Abstract
Purpose :
The death of retinal ganglion cells (RGCs) is a hallmark of glaucoma and other optic neuropathies. Administration of growth hormone-releasing hormone receptor (GHRHR) antagonist has been shown to protect RGCs following optic nerve injury, while the molecular mechanisms have not been fully elucidated. We aim to investigate underlying mechanisms of GHRHR signaling in experimental models of optic neuropathies.
Methods :
Three experimental mouse models of optic neuropathies: retinal ischemia-reperfusion (IR), microbead induced glaucoma, and optic nerve crush (ONC), were induced in C57BL/6 wild type and GHRHR knockout (KO) mice. The retina was evaluated with fundus photo, optical coherence tomography and fluorescein angiography. Immunofluorescence and H&E stains were used to study retinal morphology. Dark-adapted electroretinogram (ERG) was recorded to analyze retinal functions. RT-qPCR and western blot were used to measure mRNA and protein levels. In addition, primary RGCs were purified from rat retinas for GHRHR antagonist treatment. Data were analyzed with one-way ANOVA and presented as mean±standard error of mean.
Results :
GHRHR deficiency via both GHRHR antagonist MIA602 and GHRHR KO significantly inhibited the decrease of RGCs in three mouse models [WT-IR-Day7: (2716+/-66.93) cells/mm2; GHRHR KO-IR-Day7: (2962+/-32.31) cells/mm2, p<0.05]. GHRHR deficiency mice had significantly reduced mean retinal thickness [WT-IR-Day7: (252.3+/-3.35)µm; GHRHR KO-IR-Day7: (234.7+/-1.98)µm] and increased mean retinal vessel diameter [WT-IR-Day5: (292.1+/-5.91)µm; GHRHR KO-IR-Day5: (342.7+/-8.48)µm] after IR (p<0.05). Moreover, ERG recording showed the reduced amplitudes of a-wave, b-wave, and pSTR were partially rescued by the deficiency of GHRHR in three mouse models (p<0.05) (Figure 1). Mechanistically, marked accumulation of pro-ferroptosis marker ACSL4 and depletion of anti-ferroptosis marker GPX4 in retinas of I/R model, accompanied by increased iron level and lipid peroxidation. Deficiency of GHRHR reversed these changes of ferroptosis features (p<0.05).
Conclusions :
Our results indicate potential neuroprotective effects of GHRHR deficiency on RGCs by modulating ferroptosis pathways in optic neuropathies.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.