Regulation of 12-lipoxygenase in rat intestinal epithelial cells during differentiation and apoptosis induced by sodium butyrate

We evaluated the expression and activity of rat 12-lipoxygenase (LO) in rat intestinal epithelial (RIE) cells during apoptosis and cell differentiatio n. Sodium butyrate (NaBT) treatment induced wildtype RIE (W-RIE) cells to u ndergo differentiation and apoptosis. Alkaline phosphatase (ALP) activity, a marker of cell differentiation, and DNA fragmentation, an index of apopto sis, were increased by NaBT treatment. Arachidonic acid was metabolized pri marily to 12-hydroxyeicosatetraenoic acid (HETE) suggesting induction of 12 -LO activity. In contrast, sense-RIE (S-RIE) cells engineered to overexpres s COX-2 were resistant to apoptosis by treatment with 5 mM NaBT and NaBT di d not induce 12-LO activity, The upregulation of 12-LO expression by NaBT i n W-RIE cells was confirmed at both the transcriptional and translational l evel but 12-LO was undetectable in S-RIE cells following NaBT treatment. Th e expression of 12-LO mRNA in W-RIE cells occurs as early as 6 h after trea tment and reaches maximum expression at 24 h following treatment. This indu cible 12-LO was isolated by RT-PCR and identified as rat "leukocyte-type" 1 2-LO. The level of 12-LO expression in W-RIE cells was dependent on the con centration of NaBT and appears to reflect the extent of cell differentiatio n. NDGA, a lipoxygenase inhibitor, attenuated induction of ALP activity by NaBT treatment of W-RIE cells. These observations suggested that 12-LO is r egulated by treatment with NaBT and is associated with cell differentiation in rat intestinal epithelial cells. (C) 1999 Academic Press.