Modification of phospholipid metabolism during T cell activation has been repeatedly reported. Recently, we have shown that phytohaemagglutinin, CD3 and CD2 mAbs, which are potent in vitro activators of helper T lymphocytes, markedly inhibit phosphatidylserine synthesis concomitantly as they induce the secretion of IL-2. In this paper, we show evidence that in T lymphocytes K+ channels, which have been shown to participate in the cell activation process, are also reciprocally related to phosphatidylserine synthesis. In fact, in resting T cells the drugs affecting the activity of K+ channels, such as quinine and 4-aminopyridine, induce a rise of phosphatidylserine synthesis. In activated cells, quinine and 4-amidopyridine also caused a rise in phosphatidylserine synthesis which paralleled a decreased production of IL-2, strongly suggesting that these two events are correlated in a reciprocal manner. More precisely, phosphatidylserine synthesis was stimulated by drugs which have been reported to inhibit potassium channels in lymphocytes, e.g. quinine, 4-aminopyridine, tetraethylammonium. These data suggest that the decreased PS synthesis observed during T cell activation intervenes in the cascade of events leading to IL-2 secretion. The decrease in the biosynthesis of this phospholipid seems to be dependent on the activity of K+ channels.

4-Aminopyridine↗

PubMedDate not supplied

Insulin-like growth factor I/somatomedin C action on 2-deoxyglucose and alpha-amino isobutyrate uptake in chick embryo fibroblasts.

Maximum 125I-IGF-I/Sm-C total binding to chick embryo fibroblasts was 3% at +37 degrees C and decreased to less than 1% in presence of 2.8 X 10(-9) M unlabelled IGF-I/Sm-C. Insulin did not compete with IGF-I/Sm-C for the binding to cells. Biological action of IGF-I/Sm-C was evaluated on 2-deoxyglucose and alpha-aminoisobutyrate uptake. Results are compared with those obtained with insulin. Maximal peptide effects on the two transport processes were obtained at a 0.65 X 10(-7) M concentration and for a 120 minute association time, whereas cells were markedly less sensitive to insulin and time response curves were different. These results suggest that insulin action on nutrient uptake in chick embryo fibroblasts is not mediated by the binding of the hormone to IGF-I/Sm-C receptors.

Aminoisobutyric Acids↗

PubMedDate not supplied

TNF-alpha and IL-6 synergistically inhibit ketogenesis from fatty acids and alpha-ketoisocaproate in isolated rat hepatocytes.

BACKGROUND: During sepsis, lipid metabolism is shunted toward triacylglycerol synthesis and hepatic lipogenesis. A decrease in ketogenesis from free fatty acids also is observed, probably mediated by cytokines involved in host response to infection. Whether such an inhibition of ketogenesis occurs with other ketone body precursors such as ketoacids is not known. The aim of this study was to determine the effects of tumor necrosis factor alpha (TNF-alpha) and interleukin 6 (IL-6) on hepatic ketone body production from octanoic acid, a medium-chain fatty acid, and from alpha-ketoisocaproate (KIC), the ketoanalogue of leucine. METHODS: The experiments were conducted in cultured hepatocytes isolated from 24-hour-fasted Sprague-Dawley rats. Hepatocyte monolayers were incubated for 6 hours, with either KIC or octanoic acid (1 mmol/L), in the presence of glucagon and TNF-alpha (25 micro/L) IL-6 (15 microg/L) and/or IL-6. Acetoacetate, beta-hydroxybutyrate, and free fatty acids were determined in culture medium by enzymatic methods and KIC was measured by high-performance liquid chromatography. RESULTS: KIC and octanoic acid uptake by hepatocytes was 79% and 92%, respectively, over 6 hours, and cytokines had no influence. However, TNF-alpha and IL-6 caused inhibition of ketogenesis from alpha-ketoisocaproate (5.6% +/- 2.3% and 4.4% +/- 3.0%, respectively), and from octanoic acid (7.9% +/- 2.9%, 5.7% +/- 3.2%, respectively). In addition, when the two cytokines were present together in the culture medium, the inhibition was enhanced (inhibition of ketogenesis from KIC: 14.0% +/- 4.8%; from octanoic acid: 11.6% +/- 3.4%). CONCLUSIONS: In our experimental conditions, cytokines mediate an inhibition of ketogenesis; this process could be explained by a direct effect of cytokines on metabolic pathways of octanoic acid and KIC oran indirect effect by modification of the mitochondrial redox state.

3-Hydroxybutyric Acid↗

PubMedDate not supplied

[Nutrition in the elderly: importance and traps of biological investigations].

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Aged↗

PubMedDate not supplied

Is biolectrical impedance analysis a tool at bedside, during heat waves to assist geriatricians with discriminative diagnosis of hypertonic dehydration?

OBJECTIVES: To assess BIA data given by Analycor 3 and some bio-impedance equations to assist geriatricians with discriminative diagnosis of hypertonic dehydration, during heat waves. DESIGN: Prospective study: a dehydrated patients group has been compared with a randomised control group. SETTING: The study was carried out in a French geriatric department, in the Emile Roux geriatric hospital. PARTICIPANTS: 36: six men and twelve women in each group. MEASUREMENTS: The most valuable clinical indicators of dehydration severity were recorded and scored. BIA measurements were performed with an Analycor 3 analyzer; TBW was calculated from impedances at 50 and 100 kHz, ECW from impedance at 5 kHz; Calculations were made also with formula described in the literature, validated in healthy or in institutionalised elderly subjects. RESULTS: TBW and ECW values were always lower in dehydrated group than in control group, but without significance, whatever the applied formula; however ICW values calculated with "manufacturers equations" significantly decreased in dehydrated group. Data given by the analyzer used in this study, as well as BIA age specific equations discriminated the severely hypertonic dehydrated patients sub-group, but not the mildly hypertonic dehydrated patients sub-group. CONCLUSION: The BIA data given by the analyzer used in this study assist geriatricians at bedside with discriminative diagnosis of hypertonic dehydration, especially in severe hypertonic dehydration, but data given by the analyzer used in this study, as well as age specific equations are sometimes in poor agreement with clinical and biological parameters usually selected to assess dehydration, in mildly dehydrated patients.

Aged↗

PubMedDate not supplied

Calcium-dependent regulation of phosphatidylserine synthesis in control and activated Jurkat T cells.

Activation of Jurkat T cells with phytohemagglutinin (PHA), CD3 or CD2 monoclonal antibodies (mAbs) results in a marked inhibition of phosphatidylserine (PS) synthesis. Activation of Jurkat T cells with PHA in a Ca(2+)-free medium resulted in an arrest of PS synthesis which was not reversed by the addition of Ca2+. The use of BAPTA to chelate Ca2+ ions released from intracellular stores prevented PHA-induced inhibition of PS synthesis. In addition, it was found that during activation, in the presence of BAPTA, a net Ca2+ influx paralleled an increase in PS synthesis, demonstrating that Ca2+ uptake caused an enhanced PS synthesis rather than an inhibition. The use of a CD2 mAb, D66, able to mobilize exclusively Ca2+ from intracellular stores, resulted in 51% inhibition of PS synthesis. N-Ethylmaleimide (NEM), which inhibits both the release of Ca2+ from internal stores and the influx of Ca2+, totally prevents the inhibition of PS synthesis induced by PHA, anti-CD3 or anti-CD2 mAbs. The presence, in the incubation medium, of either NDGA, TPCK or TPA, three drugs able to markedly inhibit Ca2+ influx without modifying the release of Ca2+ from internal stores, did not modify the inhibition of PS synthesis induced by PHA. Moreover all the drugs known to interact with calmodulin were also found to prevent the PHA-induced inhibition of this phospholipid. Taken together, these results show that the inhibition of PS synthesis induced by T cell activators is regulated by both calmodulin and Ca2+ ions recruited from intracellular compartments.

Antibodies, Monoclonal↗

PubMedDate not supplied

Effects of the serine analogues isoserine and serinol on interleukin-2 synthesis and phospholipid metabolism in a human T cell line Jurkat.

Phosphatidylserine has been implicated both in the regulation of protein kinase C activity and in the regulation of T lymphocyte activation. Taking into account the fact that some serine analogues modify the activity of the base exchange enzyme system responsible for the synthesis of phosphatidylserine and to a lesser extent the synthesis of phosphatidylcholine and phosphatidylethanolamine, in vitro, we have tested the ability of both isoserine and serinol to modify phospholipid synthesis in the T cell line Jurkat. It was found that serinol was able to decrease by 75% the amount of phosphatidylserine synthesized by the cells and also to decrease the synthesis of phosphatidylcholine and phosphatidylethanolamine, while phosphatidylinositol synthesis was not affected. Concomitantly, in serinol-treated Jurkat cells, interleukin-2 production was markedly inhibited. Monitoring the production of second messengers generated by T cell activators showed that in serinol-treated cells the production of diacylglycerol was impaired while Ca2+ mobilization remained unaffected. Serinol thus appeared to be a potential immunoregulatory molecule active at the level of protein kinase C regulation either through its interaction with phosphatidylserine or through diacylglycerol production.

Calcium↗

PubMedDate not supplied

Inhibition of phosphatidylserine synthesis by phosphatidic acid in the Jurkat T cell line: role of calcium ions released from intracellular stores.

Phosphatidic acid exogenously added to Jurkat T-cells, provokes a marked inhibition of phosphatidylserine (PS) synthesis. Comparison of the efficiency of synthetic phosphatidic acids, differing in their fatty acid content, to induce inhibition of PS-synthesis have shown that short chain saturated and long chain unsaturated fatty acid-containing phosphatidic acids were the best inhibitors. Treatment of Jurkat cells with phosphatidic acid, induced a mobilization of calcium ions arising exclusively from intracellular stores, suggesting that Ca2+ from intracellular compartments might play a key role in the inhibition of PS synthesis. In activated cells, the use of R59022, a diacylglycerolkinase inhibitor, suggests that PA and probably calcium ions released by PA are the messengers responsible for the inhibition of PS synthesis in Jurkat T cells.

Antibodies, Monoclonal↗

PubMedDate not supplied

Breakdown of a phosphatidylcholine pool arising from the metabolic conversion of phosphatidylethanolamine as a novel source of diacylglycerol in activated T cells.

Activation of Jurkat T cells with either phytohemagglutinin (PHA), CD3 or CD2 monoclonal antibodies (mAbs) induces the production of diacylglycerol (DAG) from two different sources. Activation of the phosphatidylinositide cycle in activated T cells is a well-known source of the second messengers DAG and inositol triphosphate (IP3). The present report demonstrates that a particular pool of phosphatidylcholine (PC) arising from the sequential methylation of phosphatidyl-ethanolamine (PE) is probably a second source of DAG. The occurrence of two distinct sources of DAG in activated T cells is supported by the fact that DAG production was not accompanied by a decrease of phosphatidylinositol mono- and bisphosphate (PIP/PIP2) pools as measured after [3H]glycerol labeling whereas [3H]arachidonic acid PIP/PIP2 pools decrease in parallel with DAG production. The presence of a second generating pathway for DAG was demonstrated by measuring phospholipid synthesis and degradation in cells labeled with [3H]choline, [3H]ethanolamine or [3H]serine. In Jurkat cells, PHA decreased the incorporation of [3H]ethanolamine and [3H]serine but not [3H]choline into PC suggesting that the PC pool arising from the methylation of PE was utilized during activation whereas the PC pool synthesized through the CDP choline pathway was not. In [3H]ethanolamine-prelabeled cells, but not in [3H]choline-prelabeled cells, PHA, CD3 and CD2 induced the breakdown of PC. The PC breakdown was accompanied by a release of [3H]choline and the production of DAG and phosphatidic acid (PA). The breakdown of PC described in the present report strongly suggests that PC participates in T lymphocyte activation through the production of DAG.

Calcimycin↗

PubMedDate not supplied

Stimulation of alpha-(methylamino) isobutyric acid uptake by interleukin-1 in human synovial cells. Involvement of a cAMP dependent pathway.

After one hour incubation with interleukin-1 beta (IL-1 beta), the uptake of alpha-(methylamino) isobutyric acid (MeAIB) by human osteoarthritic synovial cells appeared significantly increased. This effect, observed with 0.1 to 5 ng/ml of cytokine, was inhibited by cycloheximide, indicating that protein synthesis is involved. In addition, this effect seems mediated by a pertussis toxin-sensitive G protein. Finally, intracellular cAMP concentration measurements, the use of a phorbol ester, protein kinase inhibitors and forskolin+3-isobutyl-1-methylxantine (IBMX) provided evidence that a cAMP-dependent protein kinase is associated with interleukin-1 beta-mediated alpha-(methylamino) isobutyric acid uptake.

Biological Transport, Active↗