Skip to main content
NCBI home page
NIHPA Author Manuscripts logoLink to NIHPA Author Manuscripts
. Author manuscript; available in PMC: 2017 Aug 1.
Published in final edited form as: J Nucl Med. 2016 Mar 31;57(8):1296–1301. doi: 10.2967/jnumed.115.160291

Biomarkers for radiation pneumonitis using non-invasive molecular imaging

Meetha Medhora 1,2,3,4,5, Steven Haworth 2,5, Yu Liu 6, Jayashree Narayanan 1, Feng Gao 1, Ming Zhao 7, Said Audi 2,5,8, Elizabeth R Jacobs 2,3,4,5, Brian L Fish 1, Anne V Clough 2,5,9
PMCID: PMC5053021  NIHMSID: NIHMS787935  PMID: 27033892

Abstract

Rationale

Our goal is to develop minimally-invasive biomarkers for predicting radiation-induced lung injury before symptoms develop. Currently there are no biomarkers that can predict radiation pneumonitis. Radiation damage to the whole lung is a serious risk in nuclear accidents or in case of radiological terrorism. Our previous studies have shown a single dose of 15 Gy X-rays to the thorax causes severe pneumonitis in rats by 6–8 weeks. We have also developed a mitigator for radiation pneumonitis and fibrosis that can be started as late as 5 weeks after radiation.

Methods

We used two functional single photon emission computed tomography (SPECT) probes in vivo in irradiated rat lungs. Regional pulmonary perfusion was measured by injection of technetium labeled macroaggregated albumin (99mTc-MAA). Perfused volume was determined by comparing the volume of distribution of 99mTc-MAA to the anatomical lung volume obtained by micro-CT. A second probe, technetium labeled duramycin that binds to apoptotic cells, was used to measure pulmonary cell death in the same rat model.

Results

Perfused volume of lung was decreased by ~25% at 1, 2 and 3 weeks after 15 Gy and 99mTc-duramycin uptake was more than doubled at 2 and 3 weeks. There was no change in body weight, breathing rate or lung histology between irradiated and non-irradiated rats at these times. Pulmonary vascular resistance and vascular permeability measured in isolated perfused lungs ex vivo increased at 2 weeks after 15 Gy.

Principal conclusions

Our results suggest the potential for SPECT biomarkers for predicting radiation injury to the lungs before substantial functional or histological damage is observed. Early prediction of radiation pneumonitis will benefit those receiving radiation in the context of therapy, accidents or terrorism in time to initiate mitigation.

Keywords: SPECT, radiation injury, lung perfusion, radiological terrorism, 99mTc-duramycin

1. Introduction

Injury by ionizing radiation to the lung manifests in two phases (1,2). The first phase (pneumonitis) occurs 6–12 weeks after irradiation. The second phase (pulmonary fibrosis) develops over months to years after exposure (1,2). Our goal is to develop biomarkers that can predict severe lung injury before symptoms manifest and in time for mitigating agents. This is relevant to radiotherapy and to the National Institutes of Health program to develop countermeasures for nuclear accidents or radiological terrorism. Using preclinical models we have mitigated radiation-pneumonitis and fibrosis with an angiotensin converting enzyme inhibitor, enalapril, started five weeks after irradiation (3). We are now developing non-invasive biomarkers to detect severe lung injury before this five week time point.

Since there is a latent period between irradiation and symptoms of injury to the lung biomarkers can be measured in this time to predict outcomes. Changes in regional perfusion by localized radiation but not to the whole lung have been detected by single photon emission computed tomography (SPECT) in vivo by injection of technetium-labeled macroaggregated albumin (99mTc-MAA) (4–7). The albumin is lodged within the intricate microvasculature of the lung in proportion to flow and detected by the gamma camera of the SPECT system. In general, perfusion redistribution from radiation is more frequently reported than ventilation defects (4,8) and both are more sensitive than changes in lung density identified with computed tomography (CT) (4).

A different SPECT probe 99mTc-labeled duramycin is known to have high affinity and specificity for phosphotidylethanolamine (PE) that is externalized in apoptotic and other dying cells (9). Since radiation has been reported to induce apoptosis (10–12), necrosis and mitotic cell death, this marker was used to assess whole body tissue damage after radiation exposure (13). We tested the two probes 99mTc-MAA and 99mTc-duramycin as candidate biomarkers to monitor radiation injury to the lungs at 1–4 weeks after radiation. We followed our imaging studies by histological evaluation and other methods to confirm and interpret our findings.

2. Materials and methods

2.1. Animal care

All animal protocols and euthanasia criteria were approved by the Institutional Animal Care and Use Committee as described (3,14). A separate group of animals was used to measure each endpoint.

Irradiation

Unanesthetized female WAG/RijCmcr rats were irradiated with 15 Gy to the thorax only at 9–10 weeks of age as described (15). They were studied for non-invasive or terminal end points 1, 2, 3 and 4 weeks after irradiation. Non-irradiated rats were not sham-irradiated but were of the same age, strain and gender and maintained in parallel with each batch of irradiated rats.

2.2. SPECT/CT

Macroaggregated albumin (Jubilant DraxImage) was labeled with technetium according to the kit instructions and duramycin (3,035 g/mole MW) prepared and labeled as has been previously described (16,17). One group was then administered a single dose of 24.6±3.9 (mean ± Standard Deviation (SD)) MBq of 99mTc-MAA via the tail vein using a 25 gauge catheter. Another group received a tail vein injection of 38.5±7.6 (mean ± SD) MBq of 99mTc-duramycin. The animals were positioned in a SPECT/CT scanner (Triumph, TriFoil Imaging) and all animals first underwent rapid CT scanning for anatomical localization. At 5 minutes (for rats given 99mTc-MAA) or 50 minutes (for rats given 99mTc-duramycin) post injection, i.e. each times for optimal lung uptake, in vivo radionuclide imaging was performed using multi-pinhole collimation with two gamma head detectors, a 130 to 150 keV energy window, and acquisition of 72 projections for 10 s each. SPECT and CT data were reconstructed and coregistered using inbuilt software (13).

Image analysis

The reconstructed CT and 99mTc-MAA image volumes were segmented and analyzed to determine the perfused lung volume as follows. First the lung region within the CT image volume was identified as previously described (18). A grayscale window with a lower threshold of zero (corresponding to air) and an upper threshold of the maximum grayscale value within the lung parenchyma region, excluding major blood-filled vessels, was established and used to determine the boundaries of the anatomical lung region. The total number of voxels within this lung region was then scaled by the volume of each voxel to determine the anatomical lung volume. This region served as a binary lung mask that was then applied to the reconstructed 99mTc-MAA image volume. The total number of nonzero voxels within the 99mTc-MAA SPECT lung region was determined and scaled by the volume of each SPECT voxel to determine the perfused lung volume. Finally the fraction of lung perfused was determined by dividing the perfused lung volume obtained from 99mTc-MAA by the anatomical lung volume obtained from CT. Perfused fractions were infrequently > 1, since the volume of a voxel for SPECT and CT were different.

For experiments involving 99mTc-duramycin, the reconstructed CT and SPECT image volumes were coregistered and lung boundaries obtained from CT were applied as a mask to determine the 99mTc-duramycin lung region as described above for 99mTc-MAA. 99mTc-duramycin lung uptake was then determined as average 99mTc-duramycin counts per voxel within the lung region normalized to injected dose (16,17,19).

2.3. Breathing rate

Breathing rates and body weights were measured serially in an independent group of rats as described previously (14,20).

2.4. Isolated perfused lung preparation and pulmonary vascular endothelial filtration coefficient (Kf)

The heart and lungs from an independent group of rats were isolated at the 2 week time point and suspended from a calibrated force displacement transducer (ModelFT03; Grass Instruments) and lung weight was monitored continuously as described (21). The lungs were perfused and ventilated (40 breaths/min) with end-inspiratory and end-expiratory pressures of ~ 8 and 4 cm H2O. The Kf was determined using the approach described by Bongard et al. (22). The venous pressure (PV) was set at atmospheric pressure then raised to 5 cm H2O for 10 min and 13.5 cm H2O for an additional 10 min. At the end, the lungs were removed from the perfusion system, the arterial and venous cannulas connected, and pressure drop in the cannulas (ΔPcan) was determined. The pulmonary vascular pressure, RV, was then calculated using

Rv=Pa-ΔPcanF

where Pa is the pulmonary arterial pressure measured at the end of the 10-min stabilization period with Pv set at 0 mmHg, and F is the pump flow rate (0.03 ml/min/g body wt).

2.6. Lung wet/dry weight

After the Kf studies were completed the lungs were weighed, dried at 60–80°C for 24 hours and weighed again to calculate the wet and dry weights.

2.7. Histology

Whole mount sections of the left lung were stained with hematoxylin & eosin (H&E) (Richard Allan, Kalamazoo, MI), or with antibodies to cleaved caspase 3 (Biocare, #CP229B (17)) to detect apoptotic cells (23), or with CD68 (abD Serotec no. MCA341R) to identify macrophages (24).

Histological scores were obtained in H&E stained lung sections for the following 4 endpoints as described (14,20): 1) vascular wall thickness; 2) foamy macrophages; 3) CD68+ macrophages and 4) alveolar wall thickness. Caspase 3 positive cells were counted as previously described (17) and CD68+ macrophages (24) were counted in 5 fields randomly selected from corresponding areas in each section to cover the whole mount.

2.8. Statistical analysis

Data were analyzed using StatView (v.5.0.1, SAS Institute) and expressed as means±standard deviations (SD) or medians±75% & 25% ranges if normality or equal variance tests failed. For some tests the control values at 1 and 4 weeks were pooled if they were not statistically different. For multi-group comparisons the significance of differences were assessed by ANOVA with the Holm-Sidak or Dunn’s methods and comparisons were made to the non-irradiated controls. For two-group comparisons, t-tests were used or Mann Whitney tests if normality tests failed.

3. Results

3.1. Body weight after radiation to the thorax only

Non-irradiated animals gained weight in the first week (2.7±2.4 gms (mean±SD)) but irradiated rats lost weight (−1.6±4.2 gms; p=0.041, n=5/group). There was no difference in weight gain or loss between the groups at 2, 3 or 4 weeks.

3.2. Breathing rate after radiation

The breathing rates (mean±SD) at 1, 2, 3 and 4 weeks were 99.4±4.3, 113.0±10.4, 104.6±7.9, 102.8±8.9 breaths/minute in non-irradiated controls and were not different from corresponding values of 103.2±4.3, 108.8±6.3, 108.8±9.4, 98.4±4.0 breaths/minute after 15 Gy (n=5/group).

3.3. Decrease in perfused lung volume with 99mTc-MAA SPECT after radiation

Figure 1 shows representative transaxial slices from the 99mTc-MAA (left) and 99mTc-duramycin (right) reconstructed volume of a non-irradiated control (top) and 2 week post 15 Gy irradiation (bottom) rats. Fractional perfused lung volume was determined from the MAA images as described in the Materials and Methods section at 1 and 4 weeks in non-irradiated controls. There was no difference between these groups so they were combined and compared to values obtained at 1, 2, 3 and 4 weeks after 15 Gy. Figure 2 shows all values after normalization to the median value of the controls. There was a decrease in perfused lung volume starting as early as 1 week (18%) and up to 3 weeks (27%) after irradiation as compared to non-irradiated controls.

Figure 1.

Figure 1

Open in a new tab

Typical 99mTc-MAA (left) and 99mTc-duramycin (right) transaxial slices from reconstructed volumes obtained from control (top) and 15 Gy irradiated (bottom) rats. Color images represent the segmented SPECT lung region co-registered with the gray-scale CT images.

Figure 2.

Figure 2

Open in a new tab

Decrease in perfused pulmonary volume by radiation, as determined by the ratio of 99mTc-MAA SPECT perfused volume to co-registered CT anatomical volume. Line is median value in non-irradiated (N=12) and irradiated rats at 1 (N=8), 2 (N=10), 3 (N=13), and 4 (N=9) weeks after 15 Gy to the thorax. *p<0.05 versus non-irradiated controls.

3.4. Increase in 99mTc-duramycin uptake after radiation

The 99mTc-duramycin images of Figure 1 reveal very little uptake in the control lung, consistent with our previous results (16,17), but enhanced uptake is illustrated at 2 weeks after irradiation. Figure 3 reports average 99mTc-duramycin counts per voxel within the lung region for each rat. There was no change in 99mTc-duramycin uptake at 1 week after irradiation but greater than 100% increase was observed at 2 and 3 weeks compared to non-irradiated controls.

Figure 3.

Figure 3

Open in a new tab

Increase in 99mTc-duramycin lung uptake in irradiated lungs versus controls. Line is median value in non-irradiated (N=12) and irradiated rats at 1 (N=5), 2 (N=11), and 3 (N=5) weeks after 15 Gy to the thorax, *p<0.05 vs. control; **p<0.05 versus 15 Gy at one week.

3.5. Increase in apoptotic cells in the lungs after radiation

Figure 4 shows the number of caspase 3 positive apoptotic cells per field in rat lungs. Similar to 99mTc duramycin uptake in Figure 3, there was no increase in apoptotic cells after 1 week in irradiated rats as compared to non-irradiated controls, but there was an increase in the median number of apoptotic cells/lung field at 2, 3 and 4 weeks after irradiation.

Figure 4.

Figure 4

Open in a new tab

Increase in apoptotic cells in the lung as determined by cleaved caspase 3+ cells using immunohistochemistry (see Methods). Apoptotic cells/field in non-irradiated (open circles) and irradiated rats (black circles) are shown at 1, 2, 3 and 4 weeks after 15 Gy to the thorax. Line=median value, non-irradiated (N=15) and irradiated rats (N=8/group), *p<0.05 versus control.

3.6. Histological changes in the lungs at 4 but not 1, 2 or 3 weeks after radiation

We measured key histological markers of radiation injury in non-irradiated and irradiated rat lungs (14,20): vessel wall thickness, alveolar wall thickness and macrophage counts. The values for these markers did not change in non-irradiated controls at ages corresponding to 1 and 4 weeks after irradiation. There was no difference in vessel wall thickness at 1, 2, 3 or 4 weeks in irradiated rats as compared to pooled controls at 1 and 4 weeks (results not shown). While the median score for alveolar wall thickness (Figure 5D) and macrophage count (5E) did not change at 1, 2, or 3 weeks, both values were higher at 4 weeks after 15 Gy (Figures 5D, E). Similar results were observed for CD68+ macrophages measured at 2 and 4 weeks after 15 Gy (Figure 5F).

Figure 5.

Figure 5

Open in a new tab

Histological analysis showing increase in alveolar wall thickness and macrophages after 15 Gy whole thoracic irradiation (see Methods). Representative fields of hematoxylin & eosin stained lung sections from A. non-irradiated lung, B. 2 weeks after 15 Gy and C. 4 weeks after 15 Gy. Solid arrow points to macrophages, dotted arrow to thickened alveolar wall. D. Scores for alveolar wall thickness. E. Counts for foamy macrophages. F. Counts for CD68+ macrophages. Line=median value. N=16 non-irradiated rats for each D and E, N=8 non-irradiated rats for F, and N=8 irradiated rats for each D, E and F, *p<0.05 versus control at 4 weeks.

3.7. Increase in pulmonary vascular permeability and resistance at 2 weeks after radiation

We tested the permeability and resistance of lung vessels 2 weeks after irradiation, a time point when both 99mTc-MAA distribution and 99mTc-duramycin uptake were different from non-irradiated controls. Ex vivo pulmonary vascular resistance (Torr/ml/min) increased from 0.89±0.14 in non-irradiated lungs to 1.17±0.19 in irradiated lungs after 2 weeks (n=5, p=0.028) (Figure 6 top panel). The pulmonary vascular endothelial filtration coefficient (Kf, ml/min/cm H2O/g dry lung weight) was increased by radiation from 0.017±0.005 in non-irradiated lungs to 0.050±0.010 in matched irradiated lungs at the 2 week time point (n=5, p<0.001) (Figure 6 lower panel). The wet:dry weight ratio of the perfused lungs showed an increase from 5.9±0.4 (mean±SD) in controls to 7.0±0.2 after irradiation. The mean±SD for the wet weight after perfusion at similar pressures increased from 0.81±0.07 g in non-irradiated controls to 1.16±0.09 g, an increase of 42%.

Figure 6. Increase in pulmonary vascular resistance (top) and permeability (lower panel) in the lung at 2 weeks after 15 Gy.

Figure 6

Open in a new tab

Pulmonary vascular resistance (Torr/ml/minute) and pulmonary vascular endothelial filtration coefficient (Kf) obtained from isolated perfused lungs of non-irradiated and irradiated rats at 2 weeks. Line=mean value, N=5 rats/group. Top: *p<0.05 versus control. Bottom: *p<0.001 versus control.

4. Discussion

SPECT has made it possible to develop customized physiological probes for non-invasive imaging. We have used two probes labeled with 99mTc to detect radiation-induced pre-clinical vascular changes, and increased apoptosis, two endpoints known to be altered by radiation. Characterization of these changes has potential to define biomarkers for in vivo detection of radiation injury to the lungs. The first probe, 99mTc-MAA with particle size 10–40 μm lodges in pulmonary capillaries in proportion to blood flow (18). 99mTc-MAA is in common clinical use for detection of pulmonary embolism. The second probe is the antibiotic duramycin which is a small molecule that binds to apoptotic cells (9,13) and has been labeled with 99mTc for SPECT imaging (9,13). There was ~20% decrease in the perfused volume of the lung as early as 1 week after irradiation with 15 Gy to both lungs, which was sustained up to 3 weeks. These data match our observation of increased pulmonary vascular resistance in ex vivo perfused lungs. The uptake of 99mTc-duramycin in the thorax more than doubled at 2 and 3 weeks but was not increased at 1 week after irradiation. Further studies of 99mTc-duramycin uptake from only perfused voxels of the lung may determine if there is a correspondingly higher increase in perfused areas as compared to the whole lung.

Our data provide strong evidence of pre-clinical radiation-induced vascular injury in the absence of histological changes in alveolar wall thickness and macrophage counts. Macrophages (index of inflammatory state) were counted in H&E stained sections and we confirmed with more specific CD68 staining that they were not increased at 2 weeks, when perfusion and apoptosis were already altered. Though no increase in vascular wall thickness or occlusion of vascular lumen were noted histologically up to 4 weeks, there was an increase in vascular permeability, Kf, and vascular resistance at 2 weeks, when measured in irradiated perfused lungs ex vivo. The increase in permeability was also reflected by an increase in wet:dry lung weight after perfusion. Dose-dependent increase in vascular permeability at sacrifice has previously been reported after 2 weeks in rats exposed from 5–40 Gy to one lung only (25). Molteni et al also described subendothelial and perivascular edema at 1 day after hemithorax irradiation in rats (26). They reported segmental separation of the endothelium from the basement membrane. In another study, following whole-thorax irradiation, in vivo lung vascular permeability was doubled at 2 weeks (similar to our results) and peaked to 3-times the normal value by 3 weeks (27). Increased permeability in our model may be pathophysiologically related to apoptosis of endothelial cells as has been reported for other insults (28). These studies by us and others demonstrate that the vasculature in the lungs is injured in the first 4 weeks after irradiation to the whole thorax without manifesting clinical symptoms or histological changes. They imply that roentgenographic evidence of pulmonary edema in a patient after possible or known radiation exposure could be a prelude to clinical radiation pneumonitis. Such patients may also be good candidates for SPECT imaging to detect endothelial apoptosis.

99mTc-duramycin is a recently developed biomarker for SPECT cell death imaging. It has several desirable imaging properties; it binds with very high affinity (the dissociation constant is in the low nanomolar range (29,30) and high specificity for membrane-bound phosphtidylethanolamine (31), wherein the binding is stabilized by ionic interaction. Moreover, 99mTc-duramycin has a low molecular weight (3,035 g/mole) and is rapidly cleared from the blood (half-life < 4 minutes (17, 32) thereby keeping background low.

In this study, lung uptake of 99mTc-duramycin was increased (~160%) at 2 and 3 weeks post-irradiation, which is supported by increase in cleaved caspase 3+ apoptotic cells. This is consistent with a previous study using a hyperoxic lung injury model in which 99mTc-duramycin lung uptake was shown to correlate strongly with cleaved caspase 3+ apoptotic endothelial cells (17). Though the increase in vascular permeability could contribute to an increase in 99mTc-duramycin lung signal, the high affinity and specificity of binding of 99mTc-duramycin to apoptotic cells, the rapid clearance from the blood, and the increase in cleaved caspase 3 in irradiated rats, strongly suggest the increase in the 99mTc-duramycin to be due to increased cell death, though further experiments are needed to verify this. Despite these potential limitations, the fact that the increased duramycin uptake was much higher than the degree of vascular leak suggests that increased 99mTc-duramycin uptake may serve as an early biomarker of radiation-induced lung injury.

A small increase in perfusion was recorded 4–6 weeks (the earliest time point of the study) after 25 Gy to one lung of Sprague Dawley rats (7). These measurements were done using 99mTc-MAA and analyzed by comparing perfusion between the irradiated versus the non-irradiated lung in the same animal. Perfusion in the irradiated lung was lower between 6 to 30 weeks (7). A decrease in perfusion to an irradiated lung was recorded in Fischer rats after 3 days following 28 Gy; perfusion recovered by 2 weeks and then gradually declined to as low as 15% by 10 weeks (6). Our results are difficult to compare with these studies since we irradiated both lungs and are unique to describe a redistribution of 99mTc-MAA from as early as one and up to at least three weeks after irradiation. Changes in perfusion distribution may be explained by the changes we measured in vascular resistance. In addition lung arterioles exhibit decreased ability to constrict or dilate to physiological stimuli after irradiation (33,34). Such an end-point cannot be measured in vivo, and may contribute to the changes in perfusion we detected by 99mTc-MAA. Experimentation to test the multiple and known effects of radiation on pulmonary arterioles towards the SPECT signals will take considerable time and resources. Our first goal is to apply our findings to the rapid development of biomarkers for radiation injury to the lungs.

Use of 99mTc-duramycin for whole body imaging of irradiation-induced tissue damage has been examined 72 hours after 15 Gy to the total body of a rat (13). There was increased uptake in the gut, bone and thymus at this early time. Injury to the lung occurs later (1–3). Our SPECT results using 99mTc-duramycin suggest ongoing apoptosis in the lung beginning around 2 weeks post-irradiation and continuing (Figure 3). The pattern of change in signal was similar in imaging and histology, increasing from 2 weeks after irradiation but not at one week (Figures 3 and 4). These results are important in that they imply patients with possibly injurious exposure could be screened as early as two weeks after an incident. Those with increased lung apoptosis would be excellent candidates for treatment with agents such as ACE inhibitors which mitigate lung injury when given up to 5 weeks after exposure (3).

5. Conclusions

Our results of decreased perfused volume and increased 99mTc-duramycin uptake in the lungs of irradiated animals are novel and could be developed into new methods of predicting lung injury by radiation even before substantial functional or histological damage is observed. Further studies with different doses of radiation will determine the specificity to determine lethal lung injury before symptoms develop.

Acknowledgments

Financial support: 1R01AI101898, U01-AI107305-01, HL116530, 1 I01 BX001681, R15HL129209.

We thank Dr. John E. Moulder for the helpful discussions and for critically reading the manuscript. Histological work was performed by the Pediatric Biobank and Analytic Tissue Core.

Footnotes

6. Disclosure This work was funded by National Institutes of Health/National Institute of Allergy and Infectious Diseases 1R01AI101898, U01AI107305-01; National Institutes of Health/National Heart Lung and Blood Institute HL116530, HL120209 and 1 I01 BX001681. There are no potential conflicts of interest or third party payments related to this manuscript.

References

  • 1.Gross NJ. Radiation pneumonitis in mice. Some effects of corticosteroids on mortality and pulmonary physiology. J Clin Invest. 1980;66:504–510. doi: 10.1172/JCI109881. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 2.Travis EL, Harley RA, Fenn JO, Klobukowski CJ, Hargrove HB. Pathologic changes in the lung following single and multi-fraction irradiation. Int J Radiat Oncol Biol Phys. 1977;2:475–490. doi: 10.1016/0360-3016(77)90159-6. [DOI] [PubMed] [Google Scholar]
  • 3.Gao F, Fish BL, Moulder JE, Jacobs ER, Medhora M. Enalapril mitigates radiation-induced pneumonitis and pulmonary fibrosis if started 35 days after whole-thorax irradiation. Radiat Res. 2013;180:546–552. doi: 10.1667/RR13350.1. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 4.Robbins ME, Brunso-Bechtold JK, Peiffer AM, Tsien CI, Bailey JE, Marks LB. Imaging radiation-induced normal tissue injury. Radiat Res. 2012;177:449–466. doi: 10.1667/rr2530.1. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 5.Evans ES, Hahn CA, Kocak Z, Zhou SM, Marks LB. The role of functional imaging in the diagnosis and management of late normal tissue injury. Semin Radiat Oncol. 2007;17:72–80. doi: 10.1016/j.semradonc.2006.11.003. [DOI] [PubMed] [Google Scholar]
  • 6.Fleckenstein K, Zgonjanin L, Chen L, et al. Temporal onset of hypoxia and oxidative stress after pulmonary irradiation. Int J Radiat Oncol Biol Phys. 2007;68:196–204. doi: 10.1016/j.ijrobp.2006.12.056. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 7.Ward WF. Radiation-induced pulmonary arterial perfusion defects: modification by D-penicillamine. Radiology. 1981;139:201–204. doi: 10.1148/radiology.139.1.7208923. [DOI] [PubMed] [Google Scholar]
  • 8.Boersma LJ, Damen EM, de Boer RW, et al. Recovery of overall and local lung function loss 18 months after irradiation for malignant lymphoma. J Clin Oncol. 1996;145:1431–1441. doi: 10.1200/JCO.1996.14.5.1431. [DOI] [PubMed] [Google Scholar]
  • 9.Zhao M, Li Z. A single-step kit formulation for the (99m)Tc-labeling of HYNIC-Duramycin. Nucl Med Biol. 2012;39:1006–1011. doi: 10.1016/j.nucmedbio.2012.03.006. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 10.Verheij M, Bartelink H. Radiation-induced apoptosis. Cell Tissue Res. 2000;301:133–142. doi: 10.1007/s004410000188. [DOI] [PubMed] [Google Scholar]
  • 11.Holcik M, Yeh C, Korneluk RG, Chow T. Translational upregulation of X-linked inhibitor of apoptosis (XIAP) increases resistance to radiation induced cell death. Oncogene. 2000;19:4174–4177. doi: 10.1038/sj.onc.1203765. [DOI] [PubMed] [Google Scholar]
  • 12.Garcia-Barros M, Paris F, Cordon-Cardo C, et al. Tumor response to radiotherapy regulated by endothelial cell apoptosis. Science. 2003;300:1155–1159. doi: 10.1126/science.1082504. [DOI] [PubMed] [Google Scholar]
  • 13.Johnson SE, Li Z, Liu Y, Moulder JE, Zhao M. Whole-body imaging of high-dose ionizing irradiation-induced tissue injuries using 99mTc-duramycin. J Nucl Med. 2013;54:1397–1403. doi: 10.2967/jnumed.112.112490. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 14.Medhora M, Gao F, Glisch C, et al. Whole-thorax irradiation induces hypoxic respiratory failure, pleural effusions and cardiac remodeling. J Radiat Res. 2015;56:248–260. doi: 10.1093/jrr/rru095. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 15.Medhora M, Gao F, Fish BL, Jacobs ER, Moulder JE, Szabo A. Dose-modifying factor for captopril for mitigation of radiation injury to normal lung. J Radiat Res. 2012;53:633–640. doi: 10.1093/jrr/rrs004. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 16.Clough AV, Audi SH, Haworth ST, Roerig DL. Differential lung uptake of 99mTc-hexamethylpropyleneamine oxime and 99mTc-duramycin in the chronic hyperoxia rat model. J Nucl Med. 2012;53:1984–1991. doi: 10.2967/jnumed.112.108498. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 17.Audi SH, Jacobs ER, Zhao M, Roerig DL, Haworth ST, Clough AV. In vivo detection of hyperoxia-induced pulmonary endothelial cell death using (99m)Tc-duramycin. Nucl Med Biol. 2015;42:46–52. doi: 10.1016/j.nucmedbio.2014.08.010. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 18.Wietholt C, Roerig DL, Gordon JB, Haworth ST, Molthen RC, Clough AV. Bronchial circulation angiogenesis in the rat quantified with SPECT and micro-CT. Eur J Nucl Med Mol Imaging. 2008;35:1124–1132. doi: 10.1007/s00259-007-0684-y. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 19.Audi SH, Roerig DL, Haworth ST, Clough AV. Role of glutathione in lung retention of 99mTc-hexamethylpropyleneamine oxime in two unique rat models of hyperoxic lung injury. J Appl Physiol. 2012;113:658–665. doi: 10.1152/japplphysiol.00441.2012. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 20.Gao F, Fish BL, Szabo A, et al. Short-term treatment with a SOD/catalase mimetic, EUK-207, mitigates pneumonitis and fibrosis after single-dose total-body or whole-thoracic irradiation. Radiat Res. 2012;178:468–480. doi: 10.1667/RR2953.1. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 21.Gan Z, Roerig DL, Clough AV, Audi SH. Differential responses of targeted lung redox enzymes to rat exposure to 60 or 85% oxygen. J Appl Physiol. 2011;111:95–107. doi: 10.1152/japplphysiol.01451.2010. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 22.Bongard RD, Yan K, Hoffmann RG, et al. Depleted energy charge and increased pulmonary endothelial permeability induced by mitochondrial complex I inhibition are mitigated by coenzyme Q1 in the isolated perfused rat lung. Free Radic Biol Med. 2013;65:1455–1463. doi: 10.1016/j.freeradbiomed.2013.07.040. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 23.Srinivasan A, Roth KA, Sayers RO, et al. In situ immunodetection of activated caspase-3 in apoptotic neurons in the developing nervous system. Cell Death Differ. 1998;5:1004–1016. doi: 10.1038/sj.cdd.4400449. [DOI] [PubMed] [Google Scholar]
  • 24.Gao F, Narayanan J, Joneikis C, Fish BL, Szabo A, Moulder JE, et al. Enalapril mitigates focal alveolar lesions, a histological marker of late pulmonary injury by radiation to the lung. Radiat Res. 2013;179:465–474. doi: 10.1667/RR3127.1. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 25.Travis EL, Hargrove H, Klobukowski CJ, Fenn JO, Frey GD. Alterations in vascular permeability following irradiation. Radiat Res. 1976;67:539. [Google Scholar]
  • 26.Molteni A, Wolfe LF, Ward WF, et al. Effect of an angiotensin II receptor blocker and two angiotensin converting enzyme inhibitors on transforming growth factor-beta (TGF-beta) and alpha-actomyosin (alpha SMA), important mediators of radiation-induced pneumopathy and lung fibrosis. Curr Pharm Des. 2007;13:1307–1316. doi: 10.2174/138161207780618777. [DOI] [PubMed] [Google Scholar]
  • 27.Graham MM, Evans ML, Dahlen DD, Mahler PA, Rasey JS. Pharmacological alteration of the lung vascular response to radiation. Int J Radiat Oncol Biol Phys. 1990;19:329–339. doi: 10.1016/0360-3016(90)90541-q. [DOI] [PubMed] [Google Scholar]
  • 28.Lu Q, Xu DZ, Davidson MT, Hasko G, Deitch EA. Hemorrhagic shock induces endothelial cell apoptosis, which is mediated by factors contained in mesenteric lymph. Crit Care Med. 2004;32:2464–2470. doi: 10.1097/01.ccm.0000147833.51214.03. [DOI] [PubMed] [Google Scholar]
  • 29.Hayashi F, Nagashima K, Terui Y, Kawamura Y, Matsumoto K, Itazaki H. The structure of PA48009: the revised structure of duramycin. The Journal of antibiotics. 1990;43:1421–1430. doi: 10.7164/antibiotics.43.1421. [DOI] [PubMed] [Google Scholar]
  • 30.Zimmermann N, Freund S, Fredenhagen A, Jung G. Solution structures of the lantibiotics duramycin B and C. European journal of biochemistry/FEBS. 1993;216:419–428. doi: 10.1111/j.1432-1033.1993.tb18159.x. [DOI] [PubMed] [Google Scholar]
  • 31.Zhao M. Lantibiotics as probes for phosphatidylethanolamine. Amino acids. 2011;41:1071–1079. doi: 10.1007/s00726-009-0386-9. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 32.Zhao M, Li Z, Bugenhagen S. 99mTc-labeled duramycin as a novel phosphatidylethanolamine-binding molecular probe. Journal of nuclear medicine : official publication, Society of Nuclear Medicine. 2008;49:1345–1352. doi: 10.2967/jnumed.107.048603. [DOI] [PubMed] [Google Scholar]
  • 33.Zhang R, Ghosh SN, Zhu D, et al. Structural and functional alterations in the rat lung following whole thoracic irradiation with moderate doses: Injury and recovery. Int J Radiat Biol. 2008;84:487–497. doi: 10.1080/09553000802078396. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 34.Ghosh SN, Zhang R, Fish BL, et al. Renin-Angiotensin system suppression mitigates experimental radiation pneumonitis. Int J Radiat Oncol Biol Phys. 2009;75:1528–1536. doi: 10.1016/j.ijrobp.2009.07.1743. [DOI] [PMC free article] [PubMed] [Google Scholar]

RESOURCES