Increased lymphatic vessel length is associated with the fibroblast reticulum and disease severity in usual interstitial pneumonia and nonspecific interstitial pneumonia.

BACKGROUND: Lymphangiogenesis responds to tissue injury as a key component of normal wound healing. The development of fibrosis in the idiopathic interstitial pneumonias may result from abnormal wound healing in response to injury. We hypothesize that increased lymphatic vessel (LV) length, a marker of lymphangiogenesis, is associated with parenchymal components of the fibroblast reticulum (organizing collagen, fibrotic collagen, and fibroblast foci), and its extent correlates with disease severity. METHODS: We assessed stereologically the parenchymal structure of fibrotic lungs and its associated lymphatic network, which was highlighted immunohistochemically in age-matched samples of usual interstitial pneumonia (UIP), nonspecific interstitial pneumonia (NSIP) with FVC < 80%, COPD with a Global Initiative for Obstructive Lung Disease stage 0, and normal control lungs. RESULTS: LV length density, as opposed to vessel volume density, was found to be associated with organizing and fibrotic collagen density (P < .0001). Length density of LVs and the volume density of organizing and fibrotic collagen were significantly associated with severity of both % FVC (P < .001) and diffusing capacity of the lung for carbon monoxide (P < .001). CONCLUSIONS: Severity of disease in UIP and NSIP is associated with increased LV length and is strongly associated with components of the fibroblast reticulum, namely organizing and fibrotic collagen, which supports a pathogenic role of LVs in these two diseases. Furthermore, the absence of definable differences between UIP and NSIP suggests that LVs are a unifying mechanism for the development of fibrosis in these fibrotic lung diseases.

Age and sex dimorphisms contribute to the severity of bleomycin-induced lung injury and fibrosis.

Fibrotic interstitial pneumonias are more prevalent in males of advancing age, although little is known about the underlying mechanisms. To evaluate the contributions of age and sex to the development of pulmonary fibrosis, we intratracheally instilled young (8-12 wk) and aged (52-54 wk) male and female mice with bleomycin and assessed the development and severity of fibrotic lung disease by measurements of lung collagen levels, static compliance, leukocyte infiltration, and stereological quantification of fibrotic areas in histological sections. We also quantified proinflammatory and profibrotic chemokine and cytokine levels in the bronchoalveolar lavage fluid. Aged male mice developed more severe lung disease, indicated by increased mortality, increased collagen deposition, and neutrophilic alveolitis compared with aged female mice or young mice of either sex. Aged male mice also exhibited increased levels of transforming growth factor-ß, IL-17A, and CXCL1 in their bronchoalveolar lavage fluid. Young male mice developed a more fibrotic disease after bleomycin instillation compared with female mice, regardless of age. There was no difference in fibrosis between young and aged female mice. Taken together, these findings suggest that the variables of advanced age and male sex contribute to the severity of pulmonary fibrosis in this model. Our findings also emphasize the importance of stratifying experimental groups on the basis of age and sex in experimental and epidemiological studies of this nature.

A detailed evaluation of acute respiratory decline in patients with fibrotic lung disease: aetiology and outcomes.

BACKGROUND AND OBJECTIVE: A comprehensive diagnostic evaluation is recommended for all patients with fibrotic lung disease and acute respiratory decompensation. However, the effect on clinical outcomes of this evaluation remains unknown. METHODS: We evaluated 27 consecutive patients with fibrotic lung disease who were hospitalized for an acute respiratory decline between June 2006 and April 2009. An interstitial lung disease expert assisted with the acute care of each patient. A retrospective review of the patient charts was performed to obtain demographic and clinical data, and to assess outcomes. RESULTS: Using a strict definition of acute exacerbation (AE) of fibrotic lung disease derived from the IPF Network Pulmonary Perspective statement, 10 of the 27 patients were classified as definite AE and nine as suspected AE. In eight patients, infectious agents were identified as potential explanations for the respiratory decline. No patients with congestive heart failure or pulmonary embolism were identified. Overall survival to discharge was 37.0%. One-year survival was 14.8%. There were no differences in outcomes for patients with AE compared with those for whom potential infectious aetiologies were identified (log rank, P = 0.932). Patients with IPF showed a decreased rate of survival compared with patients with non-IPF fibrotic disease (1-year survival 0% vs 28.6%, log rank, P = 0.045). CONCLUSIONS: In patients with fibrotic lung disease and an acute respiratory decline, a detailed diagnostic evaluation revealed a potential infectious aetiology in up to one-third of cases. However, there was no association between this finding and outcomes in these patients. One-year survival was dismal in patients who suffered an acute respiratory decompensation.

Diffuse alveolar hemorrhage.

Diffuse alveolar hemorrhage (DAH) is often a catastrophic clinical syndrome causing respiratory failure. Recognition of DAH often requires BAL as symptoms are nonspecific, hemoptysis is absent in up to one-third of patients, and radiographic imaging is also nonspecific and similar to other acute alveolar filling processes. Once the diagnosis is established, the underlying cause must be established in order to initiate treatment. This review discusses the diagnosis of the underlying histologies and the clinical entities that are responsible for DAH as well as treatment options.

Alterations of cellular bioenergetics in pulmonary artery endothelial cells.

Idiopathic pulmonary arterial hypertension (IPAH) is pathogenetically related to low levels of the vasodilator nitric oxide (NO). Because NO regulates cellular respiration and mitochondrial biogenesis, we hypothesized that abnormalities of bioenergetics may be present in IPAH. Evaluation of pulmonary artery endothelial cells from IPAH and control lungs in vitro revealed that oxygen consumption of IPAH cells was decreased, especially in state 3 respiration with substrates glutamate-malate or succinate, and this decrease paralleled reduction in Complex IV activity and IPAH cellular NO synthesis. IPAH pulmonary artery endothelial cells had decreased mitochondrial dehydrogenase activity and lowered mitochondrial numbers per cell and mitochondrial DNA content, all of which increased after exposure to NO donors. Although IPAH/pulmonary artery endothelial cells' ATP content was similar to control under normoxia, cellular ATP did not change significantly in IPAH cells under hypoxia, whereas ATP decreased 35% in control cells, identifying a greater dependence on cellular respiration for energy in control cells. Evidence that glucose metabolism was subserving the primary role for energy requirements of IPAH cells was provided by the approximately 3-fold greater glycolytic rate of IPAH cells. Positron emission tomography scan with [18F]fluoro-deoxy-D-glucose performed on IPAH patients and healthy controls revealed significantly higher uptake in IPAH lungs as compared with controls, confirming that the glycolytic rate was increased in vivo. Thus, there are substantial changes in bioenergetics of IPAH endothelial cells, which may have consequences for pulmonary hypertensive responses and potentially in development of novel imaging modalities for diagnosis and evaluation of treatment.

Correlation of systemic superoxide dismutase deficiency to airflow obstruction in asthma.

RATIONALE: Increased oxidative stress and decreased superoxide dismutase (SOD) activity in the asthmatic airway are correlated to airflow limitation and hyperreactivity. We hypothesized that asthmatic individuals with higher levels of oxidative stress may have greater loss of SOD activity, which would be reflected systemically in loss of circulating SOD activity and clinically by development of severe asthma and/or worsening airflow limitation. METHODS: To investigate this, serum SOD activity and proteins, the glutathione peroxidase/glutathione antioxidant system, and oxidatively modified amino acids were measured in subjects with asthma and healthy control subjects. RESULTS: SOD activity, but not Mn-SOD or Cu,Zn-SOD protein, was lower in asthmatic serum as compared with control, and activity loss was significantly related to airflow limitation. Further, serum SOD activity demonstrated an inverse correlation with circulating levels of 3-bromotyrosine, a posttranslational modification of proteins produced by the eosinophil peroxidase system of eosinophils. Exposure of purified Cu,Zn-SOD to physiologically relevant levels of eosinophil peroxidase-generated reactive brominating species, reactive nitrogen species, or tyrosyl radicals in vitro confirmed that eosinophil-derived oxidative pathways promote enzyme inactivation. CONCLUSION: These findings are consistent with greater oxidant stress in asthma leading to greater inactivation of SOD, which likely amplifies inflammation and progressive airflow obstruction.