Hydrogen peroxide: A central player in physical plasma-induced oxidative stress in human blood cells

Abstract

Plasma medicine is an interdisciplinary field and recent clinical studies showed benefits of topical plasma application to chronic wounds. Whereas most investigations have focused on plasma–skin cell interaction, immune cells are omnipresent in most tissues as well. They not only elicit specific immune responses but also regulate inflammation, which is central in healing and regeneration. Plasma generates short-lived radicals and species in the gas phase. Mechanisms of plasma–cell interactions are not fully understood but it is hypothesized that reactive oxygen and nitrogen species (RONS) mediate effects of plasma on cells. In this study human blood cells were investigated after cold atmospheric plasma treatment with regard to oxidation and viability. Plasma generates hydrogen peroxide (H₂O₂) and the responses were similar in cells treated with concentration-matched H₂O₂. Both treatments gave an equivalent reduction in viability and this was completely abrogated if catalase was added prior to plasma exposure. Further, five oxidation probes were utilized and fluorescence increase was observed in plasma-treated cells. Dye-dependent addition of catalase diminished most but not all of the probe fluorescence, assigning H₂O₂ a dominant but not exclusive role in cellular oxidation by plasma. Investigations for other species revealed generation of nitrite and formation of 3-nitrotyrosine but not 3-chlorotyrosine after plasma treatment indicating presence of RNS which may contribute to cellular redox changes observed. Together, these results will help to clarify how oxidative stress associates with physical plasma treatment in wound relevant cells.

Keywords::

• plasma medicine
• free radicals
• hydrogen peroxide
• RNS
• human blood cells
• wound healing

Acknowledgments

The authors thank Prof. Dr. Andreas Greinacher (Head of Department of Transfusion Medicine, University of Greifswald, Germany) for allocating buffy coats, and Anne Müller and Jörn Steinke for technical assistance. This work was realized within the framework of the research center ZIK plasmatis (German Federal Ministry of Education and Research, grant number 03Z2DN11) and supported in part by the Health Research Council of New Zealand.

Declaration of interest

The authors report no declarations of interest. The authors alone are responsible for the content and writing of the paper.