Reduced progression of experimental osteoarthritis in vivo by selective inhibition of inducible nitric oxide synthase

Abstract

Objective. To evaluate the in vivo therapeutic efficacy of N-iminoethyl-L-lysine (L-NIL), a selective inhibitor of inducible nitric oxide synthase (iNOS), on the progression of lesions in an experimental osteoar-thritis (OA) dog model. The effect of L-NIL on metal-loprotease activity, levels of interleukin-1P (IL-lp), prostaglandin E, (PGE,), and nitritehitrate in synovial fluid was determined. Methods. The OA model was created by sectioning the anterior cruciate ligament of the right stifle joint of mongrel dogs by a stab wound. Dogs were separated into experimental groups: Group 1 was made up of uuoperated dogs that received no treatment, group 2 were operated dogs with no treatment, and group 3 were operated dogs that received oral L-NIL (10 mg/kg/twice daily) starting immediately after surgery. The OA dogs were killed at 10 weeks after surgery. Results. Experiments showed that dog OA cartilage explants in culture produced an increased amount of NO (nitrite). Immunohistochemical study demonstrated that this was due to an increased level of iNOS in chondrocytes. OA dogs treated with L-NIL showed a reduction in the incidence of osteophytes compared with the untreated OA dogs (58% versus 92%) as well as in their size (mean ?z SEM 1.92 * 0.58 mm versus 5.08 k Supported in part by grants from thc Arthritis Society and MoiisantoISearle USA. 0.66 mm). Macroscopically, L-NIL decreased the size of the cartilage lesions by-50% both on condyles and plateaus. 'The histologic severity of both the cartilage lesions and synovial inflammation was significantly decreased in the L-NIL-treated dogs. Treatment with L-NIL also significantly decreased both collagenase and general metalloprotease activity in the cartilage and the levels of IL-lp, PGE,, and nitritehitrate in synovial fluid. Conclusion. This study demonstrated the effectiveness of a selective inhibitor of iNOS, L-NIL, in attenuating the progression of experimental OA. The data suggest that L-NIL may act by reducing the activity of metalloproteases in cartilage and the production of IL-1p by synovium, both of which are known to play a major role in the pathophysiology of OA structural changes.

The peroxisome proliferator–activated receptor γ agonist pioglitazone reduces the development of cartilage lesions in an experimental dog model of osteoarthritis: In vivo protective effects mediated through the inhibition of key signaling and catabolic pathways

“…Lesional joint cartilage in the placebo-treated group exhibited morphologic changes, including cartilage fibrillation and fissures, changes in cellularity, such as cloning and hypocellularity, and loss of Safranin O staining, as previously described (11,20,21) (Figure 2). A decrease in the histologic score of the medial femoral condyles, indicative of a reduced severity of the lesions, was observed in dogs with OA treated with pioglitazone (median histologic score 6.25 [range [3][4][5][6][7][8][9][10][11][12] in the placebo group versus 4.25 [range [3][4][5][6][7] in the 15 mg/day pioglitazone group and 5.5 [range [5][6] in the 30 mg/day pioglitazone group); this difference was sig- nificant following a dosage of 15 mg/day pioglitazone as compared with the placebo group (P Ͻ 0.05). This reduction in histologic scores was mainly related to a protective effect of pioglitazone treatment on the severity of structural changes and the loss of Safranin O staining.…”

“…Moreover, the increased level of NO has been linked to chondrocyte apoptosis (38,39). The role of NO in the pathophysiologic mechanisms of OA is also supported by a recent study showing that selective inhibition of iNOS could reduce the progression of experimental OA in dogs (11). This reduction of iNOS levels in OA chondrocytes by pioglitazone should also lead to reduced production of NO, and therefore this could be another factor that contributes to the positive effect of pioglitazone on the OA process.…”

“…This latter phenomenon is probably related to the synthesis and release, by the synovial membrane, of factors that are capable of inducing cartilage catabolism and other structural changes (1). Synovial inflammation would seem to play a determinant role in the progression of cartilage degradation, by stimulating the synthesis of proteases and catabolic factors that can degrade the extracellular matrix, for example, the matrix metalloproteinases (MMPs), proteases of the ADAMTS family, and other oxidative products such as nitric oxide (NO) (1,(11)(12)(13).…”

The Induction of Cell Death in Human Osteoarthritis Chondrocytes by Nitric Oxide Is Related to the Production of Prostaglandin E2 Via the Induction of Cyclooxygenase-2

“…Therefore, this finding suggests the positive influence of NO on PGE 2 synthesis in synovial joints of OA, particularly in the early stage of the disease, because the lesions observed in the experimental model are mild to moderate in severity. Also, the systemic administration of L-NIL reduced both the level of chondrocyte apoptosis and the progression of OA (12,13). Additional studies will determine whether COX inhibitors can prevent chondrocyte apoptosis in OA cartilage in vivo.…”

“…Besides causing degradation (10) or inhibiting the synthesis of cartilage matrix (11), NO may also induce chondrocyte apoptosis. We have previously reported that the systemic administration of iNOS inhibitor, N-iminoethyl-L-lysine (L-NIL), in experimentally induced OA in dogs has resulted in a reduction of articular cartilage damage and the levels of cell apoptosis and caspase-3, as determined immunohistochemically (12,13). In addition, there is a significant correlation between the level of nitrite production and the prevalence of apoptotic cells in cartilage tissue during experimentally induced OA in rabbits (14).…”