Raf protects against colitis by promoting mouse colon epithelial cell survival through NF-kappaB.
OBJECTIVE
Raf-1 kinase is a key regulator of a number of cellular processes, which promote the maintenance of a healthy colon epithelium. This study addresses the role of Raf in epithelial cell survival in response to dextran sulfate sodium (DSS)-induced injury and inflammation.


METHODS
Inducible intestinal epithelium-specific Raf knockout mice were generated and subjected to acute colitis followed by a short recovery period. Colon sections were analyzed by in situ oligo ligation or immunostaining for Ki67, phospho-extracellular signal regulated kinase, and nuclear factor-kappaB p65. Western blot analysis and terminal deoxynucleotidyl transferase nick-end labeling assays were performed on Raf small interfering RNA-transfected young adult mouse colon cells following DSS treatment.


RESULTS
We report that Raf protects against epithelial injury and inflammation and promotes recovery from acute DSS-induced colitis by both MAPK/ERK kinase (MEK)-dependent and -independent pathways. Furthermore, we demonstrate that Raf induces novel cell survival responses through activating nuclear factor-kappaB in a MEK-independent manner.


CONCLUSIONS
These novel findings indicate a protective role for Raf in colon epithelium following ulcerative damage through inhibiting cell apoptosis and promoting proliferation with important implications for responses such as inflammation-associated carcinogenesis.
Edelblum
Karen L
KL
Department of Cell and Developmental Biology, Vanderbilt University, Nashville, Tennessee, USA.
Washington
M Kay
MK
Koyama
Tatsuki
T
Robine
Sylvie
S
Baccarini
Manuela
M
Polk
D Brent
DB
D000818:Animals; D017209:Apoptosis; D015153:Blotting, Western; D049109:Cell Proliferation; D002470:Cell Survival; D002478:Cells, Cultured; D003092:Colitis / Q000139:chemically induced / Q000201:enzymology / Q000473:pathology / Q000503:physiopathology / Q000517:prevention & control*; D003106:Colon / Q000201:enzymology* / Q000473:pathology / Q000503:physiopathology; D016264:Dextran Sulfate; D004195:Disease Models, Animal; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D007150:Immunohistochemistry; D020287:In Situ Nick-End Labeling; D007413:Intestinal Mucosa / Q000378:metabolism / Q000473:pathology; D019394:Ki-67 Antigen / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D016328:NF-kappa B / Q000378:metabolism*; D010766:Phosphorylation; D034622:RNA Interference; D012038:Regeneration; D015398:Signal Transduction; D013997:Time Factors; D051996:Transcription Factor RelA / Q000378:metabolism; D014162:Transfection; D048490:raf Kinases / Q000235:genetics / Q000378:metabolism*
D019394:Ki-67 Antigen; D016328:NF-kappa B; C498144:Rela protein, mouse; D051996:Transcription Factor RelA; D016264:Dextran Sulfate; D048490:raf Kinases; D048049:Extracellular Signal-Regulated MAP Kinases