Total parenteral nutrition-induced apoptosis in mouse intestinal epithelium: regulation by the Bcl-2 protein family.
Apoptosis of intestinal epithelial cells (EC) plays a role in total parenteral nutrition (TPN)-induced villus atrophy. Among the mediators of apoptosis in EC are some members of the Bcl-2 family of proteins. Bcl-2 members can either be anti- (Bcl-2, Bcl-x(L), Bcl-w) or pro-apoptotic (Bax, Bak, Bid, Bad, Bcl-x(S)). To determine whether the observed increase in apoptosis induced by TPN is associated with an alteration in these Bcl-2 members' mRNA expression, mice were randomized to either TPN or oral feeding (controls). Animals were killed after 7 days and the intestine was harvested. EC were purified with magnetic beads. Apoptosis was detected by cell-surface expression of phosphatidylserine using flow cytometry. EC mRNA expression was determined by reverse-transcriptase polymerase chain reaction. Results were expressed relative to beta-actin. TPN resulted in a significant ( P < 0.05, unpaired t-test) increase in apoptosis: TPN 29.4 +/- 11.3% versus control 14.4 +/- 5.1%. The expression of the pro-apoptotic members Bax, Bak, Bid, and Bcl-x(S) was significantly ( P < 0.05) decreased after TPN. In contrast, a significant increase was observed in the anti-apoptotic member Bcl-2. mRNA expression of Bcl-w, Bad, and Bcl-x(L) was not significantly different between the control and TPN groups. Thus TPN-induced apoptosis was associated with an increased expression of anti-apoptotic factors and a decrease in pro-apoptotic factors. This contrasts with other reports where these factors showed converse effects under apoptotic conditions. Our results may demonstrate a unique regulatory pathway that may counter the observed increase in TPN-induced EC apoptosis.
Wildhaber
B E
BE
Section of Pediatric Surgery, Department of Surgery, University of Michigan Medical School and C.S. Mott Children's Hospital, Ann Arbor, MI 48109, USA.
Lynn
K N
KN
Yang
H
H
Teitelbaum
D H
DH
D000818:Animals; D017209:Apoptosis; D004847:Epithelial Cells / Q000378:metabolism; D005434:Flow Cytometry; D007413:Intestinal Mucosa / Q000378:metabolism*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D010289:Parenteral Nutrition, Total; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000502:physiology*; D012333:RNA, Messenger / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction
D019253:Proto-Oncogene Proteins c-bcl-2; D012333:RNA, Messenger