Abstract
Purpose :
Rare variants in CYP39A1, coding for a cytochrome P450 family member involved in cholesterol metabolism, are a strong risk factor for pseudoexfoliation (PEX) syndrome. In addition, excess cholesterol was found to accumulate within extracellular PEX material deposits in the eye, suggesting PEX-associated alterations in cholesterol homeostasis and transport. Here, we analyzed alterations in expression of cholesterol metabolism-related genes and levels of circulating indicators of cholesterol homeostasis in PEX and control samples, and analyzed the effects of cholesterol on ocular cells in vitro.
Methods :
Gene expression profiles of ocular tissues from PEX patients and age-matched controls were compared using the Human Cholesterol Metabolism PCR array and verified by real-time PCR assays. Levels of cholesterol, its precursors and metabolites as well as phytosterols were measured in aqueous humor and serum samples of PEX syndrome, PEX glaucoma and control patients using gas chromatography-mass spectrometry. Cultured human nonpigmented ciliary epithelial (hNPEC) and trabecular meshwork (hTMC) cells were exposed to 10-25 µg/ml cholesterol for 48 hours and analyzed by qPCR.
Results :
In ocular tissues of PEX patients, PCR arrays and real-time PCR assays showed significantly reduced expression levels of genes involved in cholesterol synthesis (e.g. HMGCR, SREBF2), efflux (e.g. ABCA1, ABCG1), transport (e.g. APOB, APOC1) and regulation (e.g. LXRA/B, RXRA) compared to age-matched control tissues. Aqueous humor samples of PEX patients were characterized by significantly increased levels of cholesterol, cholestanol, lathosterol, desmosterol and 27-hydroxycholesterol, whereas serum samples revealed reduced levels of phytosterols such as campesterol and brassicasterol. Exposure of hNPEC and hTMC to cholesterol induced downregulation of CYP39A1 and transcriptional deregulation of several genes related to inflammation (IL6, IL8), matrix metabolism (LOXL1, ELN, FBN1), cholesterol efflux and regulation (ABCA1, ABCG1, LXRA) and retinoic acid signaling (STRA6, RARA, RXRA).
Conclusions :
Our data provide evidence for a disturbed cholesterol metabolism in patients with PEX syndrome and glaucoma, possibly contributing to PEX-associated fibrosis by suppressing anti-fibrotic retinoic acid signaling and inducing pro-inflammatory conditions.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.