CSE inhibition prevents intracellular cysteine accumulation in monocytes and MoDCs. (A) THP-1 cells were nontreated (NT), treated with PPG (32mM), or treated with SAS (500μM) in the absence (white bars) or presence (black bars) of LPS for 24 hours. Cells were harvested and analyzed by mass spectrometry. Results represent the relative mean percentage of intracellular cysteine concentration compared with intracellular cysteine concentration when THP-1 cells were nontreated (NT; mean ± SEM of 2 independent experiments). In these experiments, NT cysteine levels ranged from 0.5 to 1.6 nmol of cysteine per million cells. (B) Same experiments as in panel A on freshly isolated monocytes. Results represent the mean of intracellular cysteine concentration, expressed as nanomoles of cysteine per million cells (mean ± SEM of 3 independent experiments). *P < .05. (C) Same experiments as in panel A on MoDCs. Results represent the mean of intracellular cysteine concentration, expressed as nanomoles of cysteine per million cells (mean ± SEM of 5 independent experiments, except SAS and LPS + SAS, 4 experiments). *P < .05. **P < .01.