Qing Jiang
Purdue University, USA
Title: Vitamin E metabolite 13’-carboxychromanols inhibit pro-inflammatory enzymes, induce apoptosis and autophagy in human cancer cells by modulating sphingolipids and suppress colon tumor development in mice
Biography
Biography: Qing Jiang
Abstract
Vitamin E forms are substantially metabolized to various carboxychromanols including 13’-carboxychromanols (13’-COOHs) that are found at high levels in feces. However, there is limited knowledge about functions of these metabolites. Here we studied ï¤T-13’-COOH and ï¤TE-13’-COOH, which are metabolites of ï¤-tocopherol and ï¤-tocotrienol, respectively. Both 13’-COOHs are much stronger than tocopherols in inhibition of pro-inflammatory and cancer promoting cyclooxygenase-2 (COX-2) and 5-lipoxygnease (5-LOX), and in induction of apoptosis and autophagy in colon cancer cells. The anti-cancer effects by 13’-COOHs appeared to be partially independent of inhibition of COX-2/5-LOX. Using liquid chromatography tandem mass spectrometry, we found that 13’-COOHs increased intracellular dihydrosphingosin and dihydroceramides after short-time incubation in HCT-116 cells, and enhanced ceramides while decreased sphingomyelins during prolonged treatment. Modulation of sphingolipids by 13’-COOHs was observed prior to or coinciding with biochemical manifestation of cell death. Pharmaceutically blocking the increase of these sphingolipids partially counteracted 13’-COOH-induced cell death. Further, 13’-COOH inhibited dihydroceramide desaturase without affecting the protein expression. In agreement with these mechanistic findings, ï¤TE-13’-COOH significantly suppressed the growth and multiplicity of colon tumor in mice. Our study demonstrates that 13’-COOHs have anti-inflammatory and anticancer activities, may contribute to in vivo anticancer effect of vitamin E forms and are promising novel cancer prevention agents.