LAUSR

Murine macrophages produce a large body of reactive oxygen species and nitric oxide (NO) in response to inflammatory stimuli and confer protection against bacterial infection. xCT transports cystine into cells in combination with glutamate discharge and supports glutathione synthesis. We performed characterization of macrophages from xCT-knockout (KO) mice from the aspect of redox homeostasis. Cystine uptake was observed in the wild-type (WT) macrophages at 24 h after isolation and elevated by stimulation with lipopolysaccharide (LPS) but was not detected in xCT-KO macrophages. Intracellular glutathione levels were lower in the xCT-KO macrophages compared to WT macrophages and further decreased by stimulation with LPS. xCT-KO macrophages maintained viability at least for 5 days but was more vulnerable to pro-oxidant menadione than WT macrophages. In response to stimulation with LPS, xCT-KO macrophages produced less nitric oxide compared to the WT macrophages, although levels of the NOS2 protein as well as arginine uptake rate were not significantly different. Inhibition of glutathione synthesis further decreased glutathione levels but only slightly affected nitrite levels. These data imply that macrophages possess a unique mechanism against oxidative insult, independently from the glutathione system, to cope with the bacterial infection.