Staphylococcus aureus supernatant induces the release of mouse β-defensin-14 from osteoblasts via the p38 MAPK and NF-κB pathways

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.

Ultrasound microbubbles enhance human β-defensin 3 against biofilms

“…Our recent studies identified that when mouse osteoblasts contacted with MRSA supernatant, the relevant activated signaling pathway p38 mitogen-activated protein kinase could contribute to the obvious release of MBD-14, which is the structural and functional ortholog of HBD-3 [43,44]. Meanwhile, we also indicated the potential role of increasing the release of MBD-14 in the treatment of osteomyelitis in mice [22,45]. In addition to their role of local high Fig.…”

Transcriptomic Analysis on Responses of Murine Lungs to Pasteurella multocida Infection

“…There are total 82 DEGs involved in MAPK signal pathway and 45 DEGs in NF-κB signaling. NF-κB and MAPK signaling play important roles in defense responses against bacterial infection by regulating production of cytokines, such as Enterococcus faecalis, S. aureus , and M. tuberculosis (Zhu et al, 2013; Deng et al, 2014; Zou and Shankar, 2015). Thus, the NF-κB and MAPK signaling may also have the critical importance during P. multocida infection.…”

Interleukin-17A (IL-17A) and IL-17F Are Critical for Antimicrobial Peptide Production and Clearance of Staphylococcus aureus Nasal Colonization

“…S. aureus cells treated with recombinant mBD-3 showed growth inhibition and morphological and structural changes, including delamination and perforation of the peripheral cell walls, porosity, and release of the cytoplasmic contents (22,23). mBD-14 is expressed in a wide variety of tissues, including spleen, colon, and tissues of the upper and lower respiratory tract (24), is induced in osteoblasts upon stimulation with S. aureus supernatants, and exhibits antistaphylococcal activity (25).…”