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 differentiation. Sodium butyrate (NaBT) treatment induced wild-type RIE (W-RIE) cells to undergo differentiation and apoptosis. Alkaline phosphatase (ALP) activity, a marker of cell differentiation, and DNA fragmentation, an index of apoptosis, were increased by NaBT treatment. Arachidonic acid was metabolized primarily to 12-hydroxyeicosatetraenoic acid (HETE) suggesting induction of 12-LO activity. In contrast, sense-RIE (S-RIE) cells engineered to overexpress COX-2 were resistant to apoptosis by treatment with 5 mM NaBT and NaBT did not induce 12-LO activity. The upregulation of 12-LO expression by NaBT in W-RIE cells was confirmed at both the transcriptional and translational level but 12-LO was undetectable in S-RIE cells following NaBT treatment. The expression of 12-LO mRNA in W-RIE cells occurs as early as 6 h after treatment and reaches maximum expression at 24 h following treatment. This inducible 12-LO was isolated by RT-PCR and identified as rat “leukocyte-type” 12-LO. The level of 12-LO expression in W-RIE cells was dependent on the concentration of NaBT and appears to reflect the extent of cell differentiation. NDGA, a lipoxygenase inhibitor, attenuated induction of ALP activity by NaBT treatment of W-RIE cells. These observations suggested that 12-LO is regulated by treatment with NaBT and is associated with cell differentiation in rat intestinal epithelial cells.