Evaluation of serum sphingolipids and the influence of genetic risk factors in age-related macular degeneration

Abstract

Sphingolipids are bioactive molecules associated with oxidative stress, inflammation, and neurodegenerative diseases, but poorly studied in the context of age-related macular degeneration (AMD), a prevalent sight-threatening disease of the ageing retina. Here, we found higher serum levels of hexosylceramide (HexCer) d18:1/16:0 in patients with choroidal neovascularization (CNV) and geographic atrophy (GA), two manifestations of late stage AMD, and higher ceramide (Cer) d18:1/16:0 levels in GA patients. A sensitivity analysis of genetic variants known to be associated with late stage AMD showed that rs1061170 (p.Y402H) in the complement factor H (CFH) gene influences the association of Cer d18:1/16:0 with GA. To understand the possible influence of this genetic variant on ceramide levels, we established a cell-based assay to test the modulation of genes in the ceramide metabolism by factor H-like protein 1 (FHL-1), an alternative splicing variant of CFH that also harbors the 402 residue. We first showed that malondialdehyde-acetaldehyde adducts, an oxidation product commonly found in AMD retinas, induces an increase in ceramide levels in WERI-Rb1 cells in accordance with an increased expression of ceramide synthesis genes. Then, we observed that cells exposed to the non-risk FHL-1:Y402, but not the risk associated variant FHL-1:H402 or full-length CFH, downregulated ceramide synthase 2 and ceramide glucosyltransferase gene expression. Together, our findings show that serum ceramide and hexosylceramide species are altered in AMD patients and that ceramide levels may be influenced by AMD associated risk variants.

Integrated bioinformatics analysis of aberrantly-methylated differentially-expressed genes and pathways in age-related macular degeneration

“…4 The protein-protein interaction (PPI) networks of the 153 hypermethylation-low expression genes (Hyper-LGs). 151 nodes and 73 edges were established from the Hyper-LGs metabolism [41,42], fibroblast migration [43,44], membrane [45], coenzyme [46][47][48], and DNA binding [49] have been investigated in AMD. Calcium signaling, sphingolipid metabolism, and coenzyme categories showed strong relationships with AMD, whereas the others require further evaluation.…”

Sphingolipids as critical players in retinal physiology and pathology

“…Further associations have been identified between AMD and several complement pathway-associated genes: complement factor B, complement factor H-related 1 and 3, and complement components 2 and 3 (200). Interestingly, a recent study showed that the Y402H variant in CFH gene influences the association of high serum Cer levels with geographic atrophy, and high levels of HexCer in the serum of patients with choroidal neovascularization and GA (201).…”

Sphingolipids as Emerging Mediators in Retina Degeneration

“…Oxidative stress increases both Cer and hexosyl-Cer levels in ARPE-19 cells, a human RPE cell line, promoting cell death; this death is prevented by over-expression of acid ceramidase, which increases Sph levels but not those of S1P (Sugano et al, 2018). Interestingly, increased serum levels of hexosyl-Cer have been reported in patients with late stage AMD (Pujol-Lereis et al, 2018). Noteworthy, oxidative stress leads to increased S1P levels in control RPE cells, which might reflect an attempt to counteract Cer action toward cell death (Sugano et al, 2018).…”