Cytoplasmic expression of recombinant interleukin-2 and interleukin-4 proteins results in hydrogen peroxide accumulation and reduction in catalase activity in Escherichia coli

Abstract

Background and the purpose of the study: The Reactive oxygen species (ROS) is induced in the cells following various stresses but the effect of recombinant protein expression on ROS generation has not been studied yet. In this study, H₂O₂ concentration and catalase activity variations and their correlation with cell growth following cytoplasmic expression of human interleukin-2 (hIL-2) and mouse interleukin-4 (mIL-4) in Escherichia coli were investigated. Additionally, the effect of recombinant protein expression under different conditions was compared to the effect of foreign DNA introduction on these factors.

Methods: Plasmids pEThIL-2 and pETmIL-4 were used for expression of human interleukin-2 (hIL-2) and mouse interleukin-4 (mIL-4) inside the cytoplasm of the cells. Having confirmed protein expression using SDS-PAGE analysis and ELISA assay, H₂O₂ concentration and catalase activity were measured at various ODs.

Results and major conclusion: Empty vector introduction increased significantly H₂O₂ concentration of the cells. However, H₂O₂ concentration in hIL-2 and mIL-4 expressing cells was significantly higher than its concentration in empty vector transformed cells. Catalase activity was reduced in foreign DNA introduced cells. It was more lowered following expression of recombinant proteins. Results of this study revealed the relationship between foreign DNA introduction and protein expression with H₂O₂ elevation and catalase activity reduction. There was also correlation between H₂O₂ elevation and reduction in catalase activity with the cell growth depression.