Pneumolysin Is Responsible for Differential Gene Expression and Modifications in the Epigenetic Landscape of Primary Monocyte Derived Macrophages

• Published in: Frontiers in immunology Vol. 12; p. 573266
• Main Authors: Cole, Joby, Angyal, Adrienn, Emes, Richard D, Mitchell, Tim John, Dickman, Mark J, Dockrell, David H
• Format: Journal Article
• Language: English
• Published: Switzerland Frontiers Media S.A 11.05.2021
• Subjects: Bacterial Proteins - genetics; Bacterial Proteins - metabolism; Cells, Cultured; Cytokines - genetics; Cytokines - metabolism; Epigenesis, Genetic; Gene Expression Profiling; histone post translational modifications; Histones - metabolism; Host-Pathogen Interactions; Humans; Immunology; Macrophages - metabolism; Macrophages - microbiology; Methylation; monocyte derived macrophages; pneumolysin; Protein Processing, Post-Translational; Proteome - metabolism; Proteomics - methods; Streptococcus pneumoniae; Streptococcus pneumoniae - genetics; Streptococcus pneumoniae - metabolism; Streptococcus pneumoniae - physiology; Streptolysins - genetics; Streptolysins - metabolism; tumour necrosis factor; monocyte derived macrophages; pneumolysin; tumour necrosis factor; histone post translational modifications; Streptococcus pneumoniae
• DOI: 10.3389/fimmu.2021.573266
• ISSN: 1664-3224

Epigenetic modifications regulate gene expression in the host response to a diverse range of pathogens. The extent and consequences of epigenetic modification during macrophage responses to , and the role of pneumolysin, a key virulence factor, in influencing these responses, are currently unknown. To investigate this, we infected human monocyte derived macrophages (MDMs) with and addressed whether pneumolysin altered the epigenetic landscape and the associated acute macrophage transcriptional response using a combined transcriptomic and proteomic approach. Transcriptomic analysis identified 503 genes that were differentially expressed in a pneumolysin-dependent manner in these samples. Pathway analysis highlighted the involvement of transcriptional responses to core innate responses to pneumococci including modules associated with metabolic pathways activated in response to infection, oxidative stress responses and NFκB, NOD-like receptor and TNF signalling pathways. Quantitative proteomic analysis confirmed pneumolysin-regulated protein expression, early after bacterial challenge, in representative transcriptional modules associated with innate immune responses. In parallel, quantitative mass spectrometry identified global changes in the relative abundance of histone post translational modifications (PTMs) upon pneumococcal challenge. We identified an increase in the relative abundance of H3K4me1, H4K16ac and a decrease in H3K9me2 and H3K79me2 in a PLY-dependent fashion. We confirmed that pneumolysin blunted early transcriptional responses involving TNF-α and IL-6 expression. Vorinostat, a histone deacetylase inhibitor, similarly downregulated TNF-α production, reprising the pattern observed with pneumolysin. In conclusion, widespread changes in the macrophage transcriptional response are regulated by pneumolysin and are associated with global changes in histone PTMs. Modulating histone PTMs can reverse pneumolysin-associated transcriptional changes influencing innate immune responses, suggesting that epigenetic modification by pneumolysin plays a role in dampening the innate responses to pneumococci.