Peptide Aldehyde Inhibitors of Cathepsin K Inhibit Bone Resorption Both In Vitro and In Vivo

Abstract

We have shown previously that cathepsin K, a recently identified member of the papain superfamily of cysteine proteases, is expressed selectively in osteoclasts and is the predominant cysteine protease in these cells. Based upon its abundant cell type-selective expression, potent endoprotease activity at low pH and cellular localization at the bone interface, cathepsin K has been proposed to play a specialized role in osteoclast-mediated bone resorption. In this study, we evaluated a series of peptide aldehydes and demonstrated that they are potent cathepsin K inhibitors. These compounds inhibited osteoclast-mediated bone resorption in fetal rat long bone (FRLB) organ cultures in vitro in a concentration-dependent manner. Selected compounds were also shown to inhibit bone resorption in a human osteoclast-mediated assay in vitro. Cbz-Leu-Leu-Leu-H (in vitro enzyme inhibition K i,app ‫؍‬ 1.4 nM) inhibited parathyroid hormone (PTH)-stimulated resorption in the FRLB assay with an IC-50 of 20 nM and inhibited resorption by isolated human osteoclasts cultured on bovine cortical bone slices with an IC-50 of 100 nM. In the adjuvant-arthritic (AA) rat model, in situ hybridization studies demonstrated high levels of cathepsin K expression in osteoclasts at sites of extensive bone loss in the distal tibia. Cbz-Leu-Leu-Leu-H (30 mg/kg, intraperitoneally) significantly reduced this bone loss, as well as the associated hind paw edema. In the thyroparathyriodectomized rat model, Cbz-Leu-Leu-Leu-H inhibited the increase in blood ionized calcium induced by a 6 h infusion of PTH. These data indicate that inhibitors of cathepsin K are effective at reducing osteoclastmediated bone resorption and may have therapeutic potential in diseases of excessive bone resorption such as rheumatoid arthritis or

NOD2 Contributes to Porphyromonas gingivalis–induced Bone Resorption

“…In fact, in vitro and in vivo studies suggest that the 2 types of proteases, MMP-9 and cathepsin K, are involved in bone resorption mediated by osteoclasts, performing the collagen degradation in bone (Delaisse et al, 2003;Everts et al, 1992). Votta et al (1997) found reduced bone resorption, both in vitro and in vivo, using an inhibitor of cathepsin K. Moreover, cathepsin K-deficient mice showed significant osteopetrosis (Saftig et al, 1998;Gowen et al, 1999). In periodontal area, increased levels of cathepsin K Figure 4.…”

Oligogalacturonic acid inhibit bone resorption and collagen degradation through its interaction with type I collagen

“…Inhibition of Cathepsin K activity was assessed using a fluorimetric assay as previously described (20). Z-Phe-Arg-AMC (Z-Phe-Arg 7-amido-4-methylcoumarin hydrochloride, SIGMA, France) at 10 µM was used as cathepsin K substrate.…”

Effects of Proteasome Inhibitors on Fertilization of the Sea Urchin Anthocidaris crassispina

“…In contrast, leupeptin, chymostatin, and E-64-d showed no appreciable inhibition toward fertilization at 100 mM. Although MG-132 can also inhibit cysteine protease activity, 17) the effect of MG-132 appears to be on the proteasome, since E-64-d (a potent cysteine-protease inhibitor) showed no inhibition toward fertilization (Fig. 1).…”