title: Cytoskeletal dependence of adenosine triphosphate release by human trabecular meshwork cells.
abstract: OBJECTIVE
  To test whether adenosine triphosphate (ATP) release links cytoskeletal remodeling with release of matrix metalloproteinases (MMPs), regulators of outflow facility and intraocular pressure.
  
  
  METHODS
  ATP release was measured by luciferin-luciferase. Ecto-ATPases from transformed human trabecular meshwork (TM) cells (TM5) and explant-derived TM cells were identified by RT-PCR. Actin was visualized by phalloidin staining. Cell viability was assayed by lactate dehydrogenase and thiazolyl blue tetrazolium bromide methods and propidium iodide exclusion, gene expression by real-time PCR, and MMP release by zymography. Cell volume was monitored by electronic cell sorting.
  
  
  RESULTS
  Hypotonicity (50%) and mechanical stretch increased ATP release with similar pharmacologic profiles. TM cells expressed ecto-ATPases E-NPP1-3, E-NTPD2, E-NTPD8, and CD73. Prolonged dexamethasone (DEX) exposure (≥ 2 weeks), but not brief exposure (3 days), increased cross-linked actin networks and reduced swelling-triggered ATP release. Cytochalasin D (CCD) exerted opposite effects. Neither DEX nor CCD altered the cell viability, gene expression, or pharmacologic profile of ATP-release pathways. DEX accelerated, and CCD slowed, the regulatory volume decrease after hypotonic exposure. Activating A(1) adenosine receptors (A(1)ARs) increased total MMP-2 and MMP-9 release. DEX reduced total A(1)AR-triggered MMP release, and CCD increased the active form of MMP-2 release. The A(1)AR agonist CHA and the A(1)AR antagonist DPCPX partially reversed the effects of DEX and CCD, respectively.
  
  
  CONCLUSIONS
  Cytoskeletal restructuring modulated swelling-activated ATP release, in part by changing the duration of cell swelling after hypotonic challenge. Modifying ATP release is expected to modulate MMP secretion by altering ecto-enzymatic delivery of adenosine to A(1)ARs, linking cytoskeletal remodeling and MMP-mediated modulation of outflow facility.
authors: Department of Physiology, Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104-6085, USA.
authors: Ang
authors: A
authors: Li
authors: Chi Ting
authors: CT
authors: Leung
authors: Kim
authors: K
authors: Peterson-Yantorno
authors: W Daniel
authors: WD
authors: Stamer
authors: Mortimer M
authors: MM
authors: Civan
mesh_terms: D000199:Actins / Q000378:metabolism; D000251:Adenosine Triphosphatases / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism*; D001082:Aqueous Humor / Q000378:metabolism; D002461:Cell Line, Transformed; D048429:Cell Size; D002470:Cell Survival; D002478:Cells, Cultured; D015638:Cytochalasin D / Q000494:pharmacology; D003599:Cytoskeleton / Q000187:drug effects / Q000502:physiology*; D003907:Dexamethasone / Q000494:pharmacology; D006801:Humans; D007429:Intraocular Pressure / Q000502:physiology; D020778:Matrix Metalloproteinase 2 / Q000378:metabolism; D020780:Matrix Metalloproteinase 9 / Q000378:metabolism; D018613:Microscopy, Confocal; D060888:Real-Time Polymerase Chain Reaction; D043682:Receptor, Adenosine A1 / Q000378:metabolism; D014129:Trabecular Meshwork / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*
chemical_list: D000199:Actins; D043682:Receptor, Adenosine A1; D015638:Cytochalasin D; D003907:Dexamethasone; D000255:Adenosine Triphosphate; D020778:Matrix Metalloproteinase 2; D020780:Matrix Metalloproteinase 9; D000251:Adenosine Triphosphatases