Transient generation of hydrogen peroxide is responsible for carcinostatic effects of hydrogen combined with platinum nanocolloid, together with increases intracellular ROS, DNA cleavages, and proportion of G2/M-phase

ABSTRACT

In our previous study, we demonstrated that combined treatment with hydrogen (H₂) and platinum nanocolloid (Pt-nc) exerted markedly antiproliferative effects on cancer cells compared with each treatment alone. However, because the related mechanisms remain unclear, we investigated carcinostatic mechanisms of the combined treatment with H₂ + Pt-nc. Significant suppression of cell proliferation was confirmed at 52 h following combined treatment, and the similar effect was also observed by the 30- or 40-min transient treatment with H₂ + Pt-nc. The transient treatments led to changes in cell size and morphology, loss of microvilli, and apoptosis-like cell death at 120 h after treatment. Moreover, transient combined treatment with H₂ + Pt-nc induced cell-cycle arrest, as reflected by decreased proportions of G1-phase cells and accumulation of G2/M-phase cells. In contrast, intracellular peroxide levels were temporarily and significantly increased immediately after H₂ + Pt-nc treatment but not after treatment with H₂ or Pt-nc alone. Additionally, combined treatment-induced carcinostatic effects were significantly diminished in the presence of catalase, and marked hydrogen peroxide (H₂O₂) generation was confirmed after mixing Pt-nc into cell culture media containing a high concentration of H₂. These changes are in agreement with the results that carcinostatic effects were induced after only 40 min of treatment with H₂ + Pt-nc. Thus, transient and marked generation of H₂O₂ is responsible for the carcinostatic effects of combined treatment with H₂ + Pt-nc.

KEYWORDS:

• Ehrlich ascites tumor cells
• growth arrest
• hydrogen-dissolved solution
• nanomedicine
• oxidative stress

Acknowledgements

The authors thank Mr Daigo Matsuoka for his technical assistance.

Disclosure statement

The authors report that they have no conflicts of interest.

Funding information

The present study was supported in part by a grant-in-aid for antiaging and anticancer researches to Y. S. and N. M. and Grant no. #2015-B16 from Japanese Center for AntiAging MedSciences (JCAAMS), Hiroshima, Japan.