Interaction of polyunsaturated fatty acids and sodium butyrate during apoptosis in HT-29 human colon adenocarcinoma cells.
BACKGROUND
Dysregulation of the balance between cell growth and death in the colonic epithelium is associated with cancer promotion. Understanding how cell death in this self-renewing tissue is regulated and how it is influenced by interaction of specific dietary components, especially fat and fibre, could lead to improved treatment and prevention strategies for cancer.


OBJECTIVE
The effects of two types of polyunsaturated fatty acids (PUFAs)--arachidonic (AA, 20:4, n-6) or docosahexaenoic (DHA, 22:6, n-3)--on the response of human colon adenocarcinoma HT-29 cells to sodium butyrate (NaBt) were investigated.


METHODS
The parameters reflecting cell proliferation and cell death were studied together with oxidative response, mitochondrial membrane potential (MMP) and changes of selected regulatory molecules associated with cell cycle (p27(Kip1) and p21(Cip1/WAF1)) and apoptosis (caspase-3, caspase-9, poly (ADP-ribose) polymerase--PARP, Bcl-2, Bax, Bak,Mcl-1).


RESULTS
We demonstrated that pre-treatment with either AA or DHA attenuated cell cycle arrest caused by NaBt which is associated with modulation of p27(Kip1), but not p21(Cip1/WAF1) protein expression. On the other hand, PUFAs sensitised HT-29 cells to NaBt-induced apoptosis. An increased amount of floating cells and cells in the subG(0)/G(1) population was associated with increased reactive oxygen species production, lipid peroxidation, decrease of MMP, activation of caspase-3 and -9, PARP cleavage, and decrease in the expression of antiapoptotic Mcl-1 protein. The observed effects were modulated by the addition of a protein synthesis inhibitor, cycloheximide, and partially reversed by the antioxidant Trolox.


CONCLUSIONS
PUFAs may have beneficial effects in the colon enhancing apoptosis induced by NaBt. Alteration of cell membrane lipid composition and potentiation of oxidative processes accompanied by changes in mitochondria followed by stimulation of apoptotic cascade components play a role in these effects.
Laboratory of Cytokinetics, Institute of Biophysics, Academy of Sciences of the Czech Republic, Královopolská 135, 61265 Brno, Czech Republic. hofmanova@ibp.cz
Jirina
J
Hofmanová
Alena
A
Vaculová
Antonín
A
Lojek
Alois
A
Kozubík
D000230:Adenocarcinoma / Q000378:metabolism*; D017209:Apoptosis / Q000187:drug effects; D016718:Arachidonic Acid / Q000008:administration & dosage; D015153:Blotting, Western; D002087:Butyrates / Q000378:metabolism*; D053148:Caspase 3; D053453:Caspase 9; D020169:Caspases / Q000187:drug effects / Q000378:metabolism; D002453:Cell Cycle / Q000187:drug effects; D003110:Colonic Neoplasms / Q000378:metabolism*; D004281:Docosahexaenoic Acids / Q000008:administration & dosage; D004305:Dose-Response Relationship, Drug; D005231:Fatty Acids, Unsaturated / Q000378:metabolism*; D005434:Flow Cytometry; D019073:HT29 Cells; D006801:Humans; D015227:Lipid Peroxidation / Q000187:drug effects; D008564:Membrane Potentials / Q000187:drug effects; D008856:Microscopy, Fluorescence; D011065:Poly(ADP-ribose) Polymerases / Q000187:drug effects / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000187:drug effects / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism
D002087:Butyrates; D005231:Fatty Acids, Unsaturated; D011518:Proto-Oncogene Proteins; D017382:Reactive Oxygen Species; D004281:Docosahexaenoic Acids; D016718:Arachidonic Acid; D011065:Poly(ADP-ribose) Polymerases; C505407:CASP3 protein, human; C506433:CASP9 protein, human; D053148:Caspase 3; D053453:Caspase 9; D020169:Caspases