Methotrexate chemotherapy promotes osteoclast formation in the long bone of rats via increased pro-inflammatory cytokines and enhanced NF-κB activation.
Cancer chemotherapy with methotrexate (MTX) is known to cause bone loss. However, the underlying mechanisms remain unclear. This study investigated the potential role of MTX-induced pro-inflammatory cytokines and activation of NF-κB in the associated osteoclastogenesis in rats. MTX (0.75 mg/kg per day) was administered for 5 days, and bone and bone marrow specimens were collected on days 6, 9, and 14. Compared with a normal control, MTX increased the density of osteoclasts within the metaphyseal bone and the osteoclast formation potential of marrow cells on day 9. RT-PCR analysis of mRNA expression for pro-osteoclastogenic cytokines in the metaphysis indicated that, although the receptor activator of NF-κB ligand/osteoprotegerin axis was unaffected, expression of tumor necrosis factor (TNF)-α, IL-1, and IL-6 increased on day 9. Enzyme-linked immunosorbent assay analysis of plasma showed increased levels of TNF-α on day 6 and of IL-6 on day 14. Plasma from treated rats induced osteoclast formation from normal bone marrow cells, which was attenuated by a TNF-α-neutralizing antibody. Indicative of a role for NF-κB signaling, plasma on day 6 increased NF-κB activation in RAW(264.7) cells, and plasma-induced osteoclastogenesis was abolished in the presence of the NF-κB inhibitor, parthenolide. Our results demonstrate mechanisms for MTX-induced osteoclastogenesis and show that MTX induces osteoclast differentiation by generating a pro-osteoclastogenic environment in both bone and the circulation, specifically with increased TNF-α levels and activation of NF-κB.
Sansom Institute and the School of Pharmacy and Medical Science, the University of South Australia, Adelaide, Australia.
Tristan J
TJ
King
Kristen R
KR
Georgiou
Johanna C
JC
Cool
Michaela A
MA
Scherer
Estabelle S M
ES
Ang
Bruce K
BK
Foster
Jiake
J
Xu
Cory J
CJ
Xian
D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology*; D002454:Cell Differentiation / Q000187:drug effects; D016207:Cytokines / Q000096:biosynthesis* / Q000235:genetics; D005786:Gene Expression Regulation / Q000187:drug effects; D018836:Inflammation Mediators / Q000378:metabolism*; D008297:Male; D008727:Methotrexate / Q000494:pharmacology*; D016328:NF-kappa B / Q000378:metabolism*; D010010:Osteoclasts / Q000166:cytology / Q000187:drug effects* / Q000502:physiology; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats; D017207:Rats, Sprague-Dawley; D014409:Tumor Necrosis Factor-alpha / Q000097:blood
D000970:Antineoplastic Agents; D016207:Cytokines; D018836:Inflammation Mediators; D016328:NF-kappa B; D012333:RNA, Messenger; D014409:Tumor Necrosis Factor-alpha; D008727:Methotrexate