BAFF as a novel SASP factor and regulator of senescent traits

National Institute On Aging

Investigators

Abstract

ONGOING WORK AIM 1. BAFF regulation in senescence. We confirmed that the cytokine BAFF (Steri M et al., 2017) is elevated in multiple models of senescence. Due to its high expression in myeloid cell lines, we focused on BAFF production in THP-1 (human monocytic) cells for molecular analysis. We found that BAFF is transcriptionally induced in senescent THP-1 cells with enhanced levels of BAFF pre-mRNA. We used ECRbase (https://ecrbase.dcode.org) to identify transcription factors potentially driving BAFF transcription and found that BAFF promoter harbors several binding sites for members of the Interferon Regulated Factor (IRF) transcription factor family (Sjstrand M et al., 2016). Moreover, IRF1 silencing strongly reduced BAFF pre-mRNA and BAFF protein levels in IR-induced senescence, suggesting that BAFF is transcriptionally regulated by IRF1 in senescent cells as a part of the Interferon Type I response. AIM 2. To study BAFF signaling pathways in senescence including SASP. In order to analyze the impact of BAFF on senescence, we silenced BAFF in THP-1 cells and then implemented IR-induced senescence. We observed that BAFF silencing decreased SA-betaGal activity. Interestingly, silencing BAFF decreased SASP factors including the pro-inflammatory cytokines IL-8, IL-6, IL-1/, and TNF and the anti-inflammatory cytokine IL-10. These findings prompted us to analyze NF-B pathway, a major regulator of the inflammatory responses. We observed that BAFF silencing decreased the levels of p50 and p52, representing the canonical and non-canonical NF-B pathways, respectively. Accordingly, the level of several transcripts encoding cytokines and chemokines also decreased. These findings suggest that BAFF may act as an upstream regulator of the SASP, at least in part by acting through the NF-B pathway. FUTURE PLANS 1. In-depth analysis of BAFF functions in senescence. 2. Neutralization of BAFF using Belimumab (Blair et al, 2018) in senescence and evaluation of SASP levels. 3. Quantification of circulating BAFF in human serum as a function of age in GESTALT samples.