Selective inhibition of inducible nitric oxide synthase reduces progression of experimental osteoarthritis in vivo: possible link with the reduction in chondrocyte apoptosis and caspase 3 level.
OBJECTIVE
To evaluate the in vivo therapeutic efficacy of N-iminoethyl-L-lysine (L-NIL), a selective inhibitor of inducible nitric oxide synthase, on the progression of structural lesions in the experimental canine model of osteoarthritis (OA), and to explore the effect of L-NIL on the level of chondrocyte apoptosis and of important proteins involved in the apoptotic phenomenon, i.e., caspase 3 (inducer) and Bcl-2 (inhibitor).


METHODS
The OA model was created by sectioning the anterior cruciate ligament. Dogs were placed into 4 experimental groups: unoperated dogs that received no treatment (controls), operated (OA) dogs that received placebo treatment, OA dogs that received oral L-NIL at 10 mg/kg/day, and OA dogs that received oral L-NIL at 1.0 mg/kg/day. In both L-NIL groups, treatment started immediately after surgery. The OA dogs were killed at 12 weeks after surgery.


RESULTS
OA dogs treated with L-NIL showed a reduction in the size of osteophytes and a significant decrease in the severity of macroscopic and histologic cartilage lesions on both condyles and plateaus, compared with untreated OA dogs. L-NIL treatment also significantly decreased metalloprotease activity in cartilage. Immunohistochemical analysis revealed that the levels of chondrocyte apoptosis, caspase 3, and Bcl-2 were markedly increased in OA cartilage (P < 0.0001). A positive correlation between the levels of chondrocyte apoptosis and levels of caspase 3 was found (r = 0.54, P < 0.0001). OA dogs treated with the higher dosage L-NIL showed significantly reduced levels of chondrocyte apoptosis (P < 0.003) and caspase 3 (P < 0.04), but no effect on the increased level of Bcl-2 was demonstrated.


CONCLUSIONS
This study shows that L-NIL reduces the progression of experimental OA. This effect could be related to a reduced level of chondrocyte apoptosis and is likely mediated by a decrease in the level of caspase 3 activity. A sparing effect of L-NIL on the increased level of Bcl-2 may also be a contributing factor.
Pelletier
J P
JP
Hôpital Notre-Dame, Centre Hospitalier de l'Université de Montréal, Quebec, Canada.
Jovanovic
D V
DV
Lascau-Coman
V
V
Fernandes
J C
JC
Manning
P T
PT
Connor
J R
JR
Currie
M G
MG
Martel-Pelletier
J
J
D000818:Animals; D017209:Apoptosis; D002358:Cartilage, Articular / Q000473:pathology / Q000503:physiopathology; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism; D018450:Disease Progression; D004285:Dogs; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D007150:Immunohistochemistry; D008239:Lysine / Q000031:analogs & derivatives* / Q000494:pharmacology; D020782:Matrix Metalloproteinases / Q000378:metabolism; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors*; D052247:Nitric Oxide Synthase Type II; D010003:Osteoarthritis / Q000201:enzymology* / Q000473:pathology / Q000503:physiopathology*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism
D004791:Enzyme Inhibitors; C090663:N(6)-(1-iminoethyl)lysine; D019253:Proto-Oncogene Proteins c-bcl-2; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; D053148:Caspase 3; D020169:Caspases; D020782:Matrix Metalloproteinases; D008239:Lysine