PMA-enhanced neutrophil [ 18F]FDG uptake is independent of integrin occupancy but requires PI3K activity

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Objective While respiratory burst enhances neutrophil glucose utilization, many neutrophil functions are critically influenced by extracellular matrix interaction and phosphoinositide-3-OH kinase (PI3K) signaling. We thus evaluated the role of RGD integrin occupancy and PI3K inhibition on respiratory burst and [ 18F]fluorodeoxyglucose ([ 18F]FDG) uptake of stimulated neutrophils. Methods Human neutrophils were stimulated by 100 ng/ml phorbol–myristate–acetate (PMA), and respiratory burst was measured by cumulative luminescence with lucigenin. [ 18F]FDG uptake and total hexokinase activity was measured 20 min after PMA stimulation in the presence or absence of soluble RGD peptides (200 μg/ml) and/or the PI3K inhibitor wortmannin (200 nM). Results Phorbol–myristate–acetate induced a 71.7±0.9 fold increase in neutrophil oxygen intermediate generation. [ 18F]FDG uptake was increased to 194.6±3.7% and hexokinase activity to 145.0±2.0% of basal levels (both P<.0005). RGD peptides attenuated respiratory burst activation to 35.6±0.2% ( P<.005) but did not inhibit stimulated [ 18F]FDG uptake or hexokinase activity. In contrast, without affecting respiratory burst activation, wortmannin inhibited PMA-stimulated [ 18F]FDG uptake to 66.9±1.6% and hexokinase activity to 81.0±4.2% (both P<.0005), demonstrating its dependence on PI3K activity. Neither RGD nor wortmannin reversed the other's inhibitory effect on stimulated [ 18F]FDG uptake and hexokinase activity or respiratory burst, which suggests the involvement of distinct signaling pathways. Conclusion Neutrophil [ 18F]FDG uptake is enhanced by PMA through a mechanism that requires PI3K activity but is independent of integrin receptor occupancy or respiratory burst activation.