Title

 

Authors

D. Impellizzeri¹, E. Esposito^1,2, E. Mazzon², I. Paterniti¹, R. Di Paola¹, P. Bramanti², S. Cuzzocrea<sup>1,2

1</sup>Dept of Clinical and Experimental Medicine and Pharmacology, School of Medicine, University of Messina, Italy; ²IRCCS Centro Neurolesi "Bonino-Pulejo", Messina, Italy

 

Abstract

NADPH-oxidase is an enzyme responsible for reactive oxygen species (ROS) production, and inhibition of this enzyme represents an attractive therapeutic target for the treatment of many diseases. To counteract oxidative stress, the body produces an armory of antioxidants to defend itself, which in fact are sometimes insufficient to effectively defend the organism from ROS(Luchtefeld et al., 2008).There are a lot of substances that have been researched in order to find a way to inhibit production of ROS, and thus protect the body from diseases.Apocynin (4-hydroxy-3-methoxy-acetophenone) is a constituent of the Himalayan herb Picrorhiza kurrooa Royle (Scrophulariaceae) that is well known in traditional Indian medicine (Ayurveda). It is an acetophenone to which a range of biological activities is attributed(Hougee et al., 2006).The structure of NADPH-oxidase is quite complex, consisting of two membrane-bounded elements (gp91phox or Nox 2 andp22phox ), three cytosolic components (p67phox, p47phox and p40phox), and a low-molecular-weight G protein (eitherrac 2 or rac 1). The generation of superoxide anions by NADPH oxidase serves as a host defense mechanism against invading microorganism infection and the enzyme is present in phagocytic cells, such as monocytes and neutrophils (Dorman et al., 2006).Apocynin is an inhibitor of the intracellular translocation of two critical cytosolic components of the NADPH-oxidase complex present in the cell membrane (Peters et al., 2001).The in vitro anti-inflammatory effects include the neutrophil-mediated oxidative damage,a reduction of polymorphonuclear granulocyte chemotaxis and the inhibition of peroxynitrite. In this regard, a possible explanation for the effectiveness of apocynin in the treatment of respiratory diseases might be the fact that apocynin inhibits peroxynitrite (ONOO−) formation (Muijsers et al. 2000), that is suggested to induce epithelial damage, mediator release, and consequently hyperresponsiveness.The aim of this study was to investigate the effects of  apocynin, a NADPH-oxidase inhibitor, in a mouse model of carrageenan-induced pleurisy. Injection of carrageenan into the pleural cavity of mice elicited an acute inflammatory response characterized by: infiltration of PMNs in lung tissues and subsequent lipid peroxidation, increased production of tumor necrosis factor-α , (TNF-α ) and interleukin-1β (IL-1β ) and increased expression of  intercellular adhesion molecule (ICAM-1) and platelet-adhesion molecule (P-selectin). Furthermore, carrageenan induced the expression ofnuclear factor-κB (NF-κB), inducible nitric oxide synthase (iNOS), nitrotyrosine,poly-ADP-ribosyl polymerase (PARP) as well as induced apoptosis ( TUNEL staining  FAS-ligand, Bax and Bcl-2 expression) and mitogen-activated protein kinase (MAPK) activation in the lung tissues. Administration of  apocynin(5mg/kg 10% DMSO),30 min after the challenge with carrageenan, caused a significant reduction of all the parameters of inflammation measured. Thus, based on these findings we propose that NADPH oxidase inhibitor such as apocynin, may be useful in the treatment of various inflammatory diseases.