Prevention of cisplatin-induced kidney epithelial cell apoptosis with a Cu superoxide dismutase-mimetic [copper2II(3,5-ditertiarybutylsalicylate)4(ethanol)4]

Copper2II(3,5-ditertiarybutylsalicylate)4(ethanol)4, Cu2II(3,5-DTBS)4(Eth)4, was synthesized and characterized for evaluation as an anti-apoptotic superoxide dismutase (SOD)-mimetic in an in vitro 50 μM cis-diamminedichloroplatinum(II), [PtII(NH3)2(Cl)2]-treated kidney proximal tubule epithelial cell (LLC-PK) preparation. Synthesized Cu2II(3,5-DTBS)4(Eth)4 was characterized by elemental analysis, FTIR spectrophotometry, and X-ray crystallography. The IC50 for SOD-mimetic reactivity of Cu2II(3,5-DTBS)4(Eth)4, determined with the xanthine/xanthine oxidase/nitroblue tetrazolium (NBT) system, was found to be 2.69 μM for the binuclear chelate. Pretreatment of LLC-PK cells with 20 μM Cu2II(3,5-DTBS)4(Eth)4 prevented 50 μM PtII(NH3)2(Cl)2-induced and superoxide-mediated apoptosis. This SOD-mimetic significantly suppressed PtII(NH3)2(Cl)2-induced translocation of pro-apoptotic Bax from the cytosol to the inner mitochondrial membrane, prevented PtII(NH3)2(Cl)2-induced release of cytochrome c from the inner mitochondrial membrane and the appearance of cytochrome c   in the cytosol, and prevented conversion of procaspase-3 to active caspase-3. Cu2II(3,5-DTBS)4(Eth)4 treatment inhibited PtII(NH3)2(Cl)2-mediated tubular cell injury by preventing activation of cellular mechanisms that lead to proximal tubule kidney cell death. Based on these observations, PtII(NH3)2(Cl)2- induced O2--mediated apoptosis can be mechanistically overcome with a small molecular mass SOD-mimetic, Cu2II(3,5-DTBS)4(Eth)4. Prior treatment of patients who are to undergo treatment with PtII(NH3)2(Cl)2 for their neoplastic disease with Cu2II(3,5-DTBS)4(Eth)4 may be beneficial to these patients.