Measurement of the ADP:ATP ratio in human leukaemic cell lines can be used as an indicator of cell viability, necrosis and apoptosis.

In this study the relative levels of ADP and ATP have been measured in cells undergoing apoptosis. Using HL60, CEM7, Jurkat and U937 cell lines and cytotoxic agents known to induce apoptosis, there was a significant correlation (P<0.01 for all models) between the ADP:ATP ratio and the degree of apoptosis measured by TUNEL and estimation of the sub G(0) fraction by propidium iodide staining and flow cytometry. The ratio measured in viable proliferating cells was found to be less than 0.11 compared with ratios between 0.11 and 1.0 seen in cells undergoing apoptosis. The higher the percentage of hypodiploidy the greater the ratio. Necrosis induced by heat shock resulted in ADP:ATP ratios in excess of 15.0. When primary cultures of AML blast cells were used, there was again a significant correlation between the ADP:ATP ratio and the degree of hypodiploidy. Recent evidence suggests that apoptosis is accompanied by opening of the mitochondrial permeability pores, leading to disruption of the mitochondrial transmembrane potential (DeltaPsi(m)). This results in caspase activation due to the release of cytochrome c and apoptogenic factors into the cytosol. In five experiments using CEM7 and dexamethasone the mitochondrial transmembrane potential was assessed using the fluorescent cyanine dye JC-1 and flow cytometry. Functioning mitochondria concentrate the JC-1 to produce red fluorescence. Loss of mitochondrial transmembrane potential results in green fluorescence only. The percentage of cells exhibiting red fluorescence correlated positively with the ATP values and negatively with the ADP:ATP ratio.

Biocompatibility testing using ATP bioluminescence.

This article reports on the potential use of adenosine triphosphate bioluminescence for fast and highly sensitive biocompatibility screening. Results suggest that this technology can be a useful tool for the rapid determination of proliferative and cytotoxic effects. By adding an additional step to measure adenosine diphosphate, it then becomes possible to determine whether cells die by apoptosis or necrosis.

Effects of r-metHuG-CSF on polymorphonuclear leucocyte kinetics and function in patients on continuous ambulatory peritoneal dialysis.

End-stage renal failure (ESRF) patients undergoing continuous ambulatory peritoneal dialysis (CAPD) are immunocompromised and exhibit abnormal circulating polymorphonuclear leucocyte (PMN) function, including reduced phagocytosis and intracellular killing. Six uraemic patients on CAPD were each given 300 microg granulocyte colony stimulating factor (G-CSF) every day for 5 d and PMN function tests were performed daily. By day 5 of the study CD11b expression was significantly decreased in response to N-formylmethionylleucylphenylalanine (fMLP) and opsonized Staphylococcus epidermidis stimulation, and expression of L-selectin (CD62L) was significantly decreased in response to opsonized Staphylococcus epidermidis stimulation. Further, superoxide anion production and Fc gammaRI (CD64) expression were found to be significantly increased and Fc gammaRII (CD16) expression was lowered. Circulating white cell and PMN counts were significantly elevated in response to treatment. Administration of G-CSF did not appear to have corrected the abnormalities in phagocytosis and intracellular killing. This study suggests that G-CSF does no harm to ESRF patients and influences uraemic PMN function in a manner that is comparable to its effects on PMN in non-uraemic subjects.

Ex vivo neutrophil function in response to three different doses of glycosylated rHuG-CSF (Lenograstim).

Granulocyte colony-stimulating factor (G-CSF) is being considered as adjuvant treatment for infections in non-neutropenic patients. Normal healthy donors were given rHuG-CSF (Lenograstim) at 2.5, 5.0 and 7.5 micrograms/kg subcutaneously daily for 5 d. Polymorphonuclear leucocyte (PMN) function tests were carried out on peripheral blood PMN before the first injection and at 24 h and 96 h. Circulating PMN levels were also measured at these time intervals and found to be significantly increased with all doses by 24 and 96 h. Investigation of cell surface antigen expression revealed no changes in beta 2 integrin (CD11b/ CD18) expression. L-selectin (CD62L) expression was reduced with all doses by 96 h, this being significant with the 7.5 micrograms/kg dose. Fc gamma RI (CD64) levels were significantly up-regulated with the 7.5 micrograms/kg dose by 96 h whereas Fc gamma RIII (CD16) expression was found to be reduced during G-CSF treatment. Superoxide anion production was significantly increased in response to N-formylmethionyl-leucylphenylalanine (FMLP) and opsonized Staphylococcus epidermidis stimulation at 24 h and 96 h with the 5.0 and 7.5 micrograms/kg doses. The initial rate of phagocytosis (0-2 min) appeared to have increased with the 7.5 and 5.0 micrograms/kg doses at 96 and 24 h compared with PMN responses pretreatment, although these increases were not statistically significant. These results show that G-CSF enhances the functional responses of PMN stimulated by physiological agnonists and may help in the treatment of infections.

The effect of pregnancy on polymorphonuclear leukocyte function.

Pregnancy exerts suppressive effects on a number of chronic inflammatory conditions, particularly rheumatoid arthritis. We isolated peripheral blood polymorphonuclear leukocytes (PMN) from pregnant women at 30 to 34 wk (n = 34) and showed significant reductions in respiratory burst activity compared with nonpregnant controls (n = 34), as determined by lucigenin-enhanced chemiluminescence (LUCL). Responses to FMLP were reduced by 54% (p = 0.0046) and to zymosan-activated serum (ZAS) by 69% (p = 0.0043). Following LUCL responses to these agonists in women throughout the course of their pregnancy (n = 7) revealed significantly reduced responses by the second and third trimesters (p < 0.005). Intracellular H2O2 production in PMN at 30 to 34 wk gestation was significantly reduced (p = 0.0454) in response to FMLP, compared with the nonpregnant controls. Investigation of adhesion molecule expression revealed no differences in CD11b or CD18. However, loss of CD62L from the PMN surface in response to FMLP and ZAS was significantly reduced at 30 to 34 wk, as compared with controls (FMLP, p = 0.049; ZAS, p = 0.01; n = 34). There were no significant differences in cell surface formyl peptide receptor expression, although there were statistical differences in LUCL responses to all concentrations of FMLP used (p < 0.05). Incubating PMN with TNF, IL-8, and granulocyte-macrophage CSF increased formyl peptide receptor expression but revealed no differences between the two groups. Priming of pregnancy PMN with the same cytokines gave significantly reduced LUCL when cells were subsequently stimulated with FMLP (p < 0.05; n = 6). Our results show a reduction in PMN NADPH-oxidase activity during pregnancy and may offer a partial explanation for the remission of symptoms observed in rheumatoid arthritis.

Primary and secondary granule release by polymorphonuclear leukocytes exposed to peritoneal dialysis effluent.

Peritoneal dialysis effluent from patients with end-stage renal failure contains a low-molecular-weight solute that inhibits the killing of phagocytosed Staphylococcus epidermidis by polymorphonuclear leukocytes (PMN). This observation has been investigated by using luciginen-enhanced chemiluminescence to measure PMN NADPH oxidase activity, CD11b/CD18 expression and lactoferrin release to measure secondary granule discharge, and cellular levels of beta-glucuronidase (EC 3.2.1.31) to measure changes in primary granules. Peritoneal dialysis effluent had no effect on the loss of intracellular beta-glucuronidase from normal unstimulated PMN or from PMN stimulated with S. epidermidis. It did, however, cause a concentration-dependent (0 to 70%; vol/vol) increase in expression of CD11b/CD18 and NADPH oxidase activity. CD11b/CD18 expression increased over 20 min before starting to plateau. Release of lactoferrin by the same cells demonstrated a strong positive correlation with integrin expression (P < 0.001, Spearman's rank correlation coefficient). When dialysis effluent-treated PMN were stimulated with formyl-methionylleucylphenylalanine, integrin expression, release of lactoferrin, and NADPH oxidase activity were greater than in PMN treated with formyl-methionylleucylphenylalanine alone. Under these conditions, a concentration-dependent increase in CD11b/ CD18 and lactoferrin release were observed only at a concentration between 0 and 30% (vol/vol) dialysis effluent, while a concentration-dependent increase in oxidase activity was seen at a concentration between 0 and 70% (vol/vol). The results suggest that dialysis effluent does not affect PMN primary granule release but does cause increased release of secondary granules and an increase in NADPH oxidase activity in both unstimulated and stimulated PMN.

The use of ATP bioluminescence as a measure of cell proliferation and cytotoxicity.

Adenosine triphosphate (ATP) bioluminescence was used to determine whether there was a linear relationship between cultured cell number and measured luminescence using the luciferin-luciferase reaction. In all the cells tested including peripheral blood mononuclear cells (MNC), MOLT-4, HL-60, TF-1, NFS-60 and L-929 cell lines there was a significant correlation as determined by Spearman's rank correlation coefficient (p > 0.00001). These observations were then used to determine whether ATP bioluminescence could be used as a suitable substitute for tritiated thymidine uptake as a measure of cell proliferation. The cell lines MOLT-4, HL-60, TF-1 and NFS-60 showed a strong correlation between thymidine uptake and ATP bioluminescence (p > 0.00001 for all cell types). Additionally the ATP method could detect the cytokine dependent proliferation on TF-1 and NFS-60 cells by granulocyte-macrophage colony-stimulating factor (GM-CSF) and granulocyte colony-stimulating factor (G-CSF) respectively. The tumour necrosis factor alpha (TNF)-induced cytotoxic effect on L-929 cells could also be accurately detected using this method. It would therefore appear to be possible to use ATP bioluminescence in the detection of cytokine activity in a number of different bioassays.

Effect of ingested pentoxifylline on neutrophil superoxide anion production.

Superoxide and other oxygen radicals produced by activated polymorphonuclear leukocytes (PMN) may be important causes of tissue damage in a number of inflammatory conditions. Therefore, a drug which suppresses PMN responses in vivo is potentially important. In vitro, pentoxifylline (PTOX) inhibits superoxide anion production when PMN are stimulated with an activated complement component (C5a Des Arg) or formyl peptides but only at concentrations not achieved in the circulation. The aim of this study was to determine whether PTOX has an effect on PMN responses in vivo. Superoxide anion production, monitored by lucigenin-enhanced chemiluminescence, was inhibited by 40.5% +/- 8.0% (n = 8, P < 0.009) for C5a Des Arg and 47.7% +/- 9.6% (n = 8, P < 0.009) for formyl-methionylleucylphenylalanine stimulation 1.5 h after ingestion of 400 mg of PTOX in a slow-release tablet, with some inhibitory effects persisting at 5 h. There was a strong correlation between reduced PMN response to activated complement and plasma concentrations of three PTOX metabolites (P < 0.05), but not with plasma concentrations of the parent drug. In vitro investigations with each of the four methylxanthines showed two of these metabolites to be most effective at reducing PMN respiratory burst activity, lactoferrin release, and the expression of CD11b and CD18 molecules. Furthermore, this in vitro inhibitory activity was achieved at concentrations of metabolites achievable in vivo. The results suggest that PTOX reduces oxygen radical production and protects against unwanted tissue damage in vivo by the action of its metabolites.

Regulation of cytokine release from mononuclear cells by the iron-binding protein lactoferrin.

The iron-binding protein lactoferrin (Lf) is a constituent of neutrophil secondary granules and is discharged into the surrounding medium when neutrophils are activated. Lf released from neutrophils phagocytosing opsonized particles inhibits proliferation of mixed lymphocyte cultures (MLC) and has also been shown to inhibit granulopoiesis, suppress antibody production, and regulate natural killer cell activity. All of these processes are controlled by cytokines, suggesting that Lf may modulate immune responses by inhibiting cytokine activity. When MLC were cultured in round-bottomed wells to crowd the cells together, Lf, 50% saturated with iron, inhibited both proliferation and interleukin-2 (IL-2) release into the supernatants. Inhibition was concentration-dependent and lost at concentrations of Lf greater than 10(-12) mol/L. Lf at 10(-10) mol/L inhibited release of tumor necrosis factor-alpha (TNF) and interleukin-1 beta (IL-1) into MLC supernatants, as well as inhibiting IL-2 release. TNF in the supernatant was significantly reduced at 5 and 24 hours, becoming less and losing significance by 72 hours. IL-1 in the supernatant was not significantly reduced at 5 and 24 hours, becoming significant at 48 and 72 hours. IL-2 was significantly reduced at 48 and 72 hours and followed the same time course as proliferation. Inhibition was blocked by specific antiserum to Lf, but not by a preimmune serum. Lf, 10(-10) mol/L, also inhibited the production of TNF (49.15% +/- 7.98%; n = 10, P = .032) and IL-1 (42.67% +/- 6.72%; n = 6, P = .032) from endotoxin-stimulated mononuclear cells. As with MLC, inhibition was dose-dependent and abrogated by specific antiserum. Lf did not block the biological action of TNF, IL-1, or IL-2 in specific assays using cytokine-sensitive cell lines. These data suggest that Lf, released from activated neutrophils, acts as a negative feedback mechanism to prevent recruitment and activation of leukocytes in sites of inflammation.