The biphasic immunoregulation of pyrimidylpiperazine (Y-40138) is IL-10 sensitive and requires NF-κB targeting in the alveolar epithelium

1. Pyrimidylpiperazine (Y-40138), a synthetic derivative of N-[1-(4-{[4-(pyrimidin-2-yl)piperazin-1-yl]methyl}phenyl)cyclopropyl] acetamide, is a novel dual regulator of pro- and anti-inflammatory cytokines in vivo. The aim of the present study was to determine the signal transduction mechanisms implicated in vitro. 2. In alveolar epithelial cells, pre-treatment (30 min) with Y-40138 reduced LPS-induced biosynthesis of IL-1β, IL-6 and TNF-α, an effect paralleled by up-regulating an anti-inflammatory counter-loop mediated through IL-10. 3. This differential regulation of pro- and anti-inflammatory signals was accompanied by an inhibition of the nuclear localization of selective NF-κB subunits, particularly NF-κB₁ (p50), RelA (p65), the major transactivating member of the Rel family, RelB (p68) and c-Rel (p75). In addition, Y-40138 blockaded, in a dose-dependent manner, the LPS-induced nuclear activation of NF-κB. 4. Analysis of the upstream pathway involved in Y-40138-dependent retardation of LPS-induced NF-κB translocation/activation revealed the involvement of an IκB-α sensitive pathway. Pre-treatment with Y-40138 ameliorated LPS-induced degradation of IκB-α in the cytosolic compartment and retarded its phosphorylation, suggesting the involvement of an upstream kinase. 5. Recombinant IL-10 (0-10 ng ml^-1) blockaded, in a dose-dependent manner, LPS-induced biosynthesis of IL-1β, IL-6 and TNF-α. Furthermore, rhIL-10 reduced the DNA binding activity of NF-κB. Immunoneutralization of endogenous IL-10 by a polyclonal αIL-10 (5 μg ml^-1) reversed the inhibitory effect of Y-40138 on pro-inflammatory cytokines and partially restored the DNA binding activity of NF-κB. 6. These results indicate that Y-40138 mediated dual immunoregulation of pro- and anti-inflammatory cytokines is IL-10 sensitive and mediated through the IκB-α/NF-κB signal transduction pathway.