Discovery of a New Class of Cathepsin K Inhibitors in Rhizoma Drynariae as Potential Candidates for the Treatment of Osteoporosis

Abstract

Rhizoma Drynariae (RD), as one of the most common clinically used folk medicines, has been reported to exert potent anti-osteoporotic activity. The bioactive ingredients and mechanisms that account for its bone protective effects are under active investigation. Here we adopt a novel in silico target fishing method to reveal the target profile of RD. Cathepsin K (Ctsk) is one of the cysteine proteases that is over-expressed in osteoclasts and accounts for the increase in bone resorption in metabolic bone disorders such as postmenopausal osteoporosis. It has been the focus of target based drug discovery in recent years. We have identified two components in RD, Kushennol F and Sophoraflavanone G, that can potentially interact with Ctsk. Biological studies were performed to verify the effects of these compounds on Ctsk and its related bone resorption process, which include the use of in vitro fluorescence-based Ctsk enzyme assay, bone resorption pit formation assay, as well as Receptor Activator of Nuclear factor κB (NF-κB) ligand (RANKL)-induced osteoclastogenesis using murine RAW264.7 cells. Finally, the binding mode and stability of these two compounds that interact with Ctsk were determined by molecular docking and dynamics methods. The results showed that the in silico target fishing method could successfully identify two components from RD that show inhibitory effects on the bone resorption process related to protease Ctsk.

Cathepsins in the Pathophysiology of Mucopolysaccharidoses: New Perspectives for Therapy

“…Experimental evidences suggest that inhibition of CTSS attenuates the progression of atherosclerosis during chronic kidney disease [84], improves sugar levels during type2 diabetes [208], and prevents autoantigen presentation and autoimmunity [229]. CTSK inhibitors have been proved successful improving osteoporosis [72,73,230]; however, concerns emerged over off-target effects of the inhibitors against other CTSs and CTSK inhibition at nonbone sites (i.e., skin, and cardiovascular and cerebrovascular sites). Recently, novel selective inhibitors for CTSK have been developed, showing beneficial effects on bone and cartilage in preclinical osteoarthritis models with a safety profile [71,206].…”

Chinese single herbs and active ingredients for postmenopausal osteoporosis: From preclinical evidence to action mechanism

“…Rhizoma Drynariae and its bioactive constituents were able to promote the osteoblastic proliferation, differentiation, and maturation (56,58,59,(62)(63)(64)(65)(66)(67)(68)(69)(70), inhibit osteoblastic apoptosis (71), suppress osteoclastogenesis (72)(73)(74), promote the apoptosis of osteoclasts (60), stimulate both cellular and humoral immunity (75), and inhibit cathepsins K processing (76,77).…”

A Simple Procedure for the Evaluation of Bone Vitality by Staining with a Tetrazolium Salt

“…A vast variety of growth factors, peptides or hormones coordinate the activities of various cell types (e.g., osteoblasts and osteoclasts) via complex signalling networks [ 20 , 21 , 22 , 23 , 24 , 25 ]. In addition, mechanical stimulation [ 26 ], local inflammatory activity [ 27 ] or factors controlling osteoporosis [ 28 ] are involved in the process of fracture healing. The complexity and the intricate processes of signalling in bone formation during clinical fracture scenarios are not fully understood [ 26 ].…”