Docosahexaenoic acid and butyrate synergistically induce colonocyte apoptosis by enhancing mitochondrial Ca2+ accumulation | Academic Article individual record
abstract

We have previously shown that butyrate, a short-chain fatty acid fiber fermentation product, induces colonocyte apoptosis via a nonmitochondrial, Fas-mediated, extrinsic pathway. Interestingly, fermentable fiber when combined with fish oil containing docosahexaenoic acid (DHA, 22:6n-3) exhibits an enhanced ability to induce apoptosis and protect against colon tumorigenesis. To determine the molecular mechanism of action, the effect of DHAand butyrate cotreatment on intracellular Ca 2+ homeostasis was examined. Mouse colonocytes were treated with 50 μmol/L DHA or linoleic acid (LA) for 72 h ± butyrate (0-10 mmol/L) for the final 24 h. Cytosolic and mitochondrial Ca 2+ levels were measured using Fluo-4 and Rhod-2. DHA did not alter basal Ca 2+ or the intracellular inositol trisphosphate (IP 3 ) pool after 6 h butyrate cotreatment. In contrast, at 12 and 24 h, DHA- and butyrate-treated cultures exhibited a 25% and 38% decrease in cytosolic Ca 2+ compared with LA and butyrate. Chelation of extracellular Ca 2+ abolished the effect of thapsigargin on the IP 3 -releasable Ca 2+ pool. DHAand butyrate cotreatment compared with untreated cells increased the mitochondrial-to-cytosolic Ca 2+ ratio at 6, 12, and 24 h by 73%, 18%, and 37%, respectively. The accumulation of mitochondrial Ca 2+ preceded the onset of apoptosis. RU-360, a mitochondrial-uniporter inhibitor, abrogated mitochondrial Ca 2+ accumulation and also partially blocked apoptosis in DHA and butyrate cotreated cells. Collectively, these data show that the combination of DHA and butyrate, compared with butyrate alone, further enhances apoptosis by additionally recruiting a Ca 2+ -mediated intrinsic mitochondrial pathway. ©2007 American Association for Cancer Research.

author list (cited authors)
Kolar, S., Barhoumi, R., Lupton, J. R., & Chapkin, R. S.
publication date
2007
published in
keywords
  • Mice
  • Calcium Channels
  • Homeostasis
  • Mitochondria
  • Animals
  • Colon
  • Cytosol
  • Calcium
  • Butyrates
  • Linoleic Acid
  • Ruthenium Compounds
  • Docosahexaenoic Acids
  • Drug Synergism
  • Calcium Channel Blockers
  • Apoptosis