Mutations in the SFTPC gene associated with interstitial lung disease in human patients result in misfolding, endoplasmic reticulum (ER) retention, and degradation of the encoded surfactant protein C (SP-C) proprotein. In this study, genes specifically induced in response to transient expression of two disease-associated mutations were identified by microarray analyses. Immunoglobulin heavy chain binding protein (BiP) and two heat shock protein 40 family members, endoplasmic reticulum-localized DnaJ homologues ERdj4 and ERdj5, were significantly elevated and exhibited prolonged and specific association with the misfolded proprotein; in contrast, ERdj3 interacted with BiP, but it did not associate with either wild-type or mutant SP-C. Misfolded SP-C, ERdj4, and ERdj5 coprecipitated with p97/VCP indicating that the cochaperones remain associated with the misfolded proprotein until it is dislocated to the cytosol. Knockdown of ERdj4 and ERdj5 expression increased ER retention and inhibited degradation of misfolded SP-C, but it had little effect on the wild-type protein. Transient expression of ERdj4 and ERdj5 in X-box binding protein 1 ؊/؊ mouse embryonic fibroblasts substantially restored rapid degradation of mutant SP-C proprotein, whereas transfection of HPD mutants failed to rescue SP-C endoplasmic reticulum-associated protein degradation. ERdj4 and ERdj5 promote turnover of misfolded SP-C and this activity is dependent on their ability to stimulate BiP ATPase activity.

Chronic pulmonary hypertension is associated with significant vascular remodeling. We demonstrated recently in the monocrotaline (MCT) and chronic hypoxia rat models of pulmonary hypertension that treatment with platelet-activating factor (PAF) antagonists inhibited the development of chronic pulmonary hypertension. PAF and other lipid mediators interact with interleukin-1. We postulated that chronic treatment with a recombinant human interleukin-1 receptor antagonist (IL-1ra) would inhibit development of chronic pulmonary hypertension in animal models. Rats were either injected with (60 mg/kg) MCT or exposed to a stimulated high altitude of 16,000 feet; half of the animals were treated with twice-daily injections (2 mg/kg) of IL-1ra. At 3 wk after MCT injection or 3 wk of hypoxic exposure, pulmonary artery pressure and right heart ventricle weight/(left ventricle and septum weight), RV/(LV + S), were measured. IL-1ra treatment reduced pulmonary hypertension and right heart hypertrophy in the MCT model, but not in the chronic hypoxia model. Measurement of lung homogenate IL-1 alpha by radioimmunoassay showed elevated levels in the MCT-treated rats throughout the 3-wk observation period. IL-1ra treatment reduced the levels of IL-1 alpha in lung tissue in most of the MCT-treated rats. MCT treatment was also associated with an increase in lung mRNA for IL-1 alpha, IL-1 beta, and IL-1ra. Immunohistology, using an antibody against rat IL-1 alpha, revealed staining of alveolar structures and of vascular and bronchial smooth muscle. In situ hybridization using a human IL-1 alpha cDNA probe demonstrated increased expression of the IL-1 alpha gene in the lung cells after endotoxin or MCT treatment. Northern blot analysis demonstrated low-level expression of IL-1 alpha mRNA in extracts of normal rat lung and increased expression after endotoxin or MCT treatment. We conclude that chronic treatment with human IL-1ra inhibited the development of pulmonary hypertension in the inflammatory (MCT) model, but not in the chronically hypoxic rats. This result indicates that IL-1 participates in the pathogenesis of some forms of pulmonary hypertension.

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‘LungGENS’, our previously developed web tool for mapping single-cell gene expression in the developing lung, has been well received by the pulmonary research community. With continued support from the ‘LungMAP’ consortium, we extended the scope of the LungGENS database to accommodate transcriptomics data from pulmonary tissues and cells from human and mouse at different stages of lung development. Lung Gene Expression Analysis (LGEA) web portal is an extended version of LungGENS useful for the analysis, display and interpretation of gene expression patterns obtained from single cells, sorted cell populations and whole lung tissues. The LGEA web portal is freely available at http://research.cchmc.org/pbge/lunggens/mainportal.html.

An intact endothelial cell barrier maintains normal gas exchange in the lung, and inflammatory conditions result in barrier disruption that produces life-threatening hypoxemia. Activation of store-operated Ca2+ (SOC) entry increases the capillary filtration coefficient ( K f,c) in the isolated rat lung; however, activation of SOC entry does not promote permeability in cultured rat pulmonary microvascular endothelial cells. Therefore, current studies tested whether activation of SOC entry increases macro- and/or microvascular permeability in the intact rat lung circulation. Activation of SOC entry by the administration of thapsigargin induced perivascular edema in pre- and postcapillary vessels, with apparent sparing of the microcirculation as evaluated by light microscopy. Scanning and transmission electron microscopy revealed that the leak was due to gaps in vessels ≥ 100 μm, consistent with the idea that activation of SOC entry influences macrovascular but not microvascular endothelial cell shape. In contrast, ischemia and reperfusion induced microvascular endothelial cell disruption independent of Ca2+ entry, which similarly increased K f,c. These data suggest that 1) activation of SOC entry is sufficient to promote macrovascular barrier disruption and 2) unique mechanisms regulate pulmonary micro- and macrovascular endothelial barrier functions.

We conclude that pulmonary fibrosis in naturally occurring HPS mice is driven by intracellular trafficking defects that lower the threshold for pulmonary epithelial apoptosis. Our findings demonstrate a pivotal role for the alveolar epithelium in the maintenance of alveolar homeostasis and regulation of alveolar macrophage activation.

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The lung is composed of a series of branching conducting airways that terminate in grape-like clusters of delicate gas-exchanging airspaces called pulmonary alveoli. Maintenance of alveolar patency at end expiration requires pulmonary surfactant, a mixture of phospholipids and proteins that coats the epithelial surface and reduces surface tension. The surfactant lining is exposed to the highest ambient oxygen tension of any internal interface and encounters a variety of oxidizing toxicants including ozone and trace metals contained within the 10 kl of air that is respired daily. The pathophysiological consequences of surfactant oxidation in humans and experimental animals include airspace collapse, reduced lung compliance, and impaired gas exchange. We now report that the hydrophilic surfactant proteins A (SP-A) and D (SP-D) directly protect surfactant phospholipids and macrophages from oxidative damage. Both proteins block accumulation of thiobarbituric acid-reactive substances and conjugated dienes during copper-induced oxidation of surfactant lipids or low density lipoprotein particles by a mechanism that does not involve metal chelation or oxidative modification of the proteins. Low density lipoprotein oxidation is instantaneously arrested upon SP-A or SP-D addition, suggesting direct interference with free radical formation or propagation. The antioxidant activity of SP-A maps to the carboxylterminal domain of the protein, which, like SP-D, contains a C-type lectin carbohydrate recognition domain. These results indicate that SP-A and SP-D, which are ubiquitous among air breathing organisms, could contribute to the protection of the lung from oxidative stresses due to atmospheric or supplemental oxygen, air pollutants, and lung inflammation.Air breathing is made possible through the surface tensionlowering properties of lung surfactant, an oily film located at the boundary between the aqueous pulmonary epithelial lining fluid (ELF) 1 and air in the lumen of the alveoli, the gasexchanging units of the lung. By weight, surfactant is composed of 90% phospholipids and 10% protein, including the hydrophilic surfactant proteins A (SP-A) and D (SP-D), and the hydrophobic surfactant proteins B (SP-B) and C (SP-C) (1). After secretion into the ELF, the components of surfactant form membranes at the air-liquid interface that spread readily and compress poorly during cyclical respiratory expansion and contraction of the alveolus. These properties of surfactant result in enhanced lung compliance during inspiration, which reduces the work of breathing, and very low alveolar surface tension at end expiration, which helps to maintain airspace patency. Exposure of surfactant to ambient oxygen and potent environmental oxidants such as ozone results in peroxidation of unsaturated phospholipids, surfactant inactivation, airspace collapse, and impaired gas exchange (2). Antioxidant protection of surfactant phospholipids in the ELF has classically been attributed to low molecular mass components urate, ascorbate, and reduced g...