Kjetil Ask

Circulating fibrocytes are an indicator of poor prognosis in idiopathic pulmonary fibrosis.

RATIONALE The clinical management of idiopathic pulmonary fibrosis (IPF) remains a major challenge due to lack of effective drug therapy or accurate indicators for disease progression. Fibrocytes are circulating mesenchymal cell progenitors that are involved in tissue repair and fibrosis. OBJECTIVES To test the hypothesis that assay of these cells may provide a biomarker for activity and progression of IPF. METHODS Fibrocytes were defined as cells positive for CD45 and collagen-1 by flow cytometry and quantified in patients with stable IPF and during acute exacerbation of the disease. We investigated the clinical and prognostic value of fibrocyte counts by comparison with standard clinical parameters and survival. We used healthy age-matched volunteers and patients with acute respiratory distress syndrome as control subjects. MEASUREMENTS AND MAIN RESULTS Fibrocytes were significantly elevated in patients with stable IPF (n = 51), with a further increase during acute disease exacerbation (n = 7; P < 0.001 vs. control subjects). Patients with acute respiratory distress syndrome (n = 10) were not different from healthy control subjects or stable patients with IPF. Fibrocyte numbers were not correlated with lung function or radiologic severity scores, but they were an independent predictor of early mortality. The mean survival of patients with fibrocytes higher than 5% of total blood leukocytes was 7.5 months compared with 27 months for patients with less than 5% (P < 0.0001). CONCLUSIONS Fibrocytes are an indicator for disease activity of IPF and might be useful as a clinical marker for disease progression. This study suggests that quantification of circulating fibrocytes may allow prediction of early mortality in patients with IPF.

TGF-β and Smad3 Signaling Link Inflammation to Chronic Fibrogenesis

Transient adenovirus-mediated gene transfer of IL-1β (AdIL-1β), a proinflammatory cytokine, induces marked inflammation and severe and progressive fibrosis in rat lungs. This is associated with an increase in TGF-β1 concentration in bronchoalveolar lavage (BAL) fluid. TGF-β1 is a key cytokine in the process of fibrogenesis, using intracellular signaling pathways involving Smad2 and Smad3. In this study we investigate whether inflammation induced by IL-1β is able to independently induce lung fibrosis in mice deficient in the Smad3 gene. Seven days after AdIL-1β administration, similar levels of IL-1β transgene are seen in BAL in both wild-type (WT) and knockout (KO) mice, and BAL cell profiles demonstrated a similar marked neutrophilic inflammation. Phospho-Smad2 staining was positive in areas of inflammation in both WT and KO mice at day 7. By day 35 after transient IL-1β expression, WT mice showed marked fibrosis in peribronchial areas, quantified by picrosirius red staining and morphometry. However, there was no evidence of fibrosis or collagen accumulation in IL-1β-treated KO mice, and peribronchial areas were not different from KO mice treated with the control adenovector. TGF-β1 and phospho-Smad2 were strongly positive at day 35 in fibrotic areas observed in WT mice, but no such staining was detectable in KO mice. The IL-1β-induced chronic fibrotic response in mouse lungs is dependent on Smad3. KO and WT animals demonstrated a similar inflammatory response to overexpression of IL-1β indicating that inflammation must link to the Smad3 pathway, likely through TGF-β, to induce progressive fibrosis.

VEGF ameliorates pulmonary hypertension through inhibition of endothelial apoptosis in experimental lung fibrosis in rats

Idiopathic pulmonary fibrosis (IPF) can lead to the development of secondary pulmonary hypertension (PH) and ultimately death. Despite this known association, the precise mechanism of disease remains unknown. Using a rat model of IPF, we explored the role of the proangiogenic and antiapoptotic growth factor VEGF in the vascular remodeling that underlies PH. In this model, adenoviral delivery of active TGF-beta1 induces pulmonary arterial remodeling, loss of the microvasculature in fibrotic areas, and increased pulmonary arterial pressure (PAP). Immunohistochemistry and mRNA analysis revealed decreased levels of VEGF and its receptor, which were inversely correlated with PAP and endothelial cell apoptosis in both the micro- and macrovasculature. Treatment of IPF rats with adenoviral delivery of VEGF resulted in reduced endothelial apoptosis, increased vascularization, and improved PAP due to reduced remodeling but worsened PF. These data show that experimental pulmonary fibrosis (PF) leads to loss of the microvasculature through increased apoptosis and to remodeling of the pulmonary arteries, with both processes resulting in PH. As administration of VEGF ameliorated the PH in this model but concomitantly aggravated the fibrogenic process, VEGF-based therapies should be used with caution.

TGF-β, Smad3 and the process of progressive fibrosis

Transient adenovirus-mediated gene transfer of active TGF-β1 (transforming growth factor-β1) induces severe and progressive fibrosis in rodent lung without apparent inflammation. Alternatively, transfer of IL-1β (interleukin 1β) induces marked tissue injury and inflammation, which develops into progressive fibrosis, associated with an increase in TGF-β1 concentrations in lung fluid and tissue. Both vector treatments induce a fibrotic response involving myofibroblasts and progressive matrix deposition starting at the peri-bronchial site of expression and extending over days to involve the entire lung and pleural surface. Administration of the TGF-β1 vector to the pleural space induces progressive pleural fibrosis, which minimally extends into the lung parenchyma. The mechanisms involved in progressive fibrosis need to account for the limitation of fibrosis to specific organs (lung fibrosis and not liver fibrosis or vice versa) and the lack of effect of anti-inflammatory treatments in regulating progressive fibrosis. TGF-β1 is a key cytokine in the process of fibrogenesis, using intracellular signalling pathways involving the ALK5 receptor and signalling molecules Smad2 and Smad3. Transient gene transfer of either TGF-β1 or IL-1β to Smad3-null mouse lung provides little evidence of progressive fibrosis and no fibrogenesis-associated genes are induced. These results suggest that mechanisms of progressive fibrosis involve factors presented within the context of the matrix that define the microenvironment for progressive matrix deposition.

The therapeutic effects of 4-phenylbutyric acid in maintaining proteostasis.

Recently, there has been an increasing amount of literature published on the effects of 4-phenylbutyric acid (4-PBA) in various biological systems. 4-PBA is currently used clinically to treat urea cycle disorders under the trade name Buphenyl. Recent studies however have explored 4-PBA in the context of a low weight molecular weight chemical chaperone. Its properties as a chemical chaperone prevent misfolded protein aggregation and alleviate endoplasmic reticulum (ER) stress. As the ER is responsible for folding proteins targeted for use in membranes or secreted out of the cell, failure of maintaining adequate ER homeostasis may lead to protein misfolding and subsequent cell and organ pathology. Accumulation of misfolded proteins within the ER activates the unfolded protein response (UPR), a molecular repair response. The activation of the UPR aims to restore ER and cellular proteostasis by regulating the rate of synthesis of newly formed proteins as well as initiating molecular programs aimed to help fold or degrade misfolded proteins. If proteostasis is not restored, the UPR may initiate pro-apoptotic pathways. It is suggested that 4-PBA may help fold proteins in the ER, attenuating the activation of the UPR, and thus potentially alleviating various pathologies. This review discusses the biomedical research exploring the potential therapeutic effects of 4-PBA in various in vitro and in vivo model systems and clinical trials, while also commenting on the possible mechanisms of action.

Comparison between conventional and "clinical" assessment of experimental lung fibrosis

BackgroundIdiopathic pulmonary fibrosis (IPF) is a treatment resistant disease with poor prognosis. Numerous compounds have been demonstrated to efficiently prevent pulmonary fibrosis (PF) in animal models but only a few were successful when given to animals with established fibrosis. Major concerns of current PF models are spontaneous resolution and high variability of fibrosis, and the lack of assessment methods that can allow to monitor the effect of drugs in individual animals over time. We used a model of experimental PF in rats and compare parameters obtained in living animals with conventional assessment tools that require removal of the lungs.MethodsPF was induced in rats by adenoviral gene transfer of transforming growth factor-beta. Morphological and functional changes were assessed for up to 56 days by micro-CT, lung compliance (measured via a mechanical ventilator) and VO2max and compared to histomorphometry and hydroxyproline content.ResultsStandard histological and collagen assessment confirmed the persistent fibrotic phenotype as described before. The histomorphological scores correlated both to radiological (r2 = 0.29, p < 0.01) and functional changes (r2 = 0.51, p < 0.0001). VO2max did not correlate with fibrosis.ConclusionThe progression of pulmonary fibrosis can be reliably assessed and followed in living animals over time using invasive, non-terminal compliance measurements and micro-CT. This approach directly translates to the management of patients with IPF and allows to monitor therapeutic effects in drug intervention studies.

Local Delivery of GM-CSF Protects Mice from Lethal Pneumococcal Pneumonia

The growth factor GM-CSF has an important role in pulmonary surfactant metabolism and the regulation of antibacterial activities of lung sentinel cells. However, the potential of intra-alveolar GM-CSF to augment lung protective immunity against inhaled bacterial pathogens has not been defined in preclinical infection models. We hypothesized that transient overexpression of GM-CSF in the lungs of mice by adenoviral gene transfer (Ad-GM-CSF) would protect mice from subsequent lethal pneumococcal pneumonia. Our data show that intra-alveolar delivery of Ad-GM-CSF led to sustained increased pSTAT5 expression and PU.1 protein expression in alveolar macrophages during a 28-d observation period. Pulmonary Ad-GM-CSF delivery 2–4 wk prior to infection of mice with Streptococcus pneumoniae significantly reduced mortality rates relative to control vector-treated mice. This increased survival was accompanied by increased inducible NO synthase expression, antibacterial activity, and a significant reduction in caspase-3–dependent apoptosis and secondary necrosis of lung sentinel cells. Importantly, therapeutic treatment of mice with rGM-CSF improved lung protective immunity and accelerated bacterial clearance after pneumococcal challenge. We conclude that prophylactic delivery of GM-CSF triggers long-lasting immunostimulatory effects in the lung in vivo and rescues mice from lethal pneumococcal pneumonia by improving antibacterial immunity. These data support use of novel antibiotic-independent immunostimulatory therapies to protect patients against bacterial pneumonias.

Essential Role of Osteopontin in Smoking-Related Interstitial Lung Diseases

Smoking-related interstitial lung diseases are characterized by the accumulation of macrophages and Langerhans cells, and fibrotic remodeling, which are linked to osteopontin (OPN) expression. Therefore, OPN levels were investigated in bronchoalveolar lavage (BAL) cells in 11 patients with pulmonary Langerhans cell histiocytosis (PLCH), 15 patients with desquamative interstitial pneumonitis (DIP), 10 patients with idiopathic pulmonary fibrosis, 5 patients with sarcoidosis, 13 otherwise healthy smokers, and 19 non-smoking controls. Furthermore, OPN overexpression was examined in rat lungs using adenoviral gene transfer. We found that BAL cells from patients with either PLCH or DIP spontaneously produced abundant amounts of OPN. BAL cells from healthy smokers produced 15-fold less OPN, and those cells from non-smoking healthy volunteers produced no OPN. BAL cells from patients with either idiopathic pulmonary fibrosis or sarcoidosis produced significantly less OPN, as compared with patients with PLCH. These data were confirmed by immunochemistry. Nicotine stimulation increased production of both OPN and granulocyte-macrophage colony stimulating factor by alveolar macrophages from smokers. Nicotinic acetylcholine receptor expression resembled the pattern of spontaneous OPN production and was dramatically increased in both PLCH and DIP. OPN overexpression in rat lungs induced lesions similar to PLCH with marked alveolar and interstitial accumulation of Langerhans cells. Our findings suggest a pathogenetic role of increased OPN production in both PLCH and DIP by promoting the accumulation of macrophages and Langerhans cells.

Three-dimensional computed tomography imaging in an animal model of emphysema

Emphysema is a major health problem and novel drugs are needed. Animal disease models are pivotal in their development, but the validity and sensitivity of current tools for the evaluation of drug efficacy is limited. The usefulness of micro computed tomography (CT) as an innovative tool to assess emphysema in a mouse model was investigated. Serial CT scans were performed in bi-weekly intervals in Smad3 knockout (KO) mice, which spontaneously develop airspace enlargement. Lung density was quantified in two- and three-dimensional images and correlated to mean linear intercept and lung compliance. CT scans of Smad3 KO lungs revealed a significant decrease in lung density at age 8 weeks and a further progression at age 14 weeks with respect to age-matched wild-type (WT) animals. Emphysema could be reliably assessed with both the two- and three-dimensional approach, but the three-dimensional approach was superior, due to normalisation to lung volumes and less variability. Lung compliance by week 14 was 0.053±0.005 and 0.034±0.002% of maximum volume·cmH2O−1 for KO and WT mice, respectively, reflecting significant physiologically relevant emphysema. Small animal computed tomography imaging and density quantification in a reconstructed three-dimensional image is a useful tool for quantifying emphysematous changes in an animal disease model. It adds significant information to conventional assessment.

In Vivo Role of Platelet-Derived Growth Factor–BB in Airway Smooth Muscle Proliferation in Mouse Lung

Airway smooth muscle (ASM) hyperplasia in asthma likely contributes considerably to functional changes. Investigating the mechanisms behind proliferation of these cells may lead to therapeutic benefit. Platelet-derived growth factor (PDGF)-BB is a well known ASM mitogen in vitro but has yet to be directly explored using in vivo mouse models in the context of ASM proliferation and airway responsiveness. To determine the in vivo influence of PDGF-BB on gene transcripts encoding contractile proteins, ASM proliferation, and airway physiology, we used an adenovirus overexpression system and a model of chronic allergen exposure. We used adenovirus technology to selectively overexpress PDGF-BB in the airway epithelium of mice. Outcome measurements, including airway physiology, real time RT-PCR measurements, proliferating cell nuclear antigen staining, and airway smooth muscle quantification, were performed 7 days after exposure. The same outcome measurements were performed 24 hours and 4 weeks after a chronic allergen exposure model. PDGF-BB overexpression resulted in airway hyperresponsiveness, decreased lung compliance, increased airway smooth muscle cell numbers, positive proliferating cell nuclear antigen-stained airway smooth muscle cells, and a reduction in genes encoding contractile proteins. Chronic allergen exposure resulted in elevations in lung lavage PDGF-BB, which were observed in conjunction with changes in gene transcript expression encoding contractile proteins and ASM proliferation. We demonstrate for the first time in vivo that PDGF-BB induces ASM hyperplasia and changes in lung mechanics in mice and that, during periods of allergen exposure changes in lung, PDGF-BB are associated with changes in airway structure and function.