Alterations to the kynurenine pathway after IL-6 treatment. High energy (fragmentation) mass spectra for (A) m/z 209.10 (kynurenine) and (B) m/z 166.05 (formylanthranilate). Spectra were mobility separated to isolate only product ions for 209 and 166, respectively. (A) In astrocyte cultures, we observed a decrease in normalized ion signal after IL-6 treatment, ALR = -0.86, P <0.00001, for kynurenine (m/z 209.10). (B) In contrast, we observed an increase in ion signal for formylanthranilate (m/z 166.05), also a component of the kynurenine pathway, when neuronal cultures were treated with IL-6, ALR = 2.47, P <0.001. Taken together, these data show that IL-6 exposure alters both neurons and astrocytes but does so in an opposite manner.