Isomers of trans fatty acids modify the activity of platelet 12-P lipoxygenase and cyclooxygenase/thromboxane synthase.
OBJECTIVE
Trans isomers of fatty acids (TFA) have been implicated in the initiation and progression of atherosclerosis. Previous studies have shown that trans-unsaturated fatty acids like their cis-unsaturated counterparts exert a modifying effect on platelet aggregation. The aim of this work was to determine the influence of TFA on the aforementioned enzymes: lipoxygenase and cyclooxygenase/thromboxane synthase.


METHODS
Two C18 cis-trans fatty acid pairs: oleic/elaidic and linoleic/linolelaidic were chosen. Fasting blood was sampled from 30 healthy volunteers without any lipid abnormalities and not on medication for at least 7 days prior to sampling. Platelet-rich plasma (PRP) was prepared and the platelet count was adjusted to 3 x 10(8) cells x ml(-1). Fatty acids in hexane were added to a final concentration of 7 microM and evaporated to dryness under nitrogen, 500 microl of PRP was pipetted into each tube, thoroughly mixed and incubated at 37 degrees C for 60 min. 12-P LOX activity was measured with a spectrophotometric method and expressed per mg protein. Cyclooxygenase/thromboxane synthase activity was determined by TXB(2) production with an ELISA-based assay. Statistics were done with the Kruskal-Wallis test and Statistica software package.


RESULTS
We have found that the activity of 12-P LOX was suppressed by all cis-trans fatty acids used by us. Cyclooxygenase/thromboxane synthase activity was significantly inhibited by polyunsaturated fatty acids only. Linolelaidic acid was more potent in comparison to its monounsaturated (elaidic acid) counterpart.


CONCLUSIONS
We believe that the effects of fatty acids are demonstrated at the membrane level where fatty acids may produce a perturbation in specific lipid domains. TFA are able to interact with the platelet membrane and transmembrane proteins just as the cis isomers. By interacting with proteins exposed on the cytoplasmic membrane, TFA may modify the activity of receptors and other membrane proteins. In this way, changes on the membrane surface are propagated into the cell affecting the activity of cytoplasmic enzymes like 12-P LOX and cyclooxygenase/thromboxane synthase.
Stachowska
Ewa
E
Department of Biochemistry and Chemistry, Pomeranian Medical University, Szczecin, Poland. ewast@sci.pan.szczecin.pl
Dołegowska
Barbara
B
Olszewska
Maria
M
Gutowska
Izabela
I
Chlubek
Dariusz
D
D001792:Blood Platelets / Q000187:drug effects* / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects; D004797:Enzyme-Linked Immunosorbent Assay; D006801:Humans; D007536:Isomerism; D008084:Lipoxygenase / Q000097:blood*; D015539:Platelet Activation / Q000187:drug effects / Q000502:physiology*; D011451:Prostaglandin-Endoperoxide Synthases / Q000097:blood*; D012016:Reference Values; D013930:Thromboxane-A Synthase / Q000097:blood*; D044242:Trans Fatty Acids / Q000494:pharmacology*
D044242:Trans Fatty Acids; D008084:Lipoxygenase; D011451:Prostaglandin-Endoperoxide Synthases; D013930:Thromboxane-A Synthase