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S. J. Fliesler, M. J. Richards, D. A. Ford; Progressive Lipidome Changes During Retinal Degeneration in a Rat Model of Smith-Lemli-Opitz Syndrome. Invest. Ophthalmol. Vis. Sci. 2007;48(13):2496.
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We previously described progressive retinal degeneration in an AY9944-induced rat model of Smith-Lemli-Opitz Syndrome (SLOS), a recessive disease involving defective cholesterol biosynthesis (Fliesler et al., Arch. Ophthalmol. 122:1190, 2004). In addition to well-known alterations in tissue sterol profiles, there are global changes in retinal fatty acid composition (Battaglia et al., ARVO 2006). Here, we examined age-dependent alterations in the retinal lipidome of AY9944-treated vs. control rats.
Sprague Dawley rats were treated with AY9944 as previously described (Fliesler et al., 2004) over a 3-mo course; control litters (age- and sex-matched) received no drug. All animals were maintained under dim cyclic light (12L:12D, 20-40 lux) and fed a cholesterol-free diet and water ad lib. Total lipids were extracted from individual light-adapted retinas in the presence of internal standards including di-20:0-phosphatidylcholine (PC), di-14:0 phosphatidylethanolamine (PE) and di-14:0 phosphatidylserine (PS) and subjected to electrospray ionization triple quadrupole mass spectrometric analyses (ESI-MS/MS) or liquid chromatography/mass spectrometry (LC/MS).
Phospholipid class analysis demonstrated that PC>PE>PS; also, PC exhibited the greatest diversity of the phospholipid molecular species, both in control and AY9944-treated retinas. The predominant PC molecular species in control retinas were 16:0-22:6 and 18:0-22:6; the levels of these molecular species decreased by ≥50% in rats treated for 2 or 3 mo with AY9944. In comparison to control rats, AY9944 treatment for 1, 2, or 3 mo resulted either in no loss, a ≈25% loss, or a ≈60% loss of 16:0-22:6, 18:0-22:6 and di-22:6 PE molecular species, respectively. The predominant PS molecular species in control retinas were 18:0-22:6 and di-22:6. Notably, AY9944 treatment resulted in a >90% decline in di-22:6 PS, relative to controls.
The retinal lipidome is globally altered in the SLOS rat model, relative to control rats. The most profound changes in retinal phospholipid composition following AY9944 treatment were in PC, PE and PS molecular species containing 22:6. These findings are consistent with cross-talk between the sterol pathway and phospholipid/fatty acid pathways, implicating additional metabolic compromise beyond the primary enzymatic defect in the etiology of SLOS.
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