Effect of dexamethasone on neutrophil metabolism

The effect of dexamethasone on glucose and glutamine metabolism was investigated. The consumption and oxidation of glucose and glutamine, and the production of glutamate and lactate were determined in neutrophils cultured for 3 h in the presence of dexamethasone. The activities and expression of glucose-6-phosphate dehydrogenase (G6PDH) and phosphate-dependent glutaminase were also determined under the same conditions. Addition of dexamethasone to the culture medium caused a significant increase of glucose consumption at 0.5 microm (123.9%) and 1.0 microm (78.3%) concentrations. In spite of this, however, glucose oxidation remained unchanged. The glucocorticoid did not change glutamine consumption but caused a significant increase of glutamate production and did not alter glutamine oxidation. Dexamethasone-treated neutrophils had a significant decrease of G6PDH activity and expression in particular at 1.0 microm concentration. Phosphate- dependent glutaminase activity was also decreased (about 34%) by dexamethasone treatment. A similar effect was observed on glutaminase expression as indicated by RT-PCR analysis. Thus, the effect of dexamethasone on neutrophil metabolism was particularly noticeable with respect to G6PDH and glutaminase activities where a decrease in the respective mRNA levels was demonstrated.