title: Tiludronate inhibits interleukin-6 synthesis in osteoblasts: inhibition of phospholipase D activation in MC3T3-E1 cells.
abstract: In previous studies, we have reported that PGF2alpha stimulates phosphoinositide hydrolysis by phospholipase C and phosphatidylcholine hydrolysis by phospholipase D through heterotrimeric GTP-binding protein in osteoblast-like MC3T3-E1 cells, and that PGF2alpha and PGE1 induce interleukin-6 (IL-6) synthesis via activation of protein kinase C and protein kinase A, respectively. In the present study, we investigated the effect of tiludronate, a bisphosphonate known to inhibit bone resorption, on the PGF2alpha- and PGE1-induced IL-6 synthesis in these cells. Tiludronate significantly suppressed the PGF2alpha-induced IL-6 secretion in a dose-dependent manner in the range between 0.1 and 30 microM. However, the IL-6 secretion induced by PGE1 or (Bu)2cAMP was hardly affected by tiludronate. The choline formation induced by PGF2alpha was reduced by tiludronate dose-dependently in the range between 0.1 and 30 microM. On the contrary, tiludronate had no effect on PGF2alpha-induced formation of inositol phosphates. Tiludronate suppressed the choline formation induced by NaF, known as an activator of heterotrimeric GTP-binding protein. However, tiludronate had little effect on the formation of choline induced by TPA, a protein kinase C activator. Tiludronate significantly inhibited the NaF-induced IL-6 secretion in human osteoblastic osteosarcoma Saos-2 cells. These results strongly suggest that tiludronate inhibits PGF2alpha-induced IL-6 synthesis via suppression of phosphatidylcholine-hydrolyzing phospholipase D activation in osteoblasts, and that the inhibitory effect is exerted at the point between heterotrimeric GTP-binding protein and phospholipase D.
authors.affiliation: Department of Internal Medicine, Chubu National Hospital, National Institute for Longevity Sciences, Obu, Aichi, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Tokuda
authors.forename: O
authors.initials: O
authors.lastname: Kozawa
authors.forename: A
authors.initials: A
authors.lastname: Harada
authors.forename: T
authors.initials: T
authors.lastname: Uematsu
mesh_terms: D016475:3T3 Cells; D000527:Alprostadil / Q000494:pharmacology; D000818:Animals; D002648:Child; D002794:Choline / Q000096:biosynthesis; D015237:Dinoprost / Q000494:pharmacology; D004164:Diphosphonates / Q000494:pharmacology*; D004789:Enzyme Activation; D005260:Female; D019204:GTP-Binding Proteins / Q000378:metabolism; D006801:Humans; D007295:Inositol Phosphates / Q000096:biosynthesis; D015850:Interleukin-6 / Q000096:biosynthesis; D051379:Mice; D010006:Osteoblasts / Q000187:drug effects* / Q000378:metabolism; D010739:Phospholipase D / Q000037:antagonists & inhibitors* / Q000378:metabolism; D012969:Sodium Fluoride / Q000494:pharmacology; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014407:Tumor Cells, Cultured; D000093242:Interleukin-6 Inhibitors
chemical_list: D000527:Alprostadil; D002794:Choline; D015237:Dinoprost; D004164:Diphosphonates; D019204:GTP-Binding Proteins; D007295:Inositol Phosphates; D015850:Interleukin-6; D010739:Phospholipase D; D012969:Sodium Fluoride; D013755:Tetradecanoylphorbol Acetate; D000093242:Interleukin-6 Inhibitors; C058651:tiludronic acid