Nicholas DelRaso (Committee Member), Jeffery Gearhart (Committee Member), James Olson (Committee Member), Michael Raymer (Committee Member), Nicholas Reo (Advisor)
Doctor of Philosophy (PhD)
Plasmalogens are glycerophospholipids abundant in brain and heart tissues. Evidence suggests that they have antioxidant properties. Studies from our laboratory showed that rats treated with myo-inositol plus ethanolamine (ME) have elevated ethanolamine plasmalogens (PE-Pls) in brain and are protected against phosphine-induced oxidative stress. We hypothesized that ME elevates PE-Pls levels and protects against oxidative stress through oxidation of its vinyl ether bond. We tested this hypothesis in Neuro-2A cell culture and assessed the effects of treatments with myo-inositol (M), ethanolamine (Etn), or a combination (ME) on the: (1) effects on phospholipid (PL) classes, especially Etn PLs; (2) effects on cell viability in response to H2O2-induced oxidative stress; and (3) molecular species of Etn PLs preferentially affected by ME and H2O2 treatments, especially PE-Pls and their degradation byproducts – lyso-phosphatidylethanolamines (LPE). 31P NMR data show that treating the cells with equimolar amounts (500 uM) of M or Etn for 24 h did not influence PL levels, but ME yielded a 3-fold increase in both PE-Pls and PE (p<0.001). Cells exposed to 650 uM H2O2 for 24 h decreased cell viability to 53% ± 1.7. While pretreatment with M or ME significantly increased cell survival to 62% ± 1.2 or 80% ± 0.6, respectively (p<0.05), Etn alone had no effect. Mass spectrometry showed that ME preferentially elevated the levels of PE-Pls species containing saturated fatty acids (SFA) and monounsaturated fatty acids (MUFA) by 60%, while PE-Pls containing polyunsaturated fatty acids (PUFA) increased by only 10%. H2O2 caused a significant decrease in PE-Pls (27%), producing a 39% increase in LPE and a 4-fold increase in glycerophosphoethanolamine (GPE), but had no impact on PE levels, suggesting that LPE and GPE were primarily byproducts of PE-Pls degradation. Surprisingly, all these effects were blocked by pre-treating cells with ME prior to H2O2 exposure. Taken together, these data suggest that a preferential increase in PE-Pls species containing SFA+MUFA in response to ME may protect cells from H2O2-induced oxidative stress. The mechanism for this effect is unclear, but further investigations to understand these processes may help to develop neuroprotective approaches to alleviate the progression of neurodegenerative diseases/disorders.
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