Study of Possible Mechanisms Involved in the Inhibitory Effects of Coumarin Derivatives on Neutrophil Activity

Katarína Drábiková,Juraj Harmatha,Jan Šmidrkal,Radomír Nosál’,Tomáš Perečko,Viera Jančinová

doi:10.1155/2013/136570

Abstract

To specify the site of action of the synthetic coumarin derivatives 7-hydroxy-3-(4′-hydroxyphenyl) coumarin (HHC) and 7-hydroxy-3-(4′-hydroxyphenyl) dihydrocoumarin (HHDC), we evaluated their effects on extra- and intracellular reactive oxygen species (ROS) formation in phorbol-myristate-13-acetate (PMA) stimulated human neutrophils. We studied also the effects of HHC and HHDC on possible molecular mechanisms which participate in the activation of NADPH oxidase, that is, on PKC activity, on phosphorylation of some PKC isoforms (α, βII, and δ), and on phosphorylation of the NADPH oxidase subunit p40phox. Without affecting cytotoxicity, both coumarines tested were effective inhibitors/scavengers of ROS produced by neutrophils on extracellular level. HHC markedly diminished oxidant production and also, intracellularly, decreased PKC activity and partly phosphorylation of PKCα, βII. On the other hand, we did not observe any effect of coumarin derivatives on phosphorylation of PKCδ and on phosphorylation of the NADPH oxidase subunit p40phox, which were suggested to be involved in the PMA-dependent intracellular activation process. In agreement with our previous findings, we assume that the different molecular structures of HHC and HHDC with their different physicochemical and free radical scavenging characteristics are responsible for their diverse effects on the parameters tested.

Highlights

Neutrophils are key cells of the first line of defense, but they are considered potent inflammatory cells causing tissue damage
The results indicate that treatment with increasing concentrations of HHC and HHDC did not cause neutrophil damage
We indicated that the ability of HHC and HHDC to reduce oxidant production in neutrophils might be connected with inhibition of NADPH oxidase activity, via decrease of Protein kinase C (PKC) activation [23]

Summary

Introduction

Neutrophils are key cells of the first line of defense, but they are considered potent inflammatory cells causing tissue damage. Production of reactive oxygen species (ROS) in neutrophils and other phagocytic cells is linked to the activation of NADPH oxidase, a multiprotein enzyme complex, which plays an essential role in innate immunity. Excessive ROS generation by phagocytes is involved in tissue injury associated with a number of chronic inflammatory diseases [5,6,7]. The cytosolic components (p40phox, p47phox, p67phox, and Rac2) migrate to the membranes, where they associate with the membranebound component (flavocytochrome b558) to assemble the catalytically active NADPH oxidase, resulting in the delivery of ROS into the extracellular environment or inside into the Oxidative Medicine and Cellular Longevity phagocytic vesicle [8,9,10]. Localisation of neutrophil ROS production and its possible regulation play an important role in the development of effective treatments to control the damage associated with chronic inflammation [8, 14]

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Conclusion