Positron emission tomography with [18F]fluorodeoxyglucose to evaluate neutrophil kinetics during acute lung injury

Abstract
We measured neutrophil glucose uptake with positron emission tomographic imaging and [18F]fluorodeoxyglucose ([18F]FDG-PET) in anesthetized dogs after intravenous oleic acid-induced acute lung injury (ALI; OA group, n = 6) or after low-dose intravenous endotoxin (known to activate neutrophils without causing lung injury) followed by OA (Etx + OA group, n = 7). The following two other groups were studied as controls: one that received no intervention ( n = 5) and a group treated with Etx only ( n = 6). PET imaging was performed ∼1.5 h after initiating experimental interventions. The rate of [3H]deoxyglucose ([3H]DG) uptake was also measured in vitro in cells recovered from bronchoalveolar lavage (BAL) performed after PET imaging. Circulating neutrophil counts fell significantly in animals treated with Etx but not in the other two groups. The rate of [18F]FDG uptake, measured by the influx constant Ki, was significantly elevated ( P < 0.05) in both Etx-treated groups (7.9 ± 2.6 × 10-3ml blood·ml lung-1·min-1in the Etx group, 9.3 ± 4.8 × 10-3ml blood·ml lung-1·min-1in the Etx + OA group) but not in the group treated only with OA (3.4 ± 0.8 × 10-3ml blood·ml lung-1·min-1) when compared with the normal control (1.6 ± 0.4 × 10-3ml blood·ml lung-1·min-1). [3H]DG uptake was increased (73 ± 7%) in BAL neutrophils recovered from the Etx + OA group ( P < 0.05) but not in the OA group. Kiand [3H]DG uptake rates were linearly correlated ( R2= 0.65). We conclude that the rate of [18F]FDG uptake in the lungs during ALI reflects the state of neutrophil activation. [18F]FDG-PET imaging can detect pulmonary sequestration of activated neutrophils, despite the absence of alveolar neutrophilia. Thus [18F]FDG-PET imaging may be a useful tool to study neutrophil kinetics during ALI.