Background:
The combination of fish oil-derived docosahexaenoic acid (dha) (22:6; omega 3 [n-3]) and butyrate (4:0), a fiber fermentation product, synergized to enhance colonocyte apoptosis by inducing a p53-independent, oxidation sensitive, mitochondrial ca(2+) -dependent (intrinsic) pathway.
Methods:
In this study, the authors probed the specificity of n-6 and n-3 polyunsaturated fatty acid induction of ca(2+) -dependent proapoptotic events in immortalized young adult mouse colonocytes and determined whether combinations of polyunsaturated fatty acid and butyrate could trigger endoplasmic reticulum (er) stress conditions, thereby promoting mitochondrial ca(2+) overload. cultures were treated with 0 ฮผm to 50 ฮผm of dha (22:6; n-3), epa (20:5; n-3), arachidoinic acid (aa) (20:4; n-6), linoleic acid (18:2; n-6), or oleic acid (oa) (18:1; n-9) for a total of 72 hours with or without ru-360 (to inhibit the mitochondrial ca(2+) uniporter) for 30 minutes before cotreatment with butyrate (0 mm or 5 mm).
Results:
Combined dha and butyrate maximally induced apoptosis and mitochondrial-to-cytosolic ca(2+) levels. by comparison, epa, a precursor to dha, was minimally effective. similarly, aa and oa in combination with butyrate had no effect on mitochondrial ca(2+) or apoptosis compared with butyrate alone. dha with or without butyrate cotreatment minimally altered the er stress-regulated genes dna damage-inducible transcript 3, the ccaat enhancer binding protein (c/ebp) homologous protein (chop), and eukaryotic initiation factor 2ฮฑ.
Conclusions:
The current data indicated that butyrate and dha, but not epa, worked in a coordinated fashion to trigger an er-independent, ca(2+) -dependent, intrinsic mitochondrial-mediated apoptotic pathway in colonocytes.