Overexpression of cholesterol 24-hydroxylase CYP46A1 attenuates retinal dysfunction and ganglion cell loss via regulating the Nrf2 pathway in optic nerve crush injury.

Cholesterol 24-hydroxylase CYP46A1 (CYP46A1) has been confirmed to be correlated with the processes of multiple neurological disorders, but its role in neurodegenerative optic diseases remains unclear. This article aimed to evaluate the neuroprotective effects of CYP46A1 on mouse retinal ganglion cells (RGCs) and retinal function. Mice were subjected to optic nerve crush (ONC) injury after intravitreal injection of rAAVs. RGCs' survival was quantified by immunofluorescence staining of retinal flat mounts. Retinal electrophysiological function and visual acuity were quantitatively assessed using electroretinography (ERG) and optomotor response (OMR). The TdT-mediated dUTP nick-end labeling (TUNEL) staining was employed to quantify the apoptosis of RGCs. The protein expression level of CYP46A1, B-cell lymphoma 2 (Bcl-2), BCL-2-associated X protein (Bax), Kelch-like ECH-associated protein 1 (Keap1), nuclear factor erythroid 2-related factor (Nrf2), and heme oxygenase 1 (HO1) were validated by Western blot. After ONC injury, CYP46A1 expression increased, while RGCs' survival rate, the amplitude of photopic negative response (PhNR), and visual acuity decreased; there were no significant changes in the a-wave and b-wave. Western blotting and retinal cryosection staining confirmed that intravitreal injection of rAAV-CYP46A1-EGFP upregulated CYP46A1 expression. CYP46A1 overexpression mitigated ONC-induced RGCs loss and retinal electrophysiological dysfunction. The overexpression of CYP46A1 could significantly inhibit RGCs apoptosis, reduce Bax expression and increase Bcl-2 expression. Additionally, the upregulation of CYP46A1 led to decreased Keap1 expression and increased Nrf2 and HO-1 levels. In conclusion, our results demonstrated that the overexpression of CYP46A1 could prevent the loss of RGCs and protect the electrophysiological function by activating Nrf2 signaling pathway.