Transient induction of TGF-alpha disrupts lung morphogenesis, causing pulmonary disease in adulthood.

Clinical studies have associated increased transforming growth factor (TGF)-alpha and EGF receptor with lung remodeling in diseases including bronchopulmonary dysplasia (BPD). BPD is characterized by disrupted alveolar and vascular morphogenesis, inflammation, and remodeling. To determine whether transient increases in TGF-alpha are sufficient to disrupt postnatal lung morphogenesis, we utilized neonatal transgenic mice conditionally expressing TGF-alpha. Expression of TGF-alpha from postnatal days 3 to 5 disrupted postnatal alveologenesis, causing permanent enlargement of distal air spaces in neonatal and adult mice. Lung volume-to-body weight ratios and lung compliance were increased in adult TGF-alpha transgenic mice, whereas tissue and airway elastance were reduced. Elastin fibers in the alveolar septae were fragmented and disorganized. Pulmonary vascular morphogenesis was abnormal in TGF-alpha mice, with attenuated and occasionally tortuous arterial branching. The ratios of right ventricle weight to left ventricle plus septal weight were increased in TGF-alpha mice, indicating pulmonary hypertension. Electron microscopy showed gaps in the capillary endothelium and extravasation of erythrocytes into the alveolar space of TGF-alpha mice. Hemorrhage and inflammatory cells were seen in distal air spaces at 1 mo of age. In adult TGF-alpha mice, alveolar remodeling, nodules, proteinaceous deposits, and inflammatory cells were seen. Immunostaining for pro-surfactant protein C showed that type II cells were abundant in the nodules, as well as neutrophils and macrophages. Trichrome staining showed that pulmonary fibrosis was minimal, apart from areas of nodular remodeling in adult TGF-alpha mice. Transient induction of TGF-alpha during early alveologenesis permanently disrupted lung structure and function and caused chronic lung disease.

Measuring pleural fluid pH: high correlation of a handheld unit to a traditional tabletop blood gas analyzer.

UNLABELLED: STUDY PURPOSES: To survey hospital laboratories in the United States to determine methods used for measuring pleural fluid pH, and to compare pleural fluid pH values obtained with a traditional tabletop blood gas analyzer (BGA) to those obtained with a handheld analyzer. METHODS: Hospital laboratories nationwide were contacted by telephone to survey the methods used to measure pleural fluid pH. In a second phase, pleural fluid was prospectively collected from 19 pediatric and adult patients with pleural effusions, and pleural fluid pH was measured simultaneously with a traditional tabletop BGA and with a handheld unit. RESULTS: A total of 220 hospital laboratories were contacted by telephone, and 166 responded (75%). The methods for determining pleural fluid pH for all hospital laboratories were pH meter (35%; n = 59), BGA (32%; n = 53), and litmus paper (31%: n = 51); 2% (n = 3) did not perform the test. University hospitals were more likely to use a BGA, compared to community hospitals (p < 0.014) or children's hospitals (p < 0.001). In the comparison of pleural fluid measurements, the mean pH for the traditional BGA was 7.358 +/- 0.189, and the mean pH for the handheld unit was 7.382 +/- 0.203. The absolute difference between the two machines was 0.024 U, and the two methods were correlated (p < 0.01; r = 0.993; degrees of freedom = 36). CONCLUSION: Most hospital laboratories in the United States do not measure pleural fluid pH using a traditional BGA and use alternative methods that have previously been shown to be inaccurate. Pleural fluid pH obtained by a handheld unit has a high degree of correlation to that of a traditional tabletop BGA, and it offers a satisfactory alternative for laboratories reluctant to measure pleural fluid pH with a BGA.

Attenuation of acute lung injury in transgenic mice expressing human transforming growth factor-alpha.

Transforming growth factor-alpha (TGF-alpha) is produced in the lung in experimental and human lung diseases; however, its physiological actions after lung injury are not understood. To determine the influence of TGF-alpha on acute lung injury, transgenic mouse lines expressing differing levels of human TGF-alpha in distal pulmonary epithelial cells under control of the surfactant protein C gene promoter were generated. TGF-alpha transgenic and nontransgenic control mice were exposed to polytetrafluoroethylene (PTFE; Teflon) fumes to induce acute lung injury. Length of survival of four separate TGF-alpha transgenic mouse lines was significantly longer than that of nontransgenic control mice, and survival correlated with the levels of TGF-alpha expression in the lung. The transgenic line expressing the highest level of TGF-alpha (line 28) and nontransgenic control mice were then compared at time intervals of 2, 4, and 6 h of PTFE exposure for differences in pulmonary function, lung histology, bronchoalveolar lavage fluid protein and cell differential, and lung homogenate proinflammatory cytokines. Line 28 TGF-alpha transgenic mice demonstrated reduced histological changes, decreased bronchoalveolar lavage fluid total protein and neutrophils, and delayed alterations in pulmonary function measures of airway obstruction compared with those in nontransgenic control mice. Both line 28 and nontransgenic control mice had similar increases in interleukin-1beta protein levels in lung homogenates. In contrast, interleukin-6 and macrophage inflammatory protein-2 levels were significantly reduced in line 28 transgenic mice compared with those in nontransgenic control mice. In the transgenic mouse model, TGF-alpha protects against PTFE-induced acute lung injury, at least in part, by attenuating the inflammatory response.

Immunolocalization of transforming growth factor alpha and epidermal growth factor receptor in lungs of patients with cystic fibrosis.

Transforming growth factor alpha (TGF-alpha) is expressed in respiratory epithelial cells and alveolar macrophages during development and following lung injury. In the present study, the presence and sites of synthesis of TGF-alpha and its receptor, the epidermal growth factor receptor (EGF-R), were assessed in lung tissue from patients with severe lung disease caused by cystic fibrosis (CF). Lung sections from 24 individuals with CF, obtained at the time of lung transplantation, were compared to lung sections from five lung donors without CF. Cellular sites of TGF-alpha, EGF-R, and cellular sites of proliferation were assessed by immunohistochemistry. All CF lung sections contained multiple cell types with detectable TGF-alpha. Compared to control sections, intensity of TGF-alpha immunostaining in macrophages, airway epithelial cells, and peribronchial submucosal cells was increased. EGF-R was detected in respiratory epithelial and peribronchial stromal cells but not in alveolar macrophages. The intensity of EGF-R staining in CF lung tissue did not differ from that of controls. An increased number of cells expressing Ki-67 nuclear antigen was detected in peribronchial submucosal cells but not bronchiolar epithelial cells in the CF lungs. The increased expression of TGF-alpha in CF lung tissue supports the concept that TGF-alpha plays a role in paracrine/autocrine regulation of lung remodeling associated with injury and repair in the lungs of individuals with cystic fibrosis.

Reversal of lung lesions in transgenic transforming growth factor alpha mice by expression of mutant epidermal growth factor receptor.

Transgenic mice expressing transforming growth factor alpha (TGF-alpha) in type II cells under control of the lung-specific surfactant protein-C (SP-C) promoter develop pulmonary fibrosis and marked airspace hypoplasia. To identify cellular signaling mechanisms involved in lesion formation, we generated transgenic mice expressing a mutant epidermal growth factor receptor lacking a portion of the intracytoplasmic domain (EGF-R-M) under control of the human SP-C promoter. Transcripts of the SP-C-EGF-R-M transgene were detected in distal bronchiolar and type II cells by in situ hybridization. The morphology of lungs from the SP-C-EGF-R-M transgenic mice was normal. Lung fibrosis was not detectable and airspace hypoplasia was significantly corrected in bitransgenic mice derived by breeding SP-C-TGF-alpha and SP-C-EGF-R-M mice. Correction of lung pathology in the bitransgenic mice occurred without altering the level of hTGF-alpha mRNA. To further demonstrate that reversal of TGF-alpha lesions required signaling through the EGF-R, SP-C-TGF-alpha transgenic mice were bred to mice homozygous for the wa-2 mutation which encodes a mutated EGF-R. TGF-alpha-induced lesions were reversed in homozygous wa-2 mice. Amelioration of TGF-alpha-dependent pulmonary lesions in SP-C-EGF-R-M mice or wa-2/wa-2 mice supports the concept that autocrine and paracrine signaling mediate fibrosis and airspace remodeling caused by TGF-alpha.

The role of cyclooxygenase products in lung injury induced by tumor necrosis factor in sheep.

Tumor necrosis factor-alpha (TNF alpha) has been proposed as a mediator of endotoxin-induced lung injury. When given to sheep, TNF alpha mimics endotoxin (LPS) causing hypoxemia, pulmonary hypertension, leukopenia, reduced dynamic compliance (Cdyn), increased resistance to airflow (RL), exudation of lung lymph, and enhanced airway reactivity. TNF alpha also induces rapid release of thromboxane A2 (TxA2), prostaglandin E2 (PGE2), and prostacyclin (PGI2). We hypothesized that the inflammatory effects of TNF alpha are due at least in part to cyclooxygenase products, and therefore cyclooxygenase inhibition would have similar effects on TNF alpha-induced lung injury as has previously been demonstrated for LPS-induced lung damage. Using awake sheep with chronic lung lymph fistulas, we measured Cdyn, RL, and FRC using a whole-body plethysmograph. Pulmonary artery (Ppa), left atrial (PLA), and systemic arterial (Psa) pressures were recorded continuously. Arterial blood gases (for calculating AaPO2), leukocyte counts, and lymph samples (for prostanoid levels) were collected every 30 min. Eleven animals underwent paired random-order experiments receiving ibuprofen (14 mg/kg) 1 h before human recombinant TNF alpha (10 micrograms/kg), or an identical dose of TNF alpha alone. Within 15 min of initiating TNF alpha, Ppa doubled and remained elevated for 4 h. Ibuprofen prevented the early rise in Ppa after TNF alpha. In the group receiving TNF alpha alone, increases in Ppa were accompanied by a 60% decline in leukocyte count and a 50% increase in AaPo2 within 30 min. Ibuprofen prevented increases in AaPo2, but it had no effect on leukopenia or late increases in lymph flow.(ABSTRACT TRUNCATED AT 250 WORDS)