Table of Contents
ISRN Inflammation
Volume 2012, Article ID 260453, 7 pages
Research Article

The Importance of Myeloperoxidase in Apocynin-Mediated NADPH Oxidase Inhibition

1Departamento de Química, Faculdade de Ciências, Universidade Estadual Paulista UNESP, CEP 17033-360, Bauru, SP, Brazil
2Centro de Investigação em Pediatria (CIPED), Faculdade de Ciências Médicas, Universidade Estadual de Campinas, CEP 13083-887, Campinas, SP, Brazil
3Instituto de Ciências Biomédicas, Universidade de São Paulo, CEP 05508-000, São Paulo, SP, Brazil

Received 30 January 2012; Accepted 28 February 2012

Academic Editors: E. Kurutas and B. Ryffel

Copyright © 2012 Ana Carolina de Almeida et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Apocynin is widely used as an inhibitor of the NADPH oxidase. Since myeloperoxidase (MPO) has been considered as essential for the mechanism of action of apocynin, here we used cells with different levels of MPO and compared their sensitivity to apocynin. HL-60 cells were differentiated with DMSO or IFNγ/TNFα and compared with peripheral mononuclear (PBMC) and polymorphonuclear cells (PMN). The relative MPO activity was PBMC = HL60 DMSO < HL60 IFNγ < PMN. Apocynin inhibited the intracellular reactive oxygen species production by PMN (80%) and IFNγ/TNFα-differentiated HL-60 cells (45%) but showed a minor effect in PBMC and DMSO differentiated HL-60 cells (20%). The addition of azide decreased the efficiency of apocynin in PMN and the addition of peroxidase increased the inhibition in PBMC. We also determined the gene expression of the components gp91phox, p47phox, p22phox and p67phox in the resting cells. Apocynin did not change gp91phox, p47phox or p22phox gene expression in nonstimulated PBMC, HL60 DMSO, HL60 IFNγ/TNFα, and PMN and has a subtle increase in p67phox in HL60 IFNγ/TNFα. The results from this work suggest that a rational search for better inhibitors of NADPH oxidase in leukocytes should include a correlation with their affinity as substrates for MPO.