Effect of the Δ6-desaturase inhibitor SC-26196 on PUFA metabolism in human cells

The objective of this study was to determine the effect of 2,2-diphenyl-5-(4-{[(1 E)-pyridin-3-yl-methylidene]-amino}piperazin-1-yl)pentanenitrile (SC-26196), a Delta(6)-desaturase inhibitor, on PUFA metabolism in human cells. SC-26196 inhibited the desaturation of 2 muM [1-C-14]18:2n-6 by 87-95% in cultured human skin fibroblasts, coronary artery smooth muscle cells, and astrocytes. By contrast, SC-26196 did not affect the conversion of [1-C-14] 20:3n-6 to 20:4 in the fibroblasts, demonstrating that it is selective for Delta(6)-desaturase. The IC 50 values for inhibition of the desaturation of 2 muM [1-C-14] 18:3n-3 and [3-C-14]24:5n-3 in the fibroblasts, 0.2-0.4 muM, were similar to those for the inhibition of [1-C-14] 18:2 n-6 desaturation, and the rates of recovery of [1-C-14] 18:2n-6 and [3-(14)]C24:5n-3 desaturation after removal of SC-26196 from the culture medium also were similar. SC-26196 reduced the conversion of [3-C-14]22:5n-3 and [3-C-14]24:5n-3 to DHA by 75 and 84%, respectively, but it had no effect on the retroconversion of [3-C-14]24:6n-3 to DHA. These results demonstrate that SC-26196 effectively inhibits the desaturation of 18- and 24-carbon PUFA and, therefore, decreases the synthesis of arachidonic acid, EPA, and DHA in human cells. Furthermore, they provide additional evidence that the conversion of 22:5n-3 to DHA involves A Delta(6)-desaturation.