Measures of the inflammatory response in cryptogenic fibrosing alveolitis

Safety and Tolerability of Thrombin Inhibition in Scleroderma-Associated Interstitial Lung Disease

Objective

Interstitial lung disease (ILD) is a frequent complication of systemic sclerosis (SSc) (scleroderma) and the leading cause of scleroderma‐related deaths. There exists an unmet need for a new drug therapy for ILD‐complicated SSc. Substantial evidence supports an important role for thrombin in the pathogenesis of SSc‐associated ILD (hereafter SSc‐ILD), and targeting thrombin with a direct thrombin inhibitor could prove to be a novel and effective treatment strategy. As a first step toward designing a clinical trial to test the efficacy of thrombin inhibition in SSc‐ILD, we conducted this study to test the safety and tolerability of dabigatran in patients with SSc‐ILD.

Methods

We performed a prospective, single‐center, open‐label treatment trial with the direct thrombin inhibitor, dabigatran, in patients with SSc‐ILD. Any patient with a history of gastrointestinal hemorrhage or gastric antral vascular ectasia was excluded. Blood monitoring was performed monthly, and patient‐reported outcomes, pulmonary function tests, and skin scores were obtained at baseline and at 3‐ and 6‐month visits. Bronchoscopy with bronchoalveolar lavage (BAL) was performed at baseline and at 6 months for measurement of lung thrombin activity.

Results

Of 15 patients with SSc‐ILD, 14 completed 6 months of treatment with dabigatran at 75 mg taken orally twice daily. Adverse events were uncommon and usually mild or unrelated to the study medication. No serious adverse event was observed. Dabigatran was well tolerated, and we observed no significant gastrointestinal, pulmonary, or other safety issues or intolerability. BAL fluid thrombin activity decreased or remained stable in 13 of 14 (92.8%) subjects.

Conclusion

Dabigatran appears to be safe and well tolerated in patients with SSc‐ILD. A larger randomized controlled trial to test the efficacy of direct thrombin inhibition with dabigatran can be considered.

Measurement of airway inflammation in current smokers by positron emission tomography

BACKGROUND

Accumulation of activated neutrophilic leucocytes is known to increase uptake of ¹⁸ F-fluorodeoxyglucose (¹⁸ F-FDG) into lung tissue. Available evidence suggests that smokers and subjects with chronic obstructive pulmonary disease (COPD) have neutrophilic inflammation in peripheral airways. The aim of this study was to examine whether current smokers have higher lung tissue uptake of ¹⁸ F-FDG than never-smokers when correcting for air fraction of the lungs.

METHODS

We prospectively recruited 33 current smokers and 33 never-smokers among subjects referred for diagnosis or staging of cancer, other than lung cancer, with combined positron emission tomography/computed tomography (PET/CT) with ¹⁸ F-FDG. Subjects with focal ¹⁸ F-FDG uptake or focal CT abnormalities in the lungs were excluded. The lungs were segmented in the CT image, and lung density measured. ¹⁸ F-FDG uptake was measured in the corresponding volume and corrected for air fraction.

RESULTS

Lung uptake of ¹⁸ F-FDG, corrected for air fraction, was 12·5 and 8 per cent higher in the right and left lungs, respectively, in current smokers than in never-smokers (P<0·05). Conclusion Abnormal lung tissue uptake of ¹⁸ F-FDG may be masked by reduced lung density if the uptake is not related to air fraction. Increased uptake of ¹⁸ F-FDG in lung tissue in current smokers relative to never-smokers may reflect inflammation in peripheral airways. Measurements of ¹⁸ F-FDG uptake in the lung tissue may be useful for animal and human studies of airways disease in COPD and the relation between airway and systemic inflammation.

Uncoupling of the profibrotic and hemostatic effects of thrombin in lung fibrosis

Fibrotic lung disease, most notably idiopathic pulmonary fibrosis (IPF), is thought to result from aberrant wound-healing responses to repetitive lung injury. Increased vascular permeability is a cardinal response to tissue injury, but whether it is mechanistically linked to lung fibrosis is unknown. We previously described a model in which exaggeration of vascular leak after lung injury shifts the outcome of wound-healing responses from normal repair to pathological fibrosis. Here we report that the fibrosis produced in this model is highly dependent on thrombin activity and its downstream signaling pathways. Direct thrombin inhibition with dabigatran significantly inhibited protease-activated receptor-1 (PAR1) activation, integrin αvβ6 induction, TGF-β activation, and the development of pulmonary fibrosis in this vascular leak-dependent model. We used a potentially novel imaging method - ultashort echo time (UTE) lung magnetic resonance imaging (MRI) with the gadolinium-based, fibrin-specific probe EP-2104R - to directly visualize fibrin accumulation in injured mouse lungs, and to correlate the antifibrotic effects of dabigatran with attenuation of fibrin deposition. We found that inhibition of the profibrotic effects of thrombin can be uncoupled from inhibition of hemostasis, as therapeutic anticoagulation with warfarin failed to downregulate the PAR1/αvβ6/TGF-β axis or significantly protect against fibrosis. These findings have direct and important clinical implications, given recent findings that warfarin treatment is not beneficial in IPF, and the clinical availability of direct thrombin inhibitors that our data suggest could benefit these patients.

A longitudinal study of FDG-PET in Crohn disease patients receiving granulocyte/monocyte apheresis therapy

BACKGROUND AIMS

Endoscopy is the gold standard for the diagnosis and follow-up of patients with Crohn disease (CD). However, a less invasive approach is now being sought for the management of these patients. The objective of this study was to examine whether (18)F-fluorodeoxyglucose (FDG)-positron emission tomography (PET) might be relevant for monitoring the disease activity in CD patients undergoing granulocyte/monocyte apheresis (GMA).

METHODS

This study was conducted in 12 patients with CD who were receiving treatment with 10 once-a-week GMA sessions with the Adacolumn. The response to treatment was monitored by measuring standard laboratory variables, Crohn's Disease Activity Index (CDAI) score, International Organization for the Study of Inflammatory Bowel Diseases (IOIBD) score, and regional and global bowel uptakes on FDG-PET.

RESULTS

In 6 of the 12 patients, significant improvement of the CDAI was observed after the final session of GMA. The patients who showed clinical response to GMA had a decrease in the regional and global bowel uptakes on FDG-PET, whereas those who did not respond showed no change. In the patients who responded to the GMA, the decrease in regional bowel uptake on FDG-PET in each disease area of the same patient varied in parallel. There was a significant correlation between decrease in the global bowel uptake on FDG-PET and improvement of the CDAI and IOIBD scores.

CONCLUSIONS

The longitudinal changes in FDG-PET uptakes are of potential clinical interest for assessing the regional and global bowel disease activity in CD patients undergoing GMA therapy.

Interstitial lung disease in systemic sclerosis

Lung involvement frequently complicates systemic sclerosis (SSc), provoking loss of quality of life and a poor expectation of survival. For this reason an early diagnosis of lung involvement is warranted: high-resolution computed tomography (HRCT), pulmonary function tests (PFT), lung scintigraphy with DTPA and bronchoalveolar lavage (BAL) are mandatory to define and follow-up pulmonary interstitium. Coughing and a sensation of breathlessness on exertion are the earliest symptoms of lung involvement. Lung involvement may be investigated with PFTs, which are non-invasive and require breathing into a tube via a mouthpiece. Forced vital capacity, which measures the total amount of air capable of being blown forcefully, and the diffusion capacity for carbon monoxide, a measure of how well oxygen diffuses into blood, are the most important functional measures. A routine chest X-ray may demonstrate fibrosis, but it is not very sensitive for detecting early or mild disease. For this reason, a HRCT scan is required. This non-invasive investigation provides images of multiple slices through the lung, from top (apex) to bottom (base), and can even detect lung involvement in early phases when no symptoms are present. (99m)T-DTPA is recommended in those patients with isolated diffusion deficits on lung function tests and in addition to HRCT in confirming the suspicion of vascular disease rather than early fibrosing alveolitis. Bronchoscopy with BAL is an invasive test that also may provide information about the inflammatory status of the affected areas of the lung detected during HRCT. In order to detect alveolitis, it should be performed as early as possible, to start prompt immunosuppressive treatment.

Idiopathic Pulmonary Fibrosis: Evaluation with Positron Emission Tomography

BACKGROUND

The pathogenesis of interstitial lung disease remains under investigation, but may be related to increased inflammatory or cellular activity. This activity may be detectable with physiologic imaging.

OBJECTIVES

We investigated the role of physiologic imaging using (18)F-2-fluoro-2-deoxy-D-glucose ((18)FDG)-positron emission tomography (PET) scans in idiopathic pulmonary fibrosis (IPF).

METHODS

Seven male patients with histologically confirmed IPF underwent (18)FDG-PET scans. Scans were analyzed qualitatively and interpreted as positive or negative. Patients also underwent pulmonary function tests and computed tomography (CT) scans.

RESULTS

The average total lung capacity was 71 +/- 22% predicted (mean +/- SD) and diffusing capacity for carbon monoxide was 44 +/- 14% predicted. All had changes consistent with IPF on chest CT and 2 patients had ground glass attenuation. Six of seven patients (86%) had a positive (18)FDG-PET scan. Changes in the (18)FDG-PET scan were seen in 1 patient corresponding to changes in clinical status.

CONCLUSIONS

Our findings suggest that (18)FDG-PET scans may be helpful in the evaluation of IPF. Increased activity suggests active disease and changes in response to therapy.

Molecular imaging of the lungs

An emerging suite of new imaging techniques offer the ability to monitor and quantify molecular and cellular processes in the lungs noninvasively. These techniques take advantage of dramatic advances in both imaging technology as well as molecular and cell biology. Molecular imaging is being used with increasing regularity in research protocols, and forms of molecular imaging have found their way into the patient care setting (eg, positron emission tomography imaging in cancer). Such techniques will afford the basic scientist as well as the clinician an unprecedented opportunity for in vivo study of the lung biology that drives normal pulmonary physiology as well as pathophysiology.

Positron emission tomography in the investigation of pediatric inflammatory bowel disease

BACKGROUND

Endoscopic and radiologic studies are frequently required in inflammatory bowel disease (IBD) to determine disease activity, extent of disease, and delineating disease type. Positron emission tomography (PET) using fluorine-18-fluoro-deoxyglucose to identify metabolically active tissues may offer a simple noninvasive alternative to conventional studies in identification and localization of active intestinal inflammation in children with IBD. The aim of this study was to assess the value of PET in identifying active intestinal inflammation compared with conventional endoscopic and radiologic studies, including small bowel follow-through and colonoscopy.

METHODS

Sixty-five children were enrolled in the study. This included 55 children (mean age, 13.3 yr; range, 7-18 yr; 20 girls) with newly diagnosed IBD (37) or symptoms suggestive of recurrent disease (18) and 10 children with recurrent abdominal pain (mean age, 12.7 yr; range, 8-15 yr; 7 girls) who were studied with PET, and the results were compared with small bowel follow-through with pneumocolon and/or colonoscopy. Thirty-eight patients had Crohn's disease (17 ileal, 12 ileocolic, 5 pancolonic, 3 left-sided disease, 1 right-sided disease), and 17 had ulcerative colitis (15 pan-colitis, 2 left-sided colitis). Mean time interval between PET and other studies was 30 +/- 17.6 days.

RESULTS

PET correctly identified active inflammatory disease in 80% of children with IBD (81.5% with Crohn's disease; 76.4% with ulcerative colitis) and correctly showed no evidence of inflammation in children with recurrent abdominal pain. Gluorine-18-fluoro-deoxyglucose accumulated at sites that corresponded with active disease at colonoscopy in 83.8% of patients and with small bowel follow-through with pneumocolon 75.0% of the time.

CONCLUSION

This study suggests that PET offers a noninvasive tool for identifying and localizing active intestinal inflammation in children with IBD. PET may not be able to replace conventional studies; however, it may be useful when conventional studies cannot be performed or fail to be completed.

Molecular imaging for pediatric lung diseases

Molecular imaging is a rapidly developing multidisciplinary field that combines advances in contrast agent development, instrumentation, and molecular/cell biology to follow cellular and sub-cellular events in intact organisms. Platforms for molecular imaging include radionuclide-based methods, optical methods, and magnetic resonance. To date, molecular imaging studies of the lungs have been used to monitor the effectiveness of gene transfer, neutrophilic inflammation, and cell trafficking. Eventually, the goal will be to translate these new techniques to clinical settings such as cystic fibrosis.

Gallium and other agents in diseases of the lung

The use of gallium for pulmonary diseases is hampered by its relative lack of specificity, typical 1- to 3-day delay between injection and imaging time, and suboptimal imaging characteristics. Other nuclear and nonnuclear imaging modalities, such as (18)F-fluorodeoxyglucose positron emission tomography (PET) and high-resolution chest computed tomography, have replaced gallium in many clinical algorithms. Yet gallium and other radiotracers, such as thallium, sestamibi, and labeled white blood cells, are useful in many specific clinical situations involving lymphoma and other neoplasias, inflammatory processes such as sarcoid and interstitial pneumonia, tuberculosis and other infections, and the acquired immune deficiency syndrome. Gallium and some of the other single-photon agents still have value in establishing a diagnosis, assessing the location and extent of disease, differentiating active disease from chronic scarring, guiding potential biopsy, and determining recurrence and response to therapy in patients with certain lung diseases, particularly when access to PET imaging is not available.

Pulmonary (99m)Tc-DTPA aerosol clearance and survival in usual interstitial pneumonia (UIP)

BACKGROUND

Clearance of inhaled technetium 99m-labelled diethylenetriamine penta-acetic acid ((99m)Tc-DTPA) from the lungs is a potential indicator of disease progression in patients with idiopathic pulmonary fibrosis (IPF).

METHODS

We prospectively analysed the usefulness of this technique for predicting survival in 106 non-smoking patients with usual interstitial pneumonia (UIP) pattern IPF diagnosed by high resolution CT (HRCT) scanning or histological examination (M/F 65/41, mean (SD) age 61 (11) years). DTPA clearance was analysed according to both mono-exponential and bi-exponential models. Half times for the fast (t(0.5)F) and slow (t(0.5)S) components of clearance, the percentage contribution of the fast component (fF), and half time for mono-exponential approximation to the early part of the clearance curve (t(0.5)) were calculated.

RESULTS

The patients had substantially faster t(0.5) (mean 23.9 (9.6) minutes) than normal values (>45 minutes). Thirty seven patients (35%) died during follow up (median 15 months). Univariate Cox regression analysis identified significant predictors of survival as age, forced expiratory volume in 1 second (FEV(1)), forced vital capacity (FVC), total lung capacity (TLC), % predicted TLC, carbon monoxide transfer factor (TLCO), % predicted TLCO, arterial oxygen tension (PaO(2)), oxygen saturation, t(0.5)F, and HRCT fibrosis score. Multiple stepwise Cox regression analysis identified t(0.5)F (p=0.03, hazard ratio 0.747, 95% CI 0.578 to 0.964), % predicted TLC (p=0.02, hazard ratio 0.976, 95% CI 0.956 to 0.995), % predicted TLCO (p=0.003, hazard ratio 0.960, 95% CI 0.935 to 0.986), and age (p=0.003, hazard ratio 1.062, 95% CI 1.021 to 1.104) as independent predictors of survival.

CONCLUSION

These data suggest that (99m)Tc-DTPA clearance t(0.5)F measurement may predict survival in patients with UIP pattern IPF.

Incidental detection of thoracic sarcoidosis on whole-body 18fluorine-2- fluoro-2-deoxy-D-glucose positron emission tomography

18 Fluorine-2- Fluoro-2-Deoxy-D-Glucose positron emission tomography (18FDG PET) allows imaging of sites with increased metabolic activity. Increased metabolic activity in mediastinal nodes in sarcoidosis has been described. We report the prospective diagnosis of thoracic sarcoidosis on 18FDG PET based on extensive, peripheral, upper lobe parenchymal, and mediastinal nodal tracer uptake.

F-18 fluorodeoxyglucose chest uptake in lung inflammation and infection

PURPOSE

F-18 fluorodeoxyglucose (FDG) may accumulate at sites of inflammation or infection, making interpretation of whole-body scans difficult in patients with cancer.

METHODS

More than 650 whole-body positron emission tomographic (PET) scans performed to examine patients with cancer were reviewed to identify uptake in pulmonary infection or inflammation based on the appearance of F-18 FDG chest uptake, chest radiographs, computed tomography, or all of these.

RESULTS

Ten patients had uptake in benign lung disease. Eight patients had head and neck tumors and two patients had breast cancer. Intense focal or multifocal F-18 FDG chest uptake was seen in 6 of 10 scans. This was difficult to distinguish from pulmonary metastases based on the scan appearance. However, in the remaining patients, the uptake was atypical for malignancy and displayed an apical, segmental, or lobar pattern. In all patients, the F-18 FDG lung uptake corresponded to benign radiologic changes (infiltration, consolidation, or atelectasis), and the final diagnosis was pulmonary inflammation or infection. Nine patients were asymptomatic and one patient had clinical aspiration pneumonia. Follow-up PET scans were performed in five patients to evaluate their conditions. Chest uptake disappeared completely in three patients and partially in two patients, and there were no new findings. Variable degrees of F-18 FDG chest uptake have been reported with more than 40 different benign causes. They can be classified based on the underlying mechanism into four major categories: 1) Inflammation or infection, 2) benign tumor, 3) physiologic activity, and 4) iatrogenic. Most of these false-positive cases are included in the first category.

CONCLUSIONS

Pulmonary infection or inflammation might predispose patients to localized F-18 FDG chest uptake mimicking pulmonary metastases and limiting the specificity of whole-body scans performed in patients with cancer.

F-18-FDG uptake in tuberculosis

Two patients are described who showed abnormal fluorine-18 fluorodeoxyglucose (F-18 FDG) uptake that was due to benign disease, specifically tuberculous lymphadenitis and pneumonitis. The first patient had ulceration and oozing of the left nipple that was related to Paget's disease. An F-18 FDG PET, whole-body scan, which was performed for staging, showed no breast uptake. However, there was intense multifocal uptake in mediastinal, supraclavicular, and para-aortic areas that was confirmed radiologically to represent widespread lymphadenopathy. Pathologic examination of a mediastinal lymph node showed active tuberculosis. The second patient showed intense focal F-18 FDG uptake in mediastinal and supraclavicular areas and para-aortic lymphadenopathy due to non-Hodgkin's lymphoma. In addition, there was abnormal F-18 FDG lung uptake that revealed the presence of acid-fast bacilli on bronchial lavage. Intense focal F-18 FDG uptake in widespread lymphadenopathy or in the lung could be caused by infectious diseases such as tuberculosis. This possibility should be considered when whole-body scans of patients with cancer are interpreted, especially in those with a high incidence of infectious disease.

The evaluation of lung function with PET

In many ways, the lung is an ideal organ for study with positron emission tomography (PET). First, structure-function relations are homogeneous over larger areas than in other organs (reducing problems associated with otherwise relatively poor spatial resolution and partial-volume averaging). Second, many physiologic and metabolic processes can be studied, including pulmonary blood flow, ventilation, vascular permeability, endothelial receptor and enzyme function, among others. A variety of radiotracers have been used to evaluate pulmonary blood flow with PET, including 68Ga- or 11C-albumin microspheres administered intravenously, H2 15O administered by i.v. infusion, and 13N-N2 administered by inhalation. Pulmonary ventilation has been evaluated with both 13N-N2 and 19Ne gas, also administered by inhalation. In general, the relative advantage of one approach over another depends on site-specific cyclotron capacity and experience, and on the nature and timing of concomitant studies with other positron-emitting radiopharmaceuticals. The various blood flow methods have been used primarily in studies of pulmonary gas exchange, in both experimental animals and in humans. Acute lung injury is usually defined by both an increase in extravascular water (pulmonary edema) and an increase in the permeability of the pulmonary endothelium to protein. Both processes can easily be evaluated with PET. Extravascular water is measured by a combination of scans with i.v. H2 15O and C15O. The latter is administered by inhalation to label the blood pool (to calculate intravascular water concentrations). Pulmonary vascular permeability has been evaluated with dynamic sequential imaging after either 68Ga-transferrin or 11C-methylalbumin infusions. The rate of uptake of either tracer into the pulmonary extravascular space is an index of "leakiness" of the pulmonary endothelium, and is quantified as the pulmonary transcapillary escape rate, or PTCER. PTCER appears to be a highly sensitive index of acute lung injury. Two receptor/ enzyme systems that have been evaluated include the beta-adrenergic receptor system (using 11CGP-12177 as the ligand) and angiotensin converting enzyme (using 18F-fluorocaptopril). In each case, the object is to measure Bmax, or the maximum binding-capacity for the ligand in question. Changes in Bmax can be used to infer changes in protein expression of the receptor or enzyme, or can be used to quantify adequacy of therapy with inhibitor drugs. Given the highly active nature of the pulmonary endothelium, it is likely that many other pulmonary receptor or enzyme systems can be studied in a similar fashion.

Pulmonary fibrosis correlates with duration of tissue neutrophil activation

The role of inflammatory cells such as neutrophil granulocytes in the pathogenesis of pulmonary scarring is unclear. We determined the metabolic activity of neutrophils with positron emission tomography (PET) to measure regional uptake of (18F)-2-fluoro-2-deoxy-D-glucose (18FDG) following its intravenous injection. Fibrogenic or nonfibrogenic substances were instilled into the right upper lobe of rabbit lungs. Time course and intensity of the 18FDG signal in the affected region varied markedly, depending on the stimulus. Time to peak signal (Tmax) and rate constant for its decline (k) for the test substances were, respectively: C5a 10 h (Tmax), 0.045 +/- 0.030 h-1 (k); Streptococcus pneumoniae 15 h, 0.068 +/- 0.012 h-1; bleomycin 28 h, 0.002 +/- 0.001 h-1; microcrystalline silica (microXSiO2), 90 h, 0.0012 +/- 0.0007 h-1; amorphous silica (aSiO2), no response. Response to the nonfibrogenic agents C5a, S. pneumoniae and aSiO2 was brief or nonexistent, falling to baseline values within 3 d, whereas that to the fibrogenic agents bleomycin and microXSiO2 persisted for up to 4 wk. Neutrophil numbers in the lung were proportional to the 18FDG signal following C5a and S. pneumoniae, but not bleomycin and microXSiO2. Autoradiography of lungs following administration of (3H)-deoxyglucose [(3H)-DG] showed specific localization to neutrophils in all models. Thus, 18FDG uptake provides a remarkably specific measure of neutrophil activity in situ, and the development of pulmonary fibrosis may be related to persistence of this activity.

Nuclear imaging. 67Gallium, 201thallium, 18F-labeled fluoro-2-deoxy-D-glucose positron emission tomography

67Gallium scan has been used for years in sarcoidosis as a marker of activity, a determiner of the extent and distribution of the disease, a diagnostic support, and an aid in therapeutic management. Because of its limited sensitivity and specificity for sarcoidosis, however, it is currently used mainly to assist in diagnosis in difficult cases, particularly in those with isolated extrathoracic sarcoidosis. The finding of the typical lambda or panda patterns supports the diagnosis and reinforces the indication to perform an appropriate biopsy or Kveim-Siltzbach test. In addition, the detection of clinically silent extrathoracic uptake may provide sites for biopsy. 67Gallium scans' routine use in the follow-up of pulmonary sarcoidosis under treatment has decreased because that is best accomplished by means of serial chest radiographs and PFT. 201Thallium scintigraphy studies the myocardial perfusion and is complementary to echocardiography and 24-hour electrocardiographic monitoring in the assessment of sarcoid cardiac involvement. It typically shows segmental areas of decreased uptake in the ventricular myocardium that disappear or decrease in size during stress or after intravenous administration of dipyridamole. That reverse distribution is not specific for cardiac sarcoidosis, however, because it may also occur in other cardiomyopathies. PET is based on the increase of glucose metabolism in inflamed tissues. It may have great potential to assess sarcoidosis activity, but it is still largely experimental and is not routinely employed.

[18F]fluorodeoxyglucose uptake in neonatal acute lung injury measured by positron emission tomography

The objective of this study was to evaluate positron emission tomography (PET) of [18F]fluorodexoyglucose (18FDG) uptake as a measure of neonatal acute lung injury. Inasmuch as intrapulmonary sequestration of neutrophils is a hallmark of acute lung injury, quantification of neutrophil activity using 18FDG may offer a novel, in vivo technique to examine the progression and resolution of this disease. Ten newborn piglets were studied: six received bronchoalveolar lavage followed by 4 h of high pressure ventilation of create acute lung injury. Four healthy piglets served as controls. 18FDG (0.8 mCi/kg; 29.6 MBq) was given i.v. and PET (ECAT 953/31, Siemens) was performed for 90 min. During PET, all animals were sedated, paralyzed, and ventilated to maintain normal blood gases. The time course of radioactivity in lung regions and in plasma was used to calculate the rate constant for the metabolic trapping of 18FDG in tissue according to the method of C. S. Patlak. Median 18FDG influx constants were significantly higher in injured piglets (0.0187 min-1) than in control piglets (0.0052 min-1) (p < 0.01). Moreover, consistent with the 18FDG uptake data, injured piglets had moderate to severe injury on lung histology whereas control piglets had only slight and focal histologic changes. We conclude that PET of 18FDG uptake is an accurate, readily repeatable in vivo measure of neonatal acute lung injury.

Imaging allergen-invoked airway inflammation in atopic asthma with [18F]-fluorodeoxyglucose and positron emission tomography

BACKGROUND

Airway inflammation is a feature of asthma and can be quantified invasively with bronchial lavage and endobronchial histology. Inflammatory foci can be imaged non-invasively with positron emission tomography (PET) and [18F]-fluorodeoxyglucose (18FDG) to quantify glucose uptake in activated granulocytes. We used this technique to study airway inflammation in asthma.

METHODS

Nine men with mild atopic asthma were studied. In five, we studied the effect of bronchoscopic segmental allergen challenge on 18FDG uptake. Allergen was instilled into the posterior segment of the right upper lobe; a similar volume (20 mL) of isotonic saline was instilled into the posterior segment of the left upper lobe. At 1-32 h after instillation, PET with 18FDG was done. In the other four patients, we administered aerosolised allergen.

FINDINGS

18FDG uptake was increased four-fold in the right compared with the left upper lobe (geometric mean of ratios 4.30, 95% Cl 2.39-7.72, p=0.002). Aerosolised administration of allergen did not significantly increase 18FDG uptake.

INTERPRETATION

These data show that local allergen-invoked airway inflammation can be visualised with 18FDG and PET in asthma. The cellular localisation of the 18FDG signal remains to be determined.

Fluorine-18 deoxyglucose uptake in sarcoidosis measured with positron emission tomography

Regional pulmonary glucose metabolism (MRglu; mumol h-1 g-1), extravascular lung density (D(EV); g cm-3) and vascular volume (VB; ml cm-3) were measured in a single midthoracic transaxial slice (approximately 2 cm thick) using position emission tomography (PET) in seven patients with histologically proven sarcoidosis. The measurements were repeated 1-7 months later after steroid therapy (in two cases, no treatment) in order to assess MRglu as an index of inflammation and relate it to routine pulmonary function tests, chest radiography and serum angiotensin converting enzyme (SACE) levels. MRglu was computed from serial lung scans and peripheral venous blood samples for 60 min following an i.v. injection of 18F-2-fluoro-2-deoxy-D-glucose (18FDG). Both MRglu (which was increased in six of seven patients) and elevated SACE levels returned to normal in those patients treated with high-dose steroids. Regional vascular volume was normal in six of seven cases and did not change significantly with therapy. The high tissue density measured in all patients decreased significantly in two of three patients treated with 40 mg prednisolone daily. The abnormal MRglu observed in active sarcoidosis becomes normal pari passu with SACE levels during high-dose steroid therapy. We conclude that MRglu measured with 18FDG and PET may reflect "disease activity" in sarcoidosis in quantitative terms (per gram lung tissue) and in respect of disease distribution.

Eosinophils adhere to and stimulate replication of lung fibroblasts 'in vitro'

Eosinophils have been implicated in several disorders associated with the development of fibrosis. This led us to investigate the interactions between eosinophils and fibroblasts in vitro. Adhesion between purified guinea pig peritoneal eosinophils and monolayers of human fetal lung fibroblasts was assessed using the rose bengal dye staining assay. Fibroblast replication was assessed using a colorimetric assay based upon the uptake and subsequent release of methylene blue. Addition of phorbol myristate acetate induced a rapid, time-dependent increase in eosinophil adhesion (127% and 328% over basal adhesion after 10 and 30 min, respectively). Phorbol myristate acetate-induced adhesion was inhibited by the peptides RGDS and GRGDS (48% and 42%, respectively using 1 mM peptide) and by nordihydroguaiaretic acid, an inhibitor of the lipoxygenase pathway of arachidonic acid metabolism (46% inhibition at 15 microM). In addition, 24 h culture of fibroblast monolayers with interleukin 1 alpha (IL-1 alpha) or tumour necrosis factor alpha (TNF alpha) resulted in enhanced adhesion (10 U/ml IL-1 alpha stimulated adhesion by 55% of control, 500 U/ml TNF alpha by 75% of control). Conditioned media from cultured eosinophils stimulated fibroblast replication in a time-dependent fashion with maximal stimulation at 3 h. In contrast, media from guinea pig peritoneal macrophages in culture did not show such an effect. This study indicates that eosinophils are capable of both adhering to and releasing mitogens for fibroblasts in vitro. These observations suggest that eosinophils have the capacity to play a role in the development of fibrosis in disorders where they have been shown to be present.

Clinical deterioration in patients with idiopathic pulmonary fibrosis: causes and assessment

Patients with idiopathic pulmonary fibrosis (IPF) inevitably experience declines in functional status that are most frequently due to progressive pulmonary fibrosis. However, the cause of the clinical deterioration is often uncertain, and disease progression is difficult to distinguish from disease-associated complications or adverse effects of therapy. In studies of the clinical course of IPF, mortality is most frequently due to respiratory failure (38.7%); other causes of death include heart failure (14.4%), bronchogenic carcinoma (10.4%), ischemic heart disease (9.5%), infection (6.5%), and pulmonary embolism (3.4%). Other, usually nonfatal, disease-associated complications include pneumothorax, corticosteroid-induced metabolic side effects and myopathy, and therapy-related immunosuppression. In evaluating clinical deterioration in patients with IPF, disease-associated complications and adverse effects of therapy should be distinguished from progressive pulmonary fibrosis. The cause of clinical deterioration will alter the therapeutic intervention required and will influence patient prognosis and duration of survival. This article examines the causes of clinical deterioration in patients with IPF and the diagnostic procedures for assessing disease-associated complications and staging IPF progression.