title: Tumor necrosis factor (TNF) alpha increases collagen accumulation and proliferation in intestinal myofibroblasts via TNF receptor 2.
abstract: Intestinal fibrosis is an incurable complication of Crohn's disease involving increased numbers of collagen-producing myofibroblasts. Tumor necrosis factor (TNF) alpha has defined proinflammatory roles in Crohn's disease but its role in fibrosis is unclear. We tested the hypothesis that TNFalpha increases collagen accumulation and proliferation in intestinal myofibroblasts and has additive effects in combination with insulin-like growth factor (IGF) I. The mechanisms, TNF receptor isoform, and downstream signaling pathways were examined. Intestinal myofibroblasts from wild-type (WT) mice or mice homozygous for disruption of genes encoding TNFR1 (TNFR1-/-), TNFR2 (TNFR2-/-), or both (TNFR1/2-/-), were treated with TNFalpha, IGF-I, or both. In WT cells, TNFalpha and IGF-I stimulated type I collagen accumulation and DNA synthesis in an additive manner. IGF-I, but not TNFalpha, stimulated type I collagen gene activation. TNFalpha, but not IGF-I, induced tissue inhibitor of metalloproteinase-1 (TIMP-1) expression and reduced matrix metalloproteinases-2 activity and collagen degradation. TNFalpha also activated ERK1/2. These responses to TNFalpha were absent in TNFR2-/- and TNFR1/2-/- myofibroblasts, whereas TNFR1-/- cells showed similar responses to WT. Inhibition of ERK1/2 diminished TNFalpha induced DNA synthesis in WT and TNFR1-/- cells. Differences in TNFalpha-induced STAT3/DNA binding activity and not NFkappaB and AP-1 transcriptional activation correlated with impaired collagen accumulation/TIMP-1 induction in TNFR2(-/-) cells. Constitutively active STAT3 rescued TIMP-1 expression in TNFR2-/- cells. We conclude that TNFalpha and IGF-I may additively contribute to fibrosis during intestinal inflammation. TNFR2 is a primary mediator of fibrogenic actions of TNFalpha acting through ERK1/2 to stimulate proliferation and through STAT3 to stimulate TIMP-1 and inhibit collagen degradation.
authors.affiliation: Department of Cell and Molecular Physiology, University of North Carolina, Chapel Hill, North Carolina 27599, USA.
authors.forename: Arianne L
authors.initials: AL
authors.lastname: Theiss
authors.forename: James G
authors.initials: JG
authors.lastname: Simmons
authors.forename: Christian
authors.initials: C
authors.lastname: Jobin
authors.forename: P Kay
authors.initials: PK
authors.lastname: Lund
mesh_terms: D000818:Animals; D015152:Blotting, Northern; D015153:Blotting, Western; D049109:Cell Proliferation; D003094:Collagen / Q000378:metabolism*; D004247:DNA / Q000737:chemistry / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation; D005347:Fibroblasts / Q000378:metabolism*; D005355:Fibrosis / Q000378:metabolism; D005838:Genotype; D049452:Green Fluorescent Proteins / Q000378:metabolism; D006720:Homozygote; D007249:Inflammation; D007334:Insulin-Like Growth Factor I / Q000378:metabolism; D007413:Intestinal Mucosa / Q000378:metabolism; D020778:Matrix Metalloproteinase 2 / Q000378:metabolism; D051379:Mice; D008822:Mice, Transgenic; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism*; D016328:NF-kappa B / Q000378:metabolism; D020033:Protein Isoforms; D012313:RNA / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D018124:Receptors, Tumor Necrosis Factor / Q000737:chemistry; D047889:Receptors, Tumor Necrosis Factor, Type II / Q000378:metabolism*; D050796:STAT3 Transcription Factor / Q000378:metabolism / Q000502:physiology*; D015398:Signal Transduction; D013997:Time Factors; D019715:Tissue Inhibitor of Metalloproteinase-1 / Q000378:metabolism*; D018808:Transcription Factor AP-1 / Q000378:metabolism; D014158:Transcription, Genetic; D015533:Transcriptional Activation; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism / Q000502:physiology*; D015854:Up-Regulation
chemical_list: D016328:NF-kappa B; D020033:Protein Isoforms; D012333:RNA, Messenger; D018124:Receptors, Tumor Necrosis Factor; D047889:Receptors, Tumor Necrosis Factor, Type II; D050796:STAT3 Transcription Factor; D019715:Tissue Inhibitor of Metalloproteinase-1; D018808:Transcription Factor AP-1; D014409:Tumor Necrosis Factor-alpha; D049452:Green Fluorescent Proteins; D012313:RNA; D007334:Insulin-Like Growth Factor I; D003094:Collagen; D004247:DNA; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020778:Matrix Metalloproteinase 2