In vivo crypt surface hyperproliferation is decreased by butyrate and increased by deoxycholate in normal rat colon: associated in vivo effects on c-Fos and c-Jun expression.
BACKGROUND
Studies on colon carcinogenesis suggest that the short-chain fatty acid butyrate may be protective, whereas the secondary bile acid deoxycholate may promote tumor development. Crypt surface hyperproliferation is regarded as a biomarker of colon cancer risk and can be modulated in vitro by the differentiation inducer butyrate and the tumor promoter deoxycholate. We hypothesized that butyrate decreases and deoxycholate increases crypt surface proliferation in vivo and that these effects are mediated by changes in the expression of the protooncogenes c-Fos and c-Jun, which are known to regulate proliferation and differentiation.


METHODS
Twenty-five adult Sprague-Dawley rats underwent colonic isolation and 24-hour intraluminal instillation of 10 mmol/L sodium chloride, 10 mmol/ L sodium butyrate, or 10 mmol/L sodium deoxycholate. Proliferation of the whole crypt and five crypt compartments from base to surface was assessed by proliferating cell nuclear antigen immunohistochemistry. The øh value, an index of "premalignant" hyperproliferation, was calculated as the ratio of labeled cells in the two surface compartments divided by the labeled cells in the entire crypt. Expression of c-Fos and c-Jun was evaluated by Western blot.


RESULTS
Crypt surface proliferation and the øh value were significantly decreased by butyrate and increased by deoxycholate. Butyrate increased colonic expression of c-Jun, whereas deoxycholate significantly induced c-Fos.


CONCLUSIONS
The in vivo effects on surface proliferation are consistent with a potential protective [corrected] role for butyrate and a promotive role for deoxycholate in colon carcinogenesis. The concurrently observed effects on colonic c-Jun and c-Fos expression represent a novel finding and suggest that direct or indirect modulation of protooncogene expression may be the mechanism by which these dietary byproducts regulate proliferation in vivo.
Velázquez
O C
OC
Harrison Department of Surgical Research, University of Pennsylvania Medical Center, Philadelphia, USA.
Zhou
D
D
Seto
R W
RW
Jabbar
A
A
Choi
J
J
Lederer
H M
HM
Rombeau
J L
JL
D000818:Animals; D015153:Blotting, Western; D002087:Butyrates / Q000494:pharmacology*; D020148:Butyric Acid; D002455:Cell Division / Q000187:drug effects; D002756:Cholagogues and Choleretics / Q000633:toxicity*; D003106:Colon / Q000187:drug effects* / Q000473:pathology; D003840:Deoxycholic Acid / Q000494:pharmacology*; D008297:Male; D018809:Proliferating Cell Nuclear Antigen; D016760:Proto-Oncogene Proteins c-fos / Q000187:drug effects*; D016755:Proto-Oncogene Proteins c-jun / Q000187:drug effects*; D051381:Rats; D017207:Rats, Sprague-Dawley
D002087:Butyrates; D002756:Cholagogues and Choleretics; D018809:Proliferating Cell Nuclear Antigen; D016760:Proto-Oncogene Proteins c-fos; D016755:Proto-Oncogene Proteins c-jun; D003840:Deoxycholic Acid; D020148:Butyric Acid