Application of laser scanning confocal microscopy in the analysis of particle-induced pulmonary fibrosis.

Laser scanning confocal microscopy (LSCM) allows us to simultaneously quantitate the degree of lung fibrosis and distinguish various pathological lesions of intact lung tissue. Lucifer Yellow has been shown an ideal fluorescent stain to examine the connective tissue matrix components of embedded lung tissue with LSCM. We evaluated the use of LSCM in quantitating lung fibrosis and compared this procedure with the more traditional method of assessing fibrosis by measuring hydroxyproline, a biochemical assay of collagen. CD/VAF rats were intratracheally dosed with silica (highly fibrogenic), Fe2O3 (non-fibrogenic), and saline (vehicle control) at a high dose of 10-mg/100 g body weight. At 60 days post-instillation, the left lung was dissolved in 6 M HCl and assayed for hydroxyproline. Silica induced increases of 58% and 94% in hydroxyproline content over the Fe2O3 and control groups, respectively. The right lung lobes were fixed, sectioned into blocks, dehydrated, stained with Lucifer Yellow (0.1 mg/ml), and embedded in Spurr plastic. Using LSCM and ImageSpace software, the tissue areas of ten random scans from ten blocks of tissue for each of the three groups were measured, and three-dimensional reconstructions of random areas of lung were generated. The silica group showed increases of 57% and 60% in the lung areas stained by Lucifer Yellow over the Fe2O3 and control groups, respectively. Regression analysis of hydroxyproline vs. lung tissue area demonstrated a significant positive correlation (p < 0.05) with a correlation coefficient of 0.91. Histological analysis of right lung tissue revealed a marked degree of granulomatous interstitial pneumonitis for the silica group, which was absent in the Fe2O3 and control groups. No significant differences (p < 0.05) in hydroxyproline content and measured tissue area were observed between the Fe2O3 and control groups. LSCM, and its associated advanced image analysis and three-dimensional capabilities, is an alternative method to both quickly quantitate and examine fibrotic lung disease without physical disruption of the tissue specimen.

Subchronic pulmonary inflammation and fibrosis induced by silica in rats are attenuated by amiodarone.

A previous study demonstrated that the acute phase of silica-induced lung injury in rats can be attenuated by concomitant administration of amiodarone, a cationic amphiphilic drug that inhibits phospholipase activity in the lungs. The purpose of the present study was to determine whether continued amiodarone administration could inhibit subchronic silica-induced lung injury and fibrosis. Male Fischer-344 rats were administered amiodarone (150 mg/kg, p.o., 5 days/week) for 14 days and were then instilled with silica (100 mg/kg) intratracheally. Amiodarone treatment then continued for 60 days. Injury was evaluated by parameters in bronchoalveolar lavage fluid and fibrosis was assessed by lung hydroxyproline content and trichrome staining of collagen. Within the bronchoalveolar lavage fluid, amiodarone treatment resulted in significant decreases in silica-induced elevations in albumin levels, lactate dehydrogenase activity, beta-glucuronidase activity, and neutrophil influx. Amiodarone treatment resulted in significant reductions in silica-induced increases in lung weight and hydroxyproline levels; the diminution of fibrosis due to amiodarone treatment was confirmed histologically. These results indicate that subchronic pulmonary inflammation and fibrosis induced by silica in the rat can be attenuated by the concomitant administration of amiodarone.

Metabolism of amiodarone following intratracheal instillation in hamsters.

Intratracheal instillation of the antiarrhythmic drug amiodarone (AD) in hamsters is an established animal model of AD-induced pulmonary fibrosis. A metabolite of AD, desethylamiodarone (dAD), has also been shown to produce pulmonary fibrosis in this model. It was previously reported that following intratracheal instillation of AD in hamsters, metabolite could not be detected in lung tissue. However, in studies in our laboratory dAD was detected following instillation of AD. The goal of the present study was to monitor the distribution of AD and dAD to lung and liver within 1 h of AD instillation and to investigate the site of AD metabolism. Both AD and dAD were detected in the lung and liver within 5 min of AD instillation; lung and liver concentrations of AD and dAD were also quantified at 30 and 60 min following AD instillation. Incubation of lung and liver microsomes with AD showed that the liver is a probable site of AD metabolism following the intratracheal administration of AD to hamsters.

Pulmonary responses to amiodarone in hamsters: comparison of intratracheal and oral administrations.

Amiodarone (AD) has been shown to produce a transient pulmonary fibrosis in hamsters after intratracheal (i.t.) instillation. The goal of this study was to examine bronchoalveolar lavage (BAL) parameters during the development of fibrosis after i.t. AD in hamsters and to examine the responses to oral AD in hamsters for comparison to responses to i.t. AD in an effort to explore the roles of inflammation, phospholipidosis, and lung drug burden in AD-induced pulmonary disease. Two i.t. instillations on Days 0 and 7 of AD in hamsters produced fibrosis as characterized by elevated lung hydroxyproline content and variable increases in lavage macrophage, neutrophil, and eosinophil number through Day 28. Intratracheal AD also increased the permeability of the alveolar-capillary barrier as evidenced by an increase in BAL fluid albumin only on Day 8. Pulmonary phospholipidosis was not induced by i.t. AD and only small amounts of AD and its metabolite desethyl-AD (dAD) were detected in lung tissue through Day 10 after instillation on Days 0 and 7. The repeated oral administration of AD did not result in pulmonary fibrosis during the 35-day course of this study. Oral AD did cause a sustained increase in BAL fluid neutrophil number; other BAL cells were only slightly affected. Oral AD did not increase BAL fluid albumin content but a prominent BAL cell phospholipidosis was noted. Measurement of AD and dAD in lung tissue demonstrated a substantial accumulation of drug and metabolite after oral treatment with AD. The results of this study indicate that lung drug burden, pulmonary phospholipidosis, and lung neutrophil influx are not crucial factors in the development of AD-induced pulmonary fibrosis in hamsters. This study supports the possible involvement of physical damage to the lung and/or pulmonary eosinophilia in the generation of AD-induced pulmonary fibrosis in hamsters.

Acute pulmonary inflammation in hamsters following intratracheal administration of amiodarone.

The use of the antiarrythmic drug amiodarone (AD) has been limited by the propensity of the drug to cause severe lung damage. AD has been shown to produce a transient pulmonary fibrosis in hamsters after intratracheal instillation. The goal of this study was to characterize the early inflammatory events associated with the administration of AD. Male Syrian hamsters that were instilled intratracheally with AD or saline vehicle underwent bronchoalveolar lavage (BAL). Total cells, macrophages, and eosinophils obtained by BAL were elevated by AD treatment at day 3. At both days 1 and 3 after instillation, AD-treated animals had significant elevations in neutrophil number. BAL fluid albumin was significantly elevated at day 1 in treated animals. Chemiluminescence (CL) performed on cells obtained by BAL showed an increase in CL of AD-treated samples compared to controls in phorbol myristate acetate (PMA) stimulated CL. PMA-induced increases in responsiveness were diminished by superoxide dismutase and catalase. These results indicate that oxidants such as superoxide and hydrogen peroxide may be involved in this inflammatory process. The results of this study show that intratracheal instillation of AD results in an inflammatory response that can be assessed by cellular, biochemical, and functional means.