C/EBPδ-induced epigenetic changes control the dynamic gene transcription of S100A8 and S100A9

The proinflammatory alarmins S100A8 and S100A9 are among the most abundant proteins in neutrophils and monocytes but completely silenced after differentiation to macrophages. The molecular mechanisms of the extraordinarily dynamic transcriptional regulation of s100a8 and s100a9 genes, however, are only barely understood. Using an unbiased genome-wide CRISPR/Cas9 knockout based screening approach in immortalized murine monocytes we identified the transcription factor C/EBPδ as a central regulator of S100A8 and S100A9 expression. S100a8 and S100a9 expression was further controlled by the C/EBPδ-antagonists ATF3 and FBXW7. We confirmed the clinical relevance of this regulatory network in subpopulations of human monocytes in a clinical cohort of cardiovascular patients. Moreover, we identified specific C/EBPδ-binding sites within s100a8 and s100a9 promoter regions, and demonstrated that C/EBPδ-dependent JMJD3-mediated demethylation of H3K27me3 is indispensable for their expression. Overall, our work uncovered C/EBPδ as a novel regulator of S100A8 and S100A9 expression. Therefore, C/EBPδ represents a promising target for modulation of inflammatory conditions that are characterised by S100A8 and S100A9 overexpression.

Gilteritinib-induced upregulation of S100A9 is mediated through BCL6 in Acute Myeloid Leukemia

Drug resistance and relapse are common challenges in acute myeloid leukemia (AML), particularly in an aggressive subset bearing internal tandem duplications (ITD) of the FLT3 receptor (FLT3-ITD+). The tyrosine kinase inhibitor gilteritinib is approved for the treatment of relapse/refractory AML with FLT3 mutations, yet resistance to gilteritinib remains a clinical concern of which the underlying mechanisms remain incompletely understood. Using transcriptomic analyses and functional validation studies, we identified the calcium-binding proteins, S100A8 and S100A9 (S100A8/A9), as contributors to gilteritinib resistance in FLT3-ITD+ AML. Exposure of FLT3-ITD+ AML cells to gilteritinib increased S100A8/A9 expression in vivo and in vitro, decreased free calcium levels, and genetic manipulation of S100A9 was associated with altered sensitivity to gilteritinib. Using a transcription factor screen, we identified the transcriptional corepressor BCL6, as a regulator of S100A9 expression, and found that gilteritinib decreased BCL6 binding to the S100A9 promoter, thereby increasing S100A9 expression. Furthermore, pharmacological inhibition of BCL6 accelerated the growth rate of gilteritinib-resistant FLT3-ITD+ AML cells, suggesting that S100A9 is a functional target of BCL6. These findings shed light on mechanisms of resistance to gilteritinib through regulation of a target that can be therapeutically exploited to enhance gilteritinib's anti-leukemic effects.

M2-like macrophages exert hepatoprotection in acute-on-chronic liver failure through inhibiting necroptosis-S100A9-necroinflammation axis

Necroptosis has emerged as a novel and crucial player in acute and chronic liver diseases. Necroptotic cells lead to the release of DAMPs including S100A9, followed by the development of necroinflammation. We previously have documented the beneficial hepatoprotection conferred by M2-like macrophages in acute-on-chronic liver failure (ACLF) in vitro and in vivo, namely, M2-like macrophages protect hepatocytes against apoptosis. Herein, we integrated necroptosis, S100A9, and necroinflammation into this hepatoprotection, and hypothesized M2-like macrophages exert a hepatoprotective effect through inhibiting necroptosis-S100A9-necroinflammation axis. To testify this hypothesis, control mice were pre-treated with necroptosis or S100A9 inhibitors followed by D-GalN/LPS challenge. The extent of liver injury and M1/M2 macrophage activation was assessed. Necroptosis signaling and S100A9 expression were analysed and compared in control and fibrotic mice with or without acute insult. To document the pivotal role of M2-like macrophages in necroptosis and S100A9 inhibition, loss-of-function and gain-of-function experiments were performed. In addition, necroinflammation and its dependence on necroptosis and S100A9 were analysed. Moreover, the inhibitory effects of M2-like macrophages on necroinflammation were investigated in vivo and in vitro. We found that: firstly, the inhibition of necroptosis signaling and S100A9 expression alleviated D-GalN/LPS-induced hepatic damage, which was accompanied by M2-like macrophage activation; secondly, fibrosis inhibited necroptosis signaling and S100A9 expression, which could be attributed to M2-like macrophage activation; thirdly, S100A9 may function as a downstream player of necroptosis signaling; fourthly, fibrosis suppressed necroptosis- and S100A9-dependent necroinflammation; and finally, M2-like macrophages inhibited NLRP3 inflammasome activation and resultant necroinflammation via IL-10. Therefore, M2-like macrophages exert a beneficial hepatoprotection by inhibiting necroptosis-S100A9-necroinflammation axis in ACLF. Our findings provide novel insight for treating ACLF patients by specially targeting this signaling axis.

Elevated S100A9 expression in chronic rhinosinusitis coincides with elevated MMP production and proliferation in vitro

Chronic rhinosinusitis (CRS) is a common condition associated with inflammation and tissue remodeling of the nose and paranasal sinuses, frequently occurring with nasal polyps and allergies. Here we investigate inflammation and the protease profile in nasal tissues and plasma from control non-CRS patients and CRS patients. Gene expression for several cytokines, proteases, and antiproteases was quantified in nasal tissue from non-CRS and CRS subjects with nasal polyps. Elevated expression of S100A9, IL1A, MMP3, MMP7, MMP11, MMP25, MMP28, and CTSK was observed in tissue from CRS subjects with nasal polyps compared to control tissue. Tissue protein analysis confirmed elevated levels of these targets compared to controls, and increased MMP3 and MMP7 observed in CRS subjects with nasal polyps compared to CRS subjects without polyps. Plasma concentrations of MMP3 and MMP7 were elevated in the CRS groups compared to controls. The nasal cell line, CCL-30, was exposed to S100A9 protein, resulting in increased MMP3, MMP7, and CTSK gene expression and elevated proliferation. Silencing MMP3 significantly reduced S100A9-mediated cell proliferation. Therefore, the elevated expression of S100A9 and MMPs are observed in CRS nasal tissue and S100A9 stimulated MMP3 responses to contribute to elevated nasal cell proliferation.

BET Inhibition Suppresses S100A8 and S100A9 Expression in Acute Myeloid Leukemia Cells and Synergises with Daunorubicin in Causing Cell Death

S100A8 and S100A9 are both members of the S100 family and have been shown to play roles in myeloid differentiation, autophagy, apoptosis, and chemotherapy resistance. In this study we demonstrate that the BET-bromodomain inhibitor JQ1 causes rapid suppression of S100A8 and S100A9 mRNA and protein in a reversible manner. In addition, we show that JQ1 synergises with daunorubicin in causing AML cell death. Daunorubicin alone causes a dose- and time-dependent increase in S100A8 and S100A9 protein levels in AML cell lines which is overcome by cotreatment with JQ1. This suggests that JQ1 synergises with daunorubicin in causing apoptosis via suppression of S100A8 and S100A9 levels.