Correlation between chemiluminescence response and rate of zymosan uptake by rat alveolar macrophages. Scanning electron microscope observations

A new technique, requiring small amounts of cells, for the parallel study of chemiluminescence and phagocytosis via different receptors in the same cell population

An assay permitting the parallel assessment of phagocytosis and chemiluminescence in the same cell population has been developed. The method is based on the phagocytosis of fluorescein isothiocyanate-conjugated yeast particles, either unopsonized or opsonized with complement factor C3 or IgG, by purified cells in suspension in a luminometer. Only a small number of cells (2 x 10(4)-1 x 10(5)) is required, and the reproducibility is high. Moreover, the technique permits phagocytosis to be related to oxygen-dependent killing activity in the same cell population. Since phagocytosis, degranulation and oxygen radical formation as a consequence of well-defined receptor recognition mechanisms can be characterized in very small cell populations, the method is suitable for monitoring the phagocytic function of cells from extravascular sites.

Effects of adenosine on polymorphonuclear leucocyte function, cyclic 3': 5'-adenosine monophosphate, and intracellular calcium

1. Inhibition of human polymorphonuclear leucocyte (PMN) function by adenosine was studied with respect to effects of adenosine on intracellular cyclic AMP and calcium during the PMN respiratory burst. 2. The adenosine analogue 5'-N-ethylcarboxamide-adenosine (NECA) and L-N6-phenyl-isopropyl-adenosine (L-PIA) inhibited PMN oxygen metabolite generation with relative potencies (NECA greater than adenosine greater than L-PIA) characteristic of an A2 receptor. 3. The respiratory burst was inhibited by adenosine when PMN were activated by calcium ionophore or chemotactic peptide but not when cells where activated by oleoyl-acetyl-glycerol (OAG). 4. Adenosine increased intracellular cyclic AMP during the PMN respiratory burst regardless of whether cells were stimulated by ionophore, chemotactic peptide or OAG. 5. To determine whether the differences in cell inhibition by adenosine were related to differences in intracellular calcium mobilization by each activating agent, calcium was evaluated with the fluorescent probe, indo-1. Adenosine suppressed the increase in intracellular calcium following PMN activation by calcium ionophore or chemotactic peptide. In contrast, calcium did not increase in PMN activated by OAG and adenosine did not affect intracellular calcium changes following this stimulus. 6. These results demonstrate that physiological concentrations of adenosine inhibit the PMN respiratory burst in association with an increase in intracellular cyclic AMP and reduction of intracellular calcium.

Participation of superoxide in luminol-dependent chemiluminescence triggered by mineral dust in rabbit alveolar macrophages

Luminol-dependent chemiluminescence (CL) triggered by mineral dust in rabbit alveolar macrophages depended on superoxide production as revealed by inhibition by superoxide dismutase and ferricytochrome c. The contribution of superoxide changed in the course of CL peak between 80-20%. The effects of ferricytochrome c were concentration-dependent: both stimulation and inhibition were observed. Ferricytochrome c and desferal also inhibited CL pathway which was not superoxide-dependent.

The production of reactive oxygen species in mice infected or immunized with Plasmodium berghei

The capacity of peritoneal exudate cells (PEC) obtained from mice infected or immunized with Plasmodium berghei to produce reactive oxygen species (ROS) and the biological basis of this response was investigated, using luminol-dependent zymosan-triggered chemiluminescence (CL). CL response of PEC from infected mice increased at the early stage but was significantly depressed at the later course of the infection. A similar biphasic activity of peroxidase was also observed in PEC from infected mice. On the other hand, PEC from immunized mice exhibited concomitant increases of the ability to produce CL, the activity of peroxidase and the expression of Fc and C3 receptors on cell surface. Compared with the controls, PEC from immunized mice showed an elevated background CL, responded more rapidly to the stimulation and generated considerably higher CL when triggered with opsonized zymosan. The data suggest that phagocytes in immunized mice are active in the production of ROS while those in infected mice are less active, and the inhibition of the ability of phagocytes to produce ROS may be one of the mechanisms for the parasites to escape from host immune system.

Therapeutic concentrations of theophylline and enprofylline potentiate catecholamine effects and inhibit leukocyte activation

Methylxanthines are primary agents used in treatment of hypersensitivity disease. Because polymorphonuclear leukocyte (PMN) activation is associated with generation of potent inflammatory mediators, xanthine effects on the PMN respiratory burst were studied. Enprofylline, a xanthine with important therapeutic potential, does not antagonize adenosine and was contrasted with theophylline. Although enprofylline was more potent at low concentrations, both drugs exhibited dose-dependent inhibition of PMN activation at concentrations greater than 10 mumol/L (1.8 micrograms/ml). Oxygen metabolite generation was decreased by 30% to 40% at therapeutic drug concentrations and by 85% at 1 mmol/L of theophylline. Inhibition by isoproterenol or prostaglandin E2 but not dibutyryl cAMP was potentiated by either xanthine. Isoproterenol effects were also increased when isoproterenol was evaluated in whole blood specimens obtained from subjects after a loading dose of aminophylline. Although these results were most compatible with cAMP phosphodiesterase inhibition, other commonly proposed mechanisms of methylxanthine activity were also studied. Theophylline but not enprofylline blocked adenosine inhibition of PMN activation. Neither xanthine shifted the calcium dose-response when PMNs were activated with calcium ionophore. Because oxygen metabolites generated by the FMN are mediators of inflammation and hypersensitivity, direct inhibition of PMN activation as well as potentiation of catecholamine activity may be important therapeutic effects of theophylline and enprofylline.

The chemiluminescence of rabbit alveolar macrophages induced by quartz dust particles

Quartz dust particles (respirable fraction) triggered luminol-dependent chemiluminescence (CL) when added to unstimulated rabbit alveolar macrophages (AM). It was shown by increasing the dust dose added to the same amount of cells, and conversely, that the intensity of chemiluminescent reaction depended on the ratio cells:dust particles. The ratio giving maximum CL yield was estimated.