The combined use of platinum nanoparticles and hydrogen molecules induces caspase-dependent apoptosis

We previously reported electrochemically reduced water (ERW), produced near the cathode by electrolysis, exhibits reductive activity. We also revealed that ERW contains Pt nanoparticles (Pt nps) derived from Pt-coated titanium electrodes in addition to high concentration of dissolved molecular hydrogen (H₂) by in vitro assay, and Pt nps exhibit powerful ROS scavenger activity and catalysis activity converting H₂ to active hydrogen. Our study investigates apoptosis inducibility of H₂ and synthesized Pt nps on human promyelocytic leukaemia HL60 cells. Human promyelocytic leukaemia cells (HL60) were cultured in RPMI 1640 medium supplemented with 10% FBS, 2.0 mM l-glutamine, 100 U/ml penicillin and 100 U/ml streptomycin. Cultures were incubated in an atmosphere of 75%(v/v) H₂/20%(v/v) O₂/5%(v/v) CO₂, 75%(v/v) He/20%(v/v) O₂/5%(v/v) CO₂ atmosphere or 75%(v/v) N2/20%(v/v) O₂/5%(v/v) CO₂ atmosphere for 12-48 hr after incubated with Pt nps for 2 h. Untreated cultures were included as controls. Cytotoxicity was determined by cell-counter. Apoptosis pathway of HL60 cells was investigated by Sub G-1 assay.

Growth suppression was not observed when cells were treated with Pt nps or H₂ only. Analysis of cell cycle and activity of caspase-3 suggested that combination use of both Pt nps and H₂ induced apoptosis in HL60 cells. Our caspase activity experimentation suggests that apoptosis was caused via caspase-8 activation. These results suggested that atomic hydrogen from H₂ induces caspase-8 dependent apoptosis. The cytotoxicity was not detected in Pt nps or H₂ separately treated cells. Apoptosis was determined only when cells were treated with both Pt nps and H₂, suggesaspase-8 dependent apoptosis was caused by atomic hydrogen produced from H₂ by catalyst activity of Pt nps.