Suppression of osteoclastogenesis by N,N-dimethyl-D-erythro-sphingosine: a sphingosine kinase inhibition-independent action.
N,N-Dimethyl-D-erythro-sphingosine (DMS) competitively inhibits sphingosine kinase (SPHK) and has been widely used to assess the role of SPHK during cellular events, including motility, proliferation, and differentiation. In the present study, the effect of DMS on the differentiation of bone marrow macrophages (BMMs) to osteoclasts was investigated. When the osteoclast precursor cells were treated with DMS, the receptor activator of nuclear factor kappaB ligand (RANKL)-induced osteoclastogenesis was completely blocked. We were surprised to find, however, that knock-down of SPHK by small interfering RNA (siRNA) in BMMs did not reduce osteoclastogenesis. Furthermore, both overexpression of SPHK and exogenous addition of sphingosine-1-phosphate, the product of SPHK activity, failed to overcome the antiosteoclastogenic effect of DMS. These results suggest that DMS inhibited osteoclastogenesis independently of SPHK. Subsequent characterization of the DMS-mediated suppression of osteoclastogenesis revealed that DMS did not affect RANKL-induced activation of JNK, p38, NF-kappaB, and Ca2+ oscillation. On the other hand, DMS strongly inhibited two separate signaling pathways, the RANKL-induced activation of ERK and Akt, which eventually converged on the transcription factors c-Fos and NFATc1. There was significant increase in the osteoclast formation in the presence of DMS when BMMs were overexpressed with c-Fos, suggesting that c-Fos was a critical downstream target of DMS for the inhibition of osteoclastogenesis. Taken together, our data demonstrate that DMS has an antiosteoclastogenic function independently of its SPHK inhibitory activity. Considering previously reported anticancer properties of DMS, our study may also propose that DMS is an ideal drug candidate for bone metastases, for which osteoclastic bone-resorption is crucial.
Kim
Hyung Joon
HJ
Department of Cell and Developmental Biology, Seoul National University, 28 Yeongon-Dong, Chongno-Gu, Seoul 110-749, Korea.
Lee
Youngkyun
Y
Chang
Eun-Ju
EJ
Kim
Hyun-Man
HM
Hong
Sam-Pyo
SP
Lee
Zang Hee
ZH
Ryu
Jiyoon
J
Kim
Hong-Hee
HH
D000818:Animals; D001854:Bone Marrow Cells / Q000166:cytology / Q000187:drug effects; D020013:Calcium Signaling / Q000187:drug effects; D002478:Cells, Cultured; D048049:Extracellular Signal-Regulated MAP Kinases / Q000037:antagonists & inhibitors; D016173:Macrophage Colony-Stimulating Factor / Q000494:pharmacology; D051379:Mice; D008813:Mice, Inbred ICR; D016328:NF-kappa B / Q000378:metabolism; D050778:NFATC Transcription Factors / Q000502:physiology; D010010:Osteoclasts / Q000187:drug effects* / Q000502:physiology; D010012:Osteogenesis / Q000187:drug effects*; D000081082:Phosphoinositide-3 Kinase Inhibitors; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000037:antagonists & inhibitors / Q000502:physiology*; D016760:Proto-Oncogene Proteins c-fos / Q000037:antagonists & inhibitors / Q000502:physiology; D053245:RANK Ligand / Q000494:pharmacology; D013110:Sphingosine / Q000031:analogs & derivatives* / Q000494:pharmacology; D000099157:Sphingosine Kinase
D048049:Extracellular Signal-Regulated MAP Kinases; D016173:Macrophage Colony-Stimulating Factor; D016328:NF-kappa B; D050778:NFATC Transcription Factors; D000081082:Phosphoinositide-3 Kinase Inhibitors; D017853:Phosphotransferases (Alcohol Group Acceptor); D016760:Proto-Oncogene Proteins c-fos; D053245:RANK Ligand; D013110:Sphingosine; D000099157:Sphingosine Kinase; C061800:N,N-dimethylsphingosine