title: Human corneal epithelial cells express functional PAR-1 and PAR-2.
abstract: OBJECTIVE
  The objective of this study was to examine whether HCECs express functional proteinase-activated receptor (PAR)-1 and -2 and evaluate the effects of receptor activation on corneal epithelial cell proinflammatory cytokine production.
  
  
  METHODS
  Expression of PAR-1 and -2 mRNAs was determined by RT-PCR in cultured primary human corneal epithelial cells (HCECs) and the human corneal epithelial cell line HCE-T. Localization of PAR-1 and -2 in whole normal human corneas was determined by immunofluorescence with PAR-1 and -2 antibodies. The functional competence of PAR-1 and -2 in corneal epithelial cells was assessed by measuring the rapid induction of intracellular [Ca(2+)] in response to thrombin, trypsin, and specific receptor-activating peptides derived from the tethered ligands of the PAR receptors. HCE-T expression of cytokines (IL-6, IL-8, and TNFalpha) in response to activation of PAR-1 and -2 was measured by quantitative RT-PCR and ELISA.
  
  
  RESULTS
  Functional PAR-1 and -2 were expressed in both HCECs and HCE-T cells. Immunoreactivity for PAR-1 and -2 was detected in the outer epithelial layer of the cornea in whole human corneal sections. Activation of PAR-1 and -2 led to upregulation in HCE-T cells of both expression of mRNA and secretion of the proinflammatory cytokines IL-6, IL-8, and TNFalpha.
  
  
  CONCLUSIONS
  The results show for the first time that functional PAR-1 and -2 are present in human cornea. Activation of these receptors results in the production of various corneal epithelial cell proinflammatory cytokines. These observations indicate that PAR-1 and -2 may play an important role in modulating corneal inflammatory and wound-healing responses. These receptors may be useful therapeutic targets in several corneal disease processes.
authors.affiliation: Department of Dermatology, Emory University School of Medicine, Atlanta, Georgia, USA.
authors.forename: Roland
authors.initials: R
authors.lastname: Lang
authors.forename: Peter I
authors.initials: PI
authors.lastname: Song
authors.forename: Franz J
authors.initials: FJ
authors.lastname: Legat
authors.forename: Robert M
authors.initials: RM
authors.lastname: Lavker
authors.forename: Brad
authors.initials: B
authors.lastname: Harten
authors.forename: Henner
authors.initials: H
authors.lastname: Kalden
authors.forename: Eileen F
authors.initials: EF
authors.lastname: Grady
authors.forename: Nigel W
authors.initials: NW
authors.lastname: Bunnett
authors.forename: Cheryl A
authors.initials: CA
authors.lastname: Armstrong
authors.forename: John C
authors.initials: JC
authors.lastname: Ansel
mesh_terms: D001483:Base Sequence; D002118:Calcium / Q000378:metabolism; D002460:Cell Line; D003315:Cornea / Q000378:metabolism*; D016207:Cytokines / Q000096:biosynthesis; D017931:DNA Primers / Q000737:chemistry; D004797:Enzyme-Linked Immunosorbent Assay; D004847:Epithelial Cells / Q000378:metabolism; D019084:Fluorescent Antibody Technique, Indirect; D006801:Humans; D008969:Molecular Sequence Data; D012333:RNA, Messenger / Q000378:metabolism; D044463:Receptor, PAR-1; D044464:Receptor, PAR-2; D018179:Receptors, Thrombin / Q000235:genetics* / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013917:Thrombin / Q000494:pharmacology; D014357:Trypsin / Q000494:pharmacology; D015854:Up-Regulation
chemical_list: D016207:Cytokines; D017931:DNA Primers; D012333:RNA, Messenger; D044463:Receptor, PAR-1; D044464:Receptor, PAR-2; D018179:Receptors, Thrombin; D014357:Trypsin; D013917:Thrombin; D002118:Calcium