title: Molecular targets in osteoarthritis: metalloproteinases and their inhibitors.
abstract: The debilitating destruction of joint tissues seen in osteoarthritis (OA) is due, in large part, to the degradative activity of metalloproteinase (MP) enzymes that target extracellular matrix (ECM) components within articular cartilage. Although successful in suppressing the pain and inflammation associated with this disease, conventional OA therapeutics do not inhibit the underlying tissue catabolism, allowing the disease to progress into irreversible ECM loss and chronic disability. Therapeutic inhibition of metalloproteinase activity is not a new concept, however, its transfer into clinical use has been frustrating. Disappointing results from clinical trials with small molecule inhibitors of metalloproteinases have highlighted the critical importance of inhibitor specificity, and the need to identify the individual metalloproteinases responsible for joint destruction. We discuss strategies of inhibition using small molecule inhibitors and tissue inhibitors of metalloproteinases (TIMPs) engineered to increase inhibitory specificity, and present new data using of new reagents such as ribozymes and inhibitory RNAs that repress expression of specific enzymes. Recent data has implicated the disease stage-dependent involvement of matrix metalloproteinase-1, -2, -3, -9, -13, ADAM-17/TACE (tumor-necrosis factor-alpha converting enzyme), and ADAMTS-5 (a disintegrin and metalloproteinase with thrombospondin 1 motifs) as major in vivo mediators of the ECM degradation seen in OA, and as such, they represent promising therapeutic targets. We conclude that the concept of molecular polypharmacy, in which the relevant enzymes are selectively targeted with multiple directed therapies, may offer a new therapeutic strategy that prevents joint destruction and minimizes toxicities.
authors.affiliation: Norris Cotton Cancer Center, Dartmouth-Hitchcock Medical Center, Rubin Building, Room 602, 1 Medical Center Drive, Lebanon, NH 03756, USA. brinckerhoff@dartmouth.edu
authors.forename: P S
authors.initials: PS
authors.lastname: Burrage
authors.forename: C E
authors.initials: CE
authors.lastname: Brinckerhoff
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002986:Clinical Trials as Topic; D006801:Humans; D006868:Hydrolysis; D045726:Metalloproteases / Q000037:antagonists & inhibitors* / Q000737:chemistry; D008969:Molecular Sequence Data; D010003:Osteoarthritis / Q000188:drug therapy* / Q000201:enzymology; D011480:Protease Inhibitors / Q000494:pharmacology / Q000627:therapeutic use*
chemical_list: D011480:Protease Inhibitors; D045726:Metalloproteases