Synergistic effects of highly unsaturated fatty acid-containing phosphatidyl-ethanolamine on differentiation of human leukemia HL-60 cells by dibutyryl cyclic adenosine monophosphate

Variation in Lipid Species Profiles among Leukemic Cells Significantly Impacts Their Sensitivity to the Drug Targeting of Lipid Metabolism and the Prognosis of AML Patients

Several studies have linked bad prognoses of acute myeloid leukemia (AML) to the ability of leukemic cells to reprogram their metabolism and, in particular, their lipid metabolism. In this context, we performed "in-depth" characterization of fatty acids (FAs) and lipid species in leukemic cell lines and in plasma from AML patients. We firstly showed that leukemic cell lines harbored significant differences in their lipid profiles at steady state, and that under nutrient stress, they developed common mechanisms of protection that led to variation in the same lipid species; this highlights that the remodeling of lipid species is a major and shared mechanism of adaptation to stress in leukemic cells. We also showed that sensitivity to etomoxir, which blocks fatty acid oxidation (FAO), was dependent on the initial lipid profile of cell lines, suggesting that only a particular "lipidic phenotype" is sensitive to the drug targeting of FAO. We then showed that the lipid profiles of plasma samples from AML patients were significantly correlated with the prognosis of patients. In particular, we highlighted the impact of phosphocholine and phosphatidyl-choline metabolism on patients' survival. In conclusion, our data show that balance between lipid species is a phenotypic marker of the diversity of leukemic cells that significantly influences their proliferation and resistance to stress, and thereby, the prognosis of AML patients.

Short term effects of different omega-3 fatty acid formulation on lipid metabolism in mice fed high or low fat diet

Background

Bioactivities of Docosahexaenoic acid (DHA) and Eicosapentaenoic acid (EPA) depend on their chemical forms. The present study was to investigate short term effects of triglyceride (TG), ethyl ester (EE), free fatty acid (FFA) and phospholipid (PL) forms of omega-3 fatty acid (FA) on lipid metabolism in mice, fed high fat or low fat diet.

Method

Male Balb/c mice were fed with 0.7% different Omega-3 fatty acid formulation: DHA bound free fatty acid (DHA-FFA), DHA bound triglyceride (DHA-TG), DHA bound ethyl ester (DHA-EE) and DHA bound phospholipid (DHA-PL) for 1 week, with dietary fat levels at 5% and 22.5%. Serum and hepatic lipid concentrations were analyzed, as well as the fatty acid composition of liver and brain.

Result

At low fat level, serum total cholesterol (TC) level in mice fed diets with DHA-FFA, DHA-EE and DHA-PL were significantly lower than that in the control group (P < 0.05). Hepatic TG level decreased significantly in mice fed diets with DHA-TG (P < 0.05), DHA-EE (P < 0.05) and DHA-PL (P < 0.05), while TC level in liver was significantly lower in mice fed diets with TG and EE compared with the control group (P < 0.05). At high fat level, mice fed diets with DHA-EE and DHA-PL had significantly lower hepatic TC level compared with the control diet (P < 0.05). Hepatic PL concentration experienced a significant increase in mice fed the diet with PL at high fat level (P < 0.05). Furthermore, both at low and high fat levels, hepatic DHA level significantly increased and AA level significantly decreased in all forms of DHA groups (P < 0.05), compared to control groups at two different fat levels, respectively. Additionally, cerebral DHA level in mice fed diets with DHA-FFA, DHA-EE and DHA-PL significantly increased compared with the control at high fat level (P < 0.05), but no significant differences were observed among dietary treatments for mice fed diets with low fat level.

Conclusion

The present study suggested that not only total dietary fat content but also the molecular forms of omega-3 fatty acids contributed to lipid metabolism in mice. DHA-PL showed effective bioactivity in decreasing hepatic and serum TC, TG levels and increasing omega-3 concentration in liver and brain.

Seafood consumption and components for health

In recent years, in developed countries and around the world, lifestyle-related diseases have become a serious problem. Numerous epidemiological studies and clinical trials have demonstrated that diet is one of the major factors that influences susceptibility to lifestyle-related diseases, especially the middle-senile state. Studies examining dietary habits have revealed the health benefits of seafood consumption. Seafood contains functional components that are not present in terrestrial organisms. These components include n-3-polyunsaturated fatty acids, such as eicosapentaenoic acid and docosahexsaenoic acid, which aid in the prevention of arteriosclerotic and thrombotic disease. In addition, seafood is a superior source of various nutrients, such as protein, amino acids, fiber, vitamins, and minerals. This review focuses on the components derived from seafood and examines the significant role they play in the maintenance and promotion of health.

Marine by-product phospholipids as booster of medicinal compounds

Marine phospholipids are defined as phospholipids containing docosahexaenoic acid (DHA) or eicosapentaenoic acid that would be more effective than fish oil, which is mostly composed of triacylglycerol, in exerting health benefits. Marine phospholipids would boost the effect of both the health-beneficial hydrophilic and the hydrophobic compounds such as cell differentiators, anticancer compounds, and antiobesity compounds. When marine phospholipids are served as liposomal drinks, they would be more effective than adding into solid foods or feeds. As long as the liposome bilayer is basically composed of marine phospholipids, they would promote the encapsulated functional compounds. And this is the principal advantage of choosing marine phospholipids as liposomal membrane. Bioconversion of marine phospholipid would also be advantageous in delivering DHA into the desired tissue. For example, lysophosphatidylserine obtained through phospholipase D-mediated transphosphatidylation and phospholipase A₁ or sn-1 positional specific lipase-mediated partial hydrolysis seemed to be the most effective chemical form in delivering DHA into brain.

Effects of dietary docosahexaenoic acid connecting phospholipids on the learning ability and fatty acid composition of the brain

The effects of dietary docosahexaenoic acid (DHA, C22:6n-3) connecting phospholipids on the learning ability and fatty acid composition of the brain were investigated in hypercholesterolemic mice. ICR mice were subjected to a very low level of n-3 fatty acids through two generations. At 4 wk of age, the F(1) generation, n-3 fatty acid deficient male mice were provided with an experimental diet containing four kinds of lipids (safflower oil: Saf, DHA connecting triacylglycerols: DHA-TG, DHA connecting phospholipids: DHA-PL, soybean phospholipids: Soy-PL) for 5 wk. Another group of ICR mice were obtained and fed a commercial diet (CE-2, CLEA Japan, Inc.) as a control. The learning and memory abilities of the mice were evaluated by the modified avoidance procedure. The learning and memory ability level was significantly higher in mice fed the DHA-PL diet than in those fed the Saf and Soy-PL diets, and was the same level as the control. The DHA levels of phosphatidylethanolamine in the brain were significantly higher in the mice fed the two types of DHA-containing diets than in those fed the Saf and Soy-PL diets and was not significantly different between DHA-TG and DHA-PL. The dimethylacetal levels in the brain were significantly higher in the mice fed the DHA-PL diet than in those fed the Saf and DHA-TG diets. These results suggest that the dietary DHA connecting phospholipids have the effect of improving memory learning, and may be related to the both the DHA and plasmalogen levels in the brain.

Effect of dietary docosahexaenoic acid connecting phospholipids on the lipid peroxidation of the brain in mice

The effect of dietary docosahexaenoic acid (DHA, C22:6n-3) with two lipid types on lipid peroxidation of the brain was investigated in streptozotocin (STZ)-induced diabetic mice. Each group of female Balb/c mice was fed a diet containing DHA-connecting phospholipids (DHA-PL) or DHA-connecting triacylglycerols (DHA-TG) for 5 wk. Safflower oil was fed as the control. The lipid peroxide level of the brain was significantly lower in the mice fed the DHA-PL diet when compared to those fed the DHA-TG and safflower oil diets, while the alpha-tocopherol level was significantly higher in the mice fed the DHA-PL diet than in those fed the DHA-TG and safflower oil diets. The DHA level of phosphatidylethanolamine in the brain was significantly higher in the mice fed the DHA-PL diet than in those fed the safflower oil diet. The dimethylacetal levels were significantly higher in the mice fed the DHA-PL diet than in those fed the safflower oil and DHA-TG diets. These results suggest that the dietary DHA-connecting phospholipids have an antioxidant activity on the brain lipids in mice, and the effect may be related to the brain plasmalogen.

Short-term or long-term treatments with a phosphodiesterase-4 (PDE4) inhibitor result in opposing agonist-induced Ca(2+) responses in endothelial cells

BACKGROUND AND PURPOSE

We previously reported that agonist-induced rises in cytoplasmic Ca(2+) concentration ([Ca(2+)](i)) in human umbilical vein endothelial cells (HUVEC) were inhibited after a short-term (2 min) pre-treatment with cAMP-elevating agents. The aim of this work was to study the effects of longer term (8 h) pre-treatment with dibutyryl-cAMP (db-cAMP) or rolipram, a specific inhibitor of phosphodiesterase-4 (PDE4), on [Ca(2+)](i), cAMP levels and PDE activity and expression in HUVEC.

EXPERIMENTAL APPROACH

[Ca(2+)](i) changes were measured in isolated HUVEC by Fura-2 imaging. Intracellular cAMP levels and PDE4 activity were assessed by enzyme-immunoassay and radio-enzymatic assay, respectively. PDE expression was measured by northern and western blot analysis.

KEY RESULTS

Long-term pre-treatment of HUVEC with rolipram or db-cAMP significantly increased ATP-, histamine- and thrombin-induced [Ca(2+)](i) rises. Short-term pre-treatment with rolipram was associated with an increase in cAMP, whereas long-term pre-treatment was associated with a decrease in cAMP. Long-term pre-treatment with rolipram or db-cAMP induced a significant increase in PDE4 activity and the expression of 74 kDa-PDE4A and 73 kDa-PDE4B was specifically enhanced. All these effects were suppressed by cycloheximide.

CONCLUSIONS AND IMPLICATIONS

Our data suggest that sustained inhibition of PDE4 by rolipram induced an increase in PDE4 activity, possibly as a compensatory mechanism to accelerate cAMP degradation and that PDE4A and PDE4B were implicated in the regulation of [Ca(2+)](i). Thus, isozyme-specific PDE4 inhibitors might be useful as therapeutic agents in diseases where [Ca(2+)](i) handling is altered, such as atherosclerosis, hypertension and tolerance to beta-adrenoceptor agonists.

Remarkable enhancement in PLD activity from Streptoverticillium cinnamoneum by substituting serine residue into the GG/GS motif

The gene that encodes phospholipase D (PLD) from Streptoverticillium cinnamoneum contains three consensus regions (Region I, II and IV as shown in Fig. 1A) that are conserved among the PLD superfamily. The glycine-glycine (GG) motif in Region I and the glycine-serine (GS) motif in Region IV are also conserved in the PLD superfamily. These (GG and GS) motifs are located 7 residues downstream from each HKD motif. In an investigation of fifteen GG/GS motif mutants, generated as fusion proteins with maltose-binding protein (MBP-PLDs), three highly active mutants were identified. Three of the mutants (G215S, G216S, and G216S-S489G) contained a serine residue in the GG motif, and exhibited approximately a 9-27-fold increased transphosphatidylation activity to DPPC compared with recombinant wild type MBP-PLD. When heat stability was compared between three mutants and the recombinant wild type, only G216S-S489G showed heat labile properties. It appears that the 489th serine residue in the GS motif also contributes to the thermal stability of the enzyme. In addition, the GG/GS motif was very close to the active center residue, including two HKD motifs, as shown by computer modeling. The findings suggest that the GG/GS motif of PLD is a key motif that affects catalytic function and enzymatic stability.

Effect of polyunsaturated fatty acid-enriched phosphatidylcholine and phosphatidylserine on butyrate-induced growth inhibition, differentiation and apoptosis in Caco-2 cells

Phospholipids are fascinating in terms of important bio-functional compounds. The present work investigated the effect of polyunsaturated phosphatidylcholine (PC) and phosphatidylserine (PS) on butyrate-induced growth inhibition, differentiation and apoptosis using Caco-2 cells. Growth inhibition of Caco-2 cells became apparent 24 h after addition of PC while it took 48 h with PS. Alkaline phosphatase activity of Caco-2 cells increased with combined PC or PS and sodium butyrate (NaBT) at 72 h, indicating that PC and PS enhanced cell differentiation in the presence of NaBT. An increased enrichment factor was also found when cells were treated with combinations of PC or PS and NaBT. These results suggest that marine PC and PS can be considered to be potentially useful colon cancer chemotherapy agents with high bio-availability.

Docosahexaenoic acid-containing phosphatidylethanolamine enhances HL-60 cell differentiation by regulation of c-jun and c-myc expression

18:1/docosahexaenoic acid (DHA)-containing phosphatidylethanolamine (PE) enhanced cell differentiation and growth inhibition of HL-60 induced by dibutyryl cAMP (dbcAMP) in a dose-dependent manner. The combined treatment of 200 microM dbcAMP and 50 microM 18:1/DHA-PE increased the NBT reducing activity, which is as an indicator of cell differentiation, to more than 75% from 40% of cells treated with 200 microM dbcAMP alone. In HL-60 cells treated with 50 microM 18:1/DHA-PE and 200 microM dbcAMP for 24 h, the expression level of c-jun mRNA and c-Jun protein were remarkably elevated compared to cells treated with dbcAMP alone. In contrast, there was no difference in the expression levels of c-fos mRNA and c-Fos protein between the combination of 18:1/DHA-PE + dbcAMP or dbcAMP alone. On the other hand, the combine treatment of 18:1/DHA-PE and dbcAMP markedly reduced the expression level of c-myc oncogene during 48 h incubation. The decreases of c-myc mRNA by 18:1/DHA-PE and/or dbcAMP was correlated with growth inhibition effect. Thus, 18:1/DHA-PE might enhance dbcAMP-induced HL-60 cell differentiation and growth inhibition by regulation of c-jun and c-myc mRNA and their products.

Effects of ganglioside GM3 on phospholipid turnover of human leukemic J6-2 cells

Ganglioside GM3 was reported to induce the differentiation of HL-60 cells to differentiate along the macrophage-monocytic route. We used human monocytoid leukemia J6-2 cells and successfully induced differentiation by GM3. Because differentiation is accompanied by retarded growth rate and cell cycle is intimately related to phospholipid metabolism, so we explored how GM3 was related to phospholipid metabolism. By using [32P]Pi, [3H-CH3]choline, [3H-CH3]SAM, and [3H]inositol as radioactive tracers, we studied the turnover changes of phospholipids and their metabolites induced by GM3. For the morphological changes of differentiation to occur, the cells had to be treated with GM3 at a concentration of 50 microM for 5-6 days, but the phospholipid changes occurred at a very early stage of GM3 treatment (only 1 h). Our results indicate that GM3 stimulated PE methylation pathway inhibited both CDP-choline pathway and PI cycle. The phospholipid changes may constitute the early events in differentiation induced by GM3.