Loss of CD73 prevents accumulation of alternatively activated macrophages and the formation of prefibrotic macrophage clusters in irradiated lungs.

While radiotherapy is a mainstay for cancer therapy, pneumonitis and fibrosis constitute dose-limiting side effects of thorax and whole body irradiation. So far, the contribution of immune cells to disease progression is largely unknown. Here we studied the role of ecto-5'-nucelotidase (CD73)/adenosine-induced changes in the myeloid compartment in radiation-induced lung fibrosis. C57BL/6 wild-type or CD73-/- mice received a single dose of whole thorax irradiation (WTI, 15 Gy). Myeloid cells were characterized in flow cytometric, histologic, and immunohistochemical analyses as well as RNA analyses. WTI induced a pronounced reduction of alveolar macrophages in both strains that recovered within 6 wk. Fibrosis development in wild-type mice was associated with a time-dependent deposition of hyaluronic acid (HA) and increased expression of markers for alternative activation on alveolar macrophages. These include the antiinflammatory macrophage mannose receptor and arginase-1. Further, macrophages accumulated in organized clusters and expressed profibrotic mediators at ≥25 wk after irradiation (fibrotic phase). Irradiated CD73-/- mice showed an altered regulation of components of the HA system and no clusters of alternatively activated macrophages. We speculate that accumulation of alternatively activated macrophages in organized clusters represents the origins of fibrotic foci after WTI and is promoted by a cross-talk between HA, CD73/adenosine signaling, and other profibrotic mediators.-De Leve, S., Wirsdörfer, F., Cappuccini, F., Schütze, A., Meyer, A. V., Röck, K., Thompson, L. F., Fischer, J. W., Stuschke, M., Jendrossek, V. Loss of CD73 prevents accumulation of alternatively activated macrophages and the formation of prefibrotic macrophage clusters in irradiated lungs.

Irradiation as a hazard for mucociliary clearance.

OBJECTIVES: In this paper we study effects of irradiation to pulmonary tissue on a micro and ultrastructural level to get insights into the dynamics of morphological changes and associated post-radiative physiological conditions. METHODS: Animal and human pulmonary tissue with and without radiation damage was subject to light, transmission, scanning and polarization microscopy and morphometric evaluation. RESULTS: The present investigations on the influence of irradiation on experimental and human lung tissue demonstrate that complex changes are induced in the cells which are essential for mucociliary clearance. These changes are a shortage of alveolar macrophages, cell apoptosis, proliferation of collagen ligament in the barrier of gaseous exchange, retraction of endothelial lining of capillaries and significant broadening of the gaseous exchange barrier, resulting in serious damage for the O2 and CO2 exchange. CONCLUSIONS: These changes at microscopic, cellular, and ciliary level trigger conditions for various diseases of the respiratory system, which is further assessed by a simultaneous computer aided estimation of ciliary function. With the concurrent world-wide increase of respiratory diseases, these findings are important knowledge for the clinical practice.

An experimental model-based exploration of cytokines in ablative radiation-induced lung injury in vivo and in vitro.

INTRODUCTION: Stereotactic ablative radiotherapy is a newly emerging radiotherapy treatment method that, compared with conventionally fractionated radiation therapy (CFRT), allows an ablative dose of radiation to be delivered to a confined area around a tumor. The aim of the present study was to investigate the changes of various cytokines that may be involved in ablative radiation-induced lung injury in vitro and in vivo. METHODS: In the in vivo study, ablative-dose radiation was delivered to a small volume of the left lung of C3H/HeJCr mice using a small-animal irradiator. The levels of 24 cytokines in the peripheral blood were tested at several time points after irradiation. For the in vitro study, three mouse cell types (type II pneumocytes, alveolar macrophages, and fibroblasts) known to play important roles in radiation-induced pneumonitis and lung fibrosis were analyzed using a co-culture system. RESULTS: In the in vivo study, we found obvious patterns of serum cytokine changes depending on the volume of tissue irradiated (2-mm vs. 3.5-mm collimator). Only the levels of 3 cytokines increased with the 2-mm collimator at the acute phase (1-2 weeks after irradiation), while the majority of cytokines were elevated with the 3.5-mm collimator. In the in vitro co-culture system, after the cells were given an ablative dose of irradiation, the levels of five cytokines (GM-CSF, G-CSF, IL-6, MCP-1, and KC) increased significantly in a dose-dependent manner. CONCLUSIONS: The cytokine levels in our radiation-induced lung injury model showed specific changes, both in vivo and in vitro. These results imply that biological studies related to ablative-dose small-volume irradiation should be investigated using the corresponding experimental models rather than on those simulating large-volume CFRT.

Induction of neuritogenesis in PC12 cells by a pulsed electromagnetic field via MEK-ERK1/2 signaling.

We examined the regulation of neuritogenesis by a pulsed electromagnetic field (PEMF) in rat PC12 pheochromocytoma cells, which can be induced to differentiate into neuron-like cells with elongated neurites by inducers such as nerve growth factor (NGF). Plated PC12 cells were exposed to a single PEMF (central magnetic flux density, 700 mT; frequency, 0.172 Hz) for up to 12 h per day and were then evaluated for extent of neuritogenesis or acetylcholine esterase (AChE) activity. To analyze the mechanism underlying the effect of the PEMF on the cells, its effects on intracellular signaling were examined using the ERK kinase (MEK) inhibitors PD098059 and U0126 (U0124 was used as a negative control for U0126). The number of neurite-bearing PC12 cells and AChE activity increased after PEMF exposure without the addition of other inducers of neuritogenesis. Additionally, PEMF exposure induced sustained activation of ERK1/2 in PC12 cells, but not in NR8383 rat alveolar macrophages. Furthermore, U0126 strongly inhibited PEMF-dependent ERK1/2 activation and neuritogenesis. The PEMF-dependent neuritogenesis was also suppressed by PD098059, but not U0124. These results suggest that PEMF stimulation independently induced neuritogenesis and that activation of MEK-ERK1/2 signaling was induced by a cell-type-dependent mechanism required for PEMF-dependent neuritogenesis in PC12 cells.

Low-level laser therapy (LLLT) acts as cAMP-elevating agent in acute respiratory distress syndrome.

The aim of this work was to investigate if the low-level laser therapy (LLLT) on acute lung inflammation (ALI) induced by lipopolysaccharide (LPS) is linked to tumor necrosis factor (TNF) in alveolar macrophages (AM) from bronchoalveolar lavage fluid (BALF) of mice. LLLT has been reported to actuate positively for relieving the late and early symptoms of airway and lung inflammation. It is not known if the increased TNF mRNA expression and dysfunction of cAMP generation observed in ALI can be influenced by LLLT. For in vivo studies, Balb/c mice (n = 5 for group) received LPS inhalation or TNF intra nasal instillation and 3 h after LPS or TNF-α, leukocytes in BALF were analyzed. LLLT administered perpendicularly to a point in the middle of the dissected bronchi with a wavelength of 660 nm and a dose of 4.5 J/cm(2). The mice were irradiated 15 min after ALI induction. In vitro AM from mice were cultured for analyses of TNF mRNA expression and protein and adenosine3':5'-cyclic monophosphate (cAMP) levels. One hour after LPS, the TNF and cAMP levels in AM were measured by ELISA. RT-PCR was used to measure TNF mRNA in AM. The LLLT was inefficient in potentiating the rolipram effect in presence of a TNF synthesis inhibitor. LLLT attenuated the neutrophil influx and TNF in BALF. In AM, the laser increased the cAMP and reduced the TNF-α mRNA. LLLT increases indirectly the cAMP in AM by a TNF-dependent mechanism.

IGF-1 Receptor Signaling Regulates Type II Pneumocyte Senescence and Resulting Macrophage Polarization in Lung Fibrosis.

PURPOSE: Type II pneumocyte (alveolar epithelial cells type II [AECII]) senescence has been implicated in the progression of lung fibrosis. The capacity of senescent cells to modulate pulmonary macrophages to drive fibrosis is unexplored. Insulin-like growth factor-1 receptor (IGF-1R) signaling has been implicated as a regulator of senescence and aging. METHODS AND MATERIALS: Mice with an AECII-specific deletion of IGF-1R received thoracic irradiation (n ≥ 5 per condition), and the effect of IGF-1R deficiency on radiation-induced AECII senescence and macrophage polarization to an alternatively activated phenotype (M2) was investigated. IGF-1R signaling, macrophage polarization, and senescence were evaluated in surgically resected human lung (n = 63). RESULTS: IGF-1R deficient mice demonstrated reduced AECII senescence (senescent AECII/field; intact: 7.25% ± 3.5% [mean ± SD], deficient: 2.75% ± 2.8%, P = .0001), reduced accumulation of M2 macrophages (intact: 24.7 ± 2.2 cells/field, deficient: 15.5 ± 1.2 cells/field, P = .0086), and fibrosis (hydroxyproline content; intact: 71.9 ± 21.7 µg/lung, deficient: 31.7 ± 7.9, P = .0485) after irradiation. Senescent AECII enhanced M2 polarization in a paracrine fashion (relative Arg1 mRNA, 0 Gy: 1.0 ± 0.4, 17.5 Gy: 7.34 ± 0.5, P < .0001). Evaluation of surgical samples from patients treated with chemoradiation demonstrated increased expression of IGF-1 (unirradiated: 10.2% ± 4.9% area, irradiated: 15.1% ± 11.5%, P = .0377), p21 (unirradiated: 0.013 ± 0.02 histoscore, irradiated: 0.084 ± 0.09 histoscore, P = .0002), IL-13 (unirradiated: 13.7% ± 2.8% area, irradiated: 21.7% ± 3.8%, P < .0001), and M2 macrophages in fibrotic regions relative to nonfibrotic regions (unirradiated: 11.4 ± 12.2 CD163 + cells/core, irradiated: 43.1 ± 40.9 cells/core, P = .0011), consistent with findings from animal models of lung fibrosis. CONCLUSIONS: This study demonstrates that senescent AECII are necessary for the progression of pulmonary fibrosis and serve as a targetable, chronic stimuli for macrophage activation in fibrotic lung.

Captopril reduces lung inflammation and accelerated senescence in response to thoracic radiation in mice.

The lung is sensitive to radiation and exhibits several phases of injury, with an initial phase of radiation-induced pneumonitis followed by delayed and irreversible fibrosis. The angiotensin-converting enzyme inhibitor captopril has been demonstrated to mitigate radiation lung injury and to improve survival in animal models of thoracic irradiation, but the mechanism remains poorly understood. Here we investigated the effect of captopril on early inflammatory events in the lung in female CBA/J mice exposed to thoracic X-ray irradiation of 17-17.9 Gy (0.5-0.745 Gy min-1). For whole-body + thoracic irradiation, mice were exposed to 7.5 Gy (0.6 Gy min-1) total-body 60Co irradiation and 9.5 Gy thoracic irradiation. Captopril was administered orally (110 mg kg-1 day-1) in the drinking water, initiated 4 h through to150 days post-irradiation. Captopril treatment increased survival from thoracic irradiation to 75% at 150 days compared with 0% survival in vehicle-treated animals. Survival was characterized by a significant decrease in radiation-induced pneumonitis and fibrosis. Investigation of early inflammatory events showed that captopril significantly attenuated macrophage accumulation and decreased the synthesis of radiation-induced interleukin-1ß (IL-1ß) and tumor necrosis factor-α (TNF-α) pro-inflammatory cytokines in the lungs of irradiated mice. Suppression of IL-1ß and TNF-α correlated with an increase of the anti-inflammatory cytokine IL-10 in the spleen with captopril treatment. We also found that captopril decreased markers for radiation-induced accelerated senescence in the lung tissue. Our data suggest that suppression of inflammation and senescence markers, combined with an increase of anti-inflammatory factors, are a part of the mechanism for captopril-induced survival in thoracic irradiated mice.

MALDI-MSI spatially maps N-glycan alterations to histologically distinct pulmonary pathologies following irradiation.

Radiation-induced lung injury is a highly complex combination of pathological alterations that develop over time and severity of disease development is dose-dependent. Following exposures to lethal doses of irradiation, morbidity and mortality can occur due to a combination of edema, pneumonitis and fibrosis. Protein glycosylation has essential roles in a plethora of biological and immunological processes. Alterations in glycosylation profiles have been detected in diseases ranging from infection, inflammation and cancer. We utilized mass spectrometry imaging to spatially map N-glycans to distinct pathological alterations during the clinically latent period and at 180 days post-exposure to irradiation. Results identified alterations in a number of high mannose, hybrid and complex N-glycans that were localized to regions of mucus and alveolar-bronchiolar hyperplasia, proliferations of type 2 epithelial cells, accumulations of macrophages, edema and fibrosis. The glycosylation profiles indicate most alterations occur prior to the onset of clinical symptoms as a result of pathological manifestations. Alterations in five N-glycans were identified as a function of time post-exposure. Understanding the functional roles N-glycans play in the development of these pathologies, particularly in the accumulation of macrophages and their phenotype, may lead to new therapeutic avenues for the treatment of radiation-induced lung injury.

Establishment of an in vitro model using the rat alveolar macrophage cell line NR8383.

OBJECTIVE: To establish an in vitro model of radiation-induced lung injury using rat lung alveolar macrophages (NR8383). METHODS: Using a medical electronic linear accelerator, cells were irradiated with either 0 Gy or 6 Gy X-rays. At 6, 12, 24, 30 and 48 h, the DNA damage index (8-OHdG) and lipid damage index (MDA) were measured in the two groups. We also determined the levels of tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6) and transforming growth factor-ß (TGF-ß). RESULTS: The levels of 8-OHdG and MDA in the 6 Gy irradiation group were higher than those in the 0 Gy group at 6, 12, 24, 30 and 48 h after irradiation. The levels reached the highest value -6 h after irradiation, and then gradually decreased. The levels of the inflammatory factors TNF-α, TGF-ß and IL-6 were higher in the 6 Gy irradiation group than those in the 0 Gy group at 6, 12, 24, 30 and 48 h after irradiation. CONCLUSION: Six Gy X-ray irradiated NR8383 cells can be used to establish an in-vitro model of radiation-induced lung injury. The levels of 8-OHdG, MDA, TNF-α, TGF-ß and IL-6 can be used as effective evaluation indicators.

[The influence of ecological factors of Polesky State Radioecological Reserve on spontaneous and chemically induced mutagenesis and tumor formation].

The cycle of researches of the influence of an exposion of mice of line Af in the conditions of the zone of Chernobyl disaster on spontaneous and chemically induced mutability, lung tumour (adenomas), morphological and functional condition of alveolar macrophages, and also genetic effects in natural populations wild rodents is executed. The increase in polychromatic frequency in mouse bone marrow, adenomas in lungs, and change of sensitivity of an organism to action mutagen and transgenerational transfer of genetic damages is shown.

The histopathological evaluation of the effectiveness of melatonin as a protectant against acute lung injury induced by radiation therapy in a rat model.

PURPOSE: This study presents the histopathological evaluation of the effectiveness of melatonin as a protectant against acute lung injury induced by radiation therapy. MATERIALS AND METHODS: Thirty-two Wistar rats were divided into four groups. The rats in Group 1 received melatonin and underwent radiation therapy. The rats in Group 2 received no melatonin and underwent radiation therapy. The rats in Group 3 received melatonin and underwent sham radiation therapy. The rats in Group 4 received no melatonin and underwent sham radiation therapy. Melatonin was administered at a dose of 100 mg/kg using an intraperitoneal injection. Radiation therapy was delivered on a Cobalt-60 unit using a single fraction of 18 Gy through an anterior portal covering the right lung in entirety. The rats underwent euthanasia at 6 weeks following radiation therapy. The lungs were dissected and blinded histopathological evaluation was performed. RESULTS: Concerning the right lung, a decrease in intra-alveolar edema and intra-alveolar erythrocytes was observed despite an increase in activated macrophages, intra-alveolar fibrosis, hyaline arteriosclerosis and alveolar wall thickness for the rats in Group 1 as compared to the rats in Group 2. Concerning the left lung, a decrease in alveolar neutrophils and intra-alveolar erythrocytes was evident despite an increase in activated macrophages, hyaline arteriosclerosis and alveolar wall thickness for the rats in Group 1 as compared to the rats in Group 2. CONCLUSIONS: This study puts forward the histopathological evidence regarding the effectiveness of melatonin as a protectant against acute lung injury induced by radiation therapy through restrained inflammation, regrettably at the expense of promoted fibrosis. The effectiveness of melatonin as a protectant against acute lung injury induced by radiation therapy needs to be evaluated further for the unresolved concerns regarding the safety.

Partial volume rat lung irradiation: temporal fluctuations of in-field and out-of-field DNA damage and inflammatory cytokines following irradiation.

PURPOSE: The current study investigated the early activation of inflammatory cytokines and macrophages in different regions of the lung following partial volume irradiation. We examined temporal fluctuations in DNA damage, cytokine expression and macrophage activation during 16 weeks post-irradiation. MATERIALS AND METHODS: We irradiated the lower lung of Sprague-Dawley rats with 10 Gy. A micronucleus assay was used to examine DNA damage. Real-time Reverse Transcription-Polymerase Chain Reaction (RT-PCR) was used to analyse the RNA expression of Interleukin-1 alpha (IL-1a), Interleukin-1 beta (IL-1ss), Interleukin-6 (IL-6), Tumour Necrosis Factor alpha (TNF-a) and Transforming Growth Factor beta (TGF-ss) relative to Glyceraldehyde-3-Phosphate Dehydrogenase (GAPDH). The activation of macrophages was determined using the antibody ED-1 for immunohistochemical analysis. RESULTS: The expression of DNA damage, the activation of macrophages and the expression of inflammatory cytokines all fluctuated in a cyclic pattern. The initial induction of cytokine expression and the activation of macrophages occurred at very early times (1 h) following irradiation. Waves of cytokine expression and macrophage activation were also seen at later times (up to 16 weeks) following irradiation. DNA damage also occurred in a cyclic pattern though this was less pronounced out-of-field. The levels of cytokines and activated macrophages were elevated to a similar degree both in- and out-of-field, whereas there was a greater micronuclei yield in-field than out-of-field. CONCLUSIONS: An inflammatory response triggered by the partial volume irradiation occurs in the whole rat lung at very early times following irradiation and is maintained in a cyclic pattern to later times when the onset of functional symptoms is expected. We hypothesize that Reactive Oxygen Species (ROS) induced by this response play an important role in the induction of both in-field and out-of-field DNA damage.

Morphologic changes in alveolar macrophages in response to UVEC-activated pulmonary Type II epithelial cells.

We hypothesize that Type II epithelial cells, which line the distal airspaces of the lung, are early responders to invading pathogens and release a signal, which activates and alters the phenotype and phagocytosis properties of alveolar macrophages even at a distance. The T(7) cell line is a conditionally immortalized murine Type II epithelial cell line developed in our laboratory. Using an in vitro transwell model we have previously shown that UV-irradiated Escherichia coli (UVEC)-stimulated T(7) cells cultured in the lower transwell chamber, release a diffusible signal which activates MH-S cells (immortalized murine alveolar macrophages) cultured in the upper transwell chamber, to produce nitric oxide. Using scanning electron microscopy, we show that MH-S cells activated in this manner exhibit increased cell surface ruffling, numerous long filopodia, increased lamellipodia and cell flattening. DynaBead uptake studies show that these morphologic changes are accompanied by increased phagocytosis. These findings indicate that a diffusible signal released at a distance by UVEC-stimulated Type II epithelial cells initiates changes in morphology and phagocytosis reflective of macrophage activation concomitant with the functional activation we previously reported.

Molecular biology mechanisms in the radiation induction of pulmonary injury syndromes: interrelationship between the alveolar macrophage and the septal fibroblast.

Pulmonary fibrosis is a crippling, essentially lethal chronic disease due to an interplay of events following irradiation between the pneumonitic and fibrotic phases. In this series of experiments it is demonstrated that there is no latent period after irradiation, but an immediate intercellular communication system which springs into action to initiate recovery. Latency was only a function of our inability to uncover the molecular events that precede and underlie the clinical pathologic course of organ/tissue irradiation. Current advances in understanding the production of growth factors by different cells provides new insights to autocrine, paracrine and endocrine messages as a basis for understanding radiation pathophysiology as a progressive process that is amplified by other injurious events such as chemotoxicity. This is the first demonstrated release of trophic factors (cytokines) after in vivo irradiation that persists up to a month after exposure, suggesting that the persistence of a small incremental stimulus during a silent "latent" period can be the basis for the clinical pathologic expression of a late radiation effect, that is, pulmonary interstitial fibrosis.

The effect of gamma-irradiation on the adherent capacity and iron metabolism of alveolar macrophages in mice and rats.

The effect of external gamma-irradiation on the survival of alveolar macrophages (AM) and on the extracellular release of 59Fe from AM-ingested [59Fe]iron hydroxide colloid was investigated in vitro using cells from C3H mice and Wistar rats. 59Fe release from mouse AM was enhanced by irradiation in a dose-dependent fashion, but irradiation up to 112 Gy did not affect the release from rat AM. Cell survival of AM, measured by direct counting of cell nuclei of adherent AM or vital staining with crystal violet, decreased dose dependently in mice and rats, but mouse AM were more radiosensitive than rat AM.

Alveolar macrophage kinetics after inhalation of 239PuO2 by CBA/Ca mice: changes in synthesis of DNA.

For workers in the nuclear industry, the primary route for the entry of radioactive materials into the body is by inhalation, and the rate of clearance of particles from the pulmonary region of the lung is an important factor in determining radiation dose. It is the function of alveolar macrophages (AM) to maintain the sterility of the lung and to remove insoluble particles from the respiratory surfaces and airways. The AM population is not static, and under normal conditions the loss of macrophages from the alveoli via the conducting airways is balanced by renewal. Studies of the effects of external irradiation on the kinetics of AM are numerous, but to date little is known about the effects of inhaled radioactive particles. In this investigation the effects of inhaled 239PuO2 (plutonium dioxide) particles on the synthesis of DNA by AM were studied at times up to 77 days after exposure. We also measured the number of cells recovered by bronchoalveolar lavage and the incidence of AM with nuclear aberrations. The latter provides a sensitive indicator of the effects of radiation. One of the earliest effects observed after exposure to 239PuO2 is a reduction in the number of AM recovered by lavage. This reduction is associated with a 3-fold reduction in the proportion of AM undergoing DNA synthesis at early times after exposure. The overall mean pulse labeling index of AM recovered from sham-exposed mice is 1.68%, and no trend is observed with time.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of 60Co gamma-irradiation on the nonspecific cytotoxicity of alveolar macrophages in vitro.

This paper reports on the effect of radiation on the nonspecific cytotoxicity of rat alveolar macrophages (AM). AM (effector cells) of bacille Calmette-Guerin-activated Wistar rats were irradiated with 60Co gamma rays in vitro to give doses of 0, 100, 300, and 500 Gy. Three hours after irradiation, the AM were cultured with human lung adenocarcinoma AGZY83-a and HeLa target cells in 125I-deoxyuridine-containing media for 6 hr and the cytotoxicity indexes determined. The results indicated that the cytotoxicity indexes of AM against human lung adenocarcinoma cells and HeLa cells were 94.3 +/- 0.3% and 81.3 +/- 1.9%, respectively. The cytotoxicity indexes using an effector/target cell ratio (E/T) of 10 seemed to be greater than with ratios of 20 and 30. The cytotoxicity indexes of AM (7 rats), irradiated to give doses of 0, 100, 300, and 500 Gy, against adenocarcinoma cells at an E/T ratio of 10 were 87.9 +/- 8.4%, 65.4 +/- 14.1%, 47.5 +/- 17.5%, and 36.7 +/- 9.7%, respectively. The significance of the nonspecific cytotoxicity of AM in the immunological elimination of tumors and the inhibitory effect of radiation on AM cytotoxicity are discussed.

Release of interleukin-1 by human alveolar macrophages after in vitro irradiation.

Therapeutic thoracic irradiation may induce two late pulmonary injury syndromes: radiation pneumonitis and subsequent pulmonary fibrosis. The alveolar macrophage has been considered a radioresistant cell and not a target cell involved in the pathogenesis of either type of radiation-induced lung injury. Alveolar macrophage-derived cytokines, including interleukin-1 (IL-1) and tumor necrosis factor (TNF), have been demonstrated to participate in inflammatory and fibrotic responses in the lung after various other types of lung injury. To evaluate whether the release of cytokines by alveolar macrophages is induced by radiation doses used clinically, alveolar macrophages recovered from nonsmoking volunteers were exposed in vitro to a single dose of 2 Gy and then maintained in culture for 18 h. Culture supernatants and cell lysates were then recovered and analyzed for IL-1 alpha and IL-1 beta by radioimmunoassay. Supernatants of irradiated alveolar macrophages contained significantly increased amounts of IL-1 alpha (P < 0.04) and IL-1 beta (P < 0.02) as well as total IL-1 (IL-1 alpha and IL-1 beta) (P < 0.02) compared to nonirradiated alveolar macrophages. Cell lysates of irradiated alveolar macrophages also contained increased amounts of IL-1 alpha and IL-1 beta, although differences from controls were not significant. The finding of increased release of IL-1 by alveolar macrophages after exposure to a single, clinically relevant dose of radiation suggests that the function of human alveolar macrophages is likely altered during therapeutic use of thoracic irradiation. Whether this release of IL-1 by alveolar macrophages contributes to early lung inflammation induced by thoracic irradiation is unclear.

Estimation of the dose of radon progeny to the peripheral lung and the effect of exposure to radon progeny on the alveolar macrophage.

Groups of rats were exposed to radon progeny attached to a vector aerosol of cigarette smoke particles in a closed-loop exposure system. The total exposures ranged from 70 to 1020 WLM over a 3-5-h period. Alveolar macrophages were lavaged from exposed and control rats (exposed to the vector aerosol alone). There were no differences between phagocytic capabilities of the macrophages lavaged from the controls and any group of exposed rats. The increases in the numbers of binucleated/multinucleated and micronucleated macrophages were enumerated using cytological preparations of lavaged alveolar macrophages after exposure compared to the numbers in the control rats. The peak response in numbers of binucleated/multinucleated and micronucleated macrophages occurred at 21 days after exposure, beyond which the numbers decreased. This peak response showed a significant exposure-dependent relationship. The number of micronuclei provided a sensitive indicator of exposure. The lowest exposure level used (70 WLM) resulted in a significant difference in the number of micronucleated macrophages between control and exposed rats. The alpha-particle dose to the peripheral lung was estimated by comparing formation of micronuclei in cultured macrophages exposed to alpha particles from 238Pu (where the dose was known) to micronuclei in lavaged macrophages from animals exposed to radon progeny (where the exposure concentration was known, but the dose was not known). The dose estimated in this way for the peripheral lung was 9.8 +/- 1.2 mGy/WLM. This value is three to five times higher than predicted from mathematical models currently available.

Changes in the rat lung after exposure to radon and its progeny: effects on incorporation of bromodeoxyuridine in epithelial cells and on the incidence of nuclear aberrations in alveolar macrophages.

The aim of this study was to investigate some responses of cells in the rat respiratory tract as a function of time after inhalation exposure to various levels of radon and its progeny. Rats were exposed to a constant concentration of radon and its progeny to give cumulative exposure levels of 120, 225, 440 and 990 working level months (WLM). An additional unexposed group of rats served as controls. The end points selected for investigation were (a) the incorporation of bromodeoxyuridine (BrdU) in epithelial cells of the conducting airways and of the alveolar region of the respiratory tract and (b) the incidence of alveolar macrophages with nuclear aberrations. After exposure, the incidence of epithelial cells incorporating BrdU--the labeling index--increased in all regions of the respiratory tract examined, but the increase occurred later in alveolar than in airway epithelial cells. The highest labeling index was found in bronchial epithelial cells, which probably received the highest radiation dose. After an initial induction period, the incidence of alveolar macrophages with nuclear aberrations also increased. The possibility of using the labeling index of alveolar and airway epithelial cells, and/or the incidence of nuclear aberrations in alveolar macrophages, to estimate the radiation dose to various regions of the respiratory tract after exposure of rats to radon and its progeny is discussed.