title: Epithelial atrophy in oral submucous fibrosis is mediated by copper (II) and arecoline of areca nut.
abstract: Exposure of oral cavity to areca nut is associated with several pathological conditions including oral submucous fibrosis (OSF). Histopathologically OSF is characterized by epithelial atrophy, chronic inflammation, juxtaepithelial hyalinization, leading to fibrosis of submucosal tissue and affects 0.5% of the population in the Indian subcontinent. As the molecular mechanisms leading to atrophied epithelium and fibrosis are poorly understood, we studied areca nut actions on human keratinocyte and gingival fibroblast cells. Areca nut water extract (ANW) was cytotoxic to epithelial cells and had a pro-proliferative effect on fibroblasts. This opposite effect of ANW on epithelial and fibroblast cells was intriguing but reflects the OSF histopathology such as epithelial atrophy and proliferation of fibroblasts. We demonstrate that the pro-proliferative effects of ANW on fibroblasts are dependent on insulin-like growth factor signalling while the cytotoxic effects on keratinocytes are dependent on the generation of reactive oxygen species. Treatment of keratinocytes with arecoline which is a component of ANW along with copper resulted in enhanced cytotoxicity which becomes comparable to IC(50) of ANW. Furthermore, studies using cyclic voltammetry, mass spectrometry and plasmid cleavage assay suggested that the presence of arecoline increases oxidation reduction potential of copper leading to enhanced cleavage of DNA which could generate an apoptotic response. Terminal deoxynucleotidyl transferase dUTP Nick End Labeling assay and Ki-67 index of OSF tissue sections suggested epithelial apoptosis, which could be responsible for the atrophy of OSF epithelium.
authors.affiliation: Department of Molecular Reproduction, Development and Genetics, Indian Institute of Science, Bangalore, India.
authors.forename: Imran
authors.initials: I
authors.lastname: Khan
authors.affiliation: Department of Molecular Reproduction, Development and Genetics, Indian Institute of Science, Bangalore, India.
authors.forename: Ila
authors.initials: I
authors.lastname: Pant
authors.affiliation: Department of Molecular Reproduction, Development and Genetics, Indian Institute of Science, Bangalore, India.
authors.forename: Sivakrishna
authors.initials: S
authors.lastname: Narra
authors.affiliation: Clumax Diagnostics, Bangalore, India.
authors.forename: Rekha
authors.initials: R
authors.lastname: Radhesh
authors.affiliation: Department of Oral Pathology, Ragas Dental College and Hospital, Chennai, India.
authors.forename: Kannan
authors.initials: K
authors.lastname: Ranganathan
authors.affiliation: Department of Oral and Maxillofacial Surgery, D.A. Pandu Memorial - R.V. Dental College and Hospital, Bangalore, India.
authors.forename: Somanahalli Girish
authors.initials: SG
authors.lastname: Rao
authors.affiliation: Department of Molecular Reproduction, Development and Genetics, Indian Institute of Science, Bangalore, India.
authors.forename: Paturu
authors.initials: P
authors.lastname: Kondaiah
mesh_terms: D017209:Apoptosis / Q000187:drug effects; D001114:Areca / Q000737:chemistry*; D001115:Arecoline / Q000633:toxicity*; D001284:Atrophy; D002374:Catalase / Q000378:metabolism; D049109:Cell Proliferation / Q000187:drug effects; D002478:Cells, Cultured; D003300:Copper / Q000633:toxicity*; D053837:DNA Cleavage / Q000187:drug effects; D004848:Epithelium / Q000187:drug effects / Q000473:pathology*; D005347:Fibroblasts / Q000166:cytology / Q000187:drug effects; D006801:Humans; D020287:In Situ Nick-End Labeling; D015603:Keratinocytes / Q000166:cytology / Q000187:drug effects; D019394:Ki-67 Antigen / Q000378:metabolism; D009754:Nuts / Q000737:chemistry*; D009914:Oral Submucous Fibrosis / Q000473:pathology*; D010084:Oxidation-Reduction / Q000187:drug effects; D010936:Plant Extracts / Q000633:toxicity; D017526:Receptor, IGF Type 1 / Q000378:metabolism; D013481:Superoxides / Q000378:metabolism
chemical_list: D019394:Ki-67 Antigen; D010936:Plant Extracts; D013481:Superoxides; D001115:Arecoline; D003300:Copper; D002374:Catalase; D017526:Receptor, IGF Type 1
keywords: areca nut cytotoxicity; copper; epithelial atrophy