title: Mitogen-activated protein kinase up-regulation and activation during rat parotid gland atrophy and regeneration: role of epidermal growth factor and beta2-adrenergic receptors.
abstract: The rat secretory ductal obstruction model has been widely used to assess salivary gland injury, growth, and differentiation. In this study, a novel ductal obstruction and release procedure was used to explore the signaling pathways leading to salivary gland regeneration. Rats underwent bilateral parotid ductal obstruction in which the duct was occluded against a plastic disk subcutaneously and released by external ligature removal. This ductal obstruction/release procedure was validated to produce glandular atrophy and regeneration with histological analysis and periodic acid-Schiff staining. Immunoblot analysis indicated that during ductal obstruction and the early post-release period (day 7), expression of immunoreactive proliferating cell nuclear antigen and vimentin was increased in the parotid glands compared with sham-operated animals. Immunohistochemical staining and immunoblots revealed up-regulation of the mitogen-activated protein kinases (MAPKs), extracellular signal-regulated receptor kinase (ERK)1/2, and p38 during the atrophic and regeneration phases of ductal obstruction/release. Similarly, increases in activated, i.e., phosphorylated, ERK1/2 (pERK1/2) and p38 (phospho-p38) were demonstrable in both ductal and recovering acinar cells, with pERKs expressed predominantly in the nuclei and phospho-p38 distributed throughout the cells. Furthermore, levels of epidermal growth factor (EGF) receptor and beta2-adrenergic receptor (beta2-AR) were elevated in the ligated glands and at day 7 post-release; beta1-AR levels did not change over the same time period. These results support the view that cell proliferation is involved in duct ligation-induced atrophy of the rat parotid gland and gland recovery upon ligature removal. Up-regulation of ERKs and p38, and the activation of these MAPKs by up-regulated EGF and beta2-ARs, may be important signaling components underlying glandular atrophy and subsequent regeneration.
authors.affiliation: Department of Community Dentistry, The University of Texas Health Science Center, San Antonio, TX, USA.
authors.forename: Howard
authors.initials: H
authors.lastname: Dang
authors.forename: James J
authors.initials: JJ
authors.lastname: Elliott
authors.forename: Alan L
authors.initials: AL
authors.lastname: Lin
authors.forename: Bing
authors.initials: B
authors.lastname: Zhu
authors.forename: Michael S
authors.initials: MS
authors.lastname: Katz
authors.forename: Chih-Ko
authors.initials: CK
authors.lastname: Yeh
mesh_terms: D000818:Animals; D001284:Atrophy; D002455:Cell Division; D004789:Enzyme Activation; D004790:Enzyme Induction; D066246:ErbB Receptors / Q000235:genetics / Q000378:metabolism*; D008026:Ligation; D020935:MAP Kinase Signaling System / Q000502:physiology*; D008297:Male; D019950:Mitogen-Activated Protein Kinase 1 / Q000235:genetics / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3 / Q000235:genetics / Q000378:metabolism*; D010306:Parotid Gland / Q000201:enzymology / Q000378:metabolism* / Q000473:pathology / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D018343:Receptors, Adrenergic, beta-2 / Q000235:genetics / Q000378:metabolism*; D012038:Regeneration / Q000502:physiology*; D018987:Salivary Ducts / Q000601:surgery; D013234:Stem Cells / Q000166:cytology; D015854:Up-Regulation; D048051:p38 Mitogen-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism*
chemical_list: D018343:Receptors, Adrenergic, beta-2; C483803:Egfr protein, rat; D066246:ErbB Receptors; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D048051:p38 Mitogen-Activated Protein Kinases