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Updated: May 12, 2026
A Mouse Model to Assess Innate Immune Response to Staphylococcus aureus Infection
Published on: February 28, 2019
Staphylococcus aureus supernatant induces the release of mouse β-defensin-14 from osteoblasts via the p38 MAPK and
1Department of Orthopaedic Surgery, Shanghai Jiao Tong University School of Medicine, Shanghai, People's Republic of China.
Abstract:
Mammalian β-defensins are small cationic peptides of approximately 2-6 kDa that have been implicated in mediating innate immune defenses against microbial infection. Previous studies have reported that mouse β-defensin-14 (MBD‑14), based on structural and functional similarities, appears to be an ortholog of human β-defensin-3 (HBD-3). The aim of this study was to identify the signaling pathways that contribute to the expression of MBD-14 in mouse osteoblasts (OBs) upon contact with methicillin-resistant Staphylococcus aureus (S. aureus) supernatant (SAS) to provide a theoretical basis for the use of MDB-14 as a therapeutic agent in the treatment of intramedullary infection with S. aureus in vivo. The bacterial exoproducts released by S. aureus mainly include a large amount of enterotoxins. Using mouse OBs, the release and regulation of MBD-14 was evaluated by real-time polymerase chain reaction (PCR) and enzyme‑linked immunosorbent assay (ELISA) following exposure to SAS. The activation of the p38 mitogen‑activated protein kinase (MAPK), extracellular signal-regulated kinase (ERK) and nuclear factor-κB (NF-κB) pathways was determined by western blot analysis. OBs treated with lipopolysaccharide (LPS) were used as the positive control. The results revealed that SAS significantly promoted the phosphorylation of p38 MAPK, NF-κB and the inhibitory subunit of NF-κBα (IκBα) in a time-dependent manner. The treatment of OBs with SB203580 (an inhibitor of p38 MAPK) and pyrrolidine dithiocarbamate (PDTC, an inhibitor of NF-κB) prior to stimulation with SAS significantly inhibited the phosphorylation and mRNA expression of p38 MAPK and NF-κB p65, simultaneously reducing the release of MBD-14. Our findings suggest that the release of MBD-14 is mediated at least in part through the activation of p38 MAPK and NF-κB in response to S. aureus‑secreted bacterial exoproducts. Moreover, our data demonstrate the innate immune capacity of OBs under conditions of bacterial challenge to enhance the local expression of this MBD-14, a peptide with anti‑staphylococcal activity.
Insights
Methicillin-resistant Staphylococcus aureus (S. aureus) bacterial exoproducts trigger mouse osteoblasts to release mouse beta-defensin-14 (MBD-14). This release is mediated by the p38 MAPK and NF-κB signaling pathways.
Area of Science:
- Immunology
- Molecular Biology
- Cell Biology
Background:
- Mammalian beta-defensins are key components of the innate immune system, crucial for combating microbial infections.
- Mouse beta-defensin-14 (MBD-14) is structurally and functionally similar to human beta-defensin-3 (HBD-3).
- Osteoblasts (OBs) play a role in bone immunity and can express antimicrobial peptides like MBD-14.
Purpose of the Study:
- To investigate the signaling pathways regulating MBD-14 expression in mouse osteoblasts stimulated by S. aureus.
- To establish a theoretical foundation for MBD-14's therapeutic potential against S. aureus intramedullary infections.
Main Methods:
- Mouse osteoblasts were exposed to S. aureus supernatant (SAS).
- MBD-14 release was quantified using real-time PCR and ELISA.
- Activation of p38 MAPK, ERK, and NF-κB pathways was assessed via western blot analysis.
- Specific pathway inhibitors (SB203580 for p38 MAPK, PDTC for NF-κB) were used to elucidate signaling mechanisms.
Main Results:
- SAS significantly induced time-dependent phosphorylation of p38 MAPK, NF-κB, and IκBα in osteoblasts.
- Inhibiting p38 MAPK or NF-κB pathways markedly reduced MBD-14 release and MBD-14 mRNA expression.
- These findings indicate that SAS-induced MBD-14 release is dependent on p38 MAPK and NF-κB activation.
Conclusions:
- Osteoblasts exhibit innate immune responses to S. aureus by upregulating MBD-14 expression.
- The p38 MAPK and NF-κB signaling pathways are critical mediators of MBD-14 release in response to S. aureus exoproducts.
- MBD-14 demonstrates anti-staphylococcal activity, highlighting its potential as a therapeutic agent.
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