The Journal of Rheumatology 2002; 29:7 1446 From the Osteoarthritis Research Unit, Hôpital Notre-Dame, Centre hospitalier de l’Université de Montréal, Montréal, Québec, Canada; UMR 7561CNRS-UHP, Faculté de Médecine, Université Henri Poincaré, Vandoeuvre-Lès-Nancy, France; Pharmaceutical Chemistry/Medicinal Chemistry, Eberhard Karls University, Tübingen, Germany; and Merckle GmbH, Ulm, Germany. Supported in part by grants from Merckle GmbH, Ulm, Germany; the Fonds de Recherche en Santé du Québec; and the Pôle Européen Universitaire, Nancy, France. C. Boileau, MSc, Doctoral Student, UMR 7561CNRS-UHP, Faculté de Médecine, Université Henri Poincaré; J. Martel-Pelletier, PhD, Professor of Medicine, Hôpital Notre-Dame, Centre hospitalier de l’Université de Montréal; J-Y. Jouzeau, PharmD, PhD, Assistant Professor of Pharmacology; P. Netter, MD, PhD, Professor of Medicine, UMR 7561CNRS-UHP, Faculté de Médecine, Université Henri Poincaré; F. Moldovan, MD, PhD, Assistant Professor of Medicine, Hôpital Notre- Dame, Centre hospitalier de l’Université de Montréal; S. Laufer, PhD, Professor, Pharmaceutical Chemistry/Medicinal Chemistry, Eberhard Karls University; S. Tries, PhD, Head, Preclinical Development, Merckle GmbH; J-P. Pelletier, MD, Professor of Medicine, Hôpital Notre-Dame, Centre hospitalier de l’Université de Montréal. Address request reprints to Dr. J-P. Pelletier, 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 Submitted October 12, 2001; revision accepted December 21, 2001. Licofelone (ML-3000), a Dual Inhibitor of 5-Lipoxygenase and Cyclooxygenase, Reduces the Level of Cartilage Chondrocyte Death in Vivo in Experimental Dog Osteoarthritis: Inhibition of Pro-Apoptotic Factors CHRISTELLE BOILEAU, JOHANNE MARTEL-PELLETIER, JEAN-YVES JOUZEAU, PATRICK NETTER, FLORINAMOLDOVAN, STEFAN LAUFER, SUSANNE TRIES, and JEAN-PIERRE PELLETIER ABSTRACT. Objective. To evaluate in vivo therapeutic efficacy of licofelone, a novel competitive dual inhibitor of 5-lipoxygenase (5-LOX) and cyclooxygenase (COX) in chondrocyte death in the canine ligament transection model of osteoarthritis (OA), and to explore its effect on factors involved in the apoptotic phenomenon, i.e., caspase-3, COX-2, and inducible nitric oxide synthase (iNOS). Methods. Cartilage specimens were obtained from 3 experimental groups of dogs: Group 1, dogs subjected to sectioning of the anterior cruciate ligament of the right knee and given placebo treat- ment; Groups 2 and 3, operated dogs that received oral treatment with licofelone (2.5 or 5.0 mg/kg/day, respectively) for 8 weeks starting immediately after surgery. All dogs were killed 8 weeks postsurgery. The cartilage level of chondrocyte death was detected by TUNEL reaction. Cartilage distribution of caspase-3, COX-2, and iNOS was documented by immunohistochemistry using specific antibodies, and other levels were quantified by morphometric analysis. Results. In cartilage specimens from placebo treated dogs a large number of chondrocytes in the superficial layers stained positive for TUNEL reaction. Treatment with therapeutic concentrations of licofelone (2.5 and 5.0 mg/kg/day) markedly reduced the level of chondrocyte apoptosis to the same extent in both therapeutic groups (p < 0.0001, p < 0.002, respectively). In these groups, the levels of caspase-3, COX-2, and iNOS in cartilage from both condyles and plateaus were also significantly decreased (p < 0.0001, p < 0.0001, p < 0.0002, respectively) compared to the control (placebo) group. Conclusion. Licofelone is an effective treatment in vivo, capable of reducing the level of OA chon- drocyte death. This effect is likely mediated by a decrease in the level of caspase-3 activity, which may be related to the reduced production of 2 major factors involved in chondrocyte apoptosis, NO and prostaglandin E 2 . These findings may explain some of the mechanisms by which licofelone reduces the progression of experimental OA. (J Rheumatol 2002;29:1446–53) Key Indexing Terms: LICOFELONE CHONDROCYTE DEATH EXPERIMENTAL OSTEOARTHRITIS Osteoarthritis (OA), the most common arthritic disease, includes changes at all levels of all joint tissues, namely cartilage, synovial membrane, and the subchondral bone 1 . The progressive loss of cartilage during the course of the disease is complex and likely has many origins. Based on recent studies on the pathophysiology of OA, the loss of cartilage matrix, one of the most characteristic morpholog- ical changes of OA, is related to several factors leading to an imbalance in synthetic and degradative processes 1,2 . Research has focused on factors responsible for reducing the anabolism of OA chondrocytes. Today, the role of proin- flammatory cytokines and nitric oxide (NO) seems prepon- derant 1-6 . However, an additional factor recently proposed is the death of chondrocytes. Studies have shown that apop- Personal non-commercial use only. 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