Roles of Rac and cytosolic phospholipase A2 in the intracellular signalling in response to titanium particles.
Titanium (Ti) particle is one of the prosthetic materials commonly used in implantation and has frequently been implicated in pathogenesis such as periprosthetic osteolysis. In the present study, we undertook to understand the intracellular signalling pathway stimulated by exogenous Ti at Rat-2 fibroblasts. By reporter gene analysis following transient transfections, exogenous Ti was shown to stimulate c-fos serum response element (SRE)-dependent luciferase activities in a dose-dependent manner. In addition, Ti-induced SRE activation was shown to be dramatically repressed by RacN17, a dominant negative mutant of Rac1, suggesting that Rac GTPase is essential for the signalling of Ti to c-fos SRE. Furthermore, pretreatment with MAFP, an inhibitor of cytosolic phospholipase A(2) (cPLA(2)), MK886, an inhibitor of 5-lipoxygenase (5-LO), or indomethacin, a general inhibitor of cyclooxygenase (COX), also significantly repressed Ti-induced SRE activation, suggesting mediatory roles of cPLA(2) and subsequent arachidonic acid (AA) metabolisms to leukotrienes (LTs) and prostaglandins (PGs) in the Ti signalling to c-fos SRE. Consistent with these results, intracellular levels of leukotriene B(4) (LTB(4)) and prostaglandin E(2) (PGE(2)) were Rac-dependently elevated in cells exposed to Ti particles.
Lee
Sang-Soo
SS
Graduate School of Biotechnology, Korea University, 5-1 Anam-dong, Sungbuk-gu, Seoul 136-701, South Korea.
Woo
Chang-Hoon
CH
Chang
Jun-Dong
JD
Kim
Jae-Hong
JH
D000818:Animals; D016718:Arachidonic Acid / Q000378:metabolism; D001672:Biocompatible Materials / Q000378:metabolism; D002467:Cell Nucleus / Q000378:metabolism; D002478:Cells, Cultured; D003600:Cytosol / Q000201:enzymology; D015232:Dinoprostone / Q000096:biosynthesis; D005347:Fibroblasts / Q000166:cytology / Q000187:drug effects / Q000201:enzymology; D015289:Leukotrienes / Q000096:biosynthesis; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D010741:Phospholipases A / Q000378:metabolism*; D054467:Phospholipases A2; D016760:Proto-Oncogene Proteins c-fos / Q000378:metabolism; D019908:Proto-Oncogene Proteins c-raf / Q000378:metabolism; D051381:Rats; D027602:Serum Response Element / Q000502:physiology; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D014025:Titanium / Q000494:pharmacology*; D020830:rac1 GTP-Binding Protein / Q000378:metabolism*
D001672:Biocompatible Materials; D015289:Leukotrienes; D016760:Proto-Oncogene Proteins c-fos; D016718:Arachidonic Acid; D014025:Titanium; D019908:Proto-Oncogene Proteins c-raf; D020928:Mitogen-Activated Protein Kinases; D010741:Phospholipases A; D054467:Phospholipases A2; D020830:rac1 GTP-Binding Protein; D015232:Dinoprostone