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The neurosteroid allopregnanolone protects retinal neurons by effects on autophagy and GABRs/GABA_A receptors in rat glaucoma models.

ABSTRACT: In an ex vivo rat glaucoma model using dissected retinas, the neurosteroid allopregnanolone (AlloP) protects retinal ganglion cells (RGCs) via GABR/GABA_A receptors. To determine the involvement of macroautophagy/autophagy in neuroprotection by AlloP, we examined the effects of autophagy activators, rapamycin and torin 2, and autophagy inhibitors, bafilomycin A₁ and SAR405, on retinal retinal morphology and expression of MAP1 LC3B/LC3B (microtubule-associated protein 1 light chain 3 beta) and SQSTM1 (sequestosome 1). Administration of rapamycin or torin 2 exerted partial histological neuroprotection, while combined administration of AlloP with bafilomycin A₁ or SAR405 induced severe degeneration in a hyperbaric condition. Electron microscopic analyses showed that the addition of AlloP significantly increased autophagosomes and degenerative autophagic vacuoles in the retinal nerve fiber layer. Immunoblotting showed that the addition of AlloP or autophagic activators increased the lipidated form of LC3B (LC3B-II) and suppressed SQSTM1. Moreover, bafilomycin A₁ increased LC3B-II and SQSTM1 protein levels in the presence of AlloP without changes in corresponding mRNAs compared to AlloP-treated retinas in a hyperbaric condition. These data indicate that AlloP likely induces a protective form of autophagy in this model. In an in vivo rat model of glaucoma, we also observed neuroprotective effects of AlloP. Injection of polystyrene microbeads into the anterior chamber increased intraocular pressure about 3-fold and induced RGC apoptosis. A single intravitreal injection of AlloP or autophagy activators prevented apoptosis and protected RGCs with autophagy activation. We conclude that AlloP may serve as a potential therapeutic agent for the treatment of glaucoma via diverse mechanisms.Abbreviations: 2HBCD: 2-Hydroxypropyl)-β-cyclodextrin; 3-MA: 3-methyladenine; AlloP: allopregnanolone; AP: autophagosome; AVd: degradative autophagic vacuoles; GCL: ganglion cell layer; INL: inner nuclear layer; IOP: intraocular pressure; IPL: inner plexiform layer; LC3B-I: cytosolic form of LC3B; LCB-II: lipidated form of LC3B; MAP1LC3B/LC3B: microtubule-associated protein 1 light chain 3 beta; mPTP: mitochondrial permeability transition pore; NDS: neuronal damage score; NFL: nerve fiber layer; OH: ocular hypertension; ON: optic nerve; ONL: outer nuclear layer; OPL: outer plexiform layer; p-STR: scotopic threshold response; RGC: retinal ganglion cells; RT-PCR: real-time reverse transcription polymerase chain reaction; SQSTM1: sequestosome 1; TUNEL: TdT-mediated dUTP Nick End Labeling.

SUBMITTER: Ishikawa M

PROVIDER: S-EPMC8032250 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:RationaleGR3027 is a novel small molecule GABA-A receptor-modulating steroid antagonist, which in non-clinical studies has shown promise for treatment of human disorders due to allosteric over-activation of GABA-A receptors by neurosteroids, such as allopregnanolone. We here studied its safety, pharmacokinetics, and ability to inhibit allopregnanolone effects in humans.MethodsSafety and pharmacokinetics were studied in healthy adult males receiving ascending single or multiple oral GR3027 vs. placebo. GR3027-mediated reversal of allopregnanolone effect on maximal saccadic eye velocity (SEV), and self-rated somnolence was studied in a double-blind, placebo-controlled, three-part cross-over study in which 3 or 30 mg oral GR3027 preceded 0.05 mg/kg of i.v. allopregnanolone.ResultsGR3027 was well tolerated, adverse events were generally mild and transient, and no dose-limiting toxicity or grade 3 adverse events were observed up to the highest single (200 mg) or multiple (100 mg every 12 h for 5 days) doses. The maximum concentration (Cmax) and systemic exposure (area under the plasma concentration-time curve from dose extrapolated to infinity [AUC0-∞] and/or AUC during the dosing interval [AUCτ]) varied linearly with dose; with dose-dependent accumulation ratios of 1.3-1.6. Allopregnanolone decreased SEV and induced somnolence in most, but not all subjects. By predefined analyses, 30 mg GR3027 significantly inhibited allopregnanolone-induced decrease in SEV (p = 0.03); 3 and 30 mg GR3027 non-significantly inhibited allopregnanolone-induced sedation. By post hoc analyses restricted to subjects with allopregnanolone-induced changes and the time period over which they occurred, GR3027 dose dependently inhibited allopregnanolone-induced decrease in SEV (p = 0.04 at 30 mg, non-significant at 3 mg) and allopregnanolone-induced sedation (p = 0.01/0.05 at 3/30 mg doses).ConclusionOral GR3027 mitigates inhibition of brain function induced by allopregnanolone at doses which are clinically well tolerated and associated with linear pharmacokinetics.

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The neurosteroid allopregnanolone protects retinal neurons by effects on autophagy and GABRs/GABA_A receptors in rat glaucoma models.

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The neurosteroid allopregnanolone protects retinal neurons by effects on autophagy and GABRs/GABAA receptors in rat glaucoma models.

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OmicsDI is part of the ELIXIR infrastructure

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The neurosteroid allopregnanolone protects retinal neurons by effects on autophagy and GABRs/GABA_A receptors in rat glaucoma models.