Butyrate-induced apoptosis and cell cycle arrest in bovine kidney epithelial cells: involvement of caspase and proteasome pathways.
Beyond their nutritional effect, short-chain fatty acids, especially butyrate, modulate cell differentiation, proliferation, motility, and in particular, they induce cell cycle arrest and apoptosis. A bovine kidney epithelial cell line (Madin-Darby bovine kidney; MDBK) was used to investigate the cell cycle regulatory and apoptotic effects of butyrate. Butyrate not only induced apoptosis but also induced cell cycle arrest at the G1/S boundary and M/G2 in MDBK cells (P < 0.01). The cell responses were concentration-dependent (r(2) = 0.9482, P <0.001). In examining possible mechanisms for the apoptosis and cell cycle arrest induced by butyrate, the results showed that butyrate treatment activates caspase-3 activities and induces accumulation of acetylated histone. At least two proteins, cdc6 and cdk1, become targeted for destruction on butyrate treatment. These two proteins are downregulated (P < 0.01 and P < 0.05, respectively) by proteolytic pathways. Moreover, the proteasome inhibitor MG-132 (carbobenzoxy-L-leucyl-L-leucyl-L-leucinal) reverses the cell cycle arrest induced by butyrate, indicating a multiprotein crosstalk wherein the ubiquitination/ proteasome pathway interacted with the caspase-signaling pathway. Because the proteasome inhibitor MG-132 blocked activation of caspase-3, these results functionally locate the proteasome pathway upstream of the caspase pathway. All these results indicate that butyrate functions as both a nutrient and signaling molecule regulating cell growth and proliferation.
Li
C J
CJ
Growth Biology Laboratory, Animal and Natural Resources Institute, ARS, USDA, Beltsville, MD 20705, USA. cli@anri.barc.usda.gov <cli@anri.barc.usda.gov>
Elsasser
T H
TH
D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D015153:Blotting, Western; D002087:Butyrates / Q000494:pharmacology*; D053148:Caspase 3 / Q000187:drug effects / Q000502:physiology*; D002417:Cattle; D002453:Cell Cycle / Q000187:drug effects*; D018797:Cell Cycle Proteins / Q000187:drug effects; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004847:Epithelial Cells / Q000166:cytology / Q000187:drug effects*; D005434:Flow Cytometry; D006657:Histones / Q000032:analysis / Q000187:drug effects; D020287:In Situ Nick-End Labeling / Q000379:methods; D007668:Kidney / Q000166:cytology / Q000187:drug effects; D007976:Leupeptins / Q000494:pharmacology; D009687:Nuclear Proteins / Q000187:drug effects; D046988:Proteasome Endopeptidase Complex / Q000187:drug effects / Q000502:physiology*
D002087:Butyrates; C502132:CDC6 protein, mouse; D018797:Cell Cycle Proteins; D006657:Histones; D007976:Leupeptins; D009687:Nuclear Proteins; D053148:Caspase 3; D046988:Proteasome Endopeptidase Complex; C072553:benzyloxycarbonylleucyl-leucyl-leucine aldehyde