The Nitrone Spin Trap DMPO Prevents Lipopolysaccharide-Induced Pro-Inflammatory Programming Of Macrophages.

DARIO C RAMIREZ; MEDAWAR AGUILAR V; MUÑOZ, M.D.; GOMEZ MEJIBA, SANDRA;

GEORGIA

Congreso; Free radical biology and medicine.; 2020

Pro -inflammatory M1 macrophages play an important role in tissue damage during chronic inflammatory processes. Lipopolysaccharide (LPS)-triggered toll-like receptor (TLR) signaling and downstream nuclear factor (NF)- κ B activation lead to an M1 macrophage phenotype. During this signaling the nitrone spin trap 5,5-dimethyl-1- pyrroline N-oxide (DMPO) can trap protein-centered radicals thus dampening LPS -induced macrophage priming, but the mechanism remains unknown. Herein we used an in vitro and an in-silico model to test the mechanism by which DMPO dampens LPS -induced phenotypic switch of macrophages towards an inflammatory phenotype. Our data indicates that DMPO binds tightly to four specific residues within the BB loop in the TLR2-TIR domain. For the in silico analyses we used the mouse TLR2-TIR domain because the mouse TLR4-TIR domain has not been crystalized yet. However, they share sequence, structural and functional homologies. Our functional analysis showed that DMPO can block zymosan-activated TLR2-mediated NF-kB activation using HEK cells expressing hTLR2.6. However, DMPO did not affect the overall TLR2-MyD88 protein-protein interaction. DMPO binds to the BB loop within the TIR domain and dampens downstream signaling without affecting the overall TIR-MyD88 interaction. By binding to the BB-loop DMPO blocks TLR-downstream signaling thus preventing LPS-ind uced M1-phenotypic switch of macrophages. DMPO can serve as a structural platform for the design of novel mechanism-based anti-inflammatory drugs to prevent inflammatory activation of macrophages in chronic inflammatory diseases. Supported by: PICT-2018-3435/ PIP916 / PROICO100218 and 023418 / PUE-013 IMIBIO-SL