Alzheimer's disease (AD) involves progressive neurodegeneration, amyloid-{beta} (A{beta}) pathology and chronic neuroinflammation. Elevated ceramides, generated via neutral sphingomyelinase (nSMase)-mediated sphingomyelin hydrolysis or serine palmitoyltransferase (SPT)-driven de novo synthesis, amplify these processes. Here, we performed a direct comparison of pharmacological inhibition of these pathways in the PDAPP-J20 transgenic mouse model and in fibrillized A{beta}1-42-challenged BV-2 murine microglial cell line. Eight-month-old PDAPP-J20 female mice received intraperitoneal GW4869 (nSMase inhibitor, 1.25 mg/kg) or myriocin (SPT inhibitor, 0.3 mg/kg) three times weekly for 3 weeks. Neutral SMase inhibition restored spatial learning in the Barnes maze, reduced hippocampal neuronal loss and layer atrophy, decreased amyloid plaque burden, and attenuated microglial activation (Iba1 morphology and peri-plaque reactivity). In contrast, SPT inhibition worsened thigmotaxis, failed to improve cognition, and increased plaque load. In vitro, nSMase blockade (GW4869 and cambinol) suppressed A{beta}-induced NF{kappa}B p65 nuclear translocation, blunted TNF- expression, and reduced intracellular A{beta} accumulation in microglia, suggesting enhanced endolysosomal degradation. SPT inhibition lacked these anti-inflammatory and clearance-promoting effects. These results identify nSMase as a critical node linking ceramide metabolism, microglial dysfunction, and amyloid progression in AD. Targeted nSMase inhibition offers a promising molecular strategy to interrupt neuroinflammation and restore neuronal homeostasis, while broad SPT blockade appears counterproductive. Pathway-selective modulation of ceramide signaling may open new therapeutic avenues for AD.
Bellotto, M., Gonzalez Perez, N., Bentivegna, M., Carrera, M., Presa, J., Vinuesa, A., Pomilio, C., Saravia, F., Beauquis, J.
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