PD-0200347, an alpha2delta ligand of the voltage gated calcium channel, inhibits in vivo activation of the Erk1/2 pathway in osteoarthritic chondrocytes: a PKCalpha dependent effect.
OBJECTIVE
To explore the in vivo effects of PD-0200347, an alpha(2)delta ligand of voltage gated Ca(2+) channels, on cell signalling in osteoarthritic (OA) chondrocytes from an experimental dog model, and examine the effect of PD-0200347 on the major signalling pathways involved in OA cartilage degradation.


METHODS
OA was surgically induced in dogs by sectioning the anterior cruciate ligament. OA dogs were divided into three groups and treated orally with (a) placebo; (b) 15 mg/kg/day PD-0200347, or (c) 90 mg/kg/day PD-0200347. The animals were killed 12 weeks after surgery. Cartilage specimens from femoral condyles and tibial plateaus were processed for immunohistochemistry. Specific antibodies against the phosphorylated form of PKCalpha, Ras, c-Raf, the MAP kinases Erk1/2, p38, JNK, and the transcription factors, CREB and Elk-1, were used.


RESULTS
Levels of all the tested signalling mediators were increased in the placebo treated (OA) group compared with the normal group. PD-0200347 treatment significantly reduced the levels of the active forms of PKCalpha, c-Raf, Erk1/2, and Elk-1; however, the levels of the active forms of Ras, p38, JNK, and CREB were not affected by the PD-0200347 treatment.


CONCLUSIONS
The action of PD-0200347 on OA chondrocytes is probably mediated through the inhibition of Erk1/2 activation via a Ras independent mechanism. This effect is associated with reduction of the activation of transcription factors such as Elk-1, which leads to the inhibition of the induction of the major catabolic factors involved in the degradation process of OA cartilage.
Boileau
C
C
Osteoarthritis Research Unit, Notre-Dame Hospital, University of Montreal Hospital Centre, Montreal, Quebec, Canada H2L 4M1.
Martel-Pelletier
J
J
Brunet
J
J
Schrier
D
D
Flory
C
C
Boily
M
M
Pelletier
J-P
JP
D000818:Animals; D050882:CREB-Binding Protein / Q000378:metabolism; D015220:Calcium Channels / Q000187:drug effects; D019902:Chondrocytes / Q000187:drug effects* / Q000378:metabolism; D004195:Disease Models, Animal; D004285:Dogs; D004305:Dose-Response Relationship, Drug; D008024:Ligands; D048670:MAP Kinase Kinase 4 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000187:drug effects* / Q000378:metabolism; D010003:Osteoarthritis / Q000378:metabolism / Q000473:pathology*; D051571:Protein Kinase C-alpha / Q000502:physiology*; D019908:Proto-Oncogene Proteins c-raf / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D050807:ets-Domain Protein Elk-1 / Q000378:metabolism; D005680:gamma-Aminobutyric Acid / Q000494:pharmacology*; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism; D018631:ras Proteins / Q000378:metabolism
D015220:Calcium Channels; D008024:Ligands; C497431:PD-0200347; D050807:ets-Domain Protein Elk-1; D005680:gamma-Aminobutyric Acid; D050882:CREB-Binding Protein; D019908:Proto-Oncogene Proteins c-raf; D051571:Protein Kinase C-alpha; D048052:Mitogen-Activated Protein Kinase 3; D048051:p38 Mitogen-Activated Protein Kinases; D048670:MAP Kinase Kinase 4; D018631:ras Proteins