Influence of nifedipine on plasma membrane fluidity and oxidative burst of polymorphonuclear leucocytes.

It has been demonstrated that the calcium antagonist nifedipine inhibits the reactive oxygen species (ROS) production by polymorphonuclear leucocytes (PMNLs) activated with phorbol myristate acetate (PMA), but the mechanism underlying this effect is still unknown. In the present study we investigated the influence of nifedipine on the PMNL plasma membrane using 1-(4-trimethylaminophenyl)-6-phenyl-1,3,5,hexatriene (TMA-DPH) fluorescence polarization (P) and on PMA- and N-formyl-methionyl-leucyl-phenylalanine (FMLP)-induced ROS production, measured by luminol-dependent chemiluminescence (CL). The plasma membrane fluidity of untreated PMNLs, expressed as P, was 0.371 +/- 0.008. After preincubation of 15 min, nifedipine induced a significant change in P values only at a concentration of 10(-4) M (P = 0.00018). After preincubation of 60 min significant changes in P values were also observed at concentrations of 10(-6) M (P = 0.023) and 10(-7) M (P = 0.023). PMA-induced ROS production by PMNLs was markedly inhibited by nifedipine. Nifedipine also determined a striking change in the FMLP-induced CL response, characterized by both an overall inhibition of PMNL activity and a modification of the kinetics of the oxidative burst (rapid increase in ROS production followed by a pronounced drop in the PMNL response). Such a pattern was found at concentrations of 10(-4) M (preincubation time: 15 min), 10(-6) M and 10(-7) M (preincubation time: 60 min). These findings indicate that nifedipine directly interacts with the PMNLs by inducing a marked decrease in plasma membrane fluidity and an inhibition of the oxidative burst.

Polymorphonuclear leukocytes activation: in vitro modulation by 6-methoxy-2-naphthylacetic acid, the major active metabolite of nabumetone.

Reported here are the results of a study carried out in order to assess the possible influence of the major circulating active metabolite of nabumetone, 6-methoxy-2-naphthylacetic acid, on some aspects of polymorphonuclear leukocytes activation. The action of 6-methoxy-2-naphthylacetic acid was tested on the following features of polymorphonuclear leukocytes activation: reactive oxygen species production in polymorphonuclear leukocytes stimulated with different agonists, reactive oxygen species production in polymorphonuclear leukocytes treated with pertussis toxin, NADPH-oxidase activity. The findings showed that 6-methoxy-2-naphthylacetic acid decreased reactive oxygen species production in polymorphonuclear leukocytes stimulated with N-formyl-methionyl-leucyl-phenylalanine, phorbol myristate acetate, and opsonized zymosan, but failed to provoke a decrease of reactive oxygen species production when the cells were stimulated with calcium ionophore A23187. Moreover, 6-methoxy-2-naphthylacetic acid did not influence the transduction of the signal following the binding of stimuli to membrane receptors, and NADPH-oxidase activity. Finally, our findings showed that 6-methoxy-2-naphthyl acetic acid had no scavenger effect on reactive oxygen species production.

Influence of dichloromethylene diphosphonate on reactive oxygen species production by human neutrophils.

Biphosphonates suppress bone destruction in various diseases. Several studies have demonstrated the potential use of biphosphonate in arthritis. The results of these studies indicate that the effectiveness of the biphosphonates, for inhibiting the arthritic process, is related to their antiresorptive properties. It has been shown that the generation of reactive oxygen species is associated with the formation of new osteoclasts and enhanced bone resorption. We studied the effects of the dichloromethylene diphosphonate on the reactive oxygen species production by activated polymorphonuclear leucocytes, measured by chemiluminescence. Our results indicate a dose-dependent inhibitory effect of dichloromethylene diphosphonate on reactive oxygen species production by polymorphonuclear leucocytes stimulated with N-formil-methionyl-leucyl-phenylalanine, the calcium ionophore A23187 and phorbol myristate acetate. The mechanisms by which this biphosphonate inhibits the reactive oxygen species production by activated polymorphonuclear leucocytes are discussed.

Platelet release products modulate some aspects of polymorphonuclear leukocyte activation.

The aim of this research was to evaluate in vitro interactions between platelets and polymorphonuclear leukocytes. The effects of supernatant from thrombin-activated platelets and two platelet release products (adenosine triphosphate and beta-thromboglobulin) were tested on the following features of polymorphonuclear leukocytes activation: opsonized zymosan and phorbol myristate acetate stimulated chemiluminescence, release of membrane bound calcium, NADPH-oxidase activity, and membrane fluidity (fluorescent polarization). The results showed that the addition of platelet supernatant to polymorphonuclear leukocytes induces a significant activation of cells. On the other hand, after three hours of preincubation of polymorphonuclear leukocytes with platelet supernatant, a decreased response of polymorphonuclear leukocytes to stimulation with phorbol myristate acetate, a significant decrease in NADPH-oxidase activity, and a lowered membrane fluidity were observed. Adenosine triphosphate modulated only opsonized zymosan stimulated chemiluminescence, with and without preincubation with polymorphonuclear leukocytes. Beta-thromboglobulin caused a decrease of the chemiluminescent response of polymorphonuclear leukocytes, using both agonists, with and without preincubation with polymorphonuclear leukocytes. Moreover beta-thromboglobulin only caused a decrease of the polymorphonuclear leukocytes membrane fluidity without preincubation with the cells. These results support the thesis that platelets have a "time-related" modulating activity on polymorphonuclear leukocytes.

Beta-thromboglobulin and polymorphonuclear leukocytes activation. (Effects on chemiluminescence, release of membrane bound calcium, NADPH-oxidase activity and membrane fluidity).

The aim of this paper was to evaluate the "in vitro" interaction between beta-thromboglobulin, one specific platelet release product and polymorphonuclear leukocytes. The effects of beta-thromboglobulin were tested on the following features of polymorphonuclear leukocytes activation: opsonized zymosan and phorbol myristate acetate stimulated chemiluminescence, release of membrane bound calcium, NADPH-oxidase activity, and membrane fluidity. Beta-thromboglobulin caused a decrease of the chemiluminescent response of polymorphonuclear leukocytes, using both agonists, with and without preincubation with polymorphonuclear leukocytes. We observed that beta-thromboglobulin caused a decrease also in the activity of NADPH-oxidase but not in the release of membrane bound calcium. Moreover beta-thromboglobulin caused a decrease of the polymorphonuclear leukocytes membrane fluidity. Our results suggest that the beta-thromboglobulin could play a role in the reciprocal interactions between platelets and polymorphonuclear leukocytes.