INCREASES IN 13-HYDROXYOCTADECADIENOIC ACID DEHYDROGENASE-ACTIVITY DURING DIFFERENTIATION OF CULTURED-CELLS

Recently, oxidation products of linoleic acid such as 13-hydroxyoctadecadienoic acid (HODE) have been implicated in the regulation of cellular physiology including the proliferative response to growth factor treatment. In addition, an NAD+-dependent 13-HODE dehydrogenase was recently described. To evaluate the contribution of this enzyme to cellular processes we have examined the behavior of the enzyme under different conditions. In the present report, changes in the activity of 13-hydroxyoctadecadienoic acid dehydrogenase during in vitro differentiation of two different cell lines were examined. The cell line HT-29 undergoes induced differentiation via manipulation of the medium while the Caco-2 line undergoes spontaneous differentiation upon attainment of confluence. In both cell fines, longer culture times were accompanied by increases in 13-HODE dehydrogenase activity. The increase in enzyme activity continued even after cell proliferation had ceased. Cellular differentiation was verified by the observation of increases in sucrase and alkaline phosphatase activities. In addition, the activity of 13-HODE dehydrogenase was measured in growing, early confluent and late confluent cultures of undifferentiating Swiss mouse 3T3 fibroblasts. In the fibroblast tine, no significant changes in 13-HODE dehydrogenase activity were observed during the course of the experiment. The specific activity of 13-HODE dehydrogenase was also significantly different between the three cell tines, consistent with the extent of differentiation. Highest levels of activity were found in Caco-2 cells (200-400 pmol/min/mg), intermediate levels in the HT-29 cells (20-60 pmol/min/mg) and barely detectable levels in the fibroblasts (0.6-2 pmol/min/mg). The correlation between 13-HODE dehydrogenase and cell differentiation suggests the enzyme may have a role to play in the partitioning of cells between proliferation and differentiation pathways.