Staphylococcus aureus regulates secretion of interleukin-6 and monocyte chemoattractant protein-1 through activation of nuclear factor kappaB signaling pathway in human osteoblasts

Abstract

Objective: Activation of nuclear factor kappaB by diverse bacteria regulates the secretion of chemokines and cytokines. Staphylococcus aureus (S. aureus)-infected osteoblasts can significantly increase the secretion of interleukin-6 and monocyte chemoattractant protein-1. The aim of this study was to investigate whether S. aureus can activate nuclear factor kappaB in human osteoblasts, and whether the activation of nuclear factor kappaB by S. aureus regulates the secretion of interleukin-6 and monocyte chemoattractant protein-1. Methods: Immunoblot and electrophoretic mobility shift assay were used to detect the degradation of IκBa and activation of nuclear factor kappaB in human osteoblasts in response to S. aureus, respectively. Enzyme-linked immunosorbent assay was used to measure the secretion of interleukin-6 and monocyte chemoattractant protein-1 in the supernatants. Lastly, carbobenzoxyl-l-leucinyl-l-leucinyl-l-leucinal, an inhibitor of the nuclear factor kappaB, was used to determine if activation of nuclear factor kappaB by S. aureus in human osteoblasts regulates the secretions of interleukin-6 and monocyte chemoattractant protein-1. Results: Our results for the first time demonstrated that S. aureus can induce the degradation of IκBa and activation of nuclear factor kappaB in human osteoblasts in a time and dose-dependent manner. In addition, inhibition of nuclear factor kappaB by carbobenzoxyl-l-leucinyl-l-leucinyl-l-leucinal suppressed the secretion of interleukin-6 and monocyte chemoattractant protein-1 in the supernatants of S. aureus-infected human osteoblasts in a dose-dependent manner. Conclusions: These findings suggest that S. aureus can activate nuclear factor kappaB in human osteoblasts, and subsequently regulate the secretion of interleukin-6 and monocyte chemoattractant protein-1. The nuclear factor kappaB transcription factor regulates a number of genes involved in a wide variety of biological processes. Further study of the effects of nuclear factor kappaB activation on S. aureus-infected human osteoblast may provide us new insights into discovery of the immune mechanisms in osteomyelitis.

Staphylococcus aureus-mediated blood-brain barrier injury: anin vitrohuman brain microvascular endothelial cell model

“…NF‐κB activation in response to SA infection has previously been demonstrated using immortalized bovine umbilical vein endothelial cells, an event that had direct influence on the process of SA internalization into the host cells, and which could be modulated by known activators of NF‐κB such as TNF‐α and IL‐1β (Oviedo‐Boyso et al, ). A recent study by Ning et al, () has also demonstrated how SA infection of human osteoblasts can activate NF‐κB leading to elevated production and release of IL‐6 and MCP‐1 (Ning et al, ), observations consistent with our SA:HBMvEC infection model.…”

The role of cytokines in diabetic foot osteomyelitis

“…Other authors have also reported that IL‐6 is released by infiltrating immune cells and it has been demonstrated that the osteoblast is a significant source of this cytokine . The activation of nuclear factor kappaβ (NF‐κβ) in human osteoblasts by Staphylococcus aureus may subsequently regulate the secretion of IL‐6 . However, only one third of the osteoblasts of the present study were positive for IL‐6, whereas the main source in acute cases was bone marrow neutrophils and macrophages.…”

Pathogenic potential ofEscherichia coliclinical strains from orthopedic implant infections towards human osteoblastic cells

“…The osteoblasts, derived from mesenchymal bone marrow precursors, control the bone remodeling process by synthesizing the components of bone matrix, and by modulating the activity of the bone-resorbing osteoclasts. These cells have also been shown to produce different soluble inflammatory mediators [IL-6, IL-1, TNF-α, receptor activator of NF-κB ligand (RANKL)], following S. aureus infection (Marriott 2004;Somayaji et al 2008;Wright and Nair 2010;Ning et al 2011;Claro et al 2013). Thus, the bone destruction induced by S. aureus exposure results mainly from the inflammatory reaction elicited by the infection, even if some S. aureus lineages that overexpress the newly studied family of PSM peptides share cytolytic properties following invasion of osteoblasts (Rasigade et al 2013).…”

“…Based on research in this field, bacterial adherence and biofilm formation on the implant surface represent major factors involved in the pathogenesis process, providing protection against antimicrobial therapy and host immune responses (Montanaro et al 2011;Ribeiro, Monteiro and Ferraz 2012;Molina-Manso et al 2013). Regarding bone infection, Staphylococcus aureus has been shown to invade osteoblasts, persist intracellularly and induce the secretion of key proinflammatory mediators and potent stimulators of osteoclastogenesis and bone resorption (Alexander et al 2003;Marriott 2004;Marriot et al 2005;Somayaji et al 2008;Wright and Nair 2010;Ning et al 2011;Hamza et al 2013). Several virulence determinants, such as specific microbial surface components recognizing adhesive matrix molecules with in particular the fibronectin-binding proteins (FnBPs), the surface-bound protein A (SpA) or a class of pore-forming toxins named the phenol-soluble modulins (PSMs), have been demonstrated to play a role in S. aureus invasiveness and bone destruction (Wright and Nair 2010;Cassat et al 2013;Claro et al 2013;Rasigade et al 2013).…”