Peroxidase enzymes inhibit osteoclast differentiation and bone resorption.
Myeloperoxidase (MPO) and eosinophil peroxidase (EPO) are heme-containing enzymes, well known for their antimicrobial activity, are released in abundance by innate immune infiltrates at sites of inflammation and injury. We have discovered new and previously unrecognised roles for heme peroxidases in extracellular matrix biosynthesis, angiogenesis, and bone mineralisation, all of which play an essential role in skeletal integrity. In this study we used in vitro models of osteoclastogenesis to investigate the effects of heme peroxidase enzymes on osteoclast differentiation and bone resorbing activity, pertinent to skeletal development and remodelling. Receptor activator of nuclear factor kappa B-ligand (RANKL) stimulates the formation of tartate-resistant acid phosphatase (TRAP) positive multinucleated cells and increases bone resorption when cultured with human peripheral blood mononuclear cells (PBMCs) or the RAW264.7 murine monocytic cell line. When RANKL was added in combination with either MPO or EPO, a dose-dependent inhibition of osteoclast differentiation and bone resorption was observed. Notably, peroxidases had no effect on the bone resorbing activity of mature osteoclasts, suggesting that the inhibitory effect of the peroxidases was limited to osteoclast precursor cells. Mechanistically, we observed that osteoclast precursor cells readily internalize peroxidases, and inhibited the phosphorylation of JNK, p38 MAPK and ERK1/2, important signalling molecules central to osteoclastogenesis. Our findings suggest that peroxidase enzymes, like MPO and EPO, may play a fundamental role in inhibiting RANKL-induced osteoclast differentiation at inflammatory sites of bone fracture and injury. Therefore, peroxidase enzymes could be considered as potential therapeutic agents to treat osteolytic bone disease and aberrant bone resorption.
School of Medicine, Discipline of Surgery, Basil Hetzel Institute, University of Adelaide, Adelaide, South Australia, Australia.
Vasilios
V
Panagopoulos
School of Medicine, Discipline of Surgery, Basil Hetzel Institute, University of Adelaide, Adelaide, South Australia, Australia.
Vasilios
V
Liapis
School of Medicine, Discipline of Surgery, Basil Hetzel Institute, University of Adelaide, Adelaide, South Australia, Australia.
Irene
I
Zinonos
School of Medicine, Discipline of Surgery, Basil Hetzel Institute, University of Adelaide, Adelaide, South Australia, Australia.
Shelley
S
Hay
School of Medicine, Discipline of Surgery, Basil Hetzel Institute, University of Adelaide, Adelaide, South Australia, Australia.
Damien A
DA
Leach
School of Medicine, Discipline of Surgery, Basil Hetzel Institute, University of Adelaide, Adelaide, South Australia, Australia.
Wendy
W
Ingman
School of Medicine, Discipline of Surgery, Basil Hetzel Institute, University of Adelaide, Adelaide, South Australia, Australia.
Mark O
MO
DeNichilo
Discipline of Orthopaedics and Trauma, University of Adelaide, Adelaide, South Australia, Australia.
Gerald J
GJ
Atkins
Discipline of Orthopaedics and Trauma, University of Adelaide, Adelaide, South Australia, Australia.
David M
DM
Findlay
Myeloma Research Laboratory, Discipline of Physiology, School of Medicine, Faculty of Health Sciences, University of Adelaide and Cancer Theme, South Australian Health and Medical Research Institute (SAHMRI), Adelaide, Australia.
Andrew C W
ACW
Zannettino
School of Medicine, Discipline of Surgery, Basil Hetzel Institute, University of Adelaide, Adelaide, South Australia, Australia. Electronic address: andreas.evdokiou@adelaide.edu.au.
Andreas
A
Evdokiou
D000818:Animals; D001862:Bone Resorption / Q000201:enzymology* / Q000473:pathology*; D002454:Cell Differentiation; D004705:Endocytosis / Q000187:drug effects; D006801:Humans; D016173:Macrophage Colony-Stimulating Factor / Q000494:pharmacology; D051379:Mice; D010010:Osteoclasts / Q000201:enzymology* / Q000473:pathology*; D009195:Peroxidase / Q000378:metabolism*; D053245:RANK Ligand / Q000494:pharmacology; D000067996:RAW 264.7 Cells; D015398:Signal Transduction / Q000187:drug effects
D053245:RANK Ligand; D016173:Macrophage Colony-Stimulating Factor; D009195:Peroxidase
Eosinophil peroxidase; Myeloperoxidase; Osteoclast; Resorption