Phosphorylase a activity as an indicator of neutrophil activation by chemotactic peptide

Differential effects of Quin-2 and Quin 2-AM on ciliary responses of Paramecium caudatum at moderate calcium levels

Paramecium cells were suspended in a pH 7.1 buffered solution containing various levels of total CaCl2 (3.9 to 250 μM), Quin-2 or Quin 2-AM and in the absence or presence of various concentrations of KCl, NaCl or BaCl(2). At lower calcium levels especially, Quin-2 behaved as a potent antagonist of KCl-induced continuous ciliary reversal (50% inhibition at 4 μM) and, at higher concentrations, reduced the duration of periodic ciliary reversal responses to NaCl and BaCl(2). The efficacy of Quin-2 as an antagonist of KCl-induced ciliary reversal was reduced by elevation in extracellular calcium. Quin 2-AM, in contrast, slightly increased the duration of continuous ciliary reversal behaviors to KCl and also, in a time-dependent fashion, increased the duration of the recovery time of the cells from KCl stimulation. The results clearly indicate that any use of these indicators to measure changes in ionized calcium in this cell following cation stimulation should be limited to studies at high extracellular calcium levels - concentrations where the cells' responses to cationic stimulation are markedly attenuated.

Verapamil reverses abnormal [Ca2+]i and carbohydrate metabolism of PMNL of dialysis patients

The basal levels of cytosolic calcium ([Ca2+]i) of polymorphonuclear leukocytes (PMNL) are elevated in hemodialysis (HD) patients, and this abnormality has been implicated in the dysfunction of the PMNL of these patients. The elevated [Ca2+]i appears to be due to PTH-induced entry of calcium into PMNL, an action that may be prevented by calcium channel blockers. We examined [Ca2+]i and carbohydrate metabolism of PMNL of normal subjects and of HD patients before, after eight to nine weeks of verapamil therapy (120 mg/day), and after eight to ten weeks of discontinuation of verapamil treatment. In HD patients, the basal levels of [Ca2+]i of PMNL are elevated and their glucose uptake, the activity of total and active forms of glycogen synthetase, and glycogen content are reduced compared to values in normal subjects (P < 0.01). These derangements were normalized after verapamil therapy and re-emerged after discontinuation of treatment with verapamil despite no change in blood levels of PTH. The results indicate that the elevation in [Ca2+]i of PMNL and the consequent derangements in carbohydrate metabolism of these cells are treatable with a calcium channel blocker. The data assign a valuable role for calcium channel blockers for the amelioration of some aspects of cell dysfunction of uremia.

Alterations of polymorphonuclear leukocyte glycogen metabolism and glucose uptake in dialysis patients

Human polymorphonuclear leukocytes (PMNs) are activated during extracorporeal circulation. An indicator of PMN activation may be the glycogen-degrading enzyme phosphorylase. It is unknown whether dialysis therapy may influence PMN carbohydrate metabolism. Therefore, PMNs were isolated from healthy control subjects, patients undergoing continuous ambulatory peritoneal dialysis (CAPD), and patients undergoing regular hemodialysis therapy (RDT) before, during, and at the end of hemodialysis (HD) treatment using dialyzers made of polysulfone or polymethylmethacrylate (PMMA). Nifedipine (NIF) was continuously infused during HD with PMMA in 5 patients at a dose of 18 micrograms/kg body weight per hour. Glycogen, activity of glycogen synthetase and phosphorylase (active and inactive forms of both enzymes), and glucose uptake with and without stimulation with the chemotactic peptide FMLP were determined in these PMNs. During HD with PMMA, there was a significant increase of PMN phosphorylase "a" activity 15 and 30 minutes after the start of HD. HD with polysulfone did not stimulate the active "a" form of the glycogen-degrading enzyme in PMNs. HD with PMMA significantly inhibited the active I-form of glycogen synthetase, whereas polysulfone activated glycogen synthetase I. NIF inhibited phosphorylase "a" activation during HD with PMMA. PMN glycogen content and glucose uptake were improved during HD with polysulfone, but not with PMMA. PMN glycogen content, activity of glycogen synthetase, and glucose uptake were significantly lower also in CAPD patients compared with healthy controls. These data show that HD with PMMA activates PMN glycogenolysis. This effect can be inhibited by calcium channel blockers. PMN glycogen content of RDT and CAPD patients is significantly lower compared with healthy controls due to inhibition of glycogen synthesis. Elimination of dialyzable factor(s) improves, but does not restore, PMN glycogen synthesis and glucose uptake.

Stimulation of a histone H4 protein kinase in Triton X-100 lysates of rabbit peritoneal neutrophils pretreated with chemotactic factors: lack of requirements of calcium mobilization and protein kinase C activation

The characteristics of the activation of a histone H4 kinase activity in Triton X-100 lysates of rabbit peritoneal neutrophils pretreated with fMet-Leu-Phe were studied: The activation of the kinase was a) inhibited by the antagonist of formylpeptide, t-Boc-(Phe-Leu)2(-)-Phe, b) completely inhibited by pertussis toxin pretreatment, c) not affected by the pretreatment of neutrophils with an activator of protein kinase C, phorbol-12-myristate-13-acetate, or an inhibitor of protein kinase C, 1-(5-isoquinoline-sulfonyl)-2-methyl-piperazine, and d) not inhibited in the cells preloaded with the intracellular calcium chelators, bis-(o-aminophenoxy)-ethane-N,N,N',N'-tetra acetic acid acetoxymethyl-ester (BAPTA/AM). These results suggest that the stimulus-induced activation of H4 kinase requires functional receptor and GTP-binding protein but neither calcium mobilization nor protein kinase C activation.

Impaired metabolic function and signaling defects in phagocytic cells in glycogen storage disease type 1b

Patients with glycogen storage disease (GSD) type 1b (1b), in contrast to patients with GSD type 1a (1a), are susceptible to recurrent bacterial infections suggesting an impairment in their immune system. In this study, phagocytic cell (neutrophil and monocyte) respiratory burst activity, as measured by superoxide anion generation, oxygen consumption, and hexose monophosphate shunt activity, was markedly reduced in both neutrophils and monocytes from GSD 1b patients as compared with either GSD 1a patients or healthy adult control cells. Degranulation, unlike respiratory burst activity, was not significantly different in neutrophils from GSD 1b patients as compared with controls. Both neutrophils and monocytes from GSD 1b patients showed decreased ability to elevate cytosolic calcium in response to the chemotactic peptide f-Met-Leu-Phe. In addition, calcium mobilization in response to ionomycin was also attenuated suggesting decreased calcium stores. Thus, reduced phagocytic cell function in GSD 1b is associated with diminished calcium mobilization and defective calcium stores. Defective calcium signaling is associated with a selective defect in respiratory burst activity but not degranulation.

Calcium-dependent fusion of the plasma membrane fraction from human neutrophils with liposomes

A cell-free assay monitoring lipid mixing was used to investigate the role of Ca2+ in neutrophil membrane-liposome fusion. Micromolar concentrations of Ca2+ were found to directly stimulate fusion of inside-out neutrophil plasma membrane enriched fractions (from neutrophils subjected to nitrogen cavitation) with liposomes (phosphatidylethanolamine:phosphatidic acid, 4:1 molar ratio). In contrast, right-side-out plasma membranes and granule membranes did not fuse with liposomes in the presence of Ca2+. Similar results were obtained with two different lipid mixing assays. Fusion of the neutrophil plasma membrane-enriched fraction with liposomes was dependent upon the concentration of Ca2+, with threshold and 50% maximal rate of fusion occurring at 2 microM and 50 microM, respectively. Furthermore, the fusion was highly specific for Ca2+; other divalent cations such as Ba2+, Mg2+ and Sr2+ promoted fusion only at millimolar concentrations. Red blood cell (RBC) membranes were used in control studies. Ca2(+)-dependent fusion did not occur between right-side-out or inside-out RBC-vesicles and liposomes. However, if the RBC-vesicles were exposed to conditions which depleted spectrin (i.e., low salt), then Ca2(+)-dependent fusion was detected. Other quantitative differences between neutrophil and RBC membranes were found; fusion of liposomes with RBC membranes was most readily achieved with La3+ while neutrophil membrane-liposome fusion was most readily obtained with Ca2+. Furthermore, GTP gamma S was found to enhance Ca2(+)-dependent fusion between liposomes and neutrophil plasma membranes, but not RBC membranes. These studies show that plasma membranes (enriched fractions) from neutrophils are readily capable of fusing with artificial lipid membranes in the presence of micromolar concentrations of Ca2+.

Exocytotic enzyme release from rabbit polymorphonuclear leukocytes after treatment with fluoride and calcium

Treatment of rabbit polymorphonuclear leukocytes (PMNs) with 20 mM sodium fluoride for 10 min, followed by removal of fluoride and addition of Ca2+ results in extensive exocytosis. This is apparent from a strong lysozyme release, together with a slight LDH release. During fluoride-activated Ca2+-dependent exocytosis an increase of indo fluorescence and a strong association of 45Ca with the cells occurs. Different inhibitors inhibit both 45Ca association and lysozyme release. Pretreatment of PMNs with pertussis toxin, or the presence of AI3+ in the medium has little effect on fluoride-activated Ca2+-dependent exocytosis. During pretreatment with fluoride, the ATP level strongly decreases. Exocytosis nevertheless occurs upon addition of Ca2+, indicating that a normal ATP level is not required for exocytosis. The glycogen content of the cell strongly decreases during exposure to Ca2+ after pretreatment with fluoride, but not during pretreatment with fluoride. Breakdown of glycogen and accumulation of 3-phosphoglycerate suggest that glycolysis is blocked at the enolase step, but proceeds as far as that step.

Protein kinases in neutrophils: a review

In chemotactic factor-stimulated neutrophils, rapid increases of intracellular levels of cyclic AMP, calcium, and diacylglycerol have been observed and may be linked to protein kinase activation. The study of the physiological role and regulation of protein kinases in the neutrophil and the identification of their substrates has provided valuable information on the molecular mechanism of neutrophil activation. The focus of this review is on those aspects of protein kinases that are relevant to neutrophil activation and on the substrate proteins for these protein kinases. The possible role of protein phosphorylation in neutrophil function is also discussed.

Polymorphonuclear leukocyte locomotion is insensitive to lowered cytoplasmic calcium levels

Chemotactic factors stimulate the rate of locomotion of polymorphonuclear leukocytes (PMNs). To investigate the importance of cytoplasmic calcium we have examined the ability of the chemotactic peptide N-formylnorleucyl eucylphenalanine (FNLLP) to stimulate the locomotion of PMNs whose cytoplasmic calcium levels were reduced by incubation in EGTA or in EGTA plus the calcium ionophores, ionomycin or A23187. Locomotion was assayed by migration through micropore filters and by time-lapse videomicroscopy. Cells in EGTA exhibited similar or slightly reduced rates of locomotion compared to cells in Hanks' balanced salt solution (HBSS). The peptide dose dependence for the stimulation of locomotion was similar in medium containing calcium or EGTA. The presence of 1 microM ionophore plus EGTA had no effect on the stimulation of locomotion by peptide. The presence of ionophores (1 microM) plus external calcium inhibited locomotion.

An actin-nucleating activity in polymorphonuclear leukocytes is modulated by chemotactic peptides

We examined the actin-nucleating activity in polymorphonuclear leukocyte lysates prepared at various times after chemotactic peptide addition. The actin nucleation increases two- to threefold within 15 s after peptide addition, decays to basal levels within 90 s, and is largely independent of cytoplasmic calcium fluxes. The peptide-induced nucleation sites behave as free barbed ends and therefore may increase the level of polymerized actin in vivo. The new nucleation sites may also determine the cellular sites of actin polymerization. This localization of actin polymerization could be important for the directional extension of lamellipodia during chemotaxis.