Inhibition of human platelet and neutrophil function by piriprost (U-60,257)

Co-purification of 130 kD nitric oxide synthase and a 22 kD link protein from human neutrophils

The synthesis of nitric oxide (NO) from L-arginine has been demonstrated in several cell types. Both constitutive and inducible forms of NO synthase have been described in different cells. We purified the constitutive form of NO synthase enzyme in human neutrophils using a two-column procedure. Crude 100,000g supernatant of human neutrophils was passed through a 2'-5'-ADP-agarose column followed by a DEAE-Bio-Gel A anion exchange column. NO synthase enzyme migrated as a single band (MW approximately 130,000) on sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Its activity was dependent upon nicotinamide adenine dinucleotide phosphate (NADPH) and (6R)-tetrahydro-L-biopterin (BH4). In addition, flavin adenine dinucleotide (FAD) was also found to be essential for its maximal activity. A second NADPH, FAD-dependent component (MW approximately 22kD) was also found consistently on the SDS-PAGE gel. These observations suggest co-regulation between NO synthase enzyme and this NADPH, FAD-dependent component, which may be associated with the superoxide radical generating system.

Neutrophil function in ischemic heart disease

Neutrophils contribute to the healing of and scar formation in myocardium after ischemic injury. Many recent studies indicate that neutrophils may be involved in the genesis and propagation of myocardial ischemia. To characterize neutrophil function in ischemic heart disease, neutrophil chemotaxis, leukotriene B4 (LTB4) generation, and elastase release in plasma were measured in 20 patients with stable angina, 17 patients with unstable angina or acute myocardial infarction (AMI), and 20 age-matched control subjects. Neutrophils from patients with stable angina exhibited markedly increased chemotactic activity and LTB4 generation as compared with the age-matched control subjects (p less than 0.01). Neutrophils of nine of 17 patients with unstable angina or AMI clumped spontaneously ex vivo and exhibited marked pseudopod formation and granule extrusion on electron microscopy. Subsequent chemotactic activity and LTB4 generation by neutrophils from these patients was less than in patients with stable angina, suggesting previous in vivo activation. Plasma levels of peptide B beta, a product of fibrin degradation by human neutrophil elastase, were approximately 15-fold higher (p less than 0.001) in patients with unstable angina or AMI (588 +/- 171 pmol/l, mean +/- SEM) compared with those in patients with stable angina (37 +/- 25 pmol/l) or control subjects (40 +/- 22 pmol/l), confirming intense in vivo neutrophil activation. Our study shows enhanced neutrophil function in patients with ischemic heart disease. The increased neutrophil chemotactic activity and LTB4 generation may be markers of stable angina pectoris. Intense neutrophil activation in unstable angina or AMI, as manifested by morphologic changes in neutrophils and elastase release, may relate to ongoing in vivo cellular activation.

Enhancement of human neutrophil function by platelets: effects of indomethacin

To characterize the influence of presence of platelets on human neutrophil function, neutrophil oxidative burst, chemotaxis, leukotriene B4 and prostacyclin generation were examined in the presence of physiologic concentration of platelets (40: 1). Presence of platelets significantly (P less than or equal to 0.05) increased all these neutrophil functions. To determine if cyclooxygenase products are involved in platelet-neutrophil interaction, neutrophils (+/- platelets) were incubated with indomethacin. Although high concentrations of indomethacin (10 microM) inhibited neutrophil (no platelets) chemotaxis and leukotriene B4 generation, these inhibitory effects of indomethacin were attenuated in the presence of platelets. Thus presence of platelets enhances neutrophil activity and overcomes the inhibitory effects of indomethacin on neutrophils.