Activation of human neutrophil protein kinase C in vitro by 1,2-isopropylidene-3-decanoyl-sn-glycerol (IpOCOC9)

Human basophil histamine release is differently affected by inhibitors of calmodulin, diacylglycerol kinase and peptidyl prolyl cis-trans isomerase in a secretagogue specific manner

To assess the role of calmodulin in human basophil histamine release, we triggered leukocytes with different secretagogues in the presence of putative inhibitors of calmodulin. Calcium ionophore-induced histamine release was reduced or blocked by calmidazolium, CGS 9343B, felodipine, metofenazate, and Ro 22-4839. H 186/86, a felodipine-related dihydropyridine derivative, blocked A23187-but not ionomycin-triggered histamine release, suggesting a difference in the mode of action of these ionophores. In contrast, leukocyte histamine release triggered by the purported protein kinase C (PKC) activator, 1,2-isopropylidene-3-decanoyl-sn-glycerol (IpOCOC9), was enhanced by calmidazolium, CGS 9349B and metofenazate but not affected by felodipine or Ro 22-4839, whereas the response triggered by 4 beta-phorbol 12-myristate 13-acetate (PMA) was reduced by metofenazate and Ro 22-4839 but not consistently affected by calmidazolium, CGS 9343B or felodipine. The PMA-induced histamine release was enhanced by H 186/86. Anti-IgE- and FMLP-induced responses were either unaffected or slightly enhanced by the examined calmodulin antagonists. In comparison with the calmodulin antagonists, R 59022, an inhibitor of diacylglycerol kinase, failed to reduce calcium ionophore-triggered histamine release, whereas FK506, an inhibitor of peptidyl prolyl cis-trans isomerase (PPI), reduced both anti-IgE- and ionophore-triggered responses. These results indicate that calmodulin constitutes an obligate link in signal transduction pathways leading to human leukocyte histamine release if the trigger is a calcium ionophore but not when responses are induced by anti-IgE, FMLP or PMA; a calmodulin-dependent component may rather balance responses induced by IpOCOC9.(ABSTRACT TRUNCATED AT 250 WORDS)

The generation of reactive oxygen-derived species by phagocytes

The generation of reactive oxygen-derived species is one main constituent of the microbicidal activity of professional phagocytes. This process is known as the respiratory or the oxidative burst. It is initiated by a cyanide- and azide-insensitive increase in O2-consumption and the concomitant generation of superoxide radicals catalyzed by a membrane-localized NADPH oxidase which is triggered by an appropriate stimulation of the cells. The generated O2 is converted to hydrogen peroxide, hydroxyl radicals and other reactive products of oxygen which, if released extracellularly (for example in connection with frustrated phagocytosis), are potentially harmful to the tissue. The oxidative burst is not necessarily dependent on phagocytosis, nor is it necessarily associated with degranulation. Therefore, the process constitutes an important independent variable of phagocyte activity, and researches aiming to characterize various forms of airway inflammation may derive valuable information from an examination of the oxidative burst.