METABOLISM OF 4-HYDROXY TRANS 2- NONENAL (HNE) IN CULTURED PC-12 CELLS

One of the most reactive aldehyde generated from the lipid peroxidation reactions is alpha, beta-unsaturated aldehyde, 4,hydroxyl trans-2-nonenal (HNE). Due to alpha, beta-unsaturation, HNE is extremely reactive molecule. At low concentrations, HNE is involved in cell signaling whereas higher concentrations of HNE are cytotoxic (1). The biological effects of HNE will be dependent on the metabolism of HNE. The present investigations were carried out to examine the metabolism of HNE in PC-12 cells and to study the cytotoxic effects of HNE as well as the effect of non-toxic concentrations of HNE on neurotransmitter receptors. Our data shows that in PC-12 cells, at low (physiological) concentrations HNE is primarily metabolized by glutathiolation and oxidation, whereas at higher (pathological) concentrations, in addition to glutathiolation and oxidation, a significant fraction of HNE is reduced in PC-12 cells. Moreover, at higher concentrations, HNE also shows the abundance of two hydrophobic peaks, the structural identities of which has yet not been established. Mass spectroscopic analysis also shows that glutathionyl adduct of HNE is present as two forms-GS-HNE and its reduced metabolite GS-DHN. However, unlike the cardiovascular cells, reduction of GS-HNE is not catalyzed by aldose reductase, since inhibition of aldose reductase, did not abolish the reduction of GS-HNE in PC-12 cells. However, similar to other cells, oxidation of HNE in PC-12 cells was significantly inhibited by aldehyde dehydrogenase inhibitor, benomyl, suggesting that aldehyde dehydrogenase-mediated oxidation of HNE is an important route for the elimination of HNE in neuronal cells.