Short-term anti-inflammatory effects of 5,5-dimethyl-1-pyrroline N-oxide (DMPO)

ENRIZ D; RAMIREZ, DC; MUNOZ M; GUTIERREZ L; ALVAREZ SE; GOMEZ MEJIBA, S

Congreso; SAIC 2016; 2016

5,5-dimethyl-1-pirroline N-oxide (DMPO) is a nitrone spin trap originally synthesized as a nitrone spin trap to study free radicals by electron spin resonance spectroscopy and recently by immuno-spin trapping. Herein we envisioned at studying what are the mechanisms involved in these anti-inflammatory effects of this old drug with new properties. To accomplish this goal we used a well known model of macrophage-like cells (RAW264.6) primed with LPS; which induce a well known MAPK signaling cascade that ends in activation of NF-kB?the master regulator of inflammation, inducible nitric oxide (iNOS) expression and nitric oxide synthesis. DMPO blocked NO synthesis, iNOS induction and MAPK signaling; but it did not affect LPS binding to LPS to membrane receptors. Thus we hypothesized that DMPO, and likewise other nitrones, may somehow affect very early LPS triggered signaling downstream of LPS-receptor binding. In silico data showed that DMPO binds to a very narrow sequence of aminoacids inside the TIR domain of TLR-2. TIR domains are conserved throughout TLRs (TLR-4; 6; 10) and species, particularly in a region called BB-loop which is responsible for downstream signal transduction. Molecular dynamics data shows that DMPO binds almost exclusively to these residues located at the BB-loop. Taking together, our data indicate that DMPO anti-inflammatory effect, is at least in part due to its binding to specific residues in the cytoplasmic portion of TLRs, thus further signaling is damped. Supported by PROICO 2-3214 & PICT-2014-3369 (to DCR), PROICO 10-0414 (To SEGM) and PIP2015-2017-112215-0100603CO (To DCR, SEA & SEGM).