatal risk, thus allowing prenatal care to be improved.

Mature human neutrophils constitutively express the transcription factor EGR-1.

The immediate early response gene, Early Growth Response 1 (EGR-1) has emerged as a central regulator of early inflammatory and immune processes by rapidly regulating the transcription of a wide array of downstream effector genes. Neutrophils, which are among the first circulating leukocytes to respond to inflammatory signals, exhibit a broad set of transcriptional changes immediately upon exposure to inflammatory and pathogenic stimuli. Such transcriptional changes are likely to be controlled by early gene transcription factors such as EGR-1. We therefore examined the regulation and role of EGR-1 in mature human neutrophils exposed to the inflammatory stimuli fMLP and IL-8. We report that human neutrophils rapidly and transiently up-regulate EGR-1 mRNA upon stimulation with fMLP or IL-8. However in contrast to that seen in other cells, EGR-1 mRNA expression profiles were not predictive of protein expression. Instead, we show that human neutrophils constitutively express EGR-1 protein. The cellular content of EGR-1 did not change over time or upon neutrophil activation. Confocal microscopy revealed that EGR-1 was present in both the cytoplasm and nuclei of un-stimulated neutrophils and that activation did not change this subcellular localization or promote nuclear translocation. Using chromatin immunoprecipitation, we demonstrate that EGR-1 is associated with the promoter regions of the immune regulatory genes IL-1 beta, TGFbeta-1 and MIF in both resting and activated neutrophils with increased promoter association observed upon cell activation. This novel pattern of EGR-1 protein expression may underlie the ability of the neutrophil to respond rapidly to inflammatory stimuli.

Human endothelial cells cultured on microporous filters used for leukocyte transmigration studies form monolayers on both sides of the filter.

SummaryA growing number of studies on the mechanism of leukocyte transendothelial migration use endothelial cells grown on microporous filters as an in vitro model of endothelium. Ultrastructural examination of such a model system previously demonstrated that human pulmonary artery endothelial cells (HPAEC) formed confluent monolayers on both sides of the 3-µm-pore filter (Mackarel et al., 1999). To determine whether this was a characteristic specific to pulmonary artery endothelial cells, the growth characteristics of a human pulmonary microvascular endothelial cell type (HMVEC-L) and the widely used human umbilical vein endothelial cells (HUVEC) on 3-µm microporous filters were examined by transmission electron microscopy (TEM). Similar to HPAEC, HMVEC-L and HUVEC were also found to grow on both sides of the filter. All three endothelial cell types were capable of migrating through the 3 µm pores of the filter to form a monolayer on the filter underside. The endothelial cells on the underside were orientated in an inverted position with the luminal surface facing away from the filter. Such ‘bilayer’ formation was observed at a range of seeding densities and in different culture media. Despite the presence of a bilayer of endothelial cells, TEM demonstrated that neutrophils migrated successfully across the cell-filter-cell system. Previous transmigration reports in which an in vitro model similar to ours was used have often assumed only one layer of endothelial cells. The observations reported here indicate that while endothelial cells on microporous filters are useful models for examining leukocyte-endothelial interactions, they are not appropriate for studies examining endothelial cell ‘sidedness.’

The relationship between maternal body composition in early pregnancy and foetal mid-thigh soft-tissue thickness in the third trimester in a high-risk obstetric population

Abstract Maternal obesity is an emerging challenge in contemporary obstetrics. To date there has been no study analysing the relationship between specific maternal body composition measurements and foetal soft-tissue measurements. The aim of this study was to determine whether measurement of maternal body composition at booking predicts foetal soft-tissue trajectories in the third trimester. We analysed the relationship between foetal thigh in the third trimester and both maternal BMI and body composition using the Tanita digital scales in the first trimester. Foetal subcutaneous thigh tissue measurements were obtained at intervals of 28, 32 and 36 weeks of gestation. A total of 160 women were identified. There was a direct correlation between MTST at 36 weeks and BMI (p = .002). There was a positive correlation between MTST at 36 weeks and leg fat mass (p = .13) and leg fat free mass (p = .013). There was a positive correlation between arm fat free mass and MTST at 36 weeks. We showed there is an association between maternal fat distribution and foetal subcutaneous thigh tissue measurements. MTST may be more useful in determining if a child is at risk of macrosomia. Impact statement Previous studies have suggested that maternal obesity programmes intrauterine foetal adiposity and growth. The aim of this study was to examine the relationship in a high-risk obstetric population between measurements of maternal body composition in early pregnancy and the assessment of foetal adiposity in the third trimester using serial ultrasound measurements of mid-thigh soft-tissue thickness. BMI is only a surrogate measurement of fat and does not measure fat distribution. Our study shows the distribution of both maternal fat and fat-free mass in early pregnancy may be positively associated with foetal soft-tissue measurements in the third trimester. Maternal arthropometric measurements other than BMI may help predict babies at risk of macrosomia and neonatal adiposity.

Induced sputum and BAL analysis in COPD

An essential component of airways in flammation research is the examination of airway luminal fluid. Since its development as a sampling technique over 20 years ago, bronchoalveolar lavage (BAL) has become the most widely used method of evaluation of distal airway and alveolar inflammation. The widespread use of BAL reflects its relative ease and lack of clinical complications, particularly in comparison to airway or lung biopsy. However, while BAL is now a universally used tool in research and diagnosis of interstitial lung diseases (ILDs) its use in evaluating airway inflammation in COPD is less common. The lesser use of BAL in COPD studies reflects a lower level of tolerance of the procedure in patients with moderate to severe airway obstruction and greater difficulty in obtaining adequate samples from these same patient groups [1, 2].