Differential Effects of Neutral Sphingomyelinase and Serine Palmitoyltransferase Inhibitors on Alzheimer’s-Like Neuropathology

Alzheimer’s disease (AD) involves progressive neurodegeneration, amyloid-β (Aβ) 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 Aβ1-42-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 Aβ-induced NFκB p65 nuclear translocation, blunted TNF-α expression, and reduced intracellular Aβ 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.

Highlights

• nSMase inhibition restores learning and reduces hippocampal damage in AD mice.

• GW4869 decreases amyloid plaque burden and attenuates microglial activation.

• SPT inhibition worsens anxiety-like behavior and increases hippocampal plaque load.

• nSMase blockade reduces NFκB/TNFα signaling and intracellular Aβ in BV-2 microglia.

• Pathway-specific ceramide modulation is a promising therapeutic target in AD.