In

PMA/ pt

Control

Figure 2. ERW/Pt suppressed intracellular ROS 15 min after PMA treatment.

Values were statistically significant at P<0.005 compared with samples additionally treated with PMA.

It was suggested that active hydrogen produced from hydrogen molecules by catalysis on the surface of Pt nanoparticles would scavenge intracellular ROS. ERW/Pt also suppressed ERKmapk phosphorylation and excess intracellular ROS induced by PMA in murine epidermal JB6 cells (data not shown). In the recent study, intracellular ROS was known to activate MAP kinase, such as ERKmapK phosphorylation, and then AP-1, NFkB, iNOS and NOS were activated by MAP kinase. This cascade was related to the cell transformation in promotion stage1. It was suggested that suppression mechanism for cell transformation of ERW/Pt was similar to effective antioxidant for tumorigenesis such as ASA-2P via reducing excess intracellular ROS.

In conclusion, this is the first report about the suppression of two-stage cell transformation by ERW/Pt nanoparticles. We confirmed that ERW/Pt could scavenge excess intracellular ROS and strongly suppressed cell transformation at promotion stage. The detailed action mechanism of the reducing agents in ERW responsible for the ROS scavenging activity will be reported elsewhere.

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