The metabolism of human polymorphonuclear leukocytes

A Metabolic Shift toward Pentose Phosphate Pathway Is Necessary for Amyloid Fibril- and Phorbol 12-Myristate 13-Acetate-induced Neutrophil Extracellular Trap (NET) Formation

Neutrophils are the main defense cells of the innate immune system. Upon stimulation, neutrophils release their chromosomal DNA to trap and kill microorganisms and inhibit their dissemination. These chromatin traps are termed neutrophil extracellular traps (NETs) and are decorated with granular and cytoplasm proteins. NET release can be induced by several microorganism membrane components, phorbol 12-myristate 13-acetate as well as by amyloid fibrils, insoluble proteinaceous molecules associated with more than 40 different pathologies among other stimuli. The intracellular signaling involved in NET formation is complex and remains unclear for most tested stimuli. Herein we demonstrate that a metabolic shift toward the pentose phosphate pathway (PPP) is necessary for NET release because glucose-6-phosphate dehydrogenase (G6PD), an important enzyme from PPP, fuels NADPH oxidase with NADPH to produce superoxide and thus induce NETs. In addition, we observed that mitochondrial reactive oxygen species, which are NADPH-independent, are not effective in producing NETs. These data shed new light on how the PPP and glucose metabolism contributes to NET formation.

STUDIES ON THE EFFECT OF CERTAIN MACROMOLECULAR SUBSTANCES ON THE RESPIRATORY ACTIVITY OF THE LEUCOCYTES OF PERIPHERAL BLOOD

The oxygen, uptake of lightly heparinized human blood was found to increase markedly upon the addition of bacterial endotoxins, soluble antigen-antibody complexes, or polystyrene latex particles. The effect apparently reflects a transitory stimulation of respiratory activity of the blood leucocytes. The effect did not occur in the presence of anticoagulant amounts of citrate or ethylenediaminetetraacetate, was inhibited by iodoacetate and fluoride ions, and may be related to the energy-yielding processes involved in histamine release or phagocytosis.

GLYCOLYSIS IN RAT PERITONEAL MAST CELLS

Glycolytic activity of rat peritoneal mast cells has been measured by the Cartesian ampulla diver technique. The rates of anaerobic glycolysis, expressed as CO₂ expelled from a bicarbonate medium, are 1.70 x 10^-6 µl and 1.43 x 10^-6 µl per cell per hour with and without glucose, respectively. The aerobic glycolysis rate in the presence of glucose, assuming the respiratory quotient to be 1, is 0.93 x 10^-6 µl CO₂ per cell per hour. It is pointed out that the anaerobic and non-respiratory aerobic carbon dioxide production by mast cells is much higher than the respiratory oxygen uptake reported previously. These values have been interpreted in terms of glucose utilization.

RESPIRATION OF RAT PERITONEAL MAST CELLS

Methods for microgasometry of a few hundred mast cells are described. The Cartesian ampulla diver technique is used. The sample size is determined by counting the cells within the diver. The respiration rates at 37°C, expressed in microliters per cell per hour, are 0.29 x 10^-6 without substrate and 0.47 x 10^-6 with glucose.

Studies on the sodium and potassium transport in rabbit polymorphonuclear leukocytes

Rabbit polymorphonuclear leukocytes obtained from peritoneal exudates, incubated at 37°C. following exposure to 4°C., actively reaccumulate potassium while little or no net extrusion of sodium takes place. Preventing the utilization of oxidative metabolism with potassium cyanide, 2,4-dinitrophenol, or a nitrogen atmosphere does not inhibit the recovery process. Inhibitors blocking anaerobic glycolysis (sodium iodoacetate and sodium fluoride in low concentrations) completely abolish the capacity to reaccumulate potassium and cause a further dissipation of the sodium and potassium gradients. Water movements have been shown to be secondary to cation shifts. It is postulated that separate transport mechanisms exist for sodium and potassium and that the process of potassium reaccumulation relies on anaerobic glycolysis as a source of energy.

The influence of insulin on glucose permeability and metabolism of human granulocytes

Viable human polymorphonuclear leukocytes isolated from peripheral blood were incubated for 1 h at 37 degrees C with variable concentrations of insulin in a saline medium buffered at pH 7.4. The hormone increased glucose consumption by about 40% without influencing the permeability of the membranes to glucose, whose uptake followed a passive diffusion process. The measurement of intermediates localized activation of glycolysis by insulin, down to 0.36 nM, at the phosphofructokinase step. However, the spectrophotometric measurement showed no activation of phosphofructokinase after preincubation with insulin of either intact granulocytes or crude or ultracentrifuged homogenates. The level of cyclic AMP, which is known to activate phosphofructokinase, was not modified by insulin; cyclic GMP did not activate the enzyme in the granulocyte extracts: neither of the two nucleotides can therefore be considered as a direct messenger of the action of insulin on phosphofructokinase. An important fraction of the extra glucose consumed under the influence of insulin was recovered as neither glycogen nor lactate, nor was it oxidized in the Krebs cycle. It might be assumed to have been converted into glycerolipids. However, insulin produced no detectable accumulation of triglycerides and activated neither the pentose phosphate pathway nor oxidative decarboxylation of pyruvate. The fate of the extra glucose consumed under the influence of insulin therefore remains questionable.