HDAC3 Mediates the Inflammatory Response and LPS Tolerance in Human Monocytes and Macrophages

Abstract

Histone deacetylases (HDACs) are a group of enzymes that control histone deacetylation and bear potential to direct expression of large gene sets. We determined the effect of HDAC inhibitors (HDACi) on human monocytes and macrophages, with respect to their polarization, activation, and their capabilities of inducing endotoxin tolerance. To address the role for HDACs in macrophage polarization, we treated monocytes with HDAC3i, HDAC6i or pan-HDACi prior to polarization into M1 or M2 macrophages using IFNγ or IL-4 respectively. To study the HDAC inhibition effect on cytokine expression, macrophages were treated with HDACi prior to LPS-stimulation. TNFα, IL-6, and p40 were measured with ELISA, whereas modifications of Histone 3 and STAT1 were assessed using western blot. To address the role for HDAC3 in repeated LPS challenge induction, HDAC3i or HDAC3 siRNA was added to monocytes prior to incubation with IFNγ, which were then repeatedly challenged with LPS and analyzed by means of protein analyses and transcriptional profiling. Pan-HDACi and HDAC3i reduced cytokine secretion in monocytes and M1 macrophages, whereas HDAC6i yielded no such effect. Notably, neither pan-HDACi nor HDAC3i reduced cytokine secretion in M2 macrophages. In contrast to previous reports in mouse macrophages, HDAC3i did not affect macrophage polarization in human cells. Likewise, HDAC3 was not required for IFNγ signaling or IFNβ secretion. Cytokine and gene expression analyses confirmed that IFNγ-treated macrophages consistently develop a cytokine response after LPS repeated challenge, but pretreatment with HDAC3i or HDAC3 siRNA reinstates a state of tolerance reflected by general suppression of tolerizable genes, possibly through decreasing TLRs expression, and particularly TLR4/CD14. The development of endotoxin tolerance in macrophages is important to reduce exacerbated immune response and limit tissue damage. We conclude that HDAC3 is an attractive protein target to mediate macrophage reactivity and tolerance induction in inflammatory macrophages.

Evaluation of serum antioxidative status, immune status and intestinal condition of Linwu duck challenged by lipopolysaccharide with various dosages and replications

“…On the other hand, animals that experienced repeated LPS exposures might acquire the endotoxin tolerance, resulting in reduced secretions of cytokines ( West and Heagy, 2002 ). It was proved that endotoxin tolerance could be induced in pigs ( Castegren et al., 2013 ), rats ( Santos et al., 2020 ), and human monocyte and macrophage cells ( Ghiboub et al., 2020 ). But whether birds were able to develop the endotoxin tolerance was still unknown.…”

Characterization of Histone Deacetylase Mechanisms in Cancer Development

“…HDAC3 is involved in lipopolysaccharide (LPS)-directed cytokine secretion in monocytes and M1 macrophages. HDAC3 disrupts the process by which inflammation-activated M1 macrophages mediate LPS tolerance ( 240 ).…”

Selective Targeting of Epigenetic Readers and Histone Deacetylases in Autoimmune and Inflammatory Diseases: Recent Advances and Future Perspectives

“…In humans, the HDAC enzymes family comprises 18 members divided into 4 classes: class I HDACs (HDACs 1–3 and 8), class IIa HDACs (HDACs 4, 5, 7, and 9), class IIb HDACs (HDACs 6 and 10), class III sirtuins (Sirt1–7), and class IV HDACs (HDAC11) [ 12 , 33 , 34 ]. While histone acetyltransferases (HAT) add acetyl groups to lysine residues, thereby permitting TFs binding and subsequent gene expression, histone deacetylases (HDACs) erase histone acetyl residues, leading to chromatin compaction, generally resulting in gene repression [ 33 , 34 ]. However, in contrast to the common role of HDACs for gene repression, treatment with HDAC inhibitors typically leads to a reduction rather than increase in proinflammatory gene expression by immune cells [ 35 ].…”

“…Genetic depletion of individual HDACs has demonstrated that these proteins mediate specific and unique functions [ 57 ], suggesting therapeutic relevance for selective isoform targeting. While achieving this is a challenge due to conserved structural similarity between HDAC isoforms [ 12 ], HDACi has been reported with selectivity for HDAC1, HDAC2, HDAC3 [ 33 , 58 , 59 , 60 , 61 ], HDAC8 [ 62 , 63 ], HDAC6 [ 64 ], HDAC11 [ 65 ], SIRT1, and SIRT2 [ 66 , 67 ]. However, caution should be taken in interpreting the specificity of the effects of these published inhibitors given the variability of available HDAC assays and the residual dose-dependent effects on other isoforms (Table 1).…”

“…Inhibitors with a high degree of reported selectivity toward HDAC3, including RGFP966, MI192, and ITF3100, have been shown to efficiently attenuate inflammatory responses [ 33 , 58 , 59 , 68 ] and to restore LPS tolerance in inflammatory macrophages in vitro [ 33 ]. RGFP966 has demonstrated efficacy in preclinical models of diabetes [ 69 ], osteoarthritis (OA) [ 70 ], and allergy [ 71 ] via modulating inflammatory pathways.…”