Staphylococcus aureus induces DNA damage in host cell

Abstract

Staphylococcus aureus causes serious medical problems in human and animals. Here we show that S. aureus can compromise host genomic integrity as indicated by bacteria-induced histone H2AX phosphorylation, a marker of DNA double strand breaks (DSBs), in human cervix cancer HeLa and osteoblast-like MG-63 cells. This DNA damage is mediated by alpha phenol-soluble modulins (PSMα 1–4 ), while a specific class of lipoproteins (Lpls), encoded on a pathogenicity island in S. aureus , dampens the H2AX phosphorylation thus counteracting the DNA damage. This DNA damage is mediated by reactive oxygen species (ROS), which promotes oxidation of guanine forming 7,8-dihydro-8-oxoguanine (8-oxoG). DNA damage is followed by the induction of DNA repair that involves the ATM kinase-signaling pathway. An examination of S. aureus strains, isolated from the same patient during acute initial and recurrent bone and joint infections (BJI), showed that recurrent strains produce lower amounts of Lpls, induce stronger DNA-damage and prompt the G2/M transition delay to a greater extent that suggest an involvement of these mechanisms in adaptive processes of bacteria during chronicization. Our findings redefine our understanding of mechanisms of S. aureus -host interaction and suggest that the balance between the levels of PSMα and Lpls expression impacts the persistence of the infection.

Involvement of caspase‐1 in inflammasomes activation and bacterial clearance in S. aureus ‐infected osteoblast‐like MG ‐63 cells

“…Moreover, it was suggested that early activation of NLRP3 (Ip et al, 2010;Sokolovska et al, 2013) inflammasomes is triggered by events, such as the production of ROS, that are associated with the phagocytic process in macrophages (Sokolovska et al, 2013). Recently, we demonstrated that S. aureus induces the production of ROS in WT MG-63 cells (Deplanche et al, 2019). We hypothesize that S. aureus-induced ROS plays a similar role in inflammasome activation in non-phagocytic cells.…”

“…To persist within the host cells, S. aureus also developed strategies to circumvent the host cell defenses (Alekseeva et al, 2013;Deplanche et al, 2015;Deplanche et al, 2016;Deplanche et al, 2019). Here we aimed to investigate the contributions of internalized S. aureus on alteration of host defense events such as inflammasomes activation and bacterial clearance in infected osteoblasts.…”

“…We and others showed that S. aureus can be internalized and survive within professional phagocytes, such as macrophages (Flannagan et al, 2016), as well as within non phagocytic epithelial cells or osteoblasts (Mohamed et al, 2014;Deplanche et al, 2019). To study the capacity of intracellular S. aureus to induce inflammasomes formation in human osteoblasts-like MG-63 cells, we confirmed the presence of intracellular bacteria using transmission electron microscopy (Transmission EM) at different time points.…”

“…Standards, Teddington, UK) cells and human monocyte THP1 cells (ATCC were cultured in DMEM and RPMI 1640 respectively, supplemented with 10% fetal calf serum (Gibco), 100 U/mL penicillin, and 100 µg/mL streptomycin at 37°C with 5% CO2 as described (Deplanche et al, 2019). Trypsin/EDTA (Sigma) was used for cell subculturing to release adherent cells.…”

“…Cells then were exposed to S. aureus strains at MOI 50:1. An MOI value of 50:1 was selected in order to prevent the induction of host cell death (Deplanche et al, 2019). Bacterial concentrations were estimated spectrophotometrically and were confirmed by determination of CFU.…”