title: Effects of toxic cellular stresses and divalent cations on the human P2X7 cell death receptor.
abstract: OBJECTIVE
  The purpose of this study was to investigate responses to toxic cellular stresses in different human ocular epithelia.
  
  
  METHODS
  Reactivity with a specific anti-P2X7 antibody was studied using confocal fluorescence microscopy on conjunctival, corneal, lens, and retinal cell lines as well as using impression cytology on human ocular cells. Activation of the P2X7 receptor by selective agonists (ATP and benzoylbenzoyl-ATP) and inhibition by antagonists (oATP, KN-62, and PPADS) were evaluated using the quinolinium,4-[(3-methyl-2-(3H)-benzoxazolylidene) methyl]-1-[3-(triethylammonio)propyl]di-iodide (YO-PRO-1) test in cytofluorometry. Different specific stresses were then induced by a chemical toxin (benzalkonium chloride) and a chemical oxidant (tert-butyl hydroperoxide) to assess the role of the P2X7 receptor. Modulation of P2X7 receptor activation was performed with several ionic solutions.
  
  
  RESULTS
  Our data show that four cell lines express the P2X7 cell death purinergic receptor as judged by reactivity with a specific anti-P2X7 antibody, activation by the selective P2X7 agonist benzoylbenzoyl-ATP and to a lesser extent by ATP (YO-PRO-1 dye uptake), and inhibition by three antagonists (oATP, KN-62, and PPADS). Benzalkonium chloride, a widely used preservative, induced dramatic membrane permeabilization through P2X7 pore opening on conjunctival and corneal epithelia. Reactive oxygen species, induced by tert-butyl hydroperoxide, lead to P2X7 receptor activation on retinal pigment epithelium. Modulation of P2X7 receptor activation was obtained with extracellular Ca(2+) and Mg(2+) and with a controlled ionization marine solution rich in different divalent cations. This marine solution could be proposed as a new ophthalmic solution.
  
  
  CONCLUSIONS
  Our observations reveal a novel pathway for epithelial cells apoptosis/cytolysis by inducing different toxic stresses and their modulation by using ionic solutions.
authors.affiliation: Laboratoire de Toxicologie, Faculté des Sciences Pharmaceutiques et Biologiques, Université Paris Descartes, Paris, France. melody.dutot@univ-paris5.fr
authors.forename: Mélody
authors.initials: M
authors.lastname: Dutot
authors.forename: Hong
authors.initials: H
authors.lastname: Liang
authors.forename: Thierry
authors.initials: T
authors.lastname: Pauloin
authors.forename: Françoise
authors.initials: F
authors.lastname: Brignole-Baudouin
authors.forename: Christophe
authors.initials: C
authors.lastname: Baudouin
authors.forename: Jean-Michel
authors.initials: JM
authors.lastname: Warnet
authors.forename: Patrice
authors.initials: P
authors.lastname: Rat
mesh_terms: D000255:Adenosine Triphosphate / Q000031:analogs & derivatives; D000293:Adolescent; D000328:Adult; D001548:Benzalkonium Compounds / Q000494:pharmacology; D001583:Benzoxazoles / Q000378:metabolism; D002413:Cations, Divalent / Q000494:pharmacology*; D016923:Cell Death / Q000187:drug effects; D002460:Cell Line; D003228:Conjunctiva / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D019573:Epithelium, Corneal / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D005123:Eye / Q000166:cytology* / Q000187:drug effects* / Q000378:metabolism; D006801:Humans; D007049:Iatrogenic Disease; D007908:Lens, Crystalline / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D018384:Oxidative Stress / Q000187:drug effects*; D010857:Pigment Epithelium of Eye / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D011806:Quinolinium Compounds / Q000378:metabolism; D018048:Receptors, Purinergic P2 / Q000378:metabolism*; D058486:Receptors, Purinergic P2X7
chemical_list: D001548:Benzalkonium Compounds; D001583:Benzoxazoles; D002413:Cations, Divalent; C546468:P2RX7 protein, human; C546470:P2rx7 protein, rat; D011806:Quinolinium Compounds; D018048:Receptors, Purinergic P2; D058486:Receptors, Purinergic P2X7; C089813:YO-PRO 1; C033901:3'-O-(4-benzoyl)benzoyladenosine 5'-triphosphate; D000255:Adenosine Triphosphate