Hexosaminidase inhibitors as new drug candidates for the therapy of osteoarthritis.

BACKGROUND: Articular cartilage from patients with osteoarthritis is characterized by a decreased concentration and reduced size of glycosaminoglycans. Degeneration of the cartilage matrix is a multifactorial process, which is due in part to accelerated glycosaminoglycan catabolism. Recently, we have demonstrated that hexosaminidase represents the dominant glycosaminoglycan-degrading glycosidase released by chondrocytes into the extracellular compartment and is the dominant glycosidase in synovial fluid from patients with osteoarthritis. Inhibition of hexosaminidase activity may represent a novel approach to the prevention of cartilage matrix glycosaminoglycan degradation and a potentially new strategy to treat osteoarthritis.
RESULTS: We have synthesized and investigated a series of iminocyclitols designed as transition-state analog inhibitors of human hexosaminidase, and demonstrated that the five-membered iminocyclitol 4 expresses the strongest inhibitory activity with K(i)=24 nM. Inhibition of hexosaminidase activity in human cultured articular chondrocytes and human chondrosarcoma cells with iminocyclitol 4 resulted in accumulation of hyaluronic acid and sulfated glycosaminoglycans in the cell-associated fraction. Similarly, incubation of human cartilage tissue with iminocyclitol 4 resulted in an accumulation of glycosaminoglycans in the pericellular compartment.
CONCLUSIONS: Inhibition of hexosaminidase activity represents a new strategy for preventing or even reversing cartilage degradation in patients with osteoarthritis.