Compensatory Expression of Nur77 and Nurr1 Regulates NF-κB–Dependent Inflammatory Signaling in Astrocytes

Abstract

Inflammatory activation of glial cells promotes loss of dopaminergic neurons in Parkinson disease. The transcription factor nuclear factor κB (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 NF-κB, but no approved drugs target these receptors. Therefore, we postulated that a recently developed NR4A receptor ligand, 1,1bis (3′indolyl) 1(pmethoxyphenyl) methane (C-DIM5), would suppress NF-κB-dependent inflammatory gene expression in astrocytes after treatment with 1-methyl-4-phenyl 1, 2, 3, 6-tetrahydropyridine (MPTP) and the inflammatory cytokines interferon γ and tumor necrosis factor α. C-DIM5 increased expression of Nur77 mRNA and suppressed expression of multiple neuroinflammatory genes. C-DIM5 also inhibited the expression of NFκB-regulated inflammatory and apoptotic genes in quantitative polymerase chain reaction array studies and effected p65 binding to unique genes in chromatin immunoprecipitation next-generation sequencing 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 the 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.

Alpha-Synuclein Pathology and the Role of the Microbiota in Parkinson’s Disease

“…The observation that exposure to LPS causes alpha-synuclein to adopt a fibrillar form and the specific patterns of alpha-synucleinopathies seen in mice exposed to this form of alpha-synuclein suggests that bacterial exposure may be a driving force in alpha-synucleinopathies. LPS has also been shown to induce expression of chemokines (Leow-Dyke et al, 2012; Honda and Littman, 2016; Popichak et al, 2018; Lee et al, 2019). Recent studies looking at the mechanisms underlying this interaction have identified an important role of the activation of TLR-4 causing the release of chemokines CCL5/RANTES and CXCL1 as well as TNF-alpha and IL-6 (Leow-Dyke et al, 2012; Perez-Pardo et al, 2018b; Figure 1).…”

Nur77 attenuates inflammatory responses and oxidative stress by inhibiting phosphorylated IκB-α in Parkinson’s disease cell model

“…Limited information is available regarding the role of Nur77 in PD. The recent studies demonstrated that Nur77 was involved in neurodegeneration [16,17]. Abnormalities of Nur77 may induce dopaminergic imbalances in the brain [18].…”

The orphan nuclear receptor Nr4a1 mediates perinatal neuroinflammation in a murine model of preterm labor

“…Within the adult innate immune system and with metabolic disease, Nr4a1 plays an anti-inflammatory role 58,59 . The mechanisms by which Nr4a1 reduces inflammation have been noted to involve p38, NF-kB, and ISG12 depending on the context of disease, biological modeling, and analyses 19,60,61 . In-depth molecular examination suggests p38 counters Nr4a1 in suppressing NF-kB pro-inflammatory signaling 19 .…”