diphenylhexatriene and elaidic-acid

In vivo-modified phospholipids from rat liver mitochondria were used to study the effect of trans-fatty acid incorporation into phospholipids on the steady-state fluorescence polarization of 1,6-diphenyl-1,3,5-hexatriene (DPH) embedded in phospholipid liposomes. Pure fractions of mitochondria phospholipids were prepared and analyzed for their fatty acid compositions and fatty acid positional distribution. In rats fed a diet enriched with trielaidin, elaidic acid (trans-9 18:1 acid) was extensively incorporated in position 1 of phosphatidylcholine (PC; 31% of fatty acids esterified to this position), phosphatidylethanolamine (PE; 42.5%) and phosphatidylinositol (PI; 43%). Less than 10% of the incorporated elaidic acid was esterified to position 2 of these phospholipids. More than 90% of elaidic acid esterified to position 1 displaced saturated acids. Consequently, about one-third of PC molecules and two-fifths of PE and PI molecules contained one molecule of elaidic acid instead of one saturated fatty acid molecule in their 1-position. On the other hand, cardiolipin, which is naturally practically devoid of saturated acids, was particularly resistant to elaidic acid incorporation. The fluorescence polarization of DPH incorporated in liposomes made of PC-PI and of PC-PI-PE from liver mitochondria of rats fed or not fed elaidic acid was measured. No significant differences between phospholipids containing or not containing elaidic acid could be detected. Values of DPH fluorescence polarization for all samples were comprized between 0.133 and 0.135 at 25 degrees C. We thus conclude that when elaidic acid replaces saturated fatty acids in phospholipids, even in a high proportion (one-third), the physical state of acyl chains in the hydrophobic core of membranes is not grossly modified. Thus, elaidic acid seems to behave like a saturated fatty acid, not only biochemically for the acylation of phospholipids, but also physically.

Topics: Animals; Cardiolipins; Diphenylhexatriene; Fatty Acids; Fluorescence Polarization; Fluorescent Dyes; Liposomes; Male; Mitochondria, Liver; Oleic Acid; Oleic Acids; Phosphatidylcholines; Phosphatidylethanolamines; Phosphatidylinositols; Phospholipids; Rats; Rats, Wistar; Temperature

To investigate NADPH-oxidase activation, we studied the effects of free fatty acid (FFA), their uncharged derivatives, and calcium on membrane lipid structure and superoxide anion (O2-) release from intact neutrophils and in cell-free O2(-)-generating systems. This study determined that in calcium-free phosphate-buffered saline (PBS), cis-unsaturated FFA (cis FFA), trans-unsaturated FFA (trans FFA), and to a limited extent saturated FFA decreased the polarization of the membrane lipid structure probe 1,6-diphenyl-1,3,5-hexatriene (DPH), and these decreases correlated with partitioning of the FFA into the plasmalemma and the release of O2- from intact neutrophils and in cell-free preparations. Although a decrease in DPH polarization was always observed under conditions that resulted in the release of O2-, there was not a direct correlation between the amount of decrease in DPH polarization and the release of O2-. Trans FFA did not induce a dose-dependent decrease or as dramatic a decrease in DPH polarization compared with cis FFA, yet the trans FFA stimulated a greater release of O2- at 2.5, 5, and 10 microM concentrations. In addition, responses of the neutrophil to trans FFA, but not cis FFA, were differentially affected by the presence of calcium. When 0.1 mM calcium was added to the PBS decreases in DPH polarization in response to trans FFA were reduced by greater than 60%, whereas O2- was reduced by only 25-36%. The addition of 0.1 mM calcium 3 min after the trans FFA had partitioned into the membrane also reversed by 50-65% decreases in DPH polarization but did not affect the release of O2-. In the presence of 0.9 mM calcium, only the cis FFA decreased DPH polarization or stimulated the release of O2-. Calcium is known to interact more readily with the ionized carboxyl group of trans FFA, neutralizing the anionic charge through an electrostatic interaction. In support of the requirement for the ionized carboxyl group, structurally similar uncharged cis, trans, and saturated fatty alcohols; methyl esters; and aldehydes decreased DPH polarization in the absence and presence of 0.9 mM calcium; however, none of these compounds stimulated the release of O2-. These results indicate that, in addition to the partitioning of FFA into the plasmalemma, which results in calcium-modulatable decreases in DPH polarization, activation or assembly of the NADPH-oxidase requires the ionized carboxyl group.

Topics: Animals; Arachidonic Acid; Arachidonic Acids; Calcium; Cell Membrane; Cricetinae; Diphenylhexatriene; Dose-Response Relationship, Drug; Eicosanoic Acids; Fatty Acids, Nonesterified; Linolenic Acids; Membrane Lipids; Myristic Acid; Myristic Acids; NADH, NADPH Oxidoreductases; NADPH Oxidases; Neutrophils; Oleic Acid; Oleic Acids; Stearic Acids; Superoxides