Abstract

Inflammatory activation of glial cells promotes loss of dopaminergic neurons in Parkinson's disease (PD). The transcription factor, Nuclear Factor-kappa B (NF-κB), regulates the expression of multiple neuroinflammatory cytokines and chemokines in activated glial cells that are damaging to neurons. Thus, inhibition of NF-κB signaling in glial cells could be a promising therapeutic strategy for the prevention of neuroinflammatory injury. Nuclear orphan receptors in the NR4A family, including NR4A1 (Nur77) and NR4A2 (Nurr1), can inhibit the inflammatory effects of NFκB but there are no approved drugs that target these receptors. Therefore, we postulated that a novel NR4A receptor ligand, 1,1-bis (3'-indolyl) -1-(p-methoxyphenyl) methane (C-DIM5), would suppress NF-κB-dependent inflammatory gene expression in astrocytes following treatment with 1-methyl-4-phenyl-1, 2, 3, 6-tetrahydropyridine (MPTP) and the inflammatory cytokines, IFN-γ and TNF-α. C-DIM5 increased expression of Nur77 mRNA and suppressed expression of multiple neuroinflammatory genes. C-DIM5 also inhibited the expression of NF-κB-regulated inflammatory and apoptotic genes in qPCR array studies and effected p65 binding to unique genes in ChIP-seq experiments but did not prevent p65 translocation to the nucleus, suggesting a nuclear-specific mechanism. C-DIM5 prevented nuclear export of Nur77 in astrocytes induced by MPTP treatment and simultaneously recruited Nurr1 to the nucleus, consistent with known transrepressive properties of this receptor. Combined RNAi knockdown of Nur77 and Nurr1 inhibited anti-inflammatory activity of C-DIM5, demonstrating that C-DIM5 requires these receptors to inhibit NF-κB. Collectively; these data demonstrate that NR4A1/Nur77 and NR4A2/Nurr1 dynamically regulated inflammatory gene expression in glia by modulating the transcriptional activity of NF-κB.