Platelet release products modulate some aspects of polymorphonuclear leukocyte activation

Neutrophil-platelet interactions and their relevance to bovine respiratory disease

Respiratory disease is a serious and significant health problem for the bovine industry. Classically, the clinical and research focus has been on the putative causative agents and conditions, and their interactions with host inflammatory cells, particularly alveolar macrophages and blood neutrophils. There is, currently, growing acceptance of the concept that blood platelets play a primary role in the inflammatory process. This review explores the implications of such pro-inflammatory activity, especially in the context of neutrophil-platelet interactions, and the species specificity of cellular responses. The relevance of these issues for the treatment and prevention of bovine respiratory disease is also discussed.

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.

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.