Cellular diamine levels in cancer chemoprevention: modulation by ibuprofen and membrane plasmalogens

A novel inducible animal model for studying chronic plasmalogen deficiency associated with Alzheimer's disease

Plasmalogens are vinyl-ether glycerophospholipids critical for the structure and function of neuronal membranes. Deficient plasmalogen levels are associated with neurodegenerative diseases, particularly Alzheimer's disease (AD), which has led to the hypothesis that plasmalogen deficiency might drive disease onset and progression. However, the lack of a suitable animal model with late-onset plasmalogen deficiency has prevented testing of this hypothesis. The goal of this project was therefore to develop and characterize a mouse model capable of undergoing a plasmalogen deficiency only in adulthood, mirroring the chronic decline thought to occur in AD. We report here the creation of a novel animal model containing a tamoxifen-inducible knockout of the Gnpat gene encoding the first step in the plasmalogen biosynthetic pathway. Tamoxifen treatment in adult animals resulted in a significant reduction of plasmalogens in both the circulation and tissues as early as four weeks. By four months, changes in behavior and nerve function were observed, with strong correlations between residual brain plasmalogen levels hyperactivity, and latency. The model will be useful for further elucidating the role of plasmalogens in AD and evaluating plasmalogen therapies.

Targeted Plasmalogen Supplementation: Effects on Blood Plasmalogens, Oxidative Stress Biomarkers, Cognition, and Mobility in Cognitively Impaired Persons

Plasmalogens are a specific type of glycerophospholipid found in especially high levels in neuronal membranes. Decreased blood and brain levels of docosahexaenoic acid (DHA) containing plasmalogens are associated with decreased cognition and neuromuscular function in humans. Administration of 1-O-alkyl-2-acylglycerol (AAG) plasmalogen precursors containing DHA at the sn-2 position dose-dependently increase blood DHA plasmalogens and are neuroprotective in animal models of neurodegeneration at doses between 10 and 50 mg/kg. We conducted an investigational clinical trial in 22 cognitively impaired persons to evaluate the effects of an escalating oral dosing regimen of DHA-AAG from 900 to 3,600 mg/day over a 4-month period on blood serum plasmalogen and non-plasmalogen phospholipids and oxidative stress biomarkers. Safety, tolerability and therapeutic effects on cognition and mobility were also evaluated. DHA plasmalogen levels increased with increasing dose and remained significantly elevated at all treatment doses and durations. DHA plasmalogen levels were positively associated with catalase activity and negatively associated with malondialdehyde (MDA) levels. DHA-AAG supplementation normalized catalase activity in persons with low baseline catalase activity, normalized MDA levels in persons with high baseline MDA levels, and normalized superoxide dismutase activity in persons with high baseline SOD activity. Cognition improved in nine participants, was unchanged in nine, and declined in four. Mobility improved in twelve, was unchanged in five and declined in four participants. Changes in cognition and mobility were statistically significant versus a random outcome. Baseline DHA-plasmalogen levels were not predictive of clinical response. DHA-AAG was well tolerated at all dosages and no adverse reactions were observed.

Pharmacokinetics, Mass Balance, Excretion, and Tissue Distribution of Plasmalogen Precursor PPI-1011

PPI-1011 is a synthetic plasmalogen precursor in development as a treatment for multiple plasmalogen-deficiency disorders. Previous work has demonstrated the ability of PPI-1011 to augment plasmalogens and its effects in vitro and in vivo, however, the precise uptake and distribution across tissues in vivo has not been investigated. The purpose of this study was to evaluate the pharmacokinetics, mass balance, and excretion of [¹⁴C]PPI-1011 following a single oral administration at 100 mg/kg in Sprague-Dawley rats. Further tissue distribution was examined using quantitative whole-body autoradiography after both single and repeat daily doses at 100 mg/kg/day. Non-compartmental analysis showed that following a single dose, PPI-1011 exhibited peak levels between 6 and 12 h but also a long half-life with mean t_1/2 of 40 h. Mass balance showed that over 50% of the compound-associated radioactivity was absorbed by the body, while approximately 40% was excreted in the feces, 2.5% in the urine, and 10% in expired air within the first 24 h. Quantitative whole-body autoradiography following a single dose showed uptake to nearly all tissues, with the greatest initial uptake in the intestines, liver, and adipose tissue, which decreased time-dependently throughout 168 h post-dose. Following 15 consecutive daily doses, uptake was significantly higher across the entire body at 24 h compared to single dose and remained high out to 96 h where 75% of the initially-absorbed compound-associated radioactivity was still present. The adipose tissue remained particularly high, suggesting a possible reserve of either plasmalogens or alkyl diacylglycerols that the body can pull from for plasmalogen biosynthesis. Uptake to the brain was also definitively confirmed, proving PPI-1011’s ability to cross the blood-brain barrier. In conclusion, our results suggest that oral administration of PPI-1011 results in high uptake across the body, and that repeated dosing over time represents a viable therapeutic strategy for treating plasmalogen deficiencies.

Investigation of Electron Scattering from Vinyl Ether and Its Isomers

This article reports a comprehensive theoretical study of electron scattering from vinyl ether and its isomers. The electron–molecule quantum collision problem is solved through a complex optical potential approach. From the solution of the Schrödinger equation corresponding to this scattering problem, various cross sections were obtained for energies from ionization threshold of target to 5 keV. To deal with the non-spherical and complex structure, a multi-center group additivity approach is used. Furthermore, geometrical screening correction is applied to compensate for the overestimation of results due to electron charge density overlap. We found an interesting correlation between maximum ionization cross section with polarizability and ionization energy of the target molecule. The fitting of the total cross section as a function of the incident electron energy is reported in this article. The correlation between the effective diameter of the target and the projectile wavelength at maximum ionization energy is also reported for vinyl ether and its isomers. The data presented here will be useful to biomedical field, mass spectrometry, and chemical database for military range applications. The cross sections are also important to model Mars’s atmosphere due to their presence in its atmosphere. The gas-kinetic radius and the van der Waals coefficients are estimated from the electron-impact total scattering cross sections. In addition, the current study predicts the presence of isomeric effects in the cross section.

Searching for Drug Synergy Against Cancer Through Polyamine Metabolism Impairment: Insight Into the Metabolic Effect of Indomethacin on Lung Cancer Cells

Non-small cell lung cancer (NSCLC) is the most lethal and prevalent type of lung cancer. In almost all types of cancer, the levels of polyamines (putrescine, spermidine, and spermine) are increased, playing a pivotal role in tumor proliferation. Indomethacin, a non-steroidal anti-inflammatory drug, increases the abundance of an enzyme termed spermidine/spermine-N¹-acetyltransferase (SSAT) encoded by the SAT1 gene. This enzyme is a key player in the export of polyamines from the cell. The aim of this study was to compare the effect of indomethacin on two NSCLC cell lines, and their combinatory potential with polyamine-inhibitor drugs in NSCLC cell lines. A549 and H1299 NSCLC cells were exposed to indomethacin and evaluations included SAT1 expression, SSAT levels, and the metabolic status of cells. Moreover, the difference in polyamine synthesis enzymes among these cell lines as well as the synergistic effect of indomethacin and chemical inhibitors of the polyamine pathway enzymes on cell viability were investigated. Indomethacin increased the expression of SAT1 and levels of SSAT in both cell lines. In A549 cells, it significantly reduced the levels of putrescine and spermidine. However, in H1299 cells, the impact of treatment on the polyamine pathway was insignificant. Also, the metabolic features upstream of the polyamine pathway (i.e., ornithine and methionine) were increased. In A549 cells, the increase of ornithine correlated with the increase of several metabolites involved in the urea cycle. Evaluation of the levels of the polyamine synthesis enzymes showed that ornithine decarboxylase is increased in A549 cells, whereas S-adenosylmethionine-decarboxylase and polyamine oxidase are increased in H1299 cells. This observation correlated with relative resistance to polyamine synthesis inhibitors eflornithine and SAM486 (inhibitors of ornithine decarboxylase and S-adenosyl-L-methionine decarboxylase, respectively), and MDL72527 (inhibitor of polyamine oxidase and spermine oxidase). Finally, indomethacin demonstrated a synergistic effect with MDL72527 in A549 cells and SAM486 in H1299 cells. Collectively, these results indicate that indomethacin alters polyamine metabolism in NSCLC cells and enhances the effect of polyamine synthesis inhibitors, such as MDL72527 or SAM486. However, this effect varies depending on the basal metabolic fingerprint of each type of cancer cell.

Oral administration of a synthetic vinyl-ether plasmalogen normalizes open field activity in a mouse model of rhizomelic chondrodysplasia punctata

Rhizomelic chondrodysplasia punctata (RCDP) is a rare genetic disorder caused by mutations in peroxisomal genes essential for plasmalogen biosynthesis. Plasmalogens are a class of membrane glycerophospholipids containing a vinyl-ether-linked fatty alcohol at the sn-1 position that affect functions including vesicular transport, membrane protein function and free radical scavenging. A logical rationale for the treatment of RCDP is therefore the therapeutic augmentation of plasmalogens. The objective of this work was to provide a preliminary characterization of a novel vinyl-ether synthetic plasmalogen, PPI-1040, in support of its potential utility as an oral therapeutic option for RCDP. First, wild-type mice were treated with ¹³C₆-labeled PPI-1040, which showed that the sn-1 vinyl-ether and the sn-3 phosphoethanolamine groups remained intact during digestion and absorption. Next, a 4-week treatment of adult plasmalogen-deficient Pex7^hypo/null mice with PPI-1040 showed normalization of plasmalogen levels in plasma, and variable increases in plasmalogen levels in erythrocytes and peripheral tissues (liver, small intestine, skeletal muscle and heart). Augmentation was not observed in brain, lung and kidney. Functionally, PPI-1040 treatment normalized the hyperactive behavior observed in the Pex7^hypo/null mice as determined by open field test, with a significant inverse correlation between activity and plasma plasmalogen levels. Parallel treatment with an equal amount of ether plasmalogen precursor, PPI-1011, did not effectively augment plasmalogen levels or reduce hyperactivity. Our findings show, for the first time, that a synthetic vinyl-ether plasmalogen is orally bioavailable and can improve plasmalogen levels in an RCDP mouse model. Further exploration of its clinical utility is warranted.

This article has an associated First Person interview with the joint first authors of the paper.

Summary: This article shows, for the first time, that a synthetic vinyl-ether plasmalogen is orally bioavailable and bioactive in vivo following administration in animals.

Lipidome in colorectal cancer

Colorectal cancer (CRC) is the second leading cause of cancer-related deaths. Understanding its pathophysiology is essential for developing efficient strategies to treat this disease. Lipidome, the sum of total lipids, related enzymes, receptors and signaling pathways, plays crucial roles in multiple cellular processes, such as metabolism, energy storage, proliferation and apoptosis. Dysregulation of lipid metabolism and function contributes to the development of CRC, and can be used towards the evaluation of prognosis. The strategies targeting lipidome have been applied in clinical trails and showed promising results. Here we discuss recent advances in abnormal lipid metabolism in CRC, the mechanisms by which the lipidome regulates tumorigenesis and tumor progression, and suggest potential therapeutic targets for clinical trials.

Combination of a chemopreventive agent and paclitaxel in CD44-targeted hybrid nanoparticles for breast cancer treatment

The CD44 receptor, which is upregulated in many cancer cells, provides a selective cellular surface for targeted drug delivery systems. We developed a hybrid nanocarrier for the CD44-targeted delivery of ibuprofen (IBU) and paclitaxel (PTX). The solid lipid nanoparticles (SLNs) were prepared by a hot-melt oil/water emulsion technique and then coated with hyaluronic acid (HA) by electrostatic interactions. The final SLN were spherical with a hydrodynamic diameter (Z) of 72.16 ± 2.9 nm, polydispersity index (PDI) of 0.276 ± 0.009, and zeta potential (ZP) of 28.20 ± 0.69 mV. Similarly, SLN coated with HA (SLN-HA) exhibited acceptable physical properties (Z 169.3 ± 0.55 nm, PDI 0.285 ± 0.004, and ZP - 10.5 ± 0.15 mV). Cell viability assays showed that the combination of IBU, a chemopreventive agent, and PTX exerted a synergistic inhibitory effect on the proliferation of cancer cells (CI < 1.0). Additionally, our observations indicated that both SLN and SLN-HA enhanced apoptosis and cellular uptake compared to the cocktail of free drugs. HA indicated its affinity for cancer cells through the improvement of cellular uptake and induction of apoptosis. These results clearly indicated that these nanoparticle systems hold great promise for drug delivery in breast cancer treatment.

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.

Choline plasmalogens isolated from swine liver inhibit hepatoma cell proliferation associated with caveolin-1/Akt signaling

Plasmalogens play multiple roles in the structures of biological membranes, cell membrane lipid homeostasis and human diseases. We report the isolation and identification of choline plasmalogens (ChoPlas) from swine liver by high performance thin layer chromatography (HPTLC) and high performance liquid chromatography (HPLC)/MS. The growth and viability of hepatoma cells (CBRH7919, HepG2 and SMMC7721) was determined following ChoPlas treatment comparing with that of human normal immortal cell lines (HL7702). Result indicated that ChoPlas inhibited hepatoma cell proliferation with an optimal concentration and time of 25 μmol/L and 24 h. To better understand the mechanism of the ChoPlas-induced inhibition of hepatoma cell proliferation, Caveolin-1 and PI3K/Akt pathway signals, including total Akt, phospho-Akt(pAkt) and Bcl-2 expression in CBRH7919 cells, were determined by western blot. ChoPlas treatment increased Caveolin-1 expression and reduced the expression of phospho-Akt (pAkt) and Bcl-2, downstream targets of the PI3K/Akt pathway. Further cell cycle analysis showed that ChoPlas treatment induced G1 and G1/S phase transition cell cycle arrest. The expression of essential cell cycle regulatory proteins involved in the G1 and G1/S phase transitions, cyclin D, CDK4, cyclin E and CDK2, were also analyzed by western blot. ChoPlas reduced CDK4, cyclin E and CDK2 expression. Taken together, the results indicate that swine liver-derived natural ChoPlas inhibits hepatoma cell proliferation associated with Caveolin-1 and PI3K/Akt signals.