Update in Diffuse Parenchymal Lung Disease 2006

Asymmetric dimethyl-arginine metabolism in a murine model of cigarette smoke-mediated lung inflammation

There is increasing evidence that the endogenous nitric oxide synthase (NOS) inhibitor asymmetric dimethyl-arginine (ADMA) is involved in the pathogenesis of chronic lung diseases. One important regulator of this molecule is the ADMA-metabolizing enzyme dimethyl-arginine dimethyl-aminohydrolase (DDAH). The objective of this study was to determine whether perturbation of the ADMA-DDAH pathway contributes to lung inflammation following exposure to cigarette smoke (CS). For these studies, wild-type and DDAH transgenic mice were sham or CS-exposed. Serum ADMA levels were determined by mass spectrometry. ADMA content and DDAH expression were also visualized in mouse lung tissue by immunohistochemistry. DDAH expression was determined by real-time quantitative PCR (qPCR). Inflammation was assessed by H&E staining and analyses of total cell counts and fluid tumor necrosis factor (TNF)-α levels (using ELISA) in lung lavage fluid. NF-κB binding activity in mouse lung epithelial (LA-4) cells was assessed by a transcription factor-binding assay. The results indicated that the concentration of serum ADMA was increased following exposure to CS, and this corresponded with increased ADMA content in bronchial epithelial cells in lung tissue. Total lung DDAH expression was significantly decreased in lung tissue and cultured LA-4 cells following CS exposure. Addition of exogenous ADMA increased CSE-mediated NF-κB binding activity and TNFα production in LA-4 cells more than 2-fold compared to that in CSE-exposed controls. CS-mediated lung inflammation was significantly attenuated in DDAH transgenic mice compared to in wild-type controls. These findings demonstrated that lung ADMA metabolism was altered in mice following CS exposure and suggested that ADMA played a role in CS-mediated inflammation through increasing the presence of inflammatory mediators in lung epithelial cells.

Proteomic biomarkers for acute interstitial lung disease in gefitinib-treated Japanese lung cancer patients

Interstitial lung disease (ILD) events have been reported in Japanese non-small-cell lung cancer (NSCLC) patients receiving EGFR tyrosine kinase inhibitors. We investigated proteomic biomarkers for mechanistic insights and improved prediction of ILD. Blood plasma was collected from 43 gefitinib-treated NSCLC patients developing acute ILD (confirmed by blinded diagnostic review) and 123 randomly selected controls in a nested case-control study within a pharmacoepidemiological cohort study in Japan. We generated ∼7 million tandem mass spectrometry (MS/MS) measurements with extensive quality control and validation, producing one of the largest proteomic lung cancer datasets to date, incorporating rigorous study design, phenotype definition, and evaluation of sample processing. After alignment, scaling, and measurement batch adjustment, we identified 41 peptide peaks representing 29 proteins best predicting ILD. Multivariate peptide, protein, and pathway modeling achieved ILD prediction comparable to previously identified clinical variables; combining the two provided some improvement. The acute phase response pathway was strongly represented (17 of 29 proteins, p = 1.0×10(-25)), suggesting a key role with potential utility as a marker for increased risk of acute ILD events. Validation by Western blotting showed correlation for identified proteins, confirming that robust results can be generated from an MS/MS platform implementing strict quality control.

Asymmetric dimethylarginine potentiates lung inflammation in a mouse model of allergic asthma

Nitric oxide (NO), formed by nitric oxide synthase (NOS), is an important mediator of lung inflammation in allergic asthma. Asymmetric dimethylarginine (ADMA), a competitive endogenous inhibitor of NOS, is metabolized by the enzyme dimethylarginine dimethylaminohydrolase (DDAH). Elevated ADMA has been shown to affect lung function in mice, and by inhibiting NOS it alters NO and reactive oxygen species production in mouse lung epithelial cells. However, the effects of altered ADMA levels during lung inflammation have not been explored. A model of allergen-induced airway inflammation was utilized in combination with the modulation of endogenous circulating ADMA levels in mice. Airway inflammation was assessed by quantifying inflammatory cell infiltrates in lung lavage and by histology. Lung DDAH expression was assessed by quantitative PCR and immunohistochemistry. Nitrite levels were determined in lung lavage fluid as a measure of NO production. iNOS expression was determined by immunohistochemistry, immunofluorescence, Western blot, and quantitative PCR. NF-κB binding activity was assessed by a transcription factor binding assay. Allergen-induced lung inflammation was potentiated in mice with elevated circulating ADMA and was reduced in mice overexpressing DDAH. Elevated ADMA reduced nitrite levels in lung lavage fluid in both allergen-challenged and control animals. ADMA increased iNOS expression in airway epithelial cells in vivo following allergen challenge and in vitro in stimulated mouse lung epithelial cells. ADMA also increased NF-κB binding activity in airway epithelial cells in vitro. These data support that ADMA may play a role in inflammatory airway diseases such as asthma through modulation of iNOS expression in lung epithelial cells.

Outcome of patients with idiopathic pulmonary fibrosis (IPF) ventilated in intensive care unit

Idiopathic pulmonary fibrosis (IPF) is the commonest cause of interstitial lung disease. Till date there is no proven successful treatment. The prognosis is poor with a median survival of 3 years. Patients with IPF presented with acute respiratory failure are often referred to the intensive care unit for ventilatory support. Available data showed that outcome of these patients is very poor and mechanical ventilation is mostly futile. Patients and their families should be informed about the prognosis, outcome and overall outlook before making decision about ventilation and organ support. Available outcome data should be used to develop institutional and professional guidelines to help in making these difficult decisions.

Interstitial lung disease in Japanese patients with lung cancer: a cohort and nested case-control study

RATIONALE

Interstitial lung disease (ILD) occurs in Japanese patients with non-small cell lung cancer (NSCLC) receiving gefitinib.

OBJECTIVES

To elucidate risk factors for ILD in Japanese patients with NSCLC during treatment with gefitinib or chemotherapy.

METHODS

In a prospective epidemiologic cohort, 3,166 Japanese patients with advanced/recurrent NSCLC were followed for 12 weeks on 250 mg gefitinib (n = 1,872 treatment periods) or chemotherapy (n = 2,551). Patients who developed acute ILD (n = 122) and randomly selected control subjects (n = 574) entered a case-control study. Adjusted incidence rate ratios were estimated from case-control data by odds ratios (ORs) with 95% confidence intervals (CIs) using logistic regression. Crude (observed) incidence rates and risks were calculated from cohort data.

MEASUREMENTS AND MAIN RESULTS

The observed (unadjusted) incidence rate over 12 weeks was 2.8 (95% CI, 2.3-3.3) per 1,000 person-weeks, 4.5 (3.5-5.4) for gefitinib versus 1.7 (1.2-2.2) for chemotherapy; the corresponding observed naive cumulative incidence rates at the end of 12-week follow-up were 4.0% (3.0-5.1%) and 2.1% (1.5-2.9%), respectively. Adjusted for imbalances in risk factors between treatments, the overall OR for gefitinib versus chemotherapy was 3.2 (1.9-5.4), elevated chiefly during the first 4 weeks (3.8 [1.9-7.7]). Other ILD risk factors in both groups included the following: older age, poor World Health Organization performance status, smoking, recent NSCLC diagnosis, reduced normal lung on computed tomography scan, preexisting chronic ILD, concurrent cardiac disease. ILD-related deaths in patients with ILD were 31.6% (gefitinib) versus 27.9% (chemotherapy); adjusted OR, 1.05 (95% CI, 0.3-3.2).

CONCLUSIONS

ILD was relatively common in these Japanese patients with NSCLC during therapy with gefitinib or chemotherapy, being higher in the older, smoking patient with preexisting ILD or poor performance status. The risk of developing ILD was higher with gefitinib than chemotherapy, mainly in the first 4 weeks.

Male sex hormones exacerbate lung function impairment after bleomycin-induced pulmonary fibrosis

The roles of sex hormones as modulators of lung function and disease have received significant attention as differential sex responses to various lung insults have been recently reported. The present study used a bleomycin-induced pulmonary fibrosis model in C57BL/6 mice to examine potential sex differences in physiological and pathological outcomes. Endpoints measured included invasive lung function assessment, immunological response, lung collagen deposition, and a quantitative histological analysis of pulmonary fibrosis. Male mice had significantly higher basal static lung compliance than female mice (P < 0.05) and a more pronounced decline in static compliance after bleomycin administration when expressed as overall change or percentage of baseline change (P < 0.05). In contrast, there were no significant differences between the sexes in immune cell infiltration into the lung or in total lung collagen content after bleomycin. Total lung histopathology scores measured using the Ashcroft method did not differ between the sexes, while a quantitative histopathology scoring system designed to determine where within the lung the fibrosis occurred indicated a tendency toward more fibrosis immediately adjacent to airways in bleomycin-treated male versus female mice. Furthermore, castrated male mice exhibited a female-like response to bleomycin while female mice given exogenous androgen exhibited a male-like response. These data indicate that androgens play an exacerbating role in decreased lung function after bleomycin administration, and traditional measures of fibrosis may miss critical differences in lung function between the sexes. Sex differences should be carefully considered when designing and interpreting experimental models of pulmonary fibrosis in mice.