We present evidence here that exosomes stimulate aggregation of Aβ1-42 in vitro and in vivo and interfere with uptake of Aβ by primary cultured astrocytes and microglia in vitro. Exosome secretion is prevented by inhibition of neutral sphingomyelinase 2 (nSMase2), a key regulatory enzyme generating ceramide from sphingomyelin, with GW4869. Using the 5XFAD mouse, we show that intraperitoneal injection of GW4869 reduces the levels of brain and serum exosomes, brain ceramide, and Aβ1-42 plaque load. Reduction of total Aβ1-42 as well as number of plaques in brain sections was significantly greater (40% reduction) in male than female mice. Our results suggest that GW4869 reduces amyloid plaque formation in vivo by preventing exosome secretion and identifies nSMase2 as potential drug target in AD by interfering with exosome secretion.

Supplementation of formula with 3'- or 6'-sialyllactose can enrich ganglioside SA in the brain and modulate gut-associated microbiota in neonatal pigs. We propose 2 potential routes by which sialyllactose may positively affect the neonate: serving as a source of SA for neurologic development and promoting beneficial microbiota.

Ceramide is emerging as a key sphingolipid that regulates a variety of cellular processes. To facilitate the study of ceramide localization and its interaction with cellular proteins, we have developed a novel antibody against ceramide. Our results indicate that the antibody (rabbit IgG) specifically recognizes ceramide in lipid overlay assays and detects ceramide species with different fatty acid chain lengths that include C2, C8, C16, C18, C20, and C24. The new antibody was compared with the commercially available anti-ceramide antibody (mouse IgM) in immunocytochemistry experiments to study the localization of ceramide. Although both antibodies stain the same regions on the cell membrane, the rabbit IgG reveals the distribution of ceramide in compartments that are not well identified with the commercially available antibody. In addition to staining of ceramide in protrusions of the plasma membrane, the rabbit IgG also detects ceramide in the Golgi apparatus. Pharmacological depletion or increase of ceramide levels results in a corresponding change in staining intensity, confirming the specificity of the antibody. These results indicate that the rabbit IgG is a suitable antibody to determine the localization of ceramide and its interaction with proteins by immunocytochemistry.-Krishnamurthy, K., S. Dasgupta, and E. Bieberich. Development and characterization of a novel anti-ceramide antibody. J. Lipid Res. 2007. 48: 968-975.