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

Arthritis Rheum. 2000 Jun;43(6):1290-9. doi: 10.1002/1529-0131(200006)43:6<1290::AID-ANR11>3.0.CO;2-R.


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.

Conclusion: 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.

MeSH terms

  • Animals
  • Apoptosis
  • Cartilage, Articular / pathology
  • Cartilage, Articular / physiopathology
  • Caspase 3
  • Caspases / metabolism
  • Disease Progression
  • Dogs
  • Enzyme Inhibitors / pharmacology*
  • Immunohistochemistry
  • Lysine / analogs & derivatives*
  • Lysine / pharmacology
  • Matrix Metalloproteinases / metabolism
  • Nitric Oxide Synthase / antagonists & inhibitors*
  • Nitric Oxide Synthase Type II
  • Osteoarthritis / enzymology*
  • Osteoarthritis / pathology
  • Osteoarthritis / physiopathology*
  • Proto-Oncogene Proteins c-bcl-2 / metabolism


  • Enzyme Inhibitors
  • N(6)-(1-iminoethyl)lysine
  • Proto-Oncogene Proteins c-bcl-2
  • Nitric Oxide Synthase
  • Nitric Oxide Synthase Type II
  • Caspase 3
  • Caspases
  • Matrix Metalloproteinases
  • Lysine