Systemic Nicotinamide Riboside Treatment Protects Retinal Ganglion Cells in an Aged Optic Nerve Crush Mouse Model

Abstract

Purpose : We previously demonstrated that systemic treatment with nicotinamide riboside (NR), a nicotinamide adenine dinucleotide (NAD⁺) precursor, elevated retinal NAD⁺ levels and protected retinal ganglion cells (RGCs) in a young mouse model of optic nerve crush (ONC). Because NAD⁺ levels decline in age and disease, we now compare neuroprotective effects of systemic NR treatment on young and aged mice subjected to ONC.

Methods : Young (3-6 months old) and aged (18-24 months old) C57BL/6J mice were intraperitoneally (i.p.) injected with NR (1000mg/kg) for 5 consecutive days. PBS was injected as vehicle. Two weeks later, unilateral ONC was conducted. Pattern electroretinography (PERG) was conducted 3 days after ONC. In separate cohorts, young and aged mice were injected with NR or PBS; no crush surgery was conducted. Retinas were harvested for whole-mount immunofluorescence staining with RGC marker Brn3a or NAD⁺ concentration measurement (Fig.1)

Results : Systemic NR treatment significantly elevated retinal NAD⁺ concentrations in both young(young-PBS+no crush vs young-NR+no crush:100±3vs193±10, p<0.05, n=10) and aged C57BL/6J mice(aged-PBS+no crush vs aged-NR+no crush:106±6vs192±10, p<0.05, n=10) , and also in eyes of young mice following ONC(young-naïve vs young-NR+ONC 100±3 vs. 142±9, p<0.01, n=6), but not in aged mice following ONC(aged-naïve vs aged-NR+ONC:110.2±5 vs 122.6±8, p>0.05, n=6). In both young and aged mice, PERG responses and numbers of Brn3a-positive cells from crushed retina were diminished compared with non-crushed(Table.2). NR treatment significantly preserved Brn3a-positive RGC numbers in both young and aged mice following ONC(young-PBS+ONC vs young-NR+ONC:1120±72vs1389±72 cells/field, p<0.05, n=7-9; aged-PBS+ONC vs aged-NR+ONC:1004±34vs1193±49 cells/field, p<0.05, n=7-8) and preserved PERG responses in young(young-PBS+ONC vs young-NR+ONC: P1:5.43±0.7vs8.91±0.8μV, p<0.01; N2:-8.02±0.9vs -12.2± 1.0μV, p<0.01, n=15) but not in aged mice following ONC(aged-PBS+ONC vs aged-NR+ONC:P1:2.42±0.4vs3.70±0.5μV; N2:-4.15±0.5 vs -6.03± 0.7μV, p>0.05, n=14).

Conclusions : NR treatment significantly protected against ONC-induced RGC death in both young and aged mice and significantly protected against ONC-induced RGC dysfunction in young but not in aged mice. It may be that ONC in aged mice partially suppresses NR-induced elevation of NAD⁺, preserving RGC survival but not RGC function.

This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.