In vivo detection of hyperoxia-induced pulmonary endothelial cell death using 99mTc-Duramycin

Abstract

Introduction: 99mTc-duramycin, DU, is a SPECT biomarker of tissue injury identifying cell death. The objective of this study is to investigate the potential of DU imaging to quantify capillary endothelial cell death in rat lung injury resulting from hyperoxia exposure as a model of acute lung injury. Methods: Rats were exposed to room air (normoxic) or >98% O2 for 48 or 60 hours. DU was injected i.v. in anesthetized rats, scintigraphy images were acquired at steady-state, and lung DU uptake was quantified from the images. Post-mortem, the lungs were removed for histological studies. Sequential lung sections were immunostained for caspase activation and endothelial and epithelial cells. Results: Lung DU uptake increased significantly (p < 0.001) by 39% and 146% in 48-hr and 60-hr exposed rats, respectively, compared to normoxic rats. There was strong correlation (r2 = 0.82, p = 0.005) between lung DU uptake and the number of cleaved caspase 3 (CC3) positive cells, and endothelial cells accounted for more than 50% of CC3 positive cells in the hyperoxic lungs. Histology revealed preserved lung morphology through 48 hours. By 60 hours there was evidence of edema, and modest neutrophilic infiltrate. Conclusions: Rat lung DU uptake in vivo increased after just 48 hours of >98% O2 exposure, prior to the onset of any substantial evidence of lung injury. These results suggest that apoptotic endothelial cells are the primary contributors to the enhanced DU lung uptake, and support the utility of DU imaging for detecting early endothelial cell death in vivo.

Protection by Inhaled Hydrogen Therapy in a Rat Model of Acute Lung Injury can be Tracked in vivo Using Molecular Imaging

“…For a subset of rats exposed to hyperoxia or hyperoxia+H 2 , pleural effusion within the chest cavity was determined by inserting cotton gauze into the chest cavity to absorb any pleural effusion (11). The gauze was weighed before and after use and the difference in weights was used to measure pleural effusion.…”

“…Sample sizes were chosen to achieve a power ≥ 85% using power analysis (ANOVA power) based on previously published means and standard deviations of the lung uptake of 99m Tc-HMPAO and 99m Tc-duramycin (11–13). …”

“…Furthermore, we identified a strong correlation between 99m Tc-HMPAO uptake and glutathione tissue content (12), as an indicator of oxidative stress, and between 99m Tc-duramycin uptake and cleaved-caspase 3 as a marker of apoptosis (11,14). The objective of this study was to evaluate the potential utility of 99m Tc-HMPAO and 99m Tc-duramycin to track the effectiveness of H 2 therapy in vivo in the hyperoxia rat model of human ALI/ARDS.…”

“…Recently we demonstrated the utility of single-photon emission computed tomography (SPECT) biomarker imaging to detect oxidative stress (using 99m Tc-hexamethylpropyleneamine oxime (HMPAO)) and endothelial cell death (using 99m Tc-duramycin) in lungs of rats exposed to high concentrations of O 2 (hyperoxia) or treated with the endotoxin lipopolysaccharide as models of human ALI/ARDS (8,11–13). Furthermore, we identified a strong correlation between 99m Tc-HMPAO uptake and glutathione tissue content (12), as an indicator of oxidative stress, and between 99m Tc-duramycin uptake and cleaved-caspase 3 as a marker of apoptosis (11,14).…”

Early Prediction of Tumor Response to Treatment: Preclinical Validation of 99mTc-Duramycin

“…Nevertheless, 99m Tc-annexin V failed to reach clinical usefulness because its slow clearance rate from nontargeted tissues contributes to low tumor-to-background ratios (6). In this context, the phosphatidylethanolamine-binding radiotracer 99m Tcduramycin has recently gained attention for detecting cell death in animal models of disease (8)(9)(10), exploiting its high affinity and selectivity for phosphatidylethanolamine and its optimal biodistribution profile for in vivo SPECT imaging of cell death. Recently, we demonstrated favorable dosimetry estimates together with the usefulness of 99m Tc-duramycin for the early detection of irinotecaninduced tumor cell death in a proof-of-concept study (11).…”