title: Inhibition of human rheumatoid arthritis synovial cell survival by hecogenin and tigogenin is associated with increased apoptosis, p38 mitogen-activated protein kinase activity and upregulation of cyclooxygenase-2.
abstract: We conducted our study to assess the antiproliferative and proapoptotic potential of hecogenin and tigogenin, two saponins which are structurally similar to diosgenin. We particularly focused our attention on mitogen-activated protein kinase (MAPK) activation in relation to apoptosis but also with the COX-2 expression and activity. Rheumatoid arthritis (RA) synoviocytes were isolated from fresh synovial biopsies obtained from five RA patients undergoing hip arthroplasty. Measurement of cell proliferation was determined using the MTT assay. Apoptosis was evaluated by studying caspase-8, caspase-9 and caspase-3 activities but also by quantification of DNA fragmentation. Quantification of human phospho-MAPKs was realized by ELISA. COX-2 expression was demonstrated by Western blot analysis and COX-2 activity by assay of endogenous prostaglandin E2 (PGE2) production. Tigogenin was more effective than hecogenin in inducing apoptosis in human RA fibroblast-like synoviocytes (FLS) which was caspase dependent but poly(ADP-ribose) polymerase independent and characterized by DNA fragmentation. Our results demonstrated hecogenin- and tigogenin-induced apoptosis through activation of p38 without affecting the JNK and ERK pathways. Indeed, pretreatment with a p38 inhibitor decreased saponin-induced apoptosis with a significant decrease in DNA fragmentation. Furthermore, the rate of apoptosis induced by hecogenin or tigogenin was associated with overexpression of COX-2 correlated with overproduction of endogenous PGE2. These new results provide strong evidence that a family of structurally similar plant steroids is capable of inducing apoptosis in human RA FLS with different rates and different signalling pathways. This study also confirms the discussed appearance of the downregulation or upregulation of COX-2 in cell apoptosis as a function of cell type.
authors.affiliation: Laboratoire de Biochimie, UPRES EA 4021, Faculté de Pharmacie, 87025 Limoges Cedex, France. bertrand.liagre@unilim.fr
authors.forename: Bertrand
authors.initials: B
authors.lastname: Liagre
authors.forename: Pascale
authors.initials: P
authors.lastname: Vergne-Salle
authors.forename: David Y
authors.initials: DY
authors.lastname: Leger
authors.forename: Jean-Louis
authors.initials: JL
authors.lastname: Beneytout
mesh_terms: D017209:Apoptosis / Q000187:drug effects*; D001172:Arthritis, Rheumatoid / Q000201:enzymology / Q000473:pathology*; D053181:Caspase 8 / Q000378:metabolism; D053453:Caspase 9 / Q000378:metabolism; D016923:Cell Death / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D048430:Cell Shape / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D051546:Cyclooxygenase 2 / Q000235:genetics*; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D005347:Fibroblasts / Q000187:drug effects / Q000473:pathology; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism; D008875:Middle Aged; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism; D012502:Sapogenins / Q000737:chemistry / Q000494:pharmacology*; D012503:Saponins / Q000494:pharmacology; D013150:Spirostans / Q000737:chemistry / Q000494:pharmacology*; D013582:Synovial Fluid / Q000166:cytology* / Q000187:drug effects / Q000201:enzymology; D015854:Up-Regulation / Q000187:drug effects; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism*