Chronic exposure of the RAW246.7 macrophage cell line to H2O2 leads to increased catalase expression

Abstract

Altered cellular redox states have been associated with a variety of chronic diseases, especially those correlated with inflammation. One of the primary oxidants generated during the inflammatory response is hydrogen peroxide (H2O2). Macrophages in particular are thought to produce large amounts of H2O2, however they must somehow protect themselves from the potentially lethal concentrations they produce. To investigate how immune cells protect themselves from H2O2 observed in chronic inflammatory diseases, we established an adapted population of macrophages in culture by gradually increasing sub-lethal concentrations of H2O2 in the media to typically lethal concentrations over the course of more than a month. The resulting cells were tolerant to very high concentrations of H2O2. Further investigation revealed that the cells were able to rapidly neutralize the H2O2 added to their culture media due to a dramatic upregulation of catalase. Interestingly, T cells, which are also implicated in chronic inflammation, were unable to adapt to H2O2 under the same procedure, however when T cells were cultured in media from adapted macrophages, they were able to survive typically lethal concentrations of H2O2. These data support the hypothesis that macrophages are able to protect themselves and neighboring cells during states of chronic inflammation from the oxidizing environment they create.