HOCl scavenging structures in libraries of nitrones and diterpenes

VERNI, E. R.; COSTA, P.; THOMSON, L.; GOMEZ-MEJIBA, S.; SIMIRGIOTIS, M.; RAMIREZ, D.

Ciudad de Mar del Plata

Congreso; LXI REUNION CIENTIFICA ANUAL DE LA SOCIEDAD ARGENTINA DE INVESTIGACIÓN CLÍNICA (SAIC); 2016

Sociedad Argentina de Investigacion Clinica

Neutrophilic inflammation results from activation of neutrophils at sites of chronic or acute inflammation. Activated neutrophils release myeloperoxidase (MPO), the unique enzyme that uses H2O2 to oxidize chloride anions to the powerful oxidant HOCl. HOCl damaged proteins are seen and involved in a number of inflammatory diseases. Thus the search for inhibitors of MPO and/or scavengers of HOCl is of vital importance for the treatment of neutrophilic inflammation. The aim of this work is the search for highly characterized synthetic or natural structures that react with HClO/ClO- (hypochlorous acid/hypochlorite, Ka = 7.58). We searched HOCl scavenging activity in 55 synthetic and natural compounds: 47 nitrones and 8 natural diterpenes. For this purpose, we used a screening assay to evaluate the ability to reduce luminescence caused by reaction of HClO with luminol. The variables were optimized and the method was developed for a concentration of 10 µM luminol and 50 µM HClO. Compound dilutions were prepared (0, 0.1, 1, 5, 10 and 25 µM, corresponding "0" to a HClO solution only) and then HClO and luminol solutions were added. Results showed that from the 8 diterpenes compounds, only one lessened the signal below 1 µM concentration. The rest of them probed to have this activity just above that value. Whereas, nitrones showed interesting properties: 13 showed inhibitory activity in the range of 5-10 µM, 28 compounds in 1-5 µM, 4 compounds between 0.1 and 1 µM, and finally two nitrones showed an interesting activity below 100 nM. Scavenging HOCl at sites of neutrophilic inflammation may be an interesting bioactivity for finding new leader structures in drug discovery. Further studies aimed at determining toxicity, cell permeability, mechanism of action and in vivo activity are guaranteed for leading compounds.