Fig. 1.
Ceramide levels in exosomes are higher in stressed mice than in control subjects. Wild-type mice or mice induced for deficiency of neutral sphingomyelinase 2 (i.-Nsm 2fl/fl) were stressed with either glucocorticosterone (GC) or chronic unpredictable environmental stress (CUS) for each 7 days or were left untreated as controls (-). Venous blood samples were collected at day 7, and exosomes were purified from the blood plasma by ultracentrifugation. Ceramide concentrations (expressed as sum of C16 to C24 sub-species) were determined by ceramide kinase assays and mass spectrometry (MS). Ceramide levels in the exosomes of wild-type mice after various forms of stress were higher than those in the plasma from control subjects. Induced deficiency of neutral sphingomyelinase 2 prevented the increase of ceramide levels in exosomes after stress. Deletion of neutral sphingomyelinase 2 was achieved by injection of tamoxifen 4 weeks prior to the studies. Shown are the mean ± SD, n = 6–8 for all mouse samples and n = 16–20 for all human samples. ***P < 0.001, ANOVA and post hoc Tukey test