Free radical-mediated transgene inactivation of macrophages by endotoxin

Sujatha Dokka, David Toledo, Liying Wang, Xianglin Shi, Chuanshu Huang, Stephen Leonard, Yon Rojanasakul

Research output: Contribution to journalArticlepeer-review

6 Scopus citations


Endotoxin, the lipopolysaccharide component of gram-negative bacteria, is a common contaminant of plasmid DNA preparations. The present study investigated the effect of endotoxin on gene transfection efficiency and the role of reactive oxygen species (ROS) in this process. Gene transfection studies were performed in various cell types with cytomegalovirus-luciferase as a reporter plasmid and cationic liposome as a transfecting agent. The presence of endotoxin in plasmid DNA preparations severely limited transgene expression in macrophages but had little or no effect in other cell types tested. This decreased transfection was dependent on ROS-mediated cellular toxicity induced by endotoxin. Neutralizing the endotoxin by the addition of polymyxin B effectively increased transfection efficiency and reduced toxicity. Electron spin resonance studies confirmed the formation of ROS in endotoxintreated cells and their inhibition by free radical scavengers. The ROS scavenger N-t-butyl-α-phenylnitrone, the H2O2 scavenger catalase, and the OH scavenger sodium formate effectively inhibited endotoxin-induced effects, whereas the O2/- scavenger superoxide dismutase had lesser effects. These results indicate that multiple oxidative species are involved in the transfection inactivation process and that OH formed by H2O2-dependent, metal-catalyzed Fenton reaction play a major role in this process.

Original languageEnglish
Pages (from-to)L878-L883
JournalAmerican Journal of Physiology - Lung Cellular and Molecular Physiology
Issue number5 23-5
StatePublished - 2000


  • Free radicals
  • Gene transfection
  • Macrophages

ASJC Scopus subject areas

  • Physiology
  • Pulmonary and Respiratory Medicine
  • Physiology (medical)
  • Cell Biology


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