ab21203

Diacerein reduces the level of cartilage chondrocyte DNA fragmentation and death in experimental dog osteoarthritic cartilage at the same time that it inhibits caspase-3 and inducible nitric oxide synthase

J.-P. Pelletier, F. Mineau, C. Boileau, J. Martel-Pelletier

Osteoarthritis Research Unit, Hôpital Notre-Dame, Centre hospitalier de l'Université de Montréal, Montréal, Québec, Canada.

ABSTRACT
Objective
The primary objective of this study was to evaluate the ex vivo therapeutic efficacy of diacerein and its active metabolite, rhein, on osteoarthritic (OA) cartilage chondrocyte DNA fragmentation and death in the experimental canine model of OA. The study also aimed to explore the effect of the drug on the level of important factors involved in this phenomenon, i.e., caspase-3 and inducible nitric oxide synthase (iNOS).

Methods
OA knee cartilage was obtained from dogs that had received surgical sectioning of the anterior cruciate ligament (ACL) and were sacrificed 12 weeks after surgery. Cartilage explants were cultured in the presence or absence of therapeutic concentrations of diacerein (20 mg/ml) or rhein (20 mg/ml). Cartilage specimens were stained for TUNEL reaction and immunostained using specific antibodies for active caspase-3 and iNOS. Morphometric analyses were also performed.

Results
In OA cartilage specimens, a large number of chondrocytes in the superficial layers stained positive for TUNEL reaction. Treatment with therapeutic concentrations of diacerein (20 mg/ml) or rhein (20 mg/ml) significantly reduced the level of chondrocyte DNA fragmentation to about the same extent in both treatment groups (P < 0.006, P < 0.002, respectively). The levels of caspase-3 and iNOS in cartilage explants were also significantly decreased (caspase-3, diacerein P < 0.04; caspase-3, rhein P < 0.0003; and iNOS, rhein P < 0.009, respectively) when compared to the control group.

Conclusions
This study shows that diacerein/rhein can effectively reduce the level of OA chondrocyte DNA fragmentation and death under the present experimental conditions. This effect is mediated by a decrease in the level of caspase-3 expression, which could possibly be related in part to the reduced level of iNOS and secondarily to NO production. These findings provide additional new information about the mechanisms of action of diacerein on the progression of OA.

Key words
Diacerein, chondrocyte death, experimental OA.

Supported in part by grants from Les Laboratoires Negma-Lerads, Toussus-le-Noble, Magny-les-Hameaux, France, the Fonds de la recherche en santé du Québec (FRSQ), and Le Groupe de recherche des maladies rhumatismales du Québec.
Please address correspondence to: Jean-Pierre Pelletier, MD, Osteoarthritis Research Unit, Hôpital Notre-Dame, Centre Hospitalier de l'Université de Montréal, 1560, rue Sherbrooke Est, Montréal, Québec, Canada, H2L 4M1.
E-mail: dr@jppelletier.ca