Developmental Comparison of Ceramide in Wild-Type and Cln3Δex7/8 Mouse Brains and Sera

Abstract

CLN3 disease is a neurodevelopmental disease leading to early visual failure, motor decline, and death. CLN3 pathogenesis has been linked to dysregulation of ceramide, a key intracellular messenger impacting various biological functions. Ceramide is upregulated in brains of CLN3 patients and activates apoptosis. Ceramide levels over the lifespan of WT and Cln3 Δ ex7/8 mice were measured using the DGK assay. Ceramide subspecies were determined by LC-MS. Ceramide synthesis enzymes and pre- and post-synaptic mRNA expression was measured in Cln3 Δ ex7/8 and normal mouse brains. Neuronal cell death was established by PARP cleavage and Caspases 3/6/9 and cytochrome C mRNA expression in Cln3 Δ ex7/8 and normal mouse brains. In WT mouse, a ceramide peak was noted at 3 weeks of age. The absence of this peak in Cln3 Δ ex7/8 mice might be related to early disease pathogenesis. Increase of ceramide in Cln3 Δ ex7/8 mouse brain at 24 weeks of age precedes neuronal apoptosis. The correlation between serum and brain ceramide in WT mice, and dysregulation of ceramide in serum and brain of Cln3 Δ ex7/8 mice, and the significant increase in ceramide in Cln3 Δ ex7/8 mouse brains and sera argue for use of easily accessible serum ceramide levels to track response to novel therapies in human CLN3 disease.

Exogenous Galactosylceramide as Potential Treatment for CLN3 Disease

“…GalCer reduced ceramide in serum ( p = 0.0276) and brains ( p = 0.0330) of male and female Cln3 Δex7/8 versus vehicle‐treated Cln3 Δex7/8 mice. Altered temporal ceramide values over the lifespan of WT and Cln3 Δex7/8 mice in serum and brain suggest that elevated ceramide at crucial time points in development and increased apoptosis are implicated in CLN3 disease pathogenesis . Lowering of serum ceramide of Cln3 Δex7/8 mice suggests its use as a possible biomarker to assess response to novel therapies in CLN3 disease.…”

“…8 Elevated ceramide correlates with cognitive impairment in Alzheimer disease in brain, cerebrospinal fluid, and serum of patients. Altered temporal ceramide values over the lifespan of WT and Cln3 Δex7/8 mice in serum and brain suggest that elevated ceramide at crucial time points in development 31 and increased apoptosis are implicated in CLN3 disease pathogenesis. 11 GalCer reduced ceramide in serum (p = 0.0276) and brains (p = 0.0330) of male and female Cln3 Δex7/8 versus vehicle-treated Cln3 Δex7/8 mice.…”

Exogenous Flupirtine as Potential Treatment for CLN3 Disease

“…Previous studies show that ceramide levels are increased in CLN3-deficient cells and brain of CLN3 patients [ 11 ]. Published reports demonstrate that 17 week-old Cln3 Δex7/8 mice express higher levels of ceramide in brain compared to age-matched WT mice [ 14 ]. Sptlc3 catalyzes the initial steps in formation of ceramide via the de novo pathway by condensing serine and palmitoyl Co-A to generate 3-ketoshphinganine (3-KDS) [ 10 ].…”

“…Overexpressing CLN3 protein results in a drop in ceramide levels [ 13 ]. Increased ceramide levels and neuronal cell loss are evident in brain sections from post-mortem CLN3 disease patients and in brains and sera of Cln3 Δex7/8 mice [ 14 ]. Treatment regimens for CLN3 disease are largely supportive, not curative, and do not target the underlying causes of the disease.…”