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Zinc-dependent histone deacetylases drive neutrophil extracellular trap formation and potentiate local and systemic inflammation

ABSTRACT: Summary Neutrophil extracellular traps (NETs) have been implicated in the pathogenesis of acute respiratory distress syndrome (ARDS) driven by viruses or bacteria, as well as in numerous immune-mediated disorders. Histone citrullination by the enzyme peptidylarginine deiminase 4 (PAD4) and the consequent decondensation of chromatin are hallmarks in the induction of NETs. Nevertheless, additional histone modifications that may govern NETosis are largely overlooked. Herein, we show that histone deacetylases (HDACs) play critical roles in driving NET formation in human and mouse neutrophils. HDACs belonging to the zinc-dependent lysine deacetylases family are necessary to deacetylate histone H3, thus allowing the activity of PAD4 and NETosis. Of note, HDAC inhibition in mice protects against microbial-induced pneumonia and septic shock, decreasing NETosis and inflammation. Collectively, our findings illustrate a new fundamental step that governs the release of NETs and points to HDAC inhibitors as therapeutic agents that may be used to protect against ARDS and sepsis. Graphical abstract Highlights • Zn-dependent lysine deacetylases govern neutrophil extracellular trap (NET) formation• Class I/IIb HDACs deacetylate histone H3 allowing its citrullination by PAD4• HDAC inhibition with ricolinostat protects against viral and bacterial pneumonia• In a model of endotoxic shock, ricolinostat inhibits NETosis and dampens inflammation Molecular biology; Immunology; Cell biology; Functional aspects of cell biology

SUBMITTER: Poli V

PROVIDER: S-EPMC8567386 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Neutrophils undergo a unique form of cell death to generate neutrophil extracellular traps (NETs). It is well established that citrullination of histones (e.g., CitH3) facilitates chromatin decondensation during NET formation (NETosis), particularly during calcium-induced NETosis that is independent of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase (NOX) activation. However, the importance of other forms of histone modifications in NETosis has not been established. We considered that acetylation of histones would also facilitate NETosis. To test this hypothesis, we induced NOX-dependent NETosis in human neutrophils with phorbol myristate acetate or lipopolysaccharide (from Escherichia coli 0128), and NOX-independent NETosis with calcium ionophores A23187 or ionomycin (from Streptomycesconglobatus) in the presence or absence of two pan histone deacetylase inhibitors (HDACis), belinostat and panobinostat (within their half maximal inhibitory concentration (IC50) range). The presence of these inhibitors increased histone acetylation (e.g., AcH4) in neutrophils. Histone acetylation was sufficient to cause a significant increase (~20%) in NETosis in resting neutrophils above baseline values. When acetylation was promoted during NOX-dependent or -independent NETosis, the degree of NETosis additively increased (~15⁻30%). Reactive oxygen species (ROS) production is essential for baseline NETosis (mediated either by NOX or mitochondria); however, HDACis did not promote ROS production. The chromatin decondensation step requires promoter melting and transcriptional firing in both types of NETosis; consistent with this point, suppression of transcription prevented the NETosis induced by the acetylation of histones. Collectively, this study establishes that histone acetylation (e.g., AcH4) promotes NETosis at baseline, and when induced by both NOX-dependent or -independent pathway agonists, in human neutrophils. Therefore, we propose that acetylation of histone is a key component of NETosis.

Project description:Schnitzler's syndrome is a rare autoinflammatory disorder characterized by interleukin-1ß-mediated and neutrophil-dominated inflammation. Neutrophil extracellular traps (NETs) are web-like structures of decondensed chromatin, histones, and antimicrobial peptides released by neutrophils. NETs were initially described in the context of pathogen defense but are also involved in autoimmune-mediated skin diseases. Here, we assessed the role of neutrophil extracellular trap formation (NETosis) in Schnitzler's syndrome. Immunofluorescence co-staining of myeloperoxidase and subnucleosomal complex was performed on lesional skin samples from patients with Schnitzler's syndrome, other neutrophilic dermatoses (cryopyrin-associated periodic syndrome, Sweet syndrome, and pyoderma gangrenosum), urticarial vasculitis and chronic spontaneous urticaria as well as healthy control skin. Blood neutrophils from patients with Schnitzler's syndrome and controls were isolated, and NETosis was induced by phorbol 12-myristate 13-acetate (PMA). Also, NETosis of control neutrophils induced by symptomatic Schnitzler's syndrome sera, cytokines and sub-threshold PMA doses was studied. Immunofluorescence co-staining revealed widespread and substantial NET formation in lesional skin of Schnitzler's syndrome patients but absence of NETs in chronic spontaneous urticaria and control skin. Neutrophils undergoing NETosis were observed in the skin of other neutrophilic diseases too. Correspondingly, blood neutrophils from Schnitzler's syndrome patients showed significantly elevated NETosis rates compared to control neutrophils following stimulation with PMA. Increased NETosis correlated well with high levels of C-reactive protein (CRP). SchS patients with the lowest NETosis rates had persistent joint and bone pain despite IL-1 blockade. Stimulation of control neutrophils and sub-threshold PMA with sera of symptomatic Schnitzler's syndrome patients disclosed enhanced NETosis as compared to control sera. Our results suggest that the induction of NET formation by neutrophils contributes to skin and systemic inflammation and may support the resolution of local inflammation in Schnitzler's syndrome.

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Zinc-dependent histone deacetylases drive neutrophil extracellular trap formation and potentiate local and systemic inflammation

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