Activation of lymphocytes of man and mouse: monovalent cation fluxes

Cell attachment to extracellular matrices is modulated by pulsed radiation at 820 nm and chemicals that modify the activity of enzymes in the plasma membrane

BACKGROUND AND OBJECTIVES

Adhesive interactions between cells and extracellular matrices play a regulative role in wound repair processes. The objective of this investigation is to study action mechanisms of pulsed radiation at 820 nm on cellular adhesion in vitro. Light emitting diodes (LED) at 820 nm are widely used for treatment of wounds of various etiology.

STUDY DESIGN/MATERIALS AND METHODS

The LED (820 +/- 10 nm, 10 Hz, 16-120 J/m(2)) is used for the irradiation of HeLa cell suspension. In parallel experiments, amiloride (5 x 10(-4) M), ouabain (7 x 10(-5) M, 7 x 10(-4) M), quinacrine (6 x 10(-4) M), arachidonic acid (1 x 10(-5) M), glucose (2 x 10(-4) M), and ATP (5 x 10(-5) M) are added to the cell suspension before or after the irradiation procedure. The cell-glass adhesion is studied using the adhesion assay technique described in Lasers Surg Med 1996; 18:171.

RESULTS

Cell-glass adhesion increases in a dose-dependent manner following the irradiation. Preirradiation eliminates the inhibition of cell attachment caused by ouabain, arachidonic acid, and ATP. The inhibitive effect of quinacrine on the cell attachment is eliminated by the irradiation performed after the treatment with the chemical. Irradiation and amiloride have a synergetic stimulative effect on the cell attachment. The threshold dose for the cell attachment stimulation by the irradiation is decreased by the treatment of the cell suspension with amiloride or ouabain.

CONCLUSIONS

The results obtained indicate that pulsed IR radiation at 820 nm increases the cell-matrix attachment. It is the modulation of the monovalent ion fluxes through the plasma membrane and not the release of arachidonic acid that is involved in the cellular signaling pathways activated by irradiation at 820 nm. Preirradiation has a protective effect against the inhibitive action of ouabain, arachidonic acid, ATP, and quinacrine on cell attachment process. It is supposed that irradiation activates those signaling pathways in cells which attenuate the inhibitive action of these chemicals.

Na, K-ATPase pump in activated human lymphocytes: on the mechanisms of rapid and long-term increase in K influxes during the initiation of phytohemagglutinin-induced proliferation

Functional expression of Na, K-ATPase pump as determined by ouabain-sensitive Rb influxes has been investigated in human peripheral blood lymphocytes, activated by phytohemagglutinin (PHA) from resting state to proliferation. It is found that a rapid twofold elevation of ouabain-sensitive Rb influx in response to PHA is followed by a long-term increase in pump activity, which precedes the DNA synthesis and is temporally related to the growth phase of mitogenic response. Unlike the early pump activation, the late enhanced pump activity is not the result of elevated cell Na content, it is inhibited by cycloheximide and requires new protein synthesis. Actinomycin D and alpha-amanitin, in doses, which suppress the PHA-induced increase in the RNA synthesis, do not abolish the elevated Rb influx until 20-24h of mitogenic activation and inhibit the late, growth-associated increase in Rb influx. It is concluded that (1) in mitogen-activated cells both short- and long-term control is involved in the enhanced pump activity, and (2) translational and transcriptional mechanisms may contribute to the long-term up-regulation of Na, K-ATPase pump during blast transformation of human lymphocytes.

Participation of urinary Na+, K+, pH, and L-ascorbic acid in the proliferative response of the bladder epithelium after the oral administration of various salts and/or ascorbic acid to rats

Changes in urinary parameters (particularly electrolyte levels and pH), and DNA synthesis and the morphology of the bladder epithelium were investigated in rats that were fed for 4 or 8 wk on diets containing various Na, K, Mg or Ca carbonate salts, with or without L-ascorbic acid (AsA). [The carbonate salts were fed at a level of 3% in the diet, and AsA or AsA-Na was administered at 5% in the diet. NH4Cl was at 1% in the diet.] The effects of treatment with NH4Cl (used as a urine acidifier), and of combined treatment with sodium ascorbate (AsA-Na) and NH4Cl were also investigated. Urinary pH was significantly elevated in groups given NaHCO3, K2CO3, AsA + NaHCO3, AsA + K2CO3 and AsA-Na, whereas treatment with AsA or NH4Cl alone caused a significant drop in urinary pH. An increase in urinary electrolytes or ascorbic acid was associated with the corresponding dosing regimen. DNA synthesis in the bladder epithelium was increased in groups given NaHCO3, K2CO3, AsA + NaHCO3, AsA + K2CO3 or AsA-Na. Furthermore, all treatments that induced an elevation of DNA synthesis also induced some morphological alterations in the bladder epithelium. The administration of AsA in conjunction with NaHCO3 or K2CO3 induced levels of change greater than those with either salt alone. In contrast, the degree of response in the bladder epithelium of rats given AsA-Na was reduced by the simultaneous administration of NH4Cl. These results suggest that the degree of DNA synthesis and/or morphological alteration in the rat-bladder epithelium after treatment with various bases may depend on changes in urinary concentrations of Na+ or K+ ions and/or pH, and the presence of ascorbic acid in the urine. The results are discussed in relation to the possible promotion by various treatment regimens (salts +/- AsA) of urinary bladder carcinogenesis.

Load responsiveness of protein synthesis in adult mammalian myocardium: role of cardiac deformation linked to sodium influx

Exposure of adult mammalian myocardium to increased hemodynamic loads augments cardiac protein synthesis, ultimately leading to hypertrophy of the affected chamber. This established relationship between loading conditions and protein synthesis was examined in terms of two questions. First, is there a basic difference between the anabolic effect of a passive load imposed on diastolic myocardium and that of an active load generated by systolic myocardium? This issue was addressed by measuring [3H]phenylalanine incorporation into muscle protein in either quiescent or contracting ferret papillary muscles, set at known isometric lengths. Myocardial protein synthesis increased in proportion to total muscle tension in each case, with an equivalent relation describing both quiescent and contracting muscles. Synthesis of two contractile proteins, actin and myosin heavy chain, were enhanced by muscle loading. Thus, a quantitative rather than qualitative difference between the anabolic effects of diastolic and systolic loading was demonstrated. Second, since increased sodium influx is an initial cellular response requisite to the growth-inducing activity of many substances, and since sodium entry through stretch-activated ion channels is stimulated by deformation of the sarcolemma, does cardiac deformation during increased loading promote sodium influx as a signal to increase anabolic activity? In either quiescent or contracting papillary muscles, the rate of 24Na+ uptake was found to increase with load. Streptomycin, a cationic blocker of the mechanotransducer ion channels, was without effect on protein synthesis in stimulated but slack muscles; however, it inhibited, in a dose-related manner, the augmented protein synthesis otherwise observed in contracting muscles developing tension. At 500 microM, streptomycin did not reduce active tension, but it did reduce the synthesis of both actin and myosin heavy chain. In a second pharmacologic approach, inotropic agents were chosen which uniformly increased muscle tension development but which had contrasting effects on sodium influx. Protein synthesis increased in the presence of Na+ influx enhancers, monensin or veratridine; however, protein synthesis decreased in the presence of amiloride, a sodium influx inhibitor. Thus, myocardial protein synthesis varied directly with sodium influx despite the positive inotropic effect observed with each of these agents. In addition, inhibition of protein synthesis by ouabain demonstrated that activation of the Na+ pump is required for the anabolic effect of load.(ABSTRACT TRUNCATED AT 400 WORDS)

Tissue distribution of an endogenous ligand to the Na, K ATPase molecule

A variety of evidence indicates the presence of a circulating ligand to the Na, K ATPase molecule that is involved in the regulation of extracellular sodium metabolism. To examine the potential role of endogenous ligands to the Na, K ATPase molecule in the regulation of intracellular sodium metabolism, the tissue distribution of digitalis-like activity was quantitated in several brain regions and peripheral organs. The digitalis-like activity of desalted and delipidated extracts of tissue was widely distributed and produced a displacement of tritiated ouabain that was parallel to the displacement produced by cold ouabain. These results suggest that tissue contains an endogenous ligand to the Na, K ATPase molecule and that this ligand may regulate intracellular sodium metabolism in an autocoid-like manner.

(3H)ouabain binding to leukaemic cells and intralymphocytic sodium content in chronic lymphocytic leukaemia; no evidence for alterations of the Na+/K+-pump

The number of specific (3H)ouabain binding sites and dissociation constants (Kd) were determined by Scatchard analysis of values for leucocytes from patients with B-cell chronic lymphocytic leukaemia (CLL), chronic myeloid leukaemia (CML), acute blastic leukaemia (AL) and healthy subjects. CLL lymphocytes and normal B-cells bound significantly less (3H)ouabain than did normal T-lymphocytes. CML granulocytes showed the same binding characteristics as normal granulocytes, while blast cells from AL patients bound significantly more (3H)ouabain than did normal granulocytes or B-cells. The increased binding capacity in blast cells might, at least partly, reflect their larger cell size. A decrease in Kd values was only found in CLL lymphocytes, as compared with normal B-cells. Intralymphocytic sodium content in CLL lymphocytes was significantly increased, as compared with that in T-cell-enriched normal lymphocytes. (3H)ouabain binding did not show any relationship to different prognostic variables in CLL. The present data mainly argue against altered Na+/K+-ATPase enzyme activity as an indicator of malignancy.

Activation of the Na+/K+-ATPase by interleukin-2

Activated B61.SF.1 and CTLL-2 T lymphocyte clones which are strictly dependent on interleukin-2 (IL-2) for growth were used to study the activation of Na+/K+-ATPase. 50% of [3H]thymidine maximal incorporation was obtained when the extracellular concentration of Na+ or K+ was reduced to 50 or 2 mM, respectively. 'Quiescent' CTL clones stimulated with IL-2 showed an increase of 48-380% in ouabain-sensitive 86Rb uptake. Furthermore, this stimulation was completely inhibited by a monoclonal antibody PC.61 directed at the IL-2 receptor. The activation of the pump was dependent on the dose of IL-2, took place at the same doses of IL-2 that were required to stimulate cell proliferation and was linear for at least 30 min.

Effects of insulin on the total number of [3H]ouabain binding sites in normal human lymphocytes and after stimulation in vitro with concanavalin A

The effects of insulin in vitro on the total number of [3H]ouabain binding sites were studied in normal and concanavalin A-stimulated human T-lymphocytes after incubation for 18 and 42 h with 0, 10(2) and 10(5) mIU/l of insulin. While no effect on [3H]ouabain binding could be demonstrated in non-stimulated cells, a significant decrease could be produced in concanavalin A-stimulated cells. Mean +/- SD for the total number of [3H]ouabain binding sites per cell after 18 h incubation time with concanavalin A in the absence of insulin was 46,099 +/- 6,620 as compared with 44,783 +/- 8,347 in the presence of 10(2) mIU/l of insulin (non-significant) and 42,406 +/- 7,066 in the presence of 10(5) mIU/l (p = 0.031). The corresponding 42-h values were 47,075 +/- 9,412, 43,761 +/- 9,273 (p = 0.033) and 43,824 +/- 9,312 (p = 0.005).

Evidence for coordinate genetic control of Na,K pump density in erythrocytes and lymphocytes

The erythrocyte is widely used as a model cell for studies of the Na,K pump in health and disease. However, little is known about the factors that control the number of Na,K pumps expressed on the erythrocytes of a given individual, nor about the extent to which erythrocytes can be used to validly assess the pump density on other cell types. In this report, we have compared the interindividual variance of Na,K pump density in erythrocytes of unrelated individuals to that seen with identical twins. Unlike unrelated individuals, in whom pump parameters, ie, ouabain binding sites. 86Rb uptake, cell Na concentration vary widely, identical twin pairs showed no significant intrapair variation for these values. Thus, a role for genetic factors is suggested. In addition, we established and validated a method for determining Na,K pump density and pump-mediated 86Rb uptake in human peripheral lymphocytes. Using this method, we show that whereas Na,K pump density differs markedly between erythrocytes (mean of 285 sites per cell) and lymphocytes (mean 40,600 sites per cell), there is a strong and highly significant correlation (r = 0.79, P less than 0.001) between the pump density in these cell types in any given individual. Taken together, these studies suggest that genetic factors are important determinants of Na,K pump expression, and that pump density appears to be coordinately regulated in two cell types in healthy individuals.

K channels in T lymphocytes: a patch clamp study using monoclonal antibody adhesion

Ionic fluxes are thought to be involved in mediating the proliferation of peripheral blood lymphocytes (PBLs) in response to mitogenic substances. Among the earliest events occurring after the addition of mitogen to cultured lymphocytes are changes in rates of cation transport. We were interested, therefore, in the possible role of ion channels in mediating the lymphocyte proliferative response. The development of patch clamp techniques by Neher and colleagues has made it possible to study membrane conductances in a variety of small cell types. We have developed a method which uses monoclonal antibodies to make cells adhere to solid surfaces for two major reasons: (1) it is much easier to patch clamp stationary cells, and (2) the method can be used to selectively adhere a particular cell type from a heterogeneous population. We have used these techniques here to identify whole-cell potassium currents, in lymphocytes recognized by OKT11 monoclonal antibody, which are increased 1.9-fold by mitogenic stimulation.

In vivo stimulation of nerve cells by phytohemagglutinin. II. Alterations in the rate of total and mRNA synthesis in the brain cortex of old rats

Bacto-phytohemagglutinin-P (PHA-P) was administered in form of a single intralumbar injection of 2 mg/100 g body weight dose to 24- to 28-mth-old female CGY rats. The accuracy of the injection technique was checked by adding 2% lidocaine to the injection mixture, which resulted in a transient and symmetric paralysis of the posterior limbs when reaching the cerebrospinal fluid. The total RNA content of the liver and brain cortex were measured, and phenolic extraction of RNA was performed the brain cortex. Poly(A) +RNA (mRNA) was separated from the total RNA of the brain cortex by oligo(dT)-cellulose chromatography. Pulse labeling with tritiated uridine was performed 45 min before killing the animals and the incorporation of the radiolabel was measured in the respective RNA classes and corrected for the nucleotide pool size. The rates of total and mRNA synthesis are expressed in percentages of the young untreated rats and compared to old untreated animals. The effects of PHA-P was studied at 4, 10, 20 and 44 h after its injection. A considerable increase of the total RNA content of the brain cortex was measured during the first 10 h of the experiment followed by a slow decrease. However, the RNA content of the brain cortex was still significantly higher at the end of experiment compared to untreated old rats. The rate of total RNA synthesis increased significantly during the first 10 h and remained constantly high until 44 h. The rate of mRNA synthesis increased to a higher extent than that of the total RNA, and also remained high until 44 h.

Antigen-specific stimulation of amino acid transport in bovine lymphocytes

Treatment of bovine lymphocytes isolated from animals which were either infected with Mycobacterium bovis or sensitized to a purified protein derivative (PPD-B) from this organism induced an increase in the transport of alpha-aminoisobutyric acid (AIB) and alpha-methylaminoisobutyric acid (MeAIB). PPD-B did not stimulate these transport activities in lymphocytes from nonsensitized animals. The transport stimulation was first measurable after about 7 hours of treatment, reached about a two-fold enhancement after 20 hours, and continued to increase to 30- to 40-fold after 6 days. The stimulation of AIB transport was inhibited by both ouabain and cycloheximide. Experiments to determine transport system specificities in nonstimulated lymphocytes showed that MeAIB transport was primarily by the Na+-dependent, A-system, and leucine transport was mostly by Na+-independent system(s). In contrast, AIB transport was about 25% by the A-system, 25% by at least one Na+-dependent, non-A-system, and 50% by one or more Na+-independent system(s). Analysis of the three components of AIB transport after treatment with PPD-B showed that: 1) transport by both the A-system and the Na+-independent system(s) was stimulated; 2) A-system transport was stimulated to a larger extent than Na+-independent transport; and 3) Na+-dependent, non-A-system transport was not stimulated significantly.

Ionic regulation of egg activation

Developing cells have constantly to make decisions: when to proliferate and divide, when and how to differentiate. It is an increasingly attractive idea that these decisions involve changes in intracellular cation concentrations. Our ideas about the mechanisms of changes in intracellular cations come largely from the application of biophysical techniques in the study of excitable tissues. These ideas are proving very valuable to the investigation of the control of proliferation and cell development and it is evident that the ionic mechanisms which pertain in nerve and muscle have their counterparts in other cells. Just as alterations in intracellular ion concentrations serve a signalling function in excitable tissue, so too they act as signals during development. Since almost all the quantitative data on the ionic mechanisms of fertilization come from work on sea urchins we have confined our review to sea urchin eggs.