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Inhibition of Cathepsin Activity in a Cell‐Based Assay by a Light‐Activated Ruthenium Compound
Author(s) -
Respondek Tomasz,
Sharma Rajgopal,
Herroon Mackenzie K.,
Garner Robert N.,
Knoll Jessica D.,
Cueny Eric,
Turro Claudia,
Podgorski Izabela,
Kodanko Jeremy J.
Publication year - 2014
Publication title -
chemmedchem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.817
H-Index - 100
eISSN - 1860-7187
pISSN - 1860-7179
DOI - 10.1002/cmdc.201400081
Subject(s) - ruthenium , chemistry , combinatorial chemistry , biochemistry , catalysis
Abstract Light‐activated inhibition of cathepsin activity was demonstrated in a cell‐based assay. Inhibitors of cathepsin K, Cbz‐Leu‐NHCH 2 CN ( 2 ) and Cbz‐Leu‐Ser(OBn)‐CN ( 3 ), were caged within the complexes cis ‐[Ru(bpy) 2 ( 2 ) 2 ]Cl 2 ( 4 ) and cis ‐[Ru(bpy) 2 ( 3 ) 2 ](BF 4 ) 2 ( 5 ) (bpy=2,2′‐bipyridine) as 1:1 mixtures of Δ and Λ stereoisomers. Complexes 4 and 5 were characterized by 1 H NMR, IR, and UV/Vis spectroscopies and electrospray mass spectrometry. Photochemical experiments confirm that 4 releases two molecules of 2 upon exposure to visible light for 15 min, whereas release of 3 by 5 requires longer irradiation times. IC 50 determinations against purified cathepsin K under light and dark conditions with 4 and 5 confirm that inhibition is enhanced from 35‐ to 88‐fold, respectively, upon irradiation with visible light. No apparent toxicity was observed for 4 in the absence or presence of irradiation in bone marrow macrophage (BMM) or PC3 cells, as determined by MTT assays, at concentrations up to 10 μ M . Compound 5 is well tolerated at lower concentrations (<1 μ M ), but does show growth‐inhibitory effects at higher concentrations. Confocal microscopy experiments show that 4 decreases intracellular cathepsin activity in osteoclasts with light activation. These results support the further development of caged nitrile‐based inhibitors as chemical tools for investigating spatial aspects of proteolysis within living systems.