title: Inhibition of mitochondrial gene transcription suppresses neurotensin secretion in the human carcinoid cell line BON.
abstract: Mitochondria, organelles essential for ATP production, play a central role in a number of cellular functions, including the regulation of insulin secretion. Neurotensin (NT), an important regulatory intestinal hormone, has been implicated in fatty acid translocation, gut motility and secretion, and intestinal cell growth; however, mechanisms regulating NT secretion have not been entirely defined. The purpose of this study was to determine the effect of inhibition of mitochondrial gene transcription on NT secretion. BON cells, a novel human carcinoid cell line that produces and secretes NT peptide and expresses the gene encoding NT (designated NT/N), were treated with ethidium bromide (EB; 0.05, 0.1, and 0.4 microg/ml), an inhibitor of DNA and RNA synthesis, or vehicle over a time course (1-4 days). Cells were then stimulated with either ACh (100 microM) or phorbol 12 myristate,13-acetate (PMA, 10 nM) for 30 min. Media and cells were extracted, and NT peptide measured by RIA. Treatment with EB had no effect on BON cell viability or cell cycle distribution over the 4-day course. In contrast, EB treatment produced a dose-dependent reduction of mitochondrial gene expression; however, NT/N gene expression was not altered. Mitochondrial inhibition by EB treatment suppressed NT secretion induced by ACh and PMA, both in a dose-dependent manner. EB-mediated inhibition of NT secretion and mitochondrial gene expression was reversed with removal of EB. Our results demonstrate that inhibition of mitochondrial gene transcription suppresses both ACh- and PMA-stimulated NT release. These findings are the first to demonstrate that mitochondrial function is important for agonist-mediated NT secretion.
authors.affiliation: Department of Surgery, The University of Texas Medical Branch, Galveston, Texas 77555-0536, USA.
authors.forename: Nan
authors.initials: N
authors.lastname: Li
authors.forename: Qingding
authors.initials: Q
authors.lastname: Wang
authors.forename: Jing
authors.initials: J
authors.lastname: Li
authors.forename: Xiaofu
authors.initials: X
authors.lastname: Wang
authors.forename: Mark R
authors.initials: MR
authors.lastname: Hellmich
authors.forename: Srinivasan
authors.initials: S
authors.lastname: Rajaraman
authors.forename: George H
authors.initials: GH
authors.lastname: Greeley
authors.forename: Courtney M
authors.initials: CM
authors.lastname: Townsend
authors.forename: B Mark
authors.initials: BM
authors.lastname: Evers
mesh_terms: D000109:Acetylcholine / Q000494:pharmacology; D002276:Carcinoid Tumor; D002453:Cell Cycle / Q000187:drug effects; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D004064:Digestive System / Q000166:cytology / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004996:Ethidium / Q000494:pharmacology; D006801:Humans; D008928:Mitochondria / Q000187:drug effects / Q000502:physiology*; D009496:Neurotensin / Q000096:biosynthesis / Q000378:metabolism*; D009840:Oligomycins / Q000494:pharmacology; D014158:Transcription, Genetic / Q000187:drug effects / Q000502:physiology*
chemical_list: D004791:Enzyme Inhibitors; D009840:Oligomycins; D009496:Neurotensin; D004996:Ethidium; D000109:Acetylcholine