title: Differential effects of β-catenin and NF-κB interplay in the regulation of cell proliferation, inflammation and tumorigenesis in response to bacterial infection.
abstract: Both β-catenin and NF-κB have been implicated in our laboratory as candidate factors in driving proliferation in an in vivo model of Citrobacter rodentium (CR)-induced colonic crypt hyper-proliferation and hyperplasia. Herein, we test the hypothesis that β-catenin and not necessarily NF-κB regulates colonic crypt hyperplasia or tumorigenesis in response to CR infection. When C57Bl/6 wild type (WT) mice were infected with CR, sequential increases in proliferation at days 9 and 12 plateaued off at day 19 and paralleled increases in NF-κB signaling. In Tlr4(-/-) (KO) mice, a sequential but sustained proliferation which tapered off only marginally at day 19, was associated with TLR4-dependent and independent increases in NF-κB signaling. Similarly, increases in either activated or total β-catenin in the colonic crypts of WT mice as early as day 3 post-infection coincided with cyclinD1 and c-myc expression and associated crypt hyperplasia. In KO mice, a delayed kinetics associated predominantly with increases in non-phosphorylated (active) β-catenin coincided with increases in cyclinD1, c-myc and crypt hyperplasia. Interestingly, PKCζ-catalyzed Ser-9 phosphorylation and inactivation of GSK-3β and not loss of wild type APC protein accounted for β-catenin accumulation and nuclear translocation in either strain. In vitro studies with Wnt2b and Wnt5a further validated the interplay between the Wnt/β-catenin and NF-κB pathways, respectively. When WT or KO mice were treated with nanoparticle-encapsulated siRNA to β-catenin (si-β-Cat), almost complete loss of nuclear β-catenin coincided with concomitant decreases in CD44 and crypt hyperplasia without defects in NF-κB signaling. si-β-Cat treatment to Apc(Min/+) mice attenuated CR-induced increases in β-catenin and CD44 that halted the growth of mutated crypts without affecting NF-κB signaling. The predominant β-catenin-induced crypt proliferation was further validated in a Castaneus strain (B6.CAST.11M) that exhibited significant crypt hyperplasia despite an attenuated NF-κB signaling. Thus, β-catenin and not necessarily NF-κB regulates crypt hyperplasia in response to bacterial infection.
authors.affiliation: Department of Internal Medicine, Division of Digestive Diseases and Nutrition, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, United States of America.
authors.forename: Parthasarathy
authors.initials: P
authors.lastname: Chandrakesan
authors.forename: Laxmi Uma Maheswar Rao
authors.initials: LU
authors.lastname: Jakkula
authors.forename: Ishfaq
authors.initials: I
authors.lastname: Ahmed
authors.forename: Badal
authors.initials: B
authors.lastname: Roy
authors.forename: Shrikant
authors.initials: S
authors.lastname: Anant
authors.forename: Shahid
authors.initials: S
authors.lastname: Umar
mesh_terms: D000818:Animals; D015153:Blotting, Western; D063646:Carcinogenesis / Q000378:metabolism*; D049109:Cell Proliferation; D044082:Citrobacter rodentium / Q000472:pathogenicity*; D005455:Fluorescent Antibody Technique; D007150:Immunohistochemistry; D007249:Inflammation / Q000235:genetics / Q000378:metabolism* / Q000382:microbiology; D008297:Male; D051379:Mice; D008817:Mice, Mutant Strains; D060888:Real-Time Polymerase Chain Reaction; D051197:Toll-Like Receptor 4 / Q000235:genetics / Q000378:metabolism; D051996:Transcription Factor RelA / Q000235:genetics / Q000378:metabolism*; D014945:Wound Healing / Q000235:genetics / Q000502:physiology; D051176:beta Catenin / Q000235:genetics / Q000378:metabolism*
chemical_list: C493487:Tlr4 protein, mouse; D051197:Toll-Like Receptor 4; D051996:Transcription Factor RelA; D051176:beta Catenin