Comparative effects of fish oil given by gavage and fish oil-enriched diet on leukocytes.

The comparative effects of fish oil given by gavage and fish oil enriched diet on metabolism and function of lymphocytes and macrophages were investigated. For this purpose, the following parameters were examined: 1) phagocytosis capacity, production of superoxide (O2*-) and hydrogen peroxide (H2O2) by macrophages, 2) lymphocytes proliferation capacity, 3) antioxidant enzyme activities in the mesenteric lymph nodes (MEN) and liver, 4) Thiobarbituric Acid Reactive Substances (TBARS) content in MLN, liver, and plasma, 5) total antioxidant capacity of the plasma, and 6) fatty acid composition of macrophages, MLN, liver and plasma. Both FO treatments did not affect phagocytosis capacity but increased hydrogen peroxide production by macrophages in the presence of PMA. FO given by gavage markedly increased lymphocytes proliferation both in the absence (5.8-fold) and in the presence (16.7-fold) of Con A, whereas FO-rich diet showed an increase in the presence of Con A only (53.3%). FO given by gavage raised the proliferation index by 2.9-fold and FO-rich diet increased by 29% only as compared to controls. Concomitantly, FO given by gavage was more effective to increase TBARS content in plasma. The proportion of some fatty acids in the tissues and cells was also differently changed depending on the way FO was administered to rats: in particular: myristic, arachidonic, and eicosapentaenoic acids. This fact may partially explain the differences between both FO treatments.

Metabolic fate of glutamine in lymphocytes, macrophages and neutrophils.

Eric Newsholme's laboratory was the first to show glutamine utilization by lymphocytes and macrophages. Recently, we have found that neutrophils also utilize glutamine. This amino acid has been shown to play a role in lymphocyte proliferation, cytokine production by lymphocytes and macrophages and phagocytosis and superoxide production by macrophages and neutrophils. Knowledge of the metabolic fate of glutamine in these cells is important for the understanding of the role and function of this amino acid in the maintenance of the proliferative, phagocytic and secretory capacities of these cells. Glutamine and glucose are poorly oxidized by these cells and might produce important precursors for DNA, RNA, protein and lipid synthesis. The high rate of glutamine utilization and its importance in such cells have raised the question as to the source of this glutamine, which, according to current evidence, appears to be muscle.

Effects of adrenaline on glucose and glutamine metabolism and superoxide production by rat neutrophils.

Despite the large body of information on the role of corticosteroids in regulating lymphocyte and phagocyte function, the role of the hormone adrenaline in immunoregulation is an under-investigated topic. The present study has addressed the effects of adrenaline on the rates of utilization and oxidation of glucose and glutamine, the phagocytic capacity and the rate of superoxide production by rat neutrophils. Incubation of rat neutrophils in the presence of 50 microM adrenaline caused a marked elevation in glucose metabolism, an effect that could be blocked by propranolol. Adrenaline caused a partial inhibition of glutamine utilization by neutrophils, an effect that was also blocked by propranolol. These effects of adrenaline could be mimicked by 100 microM dibutyryl cAMP. Phosphate-dependent glutaminase activity was significantly elevated in neutrophils incubated in the presence of 50 microM adrenaline or 100 microM dibutyryl cAMP for 1 h, whereas glutamine oxidation was significantly depressed (P<0.05) under these conditions. The elevation in enzyme activity was only partially blocked by propranolol. The phagocytic activity of rat neutrophils was not altered by adrenaline in the presence of either glucose or glutamine. The rate of phorbol 12-myristate 13-acetate-induced superoxide production in the presence of glucose was potently reduced by the addition of 5 nM or 50 microM adrenaline. This effect could be mimicked by dibutyryl cAMP. However, when rat neutrophils were incubated in the presence of glutamine plus adrenaline (5 nM or 50 microM), the rate of superoxide production was only marginally reduced. These findings support the proposition that adrenaline may deviate the flux of glucose from the NADPH-producing pentose phosphate pathway, thus reducing substrate availability for the superoxide-generating NADPH oxidase. However, glutamine metabolism may still give rise to substantial quantities of NADPH from the glutaminolysis pathway. We postulate that glutamine metabolism may thus provide a protective mechanism against the inhibitory effect of adrenaline on superoxide production by neutrophils.

Metabolic fate of glutamine in lymphocytes, macrophages and neutrophils

Eric Newsholme's laboratory was the first to show glutamine utilization by lymphocytes and macrophages. Recently, we have found that neutrophils also utilize glutamine. This amino acid has been shown to play a role in lymphocyte proliferation, cytokine production by lymphocytes and macrophages and phagocytosis and superoxide production by macrophages and neutrophils. Knowledge of the metabolic fate of glutamine in these cells is important for the understanding of the role and function of this amino acid in the maintenance of the proliferative, phagocytic and secretory capacities of these cells. Glutamine and glucose are poorly oxidized by these cells and might produce important precursors for DNA, RNA, protein and lipid synthesis. The high rate of glutamine utilization and its importance in such cells have raised the question as to the source of this glutamine, which, according to current evidence, appears to be muscle

Glutamine metabolism by lymphocytes, macrophages, and neutrophils: its importance in health and disease.

Many aspects of the cell biology of lymphocytes, macrophages, and neutrophils have been studied extensively. Our recent work on these cells has investigated how fuel metabolism, especially glutamine metabolism, is related to the specific function of these cells in the inflammatory response. The high rate of glutamine utilization and its metabolism in such immune cells has raised the question of why glutamine is responsible for these functions. The macrophage has access to a variety of metabolic fuels both in vivo and in vitro. The quantitatively important role of glutamine in the processes of free radical and cytokine production has been established in our laboratories. Our current understanding of the rate of utilization and the pathway of metabolism of glutamine by cells of the immune system raises some intriguing questions concerning therapeutic manipulation of utilization of this amino acid, specifically the phagocytic and secretory capacities of cells of the defense system can be beneficially altered.

Effect of indole acetic acid on oxygen metabolism in cultured rat neutrophil.

1. Indole acetic acid (IAA) stimulates O2.- and H2O2 production in cells with peroxidase activity, such as neutrophils. The effect of pharmacological IAA concentration on oxygen metabolism and neutrophil functioning and viability in culture was investigated. 2. The results led to the conclusion that: (1) IAA causes death and marked ultrastructural changes in cultured neutrophils but does not affect lymphocytes; (2) these effects are not due to a reduction in the enzymatic antioxidant capacity of the cell, as indicated by catalase (CAT), superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px); (3) these effects are mainly due to an increase in the production of O2.- and H2O2, as suggested by the protective effect exhibited by the addition of CAT and SOD to cultured neutrophils, and (4) other reactive species (possibly peroxyl radicals) might play a role in the IAA effect on cultivated neutrophil viability.