Bleomycin-induced chronic lung damage does not resemble human idiopathic pulmonary fibrosis

Administration of bleomycin into the lungs of experimental animals has been utilized as a model to understand human pulmonary fibrosis. Most of the studies, however, have focused on early stages of the lung reaction. We hypothesized that chronic stages of the model may not mimic idiopathic pulmonary fibrosis, since in preliminary studies, lung volume and compliance were not decreased. Eight male Sprague-Dawley rats receiving intratracheal bleomycin (0.5 U/100 g body weight) underwent measurement of FRC, inspiratory capacity, and lung compliance 120 d later. Lung histologic changes were evaluated using light microscopy. Eight rats without intervention served as controls. Results show that our model, in early stages, has histologic changes no different from those previously described elsewhere. In chronic stages, however, the model does not behave as a restrictive syndrome: FRC is normal or increased, whereas lung compliance is normal. Focal peribronchiolar inflammation and fibrosis associated with paracicatricial emphysematous changes are the main histologic features of long-term lung remodeling after bleomycin. We conclude that while the chronic stages of the model may be informative in understanding mechanisms of fibrosis, care should be taken not to extrapolate to human idiopathic pulmonary fibrosis. We speculate that the model might resemble a particular subgroup of human interstitial lung disease, namely, those involving peribronchiolar structures.     

Clinical aspects of lung involvement: Lessons from idiopathic pulmonary fibrosis and the scleroderma lung study

Interstitial lung disease (ILD) occurs frequently among patients with systemic slcerosis (SSc) and accounts for significant morbidity and mortality. SSc-ILD resembles idiopathic pulmonary fibrosis (IPF) in many respects; each is characterized by a restrictive ventilatory defect that results from an active fibrosing process in the lung interstitium, and each is characterized by ground glass opacification on high resolution computed tomography (HRCT) and inflammatory cells in bronchoalveolar lavage fluid (BALF). Differences in the classification of lung histopathology are noted frequently and may account for some of the difference in outcome for patients with SSc-ILD and IPF. Optimal treatment of SSc-ILD remains to be determined, but cyclophosphamide has been reported to be effective in a number of case series. A randomized controlled trial, the Scleroderma Lung Study (SLS), will be completed in 2005; the outcome of the SLS should define the efficacy of daily oral cyclophosphamide for SSc-ILD patients with alveolitis defined by BALF and HRCT.     

Validation of a method to screen for pulmonary hypertension in advanced idiopathic pulmonary fibrosis

BACKGROUND: We have developed a method to screen for pulmonary hypertension (PH) in idiopathic pulmonary fibrosis (IPF) patients, based on a formula to predict mean pulmonary artery pressure (MPAP) from standard lung function measurements. The objective of this study was to validate this method in a separate group of IPF patients. METHODS: Cross-sectional study of 60 IPF patients from two institutions. The accuracy of the MPAP estimation was assessed by examining the correlation between the predicted and measured MPAPs and the magnitude of the estimation error. The discriminatory ability of the method for PH was assessed using the area under the receiver operating characteristic curve (AUC). RESULTS: There was strong correlation in the expected direction between the predicted and measured MPAPs (r = 0.72; p < 0.0001). The estimated MPAP was within 5 mm Hg of the measured MPAP 72% of the time. The AUC for predicting PH was 0.85, and did not differ by institution. A formula-predicted MPAP > 21 mm Hg was associated with a sensitivity, specificity, positive predictive value, and negative predictive value of 95%, 58%, 51%, and 96%, respectively, for PH defined as MPAP from right-heart catheterization > 25 mm Hg. CONCLUSIONS: A prediction formula for MPAP using standard lung function measurements can be used to screen for PH in IPF patients.     

Refractory pneumothorax secondary to lung cancer in a patient with idiopathic pulmonary fibrosis

An unusual case of refractory pneumothorax secondary to lung cancer in a 69-year-old man patient with idiopathic pulmonary fibrosis (IPF) is described. High-pressure suction applied through chest tube did not resolve the large right pneumothorax. Acute exacerbation of IPF has also appeared. Respiratory state worsened acutely, and the patient died on the fifth hospital day. In the present case, the large right pneumothorax was initially thought to be associated with IPF because pneumothorax is common in patients with IPF. However, postmortem microscopic examination revealed that the refractory pneumothorax was secondary to perforation of the pleura due to a necrotic peripheral lung cancer.     

Utility of a lung biopsy for the diagnosis of idiopathic pulmonary fibrosis.

It is not known if a surgical lung biopsy is necessary in all patients for the diagnosis of idiopathic pulmonary fibrosis (IPF). We conducted a blinded, prospective study at eight referring centers. Initially, cases were evaluated by clinical history and examination, transbronchial biopsy, and high-resolution lung computed tomography scans. Pulmonologists at the referring centers then assessed their certainty of the diagnosis of IPF and provided an overall diagnosis, before surgical lung biopsy. The lung biopsies were reviewed by a pathology core and 54 of 91 patients received a pathologic diagnosis of IPF. The positive predictive value of a confident (certain) clinical diagnosis of IPF by the referring centers was 80%. The positive predictive value of a confident clinical diagnosis was higher, when the cases were reviewed by a core of pulmonologists (87%) or radiologists (96%). Lung biopsy was most important for diagnosis in those patients with an uncertain diagnosis and those thought unlikely to have IPF. These studies suggest that clinical and radiologic data that result in a confident diagnosis of IPF by an experienced pulmonologist or radiologist are sufficient to obviate the need for a lung biopsy. Lung biopsy is most helpful when clinical and radiologic data result in an uncertain diagnosis or when patients are thought not to have IPF.     

Pediatric lung disease: from proteinases to pulmonary fibrosis

One distinctive outcome of interstitial lung diseases in childhood is the abnormal accumulation of pulmonary extracellular matrix. The clinical consequence of such excessive connective tissue accumulation is known as pulmonary fibrosis. While numerous aspects of its pathogenesis have become familiar, many key events involved in its inception and progression still remain unclear. There is now compelling evidence that lung damage due to uncontrolled proteolysis may help drive critical processes that regulate fibrotic matrix remodeling. In this regard, a number of proteinases have been implicated in promoting both the initial lung injury and the fibroproliferative repair that follows. This review summarizes the knowledge of how different matrix-targeting enzymes may act to influence the development of pediatric pulmonary fibrosis. Understanding the scientific basis of this complex process may highlight opportunities to limit unwanted proteolysis and the intensity of its fibrotic sequelae.     

Exercise capacity in idiopathic pulmonary fibrosis: the effect of pulmonary hypertension

Background and objective: Increased pulmonary arterial pressure (PAP) usually coexists with impaired lung function in IPF. Data on the effect of pulmonary hypertension (PH) on cardiopulmonary responses during exercise in IPF patients is very limited. We sought to investigate the impact of PH on exercise capacity and the correlation between systolic PAP (sPAP) and pulmonary function testing, as well as cardiopulmonary exercise parameters, in patients with IPF and PH. Methods: Eighty‐one consecutive patients with IPF, who were evaluated over a 6‐year period, were retrospectively studied. Patients underwent pulmonary function testing, Doppler echocardiography and maximal cardiopulmonary exercise testing. PH was defined as sPAP > 35 mm Hg. Results: PH was diagnosed in 57% of the patients. Categorization of patients according to severity of PH indicated a significant reduction in maximum work rate, peak O₂ uptake, anaerobic threshold and peak O₂ pulse in those with sPAP > 50 mm Hg. In IPF patients with PH, estimated sPAP correlated with peak O₂ uptake, anaerobic threshold, peak O₂ pulse and end‐tidal CO₂ at anaerobic threshold, while the strongest correlation was between sPAP and ventilatory equivalent for CO₂ at anaerobic threshold (r = 0.611, P < 0.001). There were no differences in pulmonary function or exercise parameters indicative of lung volume reduction, across the patient categories, and none of these parameters correlated with sPAP. Conclusions: PH has a negative impact on exercise capacity in IPF patients. In IPF patients with PH, resting sPAP correlated with exercise parameters indicative of gas exchange and circulatory impairment, but not with defective lung mechanics.     

从细胞角度理解特发性肺间质纤维化的发病机制

特发性肺间质纤维化（idiopathic pulmonary fibrosis,IPF）是一种后果严重但病因不明的疾病。目前已知有大量的细胞因子、细胞信号通路参与其发病机制。但是,由于细胞因子网络之间错综复杂的相互作用,使得IPF发病机制显得极其繁杂。而伴随新的细胞因子和信号通路的不断被发现,又将对这一问题的认识更趋纷繁无序。然而,相对无数的细胞因子和炎症反应通路来说,肺部的细胞成分是有限的,异常的始动环节很可能发生在其中的一种或两种细胞之中。因此,着眼于IPF中关键细胞成分,了解其发病机制,不失为学习和研究IPF机制的新角度。     

Association of activated cytolytic lung lymphocytes with response to prednisone therapy in patients with idiopathic pulmonary fibrosis

Previous studies have suggested that immunologic mechanisms may contribute to pathogeneic reactions in certain interstitial lung diseases. Cytolytic lymphocytes are major effector cells of the immune response that have not been extensively studied in these disorders. To investigate the role of activated cytolytic lymphocytes in IPF, we studied B-cell and monocyte/macrophage-depleted lymphocyte preparations isolated from BAL fluid and peripheral blood of patients with this disease (n = 10) and used a lectin-dependent cytotoxicity assay to detect activated cytolytic lymphocytes. In longitudinal studies, those patients who had cytolytic activity of BAL fluid lymphocytes (range, 8 to 35 percent, n = 4) showed significant improvement in pulmonary function (mean increase in diffusing capacity, 30 +/- 2 percent) in association with decreased BAL fluid cytolytic lymphocyte activity after prednisone treatment. In contrast, patients who initially lacked cytolytic activity in BAL fluid (n = 6) did not improve with prednisone. Activated cytolytic lymphocytes were not observed in the BAL fluid of healthy subjects. These investigations suggest a causal relationship between activated cytolytic lymphocytes in the lung and disease activity in IPF and that assays of activated cytolytic lymphocytes are helpful in identifying patients who will improve with immunosuppressive therapy.