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Negative feedback by NUR77/Nr4a1 restrains B cell clonal dominance during early T-dependent immune responses.

ABSTRACT: B cell clones compete for entry into and dominance within germinal centers (GCs), where the highest-affinity B cell receptors (BCRs) are selected. However, diverse and low-affinity B cells can enter and reside in GCs for extended periods. To reconcile these observations, we hypothesize that a negative feedback loop may operate within B cells to preferentially restrain high-affinity clones from monopolizing the early GC niche. Here, we report a role for the nuclear receptor NUR77/Nr4a1 in this process. We show that NUR77 expression scales with antigen stimulation and restrains B cell expansion. Although NUR77 is dispensable for regulating GC size when GCs are elicited in a largely clonal manner, it serves to curb immunodominance under conditions where diverse clonal populations must compete for a constrained niche. We propose that this is important to preserve early clonal diversity in order to limit holes in the post-immune repertoire and to optimize GC selection.

SUBMITTER: Brooks JF

PROVIDER: S-EPMC8564879 | biostudies-literature | 2021 Aug

REPOSITORIES: biostudies-literature

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Negative feedback by NUR77/Nr4a1 restrains B cell clonal dominance during early T-dependent immune responses.

Brooks Jeremy F JF Tan Corey C Mueller James L JL Hibiya Kenta K Hiwa Ryosuke R Vykunta Vivasvan V Zikherman Julie J

Cell reports 20210801 9

B cell clones compete for entry into and dominance within germinal centers (GCs), where the highest-affinity B cell receptors (BCRs) are selected. However, diverse and low-affinity B cells can enter and reside in GCs for extended periods. To reconcile these observations, we hypothesize that a negative feedback loop may operate within B cells to preferentially restrain high-affinity clones from monopolizing the early GC niche. Here, we report a role for the nuclear receptor NUR77/Nr4a1 in this pr ...[more]

PMID: 34469720

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Project description:Osteoarthritis (OA) is the most prevalent joint disease and uncontrolled inflammation is now recognized to play vital roles in OA development. Targeting the endogenous counterpart of inflammation may develop new therapeutic approaches in resolving inflammation persistence and treating inflammatory disease including OA. The orphan nuclear receptor 4A1 (NR4A1) is a key negative regulator of inflammatory responses but its role in osteoarthritis remains unclear. In the present study, we found that the NR4A1 expression was elevated in human osteoarthritis cartilage and in vitro OA model, which could be blocked by NF-κB signal inhibitor JSH23. The overexpression of NR4A1 inhibited, whereas knockdown of NR4A1 enhanced IL-1β induced COX-2, iNOS, MMP3, MMP9 and MMP13 expression, and luciferase reporter activity of NF-κB response element. Though NR4A1 was upregulated in inflammatory stimulation and creates a negative feedback loop, persistent inflammatory stimulation inhibited NR4A1 expression and activation. The expression of NR4A1 declined rapidly after an initial peak in conditions of chronic IL-1β stimulation, which could be partially restored by HDACs inhibitor SAHA. The phosphorylation of NR4A1 was increased in human osteoarthritis cartilage, and p38 inhibitor SB203580, JNK inhibitor SP600125 and ERK inhibitor FR180204 could significantly inhibited IL-1β induced NR4A1 phosphorylation. Reactivation of NR4A1 by its agonist cytosporone B could inhibit IL-1β induced chondrocyte inflammation and expression of COX-2, iNOS, MMP3, MMP9, and MMP13. In rat OA model, intra-articular injection of cytosporone B protected cartilage damage and ameliorated osteoarthritis. Thus, our study demonstrated that the NR4A1 is a key endogenous inhibitor of chondrocyte inflammation, which was relatively inactivated under chronic inflammatory stimulation through HDACs mediated transcriptional suppression and MAKP dependent phosphorylation in osteoarthritis. NR4A1 agonist cytosporone B could reactivate and restore the inhibitory regulatory ability of NR4A1, prevent excessive inflammation, and ameliorates osteoarthritis.

Dataset Information

Negative feedback by NUR77/Nr4a1 restrains B cell clonal dominance during early T-dependent immune responses.

Publications

Negative feedback by NUR77/Nr4a1 restrains B cell clonal dominance during early T-dependent immune responses.

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