Sphingosine-1-phosphate attenuates proteoglycan aggrecan expression via production of prostaglandin E2 from human articular chondrocytes.
BACKGROUND
Sphingosine-1-phosphate (S1P), a downstream metabolite of ceramide, induces various bioactivities via two distinct pathways: as an intracellular second messenger or through receptor activation. The receptor for S1P (S1PR) is the family of Endothelial differentiation, sphingolipid G-protein-coupled receptor (EDG). We have here attempted to reveal the expression of EDG/S1PR in human articular chondrocytes (HAC), exploring the implications of S1P in cartilage degradation.


METHODS
Articular cartilage specimens were obtained from patients with rheumatoid arthritis (RA), osteoarthritis (OA) or traumatic fracture (representing normal chondrocytes) who underwent joint surgery. Isolated HAC were cultured in vitro by monolayer and stimulated with S1P in the presence or absence of inhibitors of signaling molecules. Stimulated cells and culture supernatants were collected and subjected to analyses using reverse transcription-polymerase chain reaction (RT-PCR), Western blotting, and enzyme-linked immunosorbent assay (ELISA).


RESULTS
All of the tested HAC samples showed positive results in terms of EDG/S1PR expression in basal condition. When HAC was stimulated with S1P, a significant increase in prostaglandin (PG) E2 production was observed together with enhanced expression of cyclooxygenase (COX)-2. S1P stimulated extracellular signal-regulated kinase (ERK) and p38 mitogen-activated protein kinase (MAPK) in HAC, and the PGE2 induction was abrogated by PD98059 and SB203580. Pertussis toxin inhibited the PGE2 induction from HAC by S1P, suggesting an essential role for Gi protein. S1P also attenuated the expression of proteoglycan aggrecan, a component of cartilage matrix, in HAC at transcriptional level.


CONCLUSIONS
It was suggested that the S1P-induced PGE2 was at least in part involved in the aggrecan-suppressing effect of S1P, seeing as COX inhibitors attenuated the effect. Accordingly, S1P might play an important role in cartilage degradation in arthritides.
Masuko
Kayo
K
Department of Bioregulation and Proteomics, Institute of Medical Science, St. Marianna University School of Medicine, Kanagawa, Japan. kmarianna@mac.com
Murata
Minako
M
Nakamura
Hiroshi
H
Yudoh
Kazuo
K
Nishioka
Kusuki
K
Kato
Tomohiro
T
D000368:Aged; D000369:Aged, 80 and over; D053674:Aggrecans / Q000378:metabolism*; D001172:Arthritis, Rheumatoid / Q000378:metabolism; D002358:Cartilage, Articular / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D019902:Chondrocytes / Q000187:drug effects / Q000378:metabolism*; D051546:Cyclooxygenase 2 / Q000187:drug effects / Q000378:metabolism; D015232:Dinoprostone / Q000378:metabolism*; D048049:Extracellular Signal-Regulated MAP Kinases / Q000187:drug effects / Q000378:metabolism; D005260:Female; D006801:Humans; D008246:Lysophospholipids / Q000378:metabolism* / Q000494:pharmacology; D020935:MAP Kinase Signaling System / Q000187:drug effects / Q000502:physiology; D008297:Male; D008565:Membrane Proteins / Q000187:drug effects / Q000378:metabolism; D008875:Middle Aged; D010003:Osteoarthritis / Q000378:metabolism; D049349:Receptors, Lysosphingolipid / Q000187:drug effects / Q000378:metabolism; D015290:Second Messenger Systems / Q000187:drug effects / Q000502:physiology; D013110:Sphingosine / Q000031:analogs & derivatives* / Q000378:metabolism / Q000494:pharmacology; D015854:Up-Regulation / Q000187:drug effects / Q000502:physiology; D048051:p38 Mitogen-Activated Protein Kinases / Q000187:drug effects / Q000378:metabolism
D053674:Aggrecans; D008246:Lysophospholipids; D008565:Membrane Proteins; D049349:Receptors, Lysosphingolipid; C060506:sphingosine 1-phosphate; D051546:Cyclooxygenase 2; C496540:PTGS2 protein, human; D048049:Extracellular Signal-Regulated MAP Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D015232:Dinoprostone; D013110:Sphingosine