9-trans, 11-trans-CLA:: Antiproliferative and proapoptotic effects on bovine endothelial cells

Endothelial cell function can be influenced by nutrition, especially dietary FA and antioxidants. One class of dietary FA that is found in meat and dairy products derived from ruminant animals is conjugated linoleic acids (CLA). We have examined the effects of several CLA isomers on endothelial cell proliferation. 9t,11t-CLA was the only isomer that inhibited bovine aortic endothelial cell (BAEC) [H-3]methylthymidine incorporation (I-50 35 mu M), and this antiproliferative effect was time-dependent. A small decrease (20%) in cell number was observed only at the highest concentration (60 mu M) tested. The 9c,11t-, 9c,11c-, 10t 12c-, and 11 c,13t-CLA isomers did not exhibit any anti proliferative effects over a 5-60 mu M concentration range. alpha-Tocopherol and BHT decreased BAEC proliferation, but pretreatment of cells with either of these antioxidants substantially attenuated the anti proliferative effect of 9t,11t-CLA. No difference in lipid peroxidation, as measured by the thiobarbituric acid assay for malondialdehyde, was observed on treatment of endothelial cells with either 9t,11t- or 9c,11t-CLA. However, a 43% increase in caspase-3 activity was observed after incubating BAEC with 9t,11t-CLA, suggesting that the anti proliferative effect of this isomer is partially due to an apoptotic pathway. In contrast to the above results with normal endothelial cells, these five CLA isomers all inhibited proliferation of the human leukemic cell line THP-1, with the 9t,11t isomer again being the most (I-50 = 60 mu M) effective. These results confirm that different CLA isomers have different inhibitory potencies on the proliferation of normal and leukemic cells.