title: Activation of calcitonin gene-related peptide signaling through the prostaglandin E2-EP1/EP2/EP4 receptor pathway in synovium of knee osteoarthritis patients.
abstract: BACKGROUND
  Calcitonin gene-related peptide (CGRP) is a 37-amino-acid vasodilatory neuropeptide that binds to receptor activity-modifying protein 1 (RAMP1) and the calcitonin receptor-like receptor (CLR). Clinical and preclinical evidence suggests that CGRP is associated with hip and knee joint pain; however, the regulation mechanisms of CGRP/CGRP receptor signaling in synovial tissue are not fully understood.
  
  
  METHODS
  Synovial tissues were harvested from 43 participants with radiographic knee osteoarthritis (OA; unilateral Kellgren/Lawrence (K/L) grades 3-4) during total knee arthroplasty. Correlationships between the mRNA expression levels of CGRP and those of tumor necrosis factor-α (TNF-α), interleukin (IL)-1β, IL-6, and cycloxygenase-2 (COX-2) were evaluated using real-time PCR analysis of total RNA extracted from the collected synovial tissues. To investigate the factors controlling the regulation of CGRP and CGRP receptor expression, cultured synovial cells were stimulated with TNF-α, IL-1β, IL-6, and prostaglandin E2 (PGE2) and were also treated with PGE2 receptor (EP) agonist.
  
  
  RESULTS
  CGRP and COX-2 localized in the synovial lining layer. Expression of COX-2 positively correlated with CGRP mRNA expression in the synovial tissue of OA patients. The gene expression of CGRP and RAMP1 increased significantly in synovial cells exogenously treated with PGE2 compared to untreated control cells. In cultured synovial cells, CGRP gene expression increased significantly following EP4 agonist treatment, whereas RAMP1 gene expression increased significantly in the presence of exogenously added EP1 and EP2 agonists.
  
  
  CONCLUSIONS
  PGE2 appears to regulate CGRP/CGRP receptor signaling through the EP receptor in the synovium of knee OA patients.
authors.affiliation: Department of Orthopedic Surgery, Kitasato University School of Medicine, 1-15-1 Minami-ku Kitasato, Sagamihara City, Kanagawa, 252-0374, Japan.
authors.forename: Atsushi
authors.initials: A
authors.lastname: Minatani
authors.affiliation: Department of Orthopedic Surgery, Kitasato University School of Medicine, 1-15-1 Minami-ku Kitasato, Sagamihara City, Kanagawa, 252-0374, Japan. kuchida@med.kitasato-u.ac.jp.
authors.forename: Kentaro
authors.initials: K
authors.lastname: Uchida
authors.affiliation: Department of Orthopedic Surgery, Kitasato University School of Medicine, 1-15-1 Minami-ku Kitasato, Sagamihara City, Kanagawa, 252-0374, Japan.
authors.forename: Gen
authors.initials: G
authors.lastname: Inoue
authors.affiliation: Department of Orthopedic Surgery, Kitasato University School of Medicine, 1-15-1 Minami-ku Kitasato, Sagamihara City, Kanagawa, 252-0374, Japan.
authors.forename: Shotaro
authors.initials: S
authors.lastname: Takano
authors.affiliation: Department of Orthopedic Surgery, Kitasato University School of Medicine, 1-15-1 Minami-ku Kitasato, Sagamihara City, Kanagawa, 252-0374, Japan.
authors.forename: Jun
authors.initials: J
authors.lastname: Aikawa
authors.affiliation: Department of Orthopedic Surgery, Kitasato University School of Medicine, 1-15-1 Minami-ku Kitasato, Sagamihara City, Kanagawa, 252-0374, Japan.
authors.forename: Masayuki
authors.initials: M
authors.lastname: Miyagi
authors.affiliation: Department of Orthopedic Surgery, Kitasato University School of Medicine, 1-15-1 Minami-ku Kitasato, Sagamihara City, Kanagawa, 252-0374, Japan.
authors.forename: Hisako
authors.initials: H
authors.lastname: Fujimaki
authors.affiliation: Department of Orthopedic Surgery, Kitasato University School of Medicine, 1-15-1 Minami-ku Kitasato, Sagamihara City, Kanagawa, 252-0374, Japan.
authors.forename: Dai
authors.initials: D
authors.lastname: Iwase
authors.affiliation: Department of Orthopedic Surgery, Kitasato University School of Medicine, 1-15-1 Minami-ku Kitasato, Sagamihara City, Kanagawa, 252-0374, Japan.
authors.forename: Kenji
authors.initials: K
authors.lastname: Onuma
authors.affiliation: Department of Pathology, Kitasato University School of Medicine, 1-15-1 Minami-ku Kitasato, Sagamihara City, Kanagawa, 252-0374, Japan.
authors.forename: Toshihide
authors.initials: T
authors.lastname: Matsumoto
authors.affiliation: Department of Orthopedic Surgery, Kitasato University School of Medicine, 1-15-1 Minami-ku Kitasato, Sagamihara City, Kanagawa, 252-0374, Japan.
authors.forename: Masashi
authors.initials: M
authors.lastname: Takaso
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D015740:Calcitonin Gene-Related Peptide / Q000096:biosynthesis* / Q000235:genetics / Q000502:physiology; D002478:Cells, Cultured; D051546:Cyclooxygenase 2 / Q000378:metabolism; D016207:Cytokines / Q000378:metabolism / Q000494:pharmacology; D015232:Dinoprostone / Q000494:pharmacology; D005260:Female; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D018836:Inflammation Mediators / Q000378:metabolism / Q000494:pharmacology; D008297:Male; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000378:metabolism*; D018078:Receptors, Prostaglandin E / Q000502:physiology*; D058306:Receptors, Prostaglandin E, EP1 Subtype / Q000502:physiology; D058307:Receptors, Prostaglandin E, EP2 Subtype / Q000502:physiology; D058309:Receptors, Prostaglandin E, EP4 Subtype / Q000502:physiology; D015398:Signal Transduction / Q000502:physiology; D013583:Synovial Membrane / Q000378:metabolism*
chemical_list: D016207:Cytokines; D018836:Inflammation Mediators; D018078:Receptors, Prostaglandin E; D058306:Receptors, Prostaglandin E, EP1 Subtype; D058307:Receptors, Prostaglandin E, EP2 Subtype; D058309:Receptors, Prostaglandin E, EP4 Subtype; D051546:Cyclooxygenase 2; C496540:PTGS2 protein, human; D015740:Calcitonin Gene-Related Peptide; D015232:Dinoprostone
keywords: Calcitonin gene-related peptide; Cyclooxygenase-2; Knee osteoarthritis