KMUP-1 suppresses RANKL-induced osteoclastogenesis and prevents ovariectomy-induced bone loss: roles of MAPKs, Akt, NF-κB and calcium/calcineurin/NFATc1 pathways.
BACKGROUND
KMUP-1 is a xanthine derivative with inhibitory activities on the phosphodiesterase (PDE) 3,4 and 5 isoenzymes to suppress the degradation of cyclic AMP and cyclic GMP. However, the effects of KMUP-1 on osteoclast differentiation are still unclear. In this study, we investigated whether KMUP-1 inhibits osteoclastogenesis induced by RANKL in RAW 264.7 cells and bone loss induced by ovariectomy in mice, and the underlying mechanisms.


RESULTS
In vitro, KMUP-1 inhibited RANKL-induced TRAP activity, the formation of multinucleated osteoclasts and resorption-pit formation. It also inhibited key mediators of osteoclastogenesis including IL-1β, IL-6, TNF-α and HMGB1. In addition, KMUP-1 inhibited RANKL-induced activation of signaling molecules (Akt, MAPKs, calcium and NF-κB), mRNA expression of osteoclastogensis-associated genes (TRAP, MMP-9, Fra-1, and cathepsin K) and transcription factors (c-Fos and NFATc1). Furthermore, most inhibitory effects of KMUP-1 on RANKL-mediated signal activations were reversed by a protein kinase A inhibitor (H89) and a protein kinase G inhibitor (KT5823). In vivo, KMUP-1 prevented loss of bone mineral content, preserved serum alkaline phosphate and reduced serum osteocalcin in ovariectomized mice.


CONCLUSIONS
KMUP-1 inhibits RANKL-induced osteoclastogenesis in vitro and protects against ovariectomy-induced bone loss in vivo. These effects are mediated, at least in part, by cAMP and cGMP pathways. Therefore, KMUP-1 may have a role in pharmacologic therapy of osteoporosis.
Department of Pharmacy, Chia-Nan University of Pharmacy and Science, Tainan, Taiwan.
Shu-Fen
SF
Liou
Jong-Hau
JH
Hsu
I-Ling
IL
Lin
Mei-Ling
ML
Ho
Pei-Chuan
PC
Hsu
Li-Wen
LW
Chen
Ing-Jun
IJ
Chen
Jwu-Lai
JL
Yeh
D000818:Animals; D015519:Bone Density; D050071:Bone Density Conservation Agents / Q000494:pharmacology*; D019703:Calcineurin / Q000235:genetics / Q000378:metabolism; D002118:Calcium / Q000378:metabolism*; D000242:Cyclic AMP / Q000378:metabolism; D006152:Cyclic GMP / Q000378:metabolism; D005260:Female; D005786:Gene Expression Regulation; D006801:Humans; D051379:Mice; D008807:Mice, Inbred BALB C; D020928:Mitogen-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism; D016328:NF-kappa B / Q000235:genetics / Q000378:metabolism; D050778:NFATC Transcription Factors / Q000235:genetics / Q000378:metabolism; D010010:Osteoclasts / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D010024:Osteoporosis / Q000235:genetics / Q000378:metabolism / Q000473:pathology / Q000517:prevention & control*; D010052:Ovariectomy; D010880:Piperidines / Q000494:pharmacology*; D051057:Proto-Oncogene Proteins c-akt / Q000235:genetics / Q000378:metabolism; D053245:RANK Ligand / Q000235:genetics* / Q000378:metabolism; D015398:Signal Transduction; D014970:Xanthines / Q000494:pharmacology*
D050071:Bone Density Conservation Agents; D016328:NF-kappa B; D050778:NFATC Transcription Factors; C494005:Nfatc1 protein, mouse; D010880:Piperidines; D053245:RANK Ligand; C505689:Tnfsf11 protein, mouse; D014970:Xanthines; C439304:KMUP 1; D000242:Cyclic AMP; D051057:Proto-Oncogene Proteins c-akt; D020928:Mitogen-Activated Protein Kinases; D019703:Calcineurin; D006152:Cyclic GMP; D002118:Calcium