Apocynin is a selective NADPH-oxidase inhibitor with IC50 value of 10 μM [1].

Apocynin is an intracellular inhibitor of the assembly of NADPH oxidase, concomitantly inhibiting reactive oxygen species (ROS) production, which contributes to various anti-inflammatory effects [1, 2].

In human neutrophils stimulated by serum-treated zymosan (STZ), Apocynin completely inhibited oxygen uptake at the concentration of 300 μM. Inhibition of the STZ-induced respiratory burst by Apocynin was also observed in human eosinophils, but not in human alveolar macrophages [2].

In a mouse model of carrageenan-induced pleurisy, intraperitoneal injection of Apocynin at the dose of 5 mg/kg reduced lung injury and neutrophil infiltration. Apocynin also significantly reduced NADPH oxidase activity in lung tissues [3]. In a mouse model of spinal cord injury, treatment with Apocynin (5 mg/kg, i.p.) 1 and 6 h after the trauma significantly decreased the degree of spinal cord inflammation and tissue injury. Moreover, Apocynin substantially ameliorated the loss of limb function [4].

References:

[1]. Stefanska J, Pawliczak R. Apocynin: molecular aptitudes. Mediators of Inflammation, 2008, 2008: 106507.

[2]. Stolk J, Hiltermann T J, Dijkman J H, et al. Characteristics of the inhibition of NADPH oxidase activation in neutrophils by apocynin, a methoxy-substituted catechol. American Journal of Respiratory Cell and Molecular Biology, 1994, 11(1): 95-102.

[3]. Impellizzeri D, Esposito E, Mazzon E, et al. Effect of apocynin, a NADPH oxidase inhibitor, on acute lung inflammation. Biochemical Pharmacology, 2011, 81(5): 636-648.

[4]. Impellizzeri D, Mazzon E, Esposito E, et al. Effect of Apocynin, an inhibitor of NADPH oxidase, in the inflammatory process induced by an experimental model of spinal cord injury. Free Radical Research, 2011, 45(2): 221-236.