Plasmalogen precursor mitigates striatal dopamine loss in MPTP mice.

Ethanolamine plasmalogens (PlsEtn) are a class of glycerophospholipids characterized by a vinyl-ether bond at the sn-1 position that play an important role in the structure and function of membranes. Previous reports have suggested a link between reduced blood and brain PlsEtn levels and Parkinson's disease (PD). We recently reported that the DHA containing plasmalogen precursor PPI-1011 protected striatal dopamine (DA) against MPTP toxicity in mice. In this paper, we further investigate the specificity requirements of the lipid side chains by testing the oleic acid-containing plasmalogen precursor PPI-1025. Male mice were treated for 10days with daily oral administration of PPI-1025 (10, 50 or 200mg/kg). On day 5 mice received MPTP and were sacrificed on Day 11. Treatment with PPI-1025 prevented MPTP-induced decrease of DA and serotonin, as well as their metabolites. In addition, PPI-1025 treatment prevented the MPTP-induced decrease of the striatal dopamine transporter (DAT) and vesicular monoamine transporter 2 (VMAT2) specific binding. Significant positive correlations were measured between striatal DA concentrations and DAT or VMAT2 specific binding, as well as with serum plasmalogen concentrations. The neuroprotective effect of PPI-1025 displayed a bell-curve dose-dependency losing effect at the highest dose tested. The similar protective response of oleic and docosahexaenoic acid (DHA)-containing plasmalogen precursors suggests that the neuroprotection observed is not only due to DHA but to the oleic substituent and the plasmalogen backbone.

Plasmalogen Augmentation Reverses Striatal Dopamine Loss in MPTP Mice.

Plasmalogens are a class of glycerophospholipids shown to play critical roles in membrane structure and function. Decreased plasmalogens are reported in the brain and blood of Parkinson's disease (PD) patients. The present study investigated the hypothesis that augmenting plasmalogens could protect striatal dopamine neurons that degenerate in response to 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) treatment in mice, a PD model. First, in a pre-treatment experiment male mice were treated for 10 days with the docosahexaenoic acid (DHA)-plasmalogen precursor PPI-1011 (10, 50 and 200 mg/kg). On day 5 mice received MPTP and were killed on day 11. Next, in a post-treatment study, male mice were treated with MPTP and then received daily for 5 days PPI-1011 (5, 10 and 50 mg/kg). MPTP treatment reduced serum plasmalogen levels, striatal contents of dopamine (DA) and its metabolites, serotonin, DA transporter (DAT) and vesicular monoamine transporter 2 (VMAT2). Pre-treatment with PPI-1011 (10 and 50 mg/kg) prevented all MPTP-induced effects. Positive correlations were measured between striatal DA contents and serum plasmalogen levels as well as striatal DAT and VMAT2 specific binding. Post-treatment with PPI-1011 prevented all MPTP-induced effects at 50 mg/kg but not at lower doses. Positive correlations were measured between striatal DA contents and serum plasmalogen levels as well as striatal DAT and VMAT2 specific binding in the post-treatment experiment. PPI-1011 treatment (10 days at 5, 10 and 50 mg/kg) of intact mice left unchanged striatal biogenic amine contents. These data demonstrate that treatment with a plasmalogen precursor is capable of protecting striatal dopamine markers in an animal model of PD.

Plasmalogen precursor analog treatment reduces levodopa-induced dyskinesias in parkinsonian monkeys.

L-DOPA-induced dyskinesias (LID) remain a serious obstacle in the treatment of Parkinson's disease (PD). The objective of this study was to test a new target for treatment of dyskinesias, ethanolamine plasmalogens (PlsEtn). PlsEtn play critical roles in membrane structure mediated functions and as a storage depot of polyunsaturated fatty acids such as docosahexaenoic acid (DHA, omega-3) known to reduce dyskinesias. The motor effect of a daily treatment for 12 days of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) Macaca fascicularis monkeys with DHA (100mg/kg) was compared to the DHA-PlsEtn precursor PPI-1011 (50mg/kg). PPI-1011 and DHA reduced LID while maintaining the antiparkinsonian activity of l-DOPA, however the PPI-1011 effect was observed at the first behavioral time point analyzed following drug administration (day 2) whereas the effect of DHA was not observed until after 10 days of administration. DHA treatment increased plasma DHA levels 2-3× whereas PPI-1011 had no effect. DHA and PPI-1011 increased DHA-PlsEtn levels by 1.5-2× while DHA-phosphatidylethanolamine (PtdEtn) levels remained unaffected. DHA treatment also elevated very long chain fatty acid containing PtdEtn and reduced non-DHA containing PtdEtn and PlsEtn levels. PPI-1011 had no effect on these systems. LID scores were inversely correlated with serum DHA-PlsEtn/total PlsEtn ratios levels in DHA and PPI-1011 treated monkeys. Hence, the antidyskinetic activity of DHA and PPI-1011 in MPTP monkeys appears to be associated with the increase of serum DHA-PlsEtn concentrations. This is the first study reporting an antidyskinetic response to augmentation of DHA-PlsEtn using a plasmalogen precursor thus providing a novel drug target for dyskinesias.