Hypoxia augments TNF-alpha-mediated endothelin-1 release and cell proliferation in human optic nerve head astrocytes.
The effect of hypoxia (24 h) on TNF-alpha-mediated release of endothelin-1 (ET-1) from human optic nerve head astrocytes (hONAs) and TNF-alpha- and ET-1-induced hONA proliferation was determined. ET-1 synthesis and release was quantitated using ELISA while TNF-alpha (10 nM)- and ET-1 (100 nM)-mediated hONA proliferation was assessed by CellTiter 96 aqueous one-solution cell proliferation assay, respectively. hONAs appeared to be more rounded with fewer processes following 24 h hypoxia compared to thodr seen in normoxia. Hypoxia enhanced TNF-alpha-mediated ET-1 synthesis and release (by 5-fold) and also significantly increased TNF-alpha- and ET-1-mediated hONA proliferation. PD142893 (1 microM), an ET(A/B) receptor antagonist, blocked ET-1-mediated hONA proliferation both under normoxia and hypoxia, while doing so only under normoxia following TNF-alpha treatment. Also, U0126 (10 microM; an upstream ERK1/2 inhibitor) completely blocked agonist-induced hONA proliferation in normoxia and partially blocked the same in hypoxia. These results demonstrate for the first time that hONAs secrete ET-1 and that TNF-alpha and hypoxia can regulate its levels. Moreover, hypoxia augments the proliferative responses of hONAs to TNF-alpha and ET-1. These agonist-mediated effects following hypoxia could contribute to astroglial activation as seen in glaucomatous optic nerve heads.
Desai
Devashish
D
Department of Pharmacology and Neuroscience, University of North Texas Health Science Center, Fort Worth, TX 76107, USA.
He
Shaoqing
S
Yorio
Thomas
T
Krishnamoorthy
Raghu R
RR
Prasanna
Ganesh
G
D000368:Aged; D000369:Aged, 80 and over; D016282:Aspartic Acid Endopeptidases / Q000037:antagonists & inhibitors; D001253:Astrocytes / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D002070:Butadienes / Q000494:pharmacology; D002455:Cell Division / Q000187:drug effects / Q000502:physiology; D015687:Cell Hypoxia / Q000502:physiology; D045744:Cell Line, Tumor; D002478:Cells, Cultured; D003513:Cycloheximide / Q000494:pharmacology; D003609:Dactinomycin / Q000494:pharmacology; D065128:Endothelin Receptor Antagonists; D019332:Endothelin-1 / Q000378:metabolism*; D000072396:Endothelin-Converting Enzymes; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006020:Glycopeptides / Q000494:pharmacology; D006801:Humans; D008666:Metalloendopeptidases; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors; D009570:Nitriles / Q000494:pharmacology; D009842:Oligopeptides / Q000494:pharmacology; D009898:Optic Disk / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D011480:Protease Inhibitors / Q000494:pharmacology; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*
D002070:Butadienes; D065128:Endothelin Receptor Antagonists; D019332:Endothelin-1; D004791:Enzyme Inhibitors; D006020:Glycopeptides; D009570:Nitriles; D009842:Oligopeptides; D011480:Protease Inhibitors; D014409:Tumor Necrosis Factor-alpha; C113580:U 0126; C076213:PD 142893; D003609:Dactinomycin; D003513:Cycloheximide; D020928:Mitogen-Activated Protein Kinases; D016282:Aspartic Acid Endopeptidases; D008666:Metalloendopeptidases; D000072396:Endothelin-Converting Enzymes; C008890:phosphoramidon