TY - JOUR
T1 - Neurosteroids are endogenous neuroprotectants in an ex vivo glaucoma model
AU - Ishikawa, Makoto
AU - Yoshitomi, Takeshi
AU - Zorumski, Charles F.
AU - Izumi, Yukitoshi
N1 - Funding Information:
The authors thank Yoko Hayami and Sanae Takaseki for technical support. Supported in part by JSPS KAKENHI Grant No. 24592666 (MI) and National Institutes of Health (NIH; Bethesda, MD, USA) Grants MH077791, MH101874, and AA017413 (CFZ) and the Bantly Foundation. The authors alone are responsible for the content and writing of the paper. Disclosure: M. Ishikawa, None; T. Yoshitomi, None; C.F. Zorumski, None; Y. Izumi, None
Publisher Copyright:
© 2014 The Association for Research in Vision and Ophthalmology, Inc.
PY - 2014/12/1
Y1 - 2014/12/1
N2 - PURPOSE. Allopregnanolone is a neurosteroid and powerful modulator of neuronal excitability. The neuroprotective effects of allopregnanolone involve potentiation of y-aminobutyric acid (GABA) inhibitory responses. Although glutamate excitotoxicity contributes to ganglion cell death in glaucoma, the role of GABA in glaucoma remains uncertain. The aim of this study was to determine whether allopregnanolone synthesis is induced by high pressure in the retina and whether allopregnanolone modulates pressure-mediated toxicity. METHODS. Ex vivo rat retinas were exposed to hydrostatic pressure (10, 35, and 75 mm Hg) for 24 hours. Endogenous allopregnanolone production was determined by liquid chromatography and tandem mass spectrometry (LC-MS/MS) and immunochemistry. We also examined the effects of allopregnanolone, finasteride, and dutasteride (inhibitors of 5a-reductase), picrotoxin (a GABAA receptor antagonist), and D-2-amino-5-phosphonovalerate (APV, a roadspectrum N-methyl-D-aspartate receptor [NMDAR] antagonist). RESULTS. Pressure loading at 75 mm Hg significantly increased allopregnanolone levels as measured by LC-MS/MS. Elevated hydrostatic pressure also increased neurosteroid immunofluorescence, especially in the ganglion cell layer and inner nuclear layers. Staining was negligible at lower pressures. Enhanced allopregnanolone levels and immunostaining were substantially blocked by finasteride, but more effectively inhibited by dutasteride and APV. Administration of exogenous allopregnanolone suppressed pressure-induced axonal swelling in a concentration-dependent manner, while picrotoxin overcame these neuroprotective effects. CONCLUSIONS. These results indicate that the synthesis of allopregnanolone is enhanced mainly via NMDARs in the pressure-loaded retina, and that allopregnanolone diminishes pressuremediated retinal degeneration via GABAA receptors. Allopregnanolone and other related neurosteroids may serve as potential novel therapeutic targets for the prevention of pressureinduced retinal damage in glaucoma.
AB - PURPOSE. Allopregnanolone is a neurosteroid and powerful modulator of neuronal excitability. The neuroprotective effects of allopregnanolone involve potentiation of y-aminobutyric acid (GABA) inhibitory responses. Although glutamate excitotoxicity contributes to ganglion cell death in glaucoma, the role of GABA in glaucoma remains uncertain. The aim of this study was to determine whether allopregnanolone synthesis is induced by high pressure in the retina and whether allopregnanolone modulates pressure-mediated toxicity. METHODS. Ex vivo rat retinas were exposed to hydrostatic pressure (10, 35, and 75 mm Hg) for 24 hours. Endogenous allopregnanolone production was determined by liquid chromatography and tandem mass spectrometry (LC-MS/MS) and immunochemistry. We also examined the effects of allopregnanolone, finasteride, and dutasteride (inhibitors of 5a-reductase), picrotoxin (a GABAA receptor antagonist), and D-2-amino-5-phosphonovalerate (APV, a roadspectrum N-methyl-D-aspartate receptor [NMDAR] antagonist). RESULTS. Pressure loading at 75 mm Hg significantly increased allopregnanolone levels as measured by LC-MS/MS. Elevated hydrostatic pressure also increased neurosteroid immunofluorescence, especially in the ganglion cell layer and inner nuclear layers. Staining was negligible at lower pressures. Enhanced allopregnanolone levels and immunostaining were substantially blocked by finasteride, but more effectively inhibited by dutasteride and APV. Administration of exogenous allopregnanolone suppressed pressure-induced axonal swelling in a concentration-dependent manner, while picrotoxin overcame these neuroprotective effects. CONCLUSIONS. These results indicate that the synthesis of allopregnanolone is enhanced mainly via NMDARs in the pressure-loaded retina, and that allopregnanolone diminishes pressuremediated retinal degeneration via GABAA receptors. Allopregnanolone and other related neurosteroids may serve as potential novel therapeutic targets for the prevention of pressureinduced retinal damage in glaucoma.
KW - Allopregnanolone
KW - GABA
KW - Glaucoma
KW - Neuroprotection
KW - Neurosteroid
KW - Transporter-knockout
UR - http://www.scopus.com/inward/record.url?scp=84945455364&partnerID=8YFLogxK
U2 - 10.1167/iovs.14-15624
DO - 10.1167/iovs.14-15624
M3 - Article
C2 - 25406290
AN - SCOPUS:84945455364
SN - 0146-0404
VL - 55
SP - 8531
EP - 8541
JO - Investigative Ophthalmology and Visual Science
JF - Investigative Ophthalmology and Visual Science
IS - 12
ER -