Modulation of macrophage inflammatory function through selective inhibition of the epigenetic reader protein SP140

Abstract

Background SP140 is a bromodomain-containing protein expressed predominantly in immune cells. Genetic polymorphisms and epigenetic modifications in the SP140 locus have been linked to Crohn’s disease (CD), suggesting a role in inflammation. Results We report the development of the first small molecule SP140 inhibitor (GSK761) and utilize this to elucidate SP140 function in macrophages. We show that SP140 is highly expressed in CD mucosal macrophages and in in vitro-generated inflammatory macrophages. SP140 inhibition through GSK761 reduced monocyte-to-inflammatory macrophage differentiation and lipopolysaccharide (LPS)-induced inflammatory activation, while inducing the generation of CD206+ regulatory macrophages that were shown to associate with a therapeutic response to anti-TNF in CD patients. SP140 preferentially occupies transcriptional start sites in inflammatory macrophages, with enrichment at gene loci encoding pro-inflammatory cytokines/chemokines and inflammatory pathways. GSK761 specifically reduces SP140 chromatin binding and thereby expression of SP140-regulated genes. GSK761 inhibits the expression of cytokines, including TNF, by CD14+ macrophages isolated from CD intestinal mucosa. Conclusions This study identifies SP140 as a druggable epigenetic therapeutic target for CD.

The Epigenetic Reader Protein SP140 Regulates Dendritic Cell Activation, Maturation and Tolerogenic Potential

“…It has been reported that SNPs in the SP140 locus have been strongly linked to diverse autoimmune and inflammatory diseases such as multiple sclerosis (MS) [11] and Crohn's disease (CD) [12]. In addition, our previous study demonstrated upregulated expression of SP140 in a range of inflammatory diseases such as CD, rheumatoid arthritis (RA), and systemic lupus erythematosus [10], implicating SP140 in immune-mediated pathogenesis. SP140 is an epigenetic reader protein harboring a bromodomain (Brd) [12,13]; Brd recognizes acetylated lysine residues on histone tails and regulates gene expression through mechanisms that modulate DNA accessibility to transcription factors (TFs) and the transcriptional machinery [14,15].…”

“…Speckled 140 KDa (SP140) is a nuclear body protein predominantly expressed in immune cells [9,10]. The expression of SP140 is induced during microbial infections and in response to inflammatory stimuli [9,10].…”

“…Speckled 140 KDa (SP140) is a nuclear body protein predominantly expressed in immune cells [9,10]. The expression of SP140 is induced during microbial infections and in response to inflammatory stimuli [9,10]. It has been reported that SNPs in the SP140 locus have been strongly linked to diverse autoimmune and inflammatory diseases such as multiple sclerosis (MS) [11] and Crohn's disease (CD) [12].…”

Immunoepigenetic Regulation of Inflammatory Bowel Disease: Current Insights into Novel Epigenetic Modulations of the Systemic Immune Response

“…The differential methylation of the speckled 140 kDa protein (SP140) observed in the peripheral blood mononuclear cells of patients with CD, as well as the fact that reduced SP140 expression in intestinal biopsies correlates with a good anti-TNF response, suggests a role for SP140 in IBD [ 52 ]. SP140 functions as an epigenetic reader, the inhibition of which can prevent the generation of inflammatory macrophages as well as the regulation of proinflammatory and CD-related gene expression [ 52 , 53 ]. Homologous to the speckled-protein family, the autoimmune regulator AIRE is a master regulator of central tolerance, which links transcription factors and epigenetic machinery by driving the expression of tissue-specific T-cell antigens.…”

CD4-mediated immunity shapes neutrophil-driven tuberculous pathology

“…14 Furthermore, C3HeB/FeJ mice do develop necrotizing granulomas, especially when infected with hypervirulent Mtb strains of the W-Beijing lineage. 15 A single gene that confers the extreme susceptibility and necrotic lesions of C3HeB/FeJ mice has been identified as Sp140 , an epigenetic regulator with chromatin-binding domains that can influence inflammatory gene transcription, 16 and Sp140 -/- mice on a C57BL/6 background exhibit similar TB susceptibility and pathology phenotypes as C3HeB/FeJ mice. 17 Use of these mouse models has led to the identification of critical signaling pathways that regulate Mtb infection outcomes, including type I IFN vs IL-1, as well as insights into the temporal processes driving inflammation and disease: neutrophil recruitment, cellular death, pDC sensing, and IFN production/signaling.…”